JP4563926B2 - Aromatic copolyamide fiber - Google Patents

Description

  The present invention relates to an aromatic copolyamide fiber. More specifically, the present invention relates to a novel aromatic copolyamide fiber which has fewer defects in the fiber and exhibits excellent mechanical properties as compared with conventional aromatic polyamide fibers.

  Conventionally, an aromatic polyamide fiber composed of an aromatic dicarboxylic acid component and an aromatic diamine component (hereinafter sometimes referred to as “aramid fiber”), particularly para-aramid fiber, has strength, high elastic modulus, high heat resistance, etc. Taking advantage of its characteristics, it is widely used in industrial and clothing applications.

  A typical para-aramid fiber is polyparaphenylene terephthalamide (PPTA) fiber. Although this fiber has many advantages, it has a process problem in that it is manufactured by a so-called liquid crystal spinning method using the optical anisotropy of a polymer dope, and the fiber performance is out of mechanical properties. There are drawbacks such as not necessarily high strength and low elongation and insufficient toughness.

  In order to solve this problem, an attempt was made to develop an aromatic copolyamide fiber intended to improve mechanical properties using an aromatic copolyamide having a heterocycle-containing monomer introduced while maintaining optical anisotropy. (See Patent Document 1 below). However, it has been found that such an aromatic copolyamide is difficult to exert stable performance due to factors such as instability of the polymer solution.

  Therefore, another aromatic copolyamide fiber that has high solubility in known amide solvents, can be easily spun, and the spun fiber has high tensile strength and high initial modulus after the drawing treatment is developed. Attempts have been made to form, for example, heterocycle-containing aromatic copolyamides containing at least repeating structural units of the following chemical formulas (1) and (2), which form an optically isotropic solution with respect to amide solvents. It has been proposed to produce fibers from such aromatic polyamides (see Patent Document 2 and Patent Document 3 below). However, the aromatic copolyamide fibers disclosed in these patent documents have insufficient mechanical properties such as tensile strength and initial modulus.

  Similarly, high tensile strength, high initial modulus, and the like are obtained by spinning and plasticizing and stretching an unneutralized polymer solution of an aromatic copolyamide containing at least the repeating structural units of the following chemical formulas (1) and (2). Aromatic copolyamide fibers having improved mechanical properties have been proposed (for example, see Non-Patent Document 1 below). However, in this method, since the polymer solution is unneutralized, it contains hydrochloric acid generated during polymerization, and there are problems such as polymer chain degradation at high temperatures or corrosion of equipment, so that industrially useful fibers can be obtained. Is difficult.

JP-A-51-8363 Japanese Patent Laid-Open No. 7-300534 JP 7-278303 A J. et al. W. S. "High-performance fibers" by Hearle, pages 118-120, Woodhead Publishing Limited (2001)

  The present invention provides a novel aromatic copolyamide fiber that eliminates the drawbacks of conventional aramid fibers, can be stably produced with good productivity, and has mechanical properties such as sufficient tensile strength. The purpose is to provide.

  As a result of diligent research to achieve the above-mentioned object, the present inventors have substituted a repeating structural unit containing a specific hetero ring in a molecular chain (main chain) of an aromatic polyamide and hydrogen of the aromatic ring with a halogen group. The copolyamide introduced with a specific molar ratio of the recurring structural unit can be plasticized and stretched at a sufficient draw ratio from the neutralized polymer solution. It has been found that an aromatic copolyamide fiber having good mechanical properties is obtained because the degree of defects is significantly reduced.

  The present invention has been completed by further research based on such findings, and is a heterocycle-containing aromatic copolymer substantially composed of repeating structural units represented by the following chemical formulas (1), (2) and (3). A polyamide comprising 30 to 95 mol% of repeating structural units of the chemical formula (2) and 5 to 20 mol% of repeating structural units of the chemical formula (3) with respect to the total amount of repeating structural units of the aromatic copolyamide. Related to an aromatic copolyamide fiber, characterized in that the degree of defects in the fiber measured with a small-angle X-ray scattering device is 3 nm or less in terms of average pore diameter. It is.

Ar ¹ , Ar ² and Ar ³ in the chemical formulas (1), (2) and (3) are each independently a divalent aromatic group having a bonding group in the para-coordinate or parallel axis direction. , Ar ¹ is an unsubstituted or substituted aromatic group, Ar ² is an unsubstituted aromatic group, and Ar ³ is an aromatic group substituted with a halogen group.

