Reduced polymer buildup in condenser of reactor vessel

Claim 1

In a process for the suspension polymerization of vinyl chloride monomer in an aqueous medium in the presence of a dispersing agent(s) and a monomer-soluble polymerization initiator with agitation and primary cooling in a polymerization vessel, the improvement comprising mounting a reflux condenser on said polymerization vessel, said condenser being open to the vessel throughout the entire polymeriztion reaction, polymerizing said vinyl chloride monomer by maintaining the reaction mixture at a temperature in the range of about 40° C. to about 80° C., and adding into the reaction mixture at a constant rate during the course of the polymerization reaction from about 0.003% to about 0.5% by weight, based on the weight of said vinyl chloride monomer, of a nonionic surface active agent having an HLB in the range of about 9 to about 16 and selected from the group consisting of polyoxyethylene alkylphenols, polyoxyethylene alcohols, and polyalkylene oxide block copolymers having the general formula ##STR2## wherein the sum x and z is an integer from 3 to 73 and y is an integer from 20 to 56, wherein the addition of said surface active agent is started when conversion of monomer to polymer is in the range of about 5% to about 20%, whereby splashing of the reaction mixture and polymer buildup in said condenser are substantially eliminated.