JP4032738B2 - Solid polymer electrolyte material, liquid composition, solid polymer fuel cell, fluoropolymer and fluoropolymer - Google Patents

Description

【００３１】
ここで、式（Ｉ）及び（ＩＩ）中、Ｒ^f16及びＲ^f17は同一でも異なっていてもよく、それぞれフッ素原子又はトリフルオロメチル基を示し、ｋ’は０又は１を示し、Ｙは式（２）に記載のＹと同義であり、Ｍは式（１）に記載のＭと同義である。
【００３２】
また、本発明は、パーフルオロ（３−ブテニルビニルエーテル）に基づく繰り返し単位と、上記式（ＩＩ）で表される含フッ素モノマーＤに基づく繰り返し単位とからなる共重合体であって、含フッ素モノマーＤに基づく繰り返し単位の含有率が１０〜７５モル％であり、かつ、数平均分子量が５０００〜５００００００であることを特徴とする含フッ素ポリマーを提供する。
【００３３】
更に、本発明は、パーフルオロ（２−メチレン−４−メチル−１，３−ジオキソラン）に基づく繰り返し単位と、上記式（ＩＩ）で表される含フッ素モノマーＤに基づく繰り返し単位とからなる共重合体であって、含フッ素モノマーＤに基づく繰り返し単位の含有率が１０〜７５モル％であり、かつ、数平均分子量が５０００〜５００００００であることを特徴とする含フッ素ポリマーを提供する。
【００３４】
これらの本発明の含フッ素ポリマーは、本発明の固体高分子電解質材料の中でも特にガス透過性が高くなっていると考えられるものであり、特に高いイオン伝導性も有する。更に、これらの繰り返し単位中の炭素鎖に結合したフッ素原子は撥水性に寄与している。そのため、上記の本発明の含フッ素ポリマーは、先に述べた電気化学プロセスに備えられるガス拡散電極又は高分子電解質膜の構成材料として好ましく使用することができる。また、従来のスルホン酸ポリマーよりも高い軟化温度を有し、燃料電池の高温運転に適している。
【００３５】
式（Ｉ）で表される繰り返し単位と、式（ＩＩ）で表される含フッ素モノマーＤに基づく繰り返し単位とからなる含フッ素ポリマーにおいて、含フッ素ポリマー中の含フッ素モノマーＤに基づく繰り返し単位の含有率が１０モル％未満であると、プロトン伝導性が小さくなるので好ましくない。一方、上記の含有率が７５モル％を超えると、ガス拡散性が小さくなるので好ましくない。そして、上記と同様の観点から、共重合体中の含フッ素モノマーＤに基づく繰り返し単位の含有率は、１５〜６０モル％であることがより好ましい。
【００３６】
更に、この含フッ素ポリマーの数平均分子量が５０００未満であると、膨潤度等の物性が経時的に変化するため耐久性が不十分になる。一方、数平均分子量が５００００００を超えると、溶液の調製が困難になる。そして、上記と同様の観点から、含フッ素ポリマーの数平均分子量は１００００〜３００００００であることがより好ましい。
【００３７】
また、パーフルオロ（３−ブテニルビニルエーテル）に基づく繰り返し単位と、式（ＩＩ）で表される含フッ素モノマーＤに基づく繰り返し単位とからなる含フッ素ポリマーも前述の式（Ｉ）で表される繰り返し単位を含む含フッ素ポリマーと同様にこの含フッ素ポリマー中の含フッ素モノマーＤに基づく繰り返し単位の含有率は、１０〜７５モル％であることが好ましく、１５〜６０モル％であることがより好ましい。更に、この含フッ素ポリマーの数平均分子量も５０００〜５００００００であることが好ましく、１００００〜３００００００であることがより好ましい。
【００３８】
また、パーフルオロ（２−メチレン−４−メチル−１，３−ジオキソラン）に基づく繰り返し単位と、式（ＩＩ）で表される含フッ素モノマーＤに基づく繰り返し単位とからなる含フッ素ポリマーも前述の式（Ｉ）で表される繰り返し単位を含む含フッ素ポリマーと同様にこの含フッ素ポリマー中の含フッ素モノマーＤに基づく繰り返し単位の含有率は、１０〜７５モル％であることが好ましく、１５〜６０モル％であることがより好ましい。更に、この含フッ素ポリマーの数平均分子量も５０００〜５００００００であることが好ましく、１００００〜３００００００であることがより好ましい。
【００３９】
【発明の実施の形態】
以下、本発明を固体高分子型燃料電池に適用した場合の好適な実施形態について詳細に説明する。
【００４０】
本発明の固体高分子型燃料電池は、アノードと、カソードと、アノードとカソードとの間に配置した構成を有している。ガス拡散電極であるカソード及びアノードは、何れもガス拡散層と、これらのガス拡散層に隣接した触媒層とからなる。ガス拡散層の構成材料としては、電子伝導性を有する多孔質体（例えば、カーボンクロスやカーボンペーパー）が使用される。
【００４１】
カソードの触媒層は、主として先に述べた本発明の固体高分子電解質材料（−ＳＯ₃Ｈ型）と触媒とが含有されており、電池出力の向上と、その高い電池出力を安定して得ることが可能な触媒層内の良好なイオン伝導性と撥水性の確保とガス拡散性の向上が図られている。
【００４２】
カソードの触媒層に含有される本発明の固体高分子電解質材料は、含フッ素モノマーＡに基づく繰り返し単位と、含フッ素モノマーＢに基づく繰り返し単位とを含む共重合体からなるが、含フッ素モノマーＡ、含フッ素モノマーＢともにパーフルオロモノマーであることが好ましい。特に、含フッ素モノマーＢが下記式（２）で表される化合物であることが好ましく、中でも特に式（６）で表される化合物が好ましい。
【００４３】
【化１１】

【００４４】
ここで、式（２）及び式（６）中、ｋは０〜２の整数、ｍは１〜１２の整数、ｋ’は０又は１を示し、Ｙはフッ素原子又はトリフルオロメチル基をそれぞれ示し、Ｘは前述の式（１）に記載のＸと同義である。このように、含フッ素モノマーＡと含フッ素モノマーＢとがともにパーフルオロモノマーであると、得られる固体高分子電解質材料の撥水性及び耐久性が向上する。また、含フッ素モノマーＢが式（２）で示される化合物であると、得られる固体高分子電解質材料は良好なイオン伝導性を示す。
【００４５】
そして、本発明における含フッ素モノマーＡとは、先に述べたように具体的には分子中に脂肪族環構造を有するモノマーと、環化重合性モノマーとの２種類のタイプがあるが、含フッ素モノマーＡに基づく繰り返し単位が下記式（３）〜（５）の何れかで表されることが好ましい。
【００４６】
【化１２】

【００４７】
【化１３】

【００４８】
ここで、式（３）中、ｐ、ｑ及びｒはそれぞれ独立に０又は１を示し、Ｒ^f1及びＲ^f2は同一でも異なっていてもよく、それぞれフッ素原子、炭素数１〜５のパーフルオロアルキル基又は炭素数１〜５のパーフルオロアルコキシ基の何れかを示し、Ｒ^f3は炭素数１〜３のパーフルオロアルキレン基であって、置換基として炭素数１〜５のパーフルオロアルキル基又は炭素数１〜５のパーフルオロアルコキシ基を有していてもよい。
【００４９】
また、式（４）中、ｓは０又は１を示し、Ｒ^f4、Ｒ^f5、Ｒ^f6及びＲ^f7は同一でも異なっていてもよく、それぞれフッ素原子又は炭素数１〜５のパーフルオロアルキル基の何れかを示し、Ｒ^f8はフッ素原子、炭素数１〜５のパーフルオロアルキル基又は炭素数１〜５のパーフルオロアルコキシ基を示す。ただし、上記のＲ^f4とＲ^f5とは、ｓ＝０のときに連結してスピロ環を形成してもよい。
【００５０】
更に、式（５）中、Ｒ^f9、Ｒ^f10、Ｒ^f11及びＲ^f12は同一でも異なっていてもよく、それぞれフッ素原子又は炭素数１〜５のパーフルオロアルキル基の何れかを示す。
【００５１】
前述の式（３）で示される繰り返し単位の構造は、環化重合性モノマーから形成することができ、Ｒ^f3で示されるパーフルオロアルキレン基には、置換基として炭素数１〜５のパーフルオロアルキル基又は炭素数１〜５のパーフルオロアルコキシ基が結合していてもよい。また、環化重合した場合、式（３）において、ｑ＝０のときｒ＝１であり、ｑ＝１のときｒ＝０である。当該繰り返し単位としては、具体的には、例えば、下記式（７）〜（２２）に示すものが挙げられる。
【００５２】
【化１４】

【００５３】
【化１５】

【００５４】
【化１６】

【００５５】
また、前述の式（４）で示される繰り返し単位の構造は、分子中に脂肪族環構造を有するモノマーから形成することが可能である。当該繰り返し単位としては、具体的には、例えば、下記式（２３）〜（３２）に示すものが挙げられる。更に、式（４）で示される繰り返し単位の構造において、ｓ＝０のときＲ^f4とＲ^f5とにより形成されるスピロ環が４〜６員環である場合、この環を構成する元素としてエーテル性酸素原子が含まれていてもよく、この環には置換基としてパーフルオロアルキル基が結合していてもよい。このような分子中に脂肪族環構造を有するモノマーに基づく繰り返し単位の構造としては、例えば、下記式（３３）に示すものが挙げられる。
【００５６】
【化１７】

【００５７】
【化１８】

【００５８】
更に、前述の式（５）で示される繰り返し単位の構造も、分子中に脂肪族環構造を有するモノマーから形成することが可能である。当該繰り返し単位としては、具体的には、例えば、下記式（３４）〜（３６）に示すものが挙げられる。
【００５９】
【化１９】

【００６０】
含フッ素モノマーＡに基づく繰り返し単位の中でも、特に式（７）、式（２３）、式（２４）、式（２９）及び式（３４）でそれぞれ表される繰り返し単位からなる群から選ばれる１種以上が好ましい。これらの繰り返し単位を固体高分子電解質材料を構成する共重合体中に導入するために原料として使用されるモノマー（含フッ素モノマーＡ）はそれぞれ以下のとおりである。式（７）：パーフルオロ（３−ブテニルビニルエーテル）、式（２３）：パーフルオロ（２，２−ジメチル−１，３−ジオキソール）、式（２４）：パーフルオロ（１，３−ジオキソール）、式（２９）：２，２，４−トリフルオロ−５−トリフルオロメトキシ−１，３−ジオキソール、式（３４）：パーフルオロ（２−メチレン−４−メチル−１，３−ジオキソラン）。
【００６１】
これらの繰り返し単位と、前述の式（６）で表されるモノマーに基づく繰り返し単位とを含む共重合体からなる固体高分子電解質材料は、イオン伝導性が高く、撥水性に優れかつ酸素透過性に優れるので特に好ましい。特に、上記共重合体のうち−ＳＯ₃Ｈ基を有するものを固体高分子型燃料電池のカソードの触媒層に含有させると、得られる固体高分子型燃料電池の出力を従来よりも高めることができる。
【００６２】
本発明の固体高分子電解質材料の中でも、前述の式（Ｉ）で表される繰り返し単位と、式（ＩＩ）で表される含フッ素モノマーＤに基づく繰り返し単位とから実質的になる共重合体であって、含フッ素モノマーＤに基づく繰り返し単位の含有率が１０〜７５モル％であり、かつ、数平均分子量が５０００〜５００００００である含フッ素ポリマーが好ましい。また、その他には、パーフルオロ（３−ブテニルビニルエーテル）に基づく繰り返し単位と、前述の式（ＩＩ）で表される含フッ素モノマーＤに基づく繰り返し単位とから実質的になる共重合体であって、含フッ素モノマーＤに基づく繰り返し単位の含有率が１０〜７５モル％であり、かつ、数平均分子量が５０００〜５００００００である含フッ素ポリマーも好ましい。
【００６３】
更に、その他には、パーフルオロ（２−メチレン−４−メチル−１，３−ジオキソラン）に基づく繰り返し単位と、前述の式（ＩＩ）で表される含フッ素モノマーＤに基づく繰り返し単位とから実質的になる共重合体であって、含フッ素モノマーＤに基づく繰り返し単位の含有率が１０〜７５モル％であり、かつ、数平均分子量が５０００〜５００００００である含フッ素ポリマーも好ましい。
【００６４】
そして更に、本実施形態のように本発明の固体高分子電解質材料を固体高分子型燃料電池の電解質材料として使用する場合、含フッ素モノマーＡに基づく繰り返し単位と含フッ素モノマーＢに基づく繰り返し単位とを含む共重合体の−ＳＯ₂Ｘ基が、−ＳＯ₃Ｈ基以外であるときは、酸型化処理をして−ＳＯ₃Ｈ基に変換してから使用する。なお、前駆体の−ＳＯ₂Ｆ基の部分の加水分解処理は、例えば、ＮａＯＨやＫＯＨ等の塩基の水溶液又は該塩基と水と水溶性有機溶媒との混合溶液を使用して−ＳＯ₃Ｎａ基、−ＳＯ₃Ｋ基等に変換する。これらの酸型化処理は、例えば、塩酸、硝酸や硫酸等の水溶液を使用し、−ＳＯ₃Ｈ基に変換する。
【００６５】
また、本発明の固体高分子電解質材料である共重合体の軟化温度は１００℃以上であることが好ましい。ここで、本発明における固体高分子電解質材料の軟化温度とは、固体高分子電解質材料の動的粘弾性の評価試験において、固体高分子電解質材料の温度を室温付近から徐々に昇温させながらその弾性率を測定した場合に、固体高分子電解質材料の弾性率が急激に低下しはじめるときの温度を示す。従って、本発明における軟化温度は通常ｔａｎδの値より求めるガラス転移温度とは異なり、一般に該ガラス転移温度よりも低い温度領域で観測される温度を示す。
【００６６】
この軟化温度は、具体的には熱的機械分析装置（ＴＭＡ）を用い、直径１ｍｍの石英プローブによるペネトレーション法により測定することができる。すなわち、測定する固体高分子電解質材料を溶液からキャストしてフィルムとし、このフィルムに対して石英プローブを当該フィルムの面の法線方向から接触させ、１〜１０℃／ｍｉｎの昇温速度で温度を上昇させてフィルムに対するプローブのめり込みによりフィルムの厚みが急激に減少しはじめる温度を軟化温度として計測する。
【００６７】
なお、この方法により得られる軟化温度の値が、先に述べたポリマーの弾性率の温度依存性のプロフィールに現れる急激な弾性率の低下が観測されはじめる温度の値に一致することを予め確認した。また、フィルムにかかるプローブの荷重が小さすぎる場合にはフィルムの熱膨張が観測されるが、荷重を最適化することにより支障なくフィルムの軟化温度におけるプローブのめり込みの度合いを計測することができる。
【００６８】
固体高分子型燃料電池の作動温度は一般に８０℃以下であるので、触媒層に含有される固体高分子電解質材料の軟化温度が１００℃以上であれば、電池の作動中において触媒層中の固体高分子電解質材料の膨潤度等の物性の経時的な変化を抑制することが可能となる。そのため、電池作動中における触媒層中の固体高分子電解質材料の耐久性が向上する。また、軟化温度が１００℃以上の固体高分子電解質材料をカソードの触媒層に加えて、アノードの触媒層、高分子電解質膜の材料として使用すれば、上記と同様に電池作動中におけるアノードの触媒層中の電解質材料或いは高分子電解質膜の耐久性が向上し、ひいては電池寿命を向上させることが可能となる。
【００６９】
更に、この場合には、高分子電解質膜にも軟化温度が１００℃以上の固体高分子電解質材料を用いることにより従来の固体高分子型燃料電池の作動温度を８０℃よりも高くすることができる。これにより、電池の排熱をより有効に利用することが可能となるとともに、電池の除熱が容易となるため作動中の電池の温度制御がより容易となる。
【００７０】
また、この場合には、アノード反応ガス中に含まれる一酸化炭素等による触媒被毒を軽減することが可能となり、この点においても電池寿命を向上させることが可能となる。更に、本発明の固体高分子電解質材料を固体酸触媒として使用する場合にも軟化温度を高くすることができれば反応温度を高くすることができるので、所望の反応をより高い温度領域において進行させることが可能となる。
【００７１】
高い軟化温度を有し、且つ、膜としての実用強度を得るためには、前述の式（Ｉ）で表される繰り返し単位と、式（ＩＩ）で表される含フッ素モノマーＤに基づく繰り返し単位と、テトラフルオロエチレンに基づく繰り返し単位から実質的になる共重合体であって、前述の式（Ｉ）で表される繰り返し単位が５〜７０モル％、好ましくは１０〜６０モル％、更に好ましくは２０〜６０モル％であり、テトラフルオロエチレンに基づく繰り返し単位が１０〜８５モル％、好ましくは１５〜７０モル％、更に好ましくは２０〜６０モル％であり、式（ＩＩ）で表される含フッ素モノマーＤに基づく繰り返し単位の含有率が５〜４０モル％、好ましくは１０〜３０モル％であり、かつ、数平均分子量が５０００〜５００００００である含フッ素ポリマーが特に好適である。
【００７２】
また、本発明の固体高分子電解質材料は、Ａ_Rが０．５〜２．５ミリ当量／ｇ乾燥樹脂（以下、ｍｅｑ．／ｇとする）であることが好ましい。固体高分子電解質材料のＡ_Rが０．５ｍｅｑ．／ｇ未満となると、固体高分子電解質材料の含水率が低下しそのイオン伝導性が低くなるので、固体高分子電解質材料を固体高分子型燃料電池の電極の触媒層の構成材料として使用すると、十分な電池出力を得ることが困難になる。
【００７３】
一方、固体高分子電解質材料のＡ_Rが２．５ｍｅｑ．／ｇを超えると、固体高分子電解質材料中のイオン交換基の密度が増大し、固体高分子電解質材料の強度が低くなり易い。また、固体高分子型燃料電池の電極の触媒層の構成材料として使用すると、含水率が高くなりすぎるために触媒層におけるガス拡散性或いは排水性が低下してフラッディングが発生し易くなる。なお、上記と同様の観点から本発明の固体高分子電解質材料のＡ_Rは０．７〜２．０ｍｅｑ．／ｇであることがより好ましく、０．９〜１．５ｍｅｑ．／ｇであることが更に好ましい。
【００７４】
更に、本発明の固体高分子電解質材料の数平均分子量は特に限定されず、用途に応じて共重合体の重合度を変化させることにより適宜設定してよいが、本実施形態のように固体高分子型燃料電池のカソードの触媒層の構成材料として使用する場合には、５０００〜５００００００であることが好ましく、１００００〜３００００００であることがより好ましい。固体高分子電解質材料の数平均分子量が５０００未満であると、膨潤度等の物性が経時的に変化するため耐久性が不十分になる。一方、数平均分子量が５００００００を超えると、溶液の調製が困難になる。
【００７５】
また、本発明の固体高分子電解質材料中の含フッ素モノマーＡに基づく繰り返し単位と含フッ素モノマーＢに基づく繰り返し単位との比率（物質量比）は特に限定されず、用途に応じて適宜設定してよいが、本実施形態のように固体高分子型燃料電池のカソードの触媒層の構成材料として使用する場合には、上記Ａ_Rの範囲に適合するように選定されるのが好ましい。
【００７６】
また、本発明の固体高分子電解質材料には、当該固体高分子電解質材料を構成する繰り返し単位として含フッ素モノマーＡに基づく繰り返し単位及び含フッ素モノマーＢに基づく繰り返し単位以外の他の繰り返し単位が強度の調整等の必要に応じて含有されていてもよい。このような他の繰り返し単位を与えるモノマーは特に限定されるものではないが、例えば、テトラフルオロエチレン、クロロトリフルオロエチレン、フッ化ビニリデン、ヘキサフルオロプロピレン、トリフルオロエチレン、フッ化ビニル、エチレン、下記式（３７）〜（４０）で表される含フッ素ビニル化合物等が挙げられる。
【００７７】
なお、得られる共重合体の強度を向上させる場合、これらのモノマーの中では、重合反応に対する活性の高さと、耐久性（パーフルオロ構造）と、入手の容易さとの観点からテトラフルオロエチレンを用いることが好ましい。
ＣＨ₂＝ＣＨＲ^f13 …（３７）
ＣＨ₂＝ＣＨＣＨ₂Ｒ^f13 …（３８）
【００７８】
【化２０】

