Method for producing para-type wholly aromatic polyamide fiber

Abstract

To provide a method for producing a para-type wholly aromatic polyamide fiber with an excellent quality, which reduces yarn breakage during a drawing process when a spinning speed is increased.SOLUTION: There is provided a method for producing a para-type wholly aromatic polyamide fiber. The production of the para-type wholly aromatic polyamide fiber is configured in that: after obtaining a dry yarn having a breaking elongation of 30% or more, in a step of hot-drawing the dry yarn, a draw ratio is controlled within a range that satisfies the following formula (1) by controlling an amount of polymer solution passing through a spinneret's outlet hole, and a spinning speed and spinning draft during spinning and coagulation process. Formula (1): Dry yarn breaking Elongation×0.33 / {(heat stretch ratio / 0.8)-3.0}≥1.00.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing para-type wholly aromatic polyamide fibers. More specifically, by skillfully controlling the spinning speed, spinning draft, and heat drawing ratio during the spinning and drawing of para-type wholly aromatic polyamide, it is possible to prevent yarn breakage during the drawing process and minimize the hairiness of the resulting fibers. The present invention relates to a method for producing para-type wholly aromatic polyamide fibers.

Background Art

[0002] Wholly aromatic polyamide fibers are fibers that are excellent in high strength, high modulus, high heat resistance, etc. Taking advantage of these high functional properties, they are used in various fields as industrial fibers. In recent years, as they are used in a wide range of applications, the demand for further improvement in quality and physical properties has been increasing.

[0003] As a method for producing para-type wholly aromatic polyamide fibers, for example, an isotropic solution containing para-type wholly aromatic polyamide and a solvent is discharged from a die into an inert gas, and then brought into contact with a coagulating liquid to form a coagulated yarn. Washing and drawing are performed in a water bath, and then dried to form a dried yarn. Subsequently, heat drawing is further performed at a higher temperature to obtain fibers (see Patent Document 1).

[0004] However, for the purpose of improving productivity, when the amount of polymer solution discharged from the die is increased and the spinning speed is increased, yarn breakage occurs in each stretching process after obtaining the coagulated yarn, and the hairiness of the resulting fibers increases.

[0005] Therefore, a technique for rectifying the flow of the polymer solution passing through the discharge holes of the die to reduce hairiness has been studied (see Patent Document 2). This method has the effect of reducing hairiness caused by discharge defects, but the reduction of hairiness caused by the process after discharging the polymer solution is insufficient.

[0006] In addition, a technique for reducing hairiness has been studied by setting the fineness, spinning speed, and spinning draft of the coagulated yarn within specific ranges (see Patent Document 3). Although this method has the effect of reducing hairiness caused by the coagulated yarn, further yarn breakage and reduction of hairiness in each process have been demanded.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present invention is to solve the problems in such conventional technologies, increase the amount of polymer solution discharged from the die, reduce yarn breakage in each stretching step after obtaining the coagulated yarn when the spinning speed is increased, and provide a method for producing para-type wholly aromatic polyamide fibers with excellent quality.

Means for Solving the Problems

[0009] As a result of intensive studies to solve the above problems, the present inventor has found that the above problems can be solved when the spinning speed, spinning draft, and heat stretching magnification during spinning and stretching of para-type wholly aromatic polyamide are skillfully controlled, and thus the present invention has been completed.

[0010] That is, according to the present invention, 1. A method for producing para-type wholly aromatic polyamide fibers, wherein the amount of polymer solution passing through the discharge holes of a spinning die used when discharging a para-type wholly aromatic polyamide polymer solution is 2.0 cc / min or more, in the spinning and coagulation step of coagulating the polymer solution to obtain a coagulated yarn, Set the spinning speed to 45 - 85 m / min and the spinning draft to 0.80 - 1.50, furthermore, wash and dry the coagulated yarn to obtain a dry yarn with an elongation at break of 30% or more, In the step of thermally stretching the dry yarn, set the stretching ratio within the range satisfying the following formula (1), a method for producing para - type wholly aromatic polyamide fiber characterized by that, Elongation at break of dry yarn × 0.33 / { (Thermal stretching ratio / 0.8) - 3.0} ≥ 1.00 (1) and, 2. The method for producing para - type wholly aromatic polyamide fiber according to 1 above, wherein the para - type wholly aromatic polyamide fiber is copoly - para - phenylene·3,4’ - oxydiphenylene terephthalamide fiber, is provided.

