Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02358715 2001-07-12
Specification
Polyester Yarn and its Method of Production
Technical Field
The present invention relates to polyester yarn comprising
polytrimethylene terephthalate, and to its method of
production. More particularly, it relates to polyester yarn
and to a method of producing polyester yarn characterized in
that yarn production can be carried out stably at high speeds
without package tightening and with little variation in
properties in the fibre lengthwise direction and, furthermore,
when made into a fabric, there is little sense of tightness
because it stretches at a low modulus, and it has a soft
handle.
Background Art
Polytrimethylene terephthalate fibre is outstanding in its
elastic recovery following elongation, possesses a low
Young's modulus and soft bending characteristics and has good
dyeing properties and, furthermore, chemically it has stable
properties in the same way as polyethylene terephthalate.
Hence, as may be seen for example from US Patent Nos
3,584,103 and 3,681,188, it has long been the subject of
research as a potential clothing material.
However, the starting material 1,3-propanediol is
comparatively expensive, so polytrimethylene terephthalate
has not been used as a synthetic fibre hitherto.
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In recent years, as disclosed for example in US Patent
5,304,691, a cheap method for the synthesis of 1,3-
propanediol has been discovered, so the value of
polytrimethylene terephthalate fibre has been re-examined.
According to investigations carried out by the present
inventors, if the two-stage method generally employed in the
case of polyethylene terephthalate fibre is applied as it is
to polytrimethylene terephthalate, directly after spinning
there commences a change in internal structure and, as a
result of a phenomenon referred to as package tightening,
differences in properties arise due to differences in the
extent of such changes in internal structure between the
package inner and outer layers, and so fibre of stable
quality is not obtained.
As a means for resolving this problem, there has been
proposed a method using DSD in which the spinning process and
drawing process are conducted continuously and, prior to
winding-up, the internal structure is subjected to heat
setting, as described in JP-A-52-8123. However, even by this
method it has not been possible to suppress package
tightening completely.
Objective of the Invention
The present invention has as its objective to provide a
polyester yarn which shows no package tightening in the yarn
production process so that a package of stable product
quality is obtained and, furthermore, which has a low Young's
modulus in the elastic recovery region, and is outstanding in
its soft stretch properties and softness; together with a
method for the production of this polyester yarn.
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Disclosure of the Invention
For the purposes of resolving the aforesaid problem, the
polyester yarn of the present invention has the following
constitution. Specifically, the present invention relates to
polyester yarn which is characterized in that it is a
multifilament yarn substantially comprising polytrimethylene
terephthalate, and as well as the strength from the stress-
strain curve being at least 3 cN/dtex and the Young's modulus
being no more than 25 cN/dtex, the minimum value of the
differential Young's modulus at 3-10% extension is no more
than 10 cN/dtex and the elastic recovery following 10%
elongation is at least 90%.
Furthermore, this polyester yarn can be obtained by
a method of producing polyester yarn which is characterized
in that multifilament yarn obtained by the melt spinning of
polymer substantially comprising polytrimethylene
terephthalate of intrinsic viscosity [rI] at least 0.7 is
hauled-off at a spinning rate of at least 2000 m/min and,
without winding up, subjected to drawing and heat-treatment,
after which it is continuously subjected to a relaxation heat
treatment at a relaxation factor of 6 to 20% and wound-up as
a package.
Moreover, woven fabric of the present invention has the
following constitution. Specifically, it is
a woven fabric which is characterized in that the aforesaid
polyester yarn is used as the warp yarn and/or the weft yarn
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in the form of a twisted yarn of twist coefficient 10, 000 to
20,000.
Brief Description of the Drawings
Figure 1: This is a schematic diagram showing an example of
spin-drawing equipment for obtaining the polyester yarn of
the present invention.
Figure 2: This is a schematic diagram showing another
example of spin-drawing equipment for obtaining polyester
yarn of the present invention.
Figure 3: This shows the stress-strain curve and the
differential Young's modulus-strain curve for polyester yarn
of the present invention (Example 1).
