JPH0662767B2 - Method for producing aromatic polythiazole - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an aromatic polythiazole which is a rigid aromatic polymer excellent in heat resistance, mechanical properties, chemical resistance, electrical properties and the like. In particular, it relates to a method capable of easily producing an aromatic polythiazole at a sufficiently low temperature using a conventional organic solvent.

[Conventional technology]

A polymer having a heterocyclic ring such as a thiazole ring, an imidazole ring, an oxazole ring, or an oxazinone ring in a repeating unit has high rigidity and is attracting attention as a polymer having high strength, high elastic modulus, and high heat resistance.

Among them, aromatic polythiazole having a thiazole ring is
Due to its excellent mechanical strength, it is expected to be used alone or in combination with other engineering plastics as a plastic material replacing metal materials.

However, aromatic polythiazole generally has poor solubility due to its high rigidity, and has a problem in its molding because it is soluble in only some strong acids such as metasulfonic acid and chlorosulfonic acid.

Aromatic polythiazoles have been conventionally produced from aromatic diaminodithiol compounds and dicarboxylic acid derivatives, especially chlorides. The problem remains and it is not preferable. Therefore, a method in which a precursor of an aromatic polythiazole is first synthesized and then a ring-closing reaction thereof is performed to obtain an aromatic polythiazole has been generally adopted. Since the precursor of aromatic polythiazole is soluble in an organic solvent, if the thiazole ring-closing reaction is performed after the production and processing in the precursor stage, the above-mentioned problem of moldability can be avoided and a molded product of a desired shape can be obtained. Can be obtained.

By the way, an aromatic polythiazole precursor is generally produced by heating a mixture of an aromatic diaminodithiol compound or a salt thereof and a dicarboxylic acid or a derivative thereof at a temperature of 160 ° C. or higher in the presence of polyphosphoric acid or the like. However, when heated to the above temperature in the presence of polyphosphoric acid, it is difficult to control the polymerization reaction, and in many cases, there is a problem that the reaction proceeds to polythiazole. Therefore, various attempts have been made to obtain a precursor of aromatic polythiazole. JP 60-223
No. 824 discloses a method for preparing a polythiazole precursor by reacting an aromatic and / or heterocyclic diaminodithiol compound with a dicarboxylic acid in the presence of a carboximide.

[Problems to be Solved by the Invention]

However, it is described that the reaction of the above method is carried out in the presence of carbodiimide and proceeds at a temperature at which the precursor does not change to an inactive ring-closing product, but the polythiazole precursor actually obtained is used as a photoresist. It had a low molecular weight as used, and was not suitable as a precursor of a high-strength polymer used in the molecular composite material of the present invention.

Therefore, the present applicant is characterized in that, as a method for stably producing a precursor of an aromatic polythiazole, an aromatic diaminodithiol compound or a salt thereof and a dicarboxylic acid derivative are polymerized by using an interfacial polymerization method. Method (Japanese Patent Application Sho 63
-136733), and a salt of an aromatic diaminodithiol compound and a dicarboxylic acid derivative in the presence of a phosphoric acid compound.
A patent application was filed for a method (Japanese Patent Application No. 63-140807) characterized by polymerizing under a temperature condition of 70 to 140 ° C.

According to the above-mentioned two methods, the aromatic polythiazole precursor can be stably and efficiently produced as compared with the conventional methods. However, with these methods,
The thiol group in the starting material aromatic diaminodithiol compound or salt thereof may react with the dicarboxylic acid derivative, and the thiol group partially undergoes ring closure reaction during the production process of the precursor, resulting in the formation of insoluble components. Could be generated.

Therefore, an object of the present invention is to produce an aromatic polythiazole precursor in a stable and efficient manner without worrying about by-products such as those mentioned above as a by-product, and to further improve mechanical properties of the aromatic polythiazole precursor. It is an object of the present invention to provide a method for producing an excellent aromatic polythiazole.

[Means for Solving the Problems]

As a result of intensive research in view of the above problems, the present inventor has found that if the hydrogen atom of the thiol group of the aromatic diaminothiol compound used for polysynthesis of the aromatic polythiazole precursor is substituted or substituted with an alkyl group, the precursor It was discovered that the aromatic polythiazole having good physical and chemical properties can be produced by stable and efficient production of this precursor, and further heating this precursor at an appropriate temperature, Completed the invention.

