Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
HEAT-RESISTANT FABRIC
Technical Field
The present invention relates to a heat-resistant fabric
made of a meta-type aromatic polyamide fiber.
Background Art
With respect to conventional protective garments, such as
firefighter garments, using a fabric made mainly of a meta-type
wholly aromatic polyamide fiber, etc., when they are repeatedly
used, washed with a surfactant such as a detergent, etc., or
dry-cleaned, for example, they show a decrease from the initial
surface abrasion resistance. In addition, because a fabric made
mainly of a meta-type wholly aromatic polyamide fiber is used,
the minimum surface abrasion is more than 200 rubs. In the past,
there have been problems that although the initial surface
abrasion is high, the abrasion resistance decreases due to
washing, leading to loss of high washing durability, which
results in noticeable holes after washing. Several studies have
been made in order to solve such problems.
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Patent Document 1 (JP-A-2009-249758) discloses a method
in which a high-strength, high-heat-resistance fiber is arranged
as a core yarn, another dyeable fiber or spun-dyed yarn is
arranged therearound in a substantially non-twisted state, and
further they are covered with a dyeable fiber or spun-dyed yarn
in a spiral fashion, thereby maintaining aesthetics.
Patent Document 2 (JP-A-2009-209488) discloses a
composite spun yarn including a core component made of a
para-aramid fiber and a meta-aramid fiber and a sheath component
made of a cellulose fiber, with the composite ratio of core
component/sheath component being within a range of 25/75 to 55/45,
as well as a woven or knitted fabric using the composite spun
yarn.
Patent Document 3 (JP-A-2003-147651) discloses a
core-sheath-type composite spun yarn including a core component
made of a heat-resistant, high-performance fiber and a sheath
component made of staple fibers of a synthetic fiber, a chemical
fiber, or a natural fiber, characterized in that the
heat-resistant, high-performance fiber is a crimped yarn of a
heat-resistant, high-performance fiber filament yarn.
According to the above invention, a fiber that is likely
to adversely affect washing durability is used as the core part
of a sheath-core structure yarn, thereby hiding the fiber itself
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so as to solve the problems. In these inventions, it is
indispensable to use a sheath-core structure yarn. Thus, there
is a problem that its production inevitably takes more time and
cost as compared with ordinary spun yarns.
Patent Document 1: JP-A-2009-249758
Patent Document 2: JP-A-2009-209488
Patent Document 3: JP-A-2003-147651
Summary of the Invention
Problems that the Invention is to Solve
The invention has been accomplished in view of the problems
mentioned above and is aimed at providing a heat-resistant fabric
that can be dyed to a color chosen from a wide range of color
options, is capable of maintaining high mechanical
characteristics without degradation over time/age even after
repeated uses or washes, etc., and has excellent pilling
resistance.
Means for Solving the Problems
As a result of extensive research, the present inventor
has found that the problems mentioned above can be solved by
the following heat-resistant fabric.
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The heat-resistant fabric of the invention is a
heat-resistant fabric containing a meta-type wholly aromatic
polyamide fiber, characterized in that the abrasion resistance
of the heat-resistant fabric in accordance with the JIS L1096
8.19.1 A-1 method (universal type method (plane method),
abrasion tester press load: 4.45 N (0.454 kf), paper: #600) is
200 rubs or more, the tear strength of the heat-resistant fabric
in accordance with the JIS L1096 8.17.4 D method (pendulum
method) is 20 N or more, and the retention of the abrasion
resistance and the retention of the tear strength after 100
washes in accordance with JIS L0844 No. A-1 are each 90% or more
relative to before washing.
In the heat-resistant fabric of the invention, it is
preferable that the meta-type wholly aromatic polyamide fiber
has a crystallinity of 15 to 27.
In the heat-resistant fabric of the invention, it is
preferable that the standard deviation of the single-fiber
tensile strength of the meta-type wholly aromatic polyamide
fiber is 0.60 or less.
In the heat-resistant fabric of the invention, it is
preferable that the meta-type wholly aromatic polyamide fiber
has an average single-fiber tensile strength of 4.0 cN/dtex or
less.
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In the heat-resistant fabric of the invention, it is
preferable that the meta-type wholly aromatic polyamide fiber
has an average single-fiber elongation of 35% or less.
In the heat-resistant fabric of the invention, it is
preferable that the meta-type wholly aromatic polyamide fiber
has a single-fiber toughness of 130 or less.
In the heat-resistant fabric of the invention, it is
preferable that the heat-resistant fabric is dyed, and the color
difference AE of the fabric before and after alight resistance
test in accordance with JIS L0842 and the brightness L of the
light resistance test fabric satisfy the following equation (1) :
AE 0.46L - 11.3 ... (1).
In the heat-resistant fabric of the invention, it is
preferable that the meta-type wholly aromatic polyamide fiber
contains an organic dye.
In the heat-resistant fabric of the invention, it is
preferable that the heat-resistant fabric contains at least one
member selected from a cellulose fiber, a polyester fiber, an
acrylic fiber, and a polyamide fiber in an amount of 2 to 50
mass% based on the mass of the heat-resistant fabric.
In the heat-resistant fabric of the invention, it is
preferable that the cellulose fiber is rayon.
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In the heat-resistant fabric of the invention, it is
preferable that the cellulose fiber, polyester fiber, acrylic
fiber, or polyamide fiber contains a flame retarder.
In the heat-resistant fabric of the invention, it is
preferable that the pilling resistance of the heat-resistant
fabric in accordance with the 11. JIS L1096 A method is Level
4 or higher.
In the heat-resistant fabric of the invention, it is
preferable that the heat-resistant fabric contains cellulose
and is dyed with a fluorescent dye.
The heat-resistant fabric of the invention is preferably
the heat-resistant fabric according to any one of claims 1 to
12, wherein the meta-type wholly aromatic polyamide that forms
the meta-type wholly aromatic polyamide fiber is an aromatic
polyamide obtained by copolymerizing, into an aromatic polyamide
backbone having a repeating structural unit represented by the
following formula (1) , an aromatic diamine component or aromatic
dicarboxylic acid halide component that is different from a main
unit of the repeating structure as a third component so that
the proportion of the third component is 1 to 10 mol% based on
the total repeating structural units of the aromatic polyamide:
- (NH-Arl-NH-CO-Arl-CO) ... formula (1)
wherein Arl is a divalent aromatic group having a linking group
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in a position other than the meta position or an axially parallel
direction.
