U.S. patent application number 10/995821 was filed with the patent office on 2005-05-05 for polymer filaments having profiled cross-section.
This patent application is currently assigned to INVISTA North America S.a r.l.. Invention is credited to Lancaster, Peter Michael.
Application Number | 20050095312 10/995821 |
Document ID | / |
Family ID | 34117622 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050095312 |
Kind Code |
A1 |
Lancaster, Peter Michael |
May 5, 2005 |
Polymer filaments having profiled cross-section
Abstract
The invention provides a profiled polymer filament having an
open hollow cross-sectional shape normal to the longitudinal axis
of the filament, wherein the cross-section is dimensioned to
prevent the filament from interlocking with a second filament of
the same cross-section. The invention also provides methods of
manufacture of such filaments by melt spinning a polyamide, and
spinnerets suitable for use in melt spinning such filaments.
Inventors: |
Lancaster, Peter Michael;
(Prestbury Cheltenham, GB) |
Correspondence
Address: |
INVISTA NORTH AMERICA S.A.R.L.
THREE LITTLE FALLS CENTRE/1052
2801 CENTERVILLE ROAD
WILMINGTON
DE
19808
US
|
Assignee: |
INVISTA North America S.a
r.l.
Wilmington
DE
|
Family ID: |
34117622 |
Appl. No.: |
10/995821 |
Filed: |
November 24, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10995821 |
Nov 24, 2004 |
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10333187 |
Jan 16, 2003 |
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6855425 |
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10333187 |
Jan 16, 2003 |
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PCT/US01/21251 |
Jul 5, 2001 |
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Current U.S.
Class: |
425/382.2 |
Current CPC
Class: |
D01D 5/253 20130101;
Y10T 428/2935 20150115; Y10T 428/2973 20150115; Y10T 428/2913
20150115; D01F 6/60 20130101; Y10T 428/2975 20150115 |
Class at
Publication: |
425/382.2 |
International
Class: |
D02G 003/00; D01D
005/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 10, 2000 |
GB |
0016926.8 |
Claims
1-38. (canceled)
39. A spinneret for the production of profiled filaments by melt
extrusion of a polymer into filaments, said spinneret comprisesing:
a plate having upper and lower surfaces connected by an assembly of
capillaries; and either (a) each capillary has an open hollow
transverse cross-section, or (b) each capillary comprises two
adjacent segments, whereby the profiled filament cross section
longitudinal to the axis of the filament is obtained as the molten
polymer streams from each segment coalesce at a point between the
segments, and wherein the profiled filaments having an open hollow
cross-sectional profile shape normal to the longitudinal axis of
the filament, said cross-sectional profile shape having a central
arcuate portion and first and second elongated leg portions, each
of said leg portions having proximal and distal end portions, said
proximal end portions joining to said central portion and said
distal end portions joining to foot portions on each leg portion,
said foot portions having a dimension F, said leg portions and said
central arcuate portion defining an open portion, said leg portions
oriented in a substantially parallel relationship, and said foot
portions defining an aperture leading to said open portion; said
aperture having a dimension D, wherein dimension D is less than
dimension F.
40. A spinneret according to claim 39, wherein: each capillary is
comprised of two segments; each segment is comprised of a straight
length portion having at each end a junction with a pair of
projecting portions; at the first end, the pair of projecting
portions are of equal area and each comprise a straight portion
terminating in a round portion; at the second end the pair of
projecting portions are of unequal area and each comprise a
straight portion terminating in a round portion.
41. A spinneret according to claim 40, wherein each segment is the
mirror image of the other segment.
42. A spinneret according to claim 41, wherein each segment is the
non-superimposable mirror image of the other segment.
