Process for copolymerizing vinylidene chloride and acrylonitrile

Claim 1

IN THE PROCESS FOR PREPARING NORMALLY CRYSTALLINE COPOLYMERS OF VINYLIDENE CHLORIDE AND ACRYLONITRILE IN AQUEOUS DISPERSION WHEREIN AN AQUEOUS PHASE CONSISTING OF ALL THE WATER TO BE USED, A POLYMERIZATION CATALYST, AND AN EMULSIFYING AGENT IS PREPARED, SAID AQUEOUS PHASE IS HEATED TO THE PREDETERMINED TEMPERATURE OF POLYMERIZATION, THEN THERE IS DISPERSED IN SAID HEATED AQUEOUS PHASE AN INITIAL INCREMENT OF COMONOMERS COMPOSED OF AT LEAST 70 PERCENT BY WEIGHT VINYLIDENE CHLORIDE WITH THE REMAINDER OF ACRYLONITRILE, SAID INITIAL INCREMENT BEING OF AN AMOUNT OF NOT OVER 20 PERCENT OF THE TOTAL WEIFHT OF COMONOMERS TO BE ADDED, THE DISPERSION IS ALLOWED TO ATTAIN ITS SATURATION PRESSURE AND THE POLYMERIZATION TO PROCEED UNTIL THE PRESSURE IN THE VESSEL HAS DROPPED TO AN OPERATING PRESSURE, WHICH IS AT LEAST ONE POUND PER SQUARE INCH BELOW SAID SATURATION PRESSURE, AND THE POLMERIZATION IS CONTINUED BY ADDING THE REMAINDER OF THE COMONOMERS IN THE RATIO OF THAT OF THE FINAL COPOLYMER AT A RATE SO THAT SAID OPERATING PRESSURE REMAINS SUBSTNATIALLY CONSTANT, THE IMPROVEMENT COMPRISING THE DISPERSING OF SAID INITIAL INCREMENT OF COMONOMERS IN A RATIO IN WHICH THE ACRYLONITRILE IS PRESENT IN A CONCENTRATION IN EXCESS OF FROM 50 TO 100 PERCENT BASED ON THE PERCENTAGE OF ACRYLONITRILE DESIRED IN THE COPOLYMER.