Technical Field of the Invention
[0001] The present invention relates to a fiber which is dyeable with an acid dye and has
moisture-absorption property and also to a method of manufacturing the same.
Background Art
[0002] A crosslinked acrylic acid fiber has been known to have harmonic functions such as
pH buffer property, antistatic property and water-holding property and also high moisture-absorption
rate, high moisture-absorption velocity, high moisture-absorption rate difference
or temperature adjusting and humidity adjusting functions derived therefrom and has
been used in the fields of clothing and industrial materials. However, the crosslinked
acrylic acid fiber has a problem in its dyeing property and that is a main cause for
suppressing the development of its use.
[0003] Since the crosslinked acrylic acid fiber has a carboxyl group which functions as
a dyeing site for a cationic dye, it is possible to add the color thereto using a
cationic dye in principle. However, since the ionic bond formed between the cationic
dye and the carboxyl group is weak, the cationic dye is apt to be liberated by, for
example, a change in pH. In addition, swelling property of the fiber in water is high
and, therefore, the liberated cationic dye is easily eluted therefrom. Accordingly,
it is not possible to give a color fastness which is in a level of being durable against
practical use by mere dyeing using common formulations.
[0004] For solving the problem for the dyeing property as such, Patent Documents 1 and 2
propose a dyeing method for a crosslinked acrylic acid fiber using a reactive dye.
Although the color fastness is improved by the use of a reactive dye in such a method,
it is necessary that the pH upon dyeing is made under a strongly acidic condition
and there is a problem that it is necessary to restrict the mixed fiber used together
and to cope with the device such as countermeasure for corrosion. Further, in dyeing
a fiber structure mixed with a cellulose fiber, there may be the case where the difference
is resulted in the hue from the cellulose fiber and there is a weakness in a practical
color matching.
[0005] In Patent Document 3, there is a proposal for a fiber into which sulfonic group is
introduced by impregnating a monomer having sulfonic group into a material fiber having
carboxyl group followed by polymerizing. Since this fiber has many sulfonic groups
which function as a dyeing site for a cationic dye, coloration using a cationic dye
is possible but it is difficult to achieve sufficient coloring property or color fastness
and hue stability. In addition, since there is adopted a means where sulfonic group
is introduced by impregnating a monomer having sulfonic group into a material fiber
followed by polymerizing, there is a problem that complicated operations are necessary,
which results in high production cost.
Prior Art Documents
Patent Documents
[0006]
Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2003-278079
Patent Document 2: Japanese Patent Application Laid-Open (JP-A) No. 2006-70421
Patent Document 3: Japanese Patent Application Laid-Open (JP-A) No. 2008-174849
Disclosure of the Invention
Problem that the Invention is to Solve
[0007] As mentioned hereinabove, the conventional crosslinked acrylic acid fiber has such
characteristics that the harmonic functions such as pH buffer property, antistatic
property and water-holding property and also high moisture-absorption rate, high moisture-absorption
velocity, high moisture-absorption rate difference or temperature adjusting and humidity
adjusting functions derived therefrom, but there is still a problem for its dyeing
property. The present invention has been achieved under such current circumstances
and its object is to provide a fiber where a practical dyeing with an acid dye is
possible while the characteristics of the crosslinked acrylic acid fiber such as high
moisture-absorption property or high moisture-absorption rate difference are still
available.
Means for Solving the Problem
[0008] The present inventors have carried out intensive investigations for achieving the
above object and resulted in the present invention as shown below.
[0009]
- (1) A moisture-absorptive fiber dyeable with an acid dye, comprising a region of a
polymer having a functional group acting as a dyeing site for acid dye and a region
of a polymer having a crosslinked structure and a carboxyl group, wherein the saturation
dye uptake of the acid dye to the fiber weight is 3.5 to 10% by weight and the carboxyl
group content is 1.0 to 10 mmol/g.
- (2) The moisture-absorptive fiber dyeable with an acid dye according to (1), wherein
the polymer having a functional group acting as a dyeing site for acid dye is such
a polymer where acrylonitrile is a main component and a vinyl monomer having at least
a cationic group is a copolymerizing component.
- (3) The moisture-absorptive fiber dyeable with an acid dye according to (1), wherein
the polymer having a functional group acting as a dyeing site for acid dye is such
a polymer which is produced by subjecting a polymer where acrylonitrile is a main
component to a treatment with a nitrogen-containing compound having two or more nitrogen
atoms in a molecule.
- (4) The moisture-absorptive fiber dyeable with an acid dye according to (1), wherein
the polymer having a crosslinked structure and a carboxyl group is such a polymer
which is produced by subjecting a polymer where acrylonitrile is a main component
to a treatment with a nitrogen-containing compound having two or more nitrogen atoms
in a molecule and to a hydrolyzing treatment.
- (5) A method for manufacturing the moisture-absorptive fiber dyeable with an acid
dye mentioned in (1), characterized in that, a surface layer area of a fiber comprising a polymer where acrylonitrile is a main
component and a vinyl monomer having at least a cationic group is a copolymerizing
component is subjected to a crosslinking treatment with a nitrogen-containing compound
having two or more nitrogen atoms in a molecule and to a hydrolyzing treatment.
