Patent Grant
7454816
This invention relates generally to a fiber conversion and spinning process, and more particularly concerns methods for stretch-breaking continuous filament fibers to form discontinuous filament fibers and consolidating these fibers into yarns.
Spun yarns of synthetic staple fibers have been produced by cutting continuous filaments into staple fibers, which are then assembled into individual yarn in the same manner as fibers of cotton or wool. A simpler direct spinning process is also used wherein parallel continuous filaments are stretch-broken and drafted between input rolls and delivery rolls in what is sometimes called a stretch break zone or a draft cutting zone to form a sliver of discontinuous fibers which is thereafter twisted to form a spun yarn as disclosed, for example, in U.S. Pat. No. 2,721,440 to New or U.S. Pat. No. 2,784,458 to Preston. Such early processes were slow due to the inherent speed limitations of a true twisting device. As an alternative to true twisting, Bunting et al in U.S. Pat. No. 3,110,151 discloses consolidating staple fibers to make a yarn product using an entangling, or interlacing, jet device for entangling into yarn. Such a product can be produced faster than true twisting, but is not comparable to conventional spun yarns in strength, cleanness, and uniformity. Alternatively, U.S. Pat. No. 4,080,778 to Adams et al discloses a process where a 1500-5000 denier tow of continuous filaments may be heated and drawn, and is then stretch-broken and drafted in a single zone and exits at high speed through an apertured draft roll and an aspirator to maintain co-current flow of fluid and fiber through the roll nip. The discontinuous, unconsolidated filaments are then consolidated in an entangling jet of a type disclosed in Bunting to make a yarn of 50-300 denier. Static charges are removed in the stretch-breaking and drafting zone to minimize splaying. Static removal devices are also placed adjacent the roll pairs that forward the filaments through the process. About 1.5-20% of the discontinuous filaments produced in the stretch-breaking zone exceeds 76 cm in length. The yarn axis is required to be vertical throughout the process. The resultant product is a consolidated yarn with excellent strength, generally higher than ring-spun yarns, which is slub-free and clean.
Multiple stretch-break zones are taught in U.S. Pat. No. 4,924,556 to Gilhaus for progressively reducing the discontinuous filament length for large denier tows which are built up from combining several low weight tows over tensioning guide bars and guiding members. In this way distortions of less than 4.5 can be run with low weight feed tows and production capacity remains high. The combined tows are drawn without breaking in a distortion and heating zone (zone I) at one horizontal level and then passed sequentially through one or more progressively shorter, stretch-breaking zones, (zones II-V) arranged horizontally in another level to conserve floor space. The stretch-breaking zones may comprise one or more “preliminary” breaking zones that progressively shorten the fibers, and one or more breaking zones that set the average fiber length and set the variability of fiber length (% CV). The sliver formed may be processed in an entwining mechanism (to facilitate subsequent handling), heat treated, and collected in a canister. It is expected that the sliver would be further processed, as in a spinning machine, to produce small denier yarns. The process handles feed tows of 3.0 denier per filament and 110,000-220,000 denier, and in a band having a width greater than 270 mm in the drawing and breaking zones. In the example illustrated in
A horizontal in-line process for making a fasciated yarn from a tow of fibers is taught by Minorikawa et al in U.S. Pat. No. 4,667,463. The process involves drawing the tow over a heater in an elongated area having a narrow width, draft cutting the tow, and subjecting the draft cut fibers to an amendatory draft cutting step and a yarn formation step. The length of the zone in the amendatory draft cutting step is about 0.4 to 0.9 times the length of the draft cutting zone and the draw ratio for the amendatory draft cutting is at least 2.5×. The drawing preferably occurs in two stages to achieve a draw ratio of 90-99% of the maximum draw ratio and the drawn fiber is then heat treated. The yarn formation step uses a jet system for consolidating the fibers by creating wrapper fibers around the fiber core and wrapping them around the core fibers. Occasionally, apron bands are used in the amendatory draft cutting zone and yarn formation zone to regulate the peripheral fibers. The product is described in U.S. Pat. No. 4,356,690 to Minorikawa et al as being characterized by the fact that more than about 15% of the filaments in the yarn have a filament length of less than 0.5 times the average filament length of the yarn and more than about 15% of the filaments in the yarn have a filament length greater than 1.5 times the average filament length of the yarn. In the examples shown, the maximum output speed of the process making yarns of 174 to 532 denier (30.5 to 10 cotton count) is 200 meters/minute (ex. 6) with most examples run at about 100 meters/minute.
There is a problem with the products produced by Adams et al in that the 1.5-20% of the discontinuous filaments exceeding 76 cm in length that are produced in the single stretch-breaking zone cause problems in further processing (primarily roll wraps) especially if a non-vertical process orientation is chosen. There is also a problem with long filaments in the product of Adams in that it limits the number of filament ends that are available to protrude from the yarn and provide a yarn with a comfortable feel and look for textile applications.
In the case of Gilhaus' horizontal orientation, it may only be easily applied to processing large tows where it is believed the large number of filaments contribute to good intra-bundle friction between discontinuous filaments so bundle integrity can be maintained in the process without difficulty. In the case of Adams, the small numbers of filaments in the unconsolidated discontinuous yarn provide little frictional cohesion. A vertical orientation is believed required to eliminate lateral forces on the delicate yarn due to gravity before consolidation strengthens the yarn.
