PROCESS FOR PRODUCING DIFFICULTLY INFLAMMABLE EXPANDABLE STYRENE POLYMERS

Fine particulate expandable flame retardant styrene polymers having an improved minimum mold dwell time and reduced block shrinkage are prepared by: (a) mixing together styrene monomer or a mixture of styrene and a cpolymerizable monomer with an organic halogen compound and an expanding agent in an aqueous disperson; (b) adding before or during polymerization to the mixture of (a) from 0.0001 to 0.1% by weight of an epoxidation product of an aliphatic hydrocarbon of which the epoxidated aliphatic chain comprises from 6 to 18 C atoms, this epoxidation product being soluble in the monomers; (c) carrying out a polymerization in the aqueous suspension of (a) and (b) using radical forming initiators at temperatures of 80 DEG C.-130 DEG C. to form expandable particles; (d) pre-forming the expandable particles resulting from (c); (e) ageing the pre-formed particles of (d); and (f) molding the pre-formed and aged particles of (e) in a pressure resistant mold.