WO2023276522A1 - Silicon carbide particle - Google Patents

Silicon carbide particle Download PDF

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Publication number
WO2023276522A1
WO2023276522A1 PCT/JP2022/021987 JP2022021987W WO2023276522A1 WO 2023276522 A1 WO2023276522 A1 WO 2023276522A1 JP 2022021987 W JP2022021987 W JP 2022021987W WO 2023276522 A1 WO2023276522 A1 WO 2023276522A1
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granules
silicon carbide
particles
carbide particles
present
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PCT/JP2022/021987
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French (fr)
Japanese (ja)
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祐司 増田
尚幹 牛田
拓弥 諌山
未那 佐藤
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株式会社フジミインコーポレーテッド
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Publication of WO2023276522A1 publication Critical patent/WO2023276522A1/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
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/90—Carbides
    • C01B32/914—Carbides of single elements
    • C01B32/956—Silicon carbide
    • 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
    • C04B35/56—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 carbides or oxycarbides
    • C04B35/565—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 carbides or oxycarbides based on silicon carbide

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  • the present invention relates to silicon carbide particles.
  • Silicon carbide is used in a wide variety of applications, such as abrasives, heat dissipating fillers, fillers for resins, coating materials, composite materials, and sintering materials.
  • a spherical shape is preferable from the viewpoint of filling properties, workability, and homogeneity in heat-dissipating fillers, fillers, and coating materials that are used by being mixed with a resin composition.
  • applications such as sintered materials and heat-dissipating fillers, there are many cases where close-packing is used to increase the filling amount, and it is preferable that the shapes are uniform.
  • a spherical ⁇ -type silicon carbide and a method for producing the same are disclosed, for example, in Patent Document 1.
  • a dispersant is used during granulation.
  • the primary particles adjusted to a dispersed state by the dispersant move to the surface of the granules during the drying process of the droplets, and the surface of the granules tends to become buried, resulting in a decrease in the circularity of the granules.
  • the present invention has been made in view of the above problems, and an object of the present invention is to provide silicon carbide particles with a high degree of circularity.
  • the value obtained by dividing the area value calculated by image analysis of the granule by the circle-equivalent area value calculated from the maximum diameter of the granule is 80% or more in terms of percentage.
  • the crystal system is ⁇ -type silicon carbide particles.
  • a method for producing silicon carbide particles according to an aspect of the present invention includes adding a pH adjuster to a slurry containing primary particles of silicon carbide and a solvent to adjust the pH of the slurry to the isoelectric point of the silicon carbide. and spraying and drying the pH-adjusted slurry to granulate the secondary particles of silicon carbide.
  • a composition according to an aspect of the present invention is a composition containing the above silicon carbide particles in a base material.
  • silicon carbide particles with a high degree of circularity can be provided.
  • FIG. 1 is a diagram for explaining the sphericity according to this embodiment.
  • FIG. 2 is a diagram for explaining the aspect ratio.
  • FIG. 3 is a flow chart showing a method for producing a composition containing silicon carbide particles (granules) according to an embodiment of the present invention in order of steps.
  • FIG. 4 is a diagram illustrating equivalent circle diameters of granules according to the present embodiment.
  • FIG. 5 shows SEM images of granules obtained in Examples 1 to 7 of the present invention.
  • the silicon carbide (SiC) particles according to the embodiment of the present invention are obtained by dividing the area value calculated by image analysis of the granules by the equivalent circle area value calculated from the maximum diameter of the granules. is 80% or more, and the crystal system is ⁇ -type (mainly hexagonal) silicon carbide particles.
  • a value obtained by dividing an area value calculated by image analysis of a granule by a circle-equivalent area value calculated from the maximum diameter of the granule is referred to as "sphericity”.
  • the sphericity is an index related to circularity discovered by the present inventors.
  • FIG. 1 is a diagram for explaining the sphericity according to this embodiment.
  • FIG. 2 is a diagram for explaining the aspect ratio.
  • Patent Document 1 described above evaluates the degree of circularity of particles based on the "average aspect ratio (minor axis/major axis)". As shown in FIG. 2, portions other than the short diameter and long diameter of granules are not reflected in the aspect ratio (short diameter/long diameter). Therefore, the aspect ratio may not be sufficient to evaluate the circularity of granules.
  • the "sphericity” found by the present inventors is obtained from the maximum diameter of granules obtained by image analysis, and a circle equivalent to the maximum diameter (perfect circle ), and the degree of circularity is evaluated from the ratio between the area value of the granule obtained by image analysis and the area value of the circle corresponding to the maximum diameter.
  • the "sphericity” can more accurately evaluate whether or not the granules are nearly circular (true spheres). The closer the "sphericity” is to 1, that is, the closer to 100% in terms of percentage, the closer the granules are to round (perfect sphere).
  • the silicon carbide particles according to the present embodiment can be used as abrasives, heat dissipating fillers, fillers for resins (for example, plastics, curable resins, rubbers, etc.), coating materials, composite materials, sintering materials, etc. It can be used for a wide variety of applications.
  • resins for example, plastics, curable resins, rubbers, etc.
  • coating materials for example, composite materials, sintering materials, etc. It can be used for a wide variety of applications.
  • the silicon carbide particles according to the present embodiment can be mixed as a filler (filler) with a resin such as a plastic, a curable resin, or a rubber to form a resin composition.
  • a resin such as a plastic, a curable resin, or a rubber
  • this resin composition contains the silicon carbide particles and resin according to the present embodiment, it may be composed only of the silicon carbide particles and the resin. It may be configured by blending other components.
  • this resin composition may be molded and used as, for example, a heat dissipation material.
  • the heat dissipating material may be composed of only the molded body of the resin composition containing the silicon carbide particles according to the present embodiment, or may be composed of the molded body and other members.
  • the shape of the molded body and the molding method are not particularly limited.
  • the silicon carbide particles according to the present embodiment have a sphericity of 80% or more, as described above. As the sphericity approaches 100%, the shape of the silicon carbide particles (granules) approaches a true sphere, and the granules are uniform in spherical shape, so that the effect in each application increases.
  • the granules have a shape close to a true sphere, and the shapes are aligned in a spherical shape, thereby making it possible to improve the fillability (high filling). .
  • interaction between particles can be reduced, and thickening can be suppressed (improvement of workability) when blended with resin such as plastic, curable resin, and rubber to form a resin composition.
  • the shape of the granules is close to a true sphere, and the shape of the granules is uniform. (Improvement of workability) becomes possible.
  • the shape of the granules is close to a true sphere, and the shape of the granules is uniform, thereby suppressing thickening (improving processability) and isotropic properties. (Homogeneity) can be improved.
  • Composite materials containing silicon carbide particles according to the present embodiment for example, CMC (Ceramics matrix composites), MMC (Metal matrix composites), etc., have silicon carbide particles (granules) in a shape close to a true sphere, and the shape of the granules is Suppressing thickening (improving workability) and improving isotropy (homogeneity) can be achieved by aligning the particles in a spherical shape.
  • the shape of the silicon carbide particles is close to a true sphere, and the shape of the granules is uniform in a spherical shape, thereby improving the fillability (high filling ) becomes possible.
  • All of the above-described heat dissipation material, resin composition, coating material, composite material, and sintered material are examples of the "composition" of the present invention.
  • the silicon carbide particles and resin composition according to the present embodiment will be described in more detail below.
  • the silicon carbide particles according to the present embodiment are granules granulated from primary particles of silicon carbide. You may paraphrase a granule as a secondary particle.
  • the silicon carbide particles according to the present embodiment may be granules before sintering or may be granules after sintering. Sintering may also be called firing.
  • the silicon carbide particles (granules) according to the present embodiment are granulated from silicon carbide (primary particles) having an ⁇ -type crystal system.
  • the average particle diameter D50 of the primary particles is 0.03 ⁇ m or more and 5.00 ⁇ m or less, preferably 0.05 ⁇ m or more and 3.00 ⁇ m or less, and more preferably 0.08 ⁇ m or more and 1.50 ⁇ m or less.
  • the average particle size D50 of the primary particles means a particle size at which the cumulative frequency from the small particle size side is 50% in the volume-based cumulative particle size distribution of the powder in which the primary particles are collected. In this specification, the average particle diameter D50 of primary particles is also simply referred to as "primary particle diameter".
  • the silicon carbide particles (granules) according to the present embodiment are produced by adding a solvent (e.g., water) to a powder containing primary particles to generate a slurry, and supplying this slurry to a spray device such as a spray dryer. It is formed by granulating.
  • the solid content concentration of the slurry is 5% by mass or more and 50% by mass or less, preferably 7.5% by mass or more and 45% by mass or less, more preferably 10% by mass or more and 40% by mass or less.
