Patent ID: 7179531

Claim:
A polymer composition comprising multistage polymer particles; wherein each of said multistage polymer particles comprises: a) a first polymer comprising: i) a polymerized unit of a multiethylenically unsaturated monomer, and ii) at least one pendant absorbing group selected from the group consisting of phosphorus acid groups, phosphorus acid full-ester groups, polyacid sidechain groups, and mixtures thereof, wherein said first polymer has a glass transition temperature in the range of from −60° C. to 35° C.; and b) a second polymer having a glass transition temperature in the range of from −60° C. to 35° C., wherein said second polymer is substantially free of said at least one pendant absorbing group; wherein the average weight ratio of said first polymer to said second polymer is in the range of from 1:2 to 1:20.