WO2015133191A1 - LOW-SODA α-ALUMINA POWDER HAVING EXCELLENT VISCOSITY CHARACTERISTICS, AND PRODUCTION METHOD THEREFOR - Google Patents

LOW-SODA α-ALUMINA POWDER HAVING EXCELLENT VISCOSITY CHARACTERISTICS, AND PRODUCTION METHOD THEREFOR Download PDF

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WO2015133191A1
WO2015133191A1 PCT/JP2015/051186 JP2015051186W WO2015133191A1 WO 2015133191 A1 WO2015133191 A1 WO 2015133191A1 JP 2015051186 W JP2015051186 W JP 2015051186W WO 2015133191 A1 WO2015133191 A1 WO 2015133191A1
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alumina
particle size
soda
bet
alumina powder
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French (fr)
Japanese (ja)
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和幸 山本
毅 小塚
寿治 杉山
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日本軽金属株式会社
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
    • C09K5/08—Materials not undergoing a change of physical state when used
    • C09K5/14—Solid materials, e.g. powdery or granular
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/44—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water
    • C01F7/441—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination
    • C01F7/442—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination in presence of a calcination additive
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/20—Oxides; Hydroxides
    • C08K3/22—Oxides; Hydroxides of metals
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/51—Particles with a specific particle size distribution
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/51—Particles with a specific particle size distribution
    • C01P2004/52—Particles with a specific particle size distribution highly monodisperse size distribution
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/10—Solid density
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/22—Rheological behaviour as dispersion, e.g. viscosity, sedimentation stability
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/80—Compositional purity
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/20—Oxides; Hydroxides
    • C08K3/22—Oxides; Hydroxides of metals
    • C08K2003/2227—Oxides; Hydroxides of metals of aluminium
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K2201/00—Specific properties of additives
    • C08K2201/002—Physical properties
    • C08K2201/003—Additives being defined by their diameter

Definitions

  • the present invention is an ⁇ -alumina powder produced from aluminum hydroxide obtained by the Bayer method, in particular, a low-soda ⁇ -alumina powder that is low soda and has excellent viscosity characteristics that can be filled into a resin or rubber, and its It relates to a manufacturing method.
  • Alumina has been widely used as a filler for filling various resins, and one of its main uses is as a heat dissipating filler that combines electrical insulation and chemical stability. Sheets, optical pickup parts, heat release grease, circuit board potting agents, heat-dissipating tapes and adhesives, various injection molded products, motor and IC sealing materials, copper-clad laminates, and various other types Used in a wide range of applications in the field.
  • alumina is incorporated in resin or rubber as much as possible.
  • the viscosity of the obtained alumina-filled resin composition viscosity at the time of resin filling
  • the hardness thereof increases and the flexibility becomes insufficient, making it impossible to follow the unevenness of the object to be coated, making it difficult to deaerate and generating voids.
  • the amount of alumina filling does not increase and the desired thermal conductivity cannot be obtained.
  • Patent Document 1 three types of ⁇ -alumina A, B, and C having substantially no cutting edge (fracture surface) and different particle sizes are prepared, and these three types of ⁇ -alumina A, B, and C are prepared.
  • three types of ⁇ -alumina A, B, and C having different particle sizes must be prepared and mixed at a predetermined ratio to prepare a mixed powder.
  • these three types of alumina having different particle sizes require processing for eliminating the cutting edge, increasing the number of manufacturing steps, and complicating the manufacturing equipment and quality control, resulting in increased manufacturing costs.
  • a method for widening the particle size distribution and increasing the packing has been conventionally performed.
  • such a method deteriorates the dispersibility due to the presence of fine particles, and has a sharp particle size distribution.
  • the thermal conductivity of the composition is lowered, so that it is necessary to make it higher in order to exhibit performance, and there is a problem that the mass of the composition increases. is there.
  • patent document 2 it consists of the aluminum salt obtained by methods other than the Bayer method, aluminum alkoxide, aluminum hydroxide, transition alumina, etc., the alpha alumina precursor induced
  • the ⁇ -alumina precursor obtained by a method other than the Bayer method needs to be calcined together with specific seed crystal particles in a hydrogen chloride-containing atmosphere. Seed crystal particles must be prepared, and it takes a lot of labor to handle them, and it is not practical from an industrial and cost viewpoint.
  • the resulting alumina particles are nano-sized and serve as heat dissipation fillers. Not suitable for use.
  • an alumina raw material such as aluminum hydroxide or transition alumina is added to an alumina powder such as fluoride-based mineralizer in an amount of 0.02 to 0.3% by weight and ⁇ -alumina powder having an average particle diameter of 1 ⁇ m or less.
  • a method of adding 5 to 10% by weight, filling the obtained mixture into a chamotte container, firing at a temperature of 1500 ° C. or less, and then pulverizing to produce low soda ⁇ -alumina has been proposed. ing.
  • low soda alumina for ceramics is obtained, but it is sufficiently satisfactory for use in filler applications such as heat dissipation fillers where filler properties such as viscosity properties are most important. Performance is not obtained.
  • Patent Document 5 alumina, alumina hydrate, ammonium chloride, a halide other than ammonium chloride, and a composition containing a boron compound are heat-treated in a firing container, and then dissolved in an airflow grinder.
  • a method for producing alumina made of round particles by crushing has been proposed.
  • the manufacturing process is complicated, such as the need for a mixing step of alumina and alumina hydrate.
  • the pulverized alumina is refired, an extra cost is required, which is not suitable for mass production.
  • round particles have a problem that the contact between the particles is lowered and the thermal conductivity of the composition is lowered as compared with particles whose shape is not adjusted.
  • Patent Document 6 a fluorine compound or a fluorine compound and a boron compound are added in a predetermined ratio to an alumina raw material made of pseudoboehmite and / or transition alumina, and the resulting mixture is filled in a mullite container to obtain 1100.
  • the soda (Na 2 O) content is as low as 0.1% by mass or less, the average particle size is 2 to 5 ⁇ m, the particle size distribution is sharp, and the resin or rubber is highly filled.
  • ⁇ -alumina powder which can prepare an alumina-filled resin composition having a low viscosity (viscosity at the time of resin filling), good dispersibility, and excellent moldability
  • inexpensive production using inexpensive aluminum hydroxide obtained by the buyer method as a raw material there is a demand for inexpensive production using inexpensive aluminum hydroxide obtained by the buyer method as a raw material.
  • the present inventors use inexpensive aluminum hydroxide obtained by the Bayer method, have low soda, have an average particle size of 2 to 5 ⁇ m, have a sharp particle size distribution, and are filled with resin.
  • a specific firing container was used and the molding density (molding pressure: 98.07 MPa) was 2.05 g / cm 3 or more and the BET specific surface area.
  • an object of the present invention is a low soda ⁇ -alumina powder having a low soda, an average particle diameter of 2 to 5 ⁇ m, a sharp particle size distribution, good dispersibility when filled with a resin, and low viscosity. Is to provide.
  • the present invention is an ⁇ -alumina powder produced by firing and pulverizing aluminum hydroxide obtained by the Bayer method, the soda (Na 2 O) content is 0.1% by mass or less and an average
  • the particle size (Dp50) is 2 to 5 ⁇ m, and the particle size distribution is 45 ⁇ m on the sieve (+45 ⁇ m) 100 ppm or less and the span value ((Dp90 ⁇ Dp10) / Dp50) 1.1 or less.
  • the present invention is to add and mix a halogen-based mineralizer to aluminum hydroxide having a soda (Na 2 O) content of 0.3% by mass or less obtained by the Bayer method, and the resulting mixture contains silica. Filled in a firing container made of alumina ceramic and fired in the range of 1100-1600 ° C so that the molding density (molding pressure: 98.07 MPa) is 2.05 g / cm 3 or more and the BET specific surface area is 0.9 m 2 / g or less.
  • the particle size ratio (D av / D BET) is from 1.10 to 1.45 and the average particle size after pulverization (D av) and the BET equivalent diameter before pulverization (D BET) It is a method for producing a low-soda ⁇ -alumina powder excellent in viscosity characteristics, characterized by being ground so as to be in the range of
  • the low soda ⁇ -alumina powder having excellent viscosity characteristics according to the present invention has a soda (Na 2 O) content of 0.1% by mass or less, preferably 0.08% by mass or less in consideration of electrical insulation,
  • the particle size (Dp50) is 2 ⁇ m or more and 5 ⁇ m or less, and the raw material is aluminum hydroxide derived from the Bayer method, preferably 2.5 ⁇ m or more and 4.0 ⁇ m or less in consideration of dispersibility and thermal conductivity.
  • the soda (Na 2 O) content varies depending on the use of the ⁇ -alumina powder, but for example, it is essential to be 0.1% by mass or less in the application of electronic parts. When exceeding, the problem that electrical insulation cannot be obtained will arise.
  • the average particle size (Dp50) if the average particle size is increased, the thermal conductivity of the molded product is increased accordingly.However, when aluminum hydroxide obtained by the Bayer method is used as a raw material, ⁇ -alumina It is difficult to make the primary particle diameter 5 ⁇ m or more.
  • the amount of 45 ⁇ m sieve (+45 ⁇ m) needs to be 100 ppm or less, and if the amount of 45 ⁇ m sieve (+45 ⁇ m) exceeds 100 ppm, the resin composition filled with this ⁇ -alumina powder as a filler When molding a product, coarse-grained alumina protrudes from the surface of the resin molded product, so that it cannot be used for thin resin molded products, and the adhesiveness with the heat source is impaired. The heat dissipation effect may not be obtained, and if the span value [(Dp90 ⁇ Dp10) / Dp50] is wider than 1.1, the thermal conductivity is higher than that of the filler with the same particle size and sharp particle size distribution.
  • agglomerated grains increase with the increase of the fine particles, it becomes difficult to uniformly disperse alumina, and for example, ⁇ for use in heat dissipation sheets, adhesive sheets, heat dissipation grease, etc. having a desired particle size distribution.
  • ⁇ for use in heat dissipation sheets, adhesive sheets, heat dissipation grease, etc. having a desired particle size distribution.
  • the value of the 45 ⁇ m sieve amount (+45 ⁇ m) is a value measured using a test sieve (mesh 45 ⁇ m) of JIS Z8801-1, and the span value [(Dp90 ⁇ Dp10) / Dp50] using a laser scattering particle size analyzer (Microtrac 9320HRA ( ⁇ 100) manufactured by Nikkiso Co., Ltd.), a particle size corresponding to an integrated particle size distribution rate of 90% by weight (Dp90), an integrated particle size distribution rate of 50%
  • the particle diameter (Dp50) corresponding to% and the particle diameter (Dp10) corresponding to 10% by weight of the cumulative particle size distribution were respectively measured, and the particle diameter ratio [(Dp90 ⁇ Dp10) / Dp50]
  • the value (span value) indicates the sharpness of the particle size distribution, and the smaller the span value, the sharper the particle size distribution.
