JP7703980B2 - Manufacturing method for double-sided mounting board - Google Patents

Description

The present invention relates to a method for manufacturing a double-sided mounting board.

Various methods have been considered for manufacturing double-sided mounted boards by mounting components on both sides of the board (for example, Patent Document 1).

Japanese Patent Application Publication No. 9-223856

The present invention aims to provide a new method for manufacturing double-sided mounting boards.

One aspect of the present invention relates to a method for manufacturing a double-sided mounted board, comprising a first mounting step of mounting a first electronic component on the first main surface of a board having a first main surface and a second main surface, a holding step of arranging a holding member that holds the first electronic component on the first main surface, and a second mounting step of mounting a second electronic component on the second main surface, in which, prior to the second mounting step, a heat insulating material is arranged to surround the first electronic component mounted on the first main surface.

The manufacturing method according to one embodiment may further include a covering step of covering the first electronic component with a thermal insulating material after the first mounting step, and the holding member may be a member that holds the first electronic component covered with the thermal insulating material on the first main surface.

In one embodiment, the holding step may be a step of placing a holding member that includes a base and an insulating layer that contains an insulating material and is placed on the base.

In one embodiment, the insulating material may contain aerogel particles and may further contain a water-soluble polymer having a hydrophobic group.

In one embodiment, the insulating material may be an insulating material that satisfies the following formula (A).
F1>F2 ... (A)
[In the formula, F1 represents the adhesive strength of the insulating material after heating the insulating material at 220° C. for 120 seconds, and F2 represents the adhesive strength of the insulating material after heating the insulating material at 260° C. for 30 seconds.]

In one embodiment, the insulating material may contain first hollow particles that are thermally expandable hollow particles, second hollow particles that are hollow particles other than the first hollow particles, and a matrix polymer.

Another aspect of the present invention relates to a holding member that holds a first electronic component mounted on a first main surface of a substrate having a first main surface and a second main surface, on the first main surface when a second electronic component is mounted on the second main surface, the holding member comprising a base and a thermal insulation layer containing a thermal insulation material disposed on the base.

The present invention provides a novel method for manufacturing double-sided mounting boards.

1A to 1C are diagrams for explaining an example of a method for manufacturing a double-sided mounted board. 1A to 1C are diagrams for explaining an example of a method for manufacturing a double-sided mounted board. 1A to 1C are diagrams for explaining an example of a method for manufacturing a double-sided mounted board. 1A to 1C are diagrams for explaining an example of a method for manufacturing a double-sided mounted board. 1A to 1C are diagrams for explaining an example of a method for manufacturing a double-sided mounted board. 1A to 1C are diagrams for explaining an example of a method for manufacturing a double-sided mounted board.

A preferred embodiment of the present invention is described in detail below.

The manufacturing method of the double-sided mounted board of this embodiment includes a first mounting step of mounting a first electronic component on the first main surface of a board having a first main surface and a second main surface, a holding step of arranging a holding member that holds the first electronic component on the first main surface, and a second mounting step of mounting a second electronic component on the second main surface. In the manufacturing method of this embodiment, prior to the second mounting step, a heat insulating material is arranged to surround the first electronic component mounted on the first main surface.

In the manufacturing method of this embodiment, the mounted first electronic component is protected by a heat insulating material during the second mounting process. Therefore, even if a high-temperature process such as reflow is performed in the second mounting process, poor connection due to remelting of the connection between the first electronic component and the board, deterioration of the first electronic component due to repeated heating, etc. can be avoided, and it is believed that a highly reliable double-sided mounted board can be obtained.

In recent years, lead-free solder has come to be widely used to connect electronic components to substrates, and the process temperatures are becoming higher. In such high-temperature processes, problems caused by reheating of mounted electronic components are more likely to occur, so it is believed that the effects of the manufacturing method of this embodiment will be more pronounced.

The first electronic component may have solder bumps, and the solder bumps may contain lead-free solder. The first mounting process may be, for example, a process of connecting the first electronic component and a substrate via the solder bumps.

The first mounting process may include a first reflow process in which the solder bumps are melted by reflow to connect the substrate and the first electronic component. In the first reflow process, the substrate and the first electronic component are connected by a connection portion containing solder.

The reflow temperature may be, for example, a temperature equal to or higher than the melting point of the solder that constitutes the solder bump. The reflow temperature may be, for example, 220°C or higher, or 225°C or higher, or, for example, 270°C or lower, or 260°C or lower. When the solder that constitutes the solder bump is lead-free solder, the reflow temperature may be, for example, 240°C or higher, or 245°C or higher, or, for example, 260°C or lower, or 255°C or lower.

The first mounting step may further include a first sealing step of sealing the gap between the substrate and the first electronic component with an underfill material. In the first sealing step, the gap between the substrate and the first electronic component is filled with a sealing material made of an underfill material or a cured product thereof.

The underfill material is not particularly limited, and any known underfill material can be used without any particular restrictions.

The holding member is a member that holds the first electronic component on the first main surface to prevent the first electronic component from falling off the substrate after mounting.

In the manufacturing method of this embodiment, for example, after performing a first mounting step with the first main surface on the top, the substrate can be flipped over and a second mounting step can be performed with the second main surface on the top. The holding member can be a member that supports the first electronic component on the side opposite the substrate to prevent the first electronic component from falling off the first main surface during the second mounting step.

The second electronic component may have solder bumps, and the solder bumps may contain lead-free solder. The second mounting process may be, for example, a process of connecting the second electronic component and the substrate via the solder bumps.

The second mounting process may include a second reflow process in which the solder bumps are melted by reflow to connect the substrate and the second electronic component. In the second reflow process, the substrate and the second electronic component are connected by a connection portion containing solder.

The reflow temperature may be, for example, a temperature equal to or higher than the melting point of the solder that constitutes the solder bump. The reflow temperature may be, for example, 220°C or higher, or 225°C or higher, or, for example, 270°C or lower, or 260°C or lower. When the solder that constitutes the solder bump is lead-free solder, the reflow temperature may be, for example, 240°C or higher, or 245°C or higher, or, for example, 260°C or lower, or 255°C or lower.

The second mounting step may further include a second sealing step of sealing the gap between the substrate and the second electronic component with an underfill material. In the second sealing step, the gap between the substrate and the second electronic component is filled with a sealing material made of an underfill material or a cured product thereof.

The underfill material is not particularly limited, and any known underfill material can be used without any particular restrictions.

In the manufacturing method of this embodiment, before the second mounting step, a thermal insulator is placed to surround the first electronic component mounted on the first main surface.

The placement of the insulating material may be performed, for example, by covering the first electronic component after mounting with the insulating material. In other words, the manufacturing method of this embodiment may further include a covering step of covering the first electronic component after mounting with the insulating material.

The placement of the insulating material may also be performed, for example, by using a holding member containing the insulating material. That is, in the manufacturing method of this embodiment, the holding step may be a step of placing a holding member containing the insulating material.

The retaining member containing the insulating material may be, for example, a retaining member having a base and an insulating layer containing the insulating material disposed on the base. Such a retaining member may be, for example, a known retaining member having an insulating layer containing the insulating material disposed on at least one surface of the retaining member.

Any known insulating material can be used as the insulating material without any particular restrictions.

Suitable insulating materials for this embodiment include, for example, the following insulating materials:

[Thermal insulation material (1)]
The heat insulating material may be, for example, a heat insulating material containing aerogel particles (hereinafter, heat insulating material (1)). The heat insulating material (1) containing aerogel particles may be, for example, a coating film of a coating liquid containing aerogel particles.

The coating liquid containing aerogel particles includes aerogel particles and a liquid medium. The pores of the aerogel particles in the coating liquid may be filled with the liquid medium.

<Aerogel>
In the narrow sense, a dry gel obtained by using a supercritical drying method on a wet gel is called an aerogel, a dry gel obtained by drying under atmospheric pressure is called a xerogel, and a dry gel obtained by freeze-drying is called a cryogel. In this embodiment, however, a low-density dry gel obtained regardless of these drying methods of a wet gel is called an "aerogel". That is, in this embodiment, "aerogel" means "gel composed of a microporous solid in which the dispersed phase is a gas (gel composed of a microporous solid in which the dispersed phase is a gas)" which is an aerogel in the broad sense. In general, the inside of an aerogel has a mesh-like fine structure and has a cluster structure in which particulate aerogel components of about 2 to 20 nm are bonded. Between the skeletons formed by these clusters, there are pores of less than 100 nm. As a result, the aerogel has a three-dimensional fine porous structure. The aerogel according to this embodiment is, for example, a silica aerogel containing silica as a main component. Examples of silica aerogel include so-called organic-inorganic hybrid silica aerogels in which an organic group (such as a methyl group) or an organic chain is introduced.

The aerogel according to this embodiment can be exemplified by the following aspects. By adopting these aspects, it becomes easy to obtain an aerogel that is excellent in heat insulation, flame retardancy, heat resistance, and flexibility. By adopting each aspect, it is possible to obtain an aerogel that has heat insulation, flame retardancy, heat resistance, and flexibility according to each aspect.

(First Aspect)
The aerogel according to this embodiment may have a structure represented by the following general formula (1): The aerogel according to this embodiment may have a structure represented by the following general formula (1a) as a structure including the structure represented by formula (1).

In formula (1) and formula (1a), R ¹ and R ² each independently represent an alkyl group or an aryl group, and R ³ and R ⁴ each independently represent an alkylene group. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. p represents an integer of 1 to 50. In formula (1a), two or more R ^1s may be the same or different from each other, and similarly, two or more R ^2s may be the same or different from each other. In formula (1a), two R ^3s may be the same or different from each other, and similarly, two R ^4s may be the same or different from each other.

By introducing the structure represented by the above formula (1) or formula (1a) into the skeleton of the aerogel as an aerogel component, an aerogel with low thermal conductivity and flexibility is obtained. From this viewpoint, in formula (1) and formula (1a), R ¹ and R ² each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, etc., and the alkyl group includes a methyl group, etc. In addition, in formula (1) and formula (1a), R ³ and R ⁴ each independently include an alkylene group having 1 to 6 carbon atoms, etc., and the alkylene group includes an ethylene group, a propylene group, etc. In formula (1a), p can be 2 to 30, or may be 5 to 20.

(Second Aspect)
The aerogel according to this embodiment has a ladder structure including struts and bridges, and the bridges can have a structure represented by the following general formula (2). By introducing such a ladder structure into the skeleton of the aerogel as an aerogel component, the heat resistance and mechanical strength can be improved. In this embodiment, the "ladder structure" refers to a structure having two struts and bridges connecting the struts (having a so-called "ladder" shape). In this embodiment, the skeleton of the aerogel may have a ladder structure, but the aerogel may also have a ladder structure partially.

In formula (2), ^R5 and ^R6 each independently represent an alkyl group or an aryl group, and b represents an integer of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In addition, in formula (2), when b is an integer of 2 or more, two or more ^R5s may be the same or different from each other, and similarly, two or more ^R6s may be the same or different from each other.

By introducing the above structure into the skeleton of the aerogel as an aerogel component, for example, an aerogel having a structure derived from a conventional ladder-type silsesquioxane (i.e., a structure represented by the following general formula (X)) can be obtained that has superior flexibility to aerogels. Silsesquioxane is a polysiloxane having a composition formula: (RSiO _1.5 ) _n , and can have various skeleton structures such as a cage type, a ladder type, and a random type. As shown in the following general formula (X), in an aerogel having a structure derived from a conventional ladder-type silsesquioxane, the structure of the bridge portion is -O-, but in the aerogel according to this embodiment, the structure of the bridge portion is the structure represented by the above general formula (2) (polysiloxane structure). However, the aerogel of this embodiment may have a structure derived from a silsesquioxane in addition to the structure represented by the general formula (2).

In formula (X), R represents a hydroxy group, an alkyl group, or an aryl group.

The structure that serves as the support portion and its chain length, as well as the spacing between the structures that serve as the bridging portions are not particularly limited. From the viewpoint of further improving heat resistance and mechanical strength, the ladder structure may have a ladder structure represented by the following general formula (3).

In formula (3), R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represent an alkyl group or an aryl group, a and c each independently represent an integer of 1 to 3000, and b represents an integer of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In addition, in formula (3), when b is an integer of 2 or more, two or more R ^5s may be the same or different from each other, and similarly, two or more R ^6s may be the same or different from each other. In addition, in formula (3), when a is an integer of 2 or more, two or more R ^7s may be the same or different from each other, and similarly, when c is an integer of 2 or more, two or more R ^8s may be the same or different from each other.

From the viewpoint of obtaining better flexibility, in formulas (2) and (3), R ⁵ , R ⁶ , R ⁷ and R ⁸ (wherein R ⁷ and R ⁸ are only in formula (3)) each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, etc., and examples of the alkyl group include a methyl group, etc. In formula (3), a and c each independently can be 6 to 2000, but may be 10 to 1000. In formulas (2) and (3), b can be 2 to 30, but may be 5 to 20.

(Third Aspect)
The aerogel according to this embodiment may be a dried product of a wet gel which is a condensate of a sol containing at least one selected from the group consisting of a silicon compound having a hydrolyzable functional group or a condensable functional group, and a hydrolysis product of a silicon compound having a hydrolyzable functional group (obtained by drying a wet gel generated from a sol: dried product of a wet gel derived from a sol). The aerogel described above may also be obtained by drying a wet gel generated from a sol containing a silicon compound or the like in this way.

A polysiloxane compound can be used as the silicon compound having a hydrolyzable functional group or a condensable functional group. That is, the above sol can contain at least one compound selected from the group consisting of polysiloxane compounds having a hydrolyzable functional group or a condensable functional group, and hydrolysis products of polysiloxane compounds having a hydrolyzable functional group (hereinafter sometimes referred to as the "polysiloxane compound group").

The functional groups in the polysiloxane compound are not particularly limited, but may be groups that react with the same functional groups or with other functional groups. Examples of hydrolyzable functional groups include alkoxy groups. Examples of condensable functional groups include hydroxyl groups, silanol groups, carboxyl groups, and phenolic hydroxyl groups. The hydroxyl groups may be contained in hydroxyl-containing groups such as hydroxyalkyl groups. In addition, polysiloxane compounds having hydrolyzable functional groups or condensable functional groups may further have reactive groups (functional groups that do not fall under the category of hydrolyzable functional groups and condensable functional groups) different from the hydrolyzable functional groups and condensable functional groups. Examples of reactive groups include epoxy groups, mercapto groups, glycidoxy groups, vinyl groups, acryloyl groups, methacryloyl groups, and amino groups. The epoxy groups may be contained in epoxy-containing groups such as glycidoxy groups. Polysiloxane compounds having these functional groups and reactive groups may be used alone or in combination of two or more types. Among these functional groups and reactive groups, for example, groups that improve the flexibility of the aerogel include alkoxy groups, silanol groups, hydroxyalkyl groups, etc., and among these, alkoxy groups and hydroxyalkyl groups can further improve the compatibility of the sol. In addition, from the viewpoint of improving the reactivity of the polysiloxane compound and reducing the thermal conductivity of the aerogel, the number of carbon atoms of the alkoxy groups and hydroxyalkyl groups can be 1 to 6, but from the viewpoint of further improving the flexibility of the aerogel, they may be 2 to 4.

Examples of polysiloxane compounds having a hydroxyalkyl group in the molecule include those having a structure represented by the following general formula (A): By using a polysiloxane compound having a structure represented by the following general formula (A), the structures represented by the general formulas (1) and (1a) can be introduced into the skeleton of an aerogel.

In formula (A), R ^1a represents a hydroxyalkyl group, R ^2a represents an alkylene group, R ^3a and R ^4a each independently represent an alkyl group or an aryl group, and n represents an integer of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In formula (A), two R ^1a may be the same or different, and similarly, two R ^2a may be the same or different. In formula (A), two or more R ^3a may be the same or different, and similarly, two or more R ^4a may be the same or different.

By using a wet gel (produced from a sol) that is a condensate of a sol containing a polysiloxane compound of the above structure, it becomes easier to obtain an aerogel that has low thermal conductivity and is flexible. From this viewpoint, in formula (A), R ^1a may be a hydroxyalkyl group having 1 to 6 carbon atoms, and examples of the hydroxyalkyl group include a hydroxyethyl group and a hydroxypropyl group. In addition, in formula (A), R ^2a may be an alkylene group having 1 to 6 carbon atoms, and examples of the alkylene group include an ethylene group and a propylene group. In addition, in formula (A), R ^3a and R ^4a each independently include an alkyl group, a phenyl group, and the like having 1 to 6 carbon atoms, and examples of the alkyl group include a methyl group. In addition, in formula (A), n can be 2 to 30, but may also be 5 to 20.

Commercially available polysiloxane compounds having the structure represented by the above general formula (A) can be used, such as X-22-160AS, KF-6001, KF-6002, KF-6003, and other compounds (all manufactured by Shin-Etsu Chemical Co., Ltd.), XF42-B0970, FluidOFOH 702-4%, and other compounds (all manufactured by Momentive Performance Materials Japan, LLC).

Examples of polysiloxane compounds having an alkoxy group in the molecule include those having a structure represented by the following general formula (B): By using a polysiloxane compound having a structure represented by the following general formula (B), a ladder structure having a bridge portion represented by the general formula (2) or (3) can be introduced into the skeleton of an aerogel.

In formula (B), R ^1b represents an alkyl group, an alkoxy group, or an aryl group, R ^2b and R ^3b each independently represent an alkoxy group, R ^4b and R ^5b each independently represent an alkyl group or an aryl group, and m represents an integer of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In addition, in formula (B), two R ^1b may be the same or different, two R ^2b may be the same or different, and similarly, two R ^3b may be the same or different. In addition, in formula (B), when m is an integer of 2 or more, two or more R ^4b may be the same or different, and similarly, two or more R ^5b may be the same or different.

By using a wet gel (produced from a sol) that is a condensate of a sol containing a polysiloxane compound having the above structure or a hydrolysis product thereof, it becomes easier to obtain an aerogel that has low thermal conductivity and is flexible. From this perspective, in formula (B), R1b can be an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, etc., and examples of the alkyl group or alkoxy group include a methyl group, a methoxy group, an ethoxy group, etc. In formula (B), R2b and R3b each independently include an alkoxy group having 1 to 6 carbon atoms, etc., and examples of the alkoxy group include a methoxy group, an ethoxy group, etc. In formula (B), R4b and R5b each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, etc., and examples of the alkyl group include a methyl group, etc. In formula (B), m can be 2 to 30, but may also be 5 to 20.

The polysiloxane compound having the structure represented by the above general formula (B) can be obtained by appropriately referring to the manufacturing methods reported in JP-A-2000-26609, JP-A-2012-233110, etc. In addition, XR31-B1410 (manufactured by Momentive Corporation) can also be used as the polysiloxane compound.