That is, the method of the present invention for producing an aromatic polythiazole from a salt of an aromatic diaminodithiol compound and a dicarboxylic acid derivative comprises (a) a salt of the aromatic diaminodithiol compound, and a substituted or unsubstituted alkyl group. By reacting with an alkyl halide in an alkaline aqueous solution, the hydrogen atom of the thiol group of the aromatic diaminodithiol compound is substituted with the alkyl group, (b) the resulting alkyl group-substituted aromatic diaminodithiol compound, Characterized in that an aromatic polythiazole precursor is synthesized by polymerizing with a dicarboxylic acid derivative, and (c) the aromatic polythiazole precursor is heated to cause a thiazole ring-closing reaction to thereby produce an aromatic polythiazole. To do.

The present invention is described in detail below.

The aromatic diaminodithiol compound used in the form of a salt in the present invention is a compound having an amino group and a thiol group on both sides of an aromatic residue, and the aromatic residue is not limited to a benzene ring, but two or more benzene rings. It may be an aromatic ring which has been operated, or may be one in which two or more benzene rings are bonded, such as biphenyl. The positional relationship between the amino group and the thiol group on both sides may be left-right symmetric or point-symmetric with respect to the aromatic residue. Examples of such aromatic diaminodithiol compounds include: Etc.

These aromatic diaminodithiol compounds are used in the form of salts such as hydrochloride to prevent deterioration.

The alkyl group bonded to the thiol group of the aromatic diaminodithiol compound is a substituted or unsubstituted alkyl group,
Unsubstituted alkyl groups include isopropyl group, ethyl group, n-propyl group, n-butyl group, sec-butyl group, tert.
-Butyl group and the like can be mentioned. As the alkyl group, secondary and tertiary alkyl groups are particularly preferable.

As the substituted alkyl group, an alkyl group substituted with a carboxyl group, an ester group, a cyano group, a benzene group or the like is preferable. When the alkyl group has such a substituent, the alkyl group does not need to be secondary. Examples of the alkyl group having a substituent include, for example, Etc.

In addition, among the above 6 substituted alkyl groups, in the ones in which the two ester groups shown above are substituted, the alkyl group bonded to the oxygen atom in the ester bond is not limited to a methyl group, but a long chained alkyl group. It may be a base.

In particular, when the hydrogen atom of the thiol group of the aromatic diaminodithiol compound is replaced with an alkyl group having a cyano group or an alkyl group having an ester group, the ring-closing reaction of the precursor described below will cause a low temperature of 250 ° C to 400 ° C. It is preferable because it occurs at. Further, it is convenient because these precursors can be more easily dissolved in an organic solvent such as N-methyl-2-pyrrolidone.

If the length of the carbon chain of the alkyl group to be used is set to an appropriate one (having about 2 to 5 carbon atoms), it will be excellent when using the polythiazole precursor obtained by the method of the present invention, as will be described later. A molecular composite material having physical and chemical properties can be manufactured. The molecular composite material referred to herein is a polymer blend composite material in which polythiazole is finely dispersed to a molecular level in a polymer serving as a matrix resin. This composite material is obtained by blending a polythiazole precursor and a matrix resin and then subjecting to ring closure by heating.

The above-mentioned alkyl group is used as an alkyl halide which is a halide thereof. As the halide,
Bromides, chlorinated compounds, iodides, etc. of the above alkyl groups can be used.

Further, examples of the dicarboxylic acid derivative used in the present invention include those in which each carboxyl group is substituted as follows.

The residue of the above dicarboxylic acid derivative is preferably an aromatic group, and for example, the following aromatic groups can be used. Note that terephthalic acid is particularly preferable as an example of such a dicarboxylic acid.

The dicarboxylic acid derivative is not limited to one type, and two or more types may be used in combination.

Next, a method for producing the aromatic polythiazole will be described.

The method of the present invention comprises the following three steps.

(1) A salt of an aromatic diaminodithiol compound and an alkyl halide are reacted in an alkaline aqueous solution to synthesize a monomer in which a hydrogen atom of a thiol group of an aromatic diaminodithiol compound salt is replaced with an alkyl group.

(2) The monomer obtained in step (1) above is polymerized with a dicarboxylic acid derivative to synthesize an aromatic polythiazole precursor.

(3) The aromatic polythiazole precursor is heated to cause a thiazole ring-closing reaction to produce a directional group polythiazole.

