JP3724412B2

JP3724412B2 - Hollow fiber membrane manufacturing method and hollow fiber membrane module

Info

Publication number: JP3724412B2
Application number: JP2001337400A
Authority: JP
Inventors: 浩一旦; 利之石崎; 進一峯岸; 昌弘辺見
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 2001-11-02
Filing date: 2001-11-02
Publication date: 2005-12-07
Anticipated expiration: 2021-11-02
Also published as: JP2003138422A

Description

【０００１】
【発明の属する技術分野】
本発明は、中空糸膜の製造方法に関する。さらに詳しくは、飲料水製造、浄水処理、廃水処理などの水処理に用いられる中空糸精密ろ過膜や中空糸限外ろ過膜の製造方法および該製法により製造された中空糸膜に関する。
【０００２】
【従来の技術】
中空糸膜は逆浸透膜や限外ろ過膜や精密ろ過膜等が製品化されている。精密ろ過膜や限外ろ過膜などの中空糸膜は浄水処理、廃水処理、医療用途や食品工業分野等をはじめとして様々な方面で利用されている。中空糸分離膜に求められる性能は一般に、高透水量、優れた分離特性、化学的強度および物理的強度である。中空糸膜が用いられる理由は単位体積あたりの有効膜面積が大きいからである。そのなかで飲料水製造分野、すなわち浄水処理用途においては、従来の砂濾過、凝集沈殿過程の代替に分離膜が用いられるようになっている。これらの分野では処理しなければならない水量が大きいため、中空糸膜の透水性能が優れていれば、膜面積を減らすことが可能となり、装置がコンパクトになるため設備費が節約でき、膜交換費や設置面積の点からも有利になってくる。また、さらに分離膜には耐薬品性能が求められている。浄水処理では透過水の殺菌や膜のバイオファウリング防止の目的で次亜塩素酸ナトリウムなどの殺菌剤を膜モジュール部分に添加したり、膜の薬液洗浄として、酸、アルカリ、塩素、界面活性剤などで膜を洗浄することがある。そのため近年では耐薬品性の高い素材としてポリフッ化ビニリデン系樹脂を用いた分離膜が開発され、使われている。また、浄水処理分野では、家畜の糞尿などに由来するクリプトスポリジウムなどの塩素に対して耐性のある病原性微生物が浄水場で処理しきれず処理水に混入する事故が１９９０年代から顕在化している。このことから中空糸膜には十分な分離特性と膜が切れて原水が混入しないような高い強伸度特性が要求されている。
【０００３】
ポリフッ化ビニリデン系樹脂を素材にする分離膜の製造方法にはいくつかの技術が開示されているがこれらの殆どが、特公平１−２２００３号公報で開示されているようにポリフッ化ビニリデン系樹脂を良溶媒に溶解したポリマー溶液を、ポリフッ化ビニリデン系樹脂の融点よりかなり低い温度で、口金から押出したり、ガラス板上にキャストしたりして成型した後、ポリフッ化ビニリデン系樹脂の非溶媒を含む液体に接触させて非溶媒誘起相分離により非対称多孔構造を形成させる湿式溶液法である。しかしながら湿式溶液法では、膜厚方向に均一に相分離を起こすことが困難であり、マクロボイドを含む非対称膜となるため機械的強度が十分でないという問題がある。また、膜構造や膜性能に与える製膜条件因子が多く、製膜工程の制御が難しく、再現性も乏しいといった欠点がある。また、比較的近年では特許第２８９９９０３号で開示されているようにポリフッ化ビニリデン系樹脂に無機微粒子と有機液状体を溶融混練し、ポリフッ化ビニリデン系樹脂の融点以上の温度で口金から押し出したり、プレス機でプレスしたりして成型した後、冷却固化し、その後有機液状体と無機微粒子を抽出することにより多孔構造を形成する溶融抽出法が開示されている。溶融抽出法の場合、空孔性の制御が容易で、マクロボイドは形成せず比較的均質で高強度の膜が得られるものの、無機微粒子の分散性が悪いとピンホールのような欠陥を生じる可能性がある。さらに、溶融抽出法は、製造コストが極めて高くなるといった欠点を有している製造方法である。
【０００４】
【発明が解決しようとする課題】
本発明は、上記従来技術の課題を解決せんとするものであり、耐薬品性が高いポリフッ化ビニリデン系樹脂を用いて、高強度で空孔性が高く高透水性能を有する中空糸膜を、低コストで製造することが可能になる中空糸膜の製造方法を提供することを目的とするものである。
【０００５】
【課題を解決するための手段】
すなわち本発明は、少なくとも３０〜５０重量％のポリフッ化ビニリデン系樹脂、１〜３０重量％の親水性多孔化剤、および該樹脂の貧溶媒を含有し、紡糸温度が８０〜１７５℃の範囲であるポリフッ化ビニリデン系樹脂溶液を冷却浴に吐出し凝固させる中空糸膜の製造方法であって、該冷却浴の冷却液体は、温度が０〜５０℃の範囲内であり、かつ、該冷却液体は濃度が６０〜１００重量％の範囲で貧溶媒を含有する液体であることを特徴とする中空糸膜の製造方法により達成される。さらに本発明は、上記製造方法で製造された中空糸膜を有する中空糸膜モジュール、上記中空糸膜モジュールを具備する水の分離装置を含む。
【０００６】
【発明の実施の形態】
以下、本発明の実施の形態について説明する。
【０００７】
