JP5792609B2 - PROTON CONDUCTIVE POLYMER ELECTROLYTE AND METHOD FOR PRODUCING SAME, ELECTROLYTE MEMBRANE AND METHOD FOR PRODUCING SAME, MEMBRANE / ELECTRODE ASSEMBLY USING THE SAME - Google Patents

Description

  The present invention relates to a proton-conductive polymer electrolyte and a method for producing the same, an electrolyte membrane and a method for producing the same, and a membrane / electrode assembly and a fuel cell using the same.

  In recent years, fuel cells have attracted attention as the next-generation energy source. Among them, polymer electrolyte fuel cells using proton conductive membranes as electrolyte membranes have high energy density, so they can be used in a wide range of fields such as household cogeneration power supplies, portable equipment power supplies, electric vehicle power supplies, and simple auxiliary power supplies. Use in is expected. In the polymer electrolyte fuel cell, the electrolyte membrane functions as an electrolyte for conducting protons, and also functions as a diaphragm that does not directly mix fuel such as hydrogen. Such an electrolyte membrane is required to have high ion exchange capacity, high electrochemical stability, low electrical resistance, high mechanical strength, and barrier properties against fuel gas (hydrogen gas, oxygen gas, etc.).

  As an electrolyte membrane for a fuel cell, a polymer membrane having an acidic group (particularly a sulfonic acid group) and having high proton conductivity has attracted attention. Among them, a perfluorosulfonic acid membrane (Nafion (registered trademark)) developed by DuPont is generally used. However, conventional fluorine-based polymer ion exchange membranes such as “Nafion” are excellent in chemical stability but have low ion exchange capacity representing the amount of acidic groups and insufficient water retention. .

  When these conventional electrolyte membranes are used in a polymer electrolyte fuel cell, the electrolyte membrane before starting is in a dry state. On the other hand, when the fuel cell is activated, the membrane is swollen by humidified water contained in the reaction gas or water generated by the cell reaction. Accordingly, when the starting and stopping of the polymer electrolyte fuel cell are repeated, the electrolyte membrane repeatedly swells and contracts. As a result, the electrolyte membrane may be torn or the electrode may be peeled off from the electrolyte membrane, resulting in a decrease in performance. When many acidic groups are introduced into the polymer as a countermeasure against this problem, the strength of the membrane is extremely lowered by water retention, and the membrane tends to be easily damaged or the membrane tends to dissolve in water.

In order to solve such a problem, various proposals have been conventionally made. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2003-272664) discloses a method for producing a crosslinked impregnated film having the following steps (claims 3 and 4).
(1) A perfluoro copolymer having a —SO ₂ F group and a SO ₂ NHR group (R is H, an unsubstituted hydrocarbon group or a substituted hydrocarbon group) and a liquid fluorooligoether at a predetermined ratio. Applying the mixture comprising polytetrafluoroethylene porous film,
(2) The porous film is heated to 160-340 ° C. under pressure to form an impregnated film,
(3) The impregnated film is treated with a Lewis base, followed by hydrolysis and acid treatment.

Patent Document 1 describes the following matters.
(A) The raw material mixture exhibits excellent melt molding processability due to the plasticizing effect of the fluorooligoether (paragraph [0059]),
(B) By heating under pressure, the composition containing the perfluoro copolymer is filled in the voids of the porous film, and at the same time, the separated fluorooligoether is discharged to the outside of the porous film ( Paragraph [0062]), and
(C) By treating with a Lewis base, a part of the sulfonamide group becomes a sulfonimide crosslinked structure (paragraph [0063]).

  As disclosed in Patent Document 1, a composite electrolyte membrane obtained by filling a porous membrane with a perfluoro copolymer and crosslinking it has higher mechanical strength than a membrane made only of an electrolyte. However, with this method, the equivalent weight (EW) can be reduced only to about 600 g / eq, and high electrical conductivity cannot be obtained.

Patent Document 2 (Japanese Patent Laid-Open No. 2005-174800) and Patent Document 3 (International Publication WO2007 / 114406 (A1) pamphlet) include a predetermined strong acid group (bissulfonimide group (—SO ₂ NHSO ₂ —), A solid polymer electrolyte containing a sulfoncarbonimide group (—SO ₂ NHCO—) or a biscarbonimide group (—CONHCO—)) is disclosed. The electrolyte is obtained by reacting a first monomer comprising two or more reactive functional groups A and / or B with a second monomer comprising three or more reactive functional groups A and / or B. It is formed. The reactive functional group A and the reactive functional group B are functional groups that can generate the strong acid group when they react with each other. Patent Documents 2 and 3 describe that a polymer electrolyte having high electrical conductivity can be obtained by such a method.

  Patent Document 2 discloses an electrolyte obtained by impregnating a porous membrane with a solution containing the first monomer and the second monomer, and then reacting them (Claim 5). Similarly, Patent Document 3 discloses a method for producing a composite electrolyte membrane in which the pores of the porous membrane are filled with an electrolyte (claim 14). The electrolyte filled in the pores of the porous membrane reacts with the first monomer and the second monomer filled in the porous membrane to form an imide network polymer, and then converts the imide network polymer into protons. It is formed by.

  According to the methods disclosed in Patent Documents 2 and 3, a polymer electrolyte having a large amount of strong acid groups in the molecular chain and having the molecular chain crosslinked via the strong acid group is obtained. This polymer electrolyte has much higher conductivity than conventional electrolytes. The polymer electrolyte has a structure having both chemical cross-linking and physical cross-linking formed by physical entanglement of molecular chains.

JP 2003-272664 A JP-A-2005-174800 International Publication WO2007 / 114406 (A1) Pamphlet

  However, in the methods disclosed in Patent Documents 2 and 3, an infinite network is formed beyond the gel point, so that it may be difficult to dissolve or disperse the synthesized electrolyte in the solvent. To deal with this problem, it is conceivable to prepare the electrolyte by a batch method in which each monomer solution is subjected to a gelation reaction. However, in that case, it is difficult to control the reaction, and mass production of the film may be difficult. It was. Furthermore, in the methods disclosed in Patent Documents 2 and 3, the crosslinking reaction may take several days, and a method with higher mass productivity has been demanded. In addition, in the methods disclosed in Patent Documents 2 and 3, molecular chain formation and molecular chain crosslinking are simultaneously performed by reacting a plurality of types of monomers in the porous film, and thus it is difficult to control the molecular structure. was there.

  In such a situation, one of the objects of the present invention is to provide a solid polymer electrolyte having high electrical conductivity and easy to produce, an electrolyte membrane using the same, and a method for producing them. .

In order to achieve the above object, the present invention provides a method for producing a proton-conductive polymer electrolyte. This production method comprises (i) at least one first monomer having a first chain portion and two functional groups (A) bonded to both ends of the first chain portion, Reaction with at least one second monomer having two chain portions and two functional groups (B) bonded to both ends of the second chain portion, respectively. And (ii) reacting at least one compound having three or more functional groups (C) with the oligomer, the functional groups (B) and Each of the functional groups (C) reacts with the functional group (A) to thereby form at least one acidic group selected from the group consisting of —SO ₂ NHSO ₂ —, —SO ₂ NHCO—, and —CONHCO—. Or its precursor The product, functional groups.

The polymer electrolyte of the present invention is a proton conductive polymer electrolyte comprising a plurality of chain portions and a cross-linking portion that cross-links the plurality of chain portions. _{each, -SO 2 NHSO 2 -, -} SO 2 NHCO-, and at least one acidic group selected from the group consisting of -CONHCO-, the union of the crosslinking portion and the linear portion, -SO _{2 It} contains at least one acidic group selected from the group consisting of NHSO ₂ —, —SO ₂ NHCO—, and —CONHCO—.

