Homopolymerization of vinyl acetate

Claim 1

A PROCESS FOR HOMOPOLYMERIZING VINYL ACETATE WHICH COMPRISES PASSING A LIQUID MIXTURE CONSISTING OF VINYL ACETATE MONOMER, A SOLVENT FOR SAID MONOMER, AND A POLYMERIZATION CATAYLST DOWNWARDLY THROUGH A PREHEATING ZONE CONSISTING OF AN ELONGATED COUNTERCURRENT GAS-LIQUID CONTACT ZONE, SAID CATALYST BEING A SYMMETRICAL AZONITRILE CAPABLE OF EFFECTING POLYMERIZATION OF VINYL ACETATE AND CONCURRENTLY LIBERATING NITROGEN WHEN HEATED WITH MONOMERIC VINYL ACETATE IN A SOLVENT, DURING THE INITIAL STAGE OF OPERATION SUPPLYING HEAT AND INERT GAS FROM AN EXTERNAL SOURCE TO SAID PREHEATING ZONE TO HEAT SAID LIQUID MIXTURE AND SAID INERT GAS AND PASSING THE HEATED INERT GAS UPWARDLY THROUGH SAID PREHEATING ZONE IN GAS-LIQUID CONTACT WITH SAID MIXTURE TO REMOVE OXYGEN FROM SAID MONOMER, TRANSFERRING SAID PREHEATED LIQUID MIXTURE CONSISTING OF VINYL ACETATE MONOMER FROM WHICH OXYGEN HAS BEEN REMOVED, SOLVENT AND POLYMERIZATION CATALYST INTO A POLYMERIZATION ZONE SEPARATE AND DISTINCT FROM SAID PREHEATING ZONE, POLYMERIZING VINYL ACETATE IN SAID LIQUID MIXTURE AT REFLUX TEMPERATURE IN SAID POLYMERIZTION ZONE THEREBY CAUSING THE EVOLUTION FROM SAID POLYMERIZATION ZONE OF GASES AT ELEVATED TEMPERATURE INCLUDING SOLVENT VAPORS AT SUBSTANTIALLY SAID REFLUX TEMPERATURE, AFTER THE INITIAL STAGE OF OPERATION DISCONTINUING THE SAID SUPPLY OF HEAT AND INERT GAS FROM AN EXTERNAL SOURCE TO SAID PREHEATING ZONE, TRANSFERRING THE EVOLVED GASES AT ELEVATED TEMPERATURE FROM SAID POLYMERIZATION ZONE TO SAID PREHEATING ZONE, PASSING SAID GASES UPWARDLY THROUGH SAID PREHEATING ZONE IN COUNTERCURRENT CONTACT WITH SAID LIQUID MIXTURE CONTAINING VINYL ACETATE MONOMER TO PREHEAT SAID MIXTURE AND REMOVE OXYGEN FROM SAID MONOMER, SAID GASES PROVIDING THE SOLE SOURCE OF HEAT AND THE SOLE MEANS FOR REMOVING OXYGEN FROM SAID LIQUID MIXTURE AFTER THE DISCONTINUANCE OF SAID EXTERNALLY SUPPLIED HEAT AND INERT GAS.