WO2016092951A1 - Hexagonal boron nitride powder, method for producing same, resin composition, and resin sheet - Google Patents

Hexagonal boron nitride powder, method for producing same, resin composition, and resin sheet Download PDF

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WO2016092951A1
WO2016092951A1 PCT/JP2015/079108 JP2015079108W WO2016092951A1 WO 2016092951 A1 WO2016092951 A1 WO 2016092951A1 JP 2015079108 W JP2015079108 W JP 2015079108W WO 2016092951 A1 WO2016092951 A1 WO 2016092951A1
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mass
powder
boron nitride
hbn
hexagonal boron
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French (fr)
Japanese (ja)
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雄樹 大塚
賢 深澤
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昭和電工株式会社
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00—Nitrogen; Compounds thereof
    • C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
    • C01B21/064—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with boron
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/38—Boron-containing compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L101/00—Compositions of unspecified macromolecular compounds

Definitions

  • the present invention relates to a hexagonal boron nitride (hereinafter also referred to as “hBN”) powder and a resin sheet using the hBN powder, and particularly includes a high-purity hBN powder containing an aggregate composed of primary particles of hBN.
  • the present invention relates to a method for producing the hBN powder, a resin composition using the hBN powder, and a resin sheet.
  • hBN particles have a layered structure similar to graphite, and hBN powder has excellent properties such as thermal conductivity, electrical insulation, chemical stability, solid lubricity, and thermal shock resistance. It is used as a heat dissipation material, solid lubricant / release agent, raw material for producing hBN sintered bodies, and the like.
  • hBN powder has a low crystallinity by mixing a boron compound such as boric acid or borax and a nitrogen compound such as melamine or urea and firing at a relatively low temperature in an ammonia atmosphere or a non-oxidizing gas atmosphere.
  • a crude hBN powder is produced, and then the obtained crude hBN is baked at a high temperature in a non-oxidizing gas atmosphere to grow crystals (Patent Documents 1 to 3).
  • Sheets, tapes, greases, and the like containing hBN powder as a filler in a resin material such as epoxy resin or silicon rubber, for example, have heat insulation properties to efficiently remove heat generated from electronic components. It is used as a heat conductive member such as a conductive sheet and heat conductive grease.
  • a heat conductive member such as a conductive sheet and heat conductive grease.
  • hBN generally has a scaly particle shape with a high primary particle length / thickness ratio. Therefore, increasing the filling rate makes it easier for the particles to align in the direction of the particles, resulting in differences in the properties of the resulting resin and rubber molded products. It becomes easy to produce a directivity.
  • characteristics, such as thermal conductivity of a heat conductive member, such as a heat conductive sheet, electrical insulation, a thermal shock resistance will fall.
  • boron carbide is nitrided in a nitrogen atmosphere at 1800 ° C. or higher, and then mixed with diboron trioxide and / or its precursor, and fired. Attempts have been made to obtain hBN powder by removing the carbon component (Patent Documents 6 and 7).
  • Patent Documents 6 and 7 since boron nitride of boron carbide has a very slow reaction rate, the method of reacting only boron carbide with nitrogen has a problem that it takes a long time and the manufacturing cost increases. Further, in these production methods, it is very difficult to remove the remaining carbon component, and there is a problem that black foreign matters remain. Further, there are problems that the dielectric breakdown voltage is lowered due to remaining black foreign matters and the appearance of the heat conductive sheet is deteriorated. For this reason, a thermally conductive sheet with a reduced number of black foreign bodies is desired.
  • JP-A-61-286207 Japanese Patent No. 3461651 Japanese Patent Publication No. 5-85482 JP 2011-098882 A JP 2005-343728 A Japanese Patent No. 4750220 Japanese Patent No. 5081488
  • the present invention relates to a high-purity hBN powder containing an aggregate composed of primary particles of hBN (hereinafter also simply referred to as “aggregate”), and a resin composition and a resin sheet using the hBN powder. It is an object to provide an hBN powder that can exhibit higher thermal conductivity and higher electrical insulation than before, a method for producing the hBN powder, a resin composition containing the hBN powder, and a resin sheet. To do.
  • the hBN powder contains an aggregate composed of primary particles of hBN, has a specific crystallite size and particle size, and the strength of the aggregate is in a specific range.
  • the particle size distribution curve of the hBN powder when a dispersion having one maximum (maximum) peak in a specific range and in which the hBN powder is dispersed in water is sonicated for 1 minute Focusing on the reduction rate of the maximum (maximum) peak, it was found that the strength of the aggregate can be adjusted.
  • the present invention is based on the above findings.
  • the present invention provides the following [1] to [9].
  • the maximum peak is 1 in the range of the particle size of 45 to 150 ⁇ m.
  • a peak of the maximum peak calculated by the following formula (1) when a dispersion obtained by dispersing the hexagonal boron nitride powder dispersed in water with a particle size of 45 to 106 ⁇ m in water is subjected to ultrasonic treatment for 1 minute.
  • Hexagonal boron nitride powder having a reduction rate of 40 to 90%.
  • Peak reduction rate [(maximum peak height before treatment (a)) ⁇ (maximum peak height after treatment (b))] / (maximum peak height before treatment (a)) (1)
  • the hBN powder which can express thermal conductivity and high electrical insulation, the manufacturing method of the said hBN powder, and the resin composition and resin sheet containing the said hBN powder can be provided.
  • FIG. 2 is a SEM image of an aggregate of primary particles of hBN obtained in Example 1.
  • FIG. 2 is a SEM image of an aggregate of primary particles of hBN obtained in Example 1.
  • FIG. 2 is an SEM image of an aggregate of primary particles of hBN obtained in Comparative Example 1.
  • 2 is an SEM image of an aggregate of primary particles of hBN obtained in Comparative Example 1.
  • It is a schematic diagram of the resin sheet containing the hexagonal boron nitride powder of this invention. It is a particle size distribution curve before and after the ultrasonic treatment of Examples 1 and 3.
  • the hexagonal boron nitride powder of the present invention is a hexagonal boron nitride powder having a powder content of 80% by mass or more under a sieve having an aperture of 106 ⁇ m and containing aggregates of primary particles of hexagonal boron nitride, and is 50% cumulative.
  • the particle size distribution curve of the hexagonal boron nitride powder having a particle size D 50 of 10 to 20 ⁇ m, a crystallite size of 260 to 1000 ⁇ m, and a particle size of 45 to 106 ⁇ m the particle size of 45 to 150 ⁇ m
  • the dispersion of the hexagonal boron nitride powder having one maximum peak in the range and classified to a particle size of 45 to 106 ⁇ m is dispersed in water, is ultrasonically treated for 1 minute according to the above formula (1).
  • the peak reduction rate of the calculated maximum peak is 40 to 90%.
  • a high-purity hBN powder containing an aggregate composed of primary particles of hBN which has a higher heat than before when a resin composition and a resin sheet are produced using the hBN powder.
  • An hBN powder that can exhibit conductivity and high electrical insulation is obtained. The reason why such an effect is obtained is not clear, but is considered as follows.
  • the hBN powder of the present invention is an hBN powder containing an aggregate composed of primary particles of hBN, has a specific crystallite diameter and particle size, and has an aggregate strength measured under specific conditions.
  • the hBN powder is within a specific range, when the resin composition and the resin sheet are produced using the hBN powder, the aggregate is maintained without being broken excessively, and the aggregate Since the strength of the resin is in an appropriate range, it is presumed that the resin component is well-familiar and can exhibit high thermal conductivity and high electrical insulation. However, these are estimations, and the present invention is not limited to these mechanisms.
  • the primary particle size of the hBN powder of the present invention is preferably 20 ⁇ m or less on average, more preferably 1 to 15 ⁇ m, still more preferably 5 to 13 ⁇ m, and still more preferably 8 to The thickness is 12 ⁇ m, more preferably 8.5 to 10.5 ⁇ m.
  • the hBN powder containing aggregates composed of large primary particles having a primary particle diameter of 5 ⁇ m or more is well-familiar with the resin component when producing a resin composition using the hBN powder, and has good thermal conductivity and electrical insulation. Sex can be obtained.
  • a primary particle diameter is a number average value of the major axis of a primary particle, and can be measured by the method as described in an Example.
  • the primary particles contained in the hBN powder of the present invention may be scaly.
  • “scale-like” means a shape in which the ratio of the major axis of the primary particle to the thickness of the primary particle (major axis / thickness) is 5 to 20.
  • the ratio of the major axis to the thickness (major axis / thickness) of the primary particles of the hBN powder of the present invention is preferably 5 to 20, more preferably 10 to 20, more preferably 13 to 20, from the viewpoint of improving thermal conductivity. More preferably, it is 15-18, and still more preferably 15.5-16.
  • “major diameter of primary particles” means the number average value of the major diameter of primary particles
  • “thickness of primary particles” means the number average value of the thickness of primary particles.
  • major axis means the maximum diameter in the planar direction of the scaly particles.
  • the ratio between the major axis and the thickness (major axis / thickness) of the primary particles can be measured by the method described in Examples.
  • the hBN powder of the present invention has one maximum peak in the particle size range of 45 to 150 ⁇ m in the particle size distribution curve of the hBN powder classified to a particle size of 45 to 106 ⁇ m, and a particle size of 45 to 106 ⁇ m.
  • the peak reduction rate of the maximum peak (hereinafter also referred to as “peak reduction rate”) calculated by the following formula (1) when the dispersion of the above-classified hBN powder dispersed in water is subjected to ultrasonic treatment for 1 minute. ) Is 40 to 90%.
  • Peak reduction rate [(maximum peak height before treatment (a)) ⁇ (maximum peak height after treatment (b))] / (maximum peak height before treatment (a)) (1)
  • the particle size distribution curve is measured using a particle size distribution meter by a laser diffraction scattering method, and it can be said that the lower the decrease rate, the higher the decay strength of the hBN powder.
  • the disintegration strength By adjusting the disintegration strength to an appropriate range, the hBN powder is filled in the organic matrix to prevent or suppress the breakage of the aggregates when the resin composition and the resin sheet are produced or when the resin sheet is used. In addition, it can be used well with the resin component, and can exhibit high thermal conductivity and high electrical insulation.
  • the peak reduction rate of the hBN powder is preferably 42 to 85%, more preferably 45 to 70%, still more preferably 50 to 60%, and still more preferably 50 to 55%.
  • the peak reduction rate of hBN powder is measured by the method described in the examples.
  • the hBN powder of the present invention has a powder content of 80% by mass or more under a sieve having a mesh opening of 106 ⁇ m determined using a vacuum suction type sieving machine (air jet sieve) from the viewpoint of thermal conductivity and electrical insulation.
  • the content is preferably 85% by mass or more, more preferably 87% by mass or more, still more preferably 88% by mass or more, and still more preferably 90% by mass or more.
  • the hBN powder of the present invention preferably has a powder content on a 106 ⁇ m mesh sieve determined using a vacuum suction type sieving machine (air jet sieve) from the viewpoint of improving thermal conductivity and electrical insulation.
  • the hBN powder of the present invention preferably has a powder content under a sieve having a mesh opening of 45 ⁇ m determined using a vacuum suction type sieving machine (air jet sieve), preferably 45 mass from the viewpoint of improving thermal conductivity. % Or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, and still more preferably 25% by mass or less.
  • the powder content under a sieve having an opening of 45 ⁇ m is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and still more preferably. It is 20 mass% or more. Furthermore, from the viewpoint of improving thermal conductivity and electrical insulation, the powder content under a sieve having a mesh opening of 45 ⁇ m is preferably 5 to 45% by mass, more preferably 10 to 45% by mass, and still more preferably 15 to 45%. % By mass, more preferably 20 to 45% by mass, and still more preferably 30 to 40% by mass.
  • the powder content rate under the sieve 106 ⁇ m sieve and on the sieve, and the powder content rate under the sieve 45 ⁇ m sieve are measured by the method described in the examples.
  • the BET specific surface area of the hBN powder of the present invention is preferably 1.5 to 10 m 2 / g, more preferably 2 to 10 m 2 from the viewpoint of improving the collapse strength of the aggregates and improving the electrical insulation. / G, more preferably 2.5 to 8 m 2 / g, still more preferably 3 to 7 m 2 / g, still more preferably 3 to 6 m 2 / g, still more preferably 3 to 5 m 2 / g.
  • the BET specific surface area is 10 m 2 / g or less, the specific surface area of the aggregate contained in the hBN powder also becomes small, and the amount of the resin component taken into the aggregate when producing a resin composition or a resin sheet is small. Become.
  • this BET specific surface area is measured by the method as described in an Example.
  • the 50% volume cumulative particle size (D 50 ) of the hBN powder of the present invention is preferably 10 to 20 ⁇ m, from the viewpoint of improving the disintegration strength of the aggregates and improving the filling properties in the resin composition and the resin sheet. Is 10.5 to 18 ⁇ m, more preferably 11 to 15 ⁇ m, still more preferably 11.5 to 14 ⁇ m, still more preferably 12 to 13.5 ⁇ m, still more preferably 12.2 to 13 ⁇ m.
  • the 50% volume cumulative particle diameter (D 50 ) of the hBN powder is measured by the method described in the examples.
  • the bulk density of the hBN powder of the present invention is preferably 0.3 g / cm 3 or more, more preferably 0.35 g / cm 3 or more, still more preferably 0.4 g / cm, from the viewpoint of improving the collapse strength of the aggregate. 3 or more, more preferably 0.5 g / cm 3 or more, still more preferably 0.6 g / cm 3 or more.
  • the bulk density of hBN powder is measured by the method as described in an Example.
  • the crystallite size of the hBN powder of the present invention is 260 to 1000 mm, preferably 280 to 750 mm, more preferably 300 to 500 mm, and still more preferably, from the viewpoint of improving thermal conductivity and electrical insulation. It is 320 to 400 mm, more preferably 330 to 380 mm, and still more preferably 340 to 360 mm.
  • the crystallite diameter was measured by the method described in the examples.
  • the hBN powder of the present invention contains the above-mentioned aggregate, the aggregate can maintain a granular shape, and the primary particles are in a certain direction even if the filling rate of the hBN powder in the resin composition and the resin sheet is increased.
  • the resin composition and the resin sheet obtained by using the hBN powder are excellent in thermal conductivity and electrical insulation.
  • the purity of the hBN powder of the present invention that is, the purity of hBN in the hBN powder of the present invention is preferably 96% by mass or more, more preferably 98% by mass or more, from the viewpoint of improving thermal conductivity and electrical insulation. More preferably, it is 99 mass% or more, More preferably, it is 99.5 mass% or more, More preferably, it is 99.8 mass% or more.
  • the purity of this hBN powder can be measured by the method described in the examples.
  • the amount of boron oxide in the hBN powder of the present invention (hereinafter also referred to as “B 2 O 3 amount”) is preferably 0.001 to 0 from the viewpoint of improving thermal conductivity, electrical insulation and production superiority. .12% by mass, more preferably 0.005 to 0.11% by mass, still more preferably 0.0075 to 0.10% by mass, still more preferably 0.01 to 0.05% by mass, and even more preferably 0. .015 to 0.03 mass%.
  • the amount of B 2 O 3 can be measured by the method described in the examples.
  • the content of calcium oxide (CaO) in the hBN powder of the present invention is preferably 0.5% by mass or less, more preferably 0.2% by mass or less, from the viewpoint of improving thermal conductivity and electrical insulation.
  • content of CaO in this hBN powder can be measured by the method as described in an Example.
  • the content of carbon in the hBN powder of the present invention is preferably 0.5% by mass or less, more preferably 0.2% by mass or less, and still more preferably 0.2% by mass, from the viewpoint of improving thermal conductivity and electrical insulation. 1% by mass or less, more preferably 0.05% by mass or less, still more preferably 0.04% by mass or less, still more preferably 0.03% by mass or less, and still more preferably 0.02% by mass or less.
  • the carbon content in the hBN powder can be measured by the method described in the examples.
  • Examples of the coupling agent include silane-based, titanate-based, and aluminum-based, among which silane-based coupling agents are preferable from the viewpoint of effects.
  • Examples of silane coupling agents include ⁇ -aminopropyltrimethoxysilane, ⁇ -aminopropyltriethoxysilane, ⁇ - (2-aminoethyl) aminopropyltrimethoxysilane, and ⁇ - (2-aminoethyl) aminopropyltri Ethoxysilane, ⁇ -anilinopropyltrimethoxysilane, ⁇ -anilinopropyltriethoxysilane, N- ⁇ - (N-vinylbenzylaminoethyl) - ⁇ -aminopropyltrimethoxysilane and N- ⁇ - (N-vinyl Aminosilane compounds such as (benzylaminoethyl) - ⁇ -aminopropyltrieth
  • the hexagonal boron nitride powder (hBN powder) of the present invention comprises 100 parts by mass of crude hexagonal boron nitride powder containing 20 to 90% by mass of boron nitride and 10 to 80% by mass of boron oxide, and 3 to 15 parts by mass in terms of carbon. It is preferable to obtain by a method for producing hexagonal boron nitride powder, which has a firing step in which a carbon source of 0.01 to 1 part by mass of calcium compound is mixed and molded and then fired in an atmosphere containing nitrogen gas.
  • the hBN powder of the present invention is preferably subjected to at least one of pulverization and classification after the baking step to obtain an hBN powder, more preferably both pulverization and classification to obtain an hBN powder.
  • a carbon source which are raw materials used in the production method, will be described, and then each step of mixing, molding, firing, pulverization, and classification will be described.
  • the crude hexagonal boron nitride powder (crude hBN powder) used in the above production method contains 20 to 90% by mass of boron nitride and 10 to 80% by mass of boron oxide.
  • the crude hBN powder having a high boron oxide content can be easily produced as will be described later.
  • production efficiency is high.
  • the content of boron oxide in the crude hBN powder can be measured by the method described in the examples.
  • the boron nitride content in the crude hBN powder can be measured by subtracting the boron oxide content from the total mass. The method for calculating the content of boron oxide is described in the examples.
  • the hBN powder When the content of boron nitride is 20% by mass or more, the hBN powder can be produced with high efficiency using the crude hBN powder as a raw material. When the content of boron nitride is 90% by mass or less, the raw hBN powder as a raw material can be produced with high efficiency. From this viewpoint, the content of boron nitride in the crude hBN powder is preferably 45% by mass or more, more preferably 50% by mass or more, still more preferably 55% by mass or more, and still more preferably 60% by mass or more.
  • it is preferably 85% by mass or less, more preferably 80% by mass or less, further preferably 75% by mass or less, still more preferably 70% by mass or less, and preferably 45 to 85% by mass, more preferably 50% by mass. It is ⁇ 80 mass%, more preferably 55 to 75 mass%, still more preferably 60 to 70 mass%.
  • the content of boron oxide in the crude hBN powder is preferably 15% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more, and still more preferably 30% by mass or more. Further, it is preferably 55% by mass or less, more preferably 50% by mass or less, further preferably 45% by mass or less, still more preferably 40% by mass or less, and preferably 15 to 55% by mass, more preferably 20% by mass. -50% by mass, more preferably 25-45% by mass, and still more preferably 30-40% by mass.
  • the total content of boron nitride and boron oxide in the crude hBN powder is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and still more preferably 100% by mass. is there.
  • the crude hBN powder may contain other components as long as the effects of the present invention are not impaired.
  • the content of the other components in the crude hBN powder is preferably 10% by mass or less. Preferably it is 5 mass% or less, More preferably, it is 1 mass% or less, and it is still more preferable that other components are not contained.
  • the crude hBN powder can be suitably obtained by mixing a compound containing oxygen and boron and a compound having an amino group, molding, heating, and pulverizing. First, a compound containing oxygen and boron and a compound having an amino group, which are raw materials used in the production method, will be described, and then each step of mixing, molding, heating and grinding will be described.
  • Examples of the compound containing oxygen and boron include orthoboric acid (H 3 BO 3 ), metaboric acid (HBO 2 ), tetraboric acid (H 2 B 4 O 7 ), and boric anhydride (B 2 O 3 ).
  • orthoboric acid is preferred because it is readily available and has good mixing properties with compounds having an amino group such as melamine.
  • the purity of the compound containing oxygen and boron is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and still more preferably 100% by mass.
  • Examples of the compound having an amino group include aminotriazine compounds, guanidine compounds, urea and the like.
  • aminotriazine compounds include melamine, guanamine, benzoguanamine, and condensates thereof such as melam, melem, and melon.
  • compounds having a nitrogen atom at each of the amino group and a site other than the amino group, such as melamine and guanidine, are preferable.
  • the purity of the compound having an amino group is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and still more preferably 100% by mass.
  • the compound containing oxygen and boron and the compound having an amino group are mixed.
  • wet mixing there is no restriction
  • a precursor is first formed. For example, when water is added to a mixture of boric acid or boric anhydride and melamine, a precursor represented by the molecular formula of C 3 N 3 (NH 2 ⁇ H 3 BO 3 ) 3 is obtained.
  • the wet mixing can be performed using a general mixer such as a Henschel mixer, a ball mill, or a ribbon blender.
  • the compounding ratio of the compound containing oxygen and boron to the compound having an amino group is the atomic ratio of the boron atom (B) in the compound containing oxygen and boron to the nitrogen atom (N) in the compound having an amino group (B / N) is preferably a ratio of 1/3 to 2/1.
  • B / N atomic ratio is 1/3 or more, it is prevented or suppressed that a compound having an amino group that does not become a precursor in the presence of water remains. Browning is prevented or suppressed.
  • hBN with higher crystallinity can be obtained as the number of boron atoms increases.
  • the blending amount of melamine with respect to 100 parts by mass of the compound containing oxygen and boron is preferably 30 to 65 parts by mass, more preferably 35 to 60 parts by mass, and still more preferably from the above viewpoint. Is 40 to 55 parts by mass, and more preferably 45 to 50 parts by mass.
  • boric anhydride remains at a high temperature for a long time, so that the crystal growth of hBN is promoted.
  • This molding is preferably performed so that the density of the obtained molded body is about 0.6 to 0.8 g / cm 3 .
  • the atmosphere during heating is an ammonia atmosphere or a non-oxidizing gas atmosphere.
  • the non-oxidizing gas atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon gas. Of these, an ammonia atmosphere is more preferable.
  • the heating temperature is preferably from 800 to 1400 ° C., more preferably from 900 to 1350 ° C., still more preferably from 1000 to 1300 ° C., and even more preferably from 1050 to 1200 ° C., from the viewpoint of improving reactivity and ease of grinding. .
  • the product obtained by heating is then pulverized to obtain a crude hBN powder.
  • the pulverization method There is no particular limitation on the pulverization method, and jaw pulverization, coarse roll pulverization and the like can be employed.
  • ⁇ Method for producing hexagonal boron nitride powder In the method for producing hexagonal boron nitride powder (hBN powder) of the present invention, 3 to 15 parts by mass of a carbon source (described later) and 0.01 to 1 part by mass in terms of carbon with respect to 100 parts by mass of the crude hBN powder described above. The calcium (Ca) compound mentioned later is mixed. When the carbon source is 3 parts by mass or more in terms of carbon, the growth of primary particles is promoted and the nitridation of boron oxide proceeds to improve the crystallinity of the aggregate. improves.
  • the carbon source is 15 parts by mass or less in terms of carbon, unreacted carbon components are prevented from remaining as foreign matters, that is, black foreign matters, and whiteness and electrical insulation are improved.
  • the amount of the carbon source based on 100 parts by mass of the crude hBN powder is 3 to 15 parts by mass in terms of carbon, preferably 4 to 14 parts by mass, more preferably 5 to 13 parts by mass, and still more preferably. Is 6 to 12 parts by mass, more preferably 8 to 10 parts by mass.
  • the Ca compound is 1 part by mass or less, the grain growth of primary particles is promoted while maintaining high purity, and the crystallinity can be improved.
  • the compounding amount of the Ca compound with respect to 100 parts by mass of the crude hBN powder is 0.01 to 1 part by mass, preferably 0.05 to 0.8 part by mass, and more preferably 0.1 to 0.
  • the amount is 6 parts by mass, more preferably 0.2 to 0.5 parts by mass, and still more preferably 0.3 to 0.45 parts by mass.
  • the carbon source used in the method for producing the hexagonal boron nitride powder (hBN powder) of the present invention is carbon or a carbon-containing compound.
  • the carbon source used in the present invention include graphite, carbon black, boron carbide, saccharides, melamine, phenol resin, and the like, and preferably one or two selected from graphite and boron carbide.
  • the carbon source is preferably a combination of graphite and boron carbide from the viewpoint of thermal conductivity, and graphite is preferable from the viewpoint of electrical insulation.
  • the carbon content in the carbon source is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and still more preferably 100% by mass.
  • the carbon source preferably contains boron carbide (hereinafter also referred to as “B 4 C”) from the viewpoint of thermal conductivity.
  • the compounding amount of boron carbide as a carbon source with respect to 100 parts by mass of the crude hBN powder is preferably 0.01 to 14.8 parts by mass, more preferably 0.01 to 12 parts by mass, and still more preferably 0.01 in terms of carbon.
  • To 10 parts by mass more preferably 0.05 to 8 parts by mass, even more preferably 0.1 to 6 parts by mass, still more preferably 0.5 to 5 parts by mass, and even more preferably 1 to 3 parts by mass. It is.
  • hBN primary particles This promotes grain growth in the thickness direction of the hBN primary particles and contributes to high crystallization, so that the orientation of the hBN particles can be controlled, which is advantageous for increasing the thermal conductivity.
  • boron nitride is generated starting from carbon in the boron carbide crystal
  • hBN powder maintaining the form of boron carbide particles can be produced, and generated on the graphite surface when only graphite is used as the carbon source. It is considered that the hBN primary particles can be made thicker than the hBN powder grown from the crystal nuclei by dissolution precipitation.
  • the resin composition and the resin sheet are produced by filling the organic matrix with hBN powder or when the resin sheet is used, the granular shape can be maintained, and the collapse can be prevented or suppressed. Further, by using graphite and boron carbide together as the carbon source, the firing time can be shortened and the number of black foreign matters resulting from boron carbide can be reduced as compared with the case where only boron carbide is used.
  • the boron carbide content in the boron carbide is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and still more preferably 100% by mass.
  • the mass ratio of (boron carbide / carbon source) when graphite and boron carbide are used in combination is preferably 0.003 to 0.99, more preferably 0.015 to 0.8 in terms of carbon. More preferably, it is 0.02 to 0.6, still more preferably 0.085 to 0.4, and still more preferably 0.15 to 0.3.
  • Ca compound examples of the calcium compound (hereinafter also referred to as “Ca compound”) used in the method for producing the hBN powder of the present invention include calcium oxide, calcium fluoride, calcium chloride, and preferably calcium carbonate. It is.
  • the content of calcium carbonate in the Ca compound is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and still more preferably 100% by mass.
  • the mixing method there is no particular limitation on the mixing method, and either wet mixing or dry mixing may be used, but wet mixing is preferable.
  • the wet mixing can be performed using a general mixer such as a Henschel mixer, a ball mill, or a ribbon blender.
  • Resin such as polyvinyl alcohol (PVA), a cellulose, a polyvinylidene fluoride (PVDF), is mentioned, Preferably polyvinyl alcohol is used.
  • PVA polyvinyl alcohol
  • PVDF polyvinylidene fluoride
  • Preferably polyvinyl alcohol is used.
  • the binder is preferably used as a binder aqueous solution in which these resins are dissolved in water.
