| abstract |
An extruded heat-insulating foamed polystyrene resin plate having excellent flame retardancy, low thermal conductivity, and excellent dimensional stability. A polystyrene resin is heated in an extruder, and a foamable molten resin mixture obtained by kneading with a foaming agent, a flame retardant and a cell regulator is extruded into a low pressure region through a die attached to the extruder tip. When foaming, the foaming agent is selected from (a) 20 to 70% by weight of isobutane and (b) 10 to 65% by weight of an aliphatic alcohol having 1 to 4 carbon atoms, based on the total amount of the foaming agent. One or more aliphatic alcohols, (c) 5 to 50% by weight of carbon dioxide, (d) 0 to 25% by weight of other physical blowing agents, and based on the total amount of blowing agents. The weight ratio of the aliphatic alcohol: X (% by weight) and the weight ratio of carbon dioxide to the total amount of the blowing agent: Y (% by weight) satisfy the expression (1). Formula (1): 7 ≧ X / Y ≧ 0.5 [Selection diagram] Fig. 1 |