Expandable vinyl chloride resin composition

An expandable vinyl chloride resin composition comprising (1) 100 parts by weight of a vinyl chloride resin, (2) 0.5 to 30 parts by weight of, as a processing aid, a two stage (meth)acrylic acid ester polymer having a specific viscosity of not less than 0.5 measured at 30° C. with respect to a solution of 0.1 g of the polymer dissolved in 100 ml of chloroform, the two stage polymer being obtained by emulsion-polymerizing (a) 50 to 99 parts by weight of a monomer mixture comprising 50 to 100% by weight of methyl methacrylate, 0 to 50% by weight of at least one monomer selected from the group consisting of an acrylic acid ester and a methacrylic acid ester excepting methyl methacrylate and 0 to 20% by weight of other vinyl monomer copolymerizable therewith to give a polymer having a specific viscosity of not less than 0.7 measured at 30° C. with respect to a solution of 0.1 g of the polymer dissolved in 100 ml of chloroform and polymerizing, in the presence of a latex of the obtained polymer, (b) 1 to 50 parts by weight of a monomer mixture comprising 0 to 49% by weight of methyl methacrylate, 51 to 100% by weight of at least one monomer selected from the group consisting of an acrylic acid ester and a methacrylic acid ester excepting methyl methacrylate and 0 to 20% by weight of other vinyl monomer copolymerizable therewith wherein the total of the monomer mixtures (a) and (b) is 100 parts by weight, (3) 0.3 to 25 parts by weight of a thermally decomposable inorganic blowing agent and (4) 0.01 to 15 parts by weight of a thermally decomposable organic blowing agent.