JP2011047088A - Para-oriented wholly aromatic copolyamide fiber and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a para-oriented wholly aromatic copolyamide fiber having a small variance in single yarn strength and excellent in mechanical characteristics such as tensile strength, and a method for producing the same. <P>SOLUTION: Production of the para-oriented wholly aromatic copolyamide fiber has optimal heat treatment conditions such as the widths of fiber bundles when passing through a heat treatment process, temperatures of the fiber bundles, durations of the heat treatment, tensions loaded on the fiber bundles, or oxygen concentrations of a heat treatment atmosphere. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a para-type wholly aromatic copolyamide fiber and a method for producing the same. More specifically, the present invention relates to a para-type wholly aromatic copolyamide fiber having small variations in single yarn strength and excellent mechanical properties, and a method for producing the same.

  Conventionally, para-type wholly aromatic polyamide fibers mainly composed of an aromatic dicarboxylic acid component and an aromatic diamine component have characteristics such as strength, high elastic modulus, and high heat resistance. Widely used in protective clothing applications such as bulletproof and blade-proof materials.

  As a typical para type wholly aromatic polyamide fiber, for example, polyparaphenylene terephthalamide (hereinafter referred to as PPTA) fiber is known. And this PPTA fiber has the above-mentioned characteristic and is used widely. However, since PPTA polymer is insoluble in general-purpose organic solvents, there is a problem that a polymer dope using concentrated sulfuric acid as a solvent must be used. Further, the fiber properties are not sufficiently high in tensile strength, chemical resistance, light resistance and the like, and there are some problems such as easy fiber fibrillation due to abrasion.

  Therefore, in order to solve the above-mentioned problems, it exhibits high solubility in a general-purpose amide solvent, so that it can be spun without using concentrated sulfuric acid, and high tensile strength can be obtained by hot drawing or heat treatment in the yarn making process. In addition, methods for producing para-type wholly aromatic copolyamide fibers having chemical resistance, light resistance, and fibril resistance have been developed.

  When a para-type wholly aromatic copolyamide fiber is produced using such an isotropic polymer dope, almost no orientation occurs at the discharge stage. From the viewpoints of promoting molecular orientation and densifying the molecular structure, the thermal stretching and heat treatment processes are particularly important in the manufacturing process, and these processes are related to properties such as mechanical properties of the resulting fiber. .

  From such a viewpoint, for example, Patent Documents 1 and 2 report methods for producing para-type wholly aromatic copolyamide fibers having various molecular structures using isotropic polymer dopes. However, sufficient studies have not been made on the heat treatment conditions related to the basis of the mechanical properties of the fiber.

Japanese Unexamined Patent Publication No. 7-300534 JP 2006-207064 A

  The present invention has been made against the background of such prior art, and the object of the present invention is to focus on the heat treatment step that is essential for the spinning process of para-type wholly aromatic copolyamide fibers using an isotropic polymer dope. Another object of the present invention is to provide a para-type wholly aromatic copolyamide fiber excellent in mechanical properties such as high strength.

  The present inventors have intensively studied to solve the above problems. When heat treatment is performed in a non-contact manner on a fiber bundle composed of a number of single yarns, the lamination state of the filaments constituting the fiber bundle varies in strength for each single yarn, and as a result, fibers composed of these single yarns. It was found that the strength of the bundle was greatly affected. Furthermore, it has been found that the actual physical properties and holding time of the yarn itself during heat treatment without contact also affect the mechanical properties such as strength. And the tow width of the fiber bundle at the time of performing heat treatment was kept within a certain range, and the temperature and the time at that time were found to be in a specific range, and the present invention was completed.

  That is, the present invention is a para-type wholly aromatic copolyamide fiber containing structural repeating units of the chemical structural formula (1) and the following chemical structural formula (2), and has a tensile strength of 25 to 40 cN / dtex, This is a para-type wholly aromatic copolyamide fiber having a variation coefficient of single yarn strength of 10% or less.

（Ａｒ^１およびＡｒ^２は独立であり、非置換あるいは置換された２価の芳香族基である。）

(Ar ¹ and Ar ² are independent and are unsubstituted or substituted divalent aromatic groups.)

