Composite particle, foamable resin composition, foamed cured body, laminate, and electric motor

Abstract

This composite particle comprises a foaming agent and a coating layer. The coating layer comprises a plurality of heat conductors and a first resin. The plurality of heat conductors are disposed along the surface of the foaming agent. The first resin is disposed on the surface of the foaming agent and between the heat conductors. The coating layer coats the surface of the foaming agent.

Description

Composite particles, foamed resin compositions, foamed cured products, laminates, and electric motors

[0001] The present invention relates to composite particles, foamed resin compositions, foamed cured products, laminates, and electric motors.

[0002] Conventionally, it is known that adhesives are placed between objects to be bonded, and the foaming of the adhesive causes the objects to bond together.

[0003] For example, Patent Document 1 describes an adhesive sheet. This adhesive sheet comprises a substrate, a first adhesive layer disposed on one surface of the substrate, and a second adhesive layer disposed on the other surface of the substrate. When the adhesive sheet is used in applications requiring electrical insulation, an insulating substrate is selected as the substrate. The adhesive sheet is used, for example, to bond the stator core and windings by being placed between them. The first adhesive layer contains an adhesive (A), a thermally conductive filler (B), and a foaming agent (C). For example, a coating liquid obtained by mixing an adhesive composition containing a foaming agent (C), which is a thermally expandable particle, with a thermally conductive filler is applied to the substrate to form the first adhesive layer and obtain an adhesive sheet. Since the first adhesive layer contains a foaming agent (C), the first adhesive layer expands when the objects to be bonded together, filling the gaps between the objects.

[0004] Japanese Patent Publication No. 2024-86202

[0005] As described in Patent Document 1, it is conceivable to foam a resin layer containing a thermal conductor and a foaming agent for bonding the objects to be bonded together. In the technique described in Patent Document 1, a coating liquid obtained by mixing an adhesive composition and a thermal conductive filler is applied to a substrate to form a first adhesive layer. This technique has room for reconsideration from the viewpoint of reducing the amount of thermal conductor required to achieve the desired thermal conductivity. In addition, it also has room for reconsideration from the viewpoint of increasing the bonding strength between the objects to be bonded together.

[0006] In view of these circumstances, the present invention provides composite particles that are advantageous in bonding objects together using foamed resin compositions, in terms of reducing the amount of thermal conductor required to achieve desired thermal conductivity and increasing the strength of the bond between objects.

[0007] The present invention provides a composite particle comprising a foaming agent, a plurality of heat conductors arranged along the surface of the foaming agent, and a first resin disposed on the surface of the foaming agent and between the heat conductors, and a coating layer that covers the surface of the foaming agent.

[0008] Furthermore, the present invention provides a foaming resin composition comprising the above-mentioned composite particles and a second resin, wherein the composite particles and the second resin are mixed together.

[0009] Furthermore, the present invention provides a foamed and cured product of the dried foamed resin composition described above.

[0010] Furthermore, the present invention provides a laminate comprising a base material and a resin layer disposed on the base material and containing the above-mentioned composite particles and a second resin.

[0011] Furthermore, the present invention provides a laminate comprising a base material and a foamed layer disposed on the base material and including a foamed cured resin layer containing the above-mentioned composite particles and a second resin.

[0012] Furthermore, the present invention provides an electric motor comprising the above-mentioned laminate, a stator core, and windings arranged adjacent to the stator core, wherein the laminate bonds the stator core and the windings together.

[0013] The above-mentioned composite particles are advantageous in bonding objects together using foamed resin layers, in terms of reducing the amount of thermal conductor required to achieve the desired thermal conductivity and increasing the strength of the bond between the objects.

[0014] Figure 1 shows an example of an embodiment of composite particles. Figure 2 is a cross-sectional view of composite particles with line II-II in Figure 1 as the cutting line. Figure 3 shows an example of a method for manufacturing composite particles. Figure 4 shows an example of an embodiment of a foaming resin composition. Figure 5 shows an example of a laminate before the foaming agent foams. Figure 6 shows an example of a laminate after the foaming agent foams in an electric motor. Figure 7 is a scanning electron microscope (SEM) image of the thermally expandable particles used in the examples. Figure 8 is a scanning electron microscope (SEM) image of the composite particles according to the examples. Figure 9 is an SEM image of a cross-section of a cured product according to Examples 1-2. Figure 10A is a schematic diagram showing nanoindentation measurement. Figure 10B is a graph showing the relationship between load and displacement in the nanoindentation measurement in Figure 10A.

[0015] Embodiments of the present invention will be described below with reference to the drawings. The following description is illustrative and does not limit the present invention to the following embodiments.

[0016] As shown in Figures 1 and 2, the composite particle 1a comprises a foaming agent 10 and a coating layer 20. The coating layer 20 contains a plurality of heat conductors 21 and a first resin 22. The plurality of heat conductors 21 are arranged along the surface of the foaming agent 10. The first resin 22 is arranged on the surface of the foaming agent 10 and between the heat conductors 21. The coating layer 20 covers the surface of the foaming agent 10.

[0017] When foaming a resin layer containing a heat conductor and a foaming agent for bonding objects together, it is conceivable to add the heat conductor and the foaming agent to the resin composition independently, as described in Patent Document 1. In this case, the heat conductor tends to be uniformly distributed in the resin composition. Therefore, in order for the foamed cured resin layer to exhibit the desired heat transfer properties by forming heat transfer paths through contact between the heat conductors, it may be necessary to add a large amount of heat conductor to the resin composition. Also, if the heat conductor is uniformly distributed in the resin composition, the amount of heat conductor near the surface of the foamed cured resin layer tends to be large. On the other hand, if a resin composition for bonding objects together is prepared using the above-mentioned composite particles 1a, multiple heat conductors 21 are arranged along the surface of the foaming agent 10 in the resin composition. In other words, multiple heat conductors 21 may be unevenly distributed near the surface of the foaming agent 10 in the resin composition. Therefore, for example, by foaming the foaming agent 10 so that the composite particles 1a come into contact with each other, heat transfer paths can be easily formed by the multiple heat conductors 21 contained in the multiple composite particles 1a. This makes it easier to reduce the amount of heat conductor 21 required for the foamed cured resin layer to achieve the desired heat transfer properties. Furthermore, by using composite particles 1a, the amount of heat conductor 21 present near the surface of the foamed cured resin layer is reduced. This makes it easier to increase the adhesive strength between the bonded objects. In addition, by using composite particles 1a, it is possible to avoid the increase in viscosity of the resin composition that occurs when heat conductors are uniformly distributed in the resin composition. Composite particles 1a can have these advantages when foaming a resin layer containing heat conductors and foaming agents for bonding objects together. Moreover, if heat conductors are uniformly distributed in the resin composition, the viscosity of the resin composition may increase, potentially limiting the foaming ratio. By using composite particles 1a, this possibility can be reduced.

