Coated spinel color pigments, process for their production and use

US5194089A · kind A · utility

Assignee

• Degussa AG · DE

Inventors

• Dietrich Speer · Hanau, DE
• Akos Kiss · Alzenau, DE
• Peter Kleinschmit · Hanau, DE
• Jenny Horst · Gelnhausen, DE

Key dates

• Filing date: May 9, 1991
• Grant date: Mar 16, 1993
• Expiry date: May 9, 2011

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/2993
• WIPO field: Basic materials chemistry
• WIPO sector: Chemistry

Abstract

Coated spinel color pigments with a core of a colored spinel, in particular CoAl.sub.2 O.sub.4, and a coating glassy layer of a silicate are described. The coating layer is essentially silicon dioxide and one or more oxides of the group of alkali metals, alkaline earth metals, and/or earth metals show a high resistance to bleeding in the presence of glass fluxes, as compared to uncoated spinels. The pigments are produced by sintering, for 0.5 to 5 hours, a powder mixture of the spinel, silicon dioxide, and at least one member chosen from the group of alkali metal halides, alkaline earth metal halides, earth metal halides and mixtures thereof as mineralizer at 900.degree. to 1,300.degree. C. The coated spinel color pigments are suitable for the production of ceramic decorations with improved contour sharpness.