Hereinafter, each step will be described.

First, in step (1), a salt of an aromatic diaminodithiol compound and an alkyl halide are reacted in an alkaline aqueous solvent. The alkaline aqueous solvent used at this time is water, or water and alcohol (ethanol and / or
Alternatively, a mixed solvent with methanol) in which a basic salt such as sodium hydroxide is dissolved can be used. By making the solvent alkaline, the salt of the aromatic diaminodithiol compound can be easily dissolved. It also increases the nucleophilicity of the thiol group and promotes the substitution reaction. The alkaline concentration of the alkaline aqueous solvent is preferably 30% by weight or less.

This substitution reaction can be carried out in the range of 0 ° C to 100 ° C. If the temperature is lower than 0 ° C, the reaction rate becomes slow, which is not preferable. On the other hand, if the temperature exceeds 100 ° C, a side reaction may occur, which is not preferable. More preferable reaction temperature is 0 ° C
~ 95 ° C.

Although the reaction time is not particularly limited, it is generally about 2 to 24 hours.

It is preferable to stir the solution in order to increase the reaction rate. Further, the reaction rate can be increased by making the amount of the alkyl halide excessive.

Furthermore, the reaction rate can be increased by adding cetyltrimethylammonium chloride, n-butyltriphenylphosphonium bromide, tetraphenylphosphonium bromide, 18-crown-6, etc. as a phase transfer catalyst. Such a phase transfer catalyst accelerates the reaction between the salt of the aromatic diaminodithiol compound and the alkyl halide.

By performing the substitution reaction under the above conditions, a monomer in which the hydrogen atom of the thiol group of the salt of the aromatic diaminodithiol compound is substituted with an alkyl group can be obtained.

In the reaction of step (1), the reaction between the salt of the aromatic diaminodithiol compound and the alkyl halide proceeds as follows. Here, 2,5-diamino-1,4-benzenedithiol dihydrochloride is used as an example of the salt of the aromatic diaminodithiol compound. In the formula, it represents XR alkyl halide.

Next, in step (2), the monomer obtained in step (1) and the dicarboxylic acid derivative are polymerized to synthesize an aromatic polythiazole precursor. Then step (1)
The monomer obtained in (1) and the dicarboxylic acid derivative are mixed in an equimolar amount, and polymerized under the conditions shown below.

Examples of the solvent used first include N-methyl-2-pyrrolidone, hexamethylphosphorixtriamide, N, N-dimethyliacetamide and the like, and these can be used alone or in a mixed solution. In addition, chlorides such as LiCl and CaCl ₂ at a maximum of 5% may be added to enhance the reactivity.

In the above solvent, the monomer obtained in step (1) and the dicarboxylic acid derivative are mixed in equimolar amounts in the above solvent, and -20 ° C to + 50 ° C
The polymerization reaction is carried out at the temperature of. If the temperature is lower than -20 ° C, a sufficient polymerization reaction does not occur and the degree of polymerization of the obtained precursor is low. On the other hand, if the temperature exceeds + 50 ° C, the thiazole ring-closing reaction may occur, which is not preferable. More preferably, it is in the range of -20 to -30 ° C.

Further, the concentration of the monomer is preferably 0.1 to 2 mol / about. If the concentration of the monomer exceeds 2 mol /, it is difficult to dissolve the monomer, which is not preferable.

In the reaction recoil of step (2). It is preferable to stir the solution in order to increase the reaction rate of the polymerization. In addition, the reaction time is not particularly limited, but is generally about 1 to 24 hours.

By carrying out the polymerization reaction under the above conditions, an aromatic polythiazole precursor having a large degree of polymerization can be obtained without causing a ring closure reaction. The obtained aromatic polythiazole precursor has an intrinsic viscosity of η _inh = 1.0 to 1.7 (N-methyl-2-
Pyrrolidone, 30 ° C).

In the polymerization reaction of step (2), it is considered that the reaction between the monomer obtained in step (1) and the dicarboxylic acid derivative proceeds as follows. Here, a substituted alkyl group of 2,5-diamino-1,4-benzenedithiol dihydrochloride is used as an example of the monomer obtained in step (1), and terephthalic acid dichloride is used as an example of a dicarboxylic acid derivative. Note that n represents the degree of polymerization.