43. A spinneret according to claim 39, wherein the capillaries
themselves have an open hollow cross-section, each capillary having
a cross sectional shape comprising: a second straight portion and a
third straight portion bifurcating from the first end of the first
portion, wherein the second straight portion terminates in a round
portion and the third straight portion extends to a first point of
bifurcation; a fourth straight portion and a fifth straight portion
extending from said first point of bifurcation, wherein the fourth
and fifth straight portions have unequal areas and each terminate
in round portions; a sixth straight portion and a seventh straight
portion bifurcating from the second end of the first straight
portion, wherein the sixth straight portion terminates in a round
portion and the seventh straight portion extends to a second point
of bifurcation; and an eighth straight portion and a ninth straight
portion extending from said second point of bifurcation, wherein
the eighth and ninth straight portions having unequal areas and
each terminate in round portions.
Description
FIELD OF THE INVENTION
[0001] This invention relates to synthetic polymer filaments with
an "open hollow" profiled cross section normal to the longitudinal
axis of the filament. The invention further relates to spinneret
plates for melt extrusion of the filaments, and to methods of
manufacture of the filaments by melt extrusion.
BACKGROUND
[0002] Textile fibres or filaments from synthetic polymers,
particularly polyamide polymers like nylon 66 and nylon 6, and
multifilament yarns melt extruded from the same polyamide polymers,
are produced for apparel uses typically as partially oriented yarn
(POY) and drawn yarn. POY will have an elongation to break greater
than about 55% and drawn yarn will have a lower elongation.
Circular is the most common cross sectional shape for each filament
comprising the multifilament yarns of either type, e.g. POY and
drawn yarn. Variation on the individual filament cross sectional
shapes include trilobed or 6-lobed, disclosed in Japanese Kokoku
patent document 01-20243 (Nihon Ester KK), the scalloped oval cross
section as disclosed by in U.S. Pat. No. 5,834,119 (Roop) and
hollow polyamide filaments with a single longitudinal void,
disclosed in U.S. Pat. No. 5,604,036 (Bennett et al.).
[0003] All of the foregoing examples are known variants of profiled
cross sectional shaped POY and drawn yarn. Filaments with cross
sectional shapes other than circular provide multifilament yarns
for fabrics and garments with varied visual aesthetics, opacity and
cover and lighter weight. Yarns from hollow filaments, for example
the yarns of the last mentioned United States patent; provide
lighter weight fabrics and garments and enhanced heat retentive
properties versus conventional circular filaments, without a
longitudinal void. Hollow filament yarns are particularly suited
for apparel applications when textured by the conventional
processes, e.g. air jet texturing (AJT) and false twist texturizing
(FTT) to obtain bulky yarns. Hollow flat yarns for direct use in
weaving applications are also known.
[0004] Both partially oriented and flat nylon yarns in a high void
volume hollow are disclosed by Bennett et al. However, filaments
with longitudinal voids are difficult to close perfectly at
spinning, and may also deform substantially during the texturing
process. This may result in a letter `C-shaped` filaments and/or
collapsed tube cross sectional shapes. Letter C-shaped filaments
are able to pack closely together with a loss of open space among
neighbouring filaments. In addition, letter C-shaped cross
sectional filaments and collapsed tube cross sections lead to
undesirable yarn and fabric properties as a result of such
occurrences. Increased fabric density and diminished heat retention
of the fabric and garments are among the undesirable properties.
Furthermore, yarns from filaments with varied amounts of ruptured
longitudinal voids contribute to dyed fabric streakiness and the
intact filament voids provide opportunistic bacteria with a place
to flourish.
[0005] It has now been found that the above-enumerated
disadvantages can be overcome by the production of polymer
filaments having a novel cross-section.
[0006] The present invention provides a profiled filament from
synthetic polymer having an "open hollow" cross-sectional shape
normal to the longitudinal axis of the filament. The cross-section
is dimensioned to prevent a first filament from interlocking with a
second filament having the same cross-section. This means a region
proximate to each tip of the cross-section is wider than a spacing
between said regions defining an opening to the open hollow
cross-section.
