JP4046573B2 - Method for producing highly durable polymer electrolyte - Google Patents

Description

【００８１】
図１に、耐久時間と開回路電圧との関係を示す。いずれの膜も、初期状態の開回路電圧は、約０．９５Ｖであった。しかしながら、フッ素化処理が施されていない比較例１の場合、７０００分後の開回路電圧は、０．８１Ｖまで低下した。これに対し、フッ素ガスを用いてフッ素化処理を施した実施例１の場合、７０００分後の開回路電圧は、０．８７Ｖを越えていた。
【００８２】
電解質膜が過酸化物ラジカルにより劣化すると、劣化物が触媒表面を覆い、触媒活性を低下させることが知られている。炭化水素系電解質にフッ素化処理を施すことにより、耐久性が向上するのは、炭化水素系電解質を構成する炭化水素骨格がフルオロカーボン骨格に変換されることによって耐酸化性が向上し、劣化物の生成が抑制されるためと考えられる。
【００８３】
（参考例２）
実施例１の（１）及び（２）と同一の手順に従い、ＥＴＦＥ−ｇ−ＰＳｔ−Ｓ膜を作製した。次に、この膜１ｇを、室温において、Ｎ_２ガスで希釈したフッ素ガス（Ｎ_２：０．３ｋｇ／ｃｍ^２（２．９４×１０^４Ｐａ）、Ｆ_２：０．１ｋｇ／ｃｍ^２（０．９８×１０^４Ｐａ））中に５分間放置し、膜とフッ素ガスとを反応させた。反応後、膜を１リットルの５Ｎ塩酸中で２時間還流した。さらに、膜を１リットルのイオン交換水中で１時間煮沸する処理を３回繰り返すことにより、フッ素化されたＥＴＦＥ−ｇ−ＰＳｔ−Ｓ膜を得た。
【００８４】
（実施例３）
実施例１の（１）及び（２）と同一の手順に従い、ＥＴＦＥ−ｇ−ＰＳｔ−Ｓ膜を作製した。この膜１ｇを１リットルの１Ｎ水酸化ナトリウム水溶液中に１時間浸漬し、スルホン酸基のプロトンをナトリウムイオンに置換した。次いで、膜を１リットルのイオン交換水中で１時間煮沸する処理を３回繰り返した。さらに、膜を６０℃において１２時間真空乾燥した。
【００８５】
次に、この膜に対し、参考例２と同一条件下で、フッ素ガスによるフッ素化処理を行った。さらに、参考例２と同一条件下で、塩酸による還流及びイオン交換水による煮沸を行い、フッ素化されたＥＴＦＥ−ｇ−ＰＳｔ−Ｓ膜を得た。
【００８６】
（実施例４）
実施例１の（１）及び（２）と同一の手順に従い、ＥＴＦＥ−ｇ−ＰＳｔ−Ｓ膜を作製した。この膜１ｇを１リットルの五塩化リン／オキシ塩化リン混合溶液（５塩化リン／オキシ塩化リンの体積比（ｖｏｌ．／ｖｏｌ．）＝３／７）中に９０℃で６時間浸漬し、スルホン酸基をスルホニルクロライド基に変換した。さらに、膜を溶液から取り出し、６０℃で１２時間真空乾燥した。
【００８７】
次に、この膜に対し、参考例２と同一条件下で、フッ素ガスによるフッ素化処理を行った。さらに、参考例２と同一条件下で、塩酸による還流及びイオン交換水による煮沸を行い、フッ素化されたＥＴＦＥ−ｇ−ＰＳｔ−Ｓ膜を得た。
【００８８】
（参考例５）
実施例１の（１）と同一の手順に従い、ＥＴＦＥ−ｇ−ＰＳｔ膜を作製した。次に、この膜に対し、参考例２と同一条件下で、フッ素ガスによるフッ素化処理を行った。次いで、参考例２と同一条件下で、塩酸による還流及びイオン交換水による煮沸を行った。さらに、膜を６０℃で１２時間真空乾燥した。
【００８９】
次に、この膜に対し、実施例１の（２）と同一の手順に従い、スルホン酸基を導入し、フッ素化されたＥＴＦＥ−ｇ−ＰＳｔ−Ｓ膜を得た。
【００９０】
参考例２、実施例３、実施例４、参考例５で得られた膜について、実施例１と同一条件下で固体高分子型燃料電池セルの作製及び耐久試験を行った。図２に、耐久時間と開回路電圧の関係を示す。なお、図２には、比較例１で得られた膜の結果も併せて示した。
【００９１】
希釈されたフッ素ガスを用いてフッ素化処理した参考例２、実施例３、実施例４、参考例５の場合、初期状態の開回路電圧は、０．９４〜０．９５Ｖであり、比較例１と同等であった。一方、７０００分後の開回路電圧は、０．８４Ｖを越えており、いずれも比較例１より向上した。特に、フッ素化処理の前に非プロトン化処理を行った実施例３、４の場合、７０００分後の開回路電圧は、０．８７Ｖを越えていた。
【００９２】
また、図３に、実施例４及び比較例１で得られた膜の赤外吸収スペクトルを示す。図３より、実施例４で得られた膜は、比較例１で得られた膜に比して、グラフトしたスチレンのα位の−ＣＨに由来する２９２５ｃｍ^−１付近のピークが減少していることがわかる。このピークの減少は、フッ素ガス処理によって、炭化水素骨格のフルオロカーボン骨格への変換が進行していることを示していると考えられる。
【００９３】
炭化水素系電解質を直接、フッ素化処理した場合、電解質基の脱落が生ずる場合がある。フッ素化処理の前に非プロトン化処理を行うことによって、耐久性に優れ、かつ高い電気伝導度を有する高耐久高分子電解質が得られるのは、フッ素化処理の際に生ずる電解質基の脱落を抑制しながら、炭化水素骨格のフルオロカーボン骨格への変換率を高くすることができるためと考えられる。
【００９４】
（参考例６）
実施例１の（１）及び（２）と同一の手順に従い、ＥＴＦＥ−ｇ−ＰＳｔ−Ｓ膜を作製した。この膜１ｇを、アルゴン雰囲気下において、５００ｍｌの乾燥テトラヒドロフランと４ｍｍｏｌのＮ−フルオロ−４，６−ビス（トリフルオロメチル）ピリジニウム−２−スルホネートとの混合溶液中に室温で１時間浸漬した。
【００９５】
次に、膜を溶液から取り出し、６０℃で１２時間真空乾燥した。次いで、膜を１リットルの５Ｎ塩酸中で２時間還流し、プロトン交換を行った。さらに、膜を１リットルのイオン交換水中で１時間煮沸する処理を３回繰り返すことにより、フッ素化されたＥＴＦＥ−ｇ−ＰＳｔ−Ｓ膜を得た。
【００９６】
（実施例７）
実施例１の（１）及び（２）と同一の手順に従い、ＥＴＦＥ−ｇ−ＰＳｔ−Ｓ膜を作製した。この膜１ｇを１リットルの五塩化リン／オキシ塩化リン混合溶液（５塩化リン／オキシ塩化リンの体積比（ｖｏｌ．／ｖｏｌ．）＝３／７）中に９０℃で６時間浸漬し、スルホン酸基をスルホニルクロライド基に変換した。さらに、膜を溶液から取り出し、６０℃で１２時間真空乾燥した。
【００９７】
次に、膜を溶液から取り出し、６０℃で１２時間真空乾燥した。次いで、この膜１ｇを、参考例６と同一条件下で、フッ素化処理を行った。さらに、参考例６と同一条件下で、真空乾燥、５Ｎ塩酸による還流及びイオン交換水による煮沸を行うことにより、フッ素化されたＥＴＦＥ−ｇ−ＰＳｔ−Ｓ膜を得た。
【００９８】
参考例６、実施例７で得られた膜について、実施例１と同一の条件下で固体高分子型燃料電池セルの作製及び耐久試験を行った。図４に、耐久時間と開回路電圧の関係を示す。なお、図４には、比較例１で得られた膜の結果も併せて示した。
【００９９】
フッ素化剤を用いてフッ素化処理された参考例６、実施例７の場合、初期状態の開回路電圧は、約０．９５Ｖであり、比較例１と同等であった。一方、７０００分後の開回路電圧は、０．８７Ｖを越えており、いずれも比較例１より向上した。また、フッ素化処理の前に非プロトン化処理を行った実施例７の場合、７０００分後の開回路電圧は、参考例６より若干向上した。
【０１００】
（参考例８）
実施例１の（１）及び（２）と同一の手順に従い、ＥＴＦＥ−ｇ−ＰＳｔ−Ｓ膜を作製した。この膜（６ｃｍ×６ｃｍ）を５％のフッ酸水溶液に浸漬し、陽極電流密度０．３Ａ／ｄｍ^２、槽電圧５Ｖ、浴温５℃の条件下で１０分間通電を行った。なお、陽極及び陰極には、それぞれニッケルを用いた。次に、処理後の膜を１リットルの１Ｎ塩酸中で煮沸する処理を２回繰り返した。さらに、この膜を１リットルのイオン交換水により煮沸するする処理を２回繰り返すことにより、フッ素化されたＥＴＦＥ−ｇ−ＰＳｔ−Ｓ膜を得た。
【０１０１】
参考例８で得られた膜について、実施例１と同一の条件下で固体高分子型燃料電池セルの作製及び耐久試験を行った。図５に、耐久時間と開回路電圧の関係を示す。なお、図５には、比較例１で得られた膜の結果も併せて示した。電解フッ素化を用いてフッ素化処理された参考例８の場合、初期状態の開回路電圧は、約０．９４Ｖであり、比較例１と同等であった。一方、７０００分後の開回路電圧は、０．８６Ｖ以上を越えており、比較例１より向上した。
【０１０２】
また、表２に、参考例８及び比較例１で得られた膜の面方向及び垂直方向の電気伝導度を示す。一般に、膜の電気的特性が等方的である場合には、膜の電気伝導度は方向によらずほぼ等しくなり、膜表面に絶縁層が形成されている場合には、膜の電気伝導度は方向によって変化する。参考例８で得られた膜の場合、その電気伝導度は、方向によって大きな差はなく、等方的であることがわかる。
【０１０３】
【表２】

【０１０４】
以上、本発明の実施の形態について詳細に説明したが、本発明は、上記実施の形態に何ら限定されるものではなく、本発明の要旨を逸脱しない範囲内で種々の改変が可能である。
【０１０５】
