JP2006176617A - Copolymerized polybenzazole fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To industrially provide a polybenzazole fiber which retains excellent strength and heat resistance inherent in a polybenzazole fiber, has a reduced amount of the acid solvent remaining in the fiber, exhibits only a small amount of strength reduction under a high temperature and high humidity condition, and is improved in durability. <P>SOLUTION: In the copolymerized polybenzazole fiber, repeating units expressed by general formulas (1) and (2) are random- or block-copolymerized in the molecular chain. The apparent crystal size on the (200) plane perpendicular to the axis of the fiber is ≤49 Å. In the formulas, n is a real number in the range of 0.01≤n≤0.99; X is an S or an O atom or an NH group; Z is a C-H group or an N atom; the N atom and the X atom/group in the azole ring may be in the trans position or the cis position. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to copolymerized polybenzazole fibers. More specifically, the present invention relates to a highly durable polybenzazole fiber excellent in storage stability.

Polybenzazole fiber is solidified by extruding a dope containing polybenzoxazole or polybenzothiazole polymer and an acid solvent from a spinneret, and then dipping in a coagulating fluid (water or a mixture of water and inorganic acid). In addition, it is manufactured by a method of thoroughly washing in a water washing bath to remove the solvent, passing through an aqueous bath of an inorganic base, neutralizing the acid remaining in the yarn, and drying (for example, patents) Reference 1).
However, in order to reduce the residual inorganic acid solvent concentration in the yarn, washing at a high temperature for a long time is required, and it was not easy to produce at an industrial level (for example, Patent Document 2). The remaining inorganic acid adversely affects the durability of the mechanical properties such as the strength of the polybenzazole fiber, and therefore further improvement is desired. Especially, polybenzazole having excellent durability in a high temperature and high humidity environment. The appearance of fiber is expected.
JP-A-8-170222 JP-A-8-60437

  The present invention has been made by paying attention to the above circumstances, and by introducing a copolymer component into the polybenzazole molecular chain and controlling the fiber microstructure, the original excellent strength of the polybenzazole fiber It is easy to reduce the residual amount of acid solvent in the yarn while having heat resistance, and there are few molecular chain breaks that induce a decrease in the strength of the fiber, making it more durable in high temperature and high humidity environments. It is intended to provide an improved polybenzazole-based fiber industrially.

但し、ｎは、一般式（１）および（２）で表される繰り返し単位の合計モル数に対する一般式（１）で表される繰り返し単位のモル分率であり、０．０１≦ｎ≦０．９９の範囲で表される実数である。ＸはＳ、Ｏ原子またはＮＨ基を、Ｚは、Ｃ−Ｈ基またはＮ原子を示す。アゾール環においてＮ原子とＸ原子／基はトランス位であってもシス位であってもよい。
２．繊維軸に垂直な（０１０）面の見かけの結晶サイズが２５Å以下であることを特徴とする前記１に記載の共重合ポリベンザゾール繊維。
３．繊維軸方向の真の結晶サイズが１２０Å以下であることを特徴とする前記１又は２に記載の共重合ポリベンザゾール繊維。
本発明の共重合ポリベンザゾール繊維は、上記一般式（２）で表される繰り返し単位を分子鎖中に含有せしめない場合と比較して、繊維中の結晶サイズを小さくすることができ、結晶サイズを小さくすることにより、繊維の高温高湿度に対する耐久性が改善されることを見出したのである。 That is, the present invention employs the following configuration.
1. The repeating unit represented by the following general formulas (1) and (2) in the molecular chain is random or block copolymerized, and the apparent crystal size of the (200) plane perpendicular to the fiber axis is 49 mm or less. Copolymer polybenzazole fiber characterized by.

However, n is the mole fraction of the repeating unit represented by the general formula (1) with respect to the total number of moles of the repeating units represented by the general formulas (1) and (2), and 0.01 ≦ n ≦ 0 A real number in the range of .99. X represents an S, O atom or NH group, and Z represents a C—H group or an N atom. In the azole ring, the N atom and the X atom / group may be trans or cis.
2. 2. The copolymerized polybenzazole fiber according to 1 above, wherein an apparent crystal size of a (010) plane perpendicular to the fiber axis is 25 mm or less.
3. 3. Copolymer polybenzazole fiber according to 1 or 2 above, wherein the true crystal size in the fiber axis direction is 120 mm or less.
Compared with the case where the repeating unit represented by the general formula (2) is not contained in the molecular chain, the copolymerized polybenzazole fiber of the present invention can reduce the crystal size in the fiber, It has been found that by reducing the size, the durability of the fiber against high temperature and high humidity is improved.

