Spherical alumina powder

Abstract

A spherical alumina powder according to the present invention satisfies the following requirement. An α-phase peak intensity ratio (%) is 65% or less in which the α-phase peak intensity ratio (%) is calculated by the formula: [Iα / (Iα+Iθ+Iδ)]×100 wherein Iα represents an intensity of a peak derived from an α-phase and detected at 2θ=43.0°, Iθ represents an intensity of a peak derived from a θ-phase and detected at 2θ=44.8°, and Iδ represents an intensity of a peak derived from a δ-phase and detected at 2θ=45.6° in an X-ray diffraction pattern obtained by an X-ray diffraction measurement using Cu-Kα.

Description

Technical Field

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

Background Art

[0002] Various developments have been made on spherical alumina powder so far. As this kind of technology, for example, the technology described in Patent Document 1 is known. Patent Document 1 describes spherical alumina powder having an average particle diameter (D50) of 50 μm or less and a sphericity of 0.9 or more (Claim 1 of Patent Document 1, etc.).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, as a result of investigations by the present inventor, 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 above is used in a resin molding material.

Means for Solving the Problems

[0005] As a result of further investigations by the present inventor, 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 this can be improved, and the present invention has been completed.

[0006] According to one aspect of the present invention, the following spherical alumina powder is provided. 1. Spherical alumina powder having an α-phase peak intensity ratio measured according to the following procedure of 65% or less. (Procedure) From 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 I 3 , 3 , , , , , 3 , 3 , , , , , the peak intensity of the θ-phase detected at 2θ = 44.8° is I θ , the peak intensity of the δ-phase detected at 2θ = 45.6° is I δ When this is done, the α-phase peak intensity ratio (%) is calculated based on the formula [I α / (I α + I θ + I δ )] × 100. 2. The spherical alumina powder according to 1., wherein Using I α , I θ , I δ measured according to the above procedure, the θ-phase peak intensity ratio calculated based on the formula [I θ / (I α + I θ + I[[ID=3l]] δ )] × 100 is 21% or more, a spherical alumina powder. 3. The spherical alumina powder according to 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, a spherical alumina powder. 4. The spherical alumina powder according to any one of 1. to 3., wherein The loose bulk density measured by the following procedure is 1.10 g / cm 3 or more and 1.50 g / cm 3 or less, a spherical alumina powder. (Procedure) The spherical alumina powder is allowed to fall naturally from a height of 25 cm at an input rate of 5 to 10 g per minute and is put into a measuring cup with a height of 100 cm 3 until it overflows from the cup, and a mound-shaped cup is prepared. Subsequently, for the mound-shaped cup, without tapping, after scraping off the excess that has overflowed onto the upper surface of the cup, the mass (g) of the spherical alumina powder filled in the cup is measured, and the loose bulk density (g / cm 3 ) is calculated. <00On the other hand, for the overflowing cup, after tapping it 180 times in the vertical direction (stroke length 2 cm, 1 second / tap), and leveling off the excess on the top of the cup, the mass (g) of the spherical alumina powder filled in the cup was measured, and the bulk density (g / cm³) was determined. 3 Calculate ). 5. The spherical alumina powder described in 1. to 4., When the loose bulk density measured in the above procedure is A and the firm bulk density is P, Spherical alumina powder having a compression degree of 35% or more and 55% or less, calculated based on ((PA) / P) × 100. 6. A spherical alumina powder as described in any one of items 1 to 5, In the volume frequency particle size distribution measured by the wet laser diffraction scattering method, the particle size at which the cumulative value reaches 25% is defined as D. 25 The particle size at which the cumulative value reaches 97% is D 97 In that case, D 97 / D 25 However, it is spherical alumina powder with a pH between 8.0 and 30.0. 7. A spherical alumina powder as described in any one of 1. to 6., In the volume frequency particle size distribution measured by the wet laser diffraction scattering method, the particle size at which the cumulative value reaches 50% is defined as D. 50 The particle size at which the cumulative value reaches 97% is D 97 In that case, D 97 / D 50 However, it is spherical alumina powder with a coefficient between 5.0 and 20.0. [Effects of the Invention]

[0007] According to the present invention, a spherical alumina powder is provided that exhibits excellent burr suppression and fluidity when used in resin molding materials. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view showing the configuration of a thermal spraying apparatus. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. In all drawings, similar components are denoted by the same reference numerals, and their descriptions are omitted as appropriate. Also, the drawings are schematic diagrams and do not correspond to the actual dimensional ratios.

