<p>A polymer dispersion comprises particles of a polymer composition formed at least partially by emulsion polymerization of first and second, simultaneously added, substantially styrene-free monomer feeds in the presence of an initiator in a reaction zone. The first monomer feed comprises monomers selected to produce a copolymer having a glass transition temperature less than or equal to about -10°C, while the second monomer feed comprises monomers selected to produce a copolymer having a glass transition temperature greater than or equal to about 50°C. The relative rate of addition of the first and second monomer feeds into the reaction zone is continuously changed during at least part of the emulsion polymerization and the rate of addition of the initiator is changed step-wise at least once during the addition of the first and second monomer feeds.</p>
