KR20200076026A - Copolymerized aramid fiber with excellent strength and modulus and method of manufacturing for the same - Google Patents

Abstract

According to the present invention, after spinning a polymerization solution, in which a copolymerized aramid polymer containing a repeating unit of following formula (1) is dissolved, onto a fiber, the spun fiber is coagulated with a coagulation solution of aqueous hydrochloric acid solution, and a heat treatment is performed, thereby preparing a copolymerized aramid fiber comprising (i) the repeating unit of formula (i) and (ii) at least one repeating unit selected from a repeating unit of following formula (2) and a repeating unit of following formula (3). In Formula 2, X is -C00H, and in Formula 3, X is -CONH_2. In the present invention, some of cyano groups (-CN) attached to a polymer chain of the chemically spun fiber are changed to the -COOH group or the -CONH_2 group to additionally generate hydrogen bonds between polymer chains, and simultaneously hydrogen ions are added between the polymer chains to induce ionic bonds by the hydrogen ions, thereby remarkably improving strength and elastic modulus of the copolymerized aramid fiber.

Description

Copolymerized aramid fiber with excellent strength and modulus and method of manufacturing for the same}

The present invention relates to a copolymer aramid fiber excellent in strength and modulus of elasticity and a method for producing the same, specifically, the strength and elastic modulus including simultaneously an aromatic group substituted with a -CN group and a -COOH group or a -CONH ₂ group in a polymer chain. This excellent copolymer aramid fiber and its manufacturing method.

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

Para-aramid has excellent properties such as high strength, high elasticity, and low shrinkage. The thin thread of 5 mm thickness produced therefrom has strong strength enough to lift a 2 ton car, and is used not only for bulletproof use, but also for various uses in the high-tech industry in the aerospace field.

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

The method of manufacturing aramid fiber is well described in Korean Patent Registration No. 10-0910537. According to this registered patent, an aromatic diamine is dissolved in a polymerization solvent to prepare a mixed solution, and an aromatic diacid is added thereto to prepare an aramid polymer. Subsequently, the aramid polymer is dissolved in a sulfuric acid solvent to prepare a spinning dope, and after spinning, the aramid fibers are finally completed by sequentially performing coagulation, washing, and drying processes.

However, when the aramid fiber is produced through such a process, the aramid polymer in a solid state is prepared and then melted in a sulfuric acid solvent to produce a spinning dope to spun it, thereby complicating the manufacturing process and harmful to the human body. There are problems such as deterioration of durability due to corrosion.

Moreover, the sulfuric acid solvent used to melt the aramid polymer having high chemical resistance and removed after spinning causes environmental pollution, and thus must be appropriately treated after use. The cost of treating such waste sulfuric acid is economical of aramid fibers Lowers it.

In order to solve the above problems, Korean Patent Registration No. 10-171994 discloses a method for producing aramid fibers without using a sulfuric acid solvent by directly using a copolymerized aramid polymerization solution as a spinning dope.

Specifically, in the prior art, terephthaloyl dichloride is added to and reacted with an organic solvent in which paraphenylenediamine and cyano-para-phenylenediamine are dissolved to polymerize a polymerization solution containing a copolymerized aramid polymer, followed by polymerization. After spinning the solution, the spinning material was contacted with water as a coagulating solution to prepare copolymerized aramid fibers.

However, the prior art has an advantage of not using a sulfuric acid solvent, but there is a limit to further improve the strength and elastic modulus of the copolymerized aramid fibers to a certain level or more.

In order to further improve the strength and elastic modulus of the copolymerized aramid prepared as described above with another conventional technique, a method of heat-treating and spinning and coagulating the copolymerized aramid fiber has also been carried out, but the conventional method also has the strength and elastic modulus of the aramid fiber. There was a limit to further improving the problems, and problems were complicated in the manufacturing process.

An object of the present invention is to provide a copolymerized aramid fiber having excellent strength and elastic modulus and a method for manufacturing the same, including simultaneously an aromatic group substituted with a -CN group and a -COOH group or a -CONH ₂ group in the polymer chain.

