Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
69L~
LO~-TORQUE TE~TU~ED YARN AND PROCESS
SPE CI FI CATI ON
The invention relates to a process for producing a
reduced-torque textured polyester yarn. More particularly, it
relates to such a process wherein the spun feed yarn is chosen
to have certain properties selected such that the drawn yarn
will have substantia~ texture and yet be substantially torque-
free.
False-twist ~exturing of polyester yarns is well
known in the art, and customarily includes a second heating
step (after the yarn has passed through the false-twister) under
controlled tension in order to reduce the torque in the yarn.
Such known processes use conventional POY (partially oriented
yarn) as the feed yarn, and are quite successful so long as the
drawn yarn denier is lower than about 200. At a drawn denier
of 250 or above, and part,cularly when the drawn yarn has a
denier of at least 350, the second heating step temperature
cannot be sufficiently high as to substantially eliminate torque
in the yarn, else the yarn bulk would be unduly reduced. When
~0 such heavy deniers are desired, it is therefore customary to
separately spin and draw-texture two smaller yarns of opposite
torque directions, then ply the two smaller yarns to provide a
balanced-torque final yarn of the desired denier This
customary procedure is thus cumbersome and expensive as
compared to producing a singles yarn.
These and other difficulties with prior art practices
are avoided by the present invention, which provides a
particular feed yarn which during drawtexturing surprisingly
does not develop objectionable torque.
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6~8
According to a primary aspect of the invention, there
is provided a process for producin~ a reduced-torque textured
polyester yarn, comprising, producing a spun polyester ~Jarn
having an elongation of 5S-195% and having sufficient torque-
less latent crimp to provide when hot-dra~n to an elongation
of 30% a bulk of at least 8%, and draw-texturing the spun yarn
at a temperature above the second order transition temperature
to a drawn yarn having a denier of at least 250 and an
elongation between 10 and 45%.
According to another aspect of the invention, the
spun yarn is draw-textured to an elongation between 20 and
35,'.
According to another aspect of the invention, the
drawn yarn has a denier of at least 350.
Other aspects will in part be obvious and will in
part be set orth in the following detailed description of the
invention.
It has been discovered that heavy denier low-or-zero-
torque yarns can be produced eficiently by using as feed ~arns
therefor in a draw-texturing process a spun polyester yarn
having an elongation of 55-195% and having sufficient latent
crimp to provide when hot-drawn to an elongation of 30% a
bulk of at least 8%, and draw-texturing the spun yarn at a
temperature above the second order transition temperature to
a drawn yarn having a denier of at least 250 and an elongation
between 10 and 45~/O. Such spun yarns can be produced by
combining two different molten streams with different
rheological properties, as in Privott U.S. 3,387,327, or by
spinning a molten non-round cross-sectional stream and
preferentially quenching one portion of the cross-section, as
in Ono U.S. 3,623,939 and Na~agawa U.S. 3,920,784. These
three patents are incorporated herein by reference. With
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these spinning systems, a spinning speed of about 3000 meters
per minute will provide an elongation within the range of
55-l957 for normal deniers per filament of about 4-8. For
other deniers per filament, the desired elongation range may
be obtained by selection of spinning speed. As is known,
hi~her spinning speeds give lower elongations and vice versa.
Example I
This is illustrative of the problem. Polyethyiene
terephthalate poly~er of normal molecular weignt for apparel
yarns is conventionally melt spun at a melt temperature of
290C. into a quench zone supplied with transverse quenching
air a. a temperature of 20C. The quenching air has an
average speed of 15 meters per minute, 68 round spinneret
orifices are employed having diameters of 0.38 mm, and the
yarn is wound at 3000 meters per minute to give a spun yarn
with 2 denier of 550 and an elongation of 130%.
The spun yarn is simultaneously drawn and textured
(draw-textured) on a Barmag FK-6 machine equipped with
friction-twist aggregates of the type disclosed in Yn U.S.
~0 3,g73,383. The primary heater temperature is 200C., the
draw ratio is l.70, and the texturing windup speed is 300
meters per minute.
A Lawson tube knitted from this yarn exhibits
severe torque unless the secondary heater (after the false-
twist aggregate and prior to texturing windup) has a
temperature so high as to substantially reduce the yarn bulk.
~xam~le II
This is an example according to the invention,spun
the same as in ~xample I above,except that each filament of
the feed yarn is spun from a spinneret orifice having three
slo~s r2diating from a common center and spaced 120 apart
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to give a tri-lobal filament cross-section of the general type
indicated in Figure lB of U.S 3,623,93g. The 68-filament
spun yarn has a denier of j50.
The spun yarn is draw-textured as in Example I
above.
A Lawson tube knitted from this yarn exhibits
virtually no torq-ue when the secondary heater has a temperature
of 190C.
Exa~ple III
This example simply characterizes the sp1ln yarns of
E~amples I and II. Each spun yarn is drawn over a hot shoe at
200~C. at a rate of 360 meters per minute and at a draw ratio
of 1.70. The drawn spun yarns then have their degree of latent
bulk determined as follows.
The drawn yarn packages are conditioned at 20C.
and 72,to relative humidity for 24 hours, after which 25 meters
of yarn are stripped from each bobbin and discarded. A skein
having a skein denier of 6250 and a skein circumference of
1.125 meters (that is, yarn25denier = revolutions of 1.125 meter
skein reel) is formed under a yarn tension of 0.035 grams per
denier while skeining. A 1000 gram weight is hung from the
bottom of the skein while the top of the skein is suspended
from a small hook, and, after 30 seconds, the skein length Li
is determined. The 1000 gram weight is then replaced by a
weight of 0.6 grams and the skein is then placed in a 1.20C.
oven for 5 minutes. The skein is then removed, conditioned
for 1 minute at room temperature, and a 20 gram weight is
added to the 0.6 gram weight. After 30 seconds, the skein
length is measured to determine Lf. The yarn bulk in percent
is then -~-- X 100.
.
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The spun yarn in Example I has a bulk of 4.7%,
while the spun yarn in Example II has a bulk of 11.3. The
textured yarns (run without energizing the second heater)
have respective bulks of 61.5 and 77.7% when measured by the
above bulk test. However, the Example II yarn surprisingly
can be directly used as a high-bulk, substantially-zero-
torque yarn, while the Example I yarn cannot be so used. If
the second heater is used and set at a sufficiently high
temperature to substantially eliminate torque from the Example
I yarn, the desirable bulk level is drastically reduced.
The term "polyester" as used herein means those
polymers of fiber-forming molecular weight composed of at
least 85% by weight of an ester of a dihydric alcohol and
terephthalic acid. As is known, such polymers are made
commercially by direct esterification of the alcohol with the
acid, or by an ester interchange reaction.
