Patent ID: 8535598

Claim:
A method for producing a tubular hollow foam molding having an average wall thickness of 1.0 to 3.0 mm and a thickness variation coefficient C v of 50% or less, said method comprising the steps of: (a) extruding a foamable melt comprising a polypropylene resin and a physical blowing agent through a die to obtain a tubular parison having a softened polypropylene resin foam layer, said polypropylene resin foam layer having throughout an equilibrium compliance J eo of 0.5×10 −3 to 1.8×10 −3 Pa −1 and a swell ratio S w of 2.5 or less; (b) placing said tubular parison in a mold; and (c) blowing a gas into said tubular parison to blow mold said tubular parison, thereby obtaining the tubular hollow foam molding having a hardened polypropylene resin foam layer with an apparent density of 0.35 to 0.65 g/cm3, wherein said physical blowing agent is used in an amount of 0.01 to 1.2 mols per 1 kg of said polypropylene resin.