- (6) A method for manufacturing the moisture-absorptive fiber dyeable with an acid
dye mentioned in (1), wherein a fiber comprising a polymer where acrylonitrile is
a main component is subjected to a crosslinking treatment with a nitrogen-containing
compound having two or more nitrogen atoms in a molecule and, after that, to a hydrolyzing
treatment, characterized in that, the range to which the hydrolyzing treatment is applied is made smaller than the
range to which the crosslinking treatment is applied.
Advantages of the Invention
[0010] The moisture-absorptive fiber dyeable with an acid dye according to the present invention
comprises a region of a polymer having a functional group acting as a dyeing site
for acid dye and a region of a polymer having a crosslinked structure and a carboxyl
group. As a result thereof, a practical dyeing with an acid dye is now possible and
its moisture-absorption property becomes high as well. Therefore, in the moisture-absorptive
fiber dyeable with an acid dye according to the present invention, its restriction
concerning the color is little and it also can be developed to the use such as the
use where color is regarded to be important, for which the development by the conventional
crosslinked acrylic acid fiber has been difficult.
Best Mode for Carrying Out the Invention
[0011] The moisture-absorptive fiber dyeable with an acid dye according to the present invention
comprises a region of a polymer having a functional group acting as a dyeing site
for acid dye and a region of a polymer having a crosslinked structure and a carboxyl
group.
[0012] The region of a polymer having a crosslinked structure and a carboxyl group in the
moisture-absorptive fiber dyeable with an acid dye according to the present invention
is an area which mainly plays a role of a moisture-absorption property which is one
of the big characteristics of the fiber. As mentioned already, carboxyl group existing
in such a region can form an ionic bond to cationic dye but, since ion exchange easily
takes place, the resulting color fastness is bad and the dyeing in a practical level
is not possible. In the fiber of the present invention, there is provided a region
of a polymer having a functional group acting as a dyeing site for acid dye, which
region is different from the above-mentioned region whereby the dyeing in a practical
level with acid dye is made possible.
[0013] As to the polymer having a functional group acting as a dyeing site for acid dye,
there are exemplified a polymer where acrylonitrile is a main component and a vinyl
monomer having at least a cationic group is a copolymerizing component and a polymer
which is produced by subjecting a polymer where acrylonitrile is a main component
to a treatment with a nitrogen-containing compound having two or more nitrogen atoms
in a molecule. Incidentally, in the invention of the present invention, the polymer
where acrylonitrile is a main component and a vinyl monomer having at least a cationic
group is a copolymerizing component may also be expressed as an acrylonitrile polymer
having cationic group and the polymer where acrylonitrile is a main component may
also be expressed as an acrylonitrile polymer.
[0014] Although there is no particular limitation for the functional group acting as a dyeing
site for acid dye, examples thereof include a cationic group such as primary amino
group, secondary amino group, tertiary amino group or quaternary ammonium group.
[0015] The expression reading "acrylonitrile is a main component" means that, in any of
the above cases, the polymer contains 40 to 100% by weight of acrylonitrile monomer
unit. With regard to the monomer component other than acrylonitrile, there is no particular
limitation and examples thereof include the monomers such as a (meth)acrylate compound
(e.g., methyl (meth)acrylate, ethyl (meth)acrylate and butyl (meth)acrylate), a sulfonic
group-containing monomer (e.g., metallylsulfonic acid and p-styrenesulfonic acid)
and a salt thereof; styrene and vinyl acetate. When a vinyl monomer having cationic
group is used as a copolymerizing component, the cationic group of said monomer functions
as a dyeing site for acid dye.
[0016] Examples of the vinyl monomer having cationic group as such include the monomers
represented by the following formulas 1 to 3. In the formulas 1 to 3, R1 is hydrogen
or an alkyl group of C4 or less; each of R2, R3 and R4 is an alkyl group of C4 or
less; R5 is an alkylene group or a hydroxyalkylene group of C4 or less; R6 is an alkylene
group of C4 or less; X is Cl, Br, I, CH
3COO, CH
3SO
4 or SCN; m is an integer of 2 to 4; and n is an integer of 0 or 1.
[0018] Specific examples of the vinyl monomer having cationic group as such include dimethylaminoethyl
(meth)acrylate and diethylaminoethyl (meth)acrylate.
[0019] When the acrylonitrile polymer is subjected to a treatment with a nitrogen-containing
compound having two or more nitrogen atoms in a molecule, a crosslinked structure
is formed in the polymer by the reaction of the functional group in the nitrogen-containing
compound with nitrile group derived from acrylonitrile. It is likely that the functional
group in the nitrogen-containing compound which did not react with the nitrile group,
the functional group which was by-produced from failure of formation of crosslinked
structure when the functional group in the nitrogen-containing compound reacted with
the nitrile group or the like functions as a functional group acting as the dyeing
site for acid dye.
