US2272666A - Process of dry spinning artificial thread - Google Patents

Description

Feb. 10, 1942. R. M. HOFFMAN 2,272,666

PROCESS OF DRY SPINNING ARTIFICIAL THREAD Filed Oct. 23, 1937 6% W TTORNEYS.

Patented Feb. 10, 1942 PROCESS OF DRY SPINNING ARTIFICIAL THREAD Robert M. Hoflman, Waynesboro, Va., assignor to E. I. du Pont de'Nemours & Company, Wilmington, Del., a corporation of Delaware Application October 23, 1937, Serial No. 170,617 '1 Claims. (Cl. 16-54) The instant invention pertains to the dry spinning of threads. yarns, or the like having sharp variations in denier along their length.

Previous attempts to dry spin cellulose acetate or other cellulose derivative yarn of variable or uneven denier in order to simulate the novelty effect obtainable with natural or wild silk have been attended with an indifferent amount of success. The principal difiiculty with the prior method of forming such materials has been that the size of the thickened portions and the abruptness of variation from the thin to the thick portions has not been suflicient to give the desired efiects in the finished fabric. Regenerated cellulose and similar materials formed by extrusion of a coagulable solution such as viscose into a liquid coagulating bath have attained a variation of size, frequency and abruptness of variation that is eminently satisfactory. Hitherto, however, it has not been possible to attain similar results in products which are formed by dry spinning, such as cellulose acetate.

One object of the present invention is to furnish a variable denier cellulos derivative yarn, particularly cellulose acetate. Another object is to provide a relatively simple process of dry spinning variable denier yam without causing frequent yarn breaks. Still another object is to provide a variable denier cellulose acetate yarn in which the variations are relatively large in size, abrupt, and preferably at random intervals.

These objects are accomplished in general by extruding a cellulose derivative solution such as cellulose acetate into a gaseous evaporating medium flowing countercurrently to the direction of extrusion and atthe same time periodically varying the ratio of speed of extrusion to the speed at which the yarn is withdrawn from contact with said evaporating medium.

In the drawing, Figure 1 illustrates a side elevation, partly in cross-section, of 'an apparatus for performing the invention; Figure 2 is a secevaporated, the resulting yarn is withdrawn continuously from the spinning cell at a rate which varies in relation to the rate of extrusion and then wound upon a suitable collecting device. The

variation in ratio between the take-up speed and the extrusion speed is-secured either by keeping the extrusion speed constant and varying the take-up speed or by keeping the take-up speed constant and varying the extrusion speed or by combining both methods. In practice, it is preferred to apply the former procedure in that it entails the least number of changes to existing equipment. This may be effected by any of the known methods such, for example, as described in the patent to Picard and Oriol, No. 2,120,990, filed January 28, 1936. In any case, the draw-off should be so situated and spaced with respect to the extrusion orifice that it exerts on the yarn an irregularly varying pull extending to the plastic portion of the yarn in the spinning cell. Preferably, the mechanism designed to accomplish the variations is such that variation in denier is random both with respect to size and spacing of the thickened portions. Tnis may be accomplished by means of the draw-ofimechanism disclosed in the patent to Picard and Oriol, No. 2,120,990.

The variable draw-off which, in efiect, causes alternate stretching and relaxing of the plastic portion of the cellulose acetate yarn in dry spinning, may be accomplished in almost any suitable fashion. For instance, the cellulose acetate yarn may be passed over a cylindrical roller, the rotational speed of which is changed at intervals and to amounts and for periods corresponding to the frequency, degree, and length of irregularity desired. Alternatively, cellulose acetate yarn may be passed over an elliptically or other irregularly shaped roller which varies the linear speed at which the yarn is withdrawn from the spinning cell, as in the Picard and Oriol application referred to above. If. desired, such roller may be eccentrically mounted and may be caused to move bodily, for instance to and fro, either continuous- 1y or intermittently while rotating. As another alternative, the cellulose acetate yarn may be conducted over or around a rotating roller or drum having a diameter which varies along its length. In such case, a variable draw-ofl is secured by shifting the position of the yarn along the drum either by means of a shifting guide or by traversing the drum on an axially slidable .shaft. For this purpose, the drum or roller may I be any suitable shape such as a truncated cone.

