Note: Descriptions are shown in the official language in which they were submitted.
CA 02564128 2006-10-23
DESCRIPTION
HIGH-STRENGTH SPANIZED YARN AND METHOD FOR PRODUCING THE SAME
TECHNICAL FIELD
The present invention relates to a spanized yarn and a
method for producing the same. More specifically, it relates
to such a spanized yarn that has a high strength maintenance
rate of a base yarn and suffers less fluctuation in strength,
and such a method that is capable of producing the spanized
yarn stably.
BACKGROUND ART
A high-strength fiber represented by a para-type wholly
aromatic polyamide fiber is applied to a spun yarn for a
protective clothing material in the field of clothing
materials owing to the high heat resistance and the high
incision resistance. However, a spun yarn using the
conventional high-strength fiber such problemsthat it suffers
considerable decrease in strength of the processed yarn as
compared to the base yarn before processing (i.e., low in
strength maintenance rate), and causes a large amount of
surface fluff specific to a spun yarn. Accordingly, it is
difficult to apply to such a purpose that requires a spun yarn
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CA 02564128 2006-10-23
having a high strength and causing a less amount of surface
fluff.
The strength of a spun yarn is generally in proportion
to the strength of the single yarn (base yarn) constituting
the spun yarn and the average yarn length of the single yarn.
It. is preferred that the strength maintenance rate is improved
by increasing the average yarn length of the constitutional
single yarn since there is a limitation in improving the
strength of the base yarn, but the single yarn length in the
conventional spun yarn is generally 100 mm or less, and the
strength maintenance rate of a spun yarn constituted by such
a short fiber is 500 or less at most.
However, the use of a single yarn (short fiber) having
a .length larger than the above encounters not only difficulty
in production of a spun yarn, but also such a problem that the
simple prolongation in single yarn length brings about
stiffness specific to a high-strength fiber to make uniform
orientation difficult, and thus the strength maintenance rate
is rather decreased.
In order to solve the problem, JP-B-1-16932 proposes a
thread that is like a wholly aromatic polyamide spun yarn that
is applied with conjugation property and is formed of a fiber
having an average single yarn length of from 130 to 600 mm,
which is obtained by tearing a continuous thread into a short
fiber. However, according to investigations made by the
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present inventors, upon producing a thread that is like a spun
yarn of, for example, a poly-p-phenyleneterephthalamidefiber
under the conditions described in the publication, it has been
found that such a problem arises that the strength maintenance
rate and the amount of surface fluff are liable to fluctuate.
That is, in the case where a poly-p-phenylene terephthalamide
fiber is used as the wholly aromatic polyamide fiber, the tow
is considerably expanded upon spanizing due to static charge
formed by friction of the single yarns and causes turbulence
on a roller to make uniform spanizing difficult. As a result,
the fluctuation in single yarn length is increased to decrease
the strength maintenance rate, and thus even though a high
strength fiber is used, such problems occur that the spanized
yarn is decreased in strength, the fluctuation in strength is
increased, and the amount of surface fluff is significantly
increased.
The problem of decrease in strength maintenance rate can
be improved by increasing the average single yarn length, but
it is necessary therefor to increase the spanizing length,
which brings about such a problem that the tow is further liable
to expand between rollers to make the yarn liable to twist
around the feeding roller and the spanizing roller, and thus
the spanizing process cannot be stably carried out.
As having been described, it is the current situation
that there have not been proposed such a high strength spanized
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yarn having high quality and a method for producing the same
that is produced with a fiber liable to cause static charge
due to friction of single yarns, such as a poly-p-phenylene
terephthalamide fiber, to have a large average single yarn
length with a small fluctuation in single yarn length.
DISCLOSURE OF THE INVENTION
An object of the invention is to solve the problems
associated with the conventional art to provide such a high
strength spanized yarn having high quality and a method for
stably producing the spanized yarn that has a high maintenance
rate in strength of a base yarn and a small fluctuation in single
yarn length.
As a result of cumulative investigations for solving the
problems made by the inventors, the invention has been
completed.
Accordingly, the object of the invention is attained by
a high strength spanized yarn constituted by a high strength
short fiber containing at least one polymer selected from the
group consisting of poly-p-phenylene terephthalamide,
poly-p-phenylene benzoxazole, polyethylene, polyvinyl
alcohol and wholly aromatic polyester and having a strength
of 14 cN/dtex or more, characterized in that the high strength
short fiber has an average single yarn length of from 50 to
90 cm and a coefficient of variation (CV) in average single
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yarn length of 50 0 or less; and a method for producing a high
strength spanized yarn characterized by containing steps of
tearing a high strength fiber containing at least one polymer
selected from the group consisting of poly-p-phenylene
terephthalamide, poly-p-phenylenebenzoxazole, polyethylene,
polyvinyl alcohol and wholly aromatic polyester and having a
strength of 14 cN/dtex or more, between a pair of a feeding
roller and a spanizing roller with a distance between the
rollers of from 100 to 200 cm, to which a moistening fluid having
a humidity of 80 0 or more is applied, and withdrawing the fiber
with conjugation through a fluid nozzle.
