JP7663175B2 - Method for forming heat insulating coating - Google Patents

Description

The present invention relates to hollow particles, a heat insulating paint containing hollow particles, and a heat insulating coating film containing hollow particles.

Patent Document 1 describes hollow particles and a heat insulating paint containing hollow particles, such as silica hollow particles and a heat insulating paint containing hollow particles. This heat insulating paint aims to improve heat insulating properties by dispersing the silica hollow particles uniformly in the paint.

JP 2007-070458 A

Thermal insulation is effective by suppressing the transfer of heat. However, in the coating film formed from conventional thermal insulation paints containing hollow silica particles, although the hollow silica particles are uniformly dispersed in the coating film, most of the surface layer of the coating film is covered with synthetic resin, which does not sufficiently suppress the transfer of heat, and there is a risk that the insulating properties may not be fully exhibited.

The present invention has been made in consideration of the above points, and aims to provide hollow particles that can better demonstrate the insulating properties of a thermal insulation coating film formed from a thermal insulation paint containing hollow particles.

The hollow particles of the present invention are hollow particles having a siloxane bond as a main skeleton,
The average particle size is 10 to 200 nm, and the particle is characterized by being modified with a surface modifier.

The hollow particles of the present invention have an average particle diameter of 10 to 200 nm, so that when they are added to a heat insulating paint, the heat insulating paint can form a transparent heat insulating coating film. The hollow particles are hydrophilic because they are formed from siloxane bonds, but because they are modified with a surface modifier, they can be compatible with organic solvent-based heat insulating paints. The hollow particles, which are based on hydrophilic siloxane bonds, become significantly hydrophilic when the heat insulating paint is formed, and are rejected so that the concentration increases from the inside of the heat insulating paint toward the surface layer, forming aggregates of hollow particles on the order of μm on the surface layer of the coating film. Therefore, when hollow particles are used in heat insulating paint, the heat insulating properties of the coating film can be exhibited.

Here, in the hollow particles, the surface modifier may be a compound having an organic compatible group and an inorganic bonding group.

This allows the inorganic bonding groups in the hollow particles to be copolymerized with the main skeleton of the siloxane bonds, and the organic compatible groups allow the hollow particles to be appropriately compatible with the heat insulating paint.

The hollow particles may contain 5 to 50 g of the surface modifier per 1 mol of Si in the siloxane bond.

According to this, when the insulating paint is formed, the hollow particles have a well-balanced hydrophilicity, are expelled from the inside of the insulating paint toward the surface so that the concentration increases, and as the volatile components evaporate, hollow particle aggregates on the order of μm can be formed on the surface of the coating.

The heat insulating paint of the present invention can contain 5 to 30 mass % of the hollow particles as calculated as non-volatile matter.

The heat insulating paint of the present invention allows hollow particle aggregates to be formed on the surface layer of the coating film.

The heat insulating coating of the present invention can have an aggregate of the above hollow particles on the surface layer of the coating.

The heat insulating coating of the present invention can reduce the sensation of warmth and coldness caused by contact with human skin.

In addition, in the above-mentioned heat insulating coating, the aggregates can form an uneven shape on the order of μm on the surface of the coating.

This can further reduce the sensation of warmth and coldness caused by contact with human skin.

When the hollow particles of the present invention are added to an organic solvent-based heat-insulating paint, they form aggregates of hollow particles on the surface of the coating film formed from the heat-insulating paint, allowing the coating film to exhibit its heat-insulating properties.

FIG. 1 is a cross-sectional image of a thermal barrier coating containing hollow particles according to an embodiment of the present invention. FIG. 2 is a SEM (scanning electron microscope) photograph of a cross section of a thermal barrier coating of an example. FIG. 2 is a laser microscope photograph of the surface of a thermal barrier coating of an example. FIG. 2 is a laser microscope photograph of the surface of a thermal barrier coating film of a comparative example. FIG. 1 is a diagram showing a laser microscope photograph of the surface of a coating film made of a metallic paint. FIG. 2 is a view showing an SEM photograph of an aggregate of hollow particles in an example.

