| abstract |
A process is provided comprising extruding a molten composition comprising thermoplastic polymer comprising polystyrene and blowing agent comprising either HFO-1234yf (2,3,3,3-tetrafluoropropene) or E-HFO-1336mzz (E-1,1,1,4,4,4-hexafluoro-2-butene) under the conditions (a) said composition being formed by melt mixing at a temperature of at least 180°C, (b) said melt mixing being carried out under a pressure of at least 2500 psi (172 Bar), (c) said extruding being carried out at a temperature of at least 120°C, and (d) said extruding being carried out under a pressure of at least 1250 psi (86 Bar), and obtaining as a result thereof a closed cell, smooth skin, low density foamed thermoplastic polymer comprising polystyrene, the foamed product thereby being free of macovoids and blowholes. |