[0018] The foaming agent 10 is not limited to a specific foaming agent 10, as long as a plurality of heat conductors 21 are arranged along its surface. The foaming agent 10 is, for example, spherical particles. In this case, the plurality of heat conductors 21 are easily arranged uniformly along the surface of the foaming agent 10, and the composite particles 1a tend to become spherical. As a result, for example, when a resin composition containing composite particles 1a is applied to a substrate, the composite particles 1a tend to move to desired positions along the flow of the resin composition, and the resin composition tends to foam uniformly. Spherical particles are, for example, particles in which the ratio of the maximum diameter to the minimum diameter in the projected image of the spherical particle is 2 or less. The foaming agent 10 may also have an irregular shape.

[0019] The foaming agent 10 may, for example, comprise a core 10c and a shell 10s as shown in Figure 2, with the core 10c being located inside the shell 10s.

[0020] Examples of blowing agents 10 include inorganic blowing agents, organic blowing agents, and thermally expandable particles. Examples of inorganic blowing agents include ammonium carbonate, ammonium bicarbonate, ammonium nitrite, ammonium borohydride, and azides. Examples of organic blowing agents include fluorinated alkanes such as trichloromonofluoromethane, azo compounds such as azobisisobutyronitrile, hydrazine compounds such as p-toluenesulfonyl hydrazide, semicarbazide compounds such as p-toluenesulfonyl semicarbazide, triazole compounds such as 5-morpholyl-1,2,3,4-thiatriazole, and N-nitroso compounds such as N,N-dinitrosotelephthalamide. An example of thermally expandable particles is a thermally expandable capsule in which a thermally expandable agent such as a hydrocarbon compound is encapsulated.

[0021] The foaming agent 10 is preferably a thermally expandable particle. In this case, even if foaming occurs due to the foaming agent 10, it is easier to avoid significant disruption to the positional relationship of the multiple heat conductors 21 in the composite particle 1a. For this reason, in the foamed cured resin composition containing the composite particle 1a, the multiple heat conductors 21 are more easily positioned appropriately from the viewpoint of achieving the desired heat transfer properties. In addition, compared to the case where inorganic foaming agents and organic foaming agents are used, foaming by the foaming agent 10 is less likely to affect the properties of the resin composition.

[0022] The thermally expandable particle comprises a core 10c containing, for example, a hydrocarbon compound, and a shell 10s surrounding the core 10c. The material of the shell 10s is not limited to any particular material as long as it can be thermally expanded. Examples of materials for the shell 10s are acrylonitrile copolymer and polyvinylidene chloride.

[0023] The size of the foaming agent 10 is not limited to a specific value. The particle size of the foaming agent 10 may be, for example, 1 to 500 μm, and may be 2 to 200 μm, 5 to 100 μm, or 5 to 50 μm. The particle size of the foaming agent 10 is the maximum diameter in the projected image of the foaming agent 10.

[0024] The thermal conductor 21 is not limited to a specific thermal conductor 21, as long as a plurality of thermal conductors 21 are arranged along the surface of the foaming agent 10. The thermal conductor 21 is, for example, an electrical insulator. In this case, the foamed cured resin composition containing the composite particles 1a is easily applicable to applications requiring electrical insulation. The thermal conductor 21 may be a conductor or a semiconductor. In this specification, the electrical insulator has an conductivity of 10 at 20°C. -6 It is a substance with a S / m or less ratio.

[0025] Examples of materials for the thermal conductor 21 include hexagonal boron nitride (h-BN), alumina, crystalline silica, amorphous silica, aluminum nitride, magnesium oxide, carbon fiber, silver, copper, aluminum, silicon carbide, graphite, zinc oxide, silicon nitride, silicon carbide, cubic boron nitride (c-BN), beryllia, diamond, carbon black, graphene, carbon nanotubes, carbon fiber, and aluminum hydroxide.

[0026] Examples of electrical insulators include hexagonal boron nitride (h-BN), alumina, crystalline silica, amorphous silica, aluminum nitride, magnesium oxide, zinc oxide, silicon nitride, cubic boron nitride (c-BN), and aluminum hydroxide.

[0027] The shape and dimensions of the heat conductors 21 are not limited to specific values. For example, the ratio of the particle size of the foaming agent 10 to the average maximum diameter of the heat conductors 21 is not limited to a specific value. This ratio is, for example, 2 to 100. When this ratio is 2 or more, multiple heat conductors 21 are more likely to be uniformly arranged along the surface of the foaming agent 10. In addition, when this ratio is 100 or less, the number of heat conductors 21 arranged along the surface of the foaming agent 10 tends to be smaller, and the sum of the contact thermal resistances in the composite particles 1a due to contact between the heat conductors 21 or contact between the heat conductors 21 and the first resin 22 tends to be smaller.

[0028] The ratio of the particle size of the foaming agent 10 to the average maximum diameter of the heat conductor 21 is preferably 3 or more, but may also be 4 or more, or 5 or more, and may be 50 or less, 40 or less, 30 or less, 20 or less, or 10 or less.

[0029] The average maximum diameter of the heat conductor 21 is, for example, 0.1 μm or more, and may be 0.5 μm or more or 1 μm or more, and may be, for example, 20 μm or less, and may be 10 μm or less or 5 μm or less.

[0030] The content of the thermal conductor 21 in the composite particle 1a is not limited to a specific value. This content is, for example, 1% to 50% by volume, and may be 5% to 40% or 5% to 30%.

[0031] The ratio of the average maximum diameter to the average minimum dimension of the heat conductor 21 is not limited to a specific value. This ratio is, for example, 50 or less. In this case, the heat conductor 21 is likely to be arranged along the surface of the foaming agent 10 in the direction in which its maximum diameter is determined, and a wide area of ​​the surface of the composite particles 1a is likely to be covered by multiple heat conductors 21.

[0032] The ratio of the average maximum diameter to the average minimum dimension of the heat conductor 21 is, for example, 2 or more, and may be 5 or more, 10 or more, or 15 or more, and may be 45 or less, 40 or less, or 35 or less.

[0033] The heat conductor 21 is, for example, a flake-shaped particle. In this case, the thickness of the heat conductor 21 corresponds to the minimum dimension mentioned above, and the diameter of the heat conductor 21 when viewed from above corresponds to the maximum diameter mentioned above. In this case, a wider area of ​​the surface of the composite particle 1a is more easily covered by multiple heat conductors 21. The heat conductor 21 may be spherical, rod-shaped, or have an irregular shape.

[0034] The heat conductor 21 may be a combination of two or more material types, or a combination of two or more sizes.

[0035] The shape of the composite particles 1a is not limited to a specific shape. For example, the composite particles 1a may be spherical particles. In this case, when the resin composition containing the composite particles 1a is applied to a substrate, the composite particles 1a can easily move to desired positions along the flow of the resin composition, and the resin layer can foam uniformly.

