JPWO2019188444A1 - Powder consisting of organic-inorganic composite particles - Google Patents

Abstract

The subject of the present invention is a boron nitride-based powder which is useful as a filler for a thermally conductive resin composition, has low thermal anisotropy, and is excellent in heat resistance and solvent resistance, and a method for producing the powder. Is to provide. The powder of the present invention is composed of organic-inorganic composite particles in which a plurality of randomly oriented hexagonal boron nitride particles are composited via the three-dimensional crosslinked resin, and is a volume measured by a laser diffraction / scattering type particle size distribution meter. It is a powder having a frequency of 50% particle size (D50) in the range of 2 to 65 μm.

Description

The present invention relates to organic-inorganic composite particles composed of a three-dimensional crosslinked resin and hexagonal boron nitride. Specifically, hexagonal boron nitride particles form agglomerates via a resin, and the resin component maintains the form of organic-inorganic composite particles without being easily eluted, and a thermally conductive resin composition or the like. The present invention relates to organic-inorganic composite particles suitable for producing the above.

In recent years, due to the demand for miniaturization and high performance of electronic components, the integration of semiconductor devices has progressed, and at the same time, the amount of heat radiating materials used to efficiently dissipate heat generated from the devices has increased. Improvement of heat dissipation performance of materials is required. Various heat radiating materials are used for the path of releasing the heat generated by the semiconductor element to the heat sink, the housing, or the like. Increasingly, ceramic substrates such as aluminum nitride and silicon nitride, which have high thermal conductivity, are used as substrates on which components are mounted.

Further, the use of a metal base substrate in which a heat-dissipating insulating resin layer is provided on a metal plate is increasing, and such a resin layer is filled with alumina, aluminum nitride, boron nitride or the like as a filler having high thermal conductivity. In addition, highly thermally conductive fillers are being used for encapsulants, adhesives, greases, etc. around semiconductor devices, and how to efficiently dissipate heat is becoming important.

For silica and alumina, which are common fillers to be filled in resins, methods for improving the filling properties in resins such as spheroidization and precise control of particle size distribution have been developed by improving the synthesis method. In addition, silica has many active hydroxyl groups on its surface, and surface treatment for improving dispersibility in resin is also actively performed.

On the other hand, hexagonal boron nitride is superior in thermal conductivity to silica and alumina, but has anisotropy in thermal conductivity. Hexagonal boron nitride is a flat crystal, and the thermal conductivity in the longitudinal direction of the flat plate surface is as high as 200 W / m · K or more, but the thermal conductivity in the thickness direction of the flat plate is only 2-3 W / m · K. .. Therefore, for example, when a flat plate of boron nitride filled in a heat-dissipating resin sheet is filled in parallel with the sheet surface, the thermal conductivity in the thickness direction of the sheet cannot be increased. Further, hexagonal boron nitride has a property of cleaving along a surface and has a low hardness, so that it tends to be a powder in which flat particles having a high aspect ratio occupy a large number. Due to these properties, there is a problem that anisotropy of thermal conductivity is likely to occur when hexagonal boron nitride is used as a filler.

Conventionally, in order to solve the anisotropy of thermal conductivity, attempts have been made to prevent particles having a high aspect ratio from being oriented in the same direction. A typical example is a method of randomly aggregating flat plate hexagonal boron nitride particles to obtain particles without thermal anisotropy (see, for example, Patent Documents 1 to 5).

In Patent Document 1, agglomerated particles are obtained by mixing diboron trioxide or a precursor thereof with a product obtained by calcining boron carbide in a nitrogen atmosphere and calcining the product.

In Patent Document 2, composite particles of melamine borate and boron nitride are produced and calcined to obtain aggregated particles.

In Patent Document 3, granules are formed from a slurry containing boron nitride and oxide particles, and the granulated particles are calcined to obtain aggregated particles.

In Patent Document 4, a binder such as polyvinyl alcohol of a thermoplastic resin, a sintering aid such as calcium carbonate, and a slurry in which boron nitride particles are dispersed in a solvent are spray-dried and then fired to obtain boron nitride aggregates. Is getting.

Patent Document 5 discloses a method for producing boron nitride agglomerated particles bound by a binder resin by mixing a binder resin dissolved in a solvent and boron nitride particles and further precipitating the binder resin.

JP-A-2007-308360 Japanese Unexamined Patent Publication No. 2012-171842 International Publication No. 2015/11198 Pamphlet JP-A-2018-20932 JP-A-2017-57098

However, the methods described in Patent Documents 1 to 4 and the like require firing at an extremely high temperature of 1600 to 2200 ° C. in order to obtain aggregated particles, which causes a problem in industrial production.

Further, in the method described in Patent Document 5, only a binder resin soluble in a solvent can be used due to the manufacturing method, and there are problems in solvent resistance and heat resistance.

Therefore, an object of the present invention is to provide a novel powder composed of hexagonal boron nitride agglomerated particles that satisfies both high filling in a resin composition and high thermal conductivity, and is extremely productive. There is.

As a result of diligent studies to achieve the above object, the present inventors have added a small amount of a curable resin to the hexagonal boron nitride powder, and then cured the resin to obtain hexagonal boron nitride. The present invention has been completed by finding that agglomerated particles oriented in various directions are generated.

That is, the present invention comprises organic-inorganic composite particles in which a plurality of randomly oriented hexagonal boron nitride particles are composited via a three-dimensional crosslinked resin, and the volume frequency is 50 as measured by a laser diffraction / scattering type particle size distribution meter. A powder having a% particle size (D50) in the range of 2 to 65 μm.

Further, as a method for producing the above powder, the present invention is a step of adding and mixing a three-dimensional crosslinked curable resin in an amount of 1 part by mass or more and 35 parts by mass or less with 100 parts by mass of hexagonal boron nitride powder (1). ), And then a step (2) of curing the three-dimensional crosslinked curable resin.

According to the present invention, a novel powder comprising hexagonal boron nitride agglomerated particles satisfying both high filling in a resin composition and high thermal conductivity, which is extremely productive, is provided.

Scanning electron microscope image of boron nitride particles produced in Production Example 1. Scanning electron microscope image of the organic-inorganic composite particles produced in Example 1. Scanning electron microscope image of organic-inorganic composite particles produced in Example 2. Scanning electron microscope image of organic-inorganic composite particles produced in Example 3. Scanning electron microscope image of organic-inorganic composite particles produced in Example 4. Scanning electron microscope image of organic-inorganic composite particles produced in Example 5. Scanning electron microscope image of the organic-inorganic composite particles produced in Example 6. Scanning electron microscope image of the organic-inorganic composite particles produced in Example 7. The graph which shows the particle size distribution of the raw material boron nitride powder produced in Production Example 1 and the organic-inorganic composite particle powder produced in Examples 2-4. The graph which shows the particle size distribution of the raw material boron nitride powder produced in Production Example 1 and the organic-inorganic composite particle powder produced in Examples 6 and 7.

