JP5320263B2 - Spherical alumina powder, production method and use thereof - Google Patents

Description

The present invention relates to spherical alumina powder, a method for producing the same, and use.

  In recent years, with the high performance and high functionality of electronic devices, heat dissipation of electronic components has become a problem. Among electronic members, a heat-dissipating sheet in which alumina is contained in a silicone resin is used for various applications because of its ease of use. In order to increase the thermal conductivity of the heat dissipation sheet, the content of the alumina powder may be increased.

  When a general Bayer method alumina powder is highly filled in a silicone resin, the heat conduction characteristics of alumina cannot be fully utilized due to a remarkable thickening phenomenon. In order to solve this, Patent Document 1 proposes that a spherical alumina powder is obtained by spraying aluminum hydroxide powder or a slurry of aluminum hydroxide powder into a flame from a feed tube having a strong dispersion function.

When the alumina powder is contained in the silicone resin, the alumina powder is often treated with a coupling agent. The treatment of the alumina powder with the coupling agent has the effect of increasing the adhesion between the alumina powder and the resin and increasing the strength of the heat dissipation sheet. In Patent Document 2, alumina powder is supplied into a high-temperature flame formed by LPG and oxygen gas, the average particle diameter is 50 to 2 μm, the sphericity is 0.90 or more, the number of surface OH groups (hereinafter, the number of isolated OH groups) is 3 to 6. A method for producing pieces / nm ² of spherical alumina is described. In order to further improve the adhesion between the spherical alumina powder and the silicone resin, it is important to increase the number of isolated OH groups, and there is room for improvement.

Japanese Patent Laid-Open No. 2001-19425 JP 2005-68258 A

  The present invention provides a spherical alumina powder having a high number of isolated OH groups, a method for producing the same, and a spherical alumina powder resin composition using the spherical alumina powder with improved adhesion between the spherical alumina powder and the resin.

The present invention solves the above problems by the following means.
(1) The average particle size is 100 μm or less, the average sphericity is 0.90 or more, the number of isolated OH groups is 10 to 40 / nm ² , and (number of isolated OH groups / number of hydrogen-bonded OH groups) is 1.0 or more. A spherical alumina powder characterized by being.
(2) A resin composition comprising the alumina powder according to (1).
(3) The resin composition according to (2), wherein the resin is silicone.
(4) A heat radiating member using the resin composition according to (2) or (3).
(5) The spherical material as described in (1) above, wherein an alumina raw material having an average particle size of 100 μm or less is flame-melted at 2200 to 2600 ° C., and sprayed with water at a spray amount of 40 to 120 L / hour and rapidly cooled. A method for producing alumina powder.

By using the spherical alumina powder having many isolated OH groups of the present invention, the adhesion between the spherical alumina powder and the resin can be improved, and the strength of the resin composition containing the spherical alumina powder can be increased. In particular, the strength of the sheet can be increased.

Schematic diagram of alumina powder manufacturing process

Hereinafter, the present invention will be described in detail.
In the present invention, the number of isolated OH groups in the spherical alumina powder is increased by quenching the alumina raw material by flame spraying when flame melting. Since the spherical alumina obtained by the present invention is easily bonded to the coupling agent, the adhesion with the resin can be improved.

The number of isolated OH groups in the spherical alumina powder can be controlled by changing the flame temperature at the time of melting the alumina raw material flame and the amount of water sprayed. This time, the water spray treatment was carried out by always supplying water from the trunk of the furnace body into the furnace. As the cooling medium, water, ice, water vapor or the like can be used, but it is preferable to use water in consideration of ease of handling. The flame temperature at the time of melting is 2200 to 2600 ° C., preferably 2300 to 2500 ° C., and the rapid cooling treatment is preferably performed to lower the temperature in the furnace by 100 to 250 ° C. compared to the case where water is not sprayed.

Alumina raw material As the alumina raw material of the present invention, aluminum hydroxide, alumina, or pulverized fused alumina was used. In order to produce a spherical alumina powder having a high sphericity, it is preferable to use fused alumina as a raw material.

