Process for preparing stable emulsifierfree alkali metal-free latices of vinylidene monomers

Claim 1

IN THE PROCESS FOR PREPARING A STABLE SYNTHETIC RUBBER LATEX FREE OF EMULSIFIERS AND OF ALKALI METAL IONS BY THE POLYMERIZATION IN WATER OF SYNTHETIC RUBBER PRODUCING MONOMERIC MATERIAL COMPOSED ENTIRELY OF A CONJUGATED DIENE AND AT LEAST ONE VINYL MONOMER, AT LEAST ONE OF WHICH IS SOLUBLE IN THE WATER TO THE EXTENT OF AT LEAST 0.5% BY WEIGHT AT TEMPERATURE FROM ABOUT 10 TO 50*C., IN THE PRESENCE OF AMMONIUM PERSULFATE AND SULFUR DIOXIDE AND IN THE ABSENCE OF EMULSIFIERS AND ALKALI METAL IONS, THE IMPROVEMENT, DESIGNED FOR USE ON A PLANT SCALE TO AVOID SUBSTANTIAL FORMATION OF COAGULUM IN THE LATEX, WHICH CONSISTS OF THE STEPS OF (A) CHARGING POLYMERIZATION REACTOR WITH WATER, SAID MONOMERIC MATERIAL, AMMONIUM PERSULFATE AND SULFUR DIOXIDE (B) SUBJECTING THE CONTENTS OF THE REACTOR TO POLYMERIZING CONDITIONS, INCLUDING AGITATION WITHOUT PRODUCING SUBSTANTIAL SHEARING ACTION AND MAINTENANCE OF A TEMPERATURE IN THE RANGE OF 10 TO 30*C., TO PRODUCE A CONVERSION OF MONOMER TO POLYMER AT A RATE OF ABOUT 1 TO 3% PER HOUR AND MAINTAINING SAID POLYMERIZING CONDITIONS UNTIL ABOUT 3 TO 10% OF TOTAL MONOMER IS CONVERTED TO POLYMER AND (C) THEREAFTER RAISING THE TEMPERATURE OF THE CONTENTS OF THE REACTOR BY AT LEAST ABOUT 10*C. BUT TO A TEMPERATURE NO HIGHER THAN ABOUT 50*C. AND ADDING TO THE REACTION ADDITIONAL QUANTITIES OF SULFUR DIOXIDE WHILE MAINTAINING POLYMERIZING CONDITIONS UNTIL 60 TO 100% OF THE TOTAL MONOMER IS CONVERTED TO POLYMER, THE RELATIVE PROPORTIONS OF MATERIALS USED IN STEPS (A), (B) AND (C) BEING AS FOLLOWS: PARTS BY WEIGHT MONOMERIC MATERIAL -------------------- 100 WATER -------------------------------- 100 TO 200 AMMONIUM PERSULFATE ------------------ 0.5 TO 3 SULFUR DIOXIDE, OF WHICH AT LEAST 50% BUT NOT MORE THAN 2 PARTS IS ADDED IN STEP (C)-- 0.5 TO 3