In the heat-resistant fabric of the invention, it is
preferable that the third component is an aromatic diamine of
formula (2) or (3) or an aromatic dicarboxylic acid halide of
formula (4) or (5):
H2N-Ar2-NH2 - formula (2)
H2N-Ar2-Y-Ar2-NH2 formula (3)
X0C-Ar3-COX formula (4)
X0C-Ar3-Y-Ar3-COX formula (5)
wherein Ar2 is a divalent aromatic group different from Arl,
Ar3 is a divalent aromatic group different from Arl, Y is at
least one atom or functional group selected from the group
consisting of an oxygen atom, a sulfur atom, and an alkylene
group, and X is a halogen atom.
In the heat-resistant fabric of the invention, it is
preferable that the meta-type aromatic polyamide fiber has a
residual solvent content of 0.1 mass% or less.
In the heat-resistant fabric of the invention, it is
preferable that the heat-resistant fabric contains at least one
member selected from a para-type wholly aromatic polyamide fiber,
a polybenzobisoxazol fiber, and a wholly aromatic polyester
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fiber in an amount of 1 to 20 mass% based on the mass of the
heat-resistant fabric.
In the heat-resistant fabric of the invention, it is
preferable that the para-type wholly aromatic polyamide fiber
is a paraphenylene terephthalamide fiber or a
co-paraphenylene/3,4'-oxydiphenylene terephthalamide fiber.
In the heat-resistant fabric of the invention, it is
preferable that a fiber that forms the heat-resistant fabric
contains a UV absorber and/or UV reflector.
In the heat-resistant fabric of the invention, it is
preferable that the heat-resistant fabric has a UV absorber
and/or UV reflector fixed to the surface thereof.
Advantage of the Invention
According to the invention, a heat-resistant fabric that
can be dyed to a color chosen from a wide range of options and
is highly capable of retaining surface abrasion and tear strength
over time/age even after repeated uses, washes, etc., can be
provided. Thus, the fabric can be suitably used for protective
garments, such as firefighter garments, or for industrial
materials, such as flexible heat-insulating materials.
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Mode for Carrying Out the Invention
The heat-resistant fabric of the invention is a
heat-resistant fabric containing a meta-type wholly aromatic
polyamide fiber. The fabric indispensably contains a meta-type
wholly aromatic polyamide fiber, but the presence of other kinds
of fibers is also allowed, including flame-retardant fibers such
as para-type wholly aromatic polyamide fibers, synthetic fibers
such as polyester fibers, regenerated fibers such as rayon, and
natural fibers such as cotton. However, in order for the high
heat resistance and flame retardancy, which are advantageous
characteristics of a meta-type wholly aromatic polyamide fiber,
to be exerted, it is preferable that the meta-type wholly
aromatic polyamide fiber content is 50 mass% or more based on
the total mass of the heat-resistant fabric.
The meta-type wholly aromatic polyamide fiber for use in
the invention is made of a polymer, wherein 85 mol% or more of
the repeating unit is m-phenyleneisophthalamide. The meta-type
wholly aromatic polyamide may also be a copolymer containing
a third component in an amount within a range of less than 15
mol%
In the invention, it is important that the abrasion
resistance of the heat-resistant fabric in accordance with the
JIS L1096 8.19.1 A-1 method (universal type method (plane method) ,
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abrasion tester press load: 4.45 N (0.454 kf), paper: #600) is
200 rubs or more, the tear strength of the heat-resistant fabric
in accordance with the JIS L1096 8.17.4 D method (pendulum
method) is 20 N or more, and the retention of the abrasion
resistance and the retention of the tear strength after 100
washes in accordance with JIS L0844 No. A-1 are each 90% or more
relative to before washing. As a result, even after repeated
uses, washes, etc., high durability can be maintained while
suppressing degradation with time/age, and extremely excellent
practical performance is exerted. In the case where there is
a difference in the tear strength between one direction of the
fabric and the direction perpendicular thereto (e.g.,
longitudinal direction and transverse direction), the above tear
strength and retention thereof should be satisfied in at least
one direction, but it is preferable that they are satisfied in
both directions. Incidentally, the longitudinal direction and
transverse direction herein may be arbitrarily determined. For
example, the length direction of the original fabric may be the
longitudinal direction, and the direction perpendicular thereto
may be the transverse direction.
In the invention, the above object can be achieved by using
the below-mentioned fiber having improved dyeing affinity and
discoloration/fading resistance as a meta-type wholly aromatic
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polyamide fiber to form the heat-resistant fabric. In addition,
it is preferable that appropriate materials for the
heat-resistant fabric are selected, and they are mixed in
appropriate proportions.
First, a meta-type wholly aromatic polyamide fiber that
can achieve the above excellent abrasion resistance, tear
strength, and washing durability thereof will be described.
With respect to the polymerization degree of the meta-type
wholly aromatic polyamide that forms the fiber, it is preferable
to use one having an intrinsic viscosity (I.V.) within a range
of 1.3 to 1.9 dl/g as measured with a 0.5 g/100 ml
N-methyl-2-pyrrolidone solution.
The meta-type wholly aromatic polyamide may contain an
alkylbenzenesulfonic acid onium salt. Preferred examples of
alkylbenzenesulfonic acid onium salts include compounds such
as a hexylbenzenesulfonic acid tetrabutylphosphonium salt, a
hexylbenzenesulfonic acid tributylbenzylphosphonium salt, a
dodecylbenzenesulfonic acid tetraphenylphosphonium salt, a
dodecylbenzenesulfonic acid tributyltetradecylphosphonium
salt, a dodecylbenzenesulfonic acid tetrabutylphosphonium salt,
and a dodecylbenzenesulfonic acid tributylbenzylammonium salt.
