Classifications

• • 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
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/21—Attrition-index or crushing strength of granulates

Definitions

• the present invention relates to a method for adjusting the particle crushing strength of boron nitride powder, a boron nitride powder and a method for producing the same.
• boron nitride powder having characteristics such as high thermal conductivity, high insulation property, and low relative permittivity is attracting attention.
• the shape of the agglomerates is further spheroidized to improve the filling property, the powder strength is improved, and further, the purity is increased to improve the insulating property of the heat transfer sheet or the like filled with the powder.
• the ratio of major axis to thickness of primary particles is 5 to 10 on average, and the size of aggregates of primary particles is 2 ⁇ m in average particle size (D50).
• a hexagonal boron nitride powder having a bulk density of 0.5 to 1.0 g / cm 3 or more and 200 ⁇ m or less is disclosed.
• the hexagonal boron nitride particles have a thermal conductivity of 400 W / (m ⁇ K) in the in-plane direction (a-axis direction), whereas the thermal conductivity in the thickness direction (c-axis direction) is 2 W / (m). -K), and the anisotropy of the thermal conductivity derived from the crystal structure and the scaly shape is large. Further, when the hexagonal boron nitride powder is filled in the resin, the particles are aligned and oriented in the same direction.
• the in-plane direction (a-axis direction) of the hexagonal boron nitride particles and the thickness direction of the thermal interface material become perpendicular to each other, and the in-plane direction (a-axis direction) of the hexagonal boron nitride particles. )
• the in-plane direction (a-axis direction) of the hexagonal boron nitride particles could not fully utilize the high thermal conductivity.
• Patent Document 2 in the boron nitride agglomerated particles formed by agglomerating the boron nitride primary particles, the boron nitride primary particles are oriented in the same direction by increasing the strength to such an extent that the disintegration of the agglomerated particles can be suppressed even at a predetermined molding pressure. It is described that the alignment is suppressed.
• the strength of the agglomerated particles can be increased in order to prevent the primary particles from being oriented in the same direction and lowering the thermal conductivity. It is considered important.
• the present inventors in order to obtain boron nitride agglomerated particles having desired characteristics, not only agglomerated particles having a high strength (crushing strength) but also agglomerated particles having an appropriate strength are used in combination. Was found to be effective.
• one aspect of the present invention is to provide a novel method for adjusting the particle crushing strength of the boron nitride powder.
• One aspect of the present invention includes a decarburization step of heating boron nitride powder in the presence of calcium carbonate to obtain boron nitride powder, and by adjusting the amount of calcium carbonate added in the decarburization step, boron nitride is added.
• a method for adjusting the particle crushing strength of a powder is provided.
• Another aspect of the present invention is a step of adding calcium carbonate to the boron nitride powder in order to adjust the particle crushing strength, and a step of heating the boron nitride powder in the presence of calcium carbonate to decarburize.
• a method for producing a boron nitride powder is provided.
• calcium carbonate in the step of adding calcium carbonate, may be added so as to be 0.125 to 1 part by mass with respect to 100 parts by mass of the boron nitride powder.
• Another aspect of the present invention provides a boron nitride powder having a standard deviation of particle crushing strength of 3 MPa or less.
• Another aspect of the present invention is a set composed of a plurality of aggregates, each of which has different production lots of boron nitride powder, and the particle crushing strength of the boron nitride powder in the set.
• a set is provided in which the standard deviation of is 3 MPa or less.
• the boron nitride powder in the present specification is a collection (also referred to as agglomerate particles) of agglomerated particles (also referred to as agglomerate particles) formed by agglomerating primary particles of boron nitride, and is in the same production lot (details will be described later). What you get.
• the primary particles of boron nitride may be, for example, scaly hexagonal boron nitride particles.
• the particle crushing strength refers to the crushing strength of agglomerated particles.
• the crushing strength of the boron nitride powder (crushing strength of the powder as a whole) can be obtained as a strength at which the cumulative fracture rate is 63.2% by measuring the particle crushing strength of 20 agglomerated particles.
