KR101312781B1 - Aramide Fiber and Method for Manufacturing The Same - Google Patents

Abstract

The present invention relates to an aramid fiber and a method for producing the same, which are not easily discolored and reduced in strength even after long-term exposure to external environments such as sunlight, air, moisture, and the like, and the aramid fiber according to the present invention is 0.2 To 0.8% by weight of an alkali metal, 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 filaments with an alkaline solution containing an alkali metal hydroxide such that the alkali metal content of the filament is 0.2 to 0.8 wt%.

Polyamide, aramid, strength, discoloration, neutralization, washing, sodium

Description

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

The present invention relates to an aramid fiber and a method of manufacturing the same, more specifically, aramid fiber excellent in the focusing properties between the filaments does not easily change discoloration and strength even when exposed to an external environment such as sunlight, air, moisture, etc. for a long time And to a method for producing the same.

Generally, the wholly aromatic polyamide fibers commonly referred to as aramid fibers include para-aramid fibers having a structure in which benzene rings are linearly connected through an amide group (CONH) and non-aramid fibers. 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 the 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 are generally yellow and exhibit high strength, but when exposed to external environments such as sunlight, air, moisture, etc. for a long time, discoloration occurs and there is a problem of a significant decrease in strength. This discoloration of the aramid fibers by themselves lowers the customer attraction of the aramid fibers. In addition, the deterioration in strength over time is particularly severe when a product made of aramid fibers is used in extreme environments such as high temperature and high humidity, a desert area, or a cold area, 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 is derived to solve the above problems, the object of the present invention, even if exposed to the external environment such as sunlight, air, moisture, etc. for a long time does not occur discoloration and strength deterioration, and the focusability between filaments It is to provide this excellent aramid fiber and its production method.

As an aspect of the present invention for achieving the above object, the aramid fiber of the present invention comprises 0.2 to 0.8% by weight of alkali metal.

The aramid fibers of the present invention may further include sulfur (S) in a content less than the content of the alkali metal, preferably, 0.05 to 0.50% by 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 filaments with an alkaline solution containing an alkali metal hydroxide such that the alkali metal content of the filament is 0.2 to 0.8 wt%.

The washed filaments include sulfur (S), but the content thereof is preferably less than the alkali metal content. More preferably, the washed filaments comprise 0.1 to 0.5% by weight of sulfur (S).

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

According to the aramid fiber and the manufacturing method thereof according to the present invention, not only the focusability between the filaments is excellent, but also the discoloration does not occur even when the aramid fiber is exposed to the external environment such as sunlight, air, moisture, etc. for a long time, and the initial strength is increased. I can keep it.

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 in order to increase the polymerization degree 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. The salts may be added alone or in the form of a mixture of two or more. As the addition amount of the inorganic salt increases, the degree of polymerization of the aromatic polyamide increases. However, since an inorganic salt which does not dissolve when the inorganic salt is added in an excessive amount may be present, the inorganic salt may be present in an amount of 10% .

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.

In the polymerization of the aromatic diamine and the aromatic dieside halide, the reaction proceeds at a high rate with exotherm. In this way, when the polymerization rate is high, there is a problem in that the degree of polymerization differs between the finally obtained polymers. 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 for a polymerization time of 3 to 15 minutes while maintaining the reaction temperature at 0 ~ 45 ℃, the total of the aromatic dieside halides required for the preparation of the wholly aromatic polyamide polymer Only 20 to 40% of the amount is preferably added 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.

Since aromatic dieside halides react with aromatic diamines in a 1: 1 molar ratio when preparing an aromatic polyamide polymer, the amount of aromatic dieside halide added in the final polymerization is equal to the amount of molar equivalent to the aromatic diamine when added to the prepolymerization. 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 reaction is present in the form of bread crumb, the fluidity 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 alkaline compound may be at least one selected from the group consisting of alkaline metals such as NaOH, Li ₂ CO ₃ , CaCO ₃ , LiH, CaH ₂ , LiOH, Ca (OH) ₂ , Li ₂ O or CaO, carbonates of alkaline earth metals, hydrides of alkaline earth metals, Hydroxide, or an oxide of an alkaline earth metal.

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 from 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 include a step of installing a filter in a bath equipped with an outlet, placing the polymer on the filter, pouring water, and discharging the polymerization solvent contained in the polymer together with water to the outlet.

