WO2023054414A1

WO2023054414A1 - Composite material and production method for composite material

Info

Publication number: WO2023054414A1
Application number: PCT/JP2022/036043
Authority: WO
Inventors: 智也加藤; 孝彦伊藤; 哲弥大塚
Original assignee: 日東電工株式会社
Priority date: 2021-09-30
Filing date: 2022-09-27
Publication date: 2023-04-06

Abstract

A composite material 1a includes: a framework 10 that includes a resin 11; inorganic particles 12; and voids 20. At least a portion of the inorganic particles 12 are arranged along the boundaries between the framework 10 and the voids 20. A number-based first size Sz distribution D1 obtained by measuring the size Sz of each of the voids 20 in a cross-section of the composite material 1a has at least two peaks.

Description

Composite material and method for producing composite material

The present invention relates to composite materials and methods for manufacturing composite materials.

Conventionally, attempts have been made to increase the thermal conductivity of materials with multiple voids, such as foamed materials.

For example, Patent Document 1 discloses a composite material comprising scale-like fillers made of an inorganic material and a binding resin made of a thermosetting resin that binds the fillers. This composite material is a foamed material formed so that a plurality of voids are dispersed, and the filler is accumulated on the inner wall of the void so that the flat surfaces of the filler overlap each other (claim 1 and FIG. 1 reference). Patent Document 1 describes that when the ratio of the average length of the flat surfaces of the filler to the thickness of the filler, that is, the aspect ratio is less than 50, the flat surfaces of the filler are difficult to overlap each other.

JP 2018-109101

In the technology described in Patent Document 1, thermal conductivity is improved by accumulating fillers by foaming. On the other hand, Patent Document 1 does not discuss the relationship between the size distribution of the plurality of voids and the thermal conductivity. Accordingly, the present invention provides a composite material in which multiple void sizes are distributed in an advantageous manner from the point of view of thermal conductivity.

The present invention
A composite material comprising a skeleton containing a resin, inorganic particles, and a plurality of voids,
At least part of the inorganic particles are arranged along the boundary between the void and the skeleton,
When the composite material is viewed in cross section, the first distribution of the size based on the number obtained by measuring the size of each of the plurality of voids has two or more peaks.
Provide composite materials.

In addition, the present invention
In a mixture containing a plurality of composite particles each having a first resin and inorganic particles arranged around the first resin, and a fluid resin composition filled in gaps between the composite particles, the resin reducing the fluidity of the composition to form a solid portion comprising the second resin;
Arranging at least a portion of the inorganic particles along the boundary between the plurality of voids and the solid portion while forming a plurality of voids by shrinkage or removal of the first resin;
The plurality of composite particles includes first composite particles and second composite particles,
The size of the first resin of the first composite particles is included in the first range,
The size of the first resin of the second composite particle is included in a second range having an upper limit smaller than the lower limit of the first range,
A method of manufacturing a composite material is provided.

According to the above composite material, the sizes of the plurality of voids are distributed in an advantageous manner from the viewpoint of thermal conductivity.

FIG. 1 is a cross-sectional view schematically showing an example of the composite material according to this embodiment. FIG. 2A is a graph showing an example of a first distribution of number-based void sizes in a cross-sectional view of the composite material according to the present embodiment. FIG. 2B is a graph showing an example of the second distribution of the maximum diameter of the number-based annular cross section in the cross-sectional view of the composite material according to the present embodiment. FIG. 3 is a cross-sectional view schematically showing another example of the composite material according to this embodiment. 4 is a photograph of a cross section of the composite material according to Example 1. FIG. 5 is a photograph of a cross section of the composite material according to Comparative Example 1. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description is illustrative of the invention, and the invention is not limited to the following embodiments.

As shown in FIG. 1, the composite material 1a includes a skeleton 10 containing a resin 11, inorganic particles 12, and a plurality of voids 20. In the composite material 1a, the skeleton 10, the inorganic particles 12, and the plurality of voids 20 form a porous structure. At least part of the inorganic particles 12 are arranged along the boundaries between the voids 20 and the skeleton portion 10 .

In the composite material 1a, along the boundary between the voids 20 and the skeleton portion 10, a layered structure having a predetermined thickness in which a plurality of inorganic particles 12 are stacked may be formed.

FIG. 2A shows a first distribution D1 of the number-based size Sz obtained by measuring the size Sz of each of the plurality of voids 20 when the composite material 1a is viewed in cross section. As shown in FIG. 2A, the first distribution D1 has two or more peaks.

When the first distribution D1 has two or more peaks, the volume of the boundaries between the voids 20 and the framework 10 tends to increase in the porous structure of the composite material 1a. As described above, the inorganic particles 12 are arranged along the boundaries between the voids 20 and the skeleton portion 10 , and the inorganic particles 12 can have a higher thermal conductivity than the resin 11 . Therefore, it is advantageous to increase the thermal conductivity of the composite material 1a if the volume of the boundary between the void 20 and the skeleton portion 10 is large. Therefore, the composite material 1a tends to have high thermal conductivity. In addition, since the first distribution D1 has two or more peaks, voids 20 are likely to exist at various locations in the porous structure. Therefore, the composite material 1a tends to have flexibility.

In the composite material 1a, the cross section where the size Sz is measured to obtain the first distribution D1 is not limited to a specific cross section. The composite material 1a has, for example, a flat outer surface. The cross-section for measurement of size Sz may be parallel, perpendicular or inclined to its outer surface. The cross-section on which the size Sz is measured to obtain the first distribution D1 may include multiple cross-sections. The number of voids 20 whose sizes Sz are measured to obtain the first distribution D1 is, for example, 200 or more. Observation of the cross section is performed using a microscope such as an optical microscope, a metallurgical microscope, and an electron microscope. The size Sz is, for example, the maximum diameter of the void 20 in the cross section. The maximum diameter of the gap 20 is the maximum dimension of a line segment connecting two different points within the range of the gap 20 .

As shown in FIG. 2A, the first distribution D1 can be created as a histogram, for example. In this case, the range of each section in the histogram is not limited to specific values. The range is, for example, 10-100 μm. For example, if the peak of the first distribution D1 is in a particular interval of the histogram, the median value of that interval can be taken as the size Sz corresponding to that peak.

As shown in FIG. 1, in the composite material 1a, the multiple voids 20 have multiple first voids 21 and second voids 22. As shown in FIG. The second gaps 22 are arranged, for example, between the first gaps 21 . When cross-sectionally viewing the composite material 1a, the size Sz of the first voids 21 is included in the first range, and the size Sz of the second voids 22 is included in the second range. A second range is a range having an upper limit that is less than the lower limit of the first range. According to such a configuration, the inorganic particles 12 can be arranged along the boundary between the second gaps 22 and the skeleton portion 10 between the first gaps 21 . Therefore, the composite material 1a is more likely to have high thermal conductivity. In addition, the composite material 1a tends to have more flexibility.

As shown in FIG. 2A, the first distribution D1 has, for example, a first peak P1 and a second peak P2. The size Sz of the voids 20 at the second peak P2 is smaller than the size Sz of the voids 20 at the first peak P1. The ratio N2/N1 of the number N2 of voids 20 at the second peak to the number N1 of voids 20 at the first peak P1 is not limited to a specific value. The ratio N2/N1 is, for example, 0.01-100. According to such a configuration, the composite material 1a is more likely to have high thermal conductivity. In addition, the composite material 1a tends to have more flexibility. When the first distribution D1 is a histogram, the number of voids 20 at a specific peak is the number of voids 20 in the interval to which that peak belongs in the histogram.

