U.S. patent application number 11/336723 was filed with the patent office on 2006-07-27 for staple yarn manufacturing process.
Invention is credited to Glen E. Simmonds.
Application Number | 20060165982 11/336723 |
Document ID | / |
Family ID | 36293287 |
Filed Date | 2006-07-27 |
United States Patent
Application |
20060165982 |
Kind Code |
A1 |
Simmonds; Glen E. |
July 27, 2006 |
Staple yarn manufacturing process
Abstract
The present invention is a staple-fiber yarn, an apparatus for
producing the yarn, and a process for stretch breaking filament
yarns to produce the staple yarn. The process enables the
production of a plurality of products of lot size smaller than a
large denier tow product. The process includes a draw zone, a
tension control zone, a stretch-break zone and a consolidation zone
to form a yarn of staple fibers.
Inventors: |
Simmonds; Glen E.;
(Avondale, PA) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY;LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1128
4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Family ID: |
36293287 |
Appl. No.: |
11/336723 |
Filed: |
January 20, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60645695 |
Jan 21, 2005 |
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Current U.S.
Class: |
428/364 |
Current CPC
Class: |
Y10T 428/2913 20150115;
D01G 1/08 20130101 |
Class at
Publication: |
428/364 |
International
Class: |
D02G 3/00 20060101
D02G003/00 |
Claims
1. A process for making a staple yarn from a filament yarn
comprising (a) subjecting the filament yarn to an amount of tension
at which filaments in the yarn are drawn, (b) subjecting the yarn
to an amount of tension at which the filaments in the yarn are not
further drawn and are not broken, (c) subjecting the yarn to an
amount of tension at which filaments in the yarn are broken to form
staple fibers, and (d) consolidating the staple fibers to form a
staple yarn.
2. The process of claim 1 wherein the filament yarn has not been
drawn before being drawn in step (a).
3. The process of claim 1 wherein the filament yarn has been
partially drawn before being drawn in step (a).
4. The process of claim 1 wherein the filament yarn is prepared
from one or more polymers selected from the group consisting of
polyester, polyamide and polypropylene.
5. The process of claim 1 further comprising steps of adding
continuous filaments and/or consolidated staple yarn to the staple
fibers as formed from step (c), and consolidating the continuous
filaments and/or consolidated staple yarn with the staple fibers to
from a staple yarn in step (d).
6. The process of claim 5 wherein the consolidated staple yarn is
prepared from one or more materials selected from the group
consisting of polymers, metals, glass and natural fibers.
7. The process of claim 1 further comprising steps of adding
fully-drawn filament yarn, as a second yarn, to the yarn that is
drawn in step (a), as a first yarn, and subjecting both the first
and second yarns to tension in step (b) together.
8. The process of claim 7 wherein the second yarn is prepared from
one or more materials selected from the group consisting of
polyester, polyamide, polypropylene, aramid, acetate and
regenerated cellulose.
9. The process of claim 1 wherein, in step (b), the filament yarn
is subjected to a smaller amount of tension than it is subjected to
in step (a).
10. The process of claim 1 wherein, in step (b), the filament yarn
is subjected to the same amount of tension that it is subjected to
in step (a).
11. The process of claim 1 wherein, in step (b), the filament yarn
is subjected to a greater amount of tension than it is subjected to
in step (a).
12. A spinning apparatus for making a staple yarn from filament
yarn comprising (a) a draw zone wherein the yarn is subjected to an
amount of tension at which filaments in the yarn are drawn, (b) a
tension control zone, into which the filament yarn is passed from
the draw zone, wherein the yarn is subjected to an amount of
tension at which the filaments in the yarn are not further drawn
and are not broken, (c) a stretch-break zone, into which the
filament yarn is passed from the tension control zone, wherein the
yarn is subjected to an amount of tension at which filaments in the
yarn are broken to form staple fibers, and (d) a consolidating
zone, into which the staple fibers are passed from the
stretch-break zone, wherein the staple fibers are consolidated to
form a staple yarn.
13. A staple yarn comprising staple fibers wherein the staple
fibers have a weight average fiber length of less than about 6
inches, and a fiber length distribution in the range of from less
than 1 inch to about 25 inches.
14. The yarn of claim 13 wherein more than 50% of the staple fibers
have a length that is in the range of about 0.5 to about 1.5 times
the weight average fiber length.
15. The yarn of claim 13 further comprising continuous filaments.
Description
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/645,695, filed Jan. 21, 2005, which is
incorporated in its entirety as a part hereof for all purposes.
TECHNICAL FIELD
[0002] This invention relates generally to a fiber conversion and
spinning process, and more particularly concerns methods for
stretch breaking filament yarn to form staple fibers, and
consolidating these fibers into a staple yarn. The process
comprises a drawing step, followed by a tension control step,
followed by a stretch breaking step, and, finally, a consolidation
step. The invention also relates to an apparatus for performing
such a process, and the yarn produced thereby.
BACKGROUND
[0003] Spun yarns have been produced from continuous filaments
prepared from synthetic materials such as polymers by cutting the
continuous filaments into staple fibers, which are then assembled
into yarn in the same manner as natural fibers of cotton or
wool.
