Low-alkali α-alumina powder excellent in viscosity characteristics and production method thereof

Abstract

The present invention provides a highly filling low-alkali α-alumina powder with low alkali, an average particle diameter of 2 to 5 μm, narrow particle size distribution, and low viscosity during resin filling, and a production method thereof. This powder is α-alumina powder produced by using aluminum hydroxide obtained by the Bayer process. It has a sodium oxide (Na2O) component of 0.1% by mass or less, an average particle diameter (Dp50) of 2 to 5 μm, and a particle size distribution of Low-alkali α-alumina powder with excellent viscosity characteristics having a 45 μm sieve weight (+45 μm) of 100 ppm or less and a width value [(Dp90‑Dp10) / Dp50] of 1.1 or less, which is produced by adding sodium oxide (Na2O ) component is 0.3% by mass or less of aluminum hydroxide with a halogen mineralizer added and fired so that the molding density (molding pressure: 98.07MPa) is 2.05g / cm3 or more and the BET specific surface area is 0.9m2 / g or less, Then, pulverization is performed so that the particle diameter ratio (Dav / DBET) of the average particle diameter (Dav) after pulverization to the BET equivalent diameter (DBET) before pulverization is in the range of 1.10 to 1.45.

Description

technical field [0001] The present invention relates to α-alumina powder produced by using aluminum hydroxide obtained by the Bayer process, in particular to low-alkali α-alumina powder having excellent viscosity characteristics capable of being fully filled in resin or rubber and its production method. Background technique [0002] Alumina has been widely used as a filler in various resins. One of its main uses is as a heat dissipation filler with both electrical insulation and chemical stability. For example, it is used in heat sinks, optical pickup parts, It is used in a wide range of fields, including heat dissipation grease, encapsulants for circuit boards, heat dissipation tapes and adhesives, various injection molded products, sealing materials for motors and ICs, copper foil laminated substrates, etc. . [0003] When alumina is used as a heat-dissipating filler for resin filling, in order to fully realize this purpose, not only sodium oxide (Na 2 O) There are few ...

AI Technical Summary

Problems solved by technology

However, the method described in Patent Document 1 has the following problems: it is necessary to prepare three kinds of α-alumina A, B and C with different particle sizes and blend them in a predetermined ratio to prepare a mixed powder, and in order to eliminate the three kinds of α-alumina The cutting edge of alumina with different particle sizes needs to be processed, which increases the number of manufacturing processes, and the manufacturing equipment and quality control become complicated, which leads to an increase in manufacturing costs

In addition, although the method of sufficiently filling a wide particle size distribution has been used in the past, there are problems in this method: the dispersibility is deteriorated due to the presence of fine particles, and the same amount of filler with a narrow particle size distribution is filled. Compared with the case, since the thermal conductivity of the composition becomes lower, more sufficient filling is required in order to exert performance, resulting in an increase in the mass of the composition

However, in the method described in Patent Document 6, since pseudo-boehmite and transition alumina with high specific surface area are used as alumina raw materials, a large amount of cost is required in the production of alumina raw materials. In addition, if the filling amount is the same In the case of comparison, there is a tendency that the thermal conductivity of the composition decreases with the increase of sphericity, and more sufficient filling is required.

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