Spherical alumina powder

Abstract

A spherical alumina powder in which, on the basis of an X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-K [alpha], I [alpha] represents the peak intensity derived from the [alpha] phase detected at 2 [theta] = 43.0 DEG, I [theta] represents the peak intensity derived from the [theta] phase detected at 2 [theta] = 44.8 DEG, and I [delta] represents the peak intensity derived from the [delta] phase detected at 2 [theta] = 45.6 DEG, I [alpha] represents the peak intensity derived from the [alpha] phase, I [theta] represents the peak intensity derived from the [theta] phase detected at 2 [theta] = 44.8 DEG, and I [delta] represents the peak intensity derived from the [delta] phase detected at 2 [theta] = 45.6 DEG. The alpha-phase peak intensity ratio (%) calculated according to the formula [I alpha / (I alpha + I theta + I delta)] * 100 is 65% or less.

Description

Technical Field

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

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

[0003] Prior Art Documents

[0004] Patent Documents

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

[0006] Technical Problem to be Solved by the Invention

[0007] However, as a result of research by the present inventors, it has been found that there is room for improvement in terms of fluidity and burr generation when the spherical alumina powder described in Patent Document 1 is used in a resin molding material.

[0008] Means for Solving the Technical Problem

[0009] As a result of further research by the present inventors, it has been found that by appropriately controlling the α-phase peak intensity ratio of the spherical alumina powder measured by X-ray diffraction, the fluidity during molding using a resin molding material containing the same can be improved, and thus the present invention has been completed.

[0010] According to one aspect of the present invention, the following spherical alumina powder is provided.

[0011] 1. A spherical alumina powder, wherein

[0012] the α-phase peak intensity ratio measured according to the following steps is 65% or less.

[0013] (Steps)

[0014] Based on the X-ray diffraction pattern of the spherical alumina powder obtained by X-ray diffraction using Cu-Kα, the peak intensity of the α-phase detected at 2θ = 43.0° is set as I α , the peak intensity of the θ-phase detected at 2θ = 44.8° is set as I θ , and the peak intensity of the δ-phase detected at 2θ = 45.6° is set as I δ When, according to the formula [I α / (I α+I θ +I δ )] × 100 to calculate the above α-phase peak intensity ratio (%).

[0015] 2. The spherical alumina powder according to 1., wherein,

[0016] Using I measured according to the described steps α 、I θ 、I δ , and according to the formula [I θ / (I α + I θ + I δ )] × 100, the calculated θ-phase peak intensity ratio is 21% or more.

[0017] 3. The spherical alumina powder according to 1. or 2., wherein,

[0018] The crystal grain size of alumina obtained by X-ray diffraction measurement using Cu-Kα is 400 nm or more and 800 nm or less.

[0019] 4. The spherical alumina powder according to any one of 1. to 3., wherein,

[0020] 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.

[0021] (Steps)

[0022] Let the spherical alumina powder fall naturally from a height of 25 cm at an input rate of 5 - 10 g per minute and be put into the inside of a measuring cup of 100 cm 3 , and continue until it overflows from the cup to prepare a full cup.

[0023] Next, without tamping the full cup, scrape off the part that overflows to 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 ).

[0024] On the other hand, for the full cup, after tamping it 180 times in the up and down direction (stroke length 2 cm, 1 time / second), scrape off the part that overflows to 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 ).

[0025] 5. The spherical alumina powder according to any one of 1. to 4., wherein,

[0026] When the loose bulk density measured by the above steps is set as A and the tapped bulk density is set as P, the degree of compressibility calculated as ((P - A) / P)×100 is 35% or more and 55% or less.

[0027] 6. The spherical alumina powder according to any one of 1. to 5., wherein

[0028] 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 set as D 25 and the particle size at which the cumulative value becomes 97% is set as D 97 when

[0029] D 97 / D 25 is 8.0 or more and 30.0 or less.

