KR100910537B1 - Method of making aramid fiber - Google Patents

Abstract

A method for preparing aramid fiber is provided to solve crystallinity of aramid fiber generated by impurities, orientation degree and polymerization degree, and to obtain aramid fiber having strength deviation satisfying property standards required for high-tech fields. A method for preparing aramid fiber comprises the steps of: polymerizing aromatic diamine and aromatic diacid halide in a polymerization solvent to prepare an aromatic polyamide polymer, wherein the aromatic diamine has 99.9-100% purity of para-aromatic diamine excluding meta-aromatic diamine and ortho-aromatic diamine; dissolving the aromatic polyamide polymer in a solvent to prepare a spinning dope; and spinning the spinning dope.

Description

Method of making aramid fibers {Method of making Aramid Fiber}

The present invention relates to aramid fibers, and more particularly, to aramid fibers and a method for producing the same minimizing strength variations.

Generally, the aromatic polyamide fiber, commonly referred to as aramid fiber, is a step of producing an aromatic polyamide polymer by polymerizing an aromatic diamine and an aromatic dieside chloride in a polymerization solvent containing N-methyl-2-pyrrolidone, the aromatic The polyamide polymer is prepared by dissolving a polyamide polymer in a concentrated sulfuric acid solvent to prepare a spinning dope, and spinning the spinning dope through a spinneret and then solidifying the spinning material to produce a filament.

Aramid fibers include para-aramid fibers and meta-aramid fibers having a structure in which benzene rings are linearly connected 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.

Such aramid fiber is a special fiber having high-performance physical properties, but its application fields vary, but the conventional aramid fiber has a large variation in strength, and thus there is a limitation in applying it to advanced fields.

The present invention was devised to solve the above-mentioned conventional problems, and an object of the present invention is to provide a method for producing an aromatic polyamide polymer capable of minimizing strength variation, and a method for producing aramid fibers using the method.

In order to achieve the above object, the present invention comprises the steps of dissolving aromatic diamine in a polymerization solvent to prepare a mixed solution; And adding an aromatic dieside halide to the mixed solution to polymerize the aromatic diamine and the aromatic dieside halide, wherein the aromatic diamine has a purity of 99.9% to 100%. Provided are methods for preparing aromatic polyamide polymers.

The present invention provides a process for preparing an aromatic polyamide polymer by polymerizing an aromatic diamine and an aromatic dieside halide having a purity of 99.9% to 100% in a polymerization solvent; Dissolving the aromatic polyamide polymer in a solvent to prepare a spinning dope; And it provides a method for producing aramid fibers comprising the step of spinning the spinning dope.

Aramid fibers are prepared by first preparing an aromatic polyamide polymer, preparing a spinning dope using the aromatic polyamide polymer, and spinning the spinning dope, and the inventors can minimize the strength variation of the aramid fibers. While studying the present method, it was confirmed that the purity of the aromatic diamine in the raw material used to prepare the aromatic polyamide polymer had a great influence on the strength variation of the finally obtained aramid fibers to complete the present invention.

More specifically, the aromatic polyamide polymer is prepared by polymerizing an aromatic diamine and an aromatic dieside halide, wherein the raw material aromatic diamine is prepared through various processes. As an example of the aromatic diamine, in the case of Para-PhenyleneDiamine (PPD), para-nitroaniline is obtained from chlorobenzene and para-phenylenediamine is obtained from para-nitroaniline. You get However, in the case of para-phenylenediamine obtained through the above process, mono-fucntional groups such as aniline, chloroaniline and nitroaniline, and meta-phenyl Isomers such as meta-phenylene diamine and ortho-phenylene diamine are generated, and such mono-functional groups and isomers act as impurities, thus producing aromatic diamines containing impurities. When the aromatic polyamide polymer is prepared by using this, the strength deviation of the finally obtained aramid fibers is increased.

Therefore, the present invention is to minimize the strength deviation of the aramid fibers by managing the purity of the aromatic diamine to be a raw material of the aromatic polyamide polymer, in particular obtained when the aromatic diamine has a purity in the range of 99.9% to 100% The strength deviation of aramid fibers is less than 5% to meet the physical property standards required for high-tech sectors such as bulletproof and aerospace.

According to the present invention as described above has the following effects.

Since the present invention produces aromatic polyamide polymers using aromatic diamines having a purity in the range of 99.9% to 100%, problems of crystallinity, orientation, and degree of polymerization of aramid fibers caused by impurities such as mono functional groups and isomers are reduced. As a result, aramid fibers having a strength deviation of 5% or less that meets the physical property standards required by high-tech fields such as bulletproof and aerospace can be obtained.

Hereinafter, a preferred embodiment of the present invention will be described in detail.

1. Preparation of Aromatic Polyamide Polymer

1) First, a polymerization solvent is prepared.

The polymerization solvent is prepared by adding an inorganic salt to the organic 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.

2) Next, an aromatic diamine is dissolved in the prepared polymerization solvent to prepare a mixed solution.

