Abstract: At least one vinylidene halide monomer is polymerized in an aqueous emulsion medium in admixture with ammonium persulfate and at least one ammoniated anionic emulsifier, preferably also together with hydrogen peroxide. The polymerization process is maintained at a pH of at least about 8.5 using ammonium hydroxide. The polymerization process is conducted in the substantial absence of alkali metal ions. Polymerization is both rapid and linear. The resulting polymers have excellent heat stability and water whitening resistance.

Abstract: There is disclosed a process for preparing vinyl dispersion resins by conducting the polymerization reaction of the vinyl monomer or monomers in an aqueous alkaline medium, using an oil-soluble polymerization initiator, at temperatures preferably below about 48.degree. C., in the presence of an emulsifier system comprising the ammonium salt of a high fatty acid containing from 8 to 20 carbon atoms and at least one long chain alcohol containing from 14 to 24 carbon atoms, wherein the ratio of alcohol to emulsifier is equal to or greater than 1.0 and wherein the reaction ingredients are thoroughly mixed, and preferably homogenized, prior to polymerization. The process produces paste resins having improved heat stability and flow properties and capable of producing films having high clarity and improved water resistance. More importantly, polymer build-up in the reactor is substantially reduced and multiple polymerizations can be run in the reactor without opening the same.