TECHNICAL FIELD
[0001] The present invention relates to a polyamide fiber for forming, for example, clothing
for sports and underwear, and a fiber structure formed using the polyamide fiber.
BACKGROUND ART
[0002] Known synthetic fibers, for example, polyester fibers, and polyamide fibers such
as nylon-6 and nylon-6,6, are used not only for clothing, but also for a wide range
of industrial purposes due to their good physical and chemical properties. These fibers
are of high industrial value.
[0003] Unfortunately, these synthetic fibers are low in moisture absorbency and water absorbency,
which actually limits their applications to clothing which are required to be absorbent
of moisture and water, such as underwear, intermediate garment, bed sheets, and towels.
In view of this, for polyester fibers, for example, some methods have been proposed
for improving the low moisture absorbency and water absorbency, which can be referred
to as the main shortcoming of the polyester fibers.
[0004] More specifically, the proposed methods include, for example, a method in which polyester
fibers are post-treated using a hydrophilic post-processing agent, and a method in
which polyester fibers are caused to have pores in their surfaces or interiors to
obtain moisture absorbency and water absorbency. However, according to these methods,
the moisture absorbency and water absorbency are insufficiently improved, and the
properties provided to the fibers are deteriorated by washing.
[0005] Some methods have been proposed to solve the above problems. According to such methods,
an ethylene-vinyl alcohol-based copolymer, which is obtained by saponifying an ethylene-vinyl
acetate-based copolymer, is conjugated with another thermoplastic polymer such as
polyester, polyamide, or polyolefin, and the resultant conjugated material is formed
into fibers, thereby improving dimensional stability (see, for example, Patent Documents
1-3).
CITATION LIST
PATENT DOCUMENTS
SUMMARY OF THE INVENTION
TECHNICAL PROBLEM
[0007] However, the ethylene-vinyl alcohol-based copolymer according to the above-described
known techniques has insufficient resistance to moist heat, which disadvantageously
limits its applications.
[0008] Meanwhile, regarding nylon fibers used in underwear, socks, and other clothing, it
is difficult to improve comfort of a fiber structure and clothing containing nylon
fibers sufficiently by simply providing the nylon fibers themselves with moisture
absorbency. Therefore, there is an increasing demand for moisture-absorbing, and water-absorbing
extensible fibers capable of controlling humidity.
[0009] In view of the foregoing background, it is therefore an object of the present invention
to provide a highly moisture-absorbent polyamide fiber which extends and contracts
significantly in a reversible manner upon absorbing and releasing water, and from
which a highly comfortable fiber structure can be produced. The present invention
also aims to provide a fiber structure and clothing which are formed using the polyamide
fiber.
SOLUTION TO THE PROBLEM
[0010] To achieve the object, a polyamide fiber of the present invention has a degree of
orientation equal to or higher than 0.7 and equal to or lower than 0.85.
ADVANTAGES OF THE INVENTION
[0011] The present invention provides a fiber structure which controls humidity highly effectively
and provides more comfort than ever.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012]
[FIG. 1] FIG. 1 is a photograph of an exemplary cross section of a conjugated fiber
for obtaining a fiber of the present invention.
[FIG. 2] FIG. 2 is a photograph of an exemplary cross section of a conjugated fiber
for obtaining a fiber of the present invention.
[FIG. 3] FIG. 3 is a photograph of an exemplary cross section of a conjugated fiber
for obtaining a fiber of the present invention.
[FIG. 4] FIG. 4 is a photograph of an exemplary cross section of a conjugated fiber
for obtaining a fiber of the present invention.
DESCRIPTION OF EMBODIMENTS
[0013] A polyamide fiber of the present invention has a degree of orientation equal to or
higher than 0.7 and equal to or lower than 0.85. If the degree of orientation were
lower than 0.7, sufficient colorfast could not be obtained. If the degree of orientation
were higher than 0.85, the fiber would reversibly extend and contract in an insufficient
manner upon absorbing and releasing water. This would cause the stitches in woven
or knitted fabric to open and close insufficiently and make it impossible to obtain
a highly comfortable fiber structure.
[0014] Thus, a fiber structure such as woven or knitted fabric is produced using the polyamide
fibers having a degree of orientation equal to or higher than 0.7 and equal to or
lower than 0.85. When absorbing sweat, for example, the polyamide fibers extend to
cause the stitches in the woven or knitted fabric to open, thereby releasing humidity
inside the clothing. When dried, the polyamide fibers contract to restore the original
length and cause the stitches to close, thereby preventing heat from being released
outside the clothing. Thus, the use of the polyamide fibers of the present invention
may provide woven or knitted fabric which is highly comfortable and has a so-called
self-control function.
[0015] Note that the degree of orientation of the polyamide fiber is beneficially equal
to or higher than 0.72, and more beneficially equal to or higher than 0.75. Further,
the degree of orientation of the polyamide fiber is beneficially equal to or lower
than 0.83, more beneficially equal to or lower than 0.8, and still more beneficially
lower than 0.80. The degree of orientation of the polyamide resin is calculated by
a measurement method which will be described later with reference to examples.
