JP7094545B2 - Polybenzimidazole - Google Patents

Description

The present invention relates to polybenzimidazole. More specifically, the present invention relates to polybenzimidazole and a method for producing the same, and diaminobenzineric acid and its dihydrochloride useful as a raw material for polybenzimidazole. Since the polybenzimidazole of the present invention has excellent heat resistance and ductility, it can be used for fuel cell separators, aerospace fields, automobile industry, railway vehicles, transportation equipment such as ships, electronic equipment, and the like. Be expected.

Conventionally, a 2,5-benzoxazole polymer is known as a benzoxazole compound having excellent heat resistance (see, for example, Patent Document 1). The 2,5-benzoxazole polymer is prepared, for example, by using 3-amino-4-hydroxybenzoic acid as a raw material (see, for example, paragraphs [0115]-[0116] of Patent Document 1). However, although the 2,5-benzoxazole polymer has excellent heat resistance, it has a drawback of being inferior in ductility.

In recent years, it has been desired to develop polybenzimidazole having further excellent heat resistance and ductility.

Japanese Unexamined Patent Publication No. 2008-29325

The present invention has been made in view of the above-mentioned prior art, and polybenzimidazole having excellent heat resistance and ductility, a method for producing the same, and hydro useful as a raw material used in the production of the polybenzimidazole. It is an object of the present invention to provide -3,4-diaminobenzyl acid and hydro-3,4-diaminobenzimidazole dihydrochloride.

The present invention
(1) Equation (I):

Hydro-3,4-diaminocinnamic acid, represented by
Equation (2): (II):

Hydro-3,4-diaminocinnamic acid dihydrochloride represented by,
Equation (3):

Repeat unit and equation (IV) represented by:

Polybenzimidazole, characterized by having a repeating unit represented by.
(4) The polybenzimidazole according to claim (3), which contains 5 to 40 mol% of the repeating unit represented by the formula (III) and 60 to 95 mol% of the repeating unit represented by the formula (IV), and (5). ) 3,4-Diaminobenzoic acid dihydrochloride and formula (II):

Formulation (III) characterized by polymerizing with hydro-3,4-diaminocinnamic acid dihydrochloride represented by.

Repeat unit and equation (IV) represented by:

The present invention relates to a method for producing polybenzimidazole having a repeating unit represented by.

According to the present invention, polybenzimidazole having excellent heat resistance and ductility and a method for producing the same, and hydro-3,4-diaminocineramic acid and hydro useful as raw materials used in the production of the polybenzimidazole. -3,4-Diaminobenzimidazole dihydrochloride is provided.

It is a graph which shows the ¹ H-NMR spectrum of the hydro-3,4-diaminocinnamic acid obtained in Example 1. FIG. It is a graph which shows the ¹³ C-NMR spectrum of the polybenzimidazole obtained in Example 2. FIG. It is a graph which shows the ¹³ C-NMR spectrum of the benzimidazole homopolymer obtained in the comparative example 2. FIG.

As a raw material used in the production of the polybenzimidazole of the present invention, the formula (I):

Hydro-3,4-diaminocinnamic acid represented by or formula (II):

Hydro-3,4-diaminocinnamic acid dihydrochloride represented by can be used.

By using the Hydro-3,4-diaminocinnamic acid represented by the formula (I) or the Hydro-3,4-diaminocinnamic acid dihydrochloride represented by the formula (II), the formula (III) :.

Repeat unit and equation (IV) represented by:

Polybenzimidazole having a repeating unit represented by can be prepared.

(1) Preparation of Hydro-3,4-diaminocinnamic Acid Represented by Formula (I) and Hydro-3,4-Diaminocinnamic Acid Dihydrochloride Represented by Formula (II) Hydro-Represented by Formula (I) 3,4-Diaminocinnamic acid and hydro-3,4-diaminocinnamic acid dihydrochloride represented by the formula (II) are described, for example, in the formula:

As represented by, it can be prepared using 4-hydroxycinnamic acid as a raw material. More specifically, 4-hydroxycinnamic acid is used as a raw material, and Hydro-3,4-diaminocinnamic acid represented by the formula (I) and Hydro-3 represented by the formula (II) are used based on the following methods. 4-Diaminocinnamic acid dihydrochloride can be prepared.

First, 4-hydroxycinnamic acid is reacted with methanol in the presence of sulfuric acid to methylesterify the carboxyl group of 4-hydroxycinnamic acid, thereby protecting the carboxyl group of 4-hydroxycinnamic acid.

