JP2021091579A - Powder containing composite particle and method for producing the same, and resin composition containing the powder - Google Patents

Abstract

To simply prepare a heat dissipation member from powder containing boron nitride.SOLUTION: Powder contains a plurality of composite particles. Each of the plurality of composite particles contains aggregated particles in which a plurality of boron nitride primary particles are aggregated and a resin A. The resin A is arranged in a gap between the plurality of boron nitride primary particles in the aggregated particles, and there is no mass of the resin A on an outer surface of the aggregated particles.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a powder containing composite particles, a method for producing the same, and a resin composition containing the powder.

In electronic components such as power devices, transistors, thyristors, and CPUs, it is an issue to efficiently dissipate heat generated during use. To solve this problem, a heat radiating member containing ceramic powder having high thermal conductivity is used.

As the ceramic powder, boron nitride powder having characteristics such as high thermal conductivity, high insulation property, and low relative permittivity is attracting attention. Boron nitride powder is generally composed of agglomerated particles formed by agglomerating primary particles of boron nitride. For example, in Patent Document 1, the shape of the agglomerated particles is further spheroidized to improve the filling property, the powder strength is improved, and further, the purity is increased to improve the insulating property of the heat transfer sheet or the like filled with the powder. Hexagonal boron nitride powder, which is said to have achieved improvement and stabilization of withstand voltage, is disclosed.

Japanese Unexamined Patent Publication No. 2011-98882

When the boron nitride powder is used for the heat radiating member, the above-mentioned characteristics such as thermal conductivity are of course important, but it is important that the heat radiating member can be easily produced from the state of the boron nitride powder. Therefore, an object of the present invention is to easily produce a heat radiating member from a powder containing boron nitride.

One aspect of the present invention is a powder containing a plurality of composite particles, and each of the plurality of composite particles contains agglomerated particles formed by aggregating a plurality of boron nitride primary particles and resin A, and is a resin. A is a powder in which a plurality of boron nitride primary particles are arranged in the gaps between the agglomerated particles, and no lump of the resin A is present on the outer surface of the agglomerated particles.

In the composite particles contained in this powder, since the resin A is arranged in the gaps between the boron nitride primary particles in the aggregated particles of the boron nitride primary particles, the resin A is added as compared with the case where the resin does not exist in the aggregated particles. The resin A can be further cured while binding the composite particles to each other by the pressure heat treatment. Therefore, a molded product (cured product) in which aggregated particles are dispersed in the resin A can be easily obtained by using only this powder. In addition, in this composite particle, since the lump of resin A does not exist on the outer surface of the agglomerated particles, the agglomerated particles of boron nitride come into contact with each other when a molded product (cured product) containing this powder is produced. This makes it easier to obtain a molded product (cured product) with higher thermal conductivity.

Another aspect of the present invention is a resin composition containing the resin B and the above-mentioned powder. The resin B may be a resin different from the resin A.

Another aspect of the present invention includes a step a of mixing agglomerated particles formed by aggregating a plurality of boron nitride primary particles and a resin A to prepare a composition, and a step b of pulverizing the composition. In step a, the powder production method comprises mixing 0.7 to 2.0 times the volume of the resin A with respect to the volume of the gaps between the plurality of boron nitride primary particles in the aggregated particles.

According to the present invention, a heat radiating member can be easily produced from a powder containing boron nitride.

It is an SEM image which observed the appearance of the composite particle (powder) of an Example. It is an SEM image which observed the cross section of the composite particle (powder) of an Example. It is an SEM image which observed the appearance of the aggregated particle of the boron nitride primary particle.

Hereinafter, embodiments of the present invention will be described in detail.

The powder according to one embodiment contains a plurality of composite particles. The powder can also be said to be an aggregate of a plurality of composite particles. The powder means a state in which a plurality of composite particles exist separately and independently, and for example, a state in which substantially all of the plurality of composite particles are bonded to each other by a binder (for example, a resin). Distinguished. It can be said that the powder itself exhibits fluidity and has an arbitrary angle of repose.

