US3578551A - Splittable tow - Google Patents

Abstract

A CRIMPED TOW COMPRISING A RIBBON OF CRIMPED PARALLEL CONTINUOUS FILAMENTS READILY SPLITTABLE BY PULLING OPPOSITE SIDES OF THE BAND.

Description

May 11., 1971 J. N. GRAY ETAL 3,578,551

SPLITTABLE TOW 3 Sheets-Sheet 1 Filed April 18, 1969 M ny JACK N. GRAY GEORGE A. WATSON ATTORNEY y 11, 1971 J. N. GRAY AL 3,578,551

SPLITTABLE TOW Filed April 18, 1969 Z: Sheets-Sheet 2 TiciE.

INVENTOR JACK N. GRAY GEORGE A. WATSON BY M ( ATTORNEY May 11, 1971 Y EITAL 3,578,551

SPLITTABLE TOW Filed April 18, 1969 3 Sheets-Sheet 5 INVENTOR JACK N. GRAY GEORGE A. WATSON ATTORNEY United States Patent 3,578,551 SPLI'ITABLE TOW Jack N. Gray, Columbia, S.C., and George A. Watson, Davidson, N.C., assignors to Celanese Corporation and Fiber Industries, Inc., both of New York, N.Y. Original application July 13, 1964, Ser. No. 382,017, new Patent No. 3,439,394, dated Apr. 22, 1969. Divided and this application Apr. 18, 1969, Ser. No. 817,508 Int. Cl. D02g 3/00 US. Cl. 161-173 5 Claims ABSTRACT OF THE DISCLOSURE A crimped tow comprising a ribbon of crimped parallel continuous filaments readily splittable by pulling opposite sides of the band.

This invention is a divisional application of copending application Ser. No. 382,017, filed July 13, 1964, now Pat. No. 3,439,394.

Man-made fibers which are to be cut into staple fiber length are often supplied as tows which are bundles of generally parallel continuous filaments, each such bundle containing a large number of such filaments, generally well over 500, e.g. 6,000 to 500,000. In one process for the manufacture of tows, suitable for use in making staple fibers, a number of sub-tows, each containing only a fraction of the filaments desired in the main tow, are first fed side-by-side to a draw frame where they are stretched, in a manner well known to the art (as discussed for example in Man-Made Textile Encyclopedia, edited by J. J. Press, published 1959 by Textile Book Publishers, Inc., pp. 75 and 76), to develop the desired physical properties (e.g. high tenacity and stiffness); the resulting drawn tow is then fed to a crimping device, which is preferably of the stufling box type, where the filaments are crimped, and then, in untensioned condition, onto a belt which transports the crimped tow continuously through an oven maintained at a temperature sufiiciently high to set the crimp permanently, but not high enough to damage or melt the filaments.

The draw frame, crimping device and oven are utilized most efliciently when the tow passing therethrough contains a very large number of filaments, e.g. tow whose total denier is over 200,000 and which contains over 40,- 000 filaments. However, for certain uses the crimped heatset tow must be considerably lower in weight or in filament count. For example, certain commercial tow-to-top or two-to-yarn converting machines, which are standard equipment in the mills of yarn spinners who purchase tow, are not equipped to handle heavy tows of higher total denier than 200,000.

It is an object of this invention to provide a heavy tow which may be used as such and which may also be split easily, without material damage, into a plurality of smaller tows which may be processed readily on presently available tow-to-top converting machines.

Another object of this invention is the provision of a novel process for the production of splittable tow.

Still another object of this invention is the development of a method for making a plurality of relatively light crimped heat-set tows while processing a tow of heavier weight through a draw frame and crimper.

Other objects of this invention will be apparent from the following detailed description and claims. In this decription and claims all proportions are by weight unless otherwise indicated.

In accordance with one aspect of this invention, a splittable tow is produced by passing to a crimping zone two parallel tow bands, each made up of continuous parallel untwisted filaments in which the cohesion between the filaments within each band is greater than the cohesion between the bands. The tow leaving the crimper has the same general appearance as the tow made by feeding to the crimping zone a single large band, instead of the plurality of smaller bands, and it may be handled in the same manner in the setting oven. Thus it may be laid down, as a single cohesive tow, in a sinuous path backand-forth across a moving belt passing to said oven and may be there treated to set the crimp. It is found, surprisingly, that the tow may be easily split by hand merely by grasping one side of the tow and pulling it gently while restraining the other side. The splitting takes place without any substantial breaking or tearing of the filaments of the tow, to produce two cohesive smaller crimped tows corresponding to the tow bands fed to the crimping zone; of course, if more than two bands are fed to the crimping zone, the tow will be splittable into a corresponding additional number of smaller tows.