例えば、上記実施の形態では、主に膜状に成形された固体高分子電解質又は固体高分子化合物に対して本発明を適用した例について説明したが、膜以外の形状を備えた固体高分子電解質又は固体高分子化合物に対しても本発明を同様に適用することができる。
【０１０６】
また、本発明に係る高耐久高分子電解質の製造方法により得られる高耐久性高分子電解質は、単独で種々の用途に使用することができるが、上記高耐久高分子電解質を膜状に成形し、これと他の電解質膜とを積層して用いたり、あるいは、上記高耐久高分子電解質と他の電解質とを混合して使用することもできる。
【０１０７】
さらに、本発明に係る高耐久高分子電解質の製造方法により得られる高耐久性高分子電解質は、固体高分子型燃料電池に用いられる電解質膜として特に好適であるが、本発明の用途はこれに限定されものではなく、各種電解装置、センサ類等の各種電気化学デバイスに用いられる電解質としても使用することができる。
【０１０８】
【発明の効果】
本発明に係る高耐久性高分子電解質の製造方法により得られる高耐久性高分子電解質は、炭化水素骨格から変換されたフルオロカーボン骨格を備えているので、耐久性が高いという効果がある。また、本発明に係る高耐久高分子電解質の製造方法は、炭化水素骨格を備えた固体高分子電解質を出発原料に用いているので、低コストであるという効果がある。さらに、出発原料として固体高分子電解質を用いる場合において、炭化水素骨格をフルオロカーボン骨格に変換する前に、電解質基をハライド基又は金属塩に変換しているので、耐久性及び電気伝導性に優れた高耐久高分子電解質が得られるという効果がある。
【図面の簡単な説明】
【図１】 実施例１及び比較例１で得られた膜の耐久時間と開回路電圧の関係を示す図である。
【図２】 参考例２、実施例３、実施例４、参考例５及び比較例１で得られた膜の耐久時間と開回路電圧の関係を示す図である。
【図３】 実施例４及び比較例１で得られた膜の赤外吸収スペクトルを示す図である。
【図４】 参考例６、実施例７及び比較例１で得られた膜の耐久時間と開回路電圧の関係を示す図である。
【図５】 参考例８及び比較例１で得られた膜の耐久時間と開回路電圧の関係を示す図である。[0001]
BACKGROUND OF THE INVENTION
  The present invention is a highly durable polymer electrolysis.QualityIn more detail, the electrolyte membrane used in various electrochemical devices such as fuel cells, water electrolysis devices, hydrohalic acid electrolysis devices, salt electrolysis devices, oxygen and / or hydrogen concentrators, humidity sensors, gas sensors, etc. High durability polymer electrolysis suitable asQualityIt relates to a manufacturing method.
[0002]
[Prior art]
  The solid polymer electrolyte is a solid polymer material having an electrolyte group such as a sulfonic acid group in a polymer chain. Since the solid polymer electrolyte has a property of binding firmly to specific ions or selectively permeating cations or anions, it is formed into particles, fibers or membranes, electrodialysis, It is used for various applications such as diffusion dialysis and battery diaphragm.
[0003]
  In various electrochemical devices such as a polymer electrolyte fuel cell and a water electrolysis apparatus, the polymer electrolyte is used in the form of a membrane electrode assembly (MEA) in which a membrane is formed and electrodes are bonded to both sides thereof. . As a solid polymer electrolyte membrane for an electrochemical device used under harsh conditions, a perfluoro electrolyte membrane represented by Nafion (registered trademark, manufactured by DuPont) is generally used. The use of hydrogen-based electrolyte membranes is also being studied.
[0004]
  Examples of studies on hydrocarbon electrolytes include cross-linked polystyrene graft resin membranes (Swiss Patent Appl. 02 636 / 93-6) into which sulfonic acid groups have been introduced, and polyethersulfone resins into which sulfonic acid groups have been introduced (Japanese Patent Application Laid-Open No. Hei 10). -45913) and the like are known. Japanese Patent Laid-Open No. 2000-11756 mixed a hydrocarbon-based electrolyte with a compound containing phosphorus such as polyvinylphosphonic acid or phosphonic acid-type polyethersulfone in order to improve the oxidation resistance of the hydrocarbon-based electrolyte. Solid polymer electrolytes have been disclosed by the present applicant.
[0005]
  In the polymer electrolyte fuel cell, the electrode generally includes a catalyst layer made of carbon carrying a catalyst such as a solid polymer electrolyte and platinum, and a diffusion layer for supplying reaction gas and electrons to the catalyst layer. It has a two-layer structure. The catalyst layer is a part that becomes a reaction field of the electrode reaction, and in order to continuously advance the reaction, it is necessary to maintain a three-phase interface in which the three phases of the reaction gas, the catalyst, and the electrolyte coexist. Therefore, a water-repellent substance such as tetrafluoroethylene may be added to the catalyst layer in order to impart water repellency that can sufficiently secure a three-phase interface.
