GB405691A - Improvements in the production of sheet material - Google Patents

Abstract

<PICT:0405691/IV/1> <PICT:0405691/IV/2> <PICT:0405691/IV/3> <PICT:0405691/IV/4> <PICT:0405691/IV/5> <PICT:0405691/IV/6> Apparatus for the production of foils, films, and the like comprises a vessel adapted to contain setting fluid, means for extruding a solution in sheet form into the vessel, means for guiding the extruded sheet material through the vessel, means for introducing the setting fluid into the vessel at a large number of points, and means for withdrawing it at a large number of points so as to cause the setting fluid to flow uniformly through the vessel. The apparatus may be used in the production of films from solutions of cellulose acetate or other cellulose esters or ethers, or from solutions of cellulose in cuprammonium, or of viscose. The rate of flow of the setting solution may be small and it may be constant over the run of the material in the bath or means may be provided for obtaining an accelerated flow in certain stages of the setting of the sheet material such as that immediately following extrusion. The setting solution may flow longitudinally or transversely to the film. The film may be stretched longitudinally and transversely during coagulation. As shown in Fig. 1, film-forming solution is extruded from a hopper 12 with an adjustable slit and the film is received on a drum 18 immersed in coagulating liquid. The film passes round a drum 21 which draws it from the bath and then enters a drying chamber 23 from which it passes to a winding drum 26. The bath 17 is supplied with liquid from a perforated pipe 31 running across the width of the bath. The liquid issuing from the perforations 32 is further distributed by perforations 33 in a channel 34 in which the pipe 31 is contained. The liquid is drawn off by two perforated pipes 35 on each side of the bath. The pipe 35 nearer to the extrusion device may draw off the liquid at a greater rate than the other pipe 35 so as to produce an accelerated flow near the point of extrusion. As shown in Fig. 3 liquid is introduced by a pipe 41 to a channel 42 on the outside surface of the bath 17, the channel running the length of the bath. Liquid enters the bath through perforations 43 and flows from one side to the other, being removed by perforations 44 in a trough 45 secured outside the bath and extending the whole length of the bath. As shown in Fig. 5, coagulating liquid is introduced through perforated pipes 48 contained in perforated channels 50 at opposite ends and running across the width of the bath. The liquid is removed through perforations 53 in pipe 52 which runs across the width of the bath. As shown in Fig. 6, coagulating liquid enters the bath by means of a pipe 55 conducting it to a chamber 56 from which it flows through perforations 57 to the inner side of a plate 58 closely surrounding that part of the drum 18 round which the film is passing. The liquid is withdrawn by two perforated pipes 59, one at each side of the bath. As shown in Figs. 8 and 9, the bath 62 is of such shape as to fit closely round the roller 18. A partition 63 at one side of the bath separates a small space into which coagulating liquid is fed by a pipe 65 and the liquid enters the main part of the bath through perforations 66. The liquid passes across the bath and through perforations 67 in a partition 64 at the other side and leaves through a pipe 68. The perforations 66, 67 follow the line of the film round the drum 18 and up to the guide 20. Specifications 177,868, 179,234, [both in Class 2 (ii), Cellulose &c.], 182,154, 293,325, [both in Class 102 (i), Pumps &c.], 340,324, 340,325, 340,326, 340,436, 340,437, 343,062, 378,858, and 400,589 are referred to.