Patent ID: 7776975

Claim:
A process for preparing an aqueous polymer dispersion comprising at least two disparate modes of polymer particles, comprising: providing a first polymer dispersion containing a first mode of first polymer particles dispersed in an aqueous medium; adding a hydrophobic polymerization blocker having a water solubility of less than 1 g/100 milliliter water at a temperature of 25° C. to said first polymer dispersion; and mixing the polymerization blocker and the first polymer dispersion for at least one minute; followed by adding and polymerizing ethylenically unsaturated monomer in the presence of said first polymer particles to provide a second mode of second polymer particles; wherein the polymerization blocker is allowed at least one minute after adding to partition into the first polymer particles prior to initiating polymerization of the ethylenically unsaturated monomer; and wherein said at least two disparate modes of polymer particles comprise said first mode of first polymer particles and said second mode of second polymer particles.