Patent ID: 7166248

Claim:
A method for producing an alkenyl aromatic polymer foam structure comprising: melting at least one alkenyl aromatic polymer resin; dissolving a blowing agent mixture in the at least one alkenyl aromatic polymer resin, wherein the blowing agent mixture is less than about 4.5 wt. % based on a total mixture of the at least one alkenyl aromatic polymer resin and the blowing agent mixture and wherein the blowing agent mixture comprises at least one volatile organic compound (VOC) blowing agent and acetone, the VOC blowing agent being selected from the group consisting of n-butane, propane and combinations thereof; forming an extrudate comprising the at least one alkenyl aromatic polymer resin, the at least one VOC blowing agent, and acetone, the extrudate comprising less than about 2.7 wt. % of the at least one VOC blowing agent; and permitting the extrudate to expand to produce the alkenyl aromatic polymer foam structure, the alkenyl aromatic polymer foam structure having an extruded density less than about 7 lbs/ft 3 and a basis weight of less than about 20 grams per 100 in 2 .