In addition, the method of the present invention for producing an electrolyte membrane for a fuel cell includes (I) two functional groups (A) bonded to each of the first chain portion and both ends of the first chain portion. And at least one second monomer having a second chain portion and two functional groups (B) bonded to both ends of the second chain portion, respectively. A step of synthesizing an oligomer having the functional group (A) at both ends by reacting with the monomer, and (II) at least one compound having three or more functional groups (C) and the oligomer. Reacting in a porous membrane, wherein the functional group (B) and the functional group (C) react with the functional group (A), respectively, to form —SO ₂ NHSO ₂ —, — SO ₂ NHCO-, and from -CONHCO- At least one acidic group or a functional group which forms a precursor thereof selected from the group that.

The polymer electrolyte membrane of the present invention is an electrolyte membrane comprising a porous membrane and a polymer electrolyte disposed in the porous membrane, the polymer electrolyte comprising a plurality of chain portions, and a bridging portion bridging the plurality of linear portions, a proton conductive polymer electrolyte, each of the plurality of linear _{portions, -SO 2 NHSO 2 -, -} SO 2 NHCO-, and - comprising at least one acidic group selected from the group consisting of CONHCO-, union of the crosslinking portion and the linear _{portion, -SO 2 NHSO 2 -, -} SO 2 NHCO-, and the group consisting of -CONHCO- It contains at least one acidic group selected from.

  The membrane / electrode assembly of the present invention is a membrane / electrode assembly for a fuel cell including a proton conductive electrolyte membrane, and the electrolyte membrane is the electrolyte membrane of the present invention. The fuel cell of the present invention is a fuel cell including a proton conductive electrolyte membrane, and the electrolyte membrane is the electrolyte membrane of the present invention.

  According to the present invention, a polymer electrolyte having a controlled structure can be obtained. Since this electrolyte has a strongly acidic group in the molecular chain and at the crosslinking point, the electrical conductivity increases with an increase in the chain length between crosslinks and the crosslinking density. For this reason, the polymer electrolyte of the present invention can simultaneously achieve a high crosslinking density and a high electrical conductivity. Moreover, according to the present invention, an electrolyte membrane containing a polymer electrolyte having a controlled structure can be obtained. Further, according to the present invention, it is possible to manufacture an electrolyte membrane in a short time by selecting specific conditions.

1 is a diagram showing a ¹⁹ F NMR spectrum of an oligomer synthesized in Example 1. FIG. FIG. 4 is a diagram showing a ¹⁹ F NMR spectrum of the oligomer synthesized in Example 2.

  Embodiments of the present invention will be described below. In the following description, embodiments of the present invention will be described by way of examples, but the present invention is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present invention can be obtained. Moreover, unless otherwise indicated, the compound demonstrated below may be used independently and may use multiple types together.

(Method for producing proton-conductive polymer electrolyte)
The method of the present invention for producing a proton conducting polymer electrolyte includes the following steps (i) and (ii).

  In step (i), at least one first monomer having a first chain portion and two functional groups (A) bonded to both ends of the first chain portion, and a second chain The functional group (A) is provided at both ends by reacting at least one second monomer having two functional groups (B) bonded to both ends of each of the chain-shaped portion and the second chain-shaped portion. Synthesize oligomers. More specifically, in step (i), the functional group (A) of the first monomer is reacted with the functional group (B) of the second monomer to react with the functional group (A) at both ends. Is synthesized.

  In the step (i), the functional group (A) and the functional group (B) react with each other, so that both ends of the oligomer are functional groups (A), both ends are functional groups (B), and one end is functional. There is a possibility that an oligomer having the functional group (B) at the other end of the group (A) may be produced, but at least an oligomer having the functional group (A) at both ends is synthesized. Hereinafter, the oligomer synthesized at step (i) and having both functional groups (A) may be referred to as “oligomer (O)”.

The functional group (B) reacts with the functional group (A), thereby at least one acidic group selected from the group consisting of —SO ₂ NHSO ₂ —, —SO ₂ NHCO—, and —CONHCO— or a precursor thereof. Is a functional group that generates In the _{following, -SO 2 NHSO 2 -, -} SO 2 NHCO-, and -CONHCO- and collectively, may be referred to as "imide group such (G)". In other words, the functional group (A) and the functional group (B) are functional groups that generate an imide group (G) or a precursor thereof when they react.

  Typically, the first monomer contains only two functional groups (A), and the second monomer contains only two functional groups (B). In addition, it is preferable that a functional group (A) does not react between functional groups (A) in the reaction conditions of process (i), or does not react substantially between functional groups (A). Similarly, it is preferable that the functional group (B) does not react between the functional groups (B) or does not substantially react between the functional groups (B) under the reaction conditions in the step (i). In addition, the first monomer usually does not contain any functional group (A) other than the functional group (A) that reacts with the functional group (B) under the reaction conditions of the step (i), and the functional group ( A functional group that reacts with A) is not included, and only two functional groups (A) are included. In addition, the second monomer usually does not contain a functional group that reacts with the functional group (A) under the reaction conditions of the step (i) other than the functional group (B), and the functional group ( No functional group that reacts with B) and only two functional groups (B).

  Typically, the first monomer is composed only of the first chain portion and the two functional groups (A), and the second monomer is composed of the second chain portion and the two functional groups (B). Consists of only. However, the first chain portion of the first monomer and the second chain portion of the second monomer have pendant side chains (eg, functional groups) that do not react with the functional groups (A) and (B). You may have in shape. When such a monomer is used, side chains (for example, functional groups) that do not react with the functional groups (A) and (B) are arranged in a pendant manner in the chain of the oligomer (O). On the other hand, a linear oligomer (O) is obtained by using the first and second monomers in which the first and second chain portions are linear.

  The first and second monomers may have either a C—H bond or a C—F bond in the molecule, or may have both. Prepolymers and solid polymer electrolytes having a polymer chain comprising a perfluoro skeleton and having excellent heat resistance and oxidation resistance by using a monomer containing a C—F bond and no C—H bond in the molecule Is obtained. Therefore, such a monomer is particularly suitable as a raw material for the oligomer (O).

  The functional group (A) and the functional group (B) may form imide groups (G) by reacting them directly, or a precursor of the imide groups (G) by these reactions. May be formed. The precursor of the imide group (G) is one in which the hydrogen atom of NH in the imide group (G) is another atom or atomic group. This precursor can be converted to imide groups (G) by a known appropriate treatment. For example, when the hydrogen atom of NH in the imide group (G) is a tert-butoxycarbonyl group, the NH atom is treated with a strong acid such as trifluoroacetic acid or a 4 mol / L hydrochloric acid-ethyl acetate solution. Can be converted to

There are various combinations of the functional group (A) and the functional group (B). In an example of a preferable combination, the functional group (A) is at least one functional group represented by the following formula (F1) or at least one functional group represented by the following formula (F2). The functional group (B) is at least one functional group represented by the following formula (F3) or at least one functional group represented by the following formula (F4).
(F1) -SO ₂ NZ ¹ Z ²
[However, Z ¹ and Z ² each independently represent a hydrogen atom, a metal atom, or Si (CH ₃ ) ₃ . ]
(F2) -CONZ ¹ Z ²
[However, Z ¹ and Z ² each independently represent a hydrogen atom, a metal atom, or Si (CH ₃ ) ₃ . ]
(F3) -SO ₂ X
[X represents F, Cl, Br, or I. ]
(F4) -COX
[X represents F, Cl, Br, or I. ]

Examples of metal atoms that can be used for Z ¹ and Z ² in the functional groups represented by the above (F1) and (F2) include alkali metal atoms such as K and Na, and transition metal atoms such as Cu. included.

