Patent GB-331229-A (GB)
Title: Improvements in the manufacture of threads or filaments of cellulose derivatives
IPC: D01D5/04
Filed: 1928-12-20
Abstract: 331,229. British Celanese, Ltd., Dreyfus, H., and Taylor, W. I. Dec. 20, 1928. Grant of Patent opposed. Apparatus for making filaments; cellulose esters and ethers, processes for making filaments from.-For the production ot threads or filaments of increased strength from solutions of cellulose acetate and other organic esters of cellulose or of cellulose ethers the threads while traversing in the spinning cell a, counter-current of evaporative medium, have applied to them by means of a device making non-slipping contact with the threads, a controlled and uniform stretch at a predetermined part of the threads which still contains residual solvent and is in a semi-solid or plastic condition, preferably to a part of the threads that contains 20-40 per cent of solvent. The stretch may be applied in two or more stages, and it is preferred to use a spinning cell of uniform cross-section so that the solvent con. tent of the evaporative medium diminishes steadily in the direction of travel of the threads. The stretch may be imparted at any distance from the nozzle, and the distance over which it is applied may also be adjusted. Stretching is assisted by the presence of high boiling solvents or plasticizers in the spinning solution: and particularly beneficial results are obtained by applying the stretching operation to threads spun from solutions of cellulose acetate &c. of high viscosity. A convenient arrangement for stretching comprises two or more rollers 11, 12 around which the threads are passed, the second or later rollers being moved at the appropriate higher peripheral speed or speeds. The mountings of the rollers are preferably adjustable so as to allow the distance of the first roller from the spinning jet 3 and of the distance apart of the rollers to be regulated. The rollers are connected to some part of the spinning machine. As an alternative the upper roller 11 may be mounted idlv so as to be rotated by the passage of the filaments over or round it, a brake device such as is described in Specification 329,620 being fitted to the roller, for example, a brake band 18 loaded by a weight 20 passing over a pulley 19 connected to the roller 11. If the stretching is carried out in stages, then an intermediate roller or rollers 21 may be positioned between the rollers 11, 12, and the former roller or rollers may be positively driven at speeds intermediate between those of the adjacent rollers, or they ma.y be provided with braking devices 23 similar to those used with the roller 11 but in the case of the later rollers the braking action will be diminished by making the weight 22 less than that of the weight 20 of the upper roller. Instead of a brake band there may be employed other braking devices of friction, centrifugal, air or liquid brake, or electromagnetic brake type. The upper roller, if driven, may move at a speed sufficient to effect a drawing-down of the filaments extruded from the jet, and similarly there may be a further drawing-down of the threads between the lower roller 12 and the feed roller 9 arranged outside the cell and by which they are delivered to the winding or winding and twisting device. The evaporative medium is introduced at the lower part of the cell, and is withdrawn through an outlet in proximity to the spinning jet. Specifications 165,519, 198,023 and 323,790 also are referred to.