JPH0860436A - Production of polybenzazole fiber - Google Patents

Abstract

PURPOSE: To obtain a polybenzazole fiber hardly having denier unevenness in the longitudinal direction, excellent in uniformity and having high strength and modulus by subjecting polybenzazole dope to dry wet spinning through a specific spinneret. CONSTITUTION: A polybenzazole polymer solution polymerized in a polyphosphoric acid solvent is directly used as a spinning dope and kneaded and subjected to defoaming treatment in a two-axle kneader and fed to a spinning head and spinning fine holes radially extended from the center of a spinneret are divided and perforated by a dividing zone 3 which is not perforated and discharged through spinneret having >=2.0/cm<2> and <5.0/cm<2> hole density of a spinning hole group 2 to form dope filaments to form dope filament and successively actively cooled in stream kept to 30-100 deg.C in an air gap and brought into contact with a solvent-insoluble coagulating bath of a phosphoric acid water solution and taken off to provide the objective polybenzazole fiber having relatively fine single yarn at high spinning rate of >=200m/min in good productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing polybenzazole fiber having high strength and high elastic modulus. More specifically, the present invention relates to a method for producing a polybenzazole fiber having less denier unevenness in the longitudinal direction of a fiber yarn and remarkably improved uniformity, at an industrial production rate.

[0002]

2. Description of the Related Art A method for forming a fiber from a solution containing a fiber-forming polymer by a dry-wet spinning method is polyacrylonitrile (for example, JP-A-51-35716) or aramid (for example, USP3767756, JP-A-47-3).
9458), and the like. A method for fiberizing a dope composed of polybenzazole and polyphosphoric acid solution by a dry-wet spinning method is proposed in Japanese Patent Publication No. 63-500529. The following technical contents are disclosed in the published patent publication. That is, a dope composed of polybenzazole and polyphosphoric acid is spun into the atmosphere from the spinneret,
The spun yarn is introduced into a coagulation bath to remove the solvent, and then the coagulated yarn is washed to reduce the concentration of the solvent remaining in the yarn, and then the fiber yarn is dried, and if necessary. And heat-treating the fiber yarn.

[0003]

The softening temperature of the spinning dope composed of polybenzazole and polyphosphoric acid is generally 80.
Higher than ℃. Further, the dope forms a lyotropic liquid crystal, and a dry-wet spinning method is effective. However, unlike the polymer dope used for usual wet spinning of aramid or polyacrylonitrile, the dope has an extremely high viscosity, and therefore melt fracture occurs very easily by spinning from the pores. This phenomenon can be suppressed by discharging the spinning dope from a relatively large discharge hole,
On the other hand, the dope discharge speed becomes relatively low, and when the spun yarn is drawn at a high speed, the take-up speed / discharge linear velocity ratio in the air gap (hereinafter referred to as the spin draw ratio) exceeds the limit value and becomes large. Thread breakage easily occurs.
In order to eliminate this difficulty, a method of increasing the length of the air gap (the distance from the spinneret surface to the extraction bath) has been proposed. A technique for making the air gap longer than that of aramid or the like is also described in Japanese Patent Publication No. 63-500529. However, as a result of examining the technical contents of the present inventors, the maximum spin draw ratio did not change and it did not lead to an essential solution.

The above problem can be solved to some extent by taking measures such as increasing the single yarn denier and lowering the spinning speed, but it is disadvantageous in terms of productivity when producing thin single yarn denier. Also, if the number of pores per spinneret (hereinafter referred to as pore density) is reduced, the stability of the spinning state is improved,
In order to ensure productivity, it is necessary to increase the size of the spinneret or increase the number of spinnerets per spinning head. In either case, the spinning equipment becomes huge, which causes problems in productivity and complicates workability, which is not preferable.
An object of the present invention is to provide a method for producing a high-strength, high-modulus polybenzazole fiber at a spinning speed of 200 m / min or more without enlarging the spinning equipment and complicating the workability.