  • pH value In the present embodiment, no dispersant or organic polymer (eg, binder) is added to the slurry.
  • a pH adjuster is added to adjust the pH of the slurry to the isoelectric point (aggregation range) of silicon carbide.
  • the isoelectric point of silicon carbide is around pH 3.0 to 4.0.
  • the pH value of the slurry is adjusted to 1.0 or more and 6.0 or less, preferably 3.0 or more and 5.0 or less, more preferably near the isoelectric point.
  • the surface potential (for example, zeta potential) of the primary particles of silicon carbide becomes almost zero, and the electrical forces (attraction and repulsion) acting between the primary particles are As they become smaller, the primary particles agglomerate in the slurry.
  • granulation is performed near the isoelectric point (aggregation range) of silicon carbide by adjusting the pH of the slurry without using a dispersant or an organic polymer.
  • the rearrangement of the primary particles is less likely to occur, and the granules are dried while maintaining the shape immediately after granulation, so that solid and spherical granules can be obtained. It is possible to increase the circularity of the granules.
  • degreasing is not necessary, and it is possible to reduce environmental and process loads and avoid quality defects due to residual carbon.
  • the pH adjuster added to the slurry may be either an acid or an alkali.
  • acids as pH adjusters include inorganic acids and organic acids such as carboxylic acids and organic sulfuric acids.
  • inorganic acids include sulfuric acid, nitric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid.
  • the base as the pH adjuster include alkali metal hydroxides or salts thereof, alkaline earth metal hydroxides or salts thereof, quaternary ammonium hydroxides or salts thereof, ammonia, amines, and the like. be done.
  • alkali metals include potassium and sodium.
  • alkaline earth metals include calcium and strontium.
  • specific examples of salts include carbonates, hydrogen carbonates, sulfates, acetates, and the like.
  • specific examples of quaternary ammonium include tetramethylammonium, tetraethylammonium, tetrabutylammonium and the like.
  • the sphericity of the silicon carbide particles (granules) according to the present embodiment is, as described above, 80% or more and 100% or less, preferably 85% or more and 100% or less, and more preferably. is 90% or more and 100% or less. As the sphericity approaches 100%, the shape of the silicon carbide particles (granules) approaches a true sphere, and the granules are uniform in spherical shape, so that the effect in each application increases.
  • the sphericity is the average value of a predetermined number of granules.
  • the predetermined number that is, the number of particles for calculating the sphericity of each granule, is suitably 100 or more from the viewpoint of improving measurement accuracy and reproducibility.
  • Standard deviation of sphericity The standard deviation of sphericity of the silicon carbide particles (granules) is 0.02 or more and 0.05 or less, preferably 0.02 or more and 0.04 or less. The smaller the standard deviation of the sphericity, the more uniform the shape of the granules and the smaller the variation in the effect. It is appropriate that this standard deviation is the standard deviation of a population of a predetermined number of granules when the sphericity of the granules is measured.
  • Silicon carbide particles (granules) are secondary particles granulated from primary particles of silicon carbide.
  • the average particle diameter D50 of the secondary particles is 0.5 ⁇ m or more and 100 ⁇ m or less, preferably 2 ⁇ m or more and 60 ⁇ m or less, and more preferably 4 ⁇ m or more and 50 ⁇ m or less.
  • the average particle diameter D50 of the secondary particles means the particle diameter at which the cumulative frequency from the small particle diameter side is 50% in the volume-based cumulative particle size distribution of the powder in which the secondary particles are collected.
  • the average particle diameter D50 of the secondary particles is also simply referred to as "secondary particle diameter".
  • the secondary particle diameter is indicated by the equivalent circle diameter of granules calculated from image analysis, as described in Examples below.
  • a primary particle diameter is a value measured by a laser diffraction scattering method.
  • Ratio of secondary particle size to primary particle size is 5 or more and 300 or less, preferably 10 or more and 200 or less, more preferably 15 or more and 150 or less .
  • the silicon carbide particles (granules) according to the present embodiment are blended as a filler (filler) with resins such as plastics, curable resins, and rubbers (an example of the "base material” of the present invention). It can be a resin composition.
  • FIG. 3 is a flowchart showing, in order of steps, a method for producing a composition containing silicon carbide particles (granules) according to an embodiment of the present invention.
  • powder containing primary particles of silicon carbide whose crystal system is ⁇ -type is produced, and this powder and a solvent (for example, water) are mixed to produce a slurry (step ST1 in FIG. 3).
  • a pH adjuster is added to the slurry to adjust the pH of the slurry to near the isoelectric point (aggregation range) of silicon carbide (step ST2 in FIG. 3). Note that in this embodiment, no dispersant or organic polymer (eg, binder) is added to the slurry.
  • step ST3 the slurry adjusted to near the isoelectric point is sprayed into a drying chamber using a spray dryer and dried to produce silicon carbide particles (granules) having an ⁇ -type crystal system (step ST3 in FIG. 3). ).
  • step ST3 no dispersing agent is used, and granulation is performed in the aggregation region of silicon carbide by adjusting the pH, so rearrangement of the primary particles is less likely to occur. Since the granules are dried while retaining the shape immediately after granulation, solid and spherical granules are obtained.
  • the spraying method of the spray dryer includes a fixed spraying method using a pressurized two-fluid nozzle, a spraying method using a rotating disk, and the like. Either method may be adopted, but granules with a smaller diameter can be obtained by using the fixed spray method.
  • the granules formed by spraying and drying with a spray dryer are collected in a collection vessel, cyclone, bag filter, etc. provided on the downstream side.
  • a sintering aid may be added in advance to the slurry to be sprayed.
  • the sintering of the granules can be promoted in the sintering step of the granules described below, and the interior of the granules can be made more dense.
  • step ST4 of FIG. 3 the granules obtained in step ST3 are sintered.
  • the granules obtained in step ST3 are sintered in an inert gas atmosphere such as argon (Ar).
  • the sintering temperature is, for example, 1800° C. or higher and 2000° C. or lower. This gives sintered granules.
  • the sintering atmosphere is nitrogen (N 2 )
  • the granules may be nitrided. Therefore, in the present embodiment, the sintering atmosphere is preferably Ar.
  • steps ST1 to ST3 or step ST1 to step ST4 including the sintering step are the steps for manufacturing silicon carbide particles (granules) according to the present embodiment.
  • step ST5 of FIG. 3 the sintered granules are mixed with the base material to produce a composition (step ST6 of FIG. 3).
  • a composition such as a plastic, a curable resin, or a rubber to form a resin composition.
  • Example 1 Primary particles of silicon carbide and water were mixed to obtain slurry as a raw material. The solid content concentration of the slurry is 16.1% by mass. Silicon carbide powder with a particle size of #40000 (model number: GC#40000) was used as the primary particles of silicon carbide. A primary particle diameter D50 of silicon carbide is 0.25 ⁇ m.
  • No dispersant or organic polymer was added to the slurry.
  • a stirrer was used to mix the primary particles of silicon carbide, the solvent (water), and the pH adjuster. The rotational speed of stirring by the stirrer was 6000 rpm. The stirring time was 10 minutes.
  • the slurry stirred by the stirrer was supplied to an atomization-type spray dryer using a rotating disk to granulate, thereby obtaining granules (unsintered, secondary particles) of silicon carbide.
  • Example 2 In Example 2, the granules (secondary particles) were formed smaller than in Example 1. Specifically, a stationary spray system was used. (Example 3) In Example 3, silicon carbide powder with a particle size of #8000 (model number: GC#8000) was used as the primary particles of silicon carbide. A primary particle diameter D50 of silicon carbide is 1.2 ⁇ m. Granules (unsintered, secondary particles) of Example 3 were obtained in the same manner as in Example 1 except for this.
  • Example 4 The unsintered granules obtained in Example 2 were sintered using a sintering furnace to obtain granules (sintered, secondary particles) of Example 4.
  • the operating conditions of the sintering furnace are that the atmosphere in the furnace is argon (Ar), the sintering temperature is 1800° C. or more and 2000° C. or less, and the sintering time is 4 hours.
  • Reference example 1 In Reference Example 1, the primary particle diameter D50 of silicon carbide was set to 0.35 ⁇ m. Silicon carbide granules (unsintered, secondary particles) were obtained in the same manner as in Example 1 except for this. The pH of the slurry was around 4.0 and no dispersant was added. Note that Reference Example 1 has a smaller number of samples (n) than Examples 1 to 4, and n is less than 100. For this reason, it is used as a reference example. (Reference example 2) In Reference Example 2, the pH of the slurry was adjusted to around 9.0, and granulation was carried out in the dispersion area. Silicon carbide granules (unsintered, secondary particles) were obtained in the same manner as in Reference Example 1 except for this.