  The combination of the functional group represented by (F1) or (F2) and the functional group represented by (F3) or (F4) can be easily reacted directly without adding functional group conversion. In many cases, it is particularly suitable as a combination of the functional group (A) and the functional group (B). In addition, even if these functional groups remain unreacted, they can be converted into sulfonic acid groups or carboxylic acid groups by appropriate treatment, so that prepolymers and solids having high electrical conductivity can be obtained. A molecular electrolyte is obtained.

In addition, among the functional groups represented by the above (F1) or (F2), the combination of (Z ¹ , Z ² ) is (H, H), (H, M), (Si (CH ₃ ) ₃ , M) or (H, Si (CH ₃ ) ₃ ) is highly suitable as the functional group (A) because it has high reactivity. Among the functional groups represented by the above (F3) or (F4), those in which X is composed of F, Cl, Br or I have high reactivity and are therefore suitable as the functional group (B). It is.

The first monomer may be composed of only one type of monomer, or may be composed of a plurality of types of monomers. The second monomer may be composed of only one type of monomer or may be composed of a plurality of types of monomers. For example, the functional group (B) of the second monomer may be only —SO ₂ X or a combination of —SO ₂ X and —COX.

Usually, the first chain portion of the first monomer and the second chain portion of the second monomer are each composed of a hydrocarbon chain that may be substituted with fluorine. Among these, a chain portion represented by — (CF ₂ ) _m — (where m is a natural number) is preferable. The number of carbon atoms constituting each of the first chain portion and the second chain portion may be in the range of 1 to 20, for example, in the range of 3 to 8.

There are various monomers as the first and second monomers. Among these, the following monomers (1) and (2) are suitable as the first monomer, and monomers (3) and (4) are suitable as the second monomer. Since the linear oligomer formed using these monomers has a perfluoro skeleton, a solid polymer electrolyte excellent in heat resistance and oxidation resistance can be obtained. Therefore, these monomers are suitable as raw material monomers.
^{(1) Z 1 Z 2 NO} 2 S- (CF 2) m -SO 2 NZ 1 Z 2
[In the formula (1), Z ¹ and Z ² each independently represent a hydrogen atom, a metal atom or Si (CH _{3) 3,.} m represents a natural number of 1-20. ]
^{(2) Z 1 Z 2 NOC-} (CF 2) m -CONZ 1 Z 2
[In the formula (2), Z ¹ and Z ² each independently represent a hydrogen atom, a metal atom or Si (CH _{3) 3,.} m represents a natural number of 1-20. ]
_{(3) XO 2 S- (CF} 2) m -SO 2 X
[In Formula (3), X represents F, Cl, Br, or I. m represents a natural number of 1-20. ]
_{(4) XOC- (CF 2)} m -COX
[In Formula (4), X represents F, Cl, Br, or I. m represents a natural number of 1-20. ]

  In the formulas of monomers (1) to (4), m may be in the range of 3 to 8. In addition, when two or more types of monomers selected from the group consisting of monomers (1) to (4) are used, their chain lengths (m in the formula) may be the same or different. Preferred examples of the functional groups of the monomers of the formulas (1) to (4) include the preferred examples described in the formulas (F1) to (F4).

  There is no particular limitation on the degree of polymerization of the oligomer (O). Depending on the conditions required for the polymer electrolyte, the reaction conditions (for example, reaction time, reaction temperature, amount of reaction accelerator, etc.) can be selected so that the average degree of polymerization of the oligomer (O) is in a preferable range. The oligomer (O) may be in the range of a trimer to a 15-mer, for example. As the degree of polymerization of the oligomer (O) increases, the number of imide groups (G) contained in the chain portion of the oligomer (O) increases. The chain part of the oligomer (O) is composed of a first chain part of the first monomer, a second chain part of the second monomer, and imide groups (G). In the method of the present invention, since the oligomer (O) synthesized in advance is cross-linked, the average and distribution of the chain length of the oligomer (O) and the average number of imide groups (G) contained in the oligomer (O) and Easy to control distribution.

  End groups of the oligomer synthesized in the step (i) (groups at both ends of the chain part constituted by the first chain part, the second chain part, and the imide group (G) or a precursor thereof) It is preferable that 60 mol% or more of the functional group (A). The higher the ratio, the higher the ratio of the oligomer (O) having the functional group (A) at both ends. The proportion of the functional group (A) in the terminal group of the oligomer synthesized in the step (i) may be 70 mol% or more, 80 mol% or more, 90 mol% or more, or 95 mol% or more. . By increasing this ratio, the crosslink density increases and a sufficient network structure can be formed.

  The ratio of the functional group (A) in the terminal group of the oligomer synthesized in the step (i) can be adjusted by changing the reaction conditions. For example, the proportion of the functional group (A) in the terminal group of the oligomer can be increased by increasing the molar ratio of the first monomer to the total of the first monomer and the second monomer. Specifically, it is preferable to use 1.1 to 2.5 times the molar amount of the first monomer with respect to the second monomer, and to use 1.25 to 2 times the molar amount of the first monomer. More preferred.

  The reaction in the step (i) can be performed by reacting the first monomer and the second monomer in a state of being dissolved or dispersed in a predetermined solvent. The said solvent should just be a thing which can melt | dissolve or disperse | distribute a raw material monomer on predetermined conditions. That is, the solvent may be a polar solvent or a nonpolar solvent. When the solvent is a polar solvent, the solvent may be a protic polar solvent or an aprotic polar solvent. Examples of the solvent include those described later as examples of the solvent that can be used in the reaction of step (ii).

  Among these solvents, polar solvents are preferable, and aprotic polar solvents are more preferable. From another viewpoint, the solvent is preferably an organic solvent, and more preferably an aprotic polar organic solvent. The concentration of the raw material monomer in the solvent is not particularly limited, and an appropriate concentration may be selected according to the type of the raw material monomer.

  When the raw material monomer is reacted, it is preferable to add a substance that increases the reaction rate between the functional group (A) and the functional group (B) (that is, a substance having a catalytic action: a reaction accelerator) to the solvent. Examples of such substances (reagents) include basic compounds, and specifically include basic compounds described later as examples of basic compounds that promote the reaction of step (ii). In another aspect, a Lewis base can be used as the substance having a catalytic action. An appropriate amount of the substance having a catalytic action may be selected according to the reaction conditions and the like. By selecting an appropriate amount, the viscosity of the reaction solution containing the raw material monomer can be adjusted.

  The reaction temperature in process (i) should just be a temperature which can synthesize | combine an oligomer (O) efficiently. Specifically, the reaction temperature is preferably in the range of 25 to 120 ° C, and more preferably in the range of 40 to 100 ° C. The reaction time may be selected appropriately depending on the reaction temperature. Usually, the reaction time is in the range of 1 minute to 240 hours.

  The reaction in the step (i) is preferably performed in an inert atmosphere such as argon gas or nitrogen gas in order to prevent deterioration of raw material monomers (hydrolysis and the like) (the same applies to the following step (ii)). . The reaction temperature, reaction time, and pressure during the reaction are not particularly limited, and appropriate values are selected according to the type of raw material, the concentration of the mixed solution, the type and amount of the substance having a catalytic action, and the like. do it. Moreover, it is preferable to stir, shear, or apply vibration to the reaction solution during the reaction.

Step (ii) is performed after step (i). In step (ii), at least one compound having three or more functional groups (C) is reacted with the oligomer (O). Specifically, the functional group (C) of at least one compound is reacted with the functional group (A) of the oligomer (O). Oligomer (O) is bridge | crosslinked by this reaction. The functional group (C) reacts with the functional group (A) to thereby form at least one acidic group selected from the group consisting of —SO ₂ NHSO ₂ —, —SO ₂ NHCO—, and —CONHCO—, or a precursor thereof. Is a functional group that generates In other words, the functional group (A) and the functional group (C) are functional groups that generate an imide group (G) or a precursor thereof when they react.