[0020] With regard to the nitrogen-containing compound having two or more nitrogen atoms
in a molecule, an amino compound and a hydrazine compound having two or more primary
amino groups are preferred. Although there is no particular upper limitation for the
numbers of the nitrogen atoms in a molecule, 12 or less is preferred, 6 or less is
more preferred, and 4 or less is particularly preferred. When the numbers of the nitrogen
atoms in a molecule exceeds the above upper limit, molecule of the crosslinking agent
becomes big and there may be the case where the crosslinking is hardly introduced
into the polymer.
[0021] Examples of the amino compound having two or more primary amino groups include a
diamine compound such as ethylenediamine or hexamethylenediamine; a triamine compound
such as diethylenetriamine, 3,3'-iminobis(propylamine) or N-methyl-3,3'-iminobis(propylamine);
a tetramine compound such as triethylenetetramine, N,N'-bis(3-aminopropyl)-1,3-propylenediamine
or N,N'-bis(3-aminopropyl)-1,4-butylene-diamine; and polyamine compound such as polyvinylamine
and polyallylamine having two or more primary amino groups.
[0022] Examples of the hydrazine compound include hydrazine hydrate, hydrazine sulfate,
hydrazine hydrochloride, hydrazine hydrobromide and hydrazine carbonate.
[0023] Examples of the polymer having a crosslinked structure and a carboxyl group include
the polymer which is produced by subjecting an acrylonitrile polymer to a treatment
with a nitrogen-containing compound having two or more nitrogen atoms in a molecule
and to a hydrolyzing treatment. In the former treatment, the nitrogen-containing compound
is made to react with a nitrile group derived from acrylonitrile whereupon a crosslinked
structure is formed in the polymer while, in the latter treatment, nitrile group is
hydrolyzed to form a carboxyl group. As a result, a polymer having a crosslinked structure
and a carboxyl group is produced.
[0024] Examples of the acrylonitrile polymer and the nitrogen-containing compound having
two or more nitrogen atoms in a molecule include those which are already mentioned
hereinabove. In the hydrolyzing treatment, there may be used an alkali metal salt
compound such as alkali metal hydroxide, alkali earth metal hydroxide or alkali metal
carbonate.
[0025] With regard to the above-exemplified polymer having a crosslinked structure and a
carboxyl group, although the acrylonitrile polymer is subjected to a treatment with
a nitrogen-containing compound having two or more nitrogen atoms in a molecule the
same as in the case of the polymer exemplified as the polymer having a functional
group which acts as a dyeing site for acid dye, it is not possible to conduct a practical
dyeing using an acid dye. That is likely due to the fact that, although a functional
group which acts as a dyeing site for acid dye is once formed by the crosslinking
treatment, said functional group changes by the hydrolyzing treatment conducted thereafter
whereupon it no longer functions as a dyeing site for acid dye.
[0026] Further, the moisture-absorptive fiber dyeable with an acid dye according to the
present invention may also be constituted only from the region of a polymer having
a functional group acting as a dyeing site for acid dye and a region of a polymer
having a crosslinked structure and a carboxyl group as mentioned above. Still further,
besides those regions, a region where the polymers constituting those regions exist
in a mixed state or a region constituted from a polymer being different from the polymers
constituting those regions may exist. Representative examples of the alignment of
those regions include a core-sheath structure where a region of a polymer having a
functional group acting as a dyeing site for acid dye is a central area while a region
of a polymer having a crosslinked structure and a carboxyl group is a surface layer
area; a multi-layered structure where a region of a polymer having a functional group
acting as a dyeing site for acid dye and a region of a polymer having a crosslinked
structure and a carboxyl group are alternately layered; and islands-in-a-sea structure
where one of a region of a polymer having a functional group acting as a dyeing site
for acid dye and a region of a polymer having a crosslinked structure and a carboxyl
group is a sea area while another is an island area.
[0027] With regard to the ratio of the region of a polymer having a functional group acting
as a dyeing site for acid dye to a region of a polymer having a crosslinked structure
and a carboxyl group, a fiber having higher moisture-absorption rate is produced when
the rate of the region of a polymer having a crosslinked structure and a carboxyl
group is higher but, on the other hand, the rate of the region of a polymer having
a functional group acting as a dyeing site for acid dye becomes lower whereupon the
color-developing property tends to lower. In order to manufacture a fiber where both
moisture-absorption property and color-developing property are well-balanced, it is
desirable that an area of 20 to 80% and more preferably 30 to 70% of the cross-sectional
area of the fiber in a dry state is occupied by the region of a polymer having a functional
group acting as a dyeing site for acid dye.
[0028] The above-mentioned area ratio can be calculated by such a manner that the fiber
which is subjected to a dyeing treatment with an acid dye followed by cutting and
the resulting fiber section is observed under an optical microscope. Thus, the dyed
region is a region of the polymer having the functional group acting as a dyeing site
for acid dye while the region which is not dyed or the region where dyeing cannot
be confirmed is a region of the polymer having a crosslinked structure and a carboxyl
group.