Adams proposes doing all stretch breaking in one zone and any drafting of the yarn in the same zone. Such a multipurpose zone makes independent optimization of final yarn parameters difficult or impossible.
Minorikawa et al may have a problem controlling discontinuous filaments as evidenced by the use of apron bands. This lack of control and the use of apron bands may limit the speed of his process to that disclosed in his examples which at 200 m/min is too slow for commercial production of a single low denier yarn line.
There is a need for an improved process for producing a stretch-broken yarn where the operating parameters can be independently optimized, where the process is not constrained to operate in a vertical orientation, and where excessively long filaments are not present that may separate from the filament bundle and wrap in the processing equipment and limit the number of filament ends in the yarn. There is a need for a process that can operate robustly and at a high speed above 250 m/min to make production of one yarn line at a time directly from tow economically attractive.
Applicants have developed a process, and an apparatus for performing the process, that produces a small denier, discontinuous filament yarn with filament lengths shorter than about 64 cm (25 in) that results in a high number of filament ends per inch from continuous filament feed yarn. The new process operates at rates that make production of individual yarns commercially feasible. The production rates greatly exceed those of ring spun staple yarns that traditionally have a high number of filament ends per inch. The process permits operation in either a vertical or horizontal orientation without sacrificing runnability. The process is adaptable to a variety of continuous filament yarn polymers and for blending dissimilar continuous filament yarns. In preferred embodiments, the process utilizes at least two break zones for obtaining the preferred filament lengths in the final yarn product having an average filament length greater than 6.0 inches and the speed ratio D1 of the first break zone and the speed ratio D2 of the second break zone should be at a level of at least 2.0. In addition, a relationship L2/L1 between the second break zone length L2 and the first break zone length L1, is constrained to be in a range of 0.2 to 0.6 to achieve the desired overall filament lengths, length distribution, and good system operability. Following the break zones, there is a consolidation zone for consolidating the discontinuous filaments in the yarn and intermingling them by any of a variety of means to maintain unity of the yarn. The process includes improvements to systems having one or more stretch break zones.
One feature of the new process is based on the belief that it is important to arrange for some “double gripped” filaments throughout the stretch-break and drafting process. Double-gripped filaments are those that are long enough to span the distance between two roll sets for each stretch breaking and drafting zone. Double-gripped filaments provide some support for the other filaments so there is good cohesion of the filament bundle in each zone that aids runnability, especially when making low denier yarns with few filaments. If low speed ratios are utilized in the break zones, this is believed to result in more long filaments that can serve as double-gripped filaments, but this requires more break zones to achieve a high overall speed ratio to improve productivity. It also results in more zones required to reduce the filament lengths to a low level that is desirable for producing yarns with a large number of filament ends. Protruding filament ends are believed to give the yarn a better feel, or “hand”. Applicants have discovered there is a preferred operating process for optimizing machine runnability when making small denier yarns with shorter fibers to optimize the filament ends per inch. To enhance productivity, the overall speed ratio of the process must remain high and the speed ratio increase must be shared by at least two break zones while maximizing the runnability which requires maintaining a certain minimum proportion of double gripped fibers in each zone. Applicants have discovered that to produce a desirable product certain process parameters must be carefully controlled. The relationship of speed ratio D1 of the first break zone being ≧2.0 and the speed ratio D2 of the second break zone being ≧2.0 should also preferably satisfy the following equation:
(D2−1)/(D1−1)≧0.15
More preferably, the relationship should satisfy the following equation:
(D2−1)/(D1−1)≧0.15 and is ≦2.5
In a still more preferred embodiment, the zone length of the second zone is also constrained to be less than or equal to 0.4 times the first zone length.
In another preferred embodiment, a separate zone is provided primarily for drafting the already broken filaments without further breaking.
In further embodiments, a draw zone is also utilized to draw the fiber without breaking filaments in a draw zone that precedes the break zones and can draw the fiber with or without the application of heat. Additionally an annealing zone is employed when desired to heat the fibers and control product features such as shrinkage. An annealing zone is most often part of the drawing zone, but may be applied at a variety of locations in the process.
The process produces novel products by providing the opportunity to introduce a variety of fibers to the process in a way not previously disclosed to make a wide range of stretch broken yarns. For instance, with a variety of different zones employed in the process, additional fiber can be introduced at different locations in the process to achieve unusual and novel results. Typical of such products are those that blend continuous filament yarns with the discontinuous filament yarns by introducing the continuous filament yarns at a location downstream from the break and draft zones and upstream of the consolidation zone or zones. Other products employ polymeric materials with properties not envisioned for use in a stretch-breaking process, especially one with applicant's unique operating procedures. Such products include the following:
Various improvements to conventional stretch break processes are disclosed including:
Other variations in the process and products produced thereby will be evident to one skilled in the art of fiber processing from the description that follows.
Other features of the present invention will become apparent as the following description proceeds and upon reference to the drawings, in which:
While the present invention will be described in connection with a preferred embodiment thereof, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.