[0010] The spherical alumina powder of this embodiment will now be described.

[0011] The spherical alumina powder of this embodiment is configured such that the α-phase peak intensity ratio, measured according to the following procedure, is 65% or less.

[0012] The α-phase peak intensity ratio and the θ-phase peak intensity ratio of spherical alumina powder can be measured according to the following procedure. From the X-ray diffraction pattern of the spherical alumina powder obtained by X-ray diffraction measurement using Cu-Kα, the peak intensity originating from the α phase detected at 2θ = 43.0° is I α The peak intensity originating from the θ phase detected at 2θ = 44.8° is I θ The peak intensity originating from the δ phase detected at 2θ = 45.6° is I δ Let's assume that. Equation 1: [I α / ( I α +I θ +I δ Based on )] × 100, calculate the α-phase peak intensity ratio (%). Equation 2: [I θ / ( I α +I θ +I δ Based on )] × 100, the θ-phase peak intensity ratio is calculated. Equation 3: [I δ / ( I α +I θ +I δ Based on )] × 100, calculate the δ-phase peak intensity ratio.

[0013] Although the detailed mechanism is not clear, it is thought that by controlling the surface state of spherical alumina powder, in which the luminescence intensity ratio derived from the α-crystalline phase is kept below a predetermined value, appropriate viscoelastic properties can be achieved in the resin molding material (resin composition) when it is blended with resin, thereby improving fluidity during molding.

[0014] The upper limit of the α-phase peak intensity ratio of the spherical alumina powder is 65% or less, preferably 64% or less, and more preferably 63% or less. This improves the fluidity when used in resin molding materials and suppresses the generation of burrs. Furthermore, the lower limit of the α-phase peak intensity ratio is, for example, 30% or more, preferably 35% or more, and more preferably 40% or more. This improves the thermal conductivity of the resin composition.

[0015] 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, and more preferably 25% or more. This improves the elastic modulus of the resin composition. Furthermore, the upper limit of the θ-phase peak intensity ratio is, for example, 35% or less, preferably 33% or less, and more preferably 30% or less. This improves the thermal conductivity of the resin composition.

[0016] The δ-phase peak intensity ratio / θ-phase peak intensity ratio may be, for example, 0.30 to 0.99, 0.35 to 0.95, or 0.40 to 0.90. This can improve the fluidity of the resin composition.

[0017] The crystallite size of alumina obtained by X-ray diffraction measurement using Cu-Kα may be, for example, 400 nm to 800 nm, 450 nm to 750 nm, or 500 nm to 700 nm. This can improve the flexural strength of the resin composition.

[0018] In this embodiment, the α-phase peak intensity ratio and the θ-phase peak intensity ratio can be controlled by appropriately selecting, for example, the raw material components of the spherical alumina powder and the method for producing the spherical alumina powder. Among these, appropriate control of molten flame conditions such as raw material supply amount, raw material particle size, flame temperature, combustible gas, combustion-supporting gas, and dispersion gas, heating the carrier gas of the raw material, using alumina raw material powders of different particle sizes in combination, and appropriately adjusting the opening during the classification process are examples of factors that can bring the α-phase peak intensity ratio and the θ-phase peak intensity ratio into a desired numerical range.

[0019] The spherical alumina powder may be configured such that, when the loose bulk density is A and the hard bulk density is P, the degree of compression, calculated based on ((PA) / P) × 100, is, for example, 35% or more and 55% or less.

