JP7544121B2 - Manufacturing method of the joint body - Google Patents

Description

The present invention relates to a method for manufacturing a bonded body that is suitable for applications in which dissimilar materials are easily and firmly bonded.

In recent years, with the aim of reducing product weight and improving performance, the use of multi-material parts has been progressing in various fields, including automobile parts, medical equipment, and home appliances. Multi-materialization is a method of reducing the weight and increasing the strength of materials by combining materials with different functions and properties (hereinafter referred to as dissimilar materials). To achieve multi-materialization, technology that can firmly join dissimilar materials is essential.

As a means for firmly joining different materials, a liquid adhesive, such as thermosetting epoxy resin adhesive (Patent Document 1, etc.), is widely used.
Bonding using a liquid adhesive requires a coating step of coating a liquid resin composition and a curing step of curing the resin composition by polymerization reaction after coating.
For this reason, when bonding is performed using a liquid adhesive, there is a problem that it takes a long time to apply the resin composition in the application process, and the polymerization reaction takes a long time in the curing process (i.e., the bonding process takes a long time), resulting in a lack of convenience.
In this specification, the bonding process time means the time from the start point when the bonding agent contacts at least one of the substrates constituting the bonded body to the end point when the fabrication of the bonded body is completed, including, for example, the time required for the step of applying a liquid adhesive to the substrates, the step of drying the adhesive, the step of placing a solid bonding agent, and the time required for bonding the substrates together (for example, curing the adhesive layer).

A technique has also been disclosed in which an epoxy resin composition is impregnated into or coated on a substrate, and then semi-cured (B-staged), to produce a laminate with an adhesive layer in the B-stage state, which is then used for producing a bonded body (Patent Document 2, etc.).
However, bonding using a B-stage adhesive also requires a curing step in which the adhesive layer in a semi-cured state is cured by polymerization reaction, and this poses the problem of a long bonding process time.
Furthermore, B-stage adhesives have problems in that they have poor storage stability, cannot be stored for long periods at room temperature, must be stored at low temperatures, and have a short open time, making them inconvenient.
In this specification, the open time means the time limit from when a bonding agent is applied or placed on substrate A until when substrate B is completely placed. Within the open time, the adhesive strength of the bonding agent does not decrease, and substrate A and substrate B can be bonded with sufficient adhesive strength. The longer the open time, the longer the time limit from when a bonding agent is applied or placed on substrate A until when substrate B is completely placed, and the more convenient it is.

Thermoplastic adhesive compositions (hereafter referred to as hot melt adhesives) are also used as a means of joining dissimilar materials (Patent Document 3, etc.). By using hot melt adhesives, specifically, because hot melt adhesives use a phase change that does not involve a polymerization reaction to bond, no application process is required and the curing time is quick (i.e., the joining process time is short), making them highly convenient. In addition, they can be stored for long periods at room temperature, and are also convenient in that they have a long open time.

However, conventional hot melt adhesives are made of crystalline resins or resins that contain crystalline resins in order to reduce the melt viscosity, which means that the adhesive resin has high cohesive forces and is unable to interact sufficiently with the substrate. Furthermore, when melted and bonded, the adhesive has low viscosity at high temperatures, making it prone to flowing out from the bonding surface, and the viscosity is difficult to control, resulting in an unstable film thickness. Due to these factors, there is a problem with conventional hot melt adhesives in that they are unable to stably obtain high adhesive strength.

JP 2019-157018 A Japanese Patent Application Publication No. 10-17685 Japanese Patent Application Publication No. 10-168417

As described above, among the conventional technologies, thermosetting epoxy resin adhesives with excellent adhesive properties, whether in liquid or B-stage form, have at least one of the problems of a long bonding process time and a short open time, and hot melt adhesives with a short bonding process time and a long open time have the problem of being unable to stably obtain high adhesive strength.

The present invention was made in consideration of this technical background, and aims to provide a technology for joining a substrate A, which is a magnetic substrate, and a substrate B, which is a non-magnetic substrate, which has a short joining process time, a long open time, and excellent adhesion.

In order to achieve the above object, the present invention provides the following means.
In this specification, bonding means joining two objects together, and adhesion and welding are subordinate concepts. Adhesion means joining two adherends (objects to be bonded) together using an organic material such as tape or adhesive (thermosetting resin, thermoplastic resin, etc.), while welding means melting the surface of a thermoplastic resin or the like by heat, and joining the objects by entanglement and crystallization due to molecular diffusion through contact pressure and cooling.

<Method of manufacturing bonded body - embodiment 1>
[1]
a pre-bonding process of preparing a laminate by arranging, in this order, a base material A which is a magnetic base material, a solid adhesive containing at least one amorphous thermoplastic resin selected from a thermoplastic epoxy resin and a phenoxy resin, and a base material B which is a non-magnetic base material;
a bonding step of heating and pressurizing the laminate to melt the solid bonding agent and bond the base material A and the base material B,
The method for producing a joined body, wherein the amorphous thermoplastic resin has an epoxy equivalent of 1,600 or more or does not contain an epoxy group and has a heat of fusion of 15 J/g or less.
[2]
The method for producing a bonded body according to [1], wherein the heating and pressurizing are carried out under conditions of 100 to 400° C. and 0.01 to 20 MPa.
[3]
The method for producing a bonded body according to [1] or [2], wherein the solid bonding agent before melting has a film shape.

<Method of manufacturing bonded body - embodiment 2>
[4]
A method for producing a bonded body, which is obtained by bonding, in this order, a base material A which is a magnetic base material, a solid bonding agent which contains at least one amorphous thermoplastic resin selected from a thermoplastic epoxy resin and a phenoxy resin, and a base material B which is a non-magnetic base material, the method comprising the steps of:
a first bonding step of bonding the base material A and the solid bonding agent together by melting and then solidifying the solid bonding agent in a state where the solid bonding agent is in contact with the base material A, or bonding the base material B and the solid bonding agent together by melting and then solidifying the solid bonding agent in a state where the solid bonding agent is in contact with the base material B;
a second bonding step of bonding the substrate A and the substrate B together by melting and then solidifying the solid bonding agent in a state where the pre-solid bonding agent bonded to the substrate A is brought into contact with the substrate B, or by melting and then solidifying the solid bonding agent in a state where the pre-solid bonding agent bonded to the substrate B is brought into contact with the substrate A,
The method for producing a bonded body, wherein the amorphous thermoplastic resin has an epoxy equivalent of 1,600 g/eq. or more or does not contain an epoxy group, and has a heat of fusion of 15 J/g or less.
[5]
The method for manufacturing a bonded body according to [4], wherein in the first bonding step, the melting of the solid bonding agent is performed under heating conditions of 100 to 300° C.
[6]
The method for producing a joined body according to [4] or [5], wherein in the second joining step, the solid joining agent is melted by at least one selected from the group consisting of contact heating, hot air heating, heat pressing, infrared heating, hot plate welding, ultrasonic welding, vibration welding, and high-frequency induction welding.
[7]
The method for manufacturing a bonded body according to any one of [4] to [6], wherein in the second bonding step, the melting of the solid bonding agent is performed under heating conditions of 100 to 400° C. and pressure conditions of 0.01 to 20 MPa.
[8]
The method for producing a bonded body according to any one of [1] to [7], wherein the solid bonding agent before melting has a film shape.

