JP4081956B2 - Partially carbonized asymmetric hollow fiber separation membrane, its production method and gas separation method - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、ポリイミド中空糸分離膜を部分炭素化して得られたガス分離性能が著しく高められた非対称性構造を有する中空糸分離膜に関する。また、その分離膜を使用してガス混合物からハロゲン化合物ガスを効率的に分離する方法に関する。
【０００２】
【従来の技術】
従来、透過性の高い非対称性ガス分離膜として、種々のポリマーを素材とするものが知られているが、近年、例えば、特開昭６０−１７９１０２号公報、特開平１−２２１５１８号公報などにおいて、有機ポリマー製の膜を高温で処理して、耐薬品性の優れたガス分離膜用の多孔性炭素膜を製造する方法、および、それらの方法で得られた炭素膜（中空糸炭素膜）が提案された。
【０００３】
しかしながら、特開昭６０−１７９１０２号公報で開示されているのは、ポリアクリロニトリルなどの膜を高温で長時間加熱して得られた実質的に炭素で構成された炭化膜ならびに黒鉛化膜のいずれをも含有する非対称性構造の分離膜であるが、この膜の二酸化炭素ガスと窒素ガスのガス透過速度比は極めて低レベルのものであった。また、この公報では、ポリマー製の膜を部分炭化して得られた膜については全く言及されていない。
【０００４】
また、特開平１−２２１５１８号公報で開示されているのは、３乃至５オングストロームの多数の微多孔が腹部に存在し、６オングストローム以上の大きさの分子の吸着量が０．１ｃｍ3／ｇ以下である中空糸炭素膜繊維であるので、孔径が６オングストローム以上の多孔性構造を有する部分（多孔質層）が大部分を占める非対称性構造を有する膜とは全く異なるものである。
【０００５】
一方、特開平４−１１９３３号公報、特開平４−１９３３３４号公報、特開平５−２２０３６０号公報には、芳香族ポリイミドからなる非対称性構造を有する中空糸膜を部分炭素化して得られた非対称性構造を有する中空糸分離膜およびその製造方法が開示されている。
【０００６】
ところで、ガス絶縁開閉装置、ガス遮断機、ガス絶縁変圧器、管路気中送電等のガス絶縁電気機器の電気絶縁ガスとして、ＳＦ6（六フッ化イオウ）ガス、フロンガス、四塩化炭素ガスなどを中心とするハロゲン化合物が用いられている。最近は、地球規模で課題となっている地球温暖化ガスとしての対策から、その使用量を削減するため、ハロゲン化合物とそれ以外の電気絶縁性ガス（キャリアーガス）からなる混合ガスをガス絶縁電気機器の電気絶縁ガスとして使用する試みがなされている。
【０００７】
また、半導体産業では、ガスが関与する半導体プロセスにおいて、エッチングや洗浄などに、ＣＦ4、Ｃ2Ｆ6、Ｃ3Ｆ8、Ｃ4Ｆ10、ＳＦ6、ＮＦ3等のパーフルオロ化合物がもっぱら使用されつつある。これらパーフルオロ化合物ガスは、純粋な状態で、あるいは例えば空気、窒素もしくは他の不活性ガスで希釈した状態で、または他のパーフルオロ化合物ガスもしくは他のキャリヤーガス（例えば、不活性ガス）との混合物の状態で使用される。
【０００８】
これら、キャリアーガス中に含まれるパーフルオロ化合物ガスのほとんどは、地球温暖化などの環境に悪影響を及ぼすガスであり、大気中に排出せず、回収再利用される必要がある。
【０００９】
本発明者らは、特願平１０−３６５５９８号において、これらのパーフルオロ化合物ガスの分離回収に、芳香族ポリイミドからなる非対称性構造を有する中空糸分離膜を部分炭素化して得られた非対称性構造を有する中空糸分離膜を使用することを提案し、パーフルオロ化合物ガスを効率的に分離回収できることを示した。
【００１０】
しかしながら、ガスの分離回収の効率は高い程好ましく、また回収するガスを再利用するためにはガスの純度をより高める必要があるため、さらに高い分離性能を有する分離膜が要求されている。
【００１１】
【発明が解決しようとする課題】
本発明の目的は、従来の芳香族ポリイミドからなる非対称性構造を有する中空糸分離膜を部分炭素化して得られた非対称性構造を有する中空糸分離膜を遥かに超える極めて高い透過速度および高い選択性を有する中空糸分離膜を提供することである。また、上記のパーフルオロ化合物を含めたハロゲン化合物とキャリヤーガス（窒素など）との混合物からハロゲン化合物を、従来の方法より遥かに効率良く分離回収する方法を提供することである。
【００１２】
【課題を解決するための手段】
本発明は、芳香族ポリイミドからなる非対称性構造を有する中空糸分離膜（前駆体膜）を部分炭素化して得られた非対称性構造を有する中空糸分離膜において、
（１）部分炭素化される芳香族ポリイミド中空糸膜（前駆体膜）の膜厚が８〜５０μｍであり
（２）部分炭素化して得られた中空糸分離膜の膜厚が８〜４５μｍであり
（３）部分炭素化して得られた中空糸分離膜の炭素含有率（重量％）が、部分炭素化される芳香族ポリイミド中空糸膜（前駆体膜）の炭素含有率の１．０５倍以上であり、かつ、９０重量％以下である
ことを特徴とする部分炭素化された非対称性中空糸分離膜に関する。
【００１３】
また、本発明は、芳香族ポリイミドからなる非対称性構造を有する中空糸分離膜（前駆体膜）を部分炭素化して、非対称性構造を有する部分炭素化された中空糸分離膜を製造する方法において、
（１）部分炭素化される芳香族ポリイミド中空糸膜（前駆体膜）の膜厚が８〜５０μｍであり
（２）部分炭素化して得られた中空糸分離膜の膜厚が８〜４５μｍであり
（３）部分炭素化して得られた中空糸分離膜の炭素含有率（重量％）が、部分炭素化される芳香族ポリイミド中空糸膜（前駆体膜）の炭素含有率の１．０５倍以上であり、かつ、９０重量％以下である
ことを特徴とする、部分炭素化された非対称性中空糸分離膜の製造方法に関する。
【００１４】
また、本発明は、少なくとも１種のハロゲン化合物ガスおよび少なくとも１種のキャリアーガスを包含する混合ガスを、前記に記載の部分炭素化された非対称性中空糸分離膜に供給し、膜の透過側からハロゲン化合物の含有量の減少した少なくとも１種のキャリアーガスからなるガスを取り出し、膜の非透過側から少なくとも１種のハロゲン化合物が濃縮されたガスを回収することを特徴とする、ハロゲン化合物ガスの分離方法に関する。
【００１５】
【発明の実施の形態】
以下、本発明について詳しく説明する。本発明の分離膜は、芳香族ポリイミドからなる非対称性構造を有する中空糸分離膜（前駆体膜）を部分炭素化して得られた非対称性構造を有する中空糸分離膜であり、部分炭素化される芳香族ポリイミド中空糸分離膜（前駆体膜）の膜厚が８〜５０μｍ（好ましくは２０〜５０μｍ）であり、炭素化して得られた中空糸分離膜の膜厚が８〜４５μｍ（好ましくは１４〜４５μｍ）であり、その炭素含有率（重量％）が、部分炭素化される芳香族ポリイミド中空糸膜（前駆体膜）の炭素含有率の１．０５倍以上（好ましくは１．１倍以上）であり、かつ、９０重量％以下のものである。ここで、炭素含有率とは、中空糸分離膜全体の重量に対する前記中空糸分離膜に含有される炭素の重量％のことである。
【００１６】
本発明の部分炭素化された非対称性構造を有する中空糸分離膜は、膜の少なくともひとつの表面層が０．００１〜２μｍ、好ましくは０．００５〜０．５μｍ程度の極めて薄い緻密層（均質層）であり、膜の内層部を含む残りの層は孔径が０．００５〜０．５μｍ程度の孔を多数含んでいる多孔質層であり、前記の緻密層（均質層）と前記の多孔質層とから構成された非対称構造を有する膜であり、中心部に貫通した中空部を有する中空糸を形成しているものである。
【００１７】
本発明の芳香族ポリイミド分離膜を部分炭素化した非対称性構造を有する中空糸分離膜は、極めて優れた耐熱性、耐溶剤性を有していると共に、ハロゲン化合物ガスと窒素などのキャリアーガスとの混合ガスからハロゲン化合物ガスを分離する場合のガス分離性能が改良された極めて高いレベルのものである。
【００１８】
部分炭素化とは、非対称性構造を有する中空糸分離膜を不活性ガスの雰囲気下で熱処理することにより、分離膜成分中の炭素成分の割合（炭素含有率）を増すことを意味する。
【００１９】
本発明における炭素化は、炭素化されて得られた中空糸分離膜の炭素含有率（重量％）が、炭素化される芳香族ポリイミド中空糸膜（前駆体膜）の１．０５倍以上で、かつ、９０重量％以下となるような部分炭素化であり、好ましくは、１．１倍以上で、かつ、９０重量％以下のものである。部分炭素化しても、得られた中空糸分離膜の炭素含有率が部分炭素化される芳香族ポリイミド中空糸膜（前駆体膜）の１．０５倍未満であれば、得られた中空糸分離膜のガス分離性能は改良されたものではない。また、部分炭化の程度を増して分離膜の炭素含有率が９０重量％を超えても、得られた中空糸分離膜のガス分離性能は改良されたものではない。更にそれ以上炭素化して実質的に炭素で構成された中空糸分離膜（いわゆる炭素膜）とした場合も、ガス分離性能は低く、実用的に使用出来るものではなくなる。
【００２０】
即ち、例えば、芳香族ポリイミド中空糸膜（前駆体膜）の炭素含有率が５４．４重量％のものを部分炭素化して得られる本発明の部分炭素化された中空糸分離膜は、炭素含有率が５７．１重量％〜９０．０重量％のものである。（実施例に記載）また、例えば、芳香族ポリイミド中空糸膜（前駆体膜）の炭素含有率が６７．９重量％のものを部分炭素化して得られる本発明の部分炭素化された中空糸分離膜は、炭素含有率が７１．３重量％〜９０．０重量％のものである。（実施例に記載なし）
【００２１】
部分炭素化される前の非対称性構造を有する芳香族ポリイミド中空糸膜（前駆体膜）は、その膜厚が８〜５０μｍの薄膜である。膜厚がこのように薄い中空糸膜の場合、部分炭素化するための熱処理時に膜にかかる応力が小さく、中空糸分離膜の分離活性層に欠陥が生じにくい。そのため、極めて高い分離性能を有する中空糸分離膜を得ることができる。膜厚が５０μｍを超えると、部分炭素化するための熱処理時に分離膜の内部と外部との収縮差により、中空糸分離膜の表面近くの分離層に欠陥が生じやすくなる。一方、膜厚が薄くなると、中空糸の機械的強度が小さくなり破損しやすくなるため実用的でなくなる。このため、膜厚は８μｍ以上であり、好ましくは２０μｍ以上である。
【００２２】
また、部分炭素化して得られた非対称性構造を有する中空糸分離膜の膜厚は、８〜４５μｍであり、好ましくは１４〜４５μｍである。膜厚が８μｍより小さいと、中空糸の機械的強度が小さく、破損しやすいため実用的でない。また、膜厚が４５μｍより大きいと膜表面の分離層に欠陥が発生しやすくなり、分離度が低下する。
【００２３】