本発明におけるポリフッ化ビニリデン系樹脂とは、フッ化ビニリデンホモポリマーおよび／またはフッ化ビニリデン共重合体を含有する樹脂のことである。複数の種類のフッ化ビニリデン共重合体を含有しても構わない。フッ化ビニリデン共重合体としては、フッ化ビニリデン残基構造を有するポリマーならば特に限定されず、典型的にはフッ化ビニリデンモノマーとそれ以外のフッ素系モノマーとの共重合体であり、例えば、フッ化ビニル、四フッ化エチレン、六フッ化プロピレン、三フッ化塩化エチレンから選ばれた１種類以上のフッ素系モノマーとフッ化ビニリデンとの共重合体が挙げられる。場合によっては、フッ素系モノマー以外の例えばエチレン等のモノマーが含まれていても良い。またポリフッ化ビニリデン系樹脂の重量平均分子量は、要求される中空糸膜の強度と透水性能によって適宜選択すれば良いが１０万〜１００万の範囲が好ましい。中空糸膜への加工性を考慮した場合は２５万〜６０万の範囲が好ましく、さらに３５万〜４５万の範囲が好ましい。
【０００８】
本発明において貧溶媒とは、ポリフッ化ビニリデン系樹脂を６０℃未満の低温では５重量％以上溶解させることができないが、６０℃以上かつポリフッ化ビニリデン系樹脂の融点以下（例えばポリフッ化ビニリデン系樹脂が、フッ化ビニリデンホモポリマー単独で構成される場合は１７８℃程度）の高温領域で５重量％以上溶解させることができる溶媒のことである。貧溶媒に対し、６０℃未満の低温でもポリフッ化ビニリデン系樹脂を５重量％以上溶解させることが可能な溶媒を良溶媒、ポリフッ化ビニリデン系樹脂の融点または液体の沸点まで、ポリフッ化ビニリデン系樹脂を溶解も膨潤もさせない溶媒を非溶媒と定義する。ここで貧溶媒としては、シクロヘキサノン、イソホロン、γ−ブチロラクトン、メチルイソアミルケトン、フタル酸ジメチル、プロピレングリコールメチルエーテル、プロピレンカーボネート、ジアセトンアルコール、グリセロールトリアセテート等の中鎖長のアルキルケトン、エステル、グリコールエステル及び有機カーボネート等が挙げられる。また良溶媒としては、Ｎ−メチル−２−ピロリドン、ジメチルスルホキシド、ジメチルアセトアミド、ジメチルホルムアミド、メチルエチルケトン、アセトン、テトラヒドロフラン、テトラメチル尿素、リン酸トリメチル等の低級アルキルケトン、エステル、アミド等が挙げられる。さらに非溶媒としては、水、ヘキサン、ペンタン、ベンゼン、トルエン、メタノール、エタノール、四塩化炭素、ｏ−ジクロルベンゼン、トリクロルエチレン、低分子量のポリエチレングリコール等の脂肪族炭化水素、芳香族炭化水素、塩素化炭化水素、またはその他の塩素化有機液体等が挙げられる。
【０００９】
本発明の親水性多孔化剤とは、親水性を有していて当該中空糸膜の多孔化を促す性質を有するものならば、なんら限定されるものではなく、好適には、親水性有機物の高分子乃至は低分子物質である。具体的には、ポリエチレングリコール、ポリプロピレングリコール、ポリビニルアルコール、ポリ酢酸ビニル、ポリビニルピロリドン、ポリアクリル酸などの水溶性ポリマー、ソルビタン脂肪酸エステル（モノ、トリエステル体等）等の多価アルコールのエステル体、ソルビタン脂肪酸エステルのエチレンオキサイド低モル付加物、ノニルフェノールのエチレンオキサイド低モル付加物、プルロニック型エチレンオキサイド低モル付加物等のエチレンオキサイド低モル付加物、ポリオキシエチレンアルキルエステル、アルキルアミン塩、ポリアクリル酸ソーダ等の界面活性剤、グリセリンなどの多価アルコール類、テトラエチレングリコール、トリエチレングリコールなどのグリコール類である。これらは１種類で用いても２種類以上の混合物で用いても良い。これらの親水性多孔化剤は重量平均分子量５０，０００以下のものが良い（より好ましくは３０，０００以下）。これよりも分子量の大きなものは、抽出性が悪く、紡糸原液へも均一溶解しにくいために好ましくない場合がある。
【００１０】
この親水性多孔化剤は中空糸膜が口金から吐出され冷却浴中で溶媒抽出され構造凝集が起こる時に溶媒に比べ比較的長時間中空糸膜中に残留すると考えられる。溶媒抽出に伴う構造凝集が緩やかになってから、親水性多孔化剤が抽出されるので、得られた中空糸膜は空孔性が高いものになる。構造的には親水性多孔化剤の種類、分子量、添加量等に依存するが、球状構造が連結された構造を有し、球状構造と球状構造の境界、隙間に細孔が分布する、あるいは球状構造間の隙間自体が大きくなる、または球状構造自体に５μｍ以下の細孔が多数分布した構造、あるいはこれらが複合した構造になり、空孔性が高く透水性の高いものになる。
【００１１】
なお、球状構造とは、専ら、球晶であると推定される。球晶とは、ポリフッ化ビニリデン系樹脂溶液が相分離して多孔構造を形成する際に、ポリフッ化ビニリデン系樹脂が球形に析出、固化した結晶のことである。このような構造を有する中空糸膜は、従来の湿式溶液法で得られる網目構造を有する中空糸膜と比べて、強度を高くでき、しかも透水性能も高くすることができる。
【００１２】
本発明では、まずポリフッ化ビニリデン系樹脂（以下、単にポリマーとも表記する）を３０〜５０重量％の濃度範囲で、親水性多孔化剤を１〜３０重量％、好ましくは１〜２０重量％、さらに好ましくは１〜１０重量％の濃度範囲で、該樹脂の貧溶媒に８０〜１７５℃、好ましくは１００〜１５０℃の温度範囲で溶解し、該ポリフッ化ビニリデン系樹脂溶液を調製する。
【００１３】
前記ポリフッ化ビニリデン系樹脂のポリマー濃度は高くなれば高い強伸度特性を有する中空糸膜が得られるが、高すぎると製造した中空糸膜の空孔率が小さくなり、透水性能が低下する。また、調製したポリマー溶液の粘度が適正範囲に無ければ、中空糸状に成型することが困難である。なお、前記ポリマー溶液の調製において、複数の貧溶媒を用いても良い。また、ポリマーの溶解性に支障が生じない範囲内で、前記貧溶媒に良溶媒や非溶媒が混在していても良い。従来法の湿式溶液法では、透水性能を発現させるためポリマー濃度は１０〜２０重量％程度であり、強伸度が大きい膜は得られていなかった。本発明では、ポリマー濃度を前記の通り高濃度にすることで、高い強伸度特性を発現している。
【００１４】