[0006]
  Further, in order to impart water repellency to the catalyst layer, the electrode part of MEA produced according to a conventional method was impregnated with a vinylidene fluoride polymer (PVdF) / n-methylpyrrolidone (NMP) solution and dried. A method of fluorinating PVdF by leaving it in a mixed gas atmosphere of 0.5 mol% fluorine gas and 99.5 mol% helium gas is also known (Japanese Patent Laid-Open No. 2001-283866).
[0007]
[Problems to be solved by the invention]
  In the case of a solid polymer fuel cell or a water electrolysis device, peroxide is generated by a side reaction of an electrode reaction in a catalyst layer formed at the interface between a solid polymer electrolyte membrane and an electrode. The generated peroxide becomes a peroxide radical while diffusing, and causes a deterioration reaction of the solid polymer electrolyte membrane (oxidation reaction by the peroxide radical). Therefore, in a polymer electrolyte fuel cell and a water electrolysis device, a perfluoro-based electrolyte membrane having excellent oxidation resistance is generally used.
[0008]
  The perfluoro-based electrolyte has a very high chemical stability because it has a fluorocarbon skeleton. In addition to the electrolyte membrane of the fuel cell or the water electrolysis device described above, the perfluoroelectrolyte is a salt electrolysis device or a hydrohalic acid electrolysis device. It is also used as an electrolyte membrane. In addition, it is widely applied to humidity sensors, gas sensors, oxygen concentrators, etc. by utilizing high proton conductivity. However, perfluoro-based electrolytes are disadvantageous in that they are difficult to manufacture and are very expensive.
[0009]
  On the other hand, hydrocarbon electrolytes have the advantage of being easy to manufacture and low in cost compared to perfluoro electrolytes represented by Nafion. However, conventional hydrocarbon electrolytes have a problem that they are easily eroded by peroxide radicals generated by electrode reactions and have low oxidation resistance. The reason for this is that the hydrocarbon skeleton constituting the hydrocarbon-based electrolyte is easily subjected to an oxidation reaction by a peroxide radical. In particular, since peroxide radicals are generated on the film surface, how to ensure oxidation resistance on the film surface has been a problem.
[0010]
  On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 2000-11756, when a compound containing phosphorus is mixed in a hydrocarbon-based electrolyte, the oxidation reaction of the hydrocarbon skeleton can be suppressed. However, in order to improve the durability and reduce the cost of various electrochemical devices such as solid polymer fuel cells and water electrolysis devices, it is desired to further improve the oxidation resistance of the hydrocarbon-based electrolyte.
[0011]
  The problem to be solved by the present invention is to suppress corrosion caused by peroxide radicals, to have higher durability than conventional hydrocarbon electrolytes, and at the same time, low cost and high durability polymer electrolysis.QualityIt is to provide a manufacturing method.
0012]
[Means for Solving the Problems]
  To solve the above problems, A method for producing a highly durable polymer electrolyte according to the present inventionLaw isAnd a first fluorination step of converting a part or all of the hydrocarbon skeleton constituting the solid polymer electrolyte into a fluorocarbon skeleton.e,Before the first fluorination step, a part or all of the electrolyte group of the solid polymer electrolyte is converted to a halide group or a metal salt, and after the first fluorination step, the halide group Or a protonation step of converting the metal salt into an electrolyte group.The gist.
0013]
  A solid polymer electrolyte having a hydrocarbon skeleton is easier to manufacture and less expensive than a perfluoro-based electrolyte. Therefore, if a solid polymer electrolyte having a hydrocarbon skeleton is first manufactured and then part or all of the hydrocarbon skeleton is converted to a fluorocarbon skeleton, a solid polymer electrolyte having excellent durability can be manufactured at low cost. Can do. Further, if the electrolyte group is converted to a halide group or a metal salt before fluorination of the hydrocarbon skeleton, a highly durable polymer electrolyte having excellent durability and high electric conductivity can be obtained.
0014]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described in detail. High durability polymer electrolyte according to the present inventionDurable polymer electrolyte obtained by the manufacturing method ofHas a fluorocarbon skeleton converted from a hydrocarbon skeletonThe
0015]
  As described later, such a highly durable polymer electrolyte uses a solid polymer electrolyte having a hydrocarbon skeleton as a starting material.Can be manufacturedThe
0016]
  In the present invention, a solid polymer used as a starting materialElectrolytesIsAn electrolyte group was introduced into one of the solid polymer compounds having a hydrocarbon skeletonSay things.the aboveSolid polymer compoundIt has a hydrocarbon skeleton (C—H bond) in any of the polymer chains,It may include only a hydrocarbon skeleton, or may include both a hydrocarbon skeleton and a fluorocarbon skeleton (C—F bond)..
0017]
  Specific examples of the solid polymer compound include polysulfone resin, polyether sulfone resin, polyether ether ketone resin, polycarbonate resin, polyester carbonate resin, polyarylate resin, polyoxybenzoyl resin, polybenzimidazole resin, polyester ketone resin, Chain-type phenol formaldehyde resin, cross-linked phenol formaldehyde resin, urea formaldehyde resin, melamine formaldehyde resin, linear polystyrene resin, cross-linked polystyrene resin, linear (polytrifluorostyrene) resin, cross-linked (polytrifluorostyrene) Resin, poly (2,3-diphenyl-1,4-phenylene oxide) resin, poly (phenylene oxide) resin, poly (allyl ether ketone) resin, poly (arylene ether) Rusulfone) resin, poly (phenylquinosanline) resin, poly (benzylsilane) resin, ethylenetetrafluoroethylene copolymer-graft-polystyrene resin, polyvinylidene fluoride-graft-polystyrene resin, polytetrafluoroethylene-graft-polystyrene resin , Polyimide resin, polyamide resin, polyetherimide resin, polyamideimide resin, polyester resin, polyurethane resin, polysiloxane resin, polysulfide resin, polyacetal resin, polyparaphenylene derivative resin, polyphenylene sulfide resin, and the like.
0018]
  In addition, a wholly aromatic resin or semi-aromatic resin having an aromatic ring in the main chain is composed of phenylene, biphenylene, naphthalene, etc.₂-, -O-, -S-, -S-S-, -C (O)-, -C (CH₃)₂-, -C (CF₃)₂-, An imide, an amide, a sulfonamide, an ester, a sulfone ester, urethane, urea, and the like may be a copolymer bonded through one or more functional groups. The semi-aromatic resin may contain an alkyl group or an alkylene chain in the middle of the main chain. Further, it may be a polyphosphazene derivative having a phosphazene structure in the main chain. Further, the polymer may be a block copolymer having various polymer segments, a starburst dendrimer, or a polymer blend.
0019]
  Among them, solid polymer compounds or solid polymer electrolytes in which styrene is graft-polymerized to a polymer chain partially containing a fluorocarbon skeleton, and solid polymer compounds or solid polymer electrolytes partially containing an aromatic ring are inexpensive. It is particularly suitable as a starting material because it has sufficient strength when thinned, and the conductivity can be easily controlled by adjusting the type and amount of electrolyte groups.
0020]
  As an example of a solid polymer compound in which styrene is graft-polymerized to a polymer chain partially containing a fluorocarbon skeleton, an ethylenetetrafluoroethylene copolymer is used as a main chain, and polystyrene capable of introducing an electrolyte group is used as a side chain. And an ethylene tetrafluoroethylene resin graft copolymer (ethylene tetrafluoroethylene copolymer-graft-polystyrene resin). Examples of solid polymer compounds partially containing an aromatic ring include polyethersulfone resins and polyetheretherketone resins.
0021]
  The type of the electrolyte group previously introduced into the solid polymer electrolyte or the electrolyte group subsequently introduced into the solid polymer compound (hereinafter collectively referred to as “electrolyte group”) is not particularly limited. However, it is selected according to the application of the highly durable polymer electrolyte and the required characteristics.
