Process for producing spherical and porous vinyl resin particles

Claim 1

A process for producing spherical particles of polymer having high porosity which comprises, polymerizing one or more ethylenically unsaturated monomers having at least one terminal CH 2 ═C< group in the form of discrete droplets in an aqueous reaction medium containing, a monomer-soluble free radical yielding catalyst, a dispersant comprising a water-insoluble, crosslinked interpolymer of acrylic acid, and at least one surfactant containing one or more poly (ethylene oxide) segments, agitating said medium to form droplets of monomer(s) therein said agitator being operated at an rpm. in the range of about 10 rpm to 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 gallons to about 40,000 gallons, adding a water-soluble base to said medium to neutralize the dispersant to a pH of from about 4 to about 7, polymerizing said monomer(s) in a first stage at a temperature in the range of about 1.0° C. to about 100° C. with agitation below that at which the dispersion was formed, continuing the polymerizaton at said temperature and agitation to a conversion of about 10% to about 30% then increasing the agitation in a second stage to a level not more than that at which the dispersion was formed at the same temperature as in said first stage until the reaction is complete, and recovering the spherical, porous particles of polymer having a diameter in the range of about 30 microns to about 1000 microns, wherein polymer buildup on the surfaces of the reactor is substantially reduced.