Next, a nitro group was introduced into the methyl 4-hydroxy silicate by contacting the methyl 4-hydroxy silicate having a carboxyl group methyl esterified with the mixed acid, and subsequently, the 3-nitro-4 obtained above was obtained. -Introducing an amino group into methyl 3-nitro-4-hydroxysilicate by reacting methyl hydroxycatalyst with 2-bromoisobutylamide in the presence of potassium carbonate in a solvent such as N, N-dimethylformamide. .. A hydroxyl group-amino group conversion reaction is carried out by adding an alkali such as potassium hydroxide to the reaction solution obtained above.

Hydrochloric acid is added to the reaction solution obtained above to generate 3-nitro-4-aminocineryl acid, and 3-nitro-4-aminocineryl acid is converted into a nitro group in the presence of a reduction catalyst such as palladium carbon. By hydrogen-reducing

Next, by reacting the above-mentioned hydro-3,4-diaminocinnamic acid with hydrochloric acid, hydro-3,4-diaminocinnamic acid dihydrochloride represented by the formula (II) can be obtained.

(2) Preparation of 3,4-diaminobenzoic acid dihydrochloride For 3,4-diaminobenzoic acid, for example, the formula:

As represented by, 3-amino-4-hydroxybenzoic acid is used as a raw material, and the 3-amino-4-hydroxybenzoic acid can be easily prepared by performing a Smiles rearrangement.

Next, 3,4-diaminobenzoic acid dihydrochloride can be obtained by reacting 3,4-diaminobenzoic acid with hydrochloric acid.

(3) Preparation of polybenzimidazole having a repeating unit represented by the formula (III) and a repeating unit represented by the formula (IV). The repeating unit represented by the formula (III) and the repeating unit represented by the formula (IV). Polybenzimidazole can be prepared, for example, by the following method.

3,4-Diaminobenzoic acid dihydrochloride (DABA) and hydro-3,4-diaminocineramic acid dihydrochloride (DACA) are mixed in a predetermined ratio, and the obtained mixture is mixed in the presence of polyphosphate, for example. , Nitrogen gas, argon gas and other inert gas atmospheres are reacted by heating at a temperature of about 100 to 200 ° C. for about 20 to 28 hours, and the obtained reaction mixture is, for example, nitrogen gas, argon gas and the like. By heating in an inert gas atmosphere stepwise to a temperature of 350 to 450 ° C. for about 3 to 10 hours, the repeating unit represented by the formula (III) and the repeating unit represented by the formula (IV) can be obtained. Polybenzimidazole having can be obtained.

In the polybenzimidazole, the content of the repeating unit represented by the formula (III) is preferably 5 to 40 mol% from the viewpoint of improving heat resistance and ductility, and the repeating unit represented by the formula (IV). Is preferably 60 to 95 mol% from the viewpoint of improving heat resistance and ductility. The content of the repeating unit represented by the formula (III) and the content of the repeating unit represented by the formula (IV) of the polybenzimidazole are both 3,4-diaminobenzoic acid dihydrochloride (DABA). It can be adjusted by adjusting the ratio with Hydro-3,4-diaminocinnamic acid dihydrochloride (DACA).

Since the polybenzimidazole of the present invention is sparingly soluble in water and organic solvents, it is difficult to measure the molecular weight of the polybenzimidazole by gel permeation chromatography or the like. Therefore, the polybenzimidazole of the present invention can be specified by the intrinsic viscosity, not by the molecular weight. The intrinsic viscosity (η _inh ) of the polybenzimidazole of the present invention is preferably 2.8 to 4.0 dL / g from the viewpoint of improving heat resistance and ductility. The intrinsic viscosity (η _inh ) of polybenzimidazole of the present invention is a value measured based on the method described in the following Examples.

Since the polybenzimidazole of the present invention obtained as described above can achieve both heat resistance and ductility, it can be used for transportation equipment such as fuel cell separators, aerospace fields, automobile industries, railway vehicles, and ships. It is expected to be used for electronic devices and the like.

Next, the present invention will be described in more detail based on examples, but the present invention is not limited to such examples.

Example 1
(1) Preparation of methyl 4-hydroxycinnamic acid To 30 mL of methanol, 5.0 g (30.5 mmol) of 4-hydroxycinnamic acid [manufactured by Tateyama Kasei Co., Ltd.] and a catalytic amount of sulfuric acid are added and refluxed for 24 hours. , 4-Hydroxycinnamic acid was methyl esterified. After removing the solvent from the reaction solution obtained above, 4.96 g of methyl 4-hydroxycinnamic acid was recovered by drying under reduced pressure (yield: 91.3%).

