JP4779184B2 - Method for producing fluorinated ionomer copolymer - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、スルホン酸基を含有するフッ素系アイオノマー共重合体の製造法に関する。
【０００２】
【従来の技術】
フッ素系アイオノマーとしては、ナフィオン（商標）、フレミオン（商標）などの過フッ素化ポリマー鎖にスルホン酸基ないしカルボキシル基を結合した共重合体が知られている。これらは主として食塩電解に利用されるイオン交換膜として開発され、化学センサー、分離膜、高分子超強酸触媒をはじめ、燃料電池のプロトン輸送高分子電解質などとしての利用が検討されている。
【０００３】
このフッ素系アイオノマーとしては、ＷＯ９８／４３９５２号パンフレットに下記式（１’）
【０００４】
【化４】
〔式中、Ｍはアルカリ金属又はアルカリ土類金属を示す。ｎは０，１又は２を示す。〕で表されるモノマー（以下、「Ｓモノマー」と略す）と他のモノマーとの共重合体が開示されている。
【０００６】
しかしながら、他のモノマーがテトラフルオロエチレンの場合、得られる共重合体の水性ディスパージョンは特にＳモノマーが比較的少ない場合には不安定であり、特に大量に合成した場合、得られた共重合体の精製は容易ではなかった。
【０００７】
【発明が解決しようとする課題】
本発明は、容易に精製可能なフッ素系アイオノマー共重合体の製造法を提供するものである。
【０００８】
【課題を解決するための手段】
本発明者は、上記課題に鑑み検討を重ねた結果、一般式（１）のＳモノマーとテトラフルオロエチレンに加えて第三のモノマーを共重合させることにより、得られる共重合体の水性ディスパージョンの安定性が向上し、得られた三元以上の共重合体は限外濾過法や透析等により容易に残存モノマー等の低分子量イオン性不純物質を除去し、精製できることを見出した。
【０００９】
本発明は、下記の項１〜項４に関する。
項１． （i）下記式（１）
【００１０】
【化５】
〔式中、Ｍはアルカリ金属又はアルカリ土類金属を示す。ｍは１〜４の整数を、ｎは０，１又は２を示す。〕で表される化合物と、
(ii)テトラフルオロエチレンと、
(iii)ヘキサフルオロプロピレン
を重合開始剤及びヨウ素系化合物の存在下に共重合して、スルホン酸基を含有する含フッ素ポリマー鎖セグメントＢを形成する工程；及び
含フッ素ポリマー鎖セグメントＢとテトラフルオロエチレンと、ヘキサフルオロプロピレンを重合開始剤の存在下に反応させ、含フッ素ポリマー鎖セグメントＢと異なる含フッ素ポリマー鎖セグメントＡを形成する工程
を含む、フッ素系アイオノマーブロック共重合体の製造法。
項２． （i）下記式（１）
【００１２】
【化６】
〔式中、Ｍはアルカリ金属又はアルカリ土類金属を示す。ｍは１〜４の整数を、ｎは０，１又は２を示す。〕で表される化合物、
(ii)テトラフルオロエチレン、及び
(iii)ヘキサフルオロプロピレン
の比率が、（i）：（ii）：（iii）＝５〜４９モル％：９４〜５０モル％：０．５〜２０モル％である、項１に記載の製造法。
項３． 前記セグメントＢを形成する工程は、
(i)下記式（１）
【化１０】
(ii)テトラフルオロエチレンと、
(iii)ヘキサフルオロプロピレン
を重合開始剤及びヨウ素系化合物の存在下に種重合して、ポリマー粒子を含むミセル状溶液、ゾル又はディスパージョンを生成し、
前記ミセル状溶液、ゾル又はディスパージョンと前記（i）で表される化合物を重合開始剤の存在下に重合する工程を含む、項１又は２に記載の製造法。
項４． 項１〜３のいずれかに記載の製造法により得られたフッ素系アイオノマーブロック共重合体の溶液又は分散液を限外濾過又は透析することにより、下記式（１）で表される化合物の未反応物を回収するとともに低分子量イオン性不純物質を除去する方法。
【００１４】
【化７】
〔式中、Ｍはアルカリ金属又はアルカリ土類金属を示す。ｍは１〜４の整数を、ｎは０，１又は２を示す。〕
【００１６】
【発明の実施の形態】
本発明の方法で用いられる一般式（１）で表される原料化合物は公知であり、例えばＷＯ９８／４３９５２号パンフレットに記載の方法により製造できる。すなわち、下記のスキームに従い、対応する原料の熱分解により製造できる。
【００１７】
【化８】
〔式中、Ｍはアルカリ金属又はアルカリ土類金属を示す。ｍは１〜４の整数を、ｎは０，１又は２を示す。〕
本発明の共重合体において、一般式（１）で表されるＳモノマー、テトラフルオロエチレン(TFE)及び第三モノマーとしてのヘキサフルオロプロピレン、クロロトリフルオロエチレン、ビニリデンフルオライド、パーフルオロアルキルビニルエーテル(CF2=CFORf（Rfは炭素数１〜５のパーフルオロアルキル基を示す。）)及びエチレンからなる群から選ばれる少なくとも１種の比率は、Ｓモノマー：TFE：第三モノマー＝５〜４９モル％：９４〜５０モル％：０．５〜２０モル％である。ここで、第三モノマーは生成するポリマー溶液又はポリマー分散液を安定化するためにＴＦＥに対して必要最小限の量を使用するのが好ましい。
