JP5540681B2 - Modified electrolyte, method for producing the same, and modifier - Google Patents

Description

  The present invention relates to a modified electrolyte, a production method thereof, and a modifier, and more particularly, a modified electrolyte having low EW and high solubility in a solvent, a production method thereof, and such a modification. The present invention relates to a modifier used for producing an electrolyte.

  A solid polymer fuel cell has a membrane electrode assembly (MEA) in which electrodes are bonded to both surfaces of a solid polymer electrolyte membrane as a basic unit. In the polymer electrolyte fuel cell, the electrode generally has a two-layer structure of a diffusion layer and a catalyst layer. The diffusion layer is for supplying reaction gas and electrons to the catalyst layer, and carbon paper, carbon cloth, or the like is used. The catalyst layer is a part that becomes a reaction field of electrode reaction, and generally comprises a composite of carbon carrying an electrode catalyst such as platinum and a solid polymer electrolyte (catalyst layer ionomer).

  The electrolyte membrane or catalyst layer ionomer that constitutes such an MEA has a fluorine-containing electrolyte excellent in oxidation resistance (for example, Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Corporation). ), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), etc.) are generally used. In addition, the fluorine-containing electrolyte is excellent in oxidation resistance, but is generally very expensive. Therefore, in order to reduce the cost of the polymer electrolyte fuel cell, the use of a hydrocarbon-based electrolyte has been studied.

However, in order to use the polymer electrolyte fuel cell as an in-vehicle power source, there remain problems to be solved. For example, in a polymer electrolyte fuel cell, in order to obtain high performance, it is preferable that the operating temperature of the cell is high. For this purpose, it is preferable that the heat resistance of the electrolyte membrane is high. However, the conventional fluorine-based electrolyte membrane has a problem of low mechanical strength at high temperatures.
In recent years, it has been important to operate a fuel cell at high temperature and low humidity or without humidification. In order to develop high proton conductivity even under such conditions, an electrolyte having a high ion exchange capacity is required. However, an electrolyte having a high ion exchange capacity has a high moisture content, so that the swelling change of the membrane is large. For this reason, the film shape may not be maintained or may be dissolved in water. How to overcome the trade-off between high conductivity and high water content is a major issue.

In order to solve this problem, various proposals have heretofore been made.
For example, Patent Document 1 discloses a method in which both terminal sulfonyl fluorides are allowed to act on Nafion (registered trademark) subjected to amidation treatment to cause a crosslinking reaction.

Patent Document 2 discloses that sulfonamidated Nafion (registered trademark) and FO ₂ S—CF ₂ —CF ₂ —CF ₂ —I are reacted to convert an —I group into an —SO ₂ OH group. An electrolyte manufacturing method is disclosed.
This document describes that the electrical conductivity can be increased by such a method without lowering the crystallinity of the main chain portion that bears the strength.

Patent Document 3 discloses a polymer obtained by copolymerizing CF ₂ ═CFOCF ₂ CF ₂ SO ₂ N (CF ₂ CH ₃ ) SO ₂ CF ₃ and tetrafluoroethylene.
This document describes that the EW of the polymer thus obtained is 710 to 1300 g / mol.

Patent Document 4 discloses compounds such as HO ₃ S (CF ₂ ) ₂ SO ₂ F and CF ₃ SO ₂ NHSO ₂ (CF ₂ ) ₂ SO ₂ F that are not electrolytes but are irradiated with actinic rays or radiation. (For example, these sulfonium compounds and iodonium compounds) are disclosed.

  Further, Patent Document 5 discloses a method of synthesizing a compound having a sulfone halogen and a sulfonate at the same time by reacting an acid anhydride with an inorganic salt.

US Patent Application Publication No. US 6670424 JP 2002-324559 A Japanese Patent Laying-Open No. 2005-248104 JP 2007-3619 A European Patent Publication No. EP0280392

In recent years, it has been important to operate a fuel cell at high temperature and low humidity or without humidification. In order to develop high proton conductivity even under such conditions, not only the electrolyte membrane but also the electrolyte ionomer needs to have a high ion exchange capacity.
However, when an electrolyte having a sulfonic acid group in the side chain is sulfonamidated and the sulfonamidated electrolyte is reacted with a compound having a sulfonyl halide group at both ends, only a sulfonimide group is introduced into the side chain. In addition, a cross-linking reaction between polymers occurs. Therefore, the solubility of the obtained electrolyte in the solvent is lower than that of the original electrolyte. In addition, when the decrease in solubility is significant, it is impossible to make a solution in which the electrolyte is uniformly dissolved or dispersed. Therefore, it is difficult to apply such an electrolyte to the catalyst layer ionomer.

On the other hand, as disclosed in Patent Document 2, when a sulfonamidated electrolyte and FO ₂ S—CF ₂ —CF ₂ —CF ₂ —I are reacted, the polymers are not substantially crosslinked. A sulfonimide group can be introduced into the side chain. However, this method reduces the number of steps of the reaction, and thus the process becomes complicated.
Furthermore, in order to promote the electrode reaction on the cathode side, it is necessary to efficiently supply oxygen and protons to the catalyst covered with the catalyst layer ionomer. For this purpose, the cathode-side catalyst layer ionomer needs to be excellent in oxygen permeability and proton conductivity. However, there has never been an example in which an electrolyte having a high degree of oxygen permeability and proton conductivity has been proposed.