The ratio N2/N1 may be 0.05 or more, 0.1 or more, or 0.5 or more. The ratio N2/N1 may be 100 or less, 50 or less, or 20 or less. The first distribution D1 may have three or more peaks.

As shown in FIG. 1 , when the composite material 1a is viewed in cross section, the inorganic particles 12 arranged along the boundary between the voids 20 and the skeleton portion 10 are, for example, a plurality of annular particles corresponding to the plurality of voids 20, respectively. has a cross section 12c. FIG. 2B shows a number-based second distribution D2 obtained by measuring the maximum diameter Tz of each of the plurality of annular cross-sections 12c. As shown in FIG. 2B, the second distribution D2 has, for example, a third peak P3 and a fourth peak P4. The maximum diameter Tz at the fourth peak P4 is smaller than the maximum diameter Tz at the third peak P3. The composite material 1a satisfies the conditions of, for example, L1/L2≧1.25, {(L1 ² −d1 ² )h1}/{(L2 ² −d2 ² )h2}≧0.8, and R≦0.55. Fulfill. Under these conditions, L1 is the maximum diameter Tz corresponding to the third peak P3, and L2 is the maximum diameter Tz corresponding to the fourth peak P4. d1 is the size Sz corresponding to the first peak P1, and d2 is the size Sz corresponding to the second peak P2. h1 is the number of voids 20 at the first peak P1, and h2 is the number of voids 20 at the second peak P2. R is the ratio of the cross-sectional area of the skeleton portion 10 to the cross-sectional area of the composite material 1a in a cross-sectional view of the composite material 1a. As a result of extensive studies, the inventors of the present invention have found that when L1, L2, d1, d2, h1, h2, and R are adjusted to satisfy the above conditions, the composite material 1a is high. It was found that they tended to have higher thermal conductivity. In addition, when the above conditions are satisfied, the plurality of voids 20 tend to exist in a desired state, and the composite material 1a tends to have more flexibility.

In the composite material 1a, L1/L2 may be 1.26 or more, 1.27 or more, or 1.28 or more. L1/L2 is, for example, 15 or less, and may be 12 or less.

In the composite material 1a, {(L1 ² −d1 ² )h1}/{(L2 ² −d2 ² )h2} may be 0.9 or more, 1 or more, or 1.5 or more. , 2 or more, or 2.5 or more. {(L1 ² -d1 ² )h1}/{(L2 ² -d2 ² )h2} is, for example, 7 or less, and may be 5 or less.

In the composite material 1a, the ratio R may be 0.54 or less, 0.53 or less, or 0.52 or less. The ratio R is, for example, 0.3 or more.

The second distribution D2 is obtained, for example, by measuring the maximum diameter Tz of each of the plurality of annular cross sections 12c in the same cross section as the cross section for obtaining the first distribution D1. The number of cross sections 12c for which the maximum diameter Tz is measured to obtain the second distribution D2 is, for example, 200 or more. For example, the maximum diameter Tz is measured for the annular cross section 12c corresponding to the void 20 whose size Sz has been measured for creating the first distribution D1. The maximum diameter Tz is, for example, the maximum dimension of a line segment connecting two different points within the range of the cross section 12c. The cross section 12c does not always form a perfect ring. The cross-section 12c is, for example, continuous in a portion corresponding to 80% or more of the circumference of the complete ring.

As shown in FIG. 2B, the second distribution D2 can be created as a histogram, for example. In this case, the range of each section in the histogram is not limited to specific values. The range is, for example, 10-100 μm. For example, if the peak of the second distribution D2 is in a specific section of the histogram, the median value of that section can be regarded as the maximum diameter Tz corresponding to that peak.

The arithmetic average S _AVG of the size Sz of the voids 20 obtained by measuring the size Sz of each of the multiple voids 20 when the composite material 1a is viewed in cross section is not limited to a specific value. Arithmetic average S _AVG is, for example, 50 to 1500 μm. When the arithmetic average S _AVG is 50 µm or more, the first distribution D1 tends to have two or more peaks, and the composite material 1a tends to have high thermal conductivity. In addition, the composite material 1a tends to have more flexibility. When the arithmetic average S _AVG is 1500 µm or less, the composite material 1a tends to have desired strength.

The arithmetic average S _AVG may be 50 μm or more, 100 μm or more, 250 μm or more, 350 μm or more, 400 μm or more, or 450 μm or more. It may be 500 μm or more. The arithmetic average S _AVG may be 550 μm or more, 600 μm or more, 650 μm or more, or 700 μm or more. The arithmetic average S _AVG may be 1450 μm or less, 1400 μm or less, 1350 μm or less, or 1300 μm or less. The arithmetic average S _AVG may be 1250 μm or less, 1200 μm or less, 1150 μm or less, 1100 μm or less, 1050 μm or less, or 1000 μm or less. may

As long as the first distribution D1 has two or more peaks, the relationship between the first peak P1 and the second peak P2 is not limited to a specific relationship. For example, the first peak P1 exists in the size Sz range of 500-1200 μm, and the second peak P2 exists in the size Sz range of 50-700 μm. According to such a configuration, the composite material 1a is more likely to have high thermal conductivity. In addition, the composite material 1a tends to have more flexibility.

The outer shape of the void 20 is not limited to a specific shape. The outer shape of the void 20 is, for example, spherical and may be substantially spherical. As used herein, "substantially spherical" means that the ratio of maximum diameter to minimum diameter (maximum diameter/minimum diameter) is 1.0 to 1.5. The ratio of the largest diameter to the smallest diameter of the substantially spherical void 20 may be between 1.0 and 1.3. The outer shape of the void 20 may be rod-like, polyhedral, or elliptical with a ratio of maximum diameter to minimum diameter greater than 1.5. In the composite material 1a, for example, 50% or more of the plurality of voids 20 are spherical. 80% or more of the plurality of voids 20 may be spherical. In the foaming technique, since the shape of the voids becomes irregular, it is difficult to form the voids with such a uniform shape.

In the composite material 1a, the porosity, which is the ratio of the volume of the plurality of voids 20 to the volume of the composite material 1a, is not limited to a specific value. The porosity is, for example, 10% to 60% by volume, may be 15% to 50% by volume, or may be 20% to 45% by volume.

The porosity is determined, for example, by observing the cross section of the composite material 1a, calculating the ratio of the total area of the voids 20 to the total area of the observed cross section, and averaging the ratio for 10 different cross section images. can. Alternatively, the porosity may be determined based on the results of X-ray CT scanning of the composite material 1a. On the other hand, if the manufacturing process of the composite material 1a is known, it may be determined as follows. The mass of the inorganic particles 12 contained in the composite particles is calculated from the mass of the resin particles and the mass of the composite particles in which the inorganic particles 12 are arranged on the surfaces of the resin particles, which will be described later. Separately from this, the content [% by mass] of the inorganic particles 12 in the composite material 1a is calculated based on the result of the inorganic elemental analysis of the composite material 1a. The mass of the inorganic particles 12 in the composite material 1a is calculated from the content [% by mass] of the inorganic particles 12 in the composite material 1a and the mass of the composite material 1a. The number of composite particles used in manufacturing the composite material 1a is calculated from the mass of the inorganic particles 12 in the composite material 1a and the mass of the inorganic particles 12 contained in the composite particles. The volume of the voids 20 is calculated from the average diameter of the voids 20 . The total volume of the voids 20 in the composite material 1a is obtained by multiplying the volume of the voids 20 by the number of composite particles. The porosity is calculated by dividing this value by the volume of the composite material 1a.