[0016] The polyamide fiber of the present invention beneficially has a moisture absorption
rate equal to or higher than 5% at a temperature of 35°C and a humidity of 95%RH,
and a water absorption extension rate equal to or higher than 5% at a temperature
of 20°C and a humidity of 65%RH. A moisture absorption rate lower than 5% would cause
a user to feel stickiness and sweatiness. A water absorption extension rate lower
than 5% would cause the fiber to reversibly extend and contract in an insufficient
manner upon absorbing and releasing, and would prevent stitches in woven or knitted
fabric from opening and closing sufficiently. Such moisture absorption rate and water
absorption extension rate make it impossible to obtain a highly comfortable fiber
structure.
[0017] Thus, the use of the polyamide fiber having the above-specified moisture absorption
rate and water absorption extension rate may enable the production of a fiber structure
such as woven or knitted fabric, which has the self-control function described above
and provides more comfort.
[0018] Excessive increases in the moisture absorption rate and the water absorption extension
rate tend to reduce wash-fastness, weather resistance, light resistance, and chemical
resistance, for example. In view of this, the moisture absorption rate is beneficially
equal to or higher than 5% and equal to or lower than 30%, and more beneficially equal
to or higher than 8% and equal to or lower than 25%. The water absorption extension
rate is beneficially equal to or higher than 5%, more beneficially equal to or higher
than 7%, still more beneficially equal to or higher than 8%, and particularly beneficially
equal to or higher than 10%. Further, the water absorption extension rate is beneficially
equal to or lower than 30%, more beneficially equal to or lower than 25%, and still
more beneficially equal to or lower than 20%. The moisture absorption rate and the
water absorption extension rate of the polyamide resin are measured according to a
measurement method which will be described later with reference to the examples.
[0019] The polyamide fiber has a crimp extension rate which is beneficially equal to or
higher than 1.5% and equal to or lower than 10%, more beneficially equal to or higher
than 2% and equal to or lower than 8%, and still more beneficially equal to or higher
than 2.5% and equal to or lower than 5.8%. A crimp extension rate equal to or higher
than 1.5% and equal to or lower than 10% provides silk-like feel and texture, and
makes fabric soft and pleasant to the touch.
[0020] Examples of the polyamide to be used in the present invention include: polycaproamide
(nylon-6), poly-ω-aminoheptanoic acid (nylon-7), polyundecaneamide (nylon-11), polyethylene
diamine adipamide (nylon-2,6), polytetramethylene adipamide (nylon-4,6), polyhexamethylene
adipamide (nylon-6,6), polyhexamethylene sebacamide (nylon-2,10), polyhexamethylene
dodecamide (nylon-6,12), polyoctamethylene adipamide (nylon-8,6), polydecanomethylene
adipamide (nylon-10,6), and polydodecamethylene sebacamide (nylon-10,8). Examples
of the polyamide- further include: caprolactam/lauric lactam copolymer (nylon-6/12),
caprolactam/ω-aminononanoic acid copolymer (nylon-6/9), caprolactam/hexamethylene
adipate copolymer (nylon-6/6,6), lauric lactam/hexamethylene diamine adipate copolymer
(nylon-12/6,6), hexamethylene diamine adipate/hexamethylene diamine sebacate copolymer
(nylon-6,6/6,10), ethylenediamine adipate/hexamethylene diamine adipate copolymer
(nylon-2,6/6,6), and caprolactam/hexamethylene diamine adipate/hexamethylene diamine
sebacate copolymer (nylon-6,6/6,10).
[0021] Among these substances, nylon-6 and nylon-6,6 are most suitable as the polyamide
of the present invention. Nylon-6 is still more beneficial because it is unexpansive
and versatile, and has high moisture absorbency. Among the above copolymers, nylon-6/6,6
and nylon-6/12 are beneficial. Although the composition ratio between the component
having a carbon number of 6 and the component having a carbon number of 12 that form
the nylon-6/12 is not particularly limited, the component having a carbon number of
12 beneficially constitutes 50 mol% or less, and more beneficially 40 mol% or less.
[0022] The polyamide copolymers may be caused to contain an anti-static agent, a lubricant,
an anti-blocking agent, a stabilizer, a dye, or a pigment, for example.
[0023] The polyamide fiber of the present invention may be produced by any method as long
as the polyamide fiber has the above-described degree of orientation, moisture absorption
rate, and water absorption extension rate. For example, a polyamide component (component
A) and another soluble component (component B) are formed into a conjugated fiber,
and thereafter, the component B is dissolved and removed, thereby suitably producing
the polyamide fiber of the present invention. The use of such a conjugated fiber enables
the control of the structure of the polyamide component, thereby enabling the production
of a fiber which is exclusively made of polyamide, has a specific degree of orientation,
high moisture absorbency and high water absorption extensibility, and is capable of
reversibly extending and contracting upon absorbing and releasing water.
