US3654055A

US3654055A - Tow band

Info

Publication number: US3654055A
Authority: US
Inventors: Jack N Gray
Original assignee: Fiber Industries Inc
Current assignee: Celanese Corp
Priority date: 1964-07-13
Filing date: 1970-09-08
Publication date: 1972-04-04
Anticipated expiration: 1989-04-04

Abstract

A CONTINUOUS FILAMENT POLYESTER TOW BAND PRODUCED FROM A PLURALITY OF SUBTOWS AND CHARACTERIZED BY A LIMITED AND CONTROLLED DEGREE OF INTERMINGLING OF FILAMENTS.

Description

April 4, 1912 N, Y 3,654,055

TOW BAND Filed Sept. 8, 1970 I 3 Sheets-Sheet 1 April 4, 1972 v J. N. GRAY TOW BAND Filed Sept. 8, 1970 s Sheets-Sheet 2 April 4, 1972 J. N. GRAY TOW BAND 3 Sheets-Sheet 5 Filed Sept. 8, 1970 United States Patent Office 3,654,055 Patented Apr. 4, 1972 Int. Cl. B321) 5/12 US. Cl. 161-60 7 Claims ABSTRACT OF THE DISCLOSURE A continuous filament polyester tow band produced from a plurality of subtows and characterized by a limited and controlled degree of intermingling of filaments.

This application is a continuation of copending application Ser. No. 700,960, filed Jan. 26, 1968, now abandoned which is a divisional application of copending application Ser. No. 382,328, filed July 13, 1964, now Pat. No. 3,380,131 which relates to tows of filamentary material and relates more particularly to the production of crimped tows of polyester filaments.

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. I11 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 I. J. Press, pub. 1959 by Textile Book Publishers, 1110., pages 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, preferably a stuifer crimper, after which the crimp is set, as by feeding the band of crimped tow, in untensioned condition, onto a belt which transports it 'continuously through an oven maintained at a temperature sufficiently high to set the crimp permanently but not high enough to damage or melt the filaments. The crimped tow may then be cut into staple, baled and then opened and spun into sliver and then into yarn, as is now most commonly done, or it may be fed to a device such as '21 Turbo Stapler (US. 2,748,426) or a Pacific Converter (US. 2,438,469) for direct conversion into a sliver of discontinuous filaments.

It is an objectof this invention to provide a crimped tow which processes especially well during its direct conversion to sliver.

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

In accordance with one aspect of this invention, a plurality ofundrawn sub-tows are fed to a drawing zone and, while in the form of a band in said gene and under the drawing tension, are passed over a deflecting surface inclined to the direct draw path of said band so that the deflection from said direct draw path varies along the width of said band. The use of this process makes it possible to produce novel tows in which the degree of intermingling of the filaments is controlled and is relatively uniform across the width of the tow. Thus there can be produced tows with a limited degree of intermingling which perform especially Well during direct conversion on the Turbo Stapler, producing a sliver which is uniform and has very few neps or entanglements which must be combed out. Such a tow can also be readily opened and deregistered on a patterned roll device of the type described in Canadian Patent No. 674,101 and can then be spread to form a Wide uniform band by passing it through an air spreader, or series of air Spreaders, in which a band of opened tow is passed through a confined zone while air is blown against one or both of the flat sides of the band.

In contrast, when the blending of the subtows is accomplished by laying one subtow on top of another, the resulting tow (after crimping) appears, when processed on the aforesaid patterned roll device, to be made up of distinguishable sublayers and the degree of intermingling across the width of the tow is so great that the processed tow is not significantly opened by the patterned roll device and is no spreadable on the air spreader.

In addition, the tows of this invention process exceptionally well on the Pacific Converter, particularly after they have been opened with the threaded patterned roll device previously mentioned. In fact, these tows, when so opened produce excellent slivers and yarns even when the Pacific Converter is set to cut the filaments to very short lengths.