[0007] The profiled cross sectional shape filaments of the
invention are provided by the novel shape and design of the
extrusion capillary. The filaments of this invention are prepared
directly by melt extrusion of synthetic polymer through a
multi-capillary spinneret plate. The term "open hollow" denotes a
generally C-shaped or U-shaped cross-section having a hollow
center, and a solid region defining wall portion extending around
the hollow center to enclose the hollow center, but with an opening
in one side of the wall linking the center to the outside of the
filament. The opening is narrower than the diameter of the hollow
center, thereby forming a throat or constriction between the hollow
center and the outside of the filament.
[0008] Preferably, the filament comprises a solid part
substantially enclosing a central hollow region. An opening leads
from the exterior of the filament into the central hollow region.
The solid part includes legs that terminate in feet. Confronting
surfaces of the feet define the throat (the narrowest dimension) of
the opening. The throat of the opening subtends a radial angle
alpha (.quadrature.) of not more than 90.degree., more preferably
not more than 75.degree. and most preferably from 10.degree. to
60.degree.. As seen in FIG. 1, the radial angle alpha
(.quadrature.) is that angle defined between two rays R.sub.1 and
R.sub.2 originating at a point C. The point C is that point lying
on the interior surface of the solid part of the filament that lies
farthest from a reference line R.sub.3 tangentially connecting the
tips of the feet. Each ray R.sub.1, R.sub.2 extends from the point
C and lies tangent to a point on the confronting surfaces of the
feet defining the throat of the opening D. The solid part subtends
a radial angle equal to 360.degree. minus angle alpha
(360.degree.-.quadrature.). Preferably, the solid part of the
cross-section subtends a radial angle of at least 270.degree.. More
preferably the solid part subtends a radial angle of at least
300.degree..
[0009] The filaments according to the present invention are adapted
to prevent inter-engagement or stacking of the filaments. For
example, hook-like engagement of two cross sections arising from
insertion of an end of the solid part of a first filament
cross-section through the opening in the cross-section of a second
filament is prevented. This provision can be achieved as already
described, by making the solid portion of the cross-section subtend
a large radial angle, whereby the opening in the filament
cross-section is very small. Alternatively or additionally, the
ends of the solid part of the cross section may be enlarged to
inhibit insertion into the opening of other filaments.
[0010] The solid portion of the cross-section in the filaments
according to the present invention may form a single continuous
curve. Preferably, the cross-section comprises a "central arcuate"
or base portion having first and second ends and two side or "leg"
portions. The leg portions extending in substantially side-by-side
relationship from the first and second ends of the central arcuate
portion.
[0011] In preferred embodiments, such as the filament cross section
geometry shown in FIG. 1, the filament cross sectional shape is
characterized by a central arcuate portion 1 (extending
horizontally in FIG. 1) and first and second, generally parallel,
elongated leg portions 2,3 (extending vertically in FIG. 1) joined
to the central arcuate portion. The distal portion of each leg
(2,3) opposite the juncture with the central arcuate portion 1
defines an enlarged foot portion 4. Each foot portion 4 is
characterized by dimension F, the length of the foot, as shown in
FIG. 1. The profiled filament cross-section is open in the center.
This open portion is bounded on three sides by the leg portions 2,3
and central arcuate base portion 1. The feet portions 4 are
oriented in a substantially side-by-side relationship defining an
aperture between confronting surfaces of the foot portions with
dimension D leading to the open portion, as shown in FIG. 1. The
dimension D is less than dimension F. As a result, any foot on any
leg of the profiled filament is sufficiently large with respect to
the aperture between the pair of legs on any other identical
filament to prevent a foot of the first filament from being
accommodated (interlocked) between the legs of the other filament
in a multifilament yarn bundle, as illustrated by FIG. 2.
[0012] Preferably, the polymer used to form the profiled polymer
filament according to the present invention is a polyamide. More
preferably, the polyamide polymer has a relative viscosity, by a
formic acid method, greater than 40, and still more preferably the
relative viscosity of the polyamide by a formic acid method is in
the range of 46 to 56. Preferably, the polyamide is selected from
the group consisting of nylon 66 and nylon 6 and copolyamides.