[0004] Another method of producing yarn from staple fibers is by
stretch-breaking continuous filaments to form staple fibers. This
method is further divided into two groups. In a first group, large
tows of filaments are stretch-broken to form heavy slivers of
staple fibers, as described for example in U.S. Pat. No. 4,924,556
(Gilhaus). These slivers are then processed into yarns via
conventional systems also used for cotton or wool. Because the
staple fibers obtained from the stretch-broken filaments are
processed on conventional yarn manufacturing machinery, the average
fiber length, and fiber length distribution, must be tightly
controlled. Multiple stretch-break zones are taught by Gilhaus for
progressively reducing the fiber lengths to accomplish this task.
In a second group, smaller tows are stretch broken to form small
slivers that are then spun directly into yarns, as described for
example in U.S. Pat. No. 2,721,440 (New) or U.S. Pat. No. 2,784,458
(Preston). Methods of this second group are sometimes referred to
as direct spinning.
[0005] Such early processes were slow due to the inherent speed
limitations of a true twisting device. As an alternative to true
twisting, U.S. Pat. No. 3,110,151 (Bunting) discloses consolidating
staple fibers to make a yarn product using an entangling, or
interlacing, jet device. Such a product can be produced faster than
true twisting, but is not comparable to conventional spun yarns in
strength, cleanness and uniformity.
[0006] Alternatively, U.S. Pat. No. 4,080,778 (Adams) 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. A roll-speed ratio of at least 5 in the
stretch breaking zone is required by Adams to have process
stability and good quality yarn. 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. Because there
is no requirement for further yarn processing, fiber length
restrictions are not present. In Adams, about 1.5-20% of the
discontinuous-filament fibers produced in the stretch-breaking zone
exceed 76 cm in length, and about 50 to 93.5% of the fibers are
12.7 to 76 cm long. 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.
[0007] A horizontal in-line process for making a fasciated yarn
from a tow of fibers is taught by in U.S. Pat. No. 4,667,463
(Minorikawa). 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 roll-speed 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
(Minorikawa) with reference to the fact that more than about 15% of
the discontinuous filaments in the fibers of the yarn have a
filament length of less than 0.5 times the average filament length,
and more than about 15% of the filaments in the fibers of the yarn
have a filament length greater than 1.5 times the average filament
length, where the preferred average filament length is between 50
and 500 mm. 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 (Example 6) with most examples run at
about 100 meters/minute.
[0008] In the products of the Adams process, the long average fiber
length, and the fact that 1.5 to 20% of fibers exceed 76 cm, limit
the number of fiber ends that are available to protrude from the
yarn and provide a yarn with a comfortable feel and look for many
textile applications. Adams requires these long fibers in order to
achieve a stable process and good yarn quality.
[0009] In contrast to the Adams process, both Gilhaus and
Minorikawa require at least two breaking zones to achieve the
desired average fiber length and fiber length distribution. Long
breaking zones have been thought to be required for process
stability and clean yarns while short breaking zones have been
thought to be required for short fiber lengths. When a short
breaking zone is used, the average fiber length is typically about
0.5 the length of the shortest breaking zone, with a range of the
average fiber length being about 0.4 to 0.7 times the length of the
shortest breaking zone.
[0010] WO 00/77283 (Popper) discloses a stretch-break method in
which the yarn produced has a weight average fiber length of
greater than six inches.
[0011] A need thus remains for a direct spinning process for
producing a stretch-broken yarn with an average fiber length
sufficiently short to result in aesthetics similar to conventional
staple-fiber yarns. There is also a need for a process that can
operate robustly and at a high speed (for example, above 250 m/min)
to make the production of yarn directly from a small tow or creel
in a single line economically attractive.
[0012] The existing one-break-zone processes also appear to produce
yarns having unacceptable mass uniformity. In particular, mass
variations in yarn lengths of 2 meters to 10 meters may be such
that fabrics appear to have thick and thin places despite a
measured mass uniformity (CV %) that is well within the normally
accepted range. The process of the present invention overcomes
these problems.
SUMMARY
[0013] One embodiment of this invention is a process for making a
staple yarn from a filament yarn by [0014] (a) subjecting the
filament yarn to an amount of tension at which filaments in the
yarn are drawn, [0015] (b) subjecting the yarn to an amount of
tension at which the filaments in the yarn are not further drawn
and are not broken, [0016] (c) subjecting the yarn to an amount of
tension at which filaments in the yarn are broken to form staple
fibers, and [0017] (d) consolidating the staple fibers to form a
staple yarn.
[0018] Another embodiment of this invention is a process for making
a staple yarn from a filament yarn by [0019] (a) passing the
filament yarn into a draw zone of a spinning apparatus wherein the
yarn is subjected to an amount of tension at which filaments in the
yarn are drawn, [0020] 1(b) passing the yarn out of the draw zone
into a tension control zone of the apparatus wherein the yarn is
subjected to an amount of tension at which filaments in the yarn
are not further drawn and are not broken, [0021] (c) passing the
yarn out of the tension control zone into a stretch-break zone of
the apparatus wherein the yarn is subjected to an amount of tension
at which filaments in the yarn are broken to form staple fibers,
and [0022] (d) passing the staple fibers out of the stretch-break
zone into a consolidation zone of the apparatus wherein the staple
fibers are consolidated to form a staple yarn.
[0023] A further embodiment of this invention is a spinning
apparatus for making a staple yarn from filament yarn that includes
[0024] (a) a draw zone wherein the yarn is subjected to an amount
of tension at which filaments in the yarn are drawn, [0025] (b) a
tension control zone, into which the filament yarn is passed from
the draw zone, wherein the yarn is subjected to an amount of
tension at which the filaments in the yarn are not further drawn
and are not broken, [0026] (c) a stretch-break zone, into which the
filament yarn is passed from the tension control zone, wherein the
yarn is subjected to an amount of tension at which filaments in the
yarn are broken to form staple fibers, and [0027] (d) a
consolidating zone, into which the staple fibers are passed from
the stretch-break zone, wherein the staple fibers are consolidated
to form a staple yarn.