また、本発明において、ポリフッ化ビニリデン系樹脂溶液中に、親水性多孔化剤が含まれないもしくは低いと得られた中空糸膜が十分な空孔性をもたず、透水性が得にくく、また、あまり多く親水性多孔化剤を含むと紡糸原液に均一に溶解できず、中空糸状に成型できない。また、中空糸膜にピンホール状の欠陥を与え、分離特性が低下し、強伸度も弱くなる。本発明では紡糸原液である前記ポリフッ化ビニリデン系樹脂溶液中の親水性多孔化剤濃度を前記の通りにすることで高透水性能を発現している。
【００１５】
また、貧溶媒を用いることで湿式溶液法で得られる網目構造よりも、球状の結晶よりなると推定される球状構造の膜構造が優先して形成するが、貧溶媒でない場合、あるいは、貧溶媒に貧溶媒以外の溶媒を加えすぎて、前記貧溶媒的溶解特性から逸脱した溶媒系である場合、以下の通りの問題が発生する。即ち、溶媒乃至は溶媒系が良溶媒である乃至は良溶媒的特性を有する場合、紡糸原液のポリマーに対する溶解能が低温においても高くなる。その結果、紡糸時に低温にクエンチしても降温により熱相分離した球状構造が凝固析出しにくく、球状構造の球がより大きく成長する。これにより得られる膜は少ない点で球状構造同士がむすびついており、強度的に弱いものになり不都合である。一方、非溶媒である乃至は非溶媒的特性を有する場合、ポリマーが紡糸原液に均一に溶解しにくく紡糸安定性上不都合である。
【００１６】
また、本発明では、該ポリマー溶液を８０〜１７５℃の温度範囲から、冷却液体などを用いて冷却固化させることで、球状構造が連結されて、その間に空隙を有する構造の中空糸膜を得ることができる。
【００１７】
さらに、発明者らは鋭意検討した結果、ポリマー溶液温度とともにその冷却方法で、この球状構造を制御できることを見出した。すなわち、（１）ポリマー溶液の温度が低すぎると、球状構造が発達する以前にゲル化し、固化するため、多孔構造を発現せず、透水性が得られないこと、（２）ポリマー溶液温度が高すぎると、冷却、ゲル化、固化に時間を要し、球状構造が充分発達してしまうため、球状構造が大きくなり、また、球状構造と球状構造を連結するポリマー分子の凝集体が減るため、強度的に低下する膜構造になることを見出した。
【００１８】
本発明の中空糸膜の製造方法においては、ポリマー溶液を調製した後、該ポリマー溶液を吐出して中空糸状に成形するものである。例えば中空糸膜紡糸用の二重管式口金から吐出し、必要に応じて所定の長さの乾式部を通過させた後、冷却浴中等に導いて凝固させる。二重管式口金を用いる場合、口金から吐出する前に、ポリマー溶液を、５〜１００μｍのステンレス製フィルター等で濾過することが好ましい。使用する前記口金の寸法は、製造する中空糸膜の寸法と膜構造により適宜選択すればよいが、おおよそスリット外径０．７〜１０ｍｍ、スリット内径０．５〜４ｍｍ、注入管内径０．２５〜２ｍｍの範囲であることが好ましい。また、紡糸ドラフト（引取り速度／原液の口金吐出線速度）は好ましくは０．８〜１００、より好ましくは０．９〜５０、更に好ましくは１〜３０、乾式長は好ましくは１０〜１０００ｍｍ、より好ましくは１０〜５００ｍｍ、更に好ましくは１０〜３００ｍｍの範囲である。
【００１９】
また口金の温度すなわち紡糸温度は、溶解温度と同様、８０〜１７５℃、好ましくは１００〜１７０℃の範囲にあれば良く、口金温度と溶解温度が異なっても構わない。溶解温度については、溶解を短時間に均一に行うという点から、口金温度より高い温度に設定することも好ましく採用できる。
【００２０】
前記の通り、中空糸状に成形されたポリマーは、冷却浴中に吐出され、凝固して中空糸膜となる。この際、冷却浴には、温度が０〜５０℃、好ましくは５〜３０℃であり、濃度が６０〜１００重量％、好ましくは７５〜９０重量％の範囲で貧溶媒を含有する液体を用いて、凝固させることが好ましい。冷却浴がこの温度範囲にあることにより、凝固工程において、球晶が発達しやすい冷却凝固が支配的となる。貧溶媒は、複数のものを混合して用いても良い。また、前記の濃度範囲を外れない限りにおいて、貧溶媒に、貧溶媒以外の溶媒が混合されてもよい。好ましくは非溶媒が混合されるが、場合によっては良溶媒を混合しても良い。ポリマー溶解温度から大きい温度差を与えて急冷することで、球状構造が微小になると同時に、適度に球状構造間にポリマー分子の凝集体が存在し、透水性と高い強伸度特性を有する膜構造を発現する。また、冷却液体にある程度高い濃度の貧溶媒を含有させることで、非溶媒誘起相分離を抑制し、膜表面に緻密層を形成することなく、中空糸膜状に成型することが可能となる。冷却液体に水等の非溶媒を高い濃度で含有する液体を用いると、膜表面に緻密層を形成してしまい、例え延伸しても透水性能は発現しない。
【００２１】
なお、前記冷却浴の形態としては、冷却液体と中空糸状に成形されたポリマー溶液とが十分に接触して冷却等が可能であるならば、特に限定されるものではなく、文字通り冷却液体が貯留された液槽形態であっても良いし、さらに必要により前記液槽は、温度や組成が調製された液体が循環乃至は更新されても良い。前記液槽形態が最も好適ではあるが、場合によっては、冷却液体が管内を流動している形態であっても良いし、空中に走向等している中空糸膜に冷却液体が噴射される形態であっても良い。
【００２２】
また、中空糸膜の中空部形成には、通常気体もしくは液体をポリマー溶液に随伴させるが、本発明においては、濃度が６０〜１００重量％の範囲で貧溶媒を含有する液体を中空部形成用液体として用いることが好ましく採用できる。中空部形成用液体の貧溶媒の濃度は、より好ましくは７０〜１００重量％、更に好ましくは８０〜１００重量％の範囲である。冷却浴の冷却液体同様、中空部形成用液体に高い濃度の貧溶媒を含有させることで、非溶媒誘起相分離を抑制し、微細な球状構造を形成することが可能となる。中空部形成用液体において、貧溶媒は、複数のものを混合して用いても良い。また、前記の濃度範囲を外れない限りにおいて、貧溶媒に、良溶媒や非溶媒を混合しても良い。
【００２３】