[0013] Preferably, the single filament linear density is from 0.5
to 20 dtex, and more preferably it is from 2 to 10 dtex. Most
preferably it is less than 4 dtex. Preferably, the filament
cross-sectional shape is substantially constant along the length of
the filament. Preferably, the filament non-uniformity is less than
1 Uster %.
[0014] The profiled filaments according to the present invention
provide a lighter unit weight yarn, particularly after texturing by
AJT (air jet texturizing) or FTT (false twist texturizing). The
yarn incorporates high free volume of air space. The volume of air
space contributes to enhanced thermal retention of fabrics and
garments produced from the yarn. The yarn when knitted or woven
into fabrics provides a less dense fabric than similarly
constructed fabrics from solely circular cross section filaments.
Furthermore, the yarn exhibits a high moisture wicking
capacity.
[0015] Accordingly, the present invention further provides a
multifilament yarn comprising at least a portion of the profiled
filaments according to the present invention.
[0016] Preferably, the yarn comprises at least 10% by weight of the
profiled filaments according to the present invention, more
preferably at least 25% of such filaments, still more preferably at
least 50% of such filaments and most preferably it consists
essentially of such filaments.
[0017] The present invention further provides an article comprising
at least a portion of the yarn according to the present invention.
Preferably, the article comprises a textile fabric that is knitted
or woven from a yarn according to the present invention.
[0018] A further aspect of the present invention is a spinneret for
the production of the profiled open hollow filaments according to
the present invention by melt extrusion of polymer into filaments.
The spinneret comprises a plate having upper and lower surfaces
connected by an assembly of capillaries. The shape, size and
configuration of the capillaries are adapted to the melt spinning
of filaments according to the present invention. Specifically,
either each capillary comprises two adjacent segments as in FIG.
3a, whereby the open hollow filament cross section longitudinal to
the axis of the filament is obtained as the molten polymer streams
from each segment coalesce at a point between the segments or each
capillary has an open hollow transverse cross-section as in FIG.
3b.
[0019] The preferred spinneret plate for the production of the
profiled open hollow filaments is one with each capillary comprised
of two segments in FIG. 3a. Each segment is comprised of a straight
length portion 30 having at each end a junction with a pair of
projecting portions. At the first end, the pair of projecting
portions are of equal area and each comprise a straight portion
31,32 terminating in a round portion 33,34. At the second (opposite
the first) end, are a pair of unequal area projecting portions. The
first unequal area projecting portion is comprised of straight
portion 35 and round portion 36 and the second unequal area
projecting portion is comprised of straight portion 37 and round
portion 38. Therefore, each segment of the capillary has three
equivalent projecting portions, two on one end and one on the
opposite end. The unique (longer) projecting portion present on
each segment is comprised of straight portion 37 and round portion
38. Preferably, each capillary segment is the mirror image of the
other segment. More preferably, each segment is the
nonsuperimposable mirror image of the other segment, for example as
illustrated by FIG. 3a. The nonsuperimposable mirror image
relationship means that each segment possesses handedness in the
same way as do human left and right hands.
[0020] The open hollow filament cross section normal to the
longitudinal axis of the filament is obtained as the molten
thermoplastic polymer streams from each capillary segment coalesce
at a point between projecting portions of the two segments. That
is, the open hollow filament cross section of the invention is
formed as the molten polymer stream coalesces between confronting
round portions 38 of the left and right capillary segments shown in
FIG. 3a.
