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
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L101/00—Compositions of unspecified macromolecular compounds

Definitions

• the present invention relates to boron nitride particles, a method for producing boron nitride particles, and a resin composition.
• Boron nitride has lubricity, high thermal conductivity, and insulation properties, and is used in various applications such as solid lubricants, mold release materials, raw materials for cosmetics, heat dissipation materials, and heat-resistant insulating sintered bodies. used for a purpose.
• Patent Document 1 describes a hexagonal boron nitride powder made of primary particles of hexagonal boron nitride that can impart high thermal conductivity and high dielectric strength to a resin composition obtained by filling a resin. Contains aggregated particles, has a BET specific surface area of 0.7 to 1.3 m 2 /g, and has an oil absorption amount of 80 g/100 g or less measured based on JIS K 5101-13-1. A hexagonal boron nitride powder is disclosed.
• the main objective of the present invention is to provide novel boron nitride particles.
• the present invention provides the following [1] to [7].
• Method for producing boron nitride particles. [7] A resin composition containing the boron nitride particles according to any one of [1] to [5] and a resin.
• novel boron nitride particles can be provided.
• 1 is a graph of X-ray diffraction measurement results of boron nitride particles of Examples 1 to 3.
• 1 is a SEM image of a cross section of boron nitride particles of Example 1.
• 3 is a SEM image of a cross section of boron nitride particles of Comparative Example 1.
• 1 is a binarized image of a cross section of boron nitride particles of Example 1.
• 2 is a binarized image of a cross section of boron nitride particles of Comparative Example 1.
• the boron nitride particles according to this embodiment are composed of, for example, a plurality of boron nitride pieces.
• the boron nitride particles have a plurality of voids formed between a plurality of boron nitride pieces.
• the boron nitride pieces are made of boron nitride and may have, for example, a scale-like shape.
• the plurality of boron nitride pieces may be in physical contact with each other or may be chemically bonded.
• the fact that the plurality of boron nitride pieces are chemically bonded to each other can be confirmed using a scanning electron microscope (SEM) by not observing boundaries between the boron nitride pieces at the joints between the boron nitride pieces.
• the boron nitride particles may have a cross section that includes a region where a plurality of boron nitride pieces are stacked. The fact that multiple boron nitride pieces are stacked is confirmed by observing the cross section of the boron nitride particles using SEM, and confirming that the multiple boron nitride pieces are arranged side by side in the thickness direction of the boron nitride pieces. can.
• the average thickness of the boron nitride pieces may be 0.5 ⁇ m or more, 1 ⁇ m or more, or 1.5 ⁇ m or more, and 5 ⁇ m or less.
• the average length of the boron nitride pieces in the longitudinal direction may be, for example, 1 ⁇ m or more and 10 ⁇ m or less.
• the average thickness and average length in the longitudinal direction of the boron nitride pieces can be determined by using an SEM to observe the cross section of the boron nitride particles at a magnification of 1,000 times using an image analysis software (for example, "Mac- It is defined as the average value of the thickness and longitudinal length of 40 boron nitride pieces measured in the SEM image.
• the area ratio of voids with a circular equivalent radius of less than 1 ⁇ m to the total area of multiple voids within the particle may be 30% or more. That is, the boron nitride particles according to one embodiment (first embodiment) of the present invention have a plurality of voids within the particles, and the area ratio of the voids having a circular equivalent radius of less than 1 ⁇ m to the total area of the plurality of voids is is 30% or more.
• the area ratio of voids having an equivalent circular radius of less than 1 ⁇ m to the total area of the plurality of voids may be 35% or more, or 40% or more.
• the area ratio of the voids having a circular equivalent radius of less than 1 ⁇ m to the total area of the plurality of voids may be 45% or more, 50% or more, or 55% or more, and 70% or less, 65% or less, or 60% or less. It may be.
• the area ratio of the plurality of voids may be 45% or less with respect to the total area of the region made of boron nitride and the plurality of voids. That is, the boron nitride particles according to another embodiment (second embodiment) of the present invention have a plurality of voids in the particles, and the area ratio of the plurality of voids is equal to the area consisting of boron nitride and the plurality of voids. It has a cross section that is 45% or less of the total area.
• the area ratio of the plurality of voids is 40% or less, 35% or less, 30% or less, or 25% or less with respect to the total area of the region made of boron nitride and the plurality of voids. good.