[0005]

[Means for Solving the Problems] When a spinning dope composed of polybenzazole and polyphosphoric acid is discharged from the pores into the atmosphere, the viscosity of the dope is highly temperature-dependent, so that the thinning behavior depends on the change in the ambient temperature. easily influenced. A spinning test was performed using various spinnerets with different pore densities,
The flow condition of the atmosphere below the spinneret, the temperature of the running yarn, and the thinning profile were investigated in detail. As a result, (1) the atmosphere around the yarn group discharged from the fine pores located in the center of the spinneret surface shows a stagnant or disordered flow.
(2) The yarn discharged from the pores located in the central portion of the spinneret surface has a relatively high temperature and a large fluctuation range as compared with the yarn discharged from the pores located in the outer peripheral portion, (3 ) Threads discharged from the pores located in the center of the spinneret face are delayed in thinning and have a large fluctuation range in the thinning speed, etc., compared with threads discharged from pores located in the outer peripheral portion. found.
From this experimental fact, it is suggested that uniform cooling of each spun yarn is essential for high-speed production of a fiber yarn consisting of a single yarn of thin denier while suppressing spun yarn breakage. That is, the present invention has been achieved as a result of intensive studies on a spinning stabilizing method based on the idea that the technical point is to improve the renewability of the atmosphere in contact with the spun yarn surface.

The present invention will be described in more detail below. The polybenzazole of the present invention is a polybenzazole fiber obtained by spinning a dope containing the following polybenzazole. That is, polybenzazole (PBZ) means polybenzoxazole (PBO) homopolymer, polybenzothiazole (PBT) homopolymer and their PB
O, PBT random, sequential or block copolymers. Here, polybenzoxazole, polybenzothiazole and random, sequential or block copolymers thereof are, for example,
"Liquid Crystalline Polymer Composition" by Wolfe et al.
, Process and Products "U.S. Pat. No. 4,703,103
Issue (October 27, 1987), "Liquid Crystalline
Polymer Compositions, Process and Products "US Pat. No. 4,533,692 (August 6, 1985)," Liqu
id Crystalline Poly (2,6-Benzothiazole) Compositio
n, Process and Products "U.S. Pat. No. 4,533,724 (August 6, 1985)," Liquid Crystalline Polym ".
er Compositions, Process and roducts "U.S. Pat. No. 4,533,693 (August 6, 1985), Evers," Thermooxidative-lyStable Articulated p-Benzobiso "
"xazole and p-Benzobisthiazole Polymres" U.S. Pat. No. 4,539,567 (November 16, 1982), Tasi et al., "Method for making Heterocyclic Block Copolyme".
r "U.S. Pat. No. 4,578,432 (March 25, 1986)
Date), etc. The structural unit contained in the PBZ polymer is preferably selected from lyotropic liquid crystal polymers. The monomer unit is structural formula (a)-
It consists of the monomer units described in (h), and more preferably consists essentially of the monomer units selected from structural formulas (a) to (c).

[0007]

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[0008]

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Suitable solvents for forming the polymer dope of polybenzazole include cresol and non-oxidizing acids capable of dissolving the polymer. Examples of suitable acid solvents include polyphosphoric acid, methanesulfonic acid and concentrated sulfuric acid or mixtures thereof. Further suitable solvents are polyphosphoric acid and methanesulfonic acid. The most suitable solvent is polyphosphoric acid.

The polymer concentration in the solvent is preferably at least about 7% by weight, more preferably at least 1
It is 0% by weight, most preferably at least 14% by weight. The maximum concentration is limited by practical handling characteristics such as the solubility of the polynose and the viscosity of the dope. Due to these limiting factors, the polymer concentration is usually 20% by weight.
Never exceeds.

Suitable polymers, copolymers or dopes are synthesized by known methods. For example, Wolfe et al., US Pat. No. 4,533,693 (August 6, 1985), Sy.
U.S. Pat. No. 4,772,678 to Bert et al. (September 2, 1988)
Day 0, Harris U.S. Pat. No. 4,847,350 (198).
It is synthesized by the method described in July 11, 1997). PB
Z polymers are described in US Pat. No. 5,089,591 to Gregory et al.
According to the publication (February 18, 1992), it is possible to achieve a high molecular weight at a high reaction rate in a dehydrating acid solvent under relatively high temperature and high shear conditions.