[0021] In the case where the capillaries themselves have an open
hollow cross-section, the capillary illustrated by FIG. 3b is a
preferred spinneret geometry cross section for the production of
profiled open hollow filaments. Each capillary has a cross
sectional shape comprising a first straight portion 40 with a first
end and a second end, opposite each other. Bifurcating from the
first end of the first straight portion 40 are a second straight
portion 48 and a third straight portion 50. The second straight
portion 48 terminates in a round portion 49 and the third straight
portion 50 extends to a point of bifurcation; wherein a fourth
straight portion 53 and a fifth straight portion 52 extend from
this point of bifurcation. The fourth and fifth straight portions
having unequal areas and each terminate in round portions 54 and
51. Similarly, bifurcating from the second end of the first
straight portion are a sixth straight portion 41 and a seventh
straight portion 43. The sixth straight portion 41 terminates in a
round portion 42 and the seventh straight portion 43 extends to a
point of bifurcation; wherein an eighth straight portion 46 and a
ninth straight portion 44 extend from said point of bifurcation,
the eighth and ninth straight portions having unequal areas and
each terminate in round portions 45 and 47.
[0022] In a further aspect, the invention provides a process for
making drawn yarns and partially oriented yarns (POY) with a
modified filament cross section according to the present invention.
Generally, the process comprises extruding a polyamide melt,
typically nylon 66 or nylon 6, of 40 to 60 RV (measured in formic
acid), and preferably 48 to 52 RV to form a plurality of filaments.
The spinneret according to the invention is maintained at a
temperature selected from the range 245 to 295.degree. C., more
preferably it is 280.degree. C. Multiple filaments extruded through
the spinneret are cooled in a cross flow of air to form solid
filaments. These filaments may be treated with oil, converged,
interlaced and drawn, or remain undrawn, prior to winding up a
multifilament yarn at a speed greater than 3000 meters per minute
(m/min).
[0023] Referring now to the process schematic in FIG. 5, a drawn
yarn is prepared by following path A. The melted polymer 10, a
polyamide, is pumped to the spin pack 20 and forced throught
spinneret plate 30 to form filaments 40. The emerging filaments are
cooled by a cross flow of air 50, having an air velocity of about
0.15 to 0.5 meters per minute. The cooled filaments are converged
into a yarn 60, and an oil and water finish is preferably applied
to the resulting yarn bundle at 70. The yarn 60 is forwarded
through a first air interlace jet 80 to become intermingled yarn
90. Yarn 90 is forwarded to a first godet 92 (the feed roll) and
its associated separator roll, wrapping several times to prevent
slippage, and then to a second godet 94 (the draw roll) and its
associated separator roll. The draw roll 94 is moving at a surface
speed of 60 to 100%, preferably 80%, greater than that of the feed
roll 92. The yarn bundle is thereby drawn (elongated), preferably
by a total factor of about 1.8, reducing the overall yarn titer to
form yarn 100. The drawn yarn 100 is preferably treated by a
relaxation device 110 to set the draw and to relax the yarn as is
conventionally practised in the art. Any known relaxation device
may be employed, including steam, heated fluid, hot tube, hot shoe,
heated rolls. The relaxed yarn bundle 120 is optionally passed
through a second interlace jet 130 and optionally oiled before the
relaxed yarn 140 is wound up on a tube 150 at a winding speed
greater than 3000 meters per minute, more preferably about 3800
meters per minute. The resulting drawn yarn has an elongation of 25
to 45%, preferably 40 to 45%, and a tenacity of 35 to 45
cN/tex.
[0024] Alternatively, referring now to the process schematic in
FIG. 5, a partially oriented yarn (POY) is prepared by following
path B. The melted polymer 10, a polyamide, is pumped to the spin
pack 20 and forced through spinneret plate 30 to form filaments 40.
The emerging filaments are cooled by a cross flow of air 50, having
an air velocity of about 0.15 to 0.5 meters per minute. The cooled
filaments are converged into a yarn 60, and an oil and water finish
is preferably applied to the resulting yarn bundle at 70. The yarn
60 is forwarded through a steam atmosphere containing interfloor
tube 75, as is known in the art. The steam treated yarn 85 is
intermingled at 80 partially wrapped around godet 82 and godet 84,
which control any variations in winding tension the yarn may
experience. The yarn 115 is wound up as a package of yarn on tube
160 at a speed of about 3800 meters per minute. The POY produced
preferably has an elongation of 55 to 85%, preferably 75%, and a
tenacity of 25 to 40 cN/tex, preferably about 30 cN/tex.
