JP2007211362A - Polybenzazole fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polybenzazole fiber significantly improved in durability as compared with those of conventional polybenzazole fibers. <P>SOLUTION: This polybenzazole fiber excellent in durability is provided by heating the polybenzazole fiber consisting of a polybenzazole polymer introduced with side chains such as a halogen group, methyl group, ethyl group, etc., on the benzazole skeleton of the polybenzazole at 300 to 600°C to perform cross-linking between molecular chains. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for producing a polybenzazole fiber having excellent durability.

A solution of rigid polymer, so-called liquid crystalline polymer, is highly oriented with high strength and high elasticity due to the property that molecular chains are easy to align in the flow direction and it takes a long time for the molecular chains to change to random orientation once aligned. A rate molded body can be produced. Furthermore, since a rigid polymer has a high glass transition temperature, a heat-resistant molded product can be obtained.
JP-A-6-341015

  Thus, since the fiber manufactured from the polybenzazole polymer which is a rigid polymer shows the outstanding intensity | strength, elastic modulus, and heat resistance, the utilization field is wide. However, in recent years, further improvement in performance is desired. In particular, there is a strong demand for polybenzazole fibers that have excellent durability against high temperatures and high humidity, that is, sufficient strength can be maintained even when exposed to high temperatures and high humidity for a long time. .

  The present invention has been made paying attention to the above circumstances, and an object of the present invention is to provide a polybenzazole fiber having a small decrease in strength due to long-time exposure under high temperature and high humidity.

但し、化学式１において、ｎは０以上１未満の実数である。ＸはＳ、Ｏ原子またはＮＨ基を示す。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良い。
また、化学式１におけるＹは化学式２で表され、これらが単独、または１〜ｎの範囲内でこれら３つの繰り返し単位が任意の割合で共重合していてもよい。Ｒはハロゲン原子または炭素原子数１〜６のアルキル基を示す。

またさらに、上記繰り返し単位とは、化学式３で示される単位を示す。
Ｒ'は水素原子、ハロゲン原子または炭素原子数１〜６のアルキル基を示す。

In the present invention, a polybenzazole fiber having a molecular structure represented by the following chemical formula 1 is subjected to an intermolecular cross-linking treatment by irradiation with active energy rays under an inert gas, and is cross-linked at least one site per 50 repeating units. It is a polybenzazole fiber characterized by the following.

However, in Chemical Formula 1, n is a real number of 0 or more and less than 1. X represents an S, O atom or NH group. In the azole ring, the N atom and the X atom / group may be trans or cis.
Y in Chemical Formula 1 is represented by Chemical Formula 2, and these may be used alone, or these three repeating units may be copolymerized at an arbitrary ratio within the range of 1 to n. R represents a halogen atom or an alkyl group having 1 to 6 carbon atoms.

Furthermore, the repeating unit refers to a unit represented by Chemical Formula 3.
R ′ represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms.

  According to the present invention, crosslinking between polybenzazole molecular chains is easy by heat treatment at 300 to 600 ° C., and by crosslinking one or more sites per 50 repeating units, compared to conventional polybenzazole fibers, It has become possible to provide a polybenzazole fiber excellent in durability and having a very small decrease in strength due to long-term exposure under high temperature and high humidity.

Hereinafter, the present invention will be described in detail.
The polybenzazole according to the present invention (hereinafter also referred to as PBZ) is from polybenzoxazole (hereinafter also referred to as PBO), polybenzothiazole (hereinafter also referred to as PBZT), and polybenzimidazole (hereinafter also referred to as PBI). Say the polymer chosen.
The polybenzazole polymer that forms the polybenzazole fiber according to the present invention includes an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a propyl group, and a tert-butyl group on a benzazole skeleton (azole ring), halogen It is a polybenzazole polymer having side chains such as groups, and when a heat treatment at 300 to 600 ° C. is performed after forming a fiber, radicals are generated and intermolecular chain crosslinks are formed by the action of the side chains. Is.
Preferably, it is polybenzazole in which the repeating unit represented by the general formula (1) is randomly copolymerized in the molecular chain.
The following are mentioned as a preferable homopolymer and copolymer in this invention.

