U.S. patent application number 11/088020 was filed with the patent office on 2005-07-28 for dimensionally stable yarns.
Invention is credited to Kopplin, Michael F., Rim, Peter B., Woodlee, Richard H., Zhou, Qiang.
Application Number | 20050161854 11/088020 |
Document ID | / |
Family ID | 34394365 |
Filed Date | 2005-07-28 |
United States Patent
Application |
20050161854 |
Kind Code |
A1 |
Rim, Peter B. ; et
al. |
July 28, 2005 |
Dimensionally stable yarns
Abstract
An undrawn yarn is produced at increased quench delay and
increased take-up speed to achieve improved ultimate elongation at
a given crystallinity. Particularly preferred aspects include
products comprising such yarns and methods for producing same.
Inventors: |
Rim, Peter B.; (Midlothian,
VA) ; Zhou, Qiang; (Midlothian, VA) ; Woodlee,
Richard H.; (Midlothian, VA) ; Kopplin, Michael
F.; (Esch Sur Alzette, VA) |
Correspondence
Address: |
ROBERT D. FISH
RUTAN & TUCKER LLP
611 ANTON BLVD 14TH FLOOR
COSTA MESA
CA
92626-1931
US
|
Family ID: |
34394365 |
Appl. No.: |
11/088020 |
Filed: |
March 22, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11088020 |
Mar 22, 2005 |
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10680586 |
Oct 6, 2003 |
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6902803 |
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Current U.S.
Class: |
264/130 ;
264/171.24; 264/211.12; 264/211.14; 264/211.17 |
Current CPC
Class: |
Y10T 428/2969 20150115;
D01D 5/084 20130101; D01F 6/62 20130101; Y10T 428/2913
20150115 |
Class at
Publication: |
264/130 ;
264/211.17; 264/211.12; 264/211.14; 264/171.24 |
International
Class: |
D01D 005/084; D01D
005/096; D01F 006/62 |
Claims
1. A method of producing an undrawn yarn having a predetermined
crystallinity, comprising: extruding a molten polymer through a
spinneret plate to form a plurality of filaments; and passing the
plurality of filaments through a heated sleeve to thereby provide a
quench delay, and taking up the plurality of filaments at a take-up
speed; wherein the quench delay and the take-up speed are selected
such that an ultimate elongation of the undrawn yarn increases at
the predetermined crystallinity when the quench delay
increases.
2. The method of claim 1 wherein the predetermined crystallinity is
between 10% and 40%, and wherein the undrawn yarn has a linear
density of at least 300 dtex.
3. The method of claim 2 wherein the polymer comprises
poly(ethylene terephthalate).
4. The method of claim 1 wherein the quench delay in the heated
sleeve is increased by increasing a length of the heated
sleeve.
5. The method of claim 1 wherein the length of the sleeve is at
least 300 mm.
6. The method of claim 1 wherein the quench delay in the heated
sleeve is increased by increasing a temperature in the heated
sleeve.
7. The method of claim 1 wherein the take-up speed for the
plurality of filaments is at least 3000 m/min.
8. A method of producing an undrawn yarn, comprising extruding a
molten polymer through a spinneret plate to form a plurality of
filaments, delaying quenching of the plurality of filaments in a
heated sleeve, and taking up the plurality of filaments at a
take-up speed TU (m/min) using a quench delay such that the
crystallinity of the undrawn yarn is less than
0.017.times.TU-39.
9. The method of claim 8 wherein the polymer comprises a polyester,
and wherein the yarn has a linear density of at least 300 dtex.
10. The method of claim 8 wherein the heated sleeve has a length of
at least 300 mm and wherein a temperature in the heated sleeve is
at least 250.degree. C.
11. The method of claim 8 wherein the take-up speed is between 3000
m/min and 5000 m/min.
12. The method of claim 8 further comprising drawing the plurality
of filaments after taking up to form a drawn yarn.
13. The method of claim 12 further comprising providing an
overfinish to the drawn yarn.
14. The method of claim 13 further comprising at least partially
enclosing the overfinished drawn yarn in a rubber-containing
composition.
