US2581566A

US2581566A - Production of spun yarns

Info

Publication number: US2581566A
Application number: US58432A
Authority: US
Inventors: Whitehead William; John B Stelding; Leo B Brown; William L Rooney
Original assignee: Celanese Corp
Current assignee: Celanese Corp
Priority date: 1948-11-05
Filing date: 1948-11-05
Publication date: 1952-01-08
Anticipated expiration: 1969-01-08
Also published as: GB667147A

Description

Patented Jan. 8, 1952 PRODUCTION OF SPUN YARNS William Whitehead, Forest Hills N. Y., and John B. Steiding, Midland, and Leo B. Brown and William L. Rooney, Cumberland, Md., assignors to Celanese Corporation of America, a corporation of Delaware Application November 5, 1948, Serial No. 58,432

l7 Claims.

This invention relates to textiles, and relates more particularly to a process for producing staple fibers, rovings and spun yarns.

As is well known, continuous filaments of regenerated cellulose exhibiting an exceptionally high-tenacity and dimensional stability may be produced by thesaponification of stretched filaments having a basis of an organic acid ester of cellulose. If the continuous high-tenacity regenerated cellulose filaments produced in this manner are converted to fibers of staple length, they may be employed for the production of spun yarns which find extensive application wherever yarns of unusually high strength and dimensional stability are desired. However, the manufacturing cost of these yarns has been high since the processes hitherto proposed for their production have been relatively complex.

It is an important object of this invention to provide a process for producing spun yarns of high-tenacity regenerated cellulose staple fibers which will overcome the foregoing and other disadvantages of the prior processes, and which will be especially simple and efficient in operation.

A further object of this invention is the provision of a process for producing high-tenacity regenerated cellulose staple fibers, rovings and spun yarns, in which a tow of continuous filaments having a basis of an organic acid ester of cellulose is stretched while the filaments are in a plasticized or softened state, the tow of stretched filaments is converted to a roving by breaker-drafting and twisting operations, and the roving is then saponified and spun into yarn.

Other objects of this invention, together with certain details of construction, will be apparent from the followin detailed description and claims.

In carrying out the process of our invention, we form a bundle or tow of a plurality of continuous filaments having a basis of an organic acid ester of cellulose. Thereafter, all of the filaments in the tow are plasticized or softened and the tow is stretched while the'filaments are in the plasticized or softenedstate. The filaments of the tow are restored to their unplasticized state and the tow is converted to a sliver by breaker-drafting which reduces the continuous filaments to fibers of staple length. A twist is then imparted to the sliver to convert the same into a roving. The staple fibers making up this roving are saponified by treatment of the roving with saponifying agents and, after washing and drying, the roving is spun into a yarn. By carrying out the production of spun yarns of hightenacity regenerated cellulose staple fibers in accordance with this process, many of the steps hitherto deemed necessary in the production of said yarns are completely eliminated, and the manufacturing cost of the yarns is thereby reatly reduced.

The continuous filaments which are employed into a tow directly as they leave the spinning cabinets in which they are formed, or the tow may be produced by assembling the filaments from a plurality of packages on which they have been previously wound. Any desired number of filaments between about and 15,000 may go to form the tow. The denier of each of the filaments may vary between about 2 and 40 and the total denier of the tow may vary between about 10,000 and 150,000. The number of filaments, the denier of the individual filaments and the total denier of the tow will depend largely upon the results desired and upon the manner in which the process is carried out. After being formed, the tow may be passed directly to the next stage of the process, but it is first preferably wound onto a support, coiled into a can, or otherwise suitably packaged.

After the tow has been formed, all of the filaments in the tow must be plasticized before the tow is stretched. Any of a number of expedlents may be employed, either alone or in combination, to effect this plasticization. For example, the tow may be subjected to the action of various solvents or softening materials such as dioxan, diacetone alcohol, diethylene glycol diacetate or glycerol formal. In general, however, it is preferred to plasticize the filaments by subjecting them to the action of steam or hot water having a temperature between about 100 and C., since steam and hot water are less expensive than other plasticizing agents. In addition, filaments plasticized with steam or hot water may be returned to an unplasticized state simply by permitting them to cool, whereas in returning filaments plasticized with other materials to the unplasticized state, they must be subjected to special treatments such as washing to remove the plastlcizing agents therefrom.

effect a certain draft of the sliver.

