JPH04194022A - Production of fiber of polybenzothiazoles, polybenzoxazoles or polybenzimidazoles - Google Patents

Abstract

PURPOSE:To obtain the subject fiber excellent in toughness, denseness, homogeneity, etc., by producing fiber from a wholly aromatic heterocyclic polymer at a specific concentration, a specified viscosity and a specific discharge speed to a coagulation bath under subsequent specified heat-treating conditions. CONSTITUTION:(A) A wholly aromatic heterocyclic polymer compound such as polybenzothiazole, polybenzoxazole or polybenzimidazole is dissolved in (B) polyphosphoric acid, methanesulfonic acid, sulfuric acid or their mixture so as to provide 1-50wt.% concentration and 5X10<2> to 5X10<6> P viscosity, and the resultant solution is then passed through a nozzle at 5X10<2> to 5X10<4>cm/sec average flow velocity, discharged into a coagulation bath and heat-treated at 450-700 deg.C temperature for 10sec to 3min to afford the objective fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for producing polybenzothiazole fibers, polybenzoxazole fibers, or polybenzimidazole fibers having excellent toughness, density, and homogeneity.

Technical Background of the Invention In recent years, fully aromatic heterocyclic polymer compounds such as polybenzothiazoles, polybenzoxazoles, or polybenzimidazoles have attracted attention as heat-resistant resins in place of polyimide resins. Examples of such wholly aromatic heterocyclic polymer compounds include the following compounds.

poly(p-)benzobisthiazole)poly(2)
, 6-benzothiazole) poly(P-phenylenebenzobisoxazole) poly(
2,5-Benzoxazole) Poly(P-)Unilenebenzobisimidazole) Poly(
2,5(6)-benzimidazole) Such fully aromatic heterocyclic polymer compounds have excellent heat resistance and, unlike polyimide resins, have low hydrolysis resistance. They are also extremely good at sex.

Since the wholly aromatic heterocyclic polymer compound has such a rigid skeletal structure, by using an appropriate solvent, the solution thereof can exhibit liquid crystallinity. By spinning such a liquid crystal solution, a liquid crystalline fiber made of a wholly aromatic heterocyclic polymer compound is obtained, and this fiber has liquid crystallinity.

For example, in Japanese Patent Publication No. 60-500538,
2,5-diamino-1,4-benzenedithiol dihydrochloride, 4,6-diamino-1,3-benzenediol dihydrochloride or 1.2.4
．． Polybenzothiazoles,
It is described that wholly aromatic heterocyclic polymer compounds such as polybenzoxazoles and polybenzimidazoles can be produced.

When producing fibers from such wholly aromatic heterocyclic polymer compounds, it is necessary to precipitate and separate the wholly aromatic heterocyclic polymers produced from the reaction solvent, and then dissolve them in an organic solvent again. Since this is difficult, the reaction solution obtained by carrying out the reaction as described above is used as it is or diluted as a spinning stock solution, and the wet spinning method (wet spinning method) or the dry jet/wet spinning method ( It is generally spun using a spinning method called wet-dry spinning.

By the way, such a reaction solution contains fully aromatic heterocyclic polymer compounds such as polybenzothiazoles, polybenzoxazoles, and polybenzimidazoles, usually at a high concentration of 5 to 20% by weight. In such a highly concentrated liquid, the wholly aromatic heterocyclic polymer compound may already form a liquid crystal phase in the reaction liquid.

In this case, polarized light is observed in the solution under crossed Nicols. Further, even when a liquid crystal phase is not formed, the polymer compounds are in a highly agglomerated state (for example, oriented state) with each other and form a certain type of domain structure. Then, such a reaction solution is subjected to wet spinning method (wet spinning method).
When spinning is carried out using a dry jet/wet spinning method, fibers can be obtained in which the polymer compounds are aggregated or oriented, or have almost the same structure.

Although the fibers obtained in this way have heat resistance equivalent to or higher than polyimide fibers, their mechanical properties are extremely brittle and cannot be drawn. . Therefore, this fiber has the problem of extremely low processability. As described above, in the conventional technology related to fibers made of wholly aromatic heterocyclic polymer compounds as described above, the excellent properties such as heat resistance and hydrolysis resistance possessed by wholly aromatic heterocyclic polymer compounds could not be used effectively.

