Process for producing plasticized elastomer-styrene coated beads

A process for forming coated styrenic polymer beads for use in producing low density soft foamed articles comprising:

• (a) forming an aqueous suspension of initial styrenic polymer beads with the aid of a finely divided, difficultly water-soluble, inorganic phosphate suspending agent and a modifier therefor,
• (b) forming an emulsion containing a plasticized coating composition consisting of a major amount of a styrenic monomer, a minor amount of a conjugated diene elastomer, and a minor amount of a plasticizer therefor, and containing a styrenic-monomer-soluble free-radical-producing catalyst, in an aqueous medium containing a nonionic surfactant comprising an ethylene oxide condensate of an alkylphenol, selected from octylphenols and nonylphenols, said surfactant containing at least thrity moles of ethylene oxide per mole of alkylphenol;
• (c) adding said emulsion to said styrenic polymer bead suspension to form a mixture thereof, while maintaining the suspension at an elevated temperature;
• and maintaining the mixture so formed at an elevated temperature to cause said coating composition to polymerize and form a coating about said initial styrenic polymer beads.