Figure 4: This shows the stress-strain curve and the
differential Young's modulus-strain curve for polyester yarn
lying outside the present invention (Comparative Example 4).
Explanation of the numerical codes
1: spinneret
2: cooling chimney
3: oiling guide
4: first heated roller
5: second heated roller
6: cooling roller
7: interlacing nozzle
8: winder
Best Mode for Carrying out the Invention
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The polyester yarn of the present invention is multifilament
yarn substantially comprising polytrimethylene terephthalate.
In the present invention, the polyester from which the
polyester yarn.is composed is polytrimethylene terephthalate
(hereinafter abbreviated to PTT) where at least 90 mol% of
the structural units are obtained from terephthalic acid as
the chief acid component and 1,3-propanediol as the chief
glycol component. However, there may be included copolymer
components which can form other ester bonds, in a proportion
which does not exceed 10 mol% and preferably does not exceed
6 mol%. Examples of copolymerizable compounds include
dicarboxylic acids such as isophthalic acid, succinic acid,
cyclohexanedicarboxylic acid, adipic acid, dimer acid,
sebacic acid and 5-sodiumsulphoisophthalic acid, and diols
such as ethylene glycol, diethylene glycol, dipropylene
glycol, butanediol, neopentyl glycol, cyclohexanedimethanol,
polyethylene glycol and polypropylene glycol, but there is to
be no restriction to these. Moreover, optionally, there may
be added titanium dioxide as a delustrant, fine silica or
alumina particles as a lubricant, hindered phenol derivatives
as an antioxidant, and colouring pigments, or the like.
It is important that the strength of the polyester yarn of
the present invention be at least 3 cN/dtex. If the strength
is less than 3 cN/dtex, as well as this leading to fuzzing
and yarn breaks in subsequent processing stages such as
weaving, the product obtained will also have reduced tear
strength.
Furthermore, there is an inverse correlation between the
extension at break and the frequency of occurrence of fuzzing
at the time of weaving, and the higher the breaking extension
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while still satisfying the requirement in terms of practical
strength, the more the occurrence of fuzzing can be
suppressed. Hence, the residual extension is preferably at
least 40% and more preferably at least 45%.
Again, it is important that the polyester yarn of the present
invention has a Young's modulus of no more than 25 cN/dtex
and that it has a minimum value of differential Young's
modulus at 3-10% extension of no more than 10 cN/dtex. These
properties are closely related to the elongation
characteristics and the elastic recovery characteristics in a
stretch fabric, and in order to attain the soft stretch
property which is the objective of the present invention it
is preferred that these properties have low values. That is
to say, by satisfying all the above properties, when in the
form of a fabric there is easy initial stretch (low Young's
modulus) and, furthermore, within the extension range of 3-
10%, which is the practical stretch recovery region,
elongation is possible with no resistance (low differential
Young's modulus). Hence, it is possible to produce a soft
stretch fabric which is outstanding in its comfort when worn.
The Young's modulus has a linear relationship to the flexural
stiffness of the fabric, and the lower the Young's modulus
the more outstandingly soft is the fabric handle. Hence, the
Young's modulus is preferably no more than 22 cN/dtex and
more preferably no more than 20 cN/dtex.
In the same way, the minimum value of the differential
Young's modulus at 3-10% extension is preferably no more than
8 cN/dtex and more preferably no more than 5 cN/dtex.
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The polyester yarn of the present invention has an elastic
recovery of at least 90% following 10% elongation. If the
elastic recovery is less than 90%, then there occurs the
problem known as 'sagging' where, following elongation, there
remains a portion which has undergone partial plastic
deformation, so the woven material quality is reduced. The
elastic recovery following 10% elongation is preferably at
least 95% and more preferably at least 98%.
