JP2012241297A - Para-type wholly aromatic polyamide fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a para-type wholly aromatic polyamide fiber that enhances fastness to rubbing while maintaining tensile strength.SOLUTION: Para-type wholly aromatic polyamide capable of being colored into black is obtained, by using 30-70 mol% of a p-phenylenediamine oxide and p-phenylenediamine, and 70-30 mol% of 3,4'-diaminodiphenyl ether as an aromatic diamine component (black amine) that develops black color. The black-colored fiber does not cause whitening by Martindale method even at 5,000 times of abrasions.

Description

  The present invention relates to a para type wholly aromatic polyamide fiber. More particularly, the present invention relates to a black para-type wholly aromatic polyamide fiber having improved friction fastness without reducing the tensile strength of the fiber.

  Para-type wholly aromatic polyamide fiber is a synthetic fiber that has high strength, high elastic modulus, high heat resistance, and has the flexibility and lightness peculiar to organic fibers. Because of these features, para-type wholly aromatic polyamide fibers are widely used in various fields such as tires for automobiles, motorcycles and bicycles, toothed belts for automobiles, conveyors, etc., or fiber optic cable reinforcements and ropes. It's being used. Also, in the clothing field, it has been used for various purposes such as bulletproof vests, blade-proof work gloves, protective clothing such as work clothes, sports clothing, and fire-resistant clothing that makes use of incombustibility. Yes.

Here, among the uses of the para-type wholly aromatic polyamide fiber, coloring is required particularly in the clothing field. As methods for obtaining colored fibers, there are generally known a post-dyeing method in which a fiber is dyed after dyeing with a dye, and an original method in which a fiber is added after adding a pigment to a spinning dope.
However, fiber structures using fibers obtained by these conventional methods are not always satisfactory in terms of friction fastness, and white blurring occurs on the fiber surface due to friction by repeated washing.

Therefore, for the purpose of improving the fastness to friction, carbon black-containing aromatic polyamide fibers added at a high concentration without agglomerating fine particles have been proposed (Patent Documents 1 to 3).
However, in order to improve the fastness to friction, it is necessary to add a considerable amount of carbon black, which causes a problem that the mechanical properties of the fiber such as tensile strength are greatly reduced.

Japanese Patent Application Laid-Open No. 64-085316 Japanese Patent Laid-Open No. 06-081211 JP 2007-023451 A

  The present invention has been made against the background of the above-described prior art, and an object of the present invention is to provide a para-type wholly aromatic polyamide fiber having improved friction fastness while maintaining tensile strength. is there.

  The present inventor has intensively studied to solve the above problems. Then, a polymer is produced using a monomer capable of coloring the obtained para-type wholly aromatic polyamide itself in black, and the above problem can be solved by obtaining fibers from the obtained polymer, thereby completing the present invention. It came.

  That is, the present invention is a para-type wholly aromatic polyamide fiber having a tensile strength of 23 cN / dtex or more, and the fiber structure prepared from the fiber has an L value (lightness) in the Lab colorimetric method measured according to JIS Z8729. It is a para-type wholly aromatic polyamide fiber having an L value (lightness) change of + 5% or less before and after being worn 5,000 times by the Martindale method specified in JIS L1096.

  The para type wholly aromatic polyamide fiber of the present invention is a fiber having improved friction fastness while maintaining the tensile strength. For this reason, it is useful in various protective apparel applications, and is particularly significant in the field of apparel with a high number of frictions such as washing.

Hereinafter, embodiments of the present invention will be described in detail.
<Para-type wholly aromatic polyamide>
The para-type wholly aromatic polyamide in the present invention is a polymer in which one or more divalent aromatic groups are directly linked by an amide bond. In addition, the aromatic group includes a group in which two aromatic rings are bonded via oxygen, sulfur, or an alkylene group, or a group in which two or more aromatic rings are directly bonded. Further, these divalent aromatic groups may contain a lower alkyl group such as a methyl group or an ethyl group, a halogen group such as a methoxy group, a chloro group, or the like. Note that the position of the amide bond directly linking the divalent aromatic group is a para type.

