Spherical alumina powder

Abstract

The present invention provides a spherical alumina powder having a structure in which the angle of difference is 8-20 DEG.

Description

Technical Field

[0001] The present invention relates to a spherical alumina powder. Background Art

[0002] To date, various developments have been made on spherical alumina powders. As such a technique, for example, the technique described in Patent Document 1 is known. Patent Document 1 describes a spherical alumina powder having an average particle diameter (D 50 ) of 50 μm or less and a sphericity of 0.9 or more (Claim 1 of Patent Document 1, etc.).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2015-193493 Summary of the Invention

[0006] However, as a result of research by the present inventors, it has been found that there is room for improvement in terms of burr generation or thermal conductivity when the spherical alumina powder described in Patent Document 1 is used in a resin molding material.

[0007] As a result of further research by the present inventors, it has been found that by appropriately controlling the angle of difference, which is one of the powder characteristics of the spherical alumina powder, burrs generated during molding using a resin molding material containing the same can be suppressed, and thus the present invention has been completed.

[0008] According to one aspect of the present invention, the following spherical alumina powder is provided.

[0009] 1. A spherical alumina powder, wherein

[0010] the angle of difference measured according to the following steps is 8° or more and 20° or less.

[0011] (Steps)

[0012] A funnel having an outlet diameter of 0.5 cm is installed at a position 15 cm above the horizontal plate provided in the powder tester.

[0013] Via the funnel, the spherical alumina powder is continuously supplied from the vertical direction onto the surface of the horizontal plate to form a conical deposit having a certain shape.

[0014] Using a protractor, the elevation angle formed by the side surface of the conical deposit and the surface of the horizontal plate is obtained and used as the angle of repose (°).

[0015] Next, a 110 g weight was dropped 3 times from a height of 18 cm to apply an impact to the horizontal plate. Then, a protractor was used to find the elevation angle formed by the side surface of the conical deposit and the surface of the horizontal plate, and this was taken as the collapse angle (°). The difference between the obtained angle of repose and the collapse angle was taken as the difference angle (°).

[0016] 2. The spherical alumina powder according to 1., wherein,

[0017] The angle of repose measured according to the above steps is 30° or more and 43° or less.

[0018] 3. The spherical alumina powder according to 1. or 2., wherein,

[0019] The bulk density measured by the following steps is 1.10 g / cm 3 or more and 1.50 g / cm 3 or less.

[0020] (Steps)

[0021] The spherical alumina powder was allowed to naturally fall from a height of 25 cm at an input rate of 5 - 10 g per minute and was put into the inside of a measuring cup of 100 cm 3 until it overflowed from the cup, thereby preparing a full cup.

[0022] Next, without tapping the full cup, the part that overflowed onto the upper surface of the cup was scraped off, then the mass (g) of the spherical alumina powder filled in the cup was measured, and the bulk density (g / cm 3 ) was calculated.

[0023] On the other hand, after tapping the full cup 180 times in the vertical direction (stroke length 2 cm, 1 time per second), the part that overflowed onto the upper surface of the cup was scraped off, then the mass (g) of the spherical alumina powder filled in the cup was measured, and the tapped density (g / cm 3 ) was calculated.

[0024] 4. The spherical alumina powder according to any one of 1. to 3., wherein,

[0025] When the bulk density measured by the above steps is set as A and the tapped density is set as P, the degree of compressibility calculated according to ((P - A) / P)×100 is 35% or more and 55% or less.

[0026] 5. The spherical alumina powder according to any one of 1. to 4., wherein,

[0027] In the volume frequency particle size distribution measured by the wet laser diffraction scattering method, the particle size at which the cumulative value becomes 25% is set as D 25Set the particle size at which the cumulative value becomes 97% as D 97 When

[0028] D 97 / D 25 is 8.0 or more and 30.0 or less.

[0029] 6. The spherical alumina powder according to any one of 1. to 5., wherein

[0030] In the volume frequency particle size distribution measured by the wet-based laser diffraction scattering method, set the particle size at which the cumulative value becomes 50% as D 50 Set the particle size at which the cumulative value becomes 97% as D 97 When

[0031] D 97 / D 50 is 5.0 or more and 20.0 or less.

