KR101432876B1 - Aramid Fiber and Method for Manufacturing The Same - Google Patents

Abstract

Disclosed is an aramid fiber, which can be produced without using a sulfuric acid solvent by using a radically polymerizable solution directly, and can be produced with high productivity, and a method for producing the same. The method of producing an aramid fiber according to the present invention is characterized in that an aromatic diamine containing a substituted aromatic diamine in which hydrogen of a benzene ring is substituted with -CN, -Cl, -SO ₃ H, or -CF ₃ is added to an organic solvent Dissolving; Then, adding aromatic diacid halide to the organic solvent at least in the same molar amount as the aromatic diamine to obtain a polymerization solution containing an aromatic polyamide; Extruding the polymer solution through a spinneret; And forming the filament by allowing the extruded polymerization solution to pass through the coagulation liquid.

Description

Technical Field The present invention relates to an aramid fiber,

More particularly, the present invention relates to an aramid fiber and a production method thereof, and more particularly, to an aramid fiber which can be produced without using a sulfuric acid solvent by using a polymerization solution directly as a polymerization solution and can be produced with high productivity .

Aromatic polyamides, commonly referred to as aramids, include para-aramids having a structure in which benzene rings are linearly connected through an amide group (CONH), and meta-based aramids that are not.

Para-aramid has excellent properties such as high strength, high elasticity and low shrinkage. The thin thread with a thickness of 5 mm manufactured from it has a strength enough to lift a 2 - tonne automobile and is used not only for bulletproof but also for various applications in high - tech industry in aerospace sector.

In addition, since aramid is carbonized black at a temperature of 500 ° C or higher, it is also in the spotlight where high heat resistance is required.

A common manufacturing method of aramid fibers is disclosed in Korean Patent No. 10-0910537, Korean Patent Laid-Open Nos. 10-2009-0104599, 10-2009-0124271, and 10-2009-0124272, Lt; / RTI > According to this conventional manufacturing method, an aromatic diamine is dissolved in a polymerization solvent to prepare a mixed solution, and an aromatic diacid is added to this to prepare an aramid polymer. The aramid fiber is finally completed by dissolving the aramid polymer in a sulfuric acid solvent to prepare a spinning dope, spinning the spinning dope, followed by coagulation, washing, and drying.

However, when the aramid fiber is produced through such a process, since a solid state aramid polymer is prepared and then dissolved again in a sulfuric acid solvent to prepare a spinning dope, the spinning process is complicated and harmful to the human body, And the durability is degraded due to corrosion.

Furthermore, since the sulfuric acid solvent used to dissolve the aramid polymer having high chemical resistance and removed after the spinning causes environmental pollution, it has to be appropriately treated after use. The cost for treating such spent sulfuric acid is not only economical .

Accordingly, the present invention relates to an aramid fiber and a method for producing the same, which can prevent problems due to limitations and disadvantages of the related art.

One aspect of the present invention is to provide an aramid fiber that can be produced with high productivity without the use of a sulfuric acid solvent.

Another aspect of the present invention is to provide a method of producing aramid fibers without the use of a sulfuric acid solvent by using the polymerization solution directly as a radial process, but capable of producing aramid fibers at a high spinning speed.

Other features and advantages of the invention will be set forth in the description which follows, or may be learned by those skilled in the art from the description.

According to one aspect of the present invention, there is provided an aromatic polyamide having a repeating unit represented by the following formula (1)

[Chemical Formula 1]

Wherein R ₁ is -CN, -Cl, -SO ₃ H, or -CF ₃ , Ar ₁ and Ar ₂ are each independently aromatic hydrocarbons having 1 to 4 benzene rings, Aramid fibers characterized by having a polydispersity index (PDI) of 2.4 to 3.0.

According to another aspect of the present invention, an aromatic diamine comprising a substituted aromatic diamine in which the hydrogen of the benzene ring is substituted with -CN, -Cl, -SO ₃ H, or -CF ₃ is dissolved in an organic solvent ; Then, adding aromatic diacid halide to the organic solvent at least in the same molar amount as the aromatic diamine to obtain a polymerization solution containing an aromatic polyamide; Extruding the polymer solution through a spinneret; And forming the filaments by causing the extruded polymer solution to pass through the coagulation liquid.

