Spherical Silica Powder

Abstract

A spherical silica powder according to the present invention has an angle of repose of 30° to 50°, inclusive, as measured using a powder tester.

Description

[Technical Field]

[0001] The present invention relates to a spherical silica powder. [Background technology]

[0002] Various developments have been made so far regarding spheres. For example, a technique described in Patent Document 1 is known as a technique of this type. Patent Document 1 describes a method for obtaining molten spherical silica by injecting a siliceous raw material powder into a flame to melt it. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-191317 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of investigations by the present inventors, it has been found that the fused spherical silica described in Patent Document 1 has room for improvement in terms of resin mixability and flowability. [Means for solving the problem]

[0005] After further investigation, the inventors discovered that resin mixability and flowability can be improved by appropriately controlling the particle size distribution of the spherical silica powder using the angle of repose as an indicator, and thus completed the present invention.

[0006] According to one aspect of the present invention, there is provided the following spherical silica powder. 1. A spherical silica powder having an angle of repose of 30° or more and 50° or less, measured according to Procedure A below. (Step A) A funnel with an outlet diameter of 0.5 cm is attached at a position 15 cm high from the horizontal plate installed in the powder tester. The spherical silica powder is continuously fed vertically through a funnel onto the surface of a horizontal plate to form a cone-shaped deposit that maintains a constant shape. Using a protractor, determine the angle of elevation between the side of the cone-shaped pile and the surface of the horizontal plate, and use this as the angle of repose (°). Next, a 110g weight is dropped three times from a height of 18cm onto the horizontal plate to impact it. After that, using a protractor, the angle of elevation between the side of the cone-shaped pile and the surface of the horizontal plate is calculated, and this is taken as the collapse angle (°). 2. The spherical silica powder according to 1., A spherical silica powder having a collapse angle measured according to procedure A of 15° or more and 39° or less. 3. The spherical silica powder according to 1. or 2., When the loose bulk density measured by the following procedure B is A and the hard bulk density is P, The degree of compression calculated based on ((PA) / P) x 100 is 15% or more and 50% or less. Spherical silica powder. (Step B) The spherical silica powder was allowed to fall naturally from a height of 25 cm at a rate of 5 to 10 g per minute, and then dropped to a height of 100 cm. 3 Prepare a heaping cup by pouring the contents into the measuring cup and continuing until it overflows. Next, for the heaping cup, without tapping, the amount overflowing on the top of the cup was leveled off, and then the mass (g) of the spherical silica powder filled in the cup was measured, and the loose bulk density (g / cm 3 ) is calculated. On the other hand, for the heaping cup, after tapping it up and down 180 times (stroke length 2 cm, 1 second / time), the amount that overflowed onto the top of the cup was leveled off, and the mass (g) of the spherical silica powder filled in the cup was measured, and the compacted bulk density (g / cm 3 ) is calculated. 4. The spherical silica powder according to any one of items 1 to 3, The compacted bulk density measured by the procedure B is 1.2 g / cm 3 More than 1.6g / cm 3 The following is a spherical silica powder. 5. The spherical silica powder according to any one of 1. to 4., In the volume frequency particle size distribution measured by the wet laser diffraction scattering method, the particle size at which the cumulative value reaches 10% is defined as D 10 The particle diameter at which the cumulative value reaches 50% is D 50 The particle diameter at which the cumulative value reaches 97% is D 97 When (D 97 -D 10 ) / D 50 is 1.0 or more and 10.0 or less. 6. The spherical silica powder according to any one of 1. to 5., In the volume frequency particle size distribution measured by the wet laser diffraction scattering method, the particle diameter at which the cumulative value reaches 50% is defined as D 50 The particle diameter at which the cumulative value reaches 97% is D 97 When D 97 / D 50 is 2.0 or more and 30.0 or less. [Effects of the Invention]

[0007] According to the present invention, a spherical silica powder having excellent resin mixability and flowability is provided. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the configuration of a thermal spraying device used to produce spherical silica powder. DETAILED DESCRIPTION OF THE INVENTION

[0009] The spherical silica powder of this embodiment will be outlined below.