冷却液体として、さらに、濃度が１〜４０重量％の範囲で親水性多孔化剤を含有する液体を用いて、凝固させる方法も好ましく採用される。親水性多孔化剤は、紡糸原液に含まれるものと同種の１種又は複数種のものを用いることが望ましいが、それ以外の親水性多孔化剤を用いてもよい。冷却浴に親水性多孔化剤を含有することにより、吐出した中空糸膜が冷却浴中で溶媒抽出され凝固析出するときに紡糸原液の溶媒抽出速度に比べて、濃度勾配により親水性多孔化剤の抽出速度が低下する。その結果溶媒抽出に伴う構造収縮時もより長期間構造中に親水性多孔化剤が構造中に留まり、空孔性が高く透水性が高い膜が発現する。
【００２４】
また、中空糸膜の中空部形成に、さらに、濃度が１〜４０重量％の範囲で親水性多孔化剤を含有する液体を中空部形成用液体として用いることが好ましく採用できる。中空部形成用液体の親水性多孔化剤の濃度は、より好ましくは１〜３０重量％の範囲である。冷却浴同様、中空部形成用液体に親水性多孔化剤を含有させることで、凝固析出時の親水性多孔化剤の抽出速度を抑制し、空孔性が高く透水性が高い膜を形成することが可能となる。中空部形成用液体には、親水性多孔化剤は、複数のものを混合して用いても良い。
【００２５】
冷却浴に用いる冷却液体と中空部形成用液体は、同一であっても良いし、異なっていても良く、目的とする中空糸膜の特性等に応じて適宜選択すればよい。製造工程の観点からは、ポリマー溶液、冷却浴に用いる液体、および中空部形成用の液体に用いる溶媒が同一種である場合、製造過程における溶媒の回収等で利便性が高いが特に限定されるものではない。
【００２６】
以上までの製造方法で水処理用分離膜として十分な透水性と高強伸度特性を有する中空糸膜を得ることが出来るが、さらに透水性を高めるために該中空糸膜を延伸する工程を設けても良い。具体的には５０〜１４０℃（より好ましくは５０〜１２０℃、更に好ましくは５０〜１００℃）の温度範囲で１．１〜５倍（より好ましくは１．１〜４倍、更に好ましくは１．１〜３倍）の範囲の延伸倍率に延伸することで、目的の中空糸膜が得られる。５０℃未満の低温条件で延伸した場合、安定して均質に延伸することが困難であり、構造的に弱い部分のみが破断する。５０〜１４０℃の温度で延伸した場合、球状構造の一部および球状構造と球状構造を連結するポリマー分子の凝集体が均質に延伸され、微細で細長い細孔が多数形成され、強伸度特性を維持したまま透水性能が向上する。また、親水性多孔化剤の種類、添加量にもよるが部分的に親水性多孔化剤抽出後の孔が引き裂かれて細長い細孔がより大きく成長する。この部分的な細孔肥大化は膜全体として見た場合スケールが非常に小さいので、透水性向上には寄与しても分離性能には影響を与えない。１４０℃を超える温度で延伸した場合、ポリフッ化ビニリデン系樹脂の融点に近くなるため、球状構造が融解してしまい、あまり細孔が形成されずに延伸されるため、透水性能が向上しない。また、延伸は液体中で行う方が温度制御が容易であり好ましいが、スチームなどの気体中で行っても構わない。液体としては水が簡便で好ましいが、９０℃程度以上で延伸する場合には、低分子量のポリエチレングリコールなどを用いることも好ましく採用できる。さらに水とポリエチレングリコールの混合液体等、複数の液体の混合液体中で延伸することも採用できる。
【００２７】
これら親水性多孔化剤は冷却浴中で抽出されてもよいが、例えば１００℃のグリセリン浴中でポリビニルアルコールを抽出するなど、特別な抽出工程を加えても良く、前述の延伸を行う場合も延伸中、延伸前後に抽出を行っても良い。抽出には親水性多孔化剤に対して溶解性があり、ポリフッ化ビニリデン系樹脂に対して溶解性が低い溶媒、例えば水、高級アルコール、グリコール、グリセリン、ベンゼン、トルエン、上記貧溶媒などの単独或いは混合溶媒を用い、０〜１４０℃の温度範囲の液温に調整し浸漬することが好ましいが、これに限定されない。また、親水性多孔化剤はポリフッ化ビニリデン系樹脂表面の親水性向上を目的に中空糸中に残留し続けても良い。
【００２８】
中空糸膜の外径と膜厚は、膜の強度を損なわない範囲で、中空糸膜内部長手方向の圧力損失を考慮し、膜モジュールとして透水量が目標値になるように決めればよい。即ち、外径が、太ければ圧力損失の点で有利になるが、充填本数が減り、膜面積の点で不利になる。一方、外径が細い場合は充填本数を増やせるので膜面積の点で有利になるが、圧力損失の点で不利になる。また、膜厚は強度を損なわない範囲で薄い方が好ましい。従って、おおよその目安を示すならば、中空糸膜の外径は、おおよそ好ましくは０．３〜３ｍｍ、より好ましくは０．４〜２．５ｍｍ、更に好ましくは、０．５〜２ｍｍである。また、膜厚は、好ましくは外径の０．０８〜０．４倍、より好ましくは０．１〜０．３５倍、更に好ましくは０．１２〜０．３倍である。
【００２９】
さらに上記製造方法で製造された中空糸膜は、中空糸膜モジュールとして用いることができる。モジュールとは、中空糸膜を複数本束ねて円筒状の容器に納め、両端または片端をポリウレタンやエポキシ樹脂等で固定し、透過水を集水できるようにしたものや、平板状に中空糸膜の両端を固定して透過水を集水できるようにしたもののことである。この中空糸膜モジュールの原水側にポンプや水位差などの加圧手段を設けたり、透過水側にポンプまたはサイフォン等による吸引手段を設けたりすることにより、原水の膜ろ過を行う水の分離装置として用いることができる。この水の分離装置を用いて、原水から、精製された透過水を製造することができる。原水とは、河川水、湖沼水、地下水、海水、下水、排水およびこれらの処理水等である。
【００３０】
以下に具体的実施例を挙げて本発明を説明するが、本発明はこれら実施例により何ら限定されるものではない。
【００３１】
【実施例】
