KR100589345B1 - Method for preparing sulfonated polybenzimidazole and sulfonated polybenzimidazole prepared therefrom and polymer electrolyte membrane comprising the same - Google Patents

Abstract

The present invention relates to a method for preparing sulfonated polybenzimidazole, a sulfonated polybenzimidazole prepared therefrom, and a polymer electrolyte membrane including the same. More specifically, the monomer represented by the following Chemical Formula 1 or Chemical Formula 2 and The present invention relates to a method for preparing a sulfonated polybenzimidazole, comprising the step of polymerizing a monomer represented by Formula 3, and a sulfonated polybenzimidazole prepared therefrom, and a polymer electrolyte membrane including the same.

[Formula 1]

[Formula 2]

[Formula 3]

In Formulas 1 to 3, Y ₁ , Y ₂ are each hydrogen, alkyl or aryl, preferably hydrogen, alkyl or aryl having 1 to 12 carbon atoms, R is SO ₂ or CO, and X is chlorine (Cl ) Or fluorine (F)

Polymer for forming polymer electrolyte membrane, high temperature, hydrogen ion conductivity

Description

Method for preparing sulfonated polybenzimidazole, and sulfonated polybenzimidazole prepared therefrom, and polymer electrolyte membrane comprising the same

[Industrial use]

The present invention relates to a method for preparing sulfonated polybenzimidazole and a sulfonated polybenzimidazole prepared therefrom and a polymer electrolyte membrane comprising the same, and more particularly, to a high temperature low-cost fuel cell electrolyte membrane. The present invention relates to a method for preparing sulfonated polybenzimidazole which can be used, and a sulfonated polybenzimidazole prepared therefrom and a polymer electrolyte membrane comprising the same.

[Private Technology]

A fuel cell is an electrochemical cell in which free energy changes due to fuel oxidation are converted into electrical energy. In fuel cells, organic fuels such as methanol, formaldehyde or formic acid are oxidized to carbon dioxide at the anode and air or oxygen is reduced to water at the cathode. In part, fuel cells using organic fuels are extremely attractive, both on installation and portable, because of the high specific energy of organic fuels (eg, the specific energy of methanol is 6232 wh / kg).

In fuel cells, a solid polymer membrane is positioned between an anode and a cathode and serves as a medium for proton movement between two electrodes. BACKGROUND OF THE INVENTION As a conductive solid polymer membrane of a fuel cell, a fluorine-based electrolyte membrane such as Dow or Dupon's perfluorocarbon sulfonic acid membrane (Nafion ^™ ) is widely used because of its excellent chemical stability, high ionic conductivity and excellent mechanical properties.

However, the fluorine-based electrolyte has a disadvantage in that the manufacturing process is complicated and the price is high. In addition, because the heat resistance is high, but the heat resistance limit does not exceed 100 ℃, fluorine-based electrolyte membranes are a low pollution power source for automobiles. When used in fuel cells, small-sized power sources or portable power sources, it is not necessary to cool the reformed gas or remove carbon monoxide from the reformed gas. It has become a factor that complicates the system. In addition, the proton conductivity is low at a high temperature of more than 80 ℃ or a low humidity range of less than 60%, there is a problem showing low methanol cross-over (cross-over).

Therefore, various sulfonated polymers, such as polyimide, polysulfone, polystyrene, polyphenylene and polyether ether ketone (PEEK), have been developed to obtain a polymer electrolyte membrane that can replace the fluorine-based electrolyte membrane. Celanese has developed poly [2,2 '-(m-phenylene) -5,5'-bibenzimidazole] as a material that can overcome the disadvantages of fluorine-based polymers such as Nafion. Polymer electrolyte membrane forming polymer has much lower methanol permeability than Nafion fluorine-based polymer and can be supplied at low cost because it is made of pure hydrocarbon. In addition, since it shows high conductivity at a temperature of 100 ° C. or higher, it can be used in high temperature fuel cells.

Conventionally, in order to prepare sulfonated polybenzimidazole, polybenzimidazole was prepared by a method of sulfonating. However, when this method is used, the degree of sulfonation is difficult to control, and the degree of sulfonation is not high, and a phenomenon in which the polymer is decomposed in the middle of sulfonation occurs.

The present invention is to solve the above problems, an object of the present invention is easy to control the degree of sulfonation, sulfonated polybenzimidazole manufacturing method and sulfonated polybenzimi prepared therefrom It is to provide doazole.

Another object of the present invention is to provide a polymer electrolyte membrane including the sulfonated polybenzimidazole.