The tow of continuous, plasticized filaments is subjected to a stretching operation during which the individual filaments are elongated from about 150 to 2000% based on their original length. If desired, the plasticizing' and stretching .of the tow may be carried out simultaneously by passing the tow through a chamber to which the plasticizing agent is admitted, and applying sufficient stress to the tow to obtain the required elongation of the filaments. After the stretching operation is com leted, the filaments in the tow are restored to an unplasticized state by removing the solvent or softening agents therefrom or, when water or steam have been em loyed as the plasticizing a ents, by cooling the filaments. As a result of the stretching operation the total denier of the tow will be reduced to between about 1,000 and 15,000. The tow of stretched filaments may be passed directly and continuously to the nexto eration or it may be packaged in any suitable manner.

The stretched filaments have a low extensibility as a result ofwhich they will exhibit only a small elongation when subjected to stress. In addition, the stretched filaments have a good elastic memory so that they may be stressed even to their breaking point, and the fibers produced by breaking will return to their original length and will regain their original physical properties rapidly.

One or preferably several tows containing the stretched filaments are next passed to a set of breaker-draft rollers operating at a draft ratio between about 1.5 and 3.0, or more, which will break all of the continuous filaments into individual fibers of staple length thereby converting the tow into a sliver. In addition to breaking the filaments, the breaker-draft rollers will also The length of the staple fibers, which preferably ranges from about 3 to 8 inches, will depend upon the spacing between the breaker-draft rollers, being about one or two inches le s than said spacing. Owing v to the low extensibility of the stretched filaments,

only a low draft ratio is needed to insure the breakin of all the filaments into fibers of staple length. Moreover, as a result of the good elastic memory of the stretched filaments, the fibers produced therefrom will have physical properties very similar to those of the continuous filaments. This is in sharp contrast to the behaviour of other filamentary materials whose physical properties are permanently altered by being stressed to their breaking point. Although all of the continuous filaments are broken into fibers of staple length during the drafting operation, the sliver itself retains its continuity since the filament breaks are distributed unevenly therethrough.

After the sliver leaves the breaker-draft rollers it has a twist imparted thereto producing a roving, the twist preventing the separation of the individual fibers during the subsequent liquid treatments of said roving. The twist should not be lower than about 0.25 turn per inch nor higher than about 1 turn per inch, since a lower degree of twist will permit the individual staple fibers to separate from the roving and a higher degree of twist will hinder the penetration of treating solutions into the roving thereby unduly lengthening the time of treatment. The necessary twist may be imparted to the sliver in any desired manner. For example, the sliver may be passed to a fly frame, a cap frame, or a ring frame which will simultaneously draft the sliver, impart the required number of turns per inch thereto, and wind the resultant roving onto a bobbin or other suitable package.

The roving may then be saponified' either continuously or intermittently. The packages of roving may, for example, be immersed into a saponification bath for a sufllcient period of time to effect the complete saponification of the fibers. Or, if desired, the roving may be rewound into larger packages ranging up to 6, or more pounds in weight before saponification. Alternatively, a saponification bath may be applied to the roving as it is drawn from the package on which it has been wound or directly as it leaves the twisting apparatus in which it is formed. During the saponification treatment the staple fibers decrease by approximately 39% in cross-sectional area. As a result of this decrease in cross-sectional area there is a. strong tendency for the staple fibers to separate from the roving and to snarl and mat. By having a minimum of 0.25 turn per inch in the roving before the saponification solution is applied thereto, this tendency for the staple fibers to snarl and mat is completely eliminated. When the saponification is complete, the roving may be washed to remove the residual saponification solution and the salts formed during the saponification therefrom, after which the roving is dried and is ready to be spun into yarn.

The saponification of the staple fibers in the roving may be carried out with any desired type of saponifying bath. Among the baths which are suitable for this purpose are solutions of alkaline materials such as sodium hydroxide, sodium carbonate, or ammonium hydroxide. Mixtures of such alkaline materials and buffering agents including sodium acetate, sodium citrate, or sodium sulfate may also be employed. If desired, the saponifying bath may be maintained at elevated temperatures to increase the rapidity with which it acts.