<Joint>
[9]
A bonded body obtained by bonding a substrate A, which is a magnetic substrate, and a substrate B, which is a non-magnetic substrate, via an adhesive layer,
The adhesive layer is at least one selected from a thermoplastic epoxy resin and a phenoxy resin, and the adhesive layer is formed by disposing a solid adhesive agent containing an amorphous thermoplastic resin having an epoxy equivalent of 1,600 or more and a heat of fusion of 15 J/g or less between the base material A and the base material B, heating and pressurizing the solid adhesive agent to melt the solid adhesive agent, and solidifying the solid adhesive agent.
[10]
The bonded body according to [9], wherein the heating and pressurizing are performed under conditions of 100 to 400° C. and 0.01 to 20 MPa.

The present invention provides a technology for joining a substrate A, which is a magnetic substrate, and a substrate B, which is a non-magnetic substrate, that has a short joining process time, a long open time, and excellent adhesion.

FIG. 2 is an explanatory diagram showing a configuration of a bonded body according to one embodiment of the present invention.

[Method of manufacturing a bonded body - embodiment 1]
The manufacturing method of the joined body of the first embodiment includes a pre-joining process of preparing a laminate by arranging, in this order, a base material A which is a magnetic base material, a solid adhesive containing at least one amorphous thermoplastic resin selected from a thermoplastic epoxy resin and a phenoxy resin, and a base material B which is a non-magnetic base material, and a joining process of heating and pressurizing the laminate to melt the solid adhesive and join the base material A and the base material B.
In the pre-bonding step, the substrate A and the solid adhesive and the substrate B and the solid adhesive are not bonded to each other, but are bonded to each other in the next bonding step. The solid adhesive may have tackiness, and in that case, the solid adhesive is temporarily fixed to the substrate in the pre-bonding step.

Each process is explained below.

<Pre-bonding process>
In the pre-bonding process, a laminate is prepared by arranging a substrate A, a solid bonding agent containing at least one amorphous thermoplastic resin selected from a thermoplastic epoxy resin and a phenoxy resin, and a substrate B in this order.
In the laminate, neither the base material A nor the solid adhesive is bonded to the base material B, and the solid adhesive is not bonded to the base material B, and each of the laminates is formed by overlapping independent members.
The term "solid" in the solid binder means that the solid binder is solid at room temperature, that is, has no fluidity at 23° C. without pressure.
It is desirable that the solid adhesive has the property of being able to retain its shape without deformation for 30 days or more under no pressure at 23° C., and furthermore, not being deteriorated.

(Solid adhesive)
The solid bonding agent includes at least one amorphous thermoplastic resin selected from a thermoplastic epoxy resin and a phenoxy resin, the amorphous thermoplastic resin having an epoxy equivalent of 1,600 or more and a heat of fusion of 15 J/g or less.
The amorphous resin in the present invention is a resin that has a melting point (Tm) in a measurement using a differential scanning calorimeter (DSC), but does not have a clear endothermic peak (melting point) associated with melting, or has a very small Tm. The heat of fusion is calculated from the area of the endothermic peak of the DSC and the weight of the thermoplastic resin component. When an inorganic filler or the like is contained in the solid bonding agent, it is calculated from the weight of the resin component excluding the inorganic filler. Specifically, the amorphous thermoplastic resin in the present invention refers to the following. 2-10 mg of a sample is weighed out, placed in an aluminum pan, and heated from 23°C to 200°C or higher at 10°C/min using a DSC (DSC8231 manufactured by Rigaku Corporation) to obtain a DSC curve. Next, when the heat of fusion is calculated from the area of the endothermic peak at the time of melting obtained from the DSC curve and the weighed value, the resin has a heat of fusion of 15 J/g or less.

In order to fully impart the properties of an amorphous thermoplastic resin to the solid bonding agent, the content of the amorphous thermoplastic resin is preferably 51% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, and most preferably 90% by mass or more of the resin components in the solid bonding agent. In this disclosure, "resin components in a solid thermally conductive material" refers to components other than the filler in the solid thermally conductive material.

The heat of fusion is 15 J/g or less, preferably 11 J/g or less, more preferably 7 J/g or less, even more preferably 4 J/g or less, and most preferably the melting peak is below the detection limit.
The epoxy equivalent is 1,600 or more, preferably 2,000 or more, more preferably 5,000 or more, and even more preferably 9,000 or more, and most preferably above the detection limit so that substantially no epoxy groups are detected.

By using a solid adhesive containing an amorphous thermoplastic resin with an epoxy equivalent of 1,600 or more and a heat of fusion of 15 J/g or less, the rapid viscosity drop seen in conventional hot melt adhesives does not occur when heated, and the adhesive does not reach a low viscosity (0.001 to 100 Pa·s) state even in a high temperature range exceeding 200° C. Therefore, the solid adhesive does not flow out of the laminate even in a molten state, the thickness of the adhesive layer can be stably secured, and high adhesive strength can be stably obtained.
The epoxy equivalent weight (weight of the resin containing 1 mole of epoxy groups) referred to here is the epoxy equivalent weight of the thermoplastic epoxy resin or phenoxy resin component contained in the solid adhesive before bonding, and is a value (unit: g/eq.) measured by the method specified in JIS-K7236:2001. Specifically, a potentiometric titration device was used, cyclohexanone was used as the solvent, brominated tetraethylammonium acetate solution was added, and a 0.1 mol/L perchloric acid-acetic acid solution was used, and the solvent-diluted product (resin varnish) was calculated as a solid content equivalent value from the non-volatile content. In the case of a mixture of two or more resins, it can also be calculated from the content and epoxy equivalent weight of each resin.

The melting point of the amorphous thermoplastic resin contained in the solid bonding agent is preferably 50 to 400° C., more preferably 60 to 350° C., and even more preferably 70 to 300° C. By having a melting point in the range of 50 to 400° C., the solid bonding agent is efficiently deformed and melted by heating and effectively wets and spreads over the bonding surface, resulting in high adhesive strength.
In this specification, the melting point of an amorphous thermoplastic resin means the temperature range in the process where the resin softens from a substantially solid state, acquires thermoplastic properties, and becomes meltable and adhesive.

Conventional thermosetting adhesives have problems in that it is difficult to dismantle the bonded body, making it difficult to separate and recycle the different materials that make up the bonded body (i.e., poor recyclability), and it is difficult to reattach the bonded body when there is a misalignment at the joint during the manufacturing process of the bonded body, or when the contents or adherend have a defect and need to be replaced (i.e., poor repairability), resulting in a lack of convenience. However, the solid adhesive can be softened and melted by heat and can be easily peeled off, making it highly recyclable. In addition, because the solid adhesive is thermoplastic, it can be reversibly softened, melted, and hardened repeatedly, making it highly repairable.

<Thermoplastic epoxy resin>
The thermoplastic epoxy resin is preferably a polymer of (a) a difunctional epoxy resin monomer or oligomer and (b) a difunctional compound having two identical or different functional groups selected from the group consisting of a phenolic hydroxyl group, a carboxyl group, a mercapto group, an isocyanate group, and a cyanate ester group.
By using such a compound, the polymerization reaction for forming a linear polymer proceeds preferentially, making it possible to obtain a thermoplastic epoxy resin having the desired properties.

