Note: Descriptions are shown in the official language in which they were submitted.
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CONTINUOUS FIL~ENT YARN WITH WOOL-LIKE H~ND
SPECIFICATION
The invention relates to the art of melt-spun
synthetic yarns and processes for their production, and more
particularly to such yarns which combine high bulk with a
wool-like hand.
It is known to produce somewhat bulky yarns by
combining filaments with different shrinkages into a yarn,
then shrinking so that the resulting longer filaments protrude
in loops from the yarn. This may be done by spinning the
filaments from different polymers, as in Reese U.S. patent
3,444,681, or by spinning from different filament cross-
sections from a common polymer, as typified by several
patents. Such known yarns ordinarily do not have hi~h bulk,
nor do fabrics made therefrom ordinarily provide a hand
similar to that of wool, combining an initial crispness on
light touch with softness on more firm compression.
These and other difficulties of the prior art are
avoided by the present invention~ whichprovides novel and
~seful processes and improved yarn products.
According to a first major aspect of the invention,
there is provided a process for producing a self-crimping
yarn comprising irst and second types of filaments, the
process comprising spinning the first type of filaments by
generating first and second individual streams of molten
polymer of fiber-forming molecular weight, the individual
streams travelling at diff~rent velocities; converging the
individual streams side-by-side to form a combined stream;
and quenchlng the combined stream to form a combined filament;
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spinning the second type of filaments by e~trudîng a third
stream of molten polym~r of fi~er-forming molecular weight
from an or;fice selected to give a filament with lower
shrinkage than said com~ined filament~ at a given common
spinning speed; and quenching the third stream into a fila-
ment; withdrawing the filaments from the streams at the
given common spinning speed in excess of 2200 meters per
minute; and combining the filaments into a yarn.
According to another aspect, each of the streams is
10 of polyester polymer.
According to another aspect, the spinning speed is
selected such that the yarn has a shrinkage below 20%.
According to another aspect, the spinning speed is
selected such that the yarn has a shrinka~e below 8%.
According to another major aspect of the invention,
there is provided a multifilament yarn comprising first and
second classes of filaments, each of the first class of
filaments having a periodic variation in denier of greater
than + 15% about a mean value and possessing latent crimp;
each of the second class of filaments having lower shrinkage
than the shrinkage of the filaments of the first class.
According to another aspect, each of the second
class of filaments has a denier larger than the average
denier of the first class of filaments.
According to another major aspect of the invention,
there is provided a mult.ifilamen~ yarn comprising first and
second classes of filaments; each of the filaments of the
first class having a periodic variation in denier of greater
than ~ 15% about a mean value and possessing developed crimp;
3Q each of the filaments of the second class being longer than
the filaments of the first class whereby the filaments of the
second class protrude from the yarn in loops.
According to another aspect, each of the second
class of filaments has a denier larger than the average denier
of the first class of filaments.
These and other aspects of the invention will in
part appear hereinafter and will in part appear hereinafter
in the following detailed description taken in connection
with the accompanying drawings wherein:
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FIGU~E 1 is a vertical sectional view of a spinneret
orlfice;
FIGURE 2 is a bottom plan view of the FIGUR~ 1
orifice looking up;
FIGURE 3 is a graph of s~rlnkage versus spinning
speed used in explaining the principles upon which certain
aspects of the ~nvent;on are based;
FIGURE 4 is a cross-sectional view of a filament
according to certain aspects of the invention;
ln FIGURE 5 is a side elevation view of the molten
streams issuing from the FIGUP~ 1 s~inneret according to
certain aspects of the invention;
FIGURE 6 is a graph illustrating the variation in
denier along a representative filament according to certain
aspects of the învention; and
FIGURE 7 is a graph illustrating the distribution
of the fluctuations illustrated in FIGURE 5 for a representa-
tive multiple oriice spinneret 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 generall~. "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 far obtaining the
first type of filaments accordinc to the invention. The
spinneret includes a large counterbore 20 for~ed in the upper
surface 21 of spinneret plate 22. Small counterbore 24 is
formed in the bottom of and at one side of large counterbore
20. A large capillary 25 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
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30 are each inclined four degre~s from the vertical, and thus
have an included angle of eight degrees Counterbore 20 has
a diameter of 0.113 inch (2.87 mm.), while counterbore 24 has
a diameter of 0.~52 lnch (1.32 mm.). Capillary 26 has a
dlameter of 0.016 inch (0.406 mm.) and a length of 0.146 inch
(3.71 mm.), while capillary 30 haa a diameter of 0.009 inch
(O.229 mm.) and a length of 0.032 inch (0.813 mm.). Land 32
separates capillaries 26 and 30 as they emerge at surface 28,
and ~as a width of 0.0043 inch (0.109 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 noveI 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 that
the shrinkage falls from about 65% at 3400 ypm (about 3100
mpm) to about 5% at 5000 ypm (about 4500 mpm) when using
s~inneret capillaries having diameters of 0.063 inch (1.6 mm.)
and when simultaneously 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 simul-
taneously spinning 34 such filaments to be false-twist draw-
textured to yield a textured yarn having lS0 denier. Using
different capillary diameters produces a family of curves
between, to the left, and to the right o those illustrated.
The curves also can be shifted ~for a given capillary
diameter) by varying the polymer throughput. 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
35 possible to provide a combined orifice for spinning a com- -
posite filament of a single polymer wherein one side of the
filament has a much higher shrlnkage than the other side.