  Hereinafter, at least one compound having three or more functional groups (C) may be referred to as “crosslinking monomer (M)”. In this specification, a skeleton connecting a plurality of functional groups (C) in the crosslinking monomer (M) may be referred to as a “crosslinked portion”.

  Usually, the functional group (C) is a functional group that does not react between the functional groups (C) or does not substantially react between the functional groups (C) under the reaction conditions in the step (ii). In addition, the crosslinking monomer (M) usually does not contain any functional group that reacts with the functional group (A) under the reaction conditions in the step (ii) other than the functional group (C). It does not contain a functional group that reacts with the functional group (C).

  Examples of the functional group (C) include the functional groups exemplified for the functional group (B). The functional group (B) and the functional group (C) may be the same or different. In addition, although there is no particular limitation on the cross-linked portion connecting the functional group (C), in one example, aromatic hydrocarbon (for example, benzene), hydrocarbon chain, and a part or all of these hydrogen atoms are substituted with fluorine atoms. It is made up of.

  There is no particular limitation on the molecular weight of the polymer electrolyte. Depending on the characteristics required for the polymer electrolyte, the reaction conditions (for example, reaction time, reaction temperature, amount of reaction accelerator, etc.) can be selected so that the molecular weight of the polymer electrolyte falls within a preferred range.

The polymer electrolyte (network polymer) of the present invention is synthesized by reacting an oligomer (O) with a crosslinking monomer (M). The reactivity between the functional group (A) and the functional group (C) greatly affects the productivity of the polymer electrolyte of the present invention. In the example shown in Patent Document 3, the polymerization reaction for forming the network polymer is extremely slow, taking 24 hours or more. For this reason, it becomes a big problem of mass production and cost reduction. As a result of intensive studies, the present inventors have found that when —SO ₂ Cl or —COCl is used as the functional group (C), the crosslinking reaction is extremely fast and a network polymer can be obtained in a very short time. It was.

Therefore, the functional group (C) of the crosslinking monomer (M) is preferably —SO ₂ Cl and / or —COCl. As such a crosslinking monomer (M), there are various monomers. Among these, the monomers (5) to (8) and (9) to (12) shown below are suitable as the crosslinking monomer (M). By using a crosslinking monomer (M) in which the chain portion is a fluorocarbon chain, the polymer electrolyte chain portion becomes a perfluoro skeleton, and a solid polymer electrolyte excellent in heat resistance and oxidation resistance is obtained. It is done. The “crosslinking moiety” in the present specification is a benzene ring in the monomers (5) and (9), and —CF— and / or — in the monomers (6) to (8) and (10) to (12). A perfluoro chain composed of CF ₂ —.

[In the monomer (5), Y ¹ , Y ² , and Y ³ represent SO ₂ Cl or COCl. Y ¹ = Y ² = Y ³ . Z ³ represents a hydrogen atom or a fluorine atom. ]

[In monomer (6), A shows the integer of 0-20. P ¹ , P ² , P ³ , and P ⁴ represent SO ₂ Cl or COCl. P ¹ = P ² = P ³ = P ⁴ . ]

[In monomer (7) and (8), A shows the integer of 0-20, B shows the natural number of 1-20, C shows the natural number of 1-20. P ¹ , P ² , and P ³ represent SO ₂ Cl or COCl. P ¹ = P ² = P ³ . ]

[In the monomer (9), Y ¹ , Y ² , and Y ³ represent SO ₂ Cl or COCl. Y ¹ , Y ² , and Y ³ are combinations other than Y ¹ = Y ² = Y ³ . Z ³ represents a hydrogen atom or a fluorine atom. ]

In the formula of monomer (9), examples of “a combination other than Y ¹ = Y ² = Y ³ ” include a case where Y ¹ = Y ² ≠ Y ³ , a case where Y ¹ ≠ Y ² = Y ³ , And the case where Y ² ≠ Y ³ = Y ¹ is included.

[In monomer (10), A shows the integer of 0-20. P ¹ , P ² , P ³ , and P ⁴ represent SO ₂ Cl or COCl. P ¹ , P ² , P ³ , and P ⁴ are combinations other than P ¹ = P ² = P ³ = P ⁴ . ]

[In monomer (11) and (12), A shows the integer of 0-20, B shows the natural number of 1-20, C shows the natural number of 1-20. P ¹ , P ² , and P ³ represent SO ₂ Cl or COCl. P ¹ , P ² , and P ³ are combinations other than P ¹ = P ² = P ³ . ]

In the monomer (10) formula, examples of “a combination other than P ¹ = P ² = P ³ = P ⁴ ” include P ¹ = P ² = P ³ ≠ P ⁴ , where P ¹ = P ² = When P ⁴ ≠ P ³ , P ¹ = P ³ = P ⁴ ≠ P ² , P ¹ ≠ P ² = P ³ = P ⁴ , P ¹ = P ² ≠ P ³ = P ⁴ , P ¹ = P ³ ≠ P ² = P ⁴ , and P ¹ = P ⁴ ≠ P ² = P ³ are included. In the formulas of monomers (11) and (12), examples of “a combination other than P ¹ = P ² = P ³ ” include P ¹ ≠ P ² = P ³ when P ¹ = P ² ≠ P ^3. A case where P ³ is satisfied and a case where P ² ≠ P ³ = P ¹ are included.

  In step (ii), the functional group (A) and the functional group (C) react to synthesize a network polymer. In this reaction, the crosslinking monomer (M) and the oligomer (O) may be reacted so that the functional group (A) and the functional group (C) have the same molar amount. However, in order to adjust the amount of imide groups (or their precursors) produced by the crosslinking reaction and the reactivity, the functional group (C) is 0.2 to 0.2% of the functional group (A) of the oligomer (O). You may adjust the quantity of a crosslinking monomer (M) and an oligomer (O) so that it may become the range of 3 times mole amount (for example, the range of 0.8-1.2 times mole amount).

The reaction in the step (ii) can be performed by reacting the crosslinking monomer (M) and the oligomer (O) in a state dissolved or dispersed in a predetermined solvent. The said solvent should just be a thing which can melt | dissolve or disperse | distribute a raw material monomer on predetermined conditions. That is, the solvent may be a polar solvent or a nonpolar solvent. When the solvent is a polar solvent, the solvent may be a protic polar solvent or an aprotic polar solvent. Examples of solvents include the following:
(1) Nonpolar solvents such as n-hexane, cyclohexane, benzene, carbon tetrachloride,
(2) Protic polar solvents such as water, ethanol, propanol, acetic acid,
(3) Acetonitrile (MeCN), acetone, tetrahydrofuran (THF), methyl ethyl ketone (MEK), methyl isopropyl ketone, N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), dichloromethane, HCFC- An aprotic polar solvent such as 225.

  Among these, polar solvents are preferable, and aprotic polar solvents are more preferable. From another viewpoint, the solvent is preferably an organic solvent, and more preferably an aprotic polar organic solvent. The concentration of the crosslinking monomer (M) and the oligomer (O) in the solvent is not particularly limited, and an appropriate concentration may be selected according to the type of the monomer.

  When the crosslinking monomer (M) and the oligomer (O) are reacted, a substance that increases the reaction rate between the functional group (A) and the functional group (C) (that is, a substance having a catalytic action) is added to the solvent. It is preferable. Examples of such substances (reagents) include basic compounds, specifically, triethylamine (TEA), N, N-diisopropylethylamine (DIPEA), trimethylamine (TMA), tripropylamine (TPA), Basic compounds such as tributylamine (TBA), diazabicycloundecene (DBU), potassium t-butoxide, N, N-dimethyl-4-aminopyridine (DMAP) are included. In another aspect, a Lewis base can be used as the substance having a catalytic action. An appropriate amount of the substance having a catalytic action may be selected according to the reaction conditions and the like. By selecting an appropriate amount, the viscosity of the reaction solution containing the raw material monomer can be adjusted.

