Process for manufacturing bodies of polymeric material, having a core of foamed material enclosed in an outer shell

A process for manufacturing an article of polymeric material having a core of foamed material enclosed by an outer shell, the method comprising the steps of:

• (a) providing a mold comprising a pair of separable half-molds arranged facing each other;
• (b) extruding a substantially tubular thermoplastic parison having interior walls and exterior walls between the half-molds;
• (c) closing the half-molds around the parison, the mold and the parison having dimensions whereby a hollow space is formed between the parison and the exterior walls of the mold;
• (d) simultaneously with the closing of the two half-molds from step (c), injecting into the inside of the parison a foamable thermoplastic polymeric material admixed with a physical blowing agent, the injection being carried out in a time equal to 2 seconds or less;
• (e) the foamable thermoplastic polymeric material admixed with the physical blowing agent expanding within the parison, causing the parison to expand into contact with the walls of the mold so as to conform to the shape of the mold, and thermowelding the foamable thermoplastic material to the interior walls of the parison;
• and
• (f) removing the article from the mold.