US3898710A - Process and apparatus for producing readily processible staple fiber and tow - Google Patents

Abstract

In the production of crimped staple fiber by wrapping a crimped tow about the rotating element of a cutter in succesive layers, the innermost layer resting across knife blades and being forced down on the blades by the layers building up and thereby being cut, the tow is pulled by the cutter through the nips defined by two pairs of idler rolls. Preferably the rolls are geared together so the upstream rolls can rotate only at about 2/3 the speed at which the downstream rolls are caused to rotate by the pulling on the tow. The tow is thereby deregistered so that there are few if any chips in the staple fiber which can be carded or otherwise processed with less picking, opening and other pretreatment.

Description

United States Patent n91 Cook [ PROCESS AND APPARATUS FOR PRODUCING READILY PROCESSIBLE STAPLE FIBER AND TOW [75] Inventor: Charles Wayne Cook, Salisbury,

[73] Assignee: Fiber Industries, Inc., Charlotte,

[22] Filed: Aug. 1, 1972 [21] Appl. No.: 277,026

[52] US. Cl. l9/.46; 19/65 T Aug. 12, 1975 Primary ExaminerDorsey Newton Attorney, Agent, or Firm--Robert J. Blanke [57] ABSTRACT In the production of crimped staple fiber by wrapping a crimped tow about the rotating element of a cutter in succesive layers, the innermost layer resting across knife blades and being forced down on the blades by the layers building up and thereby being cut, the tow is pulled by the cutter through the nips defined by two pairs of idler rolls. Preferably the rolls are geared together so the upstream rolls can rotate only at about 2/3 the speed at which the downstream rolls are caused to rotate by the pulling on the tow. The tow is thereby deregistered so that there are few if any chips in the staple fiber which can be carded or otherwise processed with less picking, opening and other pretreatment.

9 Claims, 2 Drawing Figures PROCESS AND APPARATUS FOR PRODUCING READILY PROCESSIBLE STAPLE FIBER AND TOW The present invention relates to an improved process and apparatus for producing crimped staple fiber which can be further processed, as in carding, with minimum effort to give superior products.

Synthetic fibrous material is usually produced in continuous filamentary form, approximating the manner in which a silk worm produces silk fibers. These filaments can be formed in bundles of limited numbers and the individual bundles, which may include from one to a few hundred filaments, can be gathered and further treated as such, i.e. they may be twisted, textured, plied, or otherwise processed as a yarn.

Such continuous filament yarns generally have a relatively smooth and slippery or silky surface. For certain purposes it is desirable that the yarns have a more cotton-like hand. Moreover, for economy it is desirable to be able to form thousands of continuous filaments simultaneously. Accordingly it is customary for such purposes to extrude many continuous filaments simultaneously, to gather the extrudate from many locations into a large bundle or tow, to crimp the tow so as to impart to it a twoor three-dimensional structure, thereafter to cut it into short lengths or staple fibers, to separate or open the staple fibers from one another and thereafter to form the staple fibers into yarns in the manner employed with cotton or wool, i.e. natural staple fibers. The fibers are carded or combed to form a loose lap or web and are oriented in longitudinal direction by drawing. Ultimately the web is condensed laterally into a sliver or loose rope and subsequently twisted into a staple fiber yarn having a hairier, less shiny and- /or silky texture than a continuous filament yarn.

Natural fibers such as cotton and wool have scales, barbs or bends which interact with those of adjacent fibers so that when processed they can be formed into a coherent picker lap or carded web. Synthetic fibers do not have equivalent structures so that they would not form coherent laps or webs; to provide a substitute, the crimps are provided. The most common form of crimping is to force or stuff the tow band into a confined chamber having a restricted outlet, the device being termed a stuffing box crimper. The crimper is usually heated externally, although the forces involved will also generate heat. In addition, steam is usually introduced into the stuffing box. The forcing of the tow into the crimper causes it to bend into generally saw toothed folds and the combination of heat, moisture, pressure and time set these crimps into the tow. The crimps may be as few as only several per inch or as many as 40 or 50 or more; there may also be visible secondary crimps of much larger size, all of which contribute to the bulkiness of the resulting structures.

Since the tows are usually wetted with water and finish during crimping, they are then passed through dryers as by being laid back and forth in tensionless state on an apron moving through an oven. Thereafter the dried crimped tow is cut into staple lengths which are baled and shipped to customers who will perform the subsequent operations.

