Note: Descriptions are shown in the official language in which they were submitted.
WOOL-LIKE ~ARN ~ITH MOISTURE TRANSPORT
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 and improved moisture transport.
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 ordinarlly do not have high 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. Nor do
such knot~ yarns provide good moisture transport.
These and other di~ficulties of the prior art are
a~oided by the present invention, which provides no~el and
useful processes and improved yarn products.
According to a first major aspect of the invention,
~here is provided a process for producing a sel-crimping yarn
comprising first and second types o 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 different velocities; converging the indi~idual
streams side-by-sidc to form a combined stream; c~nd quenching
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the combined stream to form a combined filament, spinning the
second type of filaments by extruding a third strqam of
molten polymer of fiber-forming molecular weight ~rom a
helical orifice selected to give a filamellt with a helical
cross section and lower shrinkage than the combined filament
at a given common spinning speed; and quenching the third
stream into a filament; withdrawing the filaments from the
streams at the given common spinning speed; and combining
the filaments into a yarn.
According to another aspect, each of the s~reams is
of polyester polymer.
According to another aspect, the spinning speed is
selected such that the yarn has a shrinkage below 2Q%.
According to another aspect, the spinning speed is
selected such that the yarn has a shrinkage below 8%.
According to another aspect, the spinning speed is
between 5000 and 6000 yards per minute, and each of the first
type of filaments is polyester.
According to another aspect, the helical cross-
section is open at its inner end.
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 greater ~han
+ 25% about a mean value and possessing latent crimp; each of
the second class of filaments having a helical cross-section
and having lower shrinkage than the shrinkage of the filaments
in 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 aspect, the first class of
filaments are formed from polyester.
According to another aspect, the helical cross-
section is open at its inner end.
According to another major aspect of the invention,there is provided a multifilament yarn comprising first and
second classes of filaments; each of the filaments of the
first class having a periodic variation in denier of greater
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than + 25% about a mean value and possessing a developed
crimp; each of the filaments of the second class having a
helical cross-section and ~eing longer than the filaments of
the first class whereb~ 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.
According to another aspec~, the first class of
filaments are formed from polyester.
According to another aspect, the helical cross
section is open at its inner end,
These and other aspects of the invention will in
part appear hereinafter and will in part be obvious in
the following detailed description taken in connection with
the accompanying drawings wherein:
FIGURE 1 is a vertical sectional view of a spinneret
orifice;
~ IGURE 2 is a bottom plan view of the FIGURE 1
orifice, lookIng up;
FIGURE 3 is a graph of shrinkage versus spinning
spee~ used in explaining the principles upon which cer,tain
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 the molten
streams issuing from -~he FIGURE 1 spinnexet 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 ~he invention;
FIGURE 7 is a graph illustra~ing the distribution
of the fluctuations illustrated in FIGURE 5 for a representa-
tive multiple orifice spinneret according to certain aspects
of the invention; and
FIGURE 8 is a bottom plan view of another
spinneret orifice.
The invention will be specifically exem~lified using
polyester polymer, it being understood that certain aspects of
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the invention are applîcable 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 pref~rred embodiment
of a spinnere~ design which can be employed for obtaining the
first type of filaments according to the invention. The
spinneret includes a large counterbore 20 formed in the upper
surface 21 of spinneret plate 2~. Small counterbore 24 is
formed in the bottom of and at one side of large counterbore
20. A large capillary 26 extends rom 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 comlects the
bottom of couterbore 24 with surface 28. Capillaries 26 and
30 are each inclined :~our degrees 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 0.052 inch ~1.32 mm.). Capillary 26 has a
diameter of 0.016 inch (0.406 mm.) and a length of 0.146 inch
(3.71 mm.), while capillary 30 has a diameter of 0.009 inch
(0.229 mm.) and a length of 0.032 inch (0.813 mm.). Land 32
separates capillaries 26 and 30 as they emerge at surface 23,
and has a width of 0.0043 inch (0.109 mm.). Plate 22 has a
thickness o 0.554 inch (14.07 mm.). Capillaries 26 and 30
together with counterbores 20 and 24 constitute a combined
orifice for spinni.ng various novel and useul 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) ~o about 5% at 5000 ypm (about 4500 mpm) when using
spinneret capillaries having diameters of 0.063 inch (1.6 mm.)
and when simultaneously spinning 34 such filaments to be
false-twist draw-textur~d 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 150 denier. Using
different capillary diameters produces a amily o curves
~etween, to the left, and to the righ~ of those illustrated.
The curves also can be shifted (for a given capillary
diameter) by varying the polymer throughput. In o~her words,
the curves can be shifted by varying the jet stretch, which
is the ratio o~ 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 com-
posite filament o~ a single polymer wherain one side o~ thefilament has a much higher shrinkage than the other side.
This is done by selecting the individual capillaries to give
diferent jet stretches, and also selecting the spinning
speed within the range wherein an individual filament
~uenched rom 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 of the
individual streams. Under the spinning conditions illustrated
in FIGURE 3, at a spinning speed of 5000 yards per minu~e the
individual s~reams would have shrinkages differing by about
25 percentage points. Combining these molten streams into a
side-by-side configuration results in a highly latently
crimped filament in its as-spun form, without the necessity of
drawing the yarn to develop 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.