[0036] The circularity of the projected image of the composite particle 1a is not limited to a specific value. This circularity is, for example, 0.7 or greater. In this case, when the resin composition containing the composite particle 1a is applied to a substrate, the composite particle 1a easily moves to the desired position along the flow of the resin composition, and the resin composition easily foams uniformly. The circularity of the projected image of the composite particle 1a is preferably 0.75 or greater, and more preferably 0.80 or greater. This circularity is, for example, 1 or less, and may be 0.98 or less. Circularity is defined by the following formula (1). In formula (1), S is the area of ​​the portion enclosed by the contour of the projected image of the composite particle 1a, and L is the perimeter of that contour. Circularity = 4πS / L 2 Formula (1)

[0037] The first resin 22 is not limited to a specific resin. The first resin 22 includes, for example, a crosslinked polymer. The first resin 22 may be a thermosetting resin. Examples of thermosetting resins are phenolic resins, urea resins, melamine resins, diallyl phthalate resins, polyester resins, epoxy resins, aniline resins, silicone resins, furan resins, polyurethane resins, alkylbenzene resins, guanamine resins, xylene resins, and imide resins. The curing temperature of the thermosetting resin is, for example, 25°C to 160°C. The first resin 22 may be a thermoplastic resin. The first resin 22 may contain a solvent as needed. The first resin 22 may be emulsified in water as needed.

[0038] As shown in FIG. 3, in the production of the composite particles 1a, for example, a liquid resin 22a is attached to the surface of the foaming agent 10, and a plurality of heat conductors 21 are brought into contact with the liquid resin 22a, and a plurality of heat conductors 21 are arranged along the surface of the foaming agent 10. Thereby, a coating layer 20 covering the surface of the foaming agent 10 is formed. The liquid resin 22a can be a precursor of the first resin 22.

[0039] For example, a plurality of foaming agents 10 and the liquid resin 22a are mixed to obtain a mixture. Thereby, the liquid resin 22a can adhere to the surfaces of the plurality of foaming agents 10. Next, a plurality of heat conductors 21 are added to this mixture and further mixed. Thereby, the plurality of heat conductors 21 come into contact with the liquid resin 22a adhering to the surface of the foaming agent 10, and the plurality of heat conductors 21 are arranged along the surface of the foaming agent 10. The addition of the liquid resin 22a and the addition of the plurality of heat conductors 21 may be alternately repeated. Thereby, the amount of the heat conductor 21 contained in the composite particles 1a tends to increase, and the heat dissipation property of the foam-cured body of the resin composition containing the composite particles 1a tends to increase. Also, the composite particles 1a may be produced by mixing a mixture obtained by previously mixing the liquid resin 22a and the heat conductor 21 with the foaming agent 10.

[0040] The method of mixing a plurality of foaming agents 10 and a liquid resin 22a and mixing a plurality of heat conductors 21 in the production of the composite particles 1a is not limited to a specific method. Examples of such mixing include mixing using a ball mill, a bead mill, a planetary mixer, an ultrasonic mixer, a homogenizer, a rotating and revolving mixer, a fluid mixer, a Henschel mixer, a container-rotating type blender, a ribbon blender, an axial mixer, and a conical screw blender.

[0041] In the production of the composite particles 1a, for example, the liquid resin 22a attached to the surfaces of the plurality of foaming agents 10 is cured by heating. Thereby, the plurality of heat conductors 21 are fixed to the foaming agents 10.

[0042] The properties of the surface of the composite particles 1a may be modified by a surface modifier. Examples of the surface modifier are a silane coupling agent, a thiol, a disulfide, and a carboxylic acid. The properties of the surface of the composite particles 1a may be modified by UV treatment, plasma treatment, or vapor deposition treatment.

[0043] As shown in FIG. 4, a foaming resin composition including the above-described composite particles 1a can be provided. As shown in FIG. 4, the foaming resin composition 3 includes the composite particles 1a and a second resin 2a. In the foaming resin composition 3, the composite particles 1a and the second resin 2a are mixed. For example, in the foaming resin composition 3, the composite particles 1a and the second resin 2a are dispersed. The foaming resin composition 3 has fluidity, for example.

[0044] The content of the composite particles 1a in the solid matter of the foaming resin composition 3 is not limited to a specific value. The content of the composite particles 1a in the solid matter of the foaming resin composition 3 is, for example, 1 to 50% by volume. When the content of the composite particles 1a is 1% by volume or more, the foamed cured body of the foaming resin composition 3 is likely to have a desired thermal conductivity. When the content of the composite particles 1a is 50% by volume or less, the amount of the heat conductor 21 near the surface of the foamed cured body of the foaming resin composition 3 is likely to be small. Therefore, when the foaming resin composition 3 is used for adhesion between adherends, the adhesion strength is likely to be high. The content of the composite particles 1a in the solid matter of the foaming resin composition 3 is preferably 10 to 40% by volume.

[0045] The viscosity of the foamed resin composition 3 is not limited to a specific value. For example, the foamed resin composition 3 has a viscosity of 0.01 to 100 Pa·s at 25°C. In this case, the foamed resin composition 3 is easy to coat onto the substrate.

[0046] The second resin 2a is not limited to a specific resin. The second resin 2a is, for example, a thermosetting resin. The second resin 2a is, for example, a resin that is substantially solid at 25°C, becomes fluid upon heating, and can be cured by continuing heating.

[0047] Examples of the second resin 2a include epoxy resin, poly(meth)acrylate, poly(meth)acrylate precursor, silicone, silicone precursor, polyurethane, and polyurethane precursor.

[0048] Examples of epoxy resins include bisphenol-type epoxy resins, aliphatic epoxy resins, glycidylamine-type epoxy resins, novolac-type epoxy resins, alicyclic epoxy resins, brominated epoxy resins, polyfunctional epoxy resins, and crystalline epoxy resins. Examples of bisphenol-type epoxy resins are bisphenol A-type epoxy resins and bisphenol F-type epoxy resins. An example of an aliphatic epoxy resin is hexanediol diglycidyl ether. An example of a glycidylamine-type epoxy resin is triglycidylaminophenol. Examples of novolac-type epoxy resins are phenol novolac epoxy resins and cresol novolac epoxy resins. Examples of alicyclic epoxy resins are 3,4-epoxycyclohexylmethyl, 3,4-epoxycyclohexanecarboxylate, and bis(3,4-epoxycyclohexylmethyl adipate). An example of a brominated epoxy resin is tetrabromobisphenol A diglycidyl ether. The polyfunctional epoxy resins are tris(hydroxyphenyl)methane triglycidyl ether, sorbitol polyglycidyl ether, and tetraglycidyldiaminodiphenylmethane. Examples of crystalline epoxy resins are tetramethylbisphenol F diglycidyl ether and tetramethylbiphenol diglycidyl ether. These may be used individually or in combination of two or more epoxy resins.

[0049] The foamed resin composition 3 may further contain, for example, a curing agent. The curing agent is a known curing agent capable of curing a thermosetting resin. Preferably, the curing agent is a latent curing agent. When the thermosetting resin is an epoxy resin, examples of curing agents are dicyandiamide, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct.