Purpose of the Invention The present invention aims to solve the problems in the prior art as described above, and provides polybenzothiazole fibers and polybenzoxazole fibers that have excellent toughness, density, and homogeneity. The purpose of the present invention is to provide a method for producing fibers and polybenzimidazole fibers.

Summary of the Invention The method for producing polybenzothiazole fibers, polybenzoxazole fibers, or polybenzimidazole fibers according to the present invention includes adding polyphosphoric acid, methanesulfonic acid, sulfuric acid, or a mixture thereof to polybenzothiazole fibers, polybenzothiazole fibers, or polybenzoimidazole fibers. The concentration of oxazole or polybenzimidazole is 1 to 50% by weight, and the viscosity of the solution is 5X.
The solution was dissolved at an average flow rate of 5 x 102 to 5'X 10' cm/
The fiber is passed through a nozzle and discharged into a coagulation bath for spinning to obtain a fiber, and then the obtained fiber is heat-treated at a temperature of 450° C. to 700° C. for 10 seconds to 3 minutes.

According to the production method of the present invention, polybenzothiazole fibers, polybenzoxazole fibers, or polybenzimidazole fibers having excellent toughness, density, and homogeneity can be obtained.

DETAILED DESCRIPTION OF THE INVENTION A method for producing polybenzothiazole fibers, polybenzoxazole fibers or polybenzimidazole fibers having excellent toughness, denseness and homogeneity according to the present invention will be specifically described below.

The polymer compounds used in the method for producing fibers according to the present invention are polybenzothiazoles, polybenzoxazoles, or polybenzimidazoles, and specifically, such polymer compounds include those of the above formula. PBT, ABPBTlPBOlABPBO, PBI
and fully aromatic heterocyclic polymer compounds such as ABPBI. In addition, in the present invention, the above-mentioned wholly aromatic heterocyclic polymer compounds can be used alone, or two or more types can be used in combination. When using two or more types of wholly aromatic heterocyclic polymer compounds in combination, the two or more types of wholly aromatic heterocyclic polymer compounds may be synthesized individually, for example, by the method described below. Two or more kinds of wholly aromatic heterocyclic polymer compounds can be obtained by mixing the obtained reaction solutions and further diluting them. Apart from dirt, the desired results can also be obtained with a wholly aromatic heterocyclic polymer copolymer compound using two or more types of comonomers.

Among such wholly aromatic heterocyclic polymer compounds, for example, the above PBT is 2,5-diamino-1°shiba-4-benzenebutiol dihydrochlorite (DA
It can be synthesized by reacting BDT) and terephthalic acid (TA) in the presence of polyphosphoric acid.

Moreover, PBO can be synthesized by reacting 4,6-diamitu-1,3-benzenediol dihydrochloride (DAR) and terephthalic acid (TA) in the presence of polyphosphoric acid.

Furthermore, ABPBT is 3-amino-4-hydroxybenzoic acid hydrochloride (AHAH)
can be synthesized by reacting in the presence of polyphosphoric acid.

Furthermore, FBI, ABPB I, etc. can also be manufactured according to the above method.

The polyphosphoric acid used in the above reaction acts not only as a reaction solvent but also as a reaction catalyst in this reaction.

Here, polyphosphoric acid (PPA) can generally be represented by the following formula.

H,,,2-Pゎ-03n + 1 The above polyphosphoric acid is orthophosphoric acid (H3PO,)
A method of heating and dehydrating condensation of phosphorus pentoxide (P2
It can be prepared by adding a predetermined amount of water for 0 s) and then heating it.

Such polyphosphoric acid is a polymeric protonic acid and an acid anhydride, and exists in the form of a colorless, transparent, and viscous syrup at room temperature.

For example, the reaction conditions when synthesizing a wholly aromatic heterocyclic polymer compound are
, 6-diamitu-1,3-benzenediol dihydrochloride (DAR) and terephthalic acid (TA) are added as an example. When DAR is added to PPA and heated at 50 to 80°C under reduced pressure for about 20 hours, hydrogen chloride is removed from DAR and PPA is added to DAR as shown in the following formula.

Further, when terephthalic acid (TA) is added to polyphosphoric acid (PPA), an adduct of TA and PPA is generated as shown in the following formula.

Then, such a mixed solution is further heated while being stirred in an inert gas stream. In this case, usually the initial
The reaction was carried out at a temperature of 100°C, and further -100 to 1
After reacting at a temperature of 80°C, the reaction temperature is continued at 180-200°C.
It is preferable to carry out the reaction at a temperature of .

