Process for preparing polymer dispersions with a high solids content

摘要

A process for preparing copolymers based on vinyl esters and ethylene and, if desired, further comonomers in the form of their aqueous dispersions, having a solids content of greater than 65% and a Brookfield viscosity (20 s<−1) of less than 10,000 mPa.s, by means of free-radically initiated polymerization of one or more monomers selected from vinyl esters and ethylene and, if desired, further monomers copolymerizable therewith, in the presence of one or more protective colloids, polymerization being conducted in the presence of from 2 to 15% by weight of seed latex, based on the amount of vinyl ester, said process comprisinga) polymerizing without adding emulsifier, and in the presence of one or more polyvinyl alcohols protective colloids having a degree of hydrolysis of from 80 to 95 mol % and a Höppler viscosity in 4% strength aqueous solution of from 3 to 30 mPa.s, andb) introducing the seed latex in a fraction of from 30 to 75% by weight before beginning the polymerization and metering in the remainder during the polymerization, the seed latex having an average particle size (weight average Dw) of from 200 to 2000 nm.