Among them, a dodecylbenzenesulfonic acid
tetrabutylphosphonium salt and a dodecylbenzenesulfonic acid
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tributylbenzylammonium salt are particularly preferable
because they are easily available, have excellent thermal
stability, and also have high solubility in
N-methyl-2-pyrrolidone.
In order to obtain a sufficient dye-affinity-improving
effect, the content of the alkylbenzenesulfonic acid onium salt
is preferably 2.5 mol% or more, more preferably 3.0 to 7.0 mol% ,
relative to poly-m-phenyleneisophthalamide.
As a method for mixing poly-m-phenyleneisophthalamide and
an alkylbenzenesulfonic acid onium salt, it is possible to employ
a method in which poly-m-phenyleneisophthalamide is mixed and
dissolved in a solvent, then an alkylbenzenesulfonic acid onium
salt is dissolved in the solvent, and the obtained dope is formed
into a fiber by a known method, for example.
For the purpose of improving dyeing affinity and
discoloration/fading resistance, etc., the polymer to form the
meta-type wholly aromatic polyamide fiber may also be obtained
by copolymerizing, into an aromatic polyamide backbone having
a repeating structural unit represented by the following formula
(1), an aromatic diamine component or aromatic dicarboxylic acid
halide component that is different from a main unit of the
repeating structure as a third component so that the proportion
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of the third component is 1 to 10 mol% based on the total repeating
structural units of the aromatic polyamide:
-(NH-Ar1-NH-CO-Arl-00) formula (1)
wherein Arl is a divalent aromatic group having a linking group
in a position other than the meta position or an axially parallel
direction.
Specific examples of aromatic diamines represented by
formulae (2) and (3) copolymerizable as a third component include
p-phenylenediamine,
chlorophenylenediamine,
methylphenylenediamine,
acetylphenylenediamine,
aminoanisidine, benzidine,
bis(aminophenyl)ether,
bis(aminophenyl)sulfone, diaminobenzanilide, and
diaminoazobenzene. Specific examples of aromatic dicarboxylic
acid dichlorides represented by formulae (4) and (5) include
terephthaloyl chloride, 1,4-naphthalenedicarbonyl chloride,
2,6-naphthalenedicarbonyl chloride, 4,4'-biphenyldicarbonyl
chloride, 5-chloroisophthaloyl
chloride,
5-methoxyisophthaloyl chloride, and
bis(chlorocarbonylphenyl)ether.
112N-Ar2-NH2 - formula (2)
112N-Ar2-Y-Ar2-NH2 formula (3)
X0C-Ar3-COX formula (4)
X0C-Ar3-Y-Ar3-COX formula (5)
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In the formulae, Ar2 is a divalent aromatic group different
from Arl, Ar3 is a divalent aromatic group different from Arl,
Y is at least one atom or functional group selected from the
group consisting of an oxygen atom, a sulfur atom, and an alkylene
group, and X is a halogen atom.
In addition, it is preferable that the crystallinity of
the meta-type aromatic polyamide fiber for use in the invention
is 5 to 27%, more preferably 15 to 25%. It has been found that
when the crystallinity is within such a range, the above initial
abrasion resistance and retention after washing and also the
above initial tear strength and retention after washing can be
achieved at the same time. Such crystallinity also leads to
excellent dye exhaustion properties. Accordingly, even when
dying is performed with a small amount of dye or under weak dyeing
conditions, the color can be easily adjusted as intended.
Further, the dye is less likely to be unevenly distributed on
the surface, discoloration./ fading resistance is improved, and
also the practically necessary dimensional stability can be
ensured.
In the invention, it is preferable that the standard
deviation of the single-fiber tensile strength of the meta-type
wholly aromatic polyamide fiber in accordance with the JIS L
1015-99 method is 0.60 or less, more preferably 0.55 or less.
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In the invention, it is preferable that the average
single-fiber tensile strength of the meta-type wholly aromatic
polyamide fiber in accordance with the JIS L 1015-99 method is
4.0 cN/dtex or less, more preferably 3.8 cN/dtex or less.
In the invention, it is preferable that the average
single-fiber elongation of the meta-type wholly aromatic
polyamide fiber in accordance with the JIS L 1015-99 method is
35% or less, more preferably 30% or less, and still more
preferably 28% or less.
In the invention, it is preferable that the single-fiber
toughness of the meta-type wholly aromatic polyamide fiber is
130 or less, more preferably 110 or less, and still more
preferably 100 or less.
Also by satisfying the above average strength, standard
deviation of strength, average elongation, standard deviation
of elongation, and toughness of single fibers, the above initial
abrasion resistance and retention after washing and also the
above initial tear strength and retention after washing can be
achieved at the same time. It is usually believed that tear
strength is improved with an increase in the strength of the
fiber. However, surprisingly, it has been found that by
satisfying the above properties including the standard deviation
of strength in a balanced manner, the properties regarding
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abrasion resistance and tear strength can be achieved at the
same time.
In addition, in the invention, it is preferable that the
residual solvent content of the meta-type aromatic polyamide
fiber is 0.1 mass% or less, more preferably 0.08 mass% or less,
still more preferably 0.07 mass% or less, and yet more preferably
0.05 mass% or less. It has been found that also by controlling
the residual solvent content like this, the above initial
abrasion resistance and retention and also the above initial
tear strength and retention can be achieved at the same time.
In addition, the excellent flame retardancy of the meta-type
aromatic polyamide fiber is not impaired. Further, the dye is
less likely to be unevenly distributed on the surface, and the
discoloration/fading resistance can be improved.
When the meta-type wholly aromatic polyamide fiber is a
spun-dyed fiber containing a pigment having high light
resistance over time as a coloring agent, the color of the fabric
itself can be easily retained. However, in the invention, the
meta-type wholly aromatic polyamide fiber does not have to be
a spun-dyed fiber. It is possible to perform yarn dyeing or
fabric dyeing with an organic dye, that is, the fabric may be
a so-called piece-dyed fabric. It is preferable that the
meta-type wholly aromatic polyamide fiber can be piece-dyed for
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the following reasons: the fabric can be dyed to various colors
to meet a wide variety of user needs, the fabric can be more
brightly colored, the color can be changed, small lot production
is possible, etc.
