Patent ID: 6632869
Filing Date: 2003-10-14
Classification: C08F

Abstract:
A process for preparing copolymers based on vinyl ester and ethylene comonomers and optionally further comonomers, in the form of their aqueous dispersions, said aqueous dispersions having a solids content of greater than 65% and a Brookfield viscosity of less than 10,000 mPaÂ·s, said process comprising:polymerizing one or more vinyl ester monomers and ethylene, and optionally further monomers copolymerizable therewith, in the presence of one or more protective colloids, said polymerizing conducted in the presence of a seed latex; wherein said polymerizing takes place without adding emulsifier, and in the presence of at least one polyvinyl alcohol protective colloid, said polyvinyl alcohol having a degree of hydrolysis of from 80 to 95 mol % and a HÃ¶ppler viscosity in 4% by weight aqueous solution of from 3 to 30 mPaÂ·s, and wherein from 30 to 75% of the total weight of the seed latex is introduced before beginning polymerizing and the remainder of said seed latex is metered in during polymerizing, the seed latex having a weight average particle size Dw of from 200 to 2000 nm, the total amount of said seed latex being from 2 weight percent to 15 weight percent based on the total weight of vinyl ester monomer(s).