Referring now to the drawings,
The fiber 30 is fed to a third set of rolls 62, thereby defining the second break zone 36 between roll sets 50 and 62. Roll set 62 comprises roll 64, roll 66 and roll 68. Roll 66 is driven at a predetermined speed by a conventional motor/gearbox and controller (not shown) and rolls 64 and 68 are driven by their contact with roll 66. The second break zone 36 has a length L2 between the nip of roll 54 and roll 56, which lies on line 70 between their centers, and the nip of roll 64 and 66, which lies on line 72 between their centers. The fiber speed is increased within the second break zone 36 by driving the fiber at the second speed S2 with roll set 50 and driving it at a third speed S3, higher than speed S2, with roll set 62. The comparison in speeds of the fiber at the two roll sets, 50 and 62, defines a speed ratio D2=S3/S2. There should not be any slippage between the roll and the fiber, thus, the fiber speed and roll surface speed at the driven roll 54 are the same, and the fiber speed and roll surface speed at the driven roll 66 are the same. Increasing the speed of the fiber within second break zone 36 causes most filaments in the fiber longer than the length L2 to be stretched until the break elongation of the fiber is exceeded and most filaments gripped by both roll sets (doubly gripped filaments) will be broken. In the second zone, to break the filaments, the speed ratio D2 should be such that the maximum imposed strain on the doubly gripped filaments exceeds the break elongation of the fiber, which is a known requirement for stretch-breaking of fiber having discontinuous filaments. The discontinuous filament fiber may also be drafted in the second break zone 36 to reduce the denier of the fiber as the speed of the fiber continues increasing until it reaches the speed S3 of the roll set 62.
The fiber 30 is fed to a fourth set of rolls 74, thereby defining the consolidation zone 38 between roll sets 62 and 74. Roll set 74 comprises roll 76 and roll 78. Roll 76 is driven at a predetermined speed by a conventional motor/gearbox and controller (not shown) and roll 78 is driven by its contact with roll 76. The consolidation zone 38 has a length L3 between the nip of roll 66 and roll 68, which lies on line 80 between their centers, and the nip of roll 76 and 78, which lies on line 82 between their centers. The consolidation zone includes some means of consolidation, such as an interlace jet 83 shown between the roll sets 62 and 74. The fiber speed can be decreased slightly within the consolidation zone 38 by driving the fiber at the third speed S3 with roll set 62 and driving it at a fourth lower speed S4 with roll set 74. The comparison in speeds of the fiber at the two roll sets, 62 and 74, defines a speed ratio D3=S4/S3. There should not be any slippage between the roll and the fiber, thus, the fiber speed and roll surface speed at the driven roll 66 are the same, and the fiber speed and roll surface speed at the driven roll 76 are the same. The interlace jet interconnects the filaments by entangling them with one another to form a staple yarn and in doing so it can slightly shorten the length of the fiber as the yarn is formed which accounts for the decreased speed in this particular consolidation zone. In some cases it may be desired to increase the fiber speed within the consolidation zone 38 by driving the fiber at the third speed S3 with roll set 62 and driving it at a fourth speed S4, higher than speed S3, with roll set 74. In this case some drafting would occur in the consolidation zone 38 as the speed of the fiber continues increasing until it reaches the speed S4 of the roll set 74.
With continuing reference to
Since many of the roll wraps seem to occur as the fiber is exiting a nip between rolls, it is believed to also be important to keep the fiber in contact with a rigid nip roll, such as a metallic nip roll, as the fiber leaves a resilient elastomeric nip roll regardless of whether the rigid or resilient surfaced rolls are conductive or non-conductive. In this way, if the fiber tends to get embedded in the resilient surface of the elastomeric roll, it can be “peeled” away from the resilient surface by following the rigid surface of the opposing nip roll as the fiber takes a small wrap on the rigid roll. The wrap angles around the metal surfaced rolls discussed above would accomplish this purpose. This is believed to minimize roll wraps. If the rigid roll surface is electrically conductive, this is a further advantage as mentioned above.
Throughout the industry there are a variety of meanings attributed to the term fiber. For purposes of this specification the term fiber means an elongated textile material comprising one or multiple ends or bundles of the same or different material comprising multiple filaments that can be discontinuous or continuous and are unconsolidated, thereby retaining significant mobility between the filaments. Filaments are single units of continuous or discontinuous (i.e. finite length) material. The term yarn or staple yarn means an elongated textile material that comprises a consolidated fiber including discontinuous filaments, where the consolidated fiber has a substantial tensile strength and unity along the length of the yarn and filament mobility is present, but limited. Continuous filaments may also be present in the yarn or staple yarn.
The feed fiber for the above described process may come from a wound package of fiber or may come from a container of piddled fiber from which the fiber may be freely withdrawn as will be discussed below. The consolidated yarn may be wound into a package or piddled into a container for transfer to another process or for shipping; or passed on to other machine elements for further processing.
