Inorganic powder

Abstract

This inorganic powder contains a spherical alumina powder and a spherical silica powder, and the angle of repose of the powder measured using a powder tester under conditions of room temperature at 25°C and 65% humidity is 35° to 47°.

Description

[Technical Field]

[0001] This invention relates to inorganic powders. [Background technology]

[0002] Various developments have been made regarding inorganic powders. As an example of this type of technology, the technology described in Patent Document 1 is known. Patent Document 1 describes spherical alumina powder having a silica coating layer, which has been sphericalized by flame spraying as an inorganic powder. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2013-014513 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, as a result of the inventor's investigation, it was found that the inorganic powder described in Patent Document 1 above has room for improvement in terms of fluidity when blended with resin. [Means for solving the problem]

[0005] Further investigation by the inventors revealed that by appropriately controlling the angle of repose in inorganic powders containing spherical alumina powder and spherical silica powder, the fluidity when these powders are blended into resins can be improved, thus completing the present invention.

[0006] According to one aspect of the present invention, the following inorganic powder is provided. 1. An inorganic powder containing spherical alumina powder and spherical silica powder, Inorganic powder having an angle of repose between 35° and 47°, measured according to procedure A below, under conditions of room temperature of 25°C and humidity of 65%. (Procedure A) A funnel having an outlet diameter of 0.5 cm is mounted at a position with a height of 15 cm from a horizontal plate installed on a powder tester. The inorganic powder is continuously supplied onto the surface of the horizontal plate from the vertical direction through the funnel to form a conical deposit that maintains a constant shape. A protractor is used to determine the elevation angle formed between the side surface of the conical deposit and the surface of the horizontal plate, and this angle is defined as the angle of repose (°). Subsequently, a 110 g weight is dropped three times from a height of 18 cm onto the horizontal plate to apply an impact. Thereafter, a protractor is used to determine the elevation angle formed between the side surface of the conical deposit and the surface of the horizontal plate, and this angle is defined as the collapse angle (°). 2. The inorganic powder according to 1., wherein an inorganic powder, wherein the collapse angle measured according to the aforementioned Procedure A under conditions of a room temperature of 25°C and a humidity of 65% is 20° or more and 37° or less. 3. The inorganic powder according to 1. or 2., wherein an inorganic powder, wherein the tapped bulk density measured by the following Procedure B under conditions of a room temperature of 25°C and a humidity of 55% is 1.5 g / cm 3 or more and 2.3 g / cm 3 or less. (Procedure B) The inorganic powder is naturally dropped from a height of 25 cm at a feeding rate of 5 to 10 g per minute into a 100 cm 3 measuring cup, and the feeding is continued until the powder overflows from the cup to prepare a heaped cup. Subsequently, for the heaped cup, without tapping, the overflowed powder on the top surface of the cup is struck off, then the mass (g) of the inorganic powder filled in the cup is measured, and the loose bulk density (g / cm 3 ) is calculated. On the other hand, for the heaped cup, after tapping 180 times in the vertical direction under the conditions (stroke length 2 cm, 1 time per second), the overflowed powder on the top surface of the cup is struck off, then the mass (g) of the inorganic powder filled in the cup is measured, and the tapped bulk density (g / cm 3 ) is calculated. 4. The inorganic powder according to any one of 1. to 3., wherein When the loose bulk density measured in step B is A and the tapped bulk density is P, An inorganic powder having a degree of compressibility calculated based on ((P-A) / P)×100 of 30% or more and 44% or less. 5. The inorganic powder according to any one of 1. to 4., wherein In a volume frequency particle size distribution measured by a wet laser diffraction scattering method, let D be the particle diameter at which the cumulative value is 10% 10 , let D be the particle diameter at which the cumulative value is 50% 50 , and let D be the particle diameter at which the cumulative value is 97% 97 , then (D 97 -D 10 ) / D 50 is 4 or more and 30 or less. 6. The inorganic powder according to any one of 1. to 5., wherein In a volume frequency particle size distribution measured by a wet laser diffraction scattering method, let D be the particle diameter at which the cumulative value is 10% 10 , and let D be the particle diameter at which the cumulative value is 50% 50 , then D 50 -D 10 is 0.5 µm or more and 17 µm or less. Effects of the Invention

[0007] According to the present invention, there is provided an inorganic powder excellent in fluidity when compounded into a resin. Brief Description of Drawings

[0008] [Figure 1] It is a schematic cross-sectional view showing the configuration of a thermal spraying apparatus. Mode for Carrying Out the Invention

[0009] An outline of the inorganic powder of the present embodiment will be described.

