KR101287277B1 - Aramide Fiber and Method for Manufacturing The Same - Google Patents

Abstract

The present invention relates to an aramid fiber and a method of manufacturing the same, which does not easily discolor and deteriorate even when exposed to external environments such as sunlight, air, moisture, etc. for a long time, the aramid fiber according to the invention has a pH of 6.0 to 8.5, The method for producing aramid fibers according to the present invention comprises the steps of dissolving the aromatic polyamide polymer in sulfuric acid to prepare a spin dope; Spinning the spinning dope through a spinneret; Solidifying in a coagulation bath discharged from the spinneret to form a filament; And washing the filament so that the pH of the filament is 6.0 to 8.5.

Polyamide, aramid, strength, sulfuric acid, sulfur, neutralization, cleaning

Description

TECHNICAL FIELD [0001] The present invention relates to an aramid fiber,

The present invention relates to an aramid fiber and a method for manufacturing the same, and more particularly, to an aramid fiber and a method for producing the same, which does not easily change color and decrease in strength even when exposed to an external environment such as sunlight, air, moisture or the like for a long time.

Generally, wholly aromatic polyamide fibers, collectively referred to as aramid fibers, include para-aramid fibers and meta-aramid fibers having a structure in which the benzene rings are connected linearly through an amide group (-CONH). Para-aramid fibers have excellent properties such as high strength, high elasticity and low shrinkage. They have a strong strength enough to lift 2 tons of automobile with a thin thread of 5mm thickness, Of-the-art industry. In addition, since the aramid fiber is carbonized at a temperature of 500 ° C or higher, the aramid fiber is also in the spotlight where high heat resistance is required.

Aramid fiber is a process for producing a wholly aromatic polyamide polymer by polymerizing an aromatic diamine and an aromatic dieside halide in a polymerization solvent containing N-methyl-2-pyrrolidone, dissolving this polymer in a concentrated sulfuric acid solvent to prepare a spinning dope After the step of spinning the spinning dope through the spinneret to pass through the non-coagulant fluid and coagulation bath sequentially to produce a filament, and the step of washing the filament, and drying and heat treatment .

Conventional aramid fibers prepared as described above generally exhibits high strength initially, but when exposed to external environments such as sunlight, air, and moisture for a long time, discoloration occurs and there is a problem of a considerable decrease in strength. This discoloration of the aramid fibers by themselves lowers the customer attraction of the aramid fibers. In particular, when products made of aramid fibers are used in extreme environments such as high temperature and high humidity areas, desert areas, or cold areas, the strength is severely deteriorated, which is a decisive factor that impairs the reliability of the product.

However, the cause of discoloration and strength reduction of the aramid fibers has not been clearly identified to date, and thus the situation is not proposed to minimize the discoloration and strength reduction of the aramid fibers.

The present invention was derived to solve the above problems, an object of the present invention, aramid fibers and a method of manufacturing the same, which does not occur discoloration and strength degradation well even when exposed to external environment such as sunlight, air, moisture, etc. for a long time To provide.

As an aspect of the present invention for achieving the above object, the aramid fibers of the present invention has a pH of 6.0 to 8.5.

It is preferable that the aramid fiber of this invention contains 0.05 to 0.50 weight% of sulfur (S).

As another aspect of the present invention for achieving the above object, the aramid fiber manufacturing method of the present invention, the step of dissolving the aromatic polyamide polymer in sulfuric acid to prepare a spin dope; Spinning the spinning dope through a spinneret; Solidifying in a coagulation bath discharged from the spinneret to form a filament; And washing the filament so that the pH of the filament is 6.0 to 8.5.

The washed filaments preferably comprise 0.05 to 0.50% by weight of sulfur (S).

It is preferable that the filament is washed with an alkaline solution.

The washing step includes neutralizing the filaments with an alkali solution containing 0.3 to 1.3 wt% sodium hydroxide (NaOH), and neutralizing the filament with an alkaline solution containing 0.01 to 0.15% sodium hydroxide. It is preferred to include the step of cleaning the filament.

In the washing of the filament, it is preferable to increase the relative time of the neutralization step if the pH of the filament exceeds 8.5, and to increase the relative time of the washing step if the pH of the filament is less than 6.0.

