Polymer dispersions, their preparation and use

An emulsion polymerization process comprising:

• (i) polymerizing, in a first stage, a first monomer composition comprising from 50 weight percent to 95 weight percent of vinyl acetate, from 5 weight percent to 40 weight percent of at least one vinyl ester of a C5 to C18 unsaturated carboxylic acid, optionally up to 40 weight percent of ethylene, optionally up to 40 weight percent of at least one alkyl ester of acrylic acid, and optionally up to 20 weight percent of one or more further monomers copolymerizable therewith, all based on the total weight of monomers in the first monomer composition, to produce a first stage polymer;
• and
• (ii) polymerizing, in a second stage and in the presence of said first stage polymer, a second monomer composition comprising 40 weight percent to 89.95 weight percent of at least one alkyl ester of methacrylic acid or a vinyl aromatic monomer, 10 weight percent to 59.95 weight percent of at least one alkyl ester of acrylic acid, and from 0.05 weight percent to 10 weight percent of at least one comonomer with acid functionality, based on the total weight of monomers in the second monomer composition, to produce a second stage polymer,
• wherein the weight ratio of the first stage polymer to the second stage polymer is from 95:5 to 25:75.