[0032] According to the present invention, there is provided a spherical alumina powder that is excellent in burr suppression or thermal conductivity when used in a resin molding material. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic cross-sectional view showing the structure of a spraying device. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in all the drawings, the same reference numerals are assigned to the same constituent elements, and the description will be appropriately omitted. And the figures are schematic and do not match the actual dimensional ratios.

[0035] The spherical alumina powder of the present embodiment will be described.

[0036] The spherical alumina powder of the present embodiment is configured such that the angle of difference, which is one of the powder properties, is 8° or more and 20° or less.

[0037] Regarding the powder properties of the angle of difference, angle of repose, and angle of collapse of the spherical alumina powder, they can be measured according to the following steps.

[0038] Install a funnel with an outlet diameter of 0.5 cm at a position 15 cm above the horizontal plate provided in the powder tester.

[0039] Via the funnel, continuously supply the spherical alumina powder from the vertical direction onto the surface of the horizontal plate to form a conical deposit having a certain shape.

[0040] Use a protractor to find the elevation angle formed by the side surface of the conical deposit and the surface of the horizontal plate, and use it as the angle of repose (°).

[0041] Next, a 110 g weight was dropped from a height of 18 cm three times to apply an impact to the horizontal plate. Then, a protractor was used to find the elevation angle formed by the side surface of the conical deposit and the surface of the horizontal plate, and this was taken as the collapse angle (°). The difference between the obtained angle of repose and the collapse angle was taken as the difference angle (°).

[0042] Although the detailed mechanism is not yet clear, it is considered that by controlling the difference angle of the above spherical alumina powder, high dispersibility can be achieved in the resin molding material (resin composition) when compounded into the resin, and thus burr generation during molding can be suppressed and high thermal conductivity can be exhibited.

[0043] The lower limit of the difference angle of the spherical alumina powder is 8° or more, preferably 9° or more, and more preferably 10° or more. Thereby, burr generation during molding of the resin molding material containing the spherical alumina powder can be suppressed.

[0044] The upper limit of the above difference angle is, for example, 20° or less, preferably 18° or less, and more preferably 16° or less. Thereby, the fluidity of the resin molding material can be improved.

[0045] The lower limit of the angle of repose of the spherical alumina powder is, for example, 30° or more, preferably 31° or more, and more preferably 32° or more. Thereby, the resin mixability in the resin molding material can be improved.

[0046] The upper limit of the above angle of repose is, for example, 43° or less, preferably 42° or less, and more preferably 41° or less. Thereby, the fluidity of the resin molding material can be improved.

[0047] In the present embodiment, for example, by appropriately selecting the raw material composition of the spherical alumina powder or the manufacturing method of the spherical alumina powder, etc., the above difference angle and angle of repose can be controlled. Among these, for example, elements such as appropriately controlling the raw material supply amount, raw material particle size, flame temperature, combustible gas, combustion-supporting gas, dispersion gas, etc. of the molten flame conditions, elements using alumina raw material powders of different particle sizes, or elements such as appropriately performing classification operations such as removing fine particles can be cited as elements for setting the above difference angle and angle of repose within the desired numerical range.

[0048] The spherical alumina powder can be configured as follows: when the loose bulk density measured by the following steps is set as A and the tapped density is set as P, the degree of compressibility obtained by ((P - A) / P)×100 is, for example, 35% or more and 55% or less.

[0049] Regarding the loose bulk density, tapped density, and degree of compressibility, they can be measured according to the following steps under the conditions of room temperature of 25°C and humidity of 55%.

[0050] Let the spherical alumina powder fall naturally from a height of 25 cm at an input rate of 5 to 10 g per minute and be put into the interior of a measuring cup of 100 cm 3 , and continue until it overflows from the cup to prepare a cup full of powder.

[0051] Next, without tapping the cup full of powder, scrape off the part that has overflowed onto the upper surface of the cup, then measure the mass (g) of the spherical alumina powder filled in the cup, and calculate the loose bulk density (g / cm 3 ).

[0052] On the other hand, after tapping the cup full of powder 180 times in the vertical direction (stroke length 2 cm, 1 time per second), scrape off the part that has overflowed onto the upper surface of the cup, then measure the mass (g) of the spherical alumina powder filled in the cup, and calculate the tapped density (g / cm 3 ).