A problem to be solved by the present invention is a modified electrolyte that has a low EW, can exhibit high proton conductivity, has high solubility in a solvent, and can be applied to a catalyst layer ionomer. It is in providing the manufacturing method.
Another problem to be solved by the present invention is to provide a modified electrolyte having low EW and high solubility in a solvent and a method for producing the same without complicating the process.
Another object of the present invention is to provide a modified electrolyte excellent in oxygen permeability in addition to high proton conductivity and a method for producing the same.

  In order to solve the above problems, the modified electrolyte according to the present invention is summarized as having any structure represented by the formulas (1.1) to (1.3).

A method for producing a modified electrolyte according to the present invention includes:
The sulfonamide polymer is reacted with any one or more modifiers represented by the formulas (3.1) to (3.4), and the sulfonamide polymer and the modifier are reacted with a sulfonylimide group (- A reaction step of bonding via SO ₂ NHSO ₂ —).

_{X- [O 2 S (CF 2} ) n SO 2 NH] a -SO 2 R 4 ··· (3.1)
However, X is halogen n is 1 or more integer, a, which can be arbitrarily selected in the repeating unit, an integer of 1 or more R ⁴ are, OH, or a perfluorocarbon group

_{X- [O 2 S (CF 2} ) n SO 2 NH] a -SO 2 R 5 ··· (3.2)
However, X is halogen n is an integer of 1 or more, a which may be arbitrarily selected in the repeating unit, an integer of 1 or more R ⁵ is an aromatic group

_{XO 2 S- (CF 2) n} -SO 2 R 6 ··· (3.3)
X is halogen n is an integer of 1 or more R ⁶ is OH, OM (M is an alkali metal), perfluorocarbon group, or aromatic group

  The sulfonamide polymer preferably has a structure represented by the formula (2).

Further, the modifier of the present invention is summarized in that used to modify the Bei example, electrolyte structure represented by (3.1) below.
_{X- [O 2 S (CF 2} ) n SO 2 NH] a -SO 2 R 4 ··· (3.1)
However, X is halogen n is 1 or more integer, a, which can be arbitrarily selected in the repeating unit, an integer of 1 or more R ⁴ are, OH, or a perfluorocarbon group

The modifiers represented by the formulas (3.1) to (3.3) have one sulfonyl halide group and no -I group. Moreover, it is thought that the modifier represented by the formula (3.4) generates the modifier represented by the formula (3.3) or a derivative thereof in the reaction process with the sulfonamide polymer. Therefore, when any of these is reacted with a sulfonamide polymer, a sulfonimide group can be easily introduced into the side chain. Since the sulfonimide group having both ends sandwiched between perfluoroalkyl groups functions as a strong acid group, the introduction of the sulfonimide group lowers the EW compared to the original polymer. Further, no cross-linked structure is introduced between the polymers during the reaction with the modifier. Furthermore, since the modifier represented by the formulas (3.1) to (3.4) does not have the -I group, the manufacturing process is not complicated.
Furthermore, a modified electrolyte that exhibits high proton conductivity and high oxygen permeability can be obtained by modifying with a modifier having a hydrophobic group at the end (particularly a perfluorocarbon group having no hydrophilic group). It is done.

2 is a ¹⁹ F NMR spectrum of the modified electrolyte obtained in Example 1. 3 is a ¹⁹ F NMR spectrum of the modified electrolyte obtained in Example 2. It is a figure which shows the relationship between the terminal carbon number of the modified electrolyte membrane obtained in Examples 5-7, and the electrolyte membrane of the comparative example 2, and oxygen permeability.

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Modified electrolyte (1)]
The modified electrolyte according to the first embodiment of the present invention has a structure represented by the formula (1.1).

P represents a perfluoroalkyl chain or a hydrocarbon chain. Q represents a perfluoroalkyl chain, a hydrocarbon chain or a direct bond.
A “perfluoroalkyl chain” refers to a chain structure containing a C—F bond and no C—H bond. The perfluoroalkyl chain may contain an ether bond (—O—), a sulfonyl bond (—SO ₂ —) and the like in addition to the C—F bond. The perfluoroalkyl chain may be linear or may have a branched structure.
“Hydrocarbon chain” refers to a chain structure containing a C—H bond. The hydrocarbon chain may contain a C—F bond, an ether bond (—O—), a sulfonyl bond (—SO ₂ —) and the like in addition to the C—H bond. The hydrocarbon chain may be linear or may have a branched structure.

As the perfluoroalkyl chain constituting P, specifically,
_{(1) - [CF 2 -CF} 2] x - [CF 2 -CF (-)] y -,
_{(2) - [CF 2 -CF} 2] x - [CF 2 -CF (CF 3)] y - [CF 2 -CF (-)] z -,
and so on.
As the hydrocarbon chain constituting P, specifically,
(1)-[C ₆ H ₄ -SO ₂ ] _x- (C ₆ H _3- ) _y- ,
_{(2) - (C 6 H} 4 -O) x - (C 6 H 4 -SO 2) y - (C 6 H 3 -) z -,
_{(3) - [C 6 H} 4 -C (CF 3) 2] x - (C 6 H 3 -) y -,
and so on.

As the perfluoroalkyl chain constituting Q, specifically,
_{(1) -OCF 2 CF (CF} 3) -,
_{(2) - [OCF 2 CF} (CF 3)] l -O-,
(3) -O (CF ₂ ) _2- ,
and so on.
As the hydrocarbon chain constituting Q, specifically,
_{(1) -C 6 H 4 -} ,
_{(2) - (SO 2 -C} 6 H 4) -,
and so on.

