KR100924910B1 - Aramide Fiber having Improved Discoloration Resistance and Method for Manufacturing The Same - Google Patents

Abstract

PURPOSE: A manufacturing method of aramid fiber is provided to prevent deterioration of strength due to discoloration, and to offer improved discoloration resistance. CONSTITUTION: A manufacturing method of aramid fiber includes the following steps of: manufacturing a mixed solution by dissolving aromatic diamine having Fe of 10 ppm or less in a polymerization solvent; manufacturing a polyamide polymer by adding aromatic family diacid halide in the mixed solution; manufacturing spinning dope with the polyamide polymer; and spinning the spinning dope through a spinneret.

Description

Aramide Fiber Having Improved Discoloration Resistance and Method for Manufacturing The Same

The present invention relates to an aramid fiber and a method for manufacturing the same, and more particularly, to an aramid fiber having an improved discoloration resistance that does not discolor even when exposed to an external environment such as sunlight, air, moisture, etc. for a long time and a method for producing the same. It is about.

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 fiber has excellent properties such as high strength, high elasticity, and low shrinkage. It is a thin thread of about 5mm thick and has a strong strength enough to lift 2 tons of cars. It is used in various industries in the high-tech industry. In addition, aramid fibers are carbonized at 500 ° C or higher, and thus are attracting attention in fields requiring high heat resistance.

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 .

The conventional aramid fibers prepared as described above are initially yellow, but have a problem of discoloration when exposed to external environments such as sunlight, air, and moisture for a long time. Such discoloration of aramid fibers is known not only to lower the customer attraction force of the aramid fibers alone, but also to impair the physical properties of the aramid fibers, in particular, the strength. However, the cause of discoloration of aramid fibers has not been clearly identified to date, and thus there is no proposal for minimizing discoloration of aramid fibers.

The present invention was derived to solve the above problems, an object of the present invention, aramid fibers having improved discoloration resistance that does not discolor even after long-term exposure to external environment such as sunlight, air, moisture, and the like It is to provide a manufacturing method.

As an aspect of the present invention for achieving the above object, the aramid fiber of the present invention contains Fe but the content is 40ppm or less.

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 an aromatic diamine having a Fe content of 10ppm or less in a polymerization solvent to prepare a mixed solution; Preparing a polyamide polymer by adding an aromatic dieside halide having an Fe content of 10 ppm or less to the mixed solution; Preparing a spin dope using the polyamide polymer; And spinning the spinning dope through a spinneret.

Since Fe may be further mixed with the polyamide polymer due to corrosion of the manufacturing equipment, the method may further include removing Fe from the polyamide polymer before preparing the spin dope.

Fe removal from the polyamide polymer can be carried out by repeating the washing and drying step using pure water until the content of Fe remaining in the polyamide polymer is 40 ppm or less.

Fe content remaining in the polyamide polymer can be measured by Inductively Coupled Plasma (ICP) Emission Spectroscopy.

On the other hand, when spinning the spin dope through the spinneret in order to prevent the addition of Fe to the spinning dope due to the corrosion of the spinneret, the spinneret is made of a highly corrosion-resistant material, for example 45 to 85% by weight It may be made of an alloy comprising nickel, 1-30 wt% molybdenum, 1-30 wt% chromium.

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 can maintain its inherent color. Therefore, it is possible to prevent a decrease in customer attraction force due to discoloration of aramid fibers, as well as to prevent a decrease in strength due to discoloration.

In addition, according to the present invention, there is also an effect that can maximize the process efficiency by dramatically reducing the time for maintenance of the manufacturing equipment.

According to the present invention, the degree of discoloration of the aramid fibers exposed to the external environment such as sunlight, air, moisture, etc. was found to be related to the content of Fe contained in the aramid fibers. Theoretically, when the aramid fiber is exposed to an external environment such as sunlight, air, or moisture, Fe present in the oxide is oxidized to form iron oxide (FeO), which is generally black because aramid is black. It causes discoloration and deterioration of the fiber.

Therefore, the aramid fibers according to the present invention is characterized in that the Fe content in the fiber is 40ppm or less in order to exhibit a color change of 10% or less and a decrease in strength of 10% or less.

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

First, an inorganic salt is added to an organic solvent to prepare a polymerization solvent.