[0010] The spherical silica powder of this embodiment is configured so that the angle of repose measured according to the following procedure A is 30° or more and 50° or less.

[0011] The lower limit of the angle of repose is at least 30°, preferably at least 32°, and more preferably at least 35°, which can improve the resin mixability. The upper limit of the angle of repose is 50° or less, preferably 47° or less, and more preferably 45° or less, which can improve the fluidity.

[0012] The lower limit of the collapse angle is, for example, 15° or more, preferably 17° or more, and more preferably 20° or more, which can improve the releasability. The upper limit of the collapse angle is, for example, 39° or less, preferably 35° or less, and more preferably 30° or less, which can improve the fluidity.

[0013] The spherical silica powder of this embodiment may be configured so that the compressibility calculated based on ((PA) / P)×100, where A is the loose bulk density and P is the packed bulk density, measured by the following procedure B, is, for example, 15% or more and 50% or less.

[0014] The lower limit of the compression degree is, for example, 15% or more, preferably 17% or more, and more preferably 20% or more, which can improve the handling properties. The upper limit of the degree of compression is, for example, 50% or less, preferably 40% or less, and more preferably 30% or less, which can improve the fluidity.

[0015] The lower limit of the compacted bulk density (P) is, for example, 1.2 g / cm 3 or more, preferably 1.25 g / cm 3 More preferably, 1.3 g / cm 3 This makes it possible to improve the handling characteristics. The upper limit of the compacted bulk density (P) is, for example, 1.6 g / cm 3 or less, preferably 1.50 g / cm 3 or less, more preferably 1.4 g / cm 3 This makes it possible to improve the resin mixability.

[0016] The angle of repose and the angle of collapse of spherical silica powder can be measured according to the following procedure A under conditions of room temperature of 25°C and humidity of 65%. First, a funnel with an outlet diameter of 0.5 cm is attached at a position 15 cm high from the horizontal plate installed in the powder tester. Spherical silica powder is continuously fed vertically through a funnel onto the surface of a horizontal plate to form a cone-shaped deposit that maintains a constant shape. Using a protractor, determine the angle of elevation between the side of the cone-shaped pile and the surface of the horizontal plate, and use this as the angle of repose (°). Next, a 110g weight is dropped three times from a height of 18cm onto the horizontal plate to impact it. After that, using a protractor, the angle of elevation between the side of the cone-shaped pile and the surface of the horizontal plate is calculated, and this is taken as the collapse angle (°).

[0017] The loose bulk density, packed bulk density, and compressibility of spherical silica powder can be measured according to the following procedure B under conditions of room temperature of 25°C and humidity of 55%. First, spherical silica powder was allowed to fall naturally from a height of 25 cm at a rate of 5 to 10 g per minute, and then dropped to a height of 100 cm. 3 Prepare a heaping cup by pouring the contents into the measuring cup and continuing until it overflows. Next, for the heaping cup, without tapping, the amount overflowing on the top of the cup was leveled off, and then the mass (g) of the spherical silica powder filled in the cup was measured, and the loose bulk density (g / cm 3 ) is calculated. On the other hand, for the heaping cup, after tapping it up and down 180 times (stroke length 2 cm, 1 second / time), the amount that overflowed onto the top of the cup was leveled off, and the mass (g) of the spherical silica powder filled in the cup was measured, and the compacted bulk density (g / cm 3 ) is calculated.

[0018] In this embodiment, the above-mentioned compacted bulk density, loose bulk density, and compressibility can be controlled by appropriately selecting, for example, the raw material components of the spherical silica powder, the manufacturing method of the spherical silica powder, etc. Among these, for example, appropriately controlling the powder supply amount and / or the flame formation conditions can be cited as factors for setting the above-mentioned compacted bulk density, loose bulk density, and compressibility within the desired numerical range.

[0019] The volume frequency particle size distribution of the spherical silica powder is measured by a wet laser diffraction scattering method, and the particle size at which the cumulative value reaches 10% in the volume frequency particle size distribution is defined as D 10 The particle diameter at which the cumulative value reaches 50% is D 50 The particle diameter at which the cumulative value reaches 97% is D 97 Let's say.