When the polymerization reaction is carried out using two kinds of dicarboxylic acid derivatives, a copolymer precursor as shown below is obtained. Here, Ar and Ar 'are aromatic groups of dicarboxylic acid, respectively, and m and n represent the number of repeating units (degree of polymerization).

The obtained aromatic polythiazole precursor can be washed and dried by a known method.

Next, in step (3), the precursor is heated to eliminate the alkyl group (R) and form a thiazol ring at that site to obtain an aromatic polythiazole. If the aromatic polythiazole precursor obtained by the reaction formula (2) is used as the precursor, poly-p-phenylenebenzobisthiazole having the following structural formula can be obtained.

The ring closure reaction of the precursor is carried out by heating at 250 ℃ to 500 ℃. If heated below 250 ° C, there is no sign of thiazole return. Further, when heated above 600 ° C., polythiazole starts thermal decomposition, which is not preferable. In particular, if a precursor obtained from an alkyl group-substituted aromatic diaminodithiol compound in which a hydrogen atom of a thiol group is substituted with an alkyl group having a carboxyl group, a cyano group, an ester group, etc. The cyclization reaction can be carried out at a low temperature of 400 ° C.

In the case of producing a molecular composite material using an aromatic polythiazole according to the method of the present invention, polythiazole is produced in advance and is not mixed with a matrix resin thereof, but a step of a precursor of polythiazole is performed. Then, this and the matrix resin are preferably mixed in an organic solvent. After the polythiazole precursor is uniformly dispersed in the matrix resin, the solvent is removed and then heated to cause the precursor to undergo a recapture reaction to form a molecular composite material. Therefore, it is necessary that the precursor has good solubility in the organic solvent used. When a precursor having an alkyl group of the above-mentioned size (length) and kind bound to a thiol group is used, the solubility in an organic solvent becomes large.

In addition, what can be used as a matrix resin of the molecular composite material includes aromatic polyamide, polyamic acid composed of diamine and acid anhydride, and polyimide.

Further, the liquid crystallinity of the precursor solution obtained by substituting the alkyl group as described above becomes large, and the precursor can be easily spun from the organic solvent in which the precursor is dissolved.
Therefore, by using the method of the present invention, it becomes easy to produce a polythiazole fiber. In order to increase the liquid crystallinity of the solution of the precursor, it is basically better to lengthen the alkyl group bonded to the thiol group, but in practice it is appropriate to consider the solubility in organic solvents etc. Is good.

[Work]

According to the present invention, a monomer in which a hydrogen atom of a thiol group of a salt of an aromatic diaminodithiol compound is previously substituted with an alkyl group is used, and in order to polymerize this with a dicarboxylic acid derivative, an amino group of the aromatic diaminodithiol compound is used. React selectively to give a precursor.
On the other hand, the thiol group is protected by the alkyl group and does not serve as a polymerization site.

Further, in order to use an aromatic diaminodithiol compound in which a hydrogen atom of a thiol group is substituted with an alkyl group,
The polymerization reaction with the dicarboxylic acid derivative can be carried out at a lower temperature than in the conventional method, and there is no concern that a thiazole cyclization reaction will occur during the production of the precursor. In particular, the use of the secondary alkyl group facilitates the substitution reaction and facilitates the elimination of the alkyl group when the precursor is heated, and facilitates the formation of the thiazole ring. In addition, it is preferable to use an alkyl group having a carboxyl group, an ester group, a cyano group, a benzene group or the like, because the ring closure reaction of the precursor can be performed at an extremely low temperature. Further, since the precursor having an alkyl group substituted with these groups is extremely well soluble in an organic solvent such as N-methyl-2-pyrrolidone, it is possible to produce polythiazole without using a strong acid. Have.

〔Example〕

 The present invention will be described in detail with reference to the following specific examples.

Example 1 (1) Synthesis of monomer for synthesizing precursors Sodium hydroxide (21.6 g) was dissolved in distilled water (300 ml), and 2,5-diamino-1,4-benzenethiol dihydrochloride (30.0 g) was dissolved therein.
Was added, and the mixture was cooled to 0 ° C. with ice water while stirring to dissolve it.

To the obtained solution, 29.4 ml of methyl 3-bromopropionate was added dropwise with stirring. Incidentally, 3.0 g of cetyltrimethylammonium chloride was added during the dropwise addition of methyl 3-bromopropionate. Precipitation occurred shortly after the addition of cetyltrimethyammonium chloride. The temperature of the solution was gradually raised to room temperature while continuing to stir the solution.