In addition to the meta-type wholly aromatic polyamide
fiber, the heat-resistant fabric of the invention may also
contain other kinds of fibers, including flame-retardant fibers,
synthetic fibers such as polyester fibers, regenerated fibers,
and natural fibers.
The flame-retardant fibers are fibers having a limiting
oxygen index of 20 or more excluding meta-type wholly aromatic
polyamide fibers. Preferred examples thereof include para-type
wholly aromatic polyamide fibers, polybenzobisazole fibers,
wholly aromatic polyester fibers, polysulfone amide fibers,
polyimide fibers, and polyetheramide fibers.
Preferred
examples of para-type wholly aromatic polyamide fibers include
paraphenylene terephthalamide fibers and
co-paraphenylene/3,4'-oxydiphenylene terephthalamide fibers.
The synthetic fibers such as polyester fibers are known
synthetic fibers. In addition to polyester fibers such as
polyethylene terephthalate fibers, polybutylene terephthalate
fibers, polyethylene naphthalate fibers, and polylactic acid
fibers, preferred examples thereof include polyamide fibers,
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acrylic fibers, polyolefin fibers, and polycarbonate fibers.
The regenerated fibers are known regenerated fibers. Preferred
examples thereof include cellulose fibers, particularly rayon.
The natural fibers are known natural fibers.
Preferred
examples thereof include cotton.
In the invention, in order to improve the washing
durability of abrasion resistance and tear strength, it is
preferable that the heat-resistant fabric contains at least one
member selected from a cellulose fiber, a polyester fiber, an
acrylic fiber, and a polyamide fiber in an amount of 2 to 50
mass%, more preferably 2 to 48 mass%, based on the mass of the
heat-resistant fabric.
In the invention, in order to improve the washing
durability of abrasion resistance and tear strength, it is
preferable that the heat-resistant fabric contains at least one
member selected from a para-type wholly aromatic polyamide fiber,
a polybenzobisoxazol fiber, and a wholly aromatic polyester
fiber in an amount of 1 to 20 mass%, more preferably 2 to 10
mass%, based on the mass of the heat-resistant fabric.
According to the requirements for the end use, it is also
possible to previously perform a flame-retarding treatment on
or add a flame retarder to the above fibers. In particular, with
respect to the cellulose fiber, polyester fiber, acrylic fiber,
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and polyamide fiber, it is preferable to employ those containing
a flame retarder.
The mixing proportions of these fibers are as follows.
First, in order for excellent heat resistance and flame
retardancy to be exerted, it is preferable that the proportion
of the meta-type wholly aromatic polyamide fiber is 50 mass%
or more. In addition, according to the intended use or the needs
of use, the above flame-retardant fibers, synthetic fibers,
regenerated fibers, and natural fibers may be arbitrarily mixed.
For example, in order to combine dye affinity and comfortableness ,
the mixing proportions may be as follows: meta-type wholly
aromatic polyamide fiber: 50 to 98 mass%, polyester fiber: 2
to 50 mass%, cellulose fiber: 0 to 48 mass%. The proportions
may be adjusted according to the performance to be emphasized.
In the invention, it is preferable that the fabric is
capable of retaining excellent aesthetics over time/age even
after repeated uses, washes, etc.
"Excellent aesthetics"
herein means that aesthetics are prevented from being lost due
to any remaining or deposited soil; that is, it does not happen
that due to the soil, the color/pattern looks different in some
parts or the fabric has noticeable soiling.
As indices for objectively showing this, soil resistance
and soil hide characteristics are effective. As a specific
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method and evaluation criteria, the value of color difference
AE* from the state where soil is deposited is used as an index.
Qualitatively, it can be said that the smaller the AE* value,
the higher the soil hide characteristics, that is, soiling is
less noticeable, which is more desirable.
In order to achieve such excellent aesthetics, in the
invention, it is preferable that the color difference AE between
a fabric after a light resistance test in accordance with JIS
L0842 and a fabric before the light resistance test and the
brightness L of the fabric before the light resistance test
satisfy the following equation (1) :
AE __ 0.46L - 11.3 ... equation (1) .
That is, in the invention, it has been found that when a
fabric satisfies the AE value of the above equation (1) depending
on the brightness L value of the original fabric before the light
resistance test, even in the case where the fabric is repeatedly
used, washed with a surfactant such as a detergent, etc., or
dry-cleaned, for example, it does not happen that the fabric
looks dirty due to the slightly remaining soil component or newly
deposited soil component, or that due to such soil components,
the color/pattern looks different in some parts or the fabric
has noticeable soiling; as a result, excellent aesthetics can
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be achieved. The upper limit of the AE value can be set in direct
proportion to the brightness L value of the original fabric.
When the meta-type wholly aromatic polyamide fiber used
for the heat-resistant fabric of the invention is a spun-dyed
fiber containing a pigment having high light resistance over
time as a coloring agent, the color of the fabric itself can
be easily retained. However, in the invention, the meta-type
wholly aromatic polyamide fiber does not have to be a spun-dyed
fiber. As long as the above equation (1) is satisfied, it is
possible to perform yarn dyeing or fabric dyeing with an organic
dye, that is, the fabric may be a so-called piece-dyed fabric.
However, it is preferable that the meta-type wholly aromatic
polyamide fiber can be piece-dyed.
A meta-type aromatic polyamide fiber that is suitable for
use in the invention can be produced by the following method.
In particular, by the following method, the crystallinity and
residual solvent content can be made within the above ranges.
The polymerization method for a meta-type aromatic
polyamide polymer does not have to be particularly limited, and
it is possible to use, for example, the solution polymerization
method or interfacial polymerization method described in
JP-B-35-14399, U.S. Pat. No. 3360595, JP-B-47-10863, etc.
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The spinning solution does not have to be particularly
limited. It is possible to use an amide solvent solution
containing an aromatic copolyamide polymer obtained by the above
solution polymerization or interfacial polymerization, etc.,
or it is also possible that the polymer is isolated from the
polymerization solution, dissolved in an amide solvent, and
used.