[0020] (D 97 -D 10 ) / D 50 The upper limit of is, for example, 10.0 or less, preferably 7.0 or less, and more preferably 5.0 or less, whereby the width of the particle size distribution becomes sharper and the flowability can be improved. On the other hand, (D 97 -D 10 ) / D 50 The lower limit of is, for example, 1.0 or more, preferably 1.1 or more, and more preferably 2.0 or more, whereby the particle size distribution has a certain width, and moldability can be improved.

[0021] D 97 / D 50 The upper limit of is, for example, 30.0 or less, preferably 20.0 or less, and more preferably 15.0 or less. This makes the particle size of the coarse particles sharper, and can improve the prevention of molding defects in resin molded products caused by the coarse particles. On the other hand, D 97 / D 50 The lower limit of is, for example, 2.0 or more, preferably 3.0 or more, and more preferably 5.0 or more, whereby the particle size distribution has a certain width, and the flowability and moldability can be improved.

[0022] The particle size distribution of spherical silica powder is a value based on particle size measurement using laser diffraction light scattering. Measurements can be performed 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 pretreatment involves dispersing the powder for 1 minute using a homogenizer at 200 W. The PIDS (Polarization Intensity Differential Scattering) concentration is adjusted to 45-55%. The refractive index of water is set to 1.33, while the refractive index of the powder is determined based on the refractive index of the powder material. For example, the refractive index of amorphous silica is set to 1.50.

[0023] A method for producing the spherical silica powder of this embodiment will be described.

[0024] Spherical silica powder, also known as molten spherical particles, is produced by supplying siliceous 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 it at a temperature above its melting point. If necessary, the molten spherical particles thus obtained may be classified or sieved.

[0025] An example of a schematic diagram of a thermal spraying device used to produce spherical silica powder is shown in FIG. The thermal spraying device 100 in FIG. 1 is composed of a melting furnace 2 equipped with a burner 1, cyclones 4 and 6 for classifying molten spherical particles generated by high-temperature exhaust gas from the flame by suction with a blower 9, and a bag filter 8 for collecting fine powder that could not be collected by the cyclones 4 and 6. The melting furnace 2 is constructed as a vertical furnace body, but is not limited to this, and may be a horizontal furnace or an inclined furnace that is horizontal and blows out flames horizontally. The hot exhaust gas is cooled by pipes 3, 5, and 7, which are equipped with water-cooled jackets. The blower 9 may be connected to a suction gas amount control valve and a gas exhaust port (not shown). A collected powder removal device (not shown) may be connected to the lower portions of the melting furnace 2, the cyclones 4 and 6, and the back filter 8. The classification can be carried out using known equipment such as a heavy settling chamber, a cyclone, a classifier having a rotor, etc. This classification operation may be carried out during the transportation process of the molten spheroidized product, or may be carried out in a separate line after collecting the molten spheroidized product all at once.

[0026] As the combustible gas, for example, one or more of acetylene, propane, butane, etc. may be used, but propane, butane, or a mixture thereof, which have a relatively small calorific value, are preferred. As the combustion supporting gas, for example, a gas containing oxygen is used. Generally, it is most preferable to use pure oxygen of 99% by weight or more, as it is inexpensive. In order to reduce the calorific value of the gas, an inert gas such as air or argon can be mixed with the combustion supporting gas.

[0027] The spherical silica powder may be either amorphous and / or crystalline.

[0028] The amorphous fraction of the spherical silica powder is preferably 95% or more, and more preferably 97% or more, as measured by the following method. The amorphous fraction is determined by X-ray diffraction analysis using a powder X-ray diffractometer (e.g., Rigaku Corporation, Model MiniFlex) in the 2θ range of 26° to 27.5° with CuKα radiation, and the intensity ratio of specific diffraction peaks is used to determine the amorphous fraction. In the case of siliceous powder, crystalline silica exhibits a main peak at 26.7°, while amorphous silica exhibits no peak. When amorphous and crystalline silica are mixed, a peak height at 26.7° corresponding to the proportion of crystalline silica is obtained. Therefore, the crystalline silica mixing ratio (X-ray diffraction intensity of sample / X-ray diffraction intensity of crystalline silica) is calculated from the ratio of the X-ray intensity of the sample to that of a crystalline silica standard sample, and the amorphous fraction is then calculated using the formula: amorphous fraction (%) = (1 - crystalline silica mixing ratio) × 100.

