Basf Aktiengesellschaft

Lacke & Farben Aktiengesellschaft

Roland Bauer

Werner Ostertag

Gustav Bock

Egon Liedek

Helmut Knittel

Henning Wienand

Guenter Etzrodt

Harald Gaedcke

Ruediger Braun

Thermostable rutile mixed phase pigments of the ternary system titanium, antimony and chromium contain from 0.1 to 2.0% by weight of magnesium.

Thermostable rutile mixed phase pigments

Magnetite pigments are prepared from iron(II) salt solutions by a process in which the mean particle size can be brought to a value within the range from 0.06 to 0.5 .mu.m by means of a residence stage between the precipitation stage and the oxidation stage.

Preparation of magnetite pigments: control of particle size

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.

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

Transparent, golden yellow, thermally stable two-phase pigments of the general formula xZnO.ZnFe.sub.2 O.sub.4, where x is from 0.5 to 1.5, are prepared by a method in which the pH of an aqueous phase which contains transparent iron oxide yellow in suspension and zinc ions in solution is brought to 7-10, and the product is treated at above 200.degree. C. before or after being isolated from the aqueous phase.

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Bergisch-Gladbach, Germany

Roland Bauer