  • the resin content in the aqueous binder solution is preferably 1 to 10% by mass, more preferably 1 to 5% by mass, and still more preferably 1 to 4% by mass.
  • the amount of the aqueous binder solution mixed with 100 parts by mass of the crude hBN powder is preferably 1 to 20 parts by mass, more preferably 5 to 15 parts by mass, and still more preferably 8 to 12 parts by mass.
  • a binder is also converted as said carbon source.
  • the density after molding is preferably 0.5 g / cm 3 or more, more preferably from the viewpoint of improvement in strength of the aggregate formed by agglomeration of hBN primary particles, productivity, good handling, and reactivity.
  • 0.8 g / cm 3 or more more preferably 1 g / cm 3 or more, preferably 2 g / cm 3 or less, more preferably 1.8 g / cm 3 or less, still more preferably 1.5 g / cm 3 or less. Do so.
  • the manufacturing method of the hBN powder of this invention has a baking process which bakes the molded object obtained by said shaping
  • the crude hBN powder is pressure-molded to form a compact and then fired, the boron oxide contained in the crude hBN powder in the compact reacts with the carbon contained in the carbon source, resulting in a hexagonal crystal with high compressive fracture strength. Aggregates of boron nitride (hBN) are formed, and the hBN powder of the present invention is obtained.
  • the atmosphere during firing is an atmosphere containing nitrogen gas.
  • the nitrogen gas concentration in the atmosphere containing nitrogen gas is preferably 60% by volume or more, more preferably 80% by volume or more, still more preferably 90% by volume or more, and still more preferably 99% by volume or more. Less oxygen gas is better.
  • the firing temperature is preferably 1000 to 2200 ° C. When the firing temperature is 1000 ° C. or higher, a sufficient reduction nitriding reaction proceeds. Moreover, decomposition
  • the firing time is preferably 1 to 20 hours.
  • the firing time is 1 hour or longer, the reductive nitriding reaction proceeds sufficiently, and the unreacted carbon component is prevented from remaining as a black product.
  • a calcination cost is reduced. From this viewpoint, it is preferably 1 to 15 hours, more preferably 5 to 10 hours, still more preferably 6 to 9 hours, and still more preferably 6 to 7 hours.
  • the drying temperature is preferably 150 to 400 ° C., more preferably 200 to 400 ° C., and the drying time is preferably 6 to 8 hours.
  • Pulverization Subsequently, it is preferable to grind the product obtained by baking. There is no particular limitation on the pulverization method, and jaw pulverization, coarse roll pulverization and the like can be employed.
  • Classification Subsequently, it is preferable to classify the pulverized material obtained by pulverization after the above-described firing step. There is no restriction
  • a vibration sieve apparatus it is preferable to classify with a vibration sieve apparatus.
  • a vibrating sieve device a dry vibrating sieve device [manufactured by Koei Sangyo Co., Ltd., trade name “Sato Vibrating Sieve”], using a sieve with an aperture of 106 ⁇ m, a classification time of 60 minutes It is preferable to classify with.
  • the hexagonal boron nitride powder obtained above is applied to a sieve having an aperture of 106 ⁇ m, a sieve having an aperture of 45 ⁇ m, and a vibrating sieve. After classifying into 45 to 106 ⁇ m hBN powder (hereinafter also referred to as “hBN powder (A)”) and hBN powder under a 45 ⁇ m sieve (hereinafter also referred to as “hBN powder (B)”) using an apparatus.
  • hBN powder (A) hBN powder
  • hBN powder (B) hBN powder under a 45 ⁇ m sieve
  • the mixing method is not particularly limited and may be either wet mixing or dry mixing, but dry mixing is preferable.
  • the dry mixing can be performed using a general mixer such as a Henschel mixer, a ball mill, a ribbon blender, and a V-type blender, but a V-type blender is preferable from the viewpoint of uniformly mixing the hBN powder.
  • the mixing time is preferably 20 to 90 minutes, more preferably 50 to 70 minutes.
  • the powder content on the 106 ⁇ m mesh sieve obtained using a vacuum suction type sieving machine (air jet sieve) of hBN powder (A) is preferably 5 to 20% by mass, more preferably 10 to 18% by mass, More preferably, it is 14 to 17% by mass.
  • the powder content on the 45 ⁇ m mesh sieve obtained using a vacuum suction type sieving machine (air jet sieve) of hBN powder (B) is preferably 1 to 20% by mass, more preferably 1 to 10% by mass. %, More preferably 4 to 8% by mass, and still more preferably 5 to 7% by mass.
  • the powder content rate on a 106 micrometers sieve and the powder content on a 45 micrometers sieve can be measured by the method as described in an Example.
  • the granule ratio is preferably 40 to 90% by mass, more preferably 50 to 85% by mass, still more preferably 55 to 80% by mass, and still more preferably 60 to 70% by mass, from the viewpoint of improving thermal conductivity and electrical insulation. It is.
  • the resin composition of the present invention contains 10 to 90% by volume of the aforementioned hexagonal boron nitride powder (hBN powder).
  • the content of hBN powder in the resin composition of the present invention is 10 to 90% by volume from the viewpoint of the thermal conductivity of the resin composition and the resin sheet formed by molding the resin composition and the moldability of the resin sheet. It is preferably 20 to 80% by volume, more preferably 30 to 70% by volume, still more preferably 35 to 65% by volume, and still more preferably 40 to 60% by volume.
  • the volume-based content (volume%) of the hBN powder can be determined from the specific gravity of the hBN powder and the specific gravity of various resins used as the organic matrix.
  • the resin composition of the present invention contains a resin as an organic matrix.
  • the resin used in the present invention preferably contains one or more resins selected from thermosetting resins, thermoplastic resins, various rubbers, thermoplastic elastomers, oils and the like.
  • the thermosetting resin include epoxy resins, silicone resins, phenol resins, urea resins, unsaturated polyester resins, melamine resins, polyimide resins, polybenzoxazole resins, and urethane resins.
  • thermoplastic resin examples include polyolefin resins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and liquid crystal polyester; polyvinyl chloride resin, acrylic resin, polyphenylene sulfide resin, Examples include polyphenylene ether resins, polyamide resins, polyamideimide resins, and polycarbonate resins.
  • polyolefin resins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer
  • polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and liquid crystal polyester
  • polyvinyl chloride resin acrylic resin
  • polyphenylene sulfide resin examples include polyphenylene ether resins, polyamide resins, polyamideimide resins, and polycarbonate resins.
  • Various rubbers include natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, butadiene-acrylonitrile copolymer, isobutylene-isoprene copolymer.
  • examples thereof include polymers, chloroprene rubber, silicone rubber, fluoro rubber, chloro-sulfonated polyethylene, polyurethane rubber and the like. These rubbers are preferably used after being crosslinked.
  • thermoplastic elastomer examples include olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, urethane-based thermoplastic elastomers, and ester-based thermoplastic elastomers.
  • oil component examples include greases such as silicone oil.
  • One of these organic matrices may be used alone, or two or more thereof may be used in combination.
  • the resin composition of the present invention is used for a heat conductive member obtained by using the resin composition and mechanical strength, heat resistance and durability of a heat conductive member such as a resin sheet formed by molding the resin composition.
  • a heat conductive member such as a resin sheet formed by molding the resin composition.
  • curable epoxy resins and curable silicone resins are particularly preferably used.
  • the content of the organic matrix in the resin composition is preferably 10 to 90% by volume, more preferably 20 to 80% by volume, and still more preferably, from the viewpoint of moldability of a resin sheet formed by molding the resin composition. Is 30 to 70% by volume, more preferably 35 to 65% by volume, and still more preferably 40 to 60% by volume.
  • the volume-based content (volume%) of the organic matrix can be determined from the specific gravity of hBN powder and the specific gravity of various resins used as the organic matrix.
  • the curable epoxy resin used as the organic matrix is an epoxy resin that is liquid at room temperature or a low softening point epoxy that is solid at room temperature from the viewpoint of dispersibility of the hBN powder mixture in the organic matrix. Resins are preferred.
  • the curable epoxy resin may be a compound having two or more epoxy groups in one molecule, and is not particularly limited, and any one of known compounds conventionally used as epoxy resins can be appropriately selected. It can be selected and used. Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, glycidyl ethers of polycarboxylic acids, and epoxy resins obtained by epoxidation of cyclohexane derivatives.
  • epoxy resins from the viewpoints of heat resistance and workability, bisphenol A type epoxy resins, bisphenol F type epoxy resins, and epoxy resins obtained by epoxidation of cyclohexane derivatives are suitable.
  • a curing agent for epoxy resin In order to cure the curable epoxy resin, a curing agent for epoxy resin is usually used.
  • the curing agent for epoxy resin is not particularly limited, and any one of those conventionally used as curing agents for epoxy resins can be appropriately selected and used. For example, amine-based, phenol-based, acid-based, and the like. An anhydride system etc. are mentioned.
  • Preferred examples of the amine curing agent include dicyandiamide, aromatic diamines such as m-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, and m-xylylenediamine.
  • the system curing agent include phenol novolak resin, cresol novolak resin, bisphenol A type novolak resin, triazine-modified phenol novolak resin and the like.
  • the acid anhydride curing agent include aliphatic acids such as alicyclic acid anhydrides such as methylhexahydrophthalic anhydride, aromatic acid anhydrides such as phthalic anhydride, and aliphatic dibasic acid anhydrides. And halogen-based acid anhydrides such as anhydride and chlorendic anhydride.
  • One of these curing agents may be used alone, or two or more thereof may be used in combination.
  • the amount of the epoxy resin curing agent used is usually about 0.5 to 1.5 equivalent ratio, preferably about 0.1 equivalent ratio to the curable epoxy resin, from the viewpoint of balance between curability and cured resin physical properties. It is selected in the range of 7 to 1.3 equivalent ratio.
  • an epoxy resin curing accelerator can be used in combination with the epoxy resin curing agent as necessary.
  • this hardening accelerator for epoxy resins From the things conventionally used as a hardening accelerator of an epoxy resin, arbitrary things can be selected suitably and can be used.
  • imidazoles such as 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, etc.
  • Examples thereof include compounds, 2,4,6-tris (dimethylaminomethyl) phenol, boron trifluoride amine complex, triphenylphosphine and the like.
  • These hardening accelerators may be used individually by 1 type, and may be used in combination of 2 or more type.
  • the amount of the epoxy resin curing accelerator used is usually about 0.1 to 10 parts by mass, preferably about 100 to 10 parts by mass, preferably 100 parts by mass of the curable epoxy resin, from the viewpoint of the balance between curing acceleration and cured resin properties It is selected in the range of 0.4-5 parts by mass.
  • the curable silicone resin As the curable silicone resin, a mixture of an addition reaction type silicone resin and a silicone-based crosslinking agent can be used.
  • the addition reaction type silicone resin include at least one selected from polyorganosiloxanes having an alkenyl group as a functional group in the molecule.
  • Preferred examples of the polyorganosiloxane having an alkenyl group as a functional group in the molecule include polydimethylsiloxane having a vinyl group as a functional group, polydimethylsiloxane having a hexenyl group as a functional group, and a mixture thereof. .
  • silicone-based crosslinking agent examples include polyorganosiloxane having at least two silicon-bonded hydrogen atoms in one molecule, specifically, a dimethylhydrogensiloxy group end-capped dimethylsiloxane-methylhydrogensiloxane copolymer, Examples thereof include trimethylsiloxy group-end-capped dimethylsiloxane-methylhydrogensiloxane copolymer, trimethylsiloxane group-end-capped poly (methylhydrogensiloxane), and poly (hydrogensilsesquioxane).
  • platinum compounds are usually used as the curing catalyst.
  • the platinum compound include fine platinum, fine platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, chloroplatinic acid olefin complex, palladium, rhodium catalyst, and the like. .
  • the resin composition of the present invention may contain further components as long as the effects of the present invention are obtained.
  • examples of such components include nitride particles such as aluminum nitride, silicon nitride, and fibrous boron nitride, and electrically insulating metal oxides such as alumina, fibrous alumina, zinc oxide, magnesium oxide, beryllium oxide, and titanium oxide.
  • electrically insulating carbon components such as diamond and fullerene, plasticizers, pressure-sensitive adhesives, reinforcing agents, colorants, heat resistance improvers, viscosity modifiers, dispersion stabilizers, and solvents.
  • an inorganic filler such as aluminum or magnesium hydroxide, a surface treatment agent such as a silane coupling agent that improves the interfacial adhesive strength between the inorganic filler and the matrix resin, a reducing agent, and the like may be added.
  • the resin composition of the present invention can be used for a heat conductive member such as a heat conductive sheet, a heat conductive gel, a heat conductive grease, a heat conductive adhesive, and a phase change sheet.
  • a heat conductive member such as a heat conductive sheet, a heat conductive gel, a heat conductive grease, a heat conductive adhesive, and a phase change sheet.
  • heat from heat-generating electronic components such as MPUs, power transistors, and transformers can be efficiently transferred to heat-dissipating components such as heat-dissipating fins and heat-dissipating fans.
  • the resin sheet it is preferable to use the resin sheet as a heat conductive sheet.
  • the resin sheet of the present invention comprises the resin composition or a cured product thereof, and is formed by molding the resin composition into a sheet. When the resin composition is curable, it is formed into a sheet and then cured.
  • the resin sheet of the present invention can be produced using the resin composition, for example, as follows. First, a suspension of hBN powder having a concentration of about 50 to 80% by mass is prepared by dispersing the hBN powder of the present invention in a suitable solvent. Next, an organic matrix is added to the suspension so that the hBN powder is contained in a proportion of 10 to 90% by volume in the total amount of the hBN powder and the organic matrix.
  • the weights of hBN powder and resin are set so as to be a desired volume% based on the specific gravity of hBN powder and the specific gravity of the resin used as the organic matrix, and each is weighed and mixed to prepare a resin composition.
  • a preparation method of a resin composition it can also prepare as follows. First, an organic matrix is prepared by mixing a resin and, if necessary, a curing agent and a solvent. Next, the hBN powder is added to the organic matrix so that the hBN powder is contained in a ratio of 10 to 90% by volume in the total amount of the hBN powder and the organic matrix.
  • the weights of hBN powder and resin are set so as to be a desired volume% based on the specific gravity of hBN powder and the specific gravity of the resin used as the organic matrix, and each is weighed and mixed to prepare a resin composition.
  • a curable epoxy resin is used as the main component of the organic matrix
  • a mixture of the curable epoxy resin, a curing agent for the epoxy resin, and a curing accelerator for the epoxy resin that is used as required is an organic matrix.
  • a curable silicone resin is used as the main component of the organic matrix, a mixture of an addition reaction type silicone resin, a silicone-based crosslinking agent, and a curing catalyst becomes an organic matrix.
  • the resin composition is coated on a substrate such as a releasable film such as a resin film with a release layer by a normal coating machine or the like, and when the resin composition contains a solvent, a far infrared radiation heater, It is made into a sheet by drying the solvent by hot air spraying or the like.
  • a melamine resin or the like is used as the release layer.
  • the resin film a polyester resin such as polyethylene terephthalate is used.
  • the organic matrix in the resin composition is not a curable organic matrix such as a curable epoxy resin or a curable silicone resin, the above-described resin sheet is directly used as the resin sheet of the present invention.
  • the resin sheet formed on the base material obtained above is optionally applied from the surface side where the resin composition of the base material is not coated.
  • the resin sheet of the present invention is obtained by applying pressure through the base material, and further heat-treating and curing.
  • the pressure condition is preferably 15 to 20 MPa, more preferably 17 to 19 MPa.
  • the heating conditions are preferably 80 to 200 ° C., more preferably 100 to 150 ° C.
  • substrates such as a mold release film, are finally peeled off or removed.
  • the film thickness of the resin sheet of the present invention is preferably in the range of 50 to 150 ⁇ m from the viewpoint of moldability, from the viewpoint of reducing the weight of electronic parts and the like in which the resin sheet is used, and 70 It is more preferably in the range of ⁇ 140 ⁇ m, still more preferably in the range of 100 to 130 ⁇ m.
  • the resin sheet of the present invention preferably has a thermal conductivity in the thickness direction of 3 W / m ⁇ K or more, more preferably 7 W / m ⁇ K or more, still more preferably 9 W / m ⁇ K or more, and even more preferably 10 W.
  • the resin sheet of the present invention preferably has a specific gravity ratio of 90 to 100%, more preferably 95 to 100%, still more preferably 98 to 100%, and still more preferably 100%.
  • the resin sheet of the present invention may be used by laminating or burying a sheet-like, fiber-like, or mesh-like member on one or both sides and within the sheet for the purpose of improving workability or reinforcing.
  • the resin sheet thus obtained can be peeled off from the releasable film or can be in the form of a product for use as a resin sheet in a state where the releasable film is a protective film.
  • the resin sheet of this invention is good also as a structure which further provided the adhesive layer in the upper surface or lower surface of the resin sheet, and, thereby, the convenience at the time of product use increases.
  • the resin sheet of the present invention is used to transfer heat from heat-generating electronic components such as MPUs, power transistors, and transformers to heat-radiating components such as heat-dissipating fins and heat-dissipating fans. Used in between. As a result, heat transfer between the heat-generating electronic component and the heat-dissipating component is improved, and malfunction of the heat-generating electronic component can be significantly reduced.
  • Example 1 Production of crude hBN powder A mixture of 4 g boric acid, 2 g melamine and 1 g water was stirred and mixed, placed in a mold and pressed to obtain a molded body having a density of 0.7 g / cm 3 . This molded body was dried in a dryer at 300 ° C. for 100 minutes, and calcined at 1100 ° C. for 120 minutes in an NH 3 gas atmosphere. The obtained calcined product (crude hBN) was pulverized to obtain crude hBN powder (boron oxide content of 35% by mass).
  • the powder content of the 45-106 ⁇ m hBN powder (A) on the 106 ⁇ m sieve is 15% by mass, and the hBN powder (B) mesh under the 45 ⁇ m sieve is 15% by mass.
  • the powder content on the 45 ⁇ m sieve was 9% by mass.
  • the hBN powder (A) of 45 to 106 ⁇ m and the hBN powder (B) under the 45 ⁇ m sieve were mixed so as to have the granule ratio shown in Table 1, and the hBN powder according to Example 1 was obtained.
  • the granule ratio is expressed by the ratio of the hBN powder (A) to the total amount of the hBN powder (A) of 45 to 106 ⁇ m and the hBN powder (B) under the 45 ⁇ m sieve according to the following formula.
  • Granule rate (% by mass) [(A) / [(A) + (B)]]
  • the hBN powder according to Example 1 obtained as described above was further added to the upper and lower sides of a 106 ⁇ m sieve using a vacuum suction type sieving machine (air jet sieve [manufactured by Alpine, model name “A200LS”]) described later.
  • FIG. 1 is a schematic diagram of hBN aggregates present in FIG.
  • a resin composition was prepared by stirring and mixing using a Mazerustar.
  • the volume-based content (volume%) of the hBN powder was determined from the specific gravity (2.27) of the hBN powder and the specific gravity (1.17) of the liquid curable epoxy resin used as the organic matrix.
  • Example 2 In Example 1 (2), the hBN powder, the resin composition, and the resin composition were the same as in Example 1 except that the amount of the artificial graphite fine powder added to 100 parts by mass of the crude hBN powder was 5 parts by mass. A resin sheet was produced.
  • Example 1 (2) is the same as Example 1 except that the hBN powder (A) of 45 to 106 ⁇ m and the hBN powder (B) under a 45 ⁇ m sieve are mixed so that the granule ratio is 80% by mass.
  • hBN powder, a resin composition, and a resin sheet were produced.
  • Example 4 In Example 1 (2), the blending amount of the artificial graphite fine powder added to 100 parts by mass of the crude hBN powder was 5 parts by mass, and hBN of 45 to 106 ⁇ m so that the granule ratio was 80% by mass.
  • An hBN powder, a resin composition, and a resin sheet were prepared in the same manner as in Example 1 except that the powder (A) and the hBN powder (B) under 45 ⁇ m sieve were mixed.
  • Example 5 In Example 1 (2), the amount of artificial graphite fine powder added to 100 parts by mass of the crude hBN powder was 8 parts by mass (8 parts by mass in terms of carbon), and boron carbide (manufactured by Riken Corundum Co., Ltd.). ) 10 parts by mass (2.2 parts by mass in terms of carbon) is added and mixed so that the carbon equivalent content of the carbon source with respect to 100 parts by mass of the crude hBN powder is 10.2 parts by mass, and the granule ratio is 80 parts by mass.
  • the hBN powder, the resin composition, and the resin sheet were prepared in the same manner as in Example 1 except that the hBN powder (A) of 45 to 106 ⁇ m and the hBN powder (B) under the 45 ⁇ m sieve were mixed so as to be in the range of .
  • Example 1 In Example 1 (2), without adding a Ca compound (calcium carbonate) to 100 parts by mass of the crude hBN powder, and with a hBN powder of 45 to 106 ⁇ m so that the granule ratio is 60% by mass ( An hBN powder, a resin composition, and a resin sheet were produced in the same manner as in Example 1 except that A) and hBN powder (B) under a 45 ⁇ m sieve were mixed.
  • a Ca compound calcium carbonate
  • Example 3 In Example 1 (2), without adding a Ca compound (calcium carbonate) to 100 parts by mass of the crude hBN powder, and 45 to 106 ⁇ m of hBN powder (granularity is 80% by mass) An hBN powder, a resin composition, and a resin sheet were produced in the same manner as in Example 1 except that A) and hBN powder (B) under a 45 ⁇ m sieve were mixed.
  • a Ca compound calcium carbonate
  • Example 1 (2) 30 parts by mass (6.6 masses in terms of carbon) of boron carbide (manufactured by Riken Corundum Co., Ltd.) of graphite fine powder and Ca compound (calcium carbonate) with respect to 100 parts by mass of the crude hBN powder.
  • HBN powder (A) mixed with 45 to 106 ⁇ m hBN powder (A) and hBN powder (B) under 45 ⁇ m sieve so that the granule ratio is 80% by mass. Powder, a resin composition, and a resin sheet were produced.
  • the crude hBN powder is considered to be composed of boron oxide (hereinafter also referred to as “B 2 O 3 ”) on the surface of the powder and an internal B—O—N bond structure.
  • B 2 O 3 boron oxide
  • the internal oxygen constituting the BOH bond structure of the crude hBN is reacted by a high-temperature heat treatment in the firing step when producing hBN powder from the crude hBN powder, and gradually leaches out as B 2 O 3 on the surface.
  • Amount of B 2 O 3 surfaces, the B 2 O 3 of crude hBN powder surface was eluted by acid treatment, by measuring the amount of B 2 O 3 were dissolved by an acid treatment, B 2 O 3 in terms of the amount of endogenous oxygen, The oxygen analysis of the residue after acid treatment was performed, the amount of oxygen in the residue was measured, and obtained as a B 2 O 3 equivalent amount. Specifically, it is as follows.
  • Crude hBN powder was acid treated with 0.1N dilute sulfuric acid solution.
  • the amount of ammonia generated by hydrolysis of BN in the crude hBN powder by this acid treatment was measured using a spectrophotometer [manufactured by Hitachi, Ltd., model name “U-1100”].
  • the amount of B element produced by hydrolysis of was calculated.
  • the total amount of B element present in the acid solution after the acid treatment is calculated using an ICP analyzer [SII Nano Technology Inc., model name “SPS3500”].
  • the amount of B 2 O 3 dissolved by the acid treatment was calculated from the total amount of the B element present in the acid solution after the acid treatment and the amount of the B element resulting from the hydrolysis of BN converted from the above ammonia amount. . Further, the amount of oxygen in the residue was measured using an oxygen measuring device [manufactured by LECO Japan GK, model name “TC-600”], and an amount equivalent to B 2 O 3 was calculated from the measured value. There was thus obtained, from the total amount B 2 O 3 were dissolved by acid treatment and B 2 O 3 equivalent amount, the total amount of crude hBN powder subjected to the acid treatment, the boron oxide in the crude hBN powder The content (B 2 O 3 content) was calculated.
  • BET specific surface area About the hBN powder obtained by the Example and the comparative example, the specific surface area was measured using the fully automatic BET specific surface area measuring apparatus [The Yuasa Ionics Co., Ltd. make, model name "Multisorb 16"].
  • the 50% volume cumulative particle size (D 50 ) of the hBN powder volume standard was measured using a particle size distribution meter [manufactured by Nikkiso Co., Ltd., model name “Microtrack MT3300EXII”].
  • the particle size distribution was measured using a dispersion prepared by ultrasonically treating 0.06 g of hBN powder obtained in Examples and Comparative Examples in 50 g of pure water for 3 minutes.
  • the ultrasonic treatment was performed using an ultrasonic treatment apparatus [manufactured by Nippon Seiki Seisakusho, model name “ultrasonic homogenizer US-150V”] under the conditions of an output of 150 W and an oscillation frequency of 19.5 kHz.
  • the weight of hBN powder remaining under and on the sieve was measured, and the hBN powder content under the sieve 106 ⁇ m sieve (the powder content under the sieve 106 ⁇ m sieve) and the hBN powder content over the sieve 106 ⁇ m sieve ( The content of powder on a sieve having a mesh size of 106 ⁇ m was calculated.
  • the classification was performed using the dry vibration sieve device having an aperture of 106 ⁇ m under the condition of a sieving time of 60 minutes, All the sieves with an opening of 106 ⁇ m passed.
  • the peak reduction rate was measured using a laser diffraction / scattering particle size distribution meter [manufactured by Nikkiso Co., Ltd., model name “Microtrack MT3300EXII”].
  • the sieves having openings of 106 ⁇ m and openings of 45 ⁇ m were used in a two-tiered manner, and classified by the dry vibration sieve apparatus (sieving time 60 minutes).
  • a dispersion was prepared by dispersing 0.06 g of hBN powder having a particle size in 50 g of water.
  • FIG. 7 is a particle size distribution curve of Examples 1 and 3.
  • the ultrasonic treatment in the present invention was performed using an ultrasonic treatment apparatus [manufactured by Nippon Seiki Seisakusho, model name “ultrasonic homogenizer US-150V”].
  • an ultrasonic treatment apparatus manufactured by Nippon Seiki Seisakusho, model name “ultrasonic homogenizer US-150V”
  • Comparative Examples 2 and 4 a commercial product A was used in place of the above-mentioned hBN fired product.
  • Crystallite size of hBN powder The crystallite size of the hBN powder obtained in the examples and comparative examples was calculated by X-ray diffraction measurement.
  • a model name “X'Pert PRO” manufactured by PANalytical was used, and a Cu—K ⁇ 1 line was used using a copper target.
  • hBN powders obtained in the examples and comparative examples were acid-treated with a 0.1N dilute sulfuric acid solution. By this acid treatment, at least a part of BN in the hBN powder is hydrolyzed to generate ammonia, and the B element of BN is dissolved in the acid solution. Further, boron oxide (B 2 O 3 ) in the hBN powder At least a part of it dissolves in the acid solution.
  • the total amount of B element present in the acid solution after the acid treatment (the total amount of B element due to hydrolysis of BN and the amount of B element due to dissolution of B 2 O 3 ) is calculated using an ICP analyzer [SII Nano Technology Inc. Measured by a model name “SPS3500” manufactured by KK From the total amount of element B present in the acid solution after the acid treatment, the amount of B 2 O 3 dissolved by the acid treatment was calculated.
  • the Ca element present in the acid solution after the acid treatment was measured by the ICP analyzer, and the CaO content was calculated from the Ca element amount.