The (a) bifunctional epoxy resin monomer or oligomer refers to an epoxy resin monomer or oligomer having two epoxy groups in the molecule.
Specific examples of the (a) include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bifunctional phenol novolac type epoxy resins, bisphenol AD type epoxy resins, biphenyl type epoxy resins, bifunctional naphthalene type epoxy resins, bifunctional alicyclic epoxy resins, bifunctional glycidyl ester type epoxy resins (e.g., diglycidyl phthalate, diglycidyl tetrahydrophthalate, dimer acid diglycidyl ester, etc.), bifunctional glycidyl amine type epoxy resins (e.g., diglycidyl aniline, diglycidyl toluidine, etc.), bifunctional heterocyclic epoxy resins, bifunctional diarylsulfone type epoxy resins, hydroquinone type epoxy resins (e.g., hydroquinone diglycidyl ether, 2,5-di-tert-butyl ether, etc.), t-Butylhydroquinone diglycidyl ether, resorcin diglycidyl ether, etc.), bifunctional alkylene glycidyl ether compounds (e.g. butanediol diglycidyl ether, butenediol diglycidyl ether, butynediol diglycidyl ether, etc.), bifunctional glycidyl group-containing hydantoin compounds (e.g. 1,3-diglycidyl-5,5-dialkylhydantoin, 1-glycidyl-3-(glycidoxyalkyl)-5,5-dialkylhydantoin, etc.), bifunctional glycidyl group-containing siloxanes (e.g. 1,3-bis(3-glycidoxypropyl)-1,1,3,3-tetramethyldisiloxane, α,β-bis(3-glycidoxypropyl)polydimethylsiloxane, etc.), and modified products thereof. Among these, bisphenol A type epoxy resins, bisphenol F type epoxy resins, and biphenyl type epoxy resins are preferred in terms of reactivity and workability.
Examples of the (b) bifunctional compound having a phenolic hydroxyl group include mononuclear aromatic dihydroxy compounds having one benzene ring, such as catechol, resorcin, and hydroquinone; bisphenols, such as bis(4-hydroxyphenyl)propane (bisphenol A), bis(4-hydroxyphenyl)methane (bisphenol F), and bis(4-hydroxyphenyl)ethane (bisphenol AD); compounds having a condensed ring, such as dihydroxynaphthalene; bifunctional phenol compounds having an allyl group introduced therein, such as diallyl resorcin, diallyl bisphenol A, and triallyl dihydroxybiphenyl; and dibutyl bisphenol A.
Specific examples of the carboxyl group-containing compound (b) include adipic acid, succinic acid, malonic acid, cyclohexanedicarboxylic acid, phthalic acid, isophthalic acid, and terephthalic acid.
Examples of the (b) bifunctional compound having a mercapto group include ethylene glycol bisthioglycolate and ethylene glycol bisthiopropionate.
Specific examples of the (b) isocyanate group-containing bifunctional compound include diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HMDI), and tolylene diisocyanate (TDI).
Specific examples of the (b) cyanate ester group-containing bifunctional compound include 2,2-bis(4-cyanatophenyl)propane, 1,1-bis(4-cyanatophenyl)ethane, and bis(4-cyanatophenyl)methane.
Among the above (b), a bifunctional compound having a phenolic hydroxyl group is preferred from the viewpoint of obtaining a thermoplastic polymer, a bifunctional compound having two phenolic hydroxyl groups and a bisphenol structure or a biphenyl structure is preferred from the viewpoint of heat resistance and adhesiveness, and bisphenol A, bisphenol F or bisphenol S is preferred from the viewpoint of heat resistance and cost.

When the (a) is a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a bisphenol S type epoxy resin, or a biphenyl type epoxy resin, and the (b) is bisphenol A, bisphenol F, or bisphenol S, the polymer obtained by polymerization of the (a) and (b) has a main chain having a paraphenylene structure and an ether bond as a main skeleton, the main chain being linked by an alkylene group, and a structure in which a hydroxyl group generated by polyaddition is arranged in a side chain.
The linear structure of the paraphenylene skeleton can increase the mechanical strength of the polymer after polymerization, and the hydroxyl groups arranged in the side chains can improve adhesion to the substrate. As a result, high adhesive strength can be achieved while maintaining the workability of thermosetting resins. Furthermore, in the case of thermoplastic resins, recycling and repair are possible by softening and melting with heat, and the recyclability and repairability, which are problems with thermosetting resins, can be improved.

Phenoxy resin
Phenoxy resin is a polyhydroxy polyether synthesized from bisphenols and epichlorohydrin, and has thermoplasticity. For the production of phenoxy resin, a method by direct reaction of dihydric phenols with epichlorohydrin and a method by addition polymerization reaction of diglycidyl ether of dihydric phenols with dihydric phenols are known, but the phenoxy resin used in the present invention may be obtained by either method. In the case of direct reaction of dihydric phenols with epichlorohydrin, examples of dihydric phenols include phenols such as bisphenol A, bisphenol F, bisphenol S, biphenol, biphenylenediol, and fluorenediphenyl; and aliphatic glycols such as ethylene glycol, propylene glycol, and diethylene glycol. Among them, bisphenol A, bisphenol F, and bisphenol S are preferred from the viewpoints of cost, adhesiveness, viscosity, and heat resistance. These may be used alone or in combination of two or more.
Phenoxy resin has a chemical structure similar to that of epoxy resin, with a paraphenylene structure and an ether bond as the main skeleton, a main chain connecting these, and a structure in which hydroxyl groups are arranged in the side chains.

<Physical properties of thermoplastic epoxy resin and phenoxy resin>
The thermoplastic epoxy resin and the phenoxy resin preferably have a weight average molecular weight of 10,000 to 500,000, more preferably 18,000 to 300,000, and even more preferably 20,000 to 200,000, which is a value calculated in terms of polystyrene by GPC (gel permeation chromatography). The weight average molecular weight is calculated from the elution peak position detected by GPC, and each is a value of the molecular weight in terms of standard polystyrene. When the weight average molecular weight is within this range, the balance between thermoplasticity and heat resistance is good, and a bonded body can be efficiently obtained by melting, and the heat resistance is also high. When the weight average molecular weight is 10,000 or more, the heat resistance is excellent, and when it is 500,000 or less, the viscosity during melting is low and the adhesiveness is high.

<Components other than resin components in solid adhesive>
If necessary, the solid bonding agent may contain fillers and additives as components other than the resin component, provided that the object of the present invention is not impaired.

The filler includes an inorganic filler and an organic filler (resin powder).
Examples of inorganic fillers include spherical fused silica, metal powders such as iron, silica sand, talc, calcium carbonate, mica, acid clay, diatomaceous earth, kaolin, quartz, titanium oxide, silica, phenolic resin microballoons, and glass balloons.
When a filler is contained, the content of the filler in the total amount (100 volume %) of the solid bonding agent is preferably 50 volume % or less, more preferably 30 volume % or less, even more preferably 20 volume % or less, and most preferably 10 volume % or less.
The filler content (volume %) is determined from the amount charged at 25°C. Specifically, it is calculated by the following formula 1 based on the mass % of the filler, the specific gravity of the components other than the filler, and the true specific gravity of the filler.
(Equation 1)
X=(MF/DF)÷(MF/DF+(100-MF)/DR)×100%
In formula 1,
X: Filler content (volume%)
MF: Filler content (% by mass)
DR: Specific gravity of the resin component when hardened
DF: True specific gravity of the filler.

Examples of the additives include antifoaming agents, coupling agents such as silane coupling agents, pigments, etc., and these may be contained alone or in combination of two or more.
The content of the additive in the film is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 1% by mass or less.
The content of the resin component in the film is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and still more preferably 50% by mass or more, in one embodiment 80% by mass or more, in another embodiment 90% by mass or more, and in another embodiment 99% by mass or more.