(2) Preparation of 3-nitro-4-hydroxymethylcinnamic acid To 80 mL of pure water, 1.43 g (8 mmol) of the above-mentioned methyl 4-hydroxycinnamic acid was added, and the obtained mixture was subjected to about ice-cooling. The reaction solution was obtained by stirring for 30 minutes. 16 mL of concentrated sulfuric acid was added dropwise to the reaction solution obtained above over 1 hour under ice cooling, and then 8 mL of concentrated nitric acid was added dropwise to the reaction solution over about 30 minutes under ice cooling, and then the reaction solution was used as it was. It was stirred for about 30 minutes in the state of. After the stirring is completed, the reaction solution obtained above is stirred at room temperature for 18 hours, the reaction solution is filtered, the obtained precipitate is washed with pure water, and dried under reduced pressure to obtain 3-nitro-. 1.21 g of methyl 4-hydroxycinnamic acid was obtained (yield: 67.8%).

(3) Preparation of 3-nitro-4-aminocinnamic acid 0.66 g (3 mmol) of 3-nitro-4-hydroxycinnamic acid obtained above, 18 mL of N, N-dimethylformamide and 1.24 g of potassium carbonate ( (9 mmol) was mixed and stirred at room temperature for 1.5 hours to obtain a reaction solution. 2-Bromoisobutyramide [manufactured by Tokyo Chemical Industry Co., Ltd.] 1.50 g (9 mmol) was added to the reaction solution obtained above, and the obtained mixture was reacted at 60 ° C. for 2 days. Then, 1.50 g (27 mmol) of potassium hydroxide was added to the reaction mixture obtained above, and the mixture was stirred at 60 ° C. for 4 hours. 1 mL of pure water was added to the reaction solution obtained above, and the mixture was stirred at 100 ° C. for 3 hours.

The reaction solution obtained above was dried under reduced pressure to remove water contained in the reaction solution, and then the reaction solution was reprecipitated with 400 mL of ethyl acetate. The obtained precipitate is filtered, dried under reduced pressure, dissolved in pure water, and hydrochloric acid is added until the pH becomes around 6, to neutralize the aqueous solution obtained above, thereby preparing the reaction solution. Obtained.

Ethyl acetate was added to the reaction solution obtained above, liquid-liquid extraction was performed, the ethyl acetate layer was filtered, and then the solvent was removed with an evaporator to precipitate and recover an orange solid. The solid obtained above was washed with pure water and dried under reduced pressure to obtain 0.50 g of 3-nitro-4-aminocinnamic acid (yield: 80.1%).

(4) Preparation of Hydro-3,4-Diamino Katsura Acid 0.21 g (1 mmol) of 3-nitro-4-amino katsura acid obtained above in a 30 mL two-necked flask, and palladium carbon as a reduction catalyst [Fuji] Film Wako Junyaku Co., Ltd.] 0.11 g and 20 mL of methanol are added, and the reaction solution is prepared by hydrogen-reducing 3-nitro-4-aminocinnyl acid at room temperature for 24 hours while stirring the contents of the flask. Obtained. Then, palladium carbon was removed by filtering the reaction solution obtained above, and 0.22 g of hydro-3,4-diaminocinnamic acid was obtained by removing the solvent (yield: 86.9). %).

The ¹ H-NMR spectrum of the hydro-3,4-diaminocineramic acid obtained above was measured with a nuclear magnetic resonance spectroscope [manufactured by Bruker, trade name: AVANCE III]. The results are shown in FIG. Further, mass spectrometry of the hydro-3,4-diaminocinerone acid obtained above was performed using a Fourier transform ion cyclotron resonance mass spectrometer [manufactured by Bruker Daltonix Co., Ltd., trade name: Solarix]. The results are shown below.
[Results of mass spectrometry]
-Calculated value (C ₉ H ₁₂ N ₂ O ₂ ): 181.09715
-Actual measurement value: 181.09707

From the above results, it was confirmed that the compound obtained above was hydro-3,4-diaminocinnamic acid.

(5) Preparation of Hydro-3,4-Diaminocinnate Dihydrochloride Hydro--3,4- by adding hydrochloric acid to the filtrate of the reaction solution from which palladium carbon was removed in (4) above and removing the solvent. 0.22 g of diaminosilicate dihydrochloride was obtained (yield: 86.9%).

Examples 2 to 6
15 g of polyphosphoric acid is placed in a three-necked round-bottomed flask, and the contents of the flask are heated at 120 ° C. for 1 hour while continuously flowing nitrogen gas into the flask in order to remove the water remaining in the flask. Heated.