[0028] Yet another embodiment of this invention is a staple yarn
that includes staple fibers wherein the staple fibers have a weight
average fiber length of less than about 6 inches, and a fiber
length distribution in the range of from less than 1 inch to about
25 inches.
DESCRIPTION OF THE DRAWINGS
[0029] Other features of the present invention will become apparent
from the following description and upon reference to the drawings,
in which:
[0030] FIG. 1 is a side elevation view of an apparatus of this
invention, which may be used to run the process of this invention
and which includes a draw zone, a tension control zone, a
stretch-breaking zone and a consolidation zone.
[0031] FIGS. 2.about.5 show mass uniformity spectrograms obtained
on the yarns produced in Examples 1.about.4.
[0032] FIGS. 6.about.8 illustrate alternative godet arrangements
that can be used in the process of this invention.
[0033] FIG. 9 is an illustration of an embodiment that includes a
second set of feed rolls in order to draw different feed materials
that have different draw ratios.
DETAILED DESCRIPTION
[0034] A process has been developed that produces, from a feed of
filament yarn, a staple yarn in which the staple fibers therein
have a weight average fiber length of less than about six inches
(6''), resulting in a desirably high number of fiber ends per inch.
This process is able to provide these relatively short weight
average fiber lengths using an apparatus that does not employ a
short stretch-breaking zone because the ratio of the weight average
fiber length to the length of the stretch-breaking zone can be
controlled to be less than about 0.4. This process operates at
rates that greatly exceed those at which ring-spun staple yarns are
made. The process permits operation in either a vertical or
horizontal orientation without sacrificing production speed or
efficiency. The process is adaptable to using, as the feed,
filament yarns made from a variety of materials, including a
variety of polymers.
[0035] Various improvements to conventional stretch-break processes
are disclosed including using a tension control zone to eliminate
or control the stresses in the filaments in the feed yarn prior to
stretch-breaking. This tension control results in the ability to
greatly influence the location at which the filaments in the feed
yarn break in the stretch-breaking zone, and therefore to change
the fiber length distribution, primarily the weight average fiber
length, of the staple fibers produced by stretch-breaking the
continuous filaments in the feed yarn.
[0036] In preferred embodiments, the process utilizes the following
zones in direct sequence, moving in an upstream-to-downstream
direction: a draw zone, a tension control zone, a stretch-breaking
zone, and a consolidation zone for consolidating the staple fibers
made up of discontinuous filaments, and intermingling them by any
of a variety of means to produce and maintain unity in the yarn
product. The process includes improvements to systems having one or
more stretch break zones.
[0037] In further embodiments, an annealing zone is employed when
it is desired to heat the filaments in the feed yarn and/or the
staple fibers in the product yarn, and control product features
such as shrinkage. An annealing zone is most often part of the draw
zone, but may be applied at a variety of locations in the process,
including after the consolidation zone.
[0038] A fiber is a cylindrical-shaped unit of matter characterized
by a length at least 100-times its diameter or width that is
capable of being spun into a yarn, or made into a fabric, by
various methods such as weaving, knitting, braiding, felting and
twisting. For processing on textile machinery, a fiber of the
correct length (such as about 1.about.8 inches) is needed. A staple
fiber has the correct length for such purpose because it is either
a natural fiber (e.g. from cotton or wool), and inherently has a
useful length, or it is a bundle of discontinuous lengths of
synthetic filaments that have been cut or broken from continuous
filaments to the correct machine length. A bundle of continuous
filaments, referred to herein as a filament yarn, is thus converted
to staple fibers by being processed, for example, on
stretch-breaking machine for the purpose of repeatedly breaking the
continuous filaments at locations that produce discontinuous
lengths of filament of a length suitable for consolidation into
staple fibers.
[0039] A staple yarn, as contrasted with the filament yarn
described above, is a continuous strand of staple fibers in a form
in which the fibers are consolidated, and thus sufficiently
intermingled that the yarn has an integrity and unity of
construction along the length of the yarn suitable for knitting,
weaving, or otherwise intertwining, to form a fabric. A staple yarn
may also contain continuous, unbroken filaments that have been
incorporated into the stream of broken filaments from which the
staple fibers, and ultimately the staple yarn, are produced.
[0040] The process of this invention produces a yarn constituted of
staple fibers that have a shorter weight average fiber length than
a yarn produced by a stretch-breaking system without a tension
control zone, and does so with only one or two stretch-breaking
zones. The staple yarn product of this invention is characterized
by the presence of staple fibers of different lengths, the fibers
being intermingled along the length of the yarn to maintain the
unity of the yarn, wherein the weight average length of the fibers
is less than 6 inches, and wherein the yarn has a fiber length
distribution ranging from less than 1 inch to about 25 inches.
Other products include the combination of continuous filaments with
the staple fibers in the yarn product, the continuous filaments
being added to the fibers, for example, after the stretch-breaking
zone and at the entrance to the consolidation zone.
