Patent ID: 8562858

Claim:
A process for the aqueous suspension polymerization of vinyl chloride, alone or as a mixture with less than 50% of another vinyl monomer, in the presence of a polymerization initiator comprising at least one compound chosen from dialkyl peroxydicarbonates, peroxy-tert-alkanoates and diacyl peroxides, wherein said process comprises employing a polymerization regulating agent comprising at least one mono- or di alkyl substituted N hydroxylamine having the formula: HO—N—R 1 R 2 wherein R 1 and R 2 may be the same or different, and are selected from H and C 1 -C 12 hydrocarbons, where each hydrocarbon chain may be branched, unsaturated, or have hydrogen substituted with functional groups selected from —OH, —SO, benzyl, amino, mercapto, keto, carboxyl, or where R 1 and R 2 may form together a cyclic structure, with the proviso that at least one of R 1 and R 2 is different from H in the amount of 0.0005 to 0.02 parts by weight per 100 parts by weight of monomers, along with a totally or partially hindered phenolic antioxidant, wherein the antioxidant is chosen from butylated hydroxyanisole, butylated hydroxytoluene, 2,4-dimethyl-6-sec-hexadecylphenol, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-4-sec-butylphenol, 3,5-di-t-butyl-4-hydroxyhydrocinnamic acid C 7 -C 9 alkylester and mixtures of 2,4-dimethyl-6-sec-hexadecylphenol and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.