It has been found that during the saponification, washing and drying steps there is an initial increase followed by a subsequent decrease in the length of the roving. Immediately after the saponification solution is applied, there is a rapid increase in the length of the roving which is followed by a slight shrinkage during the remainder of the saponification period. The rate of shrinkage increases during the subsequent washing and drying steps. If the saponification, washing and drying are carried out continuously as the roving passes from one point to another, provision must be made to prevent an excessive amount of slack from developing in the roving as its length in creases and to prevent excessive tensions from being built up in the roving as it shrinks. One manner in which compensation may be made for both the initial increase in the length of the roving and its subsequent shrinkage, is to carry out the treatments of the rovin as it passes over two spaced rollers, having diameters which vary along the length thereof. By having the diameter of the rollers increase sharply at their feed end, decrease slightly in the portion of the rollers adjacent the feed end and decrease more rapidly at their discharge end, there will be no opportunity for either excessive slack or excessive tensions to develop in the roving.

After the saponification, washing and drying steps have been completed, one, or a number of rovings may be spun in conventional manner to produce a yarn of any desired denier. The yarn produced in this manner exhibits a. tenacity ranging up to 4 or 5, or more, grams per denier and also has an exceptionally good dimensional stability. It may be employed either alone or inan apparatus for plasticizing and stretching a tow of continuous filaments,

Fig. 2 is a diagrammatic view of an apparatus for breaker-drafting and twisting a tow of continuous filaments to convert the same into a roving, and

Fig. 3 is a diagrammatic view of an apparatus for continuously saponifying, washing and drying a roving of staple fibers having a basis of an organic acid ester of cellulose.

Like reference numerals indicate like parts throughout the several views of the drawing.

Referring now to the drawing, the reference numeral II designates a tow of continuous filaments which is plasticized and stretched while passing through a chamber indicated generally by the reference numeral I2. The chamber I2 is defined by a lower wall I3, upper walls I4 and I6, and end walls I1 and I8. Partitions I9, 2|

and 22 divide the chamber I2 into four

compartments

23, 24, 26 and 21 through which the tow II passes in succession. The tow II enters compartment 23 through an aperture 28 in the end wall I1, passes around pulleys 29, 3| and 32, which are positively driven by any suitable means (not shown), and leaves said compartment through an aperture 33 in the partition I9. The tow I I then traverses

compartments

24, 26 and 21, passing through

apertures

34, 36, and 31 in the partitions 2| and 22 and in the end wall I6, respectively. The clearance between the tow II and the apertures through which it passes is preferably kept at a minimum, consistent with the free movement of the tow, to limit leakage oi the plasticizing agent through said apertures. Since the stretched tow has a smaller diameter than the unstretched tow, the

apertures

36 and 31 must be of smaller cross-sectional area than the

apertures

28, 33 and 34 to maintain this minimum clearance. After leaving the chamber I2, the tow II is wrapped several times around a wheel 38 which is positively driven by any suitable means (not shown).

A plasticizing agent such as steam under pressure is admitted into the compartment 26 through a pipe 39 and, after acting to plasticize the filaments in the tow II, leaves said compartment through a second pipe 4I The steam in the compartment 26 tends to escape past the tow II through the

apertures

34 and 36 exerting a strong stretching force on the plasticized tow 'II. If this fiow of steam were permitted to proceed unchecked it would break the filaments in said tow. To limit the flow of steam through the aperture 34, cold water under a pressure only slightly less than the pressure of the steam is forced into the compartment 23 through a pipe 42. The water flows from the compartment 23 through the aperture 33 past the tow II into the, compartment 24. The pressure of the water in the compartment 24 limits the fiow of steam through the aperture 34 thereby limiting the stretching force exerted by said fiow of steam on the tow II. What steam does enter the compartment 24 is condensed by the water therein, and leaves said compartment together with the water through a pipe 43. While the water in the compartment 23 flows past the tow II through the aperture 26 exerting an endwise force on the tow, this force is not objectionable since it is not transmitted past the pulleys 28, 3| and 32 and is therefore restricted to the unplasticized tow.