以下実施例の透水性能は、逆浸透膜処理水を２５℃で１．５ｍの水位差を駆動力に小型モジュール（長さ約２０ｃｍ、中空糸膜の本数１〜１０本程度）に送液し、一定時間の透過水量を測定して得た値を、１００ｋＰａ当たりに換算して算出した。但し、透水性能は、ポンプ等で一定の圧力に加圧して得た値を１００ｋＰａ当たりに換算して求めてもよい。水温についても、２５℃以外で測定し、評価液体の粘性から２５℃での値に換算してもよい。破断強伸度は、引張試験機を用いて、試験長５０ｍｍでフルスケール２０００ｇの加重をクロスヘッドスピード５０ｍｍ／分で測定し、求めた。空孔率は中空糸膜壁容積中の空孔容積の割合で、湿潤状態と乾燥状態の中空糸重量から換算して求めた。
【００３２】
実施例１
分子量２８．４万のフッ化ビニリデンホモポリマーと分子量４，０００ポリエチレングリコール、イソホロンを、それぞれ５５重量％と、５重量％、４０重量％の割合で混合し、１６０℃の温度で溶解して、ポリマー溶液を調製した。このポリマー溶液を、１００％イソホロンを中空部形成用液体として中空部に随伴させながら、１６０℃の口金から中空糸状に吐出し、温度３０℃のイソホロン９０重量％水溶液からなる冷却液体を有する冷却浴中で固化した後、９０℃水中で２．０倍に延伸した。得られた中空糸膜は、外径１．５５ｍｍ、内径０．９５ｍｍ、透水性能は２．７ｍ³／（ｍ²・ｈｒ）（差圧１００ｋＰａ、２５℃の条件）で、破断強力が７３０ｇ／本、破断伸度が５３％であった。
【００３３】
実施例２
分子量４１．７万のフッ化ビニリデンホモポリマーと分子量２１，０００のポリビニルアルコール、γ−ブチロラクトンを、それぞれ４０重量％と１０重量％５０重量％の割合で混合し、１４０℃の温度で溶解した。このポリマー溶液を、１００％γ−ブチロラクトンを中空部形成用液体として中空部に随伴させながら、１１０℃の口金から中空糸状に吐出し、温度２５℃のシクロヘキサノン８５重量％水溶液からなる冷却液体を有する冷却浴中で固化した後、８０℃熱水中でポリビニルアルコールを抽出し、１１０℃のポリエチレングリコール（分子量４００）中で２倍に延伸した。得られた中空糸膜は、外径１．４５ｍｍ、内径０．９５ｍｍ、透水性能は２．８ｍ³／（ｍ²・ｈｒ）（差圧１００ｋＰａ、２５℃の条件）で、破断強力が１１３０ｇ／本、破断伸度が５２％、空孔率７０％であった。
構造は、粒径１μｍ程度の球状構造が連結した構造になっていた。
【００３４】
比較例１
分子量４１．７万のフッ化ビニリデンホモポリマーとγ−ブチロラクトンを、それぞれ４０重量％、６０重量％の割合で混合し、１４０℃の温度で溶解した。このポリマー溶液を、１００％γ−ブチロラクトンを中空部形成用液体として中空部に随伴させながら、１１０℃の口金から中空糸状に吐出し、温度２５℃のシクロヘキサノン８５重量％水溶液からなる冷却液体を有する冷却浴中で固化した後、１１０℃のポリエチレングリコール（分子量４００）中で２倍に延伸した。得られた中空糸膜は、外径１．４２ｍｍ、内径０．９５ｍｍ、透水性能は１．５ｍ³／（ｍ²・ｈｒ）（差圧１００ｋＰａ、２５℃の条件）で、破断強力が１１３０ｇ／本、破断伸度が５２％、空孔率６５％であった。構造は、粒径１μｍ程度の球状構造が連結した構造になっていたが、球状構造間の隙間の比率が実施例２に比べ小さくなっていた。
【００３５】
比較例２
分子量４１．７万のフッ化ビニリデンホモポリマーと、分子量２１，０００のポリビニルアルコール、γ−ブチロラクトンを、それぞれ４０重量％、０．５重量％、５９．５重量％の割合で混合し、１２０℃の温度で溶解した。このポリマー溶液を１００％γ−ブチロラクトンを中空部形成用液体として中空部に随伴させながら１２０℃の口金から中空糸状に吐出し、温度２５℃のシクロヘキサノン８５重量％水溶液からなる冷却液体を有する冷却浴中で固化した後、１１０℃のポリエチレングリコール（分子量４００）中で２倍に延伸した。得られた中空糸膜は、外径１．４４ｍｍ、内径０．９６ｍｍ、透水性能は１．６ｍ³／（ｍ²・ｈｒ）（差圧１００ｋＰａ、２５℃の条件）で、破断強力が１０５０ｇ／本、破断伸度が５１％、空孔率５１％であった。
【００３６】
実施例３
分子量３５．８万のフッ化ビニリデンホモポリマーと分子量３５，０００のポリビニルピロリドン、シクロヘキサノンを、それぞれ４０重量％と１０重量％、５０重量％の割合で混合し、１３０℃の温度で溶解した。このポリマー溶液を、１００％シクロヘキサノンを中空部形成用液体として中空部に随伴させながら、１３０℃の口金から中空糸状に吐出し、温度２０℃のシクロヘキサノン８０重量％水溶液からなる冷却液体を有する冷却浴中で固化した後、８５℃水中で３．０倍に延伸した。得られた中空糸膜は、外径１．０２ｍｍ、内径０．６５ｍｍ、透水性能は３．８ｍ³／（ｍ²・ｈｒ）（差圧１００ｋＰａ、２５℃の条件）で、破断強力が８８０ｇ／本、破断伸度が４４％であった。
【００３７】
比較例３
分子量４１．７万のフッ化ビニリデンホモポリマーとテトラエチレングリコール、シクロヘキサノンを、それぞれ２０重量％と３０重量％、５０重量％の割合で混合し、１００℃の温度で溶解した。このポリマー溶液を、９５重量％のシクロヘキサノン水溶液を中空部形成用液体として中空部に随伴させながら、１００℃の口金から中空糸状に吐出し、温度１０℃のシクロヘキサノン８０重量％水溶液からなる冷却液体を有する冷却浴中で固化した後、８５℃水中で３．５倍に延伸した。得られた中空糸膜は、外径１．１０ｍｍ、内径０．７３ｍｍ、透水性能は５．２ｍ^３／（ｍ^２・ｈｒ）（差圧１００ｋＰａ、２５℃の条件）で、破断強力が６００ｇ／本、破断伸度が３０％であった。
【００３８】
実施例４
分子量５７．２万のフッ化ビニリデンホモポリマーとポリオキシエチレンソルビタンモノオレート（Ｔｗｅｅｎ８０）、シクロヘキサノンを、それぞれ３５重量％と１重量％、６４重量％の割合で混合し、１５５℃の温度で溶解した。このポリマー溶液を、１００％シクロヘキサノンを中空部形成用液体として中空部に随伴させながら、１５５℃の口金から中空糸状に吐出し、温度１５℃のシクロヘキサノン８０重量％水溶液からなる冷却液体を有する冷却浴中で固化した後、８５℃水中で４．０倍に延伸した。得られた中空糸膜は、外径１．３８ｍｍ、内径０．８６ｍｍ、透水性能は２．５ｍ^３／（ｍ^２・ｈｒ）（差圧１００ｋＰａ、２５℃の条件）で、破断強力が１４２０ｇ／本、破断伸度が４７％であった。
