JP2010150729A - Process for making of para-type fully aromatic copolyamide fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the process for making para-type fully aromatic copolyamide fiber which is free from any lowering in productivity due to entanglement of single filament under solidification. <P>SOLUTION: In manufacturing para-type fully aromatic copolyamide fiber including structural repeating unit (1) expressed by the following formula (1), the flow rate of a solidifying solution at the time of solidifying fully aromatic copolyamide solution within a solidifying bath is to be made 3.60 m/h to 5.20 m/h for each piece of filament, provided, however, that the formula (1) is expressed as: -CO-Ar<SP>1</SP>-CO-NH-Ar<SP>2</SP>-NH-(1), wherein Ar<SP>1</SP>and Ar<SP>2</SP>are respectively independent of each other, representing unsubstituted or substituted bivalent aromatic group. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a para-type wholly aromatic copolyamide fiber excellent in production efficiency in which no single yarn is mixed in wet spinning.

It is well known that para-type wholly aromatic copolyamide fibers have various excellent fiber properties such as high strength, high elastic modulus, high heat resistance, and excellent chemical resistance. And, utilizing these excellent physical and chemical properties, they are industrially used for reinforcing materials of various matrices, ropes and the like.
In recent years, with the expansion of these applications, it has been strongly desired to increase the number of spindles and increase the spinning speed in the spinning process for obtaining para-type wholly aromatic copolyamide fibers. However, in the production of aramid fibers (fully aromatic polyamide fibers), if the same coagulation bath is used for high-speed production, the coagulation liquid flow tends to increase, and the turbulence at the coagulation liquid interface increases, and as a result, Single yarn mixing easily occurred, and it was difficult to obtain a uniform process quality and good process tone.

Here, for the purpose of suppressing the mixing of the single yarn, for example, introduction of a new apparatus or introduction of a new coagulation bath has been studied. However, the introduction of a new apparatus or coagulation bath causes a problem of increased production costs.
Further, in Patent Document 1, the polymer solution flow discharged from the die is disturbed by contact with the interface by optimizing the substitution rate of the coagulating liquid and the spinning draft, that is, suppressing the liquid disturbance at the coagulating liquid interface. Methods of suppressing have been proposed. According to this method, although the liquid disturbance at the coagulating liquid interface is improved to some extent, the suppression of the single yarn mixing has not been sufficient yet.
Therefore, the actual situation is that no method for producing a wholly aromatic polyamide fiber that completely suppresses the mixing of single yarn and has excellent production efficiency has not been proposed yet.
JP-A-5-311510

  The present invention has been made against the background of the above-described prior art, and its object is to provide a method for producing para-type wholly aromatic copolyamide fiber that does not cause a decrease in productivity due to mixing of single yarn during coagulation. is there.

The present inventor has intensively studied in view of the above problems. As a result, it has been found that the above-mentioned problems can be solved by setting the flow rate of the coagulation liquid when coagulating the wholly aromatic copolyamide solution to a specific range, and the present invention has been completed.
That is, the present invention is a method for producing a para-type wholly aromatic copolyamide fiber containing a structural repeating unit (1) represented by the following formula (1), wherein the wholly aromatic copolyamide solution is coagulated in a coagulation bath. The method for producing para-type wholly aromatic copolyamide fibers is characterized in that the flow rate of the coagulation liquid is 3.60 m / h to 5.20 m / h per filament.
—CO—Ar ¹ —CO—NH—Ar ² —NH— (1)
[In Formula (1), Ar ¹ and Ar ² are each independent and represent an unsubstituted or substituted divalent aromatic group. ]

  According to the present invention, para-type wholly aromatic copolyamide fibers can be obtained without causing a decrease in productivity due to mixing of single yarns during coagulation.

Hereinafter, embodiments of the present invention will be described in detail.
<Para-type wholly aromatic copolyamide>
The para-type wholly aromatic copolyamide in the present invention (hereinafter also referred to as “fully aromatic copolyamide”) is a polymer in which one or more divalent aromatic groups are directly linked by an amide bond. . The aromatic group may be one in which two aromatic rings are bonded with oxygen, sulfur, or an alkyl group. In addition, these divalent aromatic rings may be unsubstituted or substituted with a lower alkyl group such as a methyl group or a methyl group, or a halogen group such as a methoxy group or a chlorine group. The type and the number of substituents are not particularly limited.