【００７９】
ＣＦ₂＝ＣＦＯＲ^f14Ｚ …（４０）
【００８０】
ここで、式（３７）及び式（３８）中、Ｒ^f13は炭素数１〜１２のパーフルオロアルキル基を示す。また、式（３９）中、ａは０〜３の整数を示し、Ｗはフッ素原子又はトリフルオロメチル基を示し、Ｒ^f15は直鎖又は分岐構造を有する炭素数１〜１２のパーフルオロアルキル基を示す。更に、式（４０）中、Ｒ^f14は直鎖又は分岐構造を有する炭素数１〜１２のパーフルオロアルキレン基であって、エーテル結合性の酸素原子が含まれていてもよく、Ｚは−ＣＮ、−ＣＯＯＲ^f16（Ｒ^f16は炭素数１〜６のアルキル基を示す。）又は−ＣＯＦからなる群から選ばれる何れかを示す。
【００８１】
また、本発明の固体高分子電解質材料について、含フッ素モノマーＡに基づく繰り返し単位及び含フッ素モノマーＢに基づく繰り返し単位以外に他の繰り返し単位を含有させる場合、他の繰り返し単位の含有量は、固体高分子電解質材料の用途に応じて適宜設定してよい、本実施形態のように固体高分子型燃料電池のカソードの触媒層の構成材料として使用する場合には、固体高分子電解質材料を構成する共重合体中の当該他の繰り返し単位の含有量は３５質量％未満とすることが好ましい。この値が３５質量％を超えると、燃料電池の出力アップの効果が小さくなる。
【００８２】
更に、式（３９）で表される含フッ素ビニルエーテル化合物の中では、下記式（４１）〜（４３）で表される含フッ素ビニルエーテル化合物を用いることが好ましい。ただし、下記式（４１）〜（４３）中、ｂは１〜８の整数、ｄは１〜８の整数、ｅは２又は３をそれぞれ示す。
【００８３】
【化２１】