（Ａｒ^１は非置換あるいは置換された２価の芳香族基である。）

(Ar ¹ is an unsubstituted or substituted divalent aromatic group.)

  Another aspect of the present invention is a method for producing a para-type wholly aromatic copolyamide fiber comprising a structural repeating unit represented by the following chemical structural formula (1) and the following chemical structural formula (2), A heat treatment step in which heat treatment is performed by contact, and the heat treatment step holds the actual temperature of the yarn in the furnace in the range of 400 to 500 ° C. for 1.5 to 60 seconds, and the width of the fiber bundle in the furnace It is a manufacturing method of the para type wholly aromatic copolyamide fiber controlled to satisfy the following formula (3).

（Ａｒ^１およびＡｒ^２は独立であり、非置換あるいは置換された２価の芳香族基である。）

(Ar ¹ and Ar ² are independent and are unsubstituted or substituted divalent aromatic groups.)

（Ａｒ^１は非置換あるいは置換された２価の芳香族基である。）

(Ar ¹ is an unsubstituted or substituted divalent aromatic group.)

  The para-type wholly aromatic copolyamide fiber of the present invention is a fiber having reduced mechanical strength and reduced mechanical strength. Therefore, the para-type wholly aromatic copolyamide fiber of the present invention is very useful in protective clothing applications such as bulletproof / bladeproof materials and various other industrial material applications.

  Hereinafter, embodiments of the present invention will be described in detail.

<Para-type wholly aromatic copolyamide>
The para-type wholly aromatic copolyamide used in the present invention is composed of structural repeating units represented by the following chemical structural formula (1) and the following chemical structural formula (2), and one kind or two or more kinds of divalent fragrances. It is a polymer in which a group is directly linked by an amide bond, and is generally obtained by a polycondensation reaction of an aromatic dicarboxylic acid dichloride and an aromatic diamine in an amide polar solvent according to a known method. 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.

（Ａｒ^１およびＡｒ^２は独立であり、非置換あるいは置換された２価の芳香族基である。）

(Ar ¹ and Ar ² are independent and are unsubstituted or substituted divalent aromatic groups.)

（Ａｒ^１は非置換あるいは置換された２価の芳香族基である。）

(Ar ¹ is an unsubstituted or substituted divalent aromatic group.)

  In the present invention, the content of the structural repeating unit of the chemical structural formula (1) is 10 to 70 mol based on the total of the structural repeating units of the chemical structural formula (1) and the chemical structural formula (2). % Is preferred from the standpoints of spinnability and mechanical properties of the resulting fiber. More preferably, it is 15-60 mol%, Most preferably, it is the range of 20-50 mol%.

[Raw material of para-type wholly aromatic copolyamide]
[Aromatic dicarboxylic acid dichloride]
Examples of the aromatic dicarboxylic acid dichloride used as a raw material for the para-type wholly aromatic copolyamide used in the present invention include terephthalic acid dichloride, 2-chloroterephthalic acid dichloride, 3-methylterephthalic acid dichloride, and 4,4′-biphenyl. Examples thereof include dicarboxylic acid dichloride and 2,6-naphthalenedicarboxylic acid dichloride. Among these, terephthalic acid dichloride is most preferable from the viewpoints of versatility and mechanical properties of fibers. These aromatic dicarboxylic acid dichlorides may be used alone or in combination of two or more, and the composition ratio in that case is not particularly limited.

[Aromatic diamine]
Examples of the aromatic diamine used as a raw material for the para-type wholly aromatic copolyamide used in the present invention include paraphenylenediamine, 5-amino-2- (4-aminophenylene) benzimidazole, parabiphenylenediamine, and 3,4. Examples include '-diaminodiphenyl ether and 1,4-dichloroparaphenylenediamine. In the present invention, the aromatic ring is not limited to these, and the aromatic ring may have a substituent, or may have another heterocyclic ring.