[0024] If the polyamide fiber of the present invention is produced from the conjugated fiber
as described above, the other component, i.e., the soluble component (component B)
plays an important role in the structure control. An exemplary polymer which can be
used as the component B is a water-soluble thermoplastic polyvinyl alcohol-based polymer.
This polyvinyl alcohol-based polymer beneficially has a viscosity average degree of
polymerization of 200-500, a degree of saponification of 90-99.99 mol%, and a melting
point of 160-230°C. Although the polyvinyl alcohol-based polymer may be a monopolymer
or a copolymer, it is recommended to use a copolymerized polyvinyl alcohol which is
0.1-20 mol% modified by α-olefin having a carbon number of 4 or less such as ethylene
or propylene, in order to ensure ease of melt spinning, water solubility, and fiber
physical properties. The polyamide fiber of the present invention can be suitably
obtained by removing, by using hot water, the water-soluble thermoplastic polyvinyl
alcohol-based polymer from the conjugated fiber including the component B.
[0025] A polyester-based polymer which is soluble in alkali at a high speed (easily alkali-soluble
polyester-based polymer) is another example which can be used as the component B.
Examples of such an easily alkali-soluble polyester-based polymer include a polylactic
acid, and copolymerized polyester formed by copolymerizing 1-5 mol% of 5-sodium sulfoisophthalic
acid, 5-30 wt.% of polyalkylene glycol, a conventionally used diol component, and
a conventionally used dicarboxylic acid component. From a conjugated fiber containing
this component B, the polyamide fiber of the present invention may be suitably obtained
by the removal of the easily alkali-soluble polyester-based polymer by alkaline treatment.
[0026] It is beneficial that the conjugated fiber for producing the polyamide fiber of the
present invention has a fiber cross section of which 50% or more is coated with the
soluble component (component B). It is more beneficial that the entire cross section
is coated with the soluble component (component B). That is to say, the conjugated
fiber beneficially has a sheath-core cross section in which the polyamide component
forms the core and the component B forms the sheath, or a sea-island cross section
in which the polyamide component forms the islands and the component B forms the sea.
[0027] A conjugate ratio (A:B) of the conjugated fiber of the present invention between
the polyamide component (A component) and the soluble component (B component) ranges
beneficially from 90:10 to 40:60 (weight ratio), and more beneficially from 80:20
to 60:40 (weight ratio). The ratio may be adjusted according to fiber shapes. Note
that if the component B is used in a small amount, it may become difficult to control
the polyamide structure. This may makes it impossible to achieve desired moisture
absorbency and water absorption extensibility, resulting in difficulty in humidity
control.
[0028] The cross section of the conjugated fiber of the present invention is not particularly
limited, provided that the component B is dissolved and removed by hot water treatment
or alkali treatment, and cracks are not caused in the component A. The cross section
may be of a concentric, eccentric, or multi-centric type, for example. Further, the
cross section may have, besides the circular shape shown in FIGS. 1 and 2, a multifoil
shape shown in FIG. 3, or a modified shape such as a triangle or flat shape. Furthermore,
as shown in FIG. 4, the component A may include therein a hollow portion. The cross
section may have one or multiple hollow portions, without causing any problem.
[0029] The polyamide fiber of the present invention may beneficially have a monofilament
size of 0.03-10 dtex, which is not limiting. The polyamide fiber of the present invention
may be used not only as a long fiber, but also as a short fiber or a short-cut fiber.
[0030] Once a combination of a polyamide component (component A) and the other component,
i.e., the soluble component (component B), is determined, the conjugated fiber of
the present invention may be formed by using a known conjugated fiber-spinning machine.
[0031] Setting of fiber formation conditions is important to obtain the fiber of the present
invention. It is most suitable to form the fiber by direct spinning and drawing method
at a high speed. If the fiber is melt spun at a low or intermediate speed, and subjected
to drawing thereafter, the temperature of heat treatment for the drawing is set to
a temperature lower than 100°C, and beneficially to 80°C or lower, and the drawing
rate is set to a rate lower than 2. If drawing and false twisting are performed at
the same time or continuously after the spinning, the temperature of the heat treatment
is also set to a temperature lower than 100°C, and beneficially to 80°C or lower,
and the drawing rate is limited to a rate lower than 2. If the temperature were set
to 100°C or higher, or if the drawing rate were set to 2 or higher, it would be difficult
to control the polyamide structure, and desired degree of orientation, moisture absorbency,
and water absorption extensibility could not be achieved.
