Process for preparing spherical and porous vinyl resin particles

A process for producing spherical particles of polymer having a high porosity which comprises polymerizing in an aqueous medium, in a reaction vessel having an agitator positioned therein, one or more ethylenically unsaturated monomers having a terminal CH.sub.2 .dbd.C<grouping in the form of discrete particles having a diameter in the range of about 30 microns to about 1000 microns, said aqueous medium containing a monomer-soluble free radical yielding catalyst, a dispersant comprising a substantially unneutralized, water-insoluble, crosslinked polymer of one or more carboxylic acid monomers with a polyunsaturated crosslinking monomer having a plurality of terminally unsaturated polymerizable groups and a water-soluble nonionic surfactant selected from the group consisting of polyoxyethylene alkylphenols, polyoxyethylene alcohols, polyoxyethylene esters of fatty acids, polyoxyethlene alkylamines, and polyoxyethylene alkylamides, conducting the polymerization at a temperature in the range of about 0.degree. C. to about 150.degree. C. with vigorous agitation in said aqueous medium throughout the entire polymerization reaction, said agitator being operated at an rpm in the range of about 10 rpm to about 275 rpm with a blade tip speed in the range of about 2 ft./sec. to about 65 ft./sec. using a reactor having a capacity of about 30 gallon to 40,000 gallons, and wherein polymer buildup on the surfaces of said reaction vessel is substantially reduced.