[0053] Using the loose bulk density (A) and the tapped density (P) obtained by the above steps, calculate the degree of compressibility (%) according to ((P - A) / P)×100.

[0054] The lower limit of the degree of compressibility is, for example, 35% or more, preferably 38% or more, and more preferably 40% or more. Thus, the operability of the spherical alumina powder can be improved.

[0055] The upper limit of the degree of compressibility is, for example, 55% or less, preferably 53% or less, and more preferably 50% or less. Thus, the mixing property of the resin and the spherical alumina powder can be improved.

[0056] The spherical alumina powder can be configured as follows: the loose bulk density (A) is 1.10 g / cm 3 or more and 1.50 g / cm 3 or less.

[0057] The lower limit of the loose bulk density (A) is, for example, 1.10 cm 3 / g or more, preferably 1.15 cm 3 / g or more, and more preferably 1.20 cm 3 / g or more. Thus, it is possible to improve the denseness and the strength in the molded body of the resin molding material.

[0058] The upper limit of the loose bulk density (A) is, for example, 1.50 cm 3 / g or less, preferably 1.45 cm 3 / g or less, and more preferably 1.40 cm 3 / g or less. Thus, the mixing property of the resin and the spherical alumina powder can be improved.

[0059] The volume frequency particle size distribution in spherical alumina powder is measured by a wet-based laser diffraction scattering method. In the obtained volume frequency particle size distribution, the particle size at which the cumulative value becomes 25% is defined as D 25 , the particle size at which the cumulative value becomes 50% is defined as D 50 , and the particle size at which the cumulative value becomes 97% is defined as D 97 .

[0060] D 97 / D 25 The lower limit of is, for example, 8.0 or more, preferably 9.0 or more, and more preferably 10.0 or more. Thus, the particle size distribution has a certain width, and the fluidity and moldability can be improved.

[0061] D 97 / D 25 The upper limit of is, for example, 30.0 or less, preferably 20.0 or less, and more preferably 18.0 or less. Thus, the particle size of the coarse particles becomes sharp, and the molding defect of the molded body caused by the coarse particles can be suppressed.

[0062] D 97 / D 50 The lower limit of is, for example, 5.0 or more, preferably 5.5 or more, and more preferably 6.0 or more. Thus, the particle size distribution has a certain width, and the fluidity and moldability can be improved.

[0063] D 97 / D 50 The upper limit of is, for example, 20.0 or less, preferably 10.0 or less, and more preferably 8.0 or less. Thus, the particle size of the coarse particles becomes sharp, and the molding defect of the molded body caused by the coarse particles can be suppressed.

[0064] D 90 The lower limit of is, for example, 20.0 μm or more, preferably 25.0 μm or more, and more preferably 30.0 μm or more.

[0065] D 90 The upper limit of is, for example, 80.0 μm or less, preferably 70.0 μm or less, and more preferably 60.0 μm or less.

[0066] The particle size distribution of the spherical alumina powder is based on the values measured by the laser diffraction scattering method. As a particle size distribution measuring machine, for example, "Model LS-13230" (manufactured by Beckman Instruments, Inc.) can be used for measurement. During the measurement, water is used as the solvent, and a homogenizer is used to apply an output of 200 W for 1 minute for dispersion treatment as a pretreatment. Also, it is prepared in such a way that the PIDS (Polarization Intensity Differential Scattering) concentration becomes 45 to 55%. In addition, the refractive index of water is 1.33, and for the refractive index of the powder, the refractive index of the powder material is considered. For example, for amorphous silica, the refractive index was measured as 1.50, and for alumina, the refractive index was measured as 1.68.

[0067] The manufacturing method of the spherical alumina powder of the present embodiment will be described.

[0068] Regarding the spherical alumina powder, for example, an alumina raw material powder is supplied into a high-temperature flame formed by the combustion reaction of a combustible gas and an oxidizing gas, and it is melted and spheroidized above its melting point. The particles obtained by this melting flame method are called molten spherical particles. The obtained molten spherical particles can be further subjected to classification and screening treatments as needed. A variety of raw material powders with different particle sizes are used in the alumina raw material powder.

