Modified styrenic polymer beads

Claim 1

A bead product comprising a polystyrene bead having a styrene monomer-divinylbenzene copolymer relatively uniformly dispersed throughout the bead; said copolymer consisting essentially of styrene monomer and 0.02 to 0.85 percent by weight of divinylbenzene and said copolymer comprising 8 to 35 percent by weight of the total bead product; said bead product produced by the process comprising: (a) forming an aqueous suspension of initial styrene polymer beads having a weight average molecular weight of 230,000 to 350,000 with a polydispersity (Mw/Mn) of 2 to 3.1, with the aid of a suitable suspending agent system; said initial styrene polymer beads selected from the group consisting of polymers of styrene, alpha-methylstyrene, nuclear-methylstyrene, para-tert-butylstyrene, chlorostyrene, dichlorostyrene, mixtures of these, and copolymers of at least 50% styrene and up to 50% of other mono-ethylenically unsaturated monomers copolymerizable the therewith; (b) forming a comonomer solution of a styrene monomer and divinylbenzene; said styrene monomer being selected from the group consisting of sytrene, alpha-methylstyrene, nuclearmethylstyrene, para-tert-butylstyrene, monochlorostyrene, dichlorostyrene and mixtures thereof; (c) forming an emulsion comprising a suitable emulsifier and a portion of said comonomer solution; (d) adding the emulsion to the styrene polymer bead suspension at 25°-75° C. to allow the comonomers to be absorbed into the beads; (e) forming a second emulsion comprising a suitable emulsifier, the remaining portion of said comonomer solution, and free-radical-producing catalysts; (f) adding the second emulsion to the suspension of said beads absorbed with comonomers at 25°-75° C., at a rate such that the rate of absorption of comonomer/catalyst by said beads is at least equivalent to the rate of addition of emulsified comonomer/catalyst solution, then allowing said subpension to stand for 30 minutes to 4 hours, and then raising the temperature to 80°-95° C., and maintaining the suspension at said temperature to polymerize said comonomers; and