Composite particles, mixture, composite material, and method for producing composite particles

Abstract

A composite particle 1a is provided with a hollow particle 10 and a coating layer 20. The coating layer 20 comprises a plurality of heat conductors 21 and a first resin 22. The plurality of heat conductors 21 are disposed along the surface of the hollow particle 10. The first resin 22 is disposed on the surface of the hollow particle 10 and between the heat conductors 21. The composite particles 1a satisfy at least one condition selected from the group consisting of (Id) and (IId). (Ia) The composite particle 1a has a particle diameter of 200 μm or less, and the circularity of a projection image of the composite particle 1a is 0.7 or more. (IIa) The plurality of heat conductors 21 comprise hexagonal boron nitride, and the area strength ratio RX1 is 0.07-0.14.

Description

Composite particles, mixtures, composite materials, and methods for making composite particles

[0001] The present invention relates to composite particles, mixtures, composite materials, and methods for making composite particles.

[0002] Conventionally, thermally conductive fillers having hollow particles have been known.

[0003] For example, Patent Document 1 describes a thermally conductive filler having hollow particles and a thermally conductive layer. The hollow particles have polar groups on their surfaces. The thermally conductive layer coats the surfaces of the hollow particles and contains an inorganic compound. The polar groups are bonded to the surfaces of the hollow particles via siloxane bonds. Patent Document 1 also describes a thermally conductive composite material in which this thermally conductive filler is dispersed in a matrix material, and a wire harness including this thermally conductive composite material.

[0004] Patent Document 2 describes a thermally conductive filler having hollow base particles and a coating layer. The coating layer contains a gel-like substance and a thermally conductive substance. The gel-like substance is chemically bonded to the surface of the base particles to coat the surface of the base particles. The thermally conductive substance has a higher thermal conductivity and a larger specific gravity than the base particles and the gel-like substance dispersed within the layer of the gel-like substance. The publication also describes a thermally conductive composite material in which this thermally conductive filler is dispersed in a matrix material, and a wire harness including this thermally conductive composite material.

[0005] JP 2021-98798 A JP 2022-67508 A

[0006] Although the above patent documents show that a thermally conductive filler is dispersed in a matrix material in a thermally conductive composite material, they do not anticipate obtaining a composite material by flowing a fluid containing the thermally conductive filler through a narrow space. Therefore, the technology described in the above patent documents has room for reexamination from the perspective of moving composite particles having hollow particles through a narrow space using a fluid containing the composite particles.

[0007] In view of these circumstances, the present invention provides composite particles that are advantageous from the viewpoint of moving composite particles having hollow particles into a narrow space using a fluid containing the composite particles.

[0008] The present invention provides composite particles comprising: hollow particles; a plurality of thermal conductors arranged along the surfaces of the hollow particles; and a coating layer that covers the surfaces of the hollow particles, the coating layer including a first resin arranged on the surfaces of the hollow particles and between the thermal conductors, wherein the composite particles satisfy at least one condition selected from the group consisting of (Ia) and (IIa) below: (Ia) The composite particles have a particle size of 200 μm or less, and the circularity of a projected image of the composite particles is 0.7 or more; (IIa) The plurality of thermal conductors comprise hexagonal boron nitride, and in an X-ray diffraction pattern of a powder that is an aggregate of the composite particles, the area intensity ratio of the diffraction peak derived from the (100) crystal plane of the hexagonal boron nitride to the diffraction peak derived from the (002) crystal plane of the hexagonal boron nitride is 0.07 or more and 0.14 or less.

[0009] The present invention also provides a mixture comprising composite particles and a second resin having flowability, the mixture being a mixture of the composite particles and the second resin, the composite particles including hollow particles, a plurality of thermal conductors arranged along the surfaces of the hollow particles, and a first resin arranged on the surfaces of the hollow particles and between the thermal conductors, and a coating layer coating the surfaces of the hollow particles, the mixture satisfying at least one condition selected from the group consisting of the following (Ib) and (IIb): (Ib) The mixture has a viscosity of 1 to 200 Pa·s at 25°C, and a solidified product of the mixture has a viscosity of 0.1 to 3.0 W·m -1 ・K -1 (IIb) The plurality of thermal conductors contain hexagonal boron nitride, and in an X-ray diffraction pattern of the mixture, the area intensity ratio of a diffraction peak originating from a (100) crystal plane of the hexagonal boron nitride to a diffraction peak originating from a (002) crystal plane of the hexagonal boron nitride is 0.03 or more and 0.14 or less.

[0010] The present invention also provides a composite material comprising a solid matrix and a plurality of composite particles, the plurality of composite particles being dispersed within the matrix, the composite material satisfying at least one condition selected from the group consisting of the following (Ic) and (IIc): (Ic) The composite particle is the composite particle described above. (IIc) The composite particle comprises a hollow particle and a coating layer, the coating layer comprising a plurality of thermal conductors arranged along the surface of the hollow particle and a first resin arranged on the surface of the hollow particle and between the thermal conductors, the plurality of thermal conductors comprising hexagonal boron nitride, and in an X-ray diffraction pattern of the composite material, the area intensity ratio of the diffraction peak derived from the (100) crystal plane of the hexagonal boron nitride to the diffraction peak derived from the (002) crystal plane of the hexagonal boron nitride is 0.037 or more and 0.14 or less.

[0011] The present invention also provides a method for producing composite particles, comprising: adhering a liquid resin to the surface of a hollow particle; and contacting a plurality of thermal conductors with the liquid resin to arrange the plurality of thermal conductors along the surface, thereby forming a coating layer that coats the surface of the hollow particle, wherein the composite particle satisfies at least one condition selected from the group consisting of (Id) and (IId) below: (Id) The composite particle has a particle size of 200 μm or less, and the circularity of a projected image of the composite particle is 0.7 or more. (IId) The plurality of thermal conductors comprise hexagonal boron nitride, and in an X-ray diffraction pattern of a powder that is an aggregate of the composite particles, the area intensity ratio of the diffraction peak derived from the (100) crystal plane of the hexagonal boron nitride to the diffraction peak derived from the (002) crystal plane of the hexagonal boron nitride is 0.07 or more and 0.14 or less.

[0012] The above composite particles are advantageous from the viewpoint of moving the composite particles in a narrow space using a fluid containing the composite particles.

[0013] FIG. 1 is a diagram showing an example of an embodiment of a composite particle. FIG. 2 is a cross-sectional view of a composite particle taken along line II-II in FIG. 1. FIG. 3 is a diagram showing an example of a method for producing a composite particle. FIG. 4 is a diagram showing an example of an embodiment of a mixture. FIG. 5A is a diagram showing an example of an embodiment of a composite material. FIG. 5B is a diagram showing another example of an embodiment of a composite material. FIG. 6 is a diagram showing an example of a method for producing a composite material. FIG. 7 is a photograph of a composite particle according to Example 1. FIG. 8A is a graph showing an X-ray diffraction (XRD) pattern of a powder that is an aggregate of composite particles according to Example 1. FIG. 8B is a graph showing an XRD pattern of a mixture according to Example 1. FIG. 8C is a graph showing an XRD pattern of a cured product of the mixture according to Example 1. FIG. 9A is a photograph showing an apparatus for measuring impact absorption rate. FIG. 9B is a photograph showing an apparatus for measuring impact absorption rate. FIG. 9C is a photograph showing a test sample for measuring impact absorption rate. FIG. 10A is a graph showing an XRD pattern of a mixture according to Example 4. Fig. 10B is a graph showing an XRD pattern of a cured product of the mixture according to Example 4. Fig. 11 is a photograph of a composite particle according to Comparative Example 2. Fig. 12 is a graph showing an XRD pattern of a cured product of the mixture according to Comparative Example 3. Fig. 13A is a graph showing an XRD pattern of a mixture according to Comparative Example 8. Fig. 13B is a graph showing an XRD pattern of a cured product of the mixture according to Comparative Example 8.

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following description is for illustrative purposes only and is not intended to limit the scope of the present invention.