The following describes an embodiment of hollow particles 2 according to the present invention. The hollow particles 2 of the embodiment have an average particle size of 10 to 200 nm and are modified with a surface modifier. The hollow particles 2 of the embodiment are described in detail below, but are ultimately made by coating calcium carbonate, which is dissolved to form a hollow space, with alkoxysilane and a surface modifier to form a shell body of siloxane bonds that serves as the main skeleton of the hollow particles 2. The calcium carbonate with the shell body of siloxane bonds formed thereon is treated with an acid to dissolve only the calcium carbonate, thereby forming hollow particles 2 whose main skeleton is siloxane bonds modified with a surface modifier.

The calcium carbonate of the embodiment is calcium carbonate (calcite) with a rhombohedral structure whose particle size is adjusted to nano-order size. The average particle size of the calcium carbonate used in the embodiment (average value of 50 particle sizes measured from SEM (scanning electron microscope) photographs) is preferably 10 to 100 nm. This is because when hollow particles 2 formed by coating calcium carbonate are mixed with a heat-insulating paint, the heat insulating property and transparency of the heat-insulating coating film 1 formed from the heat-insulating paint can be improved. If the average particle size of the calcium carbonate is less than 10 nm, the shell of the hollow particles 2 becomes relatively thick, and the heat insulating performance may be deteriorated. On the other hand, if it exceeds 100 nm, the transparency of the heat-insulating coating film 1 may be deteriorated. More preferably, the average particle size of the calcium carbonate is 50 to 90 nm.

An alkoxysilane is a silane compound having an alkoxy group. The alkoxy group is hydrolyzed to produce silanol, and the silanol is condensed to produce a siloxane bond that becomes the main skeleton of the hollow particle 2. In the hollow particle 2 of the embodiment, the alkoxysilane can be used without any particular limitation, and examples thereof include tetramethoxysilane (Si( _OCH3 ) ₄ ), methyltrimethoxysilane ( _SiCH3 ( _OCH3 ) ₃ ), dimethyldimethoxysilane (Si( _CH3 ) ₂ (OCH3) ₂ ), trimethylmethoxysilane (Si( _CH3 ) _3OCH3 ), ethyltrimethoxysilane ( _SiC2H5 (OCH3) ₃ ), diethyldimethoxysilane (Si( _C2H5 ) ₂ ( _OCH3 ) ₂ ), _{triethylmethoxysilane (} Si _{( C2H5} ) _3OCH3 ), propyltrimethoxysilane _{( SiC3H7} ( _OCH3 ) _{3 ) , and} tetraethoxysilane (Si( _OC2H5 ) _{4 ) .} ), methyltriethoxysilane (SiCH3( _OC2H5 ) ₃ ), dimethyldiethoxysilane ( _Si (CH3) ₂ ( _OC2H5 ) ₂ ), trimethylethoxysilane (Si( _CH3 ) _3OC2H5 ), ethyltriethoxysilane (SiC2H5( _OC2H5 ) ₃ ), diethyldiethoxysilane (Si _{( C2H5 )2 ( OC2H5 ) 2} ), triethylethoxysilane (Si _{(C2H5 ) 3OC2H5 )} , _{propyltriethoxysilane (SiC3H7(OC2H5 ) 3 ) , or a mixture thereof ,} etc. _{can be} used _.

A surface modifier is a compound having an organic compatible group and an inorganic bonding group, and is a compound that modifies the surface of the main skeleton of the hydrophilic siloxane bond with the organic compatible group by bonding the inorganic bonding group of the surface modifier to the main skeleton of the hydrophilic siloxane bond. The siloxane bond hollow particles 2 whose surfaces are modified with organic compatible groups can be made compatible with the heat insulating paint by the organic compatible groups. As a surface modifier having an organic compatible group and an inorganic bonding group, a silane coupling agent, a silicone surfactant, a modified silicone, etc. can be used.