【００３９】
実施例５
分子量３５．８万のフッ化ビニリデンホモポリマーおよび四フッ化エチレンとフッ化ビニリデンの共重合体およびグリセリン、シクロヘキサノンを、それぞれ３０重量％、１０重量％、２重量％、５８重量％の割合で混合し、１６５℃の温度で溶解した。このポリマー溶液を、１００％シクロヘキサノンを中空部形成用液体として中空部に随伴させながら、１６０℃の口金から中空糸状に吐出し、温度３０℃のシクロヘキサノン９０重量％水溶液からなる冷却液体を有する冷却浴中で固化した後、８０℃水中で１．５倍に延伸した。得られた中空糸膜は、外径１．５２ｍｍ、内径０．９０ｍｍ、透水性能は１．５ｍ^３／（ｍ^２・ｈｒ）（差圧１００ｋＰａ、２５℃の条件）で、破断強力が１６００ｇ／本、破断伸度が５８％であった。
【００４０】
比較例４
分子量４１．７万のフッ化ビニリデンホモポリマーと分子量２１，０００のポリビニルアルコール、γ−ブチロラクトンを、それぞれ２０重量％と３２重量％、４８重量％の割合で混合し、１７０℃の温度で１２時間攪拌したが、均一に溶解しなかった。
【００４１】
比較例５
分子量４１．７万のフッ化ビニリデンホモポリマーと分子量４００のポリエチレングリコール、シクロヘキサノンを、それぞれ１８重量％と５重量％、７７重量％の割合で混合し、９０℃の温度で溶解した。このポリマー溶液を、９０重量％のシクロヘキサノン水溶液を中空部形成用液体として中空部に随伴させながら、９０℃の口金から中空糸状に吐出したところ、ポリマー溶液の粘性が低すぎて中空糸状に成型できなかった。
【００４２】
比較例６
分子量４１．７万のフッ化ビニリデンホモポリマーと分子量４００のポリエチレングリコール、シクロヘキサノンを、それぞれ６１重量％と１重量％、３８重量％の割合で混合し、１６５℃の温度で溶解した。このポリマー溶液を、１００％のシクロヘキサノンを中空部形成用液体として中空部に随伴させながら、１６５℃の口金から中空糸状に吐出したところ、ポリマー溶液の粘性が高すぎて中空糸状に成型できなかった。
【００４４】
比較例７
分子量２８．４万のフッ化ビニリデンホモポリマーと分子量２１，０００のポリビニルアルコール、シクロヘキサノンを、それぞれ２０重量％と１０重量％、８０重量％の割合で混合し、１５０℃の温度で溶解した。口金温度７８℃で紡糸しようとしたが、紡糸機のホッパー中でゲル化してしまい、紡糸できなかった。
【００４８】
実施例６
分子量２８．４万のフッ化ビニリデンホモポリマーと分子量２，１０００のポリビニルアルコール、γ−ブチロラクトンを、それぞれ４５重量％と１０重量％、４５重量％の割合で混合し、１５５℃の温度で溶解した。このポリマー溶液を、１００％γ−ブチロラクトンを中空部形成用液体として中空部に随伴させながら、１５５℃の口金から中空糸状に吐出し、温度３０℃のγ−ブチロラクトン８０重量％水溶液からなる冷却液体を有する冷却浴中で固化した後、８８℃水中で１．８倍に延伸した。延伸後１００℃ポリエチレングリコール浴中に浸漬し水置換した。得られた中空糸膜は、外径１．３６ｍｍ、内径１．０３ｍｍ、透水性能は２．８ｍ^３／（ｍ^２・ｈｒ）（差圧１００ｋＰａ、２５℃の条件）で、破断強力が９８０ｇ／本、破断伸度が５０％、空孔率が５４％であった。構造は、球状構造中にポリビニルアルコールが抽出された後と思われる空孔があいていた。
【００４９】
実施例７
分子量３５．８万のフッ化ビニリデンホモポリマーと分子量３，０００のポリプロピレングリコール、γ−ブチロラクトンを、それぞれ４５重量％と１０重量％、４５重量％の割合で混合し、１４０℃の温度で溶解した。このポリマー溶液を、１００％γ−ブチロラクトンを中空部形成用液体として中空部に随伴させながら、１４０℃の口金から中空糸状に吐出し、温度２５℃のγ−ブチロラクトン８５重量％水溶液からなる冷却液体を有する冷却浴中で固化した後、１２０℃のポリエチレングリコール（分子量４００）中で１．５倍に延伸した。得られた中空糸膜は、外径１．３４ｍｍ、内径０．８３ｍｍ、透水性能は４．０ｍ^３／（ｍ^２・ｈｒ）・１００ｋＰａ，２５℃で、破断強力が９８０ｇ／本、破断伸度が５２％であった。
【００５０】
実施例８
分子量４１．７万のフッ化ビニリデンホモポリマーとポリエチレングリコール、ポリオキシエチレンソルビタモノオレート（Ｔｗｅｅｎ８０）、γ−ブチロラクトンを、それぞれ４０重量％、９重量％、１重量％、５０重量％の割合で混合し、１３０℃の温度で溶解した。このポリマー溶液を、１００％γ−ブチロラクトンを中空部形成液体として中空部に随伴させながら、１３０℃の口金から中空糸状に吐出し、温度２０℃のγ−ブチロラクトン８０重量％水溶液からなる冷却液体を有する冷却浴中で固化した後、８５℃水中で２．０倍に延伸した。得られた中空糸膜は、外径１．３５ｍｍ、内径０．８２ｍｍ、透水性能は４．４ｍ^３／（ｍ^２・ｈｒ）（差圧１００ｋＰａ、２５℃の条件）で、破断強力が１４２０ｇ／本、破断伸度が４１％であった。
【００５１】
比較例８
分子量４１．７万のフッ化ビニリデンホモポリマーと分子量４，０００のポリエチレングリコール、γ−ブチロラクトンを、それぞれ２５重量％と１０重量％、６５重量％の割合で混合し、１００℃の温度で溶解した。このポリマー溶液を、９５重量％のγ−ブチロラクトン水溶液を、中空部形成用液体として中空部に随伴させながら９５℃の口金から中空糸状に吐出し、温度１０℃のγ−ブチロラクトン８０重量％水溶液からなる冷却液体を有する冷却浴中で固化した後、８５℃水中で４．０倍に延伸した。得られた中空糸膜は、外径１．０８ｍｍ、内径０．７３ｍｍ、透水性能は４．４ｍ^３／（ｍ^２・ｈｒ）（差圧１００ｋＰａ、２５℃の条件）で、破断強力が４７０ｇ／本、破断伸度が３０％であった。
【００５３】