The foregoing general description of the present invention is intended to be illustrative of or explaining the present invention, but does not limit the scope of the present invention.

According to the present invention, aramid fibers can be produced without the use of a sulfuric acid solvent by directly using a polymerization solution with an irradiance profile. Therefore, the problems such as the complexity of the manufacturing process due to the use of the sulfuric acid solvent, the harmfulness to the human body, and the durability of the manufacturing apparatus can be solved by the present invention. In addition, a separate process for treating spent sulfuric acid which causes environmental pollution is not necessary, and as a result, the manufacturing cost of aramid fiber can be drastically reduced.

Further, according to the present invention, by using a polymerization solution containing an aramid polymer having a broad molecular weight distribution, that is, a relatively high polydispersity index (PDI), by using an emissivity pro, It is possible to prevent radioactive degradation which may be caused. That is, since the radial dope of the present invention has radioactivity comparable to that of the radial dope containing a sulfuric acid solvent, the aramid fiber can be produced at a high radial rate.

Hereinafter, embodiments of the aramid fiber and the manufacturing method thereof according to the present invention will be described in detail.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. It will be apparent to those skilled in the art that variations are possible. Therefore, the present invention encompasses all changes and modifications that come within the scope of the invention as defined in the appended claims and equivalents thereof.

The aramid fiber of the present invention is a para-aramid fiber having a structure in which benzene rings are linearly connected through an amide group (CONH). Specifically, the aromatic polyamide of the aramid fiber of the present invention includes a repeating unit represented by the following formula (1).

[Chemical Formula 1]

Wherein R ₁ is -CN, -Cl, -SO ₃ H, or -CF ₃ , and Ar ₁ and Ar ₂ are each independently aromatic hydrocarbons having 1 to 4 benzene rings. According to one embodiment of the present invention, R ₁ is -CN, and Ar ₁ and Ar ₂ are phenylene.

According to the present invention, the aromatic polyamide has a relatively high polydispersity index (PDI) of 2.4 to 3.0. That is, since the aromatic polyamide has a broad molecular weight distribution, the aramid fiber of the present invention can be produced at a high spinning speed.

The polydispersity index of an aromatic polyamide in an aramid fiber is measured by a light scattering method under the following conditions. Specifically, the polydispersity index based on the difference in light scattering degree between the reference solvent and the sample solution is automatically calculated by the following measuring apparatus.

1) Measuring device: Optilas T-Rex (DynaPro NanoStar)

2) Wavelength of light source: 658 nm

3) Reference solvent: The reference solvent is prepared by using an inorganic salt and an organic solvent which were respectively used for polymerization of aromatic polyamide. The content of the inorganic salt in the reference solvent is 3% by weight.

4) Sample solution: A sample solution was prepared by dissolving 0.5 wt% of aramid fiber in the reference solvent.

The aromatic polyamide may be a homopolymer having only the repeating unit of the above formula (1). Alternatively, the aromatic polyamide may be a copolymer further having a repeating unit represented by the following formula (2).

(2)

Here, Ar ₁ and Ar ₂ are each independently aromatic hydrocarbons having 1 to 4 benzene rings. According to one embodiment of the present invention, Ar ₁ and Ar ₂ are phenylene.

Hereinafter, a method for producing the aramid fiber of the present invention will be described in detail.

Preparation of Aromatic Polyamide Polymerization Solution

First, an inorganic salt is dissolved in an organic solvent.

The organic solvent may be an amide organic solvent, a urea organic solvent, or a mixed organic solvent thereof. Specific examples thereof include N-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide (DMAc), hexamethylphosphoramide (HMPA), N, N, N ', N'-tetramethylurea (TMU), N, N-dimethylformamide (DMF) or mixtures thereof.

The inorganic salt is added in order to increase the degree of polymerization of the aromatic polyamide. Specific examples thereof include alkali metal halides such as CaCl ₂ , LiCl, NaCl, KCl, LiBr and KBr, or alkaline earth metal halides. These inorganic salts may be added singly or in the form of a mixture of two or more.