The composite particle is a composite of boron nitride particles and a resin. More specifically, each of the composite particles contains agglomerated particles formed by aggregating a plurality of boron nitride primary particles and resin A.

The boron nitride primary particles may be, for example, scaly hexagonal boron nitride particles. In this case, the length of the boron nitride primary particles in the longitudinal direction may be, for example, 1 μm or more and 10 μm or less.

The average diameter (average particle diameter) of the agglomerated particles may be, for example, 20 μm or more, 40 μm or more, or 50 μm or more, and may be 150 μm or less, 120 μm or less, or 100 μm or less. The average diameter of the agglomerated particles means the volume average diameter measured by the laser diffraction / scattering method.

In the agglomerated particles, there are gaps (voids) between the plurality of boron nitride primary particles. The resin A is arranged in the gaps between the plurality of boron nitride primary particles in the aggregated particles. The resin A may be arranged in a part of the gap between the boron nitride primary particles, or may be arranged in the entire gap. It is preferable that the resin A is arranged as much as possible in the gaps between the boron nitride primary particles. The area ratio of the gap in the cross section of the composite particle is preferably 30% or less, 20% or less, 10% or less, or 5% or less. The area ratio is the ratio of the cross-sectional area of the gap to the cross-sectional area of the composite particle (cross-sectional area of the gap / cross-sectional area of the composite particle) in the SEM image (for example, the SEM image as shown in FIG. 2) in which the cross section of the composite particle is observed. Is measured as, and is defined as the average value of the area ratio of any 100 composite particles in which the measurement was performed.

The resin A may be arranged on a part or all of the outer surface of the agglomerated particles in addition to the gaps in the agglomerated particles. However, there is no lump of resin A on the outer surface of the agglomerated particles. Here, the lump of the resin A means a lumpy resin A having a height of 3 μm or more from the outer surface of the agglomerated particles. The presence or absence of lumps of the resin A is determined based on the SEM image obtained by observing the cross section of the composite particles.

The resin A may be a thermosetting resin or a thermoplastic resin. When the resin A is a thermosetting resin, the resin A may be in a semi-cured state or may be in a completely cured state. The semi-cured resin A contains both the cured resin A and the uncured resin A.

Examples of the resin A include epoxy resin, silicone resin, silicone rubber, acrylic resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyimide, polyamideimide, polyetherimide, polybutylene terephthalate, and polyethylene terephthalate. , Polyphenylene ether, polyphenylene sulfide, total aromatic polyester, polysulfone, liquid crystal polymer, polyether sulfone, polycarbonate, maleimide modified resin, ABS (acrylonitrile-butadiene-styrene) resin, AAS (acrylonitrile-acrylic rubber / styrene) resin, and AES (Acrylonitrile, ethylene, propylene, diene rubber-styrene) resin can be mentioned.

In addition to the resin A, other components may be present in the gaps in the agglomerated particles and on the outer surface of the agglomerated particles. That is, the composite particles may further contain other components in addition to the agglomerated particles and the resin A. Examples of other components include a curing agent, a curing accelerator (curing catalyst), a coupling agent, a wet dispersant, and a surface conditioner.

The curing agent is appropriately selected depending on the type of resin A. For example, when the resin A is an epoxy resin, examples of the curing agent include phenol novolac compounds, acid anhydrides, amino compounds, and imidazole compounds. The content of the curing agent may be, for example, 0.5 parts by mass or more or 1.0 part by mass or more, and may be 15 parts by mass or less or 10 parts by mass or less with respect to 100 parts by mass of the resin A.

Examples of the curing accelerator (curing catalyst) include phosphorus-based curing accelerators such as tetraphenylphosphonium tetraphenylborate and triphenylphosphate, and imidazole-based curing accelerators such as 2-phenyl-4,5-dihydroxymethylimidazole. Examples thereof include amine-based curing accelerators such as boron trifluoride monoethylamine.

Examples of the coupling agent include a silane-based coupling agent, a titanate-based coupling agent, and an aluminate-based coupling agent. Examples of the chemical bonding group contained in these coupling agents include a vinyl group, an epoxy group, an amino group, a methacryl group, and a mercapto group.