Description
FIELD OF THE INVENTION
[0001] The field of the invention is dimensionally stable yarns and
products incorporating same, as well as methods and apparatus for
producing such dimensionally stable yarns.
BACKGROUND OF THE INVENTION
[0002] Significant improvements in fiber materials and spinning
processes allowed spinning of multifilament yarns with high initial
modulus and low shrinkage, and numerous processes and compositions
have been developed in recent decades.
[0003] For example, Davis et al. describe in U.S. Pat. No.
4,101,525 a spinning process in which a dimensionally stable
industrial strength multifilament polyester yarn is formed by
extruding PET-containing polyester filaments using a solidification
zone almost immediately after the spinneret under high spin-line
stress to achieve almost immediate solidification of the filaments
to produce yarns with relatively high birefringence. The so formed
undrawn yarn is then drawn and further processed. Such processes
generally allow formation of dimensionally stable yarns, however,
present various difficulties in their formation. Most
significantly, as the crystallinity increases, drawability of the
yarns often significantly deteriorates.
[0004] In another example, Saito et al. describe in U.S. Pat. No.
4,491,657 formation of a dimensionally stable polyester yarn, in
which the filaments are subjected to a heating zone operated at
about the melting point of the polymer followed by a rapid cooling
zone. The so formed filaments are then drawn and twisted into cords
with relatively desirable properties. However, in most practical
applications Saito's process is generally limited to yarns with
relatively low terminal modulus, especially where the dimensionally
stable yarn is further processed into a treated cord.
[0005] To overcome at least some of the disadvantages associated
with the production of dimensionally stable yarns, polymeric
filaments may be spun under high stress conditions to form an
undrawn yarn that has crystallinity of 3 to 15 percent and a
melting point elevation of 2 to 10 degrees Centigrade as described
in U.S. Pat. Nos. 5,403,659 or 6,403,006 to Nelson et al.
Alternatively, modified process conditions (e.g., using quench
delay plus rapid cool to form a yarn with crystallinity of 3 to 13%
and a melting point elevation of 2 to 10 degrees Centigrade) may be
employed in a process of making dimensionally stable polyester yarn
for high tenacity treated cords as described in U.S. Pat. No.
5,630,976 to Nelson et al.
[0006] Similarly, Rim et al describe in U.S. Pat. No. 5,397,527 a
process for production of dimensionally stable yarns using quench
delay plus rapid cool to form a partially oriented yarn of
birefringence of at least 0.030, which is then hot-drawn to a drawn
dimensionally stable yarn. However, while such processes typically
improve various properties of undrawn yarns, drawing such yarns
frequently remains problematic, especially where crystallinity of
such yarns is relatively high.
[0007] Thus, although there are numerous processes for production
of dimensionally stable undrawn yarns known in the art, all or
almost all of them suffer from various disadvantages. Therefore,
there is still a need to provide improved yarns and processes,
especially where such yarns are dimensionally stable.
SUMMARY OF THE INVENTION
[0008] The present invention is directed to dimensionally stable
undrawn yarns, methods for producing such yarns, and products
incorporating same. More specifically, the inventors unexpectedly
discovered that undrawn yarns exhibit increased ultimate elongation
when the yarn is spun using delayed quenching at increased take-up
speed.
[0009] Therefore, in one aspect of the inventive subject matter, a
method of producing an undrawn yarn having a predetermined
crystallinity will include one step in which a molten polymer
(e.g., poly(ethylene terephthalate)) is extruded through a
spinneret plate to form a plurality of filaments. In another step,
the plurality of filaments are passed through a heated sleeve to
thereby provide a quench delay, and the plurality of filaments are
taken up at a take-up speed, wherein the quench delay and the
take-up speed are selected such that an ultimate elongation of the
undrawn yarn increases at the predetermined crystallinity when the
quench delay increases.
