KR20170109295A - Cation-exchange membrane based on polyether ether ketone, preparation method thereof and fuel cell comprising the same - Google Patents

Abstract

The present invention relates to a polyether ether ketone-based cation exchange membrane, a production method thereof, and a fuel cell including the same. More specifically, it is possible to synthesize a polyether ether ketone-based polymer with excellent processability as a fuel cell membrane by using a monomer having a sulfonic acid group and a bisphenol A-based monomer. By using the same, it is also possible to produce cation exchange membranes for fuel cells with enhanced ion conductivity and physical strength, and also to apply the same to fuel cells.

Description

TECHNICAL FIELD The present invention relates to a cation exchange membrane based on polyetheretherketone, a method for producing the same, and a fuel cell including the same,

The present invention relates to a polyetheretherketone-based cation exchange membrane, a method for producing the same, and a fuel cell comprising the same. More particularly, the present invention relates to a polyetheretherketone- The present invention relates to a technique for preparing a cation exchange membrane for a fuel cell having improved ionic conductivity and physical strength by using an ether ketone polymer, and applying the same to a fuel cell.

A fuel cell is a power generation system that continuously supplies fuel and an oxidant and extracts chemical energy when they react as power. The fuel cell is classified into an alkali-type fuel cell, a phosphoric acid-type fuel cell, and a solid polymer electrolyte fuel cell having a relatively low operating temperature depending on the type of electrolyte used, or a molten carbonate fuel cell or a solid oxide electrolyte fuel cell (Patent Document 1).

On the other hand, fluorine-based ion exchange membranes produced by Dupont and Dow Chemical of the United States, Asahi Chemical and Asahe Glass of Japan are presently available as commercial ion exchange membranes, The ion exchange membrane has a problem that the production process is complicated, the production cost is high, and its use at a high temperature is limited. In order to compensate for this, an ion exchange membrane using a hydrocarbon-based polymer having a low cost and excellent physical properties is known as a sulfonated poly (ether ether ketone), a sulfonated poly (aryl ether sulfone), a phosphorylated poly (phenylene oxide) There are poly (phenylene oxide) and sulfonated poly (benzylimidazole) and the like (Patent Document 2).

The sulfonated poly (etheretherketone) ion exchange membrane is excellent in mechanical properties and thermal stability and can be produced at a low cost. However, when a cation exchange membrane is manufactured using poly (ether ether ketone) having solvent resistance And when the sulfonic acid group is excessively introduced to improve the ionic conductivity, the physical strength is drastically reduced due to excessively absorbed moisture of the sulfonated poly (ether ether ketone), and the use thereof as a fuel cell membrane It is necessary to carry out studies to solve this problem.

Accordingly, the present inventors have been able to synthesize a polyetheretherketone-based polymer having excellent processability as a fuel cell membrane, and produce a cation exchange membrane for a fuel cell having improved ionic conductivity and physical strength by using the same, and can apply it to a fuel cell The present invention has been completed.

Patent Document 1: JP-A-10-2010-0107010 Patent Document 2: Korean Patent Publication No. 10-2015-0138884

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is a first object of the present invention to provide a polyether ether polymer excellent in workability as a fuel cell membrane and a method for producing the same.

A second object of the present invention is to provide a cation exchange membrane for a fuel cell having improved ionic conductivity and physical strength by using a polyetheretherketone-based polymer according to the present invention.

A third object of the present invention is to provide a fuel cell including the cation exchange membrane according to the present invention.

In order to accomplish the above object, the present invention provides a polyether ether ketone-based copolymer having a repeating unit represented by the following formula (1).

[Chemical Formula 1]

Wherein n is a mole fraction (%) in the repeating unit, and n is an integer of 1 to 99. [

The present invention also provides a cation-exchange membrane comprising the polyetheretherketone-based copolymer.

The present invention also provides a fuel cell comprising the cation exchange membrane.

