Technical Field
[0001] The present invention relates to a heat-resistant fabric made of a meta-type aromatic
polyamide fiber.
Background Art
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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 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
[0007] 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
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] In the heat-resistant fabric of the invention, it is preferable that the heat-resistant
fabric is dyed, and the color difference ΔE of the fabric before and after a light
resistance test in accordance with JIS L0842 and the brightness L of the light resistance
test fabric satisfy the following equation (1) :

[0016] In the heat-resistant fabric of the invention, it is preferable that the meta-type
wholly aromatic polyamide fiber contains an organic dye.
[0017] 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.
[0018] In the heat-resistant fabric of the invention, it is preferable that the cellulose
fiber is rayon.
[0019] 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.
[0020] 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.
[0021] 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.
[0022] 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-Ar1-NH-CO-Ar1-CO) formula (1)
wherein Ar1 is a divalent aromatic group having a linking group in a position other
than the meta position or an axially parallel direction.
[0023] 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):
H
2N-Ar2-NH
2 formula (2)
H
2N-Ar2-Y-Ar2-NH
2 formula (3)
XOC-Ar3-COX formula (4)
XOC-Ar3-Y-Ar3-COX formula (5)
wherein Ar2 is a divalent aromatic group different from Ar1, Ar3 is a divalent aromatic
group different from Ar1, 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.
[0024] 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.
[0025] 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 fiber in an amount
of 1 to 20 mass% based on the mass of the heat-resistant fabric.
[0026] 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.
[0027] 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.
[0028] 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
[0029] 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.
Mode for Carrying Out the Invention
[0030] 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.
[0031] 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%.
[0032] 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), 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.
[0033] 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 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.
[0034] 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.
[0035] 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.
[0036] 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 tributylbenzylammonium salt are particularly preferable because they are easily
available, have excellent thermal stability, and also have high solubility in N-methyl-2-pyrrolidone.
[0037] 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.
[0038] 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.
[0039] 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 of the third
component is 1 to 10 mol% based on the total repeating structural units of the aromatic
polyamide:
- (NH-Ar1-NH-CO-Ar1-CO) formula (1)
wherein Ar1 is a divalent aromatic group having a linking group in a position other
than the meta position or an axially parallel direction.
[0040] 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.
H
2N-Ar2-NH
2 formula (2)
H
2N-Ar2-Y-Ar2-NH
2 formula (3)
XOC-Ar3-COX formula (4)
XOC-Ar3-Y-Ar3-COX formula (5)
[0041] In the formulae, Ar2 is a divalent aromatic group different from Ar1, Ar3 is a divalent
aromatic group different from Ar1, 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] 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 abrasion resistance and tear strength can be achieved at the same time.
[0048] 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.
[0049] 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 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.
[0050] 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.
[0051] 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.
[0052] 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, 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.
[0053] 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.
[0054] 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.
[0055] 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,
and polyamide fiber, it is preferable to employ those containing a flame retarder.
[0056] 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.
[0057] 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.
[0058] As indices for objectively showing this, soil resistance and soil hide characteristics
are effective. As a specific method and evaluation criteria, the value of color difference
ΔE* from the state where soil is deposited is used as an index. Qualitatively, it
can be said that the smaller the ΔE* value, the higher the soil hide characteristics,
that is, soiling is less noticeable, which is more desirable.
[0059] In order to achieve such excellent aesthetics, in the invention, it is preferable
that the color difference ΔE 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):

[0060] That is, in the invention, it has been found that when a fabric satisfies the ΔE
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 be achieved. The upper limit of the ΔE value
can be set in direct proportion to the brightness L value of the original fabric.
[0061] 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.
[0062] 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.
[0063] 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.
[0064] 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.
[0065] 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.
[0066] 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.
[0067] 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.
[0068] 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.
[0069] 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.
[0070] 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 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.
[0071] 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.
[0072] 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.
[0073] 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.
[0074] The method for preparing the heat-resistant fabric of the invention is not particularly
limited, and any known methods may be 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.
[0075] 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.
[0076] 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.
[0077] As a UV absorber for use in the invention, a specific substituted benzotriazole is
preferable. Specific examples thereof include 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol,
2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl) phenol, 2-[2H-benzotriazol-2-yl]-4-6-bis(1-methyl-1-phenylethyl)ph
enol, and 2-[2H-benzotriazol-2-yl]-4-(1,1,3,3-tetramethylbutyl)pheno l. Among these,
2-[2H-benzotriazol-2-yl]-4-6-bis(1-methyl-1-phenylethyl)ph enol is particularly preferable
because of its high hydrophobicity and low absorption in the visible region.
[0078] 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 µm, more preferably 0.005 to 0.02 µm.
[0079] 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.
[0080] 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.
[0081] 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.
Examples
[0082] 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
[0083] 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.