  As a raw material of the para type wholly aromatic copolyamide used in the present invention, a structural repeating unit represented by the chemical structural formula (1) and a structural repeating unit represented by the chemical structural formula (2) are respectively configured. At least two kinds of aromatic diamines are used. As the combination, the combination of paraphenylenediamine and 5-amino-2- (4-aminophenylene) benzimidazole is most preferable from the viewpoints of versatility, mechanical properties of fibers, and spinnability. The composition ratio is not particularly limited, but 10 to 70 mol% of paraphenylenediamine and 30 to 90 of 5-amino-2- (4-aminophenylene) benzimidazole with respect to the total aromatic diamine amount. Preferably, the molar ratio is 15 to 60 mol%, more preferably 40 to 85 mol% of 5-amino-2- (4-aminophenylene) benzimidazole, and most preferably paraphenylenediamine. Is 20 to 50 mol%, and 5-amino-2- (4-aminophenylene) benzimidazole is 50 to 80 mol%.

[Method for producing para-type wholly aromatic copolyamide]
[Polymerization of para-type wholly aromatic copolyamide]
In the polymerization of the para type wholly aromatic copolyamide used in the present invention, an amide polar solvent is used as a polymerization solvent, and examples thereof include paraphenylenediamine and 5-amino-2- (4-aminophenylene) benzimidazole. Each of the aromatic diamines, for example, aromatic dicarboxylic acid dichlorides such as terephthalic acid dichloride is dissolved, and a polycondensation reaction is performed by a known method.

  Examples of the amide solvent used include N-methyl-2-pyrrolidone (hereinafter referred to as NMP), N, N-dimethylformamide, N, N-dimethylacetamide, dimethylimidazolidinone and the like. NMP is most preferable from the viewpoints of toxicity, handleability, solubility in para-type wholly aromatic copolyamide polymer, and the like.

[Neutralization reaction]
After completion of the reaction, hydrochloric acid is generated in the system by the polycondensation reaction and the system becomes acidic. For the purpose of neutralization, an alkali such as calcium hydroxide is added. The amount of alkali added varies depending on the type of alkali and the amount of aromatic diamine and aromatic dicarboxylic acid dichloride, but when calcium hydroxide is used, the amount added is 95 to 100 mol% with respect to the aromatic dicarboxylic acid dichloride. It is preferable to do. When calcium hydroxide is less than 95 mol%, neutralization cannot be carried out sufficiently, and the inside of the system still shows acidity, causing depolymerization. On the other hand, when it exceeds 100 mol%, the inside of the system shows alkali, which is also undesirable because it causes depolymerization.

  Calcium chloride generated by the neutralization reaction can be used as it is as a dissolution aid for enhancing the dissolution of the produced polymer in a solvent. For this reason, it is not necessary to remove from the system.

[Post-polymerization treatment, etc.]
The obtained para-type wholly aromatic copolyamide polymer is an isotropic polymer solution dissolved in an amide polar solvent such as NMP, and can be used as it is in the spinning process without isolation. However, the concentration of the para-type wholly aromatic copolyamide polymer significantly affects the viscosity and stability of the polymer solution, and consequently greatly affects the spinnability and the like in the subsequent spinning process. For this reason, it is preferable to adjust a polymer concentration in the range of 2-10 mass%. In order to adjust the polymer concentration and viscosity, an appropriate amount of an amide polar solvent such as NMP can be added to the obtained polymer solution.

<Threading of para-type wholly aromatic copolyamide fiber>
Next, the manufacturing method of the para type wholly aromatic copolyamide fiber of this invention is demonstrated. For the yarn production, a polymer dope of para-type wholly aromatic copolyamide is used.

  The “polymer dope” in the present invention refers to a polymer solution in which a para-type wholly aromatic copolyamide polymer is dissolved in a solvent that can be dissolved therein, and a liquid crystal is not formed in a state in which the polymer is dissolved in the solvent, This is a polymer solution in which polymer molecules do not have specific regularity and are randomly dissolved in a solvent. Therefore, if the solvent used in the polycondensation reaction of aromatic dicarboxylic acid dichloride and aromatic diamine is a good solvent for the para-type wholly aromatic copolyamide polymer, the polymer after the polycondensation reaction is isolated. The polymer dope can be used as it is without.