Effect of the Invention

[0011] According to the present invention, when increasing the amount of polymer solution discharged from the spinneret and speeding up the spinning speed, it is possible to reduce yarn breakage in each stretching step after obtaining the coagulated yarn, and provide a method for producing para - type wholly aromatic polyamide fiber with excellent quality.

Embodiment for Carrying Out the Invention

[0012] The method for producing para - type wholly aromatic polyamide fiber according to the present invention is characterized in that in high - speed spinning where the amount of polymer solution passing through the discharge holes of the spinneret used when discharging the polymer solution is 2.0 cc / min or more, the spinning speed is 45 - 85 m / min and the spinning draft is 0.80 - 1.50.

[0013] In addition, increasing the amount of polymer solution passing through the discharge holes of the spinneret means that the production amount per unit time of single yarn can be increased, and increasing the amount of the polymer solution to 2.0 cc / min or more is important in the effect of the present invention.

[0014] Next, by setting the spinning speed and the spinning draft within the above ranges, the elongation at break of the dried yarn obtained by washing and drying the coagulated yarn can be made 30% or more, and yarn breakage in the steps until the dried yarn is obtained can be reduced.

[0015] Next, by thermally stretching the dried yarn at a draw ratio set within the range satisfying the following formula (1), yarn breakage in the thermal stretching step can be reduced, and para-type wholly aromatic polyamide fibers can be obtained at a high winding speed. Elongation at break of dried yarn × 0.33 / {(Draw ratio / 0.8) - 3.0} ≥ 1.00 (1)

[0016] Hereinafter, the constituent elements of the present invention will be described in more detail. <Para-type wholly aromatic polyamide> The wholly aromatic polyamide to which the production method of the present invention can be applied is a polyamide in which one or more divalent aromatic groups are directly linked by an amide bond. The aromatic group includes those in which two aromatic rings are bonded via an oxygen, sulfur, or alkylene group, or those in which two or more aromatic rings are directly bonded. Further, the divalent aromatic group 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.

[0017] Examples of such para-type wholly aromatic polyamides include polyparaphenylene terephthalamide, copolyparaphenylene·3,4'-oxydiphenylene terephthalamide in which a terephthalic acid component, a 3,4'-diaminodiphenyl ether component, and a paraphenylenediamine component are copolymerized, and copolyparaphenylene·phenylbenzimidazole·terephthalamide in which a terephthalic acid component, an aromatic diamine component having a phenylbenzimidazole skeleton, and a paraphenylenediamine component are copolymerized. Further, as the para-type wholly aromatic polyamide to which the production method of the present invention can be applied, it may be a single species or a combination of two or more species.

[0018] Furthermore, in the production method of the present invention, since the mechanical strength, heat resistance, and chemical resistance are particularly excellent, it is preferable to use polyparaphenylene terephthalamide or copolyparaphenylene-3,4'-oxydiphenylene terephthalamide. Furthermore, since it is soluble in an amide solvent or the like and has excellent moldability, and the tensile properties such as strength and elastic modulus can be significantly improved by heat stretching, it is most preferable to use copolyparaphenylene-3,4'-oxydiphenylene terephthalamide.

[0019] <Method for producing para-type wholly aromatic polyamide fiber> The method for producing the para-type wholly aromatic polyamide fiber of the present invention may be a so-called wet method or a semi-dry semi-wet method. That is, a para-type wholly aromatic polyamide solution (spinning solution: dope) containing para-type wholly aromatic polyamide and a solvent is discharged from a spinneret into an inert gas (air gap), and further immersed in a coagulating liquid composed of a poor solvent, or directly discharged into the coagulating liquid to obtain a coagulated yarn. After the obtained coagulated yarn is washed with water, stretched in a water bath, etc. as necessary, drying is carried out to obtain a dried yarn, and further, processes such as heat stretching are carried out on the dried yarn to obtain the final para-type wholly aromatic polyamide fiber.

[0020] [Para-type wholly aromatic polyamide solution (spinning solution: dope)] The method for preparing a para-type wholly aromatic polyamide solution (spinning solution: dope) containing a solvent is not particularly limited, and a known method can be adopted.