  According to the present invention, by introducing a pyridine ring as a copolymerization component into a polybenzazole molecular chain, the removal of the acid solvent is facilitated, and the fiber microstructure can be easily controlled by the removal conditions of the acid solvent. The size of the crystal in the yarn can be reduced, the residual stress and stress concentration on the molecular chain can be suppressed, the molecular chain breakage that induces a decrease in fiber strength, and the durability under high temperature and high humidity environment is improved. It has become possible to provide an improved polybenzazole-based fiber.

Hereinafter, the present invention will be described in detail.
The polybenzazole fiber according to the present invention refers to a fiber made of a polybenzazole polymer, and the polybenzazole (hereinafter also referred to as PBZ) refers to polybenzoxazole (hereinafter also referred to as PBO) or polybenzothiazole (hereinafter referred to as PBOZ). , PBT) and polybenzimidazole (hereinafter also referred to as PBI), and the repeating units represented by the general formulas (1) and (2) in the molecular chain are random or block copolymerized. Polybenzazole.

Specific examples include the following structures, but the present invention is not limited to these.

  The method for synthesizing the copolymerized polybenzazole in the present invention basically includes, for example, Wolfe et al., US Pat. No. 4,533,693 (1985.8.6), Sybert et al., US Pat. No. 4,772,678 (1988.9.22). ), Harris, U.S. Pat. No. 4,847,350 (1989.7.11), Gregory et al., U.S. Pat. No. 5,089,591 (1992.2.18), and the like. That is, a suitable monomer is a stepwise or constant rate of temperature increase from about 60 ° C. to 230 ° C. in a non-oxidizing, dehydrating acid solution under high-speed stirring and high shear conditions in a non-oxidizing atmosphere. It can be made to react by raising the temperature.

Polybenzazole containing a pyridine ring is synthesized according to the following reaction formula. As a reaction solvent, polyphosphoric acid is generally used.

However, n is the mole fraction of the repeating unit represented by the general formula (1) with respect to the total number of moles of the repeating units represented by the general formulas (1) and (2), and 0.01 ≦ n ≦ 0 A real number in the range of .99. X represents an S, O atom or NH group, and Z represents a C—H group or an N atom. m represents 2 or 4. In the azole ring, the N atom and the X atom / group may be trans or cis.

The phenylenediamine derivative used here may be used as it is, but is usually used in the form of hydrochloride for stabilization. First, a phenylenediamine derivative and an aromatic dicarboxylic acid are added to polyphosphoric acid, and heated at 30 to 130 ° C. until hydrogen chloride gas is completely desorbed under an inert gas stream such as nitrogen. Next, the temperature is raised to 130 to 160 ° C. and the reaction is carried out for 3 to 20 hours to produce an oligomer having IV = 4 to 8 dL / g. Next, the temperature is raised to 170 to 250 ° C. to complete the polymerization reaction, and a high molecular weight polybenzazole having IV = 15 dL / g or more is obtained. The polyphosphoric acid can be removed by washing the polymer dope obtained by this polymerization reaction with a solvent such as water or alcohol.

The polymer concentration in the dope during polymerization and spinning is preferably at least about 7% by weight, more preferably at least 10% by weight, particularly preferably at least 12% by weight. The maximum concentration is determined by practical handling properties such as polymer solubility and dope viscosity, but the polymer concentration usually does not exceed 25% by mass and is usually 20% by mass or less.

Copolymerized polybenzazole fibers are produced from a dope containing copolymerized polybenzazole, and suitable solvents for preparing the dope include cresol and a non-oxidizing acid capable of dissolving the polymer. Can be mentioned. Examples of suitable non-oxidizing acids include inorganic acids such as polyphosphoric acid, methanesulfonic acid and high concentrations of sulfuric acid or mixtures thereof. Of these, polyphosphoric acid and methanesulfonic acid are particularly preferred. Further, after completion of the polymerization, the benzazole copolymer can be used as it is as a dope for spinning without isolation.