BRIEF DESCRIPTION OF FIGURES
[0025] FIG. 1 shows a cross section normal to the longitudinal axis
of the filament through one filament with the preferred cross
sectional shape showing the dimensions R, F and D, rays R1, R2,
reference point C, tangent reference line R3 and the angle alpha
(.quadrature.);
[0026] FIG. 2 shows a cross section normal to the longitudinal axis
of the filaments through two adjacent filaments according to the
invention;
[0027] FIG. 3a is a plan view (to scale) of a two-segment spinneret
capillary cross sectional shape according to the present
invention;
[0028] FIG. 3b is a plan view (to scale) of a one-segment spinneret
capillary cross sectional shape according to the present
invention;
[0029] FIG. 4a is a yarn bundle photomicrograph of a yarn cross
section containing 26 filaments produced by melt spinning in
accordance with the present invention from the spinneret capillary
cross sectional shape FIG. 3a.
[0030] FIG. 4b is a yarn bundle photomicrograph of a yarn cross
section containing 26 filaments produced by melt spinning in
accordance with the present invention from the spinneret capillary
cross sectional shape FIG. 3b.
[0031] FIG. 5 is a schematic of the apparatus for carrying out the
fully drawn yarn (A) and the POY (B) spinning processes according
to the present invention.
TEST METHODS
[0032] Water Wicking Test Method: The principle of the method
involves suspending a strip of fabric vertically with its lower end
immersed in water. The height to which the water rises up the
fabric in measured at fixed time intervals. The fabric samples
taken are 300 mm long and 25 mm wide. The samples are conditioned
at a relative humidity of 85% +/-5% and 20.degree. C. +/-2.degree.
C. for 16 hours. The maximum rise height of the 20.degree. C.
+/-2.degree. C. water is measured after two minutes. The height is
measured from the surface of the water to the point on the fabric
of maximum water rise. The mean value of three measurements is
reported for each perpendicular fabric direction.
[0033] Fabric Thickness Test Method: The fabric thickness is the
mean distance between upper and lower surfaces of the material
measured under a specified pressure. The fabric samples are
conditioned as for water wicking. The measuring apparatus used is a
Shirley Thickness Gauge with 50 cm2 presser foot. The pressure foot
is allowed to fall under its own momentum onto the fabric. The
measurement is repeated ten times and the mean and standard
deviation are reported to the nearest 0.05 mm.
EXAMPLES
[0034] Example 1
[0035] A first multifilament yarn (Yarn 1A) of 96 dtex and 26
filaments was spun as a POY using the apparatus shown schematically
in FIG. 5 and a spinneret plate with two segment capillaries
according to FIG. 3a.
[0036] Nylon 66 polymer chip of 49.4 RV, by the formic acid method,
was melted 10 and extruded through a filter pack 20 and through a
spinneret plate 30 with 26 capillaries of the segmented cross
sectional shape shown in FIG. 3a at a spinneret temperature of
280.degree. C.
[0037] Next, the emerging filaments 40 were cooled by a cross flow
of air 50, with an air velocity of 0.45 meters per minute. The
quench air was directed, with reference to FIG. 3a, so as to first
encounter confronting lobes 38 of the two segment capillary. The
cooled filaments 60 were converged into a yarn at 70 where an oil
and water finish was applied to the resulting yarn bundle. The
converged yarn with the finish applied was forwarded along Path B
in FIG. 5. The yarn was passed through a steam atmosphere
containing interfloor tube 75. The steam treated yarn 85 was
intermingled with apparatus 80. The intermingled yarn 115 was wound
up as a package of yarn on tube 160 at a speed of 3800 meters per
minute.
[0038] The POY produced in this way has a yarn linear density of 96
decitex, an elongation to break of about 75% and a tenacity of 30
cN/tex. The cross section of the yarn is shown in FIG. 4a.