• the filling rate of boron nitride particles increases without crushing the boron nitride particles, making it easier to obtain a heat dissipation material with high thermal conductivity.
• the area ratio of the plurality of voids is 24% or less, 22% or less, 20% or less, or 18% or less with respect to the total area of the region made of boron nitride and the plurality of voids. Often, it may be 10% or more, 15% or more, or 20% or more.
• the area ratio of the plurality of voids (the ratio of the total area of the plurality of voids) may be within the above range.
• the area ratio of the voids having a circular equivalent radius of less than 1 ⁇ m to the total area of the plurality of voids may be within the above range.
• the area ratio of voids with a circular equivalent radius of 2 ⁇ m or more to the total area of multiple voids is 80% or less, 75%. Below, it may be 70% or less, 65% or less, 60% or less, 55% or less, 50% or less, 45% or less, 40% or less, or 35% or less.
• the area ratio of the voids having a circular equivalent radius of 2 ⁇ m or more to the total area of the plurality of voids may be 30% or less, or 25% or less, 5% or more, 10% or more, 15% or more, 20% or more, Or it may be 25% or more.
• the average equivalent circular radius of the plurality of voids may be 1.8 ⁇ m or less, 1.6 ⁇ m or less, 1.5 ⁇ m or less, 1.4 ⁇ m or less, or 1.3 ⁇ m or less.
• the average circular equivalent radius of the plurality of voids may be 0.6 ⁇ m or more, 0.8 ⁇ m or more, or 0.9 ⁇ m or more.
• the average equivalent circle radius of a plurality of voids means the equivalent circle radius (median diameter) of the voids at which the cumulative area of the voids is 50% in the distribution of the equivalent circle radii of the voids.
• the area of the region made of boron nitride in the cross section of the boron nitride particles, and the area and equivalent circle radius of each of the plurality of voids can be measured by the following method.
• boron nitride particles are embedded in an epoxy resin, and the resin is cured to obtain a cured product.
• the cured product is polished to expose the cross section of the boron nitride particles, which is used as a measurement sample.
• the measurement sample is observed using a SEM at a magnification of 1000 times to obtain a bmp format image that allows confirmation of the entire cross section of one boron nitride particle.
• the image is imported into image processing software "imageJ", one boron nitride particle in the image is focused on, and a border is drawn along the outer edge of the focused boron nitride particle.
• imageJ image processing software
• the image is trimmed into a rectangle circumscribing the edged area, and the area outside the edged area (the area where the boron nitride particles of interest are not present) is masked.
• Filter processing is performed using a median filter (1 pixel), and binarization processing is performed using the Otsu method on the region consisting of boron nitride particles and the other region (resin region).
• filter processing is performed using a Maximum filter (1 pixel)
• Fill holes processing is performed, and the outline of the boron nitride particles is extracted.
• the extracted contour is applied to the binarized image, and the area outside the contour is masked to obtain an image for analysis.
• the image for analysis is imported into the image processing software "OpenCV" (language: Python), and from the image for analysis, the area made of boron nitride in the cross section of the boron nitride particle and the area of each of the multiple resin regions (voids) in the cross section of the boron nitride particle are determined. can be measured.
• the equivalent circular radius of each of the plurality of resin regions (voids) can be calculated from the area of each of the plurality of resin regions (voids).
• the maximum length of the boron nitride particles may be, for example, 20 ⁇ m or more, 30 ⁇ m or more, or 40 ⁇ m or more, and 120 ⁇ m or less, 100 ⁇ m or less, or 80 ⁇ m or less.
• the maximum length of a boron nitride particle means the maximum length of the straight-line distance between any two points on one boron nitride particle when the boron nitride particle is observed with a SEM.
• the maximum length may be measured by importing the SEM image into image analysis software (for example, "Mac-view" manufactured by Mountec Co., Ltd.).
• the boron nitride particles may consist essentially of boron nitride. That the boron nitride particles are substantially composed only of boron nitride can be confirmed by detecting only a peak derived from boron nitride in X-ray diffraction measurement.
• the novel boron nitride particles as described above have a larger proportion of small voids among the plurality of voids within the particles compared to conventional boron nitride particles. Further, in another embodiment, the novel boron nitride particles described above have a smaller overall proportion of voids within the particles than conventional boron nitride particles. Therefore, these novel boron nitride particles can exhibit higher thermal conductivity than conventional boron nitride particles when mixed with a resin and used as a thermally conductive material, for example.