[0010] In especially preferred aspects, the predetermined
crystallinity is between 10% and 40%, and the undrawn yarn has a
linear density of at least 700 dtex. Furthermore, it is generally
preferred that the quench delay in the heated sleeve is increased
by increasing a length of the heated sleeve (e.g., from 200 mm to
at least 300 mm, or even longer). Alternatively, the quench delay
in the heated sleeve may also be increased by increasing the
temperature in the heated sleeve. With respect to the take-up speed
it is generally preferred that the take-up speed for the plurality
of filaments is at least 3000 m/min.
[0011] In a further aspect of the inventive subject matter, a
method of producing an undrawn yarn may include one step in which a
molten polymer (preferably a polyester) is extruded through a
spinneret plate to form a plurality of filaments. In another step,
quenching of the plurality of filaments is delayed in a heated
sleeve, and in yet another step, the plurality of filaments are
taken up at a take-up speed TU (m/min) using a quench delay such
that the crystallinity of the undrawn yarn is less than
0.017.times.TU-39. Such produced yarns preferably have a linear
density of at least 300 dtex.
[0012] It is further preferred that in such methods the heated
sleeve has a length of at least 300 mm and that the temperature in
the heated sleeve is 250.degree. C. or higher. Additionally, or
optionally, preferred take-up speeds will generally be in the range
of between 3000 m/min and 5000 m/min. Yarns produced using such
processes may then be drawn to form a drawn yarn, which may be
further modified with an overfinish, and which may further be at
least partially embedded into a rubber-containing composition.
[0013] Thus, in still another aspect of the inventive subject
matter, an undrawn delayed-quenched dimensionally stable polyester
yarn will have a crystallinity C, and an ultimate elongation UE,
wherein UE.gtoreq.-1.6*C+121. Particularly preferred yarns will be
fabricated from poly(ethylene terephthalate) and will have a
crystallinity between 10% and 40% (typically at a linear density
between 700 and 6000 dtex). Of course, it should be recognized that
such yarns may further be drawn to form a drawn dimensionally
stable yarn, which may then be employed as a component in a
product, wherein especially contemplated products include power
transmission belts, conveyor belts, automobile tires, safety belts,
parachute harnesses, parachute lines, cargo handling nets, and
safety nets.
[0014] In a still further aspect of the inventive subject matter,
an apparatus comprises a spinneret plate that is operationally
coupled to an extruder and metering pump that provides a molten
polymer to the spinneret plate, wherein the spinneret plate
produces a plurality of filaments from the molten polymer. A heated
sleeve receives the plurality of filaments, thereby delaying
quenching at a predetermined quench delay, and a take-up roll takes
up the plurality of filaments at a take-up speed, wherein the
take-up speed and the heated sleeve are configured to operate at a
condition in which ultimate elongation of a yarn having a
predetermined crystallinity increases when the predetermined quench
delay increases. The polymer used in such apparatus will preferably
comprise a polyester, and the spinneret plate preferably comprises
at least 50 orifices that produce the plurality of filaments. The
heated sleeve in further preferred apparatus will have a length of
at least 300 mm and has a temperature of 250.degree. C. or higher,
while the take-up speed is between 3000 m/min and 5000 m/min.
[0015] Various objects, features, aspects and advantages of the
present invention will become more apparent from the following
detailed description of preferred embodiments of the invention,
along with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a graph representing an interrelationship between
ultimate elongation and crystallinity of an undrawn exemplary yarn,
wherein the yarn is spun using selected quench delays according to
the inventive subject matter.
[0017] FIG. 2 is a graph representing an interrelationship between
take-up speed and crystallinity of an undrawn exemplary yarn,
wherein the yarn is spun using selected quench delays according to
the inventive subject matter.
DETAILED DESCRIPTION
[0018] The inventors surprisingly discovered that undrawn
dimensionally stable polymeric yarns with improved ultimate
elongation over comparable yarns at the same crystallinity can be
produced in a process in which the filaments after extrusion are
subjected to a quench delay and taken up at increased take-up
speed.
