| 摘要 |
1295878 Tubular polyamide films WOLFF WALSRODE AG 23 Dec 1969 [23 Dec 1968] 62532/69 Heading B5B Deep drawable tubular polyamide films with a balanced surface stretching ratio are made by a process comprising, homogenizing the pressure and temperature of a polyamide melt in a circular slot die; extruding the melt from the die at a temperature of at least 20‹ C. above its crystalline melting point; simultaneously cooling, shaping and stretching the extruded melt by an external gas stream in circular form, which flows in the direction of movement of the film between the film and a cooling ring and a cooling device with frusto-conical surface, while stretching the film longitudinally by means of the draw off device and transversely by a volume of gas enclosed in the tube, the stretching in the direction of movement of the tube in the transverse direction being substantially equal to each other; flattening and drawing off the film by means of a flattening device and at least one pair of squeeze rollers, the polyamide having the characteristics defined by the shaded regions of Figs. 3 and 4 (not shown). As shown, the polyamide melt is extruded from the annular gap 5 forming a tubular film 8, 8a, and cooling air flows from the cooling ring 6 through die system 15 along the direction of movement of the film through die systems 16 and 17 arranged one above the other so that the inner walls of these are formed by the film 8, 8a, and the external walls by the upper part of cooling ring 6, and the upper part of cooling device 14 respectively. The longitudinal stretching of the film is carried out by the draw-off rollers 10, 10a at draw ratio between 6-15 m./min. While solidifying, the melt flows through the first die system 15 where its expansion, determined by the temperature and pressure of the inflating gas, is reduced by the cooling gas; the second die system 16 where its expansion is increased by the cooling gas; and the third die system 17 where the film is stabilized after termination of its expansion. The tube is then flattened by flattening device 9 and drawn off by rollers 10, 10a; cut open and delivered to winders 11 and 12. The use of nylon-6 and nylon-6/6 are exemplified. |