【００８４】
また、本発明におけるカソードの触媒層にそれぞれ含まれる触媒は特に限定されるものではないが、例えば、白金等の白金族金属又はその合金等をカーボンに担持した触媒が好ましい。
【００８５】
更に、カソードの触媒層において、触媒と固体高分子電解質材料との質量比の範囲は、触媒の質量（金属とカーボン担体をあわせた全質量）：固体高分子電解質材料の質量＝２０：８０〜９５：５であることが好ましく、３０：７０〜９０：１０であることがより好ましい。
【００８６】
ここで、固体高分子電解質材料に対する触媒の含有率が低すぎると、触媒量が少なくなるので反応サイトが不足する傾向がある。また、触媒を被覆する固体高分子電解質材料の被覆層の厚みが大きくなり固体高分子電解質材料中における反応ガスの拡散速度が小さくなる傾向がある。更に、反応ガスの拡散に必要な細孔が樹脂により塞がれてフラッディングの現象が生じ易くなるおそれがある。
【００８７】
一方、固体高分子電解質材料に対する触媒の含有率が高すぎると、触媒に対して当該触媒を被覆する固体高分子電解質材料の量が不足して反応サイトが少なくなり電池出力が低下する傾向がある。また、固体高分子電解質材料は、触媒層のバインダ及び触媒層と高分子電解質膜との接着剤としても機能するが、その機能が不十分となり触媒層構造を安定に維持できなくなる傾向が大きくなる。
【００８８】
また、この燃料電池のアノードの触媒層の構成は特に限定されず、従来の固体高分子型燃料電池のアノードの触媒層と同様の構成にでき、本発明の固体高分子電解質材料を含有していてもよく、他の樹脂を含有していてもよい。
【００８９】
更に、本発明におけるカソード及びアノードの触媒層の層厚は、１〜５００μｍであることが好ましく、５〜１００μｍであることがより好ましい。更に、本発明における触媒層には、必要に応じてＰＴＦＥ等の撥水化剤を含有させてもよい。ただし、撥水化剤は絶縁体であるためその量は少量であるほど望ましく、その添加量は３０質量％以下が好ましい。
【００９０】
また、本発明の固体高分子型燃料電池に使用する高分子電解質膜は、湿潤状態下で良好なプロトン伝導性を示すイオン交換膜が用いられ、耐久性の観点からパーフルオロポリマーからなるイオン交換膜が好ましい。高分子電解質膜を構成する固体高分子材料としては、例えば、本発明の固体高分子電解質材料を用いてもよく、従来の固体高分子型燃料電池に使用されているイオン交換樹脂等を用いてもよい。
【００９１】
以下、本発明において固体高分子電解質材料に用いる含フッ素ポリマーの製造方法の一例について説明する。先ず、含フッ素モノマーＢとしては、−ＳＯ₂Ｆ基又は−ＳＯ₂Ｃｌ基を有するものを用いる。含フッ素モノマーＡと含フッ素モノマーＢとの重合反応は、ラジカルが生起する条件のもとで行われるものであれば特に限定されない。例えば、バルク重合、溶液重合、懸濁重合、乳化重合、液体又は超臨界の二酸化炭素中の重合等により行なってもよい。
【００９２】
ラジカルを生起させる方法は特に限定されず、例えば、紫外線、γ線、電子線等の放射線を照射する方法を用いてもよく、通常のラジカル重合で用いられるラジカル開始剤を使用する方法を用いてもよい。重合反応の反応温度も特に限定されず、例えば、通常は１５〜１５０℃程度である。ラジカル開始剤を使用する場合、ラジカル開始剤としては、例えば、ビス（フルオロアシル）パーオキシド類、ビス（クロロフルオロアシル）パーオキシド類、ジアルキルパーオキシジカーボネート類、ジアシルパーオキシド類、パーオキシエステル類、アゾ化合物類、過硫酸塩類等が挙げられる。
【００９３】
溶液重合を行なう場合には、使用する溶媒は取り扱い性の観点から、通常は２０〜３５０℃の沸点を有していることが好ましく、４０〜１５０℃の沸点を有していることがより好ましい。そして、溶媒中に、含フッ素モノマーと含フッ素ビニル化合物とを所定量投入し、ラジカル開始剤等を添加してラジカルを生起させて重合を行なう。
【００９４】
ここで、使用可能な溶媒としては、例えば、（ｉ）パーフルオロトリブチルアミン、パーフルオロトリプロピルアミン等のポリフルオロトリアルキルアミン化合物、（ｉｉ）パーフルオロヘキサン、パーフルオロオクタン、パーフルオロデカン、パーフルオロドデカン、パーフルオロ（２，７−ジメチルオクタン）、２Ｈ，３Ｈ−パーフルオロペンタン、１Ｈ−パーフルオロヘキサン、１Ｈ−パーフルオロオクタン、１Ｈ−パーフルオロデカン、１Ｈ，４Ｈ−パーフルオロブタン、１Ｈ，１Ｈ，１Ｈ，２Ｈ，２Ｈ−パーフルオロヘキサン、１Ｈ，１Ｈ，１Ｈ，２Ｈ，２Ｈ−パーフルオロオクタン、１Ｈ，１Ｈ，１Ｈ，２Ｈ，２Ｈ−パーフルオロデカン、３Ｈ，４Ｈ−パーフルオロ（２−メチルペンタン）、２Ｈ，３Ｈ−パーフルオロ（２−メチルペンタン）等のフルオロアルカン、（ｉｉｉ）３，３−ジクロロ−１，１，１，２，２−ペンタフルオロプロパン、１，３−ジクロロ−１，１，２，２，３−ペンタフルオロプロパン、１，１−ジクロロ−１−フルオロエタン等のクロロフルオロアルカン、（ｉｖ）ヘキサフルオロプロペンの２量体、ヘキサフルオロプロペンの３量体等の分子鎖末端に二重結合を有しないフルオロオレフィン、（ｖ）パーフルオロデカリン、パーフルオロシクロヘキサン、パーフルオロ（１，２−ジメチルシクロヘキサン）、パーフルオロ（１，３−ジメチルシクロヘキサン）、パーフルオロ（１，３，５−トリメチルシクロヘキサン）、パーフルオロジメチルシクロブタン（構造異性を問わない）等のポリフルオロシクロアルカン、（ｖｉ）パーフルオロ（２−ブチルテトラヒドロフラン）等のポリフルオロ環状エーテル化合物、（ｖｉｉ）ｎ−Ｃ₃Ｆ₇ＯＣＨ₃、ｎ−Ｃ₃Ｆ₇ＯＣＨ₂ＣＦ₃、ｎ−Ｃ₃Ｆ₇ＯＣＨＦＣＦ₃、ｎ−Ｃ₃Ｆ₇ＯＣ₂Ｈ₅、ｎ−Ｃ₄Ｆ₉ＯＣＨ₃、ｉｓｏ−Ｃ₄Ｆ₉ＯＣＨ₃、ｎ−Ｃ₄Ｆ₉ＯＣ₂Ｈ₅、ｉｓｏ−Ｃ₄Ｆ₉ＯＣ₂Ｈ₅、ｎ−Ｃ₄Ｆ₉ＯＣＨ₂ＣＦ₃、ｎ−Ｃ₅Ｆ₁₁ＯＣＨ₃、ｎ−Ｃ₆Ｆ₁₃ＯＣＨ₃、ｎ−Ｃ₅Ｆ₁₁ＯＣ₂Ｈ₅、ＣＦ₃ＯＣＦ（ＣＦ₃）ＣＦ₂ＯＣＨ₃、ＣＦ₃ＯＣＨＦＣＨ₂ＯＣＨ₃、ＣＦ₃ＯＣＨＦＣＨ₂ＯＣ₂Ｈ₅、ｎ−Ｃ₃Ｆ₇ＯＣＦ₂ＣＦ（ＣＦ₃）ＯＣＨＦＣＦ₃等のヒドロフルオロエーテル類、（ｖｉｉｉ）フッ素含有低分子量ポリエーテル、（ｉｘ）tert−ブタノール等が挙げられる。なお、これらの溶媒は、単独で用いてもよいし、２種以上を混合して用いてもよい。
【００９５】
また、溶液重合を行なう場合に使用する溶媒の他の例としては、１，１，２−トリクロロ−１，２，２−トリフルオロエタン、１，１，１−トリクロロ−２，２，２−トリフルオロエタン、１，１，１，３−テトラクロロ−２，２，３，３−テトラフルオロプロパン、１，１，３，４−テトラクロロ−１，２，２，３，４，４−ヘキサフルオロブタン等のクロロフルオロカーボン類を挙げることができる。ただし、これらのクロロフルオロカーボン類は、技術的には使用できるが、地球環境に与える影響を考慮すると、その使用は好ましくない。
【００９６】
重合により得られる共重合体は−ＳＯ₂Ｆ基又は−ＳＯ₂Ｃｌ基を有しているので加水分解や必要に応じて酸型化処理を行い、−ＳＯ₃Ｍ基に変換する。
【００９７】
次に、本発明の固体高分子型燃料電池について、その製造方法の一例を説明するとともに本発明の液状組成物を固体高分子型燃料電池に適用する場合の好適な実施形態について説明する。本発明の固体高分子型燃料電池のカソード及びアノードの触媒層を有するガス拡散電極を作製するための方法は特に限定されず、公知の方法により作製することができる。
【００９８】
例えば、カソードの触媒層は、−ＳＯ₃Ｈ基を有する本発明の固体高分子電解質材料を分子中に水酸基を有する溶媒に溶解又は分散させた液状組成物に触媒を混合して調製した触媒層形成用の塗工液を用いて形成することができる。
【００９９】
本発明の固体高分子電解質材料は、−ＳＯ₃Ｍ基を有する場合、水酸基を有する有機溶媒に良好に溶解又は分散することができる。水酸基を有する有機溶媒は特に限定されないが、アルコール性の水酸基を有する有機溶媒が好ましい。
【０１００】
アルコール性の水酸基を有する有機溶媒としては、例えば、メタノール、エタノール、１−プロパノール、２−プロパノール、２，２，２−トリフルオロエタノール、２，２，３，３，３−ペンタフルオロ−１−プロパノール、２，２，３，３−テトラフルオロ−１−プロパノール、４，４，５，５，５−ペンタフルオロ−１−ペンタノール、１，１，１，３，３，３−ヘキサフルオロ−２−プロパノール、３，３，３−トリフルオロ−１−プロパノール、３，３，４，４，５，５，６，６，６−ノナフルオロ−１−ヘキサノール、３，３，４，４，５，５，６，６，７，７，８，８，８−トリデカフルオロ−１−オクタノール等が挙げられる。また、アルコール以外の有機溶媒としては、酢酸等のカルボキシル基を有する有機溶媒も使用できる。
【０１０１】
ここで、水酸基を有する有機溶媒は上記の溶媒を単独で用いてもよく、２種以上を混合して用いてもよく、更に、水又は他の含フッ素溶媒等と混合して用いてもよい。他の含フッ素溶媒としては、先に述べた固体高分子電解質材料の製造における溶液重合反応において、好ましい含フッ素溶媒として例示した含フッ素溶媒が例示される。
【０１０２】
なお、水酸基を有する有機溶媒を水又は他の含フッ素溶媒との混合溶媒として使用する場合、水酸基を有する有機溶媒の含有量は溶媒全質量に対して１０％以上であることが好ましく、２０％以上であることがより好ましい。また、この場合、はじめから固体高分子電解質材料を混合溶媒中に溶解又は分散させてもよく、また、固体高分子電解質材料を先ず水酸基を有する有機溶媒に溶解又は分散させた後、水又は他の含フッ素溶媒を混合してもよい。更に、このような溶媒に対する固体高分子電解質材料の溶解又は分散は、大気圧下又はオートクレーブなどで密閉加圧した条件のもとで、０〜２５０℃の温度範囲で行なうことが好ましく、２０〜１５０℃の範囲で行なうことがより好ましい。
【０１０３】
また、本発明の液状組成物中の固体高分子電解質材料の含有量は液状組成物全質量に対して１〜５０％であることが好ましく、３〜３０％であることがより好ましい。固体高分子電解質材料の含有量が１％未満であると、この液に触媒を混合することにより塗工液を調製し、これを用いてカソードの触媒層を作製するときに所望の厚みの触媒層を作製するのに塗工回数が多くなることや、このような塗工液は、多量の有機溶媒を含むためコストがかかりかつその除去作業の時間が長くなる等、製造作業を効率よく行ないにくい。一方、固体高分子電解質材料の含有量が５０％を超えると液状組成物の粘度が高くなりすぎて取扱いにくくなり易い。
【０１０４】
更に、液状組成物には本発明の固体高分子電解質材料に加え、これとは別の固体高分子電解質材料となる樹脂を含有させてもよく、この場合、液状組成物を原料として得られる触媒層のガス拡散性及び撥水性を十分に確保する観点から、液状組成物中の本発明の固体高分子電解質材料の含有量は液状組成物中の全ての固体高分子電解質材料の総質量に対して２０％以上であることが好ましく、５０％以上であることがより好ましい。
【０１０５】
そして、カソードの触媒層は、本発明の液状組成物に白金が担持されたカーボンブラック等の微粒子からなる触媒を混合して調製した触媒層形成用の塗工液を用いて、高分子電解質膜、ガス拡散層、又は、支持板上に厚さが均一になるように形成し、溶媒を乾燥除去後、必要に応じてホットプレスを施すなどすることにより作製できる。塗工液は所望により本発明の液状組成物と触媒とを混合した後、溶媒を留去して固形分を取り出し、別の溶媒に再分散することにより調製したものを用いてもよい。その再分散溶液は、通常前述のアルコール性溶媒から選択され、水を含んでいてもよい。このようにして、ガス拡散性及び撥水性に優れるカソードの触媒層が得られる。
【０１０６】
特に、ポリマー自体の軟化温度が１００℃以上である固体高分子電解質材料を含む液状組成物から塗工液を調製して触媒層を作製すると、層内のガス拡散性が顕著に向上する。固体高分子電解質材料の軟化温度が１００℃以上であると、塗工液から溶媒が徐々に揮発する際に固体高分子電解質材料が収縮しにくいため、固体高分子電解質材料の内部又は固体高分子電解質材料により被覆された触媒粒子の凝集体間に適度な大きさの細孔が形成されていくためであると考えられる。
【０１０７】
また、アノードの触媒層も上記のカソードの触媒層と同様にして形成することができる。ただし、アノードの触媒層形成用の塗工液は本発明の液状組成物を用いてもよく、従来の固体高分子電解質材料を所定の溶媒に溶解または分散させた液を用いて調製してもよい。
【０１０８】
そして、作製されたカソードの触媒層及びアノードの触媒層を高分子電解質膜とガス拡散層との間に配置することにより、固体高分子型燃料電池を作製できる。ここで、触媒層を高分子電解質膜上に形成した場合には、例えば、別途用意したガス拡散層を触媒層上に隣接して配置又は接合する。また、触媒層をガス拡散層上に形成し、ガス拡散電極を予め形成した場合には、例えば、別途用意した高分子電解質膜を触媒層に隣接して配置又は接合する。更に、触媒層を支持板上に形成した場合には、例えば、別途用意した高分子電解質膜に転写し、その後支持板を剥離して別途用意したガス拡散層を触媒層上に隣接して配置又は接合する。
【０１０９】
高分子電解質膜と触媒層、触媒層とガス拡散層の接合は、例えば、ホットプレスやロールプレスにより行ってもよい。このとき、パーフルオロスルホン酸ポリマー溶液等を接着剤に用いて非加熱により両者を接合させてもよい。
【０１１０】
また、先に述べたように、電池を構成する高分子電解質膜を本発明の固体高分子電解質材料を用いて作製してもよい。
【０１１１】
以上、本発明の好適な実施形態について詳細に説明したが、本発明は上記実施形態に限定されるものではない。例えば、上記の実施形態においては、アノード反応ガスとして水素を主成分とするガスを用いる場合の固体高分子型燃料電池について説明したが、本発明の固体高分子型燃料電池は、例えば、アノード反応ガスとしてメタノールガスをアノードに直接導入する構成のものであってもよい。
【０１１２】
また、上記の実施形態においては、本発明の固体高分子電解質材料を含む液状組成物を固体高分子型燃料電池の電極の触媒層に用いる場合について説明したが、他の用途にも使用できる。例えば、本発明の固体高分子電解質材料を用いて膜を形成する場合、１）食塩電解等に使用する陽イオン選択透過膜、２）水電解用の膜、３）過酸化水素製造、オゾン製造、排酸回収等に使用するプロトン選択透過膜、４）脱塩又は製塩に使用する電気透析用陽イオン交換膜等として各種の電気化学プロセスにおいて使用できる。
【０１１３】
更に、電気化学プロセス以外にも、本発明の固体高分子電解質材料を用いて膜を形成し、例えば、酸、塩基、及び塩類の分離精製に用いる拡散透析用の膜、蛋白質分離のための荷電型多孔膜（荷電型逆浸透膜、荷電型限外ろ過膜、荷電型ミクロろ過膜等）、除湿膜、加湿膜等にも使用できる。更に、本発明の固体高分子電解質材料は、例えば、リチウムイオン電池のポリマー電解質、固体酸触媒、陽イオン交換樹脂、修飾電極を用いたセンサー、空気中の微量イオンを除去するためのイオン交換フィルターやアクチュエーター等にも使用できる。
【０１１４】
【実施例】
以下、実施例及び比較例を挙げて本発明ついて更に詳しく説明するが、本発明はこれらの実施例に限定されるものではない。なお、以下の実施例及び比較例の説明において下記化合物を下記略号を用いて記載する。
ＰＳＶＥ：ＣＦ₂＝ＣＦＯＣＦ₂ＣＦ（ＣＦ₃）ＯＣＦ₂ＣＦ₂ＳＯ₂Ｆ、
ＰＳＶＥ−Ｈ：ＣＦ₂＝ＣＦＯＣＦ₂ＣＦ（ＣＦ₃）ＯＣＦ₂ＣＦ₂ＳＯ₃Ｈ、
ＢＶＥ：パーフルオロ（３−ブテニルビニルエーテル）、
ＰＤＤ：パーフルオロ（２，２−ジメチル−１，３−ジオキソール）、
ＭＭＤ：パーフルオロ（２−メチレン−４−メチル−１，３−ジオキソラン）
ＴＦＥ：テトラフルオロエチレン
ＩＰＰ：（ＣＨ₃）₂ＣＨＯＣ（＝Ｏ）ＯＯＣ（＝Ｏ）ＯＣＨ（ＣＨ₃）₂、
ＨＣＦＣ１４１ｂ：ＣＨ₃ＣＣｌ₂Ｆ、
ＨＣＦＣ２２５ｃｂ：ＣＣｌＦ₂ＣＦ₂ＣＨＣｌＦ。
【０１１５】
［合成例１］（ＰＤＤ／ＰＳＶＥ−Ｈ共重合体１）
容積０．２Ｌのステンレス製オートクレーブに、ＰＤＤ２６．０ｇ、ＰＳＶＥ１２７．８ｇ、ＩＰＰ０．４６ｇを入れ、オートクレーブ内の気体を窒素によりパージした後、窒素を全圧が０．３ＭＰａ（ゲージ圧）となるように導入した。次に、オートクレーブ内の温度を４０℃として、内容物を撹拌しながら重合を開始した。重合開始から１０時間後、オートクレーブを冷却し系内のガスをパージして重合を止め、ＨＣＦＣ２２５ｃｂで希釈後、ヘキサンに投入することでポリマーを沈殿させ、ヘキサンで２回、更にＨＣＦＣ１４１ｂで１回洗浄した。
【０１１６】
ろ過後、８０℃で１６時間、真空乾燥することにより、白色のポリマー４１．６ｇを得た。元素分析で硫黄の含有量を求め、ポリマー中のＰＤＤに基づく繰り返し単位とＰＳＶＥに基づく繰り返し単位とのモル比（ＰＤＤ／ＰＳＶＥ）とＡ_Rとを求めたところ、ＰＤＤ／ＰＳＶＥ＝５６．５／４３．５であり、Ａ_R＝１．３１ｍｅｑ．／ｇであった。また、ＧＰＣによりポリマーの数平均分子量を測定したところポリメタクリル酸メチル換算の数平均分子量は３．３万であった。重量平均分子量は５．６万であった。
【０１１７】
次に、得られたポリマーをＫＯＨの水／エタノール混合溶液に浸漬して加水分解処理し、次いで、希硫酸水溶液に浸漬して酸型化処理した。次に、ポリマーをイオン交換水により洗浄し乾燥した後、エタノールに溶解してポリマー（ＰＤＤ／ＰＳＶＥ−Ｈ共重合体１）１０質量％の透明なエタノール溶液を得た。
【０１１８】
上記のポリマーのエタノール溶液を使用してキャスト膜を作成し、先に述べた１ｍｍφ石英プローブによるペネトレーション法によりポリマーの軟化温度を測定した。先ず、ポリマーのエタノール溶液１０質量部とブタノール２質量部の混合溶液を調製し、この溶液を用いて室温でキャスト製膜し、１６０℃において３０分乾燥させることにより厚みが約２００μｍのキャスト膜を得た。次に、得られたキャスト膜をＴＭＡ（マックサイエンス社製）にセットした。
【０１１９】
そして昇温速度５℃／ｍｉｎでキャスト膜の温度を昇温させながら、キャスト膜と１ｍｍφ石英プローブとの接触部に対して０．２Ｈｚのｓｉｎカーブに基づく振動荷重（荷重振動範囲：１〜６ｇ、平均荷重：３．５ｇ）をかけて、キャスト膜の厚みの変化を測定した。そして、キャスト膜に対するプローブのめり込みにより膜の厚みが急激に減少しはじめる温度を軟化点として計測した。その結果、このポリマーの軟化温度は１５０℃であった。
【０１２０】
［合成例２］（ＰＤＤ／ＰＳＶＥ−Ｈ共重合体２）
容積０．２Ｌのステンレス製オートクレーブに、ＰＤＤ３６．４ｇ、ＰＳＶＥ１２３．１ｇ、ＩＰＰ０．４８ｇを入れ、合成例１と同様にして重合を開始した。重合開始から３．２時間後、オートクレーブを冷却し、系内のガスをパージして重合を止め、ＨＣＦＣ２２５ｃｂで希釈後ヘキサンに投入することで沈殿させ、ヘキサンで２回、更にＨＣＦＣ１４１ｂで１回洗浄した。
【０１２１】
ろ過後、８０℃で１６時間、真空乾燥することにより、白色のポリマー２５．３ｇを得た。得られたポリマーについて合成例１と同様に、加水分解、酸型化処理してＰＤＤ／ＰＳＶＥ−Ｈ共重合体２を得るとともに合成例１と同様のキャラクタリゼーションを行なった。その結果、ＰＤＤ／ＰＳＶＥ＝６９．８／３０．２、Ａ_R＝０．９９ｍｅｑ．／ｇ、ポリメタクリル酸メチル換算の数平均分子量：５．８万、重量平均分子量：９．５万、軟化温度：１８０℃であった。
【０１２２】
［合成例３］（ＢＶＥ／ＰＳＶＥ−Ｈ共重合体１）
窒素雰囲気下において、容積３００ｍＬのフラスコに、ＢＶＥ１２０．０ｇ、ＰＳＶＥ１２８．５ｇ、ＩＰＰ０．７６ｇを入れ、フラスコ内の温度を４０℃として、内容物を撹拌しながら重合を開始した。重合開始から１６．７時間後、フラスコ内を冷却して重合を止め、ヘキサンに投入することでポリマーを沈殿させ、さらにヘキサンで３回洗浄した。
【０１２３】
ろ過後、８０℃で１６時間、真空乾燥することにより、白色のポリマー４７．８ｇを得た。得られたポリマーについて合成例１と同様に、加水分解、酸型化処理してＢＶＥ／ＰＳＶＥ−Ｈ共重合体１を得るとともに合成例１と同様のキャラクタリゼーションを行なった。その結果、ＢＶＥ／ＰＳＶＥ＝６７．０／３３．０、Ａ_R＝０．９９ｍｅｑ．／ｇ、ポリメタクリル酸メチル換算の数平均分子量：２．９万、重量平均分子量４．２万、軟化温度：１１０℃であった。
【０１２４】
［合成例４］（ＢＶＥ／ＰＳＶＥ−Ｈ共重合体２）
窒素雰囲気下において、容積３００ｍＬのフラスコに、ＢＶＥ１５０．０ｇ、ＰＳＶＥ１０３．０ｇ、ＩＰＰ０．７７ｇをいれ、合成例３と同様にして重合を開始した。重合開始から１０．７時間後、フラスコ内を冷却して重合を止め、ヘキサンに投入することでポリマーを沈殿させ、ヘキサンで３回、さらにＨＣＦＣ１４１ｂで１回洗浄した。
【０１２５】
ろ過後、８０℃で１６時間、真空乾燥することにより、白色のポリマー３８．０ｇを得た。得られたポリマーについて合成例１と同様に、加水分解、酸型化処理してＢＶＥ／ＰＳＶＥ−Ｈ共重合体２を得るとともに合成例１と同様のキャラクタリゼーションを行なった。その結果、ＢＶＥ／ＰＳＶＥ＝７６．１／２３．９、Ａ_R＝０．７５ｍｅｑ．／ｇ、ポリメタクリル酸メチル換算の数平均分子量：３．８万、重量平均分子量：５．３万、軟化温度：１１０℃であった。
【０１２６】
［合成例５］（ＴＦＥ／ＰＳＶＥ−Ｈ共重合体）
固体高分子型燃料電池の電極の触媒層の材料又は高分子電解質膜の材料として従来より用いられている、ＴＦＥ／ＰＳＶＥ共重合体を公知の方法により製造した。得られたポリマーについて合成例１と同様に、加水分解、酸型化処理してＴＦＥ／ＰＳＶＥ−Ｈ共重合体を得るとともに合成例１と同様にしてキャラクタリゼーションを行なったところ、ＴＦＥ／ＰＳＶＥ＝８２．２／１７．８、Ａ_R＝１．１ｍｅｑ．／ｇ、軟化温度：８０℃であった。
【０１２７】
［合成例６］（ＭＭＤ/ＰＳＶＥ−Ｈ共重合体１）
０.２ＬのオートクレーブにＩＰＰ:０.６８ｇ、ＰＳＶＥ:２０７.１ｇ、ＭＭＤ:２０.０ｇを入れ、減圧脱気したあとに窒素で加圧パージを３回行い、窒素で全圧が０.１２ＭＰａ（ゲージ圧）となるように加圧した。４０℃に昇温し、２.５時間反応させた。重合溶液をヘキサンに注いでポリマーを凝集し、さらにヘキサンで３回洗浄した。室温で一晩、真空乾燥を行い、さらに８０℃で一晩真空乾燥を行った。収量：１６.９ｇ（収率：７.４％）。
【０１２８】
元素分析で硫黄の含有量を求め、ポリマー中のＭＭＤに基づく繰り返し単位とＰＳＶＥに基づく繰り返し単位とのモル比（ＭＭＤ／ＰＳＶＥ）とＡ_Rとを求めたところ、ＭＭＤ／ＰＳＶＥ＝７６．０／２４．０であり、Ａ_R＝０．８２ｍｅｑ．／ｇであった。また、ＧＰＣによりポリマーの数平均分子量を測定したところポリメタクリル酸メチル換算の数平均分子量は４．５万、重量平均分子量は７．０万であった。
【０１２９】
ポリマーをＫＯＨ／Ｈ₂Ｏ／ＤＭＳＯ＝１１／５９／３０(質量比)の溶液に浸漬し、９０℃で７日間保持した。室温に戻して水洗を行い、さらに９０℃で水に浸漬した。この水洗を３回繰り返した。さらに１ｍｏｌ／Ｌの塩酸に９０℃で1日浸漬し、室温に戻して水洗を行い、さらに９０℃で水に浸漬した。この水洗を３回繰り返した。８０℃で１６時間オーブン中で乾燥し、さらに８０℃で真空乾燥し、酸型化したポリマーを得た。
【０１３０】
合成例１と同様にしてこのポリマーの１０質量％のエタノール溶液を調製し、キャスト膜を作製した。キャスト膜の軟化温度は１３５℃であった。
【０１３１】
［合成例７］（ＭＭＤ/ＰＳＶＥ−Ｈ共重合体２）
仕込みのＰＳＶＥを２０７.１ｇ、ＭＭＤを１３.３ｇとし、窒素を導入して全圧を０．１１ＭＰａ（ゲージ圧）とし、反応時間を６時間とした以外は合成例６と同様にしてポリマー１９．６ｇを得た（収率：８.９％）。
【０１３２】
合成例６と同様にポリマー中のＭＭＤに基づく繰り返し単位とＰＳＶＥに基づく繰り返し単位とのモル比（ＭＭＤ／ＰＳＶＥ）とＡ_Rとを求めたところ、ＭＭＤ／ＰＳＶＥ＝６６．７／３３．３であり、Ａ_R＝１．０７ｍｅｑ．／ｇであった。また、ポリメタクリル酸メチル換算の数平均分子量は２．４万、重量平均分子量は３．９万であった。
【０１３３】
上記ポリマーを合成例６と同様にして酸型化し、ＭＭＤ／ＰＳＶＥ−Ｈ共重合体を得た。合成例１と同様にしてこのポリマーの９．６質量％のエタノール溶液を調製し、キャスト膜を作製した。キャスト膜の軟化温度は１２５℃であった。
【０１３４】
［合成例８］（ＴＦＥ／ＰＤＤ／ＰＳＶＥ−Ｈ共重合体）
０.２ＬのオートクレーブにＰＤＤを１４.３ｇ、ＰＳＶＥを５２.６ｇ、ＨＣＦＣ−２２５ｃｂを７６.９ｇ、ＩＰＰを０.３６ｇを入れ、凍結脱気した。ＴＦＥを５.９ｇ導入後、４０℃に昇温して重合を開始した。このとき圧力は０.２６ＭＰａ（ゲージ圧）であった。４０℃で１０時間反応させ、圧力が０.０７ＭＰａ（ゲージ圧）になったところで、反応を停止した。重合溶液をヘキサンに注いでポリマーを凝集し、ヘキサンで３回洗浄した。８０℃で一晩真空乾燥を行った。収量：２５.０ｇ（収率：３４.４％）。
【０１３５】
¹⁹Ｆ-ＮＭＲでポリマー組成を求めたところ、ＴＦＥ／ＰＤＤ／ＰＳＶＥ＝４２／３５／２２(モル比)であり、Ａ_Rは０．９８ｍｅｑ．／ｇであった。また、ＧＰＣによるポリメタクリル酸メチル換算の数平均分子量は５．３万、重量平均分子量は８．３万であった。
【０１３６】
１６０℃でポリマーをプレスして厚さ１００μｍのフィルムを作製した。このフィルムをＫＯＨ／Ｈ₂Ｏ／ＤＭＳＯ＝１１／５９／３０(質量比)の溶液に浸漬し、９０℃で１７時間保持して加水分解した。室温に戻して水洗を３回行った。さらに１ｍｏｌ／Ｌの硫酸に室温で２時間浸漬して水洗した。この硫酸浸漬と水洗を３回繰り返し、最後にさらに３回水洗を行った。８０℃で１６時間オーブン中で乾燥し、さらに８０℃で真空乾燥し、酸型の乾燥フィルムを得た。合成例１の手法により測定した軟化温度は１２０℃であった。引っ張り試験における最大点応力は６.１ＭＰａ、破断点伸度は３.０％であった。膜として充分な強度を有することが確認できた。
【０１３７】
上記ポリマーから合成例１と同様にして酸型化ポリマーの１４．５質量％エタノール溶液を調製することができた。
【０１３８】
なお、フィルムの引っ張り試験は、フィルムをＪＩＳ Ｋ−７１２７に規定される試験片タイプ２の形状（長さ：１５０ｍｍ、幅：１０ｍｍ、標線間距離：５０ｍｍ）に切り出し、チャック間初期距離：１００ｍｍ、引張速度５０ｍｍ／ｍｉｎ、２５℃、相対湿度５０％の条件下で行った。
【０１３９】
（実施例１）
実施例１の単位セルは、以下に説明する手順により作製した。先ず、Ｐｔ担持カーボン（Ｐｔ担持量：５４質量％）を、ＰＤＤ／ＰＳＶＥ−Ｈ共重合体１の１０質量％エタノール溶液に分散させた分散液（Ｐｔ担持カーボンの質量：上記共重合体の質量＝６：４）を調製した。次に、分散液を十分に撹拌した後、更に蒸発乾固して得られる固形物を粉砕した。次に、この粉末を２，２，３，３，３−ペンタフルオロ−１−プロパノール中に再分散させ、固形分濃度が５質量％であるカソードの触媒層形成用の塗工液を調製した。
【０１４０】
次に、Ｐｔ担持カーボン（Ｐｔ担持量：４０質量％）を、ＴＦＥ／ＰＳＶＥ−Ｈ共重合体（Ａ_R＝１．１ｍｅｑ．／ｇ）の９質量％エタノール溶液及びエタノールと混ぜて分散させ、更に水を加えて固形分濃度が８質量％であるアノードの触媒層形成用の塗工液（エタノールの質量：水の質量＝１：１、Ｐｔ担持カーボンの質量：上記共重合体の質量＝７：３）を調製した。
【０１４１】
また、アノード及びカソードのガス拡散層として、撥水性カーボンクロス（繊維織布）の片表面を撥水性カーボン粉末層（カーボンブラックとＰＴＦＥの混合物）で目詰めし、更にホットプレスを施して触媒層を形成するカーボン粉末層表面を平坦にした厚さ約３４０μｍのものを用意した。更に、高分子電解質膜として、スルホン酸型パーフルオロカーボン重合体からなる高分子電解質膜（商品名：フレミオンＨＲ、旭硝子社製、Ａ_R＝１．１ｍｅｑ．／ｇ、乾燥膜厚５０μｍ）を用意した。
【０１４２】
次に、上記ガス拡散層の撥水性カーボン粉末層側の面にカソードの触媒層形成用の塗工液をＰｔ量が０．８ｍｇ／ｃｍ²となるように一回塗布して乾燥させて触媒層を形成し、カソードを作製した。一方、アノードの触媒層形成用の塗工液をカソードと同様の手順で上記ガス拡散層シートの撥水性カーボン粉末層側の面にＰｔ量が０．５ｍｇ／ｃｍ²となるように一回塗布して乾燥させて触媒層を形成し、アノードを得た。
【０１４３】
次に、得られたカソード及びアノードを有効電極面積が２５ｃｍ²となるように切り出した。そして、カソード及びアノードともに触媒層側を内側に向けて対向させ、その間に高分子電解質膜を挟み込んだ状態でホットプレスすることでカソード及びアノードの各触媒層と高分子電解質膜とを接合させ、膜・電極接合体を作製した。
【０１４４】
（比較例１）
実施例１において調製したアノードの触媒層形成用の塗工液を用いて、アノードとカソードとの両方を作製した以外は、実施例１と同様にして膜・電極接合体を作製した。
【０１４５】
[電池特性試験]
上記の実施例１及び比較例１の各膜・電極接合体にガス流路の形成されたカーボン製のセパレータを装着して測定セルとし、電子負荷（高砂製作所社製，ＦＫ４００Ｌ）と直流電源（高砂製作所社製，ＥＸ７５０Ｌ）を用いて測定セルの電流電圧特性試験を行った。
測定条件は、水素導入口圧力；０．１５ＭＰａ、空気導入口圧力；０．１５ＭＰａ、測定セルの作動温度；８０℃とし、作動後１０時間経過後、出力電流密度をそれぞれ０．３Ａ/ｃｍ²、１．０Ａ/ｃｍ²としたときのセル電圧（ｉＲフリー）を測定した。また、この作動条件において水素利用率が７０％、空気利用率が４０％となように水素ガス及び空気の流量を調節した。その結果を表１に示す。
【０１４６】
【表１】