<<Method for manufacturing solid adhesive>>
The method for producing the solid adhesive is not particularly limited, but for example, it can be obtained by heating and polymerizing a monomer or oligomer of a bifunctional epoxy compound. A solvent may be added during polymerization to reduce the viscosity and facilitate stirring. If a solvent is added, it must be removed, and the solid adhesive may be obtained by drying or polymerization, or both, on a release film or the like.

Examples of the additives include viscosity adjusters, inorganic fillers, organic fillers (resin powders), antifoaming agents, coupling agents such as silane coupling agents, pigments, etc., and these can be used alone or in combination of two or more.
As the viscosity modifier, for example, a reactive diluent or the like can be used.
Examples of inorganic fillers include spherical fused silica, metal powders such as iron, silica sand, talc, calcium carbonate, mica, acid clay, diatomaceous earth, kaolin, quartz, titanium oxide, silica, phenolic resin microballoons, and glass balloons.
The solid bonding agent thus obtained has a small or substantially no content of unreacted monomers or terminal epoxy groups, and therefore has excellent storage stability and can be stored for long periods at room temperature.

The form of the solid adhesive is not particularly limited, but it is preferable that the adhesive has any shape selected from the group consisting of a film, a rod, a pellet, and a powder. In particular, it is preferable that at least one side of the outer shape is 5 mm or less, more preferably 3 mm or less, even more preferably 1 mm or less, even more preferably 0.5 mm or less, and most preferably 0.3 mm or less. If the size is within such a range, it can be sandwiched between substrate A and substrate B and efficiently spread over the bonding surface by heating and pressurization, resulting in high adhesive strength.

The solid adhesive may have tackiness to the extent that it does not impair the adhesive strength or heat resistance. In that case, the solid adhesive is temporarily fixed to the substrate in the laminate preparation process.

<Joining process>
In the bonding step, the laminate is heated and pressurized to melt the solid bonding agent, and then the temperature is lowered to solidify the solid bonding agent, thereby bonding the base material A and the base material B together.

The temperature for the heating and pressurization is preferably 100 to 400° C., more preferably 120 to 350° C., and even more preferably 150 to 300° C. By heating at 100 to 400° C., the solid adhesive is efficiently deformed and melted, and effectively wets and spreads over the bonding surface, resulting in high adhesive strength.
The pressure in the heating and pressing is preferably 0.01 to 20 MPa, more preferably 0.1 to 10 MPa, and even more preferably 0.2 to 5 MPa. Within this pressure range, the solid bonding agent is efficiently deformed and effectively wets and spreads over the bonding surface, resulting in high adhesive strength. When at least one of the substrates A and B is a thermoplastic resin, applying pressure at 0.01 to 20 MPa makes the solid bonding agent and the substrate compatible, resulting in high adhesive strength.

The amorphous thermoplastic resin contained in the solid adhesive has low cohesive strength within the resin and contains hydroxyl groups, which gives it strong interaction with the substrate and allows it to bond dissimilar materials with stronger adhesive strength than conventional crystalline hot melt adhesives.

In this embodiment, the bonding of the substrate A and the substrate B utilizes the phase change (solid to liquid to solid) of the solid bonding agent, and does not involve a chemical reaction, so bonding can be completed in a shorter time than with conventional thermosetting epoxy resins.

[Method of manufacturing joined body - embodiment 2]
The manufacturing method of the joined body according to the present embodiment is a manufacturing method of a joined body obtained by joining a base material A which is a magnetic base material, a solid adhesive containing at least one amorphous thermoplastic resin selected from a thermoplastic epoxy resin and a phenoxy resin, and a base material B which is a non-magnetic base material in this order, and in a state where the solid adhesive is brought into contact with the base material A, the solid adhesive is melted and then solidified to join the base material A and the solid adhesive, or in a state where the solid adhesive is brought into contact with the base material B, the solid adhesive is melted and then solidified to join the base material A and the solid adhesive. The method includes a first joining step of joining the base material B and the solid adhesive by melting and solidifying the solid adhesive in a state where the pre-solid adhesive bonded to the base material A is brought into contact with the base material B, and a second joining step of joining the base material A and the base material B by melting and solidifying the solid adhesive in a state where the pre-solid adhesive bonded to the base material B is brought into contact with the base material A, or by melting and solidifying the solid adhesive in a state where the pre-solid adhesive bonded to the base material B is brought into contact with the base material A, and the amorphous thermoplastic resin has an epoxy equivalent of 1,600 g/eq. or more or does not contain an epoxy group, and has a heat of fusion of 15 J/g or less.

In this embodiment, the bonding of the substrate A and the substrate B is also achieved by utilizing the phase change (solid-liquid-solid) of the solid bonding agent, as in the first embodiment, and does not involve a chemical reaction, so that bonding can be completed in a shorter time than with conventional thermosetting epoxy resins, and the open time is also longer. In addition, thermoplastic epoxy resins and phenoxy resins have low cohesive strength within the resin and contain hydroxyl groups, so that they have strong interactions with the substrate and can bond different materials with a stronger bonding strength than conventional crystalline hot melt adhesives.
In addition, the manufacturing method is divided into a first bonding step and a second bonding step. By dividing the steps in this way, the bonding can be performed by heating at a temperature suitable for the bonding interface, and a bonded body with excellent bonding properties can be manufactured. In addition, the heating temperature control is also easier than when the steps are not divided. Furthermore, by bonding a film to the base material A or the base material B in advance, the base material A and the base material B can be bonded with high accuracy, and the occurrence of misalignment at the bonding point can be suppressed.

<First bonding step>
The first joining process is a process of joining the base material A and the solid adhesive by melting and solidifying the solid adhesive while the solid adhesive is in contact with the base material A, or a process of joining the base material B and the solid adhesive by melting and solidifying the solid adhesive while the solid adhesive is in contact with the base material B.
In the first bonding step, the base material A or the base material B is bonded to the solid bonding agent in advance, whereby the base material A and the base material B can be bonded with high precision.
In this specification, "solidified" means a solid at room temperature, that is, a non-fluid film in the absence of pressure at 23° C. However, the film after the first bonding step may have tackiness.

The method for melting the solid adhesive may be at least one method selected from the group consisting of contact heating, hot air heating, heat pressing, hot plate welding, infrared heating, ultrasonic welding, vibration welding, and high-frequency induction welding. Among these, infrared heating is preferred from the viewpoints of ease of manufacturing and shortening the joining process.

When the solid adhesive is melted by heating, the temperature of the bonding surface of the substrate A or substrate B with the solid adhesive is preferably heated to 100 to 300° C., more preferably 120 to 250° C., and further preferably 150 to 220° C. By heating at 100 to 300° C., the film is efficiently deformed and melted, and effectively wets and spreads over the bonding surface, resulting in a high bonding strength.
Methods for solidifying the molten solid adhesive include a method of cooling at room temperature and a method of cooling using a cooling device. Note that "room temperature" means a general room temperature within the range of 5 to 30° C. Among these, the method of cooling at room temperature is preferred from the viewpoint of ease of production.

(Solid adhesive)
The solid adhesive is the same as that in the above-mentioned embodiment 1, but the solid adhesive in this embodiment is preferably a film. In the present disclosure, the film means a sheet-like material having a thickness of 10 μm to 3 mm.

Film Form
From the viewpoint of obtaining a bonded body having excellent bondability in a short bonding process time, the thickness of the film is preferably 1 mm or less, more preferably 0.5 mm or less, even more preferably 0.3 mm or less, even more preferably 0.2 mm or less, and most preferably 0.1 mm or less.
When the size falls within this range, the adhesive can be sandwiched between base material A and base material B and efficiently spread across the bonding surface by application of heat, pressure, etc., resulting in a high bonding strength.