BRIEF DESCRIPTION OF THE DRAWING
Fig. 1 is a side elevational view showing an example of
a spanizing apparatus used for producing a high strength
spanized yarn according to the invention.
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the invention will be described in
detail below.
The high strength short fiber constituting the spanized
yarn of the invention necessarily has a strength of 14 cN/dtex
or more, and preferably from 18 to 50 cN/dtex. In the case
where the strength is less than 14 cN/dtex, the strength as
the spanized yarn becomes insufficient to fail to attain the
CA 02564128 2006-10-23
object of the invention. Examples of the high strength short
fiber that is preferably used include a poly-p-phenylene
terephthalamide short fiber, a poly-p-phenylene benzoxazole
short fiber, a high strength polyethylene short fiber, a high
strength polyvinyl alcohol short fiber and a wholly aromatic
polyester short fiber, which may be used as a mixture of two
or more kinds thereof. Among these, a poly-p-phenylene
terephthalamide short fiber is preferred.
In the case where the single yarn fineness of the high
strength short fiber is too large, the number of single yarns
constituting the spanized yarn is decreased to lower the
strength of the spanized yarn due to the reduced entanglement
of the single yarns, and therefore, it is desirably 2.5 dtex
or less, preferably 1.1 dtex or less, and more preferably 0.8
dtex or less.
The average single yarn length of the high strength short
fiber constituting the spanized yarn of the invention is
necessarily in a range of from 50 to 90 cm, and particularly
in a range of from 60 to 80 cm. In the case where the average
single yarn length is less than 50 cm, the strength maintenance
rate (strength of spanized yarn/strength of short fiber) of
the spanized yarn with respect to the strength of the short
fiber (base yarn) is decreased to fail to exhibit the strength
of the base yarn sufficiently. In the case where the average
single yarn length exceeds 90 cm, on the other hand, the
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spanizing length upon spanizing is necessarily 2.0 m or more
for obtaining such spanized yarn, and as a result, the tow at
the spanizing portion is considerably unraveled to cause
winding on a roller frequently, which impairs stable
spanlzlng.
The high strength spanized yarn of the invention
necessarily has a coefficient of variation (CV) in single yarn
length of 500 or less, and particularly 400 or less. In the
case where the coefficient of variation (CV) exceeds 50 0, the
fluctuation in single yarn length becomes too large the
strength of the spanized yarn fluctuates, that is, the standard
deviation of the strength becomes large because thereby
failing to attain the object of the invention, i.e., the
provision of a uniform spanized yarn with high quality.
The high strength spanized yarn of the invention
preferably has a strength maintenance rate of 70 0 or more . In
the case where the spanized yarn is constituted by plural kinds
of short fibers, the strength maintenance rate referred herein
is a maintenance rate with respect to the strength of the short
fiber having a lower strength. In the case where the
maintenance rate is less than 70%, not only the strength of
the short fiber (base yarn) cannot be effectively exhibited,
but also the amount of surface fluff is increased due to the
short constitutional single yarn length, which restricts the
application of the spanized yarn.
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A preferred method for producing the spanized yarn of
the invention will be described in detail with reference to
the drawing. Fig. 1 shows a spanizing apparatus that is
preferably used for producing the high strength spanized yarn
according to the invention. Numeral 1 denotes a feeding nip
roller, 2 represents a shooter, 3 denotes a spanizing nip roller,
4 denotes a suction air nozzle, 5 denotes a revolving
conjugation nozzle, 6 denotes a delivery roller, 7 denotes a
wound spanized yarn, and 8 denotes a high strength fiber.
A prescribed number of the high strength fibers are
arranged before the feeding nip roller, and after superposing
while passing through the feeding nip roller, they are spanized
(tearing process) in the shooter. At this time, a moistening
fluid having a humidity of 800 or more, such as damp air, is
fed into the shooter to apply to the high strength fibers.
Subsequently, the fibers are drawn off through the spanizing
nip roller with the suction air nozzle, and applied with
conjugation property with entanglement and fluff winding
through the revolving conjugation nozzle, followed by
withdrawing with the delivery roller.