  • Carbon content in hBN powder The carbon content (carbon content) in the hBN powders obtained in Examples and Comparative Examples was measured using a carbon analyzer [manufactured by LECO Japan LLC, model name “CS230”].
  • the purity of hBN powder was determined using the total amount of B 2 O 3 , CaO content, and carbon content in the hBN powder measured as described above as the impurity amount.
  • Thermal conductivity of resin sheet About the resin sheet obtained by the Example and the comparative example, the value calculated by measuring a thermal diffusivity by the model name "LFA447 NanoFlash” made from NETZSCH, and multiplying it by the theoretical value of the specific heat and density of each resin sheet. was defined as the thermal conductivity in the thickness direction of the resin sheet.
  • the theoretical value of the density of the resin sheet of each Example or Comparative Example was calculated on the assumption that the theoretical density of boron nitride was 2.27 g / cm 3 and the theoretical density of the resin component was 1.17 g / cm 3 .
  • the specific gravity ratios of the resin sheets obtained in Examples and Comparative Examples are the electronic balance (model name “CP224S”) and the specific gravity / density measurement kit (model name “YDK01 / YDK01-”) manufactured by Sartorius Mechanitronics Japan Co., Ltd. OD / YDK01LP ”)), and dividing the specific gravity of the resin sheet of each Example or Comparative Example by the theoretical specific gravity of each Example or Comparative Example and multiplying by 100 ([Each Example Or the specific gravity measured with the resin sheet of the comparative example / theoretical specific gravity of the resin sheet of each example or comparative example) ⁇ 100].
  • the theoretical density of boron nitride was 2.27 g / cm 3 and the theoretical density of the resin component was 1.17 g / cm 3 .
  • the dielectric breakdown voltage was increased at a boosting rate of 1 kV / sec using a withstand voltage / insulation resistance measuring device (model name “TOS9201”) manufactured by Kikusui Electronics Corporation. It was measured.
  • hBN powders (A) and (B) in Table 1 represent hBN powder (A) of 45 to 106 ⁇ m and hBN powder (B) under a 45 ⁇ m sieve, respectively.
  • the resin sheets of Examples 1 to 5 have higher thermal conductivity and excellent withstand voltage characteristics than those of Comparative Examples 1 to 5, and have high thermal conductivity and high electrical insulation. It can be seen that This is because the hBN powder of the present invention maintains the granule shape as shown in the schematic diagram of FIG. 6 without excessively breaking the aggregates of the primary particles of the hBN powder during stirring and mixing, and the aggregates have an appropriate strength. This is considered to be because of familiarity with the resin component. In addition, the hBN powder of the present invention is considered to contribute to the development of good electrical insulation properties because of its low carbon content and high purity. Furthermore, the hBN powders of Examples 1 and 2 contain hBN powder having a specific content of 45 ⁇ m under-sieving powder and a moderately small particle size, so that electrical insulation is maintained while maintaining good thermal conductivity. It turns out that it is excellent.

Abstract

A hexagonal boron nitride powder containing an aggregate of hexagonal boron nitride primary particles and containing a proportion of powder which passes through a 106μm-opening sieve of 80 mass% or more, wherein: the 50% volume cumulative diameter D50 thereof is 10-20μm; the crystallite diameter thereof is 260-1,000Å; there is one maximum peak in a 45-150μm particle diameter range along a particle diameter distribution curve of the hexagonal boron nitride powder classified in the 45-106μm particle diameter range; and the peak decrease in the maximum peak calculated using formula (1) when subjecting a dispersion solution obtained by dispersing the hexagonal boron nitride powder classified in the 45-106μm particle diameter range in water to a one-minute ultrasound treatment is 40-90%. Also, a method for producing the hexagonal boron nitride powder, and a resin composition and resin sheet containing the hexagonal boron nitride powder.

Description

六方晶窒化ホウ素粉末、その製造方法、樹脂組成物及び樹脂シートHexagonal boron nitride powder, production method thereof, resin composition and resin sheet
　本発明は、六方晶窒化ホウ素（以下、「ｈＢＮ」ともいう。）粉末及びそのｈＢＮ粉末を用いた樹脂シートに関し、特にｈＢＮの一次粒子で構成された凝集体を含有し、高純度なｈＢＮ粉末、当該ｈＢＮ粉末の製造方法、当該ｈＢＮ粉末を用いた樹脂組成物及び樹脂シートに関する。 The present invention relates to a hexagonal boron nitride (hereinafter also referred to as “hBN”) powder and a resin sheet using the hBN powder, and particularly includes a high-purity hBN powder containing an aggregate composed of primary particles of hBN. The present invention relates to a method for producing the hBN powder, a resin composition using the hBN powder, and a resin sheet.
　ｈＢＮ粒子は、黒鉛類似の層状構造を有し、ｈＢＮ粉末は熱伝導性、電気絶縁性、化学的安定性、固体潤滑性、耐熱衝撃性等の特性に優れるため、これらの特性を活かして絶縁放熱材、固体潤滑・離型剤、ｈＢＮ焼結体製造用原料等として使用されている。 hBN particles have a layered structure similar to graphite, and hBN powder has excellent properties such as thermal conductivity, electrical insulation, chemical stability, solid lubricity, and thermal shock resistance. It is used as a heat dissipation material, solid lubricant / release agent, raw material for producing hBN sintered bodies, and the like.
　従来、ｈＢＮ粉末は、ホウ酸やホウ砂等のホウ素化合物とメラミンや尿素等の窒素化合物とを混合し、アンモニア雰囲気下又は非酸化性ガス雰囲気下で比較的低温で焼成して結晶性の低い粗製ｈＢＮ粉末を製造し、次にこの得られた粗製ｈＢＮを非酸化性ガス雰囲気下で高温で焼成して結晶成長させて得られることが一般的である（特許文献１～３）。 Conventionally, hBN powder has a low crystallinity by mixing a boron compound such as boric acid or borax and a nitrogen compound such as melamine or urea and firing at a relatively low temperature in an ammonia atmosphere or a non-oxidizing gas atmosphere. Generally, a crude hBN powder is produced, and then the obtained crude hBN is baked at a high temperature in a non-oxidizing gas atmosphere to grow crystals (Patent Documents 1 to 3).
　このｈＢＮ粉末をフィラーとしてエポキシ樹脂やシリコンゴム等の樹脂材料に含有させたシートやテープ、グリース等は、たとえば、電子部品から発生した熱を効率良く除去するための電気絶縁性を有した熱伝導性シートや熱伝導性グリース等の熱伝導性部材として使用されている。このような熱伝導性シート等の熱伝導性部材の更なる熱伝導性向上のために、ｈＢＮ粉末の充填率を高くする試みが行われている。しかしながら、ｈＢＮは一般に鱗片状の粒子形状であって一次粒子の長さと厚みの比が高いため、充填率を上げると粒子がある方向に揃いやすく、得られた樹脂やゴム成形品の特性に異方性が生じやすくなる。このように異方性が生じると、熱伝導性シート等の熱伝導性部材の熱伝導性、電気絶縁性、耐熱衝撃性等の特性が低下する。 Sheets, tapes, greases, and the like containing hBN powder as a filler in a resin material such as epoxy resin or silicon rubber, for example, have heat insulation properties to efficiently remove heat generated from electronic components. It is used as a heat conductive member such as a conductive sheet and heat conductive grease. In order to further improve the thermal conductivity of the thermal conductive member such as the thermal conductive sheet, an attempt has been made to increase the filling rate of the hBN powder. However, hBN generally has a scaly particle shape with a high primary particle length / thickness ratio. Therefore, increasing the filling rate makes it easier for the particles to align in the direction of the particles, resulting in differences in the properties of the resulting resin and rubber molded products. It becomes easy to produce a directivity. Thus, when anisotropy arises, characteristics, such as thermal conductivity of a heat conductive member, such as a heat conductive sheet, electrical insulation, a thermal shock resistance, will fall.
　そのため、近年、熱伝導性シートにおける異方性の抑制及びｈＢＮ粉末の充填性向上を目的として、ｈＢＮ一次粒子が凝集した二次粒子（凝集体）を含むｈＢＮ粉末を、樹脂に混合する方法が用いられている（特許文献４，５）。
　しかしながら、凝集体の強度が十分でないと、樹脂との複合化過程において凝集体が壊れてしまい、熱伝導性シートに異方性が生じたり、熱伝導性シート中におけるｈＢＮ粉末の充填率が低減したりすることにより、熱伝導性や電気絶縁性が低下するという問題がある。
　また、ｈＢＮ粉末の充填性及び電気絶縁性の向上を目的として、炭化ホウ素を窒素雰囲気中、１８００℃以上の条件で窒化処理した後、三酸化二ホウ素及び／又はその前駆体を混合し、焼成して炭素成分を除去することによりｈＢＮ粉末を得る試みがなされている（特許文献６，７）。
　しかしながら、炭化ホウ素の窒化ホウ素化は非常に反応速度が遅いため、炭化ホウ素のみを窒素と反応させる方法では、長時間を要し、製造コストが増大するという問題がある。また、これらの製造方法では、残存する炭素成分を除去することが非常に困難であり、黒色異物が残存するという問題もある。さらに、黒色異物が残存することによる絶縁破壊電圧の低下と、熱伝導性シートの外観の悪化という問題もある。このことから、黒色異物数を低減した熱伝導性シートが望まれている。 Therefore, in recent years, there is a method of mixing hBN powder containing secondary particles (aggregates) in which hBN primary particles are aggregated with a resin for the purpose of suppressing anisotropy in a heat conductive sheet and improving the filling properties of hBN powder. (Patent Documents 4 and 5).
However, if the strength of the aggregate is not sufficient, the aggregate breaks in the process of compounding with the resin, anisotropy occurs in the heat conductive sheet, or the filling rate of hBN powder in the heat conductive sheet decreases. As a result, there is a problem that the thermal conductivity and the electrical insulation are lowered.
In addition, for the purpose of improving the filling properties and electrical insulation of hBN powder, boron carbide is nitrided in a nitrogen atmosphere at 1800 ° C. or higher, and then mixed with diboron trioxide and / or its precursor, and fired. Attempts have been made to obtain hBN powder by removing the carbon component (Patent Documents 6 and 7).
However, since boron nitride of boron carbide has a very slow reaction rate, the method of reacting only boron carbide with nitrogen has a problem that it takes a long time and the manufacturing cost increases. Further, in these production methods, it is very difficult to remove the remaining carbon component, and there is a problem that black foreign matters remain. Further, there are problems that the dielectric breakdown voltage is lowered due to remaining black foreign matters and the appearance of the heat conductive sheet is deteriorated. For this reason, a thermally conductive sheet with a reduced number of black foreign bodies is desired.
特開昭６１－２８６２０７号公報JP-A-61-286207 特許第３４６１６５１号明細書Japanese Patent No. 3461651 特公平５－８５４８２号公報Japanese Patent Publication No. 5-85482 特開２０１１－０９８８８２号公報JP 2011-098882 A 特開２００５－３４３７２８号公報JP 2005-343728 A 特許第４７５０２２０号明細書Japanese Patent No. 4750220 特許第５０８１４８８号明細書Japanese Patent No. 5081488
　本発明は、ｈＢＮの一次粒子で構成された凝集体（以下、単に「凝集体」ともいう。）を含有する高純度のｈＢＮ粉末であって、当該ｈＢＮ粉末を用いて樹脂組成物及び樹脂シートを製造した際に、従来よりも高い熱伝導性及び高い電気絶縁性を発現できるｈＢＮ粉末、当該ｈＢＮ粉末の製造方法、並びに当該ｈＢＮ粉末を含む樹脂組成物及び樹脂シートを提供することを課題とする。 The present invention relates to a high-purity hBN powder containing an aggregate composed of primary particles of hBN (hereinafter also simply referred to as “aggregate”), and a resin composition and a resin sheet using the hBN powder. It is an object to provide an hBN powder that can exhibit higher thermal conductivity and higher electrical insulation than before, a method for producing the hBN powder, a resin composition containing the hBN powder, and a resin sheet. To do.
　発明者らは、鋭意検討した結果、ｈＢＮの一次粒子で構成された凝集体を含有するｈＢＮ粉末であって、特定の結晶子径及び粒径を有し、かつ凝集体の強度が特定の範囲内であって、ｈＢＮ粉末の粒径分布曲線において、特定の範囲内に極大（最大）ピークを１つ有し、当該ｈＢＮ粉末を水に分散させた分散液を１分間超音波処理したときの当該極大（最大）ピークの減少率に着目して、凝集体の強度を調整できることを見出した。
　本発明は上記の知見に立脚するものである。 As a result of intensive studies, the inventors have found that the hBN powder contains an aggregate composed of primary particles of hBN, has a specific crystallite size and particle size, and the strength of the aggregate is in a specific range. In the particle size distribution curve of the hBN powder, when a dispersion having one maximum (maximum) peak in a specific range and in which the hBN powder is dispersed in water is sonicated for 1 minute Focusing on the reduction rate of the maximum (maximum) peak, it was found that the strength of the aggregate can be adjusted.
The present invention is based on the above findings.
　すなわち、本発明は次の［１］～［９］を提供するものである。
［１］　六方晶窒化ホウ素の一次粒子の凝集体を含む目開き１０６μｍ篩下の粉末含有率が８０質量％以上の六方晶窒化ホウ素粉末であって、５０％体積累積粒径Ｄ５０が１０～２０μｍ、結晶子径が２６０～１０００Åであり、かつ、４５～１０６μｍの粒径に分級された前記六方晶窒化ホウ素粉末の粒径分布曲線において、粒径４５～１５０μｍの範囲内に最大ピークを１つ有し、４５～１０６μｍの粒径に分級された前記六方晶窒化ホウ素粉末を水に分散させた分散液を１分間超音波処理したときの下記式（１）で算出される最大ピークのピーク減少率が４０～９０％である、六方晶窒化ホウ素粉末。
　ピーク減少率＝〔（処理前の最大ピーク高さ（ａ））－（処理後の最大ピーク高さ（ｂ））〕／（処理前の最大ピーク高さ（ａ））　　　（１）
［２］　目開き４５μｍ篩下の粉末含有率が４５質量％以下である、上記［１］に記載の六方晶窒化ホウ素粉末。
［３］　ＢＥＴ比表面積が１．５～１０ｍ２／ｇである、上記［１］又は［２］に記載の六方晶窒化ホウ素粉末。
［４］　嵩密度が０．３ｇ／ｃｍ３以上である、上記［１］～［３］のいずれかに記載の六方晶窒化ホウ素粉末。
［５］　上記［１］～［４］のいずれかに記載の六方晶窒化ホウ素粉末を１０～９０体積％含有する、樹脂組成物。
［６］　上記［５］に記載の樹脂組成物又はその硬化物からなる、樹脂シート。
［７］　窒化ホウ素２０～９０質量％及び酸化ホウ素１０～８０質量％を含む粗製六方晶窒化ホウ素粉末１００質量部と、炭素換算で３～１５質量部の炭素源と０．０１～１質量部のカルシウム化合物を混合し、成形した後、窒素ガスを含む雰囲気下で焼成する焼成工程を有する、上記［１］～［４］のいずれかに記載の六方晶窒化ホウ素粉末の製造方法。
［８］　前記炭素源が、黒鉛及び炭化ホウ素から選ばれる１種又は２種である、上記［７］に記載の六方晶窒化ホウ素粉末の製造方法。
［９］　さらに、前記焼成工程後に、目開き１０６μｍの篩及び目開き４５μｍの篩を用いて、４５～１０６μｍの六方晶窒化ホウ素粉末〔ｈＢＮ粉末（Ａ）〕と４５μｍ篩下の六方晶窒化ホウ素粉末〔ｈＢＮ粉末（Ｂ）〕に分級したのち、ｈＢＮ粉末（Ａ）とｈＢＮ粉末（Ｂ）を、ｈＢＮ粉末（Ａ）及び（Ｂ）の合計量に対するｈＢＮ粉末（Ａ）の割合が４０～９０質量％となるように混合する混合工程を有する、上記［７］又は［８］に記載の六方晶窒化ホウ素粉末の製造方法。 That is, the present invention provides the following [1] to [9].
[1] Hexagonal boron nitride powder having an aggregate of primary particles of hexagonal boron nitride and having an aperture of 106 μm and having a powder content of 80% by mass or more, and having a 50% volume cumulative particle diameter D 50 of 10 to 10%. In the particle size distribution curve of the hexagonal boron nitride powder having a crystallite size of 20 μm, a crystallite size of 260 to 1000 μm, and a particle size of 45 to 106 μm, the maximum peak is 1 in the range of the particle size of 45 to 150 μm. And a peak of the maximum peak calculated by the following formula (1) when a dispersion obtained by dispersing the hexagonal boron nitride powder dispersed in water with a particle size of 45 to 106 μm in water is subjected to ultrasonic treatment for 1 minute. Hexagonal boron nitride powder having a reduction rate of 40 to 90%.
Peak reduction rate = [(maximum peak height before treatment (a)) − (maximum peak height after treatment (b))] / (maximum peak height before treatment (a)) (1)
[2] The hexagonal boron nitride powder according to the above [1], wherein the powder content under a sieve having an opening of 45 μm is 45% by mass or less.
[3] The hexagonal boron nitride powder according to [1] or [2], wherein the BET specific surface area is 1.5 to 10 m 2 / g.
[4] The hexagonal boron nitride powder according to any one of the above [1] to [3], which has a bulk density of 0.3 g / cm 3 or more.
[5] A resin composition comprising 10 to 90% by volume of the hexagonal boron nitride powder according to any one of [1] to [4].
[6] A resin sheet comprising the resin composition according to [5] or a cured product thereof.
[7] 100 parts by mass of a crude hexagonal boron nitride powder containing 20 to 90% by mass of boron nitride and 10 to 80% by mass of boron oxide, 3 to 15 parts by mass of a carbon source and 0.01 to 1 part by mass in terms of carbon The method for producing hexagonal boron nitride powder according to any one of the above [1] to [4], further comprising a firing step in which the calcium compound is mixed and molded, and then fired in an atmosphere containing nitrogen gas.
[8] The method for producing a hexagonal boron nitride powder according to [7], wherein the carbon source is one or two selected from graphite and boron carbide.
[9] Furthermore, after the firing step, using a sieve having an aperture of 106 μm and a sieve having an aperture of 45 μm, a hexagonal boron nitride powder [hBN powder (A)] of 45 to 106 μm and a hexagonal boron nitride under the sieve of 45 μm After classification into powder [hBN powder (B)], the hBN powder (A) and the hBN powder (B) are mixed at a ratio of hBN powder (A) to the total amount of hBN powder (A) and (B) of 40-90. The method for producing a hexagonal boron nitride powder according to the above [7] or [8], which has a mixing step of mixing so as to be mass%.
　本発明によれば、ｈＢＮの一次粒子で構成された凝集体を含有する高純度のｈＢＮ粉末であって、当該ｈＢＮ粉末を用いて樹脂組成物及び樹脂シートを製造した際に、従来よりも高い熱伝導性及び高い電気絶縁性を発現できるｈＢＮ粉末、当該ｈＢＮ粉末の製造方法、並びに当該ｈＢＮ粉末を含む樹脂組成物及び樹脂シートを提供することができる。 According to the present invention, a high-purity hBN powder containing aggregates composed of primary particles of hBN, which is higher than before when a resin composition and a resin sheet are produced using the hBN powder. The hBN powder which can express thermal conductivity and high electrical insulation, the manufacturing method of the said hBN powder, and the resin composition and resin sheet containing the said hBN powder can be provided.
本発明に係るｈＢＮの一次粒子の凝集体の模式図である。It is a schematic diagram of the aggregate of the primary particle of hBN which concerns on this invention. 実施例１で得られたｈＢＮの一次粒子の凝集体のＳＥＭ像である。2 is a SEM image of an aggregate of primary particles of hBN obtained in Example 1. FIG. 実施例１で得られたｈＢＮの一次粒子の凝集体のＳＥＭ像である。2 is a SEM image of an aggregate of primary particles of hBN obtained in Example 1. FIG. 比較例１で得られたｈＢＮの一次粒子の凝集体のＳＥＭ像である。2 is an SEM image of an aggregate of primary particles of hBN obtained in Comparative Example 1. 比較例１で得られたｈＢＮの一次粒子の凝集体のＳＥＭ像である。2 is an SEM image of an aggregate of primary particles of hBN obtained in Comparative Example 1. 本発明の六方晶窒化ホウ素粉末を含む樹脂シートの模式図である。It is a schematic diagram of the resin sheet containing the hexagonal boron nitride powder of this invention. 実施例１及び３の超音波処理前後の粒径分布曲線図である。It is a particle size distribution curve before and after the ultrasonic treatment of Examples 1 and 3.
［六方晶窒化ホウ素粉末］
　本発明の六方晶窒化ホウ素粉末は、六方晶窒化ホウ素の一次粒子の凝集体を含む目開き１０６μｍ篩下の粉末含有率が８０質量％以上の六方晶窒化ホウ素粉末であって、５０％体積累積粒径Ｄ５０が１０～２０μｍ、結晶子径が２６０～１０００Åであり、かつ、４５～１０６μｍの粒径に分級された前記六方晶窒化ホウ素粉末の粒径分布曲線において、粒径４５～１５０μｍの範囲内に最大ピークを１つ有し、４５～１０６μｍの粒径に分級された前記六方晶窒化ホウ素粉末を水に分散させた分散液を１分間超音波処理したときの前記式（１）で算出される最大ピークのピーク減少率が４０～９０％である。 [Hexagonal boron nitride powder]
The hexagonal boron nitride powder of the present invention is a hexagonal boron nitride powder having a powder content of 80% by mass or more under a sieve having an aperture of 106 μm and containing aggregates of primary particles of hexagonal boron nitride, and is 50% cumulative. In the particle size distribution curve of the hexagonal boron nitride powder having a particle size D 50 of 10 to 20 μm, a crystallite size of 260 to 1000 μm, and a particle size of 45 to 106 μm, the particle size of 45 to 150 μm When the dispersion of the hexagonal boron nitride powder having one maximum peak in the range and classified to a particle size of 45 to 106 μm is dispersed in water, is ultrasonically treated for 1 minute according to the above formula (1). The peak reduction rate of the calculated maximum peak is 40 to 90%.
　本発明によれば、ｈＢＮの一次粒子で構成された凝集体を含有する高純度のｈＢＮ粉末であって、当該ｈＢＮ粉末を用いて樹脂組成物及び樹脂シートを製造した際に従来よりも高い熱伝導性及び高い電気絶縁性を発現できるｈＢＮ粉末が得られる。このような効果が得られる理由は定かではないが、以下のように考えられる。
　本発明のｈＢＮ粉末は、ｈＢＮの一次粒子で構成された凝集体を含有するｈＢＮ粉末であって、特定の結晶子径及び粒径を有し、かつ特定の条件で測定した凝集体の強度が特定の範囲内であるｈＢＮ粉末であるため、当該ｈＢＮ粉末を用いて樹脂組成物及び樹脂シートを製造する際に、当該凝集体が過度に壊れることなく顆粒形状を維持し、また、当該凝集体の強度が適当な範囲であるため、樹脂成分との馴染みが良く、高い熱伝導性及び高い電気絶縁性を発現することができると推定される。但し、これらは推定であって、本発明はこれらのメカニズムに限定されない。 According to the present invention, a high-purity hBN powder containing an aggregate composed of primary particles of hBN, which has a higher heat than before when a resin composition and a resin sheet are produced using the hBN powder. An hBN powder that can exhibit conductivity and high electrical insulation is obtained. The reason why such an effect is obtained is not clear, but is considered as follows.
The hBN powder of the present invention is an hBN powder containing an aggregate composed of primary particles of hBN, has a specific crystallite diameter and particle size, and has an aggregate strength measured under specific conditions. Since the hBN powder is within a specific range, when the resin composition and the resin sheet are produced using the hBN powder, the aggregate is maintained without being broken excessively, and the aggregate Since the strength of the resin is in an appropriate range, it is presumed that the resin component is well-familiar and can exhibit high thermal conductivity and high electrical insulation. However, these are estimations, and the present invention is not limited to these mechanisms.
＜一次粒子＞
　本発明のｈＢＮ粉末の一次粒子径は、熱伝導性の向上の観点から、平均で、好ましくは２０μｍ以下であり、より好ましくは１～１５μｍ、更に好ましくは５～１３μｍ、より更に好ましくは８～１２μｍ、より更に好ましくは８．５～１０．５μｍである。一次粒子径が５μｍ以上の大きな一次粒子からなる凝集体を含むｈＢＮ粉末は、当該ｈＢＮ粉末を用いて樹脂組成物を製造する際、樹脂成分との馴染みがよく、良好な熱伝導性及び電気絶縁性を得ることができる。
　なお、一次粒子径は、一次粒子の長径の数平均値であり、実施例に記載の方法により測定することができる。
　本発明のｈＢＮ粉末に含まれる一次粒子は、鱗片状であってもよい。ここで、「鱗片状」とは、一次粒子の厚みに対する一次粒子の長径の比（長径／厚み）が５～２０である形状を意味する。このように一次粒子が鱗片状である場合であっても、凝集体にすることにより、樹脂組成物及び樹脂シート内におけるｈＢＮ粉末の充填率を上げても一次粒子が一定の方向に配向することが防止又は抑制される。
　本発明のｈＢＮ粉末の一次粒子の長径と厚みの比（長径／厚み）は、熱伝導性の向上の観点から、好ましくは５～２０、より好ましくは１０～２０、更に好ましくは１３～２０、より更に好ましくは１５～１８、より更に好ましくは１５．５～１６である。
　なお、本明細書において、「一次粒子の長径」とは、一次粒子の長径の数平均値を意味し、「一次粒子の厚み」とは一次粒子の厚みの数平均値を意味する。また、ｈＢＮの一次粒子が鱗片状粒子である場合には、「長径」とは鱗片状粒子の平面方向の最大径を意味する。一次粒子の長径と厚みの比（長径／厚み）は実施例に記載の方法により測定することができる。 <Primary particles>
From the viewpoint of improving thermal conductivity, the primary particle size of the hBN powder of the present invention is preferably 20 μm or less on average, more preferably 1 to 15 μm, still more preferably 5 to 13 μm, and still more preferably 8 to The thickness is 12 μm, more preferably 8.5 to 10.5 μm. The hBN powder containing aggregates composed of large primary particles having a primary particle diameter of 5 μm or more is well-familiar with the resin component when producing a resin composition using the hBN powder, and has good thermal conductivity and electrical insulation. Sex can be obtained.
In addition, a primary particle diameter is a number average value of the major axis of a primary particle, and can be measured by the method as described in an Example.
The primary particles contained in the hBN powder of the present invention may be scaly. Here, “scale-like” means a shape in which the ratio of the major axis of the primary particle to the thickness of the primary particle (major axis / thickness) is 5 to 20. Thus, even when the primary particles are scaly, the primary particles are oriented in a certain direction even when the hBN powder filling rate in the resin composition and the resin sheet is increased by forming an aggregate. Is prevented or suppressed.
The ratio of the major axis to the thickness (major axis / thickness) of the primary particles of the hBN powder of the present invention is preferably 5 to 20, more preferably 10 to 20, more preferably 13 to 20, from the viewpoint of improving thermal conductivity. More preferably, it is 15-18, and still more preferably 15.5-16.