Since alkoxy groups are hydrolyzed, polysiloxane compounds having alkoxy groups may exist as hydrolysis products in the sol, and the polysiloxane compounds having alkoxy groups and their hydrolysis products may be mixed. In addition, in polysiloxane compounds having alkoxy groups, all of the alkoxy groups in the molecule may be hydrolyzed, or may be partially hydrolyzed.

These polysiloxane compounds having hydrolyzable functional groups or condensable functional groups, and hydrolysis products of polysiloxane compounds having hydrolyzable functional groups, may be used alone or in combination of two or more kinds.

When preparing the aerogel according to this embodiment, silicon compounds having hydrolyzable functional groups or condensable functional groups can be silicon compounds other than the polysiloxane compounds described above. That is, the sol containing the silicon compounds described above can contain at least one selected from the group consisting of silicon compounds (excluding polysiloxane compounds) having hydrolyzable functional groups or condensable functional groups, and hydrolysis products of the silicon compounds having hydrolyzable functional groups (hereinafter sometimes referred to as "silicon compound group") in addition to the polysiloxane compounds described above, or instead of the polysiloxane compounds described above. The number of silicon atoms in the molecule of the silicon compound can be 1 or 2.

Silicon compounds having hydrolyzable functional groups in the molecule include, but are not limited to, alkyl silicon alkoxides. From the viewpoint of improving water resistance, the number of hydrolyzable functional groups in the alkyl silicon alkoxide can be three or less. Examples of such alkyl silicon alkoxides include monoalkyltrialkoxysilanes, monoalkyl dialkoxysilanes, dialkyl dialkoxysilanes, monoalkyl monoalkoxysilanes, dialkyl monoalkoxysilanes, trialkyl monoalkoxysilanes, and the like. Specific examples of such alkyl silicon alkoxides include methyl trimethoxysilane, methyl dimethoxysilane, dimethyl diethoxysilane, dimethyl dimethoxysilane, ethyl trimethoxysilane, and hexyl trimethoxysilane. Here, examples of the hydrolyzable functional groups include alkoxy groups such as methoxy and ethoxy groups.

Examples of silicon compounds having a condensable functional group include, but are not limited to, silanetetraol, methylsilanetriol, dimethylsilanediol, phenylsilanetriol, phenylmethylsilanediol, diphenylsilanediol, n-propylsilanetriol, hexylsilanetriol, octylsilanetriol, decylsilanetriol, trifluoropropylsilanetriol, etc.

The silicon compound having a hydrolyzable functional group or a condensable functional group may further have the above-mentioned reactive group different from the hydrolyzable functional group and the condensable functional group (a functional group that does not fall under the category of a hydrolyzable functional group or a condensable functional group).

As silicon compounds having three or less hydrolyzable functional groups and reactive groups, vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, etc. can also be used.

Also, examples of silicon compounds having a condensable functional group and a reactive group include vinyl silanetriol, 3-glycidoxypropyl silanetriol, 3-glycidoxypropyl methyl silanediol, 3-methacryloxypropyl silanetriol, 3-methacryloxypropyl methyl silanediol, 3-acryloxypropyl silanetriol, 3-mercaptopropyl silanetriol, 3-mercaptopropyl methyl silanediol, N-phenyl-3-aminopropyl silanetriol, and N-2-(aminoethyl)-3-aminopropyl methyl silanediol.

In addition, silicon compounds having three or less hydrolyzable functional groups at the molecular end, such as bistrimethoxysilylmethane, bistrimethoxysilylethane, bistrimethoxysilylhexane, ethyltrimethoxysilane, and vinyltrimethoxysilane, can also be used.

Silicon compounds (excluding polysiloxane compounds) having hydrolyzable functional groups or condensable functional groups, and hydrolysis products of the silicon compounds having hydrolyzable functional groups, may be used alone or in combination of two or more types.

By using the above silicon compounds (excluding polysiloxane compounds), structures represented by the following general formulas (4) to (6) can be introduced into the skeleton of the aerogel. The aerogel according to this embodiment can have any one of these structures alone, or two or more of them.

In formula (4), ^R9 represents an alkyl group, and examples of the alkyl group include those having 1 to 6 carbon atoms, such as a methyl group.

In formula (5), R ¹⁰ and R ¹¹ each independently represent an alkyl group, and examples of the alkyl group include those having 1 to 6 carbon atoms, such as a methyl group.

In formula (6), R ¹² represents an alkylene group. Here, the alkylene group may be an alkylene group having 1 to 10 carbon atoms, and examples of the alkylene group include an ethylene group and a hexylene group.

(Fourth aspect)
The aerogel according to the present embodiment may further contain silica particles in addition to the aerogel component in order to further increase toughness and to achieve even better heat insulation and flexibility. An aerogel containing an aerogel component and silica particles can also be called an aerogel composite. Although the aerogel composite is a composite of the aerogel component and the silica particles, it has a cluster structure that is characteristic of aerogel and is considered to have a three-dimensional fine porous structure.

The aerogel containing the aerogel component and silica particles can be said to be a dried product of a wet gel that is a condensation product of a sol containing silica particles and at least one selected from the group consisting of silicon compounds having hydrolyzable functional groups or condensable functional groups and hydrolysis products of silicon compounds having hydrolyzable functional groups. Therefore, the descriptions regarding the first to third aspects can be appropriately applied mutatis mutandis to the aerogel according to this embodiment.

As the silica particles, there are no particular limitations and examples thereof include amorphous silica particles. Examples of amorphous silica particles include fused silica particles, fumed silica particles, colloidal silica particles, etc. Among these, colloidal silica particles have high monodispersity and are easy to suppress aggregation in the sol. The silica particles may be silica particles having a hollow structure, a porous structure, etc.

The shape of the silica particles is not particularly limited, and examples thereof include spherical, cocoon-shaped, and association-shaped. Among these, the use of spherical silica particles as silica particles makes it easier to suppress aggregation in the sol. The average primary particle diameter of the silica particles may be 1 nm or more, 5 nm or more, or 20 nm or more, from the viewpoint of easily imparting appropriate strength and flexibility to the aerogel and easily obtaining an aerogel with excellent shrinkage resistance when dried. The average primary particle diameter of the silica particles may be 500 nm or less, 300 nm or less, or 100 nm or less, from the viewpoint of easily suppressing the solid thermal conductivity of the silica particles and easily obtaining an aerogel with excellent heat insulation. From these viewpoints, the average primary particle diameter of the silica particles may be 1 to 500 nm, 5 to 300 nm, or 20 to 100 nm.

In this embodiment, the average particle size of the aerogel components and the average primary particle size of the silica particles can be obtained by directly observing the aerogel using a scanning electron microscope (hereinafter abbreviated as "SEM"). The "diameter" here means the diameter when the cross section of the particle exposed on the cross section of the aerogel is regarded as a circle. In addition, the "diameter when the cross section is regarded as a circle" means the diameter of the perfect circle when the area of the cross section is replaced with a perfect circle of the same area. In addition, when calculating the average particle size, the diameters of the circles are obtained for 100 particles and the average is taken.

The average particle size of silica particles can also be measured from the raw material. For example, the biaxial average primary particle size is calculated as follows from the results of observing 20 random particles by SEM. That is, taking colloidal silica particles dispersed in water, which usually have a solid content concentration of about 5 to 40% by mass, as an example, a chip obtained by cutting a wafer with pattern wiring into 2 cm squares is immersed in a dispersion of colloidal silica particles for about 30 seconds, and then the chip is rinsed with pure water for about 30 seconds and dried by nitrogen blow. The chip is then placed on a sample stage for SEM observation, an accelerating voltage of 10 kV is applied, and the silica particles are observed at a magnification of 100,000 times, and an image is taken. 20 silica particles are arbitrarily selected from the obtained image, and the average particle size of those particles is taken as the average particle size.

The number of silanol groups per 1 g of silica particles may be 10×10 ¹⁸ / g or more, 50×10 18 / g or more, or 100×10 ¹⁸ / g or more, from the viewpoint of facilitating the production of an aerogel having excellent shrinkage resistance. The number of silanol groups per 1 g of silica particles may be 1000×10 ¹⁸ / g or less, 800× ^{10 18 /} g or less, or 700×10 ¹⁸ / g or less, from the viewpoint of facilitating the production of a homogeneous aerogel. From these viewpoints, the number of silanol groups per 1 g of silica particles may be 10×10 ¹⁸ to 1000×10 ¹⁸ / g, 50×10 ¹⁸ to 800×10 ¹⁸ / g, or 100×10 ¹⁸ to 700×10 ¹⁸ / g.

The content of the polysiloxane compound group contained in the sol (the total content of the polysiloxane compound having a hydrolyzable functional group or a condensable functional group and the content of the hydrolysis product of the polysiloxane compound having a hydrolyzable functional group) may be 5 parts by mass or more, or 10 parts by mass or more, relative to 100 parts by mass of the total amount of the sol, from the viewpoint of further facilitating obtaining good reactivity. The content of the polysiloxane compound group contained in the sol may be 50 parts by mass or less, or 30 parts by mass or less, relative to 100 parts by mass of the total amount of the sol, from the viewpoint of further facilitating obtaining good compatibility. From these viewpoints, the content of the polysiloxane compound group contained in the sol may be 5 to 50 parts by mass, or 10 to 30 parts by mass, relative to 100 parts by mass of the total amount of the sol.

When the sol contains a silicon compound (excluding polysiloxane compounds), the silicon compound group (the content of the silicon compound having a hydrolyzable functional group or a condensable functional group, and the total content of the hydrolysis product of the silicon compound having a hydrolyzable functional group) may be 5 parts by mass or more, or 10 parts by mass or more, relative to 100 parts by mass of the total amount of the sol, from the viewpoint of further facilitating obtaining good reactivity. The content of the silicon compound group contained in the sol may be 50 parts by mass or less, or 30 parts by mass or less, relative to 100 parts by mass of the total amount of the sol, from the viewpoint of further facilitating obtaining good compatibility. From these viewpoints, the content of the silicon compound group contained in the sol may be 5 to 50 parts by mass, or 10 to 30 parts by mass.

When the sol contains both a polysiloxane compound group and a silicon compound group, the ratio of the content of the polysiloxane compound group to the content of the silicon compound group may be 1:0.5 or more, or may be 1:1 or more, from the viewpoint of making it easier to obtain good compatibility. The ratio of the content of the polysiloxane compound group to the content of the silicon compound group may be 1:4 or less, or may be 1:2 or less, from the viewpoint of making it easier to suppress shrinkage of the gel. From these viewpoints, the ratio of the content of the polysiloxane compound group to the content of the silicon compound group may be 1:0.5 to 1:4, or may be 1:1 to 1:2.

When the sol contains silica particles, the content of the silica particles may be 1 part by mass or more, or 4 parts by mass or more, relative to 100 parts by mass of the total sol, from the viewpoint of easily imparting an appropriate strength to the aerogel and easily obtaining an aerogel having excellent shrinkage resistance when dried. The content of the silica particles may be 20 parts by mass or less, or 15 parts by mass or less, relative to 100 parts by mass of the total sol, from the viewpoint of easily suppressing the solid thermal conductivity of the silica particles and easily obtaining an aerogel having excellent heat insulation. From these viewpoints, the content of the silica particles may be 1 to 20 parts by mass, or 4 to 15 parts by mass, relative to 100 parts by mass of the total sol.

<Aerogel particles>
The aerogel particles in this embodiment can be obtained, for example, by pulverizing a bulk aerogel as described later.

The specific surface area of the aerogel particles can be 350 m ² /g or less, but may be 300 m ² /g or less, 250 m ² /g or less, or 150 m ² /g or less. This makes it easy to prepare a coating liquid with excellent film-forming properties. The lower limit of the specific surface area of the aerogel particles is not particularly limited, but from the viewpoint of suppressing aggregation in the coating liquid and improving the filling rate, it can be about 30 m ² /g. There are various methods for adjusting the specific surface area of the aerogel particles, and examples of such methods include adjusting the amount of an aerogel component having a bridge structure represented by general formula (2) and adjusting the amount of silica particles.

The specific surface area can be measured by the BET method. A gas adsorption measurement device (Autosorb-iQ (Autosorb is a registered trademark) manufactured by Quantachrome Instruments Japan, LLC) can be used as the measurement device.

The average particle diameter D50 of the aerogel particles can be 1 to 1000 μm, but may also be 3 to 700 μm, 5 to 500 μm, 10 to 100 μm, or 10 to 50 μm. When the average particle diameter D50 of the aerogel particles is 1 μm or more, it becomes easier to obtain aerogel particles with excellent dispersibility, ease of handling, etc. On the other hand, when the average particle diameter D50 is 1000 μm or less, it becomes easier to obtain aerogel particles with excellent dispersibility. The average particle diameter of the aerogel particles can be appropriately adjusted by the grinding method and grinding conditions, sieves, classification method, etc.

The average particle diameter D50 of aerogel particles can be measured by a laser diffraction/scattering method. For example, aerogel particles are added to a solvent (ethanol) so that the content of the particles is 0.05 to 5% by mass, and the aerogel particles are dispersed by vibrating a 50W ultrasonic homogenizer for 15 to 30 minutes. After that, about 10 mL of the dispersion is injected into a laser diffraction/scattering type particle size distribution measuring device, and the particle size is measured at 25°C, with a refractive index of 1.3 and an absorption of 0. The particle diameter at an integrated value of 50% (volume basis) in this particle size distribution is taken as the average particle diameter D50. For example, a Microtrac MT3000 (manufactured by Nikkiso Co., Ltd., product name) can be used as a measuring device.

In addition, commercially available products can be used as the aerogel particles. Examples of commercially available aerogel particles include ENOVA IC3100 (manufactured by CABOT Corporation) and AeroVa (manufactured by JIS AEROGEL CORPORATION).

<Method of manufacturing aerogel particles>
The method for producing the aerogel particles is not particularly limited, but for example, the aerogel particles can be produced by the following method.

The aerogel particles of this embodiment can be produced by a production method that mainly includes a sol production process, a wet gel production process in which the sol obtained in the sol production process is gelled and then aged to obtain a wet gel, a washing and solvent replacement process in which the wet gel obtained in the wet gel production process is washed and (if necessary) solvent-replaced, a drying process in which the washed and solvent-replaced wet gel is dried, and a crushing process in which the aerogel obtained by drying is crushed.

It may also be produced by a production method that mainly includes a sol production process, a wet gel production process, a wet gel crushing process for crushing the wet gel obtained in the wet gel production process, a cleaning and solvent replacement process, and a drying process.

The size of the obtained aerogel particles can be further uniformed by sieving, classification, etc. By adjusting the particle size, the dispersibility can be improved. Note that "sol" refers to the state before the gelation reaction occurs, and in this embodiment, refers to the state in which the silicon compound and, in some cases, silica particles are dissolved or dispersed in a solvent. Also, a wet gel refers to a gel solid in a wet state that does not have fluidity even though it contains a liquid medium.

(Sol generation process)
The sol generation process is a process of mixing a silicon compound and, optionally, silica particles (or a solvent containing silica particles) to carry out a hydrolysis reaction, and then generating a sol. In this process, an acid catalyst may be further added to the solvent to promote the hydrolysis reaction. In addition, as shown in Japanese Patent No. 5250900, a surfactant, a thermally hydrolyzable compound, etc. may be added to the solvent. Furthermore, for the purpose of suppressing heat radiation, etc., components such as carbon graphite, an aluminum compound, a magnesium compound, a silver compound, and a titanium compound may be added to the solvent.

As the solvent, for example, water or a mixture of water and alcohol can be used. Examples of alcohol include methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, and t-butanol. Among these, examples of alcohols that have low surface tension and low boiling points in terms of reducing the interfacial tension with the gel wall include methanol, ethanol, and 2-propanol. These may be used alone or in a mixture of two or more types.

For example, when alcohol is used as the solvent, the amount of alcohol can be 4 to 8 moles per mole of the total amount of the silicon compound group and the polysiloxane compound group, but it may also be 4 to 6.5, or 4.5 to 6 moles. By making the amount of alcohol 4 moles or more, it becomes easier to obtain good compatibility, and by making it 8 moles or less, it becomes easier to suppress the shrinkage of the gel.

Examples of acid catalysts include inorganic acids such as hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, phosphorous acid, hypophosphorous acid, bromic acid, chloric acid, chlorous acid, hypochlorous acid, etc.; acid phosphates such as acid aluminum phosphate, acid magnesium phosphate, and acid zinc phosphate; and organic carboxylic acids such as acetic acid, formic acid, propionic acid, oxalic acid, malonic acid, succinic acid, citric acid, malic acid, adipic acid, and azelaic acid. Among these, examples of acid catalysts that further improve the water resistance of the resulting aerogel include organic carboxylic acids. Examples of the organic carboxylic acid include acetic acid, but may also be formic acid, propionic acid, oxalic acid, malonic acid, etc. These may be used alone or in a mixture of two or more types.

By using an acid catalyst, the hydrolysis reaction of the silicon compound can be accelerated, allowing the sol to be obtained in a shorter time.

The amount of acid catalyst added can be 0.001 to 0.1 parts by mass per 100 parts by mass of the total amount of the polysiloxane compound group and the silicon compound group.

As the surfactant, a nonionic surfactant, an ionic surfactant, etc. can be used. These may be used alone or in combination of two or more types.

As the nonionic surfactant, for example, a compound containing a hydrophilic part such as polyoxyethylene and a hydrophobic part mainly composed of an alkyl group, or a compound containing a hydrophilic part such as polyoxypropylene can be used. Examples of compounds containing a hydrophilic part such as polyoxyethylene and a hydrophobic part mainly composed of an alkyl group include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, and polyoxyethylene alkyl ether. Examples of compounds containing a hydrophilic part such as polyoxypropylene include polyoxypropylene alkyl ether and block copolymers of polyoxyethylene and polyoxypropylene.

Examples of ionic surfactants include cationic surfactants, anionic surfactants, and amphoteric surfactants. Examples of cationic surfactants include cetyltrimethylammonium bromide and cetyltrimethylammonium chloride, and examples of anionic surfactants include sodium dodecylsulfonate. Examples of amphoteric surfactants include amino acid surfactants, betaine surfactants, and amine oxide surfactants. Examples of amino acid surfactants include acyl glutamic acid. Examples of betaine surfactants include lauryl dimethyl amino acetate betaine and stearyl dimethyl amino acetate betaine. Examples of amine oxide surfactants include lauryl dimethyl amine oxide.

These surfactants are thought to act to reduce the difference in chemical affinity between the solvent in the reaction system and the growing siloxane polymer in the wet gel formation process described below, thereby suppressing phase separation.

The amount of surfactant added depends on the type of surfactant or the type and amount of silicon compound, but can be, for example, 1 to 100 parts by mass per 100 parts by mass of the total amount of polysiloxane compounds and silicon compounds. The amount may be 5 to 60 parts by mass.