Examples of amide solvents used herein include
N,N-dimethylformamide, N,N-
dimethylacetamide,
N-methyl-2-pyrrolidone, and dimethyl sulfoxide, and
N,N-dimethylacetamide is particularly preferable.
It is preferable that the wholly aromatic polyamide
polymer solution obtained as above further contains an alkali
metal salt or an alkaline earth metal salt, as a result, the
solution becomes more stable and thus can be used at higher
concentrations and lower temperatures. It is preferable that
the proportion of the alkali metal salt or alkaline earth metal
salt is 1 mass% or less, more preferably 0.1 mass% or less, based
on the total mass of the polymer solution.
In a spinning/coagulation step, the spinning solution
obtained above (meta-type wholly aromatic polyamide polymer
solution) is extruded into a coagulation liquid and coagulated.
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The spinning apparatus is not particularly limited and may
be a conventionally known wet-spinning apparatus. In addition,
as long as stable wet spinning can be performed, there is no
need to particularly limit the number of spinning holes of a
spinneret, their arrangement, the hole shape, etc. For example,
it is possible to use a multi-hole spinneret for staple fibers,
in which the number of holes is 1,000 to 30,000 and the spinning
hole diameter is 0.05 to 0.2 mm, etc.
In addition, it is suitable that the temperature of the
spinning solution (meta-type wholly aromatic polyamide polymer
solution) upon extrusion from the spinneret is within a range
of 20 to 90 C.
As a coagulation bath used to obtain a fiber for use in
the invention, an aqueous solution containing substantially no
inorganic salt and having an amide solvent, preferably NMP,
concentration of 45 to 60 mass% is used at a bath liquid
temperature within a range of 10 to 50 C. An amide solvent
(preferably NMP) concentration of less than 45 mass% leads to
a structure with a thick skin. As a result, the washing
efficiency in a washing step decreases, making it difficult to
reduce the residual solvent content of the fiber. Meanwhile,
in the case where the amide solvent (preferably NMP)
concentration is more than 60 mass%, uniform coagulation inside
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the fiber cannot be achieved, making it difficult to reduce the
residual solvent content of the fiber. Incidentally, it is
suitable that the time of fiber immersion in the coagulation
bath is within a range of 0.1 to 30 seconds.
Subsequently, the fiber is drawn to a draw ratio of 3 to
4 in a plastic drawing bath containing an aqueous solution having
an amide solvent, preferably NMP, concentration of 45 to 60 mass%
at a bath liquid temperature within a range of 10 to 50 C. After
drawing, the fiber is thoroughly washed with an aqueous solution
at 10 to 30 C having an NMP concentration of 20 to 40 mass% and
then through a hot water bath at 50 to 70 C.
The fiber after washing is subjected to a dry heat
treatment at a temperature of 270 to 290 C, whereby a meta-type
wholly aromatic aramid fiber that satisfies the above
crystallinity and residual solvent content ranges can be
obtained.
The obtained meta-type wholly aromatic aramid fiber is cut
by a known method into staple fibers, further blend-spun into
a spun yarn with the above flame-retardant fibers such as
meta-type wholly aromatic aramid fibers, synthetic fibers such
as polyester fibers and polyamide fibers, regenerated fibers,
natural fibers, etc., and woven or knitted, whereby a
heat-resistant fabric of the invention can be obtained.
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The method for preparing the heat-resistant fabric of the
invention is not particularly limited, and any known methods
maybe employed. For example, it is possible that the above spun
yarn is prepared and then, as a single yarn or a 2-ply yarn,
woven into a twill weave, plain weave, or like structure using
a rapier loom, etc., thereby giving the heat-resistant fabric.
In addition, in the invention, a UV absorber and/or UV
reflector may be contained in any fiber that forms the
heat-resistant fabric. It is preferable that the UV absorber
is highly hydrophobic and has a solubility of less than 0.04
mg/L in water. When the solubility is 0.04 mg/L or more, such
a UV absorber and/or uv reflector is likely to elute during
carrier dyeing, and the light resistance after dyeing tends to
easily decrease; therefore, this is undesirable.
It is preferable that the UV absorber and/or UV reflector
used in the invention is a compound that efficiently shields
light near 360 nm, which is the photodegradation characteristic
wavelength of a meta-wholly aromatic polyamide mainly used in
the heat-resistant fabric of the invention, and has almost no
absorption in the visible region.
As a UV absorber for use in the invention, a specific
substituted benzotriazole is preferable. Specific examples
thereof
include
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2- (2H-benzotriazol-2-y1)-4,6-di-tert-pentylphenol,
2- [5-chloro (2H) -benzotriazol-2-yl] -4-methyl-6- (tert-butyl)p
henol,
2- [2H-benzotriazol-2-y1]-4-6-bis (1-methy1-1-phenylethyl)phe
nol, and
2- [2H-benzotriazol-2-yl] -4- (1,1,3,3-tetramethylbutyl ) phenol .
Among these,
2- [2H-benzotriazol-2-y1]-4-6-bis (1-methy1-1-phenylethyl)phe
nol is particularly preferable because of its high
hydrophobicity and low absorption in the visible region.
Examples of UV reflectors include fine particles of metal
oxides, such as titanium oxide, zinc oxide, selenium oxide,
alumina, and silica, and calcium carbonate preferably having
a particle size of 0.001 to 0.2 IAM, more preferably 0.005 to 0.02
In the heat-resistant fabric of the invention, the fiber
to contain such a UV absorber and/or uv reflector is not limited.
For example, in the case where it is contained in the meta-type
wholly aromatic polyamide fiber, in terms of production
stability and for actual use as a fabric or garment, it is
preferable that the content is 3.0 to 6.5 mass%, more preferably
4.5 to 6.5 mass%, based on the total mass of the meta-type wholly
aromatic polyamide fiber.
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In addition, in the heat-resistant fabric of the invention,
the UV absorber and/or UV reflector may also be fixed to the
fabric surface. The fixing method is not particularly limited.