In the silane coupling agent, the reactive functional group of the silane coupling agent becomes an organic compatible group, and the alkoxy group becomes an inorganic bonding group. The alkoxy group of the inorganic bonding group is hydrolyzed to generate silanol, and the silanol condenses with the alkoxysilane that becomes the main skeleton of the hollow particle 2, so that the surface modifier bonds to the siloxane bond that forms the hollow particle 2, and the reactive functional group of the organic compatible group modifies the surface of the hollow particle 2. The silane coupling agent can be one that contains an ethoxy group or a methoxy group as the alkoxy group of the inorganic bonding group, and can be one that contains a vinyl group, an epoxy group, a styryl group, a methacryl group, an acrylic group, an amino group, an isocyanate group, an isocyanurate group, a ureido group, a mercapto group, or a functional group consisting of these and an alkylene group as the reactive functional group of the organic compatible group. Specific examples of the silane coupling agent include vinyltrimethoxysilane and vinyltriethoxysilane containing a vinyl group, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane containing an epoxy group, p-styryltrimethoxysilane containing a styryl group, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane containing a methacryl group, 3-acryloxypropyltrimethoxysilane containing an acrylic group, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane containing an amino group. Containing N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, containing an isocyanate group, 3-isocyanatepropyltriethoxysilane containing an isocyanate group, tris-(trimethoxysilylpropyl)isocyanurate containing an isocyanurate group, 3-ureidopropyltrialkoxysilane containing a ureido group, 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane containing a mercapto group, or mixtures thereof can be used.

Silicone surfactants are compounds that consist of an organic group (organic compatible group) and a silicone chain (inorganic bonding group) that can condense with alkoxysilanes. Depending on the structure of the organic group, alkyl-modified silicone surfactants, polyether-modified silicone surfactants, polyether-alkyl co-modified silicone surfactants, etc. can be used.

Modified silicones are compounds that consist of an organically modified group (organically compatible group) and a silicone chain (inorganic bonding group) that can condense with alkoxysilanes. Depending on the structure of the organically modified group, amino-modified silicones, epoxy-modified silicones, carbinol-modified silicones, mercapto-modified silicones, etc. can be used.

It is preferable to include 5 to 50 g of the surface modifier per 1 mol of siloxane-bonded Si made of alkoxysilane. This is because the hollow particles 2 can be made compatible with the heat-insulating paint, and the hollow particles 2 are expelled so that the concentration increases from the inside of the heat-insulating paint toward the surface layer when the heat-insulating paint is formed, and aggregates 3 of the hollow particles 2 on the order of μm can be formed on the surface layer of the paint. If the content of the surface modifier is less than 5 g per mol of siloxane-bonded Si, the hollow particles 2 are difficult to dissolve in the heat-insulating paint, and are expelled to the surface layer of the heat-insulating paint when the heat-insulating paint is formed, and irregular aggregates 3 of the hollow particles 2 are formed on the surface layer of the paint, which makes the surface layer of the paint rough and may cause the paint to lose transparency. On the other hand, if the amount exceeds 50 g, most of the surface of the hollow particles 2 is modified with organic compatible groups, and the hollow particles 2 are compatible with the heat-insulating paint and are not excluded from the surface of the coating film, so there is a risk that the heat insulation properties cannot be improved. More preferably, the content of the surface modifier per 1 mol of Si in the siloxane bond is 10 to 30 g, and even more preferably, it is 15 to 25 g.

Hollow particles 2 are formed by adding calcium carbonate, alkoxysilane, and a surface modifier to a mixture of water and alcohol that has been made alkaline with ammonia water, and mixing the mixture, so that the calcium carbonate is coated with the alkoxysilane and the surface modifier, forming a siloxane-bonded shell that serves as the main skeleton of hollow particles 2. After the siloxane-bonded shell is formed, the calcium carbonate is dissolved by acid treatment, forming hollow particles 2 made of a siloxane-bonded shell.