The high strength fiber is formed into the short fiber
through spanizing as having been described, and the strength
thereof is necessarily 14 cN/dtex or more, and preferably from
18 to 50 cN/dtex or more. In the case where the strength is
less than 14 cN/dtex, the strength of the short fiber after
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spanizing becomes insufficient to fail to provide the spanized
yarn of the invention. Examples of the high strength fiber
that is preferably used include, as having been described, a
poly-p-phenylene terephthalamide fiber, a poly-p-phenylene
benzoxazole fiber, a high strength polyethylene fiber, a high
strength polyvinyl alcohol fiber and a wholly aromatic
polyester fiber, which may be used as a mixture of two or more
kinds thereof. Among these, a poly-p-phenylene
te~rephthalamide fiber is preferred.
In the invention, the high strength fiber is preferably
attached with an oily agent in an amount of from 0. 05 to 0. 5 0
by weight based on the weight of the fiber, and the attached
oily agent preferably has a water content of 7.0o by weight
or' less. In the case where the attached amount of the oily
agent is less than 0. 05 o by weight, the fiber is liable to be
statically charged in the tearing process described later,
whereby the tow is unfastened with repulsion due to static
charge to cause breakage of yarn frequently, and thus it is
difficult to carry out spanizing stably. In the case where
the attached amount of the oily agent exceeds 0 . 5 o by weight,
the tow is not sufficiently unraveled due to the effect of the
oily agent of unspreading the fiber, which might bring about
large fluctuation in length of the single yarns constituting
the spanized yarn. In the case where the water content of the
attached oily agent exceeds 7.0o by weight, the similar
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phenomenon might occur as in the case where the attached amount
of the oily agent exceeds 0.5o by weight, due to the effect
of the water content of unspreading the fiber.
In the invention, after forming the short fiber by
tearing the high strength fiber between the feeding roller and
the spanizing roller, it is necessary that the yarns of the
short fibers are withdrawn with conjugation by the fluid nozzle
to prevent the yarns from being drawn out in the longitudinal
direction (withdrawing direction) while preventing
disturbance in arrangement of fibers from occurring. In the
tearing process, in order to prevent as much as possible the
arrangement of the torn short fibers from being disturbed, it
is preferred that, for example, the short fibers are covered
with a guide having a funnel shape.
It is important in the invention that in the tearing
process, a moistening fluid, and preferably damp air, having
a humidity of 800 or more, preferably 900 or more, and
particularly preferably 950 or more, is applied to the high
strength fiber. In the case where the humidity of the
moistening fluid is less than 80 0, it is not preferred since
the effect of discharging static charge on the surface of the
fiber is reduced, whereby the tow is unfastened with repulsion
among the fibers to make the single yarns liable to twist around
the feeding roller and the spanizing roller, and thus it is
difficult to carry out spanizing stably. In order to reduce
CA 02564128 2006-10-23
fluctuation in spanizing length, it is necessary that the fiber
is uniformly unraveled on the surface of the spanizing roller,
but excessive unraveling brings about the single yarns
twisting around the feeding roller and the spanizing roller,
and therefore, the application of the moistening fluid is
important.
The distance (spanizing length) between the pair of the
feeding roller and the spanizing roller is necessarily in a
range of from 100 to 200 cm, and preferably in a range of from
120 to 175 cm. In the case where the spanizing length is less
than 100 cm, the average single yarn length of the resulting
spanized yarn is less than 40 cm, and the strength maintenance
rate of the base yarn becomes less than 70 0, so as to fail to
attain the object of the invention. In the case where the
spanizing length exceeds 200 cm, on the other hand, it is not
preferred since the tow width between the feeding roller and
the spanizing roller is extremely expanded to make the single
yarn liable to twist around the spanizing roller, and thus it
is difficult to carry out spanizing stably.
The spanized yarn of the invention having been described
hereinbefore may be suitably twisted and woven as a warp yarn
and/or a weft yarn into a desired density, followed by
subjecting to refining, heat setting, relaxing, calendering
and the like, to obtain a fabric.
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EXAMPLE
The constitution and advantage of the invention will be
described in more detail with reference to examples below. The
properties in the examples were obtained in the following
manner.
(1) Fineness, Breaking Strength, Breaking Elongation and
Elastic Modulus
The parameters were measured according to JIS L1013,
where the twisted number was 250 t/m.
(2) Single Yarn Length
120 threads of the single yarns were randomly withdrawn
from the spanized yarn while preventing breakage, and an
average value of the lengths of the extended single yarns was
obtained.
(3) Coefficient of Variation (CV) in Single Yarn Length
The coefficient of variation was obtained by calculating
from the standard deviation (a) and the average yarn length
(X) of the 120 threads of the single yarns obtained in the
aforementioned manner, according to the following equation.