  • the low soda ⁇ -alumina powder having excellent viscosity characteristics according to the present invention is obtained by adding 200 parts by weight of the ⁇ -alumina powder to an unsaturated polyester resin (acid value: 10.0 mgKOH / g or less, 25 ° C. viscosity: 3.7 ⁇ 0.00%).
  • the resin composition has a viscosity (viscosity when filled with a resin) of 60 poise or less, preferably less than 55 poise when measured using a Brookfield viscometer under conditions of a rotor rotational speed of 12 rpm and a measurement temperature of 25 ° C. More preferably, it is 50 poise or less.
  • a halogen-based mineralizer is added to and mixed with the above aluminum hydroxide, the resulting mixture is fired under predetermined conditions, and then the obtained fired product is pulverized under predetermined conditions.
  • aluminum hydroxide having a soda (Na 2 O) content of 0.3% by mass or less obtained by the Bayer method is used,
  • aluminum hydroxide having an average secondary particle diameter of 10 ⁇ m or more and 200 ⁇ m or less, more preferably 30 ⁇ m or more and 150 ⁇ m or less, measured with a laser scattering particle size measuring instrument [Microtrac 9320HRA ( ⁇ 100) manufactured by Nikkiso Co., Ltd.) is used.
  • the average secondary particle size of aluminum hydroxide used as the alumina raw material is smaller than 10 ⁇ m, it is difficult to obtain ⁇ alumina having a desired particle size, and handling efficiency may be deteriorated and production efficiency may be reduced. On the other hand, if it exceeds 200 ⁇ m, uneven firing occurs in the particles, the particle size distribution becomes broad, the time required for pulverization may increase, and unmilled particles may remain.
  • the alumina raw material obtained by methods other than the Bayer method, for example, the neutralization method has a generally high specific surface area, its use is difficult in the present invention.
  • examples of the halogen mineralizer added to aluminum hydroxide include fluoride mineralizers such as aluminum fluoride, sodium fluoride, cryolite, magnesium fluoride, calcium fluoride, and hydrogen chloride.
  • chloride mineralizers such as ammonium chloride and aluminum chloride; iodide mineralizers such as ammonium iodide; and the amount of halogen mineralizer added to aluminum hydroxide.
  • the blending ratio in terms of fluorine in the mixture is 0.05% by mass or more and 1.0% by mass or less, preferably 0.1% by mass. It is a ratio that is not less than 0.5% and not more than 0.5% by mass.
  • the alumina particle growth effect may be insufficient, and alumina particles having a sufficient particle size may not be obtained. If it is higher than%, the alumina particles become plate-like, resulting in problems that the viscosity is deteriorated and the particles are easily broken.
  • a mixture obtained by adding and mixing a halogen-based mineralizer to aluminum hydroxide is fired.
  • the mixture is filled in a firing container made of silica-containing alumina ceramic.
  • green density (molding pressure: 98.07MPa) the baked product 2.05 g / cm 3 or more, preferably 2.1 g / cm 3 or more 2.5 g / cm 3 or less, and a BET specific surface area 0.9m 2 / g or less, preferably 0.4 m 2 / g or more and 0.8 m 2 / g or less, and for specific firing temperature and firing time, the aluminum hydroxide used as the alumina raw material
  • the firing temperature is usually in the range of 1100 ° C.
  • the firing time Is usually several minutes to 24 hours It is preferably at most 20 hours or more to several hours.
  • the molding density (molding pressure: 98.07 MPa) of the obtained fired product is lower than 2.05 g / cm 3 , the particle shape of alumina tends to be plate-like, the viscosity becomes worse, and the target average particle diameter (Dp50)
  • Dp50 target average particle diameter
  • the average particle diameter (Dp50) may be less than 2 to 5 ⁇ m, or the span value may exceed 1.1. And if said calcination temperature becomes lower than 1100 degreeC, a primary particle will no longer be able to grow to the target particle diameter, and conversely, when it exceeds 1600 degreeC, the welding of alumina etc. will generate
  • the molding density (molding pressure: 98.07 MPa) was measured by measuring the mass and volume of a piece molded into 40 mm ⁇ 20 mm ⁇ 10 mm using a hydraulic 20-ton compression tester (manufactured by Maekawa Test Instruments Co., Ltd.).
  • the BET specific surface area is a value measured by an N 2 gas adsorption method using a specific surface area automatic measuring device (Microsorbex Flowsorb II2300 type).
  • the average particle size after pulverization (D av) and the particle diameter ratio (D av / D BET) of the BET equivalent diameter before pulverization (D BET) is It grind
  • the particle diameter ratio (D av / D BET ) between the average particle diameter after pulverization (D av ) and the BET equivalent diameter before pulverization (D BET ) is 1.10 or more and 1.45 or less.
  • the particle size ratio (D av / D BET ) with respect to the average particle size (D av ) after pulverization using the BET equivalent diameter (D BET ) as an index is in the range of 1.10 to 1.45. Grind into.
  • the means for pulverizing the fired product is not particularly limited as long as the target particle size ratio (D av / D BET ) of 1.10 or more and 1.45 or less can be achieved.
  • a container driving medium mill such as a vibration ball mill, a rotating ball mill, and a planetary mill, a medium agitation mill, an air flow type pulverizer such as a jet mill, a counter jet mill, and a jet mizer can be used.
  • the ⁇ -alumina powder produced by the above-described method of the present invention has a soda (Na 2 O) content of 0.1% by mass or less despite the fact that aluminum hydroxide obtained by the Bayer method is used as the alumina raw material.
  • the average particle size (Dp50) is 2 to 5 ⁇ m, and the particle size distribution is 45 ⁇ m on the sieve (+45 ⁇ m): 100 ppm or less and the distribution width [(Dp90 ⁇ Dp10) / Dp50]: 1.1 or less It is a sharp, high-filling low-soda ⁇ -alumina powder having a low viscosity when filled with a resin.
  • the low soda ⁇ -alumina powder having excellent viscosity characteristics according to the present invention is low soda and has an average particle diameter of 2 to 5 ⁇ m, sharp particle size distribution, good dispersibility when filled with resin, and viscosity. In addition to being useful as alumina for resin filling, it is easy to design a particle size distribution when preparing an alumina powder having a specific particle size distribution.
  • the method for producing an ⁇ -alumina powder of the present invention not only can the low-soda ⁇ -alumina powder excellent in the above-mentioned viscosity characteristics be produced at low cost by using the aluminum hydroxide obtained by the Bayer method, Process management can be carried out easily and reliably.
  • Example 1 Aluminum fluoride obtained by the Bayer method (average secondary particle size: 55 ⁇ m and soda (Na 2 O) content: 0.2% by mass) is 0.4% by mass of aluminum fluoride as a halogen-based mineralizer in terms of alumina. The mixture was added and mixed at a ratio, and the obtained mixture was filled in a firing container made of alumina ceramic containing silica, and fired in a tunnel kiln furnace at 1500 ° C. ⁇ 10 ° C. for about 15 hours. The soda (Na 2 O) content, molding density, and BET specific surface area of the fired product were measured. The results are shown in Table 1.
  • the particle size distribution was measured as a particle size distribution of 45 ⁇ m (+45 ⁇ m) and the particle size corresponding to an integrated particle size distribution rate of 90% by weight (Dp90) and the particle size corresponding to an integrated particle size distribution rate of 50% by weight.
  • the span value [(Dp90 ⁇ Dp10) / Dp50] was determined by measuring the particle size (Dp10) corresponding to (Dp50) and the cumulative particle size distribution ratio of 10% by weight, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
  • Example 2 Using a rotating ball mill (manufactured by Chuo Kako Co., Ltd.) in which 255 mm of alumina balls of 255 mm are accommodated in a 300 liter (L) mill, the average particle size after grinding of 50 kg of the fired product obtained in Example 1 (D av: Dp50) is a 3.1 .mu.m, particle size ratio of the average particle size after the pulverization (D av) and the BET equivalent diameter before pulverization (D BET) (D av / D BET) 1.27 To obtain ⁇ -alumina.
  • D av particle size ratio of the average particle size after the pulverization
  • D BET BET equivalent diameter before pulverization
  • Example 1 For the obtained ⁇ -alumina, in the same manner as in Example 1, the amount of 45 ⁇ m sieve (+45 ⁇ m) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
  • Example 3 Using the same rotating ball mill (manufactured by Chuo Kako Co., Ltd.) as in Example 2, the average particle size (D av : Dp50) after pulverization of the calcined product obtained in Example 1 was 2.9 ⁇ m. BET equivalent diameter before the average particle size after pulverization and (D av) grinding (D BET) particle with diameter ratio (D av / D BET) is ground to a 1.19 to obtain ⁇ -alumina. For the obtained ⁇ -alumina, in the same manner as in Example 1, the amount of 45 ⁇ m sieve (+45 ⁇ m) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
  • Example 4 Using a rotating ball mill (manufactured by Chuo Kako Co., Ltd.) in which a 15-mm ⁇ alumina ball was accommodated in a 300 liter (L) mill, the average particle size after pulverization (D av: Dp50) is a 3.1 .mu.m, particle size ratio of the average particle size after the pulverization (D av) and the BET equivalent diameter before pulverization (D BET) (D av / D BET) 1.27 To obtain ⁇ -alumina.
  • D av particle size ratio of the average particle size after the pulverization
  • D BET BET equivalent diameter before pulverization
  • Example 1 For the obtained ⁇ -alumina, in the same manner as in Example 1, the amount of 45 ⁇ m sieve (+45 ⁇ m) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
  • Example 5 A fired product prepared in the same manner as in Example 1 and having the soda (Na 2 O) content, molding density, and BET specific surface area shown in Table 1 was pulverized in the same manner as in Example 1 to obtain ⁇ -alumina. It was. For the obtained ⁇ -alumina, in the same manner as in Example 1, the amount of 45 ⁇ m sieve (+45 ⁇ m) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
  • Example 1 For the obtained ⁇ -alumina, in the same manner as in Example 1, the amount of 45 ⁇ m sieve (+45 ⁇ m) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
  • Example 1 For the obtained ⁇ -alumina, in the same manner as in Example 1, the amount of 45 ⁇ m sieve (+45 ⁇ m) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
  • Example 1 For the obtained ⁇ -alumina, in the same manner as in Example 1, the amount of 45 ⁇ m sieve (+45 ⁇ m) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
  • Example 1 For the obtained ⁇ -alumina, in the same manner as in Example 1, the amount of 45 ⁇ m sieve (+45 ⁇ m) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
  • each of the ⁇ -alumina powders of Examples 1 to 5 has a soda (Na 2 O) content of 0.1% by mass or less and an average particle size (Dp50) of 2
  • Dp50 average particle size
  • the amount of sieve top (+45 ⁇ m) is low, the span value is 1.1 or less, the particle size distribution is sharp, and the viscosity when filled with resin is 60 poise.