[0015] As shown in Figures 1 and 2, the composite particle 1a comprises a hollow particle 10 and a coating layer 20. The composite particle 1a has a particle size of, for example, 200 µm or less. A void 12 is formed inside the hollow particle 10. The coating layer 20 contains a plurality of thermal conductors 21 and a first resin 22. The plurality of thermal conductors 21 are arranged along the surface of the hollow particle 10. The first resin 22 is arranged on the surface of the hollow particle 10 and between the thermal conductors 21. The coating layer 20 coats the surface of the hollow particle 10. The circularity of the projected image of the composite particle 1a is, for example, 0.7 or more. The circularity is expressed by the following formula (1). In formula (1), S is the area of ​​the portion surrounded by the outline of the projected image of the composite particle 1a, and L is the circumferential length of the outline. Circularity = 4πS / L 2 Formula (1)

[0016] As described above, the composite particle 1a satisfies, for example, the condition (Ia). The composite particle 1a may also satisfy, for example, the following condition (IIa). The composite particle 1a satisfies at least one condition selected from the group consisting of the following conditions (Ia) and (IIa). The area intensity ratio R X1 can be determined, for example, according to the method described in the Examples. (Ia) The composite particles 1a have a particle size of 200 μm or less, and the circularity of the projected image of the composite particles 1a is 0.7 or more. (IIa) The plurality of thermal conductors 21 contain hexagonal boron nitride, and in the X-ray diffraction pattern of a powder that is an aggregate of the composite particles 1a, the area intensity ratio R of the diffraction peak originating from the (100) crystal plane of hexagonal boron nitride to the diffraction peak originating from the (002) crystal plane of hexagonal boron nitride is X1 is equal to or greater than 0.07 and equal to or less than 0.14.

[0017] Composite materials containing composite particles containing thermal conductors are expected to be used in applications such as heat dissipation. For example, to obtain a composite material that occupies a small space, it is conceivable to supply a fluid containing composite particles to the small space and solidify it. In this case, it is considered important that the particle size of the composite particles is small in order to arrange the composite particles at a desired density in the small space. However, according to the inventors' studies, it has been found that simply having a small particle size of the composite particles does not allow sufficient composite particles to be supplied to the small space, making it difficult for the composite material to have the desired properties in the small space.

[0018] Since the composite particles 1a include hollow particles 10, the specific gravity of the composite particles 1a is small, and it is easy to reduce the weight of a composite material including the composite particles 1a. By satisfying at least one condition selected from the group consisting of the above (Ia) and (IIa), when a fluid containing the composite particles 1a is supplied toward a narrow space, the composite particles 1a tend to move into the narrow space along with the flow of the fluid. As a result, the composite particles 1a tend to be arranged at a desired density in the narrow space.

[0019] The composite particle 1a may satisfy only the condition (Ia), may satisfy only the condition (IIa), or may satisfy both the conditions (Ia) and (IIa). X1 When condition (IIa) is satisfied, the hexagonal boron nitride contained in the plurality of thermal conductors 21 is likely to be arranged in the desired state along the surface of the hollow particle 10, and when a fluid containing the composite particles 1a is supplied toward a narrow space, it is thought that the composite particles 1a are likely to move into the narrow space along with the flow of the fluid.

[0020] Area intensity ratio R X1 may be 0.075 or more, 0.08 or more, or 0.085 or more, and may be 0.13 or less, 0.12 or less, 0.11 or less, or 0.10 or less.

[0021] The particle diameter of the composite particles 1a may be 180 μm or less, 160 μm or less, 140 μm or less, 120 μm or less, or 100 μm or less, or may be 10 μm or more, 20 μm or more, 30 μm or more, 40 μm or more, or 50 μm or more.

[0022] The circularity of the projected image of the composite particle 1a is preferably 0.75 or more, more preferably 0.78 or more, and even more preferably 0.8 or more, and may be, for example, 1 or less, or 0.98 or less.

[0023] The composite particle 1a is, for example, a spherical particle. For example, the circularity of a pair of projected images of the composite particle 1a in two directions perpendicular to each other is 0.7 or more.

[0024] The shape and dimensions of the thermal conductors 21 are not limited to specific values. For example, the ratio of the particle size of the hollow particles 10 to the maximum diameter of the thermal conductors 21 is not limited to a specific value. This ratio is, for example, 5 to 200. When this ratio is 5 or more, multiple thermal conductors 21 are likely to be uniformly arranged along the surface of the hollow particles 10. In addition, when this ratio is 200 or less, the number of thermal conductors 21 arranged along the surface of the hollow particles 10 is likely to be small, and the total contact thermal resistance caused by contact between the thermal conductors 21 or contact between the thermal conductors 21 and the first resin 22 in the composite particle 1a is likely to be small.

[0025] The ratio of the particle size of the hollow particles 10 to the maximum diameter of the thermal conductor 21 is desirably 5 or more, and may be 10 or more, 20 or more, 30 or more, 40 or more, or 50 or more, or may be 180 or less, 160 or less, 140 or less, 120 or less, or 100 or less.

[0026] The maximum diameter of the thermal conductor 21 is, for example, 0.01 μm or more, and may be 0.1 μm or more, or 1 μm or more, and may be, for example, 20 μm or less, 10 μm or less, or 5 μm or less.

[0027] 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%, or may be 5% to 40%, or 10% to 30% by volume. The volume of the voids 12 is included in the volume of the hollow particle 10.

[0028] The hollow particles 10 are, for example, spherical hollow particles. The material forming the hollow particles 10 is not particularly limited. The material may be an organic material such as an organic polymer, or an inorganic material such as glass. Examples of organic materials include acrylonitrile copolymer, polyvinylidene chloride, polymethacrylonitrile, polymethyl methacrylate, and polystyrene.

[0029] The ratio of the maximum diameter to the minimum dimension of the thermal conductors 21 is not limited to a specific value. This ratio is, for example, equal to or less than 50. In this case, the thermal conductors 21 are likely to be arranged along the surface of the hollow particle 10 in the direction determined by the maximum diameter, and a wide area of ​​the surface of the composite particle 1a is likely to be covered with multiple thermal conductors 21.

[0030] The ratio of the maximum diameter to the minimum dimension of the thermal 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.

[0031] The thermal conductors 21 are, for example, scale-like particles. In this case, the thickness of the thermal conductors 21 corresponds to the above-mentioned minimum dimension, and the diameter of the thermal conductors 21 when viewed in plan corresponds to the above-mentioned maximum diameter. In this case, a wide range of the surface of the composite particle 1a is more likely to be covered by the multiple thermal conductors 21. The thermal conductors 21 may be spherical, rod-shaped, or irregularly shaped.

[0032] 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), beryllium, diamond, carbon black, graphene, carbon nanotubes, carbon fiber, and aluminum hydroxide.

[0033] The thermal conductor 21 may have electrical insulation properties. In this case, for example, the composite particles 1a can be used in applications where both electrical insulation and heat dissipation are required. Examples of electrically insulating materials 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. In this specification, having electrical insulation properties means that the electrical conductivity at 20°C is 10 -6 The thermal conductor 21 may be a combination of two or more types of material and a combination of two or more types of size.

[0034] The first resin 22 is not limited to a specific resin. The first resin 22 includes, for example, a cross-linked polymer. The first resin 22 may be a thermosetting resin. Examples of thermosetting resins include phenolic resin, urea resin, melamine resin, diallyl phthalate resin, polyester resin, epoxy resin, aniline resin, silicone resin, furan resin, polyurethane resin, alkylbenzene resin, guanamine resin, xylene resin, and imide resin. The curing temperature of the thermosetting resin is, for example, 25°C to 160°C.

[0035] 3 , in the production of composite particle 1a, for example, a liquid resin 22a is attached to the surface of hollow particle 10, and a plurality of thermal conductors 21 are brought into contact with the liquid resin 22a, so that the plurality of thermal conductors 21 are arranged along the surface of hollow particle 10. This forms coating layer 20 that coats the surface of hollow particle 10. Liquid resin 22a can be a precursor of first resin 22.

[0036] For example, a mixture is obtained by mixing a plurality of hollow particles 10 with a liquid resin 22a. This allows the liquid resin 22a to adhere to the surfaces of the plurality of hollow particles 10. Next, a plurality of thermal conductors 21 are added to this mixture and further mixed. This brings the plurality of thermal conductors 21 into contact with the liquid resin 22a adhering to the surfaces of the hollow particles 10, and the plurality of thermal conductors 21 are arranged along the surfaces of the hollow particles 10. The addition of the liquid resin 22a and the addition of the plurality of thermal conductors 21 may be repeated alternately. This tends to increase the amount of thermal conductor 21 contained in the composite particles 1a, and tends to improve the heat dissipation property of a composite material including the composite particles 1a.