Similarly, to limit the flow of steam through the aperture 36, cold water under a pressure less than the pressure of the steam in the compartment 26 is forced into the compartment 21 through a pipe 44. The steam entering the compartment 21 is condensed by the water in said compartment and leaves the compartment to gether with the water through a pipe 46. The water in the compartment 21, in addition to controlling the rate of flow of steam through the aperture 36, also serves to cool the tow and restore it to its unplasticized state. By regulating the difference in pressure between the steam in compartment 26 and the water in compartment 21, the rate of fiow of steam through the aperture 36 may be controlled, thereby regulating the endwise force resulting from said flow on the tow. An additional endwise force is exerted on the tow I I by the flow of water from the compartment 21 past the tow I I through the aperture 31. The tow II is drawn from the chamber I2 by means of the wheel 36 which rotates at a higher peripheral speed than the

pulleys

29, 3I and 32. The cumulative effect of the endwise forces exerted on the tow II by the flow of steam through the aperture 36, the flow of water through the aperture 31 and the rotation of the wheel 36 acts to impart the desired stretch to said tow. By varying the peripheral speed of the wheel 36, with or without changing the pressures in the several compart ments of the chamber I2, the degree of stretching of tow I I may be varied over a wide range.

After the tow II has been stretched and restored to its unplasticized state, it is passed to a first set of breaker-

draft rollers

41, 48 and 49 which are positively driven at a given peripheral speed by any suitable means (not shown). Any of these three rolls may have a rigid edge embedded therein for the purpose of weakening the tow at spaced points. The tow II then passes to a second set of breaker-draft rollers 5| and 5 2 which are positively driven by any suitable means (not shown) at a higher peripheral speed than that of the first set of breaker-draft rollers. The difference in the peripheral speeds of the first and second set of breaker-draft rollers breaks the continuous filaments in the tow to fibers of staple length, produces a sliver 53 and also drafts the sliver thereby reducing its denier. The staple fibers are from one to two inches shorter than the spacing between the first and second set of breaker-draft rollers, and by varying said spacing it is possible to control the lengthof the staple fibers in the sliver 53.

From the breaker-draft rollers, the sliver 53 passes to a slubber, intermediate or fiy-frame, indicated generally by the reference numeral 54, which draws the sliver and imparts a twist thereto, converting the same into a roving 56 and winds said roving onto a bobbin 51. The flyframe 54 comprises a flyer 58 which rotates about a shaft 59, and an arm 6| which is traversed by any suitable means (not shown) to wind the roving 66 onto the bobbin 51 The roving 56, after being unwound from the bobbin 61, is passed over a pulley 62 to a set of positively-driven hollow rollers 63 upon which it is saponified, washed and finally dried in a continuous manner. At their feed end 64, the diameter of the rollers 63 increases rapidly to take up 7 the slack which develops in the roving immediately after the saponifying solution is applied thereto. Next adjacent the feed end 64, the diameter of the rollers 63 decreases slightly as at 66 to accommodate the slight shrinkage which takes place in the roving 56 as the saponifying agent continues to act thereon. Finally, at their discharge end 61, the diameter of the rollers 63 decreases more rapidly to accommodate the shrinkage of the roving 56 during the washing and drying steps.

Positioned above the rollers 63, is a header 68 provided with a plurality of jets 69 through which the saponifying bath is applied 'to the roving 56. Adjacent the header 68, is a second header 1|, similarly provided with a plurality of jets 12 by means of which wash water is applied to the roving 56 to wash away the residue of the saponifying solution. After acting on the roving, the saponifying bath.'and wash water are collected in a pan 13, from which they may be removed through a drain 14. The saponified and washed roving is then dried as it passes over the heated end of each of the rollers 63. To effect this heating, a compartment 16 is formed in each of the rollers 63 by means of internally positioned walls 11. Steam or other suitable heating medium is admitted into the compartments 16 through pipes 16, which also act as bearings upon which the rollers 63 are journalled. The condensate which is formed in the compartments (6 is discharged therefrom through pipes 19 which are positioned concentrically of the pipes 18. After being dried, the roving 56 passes from the rollers 63 over a pulley 8|, and may be packaged or led directly to a spinning frame for conversion into yarn.