By carrying out the reaction in this manner, the viscosity of the reaction liquid gradually increases as the reaction progresses. That is,
By reacting under the above conditions, the intrinsic viscosity [η] measured in methanesulfonic acid at 30°C usually becomes 2.
It is possible to obtain a wholly aromatic heterocyclic polymer compound within the range of ~50 dl/g.

The concentration of the wholly aromatic heterocyclic polymer compound in the reaction solution obtained by carrying out the reaction as described above is usually 2 to 50% by weight.

In a PPA solution of a wholly aromatic heterocyclic polymer compound having the above concentration, the wholly aromatic heterocyclic polymer compound forms a liquid crystal phase in the solution, and polarized light is observed under crossed Nicols. Such a reaction solution is used as it is or diluted to prepare a spinning stock solution, and this stock solution is used for spinning. The diluent solvent may be the same as or different from the reaction solvent. Therefore, in the present invention, the reaction solution obtained as described above can be diluted with polyphosphoric acid, methanesulfonic acid and/or sulfuric acid. In addition to the above-mentioned polyphosphoric acid, methanesulfonic acid and sulfuric acid, polar solvents such as chlorosulfuric acid and trifluorosulfuric acid can also be used within a range that does not impair the properties of the spinning dope.

Such a solution can be prepared by, for example, wet spinning,
Spun using dry jet/wet spinning method.

By the way, as mentioned above, in such solutions of wholly aromatic heterocyclic polymer compounds, because the polymer is rigid and strong intermolecular forces act, a special aggregation state ( For example, even if a liquid crystal state does not exhibit a liquid crystal state optically, a similar agglomeration state exists.)
It is known to take. Moreover, if spinning is performed in this state, the influence of this special agglomeration state will remain in the fiber after spinning and solidification. Therefore, when the above-mentioned wholly aromatic heterocyclic polymer compound is spun using conventionally known methods and conventionally known conditions, the resulting fibers are brittle and have poor toughness.
It breaks easily.

This is because when a solution of polymers in a special agglomerated state is spun as a spinning dope, part or all of that structure remains as the fiber structure, and an aggregate structure similar to domains is formed within the fiber. it is conceivable that. When repeated bending stress is applied to a fiber with such a structure, the stress concentrates at the boundary between the domains, causing peeling or shearing of this area, which becomes a starting point for the fiber to easily break. Conceivable.

This problem was solved by the applicant in the patent application No. 1-238.
The problem can be solved to some extent by using the method disclosed in the '559 specification.

That is, polybenzothiazoles, polybenzoxazoles, or polybenzimidazoles are added to polyphosphoric acid, methanesulfonic acid, sulfuric acid, or a mixture thereof.
The viscosity of the resulting solution is adjusted to 5×lo
2 to 5×1o6 poise, and the average flow rate of this solution was 5×1
02~5×10'Cm/sec, preferably 103
Polybenzothiazole fibers, polybenzoxazole fibers, or polybenzimidazole fibers with improved bending fatigue resistance are obtained by passing through a nozzle at a speed of ~2 x 10' cm/sec, discharging into a coagulation bath, and spinning. It is possible. Here, the solution viscosity is determined by the molecular weight of the polymer that is the solute, the solution concentration, the solution temperature, the solvent, etc. Solution viscosity is related to the time required for the regular agglomeration state of polymers in the solution, which were broken or fragmented by shearing force when passing through the spinning nozzle, to re-form after passing through the nozzle, that is, the magnitude of the relaxation time. do.

The present invention is a further improvement of the invention related to the above-mentioned application made by the present applicant, and it is possible to obtain fibers having excellent toughness and density as well as high homogeneity by applying a specific treatment. This was done based on the knowledge that

Therefore, in the present invention, the viscosity of the above solution is set to 5 x 102 to 5
It is set to x106 poise. By setting the viscosity of the solution within the above range, it is possible to obtain fibers with good fluidity of the solution during spinning and excellent bending fatigue resistance.

The concentration of the solution is one of the factors that determines the viscosity of the solution, but it is also the most important factor that determines the density of the fibers formed. For this reason, in the present invention, the above solution is concentrated at 1 to 50% by weight.

When the concentration of the solution is within the above range, the fluidity of the solution during spinning will be good, and fibers with excellent mechanical strength can be obtained.

