Alumina powder, inorganic powder, and resin composition

Abstract

An alumina powder according to the present invention, when examined by the wet laser diffraction / scattering method, gives a volume-frequency particle size distribution which has a maximum-peak particle diameter of 1 μm or larger but smaller than 50 μm and in which, when particle diameters at points respectively corresponding to 10%, 50%, and 97% volume cumulation from the smaller-particle side are expressed by D10, D50, and D97, then (D97-D10) / D50 is 3.0 or less.

Description

Alumina powder, inorganic powder and resin composition

[0001] The present invention relates to an alumina powder, an inorganic powder, and a resin composition.

[0002] Various developments have been made on alumina powders. One such technology is disclosed in Patent Document 1. Patent Document 1 describes an alumina powder having an average particle size (D50) of 50 μm or less.

[0003] JP 2015-193493 A

[0004] However, as a result of investigations by the present inventors, it has been found that there is room for improvement in the alumina powder described in Patent Document 1 above in terms of lowering the viscosity and increasing the thermal conductivity when blended with a resin.

[0005] After further investigation, the inventors found that by making the particle size distribution of alumina powder having a particle diameter of 1 μm or more and less than 50 μm relatively sharp, it is possible to increase the thermal conductivity while reducing the viscosity of a resin composition obtained by blending alumina powder with a sharp particle size distribution with a resin, and thus completed the present invention.

[0006] According to one aspect of the present invention, the following alumina powder and resin composition are provided: 1. The particle diameter of the maximum peak in the volume frequency particle size distribution measured by a wet laser diffraction scattering method is 1 μm or more and less than 50 μm, and the particle diameters at the points where the cumulative volume from the small particle side in the volume frequency particle size distribution is 10%, 50%, and 97% are defined as D １０ , D ５０ , D ９７ When this is done, (D ９７ -D １０ ) / D ５０ 2. The alumina powder according to 1., wherein D satisfies the following: ９７ 3. The alumina powder according to 1. or 2., wherein the particle size is 40.0 μm or less. ９７ / D ５０is 3.4 or less. 4. The alumina powder according to any one of 1. to 3., wherein the peak width of the maximum peak is 16.4 μm or less. 5. The alumina powder according to any one of 1. to 4., wherein the alumina content is 99.9 mass% or more in mass terms. 6. The alumina powder according to any one of 1. to 5., wherein the sphericity measured using a wet flow image analyzer is 0.90 or more. 7. An inorganic powder comprising the alumina powder according to any one of 1. to 6., and an inorganic filler other than the alumina powder. 8. A resin composition comprising the alumina powder according to any one of 1. to 6., and a resin.

[0007] According to the present invention, there are provided an alumina powder that is excellent in reducing viscosity and increasing thermal conductivity when blended with a resin, and an inorganic powder and a resin composition using the same.

[0008] FIG. 1 is a schematic cross-sectional view showing the configuration of a thermal spraying device.

[0009] An outline of the alumina powder of this embodiment will be described.

[0010] The alumina powder of this embodiment has a maximum peak particle diameter of 1 μm or more and less than 50 μm in a volume frequency particle size distribution measured by a wet laser diffraction scattering method, and the particle diameters at points where the cumulative volume from the small particle side in the volume frequency particle size distribution is 10%, 50%, and 97% are defined as D １０ , D ５０ , D ９７ When this is done, (D ９７ -D １０ ) / D ５０ is 3.0 or less.

[0011] According to the findings of the present inventors, it is possible to sharpen the particle size profile of the volume frequency particle size distribution of an alumina powder by removing at least one of relatively coarse particles and fine particles contained in the powder. Regarding such a sharp particle size profile, ９７ -D １０ ) / D ５０It has been found that by using this as an index, it is possible to stably evaluate the properties of a resin composition containing alumina powder and a resin, and that by setting this index to an upper limit value or less, it is possible to reduce the viscosity and increase the thermal conductivity of the resin composition.

[0012] Furthermore, if another alumina powder of this embodiment having a particle diameter of 1 μm or more and less than 50 μm is defined as alumina fine powder, and another alumina powder having a particle diameter of 50 μm or more and 150 μm or less, measured by the same method as the alumina fine powder, is defined as alumina coarse powder, the effects of lowering viscosity and increasing thermal conductivity become even more pronounced when these alumina fine powder and alumina coarse powder are used in combination.

