Process and apparatus for regenerated cellulose film production

摘要

Regenerated cellulose film is made by extruding a cellulose solution into contact with a liqud coagulant, continuously drawing the freshly extruded gel film, until it is substantially completely coagulated, in contact with a limited quantity of the liquid coagulant which has been applied to a moving endless belt and is being carried by said belt through the air, while avoiding contact of the gel film with the belt, completing regeneration of the cellulose, and washing. Preferably the cellulose solution is viscose and the liquid coagulant an acid-sulphate bath. The belt may be driven at a linear speed of about 80-125% preferably approximately 80%, of the speed of drawing the film, which is preferably drawn independently of the belt drive. The film may be extruded into a bath from which it is taken into contact with the liquid coagulant on the belt and from which the belt draws its liquid. Apparatus as shown comprises means for extruding film, 12, a vessel for liquid coagulant 14 an endless driven belt 17 disposed so as to convey coagulant thereon through the air, and means independent of the belt drive (e.g. driven roll 56) to draw the film over the belt and in contact with the liquid coagulant thereon (see inset, Fig. 1, indicating relative positions of gel film 10, layer of coagulant 13 and belt 17). Preferably the belt is so disposed with reference to the vessel that when driven it conveys liquid from the vessel on to a substantially horizontal rim of the belt, and the upper conveying portion of the belt is not submerged below the level of coagulant in the vessel. As shown, means may be provided in the vessel so that the film in the initial stages of its path is secluded from the main body of liquid in the vessel. Figs. 3-8 illustrate methods of limiting bath turbulance in the film extrusion region or of limiting the distance the freshly extruded film must travel before reaching the moving belt. Specification 852,609 is referred to.