X represents hydrogen or fluorine.
Two Xs bonded to one C may both be hydrogen or fluorine, or one may be hydrogen and the other may be fluorine. When m ≧ 2, X may be the same or different for each repeating unit.

m is an integer of 0 or more, - (CX ₂₎ - represents the number of repetitions.
In general, as m increases, the hydrophobic portion of the side chain extends, so that a hydrophilic / hydrophobic morphology structure is easily obtained. m is preferably 1 or more.
On the other hand, if m is too large, the molecular weight increases, and the proton conductivity decreases due to a decrease in acid group density. Accordingly, m is preferably 3 or less.

n is an integer of 1 or more, - (CF ₂₎ - represents the number of repetitions.
In general, the larger n is, the easier it is to synthesize the modifier used in the production of the modified electrolyte. n is preferably 2 or more, and more preferably 3 or more.
On the other hand, when n becomes too large, the modified electrolyte becomes difficult to dissolve in the solvent. In addition, since the distance between the acid groups is increased, the molecular weight is increased, and the effect of increasing the acid groups is reduced. Therefore, n is preferably 4 or less.
When a ≧ 2, n contained in the repeating unit may be the same or may be different for each repeating unit.

a is an integer of 1 or more, and represents the number of repetitions of — [SO ₂ (CF ₂ ) _n SO ₂ NH] —.
In general, the larger a is, the greater the number of acid groups and the higher the proton conductivity. In order to obtain high proton conductivity, a is preferably 2 or more.
On the other hand, if a is too large, the moisture content increases and swelling increases. Therefore, a is preferably 3 or less.

R ¹ represents OH or a perfluorocarbon group.
The “perfluorocarbon group” refers to a monovalent group containing a C—F bond and not containing a C—H bond. In addition to the C—F bond, the perfluorocarbon group includes various functional groups (for example, —CO ₂ H, —PO ₃ H ₂ , —SO ₃ H, etc.), an ether bond (—O—), a sulfonyl bond (— SO ₂ —) and the like may be included. Furthermore, the perfluorocarbon group may have a chain structure or an alicyclic structure.
The “perfluorocarbon group having a chain structure” refers to a group containing a C—F bond, no C—H bond, and no cyclic structure. The chain structure may be linear or branched. In addition, the chain structure may include only a saturated bond (single bond), or may include an unsaturated bond instead of or in addition to this.
The “perfluorocarbon group having an alicyclic structure” refers to a group having a C—F bond, no C—H bond, and having a cyclic structure other than an aromatic ring. The cyclic structure may be a three-membered ring or more, and may be crosslinked within the ring.

When R ¹ is a perfluorocarbon group, the modified electrolyte may contain any one type of R ¹ , or may contain two or more types.
Specific examples of the perfluorocarbon group R ¹ include the following.
_{(1) - (CF 2)} k CF 3 (k is 0 to 9 integer _{e.g., -CF 3, -. (CF} 2) 3 CF 3, - such as _{(CF 2) 7 CF 3.} ).
_{(2) - (CF 2)} k CF (CF 3) 2 (k is 0 to 8 integer _{example, -. (CF 2) 2} CF (CF 3) 2 and the like.).
_{(3) -C k F 2k-} 1 ( alicyclic structure:. K is 3 to 10 integer example, -C ₆ F _11, etc.).
(4)-(CF ₂ ) _k OCF ₃ (k is an integer of 1 to 10, for example,-(CF ₂ ) ₃ OCF ₃ etc.).
_{(5) - (CF 2)} k PO 3 H 2 (k is 1 to 10 integer example, -. (Such as _{CF 2) 3 PO 3 H 2} .).
_{(6) - (CF 2)} k CO 2 H (k is 1 to 10 integer example, -. (CF ₂₎ such as ₃ CO ₂ H.).
_{(7) - (CF 2)} k SO 3 H (k is 1 to 10 integer example, -. (CF ₂₎ such as ₃ SO ₃ H.).

  Among the modified electrolytes represented by the formula (1.1), those represented by the formulas (1.1.1) to (1.1.5) are particularly preferable.

In the modified electrolyte represented by the formula (1.1), EW can be lowered by optimizing the molecular structure (particularly, the number of repeating units a). Specifically, the EW is 1000 g / mol or less by optimizing the molecular structure. In order to obtain high proton conductivity, EW is more preferably 820 g / mol or less, and further preferably 740 g / mol or less.
In the modified electrolyte represented by the formula (1.1), when the molecular structure is optimized, the solubility of the modified electrolyte in the solvent can be maintained high. In the electrolyte represented by the formula (1.1), when the molecular structure is optimized, the solubility is 1 wt% or more. In order to facilitate application to the catalyst layer ionomer, the solubility is preferably 2 wt% or more, and more preferably 5 wt% or more.
Here, in the present invention, “solubility” refers to the weight concentration of the modified electrolyte. Moreover, it is preferable that the average particle diameter measured by the light scattering of the polymer fine particle in a solution is 10-1000 nm. More preferably, it is 10-500 nm.

Among the modified electrolytes represented by the formula (1.1), those in which R ¹ is a hydrophobic group (that is, a perfluorocarbon group having no hydrophilic group such as a sulfonic acid group) are preferable. When these hydrophobic groups are provided at the end of the side chain, the oxygen permeability of the modified electrolyte is improved.
In order to obtain high oxygen permeability, the carbon number of R ¹ is preferably 2 or more. More preferably, the carbon number of R ¹ is 3 or more.
On the other hand, if R ¹ has too many carbon atoms, there is a problem that it cannot be dissolved in a general solvent. Therefore, the carbon number of R ¹ is preferably 20 or less. The carbon number of R ¹ is more preferably 10 or less.
For example, when R ¹ is — (CF ₂ ) _k CF ₃ , k is preferably 1 or more and 9 or less, and more preferably 3 or more and 7 or less.
Further, when R ¹ is — (CF ₂ ) _k CF (CF ₃ ) ₂ , k is preferably 0 or more and 8 or less, and more preferably 2 or more and 6 or less.
Further, when R ¹ is -C _k F _{2k-1, k} is preferably 3 to 10, more preferably is 5 to 8.