[0029] As to the carboxyl group content in the present invention, it is preferred to be
1.0 to 10 mmol/g and more preferred to be 2.0 to 6.0 mmol/g to the fiber weight. When
the carboxyl group content is less than 1.0 mmol/g, there may be the case where no
sufficient moisture-absorption property is achieved while, when it is more than 10
mmol/g, the region of the polymer having a crosslinked structure and a carboxyl group
becomes weak upon absorption of moisture or water resulting in the detachment of the
polymer whereupon there may be the case where fiber shape and moisture-absorption
property cannot be maintained.
[0030] Although the carboxyl group may be that of an H type or of a salt type, or they may
be present in a mixed state, it is desirable that the carboxyl group is in an H type
so as to make the process such as spinning easy in the stage of after the manufacture
of the fiber while, in the stage of after dyeing or of the final product, it is desirable
that 50% or more of the carboxyl group is in a salt type so as to achieve the high
moisture-absorption rate.
[0031] Examples of the cation which constitutes such a salt-type carboxyl group include
cations of alkali metal such as Li, Na and K, alkali earth metal such as Be, Mg, Ca
and Ba, metal such as Cu, Zn, Al, Mn, Ag, Fe, Co and Ni, NH
4 and amine and a plurality of cations may be present in a mixed state.
[0032] With regard to the saturation dye uptake of the acid dye in the present invention,
it is preferred to be 3.5 to 10% by weight and more preferred to be 4 to 9% by weight
to the fiber weight. When such a saturation dye uptake is less than 3.5%, there may
be the case where dyeing in dark color is not possible and its application into the
practical use is not suitable while, when it is more than 10%, a dyeing speed is quick
and uneven dyeing is apt to happen. Incidentally, the saturation dye uptake as such
is calculated by the method which will be mentioned later.
[0033] In the moisture-absorptive fiber dyeable with an acid dye according to the present
invention, its color fastness is improved as compared with the conventional crosslinked
acrylic acid fiber and it is desirable that the color fastness to perspiration evaluated
by the following evaluating method is the third or higher grade.
(Evaluation Method) A sample is poured into a bath containing an acid dye (Supranol
Black VLG; manufactured by DyStar) in 5% by weight to the sample weight, the pH thereof
is adjusted to 4 using acetic acid and the fiber is dipped at 100°C for 30 minutes
and subjected to soaping, washing with water and drying. The resulting fiber is subjected
to the evaluation for color fastness to perspiration according to JIS-L-0848.
[0034] Although the saturated moisture-absorption rate of the moisture-absorptive fiber
dyeable with an acid dye according to the present invention under the atmosphere of
20°C temperature and 65% relative humidity cannot be unconditionally determined since
the required moisture-absorption rate is different depending upon the use, it is preferred
to be 15% by weight or more and more preferred to be 20% by weight or more.
[0035] In the moisture-absorptive fiber dyeable with an acid dye according to the present
invention, its degree of swelling is preferred to be not more than 2 g/g and more
preferred to be not more than 1.8 g/g. When the degree of swelling is more than 2
g/g, there may be the case where the fiber properties lower or the operability becomes
bad.
[0036] Several methods may be listed as a method for the manufacture of the moisture-absorptive
fiber dyeable with an acid dye according to the present invention mentioned hereinabove.
An example is a method where an acrylonitrile fiber comprising an acrylonitrile polymer
having a cationic group is used as a material fiber and said fiber is partially subjected
to a crosslinking treatment and a hydrolyzing treatment. In such a method, a part
of the acrylonitrile polymer having a cationic group is converted to a region of a
polymer having a crosslinked structure and a carboxyl group by the crosslinking treatment
and the hydrolyzing treatment while the part which is not converted becomes a region
of a polymer having a functional group acting as a dyeing site for acid dye.
[0037] In the acrylonitrile fiber comprising an acrylonitrile polymer having a cationic
group, it is desirable to have not less than 0.15 mmol/g and preferably not less than
0.17 mmol/g of cationic group to the fiber weight. When the cationic group is less
than 0.15 mmol/g, there may be the case where the region of a polymer having a crosslinked
structure and a carboxyl group needs to be made small in order to achieve a sufficient
color-developing property. Although there is no particular limitation for the upper
limit, it is desirable to be not more than 0.40 mmol/g in view of the homogeneity
of the dyeing.
[0038] Further, it is also possible to adopt a method where an acrylonitrile fiber comprising
an acrylonitrile polymer is used as a material fiber and said fiber is subjected to
a crosslinking treatment by a nitrogen-containing compound having two or more nitrogen
atoms in a molecule followed by subjecting to a hydrolyzing treatment, wherein the
range to which the hydrolyzing treatment is applied is made smaller than the range
to which the crosslinking treatment is applied. In such a method, the region comprising
a polymer having a functional group acting as a dyeing site for acid dye is firstly
formed together with a crosslinked structure by means of a crosslinking treatment
and, as a result of the hydrolyzing treatment thereafter, a part of said region is
converted to a region of a polymer having a crosslinked structure and a carboxyl group.
Incidentally, it goes without saying that, in such a method, an acrylonitrile polymer
having a cationic group may also be used as an acrylonitrile polymer.
