Plastic pipe manufacture involves extrusion of pipe material including cross-linking agent and applying steam to initiate cross-linking of plastic

摘要

A cross-linkable plastic is extruded(2) to form a tube or pipe(1) which, as it is conveyed away in a continuous length, is subjected to a system which cross-links(6) the plastic. When the cross-linkable plastic forms the inner layer of the pipe(1) the cross-linking system is introduced(6) into the interior of the pipe. The plastic pipe is cooled(4) during the cross-linking treatment in which the cross-linking agent diffuses into the plastic immediately after the extrusion stage. Cross-linking is effected by a pressurized medium, in particular steam. Steam pressure is 0.1-1bar above atmospheric pressure and at 100-200[deg]C. Pipes may be multi-layered with the cross-linkable plastic on the inside and/or outside. Wall thickness of the cross-linkable layer is 10% of the pipe wall thickness.