Process for stabilizing bismuth vanadate pigments against attack by hydrochloric acid
US5123965A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 21, 1990 |
| Grant date | Jun 23, 1992 |
| Priority date | — |
| Expiry date | Nov 21, 2010 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC08K9/02
- WIPO fieldBasic materials chemistry
- WIPO sectorChemistry
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.