• the crushing test force can be measured using a microcompression tester (for example, MCT-W500 manufactured by Shimadzu Corporation).
• the boron nitride powder has a step of adding calcium carbonate to boron nitride (B 4 CN 4 ) in order to adjust the particle crushing strength (addition step) and boron nitride in the presence of calcium carbonate. It is obtained by a manufacturing method including a step of heating powder to decarburize (decarburization step).
• Addition step comprises in one embodiment, the boron carbide (B 4 C) step of the powder was calcined to obtain the boron carbonitride nitride powder (nitriding process).
• the average particle size of the boron carbide powder may be 3 ⁇ m or more, 5 ⁇ m or more, or 10 ⁇ m or more, and may be 100 ⁇ m or less, 60 ⁇ m or less, or 40 ⁇ m or less.
• the average particle size of the boron carbide powder was measured using a laser diffraction scattering method particle size distribution measuring device (LS-13 320) manufactured by Beckman Coulter Co., Ltd. without applying a homogenizer to the sample before the measurement process, and is cumulative.
• the particle size (Median diameter, D50) is 50% of the cumulative value of the particle size distribution.
• the carbon content of the boron carbide powder is preferably smaller than B 4 C (21.7% by mass) in composition.
• the carbon content is preferably 18% by mass or more, more preferably 19% by mass or more, and may be 20.5% by mass or less.
• the carbon content is 18% by mass or more, the deviation from the theoretical composition is small, so that it is stable.
• the carbon content is 20.5% by mass or less, the amount of carbon volatilized during the decarburization step described later can be reduced, and dense agglomerated particles can be obtained.
• the carbon content of the boron carbide powder can be measured with a carbon analyzer (for example, IR-412 type manufactured by LECO).
• Boron carbide powder can be obtained by a known production method. For example, boric acid and acetylene black are mixed and then heated at 1800 to 2400 ° C. for 1 to 10 hours in an inert gas atmosphere to obtain a boron carbide mass. Boron carbide powder can be obtained by pulverizing the boron carbide mass, sieving it, washing it, removing impurities, drying it, and the like. As the boron carbide powder, a commercially available product may be used.
• the boron carbide powder is heated under a nitrogen atmosphere and under pressurized conditions. As a result, the boron carbide powder is calcined to obtain the boron nitride powder.
• the atmosphere in the nitriding step is an atmosphere in which the nitriding reaction proceeds, and may be, for example, nitrogen gas, ammonia gas, or the like, and these may be used alone or in combination of two or more.
• the atmosphere is preferably nitrogen gas from the viewpoint of ease of nitriding and cost.
• the content of nitrogen gas in the atmosphere is preferably 95% by volume or more, more preferably 99.9% by volume or more.
• the pressure (atmospheric pressure) in the nitriding step is preferably 0.6 MPa or more, more preferably 0.7 MPa or more, preferably 1.0 MPa or less, and more preferably 0.9 MPa or less.
• the pressure is more preferably 0.7 to 1.0 MPa.
• the firing temperature in the nitriding step is preferably 1800 ° C. or higher, more preferably 1900 ° C. or higher, preferably 2400 ° C. or lower, and more preferably 2200 ° C. or lower.
• the firing temperature is more preferably 1800 to 2200 ° C.
• the pressure conditions and the calcination temperature are preferably 1800 ° C. or higher and 0.7 to 1.0 MPa because the nitriding of boron carbide proceeds more preferably and the conditions are industrially appropriate.
• the firing time (heating time) in the nitriding step is appropriately selected within a range in which nitriding proceeds sufficiently, and is preferably 6 hours or more, more preferably 8 hours or more, preferably 40 hours or less, and more preferably 30 hours or less. It may be there.
• the addition step does not have to include the above-mentioned nitriding step.
• calcium carbonate is added to adjust the particle crushing strength of the finally produced boron nitride powder. That is, calcium carbonate is added for a purpose different from the purpose conventionally used, for example, the purpose as a sintering aid. When calcium carbonate is used as a sintering aid, it is sufficient that the boron nitride powder can be sufficiently sintered. Therefore, unlike the case where calcium carbonate is used for the purpose of adjusting the particle crushing strength, the addition amount is 1%. It is not necessary to make precise adjustments in the following orders. That is, in the addition step in this production method, the amount of calcium carbonate added is adjusted on the order of 1% or less. As the calcium carbonate, a commercially available product can be appropriately used.