  • the resin filling property was excellent as follows.
  • the ⁇ -alumina powder of Comparative Example 1 showed a low span value but a 45 ⁇ m sieving amount (+45 ⁇ m) and a high viscosity when filled with resin
  • the ⁇ -alumina powder of Comparative Example 2 Showed a value of 45 ⁇ m on the sieve (+45 ⁇ m) and a low viscosity when filled with resin, but the span value was high
  • the ⁇ -alumina powder of Comparative Example 3 showed a low span value.
  • the ⁇ -alumina powder of Comparative Example 4 showed a low span value, but a 45 ⁇ m sieve top amount (+45 ⁇ m) and a high resin-filling viscosity value. .

Abstract

Provided is a highly fillable low-soda α-alumina powder, which has a low soda fraction, an average particle diameter of 2 to 5 μm, a sharp particle size distribution, and a low viscosity during resin filling. Also provided is a production method therefor. The low-soda α-alumina powder, which is an α-alumina powder prepared from aluminum hydroxide obtained by the Bayer method, has excellent viscosity characteristics, a soda (Na2O) fraction of 0.1% by mass or less, an average particle diameter (Dp50) of 2 to 5 μm, a particle size distribution with an amount above 45 μm sieve (+45 μm) of 100 ppm or lower, and a span value [(Dp90 - Dp10)/Dp50] of 1.1 or lower. The α-alumina powder is prepared as follows: aluminum hydroxide having a soda (Na2O) fraction of 0.3% by mass or less is added with a halogen-type mineralization agent, fired so as to yield a formed density (forming pressure: 98.07 MPa) of 2.05 g/cm3 or greater and a BET specific surface area of 0.9 m2/g or less, and ground so that the particle size ratio (Dav/DBET), of the average particle diameter (Dav) after grinding over the BET-corresponding diameter (DBET) prior to grinding, is in the range of 1.10 to 1.45.

Description

粘度特性に優れた低ソーダαアルミナ紛体及びその製造方法Low soda α-alumina powder having excellent viscosity characteristics and method for producing the same
　この発明は、バイヤー法で得られた水酸化アルミニウムから製造されるαアルミナ紛体であり、特に低ソーダであると共に樹脂又はゴム中に高充填可能な粘度特性に優れた低ソーダαアルミナ紛体及びその製造方法に関する。 The present invention is an α-alumina powder produced from aluminum hydroxide obtained by the Bayer method, in particular, a low-soda α-alumina powder that is low soda and has excellent viscosity characteristics that can be filled into a resin or rubber, and its It relates to a manufacturing method.
　アルミナは、従来から種々の樹脂に充填するフィラーとして幅広く用いられており、その主な用途の一つとして、電気絶縁性と化学的安定性を兼ね備えた放熱フィラーとしての使用があり、例えば、放熱シート、光ピックアップ部品、放熱グリース、回路基板のポッティング剤、放熱性を付与したテープや接着剤、種々の射出成型品、モーターやＩＣの封止材、銅張積層基板等を始めとして、様々な分野で幅広い用途に使用されている。 Alumina has been widely used as a filler for filling various resins, and one of its main uses is as a heat dissipating filler that combines electrical insulation and chemical stability. Sheets, optical pickup parts, heat release grease, circuit board potting agents, heat-dissipating tapes and adhesives, various injection molded products, motor and IC sealing materials, copper-clad laminates, and various other types Used in a wide range of applications in the field.
　アルミナを樹脂充填用の放熱フィラーとして用いる場合、その目的を十分に果たすためには、ソーダ(Na2O)分が低いことに加えて、アルミナを樹脂又はゴム中に可及的に高い配合割合で充填して高い熱伝導性を達成することが求められている。しかしながら、通常、樹脂又はゴム中への充填率が高くなると、得られたアルミナ充填樹脂組成物の粘度（樹脂充填時粘度）が高くなり、流動性が悪化して成形加工性が低下し、また、放熱シート等の用途に用いた場合には、その硬度が上昇し可撓性が不足して被覆対象物の凹凸に追従できなくなることがあるほか、脱気が困難となり、ボイドが発生する。更には、アルミナの充填量が上がらず、目的の熱伝導率が得られない等の問題が生じる。 When using alumina as a heat-dissipating filler for resin filling, in order to sufficiently fulfill its purpose, in addition to low soda (Na 2 O) content, alumina is incorporated in resin or rubber as much as possible. To achieve high thermal conductivity. However, usually, when the filling rate into the resin or rubber is increased, the viscosity of the obtained alumina-filled resin composition (viscosity at the time of resin filling) is increased, the fluidity is deteriorated and the molding processability is decreased. When used for applications such as a heat-dissipating sheet, the hardness thereof increases and the flexibility becomes insufficient, making it impossible to follow the unevenness of the object to be coated, making it difficult to deaerate and generating voids. Furthermore, there is a problem that the amount of alumina filling does not increase and the desired thermal conductivity cannot be obtained.
　そこで、従来においても、この熱伝導性と成形加工性の問題を解決するために幾つかの方法が提案されている。
　例えば、特許文献１においては、実質的にカッティングエッジ(破面)がなく、また、粒度が異なる３種のαアルミナＡ、Ｂ及びＣを調製し、これら３種のαアルミナＡ、Ｂ及びＣを所定の割合で配合して混合粉末とし、この混合粉末を樹脂又はゴム中に添加して成形用樹脂又はゴム組成物とすることが提案されている。しかしながら、これら特許文献１に記載された方法においては、粒度が異なる３種のαアルミナＡ、Ｂ及びＣを調製し、これらを所定の割合で配合して混合粉末を調製しなければならず、しかも、これら３種類の粒径が異なるアルミナについてそれぞれカッティングエッジをなくすための加工が必要になり、製造工程が増加し、また、製造設備、品質管理等が煩雑になって製造コストが嵩むという問題がある。また、粒度分布を広くし、高充填化する手法については、従来から行われていたが、このような手法は、微粒の存在に起因して分散性が悪くなり、また、シャープな粒度分布を有するフィラーを同量充填した場合に比べて、組成物の熱伝導率が低くなることから、性能を発揮させるためにはより高充填化する必要があり、組成物の質量が増加するという問題もある。 Therefore, several methods have been proposed in the past to solve the problems of thermal conductivity and moldability.
For example, in Patent Document 1, three types of α-alumina A, B, and C having substantially no cutting edge (fracture surface) and different particle sizes are prepared, and these three types of α-alumina A, B, and C are prepared. Has been proposed to be mixed at a predetermined ratio to obtain a mixed powder, and this mixed powder is added to a resin or rubber to form a molding resin or rubber composition. However, in the method described in these Patent Documents 1, three types of α-alumina A, B, and C having different particle sizes must be prepared and mixed at a predetermined ratio to prepare a mixed powder. In addition, these three types of alumina having different particle sizes require processing for eliminating the cutting edge, increasing the number of manufacturing steps, and complicating the manufacturing equipment and quality control, resulting in increased manufacturing costs. There is. In addition, a method for widening the particle size distribution and increasing the packing has been conventionally performed. However, such a method deteriorates the dispersibility due to the presence of fine particles, and has a sharp particle size distribution. Compared to the case where the same amount of filler is filled, the thermal conductivity of the composition is lowered, so that it is necessary to make it higher in order to exhibit performance, and there is a problem that the mass of the composition increases. is there.
　また、特許文献２においては、バイヤー法以外の方法で得られたアルミニウム塩、アルミニウムアルコキシド、水酸化アルミニウム、遷移アルミナ等からなり、焼成によりαアルミナに誘導されるαアルミナ前駆体と、個数基準の中心粒子径４０nm以下及び粒子径１００nm超え粒子の割合１%以下の種晶粒子との混合物を、塩化水素含有量１～２０容量%の雰囲気中で焼成し、樹脂に添加するフィラーとして有用な多面体状で微細なαアルミナ粒子を製造する方法が提案されている。しかしながら、この特許文献２に記載された方法においては、バイヤー法以外の方法で得られたαアルミナ前駆体を特定の種晶粒子と共に塩化水素含有雰囲気中で焼成する必要があることから、予め微小な種晶粒子を調製しなければならず、また、その扱いに多くの手間を要し、工業的、コスト的に現実的でないほか、得られたアルミナ粒子がナノサイズであって放熱フィラーとしての用途には不向きである。 Moreover, in patent document 2, it consists of the aluminum salt obtained by methods other than the Bayer method, aluminum alkoxide, aluminum hydroxide, transition alumina, etc., the alpha alumina precursor induced | guided | derived to alpha alumina by baking, A polyhedron useful as a filler to be added to a resin by firing a mixture of seed crystal particles having a center particle size of 40 nm or less and a particle size exceeding 100 nm in a ratio of 1% or less in an atmosphere having a hydrogen chloride content of 1 to 20% by volume. A method for producing fine and fine α-alumina particles has been proposed. However, in the method described in Patent Document 2, the α-alumina precursor obtained by a method other than the Bayer method needs to be calcined together with specific seed crystal particles in a hydrogen chloride-containing atmosphere. Seed crystal particles must be prepared, and it takes a lot of labor to handle them, and it is not practical from an industrial and cost viewpoint. In addition, the resulting alumina particles are nano-sized and serve as heat dissipation fillers. Not suitable for use.
