JP2016196599A - Wholly aromatic polyamide fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wholly aromatic polyamide fiber having excellent breaking strength and rupture elongation.SOLUTION: A fiber is formed from a wholly aromatic polyamide comprising a structural repeating unit (I) represented by chemical formula (I), a structural repeating unit (II) represented by chemical formula (II), and a structural repeating unit (III) represented by chemical formula (III) at a specific rate.(Formula 1)SELECTED DRAWING: None

Description

  The present invention relates to wholly aromatic polyamide fibers, and more particularly to wholly aromatic polyamide fibers having high tensile strength and high elongation at break.

Conventionally, fibers made of wholly aromatic polyamides produced from aromatic diamines and aromatic dicarboxylic acid dihalides are very useful as high-strength fibers and have excellent heat resistance and flame retardancy. Are known.
In addition, fully aromatic polyamide fibers have higher dimensional stability, higher elastic modulus, and better fatigue resistance than general-purpose fibers. For example, rubber such as tire cords, power transmission belts, and conveyor belts. It is also suitably used for reinforcing materials, seat belts, fishing nets, safety nets and the like.

Recently, in the above-mentioned various products, there is a strong demand for further processability and fatigue resistance, and in order to satisfy them, it is necessary to improve the elongation while ensuring the mechanical strength of the wholly aromatic polyamide fiber. Has been.
However, since the wholly aromatic polyamide fiber forms a fiber structure having a high degree of crystallinity and a highly oriented polymer chain, the polymer structure is extremely stiff and it is difficult to improve the elongation.

In the development of high-strength organic fibers with high elongation, for example, in Patent Documents 1 to 4, various polyhexa having good dimensional stability, high elastic modulus, and excellent heat resistance and fatigue resistance. Methylene adipamide fibers and methods for obtaining the fibers have been proposed. However, although the fibers described in Patent Documents 1 to 4 have sufficient elongation at break, it is difficult to say that they have sufficient strength compared to wholly aromatic polyamide fibers.
In recent years, a method for obtaining a wholly aromatic polyamide having a high elongation at break has been proposed (see Patent Document 5). However, the fiber described in Patent Document 5 is still difficult to say that the breaking strength is sufficient.

JP 58-208413 A JP 59-026517 A JP-A-1-168913 JP-A-3-199421 JP 2012-207325 A

  The present invention has been made to solve the problems of the prior art as described above, and an object of the present invention is to provide a wholly aromatic polyamide fiber having high strength and at the same time high elongation. It is in.

  The present inventor has intensively studied to solve the above problems. As a result, the structural repeating unit (I) represented by the chemical formula (I), the structural repeating unit (II) represented by the chemical formula (II), and the structural repeating unit (III) represented by the chemical formula (III), It has been found that fibers made of wholly aromatic polyamides contained at a specific ratio are fibers having high mechanical strength and high elongation, and the present invention has been completed.

  That is, the present invention relates to a structural repeating unit (I) represented by the chemical formula (I), a structural repeating unit (II) represented by the chemical formula (II), and a structural repeating unit (III) represented by the chemical formula (III). Wherein the structural repeating unit (II) is a structural repeating unit (I) represented by the chemical formula (I) and a structural repeating unit (II) represented by the chemical formula (II). ) And the structural repeating unit (III) represented by the chemical formula (III) in an amount of 20 to 40 mol%, and the structural repeating unit (III) is a structural repeating unit represented by the chemical formula (I) ( A wholly aromatic polyamide fiber that is 10 to 30 mol% based on the total of the structural repeating unit (II) represented by I) and chemical formula (II) and the structural repeating unit (III) represented by chemical formula (III) It is.

  The wholly aromatic polyamide fiber of the present invention is a fiber having a high strength and dramatically improved elongation at break. For this reason, according to the fiber of this invention, the various fiber products in which high elongation is requested | required can be provided.