[0050] The content of the curing agent is not limited to a specific value. The content of the curing agent in the solid of the foamed resin composition 3 may be, for example, 1% by volume or more, and may be 2% by volume or more, 3% by volume or more, 4% by volume or more, or 5% by volume or more. The content may be, for example, 20% by volume or less, and may be 18% by volume or less, 16% by volume or less, 14% by volume or less, 12% by volume or less, or 10% by volume or less.

[0051] The foamed resin composition 3 may further contain, for example, a curing accelerator. The curing accelerator can be any known curing accelerator that can accelerate the curing of the thermosetting resin by the curing agent. When the thermosetting resin is an epoxy resin, examples of curing accelerators are imidazole-based curing accelerators and urea-based curing accelerators. An example of an imidazole-based curing accelerator is 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine. Examples of urea-based curing accelerators are 4,4'-methylenebisphenyldimethylurea and 3-(3,4-dichlorophenyl)-1,1-dimethylurea.

[0052] The content of the curing accelerator is not limited to a specific value. The content of the curing accelerator in the solid of the foamed resin composition 3 is, for example, 0.1% by volume or more, and may be 0.2% by volume or more, 0.3% by volume or more, 0.4% by volume or more, or 0.5% by volume or more. The content is, for example, 10% by volume or less, and may be 8% by volume or less, 6% by volume or less, 4% by volume or less, or 2% by volume or less.

[0053] The foaming resin composition 3 may contain a solvent as needed. The solvent is, for example, an organic solvent such as methyl ethyl ketone. The solvent content in the foaming resin composition 3 is, for example, 60% by mass or less. In this way, even when the solvent content in the foaming resin composition 3 is low, the viscosity of the foaming resin composition 3 can be easily adjusted to a desired range. The solvent content in the foaming resin composition 3 is preferably 55% by mass or less, more preferably 50% by mass, even more preferably 40% by mass or less, particularly preferably 30% by mass or less, especially preferably 25% by mass or less, extremely preferably 20% by mass or less, and most preferably 15% by mass or less. The solvent content in the foaming resin composition 3 is, for example, 5% by mass or more.

[0054] The foamed resin composition 3 may optionally contain a heat conductor in addition to the heat conductor 21 contained in the composite particles 1a. The material of this heat conductor may be the same type of material as the heat conductor 21, or it may be a different type of material.

[0055] In the foamed resin composition 3, the ratio of the hardness of the solid in contact with the foaming agent 10 to the hardness [Pa] of the cured product of the second resin 2a is, for example, greater than 1.1. This tends to increase the thermal conductivity of the foamed resin composition 3. The hardness of the cured product of the second resin 2a and the solid in contact with the foaming agent 10 are determined, for example, by nanoindentation. The ratio of the hardness of the solid in contact with the foaming agent 10 to the hardness [Pa] of the cured product of the second resin 2a is preferably 1.2 or more, more preferably 1.5 or more, and even more preferably 1.8 or more. The ratio is, for example, 30 or less. The hardness of the solid in contact with the foaming agent 10 and the cured product of the second resin 2a are values ​​at 25°C.

[0056] The foamed resin composition 3 can be used, for example, after being dried to the extent that it loses its fluidity. In this case, the drying conditions are adjusted so that foaming occurs due to the foaming agent 10 contained in the foamed resin composition 3. The drying conditions are also adjusted so that the curing reaction of the second resin 2a does not occur. By heating the dried material obtained in this way under predetermined conditions, foaming by the foaming agent 10 and flow of the second resin 2a may occur. If heating is continued further, the curing reaction of the second resin 2a will occur. In this way, a foamed cured body of the dried foamed resin composition 3 is obtained.

[0057] The expansion ratio of the foamed cured product is not limited to a specific value. For example, it may be 1.1 times or more, 1.2 times or more, 1.5 times or more, or 2 times or more. For example, it may be 10 times or less, 8 times or less, 5 times or less, or 3 times or less.

[0058] In the foamed cured body, the ratio of the hardness of the solid in contact with the bubbles derived from the foaming agent 10 to the hardness of the second resin is, for example, greater than 1.1. This tends to increase the thermal conductivity of the foamed cured body. The solid in contact with the bubbles is, for example, derived from composite particles 1a. In the foamed cured body, the hardness of the solid in contact with the bubbles and the hardness of the second resin 2a are determined, for example, by the nanoindentation method. In the foamed cured body, the ratio of the hardness of the solid in contact with the bubbles derived from the foaming agent 10 to the hardness of the second resin is preferably 1.2 or more, more preferably 1.5 or more, and even more preferably 1.8 or more. The ratio is, for example, 30 or less. In the foamed cured body, the hardness of the solid in contact with the bubbles and the hardness of the second resin 2a are values ​​at 25°C.

[0059] A laminate can be provided using composite particles 1a. As shown in Figure 5, the laminate 5a comprises a base material 4 and a resin layer 3a. The resin layer 3a is placed on the base material 4. The resin layer 3a contains composite particles 1a and a second resin 2a. In the resin layer 3a, for example, the second resin 2a is included in the continuous phase, and a plurality of composite particles 1a form the dispersed phase.

[0060] The content of the thermal conductor 21 in the resin layer 3a is, for example, 1 to 50 volume percent.

[0061] The resin layer 3a is formed, for example, by applying the foaming resin composition 3 onto the substrate 4 and drying the resulting coating under predetermined conditions. The conditions for drying the coating are adjusted so as not to cause foaming by the foaming agent 10 or curing of the second resin 2a, and so as to eliminate the fluidity of the foaming resin composition 3.

[0062] The base material 4 is not limited to a specific base material as long as the resin layer 3a is arranged therein. The base material 4 is, for example, an electrical insulator. In this case, electrical insulation between members can be achieved by arranging the laminate 5a between members that require electrical insulation. The base material 4 may contain, for example, an organic polymer. Examples of organic polymers included in the base material 4 are polyester, polycarbonate, polyimide, polyamide, acrylic resin, polysulfone, polyetherketone, and modified polyphenylene oxide. Examples of polyester are polyethylene naphthalate (PEN) and polyethylene terephthalate (PET). Examples of polyimide are polyetherimide (PEI) and polyamideimide. Examples of polyamide are polyetheramide, polyaramid, and nylon. Examples of polysulfone are polysulfone and polyethersulfone. Examples of polyetherketone are polyetherketone and polyetheretherketone. The base material 4 may contain only one type of organic polymer from these, or it may contain two or more types of organic polymers.

[0063] The thickness of the substrate 4 is not limited to a specific value. The thickness of the substrate 4 may be, for example, 1 to 1000 μm, 2 to 500 μm, 5 to 200 μm, or 10 to 100 μm.

[0064] The thickness of the resin layer 3a is not limited to a specific value. For example, the thickness of the resin layer 3a may be 1 μm to 10 mm, and may be 5 μm to 5 mm, 5 μm to 3 mm, 5 μm to 1 mm, 5 μm to 500 μm, 5 μm to 200 μm, or 5 μm to 100 μm.

[0065] The resin layer 3a may be placed on only one main surface of the base material 4, or the resin layer 3a may be placed on both main surfaces of the base material 4.