Flame melting treatment The flame melting treatment of the alumina raw material was carried out using the equipment shown in FIG. Briefly, alumina raw material is injected into the flame from the top of the furnace and melted, and water is constantly supplied into the furnace from the furnace body to cool the furnace, and the resulting spherical alumina powder is bug-filtered by a blower together with exhaust gas. Transport to and collect. The supply of water as a cooling medium will be described later. The formation of the flame is performed by injecting a fuel gas such as hydrogen, natural gas, acetylene gas, propane gas, or butane and an auxiliary combustion gas such as air or oxygen from a combustion burner set in the furnace body. Air, nitrogen, oxygen, carbon dioxide, or the like can be used as a carrier gas for supplying raw material powder. Flame temperature is 2200-2600 degreeC, and 2300-2500 degreeC is preferable. The reason why the number of isolated OH groups does not increase so much when the flame temperature is higher than 2500 ° C. is considered that the isolated OH groups are condensed and volatilized. Also, the number of isolated OH groups does not increase so much when the flame temperature is lower than 2300 ° C. This is considered because the sprayed water is not decomposed into OH groups.

Flame temperature measurement The flame temperature at the time of melting was measured using an IS5 / F radiation thermometer manufactured by Impac with a burner installed outside the furnace.

Quenching treatment The quenching treatment was performed by always spraying water into the furnace when the alumina raw material was melted by flame. The atomization of water was performed using an Atmax nozzle BN160 type manufactured by Atmax Co., and air pressurized to 5.0 kgf / cm ² with a compressor was used as a dispersed gas of the nozzle. The temperature of the sprayed water was controlled at 10 ° C. Two rapid cooling nozzles were inserted every 15 ° from the center of the furnace. The first stage nozzle position was 80 cm high from the furnace top, and the second stage position was 100 cm high from the furnace top. The spray amount of water is 40 to 120 L / Hr per hour, and preferably 40 to 80 L / H. It is preferable to lower the temperature in the furnace by 100 to 250 ° C. compared to when the water is not sprayed.

Measurement of temperature change during quenching The degree of quenching was confirmed by measuring the temperature in the furnace before and after spraying water. An R thermocouple was used for temperature measurement, and the thermocouple was inserted up to the furnace wall at a height of 100 cm from the top of the furnace.

  The average particle diameter of the spherical alumina powder is variously selected depending on the application. The average particle diameter of the spherical alumina powder can be increased or decreased by controlling the average particle diameter of the alumina raw material.

Average Particle Size Measurement The average particle size was measured using a laser diffraction particle size distribution measuring machine Cirrus granulometer “Model 1064”. For particles having an average particle diameter of 25 μm or less, sample 1 g is measured, for samples 25 to 45 μm, sample 2 g is measured, and for particles 45 to 120 μm, 4 g of sample is weighed and directly put into the sample introduction part of the Cirrus granulometer. Cirrus granulometer particle size distribution measurement was performed using water as a solvent and a pump speed of 60 rpm.

  In order to highly fill the resin with the spherical alumina powder, the average sphericity of the spherical alumina powder is preferably 0.90 or more, particularly preferably 0.95 or more. The sphericity of the spherical alumina powder can be increased or decreased by adjusting the amount of fuel gas (for example, LPG) used for flame formation and the feed amount of the raw material powder.