Of course, these may contain antioxidants, matting agents, colorants, antistatic agents, and the like. These polybenzazoles are subjected to dry or wet spinning immediately or separately as a spinning dope dissolved in polyphosphoric acid.

The spinning dope comprises a pressurizing device, a metering device, a filtration layer composed of inorganic and / or metal particles, and a porous plate having a plurality of fine pores having a diameter of 1 to 5 mm, which is disposed below the filtration. Let it pass. Then, it is introduced into a space portion called a melt pool formed by the surface of the porous plate and the back surface of the spinneret, and the knitted woven fabric or nonwoven fabric made of metal fibers provided in the space portion is passed and supplied to the spinneret. The spinning dope is spun through a spinneret in which a plurality of spinning pores are arranged in a circumferential, lattice, or staggered pattern. What is important here is the arrangement of the spinning pores on the surface of the spinneret, and by increasing the air flow penetrability in the spun yarn bundle below the spinneret, the yarn temperature between single yarns and thus the non-uniformity of the thinning profile can be improved. How to control.

FIG. 1 shows an example of the spinneret used in the present invention. As shown in the figure, the pores of the spinneret are divided into a plurality of pore groups from the geometric center of the spinneret by the zone zones in which the spinning pores are not perforated. The number of pores per unit area in the group of pores divided from the viewpoint of spinning stability is at least 2.0 pores / cm ² and 5.0 pores / cm ^2.
It is preferably less than ² . Pore density is 2.0 / cm
^{When it is} less than ² , there is no problem in spinning stability, but the productivity per spinning spinneret [total discharge amount] is unfavorably reduced beyond the economical limit. In order to maintain productivity by using a spinneret with a local pore density of less than 2.0 / cm ^2, not only must the size of the spinneret be increased, but not only the spinning equipment must be huge, but the temperature distribution in the spinneret surface must be large. On the contrary, the spinning stability is lowered due to the increase, and the object of the present invention is not met. On the other hand, when the local pore density is 5.0 pores / cm ² or more, the spinning state becomes similarly unstable when spinning is performed using a spinneret that does not divide the pores into groups.

The number of divisions of the spinning pores in the plane of the spinneret is also an important factor for the penetrability of the air flow between the single yarns of the spun yarn, and the spinneret has a group of spinning pores divided into at least two or more. Need to be formed in. The upper limit of the number of groups is not particularly limited, but it is preferably 10 groups or less in consideration of the spinneret size and the hole density. There is no particular limitation on the shape of the divided spinning pore groups, and it is preferable that they are geometrically symmetric with respect to the center of the spinneret.

The width of the unperforated compartmental zone for dividing the total spinning pores into groups is preferably at least 5 mm. If the partitioning bandwidth is less than 5 mm, the effect of improving the penetrability of the atmospheric airflow between the single yarns directly below the spinneret is small, and it is not possible to expect a reduction in the yarn temperature difference between the single yarns of the spun yarn and thus a difference in the thinning profile. Although there is no upper limit to the partition bandwidth, it is preferably 10 mm or less in consideration of the size of spinning equipment or the productivity per spinneret.

The dope filament yarn discharged from the spinning pores is cooled to below the coagulation temperature by passing through the air atmosphere, and then introduced into a coagulation bath made of a non-solvent medium. The distance from the spinneret required for cooling the spun yarn is mainly determined by the spinning dope discharge amount per spinning hole and the spinning temperature, but a length of 10 cm to 120 cm can be usually adopted. As the medium used in the coagulation bath, for example, water, phosphoric acid aqueous solution, methanol, acetone or the like can be used in a liquid or vapor state. Further, in order to bring the coagulation medium and the spun yarn into contact with each other, it is possible to adopt a method of traveling in a funnel-shaped coagulation bath, traveling in a multistage aspirator, traveling in a waterfall-like coagulation medium, or the like. . Since the spinning tension and the fiber strength of the spun yarn after discharging and cooling and solidifying the polybenzazole are relatively high as compared with the case of using other dry-wettable polymer, The extraction methods and devices described above can be used. For example, an apparatus in which a group of positively driven rollers is immersed in a coagulating liquid bath, which is the most common, can be used. It is preferable that the dope filament discharged from the spinning pores is positively blown with an air flow of 30 to 100 ° C. in the air gap portion to be cooled and then introduced into the coagulation bath. If it is less than 30 ° C., the cooling is too rapid, the spinning tension increases, and the spinning state becomes unstable, which is not preferable. On the other hand, if the temperature exceeds 100 ° C., an unstable phenomenon like draw resonance occurs, which is not preferable. More preferably, it is 50 to 90 ° C.