[0010] The inorganic powder of this embodiment comprises spherical alumina powder and spherical silica powder, and is configured such that its angle of repose is between 35° and 47°.

[0011] The upper limit of the angle of repose in inorganic powders is 47° or less, preferably 46° or less, and more preferably 45° or less. This improves the fluidity of the resin composition containing the inorganic powder. The lower limit of the angle of repose for inorganic powders is, for example, 35° or higher, preferably 36° or higher, and more preferably 37° or higher. This is expected to improve the handling properties of the powder.

[0012] The upper limit of the disintegration angle in inorganic powder is 37° or less, preferably 36° or less, and more preferably 35° or less. This further improves the fluidity of the resin composition containing inorganic powder. The lower limit of the disintegration angle in inorganic powders is, for example, 20° or more, preferably 21° or more, and more preferably 22° or more. This is expected to improve the handling properties of the powder.

[0013] (Measurement procedure for angle of repose and angle of collapse A) Procedure A for measuring the angle of repose and disintegration angle in inorganic powders is as follows: A funnel with an outlet diameter of 0.5 cm is attached to a horizontal plate installed on the powder tester, at a height of 15 cm. The inorganic powder is continuously supplied vertically onto the surface of a horizontal plate via a funnel, forming a cone-shaped deposit that maintains a constant shape. Using a protractor, determine the elevation angle between the side surface of the cone-shaped deposit and the surface of the horizontal plate, and define this as the angle of repose (°). Next, a 110g weight is dropped onto a horizontal plate three times from a height of 18cm to impart impact. Then, using a protractor, the elevation angle between the side of the conical deposit and the surface of the horizontal plate is determined and defined as the collapse angle (°).

[0014] For inorganic powders, the degree of compression is calculated based on ((PA) / P) × 100, using the loose bulk density (A) and the hard bulk density (P) obtained by procedure B below.

[0015] The upper limit of the compressibility of the inorganic powder is, for example, 44% or less, preferably 43% or less, and more preferably 42% or less. This is expected to improve the miscibility of the inorganic powder with the resin. The lower limit of the compressibility of inorganic powders is, for example, 30% or more, preferably 31% or more, and more preferably 32% or more. This is expected to improve the handling properties of the powder.

[0016] The upper limit for the firm bulk density (P) of inorganic powders is, for example, 2.3 g / cm³. 3 Preferably 2.2 g / cm³ 3 More preferably, 2.1 g / cm³ 3 The following is the result: This increases density and has the potential to improve the strength of the resin composition. The lower limit of the bulk density (P) for inorganic powders is, for example, 1.5 g / cm³. 3 Preferably 1.6 g / cm³ 3 More preferably 1.7 g / cm³ 3 That concludes the explanation. This has the potential to improve the handling properties of powders.

[0017] (Measurement procedure B for firm bulk density and loose bulk density) The inorganic powder is added at a rate of 5-10g per minute, allowed to fall naturally from a height of 25cm, and then 100cm 3 Pour the mixture into the measuring cup and continue until it overflows, preparing a heaping cup. Next, for the overflowing cup, without tapping, the amount that overflowed from the top of the cup was leveled off, and the mass (g) of the inorganic powder filled in the cup was measured, and the loose bulk density (g / cm³) was calculated. 3 Calculate ). On the other hand, for the overflowing cup, after tapping it 180 times in the vertical direction (stroke length 2 cm, 1 second / tap), and leveling off the excess powder on the top of the cup, the mass (g) of the inorganic powder filled in the cup was measured, and the bulk density (g / cm³) was determined. 3 Calculate ).

