Process for producing aqueous emulsions of vinyl chloride/vinyl acetate/ethylene terpolymers

摘要

In the process for producing the aqueous emulsion of vinyl chloride/vinyl acetate/ethylene terpolymer by polymerizing vinyl chloride, vinyl acetate and ethylene in an aqueous dispersion system under ethylene pressure in the presence of an emulsifier and/or protective colloid using a radical initiator, the improvement which comprises adding vinyl chloride and vinyl acetate to said aqueous dispersion system at substantially fixed rates while maintaining a required amount of unreacted vinyl acetate in the system, and, after completion of addition of vinyl chloride, adding additional vinyl acetate of 3 to 20% by weight based on the total amount of vinyl acetate which has been added until that time and continuing the polymerization until the concentration of vinyl acetate in the system is decreased to 1% by weight or less, wherein the volume of the aqueous dispersion system is at least 50% by volume based on the volume of the reactor when addition of the additional vinyl acetate is completed. By this process, the amount of unreacted vinyl chloride in said aqueous emulsion can be decreased to a large extent.