As the organic solvent, an amide organic solvent, a urea organic solvent, or a mixed organic solvent thereof may be used. Specific examples thereof include N-methyl-2-pyrrolidone (NMP), N, and N'-dimethylacetate. Amide (DMAc), hexamethylphosphoramide (HMPA), N, N, N ', N'-tetramethyl urea (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. Salts may be added alone or in the form of a mixture of two or more. 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.

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.

On the other hand, in the aromatic diamine, Fe may remain when Fe is used as a catalyst at the time of its preparation, or Fe may be added during the transport process. Thus, when Fe contained in aromatic diamine already exceeds 10 ppm, the aramid fiber which is a final product also has a high possibility of containing excess Fe. In order to fundamentally exclude this possibility, according to the aramid fiber manufacturing method of the present invention, it is preferable to select only the aromatic diamine having a Fe content of 10 ppm or less and dissolve it in the polymerization solvent.

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 dieside halide include terephthaloyl dichloride, 4,4'-benzoyl dichloride, 2,6-naphthalenedicarboxylic acid dichloride or 1,5-naphthalenedicarboxylic acid dichloride, but are not necessarily It is not limited.

Aromatic dieside halides such as Terephthaloyl Chloride (TPC) may have Fe remaining in the prepared terephthaloyl chloride because Fe may be used as a catalyst in its preparation. As the remaining Fe increases, terephthalic acid (TPA), isophthalic acid (IPA), trimesoyl chloride (TMC) and isophthaloyl chloride (Isophthaloyl Chloride (IPC) instead of terephthaloyl chloride The impurity content of the and so on increases, these impurities may inhibit the polymerization reaction for the production of polyamide polymer. Moreover, when the residual Fe content exceeds 10 ppm, the final product aramid fibers also contain excess Fe, thereby increasing the discoloration possibility.

Therefore, according to the present invention, it is preferable to measure the content of Fe in the aromatic dieside halide and to cook only the aromatic dieside halide whose content of the metal component is 10 ppm or less.

According to one embodiment of the present invention, the Fe content in the aromatic diamine and the aromatic dieside halide is measured by using Inductively Coupled Plasma (ICP) Emission Spectroscopy. That is, the sample is placed in an airtight container made of Teflon, wet-carbonized and oxidatively decomposed with an acid such as concentrated sulfuric acid, nitric acid, perchloric acid, and then the luminescence is measured using an inductively coupled plasma emission spectrometer to calculate the Fe content.

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 larger the difference. As such, when the degree of polymerization difference between the polymers finally obtained increases, physical property variations also increase, making it difficult to achieve 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 the aromatic polyamide polymer, the amount of aromatic dieside halides added during the final polymerization is equal to the amount of moles equivalent to the aromatic diamines 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. Thus, in view of the formation of such an insoluble material, a small amount of aromatic dieside halide may be added more than 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 is carried out for a long time. 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 alkali compound is an alkali metal of NaOH, Li ₂ CO ₃ , CaCO ₃ , LiH, CaH ₂ , LiOH, Ca (OH) ₂ , Li ₂ O or CaO, carbonate of alkaline earth metal, hydride of alkaline earth metal, alkaline earth metal It is selected from the group which consists of a hydroxide or an oxide of an alkaline earth metal.

When an inorganic alkali compound is added to an aromatic polyamide solution in a strong acid state containing a large amount of hydrochloric acid, the reaction rapidly reacts with hydrochloric acid, so that the neutralization proceeds rapidly. The reaction rate is drastically reduced and the inorganic alkali compound remains in the neutralization solution in an unreacted state. This causes a problem that the insoluble inorganic alkali compound must be filtered through a filter after the 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. This extraction process is most effective and economical to perform with 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.

On the other hand, due to the corrosion of the manufacturing equipment, Fe may be further mixed in the polyamide polymer during the manufacturing process. Therefore, according to one embodiment of the present invention, the Fe content of the dried polyamide polymer is measured and the Fe is removed from the polyamide polymer by repeating the washing and drying process using pure water until the content is 40 ppm or less. It is preferable to carry out.