For example, a water dispersion of the UV absorber and/or UV
reflector is applied to the fabric by immersion/ squeezing or
spraying, and then dried and cured. It is also possible to use
a binder such as resin or latex in order to increase the
durability of fixing. For example, in the above method, before
the fabric is treated with a water dispersion, resin or latex,
which is a binder component, may be previously mixed with the
water dispersion as an aqueous product.
With the heat-resistant fabric obtained by the above
method, which is made of a meta-type wholly aromatic aramid fiber
and preferably contains the above materials mixed therewith in
the above mixing proportions, it is possible to achieve the
excellent performance, that is, an abrasion resistance of 200
rubs or more and a tear strength of 20 N or more, with the retention
of the abrasion resistance and the retention of the tear strength
after 100 washes being each 90% or more relative to before washing.
In addition, the above strength, elongation, standard deviations
thereof, toughness, etc., can be easily achieved.
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Examples
Hereinafter, the invention will be described in detail
with reference to examples, but the invention is not limited
thereto. Incidentally, in the examples, the properties were
measured by the following methods.
(1) Average and Standard Deviation of Strength, Average and
Standard Deviation of Elongation, and Toughness of Single Fibers
The single-fiber strength and elongation were measured
from ten single fibers in accordance with the JIS L1015-99 method,
and the average and standard deviation of each were calculated.
In addition, toughness was calculated by the following equation.
Toughness = average strength x average elongation
(2) Abrasion Resistance of Fabric
Measurement was performed in accordance with the JIS L1096
8.19.1 A-1 method (universal type method (plane method) ,
abrasion tester press load: 4.45 N (0.454 kf) , paper: #600) .
The abrasion resistance of a fabric was measured before washing
(LO) and after 100 washes in accordance with JIS L0844 No. A-1
(L100) , and the retention of abrasion resistance before and after
washing (L100/L0 x 100) was calculated.
(2) Tear Strength of Fabric
Measurement was performed in accordance with the JIS L1096
8.17.4 D method (pendulum method) . The tear strength of a fabric
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was measured before washing (LO) and after 100 washes in
accordance with JIS L0844 No. A-1 (L100) , and the retention of
tear strength before and after washing (L100/L0 x 100) was
calculated.
(3) Pilling Resistance of Fabric
Measurement was performed in accordance with the JIS L1076
A method.
(4) Flame Retardancy of Fabric (Limiting Oxygen Index)
In accordance with the JIS L1091 E method, the
concentration of oxygen necessary to keep burning 50 mm or more
was defined as a limiting oxygen index (LOI) .
(5) Residual Solvent Content
About 8.0 g of a raw fiber is collected, dried at 105 C
for 120 minutes, and then allowed to cool in a desiccator, and
the fiber mass (M1) is measured. Subsequently, the fiber is
subjected to reflux extraction in methanol for 1.5 hours using
a Soxhlet extractor to extract the amide solvent contained in
the fiber. After extraction, the fiber is removed, vacuum-dried
at 150 C for 60 minutes, and then allowed to cool in a desiccator,
and the fiber mass (M2) is measured. Using the obtained M1 and
M2, the content of residual solvent in the fiber (amide solvent
mass) is calculated by the following equation.
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Residual solvent content (%) = [(M1 - M2)/M1] x 100
The obtained raw fiber was crimped and cut into staple
fibers 51 mm in length (raw stock).
(6) Crystallinity
Using an X-ray diffraction apparatus (RINT TTRIII
manufactured by Rigaku Corporation), raw fibers were bundled
into a fiber bundle of about 1 mm in diameter and mounted on
a fiber sample table to measure the diffraction profile. The
measurement conditions were as follows: Cu-Ka radiation source
(50 kV, 300 mA), scanning angle range: 10 to 35 , continuous
measurement, measurement width: 0.1 , scanning at 1 /min. From
the measured diffraction profile, air scattering and incoherent
scattering were corrected by linear approximation to give the
total scattering profile. Next, the amorphous scattering
profile was subtracted from the total scattering profile to give
the crystal scattering profile. Crystallinity was determined
from the integrated intensity of the crystal scattering profile
(crystal scattering intensity) and the integrated intensity of
the total scattering profile (total scattering intensity) by
the following equation.
Crystallinity (%) = [crystal scattering intensity/total
scattering intensity] x 100
(7) Brightness L and Light-Resistance Color Difference AE of
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Fabric
Using fabrics having a color difference AE of 0.1 or less,
one was subjected to a light resistance test in accordance with
JIS L 0842 (UV carbon arc light exposure time: 10 hours) . Using
the fabrics before and after the light resistance test,
respectively, the specimens were subjected to color measurement
using a colorimeter MacBeth Color-Eye 3100 and a color
measurement light source D65 to determine the brightness L value
and the color E value (the area of color measurement: 0.2 cm2,
the average of measurements at ten points was defined as the
E value of the fabric) , and the color difference AE between the
two fabrics was calculated.
(8) Soil-Resistance Color Difference AE* of Fabric
Rubbing fabric (soiled fabric) : Standard Cotton Duck No. 9 of
JIS L3102
Artificial soil component: a mixture of the following soil powder
and artificial sebum in a ratio of 1:10
Soil powder: an intimate mixture of the following powders:
JIS Z8901 Test Powder Class 12 (carbon black, particle size:
0.03 to 0.2 i.tm) , 25 mass%; and JIS Z8901 Test Powder Class 8 (the
loamy layer of the Kanto Plain, particle size: 8 jam), 75 mass%
Artificial sebum: a mixture of 70 mass% oleic acid and 30
mass% palmitic acid
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Used apparatus: JIS L0849 abrasion tester, Type II (JSPS type)
Procedure:
l. Instead of the waterproof abrasive paper of JIS L0849,
the rubbing fabric (soiled fabric) is attached to the loader
with a double-stick tape.
2. 0.05 g of the artificial soil component is uniformly
applied to the rubbing fabric.
3. A specimen fabric is attached to the fabric set part
of the abrasion tester with a double-stick tape.
4. The rubbing fabric prepared in 2 is attached to the
loader set part of the abrasion machine.
5. The loader is moved back and forth 50 times on the surface
of the specimen fabric to give a soil load.
6. The specimen fabric is removed from the surface abrasion
tester.
