Note: Descriptions are shown in the official language in which they were submitted.
C- 54-0288 ~ Zl~
SELF CRIMPING YARN AND PROCESS
SPECIFICATION
The invention relates to novel processes for making
polyester self-texturing yarns, and to the resulting yarns. ~--
~Iore particularly, the process invention relates to such a ~ ;
spinning process wherein two molten streams of the same~
polyester polymer are combined and spun to give novel and
useful yarns.
It is known to make~self-crimp~ing yarns by combining
converging streams~ of dlfferent~jet stretch and cooling the
combined streams into a filament, followed by a drawing
~ operatlon. Such prlor art proc~esses are di~scl~osed in U.S.
;~ patents 3,387,327;to Privott et al and 3,4g7,585 to Chapman
et al.
It has~been dlscovered that,~by operating at speeds
far in excess of those dis~closed in t~e Privott et al and
Chapman et al patents, an~improved process and uniquely
useful products are~provLded.
Accordlng~to a~flrst ma~or aspect of the mventlon, ~ ;;
there is provided a;~process~for~producing~a seIf-crlmp~ing~
filament, comprising generating two individual streams of~
molten polyester of flber-formlng~molecular weight,~the
individual streams travelling at dlfferent velocities, con-
verging the individual streams side-by-side to form a combined
stream, quenching the comblned str;eam to form a combined
filament, and withdrawlng the comblned filament from the
combined stream at~a rate of speed ln excess of 2500 meters per
,,
minute and selected such that an individual filament quenched
from one of the individual streams would have a shrinkage at
least ten percentage points hi:gher than that of an lnd~ividual
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C~ 54-0288
filament quenched from the other of the individual streams.
According to another aspect of the invention, one of the
individual streams has a velocity between 2.0 and 7 times as
high as the velocity of the other of the streams. According
to another aspect of the invention, one of the individual
streams has a velocity between 3.5 and 5.5 times as high as
the velocity of the other of the streams. According to another
aspect of the invention, one of the individual streams has a
smaller cross-sectional area than the other of the streams.
According to another aspect of the invention, the rate of s~eed
is selected such that the combined filament has a shrinkage less
than 30%. According to another aspect of the invention, the
rate of speed is selected such that the combined filamerlt has
a shrinkage less than 10%.
According to another major aspect of the invention,
the invention comprises extruding molten polyester polymer
through two spinneret passageways converging to merge substan-
tially coincident with the face of the spinneret to define a
combined orifice, the passageways being of different cross-
sectional areas at least in the vicinity of the face, q~enchingthe resulting merged stream to form a filament, and withdrawing
the filament from the merged stream at a rate of speed in
excess of 3000 meters per minute and selected such that a
filament spun solely from the larger of the passageways at the
same jet stretch for the larger of the passageways would have a
shrinkage at least ten percentage points lower tha~ that of a
filament spun solely from the smaller o~ the passageways at the
same jet stretch for the smaller of the passageways.
According to another major aspect of the invention,
there is provided a process comprising generating a pair of
streams of molten polymer of fiber-forming molecular weight
travelling at different speeds to converge at a point below a
C-14-54-0288 l~S~5
spinneret face, the speeds and momenta of the streams and the
angle at which the streams converge being selected such that the
first of the streams is slower and travels in substantially a
straight line after the point at which the streams first
touch and the second of the streams is fas~er and forms sinuous
loops back and forth between successive points of attachment
with the first of the streams.
According to another major aspect of the invention,
there is provided a process for producing a variable denier
filament, comprising generating a pair of streams of molten
polymer of fiber-for~Ling molecular weight travelling at differ-
ent speeds to converge at a point below a spinneret face, the
speeds of the streams and the angle at which the streams
converge being selected such that the first of the streams is
slower and travels in substantially a straight line àfter the
point at which the streams firs~ touch and attach and the
second of the streams is faster and orms sinuous loops back
and forth between successive points of attachment with the first
of the streams; attenuating the first of the streams whereby
the sinuous ~loops become straightened and the second of the
streams is brought into continuous contact with the first of
the streams; and quenching the resulting combined stream into
a filament. According to a further aspect of the invention,
the first of the streams is larger in cross section than the
second of the streams. According to a further a.spect of the
invention, there is provided a process for prod~Lcing a multi-
filament variable denier yarn comprising simultaneously
performing the process referred to above using a plurality of
combined orifices in a common spinneret and supp~lied by a
common poly~Ler source, the geometries of the combined orifices
and the spinning conditions being selected such that the
C-14-54-0288
resulting ~ilaments have successive thick and thin regions
which are out of phase from filament to filament.
