GB675675A - Method and apparatus for producing high tenacity artificial yarn and cord - Google Patents

Abstract

<PICT:0675675/IV (a)/1> Regenerated cellulose filaments are produced by extruding viscose having a temperature of at least 30 DEG C. into an acid regenerating and coagulating bath having a temperature of 40-75 DEG C. or higher, stretching the filaments 40-80 per cent after partial regeneration, washing the filaments, relaxing the filaments 3-10 per cent and drying them. The viscose should preferably have a temperature of 45-60 DEG C. upon reaching the spinneret and the bath preferably a temperature of 50-65 DEG C. In the preferred instance the difference in temperature between the viscose and the spinning bath is not over 10 DEG C. and the optimum difference is about 0-5 DEG C. The viscose is heated to the required temperature by heating a portion of the pipe-line conveying the viscose to the spinnerets, preferably a portion of the individual supply lines leading to the spinnerets. This heating may be carried out by means of electric heating coils, high frequency electrostatic heating devices, or heating baths. In the latter case part of the individual supply line or pipe may be bent into a helical coil so as to cause the spinning solution flowing through it to follow a tortuous path and the coil may be submerged in the spinning bath or some other bath of heated liquid. An aqueous liquid at 60-100 DEG C. may be used for treating the yarns before, after, or during stretching and may be circulated through the yarn-treating stage and the viscose-heating stage in succession in either order. A soft finish may be obtained by applying to the yarn before drying and after it has been rendered acid-free, a solution of sodium oleate, polyvinyl alcohol, ethylene-oxide-modified sorbitan di-palmitate or compositions containing such ingredients. As shown, viscose is fed to the spinning machine through a header 3 to which there are connected a number of branch outlets 4 connected to individual gear pumps 5. The discharge lines 6 from the pumps 5 lead to a candle filter 7 through a swivel joint 7a which allows the swinging of the filter 7 and pipe 8 in a counterclockwise direction from the position shown in the drawing, to remove the spinneret 9 out of the coagulating bath 10. The pipe 8 is formed with a portion 8a thereof in the form of a helical coil to provide for heat transfer from a bath 13 to the viscose in the pipe 8 before it is fed to the spinneret 9. The bath 13 may be individual for each pipe 8 or may be a trough running the length of the machine. The bath 13 may be insulated from the bath 10 by a layer 14 of material of low heat conductivity. The viscose is heated to 45 DEG C., the temperature of the heating bath 13 being 60 DEG C. The filaments formed by the coagulation of the extruded viscose in the acid coagulation bath 10, which is at a temperature of 50 DEG C., pass to a thread-advancing device comprising a pair of canted rotors 16 and 17 about which 16 yards storage of yarn is wound to provide further regeneration prior to stretching. The yarn leaves the upper rotor 16 and passes through the trough 18 into which hot water at about 90 DEG C. is continuously supplied from the pipe 19. The overflow pipe 20 continuously discharges the hot water from the trough 18 into the bath 13 for heating the viscose in the coil 8a and thence escapes via the overflow pipe 15. The yarn is drawn from the trough 18 to the thread advancing reel 21 which rotates at a peripheral speed 65 per cent higher than that of the rotors 16 and 17 and thus stretches the yarn. The yarn is washed to a neutral condition on the reel 21 with a washing liquid supplied from the sprayers 22 and 22a. The washing liquid may in general be hot or cold water or a cold or hot dilute acid or salt solution such as a solution containing 0.01-0.5 per cent sulphuric acid. After leaving reel 21 the yarn passes under a rotor 23 immersed in a bath of soft finish 24 and then proceeds around a thread-advancing device for drying comprising a pair of rotors 25 and 26 which are driven at a peripheral speed at the yarn-receiving portion somewhat less than the peripheral speed of discharge from reel 21 so that the yarn relaxes about 5 per cent on its way to the drying stage. The surfaces of the rotors have intermediate tapered portions 27 and 28 to allow about 3 per cent further shrinkage of the thread during the drying as it reaches this portion of the plant. After the yarn leaves the drums 25 and 26, it is collected by winding or by winding and twisting at 29. In other examples filaments are produced in a similar manner except that the storage on the rotors is reduced to 2 yards and the viscose is heated before extrusion to temperatures varying from 30 DEG to 70 DEG C. Data are furnished in each case for the wet and dry tenacity and elongation and fatigue rating of the yarn and compared with the properties of the yarn when spun from unheated viscose and without relaxation after stretching. The method of determining the relative fatigue rating of the yarns is described. Filaments produced according to the invention are said to have a high tenacity and increased flexing life and to be suitable for the production of cords used for reinforcing rubber goods such as tyres. Specification 675,681 is referred to.