[0030] 7. The spherical alumina powder according to any one of 1. to 6., wherein

[0031] 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 50% is set as D 50 and the particle size at which the cumulative value becomes 97% is set as D 97 when

[0032] D 97 / D 50 is 5.0 or more and 20.0 or less.

[0033] Advantages of the Invention

[0034] According to the present invention, there is provided a spherical alumina powder having excellent burr suppression and fluidity when used in a resin molding material. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic cross-sectional view showing the structure of a thermal spraying apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are assigned to the same components, and description thereof will be appropriately omitted. Also, the drawings are schematic and do not match the actual dimensional ratios.

[0037] The spherical alumina powder of the present embodiment will be described.

[0038] The spherical alumina powder of the present embodiment is configured such that the α-phase peak intensity ratio measured according to the following steps is 65% or less.

[0039] Regarding the α-phase peak intensity ratio or θ-phase peak intensity ratio of spherical alumina powder, it can be measured according to the following steps.

[0040] Based on the X-ray diffraction pattern of the spherical alumina powder obtained by X-ray diffraction measurement using Cu-Kα, the peak intensity of the α-phase detected at 2θ = 43.0° is set as I α and the peak intensity of the θ-phase detected at 2θ = 44.8° is set as I θ and the peak intensity of the δ-phase detected at 2θ = 45.6° is set as I δ .

[0041] Equation 1: Calculate the α-phase peak intensity ratio (%) according to [I α / (I α +I θ +I δ )]×100.

[0042] Equation 2: Calculate the θ-phase peak intensity ratio according to [I θ / (I α +I θ +I δ )]×100.

[0043] Equation 3: Calculate the δ-phase peak intensity ratio according to [I δ / (I α +I θ +I δ )]×100.

[0044] Although the detailed mechanism is not yet clear, it is considered that by controlling the surface state of the spherical alumina powder so that the luminescence intensity ratio derived from the α-crystalline phase is below a specified value, appropriate viscoelastic properties can be achieved in the resin molding material (resin composition) when compounded into the resin, and thus the fluidity during molding can be improved.

[0045] The upper limit of the α-phase peak intensity ratio of the spherical alumina powder is 65% or less, preferably 64% or less, more preferably 63% or less. Thereby, the fluidity when used for the resin molding material can be improved, and the generation of burrs can be suppressed.

[0046] Moreover, the lower limit of the above-mentioned α-phase peak intensity ratio is, for example, 30% or more, preferably 35% or more, more preferably 40% or more. Thereby, the thermal conductivity of the resin composition can be improved.

[0047] The lower limit of the θ-phase peak intensity ratio of the spherical alumina powder is, for example, 21% or more, preferably 23% or more, more preferably 25% or more. Thereby, the elastic modulus of the resin composition can be improved.

[0048] Moreover, the upper limit of the above θ-phase peak intensity ratio is, for example, 35% or less, preferably 33% or less, and more preferably 30% or less. Thereby, the thermal conductivity of the resin composition can be improved.

[0049] The δ-phase peak intensity ratio / θ-phase peak intensity ratio can be, for example, 0.30 or more and 0.99 or less, can also be 0.35 or more and 0.95 or less, and can also be 0.40 or more and 0.90 or less. Thereby, the fluidity of the resin composition can be improved.

[0050] The crystallite size of alumina obtained by X-ray diffraction measurement using Cu-Kα can be, for example, 400 nm or more and 800 nm or less, can also be 450 nm or more and 750 nm or less, and can also be 500 nm or more and 700 nm or less. Thereby, the flexural strength of the resin composition can be improved.

[0051] In the present embodiment, for example, by appropriately selecting the raw material components of the spherical alumina powder or the manufacturing method of the spherical alumina powder, etc., the above α-phase peak intensity ratio or θ-phase peak intensity ratio 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 for heating the carrier gas of the raw material, elements of using alumina raw material powders with different particle sizes, and elements for appropriately adjusting the opening degree during the classification treatment can be cited as elements for setting the above α-phase peak intensity ratio or θ-phase peak intensity ratio within the desired numerical range.