[2. Modified electrolyte (2)]
The modified electrolyte according to the second embodiment of the present invention has a structure represented by the formula (1.2). In the formula (1.2), P, Q, X, m, n, and a are the same as those in the formula (1.1), and the description thereof is omitted.

R ² represents an aromatic group. “Aromatic group” refers to a monovalent group having a monocyclic or polycyclic aromatic ring. Aromatic groups include ether bond (—O—), sulfonyl bond (—SO ₂ —), sulfonimide bond (—NHSO ₂ —), polyphenylene (— [C ₆ H ₄ ] _b — (b ≧ 2)), etc. May be included.
As an aromatic group, specifically,
(1) phenyl (—C ₆ H ₅ ), naphthyl (—C ₁₀ H ₇ ), anthracene (—C ₁₄ H ₉ ),
_{(2) - (C 6 H} 4) n -C 6 H 5 (n is an integer of 1 or more),
_{(3) - (C 6 H} 4) n - (SO 2 C 6 H 4) p - (C 6 H 5) (n, p is an integer of 1 or more),
and so on.

  Among the modified electrolytes represented by the formula (1.2), those represented by the formula (1.2.1) are particularly preferable.

In the modified electrolyte represented by the formula (1.2), EW can be lowered by optimizing the molecular structure (particularly, the number of repeating units a). Specifically, the EW is 1000 g / mol or less by optimizing the molecular structure. In order to obtain high proton conductivity, EW is more preferably 820 g / mol or less, and further preferably 740 g / mol or less.
In the modified electrolyte represented by the formula (1.2), when the molecular structure is optimized, the solubility of the modified electrolyte in the solvent can be maintained high. In the electrolyte represented by the formula (1.2), when the molecular structure is optimized, the solubility is 1 wt% or more. In order to facilitate application to the catalyst layer ionomer, the solubility is preferably 2 wt% or more, and more preferably 5 wt% or more.

[3. Modified electrolyte (3)]
The modified electrolyte according to the third embodiment of the present invention has a structure represented by the formula (1.3). In the formula (1.3), P, Q, X, m, and n are the same as those in the formula (1.1), and the description thereof is omitted.

R ³ represents OH, a perfluorocarbon group, or an aromatic group. The perfluorocarbon group and the aromatic group are the same as the perfluorocarbon group and the aromatic group in the formulas (1.1) and (1.2), respectively, and thus description thereof is omitted.

  Among the modified electrolytes represented by the formula (1.3), those represented by the formula (1.3.1) are particularly preferable.

In the modified electrolyte represented by the formula (1.3), EW can be lowered by optimizing the molecular structure. Specifically, the EW is 1000 g / mol or less by optimizing the molecular structure. In order to obtain high proton conductivity, EW is more preferably 820 g / mol or less, and further preferably 740 g / mol or less.
In the modified electrolyte represented by the formula (1.3), when the molecular structure is optimized, the solubility of the modified electrolyte in the solvent can be maintained high. In the electrolyte represented by the formula (1.3), when the molecular structure is optimized, the solubility is 1 wt% or more. In order to facilitate application to the catalyst layer ionomer, the solubility is preferably 2 wt% or more, and more preferably 5 wt% or more.

Of the modified electrolytes represented by the formula (1.3), those in which R ³ is a hydrophobic group are preferred. When R ³ is a hydrophobic group, the oxygen permeability of the modified electrolyte is improved. The details of the hydrophobic group are the same as those for R ^1, and thus the description thereof is omitted.

[4. Method for producing modified electrolyte]
The method for producing a modified electrolyte according to the present invention includes a reaction step of reacting a sulfonamide polymer and a modifier.

[4.1. Sulfonamide polymer]
The sulfonamide polymer refers to a polymer having a sulfonamide group (—SO ₂ NH ₂ ). In the present invention, the structure of the sulfonamide polymer is not particularly limited, and the present invention can be applied to all polymers having a sulfonamide group.
Among these, the sulfonamide polymer is preferably a polymer having a structure represented by the formula (2). Since P, Q, X, and m in the formula (2) are the same as those in the formula (1.1), description thereof is omitted.

As the sulfonamide polymer represented by the formula (2), specifically,
(1) A perfluorocarbon sulfonamide polymer obtained by converting a sulfonic acid group of a perfluorocarbon sulfonic acid polymer into a sulfonamide group,
(2) a polyether ether ketone sulfonamide polymer obtained by converting a sulfonic acid group of a polyether ether ketone sulfonic acid polymer into a sulfonamide group,
and so on.

[4.2. Modifier]
"Modifier"
(1) a compound having one reaction point (that is, a sulfonyl halide group), or
(2) A compound capable of producing a compound having one reaction point.
Specific examples of the modifier include the following. Any one of these modifiers may be used, or two or more thereof may be used in combination.