　更に、特許文献３においては、水酸化アルミニウムや遷移アルミナ等のアルミナ原料に、弗化物系鉱化剤を弗素として０．０２～０．３重量%及び平均粒径１μm以下のαアルミナ粉末を０．５～１０重量%の割合で添加し、得られた混合物をシャモット質容器内に充填して１５００℃以下の温度で焼成し、次いで解砕して低ソーダαアルミナを製造する方法が提案されている。しかしながら、この特許文献３に記載された方法においては、セラミックス用途の低ソーダアルミナは得られるものの、粘度特性等のフィラー特性が最重視される放熱フィラー等のフィラー用途で使用するのに充分満足できる性能は得られない。 Further, in Patent Document 3, an alumina raw material such as aluminum hydroxide or transition alumina is added to an alumina powder such as fluoride-based mineralizer in an amount of 0.02 to 0.3% by weight and α-alumina powder having an average particle diameter of 1 μm or less. A method of adding 5 to 10% by weight, filling the obtained mixture into a chamotte container, firing at a temperature of 1500 ° C. or less, and then pulverizing to produce low soda α-alumina has been proposed. ing. However, in the method described in Patent Document 3, low soda alumina for ceramics is obtained, but it is sufficiently satisfactory for use in filler applications such as heat dissipation fillers where filler properties such as viscosity properties are most important. Performance is not obtained.
　そして、特許文献４においては、水酸化アルミニウムにフッ化物を除くハロゲン化物を添加し、得られた混合物をアルミナ緻密質サヤやコージェライト緻密サヤからなる密閉容器中で焼成し、次いで解砕してα相を主相とするアルミナを製造する方法が提案されている。しかしながら、この特許文献４に記載された方法においては、焼成原料としてBET比表面積が３～２０m2/gの微粒の水酸化アルミニウムを用いており、焼成方法等が限定されるほか、サヤ（容器）への充填量も上がらず、生産効率が著しく悪化し、また、焼成後のハンドリング性も低下する。 And in patent document 4, the halide except a fluoride is added to aluminum hydroxide, the obtained mixture is baked in an airtight container made of alumina dense sheath or cordierite dense sheath, and then crushed. A method for producing alumina having an α phase as a main phase has been proposed. However, in the method described in Patent Document 4, fine aluminum hydroxide having a BET specific surface area of 3 to 20 m 2 / g is used as a firing raw material, and the firing method is limited. ) Is not increased, the production efficiency is remarkably deteriorated, and handling properties after firing are also reduced.
　また、特許文献５においては、アルミナ、アルミナ水和物、塩化アンモニウム、及び塩化アンモニウム以外のハロゲン化物、更にはホウ素化合物を含む組成物を焼成容器内で加熱処理し、次いで気流式粉砕機で解砕して丸み状粒子からなるアルミナを製造する方法が提案されている。しかしながら、この特許文献５に記載された方法においては、アルミナとアルミナ水和物との混合原料を焼成することから、アルミナとアルミナ水和物との混合工程が必要になる等その製造工程が複雑となり、また、粉砕したアルミナを再焼成することから余分なコストもかかり、量産化には不向きである。更には、充填量を等しくした場合には、丸み状粒子は、形状が整えられていない粒子に比べて、粒子間の接点が低下し、組成物の熱伝導率が低下するという問題もある。 In Patent Document 5, alumina, alumina hydrate, ammonium chloride, a halide other than ammonium chloride, and a composition containing a boron compound are heat-treated in a firing container, and then dissolved in an airflow grinder. There has been proposed a method for producing alumina made of round particles by crushing. However, in the method described in Patent Document 5, since the mixed raw material of alumina and alumina hydrate is fired, the manufacturing process is complicated, such as the need for a mixing step of alumina and alumina hydrate. In addition, since the pulverized alumina is refired, an extra cost is required, which is not suitable for mass production. Furthermore, when the filling amount is made equal, round particles have a problem that the contact between the particles is lowered and the thermal conductivity of the composition is lowered as compared with particles whose shape is not adjusted.
　更に、特許文献６においては、擬ベーマイト及び／又は遷移アルミナからなるアルミナ原料にフッ素化合物又はフッ素化合物及びホウ素化合物を所定の割合で添加し、得られた混合物をムライト質容器内に充填して１１００℃以上の温度で焼成し、次いで解砕して球状に近い多面体形状を有すると共に粒度分布の狭いαアルミナを製造する方法が提案されている。しかしながら、この特許文献６に記載された方法においては、高比表面積である擬ベーマイトや遷移アルミナをアルミナ原料として使用することから、アルミナ原料の製造に多くのコストがかかり、また、充填量が等しい場合で比較すると、球形度が増すにつれて組成物の熱伝導率が低下する傾向があり、より高充填化する必要がある。 Furthermore, in Patent Document 6, a fluorine compound or a fluorine compound and a boron compound are added in a predetermined ratio to an alumina raw material made of pseudoboehmite and / or transition alumina, and the resulting mixture is filled in a mullite container to obtain 1100. There has been proposed a method for producing α-alumina having a polyhedral shape close to a spherical shape and having a narrow particle size distribution by firing at a temperature of ℃ or higher and then crushing. However, in the method described in Patent Document 6, pseudoboehmite or transition alumina having a high specific surface area is used as an alumina raw material, so that a lot of costs are required for the production of the alumina raw material, and the filling amount is equal. In some cases, the thermal conductivity of the composition tends to decrease as the sphericity increases, and it is necessary to increase the filling.
　このため、ソーダ(Na2O)分が０．１質量%以下と低ソーダであると共に平均粒子径が２～５μmであり、しかも、粒度分布がシャープであって、樹脂又はゴム中に高充填率で充填しても得られたアルミナ充填樹脂組成物の粘度（樹脂充填時粘度）が低く、分散性も良く、成形加工性に優れたアルミナ充填樹脂組成物を調製することができるαアルミナ紛体の開発が求められており、しかも、原料としてバイヤー法で得られた安価な水酸化アルミニウムを用いて安価に製造することが求められている。 For this reason, the soda (Na 2 O) content is as low as 0.1% by mass or less, the average particle size is 2 to 5 μm, the particle size distribution is sharp, and the resin or rubber is highly filled. Α-alumina powder which can prepare an alumina-filled resin composition having a low viscosity (viscosity at the time of resin filling), good dispersibility, and excellent moldability In addition, there is a demand for inexpensive production using inexpensive aluminum hydroxide obtained by the buyer method as a raw material.
特許第3,937,494号公報Japanese Patent No. 3,937,494 特開2007-186,379号公報JP 2007-186,379 A 特許第3,389,642号公報Japanese Patent No. 3,389,642 特開2003-201,116号公報JP2003-201,116 特開2005-022,963号公報JP 2005-022,963 特開2008-127,257号公報JP 2008-127,257 A
　そこで、本発明者らは、バイヤー法で得られた安価な水酸化アルミニウムを用い、低ソーダであると共に平均粒子径が２～５μmであり、しかも、粒度分布がシャープであって、樹脂充填時の粘度が低いαアルミナ紛体を開発すべく鋭意検討した結果、意外なことには、特定の焼成容器を使用して成形密度(成型圧:98.07MPa)２．０５g/cm3以上及びBET比表面積０．９m2/g以下となるように焼成し、次いで粉砕後の平均粒子径(Dav)と粉砕前のBET相当径(DBET)との粒径比（Dav／DBET）が所定の値の範囲内に収まるように粉砕することにより、目的とするαアルミナを製造できることを見出し、本発明を完成した。 Therefore, the present inventors use inexpensive aluminum hydroxide obtained by the Bayer method, have low soda, have an average particle size of 2 to 5 μm, have a sharp particle size distribution, and are filled with resin. As a result of diligent research to develop an α-alumina powder having a low viscosity, it was surprising that a specific firing container was used and the molding density (molding pressure: 98.07 MPa) was 2.05 g / cm 3 or more and the BET specific surface area. 0.9 m 2 / g was calcined as follows becomes, then the average particle size after pulverization (D av) and the particle diameter ratio (D av / D BET) of the BET equivalent diameter before pulverization (D BET) is given It was found that the desired α-alumina can be produced by pulverization so as to be within the range of the above value, and the present invention was completed.
　従って、本発明の目的は、低ソーダであると共に平均粒子径が２～５μmであり、かつ、粒度分布がシャープであって、樹脂充填時の分散性が良く、粘度が低い低ソーダαアルミナ紛体を提供することにある。 Accordingly, an object of the present invention is a low soda α-alumina powder having a low soda, an average particle diameter of 2 to 5 μm, a sharp particle size distribution, good dispersibility when filled with a resin, and low viscosity. Is to provide.
　また、本発明の他の目的は、バイヤー法で得られた安価な水酸化アルミニウムを原料にして、上記の低ソーダであると共に平均粒子径が２～５μmであり、かつ、粒度分布がシャープであって、樹脂充填時の分散性が良く粘度が低い低ソーダαアルミナ紛体を製造することができる製造方法を提供することにある。 Another object of the present invention is to use inexpensive aluminum hydroxide obtained by the Bayer method as a raw material, the above-mentioned low soda, an average particle size of 2 to 5 μm, and a sharp particle size distribution. Another object of the present invention is to provide a production method capable of producing a low-soda α-alumina powder having good dispersibility and low viscosity when filled with a resin.
　すなわち、本発明は、バイヤー法で得られた水酸化アルミニウムを焼成し、粉砕して製造されたαアルミナ紛体であって、ソーダ(Na2O)分が０．１質量%以下であると共に平均粒子径(Dp50)が２～５μmであり、かつ、粒度分布が４５μm篩上量(+45μm)１００ppm以下及びスパン値〔(Dp90－Dp10)/Dp50〕１．１以下であることを特徴とする粘度特性に優れた低ソーダαアルミナ紛体である。 That is, the present invention is an α-alumina powder produced by firing and pulverizing aluminum hydroxide obtained by the Bayer method, the soda (Na 2 O) content is 0.1% by mass or less and an average The particle size (Dp50) is 2 to 5 μm, and the particle size distribution is 45 μm on the sieve (+45 μm) 100 ppm or less and the span value ((Dp90−Dp10) / Dp50) 1.1 or less. Low soda α-alumina powder with excellent viscosity characteristics.