[0037] There is no particular limitation on the method for mixing the plurality of hollow particles 10 with the liquid resin 22a and further mixing the plurality of thermal conductors 21 in the production of the composite particle 1a. Examples of such mixing include mixing using a ball mill, a bead mill, a planetary mixer, an ultrasonic mixer, a homogenizer, a planetary mixer, a rotation-revolution mixer, a fluid mixer, a Henschel mixer, a container-rotating blender, a ribbon blender, and a conical screw blender.

[0038] In the production of the composite particle 1a, for example, the liquid resin 22a attached to the surfaces of the plurality of hollow particles 10 is cured by heating, whereby the plurality of thermal conductors 21 are fixed to the hollow particles 10.

[0039] The surface properties of the composite particles 1a may be modified by a surface modifier. Examples of the surface modifier include a silane coupling agent, a thiol, a disulfide, and a carboxylic acid. The surface properties of the composite particles 1a may be modified by UV treatment, plasma treatment, or vapor deposition treatment.

[0040] As shown in FIG. 4 , a mixture 3 can be provided. The mixture 3 includes a composite particle 1b and a second resin 2a having fluidity. The mixture 3 is a mixture of the composite particle 1b and the second resin 2a. The composite particle 1b has the same configuration as the composite particle 1a, except for portions specifically described, and includes, for example, a hollow particle 10 and a coating layer 20. The coating layer 20 includes a plurality of thermal conductors 21 and a first resin 22. The plurality of thermal conductors 21 are arranged along the surface of the hollow particle 10. The first resin 22 is arranged on the surface of the hollow particle 10 and between the thermal conductors 21. The coating layer 20 coats the surface of the hollow particle 10. The composite particle 1b may have a particle size of 200 μm or less, or may have a particle size greater than 200 μm. The circularity of the composite particle 1b may be 0.7 or greater, or may be less than 0.7. For example, in the mixture 3, the second resin 2a forms a continuous phase, and a plurality of composite particles 1b form a dispersed phase. The mixture 3 has a viscosity of, for example, 1 to 200 Pa·s at 25° C. In addition, the solidified mixture 3 has a viscosity of, for example, 0.1 to 3.0 W·m -1 ・K -1 In this way, the mixture 3 satisfies, for example, the following condition (Ib). The mixture 3 may also satisfy, for example, the following condition (IIb). The mixture 3 satisfies at least one condition selected from the group consisting of the following conditions (Ib) and (IIb). The viscosity of the mixture 3 at 25°C is 1 to 200 Pa·s or the area intensity ratio R X2 When the thermal conductivity of the solidified mixture 3 is in the above range, for example, the solidified mixture 3 tends to be lightweight and tends to have the desired heat dissipation properties. The viscosity of the mixture 3 at 25°C can be measured, for example, using a rheometer. The thermal conductivity of the cured mixture 3 can be measured, for example, according to ASTM D5470-1. The area intensity ratio R of the mixture 3 under the following condition (IIb) X2(Ib) The mixture 3 has a viscosity of 1 to 200 Pa·s at 25°C, and the solidified mixture 33 has a viscosity of 0.1 to 3.0 W·m -1 ・K -1 (IIb) The plurality of thermal conductors 21 contain hexagonal boron nitride, and in an X-ray diffraction pattern of the mixture 3, the area intensity ratio R of the diffraction peak originating from the (100) crystal plane of hexagonal boron nitride to the diffraction peak originating from the (002) crystal plane of hexagonal boron nitride is X2 is equal to or greater than 0.03 and equal to or less than 0.14.

[0041] The mixture 3 may satisfy only the condition (Ib), may satisfy only the condition (IIb), or may satisfy both the conditions (Ib) and (IIb).

[0042] Area intensity ratio R X2 may be 0.032 or more, or 0.035 or more, or may be 0.13 or less, 0.12 or less, 0.11 or less, or 0.10 or less.

[0043] When mixture 3 satisfies condition (IIb), the viscosity of mixture 3 at 25°C is not limited to a specific value. The viscosity is, for example, 1 to 200 Pa s. In this case, mixture 3 can be more easily made to flow even in a narrow space.

[0044] The viscosity of mixture 3 at 25°C may be 2 Pa·s or more, 3 Pa·s or more, or 5 Pa·s or more, and may be 180 Pa·s or less, 160 Pa·s or less, 140 Pa·s or less, 120 Pa·s or less, 100 Pa·s or less, 80 Pa·s or less, 60 Pa·s or less, 40 Pa·s or less, 25 Pa·s or less, or 20 Pa·s or less.

[0045] The thermal conductivity of the solidified mixture 3 is 0.1 W m -1 ・K -1 or more than 0.5 W·m -1 ・K -1 or more, 3.0 W m -1 ・K -1 Less than or equal to 2.5 W·m -1 ・K -1 It may be the following:

[0046] The ratio r of the viscosity of the second resin 2a at 25 ° C. to the viscosity of the mixture 3 at 25 ° C. v is not limited to a specific value. v is, for example, equal to or greater than 0.001 and less than 1. With this configuration, the second resin 2 and the composite particles 1b tend to move together in the flow of the mixture 3, and when the mixture 3 is supplied toward a narrow space, the composite particles 1b tend to be uniformly arranged in the narrow space. The viscosity of the second resin 2 can be measured, for example, using a rheometer.

[0047] Ratio v may be 0.001 to 0.99 or 0.002 to 0.9.

[0048] The content of composite particles 1b in mixture 3 is not limited to a specific value. The content is, for example, 10 to 65% by volume. In this case, mixture 3 is likely to have the desired viscosity, and mixture 3 is likely to be supplied to a narrow space. In addition, the solidified product of mixture 3 is likely to have the desired heat dissipation properties.

[0049] The content of the composite particles 1b in the mixture 3 may be 1 to 70% or 10 to 60% by volume.

[0050] The second resin 2a is not limited to a specific resin. The second resin 2a may include, for example, an epoxy resin precursor, poly(meth)acrylate, a poly(meth)acrylate precursor, silicone, a silicone precursor, polyurethane, or a polyurethane precursor. The second resin 2a may include a thermal conductor to increase thermal conductivity. The second resin 2a may include hollow particles to reduce weight. The second resin 2a may include a filler to adjust viscosity. Examples of fillers include quartz, carbon black, talc, calcium carbonate, glass powder, aluminum hydroxide, and hollow particles. The second resin 2a may include a dispersant, a surfactant, or a plasticizer to reduce the viscosity of the mixture 3.

[0051] The mixture 3 may be used, for example, as a potting material. In this case, the mixture 3 may be a one-component potting material containing a curing agent. The mixture 3 may also be configured as the main component of a two-component potting material. In this case, a curing agent is added to the mixture 3 to perform potting. The mixture 3 may also be used as a molding material.

[0052] As shown in FIG. 5A, a composite material 5a including a plurality of composite particles 1a can be provided. The composite material 5a includes a plurality of composite particles 1a and a solid matrix 2. In the composite material 5a, a plurality of composite particles 1a are dispersed within the matrix 2. As shown in FIG. 5B, a composite material 5b can be provided. The composite material 5b includes a plurality of composite particles 1c and a solid matrix 2. In the composite material 5b, a plurality of composite particles 1c are dispersed within the matrix 2. The composite particle 1c has the same configuration as the composite particle 1a except for portions that are particularly described, and includes, for example, a hollow particle 10 and a coating layer 20. The coating layer 20 includes a plurality of thermal conductors 21 and a first resin 22. The plurality of thermal conductors 21 are arranged along the surface of the hollow particle 10. The first resin 22 is arranged on the surface of the hollow particle 10 and between the thermal conductors 21. The coating layer 20 coats the surface of the hollow particle 10. The composite particle 1c may or may not satisfy at least one of the conditions (Ia) and (IIa) above. In the X-ray diffraction pattern of the composite material 5b, the area intensity ratio R of the diffraction peak derived from the (100) crystal plane of hexagonal boron nitride to the diffraction peak derived from the (002) crystal plane of hexagonal boron nitride is X3 is equal to or greater than 0.037 and equal to or less than 0.14.