等が挙げられるが、もちろん本発明技術内容はこれらに限定されるものではない。

Of course, the technical contents of the present invention are not limited to these.

  Since a highly durable fiber is obtained, the number of crosslinks is 1 to 50 per 50 repeating units, preferably 1 to 35, and more preferably 1 to 25 in order to give the fiber flexibility. Outside this range, the desired high durability fiber cannot be obtained. Furthermore, the copolymerization ratio of the crosslinkable molecule having a side chain is 2 to 100%, preferably 5 to 70%, and more preferably 10 to 50% for reliable crosslinking. Outside this range, it is difficult to obtain the desired number of crosslinks, and highly durable fibers cannot be obtained.

  Polybenzazole fibers are manufactured from a dope containing a polybenzazole polymer, and suitable solvents for preparing the dope include cresol and a non-oxidizing acid capable of dissolving the polymer. Examples of suitable non-oxidizing acids include polyphosphoric acid, methanesulfonic acid and high concentrations of sulfuric acid or mixtures thereof. Of these, polyphosphoric acid and methanesulfonic acid, particularly polyphosphoric acid are preferred.

  The polymer concentration in the dope is preferably at least about 7% by weight, more preferably at least 10% by weight. The maximum concentration is limited by practical handling properties such as polymer solubility and dope viscosity. Due to their limiting factors, the polymer concentration usually does not exceed 20% by weight.

  In the present invention, suitable polymers or copolymers and dopes are synthesized by known methods. For example, Wolfe et al., US Pat. No. 4,533,693, Sybert et al., US Pat. No. 4,772,678, Harris, US Pat. No. 4,847,350, or Gregory et al., US Pat. No. 5,089,591. In summary, suitable monomers are heated in a non-oxidizing, dehydrating acid solution at a stepwise or constant rate of heating from about 60 ° C. to 230 ° C. under high-speed stirring and high shear conditions in a non-oxidizing atmosphere. It is made to react by raising.

  The dope thus obtained is extruded from the spinneret and stretched in space to form a filament. A suitable manufacturing method is described in US Pat. No. 5,034,250. 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.

  The filament after spinning is washed to avoid excessive stretching and a part of the solvent is removed. Then, it is further washed and appropriately neutralized with an inorganic base such as sodium hydroxide, calcium hydroxide or potassium hydroxide, and most of the solvent is removed. Washing here is compatible with the mineral acid dissolving the polybenzazole polymer, and the fiber or filament is brought into contact with a liquid that does not serve as a solvent for the polybenzazole polymer to remove the acid solvent from the dope. It is to be. Suitable cleaning liquids include water and mixtures of water and acid solvents. The filament is preferably washed to a residual mineral acid metal atom concentration of 8000 ppm or less by weight, more preferably 5000 ppm or less. Thereafter, the filament is subjected to drying, heat treatment, winding and the like as necessary.

  The filaments thus obtained are cross-linked by treating them under an inert gas. The treatment referred to here is heating at 300 to 600 ° C. Nitrogen, argon, etc. are generally used as the inert gas.

  In order to maintain the uniformity of the crosslinking density, the fiber diameter is preferably 200 μm or less, more preferably 0.3 to 100 μm. When the fiber diameter is smaller than 0.3 μm, uniform fiber spinning becomes difficult.

In the present invention, intermolecular crosslinking involves R in the general formula (1), that is, a side chain such as a methyl group or an ethyl group such as an ethyl group or a halogen group in the benzazole skeleton. Occurs and crosslinks between molecular chains.
For example, when R is a methyl group, the following crosslinked structure is obtained.

Such crosslinking can be confirmed by measuring ¹³ C solid state NMR of the untreated filament and the treated filament. In the case of having a methyl group, the signal based on the methyl group decreases, and a new signal based on the methylene group can be observed. Moreover, when it has an ethyl group, the signal based on an ethyl group reduces and the signal of the methylene group different from the methylene group of an ethyl group can be observed. Further, in the case of having a halogen group, a high magnetic field shift of the carbon signal to which the halogen group is bonded is observed.