[0039] Still further, it is also possible to adopt a method where an acrylonitrile fiber
comprising an acrylonitrile polymer having no functional group acting as a dyeing
site for acid dye is used as a material fiber and, after a functional group acting
as a dyeing site for acid dye is introduce therein, the resulting one is partially
subjected to a crosslinking treatment and a hydrolyzing treatment and a method where
an acrylonitrile fiber containing a polymer having a functional group acting as a
dyeing site for acid dye other than the acrylonitrile polymer is used as a material
fiber and is partially subjected to a crosslinking treatment and a hydrolyzing treatment.
[0040] Incidentally, it is preferred in the above-listed manufacturing methods that the
rate of the acrylonitrile polymer in the acrylonitrile fiber to be used as a material
fiber is 80 to 100% by weight regardless of the presence or the absence of the functional
group acting as a dyeing site for acid dye.
[0041] It is also preferred that the acrylonitrile fiber to be used as a material fiber
comprises at least two types of acrylonitrile polymers where the contents of acrylonitrile
are different from each other and that the difference in said contents is 2% by weight
or more. As a result thereof, a difference is resulted in the easiness of the crosslinking
and of the hydrolysis whereby the region of the polymer having a functional group
acting as a dyeing site for acid dye and the region of the polymer having a crosslinked
structure and carboxyl group are apt to be formed.
[0042] Although the acrylonitrile fiber as such may be either a fiber where the two types
of acrylonitrile polymers are conjugated side-by-side or are randomly mixed, a fiber
in a three-layered structure comprising the layers A-B-A or a fiber in a core-sheath
structure is more preferred. It is preferred that the area of the layer B or the core
contains much acrylonitrile and also contains many cationic groups. To be more specific,
the acrylonitrile content in the area of the layer B or the core is 82% by weight
or more, preferably 85% by weight or more, and more preferably 90% by weight or more
while the cationic group content therein is 0.15 mmol/g or more and preferably 0.17
mmol/g or more.
[0043] As to a method for manufacturing an acrylonitrile fiber in the three-layered structure
comprising the layers A-B-A, a method which is mentioned in
JP-A-2000-045126 or the like may be adopted. In that case, it is preferred that the dope viscosity
of the component A is made lower than the dope viscosity of the component B so that
exposure of the component B onto the fiber surface is made little.
[0044] With regard to a method of manufacturing a moisture-absorptive fiber dyeable with
an acid dye according to the present invention which is illustrated hereinabove, the
following method is preferred in view of the manufacturing facilities and costs. It
is such a method where an acrylonitrile fiber comprising an acrylonitrile polymer
having a cationic group is subjected to a crosslinking treatment with a nitrogen-containing
compound having two or more nitrogen atoms in a molecule followed by subjecting to
a hydrolyzing treatment with an aqueous solution of alkali metal salt or is subjecting
to those treatments at the same time whereupon the region of the polymer having a
crosslinked structure and a carboxyl group is formed on the surface layer area of
the fiber while the region of the acrylonitrile polymer having a cationic group is
remained in the core area.
[0045] In such a method, the acrylonitrile fiber comprising the acrylonitrile polymer having
a cationic group is subjected to a treatment of introducing a crosslinking with an
aqueous solution containing a nitrogen-containing compound having two or more nitrogen
atoms in a molecule and to a hydrolyzing treatment with an aqueous solution containing
an alkali metal salt compound as mentioned above. Those treatments may be carried
out by such a separate manner that the hydrolyzing treatment is done after the crosslinking
treatment or by such a simultaneous treatment using an aqueous solution in which both
of the nitrogen-containing compound having two or more nitrogen atoms in a molecule
and the alkali metal salt compound are co-existing. In any of the cases, a crosslinked
structure is formed by the reaction of the nitrogen-containing compound having two
or more nitrogen atoms in a molecule with the nitrile group in the acrylonitrile polymer
on the surface layer area of the acrylonitrile fiber while a carboxyl group is formed
by the reaction of the aqueous solution of the alkali metal salt compound with the
nitrile group whereupon conversion to the polymer having a crosslinked structure and
carboxyl group takes place.
[0046] As to a specific method for the above-mentioned crosslinking treatment and hydrolyzing
treatment, a method where the reaction is carried out under the state where the fiber
is dipped in an aqueous solution used for the treatments may be adopted. Further,
in any of the separate treatment and the simultaneous treatment, concentration of
the nitrogen-containing compound having two or more nitrogen atoms in a molecule is
preferred to be 0.1 to 5% by weight and more preferred to be 0.1 to 3% by weight.
When the concentration is too low, there may be the case where the effect of suppressing
the elution for the polymer having the crosslinked structure and the carboxyl group
cannot be achieved. On the other hand, in order to limit introduction of the crosslinked
structure to the surface layer area of the fiber, the concentration is preferred to
be made 5% by weight or less. With regard to the concentration of the alkali metal
salt compound, it is preferred to be 0.5 to 5% by weight and more preferred to be
0.5 to 4% by weight. When the concentration of the alkali metal salt compound is too
low, there may be the case where the content of the resulting carboxyl group is insufficient.
On the other hand, when the concentration is suppressed to an extent of 5% by weight
or less, it is possible that the introduction of carboxyl group is limited to the
surface area of the fiber while the region of the acrylonitrile polymer having cationic
group is remained in the core area.
