PRODUCTION OF PLATY POLYSTYRENE RESIN FOAM

摘要

PROBLEM TO BE SOLVED: To produce a low-density polystyrene resin foam even when a blowing agent other then a chlorofluorohydrocarbon(CFC) is used. SOLUTION: An expandable composition prepared by kneading a stock resin comprising a polystyrene resin and a blowing agent is extrusion-foamed to produce a platy polystyrene resin foam. In order to heighten the pressure of the resin near the lip of the extruder by keeping the MFR of the stock resin at 1-10g/10min at which the foamability and moldability into a foam are not impaired, the z-average molecular weight (Mz) of the stock resin is selected so as to be 5×10<4> or above to heighten the content of high-molecular weight component in the stock resin. The Mw/Mn ratio is selected at 3.2 or above so as to broaden the molecular weight distribution of the stock resin and to permit the presence of a moderate amount of a low-molecular weight component. Thus the existence of the low-molecular-weight component assures the flowability of the stock resin during blowing.