[0018] The volume frequency particle size distribution of inorganic powder is measured by a wet laser diffraction scattering method, and the particle size at which the cumulative value in this volume frequency particle size distribution becomes 10% is defined as D. 10 The particle size at which the cumulative value reaches 50% is D 50 The particle size at which the cumulative value reaches 97% is D 97 Let's assume that.

[0019] (D 97 -D 10 ) / D 50 The lower limit is, for example, 4 or more, preferably 5 or more, more preferably 6 or more. If the particle size distribution becomes too narrow, D 50 If the size becomes too large, the fluidity and packing properties of the powder itself may deteriorate. (D 97 -D 10 ) / D 50 The upper limit is, for example, 30 or less, preferably 25 or less, more preferably 20 or less. If the particle size distribution is too broad, D 50 By keeping the size within an appropriate range without becoming too small, the fluidity and packing properties of the powder itself can be improved.

[0020] D 50 -D 10 The upper limit is, for example, 17 μm or less, preferably 16 μm or less, and more preferably 15 μm or less. This ensures appropriate fluidity, thermal conductivity, and other properties. D 50 -D 10 The lower limit is, for example, 0.5 μm or more, preferably 1 μm or more, and more preferably 2 μm or more. This ensures proper filling.

[0021] The particle size distribution of inorganic powders is a value based on particle size measurement by laser diffraction scattering, and can be measured using a particle size distribution analyzer such as the "Model LS-13-230" (manufactured by Beckman Coulter). For measurement, water is used as the solvent, and as a pretreatment, the powder is dispersed using a homogenizer at a power of 200W for 1 minute. The PIDS (Polarization Intensity Differential Scattering) concentration is also prepared to be 45-55%. The refractive index of water is set to 1.33, and the refractive index of the powder material is taken into consideration. For example, amorphous silica is measured with a refractive index of 1.50, and alumina with a refractive index of 1.68.

[0022] In this embodiment, the angle of repose, collapse angle, bulk density, and compressibility can be controlled by appropriately selecting, for example, the types and amounts of each component contained in the inorganic powder, the method of preparing the inorganic powder, etc. Among these, for example, applying appropriate storage treatment to the alumina powder and / or silica powder immediately after collection, appropriately adjusting the opening degree during the classification treatment of these powders, and using spherical alumina powder and spherical silica powder of different particle sizes in combination are examples of factors that can bring the angle of repose, collapse angle, bulk density, and compressibility within a desired numerical range.

[0023] The inorganic powder of this embodiment will be described in detail.

[0024] The spherical alumina powder and spherical silica powder contained in the inorganic powder are also called molten spherical particles, respectively. They are produced by supplying the raw material powder into a high-temperature flame formed by the combustion reaction of a combustible gas and a combustion-supporting gas, and melting and spheroidizing them above their melting point. If necessary, the molten spherical particles obtained in this way may be subjected to classification and sieving. For example, by producing spherical alumina powder and spherical silica powder separately and mixing them, an inorganic powder can be obtained.

[0025] Figure 1 shows an example of a schematic diagram of a thermal spraying apparatus used to produce molten spherical particles. The thermal spraying apparatus 100 in Figure 1 consists of a melting furnace 2 equipped with a burner 1, a cyclone 4 for classifying molten spherical particles generated by the high-temperature exhaust gas of the flame using the suction of a blower 9, and a bag filter 8 for collecting fine particles that could not be captured by the cyclone 4. The melting furnace 2 is composed of a vertical furnace body, but is not limited to this; it may also be a horizontal furnace or inclined furnace, which is horizontal in which the flame is blown out horizontally. The high-temperature exhaust gas is cooled by pipes 3 and 5 equipped with water-cooling jackets. The blower 9 may be connected to a suction gas volume control valve (not shown) and a gas exhaust port. A collection and extraction device (not shown) may be connected to the bottom of the melting furnace 2, cyclone 4, and back filter 8. Classification can be carried out using known equipment such as heavy sedimentation chambers, cyclones, and classifiers with rotating blades. This classification operation may be incorporated into the transport process of the molten spheroidized product, or it may be carried out on a separate line after bulk collection.