  In preparing the polymer dope, an inorganic salt can also be used as a dissolution aid for the purpose of enhancing the solubility of the polymer in the solvent. Examples of the inorganic salt include, but are not limited to, calcium chloride and lithium chloride. Although the amount of the inorganic salt added to the polymer dope is not particularly limited, it is possible to improve the polymer solubility, the solubility of the inorganic salt in a solvent, the spinnability, and the mechanical properties of the resulting fiber. Therefore, the content is preferably 3 to 10% by mass with respect to the polymer dope mass.

In obtaining the para-type wholly aromatic copolyamide fiber of the present invention, yarn production is performed by polymer dope using the para-type wholly aromatic copolyamide described above.
In the yarn production, a known method for producing para-type wholly aromatic polyamide fibers can be applied, and a step of discharging a polymer dope from the spinneret through an air gap by a semi-dry semi-wet method, coagulating the discharged yarn The final fiber can be obtained through a step of performing, a step of plasticizing the fiber, a step of stretching in a plasticized state, a water washing step, a drying step, and the like. In the present invention, except for the heat treatment step described below, the conditions in each step are not particularly limited, and may be adjusted as appropriate from the properties of stringiness, process passability, obtained fiber, and the like. Can do.

[Heat treatment process]
In the production of para-type wholly aromatic polyamide fiber, a fiber oriented to some extent can be obtained through a drawing process after plasticization. However, the strength of the obtained fiber is not sufficient only by the drawing step after plasticization. Therefore, heat treatment is usually performed for the purpose of further enhancing the orientation of fibers, promoting the high crystallization, densifying the molecular structure, and the like.

  In the present invention, in producing a para-type wholly aromatic copolyamide fiber containing a structural repeating unit represented by the chemical structural formula (1) and the chemical structural formula (2), heat treatment is performed in a furnace in a non-contact manner. The heat treatment process to perform is implemented.

  As an apparatus for performing the heat treatment, a known non-contact heat treatment apparatus is preferable. When a contact-type heat treatment device such as a hot plate is used, when the fiber travels on the hot plate, the yarn breaks or wears due to rubbing with the hot plate, and the strength of the resulting fiber is high. Since it falls, it is not preferable. In addition, when a contact-type heat treatment apparatus is used, the single yarn strength varies greatly because the degree of rubbing with the hot plate differs for each single yarn.

  In the present invention, it is preferable to maintain the temperature of the fiber bundle in the furnace in the range of 400 to 500 ° C. at the actual temperature using a non-contact heat treatment apparatus. When the actual temperature of the fiber is less than 400 ° C., even if a sufficient holding time is given, the orientation and crystallization of the polymer molecules and the densification of the structure do not proceed sufficiently. Mechanical properties such as strength are lowered. On the other hand, when the temperature exceeds 500 ° C., the orientation and crystallization of the polymer molecules and the densification of the structure proceed sufficiently, but the polymer itself is deteriorated or thermally decomposed by heat, which causes a decrease in strength. Absent.

In this invention, it is more preferable to hold | maintain the temperature of the fiber bundle in a furnace in the range of 410-490 degreeC in actual temperature, and it is most preferable to hold | maintain in the range of 420-480 degreeC.
In the non-contact heat treatment apparatus, the temperature of the fiber is raised through the gas in the furnace, so that even if the furnace temperature is kept within the above temperature range, for example, compared with the contact type heat treatment such as a hot plate. Thus, the thermal conductivity to the fiber is poor, and in some cases, it may not be possible to raise the temperature to the target temperature as the actual temperature of the fiber. In the present invention, it is important that the actual temperature of the fiber is raised to and maintained in the above temperature range, and the furnace temperature is not particularly limited as long as these conditions can be satisfied.