According to the aramid fiber and the manufacturing method thereof according to the present invention, even if the aramid fiber is exposed to an external environment such as sunlight, air, moisture, or the like for a long time, discoloration does not occur and initial strength can be maintained. Therefore, it has the effect of preventing the customer attraction force degradation and reliability damage of the product due to discoloration and strength reduction of aramid fibers.

Hereinafter, an embodiment of the aramid fiber of the present invention and a manufacturing method thereof will be described in detail.

First, an inorganic salt is added to an organic solvent to prepare a polymerization 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'-dimethylacetate Amide (DMAc), hexamethylphosphoramide (HMPA), N, N, N ', N'-tetramethylurea (TMU), N, N-dimethylformamide (DMF) or mixtures thereof.

The inorganic salt is added to increase the degree of polymerization of the aromatic polyamide, and specific examples thereof include halogenated alkali metal salts or halogenated alkaline earth metal salts such as CaCl 2, LiCl, NaCl, KCl, LiBr and KBr, and these inorganic salts. Silver may be added alone or in the form of a mixture of two or more thereof. As the amount of the inorganic salt increases, the degree of polymerization of the aromatic polyamide increases, but when the inorganic salt is added in an excessive amount, there may be an inorganic salt that does not dissolve. Thus, the inorganic salt is 10% by weight or less based on the total amount of the polymerization solvent. It is preferable that it is the range of. Since the inorganic salt has poor solubility in organic solvents, the final polymerization solvent can be prepared by completely dissolving the inorganic salts by adding water and then removing the water through a dehydration process.

Next, an aromatic diamine is dissolved in the prepared polymerization solvent to prepare a mixed solution. Specific examples of aromatic diamines include para-phenylenediamine, 4,4'-diaminobiphenyl, 2,6-naphthalenediamine, 1,5-naphthalenediamine or 4,4'-diaminobenzanilide. However, the present invention is not limited thereto.

Subsequently, an aromatic dieside halide is prepared, which can be polymerized with the aromatic diamine to produce a polyamide polymer. Specific examples of the aromatic diacid halide include terephthaloyl dichloride, 4,4'-benzoyl dichloride, 2,6-naphthalene dicarboxylic acid dichloride and 1,5-naphthalene dicarboxylic acid dichloride, But is not limited thereto.

Next, while stirring the mixed solution, a predetermined amount of a preselected aromatic dieside halide is added to the mixed solution for preliminary polymerization.

Polymerization of an aromatic diamine and an aromatic diacid halide proceeds at a rapid rate with the exothermic reaction. When the polymerization rate is increased as described above, there arises a problem that the difference in degree of polymerization between the finally obtained polymers increases. More specifically, since the polymerization reaction does not proceed simultaneously in the entire mixed solution, the polymer that has first started the polymerization proceeds rapidly to form a long molecular chain, whereas the polymer that has started the polymerization first polymerizes first. There is no choice but to form shorter molecular chains than the polymer from which the reaction was initiated, and the higher the polymerization rate, the greater the difference. As described above, when the difference in degree of polymerization between the finally obtained polymers becomes large, the physical property deviation becomes large, which makes it difficult to realize the desired characteristics. Therefore, it is preferable to minimize the difference in degree of polymerization between the polymers finally obtained by preforming a prepolymer having a molecular chain of a predetermined length through a prepolymerization step, and then performing a polymerization step.

According to one embodiment of the present invention, the prepolymerization process is carried out at a low temperature, preferably 0 to 45 ℃ maintaining the reaction temperature, instead of giving a sufficient polymerization time of about 3 to 15 minutes, and fully aromatic polyamide It is preferred to add only 20-40% of the total amount of the aromatic dieside halides required for the preparation of the polymer during the prepolymerization process.

After the completion of the prepolymerization process, the temperature is lowered to 0 to 10 ° C. and an aromatic dieside halide is further added to the prepolymer to prepare a final polymer.

Aromatic dieside halides react with aromatic diamines in a 1: 1 molar ratio when producing aromatic polyamide polymers, so the amount of aromatic dieside halide added in the final polymerization is equal to the mole equivalent to the aromatic diamine when added to the prepolymerization. is determined to be mole. However, when preparing the polymerization solvent, a small amount of water added to assist in dissolving the inorganic salt may remain even after the dehydration process, in which case a small amount of water may react with the aromatic dieside halide to form an insoluble substance. Therefore, in view of the formation of such an insoluble substance, a small amount of an aromatic diacid halide may be added in a smaller amount than an aromatic diamine.