[Method for producing para-type wholly aromatic copolyamide]
The para-type wholly aromatic copolyamide used in the present invention can be obtained by a polycondensation reaction of an aromatic dicarboxylic acid dichloride and an aromatic diamine in an amide solvent according to a generally known method.

(Aromatic dicarboxylic acid dichloride)
In the wholly aromatic copolyamide of the present invention, examples of the aromatic dicarboxylic acid dichloride used in the structural repeating unit of the above formula (1) include terephthalic acid dichloride, 2-chloroterephthalic acid dichloride, and 3-methylterephthalic acid dichloride. , 4′-biphenyldicarboxylic acid dichloride, 2,6-naphthalenedicarboxylic acid dichloride, isophthalic acid dichloride, and the like. These aromatic dicarboxylic acid dichlorides can be used not only in one type but also in two or more types, and the composition ratio is not particularly limited. Among these, terephthalic acid dichloride is most preferable from the viewpoints of versatility and mechanical properties of fibers.

(Aromatic diamine)
Among the aromatic diamines used in the present invention, examples of the diamine used in the structural repeating unit (1) represented by the above formula (1) include p-phenylenediamine, 2-chloro p-phenylenediamine, 2, 5-dichloro p-phenylenediamine, 2,6-dichloro p-phenylenediamine, m-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4 '-Diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone and the like can be mentioned, but are not limited thereto. These aromatic diamines can be used not only in one kind but also in two or more kinds, and the composition ratio is not particularly limited.
In these, it is preferable to use together 2 or more types of diamine chosen from p-phenylenediamine, m-phenylenediamine, and 3,4'-diaminodiphenyl ether.

(Amide solvent)
Examples of the amide solvent used for the polymerization and spinning of the wholly aromatic copolyamide of the present invention include N-methyl-2-pyrrolidone (hereinafter referred to as NMP), N, N-dimethylformamide, N, N-dimethylacetamide. And dimethylimidazolidinone. Among these, it is most preferable to use NMP from the viewpoints of versatility, harmfulness, handleability, solubility in a wholly aromatic copolyamide polymer, and the like.

(Polycondensation reaction)
The polycondensation reaction between the aromatic diamine and the aromatic dicarboxylic acid dichloride can be performed by a known method, for example, by heating the system and using a known stirrer. The reaction conditions can be adjusted as appropriate while monitoring the progress of the polymerization.

  Hydrochloric acid is generated in the system by the polycondensation reaction and the system becomes acidic. For the purpose of neutralization, an alkali such as calcium hydroxide is added after the reaction is completed. The calcium chloride generated by the neutralization reaction can be used as it is as a solubilizing agent that enhances the dissolution of the produced polymer in the solvent, and therefore does not need to be removed from the system.

  The intrinsic viscosity of the wholly aromatic copolyamide (value measured at 30 ° C. for a solution having a polymer concentration of 0.5 g / dL in 98% sulfuric acid) is usually about 3.0 to 5.0.

  The wholly aromatic copolyamide polymer obtained by polycondensation is an isotropic polymer solution (dope) dissolved in an amide solvent such as NMP which is a polymerization solvent. The obtained polymer solution (dope) can be used as it is in the spinning process without isolating the polymer. However, the concentration of the wholly aromatic copolyamide polymer at this time significantly affects the viscosity and stability of the polymer dope, and greatly affects the spinnability and the like in the subsequent spinning process. For this reason, when using for a yarn without isolating a polymer, it is preferable that the polymer concentration in a polymer dope shall be 2-10 mass%. In adjusting the polymer concentration and viscosity, an appropriate amount of an amide solvent such as N-methyl-2-pyrrolidone can be added.