One aspect of this invention is illustrated in the drawing in which FIG. 1 is a diagrammatic side view of an embodiment of the process for making a package of crimped tow,

FIG. 2 is a plan view of the tow band in the drawing zone,

FIG. 3 is a view showing the cross-section of the tow band as it passes over the deflecting surfaces,

FIG. 4 is a plan view, of a different embodiment, showing two tow bands in the drawing zone,

FIG. 5 is a schematic view of a tow opening and spreading procedure. I

As shown in FIG. 1 of the drawing, a plurality of undrawn subtows 1 are taken from loose packages, each subtow being passed through its own aperture in a multiapertured guideboard 2 and then to a series of smooth parallel stationary tension bars 3, each of which is preferably a circular cylinder. In passing around the second tension bar 3b the tow dips into an aqueous bath 4, preferably a very dilute solution or dispersion (e.g. of about 1% concentration) of a finishing agent, such as a lubricating and antistatic agent, in water. The wet tow passes from the tension bars 3 to a set of driven feed rolls 6 and then through a heated draw Zone 7 to a set of driven draw rolls 8, 8a, 8b, all of the draw rolls being driven at a peripheral speed appreciably greater than that of the feed rolls 6. Each successive draw roll is preferably of slightly larger diameter (e.g. 0.05% larger) than the draw roll previously engaged by the tow so that although the draw rolls are all driven at the same rotational speed, the peripheral speed of these rolls, and the tow speed, increase as the tow moves over the draw rolls;

the peripheral speeds of the feed rolls are similarly increased along, the path of the tow.

of the filaments of each of these multifilarnent subtows are in direct contact with said bar, the tension on the subtows engenders forces normal to the surfaces of the' tension bars and feed rolls, which forces urge all the filaments of said subtows towards said surfaces, thus spreading the subtows until their outer filaments are in contact .or even slightly overlapped. The tow leaving the feed rolls thus has the appearance of a unitary band.

In the embodiment shown in FIGS. 1 and 3 of the drawing, the deflecting surface which engages the band of tow between the feed rolls and the draw rolls is that of a double frustoconical roll 9 mounted for free rotation on an axis generally transverse to the path of the tow, preferably on an axis lying horizontally in a vertical plane perpendicular to the direction of movement of the tow. The top of the crotch 11 of the deflector roll 9 is slightly above the direct draw path (which direct path, in the embodiment shown in the drawing, runs straight from the bottom of the last feed roll 6b to the bottom of the first draw roll 8) while the

upper shoulders

12 and 13 of the deflector roll 9 are obviously still further displaced from said direct path. The deflector roll 9 is so mounted that its crotch 11 is in the vertical plane of the center of the moving tow band. It will be seen that, because of the tension on the tow band and the position of the deflector roll 9 in relation to the tow hand, those filaments which are spaced from the surface of said roll and which are thereby not restrained by contact with said surface will tend to move relative to filaments at said surface as the tow passes over the deflector roll, as shown by the arrows in FIG. 2. By adjusting the position of the axis of the deflector roll 9 upwards or downwards, the tendency of the filaments to intermingle can be increased or decreased, respectively, as desired; in this manner the degree of cohesiveness of the resulting crimped drawn tow can be controlled, as desired. The degree of cohesiveness can also be increased or decreased by using deflecting surfaces of greater or lesser inclination to the direct tow path. As shown in the drawing the included angle at the crotch 11 is about 60; suitably this angle may be in the range of about 30-150", preferably within the range of 45-90. Despite the fact that the filaments at the outer edges of the tow band are drawn through a longer path, by virtue of their passage over the deflector roll shoulders, than those at the center of the band, it is found that the filaments are relatively uniformly drawn throughout the band.

The tow passes from the draw rolls to a dancer roll arrangement 16 and over a guide 17 to the nip of a pair of positively driven delivery rolls 18 of a stuffer crimper 19 comprising a main body 21 which forms a V-shaped stuffing chamber, rectangular in horizontal cross-section, whose width is about the same as that of the tow band and whose depth (perpendicular to said width) is about 1% inches at the top, tapering downwardly over its length of about inches. The outlet of the stuffing chamber is resiliently closed by a pivoted flapper 22, biased to closed position in a manner well known to the art. The crimped band of tow leaving the stuffing chamber, still moist at this stage, is passed through a distributor 23 which may be of the usual type comprising a pivoted tube, generally of suflicient width to accommodate said band without folding, which is swung back and forth about its pivot 24 by any suitable mechanism to deposit the tow in a sinuous path across the width of a driven endless belt 26 which carries the tow, resting thereon in substantially tensionless condition, through an oven 27 which is desirably maintained at a temperature sufficiently high to set the crimp in the filaments of the tow, eg a temperature in the range of about 85 to 180 C. After passing through the oven the belt carries the tow some distance through ambient air, whereafter the tow is distributed (as by distributor 28) back and forth and side-to-side in a carton 29 and is then compressed in said carton.