According to another major aspect of the invention
there is provided a yarn having a plurality of filaments
comprising non-round cross-sections which repe~itively vary
in area by more than ~ L0% along the lengths of the filaments,
and alternating S-twisted and Z-twisted helically crimped
sections, the variations in cross-sectional area being out of
phase from filament to filament and the helically crimped
sections being out of phase from filament to filament. Accord-
ing to another aspect of the invention, the cross-sec~ions
repetitively vary in area by more than ~ 25% (preferably more
than ~ 30%) along the length of the filaments. According to
another aspect of the invention, the yarn has a Uster une~en-
ness of at least 2~5~/o U.
According to another major aspect of the invention
there is provided a multifilament yarn comprising a plurality
of continuous filaments comprising non round cross-sectional
areas which vary repetitively along the lengths thereof, and
variable pitch S-twisted and Z-twisted helically cailed
sections, the sections being less tightly coiled in regions of
large cross-sectional areas than in regions of small cross-
sectional areas. According to another aspect of the
invention, each of the filaments is formed ~rom a single
molten polymer.
According to another aspect of the invention there is
provided a spi~neret plate comprising a combined orifice, the
combined orifice co~lprising a capillary having a large cross-
sectional area and a capillary having a small cross-sectional
area, the capillaries providing communication between the
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C-14-54-0288
face of the plate and the opposite side of the plate and
converging toward one another as the capillaries approach the
face, the lengths of the capillaries being selected such that
the capillary having a small cross-sectional area has less
resistance to polymer flow than the capillary having a large
cross-sectional area.
Other aspects of the invention will in part be
obvious and will in part be disclosed in the following
description taken in connection with the accompanying
drawings, wherein:
FIGURE 1 is a vertical sectional view of the
preferred embodiment of a spinneret usable according to the
invention;
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C-14-54-0~88 ~S~
FIGURE 2 is a bottom plan view of the FIGURE 1
spinneret, looking up;
FIGURE 3 is a graph of shrinkage versus spinning
speed used in explaining the principles upon which certain
aspects of the invention are based;
FIGURE 4 is a cross-sectional view of a filament
according to certain aspects of the invention;
FIGURE 5 is a side elevation view of ~he molten
streams issuing from the FIGURE 1 spinneret according to
certain aspec~s of the invention;
FIGURE 6 is a graph illustrating the variation in
denier along a representative filament according to certain
aspects of the invention; and
FIGURE 7 is a graph illustrating the distribution of
the fluctuations illustrated in FIGURE 5 for a representative
multiple oriice spinnere~ according to certain aspects of the
invention.
The invention will be specifically exemplified using
polyester polymer, it being understood that certain aspects of
the invention are applicable to the class of melt-spinnable
polymers generally. "Polyester;' as used herein means fiber-
forming polymers at least 85% by weight of which is formable
by reacting a dihydric alcohol with terephthalic acid.
Polyester typically is formed either by direct esterification
of ethylene glycol with terephthalic acid, or by ester inter-
change between ethylene glycol and dimethylterephthalate.
FIGURES 1 and 2 illustrate the preferred embodiment
of a spinneret design which can be employed for obtaining all
aspects of the invention. The spinneret includes a large
counterbore 20 formed in the upper surface 21 of spinneret
plate 22. Small counterbore 24 is formed in the bottom of and
at one side of large cou~terbore 20. A large capillary 26
C-14-54-02~8 ~ i S
extends from the bottom of large counterbore 20 at the side
opposite small counterbore 24, and connects the bottom of
large counterbore 20 with the lower surface 28 of plate 22.