[0053] 5A and 5B, the composite material 5a and the composite material 5b are disposed, for example, inside the case 7. The composite material 5a and the composite material 5b are in contact with the inner surface of the case 7. The composite material 5a and the composite material 5b have, for example, a portion occupying a narrow space. The minimum dimension d of this portion is Nis, for example, 2 mm or less, may be 1 mm or less or 0.5 mm or less, and is, for example, 0.3 mm or more. In the composite material 5a, as described above, the particle size of the composite particles 1a is 200 μm or less, and the circularity of the projected image of the composite particles 1a is 0.7 or more, so that the composite particles 1a are likely to exist at a desired density even in a portion occupying a narrow space in the composite material 5a. In the composite material 5b, R X3 is 0.037 or more and 0.14 or less, the composite particles 1c can be present at a desired density even in a portion occupying a narrow space in the composite material 5b.

[0054] R X3 may be 0.038 or more, or may be 0.13 or less, 0.12 or less, 0.11 or less, or 0.10 or less.

[0055] The plurality of composite particles 1a and the plurality of composite particles 1c may each include at least one pair of composite particles 1a and one pair of composite particles 1c that are in contact with each other inside the base material 2. The plurality of composite particles 1a and the plurality of composite particles 1c may each include composite particles 1a and composite particles 1c that are separated from the surrounding composite particles 1a and whose surfaces are covered only by the base material 2.

[0056] The composite materials 5a and 5b can be arranged, for example, so as to cover or surround a predetermined component (not shown) inside the case 7. The composite materials 5a and 5b contain the composite particles 1a and 1c, respectively, each having hollow particles 10, and therefore can easily absorb an impact that occurs, for example, when the case 7 is dropped, and the component covered or surrounded by the composite materials 5a and 5b is less likely to be affected by the impact.

[0057] The content of composite particles 1a in composite material 5a or the content of composite particles 1c in composite material 5b is not limited to a specific value. The content may be, for example, 1 to 70%, 5 to 65%, or 10 to 60% by volume. The volume of voids 12 is included in the volume of composite particles 1a or composite particles 1c. In this case, composite materials 5a and 5b are more likely to be lightweight and more likely to have the desired heat dissipation properties. In addition, components covered or surrounded by composite materials 5a and 5b are less likely to be affected by impact. The content of composite particles 1a in composite material 5a may be 5% or more, 10% or more, or 15% or more, and 70% or less, 65% or less, or 60% or less.

[0058] The base material 2 is, for example, a resin. The base material 2 is, for example, a solidified product of the second resin 2 a contained in the mixture 3.

[0059] The ratio d5 / d2 of the density d5 of composite material 5a or 5b to the density d2 of base material 2 is not limited to a specific value. The ratio d5 / d2 is, for example, 0.2 to 1.0. In this case, composite material 5a and composite material 5b are more likely to be lightweight. In addition, components covered or surrounded by composite material 5a and composite material 5b are less susceptible to the effects of impact. The ratio d5 / d2 may be 0.3 to 1.0 or 0.5 to 1.0. The density of a material can be determined, for example, by preparing a rectangular parallelepiped sample, measuring its dimensions, calculating the volume of the sample, and dividing the calculated volume of the sample by the mass of the sample.

[0060] The density d5 of the composite material 5a and the composite material 5b is, for example, 0.3 to 5.0 g / cm 3 is.

[0061] The compressive modulus of the base material 2 is not limited to a specific value. The compressive modulus of the base material 2 is, for example, 0.001 to 15,000 MPa. In this case, the components covered or surrounded by the composite material 5a and the composite material 5b are less susceptible to the effects of an impact. The compressive modulus of the base material 2 may be 0.005 to 5,000 MPa or 0.01 to 10 MPa. The compressive modulus of the base material 2 can be measured, for example, in accordance with Japanese Industrial Standards (JIS) K 7181:2011.

[0062] The impact absorption rate P1 of the composite materials 5a and 5b, determined by the following formula (A), is not limited to a specific value. The impact absorption rate P1 of the composite materials 5a and 5b is, for example, 30% or more. In this case, the impact is less likely to affect parts covered or surrounded by the composite materials 5a and 5b. The impact absorption rate P1 of the composite materials 5a and 5b is preferably 40% or more, more preferably 50% or more, and even more preferably 60% or more. The impact absorption rate P1 of the composite materials 5a and 5b is, for example, 90% or less. In formula (A), F0 is the maximum load [N] acting on the outside of the polycarbonate plate on the side opposite the point where a 110 g iron ball falls when a 110 g iron ball is freely dropped from a height of 200 mm onto a horizontally placed polycarbonate plate having a thickness of 3 mm. F1 is the maximum load [N] that acts on the outside of the laminate on the side opposite the point where the iron ball falls when an iron ball is dropped from a height of 200 mm onto a laminate in which the polycarbonate plate is placed on a 3 mm thick composite material 5a or 5b. Impact absorption rate P1 [%] = 100 × (F0 - F1) / F0 Formula (A)

[0063] 6, composite material 5a or composite material 5b is produced, for example, by supplying mixture 3 in which composite particles 1a are dispersed into the internal space of case 7 and solidifying mixture 3 by heating or the like. Composite material 5a or composite material 5b may also be produced by pouring mixture 3 into a predetermined mold, solidifying mixture 3 inside the mold, and removing the solidified mixture 3 from the mold. In other words, composite material 5a or composite material 5b may be a molded product.

[0064] 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. First, the evaluation methods used in the examples will be described.

[0065] Example 1: Plastic microballoons F-80DE manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd. were used as hollow particles. The hollow particles were spherical and had a particle diameter of 90 μm. The shell material of the hollow particles was an acrylonitrile (AN) copolymer. 13.3 parts by mass of a silicone resin precursor was prepared for 1 part by mass of hollow particles. DOWSIL® SE 1896 FR A / B-EG Kit was used as the silicone resin precursor. In addition, 33.3 parts by mass of flake-shaped boron nitride (hexagonal boron nitride) was prepared for 1 part by mass of hollow particles. The boron nitride was a mixture of boron nitride with an average particle diameter of 6 μm and boron nitride with an average particle diameter of 0.8 μm. The content of boron nitride with an average particle diameter of 6 μm in the total boron nitride was 75% by mass, and the content of boron nitride with an average particle diameter of 0.8 μm in the total boron nitride was 25% by mass. Therefore, the median diameter D in the particle size distribution based on the mass of boron nitride 50 was estimated to be 4.7 μm. This value was considered to be the average maximum diameter of the boron nitride. From the average thickness of boron nitride having an average particle diameter of 6 μm and the average thickness of boron nitride having an average particle diameter of 0.8 μm, and taking into account the mass-based content of each boron nitride in the entire boron nitride, the median in the mass-based thickness distribution of boron nitride was estimated to be 0.23 μm. This value was considered to be the average thickness of boron nitride. The ratio of the average maximum diameter of boron nitride to the average thickness of boron nitride was determined to be the ratio of the maximum diameter to the minimum dimension of boron nitride. This ratio was approximately 20.5. The ratio of the particle diameter of hollow particles to the average maximum diameter of boron nitride was determined to be the ratio of the particle diameter of hollow particles to the maximum diameter of boron nitride. This ratio was 19.1.

[0066] One part by mass of the hollow particles was added to a Kawata SMP-2 high-speed fluid mixer, followed by 1.66 parts by mass of the silicone resin precursor. The hollow particles and silicone resin precursor were stirred at 1,000 rpm for 1 minute using the high-speed fluid mixer, resulting in the silicone resin precursor adhering to the surfaces of the hollow particles. Next, 4.16 parts by mass of the boron nitride was added to the mixture of hollow particles and silicone resin precursor, and the mixture was stirred at 1,000 rpm for 1 minute using the high-speed fluid mixer. The silicone resin was then cured by heat treatment for 5 minutes in a 100°C thermostatic chamber. The addition and stirring of the silicone resin precursor, the addition and stirring of the boron nitride, and the curing of the silicone resin were repeated eight times to obtain composite particles according to Example 1, which contained the silicone resin precursor and boron nitride and had a coating layer covering the surfaces of the hollow particles. The median particle size distribution based on the number of the composite particles according to Example 1 was 120 μm. FIG. 7 is a photograph of the composite particles according to Example 1. Based on this photograph, the circularity of the projected image of the composite particle was determined by image processing, and the result was that the circularity of the projected image of the composite particle according to Example 1 was 0.95.