After keeping the solution at room temperature for 3 hours, the obtained reaction product was suction-filtered with a glass filter, and the precipitate was thoroughly washed with distilled water. After washing, it was dried under vacuum at 60 ° C. The solid thus obtained was yellow. Yield 23.6
It was g. The obtained solid was recrystallized using cyclohexane to obtain yellow needle crystals. The crystals obtained were dried in vacuum.

The melting point of the obtained crystal was measured and found to be 84 ° C. In addition, elemental analysis was performed. The results were as follows. The numerical values in the following elemental analysis tables represent percentages.

Elemental analysis: C ₁₄ H ₂₀ H ₂ S ₂ O ₄ Furthermore, when ¹ H-NMR was measured, single peaks were observed at 3.7 ppm and 6.8 ppm, respectively.

From the above analysis, it was confirmed that the obtained crystal had a structure shown below.

(2) Synthesis of poly-p-phenylenebenzobisthiazole precursor 0.7000 g of the crystal (monomer) obtained in (1) above was added to a solution of N-methyl-2-pyrrolidone (NMP) having a lithium chloride concentration of 5.0% by weight. It was dissolved in 4 ml.

The solution was cooled in a dry ice / ice bath and 0.4126 g of terephthaloyl chloride was added. Gradually raise the temperature while stirring the solution, and when it reaches 0 ° C, the temperature is set to 0
It was kept at ℃. When the solution became cloudy in white, a solvent (NMP containing lithium chloride) was further added, and stirring was continued so as to maintain a uniform solution state.

When the solution became viscous and its intrinsic viscosity reached about 1.0, the temperature of the solution was gradually raised to room temperature.

Three hours after the addition of terephthaloyl chloride, this solution was slowly poured into methanol. This operation was performed while stirring methanol.

After stirring for 30 minutes, the mixture was filtered and further refluxed with a water-methanol solution overnight to remove the solvent.

The obtained polymer was dried in vacuum at 100 ° C. for 24 hours.
The yield was 0.94 g, and the yield was 97%.

The intrinsic viscosity η _inh of this polymer was 1.90 (dl / g). It should be noted that the intrinsic viscosity was measured with N having a potassium chloride concentration of 5%.
The measurement was carried out by the Ubbelohde method at 30 ° C. with a polymer concentration of 0.5 g / dl in MP.

Next, elemental analysis of this polymer was performed. The results are shown below.

Elemental _{analysis: C 22 H 22 N 2 S} 2 O 6 From the above results, it was identified that this polymer was a precursor of poly-p-phenylenebenzobisthiazole in which hydrogen atoms of thiol groups were replaced with methyl propionate groups.

(3) Ring-closing reaction to poly-p-phenylenebenzobisthiazole The precursor obtained in (2) above was heated at 350 ° C. for 30 minutes in a nitrogen atmosphere.

Infrared absorption spectrum analysis (IR) of polymer after heating
I went. When the obtained IR chart was compared with that of poly-p-phenylenebenzobisthiazole produced by the polyphosphoric acid method, both were in agreement. From this, it was confirmed that the precursor obtained in (2) above undergoes a ring closure reaction by heating at 350 ° C. for 30 minutes to become poly-p-phenylenebenzobisthiazole.

Example 2 (1) Synthesis of monomer for synthesizing precursors Sodium hydroxide (21.6 g) was dissolved in distilled water (300 ml), and 2,5-diamino-1,4-benzenethiol dihydrochloride (30.0 g) was dissolved therein.
Was added, and the mixture was cooled to 0 ° C. with ice water while stirring to dissolve it.

While stirring the obtained solution, 22.4 ml of 3-bromopropiononitrile was added dropwise. Incidentally, 3.0 g of cetyltrimethylammonium chloride was added during the dropping of the 3-bromopropiononitrile. Precipitation occurred shortly after the addition of cetyltrimethyammonium chloride. While continuing to stir the solution, the temperature of the solution was raised to room temperature.

After keeping the solution at room temperature for 4 hours, the obtained reaction product was suction-filtered through a glass filter, and the precipitate was thoroughly washed with distilled water. After washing, it was dried under vacuum at 60 ° C. The solid thus obtained was yellow. Yield 51.3
It was g.

The obtained solid was recrystallized with methylene chloride to obtain yellow needle crystals. Dried in vacuum.