Hereinafter, embodiments of the present invention will be described in detail.
<Totally aromatic polyamide>
[Construction]
The wholly aromatic polyamide constituting the fiber of the present invention has a structural repeating unit (I) represented by the following chemical formula (I), a structural repeating unit (II) represented by the chemical formula (II), and a chemical formula (III). It is a polymer containing the structural repeating unit (III) represented and having one or more divalent aromatic groups linked directly by an amide bond. In this case, the aromatic group may be one in which two aromatic rings are bonded with oxygen, sulfur, or an alkyl group. These divalent aromatic rings may be unsubstituted or substituted with a lower alkyl group such as a methyl group or a methyl group, or a halogen group such as a methoxy group or a chlorine group. Even if it is bonded, there is no particular limitation, and the type of substituent and the number of substituents are not particularly limited.

  The wholly aromatic polyamide containing the structural repeating unit contained in the wholly aromatic polyamide fiber of the present invention is preferably 90 mol% or more, more preferably 95 mol% or more, based on the entire fiber mass. Preferably, it is 100 mol%, and most preferably.

[Proportion of structural repeat unit]
In the wholly aromatic polyamide used in the present invention, the structural repeating unit (II) represented by the chemical formula (II) is represented by the structural repeating unit (I) represented by the chemical formula (I) and the chemical formula (II). 20 to 40 mol%, preferably 25 to 35 mol%, based on the total of the structural repeating unit (II) and the structural repeating unit (III) represented by the chemical formula (III), and at the same time in the chemical formula (III) The structural repeating unit (III) represented is represented by the structural repeating unit (I) represented by the chemical formula (I), the structural repeating unit (II) represented by the chemical formula (II), and the chemical formula (III). It is 10-30 mol% with respect to the sum total of structure repeating unit (III), Preferably it is 15-25 mol%.

  By setting the structural repeating unit (II) represented by the chemical formula (II) and the structural repeating unit (III) represented by the chemical formula (III) to a specific ratio, the resulting fiber has a tensile strength of 24 cN / dtex or more. In addition, mechanical properties having a breaking elongation of 5.0% or more can be expressed. When the content of the structural repeating unit (II) represented by the chemical formula (II) is less than 20 mol%, desired strength and elongation are not exhibited. Moreover, when the content of the structural repeating unit (II) represented by the chemical formula (II) exceeds 40 mol%, the strength of the fiber is lowered, which is not preferable. On the other hand, when the content of the structural repeating unit (III) represented by the chemical formula (III) is less than 10 mol%, the desired elongation is not exhibited. Moreover, when the content of the structural repeating unit (III) represented by the chemical formula (III) exceeds 30 mol%, the strength of the fiber is lowered, which is not preferable.

[Intrinsic viscosity]
The aromatic polyamide constituting the fiber of the present invention has an intrinsic viscosity (IV) of 3.3 to 5.0 measured at 30 ° C. with respect to a solution having a polymer concentration of 0.5 g / dl in 98% concentrated sulfuric acid. , Preferably 3.5 to 4.8. When the intrinsic viscosity is in the above range, a fiber exhibiting mechanical properties having a tensile strength of 24 cN / dtex or more and a breaking elongation of 5.0% or more can be obtained. When the intrinsic viscosity (IV) is less than 3.3, the predetermined elongation is not exhibited. On the other hand, if it exceeds 5.0, it is difficult to mold the fiber, which is not preferable.

<Method for producing wholly aromatic polyamide>
The wholly aromatic polyamide constituting the fiber of the present invention can be produced according to a conventionally known method. For example, it can be obtained from low temperature solution polymerization or interfacial polymerization of an aromatic dicarboxylic acid dichloride component and an aromatic diamine component as raw materials in an amide polar solvent.

[Raw material of type wholly aromatic polyamide]
(Aromatic dicarboxylic acid dichloride component)
As the aromatic dicarboxylic acid dichloride component used as a raw material for the wholly aromatic polyamide, terephthalic acid dichloride is used as a main component. Here, the main component means that terephthalic acid dichloride is 50 mol% or more with respect to the whole aromatic dicarboxylic acid dichloride component, preferably 70 mol% or more, more preferably 90 mol% or more, most preferably Preferably it is 100 mol%.

  Examples of the component constituting the wholly aromatic polyamide used together with terephthalic acid dichloride include, for example, 2-chloroterephthalic acid dichloride, 3-methylterephthalic acid dichloride, 4,4′-biphenyldicarboxylic acid dichloride, and 2,6-naphthalenedicarboxylic acid. A dichloride etc. are mentioned. In the present invention, a small amount of a component such as isophthalic acid dichloride that forms a bond other than the para position may be contained.