Thermohydrolyzable compounds generate a base catalyst by thermal hydrolysis, which makes the reaction solution basic and is thought to promote the sol-gel reaction in the wet gel production process described below. Therefore, the thermohydrolyzable compound is not particularly limited as long as it is a compound that can make the reaction solution basic after hydrolysis, and examples of the compound include urea; acid amides such as formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, and N,N-dimethylacetamide; and cyclic nitrogen compounds such as hexamethylenetetramine. Among these, urea is particularly likely to achieve the above-mentioned promoting effect.

The amount of the thermohydrolyzable compound added is not particularly limited as long as it is an amount that can sufficiently promote the sol-gel reaction in the wet gel generation process described below. For example, when urea is used as the thermohydrolyzable compound, the amount added can be 1 to 200 parts by mass per 100 parts by mass of the total amount of the polysiloxane compound group and the silicon compound group. The amount added may be 2 to 150 parts by mass. By adding an amount of 1 part by mass or more, it becomes easier to obtain good reactivity, and by adding an amount of 200 parts by mass or less, it becomes easier to suppress crystal precipitation and a decrease in gel density.

The hydrolysis in the sol production process depends on the type and amount of silicon compound, silica particles, acid catalyst, surfactant, etc. in the mixed liquid, but may be carried out, for example, in a temperature environment of 20 to 60°C for 10 minutes to 24 hours, or in a temperature environment of 50 to 60°C for 5 minutes to 8 hours. This allows the hydrolyzable functional groups in the silicon compound to be sufficiently hydrolyzed, making it possible to more reliably obtain a hydrolysis product of the silicon compound.

However, when a thermohydrolyzable compound is added to the solvent, the temperature environment of the sol generation process may be adjusted to a temperature that suppresses hydrolysis of the thermohydrolyzable compound and suppresses gelation of the sol. The temperature at this time may be any temperature that can suppress hydrolysis of the thermohydrolyzable compound. For example, when urea is used as the thermohydrolyzable compound, the temperature environment of the sol generation process may be 0 to 40°C, but may also be 10 to 30°C.

(Wet gel production process)
The wet gel forming step is a step of gelling the sol obtained in the sol forming step, followed by aging to obtain a wet gel. In this step, a base catalyst can be used to promote gelling.

Examples of base catalysts include carbonates such as calcium carbonate, potassium carbonate, sodium carbonate, barium carbonate, magnesium carbonate, lithium carbonate, ammonium carbonate, copper (II) carbonate, iron (II) carbonate, and silver (I) carbonate; hydrogen carbonates such as calcium hydrogen carbonate, potassium hydrogen carbonate, sodium hydrogen carbonate, and ammonium hydrogen carbonate; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; ammonium compounds such as ammonium hydroxide, ammonium fluoride, ammonium chloride, and ammonium bromide; basic sodium phosphates such as sodium metaphosphate, sodium pyrophosphate, and sodium polyphosphate; allylamine, diallylamine, triallylamine, isopropylamine, diisopropylamine, ethylamine, diethylamine, Aliphatic amines such as amine, triethylamine, 2-ethylhexylamine, 3-ethoxypropylamine, diisobutylamine, 3-(diethylamino)propylamine, di-2-ethylhexylamine, 3-(dibutylamino)propylamine, tetramethylethylenediamine, t-butylamine, sec-butylamine, propylamine, 3-(methylamino)propylamine, 3-(dimethylamino)propylamine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, and triethanolamine; nitrogen-containing heterocyclic compounds such as morpholine, N-methylmorpholine, 2-methylmorpholine, piperazine and its derivatives, piperidine and its derivatives, and imidazole and its derivatives. Among these, ammonium hydroxide (aqueous ammonia) is highly volatile and does not easily remain in the aerogel particles after drying, so it is not likely to impair water resistance, and is also excellent in terms of economy. The above-mentioned base catalysts may be used alone or in a mixture of two or more types.

By using a base catalyst, it is possible to promote the dehydration condensation reaction or the dealcoholization condensation reaction of the silicon compound and silica particles in the sol, and the gelation of the sol can be carried out in a shorter time. This also makes it possible to obtain a wet gel with greater strength (rigidity). In particular, since ammonia is highly volatile and does not easily remain in the aerogel particles, it is possible to obtain aerogel particles with better water resistance by using ammonia as a base catalyst.

The amount of base catalyst added can be 0.5 to 5 parts by mass, but may be 1 to 4 parts by mass, per 100 parts by mass of the total amount of the polysiloxane compound group and the silicon compound group. By using an amount of 0.5 parts by mass or more, gelation can be performed in a shorter time, and by using an amount of 5 parts by mass or less, the decrease in water resistance can be further suppressed.

The gelation of the sol in the wet gel production process may be carried out in a sealed container so that the solvent and base catalyst do not volatilize. The gelation temperature may be 30 to 90°C, but may be 40 to 80°C. By setting the gelation temperature at 30°C or higher, gelation can be carried out in a shorter time, and a wet gel with higher strength (rigidity) can be obtained. In addition, by setting the gelation temperature at 90°C or lower, it becomes easier to suppress the volatilization of the solvent (especially alcohol), so gelation can be carried out while suppressing volumetric shrinkage.

The maturation in the wet gel production process may be carried out in a sealed container so that the solvent and base catalyst do not volatilize. The maturation strengthens the bonds between the components that make up the wet gel, resulting in a wet gel with sufficient strength (rigidity) to suppress shrinkage during drying. The maturation temperature may be 30 to 90°C, but may also be 40 to 80°C. By setting the maturation temperature at 30°C or higher, a wet gel with higher strength (rigidity) can be obtained, and by setting the maturation temperature at 90°C or lower, it becomes easier to suppress the evaporation of the solvent (especially alcohol), making it possible to gel while suppressing volumetric shrinkage.

In addition, since it is often difficult to determine the end point of the sol gelation, the sol gelation and the subsequent aging may be carried out in a continuous series of operations.

The gelation time and aging time can be appropriately set depending on the gelation temperature and aging temperature. When silica particles are contained in the sol, the gelation time can be particularly shortened compared to when silica particles are not contained. This is presumably because the silanol groups or reactive groups of the silicon compound in the sol form hydrogen bonds or chemical bonds with the silanol groups of the silica particles. The gelation time can be 10 to 120 minutes, but may be 20 to 90 minutes. By setting the gelation time to 10 minutes or more, it becomes easier to obtain a homogeneous wet gel, and by setting it to 120 minutes or less, it becomes possible to simplify the washing and solvent replacement process to the drying process described below. The total time of the gelation time and aging time as a whole process of gelation and aging can be 4 to 480 hours, but may be 6 to 120 hours. By setting the total of the gelation time and aging time to 4 hours or more, a wet gel with higher strength (rigidity) can be obtained, and by setting it to 480 hours or less, it becomes easier to maintain the effect of aging.

In order to reduce the density of the resulting aerogel particles or to increase the average pore size, the gelation temperature and aging temperature may be increased within the above ranges, or the total time of the gelation time and aging time may be increased within the above ranges. Also, in order to increase the density of the resulting aerogel particles or to decrease the average pore size, the gelation temperature and aging temperature may be decreased within the above ranges, or the total time of the gelation time and aging time may be decreased within the above ranges.

(Wet gel crushing process)
When the wet gel crushing step is performed, the wet gel obtained in the wet gel generation step is crushed. The crushing can be performed, for example, by putting the wet gel into a Henshall mixer, or by performing the wet gel generation step in a mixer and operating the mixer under appropriate conditions (rotation speed and time). More simply, the wet gel can be placed in a sealable container, or by performing the wet gel generation step in a sealable container, and shaking for an appropriate time using a shaking device such as a shaker. If necessary, the particle size of the wet gel can also be adjusted using a jet mill, a roller mill, a bead mill, or the like.

(Washing and solvent replacement process)
The washing and solvent replacement process includes a process of washing the wet gel obtained by the wet gel production process or the wet gel crushing process (washing process) and a process of replacing the washing liquid in the wet gel with a solvent suitable for drying conditions (drying process described later) (solvent replacement process). The washing and solvent replacement process can be carried out in a form in which only the solvent replacement process is performed without performing the process of washing the wet gel, but from the viewpoint of reducing impurities such as unreacted substances and by-products in the wet gel and enabling the production of aerogel particles with higher purity, the wet gel may be washed.

In the washing step, the wet gel obtained in the wet gel generating step or the wet gel crushing step is washed. This washing can be carried out repeatedly using, for example, water or an organic solvent. In this case, the washing efficiency can be improved by heating.

As the organic solvent, various organic solvents such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetone, methyl ethyl ketone, 1,2-dimethoxyethane, acetonitrile, hexane, toluene, diethyl ether, chloroform, ethyl acetate, tetrahydrofuran, methylene chloride, N,N-dimethylformamide, dimethyl sulfoxide, acetic acid, and formic acid can be used. The above organic solvents may be used alone or in combination of two or more.

In the solvent replacement step described below, a solvent with low surface tension can be used to suppress the shrinkage of the gel due to drying. However, low surface tension solvents generally have extremely low mutual solubility with water. Therefore, when a low surface tension solvent is used in the solvent replacement step, the organic solvent used in the washing step can be a hydrophilic organic solvent that has high mutual solubility with both water and the low surface tension solvent. The hydrophilic organic solvent used in the washing step can serve as a preliminary replacement for the solvent replacement step. Among the above organic solvents, examples of hydrophilic organic solvents include methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, etc. Methanol, ethanol, methyl ethyl ketone, etc. are economically advantageous.

The amount of water or organic solvent used in the washing step can be an amount that can sufficiently replace the solvent in the wet gel and wash it. The amount can be 3 to 10 times the volume of the wet gel. Washing can be repeated until the water content in the wet gel after washing is 10 mass% or less relative to the mass of silica.

The temperature environment in the cleaning process can be below the boiling point of the solvent used for cleaning. For example, if methanol is used, the temperature can be around 30 to 60°C.

In the solvent replacement process, the solvent of the washed wet gel is replaced with a specified replacement solvent in order to suppress the shrinkage of the aerogel in the drying process. In this case, the replacement efficiency can be improved by heating. Specifically, the replacement solvent may be a low surface tension solvent as described below when drying is performed at a temperature below the critical point of the solvent used in the drying process under atmospheric pressure. On the other hand, when supercritical drying is performed, the replacement solvent may be, for example, ethanol, methanol, 2-propanol, dichlorodifluoromethane, carbon dioxide, etc., or a mixture of two or more of these.

An example of a low surface tension solvent is a solvent having a surface tension of 30 mN/m or less at 20°C. The surface tension may be 25 mN/m or less, or 20 mN/m or less. Examples of low surface tension solvents include aliphatic hydrocarbons such as pentane (15.5), hexane (18.4), heptane (20.2), octane (21.7), 2-methylpentane (17.4), 3-methylpentane (18.1), 2-methylhexane (19.3), cyclopentane (22.6), cyclohexane (25.2), and 1-pentene (16.0); aromatic hydrocarbons such as benzene (28.9), toluene (28.5), m-xylene (28.7), and p-xylene (28.3); and halides such as dichloromethane (27.9), chloroform (27.2), carbon tetrachloride (26.9), 1-chloropropane (21.8), and 2-chloropropane (18.1). halogenated hydrocarbons; ethers such as ethyl ether (17.1), propyl ether (20.5), isopropyl ether (17.7), butyl ethyl ether (20.8), 1,2-dimethoxyethane (24.6); ketones such as acetone (23.3), methyl ethyl ketone (24.6), methyl propyl ketone (25.1), diethyl ketone (25.3); esters such as methyl acetate (24.8), ethyl acetate (23.8), propyl acetate (24.3), isopropyl acetate (21.2), isobutyl acetate (23.7), ethyl butyrate (24.6) (the values in parentheses indicate the surface tension at 20°C, in units of [mN/m]). Among these, aliphatic hydrocarbons (hexane, heptane, etc.) have low surface tension and are excellent in the working environment. Furthermore, among these, hydrophilic organic solvents such as acetone, methyl ethyl ketone, and 1,2-dimethoxyethane can be used as the organic solvent in the above-mentioned cleaning step. Among these, solvents having a boiling point of 100° C. or less at normal pressure may be used because they are easy to dry in the drying step described below. The above solvents may be used alone or in combination of two or more.

The amount of solvent used in the solvent replacement step can be an amount that can fully replace the solvent in the wet gel after washing. This amount can be 3 to 10 times the volume of the wet gel.

The temperature environment in the solvent replacement process can be a temperature below the boiling point of the solvent used for replacement. For example, when heptane is used, the temperature can be around 30 to 60°C.

When silica particles are contained in the gel, the solvent replacement process is not essential. The presumed mechanism is as follows. That is, the silica particles function as a support for the three-dimensional mesh-like skeleton, supporting the skeleton and suppressing the shrinkage of the gel during the drying process. Therefore, it is considered that the gel can be directly subjected to the drying process without replacing the solvent used for washing. In this way, the use of silica particles makes it possible to simplify the washing and solvent replacement processes to the drying process.

(drying process)
In the drying step, the wet gel that has been washed and (if necessary) subjected to solvent replacement as described above is dried. This allows an aerogel (aerogel block or aerogel particles) to be obtained. That is, an aerogel can be obtained by drying the wet gel produced from the sol.

The drying method is not particularly limited, and known methods such as normal pressure drying, supercritical drying, or freeze drying can be used. Among these, normal pressure drying or supercritical drying can be used from the viewpoint of ease of producing low-density aerogel. Furthermore, normal pressure drying can be used from the viewpoint of low-cost production. In this embodiment, normal pressure means 0.1 MPa (atmospheric pressure).

The aerogel can be obtained by drying the washed and (if necessary) solvent-substituted wet gel at atmospheric pressure at a temperature below the critical point of the solvent used for drying. The drying temperature varies depending on the type of substituted solvent (or the solvent used for washing if solvent substitution is not performed), but can be set to 20 to 150°C, taking into consideration that drying at high temperatures may accelerate the evaporation rate of the solvent and cause large cracks in the gel. The drying temperature may be 60 to 120°C. The drying time varies depending on the volume of the wet gel and the drying temperature, but can be set to 4 to 120 hours. It should be noted that applying a pressure below the critical point to accelerate the drying within a range that does not impede productivity is also included in normal pressure drying.

Aerogel can also be obtained by supercritical drying of a wet gel that has been washed and (if necessary) solvent-substituted. Supercritical drying can be performed by known techniques. Examples of methods for supercritical drying include a method in which the solvent is removed at a temperature and pressure equal to or higher than the critical point of the solvent contained in the wet gel. Alternatively, examples of methods for supercritical drying include a method in which the wet gel is immersed in liquefied carbon dioxide under conditions of, for example, 20 to 25°C and about 5 to 20 MPa, to replace all or part of the solvent contained in the wet gel with carbon dioxide that has a lower critical point than the solvent, and then the carbon dioxide alone or a mixture of carbon dioxide and the solvent is removed.

The aerogel obtained by such normal pressure drying or supercritical drying may be further dried at normal pressure at 105 to 200°C for about 0.5 to 2 hours. This makes it easier to obtain an aerogel with low density and small pores. The additional drying may be performed at normal pressure at 150 to 200°C.

(Crushing process)
When the wet gel crushing step is not performed, the aerogel (aerogel block) obtained by drying is crushed to obtain aerogel particles. For example, the aerogel can be placed in a jet mill, roller mill, bead mill, hammer mill, etc., and operated at an appropriate rotation speed for an appropriate time.

<Coating Fluid>
More specifically, the coating liquid may be the first to fourth coating liquids shown below. Among the coating liquids, those with high viscosity (for example, 1000 mPa·s or more) may be called pastes.

(First Coating Fluid)
The first coating liquid contains the above-mentioned aerogel particles having a specific surface area of 350 m ² /g or less, a binder resin, and a liquid medium. It can also be said that the first coating liquid is a mixture of the above-mentioned aerogel particles, binder resin, and liquid medium.

In the first coating liquid, the specific surface area of the aerogel particles is 350 m ² /g or less. This allows the preparation of a coating liquid with excellent film-forming properties. The reason for this is not entirely clear, but the inventors speculate as follows. It is believed that the specific surface area of the aerogel particles determines the adsorption force (adsorption amount) to the binder resin. Therefore, if the specific surface area is too large, the binder resin is taken into the aerogel particles having a porous structure together with the liquid medium, and it is difficult to make an appropriate amount of the binder resin present on the surface of the aerogel particles in the coating liquid state. As a result, when the coating liquid is dried, the binding of the aerogel particles by the binder resin is not sufficiently performed, and a coating film having good film quality cannot be obtained. On the other hand, if the specific surface area of the aerogel particles is within the above range, it is believed that an appropriate amount of the binder resin can be present on the surface of the aerogel particles, making it possible to form a coating film in which the aerogel particles are suitably bound by the binder resin.

The binder resin has the function of binding the aerogel particles together after the coating film is formed. Examples of the binder resin include epoxy resin, silicone resin, phenol resin, urea resin, melamine resin, polyurethane resin, polyethylene resin, polypropylene resin, polystyrene resin, polyester resin, acrylic resin (polymer containing acrylic acid ester or methacrylic acid ester as the main structural unit), polyvinyl chloride resin, polyvinyl acetate resin, polyamide resin, polyimide resin, cellulose-based resin, polyvinyl resin, etc. In addition, acrylic acid-based resin (polymer containing acrylic acid, acrylate, methacrylic acid, methacrylate as structural units), polyvinyl alcohol, polyethylene oxide, polyethylene glycol, etc. can also be used as the binder resin. Among these, silicone resin, acrylic resin, phenol resin, and polyester resin can be preferably used from the viewpoint of heat resistance and toughness.

Examples of cellulose-based resins include hydroxypropylmethylcellulose, ammonium carboxymethylcellulose, and hydroxyethylmethylcellulose. Examples of polyvinyl-based resins include polyvinyl alcohol and polyvinylpyrrolidone.

Examples of acrylic acid-based resins include polyacrylic acid, acrylic acid copolymers, polyacrylates, and acrylate copolymers.

When the binder resin is a thermosetting resin, the coating liquid may further contain a curing agent. The curing agent is not particularly limited and may be changed appropriately depending on the type of thermosetting resin. For example, when the thermosetting resin is an epoxy resin, a known epoxy resin curing agent can be used as the curing agent. Examples of epoxy resin curing agents include amine-based curing agents, acid anhydride-based curing agents, and polyamide-based curing agents, and from the viewpoint of reactivity, amine-based curing agents and polyamide-based curing agents can be preferably used.

Examples of liquid media include water and organic solvents. The organic solvent is not particularly limited as long as it can disperse the aerogel particles, and examples thereof include aromatic hydrocarbons such as toluene, xylene, mesitylene, cumene, and p-cymene; aliphatic hydrocarbons such as hexane, heptane, and pentane; ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane; alcohols such as methanol, ethanol, isopropanol, butanol, ethylene glycol, and propylene glycol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and 4-hydroxy-4-methyl-2-pentanone; esters such as methyl acetate, ethyl acetate, and butyl acetate; and amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone. Among these, alcohols and ketones can be used from the viewpoints of volatility, boiling point, and the like, and alcohols can be used in particular. Alcohols and ketones are easily mixed with water, water-based resins, and the like, and are therefore also suitable when used in combination with these components.