The dope thus obtained is extruded from a spinneret and stretched in space to form a filament. As a method for producing a suitable filament, the method described in US Pat. No. 5,034,250 can be adopted. The dope exiting the spinneret enters the space between the spinneret and the washing bath. This space is commonly referred to as an air gap, but need not be air. This space needs to be filled with a solvent that does not react with the dope without removing the solvent, and examples thereof include air, nitrogen, argon, helium, and carbon dioxide.

A filamentous dope (hereinafter referred to as a dope filament) formed by an air gap is guided to a coagulation / cleaning bath. In the coagulation / cleaning bath, the dope filament is brought into contact with a liquid which is compatible with an inorganic acid dissolving polybenzazole and does not serve as a solvent for polybenzazole, and the acid solvent is removed from the dope filament. As a result, the molecular chain is crystallized and a fiber microstructure is formed. Suitable extraction media include water and mixtures of water and acid solvents. Then, it is neutralized with an inorganic base such as sodium hydroxide, calcium hydroxide or potassium hydroxide as appropriate, and most of the solvent is removed.

As a result of intensive studies, the inventors of the present invention made the above-mentioned copolymer polybenzazole fiber according to the present invention by dividing the above-mentioned coagulation / cleaning bath into two stages instead of one stage, and the acid concentration and temperature of each stage. It has been found that the solvent can be easily removed and the fiber microstructure can be controlled by the management.
That is, it is important to provide a first-stage coagulation / washing bath that forms the main part of the desired fiber microstructure and a second-stage bath that removes the acid of the solvent while retaining the formed fiber microstructure. is there. The effect is exhibited if the acid concentration of the first stage coagulation / cleaning bath is approximately 30% or less, but if it is too low, the efficiency of acid recovery in the acid solution used for extraction deteriorates, which is undesirable in terms of production efficiency. The optimum acid concentration in the first stage coagulation / cleaning bath is preferably 5 to 30%, more preferably 5 to 20%.

The first-stage coagulation / cleaning bath temperature is also important, preferably 20 to 80 ° C, more preferably 30 to 70 ° C. If the bath temperature is too low, the rate of crystal structure formation by coagulation / cleaning is low, leading to densification of the fiber structure on the surface and the acid cleaning effect is reduced. Conversely, if the bath temperature is high, the rate of crystal structure formation is large and the crystals produced are small, but if the bath temperature is too high, then the crystals produced are too small, and the crystal structure formation rate is too high. As a result, the molecular chain cannot take a stable conformation state, so that residual stress is generated in the fiber interior, the molecular chain breakage is easily induced, and the fiber strength is reduced.

On the other hand, in the second stage coagulation / washing bath, it is important to remove the acid of the solvent while maintaining the crystal structure in the yarn formed in the first stage to some extent. Therefore, it is effective to make the acid concentration of the second stage coagulation / washing bath equal to or lower than the acid concentration of the first stage by a few percent, and to reduce the temperature as much as possible within the range where the extraction medium does not freeze. is there. The optimum acid concentration in the second stage is (x-3)% (x is the acid concentration in the first stage), and the optimum temperature is 5 to 10 ° C.
Through the above steps, the filament is washed so that the residual acid concentration (as an inorganic atom constituting the acid) is 8000 ppm or less, preferably 5000 ppm or less, and more preferably 3000 ppm or less. Thereafter, the filament is subjected to drying, heat treatment, winding and the like as necessary.

  The polybenzazole fiber according to the present invention desirably has a stoichiometric ratio of inorganic base and inorganic acid remaining in the fiber of 0.8 to 2: 1. If the stoichiometric ratio between the inorganic base and the inorganic acid remaining in the fiber is less than 0.8, the pH inside the yarn becomes extremely acidic, so that the hydrolysis of polybenzazole proceeds and the strength decreases. It becomes easy. This tendency becomes more prominent in polybenzazole fibers made of a homopolymer that is not copolymerized with a pyridine ring, and the strength is greatly reduced when exposed to high temperatures and high humidity for a long time. On the other hand, if the stoichiometric ratio between the inorganic base remaining in the fiber and the inorganic acid exceeds 2, the pH inside the yarn becomes extremely basic, so that the hydrolysis of PBZ molecules proceeds and the strength tends to decrease. Become. This tendency is particularly noticeable in homopolybenzazole fibers that are not copolymerized with a pyridine ring, and the strength decreases greatly when exposed to high temperatures and high humidity for a long time. From the above, it is desirable that the stoichiometric ratio of the inorganic base and the inorganic acid remaining in the fiber is 0.8 to 2: 1, more preferably 1 to 1.5: 1. It is desirable that the stoichiometric ratio is realized in any part of the fiber. Examples of the neutralization method using an inorganic base during washing include a guide oiling method, a showering method, and a dip method, but are not particularly limited.