Average sphericity measurement
The average sphericity is measured using a flow type particle image analyzer “FPIA-3000” manufactured by Sysmex. The average sphericity is obtained by squaring the average circularity value obtained from FPIA-3000. For the average circularity, the flow particle image analyzer “FPIA-3000” analyzes the circumference of one particle projection image and the circumference of a circle corresponding to the area of the particle projection image, and the equation (circularity) = ( (Perimeter of particle projection image) / (perimeter of circle corresponding to area of particle projection image). In this sphericity measurement, an average value per 36000 pieces was automatically calculated. This measurement was performed with a high-magnification imaging unit, and LUCPLFLN 20 × (magnification 20 times) was used for the objective lens, and AND-40C-70 (transmittance 70%) was used for the ND filter.
[Average sphericity of particles with an average particle size of 20 μm or more]
0.05 g of a spherical alumina powder sample is weighed in a 20 ml glass beaker container, 10 ml of a 25% by mass aqueous solution of propylene glycol is added, and then dispersed with an ultrasonic disperser for 3 minutes. All of this is put into FPIA-3000 and measured by the LPF mode / quantitative count (total count of 36000, number of repeated measurements once).
[Average sphericity of particles with an average particle diameter of less than 20 μm]
0.05 g of a spherical alumina powder sample is weighed in a 20 ml glass beaker container, 10 ml of a 25% by mass aqueous solution of propylene glycol is added, and then dispersed with an ultrasonic disperser for 3 minutes. This is all put into FPIA-3000 and measured by the HPF mode / quantitative count (total count: 36000, number of repeated measurements once).

Measurement of the number of OH groups In the present invention, the number of isolated OH groups and the number of hydrogen-bonded OH groups were determined using the Karl Fischer method. Karl Fischer measurement uses a moisture vaporizer VA-122 manufactured by Mitsubishi Chemical Corporation and a moisture analyzer CA-100 manufactured by Mitsubishi Chemical Corporation. Aquamicron AX (manufactured by Mitsubishi Chemical Corporation) is used as the anolyte of the moisture analyzer, and Used Aquamicron CXU (Mitsubishi Chemical Corporation). In the Karl Fischer measurement, the background value was fixed at 0.10 (μg / sec), and the measurement was continued until the detected water content fell below the background value. What is detected at a temperature of 550 ° C. is a hydrogen-bonded OH group, and what is detected at a temperature of 900 ° C. is derived from an isolated OH group. In the measurement, the alumina sample was previously heated at 200 ° C. for 30 minutes to remove the physical-grade water landing, and then measured in the order of 550 ° C. and 900 ° C. During the heat treatment, the alumina sample was not exposed to the outside air, and the water generated from the water vaporizer was introduced into a Karl Fischer device along with 300 ml / min of high-purity argon, and the water content was measured. The sample introduced into the moisture vaporizer was 4 g.
[Conversion of moisture content to the number of OH groups]
The moisture detected in the Karl Fischer measurement is considered that two OH groups are condensed to form one water molecule, and the number of OH groups is obtained by the following equation. (Number of OH groups [pieces / nm ² ]) = 0.0662 × (water content [ppm]) / (specific surface area [m ² / g] of spherical alumina powder sample)
[Specific surface area measurement]
The specific surface area was measured using an AUTOMATIC SURFACE ANALYZER MODEL-4232II manufactured by Microdata.

The spherical alumina powder of the present invention has many coupling agent reaction sites and is highly reactive with the coupling agent. Examples of coupling agents that can be used in the present invention include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3 -Glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyl Diethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane, N-2 (aminoethyl) -Aminopropyltrimethoxysilane, N-2 (aminoethyl) 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3 -Dimethyl-ditylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltriethoxysilane 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanatopropyltriethoxysilane, etc. Can. Of these, vinyl coupling agents are preferred because of their high tensile strength.
A surface treatment agent can also be used in place of the coupling agent. Examples of surface treatment agents include tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, hexamethyldisilazane, hexyltrimethoxysilane, and decyltrimethoxysilane. Can be used.

The spherical alumina powder of the present invention has high reactivity with the coupling agent. Therefore, the spherical alumina powder of the present invention treated with a coupling agent has good adhesion to resins other than silicone. Examples of the resin of the spherical alumina powder resin composition of the present invention include epoxy resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyimide, polyamideimide, polyetherimide, and other polyamides, polybutylene terephthalate, polyethylene Polyester such as 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 / polypropylene) Diene rubber-styrene) resin, EVA (ethylene vinyl acetate copolymer) resin, and the like can also be used. As the rubber, urethane rubber, acrylic rubber, ethylene propylene rubber, urethane rubber, or the like can be used.