Since the inorganic salt has poor solubility in an organic solvent, according to one embodiment of the present invention, water is added to completely dissolve the inorganic salt, and then water is removed through a dehydration process.

The inorganic salt functions to increase the degree of polymerization of the aromatic polyamide produced by the polymerization reaction of the aromatic diamine and the aromatic diacid halide in the organic solvent.

According to the conventional method, the amount of the inorganic salt added to the organic solvent was 6% by weight or more of the solution. That is, in the conventional method, since inorganic salts having a function of increasing the degree of polymerization of aromatic polyamide are sufficiently used, the produced aromatic polyamide has a high intrinsic viscosity (IV) exceeding 5.0 and has a solid form such as bread crumb . Since these aromatic polyamides will be dissolved in sulfuric acid solvent to produce radial dope, even if the intrinsic viscosity of the aromatic polyamide polymer exceeds 5.0, the spinning process has no problem.

However, in the present invention, in which the polymerization solution is immediately radiated without using a sulfuric acid solvent, the intrinsic viscosity of the aromatic polyamide should not exceed 5.0. Therefore, according to the present invention, the amount of the inorganic salt dissolved in the organic solvent should be not more than 5% by weight of the solution. For example, according to one embodiment of the present invention, 2 to 5% by weight of CaCl ₂ is dissolved in an NMP organic solvent. Next, immediately after the CaCl ₂ is dissolved in the organic solvent, the dehydration process is performed so that the water content of the organic solvent is 120 ppm or less.

Subsequently, an unsubstituted aromatic ring selected from the group consisting of para-phenylenediamine, 4,4'-diaminodiphenyl, 2,6-naphthalenediamine, 1,5-naphthalenediamine, and 4,4'-diaminobenzanilide A non-substituted aromatic diamine is dissolved in an organic solvent to which the inorganic salt is added. At the same time, a substituted aromatic diamine in which the hydrogen of the benzene ring of the aromatic diamine is substituted with -CN, -Cl, -SO ₃ H, or -CF ₃ is dissolved in the organic solvent to which the inorganic salt is added . The molar ratio of the substituted aromatic diamine to the unsubstituted aromatic diamine dissolved in the organic solvent containing the inorganic salt is from 9: 1 to 1: 9.

According to one embodiment of the present invention, a mixture of cyano-p-phenylenediamine and para-phenylenediamine in an NMP organic solvent to which CaCl ₂ is added at a molar ratio of 9: 1 to 1: 9 Dissolve.

When both the unsubstituted aromatic diamine and the substituted aromatic diamine are dissolved in the organic solvent, the aromatic polyamide of the copolymer can be finally obtained. Alternatively, in order to obtain an aromatic polyamide having a homopolymer, only the substituted aromatic diamine can be dissolved in an organic solvent.

Next, an aromatic diacid halide is added to the organic solvent at least in the same molar amount as the aromatic diamine in order to obtain a polymerization solution containing an aromatic polyamide. The aromatic diacid halide is terephthaloyl dichloride, 4,4'-benzoyl dichloride, 2,6-naphthalene dicarboxylic acid dichloride or 1,5-naphthalene dicarboxylic acid dichloride. According to one embodiment of the present invention, the aromatic diacid halide is terephthaloyl dichloride.

In the conventional method of producing radial dope using a sulfuric acid solvent, the unsubstituted aromatic diamine and the aromatic diacid halide are polymerized into an aromatic polyamide. At this time, polymerization reaction proceeds rapidly at high speed with heat generation and solidification becomes fast, so it is difficult to obtain a high molecular weight aromatic polyamide having a long molecular chain. In order to solve this problem, in the conventional method, an aromatic diacid halide was added in two divided portions. However, when the final polymerization is carried out after the prepolymerization, a high molecular weight aromatic polyamide can be obtained, but a molecular weight distribution of the aromatic polyamide tends to be narrowed.