7. The soil-resistance color difference AE * of the fabric
specimen between the soiled part and the non-soiled part is
measured.
The smaller the AE*, the smaller the color tone change due
to soiling, indicating higher the soil resistance. A
specification that resulted in a AE* of 20 or less was judged
as effective to serve as a product that would have sufficient
merchantability in market even after a lapse of about three years,
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while a specification that resulted in a AE* of more than 20
was judged as having no such effects.
[Production of Meta-Type Wholly Aromatic Aramid Fiber]
A meta-type wholly aromatic aramid fiber was prepared by
the following method.
20.0 parts by mass of a polymetaphenylene isophthalamide
powder having an intrinsic viscosity (I .V.) of 1.9 produced by
interfacial polymerization in accordance with the method
described in JP-B-47-10863 was suspended in 80.0 parts by mass
of N-methyl-2-pyrrolidone (NMP) cooled to -10 C, thereby forming
a slurry. Subsequently, the suspension was heated to 60 C for
dissolution to give a transparent polymer solution. A
2-[2H-benzotriazol-2-y1]-4-6-bis(1-methyl-1-phenylethyl)phe
nol powder (solubility in water: 0.01 mg/L) in an amount of 3.0
mass% relative to the polymer was mixed with and dissolved in
the polymer solution, and the mixture was defoamed under reduced
pressure to give a spinning solution (spinning dope).
In Example 1, a UV
absorber
2-[2H-benzotriazol-2-y1]-4-6-bis(1-methyl-1-phenylethyl)phe
nol was added to the spinning solution.
[Spinning/Coagulation Step]
The spinning dope was discharged and spun from a spinneret
(hole diameter: 0.07 mm, the number of holes: 500) into a
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coagulation bath at a bath temperature of 30 C. The composition
of the coagulation liquid was water/NMP = 45/55 (part by mass) .
The spinning dope was discharged and spun into the coagulation
bath at a yarn speed of 7 m/min.
[Plastic-Drawing-Bath Drawing Step]
Subsequently, drawing was performed to a draw ratio of 3.7
in a plastic drawing bath at a temperature of 40 C having the
following composition: water/NP = 45/55 (part by mass) .
[Washing Step]
After drawing, washing was performed in a bath at 20 C and
water/NP = 70/30 (immersion length: 1.8 m) and then in a water
bath at 20 C (immersion length: 3.6 m) , followed by thorough
washing through a hot water bath at 60 C (immersion length: 5.4
m) .
[Dry Heat Treatment Step]
The fiber after washing was subjected to a dry heat
treatment using a hot roller having a surface temperature of
283 C to give a meta-type aromatic polyamide fiber.
[Properties of Raw Fiber]
The obtained meta-type wholly aromatic aramid fiber had
the following properties: fineness: 1.6 dtex, residual solvent
content: 0.08 mass%, crystallinity: 20%, LOI: 30.
As raw stocks for other fibers, the following were used.
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Polyester fiber (polyethylene terephthalate fiber) ; "Tetorone"
manufactured by Teijin
Flame-retardant rayon fiber; "LenzingFRO" manufactured by
Lenzing
Para-type wholly aromatic polyamide fiber; "Twaron "
manufactured by Teijin. Aramid
[Fabric Dyeing Method]
The brightness L was adjusted with a dye so that fabrics
after dyeing had an L value of 49 (neutral color) regardless
of the foundation fabrics. Redyeing was performed as necessary
to accurately control the L value. The conditions for dyeing
and the conditions for washing a dyed product in a reducing bath
(pH 5.5) were as follows.
(Dyeing Conditions)
Cationic dye: manufactured by Nippon Kayaku, trade name:
Kayacryl Red GL-ED, 1% owf
Bath ratio; 1:20
Temperature x Time; 120 C x 30 minutes
(Reducing Bath Composition and Washing Conditions)
Reducing bath; thiourea dioxide, 1 g/1
Bath ratio; 1:20
Temperature x Time; 70 C x 15 minutes
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Subsequently, drying was performed at a temperature of
110 C for 10 minutes, followed by dry heat setting at a
temperature of 130 C for 2 minutes, thereby giving a colored
fabric.
[Example 1]
Staple fibers of a meta-type wholly aromatic polyamide
fiber (MA) , a para-type wholly aromatic polyamide fiber (PA),
a polyester fiber (PE) , and a flame-retardant rayon fiber (RY)
(each 51 mm in length) were blend-spun in a mass ratio MA/PA/PE/RY
of 55/5/15/25 into a spun yarn (36 count, 2-ply yarn) , and woven
at a weaving density of warp: 100 yarns/25.4 mm and weft: 56
yarns/25.4 mm, thereby giving a twill-woven fabric having an
areal weight of 230 g/m2. The meta-type wholly aromatic
polyamide fiber (MA) had an average strength of 3.7 cN/dtex with
a standard deviation of 0.54, an average elongation of 25% with
a standard deviation of 4.7, a toughness of 93, a crystallinity
of 20%, and a residual solvent content of 0.08 mass% . The woven
fabric was dyed by the above method to a neutral color (L value:
49) .
The abrasion resistance of the obtained fabric was
measured. As a result, the resistance before washing (LO) was
215 rubs, while the resistance after 100 washes (L100) was 200
rubs. Thus, the retention of abrasion resistance (L100 /LO x 100)
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was 93%. In addition, the tear strength of the obtained fabric
was measured. As a result, the strength before washing (LO) was
35.3 N in the longitudinal direction and 24.1 N in the transverse
direction, while the strength after 100 washes (L100) was 31.9
N in the longitudinal direction and 23.2 N in the transverse
direction. Thus, the retention of tear strength (L100/L0 x 100)
was 90% in the longitudinal direction and 96% in the transverse
direction. Further, pilling was Level 4 in the longitudinal
direction and Level 4 in the transverse direction.