【００１９】
本発明の製造法においては、ラジカル開始源の存在下に容易に共重合して製造することができ、ヨウ素系化合物の存在下に共重合することにより、フッ素系アイオノマーブロック共重合体をも製造することができる。このヨウ素系化合物を用いるヨウ素移動重合法自体は公知である（例えば、高分子論文集 第４９巻第１０号（１９９２）７６５〜７８３頁参照）。
【００２０】
用いるヨウ素系化合物としては、例えば１，３−ジヨードパーフルオロプロパン、１，４−ジヨードパーフルオロブタン、１，３−ジヨード−２−クロロパーフルオロプロパン、１，５−ジヨード−２，４−ジクロロパーフルオロペンタン、１，６−ジヨードパーフルオロヘキサン、１，８−ジヨードパーフルオロオクタン、１，１２−ジヨードパーフルオロドデカンおよび１，１６−ジヨードパーフルオロヘキサデカンなどのパーフルオロアルキレンジアイオダイド、ＣＦ2＝ＣＦＩやＣＦ2＝ＣＦＯＣＦ2ＣＦ2Ｉなどの不飽和結合を有するパーフルオロアルケニルアイオダイド、ジヨードメタン、１，２−ジヨードエタンが挙げられる。これらの化合物は単独で使用してもよく、相互に組み合わせて使用することもできる。なかでも１，４−ジヨードパーフルオロブタンが好ましい。ジヨウ素化合物の量は、各モノマーの合計重量に対して０．０１〜１重量％である。
【００２１】
本発明の製造法で使用する重合開始剤は、従来からフッ素系ポリマーの重合に使用されているものと同じものであってよい。これらの開始剤には有機及び無機の過酸化物並びにアゾ化合物がある。代表的な開始剤として、過硫酸塩類、過酸化カーボネート類、過酸化エステル類などがあり、好ましい開始剤として過硫酸アンモニウム（ＡＰＳ）が挙げられる。ＡＰＳは単独で使用してもよく、またサルファイト類、亜硫酸塩類、パーフルオロアルキルスルフィン酸塩類のような還元剤と組み合わせて使用することもできる。重合開始剤の量は、各モノマーの合計重量に対して０．０１〜１重量％である。
【００２２】
ブロック共重合体を製造する場合には、少なくとも２段階の反応で行われる。
【００２３】
ブロック共重合体の製造法を、下記の実施例１の１）段階〜４）段階を例に取り説明する。
【００２４】
実施例の１）段階は、本発明で製造される共重合体のシード（種）を調製する段階で、この段階によりＩ−Ａ−Ｉなる低分子量でポリマー鎖末端にヨウ素を結合したポリマー微小粒子よりなるミセル状溶液（ないしゾル）、場合によりディスパージョンが生成すると考えられる。ここで発生する微小粒子が次の２）〜３）段階へ移る。この２）段階〜３）段階は、Ｓモノマーの仕込量が少し異なるが基本的にはＳモノマーをできるだけ多く含有したポリマー鎖セグメント−Ｂ−を調製する。生成するポリマーはＩ−Ｂ−Ａ−Ｂ−Ｉとなる。Ｉ−Ａ−Ｉの段階でできるだけ多くの微小粒子を作っておくことにより２）段階〜３）段階（これは同じ工程でＩ−Ｂ−Ａ−Ｂ−Ｉの−Ｂ−部分の分子量とポリマー全体のＳモノマー含有量を増加していく過程）の工程で重合反応速度が本来遅くなるところを減速させないですむ効果がある。こうしてポリマー分子（Ｉ−Ｂ−Ａ−Ｂ−Ｉ）全体の分子量を増加させてから４）段階に入り、この段階でいったん３倍に希釈してＳモノマーの濃度を低下させ、１）段階と同程度に設定し、１）段階と同程度の組成の水不溶性の結晶化可能なポリマー鎖セグメント−Ａ’−を形成させて、結果としてＩ−Ａ’−Ｂ−Ａ−Ｂ−Ａ’−Ｉの形のブロック共重合体とすることができる。１）段階の−Ａ−も−Ａ’−とほぼ同じ組成を設定しているが、分子量が小さいため、場合により水溶性となることもある。
【００２５】
一般にポリマー鎖セグメントＡの分子量は約５０００〜１００万であり、ポリマー得量とヨウ素系化合物仕込量の比により調節され得る。また、ポリマー鎖セグメントＢとポリマー鎖セグメントＡ＋Ａ’の重量比は、（９８：２）〜（５：９５）、好ましくは（９５：５）〜（４０：６０）の範囲で自由に選択できる。ブロック共重合体全体の分子量は、約５０００〜約３００万である。
【００２６】
得られた共重合体またはブロック共重合体は、安定な水性ディスパージョンとして得られ、原料であるＳモノマー等の未反応物、及び低分子量のイオン性不純物質（たとえば、重合開始剤やその分解物）を限外濾過等により容易に除去することができる。
【００２７】
本発明の共重合体は、Ｓモノマーとテトラフルオロエチレンと上記第三モノマーの少なくとも１種を一定の比率で共重合してもよく、Ｓモノマーの比率の高いセグメントと、Ｓモノマーの比率を順次低減したセグメントを連結した２以上のブロック共重合体又はグラフト共重合体であってもよい。グラフト共重合体はヨウ素系化合物としてＣＦ2＝ＣＦＣＦ2ＣＦ2Ｉなどを採用した場合に得ることができる。
【００２８】
本発明の方法により製造されるアイオノマーは、例えば選択的イオン透過性、立体特異性などのイオン交換膜、センサー、選択透過膜、触媒、固体電解質やそれを用いた燃料電池などへの利用に際して有利で特異な性能を与えうる。
【００２９】
【発明の効果】