[0029] The spherical silica powder has a specific surface area S measured by the BET method. B and the theoretical specific surface area S calculated from the particle size distribution C Ratio to (S B / S C) is preferably, for example, 2.5 or less. A large ratio means that the resin composition contains a large amount of ultrafine particles that cannot be detected by a particle size distribution measuring instrument such as a laser diffraction method. From the viewpoint of suppressing an increase in viscosity when the spherical silica particles are blended into the resin composition, the above S B / S C The value is more preferably 2.5 or less, and particularly preferably 2.0 or less.

[0030] Specific surface area S B is a value based on the BET method, and can be measured using, for example, a "Model 4-SORBU2" (manufactured by Yuasa Ionics Co., Ltd.) as a specific surface area measuring device. Theoretical specific surface area S C The particle size distribution can also be calculated automatically by the particle size distribution analyzer. The principle of this analyzer is as follows: C = 6 / (ρ·D), where D is the area-average particle diameter (μm) and ρ is the density of the spherical silica powder (g / cm 3 ) For example, if the powder is amorphous silica, it is 2.21. D can be calculated using the formula D=Σ(ni·ai·di) / Σ(ni·ai). This means that in a single powder mass, there are n1, n2, ni, and nk particles with diameters d1, d2, ···di, and ··dk, in order of smallest particle diameter, and if the surface areas per particle are a1, a2, ···ai, and ··ak, respectively, D can be calculated using the formula D=(n1·a1·d1+n2·a2·d2+···+ni·ai·di+···+nk·ak·dk) / (n1·a1·+n2·a2+···+ni·ai+···+nk·ak).

[0031] It is preferable that the spherical silica powder does not substantially contain particles smaller than 50 nm, which can prevent an increase in viscosity when blended into a resin composition. "Substantially free of particles smaller than 50 nm" means that the number of particles smaller than 50 nm in 100 random photographs taken at a magnification of 50,000 times using an electron microscope is counted, and the average value per photograph is calculated to be less than 50. The fewer particles smaller than 50 nm, the better.

[0032] Electron micrographs were taken using a field emission scanning electron microscope (JEOL model "FE-SEM, JSM-6301F") at an acceleration voltage of 15 kV and an irradiation current of 3 × 10-11 A. As a pretreatment for the photographs, carbon was evaporated onto the spherical silica powder for 2 seconds using a vacuum evaporation device (JEOL model "JEE-4X"), and then gold-palladium was evaporated for 60 seconds.

[0033] As for the degree of "sphericity" of the spherical silica powder, for example, it is preferable that the average sphericity of particles having a particle diameter less than 75% (d75) of the cumulative particle size distribution is 0.90 or more, and the average sphericity of particles having a particle diameter of d75 or more is 0.85 or more. In general, increasing the average sphericity of the spherical silica powder tends to improve the flowability, but the effect of this embodiment can be further enhanced by setting the average sphericity of the coarse particles having a particle diameter of d75 or more to 0.85 or more.

[0034] The average sphericity can be measured by taking particle images taken with a stereomicroscope (for example, Nikon Model "SMZ-10"), a scanning electron microscope, or the like, and inputting them into an image analyzer (for example, Nippon Avionics), as follows: The projected area (A) and perimeter (PM) of the particle are measured from the photograph. If the area of ​​a perfect circle corresponding to the perimeter (PM) is (B), the particle's circularity can be expressed as A / B. Therefore, assuming a perfect circle with the same perimeter as the perimeter (PM) of the sample particle, PM = 2πr, B = πr 2 Therefore, B=π×(PM / 2π) 2 The sphericity of each particle is: Sphericity = A / B = A × 4π / (PM) 2 The circularity of 200 randomly selected particles thus obtained is determined, and the average value is taken as the average sphericity.