Coefficient of variation (CV) in single yarn length (o) - 6
/ X x 100
(4) Number of Breakage of Yarn
As an index of the process conditions, a number of
breakage of the yarn (breakage by twisting around the feeding
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roller or the spanizing roller) upon carrying out the spanizing
process for 8 hours was measured.
(Examples 1 to 3 and Comparative Examples 1 to 3)
By using the apparatus shown in Fig. 1, two threads of
poly-p-phenylene terephthalamide fibers (Twaron, produced by
Teijin Twaron B.V. ) each having a total fineness of l, 100 dtex
and a strength of 21 cN/dtex with the single yarn fineness and
the oily agent attached amount as shown in Table 1 were arranged
and torn among the feeding nip roller, the shooter and the
spanizing nip roller at a speed of 300 m/min with damp air
applied thereto to make a spanizing rate of about 10 times with
variation of the distance between the roller (spanizing
length) and the humidity of the damp air as shown in Table 1,
so as to obtain a bundle of short fibers.
Subsequently, the short fibers were passed through the
SLlCtion air nozzle and the revolving conjugation nozzle to make
a speed ratio between the spanizing nip roller and the delivery
roller of 100/99.5 to apply entanglement and to wind fluff of
short fibers randomly, so as to obtain a spanized yarn of about
22.0 dtex. The physical properties of the spanized yarn are
shown in Table 1.
(Comparative Example 4)
By using the apparatus shown in Fig. l, two threads of
copoly-p-phenylene-3,4'-oxydiphenylene terephthalamide
fibers (Technora, produced by Teijin Techno Products, Ltd.)
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each having a single yarn fineness of 0.84 dtex, a total
fineness of 1,100 dtex, a strength of 25 cN/dtex and an oily
agent attached amount of 0 . 2 o by weight were arranged and torn
among the feeding nip roller, the shooter and the spanizing
nip roller with a distance between the rollers (spanizing
length) of 120 cm at a speed of 300 m/min with damp air having
a humidity of 50 o applied thereto to make a spanizing rate of
about 10 times, so as to obtain a bundle of short fibers.
Subsequently, the short fibers were passed through the
suction air nozzle and the revolving conjugation nozzle to make
a speed ratio between the spanizing nip roller and the delivery
roller of 100/99.5 to apply entanglement and to wind fluff of
short fibers randomly, so as to obtain a spanized yarn of about
220 dtex. The physical properties of the spanized yarn are
shown in Table 1.
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Table 1
Unit Example Example Example
1 2 3
Kind of
base Twaron Twaron Twaron
yarn
Fineness
of dtex 1.1 1.1 1.1
Base single
yarn yarn
Oily agent
attached % by weight0.2 0.2 0.2
amount
Spanizing 120 150 175
cm
Spanizinglength
conditionHumidit
of 95 95
y
% 95
damp air
Fineness dtex 221 222 220
Strength cN/dtex 15.4 16.1 16.8
Average 51 61 75
single
yarn lengthcm
Coefficient
of
variation % 34 35 39
in
single
yarn
anized length
S
p Strength
yarn 80
maintenance% 73 77
rate
Standard
deviation cN/dtex 1.1 1.2 1.5
of
strength
Number
of
breakage per hour 0 0 0
of
yarn (8h)
CA 02564128 2006-10-23
Table 1 (continued)
ComparativeComparativeComparativeComparative
Unit Example Example Example Example
1 2 3 4
Kind of
base
Twaron Twaron Twaron Technora
yarn
Base Fineness
of
yarn dtex 1.1 1.1 1.1 1.1
single yarn
Oily agent % by
0.2 0.2 0.2 0
2
attached weight .
amount
Spanizing cm 40 80 150 120
length
Spanizing
Humidity
conditionof % 95 95 50 50
damp air
Fineness dtex 222 223 218 221
Strength cN/dtex11.1 12.1 15.9 19.8
Average
single
cm 19 42 55 50
yarn length
Coefficient
of
variation
in
% 30 31 63 34
single yarn
Spanizedlength
yarn Strength
maintenance% 44 48 76 79
rate
Standard
deviation cN/dtex1.3 1.1 3.5 1.3
of
strength
Number of
breakage per 0 0 3 0
of yarn
(8h) hour
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INDUSTRIAL APPLICABILITY
According to the invention, such a spanized yarn can be
obtained that has a high strength maintenance rate of the
spanized yarn with respect to the strength of the high strength
short fiber as compared to the conventional spanized yarn with
srr4a11 fluctuation in single yarn length thereof, so as to
provide, for example, a protective clothing material of high
quality in the field of protective clothing material.
According to the production method of the invention, the high
strength spanized yarn can be stably produced.
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