The plurality of voids 20 have, for example, external shapes similar to each other. For example, in the composite material 1a, 80% or more of the plurality of voids 20 have outlines similar to each other. The outer shapes of the plurality of voids 20 that are similar to each other are, for example, spherical. This contour may be substantially spherical. A plurality of voids formed by foaming may also come into contact with each other as they expand. In this case, however, the internal pressure generated by the foaming usually acts on the connecting portion of the voids, and greatly deforms the vicinity of the connecting portion. For this reason, the technique of foaming cannot actually form a plurality of voids that are in contact with each other and have substantially similar external shapes.

The porous structure of the composite material 1a may have through holes extending from one main surface of the composite material 1a to the other main surface. When the composite material 1a has a pair of parallel outer surfaces, the gap 20 provided on one outer surface of the composite material 1a may communicate with the space facing the other outer surface of the composite material 1a. Moreover, the void provided on one outer surface of the composite material 1a may communicate with a space in contact with a side surface intersecting one outer surface of the composite material 1a. With such a configuration, the composite material 1a can achieve both thermal conductivity and air permeability.

As shown in FIG. 1, the composite material 1a has heat transfer paths 5 formed of inorganic particles 12, for example. According to such a configuration, heat is easily conducted through the composite material 1a by heat conduction in the heat transfer path 5, and the composite material 1a tends to have a high thermal conductivity.

The heat transfer path 5 is, for example, continuously formed by a plurality of inorganic particles 12 that are in contact with or close to each other. The heat transfer path 5 extends across a plurality of gaps 20, for example. The heat transfer path 5 extends, for example, along the boundary between the skeleton portion 10 and the plurality of voids 20 without passing through the inside of the skeleton portion 10 . The composite material 1a may for example have a first outer surface 2a and a second outer surface 2b parallel to each other, the heat transfer path 5 extending from the first outer surface 2a to the second outer surface 2b. The inorganic particles 12 may be in direct contact with each other, or the inorganic particles 12 may be close to each other while a predetermined resin exists between the inorganic particles 12 .

In the composite material 1a, at least some of the multiple voids 20 may be arranged so as to be in contact with each other. In this case, a pair of gaps 20 that are in contact with each other may be connected by a connecting portion 20j containing the inorganic particles 12 . A pair of gaps 20 that are in contact with each other may be connected by a connecting portion 20k that does not contain the inorganic particles 12 . In this case, the pair of gaps 20 form one space that communicates with each other through the connecting portion 20k. The dimension of the connecting portion 20k is, for example, 25% or less of the size Sz of the gap 20, may be 20% or less, or may be 15% or less. In this case, the size Sz of each gap 20 is determined assuming that a pair of gaps 20 are partitioned by the connecting portion 20k. A pair of gaps 20 that are in contact with each other may be connected by a connection portion 20m that contains only resin and does not contain inorganic particles 12 .

Not all heat transfer paths 5 appear in a specific cross section as shown in FIG. 1, and furthermore, not all parts of a specific heat transfer path 5 appear. In a specific cross section, even if the heat transfer path 5 appears to be interrupted between the first outer surface 2a and the second outer surface 2b, the inorganic particles 12 that do not appear in the cross section It may extend to the outer surface 2b or to both the first outer surface 2a and the second outer surface 2b. Similarly, the contact of all voids 20 cannot be confirmed with only a specific cross section. For example, void 20i is isolated as far as FIG. 1 is concerned. However, the air gap 20i is in contact with another adjacent air gap 20 in the direction perpendicular to this cross section.

On the other hand, not all heat transfer paths 5 need to extend from the first outer surface 2a to the second outer surface 2b. It is not necessary that all the voids 20 included in the composite material 1a are in contact with another void 20 directly or via the inorganic particles 12 .

The material forming the inorganic particles 12 is not limited to a specific inorganic material. The material forming the inorganic particles 12 has, for example, a thermal conductivity higher than that of the resin 11 . Examples of materials forming the inorganic particles 12 include hexagonal boron nitride (h-BN), alumina, crystalline silica, amorphous silica, aluminum nitride, magnesium oxide, carbon fiber, silver, copper, aluminum, silicon carbide, and graphite. , zinc oxide, silicon nitride, silicon carbide, cubic boron nitride (c-BN), beryllia, diamond, carbon black, magnesium hydroxide, graphene, carbon nanotubes, carbon fibers, and aluminum hydroxide. Only one type of inorganic particles 12 may be used in the composite material 1a and the composite material 1b, or two or more types of inorganic particles 12 may be used in combination in the composite material 1a and the composite material 1b.

The shape of the inorganic particles 12 is not limited to a specific shape. Examples of shapes of the inorganic particles 12 are spherical, rod-like, fibrous, and scale-like. The shape of the inorganic particles 12 may be irregular-shaped lumps.

The aspect ratio of the inorganic particles 12 is not limited to a specific value. The aspect ratio of the inorganic particles 12 is, for example, less than 50, may be 40 or less, or may be 30 or less. The aspect ratio of the inorganic particles 12 may be 1, 2 or more, or 3 or more. As used herein, the aspect ratio of a particle is determined as the ratio of the second dimension of the particle to the first dimension of the particle (second dimension/first dimension), unless otherwise stated. The second dimension of the particles corresponds to the largest dimension of the particles. The first dimension of the particle is the largest dimension of the particle in a direction perpendicular to the line defining the largest dimension of the particle.

The average particle size of the inorganic particles 12 is not limited to a specific value. The average particle diameter of the inorganic particles 12 is, for example, 0.05 μm to 100 μm, may be 0.1 μm to 50 μm, may be 0.1 μm to 30 μm, and may be 0.5 μm to 10 μm. . The "average particle size" can be determined, for example, by a laser diffraction scattering method. The average particle diameter is, for example, the median diameter in the volume-based particle size distribution. The volume-based particle size distribution of the inorganic particles 12 can be obtained, for example, using a particle size distribution meter Microtrac MT3300EXII manufactured by Microtrac Bell.

The shape of the inorganic particles 12 can be determined, for example, by observation using a scanning electron microscope (SEM) or the like. For example, when the inorganic particles 12 have an aspect ratio of 1.0 or more and less than 1.7 and at least part of the outline of the inorganic particles 12 is observed as an arc, the inorganic particles 12 may be spherical. When the inorganic particles 12 are spherical, the inorganic particles 12 may have an aspect ratio of 1.0 or more and 1.5 or less, particularly 1.0 or more and 1.3 or less.

A scaly shape is a plate-like shape having a pair of main surfaces and side surfaces. The main surface is the surface of the inorganic particles 12 with the largest area. This main surface may be a flat surface or a surface having irregularities. When the inorganic particles 12 are scaly, the aspect ratio is instead defined as the ratio of the average dimension of the major surfaces to the average thickness of the inorganic particles 12 . The thickness of the scaly inorganic particles 12 means the distance between a pair of main surfaces. The average thickness can be obtained by measuring the thickness of arbitrary 50 inorganic particles 12 using SEM and calculating the average value. As the average dimension of the main surface, the value of the median diameter _d50 measured using the particle size distribution analyzer described above can be used. The aspect ratio of the scale-like inorganic particles 12 is, for example, 1.5 or more, may be 1.7 or more, or may be 5 or more. Rod-like can include shapes such as rod-like, columnar, and frusto-conical. The aspect ratio of the rod-shaped inorganic particles 12 is, for example, 1.5 or more, may be 1.7 or more, or may be 5 or more.