[0021] Examples of the solvent used for preparing the para-type wholly aromatic polyamide solution (spinning solution: dope) include N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylcaprolactam (NMC), etc. The solvent used may be a single species or a mixed solvent of two or more species. Furthermore, the solvent used for the polymerization of the para-type wholly aromatic polyamide may be used as it is.

[0022] In addition, for the purpose of imparting functionality or the like to the fibers, other optional components such as additives can be blended within a range not exceeding the gist of the present invention. The other optional components can be introduced in the preparation of the para-type wholly aromatic polyamide solution (spinning solution: dope). The method of introduction is not particularly limited. For example, it can be introduced using a stirrer or a mixer with respect to the dope.

[0023] Note that the polymer concentration in the para-type wholly aromatic polyamide solution (spinning solution: dope), that is, the concentration of the para-type wholly aromatic polyamide, is preferably in the range of 1.0 to 10% by mass. When the polymer concentration in the para-type wholly aromatic polyamide solution (spinning solution: dope) is less than 1.0% by mass, since the entanglement of the polymer is small, the viscosity required for spinning cannot be obtained, and the discharge stability during spinning decreases. On the other hand, when the polymer concentration exceeds 10% by mass, since the viscosity of the dope increases rapidly, the discharge stability during spinning decreases, and it becomes difficult to perform stable spinning due to a rapid pressure increase in the spinning pack.

[0024] In the present invention, when discharging the above dope from the discharge holes of the spinneret, it is important that the amount of the polymer solution passing through the discharge holes is 2.0 cc / min or more. When the amount of the polymer solution is less than 2.0 cc / min, the effect of increasing the production amount per unit time of the single fiber compared to the prior art becomes insufficient. The amount of the polymer solution is more preferably 2.1 cc / min or more, 2.4 cc / min or more for the purpose of increasing the production amount per unit time of the single fiber. The preferable range is 2.0 cc / min to 3.0 cc / min.

[0025] [Spinning and coagulation process] In the spinning and coagulation process, fibers are formed from the para-type wholly aromatic polyamide solution (dope) adjusted as described above by the wet spinning method or the semi-dry semi-wet spinning method provided with an air gap.

[0026] (Spinning speed) In the present invention, the spinning speed is in the range of 45 to 85 m / min. The spinning speed is preferably in the range of 50 to 80 m / min, and most preferably in the range of 55 to 75 m / min. If the spinning speed is less than 45 m / min, the spinning speed is low compared to the high winding speed, and it is necessary to increase the draw ratio in each drawing step after obtaining the coagulated yarn, making it difficult to reduce yarn breakage. If the spinning speed exceeds 85 m / min, the influence of disturbances due to turbulence and resistance of the coagulating liquid and washing liquid on the traveling fiber becomes large, and the breaking elongation of the dried yarn obtained by washing and drying the coagulated yarn decreases, resulting in more yarn breakage.

[0027] (Spinning draft) In the present invention, the spinning draft in the coagulation step is set to the range of 0.80 to 1.50. The spinning draft is more preferably 0.90 to 1.45, and most preferably 1.00 to 1.40. If the spinning draft is less than 0.80, the tension of the coagulated yarn formed in the coagulation bath is low, and the take-up stability of the coagulated yarn is reduced. On the other hand, if the spinning draft exceeds 1.50, the breaking elongation of the coagulated yarn is reduced, and the breaking elongation of the dried yarn obtained by washing and drying the coagulated yarn is also reduced, resulting in more yarn breakage in each drawing step.

[0028] In the present invention, the "spinning draft" refers to the speed at which the coagulated yarn is taken out of the coagulation bath. The value is calculated by dividing the linear velocity at which the fully aromatic polyamide solution (spinning solution: dope) is extruded from the nozzle. The linear velocity during ejection can be calculated by the following formula (2). Linear velocity=(4×V×10 -6 ) / (3.14×(D / 1000) 2 ×F) (2) V: Discharge volume from nozzle (cc / min) D: diameter of nozzle hole (mm) F: Number of filaments

[0029] [Water washing / drying process] In the washing process, the coagulated yarn obtained above is washed as necessary. Specifically a method of continuously passing the yarn through a water bath at 100°C or lower is used. If necessary, stretching may be performed in the water bath by a known method including Patent Document 1.