In the drawings, which illustrate one embodiment of the invention, particularly suitable for the making of polyester tows:

FIG. 1 is a diagrammatic view, in elevation, of the process for the production of splittable tow,

FIG. 2 is a plan view (partly broken away) showing the tow in the draw zone,

FIG. 3 is a diagrammatic view in elevation, of a modification in which the tow is split before packaging,

FIG. 4 is a diagrammatic view, in elevation, of a modification in which a divider adjacent the crimping zone is employed,

FIG. 5 is a view, also in elevation, taken at right angles to FIG. 4, and

FIG. 6 is a photograph of the splittable tow shown during the splitting thereof.

Turning now to FIG. 1, reference numeral 1 designates subtows of continuous filaments, each subtow, for example, containing in the range of about 500 to 10,000 filaments and having a total denier in the range of about 750 to 150,000. The subtows, which may be supplied as coils in suitable containers, are taken through a guideboard 2, having apertures through each of which a subtow passes, and then in parallel, closely-spaced paths over and under a set of spaced, fixed, straight, round tensioning bars 3.

During the beginning of their passage around the tension bars 3 the subtows dip into a bath 4 of aqueous finish containing in low concentration (e.g. 1%) a textile finishing agent, such as a lubricant or antistatic agent. The material then passes over a set of driven feed rolls 6 through a drawing zone 7 to a set of draw rolls 8, 8a and 8b, each of which is driven at a peripheral speed substantially greater than the peripheral speed of the feed rolls, so as to stretch the. filaments appreciably (e.g. with a draw ratio in the range of about 2.5 :1 to- 6:1). The peripheral speed of the second draw roll 8a is slightly greater than that of the first draw roll 8, and the peripheral speed of the third draw roll 8b is similarly greater than that of the second; this may be effected by making the rolls of successively greater diameters: and driving them at equal rotational speeds; the peripheral speeds of the feed rolls are similarly increased along the path of the tow. From the last draw roll the tow passes through a dancer roll arrangement 9 and then over a guide 11 to the nip between the inlet rolls 12 of a stutfer crimper 13.

The holes in the guideboard 2 are so arranged that the subtows are delivered to the tension bars 3 in two sets (with the subtows in each set being very close together and the two sets being spaced somewhat further apart). *For example, the subtows in each set may be spaced 0.5 inch on centers with the outermost filaments of one subtow on the initial tension bar 3a being only 0.1

inch from the outermost filaments of the adjacent subtow of the same set, while the outermost filaments of the adjacent sets are spaced about 1 inch apart. As the subto-ws pass over the tension bar 3 and feed rolls 6, the filaments move laterally somewhat, since the tension on the subtows engenders forces normal to the surfaces of the tension bars and feed rolls, which forces tend to flatten the subtows against these elements and thereby widen said subtows causing the outermost filaments of adjacent subtows within each set to overlap. Intermingling of the filaments takes place in the draw zone by reason of the interaction of each tow band with the corresponding sloping shoulder 16 or 17 of a converging device 18 situated near the outlet of the draw zone and consisting of a double frusto-conical freely rotatable roller mounted with its crotch 19 slightly below the straight line draw path between the bottom of the last feed roll 6b and the bottom of the first draw roll 8 and with its conical shoulders 16 and 17 (which may make an angle, for example, of 60 with the axis of the roller and thus an angle of 60 with each other) extending into that straight line path so that the tow bands 21 and 22 each engage one of said shoulders. It will be evident that because of the tension on the bands 21 and 22 their filaments will tend to migrate along the shoulders 16 and 17, respectively, towards the straight line draw path, referred to above; this will cause intermingling of the filaments of each tow band.

The tow bands which are, for example, about inch apart as they leave the converging device 18 tend to flatten out against the surfaces of the draw rolls 8, 8a and 8b under the influence of the forces, normal to said surfaces and engendered by the tension on the tow, so that the tow leaving the draw rolls and fed to the crimper has the appearance of a single band (although close inspection of the center portion of the band will reveal a line where there is little, if any, crossing over of filaments).