  The effect of intermolecular crosslinking is not clear, but is presumed as follows. Residual phosphoric acid is present in the order of several thousand ppm in the filaments produced after the spinning and the water washing neutralization step. Under high temperature and high humidity, the residual phosphoric acid dissociates in the filament and releases protons. This liberated proton and water molecules attack the polybenzazole molecules, and it is assumed that the yarn strength decreases. However, when the molecules are cross-linked, the bonds between the molecules are not broken even if the polybenzazole molecules are attacked, and therefore, it is considered that they are not easily affected by the decrease in strength. The present invention is not bound by this consideration.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited by the following examples, but 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.

(Intrinsic viscosity)
The viscosity of the polymer solution prepared to a concentration of 0.5 g / l using methanesulfonic acid as a solvent was measured and calculated in an oven at 25 ° C. using an Ostwald viscometer.

(Fiber diameter adjustment and measurement method)
The fiber diameter was adjusted by keeping the spinning speed constant and changing the winding speed. Furthermore, the fiber diameter was measured with a scanning electron microscope (manufactured by Hitachi, S-3500N).

(Confirmation of crosslinking and evaluation method for number of crosslinking)
About the pre-treatment filament and the post-treatment filament, about 300 mg of the sample was put in a 7 mmφ probe, and ¹³ C solid state NMR was measured by the DD / MAS method at room temperature, 16 to 32 integration times, and a pulse interval time of 10,000 seconds. . In the case of a polymer having a methyl group in the side chain, the number of crosslinks was calculated from the decrease in methyl group.

(Durability evaluation method under high temperature and high humidity)
The durability at high temperature and high humidity was evaluated by the retention rate of the tensile strength after treatment with respect to the tensile strength before high temperature and high humidity storage treatment.
A high temperature and high humidity storage treatment was carried out in a thermo-hygrostat with a thread sample wound around a stainless steel bobbin having a diameter of 10 cm, the sample was taken out after a predetermined time, and a tensile test was performed at room temperature. In addition, for storage processing under high temperature and high humidity, Humidic Chamber 1G43M manufactured by Yamato Kagaku is used, completely shielded from light so that light does not enter the constant temperature and humidity chamber, at 80 ° C and 80% relative humidity. For 700 hours. The tensile strength was measured with a tensile tester (manufactured by Shimadzu Corporation, model AG-50KNG) according to JIS-L1013.

Example 1
116% polyphosphoric acid 27.9 g, 4,6-diaminoresorcinol dihydrochloride 5.7 g, 2-methyl-4,6-diaminoresorcinol dihydrochloride 0.1 g, terephthalic acid 4.6 g and five 8.3 g of phosphorus oxide was added, and the mixture was stirred and mixed at 70 ° C. for 15 minutes in the reactor. Further, the temperature was raised to 120 ° C., mixed with stirring for 3.5 hours to remove hydrochloric acid, heated to 135 ° C. and stirred for 19 hours to oligomerize. Then, it heated up at 200 degreeC and superposed | polymerized and obtained the PBO polymer dope. The color of the polymer dope was yellow and the intrinsic viscosity was 28 dl / g.
The polymerized dope was extruded from a single-hole nozzle having a pore diameter of 200 μm at a spinning temperature of 175 ° C., and the filament was solidified in a water bath and wound around a yarn tube. The winding speed was 100 m / min. The wound yarn was washed with water for 18 hours, neutralized with 1% NaOH aqueous solution for 30 minutes, and further washed with water for 1 to 24 hours. Drying was performed at 80 ° C. for 4 hours.
Then, the obtained filament was heat-treated at 500 ° C. for 1 hour under a nitrogen stream. As a result of evaluating the number of crosslinks by the above-mentioned method, Table 1 shows the results of evaluating durability under high temperature and high humidity.