Finally. the variable draw-off may be secured by moving bars across the yarn path to lengthen the length of travel from the spinning cell to the wind-up. The last mentioned type is illustrated in the drawing.

The variation in yarn denier may also be effectcd by a constant draw-oi! in combination with avarying. rate of extrusion which. may be induced, for example, by production of pulsations in the delivery or the spinning solution to the spinneret, suitably actuated members such as diaphragms, pistons, or plungers being forthi's' purpose caused to vibrate, reciprocate, or oscillate in contact with the spinning solution. Any suitable means such as cams or eccentrics may be used for actuating the pulsation device. Thus, dia- .10 phragms exposed on one side of the spinning solution may be caused to vibrate by pulsations transmitted through a fluid acting on their other side,

a suitably actuated plunger being employed to produce the pulsations in the transmitting fiuid., To secure optimum variations in pump or supply delivery and thereby optimum variation in yarn denier, it is important that the connecting pipe therefrom to the spinneretbe'short and of a rigid character so that the pulsation be not excessively dampened prior to extrusion of the solution through the spinneret.

Regardless of how a varying ratio of extrusion speed to take-up speed is accomplished, it

- is essential for the securement of a sharp varia- 5 tion in denier that the flow of air or other gaseous evaporating medium inthespinning cell be directed countercurrent to the travel of the thread from the spinneret. In downward spinning, in view of the fact that gravity aids the an travel of the thread in its direction of with-' drawal, the velocity of countercurrent. air flow should, preferably be .at ieast. 60 yards per minute when thespeed oi. withdrawal of the yarn is 100 yards per minute'or more. Whatever the direc-- tion of extrusion, the speed of withdrawal should preferably average at least 100 yards per minute and the speed of counterfiow at least yards per minute. At higher withdrawal speeds; the velocity of counterflow should be somewhat 40 higher. The counterfiow should extend substantiallythe entire length of the spinning cell although beneficial eflects are still obtained, provided the air flow is countercurrent to the travel of the yarn over at least the region wherein the I yarn still remains in a plastic state. In general, with other conditions constant, the higher the ratio of velocity of counterflow to speed of extrusion, the sharper the variation in denier.

. The counterflow may be eithera continuous stream'or an intermittent flow of air. It intermittent, depending on the effect desired, the counterflow may be pulsating or may be definitely interrupted at intervals of shorter or longer duration. Likewise, the intermittent counterflow may be an inor an out-oi-phase synchronism with a variable .delivery mechanism.

The drawing illustrates one type ofapparatus designed to accomplish these'results. An acetone solution of cellulose acetate from a supply 00 pipe I is extruded through a spinneret '2 to produce a filamentary yam 8 which is led downward through a spinning cell 4 to a guide 6 from which the thread is led out of the spinning cell through the aperture 1. At the bottom of the i5 spinning cell 4, air is introduced through the opening 5 and passed upwardly through the spinning cell and withdrawn through aspiration pipe 3. After emerging from the spinning cell, the yarn 8 is led through guide is and is passed through the bars I! and M, then through guide 20 and over guide rollers l6, l1, and II and wound on a suitable -bobbin or sleeve IL The bars l3 and M are attached to a crank shaker arm II which in turn is attached rigidly at It some .to a shaft 0. At the lower end'oi'shait 0 is connected an arm lihavingaslotil'inwhichismovably mounted a pin 23 attached to a wheel 22.

The wheel 22 is given an irregular motion bymeans or the motor 25 operating-througha magnetie' clutch 24 of the type described in-the Patent No.'2,l20,990 to Picard and Oriol. The circular motion of the pin 23 gives to the arm II a rocking motion, which in turn gives bars I! and I4 a similar motion. Due to the fact that the rotation of the wheel 22 is irregular or at varying rates of speed (due to the magnetic clutch 24), the rocking motion of the bars I! and I4 is also irregular, thus giving to the thread not only a variable denier, but also variations in denier at irregular or random intervals.