【０１４７】
【発明の効果】
本発明によれば、脂肪族環構造を有する繰り返し単位が固体高分子電解質材料となる共重合体中に導入されているので、良好なイオン伝導性、撥水性を有し、かつガス透過性に優れた固体高分子電解質材料と、これを含む液状組成物並びに高い電池出力を安定的に得ることのできる固体高分子型燃料電池を提供できる。
また、本発明の固体高分子電解質材料は軟化温度が従来のものよりも高いので固体高分子型燃料電池だけでなく、他の電気化学プロセスにおけるイオン選択透過膜、逆浸透膜、ろ過膜、隔膜等として応用する際にも、高い温度で使用することができる特徴を有する。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solid polymer electrolyte material, a liquid composition, a solid polymer fuel cell, and a fluorine-containing polymer applicable to them.
[0002]
[Prior art]
Solid polymer fuel cells are expected to be practically used as power sources for mobile vehicles such as electric vehicles and small cogeneration systems because they are easy to reduce in size and weight in addition to obtaining high battery characteristics. ing. The polymer electrolyte fuel cell currently under study has a low operating temperature range and it is difficult to use the exhaust heat. Therefore, the operating conditions of the anode reaction gas such as hydrogen and the cathode reaction gas such as air are high. Are required to have high power generation efficiency and high power density.
[0003]
Conventionally, in polymer electrolyte fuel cells, fine particles of a catalyst such as metal-supported carbon black coated with the same or different ion exchange resin as the polymer electrolyte membrane have been used as the constituent material of the electrode catalyst layer, so-called catalyst layer. The battery output is improved by three-dimensionalization of the reaction sites.
[0004]
However, under the operating conditions where the reaction rate of the cell reaction as described above is relatively high, the amount of water moving with the proton moving in the polymer electrolyte membrane from the anode toward the cathode, and the cathode The amount of water produced and condensed by the electrode reaction increases. For this reason, these waters are not quickly discharged from the cathode to the outside, and the reaction gas supply pores formed in the catalyst layer of the cathode are clogged by these waters, so-called flooding phenomenon easily occurs. It was.
[0005]
When such flooding occurs, supply of the cathode reaction gas to the reaction site of the catalyst layer is hindered, and a desired battery output cannot be stably obtained. Therefore, in order to improve the battery output and stably obtain the output, it is necessary to improve the gas diffusibility and water repellency without reducing the ionic conductivity in the electrode catalyst layer.
[0006]
In contrast, the ion exchange capacity of the ion exchange resin in the catalyst layer (hereinafter referred to as A _R Is intended to ensure gas diffusibility and water repellency in the catalyst layer, the water content of the ion exchange resin will be reduced, resulting in a decrease in ion conductivity and a decrease in battery output. Further, in this case, the gas permeability of the ion exchange resin is also lowered, so that the supply of gas supplied to the reaction site is delayed. As a result, the concentration overvoltage increases and the battery output decreases.
[0007]
On the other hand, the ion exchange resin A contained in the catalyst layer. _R Is intended to improve its ion conductivity and gas permeability, the water content of the ion exchange resin increases, and flooding is likely to occur, making it difficult to stably obtain high battery output. There was a problem.
[0008]
Therefore, JP-A-5-36418 discloses polytetrafluoroethylene (hereinafter referred to as PTFE), tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / perfluoro (alkyl vinyl ether) as a water repellent. A polymer electrolyte fuel cell in which a fluorine-containing polymer such as a copolymer is contained in a cathode catalyst layer has been proposed. In the present specification, “A / B copolymer” refers to a copolymer comprising a repeating unit based on A and a repeating unit based on B.
[0009]
Japanese Patent Laid-Open No. 7-212324 proposes a polymer electrolyte fuel cell in which a fluoride pitch is contained in a cathode catalyst layer together with PTFE. Further, JP-A-7-192738 proposes a method of forming a cathode catalyst layer of a polymer electrolyte fuel cell by coating the catalyst surface with a fluorinated coating. Japanese Patent Application Laid-Open Nos. 5-251086 and 7-134993 also propose methods for providing a gradient in water repellency with respect to the thickness direction of the electrodes.
[0010]
[Problems to be solved by the invention]
However, when a water repellent is contained in the catalyst layer as in the polymer electrolyte fuel cell described in JP-A-5-36418, the electrical resistance of the cathode is increased due to the insulating property of the water repellent, Due to the decrease in gas diffusibility of the catalyst layer due to the increase in the layer thickness of the catalyst layer, there has been a problem that the polarization characteristics of the cathode are lowered and the battery output cannot be improved. In addition, reducing the content of the water repellent in the catalyst layer to increase the battery output decreases the water repellency in the catalyst layer, and the polarization characteristics of the electrode decrease in a relatively short time from startup. Had the problem of flooding.
[0011]
Further, in the polymer electrolyte fuel cell described in JP-A-7-212324 and JP-A-7-192738, it is difficult to uniformly coat the surface of the catalyst contained in the catalyst layer with an ion exchange resin. Therefore, there is a problem that a sufficient reaction site corresponding to the amount of the catalyst contained in the cathode catalyst layer cannot be secured, and a high battery output cannot be stably obtained. Further, the polymer electrolyte fuel cells described in JP-A-5-251086 and JP-A-7-134993 have a problem that the production process becomes complicated.
[0012]
The problem of ensuring good gas diffusibility and water repellency in the catalyst layer of the gas diffusion electrode as described above is also a problem when the gas diffusion electrode is applied to other electrochemical processes such as electrolysis of water and salt. In order to improve the efficiency of the process by improving the polarization characteristics, it is important.
[0013]
In addition, the polymer electrolyte fuel cell currently under study has a problem that the operating temperature range is as low as 60 to 90 ° C., and its exhaust heat is difficult to use. In automotive applications, there is a need for a fuel cell that can be operated at a temperature higher than 100 ° C. in order to reduce the size of a cooling system and reduce catalyst poisoning due to carbon monoxide contained in fuel gas.
[0014]
Currently, CF ₂ = CFOCF ₂ CF (CF _Three ) O (CF ₂ ) _n SO _Three A perfluoro ion exchange resin comprising a copolymer of H (where n represents 2 or 3) and tetrafluoroethylene is mainly used, but the softening temperature is lower than 100 ° C and higher than 100 ° C. However, since the strength decreases, it is difficult to operate the fuel cell at a high temperature of 100 ° C. or higher. In particular, a membrane material for a fuel cell is required to have a softening temperature of 100 ° C. or higher and a strength that can withstand the use of the fuel cell.
[0015]
The catalyst layers for the anode and the cathode usually contain a polymer electrolyte, but the polymer electrolyte also preferably has a softening temperature higher than the operation temperature from the viewpoint of durability at high temperature operation. In addition, CF ₂ = CFOCF ₂ CF ₂ SO _Three The copolymer of H and tetrafluoroethylene is known to have a softening temperature higher than 100 ° C (ACS Symp. Ser. (1989), Vol. 395, pp 370-400), but the production cost is high and industrial. It is difficult to manufacture.
[0016]
The present invention has been made in view of the above problems of the prior art, and includes a fluorine-containing polymer excellent in ion conductivity, water repellency and gas permeability, a solid polymer electrolyte material comprising the same, and the solid polymer electrolyte material A solid polymer fuel cell capable of stably obtaining a high battery output by including the solid polymer electrolyte material as a constituent material and a liquid composition containing the solid polymer electrolyte material With the goal.
Another object of the present invention is to provide a solid polymer electrolyte material having a softening temperature higher than that of the prior art, in order to enable operation of the solid polymer fuel cell at a higher temperature than before.
[0017]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventors have found that the fluorinated sulfonic acid polymer having an aliphatic ring structure in the polymer has high ionic conductivity. It has been found that when used as a solid polymer electrolyte material for an electrode catalyst layer of a fuel cell, the output of the fuel cell can be improved while sufficiently ensuring the ionic conductivity in the catalyst layer. Furthermore, the present inventors have found that the fluorine-containing sulfonic acid polymer having an aliphatic ring structure has high ionic conductivity and at the same time has a softening temperature higher than that of a conventional sulfonic acid polymer, and is a solid polymer type. It was found that the material is suitable for high-temperature operation of fuel cells.
[0018]
That is, the present invention comprises a repeating unit based on a fluorine-containing monomer A that gives a polymer having an aliphatic ring structure in the main chain by radical polymerization, and a repeating unit based on a fluorine-containing monomer B represented by the following formula (1). From a copolymer containing The ion exchange capacity is 0.9 to 1.5 meq / g dry resin. A solid polymer electrolyte material is provided.
CF ₂ = CF (R ^f ) _j SO ₂ X (1)
Here, in formula (1), j represents 0 or 1, and X represents a group represented by a fluorine atom, a chlorine atom or OM. And M of the group represented by OM is a hydrogen atom, an alkali metal atom or NR. ¹ R ² R ^Three R ^Four The group represented by these is shown. Furthermore, NR ¹ R ² R ^Three R ^Four R of the group represented by ¹ , R ² , R ^Three And R ^Four May be the same or different and each represents a hydrogen atom or a monovalent organic group, preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R ^f Is a C1-C20 polyfluoroalkylene group having a straight chain or branched structure, and may contain an etheric oxygen atom.
[0019]
In the present specification, the “solid polymer electrolyte material” includes a precursor thereof. That is, -SO shown in Formula (1) ₂ -SO where X of group X is OM as described above _Three In addition to ion-conducting fluoropolymer having M group in the molecule, -SO _Three -SO which is a precursor of M group ₂ F group or -SO ₂ A fluorine-containing polymer having a Cl group in the molecule is also referred to as a solid polymer electrolyte material. The solid polymer electrolyte material of the present invention is -SO ₂ F group or -SO ₂ In the case of a fluorine-containing polymer having a Cl group in the molecule, it is subjected to a hydrolysis treatment using an aqueous solution of a base, etc. _Three It can be converted into a fluorine-containing ion conductive polymer having M group in the molecule and used as a solid polymer electrolyte material.
[0020]
Therefore, when the ionic conductivity of the solid polymer electrolyte material of the present invention is discussed in the following description, the obtained solid polymer electrolyte material is represented by -SO by X shown in the formula (1). ₂ F group or -SO ₂ When it is a fluorine-containing polymer having a Cl group in the molecule, it is subjected to hydrolysis treatment, and -SO _Three The ion conductivity in the case of a fluorine-containing ion conductive polymer having an M group in the molecule is shown.
[0021]
In the present invention, the “fluorinated monomer A that gives a polymer having an aliphatic ring structure in the main chain” is a polymer that has an aliphatic ring structure in the main chain by radical polymerization. There are two types: a monomer having an aliphatic ring structure in the molecule and a cyclopolymerizable monomer that does not have an aliphatic ring structure in the molecule but forms an aliphatic ring structure as the polymerization reaction proceeds . Furthermore, “having an aliphatic ring structure in the main chain” means that at least one carbon atom of the aliphatic ring structure in the repeating unit is shared by the main chain.
[0022]
Since the solid polymer electrolyte material of the present invention has a repeating unit based on the above-mentioned fluorine-containing monomer A, it is considered that gas permeability is high. -SO ₂ Since it has a repeating unit based on the fluorine-containing monomer B having an X group, it also has high ionic conductivity. Furthermore, the fluorine atom bonded to the carbon chain in these repeating units contributes to water repellency. Therefore, if the solid polymer electrolyte material of the present invention is used as a constituent material of an electrode catalyst layer of a polymer electrolyte fuel cell, gas diffusibility is maintained while maintaining high ion conductivity and water repellency in the catalyst layer. Therefore, the battery output is improved, and the occurrence of flooding is effectively prevented, so that a high output can be stably obtained.
[0023]
As described above, the reason why the solid polymer fuel cell using the solid polymer electrolyte material of the present invention for the electrode catalyst layer exhibits high output has not been clearly clarified, but the inclusion in the solid polymer electrolyte material has not been clarified. It is thought that it originates in the aliphatic ring structure contained in the repeating unit based on the fluorine monomer A. That is, it is considered that the gas permeability is improved as compared with the conventional solid polymer electrolyte material by making the solid polymer electrolyte material amorphous due to the aliphatic ring structure. In addition, the gas diffusion electrode provided with a catalyst layer comprising the solid polymer electrolyte material of the present invention as a constituent material, or the polymer electrolyte membrane formed from the solid polymer electrolyte material of the present invention is only a solid polymer fuel cell. It can also be used for electrochemical processes such as salt electrolysis.
[0024]
Further, the present invention is the above-mentioned solid polymer electrolyte material, and the terminal -SO of the repeating unit based on the fluorine-containing monomer B. ₂ X group is -SO _Three Provided is a liquid composition in which a solid polymer electrolyte material which is an M group is dissolved or dispersed in an organic solvent having a hydroxyl group in the molecule. Here, M is synonymous with M described in Formula (1). The liquid composition may contain water, and when the boiling point of the organic solvent is lower than the boiling point of water, by adding water to the liquid composition and distilling off the organic solvent, It is also possible to obtain a liquid composition in which the sulfonic acid polymer is dissolved or dispersed in water substantially free of an organic solvent.
[0025]
Among the solid polymer electrolyte materials of the present invention, -SO ₂ X group is -SO _Three Those which are M groups can be dissolved or well dispersed in an organic solvent having a hydroxyl group in the molecule. For example, of the solid polymer electrolyte material of the present invention, -SO _Three When a liquid in which fine particles of a catalyst are dispersed in a liquid composition obtained by dissolving or dispersing an H group in an organic solvent, a catalyst layer of a polymer electrolyte fuel cell can be easily formed, and a gas A catalyst layer having excellent permeability can be provided.
[0026]
Furthermore, the present invention is a solid polymer fuel cell having an anode, a cathode, and a polymer electrolyte membrane disposed between the anode and the cathode, wherein the fluorine-containing monomer B is the electrolyte material. -SO _Three A solid polymer type fuel cell comprising a solid polymer electrolyte material having an H group as a constituent material of a cathode is provided.
[0027]
As described above, the solid polymer electrolyte fuel cell using the solid polymer electrolyte material of the present invention as a constituent material of the cathode catalyst layer can obtain a stable and high battery output over a long period of time. This is considered to be because oxygen gas diffusibility is improved while sufficiently ensuring the ionic conductivity and water repellency in the layer, so that the oxygen concentration overvoltage is reduced and flooding is effectively prevented.
[0028]
Moreover, since the solid polymer electrolyte material of the present invention has an aliphatic ring structure in the main chain, it has a softening temperature higher than that of a conventional sulfonic acid polymer and is suitable for high-temperature operation of a fuel cell.
[0029]
Furthermore, the present invention includes a repeating unit represented by the following formula (I) and a repeating unit based on the fluorine-containing monomer D represented by the following formula (II). Rana A fluorine-containing polymer having a repeating unit content based on the fluorine-containing monomer D of 10 to 75 mol% and a number average molecular weight of 5000 to 5000000. .
[0030]
[Chemical Formula 10]