Now, the fact that yarn comprising PTT has outstanding
elastic recovery is due to a considerable extent to its
molecular structure. The reasons are thought to be because,
in the crystal structure of PTT, the methylene chain of the
alkylene glycol moiety has a gauche-gauche conformation, and
interaction due to the stacking of benzene rings is low and
the density low, so that flexibility is high, and hence the
molecular chains readily stretch and recover by means of
methylene chain rotation in the alkylene glycol moiety.
In experiments by the present inventors it was shown that the
higher the degree of crystallinity the higher the elastic
recovery. Consequently, the degree of crystallinity is
preferably at least 30% and more preferably at least 35%.
Here, the measurement of the degree of crystallinity was
carried out based on the density in accordance with the
density gradient column method of JIS L1013 (Chemical Fibre
Filament Yarn Test Methods).
Furthermore, preferably, the boiling water shrinkage of the
polyester yarn of the present invention is 3-15% and,
moreover, the maximum value of the shrinkage stress is no
more than 0.3 cN/dtex and the temperature at which the
maximum value of shrinkage stress is shown is at least 120 C.
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The boiling water shrinkage is one of the most important
factors in terms of carrying out fabric design, and by making
the boiling water shrinkage at least 3%, the setting
properties are made favourable in subsequent processing
stages, while by making it no more than 15% it is possible to
obtain a fabric with a soft handle which is free of any sense
of harshness. In the same way, if the heat shrink stress is
too high, excess shrinkage will be introduced and the.fabric
handle will be harsh. Hence, in order to achieve a soft
handle with no sense of harshness, the maximum value of the
shrinkage stress is preferably no more than 0.3 cN/dtex and
more preferably 0.15 to 0.25 cN/dtex. Again, the temperature
at which the maximum value of shrinkage stress is shown is
preferably at least 120 C and more preferably at least 130 C
in order to facilitate subsequent processing such as setting
and bulking-up.
In the case of the polyester yarn of the present invention,
it is preferred that the CV% of the yarn lengthwise direction
continuous shrinkage factor be no more than 5%. The CV% of
the continuous shrinkage factor is an index of the uniformity
of internal strain in the yarn lengthwise direction, and the
smaller this value the higher the quality. In order to
obtain fabric of high quality, the CV% is preferably no more
than 5% and more preferably no more than 4%.
Again, it is preferred that the CF (coherence factor) value
lies in the range 1-30, by subjecting the polyester yarn of
the present invention to an interlacing treatment. Where the
CF value is at least 1, it is possible to suppress single
filament breaks at the time of yarn production and processing,
and also at the time of weaving. Furthermore, where the CF
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value is no more than 30, when for example performing
combination to produce a combined yarn with different
shrinkage as one component yarn, migration is facilitated, so
this is preferred. It is further preferred that the CF value
be 5 to 25.
The cross-sectional shape of the fibre from which the
polyester yarn of the present invention is composed may be of
circular cross-section, triangular cross-section, multilobal
cross-section, flattened cross-section, X-shaped cross-
section or other known profile section, and there are no
particular restrictions thereon. Suitable selection may be
made in accordance with the objectives.
Again, in order to enhance the softness when made into a
woven fabric, the single filament fineness is preferably no
more than 5 dtex and more preferably no more than 3 dtex.
In the case of the polyester yarn of the present invention,
there is a strong correlation between the twist coefficient
and the stretch property and, once the twist coefficient
exceeds a fixed value, there is a tendency for the stretch
property to rapidly increase. In practice, for a woven
fabric employing yarn of twist coefficient about 5000, the
percentage stretch is about 5%, but with a twist coefficient
of 10,000 it is about 15% and with a twist coefficient of
14,000 it is about 30%. Hence, while the polyester yarn
obtained in the present invention may be employed without
twisting, it is more preferred that it be given a medium to
hard twist with a twist coefficient of 10,000 to 20,000.
Now, the twist coefficient K is expressed by the
relationship:-
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twist coefficient K = T x Do.5
where, T = number of twists per metre of yarn length and D
yarn fineness (decitex).