<Para type wholly aromatic copolyamide fiber>
[Method for producing para-type wholly aromatic copolyamide fiber]
The method for producing a para-type wholly aromatic copolyamide fiber according to the present invention includes the step of coagulating a wholly aromatic copolyamide solution in a coagulation bath when yarn production is performed using the wholly aromatic copolyamide polymer dope obtained above. The flow rate of the coagulating liquid is set to a specific range.

(Number of holes in the base (number of filaments))
The number of holes in the die used for spinning varies depending on the area and the hole diameter of the spinneret, and is not particularly limited. However, from the viewpoint of versatility and handleability, it is preferably 40 to 4,000, more preferably 200 to 2,000. That is, the total number of single aromatic copolyamide fibers in the present invention is preferably 40 to 4,000. When the number of single yarns exceeds 4,000, it is not preferable because the yarns closely adhere to each other during discharge. On the other hand, when the number of single yarns is less than 40, the effect of the present invention cannot be sufficiently obtained because the interval between the yarns can be sufficiently secured.

(Conditions when passing through the base)
The temperature of the polymer dope when passing through the spinneret and the temperature of the spinneret are not particularly limited, but are preferably 80 to 120 ° C. from the viewpoint of spinnability and discharge pressure.

(Air gap)
Next, the polymer dope discharged from the spinneret is solidified in a coagulating liquid. At this time, when the temperatures of the spinneret and the coagulating liquid are greatly different, the respective temperatures change when the spinneret and the coagulating liquid come into contact with each other, making control difficult. An air gap can also be provided for ease of control. The length of the air gap is not particularly limited, but is preferably 5 to 15 mm from the viewpoints of temperature controllability and stringiness.

(Coagulation liquid)
The coagulation liquid used in the present invention is an aqueous solution of an amide solvent such as an NMP aqueous solution. The temperature is preferably 30 to 70 ° C., and the concentration of the amide solvent such as NMP is preferably 20 to 60% by mass. When the temperature of the coagulation liquid is less than 30 ° C., the elution of amide solvents such as NMP from the discharged polymer dope into the coagulation bath hardly occurs, so that not only the spinnability is deteriorated but also in the fiber. It is not preferable because an amide solvent such as NMP tends to remain on the surface, and it is necessary to go through many washing steps to suppress it. On the other hand, when the temperature of the coagulation liquid exceeds 70 ° C., the elution of amide solvents such as NMP from the discharged polymer dope into the coagulation bath increases, so that only the vicinity of the surface of the discharged polymer dope is present. It rapidly solidifies to form a skin layer, which makes it difficult to remove amide solvents such as NMP remaining inside the fiber. Further, not only the spinnability is deteriorated but also water in the coagulating liquid is easily evaporated, and it is difficult to adjust the concentration of amide solvent such as NMP in the coagulating liquid, which is not preferable.

  Further, when the concentration of the amide solvent such as NMP is less than 20% by mass, the elution of the amide solvent such as NMP from the discharged polymer dope into the coagulation bath increases, so that the surface of the discharged polymer dope Only the vicinity is rapidly solidified to form a skin layer, which makes it difficult to remove amide solvents such as NMP remaining inside the fiber and deteriorates the spinnability. On the other hand, when the concentration of the amide solvent such as NMP exceeds 60% by mass, elution of the amide solvent such as NMP from the discharged polymer dope into the coagulation bath hardly occurs, and therefore the spinnability is poor. In addition, amide-based solvents such as NMP are likely to remain in the fibers, and it is not preferable because many water washing steps are required to suppress them.

(Number of spindles)
In general, in the production of wholly aromatic copolyamide fibers, it is preferable that two or more spindles, more preferably three or more spindles are simultaneously spun in the same coagulation bath for the purpose of efficiently producing the fibers. .