本発明によれば、強酸性フッ素系高分子電解質として有用なスルホン酸基を含有するフッ素系アイオノマー共重合体を容易に精製可能な状態で得ることができる。特にフッ素系アイオノマーブロック共重合体は、結晶性で結果的にスルホン酸基を含有する含フッ素ポリマー鎖セグメントをも含むポリマー分子全体を、その結晶部分により拘束して成形体の機械的強度を増大するという効果を有する。
【００３０】
【実施例】
以下、本発明を実施例及び比較例を用いてより詳細に説明する。
参考例１
攪拌翼、温度計、窒素ガス（Ｎ2ガス）導入口、還流冷却管を付した１リットルのフラスコに３００ｇの新しく精留により精製したCl(CF2CFCl)3Clと脱水したジグライム４ｇを入れ、乾燥Ｎ2ガスを５０ｍｌ／分で導入しながら攪拌下に、粉末状として１３０℃で２時間加熱脱水したNaOCOCF(CF3)OCF2CF2SO3Na 240gを湿気を吸収しないよう注意して素早く仕込み、直ちにマントルヒーターで加熱を開始した。２０分後に２００℃に達したところで還流が開始し、さらに５分後に還流冷却管上より放出されるガス量が急激に増加するのを認めた。約２０分程度反応を継続後、ガスの発生がほぼ見られなくなったところでマントルヒーターのスイッチを切り、氷冷浴中で５分間フラスコを室温まで急冷した。反応温度は最高で２０７℃であった。
【００３１】
Cl(CF2CFCl)3Cl中に分散した褐色粒状粉末をガラスフィルターで濾過し、少量のHCFC225で洗浄後、風乾して若干着色した粒状粉末を収得した。次に、該粒状粉末を純水２００ｍｌに溶解し、１０％ＮａＯＨ水溶液でｐＨ＝７に調整後、再度濾別して濾液を採取した。フィルター上の白色残渣はＮａＦであった。濾液をエバポレーターにかけ、水分を蒸発して全体がほぼ湿潤状態で固化した時点で、いったん５℃の冷蔵庫で１時間保冷後、ガラスフィルター上に移し、約２時間室温大気中で減圧濾過処理した。徐々に褐色の液体がしみ出し、フィルター上には白色結晶性粉末が残存した。得られた白色結晶性粉末を水から再結晶して目的とするCF2=CFOCF2CF2SO3Na（Ｓモノマー）を得た。
実施例１
1) 温度計鞘管、ガス導入管を備えた5Lのステンレス製耐圧反応槽に純水2L、過硫酸アンモニウム(APS)0.1g、参考例１で得たＳモノマー 60g、1,4-ジヨードパーフルオロブタン0.6gを入れ、攪拌下に内部空間をヘキサフルオロプロピレン(HFP)で微加圧／真空の繰り返しにより置換後、ヘキサフルオロプロピレンガスにより0.3MPaまで加圧、次にテトラフルオロエチレン(TFE)で1MPaまで加圧した後、６０℃まで昇温した。３０分後に圧力は1.15MPaに達した後、直ぐに圧力降下が始まるので、0.1MPaの圧力低下の後２０℃以下まで降温し、放圧していったん重合反応を停止した。生成物は透明ディスパージョン状である。本段階はいわゆる"種重合"で主として安定なディスパージョンの核を得ることを目的としている。
2) 1)で生成したディスパージョンにＳモノマー 80g、APS 0.05gを添加し、ｐＨを7.5に調整後、1)と同じ操作で重合反応を開始した。６０℃に昇温後直ちに圧力降下が始まるので、８時間後に0.16MPaの圧力低下があったところで重合を停止したところ、1)と同様に無色透明のディスパージョンが得られた。
3) 2)に続いてＳモノマー 50g、APS 0.1gを追加し、2)と同様の重合操作を２回繰り返し、１６時間の後に重合を終了して無色透明のディスパージョン2160gを得た。このディスパージョンは非常に安定で、塩酸やカリ明礬溶液などの電解質溶液を添加しても凝析しないので、その一部から水分を蒸発させた後十分に乾燥し、これからアセトンで未反応のＳモノマーを溶解回収して、物質収支によりポリマー得量とポリマー中のＳモノマー含有量を算出すると、各々157g及び25.7モル％であった。
4) 3)のディスパージョン330gを純水で３倍に希釈し、APS 0.1gを添加し、1)〜3)と同じ反応槽に仕込み、同様の操作で空間をHFPガスで置換後、0.45MPaに加圧し、さらにTFEガスで0.9MPaまで昇圧し、６０℃に昇温したところ直ちに圧力降下が始まった。４時間後に0.06MPaの圧力降下があったところで、２０℃に降温、放圧して重合反応を終了した。生成物は若干白濁した透明なディスパージョンであった。
【００３２】
このディスパージョンの一部を蒸発乾固し、アセトンで抽出してＳモノマーを回収した結果から、ポリマー得量は81gであり、ポリマー中のＳモノマー含有量は7.8モル％であった。本ポリマーはブロック共重合体と考えられる。得られたディスパージョンの19F-NMRを図１，視差熱重量分析(DTGA)の結果を図２に示す。ディスパージョンでも19F-NMRスペクトルが得られ、また官能基がSO3Na型である本発明のポリマーの熱安定性が良好であることが明らかになった。
比較例１
HFPをコモノマーとして利用しない以外は、実施例１と同様にしてTFEとＳモノマーの共重合体を得ることができる。得られる２元系共重合体は、生成ディスパージョンが不安定で長時間の重合反応により共重合体の凝析が起こりやすい。また、該２元系共重合体のディスパージョンは不安定であるため、限外濾過法や透析により精製する過程で共重合体の沈降が起こりやすく、限外濾過法や透析による未反応のＳモノマーの除去、濃縮が困難である。
