Process for the reduction in the richness of vinyl chloride monomer in the vinyl chloride polymers.

摘要

1499762 Removing vinyl chloride monomer from a vinyl chloride polymer CHEMISCHE WERKE HULS AG 12 May 1975 [27 June 1974 29 Aug 1974 (2)] 19767/75 Headings C3P and C3G A process for reducing the content of unpolymerized vinyl chloride monomer in a vinyl chloride suspension polymer is characterized in that steam at a temperature of 80-150‹ C. is passed through a vinyl chloride suspension polymer which is moist with water. The duration of the steam treatment may be from 5 seconds to 10 minutes. The water content of the polymer which is moist with water may be 15-35% by weight. The weight ratio of polymer moist with water to steam may be 50 : 2- 50 : 50 and the extracted vinyl chloride monomer may be recovered from the vapour from the steam treatment. The specific examples refer to the treatment of polyvinyl chloride and an ethylene-vinyl acetate copolymer grafted with vinyl chloride (Example 3). In the case of heterogeneous gas systems the treatment with the steam may be carried out by the polymer falling freely in a fall tower, by pneumatic conveying or by fluidizing. In the case of poured polymers the treatment may be carried out on a porous base, e.g. steaming in a container provided with a porous base. Alternative continuously operating equipment are porous conveyer belts and conveyer troughs, screw conveyers, rotary filters and belt filters. The preliminary dehydration of and removal of monomer may be carried out in the same equipment, e.g. rotary filters, belt filters and screentype centrifuges.