| 摘要 |
<p>PROBLEM TO BE SOLVED: To stably produce a resin-lined steel pipe by forming a resin lining layer from a crosslinked polyethylene resin of which the max. arrival crosslinking degree is a specific value as a gel ratio. SOLUTION: A crosslinked polyethylene resin to be used is 10-80% in its max. arrival crosslinking degree as a gel ratio and a crosslinked polyethylene resin pipe has an adhesive layer comprising maleic anhydride-modified polyethylene or the like on the outer surface thereof and molded by the coextrusion from a two-layered die when a crosslinked polyethylene layer is formed. The formed resin pipe having an outer diameter smaller than the inner diameter of a steel pipe by a predetermined ratio and length larger than that of the steel pipe by a predetermined ratio is inserted in the steel pipe and heated by a high frequency heating device or a hot air oven so that the surface temp. of the steel pipe becomes predetermined temp. The resin pipe in the steel pipe is heated by the heat transfer from the steel pipe and closely bonded to the inner surface of the steel pipe by the restoring force to the shape of the resin pipe before stretching and, after cooling, the resin pipe protruded from the end part of the steel pipe is cut to obtain a resin lining steel pipe. By this constitution, the inner surface lining of steel pipe with the resin pipe can be stably performed even if time is elapsed after the production of the resin pipe.</p> |
