JP2006207064A - Method for producing aromatic copolyamide fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an aromatic copolyamide fiber having a small single yarn fineness and excellent in mechanical characteristics, such as a tensile strength and an initial modulus. <P>SOLUTION: This method for producing the aromatic copolyamide fiber comprises extruding a solution of an aromatic copolyamide containing structural repeating units of formula (1) and formula (2) through a spinneret, then coagulating the solution in an aqueous NMP solution having a temperature of 20-50°C and a concentration of 10-50 wt.%, further drawing the coagulated yarn in an aqueous NMP solution having a temperature of 20-50°C and a concentration of 30-80 wt.% at a draw ratio of 1.3 to 2.5 times, and finally heat-treating the drawn yarn. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing an aromatic copolyamide fiber having a fine single yarn fineness and excellent mechanical properties such as tensile strength and initial modulus.

  Conventionally, aramid fibers composed of an aromatic dicarboxylic acid component and an aromatic diamine component, especially para-based aramid fibers, have been widely used in industrial and clothing applications by taking advantage of their strength, high elastic modulus, and high heat resistance. It has been.

  A typical aramid fiber is, for example, polyparaphenylene terephthalamide (PPTA) fiber. Although this fiber has many advantages, it has a process defect in that it is produced by a so-called liquid crystal spinning method utilizing the optical anisotropy of polymer dope, and the fiber properties are mechanical properties. Among them, there are disadvantages such as not necessarily high strength and low elongation and insufficient toughness.

  In order to solve this problem, aromatic copolyaramid having high solubility in a known amide solvent, which can be easily spun, and the resulting fiber has high tensile strength and high initial modulus after drawing treatment Attempts have been made to develop.

  For example, JP-A-7-300534 discloses an aromatic copolyamide that forms an isotropic solution with respect to an amide solvent by polycondensation of dicarbonyl dihalides and at least two diamines. It has been proposed to produce fibers.

However, the aromatic copolyamide fiber disclosed in the above publication has insufficient mechanical properties such as tensile strength and initial modulus, and a method for producing the fiber capable of exhibiting excellent mechanical properties has not yet been developed. The actual situation is not proposed.
Japanese Patent Laid-Open No. 7-300534

  The present invention has been made against the background of the above prior art, and its object is to provide a method for producing an aromatic copolyamide fiber having a fine single yarn fineness and excellent mechanical properties such as tensile strength and initial modulus. There is.

  That is, according to the present invention, when producing an aromatic copolyamide fiber, an aromatic containing 30 to 100 mol% of structural repeating units of the following formula (1) and the following formula (2) with respect to the total amount of the structural units. After the copolyamide solution is discharged from the spinneret, the copolyamide solution is coagulated in an NMP aqueous solution having a temperature of 20 to 50 ° C. and a concentration of 10 to 50% by weight, and then in an NMP aqueous solution having a temperature of 20 to 50 ° C. and a concentration of 30 to 80%. A method for producing an aromatic copolyamide fiber is provided, which is drawn by 3 to 2.5 times and further heat-treated.

  According to the present invention, there is provided a method for producing an aromatic copolyamide fiber having a fine single yarn fineness and excellent mechanical properties such as tensile strength and initial modulus.

Hereinafter, embodiments of the present invention will be described in detail.
The aromatic copolyamide referred to in the present invention is a polymer in which one or two or more divalent aromatic groups are directly linked by an amide bond, and the two aromatic rings are oxygen atoms. , Sulfur or an alkylene group. In addition, these divalent aromatic groups may include a lower alkyl group such as a methyl group or an ethyl group, a halogen group such as a methoxy group, or a chloro group.

The aromatic copolyamide of the present invention is obtained by reacting an aromatic dicarboxylic acid chloride with an aromatic diamine in an amide polar solvent in accordance with a conventionally known method to obtain a polymer solution.
The aromatic dicarboxylic acid dichloride in the present invention may be a conventionally known one. Examples thereof include terephthalic acid dichloride, 2-chloroterephthalic acid dichloride, 3-methylterephthalic acid dichloride, 4,4′-biphenyldicarboxylic acid dichloride, 2,6-naphthalenedicarboxylic acid dichloride, and isophthalic acid dichloride.