In this specification, “major diameter of primary particles” means the number average value of the major diameter of primary particles, and “thickness of primary particles” means the number average value of the thickness of primary particles. Further, when the primary particles of hBN are scaly particles, “major axis” means the maximum diameter in the planar direction of the scaly particles. The ratio between the major axis and the thickness (major axis / thickness) of the primary particles can be measured by the method described in Examples.
　本発明のｈＢＮ粉末は、４５～１０６μｍの粒径に分級された当該ｈＢＮ粉末の粒径分布曲線において、粒径４５～１５０μｍの範囲内に最大ピークを１つ有し、４５～１０６μｍの粒径に分級された前記ｈＢＮ粉末を水に分散させた分散液を１分間超音波処理したときの下記式（１）で算出される最大ピークのピーク減少率（以下、「ピーク減少率」ともいう。）が４０～９０％である。
　ピーク減少率＝〔（処理前の最大ピーク高さ（ａ））－（処理後の最大ピーク高さ（ｂ））〕／（処理前の最大ピーク高さ（ａ））　　　（１）
　前記粒径分布曲線は、レーザー回折散乱法による粒度分布計を用いて測定され、この減少率が低いほどｈＢＮ粉末の崩壊強度は高いと言える。崩壊強度を適当な範囲に調整することにより、有機マトリックス中にｈＢＮ粉末を充填させて樹脂組成物及び樹脂シートを製造する時又は当該樹脂シートの使用時に凝集体が壊れるのを防止又は抑制することができ、また、樹脂成分との馴染みが良く、高い熱伝導性及び高い電気絶縁性を発現することができる。この観点から、ｈＢＮ粉末のピーク減少率は、好ましくは４２～８５％、より好ましくは４５～７０％、更に好ましくは５０～６０％、より更に好ましく５０～５５％である。
　なお、ｈＢＮ粉末のピーク減少率は、実施例に記載の方法により測定したものである。 The hBN powder of the present invention has one maximum peak in the particle size range of 45 to 150 μm in the particle size distribution curve of the hBN powder classified to a particle size of 45 to 106 μm, and a particle size of 45 to 106 μm. The peak reduction rate of the maximum peak (hereinafter also referred to as “peak reduction rate”) calculated by the following formula (1) when the dispersion of the above-classified hBN powder dispersed in water is subjected to ultrasonic treatment for 1 minute. ) Is 40 to 90%.
Peak reduction rate = [(maximum peak height before treatment (a)) − (maximum peak height after treatment (b))] / (maximum peak height before treatment (a)) (1)
The particle size distribution curve is measured using a particle size distribution meter by a laser diffraction scattering method, and it can be said that the lower the decrease rate, the higher the decay strength of the hBN powder. By adjusting the disintegration strength to an appropriate range, the hBN powder is filled in the organic matrix to prevent or suppress the breakage of the aggregates when the resin composition and the resin sheet are produced or when the resin sheet is used. In addition, it can be used well with the resin component, and can exhibit high thermal conductivity and high electrical insulation. From this viewpoint, the peak reduction rate of the hBN powder is preferably 42 to 85%, more preferably 45 to 70%, still more preferably 50 to 60%, and still more preferably 50 to 55%.
The peak reduction rate of hBN powder is measured by the method described in the examples.
＜ｈＢＮ粉末＞
　本発明のｈＢＮ粉末は、熱伝導性及び電気絶縁性の観点から、減圧吸引型篩分け機（エアージェットシーブ）を用いて求めた目開き１０６μｍ篩下の粉末含有率が８０質量％以上であり、好ましくは８５質量％以上、より好ましくは８７質量％以上、更に好ましくは８８質量％以上、より更に好ましくは９０質量％以上である。
　また、本発明のｈＢＮ粉末は、熱伝導性及び電気絶縁性の向上の観点から、減圧吸引型篩分け機（エアージェットシーブ）を用いて求めた目開き１０６μｍ篩上の粉末含有率が好ましくは１５質量％以下、より好ましくは１３質量％以下、更に好ましくは１２質量％以下、より更に好ましくは１０質量％以下である。
　さらに、本発明のｈＢＮ粉末は、熱伝導性の向上の観点からは、減圧吸引型篩分け機（エアージェットシーブ）を用いて求めた目開き４５μｍ篩下の粉末含有率が、好ましくは４５質量％以下、より好ましくは４０質量％以下、更に好ましくは３０質量％以下、より更に好ましくは２５質量％以下である。また、電気絶縁性の向上の観点からは、目開き４５μｍ篩下の粉末含有率が、好ましくは５質量％以上、より好ましくは１０質量％以上、更に好ましくは１５質量％以上、より更に好ましくは２０質量％以上である。更に、熱伝導性及び電気絶縁性の向上の観点からは、目開き４５μｍ篩下の粉末含有率が、好ましくは５～４５質量％、より好ましくは１０～４５質量％、更に好ましくは１５～４５質量％、より更に好ましくは２０～４５質量％、より更に好ましくは３０～４０質量％である。
　なお、目開き１０６μｍ篩下及び篩上の粉末含有率、並びに目開き４５μｍ篩下の粉末含有率は、実施例に記載の方法により測定したものである。 <HBN powder>
The hBN powder of the present invention has a powder content of 80% by mass or more under a sieve having a mesh opening of 106 μm determined using a vacuum suction type sieving machine (air jet sieve) from the viewpoint of thermal conductivity and electrical insulation. The content is preferably 85% by mass or more, more preferably 87% by mass or more, still more preferably 88% by mass or more, and still more preferably 90% by mass or more.
In addition, the hBN powder of the present invention preferably has a powder content on a 106 μm mesh sieve determined using a vacuum suction type sieving machine (air jet sieve) from the viewpoint of improving thermal conductivity and electrical insulation. It is 15 mass% or less, More preferably, it is 13 mass% or less, More preferably, it is 12 mass% or less, More preferably, it is 10 mass% or less.
Furthermore, the hBN powder of the present invention preferably has a powder content under a sieve having a mesh opening of 45 μm determined using a vacuum suction type sieving machine (air jet sieve), preferably 45 mass from the viewpoint of improving thermal conductivity. % Or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, and still more preferably 25% by mass or less. From the viewpoint of improving electrical insulation, the powder content under a sieve having an opening of 45 μm is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and still more preferably. It is 20 mass% or more. Furthermore, from the viewpoint of improving thermal conductivity and electrical insulation, the powder content under a sieve having a mesh opening of 45 μm is preferably 5 to 45% by mass, more preferably 10 to 45% by mass, and still more preferably 15 to 45%. % By mass, more preferably 20 to 45% by mass, and still more preferably 30 to 40% by mass.
In addition, the powder content rate under the sieve 106 μm sieve and on the sieve, and the powder content rate under the sieve 45 μm sieve are measured by the method described in the examples.
　本発明のｈＢＮ粉末のＢＥＴ比表面積は、凝集体の崩壊強度の向上の観点及び電気絶縁性の向上の観点から、好ましくは１．５～１０ｍ２／ｇであり、より好ましくは２～１０ｍ２／ｇ、更に好ましくは２．５～８ｍ２／ｇ、より更に好ましくは３～７ｍ２／ｇ、より更に好ましくは３～６ｍ２／ｇ、より更に好ましくは３～５ｍ２／ｇである。ＢＥＴ比表面積が１０ｍ２／ｇ以下であると、ｈＢＮ粉末に含まれる凝集体の比表面積も小さくなり、樹脂組成物や樹脂シートを製造する際に凝集体内部に取り込まれる樹脂成分の量が少なくなる。そのため、相対的に凝集体間に存在する樹脂成分の量が多くなり、凝集体の樹脂成分に対する分散性が向上し、ｈＢＮ粉末と樹脂成分との馴染みが良くなると考えられる。
　なお、このＢＥＴ比表面積は、実施例に記載の方法により測定したものである。 The BET specific surface area of the hBN powder of the present invention is preferably 1.5 to 10 m 2 / g, more preferably 2 to 10 m 2 from the viewpoint of improving the collapse strength of the aggregates and improving the electrical insulation. / G, more preferably 2.5 to 8 m 2 / g, still more preferably 3 to 7 m 2 / g, still more preferably 3 to 6 m 2 / g, still more preferably 3 to 5 m 2 / g. When the BET specific surface area is 10 m 2 / g or less, the specific surface area of the aggregate contained in the hBN powder also becomes small, and the amount of the resin component taken into the aggregate when producing a resin composition or a resin sheet is small. Become. Therefore, the amount of the resin component present between the aggregates is relatively increased, the dispersibility of the aggregate with respect to the resin component is improved, and the familiarity between the hBN powder and the resin component is improved.
In addition, this BET specific surface area is measured by the method as described in an Example.
　本発明のｈＢＮ粉末の５０％体積累積粒径（Ｄ５０）は、凝集体の崩壊強度の向上、並びに樹脂組成物及び樹脂シート内における充填性の向上の観点から、１０～２０μｍであり、好ましくは１０．５～１８μｍ、より好ましくは１１～１５μｍ、更に好ましくは１１．５～１４μｍ、より更に好ましくは１２～１３．５μｍ、より更に好ましくは１２．２～１３μｍである。
　なお、ｈＢＮ粉末の５０％体積累積粒径（Ｄ５０）は、実施例に記載の方法により測定したものである。 The 50% volume cumulative particle size (D 50 ) of the hBN powder of the present invention is preferably 10 to 20 μm, from the viewpoint of improving the disintegration strength of the aggregates and improving the filling properties in the resin composition and the resin sheet. Is 10.5 to 18 μm, more preferably 11 to 15 μm, still more preferably 11.5 to 14 μm, still more preferably 12 to 13.5 μm, still more preferably 12.2 to 13 μm.
In addition, the 50% volume cumulative particle diameter (D 50 ) of the hBN powder is measured by the method described in the examples.
　本発明のｈＢＮ粉末の嵩密度は、凝集体の崩壊強度の向上の観点から、好ましくは０．３ｇ／ｃｍ３以上、より好ましくは０．３５ｇ／ｃｍ３以上、更に好ましくは０．４ｇ／ｃｍ３以上、より更に好ましくは０．５ｇ／ｃｍ３以上、より更に好ましくは０．６ｇ／ｃｍ３以上である。
　なお、ｈＢＮ粉末の嵩密度は、実施例に記載の方法により測定したものである。 The bulk density of the hBN powder of the present invention is preferably 0.3 g / cm 3 or more, more preferably 0.35 g / cm 3 or more, still more preferably 0.4 g / cm, from the viewpoint of improving the collapse strength of the aggregate. 3 or more, more preferably 0.5 g / cm 3 or more, still more preferably 0.6 g / cm 3 or more.
In addition, the bulk density of hBN powder is measured by the method as described in an Example.
　本発明のｈＢＮ粉末の結晶子径は、熱伝導性及び電気絶縁性の向上の観点から、２６０～１０００Åであり、好ましくは２８０～７５０Åであり、より好ましくは３００～５００Åであり、更に好ましくは３２０～４００Åであり、より更に好ましくは３３０～３８０Åであり、より更に好ましくは３４０～３６０Åである。
　なお、この結晶子径は、実施例に記載の方法により測定したものである。 The crystallite size of the hBN powder of the present invention is 260 to 1000 mm, preferably 280 to 750 mm, more preferably 300 to 500 mm, and still more preferably, from the viewpoint of improving thermal conductivity and electrical insulation. It is 320 to 400 mm, more preferably 330 to 380 mm, and still more preferably 340 to 360 mm.
The crystallite diameter was measured by the method described in the examples.
　本発明のｈＢＮ粉末は、上記の凝集体を含むため、凝集体が顆粒形状を維持することができ、樹脂組成物及び樹脂シート内におけるｈＢＮ粉末の充填率を上げても一次粒子が一定の方向に配向することが防止又は抑制され、当該ｈＢＮ粉末を用いて得られる樹脂組成物及び樹脂シートは、熱伝導性及び電気絶縁性に優れる。
　本発明のｈＢＮ粉末の純度、すなわち、本発明のｈＢＮ粉末中におけるｈＢＮの純度は、熱伝導性及び電気絶縁性の向上の観点から、好ましくは９６質量％以上、より好ましくは９８質量％以上、更に好ましくは９９質量％以上、より更に好ましくは９９．５質量％以上、より更に好ましくは９９．８質量％以上である。なお、このｈＢＮ粉末の純度は、実施例に記載の方法により測定することができる。 Since the hBN powder of the present invention contains the above-mentioned aggregate, the aggregate can maintain a granular shape, and the primary particles are in a certain direction even if the filling rate of the hBN powder in the resin composition and the resin sheet is increased. The resin composition and the resin sheet obtained by using the hBN powder are excellent in thermal conductivity and electrical insulation.
The purity of the hBN powder of the present invention, that is, the purity of hBN in the hBN powder of the present invention is preferably 96% by mass or more, more preferably 98% by mass or more, from the viewpoint of improving thermal conductivity and electrical insulation. More preferably, it is 99 mass% or more, More preferably, it is 99.5 mass% or more, More preferably, it is 99.8 mass% or more. The purity of this hBN powder can be measured by the method described in the examples.
　本発明のｈＢＮ粉末中の酸化ホウ素量（以下、「Ｂ２Ｏ３量」ともいう。）は、熱伝導性、電気絶縁性及び生産優位性の向上の観点から、好ましくは０．００１～０．１２質量％、より好ましくは０．００５～０．１１質量％、更に好ましくは０．００７５～０．１０質量％、より更に好ましくは０．０１～０．０５質量％、より更に好ましくは０．０１５～０．０３質量％である。
　なお、このＢ２Ｏ３量は、実施例に記載の方法により測定することができる。
　本発明のｈＢＮ粉末中における酸化カルシウム（ＣａＯ）の含有量は、熱伝導性及び電気絶縁性の向上の観点から、好ましくは０．５質量％以下、より好ましくは０．２質量％以下、更に好ましくは０．１質量％以下、より更に好ましくは０．０５質量％以下、より更に好ましくは０．０３質量％以下、より更に好ましくは０．０２質量％以下である。なお、このｈＢＮ粉末中におけるＣａＯの含有量は、実施例に記載の方法により測定することができる。
　本発明のｈＢＮ粉末中における炭素の含有量は、熱伝導性及び電気絶縁性の向上の観点から、好ましくは０．５質量％以下、より好ましくは０．２質量％以下、更に好ましくは０．１質量％以下、より更に好ましくは０．０５質量％以下、より更に好ましくは０．０４質量％以下、より更に好ましくは０．０３質量％以下、より更に好ましくは０．０２質量％以下である。なお、このｈＢＮ粉末中における炭素の含有量は、実施例に記載の方法により測定することができる。 The amount of boron oxide in the hBN powder of the present invention (hereinafter also referred to as “B 2 O 3 amount”) is preferably 0.001 to 0 from the viewpoint of improving thermal conductivity, electrical insulation and production superiority. .12% by mass, more preferably 0.005 to 0.11% by mass, still more preferably 0.0075 to 0.10% by mass, still more preferably 0.01 to 0.05% by mass, and even more preferably 0. .015 to 0.03 mass%.
The amount of B 2 O 3 can be measured by the method described in the examples.
The content of calcium oxide (CaO) in the hBN powder of the present invention is preferably 0.5% by mass or less, more preferably 0.2% by mass or less, from the viewpoint of improving thermal conductivity and electrical insulation. Preferably it is 0.1 mass% or less, More preferably, it is 0.05 mass% or less, More preferably, it is 0.03 mass% or less, More preferably, it is 0.02 mass% or less. In addition, content of CaO in this hBN powder can be measured by the method as described in an Example.
The content of carbon in the hBN powder of the present invention is preferably 0.5% by mass or less, more preferably 0.2% by mass or less, and still more preferably 0.2% by mass, from the viewpoint of improving thermal conductivity and electrical insulation. 1% by mass or less, more preferably 0.05% by mass or less, still more preferably 0.04% by mass or less, still more preferably 0.03% by mass or less, and still more preferably 0.02% by mass or less. . The carbon content in the hBN powder can be measured by the method described in the examples.
＜表面処理＞
　本発明のｈＢＮ粉末は、樹脂成分中に分散させて樹脂組成物及び樹脂シートを製造する際に、樹脂成分に対する分散性を高め、加工性を向上させる等の目的で、必要に応じ、各種カップリング剤等を用いて表面処理を施してもよい。 <Surface treatment>
When the hBN powder of the present invention is dispersed in a resin component to produce a resin composition and a resin sheet, various cups may be used as needed for the purpose of improving dispersibility in the resin component and improving processability. Surface treatment may be performed using a ring agent or the like.
（カップリング剤）
　カップリング剤としては、シラン系、チタネート系、アルミニウム系等が挙げられるが、これらの中で効果の点から、シラン系カップリング剤が好ましい。シラン系カップリング剤としては、特にγ－アミノプロピルトリメトキシシラン、γ－アミノプロピルトリエトキシシラン、γ－（２－アミノエチル）アミノプロピルトリメトキシシラン、γ－（２－アミノエチル）アミノプロピルトリエトキシシラン、γ－アニリノプロピルトリメトキシシラン、γ－アニリノプロピルトリエトキシシラン、Ｎ－β－（Ｎ－ビニルベンジルアミノエチル）－γ－アミノプロピルトリメトキシシラン及びＮ－β－（Ｎ－ビニルベンジルアミノエチル）－γ－アミノプロピルトリエトキシシラン等のアミノシラン化合物が好ましく用いられる。 (Coupling agent)
Examples of the coupling agent include silane-based, titanate-based, and aluminum-based, among which silane-based coupling agents are preferable from the viewpoint of effects. Examples of silane coupling agents include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, and γ- (2-aminoethyl) aminopropyltri Ethoxysilane, γ-anilinopropyltrimethoxysilane, γ-anilinopropyltriethoxysilane, N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane and N-β- (N-vinyl Aminosilane compounds such as (benzylaminoethyl) -γ-aminopropyltriethoxysilane are preferably used.
［六方晶窒化ホウ素粉末の製造方法］
　本発明の六方晶窒化ホウ素粉末（ｈＢＮ粉末）は、窒化ホウ素２０～９０質量％及び酸化ホウ素１０～８０質量％を含む粗製六方晶窒化ホウ素粉末１００質量部と、炭素換算で３～１５質量部の炭素源と０．０１～１質量部のカルシウム化合物を混合し、成形した後、窒素ガスを含む雰囲気下で焼成する焼成工程を有する、六方晶窒化ホウ素粉末の製造方法により得ることが好ましい。
　なお、本発明のｈＢＮ粉末は、上記焼成工程後に、更に粉砕及び分級の少なくとも１つを実施してｈＢＮ粉末を得ることが好ましく、粉砕及び分級の両方を実施してｈＢＮ粉末を得ることがより好ましい。
　先ず、当該製造方法に用いられる原料である、粗製六方晶窒化ホウ素粉末及び炭素源について説明し、次いで、混合、成形、焼成、粉砕及び分級の各工程について説明する。 [Method for producing hexagonal boron nitride powder]
The hexagonal boron nitride powder (hBN powder) of the present invention comprises 100 parts by mass of crude hexagonal boron nitride powder containing 20 to 90% by mass of boron nitride and 10 to 80% by mass of boron oxide, and 3 to 15 parts by mass in terms of carbon. It is preferable to obtain by a method for producing hexagonal boron nitride powder, which has a firing step in which a carbon source of 0.01 to 1 part by mass of calcium compound is mixed and molded and then fired in an atmosphere containing nitrogen gas.
The hBN powder of the present invention is preferably subjected to at least one of pulverization and classification after the baking step to obtain an hBN powder, more preferably both pulverization and classification to obtain an hBN powder. preferable.
First, raw hexagonal boron nitride powder and a carbon source, which are raw materials used in the production method, will be described, and then each step of mixing, molding, firing, pulverization, and classification will be described.
（粗製六方晶窒化ホウ素粉末）
　上記製造方法で用いられる粗製六方晶窒化ホウ素粉末（粗製ｈＢＮ粉末）は、窒化ホウ素２０～９０質量％及び酸化ホウ素１０～８０質量％を含む。かかる酸化ホウ素の含有量の多い粗製ｈＢＮ粉末は、後述するとおり容易に製造することができる。また、上記製造方法では、このような粗製ｈＢＮ粉末を、焼成等の高純度化処理を実施することなくそのまま原料として用いるため、生産効率が高い。
　なお、粗製ｈＢＮ粉末中における酸化ホウ素の含有量は、実施例に記載の方法により測定することができる。また、粗製ｈＢＮ粉末中における窒化ホウ素の含有量は、全質量より酸化ホウ素の含有量を引くことにより測定することができる。酸化ホウ素の含有量の算出法は実施例に記載する。 (Crude hexagonal boron nitride powder)
The crude hexagonal boron nitride powder (crude hBN powder) used in the above production method contains 20 to 90% by mass of boron nitride and 10 to 80% by mass of boron oxide. The crude hBN powder having a high boron oxide content can be easily produced as will be described later. Moreover, in the said manufacturing method, since such crude hBN powder is used as a raw material as it is, without implementing high purification processes, such as baking, production efficiency is high.
The content of boron oxide in the crude hBN powder can be measured by the method described in the examples. The boron nitride content in the crude hBN powder can be measured by subtracting the boron oxide content from the total mass. The method for calculating the content of boron oxide is described in the examples.
　窒化ホウ素の含有量が２０質量％以上であると、当該粗製ｈＢＮ粉末を原料として用いてｈＢＮ粉末を高効率にて製造することができる。窒化ホウ素の含有量が９０質量％以下であると、原料である粗製ｈＢＮ粉末を高効率にて製造することができる。当該観点から、粗製ｈＢＮ粉末中における窒化ホウ素の含有量は、好ましくは４５質量％以上、より好ましくは５０質量％以上、更に好ましくは５５質量％以上、より更に好ましくは６０質量％以上であり、また、好ましくは８５質量％以下、より好ましくは８０質量％以下、更に好ましくは７５質量％以下、より更に好ましくは７０質量％以下であり、また、好ましくは４５～８５質量％、より好ましくは５０～８０質量％、更に好ましくは５５～７５質量％、より更に好ましくは６０～７０質量％である。 When the content of boron nitride is 20% by mass or more, the hBN powder can be produced with high efficiency using the crude hBN powder as a raw material. When the content of boron nitride is 90% by mass or less, the raw hBN powder as a raw material can be produced with high efficiency. From this viewpoint, the content of boron nitride in the crude hBN powder is preferably 45% by mass or more, more preferably 50% by mass or more, still more preferably 55% by mass or more, and still more preferably 60% by mass or more. Further, it is preferably 85% by mass or less, more preferably 80% by mass or less, further preferably 75% by mass or less, still more preferably 70% by mass or less, and preferably 45 to 85% by mass, more preferably 50% by mass. It is ˜80 mass%, more preferably 55 to 75 mass%, still more preferably 60 to 70 mass%.
　また、酸化ホウ素の含有量が１０質量％以上であると、原料である粗製ｈＢＮ粉末を高効率にて製造することができる。酸化ホウ素の含有量が８０質量％以下であると、当該粗製ｈＢＮ粉末を原料として用いてｈＢＮ粉末を高効率にて製造することができる。当該観点から、粗製ｈＢＮ粉末中における酸化ホウ素の含有量は、好ましくは１５質量％以上、より好ましくは２０質量％以上、更に好ましくは２５質量％以上、より更に好ましくは３０質量％以上であり、また、好ましくは５５質量％以下、より好ましくは５０質量％以下、更に好ましくは４５質量％以下、より更に好ましくは４０質量％以下であり、また、好ましくは１５～５５質量％、より好ましくは２０～５０質量％、更に好ましくは２５～４５質量％、より更に好ましくは３０～４０質量％である。 Further, when the content of boron oxide is 10% by mass or more, a crude hBN powder as a raw material can be produced with high efficiency. When the content of boron oxide is 80% by mass or less, the hBN powder can be produced with high efficiency using the crude hBN powder as a raw material. From this viewpoint, the content of boron oxide in the crude hBN powder is preferably 15% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more, and still more preferably 30% by mass or more. Further, it is preferably 55% by mass or less, more preferably 50% by mass or less, further preferably 45% by mass or less, still more preferably 40% by mass or less, and preferably 15 to 55% by mass, more preferably 20% by mass. -50% by mass, more preferably 25-45% by mass, and still more preferably 30-40% by mass.
　なお、粗製ｈＢＮ粉末中における、窒化ホウ素及び酸化ホウ素の合計含有量は、好ましくは９０質量％以上、より好ましくは９５質量％以上、更に好ましくは９９質量％以上、より更に好ましくは１００質量％である。
　粗製ｈＢＮ粉末は、本発明の効果を阻害しない範囲内において、その他の成分を含有していてもよいが、粗製ｈＢＮ粉末中における、その他の成分の含有量は、好ましくは１０質量％以下、より好ましくは５質量％以下、更に好ましくは１質量％以下であり、その他の成分を含有していないことがより更に好ましい。 The total content of boron nitride and boron oxide in the crude hBN powder is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and still more preferably 100% by mass. is there.
The crude hBN powder may contain other components as long as the effects of the present invention are not impaired. However, the content of the other components in the crude hBN powder is preferably 10% by mass or less. Preferably it is 5 mass% or less, More preferably, it is 1 mass% or less, and it is still more preferable that other components are not contained.
＜粗製六方晶窒化ホウ素粉末の製造方法＞
　前記粗製ｈＢＮ粉末は、酸素及びホウ素を含む化合物とアミノ基を有する化合物とを混合し、成形した後、加熱し、粉砕することにより、好適に得ることができる。
　先ず、当該製造方法に用いられる原料である、酸素及びホウ素を含む化合物とアミノ基を有する化合物について説明し、次いで、混合、成形、加熱及び粉砕の各工程について説明する。 <Method for producing crude hexagonal boron nitride powder>
The crude hBN powder can be suitably obtained by mixing a compound containing oxygen and boron and a compound having an amino group, molding, heating, and pulverizing.
First, a compound containing oxygen and boron and a compound having an amino group, which are raw materials used in the production method, will be described, and then each step of mixing, molding, heating and grinding will be described.
（酸素及びホウ素を含む化合物）
　酸素及びホウ素を含む化合物としては、オルトホウ酸（Ｈ３ＢＯ３）、メタホウ酸（ＨＢＯ２）、テトラホウ酸（Ｈ２Ｂ４Ｏ７）、無水ホウ酸（Ｂ２Ｏ３）等、一般式（Ｂ２Ｏ３）・（Ｈ２Ｏ）Ｘ〔但し、Ｘ＝０～３〕で示される化合物の一種又は二種以上が挙げられる。なかでもオルトホウ酸は入手が容易でメラミン等のアミノ基を有する化合物との混合性が良好であるので好適である。
　酸素及びホウ素を含む化合物の純度は、好ましくは９０質量％以上、より好ましくは９５質量％以上、更に好ましくは９９質量％以上、より更に好ましくは１００質量％である。 (Compound containing oxygen and boron)
Examples of the compound containing oxygen and boron include orthoboric acid (H 3 BO 3 ), metaboric acid (HBO 2 ), tetraboric acid (H 2 B 4 O 7 ), and boric anhydride (B 2 O 3 ). B 2 O 3 ) · (H 2 O) X [where X = 0 to 3] is one or two or more compounds. Of these, orthoboric acid is preferred because it is readily available and has good mixing properties with compounds having an amino group such as melamine.
The purity of the compound containing oxygen and boron is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and still more preferably 100% by mass.