[0041] Referring now to the drawings, FIG. 1 shows a direct
spinning apparatus of this invention, on which the process of this
invention may be performed. The filament yarn feed material for the
process of this invention may come from a wound package of
continuous filaments, or may come from a container of piddled
continuous filaments from which the feed yarn may be freely
withdrawn. The process of this invention can economically operate
with a relatively small denier piddled feed yarn, which eliminates
a costly winding step and permits the use of undrawn filaments that
are sometimes difficult to wind in a package successfully. The
filaments in the feed of the filament yarn may thus be undrawn
before being fed to the draw zone of the apparatus, or may have
previously been partially drawn or oriented. Feed material in
either of these forms provides economical alternatives. This is in
contrast to a sliver stretch-breaking device such as that disclosed
in Gilhaus.
[0042] Filament yarn 1 is fed to the apparatus, and is first taken
up between two sets of rolls 2 and 3, which are driven at a
predetermined speed by a conventional motor/gearbox and controller
(not shown). Roll set 3 is driven at a higher rate of speed than
roll set 2, and the feed yarn is thus subjected, in this first zone
11 (the draw zone) to an amount of tension at which the filaments
in the yarn are drawn.
[0043] A draw zone 11, and drawing a filament yarn 1, refers to
stretching continuous filaments in a way that none, or
substantially none, of the filaments are broken; the filaments
remain continuous. Drawing a filament yarn may or may not include
heating the filaments, and the draw zone 11 can thus optionally
include a heater that may take many forms, and that may contact the
filaments over a length that can easily be varied. The drawing of a
filament may occur as soon as the filament is exposed to tension in
the draw zone, and thus, for some polymers, drawing or elongation
of the filament may occur just as the filament is leaving the
upstream rolls 2, or over a very short length such as an inch or
less. In this case, a heater serves to anneal the drawn filament
rather than heat it for drawing. For this type of filament, if draw
heating is required, the rolls may be heated. Other polymers,
however, may not draw until they experience some heat by contact
with the surface of the heater, or may be drawn without heating at
all. In still other cases, the draw zone may have a roll speed
ratio that is not substantially in excess of one, the yarn will
receive minimal drawing, and the draw zone would function as much
as, or more as, an annealing zone than as a draw zone. The length
of the draw zone 11 is not critical, and is primarily sized to
accommodate the heating device when present.
[0044] The feed yarn 4, in which the filaments have been drawn, is
then passed out of the draw zone 11 and into a tension control zone
12, which is located between roll sets 3 and 5. Roll set 5 is
driven at a speed, in relation to the speed of roll set 3, at which
the tension of the filaments in this zone is controlled to an
amount that is selected to permit any residual stresses in the
filaments to be dissipated. For this purpose, the rate of speed of
roll set 5 may be less than, equal to or higher than the speed at
which roll set 3 is driven. The amount of tension to which the
filaments were subjected in the draw zone 11 is thus either
reduced, maintained or increased in the tension control zone 12. In
all cases, however, the tension to which the filaments are
subjected in the tension control zone is set at an amount at which
the filaments in the feed yarn are not further drawn and are not
broken. If the amount of tension to which the filaments are
subjected in the tension control zone 12 is higher than the amount
of tension to which they were subjected in the draw zone, this
greater amount of tension will not be large enough to cause any
further drawing in view of the temperature profile of the draw zone
11, the mechanical properties of the material from which the
filaments are made, and the amount of drawing the filaments have
already experienced in the draw zone 11.
[0045] Although in the apparatus of this invention as shown in FIG.
1, the draw zone 11 feeds directly into, and is essentially part of
the same machine as; the tension control zone 12, the step of
drawing yarn in a draw zone in the process of this invention need
not be performed on the same machine as any of the other steps in
the process.
[0046] The feed yarn 6 is then passed out of the tension control
zone 12 and into a stretch-break zone 13, which is located between
roll sets 5 and 7. The length of the stretch-break zone 13 is
measured between the nip of roll set 5 and the nip of roll set 7.
The speed of the yarn 6 is increased within the stretch-break zone
13 by driving the yarn at a higher speed with roll set 7 than with
roll set 5. There should not be any slippage between the rolls and
the yarn, thus the yarn speed and roll surface speed at the driven
roll set 5 are the same, and the yarn speed and roll surface speed
at the driven roll set 7 are the same. Increasing the speed of the
yarn within the stretch-break zone 13 subjects the filaments in the
yarn 6 to an amount of tension that causes the filaments to be
stretched until the break elongation of the filament is exceeded,
and the filaments, as gripped by both roll sets, will be broken. In
the stretch-break zone 13, to break the filaments, the ratio of the
speeds of the roll sets should be such that the maximum imposed
strain on the filaments exceeds the elongation to break of the
material from which the filaments are made. Under such conditions,
all or substantially all of the filaments will be broken in the
stretch-break zone 13 to form staple fibers.
[0047] In addition to breaking continuous filaments in the feed
yarn by running them at a high speed ratio and subjecting them to a
tension that exceeds their elongation to break, filaments may also
be broken by cutting or weakening them with a device such as a
cut-converter or breaker bar [as described, for example in New or
U.S. Pat. No. 4,547,933 (Lauterbach)], which reduces the breaking
forces imposed at the nip rolls and controls some of the randomness
of the breaking position in the filaments.