In order to solve this problem, the present invention is a polymerized solution in which a copolymerized aramid polymer containing a repeating unit represented by the following Chemical Formula 1 is dissolved in a fibrous form, and the spun fiber is coagulated with an aqueous solution of hydrochloric acid, followed by heat treatment. (Iii) A copolymerized aramid fiber is prepared comprising one or more repeating units selected from the repeating unit represented by the following Chemical Formula 1 and (ii) the repeating unit represented by the following Chemical Formula 2 and the repeating unit represented by the following Chemical Formula 3.

[Formula 1]

[Formula 2]

[X in Formula 2 is -C00H]

[Formula 3]

[X in Formula 3 is -CONH ₂ ]

The present invention converts some of the cyano groups (-CN) attached to the polymer chain of the chemically spun fiber to -COOH groups or -CONH ₂ groups to simultaneously generate hydrogen bonds between the polymer chains and at the same time between the polymer chains. By adding hydrogen ions to induce ion bonding by hydrogen ions, the strength and elastic modulus of the copolymerized aramid fibers are greatly improved.

1 is a FT-IR graph of the copolymerized aramid fibers before and after the heat treatment of the copolymerized aramid fibers of Example 1.

Hereinafter, the present invention will be described in detail.

The copolymer aramid fibers having excellent strength and elasticity according to the present invention include (i) one or more repeating units selected from the repeating unit represented by the following formula 1 and (ii) the repeating unit represented by the following formula 2 and the repeating unit represented by the following formula 3 It is characterized.

[Formula 1]

[Formula 2]

[X in Formula 2 is -C00H]

[Formula 3]

[X in Formula 3 is -CONH ₂ ]

The copolymerized aramid fiber having excellent strength and elastic modulus according to the present invention may further include a repeating unit represented by the following Chemical Formula 4.

[Formula 4]

It is preferable that the repeating unit of Formula 2 is 5 to 95 mol% in the copolymerized aramid fiber having excellent strength and elastic modulus of the present invention.

The copolymerized aramid fiber having excellent strength and elastic modulus according to the present invention is additionally formed with hydrogen bonds between polymer chains by treatment and heat treatment with a hydrochloric acid aqueous solution, and ionic bonds are formed by hydrogen ions added between the polymer chains. And the elastic modulus is further improved.

The strength of the copolymerized aramid fiber excellent in strength and elasticity according to the present invention is 28 to 35 g/d, elongation is 1 to 3%, and elasticity is 900 to 1,500 g/d. Strength and elastic modulus are improved by 10-15% more than aramid fibers or copolymerized aramid fibers in which the repeating unit of Formula 1 and the repeating unit of Formula 3 are alternately arranged.

On the other hand, the method for producing a copolymer aramid fiber excellent in strength and elastic modulus according to the present invention is (i) by adding and reacting terephthaloyl dichloride in an organic solvent in which an aromatic diamine containing cyano paraphenylenediamine is dissolved. Preparing a polymerization solution in which a copolymerized aramid polymer containing a repeating unit of Formula 1 is dissolved; (Ii) a step of coagulating the spun fiber with a coagulating solution of an aqueous hydrochloric acid solution after spinning the polymerization solution in a fibrous form; And (iii) heat-treating the coagulated fibers.

[Formula 1]

Looking at an example of implementation of the present invention, first, terephthaloyl dichloride is added to and reacted with an organic solvent in which an aromatic diamine containing cyano paraphenylenediamine is dissolved, and a copolymerized aramid polymer comprising a repeating unit represented by the following Chemical Formula 1 A dissolved polymerization solution is prepared.

In this case, cyano paraphenylenediamine is used alone as the aromatic diamine containing cyano paraphenylenediamine, or cyano paraphenylenediamine and paraphenylenediamine are used as aromatic diamines containing cyano paraphenylenediamine. It is used in a molar ratio of 1:9 to 9:1.

Specific examples of the organic solvent include N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), hexamethylphosphoamide (HMPA), N,N,N,N'-tetra Methyl urea (TMU), N,N-dimethylformamide (DMF), or mixtures thereof, more preferably N,N'-dimethylacetamide (DMAc).

As a more preferable embodiment, the inorganic salt is dissolved in the organic solvent, and then an aromatic diamine containing cyano paraphenylene is dissolved therein, followed by terephthaloyl di having the same molar amount as the aromatic diamine. Chloride is added and reacted to prepare a polymerization solution in which a copolymerized aramid polymer is dissolved.