The coating liquid may contain other ingredients such as thickeners, fibrous substances, pigments, leveling agents, film-forming aids, etc.

Thickeners can improve the viscosity of the coating liquid and improve the applicability to the target. Examples of thickeners include fine particles of organic polymers, fumed silica, layered inorganic additives, clay minerals, etc.

The fibrous material can exert an anchoring function between the aerogel particles after the coating film is formed, and can further improve the strength of the coating film. The fibrous material is not particularly limited, and examples thereof include organic fibers and inorganic fibers. Examples of organic fibers include polyamide fibers, polyimide fibers, polyvinyl alcohol fibers, polyvinylidene chloride fibers, polyvinyl chloride fibers, polyester fibers, polyacrylonitrile fibers, polyethylene fibers, polypropylene fibers, polyurethane fibers, phenolic fibers, polyether ester fibers, polylactic acid fibers, and polycarbonate fibers. Examples of inorganic fibers include glass fibers, carbon fibers, ceramic fibers, and metal fibers.

The content of aerogel particles in the coating liquid can be 0.1 to 30% by mass, but may be 1 to 25% by mass, from the viewpoint of dispersibility, the amount of aerogel particles filled, the viscosity of the coating liquid, etc. Furthermore, from the viewpoint of suitability for application using a trowel or the like, the content of aerogel particles in the coating liquid may be 2% by mass or more, or may be 3% by mass or more.

The content of the binder resin in the coating liquid can be 1 to 40% by mass, but may also be 1 to 30% by mass, from the viewpoints of the adhesiveness between the aerogel particles and the heat insulating properties of the coating film.

The content of the binder resin in the coating liquid can be, for example, 5 parts by mass or more per 100 parts by mass of the aerogel particles, but it may also be 10 parts by mass or more, 15 parts by mass or more, or 20 parts by mass or more. This makes it easier for the aerogel particles to be firmly bound by the binder resin, further improving the strength of the coating film.

The content of the binder resin can be, for example, 150 parts by mass or less per 100 parts by mass of the aerogel particles, but it may also be 130 parts by mass or less, 100 parts by mass or less, or 90 parts by mass or less. This increases the ratio of aerogel particles in the coating film, further improving the heat insulating properties of the coating film.

The content of the fibrous material in the coating liquid can be 1 to 50% by mass, but may also be 1 to 30% by mass, from the viewpoints of dispersibility in the coating liquid, expression of good anchoring function, etc.

The content of the fibrous material in the coating liquid can be, for example, 5 parts by mass or more per 100 parts by mass of aerogel particles, but it may also be 7 parts by mass or more, or 9 parts by mass or more. This makes it easier to obtain the anchor effect of the fibrous material, and further improves the strength of the coating film.

The content of the fibrous material can be, for example, 50 parts by mass or less per 100 parts by mass of aerogel particles, but it may also be 35 parts by mass or less, 25 parts by mass or less, 20 parts by mass or less, or 15 parts by mass or less. This increases the ratio of aerogel particles in the coating film, further improving the heat insulating properties of the coating film.

The amount of thickener contained can be adjusted appropriately to obtain the desired coating liquid viscosity (e.g., 1000 mPa·s or more). The viscosity of the coating liquid can also be improved by adding a binder resin, in which case it is not necessarily necessary to add a thickener.

(Second Coating Fluid)
The second coating liquid includes aerogel particles, a binder resin, a fibrous material having a fiber length of 1.5 mm or more, and a liquid medium. The second coating liquid can be said to be a mixture of the above-mentioned aerogel particles, a binder resin, a fibrous material having a fiber length of 1.5 mm or more, and a liquid medium. The second coating liquid will be described below, but the contents that overlap with the description of the first coating liquid will be omitted as appropriate.

The second coating liquid contains a fibrous material having a fiber length of 1.5 mm or more. This improves the strength of the coating film while ensuring the heat insulating properties of the coating film. The reason for this is not necessarily clear, but the inventors speculate as follows. In general, if a press molded body such as that of Patent Document 2 is to be produced, it is preferable that the fibers are randomly oriented in the molded body in order to further ensure the strength of the molded body. It is believed that the reason why short fibers are used in Patent Document 2 is that short fibers are more likely to be randomly oriented than long fibers. However, when a thin membrane-like molded body is produced, randomly orienting the fibers tends to cause a heat path through the fibers in the thickness direction (the direction in which insulation is desired), which also leads to a loss of heat insulating properties in the thickness direction. In contrast, the coating liquid of this embodiment contains long fibers. When a thin coating film is formed on a target surface using the coating liquid, it is speculated that the fibers are more likely to be oriented in the plane by deliberately using long fibers (fibrous material having a fiber length of 1.5 mm or more). It is believed that this makes it possible to maintain high heat insulating properties in the thickness direction while improving the strength in the plane direction.

From this viewpoint, the fiber length can be 2 mm or more, or 2.5 mm or more, or 3 mm or more. On the other hand, the upper limit of the fiber length is not particularly limited, but from the viewpoint of dispersibility in the coating liquid, it can be 20 mm.

The fiber diameter of the fibrous material can be 0.01 to 100 μm from the viewpoints of dispersibility in the coating liquid, good anchor function, etc.

The content of the fibrous material in the coating liquid is as described above. Furthermore, based on the total mass of the fibrous material, the content of fibers having a fiber length of 1.5 mm or more can be 30 mass% or more, but may be 50 mass% or more. The upper limit of the content can be 100 mass% (i.e., substantially all of the fibrous material in the coating liquid has a fiber length of 1.5 mm or more).

(Third Coating Fluid)
The third coating liquid includes aerogel particles, a liquid medium, a first binder resin, and a second binder resin. It can also be said that the third coating liquid is a mixture of aerogel particles, a liquid medium, a first binder resin, and a second binder resin. The third coating liquid will be described below, but the contents that overlap with the descriptions of the first and second coating liquids will be omitted as appropriate.

The first binder resin and the second binder resin have the function of binding the aerogel particles together after the coating film is formed. Both the first binder resin and the second binder resin are soluble in a liquid medium, and the solubility of the first binder resin in the liquid medium is higher than the solubility of the second binder resin in the liquid medium.

By including such a first binder resin and a second binder resin in the coating liquid, a coating film with excellent coating strength and adhesion can be obtained. The reason for this is not entirely clear, but the inventors speculate as follows. Since the first binder resin and the second binder resin have different solubilities in the liquid medium, in the drying process (process for removing the liquid medium) during coating film formation, the second binder resin saturates in the liquid medium before the first binder resin, making it easier for the second binder resin to precipitate first. It is believed that this difference in solubility leads to the formation of a characteristic binder structure during coating film formation, resulting in excellent coating film strength and adhesion.

Although the characteristic binder structure described above is not entirely clear, it is speculated that, for example, the second binder resin first binds onto the aerogel particles (and the fibrous material described below), and then the first binder resin binds between the aerogel particles (or between the aerogel particles and the fibrous material, or between the fibrous material) via the second binder resin, thereby obtaining excellent coating strength and adhesion. It is also thought that the second binder resin becomes granular, filling the spaces between the aerogel particles, and then is bound by the first binder resin, thereby firmly binding the aerogel particles together.

Examples of binder resins include the resins listed above. The first binder resin and the second binder resin may be selected from among these, and more specifically, may be selected from the resins described below.

In this embodiment, it is preferable that the content of the second binder resin is greater than the content of the first binder resin. This makes the above-mentioned effects more pronounced. The content of the second binder resin is preferably more than 100 parts by mass relative to 100 parts by mass of the first binder resin, more preferably 150 parts by mass or more, may be 200 parts by mass or more, may be 300 parts by mass or more, may be 400 parts by mass or more, or may be 600 parts by mass or more.

In addition, from the viewpoint of excellent heat insulating performance, the content of the second binder resin may be 800 parts by mass or less, preferably 700 parts by mass or less, may be 600 parts by mass or less, may be 500 parts by mass or less, or may be 400 parts by mass or less, relative to 100 parts by mass of the first binder resin.

The total content of the first binder resin and the second binder resin in the coating liquid can be 1 to 40% by mass, but may also be 1 to 30% by mass, from the viewpoints of the adhesiveness between the aerogel particles and the heat insulating properties of the coating film.

The total content of the first binder resin and the second binder resin may be, for example, 5 parts by mass or more per 100 parts by mass of the aerogel particles, preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more. This makes it easier for the aerogel particles to be firmly bound by the binder resin, further improving the strength of the coating film.

The total content of the first binder resin and the second binder resin may be, for example, 150 parts by mass or less, preferably 130 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 90 parts by mass or less, per 100 parts by mass of the aerogel particles. This increases the ratio of aerogel particles in the coating film, further improving the heat insulating properties of the coating film.

The first binder resin may be any resin that has the function of binding aerogel particles together after the coating film is formed and is soluble in the liquid medium. For example, when the liquid medium is an aqueous solvent, examples of the first binder resin include cellulose-based resins, polyvinyl alcohol, polyvinylpyrrolidone, acrylic acid-based resins, polyethylene oxide, and polyethylene glycol. Of these, cellulose-based resins, polyvinylpyrrolidone, and acrylic acid-based resins are preferably used from the viewpoint of excellent thickening properties.

The second binder resin may be any resin that is soluble in a liquid medium and has a lower solubility in the liquid medium than the first binder resin. The second binder resin may be a thermoplastic resin or a thermosetting resin.

Examples of thermoplastic resins include acrylic resins, polyvinyl alcohol, polypropylene, polyvinyl chloride, etc. Among these, acrylic resins and polyvinyl alcohol are preferably used from the viewpoint of ease of handling.

Examples of thermosetting resins include epoxy resins, silicone resins, polyurethanes, etc. Among these, epoxy resins and silicone resins are preferably used because of their excellent heat resistance.

When the second binder resin is a thermosetting resin, the coating film may further contain a curing agent. The curing agent is not particularly limited and may be changed appropriately depending on the type of thermosetting resin. For example, when the thermosetting resin is an epoxy resin, a known epoxy resin curing agent can be used as the curing agent. Examples of epoxy resin curing agents include amine-based curing agents, acid anhydride-based curing agents, and polyamide-based curing agents, and from the viewpoint of reactivity, amine-based and polyamide-based curing agents can be preferably used.

Examples of the liquid medium include water and organic solvents as described above. In a preferred embodiment, the liquid medium is preferably an aqueous solvent containing water. The aqueous solvent may be water or a mixed solvent containing water and an organic solvent. Such a liquid medium improves the dispersibility of the aerogel particles, making it easier to obtain a uniform coating film.

(Fourth Coating Fluid)
The fourth coating liquid contains aerogel particles, a water-soluble polymer having a hydrophobic group, and a liquid medium. In the fourth coating liquid, the dispersibility of the aerogel particles is improved by the water-soluble polymer having a hydrophobic group, so that the aerogel particles are less unevenly distributed and a coating film having sufficient film strength can be formed. The fourth coating liquid will be described below, but the contents that overlap with the descriptions of the first to third coating liquids will be omitted as appropriate.

The content of the aerogel particles in the fourth coating liquid may be, for example, 70 vol. % or more, preferably 72 vol. % or more, and more preferably 74 vol. % or more, based on the total volume of the solids in the coating liquid. The content of the aerogel particles in the fourth coating liquid may be, for example, 99 vol. % or less, and preferably 97 vol. % or less, based on the total volume of the solids in the fourth coating liquid.

<Water-soluble polymer>
In this embodiment, the water-soluble polymer may have a hydrophobic group and be water-soluble.

Examples of hydrophobic groups include alkyl groups (preferably long-chain alkyl groups having 6 to 26 carbon atoms), ester groups, alkoxy groups, halogens, etc. Of these, the hydrophobic group is preferably an alkyl group, more preferably a long-chain alkyl group having 8 to 26 carbon atoms, even more preferably a long-chain alkyl group having 10 to 26 carbon atoms, still more preferably a long-chain alkyl group having 12 to 26 carbon atoms, and may be a long-chain alkyl group having 15 to 26 carbon atoms.

Examples of water-soluble polymers include modified carboxyl vinyl polymers, modified polyether urethane, cellulose-based resins, polyethylene oxide, polyvinyl alcohol, polyacrylates, polyvinylpyrrolidone, dextrin-based resins, chitin-based resins, and chitosan-based resins.

As the water-soluble polymer, a cellulose-based resin can be preferably used. Examples of the cellulose-based resin include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and modified products obtained by further modifying these (e.g., hydrophobizing them).

As the cellulose-based resin, a cellulose-based resin having an alkyl group is preferable, and a cellulose-based resin having a long-chain alkyl group with 6 to 26 carbon atoms is more preferable. With such a cellulose-based resin, the effects of the present invention are more pronounced. The number of carbon atoms in the long-chain alkyl group is preferably 8 to 26, more preferably 10 to 26, even more preferably 12 to 26, and even more preferably 15 to 26.

As the cellulose-based resin, for example, a cellulose-based resin having a structural unit represented by the following formula (A-1) is preferred.

In formula (A-1), R ^A represents a hydrogen atom, an alkyl group, a hydroxyalkyl group, or a group represented by -R ^A1 -O-R ^A2 (R ^A1 represents an alkanediyl group or a hydroxyalkanediyl group, and R ^A2 represents an alkyl group). The three R ^A may be the same or different. However, of the three R ^A , at least one is an alkyl group or a group represented by -R ^A1 -O-R ^A2 .

In formula (A-1), the alkyl group in R ^A is preferably an alkyl group having 1 to 26 carbon atoms. Moreover, the alkyl group in R ^A is more preferably a short-chain alkyl group having 1 to 3 carbon atoms or a long-chain alkyl group having 6 to 26 carbon atoms. The number of carbon atoms in the long-chain alkyl group is preferably 8 to 26, more preferably 10 to 26, even more preferably 12 to 26, and even more preferably 15 to 26.

In formula (A-1), the hydroxyalkyl group for R 1 ^A is preferably a hydroxyalkyl group having 1 to 26 carbon atoms, more preferably a hydroxyalkyl group having 1 to 10 carbon atoms, and even more preferably a hydroxyalkyl group having 1 to 5 carbon atoms.

In formula (A-1), the alkanediyl group in R ^A1 is preferably an alkanediyl group having 1 to 26 carbon atoms, more preferably an alkanediyl group having 1 to 10 carbon atoms, and even more preferably an alkanediyl group having 1 to 5 carbon atoms. In addition, the hydroxyalkanediyl group in R ^A1 is preferably a hydroxyalkanediyl group having 1 to 26 carbon atoms, more preferably a hydroxyalkanediyl group having 1 to 10 carbon atoms, and even more preferably a hydroxyalkanediyl group having 1 to 5 carbon atoms.

In formula (A-1), R ^A2 is preferably an alkyl group having 1 to 26 carbon atoms. The alkyl group in R ^A2 is more preferably a short-chain alkyl group having 1 to 3 carbon atoms or a long-chain alkyl group having 6 to 26 carbon atoms, and more preferably a long-chain alkyl group. The number of carbon atoms in the long-chain alkyl group is preferably 8 to 26, more preferably 10 to 26, even more preferably 12 to 26, and even more preferably 15 to 26.

In formula (A-1), it is preferable that at least one of the three R ^A is a long-chain alkyl group, or at least one of the three R ^A is a group represented by -R ^A1 -O-R ^A2 and R ^A2 is a long-chain alkyl group.

In the cellulose-based resin, the content of long-chain alkyl groups having 6 to 26 carbon atoms is preferably 0.01 to 5 mass% based on the total amount of the cellulose-based resin, and more preferably 0.01 to 3 mass%.

In the fourth coating liquid, the content of the water-soluble polymer may be, for example, 0.01 vol.% or more, preferably 0.1 vol.% or more, and more preferably 0.3 vol.% or more, based on the total volume of the solids in the coating liquid. The content of the water-soluble polymer may be, for example, 10 vol.% or less, preferably 5 vol.% or less, and more preferably 3 vol.% or less, based on the total volume of the solids in the coating liquid.

<Liquid medium>
In the fourth coating liquid, the liquid medium is preferably an aqueous solvent containing water. The aqueous solvent may contain an organic solvent other than water. The organic solvent may be any organic solvent that is compatible with water, and examples of the organic solvent include alcohols such as methanol, ethanol, isopropanol, butanol, ethylene glycol, and propylene glycol; ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane; ketones such as acetone and methyl ethyl ketone; carboxylic acids such as acetic acid and propionic acid; and nitrogen-containing compounds such as acetonitrile, dimethylformamide, and triethylamine.

In the fourth coating liquid, the content of the liquid medium is not particularly limited and may be changed as appropriate depending on the desired viscosity of the coating liquid. For example, the content of the liquid medium may be an amount that brings the solids concentration of the coating liquid into a suitable range described below.

The solids concentration of the fourth coating liquid may be, for example, 10% by mass or more, preferably 15% by mass or more, and more preferably 20% by mass or more. The solids concentration of the fourth coating liquid may be, for example, 70% by mass or less, preferably 60% by mass or less, and more preferably 50% by mass or less.

<Other ingredients>
The fourth coating liquid may further contain components other than the aerogel particles, the water-soluble polymer, and the liquid medium.

The fourth coating liquid may further contain, for example, a binder resin. Examples of binder resins include epoxy resins, silicone resins, phenolic resins, urea resins, melamine resins, polyurethane resins, polyethylene resins, polypropylene resins, polystyrene resins, polyester resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, polyamide resins, polyimide resins, polyvinyl resins, and the like. Among these, silicone resins, acrylic resins, phenolic resins, polyester resins, and the like can be preferably used from the viewpoints of heat resistance and toughness.

When the fourth coating liquid contains a binder resin, the content of the binder resin may be, for example, 30 vol. % or less, preferably 28 vol. % or less, and more preferably 25 vol. % or less, based on the total volume of the solids. The content of the binder resin may be, for example, 0.1 vol. % or more, or 1 vol. % or more, based on the total volume of the solids.

<Method of producing coating film and coating film>
The method for producing a coating film (method for forming a coating film) includes a step of removing the liquid medium from a coating liquid containing aerogel particles and a liquid medium. More specifically, the method for producing a coating film can include a step of applying the above-mentioned coating liquid onto an object, and a step of removing the liquid medium from the coating liquid applied onto the object.

The method of applying the coating liquid to the object is not particularly limited, and examples include dip coating, spray coating, spin coating, roll coating, etc. When forming a coating film, the applied coating liquid may be left in an environment of 0 to 40°C, or the applied coating liquid may be subjected to a heating treatment (e.g., 40 to 150°C), a decompression treatment (e.g., 10,000 Pa or less), or both of these treatments.