比較例９
分子量４１．７万のフッ化ビニリデンホモポリマーと分子量３、０００のポリプロピレングリコール、γ−ブチロラクトンを、それぞれ１８重量％と３重量％、７９重量％の割合で混合し、９０℃の温度で溶解した。このポリマー溶液を、９０重量％のγ−ブチロラクトン水溶液を中空部形成用液体として中空部に随伴させながら、９０℃の口金から中空糸状に吐出したところ、ポリマー溶液の粘性が低すぎて中空糸状に成型できなかった。
【００５４】
比較例１０
分子量４１．７万のフッ化ビニリデンホモポリマーと分子量４，０００のポリエチレングリコール、γ−ブチロラクトンを、それぞれ６５重量％と１重量％、３４重量％の割合で混合し、１７０℃の温度で溶解した。ポリマー溶液の粘性が高すぎて中空糸状に成型できなかった。
【００５８】
実施例９
分子量４１．７万のフッ化ビニリデンホモポリマーと分子量４００のポリエチレングリコール、γ−ブチロラクトンを、それぞれ３８重量％と５重量％、５７重量％の割合で混合し、１４０℃の温度で溶解した。このポリマー溶液を、１００％γ−ブチロラクトンを中空部形成用液体として中空部に随伴させながら、１００℃の口金から中空糸状に吐出し、温度２０℃のγ−ブチロラクトン８０重量％水溶液からなる冷却液体を有する冷却浴中で固化した後、８５℃水中で１．３倍に延伸した。得られた中空糸膜は、外径１．８５ｍｍ、内径１．１５ｍｍ、透水性能は１．６ｍ^３／（ｍ^２・ｈｒ）（差圧１００ｋＰａ、２５℃の条件）で、破断強力が１３１０ｇ／本、破断伸度が５４％であった。
【００５９】
実施例１０
実施例９における冷却浴の冷却液体を温度２０℃のγーブチロラクトン８０重量％、分子量４００のポリエチレングリコール５重量％溶解した水溶液に変更したところ、得られた中空糸膜は、外径１．８６ｍｍ、内径１．１５ｍｍ、透水性能は１．８ｍ^３／（ｍ^２・ｈｒ）（差圧１００ｋＰａ，２５℃の条件）で、破断強力が１１８０ｇ／本、破断伸度が５４％であった。また、そのうえ中空部形成用液体を９５重量％γーブチロラクトン、５重量％分子量４００のポリエチレングリコール混合液に変更したところ、得られた中空糸膜は、外径１．８６ｍｍ、内径１．１５ｍｍ、透水性能は１．９ｍ^３／（ｍ^２・ｈｒ）（差圧１００ｋＰａ，２５℃の条件）で、破断強力が１１６０ｇ／本、破断伸度が５３％であった。
【００６２】
実施例１１
分子量４１．７万のフッ化ビニリデンホモポリマーと分子量２０，０００のポリエチレングリコール、イソホロンを、それぞれ４０重量％と１０重量％、５０重量％の割合で混合し、１５５℃の温度で溶解した。このポリマー溶液を、１００％のイソホロンを中空部形成用液体として中空部に随伴させながら、１５５℃の口金から中空糸状に吐出し、温度３０℃のイソホロン８０重量％水溶液からなる冷却液体を有する冷却浴中で固化した後、８５℃水中で２．０倍に延伸した。得られた中空糸膜は、外径１．６０ｍｍ、内径１．００ｍｍ、透水性能は２．９ｍ^３／（ｍ^２・ｈｒ）（差圧１００ｋＰａ、２５℃の条件）で、破断強力が９７０ｇ／本、破断伸度が５２％であった。
【００６３】
実施例１２
分子量４１．７万のフッ化ビニリデンホモポリマーと分子量２０，０００のポリエチレングリコール、フタル酸ジメチルを、それぞれ４０重量％と５重量％、５５重量％の割合で混合し、１６５℃の温度で溶解した。このポリマー溶液を、フタル酸ジメチル７０重量％とポリエチレングリコール（分子量４００）３０重量％とからなる溶液を中空部形成用液体として中空部に随伴させながら、１６５℃の口金から中空糸状に吐出し、フタル酸ジメチル６０重量％とポリエチレングリコール（分子量４００）４０重量％とからなる温度４０℃の冷却液体を有する冷却浴中で固化した後、１２０℃エチレングリコール（分子量４００）中で２．０倍に延伸した。得られた中空糸膜は、外径１．３５ｍｍ、内径０．７５ｍｍ、透水性能は２．０ｍ^３／（ｍ^２・ｈｒ）（差圧１００ｋＰａ、２５℃の条件）で、破断強力が１２５０ｇ／本、破断伸度が３１％であった。
【００６４】
実施例１３
分子量４１．７万のフッ化ビニリデンホモポリマーと分子量３，０００のポリエチレングリコール、γーブチロラクトンを、それぞれ３８重量％と５重量％、５７重量％の割合で混合し、１２０℃の温度で溶解した。このポリマー溶液を、１００重量％のγーブチロラクトンを中空部形成液体として中空部に随伴させながら、１２０℃の口金から中空糸状に吐出し、温度０℃のγーブチロラクトン８０重量％水溶液からなる冷却液体を有する冷却浴中で固化した後、水洗した。得られた中空糸膜は、外径１．３２ｍｍ、内径０．８６ｍｍ、透水性能は１．６ｍ^３／（ｍ^２・ｈｒ）（差圧１００ｋＰａ、２５℃の条件）で、破断強力が１６２０ｇ／本、破断伸度が６８％であった。
【００６５】
【発明の効果】
本発明では、耐薬品性が高いポリフッ化ビニリデン系樹脂を用いて、高強度で高透水性能を有する中空糸膜を、低コストで製造することが可能になる中空糸膜の製造方法が提供される。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a hollow fiber membrane. More specifically, the present invention relates to a method for producing a hollow fiber microfiltration membrane or a hollow fiber ultrafiltration membrane used for water treatment such as drinking water production, water purification treatment, and wastewater treatment, and a hollow fiber membrane produced by the production method.