(A) reacting 4,4'-difluorobenzophenone and a sulfonating agent at 110 to 120 ° C for 12 to 18 hours to obtain a sulfonated difluorobenzene Synthesizing the papers; (b) reacting the sulfonated difluorobenzophenone, bisphenol A, 4,4'-difluorobenzophenone and catalyst in an organic solvent and reacting in a nitrogen atmosphere at 150 to 170 ° C for 18 to 22 hours, To obtain a copolymer having a repeating unit represented by the general formula (3); And (c) repeating units having a repeating unit represented by the following formula (3) at 100 to 140 캜 for 3 to 28 hours to obtain a copolymer having repeating units represented by the following formula A method for producing a copolymer of polyetheretherketone series comprising

(2)

(3)

X is a mole fraction (%) in the repeating unit, and x is an integer of 1 to 99. [

[Chemical Formula 1]

Wherein n is a mole fraction (%) in the repeating unit, and n is an integer of 1 to 99. [

Wherein the sulfonating agent is one selected from the group consisting of fuming sulfuric acid, chlorosulfonic acid, sulfur trioxide, sulfuric acid and acylsulfate.

The catalyst is characterized by being potassium carbonate or cesium carbonate.

The organic solvent may be one or a mixture of two or more selected from the group consisting of dimethylformamide, diethylformamide, N-methyl-2-pyrrolidone, dimethylsulfoxide and dimethylacetamide.

In the step (a), the equivalent ratio of the 4,4'-difluorobenzophenone and the sulfonating agent is 1: 2-3.

In the step (b), the bisphenol A, sulfonated difluorobenzophenone and 4,4'-difluorobenzophenone equivalent ratio is 1: 0.05-0.3: 0.95-0.7; The bisphenol A equivalence ratio is characterized by being equal to the sum of the equivalent ratio of sulfonated difluorobenzophenone and 4,4'-difluorobenzophenone.

In the step (b), the equivalence ratio of the bisphenol A and the catalyst is 1: 2-3.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a polyether ether ketone-based polymer having excellent processability into a fuel cell membrane by using a monomer containing a sulfonic acid group and a bisphenol A-based monomer, and a process for producing the same.

Also, it is possible to provide a cation exchange membrane for a fuel cell having improved ionic conductivity and physical strength by using the polyetheretherketone-based polymer according to the present invention.

Further, the fuel cell including the cation exchange membrane according to the present invention can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing the mechanism by which cation exchange membranes are prepared from Examples 1 to 6 of the present invention. FIG.
2 is a photograph of a sample of the cation exchange membranes prepared in Comparative Example 1 of the present invention and Examples 1 to 6.
3 is a nuclear magnetic resonance (NMR) spectrum of the cation exchange membranes prepared from Comparative Examples 1, 2, 4 and 6 of the present invention.
4 is an infrared spectroscopy (FT-IR) spectrum of the cation exchange membranes prepared from Comparative Example 1, Comparative Example 2, Example 2 and Example 6 of the present invention.
5 is a graph showing physical strength of the cation exchange membranes prepared in Comparative Examples 1, 3 and Examples 1 to 6 of the present invention.
6 is a graph showing ion conductivity of the cation exchange membranes prepared in Comparative Example 1, Comparative Example 3, and Examples 1 to 6 of the present invention.

In the following, various aspects and various embodiments of the present invention will be described in more detail.

The present invention provides a polyether ether ketone-based copolymer having a repeating unit represented by the following general formula (1).

[Chemical Formula 1]

Wherein n is a mole fraction (%) in the repeating unit, and n is an integer of 1 to 99. [

In the case of conventional commercial polyetheretherketone polymers, it is difficult to prepare the membrane as a separator of a fuel cell due to its solvent resistance. In order to compensate this, it is possible to improve the solubility by adding bisphenol A to the chemical structure, thus facilitating processing as a separator.

The present invention also provides a cation exchange membrane comprising the polyetheretherketone-based copolymer and a fuel cell comprising the cation exchange membrane. When the cation exchange membrane according to the present invention is applied to a fuel cell, it is confirmed that not only the processability but also the ion conductivity are at the same level or higher than that of the commercialized polymer electrolyte.