This is done by selecting the individual capillaries to give
different jet stretches, and also selecting the spinning
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speed ~ithin th~ range ~h.erein 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 quenched from the other o -the
individual streams. ~nder the spinning conditions illustra-
ted in FIGURE 3, at a spinning speed of 5000 yards per minute
the indlvidual streams would have shrinkages differing by
a~out 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 draw-
ing the yarn to deveIop the crimp. Such combining may be
done using a spinneret design similar to that disclosed in
FIGURE 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 faster of the two
streams has a smaller cross-sectional area than the slower of
the streams, particularly in degree of crimp and spinning
stability. Productlvity is increased when the spinning speed
is selected such that the combined ~ilament has a shrinkage
less than 30%, and is maximized when the shrinkage is less
than lQ%.
Further aspects of the invention, applicable to
melt-spinnable polymers as a class, are achievable by use o
spinnerets wherein the streams intersect outside the spinneret.
As a specific example, molten polyester polymer of normal
te~tile molecular weight is metered at a temperature o 29~C.
through a spinneret having 34 combined orifices as above
specifically disclosed. The polymer throughput is adjusted to
produce fllaments of 4 average denier per filament at a
spinning speed of 5200 yards per minute, the molten streams
being conventionally quenched into filaments by -transversely
directed quenching air.
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Under these spinning conditions a remarkable
phenomenon occurs, as illustrated in FIGURE 5. Due to the
geometry of the spinneret construction, the polymer flowing
through the smaller capillaries 30 has a higher veloci~y than
that flowing through the larger capillaries. The speeds and
momenta of the paired streams issuing rom each combined
orifice and the angl~ at ~ic~ the strea~s con~erge outside
the spinneret are such that the slower streams 34 travel in
substantially straight lines after the points at which the
paired streams ~irst touch and attach, while each of the
smaller and faster of the streams 36 forms sinuous loops
back and orth between successive points o attachment 38
with its associated larger streams. This action can be
readily observe.d using a stroboscopic light directed onto
the stream immediately below the spinneret face 28. As the
molten streams accelerate away from 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 urther
attenuated somewhat until it is solidified into a filament 40
by the transverse quench air.
Each solidified ilament 40 has non-round cross-
sectional areas ~hich vary repetitively along its length, and,
ater being heated while under low tension, has variable
3a pitch S-twisted and Z-twisted helically coiled sections, the
sections being less tightly coiled in regions of large cross-
sectional area than in regions o~ small cross-sectional area.
As illustrated qualitatively in FIGURE 6, when using the above
spinning conditions, the ilament cross-sectional area repeti-
tively varies at a repetition rate of about one per meter,although this can be varied by modi~ying the spinning
conditions and the geometry of the spinneret passages.
Due to minor differences ~etween combined orifices,
temperature gradations across t~e spinneret, and other like
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deviations from exactly the same treatment for each pair of
streams, a multiple orifice spinneret wLll typically provide
somewhat di~ferent repetition rates among the several result-
ing strea~s and filaments, An example of t~is is quaLi-
tativeI~ shown in FIGURE 7, wherein is shown that varlousorifices produce somewhat different repetition rates as deter-
mined ~y stroboscopic examination of the combined streams just
below the spinneret face. In the resulting multifilament
yarn, the fîlaments have non-round cross-sections which vary
by more than + 10% along the length of the filamen~s, and
al~ernating S-twisted and Z-twisted helically crimped
sections, the variations in cross-sectional areas being out
of phase from filament to ~ilament and the helically crimped
sections being out of phase from filament to filament.
For certain effects, it is advantageous that the
filaments vary repetitively along their lengths by more than
25% (preferably more than + 30V/~) in cross-sectional area.
The effects are particulariy pronounced when the yarn has a
Uster unevenness of at least 2.5% U. The Uster measurement
is made using the Uster Evenness Tester, Model C, together
~ith integrator ITG-101 for this instrument. The yarr. speed
is 182.8 meters per minute (200 ypm), the service selector is
set on normal, and the sensitivity selec~or i9 set to 12.5%.
The % 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 u~der 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 o~en,
again subjected to a tension of 0.1 grams per denier and its
length L2 determined. Shrinkage percentage equals
Lo-L2
Lo X 100.
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The second class of ~ilam~nts may be spun from
spinneret orifices selected such that, at the given common
spi-nning speed, the filaments of the. first class will have a
higher s~rinkaOe than those of the second class.
As a specific e~ample, molten polyet~ylene tereph-
thalate polymer of normal molecular weight for textile
apparel yarns is extruded sLmultaneously through two
spinnerets, one of w~ich contains 34 combined orifices as
above descrï.bed and the other of w~ich contains 34 round
orifices having diameters of 0.009 inch (0.22g mm.). The
extrusion rates are selected such that each resulting class
of 34 filaments has a denier of 77 at a winding or spinning
speed of 5600 ypm Cabout 5100 meters per minute). The
68 molten streams are quenched into filaments by transversely
directed moving air, and the 68 filaments are converged into a
common yarn bundle and wound on a bobbin at 5600 ypm as a
yarn having a denier of 154.
The yarn is heated to 150C. while under low
tension to develop the latent crimp in those filaments of the
first class and to develop the shrinkage differences between
the two classes of filaments. Those filaments of the first
class, collected separately, have a shrinkage of 10.6%, while
those of the second class, collected separately, have a
shrinkage of 4.5%. The combined yarn has a shrinkage of
6.3%. Each filament of the first class has a periodic
.variation in denier from approximately one denier to approxi~
mately four denier, while the filaments of the second class
protrude in relatively large loops from the yarn bundle.
To produce a more wool-like hand, the denier per
filament of the filaments of the second class can be
increased, the range of about 5-9 dpf being particularly
suitable.