Generally, a narrow molecular weight distribution causes a radioactive degradation, resulting in lower productivity due to the low spinning rate. However, due to the high solubility of the polymer in the sulfuric acid solvent, the aramid fiber could be produced at a high spinning rate despite the narrow molecular weight distribution of the polymer.

In the case of the present invention which does not use a sulfuric acid solvent, since the solubility of the aromatic polyamide in the polymerization solution is relatively low, the molecular weight distribution of the aromatic polyamide has a great influence on the radiation and the spinning speed. Therefore, measures for widening the molecular weight distribution of the aromatic polyamide are required.

According to the present invention, an aromatic diacid halide is added to an organic solvent at least in the same molar amount as an aromatic diamine to produce an aromatic polyamide immediately without a prepolymerization step. The aromatic polyamide thus produced has a relatively high polydispersity index (PDI) of 2.4 to 3.0. Thanks to the broad molecular weight distribution of the aromatic polyamides, the polymerization solution can be radiated at a high rate.

That is, according to the present invention, by using the polymerization solution containing an aramid polymer having a relatively high polydispersity index as an emissivity pro- ducer, it is possible to prevent radioactivity degradation caused by not using a sulfuric acid solvent. Since the radial dope of the present invention has radioactivity comparable to that of the radial dope containing a sulfuric acid solvent, the aramid fiber can be produced at a high radial rate.

On the other hand, since the aromatic diamine used in the present invention contains an aromatic diamine having a substituent, the reactivity with the aromatic diacid halide is relatively low. Therefore, in the present invention, the polymerization reaction proceeds at a relatively slow rate and the solidification occurs later. As a result, a high molecular weight aromatic polyamide having a long molecular chain can be obtained without going through the prepolymerization step.

The aromatic polyamide of the present invention obtained by the polymerization process includes a repeating unit represented by the following formula (1).

[Chemical Formula 1]

Wherein R ₁ is -CN, -Cl, -SO ₃ H, or -CF ₃ , and Ar ₁ and Ar ₂ are each independently aromatic hydrocarbons having 1 to 4 benzene rings.

According to one embodiment of the present invention, R ₁ is -CN, and Ar ₁ and Ar ₂ are phenylene.

If both the unsubstituted aromatic diamine and the substituted aromatic diamine are dissolved in the organic solvent, the aromatic polyamide of the copolymer further containing the repeating unit represented by the following formula (2) is obtained in addition to the repeating unit represented by the above formula (1).

(2)

Here, Ar ₁ and Ar ₂ are each independently aromatic hydrocarbons having 1 to 4 benzene rings. According to one embodiment of the present invention, Ar ₁ and Ar ₂ are phenylene.

The acid (HCl) produced during the polymerization reaction is then neutralized with an alkali compound. The alkaline compound for neutralization is selected from the group consisting of an alkali metal, a carbonate of an alkaline earth metal, a hydride of an alkaline earth metal, a hydroxide of an alkaline earth metal, or an oxide of an alkaline earth metal. Specifically, the said alkaline compound is _{NaOH, Li 2 CO 3, CaCO} 3, LiH, CaH 2, LiOH, Ca (OH) 2, Li 2 O or CaO.

According to one embodiment of the present invention, for the neutralization process, the same equivalent amount of CaO as the acid (HCl) produced by the polymerization reaction is added to the polymerization solution. At the same time, water generated by the neutralization step is removed from the polymerization solution by using a vacuum. The intrinsic viscosity of the aromatic polyamide is increased to 5.0 or more by CaCl ₂ produced with water in the neutralization process by CaO, and a polymerization solution in which the polymer is uniformly dissolved in the organic solvent is obtained.

Then, the amount of the organic solvent in the polymerization solution may be adjusted so that the concentration of the aromatic polyamide in the polymerization solution is 10 to 20% by weight. When the concentration of the aromatic polyamide in the polymerization solution is out of the above range, the spinning process does not proceed smoothly, resulting in a decrease in productivity and the aramid fiber produced does not have satisfactory physical properties.