The melting point of the obtained crystal was measured and found to be 130 ° C. In addition, elemental analysis was performed. The results were as follows.

Elemental analysis: C ₁₂ H ₁₄ N ₄ S ₂ Furthermore, when ¹ H-NMR was measured, it was 2.97 ppm and 2.67 ppm.
A triplet peak and a single peak at 4.63 ppm and 6.79 ppm were observed.

From the above analysis, it was confirmed that the obtained compound was the compound shown below.

(2) Synthesis of poly-p-phenylene benzobisthiazole precursor 1.3920 g of the crystal (monomer) obtained in (1) above was added to 10 ml of N-methyl-2-pyrrolidone solution containing 5.0 wt% lithium chloride. Dissolved.

This solution is cooled in a salt ice bath and terephthalic acid chloride is added.
1.0151 g was added. The temperature was gradually raised with stirring the solution, and when the temperature reached 0 ° C, the temperature was kept at 0 ° C.
When the solution became cloudy in white, more solvent was added and stirring was continued so as to maintain a uniform solution state.

When the solution became viscous and its intrinsic viscosity reached about 1.0, the temperature of the solution was gradually raised to room temperature.

Three hours after the addition of terephthaloyl chloride, this solution was slowly poured into methanol. This operation was performed while stirring methanol.

After continuing stirring for 30 minutes, the mixture was filtered and further refluxed with a methanol-water solution overnight to remove the solvent.

The obtained polymer was dried in vacuum at 100 ° C. for 24 hours.
The yield was 2.03 g, and the yield was 99.5%.

The intrinsic viscosity η _inh of this polymer was 1.81 (dl / g). In addition, the intrinsic viscosity was measured using N with a lithium chloride concentration of 5%
The measurement was carried out by the Ubbelohde method at 30 ° C. with a polymer concentration of 0.5 g / dl in MP.

Next, elemental analysis of this polymer was performed. The results are shown below.

Elemental analysis: C ₂₀ H ₁₆ N ₄ S ₂ From the above results, this polymer is a poly-p in which the hydrogen atom of the thiol group is replaced with a 3-3 bromopropiononitrile group.
-Identified as a precursor of phenylene benzobisthiazole.

(3) Ring-closing reaction to poly-p-phenylenebenzobisthiazole The precursor obtained in (2) above was heated at 350 ° C. for 30 minutes in a nitrogen atmosphere.

Infrared absorption spectrum analysis (IR) of polymer after heating
I went. When the obtained IR-chart was compared with that of poly-p-phenylenebenzobisthiazole produced by the polyphosphoric acid method, both were in agreement. From this, it was confirmed that the precursor obtained in (2) above undergoes a ring closure reaction by heating at 350 ° C. for 30 minutes to become poly-p-phenylenebenzobisthiazole.

Example 3 (1) Synthesis of 2,5-diamino-1,4-diisopropylthiobenzene In a three-necked flask, 14.4 g of sodium hydroxide and 200 m of distilled water were added.
1 and 4.4 g of cetyltrimethylammonium chloride were added and dissolved under stirring in a nitrogen stream. 2,5-diamino
20.0 g of -1,4-benzenethiol dihydrochloride was added and stirred until a uniform solution was obtained.

This solution was cooled to 0 ° C. with ice water, and 23.0 ml of isopropyl bromide was added dropwise. After the dropping, the temperature of the solution was raised to room temperature while continuing stirring.

The obtained reaction product was suction-filtered with a glass filter, and the precipitate was thoroughly washed with distilled water. After washing, room temperature,
Dry under vacuum and then under reduced pressure of 1 mmHg, 150
It was dried at ° C. N-for the solid thus obtained
Recrystallization treatment was performed twice using hexane to obtain yellow needle crystals. The crystals obtained were dried in vacuum. Yield is 1
It was 0.3 g.

The obtained compound was subjected to elemental analysis and ¹ H-NMR measurement (CDCl method). The results were as follows.

Elemental analysis: C ₁₂ H ₂₀ N ₂ S ₂ ¹ H-NMR (CDCl ₃ ): 1.26ppm 3.24ppm 3.79ppm 6.84ppm According to the above analysis, the obtained compound was 2,5-diamino-1,4
-Confirmed to be diisopropylthiobenzene.