The mixture obtained by sufficiently mixing 3,4-diaminobenzoic acid dihydrochloride (DABA) and hydro-3,4-diaminobenzoic acid dihydrochloride (DACA) so as to have the molar ratio shown in Table 1. Was added into the flask under a nitrogen gas stream and heated at 120 ° C. for 1 hour.

Next, the contents in the flask were heated and heated at a temperature of 160 ° C. for 4 hours and at a temperature of 220 ° C. for 16 hours under a nitrogen gas stream to complete the polymerization. The adhesive rubber-like polymer obtained above was dried at 110 ° C. for 4 hours and pulverized to obtain an unreacted polyphosphoric acid-containing powder. The polymer obtained above was added to a 10% aqueous potassium hydroxide solution and left at room temperature for about 10 hours to dissolve the polymer in the aqueous potassium hydroxide solution.

The aqueous solution obtained above was filtered, and the obtained solid content was repeatedly washed with water and then heat-circulated stepwise to 400 ° C. in a nitrogen gas atmosphere to obtain polybenzimidazole. ..

The ¹³ C-NMR spectrum of polybenzimidazole obtained in Example 2 was measured with a nuclear magnetic resonance spectrometer [manufactured by Bruker, trade name: AVANCE III]. The results are shown in FIG. From the results shown in FIG. 2, it was confirmed that the polybenzimidazole obtained in Example 2 had a repeating unit represented by the formula (III) and a repeating unit represented by the formula (IV).

When the ¹³ C-NMR spectra of polybenzimidazole obtained in Examples 3 to 6 were examined in the same manner as described above, the polybenzimidazole was found to be ¹³ C, similarly to the polybenzimidazole obtained in Example 2. -Since it has an NMR spectrum, it was confirmed that it had a repeating unit represented by the formula (III) and a repeating unit represented by the formula (IV).

Comparative Example 1
Place 0.58 g (2.6 mmol) of 3,4-diaminobenzoic acid dihydrochloride (DABA) and 0.51 g (3.6 mmol) of phosphorus pentoxide in a 30 mL round-bottom flask, and put nitrogen gas into the flask. Filled.

4 mL of methanesulfonic acid as a solvent was added into the flask with a syringe, and the contents of the flask were stirred at 150 ° C. for 24 hours to obtain a reaction solution. The reaction solution obtained above was reprecipitated with 100 mL of pure water, and the obtained spherical precipitate was recovered by filtration and dried at a temperature of 110 ° C. under reduced pressure.

The dried product obtained above was pulverized, washed with pure water, and dried at a temperature of 100 ° C. under reduced pressure. The dried powder was heated stepwise to 400 ° C. in a nitrogen gas stream to form an imidazole ring to give 0.23 g of a 2,5-benzimidazole homopolymer (yield: 76.2). %).

Comparative Example 2
10 g of polyphosphoric acid is placed in a 30 mL round bottom flask, and in order to remove the water remaining in the flask, the contents of the flask are heated at 120 ° C. while continuously flowing nitrogen gas into the flask. Heated for hours.

1.265 g (5 mmol) of Hydro-3,4-diaminocinnamic acid dihydrochloride (DACA) was added into the flask under a nitrogen gas stream and heated at 120 ° C. for 1 hour.

Next, the contents of the flask were heated and heated at a temperature of 180 ° C. for 10 hours and at a temperature of 220 ° C. for 13 hours under a nitrogen gas stream, whereby the contents of the flask changed from light brown to dark brown. And the polymerization was completed. The polymer obtained above was dried at 200 ° C. for 4 hours and pulverized to obtain a powder containing unreacted polyphosphoric acid. The polymer obtained above was added to a 10% aqueous potassium hydroxide solution and left at room temperature for about 10 hours to dissolve the polymer in the aqueous potassium hydroxide solution.

The aqueous solution obtained above is filtered, the obtained solid content is repeatedly washed with water, and then thermally cyclized by gradually heating to 400 ° C. in a nitrogen gas atmosphere to obtain a benzimidazole homopolymer. rice field.

The ¹³ C-NMR spectrum of the benzimidazole homopolymer obtained in Comparative Example 2 was measured with a nuclear magnetic resonance spectroscope [manufactured by Bruker, trade name: AVANCE III]. The results are shown in FIG. From the results shown in FIG. 3, it was confirmed that the benzimidazole homopolymer obtained in Comparative Example 2 had a repeating unit represented by the formula (IV).