実施例２
実施例１の1)〜4)の各段階で生成するディスパージョンは極めて安定であるため限外濾過法の適用により未反応の残存Ｓモノマーを回収することができる。アミコン社のCentriprep（登録商標）のセルに実施例１の3)及び4)で生成したディスパージョンを入れ、室温1500Gの遠心分離条件下で処理すると、Ｓモノマーのみ限外濾過膜を透過する。更にディスパージョンをセルに追加して数回繰り返した後、次に純水を添加しながら同法を継続したところ、Ｓモノマーはほぼ完全に除去され、かつ、ポリマー濃度が60%の濃縮ディスパージョンを得ることができた。
【図面の簡単な説明】
【図１】実施例１で得られたディスパージョンの19F-NMRを示す。
【図２】実施例１で得られたディスパージョンの視差熱重量分析(DTGA)の結果を示す。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a fluorinated ionomer copolymer containing a sulfonic acid group.
[0002]
[Prior art]
As the fluorinated ionomer, a copolymer in which a sulfonic acid group or a carboxyl group is bonded to a perfluorinated polymer chain such as Nafion (trademark) or Flemion (trademark) is known. These have been developed mainly as ion exchange membranes used for salt electrolysis, and are being investigated for use as proton transport polymer electrolytes in fuel cells, including chemical sensors, separation membranes, and polymer superacid catalysts.
[0003]
As this fluorine ionomer, WO98 / 43952 pamphlet has the following formula (1 ′).
[0004]
[Formula 4]
[In the formula, M represents an alkali metal or an alkaline earth metal. n represents 0, 1 or 2. ] (Hereinafter, abbreviated as “S monomer”) and other monomers are disclosed.
[0006]
However, when the other monomer is tetrafluoroethylene, the aqueous dispersion of the resulting copolymer is unstable, especially when the amount of S monomer is relatively small, and the resulting copolymer, especially when synthesized in large quantities. Purification of was not easy.
[0007]
[Problems to be solved by the invention]
The present invention provides a process for producing a fluorine ionomer copolymer that can be easily purified.
[0008]
[Means for Solving the Problems]
As a result of repeated investigations in view of the above problems, the present inventor has obtained an aqueous dispersion of a copolymer obtained by copolymerizing a third monomer in addition to the S monomer of general formula (1) and tetrafluoroethylene. It was found that the ternary or higher copolymer obtained can be easily purified by removing low molecular weight ionic impurities such as residual monomers by ultrafiltration or dialysis.