Small capillary 30 connects the bottom of counterbore 24 with
surface 28. Capillaries 26 and 30 are each inclined four
degrees from the vertical, and thus have an included angle
of eight degrees. Counterbore 20 has a diameter of 0.0625
inch (1.588 mm.), while counterbore 24 has a diameter of
0.031 inch (0.787 mm.). Capillary 26 has a diameter of
0.0165 inch (0.419 mm.) and a length of 0.150 inch (3.81 mm.),
while capillary 30 has a diamete-r of 0.0102 inch (0.259 mm.)
and a length of 0.0286 inch (0.726 mm.). Land 32 separates
capillaries 26 and 30 as they emerge at surface 28, and has a
wldth of 0.0056 inch (0.142 mm.). Plate 22 has a thickness of
0.554 inch (14.07 mm.). Capillaries 26 and 30 together with
counterbores 20 and 24 constitute a combined orifice for
spinning various novel and useful filaments according to the
invention, as will be more particularly described hereinafter.
FIGURE 3 is a graph showing how polyester filament
shrinkage varies with spinning speed for two illustrative cases
of jet stretch. The curve in dotted lines shows tha~ the
shrinkage falls from about 65~/o at 3400 ypm (about 3100 mpm)
to about 5% at 5000 ypm (about 4500 mpm) when using spinneret
capillaries having diameters of 0.063 inch (1.6 mm.) and when
sirnultaneously spinning 34 such filaments to be false-twist
draw-textured to yield a textured yarn having 150 denier. The
solid curve shows that the shrinkage drops off at higher speeds
when using spinneret capillaries having diameters of 0.015 inch
(0.38 mm.) when similarly simultaneously spinning 34 such
filaments to be false-twist draw-textured to yield a textured
yarn having 150 denier. Using different capillary diameters
produces a family of curves between, to the left, and to the
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C-14-54-0288 ~5~ LS
right of those illustrated. The curves also can be shifted
(for a given capillary diameter) by varying the polymer through-
put. In other words, the curves can be shifted by varying the
jet stretch, which is the ratio of yarn speed just after
solidification to average speed of molten polymer in the
capillary. It is thus possible to provide a combined orifice
for spinning a composite filament of a single polymer wherein
one side of the filament has a much higher shrinkage than the
other side. This is done by selecting the individual
capillaries to give different jet stretches, and also selecting
the spinning speed within the range whereln an individual
filament quenched from one of the individual streams would have
a shrinkage at least ten percentage points higher than that of
an individual filament ~uenched from the other o the individual
streams. Under the spinning conditions illustrated in E'IGURE
3, at a spinning speed of 5000 yards per minute the individual
streams would have shrinkages differing by about 25 percentage
points. Combining these molten streams into a side-by-side
configuration results in a highly crimped filament in its as-
spun form, without the necessity of drawing the yarn to develop
the crimp as in the Privott and Chapman patents noted above.
Such combining may be done uslng a spinneret design similar to
that disclosed in FIGUR~ 1, or the spinneret may merge the two
streams at or just prior to emergence of the streams from
surface 28, In any event, the two streams merge substantially
coincident with the face of the spinneret according to this
aspect of the invention.
Advantageously, the spinneret is so designed that one
of the individual streams has a velocity in its capillary
between 2.0 and 7 times (preferably between 3.5 and 5.5 times)
the velocity of the other of the streams in its capillary.
Further advantages are obtained when the fas~er of the two
C-14-54-0288 1 ~ 54 ~ 1~
streams has a smaller cross-sectional area than the slower of
the streams, particularly in degree of crimp and spinning
stability. Productivity is increased when the spinning speed
is selected such that the combined filament has a shrinkage
less than 30%, and is maximized when the shrinkage is less than
10/~, .
Further aspects of the inventionJ applicable to
melt-spinnable polymers as a class, are achievable by use of
spinnerets wherein the streams intersect outside the spinneret.
As a specific example, molten polyester polymer of norm~l
textile molecular weight is metered at a temperature of 290C.
through a spinneret having 34 combined orifices as above
specifically disclosed. The polymer ~hroughpu~ is adjusted to
produce filaments of 4 average denier per filament at a
spinning speed of 52~0 yards per minute, the molten streams
being conventionally quenched into filaments by transversely
directed quenching air.