The film may be a single layer or a laminate made of multiple layers, but is preferably a single layer from the viewpoints of ease of production and improved bonding strength.
The film may also have tackiness to the extent that it does not impair its adhesive strength or heat resistance.

<Film manufacturing method>
The method for producing the film is not particularly limited, but for example, a resin composition may be obtained by heating and polymerizing a monomer or oligomer of a bifunctional epoxy compound, adding a solvent to the obtained resin composition as necessary, applying the composition to a release film or the like, curing and drying, and applying pressure as necessary to obtain a film.

<Second bonding step>
The second bonding process is a process of bonding the substrates A and B by melting and solidifying the solid bonding agent while the pre-solid bonding agent bonded to the substrate A is brought into contact with the substrate B, or a process of bonding the substrates A and B by melting and solidifying the solid bonding agent while the pre-solid bonding agent bonded to the substrate B is brought into contact with the substrate A.

In order to obtain a high bonding strength, it is preferable that in the second bonding step, the film is heated to a temperature equal to or higher than its melting point to melt and then solidify the film.

The method for melting the film may be at least one method selected from the group consisting of contact heating, hot air heating, heat pressing, infrared heating, hot plate welding, ultrasonic welding, vibration welding, and high-frequency induction welding. Among these, heat pressing, ultrasonic welding, and high-frequency induction welding are preferred.

The conditions for carrying out the heat press are not particularly limited.
For example, the temperature is preferably 100 to 400° C., more preferably 120 to 350° C., and even more preferably 150 to 300° C. By heating at 100 to 400° C., the film efficiently deforms and melts, and effectively wets and spreads over the bonding surface, resulting in high bonding strength.
The pressure in the heat press is preferably 0.01 to 20 MPa, more preferably 0.1 to 10 MPa, and even more preferably 0.2 to 5 MPa. Within this pressure range, the film is efficiently deformed and effectively wets and spreads over the joining surface, resulting in a high joining strength.
There are no particular limitations on the conditions for performing high-frequency induction welding.
For example, the transmission frequency is preferably 0.1 to 3 MHz, and more preferably 0.5 to 2 MHz.
From the viewpoints of adhesion and appearance, the application time of the high frequency is preferably 0.1 to 120 seconds, and more preferably 1 to 60 seconds.
When the substrate A and the substrate B are pressed together during application of the high frequency, the pressure is preferably 0.01 to 20 MPa, more preferably 0.1 to 10 MPa, and even more preferably 0.2 to 5 MPa. Within this pressure range, the solid adhesive is efficiently deformed and effectively wets and spreads over the bonding surface, resulting in high adhesive strength.

There are no particular limitations on the conditions for performing high-frequency induction welding.
For example, the output may be in the range of 100 to 10,000 W.

There are no particular limitations on the conditions for ultrasonic welding.
For example, the transmission frequency is preferably 10 to 70 kHz, and more preferably 15 to 40 kHz.
From the viewpoints of adhesion and appearance, the ultrasonic application time is preferably 0.1 to 3 seconds, and more preferably 0.2 to 2 seconds.
When applying pressure to the substrate A and the substrate B during the application of ultrasonic waves, the pressure is preferably 0.01 to 20 MPa, more preferably 0.1 to 10 MPa, and even more preferably 0.2 to 5 MPa. Within this pressure range, the solid adhesive is efficiently deformed and effectively wets and spreads over the bonding surface, resulting in high adhesive strength.

There are no particular limitations on the conditions for ultrasonic welding.
For example, the oscillation frequency may be in the range of 1 to 1500 kHz. The oscillation frequency may be adjusted to an appropriate value depending on the size and type of the substrate A and the substrate B.
The output power may range from 100 to 5000W.
The oscillation time may be adjusted depending on the size and type of the substrate A and substrate B, and is, for example, preferably 1.0 to 10.0 seconds, and more preferably 1.5 to 8.0 seconds.

As described above, the bonding of substrate A and substrate B in this embodiment utilizes the phase change (solid - liquid - solid) of the solid bonding agent, and does not involve a chemical reaction, so bonding can be completed in a shorter time than with conventional thermosetting epoxy resins.

[Conjugate]
FIG. 1 shows one embodiment of the bonded body of the present invention. The bonded body 1 shown in FIG. 1 is a bonded body in which a substrate A (3) which is a magnetic substrate and a substrate B (4) which is a non-magnetic substrate are bonded and integrated through a bonding layer 2 which is formed by melting and solidifying a film made of at least one amorphous thermoplastic resin selected from a thermoplastic epoxy resin and a phenoxy resin. The bonded body of the present invention exhibits excellent bonding strength even when it is a bonded body of different materials. The bonding strength is affected by many factors such as the thickness of the bonding layer, the molecular weight and chemical structure of the polymer constituting the film, the mechanical properties, and the viscoelastic properties in addition to the strength of the interfacial interaction between the bonding layer and the substrate A and between the bonding layer and the substrate B. Therefore, the details of the mechanism by which the bonded body of the present invention exhibits excellent bonding strength are not clear, but it is speculated that the main factors are the low cohesive force in the amorphous thermoplastic resin constituting the bonding layer 2 and the presence of hydroxyl groups in the resin, which form chemical bonds and intermolecular forces such as hydrogen bonds and van der Waals forces at the interfaces between the bonding layer and the substrate A and between the bonding layer and the substrate B. However, in the above-mentioned bonded structure, the state or characteristics of the interface of the bonded structure is an extremely thin chemical structure at the nanometer level or less, making it difficult to analyze, and it is impossible or impractical with current technology to identify and express it in a way that distinguishes it from those that are not based on the use of a film.

The bonded body of the present invention, in which the bonding layer is made of a thermoplastic resin, has excellent recyclability and repairability, and can be easily disassembled into substrate A and substrate B by heating the bonded body.

The magnetic material of the substrate A may be a magnetic metal such as iron, or a magnetic ceramic having a higher magnetic permeability than the non-magnetic material described below.
Examples of the non-magnetic material of the substrate B include aluminum, ceramics, non-magnetic ferrite ceramics, and insulating glass ceramics mainly composed of alumina and glass. In the present disclosure, ceramics is not limited to earthenware or porcelain, but refers to a sintered body obtained by heating and baking an inorganic material.

The shapes of substrate A and substrate B are not particularly limited.

High adhesive strength can be obtained by subjecting substrate A and substrate B to pretreatment appropriate for each substrate.
Examples of the pretreatment include a pretreatment for cleaning the surface of the substrate or a pretreatment for making the surface uneven.Specific examples of the pretreatment include a degreasing treatment, a UV ozone treatment, a blasting treatment, a polishing treatment, a plasma treatment, a corona discharge treatment, a laser treatment, an etching treatment, and a frame treatment.The pretreatment may be one type or two or more types.Specific methods of these pretreatments may be known methods.

The degreasing process is a method of removing dirt such as oil and grease from the surface of the substrate by dissolving it with an organic solvent such as acetone or toluene.

The UV ozone treatment is a method of cleaning or modifying a surface by using the energy of short-wavelength ultraviolet light emitted from a low-pressure mercury lamp and the power of the ozone ( _O3 ) generated by it. In the case of glass, it is one of the surface cleaning methods that removes organic impurities from the surface. In general, cleaning and surface modification equipment using a low-pressure mercury lamp is called "UV ozone cleaner", "UV cleaning equipment", "ultraviolet surface modification equipment", etc.