  Furthermore, in this invention, after heating up to the said temperature range with the actual temperature of a fiber, it hold | maintains in the said temperature range for 1.5 to 60 seconds. When the holding time is less than 1.5 seconds, the movement of the polymer molecules in the fiber cannot be sufficiently obtained, and the orientation and crystallization of the polymer molecules and the densification of the structure do not sufficiently proceed. Mechanical properties such as strength are lowered. On the other hand, when the holding time exceeds 60 seconds, the orientation and crystallization of the polymer molecules and the densification of the structure proceed sufficiently, but the heat causes deterioration of the polymer itself and thermal decomposition, leading to a decrease in strength. It is not preferable.

In the present invention, after raising the temperature to the above temperature range at the actual temperature of the fiber, it is more preferable to hold for 3 to 55 seconds in the temperature range, and most preferable to hold for 5 to 50 seconds.
Furthermore, in the present invention, the width of the fiber bundle passing through the furnace is controlled so that the value A represented by the following formula (4) is in the range of 1 ≦ A <2.5.

  When the value A exceeds 2.5, the number of single yarns stacked in the fiber bundle running in the furnace increases, all the single yarns can be held at a uniform temperature, and the same holding time can be given. It becomes difficult. As a result, the variation in single yarn strength increases, and as a result, the strength of the fiber bundle composed of these single yarns decreases. On the other hand, if it is less than 1, the constituting single yarns are uniformly arranged in a single layer, and the theoretical value A will never be less than 1.

  In the present invention, the width A of the fiber bundle passing through the furnace is more preferably controlled so that the value A represented by the above formula (4) is 1 ≦ A ≦ 2.25, and 1 ≦ A ≦ 2. Most preferably, it is controlled.

In the present invention, the oxygen concentration in the furnace in which the fiber travels is preferably 1000 ppm or less. When the oxygen concentration in the furnace exceeds 1000 ppm, even if kept in the above temperature range, it is not preferable because oxidation deterioration occurs and the strength is significantly reduced.
In the present invention, the oxygen concentration in the furnace in which the fiber travels is more preferably 800 ppm or less, and most preferably 500 ppm or less.

  Moreover, it is preferable that the tension | tensile_strength applied to a fiber bundle in a heat processing process shall be the range of 0.5-4 mN / dtex. When the tension is less than 0.5 mN / dtex, the orientation and crystallization of the polymer molecules and the densification of the structure do not proceed sufficiently, and it becomes difficult to obtain fibers having high strength. On the other hand, when the tension applied to the fiber bundle exceeds 4 mN / dtex, single yarn breakage frequently occurs in the furnace, and it becomes difficult to obtain fibers having high strength.

  In the present invention, the tension applied to the fiber bundle in the heat treatment step is more preferably controlled to 0.75 to 3.75 mN / dtex, and most preferably maintained in the range of 1 to 3.5 mN / dtex.

The non-contact type heat treatment apparatus used in the present invention is not particularly limited in its structure and heating method as long as the heat treatment apparatus satisfies the above conditions, and a known one can be applied as it is. .
After passing through the heat treatment step, an oil agent can be applied according to the application to be used, and the fiber can be wound using a commercially available winder.

<Physical properties of para-type wholly aromatic copolyamide fiber>
The para-type wholly aromatic copolyamide fiber of the present invention has a tensile strength of 25 to 40 cN / dtex, more preferably 28 to 40 cN / dtex, and a variation coefficient of the single yarn strength of 10% or less, more preferably 9 % Fiber.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, this invention is not limited to this unless it exceeds the summary.

<Measurement and evaluation method>
In Examples and Comparative Examples, the following items were measured and evaluated by the following methods.

(1) Fineness of fiber The obtained fiber was wound up by 100 m using a known measuring machine, and its mass was measured. A value obtained by multiplying the obtained mass by 100 was calculated as a fineness (dtex) per 10,000 m.