　また、本発明は、バイヤー法で得られたソーダ(Na2O)分０．３質量%以下の水酸化アルミニウムにハロゲン系鉱化剤を添加して混合し、得られた混合物を、シリカ含有アルミナセラミック製の焼成容器に充填して成形密度(成型圧:98.07MPa)２．０５g/cm3以上及びBET比表面積０．９m2/g以下となるように１１００～１６００℃の範囲で焼成し、次いで得られた焼成物を、粉砕後の平均粒子径(Dav)と粉砕前のBET相当径(DBET)との粒径比（Dav／DBET）が１．１０～１．４５の範囲になるように粉砕することを特徴とする粘度特性に優れた低ソーダαアルミナ紛体の製造方法である。 Further, the present invention is to add and mix a halogen-based mineralizer to aluminum hydroxide having a soda (Na 2 O) content of 0.3% by mass or less obtained by the Bayer method, and the resulting mixture contains silica. Filled in a firing container made of alumina ceramic and fired in the range of 1100-1600 ° C so that the molding density (molding pressure: 98.07 MPa) is 2.05 g / cm 3 or more and the BET specific surface area is 0.9 m 2 / g or less. and then the obtained baked product, the particle size ratio (D av / D BET) is from 1.10 to 1.45 and the average particle size after pulverization (D av) and the BET equivalent diameter before pulverization (D BET) It is a method for producing a low-soda α-alumina powder excellent in viscosity characteristics, characterized by being ground so as to be in the range of
　本発明の粘度特性に優れた低ソーダαアルミナ紛体は、ソーダ(Na2O)分が０．１質量%以下、電気絶縁性を考慮すると好ましくは０．０８質量%以下であり、また、平均粒子径(Dp50)が２μm以上５μm以下、原料がバイヤー法由来の水酸化アルミニウムであり、分散性や熱伝導率を考慮すると好ましくは２．５μm以上４．０μm以下であり、更に、粒度分布については、４５μm篩上量(+45μm)が１００ppm以下、好ましくは５０ppm以下であり、また、スパン値〔(Dp90－Dp10)/Dp50〕が１．１以下、好ましくは１．０以下である。 The low soda α-alumina powder having excellent viscosity characteristics according to the present invention has a soda (Na 2 O) content of 0.1% by mass or less, preferably 0.08% by mass or less in consideration of electrical insulation, The particle size (Dp50) is 2 μm or more and 5 μm or less, and the raw material is aluminum hydroxide derived from the Bayer method, preferably 2.5 μm or more and 4.0 μm or less in consideration of dispersibility and thermal conductivity. Has a 45 μm sieve top amount (+45 μm) of 100 ppm or less, preferably 50 ppm or less, and a span value [(Dp90−Dp10) / Dp50] of 1.1 or less, preferably 1.0 or less.
　ここで、ソーダ(Na2O)分については、αアルミナ紛体の用途によっても異なるが、例えば電子部品用途においては０．１質量%以下であることが必須であり、この０．１質量%を超えると電気絶縁性が得られないという問題が生じる。また、平均粒子径(Dp50)については、この平均粒子径を大きくすればそれだけ成形物の熱伝導率が高くなるが、バイヤー法で得られた水酸化アルミニウムを原料とする場合にはαアルミナの一次粒子径を５μm以上にすることが難しい。 Here, the soda (Na 2 O) content varies depending on the use of the α-alumina powder, but for example, it is essential to be 0.1% by mass or less in the application of electronic parts. When exceeding, the problem that electrical insulation cannot be obtained will arise. As for the average particle size (Dp50), if the average particle size is increased, the thermal conductivity of the molded product is increased accordingly.However, when aluminum hydroxide obtained by the Bayer method is used as a raw material, α-alumina It is difficult to make the primary particle diameter 5 μm or more.
　また、粒度分布については、４５μm篩上量(+45μm)が１００ppm以下である必要があり、この４５μm篩上量(+45μm)が１００ppmを超えると、このαアルミナ紛体をフィラーとして充填した樹脂組成物を成形した際に粗粒のアルミナが樹脂成形物の表面から突出するので厚さの薄い樹脂成形物の用途には使用できなくなり、また、熱源との間の密着性が損なわれ、所望の放熱効果が得られないことがあり、また、スパン値〔(Dp90－Dp10)/Dp50〕が１．１を超えて広くなると、同量充填した、粒度分布がシャープなフィラーと比べ、熱伝導率は低く、また、微粒分の増加に伴い凝集粒が増え、アルミナの均一分散が困難になるという問題があるほか、例えば所望の粒度分布を有する放熱シート、接着シート、放熱グリース等の用途のαアルミナ紛体を調製する際にその粒度分布設計が難しくなる。 In addition, regarding the particle size distribution, the amount of 45 μm sieve (+45 μm) needs to be 100 ppm or less, and if the amount of 45 μm sieve (+45 μm) exceeds 100 ppm, the resin composition filled with this α-alumina powder as a filler When molding a product, coarse-grained alumina protrudes from the surface of the resin molded product, so that it cannot be used for thin resin molded products, and the adhesiveness with the heat source is impaired. The heat dissipation effect may not be obtained, and if the span value [(Dp90−Dp10) / Dp50] is wider than 1.1, the thermal conductivity is higher than that of the filler with the same particle size and sharp particle size distribution. In addition to the problem that the agglomerated grains increase with the increase of the fine particles, it becomes difficult to uniformly disperse alumina, and for example, α for use in heat dissipation sheets, adhesive sheets, heat dissipation grease, etc. having a desired particle size distribution. Prepare alumina powder The particle size distribution design becomes difficult at the time.
　なお、粒子分布の決定に関して、４５μm篩上量(+45μm)の値は、JIS Z8801-1の試験用ふるい(目開45μm)を用いて測定した値であり、また、スパン値〔(Dp90－Dp10)/Dp50〕は、レーザー散乱法粒度測定器〔日機装社製Microtrac 9320HRA(×100)〕を用いて、積算粒度分布率９０重量%に対応する粒子径(Dp90)、積算粒度分布率５０重量%に対応する粒子径(Dp50)、及び積算粒度分布率１０重量%に対応する粒子径(Dp10)をそれぞれ測定して求めた値であり、粒子径比〔(Dp90－Dp10)/Dp50〕の値(スパン値)が粒度分布のシャープさを示しており、このスパン値が小さいほど粒度分布がシャープである。 Regarding the determination of the particle distribution, the value of the 45 μm sieve amount (+45 μm) is a value measured using a test sieve (mesh 45 μm) of JIS Z8801-1, and the span value [(Dp90− Dp10) / Dp50] using a laser scattering particle size analyzer (Microtrac 9320HRA (× 100) manufactured by Nikkiso Co., Ltd.), a particle size corresponding to an integrated particle size distribution rate of 90% by weight (Dp90), an integrated particle size distribution rate of 50% The particle diameter (Dp50) corresponding to% and the particle diameter (Dp10) corresponding to 10% by weight of the cumulative particle size distribution were respectively measured, and the particle diameter ratio [(Dp90−Dp10) / Dp50] The value (span value) indicates the sharpness of the particle size distribution, and the smaller the span value, the sharper the particle size distribution.
　そして、本発明の粘度特性に優れた低ソーダαアルミナ紛体は、このαアルミナ紛体２００重量部を不飽和ポリエステル樹脂（酸価：１０．０mgKOH/g以下、２５℃粘度：３．７±０．７poise、及び密度：１．０８±０．０２g/cm3）１００重量部中に添加し、高速インペラミルを用いて周速２．６m/秒及び１０分間の条件で撹拌し、得られたアルミナ充填樹脂組成物について、ブルックフィールド型粘度計を用いてローター回転速度１２rpm及び測定温度２５℃の条件で測定した際の粘度（樹脂充填時粘度）が６０ポアズ(poise)以下、好ましくは５５ポアズ未満、より好ましくは５０ポアズ以下である。この樹脂充填時粘度が６０ポアズ(poise)を超えて高くなると、樹脂との混練が困難となり、また、成形時等における流動性も悪化し、樹脂又はゴム中への充填性が低下して所望の熱伝導率を得るための高充填が困難になるほか、成型加工性が低下して樹脂成形物中にボイドが発生する等の問題が生じる。 The low soda α-alumina powder having excellent viscosity characteristics according to the present invention is obtained by adding 200 parts by weight of the α-alumina powder to an unsaturated polyester resin (acid value: 10.0 mgKOH / g or less, 25 ° C. viscosity: 3.7 ± 0.00%). 7 poise and density: 1.08 ± 0.02 g / cm 3 ) Add to 100 parts by weight, stir with high speed impeller mill under conditions of peripheral speed of 2.6 m / sec and 10 minutes, and obtain alumina filling The resin composition has a viscosity (viscosity when filled with a resin) of 60 poise or less, preferably less than 55 poise when measured using a Brookfield viscometer under conditions of a rotor rotational speed of 12 rpm and a measurement temperature of 25 ° C. More preferably, it is 50 poise or less. If the viscosity at the time of filling the resin exceeds 60 poise, kneading with the resin becomes difficult, fluidity at the time of molding and the like deteriorates, and the filling property into the resin or rubber decreases, which is desirable. In addition to difficulty in high filling in order to obtain a high thermal conductivity, there are problems such as a decrease in molding processability and the generation of voids in the resin molded product.
　次に、本発明の粘度特性に優れた低ソーダαアルミナ紛体の製造方法について詳細に説明する。
　本発明においては、上記の水酸化アルミニウムにハロゲン系鉱化剤を添加して混合し、得られた混合物を所定の条件下に焼成し、次いで得られた焼成物を所定の条件下で粉砕する。 Next, the method for producing a low soda α-alumina powder having excellent viscosity characteristics according to the present invention will be described in detail.
In the present invention, a halogen-based mineralizer is added to and mixed with the above aluminum hydroxide, the resulting mixture is fired under predetermined conditions, and then the obtained fired product is pulverized under predetermined conditions. .
　本発明の粘度特性に優れた低ソーダαアルミナ紛体を製造するに際しては、アルミナ原料として、バイヤー法で得られたソーダ(Na2O)分０．３質量%以下の水酸化アルミニウムが用いられ、好ましくはレーザー散乱法粒度測定器〔日機装社製Microtrac 9320HRA(×100)〕で測定された平均二次粒子径が１０μm以上２００μm以下、より好ましくは３０μm以上１５０μm以下である水酸化アルミニウムが用いられる。このアルミナ原料として用いる水酸化アルミニウムの平均二次粒子径が１０μmより小さいと、求める粒径のαアルミナを得るのが困難になり、また、ハンドリング性が悪化し生産効率が低下する虞があり、反対に、２００μmより大きくなると、粒子内に焼成ムラが発生し、粒度分布がブロードになり、また、粉砕に要する時間が増加したり、未粉砕粒子が残る虞がある。なお、バイヤー法以外の方法、例えば中和法で得られるアルミナ原料は、概ね高比表面積であることから、本発明においてはその使用が困難である。 When producing a low soda α-alumina powder having excellent viscosity characteristics according to the present invention, as the alumina raw material, aluminum hydroxide having a soda (Na 2 O) content of 0.3% by mass or less obtained by the Bayer method is used, Preferably, aluminum hydroxide having an average secondary particle diameter of 10 μm or more and 200 μm or less, more preferably 30 μm or more and 150 μm or less, measured with a laser scattering particle size measuring instrument [Microtrac 9320HRA (× 100) manufactured by Nikkiso Co., Ltd.) is used. When the average secondary particle size of aluminum hydroxide used as the alumina raw material is smaller than 10 μm, it is difficult to obtain α alumina having a desired particle size, and handling efficiency may be deteriorated and production efficiency may be reduced. On the other hand, if it exceeds 200 μm, uneven firing occurs in the particles, the particle size distribution becomes broad, the time required for pulverization may increase, and unmilled particles may remain. In addition, since the alumina raw material obtained by methods other than the Bayer method, for example, the neutralization method, has a generally high specific surface area, its use is difficult in the present invention.