[0026] As the flammable gas, one or more types such as acetylene, propane, and butane can be used, but propane, butane, or a mixture thereof with a relatively low calorific value is preferred. As a combustion-supporting gas, for example, a gas containing oxygen is used. Generally, using pure oxygen of 99% by mass or higher is the most inexpensive and preferable option. To reduce the calorific value of the gas, an inert gas such as air or argon can also be mixed with the combustion-supporting gas.

[0027] As the raw material powder, alumina powder with an average particle size of 3 to 70 μm may be used. The aluminum hydroxide powder may be supplied into the high-temperature flame either dry or wet by slurring it with water or the like.

[0028] As the raw material powder, silica raw material powder may be used, for example, siliceous raw materials such as quartz or natural silica, adjusted to a particle size composition in which 15-50% of the particles are 1 μm or smaller and 50-80% are 5 μm or larger.

[0029] The content of spherical silica powder in the inorganic powder is, for example, 3 to 30% by mass, preferably 3 to 20% by mass, and more preferably 3 to 10% by mass, out of 100% by mass of the total value of spherical alumina powder and spherical silica powder.

[0030] The spherical silica powder may be amorphous and / or crystalline.

[0031] The spherical silica powder preferably has an amorphous content of 95% or more, and more preferably 97% or more, as measured by the following method. The amorphous content is measured using a powder X-ray diffractometer (e.g., RIGAKU's "Model MiniFlex"), performing X-ray diffraction analysis in the range of 26° to 27.5° for CuKα rays, and is determined from the intensity ratio of specific diffraction peaks. In the case of siliceous powder, crystalline silica has a main peak at 26.7°, but amorphous silica does not have a peak. When amorphous silica and crystalline silica are mixed, a peak height of 26.7° corresponding to the proportion of crystalline silica is obtained. The crystalline silica mixing ratio (X-ray diffraction intensity of the sample / X-ray diffraction intensity of crystalline silica) is calculated from the ratio of the X-ray intensity of the sample to the X-ray intensity of a crystalline silica standard sample, and the amorphous content is determined from the formula, Amorphous Content (%) = (1 - Crystalline Silica Mixing Ratio) × 100.

[0032] In spherical alumina powder and / or spherical silica powder, the degree of "sphericity" is preferably such that, for example, the average sphericity of particles with a cumulative particle size distribution of less than 75% (d75) is 0.90 or higher, and the average sphericity of particles with a particle size of d75 or higher is 0.85 or higher. Generally, increasing the average sphericity of spherical silica powder tends to improve fluidity, but the effects of this embodiment can be further enhanced by setting the average sphericity of coarser particles with a particle size of d75 or higher to 0.85 or higher.

[0033] The average sphericity can be measured by taking particle images with a stereomicroscope (for example, Nikon's SMZ-10 model) or scanning electron microscope, and then inputting the images into an image analysis device (for example, one manufactured by Japan Avionics Co., Ltd.) as follows: The projected area (A) and perimeter (PM) of the particle are measured from the photograph. If (B) is the area of ​​a perfect circle corresponding to the perimeter (PM), then the roundness of the particle can be expressed as A / B. Therefore, assuming a perfect circle with the same perimeter (PM) as the sample particle, PM = 2πr and B = πr 2 Therefore, B = π × (PM / 2π) 2 Therefore, the sphericity of each particle is given by: Sphericity = A / B = A × 4π / (PM) 2 It can be calculated as follows. The roundness of 200 arbitrary particles obtained in this way is determined and the average value is taken as the average sphericity.

[0034] In addition to the methods described above, roundness can also be measured quantitatively and automatically using a particle image analyzer (for example, the Sysmex FPIA-1000 model), and then converted using the formula: roundness = (circularity)².

[0035] The inorganic powder of the present invention, when incorporated into a resin composition, can be suitably used as a resin molding material.

[0036] Next, the resin composition of this embodiment will be described.