The inorganic salt is added to increase the degree of polymerization of the aromatic polyamide, and specific examples thereof include a halogenated alkali metal salt or a halogenated alkaline earth metal salt such as CaCl2, LiCl, NaCl, KCl, LiBr and KBr. These inorganic salts may be added alone or in the form of a mixture of two or more.

It is preferable that the addition amount of the inorganic salt is about 2 to 5% by weight based on the weight of the organic solvent.

Next, the polymerization solution prepared as described above is used as a spinning dope as it is, and after spinning into a fibrous form through spinneret, the fiber is coagulated with an aqueous solution of hydrochloric acid, and then heat treated to obtain strength and elastic modulus according to the present invention. Excellent copolymerized aramid fibers are produced.

Some of the -CN groups included in the polymer chain of the fibers spun by the coagulation process and the heat treatment process cause chemical changes to -COOH or -CONH ₂ groups by contact and heat treatment of a coagulant aqueous hydrochloric acid solution.

At this time, nitrogen (N) in the -CN group is oxidized by heating under an acid catalyst.

Hydrogen bonds are additionally formed between the polymer chains of the fiber by the chemical change as described above, and hydrogen ions that induce ionic bonds between the polymer chains are additionally formed.

FIG. 1 shows that the -CN group in the polymer chain of the copolymerized aramid fiber decreases as compared to before heat treatment and -COOH group or -CONH ₂ group increases as compared to heat treatment by the heat treatment.

The graph a in FIG. 1 is an FT-IR graph of the heat-treated copolymerized aramid fiber, and the graph b in FIG. 1 is an FT-IR graph of the copolymerized aramid fiber before heat treatment.

Therefore, the copolymer and aramid fibers excellent in strength and modulus of elasticity produced by the present invention have improved strength and elastic modulus by about 10 to 15% compared to conventional copolymerized aramid fibers.

Hereinafter, the present invention will be described in detail through examples and comparative examples.

The embodiments of the present invention described below are merely examples for helping the understanding of the present invention and do not limit the scope of the present invention, and various changes and modifications of the present invention without departing from the technical spirit and scope of the present invention. It will be apparent to those skilled in the art that modifications are possible. Accordingly, the present invention includes all modifications and variations falling within the scope of the invention described in the claims and equivalents thereof.

Example 1

2,000 g of N,N-dimethylacetamide (organic solvent) containing 3% by weight of CaCl ₂ was placed in a reactor under a nitrogen atmosphere, and then 159 g of cyano paraphenylenediamine was added to the reactor to dissolve, and thereafter terephthal 243 g of royl dichloride was added and reacted, and 88 g of lithium carbonate (Li ₂ CO ₃ ), a neutralizing agent, was added thereto to prepare a polymerization solution in which a copolymerized aramid polymer was dissolved.

Subsequently, the polymerized solution was spun through a spinneret having a diameter of 60 µm and an L/D ratio of 2.5, and then sequentially passed through an air gap at an interval of 10 mm and a hydrochloric acid aqueous solution at 5°C (coagulation solution: hydrochloric acid concentration 0.05M). After drying at 150° C., heat treatment was performed at 300° C. for 15 seconds to prepare copolymerized aramid fibers.

The results of evaluating the properties of the prepared copolymerized aramid fibers were as shown in Table 1, and the FT-IR graphs of the copolymerized aramid fibers before and after heat treatment were shown in FIG. 1.

Example 2

2,000 g of N,N-dimethylacetamide (organic solvent) containing 3% by weight of CaCl ₂ was placed in a reactor under a nitrogen atmosphere, and then 100 g of cyano paraphenylenediamine and 59 g of paraphenylenediamine were added to the reactor. After melting, 243 g of terephthaloyl dichloride was added thereto, reacted, and 88 g of lithium carbonate (Li ₂ CO ₃ ) as a neutralizing agent was added thereto to prepare a polymerization solution in which a copolymerized aramid polymer was dissolved.