[0013] Although the detailed mechanism is unclear, it is believed that alumina fine powder with a sharp particle size distribution suppresses particle size variation and increases packing density, and when combined with alumina coarse powder, the fine powder can efficiently fill the gaps between the coarse powder particles, making it easier to form heat paths and improving thermal conductivity.Furthermore, it is believed that fine powder with suppressed particle size variation and a mixed powder of coarse and fine powders increase particle packing density, which can reduce the viscosity of the resin composition.

[0014] Each component of the alumina powder of this embodiment will be described in detail below.

[0015] The alumina powder is alumina (Al ２ 0 ３ The main component is alumina (Al) in the total amount of alumina powder, calculated by mass. ２ 0 ３ The alumina powder preferably has a high purity, but the presence of impurities that are inevitably mixed in from the raw materials or during the manufacturing process is acceptable.

[0016] In the volume frequency particle size distribution obtained by the wet laser diffraction scattering method according to the following procedure, the particle diameters at the points where the cumulative volume from the small particle side is 10%, 50%, and 97% are determined as D １０ , D ５０ , D ９７ Let's say.

[0017] The volumetric particle size distribution of the alumina powder, which is related to its particle size, can be measured by a laser diffraction light scattering method using, for example, an "MT-3300EX" manufactured by Nikkiso Co., Ltd. The measurement target was water as the solvent, and as a pretreatment, the alumina powder was dispersed using a homogenizer at 200 W output for 1 minute to obtain a dispersion. 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 was determined taking into account the refractive index of the powder material. For example, measurements were performed using a refractive index of 1.50 for amorphous silica and a refractive index of 1.76 for alumina.

[0018] (D ９７ -D １０ ) / D ５０ The upper limit of the (D) is, for example, 3.0 or less, preferably 2.9 or less, and more preferably 2.85 or less. This makes it possible to reduce the viscosity during resin blending and increase the thermal conductivity. ９７ -D １０ ) / D ５０ The lower limit of is not particularly limited, but may be, for example, 1.5 or more, 1.8 or more, or 2.0 or more. This can improve productivity.

[0019] Alumina powder D ９７ The upper limit of the thickness is, for example, 40.0 μm or less, preferably 35.0 μm or less, and more preferably 33.0 μm or less. ９７ The lower limit of D is not particularly limited, but may be, for example, 10.0 μm or more, 11.0 μm or more, or 12.0 μm or more. ９７ By making the value of the sintering agent not more than the upper limit, productivity can be improved.

[0020] D ９７ / D ５０ The upper limit of D is, for example, 3.4 or less, preferably 3.3 or less, and more preferably 3.25 or less. This allows the viscosity during resin blending to be lowered and the thermal conductivity to be increased. ９７ / D ５０The lower limit of is not particularly limited, but may be, for example, 1.8 or more, 2.0 or more, or 2.2 or more. This can improve productivity.

[0021] Alumina powder D １０ The lower limit of D is, for example, 2.5 μm or more, preferably 2.8 μm or more, and more preferably 2.9 μm or more. １０ The upper limit of D is not particularly limited, but may be 5.5 μm or less, 5.3 μm or less, or 5.0 μm or less. １０ By making the content of the polyisoprene copolymer equal to or greater than the lower limit, the thermal conductivity of the polyisoprene copolymer when blended in a resin composition can be improved.

[0022] The upper limit of the peak width of the maximum peak of the alumina powder is, for example, 16.4 μm or less, preferably 15.5 μm or less, and more preferably 15.0 μm or less. On the other hand, the lower limit of the peak width of the maximum peak is not particularly limited, but may be, for example, 4.0 μm or more, 6.0 μm or more, or 6.5 μm or more. By making the peak width equal to or less than the upper limit, the thermal conductivity when blended into a resin composition can be improved.

[0023] The lower limit of the specific surface area of ​​the alumina powder is not particularly limited, but is, for example, 0.10 m ２ The upper limit of the specific surface area of ​​the alumina powder may be, for example, 1.5 m ２ / g or less, preferably 1.0m ２ / g or less.

[0024] The lower limit of the gelatinization rate of the alumina powder is not particularly limited, but may be, for example, 5% or more. The upper limit of the gelatinization rate of the alumina powder is, for example, 80% or less, preferably 50% or less.