Furthermore, in the present invention, the above solution is
X I 04cm/sec, preferably 103~
The material is passed through a nozzle at 2 x 10' am/sec and discharged into a coagulation bath for spinning. '' That is, by controlling the shearing force that the solution receives when passing through the nozzle within the above range, fibers with excellent toughness, denseness, and homogeneity can be obtained.

More specifically, by maintaining the average flow rate within the above range, the agglomerated structure of the polymer compound formed in the solution can be destroyed or fragmented, and the spinning stock solution can be discharged in a stable state.

When the average flow velocity exceeds 5 x 102 cm/see, this agglomerated structure is sufficiently destroyed;
x 10' am/sec or less, the flow of the solution becomes stable.

As described above, the solution was heated at an average flow rate of 5 x 102 ~ 5 x
By discharging the solution through a nozzle at a rate of 10'cm/sec into a coagulation bath, it is possible to destroy or break up the aggregated structure in the solution during spinning, and solidify before the aggregated structure is re-formed. Fibers with excellent fatigue resistance can be obtained.

In this way, by controlling the viscosity and concentration of the spinning solution and the average flow rate during spinning within the above ranges, we can produce polybenzothiazole, polybenzoxazole, or polybenzimidazole fibers with excellent bending fatigue resistance. It is possible to obtain.

In the present invention, it is preferable to use a water bath as the coagulation bath. The thread discharged during coagulation is immersed in water to remove the solvent. The fibers obtained by the method of the present invention have heat resistance equivalent to or higher than that of polyimide fibers. Furthermore, unlike polyimide, the fibers obtained by the method of the present invention have excellent hydrolysis resistance and are not hydrolyzed even when they come into contact with water.

The fibers (coagulated threads) thus obtained can be pulled out of the water and then dried.

Drying as described in 2 is carried out by setting the drying temperature usually in the range of 20 to 100°C and the drying time usually for 1 minute or more. And preferably, the moisture content in the fiber (dry thread) is usually 0.1% by weight or less, preferably 0.01% by weight.
Dry as shown below.

In the present invention, the fibers obtained as described above are heat treated at high temperature for a short time.

Such heat treatment is carried out at a temperature of 450 °C to 700 °C for 10
Preferably, it is carried out for seconds to 3 minutes, and further at 450 to 550°C.
It is preferable to carry out the reaction at a temperature of 10 seconds to 60 seconds.

Normally, when heated at 600°C or higher for a long time (for example, 600°C for 1 minute or more), some of the fibers described above begin to thermally decompose, but under the heat treatment conditions of the present invention, thermal decomposition of the fibers does not occur. Through such heat treatment, the voids formed within the fibers are reduced and the crystallinity of the polymer compound constituting the fibers is improved. Therefore, by performing such heat treatment, the toughness of the fibers is improved.

The heat treatment as described above can be performed using various apparatuses.

The fibers thus obtained can be used as they are, but they can also be further drawn if necessary. Further, such stretching may be performed before or after the heat treatment as described above.

Such stretching is carried out by setting the stretching ratio usually in the range of 1 to 200% and the stretching temperature usually in the range of 20 to 500°C. Note that, after drawing, the obtained drawn fibers may be further heat-treated.

Effects of the Invention The production method according to the present invention can produce polybenzothiazoles, polybenzoxazoles, polyhencyimidazoles, etc., which have particularly excellent heat resistance and hydrolysis resistance, and excellent toughness, denseness, and homogeneity. It is possible to obtain a fiber made of a wholly aromatic heterocyclic polymer compound.

EXAMPLES Next, the present invention will be specifically explained using examples, but the present invention is not limited to these examples.

Example 1 H3P0. with a concentration of 85%. 40% by weight and concentration 115%
of polyphosphoric acid (H3PO, base) with 60% by weight to obtain a polyphosphoric acid solution with a P2O5 content of 74.9% (
PPA solution) was prepared.

88.6 g of the above PPA solution and 22.82 g of 4.6
-Diamitsu-1,3-benzenediol dihydrochloride (DAR) was mixed in a 200-bar resin kettle. After stirring this mixture, 50 to 80
Hydrogen chloride was removed from the DAR by heating to a temperature of 0.degree. C. for about 20 hours. To this compound was added 17.96 g of terephthalic acid (TA) and further 61.2 g of P2O5 to bring the content of P2O5 in this mixture to 87.2 g.
Expressed as weight%.