  In the present invention, two kinds of aromatic diamines are used. One aromatic diamine is one selected from substituted or unsubstituted para-type aromatic diamines, and may be generally known ones such as para-type phenylene diamine and para-type biphenylene diamine. The other aromatic diamine is one selected from aromatic diamines having a substituted or unsubstituted phenylbenzimidazole group. Among them, easy availability and excellent tensile strength of the resulting fiber From the viewpoint of initial modulus and the like, 5 (6) -amino-2- (4-aminophenyl) benzimidazole is preferable.

  Examples of the amide polar solvent used in the present invention include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylimidazolidinone and the like. N-methyl-2-pyrrolidone is preferred from the viewpoints of handleability and stability from polymerization of the aromatic polyamide to dope adjustment and wet spinning process, and toxicity of harmful solvents.

  The aromatic copolyamide fiber produced by the present invention needs to contain structural repeating units of the following formula (1) and the following formula (2), and the structural repeating unit of the following formula (2) is based on the total amount of the structural units. 30 to 100 mol% is necessary. The preferred content of the structural repeating unit is in the range of 50 to 100 mol%. When the content is less than 30 mol%, there arises a problem that the reaction solution becomes cloudy in the polymerization reaction, and it becomes difficult to produce a yarn with such a cloudy dope.

In the present invention, in order to increase the solubility of the aromatic copolyamide in the amide polar solvent, an appropriate amount of a known inorganic salt is generally added before, during or at the end of the polymerization. Examples of such salts include lithium chloride and calcium chloride. The amount of the salt added is preferably 3 to 10% by weight. If the addition amount exceeds 10% by weight, it is not preferable because it becomes difficult to dissolve the whole amount in the amide polar solvent. On the other hand, when it is less than 3% by weight, the effect of improving the solubility is insufficient, which is not preferable.
After completion of the reaction, a basic inorganic compound such as sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxide or the like is added and neutralized as necessary.

  The concentration of the polymer produced in the polymerization reaction with respect to the solvent is important. In order to obtain a homogeneous polymer having a high degree of polymerization, the concentration of the produced polymer is preferably 10% by weight or less. In particular, a range of 3% to 8% is advantageous for obtaining a stable polymer.

  In the present invention, the aromatic copolyamide dope is extruded into a coagulating liquid to obtain a coagulated yarn. The coagulation liquid in the present invention is composed of an aqueous solution composed of two components of an amide solvent and water. As the amide solvent, N-methyl-2-pyrrolidone is preferable from the viewpoints of handleability, stability, toxicity of harmful solvents, and the like.

The concentration of the amide solvent in the aqueous solution needs to be 10 to 50% by weight. When the concentration exceeds 50%, the coagulation of the aromatic copolyamide do not proceed, the close contact between the filamentous materials occurs, and continuous yarn production becomes difficult. On the other hand, if the concentration is less than 10%, plasticization does not proceed sufficiently, and the stretchability at the time of subsequent stretching is lowered, which is not preferable.
The temperature of the coagulation bath is closely related to the composition of the coagulation bath, but if the temperature is too high, the yarns become more closely adhered to each other and workability is also deteriorated, so the temperature needs to be 20 to 50 ° C.

In the present invention, after the aromatic copolyamide yarn is taken from the coagulation bath, it is sent into an aqueous solution composed of two components of an amide solvent and water, and 1.3 to 2.5 times in the aqueous solution. Stretched. The amide solvent concentration of the NMP aqueous solution needs to be 30 to 80%. If the concentration exceeds 80%, the aromatic copolyamide yarn dissolves in the NMP solution, and thus it is difficult to continuously produce yarn. Further, when the concentration is less than 30%, plasticization does not proceed sufficiently, and it is difficult to ensure the above draw ratio. If the temperature of the aqueous NMP solution is too high, the yarns will be closely adhered to each other and the workability will deteriorate, so the temperature needs to be 20 to 50 ° C.
Subsequently, the aromatic copolyamide yarn is subjected to heat treatment after sufficiently removing the solvent in the water washing step and sufficiently drying in the drying step.