In order to provide the polyetheretherketone-based copolymer of the present invention, the present invention provides a process for producing a polyetheretherketone-based copolymer comprising: (a) reacting 4,4'-difluorobenzophenone and a sulfonating agent at 110 to 120 ° C for 12 to 18 hours, 2, < / RTI > a sulfonated difluorobenzophenone; (b) reacting the sulfonated difluorobenzophenone, bisphenol A, 4,4'-difluorobenzophenone and catalyst in an organic solvent and reacting in a nitrogen atmosphere at 150 to 170 ° C for 18 to 22 hours, To obtain a copolymer having a repeating unit represented by the general formula (3); And (c) repeating units having a repeating unit represented by the following formula (3) at 100 to 140 캜 for 3 to 28 hours to obtain a copolymer having repeating units represented by the following formula A method for producing a copolymer of polyetheretherketone series comprising

(2)

(3)

X is a mole fraction (%) in the repeating unit, and x is an integer of 1 to 99. [

[Chemical Formula 1]

Wherein n is a mole fraction (%) in the repeating unit, and n is an integer of 1 to 99. [

In the present invention, a polyether ether ketone-based polymer having excellent ionic conductivity, excellent film production and processability as well as improved physical strength as compared with sulfonated difluorobenzophenone and bisphenol A, A cation exchange membrane to which the present invention is applied can be provided.

In addition, since more than two sulfonate groups are not introduced even if the reaction time is increased in the step (a), the reaction time is preferably not more than 18 hours.

The sulfonating agent may be one selected from the group consisting of fuming sulfuric acid, chlorosulfonic acid, sulfur trioxide, sulfuric acid and acylsulfate, preferably fuming sulfuric acid.

The catalyst may be calcium carbonate or cesium carbonate. When cesium carbonate is used, the molecular weight of the resulting polymer may be lowered, and calcium carbonate may be preferably used in view of the fact that it is more expensive than potassium carbonate.

The organic solvent is selected from the group consisting of dimethylformamide (DMF), diethylformamide (DEF), N-methyl-2-pyrrolidone (NMP), dimethylsulfoxide (DMSO), and dimethylacetamide Or a mixture of two or more of them, preferably dimethylacetamide (DMAc).

In particular, when the organic solvent is used as dimethylacetamide in step (b), the polymer may be reacted at 150 ° C. for 18 to 22 hours to synthesize a polymer having an optimal physical state. When used as 2-pyrrolidone, it was confirmed that a polymer having an optimal physical state could be synthesized by reacting at 170 ° C for 18 to 22 hours. It is preferable to carry out the reaction at 150 캜 using an organic solvent as dimethylacetamide.

In the step (c), the salt ion (Na ⁺ ) of the sulfonic part of the polymer is stably substituted with hydrogen as the acid treatment time becomes longer, but if the reaction is carried out for over 28 hours, the physical properties of the polymer may be damaged . It was confirmed that the polymer material according to the present invention stably retains physical properties even after acid treatment for 28 hours. The acid treatment is sulfuric acid (H ₂ SO ₄₎ aqueous solution, nitric acid (HNO ₃₎ solution and hydrochloric acid (HCl) can be carried out using an acid solution comprising an aqueous solution, preferably sulfuric acid in boiling 1 mole concentration in 110 ℃ RTI ID = 0.0 > 24 hours. ≪ / RTI >

In the step (a), the equivalence ratio of the 4,4'-difluorobenzophenone and the sulfonating agent may be 1: 2-3. 4,4'-difluorobenzophenone Up to two sulfonate groups can be introduced by the influence of the fluorine group (-F) and the carbonyl group (-C═O), and 3 equivalents of the sulfonating agent is used relative to the monomer The two functional groups are introduced. Preferably 2.4 equivalents relative to the monomer. As the sulfonation degree increases, the ionic conductivity may increase, but the physical strength decreases. Therefore, the polyetheretherketone-based copolymer according to the present invention preferably has a cation exchange membrane having both excellent ionic conductivity and physical strength by introducing at most two sulfonic acid groups Can be manufactured.