Examples of the blasting treatment include wet blasting, shot blasting, sand blasting, etc. Among them, wet blasting is preferred because it produces a denser surface than dry blasting.

Examples of the polishing process include buff polishing using an abrasive cloth, roll polishing using abrasive paper (sandpaper), and electrolytic polishing.

The plasma treatment involves creating a plasma beam using a high-voltage power supply and a rod, which is then struck against the surface of the material to excite the molecules and put them into a functional state. Examples of such methods include atmospheric pressure plasma treatment, which can impart hydroxyl groups or polar groups to the surface of the material.

The corona discharge treatment is a method used to modify the surface of a polymer film, in which electrons emitted from an electrode cleave the polymer main chain or side chain of the polymer surface layer, generating radicals that generate hydroxyl groups or polar groups on the surface.

The laser treatment is a technique for improving the surface characteristics by rapidly heating and cooling only the surface of the substrate using laser irradiation, and is an effective method for roughening the surface. Any known laser treatment technique can be used.

Examples of the etching process include chemical etching processes such as the alkali process, phosphoric acid-sulfuric acid process, fluoride process, chromic acid-sulfuric acid process, and iron salt process, as well as electrochemical etching processes such as the electrolytic etching process.

The flame treatment is a method of converting oxygen in the air into plasma by burning a mixture of combustion gas and air, and applying the oxygen plasma to the object to be treated to make the surface hydrophilic. Publicly known flame treatment techniques can be used.

Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples. In the following examples, substrate A and substrate B are collectively referred to as the bonding substrate.

<Bonding material>
The following bonding materials were used:

Substrate A (magnetic material):
"iron"
The surface of the SPCC-SD was blasted to obtain a test piece having a width of 10 mm, a length of 45 mm and a thickness of 2.3 mm.

Base material B (non-magnetic material):
"aluminum"
The surface of A6061-T6 was blasted to obtain a test piece having a width of 18 mm, a length of 45 mm and a thickness of 1.5 mm.
"alumina"
An alumina plate (96% purity, as-fired) was cut to obtain a test piece having a width of 18 mm, a length of 45 mm, and a thickness of 1.5 mm. The test piece was used without surface treatment.

<Weight average molecular weight, heat of fusion and epoxy equivalent>
The weight average molecular weight, heat of fusion and epoxy equivalent of the solid bonding agent were determined as follows.

(Weight average molecular weight)
The thermoplastic epoxy resin and the phenoxy resin were dissolved in tetrahydrofuran, and the properties were measured under the following conditions using Prominence 501 (manufactured by Showa Science Co., Ltd., Detector: Shodex (registered trademark) RI-501 (manufactured by Showa Denko K.K.)).
Column: Showa Denko LF-804 x 2 Column temperature: 40°C
Sample: 0.4% by mass solution of resin in tetrahydrofuran Flow rate: 1 ml/min Eluent: tetrahydrofuran Calibration method: Conversion using standard polystyrene

(Heat of Fusion)
2 to 10 mg of the thermoplastic epoxy resin and the phenoxy resin were weighed out, placed in an aluminum pan, and heated from 23° C. to 200° C. at 10° C./min using a DSC (DSC8231 manufactured by Rigaku Corporation) to obtain a DSC curve. The heat of fusion was calculated from the area of the endothermic peak at the time of melting in the DSC curve and the weighed value.

(epoxy equivalent)
The epoxy equivalent was calculated based on the epoxy content and the content of the epoxy resin in the case of a simple mixture not involving any reaction.

<Example 1-1>
(Solid adhesive P-1)
In a reaction apparatus equipped with a stirrer, a reflux condenser, a gas inlet tube, and a thermometer, 1.0 equivalent (203 g) of jER (registered trademark) 1007 (manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, weight average molecular weight about 10,000), 1.0 equivalent (12.5 g) of bisphenol S, 2.4 g of triphenylphosphine, and 1,000 g of methyl ethyl ketone were charged, and the temperature was raised to 100° C. while stirring under a nitrogen atmosphere. After visually confirming that the mixture had dissolved, the mixture was cooled to 40° C. to obtain a resin composition with a solid content of about 20% by mass. The solvent was removed from the mixture to obtain a solid. A non-adhesive fluororesin film (Nitoflon (registered trademark) No. 900UL, manufactured by Nitto Denko Corporation) was placed on the upper and lower plates of a press, and the solid was placed on the non-adhesive fluororesin film of the lower plate. The press was then heated to 160°C, and the resin composition was heat-compressed for 2 hours to obtain a film-like solid bonding agent (P-1) having a thickness of 100 μm and a solid content of 100% by mass. The weight average molecular weight was about 37,000. The epoxy equivalent was above the detection limit. No heat of fusion peak was detected by DSC.
(Conjugate)
The following two types of bonded bodies were prepared.
In addition, for the open time evaluation, a bonded body for open time evaluation was also prepared in the same manner as described below in "Iron-Aluminum" except that a solid bonding agent was placed on the aluminum (substrate B) and left to stand for three days, and then the iron (substrate A) was placed on it.
Iron and aluminum
The solid adhesive P-1 cut to a size of 10 x 15 mm was placed on the aluminum base material as the base material B, and then the iron base material was placed on top of it as the base material A so that the triangular protrusion was placed on top of it. The overlapping between these base materials was 10 mm wide and 5 mm deep. The solid adhesive P-1 was placed so as to cover the entire overlapping area between the base materials. In other words, the base material A and the base material B were not in direct contact with each other, and an unbonded laminate was prepared with the solid adhesive interposed between them. In this specification, "promptly thereafter" means within about 30 minutes. The iron and aluminum were heated by high-frequency induction using a high-frequency induction welding machine (manufactured by Seidensha Denshi Kogyo Co., Ltd., oscillator UH-2.5K, press JIS P30S), and the test pieces were bonded to each other by heating and pressing. The pressure was 110 N (pressure 2.2 MPa), and the oscillation frequency was 900 kHz. The oscillation time was 5 seconds.
Iron and alumina
A bonded body was obtained in the same manner as in the above <<Iron-Aluminum>>, except that alumina was used as the base material B instead of aluminum.

<Example 1-2>
(Conjugate)
The solid adhesive P-1 was placed on the substrate A, and the film was melted by heating it on a hot plate at 200°C for 1 minute, and then cooled at room temperature for 1 minute to solidify the film. Two types of bonded bodies, "iron/aluminum" and "iron/alumina", were produced in the same manner as in Example 1-1, except that the solid adhesive P-1 was placed on the substrate A, and the film was melted by heating it on a hot plate at 200°C for 1 minute, and then the film was solidified by cooling it at room temperature for 1 minute. After the metal substrate A and the film were bonded, the substrate B and the bonding material were laminated so that their surfaces were in contact with each other.

<Example 1-3>
(Conjugate)
The solid adhesive P-1 was placed on the substrate B, and the film was melted by heating it on a hot plate at 200°C for 1 minute, and then cooled at room temperature for 1 minute to solidify the film. Two types of bonded bodies, "iron/aluminum" and "iron/alumina", were produced in the same manner as in Example 1-1, except that the solid adhesive P-1 was placed on the substrate B, and the film was melted by heating it on a hot plate at 200°C for 1 minute, and then the film was solidified by cooling it at room temperature for 1 minute. The metal substrate B and the film were bonded, and then the substrate A and the bonding material were laminated so that their surfaces were in contact with each other.