Here, T, the number of twists per metre of yarn length, is
the value determined by untwisting the yarn with an
electrically-powered twist detector under a 90 x 10-3 cN/dtex
load, and dividing the number of 'untwists' when the yarn is
completely untwisted by the yarn length following untwisting.
The form of the fabric of the present invention may be that
of a woven material, knitted material, nonwoven material or
cushion material, etc, with suitable selection being made
according to the objectives, and'the fabric can be used in
shirts, blouses, trousers, suits, blousons and the like.
Next, an example of the method of producing the polyester
yarn of the present invention is provided.
As the method for producing the PTT which is the starting
material for the polyester yarn of the present invention,
there can be used a known method as it is. The intrinsic
viscosity [rl] of the PTT employed needs to be at least 0.7 in
order to raise the spinnability at the time of yarn
production and in order to obtain yarn of practical strength,
but at least 0.8 is preferred.
Furthermore, in the production of the polyester yarn of the
present invention, there may be employed continuous
polymerization and spinning whereby, following the
polymerization, the polymer is directly subjected to spinning
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and drawing, or alternatively the polymer may first be
converted into chip and dried, and then the spinning and
drawing carried out.
The spinning temperature at the time of the melt spinning is
preferably a temperature 10-60 C higher than the melting
point of the PTT in order to stabilize the discharge from the
spinneret, and more preferably the melt spinning is carried
out at a temperature equal to the melting point plus 20 to
50 C. Again, in order to suppress oligomer deposition in the
spinning and to enhance the spinning properties, there may be
optionally provided 2-20 cm below the spinneret a heat shroud
or suction device, or a means for generating an inert gas
such as air, steam or nitrogen for preventing oxidative
degradation of the polymer or spinneret contamination.
What is most important when producing the polyester yarn of
the present invention is that there be employed the direct
spin-draw method in which the drawing is immediately carried
out following spinning, without temporarily winding-up.
In undrawn yarn comprising PTT, as stated above, a change in
the internal structure begins right after spinning, with the
phenomenon referred to as package tightening occurring, and
this is a cause of differences in properties arising between
the package inner and outer layers. When the present
inventors carried out an investigation to suppress this
package tightening, they found that an effective method
comprises hauling-off the yarn at a spinning rate of at least
2,000 m/min and then, without temporarily winding up,
immediately subjecting the yarn to drawing and heat treatment,
after which it is continuously given a relaxation heat
treatment by a relaxation factor of 5 to 20%. By using this
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method, the problem of package tightening is markedly
improved, and it is possible to obtain yarn of high quality
in which differences between the package interior and
exterior layers are extremely small. Moreover, it has also
been discovered that, by subjecting the yarn to a relaxation
heat treatment at a high relaxation factor, there is obtained
soft stretch yarn which is easily stretched and has a low
Young's modulus in the elongation recovery region.
In order to reduce yarn unevenness and obtain uniform yarn
which does not tend to show defects such as dyeing variations,
it is important that the spinning rate be at least
2,000 m/min. By raising the spinning rate, the spinning
tension is raised, and by making the yarn less susceptible to
the effects of external disturbances the draw-down behaviour
is made stable. Hence, the spinning rate is preferably at
least' 3,000 m/min. Furthermore, in order to secure stable
spinnability, it is preferred that the spinning rate be no
more than 6,000 m/min.
Again, it is preferred that the draw ratio be set such that
the residual extension is at least 40%.
It is important that the relaxation factor at the time of the
relaxation heat treatment following the drawing be made at
least 6 to 20% in order to obtain the polyester yarn which is
the objective of the present invention. By carrying out a
relaxation heat treatment of at least 6% following drawing,
it is possible to accelerate the relaxation of internal
strain in the fibre, so the level of delayed relaxation of
the residual strain is low and package tightening is
suppressed. Furthermore, as explained above, by the
relaxation heat treatment, elongation is facilitated in the
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practical extension range (up to 10% extension) and it is
possible to confer outstanding characteristics in terms of
soft stretch properties. It is further preferred that the
relaxation factor be at least 8%. On the other hand, in
order to achieve stability of yarn passage in the yarn
production process, the relaxation factor is preferably no
more than 20% and more preferably no more than 18%.