  The aromatic copolyamide referred to in the present invention is a polymer in which two or more kinds of divalent aromatic groups are directly linked by an amide bond, and two aromatic rings are directly bonded in these aromatic groups. Alternatively, they may be bonded via an oxygen atom, a sulfur atom or an alkylene group. In addition, these divalent aromatic groups may include a lower alkyl group such as a methyl group or an ethyl group, a halogen group such as a chloro group, a fluoro group, or a bromo group, or a methoxy group.

The aromatic copolyamide that forms the fiber of the present invention is a multiple element substantially composed of three types of repeating structural units (polyamide repeating units) represented by the above chemical formulas (1), (2), and (3). It is a copolymer. In these three types of repeating structural units, the aromatic group Ar ¹ constituting the dicarboxylic acid component is obtained by substituting at least one hydrogen constituting the aromatic ring with a halogen group, a lower alkyl group, a methoxy group or the like. Also good. Moreover, it is preferable that all Ar ¹ in the chemical formulas (1) to (3) are the same aromatic group (for example, a paraphenylene group), but it is not always necessary that they are the same aromatic group.

On the other hand, the aromatic groups constituting the diamine component are different from each other in the repeating structural units of the chemical formulas (1) to (3), and Ar ² in the chemical formula (1) is an unsubstituted aromatic in which the hydrogen of the aromatic ring is not substituted. As is apparent from the chemical formula, the aromatic diamine component in the chemical formula (2) is a divalent aromatic group containing a heterocyclic ring. The aromatic group is not limited to an unsubstituted group, and may be substituted with a halogen group or the like. The chemical formula (3) Ar ³ is an aromatic group in which at least one of hydrogen in the aromatic ring is substituted with a halogen group.
As a general rule, these aromatic groups Ar ¹ , Ar ² and Ar ³ are all divalent aromatic groups having bonds in the para- or parallel-axis direction (hereinafter collectively referred to as “para-type”). It is.

  The aromatic copolyamide constituting the fiber in the present invention is a multi-component copolymer containing at least the above three types of repeating structural units. In the multi-component copolymer, the recurring structural unit of the above chemical formula (2) accounts for 30 to 95 mol%, preferably 50 to 90 mol% of the total amount (100 mol%) of the repetitive structural units, And it is necessary for the repeating structural unit of the chemical formula (3) to occupy 5 to 20 mol%, preferably 10 to 20 mol%. Further, the multi-component copolymer includes 5 mol% or more of the repeating structural unit of the chemical formula (1), and is copolymerized so that the total of the three kinds of repeating structural units is substantially 100 mol%. preferable. Among such aromatic copolyamides, the repeating structural unit of the chemical formula (1) is 10 to 20 mol%, the repeating structural unit of the chemical formula (2) is 50 to 90 mol%, the chemical formula (3) with respect to the total amount of the repeating structural units. Copolyamides containing 10 to 20 mol% of repeating structural units are particularly suitable.

In the present invention, a part of Ar ¹ , Ar ² and Ar ³ (for example, less than 10 mol% of the whole) of the repetitive structural unit is within a range that does not substantially impair the characteristics of the aromatic copolyamide fiber. The meta-type divalent aromatic group such as a metaphenylene group may be replaced. In addition, the fiber of the present invention may contain additives such as a colorant, a flame retardant, and a stabilizer as necessary.

  In addition to the above characteristics, the fiber of the present invention further has a characteristic that the degree of defects in the fiber is 3 nm or less, preferably 0.5 to 2.8 nm, expressed as an average pore diameter. In the present invention, the degree of defects in the fiber is represented by the average pore diameter (nm) in the fiber measured using a small angle X-ray scattering device.

The measurement apparatus and measurement conditions for small-angle X-ray scattering are as follows.
Device: RIGAKU small-angle X-ray scattering device (RU-200B)
Measurement conditions: λ (CuKα) = 0.154 nm, 45 kV, 70 mA
Analysis method: Measurement is performed in the small-angle region (2θ <10 °) using the above-described measuring device, and the average pore diameter (nm) in the fiber is calculated from the scattered light profile. Specifically, a Debye plot is performed from the analysis of small angle X-ray scattering, and an average pore diameter (nm) is calculated from the Debye plot by the following formula.

  According to the study by the present inventors, it has been found that the mechanical properties of the aromatic polyamide fiber greatly depend on the degree of defects in the fiber. In the aromatic copolyamide fiber having the composition of the present invention, if the degree of defects in the fiber exceeds 3 nm in terms of the average pore diameter, the mechanical properties of the fiber, particularly the tensile strength, is not preferable.