• the boron nitride particles described above can be used for various purposes as boron nitride powder, which is an aggregate thereof. That is, another embodiment of the present invention is a boron nitride powder that is an aggregate of the above boron nitride particles.
• the average particle size of the boron nitride powder may be, for example, 20 ⁇ m or more, 30 ⁇ m or more, or 40 ⁇ m or more, and 120 ⁇ m or less, 100 ⁇ m or less, or 80 ⁇ m or less.
• the average particle size of boron nitride powder means the particle size (D50) at which the volume cumulative particle size distribution is 50%, and can be measured by a laser diffraction scattering method.
• the boron nitride particles include, for example, a step (nitriding step) of obtaining boron carbonitride particles by nitriding boron carbide particles while hot isostatic pressing (also called “hot isostatic pressing"); It can be manufactured by a method comprising a step of decarburizing boron carbonitride particles to obtain boron nitride particles (decarburization step). That is, another embodiment of the present invention is a method for manufacturing such boron nitride particles.
• Boron carbide particles can be produced, for example, by a known production method. For example, there is a method in which boric acid and acetylene black are mixed and then heated in an inert gas atmosphere at 1800 to 2400° C. for 1 to 10 hours to obtain bulk boron carbide particles.
• the bulk boron carbide particles obtained by this method may be subjected to pulverization, sieving, washing, impurity removal, drying, etc. as appropriate.
• the average particle diameter of the boron carbide particles may be, for example, 5 ⁇ m or more, 10 ⁇ m or more, or 15 ⁇ m or more, and 80 ⁇ m or less, 60 ⁇ m or less, or 40 ⁇ m or less.
• the average particle diameter of boron carbide particles means the particle diameter (D50) at which the volume cumulative particle size distribution is 50%, and can be measured by a laser diffraction scattering method.
• boron carbide particles are nitrided to obtain boron carbonitride particles by heating the container filled with boron carbide particles under hot isostatic pressure in an atmosphere that allows the nitriding reaction to proceed.
• the container may be, for example, a carbon crucible.
• the hot isostatic pressing can be performed using, for example, a hot isostatic pressing device (for example, manufactured by Kobe Steel, Ltd.).
• the atmosphere in which the nitriding reaction proceeds in the nitriding step may be a nitriding gas atmosphere that nitrides boron carbide particles.
• the nitriding gas may be nitrogen gas, ammonia gas, etc. Nitrogen gas may be used from the viewpoint of ease of nitriding boron carbide particles and from the viewpoint of cost.
• the nitriding gas may be used alone or in combination of two or more, and the proportion of nitrogen gas in the nitriding gas may be 95% by volume or more, 99% by volume or more, or 99.9% by volume or more.
• the pressure in the nitriding step may be 50 MPa or more, 70 MPa or more, or 100 MPa or more.
• the pressure in the nitriding step may be 200 MPa or less or 150 MPa or less.
• the heating temperature in the nitriding step may be 1600° C. or higher or 1700° C. or higher from the viewpoint of sufficiently nitriding the boron carbide particles.
• the heating temperature in the nitriding step may be 2200°C or lower or 2000°C or lower.
• the time for pressurizing and heating in the nitriding step may be 3 hours or more, 5 hours or more, or 8 hours or more from the viewpoint of sufficiently nitriding the boron carbide particles.
• the time for pressurizing and heating in the nitriding step may be 30 hours or less, 20 hours or less, or 10 hours or less.
• the boron carbonitride particles are decarburized by heating a mixture containing the boron carbonitride particles obtained in the nitriding step and a boron source in a container.
• the container may be, for example, a boron nitride crucible.
• Boron sources include boric acid, boron oxide, or mixtures thereof.
• the mixture may further contain other additives used in the art, if necessary.
• the mixing ratio of boron carbonitride particles and boron source is selected as appropriate.
• the proportion of boric acid or boron oxide may be, for example, 50 parts by mass or more or 80 parts by mass or more, and 300 parts by mass or less, based on 100 parts by mass of boron carbonitride. Or it may be 250 parts by mass or less.
• the atmosphere in the decarburization process may be a normal pressure (atmospheric pressure) atmosphere or a pressurized atmosphere.