When -SO ₂ Cl and / or -COCl is used as the functional group (C), the solubility of the crosslinking monomer (M) is low, so that the concentration of the crosslinking monomer (M) in the reaction solution of step (ii) is preferably a concentration. It may not be possible. In such a case, the solubility of the crosslinking monomer (M) can be increased by adding the basic compound (basic compound that promotes the reaction between the functional group (A) and the functional group (C)) to the solvent. It is preferable to increase.

  The reaction temperature in step (ii) is lower than the boiling point of the solvent or reagent used, and the functional group (C) of the crosslinking monomer (M) and the functional group (A) of the oligomer (O) are reacted efficiently. Any temperature can be used. Specifically, the reaction temperature is preferably in the range of 25 to 100 ° C, more preferably in the range of 50 to 90 ° C. The reaction time may be selected appropriately depending on the reaction temperature. Since the reaction in step (ii) proceeds relatively quickly, the reaction time is usually 20 hours or less (for example, 10 hours or less, 5 hours or less, or 1 hour or less). An example reaction time is in the range of 1 second to 20 hours, but may be less than 1 second.

(Polymer electrolyte)
The polymer electrolyte of the present invention is produced by the method of the present invention for producing an electrolyte. Therefore, the matter described in the above method can be applied to the polymer electrolyte of the present invention. The polymer electrolyte of the present invention is formed by crosslinking a pre-synthesized oligomer (O). Therefore, the structure can be easily controlled as compared with the conventional method in which the formation of the chain portion and the crosslinking of the chain portion are simultaneously performed.

In another aspect, the polymer electrolyte of the present invention is a proton-conductive polymer electrolyte that includes a plurality of chain portions and a cross-linking portion that cross-links the plurality of chain portions. The said chain part is a chain part of an oligomer (O). That is, each of the plurality of chain portions includes at least one acidic group selected from the group consisting of —SO ₂ NHSO ₂ —, —SO ₂ NHCO—, and —CONHCO—. The bonding portion between the crosslinked portion and the chain portion includes at least one acidic group selected from the group consisting of —SO ₂ NHSO ₂ —, —SO ₂ NHCO—, and —CONHCO—. This polymer electrolyte can be produced by the method of the present invention for producing an electrolyte.

(Electrolyte membrane)
The electrolyte membrane of the present invention is a proton conductive electrolyte membrane and is an electrolyte membrane used in a fuel cell. This electrolyte membrane is produced by the method of the present invention for producing an electrolyte membrane. In another aspect, the electrolyte membrane of the present invention is an electrolyte membrane including a porous membrane and the polymer electrolyte of the present invention disposed in the porous membrane. The polymer electrolyte is disposed in a void or a surface layer of the porous membrane, and forms a network within the porous membrane.

The material of the porous membrane is not particularly limited, and various materials can be used according to the purpose. Examples of the material of the porous membrane include the following.
(1) Hydrocarbon polymers such as polyethylene (PE), polypropylene (PP), polyimide (PI),
(2) Fluoropolymers such as polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP),
(3) Inorganic materials such as porous silica and porous ceramics.

  The film thickness, porosity, pore diameter, etc. of the porous membrane are not particularly limited, and may be appropriately selected according to the purpose. If the porous membrane becomes too thin, the strength of the porous membrane may be insufficient, and the suppression of the dimensional change of the electrolyte accompanying swelling / shrinking may be insufficient. Moreover, handling may become difficult, so that a porous membrane becomes thin. Accordingly, the thickness of the porous film is preferably 5 μm or more. The thickness of the porous membrane is more preferably 10 μm or more. On the other hand, if the porous membrane becomes too thick, the resistance of the electrolyte membrane increases, and sufficient performance may not be obtained. Therefore, the thickness of the porous membrane is preferably 500 μm or less. The thickness of the porous membrane is more preferably 100 μm or less.

  If the porosity of the porous membrane is too low, the proportion of the electrolyte in the entire membrane may decrease and the resistance may increase. Therefore, the porosity of the porous membrane is preferably 30% or more. The porosity of the porous membrane is more preferably 50% or more, and further preferably 70% or more. On the other hand, if the porosity of the porous membrane becomes too large, the strength of the porous membrane may be insufficient and the dimensional stability of the electrolyte membrane may be reduced. Therefore, the porosity of the porous membrane is preferably 95% or less. The porosity of the porous membrane is more preferably 90% or less.

  If the pore diameter of the porous membrane becomes too small, it may be difficult to fill the electrolyte. Therefore, the average pore diameter of the porous membrane is preferably 0.1 μm or more. The average pore diameter of the porous membrane is more preferably 0.5 μm or more. On the other hand, if the pore diameter of the porous membrane becomes too large, the filled electrolyte may easily fall off from the pores. Therefore, the average pore diameter of the porous membrane is preferably 5 μm or less. The average pore diameter of the porous membrane is more preferably 3 μm or less. The average pore size of the porous membranes used in the examples and comparative examples is a measuring device (Perm Materials manufactured by Porous Materials, Inc., USA) -Mean flow pore size measured by Porometer)) was defined as the average pore size.

  If necessary, the porous membrane may be subjected to a surface treatment. For example, in the case where a polar solvent is used as the solvent, it is preferable that the porous film is lyophilic when the porous film is not well-matched with the polar solvent. As a method for lyophilic treatment, for example, a general surface modification method for a resin such as ultraviolet treatment, plasma treatment, corona treatment, and sputtering treatment can be applied.

(Method for manufacturing electrolyte membrane)
The polymer electrolyte of the present invention has a crosslinked structure and is extremely difficult to melt or dissolve in a solvent. Therefore, after impregnating the porous membrane with the solution containing the raw material, the raw material is reacted in the porous membrane to produce an electrolyte membrane in which the electrolyte is disposed in the porous membrane. The manufacturing method of the electrolyte membrane includes the following steps (I) and (II).

  In step (I), at least one first monomer having a first chain part and two functional groups (A) bonded to both ends of the first chain part, and a second chain The functional group (A) is provided at both ends by reacting at least one second monomer having two functional groups (B) bonded to both ends of each of the chain-shaped portion and the second chain-shaped portion. An oligomer (O) is synthesized. Since this step is the same as the above-described step (i), a duplicate description is omitted.

  Next, in step (II), at least one compound (crosslinking monomer (M)) having three or more functional groups (C) and an oligomer (O) are reacted in the porous membrane. Since the porous membrane has been described above, a duplicate description is omitted. Moreover, since process (II) is fundamentally the same as process (ii) except performing reaction in a porous membrane, the overlapping description is abbreviate | omitted. That is, unless otherwise specified, step (II) can be carried out using the same material and the same conditions as step (ii). In addition, the matters described for the step (II) can be applied to the step (ii).

  Usually, the step (II) is a step (II-a) in which a liquid material (for example, an organic solution) containing the at least one compound (crosslinking monomer (M)) and the oligomer (O) penetrates into the porous membrane. And a step (II-b) of reacting at least one compound (crosslinking monomer (M)) and oligomer (O) in the porous membrane. In the step (II-a), the liquid material containing the crosslinking monomer (M) and the oligomer (O) may be in a state where it can permeate into the porous membrane.

In the method of the present invention, when an oligomer (O), a crosslinking monomer (M), and a basic compound (reaction accelerator) are mixed at once in a solvent, they immediately react to synthesize a gel polymer electrolyte. As a result, it may be difficult to impregnate the porous membrane with a solution containing these materials. Furthermore, in order to produce an electrolyte membrane in a short time, it is preferable to use a polyfunctional crosslinking monomer in which the functional group (C) is —SO ₂ Cl and / or —COCl. Such a crosslinking monomer (M) Slightly soluble in organic solvents. Therefore, the concentration of the crosslinking monomer (M) in the raw material solution cannot be increased, and as a result, the amount of the electrolyte filled in the porous film is reduced.