The present invention provides a method for preparing a sulfonated polybenzimidazole comprising the step of polymerizing a monomer represented by the following formula (1) or (2) and a monomer represented by the following formula (3) to achieve the above object.

[Formula 1]

[Formula 2]

[Formula 3]

In Formulas 1 to 3, Y ₁ , Y ₂ are each hydrogen, alkyl or aryl, preferably hydrogen, alkyl or aryl having 1 to 12 carbon atoms, R is SO ₂ or CO, and X is chlorine (Cl) Or fluorine (F)

The present invention also provides a sulfonated polybenzimidazole prepared by the above method and having a repeating unit represented by Formula 11 or 12 below.

[Formula 11]

[Formula 12]

In Formulas 11 and 12, Y ₁ , Y ₂ are each hydrogen, alkyl or aryl, preferably hydrogen, alkyl or aryl having 1 to 12 carbon atoms, R is SO ₂ or CO, and n represents a degree of polymerization. .

The present invention also provides a polymer electrolyte membrane for a fuel cell comprising the sulfonated polybenzimidazole.

Hereinafter, the present invention will be described in more detail.

In the present invention, sulfonated polybenzimidazole is prepared by using a sulfonate group in the monomer itself. The method for producing the sulfonated polybenzimidazole of the present invention includes sulfonate groups in the monomer state, and is substituted with sulfonic acid groups in the polymerization step, so that the degree of sulfonation can be easily controlled, and sulfonated polybenzimides having a high degree of sulfonation. Dazole can be prepared.

 The sulfonated polybenzimidazole has a high bentonimidazole group having excellent thermal stability and mechanical properties, and has a hydrogen ion conductivity at high temperature, and has a high hydrogen ion conductivity including a sulfonic acid group in a molecule thereof, and thus for fuel cells. It is suitable for use as a polymer electrolyte membrane.

In the present invention, sulfonated polybenzimidazole is prepared from a monomer represented by the following formula (1) or (2) and a monomer represented by the following formula (3).

[Formula 1]

[Formula 2]

[Formula 3]

In Formulas 1 to 3, Y ₁ , Y ₂ are each hydrogen, alkyl or aryl, preferably hydrogen, alkyl or aryl having 1 to 12 carbon atoms, R is SO ₂ or CO, and X is chlorine (Cl ) Or fluorine (F)

In the polymerization of the sulfonic acid polybenzimidazole of the present invention, the content of the monomer represented by Formula 1 or Formula 2 and the monomer represented by Formula 3 is preferably in a molar ratio of 1.5: 1 to 1: 1.5, and 1.2: It is more preferable that it is 1-1: 1.2.

In the present invention, to prepare a sulfonated polybenzimidazole, a polymerization reaction is carried out using a catalyst such as potassium carbonate (K ₂ CO ₃ ), sodium carbonate (Na ₂ CO ₃ ) or lithium carbonate (Li ₂ CO ₃ ). It is preferable.

In addition, an acidic compound is added to replace the sulfonate group of the monomer represented by Formula 3 with a sulfonic acid group. Examples of the acidic compound may be any acidic compound that generates hydrogen ions.

The catalyst and the acidic compound may be dissolved in a polar solvent, preferably at least in a solvent such as trifluoroacetic acid, N-methylpyrrolidone or dimethylacetamide. It may be used after being dissolved in a solvent containing at least one.

The content of the catalyst contained in the solvent is preferably 0.001 to 10% by weight, more preferably 0.01 to 5% by weight. When the content of the catalyst is less than 0.001% by weight, the reaction rate is slowed to obtain a sulfonated polybenzimidazole having a sufficient molecular weight. When the content of the catalyst is more than 10% by weight, the polymerization reaction rate is accelerated, resulting in a uniform sulfonated polybenzimidazole. Can't get it.

In addition, the content of the acidic compound contained in the solvent is preferably 0.001 to 10% by weight, more preferably 0.01 to 5% by weight. If the amount of acidic compound contained in the solvent is less than 0.001% by weight, the sulfonate group is not sufficiently substituted, so that the hydrogen ion conductivity of the sulfonated polybenzimidazole is lowered. Do.

The monomer represented by Formula 1 or Formula 2 is prepared from the dehydration reaction of the hydroxybenzoic acid represented by the tetraamine-based compound represented by the following formula (4) or (5) and the formula (6), to be prepared through the following steps Can be.

[Formula 4]

[Formula 5]

[Formula 6]

The tetraamine-based compound represented by Formula 4 or Formula 5 and the hydroxybenzoic acid represented by Formula 6 are mixed in a molar ratio of 1.5: 1 to 1: 1.5, and a dehydrating agent is added. In this case, the molar ratio of the tetraamine-based compound and hydroxy benzoic acid is more preferably 1.2: 1 to 1: 1.2.