[0025] The alumina powder has a sphericity of, for example, 0.90 or more, preferably 0.91 or more, more preferably 0.92 or more, as measured using a wet flow image analyzer. This improves the fillability of the alumina powder into resin. On the other hand, the upper limit of the sphericity is not particularly limited.

[0026] The alumina powder may be one that has been surface-treated with a silane coupling agent, or may be an untreated product with no silane coupling agent attached to the surface.

[0027] In this embodiment, for example, by appropriately selecting the raw material components of the alumina powder and the manufacturing method of the alumina powder, it is possible to obtain the above (D ９７ -D １０ ) / D ５０ , D ９７ / D ５０ Among these, for example, in the case of alumina powder produced by the molten flame method, it is possible to control the particle size, peak width, and sphericity of each particle. ９７ -D １０ ) / D ５０ , D ９７ / D ５０ These are factors for setting each particle size, peak width, and sphericity within a desired numerical range.

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

[0029] 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 and spheroidizing the raw material powder at a temperature equal to or higher than its melting point. The resulting molten spherical particles may be further subjected to classification and sieving, as necessary. The sieving process preferably involves removing at least one of relatively coarse particles and fine particles contained in the powder. Specifically, if the maximum peak particle size (μm) is X, for example, coarse particles having a particle size larger than (X + α) are top-cut and / or fine particles having a particle size smaller than (X - β) are under-cut, and the remaining powder can be used as the alumina powder of this embodiment. The remaining ranges (μm) of α and β can be selected as appropriate.

[0030] The alumina raw material powder may be, for example, an alumina powder having an average particle size of about 1 to 30 μm. A plurality of raw material powders having different particle sizes may be used as the alumina raw material powder. The aluminum hydroxide powder may be supplied to the high-temperature flame in a dry manner or in a wet manner by forming a slurry with water or the like.

[0031] A resin composition containing the alumina powder of the present invention can be suitably used as a resin molding material.

[0032] The resin composition of the present embodiment contains the alumina powder of the present invention and a resin. The resin composition may contain inorganic powders and known resin additives, as described below, as needed.

[0033] In the resin composition, the alumina powder may be used alone or in a mixture with other fillers. The resin composition may contain 10 to 99 mass% of alumina powder, or 10 to 99 mass% of an inorganic powder containing alumina powder and other inorganic fillers. The content of other inorganic fillers in the inorganic powder may be, for example, 1 to 300 mass%, 3 to 150 mass%, or 10 to 100 mass% relative to 100 mass% of the alumina powder. In this specification, the symbol "to" indicates that the range includes both the upper and lower limits, unless otherwise specified.

[0034] Examples of the other inorganic fillers include alumina powder other than the alumina powder of the present invention, crystalline silica, fused silica, titania, silicon nitride, aluminum nitride, silicon carbide, talc, calcium carbonate, etc. The average particle size of the other inorganic fillers is, for example, about 0.1 to 100 μm, and there are no particular restrictions on the particle size structure and shape.

[0035] Examples of the resin include epoxy resin, silicone resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyamide such as polyimide, polyamideimide, polyetherimide, polyester such as polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, wholly aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide-modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber-styrene) resin, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin, etc. These may be used alone or in combination of two or more.

[0036] The resin composition can be produced, for example, by blending raw material components in a predetermined ratio using a blender, a Henschel mixer, or the like, kneading the mixture using a heated roll, a kneader, a single-screw or twin-screw extruder, or the like, cooling the mixture, and then pulverizing it.

[0037] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention.

[0038] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions of these examples.

[0039] <Alumina Powder> Spherical alumina powder was produced using a thermal spraying apparatus 100 shown in FIG. 1 . The thermal spraying apparatus 100 shown in FIG. 1 includes a melting furnace 2, a burner 1 installed at the top of the melting furnace 2, and a collection system line installed directly connected to the bottom of the melting furnace 2, which includes a cyclone 4 and a bag filter 8. The burner 1 has a double-pipe structure capable of forming an inner flame and an outer flame. The burner 1 is installed at the top of the melting furnace 2 and is connected to a combustible gas supply pipe 11, a combustion supporting gas supply pipe 12, and a raw material supply pipe 13. In the melting furnace 2, raw material powder is supplied to the high-temperature flame through the raw material supply pipe 13 and melted to form spheroidized molten spherical particles. The molten spherical particles that pass through the melting furnace 2 are sucked in by a blower 9 together with the combustion exhaust gas, move by air through pipes 3 and 5, and are classified and collected by the cyclone 4 or the bag filter 8.