[0039] A second multifilament partially oriented yarn (Yarn 1B) of
96 dtex and 26 filaments was spun exactly as the first POY using
the apparatus shown schematically in FIG. 5. For Yarn 1B a
spinneret plate with capillaries according to FIG. 3b was used. The
elongation and tenacity properties were the same as for the first
POY. The cross section of the Yarn 1B is shown in FIG. 4b.
[0040] A comparative multifilament yarn (Yarn 1C) of 96 dtex and 26
filaments was spun in exactly the same way as the first yarn,
except for replacing the spinneret plate with one having 26
"circular cross sectional" shaped capillaries.
[0041] All samples, 1A and 1B (yarns of the invention) and 1C (a
circular cross section comparative yarn) were separately 8-plied
and then air jet textured (AJT) using a HEBERLEIN HEMAJET
(Registered Trade Mark) to make a 730 decitex by 208 filament
(8.times.26 filaments) textured yarn. These textured yarns were
2-plied and knitted into a "full cardigan structure" and tested for
thermal transmittance.
[0042] The thermal transmittance test method was essentially that
of ASTM D1518-85 (as reapproved 1990). This method measures the
time rate of heat transfer from a warm, dry, constant-temperature,
horizontal flat-plate up through a layer of the knitted cardigan
test material to a relatively calm, cool atmosphere. Thermal
resistance was measured and the thermal insulation or CLO value
calculated. The "CLO" is a unit of "clothing thermal resistance" in
ASTM D1518 and equal to 0.155(.degree. C. m2W-1). The base
temperature was 25.degree. C. (Ti) and the head plate, temperature
was 35.degree. C. (T2). There was minimal pressure applied to the
cardigan knit, 260 Nm-2 during the test procedure. Each sample was
tested three times to give the mean result reported in Table 1
below. These test results, reported in Table 1, show a 13-15%
increase in thermal resistance for the preferred open hollow cross
section versus the circular cross section yarn in a knit
construction. Similarly, the CLO values for the open hollow cross
section versus the circular cross section yarn in a knit
construction increased by 13-15%. Clearly, the open hollow filament
yarn in the knit construction tested is a better thermal insulator
versus the circular filament yarn.
1TABLE 1 Thermal CLO value resistance Meter.sup.2 .degree. C.
Meter.sup.2 .degree. C. W.sup.-1/(0.155) Yarn used in cardigan knit
W.sup.-1 .times. (10.sup.3) ASTM D1518-85 Yarn 1A (2 .times.
730f208) 103.7 0.67 invention cross section using two segment
spinneret Yarn 1B (2 .times. 730f208) 105.0 0.68 invention cross
section using one segment spinneret Yarn 1C (2 .times. 730f208)
91.5 0.59 "circular" cross section
[0043] Example 2
[0044] POY samples from Example 1, Yarn 1A and comparative Yarn 1C,
both 96 decitex and 26 filaments as spun, were false-twist textured
(FTT) at 600 meters per minute on a DCS 1200 texturing machine. The
primary heater of the texturing machine was 220.degree. C., no
secondary heater was used. A draw-textured yarn of 78 decitex and
26 filaments (78 f26) was prepared with the texturing machine's 6
mm solid ceramic discs configured to 1/7/1 smooth/working/smooth.
The 78 f26 yarns were circular knitted into 28 gauge plain
interlock fabrics, scoured, dyed and heat set. Fabric samples of
300 mm by 25 mm were taken for water wicking tests. These samples
were hung vertically into a water bath and the vertical rise of the
water was measured after two minutes. The mean of three samples is
given in Table 2 . The fabrics constructed from yarns having
filaments of the preferred cross section showed a water wicking
advantage over identically constructed fabrics from yarns of
circular filament cross section. This advantage is at least a
2-fold improvement in water wicking capability.