本発明においては、部分炭素化による中空糸分離膜の膜厚の収縮率は０．１〜３０％が好ましく、更に、部分炭素化による中空糸分離膜の膜厚の収縮率は０．１〜２５％が特に好ましい。部分炭素化による中空糸分離膜の膜厚の収縮率は、部分炭素化される芳香族ポリイミド中空糸膜（前駆体膜）の膜厚と部分炭素化された中空糸分離膜の膜厚との差を、部分炭素化される芳香族ポリイミド中空糸膜（前駆体膜）の膜厚に対する百分率で表現される。収縮率が３０％を超えると、炭素化時に中空糸膜にかかる応力が大きく、得られる中空糸炭素膜の分離活性層に欠陥が生じやすくなるので、高いレベルの分離性能を得ることが出来ず好ましくない。
【００２４】
この発明において、前記の芳香族ポリイミドからなる非対称性構造を有する中空糸分離膜（前駆体膜）は、特開昭６０−１５０８０６号公報、特開昭６１−１３３１０６号公報などに示されているような方法で製造された単一構造の非対称性構造（表面に緻密層及び内部に多孔質層からなる単一非対称性構造）を有する中空糸分離膜、あるいは、特開平２−１６９０１９号公報、特開平２−２５１２３２号明細書などに記載されている方法などで製造された二層押出構造の非対称性構造（外層が表面の緻密層と内部の多孔質層とからなり、内層が多孔質層からなる二層押出非対称性構造）を有する中空糸膜を好適に挙げることができる。
【００２５】
前記の単一膜構造の非対称性構造を有する中空糸膜の製法は、例えば、ビフェニルテトラカルボン酸二無水物などの芳香族テトラカルボン酸成分と、ジアミノジメチルジフェニレンスルホン、ジアミノジフェニルメタン、４，４’−ジアミノジフェニルエーテルなどの芳香族ジアミン成分とを、略等モル、パラクロロフェノールなどのフェノール系溶媒中で、重合およびイミド化して、可溶性の芳香族ポリイミドの溶液を調製し、その溶液を製膜用ドープ液として使用して、チューブ・イン・オリフィスタイプの紡糸用ノズルから、窒素雰囲気中に中空糸状に押し出し、次いで、エタノール水溶液からなる凝固液中で凝固させて、非対称性構造の中空糸膜となし、最後に、その中空糸膜をエタノール洗浄してフェノール系溶媒を抽出して除去し、イソオクタン溶剤によって前記エタノールの置換を行った後、乾燥し、さらに熱処理して、好適なガス透過速度及び選択透過性を有する非対称性構造を有する中空糸分離膜を製造する方法を挙げることができる。
【００２６】
また、二層押出非対称性構造の非対称性構造を有する中空糸分離膜の製法は、前述の単一構造の中空糸分離膜の製法と同様にして２種の可溶性芳香族ポリイミド溶液を調製して、それらの溶液を使用して、二層押し出しが可能である二層押出紡糸用ノズルを使用するほかは、前述の単一構造の中空糸膜の製法とほとんど同様にして、二層押出非対称性構造を有する中空糸膜を製造する方法を挙げることができる。
【００２７】
本発明の特徴の一つは、膜厚の小さい中空糸分離膜を部分炭素化することによって、分離層に欠陥の少ない中空糸分離膜を得ることである。具体的には、芳香族ポリイミドからなる非対称構造を有する中空糸分離膜（前駆体膜）の膜厚を８〜５０μｍとし、部分炭素化の程度（炭素含有率）が適切な範囲となるように、さらに好ましくは部分炭素化に伴う膜厚の収縮率が適切な範囲となるように部分炭化することによって、分離性能を大幅に向上させた部分炭素化された非対称性中空糸分離膜を得ることにあるので、部分炭素化の方法は特に限定されず、前記の条件を満たすものであればどの様な方法であっても構わない。
【００２８】
本発明の部分炭素化は、例えば以下のとおりである。即ち、前述のようにして製造された所定の膜厚を有する芳香族ポリイミドからなる非対称性構造を有する中空糸分離膜（前駆体膜）を準備し、その中空糸分離膜を、２５０〜４９５℃、好ましくは２６０〜４５０℃の範囲内の温度であって、しかも該中空糸分離膜の非対称性構造が維持される温度、および、酸素ガス含有雰囲気で、０．１〜１００時間（特に０．３〜５０時間）、予備熱処理して熱安定化し、次いでその予備熱処理された中空糸膜を、５００〜９００℃、好ましくは５５０〜８００℃の温度範囲で、窒素ガス、ヘリウムガス、アルゴンガス等の不活性ガスの雰囲気下、部分炭素化の程度が適切な範囲（所定の炭素含有率や収縮率の範囲内）になるように、熱処理することによって部分炭素化をおこなう。不活性ガスの雰囲気下での熱処理時間は、部分炭素化の程度が適切な範囲内（所定の炭素含有率や収縮率の範囲内）であれば特に限定されないが、概して１時間以下であり、処理効率を考えれば０．１分間〜３０分間が好ましく、特に０．１分間〜１５分間が好ましい。
【００２９】
前述の酸素含有ガス中での予備熱処理（熱安定化処理）は、次の炭素化処理工程において前記の芳香族ポリイミドからなる非対称性構造を有する中空糸分離膜（前駆体膜）の非対称性構造が維持できるように、前記中空糸膜を形成している芳香族ポリイミドを一部架橋および／または一部環化させ、あるいは、不融化または不溶化して、熱的に安定である芳香族ポリイミドとするために、２５０〜４９５℃の範囲内の温度であって、前記中空糸膜の非対称性構造が維持される温度で行われる。
【００３０】
前記の芳香族ポリイミドからなる非対称性構造を有する中空糸分離膜（前駆体膜）の非対称性構造が維持される温度とは、例えば、該ポリイミドが熱機械分析（ＴＭＡ）法で測定された軟化温度を有する場合には、該ポリイミドの軟化温度よりも、５℃以上低い温度、特に１０℃以上低い温度であり、また、該ポリイミドが実質的に軟化温度又は二次転移温度を有していない場合には、その該ポリイミド製中空糸膜の非対称性構造が電子顕微鏡などで観察して大幅に変形したりしない温度、多孔質層の平均孔径が大幅に（５０％以下に）縮小したりしない温度であればよい。
【００３１】
前記の予備熱処理は、前述の温度範囲内であれば、例えば、２００℃の付近の温度から４５０℃の付近の高温まで徐々に昇温させながら行うことによる予備熱処理、あるいは、２００〜３５０℃の温度で０．５〜１００時間（好ましくは１〜５０時間）の熱処理し、次いで、３５０〜４９０℃の温度で１０〜３００分間（好ましくは２０〜２００分間）の熱処理するというように、複数段階で行う予備熱処理であってもよい。
【００３２】
前記の非対称性中空糸膜の予備熱処理は、前記芳香族ポリイミドからなる非対称性構造を有する中空糸分離膜（前駆体膜）（長尺の中空糸）を高温の加熱炉に連続的に供給して連続的に行うことができ、また、多数本の非対称性中空糸膜の糸束を形成して、その糸束を適当な温度の加熱炉内に配置してある時間加熱炉内に放置してバッチ的に熱処理を行うこともできる。
【００３３】
前記の予備熱化処理で使用する酸素含有気体としては、例えば、空気、又は、酸素と窒素等の他の不活性ガスとの種々の配合割合（特に、酸素含有割合；５〜３０容量％）の混合ガスなどを挙げることができる。上記の製法では、前述の酸素含有ガス中での予備熱処理を行わないと、その後の工程の部分炭素化工程で、中空糸膜の非対称性構造が損なわれるので適当ではなく、また、予備熱処理を余りに高い温度で行うと、芳香族ポリイミド製の非対称性中空糸膜がその非対称性構造を最適に維持できなくなり、非対称性構造が損なわれたり、著しくガス分離性能の劣った構造になったりすることがあり、最終的な非対称性中空糸分離膜が低い性能のガス分離膜となるので適当ではない。
【００３４】
前記の予備加熱された芳香族ポリイミドからなる非対称性構造を有する中空糸膜の部分炭素化処理（熱処理）は、前述の予備加熱と同様に、前記中空糸膜（長尺の中空糸）を高温の加熱炉に連続的に供給して連続的に行うことができ、また、多数本の非対称性中空糸膜の糸束を形成して、その糸束を適当な温度の加熱炉内に配置してある時間加熱炉内に放置してバッチ的に行うこともできる。
【００３５】
この製法では、前述のようにして製造された非対称性中空糸炭素膜を、さらに、２５０〜４５０℃（特に３００〜４００℃）の温度であって、酸素含有ガスの雰囲気で、０．２〜５０時間、特に０．５〜１０時間、後熱処理してもよい。
【００３６】
次に、本発明の部分炭素化された非対称性構造を有する中空糸分離膜をハロゲン化合物ガスの分離回収に使用する方法について、具体的に説明する。
【００３７】
本発明のハロゲン化合物ガスの分離回収方法は、少なくとも１種のハロゲン化合物ガスおよび少なくとも１種のキャリアーガスを包含する混合ガスを、前記部分炭素化された非対称性構造を有する中空糸分離膜に供給し、膜の透過側からハロゲン化合物の含有量の減少した少なくとも１種のキャリアーガスからなるガスを取り出し、膜の非透過側から少なくとも１種のパーフルオロ化合物が濃縮されたガスを回収することを特徴とする。
【００３８】
ガス混合物を分離する場合、ガス混合物は中空糸の外側から供給して中空糸の内側（孔側）から透過ガスを取り出す方法で行っても、またガス混合物を中空糸の一方の内側から供給して中空糸内を流動通過させてもう一方の内側から排出される間に、透過ガスを中空糸の外側に透過させる方法で行ってもよいが、後者の方法の方が効率がよいので好適である。
【００３９】
ハロゲン化合物ガスとしては、ＣＦ4、Ｃ2Ｆ6、Ｃ3Ｆ8、Ｃ4Ｆ10、ＳＦ6、ＮＦ3などのパーフルオロ化合物ガスやフルオロカーボン、フロンガス、四塩化炭素などの塩素化合物ガス、およびそれらの混合物からなる群から選ばれることが好ましい。パーフルオロ化合物は、半導体産業において半導体製造プロセスにおいてエッチングや洗浄などの目的で多量に使用されているものである。また、ＳＦ6ガスは、無色無臭で無毒の不活性ガスであり、気圧を上げることにより優れた絶縁耐力を示し、かつ、液化温度も低く、低温でも加圧して使用できることから、電気絶縁ガスとして好ましく利用されるものである。
【００４０】
さらに、キャリアーガスとしては、窒素ガス、炭酸ガス、ヘリウムガス、アルゴンガス、空気等を挙げることができる。
【００４１】
ＳＦ6ガスとこれらのガスとの混合ガスは、絶縁耐力が大きく、膜に対する透過速度比が大きく、ガス絶縁電気機器用に好ましいものである。特に、窒素ガスは毒性が無く入手が容易であるので、ＳＦ6ガスと窒素ガスの混合ガスはガス絶縁電気機器用に特に好ましく使用されている。
【００４２】
混合ガスとしては、少なくとも１種の前記のハロゲン化合物ガスと少なくも１種の前記のキャリアーガスを包含する混合ガスである。これらは用途において種々の混合割合で使用されている。本発明においては混合ガスの成分組成や濃度は特に限定されない。
【００４３】
本発明の部分炭素化して得られた非対称性構造を有する中空糸分離膜は、例えば中空糸を適当な長さに切断して多数（例えば１００〜１００００００本）束ねて形成させた中空糸膜束が、その両端の中空（孔）が塞がらないように両端をエポキシ樹脂の如き樹脂で一体的に固着して、モジュ−ル化し、これを少なくとも気体混合物（原料ガス）の供給口、未透過気体の排出口及び透過気体の排出口を有する容器に収納し、ガス分離回収装置として用いられる。
【００４４】
