ACRYLONITRILE/VINYL ACETATE/STYRENE TERPOLYMER MIXTURE

摘要

Acrylonitrile/vinyl acetate/styrene copolymers containing a high proportion of acrylonitrile (50-80% by weight) which undergo no discoloration and result in highly transparent products when thermoplastically processed are produced by continuous emulsion copolymerization the monomers in a tube reactor in which comparatively little back mixing occurs (plug flow = laminar flow = non-stationary state). A seed latex having a specified, small particle size with a narrow particle size distribution of the copolymer is obtained; the reaction mixture is then cooled, if necessary, in order to prevent further polymerization as far as possible and continuously transferred into a stirrer vessel while at the same time a stream of monomers consisting of acrylonitrile, vinyl acetate and styrene also having a specified but different percentage composition of monomers than in stage 1 is also fed into this stirrer vessel, and in this second stage of the process, polymerization is carried out at specified temperatures and with specified residence times under stationary conditions, i.e. with back mixing up to a total conversion of 70 to 90%.