Specific examples of the aromatic diamine include para-phenylenediamine, 4,4'-diaminobiphenyl, 2,6-naphthalenediamine, 1,5-naphthalenediamine or 4,4'-diaminobenzanilide. However, it is not necessarily limited thereto.

The aromatic diamine has a purity in the range of 99.9% to 100%. When using Para-PhenyleneDiamine (PPD) as the aromatic diamine, it contains 99.9% to 100% of the Para-PhenyleneDiamine (PPD), aniline (aniline), chloroaniline ( Mono-fucntional groups such as chloroaniline and nitroaniline, and at least one group selected from the group consisting of isomers such as meta-phenylene diamine and ortho-phenylene diamine One impurity is contained 0 to 0.1%, i.e. 1000 ppm or less.

The aromatic diamine having the above purity range may be obtained by controlling the manufacturing process, or may be obtained by additionally performing purification processes of various methods known in the art after preparing the aromatic diamine containing some degree of impurities.

3) Next, while stirring the mixed solution, a predetermined amount of aromatic dieside halide is added to the mixed solution and prepolymerized.

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 a shorter molecular chain than the polymer from which the reaction began. 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, the prepolymerization step is to minimize the degree of polymerization between the polymers finally obtained by forming a polymer having a molecular chain of a predetermined length in advance and then performing a polymerization step.

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.

4) Next, after the completion of the prepolymerization step, the remaining amount of the aromatic dieside halide is added to the mixed solution while stirring at 0 ~ 30 ℃ state and polymerized.

In the preparation of the aromatic polyamide, since the aromatic dieside halide reacts with the aromatic diamine in a 1: 1 molar ratio, the aromatic diamine and the aromatic dieside halide can be added in the same molar ratio.

After completing the polymerization process, it is preferable to adjust 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 addition dieside halide is added, the polymerization reaction 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 terephthalamide: PPD-T), poly (4,4'-benzanilide terephthalamide), and poly (paraphenylene-4,4 '-Biphenylene-dicarboxylic acid amide) or poly (paraphenylene-2,6-naphthalenedicarboxylic acid amide).

5) Next, an alkali compound is added to the obtained aromatic polyamide solution to neutralize the acid generated during the polymerization reaction.

When the polymerization reaction proceeds, an acid such as hydrochloric acid is generated. Since such acid causes problems such as corrosion of the polymerization apparatus, an acid generated during the polymerization reaction by adding an inorganic alkali compound or an organic alkali compound during or after the polymerization reaction. To neutralize.

At this time, since the aromatic polyamide obtained through the polymerization reaction is present in the form of bread crumb, the fluidity of the aromatic polyamide solution is not good. Therefore, in order to improve the fluidity, it is preferable to proceed with the subsequent process while adding water to the aromatic polyamide solution to make a slurry, and for this purpose, neutralizing by adding water together with an alkali compound to the aromatic polyamide solution during the neutralization process. The process can proceed.

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.

6) Next, 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.

7) Next, the polymerization solvent contained in the aromatic polyamide polymer is extracted to remove the polymerization solvent from the polymer.

Since the polymerization solvent used for the polymerization process 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 is reused in the polymerization process.

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 equipped with an outlet, placing a polymer on the filter, and then pouring water to discharge the polymerization solvent contained in the polymer together with water to the outlet.

8) Next, water remaining after the extraction process is dewatered, and then drying is completed to prepare the aromatic polyamide polymer. Thereafter, a classification process may be performed to classify the aromatic polyamide polymers by size for the spinning process.

2. Aramid  Manufacture of fibers

1) First, spinning dope is prepared by dissolving the aromatic polyamide polymer prepared by the above method in a solvent. Since the aromatic polyamide polymer of the above characteristics is used, the finally produced aramid fibers have a strength variation of 5% or less.

The solvent may be a concentrated sulfuric acid solvent having a concentration of 97 to 100%, and chloro sulfuric acid, fluoro sulfuric acid, or the like may be used instead of concentrated sulfuric acid.

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 increases, but beyond the critical concentration point, the viscosity of the spin dope decreases rapidly, with the spin dope forming an optical phase without forming a solid phase. It changes from 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.

2) Next, filaments are formed by spinning the spin dope using a spinneret and then solidifying it in a coagulation bath through an air gap.

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 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 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 tube 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, the coagulation tube is formed with a jet device (jet device) can be injected to 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. In order to solve this problem, sulfuric acid is added to form a coagulation solution.

3) Next, sulfuric acid remaining in the obtained filament is removed.

Since sulfuric acid solution is used in the preparation of the spinning dope, sulfuric acid may remain in the filament produced by the spinning process.

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.

The washing process may be carried out in a multi-step process, for example, first washing the filament containing sulfuric acid with 0.05 to 1.3% of an aqueous caustic solution, followed by 0.005 to 0.1% of a thinner caustic aqueous solution. You can do a second flush.

4) Next, 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.

Meanwhile, a tension is applied to the filament during the spinning, washing, neutralizing, and drying process, and the optimal magnitude of the tension applied to the filament during the drying process is about 0.3 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 0.3 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 a predetermined means, and the drying rolls are preferably at least partially surrounded by heat shielding means in order to prevent excessive heat from being released from the heated rolls and thereby causing heat loss.