Subsequently, the polymerized solution was spun through a spinneret having a diameter of 60 µm and an L/D ratio of 2.5, and then sequentially passed through an air gap at an interval of 10 mm and a hydrochloric acid aqueous solution at 5°C (coagulation solution: hydrochloric acid concentration 0.05M). After drying at 150° C., heat treatment was performed at 300° C. for 15 seconds to prepare copolymerized aramid fibers.

Table 1 shows the results of evaluating the physical properties of the copolymerized aramid fibers.

Comparative Example 1

2,000 g of N,N-dimethylacetamide (organic solvent) containing 3% by weight of CaCl ₂ was placed in a reactor under a nitrogen atmosphere, and then 159 g of cyano paraphenylenediamine was added to the reactor to dissolve, and thereafter terephthal 243 g of royl dichloride was added and reacted, and 88 g of lithium carbonate (Li ₂ CO ₃ ), a neutralizing agent, was added thereto to prepare a polymerization solution in which a copolymerized aramid polymer was dissolved.

Subsequently, the polymerized solution was spun through a spinneret having a diameter of 60 µm and an L/D ratio of 2.5, followed by sequentially passing through an air gap of 10 mm intervals and water (coagulation solution) at 5° C., and then drying at 150° C. , Heat-treated at 300°C for 15 seconds to prepare copolymerized aramid fibers.

Table 1 shows the results of evaluating the physical properties of the copolymerized aramid fibers.

division Example 1 Example 2 Comparative Example 1 Strength (g/d) 29 33 26 Elongation (%) 1.5% 2.3% 2.0 Elastic modulus (g/d) 1,000 1,200 800

The strength, elongation and modulus of elasticity of Table 1 were measured by the following method.

Strength and elongation of copolymerized aramid fibers

The strength of the aramid fiber is stretched until a 25 cm long sample breaks in an Instron Engineering Corp. (Canton, Mass) according to the provisions of ASTM D885, and then the strength and elongation at the breaking point are obtained. The above process was tested 5 times or more and calculated from the average value. At this time, the tensile speed was 300 mm/min, and the superload was fineness × 1/30 g.

Elastic modulus of copolymerized aramid fiber

As described above, the elastic modulus of the copolymerized aramid fiber was determined by the slope at a load in the range of 3 g/d-4 g/d on the strength-elongation-curve (S-S Curve) that appears when measuring the strength and elongation of the copolymerized aramid fiber.

a: FT-IR graph of heat-treated copolymerized aramid fibers.
b: FT-IR graph of the copolymerized aramid fiber before heat treatment.

Claims (7)

(I) Copolymerized aramid fibers having excellent strength and elasticity, comprising at least one repeating unit selected from the repeating unit represented by the following formula (1) and (ii) the repeating unit represented by the following formula (2) and the repeating unit represented by the following formula (3).
[Formula 1]

[Formula 2]

[X in Formula 2 is -C00H]
[Formula 3]

[X in Formula 3 is -CONH ₂ ] The copolymer aramid fiber of claim 1, wherein the repeating unit content of Formula 2 is 5 to 95 mol%. The copolymer aramid fiber of claim 1, further comprising a repeating unit represented by the following formula (4).
[Formula 4]

The copolymerized aramid fiber of claim 1, wherein the copolymerized aramid fiber has a strength of 28 to 35 g/d, an elongation of 1 to 3%, and an elastic modulus of 900 to 1,500 g/d. (I) Terephthaloyl dichloride is added to the organic solvent in which the aromatic diamine containing cyano paraphenylenediamine is dissolved and reacted to prepare a polymerization solution in which a copolymerized aramid polymer containing a repeating unit represented by the following Chemical Formula 1 is dissolved. Process;
(Ii) the step of solidifying the spun fiber with a coagulating solution of an aqueous hydrochloric acid solution after spinning the polymerization solution into a fibrous form; And
(Iii) heat-treating the coagulated fiber; a method for producing a copolymerized aramid fiber having excellent strength and elastic modulus, comprising a.
[Formula 1]

[6] The method of claim 4, wherein cyano paraphenylenediamine alone is used as the aromatic diamine containing cyano-phenylenediamine. The strength and elastic modulus of claim 4, wherein cyano paraphenylenediamine and paraphenylenediamine are used in a molar ratio of 1:9 to 9:1 as an aromatic diamine containing cyano paraphenylenediamine. Method for producing excellent copolymer aramid fibers.

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