[0047] With regard to the reaction temperature and time, their appropriate ranges vary depending
upon the concentration(s) of the nitrogen-containing compound having two or more nitrogen
atoms in a molecule and/or the alkali metal salt compound. In the case of the simultaneous
treatment where the concentration of the nitrogen-containing compound having two or
more nitrogen atoms in a molecule is about 0.5 to 2% by weight and the concentration
of the alkali metal salt compound is about 1 to 2% by weight, the condition of at
90 to 100°C for about 2 hours is recommended.
[0048] In the case of the above separate treatment, the fiber subjected to the crosslinking
treatment may be subjected to a treatment with an acid before the hydrolyzing treatment.
As a result of the treatment with an acid as such, coloring of the fiber can be made
hypochromic. Examples of the acid used hereinabolve include an aqueous solution of
mineral acid such as nitric acid, sulfuric acid, hydrochloric acid, and an organic
acid although there is no particular limitation therefor. An example of the treating
condition is that a fiber to be treated is dipped in an aqueous solution at the temperature
of 50 to 120°C for 0.5 to 10 hour(s) where an acid concentration is 5 to 20% by weight
and preferably 7 to 15% by weight. However, such a treatment with an acid has an effect
of progressing the hydrolysis and of decreasing the region of the acrylonitrile polymer
to be remained in the finally-prepared fiber or, in other words, the region of the
polymer having a functional group acting as a dyeing site for acid dye. Accordingly,
it is important to set the condition by taking such an effect into consideration.
[0049] The above-prepared fiber after the hydrolyzing treatment or after the simultaneous
crosslinking and hydrolyzing treatments may be utilized as it is for the moisture-absorptive
fiber dyeable with an acid dye of the present invention, but it also may be further
washed with an acidic aqueous solution. As a result thereof, a fiber in more white
degree can be prepared. Examples of the above acidic aqueous solution include an aqueous
solution of mineral acid such as nitric acid, sulfuric acid, hydrochloric acid, and
an organic acid although there is no particular limitation therefor.
[0050] As mentioned above, in the stage after the manufacture of the fiber, it is desirable
that a carboxyl group is in an H type so as to make the process such as spinning easy
while, in the stage of after dyeing or of the final product, it is desirable that
the carboxyl group is converted to the desired salt type or H type or that the different
salt types are made to exist in a mixed state. Adjustment of such a type of the carboxyl
group can be carried out by applying an ion exchange treatment using a metal salt
such as nitrate, sulfate or hydrochloride or by a pH adjusting treatment using a buffer
or the like. In case a high moisture-absorption rate is aimed, it is desirable that
50% or more of the carboxyl group is made into an salt type.
[0051] It is also a preferred method where the above-mentioned acrylonitrile fiber comprising
the acrylonitrile polymer is used as a material fiber and is subjected to a crosslinking
treatment with a nitrogen-containing compound having two or more nitrogen atoms in
a molecule followed by subjecting to a hydrolyzing treatment, wherein the range to
which the hydrolyzing treatment is applied is made smaller than the range to which
the crosslinking treatment is applied. In such a method, the crosslinking treatment
is firstly applied using a solution where the concentration of the nitrogen-containing
compound having two or more nitrogen atoms in a molecule is set high and then the
hydrolyzing treatment is carried out so that the range to which the crosslinking treatment
is applied is made broader than the range to which the hydrolysis treatment is applied.
In the case of making into a core-sheath structure for example, concentration of the
nitrogen-containing compound is made preferably 7 to 20% by weight or, more preferably,
10 to 20% by weight for applying the crosslinking treatment to whole fiber. With regard
to the condition of the hydrolyzing treatment for the surface layer area of the fiber
after the above treatment, the above-mentioned condition may be adopted and, if necessary,
the treatment with an acid and the adjustment of the carboxyl group type may be carried
out in the same way.
Examples
[0052] The present invention will now be specifically illustrated by using the following
Examples although the present invention is not limited thereto. The terms "part (s)
" and "percent (s) " used in the Examples are those by weight unless otherwise stipulated.
The method for evaluating the characteristics in the Examples are as follows.
(1) Carboxyl group content
[0053] A well-dried sample (about 1 g) is precisely weighed (A[g]), 200 ml of water is added
thereto, a 1 mol/L aqueous solution of hydrochloric acid is added to the resulting
mixture together with heating at 50°C to adjust to pH 2 and, after that, a titration
curve is determined according to the conventional method using a 0.1 mol/L aqueous
solution of sodium hydroxide. Amount of the aqueous solution of sodium hydroxide consumed
by the carboxyl group (B[ml]) is determined from the titration curve and the carboxyl
group content is calculated by the following formula.

(2) Cationic group content in a material fiber
[0054] well-dried sample (about 0.5 g) is precisely weighed (C[g]) and dipped into a beaker
containing a 0.1 mol/L aqueous solution of hydrochloric acid (D[ml]) (which is such
an amount that ion exchange is sufficiently carried out). The sample is filtered and
a phenolphthalein solution is added to the filtrate as an indicator. The filtrate
is then titrated with a 0.1 mmol/L aqueous solution of sodium hydroxide to quantify
the residual hydrochloric acid. The cationic group content is calculated by the following
formula where E [ml] is the titrated amount of sodium hydroxide.