• the pressure in the decarburization step may be, for example, 0.5 MPa or less or 0.3 MPa or less, and may be 0.01 MPa or more or 0.03 MPa or more.
• the temperature is raised to a predetermined temperature (a temperature at which decarburization can start), and then the temperature is further raised to a holding temperature at the predetermined temperature.
• the predetermined temperature temperature at which decarburization can start
• the rate of temperature increase from a predetermined temperature (temperature at which decarburization can be started) to the holding temperature may be, for example, 5° C./min or less, 4° C./min or less, 3° C./min or less, or 2° C./min or less.
• the holding temperature may be 1800° C. or higher or 2000° C. or higher from the viewpoint of facilitating good particle growth.
• the holding temperature may be 2200°C or less or 2100°C or less.
• the holding time at the holding temperature may be, for example, 0.5 hours or more, 1 hour or more, 3 hours or more, or 5 hours or more, from the viewpoint of facilitating particle growth.
• the holding time at the holding temperature may be, for example, 40 hours or less, 30 hours or less, or 20 hours or less.
• the boron nitride particles obtained as described above may be classified using a sieve (classification step) so as to obtain boron nitride particles having a desired particle size.
• boron nitride particles described above are suitable for use in, for example, heat dissipation members.
• boron nitride particles are used, for example, as a resin composition mixed with a resin. That is, another embodiment of the present invention is a resin composition containing a resin and the boron nitride particles described above.
• the content of the boron nitride particles mentioned above is 50% by volume or more and 55% by volume based on the total volume of the resin composition, from the viewpoint of improving the thermal conductivity of the resin composition and easily obtaining excellent heat dissipation performance.
• the content may be 60% by volume or more, 65% by volume or more, or 70% by volume or more.
• the content of boron nitride powder is 85% by volume or less, 80% by volume or less, or It may be 75% by volume or less.
• the resin examples include epoxy resin, silicone resin, silicone rubber, acrylic resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyimide, polyamideimide, polyetherimide, polybutylene terephthalate, polyethylene terephthalate, Polyphenylene ether, polyphenylene sulfide, fully aromatic polyester, polysulfone, liquid crystal polymer, polyether sulfone, polycarbonate, maleimide modified resin, ABS (acrylonitrile-butadiene-styrene) resin, AAS (acrylonitrile-acrylic rubber/styrene) resin, and AES ( Examples include acrylonitrile, ethylene, propylene, diene rubber (styrene) resin.
• the content of the resin may be 15% by volume or more, 20% by volume or more, or 25% by volume or more, and 50% by volume or less, 45% by volume or less, 40% by volume or less, based on the total volume of the resin composition. , 35% by volume or less, or 30% by volume or less.
• the resin composition may further contain a curing agent for curing the resin.
• the curing agent is appropriately selected depending on the type of resin.
• examples of the curing agent include phenol novolac compounds, acid anhydrides, amino compounds, and imidazole compounds.
• the content of the curing agent may be, for example, 0.5 parts by mass or more or 1.0 parts by mass or more, and 15 parts by mass or less or 10 parts by mass or less, based on 100 parts by mass of the resin.
• the resin composition may further contain other components.
• Other components may include a curing accelerator (curing catalyst), a coupling agent, a wetting and dispersing agent, a surface conditioner, and the like.
• curing accelerators examples include phosphorus curing accelerators such as tetraphenylphosphonium tetraphenylborate and triphenyl phosphate, imidazole curing accelerators such as 2-phenyl-4,5-dihydroxymethylimidazole, and trifluorocarbon curing accelerators.
• phosphorus curing accelerators such as tetraphenylphosphonium tetraphenylborate and triphenyl phosphate
• imidazole curing accelerators such as 2-phenyl-4,5-dihydroxymethylimidazole
• trifluorocarbon curing accelerators examples include amine curing accelerators such as boron monoethylamine.
• Examples of the coupling agent include silane coupling agents, titanate coupling agents, and aluminate coupling agents.
• Chemical bonding groups contained in these coupling agents include vinyl groups, epoxy groups, amino groups, methacrylic groups, mercapto groups, and the like.
• wetting and dispersing agents include phosphate ester salts, carboxylic esters, polyesters, acrylic copolymers, block copolymers, and the like.
• surface conditioners examples include acrylic surface conditioners, silicone surface conditioners, vinyl surface conditioners, fluorine surface conditioners, and the like.