[0031]
Here, in the formulas (I) and (II), R ^f16 And R ^f17 May be the same or different and each represents a fluorine atom or a trifluoromethyl group, k ′ represents 0 or 1, Y has the same meaning as Y in Formula (2), and M represents Formula (1). It is synonymous with M of description.
[0032]
The present invention also relates to a repeating unit based on perfluoro (3-butenyl vinyl ether) and a repeating unit based on the fluorine-containing monomer D represented by the above formula (II). Rana A fluorine-containing polymer having a repeating unit content based on the fluorine-containing monomer D of 10 to 75 mol% and a number average molecular weight of 5000 to 5000000. .
[0033]
Furthermore, the present invention relates to a repeating unit based on perfluoro (2-methylene-4-methyl-1,3-dioxolane) and a repeating unit based on the fluorine-containing monomer D represented by the above formula (II). Rana A fluorine-containing polymer having a repeating unit content based on the fluorine-containing monomer D of 10 to 75 mol% and a number average molecular weight of 5000 to 5000000. .
[0034]
These fluorine-containing polymers of the present invention are considered to have particularly high gas permeability among the solid polymer electrolyte materials of the present invention, and also have particularly high ionic conductivity. Furthermore, the fluorine atom bonded to the carbon chain in these repeating units contributes to water repellency. Therefore, the above-described fluoropolymer of the present invention can be preferably used as a constituent material of a gas diffusion electrode or a polymer electrolyte membrane provided in the electrochemical process described above. Moreover, it has a softening temperature higher than that of conventional sulfonic acid polymers, and is suitable for high temperature operation of fuel cells.
[0035]
A repeating unit represented by formula (I) and a repeating unit based on fluorine-containing monomer D represented by formula (II) Rana In the fluorine-containing polymer, it is not preferable that the content of the repeating unit based on the fluorine-containing monomer D in the fluorine-containing polymer is less than 10 mol% because proton conductivity is reduced. On the other hand, if the content exceeds 75 mol%, the gas diffusibility becomes small, which is not preferable. And from a viewpoint similar to the above, it is more preferable that the content rate of the repeating unit based on the fluorine-containing monomer D in a copolymer is 15-60 mol%.
[0036]
Further, when the number average molecular weight of the fluorine-containing polymer is less than 5,000, the physical properties such as the degree of swelling change with time, and the durability becomes insufficient. On the other hand, when the number average molecular weight exceeds 5000000, it is difficult to prepare a solution. And from a viewpoint similar to the above, it is more preferable that the number average molecular weight of a fluorine-containing polymer is 10000-3000000.
[0037]
In addition, a repeating unit based on perfluoro (3-butenyl vinyl ether) and a repeating unit based on the fluorine-containing monomer D represented by the formula (II) Rana Similarly to the fluorinated polymer containing the repeating unit represented by the above formula (I), the content of the repeating unit based on the fluorinated monomer D in the fluorinated polymer is 10 to 75 mol%. It is preferable that it is 15 to 60 mol%. Furthermore, the number average molecular weight of the fluorine-containing polymer is also preferably 5,000 to 5,000,000, and more preferably 10,000 to 3,000,000.
[0038]
In addition, a repeating unit based on perfluoro (2-methylene-4-methyl-1,3-dioxolane) and a repeating unit based on the fluorine-containing monomer D represented by the formula (II) Rana Similarly to the fluorinated polymer containing the repeating unit represented by the above formula (I), the content of the repeating unit based on the fluorinated monomer D in the fluorinated polymer is 10 to 75 mol%. It is preferable that it is 15 to 60 mol%. Furthermore, the number average molecular weight of the fluorine-containing polymer is also preferably 5,000 to 5,000,000, and more preferably 10,000 to 3,000,000.
[0039]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment when the present invention is applied to a polymer electrolyte fuel cell will be described in detail.
[0040]
The polymer electrolyte fuel cell of the present invention has a configuration in which an anode, a cathode, and an anode and a cathode are disposed. Each of the cathode and the anode, which are gas diffusion electrodes, includes a gas diffusion layer and a catalyst layer adjacent to these gas diffusion layers. As a constituent material of the gas diffusion layer, a porous body having electronic conductivity (for example, carbon cloth or carbon paper) is used.
[0041]
The catalyst layer of the cathode is mainly composed of the above-described solid polymer electrolyte material (-SO _Three H type) and a catalyst are contained, improving battery output, ensuring good ion output and ensuring water repellency and gas diffusibility in the catalyst layer capable of stably obtaining high battery output. Improvements are being made.
[0042]
The solid polymer electrolyte material of the present invention contained in the catalyst layer of the cathode is composed of a copolymer containing a repeating unit based on the fluorine-containing monomer A and a repeating unit based on the fluorine-containing monomer B. The fluorine-containing monomer B is preferably a perfluoromonomer. In particular, the fluorine-containing monomer B is preferably a compound represented by the following formula (2), and among them, the compound represented by the formula (6) is particularly preferable.
[0043]
Embedded image

[0044]
Here, in Formula (2) and Formula (6), k is an integer of 0 to 2, m is an integer of 1 to 12, k ′ is 0 or 1, Y is a fluorine atom or a trifluoromethyl group, respectively. X is synonymous with X described in Formula (1) above. Thus, when both the fluorine-containing monomer A and the fluorine-containing monomer B are perfluoromonomers, the water repellency and durability of the obtained solid polymer electrolyte material are improved. Further, when the fluorinated monomer B is a compound represented by the formula (2), the obtained solid polymer electrolyte material exhibits good ionic conductivity.
[0045]
The fluorine-containing monomer A in the present invention is specifically classified into two types, that is, a monomer having an aliphatic ring structure in the molecule and a cyclopolymerizable monomer as described above. It is preferable that the repeating unit based on the fluorine monomer A is represented by any one of the following formulas (3) to (5).
[0046]
Embedded image

[0047]
Embedded image

[0048]
Here, in formula (3), p, q and r each independently represent 0 or 1, and R ^f1 And R ^f2 May be the same or different and each represents a fluorine atom, a C 1-5 perfluoroalkyl group or a C 1-5 perfluoroalkoxy group, and R ^f3 Is a perfluoroalkylene group having 1 to 3 carbon atoms, and may have a perfluoroalkyl group having 1 to 5 carbon atoms or a perfluoroalkoxy group having 1 to 5 carbon atoms as a substituent.
[0049]
In formula (4), s represents 0 or 1, and R ^f4 , R ^f5 , R ^f6 And R ^f7 May be the same or different and each represents either a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms; ^f8 Represents a fluorine atom, a C 1-5 perfluoroalkyl group or a C 1-5 perfluoroalkoxy group. However, the above R ^f4 And R ^f5 May be linked when s = 0 to form a spiro ring.
[0050]
Furthermore, in formula (5), R ^f9 , R ^f10 , R ^f11 And R ^f12 May be the same or different and each represents either a fluorine atom or a C 1-5 perfluoroalkyl group.
[0051]
The structure of the repeating unit represented by the above formula (3) can be formed from a cyclopolymerizable monomer, and R ^f3 A perfluoroalkyl group having 1 to 5 carbon atoms or a perfluoroalkoxy group having 1 to 5 carbon atoms may be bonded to the perfluoroalkylene group represented by In the case of cyclopolymerization, in formula (3), r = 1 when q = 0, and r = 0 when q = 1. Specific examples of the repeating unit include those represented by the following formulas (7) to (22).
[0052]
Embedded image

[0053]
Embedded image

[0054]
Embedded image

[0055]
The structure of the repeating unit represented by the above formula (4) can be formed from a monomer having an aliphatic ring structure in the molecule. Specific examples of the repeating unit include those represented by the following formulas (23) to (32). Further, in the structure of the repeating unit represented by the formula (4), when s = 0, R ^f4 And R ^f5 When the spiro ring formed by is a 4- to 6-membered ring, an etheric oxygen atom may be contained as an element constituting this ring, and a perfluoroalkyl group is bonded to this ring as a substituent. It may be. Examples of the structure of the repeating unit based on the monomer having an aliphatic ring structure in the molecule include those represented by the following formula (33).
[0056]
Embedded image

[0057]
Embedded image

[0058]
Furthermore, the structure of the repeating unit represented by the above formula (5) can also be formed from a monomer having an aliphatic ring structure in the molecule. Specific examples of the repeating unit include those represented by the following formulas (34) to (36).
[0059]
Embedded image