(Coagulation fluid flow rate)
In the present invention, when the wholly aromatic copolyamide solution is coagulated in the coagulation bath, the flow rate of the coagulating liquid with respect to the wholly aromatic copolyamide yarn is particularly important. Here, the flow rate of the coagulation liquid refers to the flow rate of the coagulation liquid that flows in a direction perpendicular to the yarn traveling in the coagulation bath. The flow rate of the coagulation liquid in the present invention is essential to be in the range of 3.60 m / h to 5.20 m / h per filament of wholly aromatic copolyamide, and 4.00 m / h to 5.00 m / h. The range of h is preferable. When the flow velocity is out of the range of 3.60 m / h to 5.20 m / h, the flow to the yarn in the coagulation bath and the liquid disturbance at the coagulation liquid interface become large, and single yarn mixing is likely to occur. Therefore, it is difficult to obtain the effects of the present invention.
In order to make the flow rate of the coagulating liquid in the bath within the above range, for example, using a pump or the like, a flow of the coagulating liquid is made to be perpendicular to the running yarn in the coagulating bath, and the coagulating liquid from the pump What is necessary is just to adjust the liquid volume of a liquid.

(Heat treatment)
In the production method of the present invention, it is preferable to finally heat-treat the fiber after subjecting the coagulated yarn obtained by passing through the coagulation bath to known processes such as drawing, washing with water, and drying. The treatment temperature in the heat treatment is preferably in the range of 300 to 550 ° C, more preferably 320 ° C to 530 ° C, and most preferably 350 to 500 ° C. When the heat treatment temperature is less than 300 ° C., the molecular orientation does not proceed, and a high-strength fiber cannot be obtained. On the other hand, when the heat treatment temperature exceeds 550 ° C., the tensile strength of the fiber is improved by molecular orientation and cross-linking between molecules, but the fiber is thermally deteriorated due to high temperature, and the strength is lowered. .
Although the atmosphere during the heat treatment is not particularly limited, it is preferably carried out in an inert gas such as nitrogen because there is a concern about oxidative degradation of the fiber.
Further, the tension of the fiber at the time of heat treatment is not particularly limited, but for the purpose of further promoting the orientation of the fiber in the heat treatment step, the tension of the single fiber and all the fibers in the fiber is not broken. It is preferable to apply.
In addition, since the fusion | bonding of the single fibers which comprise a fiber may occur in the case of heat processing, in order to suppress it, an inorganic substance can also be made to adhere to the single fiber surface before heat processing.

[Physical properties of para-type wholly aromatic copolyamide fiber]
The wholly aromatic copolyamide fiber thus obtained has a tensile strength of 20 cN / dtex or more, preferably 25 to 40 cN / dtex, and an initial elastic modulus of 500 cN / dtex or more, preferably 500 to 1,000 cN / dtex. In order to bring the tensile strength and initial elastic modulus of the wholly aromatic copolyamide fiber to be in the above ranges, the drying temperature in the drying step, the draw ratio in the drawing step, the high temperature hot drawing temperature, etc. may be adjusted.

<Measurement method>
Each physical property value in Examples and Comparative Examples was measured by the following method.
[Intrinsic viscosity of wholly aromatic copolyamide]
The polymer was dissolved in 98% concentrated sulfuric acid to a polymer concentration of 0.5 g / dl, and measured at 30 ° C. using an Ostwald viscometer.
<Tensile strength (cN / dtex), elongation (%), elastic modulus (cN / dtex)>
Using a tensile tester (Orientec Co., Ltd., trade name: Tensilon universal tester, model: RTC-1210A), measurement was performed under the following conditions based on the procedure of ASTM D885.
(Measurement condition)
Measurement sample length: 750 mm
Measurement sample length: 500 mm
Chuck pulling speed: 250mm / min
Initial load: 0.2 cN / dtex
Test start method: Slack start method
The cross section of the obtained fiber was randomly photographed at 5 locations with a microscope (30 times), and the presence or absence of single yarn was measured by counting the number of single yarns.