<Method for producing para-type wholly aromatic polyamide>
The para-type wholly aromatic polyamide in the present invention can be produced according to a conventionally known method. For example, it can be obtained by reacting an aromatic dicarboxylic acid dichloride (hereinafter also referred to as “acid chloride”) component with an aromatic diamine component by low-temperature solution polymerization or interfacial polymerization in an amide polar solvent.

[Raw material for aromatic polyamide]
(Aromatic dicarboxylic acid dichloride component)
The aromatic dicarboxylic acid chloride component used in the production of the para-type wholly aromatic polyamide is not particularly limited, and generally known compounds can be used. Examples thereof include terephthalic acid chloride, 2-chloroterephthalic acid chloride, 2,5-dichloroterephthalic acid chloride, 2,6-dichloroterephthalic acid chloride, 2,6-naphthalenedicarboxylic acid chloride, and the like. These aromatic dicarboxylic acid dichlorides can be used not only in one type but also in two or more types, and the composition ratio is not particularly limited. Of these, terephthalic acid dichloride is preferred from the viewpoints of versatility and mechanical properties of the resulting fiber. In the present invention, a small amount of a component that forms a bond other than the para position, such as isophthalic acid chloride, may be used.

(Aromatic diamine component)
The aromatic diamine component used in the production of the para-type wholly aromatic polyamide is not particularly limited, and generally known ones can be used. For example, p-phenylenediamine, 2-chloro-p-phenylenediamine, 2,5-dichloro p-phenylenediamine, 2,6-dichloro-p-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'- Examples thereof include diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, and the like. These can use not only one type but also two or more types, and the composition ratio is not particularly limited. In the present invention, a small amount of a component that forms a bond other than the para position, such as m-phenylenediamine, may be used.

  In the present invention, in order to obtain black para-type wholly aromatic polyamide, it is important to use an aromatic diamine component (black amine) that develops black color. The aromatic diamine component expressing black is not particularly limited, but examples thereof include p-simylene-2,5-diamine, chlorazole violet N, 1,1′-diaminodiphenyl ether, and p-phenylenediamine oxide. Can be mentioned. In the present invention, it is particularly preferable to use p-phenylenediamine oxide from the viewpoint of the darkness of the resulting fiber.

  In the present invention, a combination of p-phenylenediamine and black amine and 3,4'-diaminodiphenyl ether is preferable from the viewpoint of stability at high temperature hot stretching. When paraphenylenediamine and black amine are used in combination with 3,4'-diaminodiphenyl ether, the composition ratio is not particularly limited. However, with respect to the amount of total aromatic diamine, paraphenylenediamine and The composition sum of the black amine and the composition of 3,4'-diaminodiphenyl ether are preferably 30 to 70 mol% and 70 to 30 mol%, respectively, more preferably 40 to 60 mol% and 60 to 60 mol%, respectively. It is 40 mol%, and most preferably 45-55 mol% and 55-45 mol%, respectively.

  When p-phenylenediamine oxide is used as the black amine, the composition ratio is not particularly limited, but p-phenylenediamine oxidation is performed with respect to the sum of p-phenylenediamine and p-phenylenediamine oxide. It is preferable to make a thing into the range of 0.1-20 mol%, More preferably, it is the range of 0.5-15 mol%, Most preferably, it is the range of 1.0-10 mol%.

[Raw material composition ratio]
The ratio of the aromatic dicarboxylic acid chloride component to the aromatic diamine component is preferably in the range of 0.90 to 1.10 as the molar ratio of the aromatic dicarboxylic acid chloride component to the aromatic diamine component, 0.95 More preferably, it is in the range of ˜1.05. When the molar ratio of the aromatic dicarboxylic acid chloride component is less than 0.90 or exceeds 1.10, the reaction with the aromatic diamine component does not proceed sufficiently and a high degree of polymerization cannot be obtained, which is not preferable.

[Reaction conditions]
The reaction conditions for the aromatic dicarboxylic acid chloride component and the aromatic diamine component are not particularly limited. The reaction between acid chloride and diamine is generally rapid, and the reaction temperature is preferably, for example, in the range of -25 ° C to 100 ° C, more preferably in the range of -10 ° C to 80 ° C.

