GB809273A - Manufacture of synthetic filaments - Google Patents

Abstract

<PICT:0809273/IV (a)/1> <PICT:0809273/IV (a)/2> Potentially crimpable synthetic linear polymer filaments are made by quenching a bundle of hot filaments unsymmetrically, in a melt spinning process, by causing the filaments during their travel from the spinneret to a winding device to come into contact with a continuously renewed thin film of a liquid on the surface of a solid body, which liquid is at a temperature considerably below that of the filaments, the bundle of filaments contacting the film of cooler liquid in such a manner that one side only of each filament contacts the film. The film of liquid should preferably be of such thickness that the filaments cannot be completely immersed in it during quenching, which should preferably take place while the filaments are as hot as can practically be handled, e.g. not further than 30 cm. from the spinneret when melt-spinning into air at room temperature. The filaments after quenching may be drawn in known manner, e.g. between a pair of feed rolls and a pair of draw rolls rotating faster than the feed rolls, and between the feed and draw rolls may pass over a snubbing pin and also over a hot plate. Alternatively, a tension gradient may be inserted in the spinning threadline after the unsymmetric quench, e.g. by means of a heated tension gate, or by taking advantage of the airdrag tension gradient associated with very high wind-up speds, or by passing the filaments through a long bath of liquid to impose a liquid drag on them. The filaments after drawing may be shrunk a controlled amount, e.g. by passing them between two sets of rolls via a heating zone, the feed rolls rotating at a higher surface speed than the wind-up rolls. To obtain a high degree of crimp the filaments should be allowed to shrink freely, e.g. by hanging in skeins in a hot oven. The filaments may be heated by contacting them with hot gases or vapours, hot inert liquids or hot surfaces, or by electrical infra-red or high-frequency heating. The surface covered by a film of continuously renewed cold liquid is preferably the outer surface of a porous or perforated wall of a hollow body into the interior of which the liquid is fed so that it passes through the porous or perforated wall to the exterior surface thereof and flows in a thin film down over the surface. When the extrusion holes of the spinneret are arranged in a circle, the hollow body is preferably spherical or egg-shaped. Thus, as shown in Fig. 1, 15 cm. below the spinneret 3 is a hollow porous ceramic egg-shaped body 4 which is supplied with cold water through pipe 5. The water seeps through the pores of the body wall and also overflows through an aperture at the top of the body covered by a circular baffle 6, and flows down over the surface of the body. The body may also be a circular hollow ring, the inner or outer surface of which is porous or perforated, and the cylindrical or slightly conical hollow bundle of filaments extruded from a spinneret having its extrusion orifices arranged in a circle may contact the inner or outer surface of the ring, the interior of which is fed with cold water. The body may also be a hollow, slowly rotating roller having numerous apertures in its peripheral wall, which is covered by a layer of porous fabric. The interior of the roller is supplied with water from a fixed pipe, one end of which enters axially through the side of the roller. The lower portion of the roller may be submerged in a bath of liquid so that an additional supply of liquid is picked up by the roller. Alternatively a stationary or rotated roller may be used and liquid fed on to its periphery and allowed to run down over the roller. When using a spinneret with holes in a straight line a slowly rotating roller may be used for the unsymmetrical quenching of the filaments or, as shown in Fig. 7, a chamber 18 having a flat front consisting of a perforated metal plate (or preferably a sintered metal powder plate) 19 over which is stretched fabric 20 held in position by hooks 21, 22. The quenching liquid coming from a storage tank (not shown) enters at a metered rate through the pipe 17 into the chamber 18, and the ribbon-shaped bundle of filaments coming from the spinneret contacts the wet fabric 20 over its whole width. The body for applying the quenching liquid may also be a solid, slowly rotating applicator roll dipping in a bath of the liquid. In an example, 34 polyethylene terephthalate filaments are extruded at 285 DEG C. through a spinneret having 0.2 mm. diameter holes arranged in a circle. The body shown in Fig. 1 is positioned 12 cm. below the spinneret face and cold water is forced at a rate of about 75 cc. per minute through the pores of the body. After drawing to 4 times the length as spun the tension on the filaments is released to produce a helical crimp which is increased by steam treatment of a hank of the filaments. The unsymmetrically quenched filaments may be made up into a fabric before being shrunk.