In such subsequent processing it is sometimes found that there are yarn non-uniformities and these have been traced to bundles of staple fibers sticking together with their crimps in registry. This can be eliminated or at least reduced by prolonged picking or combing of the initial staple fiber. Such extra processing obviously increases the costs and thus is undesirable if the problem could be otherwise eliminated. It has been found that the bundles of staple fibers, called chips, result from similar bundling of continuous filaments supplied to the cutter. These in turn result from the stuffing box crimping, i.e. the compressive forces cause the filaments to adhere to one another with the crimps all aligned across the bundle. Where this adhesion is light it poses no problem since it will be overcome by the light mechanical working in cutting, baling, picking and carding. Oftentimes this adhesion is of substantial magnitude and is not overcome, and this is the cause of chips of staple fiber and of imperfections in products made therefrom,

It is accordingly an object of the present invention to eliminate or reduce formation of staple fiber chips.

It is a further j'object of the invention to eliminate such chips without major modification of the existing equipment and without increasing the processing cost.

These and other objects and advantages are realized in accordance with the present invention pursuant to which the crimped tow pulled to the cutter is caused to pass through the nip defined by a pair of idler rolls of which at least one is patterned. The idler rolls rotate as a result of the pull of the tow but, due to the patterning of the roll, not all filaments in the bundle are identically pulled. As a result of the differential gripping action on adjacent filaments they are deregistered, i.e. they are disadhered from one another, so that the staple fibers ultimately produced upon cutting are free and independent of one another and do not form chips.

Advantageously, the tow passes through two such hips with the rolls of one pair being geared to the other so that the upstream pair is not permitted to rotate at as high a peripheral speed as the downstream pair, resulting in slippage of the tow over the upstream pair with improved filament deregistration.

The patterned roll of each pair preferably is grooved about its periphery, most easily performed by cutting a helical thread into its surface. Other patterns such as circular or elliptical rings or a checkerboard lattice of projections and depressions are also suitable. The patterned roll is preferably hard surfaced, such as metal, e.g. steel, while the other surface is preferably smooth and resilient, e.g'. rubber. However, both surfaces could be patterned and both of metal or resilient.

It is noted that no special drives are provided .to rotate the rolls, the motive power constituting that which normally feeds the cutter. Thus, the motive power can be driven feed rolls in advance of the cutter. In an especially desirable'embodiment the cutter has a rotating element about which the tow is wrapped, cutting blades being carried by and pointing outwardly of said member. As the element rotates more layers build up on the outside and, by applying a force on the outside of the wrapped layers the innermost layer is forced down on the knife blades, thereby being cut. The rotation of the element serves to wrap the tow and also pulls it along through the hereinabove-described nip, i.e. it is the sole motive force involved in advancing the tow, deregistering it, tensioning it as required for the cutter, wrapping it about the cutter and indirectly making the cut.

Such a cutter is described more fully in US. Pat. No. 3,485,120, the disclosure of which is incorporated herein by reference. An improvement thereon is described in US. application Ser. No. 149,682, filed June 3, 1971, now pending, the disclosure of which is also incorporated herein by reference; in such application at least one stream of air is directed downwardly adjacent the location where the actual cutting takes place so as to advance the cut fiber in the desired direction and prevent clogging.

The invention will be further described with reference to the accompanying drawing, wherein:

FIG. 1 is a schematic perspective view of an apparatus for crimping, drying and cutting tow in accordance with the invention; and

FIG. 2 is an enlarged view of one pair of idler nip rolls shown in FIG. 1.

Referring now more particularly to the drawing, in FIG. 1 there is shown a band of tow being forced by rotating rolls 12 into stuffing box crimper 14, the crimped tow emerging, passing over guide 16 and being cross-laid by reciprocating member 18 onto a perforated endless belt 20. The belt trained about driven roll 22, extends through a drying oven 24 and returns about roll 26. For simplicity the belt path through the dryer is shown as straight but it may be sinuous to give a longer residence time. The dried tow extends upwardly through a ring guide 28 and then passes successively through rolls 30, 32 and 34, 36, described more fully hereinbelow. The shafts of rolls 32 and 36 carry discs, pulleys or gears 38, 40 respectively which are connected by a V-belt 42 or like element, e.g. sproket chain or direct gear link. Since pulley 38 is larger in diameter than pulley 40 it is clear that whatever equilibrium is established roll 36 will rotate faster than roll 32. Thus if the tow is pulled through rolls 34, 36 at a particular speed there will necessarily be slippage of the tow through the nip of rolls 30, 32 because the latter are moving more slowly.