(Example 2)
116% polyphosphoric acid 28.7 g under nitrogen flow, 4,6-diaminoresorcin dihydrochloride 5.6 g, 2-methyl-4,6-diaminoresorcinol dihydrochloride 0.3 g, terephthalic acid 4.7 g and five 8.6 g of phosphorus oxide was added, and the mixture was stirred and mixed at 70 ° C. for 15 minutes in the reactor. Further, the temperature was raised to 120 ° C., mixed with stirring for 3.5 hours to remove hydrochloric acid, heated to 135 ° C. and stirred for 19 hours to oligomerize. Then, it heated up at 200 degreeC and superposed | polymerized and obtained the PBO polymer dope. The color of the polymer dope was yellow and the intrinsic viscosity was 29 dl / g.
The polymerized dope was extruded from a single-hole nozzle having a pore diameter of 200 μm at a spinning temperature of 175 ° C., and the filament was solidified in a water bath and wound around a yarn tube. The winding speed was 100 m / min. The wound yarn was washed with water for 18 hours, neutralized with 1% NaOH aqueous solution for 30 minutes, and further washed with water for 1 to 24 hours. Drying was performed at 80 ° C. for 4 hours.
Then, the obtained filament was heat-treated at 500 ° C. for 1 hour under a nitrogen stream. As a result of evaluating the number of crosslinks by the above-mentioned method, Table 1 shows the results of evaluating durability under high temperature and high humidity.

(Example 3)
116% polyphosphoric acid 28.1 g under nitrogen flow, 5.2 g of 4,6-diaminoresorcin dihydrochloride, 0.6 g of 2-methyl-4,6-diaminoresorcin dihydrochloride, 4.6 g of terephthalic acid and five 8.4 g of phosphorus oxide was added, and the mixture was stirred and mixed at 70 ° C. for 15 minutes in the reactor. Further, the temperature was raised to 120 ° C., mixed with stirring for 3.5 hours to remove hydrochloric acid, heated to 135 ° C. and stirred for 19 hours to oligomerize. Then, it heated up at 200 degreeC and superposed | polymerized and obtained the PBO polymer dope. The color of the polymer dope was yellow and the intrinsic viscosity was 29 dl / g.
The polymerized dope was extruded from a single-hole nozzle having a pore diameter of 200 μm at a spinning temperature of 175 ° C., and the filament was solidified in a water bath and wound around a yarn tube. The winding speed was 100 m / min. The wound yarn was washed with water for 18 hours, neutralized with 1% NaOH aqueous solution for 30 minutes, and further washed with water for 1 to 24 hours. Drying was performed at 80 ° C. for 4 hours.
Then, the obtained filament was heat-treated at 500 ° C. for 1 hour under a nitrogen stream. As a result of evaluating the number of crosslinks by the above-mentioned method, Table 1 shows the results of evaluating durability under high temperature and high humidity.

Example 4
116% polyphosphoric acid 28.2 g under nitrogen stream, 4,6-diaminoresorcinic dihydrochloride 3.9 g, 2-methyl-4,6-diaminoresorcinic dihydrochloride 1.8 g, terephthalic acid 4.3 g and five 8.3 g of phosphorus oxide was added, and the mixture was stirred and mixed at 70 ° C. for 15 minutes in the reactor. Further, the temperature was raised to 120 ° C., mixed with stirring for 3.5 hours to remove hydrochloric acid, heated to 135 ° C. and stirred for 19 hours to oligomerize. Then, it heated up at 200 degreeC and superposed | polymerized and obtained the PBO polymer dope. The color of the polymer dope was yellow and the intrinsic viscosity was 27 dl / g.
The polymerized dope was extruded from a single-hole nozzle having a pore diameter of 200 μm at a spinning temperature of 175 ° C., and the filament was solidified in a water bath and wound around a yarn tube. The winding speed was 100 m / min. The wound yarn was washed with water for 18 hours, neutralized with 1% NaOH aqueous solution for 30 minutes, and further washed with water for 1 to 24 hours. Drying was performed at 80 ° C. for 4 hours.
Then, the obtained filament was heat-treated at 500 ° C. for 1 hour under a nitrogen stream. As a result of evaluating the number of crosslinks by the above-mentioned method, Table 1 shows the results of evaluating durability under high temperature and high humidity.