The following example is given to illustrate this invention:

Example A tow of 1,440 cellulose acetate filaments having a total denier of about 15,552 is entered into the chamber l2. Saturated steam at a pressure of about 45 pounds per square inch above atmospheric and a temperature of about 130 C. is admitted into the compartment 26 and acts to plasticize the filaments in the tow as it passes therethrough. Simultaneously, water at room temperature of about C. is forced into the compartment 23 at a pressure of about 38 pounds per square inch above atmospheric to limit the flow of steam through the aperture 34. Water at room temperature of about 25 C. is also forced into the compartment 21 at a pressure of about 8 pounds per square inch above atmospheric to control the flow of steam through the aperture 36. After leaving the chamber 12 the tow passes around the wheel 38 which is driven at a pcripheral speed 9.5 times as great as the peripheral speed of the pulleys 29, 3| and 32. The tow is stretched in this manner to increase its length to about 9.5 times its original length while its total denier is reduced to about 1650. Two ends of the stretched tow are passed simultaneously to the breaker-draft rollers, which are spaced about six inches apart and are operated with the second set of rollers 5| and 52 having a peripheral speed about 1.6 times the speed of the first set of

rollers

41, 48 and 49. The continuous filaments making up the tow are broken into fibers of staple length as they pass through the breaker-draft rollers converting the tow into a sliver. From the breaker-draft rollers, the tow passes directly to the fly frame which twists and draws the sliver into a roving having a total denier of about 2100 and approximately 0.25 turn per inch, and winds the roving onto a package. The roving is then unwound lfrom the package and is saponified by being subjected for two minutes to the action of a saponifying bath maintained at a temperature of 98 C. and having a concentration of 3% sodium hydroxide and 8% sodium acetate. The roving is then washed for one minute and is finally dried. During the saponification, the fibers lose a portion of their weight with the result that the dried roving has a total denier of about 1300. Two ends of the roving are then doubled and converted to a yarn on a conventional ring spinning frame in which the spindles rotate at a speed of about 7500 R. P. M., operated at a draft ratio of about 30 and employing 2 inch rings. The yarn exhibits a tenacity between about 4 to 5 grams per denier and an unusually high dimensional stability.

It is to be understood that the foregoing detailed description is given merely by way of iilustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention, what we desire to secure by Letters Patent is:

1. In a process for producing spun yarns and the like of high-tenacity regenerated cellulose staple fibers from a tow of stretched continuous filaments having a basis of an organic acid ester of cellulose, the steps which comprise breakerdrafting said tow-while the filaments are in an unplasticized state to convert the continuous filaments into fibers of staple length, and saponifying the fibers to convert the organic acid ester of cellulose to regenerated cellulose.

2. In a process for producing spun yarns and the like of high-tenacity regenerated cellulose staple fibers from a tow of stretched continuous filaments having a basis of an organic acid ester of cellulose, the steps which comprise converting said tow to a sliver by breaker-drafting said tow while the filaments are in an unplasticized state to convert the continuous filaments into fibers of staple length, imparting a twist to the sliver to convert the same into a roving, and saponilying said roving to convert the organic acid ester of cellulose to regenerated cellulose.

3. In a process for producing spun yarns and the like of high-tenacity regenerated cellulose staple fibers from a tow of stretched continuous filaments having a basis of an organic acid ester of cellulose, the steps which comprise converting said tow to a sliver by breaker-drafting said tow while the filaments are in an unplasticized state to convert the continuous filaments into fibers of staple length, imparting a twist of between about 0.25 and 1 turn per inch to the sliver to convert the same into a roving, and saponifying said roving to convert the organic acid ester of cellulose to regenerated cellulose.

4. In a process for producing spun yarns and the like of high-tenacity regenerated cellulose staple fibers from a tow of continuous filaments having a basis of an organic acid ester of cellulose, the steps which comprise stretching said tow, breaker-drafting said tow while the filaments are in an unplasticized state to convert the continuous filaments into fibers of staple length, and saponifying the fibers to convert the organic acid ester of cellulose to regenerated cellulose.

5. In a process for producing spun yarns and the like oi high-tenacity regenerated cellulose staple fibers from a tow of continuous filaments having a basis of an organic acid ester of cellulose, the steps which comprise stretching said tow while the filaments are in a plasticized state, breaker-drafting said tow while the filaments are in an unplasticized state to convert the continuous filaments into fibers of staple length, and saponifying the fibers to convert the organic acid ester of cellulose to regenerated cellulose.

