Patent GB-1264911-A (GB)
IPC: D01D5/088
Filed: 1969-03-14
Abstract: 1,264,911. Synthetic monofils of circular cross-section. FARBWERKE HOECHST A.G. 14 March, 1969 [14 March, 1968], No. 13480/69. Heading B5B. Monofils of a synthetic linear high polymer having a circular cross-section are made by melt- or wet-spinning a polymer vertically downwards through a spinneret having extrusion orifices of circular cross-section into a liquid bath and guiding the resulting monofils through the bath to a take-up device which withdraws the monofils substantially vertically upwards via one or more easily rotatable rollers situated in the bath, the or each roller being circumferentially grooved in a plane normal to the axis thereof, which axis lies in a horizontal plane, there being a separate groove for each monofil, the bottom of the or each groove being rounded to a radius of curvature corresponding to the radius of the monofils when they reach the take-up device, and the or each roller having such a diameter and/or being so arranged in the bath that it guides the monofils without causing them to deviate substantially from their natural path. By the radius of the monofils when they reach the take-up device, there is meant that radius obtained in the absence of any guiding device in the bath. By the term "natural path" there is meant the path that spun filaments take when spun vertically downwards into a liquid bath and subsequently withdrawn from the bath in a substantially vertically upwards direction, in the absence of any guiding device in the bath, the length of the path of travel of the monofils in the bath in the case of a melt-spun polymer being sufficient to solidify them completely. This path is approximately catenary in form. As shown in Fig. 3, there may be provided a plurality of easily rotatable rollers 6 so arranged in the bath that they have parallel axes and successively guide the monofils 7 through the bath. Alternatively, a single roller may be used, of such a diameter that its curvature in the region in which it contacts the monofils corresponds substantially to the curvature of the natural path of the monofils. Rollers having a single groove may be used, or rollers having parallel circumferential grooves (Fig. 2, not reproduced), which may be used for guiding a plurality of monofils simultaneously through the bath. The rollers are suitably made of light materials, and desirably the two sides of each circumferential groove of a roller should include an angle in the range of from 0 to 30 degrees. In the example, the melt-spinning of polyethylene terephthalate through a circular spinneret opening having a diameter of 7 mm. into a bath containing water at 70 C. is described. The monofil is drawn off at 5 metres per minute, and after a path of travel of 1À2 metres, the monofil is guided by means of a single roller and drawn at a ratio of 4À8 : 1 whereby it acquires a final diameter of 2À0 mm. The roller used had an effective diameter of 200 mm. (i.e. the diameter between diametrically opposite points on the bottom of the groove) and the depth of the groove was 25 mm. The sides of the groove included an angle of 15 degrees and the rounded bottom of the groove had a radius of 2À2 mm. The bottom of the groove corresponded exactly to the diameter of the monofil on reaching the take-up device and the effective diameter of the roller corresponded approximately to the curvature of the lateral path of the monofil; hence a monofil having a very high degree of roundness was obtained. Polyolefins, polyvinyl chloride and polyamides may be melt-spun by the process of the invention, as well as polymers which can only be wet-spun, e.g. poly-betalactams. In the case of wet-spinning the liquid bath is used as the precipitating bath.