To provide a polystyrene-based resin-extruded foamed plate with a low apparent density, excellent in flame resistance, comprising a foaming agent using carbon dioxide as principal ingredient.
The polystyrene-based resin-extruded foamed plate is obtained by kneading a base resin comprising a polystyrene-based resin blended with an ethylenic copolymer having carbonyl group, a foaming agent comprising 60-100 mol% of carbon dioxide and 40-0 mol% of other physical foaming agent (excluding chlorofluorocarbons) to the total foaming agent, and a flame retardant, and extruding, wherein 2-8 pts.wt. of the ethylenic copolymer having carbonyl group is contained in the 100 pts.wt. of the polystyrene-based resin in the polystyrene-based resin-extruded foamed plate, the polystyrene based resin composition constituting the polystyrene-based resin-extruded foamed plate has 1.5×105-2.5×105 of the weight-average molecular weight and a ratio of Mw/Mn of weight-average molecular weight (Mw) to number-average molecular weight (Mn) of 2.3 or more, having thickness of 10 mm or more and at least 50 cm2 of cross section, 20-50 kg/m3 of apparent density, 0.1-0.7 mm of average diameter of the foam in thickness direction, and having at least 80% of closed cell ratio.
TAIRA ATSUSHI
KOGURE NAOCHIKA
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