Patent ID: 7217762

Claim:
A process for the preparation of monodisperse polymer particles having diameters of 1 to 6 μm which process comprises: forming an aqueous dispersion comprising monodisperse swellable seed particles, an anionic surfactant, and droplets comprising dioctanoyl peroxide; contacting the aqueous dispersion of seed particles with a monomer selected from the group consisting of acrylic monomers, methacrylate monomers and vinyl monomers selected from the group consisting of styrene, divinylbenzene (DVB), ethyl vinyl benzene, vinyl pyridine, amino-styrene, methyl-styrene, dimethylstyrene, ethyl styrene, ethyl-methyl-styrene, p-chlorostyrene and 2,4-dichlorostyrene; allowing the monomer to diffuse into the seed particles to form an aqueous dispersion of swollen seed particles; and initiating polymerization of the monomer in the aqueous dispersion of swollen seed particles wherein the aqueous phase of the aqueous dispersion of swollen seed particles during polymerisation further containing as a steric stabilizer a polyvinylpyrrolidone.