WO2020195298A1 - Method for producing granular boron nitride and granular boron nitride - Google Patents

Method for producing granular boron nitride and granular boron nitride Download PDF

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WO2020195298A1
WO2020195298A1 PCT/JP2020/005627 JP2020005627W WO2020195298A1 WO 2020195298 A1 WO2020195298 A1 WO 2020195298A1 JP 2020005627 W JP2020005627 W JP 2020005627W WO 2020195298 A1 WO2020195298 A1 WO 2020195298A1
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boron nitride
granular
rare earth
oxide
granular boron
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PCT/JP2020/005627
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French (fr)
Japanese (ja)
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尚史 楠瀬
佳範 卯野
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国立大学法人 香川大学
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Priority to JP2020549724A priority Critical patent/JPWO2020195298A1/ja
Publication of WO2020195298A1 publication Critical patent/WO2020195298A1/en

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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
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
    • C04B35/583—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on boron nitride
    • 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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins

Definitions

  • the present invention relates to a method for producing a granular boron nitride composition and a granular boron nitride composition obtained by the method. Further, the present invention relates to a resin composition containing a granular boron nitride composition and a resin, a molded product containing granular boron nitride and a resin obtained by molding such a resin composition, and a method for producing the same. Regarding.
  • Boron nitride (hereinafter, also referred to as “BN”) is an insulating ceramic and has various crystal types such as c-BN having a diamond structure, h-BN having a graphite structure, and t-BN having a multi-layer structure. It has been known.
  • h-BN has remarkably low thermal conductivity because it is relatively easy to synthesize and has excellent thermal conductivity, solid lubricity, chemical stability, and heat resistance. Attempts have been made to improve thermal conductivity by mixing a resin material with a filler. Such resin materials are used in the electric and electronic fields for heat dissipation members of integrated circuits.
  • h-BN has a laminated structure similar to graphite and has a large crystal anisotropy.
  • h-BN is macroscopically granular, it is microscopically a laminate of plate-like crystals.
  • the plate-like crystal plane corresponding to the a-axis direction of the crystal it is connected by a strong covalent bond, so that it exhibits a large thermal conductivity of nearly 400 W / mK.
  • the plate thickness direction corresponding to the c-axis direction since they are laminated by a weak Van der Waals force bond, they show only a small thermal conductivity of about 1 to 2 W / mK.
  • the plate-shaped boron nitride is oriented in the plate surface direction of the molded product, which is the flow direction of the resin composition at the time of molding.
  • the obtained molded product has a problem that it exhibits excellent thermal conductivity in the plate surface direction but low thermal conductivity in the thickness direction. Therefore, it is desired to improve the anisotropy of such granular BN.
  • Japanese Patent Application Laid-Open No. 2013-147363 describes a step of mixing boron nitride with an oxide of at least one rare earth metal selected from yttrium, cerium, and ytterbium and carbon, and heat-treating the mixture in a non-oxidizing gas atmosphere.
  • a method for producing a metal oxide-containing boron nitride containing the above is disclosed.
  • the boron nitride produced by this method has a resin composition even when a large amount of the resin composition is blended in the resin material for the purpose of improving thermal conductivity, solid lubricity, chemical stability, heat resistance, etc. It is possible to improve the thermal conductivity in the thickness direction of the molded product to be molded while maintaining good molding processability as a product.
  • thermal conductivity can be improved by producing boron nitride by the above-mentioned method, but the improved thermal conductivity is further improved as compared with the above-mentioned original thermal conductivity of boron nitride. There is room for. Another problem is that rare earth metal components such as yttrium are relatively expensive.
  • boron nitride when boron nitride is mixed with a resin material and a molded product is manufactured using the boron nitride, it is desired to further increase the thermal conductivity.
  • a rare earth metal component such as yttrium is used, it is desirable to reduce the amount used.
  • the present invention is described in the first gist.
  • Boron nitride component containing boron nitride (2) Rare earth components containing oxides of at least one rare earth element selected from yttrium, cerium and itterbium and / or precursor compounds thereof, and (3) calcium containing calcium oxide and / or calcium carbonate.
  • a method for producing a granular boron nitride composition which comprises a step of heat-treating a mixture containing components in a non-oxidizing gas atmosphere.
  • the present invention provides, in the second gist, a granular boron nitride composition obtained by the above-mentioned production method.
  • This includes, in addition to the granular boron nitride obtained by the heat treatment, other compounds derived from the components (1) to (3) contained in the mixture.
  • Such other compounds are mainly rare earth element oxides and calcium oxide, but also contain a small amount of, for example, complex oxides derived from elements present in the system (for example, Y—Ca—BO complex oxides). It can be.
  • the present invention provides the granular boron nitride contained in the above-mentioned granular boron nitride composition in the third gist.
  • This granular boron nitride is obtained by subjecting the above composition to a cleaning process using an acid to remove at least a portion of calcium oxide and a rare earth element oxide, most of the calcium oxide, preferably substantially the entire amount. be able to. Therefore, the present invention provides a method for producing granular boron nitride in the fourth gist, which method is characterized by acid cleaning of the granular boron nitride composition in the second gist.
  • the present invention provides, in the fifth gist, a granular boron nitride composition of the second gist or a resin composition comprising the granular boron nitride of the third gist and a resin material. Further, the present invention is obtained in the sixth gist by a molding method characterized by molding using such a resin material, and the present invention is obtained by such a molding method in the seventh gist. To provide a molded product to be manufactured.
  • the thermal conductivity of the obtained molded product is improved. Further, in a preferred embodiment, anisotropy regarding heat conduction of the molded product is suppressed. Even when a large amount is mixed, the thermal conductivity of the obtained molded product can be improved while maintaining good molding processability.
  • a heat radiating sheet that requires insulation, thermal conductivity, and moldability can be exemplified.
  • it is suitable for use in the fields of electricity and electronics.
  • the granular boron nitride composition or granular boron nitride of the present invention can be used as a filler that can be blended in a heat conductive paste, a heat conductive adhesive, a composition for a heat conductive molded product, or the like.
  • FIG. 1 shows the ratio (mass basis) of the average particle size of the granular boron nitride of the present invention and the sum of the rare earth component (2) and the calcium component (3) in the mixture to be heat-treated (that is, (2) + (3)).
  • FIG. 2 shows the ratio (mass reference percent) of the specific surface area of the granular boron nitride of the present invention and the sum of the rare earth component (2) and the calcium component (3) in the heat-treated mixture (that is, (2) + (3)).
  • FIG. 1 shows the ratio (mass basis) of the average particle size of the granular boron nitride of the present invention and the sum of the rare earth component (2) and the calcium component (3) in the mixture to be heat-treated (that is, (2) + (3)).
  • FIG. 3 shows the total of the thermal conductivity in the thickness direction of the molded product obtained by using the resin composition containing the granular boron nitride of the present invention and the rare earth component (2) and the calcium component (3) in the heat-treated mixture.
  • a table and graph of experimental results showing the relationship with the ratio (that is, (2) + (3)) (mass reference percentage) are shown.
  • FIG. 4 shows the thermal conductivity in the plane direction (direction perpendicular to the thickness direction) of the molded product obtained by using the resin composition containing the granular boron nitride of the present invention, and the rare earth component (2) in the mixture to be heat-treated.
  • FIG. 5 shows the degree of orientation of granular boron nitride in a molded product molded using the resin composition containing granular boron nitride of the present invention and the rare earth component in a mixture to be heat-treated when producing granular boron nitride (2).
  • a table and a graph of experimental results showing the relationship between the sum of the calcium component (3) and the sum (that is, (2) + (3)) are shown.
  • FIG. 6 is a typical SEM photograph of the granular boron nitride (but after washing) of the present invention obtained in Example 6.
  • FIG. 7 is a typical SEM photograph of the granular boron nitride composition of the present invention (however, before washing) obtained in Example 6.
  • FIG. 8 is an SEM photograph and an EDS photograph (for elements N and Y) of the granular boron nitride (but after washing) of the present invention containing yttrium oxide obtained in Example 36.
  • FIG. 9 is an SEM photograph and an EDS photograph (for N element, Ca element and Y element) of the granular boron nitride composition of the present invention (however, before washing) obtained in Example 11.
  • FIG. 10 is an SEM photograph and an EDS photograph (for element N) of the granular boron nitride (but after washing) of the present invention obtained in Example 12.
  • the boron nitride contained in the boron nitride component (1) is hexagonal boron nitride (h-BN) having a graphite structure, and in one embodiment.
  • Boron nitride is preferably powdery (or finely granular) boron nitride, preferably h-BN.
  • a commercially available hexagonal boron nitride component can be used.
  • the oxide of the rare earth element contained in the rare earth component (2) is, for example, yttrium oxide, cerium oxide or itterbium oxide, and the precursor of the oxide of the rare earth element is a preheat treatment and / or heating carried out prior to the heat treatment. Means a compound that results in such an oxide in the process.
  • a rare earth component (2) commercially available ones such as yttrium oxide and cerium oxide can be used.
  • the calcium component (3) contains calcium oxide and / or calcium carbonate, and as such a calcium component (3), generally commercially available calcium oxide, calcium carbonate or the like can be used.
  • boron nitride in boron nitride component contained in the mixture to heat treatment (1) BN
  • oxides of rare earth elements in the rare earth component (2) e.g., Y 2 O 3
  • the ratio of the total mass of calcium oxide and calcium hydroxide (if present) in the calcium component (3) (if present) is general.
  • boron nitride is 95 to 40%
  • boron nitride is 94 to 50%
  • more preferably 7 to 42% is 14 to 42%, for example 14 to 35%.
  • the rare earth element in the rare earth component (2): the calcium element in the calcium component (3) is preferably 1: based on the number of elements in the heat-treated mixture. It is 0.25 to 1: 4, more preferably 1: 0.5 to 1: 3, particularly preferably 1: 0.7 to 1: 2.5, for example 1: 1 to 1: 2.
  • the heat treatment is carried out in a non-oxidizing gas atmosphere.
  • the non-oxidizing gas atmosphere means an atmosphere containing no oxygen, for example, one or two kinds such as nitrogen gas, helium gas, argon gas, ammonia gas, hydrogen gas, methane gas, propane gas, and carbon monoxide gas. It is an atmosphere that includes the above.
  • the crystallization rate after dissolution of boron nitride differs depending on the type of gas used in this atmosphere. For example, in the case of argon gas, the crystallization rate becomes slow and the heat treatment time may take a long time. In order to carry out crystallization in a short time, it is particularly preferable to use nitrogen gas or a mixed gas in which nitrogen gas and another gas are used in combination.
  • the heat treatment is carried out in a nitrogen gas atmosphere.
  • the mixture to be heat-treated is preferably kept in a non-oxidizing atmosphere until it reaches a predetermined heat treatment temperature described later.
  • the non-oxidizing gas atmosphere may be in a so-called vacuum state or a reduced pressure state in which the gas is substantially contained or hardly contained.
  • the boron nitride component (1) may contain oxygen, and in that case (for example, when it is contained in the form of boron oxide), if necessary (for example, at least a part of boron oxide is converted to boron nitride).
  • the mixture may use carbon in an amount of 1% to 5% relative to the mass of boron nitride in the boron nitride component (1).
  • the mixture is carbon free, unless there is a substantial adverse effect.
  • the amount of oxygen contained is not so large (for example, it is generally based on the mass of the boron nitride component (1)). Generally, it is not necessary to use carbon because it is 5% or less, for example, 4% by mass, but the mixture may contain carbon if necessary (for example, when the amount of oxygen is large).
  • the granular boron nitride contained in the granular boron nitride composition of the present invention has an average particle diameter of preferably 9 to 25 ⁇ m, more preferably 10 to 20 ⁇ m, for example, 12 to 15 ⁇ m, and the specific surface area of the granular material. Is preferably 2 to 10 m 2 / g, more preferably 4 to 8 m 2 / g, for example 5 to 6 m 2 / g.
  • the above-mentioned average particle size and specific surface area mean values measured by the following methods, respectively:
  • the average particle size referred to in the present specification is a numerical value obtained by this measurement method regardless of the state of aggregation of the particles, and may be the average particle size of the primary particles depending on the properties of the particles. It may also be the average particle size of the secondary particles. In some cases, it is the average particle size measured in a state where both primary particles and secondary particles are mixed.
  • the granular boron nitride of the present invention produced by heat treatment is produced by dissolving boron nitride in the liquid phase formed by melting calcium oxide in addition to the rare earth element oxide in advance during the heat treatment, and then precipitating from the liquid phase. It is conceivable that. This is not bound by any theory, but the inventors have knowledge and experience regarding the formation of boron nitride and new findings regarding the above-mentioned production methods, especially SEM photographs of the resulting granules. Based on the results of the above, the formation of granules can be considered as follows. This idea is just one of the possible ideas. The present invention that boron nitride granules can be obtained by heat treatment under specific conditions is not limited by the suitability of this idea.
  • the rare earth element oxide and calcium oxide are preferentially melted to form a liquid phase, in which the granular boron nitride is dissolved.
  • the concentration of boron nitride in the liquid phase rises to a supersaturated state, and as a result, boron nitride precipitates (recrystallizes). While boron nitride is precipitated in this way, another boron nitride particle is newly dissolved in the liquid phase to become a supersaturated state, and as a result, boron nitride is further precipitated.
  • the precipitated boron nitride is bonded to form a bent form. Since there is a liquid phase in which boron nitride is dissolved exists inside and outside the bent form of boron nitride, supersaturation ⁇ precipitation occurs repeatedly there, and boron nitride crystals grow further to thicken the bent form. It becomes longer and boron nitride crystals grow gradually.
  • the bent boron nitride thus grown is bonded to another similarly grown bent boron nitride crystal, further grown inside and outside the crystal, and finally surrounded by a wall having a certain thickness.
  • boron nitride obtained by heat treatment is referred to as "granular boron nitride" in the present specification.
  • the granular boron nitride of the present invention has a strong shell structure formed by boron nitride in the form of a relatively thick wall.
  • This shell structure has a macroscopically rounded shape as a whole particle, that is, a grain (crushed) shape. In a strict sense, it is a so-called spherical, spheroidal, or polyhedral shape, and generally has a complex combination of these shapes.
  • this granular material has a relatively small aspect ratio, preferably 1 to 3, more preferably 1 to 2, and is clearly different from a granular material having a large aspect ratio such as boron nitride having a graphite structure.
  • FIG. 6 shows an example of a typical SEM photograph of the granular boron nitride of the present invention. These photographs are of granular boron nitride obtained in Example 6 described later. When this is observed in detail, it can be seen that the granular boron nitride is a so-called grain (crushed) shape having an apparent polyhedral (or spherical) shape as a whole, which is composed of bent walls.
  • An SEM photograph was also taken of the granular boron nitride composition of the present invention in a state before the oxide was removed. The photograph is shown in FIG. As can be seen by comparing the two, there was substantially no difference from the one after removing the oxide. It is possible that this can be explained by the fact that the liquid phase component composed of the added oxide remains mainly in the granular boron nitride of the shell structure.
  • the above-mentioned shell structure may include other granular boron nitride or a part thereof inside the shell structure.
  • FIG. 10 shows an SEM photograph of two different visual field parts of a cross section of a mixture of granular boron nitride obtained in Example 12 described later mixed with an epoxy resin and cured, and an EDS photograph of the nitrogen element in the photograph. Is.
  • the upper photograph is an SEM photograph.
  • the lower photograph showing the result of mapping analysis of granular boron nitride in this state for N elements using EDS (Energy Dispersive X-ray Analysis) is an EDS photograph.
  • the EDS photo corresponding to the upper left photo is the lower left photo
  • the EDS photo corresponding to the upper right photo is the lower right photo. It can be seen that the nitrogen element (white part) is present inside the shell structure of boron nitride, which appears to shine white in the SEM photograph, as can be confirmed in the EDS photograph, and therefore boron nitride is present.
  • granular boron nitride also exists inside the shell structure of granular boron nitride.
  • the internal granular boron nitride is columnar (thus three-dimensionally planar), and the inside of the outer granular boron nitride shell structure is divided, for example, bisected. ing.
  • the internal granular boron nitride fills a part of the inside of the shell structure of the granular boron nitride located on the outside.
  • the granular boron nitride thus encapsulated is a smaller shell structure, even if it is a part of the shell structure that has not yet formed the shell structure (eg, at least one or a part of the shell constituent surfaces). You may.
  • the surface constituting the shell structure may be a substantially flat surface or a bent surface forming the shell structure.
  • granular boron nitride is considered to be generated inside the shell structure in one embodiment by newly precipitating and growing boron nitride inside the already formed shell structure or a part thereof.
  • the grown granular boron nitride or a part thereof is bonded to another granular boron nitride or a part thereof, so that a part of the granular boron nitride is included.
  • the granular boron nitride containing other granular boron nitride is considered to contribute to higher the heat conduction of the granular boron nitride because it increases the heat conduction path.
  • the presence of other granular boron nitride inside also has an effect of suppressing or preventing deformation of the granular boron nitride when an external pressure is applied to the boron nitride.
  • one of the main features is that when boron nitride is precipitated from the liquid phase to form a shell as described above, a rare earth element oxide and calcium oxide are present as the liquid phase, and as a result, the result is obtained.
  • Granular boron nitride to be obtained has a thicker shell and a smaller aspect ratio. Thereby, it is possible to produce granular boron nitride having a crushing strength superior to that of various known boron nitride aggregates.
  • the degree of orientation of granular boron nitride in the molded product is about 85% or less, preferably 70% or less. It can be preferably 20 to 65%, for example 25 to 60%.
  • the particle size of the granular boron nitride particles is small, the resistance to hot press pressure is strong, so that the granular particles do not collapse and show a low (00L) plane orientation, but the resin material has high thermal conductivity.
  • granular boron nitride having a large particle size is desirable so that a high thermal conduction path can be taken for a long time.
  • the particle size of the granular boron nitride is increased, the granularity is likely to be disintegrated by hot pressing, so that the degree of orientation of the (00L) plane may be increased.
  • the granular boron nitride composition of the present invention contains a component that is finally solidified inside the shell by cooling after heating.
  • This component is mainly composed of rare earth element oxides and calcium oxide, but may contain various compounds, particularly composite oxides, as described above.
  • a portion of boron nitride that constitutes the shell structure of granular boron nitride or a part thereof may also be included.
  • the proportions of boron, rare earth elements and calcium elements contained in the granular boron nitride composition obtained by heat treatment are the proportions of these elements contained in the mixture. It is virtually the same. Therefore, the amount of rare earth element oxides and calcium oxide contained in the granular boron nitride composition is equal to the amount of rare earth element and calcium-derived oxides contained in the mixture.
  • the granular boron nitride composition usually contains 3-40%, preferably 5-37%, more preferably 8-35% of rare earth element oxides on a mass basis, in addition to boron nitride.
  • it contains 12 to 32% and contains 1 to 30%, preferably 2 to 26%, more preferably 5 to 22%, for example 8 to 15% of calcium oxide.
  • Such oxides can be reduced by acid cleaning as described above, for example, by reacting an oxide with an acid using an aqueous acid solution to convert it into a water-soluble salt, dissolving it in water, and removing it. ..
  • the thermal conductivity of the oxide is usually small, so that the oxide contained in the granular boron nitride composition does not substantially adversely affect the thermal conductivity.
  • calcium oxide can be preferentially removed by acid cleaning, so that substantially all of the calcium oxide is removed and the rare earth element oxide is partially removed.
  • the amount of rare earth element oxide contained in the granular boron nitride composition is, for example, 0.1 to 30%, preferably 1 to 15%, more preferably 2 to 12%, for example, 3 to 10% based on the mass thereof. So acid wash.
  • the present invention provides granular boron nitride with a shell structure, from at least rare earth element oxides and / or calcium oxide from the above-mentioned granules, preferably most, more preferably substantially all of the calcium oxide. It also provides another granular boron nitride obtained by removing calcium oxide. That is, the more preferred granules consist of boron, nitrogen, oxygen and rare earth elements and are substantially free of calcium.
  • the granules have a strong shell structure formed by boron nitride and contain a small amount of rare earth element oxides in addition to boron nitride.
  • the removal of the oxide may be carried out by any other suitable method other than cleaning with an acid, as long as the properties of the granular boron nitride as a filler are not excessively affected. Cleaning with an acid is advantageous in that oxides can be substantially removed without adversely affecting granular boron nitride.
  • the present invention provides a resin composition
  • a resin composition comprising granular boron nitride whose amount of oxide is preferably reduced by washing, particularly granular boron nitride which is substantially free of calcium oxide and a resin material.
  • the resin composition comprises preferably 10 to 90%, more preferably 15 to 88%, for example 30 to 85%, particularly 50 to 82% of granular boron nitride based on the total mass thereof.
  • these ranges are shown in terms of volume ratio, they correspond to about 5 to 80% by volume, about 10 to 70% by volume, and about 15 to 50% by volume, respectively, although they differ slightly depending on the apparent density of the granules.
  • the resin composition may contain the granular boron nitride composition of the present invention in the same proportion as the above-mentioned granular boron nitride.
  • the method for producing a granular boron nitride composition of the present invention is selected from a boron nitride component (1) containing boron nitride (BN, preferably hexagonal boron nitride (h-BN)), and ittrium, cerium, and itterbium.
  • BN boron nitride
  • h-BN hexagonal boron nitride
  • a mixture containing a rare earth component (2) containing an oxide and / or a precursor thereof of at least one rare earth element and a calcium component (3) is heat-treated in a non-oxidizing gas atmosphere. It is characterized by including a process.
  • the rare earth component (2) contains a precursor of an oxide of at least one rare earth element selected from yttrium, cerium and ytterbium
  • the heat treatment step or before the step is converted to the corresponding rare earth element oxide in a preheating or calcining step that may be carried out as needed.
  • the calcium component (3) contains calcium carbonate, it is similarly converted to calcium oxide. The converted material contributes to the precipitation and growth of granular boron nitride crystals as a rare earth element oxide or calcium oxide.
  • the components (1), (2) and (3) as raw materials are mixed to obtain a mixture, which is heated in a non-oxidizing gas atmosphere, for example. It is carried out by heating at 1800 to 2100 ° C.
  • the mixture may contain other components, for example, components that are inevitably contained in the production of components as raw materials.
  • the boron nitride component (1) contains excessive oxygen (for example, when it contains 5% by mass or more of oxygen because it contains boron oxide)
  • the mixture may contain carbon, and oxygen is generated by reducing with carbon. (As a result, boron nitride can be produced).
  • an appropriate dispersion medium eg ethanol, acetone, etc.
  • the slurry is uniformly mixed with a homogenizer together with a dispersion medium 5 to 20 times as much as the mixture on a mass basis. Or paste. After this is dried, it is calcined in the air (calcination, calcination or calcining) as necessary to obtain a powder in which the components constituting the mixture are uniformly mixed, and then in a non-oxidizing gas atmosphere, Heat treatment is performed at 1800 to 2100 ° C.
  • the boron nitride component (1) used in the present invention is synthesized from commercially available h-BN, commercially available t-BN, BN produced by a reduction nitride method of a boron compound and ammonia, and a nitrogen-containing compound such as a boron compound and melamine.
  • the above-mentioned BN and the like can be exemplified, and can be used without particular limitation.
  • Such a boron nitride component (1) preferably contains at least 90%, preferably at least 95%, and more preferably at least 96% of boron nitride on a mass basis.
  • the boron nitride constituting the boron nitride component (1) is preferably h-BN, but may contain other boron nitride.
  • the proportion of h-BN in boron nitride may be preferably at least 90%, more preferably at least 95%, for example at least 96%, especially at least 98%, with the rest being other boron nitride.
  • Boron nitride may be commercially available in the form of fine particles or powders.
  • boron nitride powder having a primary particle diameter of 50 nm, an agglomerated particle diameter of 3 ⁇ m, and a specific surface area of 160 m 2 / g is commercially available from Nissin Refratec Co., Ltd. as “ABN”.
  • h-BN in powder form is commercially available as "AP170S” from MARUKA Co., Ltd.
  • the boron nitride component (1) may have a total oxygen concentration of 1% by mass to 10% by mass, preferably a total oxygen concentration of 5% by mass or less. Is preferable.
  • the primary particle diameter of the boron nitride particles is generally small and the crystals are often underdeveloped, and it is easy when the boron nitride particles are mixed with other components used in the present invention and heat-treated. It is preferable because it dissolves in. If the total oxygen concentration is excessively high, when the granular boron nitride composition obtained after the heat treatment is used as a heat conductive filler, it is preferable because it contains an oxide and may not be able to achieve high heat conductivity. Absent. In that case, carbon can be added to the mixture as described above to reduce the amount of oxygen. Alternatively, the granular boron nitride composition may be washed to reduce oxides.
  • the total oxygen concentration of the boron nitride component (1) when the total oxygen concentration of the boron nitride component (1) is excessively low, it may be difficult to dissolve in the liquid phase because the purity and crystallinity of boron nitride are already good, and as a result, the crystal growth of boron nitride and the like may occur. The change is small, and it may be difficult to form an aggregated structure.
  • the total oxygen concentration in the boron nitride component (1) as a raw material can be measured by an inert gas melting-infrared absorption method using an oxygen / nitrogen analyzer manufactured by Horiba Seisakusho Co., Ltd.
  • the average particle size of boron nitride contained in the boron nitride component (1) should be 5 ⁇ m or less. Is preferable.
  • the lower limit of the average particle size is not particularly limited, but is usually 0.1 ⁇ m or more. As described above, the average particle size can be measured by a laser diffraction / scattering type particle size distribution measuring device in which granular boron nitride as a raw material is dispersed in an appropriate solvent.
  • the rare earth component (2) used in the production method of the present invention contains a precursor of an oxide of a rare earth element, this may be carried out as necessary in the heat treatment step or before the rare earth element in the baking step. It is converted into an oxide, and this oxide acts to stably precipitate and grow granular boron nitride.
  • the component that is originally an oxide contained in the rare earth component (2) also acts in the same manner.
  • the rare earth component (2) used in the production method of the present invention is heat-treated together with the boron nitride component (1), it is preferable that the rare earth component (2) has heat resistance to the heat treatment conditions.
  • rare earth element oxides such as yttrium oxide, cerium oxide, and ytterbium oxide and / or precursors thereof are used as those contained in such a rare earth component (2).
  • yttrium oxide is particularly preferable from the viewpoint of thermal conductivity and heat resistance as an oxide, and from the viewpoint of stably precipitating granular boron nitride and growing it so as to have strength.
  • the rare earth component (2) containing such an oxide a commercially available one as such an oxide can be used.
  • At least one rare earth element compound selected from yttrium, cerium and ytterbium used as a precursor for producing such an oxide may be in any suitable form, for example, liquid sol or nitrate. In the form of a water-soluble salt such as, etc., it may be carried out in the heat treatment step or before the heat treatment step as necessary, or is converted into a rare earth element oxide in the baking step.
  • the oxide is at least one selected from yttrium oxide, cerium oxide, and ytterbium oxide, and the precursor thereof brings an oxide of such a rare earth element. It is a thing.
  • at least one selected from salts of inorganic acids such as acetates, nitrates, carbonates, citrates, oxalates and sulfates of rare earth elements, salts of organic acids, chlorides and the like can be exemplified.
  • yttrium oxide, acetate of yttrium, nitrate, carbonate, citrate, oxalate, sulfate and the like are preferably used from the viewpoint of easy availability.
  • yttrium oxide, yttrium nitrate, yttrium carbonate, yttrium citrate, yttrium oxalate, yttrium sulfate and the like are used.
  • the rare earth component (2) one selected from the above-mentioned rare earth element oxide and a metal compound which is a precursor thereof may be used alone, or in another embodiment, two or more thereof may be used in combination. ..
  • the rare earth component (2) is added to the oxide of the rare earth element and / or its precursor as described above, as long as the granular boron nitride produced in the present invention is not substantially adversely affected, for example, in the production thereof. It may contain other components that are unavoidably included.
  • the calcium component (3) used in the production method of the present invention contains at least one selected from calcium oxide and calcium carbonate. Calcium carbonate is converted to calcium oxide in the heat treatment step of the present invention or prior to it, if necessary, or in a baking step.
  • the calcium component (3) may be in any suitable form, and may be, for example, a solid (for example, powder), a dispersion, or the like. Although not bound by any theory and not limiting the present invention, in consideration of the results of Examples and Comparative Examples described later, such a calcium component (3) is the above-mentioned rare earth element oxide.
  • a liquid phase capable of melting and dissolving the existing boron nitride prior to the boron nitride is provided, and then the boron nitride is crystallized (that is, recrystallized) in the liquid phase. It is considered to have a function of providing a solvent for crystallization. During such crystallization, it is considered that the boron nitride crystal grows larger and aggregates and bonds to form a shell structure having a larger particle size.
  • a calcium component (3) commercially available calcium oxide and calcium carbonate can be used.
  • the rare earth element in the rare earth component (2): the calcium element in the calcium component (3) is preferably 1: 0.25 to 1: 4 based on the number of elements in the heat-treated mixture. , More preferably 1: 0.5 to 1: 3, particularly preferably 1: 0.7 to 1: 2.5, for example 1: 1 to 1: 2. If the calcium is too low, the calcium oxide component may be inadequate to provide the large particle size of the granular boron nitride, and if the calcium is too high, the rare earth element oxides are under-presenced. In some cases, the effect, particularly the effect of firmly binding granular boron nitride, may be insufficient.
  • the amount of the rare earth element oxide contained in the rare earth component (2) in the case of a precursor, converted to the corresponding rare earth element oxide
  • the ratio of the amount of calcium oxide contained (converted to calcium oxide in the case of calcium carbonate) to the amount of boron nitride and rare earth element oxides and the amount of calcium oxide in the mixture, that is, (rare earth oxide amount +) Amount of calcium oxide) / (amount of boron nitride + amount of rare earth oxide + amount of calcium oxide) is generally 5% to 60% (hence, boron nitride is 95 to 40%), preferably 6% to 50% on a mass basis. % (Thus, boron nitride is 94-50%), more preferably 7-42%, particularly preferably 14-42%, for example 14-35%.
  • the effect of stabilizing the shell structure of granular boron nitride by the rare earth element oxide and calcium oxide during heat treatment becomes small.
  • the shell structure is likely to collapse.
  • the viscosity of the resin composition melted for molding increases. Therefore, a larger force acts on the resin composition during molding, and the effect of stabilizing the shell structure tends to decrease.
  • the amount of boron nitride contained in the obtained granular boron nitride composition becomes excessively small.
  • the effect of improving the thermal conductivity may be reduced.
  • the mixture may further contain carbon, if necessary.
  • carbon black carbon black, graphite, or a carbon precursor that can be a carbon source at high temperature can be used, but carbon black is preferable from the viewpoint of easy availability.
  • carbon black carbon black such as the furnace method and the channel method, acetylene black and the like can be used.
  • the average particle size (volume-based average particle size) of these carbon blacks is arbitrary, but is preferably 0.01 to 20 ⁇ m.
  • a carbon precursor may be used in place of or in addition to the carbon described above.
  • synthetic resin condensates such as phenol resin, melamine resin, epoxy resin and furanphenol resin, hydrocarbon compounds such as pitch and tar, and organic compounds such as cellulose, sucrose, polyvinylidene chloride and polyphenylene can be used as precursors. .. Of these, those having less metal impurities such as phenol resin, cellulose, and polyphenylene are particularly preferable. These may be used alone or in admixture of two or more.
  • the amount of carbon used (as the amount of carbon produced from the carbon precursor when a carbon precursor is used) is preferably 5% by mass or less, more preferably 3% by mass or less, based on the boron nitride component (1) on a mass basis. is there.
  • the presence of carbon during the heat treatment can prevent excessive oxygen from being present. As a result, the shell structure of the granular boron nitride obtained by the oxide during the heat treatment becomes stronger. The use of more carbon than this amount may impair the stability of the shell structure.
  • the amount of carbon used By reducing the amount of carbon used, the amount of carbon remaining after the heat treatment can be minimized, and therefore, when used as a thermally conductive filler, the effect of granular boron nitride on the insulating property can be suppressed. In this sense, it is preferable that the use of carbon can be omitted. Therefore, in the method for producing aggregates of the present invention, the mixture is carbon-free.
  • the mixture containing the components (1) to (3) may contain other components as long as the production method and the produced granular boron nitride are not adversely affected. ..
  • other components include one or more inorganic substances of aluminum compounds such as aluminum nitride, aluminum hydroxide, and aluminum oxide (alumina).
  • the amount used is generally preferably 5% or less, for example, 0.1 to 3% with respect to the boron nitride component (1) on a mass basis.
  • the boron nitride component (1), the rare earth component (2) and the calcium component (3) constituting the mixture, and the above-mentioned mixture of carbon and other components contained as necessary are mixed.
  • the method is not particularly limited, and for example, dry mixing and wet mixing can be used.
