Process for producing polyvinyl acetate polymers

Claim 1

A PROCESS OF PRODUCING BY SOLUTION POLYMERIZATION A SUBSTANTIALLY LINEAR POLYVINYL ACETATE HOMOPOLYMER SUITABLE FOR CONVERSION BY SAPONIFICATION INTO POLYVINYL ALCOHOL OF A PREDETERMINED DEGREE OF POLYMERIZATION WHICH COMPRISES THE STEPS OF CONTINUOUSLY COMBINING VINYL ACETATE WITH METHANOL AND A POLYMERIZATION CATALYST SELECTED FROM THE GROUP CONSISTING OF ORGANIC PEROXIDES AND AZO COMPOUNDS IN A MIXING ZONE WHILE HEATING THE RESULTANT MIXTURE FOR 5 TO 30 MINUTES, CONTINUOUSLY INTRODUCING A STREAM OF THE HEATED MIXTURE INTO A FIRST POLYMERIZATION ZONE WHEREIN THE CONTENTS OF SAID POLYMERIZATION ZONE ARE MAINTAINED AT REFLUX TEMPERATURE, MAINTAINING THE INTRODUCED VINYL ACETATE, METHANOL AND CATALYST IN SAID FIRST POLYMERIZATION ZONE TO EFFECT PARTIAL HOMOPOLYMERIZATION AND TO PROVIDE A CONVERSION TO HOMOPOLYMER 0F AT LEAST ABOUT 15% OF THE VINYL ACETATE IN SAID INTRODUCED STREAM, CONTINUOUSLY TRANSFERRING A PORTION OF THE RESULTANT PARTIALLY-POLYMERIZED MASS TO A SECOND POLYMERIZATION ZONE WHEREIN THE CONTENTS OF SAID SECOND POLYMERIZATION ZONE ARE MAINTAINED AT REFLUX TEMPERATURE WHILE RECYCLING THE REMAINDER OF SAID PARTIALLY POLYMERIZED MASS TO SAID FIRST ZONE, THE RATIO OF RECYCLED PARTIALLY-POLYMERIZED MASS TO THE QUANTITY OF SAID PAR-