[0032] The polyamide fiber of the present invention may be used to form various types of
fiber structures (fiber aggregates). Here, the "fiber structure" may be configured
as a multifilament thread, a spun yarn, woven or knitted fabric, non-woven fabric,
paper, synthetic leather, and wadding which are exclusively made of the polyamide
fiber of the present invention. Alternatively, the "fiber structure" may be configured
as: woven or knitted fabric or non-woven fabric, part of which is made of the polyamide
fiber of the present invention; combined woven or knitted fabric additionally containing
fibers of a different type such as natural fibers, artificial fibers, synthetic fibers,
or semi synthetic fibers; and woven or knitted fabric, cotton-containing non-woven
fabric, or fiber layered product in which the polyamide fibers of the present invention
are used as a finished yarn such as a blended yarn, a doubling-and-twisted yarn, a
confound yarn, or a crimp yarn.
[0033] The weight ratio of the polyamide fiber of the present invention with respect to
the entire woven or knitted fabric or non-woven fabric is beneficially 15 wt. % or
more, more beneficially 18 wt.% or more, particularly beneficially 23 wt.% or more.
After woven or knitted into fabric, or formed into a non-woven fabric, the fibers
of the present invention may be subjected to napping treatment by means of wire raising
or any other finishing.
[0034] If the polyamide fiber of the present invention is produced via the conjugated fiber
described above, a fiber structure may be formed using the fiber which contains polyamide
alone and from which the component B has been removed. Alternatively, the component
B may be removed from a fiber structure which has been formed using the conjugated
fiber.
EXAMPLES
[0035] The present invention will be described more specifically below with reference to
examples.
(Example 1)
(Production of Polyamide Fibers)
[0036] Nylon-6 having a reduced viscosity of 1.80 dL/g (at a concentration of 1g/dL in orthoclorophenol
at 30°C) was used as a polyamide component (component A), and a thermoplastic modified
polyvinyl alcohol (modified PVA) (product of Kuraray Co., Ltd. having a saponification
degree of 98.5, an ethylene content of 8.0 mol%, and a degree of polymerization of
390) was used as a soluble component (component B). The components A and B were separately
melted in different extruders, and a conjugated fiber having a cross section shown
in FIG. 1 was injected through a multi-component fiber-spinning nozzle with a ratio
of nylon-6:modified PVA set at 60:40 (weight ratio). Subsequently, a thread injected
through a spinneret was cooled using a horizontal cooling air blower having a length
of 1.0 m. Thereafter, water-free spinning oil including, as its components, an anti-static
agent and a lubricating agent was applied to the thread. The thread was then wound
using a roller at a take-off speed of 3500 m/min. In this manner, a conjugated fiber
(111 dtex/24 filaments) was produced. Note that the process steps of fiber production
were performed smoothly. The produced conjugated fiber was knitted into cylindrical
fabric by a circular knitting machine (28 gauge). The resultant knitted fabric was
subjected to a scouring step using hot water (90°C, 20 minutes) to dissolve and remove
the modified PVA. In this manner, the polyamide fiber of the present invention was
produced.
(Measurement of Degree of Orientation)
[0037] Next, the degree of orientation of the produced polyamide fiber was measured by using
the following measurement device under the following measurement conditions.
[0038] Measurement device: a two dimensional detector-equipped X-ray diffractometer (product
of Bruker AXS K.K., product name; "D8 Discover with GADDS")
Detector: Two-dimensional PSPC·Hi-STAR
Measurement conditions: a current of 110 mA; a voltage of 45 kV; a camera distance
of 15 cm; a collimator diameter of 0.5 mm; an exposure time of 1200 sec.; 2θ axis
at 22°; ω axis at 0°; and χ axis at 90° (equator line)·0° (meridian)
[0039] A single yarn was used as the sample. The angle of the χ axis was adjusted such that
the sample is positioned perpendicularly to the equator line and parallel to the meridian.
[0040] Thereafter, two-dimensional data in the meridian direction obtained in the foregoing
manner was converted to an X-ray diffraction intensity curve in an azimuthal direction
under the following conditions.
2θ = 9.7°-11.7°, χ = -150°= 30°, step width = 0.1°
[0041] Finally, the half-power bandwidth (Wi(°)) of an intensity map obtained in the above
manner was found. The degree of orientation of the fiber was calculated by a simple
method according to the following expression:
(Measurement of Moisture Absorption Rate)
[0042] Next, the produced polyamide fiber was maintained in a thermo-hygrostat chamber regulated
at 35°C and 90%RH for 24-hour humidity regulation. The moisture absorption rate of
the fiber was then calculated based on an absolute dry sample weight and a humidity-regulated
sample weight, according to the following expression. The results are shown in Table
1.