  • horizontal cylindrical mixer, V-type mixer, double cone type mixer, ribbon type mixer, single shaft rod or rotor type mixer with pin, paddle type mixer, cone type screw mixer, high speed Flow type mixers, rotary disk type mixers, maller type mixers, air flow stirring type mixers, etc. are used.
  • a general mixer such as a 3-roll mixer, a conider, a botator, a high-speed flow mixer, and an ultrasonic homogenizer can be used.
  • the solvent (dispersion medium) used for wet mixing is not limited, but from the viewpoint of ease of drying and simplification of the equipment, pure water, alcohols such as ethanol, methanol and propanol, and organic solvents such as ketones such as acetone are used.
  • a mixed solvent of water and these organic solvents is preferred.
  • the mass is 5 to 20 times, particularly 5 to 10 times.
  • the method for carrying out this drying is not particularly limited, and heat drying, heat vacuum drying, or the like may be used. Generally, it is preferable to perform heat drying. On small scales, heating vacuum drying is usually used. In the case of heat drying, it is preferable that the heating temperature is 100 to 120 ° C. and the heating time is about 12 to 48 hours. If the heating temperature is too low or the heating time is too short, sufficient drying cannot be performed, and conversely, if the heating temperature is too high or the heating time is too long, it is not preferable from the viewpoint of heating cost. In the case of vacuum drying by heating, the solvent is distilled off using an evaporator at a temperature of about 50 ° C.
  • the crushing after drying may be crushing with a mortar, or another ball mill or the like can be used.
  • a mortar or another ball mill or the like can be used.
  • This average particle size can be measured by the same method as the average particle size described above.
  • the atmosphere during drying and crushing may be an air atmosphere, but it is preferably in dry air having a humidity of 50% or less in order to avoid moisture absorption.
  • calcination or calcination, that is, heat treatment at a lower temperature, which is carried out prior to heat treatment
  • calcium carbonate is used as the calcium component (3), and it is converted to calcium oxide.
  • This calcination may be performed by heating at a temperature of 500 to 700 ° C. for about 1 to 5 hours in an oxidizing atmosphere such as air. If the heating temperature during calcination is too low or the heating time is too short, conversion will be insufficient, and acid will be generated during calcination or nitrogen oxides will be generated, which is not preferable because it will damage the equipment. .. When a heating furnace capable of exhausting decomposition gas or the like during heating is used, the step of calcination may be omitted, and calcination can be performed at the same time in the subsequent heat treatment.
  • the boron nitride contained in the boron nitride component (1) may be oxidized, which is not preferable. If the heating furnace is equipped with an exhaust facility, oxidation can be avoided by exhausting the air inside the furnace. In this case, oxidation of boron nitride due to a high heating temperature and a long heating time does not matter.
  • the temperature of the heat treatment is usually 1800 to 2100 ° C, preferably 1900 to 2100 ° C, and more preferably 2000 to 2100 ° C. If the temperature of the heat treatment is lower than this range, the crystallization of h-BN becomes insufficient, an amorphous portion with undeveloped crystallization remains, and the effect of improving the thermal conductivity when used as a heat conductive filler becomes small. .. If the temperature of the heat treatment exceeds the above upper limit, the rare earth element oxide may evaporate and decompose, the shell structure cannot be maintained, and boron nitride may be decomposed.
  • the heat treatment time is usually 5 hours to 20 hours, preferably 5 hours to 15 hours. If the heat treatment time is shorter than this range, crystal growth will be insufficient, and if it is longer than this range, h-BN may be partially decomposed.
  • the heat treatment is performed in a non-oxidizing gas atmosphere, it is preferable to heat the inside of the furnace while exhausting it with a vacuum pump, continue exhausting until the amount of decomposed gas and the like associated with the heating is reduced, and then non-oxidize. While introducing the sex gas, the temperature is continuously heated to a desired temperature.
  • the standard temperature for exhausting with a vacuum pump is 200 to 700 ° C, for example, about 600 ° C, and the temperature rise rate is about 20 ° C / min while maintaining the degree of vacuum up to that temperature at about 10 -1 Pa. May be heated.
  • the non-oxidizing gas is introduced to atmospheric pressure and continued to be introduced until the end of the heat treatment.
  • the flow rate of the non-oxidizing gas depends on the size of the furnace, but usually there is no problem if it is 1 ml / min or more.
  • the temperature is raised to about 1100 ° C. at 20 to 100 ° C./min, and then from 1100 ° C. to a predetermined heat treatment temperature at 2 to 20 ° C./min. After heating at this temperature for the above-mentioned heat treatment time, it is preferable to lower the temperature to room temperature at, for example, about 5 to 50 ° C./min.
  • the method for producing granular boron nitride of the present invention also includes a step of cooling the heat-treated mixture to room temperature.
  • the firing furnaces to be heat-treated include batch-type furnaces such as muffle furnaces, tubular furnaces, atmospheric furnaces, and multipurpose high-temperature furnaces, and continuous furnaces such as rotary kilns, screw conveyor furnaces, tunnel furnaces, belt furnaces, pusher furnaces, and vertical continuous furnaces. It can be mentioned and used properly according to the purpose.
  • the residue may be removed from the granular boron nitride composition obtained by the above-mentioned method.
  • This removal can be carried out by washing the granular boron nitride composition with an aqueous acid solution.
  • an oxide is removed by dissolving the salt in existing water to obtain an aqueous salt solution and removing it using a reaction that converts the residue into a corresponding water-soluble salt.
  • the acid to be used include organic acids and inorganic acids, and for example, hydrochloric acid, nitric acid, sulfuric acid and the like may be used.
  • Cleaning with this acid aqueous solution can be carried out by dispersing the granular boron nitride composition in the acid aqueous solution with stirring. Then, the composition is filtered off, washed with water to remove the residual acid, and then dried to obtain granular boron nitride. Calcium oxide and borate compounds (if present) can be easily removed in substantially all of them by acid cleaning.
  • the total amount of rare earth element oxides contained in the obtained granular boron nitride is preferably 0.1 to 30%, preferably 1 to 15%, and more preferably 3 to 10% based on the mass of the granular boron nitride. is there.
  • the remaining rare earth element oxide can be easily adjusted by appropriately selecting cleaning conditions (for example, acid concentration, amount of aqueous solution used for cleaning and / or number of cleanings).
  • the amount of rare earth element oxide in the granular boron nitride composition can be measured as follows: 1 g of an acid-washed granular boron nitride composition was added to 60 g of a 1N hydrochloric acid aqueous solution in a Teflon-lined pressure-resistant container, and after sealing, treatment was performed at 100 ° C. for 11 hours. The obtained slurry is filtered with a membrane filter, and the solution obtained by diluting the filtrate with pure water 200 times is used as an ICP (inductively coupled plasma) luminescence analyzer (ICPS-7510, manufactured by Shimadzu Corporation) for rare earth elements.
  • ICP inductively coupled plasma luminescence analyzer
  • yttrium e.g., yttrium
  • XRD analysis of the slag is confirmed to be free of peaks of rare earth element oxides.
  • the nitrogen element is present in the circumferential (or substantially circumferential) portion (that is, the cyclic portion) of the polygonal N element, and the Y element is present inside it.
  • the N element that is, boron nitride
  • Y that is, yttrium oxide
  • the granular boron nitride of the present invention is composed of a shell portion composed of boron nitride and a rare earth element oxide remaining inside the shell portion in an amount corresponding to the degree of cleaning.
  • FIG. 9 shows the results of the same analysis of the granular boron nitride composition of the present invention obtained in Example 11 described later (thus, the one in the state before the cleaning treatment was performed).
  • the upper left of FIG. 9 shows the SEM photograph
  • the upper right shows the EDS mapping result of N element
  • the lower left shows the EDS mapping result of Ca element
  • the lower right shows the EDS mapping result of Y element.
  • the N element exists in a shell structure around the granular boron nitride crystal
  • the calcium element and the yttrium element exist inside the shell structure (thus, these oxides exist).
  • the cleaning treatment reduces the amount of oxides.
  • the granular boron nitride composition of the present invention can be preferably produced by the above-mentioned method for producing a granular boron nitride composition of the present invention, and is an oxide of at least one rare earth element selected from boron nitride and ytterbium, cerium and ytterbium. And calcium oxide are contained, and boron nitride preferably has a graphite structure. These oxides can be reduced in weight by acid cleaning as described above.
  • the shell structure is strengthened by the rare earth element oxide and calcium oxide, and as a result, the strength when pressure is applied (for example, crush strength) is improved. Therefore, it can be blended with a resin material for the purpose of improving thermal conductivity anisotropy and thermal conductivity. Further, since the solid lubricity derived from granular boron nitride is maintained, the molding processability as a resin composition can be maintained well even when it is blended with a resin material, and the molded product can be formed. When manufactured, a heat conduction path in the thickness direction is likely to be formed in the molded body due to the shell structure. As a result, the thermal conductivity in the thickness direction of the molded product can be increased. In addition, the granular boron nitride of the present invention also has chemical stability, heat resistance, etc. derived from boron nitride.
  • the oxygen is generally contained as boron oxide (B 2 O 3 ).
  • boron oxide reacts with the rare earth element oxide and calcium oxide to form an oxide (for example, a composite oxide such as CaYBO 4 ) to form a liquid phase.
  • this oxide dissolves boron nitride contained in the boron nitride component (1), similarly to the rare earth element oxide and calcium oxide.
  • the shell structure can be strengthened when granular boron nitride is produced when boron nitride is recrystallized.
  • the above-mentioned composite oxides can be reduced depending on the conditions for cleaning with an acid, and substantially the entire amount can be removed.
  • the content of the rare earth element oxide in the granular boron nitride composition of the present invention is the above-mentioned present invention when the above-mentioned washing is not carried out (that is, when only the heat treatment and the subsequent cooling are carried out). It is substantially equal to the sum of the amounts of rare earth element oxides and oxides derived from their precursors (if precursors are present) contained in the mixture heat-treated by the method for producing the granular boron nitride composition of. Similarly, the content of calcium oxide is substantially equal to the sum of the amounts of calcium oxide and oxides derived from calcium carbonate (if precursors are present) contained in the heat-treated mixture.
  • the boron nitride content of the granular boron nitride composition is preferably 40 to 95%, more preferably 50 to 90%, based on the total mass of boron nitride, rare earth element oxides and calcium oxide of the granular boron nitride composition. For example, 55-85%.
  • the resin composition of the present invention particularly a thermally conductive resin composition, comprises the above-mentioned granular boron nitride and resin material of the present invention. That is, as described above, the granular boron nitride of the present invention is suitably used as a thermally conductive filler in the resin composition. In some cases, it is also possible to use a granular boron nitride composition instead of the granular boron nitride.
  • the resin material that functions as the resin that forms the matrix in the resin composition is not particularly limited, and may be, for example, a curable resin, a thermoplastic resin, or the like.
  • the curable resin may be any crosslinkable resin such as thermosetting, photocurable, and electron beam curable, but a thermosetting resin is preferable in terms of heat resistance, water absorption, dimensional stability, and the like. Especially, epoxy resin is most suitable.
  • the epoxy resin may be only an epoxy resin having one kind of structural unit, but a plurality of epoxy resins having different structural units may be combined. Further, the epoxy resin is used together with a curing agent for epoxy resin and a curing accelerator, if necessary.
  • epoxy resin an epoxy resin (hereinafter, "epoxy resin") (A) ” is preferably contained, and in particular, the mass ratio of the epoxy resin (A) to the total amount of the epoxy resin is preferably in the range of 5 to 95% by mass, more preferably 10 to 90% by mass, still more preferably. Is preferably contained in the range of 20 to 80% by mass, but is not limited to such a substance.
  • the phenoxy resin usually refers to a resin obtained by reacting epihalohydrin with a divalent phenol compound, or a resin obtained by reacting a divalent epoxy compound with a divalent phenol compound, but in the present invention.
  • a phenoxy resin which is a high molecular weight epoxy resin having a mass average molecular weight of 10,000 or more is referred to as an epoxy resin (A).
  • the mass average molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography.
  • a phenoxy resin having at least one skeleton selected from the group consisting of a naphthalene skeleton, a fluorene skeleton, a biphenyl skeleton, an anthracene skeleton, a pyrene skeleton, a xanthene skeleton, an adamantane skeleton and a dicyclopentadiene skeleton is preferable. ..
  • a phenoxy resin having a fluorene skeleton and / or a biphenyl skeleton is particularly preferable because the heat resistance is further enhanced.
  • One of these may be used alone, or two or more thereof may be mixed and used.
  • the epoxy resin other than the epoxy resin (A) is preferably an epoxy resin having two or more epoxy groups in the molecule (hereinafter, may be referred to as "epoxy resin (B)"), for example.
  • epoxy resin (B) Bisphenol A type epoxy resin, bisphenol F type epoxy resin, naphthalene type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, phenol aralkyl type epoxy resin, biphenyl type epoxy resin, triphenylmethane type epoxy resin, dicyclopentadiene
  • Examples thereof include various epoxy resins such as type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, and polyfunctional phenol type epoxy resin. One of these may be used alone, or two or more thereof may be mixed and used.
  • the epoxy resin (B) has a mass average molecular weight of preferably 100 to 5000, more preferably 200 to 2000, from the viewpoint of controlling the melt viscosity. If the mass average molecular weight is lower than 100, the heat resistance tends to be inferior, and if it is higher than 5000, the melting point of the epoxy resin tends to be high and the workability tends to be lowered.
  • the epoxy resin according to the present invention may contain an epoxy resin (hereinafter, "other epoxy resin") other than the epoxy resin (A) and the epoxy resin (B) as long as the purpose is not impaired.
  • the content of the other epoxy resin is usually 50% by mass or less, preferably 30% by mass or less, based on the total of the epoxy resin (A) and the epoxy resin (B).
  • the ratio of the epoxy resin (A) to the total epoxy resin containing the epoxy resin (A) and the epoxy resin (B) is preferably 5 as described above, with the total being 100% by mass. It is ⁇ 95% by mass, preferably 10 to 90% by mass, and more preferably 20 to 80% by mass.
  • the "total epoxy resin containing the epoxy resin (A) and the epoxy resin (B)” means that the epoxy resin contained in the resin composition of the present invention is only the epoxy resin (A) and the epoxy resin (B). Means the total of the epoxy resin (A) and the epoxy resin (B), and when another epoxy resin is contained, the total of the epoxy resin (A), the epoxy resin (B) and the other epoxy resin is used. means.
  • the ratio of the epoxy resin (A) is at least the above lower limit, the effect of improving the thermal conductivity by blending the epoxy resin (A) can be sufficiently obtained, and the desired high thermal conductivity can be obtained. ..
  • the proportion of the epoxy resin (A) is not more than the above upper limit, and in particular, when the epoxy resin (B) is 10% by mass or more of the total epoxy resin, the compounding effect of the epoxy resin (B) is exhibited, and the curable and cured product is exhibited. The physical properties of are sufficient.
  • the curing agent for epoxy resin may be appropriately selected according to the type of resin used.
  • an acid anhydride-based curing agent and an amine-based curing agent can be mentioned.
  • the acid anhydride-based curing agent include tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, and benzophenone tetracarboxylic acid anhydride.
  • amine-based curing agent examples include aliphatic polyamines such as ethylenediamine, diethylenetriamine and triethylenetetramine, aromatic polyamines such as diaminodiphenylsulfone, diaminodiphenylmethane, diaminodiphenyl ether and m-phenylenediamine, and dicyandiamide. One of these may be used alone, or two or more thereof may be mixed and used.
  • These curing agents for epoxy resins are usually blended in the range of 0.3 to 1.5 in an equivalent ratio with respect to the epoxy resin.
  • the curing accelerator may be appropriately selected according to the type of resin and curing agent used.
  • examples of the curing accelerator for the acid anhydrous curing agent include boron trifluoride monoethylamine, 2-ethyl-4-methylimidazole, 1-isobutyl-2-methylimidazole, and 2-phenyl-4-methylimidazole. Can be mentioned. One of these may be used alone, or two or more thereof may be mixed and used.
  • These curing accelerators are usually used in the range of 0.1 to 5 parts by mass with respect to 100 parts by mass of the epoxy resin.
  • the resin material used in the resin composition of the present invention may be a thermoplastic resin.
  • the thermoplastic resin include polyolefin resins such as polyethylene resin, polypropylene resin and ethylene-vinyl acetate copolymer resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyester resin such as liquid crystal polyester resin, polyvinyl chloride resin and phenoxy.
  • examples thereof include resins, acrylic resins, polycarbonate resins, polyphenylene sulfide resins, polyphenylene ether resins, polyamide resins, polyamideimide resins, polyimide resins, polyetheramideimide resins, polyetheramide resins and polyetherimide resins.
  • copolymers such as those block copolymers and graft copolymers are also included. These may be used alone or in admixture of two or more.
  • the resin material may be a rubber component, and examples of the rubber component include natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, ethylene-propylene copolymer rubber, and ethylene-propylene.
  • -Diene copolymer rubber, butadiene-acrylonitrile copolymer rubber, isobutylene-isoprene copolymer rubber, chloroprene rubber, silicone rubber, fluororubber, chloro-sulfonated polyethylene, polyurethane rubber and the like can be mentioned.
  • One of these may be used alone, or two or more thereof may be mixed and used.
  • the amount of the granular boron nitride (or the granular boron nitride composition) of the present invention contained in the resin composition of the present invention is usually preferably 10 to 90% based on the mass of the resin composition. , More preferably 15 to 88%, still more preferably 30 to 85%.
  • the amount of granular boron nitride in the resin composition is less than this range, the viscosity of the resin composition (viscosity when melted) is low, the molding processability is good, but the thermal conductivity is improved. The effect can be inadequate.
  • the amount of granular boron nitride in the resin composition is larger than such a range, the viscosity of the resin composition at the time of melting becomes high, and molding tends to be difficult.
  • the resin composition of the present invention may contain other components as long as the effects of the present invention can be obtained.
  • Such components include functional resins obtained by imparting functionality to the above-mentioned resins such as liquid crystal epoxy resins, nitride particles such as aluminum nitride, silicon nitride, and fibrous boron nitride, alumina, and fibrous alumina.
  • functional resins obtained by imparting functionality to the above-mentioned resins
  • nitride particles such as aluminum nitride, silicon nitride, and fibrous boron nitride, alumina, and fibrous alumina.
  • insulating metal oxides such as zinc oxide, magnesium oxide, berylium oxide and titanium oxide
  • insulating carbon components such as diamond and fullerene
  • resin curing agents resin curing accelerators, viscosity modifiers and dispersion stabilizers.
  • the resin composition of the present invention may contain a solvent.
  • a solvent a known solvent that dissolves the resin is used.
  • examples of such a solvent include methyl ethyl ketone, acetone, cyclohexanone, toluene, xylene, monochlorobenzene, dichlorobenzene, trichlorobenzene, phenol, and hexafluoroisopropanol. These may be used alone or in admixture of two or more.
  • the solvent is used in the range of, for example, 0 to 10,000 parts by mass with respect to 100 parts by mass of a resin such as an epoxy resin.
  • the resin composition of the present invention is subjected to surface treatment such as an inorganic filler such as aluminum hydroxide and magnesium hydroxide, and a silane coupling agent for improving the interfacial adhesive strength between the inorganic filler and the matrix resin, as long as the effect is not impaired.
  • an inorganic filler such as aluminum hydroxide and magnesium hydroxide
  • a silane coupling agent for improving the interfacial adhesive strength between the inorganic filler and the matrix resin, as long as the effect is not impaired.
  • Agents, reducing agents and the like may be added.
  • the total amount of the granular boron nitride and the inorganic filler of the present invention in the resin composition is 90% by mass or less. preferable.
  • the resin composition of the present invention can be obtained by uniformly mixing the granular boron nitride (or granular boron nitride composition) of the present invention, the resin material, and other components added as necessary by stirring or kneading. Can be done.
  • a general kneading device such as a mixer, a kneader, a single shaft or a twin shaft kneader can be used, and in the mixing, heating may be performed if necessary.
  • the molded product of the present invention is obtained by molding the resin composition of the present invention.
  • a molding method of the molded body a method generally used for molding thereof, for example, injection molding or mold molding, can be used depending on the properties of the resin composition.
  • the resin composition is heated to be fluidized or plasticized as necessary, and the resin composition is molded into a molded product using a mold or the like. Therefore, the fluidized resin Some force acts on the composition. For example, pressure acts when the resin composition is filled into a mold.
  • the resin material is a curable resin (for example, phenol resin, epoxy resin, melamine resin, urea resin, etc.), a thermoplastic resin (for example, polyethylene, polypropylene, polyvinyl chloride, polystyrene, acrylic resin, etc.) can be used. Even if there is, it is considered to be applicable.
  • a curable resin for example, phenol resin, epoxy resin, melamine resin, urea resin, etc.
  • a thermoplastic resin for example, polyethylene, polypropylene, polyvinyl chloride, polystyrene, acrylic resin, etc.
  • the resin composition of the present invention when it has plasticity and fluidity, it can be molded by curing the resin composition in a desired shape, for example, in a state of being filled in a mold.
  • a method for producing such a molded product an injection molding method, an injection compression molding method, an extrusion molding method, and a compression molding method can be used.
  • the resin composition of the present invention is a thermosetting resin composition such as an epoxy resin or a silicone resin
  • the molded product can be molded, that is, cured under curing conditions according to the respective compositions.
  • the molded product when the resin composition of the present invention is a thermoplastic resin composition, the molded product can be molded under the conditions of a temperature equal to or higher than the melting temperature of the thermoplastic resin and a predetermined molding speed and pressure.
  • the molded product of the present invention can also be obtained by cutting the resin composition of the present invention into a desired shape from a molded or cured solid bulk material.
  • the amount of the resin material is 65 to 85% on a mass basis, although it depends on the blending amount of the resin material and the granular boron nitride (or the granular boron nitride composition).
  • the thermal conductivity in the direction parallel to the direction in which the force is applied during molding is usually 10 to 25 W / (m ⁇ K), preferably 15 to 23 W / (m ⁇ K), more preferably. Is 18 to 22 W / (m ⁇ K).
  • the thermal conductivity in the direction perpendicular to the direction in which pressure is applied during molding is usually 15 to 35 W / (m ⁇ K), preferably 20 to 30 W / (m ⁇ K), and more preferably 22 to 27 W / (. m ⁇ K).
  • the thermal conductivity in the parallel direction is the thermal conductivity in the vertical direction.
  • the ratio is preferably 70 to 120%, more preferably 80 to 110%, particularly 90 to 105%, and the anisotropy of the molded product with respect to thermal conductivity can be significantly suppressed, and in some cases, the anisotropy is substantially suppressed. Can be resolved.
  • the thermal conductivity in the parallel direction is similarly the heat in the vertical direction.
  • the anisotropy can be suppressed even when the granular boron nitride contains an oxide, particularly a rare earth element oxide, a Ca-rare earth element-BO composite oxide, or the like.
  • the resin composition comprises 65-85% by weight of granular boron nitride, in which case the ratio of the parallel thermal conductivity to the vertical thermal conductivity is at least about 90-105%. Is.
  • Ethanol of the obtained slurry was removed by an evaporator, and a dried powder was obtained as a mixture.
  • This powder was placed in a boron nitride crucible and heat-treated using a multipurpose high-temperature furnace (Fuji Dempa Kogyo Co., Ltd., Hi-Multi 5000) to obtain a granular boron nitride composition.
  • the composition in addition to boron nitride, contained CaYBO 4 Ca-Y-B- O -based composite oxide such like. It is considered that BO in this composite oxide is derived from the fact that the boron nitride powder used as a raw material contains 4% by weight of oxygen.
  • the heat treatment process involves raising the temperature from room temperature to 1100 ° C. at 20 ° C./min, then raising the temperature from 1100 to 1900 ° C. at 10 ° C./min, holding at 1900 ° C. for 10 hours, and then at 20 ° C./min. It was carried out by lowering the temperature to room temperature.
  • the atmosphere of the heat treatment is maintained in a vacuum of less than 1 ⁇ 10 -1 Pa up to 400 ° C., and then nitrogen gas is introduced into the furnace to atmospheric pressure, and the state of nitrogen gas flow of 1 ml / min is maintained until the end of the heat treatment. Retained.
  • the mixture was heat-treated as described above to obtain the granular boron nitride composition of the present invention. Then, the obtained composition was washed to remove the oxides (yttrium oxide, calcium oxide) contained therein. Specifically, 2.5 g of the composition was added to 20 ml of a 3N hydrochloric acid aqueous solution in a Teflon-lined closed pressure vessel, and the mixture was reacted at 100 ° C. for 11 hours to convert the contained oxide into a water-soluble salt. Then, it was washed with pure water and filtered to remove salt, and the granular boron nitride of this invention was obtained. When the obtained granular boron nitride was subjected to XRD analysis, yttrium oxide and calcium oxide that could remain in it could not be detected.
  • Example 2 The amount of Y 2 O 3 added in Example 1 was 3.59 g (Example 2: 7.3% by volume in the total amount of the mixed powder before heat treatment), 5.70 g (Example 3: 10 in the total amount of the mixed powder before heat treatment). .9% by volume), 8.07g (Example 4: 14.6% by volume in the total amount of mixed powder before heat treatment), 10.76g (Example 5: 18.2% by volume in the total amount of mixed powder before heat treatment), 13.84 g (Example 6: 21.9% by volume in the total amount of the mixed powder before heat treatment), and the amount of CaO added in Example 1 was 0.89 g (Example 2: 2. in the total amount of the mixed powder before heat treatment).
  • Example 1 7% by volume
  • Example 3 4.1% by volume in the total amount of mixed powder before heat treatment
  • 2.00 g Example 4: 5.4% by volume in the total amount of mixed powder before heat treatment
  • Example 1 was used except for .67 g (Example 5: 6.8% by volume in the total amount of mixed powder before heat treatment) and 3.44 g (Example 6: 8.1% by volume in the total amount of mixed powder before heat treatment).
  • the granular boron nitride of the present invention was repeatedly obtained. When the obtained granular boron nitride was subjected to XRD analysis, yttrium oxide and calcium oxide that could remain in it could not be detected.
  • Example 1 the ratio of the total volume of oxides of Y 2 O 3 and Ca O contained in the mixture powder before heat treatment to the volume of the mixture was 5% by volume in Example 1 and Example 2.
  • Example 3 was 15% by volume
  • Example 4 was 20% by volume
  • Example 5 was 25% by volume
  • Example 6 was 30% by volume.
  • Example 1 was repeated except for the conditions shown in Table 1 below to obtain the granular boron nitride of the present invention.
  • the molar ratio of yttrium oxide to calcium oxide constituting the mixture is 1: 2
  • the molar ratio of yttrium oxide to calcium oxide constituting the mixture of Examples 13 to 18 is 1: 4.
  • the molar ratio of yttrium oxide to calcium oxide constituting the mixture of Examples 19 to 24 was 1: 6.
  • Example 1 was repeatedly heat-treated to obtain the granular boron nitride composition of the present invention, except that 1.97 g of CeO 2 powder was added in place of yttrium oxide to obtain 0.64 g of CaO powder, which was further washed and oxidized.
  • the granular boron nitride of the present invention from which the substance was removed was obtained.
  • cerium oxide and calcium oxide that could remain in it could not be detected.
  • Example 25 the amount of CeO 2 added was 4.15 g (Example 26: 5.9% by volume in the total amount of the mixed powder before heat treatment) and 6.59 g (Example 27: 8. in the total amount of the mixed powder before heat treatment). 8% by volume), 9.34 g (Example 28: 11.8% by volume in the total amount of mixed powder before heat treatment), 12.45 g (Example 29: 14.7% by volume in the total amount of mixed powder before heat treatment), 16.
  • Example 30 17.6% by volume in the total amount of the mixed powder before heat treatment
  • the amount of CaO added in Example 25 was 1.35 g (Example 26: 4.1 volume in the total amount of the mixed powder before heat treatment). %), 2.15 g (Example 27: 6.2% by volume in the total amount of the mixed powder before heat treatment) 3.04 g (Example 28: 8.2% by volume in the total amount of the mixed powder before heat treatment) 4.06 g
  • Example 25 was repeated except that (Example 29: 10.3% by volume in the total amount of the mixed powder before heat treatment) and 5.22 g (Example 30: 12.4% by volume in the total amount of the mixed powder before heat treatment).
  • the granular boron nitride of the present invention was obtained.
  • Example 25 the ratio of the total volume of oxides of CeO 2 and CaO contained in the mixed powder before heat treatment to the volume of the mixture was 5% by volume in Example 25 and 10 in Example 26.
  • the volume was 15% by volume in Example 27, 20% by volume in Example 28, 25% by volume in Example 29, and 30% by volume in Example 30.
  • the mixture was washed with pure water and filtered to remove salts to obtain the granular boron nitride of the present invention.
  • Treatment with the acid as compared with Example 3, because of the small concentration of hydrochloric acid used in the 100 ° C., Y 2 O 3 is partially left, other components could substantially removed.
  • 1 g of granular boron nitride obtained after filtration was added to 20 ml of a 1N hydrochloric acid aqueous solution and reacted at 100 ° C. for 11 hours in a Teflon-lined closed container, the filtrate portion was quantitatively analyzed by ICP to obtain yttrium oxide.
  • Example 4 Although it contained 1.01% by mass, the amount of calcium oxide was below the detection limit.
  • the granular boron nitride composition containing the heat-treated oxides obtained in Example 4, Example 6, Example 9, Example 11, Example 12, Example 18 and Example 24 was similarly prepared. The treatment gave the granular boron nitride of the present invention of Examples 32 to 38, respectively.
  • Comparative Example 1 was repeated by changing the amount of Y 2 O 3 powder to be added.
  • acetone was removed using an evaporator.
  • 0.8 g of a mixture as a resin composition containing granular boron nitride and an epoxy resin material remaining in a eggplant-shaped flask after removal was placed in a mold having a diameter of 15 mm, and the resin composition was thermoset by hot pressing to form a molded product.
  • the conditions for hot pressing are as follows: -Born nitrides of Comparative Examples 1 to 6, Examples 1 to 4, 7 to 10, 13 to 16, 19 to 22, 25 to 28 are hot-pressed for 120 minutes under uniaxial pressure at 125 ° C. and 70 MPa. 7. For boron nitrides of Examples 5, 6, 11, 12, 17, 18, 23, 24, 29, 30 under uniaxial pressure of 125 ° C. and 5 MPa or less, hot press for 60 minutes, followed by pressure up to 70 MPa. Hot press for 60 minutes by raising
  • ⁇ is the density of the molded body (g / cm 3 )
  • ⁇ a is the density of water at the measurement temperature (g / cm 3 )
  • m 1 is the mass of the molded body in air (g)
  • m 2 Is the mass of the molded product in water.
  • Cp is the specific heat of the molded body sample (J / g / K)
  • Cp standard is the specific heat of the reference material (J / g / K)
  • m is the weight of the molded body sample (g)
  • M is the weight of the reference material.
  • G h is the difference between the DSC curves of the empty container and the molded body sample
  • H is the difference between the DSC curves of the empty container and the reference material.
  • the thermal conductivity ( ⁇ ) is the time t 1/2 of irradiating the front surface of the molded product sample with a heat source, measuring the temperature of the back surface, and reaching 1/2 of the time ( ⁇ Tm) until the maximum temperature of the back surface is reached. Obtained from (s) and sample thickness L (m) by the following formula (3):
  • the thermal conductivity of the molded product was measured in the pressurizing direction (pressing direction) of the pressure applied during hot pressing and in the direction perpendicular to it.
  • the strength of the shell structure constituting the granular boron nitride contained in the molded body is insufficient, a part of the shell structure collapses due to hot pressing, the properties of the shell structure of the granular boron nitride are weakened, and the properties of the laminated structure are deteriorated. Become stronger. As a result, the a-axis of the broken boron nitride plate-like crystal becomes more likely to be oriented along the direction perpendicular to the hot press direction, and the (00L) plane of the boron nitride crystal (002), (004), etc. The diffraction peak becomes high.
  • the XRD diffraction pattern is measured with respect to the surface perpendicular to the pressing direction (that is, the hot pressing surface or the pressed surface) using the Lot Göring method. , Obtained by the following formula (4):
  • the lot-gering method is a method of evaluating the degree of orientation of crystals or the like using the degree of orientation calculated by the formula (4) (also referred to as a lot-gering factor).
  • the lotgering factor is 100% in the case of perfect orientation.
  • ⁇ I (hkl) is the sum of the X-ray diffraction intensities of all crystal planes (hkl) measured on the plane perpendicular to the press direction with respect to the sample of the molded product containing the aggregate.
  • ⁇ I 0 (hkl) is the sum of the X-ray diffraction intensities of all crystal planes (hkl) measured for the sample of the molded product obtained when non-oriented boron nitride is used instead of granular boron nitride.