In the step (b), the bisphenol A, sulfonated difluorobenzophenone and 4,4'-difluorobenzophenone equivalent ratio is 1: 0.05-0.3: 0.95-0.7; The equivalent ratio of bisphenol A may be equal to the sum of the equivalent ratio of sulfonated difluorobenzophenone and 4,4'-difluorobenzophenone. This reaction is a mechanism in which a polymer is formed by the reaction of a hydroxyl group (-OH) of bisphenol A with 4,4'-difluorobenzophenone and a sulfonated difluorobenzophenone fluorine group (-F) Should be equal to the sum of the equivalence ratios of 4,4'-difluorobenzophenone and sulfonated difluorobenzophenone, and if the equivalent ratio is not controlled under the above conditions, the copolymer may not be synthesized.

In the step (b), the equivalence ratio of the bisphenol A and the catalyst may be 1: 2-3, preferably 1: 2.01. If the ratio of the catalyst to the equivalent ratio is less than 2, the reaction may not be performed properly. If the ratio is more than 3, the catalyst may be used in an unnecessarily large amount, resulting in a reduction in economic efficiency.

Hereinafter, production examples and embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

Preparation Example 1: Synthesis of sulfonated difluorobenzophenone

One equivalent of 4,4'-difluorobenzophenone (DFB) was added to 2.3 equivalents of fuming sulfuric acid (21.5%) and the sulfonation reaction was carried out at 110 ° C for 14 hours. The resulting product was filtered and then vacuum dried at 60 ° C to synthesize sulfonated difluorobenzophenone (SDFB).

Example 1: Preparation of cation exchange membrane (SPD05)

(SDFB), 4,4'-difluorobenzophenone (DFB) and bisphenol A (BPA), which were synthesized from Preparation Example 1 at 30 ° C under a nitrogen atmosphere, was 0.05: 0.95 : 1, and the mixture was put into a two-neck round bottom flask equipped with a stirrer and a Dean-Stark trap, and potassium carbonate (2.01 equivalents) was added as a catalyst. As the reaction solvent, 26 mL of dimethylacetamide (DMAc) was used.

Thereafter, the temperature was gradually raised to 150 캜, and the reaction was carried out at 150 캜 for 20 hours. After completion of the reaction, the obtained reaction product was washed several times with methanol / water (v / v, 1: 4) and vacuum-dried at 60 ° C for 24 hours to synthesize a polymer.

Then, 8 g of the synthesized polymer was dissolved in chloroform, and the polymer solvent was cast on a clean glass substrate by evaporation for 4 hours at room temperature and vacuum drying in a vacuum oven at 60 ° C. for 24 hours to obtain a polymer membrane Respectively.

The resulting polymer membrane was immersed in sulfuric acid / water (98 g / 1 L) at a concentration of 1 molar at 110 DEG C for acid treatment for 24 hours and immersed in distilled water for 24 hours to prepare a cation exchange membrane (SPD05).

Example 2: Preparation of cation exchange membrane (SPD10)

Except that the equivalent ratio of the sulfonated difluorobenzophenone (SDFB), 4,4'-difluorobenzophenone (DFB) and bisphenol A (BPA) synthesized in Production Example 1 was 0.1: 0.9: 1 to prepare a cation exchange membrane (SPD10).

Example 3: Preparation of cation exchange membrane (SPD15)

Except that the equivalent ratio of the sulfonated difluorobenzophenone (SDFB), 4,4'-difluorobenzophenone (DFB) and bisphenol A (BPA) synthesized in Production Example 1 was 0.15: 0.85: 1 to prepare a cation exchange membrane (SPD15).

Example 4: Preparation of cation exchange membrane (SPD20)

Except that the equivalent ratio of the sulfonated difluorobenzophenone (SDFB), 4,4'-difluorobenzophenone (DFB) and bisphenol A (BPA) synthesized in Production Example 1 was 0.2: 0.8: 1 to prepare a cation exchange membrane (SPD20).