[0060]
Among the repeating units based on the fluorinated monomer A, 1 is particularly selected from the group consisting of repeating units represented by formula (7), formula (23), formula (24), formula (29) and formula (34), respectively. More than species are preferred. The monomer (fluorinated monomer A) used as a raw material for introducing these repeating units into the copolymer constituting the solid polymer electrolyte material is as follows. Formula (7): Perfluoro (3-butenyl vinyl ether), Formula (23): Perfluoro (2,2-dimethyl-1,3-dioxole), Formula (24): Perfluoro (1,3-dioxole) Formula (29): 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, Formula (34): perfluoro (2-methylene-4-methyl-1,3-dioxolane).
[0061]
A solid polymer electrolyte material composed of a copolymer containing these repeating units and a repeating unit based on the monomer represented by the above formula (6) has high ion conductivity, excellent water repellency, and oxygen permeability. It is particularly preferable because it is excellent. In particular, among the above copolymers, -SO _Three When the catalyst layer of the cathode of the polymer electrolyte fuel cell contains the one having an H group, the output of the obtained polymer electrolyte fuel cell can be increased as compared with the conventional one.
[0062]
Among the solid polymer electrolyte materials of the present invention, a copolymer consisting essentially of a repeating unit represented by the aforementioned formula (I) and a repeating unit based on the fluorine-containing monomer D represented by the formula (II) And the content rate of the repeating unit based on the fluorine-containing monomer D is 10-75 mol%, and the fluorine-containing polymer whose number average molecular weight is 5000-5 million is preferable. Another example is a copolymer consisting essentially of a repeating unit based on perfluoro (3-butenyl vinyl ether) and a repeating unit based on the fluorine-containing monomer D represented by the above formula (II). Further, a fluorine-containing polymer having a repeating unit content based on the fluorine-containing monomer D of 10 to 75 mol% and a number average molecular weight of 5000 to 5000000 is also preferable.
[0063]
Furthermore, in addition, it is substantially composed of a repeating unit based on perfluoro (2-methylene-4-methyl-1,3-dioxolane) and a repeating unit based on the fluorine-containing monomer D represented by the above formula (II). Also preferred is a fluorine-containing polymer having a repeating unit content based on the fluorine-containing monomer D of 10 to 75 mol% and a number average molecular weight of 5000 to 5000000.
[0064]
Furthermore, when the solid polymer electrolyte material of the present invention is used as an electrolyte material for a solid polymer fuel cell as in this embodiment, a repeating unit based on the fluorine-containing monomer A and a repeating unit based on the fluorine-containing monomer B -SO of copolymer containing ₂ X group is -SO _Three When it is other than H group, it is acidified and treated with -SO. _Three Used after conversion to H group. The precursor —SO ₂ The hydrolysis treatment of the F group portion is carried out by using, for example, an aqueous solution of a base such as NaOH or KOH or a mixed solution of the base, water and a water-soluble organic solvent. _Three Na group, -SO _Three Convert to K group etc. These acidification treatments use, for example, an aqueous solution of hydrochloric acid, nitric acid, sulfuric acid, etc., and -SO _Three Convert to H group.
[0065]
The softening temperature of the copolymer that is the solid polymer electrolyte material of the present invention is preferably 100 ° C. or higher. Here, the softening temperature of the solid polymer electrolyte material in the present invention refers to the softening temperature of the solid polymer electrolyte material while gradually raising the temperature of the solid polymer electrolyte material from around room temperature in the evaluation test of the dynamic viscoelasticity of the solid polymer electrolyte material. When the elastic modulus is measured, the temperature at which the elastic modulus of the solid polymer electrolyte material starts to rapidly decrease is shown. Therefore, the softening temperature in the present invention is different from the glass transition temperature usually obtained from the value of tan δ, and generally indicates a temperature observed in a temperature region lower than the glass transition temperature.
[0066]
Specifically, the softening temperature can be measured by a penetration method using a quartz probe having a diameter of 1 mm using a thermal mechanical analyzer (TMA). That is, the solid polymer electrolyte material to be measured is cast from a solution to form a film, and a quartz probe is brought into contact with the film from the normal direction of the surface of the film, and the temperature is increased at a temperature increase rate of 1 to 10 ° C./min. The temperature at which the thickness of the film begins to decrease rapidly due to penetration of the probe into the film is measured as the softening temperature.
[0067]
In addition, it was confirmed in advance that the softening temperature value obtained by this method coincided with the temperature value at which a sudden decrease in elastic modulus appearing in the temperature-dependent profile of the elastic modulus of the polymer described above was observed. . In addition, when the load of the probe on the film is too small, thermal expansion of the film is observed, but by optimizing the load, the degree of probe penetration at the softening temperature of the film can be measured without hindrance.
[0068]
Since the operating temperature of a polymer electrolyte fuel cell is generally 80 ° C. or lower, if the softening temperature of the solid polymer electrolyte material contained in the catalyst layer is 100 ° C. or higher, the solid in the catalyst layer during the operation of the cell It becomes possible to suppress changes with time in physical properties such as swelling degree of the polymer electrolyte material. Therefore, the durability of the solid polymer electrolyte material in the catalyst layer during battery operation is improved. In addition, if a solid polymer electrolyte material having a softening temperature of 100 ° C. or higher is added to the cathode catalyst layer and used as a material for the anode catalyst layer and polymer electrolyte membrane, the anode catalyst during battery operation as described above is used. The durability of the electrolyte material or polymer electrolyte membrane in the layer is improved, and as a result, the battery life can be improved.
[0069]
Furthermore, in this case, the operating temperature of the conventional solid polymer fuel cell can be raised above 80 ° C. by using a solid polymer electrolyte material having a softening temperature of 100 ° C. or higher for the polymer electrolyte membrane. . As a result, the exhaust heat of the battery can be used more effectively, and since the heat removal of the battery is facilitated, the temperature control of the battery during operation becomes easier.
[0070]
In this case, catalyst poisoning due to carbon monoxide or the like contained in the anode reaction gas can be reduced, and the battery life can be improved in this respect as well. Furthermore, even when the solid polymer electrolyte material of the present invention is used as a solid acid catalyst, if the softening temperature can be increased, the reaction temperature can be increased, so that the desired reaction proceeds in a higher temperature range. Is possible.
[0071]
In order to have a high softening temperature and to obtain practical strength as a film, the repeating unit represented by the above formula (I) and the repeating unit based on the fluorine-containing monomer D represented by the formula (II) And a copolymer substantially consisting of repeating units based on tetrafluoroethylene, wherein the repeating unit represented by the formula (I) is 5-70 mol%, preferably 10-60 mol%, more preferably Is 20 to 60 mol%, and the repeating unit based on tetrafluoroethylene is 10 to 85 mol%, preferably 15 to 70 mol%, more preferably 20 to 60 mol%, and represented by the formula (II) The content of repeating units based on the fluorine-containing monomer D is 5 to 40 mol%, preferably 10 to 30 mol%, and the number-average molecular weight is 5000 to 5000000. Chromatography is particularly suitable.
[0072]
The solid polymer electrolyte material of the present invention is A _R Is 0.5 to 2.5 meq / g dry resin (hereinafter referred to as meq./g). A of solid polymer electrolyte material _R 0.5 meq. When it is less than / g, the water content of the solid polymer electrolyte material is lowered and its ionic conductivity is lowered. Therefore, when the solid polymer electrolyte material is used as a constituent material of the catalyst layer of the electrode of the solid polymer fuel cell, It becomes difficult to obtain sufficient battery output.
[0073]
On the other hand, the solid polymer electrolyte material A _R 2.5 meq. When it exceeds / g, the density of the ion exchange groups in the solid polymer electrolyte material increases, and the strength of the solid polymer electrolyte material tends to decrease. Further, when used as a constituent material of the catalyst layer of the electrode of the polymer electrolyte fuel cell, the moisture content becomes too high, so that gas diffusibility or drainage in the catalyst layer is lowered and flooding is likely to occur. From the same viewpoint as described above, the solid polymer electrolyte material A of the present invention _R Is 0.7 to 2.0 meq. / G, more preferably 0.9 to 1.5 meq. More preferably, it is / g.
[0074]
Further, the number average molecular weight of the solid polymer electrolyte material of the present invention is not particularly limited, and may be appropriately set by changing the degree of polymerization of the copolymer according to the use. When used as a constituent material of the catalyst layer of the cathode of the molecular fuel cell, it is preferably 5,000 to 5,000,000, and more preferably 10,000 to 3,000,000. If the number average molecular weight of the solid polymer electrolyte material is less than 5,000, the physical properties such as the degree of swelling change over time, resulting in insufficient durability. On the other hand, when the number average molecular weight exceeds 5000000, it is difficult to prepare a solution.
[0075]
Further, the ratio (substance ratio) of the repeating unit based on the fluorine-containing monomer A and the repeating unit based on the fluorine-containing monomer B in the solid polymer electrolyte material of the present invention is not particularly limited, and is appropriately set according to the application. However, when used as a constituent material of the catalyst layer of the cathode of the polymer electrolyte fuel cell as in this embodiment, the above A _R Is preferably selected so as to meet the range of
[0076]
In the solid polymer electrolyte material of the present invention, the repeating unit constituting the solid polymer electrolyte material has a repeating unit other than the repeating unit based on the fluorine-containing monomer A and the repeating unit based on the fluorine-containing monomer B as the repeating unit. It may be contained as necessary for the adjustment of the above. Monomers that give such other repeating units are not particularly limited. For example, tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride, hexafluoropropylene, trifluoroethylene, vinyl fluoride, ethylene, Examples thereof include fluorine-containing vinyl compounds represented by the formulas (37) to (40).
[0077]
In order to improve the strength of the obtained copolymer, among these monomers, tetrafluoroethylene is used from the viewpoints of high activity for polymerization reaction, durability (perfluoro structure), and availability. It is preferable.
CH ₂ = CHR ^f13 ... (37)
CH ₂ = CHCH ₂ R ^f13 ... (38)
[0078]
Embedded image

[0079]
CF ₂ = CFOR ^f14 Z (40)
[0080]
Here, in Formula (37) and Formula (38), R ^f13 Represents a perfluoroalkyl group having 1 to 12 carbon atoms. In the formula (39), a represents an integer of 0 to 3, W represents a fluorine atom or a trifluoromethyl group, R ^f15 Represents a C1-C12 perfluoroalkyl group having a linear or branched structure. Furthermore, in formula (40), R ^f14 Is a C1-C12 perfluoroalkylene group having a straight chain or branched structure, and may contain an etheric oxygen atom, Z is -CN, -COOR ^f16 (R ^f16 Represents an alkyl group having 1 to 6 carbon atoms. ) Or -COF.
[0081]
When the solid polymer electrolyte material of the present invention contains other repeating units in addition to the repeating unit based on the fluorine-containing monomer A and the repeating unit based on the fluorine-containing monomer B, the content of the other repeating unit is solid. The polymer electrolyte material may be appropriately set according to the use of the polymer electrolyte material. When used as a constituent material of the catalyst layer of the cathode of the solid polymer fuel cell as in this embodiment, the solid polymer electrolyte material is configured. The content of the other repeating unit in the copolymer is preferably less than 35% by mass. When this value exceeds 35% by mass, the effect of increasing the output of the fuel cell is reduced.
[0082]
Furthermore, among the fluorine-containing vinyl ether compounds represented by the formula (39), it is preferable to use fluorine-containing vinyl ether compounds represented by the following formulas (41) to (43). However, in following formula (41)-(43), b is an integer of 1-8, d is an integer of 1-8, e shows 2 or 3, respectively.
[0083]
Embedded image

