Preparation of a mixed-phase pigment based on iron oxide and chromium oxide

US4643772A · kind A · utility

Assignee

• BASF SE

Inventors

• Harald Gaedcke · Leonberg, DE
• Ruediger Braun · Eschenburg, DE
• Roland Bauer · West Milford, US

Key dates

• Filing date: Aug 5, 1985
• Grant date: Feb 17, 1987
• Expiry date: Aug 5, 2005

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01P2004/84
• WIPO field: Basic materials chemistry
• WIPO sector: Chemistry

Abstract

A process for the preparation of a mixed-phase pigment based on iron oxide and chromium oxide by heating a mixture of the oxides, hydroxides or oxide hydroxides of iron and of chromium at from 600.degree. to 1100.degree. C. and then comminuting the product and working it up in a conventional manner. The essential feature of the invention is that a mixture of transparent .alpha.-iron oxide having an orthorhombic bipyramidal crystal structure and a chromium(III) hydroxide, which has been applied onto the transparent iron oxide by precipitation with an alkali, preferably sodium carbonate, is heated. The pigments according to the invention give deep colorations and are readily dispersible.