(3) Saturated moisture-absorption rate
[0055] The sample (about 5.0 g) is dipped in water, an aqueous solution of sodium hydroxide
is added thereto so that the degree of neutralization to the carboxyl group is made
70%, the dipping treatment is done at 70°C for 1 hour and, after that, washing with
water and dehydration are conducted followed by drying with air for 24 hours. The
sample being subjected to a neutralizing treatment is dried at 105°C for 16 hours
in a hot-air drier and the resulting weight is measured (F [g]). After that, the sample
is placed for 24 hours in a constant-temperature and constant-humidity container adjusted
to the condition of 20°C and 65% relative humidity. Weight of the sample moisturized
as such is measured (G[g]). Saturated moisture-absorption rate is calculated by the
following formula using the above measured result.

(4) Degree of swelling
[0056] A sample (about 3 g) is dried at 70°C for 3 hours in a hot-air drier to measure the
weight (H[g]). After that, the sample is dipped for 30 minutes in a beaker containing
300 ml of water, the swollen sample is dehydrated with a portable centrifugal dehydrator
(160G × 5 minutes) and the weight of the sample is measured (J[g]). Degree of swelling
is calculated by the following formula using the above measured result.

(5) Dyeing property
[0057] A sample is poured into a bath containing an acid dye (Supranol Black VLG; manufactured
by DyStar) in 5% by weight to the sample weight, the pH thereof is adjusted to 3.5
using acetic acid and the fiber is dipped at 100°C for 30 minutes and subjected to
soaping, washing with water and drying. The resulting fiber is subjected to the evaluation
for dyeing property by naked eye according to the following judging standards.
○: sufficiently dyeable
△: dyeable in light color
×: hardly dyeable or hue is abnormal
(6) Color fastness to perspiration
[0058] The fiber which is dyed by the same manner as mentioned in "(5) Dyeing property"
is evaluated for the color fastness to perspiration according to JIS-L-0848.
(7) Cross section ratio of the region of the acrylonitrile polymer
[0059] The fiber which is dyed by the same manner as mentioned in " (5) Dyeing property"
is cut and the fiber section is observed under an optical microscope whereupon the
cross section ratio of the region of the acrylonitrile polymer is calculated.
(8) Saturation dye uptake
[0060] A mother liquor for dyeing is prepared in a bath ratio of 1:200 containing 20% of
acid dye (Sandolan Fast Blue P-L 125%; manufactured by Sandoz) to the weight of the
sample to be poured thereinto and being adjusted to pH 3 with acetic acid. Then, the
absorbance of the mother liquor for dyeing to the light of 590 nm wavelength is measured.
After that, a sample is poured into the mother liquor for dyeing and treated at 100°C
for 30 minutes. After a gradual cooling, the dyeing bath is adjusted to pH 7 with
sodium carbonate and treated at 70°C for 30 minutes. Then water which was evaporated
during the treatment is supplemented to the dyeing bath, the bath ratio is adjusted
to 1:200 once again and the absorbance of the residual liquor for dyeing at the light
of 590 nm wavelength is measured. From the above measuring result, the saturation
dye uptake to the fiber weight is calculated using the following formula.

Each absorbance of the mother liquor for dyeing and the residual liquor for dyeing
is measured using the liquor diluted to an extent of 20-fold and U-1100 Spectrophotometer
(manufactured by Hitachi).
Example 1
[0061] An acrylonitrile polymer (limiting viscosity [η] in dimethylformamide of 30°C is
1.2) (10 parts) comprising 86% of acrylonitrile, 11% of methyl acrylate and 3% of
dimethylaminoethyl (meth) acrylate was dissolved in 90 parts of a 48% aqueous solution
of sodium rhodanate and the resulting spinning dope was spun and drafted according
to a conventional method (total drafting rate: 10 times), dried in an atmosphere where
dry bulb/wet bulb = 120°C/60°C and subjected to a moist heat treatment to give a material
fiber (fiber length: 51 mm) having single fiber fineness of 2.2 dtex. The resulting
material fiber was treated at 90°C for 2 hours in an aqueous solution containing 0.4%
of hydrazine hydrate and 2% of sodium hydroxide, washed with an aqueous solution of
nitric acid having pH of 2 or lower, washed with water and dried to give the fiber
of Example 1. Result of the evaluation of the resulting fiber is shown in Table 1.
Example 2
[0062] The material fiber of Example 1 was treated at 90°C for 1.5 hours in an aqueous solution
containing 0.4% of hydrazine hydrate and 2% of sodium hydroxide, washed with an aqueous
solution of nitric acid having pH of 2 or lower, washed with water and dried to give
the fiber of Example 2. Result of the evaluation of the resulting fiber is shown in
Table 1.