0022]
  Preferred examples of the electrolyte group include a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, a phosphoric acid group, and a sulfonimide group. The highly durable polymer electrolyte may contain any one of these electrolyte groups, or may contain two or more of them. In order to obtain a highly durable polymer electrolyte having high electrical conductivity, the electrolyte group is preferably a strong acid group, and particularly preferably a sulfonic acid group. The electrolyte group may be introduced into any part of the main chain or side chain of the solid polymer compound.
0023]
  The introduction rate of the electrolyte group may be adjusted depending on the application, usage status, type of electrolyte group, and the like. Specifically, the introduction rate of the electrolyte group is preferably 150 g / equivalent to 5000 g / equivalent, more preferably 200 g / equivalent to 2000 g / equivalent in terms of equivalent weight. When the equivalent weight is less than 150 g / equivalent, swelling due to water or a solvent may become excessively large, or the strength may be extremely reduced. On the other hand, if the equivalent weight exceeds 5000 g / equivalent, the electrical conductivity is lowered and the resistance loss is increased, which is not preferable. The introduction rate of the electrolyte group is 1 × 10 in terms of the electrical conductivity of the highly durable polymer electrolyte in the water-containing state.^-2S / cm or more is preferable, more preferably 5 × 10^-2S / cm or more.
0024]
  As a method for converting a hydrocarbon skeleton to a fluorocarbon skeleton, specifically, a method in which a solid polymer electrolyte or a solid polymer compound is brought into contact with a gas containing a fluorine gas, a solid polymer electrolyte or a solid polymer compound is fluorinated. There are a method of bringing into contact with a gas or a solution containing an agent, a method of electrolytic fluorination of a solid polymer electrolyte or a solid polymer compound, and the like. This point will be described later.
0025]
  A part of the hydrocarbon skeleton constituting the solid polymer electrolyte or the solid polymer compound may be converted into a fluorocarbon skeleton, or all may be converted into a fluorocarbon skeleton.
0026]
  For example, in polymer electrolyte fuel cells, water electrolysis devices, etc., it is considered that peroxide radicals are generated on the membrane surface of the electrolyte membrane, and oxidation by peroxide radicals proceeds from the membrane surface toward the inside. . Therefore,ObtainedWhen a highly durable polymer electrolyte is molded into a film and used for these applications, it is preferable that at least the hydrocarbon skeleton on the surface of the film is converted to a fluorocarbon skeleton. When the fluorocarbon skeleton is arranged on the film surface, the peroxide radical is discharged out of the system together with the reaction gas before reacting with the film, so that deterioration of the entire film can be suppressed.
0027]
  On the other hand, when used in an environment where peroxide radicals are randomly generated in the membrane, such as when the electrolyte membrane is heated while immersed in a peroxide solution, the solid polymer electrolyte or solid polymer It is preferable that all of the hydrocarbon skeleton constituting the compound is converted to a fluorocarbon skeleton.
0028]
  the aboveSince the high durability polymer electrolyte uses a solid polymer electrolyte or solid polymer compound having a hydrocarbon skeleton as a starting material, the cost is lower than that of a perfluoro-based electrolyte. Moreover, since the fluorocarbon skeleton converted from the hydrocarbon skeleton is provided, the oxidation resistance is improved as compared with the conventional hydrocarbon electrolyte.
0029]
  Therefore, if this is applied to, for example, a polymer electrolyte fuel cell or a water electrolysis device, decomposition of the hydrocarbon skeleton by peroxide radicals generated by electrode reaction and performance degradation due to this can be suppressed. Further, the durability is improved and the operation can be performed for a long time as compared with the case where a conventional hydrocarbon electrolyte membrane is used.
0030]
  Less thanThe method for producing a highly durable polymer electrolyte according to the present inventionIn detailexplain. The present inventionThe fruitThe manufacturing method according to the embodiment includes a non-protonation step, a first fluorination step, and a protonation step.
0031]
  First, the non-protonation process will be described. The non-protonation step is a step of converting a part or all of the electrolyte group of the solid polymer electrolyte into a halide group or a metal salt before the first fluorination step described later.
0032]
  “Converting an electrolyte group to a halide group” means replacing the —OH group at the terminal of the electrolyte group with a halogen such as —F, —Cl, —Br, —I or the like. In addition, “converting an electrolyte group to a metal salt” means a proton H at the end of the electrolyte group.⁺Is replaced with a metal ion. Specifically, the metal ion replacing the proton is Li⁺, Na⁺, K⁺Alkali metal ions such as Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺Alkaline earth metal ions such as Cu²⁺, Fe²⁺, Ni²⁺Transition metal ions such as are suitable.
0033]
  The conversion of the electrolyte group to the halide group is performed by immersing the solid polymer electrolyte in a treatment solution containing a substance having a property of donating a halide (hereinafter referred to as “halide donor”), or a halide donor. It is preferable to perform the treatment by bringing a treatment gas containing a solid polymer electrolyte into contact therewith.
0034]
  Specifically, the conversion of the electrolyte group to the halide group is performed by a method of immersing in phosphorus pentachloride, phosphorus oxychloride, or a mixed solution thereof, a method of reacting with thionyl chloride after converting the electrolyte group to a pyridine salt, and an electrolyte. It is preferable to use a method of reacting with a bromine gas, iodine gas or the like after replacing the proton of the group with an alkali metal.
0035]
  The conversion of the electrolyte group into a metal salt is performed by immersing the solid polymer electrolyte in a treatment solution containing a substance having a property of donating metal ions (hereinafter referred to as “metal ion donor”), Or it is preferable to carry out by making the process gas containing a metal ion donor contact a solid polymer electrolyte.
0036]
  The treatment solution or treatment gas containing a metal ion donor is specifically an aqueous alkali metal hydroxide solution such as sodium hydroxide or potassium hydroxide, Mg (OH)₂, Ca (OH)₂Alkali earth metal hydroxide aqueous solution such as Fe (OH)₂, Cu (OH)₂A transition metal hydroxide aqueous solution such as is suitable.
0037]
  The processing conditions such as concentration of halide donor or metal donor contained in the processing solution or processing gas, processing temperature, processing time, processing pressure, etc. are the type of halide donor or metal donor, the material of the solid polymer electrolyte, The optimum one is selected according to the processing conditions of the first fluorination step. Further, by selecting the treatment conditions, a part of the electrolyte group can be converted into a halide group or a metal salt, or the whole can be converted into a halide group or a metal salt. In order to obtain a highly durable polymer electrolyte having excellent durability and high electrical conductivity, it is preferable that all of the electrolyte groups are converted to halide groups or metal salts.
0038]
  For example, when a solid polymer electrolyte membrane having a sulfonic acid group is immersed in a mixed solution of phosphorus pentachloride / phosphorus oxychloride to convert the sulfonic acid group to a sulfonyl chloride group, phosphorus pentachloride / phosphorus oxychloride in the mixed solution The volume ratio (vol./vol.) Is preferably 1/10 or more and 4 or less, and more preferably 1/5 or more and 1 or less. The temperature of the mixed solution is preferably 30 ° C. or higher and 150 ° C. or lower, and more preferably 50 ° C. or higher and 130 ° C. or lower. The treatment time is selected according to the composition, temperature, etc. of the treatment solution so that the conversion rate of the sulfonic acid group to the sulfonyl chloride group becomes a predetermined value.