The relaxation heat treatment is now explained with reference
to Figures 1 and 2.
Figure 1 is a schematic diagram of the method using a cooling
roller in the relaxation heat treatment. Following discharge
from spinneret 1, cooling is carried out in chimney 2, then
convergence and oiling effected at oiling guide 3 and the
yarn hauled-off and the temperature raised by first heated
roller 4, after which drawing and heat setting are performed
between first heated roller 4 and second heated roller 5.
Furthermore, after passing through the drawing process, by
employing the heat of second heated roller 5, a relaxation
heat treatment is carried out between the second heated
roller 5 and cooling roller 6, and winding-up performed by
winder 8. Now, in order to conduct the relaxation heat
treatment still more efficiently, carrying out the relaxation
treatment using a heat treatment means employing hot air or
steam as a heating medium between the second heated roller 5
and cooling roller 6, or carrying out the relaxation
treatment in two stages by providing a third heated roller,
are effective means for realizing the objective of the
present invention.
Figure 2 is a schematic diagram of a method employing an
interlacing nozzle in the relaxation heat treatment, and
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interlacing nozzle 7 has the role of a yarn cooling device
and of a tension gradient controller. That is to say, by
means of the interlacing treatment it is possible to lower
the yarn tension prior to interlacing, so by utilizing the
shrinkage stress produced by the heat of second heated roller
5 it is possible to perform a relaxation heat treatment
between the second heated roller 5 and interlacing nozzle 7.
In such circumstances, the relaxation factor can be
controlled by varying the actuating air pressure of the
interlacing nozzle. Again, the relaxation treatment may also
be carried out using a heat treatment means employing hot air
or steam as a heating medium between the second heated roller
5 and interlacing nozzle 7, or in two stages by providing a
third heated roller.
In each case the relaxation factor is readily controlled and
they are methods which are favourably employed in obtaining
the polyester yarn of the present invention.
In the case of the heated roller (the second heated roller in
the examples illustrated in Figure 1 and Figure 2) which
serves both for the drawing and heat setting and for the
relaxation heat treatment, it is preferred that there be used
a textured roller of surface roughness 1.5S to 8S. The
surface roughness is the section value of the maximum height
(R,,,) described in JIS B0601, and 1.5S to 8S in practice
corresponds to the section values 1.6S, 3.2S, 6.3S. In terms
of maximum height, this corresponds to more than 0.8 m and
up to 6.3 pm. By making the surface roughness at least 1.5S,
the frictional coefficient between the yarn and roller is
considerably reduced and there is a suitable degree of slip,
so even at a high relaxation factor there is no winding of
the yarn back on the heating roller, and stable yarn
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production is possible. As the surface roughness becomes
higher, so yarn passage becomes more stable in the relaxation
process but, if it exceeds 8S, the yarn surface is
excessively abraded so a reduction in strength is brought
about. The surface roughness of the heated roller is more
preferably 3.2S to 6.3S (Rmax= 1.7-6.3 pm). Now, the surface
roughness is determined from measurement of the maximum
height Rma, using a Hommel Tester model T1000, made by the
Hommel Co., based on JIS B0601.
In order to produce yarn stably without yarn breaks, the
drawing temperature (the temperature of the first heated
roller) is preferably 10-50 C higher than the glass
transition temperature of the PTT, and more preferably the
drawing is carried out at the glass transition temperature
plus 20 to 40 C. The heat setting and relaxation heat
treatment temperature (the temperature of the second heated
roller) should be set within the range 90-180 C so as to
achieve the desired percentage heat shrinkage but, in order
to effect uniform relaxation of the residual stresses formed
by the drawing, a temperature in the range 105-180 C is more
preferred.
