| 摘要 |
Upon starting continuous extrusion, the temperature of a hard resin (32) and a soft resin (31) is increased in extrusion sections (20, 19). A screw (20a) of the extrusion section of the hard resin is set at high rpm at first. The hard resin reaches a maximum temperature ±(°C) by heating of friction with the screw, and comes to have high flowability. Upon starting conveyance of an assembly (28), a large amount of molten hard resin and a small amount of molten soft resin are extruded onto the periphery of a tubular structure (14). Upon passage of a point A of the tubular structure under annular discharge throats (30a, 29a), the extrusion amount of the hard resin starts gradually decreasing, and the extrusion amount of the soft resin starts gradually increasing. Since the temperature of the hard resin starts dropping a short time after the decrease in the extrusion amount, the hard resin maintains the high flowability.
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