When the inorganic particles 12 are spherical, the average particle size is, for example, 0.1 μm to 50 μm, may be 0.1 μm to 10 μm, or may be 0.5 μm to 5 μm. When the inorganic particles 12 are scaly, the average size of the major surfaces of the inorganic particles 12 is, for example, 0.1 μm to 20 μm, and may be 0.5 μm to 15 μm. Also, the average thickness of the inorganic particles 12 is, for example, 0.05 μm to 1 μm, and may be 0.08 μm to 0.5 μm. When the inorganic particles 12 are rod-shaped, the minimum diameter (usually the minor axis length) of the inorganic particles 12 is, for example, 0.01 μm to 10 μm, and may be 0.05 μm to 1 μm. Also, the maximum diameter (usually the major axis length) of the inorganic particles 12 is, for example, 0.1 μm to 20 μm, and may be 0.5 μm to 10 μm. If the size of the inorganic particles 12 is within this range, the inorganic particles 12 are likely to be arranged along the boundaries between the voids 20 and the skeleton portion 10, and the heat transfer paths 5 extending over the multiple voids 20 are likely to be formed. When the inorganic particles 12 are lumps of irregular shape, the average particle size of the inorganic particles 12 is, for example, 10 μm to 100 μm, and may be 20 μm to 60 μm.

The content of the inorganic particles 12 in the composite material 1a is not limited to a specific value. The content of the inorganic particles 12 in the composite material 1a is, for example, 10% by mass to 80% by mass, may be 10% by mass to 70% by mass, or may be 10% by mass to 55% by mass. In addition, the content of the inorganic particles 12 in the composite material 1a is, for example, 1% to 50% by volume, may be 2% to 45% by volume, or may be 5% to 40% by volume. , 5% to 30% by volume. By appropriately adjusting the content of the inorganic particles 12, the composite material 1a tends to have high thermal conductivity and desired flexibility.

The content [mass %] of the inorganic particles 12 in the composite material 1a can be determined by removing materials other than the inorganic particles 12 from the composite material 1a by burning or decomposing. The content [% by mass] of the inorganic particles 12 may be determined using elemental analysis. Specifically, an acid is added to the composite material 1a, microwaves are applied, and the composite material 1a is acid-decomposed under pressure. Acids that can be used include, for example, hydrofluoric acid, concentrated sulfuric acid, concentrated hydrochloric acid, and aqua regia. Elements of the solution obtained by pressure acid decomposition are analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES). The content [% by mass] of the inorganic particles 12 may be determined based on the result.

The density of the inorganic particles 12 is based on the Japanese Industrial Standards (JIS) R 1628: 1997 or JIS Z 2504: 2012 for the inorganic particles 12 remaining after the organic material is burned off by heating the composite material 1a at a high temperature in an electric furnace. can be asked for.

The resin 11 contained in the skeleton portion 10 is not limited to a specific resin. Resin 11 includes, for example, a crosslinked polymer. Resin 11 may be a thermosetting resin. Examples of thermosetting resins include 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 imides. Resin. The curing temperature of the resin 11 is, for example, 25.degree. C. to 160.degree.

The resin 11 may be a thermoplastic resin. Examples of thermoplastic resins are (meth)acrylic resins, styrene resins, polyethylene terephthalate resins, polyethylene resins, polypropylene resins, polyvinyl chloride resins, acrylonitrile-butadiene-styrene resins, and acrylonitrile-styrene resins.

The composite material 1a is, for example, a non-foam. A conventional foam such as that described in Patent Document 1 cannot have the characteristic structure shown in FIG.

An example of a method for manufacturing the composite material 1a will be described. The composite material 1a is manufactured, for example, by a method including the following steps (I) and (II). A fluid resin composition is filled in the gaps between the composite particles. Each of the plurality of composite particles has a first resin and inorganic particles arranged around the first resin.
(I) In a mixture containing a plurality of composite particles and a fluid resin composition, the fluidity of the resin composition is reduced to form a solid portion containing the second resin.
(II) By shrinking or removing the first resin, a plurality of voids are formed, and at least a portion of the inorganic particles are arranged along the boundaries between the plurality of voids and the solid portion.

In the mixture used in step (I), the plurality of composite particles includes first composite particles and second composite particles. The size of the first resin in the first composite particles is included in the first range. The size of the first resin in the second composite particles falls within a second range having an upper limit less than the lower limit of the first range. Thereby, in the composite material 1a, the first distribution D1 has two or more peaks. The size of the first resin is, for example, the maximum diameter of the first resin.

In the step (I), for example, at least part of the second composite particles are arranged between the first composite particles. In this case, in the composite material 1a, gaps 20 having a relatively small size are likely to be formed between gaps 20 having a relatively large size.

Composite particles can be produced, for example, as follows. A premix of the resin particles formed by the first resin and the binder is prepared. The adhesive contains, for example, a predetermined resin. The resin includes, for example, a crosslinkable polymer or a thermosetting resin. Next, the inorganic particles 12 are added to the preliminary mixture and mixed to obtain composite particles in which the inorganic particles 12 are arranged on the surfaces of a plurality of resin particles. The step of adding the binder to the resin particles to obtain a preliminary mixture and the step of adding the inorganic particles 12 to the preliminary mixture may be repeated multiple times. A mixing method is not limited to a specific method. Examples of methods of mixing are ball mills, bead mills, planetary mixers, ultrasonic mixers, homogenizers, rotation or revolution mixers, fluidized bed mixers, Henschel mixers, vessel rotary blenders, ribbon blenders, and mixing using conical screw blenders.

Next, the composite particles are placed inside the mold so that the composite particles are in contact with each other. A separately prepared resin composition having fluidity is added to this mold, and the gaps between the composite particles are filled with this resin composition to obtain the mixture in step (I) above. Alternatively, the composite particles and the resin composition are mixed in advance to prepare a preliminary mixture, and after the preliminary mixture is poured into a mold, the preliminary mixture is treated so that the composite particles are in contact with each other, so that the mixture in the above step (I) is may be obtained.

If necessary, air bubbles are removed from the mixture. A method for removing air bubbles from the mixture is not limited to a specific method. An example of such a method is vacuum degassing. Vacuum degassing is performed, for example, at 25° C. to 200° C. for 1 second to 10 seconds.

In the step (I), for example, the fluidity of the resin composition is lowered by heating the mixture. When the resin composition is heated, for example, the curing reaction of the thermosetting resin proceeds and the fluidity of the resin composition decreases.
In step (II), the method of shrinking or removing the first resin of the composite particles is not limited to a specific method. Examples of such methods are a method of heating the precursor of the composite material 1a and a method of immersing the precursor of the composite material 1a in a specific solvent. These methods may be used in combination. Thereby, a plurality of voids 20 are formed.

The temperature for heating the precursor of the composite material 1a is not limited to a specific temperature, as long as it can soften the first resin. The temperature is, for example, 95°C to 130°C, and may be 120°C to 160°C.