  • ⁇ I (00L) is the X-ray diffraction intensity of a specific crystal plane (for example, a (00L) plane including (002) or (004) plane) measured for a molded product containing an aggregate.
  • ⁇ I 0 (00L) is the crystal plane of the (00L) plane measured for the non-oriented material having the same composition as the hybrid material of the specific plane when the above-mentioned non-oriented boron nitride is used. It is the sum of the X-ray diffraction intensities.
  • the lot-gering method for evaluating the degree of orientation as described above is well known as a method for evaluating the degree of orientation of crystals, and for example, Japanese Patent Application Laid-Open No. 2011-37695 can be referred to.
  • the granular boron nitride obtained from each of the examples has a considerably larger average particle size than the boron nitrides of Comparative Examples 1 to 6 that do not use the calcium component, but the specific surface area is slightly smaller.
  • the thermal conductivity of the molded product of the present invention obtained by molding the resin composition of the present invention using such granular boron nitride as a heat conductive filler about 10 to 25 W / (m. K), and 15 to 35 W / (m ⁇ K) can be achieved in the direction perpendicular to it.
  • Such thermal conductivity is higher than that of a molded product obtained by using a known granular boron nitride as a filler as a comparative example.
  • Such a large thermal conductivity means that granular boron nitride can form an effective thermal conduction path due to the large particle size.
  • the thermal conductivity in the parallel direction is at least about 60% of the thermal conductivity in the vertical direction, and the anisotropy regarding the heat conduction of the molded body containing the granular boron nitride is suppressed. Has been done. In some cases, the particle size and consequently may exceed 100%, and anisotropy with respect to heat conduction may not be substantially observed.
  • the degree of orientation of granular boron nitride in the molded product affects the thermal conductivity of the molded product.
  • Boron nitride or plate-shaped boron nitride
  • the thermal conductivity in the direction parallel to the pressing direction at the time of molding becomes remarkably low, and as a result, the thermal conductivity anisotropy becomes large.
  • Comparative Example 8 since commercially available plate-shaped particles are added, the degree of orientation is high and the thermal conductivity in the direction parallel to the pressing direction is low.
  • the boron nitride particles are not plate-shaped, but synthetic boron nitride particles having a multifaceted structure are added.
  • the cohesive force of the boron nitride crystal is weak, it is considered that the polyhedral structure collapses into a plate-shaped boron nitride due to the force applied by press forming and is oriented. Therefore, as in Comparative Example 8, it is considered that the heat conduction along the direction parallel to the pressing direction is low by press forming.
  • the granular boron nitride produced in this example uses a rare earth element oxide in the production method. Since the rare earth element oxide promotes the assumption of dissolution and reprecipitation of boron nitride, it is said that it brings a stronger cohesive force than boron nitride having a multifaceted structure in Comparative Example 7 produced by adding only the conventional alkaline earth oxide. Conceivable. In particular, in the shell portion of the granular boron nitride produced in this example, it is considered that the integrated plate-shaped boron nitride tends to form a polyhedron or a sphere, which is considered to be a factor for increasing the strength of the granular boron nitride.
  • the granular boron nitride contained in the granular boron nitride particle composition contains an oxide inside before acid cleaning.
  • the degree of acid cleaning for example, by lowering the acid concentration used for cleaning, the amount of rare earth element oxide remaining inside can be changed. If the oxide remains in the granular boron nitride, it is expected that the strength of the shell structure of the formed boron nitride, particularly the compressive strength, can be improved. That is, when a resin composition is obtained using such granular boron nitride and molded by hot pressing, it is considered that the granular boron nitride is less likely to collapse and the degree of orientation of the (00L) plane of the molded product is lowered.
  • the granular boron nitride of the present invention is preferably 0.5 to 15% by mass, more preferably 3 to 10% by mass, and particularly 4 to 8%. Contains% by mass of rare earth element oxides.
  • the resin composition of the present invention and the molded product produced by molding the composition are, for example, a heat-dissipating sheet, a heat conductive paste, and a heat conductive material that require heat conductivity in the fields of electricity and electronics. It can be suitably used as a heat conductive filler in a sex adhesive or the like.

Abstract

According to the present invention, when boron nitride is mixed with a resin material and a molded body is produced by using the resultant mixture, the thermal conductivity is further increased. In addition, when using a rare earth component, the usage amount thereof is reduced.　The granular boron nitride can be produced by means of a method which is for producing a granular boron nitride composition and comprises a step for heat-treatinge, in a non-oxidizing gas atmosphere, a mixture composed of: (1) a boron nitride component containing boron nitride; (2) a rare earth component containing an oxide of at least one rare earth element selected from among yttrium, cerium, and ytterbium, and/or a precursor compound thereof; and (3) a calcium component containing calcium oxide and/or calcium carbonate.

Description

粒状窒化ホウ素の製造方法および粒状窒化ホウ素Manufacturing method of granular boron nitride and granular boron nitride
　本発明は粒状窒化ホウ素組成物の製造方法およびその方法により得られる粒状窒化ホウ素組成物に関する。更に、本発明は、粒状窒化ホウ素組成物および樹脂を含んで成る樹脂組成物、そのような樹脂組成物を成形して得られる、粒状窒化ホウ素および樹脂を含んで成る成形体、ならびにその製造方法に関する。 The present invention relates to a method for producing a granular boron nitride composition and a granular boron nitride composition obtained by the method. Further, the present invention relates to a resin composition containing a granular boron nitride composition and a resin, a molded product containing granular boron nitride and a resin obtained by molding such a resin composition, and a method for producing the same. Regarding.
　窒化ホウ素（以下、「ＢＮ」とも呼ぶ）は、絶縁性のセラミックスであり、ダイヤモンド構造を持つｃ－ＢＮ、黒鉛構造をもつｈ－ＢＮ、乱層構造を持つｔ－ＢＮ等の様々な結晶型が知られている。 Boron nitride (hereinafter, also referred to as “BN”) is an insulating ceramic and has various crystal types such as c-BN having a diamond structure, h-BN having a graphite structure, and t-BN having a multi-layer structure. It has been known.
　これらの中で、ｈ－ＢＮは、合成が比較的容易で、熱伝導性、固体潤滑性、化学的安定性、耐熱性に優れるという特徴を備えていることから、著しく低い熱伝導性を有する樹脂材料にフィラーと混合して熱伝導性を高めることが試みられている。そのような樹脂材料は、電気・電子分野では集積回路の放熱部材用として用いられている。 Among these, h-BN has remarkably low thermal conductivity because it is relatively easy to synthesize and has excellent thermal conductivity, solid lubricity, chemical stability, and heat resistance. Attempts have been made to improve thermal conductivity by mixing a resin material with a filler. Such resin materials are used in the electric and electronic fields for heat dissipation members of integrated circuits.
　しかしながら、ｈ－ＢＮは、グラファイトと同様の積層構造を有し、結晶異方性が大きい。ｈ－ＢＮはマクロ的には粒状であるが、ミクロ的には板状結晶の積層体である。結晶のａ軸方向に相当する板状晶面内では強い共有結合で繋がっているため４００Ｗ／ｍＫ近い大きい熱伝導率を示す。他方、ｃ軸方向に相当する板厚方向は弱いファンデルワールス力結合で積層しているため、１～２Ｗ／ｍＫ程度の小さい熱伝導率を示すに過ぎない。 However, h-BN has a laminated structure similar to graphite and has a large crystal anisotropy. Although h-BN is macroscopically granular, it is microscopically a laminate of plate-like crystals. In the plate-like crystal plane corresponding to the a-axis direction of the crystal, it is connected by a strong covalent bond, so that it exhibits a large thermal conductivity of nearly 400 W / mK. On the other hand, in the plate thickness direction corresponding to the c-axis direction, since they are laminated by a weak Van der Waals force bond, they show only a small thermal conductivity of about 1 to 2 W / mK.
　このような窒化ホウ素を樹脂材料に配合した樹脂組成物を成形して成形体を製造すると、板状の窒化ホウ素が成形時の樹脂組成物の流動方向である成形体の板面方向に配向することとなり、得られる成形体は、板面方向には熱伝導率に優れるものの、厚み方向には低い熱伝導率しか示さないという問題がある。従って、このような粒状ＢＮの異方性を改善することが望まれている。 When a molded product is manufactured by molding a resin composition in which such boron nitride is mixed with a resin material, the plate-shaped boron nitride is oriented in the plate surface direction of the molded product, which is the flow direction of the resin composition at the time of molding. As a result, the obtained molded product has a problem that it exhibits excellent thermal conductivity in the plate surface direction but low thermal conductivity in the thickness direction. Therefore, it is desired to improve the anisotropy of such granular BN.
　例えば、特開２０１３－１４７３６３号には、窒化ホウ素と、イットリウム、セリウム、イッテルビウムから選ばれる少なくとも1種の希土類金属の酸化物と炭素とを混合し、非酸化性ガス雰囲気下で加熱処理する工程を含む金属酸化物含有窒化ホウ素の製造方法が開示されている。この方法で製造される窒化ホウ素は、熱伝導性、固体潤滑性、化学的安定性、耐熱性等の向上を目的として樹脂材料に多量配合した樹脂組成物とした場合であっても、樹脂組成物としての成形加工性を良好に維持しながらも、成形される成形体の厚み方向の熱伝導性を改良できる。 For example, Japanese Patent Application Laid-Open No. 2013-147363 describes a step of mixing boron nitride with an oxide of at least one rare earth metal selected from yttrium, cerium, and ytterbium and carbon, and heat-treating the mixture in a non-oxidizing gas atmosphere. A method for producing a metal oxide-containing boron nitride containing the above is disclosed. The boron nitride produced by this method has a resin composition even when a large amount of the resin composition is blended in the resin material for the purpose of improving thermal conductivity, solid lubricity, chemical stability, heat resistance, etc. It is possible to improve the thermal conductivity in the thickness direction of the molded product to be molded while maintaining good molding processability as a product.
　上述の方法によって窒化ホウ素を製造すると、熱伝導率が改善され得ることが説明されているが、上述の窒化ホウ素の本来の熱伝導率と比較すると、改善される熱伝導率には更なる改善の余地がある。また、イットリウム等の希土類金属成分は比較的高価であるという問題もある。 It has been explained that the thermal conductivity can be improved by producing boron nitride by the above-mentioned method, but the improved thermal conductivity is further improved as compared with the above-mentioned original thermal conductivity of boron nitride. There is room for. Another problem is that rare earth metal components such as yttrium are relatively expensive.
特開２０１３－１４７３６３号公報Japanese Unexamined Patent Publication No. 2013-147363
　従って、窒化ホウ素を樹脂材料に混合して、それを用いて成形体を製造するに際して、熱伝導率を更に大きくすることが望まれている。また、イットリウム等の希土類金属成分を使用する場合、その使用量を減らすことが望ましい。 Therefore, when boron nitride is mixed with a resin material and a molded product is manufactured using the boron nitride, it is desired to further increase the thermal conductivity. When a rare earth metal component such as yttrium is used, it is desirable to reduce the amount used.
　上記課題について、本発明者らは、鋭意検討を重ねた結果、焼結助剤としてのカルシウム化合物および希土類元素酸化物の存在下、窒化ホウ素、特に窒化ホウ素粉末を加熱処理することによって、上述の課題の少なくともひとつを改善できる粒状窒化ホウ素を製造できることを見出した。希土類元素酸化物に加えてカルシウム化合物が存在する条件下で窒化ホウ素粉末を加熱処理することによって、大きな粒子径を有する粒状窒化ホウ素を製造できることが見出された。 As a result of diligent studies on the above problems, the present inventors have described above by heat-treating boron nitride, particularly boron nitride powder, in the presence of a calcium compound as a sintering aid and a rare earth element oxide. We have found that it is possible to produce granular boron nitride that can improve at least one of the problems. It has been found that granular boron nitride having a large particle size can be produced by heat-treating the boron nitride powder under the condition that a calcium compound is present in addition to the rare earth element oxide.
　本発明は、第１の要旨において、
　（１）窒化ホウ素を含んで成る窒化ホウ素成分、
　（２）イットリウム、セリウムおよびイッテルビウムから選択される少なくとも１つの希土類元素の酸化物および／またはその前駆体化合物を含んで成る希土類成分、および
　（３）酸化カルシウムおよび／または炭酸カルシウムを含んで成るカルシウム成分
を含んで成る混合物を、非酸化性ガス雰囲気下で加熱処理する工程を含むことを特徴とする粒状窒化ホウ素組成物の製造方法を提供する。 The present invention is described in the first gist.
(1) Boron nitride component containing boron nitride,
(2) Rare earth components containing oxides of at least one rare earth element selected from yttrium, cerium and itterbium and / or precursor compounds thereof, and (3) calcium containing calcium oxide and / or calcium carbonate. Provided is a method for producing a granular boron nitride composition, which comprises a step of heat-treating a mixture containing components in a non-oxidizing gas atmosphere.
　本発明は、第２の要旨において、上述のような製造方法により得られる粒状窒化ホウ素組成物を提供する。これには、加熱処理によって得られる粒状窒化ホウ素に加えて、混合物に含まれていた成分（１）～（３）に由来する他の化合物が含まれている。そのような他の化合物は、主として希土類元素酸化物および酸化カルシウムであるが、例えば系に存在する元素に由来する複合酸化物等（例えばＹ－Ｃａ－Ｂ－Ｏ系複合酸化物）も少量含まれ得る。 The present invention provides, in the second gist, a granular boron nitride composition obtained by the above-mentioned production method. This includes, in addition to the granular boron nitride obtained by the heat treatment, other compounds derived from the components (1) to (3) contained in the mixture. Such other compounds are mainly rare earth element oxides and calcium oxide, but also contain a small amount of, for example, complex oxides derived from elements present in the system (for example, Y—Ca—BO complex oxides). It can be.
　本発明は、第３の要旨において、上述の粒状窒化ホウ素組成物に含まれている粒状窒化ホウ素を提供する。この粒状窒化ホウ素は、酸を用いる洗浄処理に上述の組成物を付して、酸化カルシウムおよび希土類元素酸化物の少なくとも一部分、酸化カルシウムの大部分、好ましくは実質的に全量を除去することによって得ることができる。従って、本発明は、第４の要旨において、粒状窒化ホウ素を製造する方法を提供し、この方法は、第２の要旨の粒状窒化ホウ素組成物を酸洗浄することを特徴とする。 The present invention provides the granular boron nitride contained in the above-mentioned granular boron nitride composition in the third gist. This granular boron nitride is obtained by subjecting the above composition to a cleaning process using an acid to remove at least a portion of calcium oxide and a rare earth element oxide, most of the calcium oxide, preferably substantially the entire amount. be able to. Therefore, the present invention provides a method for producing granular boron nitride in the fourth gist, which method is characterized by acid cleaning of the granular boron nitride composition in the second gist.
　本発明は、第５の要旨において、第２の要旨の粒状窒化ホウ素組成物または第３の要旨の粒状窒化ホウ素および樹脂材料を含んで成る樹脂組成物を提供する。更に、本発明は、第６の要旨において、そのような樹脂材料を用いて成形することを特徴とする成形方法を、また、本発明は、第７の要旨において、そのような成形方法によって得られる成形体を提供する。 The present invention provides, in the fifth gist, a granular boron nitride composition of the second gist or a resin composition comprising the granular boron nitride of the third gist and a resin material. Further, the present invention is obtained in the sixth gist by a molding method characterized by molding using such a resin material, and the present invention is obtained by such a molding method in the seventh gist. To provide a molded product to be manufactured.
　本発明の製造方法によって得られる粒状窒化ホウ素を樹脂材料と混合した樹脂組成物を用いて成形する場合、得られる成形体の熱伝導性が向上する。また、好ましい態様では、成形体の熱伝導に関する異方性が抑制される。特に多量に混合した場合であっても、良好な成形加工性を維持しながらも、得られる成形体の熱伝導性を向上できる。 When molding using a resin composition obtained by mixing granular boron nitride obtained by the production method of the present invention with a resin material, the thermal conductivity of the obtained molded product is improved. Further, in a preferred embodiment, anisotropy regarding heat conduction of the molded product is suppressed. Even when a large amount is mixed, the thermal conductivity of the obtained molded product can be improved while maintaining good molding processability.
　成形体としては、絶縁性が要求され、かつ、熱伝導性と成形加工性が要求される放熱シートを例示できる。例えば電気・電子分野等において使用するものに好適である。また、本発明の粒状窒化ホウ素組成物または粒状窒化ホウ素は、熱伝導性ペースト、熱伝導性接着剤、熱伝導性成形物用組成物等に配合できるフィラーとして使用できる。 As the molded body, a heat radiating sheet that requires insulation, thermal conductivity, and moldability can be exemplified. For example, it is suitable for use in the fields of electricity and electronics. Further, the granular boron nitride composition or granular boron nitride of the present invention can be used as a filler that can be blended in a heat conductive paste, a heat conductive adhesive, a composition for a heat conductive molded product, or the like.
図１は、本発明の粒状窒化ホウ素の平均粒子径と加熱処理する混合物中における希土類成分（２）およびカルシウム成分（３）の総和（即ち、（２）＋（３））の割合（質量基準パーセント）との関係を示す実験結果の表およびグラフを示す。FIG. 1 shows the ratio (mass basis) of the average particle size of the granular boron nitride of the present invention and the sum of the rare earth component (2) and the calcium component (3) in the mixture to be heat-treated (that is, (2) + (3)). A table and graph of experimental results showing the relationship with (percentage) are shown. 図２は、本発明の粒状窒化ホウ素の比表面積と加熱処理する混合物中における希土類成分（２）およびカルシウム成分（３）の総和（即ち、（２）＋（３））の割合（質量基準パーセント）との関係を示す実験結果の表およびグラフを示す。FIG. 2 shows the ratio (mass reference percent) of the specific surface area of the granular boron nitride of the present invention and the sum of the rare earth component (2) and the calcium component (3) in the heat-treated mixture (that is, (2) + (3)). ) Is shown in the table and graph of the experimental results showing the relationship with). 図３は、本発明の粒状窒化ホウ素を含む樹脂組成物を用いて得られる成形体の厚さ方向の熱伝導率と加熱処理する混合物中における希土類成分（２）およびカルシウム成分（３）の総和（即ち、（２）＋（３））の割合（質量基準パーセント）との関係を示す実験結果の表およびグラフを示す。FIG. 3 shows the total of the thermal conductivity in the thickness direction of the molded product obtained by using the resin composition containing the granular boron nitride of the present invention and the rare earth component (2) and the calcium component (3) in the heat-treated mixture. A table and graph of experimental results showing the relationship with the ratio (that is, (2) + (3)) (mass reference percentage) are shown. 図４は、本発明の粒状窒化ホウ素を含む樹脂組成物を用いて得られる成形体の面方向（厚さ方向に垂直な方向）の熱伝導率と加熱処理する混合物中における希土類成分（２）およびカルシウム成分（３）の総和（即ち、（２）＋（３））の割合（質量基準パーセント）との関係を示す実験結果の表およびグラフを示す。FIG. 4 shows the thermal conductivity in the plane direction (direction perpendicular to the thickness direction) of the molded product obtained by using the resin composition containing the granular boron nitride of the present invention, and the rare earth component (2) in the mixture to be heat-treated. And the table and graph of the experimental result which shows the relationship with the ratio (mass reference percent) of the sum (that is, (2) + (3)) of the calcium component (3) are shown. 図５は、本発明の粒状窒化ホウ素を含む樹脂組成物を用いて成形した成形体中における粒状窒化ホウ素の配向度と粒状窒化ホウ素を製造する際に加熱処理する混合物中における希土類成分（２）およびカルシウム成分（３）の総和（即ち、（２）＋（３））との関係を示す実験結果の表およびグラフを示す。FIG. 5 shows the degree of orientation of granular boron nitride in a molded product molded using the resin composition containing granular boron nitride of the present invention and the rare earth component in a mixture to be heat-treated when producing granular boron nitride (2). A table and a graph of experimental results showing the relationship between the sum of the calcium component (3) and the sum (that is, (2) + (3)) are shown. 図６は、実施例６でえられた、本発明の粒状窒化ホウ素（但し、洗浄後）の典型的なＳＥＭ写真である。FIG. 6 is a typical SEM photograph of the granular boron nitride (but after washing) of the present invention obtained in Example 6. 図７は、実施例６で得られた、本発明の粒状窒化ホウ素組成物（但し、洗浄前）の典型的なＳＥＭ写真である。FIG. 7 is a typical SEM photograph of the granular boron nitride composition of the present invention (however, before washing) obtained in Example 6. 図８は、実施例３６で得られた酸化イットリウムを含む本発明の粒状窒化ホウ素（但し、洗浄後）のＳＥＭ写真およびＥＤＳ写真（Ｎ元素およびＹ元素について）である。FIG. 8 is an SEM photograph and an EDS photograph (for elements N and Y) of the granular boron nitride (but after washing) of the present invention containing yttrium oxide obtained in Example 36. 図９は、実施例１１で得られた、本発明の粒状窒化ホウ素組成物（但し、洗浄前）のＳＥＭ写真およびＥＤＳ写真（Ｎ元素、Ｃａ元素およびＹ元素について）である。FIG. 9 is an SEM photograph and an EDS photograph (for N element, Ca element and Y element) of the granular boron nitride composition of the present invention (however, before washing) obtained in Example 11. 図１０は、実施例１２で得られた、本発明の粒状窒化ホウ素（但し、洗浄後）のＳＥＭ写真およびＥＤＳ写真（Ｎ元素について）である。FIG. 10 is an SEM photograph and an EDS photograph (for element N) of the granular boron nitride (but after washing) of the present invention obtained in Example 12.
　次に、本発明の実施するための形態を詳細に説明する。 Next, a mode for carrying out the present invention will be described in detail.
　本発明の粒状窒化ホウ素組成物の製造方法において、好ましい態様では、窒化ホウ素成分（１）に含まれる窒化ホウ素は、黒鉛構造を有する六方晶窒化ホウ素（ｈ－ＢＮ）であり、１つの態様では、窒化ホウ素は好ましくは粉末状（または微細な粒状）の窒化ホウ素、好ましくはｈ－ＢＮである。このような窒化ホウ素成分（１）として、六方晶窒化ホウ素として一般的に市販されているものを用いることができる。 In the method for producing a granular boron nitride composition of the present invention, in a preferred embodiment, the boron nitride contained in the boron nitride component (1) is hexagonal boron nitride (h-BN) having a graphite structure, and in one embodiment. , Boron nitride is preferably powdery (or finely granular) boron nitride, preferably h-BN. As such a boron nitride component (1), a commercially available hexagonal boron nitride component can be used.
　希土類成分（２）に含まれる希土類元素の酸化物は、例えば酸化イットリウム、酸化セリウムまたは酸化イッテルビウムであり、希土類元素の酸化物の前駆体は、加熱処理に先だって実施する予備加熱処理および／または加熱処理において、そのような酸化物をもたらす化合物を意味する。このような希土類成分（２）として、例えば酸化イットリウム、酸化セリウム等として一般的に市販されているものを用いることができる。 The oxide of the rare earth element contained in the rare earth component (2) is, for example, yttrium oxide, cerium oxide or itterbium oxide, and the precursor of the oxide of the rare earth element is a preheat treatment and / or heating carried out prior to the heat treatment. Means a compound that results in such an oxide in the process. As such a rare earth component (2), commercially available ones such as yttrium oxide and cerium oxide can be used.
　カルシウム成分（３）は酸化カルシウムおよび／または炭酸カルシウムを含んで成るが、そのようなカルシウム成分（３）として、一般的に市販されている酸化カルシウム、炭酸カルシウム等を用いることができる。 The calcium component (3) contains calcium oxide and / or calcium carbonate, and as such a calcium component (3), generally commercially available calcium oxide, calcium carbonate or the like can be used.
　１つの好ましい態様では、加熱処理する混合物に含まれる窒化ホウ素成分（１）中の窒化ホウ素（ＢＮ）、希土類成分（２）に含まれる希土類元素の酸化物（例えばＹ２Ｏ３）およびその前駆体（存在する場合）ならびにカルシウム成分（３）に含まれる酸化カルシウム（ＣａＯ）および水酸化カルシウム（存在する場合）の総質量に対する、希土類成分（２）中の希土類元素の酸化物およびその前駆体（存在する場合）ならびにカルシウム成分（３）中の酸化カルシウムおよび水酸化カルシウム（存在する場合）の総質量の割合（例えば（Ｙ２Ｏ３＋ＣａＯ）／（ＢＮ＋Ｙ２Ｏ３＋ＣａＯ））は、一般的には５％～６０％（従って、窒化ホウ素は９５～４０％）、好ましくは６％～５０％（従って、窒化ホウ素は９４～５０％）、より好ましくは、７～４２％、特に好ましくは、１４～４２％、例えば１４～３５％である。 In one preferred embodiment, boron nitride in boron nitride component contained in the mixture to heat treatment (1) (BN), oxides of rare earth elements in the rare earth component (2) (e.g., Y 2 O 3) and their precursors Oxides of rare earth elements in the rare earth component (2) and their precursors relative to the total mass of the body (if present) and calcium oxide (CaO) and calcium hydroxide (if present) contained in the calcium component (3). The ratio of the total mass of calcium oxide and calcium hydroxide (if present) in the calcium component (3) (if present) (eg, (Y 2 O 3 + CaO) / (BN + Y 2 O 3 + CaO)) is general. 5% to 60% (hence, boron nitride is 95 to 40%), preferably 6% to 50% (hence, boron nitride is 94 to 50%), more preferably 7 to 42%, particularly preferably. Is 14 to 42%, for example 14 to 35%.
　別の好ましい態様では、加熱処理する混合物における元素数基準で希土類成分（２）中の希土類元素：カルシウム成分（３）中のカルシウム元素（例えばＹ元素数：Ｃａ元素数）は、好ましくは１：０．２５～１：４、より好ましくは１：０．５～１：３、特に好ましくは１：０．７～１：２．５、例えば１：１～１：２である。 In another preferred embodiment, the rare earth element in the rare earth component (2): the calcium element in the calcium component (3) (for example, the number of Y elements: the number of Ca elements) is preferably 1: based on the number of elements in the heat-treated mixture. It is 0.25 to 1: 4, more preferably 1: 0.5 to 1: 3, particularly preferably 1: 0.7 to 1: 2.5, for example 1: 1 to 1: 2.
　加熱処理は、非酸化性ガス雰囲気下で実施する。非酸化性ガス雰囲気とは、酸素を含まない雰囲気を意味し、例えば、窒素ガス、ヘリウムガス、アルゴンガス、アンモニアガス、水素ガス、メタンガス、プロパンガス、一酸化炭素ガスなどの１種又は２種以上を含んで成る雰囲気である。この雰囲気に用いるガスの種類によって窒化ホウ素の溶解後の結晶化速度が異なり、例えばアルゴンガスでは、結晶化の速度が遅くなり、加熱処理時間が長時間に及ぶ場合がある。結晶化を短時間で行うためには特に窒素ガス、または窒素ガスと他のガスを併用した混合ガスを用いるのが好適である。本発明の１つの態様では、加熱処理を窒素ガス雰囲気で実施する。加熱処理すべき混合物は、後述する所定の加熱処理温度に達するまでも非酸化性雰囲気下にあるのが好ましい。尚、本明細書において、非酸化性ガス雰囲気は、実質的にガスを含まない、または殆ど含まない、いわゆる真空状態または減圧状態であってもよい。 The heat treatment is carried out in a non-oxidizing gas atmosphere. The non-oxidizing gas atmosphere means an atmosphere containing no oxygen, for example, one or two kinds such as nitrogen gas, helium gas, argon gas, ammonia gas, hydrogen gas, methane gas, propane gas, and carbon monoxide gas. It is an atmosphere that includes the above. The crystallization rate after dissolution of boron nitride differs depending on the type of gas used in this atmosphere. For example, in the case of argon gas, the crystallization rate becomes slow and the heat treatment time may take a long time. In order to carry out crystallization in a short time, it is particularly preferable to use nitrogen gas or a mixed gas in which nitrogen gas and another gas are used in combination. In one aspect of the invention, the heat treatment is carried out in a nitrogen gas atmosphere. The mixture to be heat-treated is preferably kept in a non-oxidizing atmosphere until it reaches a predetermined heat treatment temperature described later. In the present specification, the non-oxidizing gas atmosphere may be in a so-called vacuum state or a reduced pressure state in which the gas is substantially contained or hardly contained.
　尚、本発明の方法において、窒化ホウ素成分（１）は、酸素を含んでよく、その場合（例えば酸化ホウ素の形態で含む場合）、必要に応じて（例えば酸化ホウ素の少なくとも一部分を窒化ホウ素に変換するために）、混合物は、炭素を窒化ホウ素成分（１）中の窒化ホウ素の質量に対して１％～５％の量で使用してよい。別の態様では、実質的な悪影響が無い限り、混合物は炭素を含まない。尚、一般的に「窒化ホウ素」として市販されているものを窒化ホウ素成分（１）として使用する場合、含まれている酸素はそれほど多くない（例えば、窒化ホウ素成分（１）の質量基準で一般的には５％以下、例えば４質量％）ので通常炭素を使用する必要はないが、必要に応じて（例えば酸素量が多い場合）、混合物は炭素を含んでよい。 In the method of the present invention, the boron nitride component (1) may contain oxygen, and in that case (for example, when it is contained in the form of boron oxide), if necessary (for example, at least a part of boron oxide is converted to boron nitride). To convert), the mixture may use carbon in an amount of 1% to 5% relative to the mass of boron nitride in the boron nitride component (1). In another aspect, the mixture is carbon free, unless there is a substantial adverse effect. When a commercially available "boron nitride" is used as the boron nitride component (1), the amount of oxygen contained is not so large (for example, it is generally based on the mass of the boron nitride component (1)). Generally, it is not necessary to use carbon because it is 5% or less, for example, 4% by mass, but the mixture may contain carbon if necessary (for example, when the amount of oxygen is large).
　本発明の粒状窒化ホウ素組成物に含まれている粒状窒化ホウ素は、その平均粒子径が好ましくは９～２５μｍ、より好ましくは１０～２０μｍ、例えば１２～１５μｍであり、また、粒状物の比表面積は、好ましくは２～１０ｍ２／ｇ、より好ましくは４～８ｍ２／ｇ、例えば５～６ｍ２／ｇである。尚、上述の平均粒子径および比表面積は、それぞれ以下の方法で測定される値を意味する： The granular boron nitride contained in the granular boron nitride composition of the present invention has an average particle diameter of preferably 9 to 25 μm, more preferably 10 to 20 μm, for example, 12 to 15 μm, and the specific surface area of the granular material. Is preferably 2 to 10 m 2 / g, more preferably 4 to 8 m 2 / g, for example 5 to 6 m 2 / g. The above-mentioned average particle size and specific surface area mean values measured by the following methods, respectively:
　（平均粒子径）
　得られた粒状物０.０２～０.０４ｇを２０ｍｌの分散媒としての石鹸水（台所用液体洗剤（キッチンフレッシュ、三協油脂製）１ｇを純水５００ｍｌに混合したもの）に入れ、超音波洗浄機によって５分撹拌して粒状物を分散させた。その後、レーザ回折式粒度分布測定装置（株式会社島津製作所：ＳＡＬＤ－２１００）を用い、体積基準の粒度累積線図を作成し、粒度累積率５０％における粒子径（Ｄｖ５０）を平均粒子径（または単に「粒子径」と呼ぶ）とする。尚、本明細書にて言及する平均粒子径は、粒子の凝集状態に関係無くこの測定法によって得られる数値であり、粒子の性質に応じて、一次粒子の平均粒子径である場合もあり、また、二次粒子の平均粒子径である場合もある。場合によっては、一次粒子と二次粒子の双方が混在した状態で測定される平均粒子径である。 (Average particle size)
0.02 to 0.04 g of the obtained granules were placed in 20 ml of soapy water as a dispersion medium (1 g of liquid kitchen detergent (Kitchen Fresh, manufactured by Sankyo Oil and Fat) mixed with 500 ml of pure water) and ultrasonically cleaned. The granules were dispersed by stirring with a washing machine for 5 minutes. After that, using a laser diffraction type particle size distribution measuring device (Shimadzu Corporation: SALD-2100), a volume-based particle size cumulative diagram was created, and the particle size (Dv50) at a particle size accumulation rate of 50% was set to the average particle size (or It is simply called "particle size"). The average particle size referred to in the present specification is a numerical value obtained by this measurement method regardless of the state of aggregation of the particles, and may be the average particle size of the primary particles depending on the properties of the particles. It may also be the average particle size of the secondary particles. In some cases, it is the average particle size measured in a state where both primary particles and secondary particles are mixed.