Example 3
[0063] An acrylonitrile polymer (limiting viscosity [η] in dimethylformamide of 30°C is
1.2) (10 parts) comprising 90% of acrylonitrile, 9.7% of methyl acrylate and 0.3%
of sodium metallylsulfonate was dissolved in 90 parts of a 48% aqueous solution of
sodium rhodanate and the resulting spinning dope was spun and drafted according to
a conventional method (total drafting rate: 10 times), dried in an atmosphere where
dry bulb/wet bulb = 120°C/60°C and subjected to a moist heat treatment to give a material
fiber (fiber length: 51 mm) having single fiber fineness of 2.2 dtex. The resulting
material fiber was treated at 110°C for 1 hour in an aqueous solution containing 10%
of hydrazine hydrate,treated at 100°C for 1 hour in an aqueous solution containing
1.6% of sodium hydroxide, washed with an aqueous solution of nitric acid having pH
of 2 or lower, washed with water and dried to give the fiber of Example 3. Result
of the evaluation of the resulting fiber is shown in Table 1.
Example 4
[0064] The material fiber of Example 1 was treated at 110°C for 1.5 hours in an aqueous
solution containing 15% of hydrazine hydrate, treated at 100°C for 1 hour in an aqueous
solution containing 2% of sodium hydroxide, washed with an aqueous solution of nitric
acid having pH of 2 or lower, washed with water and dried to give the fiber of Example
4. Result of the evaluation of the resulting fiber is shown in Table 1.
Comparative Example 1
[0065] The material fiber of Example 1 was treated at 110°C for 3 hours in a 15% aqueous
solution of hydrazine hydrate and washed. The resulting fiber was dipped in a 8% aqueous
solution of nitric acid and treated at 100°C for 1 hour. Then, it was treated at 100°C
for 1 hour in a 5% aqueous solution of sodium hydroxide, washed with an aqueous solution
of nitric acid having pH of 2 or lower, washed with water and dried to give a moisture-absorptive
fiber of Comparative Example 1. Result of the evaluation of the resulting fiber is
shown in Table 1.
Comparative Example 2
[0066] The same operation as in Example 1 was carried out except that the material fiber
of Example 3 was used as a material fiber to give a moisture-absorptive fiber of Comparative
Example 2. Result of the evaluation of the resulting fiber is shown in Table 1.

[0067] In Example 1, there was prepared a fiber having good dyeing property and color fastness
to the dyeing with acid dye and also having good moisture-absorption property. Although
the moisture-absorptive fiber of Example 2 had a broad region of the acrylonitrile
polymer as compared with the moisture-absorptive fiber of Example 1, it still had
a sufficient moisture-absorption property as a moisture-absorptive fiber and had good
dyeing property and color fastness. In Example 3, although an acrylonitrile fiber
comprising an acrylonitrile polymer having no functional group acting as a dyeing
site for acid dye was used as a starting material, a moisture-absorptive fiber having
good dyeing property and color fastness was prepared. That is probably due to the
fact that a functional group acting as a dyeing site for acid dye derived from a crosslinking
agent was introduced into the inner layer of the fiber as a result of making the crosslinking
treatment condition strong. In Example 4, it is likely that a moisture-absorptive
fiber having a high saturation dye uptake was prepared due to the following reasons
that an acrylonitrile fiber comprising an acrylonitrile polymer having a cationic
group was used as a material fiber and the crosslinking treatment condition was also
made strong whereupon the functional group acting as a dyeing site for acid dye being
effective for the dyeing becomes abundant.
[0068] On the other hand, in the fiber of Comparative Example 1, the saturation dye uptake
was low, dyeing into an intended hue was not possible and the color fastness was also
low. That is probably due to the fact that, since the hydrolyzing treatment condition
was made strong, hydrolysis happened in whole fiber and many of cationic groups in
the material fiber were lost. In addition, with regard to the functional group acting
as a dyeing site for acid dye derived from the crosslinking agent, it is also likely
that it changed to other functional group due to hydrolysis or, around the functional
group, many carboxyl groups are formed due to the hydrolysis whereupon a structure
which is apt to absorb water to swell is resulted and, even when the dye is attached,
it is apt to be flown out upon contact with water, and accordingly that the functional
group does not well function as a dyeing site for acid dye. In the fiber of Comparative
Example 2, the crosslinking treatment and the hydrolyzing treatment to the material
fiber having no functional acting as a dyeing site for acid dye are limited only to
the surface layer area of the fiber whereupon it is likely that no functional group
acting as a dyeing site for acid dye exits in the core and the surface layer area
becomes the same structure as in the fiber of Comparative Example 1 whereby the dyeing
property becomes poor. Incidentally, in the fibers of those Comparative Examples,
it was not possible to conduct an appropriate dyeing whereby it was not possible to
determine the cross section ratio of the region of the acrylonitrile polymer.
Industrial Applicability
[0069] The moisture-absorptive fiber dyeable with an acid dye according to the present invention
has a high moisture-absorption property and is excellent in terms of dyeing property
to an acid dye whereby a practical dyeing is possible. Accordingly, it is now possible
to develop to the use which has been limited because of the fact that a practical
dyeing was difficult with the conventional crosslinked acrylic acid fiber.