  • FIG. 4 is a diagram illustrating equivalent circle diameters of granules.
  • a perfect circle equivalent circle of granules
  • the diameter of the assumed perfect circle equivalent circle diameter of granules
  • the ratio of secondary particle size/primary particle size was calculated. The calculation results are shown in Table 1 below.
  • the primary particle size is the primary particle size D50 ( ⁇ m) shown in Table 1.
  • the secondary particle size is the equivalent circle diameter ( ⁇ m) of the granules shown in Table 1 below, and is the average value of the equivalent circle diameters of 100 arbitrary granules in each example.
  • Table 1 below shows the standard deviation of a population of 100 arbitrary granules when the equivalent circle diameters of the granules were measured in Examples 1 to 4.
  • (5) Aspect ratio The short diameter and long diameter of the granules obtained in Examples 1 to 4 were measured to calculate the aspect ratio (short diameter/long diameter). The calculation results are shown in Table 1 below.
  • the aspect ratio was the average value of the aspect ratios of 100 granules when the equivalent circle diameter of the granules was measured.
  • the data used to calculate the sphericity of the granules obtained in Examples 1 to 4 are shown in Table 1 below.
  • the data on which the calculation is based is the granule area ( ⁇ m 2 ) obtained by image analysis, the maximum granule diameter ( ⁇ m) obtained by image analysis, and the circular area equivalent to the maximum granule diameter calculated from the maximum granule diameter ( ⁇ m 2 ). be.
  • the granule area, the maximum granule diameter and the circular area equivalent to the maximum diameter were all average values of the granule area, the maximum granule diameter and the circular area equivalent to the maximum diameter of 100 granules when the equivalent circle diameter of the granules was measured.
  • FIG. 5 shows SEM images of granules obtained in Examples 1 to 4 and Reference Examples 1 and 2 of the present invention. As shown in FIG. 5, it was visually confirmed that the granules obtained in Examples 1 to 4 and Reference Example 1 had a high degree of circularity. Further, as shown in Table 1, the sphericity of the granules obtained in Examples 1 to 4 is 0.83 or more and 0.95 or less (83% or more and 95% or less in percentage). The standard deviation was 0.02 or more and 0.04 or less.
  • the granules obtained in Reference Example 2 have concave surfaces and are clearly low in circularity even visually.
  • granulation was carried out in the dispersed region, so it is considered that the surface of the granules was buried during the drying process of the droplets.
  • granulation was carried out in the dispersed region, as in the SEM image of Reference Example 2, granules with buried surfaces were found here and there.
  • the silicon carbide particles (granules) of this embodiment do not contain a dispersant or an organic polymer, it was confirmed that the amount of variation in sphericity was small before and after sintering.

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Abstract

Provided are silicon carbide particles that exhibit a high circularity. In α-type crystal-system silicon carbide particles according to the present invention, the value obtained by dividing an area value calculated through image analysis of granules thereof by an equivalent circle area value calculated from the maximum diameter of the granules is 80% or more as expressed in percentage.

Description

炭化珪素粒子silicon carbide particles
　本発明は、炭化珪素粒子に関する。 The present invention relates to silicon carbide particles.
　炭化珪素は、研磨材、放熱フィラー、樹脂への充填材、コーティング材、複合材、焼結材、など多岐にわたる用途で使用される。特に、樹脂組成へ混合して使用される、放熱フィラー、充填材、コーティング材においては、充填性・加工性・均質性の観点より球形状が好ましい。また、焼結材や放熱フィラーの用途においては、最密充填により充填量を高めて使用する事例が多く、形状がそろっているものが好ましい。球状α型炭化珪素及びその製造方法として、例えば特許文献１に開示されたものがある。 Silicon carbide is used in a wide variety of applications, such as abrasives, heat dissipating fillers, fillers for resins, coating materials, composite materials, and sintering materials. In particular, a spherical shape is preferable from the viewpoint of filling properties, workability, and homogeneity in heat-dissipating fillers, fillers, and coating materials that are used by being mixed with a resin composition. In addition, in applications such as sintered materials and heat-dissipating fillers, there are many cases where close-packing is used to increase the filling amount, and it is preferable that the shapes are uniform. A spherical α-type silicon carbide and a method for producing the same are disclosed, for example, in Patent Document 1.
特開２０１３－９５６３７号公報JP 2013-95637 A
　特許文献１に開示された球状α型炭化珪素の製造方法によれば、造粒時に分散剤を使用している。分散剤により分散状態に調整された一次粒子は、液滴の乾燥過程で顆粒表面に移動し、顆粒表面が埋没するなど、顆粒の円形度が低くなり易い。 According to the method for producing spherical α-silicon carbide disclosed in Patent Document 1, a dispersant is used during granulation. The primary particles adjusted to a dispersed state by the dispersant move to the surface of the granules during the drying process of the droplets, and the surface of the granules tends to become buried, resulting in a decrease in the circularity of the granules.
　本発明は、上記課題を鑑みてなされたものであり、円形度が高い炭化珪素粒子を提供することを目的とする。 The present invention has been made in view of the above problems, and an object of the present invention is to provide silicon carbide particles with a high degree of circularity.
　本発明の一態様に係る炭化珪素粒子は、顆粒の画像解析より算出される面積値を、前記顆粒の最大径から算出される円相当面積値で除算した値が、百分率で８０％以上である、結晶系がα型の炭化珪素粒子である。
　本発明の一態様に係る炭化珪素粒子の製造方法は、炭化珪素の一次粒子と溶媒とを含むスラリーにｐＨ調整剤を添加して、前記スラリーのｐＨを前記炭化珪素の等電点に調整する工程と、前記ｐＨが調整された前記スラリーを噴霧し乾燥させて、前記炭化珪素の二次粒子を造粒する工程とを含む、結晶系がα型の炭化珪素粒子の製造方法である。
　本発明の一態様に係る組成物は、上記の炭化珪素粒子を母材に含有する組成物である。 In the silicon carbide particles according to one aspect of the present invention, the value obtained by dividing the area value calculated by image analysis of the granule by the circle-equivalent area value calculated from the maximum diameter of the granule is 80% or more in terms of percentage. , the crystal system is α-type silicon carbide particles.
A method for producing silicon carbide particles according to an aspect of the present invention includes adding a pH adjuster to a slurry containing primary particles of silicon carbide and a solvent to adjust the pH of the slurry to the isoelectric point of the silicon carbide. and spraying and drying the pH-adjusted slurry to granulate the secondary particles of silicon carbide.
A composition according to an aspect of the present invention is a composition containing the above silicon carbide particles in a base material.
　本発明によれば、円形度が高い炭化珪素粒子を提供することができる。 According to the present invention, silicon carbide particles with a high degree of circularity can be provided.
図１は、本実施形態に係る真球度を説明するための図である。FIG. 1 is a diagram for explaining the sphericity according to this embodiment. 図２は、アスペクト比を説明するための図である。FIG. 2 is a diagram for explaining the aspect ratio. 図３は、本発明の実施形態に係る炭化珪素粒子（顆粒）を含む組成物の製造方法を工程順に示すフローチャートである。FIG. 3 is a flow chart showing a method for producing a composition containing silicon carbide particles (granules) according to an embodiment of the present invention in order of steps. 図４は、本実施形態に係る顆粒の円相当径を例示する図である。FIG. 4 is a diagram illustrating equivalent circle diameters of granules according to the present embodiment. 図５は、本発明の実施例１から７で得られた顆粒のＳＥＭ画像を示す図である。FIG. 5 shows SEM images of granules obtained in Examples 1 to 7 of the present invention.
　以下、本発明の実施形態について詳細に説明する。なお、以下の実施形態は、本発明の一例を示したものである。本発明は、以下の実施形態に限定されるものではない。また、以下の実施形態には種々の変更又は改良を加えることが可能であり、その様な変更又は改良を加えた形態も本発明に含まれ得る。 Hereinafter, embodiments of the present invention will be described in detail. In addition, the following embodiment shows an example of the present invention. The present invention is not limited to the following embodiments. In addition, various modifications or improvements can be added to the following embodiments, and forms with such modifications or improvements can also be included in the present invention.
　本発明の実施形態（以下、本実施形態）に係る炭化珪素（ＳｉＣ）粒子は、顆粒の画像解析より算出される面積値を、顆粒の最大径から算出される円相当面積値で除算した値が、百分率で８０％以上である、結晶系がα型（主に六方晶）の炭化珪素粒子である。
　本明細書では、「顆粒の画像解析より算出される面積値を、顆粒の最大径から算出される円相当面積値で除算した値」を「真球度」と呼称する。真球度は、本発明者が見出した、円形度に関する指標である。 The silicon carbide (SiC) particles according to the embodiment of the present invention (hereinafter referred to as the present embodiment) are obtained by dividing the area value calculated by image analysis of the granules by the equivalent circle area value calculated from the maximum diameter of the granules. is 80% or more, and the crystal system is α-type (mainly hexagonal) silicon carbide particles.