（比表面積）
　粉末形態の粒状窒化ホウ素の比表面積をガス吸着量測定装置（AUTOSORB-1，カンタクローム・インスツルメンツ合同会社）によって測定した。尚、測定前にサンプルを１１０℃で１２時間乾燥した。粒状物（０．５～１．０ｇ）の表面積の計算方法として代表的なBrunauer-Emmett-Teller（ＢＥＴ）法を用いた。ＢＥＴ多点法を使用し、P/P０＝０．１、０．２、０．３となる３点のＢＥＴプロットから比表面積を計算した（但し、Ｐは吸着平衡にある吸着質の気体の圧力、Ｐ０は吸着温度における吸着質の飽和蒸気圧である）。 (Specific surface area)
The specific surface area of granular boron nitride in powder form was measured by a gas adsorption amount measuring device (AUTOSORB-1, Cantachrome Instruments LLC). Before the measurement, the sample was dried at 110 ° C. for 12 hours. A typical Brunauer-Emmett-Teller (BET) method was used as a method for calculating the surface area of granules (0.5 to 1.0 g). Using the BET multipoint method, the specific surface area was calculated from the BET plot of three points where P / P 0 = 0.1, 0.2, 0.3 (however, P is an adsorbent gas in adsorption equilibrium). Pressure, P 0 is the saturated vapor pressure of the adsorbent at the adsorption temperature).
　加熱処理によって生成する本発明の粒状窒化ホウ素は、加熱処理に際して、希土類元素酸化物に加えて酸化カルシウムが先だって溶融して生じる液相に窒化ホウ素が溶解した後、液相から析出することによって生じると考えられる。このことは、いかなる理論によっても拘束されるものではないが、発明者らが有する、窒化ホウ素の生成に関する知識および経験ならびに上述の製造方法に関して得られた新たな知見、特に生じる粒状物のＳＥＭ写真の結果等に基づいて、粒状物の生成について、以下のように考えることができる。尚、この考えは可能な考え方のひとつに過ぎない。特定の条件下における加熱処理によって窒化ホウ素粒状物を得ることができるという本発明は、この考え方の適否によっていかなる制限を受けるものではない。 The granular boron nitride of the present invention produced by heat treatment is produced by dissolving boron nitride in the liquid phase formed by melting calcium oxide in addition to the rare earth element oxide in advance during the heat treatment, and then precipitating from the liquid phase. it is conceivable that. This is not bound by any theory, but the inventors have knowledge and experience regarding the formation of boron nitride and new findings regarding the above-mentioned production methods, especially SEM photographs of the resulting granules. Based on the results of the above, the formation of granules can be considered as follows. This idea is just one of the possible ideas. The present invention that boron nitride granules can be obtained by heat treatment under specific conditions is not limited by the suitability of this idea.
　本発明の粒状窒化ホウ素組成物の製造方法において、混合物を加熱処理すると、希土類元素酸化物および酸化カルシウムが優先的に溶融して液相を形成し、そこに粒状窒化ホウ素が溶解していく。この溶解が進行することによって液相中の窒化ホウ素濃度が上昇して過飽和状態となり、その結果、窒化ホウ素が析出する（再結晶する）ことになる。このように窒化ホウ素が析出する一方で新たに別の窒化ホウ素粒子が液相に溶解して過飽和状態となり、その結果、窒化ホウ素が更に析出することになる。このような溶解→析出を繰り返すことによって析出した窒化ホウ素が結合して屈曲形態となる。屈曲形態の窒化ホウ素の内側および外側には窒化ホウ素が溶解した液相が存在するため、そこでは過飽和→析出が繰り返して起こり、窒化ホウ素の結晶が更に成長して屈曲形態が厚くなり、また、長くなり、窒化ホウ素の結晶が徐々に成長する。このように成長した屈曲窒化ホウ素は、別に同じように成長した屈曲窒化ホウ素の結晶と結合し、更にその内側および外側で成長して、最終的にある程度の厚さを有する壁で囲まれた形態、即ち、窒化ホウ素結晶の略球状または粒（つぶ）状のシェルが形成される。この意味で、本明細書では、加熱処理によって得られる窒化ホウ素を「粒状窒化ホウ素」と呼ぶ。 In the method for producing a granular boron nitride composition of the present invention, when the mixture is heat-treated, the rare earth element oxide and calcium oxide are preferentially melted to form a liquid phase, in which the granular boron nitride is dissolved. As this dissolution progresses, the concentration of boron nitride in the liquid phase rises to a supersaturated state, and as a result, boron nitride precipitates (recrystallizes). While boron nitride is precipitated in this way, another boron nitride particle is newly dissolved in the liquid phase to become a supersaturated state, and as a result, boron nitride is further precipitated. By repeating such dissolution → precipitation, the precipitated boron nitride is bonded to form a bent form. Since there is a liquid phase in which boron nitride is dissolved exists inside and outside the bent form of boron nitride, supersaturation → precipitation occurs repeatedly there, and boron nitride crystals grow further to thicken the bent form. It becomes longer and boron nitride crystals grow gradually. The bent boron nitride thus grown is bonded to another similarly grown bent boron nitride crystal, further grown inside and outside the crystal, and finally surrounded by a wall having a certain thickness. That is, a substantially spherical or grain-shaped shell of boron nitride crystals is formed. In this sense, the boron nitride obtained by heat treatment is referred to as "granular boron nitride" in the present specification.
　このように、本発明の粒状窒化ホウ素は、比較的厚い壁の形態の窒化ホウ素により形成された強固なシェル構造を有する。このシェル構造は、粒子全体としては、巨視的には丸みを有する形態、即ち、粒（つぶ）状である。厳密な意味では、いわゆる球状、回転楕円体状、または多面体形状であり、一般的にはこれらの複雑な組み合わせの形状を有する。通常、この粒状物はアスペクト比が比較的小さい、好ましくは１～３、より好ましくは１～２であり、グラファイト構造を有する窒化ホウ素のようにアスペクト比が大きい粒状物とは明らかに異なる。 As described above, the granular boron nitride of the present invention has a strong shell structure formed by boron nitride in the form of a relatively thick wall. This shell structure has a macroscopically rounded shape as a whole particle, that is, a grain (crushed) shape. In a strict sense, it is a so-called spherical, spheroidal, or polyhedral shape, and generally has a complex combination of these shapes. Usually, this granular material has a relatively small aspect ratio, preferably 1 to 3, more preferably 1 to 2, and is clearly different from a granular material having a large aspect ratio such as boron nitride having a graphite structure.
　典型的な本発明の粒状窒化ホウ素のＳＥＭ写真の例を図６に示す。これらの写真は、後述の実施例６で得られた粒状窒化ホウ素のものである。これを詳細に観察すると、粒状窒化ホウ素は、屈曲した壁によって構成された、全体としては多面体（または球状）の見かけの形態を有する、いわゆる粒（つぶ）状であることが分かる。尚、酸化物を除去する前の状態の本発明の粒状窒化ホウ素組成物についてもＳＥＭ写真を撮影した。その写真を図７に示す。両者を比較すると分かるように、酸化物を除去した後のものと実質的に差が無かった。このことを説明できる可能性として、添加した酸化物からなる液相成分が主にシェル構造の粒状窒化ホウ素内に残っているということが考えられる。 FIG. 6 shows an example of a typical SEM photograph of the granular boron nitride of the present invention. These photographs are of granular boron nitride obtained in Example 6 described later. When this is observed in detail, it can be seen that the granular boron nitride is a so-called grain (crushed) shape having an apparent polyhedral (or spherical) shape as a whole, which is composed of bent walls. An SEM photograph was also taken of the granular boron nitride composition of the present invention in a state before the oxide was removed. The photograph is shown in FIG. As can be seen by comparing the two, there was substantially no difference from the one after removing the oxide. It is possible that this can be explained by the fact that the liquid phase component composed of the added oxide remains mainly in the granular boron nitride of the shell structure.
　上述のシェル構造を本発明の粒状窒化ホウ素において、シェル構造の内部に他の粒状窒化ホウ素またはその一部が包含されている場合がある。図１０は後述の実施例１２において得られた粒状窒化ホウ素をエポキシ樹脂に混合して硬化させたものの断面の２つの異なる視野部位におけるＳＥＭ写真と、その写真における窒素元素のＥＤＳ写真を示したものである。図１０において、上方の写真がＳＥＭ写真である。この状態の粒状窒化ホウ素をＥＤＳ(エネルギー分散型Ｘ線分析）を用いてＮ元素についてマッピング分析した結果を示す下方の写真がＥＤＳ写真である。左上の写真に対応するＥＤＳ写真が左下の写真であり、右上の写真に対応するＥＤＳ写真が右下の写真である。ＳＥＭ写真において白く光っているように見える窒化ホウ素のシェル構造の内部に、ＥＤＳ写真で確認できるように窒素元素（白っぽい部分）が、従って、窒化ホウ素が存在することが分かる。 In the granular boron nitride of the present invention, the above-mentioned shell structure may include other granular boron nitride or a part thereof inside the shell structure. FIG. 10 shows an SEM photograph of two different visual field parts of a cross section of a mixture of granular boron nitride obtained in Example 12 described later mixed with an epoxy resin and cured, and an EDS photograph of the nitrogen element in the photograph. Is. In FIG. 10, the upper photograph is an SEM photograph. The lower photograph showing the result of mapping analysis of granular boron nitride in this state for N elements using EDS (Energy Dispersive X-ray Analysis) is an EDS photograph. The EDS photo corresponding to the upper left photo is the lower left photo, and the EDS photo corresponding to the upper right photo is the lower right photo. It can be seen that the nitrogen element (white part) is present inside the shell structure of boron nitride, which appears to shine white in the SEM photograph, as can be confirmed in the EDS photograph, and therefore boron nitride is present.
　明らかなように、粒状窒化ホウ素のシェル構造の内部にも粒状窒化ホウ素が存在していることが分かる。図１０の写真の左側の態様では、内部の粒状窒化ホウ素は、柱状（従って、三次元的には面状）であり、外側に位置する粒状窒化ホウ素のシェル構造の内部が分割、例えば二分されている。他方、図１０の写真の右側の態様では、内部の粒状窒化ホウ素は、外側に位置する粒状窒化ホウ素のシェル構造の内部の一部分を充填している。このように包含された粒状窒化ホウ素は、シェル構造を形成するに到っていないシェル構造の一部分（例えばシェル構成する面の少なくとも１つまたはその一部分）であっても、より小さいシェル構造であってもよい。シェル構造を構成する面は、シェル構造を構成する実質的に平坦な面であっても、屈曲した面であってもよい。このようにシェル構造の内部に粒状窒化ホウ素は、１つの態様では、既に形成されたシェル構造またはその一部の内側で、窒化ホウ素が新たに析出して成長することによって生じると考えられる。別の態様では、成長した粒状窒化ホウ素またはその一部分が他の粒状窒化ホウ素またはその一部と結合することによって、粒状窒化ホウ素の一部分が内包されることによって生じると考えられる。このように、他の粒状窒化ホウ素が内包されている粒状窒化ホウ素は、熱伝導経路を増やすため、粒状窒化ホウ素の熱伝導をより高くすることに寄与すると考えられる。また、内部に他の粒状窒化ホウ素が存在することによって、粒状窒化ホウ素に外部から圧力が作用した場合に、変形することを抑制または防止する効果も奏すると考えられる。 As is clear, it can be seen that granular boron nitride also exists inside the shell structure of granular boron nitride. In the aspect on the left side of the photograph of FIG. 10, the internal granular boron nitride is columnar (thus three-dimensionally planar), and the inside of the outer granular boron nitride shell structure is divided, for example, bisected. ing. On the other hand, in the aspect on the right side of the photograph of FIG. 10, the internal granular boron nitride fills a part of the inside of the shell structure of the granular boron nitride located on the outside. The granular boron nitride thus encapsulated is a smaller shell structure, even if it is a part of the shell structure that has not yet formed the shell structure (eg, at least one or a part of the shell constituent surfaces). You may. The surface constituting the shell structure may be a substantially flat surface or a bent surface forming the shell structure. As described above, granular boron nitride is considered to be generated inside the shell structure in one embodiment by newly precipitating and growing boron nitride inside the already formed shell structure or a part thereof. In another aspect, it is considered that the grown granular boron nitride or a part thereof is bonded to another granular boron nitride or a part thereof, so that a part of the granular boron nitride is included. As described above, the granular boron nitride containing other granular boron nitride is considered to contribute to higher the heat conduction of the granular boron nitride because it increases the heat conduction path. Further, it is considered that the presence of other granular boron nitride inside also has an effect of suppressing or preventing deformation of the granular boron nitride when an external pressure is applied to the boron nitride.
　本発明では、上述のように窒化ホウ素が液相から析出してシェルが形成されるに際して、液相として希土類元素酸化物および酸化カルシウムが存在することが主たる特徴のひとつであり、その結果、得られる粒状窒化ホウ素は、より厚いシェルおよび小さいアスペクト比を有する。それによって、既知の種々の窒化ホウ素凝集体よりも圧壊強度に優れた粒状窒化ホウ素を生成することができる。具体的には、後述するように、樹脂材料に配合して樹脂組成物を得、これを成形した場合、成形体における粒状窒化ホウ素の配向度を約８５％以下、好ましくは７０％以下、より好ましくは２０～６５％、例えば２５～６０％にできる。粒状窒化ホウ素粒子の粒径が小さな場合は、ホットプレス圧力に対しても抵抗が強いため、粒状粒子が崩壊せずに、低い（００Ｌ）面の配向度を示すが、樹脂材料が高い熱伝導率を持つためには、高熱伝導経路が長くとれるように粒径の大きな粒状窒化ホウ素が望ましい。しかしながら、粒状窒化ホウ素の粒径が大きくなると、ホットプレスによって粒状が崩壊し易くなるため、（００Ｌ）面の配向度が大きくなる可能性がある。 In the present invention, one of the main features is that when boron nitride is precipitated from the liquid phase to form a shell as described above, a rare earth element oxide and calcium oxide are present as the liquid phase, and as a result, the result is obtained. Granular boron nitride to be obtained has a thicker shell and a smaller aspect ratio. Thereby, it is possible to produce granular boron nitride having a crushing strength superior to that of various known boron nitride aggregates. Specifically, as will be described later, when a resin composition is obtained by blending with a resin material and molded, the degree of orientation of granular boron nitride in the molded product is about 85% or less, preferably 70% or less. It can be preferably 20 to 65%, for example 25 to 60%. When the particle size of the granular boron nitride particles is small, the resistance to hot press pressure is strong, so that the granular particles do not collapse and show a low (00L) plane orientation, but the resin material has high thermal conductivity. In order to have a ratio, granular boron nitride having a large particle size is desirable so that a high thermal conduction path can be taken for a long time. However, when the particle size of the granular boron nitride is increased, the granularity is likely to be disintegrated by hot pressing, so that the degree of orientation of the (00L) plane may be increased.
　尚、上述のようにシェルが形成されるが、本発明の粒状窒化ホウ素組成物は、加熱後の冷却によって最終的にシェルの内側で固化した成分を含んで成る。この成分は、希土類元素酸化物および酸化カルシウムを主成分とするが、上述のように種々の化合物、特に複合酸化物を含んで成り得る。尚、このような成分に加えて、上述のように、粒状窒化ホウ素のシェル構造またはその一部を構成する窒化ホウ素の部分も含み得る。本発明の粒状窒化ホウ素組成物の製造方法において、加熱処理することによって得られる粒状窒化ホウ素組成物に含まれるホウ素、希土類元素およびカルシウムの元素の割合は、混合物に含まれるこれらの元素の割合と実質的に同じである。従って、粒状窒化ホウ素組成物に含まれる希土類元素酸化物および酸化カルシウムの量は、混合物に含まれる希土類元素およびカルシウムに由来する酸化物の量に等しい。 Although the shell is formed as described above, the granular boron nitride composition of the present invention contains a component that is finally solidified inside the shell by cooling after heating. This component is mainly composed of rare earth element oxides and calcium oxide, but may contain various compounds, particularly composite oxides, as described above. In addition to such components, as described above, a portion of boron nitride that constitutes the shell structure of granular boron nitride or a part thereof may also be included. In the method for producing a granular boron nitride composition of the present invention, the proportions of boron, rare earth elements and calcium elements contained in the granular boron nitride composition obtained by heat treatment are the proportions of these elements contained in the mixture. It is virtually the same. Therefore, the amount of rare earth element oxides and calcium oxide contained in the granular boron nitride composition is equal to the amount of rare earth element and calcium-derived oxides contained in the mixture.
　従って、１つの態様では、粒状窒化ホウ素組成物は、窒化ホウ素に加えて、その質量基準で希土類元素酸化物を通常３～４０％、好ましくは５～３７％、より好ましくは８～３５％、例えば１２～３２％含み、酸化カルシウムを１～３０％、好ましくは２～２６％、より好ましくは５～２２％、例えば８～１５％含んで成る。 Therefore, in one embodiment, the granular boron nitride composition usually contains 3-40%, preferably 5-37%, more preferably 8-35% of rare earth element oxides on a mass basis, in addition to boron nitride. For example, it contains 12 to 32% and contains 1 to 30%, preferably 2 to 26%, more preferably 5 to 22%, for example 8 to 15% of calcium oxide.
　このような酸化物は、上述のように酸洗浄、例えば酸水溶液を用いて酸化物と酸とを反応させて水溶性の塩に変換して水に溶解させて除去することにより減らすことができる。例えば、粒状窒化ホウ素組成物を熱伝導性フィラーとして用いる場合、酸化物の熱伝導率は通常小さいので、粒状窒化ホウ素組成物に含まれる酸化物が熱伝導率に実質的に悪影響を与えない程度まで減らすのが好ましい。例えば、酸化カルシウムは、酸洗浄によって優先的に除去できるので、酸化カルシウムを実質的に全量除去し、希土類元素酸化物を部分的に除去する。粒状窒化ホウ素組成物に含まれる希土類元素酸化物の量が、その質量基準で例えば０．１～３０％、好ましくは１～１５％、より好ましくは２～１２％、例えば３～１０％となるように酸洗浄する。 Such oxides can be reduced by acid cleaning as described above, for example, by reacting an oxide with an acid using an aqueous acid solution to convert it into a water-soluble salt, dissolving it in water, and removing it. .. For example, when a granular boron nitride composition is used as a thermally conductive filler, the thermal conductivity of the oxide is usually small, so that the oxide contained in the granular boron nitride composition does not substantially adversely affect the thermal conductivity. It is preferable to reduce to. For example, calcium oxide can be preferentially removed by acid cleaning, so that substantially all of the calcium oxide is removed and the rare earth element oxide is partially removed. The amount of rare earth element oxide contained in the granular boron nitride composition is, for example, 0.1 to 30%, preferably 1 to 15%, more preferably 2 to 12%, for example, 3 to 10% based on the mass thereof. So acid wash.
　従って、本発明は、シェル構造を有する粒状窒化ホウ素を提供し、上述の粒状物から少なくとも希土類元素酸化物および／または酸化カルシウムを、好ましくは酸化カルシウムの大部分、より好ましくは実質的に全ての酸化カルシウムを除去することによって得られる、別の粒状窒化ホウ素をも提供する。即ち、より好ましい粒状物は、ホウ素、窒素、酸素および希土類元素を含んで成り、実質的にカルシウムを含まない。この粒状物は、窒化ホウ素により形成された強固なシェル構造を有すると共に、窒化ホウ素に加えて、少量の希土類元素酸化物を含んで成る。尚、酸化物の除去は、粒状窒化ホウ素のフィラーとしての性質が過度に影響されない限り、酸による洗浄以外のいずれの他の適当な方法によって実施してもよい。酸による洗浄は、粒状窒化ホウ素に悪影響を与えることなく、実質的に酸化物を除去できる点で有利である。 Therefore, the present invention provides granular boron nitride with a shell structure, from at least rare earth element oxides and / or calcium oxide from the above-mentioned granules, preferably most, more preferably substantially all of the calcium oxide. It also provides another granular boron nitride obtained by removing calcium oxide. That is, the more preferred granules consist of boron, nitrogen, oxygen and rare earth elements and are substantially free of calcium. The granules have a strong shell structure formed by boron nitride and contain a small amount of rare earth element oxides in addition to boron nitride. The removal of the oxide may be carried out by any other suitable method other than cleaning with an acid, as long as the properties of the granular boron nitride as a filler are not excessively affected. Cleaning with an acid is advantageous in that oxides can be substantially removed without adversely affecting granular boron nitride.
　本発明は、上述のように、好ましくは洗浄によって酸化物量を減らした粒状窒化ホウ素、特に酸化カルシウムを実質的に含まない粒状窒化ホウ素および樹脂材料を含んで成る樹脂組成物を提供する。樹脂組成物は、その全体の質量基準で粒状窒化ホウ素を好ましくは１０～９０％、より好ましくは１５～８８％、例えば３０～８５％、特に５０～８２％含んで成る。これらの範囲を体積割合で示すと、粒状物の見かけ密度によって多少相違するが、一例としてそれぞれ約５～８０体積％、約１０～７０体積％、約１５～５０体積％に対応する。粒状窒化ホウ素の量が少なすぎると、粒状窒化ホウ素が接触して存在する確率が低下して熱伝導が不十分なことが有り得る。逆に、多すぎると、マトリックスとしての樹脂材料が過度に少なくなり、成形体としての強度や耐電圧に悪意影響が出ることが有り得る。また、別の態様では、樹脂組成物は、上述の粒状窒化ホウ素に代えて本発明の粒状窒化ホウ素組成物を同様の割合で含んで成ってよい。 As described above, the present invention provides a resin composition comprising granular boron nitride whose amount of oxide is preferably reduced by washing, particularly granular boron nitride which is substantially free of calcium oxide and a resin material. The resin composition comprises preferably 10 to 90%, more preferably 15 to 88%, for example 30 to 85%, particularly 50 to 82% of granular boron nitride based on the total mass thereof. When these ranges are shown in terms of volume ratio, they correspond to about 5 to 80% by volume, about 10 to 70% by volume, and about 15 to 50% by volume, respectively, although they differ slightly depending on the apparent density of the granules. If the amount of granular boron nitride is too small, the probability that the granular boron nitride will be in contact with each other is reduced, and heat conduction may be insufficient. On the contrary, if the amount is too large, the amount of the resin material as the matrix becomes excessively small, which may adversely affect the strength and withstand voltage of the molded product. In another aspect, the resin composition may contain the granular boron nitride composition of the present invention in the same proportion as the above-mentioned granular boron nitride.
＜粒状窒化ホウ素組成物および粒状窒化ホウ素の製造方法＞
　本発明の粒状窒化ホウ素組成物の製造方法は、窒化ホウ素（ＢＮ、好ましくは六方晶窒化ホウ素（ｈ－ＢＮ））を含んでなる窒化ホウ素成分（１）と、イットリウム、セリウムおよびイッテルビウムから選択される少なくとも１つの希土類の元素の酸化物および／またはその前駆体を含んで成る希土類成分（２）と、カルシウム成分（３）とを含んで成る混合物を、非酸化性ガス雰囲気下で加熱処理する工程を含むことを特徴とする。 <Granular Boron Nitride Composition and Method for Producing Granular Boron Nitride>
The method for producing a granular boron nitride composition of the present invention is selected from a boron nitride component (1) containing boron nitride (BN, preferably hexagonal boron nitride (h-BN)), and ittrium, cerium, and itterbium. A mixture containing a rare earth component (2) containing an oxide and / or a precursor thereof of at least one rare earth element and a calcium component (3) is heat-treated in a non-oxidizing gas atmosphere. It is characterized by including a process.
　本発明の粒状窒化ホウ素組成物の製造方法において、希土類成分（２）がイットリウム、セリウムおよびイッテルビウムから選択される少なくとも１つの希土類元素の酸化物の前駆体を含む場合、加熱処理工程またはその前に必要に応じて実施してよい予備加熱または仮焼工程で前駆体は対応する希土類元素酸化物に変換される。また、カルシウム成分（３）が炭酸カルシウムを含んで成る場合、同様にして酸化カルシウムに変換される。変換されたものは、希土類元素酸化物または酸化カルシウムとして、粒状窒化ホウ素結晶の析出および成長に寄与する。 In the method for producing a granular boron nitride composition of the present invention, when the rare earth component (2) contains a precursor of an oxide of at least one rare earth element selected from yttrium, cerium and ytterbium, the heat treatment step or before the step. The precursor is converted to the corresponding rare earth element oxide in a preheating or calcining step that may be carried out as needed. When the calcium component (3) contains calcium carbonate, it is similarly converted to calcium oxide. The converted material contributes to the precipitation and growth of granular boron nitride crystals as a rare earth element oxide or calcium oxide.
  本発明の粒状窒化ホウ素組成物の製造方法は、例えば原料としての成分（１）、（２）および（３）を混合して混合物を得、これを非酸化性ガス雰囲気下で加熱する、例えば１８００～２１００℃で加熱することにより実施する。混合物は、必要に応じて他の成分、例えば原料としての成分を製造するに際して不可避的に含まれてしまう成分を含んでよい。例えば、窒化ホウ素成分（１）が過度の酸素を含む場合（例えば酸化ホウ素を含むため５質量％以上の酸素を含む場合）、混合物は炭素を含んでよく、炭素を用いて還元することによって酸素を減らすことができる（その結果、窒化ホウ素が生成し得る）。 In the method for producing a granular boron nitride composition of the present invention, for example, the components (1), (2) and (3) as raw materials are mixed to obtain a mixture, which is heated in a non-oxidizing gas atmosphere, for example. It is carried out by heating at 1800 to 2100 ° C. If necessary, the mixture may contain other components, for example, components that are inevitably contained in the production of components as raw materials. For example, when the boron nitride component (1) contains excessive oxygen (for example, when it contains 5% by mass or more of oxygen because it contains boron oxide), the mixture may contain carbon, and oxygen is generated by reducing with carbon. (As a result, boron nitride can be produced).
　混合物の均一な混合を促進するために、適当な分散媒（例えばエタノール、アセトン等）を用いてよく、質量基準で混合物に対して５～２０倍の分散媒と共にホモジナイザーで均一に混合してスラリーまたはペーストとする。これを乾燥した後、必要に応じて空気中でか焼（calcination、仮焼成または焼成）して、混合物を構成する成分が均一に混合された粉末を得、その後、非酸化性ガス雰囲気下、１８００～２１００℃で加熱処理する。 In order to promote uniform mixing of the mixture, an appropriate dispersion medium (eg ethanol, acetone, etc.) may be used, and the slurry is uniformly mixed with a homogenizer together with a dispersion medium 5 to 20 times as much as the mixture on a mass basis. Or paste. After this is dried, it is calcined in the air (calcination, calcination or calcining) as necessary to obtain a powder in which the components constituting the mixture are uniformly mixed, and then in a non-oxidizing gas atmosphere, Heat treatment is performed at 1800 to 2100 ° C.
＜窒化ホウ素成分（１）＞
　本発明で用いる窒化ホウ素成分（１）としては、市販のｈ－ＢＮ、市販のｔ－ＢＮ、ホウ素化合物とアンモニアの還元窒化法により作製されたＢＮ、ホウ素化合物とメラミン等の含窒素化合物から合成されたＢＮ等を例示でき、特に制限なく使用できる。１つの態様では、ｈ－ＢＮを用いるのが好ましい。このような窒化ホウ素成分（１）は、質量基準で窒化ホウ素を少なくとも９０％、好ましくは少なくとも９５％、より好ましくは少なくとも９６％含むのが好ましい。本発明の効果を阻害しない限り、窒化ホウ素を製造するに際して不可避的に混入する他のホウ素化合物（例えば酸化ホウ素）、他の元素または成分等を含んでよい。窒化ホウ素成分（１）を構成する窒化ホウ素は、ｈ－ＢＮが好ましいが、他の窒化ホウ素を含んでもよい。ｈ－ＢＮが窒化ホウ素に占める割合は、好ましくは少なくとも９０％、より好ましくは少なくとも９５％、例えば少なくとも９６％、特に少なくとも９８％であってよく、残りは他の窒化ホウ素である。窒化ホウ素は、通常、微粒子または粉末の形態で市販されているものであってよい。例えば、日新リフラテック社から一次粒子径５０ｎｍ、凝集粒子径３μｍ、比表面積１６０ｍ２／ｇの窒化ホウ素粉末が「ＡＢＮ」として市販されている。また、株式会社ＭＡＲＵＫＡから「ＡＰ１７０Ｓ」として粉末形態のｈ－ＢＮが市販されている。 <Boron Nitride Component (1)>
The boron nitride component (1) used in the present invention is synthesized from commercially available h-BN, commercially available t-BN, BN produced by a reduction nitride method of a boron compound and ammonia, and a nitrogen-containing compound such as a boron compound and melamine. The above-mentioned BN and the like can be exemplified, and can be used without particular limitation. In one embodiment, it is preferable to use h-BN. Such a boron nitride component (1) preferably contains at least 90%, preferably at least 95%, and more preferably at least 96% of boron nitride on a mass basis. Other boron compounds (for example, boron oxide), other elements or components that are inevitably mixed in the production of boron nitride may be contained as long as the effects of the present invention are not impaired. The boron nitride constituting the boron nitride component (1) is preferably h-BN, but may contain other boron nitride. The proportion of h-BN in boron nitride may be preferably at least 90%, more preferably at least 95%, for example at least 96%, especially at least 98%, with the rest being other boron nitride. Boron nitride may be commercially available in the form of fine particles or powders. For example, a boron nitride powder having a primary particle diameter of 50 nm, an agglomerated particle diameter of 3 μm, and a specific surface area of 160 m 2 / g is commercially available from Nissin Refratec Co., Ltd. as “ABN”. In addition, h-BN in powder form is commercially available as "AP170S" from MARUKA Co., Ltd.
　本発明の粒状窒化ホウ素組成物の製造方法において、ｈ－ＢＮ結晶の成長の観点からは、原料となるｈ－ＢＮ等を含んで成る窒化ホウ素成分（１）中に酸素がある程度存在してもよい。本発明では、例えば、窒化ホウ素成分（１）は、その全酸素濃度が１質量％～１０質量％であってよく、好ましくは全酸素濃度が５質量％以下であるものを用いることが一般的に好ましい。全酸素濃度が上記範囲内である場合、一般的に窒化ホウ素粒子の一次粒子径が小さく、結晶が未発達のものが多く、本発明で用いる他の成分と混合して加熱処理した場合、容易に溶解するので好ましい。全酸素濃度が過度に高いと、加熱処理後に得られる粒状窒化ホウ素組成物を熱伝導性フィラーとして用いル場合、酸化物を含んだ状態であるので、高熱伝導化が図れない場合があるので好ましくない。その場合は、上述のように混合物に炭素を追加して酸素の量を減らすことができる。別法では、粒状窒化ホウ素組成物を洗浄して酸化物を減らしてよい。また、窒化ホウ素成分（１）の全酸素濃度が過度に少ない場合、窒化ホウ素の純度、結晶性が既に良いために、液相に溶解し難いことがあり、その結果、窒化ホウ素の結晶成長等の変化が小さく、凝集構造を形成し難くなる場合がある。尚、原料としての窒化ホウ素成分（１）中の全酸素濃度は、不活性ガス融解－赤外線吸収法により、株式会社堀場製作所製の酸素・窒素分析計を用いて測定することができる。 In the method for producing a granular boron nitride composition of the present invention, from the viewpoint of the growth of h-BN crystals, even if oxygen is present to some extent in the boron nitride component (1) containing h-BN or the like as a raw material. Good. In the present invention, for example, the boron nitride component (1) may have a total oxygen concentration of 1% by mass to 10% by mass, preferably a total oxygen concentration of 5% by mass or less. Is preferable. When the total oxygen concentration is within the above range, the primary particle diameter of the boron nitride particles is generally small and the crystals are often underdeveloped, and it is easy when the boron nitride particles are mixed with other components used in the present invention and heat-treated. It is preferable because it dissolves in. If the total oxygen concentration is excessively high, when the granular boron nitride composition obtained after the heat treatment is used as a heat conductive filler, it is preferable because it contains an oxide and may not be able to achieve high heat conductivity. Absent. In that case, carbon can be added to the mixture as described above to reduce the amount of oxygen. Alternatively, the granular boron nitride composition may be washed to reduce oxides. Further, when the total oxygen concentration of the boron nitride component (1) is excessively low, it may be difficult to dissolve in the liquid phase because the purity and crystallinity of boron nitride are already good, and as a result, the crystal growth of boron nitride and the like may occur. The change is small, and it may be difficult to form an aggregated structure. The total oxygen concentration in the boron nitride component (1) as a raw material can be measured by an inert gas melting-infrared absorption method using an oxygen / nitrogen analyzer manufactured by Horiba Seisakusho Co., Ltd.