When the precursor of the composite material 1a is immersed in a specific solvent to shrink or remove the first resin, the solvent does not dissolve the second resin and dissolves the first resin. It is not limited to solvents. Examples of solvents are toluene, ethyl acetate, methyl ethyl ketone, and acetone.

The resin particles formed by the first resin may have a hollow structure. The hollow part in the hollow structure may be a single hollow part or may be composed of a plurality of hollow parts. When the composite particles include resin particles having a hollow structure, the heat treatment softens the resin constituting the resin particles, causing the hollow portions to disappear or shrink, and a plurality of voids 20 can be formed accordingly. The resin particles formed by the first resin may be solid particles.

In the step (II), when the precursor of the composite material 1a is immersed in a specific solvent, the first resin dissolves in the solvent more easily than the second resin contained in the solid portion, for example. Therefore, voids 20 having a desired shape are easily formed. Examples of first resins are polystyrene (PS), polyethylene (PE), polymethyl methacrylate (PMMA), ethylene vinyl acetate copolymer (EVA), polyvinyl chloride (PVC), polypropylene (PP), acrylonitrile butadiene • Styrene copolymer (ABS), ethylene-propylene-diene rubber (EPDM), thermoplastic elastomer (TPE), and polyvinyl alcohol (PVA).

According to the manufacturing method described above, the plurality of voids 20 are formed without going through the foaming process.

The composite material 1a can be changed from various points of view. For example, composite material 1a may be modified as composite material 1b shown in FIG. The composite material 1b is configured in the same manner as the composite material 1a except for the parts that are particularly described. Components of the composite material 1b that are the same as or correspond to components of the composite material 1a are denoted by the same reference numerals, and detailed description thereof is omitted. The description regarding the composite material 1a also applies to the composite material 1b unless technically contradictory.

As shown in FIG. 3, particles 30 are arranged inside the voids 20 in the composite material 1b. Particles 30 are typically resin particles. The particles 30 may be resin particles that have shrunk due to heat treatment. The resin particles before shrinkage may have a shape corresponding to the voids 20 . In the composite material 1a, the resin occupying the spaces corresponding to the voids 20 is removed. On the other hand, as shown in FIG. 3, in the composite material 1b, the resin occupying the spaces corresponding to the voids 20 remains deformed. Even for particles 30 whose existence cannot be confirmed in a specific cross section, the existence of particles 30 may be confirmed when another cross section is observed.

The present invention will be described in more detail with examples. In addition, the present invention is not limited to the following examples.

<Example 1>
100 parts by weight of pure water, 0.2 parts by weight of tricalcium phosphate, and 0.01 parts by weight of sodium dodecylbenzenesulfonate were added to an autoclave equipped with a stirrer. Into this autoclave, 0.15 parts by weight of benzoyl peroxide and 0.25 parts by weight of 1,1-bis(t-butylperoxy)cyclohexane were added as initiators to prepare a mixture. 100 parts by weight of styrene monomer was added while stirring the mixture at 350 rpm. Thereafter, the polymerization reaction was carried out by raising the temperature of this solution to 98°C. When the polymerization reaction was about 80% complete, the reaction solution was heated to 120° C. over 30 minutes. Thereafter, the reaction solution was kept at 120° C. for 1 hour to prepare a solution containing styrene resin particles. After cooling the styrene resin particle-containing solution to 95° C., 2 parts by weight of cyclohexane and 7 parts by weight of butane as blowing agents were injected into the autoclave. The solution was then heated to 120°C again. After that, the solution was kept at 120° C. for 1 hour and then cooled to room temperature to obtain a polymerization slurry. Expandable styrene resin particles were obtained by dehydrating, washing and drying the polymerized slurry. The expandable styrene resin particles were sieved to obtain expandable styrene resin particles having a particle size of 0.2 mm to 0.3 mm. These expandable styrene resin particles were used in a pressurized expansion machine (BHP) manufactured by Daikai Kogyo Co., Ltd. to obtain spherical expanded polystyrene beads α having an average diameter of 650 μm to 1200 μm. The expanded polystyrene beads α were passed through a JIS test sieve with a nominal mesh size (JIS Z 8801-1:2019) of 1.18 mm and 1 mm. At this time, expanded polystyrene beads A, which passed through a sieve with a nominal opening of 1.18 mm but did not pass through a sieve with a nominal opening of 1 mm, were used to prepare samples. The expanded polystyrene beads A had an average particle size of 1050 μm and a bulk density of 0.025 g/milliliter (mL).

Spherical expanded polystyrene beads β were produced in the same manner as for the expanded polystyrene beads α, except that the BHP expansion conditions were adjusted so that the average diameter was 400 μm to 600 μm. The expanded polystyrene beads β were passed through sieves with nominal openings of 500 μm and 600 μm. At this time, expanded polystyrene beads B that passed through a sieve with a nominal opening of 600 μm but did not pass through a nominal opening of 500 μm were used for preparing samples. The expanded polystyrene beads B had an average particle diameter of 550 μm and a bulk density of 0.088 g/mL.

A coating agent was prepared by mixing silicone resin KE-106F manufactured by Shin-Etsu Chemical Co., Ltd., curing agent CAT-106F manufactured by Shin-Etsu Chemical Co., Ltd., and silicone oil KF-96-10CS manufactured by Shin-Etsu Chemical Co., Ltd. In the adhesive, the relationship of mass of silicone resin: mass of curing agent: mass of silicone oil=10:1:10 was satisfied. For 1 part by mass of foamed polystyrene beads A, 7 parts by mass of the adhesive was prepared. In addition, 14 parts by mass of scale-like boron nitride was prepared for 1 part by mass of expanded polystyrene beads A. The boron nitride had an average thickness of 0.4 μm and an aspect ratio of 20.

　1 part by mass of expanded polystyrene beads A was added to a high-speed fluid mixer SMP-2 manufactured by Kawata Corporation. Next, a mixture was prepared by adding 0.7 parts by mass of the above-mentioned impregnating agent. The mixture was stirred for 1 minute at 1000 revolutions/minute in a high-speed fluid mixer. Next, 1.4 parts by weight of boron nitride were added to the high-fluid mixer and the resulting mixture was stirred in the high-fluid mixer at 1000 rpm for 1 minute. In this way, the operation of adhering boron nitride to the expanded polystyrene beads A via the attaching agent was repeated 10 times to obtain expanded polystyrene beads M coated with boron nitride. The polystyrene beads M were heated in a constant temperature bath at 60° C. for 2 hours to cure the silicone resin as the adhesive, thereby obtaining composite particles A, which are polystyrene beads coated with boron nitride.

2 parts by mass of the above-mentioned impregnating agent was prepared for 1 part by mass of expanded polystyrene beads B. In addition, 4 parts by mass of scale-like boron nitride was prepared for 1 part by mass of expanded polystyrene beads B. The boron nitride had an average thickness of 0.4 μm and an aspect ratio of 20.

　1 part by mass of expanded polystyrene beads B was added to a high-speed fluid mixer SMP-2 manufactured by Kawata Corporation. Next, 0.2 parts by mass of the above-mentioned impregnating agent was added to prepare a mixture. The mixture was stirred for 1 minute at 1000 revolutions/minute in a high-speed fluid mixer. Next, 0.4 parts by mass of boron nitride was added to the high-fluid mixer and the resulting mixture was stirred in the high-fluid mixer at 1000 rpm for 1 minute. In this manner, the operation of adhering boron nitride to the expanded polystyrene beads B via the attaching agent was repeated 10 times to obtain expanded polystyrene beads N coated with boron nitride. The polystyrene beads N were heated in a constant temperature bath at 60° C. for 2 hours to cure the silicone resin as the adhesive, thereby obtaining composite particles B which were polystyrene beads coated with boron nitride.

