Method of dry-spinning para-aramid fiber

Abstract

The present invention provides a method for manufacturing para-aramid fibers, which includes: spinning a polymeric solution containing aramid polymer in an organic solvent through a spinneret into an inert gas to partially remove the organic solvent contained in the spun fiber; contacting the spun fiber with conditioning solution, so as to maintain residual water in fiber in a range of 10 to 15%; and subjecting the treated fiber to drawing, washing and heating in a dry-spinning manner. The present invention may greatly reduce energy consumption and costs for recovery of the solvent, as compared to a conventional manufacturing method of aramid fiber in a wet-spinning manner. Further, the present invention may solve conventional problems such as corrosion of apparatus, deterioration of working environments, or the like, since a concentrated sulfuric acid solvent is not used in a spinning process. Still further, the present invention may conduct drawing and heating after maintaining the residual water in fiber in a range of 10 to 15% before drawing, thereby remarkably improving the strength and elastic modulus of the fiber.

Claims

1. A method of dry-spinning para-aramid fiber, comprising: (i) spinning a polymeric solution, which includes an aramid copolymer having a repeat unit represented by the following Formula I dissolved in an organic solvent, through a spinneret in a fibrous form; (ii) passing the spun fiber into an inert gas to remove a part of the polymerization solvent remained in the fiber; (iii) contacting the fiber which has passed through the inert gas with a conditioning solution which contains an organic solvent and inorganic salt, so as to maintain residual water in fiber in a range of 10 to 15%; and (iv) drawing, washing, drying and heating the fiber in contact with the conditioning solution: ##STR00002## Wherein R.sub.1 is CN, Cl, SO.sub.3H or CF.sub.3, and Ar.sub.1 and Ar.sub.2 are independently each aromatic hydrocarbon having 1 to 4 benzene rings.

2. The method according to claim 1, wherein the conditioning solution is injected to the fiber which has passed through the inert gas to be in contact with the same.

3. The method according to claim 1, wherein the conditioning solution contains 5 to 40 wt. % of organic solvent and 1 to 10 wt. % of inorganic salt, and has a temperature of 30 to 100 C.

Description

BEST MODE FOR CARRYING OUT THE INVENTION

(1) Hereinafter, the present invention will be described in more detail.

(2) A method of dry-spinning aramid fiber according to the present invention, includes: (i) spinning a polymeric solution, which includes an aramid copolymer having a repeat unit represented by the following Formula I dissolved in an organic solvent, through a spinneret in a fibrous form; (ii) passing the spun fiber into an inert gas to remove a part of the polymerization solvent remained in the fiber; (iii) contacting the fiber which has passed through the inert gas with a conditioning solution which contains an organic solvent and inorganic salt so as to maintain residual water in fiber in a range of 10 to 15%; and (iv) drawing, washing, drying and heating the fiber in contact with the conditioning solution.

(3) Specifically, according to the present invention, a polymeric solution, which includes a para-aramid copolymer having a repeat unit represented by the following Formula 1 dissolved in an organic solvent, is spun through a spinneret in a fibrous form.

(4) ##STR00001##

(5) Wherein R.sub.1 is CN, Cl, SO.sub.3H or CF.sub.3, and Ar.sub.1 and Ar.sub.2 are independently each aromatic hydrocarbon having 1 to 4 benzene rings.

(6) The polymeric solution of the present invention may be prepared according to the following processes.

(7) Preparation of Polymeric Solution

(8) Firstly, inorganic salt was dissolved in an organic solvent.

(9) The organic solvent used herein may include amide organic solvents, urea organic solvents, or combined organic solvents thereof. Particular examples of the organic solvent may include N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), hexamethylphosphoamide (HMPA), N,N,N,N-tetramethylurea (TMU), N,N-dimethylformamide (DMF), or a mixture thereof.

(10) The inorganic salt is added to increase a degree of polymerization of aromatic polyamide and may include, for example, halogenated alkali-metal salts or halogenated alkali-earth metal salts such as CaCl.sub.2, LiCl, NaCl, KCl, LiBr, KBr, or the like. Such inorganic salts may be used alone or in combination of two or more thereof.

(11) Subsequently, non-substituted aromatic diamine selected from a group consisting of para-phenylenediamine, 4,4-diaminodiphenyl, 2,6-naphthalenediamine, 1,5-naphthalenediamine and 4,4-diaminobenzanilide was dissolved in an organic solvent containing inorganic salt added thereto. At the same time, substituted aromatic diamine wherein hydrogen in a benzene ring of the aromatic diamine is substituted by CN, Cl, SO.sub.3H or CF.sub.3, was dissolved in the organic solvent containing inorganic salt added thereto. The substituted aromatic diamine and non-substituted aromatic diamine dissolved in the organic solvent containing the inorganic salt may be present in a relative molar ratio ranging from 9:1 to 1:9.