[0019] It is generally recognized that increasing crystallinity of
undrawn yarns will generally result in improved dimensional
stability of the corresponding drawn yarns and treated cords
produced from such yarns. Unfortunately, as crystallinity of a yarn
increases, drawing or stretching of the yarn becomes more and more
problematic (i.e., ultimate elongation dramatically decreases with
increasing crystallinity). It is also well known in the art that
increasing quench delay will typically result in yarns with lower
crystallinity as the spin line stress is reduced. However, the
inventors unexpectedly discovered that when the ultimate elongation
of a plurality of yarns having the same crystallinity was plotted
as a function of quench delay (e.g., effected by elongation of the
heated sleeve), ultimate elongation of such yarns surprisingly
increases with increased quench delay (where the yarns are compared
at the same crystallinity). A graphical representation of this
observation is depicted in FIG. 1, where each regression line
represents data points of an undrawn yarn produced using a heated
sleeve of a length as indicated in the legend. Using this graph, it
becomes immediately apparent that ultimate elongation of such yarns
with the same crystallinity is a function of quench delay.
[0020] The undrawn dimensionally stable yarns of FIG. 1 were
produced using production parameters as listed in table 1 below. In
this example, the yarn was spun using a 125 hole spinneret, with
polyethylene terephthalate chip having an intrinsic viscosity (IV)
of 1.0 and a diethylene glycol content (% DEG) of 1.1 as the
polymer. It has been observed that the polymer type can have an
influence on the ultimate elongation, independent of other
variables. Extrusion rate was approximately 46.2 kg/hr, and
crystallinity, ultimate elongation, and linear density was
determined as in the experimental section described below. Quench
air temperature was 20 degrees centigrade.
1TABLE 1 Sleeve Ultimate Length Take-up Speed Sleeve Quench Rate
Crystallinity Elongation Denier (mm) (m/min) Temp. (.degree. C.)
(m/s) (%) (%) (dtex) 200 3000 280 0.8 4.9 112.9 2357 200 3500 280
0.8 16 94.1 2110 200 4000 280 0.8 27.8 81.3 1888 200 4500 280 0.8
34.7 66.7 1639 200 5000 280 0.8 38.8 57.4 1536 300 3000 280 0.8 5.1
121 2674 300 3500 280 0.8 13.7 100 2293 300 4000 280 0.8 25.3 86
2006 300 4500 280 0.8 33.1 75 1786 300 5000 280 0.8 37.9 63 1613
400 3000 280 0.8 3.8 136 2636 400 3500 280 0.8 8.9 110 2251 400
4000 280 0.8 21.7 94 1968 400 4500 280 0.8 31.7 81 1740 400 5000
280 0.8 36.2 70 1572
[0021] To compare the interrelationship between crystallinity and
take-up speed at a specific quench delay, the inventors prepared a
comparative yarn (with similar yarn polymer properties made in a
continuous polymerization and spinning step) using substantially
identical process parameters, but a heated sleeve of only 102 mm
length at temperatures between about 300-400 degrees centigrade.
Further process conditions for the comparative yarn are listed in
Table 2 below, and the results are graphically depicted in FIG. 2,
in which crystallinity is expressed as a function of take-up speed
at predetermined quench delays (here: effected by increasing sleeve
lengths). Data points for the inventive examples are taken from
table 1 above.
2TABLE 2 Take-up Speed Sleeve Temp. Quench Rate Crystallinity
(m/min) (.degree. C.) (in/water) (%) 2700 300 9 20.9 2500 300 15.5
22.8 2900 300 15.5 30.1 2700 300 22 28.6 2900 350 22 29.9 2500 350
22 21.1 2700 350 15.5 25.6 2900 350 9 27.4 2500 350 9 20.7 2700 400
9 17.9 2500 400 15.5 17.5 2900 400 15.5 27.5 2700 400 22 24.3
[0022] Of course, it should be recognized that the increase of
ultimate elongation at a predetermined crystallinity by increasing
quench delay is not limited to the specific conditions provided
above, and it is generally contemplated that numerous modification
may be made without departing from the inventive concept presented
herein.