The powder of the present invention is composed of organic-inorganic composite particles in which a plurality of randomly oriented hexagonal boron nitride particles (hereinafter, simply referred to as “boron nitride particles”) are composited via a three-dimensional crosslinked resin, and is subjected to laser diffraction. The volume frequency 50% particle size (D50) measured by the scattering type particle size distribution meter is in the range of 2 to 65 μm.

[Organic-inorganic composite particles]
In the organic-inorganic composite particles of the present invention, since a plurality of boron nitride particles are randomly oriented, the organic-inorganic composite particles have a boron nitride aggregate structure with little thermal anisotropy.

Here, "randomly oriented" indicates that they are oriented in various different directions, but those oriented in the same direction may be included. The powder of the present invention is substantially composed of the organic-inorganic composite particles, but may contain composite particles composed of a single boron nitride particle and a three-dimensional crosslinked resin as long as the effects of the present invention are not impaired. Also, it may contain the boron nitride particles themselves to which the three-dimensional crosslinked resin is not fixed.

The content of the three-dimensional crosslinked resin constituting the organic-inorganic composite particles is not particularly limited, but the upper limit thereof is preferably 35 parts by mass or less, more preferably 30 parts by mass with respect to 100 parts by mass of the boron nitride particles. Parts or less, more preferably 25 parts by mass or less, particularly preferably 20 parts by mass or less, and the lower limit thereof is preferably 1 part by mass or more, more preferably 1.4 parts by mass or more, still more preferably 2 parts by mass. As mentioned above, it is particularly preferably 2.5 parts by mass or more. When the amount of the three-dimensional crosslinked resin is within the above range, it is easy to keep the boron nitride particles constituting the organic-inorganic composite particles in contact with each other, and the proportion of the boron nitride particles having high thermal conductivity is relatively large. Therefore, the thermal conductivity of the organic-inorganic composite particles tends to be high. On the other hand, in order to maintain the strength of the organic-inorganic composite particles, it is preferable that the amount of the three-dimensional crosslinked resin is large.

Known resins can be used as the three-dimensional crosslinked resin without particular limitation. Specifically, phenol resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, diallyl phthalate resin, polyurethane resin, crosslinked styrene resin, and crosslinked acrylic can be used. Examples thereof include a cured product such as a resin and a silicone resin. Among them, an epoxy resin cured product, an acrylic resin cured product, or a silicone resin cured product is preferable in consideration of compatibility with a resin generally used as a heat radiating material. Further, these also have an advantage that they can be easily cured by heating or light irradiation when the production method described later is adopted.

In the present invention, since the resin is three-dimensionally crosslinked, it is also excellent in solvent resistance and mechanical strength. Therefore, for example, when organic-inorganic composite particles are kneaded with a resin to produce a resin composition, the aggregated structure of hexagonal boron nitride particles is maintained even when a strong stress is applied, and the particles are mixed with a paint or the like. When used, there are advantages such as the aggregated structure not collapsing even in the presence of a solvent.

As a criterion for determining solvent resistance, in the present invention, when the organic-inorganic composite is ultrasonically dispersed in an organic solvent such as isopropyl alcohol and washed with an organic solvent, the carbon content derived from the three-dimensional crosslinked resin is determined. A method of evaluating the rate of decrease can be used.

An example of solvent resistance evaluation when isopropyl alcohol is used as the organic solvent will be described below. 5 g of the powder to be evaluated is dispersed in 20 g of isopropyl alcohol, and the powder is dispersed by ultrasonic irradiation of about 200 W for 3 minutes. The dispersed slurry is centrifuged to separate it into a clear supernatant and a sediment, and then the supernatant is removed. Add 20 g of isopropyl alcohol to the sediment, loosen the sediment with a spatula, and disperse it by ultrasonic irradiation for 3 minutes. Centrifuge again to remove the supernatant. Redispersion and centrifugation are repeated once more, and the finally obtained precipitate is vacuum-dried at 80 ° C. for 3 hours to obtain a dried product after washing. The carbon content (C ₂ ) of the dried product is measured, and the reduction rate (C _d ) from the carbon content (C ₁ ) before cleaning is calculated by the following formula 1.

C _d = [(C _2- C ₁ ) x 100] / C ₁ (Equation 1)
In the powder composed of the organic-inorganic composite particles of the present invention, the reduction rate of the carbon content according to the above evaluation is preferably 15% by mass or less, more preferably 10% by mass or less.

The powder composed of organic-inorganic composite particles obtained in the present invention has a volume frequency of 50% particle size (D50) measured by a laser diffraction / scattering type particle size distribution meter of 2 to 65 μm, preferably 10 to 65 μm, and more preferably 15 to. It is in the range of 60 μm. D50 refers to the value of the particle size where the volume frequency is accumulated from the smaller particle size to the cumulative value of 50% in the volume frequency distribution of the measured particle size. When the D50 of the powder of the present invention is in the above range, the thermal conductivity and the insulating property are improved. The particle size distribution is measured for a liquid in which a powder composed of organic-inorganic composite particles is dispersed in ethanol at a concentration of 0.2% by mass and ultrasonic irradiation of about 200 W is performed for 2 minutes.

The method for producing the powder of the present invention is not particularly limited, but the powder can be easily produced by the following method.

That is, with respect to 100 parts by mass of the boron nitride powder, the three-dimensional crosslinked curable resin is preferably 1 part by mass or more and 35 parts by mass or less, more preferably 1.4 parts by mass or more and 30 parts by mass or less, and further preferably 2 parts by mass. A step (1) of adding and mixing in an amount of 25 parts by mass or less, particularly preferably 2.5 parts by mass or more and 20 parts by mass or less, and then a step (2) of curing the three-dimensional crosslinked curable resin. It is a method for producing a powder containing. Hereinafter, this method will be described in detail.

[Hexagonal Boron Nitride]
As the hexagonal boron nitride used in the production method of the present invention, powdered one produced by a conventionally known method can be used without particular limitation. In the present invention, the boron nitride powder before the curable resin is mixed and cured is referred to as "raw material boron nitride powder". As a method for producing the raw material boron nitride powder in the present invention, for example, boron oxide, boric acid, boron carbide or the like can be used as a raw material and synthesized by a melamine method, a reduction nitriding method or the like.