The tow next wraps in layers 44 about the rotating element 46 of cutter 48. The innermost layer 44 rests on the edges of blades 50 and a wheel 52 bears against the superposed layers do as to force a blade into the innermost layer at that point, thereby making a cut. The cut fibers 54 fall down inside the cutter 48 where a stream of air 56 prevents them from building up. The fibers 54 fall into a container such as a bale 58 which is replaced when full.

Referring now to FIG. 2 there is shown on an enlarged scale the rolls 30, 32 of FIG. 1. The rolls 34, 36 are desirably identical. Roll 32 is merely cylindrical and rubber covered at 60. Roll is metallic, preferably stainless steel, and has cut therein helical threads 62. The normal spacing between rolls 30, 32 will depend upon the size of the tow bundle being processed and must not be so large that the tow can be pulled through without causing the rolls to rotate. Rather, the pulled tow will cause rotation but some filaments will be located in the base of the threads 62 while others will be caught between the lands of threads 62 and roll 32. The caught filaments will be gripped differently and, as a result, the filaments will be deregistered, i.e. adjacent filaments will not be adhered and/or their crimps will not be in alignment. Passage through two such roll pairs, especially with different speed gearing therebetween, adds to the deregistration and permits further reduction in the processing needed to open the staple fibers in making yarn therefrom.

Turning now to the particulars of operation, the continuous filamentary material being crimped and processed may have been formed by any process, viz. dry

spinning, wet spinning or melt spinning, and may comprise any synthetic fiber, e.g. polyester, nylon, acrylics, polyolefin, acetate, etc. as those terms are employed in the Textile Fiber Identification Act. Preferred polyesters include polymers of one or more of ethylene glycol, butylene glycol, diethylene glycol, dimethylolcyclohexane, or the like, and dicarboxylic acids such as terephthalic acid, adipic acid, isophthalic acid, and the like. Hydroxyethylbenzoic acid can be copolymer ized therewith as well as other comonomers for special properties such as dyeability, molecular weight control, or the like. Polyethylene terephthalate and polybutylene terephthalate are preferred. Nylon fibers include polycaprolactam, polyhexamethylene-adipamide or -sebacamide, copolymers thereof, and the like. Preferred polyolefins include isotactic polypropylene, high density polyethylene, and the like. Preferred acrylics include acrylonitrile copolymers with small amounts, preferably less than about 15 percent and even less than about 7 percent, of methyl acrylate or like ester unsaturated comonomers and possibly dyeability imparting monomers such as methallylsulfonic acid, styrene sulfonic acid, vinyl pyridine, and the like. Cellulose acetate including the highly esterified form, cellulose triacetate, can also be used successfully.

The spun filaments are collected in bundles and are often drawn to improve their physical properties. The individual filaments making up the bundle after drawing may be as small in denier as l or less or as large as 25 or more although they are preferably 2 to 20 and preferably about 3 to 15 denier, depending upon the end use. The number of filaments in the bundle may also vary widely from as few as 20 up to several hundred thousand. Obviously the simultaneous processing of many filaments in a single step is more economical. The bundle or tow at this point may be temporarily collected but preferably it is fed to the crimper which could be a gear tooth crimper or the like, although stuffing box crimpers are most widely used.

The temperature, size and residence time in the crimper will depend upon the material being processed and its intended end use, i.e. higher crimp is desirable for softness, fewer crimps per inch for a more crisp feel. Similarly, use of steam is common but discretionary. The specific conditions may vary as known in the art although for apparel end uses with a polyethylene terephthalate tow of several hundred thousand total denier and a denier per fil of about 3 to 6, steam has proven quite satisfactory. If steam and lubricant are introduced 7 right at the stuffing box inlet the crimp is sharp, i.e. saw-toothed, whereas if finish is introduced at the inlet and steam somewhat downstream in the stuffer box the crimp is more sinusoidal.

The dryer dimensions, time and temperature are of course geared to the liquid applied to the tow and are variable within wide limits, as known in the art.