After passing through the coagulation bath in this way, the yarn is taken up by the first godet roller via the direction changing roller. The spinning speed defined by the surface speed of the first godet roller depends on the single yarn denier, and the thinner the single yarn denier, the lower the maximum speed at which continuous stable spinning is possible. That is, the maximum spin draw ratio in the air gap is mainly determined by the single yarn denier.
According to the method of the present invention, for example, a yarn composed of a single yarn of 1.5 denier can be stably spun at a take-up speed of 200 m / min or more. For example, the spin draw ratio is 54 or more when using a spinning pore having a pore diameter of 0.20 mm. As another advantage of the present invention, it is possible to easily divide the yarn using a guide in the steps from solidification to before winding, and it is also possible to easily perform multi-division winding from one spinneret. is important.

Next, the yarn is sent to the extraction / washing process through the first godet roller. Finally, in these extraction processes, the phosphoric acid contained in the yarn is 9 in terms of phosphorus atom.
9.0% by weight or more, preferably 99.5% by weight or more, and particularly preferably 99.8% by weight or more are extracted. There is no particular limitation on the type of medium used as the extraction liquid in the present invention, but it does not substantially have compatibility with the polybenzazole polymer, and may be a liquid having compatibility with phosphoric acid, and particularly From the viewpoint of handleability and other aspects, water, methyl alcohol, etc. are preferable. Alternatively, the extraction bath may be separated into multiple stages to reduce the concentration of the eluted phosphoric acid in sequence, and finally the water may be washed with phosphoric acid-free water.

The washed yarn may be wound immediately, but it is preferably wound after being dried. Further, it is preferable to apply an oil agent to the yarn before or after the drying treatment. Here, the oil agent applying means is not particularly limited, and a conventionally known method, for example, application by a roller, application by a so-called guide having a groove shape,
A method of spraying in a mist form or the like can be adopted. Performing the yarn drying treatment and the oil agent imparting treatment in-line is important for obtaining fibers having excellent physical properties without mechanical damage to the yarn. If necessary, the yarn may be heat-treated at a temperature of 300 ° C or higher, preferably 450 ° C or higher. The upper limit of the heat treatment temperature is preferably less than 650 ° C from the viewpoint of deterioration of physical properties due to thermal deterioration. After the heat treatment, the yarn is applied with a finishing oil agent and then taken off. By performing this heat treatment, the elastic modulus increases.

Conventionally, a dry-wet spinning method has been adopted for forming fibers of a lyotropic liquid crystalline polymer dope. However, when a conventionally known dry-wet spinning method is applied to a spinning dope consisting of a polybenzazole-based polymer and polyphosphoric acid to obtain a thin single-filament denier yarn at a high speed, the yarn breaks just below the spinneret. It was difficult to maintain a stable spinning state for a long period of time. Therefore, the spinning of the dope of the polybenzazole-based polymer and polyphosphoric acid, conventionally composed of pores of extremely large diameter compared to the spinning pores used in the spinning of lyotropic liquid crystalline polymer dopes such as aramid, Moreover, when the number of pores is extremely reduced, for example, when using a spinneret in which the average pore density is 3 pores / cm ^{2 to} 5 pores / cm ² and the pores are not grouped, a spinning speed of at most about 80 m / min. It was difficult to say that productivity was high from an industrial point of view because the speed was the limit. This is because the thinning behavior of the spun dope composed of polybenzazole and polyphosphoric acid is significantly different from that of other spin dopes to which the dry-wet spinning method is applied. By using the spinneret of the present invention, the air flow penetrability between the single yarns immediately below the spinneret is improved, the cooling of the yarn and thus the thinning profile becomes uniform, and the spinning state is stabilized. Therefore, the drawbacks of the conventional method have been solved, and it has become possible to stably spin a yarn composed of a single thin denier yarn at a high speed.

