Patent ID: 7855239

Claim:
An extruded propylene-based resin foam that is formed by extrusion-foaming a propylene-based resin, the extruded propylene-based resin foam having: an expansion ratio of 10 or more; and an average cell diameter of 200 μm or less, wherein the propylene-based resin is a propylene-based multistage polymer comprising the following constituents (A) and (B): (A) a first constituent having an intrinsic viscosity [η] of more than 10 dL/g and less than or equal to 20 dL/g which is measured in a tetralin solvent at 135° C. comprising a propylene homopolymer component or a copolymer component of propylene and α-olefin having a carbon number of 2 to 8, the first constituent occupying 8 to 20 mass % of the propylene-based multistage polymer; and (B) a second constituent having an intrinsic viscosity [η] of 0.5 to 3.0 dL/g which is measured in a tetralin solvent at 135° C. comprising a propylene homopolymer component or a copolymer component of propylene and α-olefin having a carbon number of 2 to 8, the second constituent occupying 80 to 92 mass % of the propylene-based multistage polymer, wherein the closed cell content of said propylene-based resin foam is 40% or more.