In the present specification, "a value obtained by dividing an area value calculated by image analysis of a granule by a circle-equivalent area value calculated from the maximum diameter of the granule" is referred to as "sphericity". The sphericity is an index related to circularity discovered by the present inventors.
　図１は、本実施形態に係る真球度を説明するための図である。図２は、アスペクト比を説明するための図である。例えば、上記の特許文献１は、粒子の円形度を「平均アスペクト比（短径／長径）」で評価している。図２に示すように、顆粒の短径及び長径以外の部分はアスペクト比（短径／長径）の数値に反映されない。このため、アスペクト比では、顆粒の円形度を十分に評価できない可能性がある。 FIG. 1 is a diagram for explaining the sphericity according to this embodiment. FIG. 2 is a diagram for explaining the aspect ratio. For example, Patent Document 1 described above evaluates the degree of circularity of particles based on the "average aspect ratio (minor axis/major axis)". As shown in FIG. 2, portions other than the short diameter and long diameter of granules are not reflected in the aspect ratio (short diameter/long diameter). Therefore, the aspect ratio may not be sufficient to evaluate the circularity of granules.
　これに対して、本発明者が見出した「真球度」は、図１に示すように、画像解析で得られる顆粒の最大径から、この最大径を直径とする最大径相当円（正円）を想定し、画像解析で得られる顆粒の面積値と最大径相当円の面積値との比率から、円形度を評価するものである。図２に示したアスペクト比による評価方法と比べて、「真球度」では、短径及び長径以外の部分についても、画像解析で得られる顆粒の面積値に含まれており、真球度の数値に反映される。このため、「真球度」は、顆粒が円形（真球）に近い形か否かをより正確に評価することができる。「真球度」が１に近いほど、すなわち、百分率で１００％に近いほど、顆粒は円形（真球）に近いといえる。 On the other hand, as shown in FIG. 1, the "sphericity" found by the present inventors is obtained from the maximum diameter of granules obtained by image analysis, and a circle equivalent to the maximum diameter (perfect circle ), and the degree of circularity is evaluated from the ratio between the area value of the granule obtained by image analysis and the area value of the circle corresponding to the maximum diameter. Compared to the evaluation method based on the aspect ratio shown in FIG. reflected in the numerical value. For this reason, the "sphericity" can more accurately evaluate whether or not the granules are nearly circular (true spheres). The closer the "sphericity" is to 1, that is, the closer to 100% in terms of percentage, the closer the granules are to round (perfect sphere).
　上記したように、本実施形態に係る炭化珪素粒子は、研磨剤、放熱フィラー、樹脂（例えば、プラスチック、硬化性樹脂、ゴム等）への充填材、コーティング材、複合材、焼結材、など多岐にわたる用途に使用可能である。 As described above, the silicon carbide particles according to the present embodiment can be used as abrasives, heat dissipating fillers, fillers for resins (for example, plastics, curable resins, rubbers, etc.), coating materials, composite materials, sintering materials, etc. It can be used for a wide variety of applications.
　例えば、本実施形態に係る炭化珪素粒子は、フィラー（充填剤）として、プラスチック、硬化性樹脂、ゴム等の樹脂に配合して樹脂組成物とすることができる。この樹脂組成物は、本実施形態に係る炭化珪素粒子と樹脂とを含有するが、炭化珪素粒子及び樹脂のみで構成されていてもよいし、炭化珪素粒子と樹脂に補強材、添加剤等の他の成分を配合して構成されていてもよい。 For example, the silicon carbide particles according to the present embodiment can be mixed as a filler (filler) with a resin such as a plastic, a curable resin, or a rubber to form a resin composition. Although this resin composition contains the silicon carbide particles and resin according to the present embodiment, it may be composed only of the silicon carbide particles and the resin. It may be configured by blending other components.
　また、この樹脂組成物を成形して、例えば放熱材料としてもよい。放熱材料は、本実施形態に係る炭化珪素粒子を含有する樹脂組成物の成形体のみで構成されていてもよいし、成形体と他の部材とで構成されていてもよい。成形体の形状や成形方法は特に限定されない。 Also, this resin composition may be molded and used as, for example, a heat dissipation material. The heat dissipating material may be composed of only the molded body of the resin composition containing the silicon carbide particles according to the present embodiment, or may be composed of the molded body and other members. The shape of the molded body and the molding method are not particularly limited.
　本実施形態に係る炭化珪素粒子は、上記したように、真球度が８０％以上である。真球度が１００％に近づくほど、炭化珪素粒子（顆粒）の形状は真球に近づき、顆粒の形状が球形に揃うため、各用途における効果が大きくなる。
　例えば、本実施形態に係る炭化珪素粒子（顆粒）を含有する放熱材料は、顆粒の形状が真球に近づき、形状が球形に揃うことによって、充填性を高めること（高充填）が可能となる。また、粒子間の相互作用を小さくでき、プラスチック、硬化性樹脂、ゴム等の樹脂に配合して樹脂組成物とする場合、増粘抑制（加工性の向上）が可能となる。 The silicon carbide particles according to the present embodiment have a sphericity of 80% or more, as described above. As the sphericity approaches 100%, the shape of the silicon carbide particles (granules) approaches a true sphere, and the granules are uniform in spherical shape, so that the effect in each application increases.
For example, in the heat dissipating material containing the silicon carbide particles (granules) according to the present embodiment, the granules have a shape close to a true sphere, and the shapes are aligned in a spherical shape, thereby making it possible to improve the fillability (high filling). . In addition, interaction between particles can be reduced, and thickening can be suppressed (improvement of workability) when blended with resin such as plastic, curable resin, and rubber to form a resin composition.
　本実施形態に係る炭化珪素粒子（顆粒）を含有する樹脂組成物は、顆粒の形状が真球に近づき、顆粒の形状が球形に揃うことによって、顆粒間の相互作用を小さくでき、増粘抑制（加工性の向上）が可能となる。 In the resin composition containing silicon carbide particles (granules) according to the present embodiment, the shape of the granules is close to a true sphere, and the shape of the granules is uniform. (Improvement of workability) becomes possible.
　本実施形態に係る炭化珪素粒子（顆粒）を含有するコーティング材は、顆粒の形状が真球に近づき、顆粒の形状が球形に揃うことによって、増粘抑制（加工性の向上）と等方性（均質性）の向上とが可能となる。 In the coating material containing the silicon carbide particles (granules) according to the present embodiment, the shape of the granules is close to a true sphere, and the shape of the granules is uniform, thereby suppressing thickening (improving processability) and isotropic properties. (Homogeneity) can be improved.
　本実施形態に係る炭化珪素粒子を含有する複合材、例えば、ＣＭＣ（Ｃｅｒａｍｉｃｓ　ｍａｔｒｉｘ　ｃｏｍｐｏｓｉｔｅｓ）、ＭＭＣ（Ｍｅｔａｌ　ｍａｔｒｉｘ　ｃｏｍｐｏｓｉｔｅｓ）等は、炭化珪素粒子（顆粒）の形状が真球に近づき、顆粒の形状が球形に揃うことによって、増粘抑制（加工性の向上）と等方性（均質性）の向上とが可能となる。
　また、本実施形態に係る炭化珪素粒子を含有する焼結材は、炭化珪素粒子（顆粒）の形状が真球に近づき、顆粒の形状が球形に揃うことによって、充填性を高めること（高充填）が可能となる。
　上記の放熱材料、樹脂組成物、コーティング材、複合材、焼結材は、いずれも、本発明の「組成物」の一例である。 Composite materials containing silicon carbide particles according to the present embodiment, for example, CMC (Ceramics matrix composites), MMC (Metal matrix composites), etc., have silicon carbide particles (granules) in a shape close to a true sphere, and the shape of the granules is Suppressing thickening (improving workability) and improving isotropy (homogeneity) can be achieved by aligning the particles in a spherical shape.
In addition, in the sintered material containing silicon carbide particles according to the present embodiment, the shape of the silicon carbide particles (granules) is close to a true sphere, and the shape of the granules is uniform in a spherical shape, thereby improving the fillability (high filling ) becomes possible.
All of the above-described heat dissipation material, resin composition, coating material, composite material, and sintered material are examples of the "composition" of the present invention.
