Patent ID: 7232867

Claim:
A process for producing a vinyl chloride-based polymer, wherein a suspension polymerization of either vinyl chloride monomer, or a mixture of vinyl chloride monomer and another copolymerizable monomer, is conducted in a polymerization vessel fitted with a reflux condenser, said process comprising: (A) adding to a reaction mixture a high-activity, oil-soluble polymerization initiator, with a 10-hour half life temperature of no more than 40° C. at a concentration of 0.1 mol/L in benzene, for a specified time within a period from commencement of heat removal using said reflux condenser through to completion of polymerization, and (B) adding an antioxidant either continuously or intermittently to said reaction mixture at least during a period from commencement of addition of said high-activity, oil-soluble polymerization initiator through to completion of said addition.