The coating liquid of this embodiment may be highly viscous (paste-like), and therefore, as shown in FIG. 1, the coating liquid can be applied to an object using a trowel (metal spatula) or the like. In FIG. 1, the coating liquid is applied to a bent portion of a pipe using a trowel. With the coating liquid of this embodiment, a coating film of a thickness that is difficult to achieve with conventional heat insulating paints can be formed in a short time. Specifically, such a coating liquid can form a coating film of at least about 2 mm in thickness with one application, and can achieve extremely high work efficiency compared to conventional paints that could only obtain a coating film of about 0.5 mm in thickness. Since the coating liquid contains aerogel particles, a coating film with superior heat insulating performance can be obtained.

When the first coating liquid is used, a first coating film containing aerogel particles having a specific surface area of 350 m ² /g or less and a binder resin (or a cured product thereof) can be obtained. The first coating film can contain 40 to 95 mass % of aerogel particles and 1 to 50 mass % of binder resin (or a cured product thereof).

When the second coating liquid is used, a second coating film containing aerogel particles, binder resin (or its cured product), and a fibrous material having a fiber length of 1.5 mm or more can be obtained. The second coating film can contain 40 to 95 mass% aerogel particles, 1 to 40 mass% binder resin (or its cured product), and 1 to 50 mass% fibrous material having a fiber length of 1.5 mm or more.

When the third coating liquid is used, a third coating film containing aerogel particles, the first binder resin, and the second binder resin (or its cured product) can be obtained.

When the fourth coating liquid is used, a fourth coating film containing aerogel particles and a water-soluble polymer having a hydrophobic group can be obtained.

The content of aerogel particles in the coating film can be, for example, 40% by mass or more, but may also be 50% by mass or more, 60% by mass or more, or 70% by mass or more. This further improves the heat insulating properties of the coating film. In addition, the content of aerogel particles in the coating film can be, for example, 95% by mass or less, but may also be 90% by mass or less. This tends to make it easier to form the coating film.

In particular, for the third coating film, the content of the first binder resin in the coating film may be, for example, 2 parts by mass or more, preferably 5 parts by mass or more, and more preferably 8 parts by mass or more, per 100 parts by mass of the aerogel particles. Also, the content of the first binder resin in the coating film may be, for example, 20 parts by mass or less, preferably 17 parts by mass or less, and more preferably 15 parts by mass or less, per 100 parts by mass of the aerogel particles.

In particular, for the third coating film, the content of the second binder resin (or its cured product) in the coating film may be, for example, 10 parts by mass or more, preferably 15 parts by mass or more, or may be 20 parts by mass or more, relative to 100 parts by mass of the aerogel particles. Also, the content of the second binder resin (or its cured product) in the coating film may be, for example, 100 parts by mass or less, preferably 80 parts by mass or less, may be 60 parts by mass or less, or may be 40 parts by mass or less, relative to 100 parts by mass of the aerogel particles.

The thickness of the coating is not particularly limited and may be, for example, 0.01 to 30 mm, 0.1 to 20 mm, or 0.01 to 5 mm.

[Insulation material (2)]

The heat insulating material may be, for example, a heat insulating material satisfying the following formula (A) (hereinafter, heat insulating material (2)).
F1>F2 ... (A)
In the formula, F1 represents the adhesive strength of the insulating material after it is heated at 220° C. for 120 seconds, and F2 represents the adhesive strength of the insulating material after it is heated at 260° C. for 30 seconds.

F1 means the adhesive strength of the insulating material, which is attached to a slide glass at 25°C and left to stand for 15 minutes, then heated at 220°C for 120 seconds and cooled to 25°C, measured using a tensile tester (e.g., Shimadzu Corporation's "EZ Test EZ-S") under conditions of 90° peeling and tensile speed: 50 mm/min. F2 means the adhesive strength of the insulating material, which is attached to a slide glass at 25°C and left to stand for 15 minutes, then heated at 260°C for 30 seconds and cooled to 25°C, measured in the same manner as above.

F1 and F2 in formula (A) can be considered to correspond to the adhesive strength of the insulating material during and after the reflow process, respectively. In other words, when the insulating material satisfies formula (A), the adhesive strength of the insulating material is relatively large during the reflow process, so that the insulating material easily adheres to the first electronic component and/or the holding member, and the first electronic component can be more effectively protected from heat, and at the same time, the adhesive strength of the insulating material is relatively small after the reflow process, so that the insulating material can be easily peeled off from the first electronic component and/or the holding member.

The heat insulating material (2) is preferably a heat insulating material that satisfies the following formula (B).
F0≦F1 ... (B)
In the formula, F0 represents the adhesive strength of the insulating material at 25° C., and F1 represents the adhesive strength of the insulating material after it has been heated at 220° C. for 120 seconds.

F0 refers to the adhesive strength measured in the same manner as above after attaching an unheated insulating material to a glass slide at 25°C and leaving it to stand for 15 minutes. Note that an insulating material having adhesiveness means that this F0 is 10 N/m or more.

F0 and F1 in formula (B) can be considered to correspond to the adhesive strength of the insulating material before the reflow process (e.g., the process of placing the insulating material on the first electronic component and/or the holding member) and during the reflow process, respectively. In other words, when the insulating material satisfies formula (B), the adhesive strength of the insulating material is relatively small before the reflow process, making it easy to handle the insulating material, and the adhesive strength of the insulating material is relatively large during the reflow process, making it easy for the insulating material to adhere to the first electronic component and/or the holding member, and thus better protecting the first electronic component from heat.

From the same viewpoint as described above, the insulating material (2) is more preferably an insulating material that satisfies both the above formula (A) and formula (B).

The heat insulating material having the above-mentioned adhesive properties contains, for example, a matrix polymer and hollow particles. The heat insulating material may be, for example, a cured product obtained by curing (polymerizing the monomer in the precursor) a heat insulating material precursor containing a monomer component constituting the monomer unit of the matrix polymer and hollow particles.

In one embodiment, the insulating material (2) may be an insulating material that has been preformed into a sheet (an insulating material precursor that has been pre-cured). In another embodiment, the insulating material (2) may be formed by placing a liquid insulating material precursor on the first electronic component and/or the holding member, and then curing the insulating material precursor.

The monomer component may contain a compound represented by the following formula (1) from the viewpoint of providing a thermal insulating material with low elasticity, excellent elongation, and improved conformability.

In formula (1), R ¹¹ and R ¹² each independently represent a hydrogen atom or a methyl group, and R ¹³ represents a divalent group having a polyoxyalkylene chain.

In one embodiment, one of R ¹¹ and R ¹² may be a hydrogen atom and the other may be a methyl group; in another embodiment, both R ¹¹ and R ¹² may be hydrogen atoms; in another embodiment, both R ¹¹ and R ¹² may be methyl groups.

In one embodiment, the polyoxyalkylene chain contains a structural unit represented by the following formula (2): This makes it possible to increase the strength of the insulating material while suppressing an excessive increase in the viscosity of the insulating material precursor.

In this case, R ¹³ may be a divalent group having a polyoxyethylene chain, and the compound represented by formula (1) is preferably a compound represented by the following formula (1-2) (polyethylene glycol di(meth)acrylate).

In formula (1-2), R ¹¹ and R ¹² have the same meanings as R ¹¹ and R ¹² in formula (1), respectively, and m is an integer of 2 or more.

In another embodiment, the polyoxyalkylene chain contains a structural unit represented by the following formula (3): This makes it possible to easily handle the heat insulating material precursor.

In this case, R ¹³ may be a divalent group having a polyoxypropylene chain, and the compound represented by formula (1) is preferably a compound represented by the following formula (1-3) (polypropylene glycol di(meth)acrylate).

In formula (1-3), R ¹¹ and R ¹² have the same meanings as R ¹¹ and R ¹² in formula (1), respectively, and n is an integer of 2 or more.

In another embodiment, the polyoxyalkylene chain is preferably a copolymer chain containing the structural unit represented by formula (2) and the structural unit represented by formula (3) described above, from the viewpoint of easily achieving both the strength of the insulating material of the compound represented by formula (1) and the ease of handling of the insulating material precursor. The copolymer chain may be any of an alternating copolymer chain, a block copolymer chain, and a random copolymer chain. The copolymer chain is preferably a random copolymer chain, from the viewpoint of further reducing the crystallinity of the compound represented by formula (1) and further facilitating the handling of the insulating material precursor.

In each of the above-described embodiments, the polyoxyalkylene chain may have an oxyalkylene group having 4 to 5 carbon atoms, such as an oxytetramethylene group, an oxybutylene group, or an oxypentylene group, as a structural unit in addition to the structural unit represented by formula (2) and the structural unit represented by formula (3).

R ¹³ may be a divalent group having, in addition to the above-mentioned polyoxyalkylene chain, another organic group. The other organic group may be a chain-like group other than a polyoxyalkylene chain, such as a methylene chain (a chain having -CH ₂ - as a structural unit), a polyester chain (a chain containing -COO- in a structural unit), a polyurethane chain (a chain containing -OCON- in a structural unit), etc.

For example, the compound represented by formula (1) may be a compound represented by the following formula (1-4).

In formula (1-4), R ¹¹ and R ¹² are the same as R ¹¹ and R ¹² in formula (1), R ¹⁴ and R ¹⁵ are each independently an alkylene group having 2 to 5 carbon atoms, and k1, k2 and k3 are each independently an integer of 2 or more. k2 may be, for example, an integer of 16 or less.

A plurality of R ¹⁴ and R ¹⁵ may be the same or different from each other. A plurality of R ¹⁴ and R ¹⁵ each preferably contains an ethylene group and a propylene group. That is, the polyoxyalkylene chain represented by (R ¹⁴ O) _k1 and the polyoxyalkylene chain represented by (R ¹⁵ O) _k3 are each preferably a copolymer chain containing an oxyethylene group (structural unit represented by the above formula (2)) and an oxypropylene group (structural unit represented by the above formula (3)).

In each of the above-described embodiments, the number of oxyalkylene groups in the polyoxyalkylene chain is preferably 100 or more. When the number of oxyalkylene groups in the polyoxyalkylene chain is 100 or more, the main chain of the compound represented by formula (1) becomes longer, so that the elongation of the insulating material is further improved and the strength of the insulating material can also be increased. The number of oxyalkylene groups corresponds to m in formula (1-2), n in formula (1-3), and k1 and k3 in formula (1-4).

The number of oxyalkylene groups in the polyoxyalkylene chain is more preferably 130 or more, 180 or more, 200 or more, 220 or more, 250 or more, 270 or more, 300 or more, or 320 or more. The number of oxyalkylene groups in the polyoxyalkylene chain may be 600 or less, 570 or less, or 530 or less.

The weight average molecular weight of the compound represented by formula (1) is preferably 5000 or more, 6000 or more, 7000 or more, 8000 or more, 9000 or more, 10000 or more, 11000 or more, 12000 or more, 13000 or more, 14000 or more, or 15000 or more, from the viewpoint of the insulation material having lower elasticity and excellent elongation. The weight average molecular weight of the compound represented by formula (1) is preferably 100000 or less, 80000 or less, 60000 or less, 34000 or less, 31000 or less, or 28000 or less, from the viewpoint of making it easier to adjust the viscosity of the insulation material precursor.

The compound represented by formula (1) may be liquid at 25°C. In this case, the viscosity of the compound represented by formula (1) at 25°C is preferably 1000 Pa·s or less, 800 Pa·s or less, 600 Pa·s or less, 500 Pa·s or less, 350 Pa·s or less, 300 Pa·s or less, or 200 Pa·s or less, from the viewpoint of facilitating application to the application surface and from the viewpoint of increasing adhesion of the insulating material to the application surface. The viscosity of the compound represented by formula (1) at 25°C may be 0.1 Pa·s or more, 0.2 Pa·s or more, 0.3 Pa·s or more, 1 Pa·s or more, 2 Pa·s or more, or 3 Pa·s or more.

The compound represented by formula (1) may be solid at 25°C. In this case, from the viewpoint of further improving the handleability of the insulating material precursor, the compound represented by formula (1) is preferably liquid at 50°C. In this case, from the viewpoint of further improving the handleability of the insulating material precursor, the viscosity of the compound represented by formula (1) at 50°C is preferably 100 Pa·s or less, more preferably 50 Pa·s or less, even more preferably 30 Pa·s or less, and particularly preferably 20 Pa·s or less. The viscosity of the compound represented by formula (1) at 50°C may be 0.1 Pa·s or more, 0.2 Pa·s or more, or 0.3 Pa·s or more.

The viscosity refers to a value measured based on JIS Z 8803, specifically, a value measured using an E-type viscometer (for example, PE-80L, manufactured by Toki Sangyo Co., Ltd.). The viscometer can be calibrated based on JIS Z 8809-JS14000. The viscosity of the compound represented by formula (1) can be adjusted by adjusting the weight average molecular weight of the compound.

From the viewpoint of the insulating material having lower elasticity and excellent elongation, the content of the compound represented by formula (1) is preferably 10 mass% or more, 20 mass% or more, 30 mass% or more, or 40 mass% or more based on the total amount of the insulating material precursor. The content of the compound represented by formula (1) may be 90 mass% or less, 80 mass% or less, 70 mass% or less, 60 mass% or less, or 50 mass% or less based on the total amount of the insulating material precursor.

From the viewpoint of providing a thermal insulating material with lower elasticity and excellent elongation, the content of the compound represented by formula (1) is preferably 20 parts by mass or more, 30 parts by mass or more, or 40 parts by mass or more per 100 parts by mass of the total of the monomer components. The content of the compound represented by formula (1) may be 80 parts by mass or less, 70 parts by mass or less, or 60 parts by mass or less per 100 parts by mass of the total of the monomer components.

The monomer component may further contain other monomers that are copolymerizable with the compound represented by formula (1) described above for the purpose of adjusting the physical properties of the insulating material precursor, etc.

The other monomer may be, for example, a compound having one (meth)acryloyl group.
The compound may be, for example, an alkyl (meth)acrylate. The other monomer may be a compound having, in addition to one (meth)acryloyl group, an aromatic hydrocarbon group, a group containing a polyoxyalkylene chain, a group containing a heterocycle, an alkoxy group, a phenoxy group, a group containing a silane group, a group containing a siloxane bond, a halogen atom, a hydroxyl group, a carboxyl group, an amino group, or an epoxy group. In particular, the heat insulating material precursor contains an alkyl (meth)acrylate, so that the viscosity of the heat insulating material precursor can be adjusted. In addition, the heat insulating material precursor contains a compound having, in addition to a (meth)acryloyl group, a hydroxyl group, a carboxyl group, an amino group, or an epoxy group, so that the adhesion of the heat insulating material precursor and the heat insulating material to the member can be further improved.

The alkyl group in the alkyl (meth)acrylate (the alkyl group portion other than the (meth)acryloyl group) may be linear, branched, or alicyclic. The number of carbon atoms in the alkyl group may be, for example, 1 to 30. The number of carbon atoms in the alkyl group may be 1 to 11, 1 to 8, 1 to 6, or 1 to 4, or may be 12 to 30, 12 to 28, 12 to 24, 12 to 22, 12 to 18, or 12 to 14.

Examples of alkyl (meth)acrylates having a linear alkyl group include alkyl (meth)acrylates having a linear alkyl group having 1 to 11 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, and undecyl (meth)acrylate. Examples of such alkyl (meth)acrylates include alkyl (meth)acrylates having a linear alkyl group having 12 to 30 carbon atoms, such as sil (meth)acrylate (lauryl (meth)acrylate), tetradecyl (meth)acrylate, hexadecyl (meth)acrylate (cetyl (meth)acrylate), octadecyl (meth)acrylate (stearyl (meth)acrylate), docosyl (meth)acrylate (behenyl (meth)acrylate), tetracosyl (meth)acrylate, hexacosyl (meth)acrylate, and octacosyl (meth)acrylate.

Examples of alkyl (meth)acrylates having a branched alkyl group include s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, isopentyl (meth)acrylate, isoamyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, and isodecyl (meth)acrylate, and other alkyl (meth)acrylates having a branched alkyl group with 1 to 11 carbon atoms, isomyristyl (meth)acrylate, and the like. Examples of the alkyl (meth)acrylate include alkyl (meth)acrylates having a branched alkyl group having 12 to 30 carbon atoms, such as isoundecyl (meth)acrylate, 2-propylheptyl (meth)acrylate, isoundecyl (meth)acrylate, isododecyl (meth)acrylate, isotridecyl (meth)acrylate, isopentadecyl (meth)acrylate, isohexadecyl (meth)acrylate, isoheptadecyl (meth)acrylate, isostearyl (meth)acrylate, and decyltetradecanyl (meth)acrylate.

Examples of alkyl (meth)acrylates having an alicyclic alkyl group (cycloalkyl group) include cyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, terpene (meth)acrylate, and dicyclopentanyl (meth)acrylate.

An example of a compound having a (meth)acryloyl group and an aromatic hydrocarbon group is benzyl (meth)acrylate.

Examples of compounds having a (meth)acryloyl group and a group containing a polyoxyalkylene chain include polyethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, polybutylene glycol (meth)acrylate, and methoxypolybutylene glycol (meth)acrylate.

An example of a compound having a (meth)acryloyl group and a group containing a heterocycle is tetrahydrofurfuryl (meth)acrylate.

Examples of compounds having a (meth)acryloyl group and an alkoxy group include 2-methoxyethyl acrylate.

An example of a compound having a (meth)acryloyl group and a phenoxy group is phenoxyethyl (meth)acrylate.

Examples of compounds having a (meth)acryloyl group and a group containing a silane group include 3-acryloxypropyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, and 10-acryloyloxydecyltriethoxysilane.

Examples of compounds having a (meth)acryloyl group and a group containing a siloxane bond include silicone (meth)acrylate.

Compounds having a (meth)acryloyl group and a halogen atom include trifluoromethyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, 1,1,1,3,3,3-hexafluoro-2-propyl (meth)acrylate, perfluoroethyl methyl (meth)acrylate, perfluoropropyl methyl (meth)acrylate, perfluorobutyl methyl (meth)acrylate, perfluoropentyl methyl (meth)acrylate, perfluorohexyl methyl (meth)acrylate, perfluoroheptyl methyl (meth)acrylate, perfluorooctyl methyl (meth)acrylate, perfluorononyl methyl (meth)acrylate, perfluorodecyl methyl (meth)acrylate, perfluoroundecyl methyl (meth)acrylate, perfluorododecyl methyl (meth)acrylate, perfluoro Examples of (meth)acrylates having fluorine atoms include tridecylmethyl (meth)acrylate, perfluorotetradecylmethyl (meth)acrylate, 2-(trifluoromethyl)ethyl (meth)acrylate, 2-(perfluoroethyl)ethyl (meth)acrylate, 2-(perfluoropropyl)ethyl (meth)acrylate, 2-(perfluorobutyl)ethyl (meth)acrylate, 2-(perfluoropentyl)ethyl (meth)acrylate, 2-(perfluorohexyl)ethyl (meth)acrylate, 2-(perfluoroheptyl)ethyl (meth)acrylate, 2-(perfluorooctyl)ethyl (meth)acrylate, 2-(perfluorononyl)ethyl (meth)acrylate, 2-(perfluorotridecyl)ethyl (meth)acrylate, and 2-(perfluorotetradecyl)ethyl (meth)acrylate.