(Example 5)
116% polyphosphoric acid 28.6 g under nitrogen flow, 3.9 g of 4,6-diaminoresorcin dihydrochloride, 1.8 g of 2-chloro-4,6-diaminoresorcin dihydrochloride, 4.3 g of terephthalic acid and five 8.1 g of phosphorus oxide was added, and the mixture was stirred and mixed at 70 ° C. for 15 minutes in the reactor. Further, the temperature was raised to 120 ° C., mixed with stirring for 3.5 hours to remove hydrochloric acid, heated to 135 ° C. and stirred for 19 hours to oligomerize. Then, it heated up at 200 degreeC and superposed | polymerized and obtained the PBO polymer dope. The color of the polymer dope was yellow and the intrinsic viscosity was 26 dl / g.
The polymerized dope was extruded from a single-hole nozzle having a pore diameter of 200 μm at a spinning temperature of 175 ° C., and the filament was solidified in a water bath and wound around a yarn tube. The winding speed was 100 m / min. The wound yarn was washed with water for 18 hours, neutralized with 1% NaOH aqueous solution for 30 minutes, and further washed with water for 1 to 24 hours. Drying was performed at 80 ° C. for 4 hours.
Then, the obtained filament was heat-treated at 500 ° C. for 1 hour under a nitrogen stream. As a result of evaluating the number of crosslinks by the above-mentioned method, Table 1 shows the results of evaluating durability under high temperature and high humidity.

(Example 6)
116% polyphosphoric acid 28.0 g under nitrogen flow, 4,6-diaminoresorcinol dihydrochloride 2.9 g, 2-methyl-4,6-diaminoresorcinol dihydrochloride 3.0 g, terephthalic acid 4.3 g and five 8.1 g of phosphorus oxide was added, and the mixture was stirred and mixed at 70 ° C. for 15 minutes in the reactor. Further, the temperature was raised to 120 ° C., mixed with stirring for 3.5 hours to remove hydrochloric acid, heated to 135 ° C. and stirred for 19 hours to oligomerize. Then, it heated up at 200 degreeC and superposed | polymerized and obtained the PBO polymer dope. The color of the polymer dope was yellow and the intrinsic viscosity was 25 dl / g.
The polymerized dope was extruded from a single-hole nozzle having a pore diameter of 200 μm at a spinning temperature of 175 ° C., and the filament was solidified in a water bath and wound around a yarn tube. The winding speed was 100 m / min. The wound yarn was washed with water for 18 hours, neutralized with 1% NaOH aqueous solution for 30 minutes, and further washed with water for 1 to 24 hours. Drying was performed at 80 ° C. for 4 hours.
Then, the obtained filament was heat-treated at 500 ° C. for 1 hour under a nitrogen stream. As a result of evaluating the number of crosslinks by the above-mentioned method, Table 1 shows the results of evaluating durability under high temperature and high humidity.

(Example 7)
116% polyphosphoric acid 28.1 g, 1,3-dimercapto-4,6-diaminobenzene dihydrochloride 2.7 g, 1,3-dimercapto-2-methyl-4,6-diaminobenzene dihydrochloride under nitrogen flow 2.7 g of salt, 3.7 g of terephthalic acid and 6.6 g of phosphorus pentoxide were added, and the mixture was stirred and mixed at 70 ° C. for 15 minutes in the reactor. Further, the temperature was raised to 120 ° C., mixed with stirring for 3.5 hours to remove hydrochloric acid, heated to 135 ° C. and stirred for 19 hours to oligomerize. Then, it heated up at 200 degreeC and superposed | polymerized and obtained the PBO polymer dope. The color of the polymer dope was yellow and the intrinsic viscosity was 27 dl / g.
The polymerized dope was extruded from a single-hole nozzle having a pore diameter of 200 μm at a spinning temperature of 175 ° C., and the filament was solidified in a water bath and wound around a yarn tube. The winding speed was 100 m / min. The wound yarn was washed with water for 18 hours, neutralized with 1% NaOH aqueous solution for 30 minutes, and further washed with water for 1 to 24 hours. Drying was performed at 80 ° C. for 4 hours.
Then, the obtained filament was heat-treated at 500 ° C. for 1 hour under a nitrogen stream. As a result of evaluating the number of crosslinks by the above-mentioned method, Table 1 shows the results of evaluating durability under high temperature and high humidity.