[0023] For example, it is contemplated that the polymer employed
for the production of the undrawn yarns may vary considerably, and
it is generally contemplated that all melt-extrudable polymers are
suitable for use in conjunction with the teachings presented
herein. However, it is generally preferred that the polymer
comprises a polyester. Therefore, particularly preferred polymers
include a poly(alkylene terephthalate) (e.g., poly(ethylene
terephthalate) (PET) or poly(butylene terephthalate)), a
poly(alkylene naphthalate) (e.g., poly(ethylene naphthalate) (PEN)
and poly(butylene naphthalate)), or a poly(cycloalkylene
naphthalate). Further preferred polyesters also include copolymers
and block-copolymers, wherein one component in the copolymer or
block-copolymer is preferably PET or PEN, and wherein the other
component comprises a glycol, a lactone, or other component.
[0024] Consequently, melting point, intrinsic viscosity, and
diethylene glycol of suitable polymers may vary substantially, and
it should be recognized that the particular melting point, IV, and
DEG will at least in part depend on the particular polymer employed
and manner in which the polymer has been produced/treated. However,
it is generally preferred that where the polymer is or comprises a
polyester, the melting point will be in the range of about 100
degrees centigrade to about 500 degrees centigrade, more preferably
in the range of about 200 degrees centigrade to about 400 degrees
centigrade, and most preferably in the range of about 230 degrees
centigrade to about 300 degrees centigrade. Similarly, the IV will
typically be in the range of about 0.5 to 2, and more typically in
the range of between about 0.6 to 1.5, and most typically in the
range of between about 0.8 to 1.2. (As measured according to U.S.
Pat. No. 5,630,976).
[0025] With respect to the melting of the polymer, the extruder
type, and the spinneret, it should be appreciated that the
particular configuration will depend at least in part on the
selected polymer, the desired number, shape, and physical
properties of the filaments, and the desired linear density of the
undrawn yarn. Therefore, the inventors contemplate that most if not
all of the known spinning equipment may be employed that can be
used for production of a dimensionally stable undrawn (or drawn)
yarn. However, configurations and equipment as described above is
generally preferred.
[0026] In further alternative aspects of the inventive subject
matter, it is contemplated that the increased quench delay may not
only be effected by increasing the length of the heated sleeve, but
also additionally (or alternatively) by increasing the temperature
within the heated sleeve and/or by modification of the quench rate.
For example, where the length of the heated sleeve should be
limited to a particular length, further increase of the quench
delay may be achieved by increasing the temperature within the
heated sleeve. In another less preferred example, quench delay may
be modified by reducing the quench rate and extending the length of
the heated sleeve, while in a still further example the quench
delay may be increased by increasing the temperature (and
optionally decreasing the quench rate).
[0027] Of course, it should be appreciated that with increasing
quench delay, the take-up speed of the plurality of filaments will
need to be increased to maintain a particularly desirable degree in
crystallinity. Viewed from another perspective, it should be
recognized that at a given take-up speed crystallinity decreases
when quench delay increases. FIG. 2 will provide a person of
ordinary skill in the art with exemplary guidance to prepare
undrawn yarns according to the inventive subject matter. Thus, and
based on the data from table 1 above, the inventors discovered that
contemplated yarns can be prepared at a take-up speed TU and quench
delay such that the crystallinity of the undrawn yarn is less than
0.017.times.TU-39, wherein the quench delay is preferably
controlled by increasing the length of the heated sleeve.
[0028] Consequently, preferred take-up speeds will generally be in
the range of between about 3000 m/min and 5000 m/min where the
quench delay is provided in a heated sleeve having a length of
about 200 mm to about 400 mm. However, where appropriate, lower
take-up speeds (e.g., between about 2000 m/min and about 3000
m/min) are also considered suitable for use herein. Similarly, and
especially where relatively high crystallinity is desired, take-up
speeds of more than 5000 m/min (e.g., between about 5000 m/min and
about 7000 m/min, or even higher) are contemplated.