　窒化ホウ素成分（１）を構成する窒化ホウ素、好ましくは粒状窒化ホウ素の粒径については特に制限はない。過度に大きい場合、混合物を調製する際に不均一な混合状態となり易いことから、窒化ホウ素成分（１）に含まれる窒化ホウ素、特に粒状窒化ホウ素の平均粒子径が、５μｍ以下のものであることが好ましい。平均粒子径の下限について特に制限はないが、通常０．１μｍ以上である。尚、平均粒子径は、上述のように、原料となる粒状窒化ホウ素を適当な溶剤に分散させ、レーザ回折／散乱式粒度分布測定装置により測定することができる。 There is no particular limitation on the particle size of boron nitride, preferably granular boron nitride, which constitutes the boron nitride component (1). If it is excessively large, a non-uniform mixed state is likely to occur when preparing the mixture. Therefore, the average particle size of boron nitride contained in the boron nitride component (1), particularly granular boron nitride, should be 5 μm or less. Is preferable. The lower limit of the average particle size is not particularly limited, but is usually 0.1 μm or more. As described above, the average particle size can be measured by a laser diffraction / scattering type particle size distribution measuring device in which granular boron nitride as a raw material is dispersed in an appropriate solvent.
＜希土類成分（２）＞
　本発明の製造方法で用いる希土類成分（２）は、希土類元素の酸化物の前駆体を含む場合、これは、加熱処理工程またはその前に必要に応じて実施してよいか焼工程で希土類元素酸化物へ変換され、この酸化物が、粒状窒化ホウ素を安定に析出・成長させるように作用する。希土類成分（２）に含まれている、元々酸化物である成分も、同様に作用する。 <Rare earth component (2)>
When the rare earth component (2) used in the production method of the present invention contains a precursor of an oxide of a rare earth element, this may be carried out as necessary in the heat treatment step or before the rare earth element in the baking step. It is converted into an oxide, and this oxide acts to stably precipitate and grow granular boron nitride. The component that is originally an oxide contained in the rare earth component (2) also acts in the same manner.
　また、本発明の製造方法において用いられる希土類成分（２）は、窒化ホウ素成分（１）と共に加熱処理されるので、加熱処理条件に対する耐熱性を有するものが好ましい。このような希土類成分（２）に含まれるものとして、本発明では、酸化イットリウム、酸化セリウム、酸化イッテルビウム等の希土類元素酸化物および／またはその前駆体を用いる。これらの中でも、酸化物としての熱伝導性と耐熱性、粒状窒化ホウ素を安定して析出させて強度を有するように成長させる観点から、酸化イットリウムが特に好適である。このような酸化物を含んで成る希土類成分（２）としては、そのような酸化物として市販されているものを使用できる。一般的には、純度が９９質量％以上のものが市販されており、これを希土類成分（２）として使用できる。また、このような酸化物を生成させるために前駆体として用いるイットリウム、セリウム、イッテルビウムから選ばれる少なくとも１種の希土類元素化合物は、いずれの適当な形態であってもよく、例えば、液状ゾル、硝酸塩等の水溶性塩の形態であって、加熱処理工程またはその前に必要に応じて実施してよいか焼工程で希土類元素酸化物に変換される。 Further, since the rare earth component (2) used in the production method of the present invention is heat-treated together with the boron nitride component (1), it is preferable that the rare earth component (2) has heat resistance to the heat treatment conditions. In the present invention, rare earth element oxides such as yttrium oxide, cerium oxide, and ytterbium oxide and / or precursors thereof are used as those contained in such a rare earth component (2). Among these, yttrium oxide is particularly preferable from the viewpoint of thermal conductivity and heat resistance as an oxide, and from the viewpoint of stably precipitating granular boron nitride and growing it so as to have strength. As the rare earth component (2) containing such an oxide, a commercially available one as such an oxide can be used. Generally, those having a purity of 99% by mass or more are commercially available, and this can be used as the rare earth component (2). Further, at least one rare earth element compound selected from yttrium, cerium and ytterbium used as a precursor for producing such an oxide may be in any suitable form, for example, liquid sol or nitrate. In the form of a water-soluble salt such as, etc., it may be carried out in the heat treatment step or before the heat treatment step as necessary, or is converted into a rare earth element oxide in the baking step.
　本発明の製造方法で用いる希土類成分（２）において、酸化物は酸化イットリウム、酸化セリウム、および酸化イッテルビウムから選ばれる少なくとも１種であり、その前駆体は、そのような希土類元素の酸化物をもたらすものである。例えば、希土類元素の酢酸塩、硝酸塩、炭酸塩、クエン酸塩、シュウ酸塩、硫酸塩等の無機酸の塩および有機酸の塩ならびに塩化物等から選ばれる少なくとも１種を例示できる。これらの中で、入手の容易さ等の観点から、酸化イットリウム、イットリウムの酢酸塩、硝酸塩、炭酸塩、クエン酸塩、シュウ酸塩、硫酸塩等が好ましく用いられる。好ましい態様では、酸化イットリウム、硝酸イットリウム、炭酸イットリウム、クエン酸イットリウム、シュウ酸イットリウム、硫酸イットリウム等が用いられる。 In the rare earth component (2) used in the production method of the present invention, the oxide is at least one selected from yttrium oxide, cerium oxide, and ytterbium oxide, and the precursor thereof brings an oxide of such a rare earth element. It is a thing. For example, at least one selected from salts of inorganic acids such as acetates, nitrates, carbonates, citrates, oxalates and sulfates of rare earth elements, salts of organic acids, chlorides and the like can be exemplified. Among these, yttrium oxide, acetate of yttrium, nitrate, carbonate, citrate, oxalate, sulfate and the like are preferably used from the viewpoint of easy availability. In a preferred embodiment, yttrium oxide, yttrium nitrate, yttrium carbonate, yttrium citrate, yttrium oxalate, yttrium sulfate and the like are used.
　希土類成分（２）として、上述の希土類元素酸化物およびその前駆体である金属化合物から選択される１種を単独で用いてもよく、別の態様では、２種以上を組み合わせて用いてもよい。尚、希土類成分（２）は、上述のような希土類元素の酸化物および／またはその前駆体に加えて、本発明において製造される粒状窒化ホウ素に実質的に悪影響が無い限り、例えばその製造に際して不可避的に含まれる他の成分を含んでよい。 As the rare earth component (2), one selected from the above-mentioned rare earth element oxide and a metal compound which is a precursor thereof may be used alone, or in another embodiment, two or more thereof may be used in combination. .. The rare earth component (2) is added to the oxide of the rare earth element and / or its precursor as described above, as long as the granular boron nitride produced in the present invention is not substantially adversely affected, for example, in the production thereof. It may contain other components that are unavoidably included.
＜カルシウム成分（３）＞
　本発明の製造方法で用いるカルシウム成分（３）に含まれるのは、酸化カルシウムおよび炭酸カルシウムから選択される少なくとも１種である。炭酸カルシウムは、本発明の加熱処理工程またはその前に必要に応じて実施してよいか焼工程で酸化カルシウムに変換される。カルシウム成分（３）は、いずれの適当な形態であってよく、例えば固体（例えば粉末状）、分散液等であってよい。いかなる理論によって拘束されるものではなく、本発明を限定するものではないが、後述の実施例および比較例の結果等を考慮すると、このようなカルシウム成分（３）は、上述の希土類元素酸化物と同様に、加熱処理工程において、窒化ホウ素に先駆けて溶融して既に存在する窒化ホウ素が溶解できる液相を提供し、そして、その後にその液相にて窒化ホウ素が結晶化（即ち、再結晶化）する溶媒をもたらす機能を有すると考えられる。このような結晶化に際して、窒化ホウ素の結晶がより大きく成長してそれが凝集して結合することによって、より大きい粒子径を有するシェル構造が形成されると考えられる。このようなカルシウム成分（３）としては、酸化カルシウム、炭酸カルシウムとして市販されているものを使用できる。一般的には、純度が９０質量％以上のもの（例えば93％以上、９５％以上等）が市販されており、これをカルシウム（２）として使用できる。尚、カルシウム成分（３）は、上述のような酸化カルシウムおよび炭酸カルシウムに加えて、本発明において製造される粒状窒化ホウ素に実質的に悪影響が無い限り、それを製造するのに不可避的に含まれることになる他の成分を含んでもよい <Calcium component (3)>
The calcium component (3) used in the production method of the present invention contains at least one selected from calcium oxide and calcium carbonate. Calcium carbonate is converted to calcium oxide in the heat treatment step of the present invention or prior to it, if necessary, or in a baking step. The calcium component (3) may be in any suitable form, and may be, for example, a solid (for example, powder), a dispersion, or the like. Although not bound by any theory and not limiting the present invention, in consideration of the results of Examples and Comparative Examples described later, such a calcium component (3) is the above-mentioned rare earth element oxide. Similarly, in the heat treatment step, a liquid phase capable of melting and dissolving the existing boron nitride prior to the boron nitride is provided, and then the boron nitride is crystallized (that is, recrystallized) in the liquid phase. It is considered to have a function of providing a solvent for crystallization. During such crystallization, it is considered that the boron nitride crystal grows larger and aggregates and bonds to form a shell structure having a larger particle size. As such a calcium component (3), commercially available calcium oxide and calcium carbonate can be used. Generally, those having a purity of 90% by mass or more (for example, 93% or more, 95% or more, etc.) are commercially available, and this can be used as calcium (2). The calcium component (3) is inevitably contained in the production of calcium oxide and calcium carbonate as described above, unless the granular boron nitride produced in the present invention is substantially adversely affected. May contain other ingredients that will be
＜各成分の使用量＞
　好ましい態様では、上述のように、加熱処理する混合物における元素数基準で希土類成分（２）中の希土類元素：カルシウム成分（３）中のカルシウム元素は、好ましくは１：０．２５～１：４、より好ましくは１：０．５～１：３、特に好ましくは１：０．７～１：２．５、例えば１：１～１：２である。カルシウムが過度に少ない場合、酸化カルシウム成分が粒状窒化ホウ素の大きい粒子径をもたらす効果が不十分になることがあり得、また、カルシウムが過度に多い場合、希土類元素酸化物が過少に存在することになり、その効果、特に粒状窒化ホウ素を強固に結合する効果が不十分となる場合がある。 <Amount of each ingredient used>
In a preferred embodiment, as described above, the rare earth element in the rare earth component (2): the calcium element in the calcium component (3) is preferably 1: 0.25 to 1: 4 based on the number of elements in the heat-treated mixture. , More preferably 1: 0.5 to 1: 3, particularly preferably 1: 0.7 to 1: 2.5, for example 1: 1 to 1: 2. If the calcium is too low, the calcium oxide component may be inadequate to provide the large particle size of the granular boron nitride, and if the calcium is too high, the rare earth element oxides are under-presenced. In some cases, the effect, particularly the effect of firmly binding granular boron nitride, may be insufficient.
　また、上述のように、加熱処理する混合物に関して、希土類成分（２）に含まれる希土類元素酸化物（前駆体の場合は、対応する希土類元素酸化物に換算）の量およびカルシウム成分（３）に含まれる酸化カルシウム（炭酸カルシウムの場合は、酸化カルシウムに換算）の量が、混合物中の窒化ホウ素の量ならびに希土類元素酸化物の量および酸化カルシウムの量に占める割合、即ち、（希土類酸化物量＋酸化カルシウム量）／（窒化ホウ素量＋希土類酸化物量＋酸化カルシウム量）は、質量基準で一般的には５％～６０％（従って、窒化ホウ素は９５～４０％）、好ましくは６％～５０％（従って、窒化ホウ素は９４～５０％）、より好ましくは、７～４２％、特に好ましくは、１４～４２％、例えば１４～３５％である。 Further, as described above, regarding the mixture to be heat-treated, the amount of the rare earth element oxide contained in the rare earth component (2) (in the case of a precursor, converted to the corresponding rare earth element oxide) and the calcium component (3) The ratio of the amount of calcium oxide contained (converted to calcium oxide in the case of calcium carbonate) to the amount of boron nitride and rare earth element oxides and the amount of calcium oxide in the mixture, that is, (rare earth oxide amount +) Amount of calcium oxide) / (amount of boron nitride + amount of rare earth oxide + amount of calcium oxide) is generally 5% to 60% (hence, boron nitride is 95 to 40%), preferably 6% to 50% on a mass basis. % (Thus, boron nitride is 94-50%), more preferably 7-42%, particularly preferably 14-42%, for example 14-35%.
　このような範囲より小さい場合、加熱処理に際して希土類元素酸化物および酸化カルシウムによる、粒状窒化ホウ素のシェル構造を安定化する効果が小さくなる。その結果、得られる粒状窒化ホウ素組成物または粒状窒化ホウ素を樹脂材料と混練すると、シェル構造が崩壊し易くなる。そのような粒状窒化ホウ素を熱伝導性フィラーとして使用して成形する場合、成形のために溶融した樹脂組成物の粘度が上昇する。従って、成形時により大きい力が樹脂組成物に作用し、シェル構造を安定化する効果が低下する傾向にある。また、このような範囲より大きい場合、得られる粒状窒化ホウ素組成物に含まれる窒化ホウ素の量が過度に少なくなる。その結果、粒状窒化ホウ素組成物を熱伝導性のフィラーとして用いた場合に熱伝導率改善効果が小さくなる可能性がある。 If it is smaller than such a range, the effect of stabilizing the shell structure of granular boron nitride by the rare earth element oxide and calcium oxide during heat treatment becomes small. As a result, when the obtained granular boron nitride composition or granular boron nitride is kneaded with the resin material, the shell structure is likely to collapse. When molding using such granular boron nitride as a thermally conductive filler, the viscosity of the resin composition melted for molding increases. Therefore, a larger force acts on the resin composition during molding, and the effect of stabilizing the shell structure tends to decrease. Further, when it is larger than such a range, the amount of boron nitride contained in the obtained granular boron nitride composition becomes excessively small. As a result, when the granular boron nitride composition is used as a thermally conductive filler, the effect of improving the thermal conductivity may be reduced.
＜炭素＞
　本発明の粒状窒化ホウ素の製造方法では、窒化ホウ素成分（１）が酸素を過度に含む場合、必要に応じて混合物は炭素を更に含んでよい。炭素としては、カーボンブラック、黒鉛、高温でカーボン源となり得るカーボン前駆体が使用できるが、入手の容易さなどの観点から、カーボンブラックが好適である。カーボンブラックは、ファーネス法、チャンネル法などのカーボンブラック、アセチレンブラックなどを使用することができる。これらカーボンブラックの平均粒子径（体積基準の平均粒子径）は、任意であるが、０．０１～２０μｍのものが好ましい。 <Carbon>
In the method for producing granular boron nitride of the present invention, when the boron nitride component (1) contains an excessive amount of oxygen, the mixture may further contain carbon, if necessary. As carbon, carbon black, graphite, or a carbon precursor that can be a carbon source at high temperature can be used, but carbon black is preferable from the viewpoint of easy availability. As the carbon black, carbon black such as the furnace method and the channel method, acetylene black and the like can be used. The average particle size (volume-based average particle size) of these carbon blacks is arbitrary, but is preferably 0.01 to 20 μm.
　また、上述の炭素に代えてまたは加えて、カーボン前駆体を使用してよい。例えば、フェノール樹脂、メラミン樹脂、エポキシ樹脂、フランフェノール樹脂等の合成樹脂縮合物、ピッチ、タール等の炭化水素化合物、セルロース、ショ糖、ポリ塩化ビニリデン、ポリフェニレン等の有機化合物を前駆体として使用できる。これらのうち、特に、フェノール樹脂、セルロース、ポリフェニレン等の金属不純物等の少ないものが好ましい。これらは、１種を単独で用いてもよく、２種以上を混合して用いてもよい。 Also, a carbon precursor may be used in place of or in addition to the carbon described above. For example, synthetic resin condensates such as phenol resin, melamine resin, epoxy resin and furanphenol resin, hydrocarbon compounds such as pitch and tar, and organic compounds such as cellulose, sucrose, polyvinylidene chloride and polyphenylene can be used as precursors. .. Of these, those having less metal impurities such as phenol resin, cellulose, and polyphenylene are particularly preferable. These may be used alone or in admixture of two or more.
　炭素の使用量（カーボン前駆体を用いた場合は、それから生成する炭素量として）は、質量基準で窒化ホウ素成分（１）に対して好ましくは５質量％以下、より好ましくは３質量％以下である。加熱処理時に炭素が存在することによって、過度に酸素が存在しないようにできる。その結果、加熱処理時に酸化物によって得られる粒状窒化ホウ素のシェル構造がより強固になる。このような量より多くの炭素を用いると、シェル構造の安定性が阻害される場合がある。使用する炭素を減らすことによって、加熱処理後に残存する炭素量を最小限にすることができ、従って、熱伝導性フィラーとして用いた場合、粒状窒化ホウ素の絶縁性に対する影響を抑制できる。この意味では、炭素の使用を省略できるのが好ましい。従って、本発明の凝集体の製造方法において、混合物は炭素を含まない。 The amount of carbon used (as the amount of carbon produced from the carbon precursor when a carbon precursor is used) is preferably 5% by mass or less, more preferably 3% by mass or less, based on the boron nitride component (1) on a mass basis. is there. The presence of carbon during the heat treatment can prevent excessive oxygen from being present. As a result, the shell structure of the granular boron nitride obtained by the oxide during the heat treatment becomes stronger. The use of more carbon than this amount may impair the stability of the shell structure. By reducing the amount of carbon used, the amount of carbon remaining after the heat treatment can be minimized, and therefore, when used as a thermally conductive filler, the effect of granular boron nitride on the insulating property can be suppressed. In this sense, it is preferable that the use of carbon can be omitted. Therefore, in the method for producing aggregates of the present invention, the mixture is carbon-free.
＜その他の成分＞
　本発明の粒状窒化ホウ素の製造方法において、成分（１）～（３）を含んで成る混合物は、この製造方法および製造される粒状窒化ホウ素に悪影響が生じない限り、他の成分を含んでよい。そのような他の成分としては、窒化アルミニウム、水酸化アルミニウム、酸化アルミニウム（アルミナ）等のアルミニウム化合物の無機物の１種または２種以上を例示できる。これらの化合物を併用することにより、得られる粒状窒化ホウ素の熱伝導性を損なわず、凝集構造の安定化をさらに図ることができる。 <Other ingredients>
In the method for producing granular boron nitride of the present invention, the mixture containing the components (1) to (3) may contain other components as long as the production method and the produced granular boron nitride are not adversely affected. .. Examples of such other components include one or more inorganic substances of aluminum compounds such as aluminum nitride, aluminum hydroxide, and aluminum oxide (alumina). By using these compounds in combination, the thermal conductivity of the obtained granular boron nitride is not impaired, and the aggregated structure can be further stabilized.
　但し、他の成分の量が多過ぎると製造される粒状窒化ホウ素中の窒化ホウ素の含有量が少なくなり過ぎ、熱伝導性フィラーとして用いた場合の熱伝導率の改善効果が不十分となることがある。よって、他の成分を併用する場合、その使用量は、質量基準で窒化ホウ素成分（１）に対して５％以下、例えば０．１～３％であるのが一般的に好ましい。 However, if the amount of other components is too large, the content of boron nitride in the produced granular boron nitride will be too small, and the effect of improving the thermal conductivity when used as a thermally conductive filler will be insufficient. There is. Therefore, when other components are used in combination, the amount used is generally preferably 5% or less, for example, 0.1 to 3% with respect to the boron nitride component (1) on a mass basis.
＜原料成分（１）～（３）の混合＞
　本発明の粒状窒化ホウ素の製造方法において、混合物を構成する窒化ホウ素成分（１）、希土類成分（２）およびカルシウム成分（３）、ならびに上述の必要に応じて含まれる炭素および他の成分の混合方法は、特に制限されるものではなく、例えば乾式混合、湿式混合を用いることが出来る。 <Mixing of raw material components (1) to (3)>
In the method for producing granular boron nitride of the present invention, the boron nitride component (1), the rare earth component (2) and the calcium component (3) constituting the mixture, and the above-mentioned mixture of carbon and other components contained as necessary are mixed. The method is not particularly limited, and for example, dry mixing and wet mixing can be used.
　乾式混合では、水平円筒型混合機、Ｖ型混合機、２重円錐型混合機、リボン型混合機、単軸ロッドまたはピン付ローター型混合機、パドル型混合機、円錐型スクリュー混合機、高速流動型混合機、回転円盤型混合機、マラー型混合機、気流攪拌型混合機などが用いられ、湿式混合では、手動で攪拌混合する以外に、自動乳鉢、ボールミル、ボニーミキサー、インターナルミキサー、３本ロールミキサー、コニーダー、ボテーター、高速流動混合機、超音波ホモジナイザーなど一般的な混合機を用いることができる。 For dry mixing, horizontal cylindrical mixer, V-type mixer, double cone type mixer, ribbon type mixer, single shaft rod or rotor type mixer with pin, paddle type mixer, cone type screw mixer, high speed Flow type mixers, rotary disk type mixers, maller type mixers, air flow stirring type mixers, etc. are used. In wet mixing, in addition to manual stirring and mixing, automatic dairy bowls, ball mills, bonnie mixers, internal mixers, etc. A general mixer such as a 3-roll mixer, a conider, a botator, a high-speed flow mixer, and an ultrasonic homogenizer can be used.
　より均一に混合するには、湿式混合が好ましく用いられる。湿式混合に用いる溶媒（分散媒）に制限はないが、乾燥の容易さ、装置の簡素化などの観点から、純水、エタノール、メタノール、プロパノール等のアルコール、アセトン等のケトン等の有機溶媒が好ましく、別の態様では、水とこれらの有機溶媒との混合溶媒が好ましい。 Wet mixing is preferably used for more uniform mixing. The solvent (dispersion medium) used for wet mixing is not limited, but from the viewpoint of ease of drying and simplification of the equipment, pure water, alcohols such as ethanol, methanol and propanol, and organic solvents such as ketones such as acetone are used. Preferably, in another aspect, a mixed solvent of water and these organic solvents is preferred.
　純水、アルコール、ケトン等の有機溶媒の使用量は、多過ぎると後で実施する乾燥時の負荷が増大し、少な過ぎると均一混合が困難であることから、窒化ホウ素成分（１）に対して質量基準で５～２０倍、特に５～１０倍とすることが好ましい。 If the amount of an organic solvent such as pure water, alcohol, or ketone is too large, the load during drying performed later will increase, and if it is too small, uniform mixing will be difficult. Therefore, with respect to the boron nitride component (1). It is preferable that the mass is 5 to 20 times, particularly 5 to 10 times.
＜乾燥・粉砕＞
　上述のように成分を混合する場合に湿式混合を採用した場合は、混合物を乾燥して溶媒を除去し、乾燥物を粉砕することが好ましく、その後、必要に応じて、か焼した後、熱処理を実施する。 <Drying / crushing>
When wet mixing is adopted when mixing the components as described above, it is preferable to dry the mixture to remove the solvent and pulverize the dried product, and if necessary, heat-treat after calcination. To carry out.
　この乾燥を実施する方法に特に制限はなく、加熱乾燥、加熱真空乾燥等を用いてよい。一般的には、加熱乾燥を行うことが好ましい。小スケールでは、通常、加熱真空乾燥を用いる。加熱乾燥の場合の条件としては１００～１２０℃の加熱温度、１２～４８時間程度の加熱時間とすることが好ましい。加熱温度が低過ぎたり、加熱時間が短か過ぎたりすると、十分な乾燥を行えず、逆に加熱温度が高過ぎたり加熱時間が長過ぎたりすると加熱コストの点から好ましくない。加熱真空乾燥の場合は、５０℃程度の温度でエバポレーターを用いて溶媒を留去する。 The method for carrying out this drying is not particularly limited, and heat drying, heat vacuum drying, or the like may be used. Generally, it is preferable to perform heat drying. On small scales, heating vacuum drying is usually used. In the case of heat drying, it is preferable that the heating temperature is 100 to 120 ° C. and the heating time is about 12 to 48 hours. If the heating temperature is too low or the heating time is too short, sufficient drying cannot be performed, and conversely, if the heating temperature is too high or the heating time is too long, it is not preferable from the viewpoint of heating cost. In the case of vacuum drying by heating, the solvent is distilled off using an evaporator at a temperature of about 50 ° C.
　乾燥後の粉砕は、乳鉢による粉砕であってもよく、その他ボールミルなどを用いることもできる。この粉砕の程度としては、平均粒子径１００μｍ以上の大きな塊が存在しない程度に粉砕されていれば問題ない。この平均粒子径は、先に説明した平均粒子径と同様の方法で測定できる。 The crushing after drying may be crushing with a mortar, or another ball mill or the like can be used. As for the degree of pulverization, there is no problem as long as it is pulverized to the extent that no large lump having an average particle diameter of 100 μm or more exists. This average particle size can be measured by the same method as the average particle size described above.
　尚、この乾燥、粉砕時の雰囲気は空気雰囲気であってよいが、吸湿を避けるために湿度５０％以下の乾燥空気中が好ましい。 The atmosphere during drying and crushing may be an air atmosphere, but it is preferably in dry air having a humidity of 50% or less in order to avoid moisture absorption.
＜か焼＞
　希土類成分（２）の希土類元素酸化物の前駆体として、例えば硝酸塩、酢酸塩、シュウ酸塩等の金属塩を用いた場合は、加熱処理に先立って、これらの前駆体を酸化物に変換するためにか焼（または仮焼成、即ち、加熱処理に先立って実施する、より低い温度における加熱処理）を行ってもよい。また、カルシウム成分（３）として炭酸カルシウムを用いる場合も同様であり、酸化カルシウムに変換する。 <Calcination>
When a metal salt such as nitrate, acetate, or oxalate is used as a precursor of the rare earth element oxide of the rare earth component (2), these precursors are converted into oxides prior to the heat treatment. Therefore, calcination (or calcination, that is, heat treatment at a lower temperature, which is carried out prior to heat treatment) may be performed. The same applies when calcium carbonate is used as the calcium component (3), and it is converted to calcium oxide.
　このか焼は、例えば５００～７００℃の温度で１～５時間程度、空気等の酸化性雰囲気下で加熱することにより行ってよい。このか焼時の加熱温度が低過ぎたり、加熱時間が短か過ぎたりすると変換が不十分となり、本か焼中に酸が発生したり、窒素酸化物が発生して装置を傷めるため好ましくない。尚、加熱時に分解ガス等を排気できる加熱炉を用いる場合、か焼の工程を省略してよく、後の加熱処理時にか焼を同時に行うことが出来る。また、か焼時の加熱温度が高過ぎたり加熱時間が長過ぎたりすると窒化ホウ素成分（１）に含まれる窒化ホウ素が酸化されてしまうことがあるので好ましくない。加熱炉が排気設備を備えている場合、炉内空気を排気することで酸化は回避できる。この場合、高い加熱温度、長い加熱時間による窒化ホウ素の酸化は問題とはならない。 This calcination may be performed by heating at a temperature of 500 to 700 ° C. for about 1 to 5 hours in an oxidizing atmosphere such as air. If the heating temperature during calcination is too low or the heating time is too short, conversion will be insufficient, and acid will be generated during calcination or nitrogen oxides will be generated, which is not preferable because it will damage the equipment. .. When a heating furnace capable of exhausting decomposition gas or the like during heating is used, the step of calcination may be omitted, and calcination can be performed at the same time in the subsequent heat treatment. Further, if the heating temperature at the time of calcination is too high or the heating time is too long, the boron nitride contained in the boron nitride component (1) may be oxidized, which is not preferable. If the heating furnace is equipped with an exhaust facility, oxidation can be avoided by exhausting the air inside the furnace. In this case, oxidation of boron nitride due to a high heating temperature and a long heating time does not matter.
＜加熱処理＞
　加熱処理の温度は、通常１８００～２１００℃、好ましくは１９００～２１００℃、更に好ましくは２０００～２１００℃である。加熱処理の温度がこの範囲より低いと、ｈ－ＢＮの結晶化が不十分となり、結晶化が未発達のアモルファス部分が残り、熱伝導性フィラーとして使用した場合の熱伝導率改善効果が小さくなる。加熱処理の温度が上記上限を超えると、希土類元素酸化物が蒸発・分解してシェル構造を保てなくなり、窒化ホウ素の分解などが生じる場合がある。 <Heat treatment>
The temperature of the heat treatment is usually 1800 to 2100 ° C, preferably 1900 to 2100 ° C, and more preferably 2000 to 2100 ° C. If the temperature of the heat treatment is lower than this range, the crystallization of h-BN becomes insufficient, an amorphous portion with undeveloped crystallization remains, and the effect of improving the thermal conductivity when used as a heat conductive filler becomes small. .. If the temperature of the heat treatment exceeds the above upper limit, the rare earth element oxide may evaporate and decompose, the shell structure cannot be maintained, and boron nitride may be decomposed.
　加熱処理時間は、通常、５時間～２０時間であり、好ましくは５時間～１５時間である。加熱処理時間が、この範囲より短い場合、結晶成長が不十分となり、この範囲より長い場合、ｈ－ＢＮが一部分解するおそれがある。 The heat treatment time is usually 5 hours to 20 hours, preferably 5 hours to 15 hours. If the heat treatment time is shorter than this range, crystal growth will be insufficient, and if it is longer than this range, h-BN may be partially decomposed.
　加熱処理は、非酸化性ガス雰囲気下で行うために、好ましくは、通常、炉内を真空ポンプで排気しながら加熱し、加熱に伴う分解ガスなどが少なくなるまで排気を継続した後、非酸化性ガスを導入しながら、続けて所望の温度まで加熱して昇温する。真空ポンプで排気を行う温度の目安としては、２００～７００℃、例えば６００℃程度であり、その温度まで真空度を１０－１Ｐａ程度に保持しながら、２０℃／分程度の昇温速度で加熱してよい。その後、非酸化性ガスを大気圧まで導入し、加熱処理終了まで導入し続ける。非酸化性ガスの流量は、炉の大きさにもよるが、通常１ｍｌ／分以上であれば問題ない。非酸化性ガス導入後は、１１００℃程度まで２０～１００℃／分で昇温し、その後１１００℃から所定の加熱処理温度まで２～２０℃／分で昇温する。この温度で上述の加熱処理時間加熱した後、例えば５～５０℃／分程度で室温まで降温することが好ましい。当然ではあるが、本発明の粒状窒化ホウ素の製造方法には、加熱処理した混合物を室温まで冷却する工程も内在する。 Since the heat treatment is performed in a non-oxidizing gas atmosphere, it is preferable to heat the inside of the furnace while exhausting it with a vacuum pump, continue exhausting until the amount of decomposed gas and the like associated with the heating is reduced, and then non-oxidize. While introducing the sex gas, the temperature is continuously heated to a desired temperature. The standard temperature for exhausting with a vacuum pump is 200 to 700 ° C, for example, about 600 ° C, and the temperature rise rate is about 20 ° C / min while maintaining the degree of vacuum up to that temperature at about 10 -1 Pa. May be heated. After that, the non-oxidizing gas is introduced to atmospheric pressure and continued to be introduced until the end of the heat treatment. The flow rate of the non-oxidizing gas depends on the size of the furnace, but usually there is no problem if it is 1 ml / min or more. After the introduction of the non-oxidizing gas, the temperature is raised to about 1100 ° C. at 20 to 100 ° C./min, and then from 1100 ° C. to a predetermined heat treatment temperature at 2 to 20 ° C./min. After heating at this temperature for the above-mentioned heat treatment time, it is preferable to lower the temperature to room temperature at, for example, about 5 to 50 ° C./min. As a matter of course, the method for producing granular boron nitride of the present invention also includes a step of cooling the heat-treated mixture to room temperature.
　加熱処理を施す焼成炉は、マッフル炉、管状炉、雰囲気炉、多目的高温炉などのバッチ式炉やロータリーキルン、スクリューコンベヤ炉、トンネル炉、ベルト炉、プッシャー炉、竪型連続炉などの連続炉が挙げられ、目的に応じて使い分けられる。 The firing furnaces to be heat-treated include batch-type furnaces such as muffle furnaces, tubular furnaces, atmospheric furnaces, and multipurpose high-temperature furnaces, and continuous furnaces such as rotary kilns, screw conveyor furnaces, tunnel furnaces, belt furnaces, pusher furnaces, and vertical continuous furnaces. It can be mentioned and used properly according to the purpose.
　この加熱処理を酸化性ガス雰囲気下で行うと、窒化ホウ素成分（１）に含まれる窒化ホウ素の大部分が酸化ホウ素などに変換されるため、加熱処理は非酸化性ガス雰囲気下であることが必要である。 When this heat treatment is performed in an oxidizing gas atmosphere, most of the boron nitride contained in the boron nitride component (1) is converted to boron oxide or the like, so that the heat treatment may be performed in a non-oxidizing gas atmosphere. is necessary.