In the present invention, the heat treatment temperature of the yarn is preferably in the range of 300 to 550 ° C. When the temperature is less than 300 ° C., the fiber cannot be sufficiently crystallized, so that sufficient tensile strength and initial modulus may not be obtained. On the other hand, when the temperature exceeds 550 ° C., sufficient tensile strength and initial modulus may not be obtained because the fiber causes thermal degradation.
The aromatic copolyamide fiber thus obtained preferably has a tensile strength of 20 cN / dtex or more and an initial modulus of 500 cN / dtex or more.

Hereinafter, the present invention will be described more specifically with reference to examples. In addition, each characteristic in an Example was evaluated in accordance with the following method.
(1) Viscosity (ηinh)
The viscosity was measured at 30 ° C. for a solution with a polymer concentration of 0.5 g / dl in 98% concentrated sulfuric acid.

[Example 1]
1.940 L of N-methyl-2-pyrrolidone (NMP) was charged into a stirring tank having a stirring blade through which nitrogen was flowing, and then 60.0 g of sufficiently dried calcium chloride was charged and dissolved. Subsequently, 11.0 g (30 mol%) of paraphenylenediamine and 53.0 g (70 mol%) of 5 (6) -amino-2- (4-aminophenyl) benzimidazole were weighed and dissolved. Subsequently, 68.6 g (100 mol%) of terephthalic acid chloride was added and reacted to obtain a polymer solution. To this product, 110.0 g of NMP dispersion containing 22.5% by weight of calcium hydroxide was added for neutralization reaction.
The viscosity (ηinh) measured for the polymer deposited from the resulting polymer solution was 6.0.

Using the obtained dope, it was discharged at a rate of 3.5 cc / min from a spinneret having a hole diameter of 0.15 mm and a hole number of 25 holes, and an NMP concentration of 30% by weight and a temperature of 50 ° C. through a void portion called an air gap Spinned into an aqueous solution to obtain a coagulated yarn. Next, the film was stretched at a stretching ratio of 2.0 times in an NMP aqueous solution having a temperature of 30 ° C. and a concentration of 70%. After drawing, it was washed with water, dried, then heat-treated at a temperature of 450 ° C., and wound at a speed of 30.0 m / min to obtain a 42 dtex / 25 fil yarn.
The mechanical properties of the fiber were a tensile strength of 24.9 cN / dtex and an initial modulus of 900 cN / dtex.

[Examples 2-6, Comparative Examples 1-2]
Aromatic copolyamide fiber in the same manner as in Example 1 except that the addition ratio of diamines, the draw ratio in the NMP aqueous solution, and the heat treatment temperature of the aromatic copolyamide fiber are as shown in Table 1 in accordance with the above production method. Got. The results are summarized in Table 1.

  According to the present invention, there is provided a method for producing an aromatic copolyamide fiber having a fine single yarn fineness and excellent mechanical properties such as tensile strength and initial modulus.

Claims (3)

When producing an aromatic copolyamide fiber, an aromatic copolyamide solution containing 30 to 100 mol% of structural repeating units of the following formula (1) and the following formula (2) with respect to the total amount of the structural units is discharged from the spinneret. After that, it is solidified in an NMP aqueous solution at a temperature of 20 to 50 ° C. and a concentration of 10 to 50% by weight, and then stretched 1.3 to 2.5 times in an NMP aqueous solution at a temperature of 20 to 50 ° C. and a concentration of 30 to 80%. A process for producing an aromatic copolyamide fiber, characterized by further performing heat treatment.

  The method for producing an aromatic copolyamide fiber according to claim 1, wherein the heat treatment temperature is 300 to 550 ° C.   The method for producing an aromatic copolyamide fiber according to claim 1 or 2, wherein the aromatic copolyamide fiber has a tensile strength of 20 cN / dtex or more and an initial modulus of 500 cN / dtex or more.