| 摘要 |
1380397 Extruded heat-shrinkable tubing BRITISH INSULATED CALLENDERS CABLES Ltd 11 May 1972 [12 May 1971] 14480/71 Heading B5A [Also in Division F2] A diametrically heat shrinkable tube of a P.V.C. composition having a B.S. softness of 10-80, e.g. containing 30-100 parts by weight of an ester type plasticizer per 100 parts resin, is continuously made by extruding a tube 3 of the composition (either horizontally or vertically); cooling the tube to a temperature above the composition softening point and at which it is predominantly elastically deformable; applying a lubricant to the exterior tube surface; passing the tube, via a steel sealing die 6 of smaller diameter than the tube, into and through a cooled chamber 6 through the walls of which suction is applied to expand the tube to the diameter of the chamber, at which it is set by cooling to below the composition softening point. The tube interior may be at above atmospheric pressure during expansion. The cooling to above the softening point may be effected through a bath of fluid which is compatible with, or may comprise the lubricant, but in the described embodiment is effected by one or more air jets 4 directed transversely, or parallel, to the extruding tube 3, e.g. from an annular nozzle through which the tube 3 passes, with the lubricant being applied from a drip feed 5. The vacuum is applied from a manifold 10 through axially spaced wall slots of the chamber, which is cooled by a surrounding water circulating jacket and is also provided with a downstream sealing die 11 through which the expanded and set tube is drawn by an endless belt device 12. The lubricant may comprise a specified silicon oil, a petroleumderived synthetic detergent which is subsequently removed by washing, or a suspension of P.T.F.E. in silicone oil. |