The specific surface area of the hollow particles 2 is preferably 50 to 400 ^{m 2} /g. This is because the heat insulating properties of the heat insulating coating 1 containing the hollow particles 2 can be exhibited. If the specific surface area of the hollow particles 2 is less than 50 m ² /g, there is a risk that the heat insulating properties cannot be exhibited sufficiently. On the other hand, if the specific surface area of the hollow particles 2 exceeds 400 m ² /g, the shell thickness of the hollow particles 2 becomes relatively thin, and there is a risk that the hollow particles 2 will be damaged when the hollow particles 2 are mixed into the heat insulating coating material. More preferably, the specific surface area of the hollow particles 2 is 100 to 300 ^{m 2} /g.

The average particle diameter of the hollow particles 2 is preferably 10 to 200 nm. This is because the heat insulating coating 1 containing the hollow particles 2 can be made clear (transparent) while having heat insulating properties. If the average particle diameter of the hollow particles 2 is less than 10 nm, the shell of the hollow particles 2 becomes relatively thick, and the heat insulating properties may be poor. On the other hand, if it exceeds 200 nm, the transparency of the heat insulating coating 1 may be poor. More preferably, the average particle diameter of the hollow particles 2 is 50 to 150 nm.

Next, an embodiment of a heat insulating paint containing hollow particles 2 will be described. The heat insulating paint of this embodiment is a paint that uses a synthetic resin diluted with an organic solvent as a binder and contains 5 to 30 mass % of hollow particles 2 calculated as non-volatile matter.

The hollow particles 2 are the hollow particles 2 described above, and are preferably contained in the heat-insulating paint in an amount of 5 to 30% by mass, calculated as non-volatile content. This is because the heat-insulating coating film 1 formed from the heat-insulating paint can exhibit its heat-insulating properties. If the content of hollow particles 2 in the heat-insulating paint is less than 5% by mass, the aggregates 3 of hollow particles 2 formed on the surface layer of the coating film may become discontinuous, and the heat-insulating properties may be poor. On the other hand, if the content exceeds 30% by mass, the heat-insulating effect may plateau, and the heat-insulating properties may become uneconomical. More preferably, the content of hollow particles 2 in the heat-insulating paint in an amount of 7 to 25% by mass, and even more preferably, 10 to 20% by mass, calculated as non-volatile content.

The heat insulating paint can be obtained by mixing hollow particles 2 and a thinner (thinner) with a base agent whose main binder is synthetic resin while stirring. Other additives such as viscosity regulators, defoamers, and UV absorbers can be added to the heat insulating paint, and the viscosity can be adjusted with a thinner as needed. The heat insulating paint can also be used as a two-liquid (three-liquid) type consisting of a base agent whose main binder is synthetic resin, a hardener that hardens the base agent, and a thinner as needed.

The hollow particles 2 mixed into the heat insulating paint are hydrophilic because they are formed from siloxane bonds, but because they are modified with a surface modifier, they can be made compatible with organic solvent-based heat insulating paints. When the heat insulating paint is applied to the workpiece 6, the hollow particles 2 that are based on hydrophilic siloxane bonds become significantly hydrophilic as the heat insulating paint forms a film, and are expelled so that their concentration increases from the inside of the heat insulating paint toward the surface, forming aggregates 3 of the hollow particles 2 on the order of μm on the surface of the coating film. Therefore, the heat insulating coating film 1 formed from the heat insulating paint can exhibit heat insulating properties.

When the insulating paint containing hollow particles 2 is applied to an object 6, an insulating coating film 1 having an aggregate 3 of hollow particles 2 on the surface layer is formed. When the object 6 touches human skin 7, the aggregate 3 of hollow particles 2 slows down the heat transfer caused by the temperature difference between the object 6 and the human body, thereby mitigating the contact thermal sensation that the human feels as being cold or hot.

The heat insulating paint containing hollow particles 2 can be applied to building materials that come into direct contact with human skin 7, such as wood, glass, concrete, siding boards, plastic materials, and sanitary ware (washstands, toilet bowls, toilet seats), as well as to parts of automobiles that come into direct contact with people, such as the metal body, and interior plastic materials, such as the dashboard and steering wheel.