Examples of compounds having a (meth)acryloyl group and a hydroxyl group include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate; and hydroxyalkyl cycloalkane (meth)acrylates such as (4-hydroxymethylcyclohexyl)methyl (meth)acrylate.

Examples of compounds having a (meth)acryloyl group and a carboxyl group include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, monohydroxyethyl phthalate acrylate (e.g., "Aronix M5400" manufactured by Toagosei Co., Ltd.), and 2-acryloyloxyethyl succinate (e.g., "NK Ester A-SA" manufactured by Shin-Nakamura Chemical Co., Ltd.).

Examples of compounds having a (meth)acryloyl group and an amino group include N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, and N,N-diethylaminopropyl (meth)acrylate.

Examples of compounds having a (meth)acryloyl group and an epoxy group include glycidyl (meth)acrylate, α-ethyl glycidyl (meth)acrylate, α-n-propyl glycidyl (meth)acrylate, α-n-butyl glycidyl (meth)acrylate, 3,4-epoxybutyl (meth)acrylate, 4,5-epoxypentyl (meth)acrylate, 6,7-epoxyheptyl (meth)acrylate, α-ethyl 6,7-epoxyheptyl (meth)acrylate, 3-methyl-3,4-epoxybutyl (meth)acrylate, 4-methyl-4,5-epoxypentyl (meth)acrylate, 5-methyl-5,6-epoxyhexyl (meth)acrylate, β-methylglycidyl (meth)acrylate, and α-ethyl β-methylglycidyl (meth)acrylate.

The monomer component may contain one of the other monomers listed above, or may contain two or more of them.

The content of other monomers may be, for example, 1 mass% or more, 5 mass% or more, 10 mass% or more, 20 mass% or more, or 30 mass% or more, and 60 mass% or less, 50 mass% or less, or 40 mass% or less, based on the total amount of the insulation precursor.

The insulating material and the insulating material precursor preferably contain thermally expandable hollow particles (hereinafter also referred to as "first hollow particles") as hollow particles. The first hollow particles have an outer shell and a hollow portion.
In this specification, the thermally expandable hollow particles are hollow particles having a maximum volume expansion ratio of 10 times or more relative to the volume at 25° C. When the first hollow particles are used, the first hollow particles expand due to heat in the reflow process, thereby reducing the adhesive area at the interface between the insulating material and the first electronic component and/or the holding member, and the insulating material can be easily removed after the reflow process.

The maximum volume expansion ratio of the first hollow particles is measured by thermomechanical analysis (TMA) as the ratio of the maximum volume of the first hollow particles when heated at a heating rate of 10°C/min to the volume at 25°C (maximum volume/volume at 25°C). The maximum volume expansion ratio of the first hollow particles may be, for example, 20 times or more, 30 times or more, or 40 times or more, or may be 120 times or less.

The shell is preferably made of a thermoplastic polymer. In this case, since the shell becomes soft when heated, the hollow particles are less likely to break and expand easily even if the liquid contained in the hollow portion vaporizes and the internal pressure increases. The thermoplastic polymer may be, for example, a polymer containing acrylonitrile, vinylidene chloride, or the like as a monomer unit. The thickness of the shell may be 2 μm or more and 15 μm or less.

The hollow portion of the first hollow particle contains, for example, a liquid. The first hollow particle is in this state at room temperature and pressure (for example, at least atmospheric pressure and 30°C). The liquid is appropriately selected, for example, depending on the heating temperature in the reflow process. The liquid is, for example, a liquid that vaporizes at a temperature equal to or lower than the maximum heating temperature in the reflow process. The liquid may be, for example, a hydrocarbon having a boiling point (at atmospheric pressure) of 50°C or higher, 100°C or higher, 150°C or higher, or 200°C or higher. In addition to the above liquid, the hollow portion of the first hollow particle may further contain a gas.

Examples of components contained within the hollow portion of the first hollow particles include hydrocarbons such as propane, propylene, butene, normal butane, isobutane, normal pentane, isopentane, neopentane, normal hexane, isohexane, heptane, isooctane, normal octane, isoalkane (carbon number: 10 to 13), and petroleum ether; low-boiling compounds such as methane halides and tetraalkylsilanes; and compounds that gasify by thermal decomposition, such as azodicarbonamide.

The average particle size of the first hollow particles may be 5 μm or more, 10 μm or more, or 20 μm or more, and may be 50 μm or less, 40 μm or less, or 30 μm or less. The average particle size of the first hollow particles is measured by a laser diffraction/scattering method (for example, using a "SALD-7500 nano" manufactured by Shimadzu Corporation).

From the viewpoint of more suitably using the composition as an insulating material in the reflow process (generally heated to 260°C), the expansion start temperature of the first hollow particles is preferably 70°C or more, 100°C or more, 130°C or more, or 160°C or more, and preferably 260°C or less. The expansion start temperature of the first hollow particles means the temperature of the intersection between the tangent to the point where a volume change of 3 times or more/5°C occurs and the straight line (horizontal axis) where the volume change is zero (initial volume) in the profile of temperature (horizontal axis) vs. volume change (vertical axis) when the temperature is increased at a heating rate of 10°C/min in thermomechanical analysis (TMA).

The maximum expansion temperature of the first hollow particles is preferably 100°C or more, 150°C or more, 200°C or more, or 220°C or more, and is preferably 290°C or less, 280°C or less, or 270°C or less. The maximum expansion temperature of the first hollow particles means the temperature at which the first hollow particles exhibit the above-mentioned maximum volume expansion ratio.

From the viewpoint of making peeling in the peeling step easier, the content of the first hollow particles may be preferably 1 mass% or more, more preferably 5 mass% or more, and even more preferably 8 mass% or more, based on the total mass of the insulating material (insulating material precursor), and may be 20 mass% or less, or 15 mass% or less.

From the viewpoint of making peeling in the peeling step even easier, the content of the first hollow particles is preferably 1 vol. % or more, more preferably 2 vol. % or more, even more preferably 3 vol. % or more, and particularly preferably 4 vol. % or more, based on the total volume of the insulating material (insulating material precursor), and may be, for example, 10 vol. % or less, 7 vol. % or less, or 5 vol. % or less.

The insulating material (insulating material precursor) may further contain hollow particles other than the first hollow particles (hereinafter also referred to as "second hollow particles") from the viewpoint of further improving the insulating properties. The second hollow particles have an outer shell and a hollow portion. That is, the second hollow particles are hollow particles whose maximum volume expansion ratio with respect to the volume at 25°C is less than 10 times. The maximum volume expansion ratio of the second hollow particles is measured in the same manner as the maximum volume expansion ratio of the first hollow particles.

The shell is preferably made of a thermoplastic polymer. In this case, the hollow particles are less likely to break even when pressurized, and can maintain their hollow structure and heat insulation. The thermoplastic polymer may be, for example, a polymer containing acrylonitrile, vinylidene chloride, or the like as a monomer unit. The thickness of the shell may be 0.005 μm or more and 15 μm or less.

The hollow portion of the second hollow particle contains, for example, a gas. The second hollow particle is in this state at room temperature and pressure (for example, at least atmospheric pressure and 30°C). In addition to the gas, the hollow portion of the second hollow particle may further contain a liquid.

Examples of components contained within the hollow portion of the second hollow particles include hydrocarbons such as propane, propylene, butene, normal butane, isobutane, normal pentane, isopentane, neopentane, normal hexane, isohexane, heptane, isooctane, normal octane, isoalkane (carbon number: 10 to 13), and petroleum ether; low-boiling compounds such as methane halides and tetraalkylsilanes; and decomposition products of compounds that gasify by thermal decomposition, such as azodicarbonamide.

From the viewpoint of improving the heat insulating properties, the average particle diameter of the second hollow particles is preferably 150 μm or less, more preferably 120 μm or less, and even more preferably 100 μm or less, and may be, for example, 10 μm or more, 20 μm or more, or 30 μm or more. The average particle diameter of the second hollow particles is measured by a laser diffraction/scattering method (for example, using "SALD-7500 nano" manufactured by Shimadzu Corporation).

The density of the second hollow particles may be 50 kg/m3 or ^less , or 40 kg/ ^m3 or less, and may be 10 kg/ ^m3 or more, or 20 kg/ ^m3 or more. The density of the second hollow particles in this specification means a density measured by a tap density method. That is, the density is calculated by the following formula, in which the second hollow particles (about 5 g) are put into a 10 mL graduated cylinder, tapped 50 times, and the volume when the uppermost surface becomes stable is defined as the stable volume.
Density = initial charge (kg) / stable volume (m ³ )

From the viewpoint of further improving the thermal insulation, the content of the second hollow particles is preferably 1 mass% or more, more preferably 3 mass% or more, and even more preferably 5 mass% or more, based on the total mass of the thermal insulation material (thermal insulation material precursor), and may be, for example, 20 mass% or less.

From the viewpoint of further improving the thermal insulation, the content of the second hollow particles is preferably 50% by volume or more, more preferably 60% by volume or more, and may be, for example, 95% by volume or less, based on the total volume of the insulation material (insulation material precursor).

The total content of hollow particles (including the content of the first hollow particles and the second hollow particles) may be, for example, 5 mass% or more, 10 mass% or more, or 15 mass% or more based on the total amount of the insulating material (insulating material precursor), and may be 40 mass% or less, 30 mass% or less, or 20 mass% or less.

The total content of hollow particles (including the content of the first hollow particles and the second hollow particles) may be, for example, 50 vol. % or more, 60 vol. % or more, or 70 vol. % or more, and may be 95 vol. % or less, based on the total volume of the insulating material (insulating material precursor).

The heat insulating material precursor may further contain a polymerization initiator. The polymerization initiator may be, for example, a thermal polymerization initiator that generates radicals by heat, or a photopolymerization initiator that generates radicals by light. The polymerization initiator is preferably a thermal polymerization initiator.

When the insulating material precursor contains a thermal polymerization initiator, the insulating material can be obtained by applying heat to the insulating material precursor to harden the precursor. In this case, the insulating material precursor may be an insulating material precursor that is hardened by heating at preferably 105°C or higher, more preferably 110°C or higher, and even more preferably 115°C or higher, and may be an insulating material precursor that is hardened by heating at, for example, 200°C or lower, 190°C or lower, or 180°C or lower. The heating time when heating the insulating material precursor may be appropriately selected depending on the composition of the insulating material precursor so that the insulating material precursor is hardened appropriately.

Thermal polymerization initiators include azo compounds such as azobisisobutyronitrile, azobis-4-methoxy-2,4-dimethylvaleronitrile, azobiscyclohexanone-1-carbonitrile, and azodibenzoyl, as well as organic peroxides such as benzoyl peroxide, lauroyl peroxide, di-t-butyl peroxide, di-t-hexyl peroxide, di-t-butylperoxyhexahydroterephthalate, t-butylperoxy-2-ethylhexanoate, 1,1-t-butylperoxy-3,3,5-trimethylcyclohexane, and t-butylperoxyisopropyl carbonate. These thermal polymerization initiators may be used alone or in combination of two or more.

When the insulating material precursor contains a photopolymerization initiator, for example, the insulating material can be obtained by irradiating the insulating material precursor with light (e.g., light having at least a portion of the wavelength of 200 to 400 nm (ultraviolet light)) to harden the precursor. The conditions for light irradiation may be set appropriately depending on the type of photopolymerization initiator.

The photopolymerization initiator may be, for example, a benzoin ether-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, an α-ketol-based photopolymerization initiator, an aromatic sulfonyl chloride-based photopolymerization initiator, a photoactive oxime-based photopolymerization initiator, a benzoin-based photopolymerization initiator, a benzyl-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a ketal-based photopolymerization initiator, a thioxanthone-based photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator, etc.

Benzoin ether photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one (e.g., BASF's "Irgacure 651"), anisole methyl ether, etc. Acetophenone photopolymerization initiators include 1-hydroxycyclohexyl phenyl ketone (e.g., BASF's "Irgacure 184"), 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (e.g., BASF's "Irgacure 2959"), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (e.g., BASF's "Irgacure 1173"), methoxyacetophenone, etc.

Examples of α-ketol photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)-phenyl]-2-hydroxy-2-methylpropan-1-one. Examples of aromatic sulfonyl chloride photopolymerization initiators include 2-naphthalenesulfonyl chloride. Examples of photoactive oxime photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime.

Benzoin-based photopolymerization initiators include benzoin, etc. Benzil-based photopolymerization initiators include benzil, etc. Benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinyl benzophenone, α-hydroxycyclohexyl phenyl ketone, etc. Ketal-based photopolymerization initiators include benzil dimethyl ketal, etc. Thioxanthone-based photopolymerization initiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, etc.

Acylphosphine photopolymerization initiators include bis(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)(2,4,4-trimethylpentyl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-n-butylphosphine oxide, bis(2,6-dimethoxybenzoyl)-(2-methylpropan-1-yl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-(1-methylpropan-1-yl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-t-butylphosphine oxide, bis(2,6-dimethoxybenzoyl)cyclohexylphosphine oxide, bis(2,6-dimethoxybenzoyl)octylphosphine oxide, and bis(2-methoxybenzoyl)(2-methyl bis(2-methoxybenzoyl)(1-methylpropan-1-yl)phosphine oxide, bis(2,6-diethoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,6-diethoxybenzoyl)(1-methylpropan-1-yl)phosphine oxide, bis(2,6-dibutoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,4-dimethoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)(2,4-dipentoxyphenyl)phosphine oxide, bis(2,6-dimethoxybenzoyl)benzylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylpropionyl phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylethylphosphine oxide, 2,6-dimethoxybenzoylbenzylbutylphosphine oxide, 2,6-dimethoxybenzoylbenzyloctylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,5-diisopropylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2-methylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-4-methylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,5-diethylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,3,5,6-tetramethylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl) bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)isobutylphosphine oxide, 2,6-dimethoxybenzoyl-2,4,6-trimethylbenzoyl-n-butylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-dibutoxyphenylphosphine oxide, 1,10-bis[bis(2,4,6-trimethylbenzoyl)phosphine oxide]decane, tri(2-methylbenzoyl)phosphine oxide, etc.

The above-mentioned photopolymerization initiators may be used alone or in combination of two or more.

The content of the polymerization initiator is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and even more preferably 0.05 parts by mass or more, per 100 parts by mass of the total monomer components, from the viewpoint of allowing the polymerization to proceed smoothly. The content of the polymerization initiator is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less, and particularly preferably 1 part by mass or less, per 100 parts by mass of the total monomer components, from the viewpoint of allowing the molecular weight of the polymer in the insulation material to fall within a suitable range and suppressing decomposition products.

The insulating material and the insulating material precursor may contain a plasticizer as an additive. By using a plasticizer, the adhesion of the insulating material precursor and the elongation of the insulating material can be further improved.
Examples of the plasticizer include tackifiers such as butadiene rubber, isoprene rubber, silicone rubber, styrene butadiene rubber, chloroprene rubber, nitrile rubber, butyl rubber, ethylene propylene rubber, urethane rubber, acrylic resin, rosin resin, terpene resin, etc., or polyalkylene glycol, etc. The content of the plasticizer may be 0.1 parts by mass or more, 1 part by mass or more, or 3 parts by mass or more, and may be 20 parts by mass or less, 15 parts by mass or less, 12 parts by mass or less, or 10 parts by mass or less, relative to 100 parts by mass of the total of the monomer components.

The insulating material and the insulating material precursor may further contain other additives as necessary. Examples of the other additives include antioxidants, surface treatment agents (e.g., silane coupling agents), dispersants, colorants, crystal nucleating agents, heat stabilizers, foaming agents, flame retardants, vibration dampers, dehydrating agents, and flame retardant assistants (e.g., metal oxides). The content of the other additives may be 0.1% by mass or more and 30% by mass or less based on the total amount of the insulating material (insulating material precursor).

The insulating material precursor is preferably liquid at 25°C. This allows it to be applied appropriately to the surface of the first electronic component and/or the holding member, and also increases adhesion to the applied surface. The insulating material precursor may be solid at 25°C, in which case it is preferable for it to become liquid upon heating (e.g., at 50°C or higher). The insulating material precursor may be applied in a liquid state and then cured, which can prevent the insulating material precursor from causing dripping and pump-out phenomena.

[Thermal insulation material (3)]
The heat insulating material may be, for example, a heat insulating material containing first hollow particles which are thermally expandable hollow particles, second hollow particles which are hollow particles other than the first hollow particles, and a matrix polymer (hereinafter, heat insulating material (3)).

The insulating material (3) may be, for example, a cured product of a composition containing first hollow particles, second hollow particles, and a polymerizable compound.

The insulating material (3) may be in sheet form.

The type and content of the first and second hollow particles contained in the heat insulating material (3) may be the same as those of the first and second hollow particles contained in the composition or composition set described below. With regard to the content, "based on the total mass of the composition" should be read as "based on the total mass of the heat insulating material (3)" and "based on the total volume of the composition" should be read as "based on the total volume of the heat insulating material (3)."

The matrix polymer contained in the insulating material (3) is a polymer (binder polymer) that serves as a base (forms a continuous phase) to hold other materials contained in the insulating material (3). The matrix polymer is a polymer of a polymerizable compound contained in the composition or composition set described below.

The content of the matrix polymer may be, for example, 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more, and 95% by mass or less, or 90% by mass or less, based on the total mass of the insulating material (3).

When the insulating material (3) is a sheet, the thickness of the sheet is not particularly limited and may be, for example, 200 μm or more and 2000 μm or less.

The heat insulating material (3) may further contain additives that may be contained in the composition or composition set described below. In that case, the content of the additives contained in the sheet may be the same as the content of the additives contained in the composition or composition set described below (the content can be read in the same way as described above).

The composition contains first hollow particles, second hollow particles, and a polymerizable compound.

(First hollow particle)
The first hollow particles have an outer shell and a hollow portion. The first hollow particles are heat-expandable (thermally expandable) hollow particles. In this specification, the thermally expandable hollow particles are hollow particles having a maximum volume expansion ratio of 10 times or more relative to the volume at 25°C. When the first hollow particles are used, the first hollow particles expand due to heat in the reflow process, thereby reducing the adhesive area at the interface between the insulating material and the device, and the insulating material (3) can be easily removed after the reflow process.

The maximum volume expansion ratio of the first hollow particles is measured by thermomechanical analysis (TMA) as the ratio of the maximum volume of the first hollow particles when heated at a heating rate of 10°C/min to the volume at 25°C (maximum volume/volume at 25°C). The maximum volume expansion ratio of the first hollow particles may be, for example, 20 times or more, 30 times or more, or 40 times or more, or may be 120 times or less.