　ここで、水酸化アルミニウムに添加するハロゲン系鉱化剤としては、例えば、弗化アルミニウム、弗化ナトリウム、氷晶石、弗化マグネシウム、弗化カルシウム等のフッ化物系鉱化剤や、塩化水素、塩化アンモニウム、塩化アルミニウム等の塩化物系鉱化剤や、沃化アンモニウム等の沃化物系鉱化剤等を挙げることができ、また、水酸化アルミニウムに対するハロゲン系鉱化剤の添加量については、使用する鉱化剤の種類によっても異なるが、例えばフッ化物系硬化剤の場合、混合物中における弗素換算の配合割合が０．０５質量%以上１．０質量%以下、好ましくは０．１質量%以上０．５質量%以下となる割合である。このハロゲン系鉱化剤の添加量が０．０５質量%より低いと、アルミナの粒子成長効果が不足し、十分な粒径のアルミナ粒子が得られない場合があり、反対に、１．０質量%より高くなると、アルミナ粒子が板状となり、粘性が悪化したり、粒子が割れ易くなるという問題が生じる。 Here, examples of the halogen mineralizer added to aluminum hydroxide include fluoride mineralizers such as aluminum fluoride, sodium fluoride, cryolite, magnesium fluoride, calcium fluoride, and hydrogen chloride. And chloride mineralizers such as ammonium chloride and aluminum chloride; iodide mineralizers such as ammonium iodide; and the amount of halogen mineralizer added to aluminum hydroxide. Depending on the type of mineralizer used, for example, in the case of a fluoride-based curing agent, the blending ratio in terms of fluorine in the mixture is 0.05% by mass or more and 1.0% by mass or less, preferably 0.1% by mass. It is a ratio that is not less than 0.5% and not more than 0.5% by mass. When the addition amount of the halogen-based mineralizer is lower than 0.05% by mass, the alumina particle growth effect may be insufficient, and alumina particles having a sufficient particle size may not be obtained. If it is higher than%, the alumina particles become plate-like, resulting in problems that the viscosity is deteriorated and the particles are easily broken.
　次に、水酸化アルミニウムにハロゲン系鉱化剤を添加して混合して得られた混合物を焼成するが、混合物の焼成においては、混合物をシリカ含有アルミナセラミック製の焼成容器に充填し、得られた焼成物の成形密度(成型圧:98.07MPa)が２．０５g/cm3以上、好ましくは２．１g/cm3以上２．５g/cm3以下であり、また、BET比表面積が０．９m2/g以下、好ましくは０．４m2/g以上０．８m2/g以下となるように焼成する必要があり、具体的な焼成温度及び焼成時間については、アルミナ原料として用いる水酸化アルミニウムの粒子径や、添加するハロゲン系鉱化剤の種類や添加量等により異なるが、通常、焼成温度が１１００℃以上１６００℃以下、好ましくは１４００℃以上１５５０℃以下の範囲であり、また、焼成時間が通常数分以上２４時間以下、好ましくは数時間以上２０時間以下である。得られた焼成物の成形密度(成型圧:98.07MPa)が２．０５g/cm3より低いと、アルミナの粒子形状が板状傾向となり、粘性が悪化したり、目的の平均粒子径(Dp50)２～５μmまで粉砕した場合、樹脂充填時粘度が６０ポアズ(poise)を超えて高くなる虞があり、また、BET比表面積が０．９m2/gを超えると、焼成による粒子成長が不十分であり、粉砕後の平均粒子径(Dav)と粉砕前のBET相当径(DBET)との粒径比（Dav／DBET）が１．１０以上１．４５以下となるよう粉砕しても、目的の平均粒子径(Dp50)２～５μmを下回ったり、スパン値が１．１を超えてしまう虞がある。そして、上記の焼成温度が１１００℃より低くなると一次粒子が目的の粒子径まで成長できなくなり、反対に、１６００℃を超えるとアルミナの溶着等が発生してハンドリング性が悪化する。 Next, a mixture obtained by adding and mixing a halogen-based mineralizer to aluminum hydroxide is fired. In firing the mixture, the mixture is filled in a firing container made of silica-containing alumina ceramic. green density (molding pressure: 98.07MPa) the baked product 2.05 g / cm 3 or more, preferably 2.1 g / cm 3 or more 2.5 g / cm 3 or less, and a BET specific surface area 0.9m 2 / g or less, preferably 0.4 m 2 / g or more and 0.8 m 2 / g or less, and for specific firing temperature and firing time, the aluminum hydroxide used as the alumina raw material Although it varies depending on the particle diameter, the type and amount of the halogen-based mineralizer to be added, etc., the firing temperature is usually in the range of 1100 ° C. to 1600 ° C., preferably 1400 ° C. to 1550 ° C., and the firing time. Is usually several minutes to 24 hours It is preferably at most 20 hours or more to several hours. When the molding density (molding pressure: 98.07 MPa) of the obtained fired product is lower than 2.05 g / cm 3 , the particle shape of alumina tends to be plate-like, the viscosity becomes worse, and the target average particle diameter (Dp50) When pulverized to 2 to 5 μm, there is a risk that the viscosity when filled with resin exceeds 60 poise, and when the BET specific surface area exceeds 0.9 m 2 / g, particle growth due to firing is insufficient. Even if the particle size ratio (Dav / DBET) between the average particle diameter (Dav) after pulverization and the BET equivalent diameter (DBET) before pulverization is 1.10 to 1.45, The average particle diameter (Dp50) may be less than 2 to 5 μm, or the span value may exceed 1.1. And if said calcination temperature becomes lower than 1100 degreeC, a primary particle will no longer be able to grow to the target particle diameter, and conversely, when it exceeds 1600 degreeC, the welding of alumina etc. will generate | occur | produce and handling property will deteriorate.
　ここで、上記の成形密度(成型圧:98.07MPa)は、油圧式２０トン圧縮試験機（前川試験機製作所製）を用い、４０mm×２０mm×１０mmに成形したピースの質量と体積とを測定して求められた値であり、また、上記のBET比表面積は、比表面積自動測定装置（マイクロメリテックス製フローソーブII2300形）を用い、Ｎ2ガス吸着法により測定された値である。 Here, the molding density (molding pressure: 98.07 MPa) was measured by measuring the mass and volume of a piece molded into 40 mm × 20 mm × 10 mm using a hydraulic 20-ton compression tester (manufactured by Maekawa Test Instruments Co., Ltd.). The BET specific surface area is a value measured by an N 2 gas adsorption method using a specific surface area automatic measuring device (Microsorbex Flowsorb II2300 type).
　以上のようにして得られた焼成物については、次に、粉砕後の平均粒子径(Dav)と粉砕前のBET相当径(DBET)との粒径比（Dav／DBET）が１．１０以上１．４５以下、好ましくは１．１５以上１．４０以下の範囲になるように粉砕する。この焼成物の粉砕において、上記の粒径比（Dav／DBET）が１．４５より低いと、粉砕不足になって樹脂充填時粘度が６０ポアズ(poise)を超えて高くなってしまい、反対に、１．１０より低いと、粉砕過多になってチッピング粒子(微粒子)の発生が多くなり、粒度分布がブロードになるほか、チッピング粒子が凝集した粗大粒子が発生し、アルミナの均一分散が困難になる。 The fired product obtained as described above, then, the average particle size after pulverization (D av) and the particle diameter ratio (D av / D BET) of the BET equivalent diameter before pulverization (D BET) is It grind | pulverizes so that it may become 1.10 or more and 1.45 or less, Preferably it is 1.15 or more and 1.40 or less. In the pulverization of the fired product, if the particle size ratio (D av / D BET ) is lower than 1.45, the pulverization is insufficient and the viscosity at the time of resin filling exceeds 60 poise, On the other hand, if it is lower than 1.10, pulverization is excessive and the generation of chipping particles (fine particles) increases, the particle size distribution becomes broad, and coarse particles in which the chipping particles are aggregated are generated, resulting in uniform dispersion of alumina. It becomes difficult.
　この焼成物の粉砕においては、粉砕後の平均粒子径(Dav)と粉砕前のBET相当径(DBET)との粒径比（Dav／DBET）を１．１０以上１．４５以下の範囲に管理するために、具体的には、焼成物の粉砕を始める前にこの焼成物のBET比表面積Ｓ(m2/g)を測定し、このBET比表面積Ｓ(m2/g)の測定値とαアルミナの密度(真比重ρ：3.98g/cm3)とを用い、下記のBET比表面積Ｓ(m2/g)及び密度(真比重)ρ(g/cm3)との関係式、すなわちBET相当径(DBET)＝６／Ｓρ（但し、ＳはBET比表面積を、また、ρはαアルミナの真比重3.98である。）からBET相当径(DBET)を算出し、このBET相当径(DBET)を指標にして粉砕後の平均粒子径(Dav)との粒径比（Dav／DBET）が１．１０以上１．４５以下の範囲内となるように粉砕を行う。 In the pulverization of the fired product, the particle diameter ratio (D av / D BET ) between the average particle diameter after pulverization (D av ) and the BET equivalent diameter before pulverization (D BET ) is 1.10 or more and 1.45 or less. to manage the range of, specifically, a BET specific surface area S of the calcined product before beginning the grinding of the fired product (m 2 / g) was measured and the BET specific surface area S (m 2 / g) And the density of α-alumina (true specific gravity ρ: 3.98 g / cm 3 ) and the following BET specific surface area S (m 2 / g) and density (true specific gravity) ρ (g / cm 3 ) The BET equivalent diameter (D BET ) is calculated from the relational expression, that is, the BET equivalent diameter (D BET ) = 6 / Sρ (where S is the BET specific surface area and ρ is the true specific gravity of α-alumina 3.98). The particle size ratio (D av / D BET ) with respect to the average particle size (D av ) after pulverization using the BET equivalent diameter (D BET ) as an index is in the range of 1.10 to 1.45. Grind into.
