Process for manufacturing high purity silica
AssigneesNitto Chemical Industry Co., Ltd., Mitsubishi Rayon Co., Ltd.
InventorsKoichi Orii, Masashi Nishida, Junsuke Yagi, Iwao Ohshima
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Abstract
This invention deals with a process for manufacturing high purity silica which comprises making an aqueous alkali silicate solution into fine fibrous gel in a coagulant, treating the fibrous gel obtained with an acid-containing solution, and then with water to extract and remove impurities; and optionallly heating a resulting silica at a temperature of 1,000.degree. C. or higher. Thus obtained silica is preferably used as a filler, especially, the one for resin compositions for encapsulating electronic parts; etc.
Claims27
A process for manufacturing high purity silica having an alkali metal content of 0 to 10 ppm, a chlorine content of 0 to 3 ppm and a uranium content of 0 to 3 ppb, said process comprising:
- (1) a step of extruding an aqueous solution of an alkali silicate represented by the general formula:
- M.sub.2 O.nSiO.sub.2
- wherein M is an alkali metal element and n is a number of moles of SiO.sub.2 of 0.5 to 5, into a coagulating bath comprising a coagulant through a spinning nozzle having a bore diameter of 1 mm or less to coagulate the same, and thereby making the same into a fibrous gel, said aqueous solution having a viscosity in the range of 2 to 500 poise, and
- (2) a step of treating the fibrous gel obtained with an acid-containing solution, and then washing the same with water to extract and remove impurities.
Dependencies are inferred from the claim text.