<Example 1>
After nitrogen was fed into the stirring tank having a stirring blade and replaced, 1.71 L of NMP was charged. To this, 22.8 g of paraphenylenediamine and 42.3 g of 3,4'-diaminodiphenyl ether were added and completely dissolved while stirring. In addition, when the total amount of aromatic diamine was 100 mol%, the molar ratios of paraphenylenediamine and 3,4'-diaminodiphenyl ether were 50 mol% and 50 mol%, respectively. After the aromatic diamine was completely dissolved, 85.3 g of terephthalic acid dichloride was added to carry out a polycondensation reaction. The amount of terephthalic acid dichloride added was 99.5 mol% with respect to the aromatic diamine. Moreover, the reaction temperature and reaction time at this time were 85 degreeC and 30 minutes, respectively. By this polycondensation reaction, a wholly aromatic copolyamide polymer was produced, and a polymer dope was obtained. Thereafter, for the purpose of neutralizing the polymer dope, 137.3 g of an NMP dispersion of 22.5% by mass of calcium hydroxide was added to the polymer dope to carry out a neutralization reaction, and the isotropic polymer dope used for yarn production. Got.
The intrinsic viscosity of the obtained wholly aromatic copolyamide was 3.50.

The wholly aromatic copolyamide polymer solution obtained above was discharged at a rate of 870 g / min from a spinneret having a pore diameter of 0.30 mm and a number of holes of 667 holes, and an NMP concentration of 30 mass through an air gap called an air gap. % In a coagulation bath at a temperature of 50 ° C. At this time, the flow rate of the coagulation liquid was adjusted to 4.20 m / h per filament filament of wholly aromatic copolyamide using a pump installed in the coagulation bath. It was washed with water, dried, and then stretched 10 times at a temperature of 500 ° C. and wound to obtain a yarn of 1,100 dtex / 667 fil.
The mechanical properties of the obtained fiber were a tensile strength of 24.3 cN / dtex and an initial elastic modulus of 580 cN / dtex, and no single yarn was observed.

[Comparative Example 1]
In the same manner as in Example 1, except that the flow rate of the coagulation liquid in the bath was adjusted to 5.61 m / h per filament of the wholly aromatic copolyamide using a pump installed in the coagulation bath. 100 dtex / 667 fil yarn was obtained.
The mechanical properties of the obtained fiber were a tensile strength of 24.1 cN / dtex and an initial elastic modulus of 540 cN / dtex, and single yarn mixing was observed.

[Comparative Example 2]
In the same manner as in Example 1, except that the flow rate of the coagulation liquid in the bath was adjusted to 3.20 m / h per filament of wholly aromatic copolyamide using a pump installed in the coagulation bath. 100 dtex / 667 fil yarn was obtained.
The mechanical properties of the obtained fiber were a tensile strength of 24.2 cN / dtex and an initial elastic modulus of 551 cN / dtex, and single yarn mixing was observed.

  The para-type wholly aromatic copolyamide fiber obtained by the present invention is particularly useful for various industrial material applications that require high strength, high elastic modulus, high heat resistance, etc., and protective clothing applications such as bulletproof and blade-proof materials. .

Claims (5)

A method for producing a para-type wholly aromatic copolyamide fiber comprising a structural repeating unit (1) represented by the following formula (1), wherein a coagulating liquid used for coagulating a wholly aromatic copolyamide solution in a coagulation bath A method for producing a para-type wholly aromatic copolyamide fiber, wherein the flow rate is set to 3.60 m / h to 5.20 m / h per filament.
—CO—Ar ¹ —CO—NH—Ar ² —NH— (1)
[In Formula (1), Ar ¹ and Ar ² are each independent and represent an unsubstituted or substituted divalent aromatic group. ]   The method for producing a para-type wholly aromatic copolyamide fiber according to claim 1, wherein the number of filaments is 40 to 4,000.   The method for producing para-type wholly aromatic copolyamide fibers according to claim 1 or 2, wherein two or more spindles are simultaneously wet-spun in the same coagulation bath.   The method for producing a para-type wholly aromatic copolyamide fiber according to any one of claims 1 to 3, wherein heat treatment is performed at a heat treatment temperature of 300 to 550 ° C after stretching.   The method for producing a para-type wholly aromatic copolyamide fiber according to any one of claims 1 to 4, wherein the obtained para-type wholly aromatic copolyamide fiber has a tensile strength of 20 cN / dtex or more and an initial elastic modulus of 500 cN / dtex or more. .