For convenience the invention has been described in terms of dry spinning a variable denier cellulose acetate yarn. Obviously, it is equally applicable to the dry spinning of an artificial variable denier yarn consisting of cellulose esters such as cellulose 'actopropionate, cellulose propionate, or cellulose ethers such as methyl, ethyl, and benzyl cellulose, or polyvinyl alcohol and/or acetals and/or ester derivatives thereof or synthetic resins such as are disclosed in Carothers U. 8. Patent No. 2,071,253.

The process .of the invention makes possible, for the first time, a, sharp transition from thick to thin portions in cellulose derivative threads. By this method it is possible to make in yarn having an average denier of 300, thick portions of less than three inches in length and have a maximum size at least 500 denier greater than the average, and in which the increase in size is at least 200 denier per cm. oi! yarn length. In addition to making possible the production or unique variable denier cellulose acetate yarn, the process 01': the invention offers the advantage of, being substantially continuous ingthat yarn breaks are comparatively Iew and far between, possibly due to the fact' that the yarn tends to be kept taut with respect to take-up members even though the ratio of extrusion speed to speed of withdrawal is varied;

..Since it is obvious that many changes and modifications may be made in the above process as described without departure from the spirit 'and nature of the inventiomit is to be understood the invention is not to be limited thereto except as set forth in the ap nded claims.

I claim:

1. The method of forming variable denier cellulose derivative yam comprising extruding a cellulose derivative solution into a gaseous evaporating medium traveling in a direction countercurrent to the direction 01' extrusion throughout the regionwhereinthe yarn is in aplastic state,

' and withdrawing said yarn through said gaseous evaporating medium at a speed varying at times greater than the speeds! extrusion thereby imparting abrupt variations in length of said yarn.

2. The method of forming variable denier cellulose acetate yam comprising extruding a cellulose-acetate solution into a gaseous evaporating medium traveling in a direction countercurrent to the direction 01' extrusion throughout the region wherein the yarn is in a plastic state, and withdrawing said yarn through said gaseous evapdenier along the crating medium at a speed varying at times greater than the speed of extrusion thereby imparting abrupt variations in denier along the length of said yarn.

3. The method 01 forming variable denier cellulose acetate yarn comprising extruding a cellulose acetate solution into a gaseous evaporating medium traveling in a direction countercurrent to the direction of extrusion throughout the region wherein the yarn is in a plastic state, and withdrawing said yarn through said gaseous evaporating medium at a speed varying at times greater than the speed of extrusion, the velocity of gaseous evaporating medium being at least 40 yards per minute and the'speed of withdrawal of the yarn at least 100 yards per minute thereby imparting abrupt variations in denier along the length of said yarn.

4. The method of forming variable denier cellu-.

lose acetate yarn comprising extruding a cellulose acetate solution in a downward direction into a gaseous evaporating medium traveling in an upward direction throughout the region wherein the yarn is in a plastic state, and withdrawing said yarn through saidgaseous evaporating medium at a speed varying at times greater than the speed of extrusion thereby imparting abrupt variations" in denier along the length of said yarn.

5. The method of forming variable denier cellulose acetate yam comprising extruding a cellulose acetate solution in a downward direction into a gaseous evaporating medium traveling in an upward direction throughout the region wherein the yarn is in a plastic state, and withdrawing said yarn through said gaseous evaporating medium at a speed varying at times greater than evaporating medium being at least 60 yards per minute and the speed of withdrawal of the yarn at least 100 yards per minute thereby imparting abrupt variations in denier along the length of said yarn.

6. The method of continuously dry spinning artificial yarn to form a variable denier artificial yarn which comprises extruding a spinning solution into a gaseous evaporating medium traveling in a direction countercurrent to the direction of extrusion throughout the region wherein the yarn is in a plastic state, and withdrawing said yarn through said gaseous evaporating medium at a speed varying at times greater than the speed of extrusion thereby imparting abrupt variations in denier along the length of said yarn.

'7. The method of continuously dry spinning superpolymer yarn to form a variable denier superpolymer yarn which comprises extruding a .superpolymer spinning solution into a gaseous evaporating 'medium traveling in a direction countercurrent to the direction of extrusion throughout the region wherein the yarn is in a plastic state, and withdrawing said yarn through said gaseous evaporating medium at a speed varying at. times greater than the speed of extrusion thereby imparting abrupt variations in denier along the length of said yarn.

ROBERT M. HOFFMAN.

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