(2) Synthesis of poly-p-phenylene benzobisthiazole precursor Hexamethylphosphoric amide (HMPA) and N-methyl-2
-Pyrrolidone (NMP) was mixed at a volume ratio of 2: 1 and lithium chloride was added thereto to prepare a solvent having a lithium chloride concentration of 3.5% by weight.

To 7.6 ml of this solvent, 0.5000 g of the compound obtained in (1) above
Was added and dissolved at room temperature.

This solution was cooled with a dry ice / acetone solution, and 0.3958 g of terephthaloyl chloride was added. The temperature was gradually raised with stirring the solution, and when the temperature reached 0 ° C, the temperature was kept at 0 ° C. When the solution became white and cloudy, the solvent was added and stirring was continued so as to maintain a uniform solution state.

When the solution became viscous and its intrinsic viscosity reached about 1.0, the temperature of the solution was gradually increased to room temperature.

Three hours after the addition of terephthaloyl chloride, this solution was slowly poured into methanol. This operation was performed while stirring methanol.

After stirring for 30 minutes, the mixture was filtered and refluxed with a methanol solution for about 2 hours to remove the solvent.

The obtained polymer was dried in vacuum at 100 ° C. for 24 hours.
The yield was 0.75 g, and the yield was 100%.

Further, IR measurement was performed on this polymer. The results are shown in Fig. 1.

From the above results, it was identified that this polymer is a precursor of poly-p-phenylene benzobisthiazole in which hydrogen atom of thiol group was replaced with isopropyl group.

(3) Ring-closing reaction to poly-p-phenylene benzobisthiazole The precursor obtained in (2) above was heated to 800 ° C at a heating rate of 10 ° C / min in a nitrogen atmosphere, and subjected to thermogravimetric analysis ( TG) was performed. Further, a differential thermal analysis (DTA) was similarly performed in air. The results of thermogravimetric analysis are shown in FIG.

As is clear from Fig. 2, as the precursor is heated
A reaction with weight loss occurs at around 320 ° C, and the reaction converges to around 440 ° C. From the result of DTA, it was confirmed that this reaction was an endothermic reaction.

To investigate the structural changes of the precursor upon heating, the precursor was heated and held at 420 ° C for 60 minutes in a nitrogen atmosphere. Next, IR measurement of the obtained substance was performed. Results are shown in FIG.

This result was significantly different from the IR measurement result before heating (IR measurement result of precursor of poly-p-phenylenebenzobisthiazole: FIG. 1).

Next, when the IR measurement result after heating (FIG. 3) was compared with the IR measurement result of poly-p-phenylenebenzobisthiazole synthesized by the polyphosphoric acid method, they were almost the same. This confirmed that the obtained compound was poly-p-phenylenebenzobisthiazole.

When the sample (poly-p-phenylenebenzobisthiazole) heated and held at 420 ° C. for 60 minutes was subjected to TG measurement again, a change accompanied by weight loss was observed at around 670 ° C. The 10% weight loss temperature was 744 ° C. From this TG curve, it was found that the thermal decomposition initiation temperature of poly-p-phenylenebenzobisthiazole was 670.6 ° C.

Example 4 First, a monomer (2,5-diamino-1,4-diisopropylthiobenzene), which is an alkyl group-substituted aromatic diaminodithiol compound, was synthesized in the same manner as in (1) of Example 3.

Next, 1.000 g of this monomer was added to a solution containing
% NMP (7.8 ml) and dissolved at room temperature.

This solution was cooled with a dry ice / acetone solution, and 0.7917 g of isophthalic acid chloride was added. While stirring the solution, the temperature was gradually raised to room temperature, and after 2 hours, 10 ml of a solvent was further added.

Then the solution was slowly poured into methanol. After stirring for a while, this was filtered and dried in the same manner as in Example 3. The yield of the obtained polymer was 1.46 g, and the yield was 96.9%. Also, the intrinsic viscosity of this polymer η _inh
Was 1.12 (dl / g). The intrinsic viscosity was measured in NMP with a lithium chloride concentration of 3% and the polymer concentration was 0.5 g.
/ Dl, and was performed by the Ubbelohde method at 30 ° C.

Further, the obtained polymer was subjected to elemental analysis. The results are shown below.

Elemental _{analysis: C 20 H 22 S 2 N} 2 O 2 The obtained polymer was dissolved again in a solvent, and a film was produced by a casting method. The resulting film was transparent and was identified by IR analysis to be the desired film.