The particle morphology of the raw material boron nitride powder may be scaly or aggregated, and may be particles having a high aspect ratio. The purity should be high from the viewpoint of thermal conductivity, and the boron nitride component should be 95% or more. The upper limit of the particle size D50 is preferably 20 μm or less, more preferably 15 μm or less, and the lower limit of D50 is preferably 0.5 μm or more, more preferably 0.8 μm or more, still more preferably 1.2 μm or more. .. If the particles are too large, it is difficult to form strong agglomerates. The particle size distribution may be monodisperse, but it is better to have a particle size distribution in order to form aggregates. By aggregating the large particles so that the voids are filled with the small particles, it is possible to form an agglomerate having few internal voids and randomly clogged flat particles with less anisotropy.

Further, the raw material boron nitride powder may be surface-treated with a silane compound, silazane or the like in advance.

[Curable resin]
In the production method of the present invention, a resin that is liquid or solvent-soluble before curing and that produces a three-dimensional crosslinked cured product by the progress of the curing reaction (polymerization reaction) can be used as the three-dimensional crosslinked curable resin. These include, for example, thermosetting resins and thermoplastic resins capable of crosslink polymerization. Examples of the thermosetting resin include phenol resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, diallyl phthalate resin, polyurethane resin, silicone resin and the like. A thermoplastic resin capable of cross-linking polymerization is originally a thermoplastic resin, but refers to a resin that can be made solvent-resistant by using a cross-linking monomer, and vinyl polymerization such as acrylic resin or polystyrene. Examples include based resins.

Among the three-dimensional crosslinked curable resins, it is preferable to use an epoxy resin, a silicone resin, or an acrylic resin in terms of compatibility with the resin mainly used for the heat radiation material described above. These are also preferable because the curing conditions can be easily controlled and the raw material resin can be obtained and handled relatively easily.

In the production method of the present invention, the term "curable resin" includes, in addition to the resin component in a narrow sense, a curing agent, a curing accelerator, a polymerization initiator, a catalyst, a reactive diluent, a silane compound, and the like. It shall refer to a resin composition.

As the three-dimensional crosslinked curable resin, it is preferable that the three-dimensional crosslinked curable resin does not gel before being sufficiently mixed at the time of addition and mixing described later, but is cured by a simple device and operation when necessary. Generally, there are thermosetting and photocuring as a curing method of a three-dimensional crosslinked curable resin, but thermosetting is preferable because necessary equipment and the like are simple. In the case of thermosetting, it is preferable that the gel does not substantially gel at room temperature to 60 ° C. for the above reason, and the curing reaction proceeds by 80% or more when a temperature of 80 ° C. to 160 ° C. is applied. The curing composition is three-dimensional so that the time for the curing reaction to proceed by 80% or more is preferably 10 minutes to 6 hours, more preferably 20 minutes to 2 hours after reaching the set curing temperature. Prepare the composition of the crosslinked curable resin. For the curing temperature and curing rate, the type and amount of the resin curing agent, curing accelerator, polymerization initiator, polymerization catalyst, etc. to be selected may be appropriately selected, and a well-known technique and a simple experiment may be performed as necessary. It is easily controllable.

The curable resin preferably used in the present invention is illustrated below.

<Epoxy resin>
The epoxy resin that can be used in the present invention is not particularly limited, and general ones can be used. Specific examples include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, alicyclic epoxy resin, heterocyclic epoxy resin, glycidyl ester type epoxy resin, and glycidylamine type epoxy. Examples thereof include polyfunctional epoxy resins such as resins, biphenyl type epoxy resins, naphthalene ring-containing epoxy resins, and cyclopentadiene-containing epoxy resins. Among these, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and biphenyl type epoxy resin are preferable.

As the curing agent for curing the epoxy resin, a general curing agent for the epoxy resin can be used. Specific examples include thermosetting agents such as amines, polyamides, imidazoles, acid anhydrides, boron trifluoride-amine complexes, dicyandiamides, organic acid hydrazides, phenol novolac resins, bisphenol novolac resins, and cresol novolac resins, and diphenyliodonium. Examples thereof include photocuring agents such as hexafluorophosphate and triphenylsulfonium hexafluorophosphate. Among these, amines, imidazoles, and acid anhydrides are preferable.

Specific examples of the amine curing agent include chain aliphatic amines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenediamine and diethylaminopropylamine, and cyclic aliphatic polyamines such as N-aminoethylpiperazine and isophoronediamine. Examples thereof include aliphatic aromatic amines such as m-xylene diamine, aromatic amines such as metaphenylenediamine, diaminodiphenylmethane and diaminodiphenylsulfone.

Specific examples of the imidazole curing agent include 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole trimerite, and epoxy imidazole adduct.

Examples of the acid anhydride curing agent include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic acid anhydride, ethylene glycol bistrimerite, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, and methyl anhydride. Endomethylenetetrahydrophthalic anhydride, methylbutenyltetrahydrododecenylhydride succinic acid, hexahydrophthalic anhydride, succinic anhydride, methylcyclohexendicarboxylic acid anhydride, alkylstyrene-maleic anhydride copolymer, chlorendate anhydride, Examples thereof include polyazelineic anhydride.

Further, in addition to the above-mentioned epoxy resin and curing agent, a curing accelerator may be added and cured if necessary. Specific examples of the curing accelerator include imidazole-based curing accelerators such as imidazole and 2-methylimidazole, phosphine derivatives such as triphenylphosphine, tris-p-methoxyphenylphosphine, and tricyclohexylphosphine, and 1,8-diazabicyclo. Examples thereof include cycloamidine derivatives such as [5.4.0] -7-undecene.

Further, when the mixture of the epoxy resin, the curing agent, and the curing accelerator has a high viscosity, a reactive diluent having an epoxy group may be further blended. As the reactive diluent, a general one can also be used. Specific examples include n-butyl glycidyl ether, allyl glycidyl ether, styrene oxide, phenyl glycidyl ether, glycidyl methacrylate, p-sec-butyl phenyl glycidyl ether, diglycidyl ether, (poly) ethylene glycol diglycidyl ether, (poly). Propylene glycol diglycidyl ether, butanediol diglycidyl ether, diglycidyl aniline, glycerin triglycidyl ether and the like can be used.

<Acrylic resin>
The acrylic resin that can be used in the present invention (in the present invention, the methacrylic resin is included) is not particularly limited, and general ones can be used. However, in the case of a monofunctional monomer having only one (meth) acrylic group in one molecule, it does not crosslink three-dimensionally by itself. Therefore, when the monofunctional monomer is used, a plurality of monofunctional monomers are used in one molecule. Must be used with a crosslinkable polyfunctional monomer having a (meth) acrylic group.