(2) Tensile strength of fiber Using a tensile tester (manufactured by INSTRON, trade name: INSTRON, model: 5565 type), a yarn test chuck was used and measurement was performed under the following conditions based on the procedure of ASTM D885. .
[Measurement condition]
Temperature: Room temperature Test piece: 75cm
Test speed: 250 mm / min Chuck distance: 500 mm

(3) Average single yarn strength and variation coefficient of single yarn strength In determining the single yarn strength, a tensile tester (manufactured by Intesco, trade name: INTERSCO, model: 201X type) is used with a flat chuck for yarn test. The tensile test was performed under the following conditions. The average of the obtained tensile strength was obtained to obtain the average single yarn strength, and the coefficient of variation of the single yarn strength was calculated.
[Measurement condition]
Test piece: 10 cm
Test speed: 10 mm / min Distance between chucks: 25 mm
Number of measurements: 100

<Example 1>
[Production of para-type wholly aromatic copolyamide]
By a known method, 100 parts by mass of terephthalic acid dichloride is added to 30 parts by mass of paraphenylenediamine and 70 parts by mass of 5-amino-2- (4-aminophenylene) benzimidazole dissolved in NMP, and a polycondensation reaction is performed. A para-type wholly aromatic copolyamide polymer dope was obtained. At this time, the polymer concentration was 5% by mass, and the intrinsic viscosity (IV) of the polymer was 5.18.

[Production of para-type wholly aromatic copolyamide fiber]
Next, after heating a spinneret having a hole diameter of 0.2 mm and a hole diameter of 150 to 105 ° C., the polymer dope heated to 105 ° C. is discharged, and NMP is passed through an air gap of 10 mm by a semi-dry semi-wet method. The solution was solidified by passing through a coagulation bath filled with an aqueous solution having a concentration of 40% by mass and 50 ° C.
Subsequently, the obtained coagulated yarn bundle was passed through a plasticizing bath filled with an aqueous solution having an NMP concentration of 65% by mass and 20 ° C. to bring the fiber into a plasticized state, and then subjected to plasticizing drawing. The plasticizing draw ratio at this time was 1.75 times. Thereafter, it was sufficiently washed with water, dried with a drying roller at 200 ° C., and a base yarn before heat treatment was obtained.

Using a non-contact heat treatment apparatus, the furnace temperature was adjusted to the condition where the oxygen concentration in the furnace was maintained at 150 ppm, and the yarn temperature in the furnace was raised to 460 ° C. at the actual temperature. For 25 seconds, and a heat treatment step was performed. The yarn tension at this time was 2.8 mN / dtex, the width of the fiber bundle passing through the heat treatment step was 1.6 mm, and the value A = 1.88 represented by the above formula (4).
Finally, it was wound up with a winder to obtain fibers. The obtained fiber had a fineness of 289 dtex, a filament count of 150, and a single yarn fineness of 1.93 dtex. Table 1 shows the tensile strength and breaking elongation of the obtained fibers, and the coefficient of variation of average single yarn strength and single yarn strength.

<Example 2>
Para-type wholly aromatic copolyamide fiber by the same method as in Example 1 except that the width of the fiber bundle passing through the heat treatment step was 1.3 mm and the value A = 2.31 represented by the formula (4) was set. Got.
The obtained fiber had a fineness of 295 dtex, a filament count of 150, and a single yarn fineness of 1.97 dtex. Table 1 shows the tensile strength and breaking elongation of the obtained fibers, and the coefficient of variation of average single yarn strength and single yarn strength.

<Example 3>
Para-type wholly aromatic copolyamide fibers were obtained by the same method as in Example 1 except that the temperature of the yarn in the furnace was changed to 490 ° C. at the actual temperature in the heat treatment step.
The obtained fiber had a fineness of 299 dtex, a filament number of 150, and a single yarn fineness of 1.99 dtex. Table 1 shows the tensile strength and breaking elongation of the obtained fibers, and the coefficient of variation of average single yarn strength and single yarn strength.

<Example 4>
Para-type wholly aromatic copolyamide fibers were obtained by the same method as in Example 1 except that the temperature of the yarn in the furnace was 460 ° C. and the holding time was 50 seconds in the heat treatment step.
The obtained fiber had a fineness of 302 dtex, a filament count of 150, and a single yarn fineness of 2.01 dtex. Table 1 shows the tensile strength and breaking elongation of the obtained fibers, and the coefficient of variation of average single yarn strength and single yarn strength.