Example 5: Preparation of cation exchange membrane (SPD25)

Except that the equivalent ratio of the sulfonated difluorobenzophenone (SDFB), 4,4'-difluorobenzophenone (DFB) and bisphenol A (BPA) synthesized in Production Example 1 was 0.25: 0.75: 1 to prepare a cation exchange membrane (SPD25).

Example 6: Preparation of a cation exchange membrane (SPD30)

Except that the equivalent ratio of the sulfonated difluorobenzophenone (SDFB), 4,4'-difluorobenzophenone (DFB) and bisphenol A (BPA) synthesized in Production Example 1 was 0.3: 0.7: 1 to prepare a cation exchange membrane (SPD30).

Comparative Example 1: Preparation of a cation exchange membrane (SPD0)

(DFB) and bisphenol A (BPA) instead of the sulfonated difluorobenzophenone (SDFB) synthesized in Preparation Example 1 were used in the same manner as in Example 1, except that 4,4'-difluorobenzophenone ) Was 1: 1 to prepare a cation exchange membrane (SPD0).

Comparative Example 2: Cation exchange membrane without acid treatment (SPD10-SO ₃ Na)

But the same procedure as in Example 2, to rule out the acid treatment process to prepare a cation exchange membrane (SPD10-SO ₃ Na).

Comparative Example 3: Nafion 115

Nafion 115 (Dupont), a commercially available polymer electrolyte membrane, was prepared.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing the mechanism by which cation exchange membranes are prepared from Examples 1 to 6 of the present invention. FIG. 1 shows the steps of synthesizing a copolymer through reaction with a sulfonated difluorobenzophenone (SDFB), bisphenol A and 4,4'-difluorobenzophenone synthesized in Production Example 1 and a catalyst, And finally synthesizing the copolymer for a cation exchange membrane through the step of FIG.

Also, it can be confirmed that the polymer synthesized through the sample photographs of the cation exchange membranes prepared in Comparative Example 1 and Examples 1 to 6 of the present invention shown in FIG. 2 is yellow.

3 is a nuclear magnetic resonance (NMR) spectrum of the cation exchange membranes prepared from Comparative Examples 1, 2, 4 and 6 of the present invention. Referring to FIG. 3, it can be confirmed that the synthesis of the polymer was performed well by analyzing the structure of the final product.

4 is an infrared spectroscopy (FT-IR) spectrum of the cation exchange membranes prepared from Comparative Example 1, Comparative Example 2, Example 2 and Example 6 of the present invention. Referring to FIG. 4, the introduction of a sulfonic acid group into the polymer can be confirmed through the generation of a characteristic peak indicated by an arrow.

Meanwhile, FIG. 5 is a graph showing the physical strengths of the cation exchange membranes prepared in Comparative Examples 1, 3 and Examples 1 to 6 of the present invention. The physical strength of the cation exchange membrane tends to decrease as the content of the sulfonic acid group increases, and it can be confirmed that the cation exchange membrane according to the present invention has better physical strength than the commercialized Nafion 115 of Comparative Example 3. [

In Table 1, the number average molecular weight (Mn), weight average molecular weight (Mw), glass transition temperature (Tg), and film density of the cation exchange membrane prepared in Comparative Example 1 and Examples 1 to 6 Respectively. As can be seen from Table 1, it can be seen that the molecular weight tends to decrease as the content of the sulfonic acid groups increases, and the film density also decreases due to the increase of the content of the sulfonic acid groups, . The ionic conductivity is expected to be further increased when the sulfonated difluorobenzophenone content is more than 30%, but the molecular weight is low and it is considered that it is not easy to process into a film.