0039]
  Further, for example, when a solid polymer electrolyte membrane having a sulfonic acid group is immersed in an aqueous sodium hydroxide solution to convert the sulfonic acid group into a sodium salt, the concentration of sodium hydroxide is preferably 0.01 N or more and 20 N or less. More preferably, it is 0.1N or more and 10N or less. The temperature of the aqueous solution is preferably 0 ° C. or higher and 100 ° C. or lower, and more preferably 25 ° C. or higher and 100 ° C. or lower. Also in this case, the treatment time is selected according to the composition of the treatment liquid, the temperature, and the like so that the conversion rate of the sulfonic acid group to the sodium salt becomes a predetermined value.
0040]
  In addition, when the solid polymer electrolyte is directly fluorinated, the electrical conductivity may be reduced as compared with the case of performing the non-protonation treatment. Deprotonation treatment has the effect of suppressing the decrease in electrical conductivity in a system in which the decrease in electrical conductivity due to such fluorination treatment occurs.The
0041]
  Next, the first fluorination step will be described. The first fluorination step is a step of converting part or all of the hydrocarbon skeleton constituting the solid polymer electrolyte into a fluorocarbon skeleton. There are the following methods for converting (fluorinating) a hydrocarbon skeleton into a fluorocarbon skeleton.
0042]
  In the first method, a solid polymer electrolyte or a solid polymer electrolyte in which an electrolyte group is converted to a halide group or a metal salt (hereinafter referred to as “precursor”) is contacted with a processing gas containing fluorine gas. Is the method. When a treatment gas containing fluorine gas is brought into contact with the solid polymer electrolyte or a precursor thereof, a hydrogen atom bonded to a carbon atom can be replaced with a fluorine atom.
0043]
  The fluorination treatment of the solid polymer electrolyte or its precursor with a treatment gas containing fluorine gas may be performed by enclosing both in a sealed container, or the solid polymer electrolyte while flowing the treatment gas at a constant flow rate. Or you may carry out by making it contact with the precursor. Further, the processing gas may contain only fluorine gas, or may be diluted with an inert gas such as argon gas or nitrogen gas.
0044]
  Processing conditions such as the concentration of fluorine gas contained in the processing gas, the pressure, temperature, and contact time of the processing gas, the material of the solid polymer electrolyte, the presence or absence of a non-protonation treatment, the characteristics required for a highly durable polymer electrolyte, etc. Select the best one according to your needs. Further, by selecting the treatment conditions, the fluorocarbon skeleton can be introduced only on the surface or can be introduced uniformly throughout.
0045]
  In general, since fluorine gas has high reactivity, the treatment time can be shortened as the concentration of the fluorine gas in the treatment gas is increased or the pressure and / or temperature of the treatment gas is increased, but the reaction proceeds vigorously.
0046]
  In order to obtain a high-quality, highly durable polymer electrolyte in a relatively short time, the fluorine gas concentration is preferably 0.001 vol% or more and 100 vol% or less, more preferably 0.01 vol% or more and 100 vol% or less. is there. The pressure of the processing gas is 0 Pa or more and 500 kPa (about 5 kg / cm²) Or less, more preferably 100 Pa (about 0.001 kg / cm²) 200 kPa (approx. 2 kg / cm)²) Furthermore, the temperature of the processing gas is preferably −189 ° C. or more and 400 ° C. or less, more preferably −100 ° C. or more and 100 ° C. or less. The treatment time is selected according to the concentration of the fluorine gas, the temperature of the treatment gas, the pressure, etc. so that the conversion rate of the hydrocarbon skeleton to the fluorocarbon skeleton becomes a predetermined value.
0047]
  The second method is a method in which a solid polymer electrolyte or a precursor thereof is contacted with a fluorinating agent. When a fluorinating agent is brought into contact with the solid polymer electrolyte or a precursor thereof, a hydrogen atom bonded to a carbon atom can be replaced with a fluorine atom.
0048]
  The “fluorinating agent” refers to a substance having a property of chemically converting a hydrocarbon skeleton to a fluorocarbon skeleton and other than fluorine gas. For that purpose, the fluorinating agent contains N in the molecule.⁺It is preferable to use an electrophilic fluorinating agent having a -F bond.
0049]
  Specific examples of the fluorinating agent include N-fluoro-4,6-dimethylpyridinium-2-sulfonate, N-fluoro-4-methylpyridinium-2-sulfonate, and N-fluoro-5- (trifluoromethyl) pyridinium. -2-sulfonate, N-fluoro-6- (trifluoromethyl) pyridinium-2-sulfonate, N-fluoro-4,6-bis (trifluoromethyl) pyridinium-2-sulfonate, N, N'-difluoro-2 , 2'-bipyridinium bis (tetrafluoroborate), N-fluoro-2,4,6-trimethylpyridinium tetrafluoroborate, N-fluoro-2,4,6-trimethylpyridinium trifluoromethanesulfonate, N-fluoropyridinium tetra Fluoroborate, N-fluoropyridi Ium trifluoromethanesulfonate, N- fluoro-2,6-dichloro pyridinium tetrafluoroborate, N- fluoro-2,6-dichloro pyridinium trifluoromethanesulfonate, etc., and derivatives thereof are preferred
0050]
  The fluorinating agent may be brought into contact with the solid polymer electrolyte or a precursor thereof in either a liquid or gas state. In addition, the fluorinating agent may be used alone, or may be used by diluting with an appropriate diluent or diluent gas. Specifically, the diluent is preferably tetrahydrofuran, acetonitrile, dichloromethane, diethyl ether, dimethylformamide, or the like. Further, as the dilution gas, specifically, an inert gas such as nitrogen is suitable.
0051]
  Treatment conditions such as the type and concentration of the fluorinating agent, the pressure, temperature, and time when contacting with the fluorinating agent are required for the material of the solid polymer electrolyte, the presence or absence of a non-protonation treatment, and the highly durable polymer electrolyte. Select the optimal one according to the characteristics. Further, by selecting the treatment conditions, the fluorocarbon skeleton can be introduced only on the surface or can be introduced uniformly throughout.
0052]
  In order to obtain a high-quality highly durable polymer electrolyte in a relatively short time and at a low cost using a treatment solution containing a fluorinating agent, the concentration of the fluorinating agent in the treatment solution is 0.001 mol / 1 to 20 mol / l is preferable, and 0.01 to 10 mol / l is more preferable. Further, the temperature of the treatment solution is preferably from −110 ° C. to 160 ° C., more preferably from 0 ° C. to 100 ° C. The treatment time is selected according to the concentration of the fluorinating agent, the temperature of the treatment solution, etc. so that the conversion rate of the hydrocarbon skeleton to the fluorocarbon skeleton becomes a predetermined value.
0053]
  In order to obtain a high-quality highly durable polymer electrolyte in a relatively short time and at a low cost using a treatment gas containing a fluorinating agent, the concentration of the fluorinating agent in the treatment gas is 0.1 vol%. The amount is preferably 100 vol% or less, and more preferably 1 vol% or more and 100 vol% or less. The pressure of the processing gas is 0 Pa or more and 1 MPa (about 10 kg / cm²) Or less, more preferably 100 Pa to 500 kPa (about 5 kg / cm²) Furthermore, the temperature of the processing gas is preferably −100 ° C. or higher and 200 ° C. or lower, and more preferably −50 ° C. or higher and 100 ° C. or lower. Also in this case, the treatment time is selected according to the concentration of the fluorinating agent, the pressure of the treatment gas, the temperature, etc. so as to obtain a predetermined conversion rate.
0054]
  The third method is a method of electrolytic fluorination of a solid polymer electrolyte or a precursor thereof. “Electrolytic fluorination” means that a solid polymer electrolyte or a precursor thereof is immersed in an electrolytic solution containing a fluorine supplying compound and energized between electrodes. When an anode, a cathode and a solid polymer electrolyte or a precursor thereof are immersed in an electrolytic solution and a predetermined voltage is applied between the electrodes, hydrogen atoms bonded to carbon atoms can be replaced with fluorine atoms.
