Bayer Aktiengesellschaft

Dieter Messer

Volker Wilhelm

Klaus Wussow

Heinrich Heine

Manfred Mansmann

Peter Kuske

Dieter Rade

Robert Endres

Spinel black pigments are prepared by annealing oxides, hydroxides or carbonates of copper, chromium and manganese and grinding the product. The manganese-yielding component is Mn.sub.3 O.sub.4.

Spinel black pigments based on copper-chromium-manganese mixed oxides, a

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

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.

Flocculation-resistant, mixed phase pigments having a rutile structure,

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Odenthal, Germany

Dieter Messer