  The fineness of the aromatic copolyamide fiber of the present invention is preferably in the range of 0.55 to 22 dtex, particularly preferably in the range of 1.67 to 16.7 dtex, in terms of single yarn fineness. If the single yarn fineness is less than 0.55 dtex, fluff and single yarn breakage are likely to occur in the yarn making process, which is not preferable. If it exceeds 22 dtex, twisted yarn, net making and the like become difficult, which is not preferable. The aromatic copolyamide fiber has a tensile strength of 20 cN / dtex or more, preferably 22 to 30 cN / dtex, and an initial modulus of 500 cN / dtex or more, preferably 600 to 1000 cN / dtex is excellent in practicality.

  According to the present invention, the fiber spun from the neutralized polymer solution can be drawn at a sufficient plasticizing draw ratio, and the degree of defects in the fiber is sufficiently reduced, so that the tensile strength, An aromatic copolyamide fiber excellent in mechanical properties such as initial modulus and elongation can be provided. The aromatic copolyamide fiber of the present invention is useful for various uses such as industrial use and protective clothing by taking advantage of its properties.

  The aromatic copolyamide that forms the fiber of the present invention forms the repeating structural units of the chemical formulas (1), (2), and (3) in an amide solvent by a solution polymerization method known per se. The obtained aromatic dicarboxylic acid chloride and aromatic diamine can be reacted to produce a polymer solution. It can be produced by a method in which an aromatic dicarboxylic acid chloride and an aromatic diamine are reacted to obtain a polymer solution.

  In this case, examples of the aromatic dicarboxylic acid dichloride preferably used include terephthalic acid dichloride, 2-chloroterephthalic acid dichloride, 3-methylterephthalic acid dichloride, 4,4′-biphenylenedicarboxylic acid dichloride, and 2,6-naphthalene. Para-type aromatic dicarboxylic acid dichloride having a functional group in the para- or parallel-axis direction such as dicarboxylic acid dichloride. These may be either unsubstituted or substituted, with terephthalic acid dichloride being particularly preferred. These aromatic dicarboxylic acid dichlorides may be used alone or in combination of two or more. It should be noted that a part of the para-type aromatic dicarboxylic acid dichloride may be replaced with a meta-type dicarboxylic acid chloride such as isophthalic acid dichloride within a range not impairing the object of the present invention.

  On the other hand, as the aromatic diamine, at least three kinds of aromatic diamines are used. The first aromatic diamine is one selected from unsubstituted para-type aromatic diamines. For example, conventional aromatic diamines such as paraphenylene diamine, 4,4′-biphenylene diamine, 3,4′-diaminodiphenyl ether, etc. What is used for manufacture of para-type aramid fiber is used suitably. These may be used alone or in combination of two or more. As such an unsubstituted para-type aromatic diamine, paraphenylenediamine is particularly preferable. It should be noted that a part of the para type aromatic diamine may be replaced with an unsubstituted meta type aromatic diamine such as metaphenylene diamine within the range not impairing the object of the present invention.

  The second aromatic diamine is one selected from aromatic diamines having a substituted or unsubstituted phenyl benzimidazole group, and among them, availability, excellent tensile strength of the resulting fiber, and From the viewpoint of the initial modulus and the like, 5 (6) -amino-2- (4-aminophenyl) benzimidazole is preferable.

  The third aromatic diamine is one selected from halogen-substituted para-type aromatic diamines, such as monochloroparaphenylenediamine, dichloroparaphenylenediamine, monofluoroparaphenylenediamine, and monobromoparaphenylenediamine. Etc. are used. As for the third aromatic diamine, a part of the halogen-substituted para-type aromatic diamine is replaced with a meta-type substituted aromatic diamine such as monochlorometaphenylene diamine within the range not impairing the object of the present invention. There is no problem.

  As described above, the aromatic copolyamide forming the fiber in the present invention has a content of the heterocyclic-containing repeating structural unit of the above chemical formula (2) of 30 to 95 mol based on the total amount of the aromatic polyamide repetitive structural unit. %, Preferably in the range of 50-95 mol%. When the content of the repeating structural unit is less than 30 mol%, there arises a problem that the reaction solution becomes cloudy in the polymerization reaction, and it is difficult to spin with such a cloudy dope. Further, the content of the repeating structural unit represented by the chemical formula (3) is set in the range of 5 to 20 mol%, preferably 10 to 20 mol% with respect to the total amount of the aromatic polyamide structural unit. When the content of the repeating structural unit is less than 5 mol%, the degree of defects in the fiber is not significantly reduced even if the spun fiber is subjected to plastic drawing and heat treatment. On the other hand, when the content is more than 20 mol%, there arises a problem that the viscosity of the spinning polymer solution is greatly lowered, and spinning is difficult. Therefore, in the present invention, in solution polymerization, it is necessary to adjust the amount of each reaction component charged so that each repetitive structural unit is in the above range in the produced polymer.