Examples of monofunctional monomers include (meth) acrylonitrile, (meth) acrylamide, (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, hydroxyethyl (meth) acrylate, and butyl (meth) acrylate. , Hydroxybutyl (meth) acrylate, 2- (meth) acryloyloxyethyl succinate, 2- (meth) acryloyloxyethyl maleate and its salts, 2- (meth) acryloyloxyethyl phthalate, trifluoroethyl (meth) ) Acrylate, perfluorobutylethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, (meth) acrylicoxyethyl hydrogen phosphate, etc. Be done.

The polyfunctional monomer may be used alone or mixed with the monofunctional monomer as described above. Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1, 9-Nonandiol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, glycerol di (meth) acrylate, tetrafluoroethyldi (meth) acrylate, hexafluoropropyldi (meth) acrylate, octafluorobutyl Di (meth) acrylate, bis [2- (meth) acrylic oxyethyl] hydrogen phosphate, di (meth) acrylate of ethylene oxide adduct or propylene oxide adduct of bisphenol A, bisphenol A-diepoxy-acrylic acid adduct, Examples thereof include tricyclodecanedimethanol diacrylate, urethane di (meth) acrylate, and pentaerythritol tri (meth) acrylate.

A thermal radical polymerization initiator can be used to polymerize and cure these (meth) acrylic group-bearing monomers. Specific examples include octanoyl peroxide, lauroyl peroxide, t-butylperoxy-2-ethylhexanoate, benzoyl peroxide, t-butylperoxyisobutyrate, t-butylperoxylaurate, and t-. Organic peroxides such as hexylperoxybenzoate and di-t-butyl peroxide, and azobis such as 2,2-azobisisobutyronitrile and 2,2-azobis- (2,4-dimervaleronitrile). A system-based polymerization initiator or the like is mentioned as a suitable polymerization initiator. Among them, when polymerizing at 80 ° C. to 160 ° C., benzoyl peroxide, t-butylperoxy-2-ethylhexanoate and the like can be preferably used. These polymerization initiators are generally used in an amount of 0.1 to 20 parts by mass, preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the monomer.

Further, when photocuring is adopted as the curing reaction, a known initiator can be adopted as the photopolymerization initiator of the (meth) acrylic group.

<Silicone resin>
The silicone resin used as the curable resin in the present invention is not particularly limited, but a low-viscosity liquid organopolysiloxane is preferably used. In order to have curability by three-dimensional cross-linking, as the organopolysiloxane, one having a reactive group as described later is adopted, and one to which a curing agent or a curing catalyst is further added is used. Any of three types of curing methods can be used: condensation reaction, cross-linking reaction, and addition reaction. Further, as the organopolysiloxane, it is preferable to use a general organopolysiloxane having a main skeleton of dimethyl type or phenylmethyl type.

The condensation reaction is a reaction of dehydrating and condensing an organopolysiloxane having a silanol group, and in this reaction, a curing agent is used to promote the reaction. Examples of the curing agent include a metal compound, an alkoxy group-containing compound, an acetoxy group-containing silane, a ketone oxime group-containing silane, and an aminoxime group-containing siloxane.

The cross-linking reaction is a method using an organic peroxide, which is a method of cross-linking an organopolysiloxane having an unsaturated hydrocarbon group such as a vinyl group using an organic peroxide or the like as a radical curing agent.

The addition reaction is a method of hydrosilylating an organopolysiloxane having a vinyl group and an organopolysiloxane having a hydrosilyl group, and in the reaction, a platinum group catalyst is generally used as a curing catalyst.

In the present invention, among the curing reactions of the silicone resin, an addition reaction type silicone resin having excellent curing controllability by heating and high heat resistance of the obtained silicone is particularly suitable.

<Other vinyl polymerized resins>
In the present invention, in addition to the acrylic resins listed above, a polymerizable monomer having a radically polymerizable unsaturated double bond can be used. Specific examples of the polymerizable monomer include styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, p-tert-butylstyrene, chloromethylstyrene, p-chlorostyrene, vinylnaphthalene, and vinyl acetate. , Methylvinylketone, vinylpyrrolidone, ethylvinyl ether, divinylsulfone, diallyl phthalate, vinylbenzyltrimethylamine, vinylbenzyltriethylamine, vinylpyridine, vinylimidazole, vinylphosphonic acid and the like.

Examples of the crosslinkable polymerizable monomer used for three-dimensionally cross-linking these monomers include polyfunctional monomers such as divinylbenzene, divinylbiphenyl, trivinylbenzene, and divinylnaphthalene.

For curing these monomers, the above-mentioned acrylic resin polymerization initiators and the like can be used.

[Additive]
In the production method of the present invention, an additive may be added to the three-dimensional crosslinked curable resin. By improving the compatibility between the boron nitride particles and the curable resin with the additive, a stronger agglomerate can be formed. Examples of such an additive include a silane compound.

Specific examples of the silane compound include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2 -Epoxy group-containing silanes such as (3,4-epyloxycyclohexyl) ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3- Methacyl group-containing silanes such as methacryloxypropylmethyldimethoxysilane and 3-methacryloxypropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminoethyl-3-aminopropyltri Methoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, 2-aminoethyl-3-aminopropylmethyldimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 3-diethylaminopropyltri Amino group-containing silanes such as methoxysilane and N-phenyl-3-aminopropyltrimethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxy Silane, Isobutyltrimethoxysilane, Isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, cyclohexyltrimethoxysilane, cyclohexylmethyldimethoxysilane, n-octyltriethoxysilane, n-decyltriethoxysilane, Alkylsilanes such as n-hexadecyltriethoxysilane and n-octadecyltriethoxysilane, alkylsilanes such as trifluoropropyltrimethoxysilane, trifluoropropylmethyldimethoxysilane, nonafluorohexyltriethoxysilane, and phenyltri. Aromatic group-containing silanes such as methoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane and diphenyldiethoxysilane, mercapto group-containing silanes such as 3-mercaptopropyltrimethoxysilane and 3-mercaptopropylmethyldimethoxysilane, vinyltri In addition to vinyl-containing silanes such as methoxysilane and vinyltriethoxysilane, p- Examples thereof include styryltrimethoxysilane, allyltrimethoxysilane, tris- (trimethoxysilylpropyl) isocyanurate, 3-isocyanatepropyltriethoxysilane, and 3-ureidopropyltriethoxysilane.

The additives listed above may be appropriately selected according to the type of curable resin to be added. The amount of the additive used may be determined according to the particle size and the specific surface area of the raw material boron nitride powder to be used. For example, 0.01 part by mass or more of the additive is used with respect to 100 parts by mass of the boron nitride powder ^{having a specific surface area of 1 m 2 / g.} The standard amount is less than 0.5 parts by mass, but 5 parts by mass or less is preferable at the maximum.