[0035] In addition, as a method for measuring circularity other than the above, the circularity of each particle is automatically and quantitatively measured using a particle image analyzer (for example, the Sysmex model "FPIA-1000"), and the circularity is calculated using the formula: circularity = (circularity) 2 It can also be calculated by converting it as follows:

[0036] A resin composition containing the spherical silica powder of the present invention can be suitably used as a resin molding material.

[0037] Next, the resin composition of this embodiment will be described.

[0038] The resin composition contains, in addition to the spherical silica powder of the present invention, a resin and known resin additives.

[0039] The resin composition may contain spherical silica powder alone or in combination with other fillers. The resin composition may contain 10 to 99% by mass of spherical silica powder, or 10 to 99% by mass of a mixed inorganic powder containing spherical silica powder and other fillers. The content of the 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 the spherical silica powder. In this specification, unless otherwise specified, the symbol "to" indicates that the upper and lower limits are included.

[0040] Examples of other fillers include alumina, titania, silicon nitride, aluminum nitride, silicon carbide, talc, calcium carbonate, etc. The average particle size of the other fillers is about 5 to 100 μm, and there are no particular restrictions on the particle size structure and shape.

[0041] Examples of the resin include epoxy resin, silicone resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyamide such as polyimide, polyamideimide, polyetherimide, polyester such as polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, wholly aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide-modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber-styrene) resin, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin, etc. These may be used alone or in combination of two or more.

[0042] The resin composition can be produced, for example, by blending raw material components in a predetermined ratio using a blender, a Henschel mixer, or the like, kneading the mixture using a heated roll, a kneader, a single-screw or twin-screw extruder, or the like, cooling the mixture, and then pulverizing it.

[0043] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. [Example]

[0044] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions of these examples.

[0045] <Production of spherical silica powder> A burner 1 was installed above a melting furnace 2, and a collection line consisting of cyclones 4 and 6 and a bag filter 8 was directly connected below the burner 1. The thermal spraying apparatus 100 shown in FIG. 1 was used to produce spherical silica powder. Burner 1 has a double-pipe structure capable of forming an inner flame and an outer flame, and is installed at the top of melting furnace 2, to which combustible gas supply pipe 11, combustion supporting gas supply pipe 12, and raw material supply pipe 13 are connected. In the melting furnace 2, siliceous raw material powder is fed into a high-temperature flame through a raw material supply pipe 13 and melted to form molten spherical particles. The molten spherical particles that have passed through the melting furnace 2 are sucked in by a blower 9 together with the combustion exhaust gas, move by the air through pipes 3, 5, and 7, and are classified and collected in cyclones 4 and 6 or a bag filter 8.

[0046] Examples 1 to 12 Using the above-mentioned thermal spraying device 100, LPG was supplied as a combustible gas from the combustible gas supply pipe 11, and oxygen was supplied as a combustion supporting gas from the combustion supporting gas supply pipe 12. A high-temperature flame was formed by combustion of the LPG and oxygen in the burner 1. A 20 Nm 3 / hr, burner combustible gas supply rate 6Nm3 / hr, auxiliary gas supply rate 20Nm 3 / hr. Natural silica powder (average particle size 5 μm to 50 μm) was supplied to the flame formed as described above to obtain spherical amorphous silica powder. The obtained powder was classified and the classified powders were mixed to obtain powders of Examples 1 to 12.

[0047] (Comparative Examples 1 and 2) A spherical silica powder was obtained in the same manner as in Example 1 above, except for the powder supply amount and the flame formation conditions. In Comparative Example 1, the powder supply amount was 1.1 times that of Example 1, and the carrier gas for the raw material was 15 Nm 3 / hr, burner flammable gas supply volume 6Nm 3 / hr, the supply of combustion support gas is 45Nm 3 / hr. In Comparative Example 2, the powder supply amount was 0.5 times that of Example 1, and the carrier gas for the raw material was 20 Nm 3 / hr, burner flammable gas supply volume 8Nm 3 / hr, the supply of combustion support gas is 40Nm 3 / hr.