  Examples of amide solvents suitable as a polymerization solvent in the present invention include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylimidazolidinone, and the like. N-methyl-2-pyrrolidone is preferable from the viewpoints of handleability and stability from polymerization of aromatic copolyamide to dope preparation and wet spinning process, and toxicity of harmful solvents.

  In the present invention, in order to improve the solubility of the aromatic copolyamide in the amide solvent, an appropriate amount of an inorganic salt can be added before, during or at the end of the polymerization. Examples of such inorganic salts include lithium chloride and calcium chloride. The amount of the inorganic salt added is preferably 3 to 10% by weight. If the addition amount exceeds 10% by weight, it is difficult to dissolve the entire amount of the inorganic salt in the amide solvent, and if the addition amount is less than 3% by weight, the effect of improving the solubility becomes insufficient. Absent.

  Since the solution after completion of the polymerization reaction contains hydrochloric acid generated by the reaction, a basic inorganic compound such as sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxide or the like is added for neutralization. The neutralized polymer solution may contain an inorganic salt such as calcium chloride generated by the neutralization reaction, but the inorganic salt contributes to improving the solubility as it is, so unless the inorganic salt concentration becomes excessive, There is no need to remove it.

  The concentration of the polymer produced in the polymerization reaction with respect to the solvent is important. In order to obtain a homogeneous polymer having a high degree of polymerization, the concentration of the produced polymer is preferably 10% by weight or less. In particular, a concentration range of 3-8% by weight is advantageous for obtaining a stable polymer.

  The above-mentioned aromatic copolyamide dope obtained by solution polymerization is extruded as it is or after appropriately adjusting the polymer concentration into a coagulating liquid according to a known spinning method of aromatic polyamide fibers to form a coagulated yarn. In the spinning process, a method of providing a short space called an air gap immediately below the spinneret and immediately introducing uncoagulated fibers (polymer dope) that has passed through this space into the coagulating liquid is preferred, but ordinary wet spinning may also be used.

  The coagulation liquid is generally composed of an aqueous solution composed of two components of an amide solvent and water. As the amide solvent used here, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylimidazolidinone and the like can be used. N-methyl-2-pyrrolidone is particularly preferably used from the viewpoint of toxicity of the solvent.

  The concentration of the amide solvent in the aqueous solution serving as the coagulation liquid is preferably 10 to 50% by weight. When the concentration exceeds 50% by weight, coagulation of the spun aromatic copolyamide dope does not progress, and the close contact between the fibrous materials occurs, making continuous yarn production difficult. On the other hand, if the concentration is less than 10% by weight, the plasticization does not proceed sufficiently, and the stretchability during the subsequent plastic stretching is undesirably reduced. The temperature of the coagulation bath has a close relationship with the composition of the coagulation bath, but if the temperature is too high, the close contact between the spun fibers becomes severe and the workability also deteriorates. The preferred temperature is 0-50 ° C.

In the present invention, since the spinning dope is optically isotropic and neutralized, the spinning property is good, stable and smooth spinning can be performed, and problems such as corrosion of equipment also occur. Absent.
The aromatic copolyamide yarn taken from the coagulation bath is plastic-drawn at a specific draw ratio in the drawing bath. That is, the draw ratio employed in the present invention is relative to the draw ratio of the heterocycle-containing aromatic copolyamide fiber having the same content ratio of the repeating structural unit of the chemical formula (2) and not containing the repeating structural unit of the chemical formula (3). The magnification at which the stretch ratio improvement rate is 150 to 300%. When the draw ratio is smaller than this, defects remain in the fiber, and not only fibers having desired mechanical properties cannot be obtained, but also the productivity is lowered because the draw ratio is low. On the other hand, if the draw ratio is excessive, yarn breakage and fluff are generated during drawing.