[0048] To achieve a practical breaking of filaments in a feed yarn
in a single stretch-break zone 13, the steady state tension
required for breaking decreases as the ratio of the speed of the
exit rolls 7 to the speed of the inlet rolls 5 increases. If a yarn
enters the stretch-break zone 13 under high tension, the filaments
therein are more likely to break closer to the inlet rolls 5. A
break closer to the inlet rolls 5 will cause a longer weight
average fiber length in the staple fibers formed from the broken,
discontinuous filaments, which may for example be a weight average
length of greater than about 0.5 times the length of the
stretch-break zone 13. If a yarn enters the stretch-break zone 13
under low tension, the filaments therein are more likely to break
closer to the exit rolls 7. A break closer to the exit rolls 7 will
cause a shorter weight average fiber length in the staple fibers
formed from the broken, discontinuous filaments, which may for
example be a weight average length of less than about 0.5 times the
length of the stretch-break zone 13. This phenomenon can be used to
create staple fibers with a weight average length of less than
about 6'' without the necessity of decreasing the length of the
stretch-break zone used, thereby maintaining good operability and
yarn quality. In the stretch-breaking of yarns, a shorter break
zone results in shorter fibers, but a longer break zone is required
for good operability and yarn quality.
[0049] Tension on a yarn is measured in grams and may be determined
by use of a tensiometer. The tension on the yarn, and thus on the
filaments therein, in the draw zone, tension control zone and the
stretch-break zone, may be determined from the mass flow, the break
elongation and the break strength of the yarn.
[0050] After the continuous filaments in the feed yarn are broken,
the assembly of discontinuous filaments, from which staple fibers
are formed, may also be drafted in the stretch-break zone to reduce
denier as its speed continues increasing until it reaches the speed
of the roll set 7. The same phenomenon mentioned above allows the
draft within the stretch-break zone to be operated over a wide
range of roll speed ratios, even less than 5, and enables use of
feed creels with a relatively small number of packages of feed yarn
of continuous filaments instead of having to create a very large
feed tow from many packages.
[0051] Staple fibers 8, as formed from the broken, discontinuous
filaments, are passed out of the stretch-break zone 13 and into a
consolidation zone 14 between roll sets 7 and 9. The fiber speed
can be decreased slightly within the consolidation zone 14, but
there should not be any slippage between the rolls and the fibers,
and thus the fiber speed and roll surface speed at the driven roll
set 7 are the same, and the fiber speed and roll surface speed at
the driven roll set 9 are the same. In other cases, it may be
desired to increase the fiber speed within the consolidation zone
by a small amount to improve the entanglement of the fibers. In
this case, some drafting would occur. One or more consolidation
devices 10, such as an aspirator jet or an interlace jet, are
located in the consolidation zone. An interlace jet interconnects
the fibers by entangling them with one another to form a staple
yarn, and, in doing so, it can slightly shorten the length of the
fibers as the yarn is formed, which accounts for the decreased
speed in the consolidation zone. An appropriate interlace jet is
described, for example, in U.S. Pat. No. 6,052,878 (Allred), in WO
03/29539 (Buchmuller), or in the Heberlein interlacing jet
catalogs. Other suitable fiber interconnecting jets are described,
for example, in U.S. Pat. No. 4,825,633 (Artzt) and in the Murata
Jet Spinner catalog. The staple fibers, after passing through the
consolidation device, become a consolidated staple yarn having good
cohesiveness and strength.
[0052] If desired, an annealing zone (not shown) can be added after
the consolidation zone 14. The annealing zone may, for example, be
operated in the same manner as discussed above where the draw zone
11 is operated with heating means but with an extremely small speed
ratio. This may be useful in a process where the final shrinkage of
the yarn product must be controlled to a specified value, and
annealing after formation of the yarn is the most direct way to
accomplish this. It may also be useful when the feed yarn is
prepared from two different materials, and the annealing heat
treatment causes each material in the yarn product to respond
differently to create a special effect in the yarn, as, for
example, when the shrinkages of the fibers are different and the
differential shrinkage produces a bulky or loopy yarn. In
alternative embodiments, there may be a small overfeed of the fiber
into the annealing zone.
[0053] In other alternative embodiments, the godet arrangements
shown in FIGS. 6.about.8 can be used in the process and apparatus
of this invention. These alternative arrangements illustrate means
to assure adequate friction between the godets and the yarn,
thereby eliminating slippage. FIG. 8 illustrates a means to process
two different feed yarns requiring different draw ratios.
[0054] Following roll set 9 the consolidated staple yarn is
directed to a winder. The consolidated yarn produced by the process
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.
[0055] The feed yarn that is used in the process of this invention
may be pre-treated such as by the application of a finish, or by a
structural manipulation such as crimping with jets, gear crimpers
or a stuffer box. Selection of any finish used on the feed yarn is,
however, a consideration for operability. If too much finish is
used, independent filament mobility and breaking in the
stretch-break zone is adversely affected. If too little finish is
used, static becomes a problem, and roll wraps are increased. A
finish level of less than about 0.1 wt % is preferred, and less
than about 0.04 wt % is more preferred, by weight of the material
from which the filaments are made. A typical finish composition may
include an ethylene oxide condensate of a fatty acid, an
ethoxylated or propoxylated alcohol capped with pelargonic acid,
the potassium salt of a phosphate acid ester, and/or the amine salt
of a phosphate acid ester. Other finishes that may be useful for
filaments to be stretch broken are described, for example, in Adams
and in JP 58(1983)-44787 (Hirose).