(Example 8)
116% polyphosphoric acid 28.5 g under a nitrogen stream, 4,6-diaminoresorcinol dihydrochloride 1.7 g, 2-methyl-4,6-diaminoresorcinol dihydrochloride 4.0 g, terephthalic acid 4.3 g and five The phosphorus oxide 8.2g was added, and it stirred and mixed in the reactor at 70 degreeC for 15 minutes. Further, the temperature was raised to 120 ° C., mixed with stirring for 3.5 hours to remove hydrochloric acid, heated to 135 ° C. and stirred for 19 hours to oligomerize. Then, it heated up at 200 degreeC and superposed | polymerized and obtained the PBO polymer dope. The color of the polymer dope was yellow and the intrinsic viscosity was 27 dl / g.
The polymerized dope was extruded from a single-hole nozzle having a pore diameter of 200 μm at a spinning temperature of 175 ° C., and the filament was solidified in a water bath and wound around a yarn tube. The winding speed was 100 m / min. The wound yarn was washed with water for 18 hours, neutralized with 1% NaOH aqueous solution for 30 minutes, and further washed with water for 1 to 24 hours. Drying was performed at 80 ° C. for 4 hours.
Then, the obtained filament was heat-treated at 500 ° C. for 1 hour under a nitrogen stream. As a result of evaluating the number of crosslinks by the above-mentioned method, Table 1 shows the results of evaluating durability under high temperature and high humidity.

Example 9
Under a nitrogen stream, 5.6 g of 2-methyl-4,6-diaminoresorcin dihydrochloride, 4.0 g of terephthalic acid and 7.7 g of phosphorus pentoxide were added to 27.8 g of 116% polyphosphoric acid. Stir and mix at 15 ° C. for 15 minutes. Further, the temperature was raised to 120 ° C., mixed with stirring for 3.5 hours to remove hydrochloric acid, heated to 135 ° C. and stirred for 19 hours to oligomerize. Then, it heated up at 200 degreeC and superposed | polymerized and obtained the PBO polymer dope. The color of the polymer dope was yellow and the intrinsic viscosity was 28 dl / g.
The polymerized dope was extruded from a single-hole nozzle having a pore diameter of 200 μm at a spinning temperature of 175 ° C., and the filament was solidified in a water bath and wound around a yarn tube. The winding speed was 100 m / min. The wound yarn was washed with water for 18 hours, neutralized with 1% NaOH aqueous solution for 30 minutes, and further washed with water for 1 to 24 hours. Drying was performed at 80 ° C. for 4 hours.
Then, the obtained filament was heat-treated at 500 ° C. for 1 hour under a nitrogen stream. As a result of evaluating the number of crosslinks by the above-mentioned method, Table 1 shows the results of evaluating durability under high temperature and high humidity.

(Comparative Example 1)
Under a nitrogen stream, 5.8 g of 4,6-diaminoresorcin, 4.4 g of terephthalic acid and 8.6 g of phosphorus pentoxide were added to 28.4 g of 116% polyphosphoric acid, and the mixture was stirred and mixed at 70 ° C. for 15 minutes. . Further, the temperature was raised to 120 ° C., mixed with stirring for 3.5 hours to remove hydrochloric acid, heated to 135 ° C. and stirred for 19 hours to oligomerize. Then, it heated up at 200 degreeC and superposed | polymerized and obtained the PBO polymer dope. The color of the polymer dope was yellow and the intrinsic viscosity was 30 dl / g.
The polymerized dope was extruded from a single-hole nozzle having a pore diameter of 200 μm at a spinning temperature of 175 ° C., and the filament was solidified in a water bath and wound around a yarn tube. The winding speed was 100 m / min. The wound yarn was washed with water for 18 hours, neutralized with 1% NaOH aqueous solution for 30 minutes, and further washed with water for 1 to 24 hours. Drying was performed at 80 ° C. for 4 hours.
Then, the obtained filament was heat-treated at 500 ° C. for 1 hour under a nitrogen stream. As a result of evaluating the number of crosslinks by the above-mentioned method, Table 1 shows the results of evaluating durability under high temperature and high humidity.

