Patent ID: 7960443

Claim:
A method for producing an extruded styrenic resin foam as a building insulating board, comprising melting and mixing a styrenic resin mixture, a blowing agent, and a flame retardant to make a foamable molten resin composition, extruding and foaming the foamable molten resin composition to obtain an extruded foam having an apparent density of 22 to 50 kg/m 3 and a thickness of 10 to 150 mm, wherein the styrenic resin mixture is composed of a mixture of a resin (A) and a styrenic resin (B), wherein the resin (A) consists of a resin (A1) composed of a polymethyl methacrylate and/or styrene-methyl methacrylate copolymer containing a methyl methacrylate component at a ratio of 40% by weight or more, and a resin (A2), different from resin (A1), composed of a styrene-methyl methacrylate copolymer containing a methyl methacrylate component at a ratio of 5% by weight or more and less than 40% by weight, and the content of a methyl methacrylate component in the styrenic resin mixture is 4 to 45% by weight with reference to the styrenic resin mixture.