[0067] A silicone resin precursor (DOWSIL® SE 1896FR A / B-EG Kit), a flowable resin manufactured by Dow Toray, was uniformly mixed with the composite particles of Example 1 to obtain a mixture of Example 1. The content of the composite particles of Example 1 in the mixture of Example 1 was 45 vol%, and the content of the resin in the mixture of Example 1 was 55 vol%. The content of plastic microballoons in the mixture of Example 1 was 29 vol%, and the content of boron nitride was 10 vol%. Using an Anton Paar MCR-302e rheometer, the sample temperature was adjusted to 25°C, and the viscosity of the mixture was measured at a shear rate of 10 [1 / sec] using parallel plates with a diameter of 25 mm. The results are shown in Table 1. Additionally, the viscosity of the flowable resin was measured in the same manner as the viscosity of the mixture.

[0068] The thermal conductivity of the mixture of Example 1 was measured as follows. The mixture was filled into a 50 mm x 50 mm x 3 mm mold and then cured by heating in a constant temperature bath at 100°C for 1 hour to obtain a molded product. The molded product obtained was punched out to have a square shape with a side length of 20 mm in plan view, and the thermal conductivity was measured in accordance with ASTM D5470-1 using a thermal conductivity measuring device TCM1011 manufactured by Rhesca. The results are shown in Table 1.

[0069] The mixture according to Example 1 was supplied toward a gap of 0.5 mm in size, and it was visually evaluated whether the composite particles were uniformly arranged in the gap. As a result, it was confirmed that when the mixture according to Example 1 was used, the composite particles were uniformly arranged in the gap.

[0070] A sample for X-ray diffraction (XRD) measurement was prepared from the powder that is an aggregate of the composite particles according to Example 1. XRD measurement of this sample was carried out using an XRD measurement device D8 Discover with GADDS manufactured by Bruker. In this XRD measurement, CuKα radiation was used as the characteristic X-ray. The XRD pattern of this sample is shown in FIG. 8A. From the XRD pattern shown in FIG. 8A, the area intensity ratio R was calculated as the ratio of the area intensity of the diffraction peak originating from the (100) crystal plane of hexagonal boron nitride to the diffraction peak originating from the (002) crystal plane of hexagonal boron nitride. X1 The results are shown in Table 1.

[0071] A sample for XRD measurement was prepared from the mixture of Example 1. XRD measurement of this sample was carried out using an XRD measurement device D8 Discover with GADDS manufactured by Bruker. In this XRD measurement, CuKα radiation was used as the characteristic X-ray. The XRD pattern of this sample is shown in FIG. 8B. From the XRD pattern shown in FIG. 8B, the area intensity ratio R was calculated as the ratio of the area intensity of the diffraction peak originating from the (100) crystal plane of hexagonal boron nitride to the diffraction peak originating from the (002) crystal plane of hexagonal boron nitride. X2 The results are shown in Table 1.

[0072] A sample for XRD measurement was prepared from the cured product of the mixture of Example 1. XRD measurement of this sample was carried out using a Bruker XRD measurement device D8 Discover with GADDS. In this XRD measurement, CuKα radiation was used as the characteristic X-ray. The XRD pattern of this sample is shown in FIG. 8C. From the XRD pattern shown in FIG. 8C, the area intensity ratio R was calculated as the ratio of the area intensity of the diffraction peak originating from the (100) crystal plane of hexagonal boron nitride to the diffraction peak originating from the (002) crystal plane of hexagonal boron nitride. X3 The results are shown in Table 1.

[0073] The impact absorption rate of the solidified mixture of Example 1 was measured as follows. The mixture was filled into a rectangular mold having an internal space measuring 50 mm x 50 mm x 3 mm, and then heated in a constant temperature bath at 100°C for 1 hour to harden the mixture and obtain a molded product. The molded product was punched out to obtain a square with a side length of 40 mm in plan view, obtaining a test specimen of Example 1. This test specimen had a thickness of 3 mm. The test specimen was placed on an 8 mm thick SUS plate to which a Brüel & Kjær TYPE 8230-003 force sensor was attached. A polycarbonate plate with a side length of 40 mm in plan view and a thickness of 3 mm was placed on the test specimen to prepare a test sample (laminate). A 110 g iron ball was dropped from a height of 200 mm onto the main surface of the test sample, which was the surface of a polycarbonate plate. The maximum load F1 acting on the outside of the test sample on the side opposite the point where the iron ball fell was measured using the force sensor. A 110 g iron ball was also dropped from a height of 200 mm onto the main surface of a blank sample, obtained by placing only the polycarbonate plate on an 8 mm thick SUS plate to which the force sensor was attached. The maximum load F0 acting on the outside of the polycarbonate plate on the side opposite the point where the iron ball fell was measured using the force sensor. The impact absorption rate P1 was calculated using the following formula (A). In the formula, F0 and F1 were each calculated using the arithmetic mean value of three measurements. Figures 9A and 9B are photographs showing the apparatus used to measure the impact absorption rate, and Figure 9C is a photograph of a test sample used to measure the impact absorption rate. Impact absorption rate P1 [%] = 100 × (F0 - F1) / F0 Formula (A)

[0074] The mass of the test piece was measured, and the measured mass was divided into 48 cm3 of the test piece. 3The density of the test piece was calculated by dividing the density by the mass of the test piece. The results are shown in Table 1. In addition, a silicone resin precursor, DOWSIL® SE 1896FR A / B-EG Kit, a flowable resin manufactured by Dow Toray, was cured by heating in a constant temperature bath at 100°C for 1 hour to obtain a cured silicone resin. The mass of this cured product was measured, and the density of the cured silicone resin was calculated by dividing the measured mass by the volume of the cured product. The ratio of the density of the test piece (composite material) to the density of the cured silicone resin (base material) is shown in Table 1.

[0075] Using test pieces prepared from the above-described cured silicone resin, the compressive modulus of the cured silicone resin (base material) was measured in accordance with JIS K 7181: 2011. The results are shown in Table 1.

[0076] Example 2 The mixture of Example 2 was obtained in the same manner as Example 1, except for the following points. Instead of the silicone resin precursor DOWSIL SE 1896 FR A / B-EG Kit, a flowable resin manufactured by Dow Toray, DOWSIL SE 1817 CV MA / B, a flowable resin manufactured by the same company, was used. The content of the composite particles of Example 1 in the mixture of Example 2 was 40% by volume, and the content of the flowable resin in the mixture of Example 2 was 60% by volume. The viscosity at 25°C of the mixture and the flowable resin of Example 2 was measured in the same manner as Example 1. The results are shown in Table 1. The thermal conductivity of the mixture of Example 2 was measured in the same manner as Example 1. The results are shown in Table 1.

[0077] The mixture of Example 2 was fed into a gap of 0.5 mm in size, and it was evaluated whether the composite particles were uniformly arranged in the gap. As a result, it was confirmed that when the mixture of Example 2 was used, the composite particles were uniformly arranged in the gap. In the same manner as in Example 1, the impact absorption rate of the solidified mixture of Example 2 was measured. The results are shown in Table 1.

[0078] The mass of the test piece for measuring the impact absorption rate was measured, and the measured mass was calculated based on the volume of the test piece, 48 cm 3The density of the test piece was calculated by dividing the density by the mass of the test piece. The results are shown in Table 1. In addition, DOWSIL SE 1817 CV MA / B, a flowable resin manufactured by Dow Toray, was cured by heating in a constant temperature bath at 100°C for 1 hour to obtain a cured silicone resin. The mass of this cured product was measured, and the density of the cured silicone resin was calculated by dividing the measured mass by the volume of the cured product. The ratio of the density of the test piece (composite material) to the density of the cured silicone resin (base material) is shown in Table 1.

[0079] Using test pieces prepared from the above-described cured silicone resin, the compressive modulus of the cured silicone resin (base material) was measured in accordance with JIS K 7181: 2011. The results are shown in Table 1.

