Process for the suspension polymerization of vinyl chloride with low polymer buildup

Claim 1

A process for preparing vinyl chloride polymer products with substantially no polymer buildup in the reactor which comprises contacting in an aqueous medium in a reactor a mixture comprising (a) vinyl chloride monomer or a mixture thereof with up to about 80% by weight of one or more vinylidene monomers having at least one terminal CH 2 ═C< grouping; (b) a dispersant for the monomer(s); (c) from about 0.0005 weight part to about 0.02 weight part, based on 100 weight parts of monomer(s) of a water-soluble inhibitor in an aqueous caustic solution, said inhibitor being selected from borohydrides having the formula ##STR2## wherein X is an alkali metal and wherein each of R, R' and R" may be hydrogen, phenyl, an alkyl group containing from 1 to 10 carbon atoms, or an alkoxy radical containing from 1 to 10 carbon atoms; and alkali metal nitrites, alkaline earth nitrites, or ammonium nitrite; (d) an oil-soluble, spirit-soluble nigrosine; (e) from about 0.001% by weight to about 1.0% by weight based on the weight of the monomer(s) of an oil-soluble, substantially water-insoluble free radical producing catalyst selected from dialkylperoxydicarbonates wherein the alkyl groups are straight chained or branched and contain from 4 to 14 carbon atoms, adjusting and maintaining the pH of said mixture greater than 7.0, and reacting said mixture at a temperature in the range of about 0° C. to about 100° C. and maintaining the pressure in the range of about 1 to 15 atmospheres throughout the reaction.