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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. Productivity is increased when the spinning speed
is seIected such that the com~ined filament has a shrinkage
less than 207, and i5 maximized when the shrinkage is less
than 8%.
Further aspects of the invention, 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 normal
textile molecular weight is metered at a temperature of 290C.
through a spinneret having 34 combined orifices as above
specifically disclosed. The pol~mer throughput is adjusted to
produce filaments of 4 average denier per filament at a
spinning speed of 5200 yards per minute, the molten streams
being conventionally quenched lnto filaments by transversely
directed quenching air.
Under these spinning conditions a remarkable
phenomenon occurs, as illustrated in FIGURE 5. Due ~o the
geometry of the spinneret construction, the polymer flowing
through the smaller capillaries 30 has a higher velocity thc~n
that flowing through the larg2r ~apillaries. The speeds and
momenta of the paired streams issuing from each combined
orifice and the angle at which the streams converge outside
the spinneret are such that the slower streams 34 travel in
substantially straight lines after the points at which the
paired streams first touch and attach, while each of the
smaller and aster 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 obser~ed using a stroboscopic light directed onto
the stream immediately below t~e spinneret face 28. As the
molten streams accelerate away from the spinneret, the
slower s.ream attenuates between the points of attachment 38
and the loops o~ the faster stream beeome 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
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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 lenglh~ and,
after being heated while under low tension, has variable
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 of sma~l 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 modifying the spinning
conditions and the geometry of the splnneret 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 repe~ition rates among the several result-
ing streams and filaments. An e~ample of this is quali-
tatively shown in FIGURE 7, wherein is shown that various
orifices produce somewhat different repetition rates as
determined by stroboscopic examination of the combined streams
just below the spinneret ace. In the resulting multifilament
yarn, the filaments have non-round cross-sections which vary
by more than + LO% along the length of the filaments, and
alternating 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.
For certain efects, it is advantageous that the
filaments vary repetitively aiong their lengths by more than
~ 25% (preferably more than 30~/0~ about a mean ~alue i~
cross-sectional area. The effects are particularly 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 with integrator ITG~101 for this instrument.
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The yarn speed is 182.8 meters per minute (200 ypm), the
service selector is set on normal, and the sensitlvi~y selec-
tor is set to 12.5%. The % U is read from the integrator
after a sample run time of 5 minutes.
FIGURE 8 s~ows the preferred embodiment of spinneret
design which can be employed for obtaining the second type of
filament according to the invention. The orifice is in the
form of a spiral slot through the spinner~et plate and extend-
ing over more than 360 degrees. An exemplary slo~ may ha~e
a width of 0.1 mm. and a length of 4 mm. along the length of
the spiral. If the clearance between the inner end and the
nearest intermediate portion of the slot is sufficiently
small, the molten stream issuing therefrom will bridge the
gap between the inner end of the spiral cross-sectioned
stream and the nearest intermediate portion of the stream
cross-section, orming a filament with a spiral cross-section
closed at its inner end. On the other hand, if the noted
cl~arance is sLightly larger, the bridging will not occur,
and the resulting filament will have a spiral cross-section
open at its inner end. Selection o the proper clearance to
provide either a clos~d inner end or an open inner end while
using particular spinning and quenching conditions can
readily be made by one skilled in the art.
Generally speaking, the filament having a cross-
section comprising a spiral closed at its inner end will havea more powerful crimp than one havi.ng a cross-section compris-
ing a spiral open at its inner end. The latter will, however,
have substantially increased moisture transport and moisture
holding capacity as compared to the former, which is itself
superior to ordinary round filaments.
The second class of filaments may be spun from
spinneret orifices selected such that, at the given common
spinning speed, the filaments of the first class will have a
higher shrinkage than those of the second class.
As a specific example, molten polyethylene tereph-
thalate polymer of normal molecular weight for text1le
apparel yarns is extruded simultaneously through two
spinnere~s, one of which contains 34 combined orifices as
above described and the other of which contains 17 spiral
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slots as above described. The extrus~on rates are selected
such that each resulting class of filaments has a total
denier o 88 at a winding or spinning speed of 5200 ypm
(about 4600 meters per minute). The molten streams are
quenched into ilaments by transversely directe~ moving air,
and the 51 filaments are converged into a common yarn bundle
and wound on a bobbin at 5200 ypm as a yarn having a denier
of 176.
The yarn is heated to 150C. while under low
tension to deve~op 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 17~/o~ while
those o~ the second class, collected separately, have a
shrinkage of 3.5~. The combined yarn has a shrinkage of 14%.
Each filament of the first class has a periodic variation in
denier from approximately one denier to approximately four
denier, while the ilaments of the second class protrude in
relatively large loops ~rom ~he yarn bundle.
To produce a more wool-like hand, ~he number or ~he
denier per ilament of the filaments of the second class can be
increased, the range of about 5 9 dpf being parti~ularly
suitable. Mois~ure transport is increased over prior art
yarns, and particularly when the spiral cross-section of ~he
second class of filaments is open at the inner end.
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 subjec~ed ~o a tenslon
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
L X 100
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