A resin precursor was prepared by mixing ingredients A and B of a thermosetting silicone resin DOWSIL SE 1817 CVM manufactured by Dow Toray at a mass ratio of 1:1. Composite particles A and composite particles B were thoroughly mixed. In this mixing, the relationship of bulk volume of composite particles A:bulk volume of composite particles B=90:10 was satisfied. Next, a mixture of Composite Particles A and Composite Particles B was filled to a height of 20 mm inside rectangular parallelepiped plastic cases having internal dimensions of 95 mm, 95 mm, and 24 mm. A plain-woven wire mesh made of stainless steel manufactured by Takashi Yoshida Co., Ltd. was laid on the mixture of composite particles A and B inside the case, and a stainless steel punching metal was laid on the plain-woven wire mesh. The diameter of the openings in the plain weave wire mesh was 0.18 mm and the mesh of the plain weave wire mesh was 50. In the punching metal, the diameter of the openings was 5 mm, and the pitch between adjacent openings was 8 mm. The thickness of the punching metal was 1 mm. The plain weave wire mesh and the punching metal were fixed with clamps.

The above resin precursor was added to the inside of the case, and the resin precursor was degassed under reduced pressure. The gauge pressure in this vacuum defoaming was adjusted to -0.08 MPa to -0.09 MPa. The operation including adding the resin precursor and degassing under reduced pressure was repeated three times to impregnate the resin precursor between the composite particles. Next, by heating so that the environment in which the resin precursor is placed is maintained at 80° C. for 2 hours, the silicone resin contained in the resin precursor is cured, and the resin molded article in which the composite particles are embedded. got This resin molded article was cut into a predetermined size, and the cut resin molded article was immersed in acetone for 30 minutes. As a result, polystyrene contained in the composite particles was dissolved in acetone and eluted from the resin molding. After that, the resin molded product was heated at 90° C. to volatilize acetone, and a composite material according to Example 1 was obtained.

<Example 2>
In the same manner as in Example 1, except that the conditions for mixing Composite Particle A and Composite Particle B were changed so that the relationship of bulk volume of Composite Particle A:bulk volume of Composite Particle B=80:20 was satisfied. A composite material according to Example 2 was produced.

<Example 3>
Example 3 was carried out in the same manner as in Example 1, except that boron nitride having an aspect ratio of 50 and an average thickness of 0.8 μm was used instead of the boron nitride used in Example 1 in the preparation of the composite particles. A composite material was made.

<Example 4>
Example 4 was prepared in the same manner as in Example 1, except that scaly graphite having an aspect ratio of 12 and an average thickness of 1.8 μm was used instead of the boron nitride used in Example 1 in the preparation of the composite particles. A composite material according to was produced.

<Example 5>
A composite material according to Example 5 was produced in the same manner as in Example 1, except for the following points. A mixture of polyurethane SU-3001A and SU-3001B manufactured by Sanyu Rec Co., Ltd. was used as a resin precursor instead of a silicone resin. In this mixture, the amounts of SU-3001A and SU-3001B were adjusted so that the relationship of SU-3001A mass:SU-3001B mass=34:100 was satisfied. The polyurethane contained in the resin precursor was cured by heating such that the environment in which the resin precursor was placed was maintained at 80° C. for 2 hours.

<Example 6>
A composite material according to Example 6 was produced in the same manner as in Example 1, except for the following points. In the production of Composite Particle A, the amount of the impregnating agent was changed to 3.5 parts by mass, and the amount of boron nitride was changed to 7 parts by mass. In the production of Composite Particle B, the amount of the impregnating agent was changed to 3 parts by mass, and the amount of boron nitride was changed to 6 parts by mass.

<Example 7>
A composite material according to Example 7 was produced in the same manner as in Example 2, except for the following points. In the production of Composite Particle A, the amount of the impregnating agent was changed to 3.5 parts by mass, and the amount of boron nitride was changed to 7 parts by mass. In the production of Composite Particle B, the amount of the impregnating agent was changed to 3 parts by mass, and the amount of boron nitride was changed to 6 parts by mass.

<Example 8>
A silicone resin precursor was prepared by mixing DOWSIL SE 1896 FR A/B agent A and agent B in a weight ratio of 1:1 as an adhesive agent. 10 parts by weight of this silicone resin precursor was prepared for 1 part by weight of plastic microballoons (Matsumoto Microsphere F-80DE) manufactured by Matsumoto Yushi Seiyaku. Separately, 25 parts by weight of scale-like boron nitride was prepared for 1 part by weight of F-80DE. The boron nitride had an aspect ratio of 20 and an average thickness of boron nitride of 0.4 μm.

One part by weight of F-80DE was added to Kawata's high-speed fluid mixer SMP-2. Next, while simultaneously adding the silicone resin precursor and the boron nitride and adding each of the silicone resin precursor and the boron nitride in equal amounts over 30 minutes, using the mixer, 1000 The mixture was stirred at revolutions/minute. This operation yielded plastic microballoons coated with boron nitride by the silicone resin precursor. The plastic microballoons were heated in a constant temperature bath at 80° C. for 2 hours to cure the silicone resin and obtain composite particles C coated with boron nitride.

A composite material according to Example 8 was produced in the same manner as in Example 1, except that the composite particles C described above were used instead of the composite particles B used in Example 1.

<Example 9>
The composite according to Example 9 was prepared in the same manner as in Example 1 except that the composite particles B were used instead of the composite particles A used in Example 1, and the composite particles C were used instead of the composite particles B. Material was made.

<Comparative Example 1>
A composite material according to Comparative Example 1 was produced in the same manner as in Example 1, except that only composite particles A were used as the composite particles to be filled in the case.

<Comparative Example 2>
A composite material according to Comparative Example 2 was produced in the same manner as in Example 4, except that only composite particles A were used as the composite particles to be filled in the case.

<Comparative Example 3>
A composite material according to Comparative Example 3 was produced in the same manner as in Example 5, except that only composite particles A were used as the composite particles to be filled in the case.

<Comparative Example 4>
A slurry mixture was prepared by mixing boron nitride having an aspect ratio of 20 and an average thickness of 0.4 μm, agents A and B of silicone resin DOWSIL SE 1817 CVM manufactured by Dow Toray Industries, Inc., and ethanol. In this mixture, the relationship of mass of boron nitride:mass of agent A:mass of agent B:mass of ethanol=23:38:38:1 was satisfied. This mixture was added into a bottomed cylindrical mold with a diameter of 50 mm and a height of 7 mm. Next, the mixture in the mold was heated at 150° C. for 1 hour to cure the foamed silicone resin while allowing the ethanol to act as a foaming agent to foam the silicone resin. Thus, a composite material according to Comparative Example 4 was produced.

<Comparative Example 5>
Comparative Example 5 was prepared in the same manner as in Comparative Example 4, except that boron nitride having an aspect ratio of 50 and an average thickness of 0.4 μm was used instead of the boron nitride used in Comparative Example 4 in the preparation of the composite particles. A composite material was made.