The polymer solution prepared as described above can be directly used as a radiation doping. That is, according to the present invention, it is possible to omit the separate steps required in the conventional method for obtaining a solid aromatic polyamide, that is, the extraction, cleaning, crushing and drying steps after the polymerization step, The process of melting the solid aromatic polyamide into the sulfuric acid solvent may be omitted.

Therefore, according to the present invention, the productivity can be greatly improved as the polymerization process and the spinning process are simultaneously and continuously performed in the same apparatus, and the manufacturing process complexity due to the use of the sulfuric acid solvent, the harmfulness to the human body, Problems such as poor durability can be solved. In addition, since aramid fibers can be produced without using a sulfuric acid solvent that causes environmental pollution, a separate process for treating spent sulfuric acid is not required, and as a result, manufacturing costs of aramid fibers can be drastically reduced.

Using the polymerization solution Aramid  Manufacture of fibers

The polymerization solution in which the aromatic polyamide is uniformly dissolved in the organic solvent is extruded through a spinneret. The extruded polymer solution is solidified while passing through the coagulation liquid in a coagulation bath through an air gap to form a filament.

The spinneret has a plurality of capillaries having a diameter of 0.1 mm or less. If the diameter of the capillary formed in the spinneret exceeds 0.1 mm, the molecular orientation of the resulting filament is deteriorated, resulting in a decrease in the strength of the filament.

The air gap may mainly be an air layer or an inert gas layer, and the air gap length of 0.1 to 15 cm is preferable for improving the physical properties of the filament to be produced.

According to the present invention, in addition to water, the coagulating solution may further contain an alcohol such as ethylene glycol and glycerol. The coagulating solution is maintained at a high temperature of 10 to 90 캜.

Next, the filament obtained through the coagulation step is washed with water or a mixed solution of water and an alkali solution.

Then, a drying process is performed to adjust the moisture content remaining in the filament. The drying process can adjust the moisture content of the filament by adjusting the time that the filament touches the heated drying roll or by adjusting the temperature of the drying roll. It is preferred that the drying roll is heated by a predetermined means and that the drying roll is surrounded at least partially by means of heat shielding in order to prevent excessive heat from being released from the heated rolls and causing heat loss.

Optionally, a heat treatment process may be performed on the dried filament.

Then, the dried and heat-treated filaments are wound around a branch pipe.

On the other hand, during the spinning process described above, a drawing process is performed in which the filaments are stretched. Filaments including a copolymer have a relatively low crystallinity and thus have high elongation and may have poor physical properties such as strength and elastic modulus. Thus, the crystallinity of the filament is increased through the stretching process, thereby improving the strength and elastic modulus of the filament. By controlling the conditions of the stretching process, the elongation of the filament can be variously adjusted according to the use.

The stretching ratio of the filament can be adjusted depending on the content of the comonomer and the use, and the stretching ratio can be adjusted within a range of 2 to 13 times. That is, when the content and the spinning speed of the comonomer, for example, the substituted aromatic diamine, are low, the stretching ratio can be set high, and in the opposite case, the stretching ratio can be set low. Accordingly, the stretching ratio can be appropriately controlled within a range of 2 to 13 times in accordance with the content and the spinning speed of the comonomer.

The stretching process may include a wet stretching process. The wet stretching step may be carried out in a coagulating liquid set in a temperature range of 40 to 90 占 폚.

Optionally, the stretching process may comprise a key stretching process. The key drawing step may be performed between the coagulation step and the winding step. That is, the key drawing process can be performed before winding the filaments solidified to a predetermined shape to the paper tube. For example, the key drawing process may be performed in a drying process and / or a heat treatment process.

The above-mentioned key drawing process can be performed within a temperature range of 150 to 300 ° C. In the case of coagulated filaments, the bonding force between the molecular chains is relatively strong and the fluidity of the molecular chains is relatively poor. Accordingly, the key drawing process for the coagulated filaments is performed at a relatively high temperature of 150 캜 or higher. On the other hand, when the temperature of the film drawing process exceeds 300 ° C, the flowability of the molecular chains increases more than necessary, which may make process control difficult.