[0069] An example of a schematic diagram of the spraying device for manufacturing the molten spherical particles is shown in Figure 1 In.

[0070] Figure 1 The spraying device 100 in consists of a melting furnace 2 provided with a burner 1, a cyclone 4 for classifying the molten spherical particles generated from the high-temperature exhaust gas of the flame by the suction of a blower 9, and a bag filter 8 for recovering the fine powder that cannot be captured by the cyclone 4.

[0071] The melting furnace 2 is composed of a vertical furnace body, but it is not limited thereto, and it can also be a so-called horizontal furnace or inclined furnace in a horizontal form with the flame blown out in the horizontal direction.

[0072] The high-temperature exhaust gas is cooled using pipes 3 and 5 equipped with a water-cooled jacket.

[0073] An unillustrated suction gas volume control valve and a gas exhaust port can be connected to the blower 9.

[0074] An unillustrated captured powder extraction device can be connected to the lower parts of the melting furnace 2, the cyclone 4, and the bag filter 8.

[0075] Regarding classification, well-known devices such as a gravity settling chamber, a cyclone, a classifier with rotating blades, etc. can be used. Regarding this classification operation, it can be integrated into the transportation process of the molten spheroidized product, or it can be captured together and carried out in other pipelines.

[0076] As the combustible gas, for example, one or more of acetylene, propane, butane, etc. can be used, but propane, butane or their mixed gas with relatively small calorific value is preferred.

[0077] As the combustion-supporting gas, for example, a gas containing oxygen can be used. Usually, it is cheap and most preferred to use pure oxygen of 99% by mass or more. In order to reduce the calorific value of the gas, an inert gas such as air or argon can also be mixed into the combustion-supporting gas.

[0078] As the alumina raw material powder of the raw material powder, for example, alumina powder with an average particle size of 3 to 70 μm can be used. The supply of aluminum hydroxide powder into the high-temperature flame can be dry or wet with a slurry such as water.

[0079] The material obtained by incorporating the spherical alumina powder of the present invention into a resin composition can be preferably used as a resin molding material.

[0080] The resin composition contains, in addition to the spherical alumina powder of the present invention, a resin or well-known resin additives, etc.

[0081] In the resin composition, the spherical alumina powder can be used alone or in combination with other fillers. In the resin composition, 10 to 99% by mass of the spherical alumina powder can be contained, or 10 to 99% by mass of a mixed inorganic powder containing the spherical alumina powder and other fillers can also be contained. And in the mixed inorganic powder, the content of other fillers can be, for example, 1 to 20% by mass, 3 to 15% by mass relative to 100% by mass of the spherical alumina powder.

[0082] In addition, in this specification, unless otherwise specifically stated, "~" means including the upper limit value and the lower limit value.

[0083] As the above-mentioned other fillers, for example, crystalline silica, fused silica, titanium dioxide, silicon nitride, aluminum nitride, silicon carbide, talc, calcium carbonate, etc. can be cited.

[0084] For the average particle size of other fillers, for example, fillers of about 5 to 100 μm are used, and there is no particular limitation on their particle size structure and shape.

[0085] Examples of the above resin include epoxy resins, silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyimides, polyamide-imides, polyether-imides, etc. polyamides, polybutylene terephthalate, polyethylene terephthalate, etc. polyesters, polyphenylene sulfide, wholly aromatic polyesters, polysulfones, liquid crystal polymers, polyethersulfones, polycarbonates, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylate rubber-styrene) resins, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins, etc. These can be used alone or in combination of two or more.

[0086] Regarding the resin composition, it can be manufactured, for example, by the following steps: After mixing the raw material components in a specified ratio using a blender or a Henschel mixer, etc., kneading is performed using a heating roll, a kneader, a single-screw or twin-screw extruder, etc. to obtain a substance, and after cooling this substance, it is pulverized.

[0087] The embodiments of the present invention have been described above, but these are examples of the present invention, and various structures other than the above can be adopted. Moreover, the present invention is not limited to the above embodiments, and modifications, improvements, etc. within the scope capable of achieving the object of the present invention are also included in the present invention.

[0088] Examples

[0089] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited by any of the descriptions of these examples.