(2) Abrasion Resistance of Fabric
[0084] 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 (L0) 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
[0085] Measurement was performed in accordance with the JIS L1096 8.17.4 D method (pendulum
method). The tear strength of a fabric was measured before washing (L0) 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
[0086] Measurement was performed in accordance with the JIS L1076 A method.
(4) Flame Retardancy of Fabric (Limiting Oxygen Index)
[0087] 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
[0088] 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.

[0089] The obtained raw fiber was crimped and cut into staple fibers 51 mm in length (raw
stock).
(6) Crystallinity
[0090] 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-Kα 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.

(7) Brightness L and Light-Resistance Color Difference ΔE of Fabric
[0091] Using fabrics having a color difference ΔE 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 cm
2, the average of measurements at ten points was defined as the E value of the fabric),
and the color difference ΔE between the two fabrics was calculated.
(8) Soil-Resistance Color Difference ΔE* 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
[0092] Soil powder: an intimate mixture of the following powders: JIS Z8901 Test Powder
Class 12 (carbon black, particle size: 0. 03 to 0.2 µm), 25 mass%; and JIS Z8901 Test
Powder Class 8 (the loamy layer of the Kanto Plain, particle size: 8 µm), 75 mass%
[0093] Artificial sebum: a mixture of 70 mass% oleic acid and 30 mass% palmitic acid
Used apparatus: JIS L0849 abrasion tester, Type II (JSPS type) Procedure:
- 1. 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 ΔE * of the fabric specimen between the soiled
part and the non-soiled part is measured.
[0094] The smaller the ΔE*, the smaller the color tone change due to soiling, indicating
higher the soil resistance. A specification that resulted in a ΔE* 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, while a specification that resulted
in a ΔE* of more than 20 was judged as having no such effects.
[Production of Meta-Type Wholly Aromatic Aramid Fiber]
[0095] A meta-type wholly aromatic aramid fiber was prepared by the following method.
[0096] 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
[0097] 2-[2H-benzotriazol-2-yl]-4-6-bis(1-methyl-1-phenylethyl)ph enol 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).
[0098] In Example 1, a UV absorber 2-[2H-benzotriazol-2-yl]-4-6-bis(1-methyl-1-phenylethyl)ph
enol was added to the spinning solution.
[Spinning/Coagulation Step]
[0099] The spinning dope was discharged and spun from a spinneret (hole diameter: 0.07 mm,
the number of holes: 500) into a 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]
[0100] 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/NMP = 45/55 (part
by mass).
[Washing Step]
[0101] After drawing, washing was performed in a bath at 20°C and water/NMP = 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]
[0102] 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]
[0103] The obtained meta-type wholly aromatic aramid fiber had the following properties:
fineness: 1.6dtex, residual solvent content: 0.08 mass%, crystallinity: 20%, LOI:
30.
[0104] As raw stocks for other fibers, the following were used. Polyester fiber (polyethylene
terephthalate fiber); "Tetoron®" manufactured by Teijin
Flame-retardant rayon fiber; "LenzingFR®" manufactured by Lenzing
[0105] Para-type wholly aromatic polyamide fiber; "Twaron®" manufactured by Teijin Aramid
[Fabric Dyeing Method]
[0106] 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/l
Bath ratio; 1:20
Temperature x Time; 70°C x 15 minutes
[0107] 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]
[0108] 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/m
2. 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).
[0109] The abrasion resistance of the obtained fabric was measured. As a result, the resistance
before washing (L0) was 215 rubs, while the resistance after 100 washes (L100) was
200 rubs. Thus, the retention of abrasion resistance (L100/L0 x 100) was 93%. In addition,
the tear strength of the obtained fabric was measured. As a result, the strength before
washing (L0) 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]
[0110] 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 5 mass% of a UV absorber 2-[2H-benzotriazol-2-yl]-4-6-bis(1-methyl-1-phenylethyl)ph
enol (51 mm 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%.
[0111] The abrasion resistance of the obtained fabric was measured. As a result, the resistance
before washing (L0) 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 (L0) 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.
[0112] The fabric had a brightness L of 49, with 0.45 x L - 11.3 being 11.25, a light-resistance
color difference ΔE of 10.73, and a soil-resistance color difference ΔE* of 15.
[Comparative Example 1]
[0113] 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 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%.
[0114] The abrasion resistance of the obtained fabric was measured. As a result, the resistance
before washing (L0) 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 (L0) 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]
[0115] 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%.
[0116] The abrasion resistance of the obtained fabric was measured. As a result, the resistance
before washing (L0) 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 (L0) 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 3]
[0117] 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).
[0118] The abrasion resistance of the obtained fabric was measured. As a result, the resistance
before washing (L0) 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 (L0) was 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]
[0119] 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.
[0120] The abrasion resistance of the obtained fabric was measured. As a result, the resistance
before washing (L0) 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 (L0) 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 direction.
Further, pilling was Level 3 in the longitudinal direction and Level 3 in the transverse
direction.
Industrial Applicability
[0121] 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.