　上記の焼成物を粉砕する手段については、目標とする粒径比（Dav／DBET）１．１０以上１．４５以下を達成できれば、特に制限されるものではないが、例えば、振動ミルや、振動ボールミル、回転ボールミル、遊星ミル等の容器駆動媒体ミルや、媒体撹拌ミルや、ジェットミル、カウンタージェットミル、ジェットマイザー等の気流式粉砕機等を用いることができる。 The means for pulverizing the fired product is not particularly limited as long as the target particle size ratio (D av / D BET ) of 1.10 or more and 1.45 or less can be achieved. In addition, a container driving medium mill such as a vibration ball mill, a rotating ball mill, and a planetary mill, a medium agitation mill, an air flow type pulverizer such as a jet mill, a counter jet mill, and a jet mizer can be used.
　上述した本発明の方法によって製造されたαアルミナ紛体は、バイヤー法で得られた水酸化アルミニウムをアルミナ原料としているにもかかわらず、ソーダ(Na2O)分が０．１質量%以下であって、平均粒子径(Dp50)が２～５μmであり、しかも、粒度分布が４５μm篩上量(+45μm)：１００ppm以下及び分布広さ〔(Dp90－Dp10)/Dp50〕：１．１以下とシャープであり、樹脂充填時粘度の低い高充填性低ソーダαアルミナ紛体である。 The α-alumina powder produced by the above-described method of the present invention has a soda (Na 2 O) content of 0.1% by mass or less despite the fact that aluminum hydroxide obtained by the Bayer method is used as the alumina raw material. The average particle size (Dp50) is 2 to 5 μm, and the particle size distribution is 45 μm on the sieve (+45 μm): 100 ppm or less and the distribution width [(Dp90−Dp10) / Dp50]: 1.1 or less It is a sharp, high-filling low-soda α-alumina powder having a low viscosity when filled with a resin.
　本発明の粘度特性に優れた低ソーダαアルミナ紛体は、低ソーダであると共に平均粒子径が２～５μmであり、しかも、粒度分布がシャープであって、樹脂充填時の分散性が良く、粘度が低く、樹脂充填用のアルミナとして有用であるばかりでなく、特定の粒度分布を有するアルミナ紛体の調製時に粒度分布設計が容易である。 The low soda α-alumina powder having excellent viscosity characteristics according to the present invention is low soda and has an average particle diameter of 2 to 5 μm, sharp particle size distribution, good dispersibility when filled with resin, and viscosity. In addition to being useful as alumina for resin filling, it is easy to design a particle size distribution when preparing an alumina powder having a specific particle size distribution.
　また、本発明のαアルミナ紛体の製造方法によれば、バイヤー法で得られた水酸化アルミニウムを用い、上記の粘度特性に優れた低ソーダαアルミナ紛体を安価に製造できるだけでなく、製造工程の工程管理を容易かつ確実に実施することができる。 Further, according to the method for producing an α-alumina powder of the present invention, not only can the low-soda α-alumina powder excellent in the above-mentioned viscosity characteristics be produced at low cost by using the aluminum hydroxide obtained by the Bayer method, Process management can be carried out easily and reliably.
　以下、実施例及び比較例に基づいて、本発明の実施の形態を具体的に説明する。
　〔実施例１〕
　バイヤー法で得られた水酸化アルミニウム（平均二次粒子径：55μm及びソーダ(Na2O)分：0.2質量%）にハロゲン系鉱化剤として弗化アルミニウムをアルミナ換算で０．４質量%の割合で添加して混合し、得られた混合物を、シリカを含むアルミナセラミックス製の焼成容器内に充填し、トンネルキルン炉を用いて１５００℃±１０℃、約１５時間の条件で焼成した。
　得られた焼成物のソーダ(Na2O)分、成形密度、及びBET比表面積を測定した。結果を表１に示す。 Hereinafter, based on an Example and a comparative example, embodiment of this invention is described concretely.
[Example 1]
Aluminum fluoride obtained by the Bayer method (average secondary particle size: 55 μm and soda (Na 2 O) content: 0.2% by mass) is 0.4% by mass of aluminum fluoride as a halogen-based mineralizer in terms of alumina. The mixture was added and mixed at a ratio, and the obtained mixture was filled in a firing container made of alumina ceramic containing silica, and fired in a tunnel kiln furnace at 1500 ° C. ± 10 ° C. for about 15 hours.
The soda (Na 2 O) content, molding density, and BET specific surface area of the fired product were measured. The results are shown in Table 1.
　次に、６リットル(L)のポット内に１５mmφのアルミナボール７．６kgが収容された振動ボールミル（中央化工機社製）を用い、上記の焼成で得られた焼成物１．５kgについて、粉砕後の平均粒子径(Dav:Dp50)が３．０μmであって、この粉砕後の平均粒子径(Dav)と粉砕前のBET相当径(DBET)との粒径比(Dav／DBET)が１．２３となるように粉砕し、αアルミナを得た。 Next, using a vibrating ball mill (made by Chuo Kako Co., Ltd.) in which 7.6 kg of 15 mmφ alumina balls are housed in a 6 liter (L) pot, 1.5 kg of the fired product obtained by the above firing is pulverized. The subsequent average particle size (D av : Dp50) is 3.0 μm, and the particle size ratio (D av / D av ) between the average particle size after this crushing (D av ) and the BET equivalent diameter (D BET ) before crushing D BET ) was ground to 1.23 to obtain α-alumina.
　得られたαアルミナについて、粒度分布として４５μm篩上量(+45μm)を測定すると共に積算粒度分布率９０重量%に対応する粒子径(Dp90)、積算粒度分布率５０重量%に対応する粒子径(Dp50)、及び積算粒度分布率１０重量%に対応する粒子径(Dp10)を測定してスパン値〔(Dp90－Dp10)/Dp50〕を求め、また、樹脂充填時粘度を測定した。結果を表１に示す。 With respect to the obtained α-alumina, the particle size distribution was measured as a particle size distribution of 45 μm (+45 μm) and the particle size corresponding to an integrated particle size distribution rate of 90% by weight (Dp90) and the particle size corresponding to an integrated particle size distribution rate of 50% by weight. The span value [(Dp90−Dp10) / Dp50] was determined by measuring the particle size (Dp10) corresponding to (Dp50) and the cumulative particle size distribution ratio of 10% by weight, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
　〔実施例２〕
　３００リットル(L)のミル内に２０mmφのアルミナボール２５５kgが収容された回転ボールミル（中央化工機社製）を用い、実施例1で得られた焼成物５０kgについて、粉砕後の平均粒子径(Dav:Dp50)が３．１μmであって、この粉砕後の平均粒子径(Dav)と粉砕前のBET相当径(DBET)との粒径比(Dav／DBET)が１．２７となるように粉砕し、αアルミナを得た。
　得られたαアルミナについて、実施例１と同様にして、粒度分布として４５μm篩上量(+45μm)を測定すると共にスパン値を求め、また、樹脂充填時粘度を測定した。結果を表１に示す。 [Example 2]
Using a rotating ball mill (manufactured by Chuo Kako Co., Ltd.) in which 255 mm of alumina balls of 255 mm are accommodated in a 300 liter (L) mill, the average particle size after grinding of 50 kg of the fired product obtained in Example 1 (D av: Dp50) is a 3.1 .mu.m, particle size ratio of the average particle size after the pulverization (D av) and the BET equivalent diameter before pulverization (D BET) (D av / D BET) 1.27 To obtain α-alumina.
For the obtained α-alumina, in the same manner as in Example 1, the amount of 45 μm sieve (+45 μm) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
　〔実施例３〕
　実施例２と同じ回転ボールミル（中央化工機社製）を用い、実施例1で得られた焼成物５０kgについて、粉砕後の平均粒子径(Dav:Dp50)が２．９μmであって、この粉砕後の平均粒子径(Dav)と粉砕前のBET相当径(DBET)との粒径比(Dav／DBET)が１．１９となるように粉砕し、αアルミナを得た。
　得られたαアルミナについて、実施例１と同様にして、粒度分布として４５μm篩上量(+45μm)を測定すると共にスパン値を求め、また、樹脂充填時粘度を測定した。結果を表１に示す。 Example 3
Using the same rotating ball mill (manufactured by Chuo Kako Co., Ltd.) as in Example 2, the average particle size (D av : Dp50) after pulverization of the calcined product obtained in Example 1 was 2.9 μm. BET equivalent diameter before the average particle size after pulverization and (D av) grinding (D BET) particle with diameter ratio (D av / D BET) is ground to a 1.19 to obtain α-alumina.
For the obtained α-alumina, in the same manner as in Example 1, the amount of 45 μm sieve (+45 μm) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
　〔実施例４〕
　３００リットル(L)のミル内に１５mmφのアルミナボール２５５kgが収容された回転ボールミル（中央化工機社製）を用い、実施例1で得られた焼成物５０kgについて、粉砕後の平均粒子径(Dav:Dp50)が３．１μmであって、この粉砕後の平均粒子径(Dav)と粉砕前のBET相当径(DBET)との粒径比(Dav／DBET)が１．２７となるように粉砕し、αアルミナを得た。
　得られたαアルミナについて、実施例１と同様にして、粒度分布として４５μm篩上量(+45μm)を測定すると共にスパン値を求め、また、樹脂充填時粘度を測定した。結果を表１に示す。 Example 4
Using a rotating ball mill (manufactured by Chuo Kako Co., Ltd.) in which a 15-mmφ alumina ball was accommodated in a 300 liter (L) mill, the average particle size after pulverization (D av: Dp50) is a 3.1 .mu.m, particle size ratio of the average particle size after the pulverization (D av) and the BET equivalent diameter before pulverization (D BET) (D av / D BET) 1.27 To obtain α-alumina.
For the obtained α-alumina, in the same manner as in Example 1, the amount of 45 μm sieve (+45 μm) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
　〔実施例５〕
　実施例１と同様にして調製され、表１に示すソーダ(Na2O)分、成形密度、及びBET比表面積を有する焼成物について、実施例１と同様の方法で粉砕し、αアルミナを得た。
　得られたαアルミナについて、実施例１と同様にして、粒度分布として４５μm篩上量(+45μm)を測定すると共にスパン値を求め、また、樹脂充填時粘度を測定した。結果を表１に示す。 Example 5
A fired product prepared in the same manner as in Example 1 and having the soda (Na 2 O) content, molding density, and BET specific surface area shown in Table 1 was pulverized in the same manner as in Example 1 to obtain α-alumina. It was.
