Patent GB-922655-A (GB)
Title: A method and an apparatus for spinning film or ribbon-shaped products such as regenerated cellulose films and products manufactured by this method
IPC: B29C48/12
Filed: 1960-04-20
Abstract: <FORM:0922655/IV(a)/1> <FORM:0922655/IV(a)/2> <FORM:0922655/IV(a)/3> Films and ribbons are made by wet-spinning a liquid spinning mass, e.g. viscose through an extrusion device extending with its extrusion slit into a liquid coagulating bath, the freshly spun film being guided between the extrusion slit and the first deflecting point through a substantially vertical shaft-like spinning casing open at both its upper and lower ends and entirely filled with coagulating bath, the casing closely enclosing the spun film and the coagulating bath being passed in laminar flow with the film through the casing in an amount greater than that necessary to offset the dragging action of the film.  The flow of coagulating bath through the casing may be accelerated in the direction of the first deflecting point and the streams of coagulating bath on each side of the film may be deflected from the film at its emergence from the casing.  Desirably, the path of the film through the casing is at least 0,5 m. and preferably 2 m. Apparatus as shown comprises an extrusion device 7 having a slit 8, a coagulating bath trough 1 with a supply system for coagulating bath liquid above the opening of the slit (e.g. supply pipes 3, 4, ejectors 16, 15 and tank 17 fitted with gauzes 19, 20), and a first deflecting member 14 at the bottom of the trough, and a substantially vertical shaft-like casing 10, 11 substantially rectangular in cross-section fitted between the slit and the deflecting member, the casing parallel to the plane of the film being slightly wider than the breadth of the film and having a dimension perpendicular to the plane of less than 5 cm., preferably less than 6 cm.  The casing walls may be closed, as shown, and a system may be provided for pumping coagulating bath through the casing on both sides of the film and in the direction of movement thereof, e.g. a rotary pump. Alternatively the casing walls may be perforated or made of gauze so as to reduce the resistance of the bath on the film.  Circulation of the coagulating bath may also be effected by constructing the casing walls as endless conveyer belts.  The casing walls may as shown be parallel at the slit outlet, forming a gradually inwardly tapering slit in the direction of the deflecting member.  The length of the casing is desirably at least 0,5 m. and preferably 2 m.  At least one pair of deflecting blades 12, 13, may be arranged between the lower edge of the casing and the deflecting member at each side of the film path in order to deflect the stream of coagulating bath outwardly from the film.  The deflecting member 14 may as shown be itself in the shape of a deflecting blade, and a stream line member 22 may also be fitted to assist the flow of coagulating bath liquid in the desired direction.  To facilitate spinning-in, a system may be provided for moving the deflecting blades 12, 13 and the member 14 towards and away from each other in a horizontal direction.  Thus spinning may be started with the blades and member as in Fig. 3. When the emergent film has been led over the withdrawal mechanism (not shown), the blades are moved to the position shown in Fig. 2. The process of the invention enables very uniform films to be obtained while using low acid concentrations in the bath and high spinning speeds.