Sample Mn Mw Tg (占 폚) Film density (g / cc) SPD00 13,491 20,344 111.72 1.13 SPD05 11,847 17,625 103.64 1.19 SPD10 11,762 18,936 101.06 1.24 SPD15 12,002 20,521 99.72 1.18 SPD20 10,157 17,147 99.35 1.16 SPD25 10,481 19,337 98.84 1.10 SPD30 10,116 23,715 96.30 1.07

6 is a graph showing ion conductivity of the cation exchange membranes prepared in Comparative Examples 1, 3, and 1 to 6 of the present invention. Referring to FIG. 6, it can be seen that the ion conductivity increases with an increase in the content of sulfonic acid group as an ion transfer medium in the cation exchange membrane. At a temperature of 70 ° C or lower, the cation exchange membrane according to Example 5 and Example 6 Ion conductivity is higher than that of Nafion 115. The ion conductivity of the cation exchange membrane according to Examples 1 to 6 of the present invention is much higher than that of Nafion 115 at a temperature of 70 ° C or higher.

Therefore, according to the present invention, it is possible to provide a polyether ether-based polymer having excellent processability into a fuel cell membrane and a method for producing the same by using a monomer containing a sulfonic acid group and a bisphenol A-based monomer, and by using the ionic conductivity and physical strength Can provide a cation exchange membrane for an improved fuel cell, and can provide a fuel cell including the same.

Claims (10)

A polyether ether ketone-based copolymer having a repeating unit represented by the following formula (1):
[Chemical Formula 1]

Wherein n is a mole fraction (%) in the repeating unit, and n is an integer of 1 to 99. [ A cation exchange membrane comprising a polyetheretherketone-based copolymer according to claim 1. A fuel cell comprising the cation exchange membrane according to claim 2. (a) synthesizing a sulfonated difluorobenzophenone, which is a monomer represented by the following formula (2) by reacting 4,4'-difluorobenzophenone and a sulfonating agent at 110 to 120 ° C for 12 to 18 hours ;
(b) reacting the sulfonated difluorobenzophenone, bisphenol A, 4,4'-difluorobenzophenone and catalyst in an organic solvent and reacting in a nitrogen atmosphere at 150 to 170 ° C for 18 to 22 hours, To obtain a copolymer having a repeating unit represented by the general formula (3); And
(c) a copolymer having repeating units represented by the following general formula (3) by acid treatment at 100 to 140 ° C for 3 to 28 hours to obtain a copolymer having a repeating unit represented by the following general formula Wherein the polyether ether ketone copolymer is a polyether ether ketone copolymer.
(2)

(3)

X is a mole fraction (%) in the repeating unit, and x is an integer of 1 to 99. [
[Chemical Formula 1]

Wherein n is a mole fraction (%) in the repeating unit, and n is an integer of 1 to 99. [ 5. The method of claim 4,
Wherein the sulfonating agent is one selected from the group consisting of fuming sulfuric acid, chlorosulfonic acid, sulfur trioxide, sulfuric acid, and acylsulfate. 5. The method of claim 4,
Wherein said catalyst is potassium carbonate or cesium carbonate. ≪ RTI ID = 0.0 > 11. < / RTI > 5. The method of claim 4,
Wherein the organic solvent is one or a mixture of two or more selected from the group consisting of dimethylformamide, diethylformamide, N-methyl-2-pyrrolidone, dimethylsulfoxide and dimethylacetamide Ether ketone based copolymer. 5. The method of claim 4,
Wherein in the step (a), the equivalent ratio of the 4,4'-difluorobenzophenone and the sulfonating agent is 1: 2-3. 5. The method of claim 4,
In the step (b), the bisphenol A, sulfonated difluorobenzophenone and 4,4'-difluorobenzophenone equivalent ratio is 1: 0.05-0.3: 0.95-0.7;
Wherein the equivalence ratio of the bisphenol A is equal to the sum of the equivalent ratio of the sulfonated difluorobenzophenone and 4,4'-difluorobenzophenone to the polyetheretherketone series copolymer. 5. The method of claim 4,
Wherein the equivalent ratio of the bisphenol A and the catalyst is 1: 2-3 in the step (b).

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