Under these spinning conditions a remarkable
phenomenon occurs, as illustrated in FIGURE ~. Due to the
geometry of the spinneret construction, the polymer flowing
through the smaller capillaries 30 has a higher velocity than
that flowing through the larger capillaries. The speeds and
momenta of the paired streams iSSUillg from each combined
ori~ice and the angle at which the streams converge outside the
spinneret are such that the slower streams 34 travel in substan-
tiallv strai~ht lines a~ter the Doints at which the paired
streams first touch and attach, while each of the smaller and
faster of the streams 36 forms sinuous loops back and forth
between successive points of attachment 38 with its associated
larger streams. This action can be readily observed using a
stroboscopic light directed onto`the streams immediately below
the spinneret face 28. As the molten streams accelerate away
_ 9 _
l:~S~ S
C~ 54-0288
rom the spinneret, the slower stream attenuates between the
points of attachment 38 and the loops of the faster stream
become straightened until the faster stream is brought into
continuous contact with the slower stream. The slower stream
attenuates more between than at the points of first attachment,
so that the resulting combined stream has a cross-section
which is larger at the points of first attachment than in the
regions between these points. The resulting combined stream
is then further attenuated somewhat until it is solidified
into a filament 40 by the transverse quench air.
Each solidified filament 40 has non-round cross-
sectional areas which vary repetitively along its length, and,
a~ter being heated while under low tension, has variable pitch
S-twisted and Z~twisted helically coiled sections, the sections
being less tigh~ly coiled in regions of large cross-sectional
area than in regions of small cross-sectional area. As
illustrated qualitatively in FIGURE 6, when using the above
spinning conditions, the filament cross-sectional area
repetitively varies at a repetition rate of about one per
meter, although this can be varied by modifying the spinning
conditions and the geometry of the spinnere~ passages.
Due to minor differences between combined orifices,
temperature gradations across the spinneret, and other like
deviations from exactly the same treatment for each pair of
streams, a multiple orifice spinneret will typically provide
somewhat different repetition rates among the several resulting
streams and ~ilaments. An example of this is qualitatively
shown in FIGURE 7, wherein is shown that various orifices
produce somewhat different repetition rates as determined by
stroboscopic examination of the comhined streams just below
the spinneret face. In the resulting multifilament yarn,
the filaments have non-round cross-sections which vary by more
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C `4~54-0288
:~S~Z~
than + lO~o along the length of the filaments, and alternating
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S-twisted and Z-twisted helically crimped sections, the
variations in cross-sectional areas being out of phase from
filament to filament and the helically crimped sections being
out of phase from filament to filament.
The multifilament yarn has various applications and
end uses. When woven into a fabric, the fabric has a pleasing
novelty effect, resembling in some respects a fabric containing
yarns spun from staple fibers. Other novelty effects can
readily be obtained by minor variations of the spinneret and
spinning conditions.
For certain of these effects, it is advantageous
that the filaments vary repetitively along their lengths by
more than + 25% (preferably more than ~ 30%~ in cross-sectional
area. The effects are particularly pronounced when the yarn
has a Uster unevenness of at least 2.5% U. The Uster measure-
ment is made using the Uster*Evenness Tester, Model C, together
with integrator ITG-101 for this instrument. The yarn speed
is 182.8 meters per minute (200 ypm), the service selector is
set on normal, and the sensitivity selector is set to 12.5%.
The /0 U is read from the integrator after a sample run time
of 5 minutes.
Shrinkage is determined by the method disclosed in
this paragraph. Generally speaking, a sample yarn's initial
length Lo is determined while the yarn is under a tension of
0.1 grams per denier. The yarn is then subjected to a tension
of 0.0025 grams per denier and placed in an oven at 120C. for
five minutes. The yarn is then removed from the oven, again
subjected to a tension of 0.1 grams per denier and its length
L2 determined. Shrinkage percentage equals
Lo~L2 X 100
Lo
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* Trademark