(Measurement of Water Absorption Extension Rate)
[0043] The produced polyamide fiber was wound into a hank, and the hank was treated at no
tension and in boiling water for 30 minutes. Thereafter, the hank was air-dried at
a temperature of 20°C and a humidity of 65%RH, thereby regulating the humidity. The
thread was then subjected to a dry heat treatment for two minutes in an atmosphere
at 160°C, at no tension, and in a contactless fashion. Then, the thread was left in
an atmosphere at a temperature of 20°C and a humidity of 65%RH for 24 hours. After
the lapse of 24 hours, the length of the thread with a load of 0.88 × 10
-3 cN/dtex applied thereto was measured. This length is referred to as "the thread length
in dry state." Thereafter, the thread was immersed in softened water having a temperature
adjusted to 20°C for one minute. The thread was then raised from the water, sandwiched
between two sheets of filter paper which had been air-dried in an atmosphere at a
temperature of 20°C and a humidity of 65%RH, and placed on a flat table. A weight
of 1.5 g/cm
2 was put and left over the thread for two seconds to remove excessive moisture on
the fiber surface. After 10 seconds, the length of the thread was measured with a
load of 0.88 × 10
-3 cN/dtex applied thereto. This length is referred to as "the thread length in water
absorption state." The water absorption extension rate of the polyamide resin was
calculated according to the following expression. Note that all the measurements were
performed in an atmosphere at a temperature of 20°C and a humidity of 65%RH.
(Evaluation Through Wear Test)
[0044] The produced polyamide fiber was knitted into some pieces of cylindrical knitted
fabric by a circular knitting machine. Ten arbitrarily chosen testers passed one day
with the resultant pieces put on their elbows and knees. The testers made sensory
evaluation concerning feeling of stickiness and sweatiness. The results of the sensory
evaluation were qualified in terms of points: "No feeling of stickiness or sweatiness
and highly comfortable" was qualified as two points, "Comfortable" as one point, and
"uncomfortable" as 0 point. The pieces of the knitted fabric were evaluated and classified
into the following four levels according to the total sums of points. Table 1 shows
the results.
- A: 15 points or more in total
- B: 8-14 points in total
- C: 5-7 points in total
- D: 4 points or less in total
(Measurement of Crimp Extension Rate)
[0045] The polyamide fiber was wound into a small hank having 20 turns by using a sizing
reel of which the frame perimeter was 1.125 m. The resultant small hank was heat-treated
in boiling water at 98°C for five minutes with no load applied to the hank. The small
hank was then left in a chamber at constant temperature and humidity (at a temperature
of 20±2°C and a relative humidity of 65±2%) for 24 hours. A load of 2 mg/d was applied
to the humidity-regulated fiber, and the hank length L
1 was measured after one minute. Next, a load of 0.1 g/d was applied to the small hank,
and the hank length L
2 was measured after one minute. The crimp extension rate is given by the following
expression:
[0046] Here, "g/d" represents a number of grams per denier.
[0047] Table 1 shows the results of these measurements and evaluation.
(Example 2)
[0048] A polyamide fiber was produced in the same manner as in Example 1, except that polyethylene
terephthalate (copolymerized PET) having a limiting viscosity number [η] of 0.52 dL/g
and copolymerized with 8 wt.% of polyethylene glycol having a molecular weight of
2000 and 5 mol% of 5-sodium sulfoisophthalic acid was used as the component B. The
degree of orientation, the moisture absorption rate, the water absorption extension
rate, and the crimp extension rate of this polyamide fiber were measured, and the
evaluation of knitted fabric of the fiber was performed through a wear test. The results
of these measurements and evaluation are shown in Table 1.
(Examples 3 and 4)
[0049] As shown in Table 1, a polyamide fiber of each of these examples was produced in
the same manner as in Example 1, except that nylon-6,6 (Example 3) or nylon-6/12 (Example
4) was used as the component A. For each fiber, the degree of orientation, the moisture
absorption rate, the- water absorption extension rate, and the crimp extension rate
were measured, and the evaluation of knitted fabric of each fiber was performed through
a wear test. The results of these measurements and evaluation are shown in Table 1.
(Examples 5 and 6)
[0050] As shown in Table 1, a polyamide fiber of each of these examples was produced in
the same manner as in Example 1, except that the conjugated fiber was caused to have
a cross section shown in FIG. 2 (Example 5) or a cross section shown in FIG. 4 (Example
6). For each fiber, the degree of orientation, the moisture absorption rate, the water
absorption extension rate, and the crimp extension rate were measured, and the evaluation
of knitted fabric of each fiber was performed through a wear test. The results of
these measurements and evaluation are shown in Table 1.
(Comparative Example 1)
[0051] A polyamide fiber was produced in the same manner as in Example 1, except that the
soluble component (component B) was omitted. The degree of orientation, the moisture
absorption rate, the water absorption extension rate, and the crimp extension rate
of this fiber were measured, and the evaluation of knitted fabric of the fiber was
performed through a wear test. The results of these measurements and evaluation are
shown in Table 1.