[4.2.1. First specific example]
A first specific example of the modifier is composed of a compound represented by the formula (3.1).
_{X- [O 2 S (CF 2} ) n SO 2 NH] a -SO 2 R 4 ··· (3.1)
However, X is halogen n is an integer of 1 or more and can be arbitrarily selected in the repeating unit a is an integer of 1 or more R ⁴ is OH or a perfluorocarbon group (3.1) In the formula, n, a, and R ⁴ are the same as n, a, and R ¹ in the formula (1.1), respectively, and thus description thereof is omitted.

Among the modifiers represented by the formula (3.1),
(1) F— [O ₂ S (CF ₂ ) ₃ SO ₂ NH] _a —SO ₃ H (a ≧ 1),
(2) F- [O ₂ S (CF ₂ ) ₃ SO ₂ NH] _a —SO ₂ CF ₃ (a ≧ 1),
(3) F- [O ₂ S (CF ₂ ) ₃ SO ₂ NH] _a —SO ₂ (CF ₂ ) ₃ CF ₃ (a ≧ 1),
(4) F— [O ₂ S (CF ₂ ) ₃ SO ₂ NH] _a —SO ₂ (CF ₂ ) ₇ CF ₃ (a ≧ 1),
(5) F— [O ₂ S (CF ₂ ) ₃ SO ₂ NH] _a —SO ₂ (CF ₂ ) ₂ CF (CF ₃ ) ₂ (a ≧ 1),
(6) F— [O ₂ S (CF ₂ ) ₃ SO ₂ NH] _a —SO ₂ C ₆ F ₁₁ (a ≧ 1),
Etc. are preferable.

[4.2.2. Second specific example]
A second specific example of the modifying agent is a compound represented by the formula (3.2).
_{X- [O 2 S (CF 2} ) n SO 2 NH] a -SO 2 R 5 ··· (3.2)
However, X is halogen n is 1 or more integer a is the integer of 1 or more R ^5, in an aromatic group (3.2) formula, n, a and R ^5, respectively, (1.2) Since it is the same as n, a and R ² in the formula, description thereof is omitted.

Among the modifiers represented by the formula (3.2),
(1) F— [O ₂ S (CF ₂ ) ₃ SO ₂ NH] _a —SO ₂ C ₆ H ₅ (a ≧ 1),
(2) F— [O ₂ S (CF ₂ ) ₃ SO ₂ NH] _a —SO ₂ (C ₆ H ₄ ) _n C ₆ H ₅ (a ≧ 1),
Etc. are preferable.

[4.2.3. Third specific example]
A third specific example of the modifying agent is a compound represented by the formula (3.3).
_{XO 2 S- (CF 2) n} -SO 2 R 6 ··· (3.3)
X is halogen n is an integer of 1 or more R ⁶ is OH, OM (M is an alkali metal), perfluorocarbon group, or aromatic group

In the formula (3.3), R ⁶ may be OM (M is an alkali metal) in addition to OH, a perfluorocarbon group or an aromatic group.
Since other points regarding R ⁶ and n in the expression (3.3) are the same as those in the expressions (3.1) and (3.2), detailed description thereof is omitted.

Among the modifiers represented by the formula (3.3), FO ₂ S— (CF ₂ ) ₃ —SO ₃ H is particularly preferable.

[4.2.4. Fourth Specific Example]
The 4th specific example of a modifier consists of a compound represented by (3.4) Formula.

(3.4) The compound represented by the formula is a cyclic sulfonic anhydride compound. When the cyclic sulfonic anhydride compound and the sulfonamide polymer are reacted, the cyclic sulfonic anhydride compound is opened, and one end of the ring-opened product is bonded to the sulfonamide group.
n represents the carbon number of the perfluoroalkyl chain contained in the cyclic sulfonic anhydride compound. In general, as n increases, there is an advantage that the molecular weight of the raw material increases and it is easy to handle. Therefore, n is preferably 2 or more, and more preferably 3 or more.
On the other hand, if n is too large, the ring structure becomes unstable. Therefore, the dehydration reaction between molecules has priority, and it becomes difficult to isolate as a monomer. Therefore, n is preferably 4 or less.

[4.3. Synthetic reaction of modified electrolyte]
For example, when a sulfonamide polymer and a modifier represented by the formulas (3.1) to (3.3) are reacted, a condensation reaction occurs, and the sulfonamide polymer and the modifier are bonded to a sulfonylimide bond ( Bonding via —SO ₂ NHSO ₂ —). At this time, if the condensation reaction is performed in the presence of a base, the condensation reaction can be promoted.
Specific examples of the base include triethylamine, trimethylamine, tripropylamine, tributylamine, DBU (diazabicycloundecene), N, N-diisopropylethylamine (DIPEA), and the like.

Formula (4.1) shows a reaction formula between a sulfonamide polymer and a modifier represented by formula (3.1) (where X = F).
Formula (4.2) shows a reaction formula between a sulfonamide polymer and a modifier (provided that X = F) represented by formula (3.3).
Formula (4.3) shows the reaction formula between the sulfonamide polymer and the modifier represented by formula (3.4).

Further, when a compound represented by the formula (3.4) (cyclic sulfonic anhydride compound) and MX (M is an alkali metal and X is halogen) are reacted, the cyclic sulfonic anhydride compound is opened, and (3 .3) A modifier represented by the formula (where R ⁶ = OM) is produced. Subsequently, when the obtained modifier and the sulfonamide polymer are reacted, both are bonded by a condensation reaction.
Equation (4.4) shows the reaction formula of these reactions.