(Comparative Example 2)
116% polyphosphoric acid 28.8 g under a nitrogen stream, 4,6-diaminoresorcinol dihydrochloride 5.8 g, 2-methyl-4,6-diaminoresorcinol dihydrochloride 0.1 g, terephthalic acid 4.7 g and five 8.6 g of phosphorus oxide was added, and the mixture was stirred and mixed at 70 ° C. for 15 minutes in the reactor. Further, the temperature was raised to 120 ° C., mixed with stirring for 3.5 hours to remove hydrochloric acid, heated to 135 ° C. and stirred for 19 hours to oligomerize. Then, it heated up at 200 degreeC and superposed | polymerized and obtained the PBO polymer dope. The color of the polymer dope was yellow and the intrinsic viscosity was 31 dl / g.
The polymerized dope was extruded from a single-hole nozzle having a pore diameter of 200 μm at a spinning temperature of 175 ° C., and the filament was solidified in a water bath and wound around a yarn tube. The winding speed was 100 m / min. The wound yarn was washed with water for 18 hours, neutralized with 1% NaOH aqueous solution for 30 minutes, and further washed with water for 1 to 24 hours. Drying was performed at 80 ° C. for 4 hours.
Then, the obtained filament was heat-treated at 500 ° C. for 1 hour under a nitrogen stream. As a result of evaluating the number of crosslinks by the above-mentioned method, Table 1 shows the results of evaluating durability under high temperature and high humidity.

  As described above, polybenzazole fibers having a structural unit in which an alkyl group such as a methyl group or an ethyl group or a halogen group is introduced onto a benzazole skeleton (a benzene ring constituting a heterocyclic ring) in an inert gas are 300 to 600. By heating at 0 ° C. and crosslinking treatment, a fiber excellent in durability at high temperature and high humidity can be obtained.

According to the present invention, it is possible to provide a polybenzazole fiber that can sufficiently maintain strength even when exposed to a high temperature and high humidity for a long time. The effect of expanding is tremendous.
That is, tension members such as cables, electric wires and optical fibers, ropes, tension materials, rocket insulation, rocket casing, pressure vessels, space suit strings, planetary exploration balloons, aviation, space materials, bulletproof materials, etc. Shock-resistant members, cut-resistant members such as gloves, fire-resistant clothing, heat-resistant felt, plant gaskets, heat-resistant fabrics, various seals, heat-resistant cushions, heat-resistant members such as filters, belts, tires, shoe soles, ropes, Rubber reinforcements such as hoses, members for electronic materials such as high-density high-performance circuit boards for mounting silicon chips, fishing lines, fishing rods, tennis rackets, table tennis rackets, badminton rackets, golf shafts, club heads, guts, strings , Sail cloth, running shoes, marathon shoes, spiked shoes, skate shoes, Athletic shoes such as ketball shoes, volleyball shoes, bicycles for competition (running) and its wheels, road racers, pis racers, mountain bikes, composite wheels, disc wheels, tension discs, spokes, brake wires, transmission wires, competitions ( Running wheelchairs and their wheels, protectors, racing suits, sports materials such as skis, stocks, helmets, parachutes, friction materials such as avant belts, clutch facings, various building material reinforcements and other rider suits, speakers Can be used for a wide range of applications, such as cones, lightweight baby carriages, lightweight wheelchairs, lightweight nursing beds, lifeboats, and life jackets.

Claims (2)

A polybenzazole fiber having a molecular structure represented by the following chemical formula 1 is subjected to an intermolecular cross-linking treatment by a heat treatment at 300 to 600 ° C., and is crosslinked at least one site per 50 repeating units. Benzazole fiber.

However, in Chemical Formula 1, n is a real number of 0 or more and less than 1. X represents an S, O atom or NH group. In the azole ring, the N atom and the X atom / group may be trans or cis.
Y in Chemical Formula 1 is represented by Chemical Formula 2, and these may be used alone or these three repeating units may be copolymerized in an arbitrary ratio within the range of 1 to n. R represents a halogen atom or an alkyl group having 1 to 6 carbon atoms.

Furthermore, the repeating unit refers to a unit represented by Chemical Formula 3.

R ′ represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 6 carbon atoms.   2. The polybenzazole fiber according to claim 1, which has a tensile strength retention of 85% or more after being exposed for 700 hours in an atmosphere at a temperature of 80 ° C. and a relative humidity of 80%.