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, it is preferable that the concentration of the polyamide polymer in the spinning dope exceeds the above critical concentration, but the concentration is excessively high. If 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, a jet device is formed in the coagulation tube to inject coagulation liquid into 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 particularly, in the commercial production process, a spray angle of 20 to 40 ° is appropriate.

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.

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 0.1% 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 the external environment such as sunlight, air, and moisture is closely related to the alkali metal content 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 the sulfuric acid and the alkali metal hydroxide are properly balanced, the alkali metal caps the unreacted sulfuric acid to stabilize the physical properties of the aramid fiber, but if the alkali metal hydroxide is present at a little less than the sulfuric acid, Unblocked sulfuric acid is present and these react 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, it is preferable that the aramid fiber which concerns on this invention contains 0.2-0.8 weight% of alkali metal. If the content of alkali metal is less than 0.2% by weight, sulfuric acid that is not blocked by the alkali metal will be present, which will increase the discoloration and decrease in strength of the aramid fiber, and if the content of the alkali metal exceeds 0.8% by weight, inorganic salts in the fiber This is because excessively present as fine particles between the filaments to lower the focusability between the filaments.

In particular, it is important that the sulfur (S) content in the aramid fibers is less than the alkali metal content, since it is important to prevent the presence of sulfuric acid not blocked by the alkali metal. It is preferable that the sulfur (S) content in the aramid fibers is 0.05 to 0.50% by weight or less, since the sulfuric acid not blocked by alkali metal is more likely to exceed 0.50% by weight.

According to the aramid fiber production method according to the present invention, the filament is washed with an alkaline solution containing an alkali metal hydrate so that the filament exiting the coagulation bath contains 0.2 to 0.8 wt% of alkali metal. When the washing step is carried out 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 alkali metal content of the filament increases with increasing neutralization time. Is higher, and the alkali metal content is lower with increasing cleaning time. Neutralization time and cleaning time can be adjusted by adjusting the winding speed and / or the size of the bath.

The preferred running time of the neutralization step is 0.5 to 3.0 seconds. If the neutralization time is less than 0.5 seconds, a sufficient neutralization reaction will not occur. Conversely, if the neutralization time exceeds 3.0 seconds, not only will the productivity be lowered, but the operation and maintenance costs will increase.

0.5 when 3.0 seconds, the neutralization time determined within the range, the neutralization time of a cleaning process performed after the process is _{0.11 <0.32 * t 1 - 0.1} * t 2 < a 0.71 formula: - wherein, t ₁ is the neutralization time (seconds) T ₂ is the cleaning time in seconds.

On the other hand, the mass ratio of the alkali metal to the sulfur remaining in the final filament is 0.2 to 20. If the mass ratio exceeds 20, the alkali metal content in the final aramid fiber becomes high, which causes a large decrease in strength. On the contrary, if the mass ratio is less than 0.2, the capping of the unreacted sulfuric acid by the alkali metal in the final aramid fiber is not completely made, causing a problem that the aramid fibers easily discolor.

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. On the contrary, when the tension in drying exceeds 7.0 gpd, there is a fear that the filament is cut, which causes manufacturing difficulties. 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. The spinning speed is 600 to 1,500 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.

Determination of Sodium (Na) Content in Aramid Fibers

The sodium (Na) content in the aramid fibers was measured using Inductively Coupled Plasma (ICP) Emission Spectroscopy. That is, 2g of aramid fiber samples were placed in a sealed container made of Teflon, wet carbonized and oxidatively decomposed with concentrated sulfuric acid-nitric acid-perchloric acid, and the content of the sodium luminescence was measured by an inductively coupled plasma luminescence analyzer.

Determination of Sulfur (S) Content in Aramid Fibers

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

Example 1

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 0.5 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 an alkali metal content of 0.2 wt% and a sulfur (S) content of 0.50 wt%.

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 0.5 seconds, respectively, and the sodium content was 0.4% by weight and the sulfur (S) content was 0.45% by weight of aramid fiber was obtained.

Example 3

Aramid fibers were prepared in the same manner as in Example 1, except that neutralization time and washing time of the effluent were 1.5 seconds and 1.0 second, respectively, and the sodium content was 0.5% by weight and the sulfur (S) content was 0.30% by weight of aramid fiber was obtained.

