| 摘要 |
974,453. Pipes and tubes. E. I. DU PONT DE NEMOURS & CO. March 15, 1963 [March 16, 1962], No. 10469/63. Heading F2P. A process for preparing a fibrous tube comprises winding a plurality of layers of sheets or strands composed predominantly of crystalline oriented film-like polymer elements around a mandrel to form a tube, compresssing the tube wall and heating the tube to weld the film-like elements together at their cross-over points without destroying the crystalline orientation of the filmlike elements at the centre of thickness of the tube wall. The film elements used have a thickness of less than 4 microns, and may be made by direct lay-down of plexifilaments on a moving belt or by cutting and beating plexifilaments in aqueous suspension and forming sheets on a screen. Plastics used are branched polyethylene, linear polyethylene polypropylene, poly- (ethylene terephthalate) and poly(hexamethylene adipamide). The sheet may be wrapped helically or normal with respect to the axis of the mandrel. The pipe may be coated on the exterior or internally lined with a water-impermeable resin containing an ultra-violet screener, carbon black or other fillers. In one example plastics material from an autoclave 101 was passed, under pressure, through a filter 103 to spinneret assemblies 110 where the plastics was extruded to impinge against a deflector 22 where the extruded strand was spread out into a wide network of filmfibrils 106 (Fig. 3) which passed through an electrostatic field 107 to improve separation and to help the fibrils to adhere to a moving belt 108 resting on a ground plate 109. Random deposit of the fibrils on the belt was enhanced by oscillating the deflector. The fibrils were passed under a static dissipator 111 and through pressure rolls 112 to produce a sheet which was wound on to roll 115. Several layers of the sheet were wound on a mandrel then removed intact to be placed in a steam jacketed cylinder 2. An expandable tube 3 was inserted in the plexifilamentary tube 4 and made air-tight by clamping it between flanges 5. Air pressure was supplied to the tube 3 and vacuum to the space between the plexifilamentary tube 4 and the wall 8 of the cylinder. The air pressure was then released and steam under pressure supplied to the cylinder 2 through inlet 12 and to the tube 3 through inlet 6. Heat and pressure were supplied to weld the fibres together at their cross-over points without destruction of the fibres or of their orientation. The cylinder was cooled by water introduced through pipe 11, air pressure released and the finished tube was removed. A rigid mandrel with external pressure rollers can be used to apply pressure to the plexifilamentary tube and electrical heating can be used. |