[0052] 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 bulk density is set as P, the compressibility calculated by ((P - A) / P)×100 becomes, for example, 35% or more and 55% or less.

[0053] Regarding the loose bulk density, tapped bulk density, and compressibility, they can be measured under the conditions of room temperature 25°C and humidity 55% according to the following steps.

[0054] Let the spherical alumina powder fall naturally from a height of 25 cm at an input amount of 5 - 10 g per minute, and be put into the inside of a measuring cup of 100 cm 3 until it overflows from the cup, thereby preparing a full cup.

[0055] Next, for the full cup, after scraping off the part that overflows to the upper surface of the cup without tamping, measure the mass (g) of the spherical alumina powder filled in the cup, and calculate the loose bulk density (g / cm 3 ).

[0056] On the other hand, for the filled cup, after tamping under the condition of 180 times in the up-and-down direction (stroke length: 2 cm, 1 time per second), the part overflowing 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 bulk density (g / cm 3 ) is calculated.

[0057] Using the loose bulk density (A) and the tapped bulk density (P) obtained through the above steps, the degree of compressibility (%) is calculated according to ((P - A) / P)×100.

[0058] The lower limit of the degree of compressibility is, for example, 35% or more, preferably 38% or more, and more preferably 40% or more. Thereby, the handleability of the spherical alumina powder can be improved.

[0059] Also, the upper limit of the degree of compressibility is, for example, 55% or less, preferably 53% or less, and more preferably 50% or less. Thereby, the mixing property of the resin and the spherical alumina powder can be improved.

[0060] The spherical alumina powder may be configured such that the loose bulk density (A) is 1.10 g / cm 3 or more and 1.50 g / cm 3 or less.

[0061] 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. Thereby, it is possible to improve the denseness and the strength in the molded body of the resin molding material.

[0062] Also, 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. Thereby, the mixing property of the resin and the spherical alumina powder can be improved.

[0063] The volume frequency particle size distribution in the spherical alumina powder is measured by the wet 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 .

[0064] D 97 / D 25The lower limit 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.

[0065] Moreover, D 97 -D 25 The upper limit 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.

[0066] D 97 -D 50 The lower limit of D

[0067] Moreover, D 97 -D 50 The upper limit 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.

[0068] D 90 The lower limit of D is, for example, 20.0 μm or more, preferably 25.0 μm or more, and more preferably 30.0 μm or more.

[0069] Moreover, D 90 The upper limit is, for example, 80.0 μm or less, preferably 70.0 μm or less, and more preferably 60.0 μm or less.

[0070] 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. At the time of measurement, water is used as the solvent, and a dispersion treatment is performed for 1 minute with a power of 200 W using a homogenizer as a pretreatment. Moreover, it is prepared such 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 material of the powder is considered. For example, for amorphous silica, the refractive index was set to 1.50 for measurement, and for alumina, the refractive index was set to 1.68 for measurement.

[0071] A method for manufacturing the spherical alumina powder of the present embodiment will be described.

[0072] Regarding spherical alumina powder, for example, alumina raw material powder is supplied into a high-temperature flame formed by the combustion reaction of a combustible gas and a combustion-supporting gas, and melted and spheroidized above its melting point for manufacturing. 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 processes as needed. Multiple raw material powders with different particle sizes are used in the alumina raw material powder.

[0073] An example of a schematic diagram of a thermal spraying device for manufacturing molten spherical particles is shown in Figure 1 it.

[0074] Figure 1 The thermal spraying device 100 in

[0075] is composed 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 fine powder that cannot be captured by the cyclone 4.

[0076] The high-temperature exhaust gas is cooled using pipes 3 and 5 equipped with a water-cooled jacket.

[0077] An unillustrated suction gas volume control valve and a gas exhaust port can be connected to the blower 9.

[0078] 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.