[Addition / mixing]
In the production method of the present invention, the above-mentioned three-dimensional crosslinked curable resin is added to the raw material boron nitride powder and mixed. Curing, which will be described later, is performed after sufficient mixing. In the present invention, this addition and mixing is carried out in a solvent-free manner or in a small amount even if a solvent is used so that the boron nitride powder maintains the powder state. Therefore, the solvent cost and the solvent removal cost are substantially unnecessary.

As a method for adding the three-dimensional crosslinked curable resin to the raw material boron nitride powder, the method for adding the liquid substance to the powder can be used without particular limitation, but preferably, the raw material boron nitride powder is stirred. A method of adding the original crosslinked curable resin by spraying or dropping is preferable.

Here, when the viscosity of the three-dimensional crosslinked curable resin to be used is high and it is difficult to spray or drop it, or when it is desired to easily spread the three-dimensional crosslinked curable resin over the entire powder, the three-dimensional crosslinked curable resin is used. May be diluted with a solvent. As the diluting solvent that can be used, any solvent that can dissolve the three-dimensional crosslinked curable resin can be used without any problem, but a solvent having relatively high volatility and low viscosity is preferable, and alcohols and ketones are particularly preferable. The amount of the diluting solvent used is preferably about 0.5 to 50% by mass of the three-dimensional crosslinked curable resin, although it depends on the viscosity after dilution. If the amount of the diluting solvent is too large, voids are likely to be bitten into the cured resin due to the presence of the solvent during curing.

In the present invention, such a diluting solvent is used by mixing with the three-dimensional crosslinked curable resin, but it is not included in the three-dimensional crosslinked curable resin.

In the production method of the present invention, the upper limit of the amount of the three-dimensional crosslinked curable resin used is preferably 35 parts by mass or less, more preferably 30 parts by mass or less, still more preferably, with respect to 100 parts by mass of the raw material boron nitride powder. Is 25 parts by mass or less, particularly preferably 20 parts by mass or less, and the lower limit thereof is preferably 1 part by mass or more, more preferably 1.4 parts by mass or more, still more preferably 2 parts by mass or more, and particularly preferably 2 parts. It is 0.5 parts by mass or more. If the amount of the three-dimensional crosslinked curable resin used is too smaller than the lower limit, the strength of the organic-inorganic composite particles becomes too low, and in some cases, an aggregated structure cannot be obtained. On the other hand, if the amount of the three-dimensional crosslinked curable resin used is too large, the boron nitride particles constituting the organic-inorganic composite particles are unlikely to come into contact with each other, and the heat conduction is higher than that of the boron nitride particles. Since the proportion of resin components with a low ratio increases, the thermal conductivity tends to decrease.

As a dry mixing device used for stirring boron nitride powder and mixing after addition of a three-dimensional crosslinked curable resin, a general mixing / stirring device can be used, for example, a planetary mixing device, a Henschel mixer, a super mixer, etc. Examples include a V-type mixer, a drum mixer, a double cone mixer, and a locking mixer. Among them, a Henschel mixer, a super mixer, and a locking mixer can be used more preferably because of their high stirring capacity. In addition, since powders tend to agglomerate in dry mixing, it is desirable that the mixing device be equipped with a mechanism such as a crushing blade or a chopper to disaggregate once formed. Furthermore, during the mixing operation, not only the powder adheres, but also depending on the stirring mechanism, the powder may be pressed against the wall of the mixing container to form a thick adhesion layer. Can no longer be maintained. Therefore, it is more preferable that the wall surface of the mixing container is equipped with a fluororesin coat or the like to prevent adhesion, a knocker or the like to remove the adhered powder, or a scraping mechanism with a devised stirring blade. Further, if these devices are provided with a heating function, the three-dimensional crosslinked curable resin can be heated and cured after the mixing step, so that the number of steps can be reduced.

The mixing time can be set as appropriate, but as a guide, it is about 10 to 180 minutes.

[Curing]
In the production method of the present invention, the three-dimensional crosslinked curable resin contained in the mixture obtained as described above is cured. The curing method may be appropriately performed depending on the three-dimensional crosslinked curable resin used. For example, when it is a thermosetting type, it is heated, and when it is a photocurable type, it is irradiated with light.

When the diluting solvent is added to the three-dimensional crosslinked curable resin, it is preferable that the diluting solvent is removed after the mixing step is completed and before the curing treatment. As the degree of removal, for example, the mass reduction rate at 120 ° C. is preferably less than 0.5%.

When a thermosetting type is used as the curing method, heat treatment may be continued from the mixing step using an apparatus having a heating function as described above, or after mixing, the product may be collected and heat-treated with a shelf board dryer or the like. You may do. The heating temperature and time may be appropriately set according to the type and amount of the resin, curing agent, curing accelerator, polymerization initiator, polymerization catalyst, etc. used. The atmosphere during the heating (hardening) treatment is preferably in vacuum, in an inert gas, or in dry air. Above all, it is desirable to use it in a vacuum or in an inert gas, which is less affected by environmental moisture.

By going through such a step, a powder made of the organic-inorganic composite particles of the present invention can be obtained, but it is not suitable for the obtained powder when there are many three-dimensional crosslinked curable resins to be composited or depending on the compounding conditions. May contain coarse aggregates as needed. A powder containing coarse particles has poor operability as a powder, and may not be sufficiently dispersed when kneaded with a resin. Further, when the powder of the present invention is used as the resin filler, it causes a poor thickness of the resin composition molded product, and when the liquid resin composition is poured and used, it causes a poor gap. In such a case, a particle size distribution suitable for the filler of the resin composition can be obtained by performing a crushing operation or a classification operation to the extent that the thermal conductivity is not impaired.

[Crushing and classification]
As a crushing method, dry crushing is good. In addition, a relatively mild method is desirable so that most of the formed aggregates are not crushed. In particular, if it is carried out with an apparatus or condition that also crushes primary particles, the effect of the present invention will be lost. Examples of the crushing device include a dry crushing device such as a millstone type grinder, a raft machine, a cutter mill, a hammer mill, and a pin mill. Among them, a millstone type grinder that can selectively crush large aggregates in a short time and has less uneven crushing is preferable. The atmosphere of the crushing treatment is preferably in the air or in an inert gas. Further, the humidity of the atmosphere is preferably not too high, specifically, the humidity is less than 70%, more preferably less than 55%.

Further, as a method for removing coarse agglomerated particles other than the crushing treatment, a classification treatment may be performed. Either a dry classification method or a wet classification method can be selected for the classification treatment, but if high-precision classification is not required, a dry classification method that omits the solvent removal step is desirable. As the dry classification method, an air flow classification or a vibrating sieve can be used.