Wet dispersants include, for example, phosphate ester salts, carboxylic acid esters, polyesters, acrylic copolymers, and block copolymers.

Examples of the surface conditioner include an acrylic surface conditioner, a silicone type surface conditioner, a vinyl type conditioner, and a fluorine type surface conditioner.

The content of the agglomerated particles (boron nitride primary particles) in the composite particles may be, for example, 30% by volume or more, 40% by volume or more, or 50% by volume or more, based on the total volume of the composite particles, and may be 80 volumes. % Or less, 70% by volume or less, or 60% by volume or less.

The content of the resin A in the composite particles may be, for example, 30% by volume or more, 40% by volume or more, or 50% by volume or more, and 70% by volume or less, 60% by volume, based on the total volume of the composite particles. It may be less than or equal to 55% by volume or less.

The content (total content) of other components in the composite particles is, for example, 10% by volume or less, 5% by volume or less, 3% by volume or less, or 1% by volume or less based on the total volume of the composite particles. It may be present, and may be 0% by volume.

The powder (composite particles) is produced, for example, by a production method including a step a of mixing agglomerated particles and a resin A to prepare a composition, and a step b of pulverizing the composition. When the resin A is a thermosetting resin, the production method may further include a step c for curing the resin A in the composition between the steps a and b.

The agglomerated particles used in step a can be produced by a known method. In step a, in addition to the agglomerated particles and the resin A, the above-mentioned other components may be further mixed if necessary, or a solvent (for example, a solvent for dissolving the resin A) may be further mixed. Examples of the solvent include alcohol solvents, glycol ether solvents, aromatic solvents, and ketone solvents. Examples of the alcohol solvent include isopropyl alcohol and diacetone alcohol. Examples of the glycol ether solvent include ethyl cellosolve and butyl cellosolve. Examples of the aromatic solvent include toluene and xylene. Examples of the ketone solvent include methyl ethyl ketone and methyl isobutyl ketone.

In step a, the resin A (and other components used as needed) enters the gaps between the plurality of boron nitride primary particles in the aggregated particles and is also arranged on the outer surface of the aggregated particles. At this time, it is necessary to appropriately set the amount of the resin A to be mixed with the agglomerated particles in the step a so that the lump of the resin A does not occur. Specifically, the blending amount of the resin A is preferably 0.7 times or more, more preferably 1.0 times or more, still more preferably 1.0 times or more, based on the volume of the gap between the plurality of boron nitride primary particles in the aggregated particles. Is 1.3 times or more, particularly preferably 1.6 times or more, preferably 2.0 times or less, more preferably 1.9 times or less, still more preferably 1.8 times or less. 0.7 to 2.0 times, 0.7 to 1.9 times, 0.7 to 1.8 times, 1.0 to 2.0 times, 1.0 to 1.9 times, 1.0 to 1 8.8 times, 1.3 to 2.0 times, 1.3 to 1.9 times, 1.3 to 1.8 times, 1.6 to 2.0 times, 1.6 to 1.9 times, or The volume may be 1.6 to 1.8 times.

In step b, the method for pulverizing the composition may be, for example, freeze pulverization. In freeze pulverization, for example, the composition is pulverized in a state of being frozen in liquid nitrogen. The conditions for pulverization are appropriately selected so that the composite particles are separated from each other. Specifically, for example, a freeze crusher is used to grind at 1500 to 3500 rpm for 1 to 30 seconds.

The method for curing the resin A in the step c is appropriately selected depending on the type of the resin A (and the curing agent used if necessary). For example, when the resin A is an epoxy resin and the above-mentioned curing agent is used together, the resin A can be cured by heating in the step c. When a solvent is used in the step a, the resin A may be cured and the solvent may be volatilized in the step c. In step c, the resin A may be semi-cured or completely cured.

In the step c, the composition prepared in the step a may be formed into a sheet before the resin A is cured. Specifically, for example, a film applicator may be used to coat the composition on a substrate to form a sheet having a thickness of 50 to 400 μm.