[Polymerization solvent]
Examples of the solvent for polymerizing the para-type wholly aromatic polyamide include organic polar amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone and N-methylcaprolactam. Water-soluble ether compounds such as tetrahydrofuran and dioxane, water-soluble alcohol compounds such as methanol, ethanol and ethylene glycol, water-soluble ketone compounds such as acetone and methyl ethyl ketone, water-soluble nitrile compounds such as acetonitrile and propionitrile, etc. It is done. These solvents can be used singly or as a mixed solvent of two or more. Note that the solvent used is preferably dehydrated.

  In the production of the para-type wholly aromatic polyamide used in the present invention, N-methyl-2-pyrrolidone (NMP) is used from the viewpoints of versatility, harmfulness, handleability, solubility in para-type wholly aromatic polyamide, and the like. Most preferably, it is used.

[Other polymerization conditions]
In order to increase the solubility of the resulting para-type wholly aromatic polyamide, an appropriate amount of a generally known inorganic salt may be added either before, during or at the end of polymerization. Examples of such inorganic salts include lithium chloride and calcium chloride.

Moreover, the terminal of para-type wholly aromatic polyamide can also be sealed. When the terminal is sealed with a terminal blocking agent, for example, phthalic acid chloride and its substituted product, aniline and its substituted product, and the like can be used as the terminal blocking agent.
In addition, aliphatic or aromatic amines, quaternary ammonium salts, and the like can be used in combination in order to capture an acid such as hydrogen chloride.

  After completion of the reaction, a basic inorganic compound such as sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxide or the like may be added as necessary to carry out a neutralization reaction.

[Post-polymerization, etc.]
The para-type wholly aromatic polyamide obtained as described above can be put into a non-solvent such as alcohol or water, precipitated, and then taken out as a pulp. The para-type wholly aromatic polyamide taken out can be dissolved again in another solvent and then used for fiber molding, but the polymer solution obtained by the polymerization reaction is directly used as a spinning solution (dope). It is also possible. The solvent used for taking out once and dissolving it again is not particularly limited as long as it dissolves the para-type wholly aromatic polyamide, and the solvent used for the polymerization of the para-type wholly aromatic polyamide and It is preferable to do.

<Method for producing para-type wholly aromatic polyamide fiber>
Although the manufacturing method of the para type wholly aromatic polyamide fiber of this invention is not specifically limited, For example, the following method is mentioned.

[Process for adjusting spinning solution (polymer dope)]
In the production of the fiber of the present invention, first, a spinning solution (polymer dope) for forming the fiber is prepared. The spinning solution (dope) contains para-type wholly aromatic polyamide and a solvent, and the method of adjusting is not particularly limited.

  As the solvent used for the preparation of the spinning solution (dope), it is preferable to use the solvent used for the polymerization of the para-type wholly aromatic polyamide. In addition, the solvent used may be one type alone or a mixed solvent obtained by mixing two or more types of solvents. In the production method of the present invention, the polymer can be used as it is without being isolated from the polymer solution obtained by the production of the para-type wholly aromatic polyamide.

  Furthermore, an inorganic salt can also be used as a solubilizing agent for the purpose of increasing the solubility of para-type wholly aromatic polyamide in a solvent. Examples of the inorganic salt include calcium chloride and lithium chloride. Although the amount of the inorganic salt added to the polymer dope is not particularly limited, it is 1 to 10% by mass with respect to the polymer dope mass from the viewpoint of the effect of improving the polymer solubility and the solubility of the inorganic salt in the solvent. It is preferable that

  Moreover, you may mix | blend other arbitrary components, such as an additive, in the range which does not exceed the summary of this invention in order to provide functionality etc. to a fiber. When an additive or the like is blended, it can be introduced in adjusting the dope. The method of introduction is not particularly limited, and for example, it can be introduced into the dope using a ruder or a mixer.

