| 摘要 |
<p>PURPOSE:To obtain the titled tube having a small longitudinal shrinkage factor and suitable for covering articles by a method wherein the resin extrusion speed and the taking-up speed are controlled so as to impart a longitudinal shrinkage factor to the tube when conducting tubular stretching, which is then heated and stretched in the radial direction. CONSTITUTION:When conducting the tubular stretching of the blank tube made of synthetic resin such as polyvinyl chloride, crosslinked polyethylene, polypropylene or the like by utilizing an internal fluid pressure, the extrusion speed of the synthetic resin and the taking-up speed are controlled so as to impart the longitudinal shrinkage factor of 4-10% to the blank tube. Then the blank tube 1 is heated by infrared rays, hot blast or the like in a heating tunnel 3 between two sets of nip rolls 2, 4, wherein the speed ratio of the upstream-side rolls 2 to the downstream- side rolls 4 is set to be 1-1.1. Compressed air B is introduced into the tube blank 1 from the downstream side, the tube blank 1 is stretched while being sized by an outside sizing sleeve 5, and then taken up by a take-up roll 6.</p> |