[0037] The resin composition includes, in addition to the inorganic powder of the present invention, a resin and known resin additives. In the resin composition, the inorganic powder may be used alone or mixed with other fillers. The resin composition may contain 10 to 99% by mass of inorganic powder, or 10 to 99% by mass of mixed inorganic powder containing inorganic powder and other fillers. Furthermore, the content of other fillers in the mixed inorganic powder may be, for example, 1 to 20% by mass or 3 to 15% by mass, relative to 100% by mass of inorganic powder. In this specification, unless otherwise specified, "~" indicates that it includes both the upper and lower limits. Other fillers include, for example, titania, silicon nitride, aluminum nitride, silicon carbide, talc, and calcium carbonate. The average particle size of these other fillers is typically around 5 to 100 μm, and there are no particular restrictions on their particle size composition or shape.

[0038] Examples of the above-mentioned resins include epoxy resins, silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyimides, polyamide-imides, polyetherimides and other polyamides, polyesters such as polybutylene terephthalate and polyethylene terephthalate, polyphenylene sulfide, fully aromatic polyesters, polysulfones, liquid crystal polymers, polyethersulfones, polycarbonates, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylic rubber-styrene) resins, and AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins. These may be used individually or in combination of two or more types.

[0039] The resin composition can be manufactured, for example, by blending raw material components in predetermined ratios using a blender or Henschel mixer, then kneading the mixture using a heated roll, kneader, single-screw or twin-screw extruder, cooling, and then grinding it.

[0040] The embodiments of the present invention have been described above, but these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0041] The present invention will be described in detail below with reference to examples, but the present invention is not limited in any way to the descriptions of these examples.

[0042] <Manufacturing of inorganic powders> Using the thermal spraying apparatus 100 shown in Figure 1, various spherical alumina powders and spherical silica powders were produced. The thermal spraying apparatus 100 shown in Figure 1 comprises a melting furnace 2, a burner 1 installed on top of the melting furnace 2, and a collection system line consisting of a cyclone 4 and a bag filter 8 installed directly connected to the bottom of the melting furnace 2. Burner 1 has a double-tube structure capable of forming an inner flame and an outer flame, and is installed at the top of the melting furnace 2, to which the combustible gas supply pipe 11, the combustion-supporting gas supply pipe 12, and the raw material supply pipe 13 are connected. In the melting furnace 2, raw material powder is supplied into a high-temperature flame from the raw material supply pipe 13 and melted to form spherical molten spherical particles. The molten spherical particles that have passed through the melting furnace 2 are sucked in by the blower 9 along with the combustion exhaust gas, move through the pipes 3 and 5 by air, and are classified and collected by the cyclone 4 or bag filter 8.

[0043] (Example 1) • Manufacturing of spherical alumina powder Using the thermal spraying apparatus 100 described above, LPG was supplied as a combustible gas from the combustible gas supply pipe 11, and atmospheric air was supplied as a combustion-supporting gas from the combustion-supporting gas supply pipe 12. A high-temperature flame was formed in the burner 1 by the combustion of LPG and oxygen. Secondary air is supplied to cyclone 4 by a rotary valve (not shown) installed in piping 3. The secondary air used was air heated in the melting furnace 2. The lower opening of cyclone 4 was set to 100%. As raw material powder, average particle size (D 50 Alumina powder having a maximum value in the range of 2 to 45 μm was used. Molten spherical particles collected by the bag filter 8 were recovered as spherical alumina powder. • Manufacturing of spherical silica powder As raw material powder, average particle size (D 50 ) uses 5μm natural silica powder, and 10Nm as the carrier gas for the raw materials. 3 / hr, the burner's flammable gas supply rate is 10 Nm³ 3 / hr, supply amount of auxiliary gas 25Nm 3The process was the same as described above for the production of spherical alumina powder, except that the value was set to / hr. The molten spherical particles collected by the bag filter 8 are processed by determining the average particle size (D 50 ) was recovered as 0.3 μm spherical silica powder.

[0044] • Manufacturing of inorganic powders The spherical silica powder was stored in an aluminum bag (manufactured by Seisan Nippon Co., Ltd., Lamizip AL) at a humidity of 60-80% and a temperature of 20-30°C for 28 days immediately after collection (storage treatment). The spherical silica powder removed immediately after opening the aluminum bag and the spherical alumina powder produced as described above were mixed in a mass ratio of 90:10 to obtain inorganic powder.