[0048] [Table 1]

[0049] <Angle of repose, angle of collapse> The angle of repose and the angle of collapse of the spherical silica powder were determined under the conditions of a room temperature of 25°C and a humidity of 65% as follows. A funnel with an outlet diameter of 0.5 cm was attached at a position 15 cm above the horizontal plate installed in the powder tester. The obtained spherical silica powder was continuously fed vertically onto the surface of the horizontal plate through a funnel to form a conical deposit that maintained a constant shape. Using a protractor, the angle of elevation between the side of the cone-shaped pile and the surface of the horizontal plate was determined, and this was taken as the angle of repose (°). Next, a 110g weight was dropped three times from a height of 18cm onto the horizontal plate to impact it. After that, a protractor was used to measure the angle of elevation between the side of the cone-shaped deposit and the surface of the horizontal plate, which was taken as the collapse angle (°).

[0050] <Loose bulk density, hard bulk density, compression degree> The loose bulk density, packed bulk density and compressibility of the spherical silica powder were determined under the conditions of room temperature of 25°C and humidity of 55% as follows. The obtained spherical silica powder was allowed to fall naturally from a height of 25 cm at a rate of 5 to 10 g per minute, and then dropped to a height of 100 cm. 3 A heaping cup was prepared by pouring the liquid into a measuring cup and continuing until it overflowed. Next, for the heaping cup, without tapping, the amount overflowing on the top of the cup was leveled off, and then the mass (g) of the spherical silica powder filled in the cup was measured, and the loose bulk density (g / cm 3 ) was calculated. On the other hand, for the heaping cup, after tapping it up and down 180 times (stroke length 2 cm, 1 second / time), the amount that overflowed onto the top of the cup was leveled off, and the mass (g) of the spherical silica powder filled in the cup was measured, and the compacted bulk density (g / cm 3 ) was calculated. When the loose bulk density obtained by the above procedure is A and the hardened bulk density is P, the compressibility (%) was calculated based on the formula: ((PA) / P)×100.

[0051] <Particle size distribution> The volume frequency particle size distribution of the obtained spherical silica powder was determined by a wet laser diffraction scattering method using a particle size distribution analyzer (Beckman Coulter, LS-13-230). Water was used as the solvent, and the powder was pre-dispersed for 1 minute using a homogenizer at 200 W output before measurement. The PIDS (Polarization Intensity Differential Scattering) concentration was adjusted to 45-55% before measurement. Based on the obtained volume frequency particle size distribution, the particle diameter D at which the cumulative value becomes X% X was calculated.

[0052] (resin miscibility) 70 parts by mass of the obtained silica powder and 30 parts by mass of bisphenol F type epoxy resin (JER-807 manufactured by Mitsubishi Chemical Corporation) were mixed at room temperature at 2000 rpm for 3 minutes using a rotation-revolution mixer (Awatori Rentaro "ARE-310") The obtained resin mixture was visually inspected for residual powder, separation, and the presence of clusters due to insufficient mixing with the resin, and samples that showed no above-mentioned appearance defects were rated as good, and samples that showed the above-mentioned appearance defects were rated as bad.

[0053] (Fluidity of Resin Composition) 90 parts by mass of the obtained silica powder, 5.5 parts by mass of biphenyl-type epoxy resin (YX-4000HK manufactured by Mitsubishi Chemical Corporation), 4.8 parts by mass of phenol resin (phenol aralkyl resin, MEHC-7800S manufactured by Meiwa Chemical Industry 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 and Engineering Co., Ltd.) at room temperature and a rotation speed of 2000 rpm. The resulting mixture was heated and kneaded in a co-rotating intermeshing twin-screw extruder kneader (screw diameter D = 25 mm, L / D = 10.2, paddle rotation speed 50 to 120 rpm, discharge rate 3.0 kg / Hr, kneaded product temperature 98 to 100°C) to obtain a resin composition. The obtained resin composition was used in a spiral flow mold in accordance with EMMI-1-66 (Epoxy Molding Material Institute; Society of Plastics Industry) at a mold temperature of 175°C, a molding pressure of 7.4 MPa, and a pressure dwell time of 90 seconds. A spiral flow of 120 cm or more was evaluated as good, and a spiral flow of less than 120 cm was evaluated as poor.