本発明の部分炭素化して得られた非対称性構造を有する中空糸分離膜をハロゲン化合物の分離回収に用いる場合に使用するガス分離回収装置の一例を図１に示した。ハロゲン化合物ガスとしてＳＦ6を例に取り、以下に説明する。ガス分離回収装置１は多数の中空糸２の形状をした分離膜が密封容器６内に内蔵されている。ＳＦ6と他の１種類以上のキャリアーガスからなる混合ガスはコンプレッサー、ブロワーなどによってガス分離回収装置１の混合ガス供給口３から連続的に供給され、中空糸２の内側を非透過ガス排出口４側に流動する。その間に分離膜を選択的に透過したガス（主にキャリアーガス）は透過ガス排出口５より排出し、分離膜を透過しなかったガス（主にＳＦ6）は非透過ガス排出口４より排出されるので、ＳＦ6を非透過ガス排出口４より分離回収することができる。なお、図１の樹脂壁７は中空糸２の両端部をエラストマ系樹脂、アクリレート系樹脂、エポキシ樹脂、フェノール樹脂などの適当な熱硬化性樹脂を固化して形成された円板状の樹脂壁で、樹脂壁内を各中空糸が貫通しており、中空糸内部の孔が樹脂壁の外に向かって開口している。樹脂壁７は接着剤などを使用して密封容器６の内壁に密封固着されている。また分離回収効率をより高めるためにガス分離装置１において透過ガス排出口５に真空ポンプ等を接続して透過ガスを減圧して回収することも有効であり、また、透過ガス排出口５のうちの一方から混合ガス中に含まれない他の種類のガスをパージガスとして供給し、透過ガス排出口の他方から透過ガスと共に排出することもできる。
【００４５】
本発明のハロゲン化合物の分離回収方法においては、混合ガスを前記ガス分離回収装置へ供給する前に、必要に応じて吸着装置、フィルター、スクラバーなどによって処理される。また、前記ガス分離回収装置から分離回収された濃縮されたハロゲン化合物ガスを、別のガス分離膜装置、吸着装置、精留装置などを用いて更に後処理することが出来る。
また、本発明のハロゲン化合物の分離回収方法は常温でも加温状態でもおこなう事が出来る。加温する場合は、前記ガス分離回収装置の耐熱性を考慮して１５０℃以下でおこなうことが望ましい。
【００４６】
【実施例】
以下、この発明を参考例および実施例によってさらに詳しく説明する。しかし、この発明はそれらの実施例によって限定されるものではない。芳香族ポリイミド中空糸膜（前駆体膜）、部分炭素化して得られた非対称性構造を有する中空糸分離膜等について、各ガスのガス透過性能および炭素含有率は、次に示す方法で測定した。
【００４７】
〔ガス透過性能〕まず、以下の実施例などで製造した中空糸膜と、ステンレスパイプと、エポキシ樹脂系接着剤とを使用して、透過性能評価用の中空糸エレメントを作成した。そして、純Ｎ2ガスの透過性能は、ステンレス容器に、透過性能評価用の中空糸膜の中空糸エレメントを装着し、５０℃の温度、１０ｋｇｆ／ｃｍ2Ｇの供給圧で、ガス透過試験を行い、ガス透過速度を算出した。また、Ｎ2とＳＦ6、Ｎ2とＣＦ4、Ｎ2とＣ2Ｆ6との混合ガスの透過性能は、５０℃の温度、２ｋｇｆ／ｃｍ2Ｇの供給圧で、ガス透過試験を行い、ガス透過速度と、Ｎ2とＳＦ6、Ｎ2とＣＦ4、および、Ｎ2とＣ2Ｆ6との透過速度比（選択透過性、分離度を示す）とを、ガスクロマトグラフィーの測定値から算出した。
〔炭素含有率〕元素分析装置（パーキンエルマー社製、２４０Ｃ型）を用いて測定した。
【００４８】
参考例１
［ポリイミド溶液の調整］ポリイミド原料の酸成分として、３，３’，４，４’−ビフェニルテトラカルボン酸二無水物（ＢＰＤＡ） ４０ミリモル、２，２’−ビス（３，４−ジカルボキシフェニル）ヘキサフルオロプロパン二無水物（６ＦＤＡ） ４５ミリモル、ピロメリット酸二無水物（ＰＭＤＡ） １５ミリモル、ジアミン成分としてジメチル−３，７−ジアミノジベンゾチオフェン−５，５−ジオキシド（ＴＳＮ） ５０ミリモル、２，２’，５，５’−テトラクロロベンジジン（ＴＣＢ） ５０ミリモルとを、パラクロロフェノール ３３１ｇとともに、攪拌機と窒素ガス導入管とが付設されたセパラブルフラスコに入れて、窒素ガスを流して、反応液を攪拌しながら、１８０℃の重合温度で１８時間重合させて、芳香族ポリイミド濃度が１６重量％である芳香族ポリイミド溶液を調整した。このポリイミド溶液は、１００℃の回転粘度が１６００ポイズであった。この芳香族ポリイミド溶液を、４００メッシュのステンレス金網で濾過して、紡糸用のドープ液を準備した。
【００４９】
〔単一構造の非対称性中空糸膜の製造〕その紡糸用ドープ液を中空糸紡糸用ノズル（円形開口部の外径；１０００μｍ、円形開口部のスリット幅；２００μｍ、芯部開口部の外径；４００μｍ）を備えた紡糸装置に仕込み、そして、窒素ガスを前記紡糸用ノズルの芯部開口部から吐出させながら、紡糸用ドープ液を前記紡糸用ノズルから中空糸状に吐出させて、その中空糸状体を窒素雰囲気中を通した後、７０重量％のエタノール水溶液からなる一次凝固液（０℃）に浸漬し、さらに、一対の案内ロールを備えた二次凝固装置内の二次凝固液（０℃）中で案内ロール間を往復させて、中空糸状体の凝固を完了させて、芳香族ポリイミド製の中空糸膜を引き取りロールで引き取りながら（引き取り速度１０ｍ／分）、紡糸を行った。
【００５０】
最後に、この中空糸膜をボビンに巻き取り、エタノールで充分に凝固溶媒等を洗浄した後、イソオクタン（置換溶媒）でエタノールを置換し、さらに、中空糸膜を１００℃に加熱して、イソオクタンの蒸発・乾燥を行い、さらに、２７０℃の温度で３０分間、中空糸膜の熱処理を行って、乾燥及び熱処理された芳香族ポリイミド製の非対称性中空糸膜（中空糸膜の外径：３５６μｍ、その膜厚：４３μｍ）を製造した。
【００５１】
参考例２
参考例１と同様な方法で、芯部の窒素吐出量と前記紡糸用ドープ液の吐出量とを変化させて、中空糸膜の外径２２０μｍ、膜厚４２μｍの芳香族ポリイミド製の非対称性中空糸膜を製造した。
【００５２】
参考例３
参考例１と同様な方法で、芯部の窒素吐出量と前記紡糸用ドープ液の吐出量とを変化させて、中空糸膜の外径４２８μｍ、膜厚７５μｍの芳香族ポリイミド製の非対称性中空糸膜を製造した。
【００５３】
参考例４
中空糸紡糸用ノズル（円形開口部の外径；１０００μｍ、円形開口部のスリット幅；１００μｍ、芯部開口部の外径；４００μｍ）を用い、芯部の窒素吐出量と前記紡糸用ドープ液の吐出量と変化させた以外は、参考例１と同様な方法で、中空糸膜の外径２７５μｍ、膜厚２２μｍの芳香族ポリイミド製の非対称性中空糸膜を製造した。
【００５４】
実施例１
参考例１で得られた非対称性中空糸膜を、空気雰囲気のオーブン中、無緊張下、４００℃で３０分間、予備熱処理して熱安定化した。次に、予備熱処理された非対称性中空糸膜は、石英ガラス管中を５００℃に調節し窒素雰囲気に保たれた電気管状炉内を、送りだしロールと引き取りロールとの間で２０ｃｍ／分の等速度で通過させて、滞留時間４分間の熱処理が行なわれ、部分炭素化された非対称性中空糸分離膜を製造した。
【００５５】
前述のようにして製造した部分炭素化された非対称性中空糸分離膜について、電子顕微鏡を使用して、中空糸分離膜破断面の１００００倍の写真を写し、その写真における中空糸分離膜の断面を観察することにより、部分炭素化された緻密層（表面層）及び多孔質層（緻密層に隣接した多孔質層）からなる非対称性構造を確認した。この中空糸分離膜について、前記の測定法に従って、ガス透過性能や炭素含有率などの測定を行った。それらの結果を表１〜表４に示す。（尚、表中、例えばＰ’（Ｎ2）／Ｐ’（ＳＦ6）は、窒素ガスとＳＦ6ガスとの透過速度比を表す。）
【００５６】
実施例２−５
実施例１の炭素化温度を５５０℃（実施例２）、６００℃（実施例３）、６５０℃（実施例４）、７００℃（実施例５）とした以外は、実施例１と同様な方法で部分炭素化処理を行い、部分炭素化された非対称性中空糸分離膜を製造した。製造した中空糸分離膜は、実施例１と同様に非対称性構造を確認し、ガス透過性能や炭素含有率などの測定を行った。その結果を表１〜表４に示す。
【００５７】
実施例６
参考例２で得られた非対称性中空糸膜を使用した以外は、実施例１と同様な方法で部分炭素化処理を行い、部分炭素化された非対称性中空糸分離膜を製造した。製造した中空糸分離膜は、実施例１と同様に非対称性構造を確認し、ガス透過性能や炭素含有率などの測定を行った。その結果を表１〜表４に示す。
【００５８】
実施例７，８
部分炭素化温度を５５０℃（実施例７）、６００℃（実施例８）とした以外は、実施例６と同様な方法で部分炭素化処理を行い、部分炭素化された非対称性中空糸分離膜を製造した。製造した中空糸分離膜は、実施例１と同様に非対称性構造を確認し、ガス透過性能や炭素含有率などの測定を行った。その結果を表１〜表４に示す。
【００５９】
実施例９，１０
参考例４で得られた非対称性中空糸膜を使用し、部分炭素化温度を５５０℃（実施例９）、６００℃（実施例１０）とした以外は、実施例１と同様な方法で部分炭素化処理を行い、部分炭素化された非対称性中空糸分離膜を製造した。製造した中空糸分離膜は、実施例１と同様に非対称性構造を確認し、ガス透過性能や炭素含有率などの測定を行った。その結果を表１〜表４に示す。
【００６０】
比較例１
参考例３で得られた非対称性中空糸膜を使用した以外は、実施例３と同様な方法で部分炭素化処理を行い、部分炭素化された非対称性中空糸分離膜を製造した。製造した中空糸炭素膜は、実施例１と同様に非対称性構造を確認し、ガス透過性能や炭素含有率などの測定を行った。その結果を表１〜表４に示す。
【００６１】
比較例２
部分炭素化温度を６５０℃とした以外は、比較例１と同様な方法で部分炭素化処理を行い、部分炭素化された非対称性中空糸分離膜を製造した。製造した中空糸分離膜は、実施例１と同様に非対称性構造を確認し、ガス透過性能や炭素含有率などの測定を行った。その結果を表１〜表４に示す。
【００６２】
比較例３
参考例１で得られた非対称性中空糸膜を、実施例１と同様の方法で予備加熱処理したのち４５０℃に調整した以外は同一の条件で（部分炭素化の程度が低い）熱処理を行った。製造した中空糸分離膜は、実施例１と同様に非対称性構造を確認し、ガス透過性能や炭素含有率などの測定を行った。その結果を表１〜表４に示す。
【００６３】
比較例４
参考例１で得られた非対称性中空糸膜を、実施例１と同様の方法で予備加熱処理したのち１０００℃に調整した以外は同一の条件で（部分炭素化の程度が過剰になるような）熱処理を行った。製造した中空糸分離膜は、実施例１と同様に非対称性構造を確認し、ガス透過性能や炭素含有率などの測定を行った。その結果を表１〜表４に示す。
【００６４】
比較例５
参考例１で得られた非対称性中空糸膜を、実施例１と同様の方法で予備加熱処理したのち１２００℃に調整した以外は同一の条件で（部分炭素化の程度が過剰になるような）熱処理を行った。製造した中空糸分離膜は、実施例１と同様に非対称性構造を確認し、ガス透過性能や炭素含有率などの測定を行った。その結果を表１〜表４に示す。
【００６５】