[0066] As shown in Figure 6, a laminate having a foamed layer can be provided. As shown in Figure 6, the laminate 5b comprises a base material 4 and a foamed layer 3b. The foamed layer 3b is disposed on the base material 4. The foamed layer 3b contains a foamed cured resin layer 3a.

[0067] By heating the resin layer 3a under predetermined conditions, foaming by the foaming agent 10 and flow of the second resin 2a can occur. Further heating causes a curing reaction of the second resin 2a. In this way, a foamed layer 3b containing the foamed cured resin layer 3a is formed. As a result, as shown in Figure 6, in the foamed layer 3b, foaming by the foaming agent 10 can cause the heat conductors 21 contained in the coating layer 20 of the composite particles 1a that were adjacent in the resin layer 3a to come into contact with each other. This can form heat transfer paths extending across multiple composite particles 1a. As a result, the foamed layer 3b can exhibit the desired heat dissipation properties.

[0068] For example, with the laminate 5a placed between objects to be bonded separated by a predetermined gap, foaming of the resin layer 3a of the laminate 5a by the foaming agent 10, flow of the second resin 2a, and curing reaction of the second resin 2a may occur. In this case, the gap between the objects to be bonded is filled by the foamed layer 3b, and the objects to be bonded together can be bonded by the laminate 5b.

[0069] As shown in Figure 6, for example, an electric motor equipped with a laminate 5b can be provided. As shown in Figure 6, the electric motor 100 comprises a laminate 5b, a stator core 7a, and windings 7b. The windings 7b are arranged adjacent to the stator core 7a. The laminate 5b adheres the stator core 7a and the windings 7b together. With this configuration, the stator core 7a and the windings 7b can be fixed together by the laminate 5b. Since the laminate 5b has heat transfer paths derived from a plurality of heat conductors 21 contained in the coating layer 20 of the composite particles 1a, efficient heat dissipation is easily achieved in the electric motor 100. As a result, the electric motor 100 is more likely to exhibit the desired performance.

[0070] Laminates 5a and 5b may be used for purposes other than the electric motor 100.

[0071] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples.

[0072] <Preparation of composite particles> FN-100SD, a heat-expandable microcapsule manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd., was used as the heat-expandable particle (foaming agent). The median diameter D in the volume-based particle size distribution of these heat-expandable particles. 50 The diameter was 13.4 μm. Figure 7 is a scanning electron microscope (SEM) image of this thermally expandable particle. As shown in Figure 7, this thermally expandable particle was spherical. For every 1 part by mass of thermally expandable particle, 0.56 parts by mass of silicone resin precursor was prepared. DOWSIL® SE 1896 FR A / B-EG Kit manufactured by Dow Toray was used as the silicone resin precursor. In addition, for every 1 part by mass of thermally expandable particle, 1.12 parts by mass of flake-like boron nitride (hexagonal boron nitride) was prepared as a thermal conductor. Median diameter D in the volume-based particle size distribution of boron nitride 50 The maximum diameter was 2.1 μm. This value was considered the average value of the maximum diameter of boron nitride. The median in the thickness distribution of boron nitride was 0.08 μm. This value was considered the average value of the thickness of boron nitride. The ratio of the average value of the maximum diameter of boron nitride to the average value of the thickness of boron nitride was determined to be the ratio of the maximum diameter to the minimum dimension of boron nitride. That ratio was 26.3.

[0073] To the high-speed flow mixer SMP-2 manufactured by Kawata Corporation, 1 part by mass of the above-mentioned thermally expandable particles was added, and then 0.14 part by mass of the above-mentioned silicone resin precursor was added. The thermally expandable particles and the silicone resin precursor were stirred at 1000 revolutions per minute for 1 minute by the high-speed flow mixer to adhere the silicone resin precursor to the surface of the thermally expandable particles. Next, 0.28 part by mass of the above-mentioned boron nitride was added to the mixture of the thermally expandable particles and the silicone resin precursor, and then this mixture was stirred at 1000 revolutions per minute for 1 minute by the high-speed flow mixer. Thereafter, the silicone resin was cured by heat treatment at 60°C for 10 minutes in a constant temperature bath. The addition and stirring of the silicone resin precursor, the addition and stirring of boron nitride, and the curing of the silicone resin were repeated 4 times to obtain composite particles according to the embodiment, in which a coating layer containing the silicone resin precursor and boron nitride and covering the surface of the thermally expandable particles was formed. FIG. 8 is a scanning electron microscope (SEM) image of the composite particles according to the embodiment.

[0074] The true density d [g / cm 3 of the composite particles according to the embodiment was measured as follows. The weight W1 [g] of the composite particles and the weight W2 [g] of the silicone resin precursor DOWSIL (registered trademark) SE 1896 FR A / B-EG Kit, which is a fluid resin manufactured by Dow Corning Toray Co., Ltd., were weighed, and they were uniformly mixed to obtain a mixture. This mixture was cured by heating in a constant temperature bath at 80°C for 1 hour to obtain a molded product. Using an electronic specific gravity meter EW-300SG manufactured by Alpha Mirage Co., Ltd., the true density d1 [g / cm 3 of the molded product was measured according to the immersion method (Archimedes' method). The obtained W1 [g], W2 [g], d1 [g / cm 3 , and the density d2 [g / cm 3 of the silicone resin precursor were introduced into the following formula (2) to calculate the true density d [g / cm 3 of the composite particles according to the embodiment. The true density d was 1.2 g / cm 3 . d = W1 × d1 / { (W1 + W2) - W2 × d1 / d2} Formula (2)

[0075] The volume-based particle size distribution of the composite particles in the example was measured using the Microtrac-Bel MT3300EXII laser diffraction / scattering particle size distribution analyzer, and the median diameter D of the composite particles in the example was determined from this particle size distribution. 50 The median diameter D was calculated. 50 It was 15.7 μm.

[0076] (Example 1-1) To 100 parts by mass of liquid silicone rubber KE-106F manufactured by Shin-Etsu Silicone Co., Ltd., 11.1 parts by mass of CAT-106F, a curing agent specifically for KE-106F, 11.1 parts by mass of silicone oil KF96-10CS manufactured by Shin-Etsu Silicone Co., Ltd., and 50 parts by mass of the above composite particles were added and uniformly dispersed. The resulting mixture was measured using an Anton Paar rheometer MCR-302e to adjust the sample temperature to 25°C, and the viscosity at a shear rate of 10 [1 / sec] was measured using a parallel plate with a diameter of 25 mm. The results are shown in Table 1. 5 g of the obtained mixture was placed in a mold with a side length of 45 mm in plan view and an internal space with a depth of 3 mm, and the mixture was cured by pressing it at 100°C for 10 minutes to obtain the cured product according to Example 1-1. The thermally expanding microcapsules contained in the cured product according to Example 1-1 did not foam (expand) (expand)

[0077] The cured material according to Example 1-1 was cut into a square shape with a side length of 20 mm in a plan view to obtain a measurement sample. The thermal conductivity of this measurement sample was measured using a thermal conductivity measuring device TCM1001 manufactured by Lesca, in accordance with the method compliant with ASTM D5470-1, and the thermal conductivity λ1 in the thickness direction of the cured material according to Example 1-1 was determined. The results are shown in Table 1.