  The polymer concentration in the spinning solution (dope), that is, the concentration of the para-type wholly aromatic polyamide is preferably in the range of 0.5 mass% to 30 mass%. When the polymer concentration in the spinning solution (dope) is less than 0.5% by mass, the entanglement of the polymer is small, so that the viscosity necessary for spinning cannot be obtained, and the ejection stability during spinning decreases. . On the other hand, when the polymer concentration exceeds 30% by mass, the viscosity of the dope increases abruptly, so that the discharge stability at the time of spinning decreases, and stable spinning becomes difficult due to the sudden increase in pressure in the spinning pack. Cheap.

[Spinning / Coagulation]
In the spinning / coagulation step, fibers are formed by a wet spinning method or a semi-dry semi-wet spinning method provided with an air gap, using the spinning solution (dope) prepared as described above. That is, first, the spinning solution (dope) obtained above is discharged from a nozzle, and subsequently brought into contact with a coagulation liquid in a coagulation bath to form a coagulated yarn.

  As the coagulation bath, a poor solvent of para-type wholly aromatic polyamide is used. Usually, the solvent of the spinning solution (polymer dope) quickly escapes and the obtained wholly aromatic polyamide coagulated yarn cannot be defective. Adjusts the coagulation rate by adding a good solvent. It is preferable to use water as the poor solvent and a solvent for para-type wholly aromatic polyamide dope as the good solvent. The mass ratio of good solvent / poor solvent is preferably in the range of 15/85 to 40/60, although it depends on the solubility and coagulability of the para-type wholly aromatic polyamide.

[Other processes]
After pulling up the solidified yarn from the coagulation liquid, the final para-type wholly aromatic polyamide fiber can be obtained by a known method. For example, the solvent is removed from the undrawn yarn formed by carrying out the water washing step, the drawing is carried out as necessary, and the final fiber is oriented by drawing as necessary after passing through the drying step and the like. Can be obtained.

[Stretching process]
The fibers of the present invention are preferably stretch-oriented. The drawing method is not particularly limited, and may be any of not only washing drawing in a coagulated yarn state and boiling water drawing but also heating drawing in a dry yarn state. Moreover, there is no restriction | limiting in particular about a draw ratio, However, It is preferable that it is 5 times or more, and it is further more preferable that it is 8 times or more. By controlling the draw ratio, the elongation and strength of the obtained para-type wholly aromatic polyamide fiber can be controlled.
When carrying out hot stretching, the temperature depends on the polymer skeleton of the para-type wholly aromatic polyamide, but is preferably 300 to 600 ° C, more preferably 350 to 550 ° C, and the draw ratio is preferably 10 times or more, more preferably 10 to 15 times.

<Physical properties of para-type wholly aromatic polyamide fiber>
[Tensile strength]
The tensile strength of the para-type wholly aromatic polyamide fiber of the present invention is preferably as high as possible, but the strength tends to decrease as the composition of the black amine is increased, and if it is less than 23 cN / dtex, the characteristics as a high-strength fiber are insufficient. Therefore, the tensile strength of the para-type wholly aromatic polyamide fiber of the present invention is preferably 23 cN / dtex or more, and more preferably 24 cN / dtex or more.

[Elongation]
The elongation of the para-type wholly aromatic polyamide fiber of the present invention is preferably 3.0% or more. If it is less than 3.0%, the twist strain becomes large when the yarn is used by twisting, and the strength utilization rate at the time of twisting is lowered. For this reason, for example, the durability may be insufficient when it is used for a use application that requires durability. The elongation is preferably in the range of 3.5 to 5.0%.

[Single yarn fineness]
The single yarn fineness of the para-type wholly aromatic polyamide fiber of the present invention is preferably in the range of 0.5 to 50 dtex, more preferably in the range of 1.0 to 10 dtex. If it is less than 0.5 dtex, the spinning property may become unstable. Moreover, since the specific surface area of the fiber is increased, it is susceptible to light resistance degradation. On the other hand, when it exceeds 50 dtex, the specific surface area of the fiber becomes small and is not easily deteriorated by light resistance. On the other hand, since the specific surface area is small, coagulation tends to be incomplete in the spinning process. The process condition at the time tends to be disturbed, and the physical properties are likely to be lowered.