[0029] Thus, it should be recognized that the ultimate elongation
of an undrawn yarn can be increased by selecting a proper quench
delay in combination with a particular take-up speed. Based on the
data presented herein (and other data not shown), the inventors
discovered that an undrawn delayed-quenched dimensionally stable
polyester yarn with a crystallinity C and an ultimate elongation UE
can be produced in which UE.gtoreq.-1.6*C+121. As used herein, the
term "delayed quenched" undrawn yarn refers to an undrawn yarn that
has a greater UE as compared to a reference yarn, wherein the
reference yarn is prepared using the same conditions as employed
for the delayed quenched yarn with the exception that (a) the
take-up speed for the reference yarn is lower than the take-up
speed for the delayed quenched yarn, and (b) the reference yarn is
quenched at a faster rate than the delayed quenched yarn.
[0030] As further used herein, the term "dimensionally stable"
drawn yarn refers to yarns having a dimensional stability defined
by E.sub.x+TS of no more than 12, and more typically of no more
than 11. Typically, first generation yarns have E.sub.x+TS in the
range of 11-12, and later improved versions are lower. Ex is the
elongation at x stress for the yarn, where x is 41 cN/tex or, for
example, 45 N for an 1100 decitex yarn, 58 N for a 1440 decitex
yarn, 67 N for a 1650 decitex yarn, and 89 N for a 2200 dtex yarn.
TS is thermal shrinkage, which can be determined using a Testrite
(Model NK5) instrument with the following procedure: To one end of
the sample, a weight equal to ((decitex).times.0.05 g) is attached,
and the sample is transferred into the instrument at the desired
temperature for 120 sec. Dimensional stability is expressed as the
sum of the elongation at .times.N and thermal shrinkage at
177.degree. C. for the tested yarn.
[0031] It is generally preferred that contemplated undrawn yarns
will have a linear density of at least 300 dtex, more preferably of
at least 500 dtex, and most preferably of at least 700 dtex. In
further preferred aspects of the inventive subject matter, it is
contemplated that the undrawn yarns may be drawn to form a drawn
dimensionally stable yarn. Drawing/stretching may be performed
on-line with the spinning process, or in a separate
drawing/stretching step. Suitable apparatus for drawing
contemplated yarn is well known in the art, and it is generally
contemplated that all of the known drawing methods are suitable for
use herein. Contemplated draw ratios will at least in part depend
on the particular use for the drawn yarn, and it should therefore
be recognized that numerous draw ratios are contemplated. However,
suitable draw ratios will generally be in the range of between
about 1.01/1.0 to about 3.5/1.0. As also used herein, the term
"about" in conjunction with a numeric value is employed to broaden
the numeric value to a range that spans 10% absolute and inclusive
around that numeric value. For example, the term "about 10%" refers
to a range of 9% (inclusive) to 11% (inclusive).
[0032] Furthermore, drawn and undrawn yarns according to the
inventive subject matter may further be processed (e.g., an
overfinish may be added), and the optionally processed yarn may
then be formed or incorporated into a product. For example, the
yarn may be twisted, corded, or woven, which may then be used
following conventional processes in the manufacture of various
products (e.g., safety belts, parachute harnesses, parachute lines,
cargo handling nets, or safety nets). Further particularly
preferred products include rubber-containing products into which
the yarn or yarn product is at least partially embedded. Therefore,
such products include power transmission belts, conveyor belts, and
automobile tires.
[0033] Consequently, the inventors contemplate a method in which an
undrawn yarn having a predetermined crystallinity is produced. In
one step of such a method, a molten polymer is extruded through a
spinneret plate to form a plurality of filaments. In another step,
the plurality of filaments is passed through a heated sleeve to
thereby provide a quench delay, and the plurality of filaments are
then taken up at a take-up speed, wherein the quench delay the
take-up speed are selected such that an ultimate elongation of the
undrawn yarn increases at the predetermined crystallinity when the
quench delay increases.
[0034] While not limiting to the inventive subject matter, it is
generally preferred that the predetermined crystallinity will be in
the range of between about 10% and about 40%. Such undrawn yarns
will preferably have a linear density of at least 300 dtex, and
more preferably at least 500 dtex. However, where desired, lower
crystallinity (e.g., between about 2% and 10%) is also deemed
suitable. Similarly, and especially where relatively high
dimensional stability is desired crystallinity of more than 40%
(typically between about 40% and about 55%, and even higher) is
also contemplated.