一般に、分離膜の性能に関しては、ガスの透過速度と混合ガスの透過速度比（分離度）が互いにトレードオフの関係にあり、透過速度が大きい分離膜は分離度が小さく、あるいは、分離度が大きい分離膜は透過速度が小さい傾向がある。本実施例、比較例および参考例で得られた透過速度と透過速度比の関係を図２〜図４に示した。図２〜図４から分かるように、本発明の実施例は、図の右上に位置し、透過速度が大きくても、さらに透過速度比（分離度）が大きく、比較例に比べ、混合ガスを極めて効率的に分離できることが分かる。
【００６６】
表２〜表４には、測定混合ガスの透過速度、透過速度比（分離度）とともに、膜性能を示す総合的評価尺度として、透過速度と透過速度比（分離度）の積Ｓを示した。表１からわかるように、膜厚が５０μｍ以下のポリイミド中空糸膜を部分炭素化して得られた膜厚が４５μｍ以下の中空糸膜は、有機膜（前駆体膜）あるいは膜厚の厚い部分炭素化して得られた分離膜に比較して、大きな窒素の透過速度と著しく大きな窒素とハロゲン化合物との透過速度比を有し、膜性能を示す総合的評価尺度である透過速度と透過速度比（分離度）の積Ｓにおいて、極めて著しい改善が見られる。
【００６７】
一方、膜厚が８μｍより小さいポリイミド中空糸膜あるいはそれを部分炭化して得られる膜厚が８μｍより小さい中空糸分離膜は、機械的強度が小さくので実用的なものではない。
【００６８】
また、表１〜表４から、部分炭素化の程度が適当である範囲においてのみ、前記の分離性能の著しい改善が見られ、部分炭素化の程度が小さい場合および部分炭素化の程度が過剰な場合には、前記の改良された分離性能は示さないことがわかる。
【００６９】
【表１】
【発明の効果】
以上のように、芳香族ポリイミドからなる非対称性構造を有する中空糸分離膜（前駆体膜）を部分炭素化して得られた非対称性構造を有する中空糸分離膜において、部分炭素化前の中空糸分離膜（前駆体膜）の厚さを薄くし、部分炭化して得られた非対称性中空糸分離膜の膜厚を８〜４５μｍとすること、および、部分炭素化された中空糸分離膜の炭素含有率を前駆体膜の１．０５倍以上で９０重量％以下とすることによって、また、好ましくは膜厚の収縮率が０．１〜３０以下とすることによって、炭素化時の分離層の欠陥の発生を抑制し、前駆体膜および従来の部分炭素化された非対称性中空糸分離膜を超える高い透過速度および高い選択性を有する極めて有用な中空糸分離膜を得ることができる。また、この膜を使用して、ハロゲン化合物の分離回収を極めて高効率で行うことが可能となる。
【図面の簡単な説明】
【図１】本願発明の部分炭素化された非対称中空糸分離膜をハロゲン化合物ガスを分離回収する際に使用する装置の１例を示す断面図である。
【図２】Ｎ2とＳＦ6との混合ガスの透過速度比とＮ2の透過速度との関係を示す図である。
【図３】Ｎ2とＣＦ4との混合ガスの透過速度比とＮ2の透過速度との関係を示す図である。
【図４】Ｎ2とＣ2Ｆ6との混合ガスの透過速度比とＮ2の透過速度との関係を示す図である。
【符号の説明】
１；ガス分離回収装置
２；部分炭素化された非対称性中空糸分離膜
３；原料ガス供給口（混合ガス供給口）
４；非透過ガス排出口
５；透過ガス排出口
６；密封容器
７；樹脂壁[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hollow fiber separation membrane having an asymmetric structure with significantly improved gas separation performance obtained by partial carbonization of a polyimide hollow fiber separation membrane. The present invention also relates to a method for efficiently separating a halogen compound gas from a gas mixture using the separation membrane.
[0002]
[Prior art]
Conventionally, as a highly permeable asymmetric gas separation membrane, those made of various polymers are known, but in recent years, for example, in JP-A-60-179102 and JP-A-1-221518, etc. , A method for producing a porous carbon membrane for gas separation membrane having excellent chemical resistance by treating an organic polymer membrane at high temperature, and a carbon membrane (hollow fiber carbon membrane) obtained by these methods Was proposed.
[0003]
However, JP-A-60-179102 discloses either a carbonized film substantially composed of carbon obtained by heating a film of polyacrylonitrile or the like for a long time at a high temperature and a graphitized film. However, the gas permeation rate ratio between carbon dioxide gas and nitrogen gas in this membrane was extremely low. In addition, this publication does not mention any film obtained by partially carbonizing a polymer film.
[0004]
JP-A-1-221518 discloses a large number of micropores of 3 to 5 angstroms in the abdomen, and the adsorption amount of molecules having a size of 6 angstroms or more is 0.1 cm. Three Since it is a hollow fiber carbon membrane fiber of / g or less, it is completely different from a membrane having an asymmetric structure in which a portion (porous layer) having a porous structure having a pore diameter of 6 angstroms or more is predominant.
[0005]
On the other hand, in JP-A-4-11933, JP-A-4-193334, and JP-A-5-220360, an asymmetric obtained by partially carbonizing a hollow fiber membrane having an asymmetric structure made of aromatic polyimide. A hollow fiber separation membrane having a porous structure and a method for producing the same are disclosed.
[0006]
By the way, SF is used as an electric insulation gas for gas-insulated electrical equipment such as gas-insulated switchgears, gas circuit breakers, gas-insulated transformers, and pipeline air transmission 6 Halogen compounds centered on (sulfur hexafluoride) gas, Freon gas, carbon tetrachloride gas and the like are used. Recently, in order to reduce the amount of use as a global warming gas, which has become a global issue, a gas-insulated electric mixture of a halogen compound and other electrically insulating gas (carrier gas) is used. Attempts have been made to use it as an electrical insulating gas for equipment.
[0007]
In the semiconductor industry, CFs are used for etching and cleaning in semiconductor processes involving gas. Four , C 2 F 6 , C Three F 8 , C Four F Ten , SF 6 , NF Three Perfluoro compounds such as are being used exclusively. These perfluoro compound gases can be pure or diluted with, for example, air, nitrogen or other inert gases, or with other perfluoro compound gases or other carrier gases (eg, inert gases). Used in the form of a mixture.
[0008]
Most of these perfluoro compound gases contained in the carrier gas are gases that adversely affect the environment such as global warming and need not be discharged into the atmosphere but recovered and reused.