  As a result of intensive studies, the present inventors have found that the above problem can be solved by adding a basic compound added for the purpose of promoting the reaction to an organic solvent to such an extent that the reaction does not proceed rapidly. That is, by adding an appropriate amount of the basic compound to the organic solvent, the solubility of the crosslinking monomer (M) that is hardly soluble in the organic solvent is improved, and a high-concentration reaction solution can be prepared. On the other hand, by setting the amount of the basic compound to be initially added to an appropriate range, it is possible to prevent the reaction solution from gelling before permeating into the porous body. Furthermore, after allowing the reaction solution to permeate the porous membrane, a basic compound (reaction accelerator) is further added to the reaction solution, thereby allowing the reaction (gelation) to proceed rapidly, so that the polymer electrolyte membrane can be made in a short time. Can be manufactured.

That is, in the method for producing an electrolyte membrane, the at least one compound (crosslinking monomer (M)) contains —SO ₂ Cl and / or —COCl as a functional group (C), and in step (II-a), organic The solution (reaction solution) may contain a basic compound that promotes the reaction between at least one compound (crosslinking monomer (M)) and the oligomer (O). In this case, in the step (II-b), it is preferable to further add a basic compound to the organic solution (reaction solution) in the porous membrane. Examples of the particularly preferable basic compound from the viewpoint of enhancing the solubility of the crosslinking monomer (M) containing SO ₂ Cl and / or —COCl as the functional group (C) include amines such as triethylamine.

  The amount of the basic compound added to the reaction solution in the step (II-a) may be an amount such that the crosslinking reaction does not proceed rapidly and the necessary amount of the crosslinking monomer (M) is dissolved in the organic solvent. . In one example, the amount of the basic compound added to the reaction solution in the step (II-a) is such that the reaction solution is in a liquid state for at least the time required for allowing the reaction solution to permeate the porous membrane (for example, 1 hour). This is the amount that is maintained (for example, in a state where it is not gelled). In another example, the amount of the basic compound added to the reaction solution in the step (II-a) is less than a predetermined amount at which the crosslinking reaction proceeds rapidly.

  Usually, the amount of the basic compound added to the reaction solution in the step (II-a) is in the range of 0.5 to 5 times the amount of the functional group (C) of the crosslinking monomer (M). It is more preferable that it is in the range of 1.1-fold mol to 3.3-fold mol.

  The raw material solution thus prepared is impregnated into the porous membrane. At this time, it is preferable to deaerate the inside of the porous membrane in order to increase the filling rate of the raw material solution. For example, the porous film may be immersed in a solvent having high wettability with respect to the porous film to remove bubbles in the porous film. Moreover, you may deaerate alone or combining the method of depressurizing the inside of a reaction container and promoting deaeration, and the method of irradiating an ultrasonic wave.

  Next, a basic compound (reaction accelerator) is further added to the raw material solution that has permeated the porous membrane to synthesize a polymer electrolyte. The amount of the basic compound added at this time may be an amount that allows crosslinking (gelation) to be performed in an arbitrary time, but is preferably an amount that forms a network polymer in a short time. Usually, the amount of the basic compound added in the step (II-b) is preferably in the range of 0.01 to 1 times the amount of the basic compound already added in the step (II-a). More preferably, it is in the range of 0.05 times to 0.4 times.

A preferred example of the production method of the present invention satisfies the following conditions.
(A) The first monomer is at least one selected from the group consisting of the above-described monomers (1) and (2).
(B) The second monomer is at least one selected from the group consisting of the monomers (3) and (4) described above.
(C) The third monomer is at least one selected from the group consisting of the monomers (5) to (12) described above, and is, for example, the monomer (5) or (9).
(D) The solvent used in step (II) is an aprotic polar organic solvent (for example, acetone or acetonitrile).
(E) The basic compound (reaction accelerator) is an amine (for example, triethylamine or diisopropylethylamine).

  In this particularly preferred example, the amount of the basic compound (reaction accelerator) added in the step (II-a) is 0.5 of the amount of the functional group (c) of the monomer (5) or (9). The amount of the basic compound (reaction accelerator) added in step (II-b) is in the range of 1 to 5 mol (for example, in the range of 1.1 to 3.3 mol). The amount of the basic compound (reaction accelerator) already added in -a) is in the range of 0.01 times to 1 time (for example, in the range of 0.05 times to 0.4 times).

(Membrane / electrode assembly and fuel cell)
The membrane / electrode assembly of the present invention is a membrane / electrode assembly used for a fuel cell, and includes a proton-conducting electrolyte membrane, and the electrolyte membrane is the electrolyte membrane of the present invention. There is no particular limitation on the portion other than the electrolyte membrane, and for example, a known configuration can be applied.

  The fuel cell of the present invention is a fuel cell including a proton conductive electrolyte membrane, and the electrolyte membrane is the electrolyte membrane of the present invention. The electrolyte membrane of the present invention is used in a membrane / electrode assembly. There are no particular limitations on the portion other than the electrolyte membrane, and for example, a known solid polymer fuel cell configuration can be applied.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples. In addition, C3F, C3A, BTSC, and BTSA used in the following examples and comparative examples can be synthesized by known methods. Specifically, it can be synthesized by the following method.

(1) Synthesis of perfluoroaliphatic disulfonyl fluoride Perfluoroaliphatic disulfonyl fluoride (FSO ₂ —R _f —SO ₂ F) is described in US Pat. No. 2,732,398. Thus, it can be obtained by electrolytic fluorination of the corresponding aliphatic disulfonyl fluoride. For example, 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl fluoride (C3F) can be obtained by electrolytic fluorination of propane-1,3-disulfonyl fluoride. .

(2) Synthesis of perfluoroaliphatic disulfonamide Perfluoroaliphatic disulfonamide (H ₂ NO ₂ S—R _f —SO ₂ NH ₂ ) is a perfluoroaliphatic disulfonyl fluoride (FSO ₂ —R _f). It can be obtained by reacting —SO ₂ F) with liquid ammonia. For example, 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonamide (C3A) is 1,1,2,2,3,3-hexafluoropropane-1,3-di It can be obtained by reacting sulfonyl fluoride (C3F) with liquid ammonia.

  Specifically, C3A was obtained by the following method. First, 1200 g of C3F was added dropwise over 1 hour to 9.6 L of liquid ammonia cooled with argon. The liquid was heated overnight, and then ammonia was removed by bubbling with argon gas. Thereafter, extraction, dehydration, and purification of the reaction product were performed to obtain white crystals (530 g) as C3A.

(3) Synthesis of 1,3,5-benzenetrisulfonyl chloride (BTSC) BTSC was synthesized by the following method. First, concentrated sulfuric acid (650 g) was added to the flask and stirred, sodium benzenesulfonate monohydrate (500 g) and sodium sulfate (371 g) were added, and the resulting mixture was heated to 340 degrees. Three batches of this mixture were prepared and mixed together. The obtained mixture was washed with water, sodium hydroxide was added with stirring to adjust the pH to 12 or more, and excess sodium hydroxide and salts were removed by filtration. Next, after stirring the liquid after filtration, concentrated sulfuric acid was added to adjust the pH to 6 to 7, and then activated carbon was added and heated to 70 ° C. After filtering the heated liquid, the reaction product in the filtrate was recrystallized. The filtrate was concentrated and recrystallization was repeated. The crystals obtained by recrystallization were dried to obtain white crystals (1.12 kg) of sodium 1,3,5-benzenetrisulfonate.

