Patent ID: 8398908

Claim:
A method for the production of a plastics pipe comprising an inner core, which is comprised of polyethylene, and an outer removable skin layer bonded thereto, which is comprised of propylene homo- or co-polymer, or propylene block co-polymer, wherein the outer removable skin layer has a thickness within the range of from 0.3 mm to 2.0 mm, which method comprises co-extruding molten polymeric materials forming the inner core and the outer removable skin layer from one or more extruder dies, bringing the polymeric materials together and allowing them to solidify, and conditioning the solidified polymeric materials, by heating externally the extruded pipe with the external heat applied being sufficient to raise a temperature of the skin layer and a bond-line between the skin layer and the inner core such that an outer surface temperature of the extruded pipe is from about 40°-100° C., and wherein the outer surface temperature of the extruded pipe is maintained for a period of from about 6 to 100 seconds, at a temperature and for a time sufficient to influence the adhesion of the outer skin layer to the inner core, such that on cooling the adhesion of the outer skin layer to the inner core is sufficient to prevent substantial undesired relative movement between the skin layer and the core during installation of the pipe, but insufficient to prevent the outer skin layer from being cleanly removed by peeling, at least at the ends of the pipe, and insufficient to cause a substantial reduction in the impact strength of the inner core.