The spherical alumina powder resin composition of the present invention is obtained by incorporating the spherical alumina powder of the present invention into a resin. Although the content rate of spherical alumina powder changes with uses, when considering heat conductive characteristics, it is preferable to set it as 40 to 90 volume%.
What contained the spherical alumina powder of this invention in the silicone is suitable as a heat radiating member. In order to develop a high thermal conductivity as a heat radiating member, it has never been better to increase the content of the spherical alumina powder, but considering characteristics such as tensile strength, flexibility, and formability, it is 65 to 80% by volume. It is preferable to make it.

The alumina raw materials 1 to 6 described below were used as the alumina raw materials.
[Alumina raw material 1]
Aluminum hydroxide BHP39 (average particle size 35 μm) manufactured by Nippon Light Metal Co., Ltd. was used.
[Alumina raw material 2]
Alumina LS-210 (average particle size 4 μm) manufactured by Nippon Light Metal Co., Ltd. was used.
[Alumina raw material 3]
Alumina LS-21 (average particle diameter 55 μm) manufactured by Nippon Light Metal Co., Ltd. was used.
[Alumina raw materials 4-6]
Alumina raw material 2 (LS-210) is melted, cooled and pulverized in an arc furnace to prepare an electrofused alumina pulverized product, and classified into alumina raw material 4 (average particle diameter 30 μm) and alumina raw material 5 (average particle diameter 92 μm). Alumina raw material 6 (average particle size 120 μm) was prepared.

  The pulverization treatment for preparing the alumina raw materials 4 to 6 was performed with a ball mill, and alumina balls were used as the pulverization media. The obtained pulverized alumina was sieved and classified to prepare alumina raw materials 4 to 6.

Flame melting treatment Flame melting treatment was performed using the manufacturing apparatus shown in FIG. The alumina raw material was supplied into the flame from a nozzle with 30 kg / Hr accompanied by oxygen gas 20 Nm ³ / Hr.

Melting and quenching treatment In order to control the number of isolated OH groups in the spherical alumina powder, when the alumina raw material was flame-melted, water was sprayed into the furnace for cooling treatment. Table 1 shows the types of alumina raw materials, melting conditions, and cooling treatment conditions.

Number of OH groups The sample of the obtained spherical alumina powder was measured for the number of OH groups (isolated OH groups and hydrogen-bonded OH groups) by Karl Fischer measurement. The results are shown in Table 2.

Average sphericity The circularity of the obtained spherical alumina powder was measured with a flow type particle image analyzer “FPIA-3000” manufactured by Sysmex, and the average sphericity was calculated. The results are shown in Table 2.

Average particle size The average particle size was measured using a laser diffraction particle size distribution measuring machine Cirrus granulometer "Model 1064". The results are shown in Table 2.

Surface treatment with a coupling agent The surface treatment with a coupling agent was performed by enclosing 1 kg of spherical alumina powder, 500 g of alumina balls (20 mm), and a coupling agent in a ball mill (AXB-15 manufactured by Seiwa Giken Co., Ltd.). A coupling agent was added, and the ball mill was processed at a rotational speed of 250 rpm for 30 minutes. Coupling agents manufactured by Shin-Etsu Chemical Co., Ltd., KBM-1003 (vinyl type), KBE-1003 (vinyl type), KBM-403 (epoxy type) were used as coupling agents. The coupling agent was added in an amount calculated by the following formula.
Addition amount of coupling agent [g] = (mass of spherical alumina powder [g]) × (specific surface area of spherical alumina powder [m ² / g]) / minimum coating area of coupling agent (m ² / g).
KBM-1003 (515 m ² / g), KBM-573 (307 m ² / g), and KBM-403 (280 m ² / g) were used as the minimum coating area of the coupling agent.
[Specific surface area measurement]
The specific surface area was measured using an AUTOMATIC SURFACE ANALYZER MODEL-4232II manufactured by Microdata.