<Physical properties of fiber structure>
The physical properties of the fiber structure produced from the para-type wholly aromatic polyamide fiber of the present invention are shown below.

[Brightness (L value)]
The lightness (L value) of the fiber structure produced from the para-type wholly aromatic polyamide fiber of the present invention is 24 or less. It is preferably 23.5 or less, and particularly preferably 23 or less. When the lightness (L value) is 24 or less, a para-type wholly aromatic polyamide fiber product having a desired black color is obtained.

[Lightness (L value) change rate]
The para-type wholly aromatic polyamide fiber of the present invention has improved friction fastness while maintaining tensile strength. That is, the fiber structure obtained from the para-type wholly aromatic polyamide fiber of the present invention can suppress the occurrence of white blurring on the fiber surface against friction due to repeated washing or the like.

  Specifically, the fiber structure made from the para-type wholly aromatic polyamide fiber of the present invention is subjected to 5,000 wear tests by the E method (Martindale method) defined in JIS L1096. The lightness (L value) change rate is + 5% or less. It is preferably + 4.5% or less, particularly preferably + 4% or less. If the lightness (L value) change rate is 5% or less, a fiber product having a desired friction fastness can be obtained.

In addition, the “lightness (L value) change rate” in the present invention is the lightness (L value) of samples before and after 5,000 wear tests by the E method (Martindale method) defined in JIS L1096. Is measured and calculated by the following equation.
(Lightness change rate) = ((L value after wear test) − (L value before wear test)) / (L value before wear test) × 100

<Applications of para-type wholly aromatic polyamide fibers>
The para-type wholly aromatic polyamide fiber of the present invention can constitute fiber structures such as braids, ropes, twisted cords, yarns, and cotton in addition to fabrics such as woven fabrics, knitted fabrics, and nonwoven fabrics.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, these Examples and Comparative Examples are for helping understanding of the present invention, and the scope of the present invention is not limited by these descriptions.

<Measurement and evaluation method>
In Examples and Comparative Examples, the following items were measured and evaluated by the following methods.
[Intrinsic viscosity (IV)]
Measurements were made at 30 ° C. for a polymer concentration of 0.5 g / dL in 98% concentrated sulfuric acid.
[Brightness (L value)]
Using a color difference meter CR-200 manufactured by MINOLTA as a measuring instrument, the brightness (L value) was measured by the Lab display method defined in JIS Z8729.
[Lightness (L value) change rate]
Abrasion test was performed 5,000 times by the E method (Martindale method) defined in JIS L 1096, and the above lightness (L value) was measured for the samples before and after the test. The brightness change rate was calculated by the following equation.
(Lightness change rate) = ((L value after wear test) − (L value before wear test)) / (L value before wear test) × 100
[Fineness]
It measured according to JIS-L-1015.
[Tensile strength of fiber]
Using a tensile tester (manufactured by INSTRON Co., Ltd., trade name: INSTRON, model: 5565 type), measurement was performed under the following conditions based on the procedure of ASTM D885.
(Measurement condition)
Temperature: Room temperature Measurement sample length: 500mm
Chuck tensile speed: 250 mm / min Initial load: 0.2 cN / dtex

<Example 1>
[Production of para-type wholly aromatic polyamide]
(Adjustment of diamine solution)
1.35 g of p-phenylenediamine is weighed and put into a mixing tank having a bowl-shaped stirring blade, heated to 220 ° C. in the atmosphere and stirred for 3 hours, and an aromatic diamine component that develops black color (black amine) It was. After cooling to room temperature, the inside was flowed with nitrogen, 2.0 L of N-methyl-2-pyrrolidone (hereinafter referred to as “NMP”) having a moisture content of about 20 ppm was added, and 25.62 g of p-phenylenediamine and 3,4 '-Diaminodiphenyl ether and 49.89 g were precisely weighed in and dissolved to obtain a diamine solution.

