Patent ID: 8247027

Claim:
A method for forming a composite particle comprising: (a) forming a first aqueous dispersion comprising a first polymeric particle having a diameter of from 100 nm to 3.5 microns comprising a core and a shell, said first polymeric particle bearing a first charge; said core comprising, when dry, at least one void; and said shell polymer having a calculated Tg greater than 50° C.; (b) forming a second aqueous dispersion comprising a second polymeric particle, said second polymeric particle bearing a charge opposite to that of said first polymeric particle, said second polymeric particle having a minimum film-forming temperature of greater than 20° C.; and (c) admixing said first aqueous dispersion and said second aqueous dispersion; wherein the ratio of the diameter of said first polymeric particle to the diameter of said second polymeric particle is from 1 to 50; wherein the ratio of the weight of said first polymeric particle to the weight of said second polymeric particle is from 0.1 to 40.