[0020] Loose bulk density, firm bulk density, and compressibility can be measured under room temperature of 25°C and humidity of 55% by following the procedure below. The spherical alumina powder is added at a rate of 5-10g per minute, allowed to fall naturally from a height of 25cm, and then 100cm 3 Pour the mixture into the measuring cup and continue until it overflows, preparing a heaping cup. Next, for the overflowing cup, without tapping, the amount that overflowed from the top of the cup was leveled off, and the mass (g) of the spherical alumina powder filled in the cup was measured, and the loose bulk density (g / cm³) was determined. 3 Calculate ). On the other hand, for the overflowing cup, after tapping it 180 times in the vertical direction (stroke length 2 cm, 1 second / tap), and leveling off the excess on the top of the cup, the mass (g) of the spherical alumina powder filled in the cup was measured, and the bulk density (g / cm³) was determined. 3 Calculate ). Using the loose bulk density (A) and the hard bulk density (P) obtained by the above procedure, the degree of compressibility (%) is calculated based on ((PA) / P) × 100.

[0021] The lower limit of the degree of compression is, for example, 35% or more, preferably 38% or more, and more preferably 40% or more. This improves the handling properties of the spherical alumina powder. Furthermore, the upper limit of the compression is, for example, 55% or less, preferably 53% or less, and more preferably 50% or less. This improves the miscibility between the resin and the spherical alumina powder.

[0022] The spherical alumina powder has a loose bulk density (A) of 1.10 g / cm³. 3 More than 1.50g / cm 3 It may be configured as follows: The lower limit of the loose bulk density (A) is, for example, 1.10 cm. 3 / g or more, preferably 1.15cm 3 / g or more, more preferably 1.20cm 3 It is 1 / g or more. This improves density and has the potential to improve the strength of molded articles made from resin molding materials. Furthermore, the upper limit of the loose bulk density (A) is, for example, 1.50 cm. 3 Less than or equal to / g, preferably 1.45cm 3 Less than or equal to / g, more preferably 1.40cm 3 The amount is less than / g. This improves the miscibility between the resin and the spherical alumina powder.

[0023] The volume frequency particle size distribution of spherical alumina powder was measured by a wet laser diffraction scattering method, and the particle size at which the cumulative value reached 25% in the obtained volume frequency particle size distribution was defined as D 25 The particle size at which the cumulative value reaches 50% is D 50 The particle size at which the cumulative value reaches 97% is D 97 Let's assume that.

[0024] D 97 / D 25 The lower limit is, for example, 8.0 or higher, preferably 9.0 or higher, and more preferably 10.0 or higher. This ensures that the particle size distribution has a certain range, improving fluidity and moldability. Also, D 97 / D 25The upper limit is, for example, 30.0 or less, preferably 20.0 or less, and more preferably 18.0 or less. This makes the particle size of coarse particles sharper, and mold defects in the molded product caused by coarse particles can be suppressed.

[0025] D 97 / D 50 The lower limit is, for example, 5.0 or higher, preferably 5.5 or higher, and more preferably 6.0 or higher. This ensures that the particle size distribution has a certain range, improving fluidity and moldability. Also, 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. This makes the particle size of coarse particles sharper, and can suppress molding defects in the molded article caused by coarse particles.

[0026] D 90 The lower limit is, for example, 20.0 μm or more, preferably 25.0 μm or more, and more preferably 30.0 μm or more. Also, 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.

[0027] The particle size distribution of spherical alumina powder is a value based on particle size measurement by laser diffraction scattering, and can be measured using a particle size distribution analyzer such as the "Model LS-13230" (manufactured by Beckman Coulter). For measurement, water was used as the solvent, and as a pretreatment, the powder was dispersed using a homogenizer at a power of 200W for 1 minute. The PIDS (Polarization Intensity Differential Scattering) concentration was adjusted to 45-55%. The refractive index of water was set to 1.33, and the refractive index of the powder material was taken into consideration. For example, a refractive index of 1.50 was used for amorphous silica and 1.68 for alumina.

[0028] The method for producing the spherical alumina powder of this embodiment will now be described.

[0029] Spherical alumina powder is produced, for example, by supplying alumina raw material powder into a high-temperature flame formed by the combustion reaction of a combustible gas and a combustion-supporting gas, and melting it into spheres above its melting point. Particles obtained by this molten flame method are called molten spherical particles. The obtained molten spherical particles may be further subjected to classification and sieving treatment as needed. Multiple raw material powders with different particle sizes are used as the alumina raw material powder.

