| 摘要 |
1,233,588. Tubular films. A. LABEK. 16 Aug., 1968, No. 39194/68. Heading B5B. A thermoplastic tubular film is formed by extruding it with at least one ribbing which is air cooled to a greater extent than the rest of the film tube, so that the breadth and thickness of the ribbing is kept constant during subsequent biaxial stretching. Carrier bags may be formed from the tube by transverse severing and welding so that the edges of the flattened tube form the top and bottom of the bags. The tubing may have diametrically opposed ribbings lying at the edges thereof when flattened. Re-entrant folds may be provided in the edges of the tube. The tube may be produced from materials of different colour or melt index. |
