A process for producing bodies of polymeric material having an outer shell and a core of foamed material is disclosed. The process includes the steps of: providing a mold having a pair of separable half-molds arranged facing each other; extruding a tubular thermoplastic parison between the half-molds;...http://www.google.com.au/patents/US5609803?utm_source=gb-gplus-sharePatent US5609803 - Process for manufacturing bodies of polymeric material, having a core of foamed material enclosed in an outer shell