After completion of the polymerization process, it is preferable to control the amount of aromatic diamine and dieside halide so that the concentration of the final polymer in the total polymerization solution is about 5 to 20% by weight. When the aromatic diamine and the dieside halide are added so that the concentration of the final polymer is less than 5% by weight, the polymerization rate is lowered and the reaction must be carried out for a long time, resulting in low economic efficiency, and the aromatic diamine so that the concentration of the polymer exceeds 20% by weight. This is because when the aromatic dieside halide is added, the polymerization does not proceed smoothly and the intrinsic viscosity of the polymer cannot be improved to 5.5 or more.

Specific examples of the aromatic polyamide polymer obtained by the polymerization step include poly (paraphenylene terephthal-amide: PPD-T), poly (4,4'-benzanilide terephthalamide), poly (paraphenylene-4, 4'-biphenylene-dicarboxylic acid amide) or poly (paraphenylene-2,6-naphthalenedicarboxylic acid amide).

Subsequently, the acid produced during the polymerization reaction is neutralized with an alkali compound.

Since the aromatic polyamide polymer obtained through the polymerization is present in the form of an acid crumb such as bread crumb, the flowability of the aromatic polyamide solution is poor. Therefore, in order to improve the fluidity, it is preferable to proceed with the subsequent process in the state of making the slurry by adding water to the aromatic polyamide solution. On the other hand, the neutralization step can be carried out simultaneously by using water in which an alkali compound is dissolved when making the aromatic polyamide polymer slurry.

The inorganic alkali compound is an alkali metal of NaOH, Li2CO3, CaCO3, LiH, CaH2, LiOH, Ca (OH) 2, Li2O or CaO, carbonate of alkaline earth metal, hydride of alkaline earth metal, hydroxide of alkaline earth metal, or oxide of alkaline earth metal It is selected from the group consisting of.

When an inorganic alkaline compound is added to a strong acidic aromatic polyamide solution containing a large amount of hydrochloric acid, it quickly reacts with hydrochloric acid to rapidly neutralize. However, once the neutralization proceeds considerably and the pH approaches 7, The reaction rate is rapidly decreased and the inorganic alkaline compound is left in the neutralized solution in an unreacted state, which causes the problem that the insoluble inorganic alkaline compound must be filtered with the filter after neutralization is completed. Therefore, in order to prevent the formation of insoluble foreign matter in the aromatic polyamide solution, the neutralization process can be carried out at several times.

Subsequently, the neutralization process is completed to grind the aromatic polyamide polymer in a crumb state in which the acid is removed.

If the particle size of the polymer is too large in the extraction process described later, the polymerization solvent extraction process takes a lot of time and the polymerization solvent extraction efficiency is lowered, so that the grinding process is performed to reduce the particle size of the polymer before the extraction process.

Next, the polymerization solvent is extracted from the pulverized aromatic polyamide polymer. Since the polymerization solvent used for the polymerization step is contained in the aromatic polyamide polymer obtained by the polymerization, such a polymerization solvent must be extracted from the polymer, and the extracted polymerization solvent can be reused in the polymerization step. Such an extraction process is most effective and economical to perform using water. The extraction process may be performed by installing a filter in a bath having a discharge port, placing a polymer in the form of a crumb on the filter, and then pouring water to discharge the polymerization solvent contained in the polymer together with water to the discharge port.

Next, the remaining water after the extraction step is dehydrated, and then the drying process is completed to complete the production of the aromatic polyamide polymer. Thereafter, a classification process may be performed to classify the aromatic polyamide polymers by size for the spinning process.

Spinning dope is prepared by dissolving the aromatic polyamide polymer prepared as above in a concentrated sulfuric acid solvent having a concentration of 97 to 103%. Instead of the concentrated sulfuric acid, chloro sulfuric acid, fluoro sulfuric acid and the like may also be used.

The polymer concentration in the spin dope is preferably 10 to 25% by weight for the fiber properties. As the polyamide polymer concentration increases, the viscosity of the spin dope also increases, but beyond the critical concentration point, the viscosity of the spin dope rapidly decreases, while the spin dope does not form a solid phase. It changes from optically isotropic to optically anisotropic. Since the anisotropic spin dope can be made of high strength aramid fibers due to its structural and functional properties without a separate drawing process, the polyamide polymer concentration in the spin dope preferably exceeds the above critical concentration, but the concentration is If too large, the viscosity of the spinning dope is too low occurs.