Table 1 shows the raw material blending amounts (mass) of hollow particles 2 of the examples, the acid treatment recipe, and the performance of hollow particles 2. In the table, hollow particles A as hollow particles 2 and heat insulating paint A using hollow particles A, hollow particles B and heat insulating paint B using hollow particles B, and hollow particles C and heat insulating paint C using hollow particles C are examples, and hollow particles D as hollow particles and heat insulating paint D using hollow particles D are comparative examples. Hollow particles A to C are hollow particles 2 whose main skeleton is formed from alkoxysilane and a surface modifier and whose surface is modified. Hollow particle D is a hollow particle whose main skeleton is formed from alkoxysilane and whose surface is not modified.

Calcium carbonate with an average particle size of 80 nm (average value of 50 particle sizes measured from SEM photographs) was used. Tetraethoxysilane was used as the alkoxysilane, 3-aminopropyltriethoxysilane, a silane coupling agent, was used as surface modifier A, XIAMETER OFX-0203, a silicone surfactant (an alkyl-modified silicone surfactant manufactured by Dow Toray Industries, Inc.), and KF-859, a modified silicone (an amino-modified silicone manufactured by Shin-Etsu Chemical Co., Ltd.), was used as surface modifier C.

Hollow particles A to C are formed through a reaction process and a dissolution process. In the reaction process, calcium carbonate is added and dispersed in a solvent consisting of ammonia water (25%), purified water, and methanol while stirring with an ultrasonic stirrer, and then alkoxysilane and surface modifier are added to the solvent in which calcium carbonate is dispersed while stirring. By continuing to stir, the calcium carbonate is covered with alkoxysilane and surface modifier, and a shell body consisting of siloxane bonds formed by condensation polymerization of the alkoxysilane and the surface modifier is formed. In the dissolution process, hydrochloric acid water is added to the solvent in which the calcium carbonate with the shell body formed is dispersed while stirring with a magnetic stirrer, dissolving the calcium carbonate and forming a shell body of siloxane bonds with a modified surface, that is, hollow particles A to C as hollow particle 2.

Hollow particles A to C each contain 20.8 g of modifier per 1 mol of Si in the siloxane bond of alkoxysilane (tetraethoxysilane). Hollow particle D was produced in the same manner as hollow particles A to C, but did not contain any modifier and formed a siloxane bond of alkoxysilane.

In hollow particle A, a layer of siloxane bonds is formed by condensation polymerization of alkoxysilane and ethoxysilane of the surface modifier 3-aminopropyltriethoxysilane. The formed layer of siloxane bonds is hydrophilic, but the surface of hollow particle A is semi-hydrophilic because of the aminopropyl group of 3-aminopropyltriethoxysilane. In hollow particle B, a layer of siloxane bonds is formed by condensation polymerization of alkoxysilane and silicone chain of alkyl-modified silicone of the surface modifier. The formed layer of siloxane bonds is hydrophilic, but the surface of hollow particle B is semi-hydrophilic because of the alkyl-modified group of alkyl-modified silicone. In hollow particle C, a layer of siloxane bonds is formed by condensation polymerization of alkoxysilane and silicone chain of amino-modified silicone of the surface modifier. The formed layer of siloxane bonds is hydrophilic, but the surface of hollow particle C is semi-hydrophilic because of the amino-modified group of amino-modified silicone. Hollow particles D are hydrophilic because they are produced by condensation polymerization of alkoxysilane only.

Hollow particles A to D can be dried to remove volatiles, resulting in hollow particles that can be used in heat insulating paints. Figure 6 shows an SEM photograph of hollow particle A. The scale bar in Figure 6 is 500 nm.