[0054] The spherical silica powders of Examples 1 to 12 showed results that they could improve the fluidity compared to Comparative Example 1, and could improve the resin mixability compared to Comparative Example 2.

[0055] This application claims priority based on Japanese Patent Application No. 2022-018508, filed February 9, 2022, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0056] 1 burner 2. Melting furnace 3 Piping 4. Cyclone 5 Piping 6. Cyclone 7 Piping 8. Bag filter 9 Blower 11 Combustible gas supply pipe 12 Combustion auxiliary gas supply pipe 13 Raw material supply pipe 100 Thermal spraying equipment

Claims

1. A spherical silica powder having an angle of repose of 30° or more and 50° or less, measured according to the following procedure A1. (Procedure A1) Under conditions of room temperature of 25° C. and humidity of 65%, a funnel with an outlet diameter of 0.5 cm is attached at a position 15 cm above a horizontal plate set in a powder tester. The spherical silica powder is continuously fed vertically through a funnel onto the surface of a horizontal plate to form a cone-shaped deposit that maintains a constant shape. Using a protractor, determine the angle of elevation between the side of the cone-shaped pile and the surface of the horizontal plate, and use this as the angle of repose (°).

2. The spherical silica powder according to claim 1, A spherical silica powder having a collapse angle of 15° or more and 39° or less, measured according to the following procedure A2. (Procedure A2) Following step A1, a 110 g weight is dropped three times from a height of 18 cm onto the horizontal plate to apply impact. After that, a protractor is used to determine the angle of elevation between the side of the conical pile and the surface of the horizontal plate, and this is taken as the collapse angle (°).

3. The spherical silica powder according to claim 1 or 2, When the loose bulk density measured by the following procedure is A and the hardened bulk density is P, The degree of compression calculated based on ((P-A) / P) x 100 is 15% or more and 50% or less. Spherical silica powder. (procedure) Under conditions of room temperature 25°C and humidity 55%, the spherical silica powder was allowed to fall naturally from a height of 25 cm at a rate of 5 to 10 g per minute, and then the powder was dropped to a height of 100 cm. ３ Prepare a heaping cup by pouring the contents into the measuring cup and continuing until it overflows. Next, for the heaping cup, the amount overflowing from the top of the cup was leveled off without tapping, and then the mass (g) of the spherical silica powder filled in the cup was measured, and the loose bulk density (g / cm ３ ) is calculated. On the other hand, the heaping cup was tapped up and down 180 times (stroke length 2 cm, 1 second / time), and then the overflowed portion on the top surface of the cup was leveled off. Then, the mass (g) of the spherical silica powder filled in the cup was measured, and the compacted bulk density (g / cm ３ ) is calculated.

4. The spherical silica powder according to claim 1 or 2, The compacted bulk density measured by the following procedure is 1.2 g / cm ３ 1.6g / cm or more ３ The spherical silica powder is as follows: (procedure) Under conditions of room temperature 25°C and humidity 55%, the spherical silica powder is allowed to fall from a height of 25 cm at a rate of 5 to 10 g per minute into a 100 cm 3 measuring cup, and this is continued until the powder overflows from the cup, preparing a heaping cup. Next, the heaping cup was tapped up and down 180 times (stroke length 2 cm, 1 second / tap), and the excess powder was leveled off from the top of the cup. The mass (g) of the spherical silica powder filled in the cup was then measured, and the compacted bulk density (g / cm3) was calculated.

5. The spherical silica powder according to claim 1 or 2, In the volume frequency particle size distribution measured by the wet laser diffraction scattering method, the particle diameter at which the cumulative value reaches 10% is defined as D １０ The particle diameter at which the cumulative value reaches 50% is D ５０ The particle diameter at which the cumulative value reaches 97% is D ９７ When (D ９７ -D １０ ) / D ５０ is 1.0 or more and 10.0 or less.

6. The spherical silica powder according to claim 1 or 2, In the volume frequency particle size distribution measured by the wet laser diffraction scattering method, the particle diameter at which the cumulative value reaches 50% is defined as D ５０ The particle diameter at which the cumulative value reaches 97% is D ９７ When D ９７ / D ５０ is 2.0 or more and 30.0 or less.

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