Furthermore, the spinning oil applied will contain lubricant,
emulsifier and antistatic agent, etc. Specifically, examples
include mineral oils such as liquid paraffin, fatty acid
esters such as octyl palmitate, lauryl oleate and isotridecyl
stearate, dibasic acid diesters such as dioleyl adipate and
dioctyl sebacate, esters of polyhydric alcohols such as
trimethylolpropane trilaurate and coconut oil, aliphatic
sulphur-containing esters such as lauryl thiodipropionate,
nonionic surfactants such as polyoxyethylene oleyl ether,
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76199-181
polyoxyet,hylene castor oil ether, polyoxyethylene nonyl
phenyl ether and trimethylolpropane trilaurate, anionic
surfactants such as alkyl sulphonate and alkyl phosphate type
metal salts or amine salts, sodium dioctylsulphosuccinate,
sodium alkanesulphonate, etc, tetramethylene oxide/ethylene
oxide copolymers, propylene oxide/ethylene oxide copolymers,
nonionic surfactants and the like, and there is employed a
formulation which enhances the passage through the yarn
production, warping and fabric production stages, in
particular passage through the reeds and heddles at the time
of weaving. Where required, there may also be used rust
preventives, antibacterial agents, antioxidants, penetrating
agents, surface tension lowering agents, phase reversal
viscosity lowering agents, wear preventing agents and other
such modifiers, or the like.
From the point of view of passage through subsequent
processing stages, the amount of oil applied is preferably
0.3 to 1.2 wt% in terms of the yarn.
Examples
Below, the present invention is explained in further detail
by means of examples. Now, the various property values in
the examples were determined by the following methods.
A. Intrinsic Viscosity [ij]
Using an Ostwald viscosity meter, a sample polymer was dissolved in
o-chlorophenol (abbreviated below to OCP) and the relative
viscosity Tir determined at a number of points, after which
the value at infinite dilution was obtained by extrapolation.
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76199-181
B. Strength, Extension and Young's Modulus (initial
resistance to stretching)
The sample was subjected to measurement using a Tensilon* UCT-
100 produced by the Orientec Co., under constant rate of
elongation conditions as described in JIS L1013 (Chemical
Fibre Filament Yarn Test Methods). The breaking extension
was determined from the elongation at the point showing the
maximum tenacity in the S-S curve.
Furthermore, the Young's modulus was measured under the
conditions given for the initial resistance to stretching in
7.10 of JIS L1013 (Chemical Fibre Filament Yarn Test Methods).
C. Differential Young's Modulus
This was determined by differentiation of stress with respect
to extension at points on the S-S curve obtained in B.
D. Elastic Recovery
Using a Tensilon* UCT-100 produced by the Orientec Co. and
with the clamp spacing at 20 cm, the sample was stretched to
10% of the clamp spacing at a rate of extension of 10 cm/min,
then the load immediately removed at the same rate, and the
elastic recovery determined from the hysteresis curve
recorded.
elastic recovery (%) = ( (3/a) x 100
a: elongation when stretched 10%
(3: recovered elongation up to the point when the stress
equals the initial load
E. Shrinkage Stress
*Trade-mark
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Measurement was carried out at a rate of temperature rise of
2.4 C/sec using a thermal stress measurement device produced
by Kanebo Engineering (Co.). The sample comprised a 2 x
10 cm loop and the initial tension = fineness (decitex) x 0.9
x (1/30) gf.
F. CV% of Continuous Shrinkage Factor in Yarn Lengthwise
Direction
Using an FTA500 made by the Toray Engineering Co.,
measurement was carried out with the set tension = fineness
(decitex) x 0.9 x (1/60) gf, treatment temperature = 100 C
(under steam), yarn velocity = 10 m/min and sample length =
10 m. The shrinkage was recorded on a chart and the CV% of
the continuous shrinkage factor in the yarn lengthwise
direction determined.
G. CF Value
Measurement was carried out under the conditions shown for
the Degree of Interlacing in 7.13 of JIS L1013 (Chemical
Fibre Filament Yarn Test Methods). The CF value (coherence
factor) was determined from the average value L (mm) of the
length of the interlace using the following formula, based on
50 measurements.