[0030] Figure 1 shows an example of a schematic diagram of a thermal spraying apparatus used to produce molten spherical particles. The thermal spraying apparatus 100 in Figure 1 consists of a melting furnace 2 equipped with a burner 1, a cyclone 4 for classifying molten spherical particles generated by the high-temperature exhaust gas of the flame using the suction of a blower 9, and a bag filter 8 for collecting fine particles that could not be captured by the cyclone 4. The melting furnace 2 is composed of a vertical furnace body, but is not limited to this; it may also be a horizontal furnace or inclined furnace, which is horizontal in which the flame is blown out horizontally. The high-temperature exhaust gas is cooled by pipes 3 and 5 equipped with water-cooling jackets. The blower 9 may be connected to a suction gas volume control valve (not shown) and a gas exhaust port. A collection and extraction device (not shown) may be connected to the bottom of the melting furnace 2, cyclone 4, and bag filter 8. Classification can be carried out using known equipment such as heavy sedimentation chambers, cyclones, and classifiers with rotating blades. This classification operation may be incorporated into the transport process of the molten spheroidized product, or it may be carried out on a separate line after bulk collection.

[0031] As the flammable gas, one or more types such as acetylene, propane, and butane can be used, but propane, butane, or a mixture thereof with a relatively low calorific value is preferred. As a combustion-supporting gas, for example, a gas containing oxygen is used. Generally, using pure oxygen of 99% by mass or higher is the most inexpensive and preferable option. To reduce the calorific value of the gas, an inert gas such as air or argon can also be mixed with the combustion-supporting gas.

[0032] As the raw material powder, alumina powder with an average particle size of 3 to 70 μm may be used. The aluminum hydroxide powder may be supplied into the high-temperature flame either dry or wet by slurring it with water or the like.

[0033] The spherical alumina powder of the present invention, when incorporated into a resin composition, can be suitably used as a resin molding material.

[0034] The resin composition includes, in addition to the spherical alumina powder of the present invention, a resin and known resin additives. In the resin composition, spherical alumina powder may be used alone or mixed with other fillers. The resin composition may contain 10 to 99% by mass of spherical alumina powder, or 10 to 99% by mass of a mixed inorganic powder containing spherical alumina powder and other fillers. In addition, the content of other fillers in the mixed inorganic powder may be, for example, 1 to 20% by mass or 3 to 15% by mass relative to 100% by mass of spherical alumina powder. In this specification, unless otherwise specified, "~" indicates that it includes both the upper and lower limits.

[0035] Other fillers mentioned above include, for example, crystalline silica, fused silica, titania, silicon nitride, aluminum nitride, silicon carbide, talc, and calcium carbonate. Other fillers typically have an average particle size of around 5 to 100 μm, and there are no particular restrictions on their particle size composition or shape.

[0036] Examples of the above-mentioned resins include epoxy resins, silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyimides, polyamide-imides, polyetherimides and other polyamides, polyesters such as polybutylene terephthalate and polyethylene terephthalate, polyphenylene sulfide, fully aromatic polyesters, polysulfones, liquid crystal polymers, polyethersulfones, polycarbonates, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylic rubber-styrene) resins, and AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins. These may be used individually or in combination of two or more types.

[0037] Resin compositions can be manufactured, for example, by blending raw material components in predetermined ratios using a blender or Henschel mixer, then kneading them using a heated roll, kneader, single-screw or twin-screw extruder, cooling, and then grinding the mixture.

[0038] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0039] The present invention will be described in detail below with reference to examples, but the present invention is not limited in any way to the descriptions of these examples.

