Alumina powder, inorganic powder, and resin composition

Abstract

To provide an alumina powder excellent in lowering viscosity and increasing thermal conductivity when blended with a resin.SOLUTION: Provided is an alumina powder in which a particle diameter at a maximum peak in a volume frequency particle size distribution measured using the wet laser diffraction scattering technique is 1 μm or more and less than 50 μm, and when particle diameters at points in the volume frequency particle size distribution at which cumulative volumes from the small particle side are 10%, 50%, and 97% are denoted by D10, D50, and D97, respectively, (D97-D10) / D50 satisfies 3.0 or less.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Various developments have been made on alumina powders up to now. One known example of this type of technology is the technology described in Patent Document 1. Patent Document 1 describes an alumina powder having an average particle size (D50) of 50 μm or less. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-193493 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of investigations by the present inventors, it has been found that 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. [Means for solving the problem]

[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 size 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, 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 (D 97 -D 10 ) / D 50 Alumina powder having a viscosity of 3.0 or less. 2. The alumina powder according to 1., D 97 The alumina powder has a particle size of 40.0 μm or less. 3. The alumina powder according to 1. or 2., D 97 / D 50 is 3.4 or less. 4. The alumina powder according to any one of 1. to 3., The alumina powder has a maximum peak width of 16.4 μm or less. 5. The alumina powder according to any one of 1. to 4., An alumina powder having an alumina content of 99.9 mass% or more, calculated as mass. 6. The alumina powder according to any one of 1. to 5., An alumina powder having a sphericity of 0.90 or more as measured using a wet flow image analyzer. 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. [Effects of the Invention]

[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. [Brief explanation of the drawings]

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

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

[0010] The alumina powder of this embodiment is The particle size 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, The particle diameters at which 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 (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 the relatively coarse particles and the relatively fine particles contained in the powder. For such a sharp particle size profile, (D 97 -D 10 ) / D 50 It 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 thought 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 particles of the coarse powder, making it easier to form heat paths and improving thermal conductivity. Furthermore, it is believed that fine powders with reduced particle size variation and mixed powders of coarse powders and fine powders have a high 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 may be any powder containing alumina (Al2O3) as the main component. The term "main component" means that the alumina powder contains 99.9 mass % or more of alumina (Al2O3) in terms of mass, based on the total amount of the alumina powder. The alumina powder preferably has a high purity, but the presence of impurities inevitably mixed in from the raw materials or during the manufacturing process is acceptable.

[0016] According to the procedure below, in the volume frequency particle size distribution obtained by the wet laser diffraction scattering method, 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, the "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 based on the refractive index of the powder material. For example, the refractive index of amorphous silica was set to 1.50, and the refractive index of alumina was set to 1.76.

[0018] (D 97 -D 10 ) / D 50 The upper limit of is, for example, 3.0 or less, preferably 2.9 or less, and more preferably 2.85 or less, which can reduce the viscosity during resin blending and increase the thermal conductivity. (D 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, thereby improving productivity.

[0019] Alumina powder D 97 The upper limit is, for example, 40.0 μm or less, preferably 35.0 μm or less, and more preferably 33.0 μm or less. D 97 The lower limit 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. In this way, D 99 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 is, for example, 3.4 or less, preferably 3.3 or less, and more preferably 3.25 or less, which can lower the viscosity during resin blending and increase the thermal conductivity. D 97 / D 50 The 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, thereby improving productivity.

[0021] Alumina powder D 10 The lower limit is, for example, 2.5 μm or more, preferably 2.8 μm or more, and more preferably 2.9 μm or more. D10 The upper limit is not particularly limited, but may be 5.5 μm or less, 5.3 μm or less, or 5.0 μm or less. In this way, D 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 in this way, the thermal conductivity can be improved when blended in a resin composition.

[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 / g or more. The upper limit of the specific surface area of ​​alumina powder is, 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, and preferably 50% or less.

[0025] The alumina powder has a sphericity of, for example, 0.90 or more, preferably 0.91 or more, and more preferably 0.92 or more, as measured using a wet flow image analyzer. This improves the fillability of the alumina powder into resin. However, 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 It is possible to control the particle size, peak width, and sphericity of each of the alumina powders. Among these, for example, in the case of alumina powders produced by the molten flame method, removing at least one of relatively coarse particles and fine particles contained in the powder is effective in achieving the above-mentioned (D 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 powder at a temperature above its melting point. The obtained molten spherical particles may be further subjected to classification and sieving treatment, if necessary. The sieving process preferably removes at least one of the relatively coarse particles and the fine particles contained in the powder. Specifically, if the particle size (μm) of the maximum peak 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 appropriately.

[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] The resin composition may contain alumina powder alone or in combination with other fillers. The resin composition may contain 10 to 99% by mass of alumina powder, or 10 to 99% by mass of 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% by mass, 3 to 150% by mass, or 10 to 100% by mass relative to 100% by mass of the alumina powder. In this specification, unless otherwise specified, the symbol "to" indicates that the upper and lower limits are included.

