| 摘要 |
PURPOSE:To obtain an expected smooth pipe with high roundness by a method wherein thermoplastic resin pipe, which is extruded from a die and is in molten state, is led to a refrigerant tank so as to heighten its melt viscosity up to a degree not so higher as the viscosity in perfectly solidified state and, after that, sized under reduced pressure at a vacuum chamber. CONSTITUTION:A sizing device 4 consisting of an extruder 1 equipped with a pipe die 3, the temperature of the mandrel of which is adjustable, and a vacuum chamber 6, which is located in a refrigerant tank 5 and equipped with sizers 8 and 8', is provided. The molten thermoplastic resin pipe extruded from the die 3 is rapidly led to the refrigerant tank 5 in order to heighten the melt viscosity of the pipe up to a degree not so higher as the viscosity in perfectly solidified state. After that, the pipe is introduced in the vacuum chamber 6 and sized under reduced pressure by means of the sizers 8 and 8' in order to obtain an desired pipe. Due to the method as mentioned above, the desired thermoplastic resin pipe excellent in transparency, roundness and surface smoothness on inner and outer surfaces can be manufactured. |
