| 摘要 |
<p>An extruder head, for the prodn. of thermoplastic tubing made up of two concentric tubes, e.g. PVC with crossgrooving on the outside and a smooth interior, has a single head with nozzle, a core, and an intermediate part to divide the polymer flow into the two concentric streams and which is best fixed on to the nozzle. The problem of longitudinal weld lines in the flow of the outer tube is eliminated, without the use of costly flow promoters to the polymer (particularly PVC).</p> |