A break zone and breaking the filaments refers to increasing the speed of fiber comprising continuous or discontinuous filaments in a zone for the primary purpose of breaking fibers in a way that more than 20% and preferably more than 40% of the filaments are broken. When continuous filaments or discontinuous filaments longer than the break zone are fed into the break zone 100% of the filaments are broken. A break zone and breaking the filaments may also include cutting or weakening all or a portion of the continuous or long discontinuous filaments such as with a cut-converter device or breaker bar device (as described in U.S. Pat. No. 2,721,440 to New or U.S. Pat. No. 4,547,933 to Lauterbach) which reduces the breaking forces imposed at the nip rolls and controls some of the randomness of the breaking position of the filaments in the fiber.
The first break zone and second break zone means two distinct break zones with the second one occurring after the first one in the progression of the fiber through the two break zones. It is intended that the second break zone does not have to be right next to the first break zone and the first break zone does not have to be the first zone in a process. The feed fiber entering the first break zone can be continuous filament fiber, a discontinuous fiber of long length filaments that are to be broken in the first break zone, or a combination of continuous and discontinuous filament fiber. It is intended that consolidating includes interconnecting the filaments in the fiber by any means of consolidating, such a single fluid jet, multiple fluid jets, a true twisting device, an alternate ply twisting device, an adhesive applicator or the like, a wrapping device, etc.
To achieve a practical breaking of fiber in a single break zone, it is known that the tension to break a fiber decreases as the speed ratio to break the fibers increases. At a very low speed ratio of less than two, the tension increases rapidly and as it does it is believed that the tension consolidates the fiber so that the friction between adjacent filaments increases and individual filament breaking becomes more difficult. As a result, the tension becomes high and very erratic which leads to operability problems and breakage of the entire fiber rather than random individual filament breaking. For this reason, it is desired to operate each break zone at a speed ratio of 2.0 or greater. This is also advantageous for product throughput efficiencies. It is also desired to provide a large number of filament ends in the consolidated yarn. This can be done by making the zone length of the second break zone considerably shorter than the first break zone to shorten the filaments in the fiber and create more filament ends per inch of consolidated yarn. It is preferred to make the second break zone length, L2, less than or equal to 0.6 times the first zone length, L1. In a more preferred embodiment, it is desired to make the second length L2 less than or equal to 0.4 times the first length L1. There is a practical limit to the minimum length of the second draw zone where it will be breaking nearly all of the fiber filaments coming from the first zone. This is undesirable since it increases the tension to a high level and it is known that the breaking forces increase as the length of the zone decreases. A practical lower limit for L2 for break zone 2 is L2≧0.2 L1. The corollary to this logic is that it is desireable to make the first zone considerably longer than the second break zone because it is known that the tension to break filaments decreases in long zones. It is believed important for L1 to be long for any given average filament length produced (e.g. established by the second break zone) to decrease the breaking forces required and to present a longer filament length to breaking forces which exposes more filament weak points for breaking. It is believed desireable to have an average filament length greater than 6.0 inches, which means from two-break-zone experience that L2 is roughly greater than about two times the average filament length or 12.0 inches, which means L1 is greater than 1.67×12.0 or 20.0 inches at the maximum desired L2/L1 ratio of 0.6.
There is a relationship between the first and second break zones that insures that the process has good operability and the yarn has certain desirable characteristics of filament length and distribution and to provide an increased frequency of filament ends in a stretch-broken yarn. Good operability also provides for the possibility of robust high speed operation at output speeds greater than 200-250 yards/minute, and especially greater than about 500 yards/minute. A definition of double gripped filaments will first be discussed in reference to
A modeling process is used to predict the number of double gripped filaments under a variety of process conditions. The analytical expression works for a single zone with continuous feed filaments. The simulation imposes the same first principles for a multi-zone process where the feed into each zone can be continuous or discontinuous. Single zone results agree well with each other. An analytic expression for a support index in a single break zone was derived from first principles using the following assumptions:
Ln=natural logarithm
D=draft=velocity ratio in the zone
eb=elongation to break of fiber; 10% is expressed as 0.1
A Monte Carlo computer simulation was developed to analyze a coupled process with multi-zone breaking and drafting. The simulation tracks fiber motion through the process, with fiber speed in each zone imposed (as an example) by gripping roll-sets. The imposed kinematics dictates the motion of single gripped and double gripped filaments. Randomness occurs during the breaking of double gripped filaments. Following the treatment of Ismail Dogu, “The Mechanics of Stretch Breaking”, (Textile Research Journal, Vol. 42, No. 7, July 1972), the filament builds up strain until the break elongation is reached, at which time it breaks randomly along the zone length. Filament breaks are independent from others in the fiber. Floating filaments are treated in a number of ways, from “ideal drafting”—filaments take on the upstream roll-set speed until the leading end reaches the downstream roll-set—to options where its speed depends on the speed of neighboring filaments. Simulation results agree well with single zone analytical predictions for the support index and process tension, and with measured process tension. The simulation model is run in Matlab® 5.2 from Mathworks, Inc. of Natick, Mass. 01760. Results can be obtained with a reasonable effort for 1000 filaments on a computer with an Intel Pentium II, 450 MHz processor. It is also practical to handle up to 3000 filaments with this system. Simulation of fiber length distribution for a two-zone breaking process agrees well with the measured distribution.