The airflow classification method or apparatus may be appropriately selected so as to have a particle size distribution suitable as a filler for the resin composition. The airflow classification method is a method in which the powder is dispersed in the airflow and separated into fine powder and coarse powder by the gravity, inertial force, centrifugal force, etc. of the particles at that time. In particular, the accuracy suitable for classifying particles of several μm can be obtained by a classifying device using inertial force and centrifugal force.

As a method of utilizing the inertial force, for example, by providing a guide blade or the like inside the device to create a swirling flow of air, an impactor that separates fine powder and coarse powder when bending a powder or granular material that has been momentum by the airflow into a curve. Examples include a semi-free vortex centrifugal type that classifies particles by applying centrifugal force, and a Coanda type that utilizes the Coanda effect. Examples of the classification device using the inertial force include a cascade impactor, a viable impactor, an aerofine classifier, an eddy classifier, an elbow jet, and a hyperplex.

The method using centrifugal force separates fine powder and coarse powder by using a vortex air flow, and examples of the device include a free vortex type and a forced vortex type. Free vortex type devices include cyclones without guide blades, multi-stage cyclones, turboplexes that use secondary air to promote elimination of aggregation, dispersion separators with guide blades to improve classification accuracy, microspins, and microcuts. Be done. The forced vortex type is a device that enhances the classification accuracy by exerting centrifugal force on the particles with a rotating body inside the device and creating another air flow inside the device, such as turbo classifier and Donacerec.

The crushing treatment and the classification treatment may be used in combination.

[Resin composition and heat dissipation composite material]
The resin composition obtained by mixing the powder composed of the organic-inorganic composite particles of the present invention with a resin can be suitably used as a heat-dissipating composite material. That is, the resin composition of the present invention contains the powder of the present invention as a filler. Further, the resin composition of the present invention includes alumina, aluminum nitride, boron nitride, aluminum hydroxide, magnesium oxide, silicon nitride, silicon carbide, diamond, silica, zinc oxide, carbon fiber, silver, copper, aluminum and the like. Other thermally conductive fillers may be added alone or in combination of two or more.

As the resin that can be used in the resin composition of the present invention, either a thermoplastic resin or a thermosetting resin can be exemplified. Examples of the thermoplastic resin include polyethylene, polypropylene, ethylene-propylene copolymer, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyacetal, and fluororesin. (For example, vinylidene fluoride, polytetrafluoroethylene, etc.), polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polystyrene, polyacrylonitrile, styrene-acrylonitrile copolymer, ABS resin, polyphenylene ether (PPE) resin, Modified PPE resin, aliphatic polyamide, aromatic polyamide, polyimide, polyamideimide, polymethacrylic acid, polymethacrylic acid ester (for example, polymethylmethacrylate), polyacrylic acid, polyacrylic acid ester (for example, methylpolyacrylic acid) , Polycarbonate, polyphenylene sulfide, polysulphon, polyethersulfon, polyethernitrile, polyetherketone, polyetheretherketone, polyketone, liquid crystal polymer, ionomer, etc .; Examples of the thermosetting resin include epoxy resin and acrylic resin. Examples thereof include urethane resin, silicone resin, phenol resin, imide resin, thermosetting modified PPE, and thermosetting PPE.

Examples of applications of the heat-dissipating composite material made of the resin composition of the present invention include materials for heat-dissipating members for efficiently dissipating heat generated from semiconductor parts mounted on home appliances, automobiles, notebook personal computers, and the like. be able to. Specific examples of these include heat-dissipating grease, heat-dissipating gel, heat-dissipating sheet, phase change sheet, adhesive, and the like. In addition to these, the composite material can also be used as an insulating layer used for, for example, a metal base substrate, a printed circuit board, a flexible substrate, etc .; a semiconductor encapsulant, an underfill, a housing, a heat radiation fin, and the like.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

The physical characteristics of the raw material boron nitride powder obtained in Production Example 1 described later and the organic-inorganic composite particle powder obtained in Examples and Comparative Examples were measured as follows.

[Specific surface area]
The BET specific surface area of the raw material boron nitride powder and the organic-inorganic composite particle powder was determined by the BET method (nitrogen adsorption 1-point method) using a specific surface area measuring device (“Flow Sorb 2-2300 type” manufactured by Shimadzu Corporation). For the measurement, 2 g of a sample, which had been previously dried at 100 ° C. for 1 hour in a nitrogen gas flow, was used.

[Particle size distribution]
The particle size distribution of the raw material boron nitride powder and organic-inorganic composite particle powder was measured by dispersing the sample in ethanol at a concentration of 0.2% by mass and irradiating with ultrasonic waves of about 200 W for 2 minutes. This was performed using a laser diffraction / scattering type particle size distribution meter "MT3000II" (manufactured by MicrotracBel). In the volume frequency distribution of the particle size, the volume frequency is accumulated from the smaller particle size, and the particle size value where the cumulative value is 50% is D50, and the particle size value where the cumulative value is 90% is D90. did. Further, in the present invention, the value of D50 is taken as the average particle size.

[Carbon analysis]
The carbon content of the organic-inorganic composite particle powder was measured with a carbon analyzer (“EMIA-110” manufactured by HORIBA, Ltd.). The samples were burned in an oxygen stream at 1350 ° C. until no carbon dioxide gas was generated, and the carbon content of each sample was quantified from the amount of carbon dioxide generated.

[Washing operation]
5 g of the organic-inorganic composite particle powder is dispersed in 20 g of isopropyl alcohol, and the powder is dispersed by ultrasonic irradiation of about 200 W for 3 minutes. The dispersed slurry is centrifuged to separate it into a clear supernatant and a sediment, and then the supernatant is removed. Add 20 g of isopropyl alcohol to the sediment, loosen the sediment with a spatula, and disperse it by ultrasonic irradiation for 3 minutes. Centrifuge again to remove the supernatant. Redispersion and centrifugation are repeated once more, and the finally obtained precipitate is vacuum-dried at 80 ° C. for 3 hours to obtain a dried product after washing. The carbon content (C ₂ ) of the dried product is measured, and the rate of decrease (C _{d ) from the carbon content (C 1} ) before cleaning is calculated by the following formula.

C _d = [(C _2- C ₁ ) x 100] / C ₁
[Measurement of thermal conductivity]
<Epoxy resin composition cured product>
Weigh 10.4 g of raw material boron nitride powder and organic-inorganic composite particle powder, 5.28 g of "jER828" (manufactured by Mitsubishi Chemical) as an epoxy resin, and 1.32 g of "CureW" (manufactured by Mitsubishi Chemical) as a curing agent, and in a mortar. Kneaded with a strong share for 15 minutes. The kneaded product was heat press molded at 150 ° C. and 20 MPa for 1 hour, and further heated at 190 ° C. for 2 hours. Both sides were polished so that the obtained cured product sample had a thickness of 0.5 mm. The thermal conductivity of the polished sample is based on the ISO standard 22007-3 plastic thermal conductivity measurement method using a thermal conductivity measuring device (“Eye Phase Model 1u” manufactured by Eye Phase Co., Ltd.), which is a temperature wave analysis method. I asked.