For the obtained α-alumina, in the same manner as in Example 1, the amount of 45 μm sieve (+45 μm) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
　〔比較例１〕
　実施例１と同様にして調製され、表１に示すソーダ(Na2O)分、成形密度、及びBET比表面積を有する焼成物について、粉砕後の平均粒子径(Dav:Dp50)が３．７μmであって、この粉砕後の平均粒子径(Dav)と粉砕前のBET相当径(DBET)との粒径比(Dav／DBET)が１．４８となるように粉砕し、αアルミナを得た。
　得られたαアルミナについて、実施例１と同様にして、粒度分布として４５μm篩上量(+45μm)を測定すると共にスパン値を求め、また、樹脂充填時粘度を測定した。結果を表１に示す。 [Comparative Example 1]
An average particle size (D av : Dp50) after pulverization of a fired product prepared in the same manner as in Example 1 and having a soda (Na 2 O) content, a molding density, and a BET specific surface area shown in Table 1. The particle size ratio (D av / D BET ) between the average particle diameter (D av ) after pulverization and the BET equivalent diameter (D BET ) before pulverization is 1.48, α-alumina was obtained.
For the obtained α-alumina, in the same manner as in Example 1, the amount of 45 μm sieve (+45 μm) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
　〔比較例２〕
　粉砕後の平均粒子径(Dp50)が３μmのアルミナ(3μmアルミナ)と粉砕後の平均粒子径(Dp50)が０．５μmのアルミナ(5μmアルミナ)とを質量比（3μmアルミナ／5μmアルミナ）８：２の割合で混合し、ソーダ(Na2O)分が０．０７質量%であって、混合後の平均粒子径(Dp50)が２．８μmのαアルミナを調製した。
　得られたαアルミナについて、実施例１と同様にして、粒度分布として４５μm篩上量(+45μm)を測定すると共にスパン値を求め、また、樹脂充填時粘度を測定した。結果を表１に示す。 [Comparative Example 2]
Mass ratio (3 μm alumina / 5 μm alumina) of alumina (3 μm alumina) having an average particle diameter (Dp50) of 3 μm after pulverization and alumina (5 μm alumina) having an average particle diameter (Dp50) of 0.5 μm after pulverization: An α-alumina having a soda (Na 2 O) content of 0.07% by mass and an average particle diameter (Dp50) of 2.8 μm after mixing was prepared.
For the obtained α-alumina, in the same manner as in Example 1, the amount of 45 μm sieve (+45 μm) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
　〔比較例３〕
　実施例１と同様にして調製され、表１に示すソーダ(Na2O)分、成形密度、及びBET比表面積を有する焼成物について、粉砕後の平均粒子径(Dav:Dp50)が２．７μmであって、この粉砕後の平均粒子径(Dav)と粉砕前のBET相当径(DBET)との粒径比(Dav／DBET)が１．９３となるように粉砕し、αアルミナを得た。
　得られたαアルミナについて、実施例１と同様にして、粒度分布として４５μm篩上量(+45μm)を測定すると共にスパン値を求め、また、樹脂充填時粘度を測定した。結果を表１に示す。 [Comparative Example 3]
An average particle size (D av : Dp50) after pulverization of a fired product prepared in the same manner as in Example 1 and having a soda (Na 2 O) content, a molding density, and a BET specific surface area shown in Table 1. a 7 [mu] m, average particle size after the pulverization (D av) and the particle diameter ratio (D av / D BET) of the BET equivalent diameter before pulverization (D BET) is ground to a 1.93, α-alumina was obtained.
For the obtained α-alumina, in the same manner as in Example 1, the amount of 45 μm sieve (+45 μm) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
　〔比較例４〕
　実施例１と同様にして調製され、表１に示すソーダ(Na2O)分、成形密度、及びBET比表面積を有する焼成物について、粉砕後の平均粒子径(Dav:Dp50)が３．８μmであって、この粉砕後の平均粒子径(Dav)と粉砕前のBET相当径(DBET)との粒径比(Dav／DBET)が１．５７となるように粉砕し、αアルミナを得た。
　得られたαアルミナについて、実施例１と同様にして、粒度分布として４５μm篩上量(+45μm)を測定すると共にスパン値を求め、また、樹脂充填時粘度を測定した。結果を表１に示す。 [Comparative Example 4]
An average particle size (D av : Dp50) after pulverization of a fired product prepared in the same manner as in Example 1 and having a soda (Na 2 O) content, a molding density, and a BET specific surface area shown in Table 1. a 8 [mu] m, average particle size after the pulverization (D av) and the particle diameter ratio (D av / D BET) of the BET equivalent diameter before pulverization (D BET) is ground to a 1.57, α-alumina was obtained.
For the obtained α-alumina, in the same manner as in Example 1, the amount of 45 μm sieve (+45 μm) was measured as the particle size distribution, the span value was determined, and the viscosity at the time of resin filling was measured. The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１に示す結果から明らかなように、各実施例１～５のαアルミナ紛体は、いずれもソーダ(Na2O)分が０．１質量%以下であると共に平均粒子径(Dp50)が２～５μmであるばかりでなく、４５μm篩上量(+45μm)が低くてスパン値が１．１以下であってシャープな粒度分布を有しており、また、樹脂充填時粘度が６０ポアズ(poise)以下と樹脂充填性に優れていた。 As is apparent from the results shown in Table 1, each of the α-alumina powders of Examples 1 to 5 has a soda (Na 2 O) content of 0.1% by mass or less and an average particle size (Dp50) of 2 In addition to ˜5 μm, the amount of sieve top (+45 μm) is low, the span value is 1.1 or less, the particle size distribution is sharp, and the viscosity when filled with resin is 60 poise. ) The resin filling property was excellent as follows.
　これに対して、比較例１のαアルミナ紛体は、スパン値は低い値を示したが、４５μm篩上量(+45μm)と樹脂充填時粘度が高い値を示し、比較例２のαアルミナ紛体は、４５μm篩上量(+45μm)と樹脂充填時粘度が低い値を示したが、スパン値が高く、また、比較例３のαアルミナ紛体は、スパン値は低い値を示したが、樹脂充填時粘度が極めて高い値を示し、更に、比較例４のαアルミナ紛体は、スパン値は低い値を示したが、４５μm篩上量(+45μm)と樹脂充填時粘度が高い値を示した。 On the other hand, the α-alumina powder of Comparative Example 1 showed a low span value but a 45 μm sieving amount (+45 μm) and a high viscosity when filled with resin, and the α-alumina powder of Comparative Example 2 Showed a value of 45 μm on the sieve (+45 μm) and a low viscosity when filled with resin, but the span value was high, and the α-alumina powder of Comparative Example 3 showed a low span value. In addition, the α-alumina powder of Comparative Example 4 showed a low span value, but a 45 μm sieve top amount (+45 μm) and a high resin-filling viscosity value. .

Claims (3)

  1. 　バイヤー法で得られた水酸化アルミニウムを焼成し、粉砕して製造されたαアルミナ紛体であって、
    　ソーダ(Na2O)分が０．１質量%以下であると共に平均粒子径(Dp50)が２～５μmであり、かつ、粒度分布が４５μm篩上量(+45μm)１００ppm以下及びスパン値〔(Dp90－Dp10)/Dp50〕１．１以下であることを特徴とする粘度特性に優れた低ソーダαアルミナ紛体。     An α-alumina powder produced by firing and pulverizing aluminum hydroxide obtained by the buyer method,
    The soda (Na 2 O) content is 0.1% by mass or less, the average particle size (Dp50) is 2 to 5 μm, the particle size distribution is 45 μm on the sieve (+45 μm) 100 ppm or less and the span value [( Dp90-Dp10) / Dp50] A low soda α-alumina powder excellent in viscosity characteristics, characterized by being 1.1 or less.
  2. 　前記αアルミナ紛体は、このαアルミナ紛体２００重量部を不飽和ポリエステル樹脂１００重量部中に添加し、周速２．６m/秒及び１０分間の条件で撹拌してアルミナ充填樹脂組成物を調製した際に、得られたアルミナ充填樹脂組成物について、ブルックフィールド型粘度計を用いてローター回転速度１２rpm及び測定温度２５℃の条件で測定した際のアルミナ充填樹脂組成物の粘度（樹脂充填時粘度）が６０ポアズ(poise)以下である請求項１に記載の粘度特性に優れた低ソーダαアルミナ紛体。 The α-alumina powder was prepared by adding 200 parts by weight of this α-alumina powder to 100 parts by weight of unsaturated polyester resin and stirring the mixture under conditions of a peripheral speed of 2.6 m / second and 10 minutes to prepare an alumina-filled resin composition. At that time, the viscosity of the alumina-filled resin composition measured with the Brookfield viscometer on the condition of the rotor rotational speed of 12 rpm and the measurement temperature of 25 ° C. (viscosity during resin filling) The low-soda α-alumina powder having excellent viscosity characteristics according to claim 1, wherein is not more than 60 poise.
  3. 　バイヤー法で得られたソーダ(Na2O)分０．３質量%以下の水酸化アルミニウムにハロゲン系鉱化剤を添加して混合し、得られた混合物を、シリカ含有アルミナセラミックス製の焼成容器に充填して成形密度(成型圧:９８．０７MPa)２．０５g/cm3以上及びBET比表面積０．９m2/g以下となるように１１００～１６００℃の範囲で焼成し、次いで得られた焼成物を、粉砕後の平均粒子径(Dav)と粉砕前のBET相当径(DBET)との粒径比（Dav／DBET）が１．１０～１．４５の範囲になるように粉砕することを特徴とする粘度特性に優れた低ソーダαアルミナ紛体の製造方法。 A soda (Na 2 O) content obtained by the Bayer method is mixed with 0.3% by mass or less of aluminum hydroxide by adding a halogen-based mineralizer and mixing the resulting mixture with a silica-containing alumina ceramic firing container. And then fired in the range of 1100 to 1600 ° C. so that the molding density (molding pressure: 98.07 MPa) is 2.05 g / cm 3 or more and the BET specific surface area is 0.9 m 2 / g or less. The calcined product has a particle size ratio (D av / D BET ) between the average particle diameter after pulverization (D av ) and the BET equivalent diameter before pulverization (D BET ) in the range of 1.10 to 1.45. A method for producing a low-soda α-alumina powder having excellent viscosity characteristics, characterized in that the powder is pulverized into two.
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EP3828135A4 (en) * 2018-07-26 2022-03-30 DIC Corporation Tabular alumina particle and method for manufacturing tabular alumina particle
JP2022186630A (en) * 2021-06-04 2022-12-15 住友化学株式会社 Alumina particle and resin composition using the same
WO2023190464A1 (en) * 2022-03-30 2023-10-05 日本軽金属株式会社 PRODUCTION METHOD FOR α-ALUMINA POWDER

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