  In the polybenzazole fiber according to the present invention, the component represented by the general formula (2) is 1 to 99 mol%, preferably 5 to 99 mol%, more preferably 10 to 99 mol%. If the copolymerization component is less than 5 mol%, the effect expected by introducing a pyridine ring structure into the fiber structure, that is, the effect of suppressing the strength decrease in a high temperature and high humidity environment is reduced. When the copolymerization component is in the range of 5 to 99 mol%, the initial strength of the fiber is not lowered, and the same strength and elastic modulus as those of polybenzazole not containing a pyridine ring are exhibited. Good operability and good operability without thread breakage are possible.

About the effect | action of the component represented by General formula (2) in a molecular chain, it estimates as follows.
That is, the polybenzazole-based fiber according to the present invention has at least a part of the benzene ring in the molecular chain replaced with a pyridine ring, as compared with a polybenzazole fiber that does not have a pyridine ring structure in the fiber structure. In addition, the interatomic distance of the ring portion slightly changes, and a highly disordered crystal structure is formed. Therefore, the polybenzazole-based fiber having a pyridine ring in the fiber structure has an apparent crystal size in the a-axis and b-axis directions perpendicular to the fiber axis, compared to a polybenzazole fiber having no pyridine ring in the fiber structure. When the true crystal size in the fiber axis direction is reduced and the crystal size is reduced, amorphous portions frequently appear at short intervals between crystals in the fiber.
Microscopically, the part that follows the bending of the fiber is considered to be a molecular chain of an amorphous part.Therefore, the size of each crystal is small, and there are many amorphous parts at short intervals, so the fiber is bent. It is considered that the molecular chain can easily follow the bending and the molecular chain breakage is less likely to occur.
On the other hand, the presence of a broken molecular chain in the fiber is considered to be a starting point for further degradation of the molecular chain due to exposure in a high-temperature and high-humidity environment, and one of the factors that cause a decrease in strength.

By the way, in the fiber manufacturing process, there is an unavoidable possibility that the fiber is subjected to various stresses during the manufacturing process such as contact with a roller, an oiling guide, etc. during the spinning process, bending by a rotating part, and the like, leading to molecular chain breakage. Therefore, in the present invention, by forming a fiber structure that easily follows the stress applied in the fiber manufacturing process, the processability of the yarn is improved, and even a small molecular scratch is reduced. It can be considered that durability can be improved because chain breakage and thus molecular chain degradation can be suppressed. Further, it is considered that the durability can be improved even with a twisted yarn by the same mechanism.

  Of course, since the crystal portion in the fiber plays an important role in developing the strength of the fiber, if the crystal size is too small, the desired strength cannot be exhibited. By controlling the process conditions and controlling the fiber microstructure, it was possible to reduce the crystal size without reducing the fiber strength.

The copolymer polybenzazole fiber according to the present invention has a single yarn average diameter D of 5 to 22 μm, preferably 10 to 20 μm. The fiber diameter may be measured by either an optical technique or a mechanical technique such as a micrometer. However, a scanning electron microscope (SEM) or laser-type outer diameter measurement is used because of the simplicity of measurement work. An optical method such as a vessel is preferred. In order to reflect the entire image of the fiber population, it is preferable to measure many single yarns, and it is appropriate to measure approximately 50 to 100 single yarns.
The average strength of the copolymerized polybenzazole fiber of the present invention is preferably 4.5 GPa or more, and more preferably 5.0 to 8.0 GPa.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited by the following examples, and may be implemented with appropriate modifications within a range that can meet the gist of the preceding and following descriptions. Of course, it is also possible, and they are all included in the technical scope of the present invention.