With continuing reference to
Reference is now made to
Looking at the single break zone in
Dt=25
D1>=2.0; D2>=2.0
L2=0.33 L1
eb=0.1
Since the second zone speed ratio is in the numerator, the curve 100 for the second zone has the shape of the curves in
The modeling simulation process was applied to additional two zone cases and was used to explore the sensitivity of the optimum values for (D2−1)/(D1−1) to maximize the number of double gripped fibers to give an acceptable value of Ndg/Nuc for good operability.
Dt=25
D1>=2.0; D2>=2.0
L2=0.33 L1
It can be seen that the number of double gripped fibers increases with an increase in eb from 0.05 to 0.15, but the value for the optimum of (D2−1)/(D1−1) stays about the same at about 0.7, where dashed line 116 passes through the intersection of each pair of zone curves and the horizontal axis. If one wished to improve operability of a given two break zone process, one could keep all process parameters except eb the same, and add some fibers that have a higher elongation to break to improve the operability. However, this may change the yarn product properties.
Dt=25
D1>2.0; D2>2.0
eb=0.1
For zone 1, all three curves are the same and fall on top of one another. It can be seen that the number of double gripped fibers (Ndg/Nuc ratio) increases only slightly as L2 decreases from 0.5L1 to 0.25 L1, and at the same time the value for the optimum of (D2−1)/(D1−1) changes only slightly from about 0.5 to about 0.8. This change in (D2−1)/(D1−1) can be seen between where dashed line 118 passes through the intersection of each pair of zone curves for L2=0.5 L1 and the horizontal axis, and where dashed line 120 passes through the intersection of each pair of zone curves for L2=0.25 L1 and the horizontal axis. It seems that in a two break zone process, varying the ratio between L2 and L1 by reducing L2 from 0.5 L1 to 0.25 L1 can improve operability of the process slightly.
eb=0.1
D1≧2.0; D2≧2.0
L2=0.33 L1
It can be seen that the number of double gripped fibers increases with a decrease in Dt from 50 to 4, but the value for the optimum of (D2−1)/(D1−1) stays about the same at about 0.7, where dashed line 122 passes through the intersection of each pair of zone curves and the horizontal axis. If one wished to improve operability of a given two break zone process, one could keep all process parameters except Dt the same, and decrease Dt to improve the operability. Since process productivity is highly dependent on Dt, however, this change to improve operability may make the process uneconomical.
Within the draw zone 124 there can be a fiber heater 140 that may take many forms; the form shown here is a curved surface 142 that contacts the fiber over a length that can easily be varied by changing the length of the arc the fiber follows over the surface 142. For longer heating times at a given fiber speed at the upstream end 126 and a given draw speed ratio D4, the arc and contact length would be longer. Drawing of the fiber may occur as soon as the fiber is exposed to the tension in the draw zone 124, so for some polymers, the drawing or elongation of the fiber may occur just as the fiber is leaving the nip of the upstream rolls, such as rolls 132 and 134. For some polymers, the draw occurs over a very short length, such as less than 1.0 inch. In this case, the heater serves to anneal the drawn fiber rather than heat it for drawing. For this type of fiber, if draw heating is required, the rolls 132 and 134 may be heated. Other polymers may not draw until they experience some heat by contact with the surface of the heater 140. The length of the draw zone is not critical, and is primarily sized to accommodate the heating device 140. In some cases of operating the draw zone, the fiber would be drawn without heating (the heater would be turned off and retracted from contact with the fiber) and in other cases, the fiber would be heated during the drawing process as shown. In some cases, the fiber may have a draw speed ratio D4 equal to about one and the fiber may only be heated without stretching. In this case, the draw zone would function as an annealing zone.
A draw zone and drawing the fiber refers to stretching continuous filament fiber in a way that essentially none of the filaments are broken; the filaments remain continuous. Heating the fiber may or may not be included in drawing. An annealing zone and annealing the fibers refers to heating a continuous or discontinuous filament fiber while constraining the length of fiber without significant stretching, and may include some small overfeed of the fiber into the annealing zone where D4 is a number slightly less than 1.0.
Using the process of
A draft zone and drafting the fiber refers to increasing the fiber speed in a zone for the primary purpose of reducing the denier of discontinuous filament fiber in a way that more than 80% of the fibers remain their same length, that is, 20% or less of the fibers are broken. It is intended that the draft zone can be at various locations as long as it is upstream from the consolidation zone, for instance, it may be between the first break zone and second break zone.
A process approximating that illustrated in
Referring again to
An apparatus that can be used for operating the processes of
Following roll set 42a is a first break zone 34 with roll set 50a at the downstream end which is identical to the roll set 50 in
Referring now to
Another way to accomplish the method of gathering the loose filament ends in the break zone and adjacent the exit nip rolls and directing them toward the fiber core is to use a trough as shown in
The trough 450 may only be adjacent the nip rolls exiting the zone and extend a short distance therefrom, or it may extend for nearly the entire length of zone 34 to maintain control of the loose filaments throughout the zone. The trough 450 may optionally have a cover 480 to fully contain the loose filaments in all directions, however, it is most important that the trough contain the filaments laterally to keep them from extending to the ends of the nip rolls where they are susceptible to wrapping on the nip rolls. If a cover is used, it should have access for an air ionizing device.