[0009]
In Japanese Patent Application No. Hei 10-365598, the present inventors have disclosed the asymmetry obtained by partial carbonization of a hollow fiber separation membrane having an asymmetric structure made of aromatic polyimide for the separation and recovery of these perfluoro compound gases. It was proposed to use a hollow fiber separation membrane having a structure, and it was shown that perfluoro compound gas can be separated and recovered efficiently.
[0010]
However, the higher the efficiency of gas separation and recovery, the better. Also, in order to reuse the recovered gas, it is necessary to increase the purity of the gas, and therefore a separation membrane having higher separation performance is required.
[0011]
[Problems to be solved by the invention]
The object of the present invention is to achieve a very high permeation rate and high selection far exceeding the hollow fiber separation membrane having an asymmetric structure obtained by partial carbonization of a hollow fiber separation membrane having an asymmetric structure made of a conventional aromatic polyimide. It is providing the hollow fiber separation membrane which has property. Another object of the present invention is to provide a method for separating and recovering a halogen compound from a mixture of a halogen compound including the perfluoro compound and a carrier gas (such as nitrogen) much more efficiently than the conventional method.
[0012]
[Means for Solving the Problems]
The present invention relates to a hollow fiber separation membrane having an asymmetric structure obtained by partial carbonization of a hollow fiber separation membrane (precursor membrane) having an asymmetric structure made of aromatic polyimide.
(1) The film thickness of the aromatic polyimide hollow fiber membrane (precursor membrane) to be partially carbonized is 8 to 50 μm
(2) The film thickness of the hollow fiber separation membrane obtained by partial carbonization is 8 to 45 μm
(3) The carbon content (% by weight) of the hollow fiber separation membrane obtained by partial carbonization is 1.05 times or more of the carbon content of the aromatic polyimide hollow fiber membrane (precursor membrane) to be partially carbonized. And 90% by weight or less
The present invention relates to a partially carbonized asymmetric hollow fiber separation membrane.
[0013]
The present invention also relates to a method for producing a partially carbonized hollow fiber separation membrane having an asymmetric structure by partially carbonizing a hollow fiber separation membrane (precursor membrane) having an asymmetric structure made of an aromatic polyimide. ,
(1) The film thickness of the aromatic polyimide hollow fiber membrane (precursor membrane) to be partially carbonized is 8 to 50 μm
(2) The film thickness of the hollow fiber separation membrane obtained by partial carbonization is 8 to 45 μm
(3) The carbon content (% by weight) of the hollow fiber separation membrane obtained by partial carbonization is 1.05 times or more of the carbon content of the aromatic polyimide hollow fiber membrane (precursor membrane) to be partially carbonized. And 90% by weight or less
The present invention relates to a method for producing a partially carbonized asymmetric hollow fiber separation membrane.
[0014]
The present invention also provides a mixed gas containing at least one halogen compound gas and at least one carrier gas to the partially carbonized asymmetric hollow fiber separation membrane described above, and the permeation side of the membrane A gas comprising at least one carrier gas having a reduced halogen compound content is taken out from the gas, and a gas enriched with at least one halogen compound is recovered from the non-permeating side of the membrane. It is related with the separation method.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below. The separation membrane of the present invention is a hollow fiber separation membrane having an asymmetric structure obtained by partial carbonization of a hollow fiber separation membrane (precursor membrane) having an asymmetric structure made of aromatic polyimide. The thickness of the aromatic polyimide hollow fiber separation membrane (precursor membrane) is 8 to 50 μm (preferably 20 to 50 μm), and the hollow fiber separation membrane obtained by carbonization has a thickness of 8 to 45 μm (preferably 14 to 45 μm), and the carbon content (% by weight) is 1.05 or more (preferably 1.1 times) the carbon content of the aromatic polyimide hollow fiber membrane (precursor membrane) to be partially carbonized. And 90% by weight or less. Here, the carbon content is the weight percent of carbon contained in the hollow fiber separation membrane with respect to the weight of the entire hollow fiber separation membrane.
[0016]
The hollow fiber separation membrane having a partially carbonized asymmetric structure of the present invention has an extremely thin dense layer (homogeneous) in which at least one surface layer of the membrane is 0.001 to 2 μm, preferably about 0.005 to 0.5 μm. The remaining layers including the inner layer portion of the membrane are porous layers containing a large number of pores having a pore diameter of about 0.005 to 0.5 μm, and the dense layer (homogeneous layer) and the porous layer It is a membrane having an asymmetric structure composed of a porous layer, and forms a hollow fiber having a hollow portion penetrating through a central portion.
[0017]
The hollow fiber separation membrane having an asymmetric structure in which the aromatic polyimide separation membrane of the present invention is partially carbonized has extremely excellent heat resistance and solvent resistance, and also contains a halogen compound gas and a carrier gas such as nitrogen. The gas separation performance when separating the halogen compound gas from the mixed gas is extremely high.
[0018]
Partial carbonization means increasing the proportion (carbon content) of the carbon component in the separation membrane component by heat-treating the hollow fiber separation membrane having an asymmetric structure in an inert gas atmosphere.
[0019]
In the carbonization in the present invention, the carbon content (% by weight) of the hollow fiber separation membrane obtained by carbonization is 1.05 times or more of the aromatic polyimide hollow fiber membrane (precursor membrane) to be carbonized. In addition, partial carbonization is 90% by weight or less, preferably 1.1 times or more and 90% by weight or less. If the carbon content of the obtained hollow fiber separation membrane is less than 1.05 times that of the aromatic polyimide hollow fiber membrane (precursor membrane) to be partially carbonized even after partial carbonization, the obtained hollow fiber separation is obtained. The gas separation performance of the membrane is not improved. Further, even if the degree of partial carbonization is increased and the carbon content of the separation membrane exceeds 90% by weight, the gas separation performance of the obtained hollow fiber separation membrane is not improved. Further, even when a hollow fiber separation membrane (so-called carbon membrane) composed of carbon by further carbonization is used, the gas separation performance is low and it cannot be used practically.
[0020]
That is, for example, the partially carbonized hollow fiber separation membrane of the present invention obtained by partial carbonization of an aromatic polyimide hollow fiber membrane (precursor membrane) having a carbon content of 54.4% by weight is carbon-containing. The rate is from 57.1% to 90.0% by weight. (Described in Examples) Further, for example, the partially carbonized hollow fiber of the present invention obtained by partial carbonization of an aromatic polyimide hollow fiber membrane (precursor membrane) having a carbon content of 67.9% by weight The separation membrane has a carbon content of 71.3% by weight to 90.0% by weight. (Not described in the examples)
[0021]
The aromatic polyimide hollow fiber membrane (precursor membrane) having an asymmetric structure before being partially carbonized is a thin film having a thickness of 8 to 50 μm. In the case of such a thin hollow fiber membrane, the stress applied to the membrane during the heat treatment for partial carbonization is small, and defects are hardly generated in the separation active layer of the hollow fiber separation membrane. Therefore, a hollow fiber separation membrane having extremely high separation performance can be obtained. When the film thickness exceeds 50 μm, a defect tends to occur in the separation layer near the surface of the hollow fiber separation membrane due to a difference in shrinkage between the inside and the outside of the separation membrane during the heat treatment for partial carbonization. On the other hand, when the film thickness is reduced, the mechanical strength of the hollow fiber is reduced and easily broken, which is not practical. For this reason, a film thickness is 8 micrometers or more, Preferably it is 20 micrometers or more.
[0022]
The film thickness of the hollow fiber separation membrane having an asymmetric structure obtained by partial carbonization is 8 to 45 μm, preferably 14 to 45 μm. If the film thickness is less than 8 μm, the mechanical strength of the hollow fiber is small and easily damaged, which is not practical. On the other hand, if the film thickness is larger than 45 μm, defects are likely to occur in the separation layer on the film surface, and the degree of separation decreases.
[0023]
In the present invention, the shrinkage rate of the film thickness of the hollow fiber separation membrane by partial carbonization is preferably 0.1 to 30%, and the shrinkage rate of the film thickness of the hollow fiber separation membrane by partial carbonization is 0.1 to 30%. 25% is particularly preferred. The shrinkage of the film thickness of the hollow fiber separation membrane by partial carbonization is the difference between the film thickness of the aromatic polyimide hollow fiber membrane (precursor membrane) that is partially carbonized and the film thickness of the partially carbonized hollow fiber separation membrane. The difference is expressed as a percentage of the film thickness of the aromatic polyimide hollow fiber membrane (precursor membrane) that is partially carbonized. If the shrinkage rate exceeds 30%, the stress applied to the hollow fiber membrane during carbonization is large, and defects are likely to occur in the separation active layer of the resulting hollow fiber carbon membrane, so that a high level of separation performance cannot be obtained. It is not preferable.
[0024]
In the present invention, hollow fiber separation membranes (precursor membranes) having an asymmetric structure made of the above-mentioned aromatic polyimide are disclosed in JP-A-60-150806 and JP-A-61-133106. A hollow fiber separation membrane having a single structure asymmetric structure (single asymmetric structure consisting of a dense layer on the surface and a porous layer inside) manufactured by such a method, or JP-A-2-169919, An asymmetric structure of a two-layer extrusion structure manufactured by the method described in JP-A-2-251232 and the like (the outer layer is composed of a dense layer on the surface and an inner porous layer, and the inner layer is a porous layer) A hollow fiber membrane having a two-layer extrusion asymmetric structure made of
[0025]
The method for producing the hollow fiber membrane having an asymmetric structure of the single membrane structure is, for example, an aromatic tetracarboxylic acid component such as biphenyltetracarboxylic dianhydride, diaminodimethyldiphenylenesulfone, diaminodiphenylmethane, 4, 4 An aromatic diamine component such as' -diaminodiphenyl ether is polymerized and imidized in an approximately equimolar phenol solvent such as parachlorophenol to prepare a soluble aromatic polyimide solution, and the solution is formed into a film. A hollow fiber membrane with an asymmetric structure that is extruded as a hollow fiber from a tube-in-orifice type spinning nozzle into a nitrogen atmosphere and then coagulated in a coagulating liquid consisting of an aqueous ethanol solution. Finally, the hollow fiber membrane is washed with ethanol to extract and remove the phenolic solvent. And a method for producing a hollow fiber separation membrane having an asymmetric structure having a suitable gas permeation rate and permselectivity after substitution of the ethanol with an isooctane solvent, followed by drying and further heat treatment. .
[0026]
In addition, the method for producing a hollow fiber separation membrane having an asymmetric structure of a two-layer extrusion asymmetric structure is the same as the method for producing a hollow fiber separation membrane having a single structure described above, and two types of soluble aromatic polyimide solutions are prepared. The bilayer extrusion asymmetry is almost the same as the above-mentioned process for producing a single-layer hollow fiber membrane, except that a two-layer extrusion spinning nozzle that can be used for two-layer extrusion is possible. The method of manufacturing the hollow fiber membrane which has a structure can be mentioned.