(Twisting method)
In accordance with JIS-L1013, using a tester, setting the grip interval to 50 cm, attaching the sample to the tester under the prescribed load obtained from the following formula, and twisting so that the twist coefficient is 30 went. The twisting was S twisting. After leaving for 30 seconds, untwisting was performed until the number of twists reached 6 by S twist, and a sample (twisted yarn) having a twist coefficient 6 of S twist was obtained. In addition, the calculation formula of the predetermined load (a) at the time of applying a twist, and the relational expression of a twist coefficient (K) and the number of twists (Tw) are shown below.
a = (1/10) D
K = 0.124 × Tw × D1 / 2
a: Predetermined load (g)
Tw: Number of twists (times / inch)
D: Filament fineness (Dtex)

(High temperature and high humidity treatment method and durability evaluation method)
A thermo-hygrostat (Yamato Science) with a yarn sample wound around a resin bobbin having a diameter of 10 cm and a sample twisted by the above-described twisting method (S twist factor 6). In a chamber (Humic Chamber 1G43M) and completely shielded from light so as not to enter the thermo-hygrostat, and the exposure treatment was carried out under conditions of 80 ° C. and 80% relative humidity. The treated sample and the untreated sample were measured for tensile strength with a tensile tester (manufactured by Shimadzu Corporation, model AG-50KNG) according to JIS-L1013.
From the measured values obtained, the following tensile strength retention ratio (%) was determined to evaluate the durability.
Tensile strength retention rate (%) = (treated sample tensile strength / untreated sample tensile strength) × 100

(Measurement method of apparent crystal size in the a-axis and b-axis directions)
The apparent crystal size in the direction perpendicular to the (200) plane and the direction perpendicular to the (010) plane in the fiber structure (hereinafter simply referred to as ACS) appears in the reflection in the equatorial direction (200). It was calculated from the measured half-value width β obs derived from diffraction and (010) diffraction using the following formula.
β = (βobs2-β02) 1/2
ACS = (0.9 λ) / (β cos θ)
Here, β0 is the spread (half width) of incident X-rays used for measurement, λ is the wavelength of X-rays, and 2θ is the diffraction angle.

(Measurement method of true crystal size in fiber axis direction)
The true crystal size D in the fiber axis direction in the fiber structure was determined from the intercept of the Rosemann plot. That is, the integral width δβ of each meridian peak obtained from the (00m) plane of wide angle X-ray diffraction was calculated using the following formula:
δβ = δβ0 + (πgm) 2 / c
D = 1 / δβ0
Here, δβ0 is an integral width determined only by the true crystal size in the fiber axis direction, π is the circular ratio, g is an order parameter of the crystal lattice, m is an index of the meridian diffraction peak, and c is a plane spacing of the (001) plane. It is. That is, if m2 is taken on the horizontal axis and the integration width δβ of the meridian diffraction peak corresponding to m is plotted on the vertical axis, if the plotted points are linearly approximated, δβ0 can be obtained at the intercept.

(Wide-angle X-ray diffraction)
Using a Rigaku Lint 2500 diffractometer (copper counter electrode, output 40 kV, 200 mA), the target transmission method was used.

(Residual acid concentration and sodium concentration in the filament)
The sample was solidified into a pellet and the residual phosphorus concentration (ppm) and the residual sodium concentration (ppm) were measured using a scanning X-ray fluorescence analyzer (Rigaku ZSX 100e).

(Fiber diameter)
The single yarn diameter was measured at a magnification of 5000 using a scanning electron microscope (SEM).

(Example 1-4, Comparative example 1-3)
Under a nitrogen stream, 381.6 g of 4,6-diaminoresorcinol dihydrochloride, 29.8 g of terephthalic acid, 269.4 g of 2,5-pyridinedicarboxylic acid, 1880.8 g of 116% polyphosphoric acid, and 570.1 g of diphosphorus pentoxide After stirring at 60 ° C. for 1 hour, the temperature was slowly raised and reacted at 135 ° C. for 25 hours, 150 ° C. for 5 hours, and 170 ° C. for 40 hours. The obtained polymer had an intrinsic viscosity of 22 dL / g measured with a methanesulfonic acid solution at 30 ° C. Spinning was performed using 2.0 kg of the obtained polymer dope under the condition that the single filament diameter was 11.5 μm.
That is, a spinning dope is extruded from a nozzle having a hole diameter of 0.18 mm and a hole number of 166 at a spinning temperature of 175 ° C. to form a dope filament, which is arranged to converge at a suitable position to form a multifilament. It was immersed in a washing bath and solidified, and subsequently immersed in a second-stage coagulation / washing bath and washed.
The concentration and temperature of the first stage and second stage coagulation / washing are performed under the conditions shown in Table 1, and the air gap between the spinning nozzle and the first stage coagulation / washing bath. The quench chamber was installed so that the filament was stretched at a more uniform temperature, and the quench temperature was 65 ° C.
The washed filament was wound around a resin bobbin at a winding speed of 200 m / min without drying.
The wound filament yarn was neutralized with a 1% NaOH aqueous solution for 10 seconds, then washed with water for 15 seconds, and then dried at 80 ° C. for 4 hours to produce an untwisted yarn. Each of the untwisted yarn and the twisted yarn twisted by the above-described method was evaluated for durability under a high temperature and high humidity environment. For untwisted yarns, the true crystal size in the ACS and fiber axis directions was calculated from the wide-angle X-ray diffraction results. These measurement results and evaluation results are shown in Tables 1 and 2.