• Example 1 Boron carbide particles with an average particle diameter (D50) of 26 ⁇ m were filled in a carbon crucible, and heated at 1750°C in a nitrogen gas atmosphere using a hot isostatic pressurizer (manufactured by Kobe Steel, Model 02-SYSTEM15X). , 196 MPa for 1.5 hours by HIP method to nitride the boron carbide particles to obtain boron carbonitride particles (B 4 CN 4 ). After 100 parts by mass of the obtained boron carbonitride particles and 150 parts by mass of boric acid were mixed using a Henschel mixer, the mixture was filled into a boron nitride crucible and heated using a resistance heating furnace at normal pressure in a nitrogen gas atmosphere.
• D50 average particle diameter
• Coarse particles were obtained by heating at a holding temperature of 2000° C. and 0.03 MPa for a holding time of 5 hours. After crushing the coarse particles in a mortar for 10 minutes, they were classified using a nylon sieve with a mesh size of 175 ⁇ m. As a result, a particle aggregate (powder) was obtained.
• Example 2 A particle aggregate (powder) was obtained in the same manner as in Example 1, except that the temperature at which the boron carbide particles were nitrided was changed to 1800°C.
• Example 3 A particle aggregate (powder) was obtained in the same manner as in Example 2, except that the amount of boric acid was changed to 100 parts by mass.
• Example 1 The same as in Example 1 except that boron carbide particles were nitrided by heating and pressurizing in a nitrogen gas atmosphere at 2000° C. and 0.85 MPa for 25 hours using a resistance heating furnace to obtain boron carbonitride particles. An aggregate (powder) of boron nitride particles was obtained.
• the image was imported into image processing software "imageJ", one boron nitride particle in the image was focused on, and a border was drawn along the outer edge of the focused boron nitride particle.
• the image was trimmed into a rectangle circumscribing the edged area, and the area outside the edged area (the area where the boron nitride particles of interest were not present) was masked.
• filter processing was performed using a median filter (1 pixel)
• a binarization process was performed using the Otsu method on the region made of boron nitride particles and the other region (resin region).
• the extracted contour was applied to the binarized image, the area outside the contour was masked, and an image for analysis was obtained.
• the image for analysis is imported into the image processing software "OpenCV" (language Python), and from the image for analysis, the area made of boron nitride in the cross section of the boron nitride particle and the area of each of the multiple resin regions (voids) in the cross section of the boron nitride particle are determined. was measured, and the circle equivalent radius of each of the plurality of resin regions (voids) was calculated from the area of each of the plurality of resin regions (voids).
• the area ratio of the plurality of voids to the total area of the region made of boron nitride and the plurality of voids, the average equivalent circle radius, and the maximum equivalent circle radius were calculated. The calculation results are shown in Table 1.
• a SEM image of the cross section of the boron nitride particles of Example 1 is shown in FIG.
• FIG. 3 a SEM image of the cross section of the boron nitride particles of Comparative Example 1 is shown in FIG. 3, and the cross section of the boron nitride particles of Example 1 is binarized.
• FIG. 4 An image is shown in FIG. 4, and a binarized image of the cross section of the boron nitride particles of Comparative Example 1 is shown in FIG.
• press heating and pressing was performed for 60 minutes at a temperature of 150° C. and a pressure of 160 kg/cm 2 to produce a 0.5 mm sheet-like heat dissipating material.
• a measurement sample with a size of 10 mm x 10 mm was cut out from the prepared heat dissipation material, and the thermal diffusivity A (m 2 /sec) of the measurement sample was measured using a laser flash method using a xenon flash analyzer (manufactured by NETZSCH, LFA447NanoFlash). was measured. Further, the specific gravity B (kg/m 3 ) of the measurement sample was measured by the Archimedes method.
• the thermal conductivity of the heat dissipation material produced using the boron nitride particles obtained in Example 2 was 22 W/(m ⁇ K), and that of the heat dissipation material produced using the boron nitride particles obtained in Example 3.
• the thermal conductivity was 24 W/(m ⁇ K), and the thermal conductivity of the heat dissipating material produced using the boron nitride particles obtained in Comparative Example 1 was 17 W/(m ⁇ K).

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• 2023
  • 2023-08-22 WO PCT/JP2023/030199 patent/WO2024048376A1/ja not_active Ceased
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