[0078] (Example 1-2) A cured product according to Example 1-2 was obtained in the same manner as in Example 1-1, except that the curing temperature of the mixture was changed to 160°C. When the mixture was pressed at 160°C, curing of the liquid silicone rubber and foaming (thermal expansion) of the thermally expanding microcapsules occurred simultaneously. As a result, the cured product according to Example 1-2 had a porous structure. Figure 9 is an SEM image of a cross-section of the cured product according to Example 1-2. Scale-like boron nitride is arranged in an overlapping manner along the wall surface of the solid portion in contact with the voids. The thermal conductivity λ1 in the thickness direction of the cured product according to Example 1-2 was measured in the same manner as in Example 1-1. The results are shown in Table 1.

[0079] (Example 1-3) A cured product according to Example 1-3 was obtained in the same manner as in Example 1-1, except that the amount of mixture to be placed in the mold was changed to 1.5 g and the curing temperature of the mixture was changed to 160°C. When the mixture was pressed at 160°C, the curing of the liquid silicone rubber and the foaming (thermal expansion) of the thermally expanding microcapsules occurred simultaneously. As a result, the cured product according to Example 1-3 had a porous structure. The thermal conductivity λ1 in the thickness direction of the cured product according to Example 1-3 was measured in the same manner as in Example 1-1. The results are shown in Table 1.

[0080] (Example 2-1) A cured product according to Example 2-1 was obtained in the same manner as in Example 1-1, except that the amount of composite particles added was changed to 72.2 parts by mass. The thermally expanding microcapsules contained in the cured product according to Example 2-1 did not foam (expand thermally). The viscosity of the mixture before curing and the thermal conductivity λ1 in the thickness direction of the cured product according to Example 2-1 were measured in the same manner as in Example 1-1. The results are shown in Table 1.

[0081] (Example 2-2) A cured product according to Example 2-2 was obtained in the same manner as in Example 1-1, except that the amount of composite particles added was changed to 72.2 parts by mass and the curing temperature of the mixture was changed to 160°C. When the mixture was pressed at 160°C, curing of the liquid silicone rubber and foaming (thermal expansion) of the thermally expanding microcapsules occurred simultaneously. As a result, the cured product according to Example 2-2 had a porous structure. The thermal conductivity λ1 in the thickness direction of the cured product according to Example 2-2 was measured in the same manner as in Example 1-1. The results are shown in Table 1.

[0082] (Comparative Example 1-1) To 100 parts by mass of liquid silicone rubber KE-106F, 11.1 parts by mass of CAT-106F, 24 parts by mass of silicone oil KF96-10CS, 11.5 parts by mass of thermally expandable microcapsules FN-100SD, and 25.7 parts by mass of the flaky boron nitride used in the preparation of the above composite particles were added and uniformly dispersed. 5 g of the obtained mixture was placed in a mold having a side length of 45 mm and an internal space depth of 3 mm in a plan view, and the mixture was cured by pressing the mold at 100°C for 10 minutes to obtain a cured product according to Comparative Example 1-1. The thermally expandable microcapsules contained in the cured product according to Comparative Example 1-1 did not foam (expand) (expand)

[0083] (Comparative Example 1-2) A cured product according to Comparative Example 1-2 was obtained in the same manner as in Comparative Example 1-1, except that the amount of mixture to be placed in the mold was changed to 4 g and the curing temperature of the mixture was changed to 160°C. When the mixture was pressed at 160°C, the curing of the liquid silicone rubber and the foaming (thermal expansion) of the thermally expanding microcapsules occurred simultaneously. As a result, the cured product according to Comparative Example 1-2 had a porous structure. The thermal conductivity λ1 in the thickness direction of the cured product according to Comparative Example 1-2 was measured in the same manner as in Example 1-1. The results are shown in Table 1.

[0084] (Comparative Example 1-3) A cured product according to Comparative Example 1-3 was obtained in the same manner as in Comparative Example 1-1, except that the amount of mixture to be placed in the mold was changed to 1.5 g and the curing temperature of the mixture was changed to 160°C. When the mixture was pressed at 160°C, the curing of the liquid silicone rubber and the foaming (thermal expansion) of the thermally expanding microcapsules occurred simultaneously. As a result, the cured product according to Comparative Example 1-3 had a porous structure. The thermal conductivity λ1 in the thickness direction of the cured product according to Comparative Example 1-3 was measured in the same manner as in Example 1-1. The results are shown in Table 1.

[0085] (Comparative Example 2-1) To 100 parts by mass of liquid silicone rubber KE-106F manufactured by Shin-Etsu Silicone Co., Ltd., 11.1 parts by mass of CAT-106F, 11.1 parts by mass of silicone oil KF96-10CS, 11.5 parts by mass of thermal expansion microcapsules FN-100SD, and 40 parts by mass of flaky boron nitride used in the production of composite particles were added and uniformly dispersed. The viscosity of the obtained mixture was measured in the same manner as in Example 1-1. The results are shown in Table 1. 5 g of the obtained mixture was placed in a mold having a side length of 45 mm and an internal space with a depth of 3 mm in a plan view, and the mixture was cured by pressing the mold at 100°C for 10 minutes to obtain a cured product according to Comparative Example 2-1. The thermal expansion microcapsules contained in the cured product according to Comparative Example 2-1 did not foam (thermal expansion). The thermal conductivity λ1 in the thickness direction of the cured product according to Comparative Example 2-1 was measured in the same manner as in Example 1-1. The results are shown in Table 1.

[0086] (Comparative Example 2-2) A cured product according to Comparative Example 2-2 was obtained in the same manner as in Comparative Example 2-1, except that the amount of mixture to be placed in the mold was changed to 4 g and the curing temperature of the mixture was changed to 160°C. When the mixture was pressed at 160°C, curing of the liquid silicone rubber and foaming (thermal expansion) of the thermally expanding microcapsules occurred simultaneously. As a result, the cured product according to Comparative Example 2-2 had a porous structure. The viscosity of the mixture before curing and the thermal conductivity λ1 in the thickness direction of the cured product according to Comparative Example 2-2 were measured in the same manner as in Example 1-1. The results are shown in Table 1.

[0087] As shown in Table 1, although the thermal conductor content in the solid portion of the cured product in Example 1-2 and the thermal conductor content in the solid portion of the cured product in Comparative Example 1-2 are almost the same, the thermal conductivity in the thickness direction of the cured product in Example 1-2 is higher than that of the cured product in the thickness direction of Comparative Example 1-2. The same can be said for the comparison between Example 1-3 and Comparative Example 1-3, and between Example 2-2 and Comparative Example 2-2. The composite particles in the examples are advantageous from the viewpoint of reducing the amount of thermal conductor required to impart the desired heat transfer properties to the foam produced from the foaming composition containing these composite particles. Furthermore, the viscosity of the mixture before curing in Example 1 is lower than that of the mixture before curing in Comparative Example 1. In addition, the viscosity of the mixture before curing in Example 2 is lower than that of the mixture before curing in Comparative Example 2. The use of composite particles is advantageous from the viewpoint of handling the mixture before curing, foaming (thermal expansion), and the possibility of adding further particles.

