GB741317A - Improvements relating to spinning processes for the production of high strength artificial silk from cuprammonium-cellulose solution - Google Patents

Abstract

<PICT:0741317/IV(a)/1> In the production of high-tenacity artificial silk from cuprammonium cellulose solutions by funnel stretch-spinning, the filaments in the liquid state are drawn out to not less than twice their final cross-sectional area in a funnel, into the upper part of which water is introduced at a rate sufficient to keep it full, and through which the water passes in the same direction as the filaments, the filament substance having at the end of the funnel a viscosity of 50,000-60,000 poises at the temperature prevailing at that end. Thereafter the filaments pass into a vessel through which a bath-liquid passes at a temperature higher than that of the water passed through the funnel, and the filaments are stretched in this vessel by drawing them over a series of guide rods in such a manner that the time, in seconds, which the filaments require in order to coagulate from the condition where the filament substance has a viscosity of 50,000-60,000 poises up to the blue-filament condition, divided by the ratio of the filament cross-sectional area before and after the stretching, is at least 0.3. A formula is given showing the relationship between the distance from the spinning nozzle at which the viscosity of the filament substance is 50,000-60,000 poises, the filament withdrawal speed and the titre of the individual filaments. The tension under which the filaments are stretched should not exceed 50 dyn./sq. cm. As shown, cuprammonium cellulose spinning solution is extruded from a spinneret 1 at a withdrawal speed of about 10 m./min. to form liquid filaments in a funnel 2, which is 10 cm. long and through which water at 15 DEG C. flows downwards at a rate of 3-5 c.cs. per second into the vessel 3 containing a precipitation bath. Precipitation liquid enters the vessel 3 at the inlet 4 and overflows from the top of the vessel, the temperature in the latter being maintained at 21-22 DEG C. The mean speed of the filaments in the funnel 2 is 7.5 m./min., the length of travel of the filaments from the 50,000-60,000 poises condition to the blue filament condition is 8 cm. and the time required for the filaments to travel this distance is 0.6 second. The filaments are stretched in the vessel 3 by their passage over guide-rods 5, which are so arranged that the angles between the paths of the filaments become progressively more acute as the filaments travel down through the vessel. The filaments then pass into a discharge tube at the bottom of the vessel 3, in which tube the filaments are finally coagulated. The outlet of the discharge tube is constricted to a diameter of about 3-4 mm. to limit the rate of flow of bath liquid through the tube. After leaving the tube, the filaments are deflected into a horizontal path in the usual manner by means of a rod, de-acidified and wound.