According to one embodiment of the present invention, the Fe content in the polyamide polymer is measured by using Inductively Coupled Plasma (ICP) Emission Spectroscopy. That is, the sample is placed in an airtight container made of Teflon, wet-carbonized and oxidatively decomposed with an acid such as concentrated sulfuric acid, nitric acid, perchloric acid, and then the luminescence is measured using an inductively coupled plasma emission spectrometer to calculate the Fe content.

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 from 10 to 25% by weight of 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.

On the other hand, when Fe is excessively contained in the polyamide polymer, iron sulfate (FeSO ₄ ) is produced during the production of spinning dope, and the iron sulfate may block the pores of the dope filter. If the hole in the dope filter is clogged, process efficiency can be reduced because the process must be interrupted and the hole must be drilled or the dope filter replaced. Therefore, according to the present invention which manages the Fe content of the polyamide polymer to 40 ppm or less, it is also possible to achieve the effect of maximizing the process efficiency by drastically reducing the time for maintenance or replacement of the 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.

On the other hand, since the spinning dope contains concentrated sulfuric acid, when the spinning dope passes through the spinneret, the spinneret is corroded, and there is a risk of Fe being added to the spinning dope. In order to prevent this, the spinneret is preferably made of a material having high corrosion resistance, for example 45 to 85 wt% nickel, 1 to 30 wt% molybdenum, 1 to 30 wt% chromium, and other cobalt And tungsten, iron, silicon, manganese, carbon, vanadium, and the like.

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 the bottom of the spinneret and a coagulation solution is stored therein, and a coagulation tube is formed at the bottom of the coagulation bath. Accordingly, the radiant passing through the capillary of the spinneret is solidified while sequentially descending through the air gap and the coagulating liquid to form a filament, and the filament is discharged while passing through the coagulation tube below the coagulation bath. In addition to the filament, the coagulation solution is discharged through the coagulation tube, so that the coagulation solution must be continuously supplied to the coagulation bath as much as the discharge 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 injection device has a plurality of jet openings and injects the coagulating liquid toward the filaments from the plurality of injection openings. 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 sulfuric acid to water, ethylene glycol, glycerol, alcohol, or a mixture thereof, and is maintained at -20 to +90 ℃. 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 the problem of the uniformity of the filament may be lowered, sulfuric acid is added to the coagulating solution in order to prevent sulfuric acid from escaping rapidly from the surface of the radiant.

Next, 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. Sulfuric acid remaining in the filament may be removed through a washing process using water or a mixed solution of water and an alkaline solution.

Subsequently, a drying process is performed to control the water content remaining in the filament. In the drying process, the filament may reach the heated drying roll, or the moisture content of the filament may be adjusted by controlling the temperature of the drying roll.

Meanwhile, a tension is applied to the filament during the spinning, washing, neutralizing, and drying process, and the optimum magnitude of the tension applied to the filament during the drying process is about 3.0 to 7.0 gpd although it is determined by the overall spinning condition. It is preferable to dry the filament under the tension of. If the tension during drying is less than 3.0 gpd, the molecular orientation is reduced 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 for 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. However, the following examples are only intended to help the understanding of the present invention, and the scope of the present invention should not be limited thereto.

Fe content measurement

Fe content in the raw material such as para-phenylenediamine and terephthaloyl dichloride and aramid fibers was measured using Inductively Coupled Plasma (ICP) Emission Spectroscopy. That is, 2 g of the sample was placed in an airtight container made of Teflon, wet-carbonized and oxidatively decomposed with concentrated sulfuric acid, nitric acid, and perchloric acid, and the content of the Fe was measured by measuring the luminescence of Fe using an inductively coupled plasma emission spectrometer.

Example 1

A mixed solution was prepared by dissolving 5.00 g of para-phenylenediamine containing 1.0 ppm of Fe 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 containing 1.0 ppm of Fe component was added to the mixed solution to polymerize with para-phenylenediamine to prepare poly (paraphenylene terephthal-amide: PPD-T). Subsequently, 19 g of the poly (paraphenylene terephthal-amide) was dissolved in 100% concentrated sulfuric acid to prepare a dispersing dope. After the spinning dope was spun through spinnerets, aramid fibers were obtained through coagulation, washing and drying.

Example 2

Aramid fibers were prepared in the same manner as in Example 1, except that each of para-phenylenediamine and terephthaloyl dichloride used for the polymerization contained 2.0 ppm of Fe component.