[0040] (Alumina fine powder) Fine powder 1: Alumina powder (specific surface area: 0.32 m ２ / g, D50: 11.6 μm) Using the above thermal spraying device 100 and the following conditions and raw material powder, an alumina powder was produced, designated as fine powder 1. LPG was supplied as a combustible gas from a combustible gas supply pipe 11, and oxygen was supplied as a combustion supporting gas from a combustion supporting gas supply pipe 12. A high-temperature flame was formed in the burner 1 by combustion of the LPG and oxygen. Secondary air was supplied to the cyclone 4 by a rotary valve (not shown) installed in the pipe 3. Air from the atmosphere was used as the secondary air. The degree of opening and closing of the lower valve in the cyclone 4 (lower opening) was set to 100%. The raw material powder was prepared using alumina powder having an average particle size (D ５０ The amount of the raw material carrier gas heated to 500°C was 15 Nm ３ / hr, burner flammable gas 5Nm ３ / hr, combustion support gas 10Nm ３ The molten spherical particles collected by the bag filter 8 were recovered as spherical alumina powder, which was designated as fine powder 1.

[0041] Fine powder 2: The alumina powder of fine powder 1 was sieved through a sieve A1 with a mesh size of 25 μm, and the fraction that passed through sieve A1 was sieved through a sieve B1 with a mesh size of 3 μm, and the alumina powder remaining on sieve B1 was used as fine powder 2. Fine powder 3: The alumina powder of fine powder 1 was sieved through a sieve A2 with a mesh size of 25 μm, and the fraction that passed through sieve A2 was sieved through a sieve B2 with a mesh size of 1 μm, and the alumina powder remaining on sieve B2 was used as fine powder 3. Fine powder 4: The alumina powder of fine powder 1 was sieved through a sieve A3 with a mesh size of 20 μm, and the fraction that passed through sieve A3 was sieved through a sieve B3 with a mesh size of 1 μm, and the alumina powder remaining on sieve B3 was used as fine powder 4.

[0042] (Alumina coarse powder) Coarse powder 1: Alumina powder (specific surface area: 0.09 m ２ / g, D50: 136 μm) As the raw material powder, the average particle size (D ５０ Alumina powder was produced in the same manner as in the fine powder 1, except that a plurality of alumina powders having a maximum value of σ in the range of 60 to 250 μm were used, and this was designated as coarse powder 1.

[0043] (Examples 1 to 3 and Comparative Example 1) Fine powder 1 shown in Table 1 was used as the alumina powder in Comparative Example 1, and fine powders 2 to 4 were used as the alumina powders in Examples 1 to 3, respectively.

[0044] <Particle size distribution> The volume frequency particle size distribution relating to the particle size of the powder was determined by a wet laser diffraction scattering method using a particle size distribution measuring device (MT-3300EX, manufactured by Nikkiso Co., Ltd.). In this case, water was used as the solvent, and as a pretreatment, the powder was dispersed in the solvent using a homogenizer at an output of 200 W for 1 minute, and the dispersion obtained was used as the measurement subject. The PIDS (Polarization Intensity Differential Scattering) concentration was adjusted to 45 to 55%, and then the measurement was performed. Based on the obtained volume frequency particle size distribution, the particle size, frequency, and peak width of the maximum peak, and the particle size at which the cumulative value from the small particle size side reaches X% (D Ｘ ) was calculated.

[0045] <Sphericity> The sphericity of the powder was determined as follows under conditions of room temperature 25°C and humidity 70%. The sphericity of the obtained spherical alumina powder was measured using a wet flow image analyzer (FPIA-3000, manufactured by Sysmex Corporation). [Measurement Procedure] The measurement sample used in the wet flow image analyzer was prepared as follows. 0.05 g of a spherical alumina powder sample was weighed into a 20 ml glass beaker, 10 ml of a 25% by mass aqueous solution of propylene glycol was added, and the mixture was dispersed for 3 minutes using an ultrasonic disperser (ASU-10M, manufactured by AS ONE Corporation). The entire amount was placed in the FPIA-3000 and measured using LPF mode / quantitative counting (total count number 100, repeated measurement once). Using the wet flow image analyzer, the perimeter of a single particle's projected image and the perimeter of a circle corresponding to the area of ​​the particle's projected image were analyzed, and the circularity was calculated using the following formula: Circularity = (perimeter of projected particle image) / (perimeter of circle equivalent to the area of ​​projected particle image) Sphericity and circularity are average values ​​for particles within the range of each particle size class. Sphericity was calculated as the square of the circularity for each particle size class.