(Aromatic diamine component)
Examples of the aromatic diamine component used as a raw material for the type wholly aromatic polyamide include the structural repeating unit (I) represented by the chemical formula (I), the structural repeating unit (II) represented by the chemical formula (II), and the chemical formula ( In order to constitute each of the structural repeating units (III) represented by III), at least three kinds of aromatic diamines are used, and combinations thereof include paraphenylenediamine, 3,4'-diaminophenyl ether, and 4,4 It is necessary to have '-diaminophenyl ether as a main component. Here, the main component means that the total amount of these three kinds of aromatic diamine components is 50 mol% or more, preferably 70 mol% or more, more preferably 90 mol%, based on the whole aromatic diamine component. More than mol%, most preferably 100 mol%.

  As the aromatic diamine component constituting the wholly aromatic polyamide constituting the fiber of the present invention, in addition to the above three kinds of aromatic diamine components, for example, parabiphenylenediamine, 5-amino-2- (4-aminophenylene) ) Benzimidazole, 1,4-dichloroparaphenylenediamine and the like. In addition, in this invention, components, such as metaphenylenediamine which forms a bond other than para position, may be contained in a small amount.

  In the present invention, as described above, the structural repeating unit (II) represented by the chemical formula (II) is represented by the structural repeating unit (I) represented by the chemical formula (I) and the chemical formula (II). 20 to 40 mol%, preferably 25 to 35 mol%, based on the total of the structural repeating unit (II) and the structural repeating unit (III) represented by the chemical formula (III), and at the same time in the chemical formula (III) The structural repeating unit (III) represented is represented by the structural repeating unit (I) represented by the chemical formula (I), the structural repeating unit (II) represented by the chemical formula (II), and the chemical formula (III). It is 10-30 mol% with respect to the sum total of structure repeating unit (III), Preferably it is 15-25 mol%. Therefore, the composition ratio of 3,4'-diaminophenyl ether is 20 to 40 mol% with respect to the total of paraphenylenediamine, 3,4'-diaminophenyl ether, and 4,4'-diaminophenyl ether. At the same time, preferably 25 to 35 mol%, and at the same time, the composition ratio of 4,4′-diaminophenyl ether is paraphenylenediamine, 3,4′-diaminophenyl ether, and 4,4′-diamino. It is essential to set it as 10-30 mol% with respect to the sum total with phenyl ether, Preferably it is 15-25 mol%.

[Raw material composition ratio]
The ratio of the aromatic dicarboxylic acid chloride component to the aromatic diamine component is preferably 0.90 to 1.10, more preferably 0.95 to 1 as the molar ratio of the aromatic dicarboxylic acid chloride component to the aromatic diamine component. .05 range. 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 wholly aromatic polyamide include organic polar amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, tetrahydrofuran, and the like. And water-soluble ether compounds such as dioxane, water-soluble alcohol compounds such as methanol, ethanol and ethylene glycol, water-soluble ketone compounds such as acetone and methyl ethyl ketone, and water-soluble nitrile compounds such as acetonitrile and propionitrile. These solvents can be used alone or as a mixed solvent of two or more. The solvent is preferably dehydrated.

In the production of wholly aromatic polyamides, N-methyl-2-pyrrolidone (NMP) is most preferably used from the viewpoints of versatility, harmfulness, handling properties, solubility in wholly aromatic polyamides, and the like.
In order to increase the solubility, an appropriate amount of a known inorganic salt may be added before, during or after the polymerization. Examples of such inorganic salts include lithium chloride and calcium chloride.

[Neutralization reaction]
After completion of the reaction, it is preferable to carry out a neutralization reaction by adding a basic inorganic compound such as sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxide or the like, if necessary.

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

[Polymer polymerization degree]
The degree of polymerization of the wholly aromatic polyamide is not particularly limited. However, if the polymer is soluble in a solvent, it is preferable that the degree of polymerization is large as long as the moldability is not impaired. In order to control the degree of polymerization, either the aromatic dicarboxylic acid dichloride component or the aromatic diamine component can be used in excess. Moreover, you may use terminal blockers, such as a monofunctional acid component and an amine component.