　以下に、本実施形態に係る炭化珪素粒子及び樹脂組成物について、さらに詳細に説明する。本実施形態に係る炭化珪素粒子は、炭化珪素の一次粒子から造粒された顆粒である。顆粒を二次粒子と言い換えてもよい。本実施形態に係る炭化珪素粒子は、焼結前の顆粒であってもよいし、焼結後の顆粒であってもよい。焼結は、焼成と言い換えてもよい。 The silicon carbide particles and resin composition according to the present embodiment will be described in more detail below. The silicon carbide particles according to the present embodiment are granules granulated from primary particles of silicon carbide. You may paraphrase a granule as a secondary particle. The silicon carbide particles according to the present embodiment may be granules before sintering or may be granules after sintering. Sintering may also be called firing.
（一次粒子）
　本実施形態に係る炭化珪素粒子（顆粒）は、結晶系がα型の炭化珪素（一次粒子）から造粒される。一次粒子の平均粒子径Ｄ５０は、０．０３μｍ以上５．００μｍ以下であり、好ましくは０．０５μｍ以上３．００μｍ以下であり、より好ましくは０．０８μｍ以上１．５０μｍ以下である。一次粒子の平均粒子径Ｄ５０とは、一次粒子を集めた粉末の体積基準の積算粒子径分布において、小粒径側からの積算頻度が５０％となる粒子径を意味する。本明細書では、一次粒子の平均粒子径Ｄ５０を、単に「一次粒子径」ともいう。 (Primary particles)
The silicon carbide particles (granules) according to the present embodiment are granulated from silicon carbide (primary particles) having an α-type crystal system. The average particle diameter D50 of the primary particles is 0.03 μm or more and 5.00 μm or less, preferably 0.05 μm or more and 3.00 μm or less, and more preferably 0.08 μm or more and 1.50 μm or less. The average particle size D50 of the primary particles means a particle size at which the cumulative frequency from the small particle size side is 50% in the volume-based cumulative particle size distribution of the powder in which the primary particles are collected. In this specification, the average particle diameter D50 of primary particles is also simply referred to as "primary particle diameter".
（スラリー）
（１）固形分濃度
　本実施形態に係る炭化珪素粒子（顆粒）は、一次粒子を含む粉末に溶媒（例えば、水）を加えてスラリーを生成し、このスラリーをスプレードライヤ等の噴霧装置に供給し造粒することで形成される。スラリーの固形分濃度は、５質量％以上５０質量％以下であり、好ましくは７．５質量％以上４５質量％以下であり、より好ましくは１０質量％以上４０質量％以下である。
（２）ｐＨ値
　本実施形態において、スラリーには、分散剤及び有機ポリマー（例えば、バインダー）を添加しない。分散剤及び有機ポリマーを添加せず、ｐＨ調整剤を添加して、スラリーのｐＨを炭化珪素の等電点（凝集域）に調整する。炭化珪素の等電点は、ｐＨ３．０～４．０付近である。例えば、スラリーのｐＨ値を１．０以上６．０以下、好ましくは３．０以上５．０以下、より好ましくは等電点付近に調整する。スラリーのｐＨ値が等電点付近に調整されることで、炭化珪素の一次粒子の表面電位（例えば、ゼータ電位）はほぼゼロになり、一次粒子間に働く電気的力（引力及び斥力）が小さくなるので、スラリー中で一次粒子は凝集する。 (slurry)
(1) Solid content concentration The silicon carbide particles (granules) according to the present embodiment are produced by adding a solvent (e.g., water) to a powder containing primary particles to generate a slurry, and supplying this slurry to a spray device such as a spray dryer. It is formed by granulating. The solid content concentration of the slurry is 5% by mass or more and 50% by mass or less, preferably 7.5% by mass or more and 45% by mass or less, more preferably 10% by mass or more and 40% by mass or less.
(2) pH value In the present embodiment, no dispersant or organic polymer (eg, binder) is added to the slurry. Without adding a dispersant and an organic polymer, a pH adjuster is added to adjust the pH of the slurry to the isoelectric point (aggregation range) of silicon carbide. The isoelectric point of silicon carbide is around pH 3.0 to 4.0. For example, the pH value of the slurry is adjusted to 1.0 or more and 6.0 or less, preferably 3.0 or more and 5.0 or less, more preferably near the isoelectric point. By adjusting the pH value of the slurry to near the isoelectric point, the surface potential (for example, zeta potential) of the primary particles of silicon carbide becomes almost zero, and the electrical forces (attraction and repulsion) acting between the primary particles are As they become smaller, the primary particles agglomerate in the slurry.
（３）分散剤及び有機ポリマーの不使用
　分散剤が添加されたスラリー、または分散剤を含まないがｐＨ値が分散域に調整された液滴を乾燥させて造粒する場合は、液滴の乾燥過程で一次粒子が顆粒表面に移動し、表面が埋没するなど、円形度が低くなり易い。また、分散剤や有機ポリマーを使用すると、脱脂が必要となり、環境・工程負荷が大きくなり易い。脱脂が不十分の場合は、残炭による品質不良が発生する可能性がある。 (3) Non-use of dispersant and organic polymer When slurry to which a dispersant is added or droplets that do not contain a dispersant but whose pH value is adjusted to the dispersion range are dried and granulated, the droplets During the drying process, the primary particles move to the surface of the granules, and the surface tends to become buried, resulting in a decrease in circularity. Moreover, the use of a dispersant or an organic polymer requires degreasing, which tends to increase environmental and process loads. Insufficient degreasing may result in quality defects due to residual coal.
　これに対し、本実施形態では、分散剤や有機ポリマーを使用せず、スラリーのｐＨ調整により、炭化珪素の等電点（凝集域）付近で造粒する。これにより、一次粒子の再配列が起こり難く、造粒直後の形状が保持されて乾燥されるため、中実かつ球形な顆粒を得ることができる。顆粒の円形度を高めることが可能である。
　また、分散剤や有機ポリマーを使用しないため、脱脂が不要となり、環境・工程負荷低減や、残炭による品質不良の発生を回避することが可能である。 In contrast, in the present embodiment, granulation is performed near the isoelectric point (aggregation range) of silicon carbide by adjusting the pH of the slurry without using a dispersant or an organic polymer. As a result, the rearrangement of the primary particles is less likely to occur, and the granules are dried while maintaining the shape immediately after granulation, so that solid and spherical granules can be obtained. It is possible to increase the circularity of the granules.
In addition, since no dispersant or organic polymer is used, degreasing is not necessary, and it is possible to reduce environmental and process loads and avoid quality defects due to residual carbon.
（ｐＨ調整剤）
　スラリーに添加するｐＨ調整剤は、酸及びアルカリのいずれであってもよい。ｐＨ調整剤としての酸の具体例としては、無機酸や、カルボン酸、有機硫酸等の有機酸が挙げられる。無機酸の具体例としては、硫酸、硝酸、ホウ酸、炭酸、次亜リン酸、亜リン酸、リン酸等が挙げられる。 (pH adjuster)
The pH adjuster added to the slurry may be either an acid or an alkali. Specific examples of acids as pH adjusters include inorganic acids and organic acids such as carboxylic acids and organic sulfuric acids. Specific examples of inorganic acids include sulfuric acid, nitric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid.
　ｐＨ調整剤としての塩基の具体例としては、アルカリ金属の水酸化物又はその塩、アルカリ土類金属の水酸化物又はその塩、水酸化第四級アンモニウム又はその塩、アンモニア、アミン等が挙げられる。アルカリ金属の具体例としては、カリウム、ナトリウム等が挙げられる。また、アルカリ土類金属の具体例としては、カルシウム、ストロンチウム等が挙げられる。さらに、塩の具体例としては、炭酸塩、炭酸水素塩、硫酸塩、酢酸塩等が挙げられる。さらに、第四級アンモニウムの具体例としては、テトラメチルアンモニウム、テトラエチルアンモニウム、テトラブチルアンモニウム等が挙げられる。 Specific examples of the base as the pH adjuster include alkali metal hydroxides or salts thereof, alkaline earth metal hydroxides or salts thereof, quaternary ammonium hydroxides or salts thereof, ammonia, amines, and the like. be done. Specific examples of alkali metals include potassium and sodium. Specific examples of alkaline earth metals include calcium and strontium. Furthermore, specific examples of salts include carbonates, hydrogen carbonates, sulfates, acetates, and the like. Further, specific examples of quaternary ammonium include tetramethylammonium, tetraethylammonium, tetrabutylammonium and the like.