<Silicone resin composition cured product>
20 g of raw material boron nitride powder or organic-inorganic composite particle powder and 13 g of "CY52-276A" (manufactured by Dow Corning) as a silicone resin were weighed and kneaded in a mortar for 3 minutes to obtain Agent A. On the other hand, 20 g of raw material boron nitride powder or organic-inorganic composite particle powder and 13 g of "CY52-276B" (manufactured by Dow Corning) as a silicone resin were weighed and kneaded in a mortar for 3 minutes to prepare Agent B. 1 g each of Agent A and Agent B were weighed, and the kneaded paste was heat-press molded at 80 ° C. and 20 MPa for 1 hour to prepare a 0.5 mm thick silicone cured product sample. The thermal conductivity of the sample is determined in accordance with the ISO standard 22007-3 plastic thermal conductivity measurement method using a thermal conductivity measuring device (“Eye Phase Model 1u” manufactured by Eye Phase Co., Ltd.), which is a temperature wave analysis method. It was.

[Compressive strength]
The compressive strength of the raw material boron nitride powder (Comparative Example 1) and the organic-inorganic composite particle powder (epoxy resin composition cured product; Examples 1 to 5) was measured using a microcompression tester (“MCT-211” manufactured by Shimadzu Corporation). Was measured. The measurement was carried out using a flat indenter having a diameter of 200 μm and a load speed of 5 mN / min. The measurement was performed on 10 particles having a particle size of 10 to 80 μm, and the average value thereof was determined. When a silicone resin was used, the results could not be measured due to its material, so the results are not shown in Table 2.

[Viscosity evaluation]
In order to evaluate the properties of the raw material boron nitride powder (Comparative Example 2) and the organic-inorganic composite particle powder (silicone resin composition cured product; Examples 6 and 7) as fillers, each powder and a liquid resin are kneaded. The viscosity of the obtained resin composition was measured. As the viscosity measuring device, a rotary viscometer "RVDV-II + CP" (φ12 mm, using a cone plate with an angle of 3 degrees) manufactured by Brookfield Co., Ltd. was used. As a liquid resin, 1 g of 1000 mPa · s dimethyl silicone oil (manufactured by Dow Corning) was used, and 1 g of each powder was used. For kneading, an automatic shaving machine was used, and the kneading and scraping operations were repeated 3 times for 3 minutes to obtain a paste in which the powder was dispersed. The viscosity of the obtained paste was measured at 30 ° C. Viscosity measurements were performed at different share rates. Table 2 shows the values when the share rate is 2s-1 and when the share rate is 5s-1.

In order to improve the thermal conductivity of the heat-dissipating composite material, it is effective to increase the filling rate of the boron nitride particles in the resin constituting the heat-dissipating composite material. The compatibility between the resin and the organic-inorganic composite particles is good, that is, the organic-inorganic composite particles having a low viscosity when filled in the resin can have a higher filling rate even if the amount of the resin is small.

[Scanning electron microscope image]
Using S-2600N manufactured by Hitachi High-Technologies Corporation, secondary electron images of raw material boron nitride powder and organic-inorganic composite particles were observed at an acceleration voltage of 25 kV.

[aspect ratio]
The raw material boron nitride particles produced in Production Example 1 described later were photographed at a magnification of 2500 using a scanning electron microscope. The length and thickness of the obtained image were read, and the length / thickness ratio was obtained. The average aspect ratio was calculated as an arithmetic mean value of the observation results of 50 particles.

Manufacturing example 1
100 g of boric anhydride, 43 g of carbon black, and 28 g of calcium carbonate were mixed in a ball mill. The obtained mixture was heated to 1400 ° C. at 15 ° C./min in a nitrogen gas atmosphere using a graphite tanman furnace, held at 1400 ° C. for 4 hours, and then heated to 1800 ° C. at 15 ° C./min. , Further kept at 1800 ° C. for 2 hours. The obtained crude hexagonal boron nitride powder was washed with hydrochloric acid, washed with water, and dried to obtain a high-purity white hexagonal boron nitride powder (raw material boron nitride powder). A scanning electron microscope image of the obtained raw material boron nitride powder is shown in FIG. The average aspect ratio of the obtained raw material boron nitride was 5.8.

Example 1
40 g of the raw material boron nitride powder obtained in Production Example 1 was placed in a fluororesin beaker (500 ml), and 1 g of the following epoxy resin (2.5 parts by mass with respect to 100 parts by mass of the boron nitride powder) and isopropyl alcohol were added to the powder. (Wako Pure Chemical Industries, Ltd., special grade) 0.1 g of mixed liquid was added dropwise. Next, the stirring operation was carried out in the air at room temperature for 30 minutes using a stirring blade made of fluororesin. The resulting mixture was placed in a dryer in a beaker and heated at 150 ° C. for 3 hours in a nitrogen atmosphere. The obtained organic-inorganic composite particle powder was evaluated for particle size distribution, specific surface area, carbon analysis, carbon analysis after cleaning operation, and thermal conductivity of the cured product packed in the epoxy resin composition (Table 1). Moreover, the scanning electron microscope image of the obtained organic-inorganic composite particle powder is shown in FIG. It was confirmed that the organic-inorganic composite particles contained a plurality of randomly oriented hexagonal boron nitride particles.

-Epoxy resin: 100 parts by mass of bisphenol A type epoxy resin "jER828" (Mitsubishi Chemical), 110 parts by mass of acid anhydride type curing agent "YH307" (Mitsubishi Chemical) and curing accelerator "triphenylphosphine" (Wako Pure Chemical Industries) ) A mixture consisting of 5 parts by mass.

Example 2
An organic-inorganic composite particle powder was obtained in the same manner as in Example 1 except that 2 g of the epoxy resin was used (5 parts by mass with respect to 100 parts by mass of the boron nitride powder). The obtained organic-inorganic composite particle powder was evaluated for particle size distribution, specific surface area, carbon analysis, carbon analysis after cleaning operation, and thermal conductivity of the cured product packed in the epoxy resin composition (Table 1). Moreover, the scanning electron microscope image of the obtained organic-inorganic composite particle powder is shown in FIG. It was confirmed that the organic-inorganic composite particles contained a plurality of randomly oriented hexagonal boron nitride particles.

