| 摘要 |
PROBLEM TO BE SOLVED: To easily obtain a composite pipe different in diameter and wall thickness by extruding a foamable resin or a composite resin consisting of the foamable resin and a non-foamable resin in a tubular shape from an extrusion mold to expand the same, and passing the expanded extrudate through a forming tube having an inner diameter smaller than the outer diameter of the tubular resin at a time of extrusion at a speed faster than the extrusion speed from the extrusion mold. SOLUTION: A foamable resin 10 is extruded in a tubular shape through the space between the core 21 and land 22 of an extrusion mold 20, and the extrudate is pulled out at a speed faster than an extrusion speed by a pulling out device and passed through the forming tube 31 provided in a water tank 30 to be cooled by cooling water of spray orifices 32. The inner diameter (d) of the forming tube 31 is made smaller than the outer diameter D of the space part 23. Since the foamable resin 10 becomes a large outer diameter D' immediately after extrusion, it comes into close contact with the inner peripheral surface of the forming tube 31 and is mold into a pipe having wall thickness (t) less than the wall thickness T of the tubular resin immediately after extruded from the extrusion mold 20. In this case, this method can be also adapted to a resin composite pipe consisting of a foamable resin and a non-foamable resin.
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