Bayer Aktiengesellschaft

Wolfgang D Muller

Gunter Lailach

Gerhard Wiederhoft

Rudolf Gerken

Eckhard Bayer

Helmut Ohse

Walter Gutsche

Armin Burkholz

Jurgen Walther

Walter Hofmann

A process for the preparation of an improved quality TiO.sub.2 pigment by hydrolysis of titanyl sulphate, isolation of the hydrolysis product form the waste acid produced during the hydrolysis, washing of the hydrolysis product and calcination of the hydrolysis product to form the TiO.sub.2 pigment, wherein the hydrolysis of the titanyl sulphate is carried out using separately produced hydrolysis nuclei which have been produced by a reaction of titanium salts with alkaline reagents, and in which waste acid and/or wash liquid containing waste acid is added after at least 50% of the total duration of the hydrolysis process.

Process for the recorvery of sulphuric acid in the production of

In the preparation of titanium dioxide comprising autothermically digestion a titanium-containing raw material with sulphuric acid to form a solid relatively easily soluble digestion cake containing titanyl sulphate, extracting metal sulphates from this cake by water or dilute sulphuric acid, separating the undissolved residues and, optionally after crystallization of iron sulphate heptahydrate, hydrolyzing the titanyl sulphate to produce titanium oxide hydrate, and calcining the titanium oxide hydrate to titanium dioxide, the improvement which comprises adding to the raw material a metal sulphate and effecting the autothermic decomposition with sulphuric acid of about 80 to 88% concentration. Advantageously the acid is obtained by mixing dilute acid with concentrated sulphuric acid or oleum, some of the dilute acid and metal sulphate coming from a by-product filter cake produced in the course of the process.

Process for the preparation of titanium dioxide

To increase the degree of separation of liquid droplets from a stream of gas by means of a separator consisting of a packet of wire gauze arranged in a pipe, the packet is subdivided along its height by discharge channels arranged transverse to the direction of flow.

Separator for separating liquid droplets from a stream of gas

The invention relates to a process for the production of a false-twist textured, highly elastic, synthetic crimp yarn with low residual shrinkage and latently bound crimp by stretching, false-twisting, heat-fixing and thermal after-treatment of the synthetic yarn at yarn draw-off rates of from 400 to 900 m/min, in which the thread tension during thermal after-treatment is 6-25% of the thread tension during heat-fixing, the time of thermal after-treatment is 2-5% of the time spent in heat-fixing and the temperature of the yarn during the thermal after-treatment is 30.degree.-100.degree. C.

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Krefeld, Germany

Wolfgang D Muller