The preferred tow of this invention is a band of substantially parallel crimped drawn glycol terephthalate polyester continuous filaments of tenacity greater than 2 grams per denier, the crimps of adjacent filaments being in registry so that there are ridges, extending across the tow, formed from the crests and valleys of the crimps of adjacent filaments, said filaments having portions crossing over adjacent filaments at small angles of less than 1 to the general direction of said filaments, the filament density and degree of such crossing over being substantially uniform across the width of tow band, said band, after the crimps have been deregistered without further intermingling of the filaments, being readily spreadable laterally by a confined air stream to form a uniform web of a width at least six times the width of said band. Preferably the band is cohesive and non-delaminable throughout its thickness; i.e. it does not readily separate into layers without substantial filament breakage.

The following examples are given to illustrate the practice of this invention further.

EXAMPLE I 7 undrawn subtows, each containing 3,530 filaments of polyethylene terephthalate of 23 denier per filament, were fed with their centerlines spaced /2 inch apart to the tension bars of an apparatus as shown in 'FIGS. 1 and 2. In the drawing zone the tow band was subjected to an atmosphere of a hot fluid, preferably steam. The draw ratio was about 4.611. The tow band leaving the last feed roll was 5 inches wide. The filaments necked down, under the drawing tension, at a point within the heated draw zone near the last feed roll 6b. The deflector roll, whose surface was of smooth metal, had a crotch 1 /2 inches in diameter and shoulders which sloped toward the crotch at an angle of 60 to the axis of said roll, forming a 60 notch. The horizontal direct draw path joining the bottom of the last feed roll and the bottom of the first draw roll was 8 feet long, and the uppermost part of the crotch of the delivery roll was located 4 inch above this direct path, 16 inches forward of the axis of the first draw roll. The drawn tow, at its zone of contact with the deflector roll, was inch wide, measured horizontally; at the surface of the first draw roll it formed a band 1 inch wide, so that the total denier per inch of width was 128,000. At the deflector roll the outer edges of the tow band were about inch thick, measured perpendicular to the surface of the sloping shoulder, this thickness increased gradually toward the center of the band; above the crotch of the deflector roll the tow band was A; inch thick, measured perpendicular to the axis of the roll. In the stuffer crimper the tow was subjected to direct steam (supplied at 20 p.s.i.g.) and was given a fine crimp of 12 crimps per inch superimposed on a coarse crimp (of much larger amplitude) of about 3 crimps per inch. The crimp was set at a temperature of C. for 20 minutes. The set tow band, when cooled, had a degree of crimp of about 60%; the percent crimp, as used herein, being where L0 is the length of any predetermined portion of the tow and Ls is the average length of the filaments of said predetermined portion when under a tension just suflicient to remove the crimp. Its tenacity was 4.5 grams per denier.

The set tow band could be passed directly from the oven, after cooling, through a threaded roll opener to produce a uniform deregistered tow band, 8 inches wide, which could be spread easily to a width or more than 50 inches by passing it, directly after leaving the last of the threaded rolls, through two stages of air spreading. In each stage there was an air spreader made up of a pair of parallel horizontal plates between which the tow band passed, the plates being spaced apart slightly more than the thickness of the tow band, one of the plates being slitted and forming a wall of plenum chamber which extended for the full area of the slitted plate and which was connected to a source of air under pressure so that air was blown through the slits in that plate in a substantially uniform manner across the whole width of the moving tow band. Between successive air spreaders the tow passed through tight nips of rolls driven at such a speed that the tow was pulled, under slight tension, through the spreaders. Even though the resultant web was extremely light, it was sufliciently cohesive that it would not split when a stream of air was blown against it by a fan, but instead ballooned out like a sail before the wind.

The tow opening and spreading procedure referred to in theabove example utilizes the apparatus shown in FIG. 5, in the following manner: The tow band is drawn from a bale 32 through a banding jet 33 comprising a cylinder 34, having a slit running lengthwise of the cylinder at its highest point, and a curved baflle member 36 parallel to, and spaced V inch from, the adjacent surface of said cylinder, so that the tow band 31 passes between said baflle member 36 and said cylinder 34. Air under pressure is supplied to the interior of the cylinder 34 and emerges as a stream, from the slit of said cylinder, against the tow band and the baffle member 36. The tow band 31, now about 8 inches wide, passes around stationary tensioning bars 37, 38 and then into the nip between a pair of rolls 39, 41, both rubber-surfaced, driven at a peripheral speed of 60 feet per minute and then horizontally to the nip between a rubber-surfaced roll 42 and a threaded steel roll 43, driven at a peripheral speed of 102 feet per minute, said threaded roll having helical threads of 14 turns per inch cut about inch deep into its outer surface. The tow entering the nip between

