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:
Jun. 23, 1992
Filed:
Nov. 21, 1990
Fritz Herren, Dudingen, CH;
Leonardus J Erkens, Maastricht, NL;
Ciba-Geigy Corporation, Ardsley, NY (US);
Abstract
A process for stabilizing bismuth vanadate pigments against attack by hydrochloric acid by treating said pigments with a metal phosphate, which process comprises treating an aqueous suspension of a bismuth vanadate pigment with 2-20% by weight, based on said pigment, of an orthophosphate selected from the group consisting of calcium, magnesium, aluminium, zirconium and titanium orthophosphate, of a mixture of such orthophosphates with one another or of such orthophosphates with zinc orthophosphate, with stirring, in the temperature range from 20.degree. to 100.degree. C. and in the pH range from 2 to 8, which orthophosphate is precipitated in situ from the appropriate metal salt of a strong mineral acid and orthophosphoric acid or from an alkali metal salt thereof, and isolating the resultant product by conventional methods. The pigments so obtained have excellent resistance to hydrochloric acid.