Patent GB-514638-A (GB)
Title: Improvements in the manufacture of artificial silk
IPC: D01D5/30
Filed: 1938-05-11
Abstract: 514,638. Cored threads. I. G. FARBENINDUSTRIE AKT.-GES. May 11, 1938, No. 14065. Convention date, May 11, 1937. [Class 120 (iii)] [Also in Groups IV and V] Artificial fibres are spun from two different liquids of which at least one contains a coagulable spinning substance with the aid of a spinning nozzle comprising two parallel multiperforated plates at relatively small distances apart of which one plate forms an outer wall of the nozzle and the other plate divides the interior of the nozzle into two separate compartments, each plate containing the same number of perforations and the opposed perforations in the respective plates being substantially coaxial. One liquid is supplied to each of the compartments. Thus, in the Figure, the plate b forms the outer wall of the nozzle, while the plate a divides the interior of the nozzle into two separate compartments c and d. One liquid is fed in at e into compartment c and is extruded through the perforations g in plate a into compartment d. The jets of liquid extruded from plate a pass straight across compartment d and through the perforations g in plate b, but in doing so they drag with them some of the second liquid which is fed in at f so that the jets of liquid extruded from the plate b into the coagulating medium h consist of a core of the first liquid surrounded by an outer layer of the second liquid. The perforations on each plate may be arranged on the circumference of a circle or on the circumference of a number of concentric circles and may be in annular grooves formed in the plate, which grooves protrude towards the other plate. The process is applicable to dry or wet spinning. The two liquids which are spun may each contain different coagulable spinning substances or they may contain the same coagulable spinning substance. In the latter case, the liquids may differ in the kind of solvent or the concentration of the spinning substance. Alternatively, the two liquids may contain the same spinning substance but at different degrees of ripeness or at different degrees of polymerisation. Moreover, the two liquids may differ by the presence in one or both of them of solid, liquid or gaseous substances which are not coagulable, for instance pigments, dyestuffs, roughening agents, softening agents, agents for improving the feel, fats, oils, soaps, resins, medicinal substances, phosphorescent substances, substances evolving gases, etc. In wet spinning, the appearance of the fibres depends on the character of the coagulating bath. Where both liquids contain coagulable spinning substances, the fibres obtained will ordinarily be of circular cross-section, the two substances forming concentric layers in the finished fibre. But when a coagulating bath having a powerful shrinking action is used, fibres of strongly lobed or denticulate crosssection are obtained and both spinning substances appear on the surface of the fibres. Further only one of the liquids need contain a coagulable spinning substance, or both liquids may contain a coagulable spinning substance and one of these may subsequently be dissolved out of the fibres. In the latter case hollow fibres or fibres of exceptional fineness are produced, according to whether the liquid containing no coagulable spinning substance or containing a spinning substance which can subsequently be dissolved out forms the core or the periphery of the extruded jet. In examples the two liquids spun are (1) solutions of cellulose acetate of different concentrations; (2) solutions of cellulose in sulphuric acid at different degrees of degradation; (3) viscose solutions prepared from alkali celluloses of different degrees of ripeness ; (4) viscose solutions of different degrees of ripeness; (5) cuprammonium cellulose solutions, one of which contains a dyestuff (6) viscose solutions one of which contains calcium carbonate as pigment and glass powder as roughening agent; (7) viscose solution and alkali casein solution; (8) cellulose acetate solution and polyvinyl chloride solution ; (9) viscose solution and a foam of alkali casein solution; (10) cuprammonium cellulose solution and cellulose glycollic acid ether solution, the cellulose glycollic acid ether forming the core and subsequently being dissolved out; (11) viscose solution and paraffin wax emulsion ; (12) viscose and a latex of natural or artiflcial rubber; (13) sulphuric acid and a solution of cellulose in sulphuric acid; (14) viscose solution and cellulose glycollic acid ether solution, the cellulose glycollic acid ether forming the periphery and subsequently being dissolved away. Specifications 446,757 and 450,257, [both in Group IV], are referred to.