The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 13, 1993
Filed:
Feb. 20, 1990
Naotake Watanabe, Yokosuka, JP;
Koichi Orii, Yokohama, JP;
Junsuke Yagi, Yokohama, JP;
Iwao Ohshima, Yokohama, JP;
Nitto Chemical Industry Co., Ltd., Tokyo, JP;
Abstract
A process for preparing silica having a low silanol content which comprises heating amorphous silica in an atmosphere of a low partial pressure of water vapor to maintain the amorphous silica at a temperature in a range of from 600.degree. to 1000.degree. C. at a first heating step and then maintain at a temperature of 1200.degree. C. or more at a second heating step. The silica having a low silanol content obtained according to the present invention is advantageously used as a raw material for quartz glass, particularly as a raw material for preparing crucibles used to pull up silicon single crystals.