[0022]

EXAMPLES The present invention will be described below with reference to examples, but of course the present invention is not limited thereto. The method of measuring physical properties and the method of measuring spinning stability used in the evaluation of the present invention are as follows. [Method for measuring intrinsic viscosity] Polybenzazole was dissolved in methanesulfonic acid, the reduced viscosity was measured at a temperature of 30 ° C, and the solvent concentration was extrapolated to zero. The [single yarn denier] sample was adjusted in a test room in a standard condition [temperature of 20 ± 2 ° C., relative humidity of 65 ± 2%] for at least 16 hours, and then 90 m of the sample was sampled using a lap reel and weighed. The yarn denier was measured and converted into a weight of 9000 m to obtain a yarn denier, which was divided by the number of filaments to obtain a single yarn denier. [Evaluation method of spinnability] After the yarn is applied to the take-up roller (group) without contacting with the coagulating / extracting liquid, the peripheral speed of the roller is increased at a constant rising speed to cause yarn breakage. It was defined as the ratio of the spinning speed (Vw), the discharge rate of a single hole, and the discharge linear velocity (Vo) in the pore, which was determined from the pore diameter. Spin draw ratio = Vw / Vo [Spinning stability determination method] Spinning was performed at a speed of 200 m / min, and the occurrence frequency of yarn breakage was counted and converted into the number of occurrences per hour. [Fluff measurement method] The yarn wound on the package is spun at a speed of 10
While unwinding at 0 m / min, it was counted by a photoelectric tube type fluff detector and converted into the occurrence frequency per 10,000 m. [Measurement method of strength and elongation] JIS L 1013 (198)
In accordance with 1), with a Tensilon manufactured by Orientec Co., Ltd., a gripping interval of 5 cm, a pulling speed of 100% / min, and n =
Thirty measurements were performed and the breaking strength and elongation and the tensile elastic modulus arithmetic mean were determined.

[Examples 1 to 3, Comparative Examples 1 to 3] 4,6-diamino-1,3benzenediol dihydrochloride (50.
0 g, 0.235 mol) was stirred with 200 g of polyphosphoric acid (phosphorus pentoxide content 83.3% by weight) at 40 ° C. for 12 hours under a nitrogen stream. Then, the temperature was raised to 60 ° C., and dehydrochlorination was performed under a reduced pressure of about 50 mmHg. Terephthalic acid (39.0 g, 0.236 mol) and 103 g of phosphorus pentoxide were added thereto, and the mixture was kept under a nitrogen stream at 60 ° C. for 8 hours,
Then 120 ° C for 9 hours, 150 ° C for 15 hours, 1
Polymerization was carried out at 80 ° C. for 24 hours. The polybenzazole polymer solution obtained by polymerization in this way was used as it was for spinning dope. A part of the obtained polymer was mixed with water by using a process mixer to repeat stirring several times to make the polymer powder. When the powdered polymer was redissolved in methanesulfonic acid and the viscosity was measured at 25 ° C., the intrinsic viscosity [η] was 30.5 dl / g. The concentration of the solid content obtained in the above reaction is 14.0% by weight, and the concentration of the solvent when the polyphosphoric acid composition is phosphorus pentoxide is 86.0% by weight. The dope was kneaded and defoamed with a biaxial kneader, and then transferred to a spinning head via a metering pump. In the spinning head part, a particle-filled layer (thickness of 50 mm, made of an inorganic material) (average particle size and average aspect ratio were variously changed) was passed, and then a plurality of pores having a diameter of 2 mm were perforated in a lattice pattern. The plate was passed through, and further passed through a laminate layer composed of a metal fiber cloth having a diameter of 10 μm and having a transmittance of particles of 15 μm or more of 2.5%. A pore having a pore diameter of 0.20 mm, a pore length of 0.20 m, an introduction angle of 20 degrees, and a pore number of 284 has a zone width [W] of 8.6 mm as shown in FIG. 1A.
Through a spinneret with a hole density of 4.8 holes / cm ² divided into 3 groups with a spinneret surface temperature of 160 ° C and a discharge rate of 64.2 g.
Spinning was performed under the condition of / min. Subsequently, the spun yarn was introduced into a funnel-type coagulating device arranged 35 cm below the surface of the spinneret and circulating a phosphoric acid aqueous solution having a concentration of 20% maintained at a temperature of 22 ± 2 ° C. Furthermore, after winding around the roller (group) arranged below the extraction bath to change the traveling direction of the yarn,
Furthermore, the yarn is wound around a godet roller (group) to release the spinning tension, and at the same time, water is sprayed on the running yarn by a spray device arranged close to the roller to extract and wash phosphoric acid in the yarn. It was In this state, the spinnability was evaluated by speeding up all the rollers at once. After the evaluation was completed, the total roller speed was readjusted to 200 m / min, passed through a hot air circulation type drying device to reduce the water content to 2.0 wt% or less, and then wound into a package.

