Process for extruding stabilized expanded polystyrene composition

Claim 1

A process of preparing expanded polystyrene which comprises preparing a foam extruder feed material comprising from about 20 to about 50 parts by weight of solid pellets of previously expanded recycle foam polystyrene, said recycle polystyrene having been reduced from expanded foam by compaction and extrusion at temperatures in the 400°-550° F. range and by repelletization, and from about 80 to about 50 parts by weight of pellets of virgin polystyrene; and from about 0.01 to about 0.5 parts by weight of 1,1,3-tris(2-methyl-4-hydroxy-5-tertiary butyl phenyl) butane and from about 0.02 to about 1.0 parts by weight of tris(mixed mono- and dinonyl phenyl) phosphite; feeding said feed material to a first stage being an extruder operating at temperatures of from 400°-550° F. so as to melt and homogeneously mix the feed material; adding blowing agent to said molten material in the first stage, and dispersing the blowing agent within the molten material therein; feeding the material to a second stage being a section of said extruder or a second extruder operating at lower temperatures so as to cool the feed material to temperatures of from about 230°-315° F.; and extruding the material from said second stage through a die, at a temperature of from about 230°-215° F., and foaming the extrudate.