The dimensions of rolls 30, 32, 34, 36 are not critical. Their loading, i.e. bias toward one another, must be such that they will rotate as the tow is pulled therethrough. It should not be so great as to cause breakage of some of the filaments nor so light as to permit significant slippage between the tow and downstream rolls. As noted, preferably two sets ofidler rolls are provided; more than two affords no significant advantage. The two roll pairs can be independent of one another in which case they will be caused to rotate at about the same speed, although preferably they are interconnected so that the upstream rolls run more slowly. Advantageously the gear ratio is about 1.2 to 2 and prefer ably about 1.5 since this produces best overall deregistration.

The threaded rolls 32, 36 may have any number of threads but about 3 to 8 and preferably about 4 to 6 per inch at a pitch angle of about 1 to 2 and a depth of about 0.1 to 0.5 and preferably about 0.15 to 0.30 inch has proven quite satisfactory.

The pull on the tow also serves temporarily to straighten out the crimp which is desirable and necessary for the preferred cutter. Since successive layers wrap about one another, as the tow progresses inwardly a circumferential path is shorter and the crimp returns due to the shortened path. The cutter speed is of course geared to the speed of the initial tow line. The spacing between successive knife blades determines the length of the staple fiber and may be varied.

The invention will be further described in the following illustrative examples with reference to the apparatus illustrated in the drawing.

EXAMPLE 1 a. A 750,000 denier tow of drawn 1.5 dpf polyethylene terephthalate, leaving the drawing apparatus at 400 feet per minute, was introduced into a stuffer box crimper 4.5 inches wide and 2 feet long with a residence time therein of seconds. The crimper was maintained at a temperature of 90-96C., 0.012 percent by weight of the tow of a standard crimper finish was admitted near the inlet along with -30 pounds per hour of saturated steam at 110C. The tow received 12.5 crimps per inch and was laid in tensionless condi tion on the apron which carried it through the oven. The tow passed through four successive zones with the total residence time of 20 minutes approximately equally split therebetween; the zones were successively at 120C, 85C. and room temperature, air being supplied to carry off moisture and heating being effected by hot air.

The cooled tow was passed through two sets of rolls, the upper roll of each set being covered with rubber of 40 Duro hardness and being 8 inches long and 8 inches in diameter. The lower rolls of each pair were of the same length and diameter as the upper rolls but were of stainless steel with 4 threads per inch ofa pitch angle of 15 cut therein to a depth of 0.25 inch; the tops of the threads were somewhat flattened. The two lower rolls were geared together so that the upstream roll could only rotate at two-third the speed of the downstream roll, i.e. a 1.5 roll ratio. The upper and lower rolls of each pair bore against one another with a total force of about 10 pounds. 1f the tow were pulled manually through the nips using a laundry spring scale it would take a pull of at least 20 pounds to permit the downstream rolls to rotate and advance the tow.

The tow then passed to the cutter operating at 400 feet per minute and provided with blades to produce 1.5 inch staple fiber. The resulting fibers were free of chips and capable of being carded by chute feeding without special picking pretreatments. A standard length of the tensioned fiber when relaxed was only about 2 percent longer than the relaxed length of the same standard length of fiber which had not passed through the threaded rolls, i.e. the crimp loss was only about 2 percent.

b. In a run identical except that the roll ratio was 1.2 deregistration was much poorer precluding chute-feed carding and requiring much picking and opening to make a satisfactory yarn. At a ratio of 2, deregistration was excessive, i.e. the crimp loss was about 10 percent which precluded satisfactory lap formation due to unsatisfactory fiber to fiber friction.

It will be appreciated that the instant specification and examples are set forth by way of illustration and not limitation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention.

What is claimed is:

l. A method of producing crimped staple fibers from a crimped filamentary tow, said method comprising pulling said crimped tow by a cutting means through two nips defined by two pairs of idler rolls, prior to cutting said tow, at least one roll of each of said pairs of idler rolls being provided with a patterned surface, said pairs being geared to one another such that the upstream pair is not permitted to rotate at as high a peripheral speed as the downstream pair and such that a differential pulling of said filaments through said nips relative to one another is obtained, thereby deregistering adjacent filaments, and then cutting said deregistered filaments with said cutting means.

2. The process of claim 1, wherein the gear ratio of the downstream rolls to the upstream rolls is about 1.5.

3. The process of claim 1, wherein said cutter wraps the tensioned tow in successive layers about a rotating reel including outwardly pointing knife blades, the buildup of further layers causing the innermost layer to be severed into staple fibers by being forced against the knife blades.