After the condensation reaction, it is washed with an aqueous NaOH solution or a mixed solvent of an aqueous NaOH solution and an alcohol (for example, ethanol). When the sulfonamide polymer and the modifier are reacted in the presence of a base, it is considered that the acid group and base of the polymer are bonded to form a salt. Washing with NaOH is performed to convert the base salt to the Na salt.
After washing, it is treated with H ₂ O ₂ and HNO ₃ . The H ₂ O ₂ treatment is performed to remove residual organic components. Residual organic components become poisonous substances such as Pt. Further, HNO ₃ treatment is performed to the Na salt to acid derivative.

[4.4. Reaction conditions]
When the sulfonamide and the modifier are subjected to a condensation reaction, the reaction temperature is preferably less than 80 ° C. If the reaction temperature is too high, the reaction becomes complicated and a decomposition product is generated.

[5. Method for producing modifier]
[5.1. Synthetic reaction of modifier]
The above-mentioned modifier is commercially available, or can be produced by a known reaction using a commercially available compound having a similar molecular structure as a starting material.
For example, FO ₂ S (CF ₂ ) _n SO ₃ H (CnSF, n is an integer greater than or equal to 1) is located relative to FO ₂ S (CF ₂ ) _n SO ₂ F (CnF, n is an integer greater than or equal to 1). It can be produced by adding a fixed amount of water and a base (for example, DIPEA) and reacting them.
XO ₂ S (CF ₂ ) _n SO ₃ M (X is halogen, M is an alkali metal, and n is an integer of 1 or more) is a cyclic sulfonic anhydride compound represented by the formula (3.4) and MX ( M is an alkali metal, and X is a halogen).

The modifier represented by the formula (3.1) is
(1) As shown in the formula (5.1.1), a sulfonyl halide monomer and a sulfonylamide monomer are reacted at a molar ratio of (k + 1): k,
(2) As shown in the formula (5.1.2), using HR ⁷ , functional group conversion is performed only on one end of the obtained oligomer.
Can be obtained.
At this time, when a sulfonyl halide monomer and a sulfonylamide monomer having the same carbon number n are used as starting materials, a modifier having the same n contained in the repeating unit is obtained. On the other hand, when a sulfonyl halide monomer and / or sulfonylamide monomer having a different carbon number n is used as a starting material, a modifier having a different n for each repeating unit is obtained.

For example, in the formula (5.1.2), when H ₂ O is used as HR ⁷ , a modifier represented by the following formula (3.1.1) is obtained.
_{FO 2 S (CF 2) n} - [SO 2 NHSO 2 (CF 2) n] 2k -SO 3 H
≡F- [O ₂ S (CF ₂ ) _n SO ₂ NH] _2k —SO ₂ (CF ₂ ) _n SO ₃ H (3.1.1)

Alternatively, first, H ₂ NO ₂ S (CF ₂ ) _n SO ₃ H (CnSA, n is an integer of 1 or more) is synthesized from CnSF and a base (for example, ammonia, LiNTMS ₂ or the like). An example of the synthesis reaction of CnSA is shown in the following formula (5.2).
FO ₂ S (CF ₂ ) _n SO ₃ H + LiNTMS ₂ → H ₂ NO ₂ S (CF ₂ ) _n SO ₃ H
.. (5.2)
Next, in the formula (5.1.2), when CnSA is used in place of HR ⁷ , a modifier represented by the following formula (3.1.2) is obtained.
_{FO 2 S (CF 2) n} - [SO 2 NHSO 2 (CF 2) n] 2k -SO 2 NHSO 2 (CF 2) n SO 3 H
_{≡F- [O 2 S (CF 2} ) n SO 2 NH] 2k + 1 -SO 2 (CF 2) n SO 3 H ·· (3.1.2)

(3.1) A modifier represented by the formula wherein R ⁴ is — (CF ₂ ) _n PO ₃ H is obtained by subjecting — (CF ₂ ) _n —PO (OMe) ₂ to an acid treatment. Can be manufactured.
(3.1) A modifier represented by the formula, wherein R ⁴ is — (CF ₂ ) _n CO ₂ H, may be produced by hydrolyzing — (CF ₂ ) _n —COF. it can.
(3.1) A modifier represented by the formula, wherein R ⁴ is — (CF ₂ ) _n OCF ₃ , is produced by electrolytic fluorination of — (CH ₂ ) _n —OCH _3. Can do.
The modifier represented by the formula (3.2) can be produced by reacting FO ₂ S (CF ₂ ) _n SO ₂ F with H ₂ NSO ₂ C ₆ H ₅ .
Other modifiers can also be produced by the same method as described above.

[5.2. Reaction conditions]
When only one end of a starting material having both ends of a sulfonyl halide group such as C3F is converted into a sulfonic acid group, starting material: 1 equivalent, base (eg, DIPEA): 2 equivalents and reactant ( For example, water): add 1 equivalent. The reason why the target modifier can be obtained by adding the base is considered to be to neutralize the acid group portion of the modifier generated by the reaction and reduce the reactivity (to increase the stability). .
The reaction temperature at this time is preferably less than 80 ° C. If the reaction temperature is too high, the reaction becomes complicated and a decomposition product is generated. For this reason, it is difficult to separate the generated modifier. The reaction temperature is preferably 0 ° C. to room temperature.