The dehydrating agent is a mixture of poly phosphoric acid (polyphosphoric acid), P ₂ O _5, and poly phosphoric acid mixture, or P ₂ O ₅ and CX ₃ SO ₃ H (X is hydrogen or fluorine) of (polyphosphoric acid), etc. It may be used, preferably a mixture of P ₂ O ₅ and CX ₃ SO ₃ H (X is hydrogen or fluorine) can be used.

In particular, in the case of using a mixture of P ₂ O ₅ and CX ₃ SO ₃ H (X is hydrogen or fluorine), it is preferable to mix and use in advance to make a uniform solution state, each component is from 0.5: 10 to It is preferred to mix in a weight ratio of 2:10.

The dehydration reaction is carried out for 10 minutes to 10 hours at 100 to 300 ℃, in the case of using a mixture of polyphosphoric acid or P ₂ O ₅ and polyphosphoric acid as a dehydrating agent at a temperature of 200 to 300 ℃ It is preferable to carry out reaction for 10 hours, and when using a mixture of P ₂ O ₅ and CX ₃ SO ₃ H (X is hydrogen or fluorine), the reaction is carried out at 100 to 200 ° C. for about 10 to 120 minutes. It is preferable.

The monomer prepared through the dehydration reaction is represented by the following formula (7) or formula (8).

[Formula 7]

[Formula 8]

The monomer represented by the above formula (7) or (8) may be used for the preparation of sulfonated polybenzimidazole, and may be used by substituting alkyl or aryl with hydrogen of the imidazole group of the monomer as necessary.

 In the formula (7) or (8), the monomer in which hydrogen of the imidazole group is substituted with alkyl or aryl is represented by the following formula (9) or (10).

[Formula 9]

[Formula 10]

In Formulas 9 and 10, R ₁ and R ₂ are each alkyl or aryl, preferably hydrogen, alkyl or aryl having 1 to 12 carbon atoms, respectively.

The sulfonated polybenzimidazole of the present invention prepared by the above method has a repeating unit represented by the following formula (11) or (12).

[Formula 11]

[Formula 12]

In Formulas 11 and 12, Y ₁ , Y ₂ are each hydrogen, alkyl or aryl, preferably hydrogen, alkyl or aryl having 1 to 12 carbon atoms, R is SO ₂ or CO, and n represents a degree of polymerization. .

The sulfonated polybenzimidazole preferably has a weight average molecular weight of 1,000 to 10,000,000, more preferably 100,000 to 8,000,000.

As shown in Formula 11 or Formula 12, the sulfonated polybenzimidazole of the present invention can be seen to include a benzimidazole group in the molecular chain and excellent thermal stability and mechanical properties. In addition, since the sulfonic acid group is included in each repeating unit, high hydrogen ion conductivity is shown.

The sulfonated polybenzimidazole may be prepared as a polymer electrolyte membrane for a fuel cell by casting the reaction solution itself on the substrate after the polymerization process, and further, purified and cast again on a substrate to be dissolved in an organic solvent and dried. To produce a polymer electrolyte membrane for a fuel cell.

Examples of the organic solvent used in the casting include dimethylacetamide, dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone or trifluoroacetic acid, and the like, or may be used by mixing two or more thereof. Can be.

The casting method is the same as a conventional method, and the casting method is generally known, and thus detailed description thereof is omitted in the specification of the present invention.

Since the sulfonated polybenzimidazole polymer electrolyte membrane obtained by the above method has high hydrogen ion conductivity at high temperature, it can be used in a fuel cell as an electrolyte membrane of a fuel cell membrane-electrode assembly (MEA).

Hereinafter, preferred embodiments of the present invention are described. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.

EXAMPLE

Example 1 (Preparation of Sulfonated Polybenzimidazole Represented by Formula 11)

1-1: Preparation of Monomer represented by Chemical Formula 7

2 g of P ₂ O ₅ and 20 ml of CH ₃ SO ₃ H were mixed and stirred for 12 hours to obtain a uniform dehydrating solution. A monomer was prepared by adding 1 mole of 1,2,4,5-benzenetetraamine and 1 mole of 4-hydroxy benzoic acid to the prepared dehydrating agent solution, stirring at 160 ° C. for 30 minutes and reacting under a nitrogen atmosphere.