0055]
  The “fluorine supplying compound” refers to a compound having a property of donating a fluorine atom in an environment to which an electric field is applied. Specifically, the hydrofluoric acid compound is preferably anhydrous hydrofluoric acid.
0056]
  The concentration of the fluorine supply compound in the electrolytic solution is preferably 50 mol% or more. If the concentration of the fluorine supply compound is less than 50 mol%, the current efficiency is undesirably lowered. The concentration of the fluorine supply compound is more preferably 80 mol% or more.
0057]
  The reaction temperature is preferably 0 ° C. or higher and 30 ° C. or lower. If the reaction temperature is less than 0 ° C., the reaction rate decreases, such being undesirable. On the other hand, if the reaction temperature exceeds 30 ° C., the reaction becomes violent and side reactions are caused, which is not preferable. The reaction temperature is more preferably 0 ° C. or higher and 20 ° C. or lower.
0058]
  The anode current density is 0.1 A / dm²3.0 A / dm or more²The following is preferred. Anode current density is 0.1 A / dm²If it is less than 1, the reaction rate is lowered, which is not preferable. On the other hand, the anode current density is 3.0 A / dm²Exceeding this is not preferable because the reaction becomes violent and a side reaction occurs. The anode current density is more preferably 0.1 A / dm.²2.0 A / dm or more²It is as follows.
0059]
  The cell voltage is preferably 2.0 V or more and 10.0 V or less. If the cell voltage is less than 2.0 V, the reaction rate decreases, which is not preferable. On the other hand, if the cell voltage exceeds 10.0 V, the reaction becomes violent and side reactions are caused, which is not preferable. The cell voltage is more preferably 2.0 V or more and 8.0 V or less.
0060]
  Nickel is preferably used for the anode. In addition, nickel, iron or the like is preferably used for the cathode. Furthermore, when the electrical conductivity of the electrolytic solution is insufficient, it is preferable to add a conductivity increasing agent to the electrolytic solution as necessary. Specifically, the conductivity increasing agent is preferably an alkali metal fluoride such as NaF or KF, a C1-C18 perfluorosulfonic acid, a C1-C18 perfluorocarboxylic acid, or the like.
0061]
  Next, the protonation process will be described. The protonation step is a step of converting a halide group or a metal salt into an electrolyte group after the first fluorination step. In order to convert a halide group or metal salt into an electrolyte group, the precursor is immersed in an appropriate acid aqueous solution (for example, hydrochloric acid aqueous solution) for a predetermined time and then boiled with ion-exchanged water, or simply boiled with ion-exchanged water. There are a method and a method in which the precursor is immersed in an alkali metal hydroxide aqueous solution (for example, NaOH aqueous solution, KOH aqueous solution, etc.) for a predetermined time, and then immersed in an acid aqueous solution for a predetermined time.
0062]
  As the protonation treatment method, an optimum method is selected according to the ease of proton exchange of the halide group or metal salt. For example, when the electrolyte group is converted to a functional group that is relatively easy to exchange protons, such as a chloride group or a metal salt, it is preferable to perform proton exchange by acid treatment + boiling in water. On the other hand, when the electrolyte group is converted to a functional group that is relatively difficult to exchange protons such as a fluoride group, it is preferable to perform proton exchange by alkali metal hydroxide aqueous solution treatment + acid treatment.
0063]
  When the solid polymer electrolyte is directly fluorinated without performing a non-protonation treatment, the protonation treatment can be omitted. In addition, since some electrolyte groups may be fluoride groups during the fluorination treatment, the protonation treatment is performed even when the non-protonation treatment is not performed, so that a complete proton type is obtained. It is desirable.
0064]
  Next, the operation of the method for producing a highly durable polymer electrolyte according to the present invention will be described. When a solid polymer electrolyte having a hydrocarbon skeleton or a precursor thereof is brought into contact with a treatment gas containing a fluorine gas, or a treatment gas or treatment solution containing a fluorinating agent, or subjected to an electrolytic fluorination treatment, a hydrocarbon is generated by a chemical reaction. A hydrogen atom bonded to the skeleton is replaced with a fluorine atom. Further, by selecting the treatment conditions, part or all of the hydrocarbon skeleton can be converted into a fluorocarbon skeleton.
0065]
  The polymer electrolyte thus obtained uses a hydrocarbon-based electrolyte or compound as a starting material, and is therefore less expensive than a perfluoro-based electrolyte. Further, since at least a part of the hydrocarbon skeleton is converted to the fluorocarbon skeleton, the oxidation resistance is improved as compared with the conventional hydrocarbon electrolyte.
0066]
  Therefore, if this is applied to, for example, a polymer electrolyte fuel cell or a water electrolysis device, decomposition of the hydrocarbon skeleton by peroxide radicals generated by electrode reaction and performance degradation due to this can be suppressed. Further, the durability is improved and the operation can be performed for a long time as compared with the case where a conventional hydrocarbon electrolyte membrane is used.
0067]
  In addition, before the fluorination treatment of the solid polymer electrolyte, the electrolyte group is subjected to a non-protonation treatment.ByAs compared with the case where the solid polymer electrolyte is directly fluorinated, a highly durable polymer electrolyte having excellent durability and high electric conductivity can be obtained.
0068]
【Example】
Example 1
(1) Production of ethylenetetrafluoroethylene-graft-polystyrene membrane (hereinafter referred to as “ETFE-g-PSt membrane”)
  First, an ethylenetetrafluoroethylene copolymer film (ETFE film) having a thickness of 50 μm and a size of 50 mm × 50 mm is irradiated with an electron beam of 2 MeV and 20 kGy under dry ice cooling to generate radicals inside the ETFE film. It was.
0069]
  This ETFE membrane was stored under dry ice cooling, returned to room temperature, and then immediately immersed in an excess amount of styrene monomer (containing 6% divinylbenzene). Next, the inside of the reaction vessel was purged with nitrogen, followed by heat treatment at 60 ° C. for 60 hours to introduce polystyrene graft chains into ETFE. After the reaction, the non-grafted components (styrene monomer and homopolymer) were extracted and removed by refluxing with chloroform and dried under reduced pressure at 80 ° C. The graft ratio of the obtained ETFE-g-PSt film was 40%. The graft ratio was calculated by the following equation (1).
0070]
[Expression 1]
    Graft rate (%) = (W_ETFE-g-PSt-W_ETFE) X100 / W_ETFE
        However, W_ETFE-g-PSt: Membrane weight after grafting reaction (g)
              W_ETFE      : Membrane weight before reaction (g)
0071]
(2) Preparation of sulfonic acid type ethylenetetrafluoroethylene-graft-polystyrene membrane (hereinafter referred to as “ETFE-g-PSt-S membrane”)
  The ETFE-g-PSt membrane was immersed in a mixed solution of 30 parts by weight of chlorosulfonic acid and 70 parts by weight of tetrachloroethane for 1 hour to introduce sulfonyl chloride groups to the styrene units of the membrane. After the reaction, the membrane was washed with ethanol to remove unreacted components, and an ETFE-g-PSt membrane into which a sulfonyl chloride group was introduced was obtained.
0072]
  Next, this membrane was immersed in a 1N aqueous potassium hydroxide solution and heated to reflux for 1 hour to hydrolyze the sulfonyl chloride group. Next, proton exchange of sulfonic acid groups was performed by boiling with 1N sulfuric acid for 1 hour. Further, the membrane was washed with distilled water and then dried under reduced pressure at 80 ° C. The equivalent weight of the obtained ETFE-g-PSt-S film was 450 g / eq.