[0090] <Manufacture of spherical alumina powder>

[0091] Using Figure 1 the spraying device 100 shown in the figure, spherical alumina powder was manufactured.

[0092] Figure 1 The spraying device 100 shown in the figure includes a melting furnace 2, a burner 1 provided above the melting furnace 2, and a capture system pipeline directly connected to the lower part of the melting furnace 2 and composed of a cyclone 4 and a bag filter 8.

[0093] The burner 1 has a double-tube structure capable of forming an inner flame and an outer flame, is provided at the top upper part of the melting furnace 2, and is respectively connected to a combustible gas supply pipe 11, an auxiliary combustion gas supply pipe 12, and a raw material supply pipe 13.

[0094] In the melting furnace 2, the raw material powder can be supplied into the high-temperature flame through the raw material supply pipe 13 and melted to form spherical molten particles. The molten spherical particles that have passed through the melting furnace 2 are sucked by a blower 9 together with the combustion exhaust gas, move through the air in the pipes 3 and 5, and are classified and captured using a cyclone 4 or a bag filter 8.

[0095] (Example 1)

[0096] Using the above spraying device 100, LPG was supplied as the combustible gas from the combustible gas supply pipe 11, and oxygen was supplied as the combustion-supporting gas from the combustion-supporting gas supply pipe 12. In the burner 1, a high-temperature flame was formed by the combustion of LPG and oxygen.

[0097] Secondary air was supplied to the cyclone 4 through a rotary valve (not shown) provided in the pipe 3. The secondary air used the air in the atmosphere. And the opening / closing degree (lower opening degree) of the valve at the lower part in the cyclone 4 was set to 100%.

[0098] In addition, as the raw material powder, various alumina powders having a maximum value in the range of the average particle size (D 50 ) of 2 to 45 μm were used. Regarding the supply amount, the carrier gas of the raw material heated to 500 °C was set to 15 Nm 3 / hr, the combustible gas of the burner was set to 5 Nm 3 / hr, and the combustion-supporting gas was set to 10 Nm 3 / hr. The molten spherical particles captured by the bag filter 8 were recovered as spherical alumina powder.

[0099] (Examples 2 to 4)

[0100] When performing classification treatment in the manufacture of spherical alumina powder, the lower opening degrees were changed to 20%, 25%, and 35% respectively. Except for this, spherical alumina powder was recovered in the same manner as in Example 1 above.

[0101] (Comparative Example 1)

[0102] In the manufacture of spherical alumina powder, the spherical alumina powder obtained in Example 2 was used, and the fine particles smaller than 2 μm were removed by classification treatment, and the spherical alumina powder was recovered.

[0103] <Angle of repose, angle of collapse, angle of difference>

[0104] Under the conditions of room temperature of 25 °C and humidity of 65%, the angle of repose, angle of collapse, and angle of difference of the spherical alumina powder were obtained as follows.

[0105] A funnel with an outlet diameter of 0.5 cm was installed at a position 15 cm above the horizontal plate provided in the powder tester.

[0106] Via the funnel, the obtained spherical alumina powder was continuously supplied from the vertical direction onto the surface of the horizontal plate, forming a conical deposit maintaining a certain shape.

[0107] Using a protractor, find the elevation angle formed by the side surface of the conical deposit and the surface of the horizontal plate, and take it as the angle of repose (°).

[0108] Next, a 110 g weight was dropped 3 times from a height of 18 cm to apply an impact to the horizontal plate. Then, using a protractor, find the elevation angle formed by the side surface of the conical deposit and the surface of the horizontal plate, and take it as the angle of collapse (°). Take the difference between the obtained angle of repose and the angle of collapse as the differential angle (°).

[0109] <Loose bulk density, tapped bulk density>

[0110] In the obtained spherical alumina powder, under the conditions of room temperature of 25 °C and humidity of 55%, the loose bulk density and the tapped bulk density were measured using a powder tester (manufactured by Hosokawa Micron Corporation, model PT-E).

[0111] The specific steps are as follows.

[0112] Let the spherical alumina powder as the measurement sample naturally fall from a height of 25 cm at an input rate of 5 - 10 g per minute, and input it into the interior of a 100 cm 3 measurement cup until it overflows, thus preparing a full cup.