• calcium carbonate and boron nitride powder may be mixed using a ball mill, a low-frequency resonance acoustic mixer, or the like in order to allow calcium carbonate to act uniformly on the boron nitride powder. Thereby, the particle crushing strength can be adjusted more accurately.
• the amount of calcium carbonate added is adjusted to obtain the desired particle crushing strength.
• the amount of calcium carbonate added is not particularly limited, but may be set in the range of 0.125 to 1 part by mass with respect to 100 parts by mass of boron nitride. When setting in this range, an appropriate addition amount is set from the range of 0.125 to 1 part by mass according to the desired particle crushing strength. Here, it is important for adjusting the particle crushing strength to adjust so that the set addition amount does not vary.
• the fact that the set addition amount does not vary means that the mixture is added within a range of ⁇ 0.05 parts by mass of the set addition amount with respect to 100 parts by mass of boron nitride.
• the appropriate addition amount may be determined by obtaining the relationship between the addition amount of calcium carbonate and the particle crushing strength in advance, or may be determined based on the past measurement results. Further, as described below, the particle crushing strength tends to increase as the amount of calcium carbonate added decreases, and the particle crushing strength tends to decrease as the amount of calcium carbonate added increases.
• the amount of calcium carbonate added is 0.025 parts by mass or more, 0 by mass with respect to 100 parts by mass of the boron nitride powder, in order to make the particle crushing strength of the boron nitride powder 6 MPa or more, 6.5 MPa or more, or 7 MPa or more. It may be .075 parts by mass or more, 0.125 parts by mass or more, 0.45 parts by mass or less, 0.375 parts by mass or less, or 0.325 parts by mass or less.
• the amount of calcium carbonate added is 0.375 parts by mass or more and 0 by mass with respect to 100 parts by mass of the boron nitride powder so that the particle crushing strength of the boron nitride powder is less than 6 MPa, 5.5 MPa or less, or 5 MPa or less. It may be .45 parts by mass or more, 0.5 parts by mass or more, and may be 1 part by mass or less, 0.95 parts by mass or less, or 0.875 parts by mass or less.
• the amount of calcium carbonate added is based on 100 parts by mass of the boron nitride powder from the viewpoint of making it easier to obtain a boron nitride powder having a higher particle crushing strength and making it easier to obtain a boron nitride powder having a small variation in particle crushing strength. It is preferably 0.125 parts by mass or more, more preferably 0.15 parts by mass or more, and further preferably 0.2 parts by mass or more.
• the amount of calcium carbonate added is based on 100 parts by mass of the boron nitride powder from the viewpoint of making it easier to obtain a boron nitride powder having a smaller particle crushing strength and making it easier to obtain a boron nitride powder having a small variation in crushing strength. It is preferably 1 part by mass or less, more preferably 0.9 part by mass or less, and further preferably 0.88 part by mass or less.
• the amount of calcium carbonate added is small, the particle crushing strength can be adjusted in a large range, and when the amount of calcium carbonate added is large, the particle crushing strength tends to be adjusted in a small range.
• a boron source may be further added in addition to the boron nitride powder.
• Boron sources include boric acid, boron oxide, or mixtures thereof.
• the ratio of the boron source added to the amount of boron nitride powder may be appropriately selected.
• the ratio of the boron source may be, for example, 100 parts by mass or more, preferably 150 parts by mass or more, and may be, for example, 300 parts by mass or less, preferably 100 parts by mass or more, with respect to 100 parts by mass of the boron nitride powder. It is 250 parts by mass or less.
• additives used in the technical field may be further added to the boron nitride powder, if necessary.
• the above-mentioned boron nitride powder (including the boron nitride powder to which a boron source is added) is decarburized by heating in the presence of calcium carbonate to obtain a boron nitride powder (decarburization step). ).