[Polymer concentration]
The polymer concentration of the obtained wholly aromatic polyamide solution is preferably in the range of 0.5 to 30% by mass, more preferably 1 to 10% by mass. When the polymer concentration is less than 0.5% by mass, the polymer has little entanglement and the viscosity necessary for spinning cannot be obtained. On the other hand, when the polymer concentration exceeds 30% by mass, when the fiber is produced using the polyamide solution as it is, the flow tends to become unstable when discharged from the nozzle, and it becomes difficult to perform stable spinning.

<Method for producing wholly aromatic polyamide fiber>
The wholly aromatic polyamide fiber of the present invention is prepared by preparing a spinning solution (polymer dope) comprising a wholly aromatic polyamide solution (which may be a polymer dope produced during the production of wholly aromatic polyamide), and wet spinning or dry spinning. Then, it is obtained by removing the solvent.

[Process for preparing spinning solution (polymer dope)]
That is, to obtain the wholly aromatic polyamide fiber of the present invention, first, a spinning solution (polymer dope) containing the wholly aromatic polyamide and the solvent is prepared. Here, as long as the wholly aromatic polyamide is dissolved, the method for adjusting the spinning solution (polymer dope) is not limited, and the polymer is obtained from the polymer solution obtained by producing the wholly aromatic polyamide. It may be used as it is without being isolated, or it may be one obtained by dissolving an isolated wholly aromatic polyamide in an organic solvent.

Here, as a solvent used, the solvent used for superposition | polymerization of above-mentioned wholly aromatic polyamide can be used. Moreover, the solvent used may be 1 type individual, or may use 2 or more types together.
In addition, in this invention, you may mix | blend other arbitrary components, such as a filler and an additive, in the range which does not impair a physical property in order to provide functionality etc. to a fiber. When an additive or the like is blended, it can be introduced in the preparation of a spinning solution (polymer dope). The introduction method is not particularly limited, and examples thereof include a method of introducing the dope using a ruder, a mixer, or the like.

[Spinning and coagulation process]
In the production of the fiber of the present invention, the fiber is formed by a wet spinning method or a semi-dry semi-wet spinning method 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 for wholly aromatic polyamide is used, but it is usually good so that the solvent of the spinning solution (polymer dope) quickly escapes and the obtained wholly aromatic polyamide coagulated yarn cannot be defective. A solvent is added to adjust the coagulation rate. It is preferable to use water as the poor solvent and a solvent for the 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 wholly aromatic polyamide.

[Other processes]
After pulling up the coagulated yarn from the coagulation liquid, a final wholly aromatic polyamide fiber can be obtained by a known method. For example, a water washing step is performed to remove the solvent, stretching is performed as necessary, and after passing through a drying step and the like, stretching and orientation are performed as necessary to obtain a final fiber.

[Stretching process]
It is preferable that the wholly aromatic polyamide fiber of the present invention is highly oriented and crystallized by carrying out heat stretching and having a crystal orientation degree of 89% or more and a crystallinity degree of 74% or more determined by wide-angle X-ray diffraction. . When either one or both of the crystal orientation degree and the crystallinity degree are low, the mechanical properties of the resulting fiber tend to be insufficient. The temperature of hot stretching depends on the polymer skeleton of the wholly aromatic polyamide, but is preferably 300 to 550 ° C, more preferably 350 to 500 ° C, and the stretching ratio is preferably 4 times or more, more preferably 4 to 15 times.

<Totally aromatic polyamide fiber>
[Physical properties of wholly aromatic polyamide fiber]
(Single yarn fineness)
The single yarn fineness of the wholly aromatic polyamide fiber of the present invention is preferably 0.5 to 50 dtex, more preferably 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, if it exceeds 50 dtex, the specific surface area of the fiber becomes small and it is difficult to undergo light resistance deterioration. However, since the specific surface area is small, coagulation tends to be incomplete in the spinning process. The condition is likely to be disturbed, and the physical properties are also likely to deteriorate.

(Strength)
The tensile strength of the wholly aromatic polyamide fiber of the present invention is preferably as high as possible, and if it is less than 24 cN / dtex, the characteristics as a high-strength fiber are insufficient. Preferably, it is 24 cN / dtex or more.

