US Patent 7462307 Singlelayer and multilayer polyolefin foam pipes

Process for producing single layer and multilayer polyolefin foam pipes with improved compression resistance having a polyolefin foam layer which consists of mixtures of modified propylene polymers having strain hardening behaviour or propylene homopolymers with a stereospecificity index >98% or propylene copolymers with a stereospecificity index of the homopolymer matrix of >96%. The polyolefin foam pipes include coated steel pipes for transporting crude oil or gas products or district heating applications, single layer pipes for insulation purposes and for non- or low-pressure applications and multilayer plastic pipes for the transportation of hot or cold fluids.