[0113] Next, without tapping the full cup, scrape off the part that overflows onto the upper surface of the cup, then measure the mass (g) of the spherical alumina powder filled in the cup, and calculate the loose bulk density (g / cm 3 ).

[0114] On the other hand, after tapping the full cup 180 times in the up - down direction (stroke length 2 cm, 1 time per second), scrape off the part that overflows onto the upper surface of the cup, then measure the mass (g) of the spherical alumina powder filled in the cup, and calculate the tapped bulk density (g / cm 3 ).

[0115] When the loose bulk density obtained through the above steps is set as A and the tapped bulk density is set as P, the degree of compressibility (%) is calculated according to the formula: ((P - A) / P) × 100.

[0116] <Particle size distribution>

[0117] For the obtained spherical alumina powder, a particle size distribution measuring device (manufactured by Beckman Instruments, Inc., LS-13230) was used, and the volume frequency particle size distribution was determined by the wet laser diffraction scattering method. Water was used as the solvent, and a homogenizer was used to apply an output of 200 W for 1 minute for dispersion treatment as a pretreatment. Also, it was prepared so that the PIDS (Polarization Intensity Differential Scattering) concentration was 45 to 55%, and the measurement was carried out.

[0118] Based on the obtained volume frequency particle size distribution, the particle diameter D at which the cumulative value became X% was calculated. X 。

[0119] [Table 1]

[0120]

[0121] The following evaluations were performed on the obtained spherical alumina powder of each example and each comparative example.

[0122] The results are shown in Table 1. In Table 1, "-" indicates not measured.

[0123] <Burr suppression>

[0124] Using a Henschel mixer (manufactured by NIPPON COKE&ENGINEERING.CO.,LTD., model "FM-20C / I"), 90.1 parts by mass of the obtained spherical alumina powder, 4.8 parts by mass of a terphenyl aralkyl phenol type epoxy resin (manufactured by Nippon Kayaku Co.,Ltd., product name: NC-3000, epoxy equivalent 275, softening point 56°C), 3.7 parts by mass of a phenolic resin (a phenol aralkyl resin, MEHC-7800S manufactured by Meiwa-Chemical Industry Co.,Ltd.), 0.19 parts by mass of triphenylphosphine (manufactured by HOKKO CHEMICAL INDUSTRY CO.,Ltd.: TPP), and 0.35 parts by mass of N-phenyl-3-aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co.,Ltd.: KBM-573) were mixed at normal temperature and a rotation speed of 2000 rpm. Then, the obtained mixture was heated and kneaded using a co-rotating twin-screw extruder (screw diameter D = 25 mm, L / D = 10.2, blade rotation speed 50 - 120 rpm, discharge rate 3.0 kg / Hr, kneaded material temperature 98 - 100°C) to obtain a resin composition.

[0125] Regarding the obtained resin composition, a burr measurement die with slits of 2μm, 5μm, 10μm, and 30μm was used, and the resin flowing out into the slits during molding was measured with a vernier caliper under the conditions of a molding temperature of 175°C and a molding pressure of 7.4 MPa. The values measured in each slit were averaged to obtain the burr length (μm).

[0126] When the burr length is 5 mm or less, it is evaluated that burr generation during molding can be suppressed (good), and when the burr length exceeds 5 mm, it is evaluated that burrs may be generated during molding (bad).

[0127] <Flowability>

[0128] Using the resin composition obtained above, a spiral flow die was used and carried out in accordance with EMMI-1-66 (Epoxy Molding Material Institute; Society of Plastic Industry). The mold temperature was set at 175°C, the molding pressure was set at 7.4 MPa, and the holding pressure time was set at 90 seconds.

[0129] A spiral flow of 150 cm or more was evaluated as good, and less than 150 cm was evaluated as bad.

[0130] <Thermal conductivity>

[0131] Using the resin composition obtained above, the resin composition was injected into a mold provided with a disk-shaped hole having a diameter of 28 mm and a thickness of 3 mm, and after degassing, it was molded at 150 °C for 20 minutes. For the obtained molded body and for the obtained resin composition, using a thermal conductivity measuring device (resin material thermal resistance measuring device "TRM-046RHHT" (product name) manufactured by Hitachi Technologies and Services, Ltd.), the thermal conductivity (W / m·K) was measured by the steady-state method in accordance with ASTM D5470. The resin composition was processed into a width of 10 mm × 10 mm, and the measurement was carried out while applying a load of 2 N on one side.