[0040] <Manufacturing of spherical alumina powder> Spherical alumina powder was produced using the thermal spraying apparatus 100 shown in Figure 1. The thermal spraying apparatus 100 shown in Figure 1 comprises a melting furnace 2, a burner 1 installed on top of the melting furnace 2, and a collection system line consisting of a cyclone 4 and a bag filter 8 installed directly connected to the bottom of the melting furnace 2. Burner 1 has a double-tube structure capable of forming an inner flame and an outer flame, and is installed at the top of the melting furnace 2, to which the combustible gas supply pipe 11, the auxiliary combustion gas supply pipe 12, and the raw material supply pipe 13 are connected. In the melting furnace 2, raw material powder is supplied into a high-temperature flame from the raw material supply pipe 13 and melted to form spherical molten spherical particles. The molten spherical particles that have passed through the melting furnace 2 are sucked in by the blower 9 along with the combustion exhaust gas, move through the pipes 3 and 5 by air, and are classified and collected by the cyclone 4 or bag filter 8.

[0041] (Example 1) Using the thermal spraying apparatus 100 described above, LPG was supplied as a combustible gas from the combustible gas supply pipe 11, and atmospheric air was supplied as a combustion aid gas from the combustion aid gas supply pipe 12. A high-temperature flame was formed in the burner 1 by the combustion of LPG and oxygen. Secondary air is supplied to cyclone 4 by a rotary valve (not shown) installed in piping 3. Atmospheric air was used as the secondary air. The degree of opening / closing of the lower valve in cyclone 4 (lower opening) was set to 100%. Furthermore, the raw material powder has an average particle size (D 50 Multiple alumina powders with maximum values ​​in the range of 2 to 45 μm were used. The supply amount was 15 Nm³ of carrier gas for the raw materials heated to 500°C. 3 / hr, the burner's flammable gas is 5Nm 3 / hr, auxiliary gas at 10Nm³ 3 The value was set to / hr. The molten spherical particles collected by the bag filter 8 were recovered as spherical alumina powder.

[0042] (Examples 2-4) In the production of spherical alumina powder, the spherical alumina powder was recovered in the same manner as in Example 1 above, except that the lower opening was changed to 20%, 25%, and 35% during the classification process.

[0043] (Comparative Example 1) To the spherical alumina powder recovered in the same manner as in Example 1, spherical alumina fine powder (Denka Co., Ltd., DAW-01, average particle size D50 : After adding (particle size: 2 μm) to adjust the particle size distribution in Table 1, the spherical alumina powder of Comparative Example 1 was obtained by firing at 1200 °C for 30 minutes using an electric furnace.

[0044] <X-ray Diffraction Measurement> For the obtained spherical alumina powder, an X-ray diffraction pattern was measured under the following measurement conditions using an X-ray diffractometer D8 ADVANCE (manufactured by Bruker) with Cu-Kα radiation. (Measurement Conditions) X-ray source: Cu-Kα radiation (λ = 1.5406 Å) Output setting: 40 kV·40 mA Optical system: Convergent beam method Detector: LynxEye Optical conditions during measurement: Divergence slit = 0.5° Solar slit = 2.5° Receiving slit = Open Position of diffraction peak = 2θ (diffraction angle) Measurement range: 2θ = 1°~70° Scan speed: 0.017° / 0.5 sec, continuous scan Scanning axis: 2θ / θ Sample preparation: The powdered spherical alumina powder was placed on a sample holder. The peak intensity was taken as the value obtained after background correction.

[0045] From the obtained X-ray diffraction pattern, the peak intensity (I α ) derived from the α-phase detected at 2θ = 43.0°, the peak intensity (I θ ) derived from the θ-phase detected at 2θ = 44.8°, and the peak intensity (I δ ) derived from the δ-phase detected at 2θ = 45.6° were determined. Regarding the peak intensity ratio of each obtained crystal phase, Equation 1: [I α / (I α + I θ + I δ )] × 100 was used for the α-phase peak intensity ratio (%), and Equation 2: [I θ / (I α + I θ + I δ)] × 100 with θ-phase peak intensity ratio (%), Equation 3: [I δ / ( I α +I θ +I δ The delta-phase peak intensity ratio (%) was calculated by multiplying () by 100. The results are shown in Table 1.