（顆粒）
（１）真球度
　本実施形態に係る炭化珪素粒子（顆粒）の真球度は、上記したように８０％以上１００％以下であるが、好ましくは８５％以上１００％以下であり、より好ましくは９０％以上１００％以下である。真球度が１００％に近づくほど、炭化珪素粒子（顆粒）の形状は真球に近づき、顆粒の形状が球形に揃うため、各用途における効果が大きくなる。なお、真球度は所定個数の顆粒の平均値である。当該所定個数、すなわち顆粒毎の真球度を算出する粒子の個数は、測定精度や再現性を高める観点から、１００個以上とすることが適当である。 (granule)
(1) Sphericality The sphericity of the silicon carbide particles (granules) according to the present embodiment is, as described above, 80% or more and 100% or less, preferably 85% or more and 100% or less, and more preferably. is 90% or more and 100% or less. As the sphericity approaches 100%, the shape of the silicon carbide particles (granules) approaches a true sphere, and the granules are uniform in spherical shape, so that the effect in each application increases. The sphericity is the average value of a predetermined number of granules. The predetermined number, that is, the number of particles for calculating the sphericity of each granule, is suitably 100 or more from the viewpoint of improving measurement accuracy and reproducibility.
（２）真球度の標準偏差
　また、炭化珪素粒子（顆粒）の真球度の標準偏差は、０．０２以上０．０５以下であり、好ましくは０．０２以上０．０４以下である。真球度の標準偏差が小さいほど、顆粒の形状がさらに揃い、効果のばらつきを小さくすることができる。なお、この標準偏差は、上記顆粒の真球度を測定した際の所定個数の顆粒を母集団とした標準偏差であることが適当である。 (2) Standard deviation of sphericity The standard deviation of sphericity of the silicon carbide particles (granules) is 0.02 or more and 0.05 or less, preferably 0.02 or more and 0.04 or less. The smaller the standard deviation of the sphericity, the more uniform the shape of the granules and the smaller the variation in the effect. It is appropriate that this standard deviation is the standard deviation of a population of a predetermined number of granules when the sphericity of the granules is measured.
（３）平均粒子径
　本実施形態に係る炭化珪素粒子（顆粒）は、炭化珪素の一次粒子から造粒される二次粒子である。二次粒子の平均粒子径Ｄ５０は、０．５μｍ以上１００μｍ以下であり、好ましくは２μｍ以上６０μｍ以下であり、より好ましくは４μｍ以上５０μｍ以下である。二次粒子の平均粒子径Ｄ５０とは、二次粒子を集めた粉末の体積基準の積算粒子径分布において、小粒径側からの積算頻度が５０％となる粒子径を意味する。本明細書では、二次粒子の平均粒子径Ｄ５０を、単に「二次粒子径」ともいう。
　二次粒子径は、後述の実施例で説明するように、画像解析から算出される顆粒の円相当径で示される。一次粒子径は、レーザー回折散乱法により測定される値である。 (3) Average Particle Size Silicon carbide particles (granules) according to the present embodiment are secondary particles granulated from primary particles of silicon carbide. The average particle diameter D50 of the secondary particles is 0.5 μm or more and 100 μm or less, preferably 2 μm or more and 60 μm or less, and more preferably 4 μm or more and 50 μm or less. The average particle diameter D50 of the secondary particles means the particle diameter at which the cumulative frequency from the small particle diameter side is 50% in the volume-based cumulative particle size distribution of the powder in which the secondary particles are collected. In this specification, the average particle diameter D50 of the secondary particles is also simply referred to as "secondary particle diameter".
The secondary particle diameter is indicated by the equivalent circle diameter of granules calculated from image analysis, as described in Examples below. A primary particle diameter is a value measured by a laser diffraction scattering method.
（４）一次粒子径に対する二次粒子径の比
　一次粒子径に対する二次粒子径の比は、５以上３００以下であり、好ましくは１０以上２００以下であり、より好ましくは１５以上１５０以下である。 (4) Ratio of secondary particle size to primary particle size The ratio of secondary particle size to primary particle size is 5 or more and 300 or less, preferably 10 or more and 200 or less, more preferably 15 or more and 150 or less .
（樹脂組成物）
　上記したように、本実施形態に係る炭化珪素粒子（顆粒）は、フィラー（充填剤）として、プラスチック、硬化性樹脂、ゴム等の樹脂（本発明の「母材」の一例）に配合して樹脂組成物とすることができる。 (resin composition)
As described above, the silicon carbide particles (granules) according to the present embodiment are blended as a filler (filler) with resins such as plastics, curable resins, and rubbers (an example of the "base material" of the present invention). It can be a resin composition.
（製造方法）
　図３は、本発明の実施形態に係る炭化珪素粒子（顆粒）を含む組成物の製造方法を工程順に示すフローチャートである。まず、結晶系がα型である炭化珪素の一次粒子を含む粉体を生成し、この粉体と溶媒（例えば、水）とを混合して、スラリーを生成する（図３のステップＳＴ１）。
　次に、スラリーにｐＨ調整剤を添加して、スラリーのｐＨを炭化珪素の等電点（凝集域）付近に調整する（図３のステップＳＴ２）。なお、本実施形態において、分散剤及び有機ポリマー（例えば、バインダー）はスラリーに添加しない。 (Production method)
FIG. 3 is a flowchart showing, in order of steps, a method for producing a composition containing silicon carbide particles (granules) according to an embodiment of the present invention. First, powder containing primary particles of silicon carbide whose crystal system is α-type is produced, and this powder and a solvent (for example, water) are mixed to produce a slurry (step ST1 in FIG. 3).
Next, a pH adjuster is added to the slurry to adjust the pH of the slurry to near the isoelectric point (aggregation range) of silicon carbide (step ST2 in FIG. 3). Note that in this embodiment, no dispersant or organic polymer (eg, binder) is added to the slurry.
　次に、等電点付近に調整されたスラリーを、スプレードライヤを用いて乾燥室内に噴霧し乾燥させて、結晶系がα型である炭化珪素粒子（顆粒）を生成する（図３のステップＳＴ３）。ステップＳＴ３では、分散剤を使用せず、ｐＨ調整により炭化珪素の凝集域で造粒するため、一次粒子の再配列が起こり難い。顆粒は、造粒直後の形状を保持した状態で乾燥されるため、中実かつ球形な顆粒が得られる。 Next, the slurry adjusted to near the isoelectric point is sprayed into a drying chamber using a spray dryer and dried to produce silicon carbide particles (granules) having an α-type crystal system (step ST3 in FIG. 3). ). In step ST3, no dispersing agent is used, and granulation is performed in the aggregation region of silicon carbide by adjusting the pH, so rearrangement of the primary particles is less likely to occur. Since the granules are dried while retaining the shape immediately after granulation, solid and spherical granules are obtained.
　スプレードライヤの噴霧方式としては、加圧２流体ノズルによる固定噴霧方式、回転ディスクによる噴霧方式等がある。いずれの方式を採用してもよいが、固定噴霧方式を使用する事でより微小径の顆粒を得ることが出来る。
　スプレードライヤによる噴霧と乾燥とにより形成された顆粒は、後流側に設けられた捕集容器、サイクロン、バグフィルター等に捕集される。 The spraying method of the spray dryer includes a fixed spraying method using a pressurized two-fluid nozzle, a spraying method using a rotating disk, and the like. Either method may be adopted, but granules with a smaller diameter can be obtained by using the fixed spray method.
The granules formed by spraying and drying with a spray dryer are collected in a collection vessel, cyclone, bag filter, etc. provided on the downstream side.
　なお、本実施形態では、噴霧されるスラリーに予め焼結助剤を添加しておいてもよい。これにより、次に説明する顆粒の焼結工程で、顆粒の焼結を促進することができ、顆粒の内部をより緻密化することが可能である。 In addition, in this embodiment, a sintering aid may be added in advance to the slurry to be sprayed. As a result, the sintering of the granules can be promoted in the sintering step of the granules described below, and the interior of the granules can be made more dense.
　次に、図３のステップＳＴ４では、ステップＳＴ３で得られた顆粒を焼結する。例えば、ステップＳＴ３で得られた顆粒をアルゴン（Ａｒ）等の不活性ガスの雰囲気下で焼結する。焼結の温度は、例えば１８００℃以上２０００℃以下である。これにより、焼結された顆粒が得られる。なお、焼結の雰囲気を窒素（Ｎ２）とすると顆粒が窒化される可能性があるため、本実施形態においては焼結の雰囲気をＡｒとすることが好ましい。 Next, in step ST4 of FIG. 3, the granules obtained in step ST3 are sintered. For example, the granules obtained in step ST3 are sintered in an inert gas atmosphere such as argon (Ar). The sintering temperature is, for example, 1800° C. or higher and 2000° C. or lower. This gives sintered granules. Note that if the sintering atmosphere is nitrogen (N 2 ), the granules may be nitrided. Therefore, in the present embodiment, the sintering atmosphere is preferably Ar.
　以上のステップＳＴ１からＳＴ３まで、又は、ステップＳＴ１から焼結工程を含むステップＳＴ４までが、本実施形態に係る炭化珪素粒子（顆粒）の製造工程である。 The above steps ST1 to ST3 or step ST1 to step ST4 including the sintering step are the steps for manufacturing silicon carbide particles (granules) according to the present embodiment.