• the decarburization step it is possible to obtain agglomerated particles of boron nitride formed by decarburizing and further crystallizing primary particles of boron nitride (hexagonal boron nitride having scaly primary particles).
• the atmosphere in the decarburization step may be, for example, nitrogen gas, ammonia gas, or the like, and may be one kind alone or a combination of two or more kinds thereof.
• the atmosphere is preferably nitrogen gas from the viewpoint of ease of decarburization and cost.
• the content of nitrogen gas in the atmosphere is preferably 95% by volume or more, more preferably 99.9% by volume or more.
• the pressure (atmospheric pressure) in the decarburization step may be normal pressure (atmospheric pressure) or may be more pressurized than normal pressure.
• the pressure When the pressure is pressurized, the pressure may be, for example, 0.5 MPa or less, or 0.3 MPa or less.
• the temperature of the boron nitride powder is raised to a predetermined temperature (a temperature at which decarburization can be started), and then the temperature is further raised to a holding temperature at a predetermined temperature.
• the predetermined temperature can be set according to the system, and may be, for example, 1000 ° C. or higher, 1500 ° C. or lower, and preferably 1200 ° C. or lower.
• the rate of temperature rise from a predetermined temperature (temperature at which decarburization can be started) to the holding temperature may be, for example, 5 ° C./min or less, preferably 4 ° C./min or less, 3 ° C./min or less, or 2 ° C. It may be less than / minute.
• the holding temperature is preferably 1600 ° C. or higher, more preferably 1800 ° C. or higher, from the viewpoint that particle growth is likely to occur satisfactorily and the thermal conductivity of the obtained boron nitride powder can be improved.
• the holding temperature is preferably 2200 ° C. or lower, more preferably 2100 ° C. or lower.
• the holding time at the holding temperature is appropriately selected within a range in which crystallization proceeds sufficiently, for example, it may be more than 0.5 hours, and from the viewpoint that particle growth is likely to occur well, it is preferably 1 hour or more, more preferably. It is 3 hours or more, more preferably 5 hours or more.
• the holding time at the holding temperature may be, for example, less than 40 hours, and is preferably 30 hours or less from the viewpoint of reducing the decrease in crushing strength due to excessive particle growth and reducing industrial inconvenience. More preferably, it is 20 hours or less.
• the rate of temperature rise to the holding temperature is set within the range of 5 ° C./min or less, and the holding time is 1 hour or more and 30 hours so that the heat applied to the boron nitride particles becomes uniform. It is preferable to set in the following range. If the temperature rising rate is slow and the holding time is set long, heat is applied more uniformly, and variations in particle crushing strength of aggregated particles can be suppressed.
• the boron nitride powder thus obtained is a powder having agglomerated particles in which primary particles are agglomerated. If necessary, the boron nitride powder may be classified by a sieve so that the boron nitride powder having a desired particle size distribution can be obtained (classification step).
• the particle crushing strength of the agglomerated particles is adjusted by adjusting the amount of calcium carbonate added. Therefore, according to the above-mentioned production method, agglomerated particles having a desired particle crushing strength can be obtained, and further, a boron nitride powder having a desired crushing strength can be obtained.
• the amount of boron source added is known as a factor that affects the particle crushing strength.
• carbon is added to the boron nitride powder rather than the amount of boron source added. Is less likely to remain, and the yield of boron nitride powder can be increased.
• the average particle size of the boron nitride powder is not particularly limited, but may be 2 ⁇ m or more, 4 ⁇ m or more, 6 ⁇ m or more, or 8 ⁇ m or more, and may be 40 ⁇ m or less, 30 ⁇ m or less, 20 ⁇ m or less, or 15 ⁇ m or less.
• the average particle size may be larger than 40 ⁇ m and may be 45 ⁇ m or more, 50 ⁇ m or more, or 55 ⁇ m or more, and may be 100 ⁇ m or less, 80 ⁇ m or less, or 75 ⁇ m or less.