5) Next, the dried filament is wound on the branch pipe. Spinning speed is 600 to 1500 m / min.

3. Example  And Comparative example

1) Example 1

CaCl 2 was added to N-methyl-2-pyrrolidone (NMP) to prepare a polymerization solvent, and then a mixed solution was prepared by dissolving para-phenylenediamine having a purity of 99.9% in the polymerization solvent.

Purity is measured using potentiometric titrators. Specifically, 0.09 g of a sample is dissolved in 50 ml of acetic acid, and purity is measured using a potentiometric titrator (lectrode: Metrohm Solvotrode 6.0229.100) with 0.1 N-HClO4 standard acetic acid solution.

Purity (%) =

Where

i) V is the amount of 0.1 N-HClO4 standard acetate solution consumed in the titration (ml),

ii) 0.1 is the normal concentration of 0.1N-HClO4 standard acetic acid solution,

iii) W is the sampling rate (g),

iv) 54.07 is the equivalent of one equivalent of amine (molecular weight / 2 equivalent = 108.14 / 2) of para-phenylenediamine,

v) F is the titer of 0.1N-HClO4 standard acetic acid solution, and is calculated by the following formula.

F =

Thereafter, while stirring the mixed solution, terephthaloyl dichloride of the same mole as the para-phenylenediamine was added to the mixed solution in two portions to produce a poly (paraphenylene terephthalamide) polymer. Thereafter, water and NaOH were added to the polymerization solution containing the polymer to neutralize the acid. Thereafter, after pulverizing the polymer, the polymerization solvent contained in the aromatic polyamide polymer was extracted using water, and finally, the aromatic polyamide polymer was obtained through a dehydration and drying process.

Thereafter, the obtained aromatic polyamide polymer was dissolved in 100% concentrated sulfuric acid to prepare a spinning dope. The polymer concentration in the spinning dope was adjusted to 20% by weight. Thereafter, the spinning dope was spun through a spinneret, and then passed through a 7 mm air layer and coagulated while passing through a coagulation bath containing a sulfuric acid aqueous solution and a coagulation tube below the coagulation bath to prepare a filament. While passing the coagulation tube, an aqueous sulfuric acid solution was injected into the filament through an injection device. Thereafter, the filament was washed with water to remove residual sulfuric acid, dried, and wound up to obtain aramid fibers.

2) Example 2

Aramid fibers were obtained in the same manner as in Example 1, except that the mixed solution was prepared using para-phenylenediamine having a purity of 99.95% in Example 1 above.

3) Comparative Example 1

Aramid fibers were obtained in the same manner as in Example 1, except that the mixed solution was prepared using para-phenylenediamine having a purity of 99.50% in Example 1 above.

4) Comparative Example 2

Aramid fibers were obtained in the same manner as in Example 1, except that the mixed solution was prepared using para-phenylenediamine having a purity of 99.80% in Example 1 above.

4. Experimental Example

1) Measurement of strength deviation of aramid fibers

Aramid fibers according to Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were cut into 25 cm to prepare respective samples. The strength was measured according to the ASTM D-885 test method. Specifically, the strength (g) when each sample was broken at a tensile rate of 300 mm / min using an Instron Engineering Corp. (Canton, Mass) was measured. The measurement was performed and the measured value was divided by the denier of the sample to obtain the intensity (g / d). After 20 such procedures, the intensity deviation of each sample was calculated based on the values for a total of 16 times, except for the measured values of the top 10% and bottom 10%, and the results are shown in Table 1 below. Same as

Table 1

division Intensity deviation (%) Example 1 4.9 Example 2 3.9 Comparative Example 1 8.5 Comparative Example 2 7.2

Claims (7)

delete delete delete Preparing an aromatic polyamide polymer by polymerizing an aromatic diamine halide with an aromatic diamine having a purity of 99.9% to 100% of only para aromatic diamine except for meta aromatic diamine and ortho aromatic diamine in a polymerization solvent; Dissolving the aromatic polyamide polymer in a solvent to prepare a spinning dope; And It comprises a step of spinning the spinning dope, the method of producing aramid fiber, characterized in that the strength deviation is 5% or less. The method of claim 4, wherein The process for preparing the aromatic polyamide polymer Preparing an aromatic diamine having a purity of 99.9% to 100% through a purification process; Dissolving aromatic diamine in a polymerization solvent to prepare a mixed solution; And A method for producing aramid fibers comprising the step of adding an aromatic dieside halide to the mixed solution to polymerize the aromatic diamine and an aromatic dieside halide. The method of claim 4, wherein The aromatic diamine contains 99.9% to 100% of Para-PhenyleneDiamine (PPD), aniline, chloroaniline, nitroaniline, and meta-phenylenediamine. -PhenyleneDiamine, and ortho-phenylenediamine (Ortho-PhenyleneDiamine) at least one of the impurities containing 0 to 0.1% of the method for producing aramid fibers. delete