Bayer Aktiengesellschaft

Volker Wilhelm

Jakob Rademachers

Dieter Messer

Heinrich Heine

Wilfried Burow

Manfred Mansmann

Robert Endres

Siegfried Keifer

A process for the preparation of chromate-free, Cr.sub.2 O.sub.3 -containing pigments having a spinel, haematite or corundum structure comprises blending pigment-forming raw materials corresponding to the Cr.sub.2 O.sub.3 -containing pigments with from 0.5 to 10% by weight of boric acid or phosphoric acid, calculated as B.sub.2 O.sub.3 or P.sub.2 O.sub.5, respectively, and then annealing the blend whereby the chromate-free, Cr.sub.2 O.sub.3 -containing pigment is obtained.

Process for the preparation of pigments containing Cr.sub.2 O.sub.3

Thermostable pigments for coloring stoving lacquers, coil coat lacquers, plastics, sand granulates, lime sandstone, enamel or ceramic glazes are zinc ferrite color pigments containing from 0.01 to 0.5% by weight of lithium.

Thermostable zinc ferrite color pigments containing 0.05-0.5 wt %

A process for the production of rutile mixed-phase pigments comprising calcinating of a solid mixture of titanium dioxide or titanium oxide hydroxide with a dye-producing compound of a metal, in one or more directly heated, continuously operated rotary kilns, wherein in terms of material flow, air is introduced into the kiln atmosphere countercurrently to the direction of flow of the solids in the second half of the rotary kiln.

Process for the production of rutile mixed-phase pigments

Chromium-antimony-rutile mixed phase pigments containing from 0.01 to 0.25% by weight of lithium are surprisingly insensitive to rapid cooling and chilling and are used for coloring plastic compositions such as polyamide or ABS plastics.

Rutile mixed phase pigments with improved coloristic properties

Coated rutile mixed phase pigments comprise a mixed phase rutile pigment having a first coating of an oxide or hydrated oxide of titanium, zirconium, tin or a mixture thereof and a subsequent coating of an oxide or hydroxide of aluminum, and those pigments exhibit an improved tendency against flocculation in lacquers hardened with acid catalysts.

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Bergisch-Gladbach, Germany

Volker Wilhelm