Process for producing coated beads with macromonomer-styrene polymerizate coating

Claim 1

A process for forming coated styrenic polymer beads which exhibit anti-lumping properties upon preexpansion and which are useful in producing soft foamed articles comprising: (a) forming an aqueous suspension of initial styrenic polymer beads with the aid of a finely divided, difficulty water-soluble, inorganic phosphate suspending agent and a modifier therefore; (b) forming an emulsion containing a coating composition, consisting of a major amount of a styrenic monomer and a minor amount of a conjugated diene-styrene macromonomer, which is an anionically prepared polymer of molecular weight between 5000 and 50,000 terminated with a reactive monofunctional polymerizable group, 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 surfactants containing at least thirty 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 temprature; and maintaining the mixture so formed at an elevated temperature to cause said coating composition to polymerize and form a coating about said initial styrene beads.