The spinning dope prepared in this way is filtered using a Dope Filter.

The filament is formed by spinning the spin dope filtered by a dope filter using a spinneret and then coagulating in a coagulation bath through an air gap.

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 poor, resulting in a decrease in the strength of the filament.

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

The coagulation bath is located at a lower portion of the spinneret, and a coagulation bath is stored in the lower portion of the coagulation bath. Therefore, the radiation passing through the capillary of the spinneret goes down while the air gap and the coagulating solution sequentially pass to form a filament. The filament is discharged through the coagulation tube under the coagulation bath. Since the coagulating liquid along with the filament is also discharged through the coagulating tube, the coagulating liquid should be continuously supplied to the coagulating bath as much as the discharged liquid.

In addition, the coagulation tube is formed with a jet device (jet device) can be injected to the filament passing through the coagulation tube. The injector has a plurality of jet openings and injects the coagulation liquid from the plurality of injection openings toward the filament. The plurality of injection holes are preferably aligned so that the coagulating liquid can be sprayed in perfect symmetry with respect to the filament. The spray angle of the coagulating liquid is preferably 0 to 85 ° with respect to the axial direction of the filament, and in particular, a spray angle of 30 ° is suitable for a commercial production process.

The coagulating solution may be added with sulfuric acid to water, ethylene glycol, glycerol, alcohol, or a mixture thereof, and is maintained at -20 to + 90 ° C. When the radiation passed through the spinneret passes through the coagulating solution, the sulfuric acid in the emission is removed and filaments are formed. When sulfuric acid is rapidly removed from the surface, the surface is solidified before the sulfuric acid contained therein escapes. Since a problem of inferior uniformity of the filament may occur, a small amount of sulfuric acid is added to the coagulating solution in order to prevent the sulfuric acid from escaping rapidly from the surface of the radiant.

Subsequently, the sulfuric acid remaining in the obtained filament is removed.

Sulfuric acid used in the manufacture of the spinning dope can remain but is not completely removed, although most of the emissions are passed through the coagulation bath. Moreover, when sulfuric acid is added to the coagulation liquid of a coagulation tank in order to make sulfuric acid escape | emit uniformly from a effluent, there is a high possibility that sulfuric acid will remain in the filament obtained. It is very important to remove sulfuric acid remaining in the filament because sulfuric acid remaining in the filament may adversely affect the aramid fiber properties, no matter how small the amount.

Sulfuric acid remaining in the filament may be removed by washing with water or an alkaline solution. The washing process may be carried out in a multi-step process, for example, first washing the filament containing sulfuric acid with an alkaline solution containing 0.3 to 1.3% by weight of sodium hydroxide (NaOH), followed by 0.01 to 0.15% Secondary washing with dilute alkaline solution containing sodium hydroxide can be carried out. In this case, it can be said that the primary water washing has a larger purpose of neutralization, and the secondary water washing has a larger purpose of washing.

According to the present invention, it has been found that the degree of discoloration and strength reduction of aramid fibers exposed to external environments such as sunlight, air, and moisture is closely related to the pH of the aramid fibers. Theoretically explaining this is as follows.

When washing a filament containing sulfuric acid with an alkali solution containing an alkali metal hydroxide, sulfate may be formed together with water, but sulfuric acid and alkali metal hydroxide may be present in an unreacted state. At this time, when sulfuric acid and alkali metal hydroxide are properly balanced, the alkali metal may block the unreacted sulfuric acid to stabilize the physical properties of the aramid fiber. Sulfuric acid is unblocked by them, which reacts with the active radicals in the molecular structure of the aramid fibers over time, causing discoloration and deterioration of the aramid fibers.

On the contrary, when the alkali metal hydroxide is present in the washed filaments in excess of sulfuric acid, a large amount of inorganic salts are present in the aramid fibers, which act as foreign matters, deteriorating the focusability between the filaments.

Therefore, the aramid fibers according to the present invention preferably has a pH of 6 to 8, and particularly preferably the concentration of sulfur (S) in the aramid fibers is 0.05 to 0.5% by weight.