Example 3

Aramid fibers were prepared in the same manner as in Example 1, except that each of para-phenylenediamine and terephthaloyl dichloride used for the polymerization contained 4.0 ppm of Fe component.

Example 4

Aramid fibers were prepared in the same manner as in Example 1, except that each of para-phenylenediamine and terephthaloyl dichloride used for the polymerization contained 6.0 ppm of Fe component.

Example 5

Aramid fibers were prepared in the same manner as in Example 1, except that each of para-phenylenediamine and terephthaloyl dichloride used for the polymerization contained 8.0 ppm of Fe component.

Example 6

Aramid fibers were prepared in the same manner as in Example 1, except that each of para-phenylenediamine and terephthaloyl dichloride used for the polymerization contained 10.0 ppm of Fe component.

Example 7

Aramid fibers were prepared in the same manner as in Example 6, except that the Fe component was removed from the poly (paraphenylene terephthal-amide) by washing and drying before the spinning dope was prepared.

Comparative Example 1

Aramid fibers were prepared in the same manner as in Example 6, except that the para-phenylenediamine used for the polymerization contained 11.0 ppm of Fe component.

Comparative Example 2

Aramid fibers were prepared in the same manner as in Example 6, except that the terephthaloyl dichloride used for the polymerization contained 11.0 ppm of Fe component.

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) when left for 24h was calculated as (△ 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 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 Example 7 Comparative Example 1 Comparative Example 2 Fe content of PPD (ppm)  1.0  2.0  4.0  6.0  8.0  10.0  10.0  11.0  10.0 Fe content of TPC (ppm)  1.0  2.0  4.0  6.0  8.0  10.0  10.0  10.0  11.0 Fe removal from polymer × × × × × × ○ × × Fe content of aramid fibers (ppm)  11  15  29  27  32  39  34  45  43 Color change of aramid fiber (%)  3  4  6  7  7  9  7  15  14 Decreased strength of aramid fiber (%)  2  3  5  6  7  9  8  16  15

As can be seen from Table 1, in the case of Examples 1 to 7 where both the Fe content of the PPD and TPC is 10 ppm or less, the Fe content of the aramid fiber was found to be less than 40 ppm, wherein the color change and strength of the aramid fiber The degradation was all good at less than 10%. On the other hand, in the case of Comparative Examples 1 and 2 in which either the Fe content of the PPD and TPC exceeds 10 ppm, the Fe content of the aramid fibers exceeds 40 ppm, causing about 15% color change and strength reduction.

On the other hand, when comparing the Examples 6 and 7 in which the Fe content of both PPD and TPC is 10 ppm, the aramid fiber of Example 7 which further performed the step of removing Fe from the polyamide polymer was added to the aramid fiber of Example 6 It was found to contain less Fe in comparison, which was much better in terms of color change and strength change of aramid fibers.

Claims (10)

Dissolving an aromatic diamine having a Fe content of 10 ppm or less in a polymerization solvent to prepare a mixed solution; Preparing a polyamide polymer by adding an aromatic dieside halide having an Fe content of 10 ppm or less to the mixed solution; Preparing a spin dope using the polyamide polymer; And Method for producing aramid fibers comprising the step of spinning the spin dope through the spinneret. The method of claim 1, And removing Fe from the polyamide polymer prior to preparing the spin dope. The method of claim 2, Removing the Fe from the polyamide polymer is carried out by washing and drying the polyamide polymer. The method of claim 1, Method for producing aramid fibers, characterized in that it further comprises the step of measuring the content of Fe contained in the polyamide polymer. The method of claim 4, wherein The Fe content contained in the polyamide polymer is a method for producing aramid fibers, characterized in that measured by Inductively Coupled Plasma (ICP) Emission Spectroscopy. The method of claim 4, wherein The method of producing a wholly aromatic polyamide polymer, characterized in that it further comprises the step of removing Fe from the polyamide polymer when the content of Fe contained in the polyamide polymer exceeds 40 ppm. The method of claim 6, Removing the Fe from the polyamide polymer is carried out by washing and drying the polyamide polymer. The method of claim 1, The spinneret is 45 to 85% by weight of nickel, 1 to 30% by weight of molybdenum, 1 to 30% by weight of chromium comprising a method comprising a method for producing aramid fibers. delete delete