（アミノ基を有する化合物）
　アミノ基を有する化合物としては、アミノトリアジン化合物、グアニジン化合物、尿素等が挙げられる。アミノトリアジン化合物としては、メラミン、グアナミン、ベンゾグアナミン、及びそれらの縮合物であるメラム、メレム、メロン等が挙げられる。
　これらの化合物の中でも、メラミン、グアニジン等のように、アミノ基とアミノ基以外の部位とのそれぞれに窒素原子を有する化合物が好ましい。
　アミノ基を有する化合物の純度は、好ましくは９０質量％以上、より好ましくは９５質量％以上、更に好ましくは９９質量％以上、より更に好ましくは１００質量％である。 (Compound having an amino group)
Examples of the compound having an amino group include aminotriazine compounds, guanidine compounds, urea and the like. Examples of aminotriazine compounds include melamine, guanamine, benzoguanamine, and condensates thereof such as melam, melem, and melon.
Among these compounds, compounds having a nitrogen atom at each of the amino group and a site other than the amino group, such as melamine and guanidine, are preferable.
The purity of the compound having an amino group is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and still more preferably 100% by mass.
（混合）
　先ず、上記の酸素及びホウ素を含む化合物とアミノ基を有する化合物とを混合する。
　この混合方法には特に制限はなく、湿式混合及び乾式混合のいずれでもよいが、湿式混合が好ましい。湿式混合を行うことにより、先ず前駆体が形成される。例えば、ホウ酸或いは無水ホウ酸とメラミンとを混合したものに水を加えると、Ｃ３Ｎ３（ＮＨ２・Ｈ３ＢＯ３）３の分子式で示される前駆体が得られる。湿式混合は、ヘンシェルミキサー、ボールミル、リボンブレンダー等の一般的な混合機を用いて行うことができる。
　酸素及びホウ素を含む化合物とアミノ基を有する化合物との配合割合は、酸素及びホウ素を含む化合物中のホウ素原子（Ｂ）とアミノ基を有する化合物中の窒素原子（Ｎ）との原子比（Ｂ／Ｎ）が、好ましくは１／３～２／１となる割合である。Ｂ／Ｎ原子比が１／３以上であると、水の存在下で前駆体にならないアミノ基を有する化合物が残存することが防止又は抑制されるため、焼成中に炭化し窒化ホウ素を黒色或いは褐色化することが防止又は抑制される。また、Ｂ／Ｎ原子比が２／１以下までは、ホウ素原子が多いほど結晶性の高いｈＢＮが得られる。
　アミノ基を有する化合物としてメラミンを用いる場合、酸素及びホウ素を含む化合物１００質量部に対するメラミンの配合量は、上記観点から、好ましくは３０～６５質量部、より好ましくは３５～６０質量部、更に好ましくは４０～５５質量部、より更に好ましくは４５～５０質量部である。 (mixture)
First, the compound containing oxygen and boron and the compound having an amino group are mixed.
There is no restriction | limiting in particular in this mixing method, Although any of wet mixing and dry mixing may be sufficient, wet mixing is preferable. By performing wet mixing, a precursor is first formed. For example, when water is added to a mixture of boric acid or boric anhydride and melamine, a precursor represented by the molecular formula of C 3 N 3 (NH 2 · H 3 BO 3 ) 3 is obtained. The wet mixing can be performed using a general mixer such as a Henschel mixer, a ball mill, or a ribbon blender.
The compounding ratio of the compound containing oxygen and boron to the compound having an amino group is the atomic ratio of the boron atom (B) in the compound containing oxygen and boron to the nitrogen atom (N) in the compound having an amino group (B / N) is preferably a ratio of 1/3 to 2/1. When the B / N atomic ratio is 1/3 or more, it is prevented or suppressed that a compound having an amino group that does not become a precursor in the presence of water remains. Browning is prevented or suppressed. Also, up to a B / N atomic ratio of 2/1 or less, hBN with higher crystallinity can be obtained as the number of boron atoms increases.
When melamine is used as the compound having an amino group, the blending amount of melamine with respect to 100 parts by mass of the compound containing oxygen and boron is preferably 30 to 65 parts by mass, more preferably 35 to 60 parts by mass, and still more preferably from the above viewpoint. Is 40 to 55 parts by mass, and more preferably 45 to 50 parts by mass.
（成形）
　次いで、上記の混合により得られた前駆体を含む混合物を成形することが好ましい。
　この前駆体を含む混合物を成形して成形体とすることにより、混合物の嵩密度が高くなり、一定容量の加熱装置に多量の混合物を装填できるため、生産性が向上する。また、成形すると嵩密度が高くなることにより熱伝導性がよくなり、急速な昇温が可能になると共に、混合物が均一に加熱される。また、混合物の加熱分解により発生するガスが、成形体同士の間の隙間から容易に放出できるため、混合物の吹き上げや飛散が防止される。更に、成形すると嵩密度が高くなることにより、無水ホウ酸が高温で長時間残留するため、ｈＢＮの結晶成長が促進する。この成形は、得られる成形体の密度が０．６～０．８ｇ／ｃｍ３程度になるように行うことが好ましい。 (Molding)
Subsequently, it is preferable to shape | mold the mixture containing the precursor obtained by said mixing.
By molding the mixture containing this precursor into a molded body, the bulk density of the mixture is increased, and a large amount of the mixture can be loaded in a heating device having a constant capacity, so that productivity is improved. Moreover, when it shape | molds, heat conductivity improves because a bulk density becomes high, rapid temperature rise is attained, and a mixture is heated uniformly. Moreover, since the gas generated by the thermal decomposition of the mixture can be easily released from the gaps between the molded bodies, the mixture is prevented from being blown up or scattered. Furthermore, since the bulk density is increased by molding, boric anhydride remains at a high temperature for a long time, so that the crystal growth of hBN is promoted. This molding is preferably performed so that the density of the obtained molded body is about 0.6 to 0.8 g / cm 3 .
（加熱）
　次いで、上記の成形により得られた成形体を加熱する。この加熱により、成形体中の酸素及びホウ素を含む化合物とアミノ基を有する窒素化合物とが反応し、ｈＢＮが生成する。
　加熱時の雰囲気は、アンモニア雰囲気又は非酸化性ガス雰囲気である。非酸化性ガス雰囲気としては、窒素ガス雰囲気、又はアルゴンガス等の不活性ガス雰囲気が好ましい。なかでも、アンモニア雰囲気がより好ましい。
　加熱温度は、反応性の向上及び粉砕の容易性の観点から、好ましくは８００～１４００℃、より好ましくは９００～１３５０℃、更に好ましくは１０００～１３００℃、より更に好ましくは１０５０～１２００℃である。
（粉砕）
　次いで、加熱により得られた生成物を、粉砕することにより、粗製ｈＢＮ粉末が得られる。
　粉砕方法には特に制限はなく、ジョー粉砕、粗ロール粉砕等を採用することができる。 (heating)
Next, the molded body obtained by the above molding is heated. By this heating, the compound containing oxygen and boron in the molded body reacts with the nitrogen compound having an amino group, thereby generating hBN.
The atmosphere during heating is an ammonia atmosphere or a non-oxidizing gas atmosphere. The non-oxidizing gas atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon gas. Of these, an ammonia atmosphere is more preferable.
The heating temperature is preferably from 800 to 1400 ° C., more preferably from 900 to 1350 ° C., still more preferably from 1000 to 1300 ° C., and even more preferably from 1050 to 1200 ° C., from the viewpoint of improving reactivity and ease of grinding. .
(Pulverization)
The product obtained by heating is then pulverized to obtain a crude hBN powder.
There is no particular limitation on the pulverization method, and jaw pulverization, coarse roll pulverization and the like can be employed.
＜六方晶窒化ホウ素粉末の製造方法＞
　本発明の六方晶窒化ホウ素粉末（ｈＢＮ粉末）の製造方法では、前述した粗製ｈＢＮ粉末１００質量部に対して、炭素換算で３～１５質量部の後述する炭素源と０．０１～１質量部の後述するカルシウム（Ｃａ）化合物を混合する。
　炭素源が炭素換算で３質量部以上である場合には、一次粒子の粒成長が促進されると共に、酸化ホウ素の窒化が進んで凝集体の結晶性が向上するため、凝集体の崩壊強度が向上する。炭素源が炭素換算で１５質量部以下である場合には、未反応の炭素成分が異物すなわち黒色異物として残留することが防止され、白色度や電気絶縁性が向上する。
　当該観点から、粗製ｈＢＮ粉末１００質量部に対する、炭素源の配合量は、炭素換算で、３～１５質量部であり、好ましくは４～１４質量部、より好ましくは５～１３質量部、更に好ましくは６～１２質量部、より更に好ましくは８～１０質量部である。
　また、Ｃａ化合物が１質量部以下である場合には、高純度を保ちながら、一次粒子の粒成長が促進され、結晶性を向上させることができる。
　当該観点から、粗製ｈＢＮ粉末１００質量部に対する、Ｃａ化合物の配合量は、０．０１～１質量部であり、好ましくは０．０５～０．８質量部、より好ましくは０．１～０．６質量部、更に好ましくは０．２～０．５質量部、より更に好ましくは０．３～０．４５質量部である。 <Method for producing hexagonal boron nitride powder>
In the method for producing hexagonal boron nitride powder (hBN powder) of the present invention, 3 to 15 parts by mass of a carbon source (described later) and 0.01 to 1 part by mass in terms of carbon with respect to 100 parts by mass of the crude hBN powder described above. The calcium (Ca) compound mentioned later is mixed.
When the carbon source is 3 parts by mass or more in terms of carbon, the growth of primary particles is promoted and the nitridation of boron oxide proceeds to improve the crystallinity of the aggregate. improves. When the carbon source is 15 parts by mass or less in terms of carbon, unreacted carbon components are prevented from remaining as foreign matters, that is, black foreign matters, and whiteness and electrical insulation are improved.
From this point of view, the amount of the carbon source based on 100 parts by mass of the crude hBN powder is 3 to 15 parts by mass in terms of carbon, preferably 4 to 14 parts by mass, more preferably 5 to 13 parts by mass, and still more preferably. Is 6 to 12 parts by mass, more preferably 8 to 10 parts by mass.
Moreover, when the Ca compound is 1 part by mass or less, the grain growth of primary particles is promoted while maintaining high purity, and the crystallinity can be improved.
From this viewpoint, the compounding amount of the Ca compound with respect to 100 parts by mass of the crude hBN powder is 0.01 to 1 part by mass, preferably 0.05 to 0.8 part by mass, and more preferably 0.1 to 0. The amount is 6 parts by mass, more preferably 0.2 to 0.5 parts by mass, and still more preferably 0.3 to 0.45 parts by mass.
（炭素源）
　本発明の六方晶窒化ホウ素粉末（ｈＢＮ粉末）の製造方法に用いられる炭素源は、炭素又は炭素含有化合物である。本発明で用いられる炭素源としては、黒鉛の他、カーボンブラック、炭化ホウ素、糖類、メラミン、フェノール樹脂等が挙げられ、好ましくは黒鉛及び炭化ホウ素から選ばれる１種又は２種である。また、炭素源は、熱伝導性の観点からは、黒鉛及び炭化ホウ素の併用が好ましく、電気絶縁性の観点からは、黒鉛が好ましい。
　炭素源中における炭素の含有量は、好ましくは９０質量％以上、より好ましくは９５質量％以上、更に好ましくは９９質量％以上、より更に好ましくは１００質量％である。 (Carbon source)
The carbon source used in the method for producing the hexagonal boron nitride powder (hBN powder) of the present invention is carbon or a carbon-containing compound. Examples of the carbon source used in the present invention include graphite, carbon black, boron carbide, saccharides, melamine, phenol resin, and the like, and preferably one or two selected from graphite and boron carbide. The carbon source is preferably a combination of graphite and boron carbide from the viewpoint of thermal conductivity, and graphite is preferable from the viewpoint of electrical insulation.
The carbon content in the carbon source is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and still more preferably 100% by mass.
（炭化ホウ素）
　本発明のｈＢＮ粉末の製造方法において、炭素源は、熱伝導性の観点から、炭化ホウ素（以下、「Ｂ４Ｃ」ともいう。）を含むことが好ましい。粗製ｈＢＮ粉末１００質量部に対する、炭素源として炭化ホウ素の配合量は、炭素換算で好ましくは０．０１～１４．８質量部、より好ましくは０．０１～１２質量部、更に好ましくは０．０１～１０質量部、より更に好ましくは０．０５～８質量部、より更に好ましくは０．１～６質量部、より更に好ましくは０．５～５質量部、より更に好ましくは１～３質量部である。
　これにより、ｈＢＮ一次粒子の厚み方向への粒成長を促進し、高結晶化にも寄与するため、ｈＢＮ粒子の配向を制御することができ、高熱伝導率化にも有利である。また、炭化ホウ素結晶内の炭素を起点として窒化ホウ素の生成が進むため、炭化ホウ素粒子の形態を維持したｈＢＮ粉末を製造することができ、炭素源として黒鉛のみを用いた際の黒鉛表面で生成した結晶核から溶解析出により成長したｈＢＮ粉末よりも、ｈＢＮ一次粒子の厚みを厚くすることができると考えられる。よって、有機マトリックス中にｈＢＮ粉末を充填させて樹脂組成物及び樹脂シートを製造する時又は当該樹脂シートの使用時に顆粒形状を維持し、崩壊することを防止又は抑制することができる。
　また、炭素源として黒鉛及び炭化ホウ素を併用することにより、炭化ホウ素のみを用いた場合と比較して、焼成時間を短く、かつ、炭化ホウ素に起因する黒色異物数を低減することができる。
　炭化ホウ素中における炭化ホウ素の含有量は、好ましくは９０質量％以上、より好ましくは９５質量％以上、更に好ましくは９９質量％以上、より更に好ましくは１００質量％である。
　また、黒鉛及び炭化ホウ素を併用する場合における（炭化ホウ素／炭素源）の質量比は、炭素換算で好ましくは０．００３～０．９９であり、より好ましくは０．０１５～０．８であり、更に好ましくは０．０２～０．６であり、より更に好ましくは０．０８５～０．４、より更に好ましくは０．１５～０．３である。 (Boron carbide)
In the method for producing hBN powder of the present invention, the carbon source preferably contains boron carbide (hereinafter also referred to as “B 4 C”) from the viewpoint of thermal conductivity. The compounding amount of boron carbide as a carbon source with respect to 100 parts by mass of the crude hBN powder is preferably 0.01 to 14.8 parts by mass, more preferably 0.01 to 12 parts by mass, and still more preferably 0.01 in terms of carbon. To 10 parts by mass, more preferably 0.05 to 8 parts by mass, even more preferably 0.1 to 6 parts by mass, still more preferably 0.5 to 5 parts by mass, and even more preferably 1 to 3 parts by mass. It is.
This promotes grain growth in the thickness direction of the hBN primary particles and contributes to high crystallization, so that the orientation of the hBN particles can be controlled, which is advantageous for increasing the thermal conductivity. In addition, since boron nitride is generated starting from carbon in the boron carbide crystal, hBN powder maintaining the form of boron carbide particles can be produced, and generated on the graphite surface when only graphite is used as the carbon source. It is considered that the hBN primary particles can be made thicker than the hBN powder grown from the crystal nuclei by dissolution precipitation. Therefore, when the resin composition and the resin sheet are produced by filling the organic matrix with hBN powder or when the resin sheet is used, the granular shape can be maintained, and the collapse can be prevented or suppressed.
Further, by using graphite and boron carbide together as the carbon source, the firing time can be shortened and the number of black foreign matters resulting from boron carbide can be reduced as compared with the case where only boron carbide is used.
The boron carbide content in the boron carbide is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and still more preferably 100% by mass.
The mass ratio of (boron carbide / carbon source) when graphite and boron carbide are used in combination is preferably 0.003 to 0.99, more preferably 0.015 to 0.8 in terms of carbon. More preferably, it is 0.02 to 0.6, still more preferably 0.085 to 0.4, and still more preferably 0.15 to 0.3.
（Ｃａ化合物）
　本発明のｈＢＮ粉末の製造方法に用いられるカルシウム化合物（以下、「Ｃａ化合物」ともいう。）としては、炭酸カルシウムの他、酸化カルシウム、フッ化カルシウム、塩化カルシウムが挙げられるが、好ましくは炭酸カルシウムである。
　Ｃａ化合物中における炭酸カルシウムの含有量は、好ましくは９０質量％以上、より好ましくは９５質量％以上、更に好ましくは９９質量％以上、より更に好ましくは１００質量％である。 (Ca compound)
Examples of the calcium compound (hereinafter also referred to as “Ca compound”) used in the method for producing the hBN powder of the present invention include calcium oxide, calcium fluoride, calcium chloride, and preferably calcium carbonate. It is.
The content of calcium carbonate in the Ca compound is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and still more preferably 100% by mass.
（混合）
　混合方法には特に制限はなく、湿式混合及び乾式混合のいずれでもよいが、湿式混合が好ましい。湿式混合は、ヘンシェルミキサー、ボールミル、リボンブレンダー等の一般的な混合機を用いて行うことができる。
　また、混合の際、バインダーを添加して混合してもよい。このバインダーとしては、特に制限はないが、ポリビニルアルコール（ＰＶＡ）、セルロース、ポリフッ化ビニリデン（ＰＶＤＦ）等の樹脂が挙げられ、好ましくはポリビニルアルコールが用いられる。
　バインダーは、これらの樹脂を水に溶解させたバインダー水溶液として用いるのが好ましい。このバインダー水溶液中の樹脂含有量は、好ましくは１～１０質量％、より好ましくは１～５質量％、更に好ましくは１～４質量％である。粗製ｈＢＮ粉末１００質量部に対する、バインダー水溶液の混合は、好ましくは１～２０質量部、より好ましくは５～１５質量部、更に好ましくは８～１２質量部である。
　なお、このようにバインダーを添加して混合する場合、バインダーも上記の炭素源として換算される。 (mixture)
There is no particular limitation on the mixing method, and either wet mixing or dry mixing may be used, but wet mixing is preferable. The wet mixing can be performed using a general mixer such as a Henschel mixer, a ball mill, or a ribbon blender.
Moreover, you may add and mix a binder in the case of mixing. Although there is no restriction | limiting in particular as this binder, Resin, such as polyvinyl alcohol (PVA), a cellulose, a polyvinylidene fluoride (PVDF), is mentioned, Preferably polyvinyl alcohol is used.
The binder is preferably used as a binder aqueous solution in which these resins are dissolved in water. The resin content in the aqueous binder solution is preferably 1 to 10% by mass, more preferably 1 to 5% by mass, and still more preferably 1 to 4% by mass. The amount of the aqueous binder solution mixed with 100 parts by mass of the crude hBN powder is preferably 1 to 20 parts by mass, more preferably 5 to 15 parts by mass, and still more preferably 8 to 12 parts by mass.
In addition, when adding and mixing a binder in this way, a binder is also converted as said carbon source.
（成形）
　次いで、上記の混合により得られた混合物を適当な形状に成形する。
　成形は、ｈＢＮ一次粒子が凝集してなる凝集体の強度の向上、生産性、ハンドリングの良さ、反応性の観点から、成形後の密度が、好ましくは０．５ｇ／ｃｍ３以上、より好ましくは０．８ｇ／ｃｍ３以上、更に好ましくは１ｇ／ｃｍ３以上となり、また、好ましくは２ｇ／ｃｍ３以下、より好ましくは１．８ｇ／ｃｍ３以下、更に好ましくは１．５ｇ／ｃｍ３以下となるように行う。 (Molding)
Next, the mixture obtained by the above mixing is formed into an appropriate shape.
In the molding, the density after molding is preferably 0.5 g / cm 3 or more, more preferably from the viewpoint of improvement in strength of the aggregate formed by agglomeration of hBN primary particles, productivity, good handling, and reactivity. 0.8 g / cm 3 or more, more preferably 1 g / cm 3 or more, preferably 2 g / cm 3 or less, more preferably 1.8 g / cm 3 or less, still more preferably 1.5 g / cm 3 or less. Do so.
（焼成）
　本発明のｈＢＮ粉末の製造方法は、上記の成形により得られた成形体を焼成する焼成工程を有する。粗製ｈＢＮ粉末を加圧成形して成形体としてから焼成することにより、成形体中の粗製ｈＢＮ粉末に含まれる酸化ホウ素と炭素源に含まれる炭素とが反応して、圧縮破壊強度の高い六方晶窒化ホウ素（ｈＢＮ）の凝集体が生成し、本発明のｈＢＮ粉末が得られる。なお、成形せずに焼成を行った場合、崩壊強度の高いｈＢＮ凝集体を十分に製造することは困難である。
　焼成時の雰囲気は、窒素ガスを含む雰囲気である。窒素ガスを含む雰囲気中における、窒素ガス濃度は、好ましくは６０体積％以上、より好ましくは８０体積％以上、更に好ましくは９０体積％以上、より更に好ましくは９９体積％以上である。酸素ガスは少ない方がよい。
　焼成温度は、好ましくは１０００～２２００℃である。焼成温度は１０００℃以上であると十分な還元窒化反応が進む。また２２００℃以下であるとｈＢＮの分解が起こることが防止される。この観点から、焼成温度は、好ましくは１５００～２２００℃、より好ましくは１６００～２２００℃、更に好ましくは１７００～２２００℃、より更に好ましくは１７３０～２１９０℃である。
　焼成時間は、好ましくは１～２０時間である。焼成時間は１時間以上では十分に還元窒化反応が進み、未反応の炭素成分が黒色物として残留することが防止される。また２０時間以下では、焼成コストが低減される。この観点から、好ましくは１～１５時間、より好ましくは５～１０時間、更に好ましくは６～９時間、より更に好ましくは６～７時間である。 (Baking)
The manufacturing method of the hBN powder of this invention has a baking process which bakes the molded object obtained by said shaping | molding. When the crude hBN powder is pressure-molded to form a compact and then fired, the boron oxide contained in the crude hBN powder in the compact reacts with the carbon contained in the carbon source, resulting in a hexagonal crystal with high compressive fracture strength. Aggregates of boron nitride (hBN) are formed, and the hBN powder of the present invention is obtained. In addition, when baking without shaping | molding, it is difficult to fully manufacture an hBN aggregate with high collapse strength.
The atmosphere during firing is an atmosphere containing nitrogen gas. The nitrogen gas concentration in the atmosphere containing nitrogen gas is preferably 60% by volume or more, more preferably 80% by volume or more, still more preferably 90% by volume or more, and still more preferably 99% by volume or more. Less oxygen gas is better.
The firing temperature is preferably 1000 to 2200 ° C. When the firing temperature is 1000 ° C. or higher, a sufficient reduction nitriding reaction proceeds. Moreover, decomposition | disassembly of hBN is prevented as it is 2200 degrees C or less. From this viewpoint, the firing temperature is preferably 1500 to 2200 ° C., more preferably 1600 to 2200 ° C., still more preferably 1700 to 2200 ° C., and still more preferably 1730 to 2190 ° C.
The firing time is preferably 1 to 20 hours. When the firing time is 1 hour or longer, the reductive nitriding reaction proceeds sufficiently, and the unreacted carbon component is prevented from remaining as a black product. Moreover, in 20 hours or less, a calcination cost is reduced. From this viewpoint, it is preferably 1 to 15 hours, more preferably 5 to 10 hours, still more preferably 6 to 9 hours, and still more preferably 6 to 7 hours.
　なお、焼成の前に乾燥を行ってもよい。乾燥温度は、好ましくは１５０～４００℃、より好ましくは２００～４００℃であり、乾燥時間は、好ましくは６～８時間である。
（粉砕）
　次いで、焼成により得られた生成物を、粉砕することが好ましい。
　粉砕方法には特に制限はなく、ジョー粉砕、粗ロール粉砕等を採用することができる。
（分級）
　次いで、上記焼成工程後に、粉砕により得られた粉砕物を、分級することが好ましい。
　分級方法には特に制限はなく、振動篩装置、気流分級、水篩、遠心分離等により分級することができる。なかでも、振動篩装置により分級することが好ましい。振動篩装置を用いる場合には、乾式振動篩装置［晃栄産業（株）製、商品名「佐藤式振動ふるい機」］を用いて、目開き１０６μｍの篩を用いて分級時間６０分の条件にて分級することが好ましい。 In addition, you may dry before baking. The drying temperature is preferably 150 to 400 ° C., more preferably 200 to 400 ° C., and the drying time is preferably 6 to 8 hours.
(Pulverization)
Subsequently, it is preferable to grind the product obtained by baking.
There is no particular limitation on the pulverization method, and jaw pulverization, coarse roll pulverization and the like can be employed.
(Classification)
Subsequently, it is preferable to classify the pulverized material obtained by pulverization after the above-described firing step.
There is no restriction | limiting in particular in the classification method, It can classify | categorize with a vibration sieve apparatus, an airflow classification, a water sieve, centrifugation, etc. Especially, it is preferable to classify with a vibration sieve apparatus. When using a vibrating sieve device, a dry vibrating sieve device [manufactured by Koei Sangyo Co., Ltd., trade name “Sato Vibrating Sieve”], using a sieve with an aperture of 106 μm, a classification time of 60 minutes It is preferable to classify with.
（ｈＢＮ粉末の混合）
　さらに、本発明のｈＢＮ粉末の製造方法は、熱伝導性及び電気絶縁性の向上の観点から、上記で得られた六方晶窒化ホウ素粉末を目開き１０６μｍの篩、目開き４５μｍの篩及び振動篩装置を用いて、４５～１０６μｍのｈＢＮ粉末（以下、「ｈＢＮ粉末（Ａ）」ともいう。）と４５μｍ篩下のｈＢＮ粉末（以下、「ｈＢＮ粉末（Ｂ）」ともいう。）に分級したのち、ｈＢＮ粉末（Ａ）とｈＢＮ粉末（Ｂ）を、ｈＢＮ粉末（Ａ）及び（Ｂ）の合計量に対するｈＢＮ粉末（Ａ）の割合（以下、顆粒率（質量％）＝［（Ａ）／〔（Ａ）＋（Ｂ）〕］ともいう。）が４０～９０質量％となるように混合する混合工程を有することが好ましい。
　混合方法は、特に制限はなく、湿式混合及び乾式混合のいずれでもよいが、乾式混合が好ましい。乾式混合は、ヘンシェルミキサー、ボールミル、リボンブレンダー、及びＶ型ブレンダー等の一般的な混合機を用いて行うことができるが、均一にｈＢＮ粉末を混合する観点からＶ型ブレンダーが好ましい。混合時間は、好ましくは２０～９０分であり、より好ましくは５０～７０分である。
　ｈＢＮ粉末（Ａ）の減圧吸引型篩分け機（エアージェットシーブ）を用いて求めた目開き１０６μｍ篩上の粉末含有率は、好ましくは５～２０質量％、より好ましくは１０～１８質量％、更に好ましくは１４～１７質量％である。また、ｈＢＮ粉末（Ｂ）の減圧吸引型篩分け機（エアージェットシーブ）を用いて求めた目開き４５μｍ篩上の粉末含有率は、好ましくは１～２０質量％、より好ましくは１～１０質量％、更に好ましくは４～８質量％、より更に好ましくは５～７質量％である。なお、目開き１０６μｍ篩上の粉末含有率及び目開き４５μｍ篩上の粉末含有率は、実施例に記載の方法により測定することができる。
　顆粒率は、熱伝導性及び電気絶縁性の向上の観点から、好ましくは４０～９０質量％、より好ましくは５０～８５質量％、更に好ましく５５～８０質量％、より更に好ましく６０～７０質量％である。 (Mixing of hBN powder)
Furthermore, in the method for producing hBN powder of the present invention, from the viewpoint of improvement in thermal conductivity and electrical insulation, the hexagonal boron nitride powder obtained above is applied to a sieve having an aperture of 106 μm, a sieve having an aperture of 45 μm, and a vibrating sieve. After classifying into 45 to 106 μm hBN powder (hereinafter also referred to as “hBN powder (A)”) and hBN powder under a 45 μm sieve (hereinafter also referred to as “hBN powder (B)”) using an apparatus. , HBN powder (A) and hBN powder (B), the ratio of hBN powder (A) to the total amount of hBN powder (A) and (B) (hereinafter referred to as granule ratio (mass%) = [(A) / [ (A) + (B)]]) is preferably mixed so as to be 40 to 90% by mass.
