PROCESS FOR THE PRODUCTION OF ACRYLONITRILE-VINYL CHLORIDE COPOLYMERS WITH IMPROVED WHITENESS

摘要

The invention relates to a process for the production of chemically uniform acrylonitrile-vinyl chloride copolymers with improved whiteness and improved thermal stability comprising from 25 to 60 % by weight of actylonitrile and from 40 to 75 % by weight of vinyl chloride and, optionally, up to 15 % by weight of other copolymerised ethylenically unsaturated compounds by emulsion polymerisation using a redox catalyst of persulphate and compounds of sulphurous acid, wherein the ratio by weight of reducing component to oxidising component is at least 4 : 1 and wherein polymerisation is carried out at a pH-value in the range of from 2.5 to 4.