2TABLE 2 Vertical rise in Vertical rise in Textured yarn used in mm
(fabric in mm (fabric in circular knit longest direction) shortest
direction) 78f26 comparative circular 1.5 0 cross section (Yarn 1C)
false twist textured yarn 78f26 invention cross 3.7 2.7 section
(Yarn 1A) false twist textured yarn
[0045] Example 3
[0046] A drawn yarn of 192 decitex and 52 filaments was spun with
the apparatus of FIG. 5 and using the spinneret plate with 52
capillaries of the cross sectional shape of FIG. 3a. Nylon 66
polymer of 49.4 RV (by the formic acid method) was melted 10,
extruded through a polymer filter pack 20 and then through the
above spinneret 30 maintained at a temperature of 280.degree. C.
The extruded filaments 40 were cooled by a cross flow of air 50
flowing at 0.4 meters per minute. The cross flow of air 50 was
directed to first encounter confronting lobes 38 of the two segment
capillary shown in FIG. 3a. The cooled filaments were converged
into a yarn bundle 60 with oil and water application and forwarded
along alternative Path A. The yarn was intermingled with an air jet
80, as typically practised in the art. The intermingled yarn 90 was
then fed via feed roll 92 and associated separator roll (making
several wraps on the roll to prevent slipping) to a second godet 94
and associated separator roll (the draw roll), moving at a surface
speed 80% greater than that of the feed roll 92. The intermingled
yarn bundle 90 was drawn, by a total factor of 1.8, reducing the
overall yarn titer. The drawn yarn 100 was treated by a steam jet
110 to set the draw and to relax the yarn. The relaxed yarn bundle
120 was passed through a second interlace jet 130 and then the yarn
140 was wound up on a tube 150 at a speed of 3800 meters per
minute. This process provided cakes of fully drawn yarn (FDY) with
a yarn linear density of 192 decitex, a breaking elongation of
42.8%, tenacity of 41 cN/tex. The yarn in dry form had an RV of
50.3 by the formic acid method. Filaments of this 52 filament yarn
have a cross sectional shape normal to the longitudinal axis which
is substantially similar to those filaments shown in FIG. 4a.
[0047] This yarn, Yarn 3A, was used as the weft yarn of a woven
fabric of 3/1 twill weave where the warp yarns were 78 decitex (51
circular filaments). Weaving and fabric finishing details are given
in Table 3. As a comparative example, a fully drawn yarn of 192
decitex and 52 filaments was spun in exactly the same way as above
but using a spinneret plate with "circular cross section"
capillaries, this yarn was called Yarn 3B. A second fabric sample
was woven using Yarn 3B in the weft as above. Weaving and fabric
finishing details are given in Table 3. The two fabrics were
finished identically in greige, dyed and heat-set form. From each
fabric specimen (greige, dyed and heat-set) 10 samples of 75 square
millimeters were cut. These samples were measured for fabric
thickness in the same way using a micrometer. The results of the
fabric thickness measurements (mean of 10 measurements) are
provided in Table 3. The fabrics containing the preferred cross
section filaments in the weft were thicker than that woven of
entirely circular cross section filaments in the warp and weft. As
a result, the woven fabrics having the preferred cross section
filaments in the weft provided a lower density fabric with a
lightweight aesthetic.
3 TABLE 3 Greige Greige Dyed Dyed Heatset Heatset fabric fabric
fabric fabric fabric fabric Yarn 3B Yarn 3A Yarn 3B Yarn 3A Yarn 3B
Yarn 3A Warp ends 57.5 .times. 38.8 58.2 .times. 39.7 61.3 .times.
40 62.2 .times. 39.8 61.5 .times. 41 61.6 .times. 41 per cm .times.
weft picks per cm Woven 0.22 0.24 0.20 0.22 0.20 0.21 fabric
thickness millimeters
[0048] The above embodiments have been described by way of example
only. Many other embodiments of the filaments, yarns, spinnerets
and processes according to the present invention will be apparent
to the skilled reader.
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