Patent ID: 7803878

Claim:
An aqueous polymer emulsion comprising water and swollen multi-stage emulsion polymer wherein the dry bulk density of the swollen multi-stage emulsion is: less than 0.77 g/cc when the swollen multi-stage emulsion polymer has a particle size below 275 nm; less than 0.74 g/cc when the swollen multi-stage emulsion polymer has a particle size of from 275 to 500 nm; less than 0.59 g/cc when the swollen multi-stage emulsion polymer has a particle size of from 501 to 750 nm; less than 0.46 g/cc when the swollen multi-stage emulsion polymer has a particle size of from 751 to 1300 nm; wherein said multi-stage emulsion polymer comprises (I) a core stage polymer that comprises, as polymerized units, from 5 to 100 percent by weight, based on the weight of the core stage polymer, of hydrophilic monoethylenically unsaturated monomer, and from 0 to 95 percent by weight, based on the weight of the core stage polymer, of at least one nonionic monoethylenically unsaturated monomer; (II) a shell stage polymer that comprises, as polymerized units, at least 50 percent by weight of nonionic monoethylenically unsaturated monomer; (III) an intermediate stage polymer that partially or fully encapsulates said core stage polymer and that is partially or fully encapsulated by said shell stage polymer, wherein said intermediate stage polymer consists of as polymerized units, (a) 0.3 to 20 percent by weight, based on the weight of said core stage polymer, at least one hydrophilic monoethylenically unsaturated monomer, (b) 80 to 99.7 percent by weight, based on the weight of said core stage polymer, at least one nonionic monoethylenically unsaturated monomer.