＜粒状窒化ホウ素組成物の洗浄（粒状窒化ホウ素の製造）＞
　上述のようにして得られる、本発明の粒状窒化ホウ素組成物には、希土類元素酸化物および酸化カルシウムが残留している。また、これらの酸化物を構成する元素の複合酸化物（ホウ酸カルシウムイットリウム（ＣａＹＢＯ４）等）、ホウ酸塩化合物（ホウ酸カルシウム（ＣａＢ２Ｏ４）等）も含まれることが有り得、残留し得る。これらの残留物の熱伝導率は、窒化ホウ素よりも小さいことが多いので、好ましい１つの態様では、残留物を除去して減らすことによって粒状窒化ホウ素の熱伝導率が向上する。そこで、必要に応じて、この上述の方法で得られる粒状窒化ホウ素組成物から残留物を除去してよい。この除去は、粒状窒化ホウ素組成物を酸水溶液によって洗浄することにより実施できる。詳しくは、残留物をそれに対応する水溶性の塩に変換する反応を用いて、存在する水に塩を溶解させて塩水溶液を得、これを除去することによって酸化物を除去する。用いる酸として有機酸および無機酸を挙げることができ、例えば塩酸、硝酸、硫酸等を使用してよい <Washing of Granular Boron Nitride Composition (Manufacturing of Granular Boron Nitride)>
Rare earth element oxides and calcium oxide remain in the granular boron nitride composition of the present invention obtained as described above. In addition, complex oxides of elements constituting these oxides (calcium borate yttrium (CaYBO 4 ), etc.) and borate compounds (calcium borate (CaB 2 O 4 ), etc.) may also be contained and remain. Can be. Since the thermal conductivity of these residues is often lower than that of boron nitride, in one preferred embodiment, removing and reducing the residue improves the thermal conductivity of the granular boron nitride. Therefore, if necessary, the residue may be removed from the granular boron nitride composition obtained by the above-mentioned method. This removal can be carried out by washing the granular boron nitride composition with an aqueous acid solution. Specifically, an oxide is removed by dissolving the salt in existing water to obtain an aqueous salt solution and removing it using a reaction that converts the residue into a corresponding water-soluble salt. Examples of the acid to be used include organic acids and inorganic acids, and for example, hydrochloric acid, nitric acid, sulfuric acid and the like may be used.
　この酸水溶液による洗浄は、酸水溶液中に粒状窒化ホウ素組成物を、撹拌下、分散させることによって実施できる。その後、組成物を濾別した後、水洗することによって残存する酸を除去した後、乾燥させて粒状窒化ホウ素を得る。酸化カルシウムおよびホウ酸塩化合物（存在する場合）は酸洗浄で実質的にその全量を容易に除去できる。この得られた粒状窒化ホウ素に含まれる希土類元素酸化物の総量は、粒状窒化ホウ素の質量基準で、好ましくは０．１～３０％、好ましくは１～１５％、より好ましくは３～１０％である。尚、残存する希土類元素酸化物は、洗浄条件（例えば酸の濃度、洗浄に用いる水溶液量および／または洗浄回数）を適宜選択することによって、容易に調節できる。 Cleaning with this acid aqueous solution can be carried out by dispersing the granular boron nitride composition in the acid aqueous solution with stirring. Then, the composition is filtered off, washed with water to remove the residual acid, and then dried to obtain granular boron nitride. Calcium oxide and borate compounds (if present) can be easily removed in substantially all of them by acid cleaning. The total amount of rare earth element oxides contained in the obtained granular boron nitride is preferably 0.1 to 30%, preferably 1 to 15%, and more preferably 3 to 10% based on the mass of the granular boron nitride. is there. The remaining rare earth element oxide can be easily adjusted by appropriately selecting cleaning conditions (for example, acid concentration, amount of aqueous solution used for cleaning and / or number of cleanings).
　尚、粒状窒化ホウ素組成物中の希土類元素酸化物の量は、次のようにして測定できる：
テフロン内張耐圧容器に酸洗浄した粒状窒化ホウ素組成物１ｇを１規定の塩酸水溶液６０ｇに添加し、密封後に１００℃で１１時間処理を行った。得られたスラリーをメンブレンフィルターで濾過をし、濾液を純水によって２００倍に希釈した溶液をＩＣＰ（イオン誘導結合プラズマ）発光分析装置（島津製作所株式会社製、ICPS-7510）を用いて希土類元素（例えばイットリウム）の濃度を分析し、それに基づいて組成物に含まれている希土類元酸化物（例えばＹ２Ｏ３）の量を算出する。また、濾滓をＸＲＤ分析して希土類元素酸化物のピークがないことを確認する。 The amount of rare earth element oxide in the granular boron nitride composition can be measured as follows:
1 g of an acid-washed granular boron nitride composition was added to 60 g of a 1N hydrochloric acid aqueous solution in a Teflon-lined pressure-resistant container, and after sealing, treatment was performed at 100 ° C. for 11 hours. The obtained slurry is filtered with a membrane filter, and the solution obtained by diluting the filtrate with pure water 200 times is used as an ICP (inductively coupled plasma) luminescence analyzer (ICPS-7510, manufactured by Shimadzu Corporation) for rare earth elements. (e.g., yttrium) analyzing the concentration of, for calculating the amount of rare-earth oxide contained in the composition based on it (for example, Y 2 O 3). In addition, XRD analysis of the slag is confirmed to be free of peaks of rare earth element oxides.
　尚、濾別される粒子が粒状窒化ホウ素（ｈ－ＢＮ）であることの確認は、Ｘ線回折パターンにより確認した。また、ＳＥＭによって、窒化ホウ素結晶のｃ面が折れ曲がって多面体（または略球状）を形成している観察結果を得た。尚、粒状窒化ホウ素がシェル構造を有することについては、粒状窒化ホウ素をエポキシ樹脂に添加して硬化したものをアルゴンイオンビームでエッチングすることによって作製したＳＥＭ観察用サンプルを用い調べた。粒状窒化ホウ素粒子はエッチングによって輪切りにした場合、窒化ホウ素のｃ面の積層が円状に繋がりシェルを形成し、その中に窒化ホウ素以外の物質が存在することをＳＥＭ観察することによって確認できる。 The confirmation that the particles to be filtered out were granular boron nitride (h-BN) was confirmed by an X-ray diffraction pattern. Further, by SEM, an observation result was obtained in which the c-plane of the boron nitride crystal was bent to form a polyhedron (or substantially spherical shape). The fact that the granular boron nitride had a shell structure was investigated by using an SEM observation sample prepared by adding granular boron nitride to an epoxy resin and curing it by etching with an argon ion beam. When the granular boron nitride particles are sliced by etching, it can be confirmed by SEM observation that the c-plane stacks of boron nitride are connected in a circular shape to form a shell and a substance other than boron nitride is present in the shell.
　例えば、上述のように輪切り状態の粒状窒化ホウ素（後述の実施例３６（酸化物が部分的に残存する実施例）において得られた粒状窒化ホウ素（但し、酸化イットリウムを約８．６５％含む））のＳＥＭ写真を図８の左上に示す。また、この状態の粒状窒化ホウ素をＥＤＳ(エネルギー分散型Ｘ線分析）を用いてマッピング分析した結果を図８の右上（Ｎ元素）および左下（Ｙ元素）に示す。これらのマッピング結果とＳＥＭ写真とを組み合わせると、Ｎ元素が多角形の周（または略円周状）の部分（即ち、環状部分）に窒素元素が存在し、その内部にＹ元素が存在することが分かる。これらの結果から、Ｎ元素（即ち、窒化ホウ素）がシェル構造を構成し、そのシェル構造の内部にＹ（即ち、酸化イットリウム）が存在すると理解できる。即ち、本発明の粒状窒化ホウ素は、窒化ホウ素により構成されたシェル部分、および洗浄の程度に応じた量でその内部に残存する希土類元素酸化物によって構成される。 For example, as described above, granular boron nitride in a sliced state (granular boron nitride obtained in Example 36 (Example in which an oxide partially remains) described later (however, containing about 8.65% yttrium oxide)). ) Is shown in the upper left of FIG. The results of mapping analysis of granular boron nitride in this state using EDS (Energy Dispersive X-ray Analysis) are shown in the upper right (N element) and lower left (Y element) of FIG. Combining these mapping results with the SEM photograph, the nitrogen element is present in the circumferential (or substantially circumferential) portion (that is, the cyclic portion) of the polygonal N element, and the Y element is present inside it. I understand. From these results, it can be understood that the N element (that is, boron nitride) constitutes the shell structure, and Y (that is, yttrium oxide) exists inside the shell structure. That is, the granular boron nitride of the present invention is composed of a shell portion composed of boron nitride and a rare earth element oxide remaining inside the shell portion in an amount corresponding to the degree of cleaning.
　また、後述の実施例１１において得られた本発明の粒状窒化ホウ素組成物（従って、洗浄処理を実施する前の状態のもの）を同様に分析した結果を図９に示す。図９の左上はＳＥＭ写真、右上はＮ元素のＥＤＳマッピング結果、左下はＣａ元素のＥＤＳマッピング結果、右下はＹ元素のＥＤＳマッピング結果を示す。図８と同様に、Ｎ元素が粒状窒化ホウ素の結晶の周囲にシェル構造で存在し、その内部にカルシウム元素およびイットリウム元素が存在する（従って、これらの酸化物が存在する）ことが分かる。更に、洗浄処理によって、酸化物の量が減少することも理解できる。 Further, FIG. 9 shows the results of the same analysis of the granular boron nitride composition of the present invention obtained in Example 11 described later (thus, the one in the state before the cleaning treatment was performed). The upper left of FIG. 9 shows the SEM photograph, the upper right shows the EDS mapping result of N element, the lower left shows the EDS mapping result of Ca element, and the lower right shows the EDS mapping result of Y element. Similar to FIG. 8, it can be seen that the N element exists in a shell structure around the granular boron nitride crystal, and the calcium element and the yttrium element exist inside the shell structure (thus, these oxides exist). Furthermore, it can be understood that the cleaning treatment reduces the amount of oxides.
＜粒状窒化ホウ素組成物＞
　本発明の粒状窒化ホウ素組成物は、好ましくは上述の本発明の粒状窒化ホウ素組成物の製造方法により製造でき、窒化ホウ素とイットリウム、セリウムおよびイッテルビウムから選ばれる少なくも１種の希土類元素の酸化物と酸化カルシウムとを含有し、好ましくは窒化ホウ素が黒鉛構造を持つものである。これらの酸化物は、上述のように酸洗浄によって、減量できる。 <Granular Boron Nitride Composition>
The granular boron nitride composition of the present invention can be preferably produced by the above-mentioned method for producing a granular boron nitride composition of the present invention, and is an oxide of at least one rare earth element selected from boron nitride and ytterbium, cerium and ytterbium. And calcium oxide are contained, and boron nitride preferably has a graphite structure. These oxides can be reduced in weight by acid cleaning as described above.
　本発明の粒状窒化ホウ素組成物は、希土類元素酸化物および酸化カルシウムによってシェル構造が強化され、その結果、圧力が作用した場合の強度（例えば圧壊強度）が改善されている。従って、熱伝導異方性の改善や熱伝導率の向上を目的として、樹脂材料に配合できる。更に、粒状窒化ホウ素に由来する固体潤滑性を維持しているので樹脂材料に配合した場合であっても、樹脂組成物としての成形加工性を良好に維持することができ、しかも、成形体を作製した場合、成形体中でシェル構造に由来して厚み方向の熱伝導パスが形成され易くなる。その結果、成形体の厚み方向の熱伝導率を高くできる。加えて、本発明の粒状窒化ホウ素は、窒化ホウ素に由来する、化学的安定性、耐熱性等をも備えている。 In the granular boron nitride composition of the present invention, the shell structure is strengthened by the rare earth element oxide and calcium oxide, and as a result, the strength when pressure is applied (for example, crush strength) is improved. Therefore, it can be blended with a resin material for the purpose of improving thermal conductivity anisotropy and thermal conductivity. Further, since the solid lubricity derived from granular boron nitride is maintained, the molding processability as a resin composition can be maintained well even when it is blended with a resin material, and the molded product can be formed. When manufactured, a heat conduction path in the thickness direction is likely to be formed in the molded body due to the shell structure. As a result, the thermal conductivity in the thickness direction of the molded product can be increased. In addition, the granular boron nitride of the present invention also has chemical stability, heat resistance, etc. derived from boron nitride.
　窒化ホウ素成分が酸素を含む場合、その酸素は、一般的には酸化ホウ素（Ｂ２Ｏ３）として含まれることが多い。この場合、酸化ホウ素は、希土類元素酸化物および酸化カルシウムと反応して酸化物（例えばＣａＹＢＯ４のような複合酸化物）となり液相を構成する。この酸化物は、本発明の粒状窒化ホウ素組成物の製造方法において加熱処理を実施する場合、希土類元素酸化物および酸化カルシウムと同様に、窒化ホウ素成分（１）に含まれている窒化ホウ素が溶解する液相を形成する。窒化ホウ素が再結晶する際に粒状窒化ホウ素が生成する際にシェル構造を強化できると考えられる。尚、上述の複合酸化物も、希土類元素酸化物と同様に、酸による洗浄の条件に応じて減らすことができ、また、実質的に全量を除去することもできる。 When the boron nitride component contains oxygen, the oxygen is generally contained as boron oxide (B 2 O 3 ). In this case, boron oxide reacts with the rare earth element oxide and calcium oxide to form an oxide (for example, a composite oxide such as CaYBO 4 ) to form a liquid phase. When heat treatment is carried out in the method for producing a granular boron nitride composition of the present invention, this oxide dissolves boron nitride contained in the boron nitride component (1), similarly to the rare earth element oxide and calcium oxide. To form a liquid phase. It is considered that the shell structure can be strengthened when granular boron nitride is produced when boron nitride is recrystallized. As with the rare earth element oxides, the above-mentioned composite oxides can be reduced depending on the conditions for cleaning with an acid, and substantially the entire amount can be removed.
　尚、本発明の粒状窒化ホウ素組成物中の希土類元素酸化物の含有量は、上述のような洗浄を実施しない場合（即ち、加熱処理およびその後の冷却のみを実施する場合）、前述の本発明の粒状窒化ホウ素組成物の製造方法で加熱処理される混合物に含まれる希土類元素酸化物およびその前駆体に由来する酸化物（前駆体が存在する場合）の量の和に実質的に等しく、また、酸化カルシウムの含有量は、同様に、加熱処理される混合物に含まれる酸化カルシウムおよび炭酸カルシウムに由来する酸化物（前駆体が存在する場合）の量の和に実質的に等しい。通常、粒状窒化ホウ素組成物の窒化ホウ素含有量は、粒状窒化ホウ素組成物の窒化ホウ素、希土類元素酸化物および酸化カルシウムの総質量基準で、好ましくは４０～９５％、より好ましくは５０～９０％、例えば５５～８５％である。 The content of the rare earth element oxide in the granular boron nitride composition of the present invention is the above-mentioned present invention when the above-mentioned washing is not carried out (that is, when only the heat treatment and the subsequent cooling are carried out). It is substantially equal to the sum of the amounts of rare earth element oxides and oxides derived from their precursors (if precursors are present) contained in the mixture heat-treated by the method for producing the granular boron nitride composition of. Similarly, the content of calcium oxide is substantially equal to the sum of the amounts of calcium oxide and oxides derived from calcium carbonate (if precursors are present) contained in the heat-treated mixture. Generally, the boron nitride content of the granular boron nitride composition is preferably 40 to 95%, more preferably 50 to 90%, based on the total mass of boron nitride, rare earth element oxides and calcium oxide of the granular boron nitride composition. For example, 55-85%.
＜粒状窒化ホウ素を含む樹脂組成物＞
　本発明の樹脂組成物、特に熱伝導性の樹脂組成物は、上述の本発明の粒状窒化ホウ素および樹脂材料を含んで成る。即ち、本発明の粒状窒化ホウ素は、上述のように、樹脂組成物において熱伝導性フィラーとして好適に用いられる。尚、場合により、粒状窒化ホウ素に代えて、粒状窒化ホウ素組成物を使用することも可能である。 <Resin composition containing granular boron nitride>
The resin composition of the present invention, particularly a thermally conductive resin composition, comprises the above-mentioned granular boron nitride and resin material of the present invention. That is, as described above, the granular boron nitride of the present invention is suitably used as a thermally conductive filler in the resin composition. In some cases, it is also possible to use a granular boron nitride composition instead of the granular boron nitride.
＜樹脂材料＞
　樹脂組成物においてマトリックスを形成することになる樹脂として機能する樹脂材料は特に限定されるものではなく、例えば硬化性樹脂、熱可塑性樹脂等であってよい。硬化性樹脂としては、熱硬化性、光硬化性、電子線硬化性などの架橋可能なものであればよいが、耐熱性、吸水性、寸法安定性などの点で、熱硬化性樹脂が好ましく、特にエポキシ樹脂が最適である。 <Resin material>
The resin material that functions as the resin that forms the matrix in the resin composition is not particularly limited, and may be, for example, a curable resin, a thermoplastic resin, or the like. The curable resin may be any crosslinkable resin such as thermosetting, photocurable, and electron beam curable, but a thermosetting resin is preferable in terms of heat resistance, water absorption, dimensional stability, and the like. Especially, epoxy resin is most suitable.
　エポキシ樹脂は１種類の構造単位を有するエポキシ樹脂のみであってもよいが、構造単位の異なる複数のエポキシ樹脂を組み合わせてもよい。また、エポキシ樹脂は、必要に応じて、エポキシ樹脂用硬化剤、硬化促進剤と共に用いられる。 The epoxy resin may be only an epoxy resin having one kind of structural unit, but a plurality of epoxy resins having different structural units may be combined. Further, the epoxy resin is used together with a curing agent for epoxy resin and a curing accelerator, if necessary.
　ここで、塗工性または成膜性、接着性と併せて、硬化物中のボイドを低減して高熱伝導の硬化物を得るために、エポキシ樹脂として少なくとも後述するフェノキシ樹脂（以下、「エポキシ樹脂（Ａ）」と称す。）を含むことが好ましく、特にエポキシ樹脂全量に対するエポキシ樹脂（Ａ）の質量比率が、好ましくは５～９５質量％の範囲、より好ましくは１０～９０質量％、さらに好ましくは２０～８０質量％の範囲で含有されることが好ましいが、何らこのようなものに限定されるものではない。 Here, in order to reduce voids in the cured product and obtain a cured product having high thermal conductivity in addition to coatability, film forming property, and adhesiveness, at least a phenoxy resin described later as an epoxy resin (hereinafter, "epoxy resin") (A) ”is preferably contained, and in particular, the mass ratio of the epoxy resin (A) to the total amount of the epoxy resin is preferably in the range of 5 to 95% by mass, more preferably 10 to 90% by mass, still more preferably. Is preferably contained in the range of 20 to 80% by mass, but is not limited to such a substance.
　フェノキシ樹脂とは、通常、エピハロヒドリンと２価フェノール化合物とを反応させて得られる樹脂、または２価のエポキシ化合物と２価のフェノール化合物とを反応させて得られる樹脂を指すが、本発明においてはこれらのうち、特に質量平均分子量１００００以上の高分子量エポキシ樹脂であるフェノキシ樹脂をエポキシ樹脂（Ａ）という。尚、質量平均分子量とは、ゲルパーミエイションクロマトグラフィーで測定したポリスチレン換算の値である。 The phenoxy resin usually refers to a resin obtained by reacting epihalohydrin with a divalent phenol compound, or a resin obtained by reacting a divalent epoxy compound with a divalent phenol compound, but in the present invention. Among these, a phenoxy resin which is a high molecular weight epoxy resin having a mass average molecular weight of 10,000 or more is referred to as an epoxy resin (A). The mass average molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography.
　エポキシ樹脂（Ａ）としては、ナフタレン骨格、フルオレン骨格、ビフェニル骨格、アントラセン骨格、ピレン骨格、キサンテン骨格、アダマンタン骨格およびジシクロペンタジエン骨格からなる群から選択された少なくとも１つの骨格を有するフェノキシ樹脂が好ましい。中でも、耐熱性がより一層高められるので、フルオレン骨格および／またはビフェニル骨格を有するフェノキシ樹脂が特に好ましい。これらは１種を単独で用いてもよく、２種以上を混合して用いてもよい。 As the epoxy resin (A), a phenoxy resin having at least one skeleton selected from the group consisting of a naphthalene skeleton, a fluorene skeleton, a biphenyl skeleton, an anthracene skeleton, a pyrene skeleton, a xanthene skeleton, an adamantane skeleton and a dicyclopentadiene skeleton is preferable. .. Among them, a phenoxy resin having a fluorene skeleton and / or a biphenyl skeleton is particularly preferable because the heat resistance is further enhanced. One of these may be used alone, or two or more thereof may be mixed and used.
　上記エポキシ樹脂（Ａ）以外のエポキシ樹脂としては、分子内に２個以上のエポキシ基を有するエポキシ樹脂（以下「エポキシ樹脂（Ｂ）」と称す場合がある。）であることが好ましく、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、ナフタレン型エポキシ樹脂、フェノールノボラック型エポキシ樹脂、クレゾールノボラック型エポキシ樹脂、フェノールアラルキル型エポキシ樹脂、ビフェニル型エポキシ樹脂、トリフェニルメタン型エポキシ樹脂、ジシクロペンタジエン型エポキシ樹脂、グリシジルエステル型エポキシ樹脂、グリシジルアミン型エポキシ樹脂、多官能フェノール型エポキシ樹脂等の、各種エポキシ樹脂が挙げられる。これらは１種を単独で用いてもよく、２種以上を混合して用いてもよい。 The epoxy resin other than the epoxy resin (A) is preferably an epoxy resin having two or more epoxy groups in the molecule (hereinafter, may be referred to as "epoxy resin (B)"), for example. Bisphenol A type epoxy resin, bisphenol F type epoxy resin, naphthalene type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, phenol aralkyl type epoxy resin, biphenyl type epoxy resin, triphenylmethane type epoxy resin, dicyclopentadiene Examples thereof include various epoxy resins such as type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, and polyfunctional phenol type epoxy resin. One of these may be used alone, or two or more thereof may be mixed and used.
　エポキシ樹脂（Ｂ）は、溶融粘度制御の観点から、その質量平均分子量が、好ましくは１００～５０００であり、より好ましくは２００～２０００である。質量平均分子量が１００より低いものでは、耐熱性が劣る傾向にあり、５０００より高いと、エポキシ樹脂の融点が高くなり、作業性が低下する傾向がある。 The epoxy resin (B) has a mass average molecular weight of preferably 100 to 5000, more preferably 200 to 2000, from the viewpoint of controlling the melt viscosity. If the mass average molecular weight is lower than 100, the heat resistance tends to be inferior, and if it is higher than 5000, the melting point of the epoxy resin tends to be high and the workability tends to be lowered.
　また、本発明に係るエポキシ樹脂は、その目的を損なわない範囲において、エポキシ樹脂（Ａ）とエポキシ樹脂（Ｂ）以外のエポキシ樹脂（以下、「他のエポキシ樹脂」）を含んでいてもよい。他のエポキシ樹脂の含有量は、エポキシ樹脂（Ａ）とエポキシ樹脂（Ｂ）の合計に対して、通常５０質量％以下、好ましくは３０質量％以下である。 Further, the epoxy resin according to the present invention may contain an epoxy resin (hereinafter, "other epoxy resin") other than the epoxy resin (A) and the epoxy resin (B) as long as the purpose is not impaired. The content of the other epoxy resin is usually 50% by mass or less, preferably 30% by mass or less, based on the total of the epoxy resin (A) and the epoxy resin (B).
　本発明の樹脂組成物において、エポキシ樹脂（Ａ）とエポキシ樹脂（Ｂ）を含む全エポキシ樹脂中のエポキシ樹脂（Ａ）の割合は、その合計を１００質量％として、前述の如く、好ましくは５～９５質量％、好ましくは１０～９０質量％、更に好ましくは２０～８０質量％である。なお、「エポキシ樹脂（Ａ）とエポキシ樹脂（Ｂ）を含む全エポキシ樹脂」とは、本発明の樹脂組成物に含まれるエポキシ樹脂が、エポキシ樹脂（Ａ）及びエポキシ樹脂（Ｂ）のみの場合には、エポキシ樹脂（Ａ）とエポキシ樹脂（Ｂ）の合計を意味し、さらに他のエポキシ樹脂を含む場合には、エポキシ樹脂（Ａ）、エポキシ樹脂（Ｂ）及び他のエポキシ樹脂の合計を意味する。 In the resin composition of the present invention, the ratio of the epoxy resin (A) to the total epoxy resin containing the epoxy resin (A) and the epoxy resin (B) is preferably 5 as described above, with the total being 100% by mass. It is ~ 95% by mass, preferably 10 to 90% by mass, and more preferably 20 to 80% by mass. The "total epoxy resin containing the epoxy resin (A) and the epoxy resin (B)" means that the epoxy resin contained in the resin composition of the present invention is only the epoxy resin (A) and the epoxy resin (B). Means the total of the epoxy resin (A) and the epoxy resin (B), and when another epoxy resin is contained, the total of the epoxy resin (A), the epoxy resin (B) and the other epoxy resin is used. means.
　エポキシ樹脂（Ａ）の割合が上記下限以上であることにより、エポキシ樹脂（Ａ）を配合することによる熱伝導性の向上効果を十分に得ることができ、所望の高熱伝導性を得ることができる。エポキシ樹脂（Ａ）の割合が上記上限以下で、特にエポキシ樹脂（Ｂ）が全エポキシ樹脂の１０質量％以上であることにより、エポキシ樹脂（Ｂ）の配合効果が発揮され、硬化性、硬化物の物性が十分なものとなる。 When the ratio of the epoxy resin (A) is at least the above lower limit, the effect of improving the thermal conductivity by blending the epoxy resin (A) can be sufficiently obtained, and the desired high thermal conductivity can be obtained. .. When the proportion of the epoxy resin (A) is not more than the above upper limit, and in particular, when the epoxy resin (B) is 10% by mass or more of the total epoxy resin, the compounding effect of the epoxy resin (B) is exhibited, and the curable and cured product is exhibited. The physical properties of are sufficient.
　エポキシ樹脂用硬化剤は、用いられる樹脂の種類に応じて適宜選べばよい。例えば、酸無水物系硬化剤やアミン系硬化剤が挙げられる。酸無水物系硬化剤としては、例えば、テトラヒドロフタル酸無水物、メチルテトラヒドロフタル酸無水物、ヘキサヒドロフタル酸無水物、及びベンゾフェノンテトラカルボン酸無水物が挙げられる。アミン系硬化剤としては、例えば、エチレンジアミン、ジエチレントリアミン、トリエチレンテトラミン等の脂肪族ポリアミン、ジアミノジフェニルスルホン、ジアミノジフェニルメタン、ジアミノジフェニルエーテル、ｍ－フェニレンジアミン等の芳香族ポリアミン及びジシアンジアミドが挙げられる。これらは１種を単独で用いてもよく、２種以上を混合して用いてもよい。これらのエポキシ樹脂用硬化剤は、通常、エポキシ樹脂に対して当量比で、０．３～１．５の範囲で配合される。 The curing agent for epoxy resin may be appropriately selected according to the type of resin used. For example, an acid anhydride-based curing agent and an amine-based curing agent can be mentioned. Examples of the acid anhydride-based curing agent include tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, and benzophenone tetracarboxylic acid anhydride. Examples of the amine-based curing agent include aliphatic polyamines such as ethylenediamine, diethylenetriamine and triethylenetetramine, aromatic polyamines such as diaminodiphenylsulfone, diaminodiphenylmethane, diaminodiphenyl ether and m-phenylenediamine, and dicyandiamide. One of these may be used alone, or two or more thereof may be mixed and used. These curing agents for epoxy resins are usually blended in the range of 0.3 to 1.5 in an equivalent ratio with respect to the epoxy resin.
　硬化促進剤は、用いられる樹脂や硬化剤の種類に応じて適宜選べばよい。例えば前記酸無水系硬化剤用の硬化促進剤としては、例えば三フッ化ホウ素モノエチルアミン、２－エチル－４－メチルイミダゾール、１－イソブチル－２－メチルイミダゾール、２－フェニル－４－メチルイミダゾールが挙げられる。これらは１種を単独で用いてもよく、２種以上を混合して用いてもよい。これらの硬化促進剤は、通常、エポキシ樹脂１００質量部に対して０．１～５質量部の範囲で用いられる。 The curing accelerator may be appropriately selected according to the type of resin and curing agent used. For example, examples of the curing accelerator for the acid anhydrous curing agent include boron trifluoride monoethylamine, 2-ethyl-4-methylimidazole, 1-isobutyl-2-methylimidazole, and 2-phenyl-4-methylimidazole. Can be mentioned. One of these may be used alone, or two or more thereof may be mixed and used. These curing accelerators are usually used in the range of 0.1 to 5 parts by mass with respect to 100 parts by mass of the epoxy resin.
　また、本発明の樹脂組成物に用いる樹脂材料は、熱可塑性樹脂であってもよい。熱可塑性樹脂としては、例えば、ポリエチレン樹脂、ポリプロピレン樹脂、エチレン－酢酸ビニル共重合体樹脂等のポリオレフィン樹脂、ポリエチレンテレフタレート樹脂、ポリブチレンテレフタレート樹脂、液晶ポリエステル樹脂等のポリエステル樹脂、ポリ塩化ビニル樹脂、フェノキシ樹脂、アクリル樹脂、ポリカーボネート樹脂、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、ポリイミド樹脂、ポリエーテルアミドイミド樹脂、ポリエーテルアミド樹脂及びポリエーテルイミド樹脂などが挙げられる。また、それらのブロック共重合体、グラフト共重合体等の共重合体も含まれる。これらは、１種を単独で用いてもよく、２種以上を混合して用いてもよい。 Further, the resin material used in the resin composition of the present invention may be a thermoplastic resin. Examples of the thermoplastic resin include polyolefin resins such as polyethylene resin, polypropylene resin and ethylene-vinyl acetate copolymer resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyester resin such as liquid crystal polyester resin, polyvinyl chloride resin and phenoxy. Examples thereof include resins, acrylic resins, polycarbonate resins, polyphenylene sulfide resins, polyphenylene ether resins, polyamide resins, polyamideimide resins, polyimide resins, polyetheramideimide resins, polyetheramide resins and polyetherimide resins. In addition, copolymers such as those block copolymers and graft copolymers are also included. These may be used alone or in admixture of two or more.
　また、樹脂材料は、ゴム成分であってもよく、ゴム成分としては、例えば、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ゴム、エチレン－プロピレン－ジエン共重合体ゴム、ブタジエン－アクリロニトリル共重合体ゴム、イソブチレン－イソプレン共重合体ゴム、クロロプレンゴム、シリコーンゴム、フッ素ゴム、クロロ・スルホン化ポリエチレン、ポリウレタンゴムなどが挙げられる。これらは１種を単独で用いてもよく、２種以上を混合して用いてもよい。 The resin material may be a rubber component, and examples of the rubber component include natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, ethylene-propylene copolymer rubber, and ethylene-propylene. -Diene copolymer rubber, butadiene-acrylonitrile copolymer rubber, isobutylene-isoprene copolymer rubber, chloroprene rubber, silicone rubber, fluororubber, chloro-sulfonated polyethylene, polyurethane rubber and the like can be mentioned. One of these may be used alone, or two or more thereof may be mixed and used.
＜粒状窒化ホウ素の配合量＞
　本発明の樹脂組成物に含まれる、本発明の粒状窒化ホウ素（または粒状窒化ホウ素組成物）の量は、上述のように、樹脂組成物の質量基準で通常１０～９０％であることが好ましく、より好ましくは１５～８８％、更に好ましくは３０～８５％である。樹脂組成物中の粒状窒化ホウ素の量がこのような範囲より少ない場合、樹脂組成物としての粘度（溶融した場合の粘度）は低く、成形加工性は良好であるものの、熱伝導性を改善する効果が不十分となり得る。樹脂組成物中の粒状窒化ホウ素の量が、このような範囲より大きい場合、溶融時の樹脂組成物の粘度が高くなり、成形が困難になる傾向がある。 <Amount of granular boron nitride blended>
As described above, the amount of the granular boron nitride (or the granular boron nitride composition) of the present invention contained in the resin composition of the present invention is usually preferably 10 to 90% based on the mass of the resin composition. , More preferably 15 to 88%, still more preferably 30 to 85%. When the amount of granular boron nitride in the resin composition is less than this range, the viscosity of the resin composition (viscosity when melted) is low, the molding processability is good, but the thermal conductivity is improved. The effect can be inadequate. When the amount of granular boron nitride in the resin composition is larger than such a range, the viscosity of the resin composition at the time of melting becomes high, and molding tends to be difficult.
