PURPOSE: An aqueous dispersion of vinyl chloride polymer bearing sulfide groups is treated with a vinyl monomer with negative e under heating to produce the titled polymer with high thermal stability and less discoloration.
CONSTITUTION: An aqueous dispersion of vinyl chloride polymer bearing sulfide groups, produced, e.g., by the polymerization of vinyl chloride monomer in an aqueous medium in the presence of an organic mercaptan, is combined with a vinyl monomer with negative e, preferably -0.20W-1.50 such as styrene, preferably by 0.5W10pts.wt. per 100pts. of the vinyl chloride polymer and they are heat treated, e.g., at 50W75°C for 30minW5hr to produce the objective polymer. The vinyl monomer is preferably added at any stage from the time when the conversion of vinyl chloride polymerization reaches higher than 50% to the salting out of the polymer from the aqueous dispersion.
MAEHARA TAKASHI
MIZUTANI YUKIO