Referring again to
Following roll set 62a is a draft zone 144 with roll set 148a at the downstream end which is identical to the roll set 148 in
Following roll set 148a is a consolidation zone 38 with roll set 74a at the downstream end which is identical to the roll set 74 in
The Artz jet is discussed further referring to
The first nozzle or injector component 350 has pressurized gas, preferably air, supplied through a line 380 into a ring channel 382 that directs the fluid to multiple compressed fluid channels, such as 384 and 386. Channels 384 and 386 intersect the spinning bore 351, having a diameter dI, in a known fashion at a location tangent to the bore diameter and at an angle 388 slanted toward the direction of fiber travel through the bore. The intake opening 389 of bore 351 of first nozzle 350 may be a straight cylindrical shape as shown or may be conically tapered and include notches to influence the propagation of twist in the fiber. The second nozzle or torsion component 352 likewise has air supplied through a line 390 into a ring channel 392 that directs the fluid to multiple compressed fluid channels, such as 394 and 396 which intersect bore 353, having a diameter dD. First nozzle 350 has a characteristic distance lI from end 360 to a channel such as 386, and second nozzle 352 has a characteristic distance lD from an entrance end 398 to a channel such as 396. The first nozzle 350 is spaced from the second nozzle 352 by a distance “a” measured between compressed fluid channels where they intersect the spinning bore of each nozzle. This distance is adjusted for the particular fiber being processed and may be larger for fibers that have a large average filament length and smaller for fibers having a small average filament length. The first and second nozzles 350 and 352 are adjustably held in place in common holding device 354 by fasteners, such as setscrews (not shown) to facilitate adjustment of the distance “a”. Alternatively, each nozzle may have independent holding devices and be mounted spaced apart on the machine frame (not shown). For any process for consolidating discontinuous filament fiber having an average filament length greater than 4.0 inches, and preferably greater than 6.0 inches, it has been surprisingly discovered that the strength uniformity of the yarn is maximized when the distance “a” is set proportional to the average filament length of the fiber.
Referring to the apparatus of
Referring to
Referring to
This folding of the paths of the fiber through the functional zones, so that when a path vector in a first functional zone is placed tail to tail with a path vector in a next sequential functional zone there is defined an included angle that is between 45 degrees and 180 degrees, results in a compact floor space for the apparatus to practice the stretch breaking process. In a case where there are more than two functional zones, there may be a plurality of included angles, each between sequential functional zones where the fiber path is folded. In the case where there are a plurality of folds and included angles, the folded path system of the invention is alternatively defined when the sum of the absolute value of all the individual included angles between sequential functional zones is preferably 90 degrees or more and is most preferably 180 degrees or more. The arrangement shown in
The yarn produced by the apparatus of
The piddled fiber is preferably obtained most economically by a modified method of operating a staple fiber spinning machine having a single polymer supply system feeding multiple spinning positions normally combined together to make a single large denier tow product collected into a container to be later converted to staple fiber.
Referring now to
The new method of operating the staple spinning machine also includes changing the fiber product characteristics for at least one spinning position making the low denier product such that the fiber product characteristics differ from the remaining spinning positions making either the low denier product or the large denier product. Such changed fiber product characteristics may include a different denier per filament, a different finish, a different color by direct color injection at the spinning position, a different filament cross section, or other fiber differences commonly available at an individual spinning position.
The new method of operating the staple spinning machine further comprises providing a means to process the low denier tow product from at least one spinning position to convert the low denier tow product to a spun yarn product. Such means illustrated in
The feed yarn 30 can be provided in the piddle container 160 of
The processes as illustrated in
The histogram in
Values of the actual test and simulation fall within the limits of the yarn product invention as follows:
Table I below illustrates other simulated operating conditions including some comparative example simulations and shows various ranges of operating parameters that fall within the limits of the invention. Some actual test with actual and simulated results are also included.