[0034] Examples of the other inorganic fillers include alumina powders other than the alumina powder of the present invention, crystalline silica, fused silica, titania, silicon nitride, aluminum nitride, silicon carbide, talc, calcium carbonate, and the like. The other inorganic fillers have an average particle size of, 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. [Example]

[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> A spherical alumina powder was produced using the thermal spraying apparatus 100 shown in FIG. The thermal spraying device 100 shown in FIG. 1 includes a melting furnace 2, a burner 1 installed in the upper part 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 lower part of the melting furnace 2. Burner 1 has a double-pipe structure capable of forming an inner flame and an outer flame, and is installed at the top of melting furnace 2, to which combustible gas supply pipe 11, combustion supporting gas supply pipe 12, and raw material supply pipe 13 are connected. In the melting furnace 2, raw material powder is fed into a high-temperature flame through a raw material supply pipe 13 and melted to form molten spherical particles. The molten spherical particles that have passed through the melting furnace 2 are sucked in by a blower 9 together with the combustion exhaust gas, move by the air through pipes 3 and 5, and are classified and collected in a cyclone 4 or a bag filter 8.

[0040] (alumina fine powder) Fine powder 1: Alumina powder (specific surface area: 0.32 m 2 / g, D50:11.6μm) Using the above-mentioned thermal spraying device 100 and the raw material powders under the following conditions, an alumina powder was produced, which was 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 by combustion of the LPG and oxygen in the burner 1. Secondary air was supplied to the cyclone 4 by a rotary valve (not shown) installed in the pipe 3. Atmospheric air was used as the secondary air. The degree of opening / closing of the lower valve in the cyclone 4 (lower opening) was set to 100%. As raw material powder, the average particle size (D 50 ) in the range of 2 to 45 μm was used. The supply rate was 15 Nm of carrier gas for the raw material heated to 500°C. 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 25 μm openings, and the part that passed through sieve A1 was sieved through a sieve B1 with 3 μm openings. 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 sieve A2 with 25 μm openings, and the part that passed through sieve A2 was sieved through sieve B2 with 1 μm openings. 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 sieve A3 with 20 μm openings, and the part that passed through sieve A3 was sieved through sieve B3 with 1 μm openings. The alumina powder remaining on sieve B3 was used as fine powder 4.

[0042] (coarse alumina powder) Coarse powder 1: Alumina powder (specific surface area: 0.09 m 2 / g, D50:136μm) As raw material powder, the average particle size (D 50 Coarse powder 3 was prepared by the same method as for 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.

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

[0044] <Particle size distribution> The volume frequency particle size distribution of the powder was determined by a wet laser diffraction scattering method using a particle size distribution analyzer (MT-3300EX, manufactured by Nikkiso Co., Ltd.). Water was used as the solvent, and the powder was dispersed in the solvent for 1 minute using a homogenizer at 200 W output. The dispersion was used as the measurement target. The PIDS (Polarization Intensity Differential Scattering) concentration was adjusted to 45-55% for measurement. 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 becomes X% (D X ) was calculated.

[0045] <Sphericity> The sphericity of the powder was determined as follows under the conditions of room temperature of 25°C and humidity of 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 above-mentioned wet flow type image analyzer was prepared as follows. 0.05 g of spherical alumina powder sample was weighed into a 20 ml glass beaker, 10 ml of a 25% by mass propylene glycol aqueous solution 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 into the FPIA-3000 and measured using the LPF mode / quantitative counting method (total count of 100 particles, repeated measurement once). The perimeter of a single particle projected image and the perimeter of a circle corresponding to the area of ​​the particle projected image were analyzed using the above-mentioned wet flow type image analyzer, and the circularity was calculated using the following formula. Circularity = (perimeter of the projected particle image) / (perimeter of the circle equivalent to the area of ​​the projected particle image) The sphericity and circularity are average values ​​for particles within each particle size class. The sphericity was calculated as the square of the circularity of each particle size class.

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

[0047] [Table 1]

[0048] [Table 2]

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

[0050] <Method for measuring thermal conductivity> 40 mass % of the alumina powder (fine powders 1 to 4) of each of the Examples and Comparative Examples shown in Table 1 was mixed with 60 mass % of the above 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 planetary centrifugal 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 resulting sample was cut into a 20 mm long x 20 mm wide x 3 mm thick sheet. The upper heater, sample (cut out), 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 10 samples is shown in Table 2.

[0051] <Viscosity measurement method> The inorganic powder prepared in the above <Method for measuring thermal conductivity> was mixed with bisphenol F-type epoxy (Epikote 807) in a liquid state 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 using a rheometer at 25°C and a shear rate of 36 [1 / s]. Table 2 shows the relative viscosity values ​​when the viscosity of Comparative Example 1 is normalized to 100.

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

[0053] 1 burner 2. Melting furnace 3 Piping 4. Cyclone 5 Piping 8. Bag 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. The particle size 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, 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. 2. The alumina powder according to claim 1, D ９７ is 40.0 μm or less.

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

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

5. 3. The alumina powder according to claim 1 or 2, An alumina powder having an alumina content of 99.9 mass% or more in terms of mass.

6. 3. The alumina powder according to claim 1 or 2, An alumina powder having a sphericity of 0.90 or more as measured using a wet flow image analyzer.

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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