0073]
  The equivalent weight EW was measured by the following procedure. That is, 0.1 to 0.2 g of the dried membrane was immersed in 20 ml of a 0.1N aqueous sodium hydroxide solution at room temperature for 12 hours to exchange sodium for sulfonic acid groups in the membrane. At the same time, a sodium hydroxide aqueous solution to which no membrane was added was prepared in the same manner as a blank.
0074]
  After immersion, the membrane was taken out from the sodium hydroxide solution, washed with distilled water, and the washing solution added to the immersion solution was used as a titration sample. Using an automatic titrator (Hiranuma Comtitite T-900), titrate the sample and blank with 0.5N hydrochloric acid, obtain the end point from the inflection point of the titration curve, and calculate the EW of the membrane by the following equation (2) did.
0075]
[Expression 2]
    EW (g / eq) =
        W / ((Q_blank-Q_sample) /1000×0.5×F_HCl)
        Where W: membrane weight (g)
              Q_blank: Titration volume to blank (ml)
              Q_sample: Titration volume to sample (ml)
              F_HCl: 0.5N hydrochloric acid titer
0076]
(3) Fluorination treatment of ETFE-g-PSt-S film
  1 g of ETFE-g-PSt-S membrane was placed in 1 liter of phosphorus pentachloride / phosphorus oxychloride mixed solution (phosphorus pentachloride / phosphorus oxychloride volume ratio (vol./vol.)=3/7) at 90 ° C. After immersing for 6 hours, the sulfonic acid group was converted to a sulfonyl chloride group. Further, the membrane was taken out from the solution, immersed in dried ethanol for 1 hour, and then vacuum-dried at 60 ° C. for 12 hours.
0077]
  Next, this film was left at 25 ° C. in 100% fluorine gas for 60 minutes. The membrane was then refluxed with 5N hydrochloric acid for 2 hours to perform proton exchange. Furthermore, the process of boiling the membrane in 1 liter of ion exchange water for 1 hour was repeated three times to obtain a fluorinated ETFE-g-PSt-S membrane.
0078]
(Comparative Example 1)
  The ETFE-g-PSt-S membrane produced according to the same procedure as (1) and (2) of Example 1 was used for the experiment as it was.
0079]
  Each of the membranes obtained in Example 1 and Comparative Example 1 was vacuum-dried at 60 ° C. for 12 hours, and then electrodes were joined to both surfaces of the membrane to produce a polymer electrolyte fuel cell. Furthermore, durability evaluation was performed using the obtained cell. The durability evaluation was performed under the conditions shown in Table 1 below. The evaluation was performed by leaving the circuit in an open circuit state for about 7000 minutes without monitoring the current, and monitoring the open circuit voltage at this time.
0080]
[Table 1]

0081]
  FIG. 1 shows the relationship between endurance time and open circuit voltage. Both films had an initial open circuit voltage of about 0.95V. However, in the case of Comparative Example 1 where the fluorination treatment was not performed, the open circuit voltage after 7000 minutes decreased to 0.81V. On the other hand, in the case of Example 1 in which the fluorination treatment was performed using fluorine gas, the open circuit voltage after 7000 minutes exceeded 0.87V.
0082]
  It is known that when the electrolyte membrane is deteriorated by peroxide radicals, the deteriorated material covers the catalyst surface and lowers the catalyst activity. The durability is improved by subjecting the hydrocarbon electrolyte to fluorination treatment because the hydrocarbon skeleton constituting the hydrocarbon electrolyte is converted to the fluorocarbon skeleton, and the oxidation resistance is improved. This is considered to be because the generation is suppressed.
0083]
(referenceExample 2)
  According to the same procedure as (1) and (2) of Example 1, an ETFE-g-PSt-S film was produced. Next, 1 g of this film was formed at room temperature with N₂Fluorine gas diluted with gas (N₂: 0.3kg / cm²(2.94 × 10⁴Pa), F₂: 0.1 kg / cm²(0.98 × 10⁴Pa)) for 5 minutes to react the membrane with fluorine gas. After the reaction, the membrane was refluxed in 1 liter of 5N hydrochloric acid for 2 hours. Furthermore, the process of boiling the membrane in 1 liter of ion exchange water for 1 hour was repeated three times to obtain a fluorinated ETFE-g-PSt-S membrane.
0084]
(Example 3)
  According to the same procedure as (1) and (2) of Example 1, an ETFE-g-PSt-S film was produced. 1 g of this membrane was immersed in 1 liter of 1N aqueous sodium hydroxide solution for 1 hour to replace the protons of the sulfonic acid groups with sodium ions. Subsequently, the process of boiling the membrane in 1 liter of ion exchange water for 1 hour was repeated three times. Further, the membrane was vacuum-dried at 60 ° C. for 12 hours.
0085]
  Next, for this membrane,referenceUnder the same conditions as in Example 2, fluorination treatment with fluorine gas was performed. further,referenceUnder the same conditions as in Example 2, refluxing with hydrochloric acid and boiling with ion-exchanged water were performed to obtain a fluorinated ETFE-g-PSt-S membrane.
0086]
Example 4
  According to the same procedure as (1) and (2) of Example 1, an ETFE-g-PSt-S film was produced. 1 g of this membrane was immersed in 1 liter of phosphorus pentachloride / phosphorus oxychloride mixed solution (volume ratio of phosphorus pentachloride / phosphorus oxychloride (vol./vol.)=3/7) at 90 ° C. for 6 hours to obtain sulfone. The acid group was converted to a sulfonyl chloride group. Further, the membrane was taken out from the solution and vacuum-dried at 60 ° C. for 12 hours.
0087]
  Next, for this membrane,referenceUnder the same conditions as in Example 2, fluorination treatment with fluorine gas was performed. further,referenceUnder the same conditions as in Example 2, refluxing with hydrochloric acid and boiling with ion-exchanged water were performed to obtain a fluorinated ETFE-g-PSt-S membrane.
0088]
(referenceExample 5)
  According to the same procedure as (1) of Example 1, an ETFE-g-PSt film was produced. Next, for this membrane,referenceUnder the same conditions as in Example 2, fluorination treatment with fluorine gas was performed. ThenreferenceUnder the same conditions as in Example 2, refluxing with hydrochloric acid and boiling with ion-exchanged water were performed. Further, the membrane was vacuum-dried at 60 ° C. for 12 hours.
0089]
  Next, in accordance with the same procedure as (2) of Example 1, a sulfonic acid group was introduced into this membrane to obtain a fluorinated ETFE-g-PSt-S membrane.
0090]
  referenceExample 2Example 3, Example 4, Reference ExampleThe membrane obtained in 5 was subjected to production and durability test of a polymer electrolyte fuel cell under the same conditions as in Example 1. FIG. 2 shows the relationship between endurance time and open circuit voltage. FIG. 2 also shows the results of the film obtained in Comparative Example 1.
0091]
  Fluorinated using diluted fluorine gasreferenceExample 2Example 3, Example 4, Reference ExampleIn the case of 5, the open circuit voltage in the initial state was 0.94 to 0.95 V, which was equivalent to Comparative Example 1. On the other hand, the open circuit voltage after 7000 minutes exceeded 0.84 V, and both improved from Comparative Example 1. In particular, in Examples 3 and 4 in which a non-protonation treatment was performed before the fluorination treatment, the open circuit voltage after 7000 minutes exceeded 0.87V.
0092]
  FIG. 3 shows infrared absorption spectra of the films obtained in Example 4 and Comparative Example 1. From FIG. 3, the film obtained in Example 4 is 2925 cm derived from —CH at the α-position of the grafted styrene as compared with the film obtained in Comparative Example 1.^-1It can be seen that nearby peaks are decreasing. This decrease in the peak is considered to indicate that the conversion of the hydrocarbon skeleton to the fluorocarbon skeleton proceeds by the fluorine gas treatment.