[0027]
One of the features of the present invention is to obtain a hollow fiber separation membrane having few defects in the separation layer by partially carbonizing the hollow fiber separation membrane having a small film thickness. Specifically, the film thickness of the hollow fiber separation membrane (precursor membrane) having an asymmetric structure made of aromatic polyimide is 8 to 50 μm, and the degree of partial carbonization (carbon content) is in an appropriate range. More preferably, a partially carbonized asymmetric hollow fiber separation membrane with significantly improved separation performance is obtained by partial carbonization so that the shrinkage rate of the film thickness accompanying partial carbonization falls within an appropriate range. Therefore, the method of partial carbonization is not particularly limited, and any method may be used as long as the above conditions are satisfied.
[0028]
The partial carbonization of the present invention is, for example, as follows. That is, a hollow fiber separation membrane (precursor membrane) having an asymmetric structure made of an aromatic polyimide having a predetermined thickness produced as described above is prepared, and the hollow fiber separation membrane is prepared at 250 to 495 ° C. Preferably, the temperature is in the range of 260 to 450 ° C., and the temperature at which the asymmetric structure of the hollow fiber separation membrane is maintained, and in an oxygen gas-containing atmosphere, 0.1 to 100 hours (particularly 0. 3 to 50 hours), preheated and thermally stabilized, and then the preheated hollow fiber membrane is heated to 500 to 900 ° C, preferably 550 to 800 ° C, such as nitrogen gas, helium gas, argon gas, etc. In an inert gas atmosphere, partial carbonization is performed by heat treatment so that the degree of partial carbonization falls within an appropriate range (within a predetermined range of carbon content and shrinkage). The heat treatment time in an inert gas atmosphere is not particularly limited as long as the degree of partial carbonization is within an appropriate range (within a predetermined carbon content and shrinkage range), but is generally 1 hour or less, Considering the treatment efficiency, it is preferably 0.1 minutes to 30 minutes, particularly preferably 0.1 minutes to 15 minutes.
[0029]
The pre-heat treatment (thermal stabilization treatment) in the oxygen-containing gas described above is the asymmetric structure of the hollow fiber separation membrane (precursor membrane) having the asymmetric structure made of the aromatic polyimide in the next carbonization treatment step. The aromatic polyimide forming the hollow fiber membrane is partially crosslinked and / or partially cyclized, or infusible or insolubilized, and is thermally stable. In order to do this, the temperature is in the range of 250 to 495 ° C., and the temperature at which the asymmetric structure of the hollow fiber membrane is maintained.
[0030]
The temperature at which the asymmetric structure of the hollow fiber separation membrane (precursor membrane) having an asymmetric structure made of the aromatic polyimide is maintained is, for example, the softening of the polyimide measured by a thermomechanical analysis (TMA) method. When it has a temperature, it is a temperature that is 5 ° C. or more lower than the softening temperature of the polyimide, particularly 10 ° C. or more, and the polyimide has substantially no softening temperature or secondary transition temperature. In such a case, the temperature at which the asymmetric structure of the polyimide hollow fiber membrane is not significantly deformed by observation with an electron microscope or the like, and the average pore diameter of the porous layer is not significantly reduced (to 50% or less). Any temperature is acceptable.
[0031]
If the said pre-heat treatment is in the above-mentioned temperature range, for example, the pre-heat treatment is performed by gradually raising the temperature from about 200 ° C. to about 450 ° C., or 200 to 350 ° C. Heat treatment at a temperature of 0.5 to 100 hours (preferably 1 to 50 hours), followed by heat treatment at a temperature of 350 to 490 ° C. for 10 to 300 minutes (preferably 20 to 200 minutes). It may be a preliminary heat treatment performed in step (b).
[0032]
In the preliminary heat treatment of the asymmetric hollow fiber membrane, a hollow fiber separation membrane (precursor membrane) (long hollow fiber) having an asymmetric structure made of the aromatic polyimide is continuously supplied to a high-temperature heating furnace. In addition, a large number of asymmetric hollow fiber membrane yarn bundles are formed, and the yarn bundles are placed in a heating furnace at an appropriate temperature and left in the heating furnace for a period of time. Heat treatment can be performed batchwise.
[0033]
As the oxygen-containing gas used in the preheating treatment, for example, various blending ratios of air or other inert gas such as oxygen and nitrogen (particularly oxygen content ratio: 5 to 30% by volume) Or a mixed gas thereof. In the above production method, if the preliminary heat treatment in the oxygen-containing gas is not performed, the asymmetric structure of the hollow fiber membrane is impaired in the subsequent partial carbonization step. If performed at too high a temperature, the asymmetric hollow fiber membrane made of aromatic polyimide will not be able to maintain its asymmetric structure optimally, resulting in damage to the asymmetric structure or a significantly inferior gas separation performance. Therefore, the final asymmetric hollow fiber separation membrane is not suitable because it becomes a gas separation membrane with low performance.
[0034]
In the partial carbonization treatment (heat treatment) of the hollow fiber membrane having an asymmetric structure made of the preheated aromatic polyimide, the hollow fiber membrane (long hollow fiber) is heated at a high temperature in the same manner as the preheating described above. It is possible to carry out the process continuously by supplying continuously to a heating furnace, and forming a bundle of many asymmetric hollow fiber membranes and placing the bundle in a heating furnace at an appropriate temperature. It can also be carried out batchwise by leaving it in a heating furnace for a certain period of time.
[0035]
In this production method, the asymmetric hollow fiber carbon membrane produced as described above is further heated to 250 to 450 ° C. (particularly 300 to 400 ° C.) in an oxygen-containing gas atmosphere at 0.2 to You may post-heat-process for 50 hours, especially 0.5 to 10 hours.
[0036]
Next, a method for using the hollow fiber separation membrane having a partially carbonized asymmetric structure according to the present invention for separation and recovery of a halogen compound gas will be specifically described.
[0037]
In the method for separating and recovering a halogen compound gas of the present invention, a mixed gas containing at least one halogen compound gas and at least one carrier gas is supplied to the hollow fiber separation membrane having a partially carbonized asymmetric structure. And removing a gas composed of at least one carrier gas having a reduced halogen compound content from the permeate side of the membrane and recovering a gas enriched with at least one perfluoro compound from the non-permeate side of the membrane. Features.
[0038]
When separating the gas mixture, the gas mixture is supplied from the outside of the hollow fiber and the permeate gas is taken out from the inside (hole side) of the hollow fiber, or the gas mixture is supplied from the inside of one of the hollow fibers. While passing through the hollow fiber and being discharged from the other inside, the permeated gas may be permeated to the outside of the hollow fiber, but the latter method is preferred because it is more efficient. is there.
[0039]
As the halogen compound gas, CF Four , C 2 F 6 , C Three F 8 , C Four F Ten , SF 6 , NF Three It is preferably selected from the group consisting of perfluoro compound gases such as fluorocarbon, chlorofluorocarbon gas, chlorine compound gas such as carbon tetrachloride, and mixtures thereof. Perfluoro compounds are used in large amounts in the semiconductor industry for purposes such as etching and cleaning in the semiconductor manufacturing process. SF 6 The gas is a colorless, odorless, non-toxic inert gas that exhibits excellent dielectric strength by raising the atmospheric pressure, and has a low liquefaction temperature, and can be used by being pressurized even at low temperatures. Therefore, it is preferably used as an electrical insulating gas. Is.
[0040]
Furthermore, examples of the carrier gas include nitrogen gas, carbon dioxide gas, helium gas, argon gas, and air.
[0041]
SF 6 A mixed gas of a gas and these gases has a high dielectric strength and a high permeation rate ratio with respect to the membrane, and is preferable for gas-insulated electrical equipment. In particular, nitrogen gas is not toxic and is easily available. 6 A mixed gas of gas and nitrogen gas is particularly preferably used for gas-insulated electrical equipment.
[0042]
The mixed gas is a mixed gas including at least one kind of the halogen compound gas and at least one kind of the carrier gas. These are used in various mixing ratios in the application. In the present invention, the component composition and concentration of the mixed gas are not particularly limited.
[0043]
The hollow fiber separation membrane having an asymmetric structure obtained by partial carbonization of the present invention is, for example, a hollow fiber membrane bundle formed by cutting a hollow fiber into an appropriate length and bundling a large number (for example, 100 to 1,000,000). However, both ends are integrally fixed with a resin such as an epoxy resin so that the hollows (holes) at both ends are not blocked, and modularized, and this is at least a gas mixture (source gas) supply port, an unpermeated gas. And is used as a gas separation and recovery device.
[0044]
An example of a gas separation and recovery apparatus used when the hollow fiber separation membrane having an asymmetric structure obtained by partial carbonization of the present invention is used for separation and recovery of a halogen compound is shown in FIG. SF as the halogen compound gas 6 Is described below as an example. In the gas separation and
[0045]
In the halogen compound separation and recovery method of the present invention, the mixed gas is treated by an adsorbing device, a filter, a scrubber or the like, if necessary, before being supplied to the gas separation and recovery device. Further, the concentrated halogen compound gas separated and recovered from the gas separation and recovery device can be further post-treated using another gas separation membrane device, an adsorption device, a rectification device, or the like.
Further, the method for separating and recovering a halogen compound of the present invention can be carried out at room temperature or in a heated state. When heating, it is desirable to carry out at 150 degrees C or less considering the heat resistance of the said gas separation collection | recovery apparatus.
[0046]
【Example】
Hereinafter, the present invention will be described in more detail by reference examples and examples. However, the present invention is not limited to these examples. Regarding aromatic polyimide hollow fiber membrane (precursor membrane), hollow fiber separation membrane having asymmetric structure obtained by partial carbonization, etc., the gas permeation performance and carbon content of each gas were measured by the following methods. .
[0047]
[Gas Permeation Performance] First, a hollow fiber element for evaluating permeation performance was prepared using a hollow fiber membrane manufactured in the following examples, a stainless steel pipe, and an epoxy resin adhesive. And pure N 2 The gas permeation performance is as follows. A stainless steel container is equipped with a hollow fiber element of a hollow fiber membrane for permeation performance evaluation, a temperature of 50 ° C., 10 kgf / cm. 2 A gas permeation test was performed at a supply pressure of G, and a gas permeation rate was calculated. N 2 And SF 6 , N 2 And CF Four , N 2 And C 2 F 6 The mixed gas permeation performance is 50 ° C., 2 kgf / cm 2 A gas permeation test was performed at the supply pressure of G, 2 And SF 6 , N 2 And CF Four And N 2 And C 2 F 6 The permeation rate ratio (indicating selective permeability and degree of separation) was calculated from the measured values of gas chromatography.