• the average particle size of the boron nitride powder was measured using a laser diffraction scattering method particle size distribution measuring device (LS-13 320) manufactured by Beckman Coulter Co., Ltd. without applying a homogenizer to the sample before the measurement process, and is cumulative.
• the particle size (Median diameter, D50) is 50% of the cumulative value of the particle size distribution.
• the particle crushing strength of the boron nitride powder may be 1 MPa or more, 1.5 MPa or more, or 2 MPa or more, and may be 20 MPa or less, 15 MPa or less, or 10 MPa or less.
• the particle crushing strength may be 1 MPa or more, 1.5 MPa or more, or 2 MPa or more, and is 10 MPa or less, 7 MPa or less, or 5 MPa or less. May be good.
• the particle crushing strength may be 1 MPa or more, 3 MPa or more, 5 MPa or more, or 7 MPa or more, and 20 MPa or less, 15 MPa or less, or 10 MPa or less. May be good.
• the crushing strength of the boron nitride powder may be 1 MPa or more, 1.5 MPa or more, or 2 MPa or more, and may be 20 MPa or less, 15 MPa or less, or 10 MPa or less. ..
• Another embodiment of the present invention comprises a decarburization step of heating the boron nitride powder in the presence of calcium carbonate to obtain the boron nitride powder, and by adjusting the amount of calcium carbonate added in the decarburization step.
• it is a method of adjusting the particle crushing strength of the boron nitride powder (a method of adjusting the particle crushing strength).
• the detailed embodiment of the decarburization step is as described above. This method facilitates adjusting the particle crushing strength of the boron nitride powder to a desired range.
• the production method by adjusting the amount of calcium carbonate added in the decarburization step, it is possible to obtain a boron nitride powder in which variation in particle crushing strength is suppressed.
• the variation in the particle crushing strength in the boron nitride powder means that the standard deviation of the particle crushing strength among the agglomerated particles contained in the boron nitride powder is small.
• the boron nitride powder in the present specification refers to those obtained in the same production lot, the fact that the variation in particle crushing strength is small in this boron nitride powder means that the aggregated particles of the boron nitride powder in the same production lot. It means that the variation of is small.
• the production lot in the present specification refers to boron nitride powder produced at once by a series of steps in the same equipment by the above-mentioned production method.
• Another embodiment of the present invention can be said to be a boron nitride powder having a standard deviation of particle crushing strength of 3 MPa or less. That is, this boron nitride powder is a boron nitride powder of the same production lot, and the standard deviation of the particle crushing strength between the agglomerated particles is 3 MPa or less.
• the standard deviation of the particle crushing strength between the agglomerated particles is obtained by taking out 20 agglomerated particles from the boron nitride powder obtained by the above-mentioned production method, measuring the particle crushing strength of each particle, and then calculating the standard deviation. can get.
• the standard deviation of the particle crushing strength is 3 MPa or less, and may be 2.9 MPa or less, 2.5 MPa or less, 2.3 MPa or less, or 2 MPa or less.
• the standard deviation of the particle crushing strength of the boron nitride powder may be 3 MPa or less, 2.5 MPa or less, 2 MPa or less, or 1.7 MPa or less when the average particle size of the boron nitride powder is 40 ⁇ m or less.
• the standard deviation of the particle crushing strength of the boron nitride powder may be 3 MPa or less, 2.9 MPa or less, or 2.5 MPa or less when the average particle size of the boron nitride powder exceeds 40 ⁇ m.
• Another embodiment of the present invention is a set composed of a plurality of aggregates, each having different production lots of boron nitride powder, and particle crushing of the boron nitride powder in the set. It can be said that the set has a standard deviation of strength of 3 MPa or less.
• the set according to one embodiment is composed of a plurality of aggregates.
• Each of the plurality of aggregates has a boron nitride powder obtained by the above-mentioned production method, and each of the plurality of aggregates has a boron nitride powder of a production lot different from each other.
• the first aggregate among the plurality of aggregates constituting the set has one production lot of boron nitride powder obtained by the production method described above.
• the first aggregate may be composed of only one production lot (referred to as lot A) of boron nitride powder.