(Microscopic observation)
A cross section of the composite material according to each example and each comparative example was observed using a digital microscope VHX-7000 manufactured by Keyence Corporation. In this observation, a plurality of cross sections to be observed were selected so that 200 or more voids could be confirmed. In this observation, the maximum diameter of each void was measured. Based on the measurement results, the distribution of the maximum diameter (size) of the number-based voids in each composite material was determined. This distribution was generated as a histogram, and the range of each interval in the histogram was 50 μm. The median value of the interval corresponding to the peak in this distribution was taken as the pore size corresponding to that peak. When this distribution had multiple peaks, the size of the void corresponding to the peak (first peak) with the largest void size among the multiple peaks was determined as d1. In addition, the pore size corresponding to the second largest peak (second peak) among the plurality of peaks was determined as d2. The range of each interval of the histogram used for determination of d2 in Examples 8 and 9 was 20 μm. The frequency (number) of intervals including d1 in the histogram was determined as h1, and the frequency (number) of intervals including d2 in the histogram was determined as h2. In addition, the arithmetic mean of the maximum diameter of the voids was obtained based on the measurement results. The results are shown in Tables 1 and 2. A photograph of a cross section of the composite material according to Example 1 and a photograph of a cross section of the composite material according to Comparative Example 1 are shown in FIGS. 4 and 5, respectively.

In the cross section of the above composite material, boron nitride or graphite agglomerated to form 200 annular cross sections corresponding to each of the 200 or more voids whose maximum diameter was measured. The maximum diameter of each of these 200 annular cross-sections was measured. Based on this measurement result, the distribution of the maximum diameter of the annular cross section in each composite material was obtained. This distribution was generated as a histogram, and the range of each interval in the histogram was 50 μm. The median value of the interval corresponding to the peak in this distribution was taken as the maximum diameter of the circular cross-section corresponding to that peak. When this distribution has a plurality of peaks, the maximum diameter of the annular cross section corresponding to the peak (third peak) at which the maximum diameter of the annular cross section is maximum among the plurality of peaks was determined as L1. In addition, the maximum diameter of the annular cross section corresponding to the peak (fourth peak) having the second largest maximum diameter of the annular cross section among the plurality of peaks was determined as L2. The range of each section of the histogram used for determining L2 in Examples 8 and 9 was 20 μm. Table 1 shows the results.

The ratio R of the cross-sectional area of the skeletal part to the cross-sectional area of the entire cross section of the observation target was obtained. The cross-sectional area of the skeleton was determined by subtracting the sum of the area of the voids in the cross-section and the area of the above-mentioned annular cross-section where boron nitride or graphite agglomerates from the entire cross-sectional area of the cross-section to be observed. Table 1 shows the results.

(Calculation of content [mass%] of inorganic particles)
The content [% by mass] of the inorganic particles was determined as follows. First, about 10 mg of the composite material was weighed and added to a fluororesin container. Hydrofluoric acid was added to a fluororesin container and the container was sealed. A container made of fluororesin was irradiated with microwaves, and pressurized acid decomposition was carried out at a maximum temperature of 220°C. Ultrapure water was added to the resulting solution to adjust the volume to 50 mL. Boron atoms (B) were quantitatively analyzed by ICP-AES SPS-3520UV manufactured by Hitachi High-Tech Science Co., Ltd., and the boron nitride content [% by mass] was calculated from the detected boron atom content. When the inorganic particles were graphite, the content of the inorganic particles [% by mass] was calculated by filtering the solution after pressure decomposition of the composite material with hydrofluoric acid and measuring the weight of the residue. Table 2 shows the results.

(Measurement of thermal conductivity)
In accordance with the American Society for Testing and Materials Standard (ASTM) D5470-01 (unidirectional heat flow steady state method), using a thermal conductivity measurement device TCM1001 manufactured by Lesca, one test piece and a symmetrical configuration method are used for the heat flow measurement method. was used to measure the thermal conductivity of the composite material according to each example and each comparative example. Each composite material having a thickness t was cut into a square having a side length of 20 mm in plan view to obtain a test piece. Silicone grease SCH-20 manufactured by Sanhayato Co., Ltd. was applied to both main surfaces of the test piece so that the silicone grease layer had a thickness of 100 μm. The thermal conductivity of silicone grease was 0.84 W/(m·K). As standard rods, an upper rod with a heating block adjusted to 110° C. and a lower rod with a cooling block adjusted to 20° C. were used. A block made of oxygen-free copper was used as a test block. A measurement sample was prepared by sandwiching the test piece between blocks made of oxygen-free copper with a silicone grease layer interposed therebetween. This measurement sample was sandwiched between the upper rod and the lower rod. Heat was applied in the thickness direction of the test piece.

A temperature difference ΔT _S between the upper and lower surfaces of the test piece was determined according to the following equations (1) and (2). In equations (1) and (2), ΔT _C is the temperature difference between the top and bottom surfaces of the oxygen-free copper block (test block). In addition, q ₁ is the heat flux [W/m ² ] determined by the temperature gradient calculated based on the temperature difference at the multiple temperature measuring points of the upper rod, and q ₂ is the multiple It is the heat flux [W/m ² ] determined by the temperature gradient calculated based on the temperature difference at the temperature measuring points. t _b is the sum of the thicknesses of the oxygen-free copper blocks. _kb is the thermal conductivity of the oxygen-free copper block.
ΔT _S =ΔT _C −(q _S ×t _b )/k _b formula (1)
q _S =(q ₁ +q ₂ )/2 Formula (2)

The thermal conductivity λ [W/(m·K)] in the thickness direction of the test piece was determined according to the following formula (3). Table 2 shows the results. The thickness t of the test piece was measured using a camera. In addition, the thermal resistance value R _T was obtained from the relationship of Equation (4). Table 2 shows the results.
λ=q _S ×t/ΔT _S formula (3)
R _T =t/λ Formula (4)

(Compression test)
A test piece for compression test having a thickness of 3 mm was produced from the composite material according to each example and each comparative example. Using a testing machine EZ-test manufactured by Shimadzu Corporation, a compression test was performed at a compression speed of 0.5 mm/min so that a compression strain of 30% was generated in the test piece. The stress corresponding to 30% compressive strain was measured. Table 2 shows the results.

According to the comparison between Examples 1 to 3 and Comparative Examples 1, 4, and 5, the pore size distribution of the composite material has two peaks, so that the thermal conductivity of the composite material tends to increase. is understood. In addition, it is understood that the presence of two peaks in the pore size distribution of the composite material tends to reduce the compressive stress of the composite material and increase the flexibility of the composite material. The same is understood from the comparison between Example 4 and Comparative Example 2 and the comparison between Example 5 and Comparative Example 3.

As shown in Table 1, in Examples 1 to 9, L1/L2≧1.25, {(L1 ² −d1 ² )h1}/{(L2 ² −d2 ² )h2}≧0.8, and R≦ The 0.55 condition was met. According to Examples 1 to 7, it was suggested that the thermal conductivity of the composite material tends to be high when such conditions are satisfied.

A first aspect of the present invention is
A composite material comprising a skeleton containing a resin, inorganic particles, and a plurality of voids,
At least part of the inorganic particles are arranged along the boundary between the void and the skeleton,
When the composite material is viewed in cross section, the first distribution of the size based on the number obtained by measuring the size of each of the plurality of voids has two or more peaks.
Provide composite materials.