Instead of the spinneret of Example 1, a pore size of 0.2
A spinneret having 0 mm, a hole length of 0.20 mm, an introduction angle of 20 degrees and a hole density of 3.4 and 4.0 holes / cm ² was used. Dry-wet spinning was performed under the same spinning dope and conditions as in Example 1 to obtain Examples 2 and 3.

Instead of the spinneret of Example 1, a spinneret in which the spinning pores were not divided into groups by non-perforated compartments was used. The specifications of the spinneret are a hole diameter of 0.20 mm, a hole density of 4.0 holes / cm ² , and a number of holes of 284. Dry-wet spinning was performed under the same spinning dope and conditions as in Example 1 to obtain Comparative Example 1.

Instead of the spinneret of Example 1, a pore size of 0.2
A spinneret having a hole density of 0 mm, a hole length of 0.20 mm, an introduction angle of 20 ° and a hole density of 5.4 and 1.4 holes / cm ² was used. Dry-wet spinning was performed under the same spinning dope and conditions as in Example 1 to obtain Comparative Examples 2 and 3. The above experimental results are summarized in Table 1.

[0027]

[Table 1]

As can be seen from Table 1, Examples 1 to 3 belonging to the present invention have a high spinning speed (200 m /
The number of occurrences of single yarn breakage during spinning was small, and the fluff of the wound yarn was practically no problem. The obtained fiber had a single yarn denier of about 1.5 and had no change in the physical properties of the fiber and had high strength and high elastic modulus. On the other hand, Comparative Example 1 using a spinneret in which the spinning pores are not divided into groups has a lower spin draw ratio (poor spinnability) as compared to Example 1, which is an early object of the present invention. It has been difficult to spin a single yarn denier yarn at an unprecedentedly high speed, for example, 200 m / min. In Comparative Example 2 in which the density of the spinning pores was out of the range of the present invention, a single yarn flow frequently occurred during spinning, and a large number of fluffs were present in the wound yarn, which was not practical. Comparative Example 3 in which the spinning pore density is out of the range of the present invention is excellent in spinnability and spinning stability, but the productivity per spinneret evaluated by the discharge amount is about 1/3 of that in Example 1.
And extremely low and not practical.

[Examples 4 to 5 and Comparative Example 4] Instead of the spinneret of Example 1, the width [W] of the partition zone for dividing the spinning pores into groups was 6.5 mm [Example 4], 9. Spinning was performed using the spinning dope, conditions and method described in Example 1 except that the thickness was changed to 9 mm [Example 5] and 4.7 mm [Comparative Example 4]. The results are shown in Table 2.

[0030]

[Table 2]

As is clear from Table 2, those belonging to the present invention (Examples 4 to 5) are recognized to have remarkably improved high-speed spinning property. On the other hand, Comparative Example 4, which does not belong to the present invention, had a low spin draw ratio [spinnability] and was difficult to spin at a speed of 200 m / min.