[Carbon content] It was measured using an elemental analyzer (manufactured by Perkin Elmer, 240C type).
[0048]
Reference example 1
[Preparation of polyimide solution] As an acid component of a polyimide raw material, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) 40 mmol, 2,2′-bis (3,4-dicarboxyphenyl) ) Hexafluoropropane dianhydride (6FDA) 45 mmol, pyromellitic dianhydride (PMDA) 15 mmol, dimethyl-3,7-diaminodibenzothiophene-5,5-dioxide (TSN) 50 mmol as diamine component, 2 , 2 ′, 5,5′-tetrachlorobenzidine (TCB) 50 mmol together with 331 g of parachlorophenol was put into a separable flask equipped with a stirrer and a nitrogen gas introduction tube, and nitrogen gas was allowed to flow. While stirring the reaction solution, polymerization was carried out at a polymerization temperature of 180 ° C. for 18 hours, and the aromatic polyimide concentration was 16 The aromatic polyimide solution is an amount% was prepared. This polyimide solution had a rotational viscosity at 100 ° C. of 1600 poise. This aromatic polyimide solution was filtered through a 400 mesh stainless steel wire mesh to prepare a dope solution for spinning.
[0049]
[Manufacture of Single Structure Asymmetric Hollow Fiber Membrane] The spinning dope is made into a hollow fiber spinning nozzle (outer diameter of circular opening: 1000 μm, slit width of circular opening: 200 μm, outer diameter of core opening) And 400 μm), and while discharging nitrogen gas from the core nozzle opening of the spinning nozzle, the spinning dope liquid is discharged from the spinning nozzle into a hollow fiber shape. After passing the body through a nitrogen atmosphere, the body was immersed in a primary coagulation liquid (0 ° C.) composed of a 70% by weight ethanol aqueous solution, and a secondary coagulation liquid (0 The hollow fiber-like body was solidified by reciprocating between the guide rolls in [° C.], and spinning was performed while the hollow fiber membrane made of aromatic polyimide was taken up by the take-up roll (take-up speed 10 m / min).
[0050]
Finally, the hollow fiber membrane is wound around a bobbin, and after the coagulation solvent is sufficiently washed with ethanol, the ethanol is replaced with isooctane (substitution solvent), and the hollow fiber membrane is heated to 100 ° C. to obtain isooctane. Then, the hollow fiber membrane was heat-treated at a temperature of 270 ° C. for 30 minutes, and the dried and heat-treated aromatic polyimide asymmetric hollow fiber membrane (outer diameter of the hollow fiber membrane: 356 μm) , Its film thickness: 43 μm).
[0051]
Reference example 2
In the same manner as in Reference Example 1, the amount of nitrogen discharged from the core and the amount of the spinning dope discharged was changed to make an asymmetric hollow made of aromatic polyimide having an outer diameter of 220 μm and a thickness of 42 μm. A yarn membrane was produced.
[0052]
Reference example 3
In the same manner as in Reference Example 1, the amount of nitrogen discharged from the core and the amount of the dope for spinning is changed, and the hollow fiber asymmetric hollow made of aromatic polyimide having an outer diameter of 428 μm and a film thickness of 75 μm. A yarn membrane was produced.
[0053]
Reference example 4
Using a hollow fiber spinning nozzle (circular opening outer diameter: 1000 μm, circular opening slit width: 100 μm, core opening outer diameter: 400 μm), the nitrogen discharge amount of the core and the spinning dope An asymmetric hollow fiber membrane made of aromatic polyimide having a hollow fiber membrane outer diameter of 275 μm and a film thickness of 22 μm was produced in the same manner as in Reference Example 1 except that the discharge amount was changed.
[0054]
Example 1
The asymmetric hollow fiber membrane obtained in Reference Example 1 was heat-stabilized by preliminary heat treatment at 400 ° C. for 30 minutes under no tension in an air atmosphere oven. Next, the pre-heat-treated asymmetric hollow fiber membrane is adjusted in a quartz glass tube at 500 ° C. and maintained in a nitrogen atmosphere, and the 20% / min between the feed roll and the take-up roll. The asymmetric hollow fiber separation membrane having a partially carbonized state was manufactured by passing through at a rate and performing a heat treatment for a residence time of 4 minutes.
[0055]
About the partially carbonized asymmetric hollow fiber separation membrane produced as described above, using an electron microscope, a photograph of 10,000 times the fracture surface of the hollow fiber separation membrane is taken, and the cross section of the hollow fiber separation membrane in the photograph Was observed to confirm an asymmetric structure composed of a partially carbonized dense layer (surface layer) and a porous layer (porous layer adjacent to the dense layer). This hollow fiber separation membrane was measured for gas permeation performance, carbon content, and the like according to the measurement method described above. The results are shown in Tables 1 to 4. (In the table, for example, P ′ (N 2 ) / P '(SF 6 ) Nitrogen gas and SF 6 It represents the permeation rate ratio with gas. )
[0056]
Example 2-5
Example 1 was the same as Example 1 except that the carbonization temperature was 550 ° C. (Example 2), 600 ° C. (Example 3), 650 ° C. (Example 4), and 700 ° C. (Example 5). Partial carbonization treatment was performed by the method to produce a partially carbonized asymmetric hollow fiber separation membrane. The produced hollow fiber separation membrane was confirmed to have an asymmetric structure in the same manner as in Example 1, and the gas permeation performance and the carbon content were measured. The results are shown in Tables 1 to 4.
[0057]
Example 6
Except for using the asymmetric hollow fiber membrane obtained in Reference Example 2, partial carbonization was performed in the same manner as in Example 1 to produce a partially carbonized asymmetric hollow fiber separation membrane. The produced hollow fiber separation membrane was confirmed to have an asymmetric structure in the same manner as in Example 1, and the gas permeation performance and the carbon content were measured. The results are shown in Tables 1 to 4.
[0058]
Examples 7 and 8
Except for the partial carbonization temperature of 550 ° C. (Example 7) and 600 ° C. (Example 8), partial carbonization treatment was performed in the same manner as in Example 6 to separate the partially carbonized asymmetric hollow fiber. A membrane was produced. The produced hollow fiber separation membrane was confirmed to have an asymmetric structure in the same manner as in Example 1, and the gas permeation performance and the carbon content were measured. The results are shown in Tables 1 to 4.
[0059]
Examples 9 and 10
Using the asymmetric hollow fiber membrane obtained in Reference Example 4, the partial carbonization temperature was changed to 550 ° C. (Example 9) and 600 ° C. (Example 10). Carbonization treatment was performed to produce a partially carbonized asymmetric hollow fiber separation membrane. The produced hollow fiber separation membrane was confirmed to have an asymmetric structure in the same manner as in Example 1, and the gas permeation performance and the carbon content were measured. The results are shown in Tables 1 to 4.
[0060]
Comparative Example 1
Except for using the asymmetric hollow fiber membrane obtained in Reference Example 3, partial carbonization was performed in the same manner as in Example 3 to produce a partially carbonized asymmetric hollow fiber separation membrane. The produced hollow fiber carbon membrane was confirmed to have an asymmetric structure in the same manner as in Example 1 and measured for gas permeation performance and carbon content. The results are shown in Tables 1 to 4.
[0061]
Comparative Example 2
Except for setting the partial carbonization temperature to 650 ° C., a partial carbonization treatment was performed in the same manner as in Comparative Example 1 to produce a partially carbonized asymmetric hollow fiber separation membrane. The produced hollow fiber separation membrane was confirmed to have an asymmetric structure in the same manner as in Example 1, and the gas permeation performance and the carbon content were measured. The results are shown in Tables 1 to 4.
[0062]
Comparative Example 3
The asymmetric hollow fiber membrane obtained in Reference Example 1 was subjected to a heat treatment under the same conditions (low degree of partial carbonization) except that the asymmetric hollow fiber membrane was preheated in the same manner as in Example 1 and then adjusted to 450 ° C. It was. The produced hollow fiber separation membrane was confirmed to have an asymmetric structure in the same manner as in Example 1, and the gas permeation performance and the carbon content were measured. The results are shown in Tables 1 to 4.
[0063]
Comparative Example 4
The asymmetric hollow fiber membrane obtained in Reference Example 1 was preheated by the same method as in Example 1 and then adjusted to 1000 ° C. under the same conditions (excessive degree of partial carbonization) ) Heat treatment was performed. The produced hollow fiber separation membrane was confirmed to have an asymmetric structure in the same manner as in Example 1, and the gas permeation performance and the carbon content were measured. The results are shown in Tables 1 to 4.
[0064]
Comparative Example 5
The asymmetric hollow fiber membrane obtained in Reference Example 1 was preheated in the same manner as in Example 1 and then adjusted to 1200 ° C. under the same conditions (excessive degree of partial carbonization) ) Heat treatment was performed. The produced hollow fiber separation membrane was confirmed to have an asymmetric structure in the same manner as in Example 1, and the gas permeation performance and the carbon content were measured. The results are shown in Tables 1 to 4.
[0065]
In general, regarding the performance of the separation membrane, the gas permeation rate and the permeation rate ratio (separation degree) of the mixed gas are in a trade-off relationship with each other. Large separation membranes tend to have a low permeation rate. The relationship between the transmission rate and the transmission rate ratio obtained in this example, comparative example, and reference example is shown in FIGS. As can be seen from FIGS. 2 to 4, the embodiment of the present invention is located in the upper right of the figure, and even if the transmission speed is large, the transmission speed ratio (separation degree) is further large. It turns out that it can isolate | separate very efficiently.
[0066]
Tables 2 to 4 show the product S of the permeation speed and the permeation speed ratio (separation degree) as a comprehensive evaluation scale showing the membrane performance together with the permeation speed and permeation speed ratio (separation degree) of the measured mixed gas. . As can be seen from Table 1, a hollow fiber membrane having a film thickness of 45 μm or less obtained by partial carbonization of a polyimide hollow fiber membrane having a film thickness of 50 μm or less is an organic film (precursor film) or a thick partial carbon. Compared to the separation membrane obtained by the process, the permeation rate and the permeation rate ratio, which is a comprehensive evaluation scale showing membrane performance, have a large permeation rate of nitrogen and a permeation rate ratio of nitrogen and halogen compounds. A very significant improvement is seen in the product S of the degree of separation.