[0035] Therefore, it should be recognized that a method of
producing an undrawn yarn, may have one step in which a molten
polymer is extruded through a spinneret plate to form a plurality
of filaments. In another step, quenching of the plurality of
filaments is delayed in a heated sleeve, and the plurality of
filaments are taken up at a take-up speed TU (m/min) using a quench
delay such that the crystallinity of the undrawn yarn is less than
0.017.times.TU-39.
[0036] As already addressed above, it is generally preferred in
such methods to increase the quench delay by increasing the length
of the heated sleeve (e.g., from 100 mm or 200 mm to at least about
300 mm, and more preferably at least about 400 mm) and to employ
take-up speed of at least about 3000 m/min to about 5000 m/min.
Most preferably, the polymer comprises a polyester (e.g., PET, or
PET copolymer), and the temperature in the heated sleeve is at
least 250.degree. C. or higher.
[0037] Thus, it should be recognized that undrawn delayed-quenched
dimensionally stable polyester yarns (most preferably comprising
PET) may be produced having a crystallinity C, and an ultimate
elongation UE, wherein UE.gtoreq.-1.6*C+121. Especially preferred
delayed-quenched dimensionally stable polyester yarns will exhibit
crystallinity between about 10% and about 40%, and may have a
linear density of between about 700 and about 6000 dtex. As already
discussed above, such yarns may further be drawn/stretched to form
a drawn dimensionally stable yarn, which may then be incorporated
or formed into a product.
[0038] Moreover, the inventors contemplate that the yarns according
to the inventive subject matter may be prepared using an apparatus
that includes a spinneret plate that is operationally coupled to an
extruder and metering pump that provides a molten polymer to the
spinneret plate, wherein the spinneret plate (e.g., with at least
50 orifices) produces a plurality of filaments from the molten
polymer. A heated sleeve is coupled to the apparatus and receives
the plurality of filaments, thereby delaying quenching at a
predetermined quench delay, and a take-up roll takes up the
plurality of filaments at a take-up speed, wherein the take-up
speed and the heated sleeve are configured to operate at a
condition in which ultimate elongation of a yarn having a
predetermined crystallinity increases when the predetermined quench
delay increases.
EXPERIMENTS
[0039] Ultimate elongation was determined with a Statimat M Tester
with 500 mm length, 500 mm/min test speed, and 0.50 cN/tex
pre-tension.
[0040] Percent crystallinity was determined from density data using
the equation: percent
crystallinity=[(density-1.335)/0.12](1.455/density)(100- ).
[0041] Density was determined at 23.degree. C. using a carbon
tetrachloride/n-heptane density gradient column according to ASTM
D1505 by comparing the position of the sample with glass bead
standards of known density. Five specimens (.about.1 cm in length)
were prepared for each sample tested using a single filament from
the sample to tie and hold the filaments together. The specimens
were wetted by placing in a mixture of carbon
tetrachloride/n-heptane in a flask and degassed by applying a
vacuum for 10 seconds. The specimens were immediately placed in the
density gradient column using long-handled tongs and the positions
of specimens and glass bead standards recorded after 2.0 hours.
[0042] Linear density was determined by reeling 100 meters of yarn
on a 1 meter reel. Yarn weight was then determined by an analytical
balance, and dtex was calculated as:
dtex=weight(g).times.100
[0043] Thus, specific embodiments and applications of improved
dimensionally stable yarns have been disclosed. It should be
apparent, however, to those skilled in the art that many more
modifications besides those already described are possible without
departing from the inventive concepts herein. The inventive subject
matter, therefore, is not to be restricted except in the spirit of
the appended claims. Moreover, in interpreting both the
specification and the claims, all terms should be interpreted in
the broadest possible manner consistent with the context. In
particular, the terms "comprises" and "comprising" should be
interpreted as referring to elements, components, or steps in a
non-exclusive manner, indicating that the referenced elements,
components, or steps may be present, or utilized, or combined with
other elements, components, or steps that are not expressly
referenced.
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