The mixing method is not particularly limited and may be either wet mixing or dry mixing, but dry mixing is preferable. The dry mixing can be performed using a general mixer such as a Henschel mixer, a ball mill, a ribbon blender, and a V-type blender, but a V-type blender is preferable from the viewpoint of uniformly mixing the hBN powder. The mixing time is preferably 20 to 90 minutes, more preferably 50 to 70 minutes.
The powder content on the 106 μm mesh sieve obtained using a vacuum suction type sieving machine (air jet sieve) of hBN powder (A) is preferably 5 to 20% by mass, more preferably 10 to 18% by mass, More preferably, it is 14 to 17% by mass. Further, the powder content on the 45 μm mesh sieve obtained using a vacuum suction type sieving machine (air jet sieve) of hBN powder (B) is preferably 1 to 20% by mass, more preferably 1 to 10% by mass. %, More preferably 4 to 8% by mass, and still more preferably 5 to 7% by mass. In addition, the powder content rate on a 106 micrometers sieve and the powder content on a 45 micrometers sieve can be measured by the method as described in an Example.
The granule ratio is preferably 40 to 90% by mass, more preferably 50 to 85% by mass, still more preferably 55 to 80% by mass, and still more preferably 60 to 70% by mass, from the viewpoint of improving thermal conductivity and electrical insulation. It is.
［樹脂組成物］
　本発明の樹脂組成物は、前述の六方晶窒化ホウ素粉末（ｈＢＮ粉末）を１０～９０体積％含有する。本発明の樹脂組成物におけるｈＢＮ粉末の含有量は、樹脂組成物及び当該樹脂組成物を成形してなる樹脂シートの熱伝導性及び樹脂シートの成形性の観点から、１０～９０体積％であり、好ましくは２０～８０体積％、より好ましくは３０～７０体積％、更に好ましくは３５～６５体積％、より更に好ましくは４０～６０体積％である。
　前述のｈＢＮ粉末を用いることにより、樹脂組成物を製造する際、樹脂成分との馴染みが良く、当該樹脂組成物の低粘度化及び良好な電気絶縁性を得ることができる。
　本発明において、ｈＢＮ粉末の体積基準の含有量（体積％）は、ｈＢＮ粉末の比重及び有機マトリックスとして用いられる各種樹脂の比重から求めることができる。 [Resin composition]
The resin composition of the present invention contains 10 to 90% by volume of the aforementioned hexagonal boron nitride powder (hBN powder). The content of hBN powder in the resin composition of the present invention is 10 to 90% by volume from the viewpoint of the thermal conductivity of the resin composition and the resin sheet formed by molding the resin composition and the moldability of the resin sheet. It is preferably 20 to 80% by volume, more preferably 30 to 70% by volume, still more preferably 35 to 65% by volume, and still more preferably 40 to 60% by volume.
By using the hBN powder described above, when the resin composition is produced, the resin composition is well-familiar with the resin composition, and a low viscosity and good electrical insulation of the resin composition can be obtained.
In the present invention, the volume-based content (volume%) of the hBN powder can be determined from the specific gravity of the hBN powder and the specific gravity of various resins used as the organic matrix.
（有機マトリックス）
　本発明の樹脂組成物は、有機マトリックスとして樹脂を含有する。
　本発明に用いる樹脂としては、熱硬化性樹脂、熱可塑性樹脂、各種ゴム、熱可塑性エラストマー、オイル等から選ばれる一種以上の樹脂を含有することが好ましい。
　熱硬化性樹脂としては、例えば、エポキシ樹脂、シリコーン樹脂、フェノール樹脂、ユリア樹脂、不飽和ポリエステル樹脂、メラミン樹脂、ポリイミド樹脂、ポリベンゾオキサゾール樹脂、ウレタン樹脂等が挙げられる。
　熱可塑性樹脂としては、例えば、ポリエチレン、ポリプロピレン、エチレン－酢酸ビニル共重合体等のポリオレフィン樹脂；ポリエチレンテレフタレート、ポリブチレンテレフタレート、液晶ポリエステル等のポリエステル樹脂；ポリ塩化ビニル樹脂、アクリル樹脂、ポリフェニレンサルファイド樹脂、ポリフェニレンエーテル樹脂、ポリアミド樹脂、ポリアミドイミド樹脂、及びポリカーボネート樹脂等が挙げられる。
　各種ゴムとしては、天然ゴム、ポリイソプレンゴム、スチレン－ブタジエン共重合体ゴム、ポリブタジエンゴム、エチレン－プロピレン共重合体、エチレン－プロピレン－ジエン共重合体、ブタジエン－アクリロニトリル共重合体、イソブチレン－イソプレン共重合体、クロロプレンゴム、シリコ－ンゴム、フッソゴム、クロロ－スルホン化ポリエチレン、ポリウレタンゴム等が挙げられる。これらゴムは、架橋して用いることが好ましい。
　熱可塑性エラストマーとしては、オレフィン系熱可塑性エラストマー、スチレン系熱可塑性エラストマー、塩化ビニル系熱可塑性エラストマー、ウレタン系熱可塑性エラストマー、エステル系熱可塑性エラストマー等が挙げられる。
　オイル成分としては、シリコーンオイル等のグリース類が挙げられる。
　これらの有機マトリックスは、一種を単独で用いてもよく、二種以上を組み合わせて用いてもよい。 (Organic matrix)
The resin composition of the present invention contains a resin as an organic matrix.
The resin used in the present invention preferably contains one or more resins selected from thermosetting resins, thermoplastic resins, various rubbers, thermoplastic elastomers, oils and the like.
Examples of the thermosetting resin include epoxy resins, silicone resins, phenol resins, urea resins, unsaturated polyester resins, melamine resins, polyimide resins, polybenzoxazole resins, and urethane resins.
Examples of the thermoplastic resin include polyolefin resins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and liquid crystal polyester; polyvinyl chloride resin, acrylic resin, polyphenylene sulfide resin, Examples include polyphenylene ether resins, polyamide resins, polyamideimide resins, and polycarbonate resins.
Various rubbers include natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, butadiene-acrylonitrile copolymer, isobutylene-isoprene copolymer. Examples thereof include polymers, chloroprene rubber, silicone rubber, fluoro rubber, chloro-sulfonated polyethylene, polyurethane rubber and the like. These rubbers are preferably used after being crosslinked.
Examples of the thermoplastic elastomer include olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, urethane-based thermoplastic elastomers, and ester-based thermoplastic elastomers.
Examples of the oil component include greases such as silicone oil.
One of these organic matrices may be used alone, or two or more thereof may be used in combination.
　本発明の樹脂組成物は、当該樹脂組成物を用いて得られる熱伝導性部材の用途や当該樹脂組成物を成形してなる樹脂シート等の熱伝導性部材の機械的強度、耐熱性、耐久性、柔軟性、可撓性等の要求特性に応じて、従来樹脂シートの有機マトリックスとして使用されている各種の熱硬化性樹脂、熱可塑性樹脂、各種ゴム及び熱可塑性エラストマー等の中から選ばれる一種以上の樹脂を含有することが好ましい。これらの有機マトリックスは、一種を単独で用いてもよく、二種以上を組み合わせて用いてもよいが、本発明においては、特に硬化性エポキシ樹脂や、硬化性シリコーン樹脂が好適に用いられる。
　当該樹脂組成物中の有機マトリックスの含有量は、当該樹脂組成物を成形してなる樹脂シートの成形性の観点から、好ましくは１０～９０体積％、より好ましくは２０～８０体積％、更に好ましくは３０～７０体積％、より更に好ましくは３５～６５体積％、より更に好ましくは４０～６０体積％である。
　本発明において、有機マトリックスの体積基準の含有量（体積％）は、ｈＢＮ粉末の比重及び有機マトリックスとして用いられる各種樹脂の比重から求めることができる。 The resin composition of the present invention is used for a heat conductive member obtained by using the resin composition and mechanical strength, heat resistance and durability of a heat conductive member such as a resin sheet formed by molding the resin composition. Selected from various thermosetting resins, thermoplastic resins, various rubbers, thermoplastic elastomers, etc., which are conventionally used as the organic matrix of resin sheets, according to the required properties such as properties, flexibility and flexibility It is preferable to contain one or more resins. These organic matrices may be used singly or in combination of two or more. In the present invention, curable epoxy resins and curable silicone resins are particularly preferably used.
The content of the organic matrix in the resin composition is preferably 10 to 90% by volume, more preferably 20 to 80% by volume, and still more preferably, from the viewpoint of moldability of a resin sheet formed by molding the resin composition. Is 30 to 70% by volume, more preferably 35 to 65% by volume, and still more preferably 40 to 60% by volume.
In the present invention, the volume-based content (volume%) of the organic matrix can be determined from the specific gravity of hBN powder and the specific gravity of various resins used as the organic matrix.
（硬化性エポキシ樹脂）
　本発明の樹脂組成物において、有機マトリックスとして用いられる硬化性エポキシ樹脂としては、ｈＢＮ粉末混合物の有機マトリックスに対する分散性の観点から、常温で液状のエポキシ樹脂や、常温で固体状の低軟化点エポキシ樹脂が好ましい。
　この硬化性エポキシ樹脂としては、一分子中に２個以上のエポキシ基を有する化合物であればよく、特に制限されず、従来エポキシ樹脂として使用されている公知の化合物の中から任意のものを適宜選択して用いることができる。このようなエポキシ樹脂としては、例えばビスフェノールＡ型エポキシ樹脂、ビスフェノールＦ型エポキシ樹脂、ポリカルボン酸のグリシジルエーテル、シクロヘキサン誘導体のエポキシ化により得られるエポキシ樹脂等が挙げられる。これらは一種を単独で用いてもよく、二種以上を組み合わせて用いてもよい。前記エポキシ樹脂の中では、耐熱性、及び作業性等の観点からは、ビスフェノールＡ型エポキシ樹脂、ビスフェノールＦ型エポキシ樹脂、シクロヘキサン誘導体のエポキシ化により得られるエポキシ樹脂が好適である。 (Curable epoxy resin)
In the resin composition of the present invention, the curable epoxy resin used as the organic matrix is an epoxy resin that is liquid at room temperature or a low softening point epoxy that is solid at room temperature from the viewpoint of dispersibility of the hBN powder mixture in the organic matrix. Resins are preferred.
The curable epoxy resin may be a compound having two or more epoxy groups in one molecule, and is not particularly limited, and any one of known compounds conventionally used as epoxy resins can be appropriately selected. It can be selected and used. Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, glycidyl ethers of polycarboxylic acids, and epoxy resins obtained by epoxidation of cyclohexane derivatives. These may be used individually by 1 type, and may be used in combination of 2 or more types. Among the epoxy resins, from the viewpoints of heat resistance and workability, bisphenol A type epoxy resins, bisphenol F type epoxy resins, and epoxy resins obtained by epoxidation of cyclohexane derivatives are suitable.
（エポキシ樹脂用硬化剤）
　硬化性エポキシ樹脂を硬化させるために、通常エポキシ樹脂用硬化剤が用いられる。このエポキシ樹脂用硬化剤としては、特に制限はなく、従来エポキシ樹脂の硬化剤として使用されているものの中から、任意のものを適宜選択して用いることができ、例えばアミン系、フェノール系、酸無水物系等が挙げられる。アミン系硬化剤としては、例えばジシアンジアミドや、ｍ－フェニレンジアミン、４，４’－ジアミノジフェニルメタン、４，４’－ジアミノジフェニルスルホン、ｍ－キシリレンジアミン等の芳香族ジアミン等が好ましく挙げられ、フェノール系硬化剤としては、例えばフェノールノボラック樹脂、クレゾールノボラック樹脂、ビスフェノールＡ型ノボラック樹脂、トリアジン変性フェノールノボラック樹脂等が好ましく挙げられる。また、酸無水物系硬化剤としては、例えばメチルヘキサヒドロ無水フタル酸等の脂環式酸無水物、無水フタル酸等の芳香族酸無水物、脂肪族二塩基酸無水物等の脂肪族酸無水物、クロレンド酸無水物等のハロゲン系酸無水物等が挙げられる。
　これらの硬化剤は、一種を単独で用いてもよく、二種以上を組み合わせて用いてもよい。このエポキシ樹脂用硬化剤の使用量は、硬化性及び硬化樹脂物性のバランス等の点から、前記硬化性エポキシ樹脂に対する当量比で、通常０．５～１．５当量比程度、好ましくは０．７～１．３当量比の範囲で選定される。 (Curing agent for epoxy resin)
In order to cure the curable epoxy resin, a curing agent for epoxy resin is usually used. The curing agent for epoxy resin is not particularly limited, and any one of those conventionally used as curing agents for epoxy resins can be appropriately selected and used. For example, amine-based, phenol-based, acid-based, and the like. An anhydride system etc. are mentioned. Preferred examples of the amine curing agent include dicyandiamide, aromatic diamines such as m-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, and m-xylylenediamine. Preferable examples of the system curing agent include phenol novolak resin, cresol novolak resin, bisphenol A type novolak resin, triazine-modified phenol novolak resin and the like. Examples of the acid anhydride curing agent include aliphatic acids such as alicyclic acid anhydrides such as methylhexahydrophthalic anhydride, aromatic acid anhydrides such as phthalic anhydride, and aliphatic dibasic acid anhydrides. And halogen-based acid anhydrides such as anhydride and chlorendic anhydride.
One of these curing agents may be used alone, or two or more thereof may be used in combination. The amount of the epoxy resin curing agent used is usually about 0.5 to 1.5 equivalent ratio, preferably about 0.1 equivalent ratio to the curable epoxy resin, from the viewpoint of balance between curability and cured resin physical properties. It is selected in the range of 7 to 1.3 equivalent ratio.
（エポキシ樹脂用硬化促進剤）
　本発明の樹脂組成物において、エポキシ樹脂用硬化剤と共に、必要に応じてエポキシ樹脂用硬化促進剤を併用することができる。
　このエポキシ樹脂用硬化促進剤としては、特に制限はなく、従来エポキシ樹脂の硬化促進剤として使用されているものの中から、任意のものを適宜選択して用いることができる。例えば２－エチル－４－メチルイミダゾール、１－ベンジル－２－メチルイミダゾール、２－メチルイミダゾール、２－エチルイミダゾール、２－イソプロピルイミダゾール、２－フェニルイミダゾール、２－フェニル－４－メチルイミダゾール等のイミダゾール化合物、２，４，６－トリス（ジメチルアミノメチル）フェノール、三フッ化ホウ素アミン錯体、トリフェニルホスフィン等を例示することができる。これらの硬化促進剤は、一種を単独で用いてもよく、二種以上を組み合わせて用いてもよい。このエポキシ樹脂用硬化促進剤の使用量は、硬化促進性及び硬化樹脂物性のバランス等の点から、前記硬化性のエポキシ樹脂１００質量部に対し、通常０．１～１０質量部程度、好ましくは０．４～５質量部の範囲で選定される。 (Curing accelerator for epoxy resin)
In the resin composition of the present invention, an epoxy resin curing accelerator can be used in combination with the epoxy resin curing agent as necessary.
There is no restriction | limiting in particular as this hardening accelerator for epoxy resins, From the things conventionally used as a hardening accelerator of an epoxy resin, arbitrary things can be selected suitably and can be used. For example, imidazoles such as 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, etc. Examples thereof include compounds, 2,4,6-tris (dimethylaminomethyl) phenol, boron trifluoride amine complex, triphenylphosphine and the like. These hardening accelerators may be used individually by 1 type, and may be used in combination of 2 or more type. The amount of the epoxy resin curing accelerator used is usually about 0.1 to 10 parts by mass, preferably about 100 to 10 parts by mass, preferably 100 parts by mass of the curable epoxy resin, from the viewpoint of the balance between curing acceleration and cured resin properties It is selected in the range of 0.4-5 parts by mass.
（硬化性シリコーン樹脂）
　硬化性シリコーン樹脂としては、付加反応型シリコーン樹脂とシリコーン系架橋剤との混合物を用いることができる。付加反応型シリコーン樹脂としては、例えば分子中に官能基としてアルケニル基を有するポリオルガノシロキサンの中から選ばれる少なくとも一種を挙げることができる。上記の分子中に官能基としてアルケニル基を有するポリオルガノシロキサンの好ましいものとしては、ビニル基を官能基とするポリジメチルシロキサン、ヘキセニル基を官能基とするポリジメチルシロキサン及びこれらの混合物等が挙げられる。 (Curable silicone resin)
As the curable silicone resin, a mixture of an addition reaction type silicone resin and a silicone-based crosslinking agent can be used. Examples of the addition reaction type silicone resin include at least one selected from polyorganosiloxanes having an alkenyl group as a functional group in the molecule. Preferred examples of the polyorganosiloxane having an alkenyl group as a functional group in the molecule include polydimethylsiloxane having a vinyl group as a functional group, polydimethylsiloxane having a hexenyl group as a functional group, and a mixture thereof. .
　シリコーン系架橋剤としては、例えば一分子中に少なくとも２個のケイ素原子結合水素原子を有するポリオルガノシロキサン、具体的には、ジメチルハイドロジェンシロキシ基末端封鎖ジメチルシロキサン－メチルハイドロジェンシロキサン共重合体、トリメチルシロキシ基末端封鎖ジメチルシロキサン－メチルハイドロジェンシロキサン共重合体、トリメチルシロキサン基末端封鎖ポリ（メチルハイドロジェンシロキサン）、ポリ（ハイドロジェンシルセスキオキサン）等が挙げられる。 Examples of the silicone-based crosslinking agent include polyorganosiloxane having at least two silicon-bonded hydrogen atoms in one molecule, specifically, a dimethylhydrogensiloxy group end-capped dimethylsiloxane-methylhydrogensiloxane copolymer, Examples thereof include trimethylsiloxy group-end-capped dimethylsiloxane-methylhydrogensiloxane copolymer, trimethylsiloxane group-end-capped poly (methylhydrogensiloxane), and poly (hydrogensilsesquioxane).
　また、硬化触媒としては、通常白金系化合物が用いられる。この白金系化合物の例としては、微粒子状白金、炭素粉末担体上に吸着された微粒子状白金、塩化白金酸、アルコール変性塩化白金酸、塩化白金酸のオレフィン錯体、パラジウム、ロジウム触媒等が挙げられる。 Also, platinum compounds are usually used as the curing catalyst. Examples of the platinum compound include fine platinum, fine platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, chloroplatinic acid olefin complex, palladium, rhodium catalyst, and the like. .
　本発明の樹脂組成物は、本発明の効果が得られる範囲において、さらなる成分を含有していてもよい。そのような成分としては、例えば、窒化アルミニウム、窒化ケイ素、繊維状窒化ホウ素等の窒化物粒子、アルミナ、繊維状アルミナ、酸化亜鉛、酸化マグネシウム、酸化ベリリウム、酸化チタン等の電気絶縁性金属酸化物、ダイヤモンド、フラーレン等の電気絶縁性炭素成分、可塑剤、粘着剤、補強剤、着色剤、耐熱向上剤、粘度調整剤、分散安定剤、及び溶剤が挙げられる。
　また、本発明の六方晶窒化ホウ素粉末を含有する樹脂組成物には、その効果を損なわない限り、上記の窒化物粒子や電気絶縁性金属酸化物として例示されているものに加えて、水酸化アルミニウム、水酸化マグネシウム等の無機フィラー、無機フィラーとマトリックス樹脂の界面接着強度を改善するシランカップリング剤等の表面処理剤、還元剤等を添加してもよい。 The resin composition of the present invention may contain further components as long as the effects of the present invention are obtained. Examples of such components include nitride particles such as aluminum nitride, silicon nitride, and fibrous boron nitride, and electrically insulating metal oxides such as alumina, fibrous alumina, zinc oxide, magnesium oxide, beryllium oxide, and titanium oxide. And electrically insulating carbon components such as diamond and fullerene, plasticizers, pressure-sensitive adhesives, reinforcing agents, colorants, heat resistance improvers, viscosity modifiers, dispersion stabilizers, and solvents.
Further, in the resin composition containing the hexagonal boron nitride powder of the present invention, as long as the effect is not impaired, in addition to those exemplified as the nitride particles and the electrically insulating metal oxide, An inorganic filler such as aluminum or magnesium hydroxide, a surface treatment agent such as a silane coupling agent that improves the interfacial adhesive strength between the inorganic filler and the matrix resin, a reducing agent, and the like may be added.
　本発明の樹脂組成物は、熱伝導性シート、熱伝導性ゲル、熱伝導性グリース、熱伝導性接着剤、フェーズチェンジシート等の熱伝導性部材に用いることができる。その結果、ＭＰＵやパワートランジスタ、トランス等の発熱性電子部品からの熱を放熱フィンや放熱ファン等の放熱部品に効率よく伝達することができる。
　上記熱伝導性部材のなかでも、熱伝導性シートとして樹脂シートに用いることが好ましい。前記樹脂組成物を樹脂シートに用いることにより、熱伝導性及び電気絶縁性の向上の観点から、特にその効果を発揮できる。 The resin composition of the present invention can be used for a heat conductive member such as a heat conductive sheet, a heat conductive gel, a heat conductive grease, a heat conductive adhesive, and a phase change sheet. As a result, heat from heat-generating electronic components such as MPUs, power transistors, and transformers can be efficiently transferred to heat-dissipating components such as heat-dissipating fins and heat-dissipating fans.
Among the heat conductive members, it is preferable to use the resin sheet as a heat conductive sheet. By using the resin composition for the resin sheet, the effect can be exhibited particularly from the viewpoint of improving thermal conductivity and electrical insulation.
［樹脂シート］
　本発明の樹脂シートは、前記樹脂組成物又はその硬化物からなるものであり、前記樹脂組成物をシートに成形してなる。前記樹脂組成物が硬化性の場合には、シートへ成形した後、硬化させてなる。
　本発明の樹脂シートは、前記樹脂組成物を用い、例えば下記のようにして作製することができる。
　まず、本発明のｈＢＮ粉末を、適当な溶媒中に分散させてなる、濃度５０～８０質量％程度のｈＢＮ粉末の懸濁液を調製する。
　次いで、この懸濁液に、有機マトリックスを、当該ｈＢＮ粉末及び当該有機マトリックスの総量中に当該ｈＢＮ粉末が１０～９０体積％の割合で含まれるように加える。ｈＢＮ粉末の比重と有機マトリックスとして使用される樹脂の比重により所望の体積％となるように、ｈＢＮ粉末及び樹脂の重量を設定し、それぞれを秤量後混合し、樹脂組成物を調製する。
　また、樹脂組成物の調製方法としては下記のようにして調製することもできる。
　まず、樹脂、並びに必要に応じて硬化剤及び溶媒を混合して有機マトリックスを調製する。
　次いで、この有機マトリックスに前記ｈＢＮ粉末を、当該ｈＢＮ粉末及び当該有機マトリックスの総量中に当該ｈＢＮ粉末が１０～９０体積％の割合で含まれるように加える。ｈＢＮ粉末の比重と有機マトリックスとして使用される樹脂の比重により所望の体積％となるように、ｈＢＮ粉末及び樹脂の重量を設定し、それぞれを秤量後混合し、樹脂組成物を調製する。
　有機マトリックスの主成分として、硬化性エポキシ樹脂を用いる場合には、この硬化性エポキシ樹脂と、エポキシ樹脂用硬化剤と、必要に応じて用いられるエポキシ樹脂用硬化促進剤との混合物が有機マトリックスとなる。
　また、有機マトリックスの主成分として、硬化性シリコーン樹脂を用いる場合には、付加反応型シリコーン樹脂と、シリコーン系架橋剤と、硬化触媒との混合物が有機マトリックスとなる。 [Resin sheet]
The resin sheet of the present invention comprises the resin composition or a cured product thereof, and is formed by molding the resin composition into a sheet. When the resin composition is curable, it is formed into a sheet and then cured.
The resin sheet of the present invention can be produced using the resin composition, for example, as follows.
First, a suspension of hBN powder having a concentration of about 50 to 80% by mass is prepared by dispersing the hBN powder of the present invention in a suitable solvent.
Next, an organic matrix is added to the suspension so that the hBN powder is contained in a proportion of 10 to 90% by volume in the total amount of the hBN powder and the organic matrix. The weights of hBN powder and resin are set so as to be a desired volume% based on the specific gravity of hBN powder and the specific gravity of the resin used as the organic matrix, and each is weighed and mixed to prepare a resin composition.
Moreover, as a preparation method of a resin composition, it can also prepare as follows.
First, an organic matrix is prepared by mixing a resin and, if necessary, a curing agent and a solvent.
Next, the hBN powder is added to the organic matrix so that the hBN powder is contained in a ratio of 10 to 90% by volume in the total amount of the hBN powder and the organic matrix. The weights of hBN powder and resin are set so as to be a desired volume% based on the specific gravity of hBN powder and the specific gravity of the resin used as the organic matrix, and each is weighed and mixed to prepare a resin composition.
When a curable epoxy resin is used as the main component of the organic matrix, a mixture of the curable epoxy resin, a curing agent for the epoxy resin, and a curing accelerator for the epoxy resin that is used as required is an organic matrix. Become.
When a curable silicone resin is used as the main component of the organic matrix, a mixture of an addition reaction type silicone resin, a silicone-based crosslinking agent, and a curing catalyst becomes an organic matrix.
　樹脂組成物は、通常のコーティング機等で、離型層付き樹脂フィルム等の離型性フィルム等の基材上に塗工され、前記樹脂組成物が溶媒を含む場合には遠赤外線輻射ヒーター、温風吹付け等によって溶媒を乾燥することにより、シート化される。
　離型層としては、メラミン樹脂等が用いられる。また、樹脂フィルムとしては、ポリエチレンテレフタレート等のポリエステル樹脂等が用いられる。
　樹脂組成物における有機マトリックスが、硬化性エポキシ樹脂や、硬化性シリコーン樹脂のような硬化性有機マトリックスでない場合には、前記のシート化された樹脂シートがそのまま本発明の樹脂シートとなる。 The resin composition is coated on a substrate such as a releasable film such as a resin film with a release layer by a normal coating machine or the like, and when the resin composition contains a solvent, a far infrared radiation heater, It is made into a sheet by drying the solvent by hot air spraying or the like.
As the release layer, a melamine resin or the like is used. As the resin film, a polyester resin such as polyethylene terephthalate is used.
When the organic matrix in the resin composition is not a curable organic matrix such as a curable epoxy resin or a curable silicone resin, the above-described resin sheet is directly used as the resin sheet of the present invention.