Example 2
(Solid adhesive P-2)
In a reaction apparatus equipped with a stirrer, a reflux condenser, a gas inlet tube, and a thermometer, 20 g of Enotote (registered trademark) YP-50S (manufactured by Nippon Steel Chemical & Material Co., Ltd., phenoxy resin, weight average molecular weight about 50,000) and 80 g of cyclohexanone were charged, and the temperature was raised to 60°C while stirring, and dissolution was confirmed visually, and the mixture was cooled to 40°C to obtain a resin composition with a solid content of 20% by mass. The solvent was removed from this to obtain a film-like solid bonding agent (P-2) with a thickness of 100 μm and a solid content of 100% by mass. The weight average molecular weight was 50,000, and the epoxy equivalent was above the detection limit. No heat of fusion peak was detected in DSC.
(Conjugate)
Two types of bonded bodies, "iron-aluminum" and "iron-alumina", and a bonded body for open time evaluation were prepared in the same manner as in Example 1-1, except that P-2 was used as the solid bonding agent.

Example 3
(Solid adhesive P-3)
The resin composition P-2 and a crystalline epoxy resin YSLV-80XY (manufactured by Nippon Steel Chemical & Material Co., Ltd.) were mixed in a mass ratio of 98:2 to obtain a solid bonding agent (P-3). The weight average molecular weight was 36,000, the epoxy equivalent was 9600 g/eq, and the heat of fusion was 2 J/g.
(Conjugate)
Two types of bonded bodies, "iron-aluminum" and "iron-alumina", and a bonded body for open time evaluation were prepared in the same manner as in Example 1-1, except that P-3 was used as the solid bonding agent.

Example 4
(Solid adhesive P-4)
The resin composition P-2 and a crystalline epoxy resin YSLV-80XY (manufactured by Nippon Steel Chemical & Material Co., Ltd.) were mixed in a mass ratio of 94 to 6 to obtain a solid bonding agent (P-4). The weight average molecular weight was 35,000, the epoxy equivalent was 2100 g/eq, and the heat of fusion was 4 J/g.
(Conjugate)
Two types of bonded bodies, "iron-aluminum" and "iron-alumina", and a bonded body for open time evaluation were prepared in the same manner as in Example 1-1, except that P-4 was used as the solid bonding agent.

Example 5
(Solid adhesive P-5)
The resin composition P-2 and a crystalline epoxy resin YSLV-80XY (manufactured by Nippon Steel Chemical & Material Co., Ltd.) were mixed in a mass ratio of 89 to 11 to obtain a solid bonding agent (P-5). The weight average molecular weight was 33,000, the epoxy equivalent was 1700 g/eq, and the heat of fusion was 11 J/g.
(Conjugate)
Two types of bonded bodies, "iron-aluminum" and "iron-alumina", and a bonded body for open time evaluation were prepared in the same manner as in Example 1-1, except that P-5 was used as the solid bonding agent.

Example 6
(Solid adhesive P-6)
In a reaction apparatus equipped with a stirrer, a reflux condenser, a gas inlet tube, and a thermometer, 1.0 equivalent (203 g) of jER (registered trademark) 1007 (manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, molecular weight about 4060), 0.6 equivalent (12.5 g) of bisphenol S (molecular weight 250), 2.4 g of triphenylphosphine, and 1,000 g of methyl ethyl ketone were charged, and the mixture was heated to 100° C. while stirring under a nitrogen atmosphere. After visually confirming that the mixture had dissolved, the mixture was cooled to 40° C. to obtain a resin composition with a solid content of about 20% by mass. The solvent was removed from the mixture to obtain a solid. A non-adhesive fluororesin film (Nitoflon (registered trademark) No. 900UL, manufactured by Nitto Denko Corporation) was placed on the upper and lower plates of a press, and the solid was placed on the non-adhesive fluororesin film of the lower plate. The press was then heated to 160°C, and the resin composition was heat-compressed for 2 hours to obtain a solid adhesive (P-6) in the form of a film having a thickness of 100 μm and a solid content of 100% by mass. The weight average molecular weight was about 30,000, and the epoxy equivalent was above the detection limit. No heat of fusion peak was detected by DSC.
(Conjugate)
The method for producing the bonded bodies was the same as in Example 1-1, except that P-6 was used as the solid bonding agent, to produce two types of bonded bodies, "iron-aluminum" and "iron-alumina", and a bonded body for open time evaluation.

<Comparative Example 1>
(Solid Adhesive Q-1)
Two liquids of thermosetting liquid epoxy adhesive E-250 (Konishi Co., Ltd., two-liquid type of bisphenol type epoxy resin and amine curing agent) were mixed, applied to a release film, cured at 100°C for 1 hour, cooled, and peeled off from the release film to obtain a film-like solid adhesive (Q-1) with a thickness of 100 μm. No heat of fusion peak was detected by DSC. The epoxy equivalent and weight average molecular weight could not be measured because it was insoluble in a solvent.
(Conjugate)
Two types of bonded bodies, "iron-aluminum" and "iron-alumina", and a bonded body for open time evaluation were prepared in the same manner as in Example 1-1, except that Q-1 was used as the solid bonding agent.

<Comparative Example 2>
(Solid adhesive Q-2)
An amorphous polycarbonate film (Iupilon (registered trademark) FE2000, manufactured by Mitsubishi Engineering Plastics Corporation, thickness 100 μm) was used as the solid joint body Q-2. No heat of fusion peak was detected by DSC.
(Conjugate)
Two types of bonded bodies, "iron-aluminum" and "iron-alumina", and a bonded body for open time evaluation were prepared in the same manner as in Example 1-1, except that Q-2 was used as the solid bonding agent.

<Comparative Example 3>
(Solid adhesive Q-3)
Crystalline epoxy resin YSLV-80XY (manufactured by Nippon Steel Chemical & Material Co., Ltd.) was used as a solid bonding agent (Q-3). The epoxy equivalent was 192 g/eq. The weight average molecular weight was 340. The heat of fusion was 70 J/g.
(Conjugate)
Two types of bonded bodies, "iron-aluminum" and "iron-alumina", and a bonded body for open time evaluation were prepared in the same manner as in Example 1-1, except that Q-3 was used as the solid bonding agent.

<Comparative Example 4>
(Conjugate)
Two liquid components of thermosetting liquid epoxy adhesive E-250 (Konishi Corporation, a two-liquid type consisting of bisphenol-type epoxy resin and amine curing agent) were mixed and applied to two types of substrates A and B similar to those in Example 1, respectively, and bonded together within one minute. After that, the substrates were fixed with clips and left to stand in an oven at 100°C for one hour to cure the adhesive components, and then cooled to room temperature to produce two types of bonded bodies, "iron/aluminum" and "iron/alumina."
In addition, a bonded body for open time evaluation was also prepared in the same manner as above, except that the thermosetting liquid epoxy adhesive E-250 was applied to the substrate A and the substrate B, and then the substrates were left to stand for 3 days before bonding.

<Comparative Example 5>
In a flask, 1.0 equivalent (203 g) of jER (registered trademark) 1007 (manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, weight average molecular weight about 10,000), 1.0 equivalent (12.5 g) of bisphenol S, 2.4 g of triphenylphosphine, and 1,000 g of methyl ethyl ketone were charged and stirred at room temperature to obtain a liquid resin composition with a solid content of about 20 mass%. The liquid resin composition was bar-coated on two types of substrate B similar to those in Example 1, dried at room temperature for 30 minutes, and then left to stand in an oven at 160 ° C. for 2 hours to form a solid thermoplastic epoxy resin polymer coating layer with a thickness of 100 μm on the surface of the substrate B. The weight average molecular weight of the coating layer was about 40,000. The epoxy equivalent was above the detection limit. No heat of fusion peak was detected in DSC.
(Conjugate)
Two types of bonded bodies, "iron-aluminum" and "iron-alumina", were produced in the same manner as in Example 1-1, except that base material A was placed directly on base material B having the coating layer.
In addition, for the purpose of open time evaluation, a joint for open time evaluation was also prepared in the same manner as above, except that a thermoplastic epoxy resin polymer coating layer was formed on the surface of substrate B, allowed to stand for 3 days, and then laminated with substrate A.