(Elongation)
The elongation of the wholly aromatic polyamide fiber of the present invention is 5.0% or more. If it is less than 5.0%, the durability required for applications such as rubber reinforcement cannot be satisfied. The elongation is preferably 5.4% or more, and most preferably 5.9% or more.

[Use of fully aromatic polyamide fiber]
The wholly aromatic polyamide fiber of the present invention is a fiber having high elongation while having the high strength inherent to the wholly aromatic polyamide fiber. Therefore, in addition to the fields where these characteristics are required, various fiber structures such as braids, ropes, twisted cords, yarns, cotton, etc. are manufactured in addition to fabrics such as woven fabrics, knitted fabrics, and nonwoven fabrics. Can be used in

  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.
(1) Intrinsic viscosity (IV)
Measurements were made at 30 ° C. for a polymer concentration of 0.5 g / dL in 98% concentrated sulfuric acid.
(2) Fineness It measured according to JIS-L-1015.
(3) Tensile strength, elongation at break, elastic modulus of fiber Using a tensile tester (manufactured by INSTRON, trade name: INSTRON, model: 5565 type), measurement is performed under the following conditions based on the procedure of ASTM D885. did.
[Measurement condition]
Temperature: Room temperature Test sample length: 500mm
Initial load: 0.2 cN / dtex
Test speed: 250 mm / min

<Example 1>
[Polymerization of wholly aromatic polyamide]
N-methyl-2-pyrrolidone (NMP) 2.139 L, paraphenylenediamine 28.5 g (25 mol%), 3,4'-diaminodiphenyl ether 21.1 g (10 mol%), 4,4'-diaminodiphenyl ether 31. 7 g (15 mol%) was weighed and added, and dissolved at room temperature. To the obtained diamine solution, 106.9 g (50 mol%) of terephthalic acid chloride was added and reacted to polymerize the polymer. Subsequently, 172.2 g of NMP dispersion containing 22.5% by mass of calcium hydroxide was added for neutralization to obtain a polymer solution.
The resulting copolyamide had an intrinsic viscosity (IV) (measured at 30 ° C. for a solution having a polymer concentration of 0.5 g / dl in 98% concentrated sulfuric acid) of 4.12. The obtained solution was prepared as an NMP melt spinning solution having a concentration of 6% by mass to obtain a spinning solution (polymer dope).

[Production of wholly aromatic polyamide fiber]
The obtained spinning solution (polymer dope) was 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 to be solidified (semi-dry half Wet spinning method), washing with water, drying, and then drawing after 9.4 times stretching at a temperature of 500 ° C. to obtain a wholly aromatic polyamide fiber. Table 1 shows the physical properties and the like of the obtained fiber.

<Example 2>
[Polymerization of wholly aromatic polyamide]
N-methyl-2-pyrrolidone (NMP) 2.139 L, paraphenylenediamine 28.5 g (25 mol%), 3,4'-diaminodiphenyl ether 21.1 g (10 mol%), 4,4'-diaminodiphenyl ether 31. 7 g (15 mol%) was weighed and added, and dissolved at room temperature. To the obtained diamine solution, 106.9 g (50 mol%) of terephthalic acid chloride was added and reacted to polymerize the polymer. Subsequently, 172.2 g of NMP dispersion containing 22.5% by mass of calcium hydroxide was added for neutralization to obtain a polymer solution.
The resulting copolyamide had an intrinsic viscosity (IV) (measured at 30 ° C. for a solution having a polymer concentration of 0.5 g / dl in 98% concentrated sulfuric acid) of 3.61. The obtained solution was prepared as an NMP melt spinning solution having a concentration of 6% by mass to obtain a spinning solution (polymer dope).

[Production of wholly aromatic polyamide fiber]
The obtained spinning solution (polymer dope) was 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 to be solidified (semi-dry half Wet spinning method), washing with water, drying, and then drawing 8.5 times after stretching at a temperature of 500 ° C. to obtain a wholly aromatic polyamide fiber. Table 1 shows the physical properties and the like of the obtained fiber.