According to the aramid fiber production method according to the present invention, the filament is washed with water until the filament exiting the coagulation bath exhibits a pH of 6.0 to 8.5. When the washing step is performed in multiple stages, that is, when the solidified filament is neutralized with a relatively high concentration of alkaline solution and then the neutralized filament is washed with a relatively low concentration of alkaline solution, the pH of the filament becomes higher as the neutralization time increases. As the cleaning time increases, the pH decreases. Neutralization time and cleaning time can be adjusted by adjusting the winding speed and / or the size of the bath.

On the other hand, when the effluent passes through the coagulation bath, the effluent coagulates as the sulphate contained in the effluent exits to form a filament. Therefore, the coagulation step may be regarded as a kind of cleaning process in terms of sulfuric acid removal. Therefore, by adjusting the solidification time in the coagulation bath, the pH of the filament can be made to a predetermined value before the washing step. Here, the solidification time means the time for which the radiant stays in the solidification bath. Therefore, the coagulation time can be adjusted by adjusting the winding speed and / or the size of the coagulation bath.

After the washing process, a drying process is performed to control the water content remaining in the filament. The drying process may control the time for which the filament is in contact with the heated drying roll, or the moisture content of the filament by adjusting the temperature of the drying roll.

On the other hand, during the spinning, washing, neutralizing and drying processes, tension is applied to the filament. The optimum amount of tension applied to the filament during the drying process is about 3.0 to 7.0 gpd It is preferable to dry the filament under a tensile force of. When the tensile strength at the time of drying is less than 3.0 gpd, the degree of molecular orientation is decreased and ultimately the strength of the fiber is lowered. Conversely, if the tensile strength during drying exceeds 7.0 gpd, the filament may be cut, resulting in difficulty in manufacturing. On the other hand, the magnitude of the tension applied to the filament can be adjusted by appropriately controlling the surface speed of the roll moving the filament.

The drying rolls are heated by some means, and the drying rolls are preferably at least partly surrounded by heat blocking means in order to prevent excessive heat from being released from the heated rolls and thereby causing heat loss.

Subsequently, the dried filament is wound on a branch pipe. Spinning speed is 300 to 1500 m / min.

Hereinafter, the present invention will be described in detail through Examples and Comparative Examples. It should be noted, however, that the following examples are intended to assist the understanding of the present invention and should not limit the scope of the present invention.

Aramid  Determination of sulfur (S) content of fiber

The sulfur (S) content of aramid fibers was measured using ELTRA CS-2000 (Carbon / Sulfur Determinator).

Aramid  Fiber pH  Measure

5 g of aramid fiber and 25 g of distilled water were placed in a sealed container made of Teflon, and placed in a steel blocking container, which is a pressure tube, heated at 100 ° C. for 1 hour, and the pH of the water in the pressure tube was measured by a pH meter.

Example  One

A mixed solution was prepared by dissolving 5.00 g of para-phenylenediamine in 100 ml of a polymerization solvent in which 7 wt% of CaCl 2 was added to N-methyl-2-pyrrolidone (NMP). Subsequently, 9.44 g of terephthaloyl dichloride was added to the mixed solution to polymerize with para-phenylenediamine to prepare poly (paraphenylene terephthal-amide: PPD-T). Dissipative dope was prepared by taking 19 g of the poly (paraphenylene terephthal-amide) and dissolving it in 100 ml of 100% sulfuric acid. After the spinning dope was spun through a spinneret, the filament was formed by solidifying the spinner for 0.2 seconds in a coagulation bath in which a coagulant solution containing 8.0 wt% sulfuric acid was stored. The filaments were neutralized with an alkaline solution containing 1.0 wt% sodium hydroxide (NaOH) for 1.0 seconds, and the neutralized filaments were washed with an alkaline solution containing 0.1 wt% sodium hydroxide (NaOH) for 0.5 seconds. Subsequently, the filament was dried to obtain aramid fibers having a sulfur content of 0.50% by weight and a pH of 6.0.

Example  2

Aramid fibers were produced in the same manner as in Example 1, except that the neutralization time and the washing time of the effluent were 1.0 and 1.0 seconds, respectively. Got.

Example  3

Aramid fibers were prepared in the same manner as in Example 1, except that the neutralization time and the washing time of the effluent were 1.5 and 1.0 seconds, respectively. The aramid fibers having a sulfur content of 0.30 wt% and a pH of 7.0 were obtained. Got.

Example  4

The aramid fibers were produced in the same manner as in Example 1, except that the neutralization time and the washing time of the effluent were 2.0 seconds and 1.5 seconds, respectively. The aramid fibers having a sulfur content of 0.25 wt% and a pH of 7.3 were obtained. Got.