Examples CE1 and CE2 are comparative simulation examples operating at a total speed ratio of Dt=25. In ex. CE1, the break zone length L1 is 30″ and the percentage of double gripped filaments is low. When the filament distribution of CE1 is plotted in
Examples A, B, C, D, E, and F are simulation examples that were also run at a total speed ratio of Dt=25. Example A illustrates a high speed ratio in the second break zone of D2=10 which resulted in a low percentage of double gripped filaments in the second break zone, although the percentage is more than 50% greater than that in the single break zones of the comparative examples. Example A1 shows that a reduction in the second break zone speed ratio and increase in the first break zone ratio results in a favorable value for (D2−1)/(D1−1) of 2.0. It is expected this would result in an operability improvement over example A. Example B shows a condition where the first and second break zones are operated at the same speed ratio of 5. This gives good results for percentage of double gripped filaments, although the second break zone has a lower value so operability problems would be more likely there. Example B1 illustrates that by reducing the second break zone speed ratio and increasing the first break zone speed ratio one would expect to improve the operability of the second zone so both zones have the same high percentage of double gripped filaments. The approximated value of 3.8% is obtained from the plot of
Examples G, H, J, and K are simulation examples that were run at a higher total speed ratio of Dt=30. Different zone lengths were used, but still L2=0.33 L1 for examples G and H. They compare favorably with examples B and C respectively in terms of percentage of double gripped filaments, since the increase in Dt was not significant enough to decrease the percentage much. The filament distribution for example G is shown in
The stretch breaking process of the invention is useful when blending fibers that may have already been processed to some degree, such as by incorporating color or a surface treatment that gives the fiber some visual characteristic that can be detected with the unaided eye. Stretch breaking is a useful way to make specialty yarns without involving a lot of additional steps, such as is required in conventional staple blending where the sliver must first be prepared by chopping (cutting), blending, carding, combing, and the like as was generally illustrated at 516 and 518 in
Table II illustrates various products made following the teachings of the invention, in general practicing the process illustrated in
Test 1 shows a process condition for making a nylon yarn having a final denier of 137. The process had a draw zone, a first break zone, a second break zone, a draft zone, and a consolidation zone similar to the process in
Test 2 shows a process condition similar to test 1 which has a draw zone, a first break zone, and a second break zone approximately the same as that used to make the product illustrated in
Test 3 shows a product made using a polymer that has an interfilament friction coefficient less that 0.1 which is a fluoropolymer made by E. I. DuPont de Nemours & Company (hereinafter “DuPont”) under the trade name Teflon®. The process produced a staple Teflon® product which is difficult to produce economically by other means. An “omega” wrap as depicted in
Test 4 shows a product made by a process similar to that illustrated in
Test 5 shows a product made by a process similar to that in test 3 where an aramid fiber (DuPont trademark Kevlar®) and a fluoropolymer (DuPont trademark Teflon®) fiber were fed in together and were neither heated nor drawn in the draw zone; the draw zone was only used as a convenient way to transport the fibers to the first break zone. The Kevlar® and Teflon® were then stretch broken, drafted, and consolidated together to produce a blended yarn with a 274 denier. An “omega” wrap as depicted in
Test 6 shows a product made by a process similar to that in test 5 where an aramid fiber (DuPont trademark Kevlar®) and a high temperature fiber (DuPont trademark Nomex®) were fed in together and were neither heated nor drawn in the draw zone; the draw zone was only used as a convenient way to transport the fibers to the first break zone. The Kevlar® and Nomex® were then stretch broken, drafted, and consolidated together to produce a blended yarn with a 230 denier. An “omega” wrap as depicted in
Test 7 shows a product made by a process similar to that in test 3 where an aramid fiber (DuPont trademark Kevlar®) was fed in and was neither heated nor drawn in the draw zone; the draw zone was only used as a convenient way to transport the fiber to the first break zone. An “omega” wrap was used. A Kevlar® yarn with a low denier of 101 was produced that would be difficult to produce economically by other means. It is believed this product has filament length characteristics similar to those of test 1.
Test 8 shows a product made by a process similar to that illustrated in test 4 except a fluoropolymer fiber (DuPont trademark Teflon®) was fed in upstream of the roll set 42 (42a in
Test 9 shows a process similar to that in test 1 except a polyester fiber is used. A yarn is made having a denier of 274. It is believed this product has filament length characteristics similar to those of test 1.
Test 10 shows a product made by a process similar to that illustrated in
Test 11 shows a process similar to that in test 9, except the polyester filaments had a cross-section like that illustrated in
Test 12 shows a process similar to that in test 1, except the feed fiber consisted of two different fibers, each a different color. The colored fibers were combined before drawing and were drawn and stretch broken together as a single bundle of fiber. The first fiber was a distinct pink color and the second was a distinct purple color. It is believed these two colors would each be non-neutral colors having a lightness less than 90%, and they would have a color difference of at least 2.0 CIELAB units. The resultant yarn had a color distinctly different than either of the feed fiber colors and it is believed that when this yarn would be woven into a fabric, the fabric would have a heather look.
Test 13 shows a process similar to test 12, except the pink colored fiber was replaced with a light gray fiber that it is believed would be a neutral color having a lightness of greater than 90%. The resultant yarn had a color distinctly different than either of the feed colors and the yarn itself had a distinct heather look.
Test 14 shows a process similar to that of
Test 15 shows a process similar to that in
Test 16 shows a process similar to test 1 where two separate feed fibers were supplied to the process to create a large denier feed fiber of close to 20,000 denier going into the draw zone. In the draw zone two temperature zones were used on the heater 140 of
Test 17 illustrates a product made following the teachings of the invention, in particular practicing the process illustrated in
Test 18 is the same process as test 17 except the interlace jet of
Test 19 shows results similar to test 18 where the final output speed was 269 ypm making a 198 denier Dacron® product.
