Patent ID: 6245851
Filing Date: 2001-06-12
Classification: C08F

Abstract:
In a process for producing a vinyl acetate/ethylene aqueous based emulsion containing polymerized vinyl acetate/ethylene resin particles, wherein said polymerized resin particles contain from 65% to 95% vinyl acetate by weight, from about 5-35% ethylene by weight and 0 to 10% of a comonomer by weight, the improvement for producing a vinyl acetate/ethylene based emulsion having a solids content of from 65 to 70% by weight and a particle size diameter ratio wherein the weight average particle size diameter D.sub.w to number average particle size diameter D.sub.n is greater than 3 which comprises:effecting polymerization in at least two backmixed reaction vessels in series comprised of a primary vessel reaction vessel and a secondary reaction vessel wherein the reactants and products are continuously and sequentially introduced and removed respectively;effecting polymerization in said primary vessel at a pressure of from 500 to 1000 psig while maintaining an unreacted vinyl acetate content of from 25 to 45% by weight;transferring the contents from the primary vessel to the secondary vessel without venting the ethylene;effecting polymerization in the secondary vessel at a pressure of from 200 to 400 psig while maintaining an unreacted vinyl acetate content of less than 5% by weight; and,effecting polymerization in the presence of a stabilizing system consisting essentially of low molecular weight poly(vinyl alcohol) having a degree of polymerization of from 200 to 1000 and having a molar hydrolysis value of from 87 to 99%.