Abstract: A process for producing monodispersed fine particles of a vinyl polymer is disclosed, which comprises polymerizing monomers containing at least one vinyl monomer selected from the group consisting of aromatic vinyl compounds, acrylic esters, and a methacrylic ester in the presence of (1) a surface active agent represented by formula (I) ##STR1## wherein R.sub.1 and R.sub.2, which may be the same or different, each represents a substituted or unsubstituted alkyl group having from 4 to 8 carbon atoms, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted cyclohexyl group and M represents an alkali metal, (2) from 10.sup.-3 to 10.sup.-1 mol/l of a persulfate as a polymerization initiator, and (3) from 10.sup.-4 to 10.sup.-2 mol/l of a divalent metal sulfate as an electrolyte. Monodispersed vinyl polymer fine particles having a particle size of 1 .mu.m or greater with a very narrow size distribution are obtained.

Abstract: A process for producing monodispersed fine particles of a vinyl polymer is disclosed, which comprises polymerizing monomers containing at least one vinyl monomer selected from the group consisting of aromatic vinyl compounds, acrylic esters, and a methacrylic ester in the presence of (1) a surface active agent represented by formula (I) ##STR1## wherein R.sub.1 and R.sub.2, which may be the same or different, each represents a substituted or unsubstituted alkyl group having from 4 to 8 carbon atoms, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted cyclohexyl group and M represents an alkali metal, (2) from 10.sup.-3 to 10.sup.-1 mol/l of a persulfate as a polymerization initiator, and (3) from 10.sup.-4 to 10.sup.-2 mol/l of a divalent metal sulfate as an electrolyte. Monodispersed vinyl polymer fine particles having a particle size of 1 .mu.m or greater with a very narrow size distribution are obtained.

Abstract: A process for producing monodisperse vinyl polymer fine particles is disclosed, which comprises polymerizing at least one monomer selected from the group consisting of vinyl aromatic compounds, acrylic esters, and methacrylic esters as dissolved in an organic solvent or a mixed solvent of water and an organic solvent, which is capable of dissolving said monomer or monomers but incapable of dissolving a produced polymer, wherein said polymerizing is carried out in the presence of partially saponified polyvinyl alcohol having a degree of saponification of from 5 to 75 mol % and a number average degree of polymerization of from 100 to 3,000 as a dispersion stabilizer and in the presence of a polymerization initiator. Monodisperse polymer particles having a particle size of the order of micron with a narrow size distribution can be obtained through the one-step polymerization.

Abstract: A process for producing a surface treated pigment wherein pigment particles are dispersed in a solution of a water soluble high polymer having radical generation sites to adsorb the water soluble high polymer on the surfaces of the pigment particles, adding a vinyl monomer to the resulting aqueous liquid dispersion of the pigment particles subjected to the adsorption treatment and polymerizing in the presence of a polymerization initiator, if desired, to form a polymer layer on the surfaces of the pigment particles. Formation of the white polymer particles composed only of polymer can be prevented and dispersion stability can be improved.