(Comparative Example 2)
[0052] A conjugated fiber (size: 275 dtex) having a cross section shown in FIG. 1 was injected
through a multi-component fiber spinning nozzle, in the same manner as in Example
1. Subsequently, a thread injected from a spinneret was cooled using a horizontal
cooling air blower having a length of 1.0 m. Thereafter, water-free spinning oil including,
as its components, an anti-static agent and a lubricating agent was applied to the
thread. The thread was then taken off using a roller at a speed of 1000 m/min., and
drawn continuously without being wound. The thread was drawn until its length became
2.5 times as long as the original length, while being thermo-set at 150°C. In this
manner, a conjugated fiber (110 dtex/24 filaments) was produced at a speed of 2500
m/min. The produced conjugated fiber was knitted into cylindrical fabric by a circular
knitting machine (28 gauge). The resultant knitted fabric was subjected to a scouring
step using hot water (90°C, 20 minutes) to dissolve and remove the modified PVA. In
this manner, the polyamide fiber of this comparative example was produced.
[0053] Next, the degree of orientation and the water absorption extension rate of the polyamide
fiber were measured, and the evaluation of knitted fabric of the fiber was performed
through a wear test, in the same manner as in Example 1. Note that the moisture absorption
rate and the crimp extension rate were not measured. The results of these measurements
and evaluation are shown in Table 1.
(Comparative Example 3)
[0054] A polyamide fiber was produced in the same manner as in Example 1, except that nylon-12
was used as the component A. The degree of orientation and the water absorption extension
rate of this polyamide fiber were measured, and the evaluation of knitted of the fiber
was performed through a wear test. Note that the moisture absorption rate and the
crimp extension rate were not measured. The results of these measurements and evaluation
are shown in Table 1.
(Comparative Example 4)
[0055] A conjugated fiber (size: 275 dtex) having a cross section shown in FIG. 1 was injected
through a multi-component fiber spinning nozzle, in the same manner as in Example
1. Subsequently, a thread injected through a spinneret was cooled using a horizontal
cooling air blower having a length of 1.0 m. Thereafter, water-free spinning oil including,
as its components, an anti-static agent and a lubricating agent was applied to the
thread. The thread was then taken off using a roller at a speed of 2000 m/min., thereby
obtaining undrawn thread. The obtained undrawn thread was knitted into cylindrical
fabric by a circular knitting machine (28 gauge). The resultant knitted fabric was
subjected to a scouring step using hot water (90°C, 20 minutes) to dissolve and remove
the modified PVA. In this manner, the polyamide fiber of this comparative example
was produced.
[0056] Next, the degree of orientation and the water absorption extension of this polyamide
fiber were measured, and the evaluation of knitted fabric of the fiber was performed
through a wear test in the same manner as in Example 1. Note that the moisture absorption
rate and the crimp extension rate were not measured. The results of these measurements
and evaluation are shown in Table 1.
[Table 1]
|
Polyamide Component (Component A) |
Soluble Component (ComponentB) |
Conjugate Ratio A:B |
Cross Section |
Degree of Orientation |
Moisture Absorption Rate (%) |
Water Absorption Extension Rate (%) |
Evaluation through Wear Test |
Crimp Extension Rate (%) |
Example 1 |
Nylon-6 |
Modified PVA |
60:40 |
FIG. 1 |
0.78 |
9 |
11 |
A |
4.8 |
Example 2 |
Nylon-6 |
Copolymerized PET |
60:40 |
FIG. 1 |
0.84 |
7 |
5 |
B |
3.6 |
Example 3 |
Nylon-6,6 |
Modified PVA |
60:40 |
FIG. 1 |
0.75 |
9 |
11 |
A |
5.3 |
Example 4 |
Nylon-6/12 |
Modified PVA |
60:40 |
FIG. 1 |
0.74 |
8 |
8 |
B |
4.5 |
Example 5 |
Nylon-6 |
Modified PVA |
60:40 |
FIG. 2 |
0.7 |
10 |
13 |
A |
5.8 |
Example 6 |
Nylon-6 |
Modified PVA |
60:40 |
FIG. 4 |
0.8 |
6 |
9 |
A |
2.8 |
Comparative Example 1 |
Nylon-6 |
- |
- |
Circular |
0.95 |
3 |
0 |
D |
1.3 |
Comparative Example 2 |
Nylon-6 |
Modified PVA |
60:40 |
FIG. 1 |
0.88 |
- |
2 |
C |
- |
(Comparative Example 3 |
Nylon-12 |
Modified PVA |
60:40 |
FIG. 1 |
0.9 |
- |
0 |
D |
- |
Comparative Example 4 |
Nylon-6 |
Modified PVA |
60:40 |
FIG. 1 |
0.5 |
- |
32 |
D |
- |
[0057] As shown in Table 1, the polyamide fibers of Examples 1-6 have a degree of orientation
equal to or higher than 0.7 and equal to or lower than 0.85. Therefore, these fibers
have a water absorption extension rate of 5% or more at a temperature of 20°C and
a humidity of 65%RH. This means that these polyamide fibers effectively control humidity,
and knitted fabric made of these fibers is highly comfortable when worn.
