Process for the preparation of a dispersible vinyl acetate/ethylene polymer powder

Claim 1

A PROCESS FOR THE PREPARATION OF A FREE-FLOWING AND EASILY DISPERSIBLE POLYMER POWDER COMPRISING A COPOLYMER OF VINYL ACETATE AND THYLENE AND OPTIONALLY AT LEAST ONE FURTHER OLEFININCALLY INSATURATED MONOMER, WHEREIN SAID COPOLYMER IS DRIED IN A TOWER AS AN AQUEOUS DISPERSION PREPARED BY COPOLYMERIZATION OF THE MONOMERS IN AN AQUEOUS SYSTEM AT AN ETHYLENE PRESSURE OF UP TO 100 ATMOSPHERES AND IN THE PRESENCE OF FROM 0 TO 1 % BY WEIGHT, CALCULATED ON THE POLYMER, OF AN IONIC EMULSIFIER, THE IMPROVEMENT COMPRISING ADDING TO SAID AQUEOUS SYSTEM FOR 5 TO 20% BY WEIGHT, CALCULATED ON THE POLYMER, OF AT LEAST ONE POLYVINYL ALCOHOL WITH A DEGREE OF SAPONIFICATION OF FROM 80 TO 92 MOL % AND A VISCOSITY OF A 4% AQUEOUS SOLUTION OF SAID POLYVINYL ALCOHOL AT 20*C FROM 3 TO 35 CP, SAID COPOLYMERIZATION BEING IN THE PRESENCE OF A FREE RADICAL INITIATOR IN SAID AQUEOUS SYSTEM, AND SPRAY DRYING SAID AQUEOUS DISPERSION BY SIMULTANEOUSLY INTRODUCING INTO A SPRAY-DURING TOWER AT LEAST ONE DRY ANTICAKING AGENT SELECTED FROM THE GROUP CONSISTING OF ALUMINUM SILICATE, SILICA AND CALCIUM CARBONATE IN AN AMOUNT OF FROM 3 TO 30 % BY WEIGHT, CALCULATED ON THE SOLIDS CONTENT OF THE AQUEOUS DISPERSION, SAID ANTICAKING AGENT HAVING AN AVERAGE PARTICLE SIZE OF FROM 0.01 TO 0.5 $.