The tow entering the stufi'er crimper 13 is still moist, having a moisture content in the range of about 20 to 50%, for example. The stuffer crimper 13 may be of conventional type having a pair of feed rolls 12 leading to a rectangular main body 26 whose width is about the same as that of the tow fed to the crimper feed rolls 12 usually in the range of about 1 to 2 inches, e.g. about 1 /2 inches) and whose depth, perpendicular to said width, is about 1% inches at the top and less at the bottom, the body being tapered downwardly. The outlet of the main body 26 is resiliently closed off by a suitably biased flapper 27, as is well known in the art.

The single band of tow leaving the stutter crimper has numerous crimps in approximate registry across the width of the band; generally it has a fine crimp, for example, in the range of about 4 to 20, e.g. to 16, crimps per inch superimposed on a coarse crimp, of much larger amplitude; thus there may be about 2 to 5 coarse crimps per inch. The tow band (still containing about 5 to 15% moisture at this stage) is passed through a distributor 28, which may be of the usual type comprising a pivoted tube, generally of sufficient width to accommodate said band without folding, which is swung back and forth about its pivot 29 by any suitable mechanism to deposit the tow in a sinuous path across the width of a driven endless belt 31 which carries the tow, resting thereon in substantially tensionless condition, through an oven 32 which is desirably maintained at a temperature sufiiciently high to set the crimp in the filaments of the tow (e.g. a temperature in the range of about 85 to 180 (1.).

The tow leaving the oven 32 may be drawn off the belt 31, cooled to room temperature, and laid into a carton 33 in the usual manner, as by means of a distributor 34 which traverses the tow back and forth and side to side, followed by pressing of the thus formed bale in the carton, e.g. to a density in the range of about to 30 lbs. per cu. ft. e.g. about 20 lbs. per cu. ft.

Alternatively the tow leaving the oven may simultaneously split into two bands and drawn off the belt 31, as shown in FIG. 3, with each band going to its own carton, Where it is baled as described above.

The splittable tow of this invention preferably has the same overall appearances as the known non-splittable tows and may be handled, e.g., coiled, baled, etc., as a unitary tow in the same way that such known tows are handled. It is composed of generally parallel crimped filaments, with such filaments crossing and intermingling on each side of the splittable line. If the tow is not treated to deregister the crimps, the crimps (particularly the coarse crimps, previously mentioned) will be in registry giving the appearance of waves extending for substantial portions of the width of the tow, with most of the waves, or at least a large fraction thereof, extending across the splittable line so that the line is not readily distinguishable (see FIG. 6). One convenient technique for locating that line is by snapping a segment of the tow, as by holding the tow manually, with the hands spaced apart along its length, bringing the hands close together to allow the segment of tow to hang loosely between them, and then moving the hands, still gripping the tow, sharply apart to place the segment of tow under tension; when this is done, the tow opens up along the splittable line and the resulting split may be readily propagated, without any tearing or snarling of filaments, by simply pulling one-half of the tow from the other, as FIG. 6.

In one specific example of the process described above, there were used 14 undrawn subtows, each of 71,000 total denier and each containing 2,130 filaments. The two bands on the last feed roll were each 2.5 inches wide and were each narrowed to a Width of inch on the coverging device. In the drawing operation the tow was drawn through a draw zone which was heated with steam at atmospheric pressure using a draw ratio of 4.6:1 so that the total denier of the band leaving the last draw roll 8b was 215,000. At this point, the band was 1% inches Wide. The entrance to the main body 26 of the stuffer crimper was 1 /2 inches wide. In the stuifer crimper the tow was subjected also to direct contact with steam supplied in saturated condition at 20 p.s.i.g.

The tow leaving the outlet of the stuifer crimper was 1 /2 inches wide and had 12 fine crimps per inch, the amplitude of the fine crimps being about 0.06 (measured from peak to valley for single yarns) and 3 coarse crimps per inch. The moisture content of the tow entering the crimper was 30%; on leaving he crimper it was 10%. After heat setting for 20 minutes at a temperature of about C. in the oven 32, the resulting splittable tow was baled and compressed in the usual manner to a density of about 20 lbs. cu. it. On unbailing, after the splittable line was located and the split started by snapping the tow, the tow could be split easily into two identical non-splittable tows. The tow had a tenacity of about 4.5 grams per denier.