[0058] On the other hand, the polyamide fibers of Comparative Examples 1-3 have a degree
of orientation equal to or higher than 0.85. Therefore, these fibers have a water
absorption extension rate lower than 5% at a temperature of 20°C and a humidity of
65%RH. This means that these fibers control humidity less effectively and the knitted
fabric made of the fibers of these comparative examples is notably uncomfortable when
worn, as compared to the fibers of Examples 1-6. In particular, nylon-12 used in Comparative
Example 3 is highly hydrophobic and has a high crystal orientation among polyamide
resin. Consequently, the fiber of Comparative Example 3 has a high degree of orientation
as shown in Table 1, which means that the obtained knitted fabric exhibits no water
absorption extension rate and is remarkably uncomfortable when worn.
[0059] The polyamide fiber of Comparative Example 4 has a degree of orientation lower than
0.7. Therefore, the water absorption extension rate of this polyamide fiber is excessively
high, resulting in that the fabric made of this fiber is remarkably uncomfortable
when worn.
(Example 7)
[0060] Nylon-6 having a reduced viscosity of 1.80 dL/g (at a concentration of 1g/dL in orthoclorophenol
at 30°C) was used as a polyamide component (component A), and a thermoplastic modified
polyvinyl alcohol (modified PVA) (product of Kuraray Co., Ltd. having a saponification
degree of 98.5, an ethylene content of 8.0 mol%, and a degree of polymerization of
380) was used as the other component, i.e., the soluble component (component B). The
components A and B were separately melted in different extruders, and a conjugated
fiber having a cross section shown in FIG. 1 was injected through a multi-component
fiber-spinning nozzle with a ratio of nylon-6: modified PVA set to 70:30 (weight ratio).
Subsequently, a thread injected through a spinneret was cooled using a horizontal
cooling air blower having a length of 1.0 m. Thereafter, water-free spinning oil including,
as its components, an anti-static agent and a lubricating agent was applied to the
thread. The thread was then wound using a roller at a take-off speed of 3500 m/min.
In this manner, a conjugated fiber (111 dtex/24 filaments) was produced. Note that
the process steps of fiber production were performed smoothly. The produced conjugated
fiber was knitted into cylindrical fabric by a circular knitting machine (28 gauge).
The resultant knitted fabric was subjected to a scouring step using hot water (90°C,
20 minutes) to dissolve and remove the modified PVA.
[0061] In the same manner as in Example 1, the degree of orientation, the moisture absorption
rate, the water absorption extension rate, and the crimp extension rate of this polyamide
fiber were measured, and the evaluation of knitted fabric of the fiber was performed
through a wear test. The results of these measurements and evaluation are shown in
Table 2.
(Examples 8 and 9)
[0062] A polyamide fiber of Example 8 was produced in the same manner as in Example 7, except
that polyethylene terephthalate (copolymerized PET) having a limiting viscosity number
[η] of 0.52 dL/g and copolymerized with 8 wt.% of polyethylene glycol having a molecular
weight of 2000 and 5 mol% of 5-sodium sulfoisophthalic acid was used as the component
B. A polyamide fiber of Example 9 was produced in the same manner as in Example 7,
except that polylactic acid was used as the soluble component (component B), and a
ratio of nylon-6:component B was set to 67:33. The degree of orientation, the moisture
absorption rate, the water absorption extension rate, and the crimp extension rate
of each polyamide fiber were measured, and the evaluation of knitted fabric of each
fiber was performed through a wear test. The results of these measurements and evaluation
are shown in Table 2.
(Examples 10 and 11)
[0063] As shown in Table 2, a polyamide fiber of each of these examples was produced in
the same manner as in Example 7, except that nylon-6,6 (Example 10) or nylon-6/12
(Example 11) was used as the component A. For each fiber, the degree of orientation,
the moisture absorption rate, the water absorption extension rate, and the crimp extension
rate were measured, and the evaluation of knitted fabric of each fiber was performed
through a wear test. The results of these measurements and evaluation are shown in
Table 2.
(Examples 12 and 13)
[0064] As shown in Table 2, a polyamide fiber of each of these examples was produced in
the same manner as in Example 7, except that the conjugated fiber was caused to have
a cross section shown in FIG. 2 (Example 12) or a cross section shown in FIG. 3 (Example
13). For each fiber, the degree of orientation, the moisture absorption rate, the
water absorption extension rate, and the crimp extension rate were measured, and the
evaluation of knitted fabric of each fiber was performed through a wear test. The
results of these measurements and evaluation are shown in Table 2.
(Comparative Example 5)
[0065] A conjugated fiber (size: 220 dtex) having a cross section shown in FIG. 1 was injected
through a multi-component fiber spinning nozzle, in the same or similar manner to
Example 7. Subsequently, a thread injected through a spinneret was cooled using a
horizontal cooling air blower having a length of 1.0 m. Thereafter, water-free spinning
oil including, as its components, an anti-static agent and a lubricating agent was
applied to the thread. The thread was then taken off using a roller at a speed of
1000 m/min., and drawn continuously without being wound. The thread was drawn until
its length became 2.5 times as long as the original length, while being thermo-set
at 150°C. In this manner, a conjugated fiber (110 dtex/24 filaments) was produced
at a speed of 2500 m/min. The produced conjugated fiber was knitted into cylindrical
fabric by a circular knitting machine (28 gauge). The resultant knitted fabric was
subjected to a scouring step using hot water (90°C, 20 minutes) to dissolve and remove
the modified PVA. In this manner, the polyamide fiber of this comparative example
was produced.