6. In a process for producing spun yarns and the like of high-tenacity regenerated cellulose staple fibers from a tow of continuous filaments having a basis of an organic acid ester of cellulose, the steps which comprise stretching said tow while the filaments are in a plasticized state, converting said tow to a sliver by breaker-drafting said tow while the filaments are in an unplasticized state to convert the continuous filaments into fibers of staple length, imparting a twist to the sliver to convert the same into a roving, and saponifying said roving to convert the organic acid ester of cellulose to regenerated cellulose.

'7. In a process for producing spun yarns and the like of high-tenacity regenerated cellulose staple fibers from a tow of continuous filaments having a basis of an organic acid ester of cellulose, the steps which comprise plasticizing the filaments in said tow, stretching said tow while the filaments are in a plasticized state, returning the filaments in said tow to an unplasticized state, converting said tow to a sliver by breakerdrafting said tow while the filaments are in an unplasticized state to convert the continuous filaments into fibers of staple length without interrupting the continuity of the tow, imparting a twist to the sliver to convert the same into a roving, and saponifying said roving to convert the organic acid ester of cellulose to regenerated cellulose.

8. In a process for producing spun yarns and the like of high-tenacity regenerated cellulose staple fibers from a tow of continuous filaments having a basis of an organic acid ester of cellulose, the steps which comprise plasticizing the filaments in said tow by subjecting said filaments to the action of steam or hot water, stretching said tow while the filaments are in a plasticized state, returning the filaments in said tow to an unplasticized state by cooling said filaments, converting said tow to a sliver by breaker-drafting said tow while the filaments are in an unplasticized state to convert the continuous filaments into fibers of staple length without interrupting the continuity of the tow, imparting a twist to the sliver to convert the same into a roving, and saponifying said roving to convert the organic acid ester of cellulose to regenerated cellulose.

9. In a process for producing spun yarns and the like of high-tenacity regenerated cellulose staple fibers from a tow of continuous filaments having a basis of an organic acid ester of cellulose, the steps which comprise plasticizing the filaments in said tow, stretchin said tow while the filaments are in a plasticized state, returning the filaments in said tow to the unplasticized state, converting said tow to a sliver by breakerdrafting said tow while the filaments are in an unplasticized state to convert the continuous filaments into fibers of staple length without interrupting the continuity of the tow, imparting a twist to and drafting the sliver to convert the same into a roving, and saponifying said roving to convert the organic acid ester of cellulose to regenerated cellulose.

10. In a process for producing spun yarns and the like of high-tenacity regenerated cellulose staple fibers from a tow of stretched continuous filaments having a basis of cellulose acetate, the steps which comprise converting said tow to a sliver by breaker-drafting said tow while the filaments are in an unplasticized state to convert the continuous filaments into fibers of staple length, and saponifying the fibers to convert the cellulose acetate to regenerated cellulose.

11. In a process for producing spun yarns and the like of high-tenacity regenerated. cellulose staple fibers from a tow of stretched continuous filaments having a basis of cellulose acetate, the steps which comprise converting said tow to a sliver by breaker-draiting said tow While the filaments are in an unplasticized state to convert the continuous filaments into fibers of staple length, imparting a twist to the sliver to convert the same into a roving, and saponifying said roving to convert the cellulose acetate to regenerated cellulose.

12. In a process for producing spun yarns and the like of high-tenacity regenerated cellulose staple fibers from a tow of continuous filaments having a basis of cellulose acetate, the steps which comprise stretching said tow while the filaments are in a plasticized state, converting said tow to a sliver by breaker-drafting said tow while the filaments are in an unplasticized state to convert the continuous filaments into fibers of staple length, imparting a twist to the sliver to convert the same into a roving, and saponifying said roving to convert the cellulose acetate to regenerated cellulose.

13. In a process for producing spun yarns and the like of high-tenacity regenerated cellulose staple fibers from a tow of continuous filaments having a basis of cellulose acetate, the steps which comprise plasticizing the filaments in said tow, stretching said tow while the filaments are in a plasticized state, returning the filaments in said tow to an unplasticized state, converting said tow to a sliver by breaker-drafting said tow while the filaments are in an unplasticiz ed state to convert the continuous filaments into fibers of staple length without interrupting the continuity of the tow, imparting a twist to the sliver to convert the same into a roving, and saponifying said roving to convert the cellulose acetate to regenerated cellulose.