Example 4
Under a nitrogen stream, 381.6 g of 4,6-diaminoresorcinol dihydrochloride, 148.8 g of terephthalic acid, 149.7 g of 2,5-pyridinedicarboxylic acid, 1880.8 g of 116% polyphosphoric acid, and 570.1 g of diphosphorus pentoxide. After stirring at 60 ° C. for 1 hour, the temperature was slowly raised and reacted at 135 ° C. for 25 hours, 150 ° C. for 5 hours, and 170 ° C. for 20 hours. The obtained polymer had an intrinsic viscosity of 25 dL / g measured with a methanesulfonic acid solution at 30 ° C. Using the obtained polymer dope 2.0 kg, the spinning dope was extruded from a nozzle having a hole diameter of 0.18 mm and a hole number of 166 at a spinning temperature of 175 ° C. so that the single yarn filament diameter would be 11.5 μm to form a dope filament, It was immersed in a first-stage coagulation / cleaning bath arranged to converge at an appropriate position to form a multifilament and solidified, and subsequently immersed in a second-stage coagulation / cleaning bath for cleaning. The concentration and temperature of the first stage and second stage coagulation / washing are performed under the conditions shown in Table 1, and the air gap between the spinning nozzle and the first stage coagulation / washing bath. The quench chamber was installed so that the quench temperature was 65 ° C.
The cleaned filament is wound around a resin bobbin at a winding speed of 200 m / min without drying, and the wound yarn is neutralized with a 1% NaOH aqueous solution for 10 seconds, washed with water for 15 seconds, and then dried at 80 ° C. for 4 hours. Thus, untwisted yarn was produced. Each of the untwisted yarn and the twisted yarn twisted by the above-described method was evaluated for durability under a high temperature and high humidity environment. For untwisted yarns, the true crystal size in the ACS and fiber axis directions was calculated from the wide-angle X-ray diffraction results. The analysis results, measurement results, and evaluation results of these fibers are shown in Tables 1 and 2.

(Example 5)
Under a nitrogen stream, 381.6 g of 4,6-diaminoresorcinol dihydrochloride, 208.3 g of terephthalic acid, 89.8 g of 2,5-pyridinedicarboxylic acid, 1880.8 g of 116% polyphosphoric acid, and 570.1 g of diphosphorus pentoxide. After stirring at 60 ° C. for 1 hour, the temperature was slowly raised and reacted at 135 ° C. for 25 hours, 150 ° C. for 5 hours, and 170 ° C. for 20 hours. The obtained polymer had an intrinsic viscosity of 25 dL / g measured with a methanesulfonic acid solution at 30 ° C.
Using the obtained polymer dope, a copolymerized polybenzazole fiber was produced in the same manner as in Example 4. The fiber was analyzed, measured, and evaluated in the same manner as in Example 4. The obtained results are shown in Tables 1 and 2.

(Example 6)
Under a nitrogen stream, 381.6 g of 4,6-diaminoresorcinol dihydrochloride, 238.1 g of terephthalic acid, 59.9 g of 2,5-pyridinedicarboxylic acid, 1880.8 g of 116% polyphosphoric acid, and 570.1 g of diphosphorus pentoxide. After stirring at 60 ° C. for 1 hour, the temperature was slowly raised and reacted at 135 ° C. for 25 hours, 150 ° C. for 5 hours, and 170 ° C. for 20 hours. The obtained polymer had an intrinsic viscosity of 26 dL / g measured with a methanesulfonic acid solution at 30 ° C.
Using the obtained polymer dope, a copolymerized polybenzazole fiber was produced in the same manner as in Example 4. The fiber was analyzed, measured, and evaluated in the same manner as in Example 4. The obtained results are shown in Tables 1 and 2.