[0066] Next, the degree of orientation and the water absorption extension rate of this polyamide
fiber were measured, and the evaluation of knitted fabric of the fiber was performed
through a wear test, in the same or similar manner to Example 7. Note that the moisture
absorption rate and the crimp extension rate were not measured. The results of these
measurements and evaluation are shown in Table 2.
(Comparative Example 6)
[0067] A polyamide fiber was produced in the same manner as in Example 7, except that nylon-12
was used as the component A. The degree of orientation and the water absorption extension
rate of this polyamide fiber were measured, and the evaluation of knitted fabric of
the fiber was performed through a wear test. Note that the moisture absorption rate
and the crimp extension rate were not measured. The results of these measurements
and evaluation are shown in Table 2.
[Table 2]
|
Polyamide Component (Component A) |
Soluble Component (Component B) |
Conjugate Ratio A:B |
Cross Section |
Degree of Orientation |
Moisture Absorption Rate (%) |
Water Absorption Extension Rate (%) |
Evaluation through Wear Test |
Crimp Extension Rate (%} |
Example 7 |
Nylon-6 |
Modified PVA |
70:30 |
FIG. 1 |
0.78 |
8 |
10 |
A |
4.3 |
Example 8 |
Nylon-6 |
Copolymerized PET |
67:33 |
FIG. 1 |
0.84 |
6 |
5 |
B |
3.4 |
Example 9 |
Nylon-6 |
Polylactic Acid |
67:33 |
FIG. 1 |
0.82 |
6 |
5 |
B |
3 |
Example 10 |
Nylon-6,6 |
Modified PVA |
70:30 |
FIG. 1 |
0.77 |
7 |
10 |
A |
5.5 |
Example 11 |
Nylon-6/12 |
Modified PVA |
70:30 |
FIG. 1 |
0.75 |
5 |
7 |
B |
4.7 |
Example 12 |
Nylon-6 |
Modified PVA |
70:30 |
FIG. 2 |
0.71 |
9 |
12 |
A |
5.6 |
Example 13 |
Nylon-6 |
Modified PVA |
70:30 |
FIG. 3 |
0.8 |
6 |
8 |
A |
2.5 |
Comparative Example 5 |
Nylon-6 |
Modified PVA |
70:30 |
FIG. 1 |
- |
4 |
1 |
C |
- |
Comparative Example 6 |
Nylon-12 |
Modified PVA |
70:30 |
FIG. 1 |
- |
2 |
0 |
D |
- |
[0068] As shown in Table 2, the polyamide fibers of Examples 7-13 have a moisture absorption
rate equal to or higher than 5% at a temperature 35°C and a humidity 95%RH, and a
water absorption extension rate equal to or higher than 5% at a temperature 20°C and
a humidity of 65%RH. This means that these polyamide fibers effectively control humidity,
and knitted fabric made of these fibers is highly comfortable when worn.
[0069] On the other hand, the polyamide fibers of Comparative Examples 5 and 6 have a moisture
absorption rate lower than 5% at a temperature of 35°C and a humidity of 95%RH, and
a water absorption extension rate lower than 5% at a temperature of 20°C and a humidity
of 65%RH. This means that the fibers of these comparative examples control humidity
less effectively and knitted fabric made of the fibers of these comparative examples
is notably uncomfortable when worn, as compared to the fibers of Examples 7-13. In
particular, nylon-12 used in Comparative Example 6 is highly hydrophobic and has high
crystal orientation among polyamide resin. Consequently, the fiber of Comparative
Example 6 has a notably reduced moisture absorption rate, as shown in Table 2, which
means that the obtained knitted fabric exhibits no water absorption extension rate
and is remarkably uncomfortable when worn.
INDUSTRIAL APPLICABILITY
[0070] The polyamide fiber of the present invention suitably absorbs and releases moisture,
and extends and contracts reversibly upon absorbing and releasing water. Therefore,
a fiber structure containing the polyamide fiber of the present invention exhibits
a self-control function by which the opening degree of stitches in the fiber structure
is varied depending on absorption and release of water. Thus, the polyamide fiber
of the present invention may enable the production of a highly comfortable fiber structure.
The polyamide fiber of the present invention is highly suitable for the field of clothing,
and exhibits good performance when used in sportswear, underwear, lining, pantyhose,
socks, and other types of clothing.
DESCRIPTION OF REFERENCE CHARACTERS
[0071]
- 1
- Polyamide Component (Component A) in Conjugated fiber
- 2
- Soluble Component (Component B) in Conjugated fiber
- 3
- Hollow Portion in Conjugated fiber