　さらに、有機マトリックスが硬化性マトリックスである場合には、前記で得られた基材上に形成された樹脂シートを、必要に応じて当該基材の樹脂組成物が塗工されていない面側から当該基材を介して加圧し、さらに加熱処理して硬化させることにより、本発明の樹脂シートが得られる。加圧条件は、好ましくは１５～２０ＭＰａ、より好ましくは１７～１９ＭＰａである。また、加熱条件は、好ましくは８０～２００℃、より好ましくは１００～１５０℃である。なお、離型性フィルム等の基材は、通常、最終的に剥離、又は除去される。 Further, when the organic matrix is a curable matrix, the resin sheet formed on the base material obtained above is optionally applied from the surface side where the resin composition of the base material is not coated. The resin sheet of the present invention is obtained by applying pressure through the base material, and further heat-treating and curing. The pressure condition is preferably 15 to 20 MPa, more preferably 17 to 19 MPa. The heating conditions are preferably 80 to 200 ° C., more preferably 100 to 150 ° C. In addition, normally, substrates, such as a mold release film, are finally peeled off or removed.
　このようにして得られる本発明の樹脂シートの膜厚は、成形性の観点から、当該樹脂シートが用いられる電子部品等の軽薄化の観点から、５０～１５０μｍの範囲であることが好ましく、７０～１４０μｍの範囲であることがより好ましく、１００～１３０μｍの範囲であることが更に好ましい。
　また、本発明の樹脂シートは、好ましくは厚み方向の熱伝導率が３Ｗ／ｍ・Ｋ以上、より好ましくは７Ｗ／ｍ・Ｋ以上、更に好ましくは９Ｗ／ｍ・Ｋ以上、より更に好ましくは１０Ｗ／ｍ・Ｋ以上、より更に好ましくは１４Ｗ／ｍ・Ｋ以上、より更に好ましくは１８Ｗ／ｍ・Ｋ以上である。
　本発明の樹脂シートは、電気絶縁性の観点から、好ましくは比重率が９０～１００％、より好ましくは９５～１００％、更に好ましくは９８～１００％、より更に好ましくは１００％である。
　本発明の樹脂シートは、その片面又は両面及びシート内に、作業性向上や補強目的でシート状、繊維状、網目状の部材を積層したり、埋没させたりして用いてもよい。 The film thickness of the resin sheet of the present invention thus obtained is preferably in the range of 50 to 150 μm from the viewpoint of moldability, from the viewpoint of reducing the weight of electronic parts and the like in which the resin sheet is used, and 70 It is more preferably in the range of ˜140 μm, still more preferably in the range of 100 to 130 μm.
The resin sheet of the present invention preferably has a thermal conductivity in the thickness direction of 3 W / m · K or more, more preferably 7 W / m · K or more, still more preferably 9 W / m · K or more, and even more preferably 10 W. / M · K or more, more preferably 14 W / m · K or more, and still more preferably 18 W / m · K or more.
From the viewpoint of electrical insulation, the resin sheet of the present invention preferably has a specific gravity ratio of 90 to 100%, more preferably 95 to 100%, still more preferably 98 to 100%, and still more preferably 100%.
The resin sheet of the present invention may be used by laminating or burying a sheet-like, fiber-like, or mesh-like member on one or both sides and within the sheet for the purpose of improving workability or reinforcing.
　このように得られた樹脂シートは、離型性フィルムから剥がし、あるいは、離型性フィルムを保護フィルムとした状態で、樹脂シートとしての使用に供するための製品の形とすることができる。
　また、本発明の樹脂シートは、粘着性層を樹脂シートの上面又は下面にさらに設けた構成としてもよく、これにより、製品使用時の利便性が高まる。 The resin sheet thus obtained can be peeled off from the releasable film or can be in the form of a product for use as a resin sheet in a state where the releasable film is a protective film.
Moreover, the resin sheet of this invention is good also as a structure which further provided the adhesive layer in the upper surface or lower surface of the resin sheet, and, thereby, the convenience at the time of product use increases.
　本発明の樹脂シートは、例えばＭＰＵやパワートランジスタ、トランス等の発熱性電子部品からの熱を放熱フィンや放熱ファン等の放熱部品に伝熱させるために使用され、発熱性電子部品と放熱部品の間に挟み込まれて使用される。これによって、発熱性電子部品と放熱部品間の伝熱が良好となり、発熱性電子部品の誤作動を著しく軽減させることができる。 The resin sheet of the present invention is used to transfer heat from heat-generating electronic components such as MPUs, power transistors, and transformers to heat-radiating components such as heat-dissipating fins and heat-dissipating fans. Used in between. As a result, heat transfer between the heat-generating electronic component and the heat-dissipating component is improved, and malfunction of the heat-generating electronic component can be significantly reduced.
　以下、実施例及び比較例を挙げてさらに具体的に本発明を説明するが、本発明はこれらの例によってなんら限定されるものではない。 Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.
［実施例１］
（１）粗製ｈＢＮ粉末の作製
　ホウ酸４ｇ、メラミン２ｇ及び水１ｇを加えたものを撹拌混合し、金型内に入れて加圧し、密度０．７ｇ／ｃｍ３の成形体を得た。この成形体を乾燥機中にて３００℃で１００分間乾燥させたものをＮＨ３ガス雰囲気下１１００℃で１２０分間仮焼きした。この得られた仮焼物（粗製ｈＢＮ）を粉砕して粗製ｈＢＮ粉末（酸化ホウ素の含有量３５質量％）を得た。 [Example 1]
(1) Production of crude hBN powder A mixture of 4 g boric acid, 2 g melamine and 1 g water was stirred and mixed, placed in a mold and pressed to obtain a molded body having a density of 0.7 g / cm 3 . This molded body was dried in a dryer at 300 ° C. for 100 minutes, and calcined at 1100 ° C. for 120 minutes in an NH 3 gas atmosphere. The obtained calcined product (crude hBN) was pulverized to obtain crude hBN powder (boron oxide content of 35% by mass).
（２）ｈＢＮ粉末の作製
　上記粗製ｈＢＮ粉末１００質量部に対して、炭素源として昭和電工（株）製の人造黒鉛微粉「ＵＦ－Ｇ３０」を１０質量部、Ｃａ化合物として炭酸カルシウム０．４質量部及びＰＶＡ水溶液（濃度２．５質量％）を１０質量部加えることにより、粗製ｈＢＮ粉末１００質量部に対する炭素源の炭素換算含有量が１０質量部、Ｃａ化合物の含有量が０．４質量部である混合物を得た。この混合物をミキサーで撹拌混合した後、金型内に入れて、加圧し、密度１．２ｇ／ｃｍ３の成形体を得た。この成形体を乾燥機中にて３００℃で６時間乾燥させて乾燥物を得た。この乾燥物を、高周波炉において、窒素ガス雰囲気下、１７５０℃～２２００℃で合計６時間焼成することでｈＢＮ焼成物を得た。
　得られたｈＢＮ焼成物をジョークラッシャー及びピンミルを用いて粉砕後、乾式振動篩装置［晃栄産業（株）製、商品名「佐藤式振動ふるい機」］を用いて、篩分け時間６０分の条件にて目開き１０６μｍの篩及び目開き４５μｍの篩を用いて、４５～１０６μｍのｈＢＮ粉末（Ａ）と４５μｍ篩下のｈＢＮ粉末（Ｂ）に分級した。上記のように得られた４５～１０６μｍのｈＢＮ粉末（Ａ）と４５μｍ篩下のｈＢＮ粉末（Ｂ）について、後述する減圧吸引型篩分け機（エアージェットシーブ［アルパイン社製、機種名「Ａ２００ＬＳ」］）を用いて粉末含有率を測定したところ、４５～１０６μｍのｈＢＮ粉末（Ａ）の目開き１０６μｍ篩上の粉末含有率は１５質量％であり、４５μｍ篩下のｈＢＮ粉末（Ｂ）の目開き４５μｍ篩上の粉末含有率は９質量％であった。４５～１０６μｍのｈＢＮ粉末（Ａ）と４５μｍ篩下のｈＢＮ粉末（Ｂ）を表１に示す顆粒率となるように混合し、実施例１に係るｈＢＮ粉末を得た。
　なお、顆粒率は下記式により、４５～１０６μｍのｈＢＮ粉末（Ａ）と４５μｍ篩下のｈＢＮ粉末（Ｂ）の合計量に対するｈＢＮ粉末（Ａ）の割合で表される。
　顆粒率（質量％）＝［（Ａ）／〔（Ａ）＋（Ｂ）〕］
　上記のように得られた実施例１に係るｈＢＮ粉末を、さらに後述する減圧吸引型篩分け機（エアージェットシーブ［アルパイン社製、機種名「Ａ２００ＬＳ」］）を用いて、目開き１０６μｍ篩上下に篩分けしたところ、ｈＢＮ粉末の目開き１０６μｍ篩上の粉末含有率は６質量％であり、目開き１０６μｍ篩下の粉末含有率は９４質量％であった。また、前記減圧吸引型篩分け機を用いて、目開き４５μｍ篩上下に篩分けしたところ、目開き４５μｍ篩下の粉末含有率は３９質量％であった。
　このｈＢＮ粉末をＳＥＭで観察したところ、図２に示されるように一次粒子がランダムな方向を向いたｈＢＮ凝集体を含むことが確認された。なお、図１は、図２中に存在するｈＢＮ凝集体の模式図である。 (2) Production of hBN powder 10 parts by mass of artificial graphite fine powder “UF-G30” manufactured by Showa Denko KK as a carbon source and 0.4 parts by mass of calcium carbonate as a Ca compound with respect to 100 parts by mass of the crude hBN powder. And 10 parts by weight of PVA aqueous solution (concentration 2.5% by weight), the carbon equivalent content of the carbon source to 100 parts by weight of the crude hBN powder is 10 parts by weight, and the content of the Ca compound is 0.4 parts by weight A mixture was obtained. The mixture was stirred and mixed with a mixer, then placed in a mold and pressed to obtain a molded body having a density of 1.2 g / cm 3 . The molded body was dried in a dryer at 300 ° C. for 6 hours to obtain a dried product. This dried product was fired in a high-frequency furnace at 1750 ° C. to 2200 ° C. for 6 hours in a nitrogen gas atmosphere to obtain a fired hBN product.
The obtained hBN fired product is pulverized using a jaw crusher and a pin mill, and then sieving time is 60 minutes using a dry vibration sieving machine [manufactured by Koei Sangyo Co., Ltd., trade name “Sato Vibrating Sieve”]. Using a sieve having an aperture of 106 μm and a sieve having an aperture of 45 μm under the conditions, it was classified into 45 to 106 μm hBN powder (A) and hBN powder (B) under a 45 μm sieve. For the 45 to 106 μm hBN powder (A) obtained as described above and the hBN powder (B) under the 45 μm sieve, a vacuum suction type sieving machine (air jet sheave [manufactured by Alpine, model name “A200LS”) described later is used. ]), The powder content of the 45-106 μm hBN powder (A) on the 106 μm sieve is 15% by mass, and the hBN powder (B) mesh under the 45 μm sieve is 15% by mass. The powder content on the 45 μm sieve was 9% by mass. The hBN powder (A) of 45 to 106 μm and the hBN powder (B) under the 45 μm sieve were mixed so as to have the granule ratio shown in Table 1, and the hBN powder according to Example 1 was obtained.
The granule ratio is expressed by the ratio of the hBN powder (A) to the total amount of the hBN powder (A) of 45 to 106 μm and the hBN powder (B) under the 45 μm sieve according to the following formula.
Granule rate (% by mass) = [(A) / [(A) + (B)]]
The hBN powder according to Example 1 obtained as described above was further added to the upper and lower sides of a 106 μm sieve using a vacuum suction type sieving machine (air jet sieve [manufactured by Alpine, model name “A200LS”]) described later. As a result, the powder content of the hBN powder on the 106 μm sieve was 6% by mass, and the powder content under the 106 μm sieve was 94% by mass. Further, when the above-mentioned vacuum suction type sieving machine was used for sieving above and below the sieve with an opening of 45 μm, the powder content under the sieve with an opening of 45 μm was 39% by mass.
When this hBN powder was observed with an SEM, it was confirmed that the primary particles contained hBN aggregates oriented in random directions as shown in FIG. FIG. 1 is a schematic diagram of hBN aggregates present in FIG.
（３）樹脂組成物の調製
　有機マトリックスとして、液状硬化性エポキシ樹脂［ジャパンエポキシレジン（株）製、商品名「ｊＥＲ８２８」、ビスフェノールＡ型、エポキシ当量１８４－１９４ｇ／ｅｑ］１００質量部と、硬化剤としてのイミダゾール［四国化成工業（株）製、商品名「２Ｅ４ＭＺ－ＣＮ」］５質量部との併用物を用いた。
　まず、前記の有機マトリックス１００質量部に対して、前記のｈＢＮ粉末を当該ｈＢＮ粉末及び当該有機マトリックスの総量中におけるｈＢＮ粉末含有量が６０体積％となるように加え、倉敷紡績（株）製、マゼルスターを用いて撹拌混合し樹脂組成物を調製した。
　なお、前記ｈＢＮ粉末の体積基準の含有量（体積％）は、ｈＢＮ粉末の比重（２．２７）及び有機マトリックスとして用いられる液状硬化性エポキシ樹脂の比重（１．１７）から求めた。 (3) Preparation of resin composition As organic matrix, liquid curable epoxy resin [manufactured by Japan Epoxy Resin Co., Ltd., trade name “jER828”, bisphenol A type, epoxy equivalent 184-194 g / eq] 100 parts by mass, cured A combination product with 5 parts by mass of imidazole [manufactured by Shikoku Kasei Kogyo Co., Ltd., trade name “2E4MZ-CN”] as an agent was used.
First, with respect to 100 parts by mass of the organic matrix, the hBN powder is added so that the hBN powder content in the total amount of the hBN powder and the organic matrix is 60% by volume, manufactured by Kurashiki Boseki Co., Ltd. A resin composition was prepared by stirring and mixing using a Mazerustar.
The volume-based content (volume%) of the hBN powder was determined from the specific gravity (2.27) of the hBN powder and the specific gravity (1.17) of the liquid curable epoxy resin used as the organic matrix.
（４）樹脂シートの作製
　横１０．５ｃｍ、縦１３ｃｍに切り取った離型フィルム上に、硬化膜厚が５００μｍ以下となるように金型を用いて成形したのち、金型ごと離型フィルムに挟み、離型フィルムを介して、１２０℃、１８ＭＰａの条件で１０分間圧着することにより、樹脂組成物を硬化させ、樹脂シートを作製した。 (4) Production of resin sheet After forming using a mold so that the cured film thickness is 500 μm or less on a release film cut to a width of 10.5 cm and a length of 13 cm, the entire mold is sandwiched between release films. The resin composition was cured by pressure bonding for 10 minutes under the conditions of 120 ° C. and 18 MPa through a release film to prepare a resin sheet.
［実施例２］
　実施例１の（２）において、上記粗製ｈＢＮ粉末１００質量部に対して加える人造黒鉛微粉の配合量を５質量部にしたこと以外は実施例１と同様にして、ｈＢＮ粉末、樹脂組成物及び樹脂シートを作製した。 [Example 2]
In Example 1 (2), the hBN powder, the resin composition, and the resin composition were the same as in Example 1 except that the amount of the artificial graphite fine powder added to 100 parts by mass of the crude hBN powder was 5 parts by mass. A resin sheet was produced.
［実施例３］
　実施例１の（２）において、上記顆粒率が８０質量％となるように４５～１０６μｍのｈＢＮ粉末（Ａ）と４５μｍ篩下のｈＢＮ粉末（Ｂ）を混合したこと以外は実施例１と同様にして、ｈＢＮ粉末、樹脂組成物及び樹脂シートを作製した。 [Example 3]
Example 1 (2) is the same as Example 1 except that the hBN powder (A) of 45 to 106 μm and the hBN powder (B) under a 45 μm sieve are mixed so that the granule ratio is 80% by mass. Thus, hBN powder, a resin composition, and a resin sheet were produced.
［実施例４］
　実施例１の（２）において、上記粗製ｈＢＮ粉末１００質量部に対して加える人造黒鉛微粉の配合量を５質量部にしたこと、及び顆粒率が８０質量％となるように４５～１０６μｍのｈＢＮ粉末（Ａ）と４５μｍ篩下のｈＢＮ粉末（Ｂ）を混合したこと以外は実施例１と同様にして、ｈＢＮ粉末、樹脂組成物及び樹脂シートを作製した。 [Example 4]
In Example 1 (2), the blending amount of the artificial graphite fine powder added to 100 parts by mass of the crude hBN powder was 5 parts by mass, and hBN of 45 to 106 μm so that the granule ratio was 80% by mass. An hBN powder, a resin composition, and a resin sheet were prepared in the same manner as in Example 1 except that the powder (A) and the hBN powder (B) under 45 μm sieve were mixed.
［実施例５］
　実施例１の（２）において、上記粗製ｈＢＮ粉末１００質量部に対して加える人造黒鉛微粉の配合量を８質量部（炭素換算で８質量部）にし、さらに炭化ホウ素（理研コランダム（株）製）１０質量部（炭素換算で２．２質量部）を添加し、粗製ｈＢＮ粉末１００質量部に対する炭素源の炭素換算含有量が１０．２質量部となるように混合し、顆粒率が８０質量％となるように４５～１０６μｍのｈＢＮ粉末（Ａ）と４５μｍ篩下のｈＢＮ粉末（Ｂ）を混合したこと以外は実施例１と同様にして、ｈＢＮ粉末、樹脂組成物及び樹脂シートを作製した。 [Example 5]
In Example 1 (2), the amount of artificial graphite fine powder added to 100 parts by mass of the crude hBN powder was 8 parts by mass (8 parts by mass in terms of carbon), and boron carbide (manufactured by Riken Corundum Co., Ltd.). ) 10 parts by mass (2.2 parts by mass in terms of carbon) is added and mixed so that the carbon equivalent content of the carbon source with respect to 100 parts by mass of the crude hBN powder is 10.2 parts by mass, and the granule ratio is 80 parts by mass. The hBN powder, the resin composition, and the resin sheet were prepared in the same manner as in Example 1 except that the hBN powder (A) of 45 to 106 μm and the hBN powder (B) under the 45 μm sieve were mixed so as to be in the range of .
［比較例１］
　実施例１の（２）において、上記粗製ｈＢＮ粉末１００質量部に対してＣａ化合物（炭酸カルシウム）を添加せずに、また、顆粒率が６０質量％となるように４５～１０６μｍのｈＢＮ粉末（Ａ）と４５μｍ篩下のｈＢＮ粉末（Ｂ）を混合したこと以外は実施例１と同様にして、ｈＢＮ粉末、樹脂組成物及び樹脂シートを作製した。 [Comparative Example 1]
In Example 1 (2), without adding a Ca compound (calcium carbonate) to 100 parts by mass of the crude hBN powder, and with a hBN powder of 45 to 106 μm so that the granule ratio is 60% by mass ( An hBN powder, a resin composition, and a resin sheet were produced in the same manner as in Example 1 except that A) and hBN powder (B) under a 45 μm sieve were mixed.
［比較例２］
　市販品Ａを前記乾式振動篩装置と目開き１０６μｍの篩及び目開き４５μｍの篩を用いて、篩分け時間６０分の条件にて、４５～１０６μｍのｈＢＮ粉末（Ａ）と４５μｍ篩下のｈＢＮ粉末（Ｂ）に分級した。この４５～１０６μｍのｈＢＮ粉末（Ａ）（目開き１０６μｍ篩上の粉末含有率は２質量％）と４５μｍ篩下のｈＢＮ粉末（Ｂ）（目開き４５μｍ篩上の粉末含有率は４質量％）を顆粒率が６０質量％となるように混合したこと以外は実施例１と同様にして、ｈＢＮ粉末、樹脂組成物及び樹脂シートを作製した。 [Comparative Example 2]
Commercially available product A using the dry vibration sieve device, a sieve with an opening of 106 μm and a sieve with an opening of 45 μm, and a sieving time of 60 minutes, 45 to 106 μm of hBN powder (A) and hBN under the sieve of 45 μm The powder was classified into powder (B). This 45 to 106 μm hBN powder (A) (powder content on sieve 106 μm sieve is 2 mass%) and hBN powder (B) under 45 μm sieve (powder content on sieve 45 μm sieve is 4 mass%) HBN powder, a resin composition, and a resin sheet were produced in the same manner as in Example 1 except that was mixed so that the granule ratio was 60% by mass.
［比較例３］
　実施例１の（２）において、上記粗製ｈＢＮ粉末１００質量部に対してＣａ化合物（炭酸カルシウム）を添加せずに、また、顆粒率が８０質量％となるように４５～１０６μｍのｈＢＮ粉末（Ａ）と４５μｍ篩下のｈＢＮ粉末（Ｂ）を混合したこと以外は実施例１と同様にして、ｈＢＮ粉末、樹脂組成物及び樹脂シートを作製した。 [Comparative Example 3]
In Example 1 (2), without adding a Ca compound (calcium carbonate) to 100 parts by mass of the crude hBN powder, and 45 to 106 μm of hBN powder (granularity is 80% by mass) An hBN powder, a resin composition, and a resin sheet were produced in the same manner as in Example 1 except that A) and hBN powder (B) under a 45 μm sieve were mixed.
［比較例４］
　比較例２で用いた市販品Ａの４５～１０６μｍのｈＢＮ粉末（Ａ）（目開き１０６μｍ篩上の粉末含有率は２質量％）と４５μｍ篩下のｈＢＮ粉末（Ｂ）（目開き４５μｍ篩上の粉末含有率は４質量％）を顆粒率が８０質量％となるように混合したこと以外は実施例１と同様にして、ｈＢＮ粉末、樹脂組成物及び樹脂シートを作製した。 [Comparative Example 4]
45-106 μm hBN powder (A) of commercial product A used in Comparative Example 2 (powder content on sieve 106 μm sieve is 2 mass%) and hBN powder (B) under 45 μm sieve (on sieve 45 μm sieve) The hBN powder, the resin composition, and the resin sheet were prepared in the same manner as in Example 1 except that the powder content was 4% by mass) and the granule rate was 80% by mass.
［比較例５］
　実施例１の（２）において、上記粗製ｈＢＮ粉末１００質量部に対して黒鉛微粉及びＣａ化合物（炭酸カルシウム）を炭化ホウ素（理研コランダム（株）製）３０質量部（炭素換算で６．６質量部）に変更し、顆粒率が８０質量％となるように４５～１０６μｍのｈＢＮ粉末（Ａ）と４５μｍ篩下のｈＢＮ粉末（Ｂ）を混合したこと以外は実施例１と同様にして、ｈＢＮ粉末、樹脂組成物及び樹脂シートを作製した。 [Comparative Example 5]
In Example 1 (2), 30 parts by mass (6.6 masses in terms of carbon) of boron carbide (manufactured by Riken Corundum Co., Ltd.) of graphite fine powder and Ca compound (calcium carbonate) with respect to 100 parts by mass of the crude hBN powder. HBN powder (A) mixed with 45 to 106 μm hBN powder (A) and hBN powder (B) under 45 μm sieve so that the granule ratio is 80% by mass. Powder, a resin composition, and a resin sheet were produced.
［評価］
　得られた粗製ｈＢＮ粉末、ｈＢＮ粉末、樹脂組成物及び樹脂シートについて、次の評価を行った。 [Evaluation]
The following evaluation was performed about the obtained crude hBN powder, hBN powder, the resin composition, and the resin sheet.
（粗製ｈＢＮ粉末中における、酸化ホウ素の含有量）
　粗製ｈＢＮ粉末は、当該粉末の表面の酸化ホウ素（以下、「Ｂ２Ｏ３」ともいう。）と内部のＢ－Ｏ－Ｎ結合構造により構成されていると考えられる。粗製ｈＢＮのＢ－Ｏ－Ｎ結合構造を構成する内在酸素は、粗製ｈＢＮ粉末からｈＢＮ粉末を製造する際の焼成工程における高温熱処理により反応が進み、徐々に表面にＢ２Ｏ３として浸み出してくる。そこで、粗製ｈＢＮ粉末からｈＢＮ粉末を製造する際の炭素源の炭素と反応するＢ２Ｏ３の粗製ｈＢＮ粉末中の含有量は、表面のＢ２Ｏ３量と内在酸素のＢ２Ｏ３換算量との総量として得た。
　表面のＢ２Ｏ３量は、酸処理により粗製ｈＢＮ粉末表面のＢ２Ｏ３を溶出させ、酸処理により溶解したＢ２Ｏ３量を測定し、内在酸素のＢ２Ｏ３換算量は、酸処理後の残渣の酸素分析を行い、残渣中の酸素量を測定し、Ｂ２Ｏ３換算量として得た。
　具体的には、以下のとおりである。粗製ｈＢＮ粉末を０．１Ｎ希硫酸溶液で酸処理した。
　この酸処理による粗製ｈＢＮ粉末中のＢＮの加水分解により発生したアンモニア量を分光光度計［日立製作所（株）製、機種名「Ｕ－１１００」］を用いて測定し、このアンモニア量から、ＢＮの加水分解により生じたＢ元素量を算出した。また、酸処理後の酸溶液中に存在するＢ元素の総量（ＢＮの加水分解に起因するＢ元素量とＢ２Ｏ３の溶解に起因するＢ元素量の総量）をＩＣＰ分析装置［SII Nano Technology Inc.社製、機種名「ＳＰＳ３５００」］により測定した。この酸処理後の酸溶液中に存在するＢ元素の総量と、上記のアンモニア量から換算したＢＮの加水分解に起因するＢ元素量とから、酸処理により溶解したＢ２Ｏ３量を算出した。
　また、残渣中の酸素量を酸素測定装置［ＬＥＣＯジャパン合同会社製、機種名「ＴＣ－６００」］を用いて測定し、この測定値から、Ｂ２Ｏ３換算量を算出した。
　このようにして求められた、酸処理により溶解したＢ２Ｏ３量及びＢ２Ｏ３換算量の総量と、酸処理に供した粗製ｈＢＮ粉末の総量とから、粗製ｈＢＮ粉末中における酸化ホウ素の含有量（Ｂ２Ｏ３含有量）を算出した。 (Boron oxide content in crude hBN powder)
The crude hBN powder is considered to be composed of boron oxide (hereinafter also referred to as “B 2 O 3 ”) on the surface of the powder and an internal B—O—N bond structure. The internal oxygen constituting the BOH bond structure of the crude hBN is reacted by a high-temperature heat treatment in the firing step when producing hBN powder from the crude hBN powder, and gradually leaches out as B 2 O 3 on the surface. Come. Therefore, the content in the crude hBN powder B 2 O 3 to react with the carbon of the carbon source in the production of hBN powder from the crude hBN powders, the surface of the amount of B 2 O 3 and endogenous oxygen terms of B 2 O 3 Obtained as a total amount with the amount.
Amount of B 2 O 3 surfaces, the B 2 O 3 of crude hBN powder surface was eluted by acid treatment, by measuring the amount of B 2 O 3 were dissolved by an acid treatment, B 2 O 3 in terms of the amount of endogenous oxygen, The oxygen analysis of the residue after acid treatment was performed, the amount of oxygen in the residue was measured, and obtained as a B 2 O 3 equivalent amount.
Specifically, it is as follows. Crude hBN powder was acid treated with 0.1N dilute sulfuric acid solution.
The amount of ammonia generated by hydrolysis of BN in the crude hBN powder by this acid treatment was measured using a spectrophotometer [manufactured by Hitachi, Ltd., model name “U-1100”]. The amount of B element produced by hydrolysis of was calculated. Further, the total amount of B element present in the acid solution after the acid treatment (the total amount of B element due to hydrolysis of BN and the amount of B element due to dissolution of B 2 O 3 ) is calculated using an ICP analyzer [SII Nano Technology Inc., model name “SPS3500”]. The amount of B 2 O 3 dissolved by the acid treatment was calculated from the total amount of the B element present in the acid solution after the acid treatment and the amount of the B element resulting from the hydrolysis of BN converted from the above ammonia amount. .