[0009]
The present invention relates to the following items 1 to 4 .
Item 1. (I) The following formula (1)
[0010]
[Chemical formula 5]
[In the formula, M represents an alkali metal or an alkaline earth metal. m represents an integer of 1 to 4, and n represents 0, 1 or 2. And a compound represented by
(ii) tetrafluoroethylene,
(iii) F hexafluorobutene Pro pyrene emission
To form a fluoropolymer chain segment B containing a sulfonic acid group by copolymerizing in the presence of a polymerization initiator and an iodine-based compound ; and
A step of reacting fluorine-containing polymer chain segment B, tetrafluoroethylene, and hexafluoropropylene in the presence of a polymerization initiator to form a fluorine-containing polymer chain segment A different from fluorine-containing polymer chain segment B
A process for producing a fluorinated ionomer block copolymer.
Item 2. (I) The following formula (1)
[0012]
[Chemical 6]
[In the formula, M represents an alkali metal or an alkaline earth metal. m represents an integer of 1 to 4, and n represents 0, 1 or 2. A compound represented by]
(ii) tetrafluoroethylene , and
(iii) F hexafluorobutene Pro pyrene emission
The manufacturing method of claim | item 1 whose ratio is (i) :( ii) :( iii) = 5-49 mol%: 94-50 mol%: 0.5-20 mol%.
Item 3. The step of forming the segment B includes:
(i) The following formula (1)
[Chemical Formula 10]
(ii) tetrafluoroethylene,
(iii) hexafluoropropylene
Is seeded in the presence of a polymerization initiator and an iodine-based compound to produce a micellar solution, sol or dispersion containing polymer particles,
Item 3. The production method according to Item 1 or 2, comprising a step of polymerizing the micelle solution, sol or dispersion and the compound represented by (i) in the presence of a polymerization initiator.
Item 4. Claim 1 by ultrafiltration or dialysis solution or dispersion of the obtained by the production method off Tsu-containing ionomer block copolymer according to to 3 or of a compound represented by the following formula (1) Of recovering unreacted substances and removing low molecular weight ionic impurities.
[0014]
[Chemical 7]
[In the formula, M represents an alkali metal or an alkaline earth metal. m represents an integer of 1 to 4, and n represents 0, 1 or 2. ]
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The raw material compound represented by the general formula (1) used in the method of the present invention is known and can be produced, for example, by the method described in WO98 / 43952 pamphlet. That is, it can be produced by thermal decomposition of the corresponding raw material according to the following scheme.
[0017]
[Chemical 8]
[In the formula, M represents an alkali metal or an alkaline earth metal. m represents an integer of 1 to 4, and n represents 0, 1 or 2. ]
In the copolymer of the present invention, the S monomer represented by the general formula (1), tetrafluoroethylene (TFE), and hexafluoropropylene, chlorotrifluoroethylene, vinylidene fluoride as a third monomer, perfluoroalkyl vinyl ether ( The ratio of at least one selected from the group consisting of CF2 = CFORf (Rf represents a perfluoroalkyl group having 1 to 5 carbon atoms) and ethylene is S monomer: TFE: third monomer = 5-49 mol%. : 94-50 mol%: 0.5-20 mol%. Here, the third monomer is preferably used in the minimum amount necessary for TFE in order to stabilize the resulting polymer solution or polymer dispersion.
[0019]
In the production method of the present invention, the copolymer can be easily copolymerized in the presence of a radical initiator, and the fluorine ionomer block copolymer is also produced by copolymerization in the presence of an iodine compound. can do. The iodine transfer polymerization method using this iodine-based compound is known per se (see, for example, Polymer Journal Vol. 49, No. 10 (1992), pages 765-783).
[0020]
Examples of the iodine compound used include 1,3-diiodoperfluoropropane, 1,4-diiodoperfluorobutane, 1,3-diiodo-2-chloroperfluoropropane, and 1,5-diiodo-2,4. Perfluoroalkyls such as dichloroperfluoropentane, 1,6-diiodoperfluorohexane, 1,8-diiodoperfluorooctane, 1,12-diiodoperfluorododecane and 1,16-diiodoperfluorohexadecane range iodide, CF 2 = CFI and CF 2 = CFOCF 2 CF 2 I perfluoroalkenyl iodide having an unsaturated bond such as, diiodomethane, 1,2-diiodoethane and the like. These compounds may be used alone or in combination with each other. Of these, 1,4-diiodoperfluorobutane is preferable. The amount of the diiodine compound is 0.01 to 1% by weight based on the total weight of each monomer.