[6. Modified electrolyte, production method thereof, and action of modifier]
The modifiers represented by the formulas (3.1) to (3.3) have one sulfonyl halide group and no -I group. Moreover, it is thought that the modifier represented by the formula (3.4) generates the modifier represented by the formula (3.3) or a derivative thereof in the reaction process with the sulfonamide polymer.
Therefore, when any of these is reacted with a sulfonamide polymer, a sulfonimide group can be easily introduced into the side chain. Since the sulfonimide group having both ends sandwiched between perfluoroalkyl groups functions as a strong acid group, the introduction of the sulfonimide group lowers the EW compared to the original polymer. Further, no cross-linked structure is introduced between the polymers during the reaction with the modifier. Furthermore, since the modifier represented by the formulas (3.1) to (3.4) does not have the -I group, the manufacturing process is not complicated.

The method for producing a modified electrolyte according to the present invention can reduce EW by modifying a polymer, and can be applied to all polymers having a sulfonamide group. Further, since no chemical cross-linking occurs between the polymers, the physical properties of the original polymer are hardly impaired. Therefore, the modified electrolyte obtained by the method according to the present invention can be dissolved in a solvent and can be used as a catalyst layer ionomer. Since the modified electrolyte according to the present invention has high conductivity and low resistance, there is a possibility that it can be operated under a high temperature and low humidification condition as compared with a fuel cell using a conventional electrolyte (for example, Nafion (registered trademark)). There is.
Furthermore, when a hydrophobic group (particularly a perfluorocarbon group having no hydrophilic group) is introduced at the terminal during bifunctional modification of the sulfonamide polymer, high proton conductivity and high oxygen permeability can be achieved at the same time. Since oxygen diffuses in the vicinity of the interface between the polymer and water, it is considered that the hydrophobic group enhances oxygen permeability. When such a modified electrolyte is used as the catalyst layer ionomer on the cathode side of the MEA, it exhibits high performance under high temperature and low humidification conditions as compared with the conventional MEA. This is probably because protons and oxygen are sufficiently supplied to the catalyst even under low humidity. Furthermore, since conventional polymers can be used for modification, it is not necessary to newly go through a multi-stage synthesis route, and the manufacturing cost can be reduced.

Example 1
[1. Preparation of sample]
FO ₂ S (CF ₂ ) ₃ SO ₃ H by adding 1 equivalent of water to 30 g and DIPEA (33 mL) at 0 ° C. in acetonitrile at FO ₂ S (CF ₂ ) ₃ SO ₂ F (C3F) (C3SF) was generated (confirmed by ¹⁹ F NMR spectrum).
To this, Nafion (registered trademark) (10 g) having sulfonamidated side chains and DIPEA (33 mL) were added and reacted at 80 ° C. for 2 weeks. After removing the solvent, it was washed with a NaOH aqueous solution / EtOH mixed solvent and treated with H ₂ O ₂ and HNO ₃ , so that a polymer having both a sulfonimide group and a sulfonic acid group on the same side chain (12 g ) The synthesis reaction formula is shown in (6.1) Formula.

[2. Evaluation]
The structure of the obtained polymer (modified electrolyte) was confirmed by ¹⁹ F NMR spectrum and IR spectrum. FIG. 1 shows the ¹⁹ F NMR spectrum of the obtained polymer. FIG. 1 shows that the target compound is obtained.
The obtained modified electrolyte could be made into a solution by autoclaving with a mixed solvent of ethanol and water (weight ratio 1: 1), and a catalyst ink could be produced. Moreover, when MEA using this as a catalyst layer was produced and fuel cell evaluation was performed, it confirmed that electric power generation was possible.

(Example 2)
[1. Preparation of sample]
CF ₃ SO ₂ NH ₂ (0.47 g) was allowed to act on C3F (1.4 g) to trifluoromethylate one side. By reacting this with Nafion (registered trademark) (0.70 g) whose side chain was sulfonamidated in acetonitrile, a polymer (1.0 g) having two sulfonimide groups on the same side chain was obtained. . The synthesis reaction formula is shown in formula (6.2).

[2. Evaluation]
The structure of the obtained polymer (modified electrolyte) was confirmed by ¹⁹ F NMR spectrum and IR spectrum. FIG. 2 shows the ¹⁹ F NMR spectrum of the obtained polymer. FIG. 2 shows that the target compound is obtained.

(Example 3)
[1. Preparation of sample]
[1.1. Preparation of modifier]
In acetonitrile, C3F: 22.5 g and C3A: 11.0 g were mixed (corresponding to (k + 1): k in molar ratio) and reacted with a base (DIPEA) at 0 ° C., so that both ends were SO ₂ F. A polysulfonimide was obtained. Base (DIPEA) (18.5 g) and 1 equivalent of water were added to the obtained polysulfonimide, and only one side of the polysulfonimide was converted into a sulfonic acid group. (6.3) Formula shows the synthesis reaction formula.

[1.2. Preparation of modified electrolyte]
[1.1. A modified electrolyte was produced in the same manner as in Example 1 except that the modifier obtained in the above was used.
[2. Evaluation]
It was confirmed by the ¹⁹ F NMR spectrum and IR spectrum that the desired modified electrolyte was obtained.

(Comparative Example 1)
C3F and C3A were mixed 2: 1 in acetonitrile, and a base (DIPEA) was added and heated at 80 ° C. Since the reaction temperature was high, a decomposition product was generated, and the target product could not be separated.

Example 4
[1. Preparation of sample]
A compound having a sulfonimide group and a sulfonic acid group in the side chain was synthesized by reacting cyclic sulfonic anhydride (n = 3) with polysulfonamide polymer in the presence of a base. (6.4) Formula shows a synthesis reaction formula.

[2. Evaluation]
It was confirmed by IR spectrum that the desired modified electrolyte was obtained.