[0080] Example 3 A mixture according to Example 3 was obtained in the same manner as in Example 2, except for the following points. The content of the composite particles according to Example 1 in the mixture according to Example 3 was adjusted to 20% by volume. The viscosity at 25°C of the mixture according to Example 3 and the flowable resin was measured in the same manner as in Example 1. The results are shown in Table 1. The thermal conductivity of the mixture according to Example 3 was measured in the same manner as in Example 1. The results are shown in Table 1. The mixture according to Example 3 was supplied toward a gap of 0.5 mm, and it was evaluated whether the composite particles were uniformly arranged in the gap. As a result, it was confirmed that when the mixture according to Example 3 was used, the composite particles were uniformly arranged in the gap. Furthermore, the impact absorption rate of a solidified product of the mixture according to Example 3 was measured in the same manner as in Example 1. The results are shown in Table 1. Additionally, the density of a test piece for measuring the impact absorption rate and the ratio of the density of the test piece (composite material) to the density of the silicone resin cured product (base material) were determined in the same manner as in Example 1. The results are shown in Table 1.

[0081] Example 4 Composite particles and a mixture according to Example 4 were obtained in the same manner as in Example 1, except for the following points. In the process of obtaining the composite particles, the number of cycles of adding and stirring the silicone resin precursor, adding and stirring the boron nitride, and curing the silicone resin was changed to six, resulting in composite particles. The average particle size of the boron nitride was 7.8 μm. The median particle size distribution based on the number of composite particles according to Example 4 was 116 μm. A silicone resin precursor (DOWSIL® SE 1896FR A / B-EG Kit), a flowable resin manufactured by Dow Toray Industries, Inc., the composite particles according to Example 4, and aluminum hydroxide CW-310LV manufactured by Sumitomo Chemical Co., Ltd. were uniformly mixed to obtain a mixture according to Example 4. The content of the composite particles according to Example 4 in the mixture according to Example 4 was 35 vol. %, the content of the resin in the mixture according to Example 4 was 53 vol. , and the content of aluminum hydroxide was 12 vol. The mixture according to Example 4 was evaluated in the same manner as the mixture according to Example 1. The results are shown in Table 1.

[0082] Samples for XRD measurement were prepared from the mixture of Example 4 and a cured product of the mixture of Example 4, and XRD measurement was carried out using these samples in the same manner as in Example 1. Figure 10A shows the XRD pattern of the sample prepared from the mixture of Example 4, and Figure 10B shows the XRD pattern of the sample prepared from the cured product of the mixture of Example 4. From the XRD patterns shown in Figure 10A, the ratio of the area intensity of the diffraction peak originating from the (100) crystal plane of hexagonal boron nitride to the diffraction peak originating from the (002) crystal plane of hexagonal boron nitride was calculated as the area intensity ratio R X2 The results are shown in Table 1. From the XRD pattern shown in FIG. 10B, the ratio of the area intensity of the diffraction peak originating from the (100) crystal plane of hexagonal boron nitride to the diffraction peak originating from the (002) crystal plane of hexagonal boron nitride was determined as the area intensity ratio R X3 The results are shown in Table 1.

[0083] Comparative Example 1 Composite particles according to Comparative Example 1 were prepared in the same manner as in Example 1, except for the following points. Expanded polystyrene particles were used as hollow particles instead of plastic microballoons F-80DE. The average particle diameter of these hollow particles was 1000 μm, and the bulk density of these hollow particles was 0.025 g / cm. 3 In the same manner as in Example 1, the ratio of the maximum diameter to the minimum dimension of the boron nitride and the ratio of the particle size of the hollow particles to the maximum diameter of the boron nitride were determined. The results are shown in Table 2. In addition, in the same manner as in Example 1, the circularity of the projected image of the composite particle according to Comparative Example 1 was determined. The circularity was 0.88.

[0084] A mixture according to Comparative Example 1 was obtained in the same manner as in Example 2, except for the following points. The composite particles according to Comparative Example 1 were used instead of the composite particles according to Example 2. The content of the composite particles according to Comparative Example 1 in the mixture according to Comparative Example 1 was 40% by volume, and the content of the resin in the mixture according to Comparative Example 1 was 60% by volume. In the mixture according to Comparative Example 1, the composite particles and the resin were not mixed uniformly, and even when the mixture according to Comparative Example 1 was supplied toward a gap of 0.5 mm in size, the composite particles could not be uniformly arranged in the gap.

[0085] Comparative Example 2: Potters Ballotini glass hollow particles, Qcel7014, were used as hollow particles. The average particle diameter of these glass hollow particles was 80 μm. 5 g of the glass hollow particles and 300 mL of acetone were placed in a recovery flask and gently stirred at room temperature to suspend the glass hollow particles, yielding a suspension. While continuing to stir the suspension, 0.5 g of 3-aminopropyltriethoxysilane (AP) ((C2H5O)3Si-C3H6-NH2) was added to the suspension. After stirring at room temperature for 2 hours, a cooling tube was attached, 400 mL of pure water was added, and the suspension was stirred at 50°C for 24 hours. The suspension was then filtered, air-dried, and further heat-treated in an oven at 140°C for 24 hours. Through these steps, base particles surface-treated with aminopropyltriethoxysilane were obtained. It is believed that aminopropyltriethoxysilane is bonded to the surface of the hollow particles via siloxane bonds, leaving amino groups bonded to the surface of the particles.

[0086] 34 mL of tetrahydrofuran (THF) and 66 mL of pure water were added to a recovery flask, a reflux condenser was attached, and the mixture was stirred at 60°C for 12 hours. 1.4 g of polyacrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added and dissolved and dispersed to obtain a polyacrylic acid solution. This polyacrylic acid had an average molecular weight of approximately 1,000,000. While continuing to stir the polyacrylic acid solution, the same type of boron nitride as used in Example 1 was added, and the reflux condenser was attached again. The mixture was stirred at 60°C for 2 hours to disperse the boron nitride. In this way, a mixed gel was prepared.

[0087] To this mixed gel, 1.4 g of the base particles surfaced with the aminopropyltriethoxysilane was added, and the reflux tube was attached again. The mixture was stirred at 60°C for 2 hours to disperse the base particles, obtaining a dispersion. The dispersion was then cooled to room temperature. 2 L of isopropanol was added little by little in another beaker while stirring, obtaining a suspension. The resulting suspension was subjected to suction filtration, and the resulting filtrate was dried at 80°C for 24 hours. In this way, composite particles according to Comparative Example 2 were obtained. FIG. 11 is a photograph of the composite particles according to Comparative Example 2.

[0088] The ratio of the maximum diameter to the minimum dimension of the boron nitride and the ratio of the particle diameter of the hollow particles to the maximum diameter of the boron nitride were determined in the same manner as in Example 1. The results are shown in Table 2. In addition, the circularity of the projected image of the composite particle according to Comparative Example 2 was determined in the same manner as in Example 1. The circularity was 0.66.

[0089] A mixture according to Comparative Example 2 was obtained in the same manner as in Example 2, except for the following points. The composite particles according to Comparative Example 2 were used instead of the composite particles according to Example 2. The content of the composite particles according to Comparative Example 2 in the mixture according to Comparative Example 2 was 40% by volume, and the content of the resin in the mixture according to Comparative Example 2 was 60% by volume. Even when the mixture according to Comparative Example 2 was supplied toward a gap of 0.5 mm in size, mainly only the resin was guided, and it was not possible to uniformly arrange the composite particles in the gap.

[0090] Comparative Example 3 To 135 parts by mass of the silicone resin precursor DOWSIL (registered trademark) SE 1896FR A / B-EG Kit, 1 part by mass of plastic microballoons F-80DE, which are hollow particles, and 65 parts by weight of the hexagonal boron nitride used in Example 1 were added, and the mixture was stirred and degassed for 3 minutes at 2000 rpm using a planetary centrifugal mixer ARE-310 manufactured by Thinky Corporation, to obtain a mixture according to Comparative Example 3.

[0091] The viscosity at 25°C of the mixture and flowable resin of Comparative Example 3 was measured in the same manner as in Example 1. The results are shown in Table 2. The thermal conductivity of the cured product of the mixture of Comparative Example 3 was measured in the same manner as in Example 1. The results are shown in Table 2.