[0056] The staple yarn product of this invention is prepared from
consolidated staple fibers of discontinuous filaments of different
lengths, the fibers being intermingled along the length of the yarn
to maintain the integrity and unity of the yarn. The yarn product
has a denier that can be readily used in textile applications
without further preparation other than conventional dyeing or the
like. The linear density of the yarn product is typically less than
or equal to about 1000 denier. Alternatively, however, the yarn
product may have a linear density of greater than about 1000
denier, and the fibers from which the yarn is made may have in such
case a total of about 500 or fewer filaments in a cross-section of
the yarn. In a preferred embodiment, the staples fibers in the yarn
product have a weight average fiber length of less than about 6
inches, and they have a fiber length distribution wherein the
fibers range from a minimum of less than 1 inch to a maximum of
about 25 inches. The maximum length of about 99% of the fibers is
less than about 25 inches, and more than about 50% of fibers have a
length that is in the range of about 0.5 to about 1.5 times the
weight average length fiber. The number average fiber length is
also less than about 6 inches. The yarn product has a useful number
of fiber ends per inch, and a substantial percentage of these fiber
ends can be found as protruding ends extending from the central
portion of the yarn to give the yarn a desirable feel or
"hand".
[0057] In making the yarn product of this invention, two or more
different kinds of feed yarns may be used. In one embodiment,
different feed yarns would go through the draw, tension control,
stretch-break and consolidation zones together. The different yarns
could be combined together into a single yarn before being fed into
the apparatus, or could simply be fed separately but
simultaneously.
[0058] In another embodiment, however, the yarn of this invention
may be made by introducing one or more additional feed yarns at the
downstream end of the draw zone or at the downstream end of the
tension control zone. This is a useful approach if filament yarns
that do not require drawing are to be added to yarns that do need
to be drawn. All yarns would be broken at the same time in the
stretch-break zone, and would continue to be treated together
throughout the remainder of the process.
[0059] In a further embodiment, the yarn product of this invention
may be made by introducing a first additional feed yarn(s) at the
downstream end of the draw zone or the downstream end of the
tension control zone, and by introducing a second additional feed
yarn(s) at the upstream end of the consolidation zone. In this
embodiment, the first additional feed yarn(s) would pass through
the stretch-break zone, and thus be broken into discontinuous
filaments, but the second feed yarn(s) would not pass through the
stretch-break zone. As a result, the second feed yarn(s) could be a
filament yarn as to which it is intended that the filaments remain
continuous and thus unbroken, and/or the second feed yarn(s) could
be a previously-prepared staple yarn that already incorporates
staple fibers. In yet another embodiment, one or more additional
feed yarns may be introduced only at the upstream end of the
consolidation zone.
[0060] Where there are differences between feed yarns, the
differences may, for example, be in denier per filament where one
yarn has a denier per filament (dpf) of less than about 0.9, and
the other yarn has a denier per filament of greater than about 1.5.
The advantage of making the yarn product from two or more yarns
having a difference in dpf is that the structural stiffness of the
yarn product can be determined by the larger dpf feed yarn while
the softness can be controlled by the smaller dpf feed yarn. This
overcomes some problems with small dpf yarns that have a good hand
but are too limp when made into fabric.
[0061] When different feed yarns are used, the elongation to break
of each should be similar for desirable performance in the draw
zone. If the different yarns do not have similar elongation to
break, one of them could be partially pre-drawn to be compatible
with the other. Alternatively, a second, independent set of feed
rolls (2A) could be installed in the apparatus, as shown in FIG. 9,
that operate at a speed different than roll set 2 so that the
different yarns could be drawn at different speed ratios while
still being joined together at the draw rolls 3.
[0062] Where different feed yarns are used in this invention, they
may contain filaments prepared from different polymers, such as two
different nylon polymers, two different polyesters, or a nylon
polymer and a polyester. Different polymers as used in the feed
yarn should be compatible so that they stick together and can be
cospun. For this purpose, they should have a similar thermal
response and functional spinning viscosity, or have some specific
interaction such as a chemical interaction. In a further
embodiment, feed yarns having filaments with different structures
may also be used, such as a bicomponent and/or biconstituent
filament. A bicomponent filament has one or more distinct
structural domains or regimes such as a sheath/core structure,
whereas a biconstitutent filament is characterized by a much more
intimate blend of the polymers from which the filament is made
without discernable structural domains or domains that have any
substantial functional effect. The weight percent ratio at which
different polymers may be used in the feed yarn(s) may vary
considerably, but is generally between about 80/20 and about 20/80,
and preferably about 70/30 to about 30/70.
[0063] A bicomponent filament in a feed yarn may be made, for
example, from a core polymer that is highly elastic (or "soft"),
such as a Lycra.RTM. elastomer, and from an inelastic ("hard")
polymer that is attached as "wings" or longitudinal ribs during the
spinning process. After spinning, the latent elasticity of the
filament can be activated by heat that causes the soft core polymer
to shrink considerably more than the hard "wing" polymer, and this
causes the composite structure to coil helically, giving it the
appearance and structure of a screw thread. This filament structure
also has some crimp after spinning and drawing and before heat
treating.
[0064] Other combinations of polymers from which a bicomponent or
biconstituent filament in a feed yarn may be made include a
4GT/4GT-4GO polyester (such as HYTREL.RTM. polyester from DuPont)
and nylon/PEBAX.RTM. polymer (from DuPont); or a homopolymer/block
copolymer pair in which one block of the copolymer is the same as
the homopolymer.
