Patent GB-349999-A (GB)
Title: Improvements in or relating to the production of artificial filaments
IPC: D01F2/30
Filed: 1930-02-26
Abstract: In order to cause the individual filaments of a bundle of artificial filaments to merge together to form a single filament of larger cross section, the associated filaments either before or after the initial association or adherence, while they are still in a sticky or tacky condition, are subjected to stretching.  The resulting filament has in general a round cross section and a smooth or comparatively smooth surface, although these may vary somewhat depending on the condition of stickiness and the extent of the stretching.  The process may take place continuously with the production of the filaments, particularly their production by the dry or evaporative method, and in this case the stretching may be applied at a stage where the filaments are still sticky or tacky due to the presence of residual solvent, the merging of the filaments being assisted by extending the stretching over a relatively long run, of, say, 4-6 feet, or by the employment of a spinning solution containing a solvent, such as vinyl acetate, not readily volatile.  Alternatively the necessary stickiness in the filaments to be united may be produced by the application of a substance that exerts a solvent or swelling action upon their substance, the latter being applied in limited quantity, preferably in the form of an extremely thin film, as by means of a wick, in a moistened rod, roller, &c., as described in Specificatin 326,462 [Class 2 (ii), Cellulose &c.], or as a spray or in the form of vapour, or the filaments may be led through a bath of the liquid; the solvent may be applied continuously along the length of the filaments, or intermittently along their length as described in Specification 325,823, [Class 2 (ii), Cellulose &c.].  Another alternative applicable to materials of a thermoplastic character such as cellulose acetate consists in applying heat to the materials, and this method may be used in conjunction with the application of solvent &c.  By the intermittent application of the above agencies, alternations of coalesced and filamentary portions may be produced along the length of the threads, or if sufficient stretch has been applied a coalesced thread made up of alternations of smooth round section and bulky irregular section.  In carrying out the method, a bundle of filaments is withdrawn from a dry spinning cell by means of a feed roller, and is passed over a second roller whose peripheral speed is greater than that of the feed roller; before or after passing round the first roller, the filaments may be moistened, as by passage over a wick, with solvent either of the low boiling type, or of the high boiling or plasticizing types since these impart increased pliability to the product; before or after passing round the second stretching roller, the united filament may be moistened with a lubricant as by a wick.  If the filaments are to be united by means of heat, they are led round a heated roller which may be the feed roller, or they are passed through a heated chamber before or during the stretching operation.  To produce a flattened, intermittently flattened, or crinkled or embossed product, the united filament may be passed through nipping rollers, which may then be used as stretching rollers.  It is preferred to employ twisted threads, since with these the union of the filaments occurs the more easily.  Composite threads consisting of one or more uniting filaments and one or more primary or uniting filaments may be made according to the process. These may be incorporated in the product, dyes or other effect materials, or metallic or other strands or wires; and the product may be partly or wholly delustred, for example, by the application of water or other aqueous liquids, alcohol, steam, &c., or by pretreatment of the individual filaments with a solution of a salt of barium, strontium, calcium, &c., either in conjunction with the solvent for rendering the filaments capable of being united, or as a separate application, and then after union of the filaments converting the metal salt into an insoluble compound by an appropriate treatment; and these treatments may be applied intermittently or continuously along the length of the filament. Ornamental effects may be produced by associating with the filaments to be united other yarns having different delustring or dyeing properties, or yarns which have been dyed or delustred in a different manner, for example, natural silk, wool or cotton, and in the case of cellulose acetate &c. filaments, viscose or other regenerated cellulose yarns, or vice versa; in some cases it is preferred that the incorporation should take place during stretching or towards the end of that operation.  Metallized effects may be produced by associating with the material tinsel strips or metallized threads; and bronze or aluminium powder may be incorporated before or after the union of the filaments.  For the production of coloured filaments, the dyestuff may be applied in solution in organic solvents as described in Specification 313,451, [Class 2 (ii), Cellulose &c.], and such solvents may constitute the softening agent for the filaments.  Specifications 326,461 and 328,312, [both in Class 2 (ii), Cellulose &c.], are also referred to.