Patent ID: 7638576

Claim:
An aqueous polymer dispersion comprising multi-stage polymeric particles of from 20 to 80 wt. %, based on the weight of the said polymeric particles, of one or more first polymer formed by polymerizing a first monomer mixture of a) one or more non-ionic ethylenically unsaturated monomers and b) from 0.5 to 10 wt. %, based on the total weight of a) and b), of one or more ethylenically unsaturated acid monomers, and one or more second polymer formed by polymerization in the presence of an aqueous dispersion of the said one or more first polymer of a second monomer mixture comprising from 1 to 90 wt. %, based on the total weight of the said second monomer mixture, of one or more ethylenically unsaturated monomers bearing one or more epoxy groups, wherein 90 mole % or more of the said epoxy groups, based on the moles of epoxy groups in the said second monomer mixture, are retained in the aqueous dispersion after said dispersion is stored in a sealed container for 10 days at 60° C.