Sachtleben Chemie Gmbh

Udo Selter

Djamschid Amirzadeh-Asl

Jürgen Bäuml

This patent describes the use of barium sulfate as filler for thermosetting and thermoplastic plastics, elastomers, sealants, adhesives, fillers, varnishes, paints, paper, glass and as substrate for colored pigment formulations as well as for single-layer or multilayer coatings consisting of metal oxides, metal oxide mixtures and/or metal compounds, as a nucleus of crystallization for lead sulfate in the negative electrode paste of lead accumulators and as an X-ray contrast medium, the barium sulfate being produced by a continuous process wherein a barium salt solution and a sulfate solution are simultaneously and continuously brought together in equimolar quantities in a precipitating suspension at a temperature of 30 to 90&#xb0; C., with constant stirring, the precipitating suspension is withdrawn continuously in a steady volume and the barium sulfate precipitate is filtered, washed and optionally dried, wherein the barium salt solution has a concentration of 0.1 to 0.8 Bamol/l and the sulfuric acid has a concentration of 0.1 to 2.0 SOmol/l, and the flow rate and stirring speed are controlled, at a constant precipitation volume, in such a way that a pH value of 1 to 5 is obtained in the precipitating suspension, and the lamellar barium sulfate particles produced as result of the precipitation are 0.1 to 50 &#x3bc;m wide, 0.1 to 50 &#x3bc;m long and 0.1 to 2 &#x3bc;m thick and the needle-shaped particles produced as result of the precipitation are 1 to 50 &#x3bc;m long and 0.1 to 2 &#x3bc;m thick, the ratio of length or width to the thickness being 3:1 to 500:1.

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Moers, Germany

Udo Selter