Example 5 First, a monomer (2,5-diamino-1,4-diisopropylthiobenzene), which is a substituted alkyl group of an aromatic diaminodithiol compound, was synthesized in the same manner as in (1) of Example 3.

Next, 0.5000 g of this monomer was added to 9.75 ml of NMP solution and dissolved under a nitrogen atmosphere at room temperature.

This solution was cooled with dry ice / acetone solution to obtain 4,4 '
0.5755 g of diferether dicarboxylic acid chloride are added. The temperature was gradually raised to 0 ° C. with stirring the solution. After the solution became viscous while maintaining a uniform and transparent state, the temperature was further raised to room temperature. After 2 hours, the solvent (N
MP) 10 ml.

The solution was then slowly poured into methanol. After stirring for a while, the mixture was filtered and dried as in Example 3.

The intrinsic viscosity η _inh of the obtained polymer was 0.5 (dl / g).

Further, the obtained polymer was redissolved in NMP, and a film was trial-produced by a casting method. The obtained film was transparent and was identified by IR analysis to be the desired film.

〔The invention's effect〕

As described in detail above, in the method of the present invention, the hydrogen atom of the thiol group of the salt of the aromatic diaminodithiol compound is previously substituted with an alkyl group, and this and the dicarboxylic acid derivative are polymerized, so the thiol group is an alkyl group. This means that the amino group is protected, so to speak, that the amino group reacts selectively. This makes it possible to reliably produce a precursor in which the amino group of the aromatic diaminodithiol compound and the dicarboxylic acid derivative are polymerized without producing an insoluble component as a by-product.

In particular, when an alkyl group containing a carboxyl group, an ester group, a cyano group, or a benzene group is used as the alkyl group substituting the hydrogen atom of the thiol group, the ring closure reaction of the precursor can be carried out at a low temperature, which is preferable.

The aromatic polythiazole obtained by the method of the present invention is
Due to various properties such as good mechanical strength, heat resistance and solvent resistance, it can be used as a high strength and high heat resistance engineering plastic material for automobile parts, aviation parts and the like.

Further, by using the polythiazole precursor obtained as an intermediate product in the method of the present invention, an excellent molecular composite material can be produced.

[Brief description of drawings]

FIG. 1 shows an infrared absorption spectrum of a product obtained by a polymerization reaction of a substitution product of an aromatic diaminodithiol compound and a dicarboxylic acid derivative in Example 3, and FIG. FIG. 3 shows the results of thermogravimetric analysis of the product obtained by the polymerization reaction of the substituted dithiol compound and the dicarboxylic acid derivative. FIG. 3 shows the substituted dicarboxylic acid derivative and the dicarboxylic acid derivative in Example 3. The infrared absorption spectrum of the substance obtained by heating the product obtained by the above-mentioned polymerization reaction at 420 ° C. for 60 minutes is shown.

Claims (6)

[Claims] 1. A salt of an aromatic diaminodithiol compound,
In the method for producing an aromatic polythiazole from a dicarboxylic acid derivative, (a) by reacting a salt of the aromatic diaminodithiol compound and an alkyl halide having a substituted or unsubstituted alkyl group in an alkaline aqueous solution, The hydrogen atom of the thiol group of the aromatic diaminodithiol compound is substituted with the alkyl group, (b) the resulting alkyl group-substituted aromatic diaminodithiol compound and the dicarboxylic acid derivative are polymerized to produce an aromatic polythiazole precursor. A method comprising synthesizing a substance, and (c) heating the aromatic polythiazole precursor to cause a thiazole ring closure reaction, thereby producing an aromatic polythiazole. 2. The method according to claim 1, wherein the alkyl halide is a halide of a substituted or unsubstituted secondary alkyl group. 3. The method according to claim 1, wherein the alkyl group of the alkyl halide has a substituent consisting of a carboxyl group, an ester group, a cyano group or a benzyl group. 4. The method according to claim 1, wherein the polymerization reaction of the alkyl group-substituted aromatic diaminodithiol compound and the dicarboxylic acid derivative is
A method characterized by performing at a temperature of 20 ° C to + 50 ° C. 5. The method according to claim 1, wherein the dicarboxylic acid derivative is terephthalic acid dichloride. 6. The method according to claim 1, wherein the aromatic polythiazole precursor is 250.degree.
A method comprising forming a thiazole ring by heating at 500 ° C. to produce an aromatic polythiazole.