  Under an argon gas atmosphere, sodium 1,3,5-benzenetrisulfonate (1100 g) was placed in a flask, and thionyl chloride (5 L) and dimethylformamide (660 mL) were added dropwise thereto. The reaction solution was heated to reflux at 70 ° C. for 18 hours. Thereafter, the reaction solution was poured into ice water to stop the reaction and stirred for a while. The precipitated crystals were separated by filtration and dried under reduced pressure. Ethyl acetate was added to the obtained crystals and heated, followed by filtration. Recrystallization of the reaction product in the obtained filtrate was repeated to obtain BTSC white crystals (620 g).

(4) Synthesis of 1,3,5-benzenetrisulfonamide (BTSA) BTSA was synthesized by the following method. First, under a stream of argon, 150 ml of liquid ammonia was reacted with a tetrahydrofuran solution (80 mL) of BTSC 7.48 g (20 mmol), then volatile components were removed, and 1N hydrochloric acid was added. The solid was filtered off from the obtained liquid to obtain 5.2 g of BTSA (white powder).

Example 1
In Example 1, an electrolyte membrane (proton conductive membrane) of the present invention was produced.

1-1. Synthesis of linear oligomer 1 In an N ₂ atmosphere, 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonamide (C3A): 46.5 g (0.150 mol), 1 , 1,2,2,3,3-hexafluoropropane-1,3-disulfonyl fluoride (C3F): 31.6 g (0.100 mol) and N, N-diisopropylethylamine (DIPEA): 64.6 g While stirring, an acetonitrile (MeCN) solution containing (0.500 mol) was reacted at 80 ° C. for 48 hours to obtain a brown solution. This reaction is shown below.

After removing the solvent of the brown solution obtained by the above reaction with an evaporator, 250 mL of 4N aqueous sodium hydroxide solution was added, and then the organic layer was extracted with acetonitrile. The extracted organic layer was concentrated with an evaporator, 250 mL of 2N aqueous hydrochloric acid was added, and the mixture was stirred as it was for 30 minutes. Next, after the organic layer was washed with diethyl ether, the solvent was completely removed by vacuum drying to obtain 61.8 g of a light skin-colored solid. About the obtained solid substance, the ¹⁹ F NMR spectrum was measured. The measurement results are shown in FIG.

In the spectrum of FIG. 1, from the integration ratio of the peak (3d + 2d) and 1c, the average number of repeating units m in the equation of FIG. 1 is m≈4.0. From this, the linear oligomer obtained by the above reaction (hereinafter sometimes referred to as “linear oligomer 1”) was calculated to be an average 6.0-mer. Further, among the terminal groups of linear oligomers 1, 93.5mol% is -SO ₂ NH _2, 6.5mol% was -SO ₃ H.

1-2. Preparation of Electrolyte Membrane Under N ₂ atmosphere, linear oligomer 1: 9.12 g (5.10 mmol) and 1,3,5-benzenetrisulfonyl chloride (BTSC): 1.19 g (3.18 mmol) Then, 18.2 mL of acetone was added and stirred. In this liquid, BTSC hardly dissolved. When triethylamine (Et ₃ N): 2.55 g (25.2 mmol) was added dropwise to the liquid little by little, undissolved BTSC was dissolved to obtain a raw material monomer solution. After the porous membrane was immersed in this raw material monomer solution, deaeration was performed by reducing the pressure and applying ultrasonic waves, and the voids in the porous membrane were impregnated with the raw material monomer solution. As the porous membrane, a porous membrane made of ultra high molecular weight polyethylene (manufactured by Teijin Solfil Co., Ltd., porosity 82%, average pore diameter 0.8 μm, film thickness 20 μm) was used. Next, when triethylamine (TEA): 0.637 g (6.29 mmol) was added to the raw material monomer solution in which the porous membrane was immersed, gelation occurred after 10 seconds. The reaction was allowed to proceed by holding the reaction solution in which the porous membrane was immersed at 70 ° C. for 50 minutes. This reaction is shown below.

  In the reaction product of the above reaction formula, the chain part derived from the chain part of the oligomer contains an imide group (G), and the binding part between the chain part and the crosslinking part (the benzene ring of BTSC) Including imide groups (G).

  The membrane obtained by the above reaction was washed with a 10 wt% sodium hydroxide aqueous solution, 10 vol% sulfuric acid aqueous solution, and ultrapure water, and then dried to obtain the electrolyte membrane (proton conductive membrane 1) of Example 1.

(Example 2)
In Example 2, the electrolyte membrane (proton conductive membrane) of the present invention was produced.

2-1. Synthesis of linear oligomer 2 In an N ₂ atmosphere, 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonamide (C3A): 27.1 g (87.5 mmol), 1 , 1,2,2,3,3-hexafluoropropane-1,3-disulfonyl fluoride (C3F): 22.1 g (70.0 mmol) and N, N-diisopropylethylamine (DIPEA): 45.2 g While stirring, an acetonitrile (MeCN) solution containing (350 mmol) was reacted at 80 ° C. for 96 hours to obtain a brown solution. The reaction formula of this reaction is the same as the reaction formula shown in the synthesis reaction of the linear oligomer 1 of Example 1.

After removing the solvent of the brown solution obtained by the above reaction with an evaporator, 250 mL of 4N aqueous sodium hydroxide solution was added, and then the organic layer was extracted with acetonitrile. The extracted organic layer was concentrated with an evaporator, 250 mL of 2N aqueous hydrochloric acid was added, and the mixture was stirred as it was for 30 minutes. Next, the organic layer was washed with diethyl ether, and then the solvent was completely removed by vacuum drying to obtain 43.3 g of a brown solid. About the obtained solid substance, the ¹⁹ F NMR spectrum was measured. The measurement results are shown in FIG.

In the spectrum of FIG. 2, from the integration ratio of the peak (3d + 2d) and 1c, the average number of repeating units m in the equation of FIG. 2 is m≈6.2. From this, the linear oligomer obtained by the above reaction (hereinafter sometimes referred to as “linear oligomer 2”) was calculated to be an average 8.2-mer. Further, among the terminal groups of linear oligomers 2, 86.8mol% is -SO ₂ NH _2, 13.2mol% were -SO ₃ H.

2-2. Preparation of Electrolyte Membrane Under N ₂ atmosphere, linear oligomer 2: 10.3 g (4.00 mmol) and 1,3,5-benzenetrisulfonyl chloride (BTSC): 0.895 g (2.39 mmol) Then, 9.73 mL of acetonitrile (MeCN) was added and stirred. In this liquid, BTSC hardly dissolved. When triethylamine (TEA): 1.12 g (9.48 mmol) was added dropwise to the liquid little by little, the undissolved BTSC was dissolved to obtain a raw material monomer solution. After the porous membrane was immersed in this raw material monomer solution, deaeration was performed by reducing the pressure and applying ultrasonic waves, and the voids in the porous membrane were impregnated with the raw material monomer solution. As the porous membrane, a porous membrane made of ultra high molecular weight polyethylene (manufactured by Teijin Solfil Co., Ltd., porosity 82%, average pore diameter 0.8 μm, film thickness 20 μm) was used. Next, when triethylamine (TEA): 0.640 g (6.32 mmol) was added to the raw material monomer solution in which the porous membrane was immersed, gelation occurred after 5 seconds. The reaction was allowed to proceed by holding the reaction solution in which the porous membrane was immersed at 70 ° C. for 50 minutes. This reaction is shown below.

  The membrane obtained by the above reaction was washed with a 10 wt% aqueous sodium hydroxide solution, a 10 vol% sulfuric acid aqueous solution, and ultrapure water, and then dried to obtain an electrolyte membrane (proton conductive membrane 2) of Example 2.

(Comparative Example 1)
In Comparative Example 1, the first and second monomers and the crosslinking monomer (M) were reacted at once in the porous membrane.