[0088]

[0089] Cross-sectional samples were prepared by ion polishing after resin embedding for the cured product (foamed resin composition) according to Example 1-1, the cured product (foamed cured body) according to Example 1-2, the cured product (foamed resin composition) according to Comparative Example 1-1, and the cured product (foamed cured body) according to Comparative Example 1-2. These cross-sectional samples were fixed to a predetermined support to obtain samples for nanoindentation measurement. Figure 10A is a schematic diagram showing nanoindentation measurement. In nanoindentation measurement, after pressing the indenter Id into the sample Sa to a predetermined indentation depth hmax, the load is removed, and a graph (load-displacement curve) showing the relationship between load [μN] and displacement [nm] as shown in Figure 10B is obtained. In Figures 10A and 10B, hmax is the maximum displacement, hc is the contact depth, Pmax is the maximum load, and hf is the amount of plastic deformation.

[0090] Using a Triboindentor TI 950 and a Berkovich (triangular pyramidal) indenter manufactured by Bruker, single-indentation measurements were performed on the above-mentioned nanoindentation measurement sample under conditions of an indentation depth of 1000 nm and a temperature of 25°C. Based on these measurement results, the hardness [Pa] was calculated by dividing the maximum load (Pmax) by the contact area of ​​the indenter with the sample (contact projection area A). Specifically, the maximum load Pmax was identified in the load-displacement curve shown in Figure 10B. Furthermore, the displacement at the intersection of the tangent line at the maximum displacement hmax with respect to the curve during unloading and the horizontal axis was identified as the contact depth hc, and the contact projection area A, which is the cross-sectional area of ​​the indenter corresponding to the contact depth hc, was calculated from the contact depth hc. For the unfoamed foaming resin composition, nanoindentation measurements were performed at five locations each in the solid portion in contact with the foaming agent (in Example 1-1, the coating layer of composite particles) and the resin portion other than the solid portion in contact with the foaming agent (second resin portion), and the average hardness was calculated. For the foamed cured product, nanoindentation measurements were performed at five locations each in the solid portion in contact with the bubbles originating from the randomly selected composite particles and the resin portion other than the solid portion in contact with the bubbles (second resin portion), and the average hardness was calculated. The results are shown in Table 2.

[0091]

[0092] As shown in Table 2, the hardness of the composite particle coating layer in Example 1-1 and the hardness of the solid portion in contact with the bubbles in Example 1-2 were both higher than the hardness of the second resin portion in each example, and the ratio of the hardness of the foaming agent or the solid portion in contact with the bubbles to the hardness of the second resin portion was greater than 1.1. These examples suggest that a thermal conductor with a higher hardness than the resin accumulates in contact with the foaming agent or the bubbles generated by the foaming of the foaming agent. Therefore, it is thought that the thermal conductivity of the cured product is higher when composite particles are used, when compared at the same foaming ratio.

[0093] (Example 3-1) The following raw materials for the base layer and adhesive layer were prepared. <Base Layer> Polyethylene naphthalate (PEN) resin film Product name: "Teonex" series (manufactured by Toyobo Co., Ltd.) Thickness: 75 μm <Raw Materials for Adhesive Layer> [Polymer component] Epoxy (novolac type epoxy resin / o-cresol novolac type) Epoxy equivalent: Approximately 208 (g / eq) Product name: YDCN-704 (manufactured by Nippon Steel Chemical & Material Co., Ltd.) [Curing agent] Dicyandiamide (DICY) (commercial product) Imidazole compound (2-phenyl-4-methyl-5-hydroxymethylimidazole) Product name: 2P4MHZ-PW (manufactured by Shikoku Chemicals Co., Ltd.) [Foaming agent (thermal expansion agent)] Composite particles according to the above example

[0094] A mixture was prepared by adding each of the above raw materials for the adhesive layer to methyl ethyl ketone in the amounts shown in Table 3. This amount represents the ratio of each raw material to the total amount of raw materials added to the methyl ethyl ketone. The methyl ethyl ketone content in the mixture was 50% by mass. The mixture obtained was coated onto one main surface of the above substrate layer using a bar coater so that the thickness of one adhesive layer after drying was 35 μm. The substrate layer coated with the mixture was dried in an environment of 110°C for 5 minutes to volatilize the organic solvent contained in the mixture. In this way, an adhesive layer was formed on one main surface of the substrate layer. An adhesive layer was similarly formed on the other main surface of the substrate layer, and an adhesive sheet according to Example 3-1 with a three-layer structure in which the substrate layer was arranged between the pair of adhesive layers was obtained. The thickness of the adhesive sheet according to Example 3-1 was 145 μm.

[0095] <Measurement of Thermal Conductivity λ²> The adhesive sheet according to Example 3-1 was cut into a square shape with a side length of 30 mm in a plan view. Two fluororesin sheets manufactured by Nitto Denko Corporation were prepared. The adhesive sheet according to Example 3-1 and a spacer with a thickness of 200 μm surrounding the entire circumference of the adhesive sheet were placed on one of the fluororesin sheets, and the other fluororesin sheet was placed on top of the adhesive sheet and spacer. In this state, the laminate of the two fluororesin sheets and the adhesive sheet was hot-pressed at 170°C for 15 minutes. This obtained a foamed cured body with a thickness of 200 μm. A foamed cured body with a thickness of 350 μm was obtained using the same procedure, except that a spacer with a thickness of 350 μm was used instead of a spacer with a thickness of 200 μm. These foamed cured bodies and the adhesive sheet before foaming curing were used as test specimens for measuring thermal conductivity, and the thermal conductivity was measured. The thermal conductivity λ2 in the thickness direction of these test specimens was measured using a thermal conductivity measuring device manufactured by Eiko Seiki Co., Ltd., in accordance with the US standard ASTME1530 (disk heat flow meter method). The results are shown in Table 3.