[0079] Regarding classification, known equipment such as a gravity settling chamber, a cyclone, and a classifier with rotating blades can be used. Regarding this classification operation, it can be integrated in the conveying process of the molten spherical product, or captured together and then carried out in other pipelines.

[0080] As the combustible gas, for example, one or more of acetylene, propane, butane, etc. can be used, but propane, butane, or a mixed gas thereof with relatively small calorific value is preferred.

[0081] As the combustion-supporting gas, for example, a gas containing oxygen can be used. Generally, it is inexpensive and most preferred to use pure oxygen of 99 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.

[0082] 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 either dry or wet in the form of a slurry with water or the like.

[0083] Preferably, a material obtained by incorporating the spherical alumina powder of the present invention into a resin composition can be used as a resin molding material.

[0084] In addition to the spherical alumina powder of the present invention, the resin composition contains a resin or known resin additives, etc.

[0085] 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.

[0086] In addition, in this specification, unless otherwise specifically stated, "~" means including the upper limit value and the lower limit value.

[0087] 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.

[0088] For other fillers, for example, fillers having an average particle size of about 5 to 100 μm are used, and there are no particular restrictions on their particle size structure and shape.

[0089] As the above-mentioned resin, for example, epoxy resin, silicone resin, phenolic resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyimide, polyamideimide, polyetherimide and other polyamides, polybutylene terephthalate, polyethylene terephthalate and other polyesters, polyphenylene sulfide, wholly aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide-modified resin, ABS resin, AAS (acrylonitrile-acrylate rubber-styrene) resin, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin, etc. These can be used alone or in combination of two or more.

[0090] Regarding the resin composition, for example, it can be manufactured by the following steps: After mixing the raw material components in a specified ratio using a mixer 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 the substance, it is pulverized.

[0091] 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. And, the present invention is not limited to the above embodiments, and modifications, improvements, etc. within the range capable of achieving the object of the present invention are also included in the present invention.

[0092] Example

[0093] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to any of the descriptions of these examples.

[0094] <Manufacture of spherical alumina powder>

[0095] Using Figure 1 the thermal spraying apparatus 100 shown in the figure, spherical alumina powder was manufactured.

[0096] Figure 1 The thermal spraying apparatus 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.

[0097] The burner 1 has a double-tube structure capable of forming an inner flame and an outer flame, is provided at the top 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.

[0098] In the melting furnace 2, raw material powder can be supplied into a 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.

[0099] (Example 1)

[0100] Using the above thermal spraying apparatus 100, LPG was supplied as a combustible gas from the combustible gas supply pipe 11, and air in the atmosphere was supplied as an auxiliary combustion gas from the auxiliary combustion gas supply pipe 12. In the burner 1, a high-temperature flame was formed by the combustion of LPG and oxygen.

[0101] Secondary air was supplied to the cyclone 4 through a rotary valve (not shown) provided in the pipe 3. The secondary air used air in the atmosphere. And the opening degree (lower opening) of the valve in the lower part of the cyclone 4 was set to 100%.

[0102] In addition, as the raw material powder, various alumina powders having a maximum value in the range of the average particle diameter (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 15 Nm 3 / hr, the combustible gas of the burner was 5 Nm 3 / hr, and the auxiliary combustion gas was 10 Nm 3 / hr. The molten spherical particles captured by the bag filter 8 were recovered as spherical alumina powder.

[0103] (Examples 2 to 4)

[0104] When performing classification treatment in the production of spherical alumina powder, the lower opening degrees were changed to 20%, 25%, and 35% respectively, and except for this, the spherical alumina powder was recovered in the same manner as in Example 1 above.

[0105] (Comparative Example 1)

[0106] Spherical alumina fine powder (manufactured by Denka Company Limited., DAW-01, average particle size D 50 : 2 μm) was added to the spherical alumina powder recovered in the same manner as in Example 1. After adjusting the particle size distribution in Table 1, it was calcined at 1200 °C for 30 minutes using an electric furnace, thereby obtaining the spherical alumina powder of Comparative Example 1.

