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. 10, 1979
Filed:
Jul. 12, 1976
Siegfried Schneider, Cologne, DE;
Hans Niederprum, Monheim, DE;
Bayer Aktiengesellschaft, Leverkusen, DE;
Abstract
In the production of a synthetic fluorspar of low silicon dioxide content wherein hexafluosilicic acid is added in an amount ranging from slightly below up to about stoichiometric amount to an aqueous calcium carbonate suspension at a temperature from about 0.degree. to 40.degree. C., and the calcium fluoride formed is separated off from the dilute silica sol and optionally washed out, the improvement which comprises reacting the calcium carbonate with the hexafluosilicic acid in such a way that the pH-value of the fully reacted solution amounts to between about 3.6 and 4.6, and adding a fast-reacting proton acceptor to the reaction mixture immediately before separation of the calcium fluoride in amount sufficient to raise the pH to about 5.0 to 6.4, preferably about 5.8 to 6.2. Suitable proton acceptors include the alkali metal and ammonium hydroxides carbonates and hydrogen carbonates or alkaline earth metal hydroxide. Anionic or non-ionic dispersants may also be added and the calcium fluoride is separated by decanting or centrifugation within about 1 second to 10 minutes, preferably about 4 to 10 seconds, after raising the pH. The separated calcium fluoride may be washed to remove silica sol therefrom and then again be treated to raise its pH before separation.