Heat stabilizers for expandable styrene polymers

Claim 1

In a process for making styrene polymer particles less flammable by impregnating the polymer particles by heating in aqueous suspension in the presence of an organic halogen compound known to impart reduced flammability to styrene polymer particles and a blowing agent at temperatures greater that 100° C., the improvement comprising adding, prior to impregnation, about 0.2 to 4.0 percent by weight of a thermal stabilizer system for the organic halogen compound; said stabilizer system consisting essentially of a mixture of: (a) 0.06-1.2 percent by weight of barium nonylphenoxide; (b) 0.02-0.4 percent by weight of cadmium 2-ethylhexanoate; (c) 0.02-0.4 percent by weight of tricresyl phosphite; (d) 0.07-1.40 percent by weight of epoxidized soybean oil; and (e) 0.03-0.60 percent by weight of 2,2-bis [p-(1,2-epoxypropoxy) phenyl] propane, wherein the sum of (a), (b) and (c) is equal to the sum of (d) and (e), and all percents are based on the weight of styrene polymer particles; whereby the polymer molecular weight is not degraded during the impregnation process.