rolls

42, 43 is still about 8 inches wide. From these rolls it passes still in the same horizontal plane to an air spreader having a tow-receiving slot 46 which is 24 inches wide and 4 inches long. The tow-receiving slot 46 is defined by an upper wall 47 and a lower wall 48 spaced A inch apart. Below the lower wall 48 is a plenum chamber 49 supplied with air under a constant pressure of 3 p.s.i.g. from a suitable source (not shown) and communicating with the tow-receiving slot46 through air slits 51, each 0.007 inch wide at their outlet ends and tapered to said outlets at an included angle of 45, said slits being each inches long and soarranged that the end of one slit is aligned, in the direction of movement of the tow, with theend of the adjacent slit, so that air is supplied to the tow band across thefull 24-inch width of the slot 46. The slits are arranged at small angles (e.g. about 5) to the line perpendicular to .the direction of movement of the tow with the slits on opposite sides of the median line of the spreader being mirror images.

The tow band diverges uniformly from its 8 inch width at

rolls

42, 43 to the full 24-inch width at the exit of spreader 44, the entrance of which is located 1 foot from the nip of

rolls

42, 43. The tow is pulled through the spreader 44 by the action of a pair of rolls 56, 57, making an S-wrap around these rolls, that is, passing 180 around steel roll 56 then passing through the nip between the rolls and then making another 180 wrap around rubber-surfaced roll 57. The tow web keeps its 24-inch width during its travel to and around the rolls 56, 57 which are moving at a peripheral speed of 61 feet per minute.

From the lower portion of roll 57 the tow then passes to the entrance of air spreader 58 which is located 3 feet horizontally from, and one foot below, the entrance of air spreader 58, which is located at the same horizontal level as the bottom of roll 57. The spreader 58 is of the same design as spreader 44, except that its tow-receiving slot is 50 inches wide, and it is operated under the same air pressure (3 p.s.i.g.) as spreader 44. The tow web spreads uniformly in its horizontal passage to spreader 58, at which it reaches its 50-inch width and then maintains the same Width during its passage to a pair of rolls 59, 61, driven at a peripheral speed of 59 feet per minute, which serve to pull the web through the spreader 58. Roll 59 is a rubber-surfaced roll while roll 61 is steel-surfaced; the top of roll 59 is on a level with the tow-receiving slot of spreader 58 and with the bottom of roll 57 The tow makes an S-wrap about the rolls 59, 61, falling from the roll 61 in a freely hanging shallow catenary onto the horizontal moving surface of a wide endless take up belt 63. An idler roll 64, mounted on lever arms 66 pivoted at 67, extends across the full width of the tow web on belt 63. The path of the belt is 2 feet below the bottom of roll 61 while the roll 64 is mounted inches forward (in the direction of movement of the belt) of the center of roll 61. The web 'on belt 63 has a width of 50 inches.

The bottom rolls of the roll pairs are each positively driven while the top rolls are spring pressed downward and are rotated by the movement of the tow passing through the nip, with no appreciable slippage.

EXAMPLE II Using the procedure and apparatus set forth in Example I there was produced an intermingled drawn polyethylene terephthalate tow having a total denier of 200,000 and a denier per filament of 1 /2, a crimp frequency of 15 crimps per inch and a percent crimp of 20%. In this example there were used 16 subtows, the draw ratio was 3.4:1, no steam (or other heat) was supplied during crimping, and the oven temperature was 112 C. After cooling, the tow was continuously laid into a carton and compressed to form a bale having a density of 210 lbs. per cu. ft. Bales of this tow were fed to a Turbo Stapler and there performed extremely efificiently, giving a sliver with very low count of neps or entanglements.

EXAMPLE II'I .By raising the axis of the deflector roll so that its crotch was /2 inch above the direct draw path, and keeping all other conditions the same as set forth in Example I, the degree of intermingling was increased. The cross-section of the tow at the crotch of the deflector roll was much more compact, being substantially an equilateral triangle, approximately A inch on each side. The tow was very cohesive and resisted opening and spreading; it was substantially uniformly intermingled throughout its thickness and showed no signs of separation into sublayers.

