Insulating thermoplastic foams made with methyl formate-based blowing agents

A process for preparing a foam structure aromatic polymer insulating alkenyl comprising: melting a thermoplastic alkenyl aromatic polymer; dissolving an effective amount of a combination of blowing agent in the alkenyl aromatic polymer to define a mixture, comprising combining blowing agent methyl formate and at least one co-blowing agent; form an extruded from the mixture; and expanding the extrudate to produce the foam structure characterized alkenyl aromatic polymer that the at least one co-agent is selected from the group blower consisting of a hydrocarbon, methyl fluoride, difluoromethane (HFC-32), trifluoromethane (HFC- 23), perfluoromethane, chlorodifluoromethane (HCFC-22), methylene chloride, ethyl chloride, ethyl fluoride, 1, 2-difluoroethane (HFC-152), 1, 1-difluoroethane (HFC-152a), 1, 1, 1-trifluoroethane (HFC-143a), 1, 1, 1, 2-tetrafluoroethane (HFC-134a), pentafluoroethane (HFC-125), perfluoroethane, 1, 1-dichloro-1-fluoroethane (HCFC-141b), 1 -chloro-1, 1-difluoroethane (HCFC-142b), 1, 1-dichloro-2, 2, 2trifluoroetano (HCFC-123) and 1-chloro-1, 2, 2, 2-tetrafluoroethane (HCFC-124), difluoropropane, 1, 1, 1-trifluoropropane, 1, 1, 1, 3, 3-pentafluoropropane (HFC-245fa), 1, 1, 1, 2, 3, 3-hexafluoropropane (HFC-236ea), 1, 1, 1, 2, 3, 3, 3heptafluoropropano (HFC-227ea), perfluoropropane, 2, 2, 4, 4, 4-pentafluorobutane (HFC-365mfc), perfluorobutane, perfluorocyclobutane, vinyl fluoride, an ester, an acetal, an alkanol , a carbonate, an amine, a ketone, an inorganic agent and a chemical blowing agent and the foam structure of the alkenyl aromatic polymer is a foam structure aromatic polymer insulating alkenyl with a value of R 4 per inch ( 1, 57 cm) or greater.