CF value = 1000/L
H. Degree of Crystallinity
The density was measured in accordance with the Density
Gradient Column Method in 7.14.2 of JIS L1013 (Chemical Fibre
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Filament Yarn Test Methods) and the degree of crystallinity
obtained by the following formula.
X. [~] _{dc x(d - da)}/(d x(dc - d8)) x 100
Xc: degree of crystallinity (%)
d: measured yarn density
d,: density of completely crystalline region
da: density of completely amorphous region
Here, dc = 1.387 g/cm3, da = 1.295 g/cm3
Example 1
Using the spin-draw machine shown in Figure 1, homo-PTT of
intrinsic viscosity [1] 0.96 was melted and spun from 24-hole
spinneret 1 at a spinning temperature of 265 C and, after
cooling in chimney 2 and then converging and oiling at oiling
guide 3, haul-off was performed at 3,000 m/min by means of
first heated roller 4, and having raised the temperature of
the yarn by five laps at 70 C, drawing was carried out by
means of second heated roller 5 at a drawing rate of
4800 m/min (draw ratio = 1.6). After heat-setting by five
laps at 140 C, relaxation was performed by a relaxation
factor of 10% between second heated roller 5 and cold roller
6, and then while performing an interlacing treatment at an
actuating pressure of 0.2 MPa using interlacing device 7,
wind-up was performed at 4220 m/min with winder 8, and 54
decitex, 24 filament, drawn yarn obtained. Now, for second
heated roller 5 there was used a textured roll of surface
hardness 3.2S (Rma,: 3pun ).
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~. .
The yarn production characteristics were good and there were
no yarn breaks or filament wrap-around. Furthermore, the
strength of the polyester yarn obtained was 3.6 cN/dtex, the
Young's modulus (initial resistance to stretching) was
20.8 cN/dtex, the minimum value of the differential Young's
modulus at an extension of 3-10% was 1.8 cN/dtex, and the
elastic recovery following 10% elongation was 97.8%. The
physical properties are shown in Table 1, and the stress-
strain curve and the differential Young's modulus-strain
curve are shown in Figure 3.
Moreover, when weaving was carried out as a 1/4 twill using
this multifilament yarn as the warp/weft, the weaving
characteristics and the woven material quality were good and
the material possessed light stretchability.
Example.2, Example 3
The same conditions were employed as in Example 1 except that
the drawing rate was either 4350 m/min (draw ratio = 1.45)
[Example 2] or 5000 m/min (draw ratio = 1.67) [Example 3].
The polyester yarn of Example 2 had a strength of 3.3 cN/dtex,
which was lower than that of Example 1. Other
characteristics were good in the same way as in Example 1.
Moreover, while in the case of the polyester yarn of Example
3 the number of machine stoppages at the time of weaving
increased to about twice when compared to Example 1, other
properties were good.
Example 4, Example 5
The same conditions were used as in Example 1 except that the
relaxation factor between the,second heated roller 5 and the
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cold roller 6 was made 6% [Example 4] or 18% [Example 5].
The polyester yarns of Example 4 and Example 5 were good in
terms of their yarn production properties and woven material
quality in the same way as in Example 1, and they had light
soft stretchability. In particular, the woven material of
Example 5 was even more outstanding in its softness than that
of Example 1.
Comparative Example 1
The same conditions were used as in Example 1 except that
there was employed homo-PTT of intrinsic viscosity [rj] 0.68.
The spinnability of the polyester of Comparative Example 1
was poor and there were numerous yarn breaks in the drawing
zone, so sampling was impossible.
Comparative Example 2
The same conditions were used as in Example 1 except that the
drawing rate was made 3900 m/min (draw ratio = 1.3). The
polyester yarn of Comparative Example 2 had low strength and
high bxtension, the strength being 2.9 cN/dtex and the
extension 73.5%, and furthermore its elastic recovery
following 10% stretching was low and the practical durability
after forming a fabric was poor.