In the composite particles contained in the powder described above, since the resin A is arranged in the gaps between the boron nitride primary particles in the aggregated particles of the boron nitride primary particles, compared with the case where the resin does not exist in the aggregated particles. The resin A can be further cured while binding the composite particles to each other by the pressure heat treatment. Therefore, a molded product (cured product) in which aggregated particles are dispersed in the resin A can be easily obtained by using only this powder. Such a molded body (cured body) is preferably used as a heat radiating member.

Further, when a lump of resin is present on the surface of the agglomerated particles, the resin is likely to be present between the agglomerated particles when a molded product (cured product) is produced, and this resin may prevent the agglomerated particles from coming into contact with each other. There is. On the other hand, in the above-mentioned composite particles, since the lump of resin A does not exist on the outer surface of the aggregated particles, the aggregated particles easily come into contact with each other when a molded body (cured product) containing this powder is produced. Therefore, a molded product (cured product) having a higher thermal conductivity can be obtained as compared with the case where a resin mass is present on the surface of the aggregated particles.

The powder may consist of only composite particles, and may further contain other particles in addition to the composite particles. The other particles may be composed of, for example, an inorganic material. Examples of the inorganic material include boron nitride, aluminum nitride, silicon nitride, aluminum oxide, silicon dioxide, magnesium oxide, silicon carbide, metallic aluminum, and graphite. The content of the composite particles in the powder is, for example, 40% by volume or more, 50% by volume or more, 60% by volume or more, 70% by volume or more, 80% by volume or more, or 90% by volume based on the total volume of the powder. It may be% or more.

Other particles include agglomerated particles formed by aggregating a plurality of boron nitride primary particles and a resin, and the resin is arranged in a gap between a plurality of boron nitride primary particles in the agglomerated particles, and the agglomerated particles. The particles may be particles in which the resin lumps are present on the outer surface of the above-mentioned composite particles (that is, particles having the same configuration as the above-mentioned composite particles except that the resin lumps are present on the outer surface of the aggregated particles). .. In this case, the number ratio of the above-mentioned composite particles is such that many agglomerated particles can come into contact with each other and the decrease in thermal conductivity due to the resin between the agglomerated particles can be suppressed. It is preferably 70% by number or more, 80% by number or more, or 90% by number or more based on the total amount of the particles. The number ratio is calculated from the number of the composite particles having no resin lumps by observing the cross section of 100 particles by SEM to determine the presence or absence of resin lumps.

Another embodiment of the present invention is a resin composition containing the above powder (composite particles) and resin B. Such a resin composition is also preferably used as a heat radiating member.

The resin B may be the same resin as the resin A described above, or may be a resin different from the resin A, and is preferably a resin different from the resin A from the viewpoint of easily obtaining the characteristics required for the heat radiating member. The example of the resin B is the same as the resin described as the example of the resin A.

The content of the composite particles in the resin composition is preferably 30% by volume from the viewpoint of improving the thermal conductivity of the resin composition and easily obtaining excellent heat dissipation performance based on the total volume of the resin composition. The above may be 40% by volume or more, 50% by volume or more, or 60% by volume or more, and is preferably 85% by volume or less or 80% by volume or less from the viewpoint of suppressing a decrease in insulating property and mechanical strength. Good.

The content of the resin B in the resin composition may be, for example, 15% by volume or more, 20% by volume or more, 30% by volume or more, or 40% by volume or more, based on the total volume of the resin composition. It may be 50% by volume or less or 60% by volume or less.

The resin composition may further contain composite particles and other components other than the resin B. Other components may further contain, for example, a curing agent that cures the resin B. The curing agent is appropriately selected according to the type of resin B. The content of the curing agent may be, for example, 0.5 parts by mass or more or 1.0 part by mass or more, and may be 15 parts by mass or less or 10 parts by mass or less with respect to 100 parts by mass of the resin B.

The content (total content) of other components in the resin composition is, for example, 10% by volume or less, 5% by volume or less, 3% by volume or less, or 1% by volume based on the total volume of the resin composition. It may be less than or equal to 0% by volume.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to the following Examples.