FIGS. 4 and 5 show another arrangement within the broad scope of the invention but generally less desirable because it usually involves some tearing of filaments and thus may produce a splittable tow leaving some broken filaments along the splittable line. In this embodiment a single tow band with its filaments intermingled is fed from the draw zone to the crimper feed rolls 12. Just before the entrance to the nip of said feed rolls, there is mounted a divider which may suitably be a bar 36 having a rounded leading surface engaging the middle of the oncoming tow band. The divider need not be large; thus good results have been obtained with a divider 0.05 inch wide (measured in the plane of the tow band perpendicular to the direction of movement of the tow). The resulting two smaller bands formed by the presence of the divider are brought together at, or shortly past, the crimper feed rolls 12 and, as in the preferred arrangement, the tow leaves the crimper as a single crimped band. In this embodiment it is preferred that any intermingling of filaments along the line to be contacted by the divider 36 be limited, since if there is considerable intermingling along this line in the tow approaching the divider there will be considerable breakage of filaments at the divider, and also the force needed to pull the tow past the divider will be high, particularly when the tow is made of filaments of relatively high tenacity (e.g. above 2 grams per denier).

As previously mentioned, more than two bands may be fed to the crimping zone. This may be effected, for example, by the replacement of the converging device 18 by a similar device having additional frusto-conical sections along its length or by the use of additional bars 36. This, of course, results in a crimped splittable tow in which there are more than two non-splittable portions (i.e. more than two bands running lengthwise of the tow in which the filaments are somewhat intermingled). Advantageously, at least one of these non-splittable bands, and preferably all of them, have a total denier of at least 50,000 and contain at least 10,000 continuous filaments. Thus the splittable tow may, for example, include several such bands, separated by splittable lines as previously described, with each such band having a total denier of about 25,000 to 1,000,000 and containing about 300 to 200,000 filaments, and made up of about 2 to 40 subtows.

The invention has been described particularly with respect to tows whose filaments are of polyethylene terephthalate. It will be understood that it is within the broad scope of the invention to carry it out with other tows, such as those made of other polyesters (e. g. the polyesters of the terephthalic acid and other glycols such as dimethylol cyclohexane), polyamides (such as nylon 6 or nylon 6,6), polyacrylonitrile and copolymers thereof, polyolefines such as isotactic polypropylene, etc. These polymers may, if desired, be of the more easily dyeable type containing groups, e.g. SO Na or NH groups, which promote dyeability.

The splittable tows may be split to form two tow bands, each of which may be passed through a separate patterned roll arrangement (shown in Canadian Pat. 674,101, for example) and then through spreaders to form lightweight webs suitable for manufacture of battings and other products. v

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

The embodiments of the invention in which an exclusive property privilege is claimed are defined as follows:

1. A crimped tow comprising a plurality of sub-tows in the form of a coherent ribbon of crimped, generally parallel, continuous filaments, with said continuous filaments crossing and intermingling on each side of at least one splittable line, said crimped toW being readily splittable to a plurality of corresponding tub-tows without any substantial broken or torn filaments by pulling opposite sides of said crimped tow, the portions of the tow of each side of said one or more splittable lines being not so splittable owing to intermingling and crossing over of the generally parallel filaments within said portions.

2. The product of claim 1 wherein two sub-tows make up said coherent ribbon of crimped, parallel continuous filaments.

3. The product of claim 1 wherein said filaments are polyester continuous filaments.

4. A crimped tow as set forth in claim 1, and having crimps in registry with ridges and troughs of registered crimps, extending across said line, said tow being so cohesive that it may be folded, baled and unbaled without splitting along said line.

5. A crimped tow as set forth in claim 1, in Which said filaments are of a glycol terephthalate polyester and have 4 to 20 crimps per inch, at least one of said non-splittable portions having a total denier of about 25,000 to 1,000,000 and containing about 300 to 200,00 filaments.

References Cited UNITED STATES PATENTS 3,235,442 2/1966 Stump 161-173 3,277,537 10/1966 Roeder et al 19-66-T 3,384,932 5/1968 Watson 19-66T WILLIAM A. POWELL, Primary Examiner U.S. Cl. X.R.

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