<Example 3>
[Polymerization of wholly aromatic polyamide]
N-methyl-2-pyrrolidone (NMP) 2.139 L, paraphenylenediamine 28.5 g (25 mol%), 3,4'-diaminodiphenyl ether 31.7 g (15 mol%), 4,4'-diaminodiphenyl ether 21. 1 g (10 mol%) was weighed and added, and dissolved at room temperature. To the obtained diamine solution, 110.5 g (50 mol%) of terephthalic acid chloride was added and reacted to polymerize the polymer. Subsequently, 178.0 g of NMP dispersion containing 22.5% by mass of calcium hydroxide was added for neutralization to obtain a polymer solution.
The intrinsic viscosity (IV) of the obtained copolyamide (measured at 30 ° C. for a solution having a polymer concentration of 0.5 g / dl in 98% concentrated sulfuric acid) was 4.10. The obtained solution was prepared as an NMP melt spinning solution having a concentration of 6% by mass to obtain a spinning solution (polymer dope).

[Production of wholly aromatic polyamide fiber]
The obtained spinning solution (polymer dope) was discharged from a spinneret with 25 holes and spun into an aqueous solution having an NMP concentration of 30% by weight through an air gap of about 10 mm to be solidified (half dry half) Wet spinning method), washing with water, drying, and then drawing by 8.6 times at a temperature of 500 ° C. to obtain a wholly aromatic polyamide fiber. Table 1 shows the physical properties and the like of the obtained fiber.

<Example 4>
[Polymerization of wholly aromatic polyamide]
N-methyl-2-pyrrolidone (NMP) 2.139 L, paraphenylenediamine 42.2 g (25 mol%), 3,4'-diaminodiphenyl ether 31.7 g (20 mol%), 4,4'-diaminodiphenyl ether 10. 6 g (5 mol%) was weighed and added, and dissolved at room temperature. To the obtained diamine solution, 110.5 g (50 mol%) of terephthalic acid chloride was added and reacted to polymerize the polymer. Subsequently, 178.0 g of NMP dispersion containing 22.5% by mass of calcium hydroxide was added for neutralization to obtain a polymer solution.
The intrinsic viscosity (IV) of the obtained copolyamide (measured at 30 ° C. for a solution having a polymer concentration of 0.5 g / dl in 98% concentrated concentrated sulfuric acid) was 3.95. The obtained solution was prepared as an NMP melt spinning solution having a concentration of 6% by mass to obtain a spinning solution (polymer dope).

[Production of wholly aromatic polyamide fiber]
The obtained spinning solution (polymer dope) was discharged from a spinneret with 25 holes and spun into an aqueous solution having an NMP concentration of 30% by weight through an air gap of about 10 mm to be solidified (half dry half) Wet spinning method), washing with water, drying, and then drawing at 10.3 times at a temperature of 520 ° C. to obtain a wholly aromatic polyamide fiber. Table 1 shows the physical properties and the like of the obtained fiber.

<Comparative Example 1>
[Polymerization of wholly aromatic polyamide]
To 2.139 L of N-methyl-2-pyrrolidone (NMP), 42.2 g (25 mol%) of paraphenylenediamine and 52.8 g (25 mol%) of 3,4'-diaminodiphenyl ether were weighed and put at room temperature. And dissolved. To the obtained diamine solution, 110.5 g (50 mol%) of terephthalic acid chloride was added and reacted to polymerize the polymer. Subsequently, 178.0 g of NMP dispersion containing 22.5% by mass of calcium hydroxide was added for neutralization to obtain a polymer solution.
The intrinsic viscosity (IV) of the obtained copolyparaphenylene 3,4'-oxydiphenylene terephthalamide (measured at 30 ° C. for a solution having a polymer concentration of 0.5 g / dl in 98% concentrated concentrated sulfuric acid) is 3 .38. The obtained solution was prepared as an NMP melt spinning solution having a concentration of 6% by mass to obtain a spinning solution (polymer dope).

[Production of wholly aromatic polyamide fiber]
The obtained spinning solution (polymer dope) was discharged from a spinneret with 25 holes and spun into an aqueous solution having an NMP concentration of 30% by weight through an air gap of about 10 mm to be solidified (half dry half) Wet spinning method), washing with water, drying, and then drawing 11.0 times at a temperature of 530 ° C. and winding up to obtain a wholly aromatic polyamide fiber. Table 1 shows the physical properties and the like of the obtained fiber.