  The “stretch ratio improvement rate” mentioned here does not include the repeating structural unit represented by the chemical formula (3) as described above, and the content (mol%) of the repeating structural unit represented by the chemical formula (2) is the same. Of the heterocycle-containing aromatic copolyamide (target fiber) is plastic-drawn at the same speed in an amide-based aqueous solution having the same composition and temperature as that applied to the fiber of the present invention, and the yarns and fluffs (single fibers) The highest draw ratio (maximum draw ratio) that can be satisfactorily stretched without occurrence of fiber breakage or the like is determined, and refers to a high draw ratio corresponding to 150% to 300% with respect to the maximum draw ratio. For example, an aromatic copolyamide which does not include the repeating structural unit represented by the chemical formula (3), is composed only of the repeating structural units represented by the chemical formulas (1) and (2), and has the same content of the recurring structural unit represented by the chemical formula (2). When the maximum draw ratio of the fiber (target fiber) is 2.0 times, the fiber of the present invention is produced at a relatively high magnification of 3.0 to 6.0 times corresponding to 150% to 300%. Plastic stretching. The range of the draw ratio actually applied in the present invention varies depending on the composition of the polymer forming the fiber, the composition of the draw bath, the temperature, etc., but is usually about 2.3 to 4.5 times.

  In the present invention, an aqueous solution of an amide solvent is used as a stretching bath in order to perform plastic stretching, that is, stretching in a state where the fiber is plasticized. Examples of the amide solvent used here include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylimidazolidinone and the like, among which N-methyl 2-Pyrrolidone is preferred.

  The concentration of the amide solvent in the aqueous solution constituting the stretching bath is preferably 30 to 80% by weight. If the concentration exceeds 80% by weight, the aromatic copolyamide yarn dissolves in the aqueous solution, making continuous yarn production difficult. Further, if the concentration is less than 30% by weight, the plasticization of the fibers does not proceed sufficiently, and it is difficult to ensure the above draw ratio. The temperature of the aqueous solution is preferably 0 to 50 ° C., because if the temperature is too high, the adhesion between the fibers becomes intense and the workability also deteriorates.

  Subsequent to stretching, the aromatic copolyamide fiber is sufficiently removed of the solvent in the water washing step and sufficiently dried in the drying step, followed by heat treatment. The heat treatment temperature of the fiber in the present invention is preferably in the range of 300 to 550 ° C. When the heat treatment temperature is less than 300 ° C., the fiber cannot sufficiently cause orientation crystallization, so that sufficient tensile strength and initial modulus cannot be obtained. On the other hand, when the heat treatment temperature exceeds 550 ° C., the fiber causes thermal deterioration, so that sufficient tensile strength and initial modulus cannot be obtained. This heat treatment is suitably carried out under a constant length or under a stretching or restriction shrinkage within 15% of the original length before the treatment.

  In the aromatic copolyamide fiber having the composition specified in the present invention, defects in the fiber are significantly reduced by adopting the production method as described above, and the average pore diameter is 3.0 nm or less, preferably 0.5. It is ˜2.8 nm and exhibits excellent mechanical properties as described above.

The fineness of the aromatic copolyamide fiber of the present invention is preferably in the range of 0.55 to 22 dtex, and particularly preferably in the range of 1.67 to 16.7 dtex, as the single yarn fineness. If the single yarn fineness is less than 0.55 dtex, fluff and single yarn breakage are likely to occur in the yarn making process, and if the single yarn fineness exceeds 22 dtex, twisted yarn, net making, etc. become difficult.
Thus, according to the present invention, a high-performance aromatic copolyamide fiber with few defects inside the fiber is provided.

Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to the description. In addition, each characteristic value in an Example was measured with the following method.
<Viscosity (ηinh)>
Measurement was performed at a solution temperature of 30 ° C. for a solution having a polymer concentration of 0.5 g / dl in 98% concentrated sulfuric acid.
<Stretch ratio improvement rate>
The stretch ratio improvement rate is the same as the stretch ratio of each aromatic copolyamide described in the Examples, in which the mol% of the repeating structural unit of the above chemical formula (2) is the same and does not include the repeating structural unit of the above chemical formula (3). As a ratio with respect to the draw ratio of the containing aromatic copolyamide fiber (fiber of Comparative Example 1), it was expressed as a percentage.
<Defect in fiber>
The defects in the fibers shown in Table 1 were measured by the above-described method using a small angle X-ray scattering apparatus. The measurement sample is a fiber bundle having a length of several tens of centimeters.