[0132] Thermal conductivity (W / m·K) = thickness of the molded body (m) / {thermal resistance (°C / W) × heat transfer area (m 2 )}

[0133] Compared with Comparative Example 1, the spherical alumina powders of Examples 1 to 4 showed results of improving the thermal conductivity of the resin molding material. Also, the spherical alumina powders of Examples 1 to 4 showed results of being able to suppress burr generation during molding of the resin composition and having excellent fluidity when used in the resin molding material.

[0134] This application claims priority based on Japanese Patent Application No. 2022-201018 filed on December 16, 2022, and incorporates all the contents of this disclosure therein.

[0135] Symbol Explanation

[0136] 1 Burner

[0137] 2 Melting furnace

[0138] 3 Pipe

[0139] 4 Cyclone

[0140] 5 Pipe

[0141] 8 Bag filter

[0142] 9 Blower

[0143] 11 Combustible gas supply pipe

[0144] 12 Combustion-supporting gas supply pipe

[0145] 13 Raw material supply pipe

[0146] 100 Spraying device

Claims

1. A spherical alumina powder, wherein, the difference angle measured according to the following steps is 8° or more and 20° or less, the steps are as follows: Install a funnel with an outlet diameter of 0.5 cm at a position 15 cm above the horizontal plate of the powder tester; Via the funnel, continuously supply the spherical alumina powder from the vertical direction onto the surface of the horizontal plate to form a conical deposit with a certain shape; Use a protractor to find the elevation angle formed by the side surface of the conical deposit and the surface of the horizontal plate, and take it as the angle of repose (°); Next, drop an 110 g weight from a height of 18 cm 3 times to apply an impact to the horizontal plate; then, use a protractor to find the elevation angle formed by the side surface of the conical deposit and the surface of the horizontal plate, and take it as the collapse angle (°); and take the difference between the obtained angle of repose and the collapse angle as the difference angle (°).

2. The spherical alumina powder according to claim 1, wherein, the angle of repose measured according to the above steps is 30° or more and 43° or less.

3. The spherical alumina powder according to claim 1 or 2, wherein, The loose bulk density measured by the following steps is 1.10 g / cm 3 or more and 1.50 g / cm 3 or less. the steps are as follows: Let the spherical alumina powder fall naturally from a height of 25 cm at an input rate of 5 to 10 g per minute and be put into the interior of a measuring cup of 100 cm 3 until it overflows from the cup, thereby preparing a cup full of the powder; Next, without lightly tapping the filled cup and scraping off the portion that will overflow onto the upper surface of the cup, measure the mass (g) of the spherical alumina powder filled in the cup, and calculate the loose bulk density (g / cm 3 ); and On the other hand, after tapping the filled cup under the condition of 180 times in the vertical direction, that is, a stroke length of 2 cm and a condition of 1 second per time, the portion that overflows onto the upper surface of the cup is scraped off, and then the mass (g) of the spherical alumina powder filled in the cup is measured, and the tapped density (g / cm 3 ) is calculated.

4. The spherical alumina powder according to claim 3, wherein, when the loose bulk density measured by the above steps is set as A and the tapped density is set as P, the degree of compressibility calculated according to ((P - A) / P)×100 is 35% or more and 55% or less.

5. The spherical alumina powder according to claim 1 or 2, wherein, In the volume frequency particle size distribution measured by the wet-based laser diffraction scattering method, the particle size at which the cumulative value becomes 25% is defined as D 25 and the particle size at which the cumulative value becomes 97% is defined as D 97 when D 97 / D 25 It is 8.0 or more and 30.0 or less.

6. The spherical alumina powder according to claim 1 or 2, wherein, In the volume frequency particle size distribution determined by the wet-based laser diffraction scattering method, the particle size at which the cumulative value becomes 50% is defined as D 50 and the particle size at which the cumulative value becomes 97% is defined as D 97 when D 97 / D 50 It is 5.0 or more and 20.0 or less.

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