[0067]
On the other hand, a polyimide hollow fiber membrane having a film thickness of less than 8 μm or a hollow fiber separation membrane having a film thickness of less than 8 μm obtained by partial carbonization thereof is not practical because of its low mechanical strength.
[0068]
In addition, from Tables 1 to 4, the separation performance is significantly improved only in a range where the degree of partial carbonization is appropriate. When the degree of partial carbonization is small, the degree of partial carbonization is excessive. In some cases, it can be seen that the improved separation performance is not exhibited.
[0069]
[Table 1]
【The invention's effect】
As described above, in the hollow fiber separation membrane having an asymmetric structure obtained by partial carbonization of the hollow fiber separation membrane (precursor membrane) having an asymmetric structure made of aromatic polyimide, the hollow fiber before partial carbonization is obtained. The thickness of the separation membrane (precursor membrane) is reduced, and the thickness of the asymmetric hollow fiber separation membrane obtained by partial carbonization is 8 to 45 μm. By setting the carbon content to 1.05 times or more and 90% by weight or less of the precursor film, and preferably by setting the shrinkage rate of the film thickness to 0.1 to 30 or less, the separation layer at the time of carbonization Generation of defects can be suppressed, and a very useful hollow fiber separation membrane having a high permeation rate and high selectivity over the precursor membrane and the conventional partially carbonized asymmetric hollow fiber separation membrane can be obtained. Moreover, it becomes possible to perform separation and recovery of halogen compounds with extremely high efficiency using this membrane.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of an apparatus used for separating and recovering a halogen compound gas from a partially carbonized asymmetric hollow fiber separation membrane of the present invention.
FIG. 2 N 2 And SF 6 Of gas mixture with N and N 2 It is a figure which shows the relationship with the transmission speed of.
FIG. 3 N 2 And CF Four Of gas mixture with N and N 2 It is a figure which shows the relationship with the transmission speed of.
FIG. 4 N 2 And C 2 F 6 Of gas mixture with N and N 2 It is a figure which shows the relationship with the transmission speed of.
[Explanation of symbols]
1: Gas separation and recovery device
2; Partially carbonized asymmetric hollow fiber separation membrane
3: Source gas supply port (mixed gas supply port)
4; Non-permeate gas outlet
5; Permeate gas outlet
6; Sealed container
7; Resin wall
Claims (3)
（１）部分炭素化される芳香族ポリイミド中空糸膜（前駆体膜）の膜厚が８〜５０μｍであり
（２）部分炭素化して得られた中空糸分離膜の膜厚が８〜４５μｍであり
（３）部分炭素化して得られた中空糸分離膜の炭素含有率（重量％）が、部分炭素化される芳香族ポリイミド中空糸膜（前駆体膜）の炭素含有率の１．０５倍以上であり、かつ、９０重量％以下であり
（４）部分炭素化による中空糸分離膜の膜厚の収縮率が０．１〜３０％であり
（５）窒素ガスとＳＦ 6 ガスとの５０℃におけるガス透過速度比（窒素ガスの透過速度／ＳＦ 6 ガスの透過速度）が５００以上であり、且つ窒素ガスの透過速度が１．８９×１０ −５ ｃｍ ３ ／ｃｍ ２ ・ｓｅｃ・ｃｍＨｇ以上である
ことを特徴とする、部分炭素化された非対称性中空糸分離膜。In a hollow fiber separation membrane having an asymmetric structure obtained by partial carbonization of a hollow fiber separation membrane (precursor membrane) having an asymmetric structure made of aromatic polyimide,
(1) The thickness of the aromatic polyimide hollow fiber membrane (precursor membrane) to be partially carbonized is 8 to 50 μm, and (2) the thickness of the hollow fiber separation membrane obtained by partial carbonization is 8 to 45 μm. Yes (3) The carbon content (wt%) of the hollow fiber separation membrane obtained by partial carbonization is 1.05 times the carbon content of the aromatic polyimide hollow fiber membrane (precursor membrane) to be partially carbonized And 90% by weight or less
(4) The shrinkage of the film thickness of the hollow fiber separation membrane by partial carbonization is 0.1 to 30%
(5) The gas transmission rate ratio (nitrogen gas transmission rate / SF 6 gas transmission rate ) of nitrogen gas and SF 6 gas at 50 ° C. is 500 or more, and the nitrogen gas transmission rate is 1.89 × 10 6. -5 cm < 3 > / cm < 2 > / sec * cmHg or more , The partially carbonized asymmetric hollow fiber separation membrane characterized by the above-mentioned.
次いで、前記芳香族ポリイミド中空糸膜を酸素ガス含有雰囲気下２５０〜４９５℃且つ非対称性が保持される温度で予備熱処理し、さらに、前記芳香族ポリイミド中空糸膜を、不活性ガス雰囲気下５００〜９００℃の温度で、
（２）中空糸分離膜の膜厚が８〜４５μｍ
（３）炭素含有率（重量％）が、芳香族ポリイミド中空糸膜（前駆体膜）の炭素含有率の１．０５倍以上、かつ、９０重量％以下、
（４）中空糸分離膜の膜厚の収縮率が０．１〜３０％
となるように熱処理して、
（５）窒素ガスとＳＦ 6 ガスとの５０℃におけるガス透過速度比（窒素ガスの透過速度／ＳＦ 6 ガスの透過速度）が５００以上であり、且つ窒素ガスの透過速度が１．８９×１０ −５ ｃｍ ３ ／ｃｍ ２ ・ｓｅｃ・ｃｍＨｇ以上の部分炭素化された非対称性中空糸分離膜を得ることを特徴とする、部分炭素化された中空糸分離膜を製造する方法。In a method for producing a partially carbonized hollow fiber separation membrane having an asymmetric structure by partially carbonizing a hollow fiber separation membrane (precursor membrane) having an asymmetric structure made of aromatic polyimide, (1) film thickness Prepared an aromatic polyimide hollow fiber membrane (precursor membrane) of 8-50 μm,
Next, the aromatic polyimide hollow fiber membrane is preheated at 250 to 495 ° C. in an oxygen gas-containing atmosphere and at a temperature at which asymmetry is maintained, and the aromatic polyimide hollow fiber membrane is further heated to 500 to 500 in an inert gas atmosphere. At a temperature of 900 ° C,
(2) The thickness of the hollow fiber separation membrane is 8 to 45 μm.
(3) The carbon content (% by weight) is 1.05 times or more and 90% by weight or less of the carbon content of the aromatic polyimide hollow fiber membrane (precursor membrane),
(4) The shrinkage ratio of the hollow fiber separation membrane is 0.1 to 30%.
Heat treatment to become
(5) The gas transmission rate ratio (nitrogen gas transmission rate / SF 6 gas transmission rate ) of nitrogen gas and SF 6 gas at 50 ° C. is 500 or more, and the nitrogen gas transmission rate is 1.89 × 10 6. A method for producing a partially carbonized hollow fiber separation membrane , characterized by obtaining a partially carbonized asymmetric hollow fiber separation membrane of -5 cm 3 / cm 2 · sec · cmHg or more .
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| JP4089223B2 (en) * | 2001-12-26 | 2008-05-28 | 宇部興産株式会社 | Halogen compound gas separation and recovery apparatus and separation and recovery method |
| KR100450211B1 (en) * | 2001-05-16 | 2004-09-24 | 학교법인 한양학원 | Method for manufacturing silicon-containing carbon molecular sieve membrane for gas separation |
| JP3727551B2 (en) * | 2001-05-31 | 2005-12-14 | 財団法人地球環境産業技術研究機構 | Method and apparatus for separating and recovering perfluoro compound gas |
| GB0807267D0 (en) * | 2008-04-21 | 2008-05-28 | Ntnu Technology Transfer As | Carbon membranes from cellulose esters |
| WO2012148563A1 (en) * | 2011-03-07 | 2012-11-01 | Georgia Tech Research Corporation | Polyimide-based carbon molecular sieve membrane for ethylene/ethane separations |
| DE102011016468B3 (en) * | 2011-04-08 | 2012-02-23 | Heraeus Quarzglas Gmbh & Co. Kg | Porous carbon composite laminate, process for its manufacture and use |
| MY188200A (en) * | 2011-12-20 | 2021-11-24 | Shell Int Research | Stabilization of porous morphologies for high performance carbon molecular sieve hollow fiber membranes |
| KR101474545B1 (en) * | 2013-04-03 | 2014-12-22 | (주)에어레인 | Method for manufacturing asymmetric hollow fiber membranes for fluorinated gas separation and asymmetric hollow fiber membranes for fluorinated gas separation manufactured thereby |
| US9815030B2 (en) * | 2013-09-30 | 2017-11-14 | Shell Oil Company | Asymmetric modified carbon molecular sieve hollow fiber membranes having improved permeance |
| KR101562307B1 (en) * | 2014-04-29 | 2015-10-22 | (주)에어레인 | Method for preparation of carbon molecular sieve hollow fiber membrane precursor, and carbon molecular sieve hollow fiber membrane precursor and carbon molecular sieve hollow fiber membrane manufactured thereby |
| WO2016002990A1 (en) * | 2014-07-04 | 2016-01-07 | (주)에어레인 | Method for manufacturing asymmetric hollow fiber membrane for separating fluorinated gases, and asymmetric hollow fiber membrane for separating fluorinated gases manufactured thereby |
| EA201792360A1 (en) * | 2015-06-01 | 2018-06-29 | Джорджия Тек Рисёч Корпорейшн | ULTRA-SELECTIVE CARBON MOLECULAR-SITE MEMBRANE AND METHOD FOR ITS MANUFACTURE |
| CN109070009A (en) * | 2016-03-21 | 2018-12-21 | 陶氏环球技术有限责任公司 | The improved method for manufacturing Carbon Molecular Sieve Membrane |
| EP4070880A1 (en) * | 2016-11-10 | 2022-10-12 | Dow Global Technologies LLC | Improved method to make carbon molecular sieve hollow fiber membranes |
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| JP2626837B2 (en) * | 1990-11-27 | 1997-07-02 | 宇部興産株式会社 | Manufacturing method of asymmetric hollow fiber carbon membrane |
| JPH07121344B2 (en) * | 1990-04-27 | 1995-12-25 | 宇部興産株式会社 | Asymmetric hollow fiber carbon membrane and method for producing the same |
| CA2275960A1 (en) * | 1997-01-23 | 1998-07-30 | Gil Dagan | Recovery of perfluorinated compounds and hydrofluorocarbon gases using molecular sieve membranes |
| JP2000185212A (en) * | 1998-12-22 | 2000-07-04 | Ube Ind Ltd | Method for separating and recovering perfluoro compound gas and device therefor |
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