＜その他の成分＞
　本発明の樹脂組成物は、本発明の効果が得られる限り、他の成分を含有してもよい。このような成分としては、例えば、液晶性エポキシ樹脂等の上述の樹脂に機能性を付与した機能性樹脂、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、酸化チタン等の絶縁性金属酸化物、ダイヤモンド、フラーレン等の絶縁性炭素成分、樹脂硬化剤、樹脂硬化促進剤、粘度調整剤、分散安定剤が挙げられる。 <Other ingredients>
The resin composition of the present invention may contain other components as long as the effects of the present invention can be obtained. Examples of such components include functional resins obtained by imparting functionality to the above-mentioned resins such as liquid crystal epoxy resins, nitride particles such as aluminum nitride, silicon nitride, and fibrous boron nitride, alumina, and fibrous alumina. Examples thereof include insulating metal oxides such as zinc oxide, magnesium oxide, berylium oxide and titanium oxide, insulating carbon components such as diamond and fullerene, resin curing agents, resin curing accelerators, viscosity modifiers and dispersion stabilizers.
　また、樹脂組成物の粘度を下げる観点から、本発明の樹脂組成物は溶剤を含んでよい。この溶剤として、樹脂を溶解する公知の溶剤が用いられる。このような溶剤としては、例えば、メチルエチルケトン、アセトン、シクロヘキサノン、トルエン、キシレン、モノクロルベンゼン、ジクロルベンゼン、トリクロルベンゼン、フェノール、及びヘキサフルオロイソプロパノールが挙げられる。これらは、１種を単独で用いてもよく、２種以上を混合して用いてもよい。溶剤は、エポキシ樹脂等の樹脂１００質量部に対して、例えば０～１０，０００質量部の範囲で用いられる。 Further, from the viewpoint of lowering the viscosity of the resin composition, the resin composition of the present invention may contain a solvent. As this solvent, a known solvent that dissolves the resin is used. Examples of such a solvent include methyl ethyl ketone, acetone, cyclohexanone, toluene, xylene, monochlorobenzene, dichlorobenzene, trichlorobenzene, phenol, and hexafluoroisopropanol. These may be used alone or in admixture of two or more. The solvent is used in the range of, for example, 0 to 10,000 parts by mass with respect to 100 parts by mass of a resin such as an epoxy resin.
　また、本発明の樹脂組成物には、その効果を損なわない限り、水酸化アルミニウム、水酸化マグネシウムなどの無機フィラー、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などの表面処理剤、還元剤などを添加してもよい。 Further, the resin composition of the present invention is subjected to surface treatment such as an inorganic filler such as aluminum hydroxide and magnesium hydroxide, and a silane coupling agent for improving the interfacial adhesive strength between the inorganic filler and the matrix resin, as long as the effect is not impaired. Agents, reducing agents and the like may be added.
　尚、上述の無機フィラーについては、樹脂組成物中の成形加工性を維持する目的で、樹脂組成物中の本発明の粒状窒化ホウ素と無機フィラーとの合計量で９０質量％以下であることが好ましい。 Regarding the above-mentioned inorganic filler, for the purpose of maintaining the molding processability in the resin composition, the total amount of the granular boron nitride and the inorganic filler of the present invention in the resin composition is 90% by mass or less. preferable.
＜樹脂組成物の製造・成形＞
　本発明の樹脂組成物は、本発明の粒状窒化ホウ素（または粒状窒化ホウ素組成物）、樹脂材料、及び必要に応じて添加されるその他の成分を撹拌や混練によって均一に混合することによって得ることができる。その混合には、例えば、ミキサー、ニーダー、単軸又は二軸混練機等の一般的な混練装置を用いることができ、混合に際しては、必要に応じて加熱してもよい。 <Manufacturing and molding of resin composition>
The resin composition of the present invention can be obtained by uniformly mixing the granular boron nitride (or granular boron nitride composition) of the present invention, the resin material, and other components added as necessary by stirring or kneading. Can be done. For the mixing, for example, a general kneading device such as a mixer, a kneader, a single shaft or a twin shaft kneader can be used, and in the mixing, heating may be performed if necessary.
＜成形体＞
　本発明の成形体は、本発明の樹脂組成物を成形して得られる。成形体の成形方法は、樹脂組成物の性質に応じて、その成形に一般に用いられる方法、例えば、射出成形、型成形、を用いることができる。いずれの成形方法であっても、樹脂組成物を必要に応じて加熱して流動化または可塑化させ、型等を用いて樹脂組成物を成形体に成形することになるので、流動化した樹脂組成物に何等かの力が作用する。例えば、樹脂組成物を型に充填する際に圧力が作用する。このことは、樹脂材料が硬化性樹脂（例えばフェノール樹脂、エポキシ樹脂、メラミン樹脂、尿素樹脂等）であっても、熱可塑性樹脂（例えばポリエチレン、ポリプロピレン、ポリ塩化ビニル、ポリスチレン、アクリル樹脂等）であっても、当て嵌まると考えられる。 <Molded body>
The molded product of the present invention is obtained by molding the resin composition of the present invention. As a molding method of the molded body, a method generally used for molding thereof, for example, injection molding or mold molding, can be used depending on the properties of the resin composition. Regardless of the molding method, the resin composition is heated to be fluidized or plasticized as necessary, and the resin composition is molded into a molded product using a mold or the like. Therefore, the fluidized resin Some force acts on the composition. For example, pressure acts when the resin composition is filled into a mold. This means that even if the resin material is a curable resin (for example, phenol resin, epoxy resin, melamine resin, urea resin, etc.), a thermoplastic resin (for example, polyethylene, polypropylene, polyvinyl chloride, polystyrene, acrylic resin, etc.) can be used. Even if there is, it is considered to be applicable.
　例えば、本発明の樹脂組成物が可塑性および流動性を有する場合、樹脂組成物を所望の形状で、例えば型へ充填した状態で硬化させることによって成形することができる。このような成形体の製造法としては、射出成形法、射出圧縮成形法、押出成形法、及び圧縮成形法を用いることができる。また、本発明の樹脂組成物がエポキシ樹脂、シリコーン樹脂等の熱硬化性樹脂組成物である場合、成形体の成形、即ち、硬化は、それぞれの組成に応じた硬化条件で行うことができる。更に、本発明の樹脂組成物が熱可塑性樹脂組成物である場合、成形体の成形は、熱可塑性樹脂の溶融温度以上の温度及び所定の成形速度や圧力の条件で行うことができる。尚、本発明の成形体は、本発明の樹脂組成物を成形または硬化した固形状のバルク材料から所望の形状に削り出すことによっても得ることができる。 For example, when the resin composition of the present invention has plasticity and fluidity, it can be molded by curing the resin composition in a desired shape, for example, in a state of being filled in a mold. As a method for producing such a molded product, an injection molding method, an injection compression molding method, an extrusion molding method, and a compression molding method can be used. When the resin composition of the present invention is a thermosetting resin composition such as an epoxy resin or a silicone resin, the molded product can be molded, that is, cured under curing conditions according to the respective compositions. Further, when the resin composition of the present invention is a thermoplastic resin composition, the molded product can be molded under the conditions of a temperature equal to or higher than the melting temperature of the thermoplastic resin and a predetermined molding speed and pressure. The molded product of the present invention can also be obtained by cutting the resin composition of the present invention into a desired shape from a molded or cured solid bulk material.
　上述のようにして得られる本発明の成形体では、樹脂材料および粒状窒化ホウ素（または粒状窒化ホウ素組成物）の配合量に依存するが、質量基準で樹脂材料の量が６５～８５％の樹脂組成物の１つの態様では、成形に際して力を加える方向に対して平行な方向の熱伝導率が通常１０～２５Ｗ／（ｍ・Ｋ）、好ましくは１５～２３Ｗ／（ｍ・Ｋ）、より好ましくは１８～２２Ｗ／（ｍ・Ｋ）である。また、成形に際して圧力を加える方向に対して垂直な方向の熱伝導率が通常１５～３５Ｗ／（ｍ・Ｋ）、好ましくは２０～３０Ｗ／（ｍ・Ｋ）、より好ましくは２２～２７Ｗ／（ｍ・Ｋ）である。 In the molded article of the present invention obtained as described above, the amount of the resin material is 65 to 85% on a mass basis, although it depends on the blending amount of the resin material and the granular boron nitride (or the granular boron nitride composition). In one aspect of the composition, the thermal conductivity in the direction parallel to the direction in which the force is applied during molding is usually 10 to 25 W / (m · K), preferably 15 to 23 W / (m · K), more preferably. Is 18 to 22 W / (m · K). Further, the thermal conductivity in the direction perpendicular to the direction in which pressure is applied during molding is usually 15 to 35 W / (m · K), preferably 20 to 30 W / (m · K), and more preferably 22 to 27 W / (. m ・ K).
　従って、本発明の粒状窒化ホウ素を使用して樹脂組成物を調製し、これを用いて成形して成形体を製造すると、一般的には、平行方向の熱伝導率は、垂直方向の熱伝導率の好ましくは７０～１２０％、より好ましくは８０～１１０％、特に９０～１０５％であり、熱伝導に関する成形体の異方性は大幅に抑制でき、場合によっては、異方性を実質的に解消できる。また、この傾向は、粒状窒化ホウ素に代えて、本発明の粒状窒素組成物と樹脂材料を混合して成形体を得る場合であっても、同様に平行方向の熱伝導率は垂直方向の熱伝導率より小さい。即ち、粒状窒化ホウ素が酸化物、特に希土類元素酸化物、Ｃａ－希土類元素－Ｂ－Ｏ系複合酸化物等を含む場合にも異方性を抑制できる。特に好ましい１つの態様では、樹脂組成物は、６５～８５質量％の粒状窒化ホウ素を含み、その場合、平行方向の熱伝導率の垂直方向の熱伝導率に対する割合は、少なくとも約９０～１０５％である。 Therefore, when a resin composition is prepared using the granular boron nitride of the present invention and molded using the resin composition to produce a molded product, in general, the thermal conductivity in the parallel direction is the thermal conductivity in the vertical direction. The ratio is preferably 70 to 120%, more preferably 80 to 110%, particularly 90 to 105%, and the anisotropy of the molded product with respect to thermal conductivity can be significantly suppressed, and in some cases, the anisotropy is substantially suppressed. Can be resolved. Further, this tendency is that even when the granular nitrogen composition of the present invention and the resin material are mixed to obtain a molded product instead of the granular boron nitride, the thermal conductivity in the parallel direction is similarly the heat in the vertical direction. Less than conductivity. That is, the anisotropy can be suppressed even when the granular boron nitride contains an oxide, particularly a rare earth element oxide, a Ca-rare earth element-BO composite oxide, or the like. In one particularly preferred embodiment, the resin composition comprises 65-85% by weight of granular boron nitride, in which case the ratio of the parallel thermal conductivity to the vertical thermal conductivity is at least about 90-105%. Is.
　以下に、実施例を説明して本発明をより具体的に説明するが、本発明はそのような実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail by explaining examples, but the present invention is not limited to such examples.
[使用原料]
　以下の実施例及び比較例で用いた原料の仕様は、以下の通りである。
＜窒化ホウ素成分（１）＞
　窒化ホウ素粉末：三井化学株式会社製、商品名：MBN-250
　　（全酸素濃度４質量％、平均粒子径：１．８μｍ）
＜希土類成分（２）＞
　微粉末酸化イットリウム：日本イットリウム株式会社製
　　Ｙ２Ｏ３　99.9％、平均粒子径０．９１μｍ
　微粉末酸化セリウム：日本イットリウム株式会社製
　　ＣｅＯ２　99.9％、平均粒子径０．５８μｍ
＜カルシウム成分（３）＞
　粉末酸化カルシウム：足立石灰工業株式会社製
　　ＣａＯ　９８．５％、平均粒子径１５０μm
＜エポキシ樹脂材料＞
　エポキシ樹脂：三菱化学株式会社製、商品名：JER828、
　同エポキシ樹脂硬化剤：三菱化学株式会社製、商品名：YH306
　同エポキシ硬化促進剤：三菱化学株式会社製、商品名：EMI24
　混合比（質量基準）JER828：YH306：EMI24＝１００：８０：２ [Raw materials used]
The specifications of the raw materials used in the following examples and comparative examples are as follows.
<Boron Nitride Component (1)>
Boron Nitride Powder: Mitsui Chemicals, Inc., Product Name: MBN-250
(Total oxygen concentration 4% by mass, average particle size: 1.8 μm)
<Rare earth component (2)>
Fine powder yttrium oxide: manufactured by Japan Yttrium Co., Ltd. Y 2 O 3 99.9%, average particle size 0.91 μm
Fine powder cerium oxide: Made by Nippon Ittorium Co., Ltd. CeO 2 99.9%, average particle size 0.58 μm
<Calcium component (3)>
Powdered calcium oxide: Made by Adachi Lime Industry Co., Ltd. CaO 98.5%, average particle size 150 μm
<Epoxy resin material>
Epoxy resin: manufactured by Mitsubishi Chemical Corporation, product name: JER828,
Epoxy resin curing agent: manufactured by Mitsubishi Chemical Corporation, product name: YH306
Epoxy curing accelerator: manufactured by Mitsubishi Chemical Corporation, product name: EMI24
Mixing ratio (mass basis) JER828: YH306: EMI24 = 100: 80: 2
［粒状窒化ホウ素組成物および粒状窒化ホウ素の製造］
＜実施例１＞
　３００ｍｌビーカーに、窒化ホウ素成分（１）として窒化ホウ素粉末２０ｇ、希土類成分（２）としてＹ２Ｏ３粉末１.７０ｇ（熱処理前混合粉末総量中の３．６体積％）、カルシウム成分（３）としてＣａＯ粉末０．４２ｇ（熱処理前混合粉末総量中の１．４体積％）を加えて、更にエタノール１５０ｍｌを加え、均一に混合するために超音波ホモジナイザー（ＩＫＡ社製　Ｕ２００　Ｃｏｎｔｏｒｏｌｓ）を用い、５分間超音波処理を行い、混合物のスラリーを得た。 [Production of Granular Boron Nitride Composition and Granular Boron Nitride]
<Example 1>
In 300ml beaker, the boron nitride powder 20g as boron nitride component (1), (3.6% by volume of the heat treatment prior to mixing the powder in a total volume) Y 2 O 3 powder 1.70g rare earth component (2), calcium component (3) As a result, 0.42 g of CaO powder (1.4% by volume in the total amount of the mixed powder before heat treatment) was added, 150 ml of ethanol was further added, and an ultrasonic homogenizer (U200 Controls manufactured by IKA) was used for uniform mixing. Ultrasonic treatment was carried out for 1 minute to obtain a slurry of the mixture.
　得られたスラリーのエタノールをエバポレーターで除去し、乾燥した粉末を混合物として得た。この粉末を窒化ホウ素製坩堝に入れ、多目的高温炉（富士電波工業株式会社、ハイマルチ５０００）を用いて加熱処理を行い、粒状窒化ホウ素組成物を得た。この組成物は、窒化ホウ素に加えて、ＣａＹＢＯ４等のＣａ－Ｙ－Ｂ－Ｏ系複合酸化物等を含んでいた。この複合酸化物中のＢ－Ｏは、原料として用いた窒化ホウ素粉末が４重量％の酸素を含むことに由来したものであると考えられる。 Ethanol of the obtained slurry was removed by an evaporator, and a dried powder was obtained as a mixture. This powder was placed in a boron nitride crucible and heat-treated using a multipurpose high-temperature furnace (Fuji Dempa Kogyo Co., Ltd., Hi-Multi 5000) to obtain a granular boron nitride composition. The composition, in addition to boron nitride, contained CaYBO 4 Ca-Y-B- O -based composite oxide such like. It is considered that BO in this composite oxide is derived from the fact that the boron nitride powder used as a raw material contains 4% by weight of oxygen.
　加熱処理処理は、室温から１１００℃まで２０℃／分で昇温し、続いて１１００～１９００℃まで１０℃／分で昇温し、１９００℃で１０時間保持し、その後、２０℃／分で室温まで降温することにより実施した。加熱処理の雰囲気は、４００℃まで１×１０－１Ｐａ未満の真空で保持し、続いて窒素ガスを大気圧まで炉内に導入し、加熱処理終了まで１ｍｌ／分の窒素ガスフローの状態を保持した。 The heat treatment process involves raising the temperature from room temperature to 1100 ° C. at 20 ° C./min, then raising the temperature from 1100 to 1900 ° C. at 10 ° C./min, holding at 1900 ° C. for 10 hours, and then at 20 ° C./min. It was carried out by lowering the temperature to room temperature. The atmosphere of the heat treatment is maintained in a vacuum of less than 1 × 10 -1 Pa up to 400 ° C., and then nitrogen gas is introduced into the furnace to atmospheric pressure, and the state of nitrogen gas flow of 1 ml / min is maintained until the end of the heat treatment. Retained.
　上述のように混合物を加熱処理して本発明の粒状窒化ホウ素組成物を得た。その後、得られた組成物を洗浄して含まれている酸化物（酸化イットリウム、酸化カルシウム）を除去した。詳しくは、テフロン内張密閉圧力容器中に組成物２.５ｇを３規定の塩酸水溶液２０ｍｌに添加し、1００℃で１１時間反応させて含まれている酸化物を水溶性の塩に変換した。その後、純水にて洗浄・濾過して塩を除去して、本発明の粒状窒化ホウ素を得た。得られた粒状窒化ホウ素をＸＲＤ分析したところ、それに残存し得る酸化イットリウムおよび酸化カルシウムは検出できなかった。 The mixture was heat-treated as described above to obtain the granular boron nitride composition of the present invention. Then, the obtained composition was washed to remove the oxides (yttrium oxide, calcium oxide) contained therein. Specifically, 2.5 g of the composition was added to 20 ml of a 3N hydrochloric acid aqueous solution in a Teflon-lined closed pressure vessel, and the mixture was reacted at 100 ° C. for 11 hours to convert the contained oxide into a water-soluble salt. Then, it was washed with pure water and filtered to remove salt, and the granular boron nitride of this invention was obtained. When the obtained granular boron nitride was subjected to XRD analysis, yttrium oxide and calcium oxide that could remain in it could not be detected.
＜実施例２～６＞
　実施例１におけるＹ２Ｏ３の添加量を３．５９ｇ（実施例２：熱処理前混合粉末総量中の７.３体積％）、５．７０ｇ（実施例３：熱処理前混合粉末総量中の１０．９体積％）、８.０７ｇ（実施例４：熱処理前混合粉末総量中の１４.６体積％）、１０．７６ｇ（実施例５：熱処理前混合粉末総量中の１８.２体積％）、１３．８４ｇ（実施例６：熱処理前混合粉末総量中の２１.９体積％）とし、実施例１におけるＣａＯの添加量を、０.８９ｇ（実施例２：熱処理前混合粉末総量中の２.７体積％）、１．４１ｇ（実施例３：熱処理前混合粉末総量中の４．１体積％）、２.００ｇ（実施例４：熱処理前混合粉末総量中の５.４体積％）、２.６７ｇ（実施例５：熱処理前混合粉末総量中の６.８体積％）、３.４４ｇ（実施例６：熱処理前混合粉末総量中の８.１体積％）とした以外は実施例１を繰り返して本発明の粒状窒化ホウ素を得た。得られた粒状窒化ホウ素をＸＲＤ分析したところ、それに残存し得る酸化イットリウムおよび酸化カルシウムは検出できなかった。 <Examples 2 to 6>
The amount of Y 2 O 3 added in Example 1 was 3.59 g (Example 2: 7.3% by volume in the total amount of the mixed powder before heat treatment), 5.70 g (Example 3: 10 in the total amount of the mixed powder before heat treatment). .9% by volume), 8.07g (Example 4: 14.6% by volume in the total amount of mixed powder before heat treatment), 10.76g (Example 5: 18.2% by volume in the total amount of mixed powder before heat treatment), 13.84 g (Example 6: 21.9% by volume in the total amount of the mixed powder before heat treatment), and the amount of CaO added in Example 1 was 0.89 g (Example 2: 2. in the total amount of the mixed powder before heat treatment). 7% by volume), 1.41g (Example 3: 4.1% by volume in the total amount of mixed powder before heat treatment), 2.00 g (Example 4: 5.4% by volume in the total amount of mixed powder before heat treatment), 2 Example 1 was used except for .67 g (Example 5: 6.8% by volume in the total amount of mixed powder before heat treatment) and 3.44 g (Example 6: 8.1% by volume in the total amount of mixed powder before heat treatment). The granular boron nitride of the present invention was repeatedly obtained. When the obtained granular boron nitride was subjected to XRD analysis, yttrium oxide and calcium oxide that could remain in it could not be detected.
　尚、実施例１～６において、加熱処理前の混合物粉末に含まれるＹ２Ｏ３とＣａＯを合計した酸化物の体積の混合物の体積に対する割合は、実施例１では５体積％、実施例２では１０体積％、実施例３では１５体積％、実施例４では２０体積％、実施例５では２５体積％、実施例６では３０体積％であった。 In Examples 1 to 6, the ratio of the total volume of oxides of Y 2 O 3 and Ca O contained in the mixture powder before heat treatment to the volume of the mixture was 5% by volume in Example 1 and Example 2. Was 10% by volume, Example 3 was 15% by volume, Example 4 was 20% by volume, Example 5 was 25% by volume, and Example 6 was 30% by volume.
＜実施例７～２４＞
　以下に示す表１に記載の条件とした以外は実施例１を繰り返して本発明の粒状窒化ホウ素を得た。実施例７～１２では、混合物を構成する酸化イットリウムと酸化カルシウムのモル比は１：２であり、実施例１３～１８混合物を構成する酸化イットリウムと酸化カルシウムのモル比は１：４であり、実施例１９～２４混合物を構成する酸化イットリウムと酸化カルシウムのモル比は１：６であった。 <Examples 7 to 24>
Example 1 was repeated except for the conditions shown in Table 1 below to obtain the granular boron nitride of the present invention. In Examples 7 to 12, the molar ratio of yttrium oxide to calcium oxide constituting the mixture is 1: 2, and the molar ratio of yttrium oxide to calcium oxide constituting the mixture of Examples 13 to 18 is 1: 4. The molar ratio of yttrium oxide to calcium oxide constituting the mixture of Examples 19 to 24 was 1: 6.
＜実施例２５＞
　酸化イットリウムに代えてＣｅＯ２粉末１．９７ｇを加え、ＣａＯ粉末０．６４ｇとした以外は、実施例１を繰り返して加熱処理して本発明の粒状窒化ホウ素組成物を得、更に洗浄して酸化物を除去した本発明の粒状窒化ホウ素を得た。得られた粒状窒化ホウ素をＸＲＤ分析したところ、それに残存し得る酸化セリウムおよび酸化カルシウムは検出できなかった。 <Example 25>
Example 1 was repeatedly heat-treated to obtain the granular boron nitride composition of the present invention, except that 1.97 g of CeO 2 powder was added in place of yttrium oxide to obtain 0.64 g of CaO powder, which was further washed and oxidized. The granular boron nitride of the present invention from which the substance was removed was obtained. When the obtained granular boron nitride was subjected to XRD analysis, cerium oxide and calcium oxide that could remain in it could not be detected.
＜実施例２６～３０＞
　実施例２５において、ＣｅＯ２の添加量を４.１５ｇ（実施例２６：熱処理前混合粉末総量中の５.９体積％）、６．５９ｇ（実施例２７：熱処理前混合粉末総量中の８．８体積％）、９.３４ｇ（実施例２８：熱処理前混合粉末総量中の１１.８体積％）、１２.４５ｇ（実施例２９：熱処理前混合粉末総量中の１４.７体積％）、１６.０１ｇ（実施例３０：熱処理前混合粉末総量中の１７.６体積％）とし、実施例２５におけるＣａＯの添加量を１.３５ｇ（実施例２６：熱処理前混合粉末総量中の４.１体積％）、２．１５ｇ（実施例２７：熱処理前混合粉末総量中の６．２体積％）、３.０４ｇ（実施例２８：熱処理前混合粉末総量中の８.２体積％）、４.０６ｇ（実施例２９：熱処理前混合粉末総量中の１０.３体積％）、５.２２ｇ（実施例３０：熱処理前混合粉末総量中の１２.４体積％）とした以外は、実施例２５を繰り返して本発明の粒状窒化ホウ素を得た。 <Examples 26 to 30>
In Example 25, the amount of CeO 2 added was 4.15 g (Example 26: 5.9% by volume in the total amount of the mixed powder before heat treatment) and 6.59 g (Example 27: 8. in the total amount of the mixed powder before heat treatment). 8% by volume), 9.34 g (Example 28: 11.8% by volume in the total amount of mixed powder before heat treatment), 12.45 g (Example 29: 14.7% by volume in the total amount of mixed powder before heat treatment), 16. It was set to .01 g (Example 30: 17.6% by volume in the total amount of the mixed powder before heat treatment), and the amount of CaO added in Example 25 was 1.35 g (Example 26: 4.1 volume in the total amount of the mixed powder before heat treatment). %), 2.15 g (Example 27: 6.2% by volume in the total amount of the mixed powder before heat treatment) 3.04 g (Example 28: 8.2% by volume in the total amount of the mixed powder before heat treatment) 4.06 g Example 25 was repeated except that (Example 29: 10.3% by volume in the total amount of the mixed powder before heat treatment) and 5.22 g (Example 30: 12.4% by volume in the total amount of the mixed powder before heat treatment). The granular boron nitride of the present invention was obtained.
　尚、上記実施例２５～３０において、熱処理前の混合粉末に含まれるＣｅＯ２とＣａＯを合計した酸化物の体積の混合物の体積に対する割合は、実施例２５では５体積％、実施例２６では１０体積％、実施例２７では１５体積％、実施例２８では２０体積％、実施例２９では２５体積％、実施例３０では３０体積％であった。 In Examples 25 to 30, the ratio of the total volume of oxides of CeO 2 and CaO contained in the mixed powder before heat treatment to the volume of the mixture was 5% by volume in Example 25 and 10 in Example 26. The volume was 15% by volume in Example 27, 20% by volume in Example 28, 25% by volume in Example 29, and 30% by volume in Example 30.
＜実施例３１～３８＞
　実施例３で得られた加熱処理後の酸化物を含む粒状窒化ホウ素組成物３ｇを３規定の塩酸水溶液６５ｍｌに添加し、スターラーを用いて２５℃で１１時間攪拌を行った後、濾過・乾燥を行い、酸化カルシウム成分を部分的に除去した粒状窒化ホウ素組成物の粉末を得た。更に、得られた粉末を０．６規定の塩酸水溶液１０ｍｌに添加し、テフロン内張密閉容器中1００℃にて１１時間反応させて含まれている酸化物の大部分を水溶性の塩に変換した。その後、上述と同様に純水にて洗浄・濾過して塩を除去して本発明の粒状窒化ホウ素を得た。この酸による処理は、実施例３と比較して、１００℃で用いる塩酸濃度を小さくしたため、Ｙ２Ｏ３は部分的に残存したが、他の成分は実質的に除去できた。濾別後に得られた粒状窒化ホウ素１ｇを１規定の塩酸水溶液２０ｍｌに添加し、テフロン内張密閉容器中１００℃にて１１時間反応した後、濾液部分をＩＣＰにより定量分析したところ、酸化イットリウムを１．０１質量％含んでいたが、酸化カルシウムの量は検出限界以下であった。同様に、実施例４、実施例６、実施例９、実施例１１、実施例１２、実施例１８および実施例２４で得られた加熱処理後の酸化物を含む粒状窒化ホウ素組成物を同様に処理して、それぞれ実施例３２～３８の本発明の粒状窒化ホウ素を得た。 <Examples 31 to 38>
3 g of the granular boron nitride composition containing the oxide after the heat treatment obtained in Example 3 was added to 65 ml of a 3N hydrochloric acid aqueous solution, stirred at 25 ° C. for 11 hours using a stirrer, and then filtered and dried. Was carried out to obtain a powder of a granular boron nitride composition from which the calcium oxide component was partially removed. Further, the obtained powder was added to 10 ml of a 0.6N hydrochloric acid aqueous solution and reacted at 100 ° C. for 11 hours in a Teflon-lined closed container to convert most of the contained oxides into water-soluble salts. did. Then, in the same manner as described above, the mixture was washed with pure water and filtered to remove salts to obtain the granular boron nitride of the present invention. Treatment with the acid, as compared with Example 3, because of the small concentration of hydrochloric acid used in the 100 ° C., Y 2 O 3 is partially left, other components could substantially removed. After 1 g of granular boron nitride obtained after filtration was added to 20 ml of a 1N hydrochloric acid aqueous solution and reacted at 100 ° C. for 11 hours in a Teflon-lined closed container, the filtrate portion was quantitatively analyzed by ICP to obtain yttrium oxide. Although it contained 1.01% by mass, the amount of calcium oxide was below the detection limit. Similarly, the granular boron nitride composition containing the heat-treated oxides obtained in Example 4, Example 6, Example 9, Example 11, Example 12, Example 18 and Example 24 was similarly prepared. The treatment gave the granular boron nitride of the present invention of Examples 32 to 38, respectively.
＜比較例１＞
　３００ｍｌビーカーに、窒化ホウ素粉末２０ｇ、Ｙ２Ｏ３粉末２．３２ｇ（熱処理前混合粉末総量中の５体積％）を加え、更にエタノールを１５０ｍｌ加え、均一に混合するために超音波ホモジナイザー（ＩＫＡ社製　Ｕ２００　Ｃｏｎｔｏｒｏｌｓ）を用い、５分間超音波処理を行い、混合物のスラリーを得た。得られたスラリーのエタノール溶媒をエバポレーターで除去し、乾燥した粉末を混合物として得た。この粉末を実施例１と同様に、混合物の加熱処理およびその後の洗浄を実施して、窒化ホウ素を得た。 <Comparative example 1>
In 300ml beaker, the boron nitride powder 20g, Y 2 O 3 (5% by volume of the heat treatment prior to mixing the powder in a total volume) powder 2.32g was added, further ethanol was added 150 ml, uniformly for mixing ultrasonic homogenizer (IKA Co. A slurry of the mixture was obtained by ultrasonic treatment for 5 minutes using U200 Controls manufactured by U200. The ethanol solvent of the obtained slurry was removed by an evaporator, and a dried powder was obtained as a mixture. The powder was subjected to heat treatment of the mixture and subsequent washing in the same manner as in Example 1 to obtain boron nitride.
＜比較例２～６＞
　加えるＹ２Ｏ３粉末量を変えて比較例１を繰り返した。 <Comparative Examples 2 to 6>
Comparative Example 1 was repeated by changing the amount of Y 2 O 3 powder to be added.
＜比較例７＞
　特開２０１７－１４０６４号の記載に基づき、Ｈ３ＢＯ３粉末（和光純薬工業株式会社製、試薬特級）４４.４１ｇ、ＣａＯ１２.４８ｇ、蒸留水２００ｍｌを蓋付きガラス瓶（容量２５０ｍｌ）に加え（ＣａＯ／Ｂ２Ｏ３モル比＝０．６２）、蓋をして９５℃のオイルバスで２時間攪拌しながら、Ｃａ２Ｂ２Ｏ５・Ｈ２ＯとＣａ３Ｂ２０Ｏ３３・１２Ｈ２Ｏの複合酸化物の混合物４８.０ｇを合成した。この合成物に、原料のＨ３ＢＯ３のＢに対して元素比Ｂ／Ｃ＝０．７９となるようにカーボン粉末（三菱化学株式会社製：２３００Ｂ）を９.２ｇ添加し、ボールミル混合して粉末を混合物として得た。その後、実施例１と同様に混合物の加熱処理および洗浄を実施して、多面構造の窒化ホウ素を得た。 <Comparative Example 7>
Based on the description of JP-A-2017-14064, 44.41 g of H 3 BO 3 powder (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent), 12.48 g of CaO, and 200 ml of distilled water are added to a glass bottle with a lid (capacity 250 ml) (capacity: 250 ml). CaO / B 2 O 3 molar ratio = 0.62), with stirring for 2 hours in an oil bath at to 95 ° C. the lid, Ca 2 B 2 O 5 · H 2 O and Ca 3 B 20 O 33 · 12H 2 48.0 g of a mixture of composite oxides of O was synthesized. To this composite, 9.2 g of carbon powder (manufactured by Mitsubishi Chemical Corporation: 2300B) was added so that the element ratio was B / C = 0.79 with respect to B of the raw material H 3 BO 3 , and the mixture was mixed with a ball mill. The powder was obtained as a mixture. Then, the mixture was heat-treated and washed in the same manner as in Example 1 to obtain boron nitride having a multifaceted structure.