[0046] <crystallite size> The crystallite size was calculated quantitatively from the obtained powder X-ray diffraction pattern using Rietveld analysis with TOPAS, the powder X-ray diffraction pattern analysis software attached to the powder X-ray diffractometer.

[0047] <Loose bulk density, firm bulk density> The loose and hard bulk densities of the obtained spherical alumina powder were measured using a powder tester (Hosokawa Micron Corporation, PT-E type) under conditions of room temperature (25°C) and humidity (55%). The specific steps are as follows: The spherical alumina powder, which is the measurement sample, is allowed to fall naturally from a height of 25 cm at a rate of 5-10 g per minute, and then measured at 100 cm. 3 I poured it into the measuring cup and continued until it overflowed, preparing a heaping cup. Next, for the overflowing cup, without tapping, the amount that overflowed from the top of the cup was leveled off, and the mass (g) of the spherical alumina powder filled in the cup was measured, and the loose bulk density (g / cm³) was determined. 3 ) was calculated. On the other hand, for the overflowing cup, after tapping it 180 times in the vertical direction (stroke length 2 cm, 1 second / tap), and leveling off the excess on the top of the cup, the mass (g) of the spherical alumina powder filled in the cup was measured, and the bulk density (g / cm³) was determined. 3 ) was calculated. When the loose bulk density obtained using the above procedure is denoted as A and the stiff bulk density as P, the degree of compressibility (%) was calculated based on the formula: ((PA) / P) × 100.

[0048] <Particle size distribution> For the obtained spherical alumina powder, the volume frequency particle size distribution was determined by the wet laser diffraction scattering method using a particle size distribution measuring device (LS-13230, manufactured by Beckman Coulter). Water was used as the solvent, and as a pretreatment, a dispersion treatment was carried out using a homogenizer at an output of 200 W for 1 minute. Also, the measurement was carried out after adjusting the PIDS (Polarization Intensity Differential Scattering) concentration to 45 - 55%. Based on the obtained volume frequency particle size distribution, the particle diameter D at which the cumulative value becomes X% X was calculated.

[0049]

Table 1

[0050] For the obtained spherical alumina powders of each example and each comparative example, the following evaluations were carried out. The results are shown in Table 1. In Table 1, "-" means unmeasured.

[0051] <Burr suppression> 90.1 parts by mass of the obtained spherical alumina powder, 4.8 parts by mass of a biphenylene aralkylphenol type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., trade name; NC-3000, epoxy equivalent 275, softening point 56°C), 3.7 parts by mass of a phenol resin (phenol aralkyl resin, MEHC-7800S manufactured by Meiwafosis Co., Ltd.), 0.19 parts by mass of triphenylphosphine (manufactured by Kitakyo 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 using a Henschel mixer (manufactured by Nippon Coke Industry Co., Ltd. "FM-20C / I") under the conditions of normal temperature and a rotation speed of 2000 rpm. The obtained mixture was heated and kneaded using a co-rotating double screw extrusion kneader (screw diameter D = 25 mm, L / D = 10.2, paddle rotation speed 50 - 120 rpm, discharge rate 3.0 kg / Hr, kneaded product temperature 98 - 100°C) to obtain a resin composition.

[0052] The obtained resin composition was molded using a burr measuring mold with slits of 2 μm, 5 μm, 10 μm, and 30 μm. The molding temperature was 175°C and the molding pressure was 7.4 MPa. The resin that flowed out of the slits was measured with calipers, and the values ​​measured in each slit were averaged to determine the burr length (μm). If the burr length was 2 mm or less, it was evaluated as good (successful) as it could suppress burr generation during molding; if it exceeded 2 mm, it was evaluated as poor (there is a risk of burr generation during molding).

[0053] <Liquidity> The resin composition obtained above was used, and the molding process was carried out using a spiral flow mold in accordance with EMMI-1-66 (Epoxy Molding Material Institute; Society of Plastic Industry). The mold temperature was 175°C, the molding pressure was 7.4 MPa, and the holding pressure time was 90 seconds. A spiral flow of 150 cm or more was considered good, while a spiral flow of less than 150 cm was considered poor.