(polymerization)
The obtained diamine solution was cooled to 20 ° C., and while stirring, 100.68 g of terephthalic acid chloride was precisely weighed in and stirred for 60 minutes, then heated to 70 ° C. and further heated for 60 minutes. Stirring was carried out to carry out a polymerization reaction. Subsequently, 163.90 g of NMP slurry containing 22.5% of calcium hydroxide was added and stirring was continued at 70 ° C. for 60 minutes, so that copolyparaphenylene-3,44′-oxydiphenylene terephthalate having a pH of 4.8 was obtained. An amide solution was obtained. The obtained polymer had an intrinsic viscosity (IV) of 3.6 and a polymer concentration of 6%.

[Production of para-type wholly aromatic polyamide fiber]
Using the obtained copolyparaphenylene 3,4'-oxydiphenylene terephthalamide solution as a spinning solution, the solution was discharged from a spinneret with 25 holes and an NMP concentration of 30% by mass through an air gap of about 10 mm. After spinning inside and coagulating (semi-dry semi-wet spinning method), washing and drying, and then drawing 10 times at a temperature of 530 ° C. and winding up to obtain a black para-type wholly aromatic polyamide fiber It was. Table 1 shows the physical properties of the obtained fiber.

[Production of woven fabric]
Using the obtained para-type wholly aromatic polyamide fiber as a spun yarn (20/2), a woven fabric (weighing 150 g / m ² ) woven into a 2/1 twill weave was prepared. Subsequently, a scouring process was performed by a known method to remove the paste and oil agent on the surface of the fabric. Table 1 shows the physical properties of the obtained fabric.

<Example 2>
[Production of para-type wholly aromatic polyamide]
(Adjustment of diamine solution)
2.70 g of p-phenylenediamine is weighed and put into a mixing tank having a bowl-shaped stirring blade, heated to 220 ° C. in the atmosphere and stirred for 3 hours, and an aromatic diamine component that develops black color (black amine) It was. After cooling to room temperature, the inside was flowed with nitrogen, NMP 2.0 L having a moisture content of about 20 ppm was added, and 24.27 g of p-phenylenediamine and 49.89 g of 3,4'-diaminodiphenyl ether were precisely weighed and charged. To obtain a diamine solution.

(polymerization)
Using the obtained diamine solution, a para-type wholly aromatic polyamide solution was obtained in the same manner as in Example 1. The obtained polymer had an intrinsic viscosity (IV) of 3.3.

[Preparation of para-type wholly aromatic polyamide fiber]
Using the obtained para-type wholly aromatic polyamide solution as a spinning solution, para-type wholly aromatic polyamide fibers were obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained fiber.

[Production of woven fabric]
A woven fabric was produced in the same manner as in Example 1 using the obtained para-type wholly aromatic polyamide fiber. Table 1 shows the physical properties of the obtained fabric.

<Example 3>
[Production of para-type wholly aromatic polyamide]
(Adjustment of diamine solution)
An aromatic diamine component (black amine) that develops black color by weighing 0.27 g of p-phenylenediamine into a mixing tank having a bowl-shaped stirring blade, and heating to 220 ° C. in the atmosphere and stirring for 3 hours. It was. After cooling to room temperature, the inside was flowed with nitrogen, NMP 2.0 L having a moisture content of about 20 ppm was charged, and 26.70 g of p-phenylenediamine and 49.89 g of 3,4'-diaminodiphenyl ether were precisely weighed and charged. To obtain a diamine solution.

(polymerization)
Using the obtained diamine solution, a para-type wholly aromatic polyamide solution was obtained in the same manner as in Example 1. The obtained polymer had an intrinsic viscosity (IV) of 3.5.

[Production of para-type wholly aromatic polyamide fiber]
Using the obtained para-type wholly aromatic polyamide solution as a spinning solution, para-type wholly aromatic polyamide fibers were obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained fiber.

[Production of woven fabric]
A woven fabric was produced in the same manner as in Example 1 using the obtained para-type wholly aromatic polyamide fiber. Table 1 shows the physical properties of the obtained fabric.

<Comparative Example 1>
[Production of para-type wholly aromatic polyamide]
(Adjustment of diamine solution)
The inside of the mixing vessel having a bowl-shaped stirring blade is flowed with nitrogen, 2.0 L of NMP having a moisture content of about 20 ppm is charged, and 26.97 g of p-phenylenediamine and 49.89 g of 3,4'-diaminodiphenyl ether are purified. A diamine solution was obtained by weighing and dissolving.