　次に、図３のステップＳＴ５で、焼結した顆粒を母材に配合して組成物を生成する（図３のステップＳＴ６）。例えば、焼結した顆粒をフィラーとして、プラスチック、硬化性樹脂、ゴム等の樹脂に配合して、樹脂組成物を生成する。以上の工程を経て、本実施形態に係る組成物が完成する。 Next, in step ST5 of FIG. 3, the sintered granules are mixed with the base material to produce a composition (step ST6 of FIG. 3). For example, sintered granules are used as a filler and blended with a resin such as a plastic, a curable resin, or a rubber to form a resin composition. Through the above steps, the composition according to the present embodiment is completed.
　次に実施例を示し、本発明をさらに具体的に説明する。
（実施例１）
　炭化珪素の一次粒子と水とを混合して、原料であるスラリーを得た。スラリーの固形分濃度は１６．１質量％である。炭化珪素の一次粒子として、粒度＃４００００の炭化珪素粉末（型番：ＧＣ＃４００００）を用いた。炭化珪素の一次粒子径Ｄ５０は、０．２５μｍである。 EXAMPLES Next, the present invention will be explained more specifically by showing examples.
(Example 1)
Primary particles of silicon carbide and water were mixed to obtain slurry as a raw material. The solid content concentration of the slurry is 16.1% by mass. Silicon carbide powder with a particle size of #40000 (model number: GC#40000) was used as the primary particles of silicon carbide. A primary particle diameter D50 of silicon carbide is 0.25 μm.
　次に、このスラリーにｐＨ調整剤を添加して、スラリーのｐＨを炭化珪素の凝集域であるｐＨ４．０付近（＝炭化珪素の等電点）に調整した。スラリーには、分散剤や有機ポリマーは添加しなかった。
　炭化珪素の一次粒子、溶媒（水）及びｐＨ調整剤の混合は、攪拌機を用いて行った。攪拌機による攪拌の回転数は、６０００ｒｐｍとした。攪拌時間は、１０ｍｉｎとした。 Next, a pH adjuster was added to this slurry to adjust the pH of the slurry to around pH 4.0 (=isoelectric point of silicon carbide), which is the aggregation range of silicon carbide. No dispersant or organic polymer was added to the slurry.
A stirrer was used to mix the primary particles of silicon carbide, the solvent (water), and the pH adjuster. The rotational speed of stirring by the stirrer was 6000 rpm. The stirring time was 10 minutes.
　攪拌機で攪拌されたスラリーを、回転ディスクによる噴霧方式のスプレードライヤに供給して造粒を行い、炭化珪素の顆粒（未焼結、二次粒子）を得た。 The slurry stirred by the stirrer was supplied to an atomization-type spray dryer using a rotating disk to granulate, thereby obtaining granules (unsintered, secondary particles) of silicon carbide.
（実施例２）
　実施例２では、実施例１よりもさらに、顆粒（二次粒子）を小さく形成した。具体的には、固定式噴霧方式を用いた。
（実施例３）
　実施例３では、炭化珪素の一次粒子として、粒度＃８０００の炭化珪素粉末（型番：ＧＣ＃８０００）を用いた。炭化珪素の一次粒子径Ｄ５０は、１．２μｍである。これ以外は、実施例１と同様にして、実施例３の顆粒（未焼結、二次粒子）を得た。 (Example 2)
In Example 2, the granules (secondary particles) were formed smaller than in Example 1. Specifically, a stationary spray system was used.
(Example 3)
In Example 3, silicon carbide powder with a particle size of #8000 (model number: GC#8000) was used as the primary particles of silicon carbide. A primary particle diameter D50 of silicon carbide is 1.2 μm. Granules (unsintered, secondary particles) of Example 3 were obtained in the same manner as in Example 1 except for this.
（実施例４）
　実施例２で得られた未焼結の顆粒を、焼結炉を用いて焼結して、実施例４の顆粒（焼結済み、二次粒子）を得た。焼結炉の運転条件は、炉内の雰囲気がアルゴン（Ａｒ）、焼結温度が１８００℃以上２０００℃以下、焼結時間が４時間である。 (Example 4)
The unsintered granules obtained in Example 2 were sintered using a sintering furnace to obtain granules (sintered, secondary particles) of Example 4. The operating conditions of the sintering furnace are that the atmosphere in the furnace is argon (Ar), the sintering temperature is 1800° C. or more and 2000° C. or less, and the sintering time is 4 hours.
（参考例１）
　参考例１では、炭化珪素の一次粒子径Ｄ５０を０．３５μｍとした。これ以外は、実施例１と同様の方法で、炭化珪素の顆粒（未焼結、二次粒子）を得た。スラリーのｐＨは４．０付近であり、分散剤は添加していない。なお、参考例１は、実施例１～４と比べてサンプル数（ｎ）が少なく、ｎが１００未満である。これが理由で、参考例とした。
（参考例２）
　参考例２では、スラリーのｐＨを９．０付近とし、分散域での造粒を実施した。これ以外は、参考例１と同様の方法で、炭化珪素の顆粒（未焼結、二次粒子）を得た。 (Reference example 1)
In Reference Example 1, the primary particle diameter D50 of silicon carbide was set to 0.35 μm. Silicon carbide granules (unsintered, secondary particles) were obtained in the same manner as in Example 1 except for this. The pH of the slurry was around 4.0 and no dispersant was added. Note that Reference Example 1 has a smaller number of samples (n) than Examples 1 to 4, and n is less than 100. For this reason, it is used as a reference example.
(Reference example 2)
In Reference Example 2, the pH of the slurry was adjusted to around 9.0, and granulation was carried out in the dispersion area. Silicon carbide granules (unsintered, secondary particles) were obtained in the same manner as in Reference Example 1 except for this.
（得られた顆粒の物性）
（１）顆粒の画像解析と、顆粒の円相当径の算出
　実施例１から４で得られた顆粒について、走査型電子顕微鏡（ＳＥＭ：Ｓｃａｎｎｉｎｇ　Ｅｌｅｃｔｒｏｎ　Ｍｉｃｒｏｓｃｏｐｅ）を用いて表面を観察し、ＳＥＭ画像を撮影した。また、得られたＳＥＭ画像を解析して顆粒の面積値を算出した。そして、算出した面積値から、顆粒の円相当径を算出した。 (Physical properties of obtained granules)
(1) Image Analysis of Granules and Calculation of Equivalent Circle Diameter of Granules The surfaces of the granules obtained in Examples 1 to 4 were observed using a scanning electron microscope (SEM), and SEM images were obtained. I took a picture. Also, the obtained SEM image was analyzed to calculate the area value of the granules. Then, the equivalent circle diameter of the granules was calculated from the calculated area value.
　図４は、顆粒の円相当径を例示する図である。例えば図４に示すように、算出した顆粒の面積値と同じ面積値となる正円（顆粒の相当円）を想定し、想定した正円の径（顆粒の円相当径）を算出した。画像解析から算出した顆粒の円相当径を下記の表１に示す。 FIG. 4 is a diagram illustrating equivalent circle diameters of granules. For example, as shown in FIG. 4, a perfect circle (equivalent circle of granules) having the same area value as the calculated area value of granules was assumed, and the diameter of the assumed perfect circle (equivalent circle diameter of granules) was calculated. The equivalent circle diameter of the granules calculated from image analysis is shown in Table 1 below.
（２）二次粒子径／一次粒子径　比
　実施例１から４で得られた顆粒について、一次粒子径と二次粒子径との比を算出した。算出結果を下記の表１に示す。
　一次粒子径は、表１に示した一次粒子径Ｄ５０（μｍ）である。二次粒子径は、下記の表１に示した顆粒の円相当径（μｍ）であり、各実施例の任意の１００個の顆粒の円相当径の平均値である。 (2) Ratio of secondary particle size/primary particle size For the granules obtained in Examples 1 to 4, the ratio of primary particle size to secondary particle size was calculated. The calculation results are shown in Table 1 below.
The primary particle size is the primary particle size D50 (μm) shown in Table 1. The secondary particle size is the equivalent circle diameter (μm) of the granules shown in Table 1 below, and is the average value of the equivalent circle diameters of 100 arbitrary granules in each example.