＜比較例８＞
　使用原料
　市販の板状窒化ホウ素を熱伝導性フィラーとして用いて、以下のようにして成形体を製造した：
　[窒化ホウ素成分]
　板状窒化ホウ素粉末：電気化学工業(株)製、商品名：デンカボロンナイトライドGP
　（全酸素濃度０．１質量％、平均粒子径：８．０μｍ、比表面積：８ｍ２／ｇ）
　窒化ホウ素をエポキシ樹脂材料に添加・混合して樹脂組成物を得た。樹脂組成物の組成は、粒状窒化ホウ素８１.７質量％（７０体積％）およびエポキシ樹脂材料１８.３質量％（３０体積％）であった。尚、特に言及しない処理条件は、比較例の条件と同様である。 <Comparative Example 8>
Raw Materials Used Commercially available plate-shaped boron nitride was used as a thermally conductive filler to produce a molded product as follows:
[Boron nitride component]
Plate Boron Nitride Powder: Made by Electrochemical Industry Co., Ltd., Product Name: Denka Boron Nitride GP
(Total oxygen concentration 0.1% by mass, average particle diameter: 8.0 μm, specific surface area: 8 m 2 / g)
Boron nitride was added to and mixed with the epoxy resin material to obtain a resin composition. The composition of the resin composition was 81.7% by mass (70% by volume) of granular boron nitride and 18.3% by mass (30% by volume) of the epoxy resin material. The processing conditions not particularly mentioned are the same as the conditions of the comparative example.
＜樹脂組成物および成形体の製造＞
　実施例１～３０で得られた本発明の粒状窒化ホウ素および比較例１～７で得られた窒化ホウ素を、それぞれエポキシ樹脂材料に添加・混合して樹脂組成物を得た。樹脂組成物の質量基準の組成は、粒状窒化ホウ素８１.７％（７０体積％）およびエポキシ樹脂材料１８.３％（３０体積％）であった。 <Manufacturing of resin composition and molded product>
The granular boron nitride of the present invention obtained in Examples 1 to 30 and the boron nitride obtained in Comparative Examples 1 to 7 were added and mixed with the epoxy resin material, respectively, to obtain a resin composition. The mass-based composition of the resin composition was 81.7% (70% by volume) of granular boron nitride and 18.3% (30% by volume) of the epoxy resin material.
　詳しくは、１００ｍｌのナス型フラスコに、得られた窒化ホウ素１.０ｇ、ビスフェノールＡ型液状エポキシ（主剤）（三菱化学株式会社製　JER８２８）０.１２２９ｇ、テトラヒドロメチル無水フタル酸（硬化剤）（三菱化学株式会社製　YH３０６）０.０９８３ｇ、２－エチル-４（５）-メチルイミダゾール（硬化促進剤）（三菱化学株式会社製　EMI-２４）０．００２４６ｇ、アセトン（和光純薬工業株式会社聖　試薬特級）２０ｇを加え、超音波ホモジナイザーを用い５分間混合を行った。 Specifically, in a 100 ml eggplant-shaped flask, 1.0 g of obtained boron nitride, bisphenol A type liquid epoxy (main agent) (JER828 manufactured by Mitsubishi Chemical Industries, Ltd.) 0.1229 g, tetrahydromethylphthalic anhydride (curing agent) (Mitsubishi) YH306 manufactured by Kagaku Co., Ltd. 0.0983 g, 2-ethyl-4 (5) -methylimidazole (curing accelerator) (EMI-24 manufactured by Mitsubishi Chemical Industries, Ltd.) 0.00246 g, acetone (Wako Pure Chemical Industries, Ltd. Holy Reagent) 20 g of (special grade) was added, and mixing was performed for 5 minutes using an ultrasonic homogenizer.
　続いて、エバポレーターを使用してアセトンを除去した。除去後にナス型フラスコに残った粒状窒化ホウ素とエポキシ樹脂材料を含む樹脂組成物としての混合物０.８ｇを直径１５ｍｍ金型に入れて、ホットプレスすることにより樹脂組成物を熱硬化して成形体を得た。 Subsequently, acetone was removed using an evaporator. 0.8 g of a mixture as a resin composition containing granular boron nitride and an epoxy resin material remaining in a eggplant-shaped flask after removal was placed in a mold having a diameter of 15 mm, and the resin composition was thermoset by hot pressing to form a molded product. Got
　ホットプレスの条件は、以下の通りである：
　・比較例１～６、実施例１～４、７～１０、１３～１６、１９～２２、２５～２８の窒化ホウ素について
　１２５℃、７０ＭＰａの一軸加圧下で、１２０分間のホットプレス
　・比較例７、実施例５、６、１１、１２、１７、１８、２３、２４、２９、３０の窒化ホウ素について
　１２５℃、５ＭＰａ以下の一軸加圧下で、６０分間のホットプレス、続いて７０ＭＰａまで圧力を上昇させて６０分間のホットプレス The conditions for hot pressing are as follows:
-Born nitrides of Comparative Examples 1 to 6, Examples 1 to 4, 7 to 10, 13 to 16, 19 to 22, 25 to 28 are hot-pressed for 120 minutes under uniaxial pressure at 125 ° C. and 70 MPa. 7. For boron nitrides of Examples 5, 6, 11, 12, 17, 18, 23, 24, 29, 30 under uniaxial pressure of 125 ° C. and 5 MPa or less, hot press for 60 minutes, followed by pressure up to 70 MPa. Hot press for 60 minutes by raising
＜成形体の熱伝導率の測定＞
　得られた成形体の密度、比熱および熱拡散率をそれぞれ測定し、次の式に基づいて成形体の熱伝導率を算出した：
　　熱伝導率＝密度×比熱×熱拡散率 <Measurement of thermal conductivity of molded product>
The density, specific heat and thermal diffusivity of the obtained molded product were measured, respectively, and the thermal conductivity of the molded product was calculated based on the following formula:
Thermal conductivity = density x specific heat x thermal diffusivity
＜密度の測定＞
　エポキシ/窒化ホウ素の成形体について水中アルキメデス法により測定を行い、以下の（式１）により密度を求めた： <Density measurement>
The epoxy / boron nitride molded product was measured by the Archimedes method in water, and the density was determined by the following (Equation 1):
Figure JPOXMLDOC01-appb-M000001
 　式中、ρは成形体の密度（ｇ／ｃｍ３）、ρａは測定温度での水の密度（ｇ／ｃｍ３）、ｍ１は空気中での成形体の質量（ｇ）、ｍ２は水中での成形体の質量である。
Figure JPOXMLDOC01-appb-M000001
In the formula, ρ is the density of the molded body (g / cm 3 ), ρ a is the density of water at the measurement temperature (g / cm 3 ), m 1 is the mass of the molded body in air (g), m 2 Is the mass of the molded product in water.
＜比熱の測定＞
　示差走査熱量計（Netzsch製　DSC200F3 Maia）を用いて、既知の基準物質（本測定ではサファイア）と試料としての成形体に一定の熱を加えながらこれらの温度を測定し、その温度差を計測して熱分析を行って比熱を得た。試料の比熱を下記（式２）により求めた。尚、温度測定範囲は－５０℃～１００℃とし、下記の熱拡散率と同じ測定温度である２５℃の比熱を熱伝導率の計算に用いた。 <Measurement of specific heat>
Using a differential scanning calorimeter (DSC200F3 Maia manufactured by Netzsch), measure these temperatures while applying constant heat to a known reference substance (sapphire in this measurement) and a molded body as a sample, and measure the temperature difference. The thermal analysis was performed to obtain the specific heat. The specific heat of the sample was determined by the following (Equation 2). The temperature measurement range was −50 ° C. to 100 ° C., and the specific heat of 25 ° C., which is the same measurement temperature as the thermal diffusivity described below, was used for the calculation of the thermal conductivity.
Figure JPOXMLDOC01-appb-M000002
 　式中、Ｃｐは成形体試料の比熱（Ｊ／ｇ／Ｋ）、Ｃｐstandardは基準物質の比熱（Ｊ／ｇ／Ｋ）、ｍは成形体試料の重量（ｇ）、Ｍは基準物質の重量（ｇ）、ｈは空容器と成形体試料のＤＳＣ曲線の差、Ｈは空容器と基準物質のＤＳＣ曲線の差である。
Figure JPOXMLDOC01-appb-M000002
In the formula, Cp is the specific heat of the molded body sample (J / g / K), Cp standard is the specific heat of the reference material (J / g / K), m is the weight of the molded body sample (g), and M is the weight of the reference material. (G), h is the difference between the DSC curves of the empty container and the molded body sample, and H is the difference between the DSC curves of the empty container and the reference material.
＜熱拡散率の測定＞
　キセノンフラッシュ法熱定数測定装置（Netzsch製　Xeフラッシュアナライザー　LFA447　Nanoflash）を使用して実施した。熱伝導率（α）は、成形体試料の表面に熱源を照射して裏面の温度を測定し、裏面の最高温度に到達するまでの時間（ΔＴｍ）の１／２に達する時間ｔ１／２（ｓ）と試料厚さＬ（ｍ）から下記の式（３）により求める： <Measurement of thermal diffusivity>
The xenon flash method was performed using a thermal constant measuring device (Netzsch Xe flash analyzer LFA447 Nanoflash). The thermal conductivity (α) is the time t 1/2 of irradiating the front surface of the molded product sample with a heat source, measuring the temperature of the back surface, and reaching 1/2 of the time (ΔTm) until the maximum temperature of the back surface is reached. Obtained from (s) and sample thickness L (m) by the following formula (3):
Figure JPOXMLDOC01-appb-M000003
Figure JPOXMLDOC01-appb-M000003
　尚、成形体の熱伝導率は、ホットプレス時に適用した圧力の加圧方向（プレス方向）およびそれに対して垂直な方向について測定した。 The thermal conductivity of the molded product was measured in the pressurizing direction (pressing direction) of the pressure applied during hot pressing and in the direction perpendicular to it.
＜成形体中における粒状窒化ホウ素の配向度の測定＞
　粒状窒化ホウ素の強さ（詳しくは、粒状窒化ホウ素に外部から加えられる力に抗する能力、即ち、圧壊強度）の評価を、７０ＭＰａ加圧のホットプレスにより得た成形体のエポキシ樹脂材料中における粒状窒化ホウ素の（００Ｌ）面の配向度によって調べた。 <Measurement of the degree of orientation of granular boron nitride in the molded product>
The strength of the granular boron nitride (specifically, the ability to withstand the force applied to the granular boron nitride from the outside, that is, the crushing strength) was evaluated in the epoxy resin material of the molded product obtained by hot pressing under 70 MPa pressure. It was examined by the degree of orientation of the (00L) plane of granular boron nitride.
　成形体に含まれる粒状窒化ホウ素を構成するシェル構造の強度が不十分であると、ホットプレスによってシェル構造一部が崩壊し、粒状窒化ホウ素のシェル構造の性質が弱化して積層構造の性質が強くなる。その結果、ホットプレス方向に対して垂直な方向に沿って壊れた窒化ホウ素板状結晶のａ軸が配向する傾向が強まり、窒化ホウ素結晶の（００２）や（００４）等の（００Ｌ）面の回折ピークが高くなる。 If the strength of the shell structure constituting the granular boron nitride contained in the molded body is insufficient, a part of the shell structure collapses due to hot pressing, the properties of the shell structure of the granular boron nitride are weakened, and the properties of the laminated structure are deteriorated. Become stronger. As a result, the a-axis of the broken boron nitride plate-like crystal becomes more likely to be oriented along the direction perpendicular to the hot press direction, and the (00L) plane of the boron nitride crystal (002), (004), etc. The diffraction peak becomes high.
　即ち、窒化ホウ素（００Ｌ）面の回折ピークの高さによって、窒化ホウ素の板状晶がプレス方向に対して平行な方向に配向したか見積もることができる。即ち、粒状窒化ホウ素の圧壊強度が不十分であると、シェル構造の一部分が壊れてその断片がプレス方向に並び易くなる。換言すれば、プレス方向に並んでいる断片の割合が多いほど、強度が小さいことを意味する。 That is, it can be estimated from the height of the diffraction peak of the boron nitride (00L) plane whether the plate-like crystals of boron nitride are oriented in a direction parallel to the pressing direction. That is, if the crushing strength of the granular boron nitride is insufficient, a part of the shell structure is broken and the pieces are easily arranged in the pressing direction. In other words, the greater the proportion of fragments lined up in the press direction, the lower the strength.
　ホットプレス後の成形体における窒化ホウ素（００Ｌ）面の配向度の測定は、ロットゲーリング法を用いてプレス方向に垂直な面（即ち、ホットプレス面または加圧面）に対しＸＲＤ回折パターンを測定し、下記の式（４）により求めた： To measure the degree of orientation of the boron nitride (00L) surface in the molded product after hot pressing, the XRD diffraction pattern is measured with respect to the surface perpendicular to the pressing direction (that is, the hot pressing surface or the pressed surface) using the Lot Göring method. , Obtained by the following formula (4):
Figure JPOXMLDOC01-appb-M000004
Figure JPOXMLDOC01-appb-M000004
　尚、ロットゲーリング法とは、式（４）によって算出される配向度（ロットゲーリングファクターとも呼ぶ）を用いて結晶等の配向度を評価する方法をいう。ロットゲーリングファクターは、完全配向の場合は１００％となる。この式（４）において、ΣＩ（ｈｋｌ）は、凝集体を含む成形体の試料に関してプレス方向に垂直な面にて測定されたすべての結晶面（ｈｋｌ）のＸ線回折強度の総和であり、ΣＩ0（ｈｋｌ）は、粒状窒化ホウ素に代えて無配向の窒化ホウ素を用いた場合に得られる成形体の試料について測定されたすべての結晶面（ｈｋｌ）のＸ線回折強度の総和である。また、ΣＩ（００Ｌ）は凝集体を含む成形体について測定された結晶学的に等価な特定の結晶面（例えば（００２）や（００４）面などを含む（００Ｌ）面）のＸ線回折強度の総和であり、ΣＩ0（００Ｌ）は、上述の無配向の窒化ホウ素を用いた場合の特定面のハイブリッド材料と同一組成であり無配向のものについて測定された（００Ｌ）面の結晶面のＸ線回折強度の総和である。このように配向度を評価するロットゲーリング法は、結晶の配向度を評価する手法として周知であり、例えば特開２０１１－３７６９５号公報を参照できる。 The lot-gering method is a method of evaluating the degree of orientation of crystals or the like using the degree of orientation calculated by the formula (4) (also referred to as a lot-gering factor). The lotgering factor is 100% in the case of perfect orientation. In this formula (4), ΣI (hkl) is the sum of the X-ray diffraction intensities of all crystal planes (hkl) measured on the plane perpendicular to the press direction with respect to the sample of the molded product containing the aggregate. ΣI 0 (hkl) is the sum of the X-ray diffraction intensities of all crystal planes (hkl) measured for the sample of the molded product obtained when non-oriented boron nitride is used instead of granular boron nitride. Further, ΣI (00L) is the X-ray diffraction intensity of a specific crystal plane (for example, a (00L) plane including (002) or (004) plane) measured for a molded product containing an aggregate. ΣI 0 (00L) is the crystal plane of the (00L) plane measured for the non-oriented material having the same composition as the hybrid material of the specific plane when the above-mentioned non-oriented boron nitride is used. It is the sum of the X-ray diffraction intensities. The lot-gering method for evaluating the degree of orientation as described above is well known as a method for evaluating the degree of orientation of crystals, and for example, Japanese Patent Application Laid-Open No. 2011-37695 can be referred to.
＜実施例の条件および測定結果＞
　上述の実施例および比較例の条件ならびに種々の測定結果を以下の表１～表５に示す： <Conditions and measurement results of Examples>
The conditions of the above-mentioned Examples and Comparative Examples and various measurement results are shown in Tables 1 to 5 below:
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000007
Figure JPOXMLDOC01-appb-T000007
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000009
Figure JPOXMLDOC01-appb-T000009
　いずれの実施例から得られた粒状窒化ホウ素も、カルシウム成分を用いない比較例１～６の窒化ホウ素と比べて、相当大きい平均粒子径を有するが、比表面積は若干小さい。そのような粒状窒化ホウ素を熱伝導性フィラーとして用いた本発明の樹脂組成物を成形して得られる本発明の成形体の熱伝導率に関して、力が加わる方向では約１０～２５Ｗ／（ｍ・Ｋ）、また、それに対して垂直な方向では１５～３５Ｗ／（ｍ・Ｋ）を達成できる。このような熱伝導率は、比較例としての既知の粒状窒化ホウ素をフィラーとして用いて得られる成形体の場合より大きい。このように大きい熱伝導率は、粒子径が大きいことによって粒状窒化ホウ素が有効な熱伝導パスを形成できることを意味する。 The granular boron nitride obtained from each of the examples has a considerably larger average particle size than the boron nitrides of Comparative Examples 1 to 6 that do not use the calcium component, but the specific surface area is slightly smaller. Regarding the thermal conductivity of the molded product of the present invention obtained by molding the resin composition of the present invention using such granular boron nitride as a heat conductive filler, about 10 to 25 W / (m. K), and 15 to 35 W / (m · K) can be achieved in the direction perpendicular to it. Such thermal conductivity is higher than that of a molded product obtained by using a known granular boron nitride as a filler as a comparative example. Such a large thermal conductivity means that granular boron nitride can form an effective thermal conduction path due to the large particle size.
　尚、本発明の成形体において、平行方向の熱伝導率は、垂直方向の熱伝導率の少なくとも６０％程度でありであり、この粒状窒化ホウ素を含む成形体の熱伝導に関する異方性は抑制されている。場合によっては、粒子径および結果的に１００％を越える場合もあり、熱伝導に関する異方性が実質的に認められない場合も有り得る。 In the molded body of the present invention, the thermal conductivity in the parallel direction is at least about 60% of the thermal conductivity in the vertical direction, and the anisotropy regarding the heat conduction of the molded body containing the granular boron nitride is suppressed. Has been done. In some cases, the particle size and consequently may exceed 100%, and anisotropy with respect to heat conduction may not be substantially observed.
　成形体における粒状窒化ホウ素の配向度は、成形体の熱伝導性に影響を及ぼす。成形時のプレスにより加えられる力によって板状になった窒化ホウ素（または元々板状の窒化ホウ素）はプレス方向に対して平行でない方向、特に垂直な方向に沿って配向して樹脂中で並ぶ傾向が強くなるため、成形時のプレス方向に対して平行な方向の熱伝導率が著しく低くなり、その結果、熱伝導異方性が大きくなる。例えば、比較例８は市販の板状粒子が添加されているため、配向度が高く、プレス方向に平行な方向の熱伝導率が低くなっている。 The degree of orientation of granular boron nitride in the molded product affects the thermal conductivity of the molded product. Boron nitride (or plate-shaped boron nitride) that has become plate-shaped due to the force applied by the press during molding tends to be oriented in a direction that is not parallel to the pressing direction, especially along a direction perpendicular to the pressing direction, and line up in the resin. As a result, the thermal conductivity in the direction parallel to the pressing direction at the time of molding becomes remarkably low, and as a result, the thermal conductivity anisotropy becomes large. For example, in Comparative Example 8, since commercially available plate-shaped particles are added, the degree of orientation is high and the thermal conductivity in the direction parallel to the pressing direction is low.
　比較例７では、窒化ホウ素粒子が板状ではなく、合成された多面構造の窒化ホウ素粒子を添加されている。しかしながら、窒化ホウ素結晶の凝集力が弱いために、プレス成形によって加えられる力によって多面体構造が板状の窒化ホウ素に崩壊してそれが配向していると考えられる。そのため、比較例８と同様に、プレス成形によって、プレス方向に平行な方向に沿った熱伝導が低いと考えられる。 In Comparative Example 7, the boron nitride particles are not plate-shaped, but synthetic boron nitride particles having a multifaceted structure are added. However, since the cohesive force of the boron nitride crystal is weak, it is considered that the polyhedral structure collapses into a plate-shaped boron nitride due to the force applied by press forming and is oriented. Therefore, as in Comparative Example 8, it is considered that the heat conduction along the direction parallel to the pressing direction is low by press forming.
　本実施例で製造した粒状窒化ホウ素は、製造方法において希土類元素酸化物を用いる。希土類元素酸化物は窒化ホウ素の溶解・再析出仮定を促進するため、従来のアルカリ土類酸化物のみを添加して作製された比較例７多面構造を有する窒化ホウ素よりも強い凝集力をもたらすと考えられる。特に、本実施例で製造した粒状窒化ホウ素のシェル部分は一体となった板状窒化ホウ素が多面体または球体を形成する傾向にあると考えられ、これが粒状窒化ホウ素の強度を高める要因と考えられる。その結果、プレス成形によって加えられる力に抗して崩壊して板状の窒化ホウ素に変換され難い。よって、これを用いてプレス成形して得られる成形体の配向度は、比較例７および比較例８の配向度より相当小さい。 The granular boron nitride produced in this example uses a rare earth element oxide in the production method. Since the rare earth element oxide promotes the assumption of dissolution and reprecipitation of boron nitride, it is said that it brings a stronger cohesive force than boron nitride having a multifaceted structure in Comparative Example 7 produced by adding only the conventional alkaline earth oxide. Conceivable. In particular, in the shell portion of the granular boron nitride produced in this example, it is considered that the integrated plate-shaped boron nitride tends to form a polyhedron or a sphere, which is considered to be a factor for increasing the strength of the granular boron nitride. As a result, it is difficult to disintegrate against the force applied by press forming and convert it into plate-shaped boron nitride. Therefore, the degree of orientation of the molded product obtained by press molding using this is considerably smaller than the degree of orientation of Comparative Example 7 and Comparative Example 8.
　また、発明者らの検討では、加熱処理する混合物において、酸化物におけるＹ２Ｏ３のような希土類元素酸化物の割合が高いほど、シェル部分の層の厚さが、粒状窒化ホウ素の直径に比べ、厚くなる傾向が観察される。本発明の粒状窒化ホウ素が強い形状維持能を有する理由であると考え得る。 Also, in the study by the inventors, in a mixture to heat treatment, as the ratio of the rare earth element oxides such as Y 2 O 3 is high in the oxide, the thickness of the layer of the shell portion, the diameter of the particulate boron nitride In comparison, a tendency to thicken is observed. It can be considered that this is the reason why the granular boron nitride of the present invention has a strong shape-retaining ability.
　粒状窒化ホウ素粒子組成物に含まれる粒状窒化ホウ素は、酸洗浄する前、その内部に酸化物を包含している。酸洗浄の程度を変えることによって、例えば洗浄に用いる酸濃度を低くすることによって、内部に残存する希土類元素酸化物の量を変えることができる。粒状窒化ホウ素内に酸化物が残っていると、形成される窒化ホウ素のシェル構造の強度、特に圧縮強度を向上させることができると予想される。即ち、そのような粒状窒化ホウ素を用いて樹脂組成物を得、これをホットプレスで成形すると、粒状窒化ホウ素が崩壊し難くくなり、成形体の（００Ｌ）面の配向度が低くなると考えられる。表５に示す結果は、この考えに沿っており、この観点からは、本発明の粒状窒化ホウ素は、好ましくは０．５～１５質量％、より好ましくは３～１０質量％、特に４～８質量％の希土類元素酸化物を含む。 The granular boron nitride contained in the granular boron nitride particle composition contains an oxide inside before acid cleaning. By changing the degree of acid cleaning, for example, by lowering the acid concentration used for cleaning, the amount of rare earth element oxide remaining inside can be changed. If the oxide remains in the granular boron nitride, it is expected that the strength of the shell structure of the formed boron nitride, particularly the compressive strength, can be improved. That is, when a resin composition is obtained using such granular boron nitride and molded by hot pressing, it is considered that the granular boron nitride is less likely to collapse and the degree of orientation of the (00L) plane of the molded product is lowered. .. The results shown in Table 5 are in line with this idea, and from this point of view, the granular boron nitride of the present invention is preferably 0.5 to 15% by mass, more preferably 3 to 10% by mass, and particularly 4 to 8%. Contains% by mass of rare earth element oxides.
　従って、本発明の樹脂組成物および該組成物を成形して作製された成形体は、例えば、電気・電子分野などで熱伝導性が要求されるような放熱シート、熱伝導性ペースト、熱伝導性接着剤等において熱伝導性フィラーとして好適に用いることが出来る。 Therefore, the resin composition of the present invention and the molded product produced by molding the composition are, for example, a heat-dissipating sheet, a heat conductive paste, and a heat conductive material that require heat conductivity in the fields of electricity and electronics. It can be suitably used as a heat conductive filler in a sex adhesive or the like.
関連出願の相互参照Cross-reference of related applications
　本出願は、日本国特許出願第２０１９－０６４１２０号（出願日：２０１９年３月２８日、発明の名称：粒状窒化ホウ素の製造方法および粒状窒化ホウ素）に基づく優先権を主張し、ここで該特許出願を引用することによって該特許出願に記載事項は本願の明細書を構成する。 This application claims priority based on Japanese Patent Application No. 2019-064120 (Filing date: March 28, 2019, Title of invention: Method for producing granular boron nitride and granular boron nitride). By quoting a patent application, the matters described in the patent application constitute the specification of the present application.

Claims (23)

  1. 　（１）窒化ホウ素を含んで成る窒化ホウ素成分、
    　（２）イットリウム、セリウムおよびイッテルビウムから選択される少なくとも１つの希土類元素の酸化物および／またはその前駆体化合物を含んで成る希土類成分、および
    　（３）酸化カルシウムおよび／または炭酸カルシウムを含んで成るカルシウム成分
    を含んで成る混合物を、非酸化性ガス雰囲気下で加熱処理する工程を含むことを特徴とする粒状窒化ホウ素組成物の製造方法。     (1) Boron nitride component containing boron nitride,
    (2) Rare earth components containing oxides of at least one rare earth element selected from yttrium, cerium and itterbium and / or precursor compounds thereof, and (3) calcium containing calcium oxide and / or calcium carbonate. A method for producing a granular boron nitride composition, which comprises a step of heat-treating a mixture containing components in a non-oxidizing gas atmosphere.
  2. 　加熱処理する混合物に含まれる窒化ホウ素成分（１）中の窒化ホウ素、希土類成分（２）に含まれる希土類元素の酸化物ならびにカルシウム成分（３）に含まれる酸化カルシウムの総質量に対する、希土類成分（２）中の希土類元素の酸化物ならびにカルシウム成分（３）中の酸化カルシウムの総質量の割合は、５％～６０％であることを特徴とする請求項１に記載の粒状窒化ホウ素組成物の製造方法。 Rare earth component (rare earth component) with respect to the total mass of boron nitride in the boron nitride component (1) contained in the heat-treated mixture, the oxide of the rare earth element contained in the rare earth component (2), and calcium oxide contained in the calcium component (3). The granular boron nitride composition according to claim 1, wherein the ratio of the total mass of the oxide of the rare earth element in 2) and the calcium oxide in the calcium component (3) is 5% to 60%. Production method.
  3. 　加熱処理する混合物における元素数基準で希土類成分（２）中の希土類元素：カルシウム成分（３）中のカルシウム元素は、１：０．２５～１：４であることを特徴とする請求項１または２に記載の粒状窒化ホウ素組成物の製造方法。 The rare earth element in the rare earth component (2): the calcium element in the calcium component (3) is 1: 0.25 to 1: 4 based on the number of elements in the mixture to be heat-treated. 2. The method for producing a granular boron nitride composition according to 2.
  4. 　窒化ホウ素成分（１）は、５質量％以下の酸素を含むことを特徴とする請求項１～３のいずれかに記載の粒状窒化ホウ素組成物の製造方法。 The method for producing a granular boron nitride composition according to any one of claims 1 to 3, wherein the boron nitride component (1) contains 5% by mass or less of oxygen.
  5. 　加熱処理は、混合物を１８００～２１００℃にて５～２０時間加熱することを特徴とする請求項1から４のいずれかに記載の粒状窒化ホウ素組成物の製造方法。 The method for producing a granular boron nitride composition according to any one of claims 1 to 4, wherein the heat treatment is performed by heating the mixture at 1800 to 2100 ° C. for 5 to 20 hours.
  6. 　平均粒子径が９～２５μｍ、比表面積が２～１０ｍ２／ｇであるシェル構造を有する粒状窒化ホウ素、ならびにイットリウム、セリウムおよびイッテルビウムから選択される少なくとも１つの希土類元素の酸化物を含んで成ることを特徴とする粒状窒化ホウ素組成物。 Containing granular boron nitride having a shell structure with an average particle size of 9 to 25 μm and a specific surface area of 2 to 10 m 2 / g, and an oxide of at least one rare earth element selected from yttrium, cerium and ytterbium. A granular boron nitride composition comprising.
  7. 　質量基準で希土類元素酸化物を３～４０％含み、酸化カルシウムを１～３０％含んで成ることを特徴とする請求項６に記載の粒状窒化ホウ素組成物。 The granular boron nitride composition according to claim 6, which contains 3 to 40% of a rare earth element oxide and 1 to 30% of calcium oxide on a mass basis.
  8. 　請求項１～５のいずれかに記載の方法によって製造されることを特徴とする請求項６または７に記載の粒状窒化ホウ素組成物。 The granular boron nitride composition according to claim 6 or 7, wherein it is produced by the method according to any one of claims 1 to 5.
  9. 　請求項１～５のいずれかに記載の粒状窒化ホウ素組成物の製造方法により得られる粒状窒化ホウ素組成物を酸洗浄により処理することによって酸化物を除去することによって得られることを特徴とする粒状窒化ホウ素の製造方法。 Granularity obtained by removing oxides by treating the granular boron nitride composition obtained by the method for producing a granular boron nitride composition according to any one of claims 1 to 5 by acid cleaning. Method for producing boron nitride.
  10. 　除去する酸化物は、実質的に全量の酸化カルシウムおよび少なくとも一部の希土類元素酸化物であることを特徴とする請求項９に記載の粒状窒化ホウ素の製造方法。 The method for producing granular boron nitride according to claim 9, wherein the oxide to be removed is substantially the entire amount of calcium oxide and at least a part of the rare earth element oxide.
  11. 　平均粒子径が９～２５μｍ、比表面積が２～１０ｍ２／ｇであるシェル構造を有することを特徴とする粒状窒化ホウ素。 Granular boron nitride having a shell structure having an average particle size of 9 to 25 μm and a specific surface area of 2 to 10 m 2 / g.
  12. 　粒状窒化ホウ素の質量基準で、１％～１５％の希土類元素酸化物を含むことを特徴とする請求項１１に記載の粒状窒化ホウ素。 The granular boron nitride according to claim 11, which contains 1% to 15% of a rare earth element oxide based on the mass of the granular boron nitride.
  13. 　請求項６～８のいずれかに記載の粒状窒化ホウ素組成物に含まれることを特徴とする請求項１１または１２に記載の粒状窒化ホウ素。 The granular boron nitride according to claim 11 or 12, which is contained in the granular boron nitride composition according to any one of claims 6 to 8.
  14. 　請求項９または１０に記載の製造方法によって製造されることを特徴とする請求項１１～１３のいずれかに記載の粒状窒化ホウ素。 The granular boron nitride according to any one of claims 11 to 13, which is produced by the production method according to claim 9 or 10.
  15. 　請求項６～８のいずれかに記載の粒状窒化ホウ素組成物および樹脂材料を含んで成ることを特徴とする樹脂組成物。 A resin composition comprising the granular boron nitride composition according to any one of claims 6 to 8 and a resin material.
  16. 　粒状窒化ホウ素組成物の量は、樹脂組成物の質量基準で１０～９０％であることを特徴とする請求項１５に記載の樹脂組成物。 The resin composition according to claim 15, wherein the amount of the granular boron nitride composition is 10 to 90% based on the mass of the resin composition.
  17. 　請求項１１～１４のいずれかに記載の粒状窒化ホウ素および樹脂材料を含んで成ることを特徴とする樹脂組成物。 A resin composition comprising the granular boron nitride according to any one of claims 11 to 14 and a resin material.
  18. 　粒状窒化ホウ素の量は、樹脂組成物の質量基準で１０～９０％であることを特徴とする請求項１７に記載の樹脂組成物。 The resin composition according to claim 17, wherein the amount of granular boron nitride is 10 to 90% based on the mass of the resin composition.
  19. 　樹脂材料はエポキシ樹脂であることを特徴とする請求項１５～１８のいずれかに記載の樹脂組成物。 The resin composition according to any one of claims 15 to 18, wherein the resin material is an epoxy resin.
  20. 　請求項１５～１９のいずれかに記載の樹脂組成物を成形することを特徴とする成形体の製造方法。 A method for producing a molded product, which comprises molding the resin composition according to any one of claims 15 to 19.
  21. 　請求項１５～１９のいずれかに記載の樹脂組成物を用いて製造することを特徴とする成形体。 A molded product produced by using the resin composition according to any one of claims 15 to 19.
  22. 　成形に際して圧力を加える方向に対して平行な方向の熱伝導率が１０～２５Ｗ／（ｍ・Ｋ）である請求項２１に記載の成形体。 The molded product according to claim 21, wherein the thermal conductivity in the direction parallel to the direction in which pressure is applied during molding is 10 to 25 W / (m · K).
  23. 　成形に際して圧力を加える方向に対して垂直な方向の熱伝導率が１５～３５Ｗ／（ｍ・Ｋ）である請求項２１または２２に記載の成形体。 The molded product according to claim 21 or 22, wherein the thermal conductivity in the direction perpendicular to the direction in which pressure is applied during molding is 15 to 35 W / (m · K).
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