In the embodiment shown in FIG. 4, two spaced tow bands are separately deflected on the deflector roll 9 which is, in that embodiment, mounted with its axis and the upper part of its crotch below the direct draw path so that the two tow bands do not tend to converge at the crotch. Here the intermingling takes place, as in the embodiment shown in FIG. 2, by movement of filaments in a direction towards the crotch, but without intermingling at the crotch which occurs in the embodiment shown in FIG. 2.

It will be understood that the arrangements shown in the drawings are illustrative and may be varied as desired. Thus, the deflector roll may be placed above the tow so that the tow passing over the deflecting surface is below the axis of the deflector roll; or the tow path from feed roll to draw roll may be generally vertical or inclined, with the deflector roll placed on either side of that tow path. A plurality of deflector surfaces successively engaged by the tow band may be used, and the inclination of the deflector surfaces may vary across the width of the band, e.g. by using surfaces which present a curved, rather than straight, line to the tow. In place of a freely rotatable deflector roll a stationary surface over which the tow slides may be employed. Thus, the roll may be stationary or it may be replaced by a V-shaped deflector bar which presents a similar surface to the tow band. Similarly, in place of the deflector arrangement shown in FIGS. 2 and 4, a pair of inclined deflector bars may be used; these may be both inclined in the same direction or oppositely inclined and both need not, of course, be in the same plane. By suitably increasing the number of deflector surfaces, a number of tows may be processed, separately and in parallel, on a single draw frame.

It is advantageous to increase the Wear resistance and slip properties of the deflector surfaces by a flame-spraying procedure such as described in US. Pat. 2,714,563. By the flame-spraying technique, a material such as aluminum oxide, chromic oxide, titanium oxide, and the like is heated in a molten state and sprayed upon the metallic deflector surface in the form of fine globules which are thereby bonded to the metallic surface which may be of brass, stainless steel, aluminum, etc.

The invention is particularly suitable for the processing of tows of polyethylene terephthalate in which the weight of the drawn tow is above about 40,000 denier per inch of tow width on the first draw roll and the drawn filament denier is below 25. Advantageously, the filament denier is in the range of about 1 to 25, usually about 1 /2 to 1 8, preferably about 1 /2 to 8, and the number of filaments in the tow is over 1,000, e.g. about 2,500 to 300,000. The tow is advantageously given about 3 to 80 crimps per inch, preferably about 5 to 20 crimps per inch. The number of subtows used to produce a single tow in the process of this invention may be, advantageously, in the range of about 2 to 75 or more, advantageously 5 to 50.

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 terephthalic acid and other glycols such as dirnethylol 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, eg, SO Na or NH groups, which promote dyeability.

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.

What is claimed is:

1. A tow band comprising a single thickness of a plurality of sub-tows, all of said sub-tows being positioned side-by-side, crimped together, said tow band having a tenacity greater than 2 grams per denier, substantially parallel crimped and drawn polyester continuous filaments of tenacity greater than 2 grams per denier, the crimps of adjacent filaments being in registry so that there are ridges, extending across the tow, formed from the crests and valleys of the crimps of adjacent filaments, said filaments having at least some portions crossing over adjacent filaments at small angles of less than 1 to the general direction of said filaments to coalesce said subtows into a single unitary tow, the filament density and degree of such crossing over being substantially uniform across the width of tow band, said band, after the crimps have been deregistered without further intermingling of the filaments, being readily spreadable laterally by a confined air stream to form a uniform web of a width at least six times the width of said band.

2. A tow band as set' forth in claim 1 in which the denier per filament is about 1 to 25 and the crimp frequency is about 3 to 20 crimps per inch, said band being cohesive and non-delaminable throughout its thickness.

3. A tow band as set forth in claim 2, said band being composed of a single thickness of a plurality of subtows all side-by-side, crimped together, said crossing portions extending from each sub-tow to the adjacent subtows.

4. The tow band of claim 1 wherein the polyester is glycol terephthalate polyester.

5. The tow band of claim 1 wherein the tow band consists of 2,500 to 300,000 filaments.

6. The tow band of claim 1 wherein the tow band comprises 2 to sub-tows.

7. The tow band of claim 1 wherein the tow band has a fine crimp of about 12 crimps per inch superimposed on a coarse crimp of about 3 crimps per inch.

References Cited UNITED STATES PATENTS 3,016,581 1/1962 Smith 1965 3,145,429 8/1964 Resor l9l57 3,235,442 2/1966 Stump 161l73 3,277,537 10/1966 Roeder et al 19-161 3,384,932 5/1968 Watson 19-65 WILLIAM A. POWELL, Primary Examiner US. Cl. X.R.