The shell is preferably made of a thermoplastic polymer. In this case, since the shell becomes soft when heated, the hollow particles are less likely to break and expand easily even if the liquid contained in the hollow portion vaporizes and the internal pressure increases. The thermoplastic polymer may be, for example, a polymer containing acrylonitrile, vinylidene chloride, or the like as a monomer unit. The thickness of the shell may be 2 μm or more and 15 μm or less.

The hollow portion of the first hollow particle contains, for example, a liquid. The first hollow particle is in this state at room temperature and pressure (for example, at least atmospheric pressure and 30°C). The liquid is appropriately selected, for example, depending on the heating temperature in the reflow process. The liquid is, for example, a liquid that vaporizes at a temperature equal to or lower than the maximum heating temperature in the reflow process. The liquid may be, for example, a hydrocarbon having a boiling point (at atmospheric pressure) of 50°C or higher, 100°C or higher, 150°C or higher, or 200°C or higher. In addition to the above liquid, the hollow portion of the first hollow particle may further contain a gas.

Examples of components contained within the hollow portion of the first hollow particles include hydrocarbons such as propane, propylene, butene, normal butane, isobutane, normal pentane, isopentane, neopentane, normal hexane, isohexane, heptane, isooctane, normal octane, isoalkane (carbon number: 10 to 13), and petroleum ether; low-boiling compounds such as methane halides and tetraalkylsilanes; and compounds that gasify by thermal decomposition, such as azodicarbonamide.

The average particle size of the first hollow particles may be 5 μm or more, 10 μm or more, or 20 μm or more, and may be 50 μm or less, 40 μm or less, or 30 μm or less. The average particle size of the first hollow particles is measured by a laser diffraction/scattering method (for example, using a "SALD-7500 nano" manufactured by Shimadzu Corporation).

From the viewpoint that the insulating material (3) is more suitably used as an insulating material in the reflow process (which is generally heated to 260°C), the expansion start temperature of the first hollow particles is preferably 70°C or more, 100°C or more, 130°C or more, or 160°C or more, and preferably 260°C or less. The expansion start temperature of the first hollow particles means the temperature at the intersection of the tangent to the point where a volume change of 3 times or more/5°C occurs and the straight line (horizontal axis) where the volume change is zero (initial volume) in the profile of temperature (horizontal axis) vs. volume change (vertical axis) when the temperature is increased at a heating rate of 10°C/min in thermomechanical analysis (TMA).

From the viewpoint of more suitably using the insulating material (3) as an insulating material in the reflow process, the maximum expansion temperature of the first hollow particles is preferably 100°C or more, 150°C or more, 200°C or more, or 220°C or more, and preferably 290°C or less, 280°C or less, or 270°C or less. The maximum expansion temperature of the first hollow particles means the temperature at which the first hollow particles exhibit the above-mentioned maximum volume expansion ratio.

From the viewpoint of making it easier to remove the insulating material (3) after the reflow process, the content of the first hollow particles may be preferably 1 mass % or more, more preferably 5 mass % or more, and even more preferably 8 mass % or more, based on the total mass of the composition, and may be 20 mass % or less, or 15 mass % or less.

From the viewpoint of making it easier to remove the insulating material (3) after the reflow process, the content of the first hollow particles is preferably 1 vol% or more, more preferably 2 vol% or more, even more preferably 3 vol% or more, and particularly preferably 4 vol% or more, based on the volume of the composition, and may be, for example, 10 vol% or less, 7 vol% or less, or 5 vol% or less.

(Second hollow particle)
The second hollow particles have an outer shell and a hollow portion. The second hollow particles are hollow particles other than the first hollow particles. That is, the second hollow particles are hollow particles having a maximum volume expansion ratio of less than 10 times the volume at 25°C. By using the second hollow particles, the heat insulating property of the heat insulating material (3) is further improved. The maximum volume expansion ratio of the second hollow particles is measured by the same method as the maximum volume expansion ratio of the first hollow particles.

The shell is preferably made of a thermoplastic polymer. In this case, the hollow particles are less likely to break even when pressurized, and can maintain their hollow structure and heat insulation. The thermoplastic polymer may be, for example, a polymer containing acrylonitrile, vinylidene chloride, or the like as a monomer unit. The thickness of the shell may be 0.005 μm or more and 15 μm or less.

The hollow portion of the second hollow particle contains, for example, a gas. The second hollow particle is in this state at room temperature and pressure (for example, at least atmospheric pressure and 30°C). In addition to the gas, the hollow portion of the second hollow particle may further contain a liquid.

Examples of components contained within the hollow portion of the second hollow particles include hydrocarbons such as propane, propylene, butene, normal butane, isobutane, normal pentane, isopentane, neopentane, normal hexane, isohexane, heptane, isooctane, normal octane, isoalkane (carbon number: 10 to 13), and petroleum ether; low-boiling compounds such as methane halides and tetraalkylsilanes; and decomposition products of compounds that gasify by thermal decomposition, such as azodicarbonamide.

From the viewpoint of improving the heat insulating properties, the average particle diameter of the second hollow particles is preferably 150 μm or less, more preferably 120 μm or less, and even more preferably 100 μm or less, and may be, for example, 10 μm or more, 20 μm or more, or 30 μm or more. The average particle diameter of the second hollow particles is measured by a laser diffraction/scattering method (for example, using "SALD-7500 nano" manufactured by Shimadzu Corporation).

The density of the second hollow particles may be 50 kg/m3 or ^less , or 40 kg/ ^m3 or less, and may be 10 kg/ ^m3 or more, or 20 kg/ ^m3 or more. The density of the second hollow particles in this specification means a density measured by a tap density method. That is, the density is calculated by the following formula, in which the second hollow particles (about 5 g) are put into a 10 mL graduated cylinder, tapped 50 times, and the volume when the uppermost surface becomes stable is defined as the stable volume.
Density = initial charge (kg) / stable volume (m ³ )

From the viewpoint of improving the thermal insulation properties of the insulating material (3), the content of the second hollow particles is preferably 1 mass % or more, more preferably 3 mass % or more, and even more preferably 5 mass % or more, based on the total mass of the composition, and may be, for example, 20 mass % or less.

From the viewpoint of improving the insulating properties of the insulating material (3), the content of the second hollow particles is preferably 50% by volume or more, more preferably 60% by volume or more, and may be, for example, 95% by volume or less, based on the total volume of the composition.

The total content of hollow particles (including the content of the first hollow particles and the second hollow particles) may be, for example, 5% by mass or more, 10% by mass or more, or 15% by mass or more, and 40% by mass or less, 30% by mass or less, or 20% by mass or less, based on the total mass of the composition.

The total content of hollow particles (including the content of the first hollow particles and the second hollow particles) may be, for example, 50 vol. % or more, 60 vol. % or more, or 70 vol. % or more, and may be 95 vol. % or less, based on the total volume of the composition.

(Polymerizable compound)
The polymerizable compound is not particularly limited, but may include, for example, a compound represented by the following formula (1).

In formula (1), R ¹¹ and R ¹² each independently represent a hydrogen atom or a methyl group, and R ¹³ represents a divalent group having a polyoxyalkylene chain.

When the polymerizable compound is a compound represented by the above formula (1), the cured product of the composition has low elasticity and excellent elongation, and can improve conformability to the adherend.

In one embodiment, one of R ¹¹ and R ¹² may be a hydrogen atom and the other may be a methyl group; in another embodiment, both R ¹¹ and R ¹² may be hydrogen atoms; in another embodiment, both R ¹¹ and R ¹² may be methyl groups.

In one embodiment, the polyoxyalkylene chain contains a structural unit represented by the following formula (2): This makes it possible to increase the strength of the cured product while suppressing an excessive increase in the viscosity of the composition.

In this case, R ¹³ may be a divalent group having a polyoxyethylene chain, and the compound represented by formula (1) is preferably a compound represented by the following formula (1-2) (polyethylene glycol di(meth)acrylate).

In formula (1-2), R ¹¹ and R ¹² have the same meanings as R ¹¹ and R ¹² in formula (1), respectively, and m is an integer of 2 or more.

In another embodiment, the polyoxyalkylene chain contains a structural unit represented by the following formula (3): This can facilitate handling of the composition.

In this case, R ¹³ may be a divalent group having a polyoxypropylene chain, and the compound represented by formula (1) is preferably a compound represented by the following formula (1-3) (polypropylene glycol di(meth)acrylate).

In formula (1-3), R ¹¹ and R ¹² have the same meanings as R ¹¹ and R ¹² in formula (1), respectively, and n is an integer of 2 or more.

In another embodiment, the polyoxyalkylene chain is preferably a copolymer chain containing the structural unit represented by formula (2) and the structural unit represented by formula (3) described above, from the viewpoint of easily achieving both the strength of the cured product of the compound represented by formula (1) and the ease of handling of the composition. The copolymer chain may be any of an alternating copolymer chain, a block copolymer chain, and a random copolymer chain. The copolymer chain is preferably a random copolymer chain, from the viewpoint of further reducing the crystallinity of the compound represented by formula (1) and further facilitating the handling of the composition.

In each of the above-described embodiments, the polyoxyalkylene chain may have an oxyalkylene group having 4 to 5 carbon atoms, such as an oxytetramethylene group, an oxybutylene group, or an oxypentylene group, as a structural unit in addition to the structural unit represented by formula (2) and the structural unit represented by formula (3).

R ¹³ may be a divalent group having, in addition to the above-mentioned polyoxyalkylene chain, another organic group. The other organic group may be a chain-like group other than a polyoxyalkylene chain, such as a methylene chain (a chain having -CH ₂ - as a structural unit), a polyester chain (a chain containing -COO- in a structural unit), a polyurethane chain (a chain containing -OCON- in a structural unit), etc.

For example, the compound represented by formula (1) may be a compound represented by the following formula (1-4).

In formula (1-4), R ¹¹ and R ¹² are the same as R ¹¹ and R ¹² in formula (1), R ¹⁴ and R ¹⁵ are each independently an alkylene group having 2 to 5 carbon atoms, and k1, k2 and k3 are each independently an integer of 2 or more. k2 may be, for example, an integer of 16 or less.

A plurality of R ¹⁴ and R ¹⁵ may be the same or different from each other. A plurality of R ¹⁴ and R ¹⁵ each preferably contains an ethylene group and a propylene group. That is, the polyoxyalkylene chain represented by (R ¹⁴ O) _k1 and the polyoxyalkylene chain represented by (R ¹⁵ O) _k3 are each preferably a copolymer chain containing an oxyethylene group (structural unit represented by the above formula (2)) and an oxypropylene group (structural unit represented by the above formula (3)).

In each of the above-described embodiments, the number of oxyalkylene groups in the polyoxyalkylene chain is preferably 100 or more. When the number of oxyalkylene groups in the polyoxyalkylene chain is 100 or more, the main chain of the compound represented by formula (1) becomes longer, so that the elongation of the cured product is more excellent and the strength of the cured product can be increased. The number of oxyalkylene groups corresponds to m in formula (1-2), n in formula (1-3), and k1 and k3 in formula (1-4).

The number of oxyalkylene groups in the polyoxyalkylene chain is more preferably 130 or more, 180 or more, 200 or more, 220 or more, 250 or more, 270 or more, 300 or more, or 320 or more. The number of oxyalkylene groups in the polyoxyalkylene chain may be 600 or less, 570 or less, or 530 or less.

The weight average molecular weight of the compound represented by formula (1) is preferably 5000 or more, 6000 or more, 7000 or more, 8000 or more, 9000 or more, 10000 or more, 11000 or more, 12000 or more, 13000 or more, 14000 or more, or 15000 or more, from the viewpoint of a cured product having lower elasticity and excellent elongation. The weight average molecular weight of the compound represented by formula (1) is preferably 100000 or less, 80000 or less, 60000 or less, 34000 or less, 31000 or less, or 28000 or less, from the viewpoint of making it easier to adjust the viscosity of the composition.

The compound represented by formula (1) may be liquid at 25°C. In this case, the viscosity of the compound represented by formula (1) at 25°C is preferably 1000 Pa·s or less, 800 Pa·s or less, 600 Pa·s or less, 500 Pa·s or less, 350 Pa·s or less, 300 Pa·s or less, or 200 Pa·s or less, from the viewpoint of facilitating application to the coating surface and from the viewpoint of increasing the adhesion of the cured product to the coating surface. The viscosity of the compound represented by formula (1) at 25°C may be 0.1 Pa·s or more, 0.2 Pa·s or more, 0.3 Pa·s or more, 1 Pa·s or more, 2 Pa·s or more, or 3 Pa·s or more.

The compound represented by formula (1) may be solid at 25°C. In this case, from the viewpoint of further improving the handleability of the composition, the compound represented by formula (1) is preferably liquid at 50°C. In addition, in this case, from the viewpoint of further improving the handleability of the composition, the viscosity of the compound represented by formula (1) at 50°C is preferably 100 Pa·s or less, more preferably 50 Pa·s or less, even more preferably 30 Pa·s or less, and particularly preferably 20 Pa·s or less. The viscosity of the compound represented by formula (1) at 50°C may be 0.1 Pa·s or more, 0.2 Pa·s or more, or 0.3 Pa·s or more.

The viscosity refers to a value measured based on JIS Z 8803, specifically, a value measured using an E-type viscometer (for example, PE-80L, manufactured by Toki Sangyo Co., Ltd.). The viscometer can be calibrated based on JIS Z 8809-JS14000. The viscosity of the compound represented by formula (1) can be adjusted by adjusting the weight average molecular weight of the compound.

From the viewpoint of providing a cured product with lower elasticity and excellent elongation, the content of the compound represented by formula (1) is preferably 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more based on the total mass of the composition. The content of the compound represented by formula (1) may be 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less based on the total mass of the composition.

The composition may contain only the compound represented by formula (1) as the polymerizable compound. The composition may further contain other polymerizable compounds (details will be described later) other than the compound represented by formula (1). In this case, the content of the compound represented by formula (1) is preferably 20 parts by mass or more, 30 parts by mass or more, or 40 parts by mass or more per 100 parts by mass of the total of the compound represented by formula (1) and the other polymerizable compounds (hereinafter referred to as the "total content of polymerizable components"), from the viewpoint of a cured product having lower elasticity and excellent elongation. The content of the compound represented by formula (1) may be 80 parts by mass or less, 70 parts by mass or less, or 60 parts by mass or less per 100 parts by mass of the total content of polymerizable components.

The polymerizable compound may include a polymerizable compound other than the compound represented by formula (1).

The other polymerizable compound may be, for example, a compound having one (meth)acryloyl group. The compound may be, for example, an alkyl (meth)acrylate. The other polymerizable compound may be a compound having, in addition to one (meth)acryloyl group, an aromatic hydrocarbon group, a group containing a polyoxyalkylene chain, a group containing a heterocycle, an alkoxy group, a phenoxy group, a group containing a silane group, a group containing a siloxane bond, a halogen atom, a hydroxyl group, a carboxyl group, an amino group, or an epoxy group. In particular, the viscosity of the composition can be adjusted by the composition containing an alkyl (meth)acrylate. In addition, the composition can further improve the adhesion of the composition and the heat insulating material to the member by containing a compound having a hydroxyl group, a carboxyl group, an amino group, or an epoxy group in addition to a (meth)acryloyl group.

The alkyl group in the alkyl (meth)acrylate (the alkyl group portion other than the (meth)acryloyl group) may be linear, branched, or alicyclic. The number of carbon atoms in the alkyl group may be, for example, 1 to 30. The number of carbon atoms in the alkyl group may be 1 to 11, 1 to 8, 1 to 6, or 1 to 4, or may be 12 to 30, 12 to 28, 12 to 24, 12 to 22, 12 to 18, or 12 to 14.

Examples of alkyl (meth)acrylates having a linear alkyl group include alkyl (meth)acrylates having a linear alkyl group having 1 to 11 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, and undecyl (meth)acrylate. Examples of such alkyl (meth)acrylates include alkyl (meth)acrylates having a linear alkyl group having 12 to 30 carbon atoms, such as sil (meth)acrylate (lauryl (meth)acrylate), tetradecyl (meth)acrylate, hexadecyl (meth)acrylate (cetyl (meth)acrylate), octadecyl (meth)acrylate (stearyl (meth)acrylate), docosyl (meth)acrylate (behenyl (meth)acrylate), tetracosyl (meth)acrylate, hexacosyl (meth)acrylate, and octacosyl (meth)acrylate.

Examples of alkyl (meth)acrylates having a branched alkyl group include s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, isopentyl (meth)acrylate, isoamyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, and isodecyl (meth)acrylate, and other alkyl (meth)acrylates having a branched alkyl group with 1 to 11 carbon atoms, isomyristyl (meth)acrylate, and the like. Examples of the alkyl (meth)acrylate include alkyl (meth)acrylates having a branched alkyl group having 12 to 30 carbon atoms, such as isoundecyl (meth)acrylate, 2-propylheptyl (meth)acrylate, isoundecyl (meth)acrylate, isododecyl (meth)acrylate, isotridecyl (meth)acrylate, isopentadecyl (meth)acrylate, isohexadecyl (meth)acrylate, isoheptadecyl (meth)acrylate, isostearyl (meth)acrylate, and decyltetradecanyl (meth)acrylate.

Examples of alkyl (meth)acrylates having an alicyclic alkyl group (cycloalkyl group) include cyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, terpene (meth)acrylate, and dicyclopentanyl (meth)acrylate.

An example of a compound having a (meth)acryloyl group and an aromatic hydrocarbon group is benzyl (meth)acrylate.

Examples of compounds having a (meth)acryloyl group and a group containing a polyoxyalkylene chain include polyethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, polybutylene glycol (meth)acrylate, and methoxypolybutylene glycol (meth)acrylate.

An example of a compound having a (meth)acryloyl group and a group containing a heterocycle is tetrahydrofurfuryl (meth)acrylate.

Examples of compounds having a (meth)acryloyl group and an alkoxy group include 2-methoxyethyl acrylate.

An example of a compound having a (meth)acryloyl group and a phenoxy group is phenoxyethyl (meth)acrylate.

Examples of compounds having a (meth)acryloyl group and a group containing a silane group include 3-acryloxypropyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, and 10-acryloyloxydecyltriethoxysilane.

Examples of compounds having a (meth)acryloyl group and a group containing a siloxane bond include silicone (meth)acrylate.