Example 4

Aramid fibers were prepared in the same manner as in Example 1, except that neutralization time and washing time of the effluent were 2.0 seconds and 1.5 seconds, respectively. As a result, sodium content was 0.6% by weight and sulfur (S) content was increased. 0.25% by weight of aramid fiber was obtained.

Example 5

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 2.5 and 2.0 seconds, respectively, and the sodium content was 0.7% by weight and the sulfur (S) content was 0.15% by weight of aramid fiber was obtained.

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. 0.05% by weight of aramid fiber was obtained.

Comparative Example 1

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, and the sodium content was 0.1% by weight and the sulfur (S) content was Aramid fibers of 0.60 wt% were obtained.

Comparative Example 2

Aramid fibers were prepared in the same manner as in Example 1, except that neutralization time and washing time of the effluent were 3.5 seconds and 3.0 seconds, respectively, and the sodium content was 0.9% by weight and the sulfur (S) content was Aramid fibers of 0.02% by weight were obtained.

The color change and the strength reduction of the aramid fibers obtained by the above Examples and Comparative Examples were measured by the following method.

Color Change Measurement of Aramid Fiber

The color of aramid fiber refers to the L value measured using KURABO's COLOR-7X, and “color change” refers to the aramid fiber whose initial color is L ₁ , Black Panel Temperature (65 + 3 ° C), Exposure Light Source ( Xenon-Arc), Irradiance (0.35W / m ² @ 340nm), and Exposure Cycle (102min of Light only / 18min Light and Water Spray) under the conditions of 24h when the color change occurs when △ L, (△ L / L ₁ ) × 100.

Decreased strength measurement of aramid fibers

The strength of the sample was determined by measuring the strength (g) when a 25 cm long sample was broken in an Instron tester (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 the aramid fibers, the aramid fibers having an initial average strength of T ₁ was Black Panel Temperature (65 ± 3 ℃), Exposure Light Source (Xenon-Arc), Irradiance (0.35 W / m ² @ 340 nm), When ΔT is a decrease in the average intensity that occurs when left for 24 h under an exposure cycle (102 min of light only / 18 min Light and Water Spray), it is calculated as (ΔT / T ₁ ) × 100.

 The color change and the decrease in strength measured for the aramid fibers obtained by the above Examples and Comparative Examples are as shown in Table 1 below.

[Table 1]

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Of aramid fiber
Sodium (Na) content
(weight%)
0.2
0.4
0.5
0.6
0.7
0.8
0.1
0.9 Of aramid fiber
Sulfur (S) content
(weight%)
0.50
0.45
0.30
0.25
0.15
0.05
0.60
0.02 Mass ratio of sodium to sulfur 0.4 0.89 1.67 2.4 4.67 16 0.17 45 Of aramid fiber
Color change (%) 7 6 5 4 4 3 14 3 Of aramid fiber
Strength reduction (%) 8 4 3 2 5 6 11 13

As shown in Table 1 above, when the sodium content in the aramid fiber is less than 0.2% by weight, both color change and the decrease in strength were caused by a considerable size of 10% or more, and when the sodium content of the aramid fiber exceeds 0.8% by weight The change was good, but the strength decreased more than 10%.

Claims (6)

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 with an alkaline solution comprising sodium hydroxide such that the sodium content of the filament is 0.2-0.8 wt% and the sulfur content is 0.05-0.50 wt%, The sodium content and the sulfur content are the content including sodium and sulfur contained in the sulfates generated during the washing step, as well as sodium and sulfur contained in the unreacted sodium hydroxide and sulfuric acid, respectively, The sodium content contained in the washed filament is greater than the sulfur content method for producing aramid fibers. delete delete Aramid fibers produced by spinning an aromatic polyamide polymer produced by polymerization of an aromatic diamine and an aromatic dieside halide, The aramid fiber comprises 0.2 to 0.8 wt% sodium and 0.05 to 0.50 wt% sulfur, The sodium content and the sulfur content are sodium and sulfur contained in the sulfate, as well as sodium and sulfur contained in the unreacted sodium hydroxide and sulfuric acid, respectively, Aramid fiber, characterized in that the content of sodium is more than the sulfur content. delete delete