<Comparative Example 6>
A reactor equipped with a stirrer, a reflux condenser, a gas inlet tube, and a thermometer was charged with 20 g of FENOTOTE (registered trademark) YP-50S (manufactured by Nippon Steel Chemical & Material Co., Ltd., phenoxy resin, weight average molecular weight about 50,000) and 80 g of cyclohexanone, and the temperature was raised to 60°C while stirring. Dissolution was confirmed by visual inspection, and the mixture was cooled to 40°C to obtain a liquid resin composition with a solid content of 20% by mass. The liquid resin composition was bar-coated on two types of substrate B similar to those in Example 1, and the substrate was left to stand in an oven at 70°C for 30 minutes to form a phenoxy resin coating layer with a thickness of 100 μm on the surface of the substrate B. The weight average molecular weight of the coating layer was about 50,000. The epoxy equivalent was above the detection limit. No heat of fusion peak was detected by DSC.
(Conjugate)
Two types of bonded bodies, "iron-aluminum" and "iron-alumina", were prepared in the same manner as in Example 1-1, except that the substrate A was placed directly on the substrate B having the phenoxy resin coating layer.
In addition, for the open time evaluation, a joint for open time evaluation was also prepared in the same manner as above, except that a phenoxy resin coating layer was formed on the surface of substrate B, which was then left to stand for 3 days and then laminated with substrate A.

<Comparative Example 7>
(Conjugate)
Crystalline polyamide-based hot melt adhesive film NT-120 (manufactured by Nihon Matai Co., Ltd., thickness 100 μm) was used as the solid adhesive. Two types of bonded bodies, "iron-aluminum" and "iron-alumina", and a bonded body for open time evaluation were prepared in the same manner as in Example 1-1. The heat of fusion was 60 J/g.

[Shear adhesive strength]
The bonded bodies obtained in Examples 1-1 to 6 and Comparative Examples 1 to 7 were allowed to stand at the measurement temperature (23° C. or 80° C.) for 30 minutes or more, and then subjected to a tensile shear adhesive strength test in an atmosphere of 23° C. and 80° C. in accordance with ISO 19095 using a tensile tester (Universal testing machine autograph "AG-X plus" (manufactured by Shimadzu Corporation); load cell 10 kN, tensile speed 10 mm/min) to measure the bond strength. The measurement results are shown in Tables 1-1 and 1-2.

[Bonding process time]
The bonding process time was measured as follows.
The time from the start point when the bonding agent contacted at least one of the substrates that constitute the bonded body to the end point was measured, and the end point was when the fabrication of the bonded body was completed. The heating and pressing time was the average of the heating and pressing times for the two types of bonded bodies. The measurement results are shown in Tables 1-1 and 1-2.

[Recyclability]
The bonded body was placed on a hot plate at 200°C and heated for 1 minute, and then it was judged whether it could be easily peeled off with a force of 1 N or less. If it could be peeled off, it was rated as good (A), and if it could not be peeled off, it was rated as unsatisfactory (B). The evaluation results are shown in Tables 1-1 and 1-2.

[Repairability]
Of the test pieces (where a layer of the bonded solid remains on the surface of substrate A or B or both) whose adhesive surface broke after the tensile shear strength test at 23°C, substrate A was placed on substrate B, and a bonded structure was prepared in the same manner as in Example 1 to obtain a repair bonded structure. The shear adhesive strength of the repaired bonded structure at 23°C was measured in the same manner as in the test method, and if it was 80% or more of the first shear adhesive strength, it was judged as good (A), and if it was less than 80%, it was judged as unsatisfactory (B). The evaluation results are shown in Tables 1-1 and 1-2.

[Open time evaluation]
The tensile shear adhesive strength test was carried out at 23° C. using the bonded bodies for open time evaluation. If the shear adhesive strength was 80% or more compared to the test pieces prepared by the methods of the examples and comparative examples, it was rated as good (A), and if it was less than 80%, it was rated as unsatisfactory (B). A good open time rating (A) means that the open time is long and the convenience is excellent. The evaluation results are shown in Tables 1-1 and 1-2.

The joints obtained by the manufacturing method of the present invention are used, for example, as door side panels, bonnet roofs, tailgates, steering hangers, A-pillars, B-pillars, C-pillars, D-pillars, crash boxes, power control unit (PCU) housings, electric compressor components (inner wall parts, intake ports, exhaust control valve (ECV) insertion parts, mount boss parts, etc.), lithium ion battery (LIB) spacers, battery cases, LED headlamps and other automotive parts, as well as smartphones, notebook computers, tablet computers, smart watches, large liquid crystal televisions (LCD-TVs), outdoor LED lighting structures, etc., but are not limited to these illustrative uses.

1 Joined body 2 Adhesive layer 3 Base material A
4. Substrate B

Claims (4)

A method for producing a bonded body, which is obtained by bonding, in this order, a substrate A which is a magnetic substrate, a film which contains at least one amorphous thermoplastic resin selected from a thermoplastic epoxy resin and a phenoxy resin, and a substrate B which is a non-magnetic substrate, the method comprising the steps of:
The content of the amorphous thermoplastic resin in the resin components of the film is 80 mass% or more,
The content of the resin component in the film is 20% by mass or more,
The thermoplastic epoxy resin is a polymer of (a) a bifunctional epoxy resin monomer or oligomer and (b) a bifunctional compound having two identical or different functional groups selected from the group consisting of a phenolic hydroxyl group, a carboxyl group, a mercapto group, an isocyanate group, and a cyanate ester group (excluding bisphenols and polyhydroxy polyethers synthesized from epichlorohydrin),
The phenoxy resin is a polyhydroxy polyether synthesized from bisphenols and epichlorohydrin,
The film, the magnetic substrate A, and the non-magnetic substrate B are each prepared separately,
The film prepared here has a thickness of 10 μm to 1 mm, and then
a first joining step of joining the substrate A and the film by melting and solidifying the film in a state where the film is in contact with the substrate A, or joining the substrate B and the film by melting and solidifying the film in a state where the film is in contact with the substrate B;
a second joining step of joining the substrate A and the substrate B by melting and solidifying the film in a state where the film joined to the substrate A is in contact with the substrate B, or by melting and solidifying the film in a state where the film joined to the substrate B is in contact with the substrate A,
The resin component has an epoxy equivalent of 1,600 g/eq. or more or does not contain an epoxy group, and has a heat of fusion of 15 J/g or less. The method for manufacturing a bonded body according to claim 1, wherein the film is melted under heating conditions of 100 to 300°C in the first bonding step. The method for producing a bonded body according to claim 1, wherein in the second bonding step, the film is melted by at least one method selected from the group consisting of contact heating, hot air heating, heat pressing, infrared heating, hot plate welding, ultrasonic welding, vibration welding, and high-frequency induction welding. The method for manufacturing a bonded body according to claim 1, wherein in the second bonding step, the film is melted under heating conditions of 100 to 400°C and pressure conditions of 0.01 to 20 MPa.