[Examples 6 to 8] As described in Example 1, except that the spinneret of Example 1 was replaced by a spinneret having 2, 6 and 8 partition zones for dividing the spinning pores into groups. Spinning dope,
Spinning was carried out using the conditions and methods described in Example 6,
7 and 8. The results are shown in Table 3.

[0033]

[Table 3]

As is clear from Table 3, all of the materials belonging to the present invention (Examples 6 to 8) had remarkably improved spinnability. However, as the diameter of the spinneret increases, the number of occurrences of single yarn flow (single yarn breakage) during spinning increases,
Many fluffs will be seen on the wound yarn. This is because the temperature distribution on the spinneret surface increased due to the increase in diameter. Therefore, it is preferable to divide the spinning pore group into 8 or less.

[Examples 9 to 11, Comparative Examples 5 to 7] Using the spinneret described in Example 1, the single hole discharge rate was 0.69 g.
Per minute, and the temperature is 55 ° C. to 95 ° C. and the average flow velocity is 0.7 m to the discharged dope filament in the air gap part.
It was cooled by blowing a rectified air flow of 1 / sec. Spinning was performed using the spinning dope, coagulation and extraction conditions / methods described in Example 1 except that the single hole discharge rate was changed and the cooling airflow was used. The temperature of the cooling airflow should be 2
It changed to 5 degreeC and 105 degreeC, and set this as Comparative Examples 5-6.
Further, Comparative Example 7 is a case where the positive cooling by the cooling airflow was not performed in the air gap portion. The results are shown in Table 4.

[0036]

[Table 4]

As is apparent from Table 4, in Examples 9 to 11 belonging to the present invention in which the spinneret in which the spinning pores were divided into groups were used and which was positively cooled in the air gap portion, the spinning speed was high. It can be seen that despite this, it exhibits good spinnability.
On the other hand, in Comparative Examples 5 to 6 in which the temperature of the cooling air flow is out of the range of the present invention and Comparative Example 7 in which the positive cooling is not performed, it is understood that the effect of improving the spinnability cannot be expected. Therefore, at a spinning speed such that the spinning speed exceeds 600 m / min, it is preferable to use cooling of the dope filament in combination with an air flow at a temperature of 30 to 100 ° C. in the air gap portion.

[0038]

EFFECTS OF THE INVENTION It has been conventionally considered difficult to produce a fiber having a relatively thin single yarn denier and high fiber properties while maintaining high productivity because polybenzazole has a unique spinning behavior. However, according to the present invention, the following surprising effects can be obtained. That is, by dividing the spinning pores in the surface of the spinneret into a plurality of pore groups in the non-perforated division zone, and improving the penetration of the cooling air flow between the spun yarns,
A yarn composed of a relatively thin single yarn (for example, 1.5 denier), which has been considered to be difficult in the past, has a high spinning speed (for example, 20).
0 m / min or more). This also greatly contributes to the industrial world in terms of productivity.

[Brief description of drawings]

FIG. 1 is a view showing an example of a spinneret for dry and wet spinning according to the present invention.

[Explanation of symbols]

 1 Spinning pores 2 Spinning pores group 3 Partition zone in which spinning pores are not perforated 4 Zone width of partition zone in which spinning pores are not perforated

Claims (3)

[Claims] 1. A spinning dope composed of a polybenzazole polymer and polyphosphoric acid is spun from a spinneret to form a dope filament, and then the dope filament is introduced into an air atmosphere and cooled, and a non-solvent In the spinning method of polybenzazole fiber which is taken out after being brought into contact with the coagulation liquid, the pores for discharging the spinning dope are continuously extended radially from the center of the spinneret, and the fine pores are divided by undivided zones. A method for producing a polybenzazole fiber, which is perforated so as to form a group of holes. 2. The pore density in the pore group divided by the non-perforated partition zone is 2.0 or more and 5.0 pores / cm ^2.
The method for producing a polybenzazole fiber according to claim 1, wherein the amount is less than 1. 3. A spinning dope is spun from a spinneret to form a dope filament, and subsequently, a so-called air gap between the spinneret and a coagulating bath is positively cooled by using an air stream of 30 to 100 ° C. The method for producing a polybenzazole fiber according to claim 1, wherein