• the first aggregate may be composed of the boron nitride powder of Lot A contained in one packaging bag or the like, and may be composed of the boron nitride powder of Lot A divided into a plurality of packaging bags or the like. It may be composed of groups.
• the first aggregate may be a mixture of the boron nitride powder of lot A and the boron nitride powder of one or more production lots different from lot A (referred to as mixture A).
• the first aggregate may be composed of the boron nitride powder of the mixture A contained in one packaging bag or the like, and may be composed of the boron nitride powder of the mixture A divided into a plurality of packaging bags or the like. It may be composed of groups.
• the second aggregate in the plurality of aggregates has at least a lot (lot B) of boron nitride powder different from lot A.
• “Manufacturing lot different from lot A” means a lot manufactured at a time different from that of lot A, although the manufacturing conditions are set in the same manner as in lot A and the lot is manufactured by the same equipment or the like. The same meaning is used in expressions such as "manufacturing lot different from lot B".
• the second aggregate may be composed only of lot B boron nitride powder.
• the second aggregate may be composed of the boron nitride powder of Lot B put in one packaging bag or the like, and the boron nitride powder of Lot B put in a plurality of packaging bags or the like separately. It may be composed of groups.
• the second aggregate may be a mixture (mixture B) of the boron nitride powder of lot B and the boron nitride powder of one or more production lots different from lot B.
• the second aggregate may be composed of the mixture B contained in one packaging bag or the like, or may be composed of a group of the mixture B contained in a plurality of packaging bags or the like.
• Mixture B may contain lot A boron nitride powder as long as the first and second aggregates are not exactly the same.
• the set may further include other aggregates (third aggregate, fourth aggregate, etc.). At this time, the relationship between the aggregates is the same as the relationship between the first aggregate and the second aggregate described above.
• the set described above has the boron nitride powder produced by the above-mentioned production method, it is possible to reduce the variation in the particle crushing strength of the boron nitride powder among a plurality of aggregates. That is, in this set, the standard deviation of the particle crushing strength between the aggregates can be set to 3 MPa or less.
• the particle crushing strength in the set is obtained by taking out 20 aggregated particles of boron nitride powder from each of the aggregates constituting the set, measuring the particle crushing strength of all the particles, and then calculating the standard deviation thereof. Be done.
• the standard deviation of the particle crushing strength in the set is 3 MPa or less, and may be 2.9 MPa or less, 2.5 MPa or less, 2.3 MPa or less, or 2 MPa or less.
• the standard deviation of the particle crushing strength in the set may be 3 MPa or less, 2.5 MPa or less, 2 MPa or less, or 1.7 MPa or less when the average particle size of the boron nitride powder is 40 ⁇ m or less.
• the standard deviation of the particle crushing strength in the set may be 3 MPa or less, 2.9 MPa or less, or 2.5 MPa or less when the average particle size of the boron nitride powder exceeds 40 ⁇ m.
• the set exists in the state of a plurality of packages for the boron nitride powder of the same product, and the state in which the plurality of packages are present and stored in close proximity to each other in a warehouse or the like is not present. It corresponds to the set. Further, even if there is no situation in which a plurality of aggregates exist at the same time in terms of time, the same manufacturing entity manufactures a plurality of aggregates, and each aggregate is immediately carried out after the manufacture, which also corresponds to the production of a set. Further, a case where a package carried out from a warehouse, a manufacturing factory, or the like is subsequently stored as a raw material for the same product is also a set. Further, even if the time is not the same, if a plurality of packages are purchased for the production of the same product, it corresponds to the purchase of a set.
• a resin composition filled with the boron nitride powder can be produced by using the above-mentioned boron nitride powder and a set consisting of a plurality of aggregates having the boron nitride powder.
• a resin composition having desired properties is used. Can be manufactured stably.
• boron nitride powder 100 parts by mass of orthoboric acid (manufactured by Nippon Denko Co., Ltd., hereinafter simply referred to as "boric acid") and 35 parts by mass of acetylene black (HS100, manufactured by Denka Co., Ltd.) are mixed using a Henschel mixer, and then in a graphite crucible. Filled in. Put this graphite crucible an arc furnace, in argon atmosphere, and heated for 5 hours at 2200 ° C., it was synthesized boron carbide (B 4 C) powder bulk.
