COMPOSICION DE AGENTE PROPULSOR PARA LA PRODUCCION DE MATERIALES SINTETICOS TERMOPLASTICOS ESPONJADOS

Composición de agentes propulsores que contiene o se compone de < 50% en peso de 1,1,1,3,3-pentafluorobutano (HFC-365mfc) y > 50% en peso de 1,1,1,3,3-pentafluoropropano (HFC-245fa). Foamed, thermoplastic polymers are prepared using a propellant composition comprising pentafluoropropane and/or pentafluorobutane and at least a further propellant. A process for the production of foamed thermoplastic polymers (I) by foaming of a thermoplastic polymer using a propellant composition (II) is claimed. The propellant (II) comprises: (A) pentafluoropropane, preferably 1,1,1,3,3-pentafluoropropane (HFC-245 fa) and/or pentafluorobutane, preferably 1,1,1,3,3-pentafluorobutane (HFC-365 mfc) and (B) at least a further propellant consisting of low boiling , optionally halogenated hydrocarbons, ethers and halogenated ethers, difluoroethane (HFC-32), difluoroethane, preferably 1,1-difluoroethane (HFC-152a), 1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,2-tetrafluoroethane (HFC-134a), pentafluoropropane, preferably 1,1,1,3,3-pentafluoropropane (HFC-245 fa), hexafluoropropane, preferably 1,1,2,3,3,3-hexafluoro-propane (HFC-245a), hexafluoropropane, preferably 1,1,2,3,3,3-hexafluoropropane (HFC-236ea), 1,1,1,3,3,3-hexafluoropropane (HFC-236a) and/or heptafluoropropane, preferably 1,1,1,2,3,3,3-heptafluoropropane(HFC-227ea). Independent claims are included for: (i) the propellant composition (II) and (ii) a closed cell, thermoplastic foam, preferably of polystyrene, polyethylene, polypropylene, PVC or PET, preferably polystyrene, prepared by the process and containing (II) in the closed cells.