This mixture was heated to 100°C using an oil bath under a stream of argon.
The mixture was stirred for 15 hours. No significant increase in the bulk viscosity of the mixed liquid was observed by heating and stirring.

Then, while stirring the mixture vigorously, the temperature of the oil bath was increased from 100°C to 178°C within 40 minutes, and at this temperature 2
It was maintained for 5 hours, then raised to 185° C. within 1 hour and reacted at this temperature for 25 hours.

As described above, a reaction solution containing 13.6% by weight of poly(p-phenylenebenzobisoxazole) (PBO) was obtained.

A part of this reaction solution was taken out and the PP prepared during the reaction was
Solution A was added and thoroughly stirred to prepare a diluted solution with a PBO concentration of 3.52% by weight. The intrinsic viscosity of this PBO is 11
．． 1 dl/g (30°C, methanesulfonic acid).

The viscosity of the solution (90°C 1 slip rate 15ec-') is 10
It was 4 poise. This solution was subjected to dry-wet spinning (air gap 1, 5 cm) using an extrusion type spinning device, spun into a coagulation bath containing a large amount of water, and washed with water at 25° C. for 24 hours. The discharge pressure was 200 Kg/cd, and the average flow rate of the solution through the nozzle was 3.5×10 cm/sec. After washing with water, the concentration of P2O in the system decreased to 0.0021% by weight. The elongation at break of this fiber evaluated in the wet state was 120%.

The fibers were taken out of the water and dried at 80°C for 12 hours. The moisture content of the dried yarn was 0.01% by weight, and the diameter was 32 μm. The properties of this dry yarn are shown in Table 1 along with comparative examples.

Comparative Example 1.2 The average flow rate of the spinning stock solution passing through the nozzle was 2 x 102 cm/see in Comparative Example 1 and 5 in Comparative Example 2.
Fibers were obtained in the same manner as in Example 1 except that the speed was 102 cm/sec. The P2O5 concentration in the system after washing with water is 0.
．． 0021% by weight, the elongation at break of the wet fiber is 60.
5%, the moisture content of the yarn dried at 80°C for 12 hours was 0.
It was 0.01% by weight. Regarding this fiber, strength, elongation,
The density, Young's modulus, small-angle X-ray scattering ability, and the number of times required to repeatedly bend the fibers by 180° until cutting were measured. The results are shown in Table 1.

Regarding these properties, the density and small-angle X-ray scattering ability are measures of compactness and homogeneity, and the number of bends is a measure of toughness. There is a clear difference in toughness between Example 1 and Comparative Example 1. This indicates that the domain structure within the fibers is destroyed and the toughness is improved by an appropriate flow rate.

Examples 2 to 5 and Comparative Examples 3 to 4 The fibers obtained in Example 1 were heat treated and the effects of the heat treatment were compared.

The results are shown in Table 2.

From these results, it is clear that when the heat treatment temperature is 400°C, the heat treatment effect is small even if the heat treatment time is increased by 3 minutes or more.Also, when the heat treatment temperature is 575°C, the heat treatment time is increased to 1 minute. It can also be seen that thermal decomposition occurs and deterioration of the delicate material begins.

Examples 6 to 8 and Comparative Examples 5 to 6 The fibers obtained in Example 1 were heat treated at high temperature for a short time, and the effects of the heat treatment were compared. The properties of the obtained fibers were compared in the same manner as Examples 2-5 and Comparative Examples 3-4.

The results are shown in Table 3.

As is clear from these results, it can be seen that according to the present invention, even at high temperatures, a sufficient heat treatment effect can be achieved by short-time heat treatment without causing thermal decomposition.

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Claims (1)

[Claims] (1) Add polybenzothiazoles, polybenzoxazoles or polybenzimidazoles to polyphosphoric acid, methanesulfonic acid, sulfuric acid or a mixture thereof so that the concentration of the polymer is 1 to 50% by weight and the viscosity of the solution is 5
Dissolve it so that it becomes ×10^2~5 ×10^6 poise,
This solution was passed through a nozzle at an average flow rate of 5 x 10^2 to 5 x 10^4 cm/sec and spun into a coagulation bath to obtain fibers. 1. A method for producing polybenzothiazole fibers, polybenzoxazole fibers, or polybenzimidazole fibers, which comprises heat-treating the fibers at a temperature of 10 seconds to 3 minutes.