[0092] The mixture of Comparative Example 3 was supplied toward a gap of 0.5 mm in size, and an optical microscope was used to evaluate whether the hollow particles and boron nitride were uniformly arranged in the gap. As a result, it was difficult for the mixture of Comparative Example 3 to uniformly fill the gap.

[0093] A sample for XRD measurement was prepared from the cured product of the mixture of Comparative Example 3. XRD measurement of this sample was carried out using an XRD measurement device D8 Discover with GADDS manufactured by Bruker. In this XRD measurement, CuKα radiation was used as the characteristic X-ray. The XRD pattern of this sample is shown in FIG. 12. From the XRD pattern shown in FIG. 12, the area intensity ratio R was calculated as the ratio of the area intensity of the diffraction peak originating from the (100) crystal plane of hexagonal boron nitride to the diffraction peak originating from the (002) crystal plane of hexagonal boron nitride. X3 The results are shown in Table 2.

[0094] Comparative Example 4: DOWSIL SE 1817 CV MA / B was filled into a mold having an internal space measuring 50 mm x 50 mm x 3 mm, and then cured by heating in a constant temperature bath at 100°C for 1 hour to obtain a molded article. The molded article was punched out to obtain a square shape with a side length of 40 mm in plan view, to obtain a test piece according to Comparative Example 4. The test piece had a thickness of 3 mm. The impact absorption rate of the cured DOWSIL SE 1817 CV MA / B was measured in the same manner as in Example 1, except that the test piece according to Comparative Example 4 was used instead of the test piece according to Example 1. The results are shown in Table 2.

[0095] Comparative Example 5 A mixture according to Comparative Example 5 was obtained in the same manner as in Example 2, except for the following points. In preparing the mixture, a mixture of plastic microballoons F-80DE and boron nitride having an average particle size of 7.8 μm was used instead of the composite particles, and this was uniformly mixed with flowable resin DOWSIL SE 1817 CV MA / B to obtain the mixture according to Comparative Example 5. The content of plastic microballoons in the mixture according to Comparative Example 5 was 25 vol%, the content of boron nitride was 9 vol%, and the content of flowable resin was 66 vol%. The mixture according to Comparative Example 5 was evaluated in the same manner as the mixture according to Example 1. The results are shown in Table 2.

[0096] Comparative Example 6 A mixture according to Comparative Example 6 was obtained in the same manner as in Example 3, except for the following points. In preparing the mixture, a mixture of plastic microballoons F-80DE and boron nitride having an average particle size of 7.8 μm was used instead of the composite particles, and these were uniformly mixed with flowable resin DOWSIL SE 1817 CV MA / B to obtain the mixture according to Comparative Example 6. The mixture according to Comparative Example 6 had a plastic microballoon content of 13 vol%, a boron nitride content of 4 vol%, and a flowable resin content of 83 vol%. The mixture according to Comparative Example 6 was evaluated in the same manner as the mixture according to Example 1. The results are shown in Table 2.

[0097] Comparative Example 7 A mixture according to Comparative Example 7 was obtained in the same manner as in Example 4, except for the following points. In preparing the mixture, a mixture of plastic microballoons F-80DE and boron nitride having an average particle size of 7.8 μm was used instead of the composite particles, and these were uniformly mixed with flowable resin DOWSIL SE 1817 CV MA / B to obtain the mixture according to Comparative Example 7. The content of plastic microballoons in the mixture according to Comparative Example 7 was 40 vol%, the content of boron nitride was 14 vol%, and the content of flowable resin was 46 vol%. The mixture according to Comparative Example 7 was evaluated in the same manner as the mixture according to Example 1. The results are shown in Table 2.

[0098] Comparative Example 8 The mixture of Comparative Example 8 was obtained in the same manner as in Example 4, except for the following points. Instead of composite particles, a mixture of plastic microballoons F-80DE and boron nitride having an average particle size of 7.8 μm was used. This mixture was uniformly mixed with flowable resin DOWSILSE 1896FR A / B-EG Kit and aluminum hydroxide CW-310LV to obtain the mixture of Comparative Example 8. The mixture of Comparative Example 8 contained 23 vol% plastic microballoons, 6 vol% boron nitride, 59 vol% flowable resin, and 12 vol% aluminum hydroxide. The mixture of Comparative Example 8 was evaluated in the same manner as the mixture of Example 1. The results are shown in Table 2.

[0099] Samples for XRD measurement were prepared from the mixture of Comparative Example 8 and a cured product of the mixture of Comparative Example 8, and XRD measurement was performed using these samples in the same manner as in Example 1. Fig. 13A shows the XRD pattern of the sample prepared from the mixture of Comparative Example 8, and Fig. 13B shows the XRD pattern of the sample prepared from the cured product of the mixture of Comparative Example 8. From the XRD patterns shown in Fig. 13A, the ratio of the area intensity of the diffraction peak derived from the (100) crystal plane of hexagonal boron nitride to the diffraction peak derived from the (002) crystal plane of hexagonal boron nitride was calculated as the area intensity ratio R X2The results are shown in Table 2. From the XRD pattern shown in FIG. 13B, the ratio of the area intensity of the diffraction peak originating from the (100) crystal plane of hexagonal boron nitride to the diffraction peak originating from the (002) crystal plane of hexagonal boron nitride was defined as the area intensity ratio R X3 The results are shown in Table 2.

[0100] Comparing Examples 2 to 5 with Comparative Examples 5 to 8 suggests that in Examples 2 to 5, even if the boron nitride content is about the same, the thermal conductivity of the composite material tends to be higher.

[0101]

[0102]

[0103] A first aspect of the present invention provides a composite particle comprising: a hollow particle; a plurality of thermal conductors arranged along the surface of the hollow particle; and a coating layer that covers the surface of the hollow particle, the coating layer including a first resin arranged on the surface of the hollow particle and between the thermal conductors, wherein the composite particle satisfies at least one condition selected from the group consisting of (Ia) and (IIa) below: (Ia) The composite particle has a particle size of 200 μm or less, and the circularity of a projected image of the composite particle is 0.7 or more. (IIa) The plurality of thermal conductors comprise hexagonal boron nitride, and in an X-ray diffraction pattern of a powder that is an aggregate of the composite particles, the area intensity ratio of a diffraction peak derived from a (100) crystal plane of the hexagonal boron nitride to a diffraction peak derived from a (002) crystal plane of the hexagonal boron nitride is 0.07 or more and 0.14 or less.

[0104] A second aspect of the present invention provides the composite particles according to the first aspect, wherein the ratio of the particle diameter of the hollow particles to the maximum diameter of the thermal conductor is 5 to 200.

[0105] A third aspect of the present invention provides a composite particle according to the first or second aspect, wherein the ratio of the maximum diameter of the thermal conductor to the minimum dimension of the thermal conductor is 50 or less.

[0106] A fourth aspect of the present invention provides the composite particle according to any one of the first to third aspects, wherein the thermal conductor has electrical insulation properties.

[0107] A fifth aspect of the present invention provides a mixture comprising composite particles and a second resin having flowability, the mixture being a mixture of the composite particles and the second resin, the composite particles comprising hollow particles, a plurality of thermal conductors arranged along the surfaces of the hollow particles, and a first resin arranged on the surfaces of the hollow particles and between the thermal conductors, and a coating layer covering the surfaces of the hollow particles, the mixture satisfying at least one condition selected from the group consisting of the following (Ib) and (IIb): (Ib) The mixture has a viscosity of 1 to 200 Pa·s at 25°C, and a solidified product of the mixture has a viscosity of 0.1 to 3.0 W·m -1 ・K -1 (IIb) The plurality of thermal conductors contain hexagonal boron nitride, and in an X-ray diffraction pattern of the mixture, the area intensity ratio of a diffraction peak originating from a (100) crystal plane of the hexagonal boron nitride to a diffraction peak originating from a (002) crystal plane of the hexagonal boron nitride is 0.03 or more and 0.14 or less.

[0108] A sixth aspect of the present invention provides the mixture according to the fifth aspect, in which the ratio of the viscosity of the second resin at 25°C to the viscosity of the mixture at 25°C is 0.001 or more and less than 1.

[0109] A seventh aspect of the present invention provides a mixture according to the fifth or sixth aspect, wherein the mixture satisfies the condition (IIb) above, and has a viscosity of 1 to 200 Pa s at 25°C.

