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:
May. 03, 1994
Filed:
Dec. 08, 1992
Michael Kotzian, Erftstadt, DE;
Gunther Schimmel, Erftstadt, DE;
Alexander Tapper, Monchengladbach, DE;
Knut Bauer, Kelkheim-Hornau, DE;
Hoechst Aktiengesellschaft, Frankfurt am Main, DE;
Abstract
To prepare crystalline sodium disilicates having a laminar structure, a molar ratio of SiO.sub.2 to Na.sub.2 O of (1.9 to 2.1) 1 and a water content of less than 0.3% by weight, a water glass solution is first obtained by reacting sand with sodium hydroxide solution in a molar ratio of SiO.sub.2 to Na.sub.2 O of (2.0 to 2.3) : 1 at temperatures of 180.degree. to 240.degree. C. and pressures of 10 to 30 bar. This water glass solution having at least 20% by weight of solids is treated in a spray drier with hot air at 200.degree. to 300.degree. C. with the formation of a pulverulent amorphous sodium disilicate having a water content (determined as loss on heating at 700.degree. C.) of 15 to 23% by weight and a bulk density of at least 300 g/l. The spray-dried pulverulent, amorphous sodium disilicate is ground. The ground sodium disilicate is introduced into a rotary kiln equipped with devices for moving solids, externally heated via the wall and having in its interior a plurality of different temperature zones, and is treated therein at temperatures of 400.degree. to 800.degree. C. for 1 to 60 minutes with formation of crystalline sodium disilicate.