[0054] <Thermal conductivity> Using the resin composition obtained above, the resin composition was poured into a mold with a disc-shaped hole measuring 28 mm in diameter and 3 mm in thickness, and molded at 150°C for 20 minutes after degassing. The thermal conductivity (W / m·K) of the obtained molded body and the obtained resin composition was measured using a thermal conductivity measuring device (Hitachi Technology & Services Co., Ltd. resin material thermal resistance measuring device "TRM-046RHHT" (product name)) in accordance with the steady-state method in accordance with ASTM D5470. The resin composition was processed into a 10 mm wide x 10 mm wide piece, and the measurement was performed while applying a load of 2 N. Thermal conductivity (W / m·K) = Thickness of molded body (m) / {Thermal resistance (°C / W) × Heat transfer area (m²)} 2 )}

[0055] Compared to Comparative Example 1, the spherical alumina powders of Examples 1 to 4 showed that they could suppress the generation of burrs during molding of the resin composition and improved the fluidity of the resin composition during molding. Furthermore, the spherical alumina powders of Examples 1 to 4 showed that they could improve the thermal conductivity of the resin molding material.

[0056] This application claims priority based on Japanese Patent Application No. 2022-201022, filed on 16 December 2022, and incorporates all of its disclosures herein. [Explanation of Symbols]

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

Claims

1. Spherical alumina powder having an α-phase peak intensity ratio of 65% or less, as measured according to the following procedure. (procedure) From the X-ray diffraction pattern of the spherical alumina powder obtained by X-ray diffraction measurement using Cu-Kα, the peak intensity originating from the α phase detected at 2θ = 43.0° is I α The peak intensity originating from the θ phase detected at 2θ = 44.8° is I θ The peak intensity originating from the delta phase detected at 2θ = 45.6° is I δ When this is the case, the equation [I α / (I α +I θ +I δ Based on the above α-phase peak intensity ratio (%), calculate the α-phase peak intensity ratio (%).

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

3. A spherical alumina powder according to claim 1 or 2, Spherical alumina powder in which the crystallite size of alumina obtained by X-ray diffraction measurement using Cu-Kα is between 400 nm and 800 nm.

4. A spherical alumina powder according to claim 1 or 2, The loosened bulk density, measured using the following procedure, is 1.10 g / cm³. ３ 1.50g / cm or more ３ The following is spherical alumina powder. (procedure) The spherical alumina powder is added at a rate of 5 to 10 g per minute, allowed to fall naturally from a height of 25 cm, and then 100 cm. ３ Pour the mixture into the measuring cup and continue until it overflows, preparing a heaping cup. Next, for the overflowing cup, without tapping, the amount that overflowed from the top of the cup was leveled off, and the mass (g) of the spherical alumina powder filled in the cup was measured, and the loose bulk density (g / cm³) was determined. ３ Calculate the result. On the other hand, for the overflowing cup, after tapping it 180 times in the vertical direction (stroke length 2 cm, 1 second / tap), and leveling off the excess on the top surface of the cup, the mass (g) of the spherical alumina powder filled in the cup was measured, and the bulk density (g / cm³) was determined. ３ Calculate the result.

5. The spherical alumina powder according to claim 4, When the loose bulk density measured in the above procedure is A and the firm bulk density is P, Spherical alumina powder having a compression degree of 35% or more and 55% or less, calculated based on ((P-A) / P) × 100.

6. A spherical alumina powder according to claim 1 or 2, In the volume frequency particle size distribution measured by the wet laser diffraction scattering method, the particle size at which the cumulative value reaches 25% is defined as D. ２５ The particle size at which the cumulative value reaches 97% is D ９７ In that case, D ９７ / D ２５ However, spherical alumina powder with a coefficient between 8.0 and 30.

0.

7. A spherical alumina powder according to claim 1 or 2, In the volume frequency particle size distribution measured by the wet laser diffraction scattering method, the particle size at which the cumulative value reaches 50% is defined as D. ５０ The particle size at which the cumulative value reaches 97% is D ９７ In that case, D ９７ / D ５０ However, spherical alumina powder with a coefficient between 5.0 and 20.0.

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