Tensile strength evaluation Examples 1 to 11 and Comparative Examples 1 to 6 were prepared by mixing the spherical alumina powder prepared in Table 1 with a coupling agent and mixing it with 35% by volume of liquid silicone and 65% by volume of spherical alumina powder. A spherical alumina powder-containing silicone resin composition was prepared, and its tensile strength was evaluated according to the following. In Example 12, the composition was changed to 25% by volume of liquid silicone and 75% by volume of spherical alumina powder to produce a silicone resin composition containing spherical alumina powder in the same manner as in Examples 1 to 11, and the tensile strength was evaluated. . The results are shown in Table 3.
[Preparation of spherical alumina powder-containing silicone resin composition]
For liquid silicone, YE5822 (A) and YE5822 (B) manufactured by MOMENTIVE performance materials were used, and the ratio of YE5822 (A) and YE5822 (B) was 10: 1 [mass ratio]. The spherical alumina powder surface-treated with the coupling agent described in paragraph (0032), YE5822 (A), and YE5822 (B) were mixed for 60 seconds with a planetary stirring and defoaming device (MAZERUSTAR KK-400W). A silicone resin composition was prepared. The thickness of the spherical alumina powder-containing silicone resin composition was 2.5 mm.
[Preparation of tensile strength measurement specimen]
A spherical alumina powder-containing silicone resin composition formed into a sheet having a thickness of 2.5 mm was punched into a dumbbell shape with a test piece punching blade JIS1 manufactured by Kobunshi Keiki Co., Ltd. to prepare a test piece for measuring tensile strength.
[Tensile strength measurement]
Tensile strength measurement was performed according to JIS K6251 using Shimadzu Autograph AG-2000D.

Measurement of thermal conductivity Spherical alumina powder-containing silicone resin composition is molded to 25 x 25 mm and thickness 2.5 mm, sandwiched between a 15 x 15 mm copper heater case and a copper plate, and set with a tightening torque of 5 kgf / cm Then, 15 W of electric power is applied to the copper heater case and held for 4 minutes, the temperature difference between the copper heater case and the copper plate is measured, and the thermal resistance is measured. Thermal resistance can be calculated by (thermal resistance [° C./W])=(temperature difference between copper heater case and copper plate [° C.]) / (Heater power [W]). The thermal conductivity can be calculated from the thermal resistance [° C./W], the heat transfer area (area of the copper heater case) [m ² ], and the molded body thickness [m] when the tightening torque is 5 kgf / cm. The calculation formula of thermal conductivity is (thermal conductivity [W / m · K]) = (molded body thickness [m]) / {(thermal resistance [° C./W])×(heat transfer area [m ² ])} It is. The results of thermal conductivity are shown in Table 3.

As is apparent from Table 3, the spherical alumina powder-containing silicone resin composition using the spherical alumina powder of the present invention is excellent in thermal conductivity and high in tensile strength.
Therefore, it is estimated that the adhesion between the spherical alumina powder of the present invention and the silicone resin is remarkably improved.
Especially the resin composition using the spherical alumina powder of this invention can be used conveniently for the use of a heat radiating member.

  The spherical alumina powder of the present invention is used as a filler for a resin composition. The resin composition of the present invention can be used for heat radiation sheets, molding compounds, etc. for automobiles, portable electronic devices, industrial devices, household appliances and the like.

1 Melting furnace 2 Burner 3 Fuel gas supply pipe 4 Auxiliary combustion gas supply pipe 5 Raw material powder supply pipe 6 Cooling medium supply port 7 Bag filter 8 Blower 9 R Thermocouple

Claims (5)

The average particle size is 100 μm or less, the average sphericity is 0.90 or more, the number of isolated OH groups is 10 to 40 / nm ² , and (number of isolated OH groups / number of hydrogen-bonded OH groups) is 1.0 or more. Features spherical alumina powder.   A resin composition comprising the spherical alumina powder according to claim 1.   The resin composition according to claim 2, wherein the resin is silicone. The heat radiating member using the resin composition of Claim 2 or 3. 2. The production of spherical alumina powder according to claim 1, wherein an alumina raw material having an average particle size of 100 μm or less is flame-melted at 2200 to 2600 ° C., and sprayed with water at a spraying amount of 40 to 120 L / hour and rapidly cooled. Method.

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