Alternatively, the stretching process may be performed through a two-step stretching including both a wet stretching process and a key stretching process. Through such two-step stretching, the stability of the process can be improved by preventing the rapid change of the molecular structure.

Hereinafter, the present invention will be described in detail with reference to examples and comparative examples. It is to be understood, however, that the following examples are intended to assist the understanding of the present invention, and the scope of the present invention is not limited thereby.

Example

An N-methyl-2-pyrrolidone (NMP) organic solvent containing 3% by weight of CaCl ₂ was placed in a reactor under a nitrogen atmosphere, and 50 mol% of para-phenylenediamine and 40% 50 mol% of cyano-p-phenylenediamine was dissolved in the reactor to prepare a mixed solution.

Then, 100 mol% of terephthaloyl dichloride was added to the reactor containing the mixed solution to obtain a polymerization solution containing the aramid polymer.

Subsequently, CaO as an alkali compound was added to the polymerization solution to neutralize the hydrochloric acid generated during the polymerization reaction, and at the same time, water generated by using vacuum was removed.

The polymerization solution containing the aramid polymer was then heated and the amount of the organic solvent was adjusted to adjust the concentration of the aramid polymer to 16 wt%.

Subsequently, the polymer solution was extruded through a spinneret, and then passed through an air gap and a coagulating liquid sequentially to form a multifilament having a linear density of 3,000 denier. The pressure in the spinning pack was 2,800 psi and the spinning speed was 600 mpm (meter per minuite).

Then, the multifilament was washed with water, and the washed multifilament was dried and drawn on a drying roller set at a temperature of 150 ° C. The drawn multifilament was heat-treated at 250 ° C. and wound up to produce an aramid fiber.

Comparative Example  One

An N-methyl-2-pyrrolidone (NMP) organic solvent containing 3% by weight of CaCl ₂ was placed in a reactor under a nitrogen atmosphere, and 50 mol% of para-phenylenediamine and 50 mol of cyanopara- % Were added to the reactor and dissolved to prepare a mixed solution.

40 mol% of terephthaloyl dichloride was added to the mixed solution to prepare a prepolymer, and 60 mol% of terephthaloyl dichloride was added to the reactor containing the prepolymer to obtain a polymerization solution.

Subsequently, CaO as an alkali compound was added to the polymerization solution to neutralize the hydrochloric acid generated during the polymerization reaction, and at the same time, water generated by using vacuum was removed.

The polymerization solution containing the aramid polymer was then heated and the amount of the organic solvent was adjusted to adjust the concentration of the aramid polymer to 16 wt%.

Subsequently, the polymer solution was extruded through a spinneret, and then passed through an air gap and a coagulating liquid sequentially to form a multifilament having a linear density of 3,000 denier. The pressure of the spinning pack was 2,300 psi and the spinning speed was 500 mpm.

Then, the multifilament was washed with water, and the washed multifilament was dried and drawn on a drying roller set at a temperature of 150 ° C. The drawn multifilament was heat-treated at 250 ° C. and wound up to produce an aramid fiber.

Comparative Example  2

After the polymerization solution was prepared in the same manner as in Comparative Example 1, the polymerization solution was extruded through spinneret under the same conditions as in Example 1 described above (pressure of spinning pack: 2,800 psi, spinning speed: 600 mpm). However, damage to the spinneret occurred. If the degree of damage (%) of the spinneret defined as the ratio of the area after deformation to the original area is over 102%, it becomes impossible to use. In this comparative example, the spinneret's damage degree was 105.2%.

The polydispersity index (PDI), tensile strength and elongation of the aramid fibers obtained by the above Examples and Comparative Examples were measured by the following methods, respectively, and the results are shown in Table 1.

Aramid  Of aromatic polyamide in fiber Dispersed  Indices( PDI )

The polydispersity index of the aromatic polyamide in the aramid fiber was measured by the light scattering method under the following conditions. Specifically, the polydispersity index based on the difference in light scattering degree between the reference solvent and the sample solution was automatically calculated by the following measuring apparatus.

