| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a biaxially oriented thermoplastic resin pipe, by which a biaxially oriented molding process can be smoothly started and a finished product showing an outstanding strength in the axial and the peripheral direction can be continuously obtained. SOLUTION: This method for manufacturing a biaxially oriented thermoplastic resin pipe comprises the steps to adjust the temperature of a thermoplastic resin pipe 21 extruded from an extrusion mold 12 to a specified orientation temperature level, to expand the diameter of the pipe 12 by making it pass over a diameter expansion mold 17 connected to the extrusion mold 12, and to biaxialy orient/mold the diameter- expanded pipe 21 in the peripheral and the axial direction while taking it up with the help of a take-up unit 19. The diameter expansion mold 17 is of such a structure that a headless conical part 171 has diameter gradually expanded in a direction where the pipe 21 proceeds. In addition, a recessed groove having a width which is 2/3 or less the wall thickness of the resin pipe 21, is formed, in the peripheral direction, on the surface of the headless conical part 171. Further, the area ratio of the recessed groove of the surface of the headless conical part to a part other than the recessed groove is set to be 1/4 or more. |