1-2: Preparation of sulfonated polybenzimidazole

The monomer prepared in Example 1-1 and the monomer of Formula 3 (X is chlorine and R is SO ₂ ) are mixed with dimethylacetamide in a molar ratio of 1: 1, and potassium carbonate (K ₂ CO ₃ ) And acetic acid (CH ₃ COOH) were added at 1% by weight to prepare a mixed solution. The sulfonated polybenzimidazole was prepared by polymerizing the mixed solution under a nitrogen atmosphere.

Example 2 (Preparation of Sulfonated Polybenzimidazole Represented by Formula 12)

2-1: Preparation of Monomer represented by Chemical Formula 8

[1,1'-biphenyl] -3,3 ', 4,4'-tetraamine ([1,1'-biphenyl] -3,3', instead of 1,2,4,5-benzenetetraamine A monomer was prepared in the same manner as in Example 1-1 except for using 4,4'-tetramine.

2-2: Preparation of Sulfonated Polybenzimidazole

The same method as Example 1-2 except for mixing the monomer prepared according to Example 2-1 and the monomer of Formula 3 (X is chlorine, R is SO ₂ ) in a molar ratio of 1: 1. Sulfonated polybenzimidazole was prepared.

The sulfonated polybenzimidazole and polymer electrolyte membrane prepared according to the method of the present invention have excellent hydrogen ion conductivity and mechanical properties, and are suitable for use as an electrolyte membrane of a fuel cell membrane-electrode assembly (MEA).

Claims (9)

A method for producing a sulfonated polybenzimidazole comprising polymerizing a monomer represented by Formula 1 or Formula 2 below and a monomer represented by Formula 3 below. [Formula 1]

[Formula 2]

[Formula 3]

In Formulas 1 to 3, Y ₁ , Y ₂ are each hydrogen, alkyl or aryl, R is SO ₂ or CO, and X is chlorine (Cl) or fluorine (F). The method of claim 1, wherein the molar ratio of the monomer represented by Formula 1 or Formula 2 and the monomer represented by Formula 3 is 1.5: 1 to 1: 1.5. The method of claim 1, wherein the polymerization is carried out using one or more catalysts selected from the group consisting of potassium carbonate (K ₂ CO ₃ ), sodium carbonate (Na ₂ CO ₃ ), and lithium carbonate (Li ₂ CO ₃ ). Method for producing a sulfonated polybenzimidazole. The method of claim 1, wherein the sulfonated polybenzimidazole is prepared by the monomer represented by the following Chemical Formulas 7 to 10 from a tetraamine-based compound represented by the following Chemical Formula 4 or 5 and a hydroxybenzoic acid represented by the following Chemical Formula 6. Method for producing a sulfonated polybenzimidazole further comprises the step of synthesizing. [Formula 4]

[Formula 5]

[Formula 6]

[Formula 7]

[Formula 8]

[Formula 9]

[Formula 10]

In Formulas 4 to 10, R ₁ , R ₂ are each alkyl or aryl The method of claim 4, wherein the monomer represented by Formula 7 or Formula 8 are poly phosphoric acid (polyphosphoric acid), P ₂ O _5, and poly phosphoric acid (polyphosphoric acid) mixture, and P ₂ O ₅ and CX ₃ SO of A process for producing sulfonated polybenzimidazole, which is synthesized using at least one dehydrating agent selected from the group consisting of a mixture of ₃ H (X is hydrogen or fluorine). The method according to claim 5, wherein the P ₂ O ₅ and CX ₃ SO ₃ H (X is hydrogen or fluorine) is used in a mixture of 0.5: 10 to 2:10 by weight ratio. . According to claim 4, wherein the step of synthesizing the monomer represented by the formula (7) or formula (8) is a method for producing a sulfonated polybenzimidazole is synthesized for 10 minutes to 10 hours at 100 to 300 ℃. A sulfonated polybenzimidazole prepared according to any one of claims 1 to 7, having a repeating unit represented by Formula 11 or 12, and having a weight average molecular weight of 1,000 to 10,000,000. [Formula 11]

[Formula 12]

In Formulas 11 and 12, Y ₁ , Y ₂ are each hydrogen, alkyl or aryl, R is SO ₂ or CO, and n represents a degree of polymerization. A polymer electrolyte membrane for a fuel cell having a repeating unit represented by Formula 11 or 12 and comprising a sulfonated polybenzimidazole having a weight average molecular weight of 1,000 to 10,000,000. [Formula 11]

[Formula 12]

In Formulas 11 and 12, Y ₁ , Y ₂ are each hydrogen, alkyl or aryl, R is SO ₂ or CO, and n represents a degree of polymerization.