(12) Following this, aromatic diacid halide was added to the organic solvent in at least the same molar amount as of the aromatic diamine, thus preparing the polymeric solution. The aromatic diacid halide may be terephthaloyl dichloride, 4,4-benzoyl dichloride, 2,6-naphthalene dicarboxylic acid dichloride or 1,5-naphthalene dicarboxylic acid dichloride. According to one embodiment of the present invention, the aromatic diacid halide may be terephthaloyl dichloride.

(13) Next, the spun fiber was passed into an inert gas to remove a part of the polymerization solvent remained in the fiber.

(14) Then, the fiber which has passed through the inert gas was contacted with a conditioning solution which contains inorganic salt and an organic solvent, thereby maintaining the residual water in fiber in a range of 10 to 15%.

(15) The conditioning solution may contain 5 to 40 wt. % of organic solvent and 1 to 10 wt. % of inorganic salt, and preferably, have a temperature of 30 to 100 C.

(16) Herein, the conditioning solution is preferably injected to the spun fiber to be in contact with the same.

(17) By contacting the spun fiber with the conditioning solution to maintain the residual water in fiber in a range of 10 to 15%, cut-off of the spun fiber during drawing as a following process may be effectively prevented while improving the strength and elastic modulus of the fiber.

(18) If the residual water in fiber is out of the foregoing range, the fiber does not have desirably improved strength and elastic modulus even after completing following processes such as drawing and heating.

(19) Subsequently, the fiber in contact with the conditioning solution may be subjected to drawing, washing, drying and heating in a dry-spinning manner, thereby manufacturing the para-aramid fiber.

(20) Hereinafter, the present invention will be more clearly understood by the following examples and comparative examples. However, these examples are proposed for concretely explaining the present invention, while not limiting the scope of the present invention to be protected.

Example 1

(21) After providing an organic solvent, that is, N-methyl-2-pyrrolidone (NMP) containing 3 wt. % of CaCl.sub.2 in a reactor under a nitrogen atmosphere, 50 mol % of p-phenylenediamine and 50 mol % of cyano-p-phenylenediamine were added to the reactor then dissolved to prepare a mixed solution.

(22) Then, 100 mol % of terephthaloyl dichloride was added to the reactor filled with the mixed solution, to prepare a polymeric solution containing aramid polymer.

(23) Next, by adding CaO as an alkaline compound to the polymeric solution, hydrochloric acid produced during polymerization was neutralized while removing generated water under vacuum.

(24) After then, the polymeric solution containing the aramid polymer was heated and an amount of the organic solvent was regulated to control a concentration of the aramid polymer to about 16 wt. %.

(25) Subsequently, after spinning the polymeric solution through a spinneret in a fibrous form, the spun fiber passed through a nitrogen gas as an inert gas in order to evaporate and remove about 50% of polymerization solvent remained in the fiber, and then, a water-soluble conditioning solution, which contains 30 wt. % of N-methyl-2-pyrrolidone organic solvent and 5 wt. % of CaCl.sub.2 inorganic salt and has a temperature of 40 C., was injected to the fiber which has passed through the nitrogen gas to be in contact with the same, thus maintaining the residual water in fiber of about 13%. Continuously, the fiber in contact with the conditioning solution was subjected to drawing in a draw ratio of 4.0, washing, drying and heating, thereby manufacturing the para-aramid fiber.

(26) Results of measuring the strength and elastic modulus of the manufactured para-aramid fiber are shown in Table 2.

Examples 2 to 4 and Comparative Examples 1 to 4

(27) Except that the residual water in fiber and draw ratio after contacting the fiber with the conditioning solution were altered as shown in Table 1, the same procedures as described in Example 1 were executed to manufacture the para-aramid fiber.

(28) Results of measuring the strength and elastic modulus of the manufactured para-aramid fiber are shown in Table 2.

(29) TABLE-US-00001 TABLE 1 Conditions of manufacturing Section Residual water (%) Draw ratio Example 1 13 4 Example 2 10 2 Example 3 12 3 Example 4 14 5 Comparative Example 1 8 4 Comparative Example 2 7 2 Comparative Example 3 18 4 Comparative Example 4 22 4

(30) TABLE-US-00002 TABLE 2 Results of evaluation of physical properties Section Strength (g/d) Elastic modulus (g/d) Example 1 25.4 780 Example 2 23.7 750 Example 3 26.2 820 Example 4 27.7 850 Comparative Example 1 21.5 650 Comparative Example 2 20.7 550 Comparative Example 3 22.3 650 Comparative Example 4 21.4 580

INDUSTRIAL APPLICABILITY

(31) The present invention may be applied to manufacturing of para-aramid with improved strength and elastic modulus according to a dry-spinning process.