Abstract: Expandable styrene polymer particles are surface-coated with calcium polysilicate to prevent the particles from lumping together during expansion. The coating is applied by adding 0.02-0.05 part of calcium polysilicate to an aqueous suspension containing 100 parts of polymer particles subsequent to impregnating the mixture with a blowing agent, or by dry-blending polymer particles with the polysilicate.

Abstract: Expandable styrene polymer particles which have fast cooling rates during molding are produced by suspending styrene polymer particles in an aqueous medium and impregnating a blowing agent into the particles in the presence of 0.05 to 0.4 parts of silicone surfactant per 100 parts of polymer particles. The silicone surfactant is selected from the siloxane-oxyalkylene copolymers having at least one polysiloxane block which contains mers of the general formula R.sub.2 SiO, where R is selected from the group consisting of alkyl having 1 to 4 carbon atoms and halogenated alkyl having 1 to 4 carbon atoms, and at least one polyoxyalkylene block containing mers of general formula C.sub.n H.sub.2n O, where n is 2, 3 or 4, attached to said polysiloxane block and terminated by hydroxyl groups.

Abstract: Expandable styrene polymer particles which have fast cooling rates during molding are produced by dry blending styrene polymer particles in the presence of 0.05 to 0.4 parts of silicone surfactant per 100 parts of polymer particles. The silicone surfactant is selected from the siloxane-oxyalkylene copolymers having at least one polysiloxane block which contains mers of the general formula R.sub.2 SiO, where R is selected from the group consisting of alkyl having 1 to 4 carbon atoms and halogenated alkyl having 1 to 4 carbon atoms, and at least one polyoxyalkylene block containing mers of general formula C.sub.n H.sub.2n O, where n is 2, 3 or 4, attached to said polysiloxane block and terminated by acetoxy or alkyl ether groups.