[0096] <Evaluation of Shear Adhesion Strength> Two cold-rolled steel sheets SPCC-SD, each 1.0 mm thick, 15 mm wide, and 100 mm long, were prepared. Two spacers were placed at a predetermined interval along the length of one cold-rolled steel sheet (cold-rolled steel sheet A) on one end of the sheet. The thickness of these spacers was 200 μm. Next, an adhesive sheet according to Example 3-1, cut into a rectangular shape with a short side length of 10 mm and a long side length of 15 mm in a plan view, was placed between the two spacers. One end of cold-rolled steel sheet A and one end of the other cold-rolled steel sheet (cold-rolled steel sheet B) were overlapped so that the two spacers were covered. A clamp was used to fix the overlapping portion of cold-rolled steel sheet A and cold-rolled steel sheet B, and a preliminary test specimen was prepared. Next, the ambient temperature of the preliminary test specimen was raised from room temperature (5-35°C) to 170°C over 3 minutes, and the ambient temperature was maintained at 170°C for 15 minutes. This cured the adhesive layer of the adhesive sheet, and test specimen A, containing the cured foam, with a thickness of 200 μm, was obtained for evaluating shear adhesion strength. Using the same procedure, except that the thickness of the two spacers was set to 300 μm, test specimen B, containing the cured foam, with a thickness of 300 μm, was obtained. Using the same procedure, except that the thickness of the two spacers was set to 350 μm, test specimen C, containing the cured foam, with a thickness of 350 μm, was obtained for evaluating shear adhesion strength.

[0097] Using a tensile testing machine manufactured by Shimadzu Corporation, the above-mentioned test specimens A, B, and C were fixed using a chuck, and their shear strength was measured at a tensile speed of 5 mm / min. This measurement was performed at room temperature (15-30°C). The results are shown in Table 3.

[0098] <Calculation of Expansion Ratio> The expansion ratio was calculated for the foamed cured bodies of the test specimen, test piece A, test piece B, and test piece C used for thermal conductivity measurement, according to the following formula (3). The results are shown in Table 3. Expansion ratio = (Thickness of adhesive sheet after foaming and curing - Thickness of substrate layer) / (Thickness of adhesive sheet before curing - Thickness of substrate layer) Formula (3)

[0099] (Comparative Example 3-1) An adhesive sheet according to Comparative Example 3-1 was prepared in the same manner as in Example 3-1, except for the following points. Instead of the composite particles according to the example, FN-100SD, a heat-expandable capsule manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd., was used as the foaming agent (thermal expansion agent). The amounts of each raw material were adjusted as shown in Table 3. Except for using the adhesive sheet according to Comparative Example 3-1 instead of the adhesive sheet according to Example 3-1, thermal conductivity λ2 measurement, shear adhesion strength evaluation, and expansion ratio calculation were performed in the same manner as in Example 3-1. The results are shown in Table 3.

[0100] (Comparative Example 3-2) An adhesive sheet according to Comparative Example 3-2 was prepared in the same manner as in Example 3-1, except for the following points. Instead of the composite particles according to the example, FN-100SD, a heat-expandable capsule manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd., was used as the foaming agent (thermal expansion agent). In addition, the flaky boron nitride used in the preparation of the composite particles was used. The amounts of each raw material were adjusted as shown in Table 3. Except for using the adhesive sheet according to Comparative Example 3-2 instead of the adhesive sheet according to Example 3-1, thermal conductivity λ2 measurement, shear adhesion strength evaluation, and expansion ratio calculation were performed in the same manner as in Example 3-1. The results are shown in Table 3.

[0101] As shown in Table 3, the thermal conductivity in the thickness direction of the specimen according to Example 3-1 was higher than that of the specimen according to Comparative Example 3-1, which was under the same curing conditions. This suggests that using the composite particles according to the example as a foaming agent (thermal expansion agent) increases the thermal conductivity of the foamed cured body containing the composite particles. The shear strengths of specimens B (thickness 300 μm) and C (thickness 350 μm) according to Example 3-1 were greater than the shear strengths of specimens B and C, respectively, according to Comparative Example 3-2. Therefore, it can be said that using the composite particles according to the example tends to increase the adhesive strength of the foamed cured body of the adhesive layer compared to adding the thermal conductor and thermal expansion capsule separately.

[0102]

[0103] A first aspect of the present invention provides a composite particle comprising a foaming agent, a plurality of heat conductors arranged along the surface of the foaming agent, and a first resin disposed on the surface of the foaming agent and between the heat conductors, and a coating layer covering the surface of the foaming agent.

[0104] A second aspect of the present invention is to provide composite particles in which, in the first aspect, the foaming agent is spherical particles.

[0105] A third aspect of the present invention is to provide composite particles in which, in the first or second aspect, the foaming agent is a thermally expandable particle.

[0106] A fourth aspect of the present invention provides a composite particle in which, in any one of the first to third aspects, the heat conductor is an electrical insulator.

[0107] A fifth aspect of the present invention provides a foamable resin composition comprising composite particles described in any one of the first to fourth aspects and a second resin, wherein the composite particles and the second resin are mixed.

[0108] A sixth aspect of the present invention provides a foamable resin composition in which, in the fifth aspect, the ratio of the hardness of the solid in contact with the foaming agent to the hardness of the cured product of the second resin is greater than 1.1.

[0109] The seventh aspect of the present invention provides a foamed and cured product of a dried foamed resin composition relating to the fifth or sixth aspect.

[0110] The eighth aspect of the present invention provides a foamed cured body in which, in the seventh aspect, the ratio of the hardness of the solid in contact with the bubbles derived from the foaming agent to the hardness of the second resin is greater than 1.1.

[0111] The ninth aspect of the present invention provides a laminate comprising a base material and a resin layer disposed on the base material and containing composite particles described in any one of the first to fourth aspects and a second resin.

[0112] The tenth aspect of the present invention provides a laminate comprising a base material and a foamed layer disposed on the base material, wherein the foamed layer includes a foamed cured resin layer containing the composite particles and a second resin described in any one of the first to fourth aspects.

[0113] An eleventh aspect of the present invention provides an electric motor comprising a laminate described in the tenth aspect, a stator core, and windings arranged adjacent to the stator core, wherein the laminate bondes the stator core and the windings together.

Claims

1. A composite particle comprising a foaming agent, a plurality of heat conductors arranged along the surface of the foaming agent, and a first resin disposed on the surface of the foaming agent and between the heat conductors, the coating layer covering the surface of the foaming agent.

2. The composite particle according to claim 1, wherein the foaming agent is spherical particles.

3. The composite particle according to claim 1, wherein the foaming agent is a thermally expandable particle.

4. The composite particle according to claim 1, wherein the heat conductor is an electrical insulator.

5. A foaming resin composition comprising composite particles according to any one of claims 1 to 4 and a second resin, wherein the composite particles and the second resin are mixed.

6. The foaming resin composition according to claim 5, wherein the ratio of the hardness of the solid in contact with the foaming agent to the hardness of the cured product of the second resin is greater than 1.

1.

7. A foamed and cured product of a dried foamed resin composition according to claim 5.

8. The foamed cured body according to claim 7, wherein the ratio of the hardness of the solid in contact with the bubbles derived from the foaming agent to the hardness of the second resin is greater than 1.

1.

9. A laminate comprising a base material, and a resin layer disposed on the base material and containing composite particles according to any one of claims 1 to 4 and a second resin.

10. A laminate comprising a base material and a foamed layer disposed on the base material and comprising a foamed and cured resin layer containing composite particles and a second resin as described in any one of claims 1 to 4.

11. An electric motor comprising: a laminate according to claim 10; a stator core; and windings arranged adjacent to the stator core, wherein the laminate bondes the stator core and the windings together.

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