Compounds having a (meth)acryloyl group and a halogen atom include trifluoromethyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, 1,1,1,3,3,3-hexafluoro-2-propyl (meth)acrylate, perfluoroethyl methyl (meth)acrylate, perfluoropropyl methyl (meth)acrylate, perfluorobutyl methyl (meth)acrylate, perfluoropentyl methyl (meth)acrylate, perfluorohexyl methyl (meth)acrylate, perfluoroheptyl methyl (meth)acrylate, perfluorooctyl methyl (meth)acrylate, perfluorononyl methyl (meth)acrylate, perfluorodecyl methyl (meth)acrylate, perfluoroundecyl methyl (meth)acrylate, perfluorododecyl methyl (meth)acrylate, perfluoro Examples of (meth)acrylates having fluorine atoms include tridecylmethyl (meth)acrylate, perfluorotetradecylmethyl (meth)acrylate, 2-(trifluoromethyl)ethyl (meth)acrylate, 2-(perfluoroethyl)ethyl (meth)acrylate, 2-(perfluoropropyl)ethyl (meth)acrylate, 2-(perfluorobutyl)ethyl (meth)acrylate, 2-(perfluoropentyl)ethyl (meth)acrylate, 2-(perfluorohexyl)ethyl (meth)acrylate, 2-(perfluoroheptyl)ethyl (meth)acrylate, 2-(perfluorooctyl)ethyl (meth)acrylate, 2-(perfluorononyl)ethyl (meth)acrylate, 2-(perfluorotridecyl)ethyl (meth)acrylate, and 2-(perfluorotetradecyl)ethyl (meth)acrylate.

Examples of compounds having a (meth)acryloyl group and a hydroxyl group include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate; and hydroxyalkyl cycloalkane (meth)acrylates such as (4-hydroxymethylcyclohexyl)methyl (meth)acrylate.

Examples of compounds having a (meth)acryloyl group and a carboxyl group include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, monohydroxyethyl phthalate acrylate (e.g., "Aronix M5400" manufactured by Toagosei Co., Ltd.), and 2-acryloyloxyethyl succinate (e.g., "NK Ester A-SA" manufactured by Shin-Nakamura Chemical Co., Ltd.).

Examples of compounds having a (meth)acryloyl group and an amino group include N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, and N,N-diethylaminopropyl (meth)acrylate.

Examples of compounds having a (meth)acryloyl group and an epoxy group include glycidyl (meth)acrylate, α-ethyl glycidyl (meth)acrylate, α-n-propyl glycidyl (meth)acrylate, α-n-butyl glycidyl (meth)acrylate, 3,4-epoxybutyl (meth)acrylate, 4,5-epoxypentyl (meth)acrylate, 6,7-epoxyheptyl (meth)acrylate, α-ethyl 6,7-epoxyheptyl (meth)acrylate, 3-methyl-3,4-epoxybutyl (meth)acrylate, 4-methyl-4,5-epoxypentyl (meth)acrylate, 5-methyl-5,6-epoxyhexyl (meth)acrylate, β-methylglycidyl (meth)acrylate, and α-ethyl β-methylglycidyl (meth)acrylate.

The composition may contain one or more of the above-mentioned other polymerizable compounds as the polymerizable compound. In addition, the composition may or may not further contain a compound represented by formula (1).

The content of the polymerizable compound other than the compound represented by formula (1) may be, for example, 1 mass% or more, 5 mass% or more, 10 mass% or more, 20 mass% or more, or 30 mass% or more, and 60 mass% or less, 50 mass% or less, or 40 mass% or less, based on the total mass of the composition.

The content of the polymerizable compound (the total content of the compound represented by formula (1) and other polymerizable compounds) may be, for example, 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more, and 95% by mass or less, or 90% by mass or less, based on the total mass of the composition.

The composition may further contain a polymerization initiator. The polymerization initiator may be, for example, a thermal polymerization initiator that generates radicals by heat, a photopolymerization initiator that generates radicals by light, etc. The polymerization initiator is preferably a thermal polymerization initiator.

When the composition contains a thermal polymerization initiator, a cured product of the composition can be obtained by applying heat to the composition. In this case, the composition may be a composition that is cured by heating at preferably 105°C or higher, more preferably 110°C or higher, and even more preferably 115°C or higher, and may be a composition that is cured by heating at, for example, 200°C or lower, 190°C or lower, or 180°C or lower. The heating time when the composition is heated may be appropriately selected according to the composition of the composition so that the composition is suitably cured.

Thermal polymerization initiators include azo compounds such as azobisisobutyronitrile, azobis-4-methoxy-2,4-dimethylvaleronitrile, azobiscyclohexanone-1-carbonitrile, and azodibenzoyl, as well as organic peroxides such as benzoyl peroxide, lauroyl peroxide, di-t-butyl peroxide, di-t-hexyl peroxide, di-t-butylperoxyhexahydroterephthalate, t-butylperoxy-2-ethylhexanoate, 1,1-t-butylperoxy-3,3,5-trimethylcyclohexane, and t-butylperoxyisopropyl carbonate. These thermal polymerization initiators may be used alone or in combination of two or more.

When the composition contains a photopolymerization initiator, for example, a cured product of the composition can be obtained by irradiating the composition with light (e.g., light having at least a portion of the wavelength of 200 to 400 nm (ultraviolet light)). The conditions for light irradiation may be appropriately set depending on the type of photopolymerization initiator.

The photopolymerization initiator may be, for example, a benzoin ether-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, an α-ketol-based photopolymerization initiator, an aromatic sulfonyl chloride-based photopolymerization initiator, a photoactive oxime-based photopolymerization initiator, a benzoin-based photopolymerization initiator, a benzyl-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a ketal-based photopolymerization initiator, a thioxanthone-based photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator, etc.

Benzoin ether photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one (e.g., BASF's "Irgacure 651"), anisole methyl ether, etc. Acetophenone photopolymerization initiators include 1-hydroxycyclohexyl phenyl ketone (e.g., BASF's "Irgacure 184"), 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (e.g., BASF's "Irgacure 2959"), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (e.g., BASF's "Irgacure 1173"), methoxyacetophenone, etc.

Examples of α-ketol photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)-phenyl]-2-hydroxy-2-methylpropan-1-one. Examples of aromatic sulfonyl chloride photopolymerization initiators include 2-naphthalenesulfonyl chloride. Examples of photoactive oxime photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime.

Benzoin-based photopolymerization initiators include benzoin, etc. Benzil-based photopolymerization initiators include benzil, etc. Benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinyl benzophenone, α-hydroxycyclohexyl phenyl ketone, etc. Ketal-based photopolymerization initiators include benzil dimethyl ketal, etc. Thioxanthone-based photopolymerization initiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, etc.

Acylphosphine photopolymerization initiators include bis(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)(2,4,4-trimethylpentyl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-n-butylphosphine oxide, bis(2,6-dimethoxybenzoyl)-(2-methylpropan-1-yl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-(1-methylpropan-1-yl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-t-butylphosphine oxide, bis(2,6-dimethoxybenzoyl)cyclohexylphosphine oxide, bis(2,6-dimethoxybenzoyl)octylphosphine oxide, and bis(2-methoxybenzoyl)(2-methyl bis(2-methoxybenzoyl)(1-methylpropan-1-yl)phosphine oxide, bis(2,6-diethoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,6-diethoxybenzoyl)(1-methylpropan-1-yl)phosphine oxide, bis(2,6-dibutoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,4-dimethoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)(2,4-dipentoxyphenyl)phosphine oxide, bis(2,6-dimethoxybenzoyl)benzylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylpropionyl phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylethylphosphine oxide, 2,6-dimethoxybenzoylbenzylbutylphosphine oxide, 2,6-dimethoxybenzoylbenzyloctylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,5-diisopropylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2-methylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-4-methylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,5-diethylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,3,5,6-tetramethylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl) bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)isobutylphosphine oxide, 2,6-dimethoxybenzoyl-2,4,6-trimethylbenzoyl-n-butylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-dibutoxyphenylphosphine oxide, 1,10-bis[bis(2,4,6-trimethylbenzoyl)phosphine oxide]decane, tri(2-methylbenzoyl)phosphine oxide, etc.

The above-mentioned photopolymerization initiators may be used alone or in combination of two or more.

The content of the polymerization initiator is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and even more preferably 0.05 parts by mass or more, per 100 parts by mass of the total content of the polymerizable components, from the viewpoint of allowing the polymerization to proceed smoothly. The content of the polymerization initiator is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less, and particularly preferably 1 part by mass or less, per 100 parts by mass of the total content of the polymerizable components, from the viewpoint of allowing the molecular weight of the polymer in the cured product of the composition to be in a suitable range and suppressing decomposition products.

The composition may contain a plasticizer as an additive. The inclusion of a plasticizer in the composition can further increase the adhesion of the composition and the elongation of the cured product. Examples of plasticizers include tackifiers such as butadiene rubber, isoprene rubber, silicone rubber, styrene butadiene rubber, chloroprene rubber, nitrile rubber, butyl rubber, ethylene propylene rubber, urethane rubber, acrylic resin, rosin resin, and terpene resin, and polyalkylene glycol. The content of the plasticizer may be 0.1 parts by mass or more, 1 part by mass or more, or 3 parts by mass or more, relative to 100 parts by mass of the total content of the polymerizable components, and may be 20 parts by mass or less, 15 parts by mass or less, 12 parts by mass or less, or 10 parts by mass or less.

The composition may further contain other additives as necessary. Examples of the other additives include antioxidants, surface treatment agents (e.g., silane coupling agents), dispersants, curing accelerators, colorants, crystal nucleating agents, heat stabilizers, foaming agents, flame retardants, vibration dampers, dehydrating agents, and flame retardant assistants (e.g., metal oxides). The content of the other additives may be 0.1% by mass or more and 30% by mass or less based on the total mass of the composition.

The composition is preferably liquid at 25°C. This allows it to be applied to the surface of an object in an appropriate manner and also enhances adhesion to the applied surface. The composition may be solid at 25°C, in which case it is preferable for it to become liquid upon heating (e.g., at 50°C or higher). The composition may be applied in a liquid state and then cured, which can prevent the composition from causing dripping and pumping out.

The above-mentioned composition may be in the form of a multi-liquid composition (composition set). The composition set according to one embodiment is a composition set including a first liquid containing an oxidizing agent and a second liquid containing a reducing agent. The above-mentioned first hollow particles, second hollow particles, and polymerizable compound are each contained in at least one of the first liquid and the second liquid. By mixing the first liquid and the second liquid, the oxidizing agent and the reducing agent react to generate free radicals, and polymerization of the polymerizable compound proceeds. According to the composition set according to this embodiment, by mixing the first liquid and the second liquid, a cured product of the mixture of the first liquid and the second liquid is immediately obtained. In other words, according to the composition set, a cured product of the composition is obtained at a high speed.

In the composition set, the first liquid preferably contains an oxidizing agent, a polymerizable compound, a first hollow particle, and a second hollow particle, and the second liquid preferably contains a reducing agent, a polymerizable compound, a first hollow particle, and a second hollow particle, and more preferably, the first liquid contains an oxidizing agent, a polymerizable compound represented by formula (1), a first hollow particle, and a second hollow particle, and the second liquid contains a reducing agent, a polymerizable compound represented by formula (1), a first hollow particle, and a second hollow particle.

The content of the compound represented by formula (1) based on the total mass of the liquids constituting the composition set (for example, in the case of a two-liquid composition set, the total amount of the first liquid and the second liquid) may be the same as the range of the content of the compound represented by formula (1) based on the total mass of the composition described above.
The same applies to the content of hollow particles contained in the composition set.

The oxidizing agent contained in the first liquid acts as a polymerization initiator (radical polymerization initiator). The oxidizing agent may be, for example, an organic peroxide or an azo compound. The organic peroxide may be, for example, a hydroperoxide, a peroxydicarbonate, a peroxyester, a peroxyketal, a dialkyl peroxide, a diacyl peroxide, etc. The azo compound may be, for example, AIBN (2,2'-azobisisobutyronitrile), V-65 (azobisdimethylvaleronitrile), etc. The oxidizing agent may be used alone or in combination of two or more types.

Examples of hydroperoxides include diisopropylbenzene hydroperoxide and cumene hydroperoxide.

Examples of peroxydicarbonates include di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis(4-t-butylcyclohexyl) peroxydicarbonate, di-2-ethoxymethoxyperoxydicarbonate, di(2-ethylhexylperoxy)dicarbonate, dimethoxybutyl peroxydicarbonate, and di(3-methyl-3-methoxybutylperoxy)dicarbonate.

Peroxy esters include cumyl peroxy neodecanoate, 1,1,3,3-tetramethylbutyl peroxy neodecanoate, 1-cyclohexyl-1-methylethyl peroxy neodecanoate, t-hexyl peroxy neodecanoate, t-butyl peroxy pivalate, 1,1,3,3-tetramethylbutyl peroxy 2-ethylhexanoate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, 1-cyclohexyl-1-methylethyl peroxy t-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, 1,1-bis(t-butylperoxy)cyclohexane, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, 2,5-dimethyl-2,5-di(m-toluoylperoxy)hexane, t-hexylperoxybenzoate, t-butylperoxyacetate, etc.

Examples of peroxyketals include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclododecane, and 2,2-bis(t-butylperoxy)decane.

Examples of dialkyl peroxides include α,α'-bis(t-butylperoxy)diisopropylbenzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and t-butylcumyl peroxide.

Examples of diacyl peroxides include isobutyl peroxide, 2,4-dichlorobenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, succinic peroxide, benzoylperoxytoluene, and benzoyl peroxide.

From the viewpoint of storage stability, the oxidizing agent is preferably a peroxide, more preferably a hydroperoxide, and even more preferably cumene hydroperoxide.

The content of the oxidizing agent may be 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more, and may be 10% by mass or less, 5% by mass or less, or 3% by mass or less, based on the total mass of the liquid constituting the composition set.

The reducing agent contained in the second liquid may be, for example, a tertiary amine, a thiourea derivative, a transition metal salt, etc. Examples of tertiary amines include triethylamine, tripropylamine, tributylamine, and N,N-dimethyl-p-toluidine. Examples of thiourea derivatives include 2-mercaptobenzimidazole, methylthiourea, dibutylthiourea, tetramethylthiourea, and ethylenethiourea. Examples of transition metal salts include cobalt naphthenate, copper naphthenate, and vanadyl acetylacetonate. The reducing agents can be used alone or in combination of two or more.

From the viewpoint of excellent curing speed, the reducing agent is preferably a thiourea derivative or a transition metal salt. The thiourea derivative may be, for example, ethylene thiourea. From the same viewpoint, the transition metal salt is preferably vanadyl acetylacetonate.

The content of the reducing agent may be 0.05% by mass or more, 0.1% by mass or more, or 0.3% by mass or more, and may be 5% by mass or less, 3% by mass or less, or 1% by mass or less, based on the total mass of the liquid constituting the composition set.

The composition set may further contain the additives described above. The additives may be contained in one or both of the first and second liquids, or may be contained in a third liquid that is different from the first and second liquids. The content of the additives based on the total mass of the liquids constituting the composition set may be the same as the range of the content of the additives based on the total mass of the composition described above.

Figures 1 to 5 are diagrams for explaining an example of a method for manufacturing a double-sided mounted board (hereinafter, manufacturing method (1)).

In manufacturing method (1), as shown in FIG. 1, a substrate 10 having a first main surface 10A and a second main surface 10B and a first electronic component 21 having solder bumps 22 arranged on a connection surface are prepared, and the first electronic component 21 is arranged on the first main surface 10A of the substrate 10.

Then, the first electronic component 21 is mounted on the substrate 10. Specifically, the solder bumps 22 are melted by reflow to connect the substrate 10 and the first electronic component 21. Next, the gap between the substrate 10 and the first electronic component 21 is sealed with an underfill material. As shown in FIG. 2, the first electronic component 21 after mounting is connected to the substrate 10 by a connection portion 23 made of solder, and the gap between the first electronic component 21 and the substrate 10 is sealed with a sealant 24 made of an underfill material or its hardened product.

Next, as shown in FIG. 3, the first electronic component 21 after mounting is covered with a heat insulating material 30 and held by a holding member 40, and the whole is turned over, and a second electronic component 51 is placed on the second main surface 10B.

Then, the second electronic component 51 is mounted on the substrate 10. Specifically, the solder bumps 52 are melted by reflow to connect the substrate 10 and the second electronic component 51. Next, the gap between the substrate 10 and the second electronic component 51 is sealed with an underfill material. As shown in FIG. 4, the second electronic component 51 after mounting is connected to the substrate 10 by a connection portion 53 made of solder, and the gap between the second electronic component 51 and the substrate 10 is sealed with a sealant 54 made of an underfill material or its hardened product.

Then, the holding member 40 and the insulating material 30 are removed to obtain the double-sided mounting board shown in Figure 5.

In manufacturing method (1), the insulating material 30 is arranged so as to be in direct contact with the first electronic component 21, but in this embodiment, the arrangement of the insulating material is not limited to this. For example, as shown in FIG. 6, the insulating material may be arranged on one side of the holding member 40 to form an insulating layer 31. In other words, in the manufacturing method of this embodiment, the holding step may be performed using a holding member that includes a base body 40 and an insulating layer 31 as the holding member.

10...substrate, 21...first electronic component, 22, 52...solder bumps, 23, 53...connection portion, 24, 54...sealing material, 30...insulating material, 31...insulating layer, 40...holding member, 51...second electronic component.

Claims (7)

a first mounting step of mounting a first electronic component on the first main surface of a substrate having a first main surface and a second main surface;
a holding step of disposing a holding member that holds the first electronic component on the first main surface;
a second mounting step of mounting a second electronic component on the second main surface;
Equipped with
A method for manufacturing a double-sided mounted board, comprising: prior to the second mounting step, arranging a heat insulating material that satisfies the following formula (A) so as to surround the first electronic component mounted on the first main surface:
F1>F2 ... (A)
[In the formula, F1 represents the adhesive strength of the insulating material after heating the insulating material at 220° C. for 120 seconds, and F2 represents the adhesive strength of the insulating material after heating the insulating material at 260° C. for 30 seconds.] The method further includes a covering step of covering the first electronic component with a heat insulating material after the first mounting step,
The manufacturing method according to claim 1 , wherein the holding member holds the first electronic component covered with the thermal insulating material on the first main surface. The manufacturing method according to claim 1, wherein the holding step is a step of placing a holding member having a base and an insulating layer containing an insulating material placed on the base. The manufacturing method according to any one of claims 1 to 3, wherein the insulating material contains aerogel particles. The manufacturing method according to claim 4, wherein the heat insulating material further contains a water-soluble polymer having a hydrophobic group. The manufacturing method according to any one of claims 1 to 3, wherein the heat insulating material contains first hollow particles that are thermally expandable hollow particles, second hollow particles that are hollow particles other than the first hollow particles, and a matrix polymer. A holding member that holds a first electronic component mounted on a first main surface of a substrate having a first main surface and a second main surface, on the first main surface when a second electronic component is mounted on the second main surface,
A substrate;
a thermal insulation layer comprising a thermal insulation material disposed on the substrate;
Equipped with
The retaining member , wherein the insulating material satisfies the following formula (A) :
F1>F2 ... (A)
[In the formula, F1 represents the adhesive strength of the insulating material after heating the insulating material at 220° C. for 120 seconds, and F2 represents the adhesive strength of the insulating material after heating the insulating material at 260° C. for 30 seconds.]

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