[0107] <X-ray diffraction measurement>

[0108] For the obtained spherical alumina powder, an X-ray diffraction pattern was measured using an X-ray diffractometer D8 ADVANCE (manufactured by Bruker Corporation) and using Cu-Kα rays under the following measurement conditions.

[0109] (Measurement conditions)

[0110] X-ray source: Cu-Kα rays

[0111] Output setting: 40 kV·40 mA

[0112] Optical system: Convergent method

[0113] Detector: LynxEye

[0114] Optical conditions during measurement: Divergence slit = 0.5°

[0115] Soller slit = 2.5°

[0116] Receiving slit = Open

[0117] Position of diffraction peak = 2θ (diffraction angle)

[0118] Measurement range: 2θ = 10° to 70°

[0119] Scanning speed: 0.017° / 0.5 sec, continuous scanning

[0120] Scanning axis: 2θ / θ

[0121] Sample preparation: The powdered spherical alumina powder was placed on the sample holder.

[0122] The peak intensity is the value obtained after background correction.

[0123] From the obtained X-ray diffraction pattern, the peak intensity (I α ) of the α-phase detected at 2θ = 43.0°, the peak intensity (I θ ) of the θ-phase detected at 2θ = 44.8°, and the peak intensity (I δ ) of the δ-phase detected at 2θ = 45.6° were determined.

[0124] Regarding the peak intensity ratio of each crystal phase obtained, the α-phase peak intensity ratio (%) was calculated from Equation 1: [I α / (I α +I θ +I δ )]×100, the θ-phase peak intensity ratio (%) was calculated from Equation 2: [I θ / (I α +I θ +I δ )]×100, and the δ-phase peak intensity ratio (%) was calculated from Equation 3: [I δ / (I α +I θ +I δ )]×100. The results are shown in Table 1.

[0125] <Microcrystalline size>

[0126] Regarding the microcrystalline size, based on the obtained powder X-ray diffraction pattern, it was calculated by quantitative analysis using the Rietveld analysis of the powder X-ray diffraction pattern analysis software TOPAS attached to the powder X-ray diffractometer.

[0127] <Loose bulk density, tapped bulk density>

[0128] In the obtained spherical alumina powder, the loose bulk density and tapped bulk density were measured at room temperature of 25°C and humidity of 55% using a powder tester (manufactured by Hosokawa Micron Corporation, model PT-E).

[0129] The specific steps are as follows.

[0130] The spherical alumina powder used as the measurement sample was allowed to fall naturally from a height of 25 cm at an input rate of 5 - 10 g per minute and was put into a 100 cm 3Inside the measuring cup, it continued until it overflowed from the cup, thus preparing a full cup.

[0131] Next, without tamping the full cup, the portion overflowing 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 loose bulk density (g / cm 3 ) was calculated.

[0132] On the other hand, for the full cup, after tamping it 180 times in the vertical direction under the conditions of a stroke length of 2 cm and 1 time / second, the portion overflowing 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 bulk density (g / cm 3 ) was calculated.

[0133] When the loose bulk density obtained by the above steps was designated as A and the tapped bulk density was designated as P, the degree of compressibility (%) was calculated according to the formula: ((P - A) / P) × 100.

[0134] <Particle Size Distribution>

[0135] For the obtained spherical alumina powder, using a particle size distribution measuring device (manufactured by Beckman Instruments, Inc., LS - 13230), the volume frequency particle size distribution was determined by the laser diffraction scattering method based on the wet 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. And it was prepared so that the PIDS (Polarization Intensity Differential Scattering) concentration was 45 - 55%, and the measurement was carried out.

[0136] Based on the obtained volume frequency particle size distribution, the particle diameter D at which the cumulative value became X% was calculated X .

[0137]

[0138] The following evaluations were performed on the obtained spherical alumina powder of each example and each comparative example.

[0139] The results are shown in Table 1. In Table 1, "-" indicates not measured.