Next, the heat insulating paint will be described. Heat insulating paints A to C of the examples contain hollow particles A to C of the examples, respectively, and are composed of a base agent with synthetic resin as a binder, a hardener, and a thinner, which are mixed together to become a paint. The base agent, hardener, and thinner were each produced by mixing the raw materials in a dissolver mixer. Heat insulating paint D of the comparative example was produced in the same manner, using hollow particles D instead of hollow particles A to C. The raw material blend amounts (mass) of heat insulating paints A to D and the performance of the heat insulating coating film formed from heat insulating paints A to D are listed in Table 2. The raw material blend amounts are listed in non-volatile content conversion, excluding volatile content, and the volatile content (ester-based solvent) is added to the volatile content contained in the raw materials listed in non-volatile content conversion. The thermal conductivity was measured using a disk heat flow meter method (ASTM E 1530 JIS A 1412-2).

The main binder resin of heat-insulating paints A to D is acrylic polyol resin, and the hardener is isocyanate, which becomes a urethane-modified acrylic resin when mixed. The average molecular weight of the acrylic polyol resin is 35,000, and the glass transition temperature (Tg) is -10°C. Silicon-based additives include viscosity adjusters, defoamers, and UV absorbers. The ester-based solvent is ethyl acetate and/or butyl acetate.

Thermal insulation paints A to D are made by mixing the base agent, hardener, and thinner in a mass ratio of 100:25:75. The thermal insulation paint forms a thermal insulation coating when applied to the object 6 to be painted. In the examples, a wooden board (cedar board) was used as the object 6 to be painted.

When the insulating paints A to C are formed, the aminopropyl groups, alkyl-modified groups, and amino-modified groups of the semi-hydrophilic hollow particles A to C blend with the paint, but because the siloxane bond layer is hydrophilic, they are gradually expelled to the surface of the coating film. Therefore, when the coating is formed, the hollow particles A to C are present in such a way that the concentration of the hollow particles A to C increases toward the surface of the coating film. On the surface of the coating film, the volatile components evaporate, and the hollow particles A to C aggregate to form aggregates 3 with an uneven shape on the order of μm. The uneven shape on the order of μm reduces the contact area between the coating film and the human skin 7, and an air layer is interposed in the uneven shape, suppressing heat transfer, and the insulating paint film 1 has excellent thermal insulation properties (thermal conductivity). In addition, the transparency of the insulating coating film 1 was not hindered by the hollow particles A to C, and it remained transparent.

Figure 2 shows an SEM photograph of a cross section of the thermal insulation coating film 1 formed from thermal insulation paint A. From roughly the center of the upper part of Figure 2 to the lower right, it can be seen that the agglomerates 3 of hollow particles 2 form an uneven shape on the order of μm. To be precise, the agglomerates 3 of hollow particles 2 form an uneven shape of 0.2 to 2 μm. The lower left side of the uneven shape is the thermal insulation coating film 1.

Figure 3 shows a laser microscope photograph of a coating film formed from heat insulating paint A. The scale bar in Figure 3 is 100 μm. Figure 5 shows a laser microscope photograph of a coating film made of metallic paint, and the scale bar in Figure 5 is 100 μm. It can be confirmed that the coating film formed from heat insulating paint A containing semi-hydrophilic hollow particles A is smoother than the coating film formed from metallic paint. The surface of the heat insulating coating film 1 formed from heat insulating paint A was formed with an uneven shape on the order of μm, giving a smooth and dry feeling to the finger as skin 7. On the other hand, the surface of the coating film formed from metallic paint was formed with vein-like unevenness, giving a moist feeling to the finger.

In the case of the heat insulating paint D, the siloxane layer of the hollow particles D is hydrophilic, so that the hollow particles D are expelled to the surface of the coating film when the coating is formed. Therefore, the hollow particles D are present in a layer on the surface of the coating film, and shrink when the volatile components evaporate, forming a large (100 μm or more) uneven shape. Due to the large uneven shape, the coating film surface is rough, giving a rough feeling to the fingers. Because the coating film surface is rough, the area that comes into contact with the skin 7 of the human body is small, and in the measurement method of the embodiment, the heat insulating paint D has better heat insulation (thermal conductivity) than the heat insulating paints A to C. A laser microscope photograph of the coating film formed from the heat insulating paint D is shown in FIG. 4. The scale bar in FIG. 4 is 200 μm. It can be confirmed that the coating film formed from the heat insulating paint B has an uneven shape of 100 μm or more.