[0045] (Examples 2-4) In the production of spherical alumina powder, an inorganic powder was obtained using spherical alumina powder obtained in the same manner as in Example 1 above, except that the lower opening was changed to 20%, 25%, and 35% during the classification process.

[0046] (Comparative Example 1) The spherical alumina powder described above was used as an inorganic powder without mixing it with spherical silica powder.

[0047] (Comparative Example 2) In the production of inorganic powders, the average particle size (D) is changed by altering the classification conditions. 50 A silica powder with a diameter of 5 μm was obtained. The obtained spherical silica powder and the above-mentioned spherical alumina powder were mixed in a mass ratio of 90:10 to obtain an inorganic powder.

[0048] (Comparative Example 3) An inorganic powder was obtained using spherical alumina powder obtained in the same manner as in Example 1 above, except that secondary air was not supplied and the lower opening of cyclone 4 was set to 0%.

[0049] (Comparative Example 4) An inorganic powder was obtained using silica powder obtained in the same manner as in Example 3 above, except that the spherical silica powder was not stored in an aluminum bag during its production.

[0050] [Table 1]

[0051] <Loose bulk density, firm bulk density> The obtained inorganic powder was subjected to measurements of loose and hard bulk density using a powder tester (Hosokawa Micron Corporation, PT-E type) under conditions of room temperature (25°C) and humidity (55%). The specific steps are as follows: The inorganic powder, which is the measurement sample, is dropped naturally from a height of 25 cm at a rate of 5-10 g per minute, and then measured at 100 cm. 3 I poured it into the measuring cup and continued until it overflowed, preparing a heaping cup. Next, for the overflowing cup, without tapping, the amount that overflowed from the top of the cup was leveled off, and the mass (g) of the inorganic powder filled in the cup was measured, and the loose bulk density (g / cm³) was calculated. 3 ) was calculated. On the other hand, for the overflowing cup, after tapping it 180 times in the vertical direction (stroke length 2 cm, 1 second / tap), and leveling off the excess powder on the top of the cup, the mass (g) of the inorganic powder filled in the cup was measured, and the bulk density (g / cm³) was determined. 3 ) was calculated. When the loose bulk density obtained using the above procedure is denoted as A and the stiff bulk density as P, the degree of compressibility (%) was calculated based on the formula: ((PA) / P) × 100.

[0052] <Angle of repose, angle of collapse> The angle of repose and angle of disintegration of the obtained inorganic powder were measured using a powder tester (Hosokawa Micron Corporation, PT-E type) under conditions of room temperature (25°C) and humidity (65%). The specific steps are as follows: A funnel with an outlet diameter of 0.5 cm was attached to a horizontal plate installed on the powder tester, at a height of 15 cm. Inorganic powder was continuously supplied vertically onto the surface of a horizontal plate via a funnel, forming a cone-shaped deposit that maintained a constant shape. Using a protractor, the elevation angle between the side surface of the conical sediment and the surface of the horizontal plate was determined and defined as the angle of repose (°). Next, a 110g weight was dropped onto a horizontal plate three times from a height of 18cm to impart impact. Then, using a protractor, the elevation angle between the side of the conical deposit and the surface of the horizontal plate was determined and defined as the collapse angle (°).

[0053] <Particle size distribution> The obtained inorganic powder was analyzed using a wet laser diffraction scattering method to determine its volume frequency particle size distribution. Water was used as the solvent, and as a pretreatment, the powder was dispersed using a homogenizer at 200W for 1 minute. The PIDS (Polarization Intensity Differential Scattering) concentration was adjusted to 45-55% for the measurement. Based on the obtained volume frequency particle size distribution, the particle size D at which the cumulative value is X% X The result was calculated.