• orthoboric acid manufactured by Nippon Denko Co., Ltd.
• HS100 acetylene black
• the synthesized massive boron carbide powder was pulverized with a ball mill for 1 hour and sieved to a particle size of 75 ⁇ m or less using a sieve net.
• the boron carbide powder after sieving was further washed with aqueous nitric acid to remove impurities such as iron, by filtration and drying, to produce boron carbide powder having an average particle size of 39.9 ⁇ m and (B 4 C powder).
• the prepared boron carbide powder was filled in a boron nitride crucible.
• Boron nitride (B 4 CN 4 ) powder was obtained by heating the boron carbide powder at 2000 ° C. and 0.85 MPa for 20 hours in a nitrogen gas atmosphere using a resistance heating furnace.
• boron nitride powder (also referred to as “BN powder”) having an average particle size of 55.8 ⁇ m was obtained.
• Examples 2 to 7 The average particle diameter of raw material is boron carbide powder (B 4 C powder), and / or was changed as described in Table 1 the amount of calcium carbonate, a boron nitride powder in the same manner as in Example 1 Made. In each of Examples 2 to 7, boron nitride powder was prepared in 3 lots at a time.
• the particle crushing strength of the boron nitride powder according to the examples was measured according to JIS R1639-5: 2007.
• a microcompression tester MCT-W500, manufactured by Shimadzu Corporation
• Table 1 shows the values of the crushing strength of the boron nitride powder at the cumulative fracture rate of 63.2%. As shown in Table 1, it was found that the particle crushing strength can be adjusted by adjusting the amount of calcium carbonate added in the production of the boron nitride powder, and thereby the crushing strength of the boron nitride powder can be adjusted.
• Example 1 the standard deviation of the particle crushing strength for 20 agglomerated particles of the same lot was calculated.
• Table 1 the standard deviations in each of the three lots were equivalent ( ⁇ 0.2), so one representative value was shown.
• Table 1 in the boron nitride powder according to the example, the variation in the particle crushing strength of the boron nitride powder in the same production lot was small.
• Example 2 the crushing strength of the boron nitride powder is the same, but in Example 2 in which the amount of calcium carbonate added is increased, the standard deviation is smaller than that in Example 1, and the particle crushing strength is higher. It was found that the variation was further reduced.
• the first lot of boron nitride powder is the first aggregate
• the second lot of boron nitride powder is the second aggregate
• the third lot of boron nitride powder is the third aggregate.
• a set of boron nitride powder consisting of three aggregates was constructed. Twenty agglomerated particles were taken out from each of the aggregates, and the standard deviation of the particle crushing strength (standard deviation of 60 particles in total) was calculated as the standard deviation of the set (standard deviation between the aggregates).
• the standard deviation between the aggregates in each example was a value that could be said to be equivalent ( ⁇ 0.2) to the standard deviation in the lot described above.
• one lot of boron nitride powder produced by the method of Example 2 was used as the first aggregate, and one lot of boron nitride powder produced by the method of Example 3 was used as the second aggregate.
• One lot of boron nitride powder produced by the method of Example 4 was used as a third aggregate to form a set of boron nitride powder composed of three aggregates. Twenty agglomerated particles were taken out from each of the aggregates, and the standard deviation of the particle crushing strength (standard deviation of 60 particles in total) was calculated as the standard deviation of the set (standard deviation between the aggregates). there were.
• Example 1 when the boron nitride powder of the above three production lots was separately used to produce a resin composition, a resin composition having desired characteristics was obtained under the same production conditions.
• Example 5 a resin composition could be obtained using boron nitride powders of three production lots in the same manner, but the production conditions were different because the particle crushing strength was different from that of Example 1. Since it is practically very difficult to produce a resin composition while finely changing the production conditions, a resin composition having desired properties can be obtained by adjusting the particle crushing strength according to the amount of calcium carbonate added. It can be said that can be stably manufactured.

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• 2020
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