Copolymerization of vinyl chloride and vinyl acetate

Claim 1

A PROCESS FOR PREPARING WHITE, GRANULAR, FREE FLOWING COPOLYMERS OF VINYL CHLORIDE AND VINYL ACETATE BY AQUEOUS SUSPENSION POLYMERIZATION, WHICH COMPRISES POLYMERIZING A VINYL CHLORIDE-VINYL ACETATE MONOMER MIXTURE IN AN AQUEOUS SUSPENSION POLYMERIZATION SYSTEM, SAID MONOMER MIXTURE CONTAINING FROM ABOUT 75% TO 95% BY WEIGHT OF VINYL CHLORIDE AND FROM ABOUT 5% TO 25% BY WEIGHT OF VINYL ACETATE, SAID SYSTEM CONTAINING FROM ABOUT 0.15% TO ABOUT 0.4% BY WEIGHT OF SAID MONOMER MIXTURE OF A POLYVINYL ALCOHOL BEING FROM 80% TO 95% HYDROLYZED AND HAVING A VISCOSITY OF ABOUT 25 CENTIPOISES TO ABOUT 100 CENTIPOISES IN A 4% AQUEOUS SOLUTION AT 20* C., SAID SYSTEM CONTAINING FROM ABOUT 0.5% TO ABOUT 3% BY WEIGHT OF SAID MONOMER MIXTURE OF A CHLORINATED HYDROCARBON CONTAINING FROM 1 TO 3 CARBON ATOMS, SAID SYSTEM CONTAINING FROM ABOUT 0.1% TO ABOUT 0.5% BY WEIGHT OF SAID MONOMER MIXTURE OF A FREE RADICAL INITIATOR EFFECTIVE FOR THE POLYMERIZATION OF VINYL COMPOUNDS, SAID SYSTEM CONTAINING AN AMOUNT OF ALKALINE BUFFER COMPATIBLE WITH SAID POLYVINYL ALCOHOL AND SUFFICIENT TO ADJUST THE INITIAL PH OF SAID SYSTEM TO ABOUT 7.5 TO ABOUT 8.0, WHERE THE INITIAL PRESSURE OF SAID SYSTEM IS FROM ABOUT 80 P.S.I.G. TO ABOUT 150 P.S.I.G. AND WHERE THE TEMPERATURE OF SAID SYSTEM DURING SAID POLYMERIZATION IS WITHIN THE RANGE FROM ABOUT 50*C. TO ABOUT 70*C., AND TERMINATING SAID POLYMERIZATION BEFORE ALL OF SAID VINYL CHLORIDE AND ALL OF SAID VINYL ACETATE HAVE REACTED.