| 摘要 |
PURPOSE:To make it possible to produce continuously a plastic tube whose shape would not collapse and that is excellent in roundness, by passing a melted plastic tube, which has been extruded, into sizers containing a refrigerant as a lubricant within a short period, and cooling it completely in a pressure decreased chamber. CONSTITUTION:A melted plastic tube, which has been extruded from a die of an extruder, is passed through a throttle 16 of a refrigerant tank 11, sizes 17, 17' of a pressure decreased chamber 12 containing a refrigerant 10, and a throttle 16' of the refrigerant tank 11 successively, and is taken up with it being pinched by a take-up and the pressure in the presure decreased chamber 12 being lowered. The plastic tube immediately after the extrusion is high in melt viscosity and is liable to collapse near the throttle 16, therefore it is cooled by the refrigerant 10 until it reaches the sizer 17 to such a degree that it is not solidified completely. When the plastic tube is passed through the sizer 17 and is brought into the pressure decreased chamber 12, it is increased diametrically, and as the refrigerant serves as a lubricant, it becomes a plastic tube whose shape is hardly deformable and is excellent in roundness. |
