Abstract: There is described a method of making a styrene-type polymer composition which comprises a step of suspension polymerizing a styrene-type monomer composition in an aqueous medium comprising water, polyvinyl alcohol and a water-soluble sulfonated polystyrene, a water-soluble sulfonated styrene-maleic anhydride copolymer or a mixture thereof. Optionally, the styrene-type monomer composition may contain a rubbery material as a toughening agent. Optionally, the suspension polymerization step may be conducted subsequent to a prepolymerization step conducted in mass.

Abstract: Styrenic polymer particles having a uniform particle size distribution are prepared without the formation of fine polymer powders. The suspension polymerization process which comprises providing a stirred, aqueous suspension of polymeric seed particles, adding gradually to the suspension styrenic monomer and polymerizing it therein, and continuing the addition of monomer as the polymerization proceeds, may be improved by introducing the styrenic monomer below the surface of the suspension.