Example 3
An organic-inorganic composite particle powder was obtained in the same manner as in Example 1 except that 4 g of the epoxy resin was used (10 parts by mass with respect to 100 parts by mass of the boron nitride powder). The obtained organic-inorganic composite particle powder was evaluated for particle size distribution, specific surface area, carbon analysis, carbon analysis after cleaning operation, compressive strength, and thermal conductivity of the cured product packed in the epoxy resin composition (Table 1). Moreover, the scanning electron microscope image of the obtained organic-inorganic composite particle powder is shown in FIG. It was confirmed that the organic-inorganic composite particles contained a plurality of randomly oriented hexagonal boron nitride particles.

Example 4
An organic-inorganic composite particle powder was obtained in the same manner as in Example 1 except that 8 g of the epoxy resin (20 parts by mass with respect to 100 parts by mass of the boron nitride powder) was used. The obtained organic-inorganic composite particle powder was evaluated for particle size distribution, specific surface area, carbon analysis, carbon analysis after cleaning operation, and thermal conductivity of the cured product packed in the epoxy resin composition (Table 1). Further, a scanning electron microscope image of the obtained organic-inorganic composite particle powder is shown in FIG. It was confirmed that the organic-inorganic composite particles contained a plurality of randomly oriented hexagonal boron nitride particles.

Example 5
40 g of the raw material boron nitride powder obtained in Production Example 1 was placed in a fluororesin beaker, and 1 g of the epoxy resin (2.5 parts by mass with respect to 100 parts by mass of the boron nitride powder) and additive A (3) were added to the powder. -A mixed liquid of 0.3 g of glycidoxypropyltrimethoxysilane, manufactured by Tokyo Chemical Industry Co., Ltd.,> 97%) and 0.1 g of isopropyl alcohol was added dropwise. Next, the stirring operation was carried out in the air at room temperature for 30 minutes using a stirring blade made of fluororesin. The resulting mixture was placed in a dryer in a beaker and heated at 150 ° C. for 3 hours in a nitrogen atmosphere. The obtained organic-inorganic composite particle powder was evaluated for particle size distribution, specific surface area, carbon analysis, carbon analysis after cleaning operation, and thermal conductivity of the cured product packed in the epoxy resin composition (Table 1). Further, a scanning electron microscope image of the obtained organic-inorganic composite particle powder is shown in FIG. It was confirmed that the organic-inorganic composite particles contained a plurality of randomly oriented hexagonal boron nitride particles.

Comparative Example 1
With respect to the hexagonal boron nitride powder obtained in Production Example 1, the particle size distribution, specific surface area, carbon analysis, compressive strength and thermal conductivity of the cured product packed in the epoxy resin composition were evaluated (Table 1).

Example 6
40 g of the raw material boron nitride powder obtained in Production Example 1 was placed in a fluororesin beaker (500 ml), and 2 g of the following silicone resin (5 parts by mass with respect to 100 parts by mass of the boron nitride powder) was added dropwise to the powder. Next, the stirring operation was carried out in the air at room temperature for 30 minutes using a fluororesin stirring blade. The resulting mixture was placed in a dryer in a beaker and heated at 150 ° C. for 3 hours in a nitrogen atmosphere. The obtained organic-inorganic composite particle powder was subjected to particle size distribution, specific surface area, carbon analysis, carbon analysis after cleaning operation, and thermal conductivity of the cured product filled in the silicone resin composition (Table 2). Further, the obtained powder was added to dimethyl silicone oil having a viscosity of 1000 mPa · s at 30 vol. The viscosity of the% filled resin composition was measured (Table 2). Moreover, the scanning electron microscope image of the obtained organic-inorganic composite particle powder is shown in FIG. It was confirmed that the organic-inorganic composite particles contained a plurality of randomly oriented hexagonal boron nitride particles.

-Silicone resin: A mixture consisting of 100 parts by mass of an addition reaction type silicone resin "KE-1013A" (Shin-Etsu Chemical Co., Ltd.) and 100 parts by mass of "KE-1013B" (Shin-Etsu Chemical Co., Ltd.).

Example 7
An organic-inorganic composite particle powder was obtained in the same manner as in Example 6 except that 4 g of the silicone resin was used (10 parts by mass with respect to 100 parts by mass of the boron nitride powder). The obtained organic-inorganic composite particle powder was subjected to particle size distribution, specific surface area, carbon analysis, carbon analysis after cleaning operation, and thermal conductivity of the cured product filled in the silicone resin composition (Table 2). Further, the obtained powder was added to dimethyl silicone oil having a viscosity of 1000 mPa · s at 30 vol. The viscosity of the% filled resin composition was measured (Table 2). Further, a scanning electron microscope image of the obtained organic-inorganic composite particle powder is shown in FIG. It was confirmed that the organic-inorganic composite particles contained a plurality of randomly oriented hexagonal boron nitride particles.

Comparative Example 2
Regarding the hexagonal boron nitride powder obtained in Production Example 1, the particle size distribution, specific surface area, carbon analysis, and thermal conductivity of the cured product packed in the silicone resin composition were evaluated (Table 2). Further, 30 vol. In dimethyl silicone oil having a viscosity of 1000 mPa · s. The viscosity of the% filled resin composition was measured (Table 2).

Claims (8)

It consists of organic-inorganic composite particles in which a plurality of randomly oriented hexagonal boron nitride particles are composited via a three-dimensional crosslinked resin, and has a volume frequency of 50% particle size (D50) measured by a laser diffraction / scattering type particle size distribution meter. ) Is in the range of 2 to 65 μm. The powder according to claim 1, wherein the three-dimensional crosslinked resin is an epoxy resin cured product, an acrylic resin cured product, or a silicone resin cured product. The powder according to claim 1 or 2, wherein the three-dimensional crosslinked resin is contained in an amount of 1 part by mass or more and 35 parts by mass or less with respect to 100 parts by mass of hexagonal boron nitride particles. The powder according to any one of claims 1 to 3, which is used as a filler for a resin composition. A resin composition containing the powder according to any one of claims 1 to 3 as a filler. The step of adding and mixing a three-dimensional crosslinked curable resin in an amount of 1 part by mass or more and 35 parts by mass or less with respect to 100 parts by mass of hexagonal boron nitride particles according to the method for producing powder according to claim 1. A method for producing a powder, which comprises (1) and then a step (2) of curing the three-dimensional crosslinked curable resin. The method for producing a powder according to claim 6, wherein the three-dimensional crosslinked curable resin is a thermosetting resin. According to claim 6 or 7, the volume frequency 50% particle size (D50) of the hexagonal boron nitride particles used in the step (1), which is measured by a laser diffraction / scattering type particle size distribution meter, is in the range of 0.5 to 20 μm. The method for producing a powder according to the above.

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