<Comparative example 2>
[Polymerization of wholly aromatic polyamide]
To 2.139 L of N-methyl-2-pyrrolidone (NMP), 42.2 g (25 mol%) of paraphenylenediamine and 52.8 g (25 mol%) of 4,4′-diaminodiphenyl ether were weighed and charged. And dissolved. To the obtained diamine solution, 110.5 g (50 mol%) of terephthalic acid chloride was added and reacted to polymerize the polymer. Subsequently, 178.0 g of NMP dispersion containing 22.5% by mass of calcium hydroxide was added for neutralization to obtain a polymer solution.
The intrinsic viscosity (IV) of the obtained copolyparaphenylene-4,4′-oxydiphenylene terephthalamide (measured at 30 ° C. for a solution having a polymer concentration of 0.5 g / dl in 98% concentrated concentrated sulfuric acid) is 4 .23. The obtained solution was prepared as an NMP melt spinning solution having a concentration of 6% by mass to obtain a spinning solution (polymer dope).

[Production of wholly aromatic polyamide fiber]
The obtained spinning solution (polymer dope) was discharged from a spinneret with 25 holes and spun into an aqueous solution having an NMP concentration of 30% by weight through an air gap of about 10 mm to be solidified (half dry half) Wet spinning method), washing with water, drying, and then drawing 5.0 times at a temperature of 460 ° C. and then winding up to obtain a wholly aromatic polyamide fiber. Table 1 shows the physical properties and the like of the obtained fiber.

<Comparative Example 3>
[Polymerization of wholly aromatic polyamide]
N-methyl-2-pyrrolidone (NMP) 2.139 L, paraphenylenediamine 28.5 g (25 mol%), 3,4'-diaminodiphenyl ether 10.6 g (5 mol%), 4,4'-diaminodiphenyl ether 31. 7 g (20 mol%) was weighed and added, and dissolved at room temperature. To the obtained diamine solution, 106.9 g (50 mol%) of terephthalic acid chloride was added and reacted to polymerize the polymer. Subsequently, 172.2 g of NMP dispersion containing 22.5% by mass of calcium hydroxide was added for neutralization to obtain a polymer solution.
The resulting copolyamide had an intrinsic viscosity (IV) (measured at 30 ° C. for a solution having a polymer concentration of 0.5 g / dl in 98% concentrated sulfuric acid) of 4.12. The obtained solution was prepared as an NMP melt spinning solution having a concentration of 6% by mass to obtain a spinning solution (polymer dope).

[Production of wholly aromatic polyamide fiber]
The obtained spinning solution (polymer dope) was 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 to be solidified (semi-dry half Wet spinning method), washing with water, drying, and then drawing 6.1 times at a temperature of 460 ° C. and then winding up to obtain a wholly aromatic polyamide fiber. Table 1 shows the physical properties and the like of the obtained fiber.

  The wholly aromatic polyamide fiber of the present invention is a fiber having a high elongation at break while having the high strength inherent in the wholly aromatic polyamide fiber. For this reason, it is particularly useful in a field that requires these characteristics, for example, as a rubber reinforcing material such as a tire cord, a transmission belt, a conveyor belt, an industrial application such as a seat belt, a fishing net, a safety net, etc. Useful.

Claims (2)

A wholly aromatic group comprising a structural repeating unit (I) represented by chemical formula (I), a structural repeating unit (II) represented by chemical formula (II), and a structural repeating unit (III) represented by chemical formula (III) A fiber comprising polyamide,
The structural repeating unit (II) is a structural repeating unit (I) represented by the chemical formula (I), a structural repeating unit (II) represented by the chemical formula (II), or a structural repeating unit represented by the chemical formula (III). 20 to 40% by weight relative to the total of (III),
The structural repeating unit (III) is a structural repeating unit (II) represented by the chemical formula (I), a structural repeating unit (II) represented by the chemical formula (II), or a structural repeating unit represented by the chemical formula (III). Totally aromatic polyamide fiber, which is 10 to 30 mol% with respect to the total of (III).

  The intrinsic viscosity (IV) measured at 30 ° C. for a solution having a polymer concentration of 0.5 g / dl in 98% concentrated concentrated sulfuric acid is 3.3 to 5.0, and the elongation at break is 5.0% or more. The wholly aromatic polyamide fiber according to claim 1, which has a tensile strength of 24 cN / dtex or more.