[0021]
The polymerization initiator used in the production method of the present invention may be the same as that conventionally used for the polymerization of fluoropolymers. These initiators include organic and inorganic peroxides and azo compounds. Typical initiators include persulfates, carbonates, peroxides, and the like, and preferred initiators include ammonium persulfate (APS). APS may be used alone or in combination with a reducing agent such as sulfites, sulfites, and perfluoroalkylsulfinates. The amount of the polymerization initiator is 0.01 to 1% by weight based on the total weight of each monomer.
[0022]
When producing a block copolymer, it is performed by reaction of at least 2 steps.
[0023]
The production method of the block copolymer will be described by taking steps 1) to 4) of Example 1 below as an example.
[0024]
The step 1) of the example is a step of preparing a seed of the copolymer produced in the present invention. By this step, a polymer microparticle having iodine at a low molecular weight of IA-I and bound to the end of the polymer chain. It is considered that a micellar solution (or sol) composed of particles, and in some cases, a dispersion is generated. The fine particles generated here move to the following steps 2) to 3). In steps 2) to 3), the polymer chain segment -B- containing basically as much S monomer as possible is prepared although the amount of S monomer charged is slightly different. The resulting polymer is I-B-A-B-I. By preparing as many microparticles as possible at the stage of I-A-I, the molecular weight of the -B- moiety of the I-B-A-B-I and polymer In the process of increasing the total S monomer content, there is an effect that it is not necessary to decelerate where the polymerization reaction rate is inherently slow. In this way, the molecular weight of the whole polymer molecule (I-B-A-B-I) is increased, and then the step 4) is started. In this step, the concentration of S monomer is decreased by 3 times to reduce the concentration of S monomer. 1) to form a water-insoluble crystallizable polymer chain segment -A'- having the same composition as in step 1), resulting in IA'-BABA-A'- It can be a block copolymer of the form I. 1) -A- has the same composition as -A'- but has a small molecular weight and may be water-soluble in some cases.
[0025]
Generally, the molecular weight of the polymer chain segment A is about 5,000 to 1,000,000, and can be adjusted by the ratio of the polymer yield and the iodine compound charge. The weight ratio of the polymer chain segment B and the polymer chain segment A + A ′ can be freely selected in the range of (98: 2) to (5:95), preferably (95: 5) to (40:60). The overall molecular weight of the block copolymer is about 5000 to about 3 million.
[0026]
The obtained copolymer or block copolymer is obtained as a stable aqueous dispersion, and unreacted materials such as S monomer as a raw material and low molecular weight ionic impurities (for example, a polymerization initiator and its decomposition) Can be easily removed by ultrafiltration or the like.
[0027]
The copolymer of the present invention may copolymerize S monomer, tetrafluoroethylene, and at least one of the above third monomers at a certain ratio, and sequentially increase the S monomer ratio segment and the S monomer ratio in order. It may be two or more block copolymers or graft copolymers in which reduced segments are connected. The graft copolymer can be obtained when CF 2 = CFCF 2 CF 2 I or the like is adopted as the iodine compound.
[0028]
The ionomer produced by the method of the present invention is advantageous for use in ion exchange membranes such as selective ion permeability and stereospecificity, sensors, selective permeation membranes, catalysts, solid electrolytes and fuel cells using the same. Can give unique performance.
[0029]
【The invention's effect】
According to the present invention, a fluorinated ionomer copolymer containing a sulfonic acid group useful as a strongly acidic fluorinated polymer electrolyte can be obtained in a readily purifiable state. In particular, fluorine-based ionomer block copolymers increase the mechanical strength of the compact by constraining the entire polymer molecule, including the fluorinated polymer chain segment, which is crystalline and consequently contains sulfonic acid groups, by the crystalline portion. Has the effect of
[0030]
【Example】
Hereinafter, the present invention will be described in more detail using examples and comparative examples.
Reference example 1
A 1 liter flask equipped with a stirring blade, thermometer, nitrogen gas (N 2 gas) inlet and reflux condenser was charged with 300 g of newly purified rectified Cl (CF 2 CFCl) 3 Cl and 4 g of dehydrated diglyme and dried N 2 Gasodium NaOCOCF (CF3) OCF2CF2SO3Na 240g, which was dehydrated by heating at 130 ° C for 2 hours under stirring while introducing gas at a rate of 50ml / min, was charged quickly, taking care not to absorb moisture, and immediately started heating with a mantle heater. did. After 20 minutes, when the temperature reached 200 ° C., refluxing was started, and after 5 minutes, the amount of gas released from the reflux condenser was abruptly increased. After the reaction was continued for about 20 minutes, the mantle heater was turned off when almost no gas generation was observed, and the flask was rapidly cooled to room temperature in an ice-cooled bath for 5 minutes. The maximum reaction temperature was 207 ° C.