The second aspect according to the present invention is, in the first aspect,
The plurality of voids has a plurality of first voids and second voids arranged between the first voids,
When the composite material is viewed in cross section, the size of the first voids is included in the first range, and the size of the second voids is in a second range having an upper limit smaller than the lower limit of the first range. include,
Provide composite materials.

A third aspect according to the present invention is, in the first aspect or the second aspect,
The first distribution has a first peak and a second peak,
the size at the second peak is smaller than the size at the first peak;
When the composite material is viewed in cross section, the inorganic particles arranged along the boundary have a plurality of annular cross sections corresponding to the plurality of voids,
A number-based second distribution obtained by measuring the maximum diameter of each of the plurality of annular cross sections has a third peak and a fourth peak,
The maximum diameter at the fourth peak is smaller than the maximum diameter at the third peak,
The composite material satisfies the conditions of L1/L2≧1.25, {(L1 ² −d1 ² )h1}/{(L2 ² −d2 ² )h2}≧0.8, and R≦0.55;
In the above conditions, L1 is the maximum diameter corresponding to the third peak, L2 is the maximum diameter corresponding to the fourth peak, d1 is the size corresponding to the first peak, and d2 is is the size corresponding to the second peak, h1 is the number at the first peak, h2 is the number at the second peak, and R is the cross-sectional area of the composite material in cross-sectional view of the composite material is the ratio of the cross-sectional areas of the skeleton,
Provide composite materials.

A fourth aspect of the present invention is, in the first aspect or the second aspect,
The first distribution has a first peak and a second peak,
the size at the second peak is smaller than the size at the first peak;
The ratio of the number of voids in the second peak to the number of voids in the first peak is 0.01 to 100.
Provide composite materials.

The fifth aspect of the present invention is any one of the first to fourth aspects,
When the composite material is viewed in cross section, the arithmetic mean of the size obtained by measuring the size of each of the plurality of voids is 50 to 1500 μm.
Provide composite materials.

The sixth aspect of the present invention, in any one of the first to fifth aspects,
The first distribution has a first peak and a second peak,
the first peak is present in the size range of 500-1200 μm and the second peak is present in the size range of 50-700 μm;
Provide composite materials.

The seventh aspect of the present disclosure, in any one of the first to sixth aspects,
Having a heat transfer path formed by the inorganic particles,
Provide composite materials.

The eighth aspect of the present disclosure is, in the seventh aspect,
The composite material has a first major surface and a second major surface parallel to each other,
at least one of the heat transfer paths extends from the first major surface to the second major surface;
Provide composite materials.

The ninth aspect of the present disclosure, in any one of the first to eighth aspects,
the plurality of voids have external shapes that are similar to each other;
Provide composite materials.

The tenth aspect of the present disclosure includes, in any one of the first to ninth aspects,
wherein the composite material is non-foamed;
Provide composite materials.

An eleventh aspect of the present disclosure includes:
In a mixture containing a plurality of composite particles each having a first resin and inorganic particles arranged around the first resin, and a fluid resin composition filled in gaps between the composite particles, the resin reducing the fluidity of the composition to form a solid portion comprising the second resin;
Arranging at least a portion of the inorganic particles along the boundary between the plurality of voids and the solid portion while forming a plurality of voids by shrinkage or removal of the first resin;
The plurality of composite particles includes first composite particles and second composite particles,
The size of the first resin of the first composite particles is included in the first range,
The size of the first resin of the second composite particle is included in a second range having an upper limit smaller than the lower limit of the first range,
A method of manufacturing a composite material is provided.

A twelfth aspect of the present disclosure, in the eleventh aspect,
At least part of the second composite particles are arranged between the first composite particles,
A method of manufacturing a composite material is provided.

A thirteenth aspect of the present disclosure, in the eleventh or twelfth aspect,
The plurality of voids are formed without undergoing a foaming process,
A method of manufacturing a composite material is provided.

Claims

A composite material comprising a skeleton containing a resin, inorganic particles, and a plurality of voids,
At least part of the inorganic particles are arranged along the boundary between the void and the skeleton,
When the composite material is viewed in cross section, the first distribution of the size based on the number obtained by measuring the size of each of the plurality of voids has two or more peaks.
Composite material.
The plurality of voids has a plurality of first voids and second voids arranged between the first voids,
When the composite material is viewed in cross section, the size of the first voids is included in the first range, and the size of the second voids is in a second range having an upper limit smaller than the lower limit of the first range. include,
A composite material according to claim 1 .
The first distribution has a first peak and a second peak,
the size at the second peak is smaller than the size at the first peak;
When the composite material is viewed in cross section, the inorganic particles arranged along the boundary have a plurality of annular cross sections corresponding to the plurality of voids,
A number-based second distribution obtained by measuring the maximum diameter of each of the plurality of annular cross sections has a third peak and a fourth peak,
The maximum diameter at the fourth peak is smaller than the maximum diameter at the third peak,
The composite material satisfies the conditions of L1/L2≧1.25, {(L1 2 −d1 2 )h1}/{(L2 2 −d2 2 )h2}≧0.8, and R≦0.55;
In the above conditions, L1 is the maximum diameter corresponding to the third peak, L2 is the maximum diameter corresponding to the fourth peak, d1 is the size corresponding to the first peak, and d2 is is the size corresponding to the second peak, h1 is the number at the first peak, h2 is the number at the second peak, and R is the cross-sectional area of the composite material in cross-sectional view of the composite material is the ratio of the cross-sectional areas of the skeleton,
A composite material according to claim 1 .
The first distribution has a first peak and a second peak,
the size at the second peak is smaller than the size at the first peak;
The ratio of the number of voids in the second peak to the number of voids in the first peak is 0.01 to 100.
A composite material according to claim 1 .
The composite material according to claim 1, wherein when the composite material is viewed in cross section, the arithmetic mean of the size obtained by measuring the size of each of the plurality of voids is 50 to 1500 μm.
The first distribution has a first peak and a second peak,
the first peak is present in the size range of 500-1200 μm and the second peak is present in the size range of 50-700 μm;
A composite material according to claim 1 .
Having a heat transfer path formed by the inorganic particles,
A composite material according to claim 1 .
The composite material has a first major surface and a second major surface parallel to each other,
at least one of the heat transfer paths extends from the first major surface to the second major surface;
A composite material according to claim 7 .
the plurality of voids have external shapes that are similar to each other;
A composite material according to claim 1 .
wherein the composite material is non-foamed;
A composite material according to claim 1 .
In a mixture containing a plurality of composite particles each having a first resin and inorganic particles arranged around the first resin, and a fluid resin composition filled in gaps between the composite particles, the resin reducing the fluidity of the composition to form a solid portion comprising the second resin;
Arranging at least a portion of the inorganic particles along the boundary between the plurality of voids and the solid portion while forming a plurality of voids by shrinkage or removal of the first resin;
The plurality of composite particles includes first composite particles and second composite particles,
The size of the first resin of the first composite particles is included in the first range,
The size of the first resin of the second composite particle is included in a second range having an upper limit smaller than the lower limit of the first range,
A method of manufacturing a composite material.
At least part of the second composite particles are arranged between the first composite particles,
A method for manufacturing a composite material according to claim 11 .
The plurality of voids are formed without undergoing a foaming process,
A method for manufacturing a composite material according to claim 11 .