Comparative Example 3, Comparative Example 4
The same conditions were used as in Example 1 except that the
relaxation factor between the second heated roller 5 and the
cold roller 6 was made 22% or 3%. In the case of the
polyester yarn of Comparative Example 3 where the relaxation
factor was 22%, there was considerable yarn oscillation over
21
CA 02358715 2001-07-12
the second heated roller and, furthermore, yarn breaks
occurred with yarn twisting around the second heated roller.
In the case of Comparative Example 4 where the relaxation
factor was 3%, differences in properties arose between the
package inner layer and outer layer due to occurrence of
package tightening, and there were variations in thickness
matching the package end face period. Furthermore, the
weaving properties were poor and the quality of the dyed
product was bad. Again, while the fabric possessed
stretchability, it exhibited elongation characteristics where
stretching was extremely difficult. The physical properties
are shown in Table 1, and the stress-strain curve and the
differential Young's modulus-strain curve are shown in Figure
4.
Comparative Example 5
The same conditions were used as in Example'1 except that the
drawing rate was made 5250 m/min (draw ratio = 1.75), cold
roller 6 was removed and the relaxation factor was made 0%.
In the case of Comparative Example 5, there was marked
package tightening exceeding even that of Comparative Example
4 and, furthermore, the fabric obtained had stretch
characteristics in which elongation was extremely difficult,
and it was inferior too in its softness.
Example 6
The same conditions were used as in Example 1 except that the
first heated roller 4 velocity was made 1000 m/min and the
second heated roller 5 velocity was made 3500 m/min (draw
ratio = 3.5). Fabric comprising the polyester yarn of
22
CA 02358715 2001-07-12
Example 6 showed good stretch characteristics in the same way
as in Example 1, but dyeing unevenness arose in the dyed
fabric which was thought to be due to yarn unevenness.
Example 7
The same conditions were used as in Example 1 except that the
second heated roller 5 was changed to a 0.8S (R,,,: no more
than 0.8 m) mirror surface roll. In the case of Example 7,
the travelling yarn in the relaxation zone between the second
heated roller and cold roller 6 was unstable, and oscillation
occurred on the second heated roller, with winding back on
the roller and numerous yarn breaks occurring. Hence,
compared to Example 1 the number of yarn breaks was about 10-
fold.
Example 8
The polyester yarn obtained in Example 1 was subjected to
2000 t/m (twist coefficient K: 14700) S/Z twisting to produce
warp and weft yarns, and then a 1/4 twill fabric was produced.
This was subjected to relaxation scouring at 98 C by the
usual method, and then intermediate setting carried out at
160 C. Subsequently, 15 wt% weight reduction was carried out
with hot aqueous 3% NaOH solution, dyeing then performed and
finish setting carried out. The fabric obtained was soft and
its stretch properties were extremely outstanding.
In the table, 'relaxation factor' refers to the 'relaxation
factor between the second heated roller and the cold roller
6'; the 'differential Young's modulus' refers to the 'minimum
value of differential Young's modulus at an extension of 3 to
23
CA 02358715 2001-07-12
10t'; the 'elastic recovery' refers to the 'elastic recovery
following 10% elongation'; the 'shrinkage stress' refers to
the 'maximum value of shrinkage stress'; the 'peak
temperature' refers to the 'temperature showing the maximum
value of shrinkage stress'; the 'shrinkage CV%' refers to the
'CV% of the lengthwise direction continuous shrinkage'; and
the 'woven fabric quality' refers to the 'quality of the
appearance of the woven fabric after dyeing (functional
evaluation)'.
Industrial Applicability
With regard to the polyester yarn of the present invention
and its method of production, as well as there being no
package tightening in the yarn production stage and the
package having a stable quality, it is possible to obtain
woven fabric of low Young's modulus in the elastic recovery
region and which is outstanding in its soft-stretch
properties and softness.
24
CA 02358715 2001-07-12
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