[Example 2]
The same procedure as in Example 1 was performed, except
that the meta-type wholly aromatic polyamide fiber (MA) was
changed to a meta-type wholly aromatic aramid fiber containing
mass% of a UV absorber
2- [2H-benzotriazol-2-y1]-4-6-bis (1-methy1-1-phenylethyl)phe
nol (51 min in length) , the para-type wholly aromatic polyamide
fiber (PA) was not used, and the mass ratio was MA/PA/PE/RY =
60/0/15/25. The meta-type wholly aromatic polyamide fiber (MA)
had an average strength of 3.6 cN/dtex with a standard deviation
of 0.55, an average elongation of 25% with a standard deviation
of 4.8, a toughness of 90, a crystallinity of 20%, and a residual
solvent content of 0.05 mass%.
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The abrasion resistance of the obtained fabric was
measured. As a result, the resistance before washing (LO) was
209 rubs, while the resistance after 100 washes (L100) was 200
rubs. Thus, the retention of abrasion resistance (L100/L0 x 100)
was 96%. In addition, the tear strength of the obtained fabric
was measured. As a result, the strength before washing (LO) was
32.4 N in the longitudinal direction and 23.2 N in the transverse
direction, while the strength after 100 washes (L100) was 29.8
N in the longitudinal direction and 22.5 N in the transverse
direction. Thus, the retention of tear strength (L100/L0 x 100)
was 92% in the longitudinal direction and 97% in the transverse
direction. Further, pilling was Level 4 in the longitudinal
direction and Level 4 in the transverse direction.
The fabric had a brightness L of 49, with 0.45 x L - 11.3
being 11.25, a light-resistance color difference AE of 10.73,
and a soil-resistance color difference AE* of 15.
[Comparative Example 1]
The same procedure as in Example 1 was performed, except
that in the production of a meta-type wholly aromatic polyamide
fiber (MA) , the composition of the coagulation liquid in the
coagulation step was changed to water/NMP = 40/60 (part by mass) .
The results are shown in Table 1. The meta-type wholly aromatic
polyamide fiber (MA) had an average strength of 4.2 cN/dtex with
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a standard deviation of 0.61, an average elongation of 29% with
a standard deviation of 4.8, a toughness of 121, a crystallinity
of 20%, and a residual solvent content of 0.15 mass%.
The abrasion resistance of the obtained fabric was
measured. As a result, the resistance before washing (LO) was
211 rubs, while the resistance after 100 washes (L100) was 185
rubs. Thus, the retention of abrasion resistance (L100/L0 x 100)
was 88%. In addition, the tear strength of the obtained fabric
was measured. As a result, the strength before washing (LO) was
36.3 N in the longitudinal direction and 24.1 N in the transverse
direction, while the strength after 100 washes (L100) was 30.4
N in the longitudinal direction and 23.0 N in the transverse
direction. Thus, the retention of tear strength (L100/L0 x 100)
was 84% in the longitudinal direction and 95% in the transverse
direction. Further, pilling was Level 3 in the longitudinal
direction and Level 3 in the transverse direction.
[Comparative Example 2]
The same procedure as in Example 1 was performed, except
that in the production of a meta-type wholly aromatic polyamide
fiber (MA) , the surface temperature of the hot roller in the
dry heat treatment step was changed to 315 C. The meta-type
wholly aromatic polyamide fiber (MA) had a crystallinity of 28%
and a residual solvent content of 0.08 mass%.
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The abrasion resistance of the obtained fabric was
measured. As a result, the resistance before washing (LO) was
250 rubs, while the resistance after 100 washes (L100) was 200
rubs. Thus, the retention of abrasion resistance (L100/L0 x 100)
was 80%. In addition, the tear strength of the obtained fabric
was measured. As a result, the strength before washing (LO) was
36.3 N in the longitudinal direction and 24.2 N in the transverse
direction, while the strength after 100 washes (L100) was 31.8
N in the longitudinal direction and 23.1 N in the transverse
direction. Thus, the retention of tear strength (L100/L0 x 100)
was 86% in the longitudinal direction and 95% in the transverse
direction. Further, pilling was Level 3 in the longitudinal
direction and Level 3 in the transverse direction.
[Comparative Example 31!
The same procedure as in Example 1 was performed, except
that the spun yarn was changed to a spun yarn made only of a
flame-retardant rayon fiber (RY) .
The abrasion resistance of the obtained fabric was
measured. As a result, the resistance before washing (LO) was
57 rubs, while the resistance after 100 washes (L100) was 40
rubs. Thus, the retention of abrasion resistance (L100/L0 x 100)
was 70%. In addition, the tear strength of the obtained fabric
was measured. As a result, the strength before washing (LO) was
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20 N in the longitudinal direction and 12 N in the transverse
direction, while the strength after 100 washes (L100) was 10
N in the longitudinal direction and 7 N in the transverse
direction. Thus, the retention of tear strength (L100/L0 x 100)
was 50% in the longitudinal direction and 58% in the transverse
direction. Further, pilling was Level 3 in the longitudinal
direction and Level 3 in the transverse direction.
[Comparative Example 4]
The same procedure as in Example 1 was performed, except
that the spun yarn was changed to a spun yarn made only of a
polyester fiber (PE). The results are shown in Table 1.
The abrasion resistance of the obtained fabric was
measured. As a result, the resistance before washing (LO) was
67 rubs, while the resistance after 100 washes (L100) was 41
rubs. Thus, the retention of abrasion resistance (L100/L0 x 100)
was 61%. In addition, the tear strength of the obtained fabric
was measured. As a result, the strength before washing (LO) was
21 N in the longitudinal direction and 10 N in the transverse
direction, while the strength after 100 washes (L100) was 11
N in the longitudinal direction and 6 N in the transverse
direction. Thus, the retention of tear strength (L100/L0 x 100)
was 52% in the longitudinal direction and 60% in the transverse
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direction. Further, pilling was Level 3 in the longitudinal
direction and Level 3 in the transverse direction.
Industrial Applicability
The heat-resistant fabric of the invention is excellent
in terms of surface abrasion characteristics, tear
characteristics, and the washing durability of these
characteristics, and also has pilling resistance, a color tone
that meets various user needs, and heat resistance. Therefore,
the heat-resistant fabric of the invention is applicable to
protective garments, such as firefighter garments, and
industrial materials, such as flexible heat-insulating
materials, and thus is industrially extremely useful.
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