(Example 7)
Under a nitrogen stream, 381.6 g of 4,6-diaminoresorcinol dihydrochloride, 267.8 g of terephthalic acid, 30.0 g of 2,5-pyridinedicarboxylic acid, 1880.8 g of 116% polyphosphoric acid, and 570.1 g of diphosphorus pentoxide. After stirring at 60 ° C. for 1 hour, the temperature was slowly raised and reacted at 135 ° C. for 25 hours, 150 ° C. for 5 hours, and 170 ° C. for 20 hours. The obtained polymer had an intrinsic viscosity of 27 dL / g measured with a methanesulfonic acid solution at 30 ° C.
Using the obtained polymer dope, a copolymerized polybenzazole fiber was produced in the same manner as in Example 4. The fiber was analyzed, measured, and evaluated in the same manner as in Example 4. The obtained results are shown in Table 1.

(Comparative Example 4)
In a nitrogen stream, 334.5 g of 4,6-diaminoresorcinol dihydrochloride, 260.8 g of terephthalic acid, and 2078.2 g of 122% polyphosphoric acid were stirred at 60 ° C. for 1 hour, then slowly heated to 25 ° C. at 135 ° C. The reaction was carried out at 150 ° C. for 5 hours and at 170 ° C. for 20 hours. The obtained poly (p-phenylenebenzobisoxazole) had an intrinsic viscosity of 29 dL / g measured with a methanesulfonic acid solution at 30 ° C.
Using the obtained polymer dope, polybenzazole fiber was produced in the same manner as in Example 4, and analysis, measurement and evaluation of the fiber were carried out in the same manner as in Example 4. The obtained results are shown in Tables 1 and 2.

表１より、比較例と比べ、実施例の共重合ポリベンザゾール繊維は、（２００）面及び（０１０）面のＡＣＳ、および繊維軸方向の見かけの結晶サイズが小さく、高温高湿度環境下における耐久性が良好であることがわかる。表２より、応力が加えられ、微細な切断した分子鎖をも含む可能性がある撚り糸においても、高い強度保持性が得られることがわかる。

From Table 1, compared with the comparative example, the copolymer polybenzazole fiber of the example has a small (200) plane ACS and (010) plane ACS, and an apparent crystal size in the fiber axis direction, in a high temperature and high humidity environment. It can be seen that the durability is good. From Table 2, it can be seen that high strength retention is obtained even in a twisted yarn to which stress is applied and which may include finely cut molecular chains.

The copolymerized polybenzazole fiber of the present invention can easily reduce the residual amount of the acid solvent and can be easily manufactured industrially. Furthermore, there are few molecular chain | strand breaks which induce the fall of the intensity | strength of a fiber, and intensity | strength can fully be maintained even when it is a case where it exposes for a long time in a high temperature, high humidity environment.
For this reason, as an industrial material, practicality can be improved more and the effect which expands a utilization field is great. In other words, uses processed into woven fabrics, knitted fabrics, braids, ropes, cords, etc., such as tension members such as cables, electric wires and optical fibers, ropes, tension members such as ropes, impact resistance absorbing members such as elasticity, gloves, etc. It can be used for a wide range of applications such as cut-resistant members, belts, tires, shoe soles, ropes, hoses, and other rubber reinforcements.

Claims (3)

The repeating unit represented by the following general formulas (1) and (2) in the molecular chain is random or block copolymerized, and the apparent crystal size of the (200) plane perpendicular to the fiber axis is 49 mm or less. Copolymer polybenzazole fiber characterized by.

However, n is the mole fraction of the repeating unit represented by the general formula (1) with respect to the total number of moles of the repeating units represented by the general formulas (1) and (2), and 0.01 ≦ n ≦ 0 A real number in the range of .99. X represents an S, O atom or NH group, and Z represents a C—H group or an N atom. In the azole ring, the N atom and the X atom / group may be trans or cis.   The copolymer polybenzazole fiber according to claim 1, wherein an apparent crystal size of a (010) plane perpendicular to the fiber axis is 25 mm or less. The copolymer polybenzazole fiber according to claim 1 or 2, wherein a true crystal size in a fiber axis direction is 120 mm or less.