[0030] In the drying process, the coagulated yarn washed as necessary is dried to obtain a dried yarn. Specifically drying by a heating roller at 120 to 220°C is used. It is important that the elongation at break of the dried yarn thus obtained is 30% or more. If the elongation at break of the dried yarn is less than 30%, since the elongation at break of the yarn in the spinning and coagulation processes and the washing process is also low, yarn breakage occurs during stretching in each process.

[0031] On the other hand, it is preferable that the elongation at break of the dried yarn is 60% or less. If the elongation at break of the dried yarn exceeds 60%, it is likely to fall below the lower limits of the spinning speed and the spinning draft in the present invention, which is not preferable.

[0032] [Thermal stretching and other processes] In the step of thermally stretching the dried yarn, it is important to set the stretching ratio within a range that satisfies the following formula (1). Elongation at break of dried yarn × 0.33 / {(Thermal stretching ratio / 0.8) - 3.0} ≧ 1.00 (1)

[0033] In the present invention, the preferable range of the thermal stretching ratio is 10 to 18 times, 10.5 to 17.5 times, and most preferably in the range of 11 to 17 times. If the thermal stretching ratio is less than 10 times, it is necessary to increase the spinning speed with respect to the high winding speed, so the elongation at break of the dried yarn decreases and the number of yarn breakages may increase. On the other hand, if the thermal stretching ratio exceeds 18 times, the yarn orientation due to thermal stretching progresses excessively, and stretching may not be possible due to yarn breakage. Also, if sequential stretching is employed, the stretching stability can be improved.

Examples

[0034] The present invention will be described in more detail with reference to the following examples. It should be noted that the examples are illustrative and the present application is not limited thereto.

[0035] <Measurement and Evaluation Methods> (1) Yarn breakage in the water washing process The coagulated yarn was continuously passed through a water bath, and the speed of the conveying roller on the outlet side of the water bath was set to 1.2 times the speed of the conveying roller on the inlet side (spinning speed). The presence or absence of yarn winding around the conveying roller due to yarn breakage was observed. When no yarn winding occurred during the acquisition of 6000 m of the washed coagulated yarn, it was regarded as "no" yarn breakage in the water washing process; when yarn winding occurred, it was regarded as "yes" yarn breakage in the water washing process.

[0036] (2) Hairiness generation rate The fibers obtained in the hot stretching process were rewound by 1000 m and visually observed to count the number of hairiness.

[0037] (3) Elongation at break of the dry yarn The dry yarn was measured under the following measurement conditions using a tensile testing machine (manufactured by Instron Corporation, model: Instron 201X type). [Measurement Conditions] Temperature: Room temperature Measurement sample length: 25.4 mm Tensile speed: 10 mm / min Number of test specimens: 20

[0038] <Example 1> [Preparation Process of Spinning Solution] As a spinning solution (dope), a 6 mass% N-methylpyrrolidone (NMP) solution of copolyparaphenylene·3,4'-oxydiphenylene terephthalamide (an all-aromatic polyamide with a copolymerization molar ratio of 1:1) was prepared.

[0039] [Spinning and Coagulation Process] The spinning solution (dope) was discharged from a spinneret having 1000 discharge holes, and spun into a coagulation bath filled with an aqueous solution at 50 °C with an NMP concentration of 30% by mass through an air gap to obtain coagulated yarns (semi-dry semi-wet spinning method). At this time, the amount of the polymer solution passing through the discharge holes of the spinneret was 2.7 cc / min, the spinning speed was 70 m / min, and the spinning draft was 1.3.

[0040] [Washing and Drying Process] The coagulated yarns were washed in a water bath at 60 °C while evaluating the breakage of the yarns during the washing process. No yarn breakage occurred. The drawn yarns in the washing process were dried on a heating roller at 220 °C to obtain dried yarns. The elongation at break of the dried yarns was 38.2%.

[0041] [Hot Drawing and Other Processes] Finally, the dried yarns were drawn 11.7 times at a temperature of 540 °C and wound up to obtain copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fibers with a single fiber fineness of 1.67 dtex. The hairiness generation rate is shown in Table 1.