Further, the amount of oxygen in the residue was measured using an oxygen measuring device [manufactured by LECO Japan GK, model name “TC-600”], and an amount equivalent to B 2 O 3 was calculated from the measured value.
There was thus obtained, from the total amount B 2 O 3 were dissolved by acid treatment and B 2 O 3 equivalent amount, the total amount of crude hBN powder subjected to the acid treatment, the boron oxide in the crude hBN powder The content (B 2 O 3 content) was calculated.
（ｈＢＮ粉末の一次粒子径）
　実施例及び比較例で得られたｈＢＮ粉末のＳＥＭ写真を撮影し、ＳＥＭ写真内から選ばれた任意の１００個のｈＢＮ一次粒子について、長径の長さを測定し、長径の数平均値をｈＢＮ粉末の一次粒子径とした。 (Primary particle size of hBN powder)
SEM photographs of the hBN powders obtained in the examples and comparative examples were taken, the length of the major axis was measured for any 100 hBN primary particles selected from the SEM photograph, and the number average value of the major axis was determined as hBN. The primary particle size of the powder was used.
（ｈＢＮ粉末の一次粒子の比（長径／厚み））
　実施例及び比較例で得られたｈＢＮ粉末のＳＥＭ写真を撮影し、ＳＥＭ写真内から選ばれた任意の１００個のｈＢＮ一次粒子について、長径及び厚みを測定し、長径の数平均値と厚みの数平均値から、一次粒子の長径と厚みの比（長径／厚み）を算出した。 (Ratio of primary particles of hBN powder (major axis / thickness))
SEM photographs of the hBN powders obtained in the examples and comparative examples were taken, the major axis and thickness were measured for any 100 hBN primary particles selected from the SEM photograph, and the number average value and thickness of the major axis were measured. From the number average value, the ratio between the major axis and the thickness (major axis / thickness) of the primary particles was calculated.
（ＢＥＴ比表面積）
　実施例及び比較例で得られたｈＢＮ粉末について、全自動ＢＥＴ比表面積測定装置［ユアサアイオニクス（株）製、機種名「マルチソーブ１６」］を用い、比表面積を測定した。 (BET specific surface area)
About the hBN powder obtained by the Example and the comparative example, the specific surface area was measured using the fully automatic BET specific surface area measuring apparatus [The Yuasa Ionics Co., Ltd. make, model name "Multisorb 16"].
（ｈＢＮ粉末の５０％体積累積粒径（Ｄ５０））
　粒度分布計［日機装（株）製、機種名「マイクロトラックＭＴ３３００ＥＸＩＩ」］を用いてｈＢＮ粉末体積規準の５０％体積累積粒径（Ｄ５０）を測定した。
　粒度分布測定は実施例及び比較例で得られたｈＢＮ粉末０．０６ｇを純水５０ｇに３分間超音波処理することで調製した分散液を用いて行った。超音波処理は出力１５０Ｗ、発振周波数１９．５ｋＨｚの条件で超音波処理装置［（株）日本精機製作所製、機種名「超音波ホモジナイザーＵＳ－１５０Ｖ」］を用いて行った。 (50% volume cumulative particle size of hBN powder (D 50 ))
The 50% volume cumulative particle size (D 50 ) of the hBN powder volume standard was measured using a particle size distribution meter [manufactured by Nikkiso Co., Ltd., model name “Microtrack MT3300EXII”].
The particle size distribution was measured using a dispersion prepared by ultrasonically treating 0.06 g of hBN powder obtained in Examples and Comparative Examples in 50 g of pure water for 3 minutes. The ultrasonic treatment was performed using an ultrasonic treatment apparatus [manufactured by Nippon Seiki Seisakusho, model name “ultrasonic homogenizer US-150V”] under the conditions of an output of 150 W and an oscillation frequency of 19.5 kHz.
（目開き１０６μｍ篩下及び目開き１０６μｍ篩上のｈＢＮ粉末含有率）
　径が２０ｃｍ、高さ４．５ｃｍの目開き１０６μｍの篩を準備し、実施例及び比較例で得られたｈＢＮ粉末を１０ｇ乗せ、減圧吸引型篩分け機［アルパイン社製、機種名「エアージェットシーブＡ２００ＬＳ」］にセットした。篩の下部から粉末を差圧１ｋＰａで吸引し、篩分け時間を３６０秒間として、篩分けした。篩の下及び篩の上に残ったｈＢＮ粉末の重量を測定し、目開き１０６μｍ篩下のｈＢＮ粉末含有率（目開き１０６μｍ篩下粉末含有率）及び目開き１０６μｍ篩上のｈＢＮ粉末含有率（目開き１０６μｍ篩上粉末含有率）を算出した。
　なお、実施例及び比較例で得られたｈＢＮ焼成物を粉砕後、目開き１０６μｍの前記乾式振動篩装置を用いて、篩分け時間６０分の条件にて分級した際には、ｈＢＮ粉末は目開き１０６μｍの篩を全て通過した。 (Content of hBN powder on sieve 106 μm and sieve 106 μm)
A sieve having a diameter of 20 cm and a height of 4.5 cm and a mesh opening of 106 μm was prepared, and 10 g of hBN powder obtained in Examples and Comparative Examples was placed thereon, and a vacuum suction type sieving machine [manufactured by Alpine, model name “air jet” Sheave A200LS ”]. The powder was sucked from the lower part of the sieve with a differential pressure of 1 kPa and sieved for 360 seconds. The weight of hBN powder remaining under and on the sieve was measured, and the hBN powder content under the sieve 106 μm sieve (the powder content under the sieve 106 μm sieve) and the hBN powder content over the sieve 106 μm sieve ( The content of powder on a sieve having a mesh size of 106 μm was calculated.
In addition, after pulverizing the hBN fired products obtained in the examples and comparative examples, when the classification was performed using the dry vibration sieve device having an aperture of 106 μm under the condition of a sieving time of 60 minutes, All the sieves with an opening of 106 μm passed.
（目開き４５μｍ篩下のｈＢＮ粉末含有率）
　径が２０ｃｍ、高さ４．５ｃｍの目開き４５μｍの篩を準備し、実施例及び比較例で得られたｈＢＮ粉末を１０ｇ乗せ、減圧吸引型篩分け機［アルパイン社製、機種名「エアージェットシーブＡ２００ＬＳ」］にセットした。篩の下部から粉末を差圧１ｋＰａで吸引し、篩分け時間を１８０秒間として、篩分けした。篩の下及び篩の上に残ったｈＢＮ粉末の重量を測定し、目開き４５μｍ篩下のｈＢＮ粉末含有率（目開き４５μｍ篩下粉末含有率）を算出した。 (Content of hBN powder under sieve with opening of 45 μm)
A sieve having a diameter of 20 cm and a height of 4.5 cm and an opening of 45 μm was prepared, and 10 g of hBN powder obtained in Examples and Comparative Examples was placed thereon, and a vacuum suction type sieving machine [manufactured by Alpine, model name “Air Jet” Sheave A200LS ”]. The powder was sucked from the lower part of the sieve with a differential pressure of 1 kPa and sieved for 180 seconds. The weight of the hBN powder remaining under and above the sieve was measured, and the hBN powder content under the sieve having an opening of 45 μm (the powder content of the sieve under 45 μm) was calculated.
（ｈＢＮ粉末の嵩密度）
　３００ｍｌメスシリンダーに１００ｇの実施例及び比較例で得られたｈＢＮ粉末を投入し、振とう機により３分振動させた後のｈＢＮ粉末の振動嵩密度により、嵩密度を測定した。
（ｈＢＮ粉末の成形体及び粗製ｈＢＮ粉末の成形体の密度）
　成形体の質量及び体積を測定し、これらの値から、成形体の密度を算出した。 (Bulk density of hBN powder)
100 g of the hBN powder obtained in Examples and Comparative Examples was put into a 300 ml graduated cylinder, and the bulk density was measured by the vibration bulk density of the hBN powder after vibrating for 3 minutes with a shaker.
(Density of hBN powder compact and crude hBN powder compact)
The mass and volume of the compact were measured, and the density of the compact was calculated from these values.
（ピーク減少率）
　本発明において、ピーク減少率の測定はレーザー回折散乱法の粒度分布計［日機装（株）製、機種名「マイクロトラックＭＴ３３００ＥＸＩＩ」］を用いて行った。
　実施例及び比較例のｈＢＮ焼成物を粉砕後、目開き１０６μｍ及び目開き４５μｍの篩を２段重ねで用いて、前記乾式振動篩装置（篩分け時間６０分）にて分級した４５～１０６μｍの粒径を有するｈＢＮ粉末０．０６ｇを水５０ｇに分散させた分散液を調製した。当該分散液を出力１５０Ｗ、発振周波数１９．５ｋＨｚの条件で１分間超音波処理した際の４５～１５０μｍの間に発生する最大ピークと超音波処理前４５～１５０μｍの間に発生する最大ピークとを比較した。図７は、実施例１及び３の粒径分布曲線図である。この図において、ピーク減少率［＝〔（処理前の最大ピーク高さ（ａ））－（処理後の最大ピーク高さ（ｂ））〕／（処理前の最大ピーク高さ（ａ））］を算出した。このピーク減少率が低いほど崩壊強度は高いと言える。また、本発明における超音波処理は、超音波処理装置［（株）日本精機製作所製、機種名「超音波ホモジナイザーＵＳ－１５０Ｖ」］を用いて行った。
　なお、比較例２及び４については、上記ｈＢＮ焼成物にかえて市販品Ａを用いた。 (Peak reduction rate)
In the present invention, the peak reduction rate was measured using a laser diffraction / scattering particle size distribution meter [manufactured by Nikkiso Co., Ltd., model name “Microtrack MT3300EXII”].
After pulverizing the hBN fired products of Examples and Comparative Examples, the sieves having openings of 106 μm and openings of 45 μm were used in a two-tiered manner, and classified by the dry vibration sieve apparatus (sieving time 60 minutes). A dispersion was prepared by dispersing 0.06 g of hBN powder having a particle size in 50 g of water. The maximum peak generated between 45 and 150 μm and the maximum peak generated between 45 and 150 μm before sonication when the dispersion was sonicated for 1 minute under the conditions of an output of 150 W and an oscillation frequency of 19.5 kHz. Compared. FIG. 7 is a particle size distribution curve of Examples 1 and 3. In this figure, the peak reduction rate [= [(maximum peak height before processing (a)) − (maximum peak height after processing (b))] / (maximum peak height before processing (a))] Was calculated. It can be said that the lower the peak reduction rate, the higher the decay strength. In addition, the ultrasonic treatment in the present invention was performed using an ultrasonic treatment apparatus [manufactured by Nippon Seiki Seisakusho, model name “ultrasonic homogenizer US-150V”].
In Comparative Examples 2 and 4, a commercial product A was used in place of the above-mentioned hBN fired product.
（ｈＢＮ粉末の結晶子径）
　Ｘ線回折測定により、実施例及び比較例で得られたｈＢＮ粉末の結晶子径を算出した。Ｘ線回折測定装置としては、ＰＡＮａｌｙｔｉｃａｌ社製、機種名「Ｘ’Ｐｅｒｔ　ＰＲＯ」を用い、銅ターゲットを使用してＣｕ－Ｋα１線を用いた。 (Crystallite size of hBN powder)
The crystallite size of the hBN powder obtained in the examples and comparative examples was calculated by X-ray diffraction measurement. As an X-ray diffraction measurement apparatus, a model name “X'Pert PRO” manufactured by PANalytical was used, and a Cu—Kα1 line was used using a copper target.
（ｈＢＮ粉末の酸化ホウ素（Ｂ２Ｏ３）含有量、ＣａＯ含有量）
　実施例及び比較例で得られたｈＢＮ粉末を０．１Ｎ希硫酸溶液で酸処理した。この酸処理により、ｈＢＮ粉末中のＢＮの少なくとも一部が加水分解されてアンモニアが発生すると共にＢＮのＢ元素が酸溶液中に溶解し、また、ｈＢＮ粉末中の酸化ホウ素（Ｂ２Ｏ３）の少なくとも一部が酸溶液中に溶解する。
　酸処理後の酸溶液中に存在するＢ元素の総量（ＢＮの加水分解に起因するＢ元素量とＢ２Ｏ３の溶解に起因するＢ元素量の総量）をＩＣＰ分析装置［SII Nano Technology Inc.社製、機種名「ＳＰＳ３５００」］により測定した。この酸処理後の酸溶液中に存在するＢ元素の総量から、酸処理により溶解したＢ２Ｏ３量を算出した。
　上記の酸処理後の酸溶液中に存在するＣａ元素を上記ＩＣＰ分析装置により測定し、Ｃａ元素量からＣａＯ含有量を算出した。 (Boron oxide (B 2 O 3 ) content of hBN powder, CaO content)
The hBN powders obtained in the examples and comparative examples were acid-treated with a 0.1N dilute sulfuric acid solution. By this acid treatment, at least a part of BN in the hBN powder is hydrolyzed to generate ammonia, and the B element of BN is dissolved in the acid solution. Further, boron oxide (B 2 O 3 ) in the hBN powder At least a part of it dissolves in the acid solution.
The total amount of B element present in the acid solution after the acid treatment (the total amount of B element due to hydrolysis of BN and the amount of B element due to dissolution of B 2 O 3 ) is calculated using an ICP analyzer [SII Nano Technology Inc. Measured by a model name “SPS3500” manufactured by KK From the total amount of element B present in the acid solution after the acid treatment, the amount of B 2 O 3 dissolved by the acid treatment was calculated.
The Ca element present in the acid solution after the acid treatment was measured by the ICP analyzer, and the CaO content was calculated from the Ca element amount.
（ｈＢＮ粉末中における炭素の含有量）
　炭素分析装置［ＬＥＣＯジャパン合同会社製、機種名「ＣＳ２３０」］を用いて、実施例及び比較例で得られたｈＢＮ粉末中における炭素の含有量（炭素含有量）を測定した。 (Carbon content in hBN powder)
The carbon content (carbon content) in the hBN powders obtained in Examples and Comparative Examples was measured using a carbon analyzer [manufactured by LECO Japan LLC, model name “CS230”].
（ｈＢＮ粉末の純度）
　上述のとおり測定したｈＢＮ粉末中におけるＢ２Ｏ３量、ＣａＯ含有量及び炭素の含有量の総量を不純物量として、ｈＢＮ粉末の純度を求めた。 (Purity of hBN powder)
The purity of hBN powder was determined using the total amount of B 2 O 3 , CaO content, and carbon content in the hBN powder measured as described above as the impurity amount.
（黒色異物数）
　実施例及び比較例で得られたｈＢＮ粉末１ｇを５０ｃｃスクリュー管瓶に量りとり、この中にメタノール約４０ｃｃを加えてよく撹拌した後、３時間以上経過した段階でスクリュー管瓶底部をスキャナで撮影し、その画像中の黒色物の存在数（黒色異物数）を測定した。なお、この黒色物は、未反応の炭素成分であると考えられる。 (Number of black foreign bodies)
1 g of hBN powder obtained in Examples and Comparative Examples was weighed into a 50 cc screw tube bottle, about 40 cc of methanol was added and stirred well, and the bottom of the screw tube bottle was photographed with a scanner after 3 hours or more had passed. Then, the number of black objects in the image (the number of black foreign objects) was measured. This black product is considered to be an unreacted carbon component.
（樹脂シートの熱伝導率）
　実施例及び比較例で得られた樹脂シートについて、ＮＥＴＺＳＣＨ社製、機種名「ＬＦＡ４４７　ＮａｎｏＦｌａｓｈ」により熱拡散率を測定し、それにそれぞれの樹脂シートの比熱と密度の理論値を掛けることにより算出した値を、樹脂シートの厚み方向の熱伝導率とした。
　なお、各実施例又は比較例の樹脂シートの密度の理論値は、窒化ホウ素の理論密度を２．２７ｇ／ｃｍ３、樹脂成分の理論密度を１．１７ｇ／ｃｍ３として計算した。 (Thermal conductivity of resin sheet)
About the resin sheet obtained by the Example and the comparative example, the value calculated by measuring a thermal diffusivity by the model name "LFA447 NanoFlash" made from NETZSCH, and multiplying it by the theoretical value of the specific heat and density of each resin sheet. Was defined as the thermal conductivity in the thickness direction of the resin sheet.
In addition, the theoretical value of the density of the resin sheet of each Example or Comparative Example was calculated on the assumption that the theoretical density of boron nitride was 2.27 g / cm 3 and the theoretical density of the resin component was 1.17 g / cm 3 .
（樹脂シートの比重率）
　実施例及び比較例で得られた樹脂シートの比重率は、ザルトリウス・メカニトロニクス・ジャパン（株）製の電子天秤（機種名「ＣＰ２２４Ｓ」）及び比重／密度測定キット（機種名「ＹＤＫ０１／ＹＤＫ０１－ＯＤ／ＹＤＫ０１ＬＰ」）を用いてアルキメデス法によって測定した各実施例又は比較例の樹脂シートの比重を、各実施例又は比較例の樹脂シートの理論比重で割り、１００倍すること〔（各実施例又は比較例の樹脂シートで測定した比重／各実施例又は比較例の樹脂シートの理論比重）×１００〕により算出した。
　なお、各実施例又は比較例の樹脂シートの理論比重の計算では、窒化ホウ素の理論密度を２．２７ｇ／ｃｍ３、樹脂成分の理論密度を１．１７ｇ／ｃｍ３として計算した。 (Specific gravity ratio of resin sheet)
The specific gravity ratios of the resin sheets obtained in Examples and Comparative Examples are the electronic balance (model name “CP224S”) and the specific gravity / density measurement kit (model name “YDK01 / YDK01-”) manufactured by Sartorius Mechanitronics Japan Co., Ltd. OD / YDK01LP ”)), and dividing the specific gravity of the resin sheet of each Example or Comparative Example by the theoretical specific gravity of each Example or Comparative Example and multiplying by 100 ([Each Example Or the specific gravity measured with the resin sheet of the comparative example / theoretical specific gravity of the resin sheet of each example or comparative example) × 100].
In the calculation of the theoretical specific gravity of the resin sheet of each example or comparative example, the theoretical density of boron nitride was 2.27 g / cm 3 and the theoretical density of the resin component was 1.17 g / cm 3 .
（絶縁破壊電圧）
　実施例及び比較例で得られた樹脂シートについて、菊水電子工業（株）製の耐電圧／絶縁抵抗測定装置（機種名「ＴＯＳ９２０１」）を用いて、１ｋＶ／ｓｅｃの昇圧速度で絶縁破壊電圧を測定した。 (Dielectric breakdown voltage)
With respect to the resin sheets obtained in Examples and Comparative Examples, the dielectric breakdown voltage was increased at a boosting rate of 1 kV / sec using a withstand voltage / insulation resistance measuring device (model name “TOS9201”) manufactured by Kikusui Electronics Corporation. It was measured.
　以上の実施例及び比較例のｈＢＮ粉末の作製条件を表１に、評価結果を表２に示した。
　なお、表１中の炭素源及びＣａ化合物は、ｈＢＮ粉末を作製する際、粗製ｈＢＮ粉末、炭素源及びＣａ化合物を混合して得られる混合物中における粗製ｈＢＮ粉末１００質量部に対する含有量を示す。また、表１中のｈＢＮ粉末（Ａ）及び（Ｂ）は、それぞれ４５～１０６μｍのｈＢＮ粉末（Ａ）及び４５μｍ篩下のｈＢＮ粉末（Ｂ）を示す。 The production conditions of the hBN powders of the above examples and comparative examples are shown in Table 1, and the evaluation results are shown in Table 2.
In addition, the carbon source and Ca compound of Table 1 show content with respect to 100 mass parts of crude hBN powder in the mixture obtained by mixing crude hBN powder, a carbon source, and Ca compound, when producing hBN powder. Further, hBN powders (A) and (B) in Table 1 represent hBN powder (A) of 45 to 106 μm and hBN powder (B) under a 45 μm sieve, respectively.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表２に示すとおり、実施例１～５の樹脂シートは、比較例１～５の樹脂シートと比べて、熱伝導率が高く、耐電圧特性にも優れ、高い熱伝導性及び高い電気絶縁性を同時に満たしていることが分かる。これは、本発明のｈＢＮ粉末が、撹拌混合時にｈＢＮ粉末の一次粒子の凝集体が過度に壊れることなく、図６に示す模式図のように顆粒形状を維持し、当該凝集体が適当な強度を有し、樹脂成分との馴染みが良いためと考えられる。また、本発明のｈＢＮ粉末は、炭素含有量が低く高純度であることも良好な電気絶縁性の発現に寄与していると考えられる。さらに、実施例１及び２のｈＢＮ粉末は、４５μｍ篩下粉末含有率が特定の範囲であり適度に粒径の小さなｈＢＮ粉末を含有するため、良好な熱伝導性を維持しつつ、電気絶縁性にも優れていることが分かる。 As shown in Table 2, the resin sheets of Examples 1 to 5 have higher thermal conductivity and excellent withstand voltage characteristics than those of Comparative Examples 1 to 5, and have high thermal conductivity and high electrical insulation. It can be seen that This is because the hBN powder of the present invention maintains the granule shape as shown in the schematic diagram of FIG. 6 without excessively breaking the aggregates of the primary particles of the hBN powder during stirring and mixing, and the aggregates have an appropriate strength. This is considered to be because of familiarity with the resin component. In addition, the hBN powder of the present invention is considered to contribute to the development of good electrical insulation properties because of its low carbon content and high purity. Furthermore, the hBN powders of Examples 1 and 2 contain hBN powder having a specific content of 45 μm under-sieving powder and a moderately small particle size, so that electrical insulation is maintained while maintaining good thermal conductivity. It turns out that it is excellent.

Claims (9)

  1. 　六方晶窒化ホウ素の一次粒子の凝集体を含む目開き１０６μｍ篩下の粉末含有率が８０質量％以上の六方晶窒化ホウ素粉末であって、５０％体積累積粒径Ｄ５０が１０～２０μｍ、結晶子径が２６０～１０００Åであり、かつ、４５～１０６μｍの粒径に分級された前記六方晶窒化ホウ素粉末の粒径分布曲線において、粒径４５～１５０μｍの範囲内に最大ピークを１つ有し、４５～１０６μｍの粒径に分級された前記六方晶窒化ホウ素粉末を水に分散させた分散液を１分間超音波処理したときの下記式（１）で算出される最大ピークのピーク減少率が４０～９０％である、六方晶窒化ホウ素粉末。
    　ピーク減少率＝〔（処理前の最大ピーク高さ（ａ））－（処理後の最大ピーク高さ（ｂ））〕／（処理前の最大ピーク高さ（ａ））　　　（１）     A hexagonal boron nitride powder containing an aggregate of primary particles of hexagonal boron nitride and having an aperture of 106 μm and having a powder content of 80% by mass or more under a sieve is 50% by volume cumulative particle diameter D 50 of 10 to 20 μm, crystals In the particle size distribution curve of the hexagonal boron nitride powder having a child diameter of 260 to 1000 mm and classified to a particle size of 45 to 106 μm, it has one maximum peak in the particle size range of 45 to 150 μm. The peak reduction rate of the maximum peak calculated by the following formula (1) when the dispersion obtained by dispersing the hexagonal boron nitride powder classified to a particle size of 45 to 106 μm in water is subjected to ultrasonic treatment for 1 minute is Hexagonal boron nitride powder, 40-90%.
    Peak reduction rate = [(maximum peak height before treatment (a)) − (maximum peak height after treatment (b))] / (maximum peak height before treatment (a)) (1)
  2. 　目開き４５μｍ篩下の粉末含有率が４５質量％以下である、請求項１に記載の六方晶窒化ホウ素粉末。 The hexagonal boron nitride powder according to claim 1, wherein the powder content under a sieve having an opening of 45 μm is 45 mass% or less.
  3. 　ＢＥＴ比表面積が１．５～１０ｍ２／ｇである、請求項１又は２に記載の六方晶窒化ホウ素粉末。 The hexagonal boron nitride powder according to claim 1 or 2, wherein the BET specific surface area is 1.5 to 10 m 2 / g.
  4. 　嵩密度が０．３ｇ／ｃｍ３以上である、請求項１～３のいずれかに記載の六方晶窒化ホウ素粉末。 The hexagonal boron nitride powder according to any one of claims 1 to 3, having a bulk density of 0.3 g / cm 3 or more.
  5. 　請求項１～４のいずれかに記載の六方晶窒化ホウ素粉末を１０～９０体積％含有する、樹脂組成物。 A resin composition comprising 10 to 90% by volume of the hexagonal boron nitride powder according to any one of claims 1 to 4.
  6. 　請求項５に記載の樹脂組成物又はその硬化物からなる、樹脂シート。 A resin sheet comprising the resin composition according to claim 5 or a cured product thereof.
  7. 　窒化ホウ素２０～９０質量％及び酸化ホウ素１０～８０質量％を含む粗製六方晶窒化ホウ素粉末１００質量部と、炭素換算で３～１５質量部の炭素源と０．０１～１質量部のカルシウム化合物を混合し、成形した後、窒素ガスを含む雰囲気下で焼成する焼成工程を有する、請求項１～４のいずれかに記載の六方晶窒化ホウ素粉末の製造方法。 100 parts by mass of a crude hexagonal boron nitride powder containing 20 to 90% by mass of boron nitride and 10 to 80% by mass of boron oxide, 3 to 15 parts by mass of carbon source and 0.01 to 1 part by mass of calcium compound in terms of carbon The method for producing hexagonal boron nitride powder according to any one of claims 1 to 4, further comprising: a firing step of firing and mixing in a nitrogen gas-containing atmosphere after forming.
  8. 　前記炭素源が、黒鉛及び炭化ホウ素から選ばれる１種又は２種である、請求項７に記載の六方晶窒化ホウ素粉末の製造方法。 The method for producing hexagonal boron nitride powder according to claim 7, wherein the carbon source is one or two selected from graphite and boron carbide.
  9. 　さらに、前記焼成工程後に、目開き１０６μｍの篩及び目開き４５μｍの篩を用いて、４５～１０６μｍの六方晶窒化ホウ素粉末〔ｈＢＮ粉末（Ａ）〕と４５μｍ篩下の六方晶窒化ホウ素粉末〔ｈＢＮ粉末（Ｂ）〕に分級したのち、ｈＢＮ粉末（Ａ）とｈＢＮ粉末（Ｂ）を、ｈＢＮ粉末（Ａ）及び（Ｂ）の合計量に対するｈＢＮ粉末（Ａ）の割合が４０～９０質量％となるように混合する混合工程を有する、請求項７又は８に記載の六方晶窒化ホウ素粉末の製造方法。 Further, after the firing step, using a sieve having an aperture of 106 μm and a sieve having an aperture of 45 μm, a hexagonal boron nitride powder [hBN powder (A)] of 45 to 106 μm and a hexagonal boron nitride powder [hBN] under a sieve of 45 μm are used. After being classified into powder (B)], hBN powder (A) and hBN powder (B) are mixed at a ratio of hBN powder (A) to 40-90 mass% with respect to the total amount of hBN powder (A) and (B). The method for producing hexagonal boron nitride powder according to claim 7 or 8, further comprising a mixing step of mixing.
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