Experimental Example 1
The physical characteristics of the polymers obtained in each example and each comparative example are 10% weight loss temperature (T _d10 ), intrinsic viscosity (η _inh ), Young's modulus (σ), tensile strength (E) and elongation at break. (Ε) was investigated based on the following method. The results are shown in Table 1.

[10% weight loss temperature (T _d10 )]
Using a thermogravimetric-differential heat simultaneous measuring device [Hitachi High-Technologies Corporation, trade name: STA7200], the polymer is heated to 800 ° C at a heating rate of 10 ° C / min in a nitrogen gas atmosphere or in air. The degree of weight loss was measured.

In Table 1, the 10% weight loss temperature measured in a nitrogen gas atmosphere is referred to as “T _d10 ^a ”, and the 10% weight loss temperature measured in air is referred to as “T _d10 ^b ”.

[Intrinsic viscosity (indicated as "η _inh " in the table)]
20 mL of a polymer solution of concentrated sulfuric acid having a polymer concentration of 0.5 g / dL was placed in a Ubbelohde-type viscosity measuring capillary tube, and the viscosity measuring capillary tube was fixed in a constant temperature bath for viscosity measurement set at 30 ° C. for 30 minutes. It was left still. Then, the time (t) until the meniscus passed between the upper line and the lower line shown on the viscosity measuring capillary tube was measured with a stopwatch.

For the concentrated sulfuric acid, the time (t ₀ ) until the meniscus passed between the upper line and the underline shown on the viscosity measuring capillary tube was measured with a stopwatch under the same conditions as described above.

Next, based on the time (t) and time (t ₀ ) obtained above, the equation:
[Intrinsic viscosity (dL / g)] = (t-t ₀ ) / t ₀
The intrinsic viscosity (η _inh ) was determined according to the above.

[Young's modulus (indicated as "σ" in the table), tensile strength (indicated as "E" in the table) and elongation at break (indicated as "ε" in the table)]
Young's modulus (σ), tensile strength (E) and elongation strain (ε) at break were measured using a tensile tester [Instron Japan Company Limited, trade name: INSTRON 3365] as a measuring device.

From the results shown in Table 1, the 10% weight loss temperature (T _d10 ^a ) of the polybenzimidazole obtained in each example in the nitrogen gas atmosphere was 587 ° C. or higher, which was obtained in Example 2. Since the 10% weight loss temperature (T _d10 ^a ) of polybenzimidazole in the nitrogen gas atmosphere is 726 ° C., it can be seen that the heat resistance is remarkably excellent.

Further, among Examples 2 to 6, the polybenzimidazoles obtained in Examples 2 and 3 have a 10% weight loss temperature (T _d10 ^b ) in the air, and thus the formula is 546 ° C. or higher. When the repeating unit represented by (III) is 60 to 95 mol% and the repeating unit represented by the formula (IV) is 5 to 40 mol%, the repeating unit represented by the formula (III) and the repeating unit represented by the formula (IV) are represented. Due to the synergistic effect of the combined use with the repeating unit, it can be seen that the homopolymer composed of the repeating unit represented by the formula (III) and the homopolymer composed of the repeating unit represented by the formula (IV) are superior in heat resistance.

Further, from the results shown in Table 1, the polybenzimidazoles obtained in each example had a Young's modulus (σ) of 43 to 66 MPa and an elongation strain (ε) at break of 0.036 mm /. Since it is mm or more, it is stretched with a smaller stress than the homopolymer composed of the repeating unit represented by the formula (IV) obtained in Comparative Example 1, so that it is excellent in stretchability and the tensile strength (E) is eventually increased. Since it is 1.4 GPa or more, it is superior in mechanical strength to the homopolymer composed of the repeating unit represented by the formula (III) obtained in Comparative Example 2, so that both heat resistance and ductility can be achieved at the same time. It turns out that it is a thing.

Since the polybenzimidazole of the present invention can achieve both heat resistance and ductility, it should be used for fuel cell separators, aerospace fields, automobile industry, railway vehicles, transportation equipment such as ships, electronic equipment, and the like. There is expected.

Claims (3)

Equation (III):

Repeat unit and equation (IV) represented by:

Polybenzimidazole characterized by having a repeating unit represented by. The polybenzimidazole according to claim 1 , which contains 5 to 40 mol% of the repeating unit represented by the formula (III) and 60 to 95 mol% of the repeating unit represented by the formula (IV). 3,4-Diaminobenzoic acid dihydrochloride and formula (II):

Formulation (III) characterized by polymerizing with hydro-3,4-diaminocinnamic acid dihydrochloride represented by.

Repeat unit and equation (IV) represented by:

A method for producing polybenzimidazole having a repeating unit represented by.

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