[0054] <Flowability of resin compositions> 90 parts by mass of each obtained inorganic powder, 5.5 parts by mass of biphenyl-type epoxy resin (YX-4000HK, manufactured by Japan Epoxy Resin Co., Ltd.), 4.8 parts by mass of phenol resin (phenol aralkyl resin, MEHC-7800S, manufactured by Meiwa Kasei Co., Ltd.), 0.15 parts by mass of triphenylphosphine (TPP, manufactured by Hokko Chemical Industry Co., Ltd.), and 0.35 parts by mass of N-phenyl-3-aminopropyltrimethoxysilane (KBM-573, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed using a Henschel mixer (FM-20C / I, manufactured by Nippon Coke Industries Co., Ltd.) at room temperature and a rotation speed of 2000 rpm. The resulting mixture was heated and kneaded in a co-axis twin-screw extruder (screw diameter D=25 mm, L / D=10.2, paddle rotation speed 50~120 rpm, discharge rate 3.0 kg / Hr, kneaded material temperature 98~100°C) to obtain a resin composition. The obtained resin composition was used in a spiral flow mold, and the molding process was carried out in accordance with EMMI-1-66 (Epoxy Molding Material Institute; Society of Plastic Industry). The mold temperature was 175°C, the molding pressure was 7.4 MPa, and the holding pressure time was 90 seconds. A spiral flow of 200 cm or more was considered good, while a spiral flow of less than 200 cm was considered poor.

[0055] The inorganic powders of Examples 1-4 showed that they could improve the fluidity of the resin composition compared to Comparative Examples 1-4.

[0056] This application claims priority based on Japanese Patent Application No. 2022-018507, filed on 9 February 2022, and incorporates all of its disclosures herein. [Explanation of Symbols]

[0057] 1 burner 2. Melting furnace 3 Piping 4 Cyclone 5 Piping 8. Bug Filter 9 Blower 11. Combustible gas supply pipe 12. Fuel supply pipe 13 Raw material supply pipe 100 Thermal spraying equipment

Claims

1. An inorganic powder consisting of spherical alumina powder and spherical silica powder, Under conditions of room temperature of 25°C and humidity of 65%, the angle of repose measured according to procedure A below is between 35° and 47°. In the volume frequency particle size distribution measured by the wet laser diffraction scattering method, when the particle size at which the cumulative value is 10% is defined as D10, the particle size at which the cumulative value is 50% is defined as D50, and the particle size at which the cumulative value is 97% is defined as D97, (D 97 - D 10) / D 50 is between 4 and 30, Inorganic powder in which D50 - D10 is between 0.5 μm and 17 μm. (Procedure A) A funnel with an outlet diameter of 0.5 cm is attached to a horizontal plate installed on the powder tester, at a height of 15 cm. The inorganic powder is continuously supplied vertically onto the surface of a horizontal plate via a funnel, forming a cone-shaped deposit that maintains a constant shape. Using a protractor, determine the elevation angle between the side surface of the cone-shaped deposit and the surface of the horizontal plate, and define this as the angle of repose (°). Next, a 110g weight is dropped onto a horizontal plate three times from a height of 18cm to impart impact. Then, using a protractor, the elevation angle between the side of the conical deposit and the surface of the horizontal plate is determined and defined as the collapse angle (°).

2. The inorganic powder according to claim 1, An inorganic powder whose disintegration angle, measured according to procedure A under conditions of room temperature of 25°C and humidity of 65%, is between 20° and 37°.

3. The inorganic powder according to claim 1 or 2, Under conditions of room temperature of 25°C and humidity of 55%, the bulk density measured by procedure B below is 1.5 g / cm³. ３ 2.3g / cm or more ３ The following are inorganic powders. (Procedure B) The inorganic powder is added at a rate of 5-10 g per minute, allowed to fall naturally from a height of 25 cm, and then 100 cm ３ Pour the mixture into the measuring cup and continue until it overflows, preparing a heaping cup. Next, for the overflowing cups, without tapping, the amount that overflowed from the top of the cup was leveled off, and the mass (g) of the inorganic powder filled in the cup was measured, and the loose bulk density (g / cm³) was determined. ３ Calculate the result. On the other hand, for the overflowing cup, after tapping it 180 times in the vertical direction (stroke length 2 cm, 1 second / tap), and leveling off the excess powder on the top of the cup, the mass (g) of the inorganic powder filled in the cup was measured, and the bulk density (g / cm³) was determined. ３ Calculate the result.

4. The inorganic powder according to claim 3, When the loose bulk density measured in procedure B above is A and the firm bulk density is P, An inorganic powder whose degree of compression, calculated based on ((P - A) / P) × 100, is between 30% and 44%.

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