[0110] An eighth aspect of the present invention provides a composite material comprising a solid matrix and a plurality of composite particles, the plurality of composite particles being dispersed within the matrix, and the composite material satisfies at least one condition selected from the group consisting of (Ic) and (IIc) below. (Ic) The composite particle is a composite particle according to any one of the first to fourth aspects. (IIc) The composite particle comprises a hollow particle and a coating layer, the coating layer including a plurality of thermal conductors arranged along the surface of the hollow particle and a first resin arranged on the surface of the hollow particle and between the thermal conductors, the plurality of thermal conductors including hexagonal boron nitride, and in an X-ray diffraction pattern of the composite material, the area intensity ratio of a diffraction peak derived from a (100) crystal plane of the hexagonal boron nitride to a diffraction peak derived from a (002) crystal plane of the hexagonal boron nitride is 0.037 or more and 0.14 or less.

[0111] A ninth aspect of the present invention provides the composite material according to the eighth aspect, in which the volumetric content of the plurality of composite particles is 1 to 70%.

[0112] A tenth aspect of the present invention provides the composite material according to the eighth or ninth aspect, in which the ratio of the density of the composite material to the density of the matrix is ​​0.2 to 1.0.

[0113] An eleventh aspect of the present invention provides the composite material according to any one of the eighth to tenth aspects, in which the base material has a compressive modulus of elasticity of 0.001 to 15,000 MPa.

[0114] A twelfth aspect of the present invention provides a composite material according to any one of the eighth to eleventh aspects, wherein the composite material has an impact absorption rate of 30% or more, and the impact absorption rate is determined by the following formula (A), where F0 is the maximum load acting on the outside of the polycarbonate plate on the opposite side of the point where the iron ball was dropped when a 110 g iron ball is allowed to freely fall from a height of 200 mm onto a horizontally placed polycarbonate plate having a thickness of 3 mm, and F1 is the maximum load acting on the outside of the laminate on the opposite side of the point where the iron ball was dropped when the iron ball is allowed to freely fall from the height onto a laminate formed by placing the polycarbonate plate on the 3 mm thick composite material. Impact absorption rate [%] = 100 × (F0 - F1) / F0 Formula (A)

[0115] A thirteenth aspect of the present invention provides a method for producing composite particles, comprising: adhering a liquid resin to the surface of a hollow particle; and contacting a plurality of thermal conductors with the liquid resin to arrange the plurality of thermal conductors along the surface, thereby forming a coating layer that coats the surface of the hollow particle, wherein the composite particle satisfies at least one condition selected from the group consisting of (Id) and (IId) below: (Id) The composite particle has a particle size of 200 μm or less, and the circularity of a projected image of the composite particle is 0.7 or more. (IId) The plurality of thermal conductors comprise hexagonal boron nitride, and in an X-ray diffraction pattern of a powder that is an aggregate of the composite particles, the area intensity ratio of the diffraction peak derived from the (100) crystal plane of the hexagonal boron nitride to the diffraction peak derived from the (002) crystal plane of the hexagonal boron nitride is 0.07 or more and 0.14 or less.

Claims

1. A composite particle comprising: a hollow particle; a plurality of thermal conductors arranged along the surface of the hollow particle; and a coating layer including a first resin arranged on the surface of the hollow particle and between the thermal conductors, the coating layer coating the surface of the hollow particle, the composite particle satisfying at least one condition selected from the group consisting of (Ia) and (IIa) below: (Ia) The composite particle has a particle size of 200 μm or less, and the circularity of a projected image of the composite particle is 0.7 or more. (IIa) The plurality of thermal conductors include hexagonal boron nitride, and in an X-ray diffraction pattern of a powder that is an aggregate of the composite particles, the area intensity ratio of a diffraction peak derived from a (100) crystal plane of the hexagonal boron nitride to a diffraction peak derived from a (002) crystal plane of the hexagonal boron nitride is 0.07 or more and 0.14 or less.

2. The composite particle according to claim 1, wherein the ratio of the particle size of the hollow particle to the maximum diameter of the thermal conductor is 5 to 200.

3. The composite particle according to claim 1, wherein the ratio of the maximum diameter of the thermal conductor to the minimum dimension of the thermal conductor is 50 or less.

4. The composite particle according to claim 1, wherein the thermal conductor has electrical insulation properties.

5. A mixture comprising composite particles and a second resin having fluidity, the mixture being a mixture of the composite particles and the second resin, the composite particles including hollow particles, a plurality of thermal conductors arranged along the surfaces of the hollow particles, and a first resin arranged on the surfaces of the hollow particles and between the thermal conductors, and a coating layer that coats the surfaces of the hollow particles, the mixture satisfying at least one condition selected from the group consisting of (Ib) and (IIb) below: (Ib) The mixture has a viscosity of 1 to 200 Pa·s at 25°C, and a solidified product of the mixture has a viscosity of 0.1 to 3.0 W·m -1 K -1 (IIb) The plurality of thermal conductors contain hexagonal boron nitride, and in an X-ray diffraction pattern of the mixture, an area intensity ratio of a diffraction peak originating from a (100) crystal plane of the hexagonal boron nitride to a diffraction peak originating from a (002) crystal plane of the hexagonal boron nitride is 0.03 or more and 0.14 or less.

6. The mixture according to claim 5, wherein the ratio of the viscosity of the second resin at 25°C to the viscosity of the mixture at 25°C is 0.001 or more and less than 1.

7. The mixture according to claim 5, wherein the mixture satisfies the condition (IIb), and the mixture has a viscosity of 1 to 200 Pa·s at 25°C.

8. A composite material comprising a solid base material and a plurality of composite particles, the plurality of composite particles being dispersed inside the base material, and the composite material satisfying at least one condition selected from the group consisting of the following (Ic) and (IIc). (Ic) The composite particle is the composite particle according to any one of claims 1 to 4. (IIc) The composite particle comprises a hollow particle and a coating layer, the coating layer includes a plurality of thermal conductors arranged along the surface of the hollow particle and a first resin arranged on the surface of the hollow particle and between the thermal conductors, the plurality of thermal conductors include hexagonal boron nitride, and in an X-ray diffraction pattern of the composite material, an area intensity ratio of a diffraction peak derived from a (100) crystal plane of the hexagonal boron nitride to a diffraction peak derived from a (002) crystal plane of the hexagonal boron nitride is 0.037 or more and 0.14 or less.

9. The composite material according to claim 8, wherein the volumetric content of the plurality of composite particles is 1 to 70%.

10. The composite material according to claim 8, wherein the ratio of the density of the composite material to the density of the base material is 0.2 to 1.

0.

11. The composite material according to claim 8, wherein the matrix has a compressive modulus of elasticity of 0.001 to 15,000 MPa.

12. The composite material according to claim 8, wherein the composite material has an impact absorption rate of 30% or more, and the impact absorption rate is determined by the following formula (A), in which F0 is the maximum load acting on the outside of the polycarbonate plate on the opposite side to the point where the iron ball is dropped when a 110 g iron ball is allowed to fall freely from a height of 200 mm onto a horizontally placed polycarbonate plate having a thickness of 3 mm, and F1 is the maximum load acting on the outside of the laminate on the opposite side to the point where the iron ball is dropped when the iron ball is allowed to fall freely from said height onto a laminate in which the polycarbonate plate is placed on the composite material having a thickness of 3 mm. Impact Absorption Rate [%]=100×(F0-F1) / F0} Formula (A) 13. A method for producing composite particles, comprising: attaching a liquid resin to a surface of a hollow particle, and contacting a plurality of thermal conductors with the liquid resin to arrange the plurality of thermal conductors along the surface, thereby forming a coating layer that coats the surface of the hollow particle, wherein the composite particle satisfies at least one condition selected from the group consisting of (Id) and (IId) below: (Id) The composite particle has a particle size of 200 μm or less, and the circularity of a projected image of the composite particle is 0.7 or more. (IId) The plurality of thermal conductors include hexagonal boron nitride, and in an X-ray diffraction pattern of a powder that is an aggregate of the composite particles, the area intensity ratio of a diffraction peak originating from a (100) crystal plane of the hexagonal boron nitride to a diffraction peak originating from a (002) crystal plane of the hexagonal boron nitride is 0.07 or more and 0.14 or less.