（３）真球度（顆粒面積／最大径相当円面積　比）
　実施例１から４で得られた顆粒について、真球度（顆粒の画像解析で得られた面積値と、顆粒の最大径から算出される最大径相当円の面積値との比）を算出した。真球度の算出結果を下記の表１に示す。なお、真球度は上記顆粒の円相当径を測定した際の顆粒１００個の真球度の平均値とした。
（４）真球度の標準偏差
　実施例１から４で得られた顆粒について、真球度の標準偏差を算出した。実施例１から４において、上記顆粒の円相当径を測定した際の任意の１００個の顆粒を母集団とした標準偏差を下記の表１に示す。
（５）アスペクト比
　実施例１から４で得られた顆粒について、短径、長径を測定して、アスペクト比（短径／長径）を算出した。算出結果を下記の表１に示す。なお、アスペクト比は上記顆粒の円相当径を測定した際の顆粒１００個のアスペクト比の平均値とした。 (3) Sphericality (Granule area/maximum diameter equivalent circular area ratio)
For the granules obtained in Examples 1 to 4, the sphericity (the ratio of the area value obtained by image analysis of the granule to the area value of the circle corresponding to the maximum diameter calculated from the maximum diameter of the granule) was calculated. . The sphericity calculation results are shown in Table 1 below. The sphericity was the average value of the sphericity of 100 granules when the equivalent circle diameter of the granules was measured.
(4) Standard deviation of sphericity For the granules obtained in Examples 1 to 4, the standard deviation of sphericity was calculated. Table 1 below shows the standard deviation of a population of 100 arbitrary granules when the equivalent circle diameters of the granules were measured in Examples 1 to 4.
(5) Aspect ratio The short diameter and long diameter of the granules obtained in Examples 1 to 4 were measured to calculate the aspect ratio (short diameter/long diameter). The calculation results are shown in Table 1 below. The aspect ratio was the average value of the aspect ratios of 100 granules when the equivalent circle diameter of the granules was measured.
（６）真球度算出の元となるデータ
　実施例１から４で得られた顆粒の真球度について、算出の元となるデータを下記の表１に示す。算出の元となるデータは、画像解析による顆粒面積（μｍ２）と、画像解析による顆粒最大径（μｍ）と、顆粒最大径から算出した顆粒の最大径相当円面積（μｍ２）と、である。顆粒面積、顆粒最大径および最大径相当円面積はいずれも上記顆粒の円相当径を測定した際の顆粒１００個の顆粒面積、顆粒最大径、最大径相当円面積の平均値とした。
Figure JPOXMLDOC01-appb-T000001
 (6) Data used to calculate the sphericity The data used to calculate the sphericity of the granules obtained in Examples 1 to 4 are shown in Table 1 below. The data on which the calculation is based is the granule area (μm 2 ) obtained by image analysis, the maximum granule diameter (μm) obtained by image analysis, and the circular area equivalent to the maximum granule diameter calculated from the maximum granule diameter (μm 2 ). be. The granule area, the maximum granule diameter and the circular area equivalent to the maximum diameter were all average values of the granule area, the maximum granule diameter and the circular area equivalent to the maximum diameter of 100 granules when the equivalent circle diameter of the granules was measured.
Figure JPOXMLDOC01-appb-T000001
（評価）
　図５は、本発明の実施例１から４と、参考例１、２で得られた顆粒のＳＥＭ画像を示す図である。図５に示すように、実施例１から４と、参考例１で得られた顆粒は、目視で円形度が高いことが確認された。
　また、表１に示すように、実施例１から４で得られた顆粒の真球度は０．８３以上０．９５以下（百分率で、８３％以上９５％以下）であり、真球度の標準偏差は０．０２以上０．０４以下であった。 (evaluation)
FIG. 5 shows SEM images of granules obtained in Examples 1 to 4 and Reference Examples 1 and 2 of the present invention. As shown in FIG. 5, it was visually confirmed that the granules obtained in Examples 1 to 4 and Reference Example 1 had a high degree of circularity.
Further, as shown in Table 1, the sphericity of the granules obtained in Examples 1 to 4 is 0.83 or more and 0.95 or less (83% or more and 95% or less in percentage). The standard deviation was 0.02 or more and 0.04 or less.
　一方、参考例２で得られた顆粒は、表面が凹んでおり、目視でも明らかに円形度が低い。参考例２では、造粒を分散域で実施したため、液滴の乾燥過程で顆粒表面が埋没したと考えられる。造粒を分散域で実施すると、参考例２のＳＥＭ画像ように、表面が埋没した顆粒が散見された。 On the other hand, the granules obtained in Reference Example 2 have concave surfaces and are clearly low in circularity even visually. In Reference Example 2, granulation was carried out in the dispersed region, so it is considered that the surface of the granules was buried during the drying process of the droplets. When granulation was carried out in the dispersed region, as in the SEM image of Reference Example 2, granules with buried surfaces were found here and there.
　実施例２、４のデータを比較して分かるように、一次粒子径が０．２５μｍであり二次粒子径が約４μｍである場合、二次粒子（顆粒）の真球度は焼結前後で変化量が小さいことが確認された。 As can be seen by comparing the data of Examples 2 and 4, when the primary particle diameter is 0.25 μm and the secondary particle diameter is about 4 μm, the sphericity of the secondary particles (granules) before and after sintering is It was confirmed that the amount of change was small.
　また、実施例２、４のデータを比較して分かるように、二次粒子（顆粒）の真球度の標準偏差（すなわち、ばらつき）は、二次粒子を焼結することで大きな変化は無い事が確認された。 Also, as can be seen by comparing the data of Examples 2 and 4, the standard deviation (that is, variation) of the sphericity of the secondary particles (granules) does not change significantly by sintering the secondary particles. matter was confirmed.
　本実施形態の炭化珪素粒子（顆粒）は分散剤や有機ポリマーを含まないため、真球度は、焼結前と焼結後とで変動量が小さいことが確認された。 Since the silicon carbide particles (granules) of this embodiment do not contain a dispersant or an organic polymer, it was confirmed that the amount of variation in sphericity was small before and after sintering.

Claims (5)

  1. 　顆粒の画像解析より算出される面積値を、前記顆粒の最大径から算出される円相当面積値で除算した値が、百分率で８０％以上である、結晶系がα型の炭化珪素粒子。 Silicon carbide particles with an α-type crystal system, in which the value obtained by dividing the area value calculated by image analysis of the granule by the circle-equivalent area value calculated from the maximum diameter of the granule is 80% or more in percentage.
  2. 　前記顆粒の画像解析より算出される面積値を、前記顆粒の最大径から算出される円相当面積値で除算した値の標準偏差が、０．０２以上０．０５以下である、請求項１に記載の炭化珪素粒子。 2. The standard deviation of the value obtained by dividing the area value calculated by image analysis of the granule by the circle-equivalent area value calculated from the maximum diameter of the granule is 0.02 or more and 0.05 or less. Silicon carbide particles as described.
  3. 　前記顆粒の平均粒子径が、０．５μｍ以上１００μｍ以下である、請求項１又は２に記載の炭化珪素粒子。 The silicon carbide particles according to claim 1 or 2, wherein the granules have an average particle size of 0.5 µm or more and 100 µm or less.
  4. 　前記顆粒の造粒に用いられる一次粒子の平均粒子径に対する前記顆粒の平均粒子径の比は、１５以上１５０以下である、請求項１から３のいずれか１項に記載の炭化珪素粒子。 The silicon carbide particles according to any one of claims 1 to 3, wherein the ratio of the average particle size of said granules to the average particle size of primary particles used for granulation of said granules is 15 or more and 150 or less.
  5. 　前記顆粒は分散剤及び有機ポリマーを含有しない、請求項１から４のいずれか１項に記載の炭化珪素粒子。 The silicon carbide particles according to any one of claims 1 to 4, wherein the granules do not contain a dispersant and an organic polymer.
PCT/JP2022/021987 2021-06-29 2022-05-30 Silicon carbide particle WO2023276522A1 (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013095637A (en) * 2011-11-01 2013-05-20 Shinano Denki Seiren Kk SPHERICAL α-TYPE SILICON CARBIDE, PRODUCTION METHOD THEREOF, AND SINTERED BODY OR ORGANIC RESIN COMPOSITE USING THE SILICON CARBIDE AS RAW MATERIAL
WO2020235651A1 (en) * 2019-05-22 2020-11-26 住友大阪セメント株式会社 Composite sintered body, electrostatic chuck member, electrostatic chuck device, and method for manufacturing composite sintered body

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013095637A (en) * 2011-11-01 2013-05-20 Shinano Denki Seiren Kk SPHERICAL α-TYPE SILICON CARBIDE, PRODUCTION METHOD THEREOF, AND SINTERED BODY OR ORGANIC RESIN COMPOSITE USING THE SILICON CARBIDE AS RAW MATERIAL
WO2020235651A1 (en) * 2019-05-22 2020-11-26 住友大阪セメント株式会社 Composite sintered body, electrostatic chuck member, electrostatic chuck device, and method for manufacturing composite sintered body

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