Tests 20, 21, 22, and 23 were run with a setup similar to test 17 to examine the preferred distance “a” between the nozzles of the consolidation device of
Test 20 was set up to produce a yarn with an average filament length of 8.9 inches as determined by simulation. The results were plotted in
Test 21 was run the same as test 20 except the break zone lengths were changed to produce a yarn made of Dacron® polyester fiber with an average filament length of 17.5 inches. This set of conditions also was run with a high L2/L1 ratio of 0.58. The results were plotted in
Test 22 was run the same as test 20 except the break zone lengths were changed to produce a yarn made of Dacron® polyester fiber with an average filament length of 6.4 inches. The results were plotted in
Test 23 was run without breaking the fiber in the first break zone and only breaking it in the second zone to simulate a single break zone process. It was set up to produce a yarn with an average filament length of 8.0 inches. The results were plotted in
Looking at the results of tests 20, 21, 22, and 23, the value for the spacing “a” between the first nozzle and second nozzle ranges from 0.74 to 1.53, or about 0.5 to 2.0 times the average filament length for fibers/yarns with an average filament length greater than about 6.0 inches. Taking the three values of “a” and averaging them, the preferred value for “a” is about 1.1 times the average filament length. Although test 22 did not have a point of maximum strength, it did have a point of diminished strength that could be avoided in the set up of the process if the teachings of the invention were followed and the nozzles were set to the preferred value of 1.1 avg. This would result in a value of “a” of 1.1×6.4=7.0 inches. This avoids the 5.0 inch position of diminished strength.
Test 24 was run with a setup similar to test 17 using the consolidation device of
Test 25 uses a process similar to that in test 17. The feed material in test 21 is a bicomponent elastic yarn wherein each filament has a circular cross section with one half of the cross-section comprising 2GT polyester and the other half cross-section comprising 3GT polyester. Such a feed material is described in U.S. Pat. Nos. 3,671, 379 to Evans et al., hereby incorporated herein by reference. Related patents to others are U.S. Pat. Nos. 3,562,093; 3,454,460; and 2,439,815. The two different polymers in the cross-section have different shrinkage characteristics after spinning so that after heat treatment, the fiber becomes a crimped fiber where the filaments curls into a coiled springy structure. Before heat treatment to activate the fiber latent elasticity, the fiber still has a significant amount of elasticity or crimp, which has caused a problem in the past making staple yarn using conventional combing and carding equipment. As a result, it is believed that staple yarn of bicomponent fiber is not known in the textile trade. The resultant multifilament yarn is very springy and has a substantial elasticity from no tension to a maximum tension, where all the elasticity is removed without plastic deformation of the filaments. This elasticity is characterized as percent crimp development, CD, that can be developed with wet heat and measured following the guidelines in the '379 and '460 reference above. The finished yarn must be heat treated after stretch breaking to recover its latent elasticity and obtain its final elastic characteristics.
Test 25 shows a process condition for making a bicomponent yarn of 2GT polyester and 3GT polyester components (designated BC23) having a final denier of 160. The process has a heat treating zone, a first break zone, a second break zone, and a consolidation zone similar to the process in
Test 26 shows a process condition for making a bicomponent yarn of 2GT and 3GT components (BC23) with a 50:50 ratio of components and the consolidated yarn having a final denier of 176. The process has a drawing and heat treating (annealing) zone, a first break zone, a second break zone, and a consolidation zone similar to the process in
The results of test 24 and 25 are surprising in that a staple stretch broken yarn can be made with good runnability from either pre-drawn or undrawn fiber by first removing all feed yarn stretch with pretension, and then heating the yarn to anneal both the pre-drawn or just-drawn fiber before stretch breaking the filaments. The stretch characteristics of the feed yarn are substantially retained in the finished staple yarn.
It is believed that other elastic fibers, i.e. crimped fibers, can also be successfully processed using the teachings of the invention. Other fibers may comprise different polymer combinations, such as a different nylon polymers, or different structures, such as biconstituent fibers. A biconstituent fiber is typically one with a core polymer that is highly elastic (or “soft”), such as a Lycras elastomer, that has “wings” of an inelastic (“hard”) polymer attached as longitudinal ribs during the spinning process. After spinning, the latent elasticity of the fiber can be activated by heat that causes the soft core polymer to shrink considerably more than the hard wing polymer which causes the composite structure to helically coil up to look like a screw thread. This fiber structure also has some “crimp” after spinning and drawing and before heat treating, similar to the bicomponent fiber. Polymer pairs should be compatible so they stick together, and can be cospun. For that, they have to have a similar thermal response and functional spinning viscosity. Useful pairs are therefore usually pretty similar chemically, or have some specific interaction. Common bicomponents are two polyesters, two nylons, etc., while the biconstituents are e.g. 4GT/4GT-4GO (HYTREL®) and nylon/PEBAX®; homopolymer/block copolymer pairs in which one block of the copolymer is the same as the homopolymer. Ratios can vary considerably, but are generally limited to somewhere between 80/20 and 20/80, preferably 70/30 to 30/70. Other conventional crimped fibers, such as those crimped by jets, gear crimpers, stuffer box crimpers and the like could also be converted to a staple yarn using the process of the invention.
It is, therefore apparent that there has been provided in accordance with the present invention, methods for stretch-breaking continuous filament fibers to form discontinuous filament fibers and consolidating these fibers into yarns, that fully satisfies the aims and advantages hereinbefore set forth. While this invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.
This application is a continuation of U.S. application Ser. No. 09/979,808, which was filed Nov. 21, 2001 now U.S. Pat. No. 7,100,246 off of International Application No. PCT/US00/16231 (filed Jun. 13, 2000), which claimed the benefit of U.S. provisional application Ser. No. 60/139,096, filed Jun. 14, 1999.
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| Child | 11034296 | US |