[0031]
The brown granular powder dispersed in Cl (CF2CFCl) 3Cl was filtered through a glass filter, washed with a small amount of HCFC225, and then air-dried to obtain a slightly colored granular powder. Next, the granular powder was dissolved in 200 ml of pure water, adjusted to pH = 7 with a 10% NaOH aqueous solution, filtered again, and the filtrate was collected. The white residue on the filter was NaF. When the filtrate was applied to an evaporator and the water was evaporated and the whole solidified almost in a wet state, the filtrate was once kept in a refrigerator at 5 ° C. for 1 hour, then transferred onto a glass filter, and filtered under reduced pressure in room temperature atmosphere for about 2 hours. A brown liquid gradually oozed out and a white crystalline powder remained on the filter. The obtained white crystalline powder was recrystallized from water to obtain the target CF2 = CFOCF2CF2SO3Na (S monomer).
Example 1
1) In a 5L stainless steel pressure-resistant reactor equipped with a thermometer sheath tube and gas inlet tube, 2L of pure water, 0.1g of ammonium persulfate (APS), 60g of S monomer obtained in Reference Example 1, 1,4-diiodoper Add 0.6 g of fluorobutane, replace the internal space with hexafluoropropylene (HFP) under repeated stirring by repeating slight pressurization / vacuum, pressurize to 0.3 MPa with hexafluoropropylene gas, and then tetrafluoroethylene (TFE) After pressurizing to 1 MPa, the temperature was raised to 60 ° C. After 30 minutes, the pressure started to drop immediately after reaching 1.15 MPa. Therefore, the temperature was lowered to 20 ° C. or lower after the pressure drop of 0.1 MPa, the pressure was released, and the polymerization reaction was once stopped. The product is in the form of a transparent dispersion. This stage is the so-called "seed polymerization" and is aimed mainly at obtaining stable dispersion nuclei.
2) After adding 80 g of S monomer and 0.05 g of APS to the dispersion produced in 1) and adjusting the pH to 7.5, the polymerization reaction was started in the same manner as in 1). Since the pressure drop started immediately after the temperature was raised to 60 ° C., the polymerization was stopped when the pressure dropped 0.16 MPa after 8 hours, and a colorless and transparent dispersion was obtained as in 1).
3) Following 2), 50 g of S monomer and 0.1 g of APS were added, and the same polymerization procedure as 2) was repeated twice. After 16 hours, the polymerization was terminated to obtain 2160 g of a colorless and transparent dispersion. This dispersion is very stable and does not coagulate even when an electrolyte solution such as hydrochloric acid or potassium alum solution is added. Therefore, after water is evaporated from a part of the dispersion, it is sufficiently dried and then unreacted with acetone. When the monomer was dissolved and recovered, and the polymer yield and the S monomer content in the polymer were calculated from the mass balance, they were 157 g and 25.7 mol%, respectively.
4) Dilute 330g of 3) 3 times with pure water, add 0.1g of APS, charge into the same reaction tank as 1) to 3), replace the space with HFP gas in the same way, 0.45 When the pressure was increased to MPa, the pressure was further increased to 0.9 MPa with TFE gas and the temperature was raised to 60 ° C., the pressure drop immediately started. After 4 hours, when the pressure drop was 0.06 MPa, the temperature was lowered to 20 ° C. and the pressure was released to complete the polymerization reaction. The product was a clear dispersion with a slight cloudiness.
[0032]
A part of this dispersion was evaporated to dryness and extracted with acetone to recover the S monomer. As a result, the polymer yield was 81 g, and the S monomer content in the polymer was 7.8 mol%. The polymer is considered a block copolymer. 19 F-NMR of the obtained dispersion is shown in FIG. 1, and the results of parallax thermogravimetric analysis (DTGA) are shown in FIG. A 19 F-NMR spectrum was also obtained by dispersion, and it was revealed that the thermal stability of the polymer of the present invention having a functional group of SO3Na type was good.
Comparative Example 1
A copolymer of TFE and S monomer can be obtained in the same manner as in Example 1 except that HFP is not used as a comonomer. The resulting binary copolymer has an unstable dispersion and is prone to coagulation due to a long polymerization reaction. In addition, since the dispersion of the binary copolymer is unstable, the copolymer is likely to precipitate during the process of purification by ultrafiltration or dialysis, and unreacted S due to ultrafiltration or dialysis. It is difficult to remove and concentrate the monomer.
Example 2
Since the dispersion produced in each step 1) to 4) of Example 1 is extremely stable, unreacted residual S monomer can be recovered by applying an ultrafiltration method. When the dispersion produced in 3) and 4) of Example 1 is placed in a Centriprep (registered trademark) cell manufactured by Amicon and treated under centrifugation conditions at room temperature of 1500 G, only the S monomer permeates the ultrafiltration membrane. After adding the dispersion to the cell and repeating it several times, the process was continued with the addition of pure water, and the S monomer was almost completely removed and the concentrated dispersion had a polymer concentration of 60%. Could get.