[0084]
The catalyst contained in each of the cathode catalyst layers in the present invention is not particularly limited. For example, a catalyst in which a platinum group metal such as platinum or an alloy thereof is supported on carbon is preferable.
[0085]
Furthermore, in the cathode catalyst layer, the mass ratio of the catalyst to the solid polymer electrolyte material is the mass of the catalyst (the total mass of the metal and the carbon support): the mass of the solid polymer electrolyte material = 20: 80 to The ratio is preferably 95: 5, and more preferably 30:70 to 90:10.
[0086]
Here, if the content of the catalyst with respect to the solid polymer electrolyte material is too low, the amount of catalyst tends to be small, and the reaction sites tend to be insufficient. In addition, the thickness of the coating layer of the solid polymer electrolyte material covering the catalyst tends to increase, and the diffusion rate of the reaction gas in the solid polymer electrolyte material tends to decrease. Furthermore, the pores necessary for the diffusion of the reaction gas may be clogged with the resin, so that the flooding phenomenon is likely to occur.
[0087]
On the other hand, if the content of the catalyst with respect to the solid polymer electrolyte material is too high, the amount of the solid polymer electrolyte material that covers the catalyst with respect to the catalyst tends to be insufficient, resulting in fewer reaction sites and a decrease in battery output. . The solid polymer electrolyte material also functions as a binder for the catalyst layer and an adhesive between the catalyst layer and the polymer electrolyte membrane, but its function becomes insufficient, and the tendency for the catalyst layer structure to be unable to be maintained stably increases. .
[0088]
The structure of the anode catalyst layer of the fuel cell is not particularly limited, and can be the same structure as the anode catalyst layer of a conventional solid polymer fuel cell, and contains the solid polymer electrolyte material of the present invention. It may also contain other resins.
[0089]
Furthermore, the layer thickness of the cathode and anode catalyst layers in the present invention is preferably 1 to 500 μm, and more preferably 5 to 100 μm. Furthermore, the catalyst layer in the present invention may contain a water repellent such as PTFE as necessary. However, since the water repellent agent is an insulator, the amount thereof is preferably as small as possible, and the addition amount is preferably 30% by mass or less.
[0090]
In addition, the polymer electrolyte membrane used in the solid polymer fuel cell of the present invention is an ion exchange membrane that exhibits good proton conductivity under wet conditions. From the viewpoint of durability, an ion exchange membrane made of a perfluoropolymer is used. A membrane is preferred. As the solid polymer material constituting the polymer electrolyte membrane, for example, the solid polymer electrolyte material of the present invention may be used, and an ion exchange resin or the like used in a conventional solid polymer fuel cell is used. Also good.
[0091]
Hereinafter, an example of a method for producing a fluorine-containing polymer used for the solid polymer electrolyte material in the present invention will be described. First, as the fluorine-containing monomer B, -SO ₂ F group or -SO ₂ Those having a Cl group are used. The polymerization reaction between the fluorinated monomer A and the fluorinated monomer B is not particularly limited as long as it is carried out under conditions where radicals are generated. For example, bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, polymerization in liquid or supercritical carbon dioxide may be used.
[0092]
The method for generating radicals is not particularly limited. For example, a method of irradiating radiation such as ultraviolet rays, γ rays, and electron beams may be used, and a method using a radical initiator used in normal radical polymerization may be used. Also good. The reaction temperature of the polymerization reaction is not particularly limited, and is usually about 15 to 150 ° C., for example. When a radical initiator is used, examples of the radical initiator include bis (fluoroacyl) peroxides, bis (chlorofluoroacyl) peroxides, dialkyl peroxydicarbonates, diacyl peroxides, peroxyesters, Examples include azo compounds and persulfates.
[0093]
In the case of performing solution polymerization, the solvent used usually has a boiling point of 20 to 350 ° C., more preferably 40 to 150 ° C., from the viewpoint of handleability. . Then, a predetermined amount of a fluorine-containing monomer and a fluorine-containing vinyl compound is added to the solvent, and a radical initiator or the like is added to generate radicals to perform polymerization.
[0094]
Here, examples of the usable solvent include (i) polyfluorotrialkylamine compounds such as perfluorotributylamine and perfluorotripropylamine, (ii) perfluorohexane, perfluorooctane, perfluorodecane, and perfluorodecane. Fluorododecane, perfluoro (2,7-dimethyloctane), 2H, 3H-perfluoropentane, 1H-perfluorohexane, 1H-perfluorooctane, 1H-perfluorodecane, 1H, 4H-perfluorobutane, 1H, 1H, 1H, 2H, 2H-perfluorohexane, 1H, 1H, 1H, 2H, 2H-perfluorooctane, 1H, 1H, 1H, 2H, 2H-perfluorodecane, 3H, 4H-perfluoro (2-methyl Pentane), 2H, 3H-perfluoro (2-me (Alpentane), (iii) 3,3-dichloro-1,1,1,2,2-pentafluoropropane, 1,3-dichloro-1,1,2,2,3-pentafluoropropane, A fluoroolefin having no double bond at the molecular chain end, such as a chlorofluoroalkane such as 1,1-dichloro-1-fluoroethane, (iv) a dimer of hexafluoropropene, a trimer of hexafluoropropene, v) perfluorodecalin, perfluorocyclohexane, perfluoro (1,2-dimethylcyclohexane), perfluoro (1,3-dimethylcyclohexane), perfluoro (1,3,5-trimethylcyclohexane), perfluorodimethylcyclobutane ( Polyfluorocycloalkanes, etc. (regardless of structural isomerism), (vi) perful B (2-butyl tetrahydrofuran) polyfluoro cyclic ether compounds such as, (vii) n-C _Three F ₇ OCH _Three , N-C _Three F ₇ OCH ₂ CF _Three , N-C _Three F ₇ OCHFCF _Three , N-C _Three F ₇ OC ₂ H _Five , N-C _Four F ₉ OCH _Three , Iso-C _Four F ₉ OCH _Three , N-C _Four F ₉ OC ₂ H _Five , Iso-C _Four F ₉ OC ₂ H _Five , N-C _Four F ₉ OCH ₂ CF _Three , N-C _Five F ₁₁ OCH _Three , N-C ₆ F ₁₃ OCH _Three , N-C _Five F ₁₁ OC ₂ H _Five , CF _Three OCF (CF _Three CF ₂ OCH _Three , CF _Three OCHFCH ₂ OCH _Three , CF _Three OCHFCH ₂ OC ₂ H _Five , N-C _Three F ₇ OCF ₂ CF (CF _Three ) OCHFCF _Three Hydrofluorethers such as (viii) fluorine-containing low molecular weight polyether, (ix) tert-butanol and the like. In addition, these solvents may be used independently and may be used in mixture of 2 or more types.
[0095]
Other examples of solvents used for solution polymerization include 1,1,2-trichloro-1,2,2-trifluoroethane, 1,1,1-trichloro-2,2,2- Trifluoroethane, 1,1,1,3-tetrachloro-2,2,3,3-tetrafluoropropane, 1,1,3,4-tetrachloro-1,2,2,3,4,4- Mention may be made of chlorofluorocarbons such as hexafluorobutane. However, these chlorofluorocarbons can be used technically, but their use is not preferable in consideration of the influence on the global environment.
[0096]
The copolymer obtained by polymerization is -SO. ₂ F group or -SO ₂ Since it has a Cl group, hydrolysis or acidification treatment is performed if necessary, and -SO _Three Convert to M group.
[0097]
Next, an example of a method for producing the polymer electrolyte fuel cell of the present invention will be described, and a preferred embodiment when the liquid composition of the present invention is applied to a polymer electrolyte fuel cell will be described. The method for producing the gas diffusion electrode having the cathode and anode catalyst layers of the polymer electrolyte fuel cell of the present invention is not particularly limited, and can be produced by a known method.
[0098]
For example, the catalyst layer of the cathode is -SO _Three It is formed using a coating liquid for forming a catalyst layer prepared by mixing a catalyst in a liquid composition in which a solid polymer electrolyte material of the present invention having an H group is dissolved or dispersed in a solvent having a hydroxyl group in the molecule. be able to.
[0099]
The solid polymer electrolyte material of the present invention contains -SO _Three When it has M group, it can melt | dissolve or disperse | distribute favorably in the organic solvent which has a hydroxyl group. The organic solvent having a hydroxyl group is not particularly limited, but an organic solvent having an alcoholic hydroxyl group is preferable.
[0100]
Examples of the organic solvent having an alcoholic hydroxyl group include methanol, ethanol, 1-propanol, 2-propanol, 2,2,2-trifluoroethanol, 2,2,3,3,3-pentafluoro-1- Propanol, 2,2,3,3-tetrafluoro-1-propanol, 4,4,5,5,5-pentafluoro-1-pentanol, 1,1,1,3,3,3-hexafluoro- 2-propanol, 3,3,3-trifluoro-1-propanol, 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexanol, 3,3,4,4,5 5,6,6,7,7,8,8,8-tridecafluoro-1-octanol and the like. Moreover, as an organic solvent other than alcohol, an organic solvent having a carboxyl group such as acetic acid can also be used.
[0101]
Here, as the organic solvent having a hydroxyl group, the above-mentioned solvents may be used alone, or two or more kinds thereof may be mixed and used, or may be further used by mixing with water or other fluorine-containing solvent. . Examples of other fluorine-containing solvents include the fluorine-containing solvents exemplified as preferred fluorine-containing solvents in the solution polymerization reaction in the production of the solid polymer electrolyte material described above.
[0102]
In addition, when using the organic solvent which has a hydroxyl group as water or a mixed solvent with another fluorine-containing solvent, it is preferable that content of the organic solvent which has a hydroxyl group is 10% or more with respect to the solvent total mass, 20% More preferably. In this case, the solid polymer electrolyte material may be dissolved or dispersed in the mixed solvent from the beginning, and the solid polymer electrolyte material is first dissolved or dispersed in the organic solvent having a hydroxyl group, and then water or other components. These fluorine-containing solvents may be mixed. Further, the dissolution or dispersion of the solid polymer electrolyte material in such a solvent is preferably carried out in a temperature range of 0 to 250 ° C. under conditions of atmospheric pressure or hermetically pressurized with an autoclave or the like. It is more preferable to carry out in the range of 150 ° C.
[0103]
Further, the content of the solid polymer electrolyte material in the liquid composition of the present invention is preferably 1 to 50%, more preferably 3 to 30% with respect to the total mass of the liquid composition. When the content of the solid polymer electrolyte material is less than 1%, a coating liquid is prepared by mixing a catalyst with this liquid, and a catalyst having a desired thickness is prepared when a cathode catalyst layer is produced using the coating liquid. The number of times of coating is increased to produce the layer, and such a coating solution contains a large amount of organic solvent, which is costly and takes a long time for the removal operation. Hateful. On the other hand, when the content of the solid polymer electrolyte material exceeds 50%, the viscosity of the liquid composition becomes too high and it is difficult to handle.
[0104]
Furthermore, in addition to the solid polymer electrolyte material of the present invention, the liquid composition may contain a resin that is another solid polymer electrolyte material. In this case, a catalyst obtained using the liquid composition as a raw material From the viewpoint of sufficiently ensuring the gas diffusibility and water repellency of the layer, the content of the solid polymer electrolyte material of the present invention in the liquid composition is based on the total mass of all the solid polymer electrolyte materials in the liquid composition. It is preferably 20% or more, and more preferably 50% or more.
[0105]
The cathode catalyst layer is prepared by using a coating solution for forming a catalyst layer prepared by mixing a catalyst composed of fine particles such as carbon black carrying platinum on the liquid composition of the present invention. Further, it can be produced by forming the gas diffusion layer or the support plate so as to have a uniform thickness, drying and removing the solvent, and performing hot pressing as necessary. If desired, the coating liquid may be prepared by mixing the liquid composition of the present invention and the catalyst, then distilling off the solvent, taking out the solid content, and redispersing in another solvent. The redispersed solution is usually selected from the aforementioned alcoholic solvents and may contain water. In this way, a cathode catalyst layer excellent in gas diffusibility and water repellency can be obtained.
[0106]
In particular, when a coating liquid is prepared from a liquid composition containing a solid polymer electrolyte material in which the softening temperature of the polymer itself is 100 ° C. or higher, the gas diffusibility in the layer is significantly improved. If the softening temperature of the solid polymer electrolyte material is 100 ° C. or higher, the solid polymer electrolyte material is less likely to shrink when the solvent gradually evaporates from the coating solution. This is presumably because pores of an appropriate size are formed between the aggregates of the catalyst particles coated with the electrolyte material.
[0107]
The anode catalyst layer can also be formed in the same manner as the cathode catalyst layer. However, the coating liquid for forming the catalyst layer of the anode may use the liquid composition of the present invention, or may be prepared using a liquid obtained by dissolving or dispersing a conventional solid polymer electrolyte material in a predetermined solvent. Good.
[0108]
A solid polymer fuel cell can be manufactured by disposing the prepared cathode catalyst layer and anode catalyst layer between the polymer electrolyte membrane and the gas diffusion layer. Here, when the catalyst layer is formed on the polymer electrolyte membrane, for example, a separately prepared gas diffusion layer is disposed or joined adjacent to the catalyst layer. When the catalyst layer is formed on the gas diffusion layer and the gas diffusion electrode is formed in advance, for example, a separately prepared polymer electrolyte membrane is disposed or joined adjacent to the catalyst layer. Further, when the catalyst layer is formed on the support plate, for example, it is transferred to a separately prepared polymer electrolyte membrane, and then the support plate is peeled off and a separately prepared gas diffusion layer is disposed adjacent to the catalyst layer. Or join.
[0109]
The polymer electrolyte membrane and the catalyst layer, and the catalyst layer and the gas diffusion layer may be joined by, for example, hot pressing or roll pressing. At this time, both may be joined by non-heating using a perfluorosulfonic acid polymer solution or the like as an adhesive.
[0110]
Further, as described above, the polymer electrolyte membrane constituting the battery may be produced using the solid polymer electrolyte material of the present invention.
[0111]
The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment. For example, in the above embodiment, the polymer electrolyte fuel cell has been described in the case where a gas containing hydrogen as a main component is used as the anode reaction gas. However, the polymer electrolyte fuel cell of the present invention is, for example, an anode reaction gas. A configuration may be adopted in which methanol gas is directly introduced into the anode as the gas.
[0112]
In the above embodiment, the case where the liquid composition containing the solid polymer electrolyte material of the present invention is used for the catalyst layer of the electrode of the solid polymer fuel cell has been described. However, the liquid composition can be used for other applications. For example, when forming a membrane using the solid polymer electrolyte material of the present invention, 1) a cation selective permeable membrane used for salt electrolysis and the like, 2) a membrane for water electrolysis, 3) hydrogen peroxide production, ozone production It can be used in various electrochemical processes as a proton selective permeable membrane used for waste acid recovery and the like, and 4) a cation exchange membrane for electrodialysis used for desalting or salt production.
[0113]
In addition to the electrochemical process, a membrane is formed using the solid polymer electrolyte material of the present invention, for example, a membrane for diffusion dialysis used for separation and purification of acids, bases, and salts, and a charge for protein separation. It can also be used for type porous membranes (charged reverse osmosis membranes, charged ultrafiltration membranes, charged microfiltration membranes, etc.), dehumidifying membranes, humidifying membranes and the like. Further, the solid polymer electrolyte material of the present invention includes, for example, a polymer electrolyte of a lithium ion battery, a solid acid catalyst, a cation exchange resin, a sensor using a modified electrode, and an ion exchange filter for removing trace ions in the air. It can also be used for actuators.
[0114]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in more detail, this invention is not limited to these Examples. In the following description of Examples and Comparative Examples, the following compounds are described using the following abbreviations.
PSVE: CF ₂ = CFOCF ₂ CF (CF _Three OCF ₂ CF ₂ SO ₂ F,
PSVE-H: CF ₂ = CFOCF ₂ CF (CF _Three OCF ₂ CF ₂ SO _Three H,
BVE: perfluoro (3-butenyl vinyl ether),
PDD: perfluoro (2,2-dimethyl-1,3-dioxole),
MMD: perfluoro (2-methylene-4-methyl-1,3-dioxolane)
TFE: Tetrafluoroethylene
IPP: (CH _Three ) ₂ CHOC (= O) OOC (= O) OCH (CH _Three ) ₂ ,
HCFC141b: CH _Three CCl ₂ F,
HCFC225cb: CCIF ₂ CF ₂ CHClF.
[0115]
[Synthesis Example 1] (PDD / PSVE-H copolymer 1)
Put 26.0 g of PDD, 127.8 g of PSVE, 0.46 g of IPP in a 0.2 L stainless steel autoclave, purge the gas in the autoclave with nitrogen, and then adjust the total pressure of nitrogen to 0.3 MPa (gauge pressure) Introduced. Next, the temperature in the autoclave was set to 40 ° C., and polymerization was started while stirring the contents. Ten hours after the start of polymerization, the autoclave was cooled and the gas in the system was purged to stop the polymerization. After dilution with HCFC225cb, the polymer was precipitated by adding it to hexane, washed twice with hexane, and once with HCFC141b. did.
[0116]
After filtration, it was vacuum-dried at 80 ° C. for 16 hours to obtain 41.6 g of a white polymer. The sulfur content is determined by elemental analysis, and the molar ratio of the repeating unit based on PDD and the repeating unit based on PSVE in the polymer (PDD / PSVE) and A _R And PDD / PSVE = 56.5 / 43.5, and A _R = 1.31 meq. / G. Moreover, when the number average molecular weight of the polymer was measured by GPC, the number average molecular weight in terms of polymethyl methacrylate was 33,000. The weight average molecular weight was 56,000.
[0117]
Next, the obtained polymer was immersed in a water / ethanol mixed solution of KOH for hydrolysis treatment, and then immersed in a dilute sulfuric acid aqueous solution for acidification treatment. Next, the polymer was washed with ion-exchanged water, dried, and then dissolved in ethanol to obtain a 10% by mass transparent ethanol solution of the polymer (PDD / PSVE-H copolymer 1).
[0118]
A cast film was prepared using the above ethanol solution of the polymer, and the softening temperature of the polymer was measured by the penetration method using a 1 mmφ quartz probe described above. First, a mixed solution of 10 parts by weight of a polymer ethanol solution and 2 parts by weight of butanol is prepared, cast into a film at room temperature using this solution, and dried at 160 ° C. for 30 minutes to form a cast film having a thickness of about 200 μm. Obtained. Next, the obtained cast film was set in TMA (manufactured by Mac Science).
[0119]
Then, while raising the temperature of the cast film at a temperature rising rate of 5 ° C./min, a vibration load based on a sin curve of 0.2 Hz (load vibration range: 1 to 6 g) with respect to the contact portion between the cast film and the 1 mmφ quartz probe. , Average load: 3.5 g), and the change in the thickness of the cast film was measured. Then, the temperature at which the thickness of the film began to decrease rapidly due to the penetration of the probe into the cast film was measured as the softening point. As a result, the softening temperature of this polymer was 150 ° C.
[0120]
[Synthesis Example 2] (PDD / PSVE-H Copolymer 2)
In a 0.2 L stainless steel autoclave, 36.4 g of PDD, 123.1 g of PSVE, and 0.48 g of IPP were added, and polymerization was started in the same manner as in Synthesis Example 1. 3.2 hours after the start of the polymerization, the autoclave is cooled, the gas in the system is purged to stop the polymerization, and the mixture is diluted with HCFC225cb and then poured into hexane to precipitate, washed twice with hexane and once with HCFC141b. did.
[0121]
After filtration, the resultant was vacuum-dried at 80 ° C. for 16 hours to obtain 25.3 g of a white polymer. The obtained polymer was subjected to hydrolysis and acidification treatment in the same manner as in Synthesis Example 1 to obtain PDD / PSVE-H copolymer 2, and the same characterization as in Synthesis Example 1 was performed. As a result, PDD / PSVE = 69.8 / 30.2, A _R = 0.99 meq. / G, polymethyl methacrylate conversion number average molecular weight: 58,000, weight average molecular weight: 95,000, softening temperature: 180 ° C.
[0122]
[Synthesis Example 3] (BVE / PSVE-H copolymer 1)
Under a nitrogen atmosphere, 120.0 g of BVE, 128.5 g of PSVE, and 0.76 g of IPP were placed in a 300 mL volume flask, the temperature in the flask was set to 40 ° C., and polymerization was started while stirring the contents. After 16.7 hours from the start of the polymerization, the inside of the flask was cooled to stop the polymerization, and the polymer was precipitated by adding to hexane, and further washed with hexane three times.
[0123]
After filtration, it was vacuum dried at 80 ° C. for 16 hours to obtain 47.8 g of a white polymer. The obtained polymer was subjected to hydrolysis and acidification treatment in the same manner as in Synthesis Example 1 to obtain a BVE / PSVE-H copolymer 1, and the same characterization as in Synthesis Example 1 was performed. As a result, BVE / PSVE = 67.0 / 33.0, A _R = 0.99 meq. / G, polymethyl methacrylate conversion number average molecular weight: 29,000, weight average molecular weight: 42,000, softening temperature: 110 ° C.
[0124]
[Synthesis Example 4] (BVE / PSVE-H copolymer 2)
Under a nitrogen atmosphere, 150.0 g of BVE, 103.0 g of PSVE, and 0.77 g of IPP were placed in a 300 mL volume flask, and polymerization was started in the same manner as in Synthesis Example 3. After 10.7 hours from the start of the polymerization, the inside of the flask was cooled to stop the polymerization, and the polymer was precipitated by adding it to hexane, followed by washing with hexane three times and further with HCFC 141b.
[0125]
After filtration, it was vacuum-dried at 80 ° C. for 16 hours to obtain 38.0 g of a white polymer. The obtained polymer was subjected to hydrolysis and acidification treatment in the same manner as in Synthesis Example 1 to obtain BVE / PSVE-H copolymer 2, and the same characterization as in Synthesis Example 1 was performed. As a result, BVE / PSVE = 76.1 / 23.9, A _R = 0.75 meq. / G, polymethyl methacrylate conversion number average molecular weight: 38,000, weight average molecular weight: 53,000, softening temperature: 110 ° C.
[0126]
[Synthesis Example 5] (TFE / PSVE-H copolymer)
A TFE / PSVE copolymer conventionally used as a material for a catalyst layer of a polymer electrolyte fuel cell electrode or a material for a polymer electrolyte membrane was produced by a known method. The obtained polymer was hydrolyzed and acidified in the same manner as in Synthesis Example 1 to obtain a TFE / PSVE-H copolymer and characterized in the same manner as in Synthesis Example 1. As a result, TFE / PSVE = 82.2 / 17.8, A _R = 1.1 meq. / G, softening temperature: 80 ° C.
[0127]
[Synthesis Example 6] (MMD / PSVE-H copolymer 1)
A 0.2 L autoclave was charged with IPP: 0.68 g, PSVE: 207.1 g, MMD: 20.0 g, degassed under reduced pressure, and then purged with nitrogen three times. The total pressure with nitrogen was 0.12 MPa. (Gauge pressure) was applied. The temperature was raised to 40 ° C. and reacted for 2.5 hours. The polymerization solution was poured into hexane to aggregate the polymer, and further washed with hexane three times. Vacuum drying was performed overnight at room temperature, and further vacuum drying was performed overnight at 80 ° C. Yield: 16.9 g (Yield: 7.4%).
[0128]
The sulfur content is determined by elemental analysis, and the molar ratio (MMD / PSVE) of the repeating unit based on MMD and the repeating unit based on PSVE in the polymer is _R And MMD / PSVE = 76.0 / 24.0, and A _R = 0.82 meq. / G. When the number average molecular weight of the polymer was measured by GPC, the number average molecular weight in terms of polymethyl methacrylate was 45,000, and the weight average molecular weight was 70000.
[0129]
Polymer is KOH / H ₂ It was immersed in a solution of O / DMSO = 11/59/30 (mass ratio) and kept at 90 ° C. for 7 days. It returned to room temperature, washed with water, and further immersed in water at 90 ° C. This washing with water was repeated three times. Further, it was immersed in 1 mol / L hydrochloric acid at 90 ° C. for 1 day, returned to room temperature, washed with water, and further immersed in water at 90 ° C. This washing with water was repeated three times. The polymer was dried in an oven at 80 ° C. for 16 hours and further vacuum dried at 80 ° C. to obtain an acidified polymer.
[0130]
A 10% by mass ethanol solution of this polymer was prepared in the same manner as in Synthesis Example 1 to prepare a cast film. The softening temperature of the cast film was 135 ° C.
[0131]
[Synthesis Example 7] (MMD / PSVE-H copolymer 2)
Polymer 19 was prepared in the same manner as in Synthesis Example 6, except that the charged PSVE was 207.1 g, the MMD was 13.3 g, nitrogen was introduced to make the total pressure 0.11 MPa (gauge pressure), and the reaction time was 6 hours. 0.6 g was obtained (yield: 8.9%).
[0132]
Similar to Synthesis Example 6, the molar ratio (MMD / PSVE) of the repeating unit based on MMD to the repeating unit based on PSVE in the polymer and A _R And MMD / PSVE = 66.7 / 33.3, and A _R = 1.07 meq. / G. Moreover, the number average molecular weight of polymethyl methacrylate conversion was 24,000, and the weight average molecular weight was 39,000.
[0133]
The polymer was acidified in the same manner as in Synthesis Example 6 to obtain an MMD / PSVE-H copolymer. A 9.6 mass% ethanol solution of this polymer was prepared in the same manner as in Synthesis Example 1 to prepare a cast film. The softening temperature of the cast film was 125 ° C.
[0134]
[Synthesis Example 8] (TFE / PDD / PSVE-H copolymer)
A 0.2 L autoclave was charged with 14.3 g of PDD, 52.6 g of PSVE, 76.9 g of HCFC-225cb, and 0.36 g of IPP, and freeze degassed. After introducing 5.9 g of TFE, the temperature was raised to 40 ° C. to initiate polymerization. At this time, the pressure was 0.26 MPa (gauge pressure). The reaction was carried out at 40 ° C. for 10 hours, and the reaction was stopped when the pressure reached 0.07 MPa (gauge pressure). The polymerization solution was poured into hexane to aggregate the polymer, and washed with hexane three times. Vacuum drying was performed overnight at 80 ° C. Yield: 25.0 g (Yield: 34.4%).
[0135]
¹⁹ When the polymer composition was determined by F-NMR, it was TFE / PDD / PSVE = 42/35/22 (molar ratio), and A _R Is 0.98 meq. / G. Moreover, the number average molecular weight of polymethyl methacrylate conversion by GPC was 53,000, and the weight average molecular weight was 83,000.
[0136]
The polymer was pressed at 160 ° C. to produce a film having a thickness of 100 μm. This film is KOH / H ₂ It was immersed in a solution of O / DMSO = 11/59/30 (mass ratio) and hydrolyzed by maintaining at 90 ° C. for 17 hours. It returned to room temperature and washed with water 3 times. Furthermore, it was immersed in 1 mol / L sulfuric acid at room temperature for 2 hours and washed with water. This sulfuric acid immersion and water washing were repeated three times, and finally water washing was further performed three times. The film was dried in an oven at 80 ° C. for 16 hours and further vacuum dried at 80 ° C. to obtain an acid-type dry film. The softening temperature measured by the method of Synthesis Example 1 was 120 ° C. The maximum point stress in the tensile test was 6.1 MPa, and the elongation at break was 3.0%. It was confirmed that the film had sufficient strength.
[0137]
In the same manner as in Synthesis Example 1, a 14.5% by mass ethanol solution of an acidified polymer could be prepared from the above polymer.
[0138]
The film tensile test was performed by cutting the film into the shape of test piece type 2 (length: 150 mm, width: 10 mm, distance between marked lines: 50 mm) defined in JIS K-7127, and initial distance between chucks: 100 mm. , Under the conditions of a tensile speed of 50 mm / min, 25 ° C., and a relative humidity of 50%.
[0139]
Example 1
The unit cell of Example 1 was produced according to the procedure described below. First, a dispersion obtained by dispersing Pt-supported carbon (Pt-supported amount: 54% by mass) in a 10% by mass ethanol solution of PDD / PSVE-H copolymer 1 (mass of Pt-supported carbon: mass of the copolymer). = 6: 4) was prepared. Next, after sufficiently stirring the dispersion, the solid obtained by further evaporating to dryness was pulverized. Next, the powder was redispersed in 2,2,3,3,3-pentafluoro-1-propanol to prepare a coating solution for forming a cathode catalyst layer having a solid content concentration of 5% by mass. .
[0140]
Next, Pt-supported carbon (Pt-supported amount: 40% by mass) was converted into a TFE / PSVE-H copolymer (A _R = 1.1 meq. / G) a 9% by mass ethanol solution and ethanol and dispersed, and further water is added to form a coating solution for forming an anode catalyst layer having a solid content concentration of 8% by mass (ethanol mass: water mass = 1: 1, mass of Pt-supported carbon: mass of the above copolymer = 7: 3).
[0141]
Also, as a gas diffusion layer for the anode and cathode, one surface of a water-repellent carbon cloth (fiber woven fabric) is clogged with a water-repellent carbon powder layer (a mixture of carbon black and PTFE), and further subjected to hot pressing to form a catalyst layer A carbon powder layer having a thickness of about 340 μm was prepared. Furthermore, as a polymer electrolyte membrane, a polymer electrolyte membrane made of a sulfonic acid type perfluorocarbon polymer (trade name: Flemion HR, manufactured by Asahi Glass Co., Ltd., A _R = 1.1 meq. / G, dry film thickness 50 μm).
[0142]
Next, a coating solution for forming a cathode catalyst layer is applied to the surface of the gas diffusion layer on the water-repellent carbon powder layer side with a Pt amount of 0.8 mg / cm 2. ² Then, it was applied once and dried to form a catalyst layer, thereby producing a cathode. On the other hand, a coating solution for forming the catalyst layer of the anode was subjected to a procedure similar to that for the cathode, with a Pt amount of 0.5 mg / cm ² Then, it was applied once and dried to form a catalyst layer to obtain an anode.
[0143]
Next, the effective cathode area of the obtained cathode and anode is 25 cm. ² It cut out so that it might become. Then, both the cathode and the anode are opposed to each other with the catalyst layer side facing inward, and the catalyst layer and the polymer electrolyte membrane of the cathode and the anode are joined by hot pressing with the polymer electrolyte membrane sandwiched therebetween, A membrane / electrode assembly was prepared.
[0144]
(Comparative Example 1)
A membrane / electrode assembly was produced in the same manner as in Example 1 except that both the anode and the cathode were produced using the anode catalyst layer forming coating solution prepared in Example 1.
[0145]
[Battery characteristics test]
Each membrane / electrode assembly of Example 1 and Comparative Example 1 is fitted with a carbon separator having a gas flow path to form a measurement cell, and an electronic load (manufactured by Takasago Seisakusho, FK400L) and a DC power source ( The current-voltage characteristic test of the measurement cell was performed using Takasago Seisakusho, EX750L).
The measurement conditions were: hydrogen inlet pressure: 0.15 MPa, air inlet pressure: 0.15 MPa, operating temperature of the measuring cell: 80 ° C., and after 10 hours of operation, the output current density was 0.3 A / cm, respectively. ² 1.0 A / cm ² The cell voltage (iR free) was measured. In addition, the flow rates of hydrogen gas and air were adjusted so that the hydrogen utilization rate was 70% and the air utilization rate was 40% under these operating conditions. The results are shown in Table 1.
[0146]
[Table 1]