0093]
  When the hydrocarbon electrolyte is directly fluorinated, the electrolyte group may be removed. By performing a non-protonation treatment prior to the fluorination treatment, a highly durable polymer electrolyte having excellent durability and high electrical conductivity can be obtained by removing the electrolyte groups generated during the fluorination treatment. It is considered that the conversion rate of the hydrocarbon skeleton to the fluorocarbon skeleton can be increased while suppressing.
0094]
(referenceExample 6)
  According to the same procedure as (1) and (2) of Example 1, an ETFE-g-PSt-S film was produced. 1 g of this film was immersed in a mixed solution of 500 ml of dry tetrahydrofuran and 4 mmol of N-fluoro-4,6-bis (trifluoromethyl) pyridinium-2-sulfonate at room temperature for 1 hour under an argon atmosphere.
0095]
  Next, the membrane was removed from the solution and vacuum dried at 60 ° C. for 12 hours. The membrane was then refluxed in 1 liter of 5N hydrochloric acid for 2 hours for proton exchange. Furthermore, the process of boiling the membrane in 1 liter of ion exchange water for 1 hour was repeated three times to obtain a fluorinated ETFE-g-PSt-S membrane.
0096]
(Example 7)
  According to the same procedure as (1) and (2) of Example 1, an ETFE-g-PSt-S film was produced. 1 g of this membrane was immersed in 1 liter of phosphorus pentachloride / phosphorus oxychloride mixed solution (volume ratio of phosphorus pentachloride / phosphorus oxychloride (vol./vol.)=3/7) at 90 ° C. for 6 hours to obtain sulfone. The acid group was converted to a sulfonyl chloride group. Further, the membrane was taken out from the solution and vacuum-dried at 60 ° C. for 12 hours.
0097]
  Next, the membrane was removed from the solution and vacuum dried at 60 ° C. for 12 hours. Then, 1 g of this membranereferenceThe fluorination treatment was performed under the same conditions as in Example 6. further,referenceUnder the same conditions as in Example 6, vacuum drying, refluxing with 5N hydrochloric acid and boiling with ion-exchanged water were performed to obtain a fluorinated ETFE-g-PSt-S membrane.
0098]
  referenceExample 6,ExampleThe membrane obtained in 7 was subjected to the production of a polymer electrolyte fuel cell and the durability test under the same conditions as in Example 1. FIG. 4 shows the relationship between endurance time and open circuit voltage. FIG. 4 also shows the results of the film obtained in Comparative Example 1.
0099]
  Fluorinated with a fluorinating agentreferenceExample 6,ExampleIn the case of 7, the open circuit voltage in the initial state was about 0.95 V, which was equivalent to Comparative Example 1. On the other hand, the open circuit voltage after 7000 minutes exceeded 0.87 V, and both improved from Comparative Example 1. Further, in the case of Example 7 in which a non-protonation treatment was performed before the fluorination treatment, the open circuit voltage after 7000 minutes wasreferenceSlightly improved from Example 6.
[0100]
(referenceExample 8)
  According to the same procedure as (1) and (2) of Example 1, an ETFE-g-PSt-S film was produced. This film (6 cm × 6 cm) was immersed in a 5% hydrofluoric acid aqueous solution, and the anode current density was 0.3 A / dm.²Then, electricity was applied for 10 minutes under the conditions of a cell voltage of 5 V and a bath temperature of 5 ° C. Note that nickel was used for each of the anode and the cathode. Next, the treatment of boiling the treated membrane in 1 liter of 1N hydrochloric acid was repeated twice. Furthermore, the process of boiling this membrane with 1 liter of ion exchange water was repeated twice to obtain a fluorinated ETFE-g-PSt-S membrane.
[0101]
  referenceThe membrane obtained in Example 8 was subjected to the production and durability test of a polymer electrolyte fuel cell under the same conditions as in Example 1. FIG. 5 shows the relationship between endurance time and open circuit voltage. FIG. 5 also shows the result of the film obtained in Comparative Example 1. Fluorinated using electrolytic fluorinationreferenceIn the case of Example 8, the open circuit voltage in the initial state was about 0.94 V, which was equivalent to Comparative Example 1. On the other hand, the open circuit voltage after 7000 minutes exceeded 0.86 V or more, which was improved from Comparative Example 1.
[0102]
  In Table 2,referenceThe electric conductivity of the film | membrane direction obtained in Example 8 and Comparative Example 1 and the perpendicular direction is shown. In general, when the electrical characteristics of the film are isotropic, the electrical conductivity of the film is almost equal regardless of the direction, and when an insulating layer is formed on the film surface, the electrical conductivity of the film Changes with direction.referenceIn the case of the film obtained in Example 8, the electrical conductivity is isotropic with no significant difference depending on the direction.
[0103]
[Table 2]

[0104]
  The embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention.
[0105]
  For example, in the above-described embodiment, the example in which the present invention is applied to a solid polymer electrolyte or a solid polymer compound mainly formed in a film shape has been described. However, a solid polymer electrolyte having a shape other than a membrane has been described. Alternatively, the present invention can be similarly applied to solid polymer compounds.
[0106]
  Further, the highly durable polymer electrolyte according to the present inventionDurable polymer electrolyte obtained by the manufacturing method ofCan be used alone for various purposes,the aboveA highly durable polymer electrolyte is molded into a film, and this and other electrolyte membranes are laminated or used.the aboveA highly durable polymer electrolyte and other electrolytes can be mixed and used.
[0107]
  Furthermore, the highly durable polymer electrolyte according to the present inventionDurable polymer electrolyte obtained by the manufacturing method ofIs particularly suitable as an electrolyte membrane used in a polymer electrolyte fuel cell, but the application of the present invention is not limited to this, and as an electrolyte used in various electrochemical devices such as various electrolytic devices and sensors. Can also be used.
[0108]
【The invention's effect】
  High durability polymer electrolyte according to the present inventionDurable polymer electrolyte obtained by the manufacturing method ofHas a fluorocarbon skeleton converted from a hydrocarbon skeleton, and therefore has an effect of high durability. Further, the highly durable polymer electrolysis according to the present inventionQualityThe manufacturing method is a solid polymer electrolysis with a hydrocarbon skeleton.QualitySince it is used as a starting material, there is an effect of low cost. Furthermore, when using a solid polymer electrolyte as a starting material, convert the electrolyte group to a halide group or metal salt before converting the hydrocarbon skeleton to the fluorocarbon skeleton.BecauseThere is an effect that a highly durable polymer electrolyte excellent in durability and electric conductivity can be obtained.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the endurance time and open circuit voltage of the films obtained in Example 1 and Comparative Example 1. FIG.
[Figure 2]referenceExample 2Example 3, Example 4, Reference Example5 is a graph showing the relationship between the endurance time and the open circuit voltage of the films obtained in Comparative Example 1 and FIG.
3 is a diagram showing infrared absorption spectra of films obtained in Example 4 and Comparative Example 1. FIG.
[Fig. 4]referenceExample 6,Example7 is a graph showing the relationship between the endurance time of the films obtained in Example 7 and Comparative Example 1 and the open circuit voltage.
[Figure 5]referenceIt is a figure which shows the relationship between the durable time of the film | membrane obtained in Example 8 and Comparative Example 1, and the open circuit voltage.

Claims (1)

A first fluorination step of converting a part or all of the hydrocarbon skeleton constituting the solid polymer electrolyte into a fluorocarbon skeleton,
Before the first fluorination step, a non-protonation step of converting a part or all of the electrolyte group of the solid polymer electrolyte into a halide group or a metal salt;
After said first fluorination step, the method of producing a high durability polyelectrolyte example Bei the protonation step of converting the halide groups or the metal salt to the electrolyte based.

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