Wacker-chemie Gmbh

Helmut E Thyret

Johann Bauer

Thomas Balwe

Josef Hanzalik

Gerhard Beier

Herbert Furst

An improvement in the process of producing polyvinyl chloride by the suspension process in the presence of protective colloids by utilizing a protective colloid mixture of from 20% to 80% of the protective colloid mixture of a polyvinyl acetate having a hydrolysis degree of 40 to 55 mol % and the remainder of the protective colloid mixture of (1) a water-soluble polyvinyl alcohol having a hydrolysis degree of 70 to 90 mol %, or (2) an aminoethyl-hydroxypropyl cellulose having a molar substitution of from 0.05 to 1.5 mols of aminoethyl groups and 3 to 5 mols of hydroxypropyl groups, or (3) a vinyl acetate/vinyl pyrrolidone copolymer having a ratio of vinyl pyrrolidone to vinyl acetate in the copolymer of 50% to 70% by weight to 30% to 50% by weight and a K-value of 25 to 40. By the use of this protective colloid mixture, the polyvinyl chloride produced exhibits a large absorption of plasticizer and gives finished products having a low number of specks.

Process for suspension polymerization of vinyl chloride employing mixed

A polymerization autoclave for the suspension polymerization of vinyl compounds in the aqueous phase having a volume of from 50 to 200 m.sup.3, an impeller agitator driven from below at the bottom of the autoclave and two cylindrical displacement bodies acting as flow interrupters, secured downwardly from the autoclave dome, where the autoclave has a height-to-diameter ratio of from 2.4 to 3 with a critically dimensioned agitator and critically dimensioned flow interrupter fittings. By the use of this invention in the case large-scale autoclaves, the heat of polymerization can be removed merely by wall-cooling. The autoclave according to the invention are very economical, as shown by, for example, a spatial capacity of 0.3 to 0.4 metric tons of polyvinyl chloride per m.sup.3 autoclave volume.

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Burghausen, Germany

Helmut E Thyret