Specifically, first, in N ₂ atmosphere, 1,1,2,2,3,3-hexafluoropropane-1,3-sulfonamide (C3A): and 13.0 g (42.0 mmol), 1 , 3,5-benzenetrisulfonamide (BTSA): 4.41 g (14.0 mmol), acetonitrile (MeCN): 45.6 mL, and triethylamine (TEA): 28.1 g (277 mmol) did. And after immersing a porous membrane in this solution, it deaerated by pressure reduction and ultrasonic irradiation, and the void in a porous membrane was impregnated with this solution. As the porous membrane, a porous membrane made of ultra high molecular weight polyethylene (manufactured by Teijin Solfil Co., Ltd., porosity 82%, average pore diameter 0.8 μm, film thickness 20 μm) was used. Next, 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl fluoride (C3F): 19.9 g (63.0 mmol) was added to the solution in which the porous membrane was immersed. Was added and allowed to permeate for 30 minutes to uniformly impregnate the porous membrane. The reaction was allowed to proceed by holding the reaction solution in which the porous membrane was immersed at 50 ° C. for 264 hours (gelation started in 72 hours). Thereafter, the mixture was further reacted at 90 ° C. for 72 hours. This reaction is shown below.

  The membrane obtained by the above reaction was washed with 10 wt% sodium hydroxide aqueous solution, 10 vol% sulfuric acid aqueous solution, and ultrapure water, and then dried to obtain the electrolyte membrane (proton conductive membrane 3) of Comparative Example 1.

(Characteristic evaluation method)
(A) Ion exchange capacity (IEC)
The electrolyte membranes (area: about 12 cm ² ) of Examples and Comparative Examples were immersed in a 3 mol / L sodium chloride aqueous solution and reacted in a water bath at 60 ° C. for 12 hours or more. The electrolyte membrane was cooled to room temperature and then thoroughly washed with ion exchange water. The obtained electrolyte membrane was titrated with a 0.05N aqueous sodium hydroxide solution using an automatic potentiometric titrator (AT-510; manufactured by Kyoto Electronics Industry Co., Ltd.), and the ion exchange capacity was calculated.

(B) Proton conductivity (σ)
The electrolyte membrane cut to a width of 10 mm was immersed in ultrapure water overnight, and then the AC impedance was measured by a four-terminal method in an ultrapure water at 25 ° C. using an LCR meter (HIOKI Chemical Impedance meter 3532-80). It was measured. The measurement frequency range was 10 kHz to 1 MHz. Plotting was performed with the real part of the obtained impedance on the horizontal axis and the imaginary part on the vertical axis, and the value of the real part of the minimum value was defined as the membrane resistance R (Ω). The proton conductivity σ [S / cm] was determined from the following equation, where the membrane thickness was t [cm], the sample width was h [cm], and the electrode mounting distance was L [cm].
σ = L / (R × t × h)

(Evaluation results)
The evaluation results of the produced polymer electrolyte membrane are shown below.

  The proton conductive membranes 1 and 2 of Examples 1 and 2 are equivalent to or higher than the proton conductive membrane 3 of Comparative Example 1 obtained by simultaneously forming a chain portion and a crosslinked portion. Showed conductivity. Further, the gelation time and the reaction time were overwhelmingly shorter in Example 1 and Example 2. Thus, according to the present invention, mass production of electrolyte membranes and cost reduction are possible. In addition, in the method of Comparative Example 3 in which the chain portion and the crosslinked portion are simultaneously formed, it is difficult to control the molecular structure, but in the method of the present invention, the reaction for forming the chain portion and the crosslinking reaction are separated. Thus, the molecular chain length between crosslinks can be controlled, and the molecular structure can be easily controlled.

  INDUSTRIAL APPLICABILITY The present invention can be used for proton conductive polymer electrolytes and electrolyte membranes, membrane / electrode assemblies and fuel cells using them.

Claims (8)

A method for producing a proton conductive polymer electrolyte, comprising:
(I) at least one first monomer having a first chain part and two functional groups (A) bonded to both ends of the first chain part, and a second chain part And at least one second monomer having two functional groups (B) bonded to both ends of the second chain portion, thereby providing the functional groups (A) at both ends. Synthesizing oligomers;
(Ii) reacting at least one compound having three or more functional groups (C) with the oligomer,
The functional group (B) and the functional group (C) are reacted with the functional group (A), respectively, to thereby be selected from the group consisting of —SO ₂ NHSO ₂ —, —SO ₂ NHCO—, and —CONHCO—. A method for producing a polymer electrolyte, which is a functional group that generates at least one selected acidic group or a precursor thereof.   The manufacturing method of Claim 1 whose 60 mol% or more of the terminal group of the oligomer synthesize | combined at the process of said (i) is the said functional group (A). The functional group (A) is at least one functional group represented by the following formula (F1) or at least one functional group represented by the following formula (F2):
The functional group (B) and the functional group (C) are each independently at least one functional group represented by the following formula (F3), or at least one represented by the following formula (F4). The manufacturing method of Claim 1 or 2 which is a seed | species functional group.
(F1) -SO ₂ NZ ¹ Z ²
[However, Z ¹ and Z ² each independently represent a hydrogen atom, a metal atom, or Si (CH ₃ ) ₃ . ]
(F2) -CONZ ¹ Z ²
[However, Z ¹ and Z ² each independently represent a hydrogen atom, a metal atom, or Si (CH ₃ ) ₃ . ]
(F3) -SO ₂ X
[X represents F, Cl, Br, or I. ]
(F4) -COX
[X represents F, Cl, Br, or I. ] A method for producing an electrolyte membrane for a fuel cell, comprising:
(I) at least one first monomer having a first chain part and two functional groups (A) bonded to both ends of the first chain part, and a second chain part And at least one second monomer having two functional groups (B) bonded to both ends of the second chain portion, thereby providing the functional groups (A) at both ends. Synthesizing oligomers;
(II) reacting at least one compound having three or more functional groups (C) with the oligomer in a porous membrane,
The functional group (B) and the functional group (C) are reacted with the functional group (A), respectively, to thereby be selected from the group consisting of —SO ₂ NHSO ₂ —, —SO ₂ NHCO—, and —CONHCO—. A method for producing an electrolyte membrane, which is a functional group that generates at least one selected acidic group or precursor thereof. The manufacturing method of Claim 4 whose 60 mol% or more of the terminal group of the oligomer synthesize | combined at the process of said (I) is said functional group (A). The functional group (A) is at least one functional group represented by the following formula (F1) or at least one functional group represented by the following formula (F2):
The functional group (B) and the functional group (C) are each independently at least one functional group represented by the following formula (F3), or at least one represented by the following formula (F4). The manufacturing method of Claim 4 or 5 which is a functional group of a seed | species.
(F1) -SO ₂ NZ ¹ Z ²
[However, Z ¹ and Z ² each independently represent a hydrogen atom, a metal atom, or Si (CH ₃ ) ₃ . ]
(F2) -CONZ ¹ Z ²
[However, Z ¹ and Z ² each independently represent a hydrogen atom, a metal atom, or Si (CH ₃ ) ₃ . ]
(F3) -SO ₂ X
[X represents F, Cl, Br, or I. ]
(F4) -COX
[X represents F, Cl, Br, or I. ] The step (II)
(II-a) impregnating an organic solution containing the at least one compound and the oligomer into the porous membrane;
(II-b) wherein the porous film, the includes a step of reacting the at least one compound oligomer process according to any one of claims 4-6. The at least one compound comprises —SO ₂ Cl and / or —COCl as the functional group (C);
In the step (II-a), the organic solution contains a basic compound that promotes the reaction between the at least one compound and the oligomer,
The manufacturing method according to claim 7 , wherein in the step (II-b), the basic compound is further added to the organic solution in the porous membrane.

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