[0147]
【The invention's effect】
According to the present invention, since the repeating unit having an aliphatic ring structure is introduced into the copolymer that becomes the solid polymer electrolyte material, it has good ion conductivity, water repellency, and gas permeability. It is possible to provide an excellent solid polymer electrolyte material, a liquid composition containing the material, and a solid polymer fuel cell capable of stably obtaining a high battery output.
In addition, since the solid polymer electrolyte material of the present invention has a softening temperature higher than that of the conventional one, not only the polymer electrolyte fuel cell but also ion selective permeable membrane, reverse osmosis membrane, filtration membrane, diaphragm in other electrochemical processes Even when applied as such, it has a feature that it can be used at a high temperature.

Claims (14)

A repeating unit based on the fluorine-containing monomer A which gives a polymer having an aliphatic ring structure in the main chain by radical polymerization;
Ri Do a copolymer comprising repeating units based on the fluoromonomer B of the following formula (1),
Solid polymer electrolyte material ion exchange capacity, characterized in 0.9-1.5 meq / g dry resin der Rukoto.
CF ₂ = CF (R ^f ) _j SO ₂ X (1)
[In the formula (1), j represents 0 or 1,
X is a fluorine atom, a chlorine atom or OM {M is a hydrogen atom, an alkali metal atom or NR ¹ R ² R ³ R ⁴ (R ¹ , R ² , R ³ and R ⁴ may be the same or different; A hydrogen atom or a monovalent organic group), a group represented by
^Rf is a C1-C20 polyfluoroalkylene group having a linear or branched structure, and may contain an etheric oxygen atom. ] The fluorine-containing monomer A is a perfluoromonomer,
The solid polymer electrolyte material according to claim 1, wherein the fluorine-containing monomer B is represented by the following formula (2).

[In the formula (2), k represents an integer of 0 to 2, m represents an integer of 1 to 12, Y represents a fluorine atom or a trifluoromethyl group, and X has the same meaning as X in the formula (1). is there. ] 3. The solid polymer electrolyte material according to claim 1, wherein the repeating unit based on the fluorine-containing monomer A is represented by any one of the following formulas (3) to (5).

[In the formula (3), p, q and r each independently represent 0 or 1,
R ^f1 and R ^f2 may be the same or different and each represents a fluorine atom, a C 1-5 perfluoroalkyl group or a C 1-5 perfluoroalkoxy group,
R ^f3 is a perfluoroalkylene group having 1 to 3 carbon atoms, and may contain a perfluoroalkyl group having 1 to 5 carbon atoms or a perfluoroalkoxy group having 1 to 5 carbon atoms as a substituent. ]

[In the formula (4), s represents 0 or 1,
R ^f4 , R ^f5 , R ^f6 and R ^f7 may be the same or different and each represents either a fluorine atom or a C 1-5 perfluoroalkyl group (provided that R ^f4 and R ^f5 are they may be linked to form a spiro ring when s = 0),
R ^f8 represents a fluorine atom, a C 1-5 perfluoroalkyl group or a C 1-5 perfluoroalkoxy group. ]

[In Formula (5), R ^f9 , R ^f10 , R ^f11 and R ^f12 may be the same or different and each represents a fluorine atom or a C 1-5 perfluoroalkyl group. ] The fluorine-containing monomer A is perfluoro (3-butenyl vinyl ether), perfluoro (2,2-dimethyl-1,3-dioxole), perfluoro (1,3-dioxole), 2,2,4-triol. At least one selected from the group consisting of fluoro-5-trifluoromethoxy-1,3-dioxole and perfluoro (2-methylene-4-methyl-1,3-dioxolane);
The solid polymer electrolyte material according to claim 3, wherein the fluorine-containing monomer B is represented by the following formula (6).

[In Formula (6), k 'shows 0 or 1, X is synonymous with X as described in said Formula (1), Y is synonymous with Y as described in said Formula (2). ] The fluorine-containing monomer A is perfluoro (2,2-dimethyl-1,3-dioxole),
5. The solid polymer electrolyte material according to claim 4, further comprising a repeating unit based on tetrafluoroethylene in addition to the fluorine-containing monomer A and the fluorine-containing monomer B. It is a solid polymer electrolyte material in which the terminal -SO ₂ X group of the repeating unit based on the fluorine-containing monomer B is a -SO ₃ H group, and is used as a constituent material of a solid polymer fuel cell The solid polymer electrolyte material according to any one of claims 1 to 5 , wherein The solid polymer electrolyte material according to any one of claims 1 to 6 , wherein a softening temperature of the copolymer is 100 ° C or higher. Claim 1-7 a solid polymer electrolyte material according to any one of, and, -SO ₂ X group is -SO ₃ M {M terminal of the repeating unit based on the fluoromonomer B is a hydrogen atom, A group represented by an alkali metal atom or NR ¹ R ² R ³ R ⁴ (R ¹ , R ² , R ³ and R ⁴ may be the same or different and each represents a hydrogen atom or a monovalent organic group); A liquid composition, wherein the solid polymer electrolyte material, which is a group, is dissolved or dispersed in an organic solvent having a hydroxyl group in the molecule. A solid polymer fuel cell having an anode, a cathode, and a polymer electrolyte membrane disposed between the anode and the cathode,
A solid polymer electrolyte fuel cell comprising the solid polymer electrolyte material according to claim 6 as a constituent material of the cathode. A repeating unit represented by the following formula (I), a copolymer Ru repeating units Toka Rana based on fluoromonomer D represented by the following formula (II),
The content of repeating units based on the fluorine-containing monomer D is 10 to 75 mol%, and
A fluorine-containing polymer having a number average molecular weight of 5,000 to 5,000,000.

[In the formulas (I) and (II), R ^f16 and R ^f17 may be the same or different and each represents a fluorine atom or a trifluoromethyl group, k ′ represents 0 or 1, and Y represents a fluorine atom or Represents a trifluoromethyl group, and M represents a hydrogen atom, an alkali metal atom or NR ¹ R ² R ³ R ⁴ (R ¹ , R ² , R ³ and R ⁴ may be the same or different, and each represents a hydrogen atom or Represents a monovalent organic group). ] And repeating units based on perfluoro (3-butenyl vinyl ether), a copolymer Ru repeating units Toka Rana based on fluoromonomer D represented by the following formula (II),
The content of repeating units based on the fluorine-containing monomer D is 10 to 75 mol%, and
A fluorine-containing polymer having a number average molecular weight of 5,000 to 5,000,000.

[In formula (II), k ′ represents 0 or 1, Y represents a fluorine atom or a trifluoromethyl group, M represents a hydrogen atom, an alkali metal atom, or NR ¹ R ² R ³ R ⁴ (R ¹ , R ² , R ³ and R ⁴ may be the same or different and each represents a hydrogen atom or a monovalent organic group. ] And repeating units based on perfluoro (2-methylene-4-methyl-1,3-dioxolane), a copolymer Ru repeating units Toka Rana based on fluoromonomer D of the following formula (II) ,
The content of repeating units based on the fluorine-containing monomer D is 10 to 75 mol%, and
A fluorine-containing polymer having a number average molecular weight of 5,000 to 5,000,000.

[In formula (II), k ′ represents 0 or 1, Y represents a fluorine atom or a trifluoromethyl group, M represents a hydrogen atom, an alkali metal atom, or NR ¹ R ² R ³ R ⁴ (R ¹ , R ² , R ³ and R ⁴ may be the same or different and each represents a hydrogen atom or a monovalent organic group. ] A repeating unit represented by the following formula (I), a repeating unit or Rana Ru copolymer based on repeating units and tetrafluoroethylene-based fluorine-containing monomer D represented by the following formula (II),
The content of the repeating unit represented by the following formula (I) is 5 to 70 mol%, the content of the repeating unit based on tetrafluoroethylene is 10 to 85 mol%, and the content of the repeating unit based on the fluorine-containing monomer D Is 5 to 40 mol%, and
A fluorine-containing polymer having a number average molecular weight of 5,000 to 5,000,000.

[In the formulas (I) and (II), R ^f16 and R ^f17 may be the same or different and each represents a fluorine atom or a trifluoromethyl group, k ′ represents 0 or 1, and Y represents a fluorine atom or Represents a trifluoromethyl group, and M represents a hydrogen atom, an alkali metal atom or NR ¹ R ² R ³ R ⁴ (R ¹ , R ² , R ³ and R ⁴ may be the same or different, and each represents a hydrogen atom or Represents a monovalent organic group). ] A solid polymer electrolyte membrane comprising the fluorine-containing polymer according to claim 13 .