GB390860A - Improvements in the manufacture of artificial filaments and the like - Google Patents

Abstract

Artificial filaments, threads, yarns, ribbons, and like materials are obtained by extruding solutions into an evaporative medium, secluding the filaments in the initial stages of spinning from the effect of the main current of evaporative medium so as to retard the initial evaporation of solvent from the filaments, and submitting them to a stretching operation in <PICT:0390860/IV/1> <PICT:0390860/IV/2> <PICT:0390860/IV/3> <PICT:0390860/IV/4> such manner that the whole of the stretch does not extend back to the spinning nozzle. Seclusion of the filaments may be obtained by surrounding them in the neighbourhood of the nozzle with a shield device such as a tube, pipe, or funnel, or by providing the spinning cell with two or more compartments. Seclusion of the filaments may also be obtained by introducing the evaporative medium at a point beyond the nozzle and causing it to flow in the same direction as the filaments, or by withdrawing a countercurrent of evaporative medium at a point short of the nozzle. The space around the nozzle may contain a stagnant vapour, or a slow current of gas or vapour may be passed through and if desired solvent vapours may be injected. Evaporation is further retarded by incorporating high boiling point solvents or diluents in the spinning solution, such solvents as produce high viscosity solutions being preferred. Examples of such solvents are mono-acetin, diacetin, glycol mono-acetate, methyl glycol acetate, methyl glycol dioxane, and dimethylene dioxide. Rollers or tension devices may be used to restrict the stretching force from extending back to the nozzle. The stretching rollers may be mounted in ball bearings, and provided with braking devices, such as metal discs rotating in an electrically controlled magnetic field or vanes rotating against the resistance of a gas or liquid. They may be of light material such as aluminium or of a synthetic resin such as a phenol-aldehyde resin, and they may be grooved to receive the threads. If desired, they may be positively driven at different speeds. The process is applicable to filaments of cellulose acetate, formate, propionate, butyrate, nitrate, nitro-acetate, methyl cellulose, and benzyl cellulose. As shown in Fig. 1, filaments 14 pass from the jet 13, over tension rods 15, down the cell 10, out through an aperture 17, over a freely rotating roller 28 which supplies a solvent or swelling agent, over the stretching rollers 31, 32, and finally to a cap-spinning device 35. In order to seclude the filaments in the region of the jet from the main countercurrent of evaporative medium, a cowl made up of two telescoping parts 26, 27 is provided. The pull of the roller 31 is prevented from extending back to the region of the jets by means of the tension rods 15. If desired the cowl may be connected to a flexible pipe through which solvent vapours may be introduced or removed. As shown in Fig. 3, the evaporative medium is introduced at some distance below the jet, through an annular pipe 41, and passes concurrently with the filaments 14. As shown in Fig. 4, a partition 53 is provided for secluding the filaments from the main evaporative current which leaves the cell by the pipe 51. A small part of the evaporative medium may be allowed to pass the partition 53 and be drawn off through the pipe 54. In Fig. 5, the filaments are stretched between rollers 57, 58, 32. Stretch is prevented wholly or partly from extending back to the jet by means of the roller 57 which has an adjustable band brake 63. Specifications 182,166, 312,203, 333,926, [all in Class 2 (ii), Cellulose &c.], 353,956, 358,500, and 364,654 are referred to.