1) Measuring device: Optilas T-Rex (DynaPro NanoStar)

2) Wavelength of light source: 658 nm

3) Reference solvent: N-methyl-2-pyrrolidone (NMP) with 3% by weight of CaCl ₂ added in an organic solvent

4) Sample solution: A sample solution was prepared by dissolving 0.5 wt% of aramid fiber in the reference solvent.

Aramid  Tensile strength and elongation of fiber

The tensile strength and elongation of the aramid fibers were measured by tensile strength and elongation at the breaking point after stretching until a sample of 25 cm in length was broken in an Instron Tester (Instron Engineering Corp., Canton, Mass.) According to ASTM D885 The above process was tested five or more times, and the average value was obtained. At this time, the tensile speed was 300 mm / min, and the initial load was fineness × 1/30 g.

division The polydispersity index (PDI) Tensile strength (g / d) Shinto (%) Example 2.5 22 3.4 Comparative Example 1 2.2 23 3.5 Comparative Example 2 Damage to spinning detention occurred

Claims (15)

An aromatic polyamide having a repeating unit represented by the following formula (1)
[Chemical Formula 1]

Wherein R ₁ is -CN, Ar ₁ and Ar ₂ are each independently aromatic hydrocarbons having 1 to 4 benzene rings,
Wherein the aromatic polyamide has a polydispersity index (PDI) of 2.4 to 3.0. The method according to claim 1,
Wherein Ar ₁ and Ar ₂ are phenylene. The method according to claim 1,
Wherein the aromatic polyamide is a homopolymer having only the repeating unit of the formula (1). The method according to claim 1,
Wherein the aromatic polyamide is a copolymer having a repeating unit represented by the following formula (2): < EMI ID =
(2)

Wherein Ar ₁ and Ar ₂ are each independently aromatic hydrocarbons having 1 to 4 benzene rings. 5. The method of claim 4,
Wherein Ar ₁ and Ar ₂ in the above Chemical Formulas 1 and ₂ are phenylene. Dissolving in an organic solvent an aromatic diamine comprising a substituted aromatic diamine wherein the hydrogen of the benzene ring is substituted with -CN, -Cl, -SO ₃ H, or -CF ₃ ;
Then, adding aromatic diacid halide to the organic solvent at least in the same molar amount as the aromatic diamine to obtain a polymerization solution containing an aromatic polyamide;
Extruding the polymer solution through a spinneret; And
And allowing the extruded polymer solution to pass through the coagulation liquid to form a filament. The method according to claim 6,
Wherein the aromatic diamine dissolved in the organic solvent contains only the substituted aromatic diamine. 8. The method of claim 7,
Wherein said substituted aromatic diamine is cyano-p-phenylenediamine,
Wherein said aromatic diacid halide is terephthaloyl dichloride. ≪ RTI ID = 0.0 > 11. < / RTI > The method according to claim 6,
Wherein the aromatic diamine dissolved in the organic solvent further comprises an unsubstituted aromatic diamine. 10. The method of claim 9,
Wherein the molar ratio of the substituted aromatic diamine and the unsubstituted aromatic diamine dissolved in the organic solvent is 1: 9 to 9: 1. 10. The method of claim 9,
Wherein said substituted aromatic diamine and said unsubstituted aromatic diamine are cyano-para-phenylenediamine and para-phenylenediamine, respectively,
Wherein said aromatic diacid halide is terephthaloyl dichloride. ≪ RTI ID = 0.0 > 11. < / RTI > 10. The method of claim 9,
Further comprising the step of dissolving 2 to 5% by weight of CaCl ₂ in the organic solvent before the substituted aromatic diamine and the unsubstituted aromatic diamine are dissolved in the organic solvent. 13. The method of claim 12,
Further comprising the step of dehydrating the organic solvent so that the water content of the organic solvent is 120 ppm or less immediately after dissolving the CaCl ₂ in the organic solvent. The method according to claim 6,
Further comprising the step of adding CaO to the polymerization solution to neutralize the HCl generated in the polymerization process before the polymerization solution is extruded. 15. The method of claim 14,
Further comprising the step of adding the CaO to the polymerization solution and removing water from the polymerization solution.