[0046] <Specific Surface Area> The specific surface area of ​​the powder was measured by the BET single-point method using nitrogen gas adsorption. Specifically, using a specific surface area measuring device (manufactured by Yuasa Ionics, device name: MONOSORB) using nitrogen gas as the adsorption gas and helium gas as the carrier gas, 1 g of the sample was dried and degassed at 300°C for 30 minutes before measurement.

[0047]

[0048]

[0049] The alumina powders of each example and comparative example were evaluated for the following items.

[0050] <Method for Measuring Thermal Conductivity> 40% by mass of the alumina powder (fine powders 1 to 4) of each Example and Comparative Example listed in Table 1 was mixed with 60% by mass of the above-mentioned coarse alumina powder (coarse powder 1) to prepare an inorganic powder. 78% by volume of the obtained inorganic powder was mixed with 12% by volume of a liquid silicone resin (DOWSIL SE1885A) and 10% by volume of a liquid silicone resin (DOWSIL SE1885B) using a rotation / revolution mixer. The resulting mixture was processed into a 3 mm thick sheet and heat-treated in a dryer at 120°C for 2 hours to obtain a sample. The obtained sample was cut into a length of 20 mm, width of 20 mm, and thickness of 3 mm. The upper heater, sample (cut-out sample), heat flux meter, lower heater, and heat sink were stacked in this order, and the thermal conductivity was measured using the heat flow meter method in accordance with ASTM E 1530. The average thermal conductivity of the 10 samples is shown in Table 2.

[0051] <Viscosity Measurement Method> The inorganic powder prepared in the above <Thermal Conductivity Measurement Method> was mixed with bisphenol F-type epoxy (Epikote 807) liquid at 25°C so that the content was 65 mass%, to prepare a resin varnish for evaluation. The viscosity of the obtained resin varnish for evaluation was measured at 25°C and a shear rate of 36 [1 / s] using a rheometer. The relative viscosity values ​​when the viscosity of Comparative Example 1 is normalized to 100 are shown in Table 2.

[0052] The results in Table 2 show that the alumina powders of Examples 1 to 3 can lower the viscosity and increase the thermal conductivity of the resin compositions prepared by blending them with the resin, compared to the alumina powders of Comparative Example 1.

[0053] This application claims priority based on Japanese Patent Application No. 2024-073450, filed April 30, 2024, the disclosure of which is incorporated herein by reference in its entirety.

[0054] REFERENCE SIGNS LIST 1 burner 2 melting furnace 3 piping 4 cyclone 5 piping 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. The particle diameter of the maximum peak in the volume frequency particle size distribution measured by a wet laser diffraction scattering method is 1 μm or more and less than 50 μm, and the particle diameters at the points where the cumulative volume from the small particle side in the volume frequency particle size distribution is 10%, 50%, and 97% are defined as D １０ , D ５０ , D ９７ When this is done, (D ９７ -D １０ ) / D ５０ Alumina powder having a viscosity of 3.0 or less.

2. The alumina powder according to claim 1, ９７ is 40.0 μm or less.

3. The alumina powder according to claim 1 or 2, ９７ / D ５０ is 3.4 or less.

4. The alumina powder according to claim 1 or 2, wherein the peak width of the maximum peak is 16.4 μm or less.

5. The alumina powder according to claim 1 or 2, wherein the alumina content is 99.9 mass% or more in mass terms.

6. The alumina powder according to claim 1 or 2, wherein the sphericity measured using a wet flow type image analyzer is 0.90 or more.

7. An inorganic powder comprising the alumina powder according to claim 1 or 2 and an inorganic filler other than the alumina powder.

8. A resin composition comprising the alumina powder according to claim 1 or 2 and a resin.

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