4. The process of claim 3, wherein the tow is polyethylene terephthalate of about 530 thousand to 1.2 million total denier, about 1.0 to 20 denier per filament and about 9 to 15 crimps per inch.

5. Apparatus for the production of crimped staple fiber from a crimped filamentary tow, said apparatus comprising a continuous supply of tow, a cutter means for pulling said tow from said supply to said cutter and for cutting said tow, and two pairs of idler rolls positioned between said tow supply and said cutter defining a pair of nips through which said tow is pulled so as to tension said tow and temporarily at least partially to straighten said tow upon reaching said cutter, the two pairs of idler rolls being geared to one another so that the upstream pair is not permitted to rotate at as high a peripheral speed as the downstream pair, at least one roll of each of said pairs of idler rolls being provided with a patterned surface, whereby said filaments pulled through said roll nips are differentially gripped relative to one another so that adjacent filaments are caused to slip and deregister and the staple fibers produced at said cutter are readily capable of being carded.

6. The apparatus of claim 5, wherein each roll pair comprises a resilient roll and a pattern roll, the pattern comprising a plurality of circumferential grooves.

7. The apparatus of claim 6, wherein the grooves comprise about 3 to 8 helical threads per inch having a depth of about 0.1 to 0.5 inch.

8. The apparatus of claim 5, wherein the tow supply comprises a stuffing box crimper, and a substantially tensionless dryer, in sequence.

9. The apparatus of claim 5, wherein said cutter means includes a plurality of outwardly pointing knife blades, and means for rotating said blades as a unit with said tow wrapped thereabout in successive layers, the build-up of further layers causing the innermost layers to be severed into staple fibers by being forced against the knife blades.

Claims (9)

1. A method of producing crimped staple fibers from a crimped filamentary tow, said method comprising pulling said crimped tow by a cutting means through two nips defined by two pairs of Idler rolls, prior to cutting said tow, at least one roll of each of said pairs of idler rolls being provided with a patterned surface, said pairs being geared to one another such that the upstream pair is not permitted to rotate at as high a peripheral speed as the downstream pair and such that a differential pulling of said filaments through said nips relative to one another is obtained, thereby deregistering adjacent filaments, and then cutting said deregistered filaments with said cutting means.

2. The process of claim 1, wherein the gear ratio of the downstream rolls to the upstream rolls is about 1.5.

3. The process of claim 1, wherein said cutter wraps the tensioned tow in successive layers about a rotating reel including outwardly pointing knife blades, the build-up of further layers causing the innermost layer to be severed into staple fibers by being forced against the knife blades.

4. The process of claim 3, wherein the tow is polyethylene terephthalate of about 530 thousand to 1.2 million total denier, about 1.0 to 20 denier per filament and about 9 to 15 crimps per inch.

5. Apparatus for the production of crimped staple fiber from a crimped filamentary tow, said apparatus comprising a continuous supply of tow, a cutter means for pulling said tow from said supply to said cutter and for cutting said tow, and two pairs of idler rolls positioned between said tow supply and said cutter defining a pair of nips through which said tow is pulled so as to tension said tow and temporarily at least partially to straighten said tow upon reaching said cutter, the two pairs of idler rolls being geared to one another so that the upstream pair is not permitted to rotate at as high a peripheral speed as the downstream pair, at least one roll of each of said pairs of idler rolls being provided with a patterned surface, whereby said filaments pulled through said roll nips are differentially gripped relative to one another so that adjacent filaments are caused to slip and deregister and the staple fibers produced at said cutter are readily capable of being carded.

6. The apparatus of claim 5, wherein each roll pair comprises a resilient roll and a pattern roll, the pattern comprising a plurality of circumferential grooves.

7. The apparatus of claim 6, wherein the grooves comprise about 3 to 8 helical threads per inch having a depth of about 0.1 to 0.5 inch.

8. The apparatus of claim 5, wherein the tow supply comprises a stuffing box crimper, and a substantially tensionless dryer, in sequence.

9. The apparatus of claim 5, wherein said cutter means includes a plurality of outwardly pointing knife blades, and means for rotating said blades as a unit with said tow wrapped thereabout in successive layers, the build-up of further layers causing the innermost layers to be severed into staple fibers by being forced against the knife blades.

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