<Comparative Example 1>
The width of the fiber bundle passing through the heat treatment step is 0.9 mm, and the value A = 3.30 expressed by the above formula (4), and the temperature of the yarn in the furnace in the heat treatment step is 380 ° C. at the actual temperature, A para type wholly aromatic copolyamide fiber was obtained by the same method as in Example 1 except that the holding time was 1.2 seconds.
The obtained fiber had a fineness of 304 dtex, a filament count of 150, and a single yarn fineness of 2.03 dtex. Table 1 shows the tensile strength and breaking elongation of the obtained fibers, and the coefficient of variation of average single yarn strength and single yarn strength.

<Comparative Example 2>
Para-type wholly aromatic copolyamide fiber by the same method as in Example 1 except that the width of the fiber bundle passing through the heat treatment step was 0.9 mm, and the value A = 3.30 represented by the above formula (4) was used. Got.
The obtained fiber had a fineness of 300 dtex, a filament count of 150, and a single yarn fineness of 2.00 dtex. Table 1 shows the tensile strength and breaking elongation of the obtained fibers, and the coefficient of variation of average single yarn strength and single yarn strength.

<Comparative Example 3>
Para-type wholly aromatic copolyamide fibers were obtained by the same method as in Example 1 except that the temperature of the yarn in the furnace was changed to 380 ° C. in the heat treatment step.
The obtained fiber had a fineness of 298 dtex, a filament number of 150, and a single yarn fineness of 1.99 dtex. Table 1 shows the tensile strength and breaking elongation of the obtained fiber, and the average single yarn strength and coefficient of variation of single yarn strength.

<Comparative example 4>
Para-type wholly aromatic copolyamide fibers were obtained by the same method as in Example 1 except that the temperature of the yarn in the furnace was 460 ° C. and the holding time was 1.2 seconds in the heat treatment step.
The obtained fiber had a fineness of 303 dtex, a filament count of 150, and a single yarn fineness of 2.02 dtex. Table 1 shows the tensile strength and breaking elongation of the obtained fibers, and the coefficient of variation of average single yarn strength and single yarn strength.

  The para-type wholly aromatic polyamide fiber of the present invention is a high-strength fiber excellent in mechanical properties and having a single yarn strength variation suppressed. Therefore, the para-type wholly aromatic copolyamide fiber of the present invention is useful as various industrial materials, and particularly useful in protective clothing applications such as bulletproof / bladeproof materials.

Claims (5)

A para type comprising the following chemical structural formula (1) and structural repeating units represented by the following chemical structural formula (2), having a tensile strength of 25 to 40 cN / dtex and a variation coefficient of single yarn strength of 10% or less Totally aromatic copolyamide fiber.

(Ar ¹ and Ar ² are independent and are unsubstituted or substituted divalent aromatic groups.)

(Ar ¹ is an unsubstituted or substituted divalent aromatic group.)   The content of the structural repeating unit of the chemical structural formula (1) is 10 to 70 mol% based on the total of the structural repeating units of the chemical structural formula (1) and the chemical structural formula (2). The para-type wholly aromatic copolyamide fiber according to 1. A process for producing a para-type wholly aromatic copolyamide fiber comprising the following chemical structural formula (1) and a structural repeating unit represented by the following chemical structural formula (2):
It has a heat treatment process that performs heat treatment in a furnace in a non-contact manner,
The heat treatment step is a para type in which the actual temperature of the yarn in the furnace is kept in the range of 400 to 500 ° C. for 1.5 to 60 seconds, and the width of the fiber bundle in the furnace is controlled to satisfy the following formula (3). Method for producing wholly aromatic copolyamide fiber.

(Ar ¹ and Ar ² are independent and are unsubstituted or substituted divalent aromatic groups.)

(Ar ¹ is an unsubstituted or substituted divalent aromatic group.)

  The method for producing a para-type wholly aromatic copolyamide fiber according to claim 3, wherein the heat treatment step sets the oxygen concentration in the furnace to 1000 ppm or less.   5. The method for producing para-type wholly aromatic copolyamide fibers according to claim 3, wherein the heat treatment step sets the tension of the fiber bundle passing through the step to 0.5 to 4 mN / dtex.