[0065] Differences in feed yarns as used in this invention may
involve differences other than or in addition to differences in
choice of polymer, such as differences in color or differences in a
surface treatment that gives the yarn some other visual
characteristic that can be detected with the unaided eye, such as
differences in the reflectance, absorbence or wettability of the
yarns. The process of this invention provides a useful way to make
specialty yarns characterized by visual effect without involving
numerous steps, such as is required in the conventional blending of
staple fibers where a sliver must first be prepared by chopping
(cutting), blending, carding, combing and the like. In the
conventional system, a large quantity of feed fiber must be
prepared to make the process worthwhile, since cleaning the
processing equipment after each product run is very labor intensive
and time consuming. In the process of this invention, however, a
color-blended yarn product, for example, that has a different color
than either of the feed yarns, may be made on a much smaller scale
as there is practically no cleanup required to switch to another
feed blend other than changing packages in a creel.
[0066] The differences in color between different feed yarns as
used in this invention may include, for example, two colors that
are essentially non-white and non-beige variations, although one
yarn may have a color that is a white or beige, and the other yarn
may have a color that is a distinctly non-white, non-beige color.
The different colors of the feed yarns will be selected such that
the combination of the two in the yarn product achieves a new color
that is distinctly different from either of the feeds. Differences
in color may be determined and describe according to ASTM Sandard
E-284-05a, Committee E12.01, 2005, which describes a means to
distinguish neutral colors, such as white and beige, based on a
lightness measurement with white and beige having a lightness
greater than 90%. It also permits distinguishing color hue and
shade to detect color difference by using CIELAB units where
different colors as used herein would have a CIELAB unit difference
of at least 2.0. Blending two or more yarns having different colors
where only one yarn has a lightness greater than 90%, and the yarns
have a color difference in CIELAB units of at least 2.0, creates a
yarn having a new color that is suitably different from the colors
of either feed yarn. When the yarn product is fabricated further
into a textile or fabric, the blended color has a mild heather
appearance.
[0067] When an additional feed yarn is introduced at the downstream
end of the draw zone or at the downstream end of the tension
control zone, to be broken in the stretch-break zone along with the
primary feed yarn, the primary feed yarn and/or the additional feed
yarn may be prepared from any one or more polymers selected from
the group consisting of nylon, polyester, an aramid, a
fluoropolymer, an acetate polymer or copolymer, an acrylic polymer
or copolymer, polyacetal, an acrylate polymer or copolymer,
polyacrylonitrile, a cellulose polymer, an olefin polymer or
copolymer, polyimide, a styrenic polymer or copolymer, an
ether/ester copolymer, a copolymer of an amide with an ether and/or
ester, a vinyl polymer, and a polyimide. For example, the
additional feed yarn may be prepared from one or more polymers
selected from the group consisting of aramid polymers and
fluoropolymers, and that additional feed yarn may be added to a
primary feed yarn that is prepared from one or more polymers
selected from the group consisting of nylon, polypropylene and
polyester.
[0068] As noted above, when an additional feed yarn is introduced
at the upstream end of the consolidation zone, it is not subjected
to any stretch-breaking. If that yarn contains any continuous
filaments, they will retain their continuous character. A feed yarn
added at the upstream end of the consolidation zone may be prepared
from any one or more polymers selected from the group consisting of
nylon, polyester, an aramid, a fluoropolymer, an acetate polymer or
copolymer, an acrylic polymer or copolymer, polyacetal, an acrylate
polymer or copolymer, polyacrylonitrile, a cellulose polymer, an
olefin polymer or copolymer, polyimide, a styrenic polymer or
copolymer, an ether/ester copolymer, a copolymer of an amide with
an ether and/or ester, a vinyl polymer, a polyimide, a
polyurethane, a copolymer having blocks of polyurethane and blocks
of polymerized ethers and/or esters, a natural fiber, a metallic
fiber or wire (e.g. copper or steel), a glass fiber, and a ceramic
fiber. It is preferred but not required that a yarn added at the
upstream end of the consolidation zone be prepared from a different
material than a yarn added at any other stage of the process. For
example, a yarn added at the upstream end of the consolidation zone
may be prepared from an elastane or spandex-type filament, a
Lycra.RTM. elastic polymer, high strength filaments with low
elasticity such as those made from an aramid polymer, or filaments
with high elasticity such as those made from a 2GT [1,2-ethane diol
(or ethylene glycol) esterified with terephthalic acid] or a 3GT
[1,3-propanediol (or 1,3 propylene glycol) esterified with
terephthalic acid] polyester. Filaments, when made from a
spandex-type polymer, preferably have an elongation to break
greater than about 100% and an elastic recovery of at least 30%
from an extension of about 50%. These additional feed yarns can be
added to a primary feed yarn that is prepared from a polymer such
as nylon, polyester, polypropylene, a fluoropolymer or an aramid
polymer such as a Nomex.RTM. polymer [a polymer made from
isophthaloyl chloride and methylphenylene diamine (from DuPont)] or
a Kevlar.RTM. polymer [a polymer made from terephthaloyl chloride
and methylphenylene diamine (from DuPont)].
EXAMPLES
[0069] The advantageous effects of this invention are demonstrated
by a series of examples, as described below. The embodiments of the
invention on which the examples are based are illustrative only,
and do not limit the scope of the appended claims.
