SUBSTANTIALLY FLAT SURFACED VINYL POLYMER EMULSION PARTICLES HAVING A CONCAVITY AND A PROCESS FOR PREPARING THEM

摘要

Substantially flat surfaced emulsion particles of polymerized vinyl monomer, having a concavity in at least one of the flat surfaces, diameter (D) of from 0.1 to 5.0 mu m, and a particle diameter/thickness (d) ratio (D/d) of 1.2 to 5.0, prepared by the step of (1) aqueous emulsion polymerizing a first vinyl monomer or mixture of monomers (a) to form vinyl polymer seed particles; and (2) aqueous emulsion polymerizing a second vinyl monomer or mixture of monomers (b) in the presence of the vinyl polymer seed particles and a non-aqueous organic solvent having a surface tension to water at 20 DEG C of 48 dyne/cm or more, in a weight ratio of monomer (a) to monomer (b) of 0.5/99.5 to 50/50; are useful in high performance recording material, paint compositions and paper coating compositions.