The following can be understood from the results of the examples:

The heat insulating coating film 1 formed from the heat insulating paint of the embodiment can have a surface roughness (Ra) of 0.1 to 0.4. This allows for a coating film with excellent smoothness and heat insulating properties. More preferably, the surface roughness (Ra) of the heat insulating coating film 1 formed from the heat insulating paint is 0.2 to 0.3.

The heat insulating coating film 1 formed from the heat insulating paint of the embodiment can have a surface haze measurement value of 40 to 90%. This allows the coating film to have a glossy finish. More preferably, the haze measurement value of the heat insulating coating film 1 formed from the heat insulating paint is 40 to 80%, and even more preferably, 50 to 70%.

The heat insulating coating film 1 formed from the heat insulating paint of the embodiment can have a thermal conductivity of 0.02 to 0.1 W/mK. This allows for a coating film with excellent heat insulating properties. More preferably, the heat insulating coating film 1 formed from the heat insulating paint has a thermal conductivity of 0.025 to 0.05 W/mK.

Other technical ideas that can be understood from the embodiments are described below.

Hollow particles characterized in that the alkoxysilane that forms the siloxane bond is tetraethoxysilane, the surface modifier is 3-aminopropyltriethoxysilane, and the surface modifier is contained in an amount of 5 to 30 parts by mass per 100 parts by mass of the alkoxysilane. This makes it possible to make the hollow particles semi-hydrophilic, and when a heat insulating coating containing the hollow particles is formed, the hollow particles have a well-balanced hydrophilicity, are expelled so that the concentration increases from the inside of the heat insulating coating toward the surface layer, and the volatile components volatilize, forming aggregates 3 of hollow particles on the order of μm on the surface layer of the coating. More preferably, the content of the surface modifier per 100 parts by mass of the alkoxysilane is 8 to 20 parts by mass.

The heat-insulating paint is characterized in that the glass transition temperature (Tg) of the synthetic resin used as the binder is -30 to 10°C. This allows the coating film formed from the heat-insulating paint to have flexibility that allows it to follow the expansion and contraction of the base, and the appropriate flexibility reduces adhesion of dirt to the coating film, allowing the coating film to maintain its beautiful appearance.

1...Thermal insulation coating, 2...Hollow particles, 3...Agglomerates, 6...Subject to be coated, 7...Skin.

Claims (5)

A method for forming a heat insulating coating film formed from a heat insulating paint, the method comprising the steps of:
The hollow particles have an average particle diameter of 10 to 200 nm, have a main skeleton of a siloxane bond formed from tetraethoxysilane as an alkoxysilane, and are modified with 3-aminopropyltriethoxysilane as a surface modifier;
The heat insulating coating composition has a binder resin as a main component that is an acrylic polyol resin, a curing agent that is an isocyanate, and contains 5 to 30 mass % of the hollow particles calculated as non-volatile matter,
When the heat insulating coating film is formed from the heat insulating paint, the hollow particles are expelled from the inside of the heat insulating paint toward the surface layer so that the concentration of the hollow particles increases, and an aggregate of hollow particles is formed on the surface layer of the heat insulating coating film.
A method for forming a heat insulating coating film. The method for forming a heat insulating coating film according to claim 1, characterized in that the hollow particles contain 5 to 50 g of the surface modifier per 1 mol of Si in the siloxane bond. The method for forming a heat insulating coating film according to claim 1, characterized in that the hollow particles contain 5 to 30 parts by mass of the surface modifier per 100 parts by mass of the alkoxysilane. The method for forming a heat insulating coating film according to any one of claims 1 to 3, characterized in that the glass transition temperature (Tg) of the synthetic resin used as the binder of the heat insulating coating is -30 to 10°C. The method for forming a heat insulating coating according to any one of claims 1 to 4, characterized in that the aggregates form an uneven shape on the order of μm on the surface of the coating.

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