14. In a process for producing spun yarns and the like of high-tenacity regenerated cellulose staple fibers from a tow of continuous: filaments having a basis of cellulose acetate, the steps which comprise plasticizing the filaments in said tow by subjecting said filaments to the action of steam or hot Water, stretching said tow while the filaments are in a plasticized state, returning the filaments in said tow to an unplasticized state by cooling said filaments, converting said tow to a sliver by breaker-drafting said. tow while the filaments are in an unplasticized state to convert the continuous filaments into fibers of staple length without interrupting the continuity of the tow, imparting a twist to the sliver to convert the same into a roving, and saponifying said roving to convert the cellulose acetate to regenerated cellulose.

15. In a process for producing spun yarns and the like of high-tenacity regenerated cellulose staple fibers from a tow of continuous filaments having a basis of cellulose acetate, the steps which comprise plasticizing the filaments in said tow, stretching said tow while the filaments are in a plasticized state, returning the filaments in said tow to an unplasticized state, converting said tow to a sliver by breaker-drafting said tow while menses the filaments are in an unplasticized state to convert the continuous filaments into fibers of staple length without interrupting the continuity of the tow, imparting a twist to and drafting the sliver to convert the same into a roving, and saponitying said roving to convert the cellulose acetate to regenerated cellulose.

16. In a process 'for producing spun yarns and the like of high-tenacity regenerated cellulose staple fibers from a tow of between about 100 and 15,000 continuous filaments having a basis of an organic acid ester of cellulose and a total denier of between about 10,000 and 150,000, the steps which comprise stretching said tow to increase the length of the filaments in said tow by between about 150 to 2000% based on their original length while the filaments in said tow are in a plasticized state, converting said tow to a sliver by breaker-drafting said tow while the filaments are in an unplasticized state to convert the continuous filaments into fibers having a length of between about 3 and 8 inches, imparting a twist of between about 0.25 and 1 turn per inch to the sliver to convert the same into a roving, and saponifying said roving. to convert the organic acid ester of cellulose to regenerated eellulose.

17. In a process for producing spun yarns and the like of high-tenacity regenerated cellulose 12 the filaments in said tow are in a plasticized state, converting said tow to a sliver by breakerdratting said tow while the filaments are in an unplasticized state to convert the continuous filaments into fibers having a length of between about 3 and 8 inches, imparting a twist of between about 0.25 and 1 turn per inch to the sliver to convert the same into a roving, and saponiiying said roving to convert the cellulose acetate to regenerated cellulose.

WILLIAM WHITEHEAD. JOHN B. STEIDING. LEO B. BROWN. WILLIAM L. ROONEY.

REFERENCES CITED The following references are or record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,003,400 Taylor et a1. June 4, 1935 2,053,766 Dreyfus Sept. 8, 1936 2,067,062 Gswald Jan. 5, 1937 2,091,967 Dreyfus Sept. 7, 1937 2,098,981 Sowter Nov. 16, 1937 2,127,283 Beek et a1. Aug. 16, 1939 2,211,920 Aiibert.. Aug. 20, 1940 2,427,955 Furness Sept. 23, 1947 2,432,355 tt Dec. 9, 1947 EDGE? PA 5- Number Country Date 635,987 Great Britain Mar. 8, 1935 467,251

Great Britain Sept. 9, 1935

Claims

1. IN A PROCESS FOR PRODUCING SPUN YARNS AND THE LIKE OF HIGH-TENACITY REGENERATED CELLULOSE STAPLE FIBERS FROM A TOW OF STRETCHED CONTINUOUS FILAMENTS HAVING A BASIS OF AN ORGANIC ACID ESTER OF CELLULOSE, THE STEPS WHICH COMPRISE BREAKERDRAFTING SAID TOW WHILE THE FILAMENTS ARE IN AN UNPLASTICIZER STATE TO CONVERT THE CONTINUOUS FILAMENTS INTO FIBERS OF STAPLE LENGTH, AND SAPONIFYING THE FIBERS TO CONVERT THE ORGANIC ACID ESTER OF CELLULOSE TO REGENERATED CELLULOSE.