[0042] [Example 2] In the washing and drying process, copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fibers with a single fiber fineness of 1.67 dtex were obtained in the same manner as in Example 1 except that the temperature of the water bath was 75 °C. No yarn breakage occurred in the evaluation of yarn breakage during the washing process. The elongation at break of the dried yarns obtained in the drying process was 38.9%. The hairiness generation rate of the obtained fibers is shown in Table 1.

[0043] [Example 3] In the spinning and coagulation process, the spinning speed was 60 m / min and the spinning draft was 1.1. In the washing and drying process, the temperature of the water bath was 75 °C. In the hot drawing process, copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fibers with a single fiber fineness of 1.67 dtex were obtained in the same manner as in Example 1 except that the fibers were drawn 13.7 times. No yarn breakage occurred in the evaluation of yarn breakage during the washing process. The elongation at break of the dried yarns obtained in the drying process was 49.2%. The hairiness generation rate of the obtained fibers is shown in Table 1.

[0044] <Comparative Example 1> In the spinning and coagulation process, except that the spinning speed was 89 m / min and the spinning draft was 1.6, the process was carried out in the same manner as in Example 2 to obtain copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fibers. However, yarn breakage occurred in the water washing process, so it could not be subjected to the heat drawing process, and the evaluation up to the drying process was carried out. The elongation at break of the obtained dried yarn was 25.9%.

[0045] <Comparative Example 2> In the water washing and drying process, except that the temperature of the water bath was 60°C, the process was carried out in the same manner as in Example 3 to obtain copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fibers with a single fiber fineness of 1.67 dtex. In the evaluation of yarn breakage in the water washing process, no yarn breakage occurred. The elongation at break of the dried yarn obtained in the drying process was 40.2%. The hairiness generation rate of the obtained fibers is shown in Table 1.

[0046] <Comparative Example 3> In the spinning and coagulation process, except that the spinning speed was 52 m / min and the spinning draft was 0.95, and in the heat drawing process, it was drawn 15.6 times, the process was carried out in the same manner as in Example 1 to obtain copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fibers with a single fiber fineness of 1.67 dtex. In the evaluation of yarn breakage in the water washing process, no yarn breakage occurred. The elongation at break of the dried yarn obtained in the drying process was 40.9%. The hairiness generation rate of the obtained fibers is shown in Table 1.

[0047] <Comparative Example 4> In the spinning and coagulation process, except that the spinning speed was 43 m / min and the spinning draft was 0.78, and in the heat drawing process, it was drawn 19.0 times, the process was carried out in the same manner as in Example 1 to attempt to obtain copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fibers. However, in the evaluation of yarn breakage in the water washing process, although no yarn breakage occurred, yarn breakage occurred in the heat drawing process, and no fiber sample for evaluating the hairiness generation rate was obtained. In addition, the elongation at break of the dried yarn obtained in the drying process was 43.3%.

[0048]

Table 1

Industrial Applicability

[0049] According to the present invention, when the amount of the polymer solution discharged from the nozzle is increased and the spinning speed is increased, yarn breakage in each stretching step after obtaining the coagulated yarn can be reduced, and a method for producing para-type wholly aromatic polyamide fibers with excellent quality can be provided. Therefore, the industrial applicability is high and its industrial value is extremely large.

Claims

1. A method for producing para-type wholly aromatic polyamide fibers, wherein the amount of the polymer solution passing through the discharge holes of a spinneret used when discharging a para-type wholly aromatic polyamide polymer solution is 2.0 cc / min or more, in the spinning and coagulation step of coagulating the polymer solution to obtain coagulated yarns, the spinning speed is 45 to 85 m / min and the spinning draft is 0.80 to 1.50, further, a step of washing and drying the coagulated yarns to obtain dried yarns having an elongation at break of 30% or more, and in the step of thermally stretching the dried yarns, the draw ratio is set within a range satisfying the following formula (1). A method for producing para-type wholly aromatic polyamide fibers, characterized in that: Elongation at break of dried yarn × 0.33 / {(Draw ratio / 0.8) - 3.0} ≥ 1.00 (1)

2. The method for producing para-type wholly aromatic polyamide fibers according to claim 1, wherein the para-type wholly aromatic polyamide fibers are copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fibers.

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