(Examples 5-7, Comparative Example 2)
[1. Preparation of sample]
_{Modifier: FSO 2 (CF 2) 3} SO 2 NHSO 2 R 4 (R 4 = - (CF 2) 3 CF 3, -CF 3, or, -OH) modification of Nafion (registered trademark) using a And a perfluorobutyl group (Example 5), a trifluoromethyl group (Example 6), or a sulfonic acid group (Example 7) was introduced at the terminal. A mixed solvent of ethanol and water was added to these modified electrolytes and autoclaved at 200 ° C. Thereafter, the solution was homogenized. A cast film was prepared from this solution. The cast film was dried at 140 ° C. and then washed with 1N NaOH aqueous solution, H ₂ O ₂ aqueous solution, and 1N HNO ₃ aqueous solution.
As a comparison, a commercially available Nafion (registered trademark) membrane (Comparative Example 2) was also used in the test.

[2. Test method]
[2.1. Equivalent weight EW and water content]
The equivalent weight EW and moisture content of the washed membrane were measured. A titration method was used to measure the equivalent weight EW. The moisture content was determined by immersing the membrane in water at room temperature for 24 hours and dividing the difference between the weight at that time and the weight when dried at 60 ° C. by the dry weight.
Water content (%) = (moisture content−dry weight) × 100 / dry weight [2.2. Proton conductivity]
The proton conductivity (25 ° C.) of the washed membrane was measured. The alternating current two-terminal method was used for the measurement of proton conductivity.
[2.3. Oxygen permeability]
The oxygen permeability (80 ° C.) of the washed membrane was measured. For measurement of oxygen permeability, a potential step method using a microelectrode was used.

[3. result]
Table 1 shows the equivalent weight EW, water content, proton conductivity and oxygen permeability. FIG. 3 shows the relationship between the carbon number (terminal carbon number) of the terminal group R ⁴ (= R ¹ ) and the oxygen permeability.
Table 1 and FIG. 3 show the following.
(1) In the case of the modified electrolyte having a sulfonic acid group introduced at the terminal (Example 7), its oxygen permeability is almost the same as that of Comparative Example 2, but its proton conductivity is improved as compared with Comparative Example 2.
(2) In the case of a modified electrolyte having a hydrophobic group introduced at the end (Examples 5 and 6), the proton conductivity is slightly inferior to the modified electrolyte having a sulfonic acid group introduced at the end (Example 7). The oxygen permeability is improved from that in Example 7.
(3) The oxygen permeability of the electrolyte improves as the number of terminal carbons increases.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention.

The modified electrolyte and the method for producing the same according to the present invention include various types such as a polymer electrolyte fuel cell, a water electrolysis apparatus, a hydrohalic acid electrolysis apparatus, a salt electrolysis apparatus, an oxygen and / or hydrogen concentrator, a humidity sensor, and a gas sensor. It can be used as an electrolyte membrane used in an electrochemical device, an electrolyte in a catalyst layer, and a manufacturing method thereof.
Moreover, the modifier according to the present invention can be used as a raw material for producing such a modified electrolyte.

Claims (9)

(1.1) A modified electrolyte having a structure represented by the formula:

R ¹ is
-(CF ₂ ) _k CF ₃ (where k is an integer from 1 to 9),
-(CF ₂ ) _k CF (CF ₃ ) ₂ (where k is an integer from 0 to 8), or
-C _k F _2k-1 (where k is an integer from 3 to 10)
The modified electrolyte according to claim 1, wherein (1.2) A modified electrolyte having a structure represented by the formula:

(1.3) A modified electrolyte having a structure represented by the formula:

R ³ is
-(CF ₂ ) _k CF ₃ (where k is an integer from 1 to 9),
-(CF ₂ ) _k CF (CF ₃ ) ₂ (where k is an integer from 0 to 8), or
-C _k F _2k-1 (where k is an integer from 3 to 10)
The modified electrolyte according to claim 4, wherein   The modified electrolyte according to any one of claims 1 to 5, which is used as a catalyst layer ionomer. The sulfonamide polymer is reacted with any one or more modifiers represented by formulas (3.1) to (3.4), and the sulfonamide polymer and the modifier are reacted with a sulfonylimide group (- A method for producing a modified electrolyte, comprising a reaction step of bonding via SO ₂ NHSO ₂ —).
_{X- [O 2 S (CF 2} ) n SO 2 NH] a -SO 2 R 4 ··· (3.1)
However, X is halogen n is an integer of 1 or more, a which may be arbitrarily selected in the repeating unit, an integer of 1 or more R ⁴ are, OH, or a perfluorocarbon group X- [O _{2 S (CF 2) n SO 2} NH] a -SO 2 R 5 ··· (3.2)
However, X is halogen n is an integer of 1 or more, a which may be arbitrarily selected in the repeating unit, an integer of 1 or more R ⁵ is an aromatic group XO ₂ S- (CF _{2) n} -SO ₂ R ⁶ ··· (3.3)
X is halogen n is an integer of 1 or more R ⁶ is OH, OM (M is an alkali metal), perfluorocarbon group, or aromatic group

The said sulfonamide polymer is a manufacturing method of the modified electrolyte of Claim 7 provided with the structure represented by (2) Formula.

(3.1) A modifier having a structure represented by the formula and used for modifying an electrolyte .
_{X- [O 2 S (CF 2} ) n SO 2 NH] a -SO 2 R 4 ··· (3.1)
However, X is halogen n is 1 or more integer, a, which can be arbitrarily selected in the repeating unit, an integer of 1 or more R ⁴ are, OH, or a perfluorocarbon group

Images