Patent GB-778395-A (GB)
Title: Improvements in the manufacture of cellulose triacetate yarns
Inventor: FINLAYSON DONALD
IPC: D01F2/28
Filed: 1954-05-26
Abstract: <PICT:0778395/IV(a)/1> <PICT:0778395/IV(a)/2> The degree of crystallinity of the cellulose triacetate in a cellulose triacetate yarn or monofil, as indicated by an increase in the sharpness of the X-ray diagram of the yarn, is increased by annealing it under a tension such that it is simultaneously stretched irreversibly, i.e. to a degree which is substantially retained when the yarn is no longer subjected to the annealing conditions and is free from tension.  The annealing process may consist in subjecting the yarn to dry heat at a temperature above 170 DEG  C. or to the action of a hot softening agent such as water or steam at 120-160 DEG  C., or in subjecting the yarn for a sufficient time and at a suitable temperature to the action of an organic liquid which is a swelling agent for the cellulose triacetate, e.g. a hydrocarbon or an alkyl halide boiling above about 50 DEG  C., employed at 60-90 DEG  C., a monohydric alcohol containing up to 3 carbon atoms in the molecule, employed at 50-80 DEG  C.; or a mixture of acetone with water or with one of the above alcohols employed at about 15-40 DEG  C.  When the treatment is applied to a running yarn the annealing agents are employed at temperatures towards the upper ends of the specified ranges, e.g. dry heat at about 215-225 DEG  C., steam or hot water at 140-160 DEG  C., hydrocarbons or alkyl halides at about 75-90 DEG C., the alcohols at about 65-80 DEG  C., and acetone/water and acetone/alcohol mixtures at about 25-40 DEG  C.  The yarn is stretched preferably by at least 3.5 per cent of its length.  As shown in Fig. 1, a yarn 24 is fed from a positively driven feed roll 20 with its associated skew idler roll 22 through a hole 18 in the removable cover 17 of a tank 11 of rectangular cross-section surrounded by a jacket 12 for a heating fluid.  In the tank 11 the yarn 24 passes over the rolls 25, 26, 27 and it is then withdrawn from the tank by means of a positively driven drawing roll 1 with its associated skew idler roll 23 and passed to a washing device (not shown).  The drawing roll 21 is driven through an infinitely variable gear so that it may be given the same peripheral speed as the feed roll 20, or any desired higher speed, and the rolls 25, 26, 27 are either free running or are positively driven at peripheral speeds between those of the rolls 20 and 21.  The tank 11 is filled by the inlet pipe 15 to a level, which may be above that of the roll 27, with a liquid such as methylated spirits (used, for example, at 70-75 DEG  C.) or a 30/70 by volume acetone/methylated spirits mixture used, for example, at 30-35 DEG  C.  As shown in Fig. 2, a feed roll 40 provided with a skew idler roll 41 feeds a yarn 36 to an injector 32 having an outer converging annular passageway 33, fitted with a steam inlet 34 and closed at its outer end, and a central narrow cylindrical passageway 35 open at both ends for the passage of the yarn into a thermally insulated tube 31.  Wet steam at the desired temperature is fed through the supply line 46 and the inlet 34 to the converging passageway 33 in the injector 32, and thence into the tube 31.  The drawing roll 42 with its associated skew idler roll 41 draws the yarn 36 through the tube 31 through a small orifice 39 at the outlet end of the tube of about the same diameter as the yarn, while the steam escapes from the tube 31 through a restricted outlet 37. Between the orifice 39 and the drawing roll 42 the yarn contacts a pivoted member 44 which is sensitive to changes in the tension of the yarn and which operates a control means 45 (described in Specification 540,108) comprising a valve (not shown) in the steam supply line 46.  The control means may, instead or in addition, control the speeds of the rolls 40 and 42.  The process increases the safe ironing temperature of the yarns and their dimensional stability at high temperatures.  Specifications 687,414, 719,853, 719,860, 721,674, 726,900, 731,930, 748,772, 758,442, 772,281, 772,282, [Group XXIX], and 776,346 also are referred to.