[0140] <Burr Inhibition>

[0141] Using a Henschel mixer (“FM-20C / I” manufactured by NIPPON COKE & ENGINEERING.CO., LTD.), 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. 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 to 120 rpm, discharge rate 3.0 kg / Hr, kneaded material temperature 98 to 100°C), thereby obtaining a resin composition.

[0142] Regarding the obtained resin composition, using a burr measurement die having slits of 2 μm, 5 μm, 10 μm, and 30 μm, 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).

[0143] When the burr length is 2 mm or less, it is evaluated that burr generation during molding can be suppressed (good), and when the burr length exceeds 2 mm, it is evaluated that burrs may be generated during molding (bad).

[0144] <Flowability>

[0145] 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 to 175°C, the molding pressure was set to 7.4 MPa, and the holding pressure time was set to 90 seconds.

[0146] Evaluate those with a spiral flow of more than 150 cm as good and those less than 150 cm as bad.

[0147] <Thermal conductivity>

[0148] Using the resin composition obtained above, the resin composition was injected into a mold provided with a disc-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.

[0149] Thermal conductivity (W / m·K) = thickness of the molded body (m) / {thermal resistance (°C / W) × heat transfer area (m 2 )}

[0150] Compared with Comparative Example 1, the spherical alumina powders of Examples 1 to 4 showed results that could suppress the generation of burrs during molding of the resin composition and improve the fluidity of the resin composition during molding. Also, the spherical alumina powders of Examples 1 to 4 showed results of improving the thermal conductivity of the resin molding material.

[0151] This application claims priority based on Japanese Patent Application No. 2022-201022 filed on December 16, 2022, and incorporates all the contents of this disclosure therein.

[0152] Symbol description

[0153] 1 - burner, 2 - melting furnace, 3 - pipe, 4 - cyclone, 5 - pipe, 8 - bag filter, 9 - blower, 11 - combustible gas supply pipe, 12 - combustion-supporting gas supply pipe, 13 - raw material supply pipe, 100 - thermal spraying device.

Claims

1. A spherical alumina powder, The intensity ratio of the α-phase peak measured according to the following steps is 65% or less, The steps are as follows: Based on the X-ray diffraction pattern of the spherical alumina powder obtained by X-ray diffraction measurement using Cu-Kα, the peak intensity of the α-phase detected at 2θ = 43.0° is set as I α , the peak intensity of the θ-phase detected at 2θ = 44.8° is set as I θ , and the peak intensity of the δ-phase detected at 2θ = 45.6° is set as I δ . When [I α / (I α + I θ + I δ )] × 100 is calculated, the above α-phase peak intensity ratio is obtained, which is in %.

2. The spherical alumina powder according to claim 1, Using I measured according to the described steps α 、I θ 、I δ , according to formula [I θ / (I α +I θ +I δ )]×100, the θ-phase peak intensity ratio calculated is 21% or more.

3. The spherical alumina powder according to claim 1 or 2, wherein The crystallite size of alumina obtained by X-ray diffraction measurement using Cu-Kα is 400 nm or more and 800 nm or less.

4. The spherical alumina powder according to claim 1 or 2, 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 naturally fall 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 full cup; Next, for the filled cup, without tamping, the portion that has overflowed onto the upper surface of the cup is scraped off, and then the mass of the spherical alumina powder filled in the cup is measured in g, and the loose bulk density is calculated in g / cm 3 ; On the other hand, for the filled cup, after tamping is performed under the conditions of 180 times in the vertical direction, a stroke length of 2 cm, and 1 second per time, the portion that has overflowed onto the upper surface of the cup is scraped off, and then the mass of the spherical alumina powder filled in the cup is measured in g, and the tapped bulk density is calculated in g / cm 3 .

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

6. The spherical alumina powder according to claim 1 or 2, 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 designated as D 25 and the particle size at which the cumulative value becomes 97% is designated as D 97 when D 97 / D 25 It is 8.0 or more and 30.0 or less.

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

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