[Brief description of the drawings]
1 shows the 19 F-NMR of the dispersion obtained in Example 1. FIG.
FIG. 2 shows the results of parallax thermogravimetric analysis (DTGA) of the dispersion obtained in Example 1.
Claims (4)
(ii)テトラフルオロエチレンと、
(iii)ヘキサフルオロプロピレン
を重合開始剤及びヨウ素系化合物の存在下に共重合して、スルホン酸基を含有する含フッ素ポリマー鎖セグメントＢを形成する工程；及び
含フッ素ポリマー鎖セグメントＢとテトラフルオロエチレンと、ヘキサフルオロプロピレンを重合開始剤の存在下に反応させ、含フッ素ポリマー鎖セグメントＢと異なる含フッ素ポリマー鎖セグメントＡを形成する工程
を含む、フッ素系アイオノマーブロック共重合体の製造法。(i) The following formula (1)
(ii) tetrafluoroethylene,
(iii) F hexafluorobutene Pro pyrene emission
To form a fluoropolymer chain segment B containing a sulfonic acid group by copolymerizing in the presence of a polymerization initiator and an iodine-based compound ; and
A step of reacting fluorine-containing polymer chain segment B, tetrafluoroethylene, and hexafluoropropylene in the presence of a polymerization initiator to form a fluorine-containing polymer chain segment A different from fluorine-containing polymer chain segment B
A process for producing a fluorinated ionomer block copolymer.
(ii)テトラフルオロエチレン、及び(ii) tetrafluoroethylene, and
(iii)ヘキサフルオロプロピレン(iii) hexafluoropropylene
の比率が、（i）：（ii）：（iii）＝５〜４９モル％：９４〜５０モル％：０．５〜２０モル％である、請求項１に記載の製造法。The production method according to claim 1, wherein the ratio of (i) :( ii) :( iii) = 5 to 49 mol%: 94 to 50 mol%: 0.5 to 20 mol%.
(i)下記式（１）
(ii)テトラフルオロエチレンと、
(iii)ヘキサフルオロプロピレン
を重合開始剤及びヨウ素系化合物の存在下に種重合して、ポリマー粒子を含むミセル状溶液、ゾル又はディスパージョンを生成し、
前記ミセル状溶液、ゾル又はディスパージョンと前記（i）で表される化合物を重合開始剤の存在下に重合する工程を含む、請求項１又は２に記載の製造法。 The step of forming the segment B includes:
(i) The following formula (1)
(ii) tetrafluoroethylene,
(iii) hexafluoropropylene
Is seeded in the presence of a polymerization initiator and an iodine-based compound to produce a micellar solution, sol or dispersion containing polymer particles,
The manufacturing method of Claim 1 or 2 including the process of superposing | polymerizing the said micelle solution, sol, or dispersion and the compound represented by said (i) in presence of a polymerization initiator.
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| JP2000038704A JP4779184B2 (en) | 2000-02-16 | 2000-02-16 | Method for producing fluorinated ionomer copolymer |
| DE60119307T DE60119307T2 (en) | 2000-02-16 | 2001-02-16 | METHOD FOR PRODUCING A FLUORIONOMER, METHOD FOR CLEANING AND CONCENTRATING IONOMERS AND METHOD FOR FILM-FORMING |
| PCT/JP2001/001128 WO2001060876A1 (en) | 2000-02-16 | 2001-02-16 | Process for producing fluoroionomer, method for purification and concentration of the ionomer, and method of film formation |
| US10/182,737 US7482415B2 (en) | 2000-02-16 | 2001-02-16 | Process for producing fluoroionomer, method for purification and concentration of the ionomer, and method of film formation |
| EP01904513A EP1283225B1 (en) | 2000-02-16 | 2001-02-16 | Process for producing fluoroionomer, method for purification and concentration of the ionomer, and method of film formation |
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| JPH11130743A (en) * | 1997-08-27 | 1999-05-18 | Mitsubishi Heavy Ind Ltd | Production of perfluoroalkylvinyl ether derivative |
| US6025092A (en) * | 1998-02-13 | 2000-02-15 | E. I. Du Pont De Nemours And Company | Fluorinated ionomers and their uses |
| JP4150867B2 (en) * | 1998-05-13 | 2008-09-17 | ダイキン工業株式会社 | Materials for solid polymer electrolytes suitable for use in fuel cells |
| CN1342172A (en) * | 1999-03-02 | 2002-03-27 | 纳幕尔杜邦公司 | Free radical polymerization method for fluorinated copolymers |
| JP2000327809A (en) * | 1999-05-21 | 2000-11-28 | Asahi Glass Co Ltd | Preparation of ion exchange membrane |
| WO2000077057A2 (en) * | 1999-06-16 | 2000-12-21 | E.I. Du Pont De Nemours And Company | Fluorinated ionic polymers |
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