Aggregated particles of boron nitride primary particles (average particle size: 87 μm, void ratio: 49%) 50 parts by volume, epoxy resin (manufactured by DIC, product name: HP4032) 41.5 parts by volume, and curing agent (manufactured by DIC) , Product name: VH4150) 5.1 parts by volume, 2 types of curing accelerator (curing catalyst) (manufactured by Hokuko Chemical Co., Ltd., product name: TPP) 0.3 parts by volume and (manufactured by Shikoku Kasei Kogyo Co., Ltd., product name: 2PHZ-PW) 0.5 part by volume, coupling agent (manufactured by Toray Dow Corning, product name: Z6040) 1.6 parts by volume, wet dispersant (manufactured by Big Chemie Japan, product name: DIS-111) ) 0.3 parts by volume, 0.4 parts by volume of surface conditioner (manufactured by Big Chemie Japan, product name: BYK-300), and a solvent that is a volatile component with respect to a total of 100 parts by volume of each of these components. (Manufactured by Tokyo Kasei Kogyo Co., Ltd., product name: diacetone alcohol) 6.5 parts by volume using a planetary stirrer (Sinky's "Awatori Rentaro AR-250") at a revolution speed of 2000 rpm and a rotation speed of 800 rpm. The composition was obtained by kneading under the condition of (× 2 minutes).

Subsequently, the obtained composition was formed into a sheet having a thickness of 100 μm using a film applicator, and then an epoxy resin was used under the conditions of 60 ° C. for 30 minutes and 100 ° C. for 70 minutes using a hot air dryer. Was semi-cured.

Subsequently, using a freeze crusher (PV1001 (S) manufactured by Yasui Kiki Co., Ltd.), 3 g of the semi-cured sheet-like composition was freeze-crushed at 2800 rpm for 15 seconds. .. As a result, a powder composed of composite particles was obtained.

FIG. 1 shows an SEM image of observing the appearance of the obtained composite particles (powder). Further, FIG. 2 shows one of the SEM images obtained by observing the cross sections of each of the four obtained composite particles (powder). For comparison, FIG. 3 shows an SEM image of the appearance of aggregated particles (without resin) of the boron nitride primary particles. 1 (a) and 3 (a) are SEM images at 500 times, FIGS. 1 (b) and 3 (b) are 2000 times, and FIG. 2 is 1000 times SEM images.

As can be seen from FIGS. 1 and 2 (further, comparison with FIG. 3), in the obtained composite particles, the epoxy resin is arranged in the gaps between the plurality of boron nitride primary particles in the aggregated particles and is aggregated. It is also placed on the outer surface of the particles. Further, as can be seen from FIG. 2, no lump of epoxy resin is present on the outer surface of the agglomerated particles. The same was true for the remaining 3 composite particles out of the 4 composite particles observed.

Moreover, when the density of the composite particle was measured by the underwater substitution method (Archimedes method), it was substantially the same as the ^{theoretical density of 1.735 g / cm 3.} From this, it can be said that the epoxy resin is arranged in the gaps between the plurality of boron nitride primary particles in the aggregated particles.

Claims (4)

A powder containing a plurality of composite particles
Each of the plurality of composite particles contains agglomerated particles formed by aggregating a plurality of boron nitride primary particles and resin A.
The resin A is arranged in the gaps between the plurality of boron nitride primary particles in the aggregated particles.
A powder in which no lump of the resin A is present on the outer surface of the agglomerated particles. A resin composition containing the resin B and the powder according to claim 1. The resin composition according to claim 2, wherein the resin B is a resin different from the resin A. Step a of preparing a composition by mixing the agglomerated particles formed by aggregating a plurality of boron nitride primary particles and the resin A,
The step b of pulverizing the composition is provided.
A method for producing a powder, wherein in the step a, the resin A having a volume 0.7 to 2.0 times the volume of the gaps between the plurality of boron nitride primary particles in the aggregated particles is mixed.

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