[Example 1]
After charging 1.840 L of N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) into a stirring tank having a stirring blade that flows nitrogen inside, 160.0 g of sufficiently dried calcium chloride is added. Dissolved. Next, 3.6 g (10 mol%) of paraphenylenediamine, 51.8 g (70 mol%) of 5 (6) -amino-2- (4-aminophenyl) benzimidazole, and 9.4 g of monochloroparaphenylenediamine (20 Mol%) was weighed in and dissolved. Subsequently, 66.8 g (100 mol%) of terephthalic acid chloride was added and reacted to obtain a polymer solution of an aromatic copolyamide. To this product, 107.5 g of NMP dispersion containing 22.5% by weight of calcium hydroxide was added and neutralized to obtain a polymer solution.
The viscosity (ηinh) measured for the polymer precipitated from the obtained polymer solution was 5.5.

Using the obtained polymer solution (dope), it was discharged at a rate of 2.5 cc per minute from a spinneret having a pore diameter of 0.15 mm and a hole number of 25 holes, passed through a short gap portion called an air gap, and then an NMP concentration of 30 Spinning into an aqueous solution of 50% by weight and a temperature of 50 ° C. was taken up at a speed of 6 m / min to obtain a coagulated yarn.
The coagulated yarn was subsequently subjected to plastic drawing at a draw ratio of 4.5 times in an NMP aqueous solution having a temperature of 30 ° C. and a concentration of 70% by weight. The plastic-drawn yarn was washed with water, dried, then subjected to tension heat treatment at a temperature of 450 ° C., and wound at a speed of 30.0 m / min to obtain a 42 dtex / 25 fil yarn. When the defects in the fibers of this yarn were examined, the average pore diameter was 1.0 nm. The results are shown in Example 1 column of Table 1.

[Examples 2 to 5]
Aromatic copolyamide fibers are produced in the same manner as in Example 1 except that the addition ratio of diamines and the draw ratio in the NMP aqueous solution are changed as shown in Table 1 in accordance with the production method similar to Example 1. did. These results are summarized in the columns of Examples 2 to 5 in Table 1.

[Comparative Examples 1-4]
According to the same production method as in Example 1, the addition ratio of diamines and the draw ratio in NMP aqueous solution were changed to the outside of the scope of the present invention as shown in Table 1, and the fragrance was the same as in Example 1. Group copolyamide fibers were produced. These results are shown together in Comparative Examples 1 to 3 in Table 1. In addition, the comparative example 1 does not contain the repeating structural unit of the said Chemical formula (3), and the fiber whose mol% of the repeating structure unit diamine component of the heterocyclic formula containing the chemical formula (2) was obtained from the same polymer as Example 1 is obtained. The comparative examples 2 to 4 are experimental examples in which the molar ratio of copolymerization is outside the range specified in the present invention.

  According to the present invention, the neutralized polymer solution can be stretched at a sufficient plasticizing stretch ratio, and the degree of defects in the fiber is sufficiently reduced, resulting in mechanical properties such as strength and modulus. Since excellent aromatic copolyamide fibers can be provided, the present invention is very useful for the textile industry.

Claims (4)

A heterocycle-containing aromatic copolyamide substantially consisting of repeating structural units represented by the following chemical formulas (1), (2) and (3), with respect to the total amount of the repeating structural units of the aromatic copolyamide, A fiber composed of an aromatic copolyamide containing 30 to 95 mol% of the repeating structural unit of the chemical formula (2) and 5 to 20 mol% of the repeating structural unit of the chemical formula (3), and using a small angle X-ray scattering apparatus An aromatic copolyamide fiber characterized in that the degree of defects in the fiber to be measured is an average pore diameter of 3 nm or less.

[In the above chemical formulas (1), (2), and (3), Ar ¹ , Ar ^2, and Ar ³ are all divalent aromatic groups that are independent of each other and have a bonding group in the para-coordinate or parallel axis direction. Ar ¹ is an unsubstituted or substituted divalent aromatic group, Ar ² is an unsubstituted divalent aromatic group, and Ar ³ is a divalent aromatic group substituted with a halogen group. It is a family group. ]   The aromatic copolyamide is 10 to 20 mol% of the repeating structural unit of the chemical formula (1), 50 to 90 mol% of the repeating structural unit of the chemical formula (2), based on the total amount of all the repeating structures of the copolyamide. The aromatic copolyamide fiber according to claim 1, comprising 10 to 20 mol% of the repeating structural unit (3).   The aromatic copolyamide fiber according to claim 1 or 2, wherein the single yarn fineness is 0.55 to 22 dtex.   The aromatic copolyamide fiber according to any one of claims 1 to 3, wherein the tensile strength is 20 cN / dtex or more and the initial modulus is 500 cN / dtex or more.