(polymerization)
The obtained diamine solution was cooled to 20 ° C., and while stirring, 100.68 g of terephthalic acid chloride was precisely weighed in and stirred for 60 minutes, then heated to 70 ° C. and further heated for 60 minutes. Stirring was carried out to carry out a polymerization reaction. Subsequently, 163.90 g of NMP slurry containing 22.5% of calcium hydroxide was added, and stirring was continued at 70 ° C. for 60 minutes to obtain copolyparaphenylene-3,4′-oxydiphenylene terephthalate having a pH of 4.8. An amide solution was obtained. The obtained polymer had an intrinsic viscosity (IV) of 3.4 and a polymer concentration of 6%.
To the obtained copolyparaphenylene 3,4'-oxydiphenylene terephthalamide solution, an NMP dispersion of carbon black (manufactured by Dainichi Seika Kogyo Co., Ltd., MPS-1100 Black (T)) is added to the polymer. In addition to adding 5% by mass of black, followed by heating and kneading at 80 ° C. for 2 hours using a planetary mixer (product name: PVM-5) manufactured by Asada Tekko Co., Ltd. A fully aromatic polyamide solution was obtained.

[Production of para-type wholly aromatic polyamide fiber]
The obtained carbon black-containing para-type wholly aromatic polyamide solution was used as a spinning solution, discharged from a spinneret with 25 holes, and spun into an aqueous solution having an NMP concentration of 30% by mass through an air gap of about 10 mm. After coagulation (semi-dry semi-wet spinning method), washing with water and drying were carried out, and then stretched 10 times at a temperature of 530 ° C. and wound up to obtain a black para-type wholly aromatic polyamide fiber. Table 1 shows the physical properties and the like of the obtained fiber.

[Production of woven fabric]
A woven fabric was produced in the same manner as in Example 1 using the obtained para-type wholly aromatic polyamide fiber. Table 1 shows the physical properties of the obtained fabric.

<Comparative example 2>
[Production of para-type wholly aromatic polyamide]
A para-type wholly aromatic polyamide solution in which carbon black was dispersed was obtained in the same manner as in Comparative Example 1, except that the content of carbon black was 10% by mass.

[Production of para-type wholly aromatic polyamide fiber]
Using the obtained para-type wholly aromatic polyamide solution as a spinning solution, para-type wholly aromatic polyamide fibers were obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained fiber.

[Production of woven fabric]
A woven fabric was produced in the same manner as in Example 1 using the obtained para-type wholly aromatic polyamide fiber. Table 1 shows the physical properties of the obtained fabric.

<Comparative Example 3>
[Production of para-type wholly aromatic polyamide]
A para-type wholly aromatic polyamide solution in which carbon black was dispersed was obtained in the same manner as in Comparative Example 1, except that the content of carbon black was 15% by mass.

[Production of para-type wholly aromatic polyamide fiber]
Using the obtained para-type wholly aromatic polyamide solution as a spinning solution, para-type wholly aromatic polyamide fibers were obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained fiber.

[Production of woven fabric]
A woven fabric was produced in the same manner as in Example 1 using the obtained para-type wholly aromatic polyamide fiber. Table 1 shows the physical properties of the obtained fabric.

Claims (3)

A para-type wholly aromatic polyamide fiber having a tensile strength of 23 cN / dtex or more,
The fiber structure produced from the fiber has an L value (lightness) of 24 or less in the Lab color method, and before and after being worn 5,000 times by the E method (Martindale method) defined in JIS L1096. A para-type wholly aromatic polyamide fiber having an L value (lightness) change rate of + 5% or less.   The para-type wholly aromatic polyamide fiber according to claim 1, having an elongation of 3.0% or more.   The para-type wholly aromatic polyamide fiber according to claim 1 or 2, wherein the para-type wholly aromatic polyamide is copolyparaphenylene 3,4'-oxydiphenylene terephthalamide.