Bayer Aktiengesellschaft

Hilmar Rieck

Peter Woditsch

Jurgen Kischkewitz

Fritz Rodi

Peter Panek

Gerhard Wiederhoft

Rolf-Michael Braun

Rolf Michael Braun

Bernd-Michael Holle

Klaus Kohler

Walter Gutsche

Udo Holtmann

Peter Beumer

This invention relates to a process for the production of inorganically coated pigments and fillers and to the use thereof.

Process for the production of inorganically coated pigments and fillers

A process for calcining a filter cake in a directly heated rotary kiln wherein part of the filter cake is separated from the entire mass of filter cake, the separated portion is predried and recombined with the remainder portion and the combined predried and remainder portion is calcined. The filter cake can be inorganic solids such as oxides of titanium, chromium (III), zinc and iron.

Process for the calcination of filter cakes with high solids contents

An inorganically after-treated TiO.sub.2 pigment with a coating of hydrophobicizing and hydrophilicizing organic substances, which pigment comprises more than about 95% by weight of TiO.sub.2, shows a loss on annealing of less than about 0.8% (after subtraction of the carbon content) and has a grindometer value smaller than about 30, corresponding to a value of more than about 5.6 on the Hegman scale, is produced by micronizing a mixture of an inorganically after-treated TiO.sub.2 pigment, an untreated TiO.sub.2 pigment and hydrophobicizing and hydrophilicizing organic substances, the after-treated pigment being employed in about 1 to 40% by weight of total TiO.sub.2 pigment and the hydrophobicing and hydrophilicizing substances being employed in about 0.3 to 5% by weight of TiO.sub.2 pigment. The pigments are readily dispersible which simplifies their use in pigmenting lacquers, plastics and paper.

Readily dispersible TiO.sub.2 pigment

A process for the preparation of a hydrolyzable titanyl sulphate solution comprising adding sulphuric acid having a concentration greater than about 86% to a ternary mixture of two slags and an ilmenite to bring the proportion by weight of H.sub.2 SO.sub.4 to TiO.sub.2 to from about 1.7:1 to 2.2:1 and adding water, dilute sulphuric acid or oleum in amount sufficient to bring the H.sub.2 SO.sub.4 concentration to from about 86 to 96%, thereby to form the titanyl sulphate solution, the first slag having a TiO.sub.2 content greater than about 80% and a Ti(III) content of about 22 to 40%, the second slag having a TiO.sub.2 content of about 60 to 80% and a Ti(III) content of about 5 to 15%, and the ilmenite having a ratio of Fe(III) to Fe(II) of from about 1:1 to 10:1, the slags and ilmenite being present in such proportions that the ternary mixture of raw materials obtained has a molar ratio of Ti(III) to Fe(III).gtoreq.1.4.

Hydrolyzable titanyl sulphate solutions by decomposition of ternary raw

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Krefeld, Germany

Hilmar Rieck