[0070] A test for uniformity, in terms of evenness and frequently
occurring yarn faults, were performed using a standard Uster UT-3
yarn testing instrument (Uster Technologies AG, Zellweger Uster,
Uster Switzerland), per the methods recommended by the
manufacturer, on four samples of staple yarns (Examples 1.about.4)
prepared according to the process of this invention. In the
uniformity test, the yarn is passed between two parallel capacitor
plates, and variations in the mass of the yarn cause a change in
the dielectric of the air between the plates, causing a
proportional change in the electric signal from the sensor. Tests
of yarn strength were also performed on the same yarn samples using
an Uster TensoJet.
[0071] The yarns of Examples 1.about.4 as tested herein were each
made from three feed packages of partially drawn polyester filament
yarns wherein each filament had a denier of 255 and each yarn
contained approximately 200 filaments. The feed yarns were used to
produce a staple yarn product on an apparatus of this invention
having a stretch-break zone length of about 16 inches. Operating
conditions by which each staple yarn was made are outlined in Table
I.
[0072] The result of the yarn uniformity test are shown in Table
II, the results of the yarn strength test are shown in Table III,
and the mass uniformity spectrogram for the yarns of Examples
1.about.4 are shown, respectively, in FIGS. 2.about.5. In Table II,
CVm is the coefficient of mass variation, which expresses the
amount of variation in the yarn around a mean value of the mass. It
is obtained by dividing the standard deviation by the mean and
multiplying by 100, and is expressed as a percentage deviation from
the mean. In Table II, the count of 50% thin places, locations
where the mass of the yarn decreases by 50% or more from the mean
yarn mass, and the count of 50% thick places, locations where the
mass of the yarn increases by 50% or more from the mean yarn mass,
are set forth; as is the count of 280% Neps, locations where the
mass of the yarn increases by 280% or more from the mean yarn mass.
In Tables II and III, yarn count is expressed in terms of Nec,
Number English Cotton, which is the number of 840 yard lengths in
the yarn per pound. In Table III, tex is the number of grams in a
kilometer of yarn. TABLE-US-00001 TABLE I Roll Speed Draw Roll
Stretch Ratio in Temper- Tension Break Consoli- Output Exam- Draw
ature Control Zone dation Speed ple Zone (.degree. C.) Ratio Ratio
Zone Ratio (m/min) 1 2.0 220 1.02 2.20 1.01 703 2 2.0 220 1.00 2.20
1.01 703 3 2.0 220 0.995 2.20 1.01 703 4 2.0 220 0.990 2.20 1.01
703
[0073] TABLE-US-00002 TABLE II Yarn Evenness as tested on Uster
Tester 3 Thin Places Thick Places Neps Exam- CVm Final Yarn (-50%
per (+50% per (+280% per ple (%) Count (Nec) 1000 yds) 1000 yds)
1000 yds) 1 10.45 31.82 0 5 8 2 10.05 31.31 0 1 3 3 10.5 31.05 0 0
6 4 10.48 30.96 2 3 11
[0074] TABLE-US-00003 TABLE III Yarn Strength as tested on Uster
TensoJet set to 500 Mean Mean Count Mean Break Mean Tenacity
Example (Nec) Force (cN) Elongation (%) (cN/tex) 1 31.82 376.4 5.27
20.28 2 31.31 351.0 5.33 18.61 3 31.05 333.3 5.35 17.52 4 30.96
330.0 5.40 17.3
[0075] The mass uniformity wavelength spectrogram for a yarn made
from staple fibers of uniform length has a different appearance
than that for a yarn made from fibers of varying, i.e. distributed,
lengths. In either case, however, there is a well defined peak in
the shape of the curve of the spectrogram, even for an ideal yarn
of completely random fiber arrangement. The curve of the
spectrogram for an ideal yarn can be mathematically determined from
the fiber length distribution. Likewise, the peak of the curve has
the mathematical relationship to the weight average fiber length of
2.7 times the weight average fiber length for a yarn comprised of
fibers of equal length; and approximately 2.8 times the weight
average fiber length of a yarn comprised of fibers of unequal, or
distributed, lengths. These mathematical relationships can be used
to quickly and easily determine the weight average fiber length of
any staple yarn, thereby eliminating the need for difficult and
time-consuming measurements of individual fibers within the
yarn.
[0076] FIGS. 2 through 5 show the spectrograms of various polyester
yarns made in accordance with the invention. It can be seen that
the major peak of each of the curves are all less than about 16
inches. From the mathematical model, the weight average fiber
length in these yarns may therefore be determined to be less than 6
inches. The spectrograms for Examples 1 and 2 have a slight
depression at about 3.6 inches, which is an indication of a
significant proportion of the fibers being about this length. By
comparison, a conventional yarn of short staple fibers has a peak
at less than 0.1 yards (3.6'') because of the short fiber lengths
of approximately 1 inch or less. Typical long staple fibers
including wool or synthetic fibers made using a conventional
multiple-zone stretch-break process such as described by Gilhaus,
have a spectrogram peak of approximately 0.25 yards (9'') which
corresponds to an average fiber lengths of about 3 inches.
Therefore, the shorter fibers in the yarns of this invention
provide a large number of fiber ends in the consolidated yarn when
compared to yarns made with a single stretch breaking zone process
without the benefit of a tension control zone.
[0077] It is therefore apparent that there has been provided, in
accordance with the present invention, methods for stretch-breaking
filament yarns (containing continuous filaments) to form staple
fibers (containing discontinuous filaments), and consolidating
these staple fibers into staple yarns, that fully satisfy 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 scope of the appended
claims.
[0078] Each patent or other publication mentioned above is
incorporated in its entirety as a part hereof for all purposes.
* * * * *