Example  5

The aramid fibers were produced in the same manner as in Example 1, except that the neutralization time and the washing time of the effluent were 2.5 seconds and 2.0 seconds, respectively. Got.

Example  6

The aramid fibers were prepared in the same manner as in Example 1, except that the neutralization time and the washing time of the effluent were 3.0 seconds and 2.5 seconds, respectively. Got.

Comparative example  One

The aramid fibers were produced in the same manner as in Example 1, except that the neutralization time and the washing time of the effluent were 0.3 seconds and 0.4 seconds, respectively. Got.

Comparative example  2

Aramid fibers were prepared in the same manner as in Example 1, except that the neutralization time and the washing time of the sintered materials were 3.5 seconds and 3.5 seconds, respectively. Got.

The color change and the strength reduction of the aramid fibers obtained by the above Examples and Comparative Examples was measured by the following method, the results shown in Table 1 below.

Aramid  Fiber Color change  Measure

The color of aramid fiber refers to the L value measured using KURABO's COLOR-7X, and “color change” means that the aramid fiber with the initial color of L1 is black panel temperature (65 + 3 ° C.) and exposure light source (Xenon). -Arc), Irradiance (0.35W / m2 @ 340nm), Exposure Cycle (102min of Light only / 18min Light and Water Spray) when left for 24h color change occurs when △ L, (△ L / L1) x 100.

Aramid  Determination of strength reduction of fiber

The strength of the sample was determined by measuring the strength (g) when a 25 cm long sample was broken in an Instron Engineering Corp. (Canton, Mass) and dividing it by the denier of the sample. At this time, the tensile speed was 300mm / min, the super-load was fineness × 1 / 30g. The strength of the aramid fibers was obtained from the average value after testing five samples. On the other hand, the strength reduction of aramid fiber, the aramid fiber having the initial average strength of T1 was Black Panel Temperature (65 + 3 ℃), Exposure Light Source (Xenon-Arc), Irradiance (0.35W / m2 @ 340nm), Exposure Cycle When ΔT is the decrease in the average intensity that occurs when left for 24 h under (102min of Light only / 18min Light and Water Spray) conditions, it was calculated as (ΔT / T1) × 100.

[Table 1]

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 PH of Aramid Fiber 6.0 6.5 7.0 7.3 7.5 8.5 5.5 8.6 Sulfur (S) content of aramid fibers
(weight%)
0.50
0.40
0.30
0.25
0.15
0.05
0.60
0.02 Color change of aramid fiber (%) 9 7 4 5 3 3 14 3 Of aramid fiber
Strength reduction (%) 6 4 3 2 4 5 12 11

As shown in Table 1 above, when the pH of the aramid fiber is less than 6.0 and when the sulfur (S) content of the aramid fiber exceeds 0.50, both color change and strength decrease were caused to a considerable size, and the pH of the aramid fiber was increased. In the case of more than 8.5 and the sulfur content of the aramid fiber is less than 0.05, the color change was good, but the strength decrease was more than 10%.

Claims (7)

Dissolving the aromatic polyamide polymer in sulfuric acid to produce a spin dope; Spinning the spinning dope through a spinneret; Solidifying in a coagulation bath discharged from the spinneret to form a filament; And Washing the filament such that the pH of the filament is 6.0 to 8.5, The washed filament is 0.05 to 0.50% by weight of sulfur (S) manufacturing method of the aramid fiber. delete The method of claim 1, The filament is washed with an alkaline solution. The method of claim 3, wherein the washing of the filament comprises: Neutralizing the filaments with an alkaline solution comprising 0.3 to 1.3 wt% sodium hydroxide (NaOH); And Next, the method for producing aramid fibers comprising the step of cleaning the neutralized filament with an alkaline solution containing 0.05 to 0.15% sodium hydroxide. The method of claim 4, wherein washing the filament comprises And increasing the relative time of the neutralization step if the pH of the filament exceeds 8.5, and increasing the relative time of the washing step if the pH of the filament is less than 6.0. In the aramid fibers produced by spinning an aromatic polyamide polymer prepared by the polymerization of an aromatic diamine and an aromatic dieside chloride, The aramid fibers have a pH of 6.0 to 8.5, The aramid fiber is characterized in that it comprises 0.05 to 0.50% by weight of sulfur (S). delete