[0002]
[Prior art]
As hollow fiber membranes, reverse osmosis membranes, ultrafiltration membranes, microfiltration membranes, and the like have been commercialized. Hollow fiber membranes such as microfiltration membranes and ultrafiltration membranes are used in various fields including water purification treatment, wastewater treatment, medical use and food industry. The performance required for the hollow fiber separation membrane is generally high water permeability, excellent separation characteristics, chemical strength and physical strength. The reason why the hollow fiber membrane is used is that the effective membrane area per unit volume is large. Among them, in the drinking water production field, that is, in the water purification treatment application, separation membranes are used in place of conventional sand filtration and coagulation sedimentation processes. Since the amount of water that must be treated in these fields is large, if the water permeability of the hollow fiber membrane is excellent, the membrane area can be reduced, and the equipment can be made compact, so that equipment costs can be saved and membrane replacement costs can be reduced. It is also advantageous in terms of installation area. Further, the separation membrane is required to have chemical resistance. In water purification treatment, disinfectants such as sodium hypochlorite are added to the membrane module for the purpose of sterilizing permeate and preventing biofouling of the membrane, and acid, alkali, chlorine, surfactants are used as membrane chemical cleaning. The membrane may be washed with Therefore, in recent years, a separation membrane using a polyvinylidene fluoride resin as a material having high chemical resistance has been developed and used. In the field of water purification, accidents in which pathogenic microorganisms resistant to chlorine such as Cryptosporidium derived from livestock excreta cannot be treated at the water purification plant and have been mixed into the treated water have emerged since the 1990s. For this reason, hollow fiber membranes are required to have sufficient separation properties and high strength and elongation properties so that the membrane is cut and raw water is not mixed.
[0003]
Several techniques have been disclosed for manufacturing separation membranes made of polyvinylidene fluoride resin, but most of these are disclosed in JP-B 1-2003, as described in Japanese Patent Publication No. 1-2003. After a polymer solution in which is dissolved in a good solvent is extruded from a die at a temperature considerably lower than the melting point of the polyvinylidene fluoride resin or cast on a glass plate, the non-solvent of the polyvinylidene fluoride resin is removed. This is a wet solution method in which an asymmetric porous structure is formed by non-solvent-induced phase separation in contact with a contained liquid. However, in the wet solution method, it is difficult to cause phase separation uniformly in the film thickness direction, and there is a problem that mechanical strength is not sufficient because an asymmetric film containing macrovoids is obtained. Further, there are many film forming condition factors given to the film structure and film performance, and there are drawbacks that the film forming process is difficult to control and the reproducibility is poor. Further, in recent years, as disclosed in Japanese Patent No. 2899903, inorganic fine particles and an organic liquid are melt-kneaded into a polyvinylidene fluoride resin, and extruded from a die at a temperature equal to or higher than the melting point of the polyvinylidene fluoride resin. A melt extraction method is disclosed in which a porous structure is formed by pressing and molding with a press machine, solidifying by cooling, and then extracting an organic liquid and inorganic fine particles. In the case of the melt extraction method, the porosity can be easily controlled and a macrovoid is not formed, and a relatively homogeneous and high-strength film is obtained. However, if the dispersibility of inorganic fine particles is poor, defects such as pinholes are generated. there is a possibility. Furthermore, the melt extraction method is a production method having a drawback that the production cost is extremely high.
[0004]
[Problems to be solved by the invention]
The present invention is intended to solve the above-mentioned problems of the prior art, and using a polyvinylidene fluoride resin having high chemical resistance, a hollow fiber membrane having high strength, high porosity and high water permeability, An object of the present invention is to provide a method for producing a hollow fiber membrane that can be produced at low cost.
[0005]
[Means for Solving the Problems]
  That is, the present invention at least30-50Containing 1% by weight of a polyvinylidene fluoride-based resin, 1-30% by weight of a hydrophilic porogen, and a poor solvent for the resin,spinningA polyvinylidene fluoride resin solution having a temperature in the range of 80 to 175 ° C. is discharged into a cooling bath and solidified.The cooling liquid in the cooling bath has a temperature in the range of 0 to 50 ° C., and the cooling liquid has a poor solvent in the concentration range of 60 to 100% by weight. Contains liquidThis is achieved by the method for producing a hollow fiber membrane. Furthermore, the present invention includes a hollow fiber membrane module having a hollow fiber membrane produced by the above production method, and a water separation device comprising the hollow fiber membrane module.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0007]
The polyvinylidene fluoride resin in the present invention is a resin containing a vinylidene fluoride homopolymer and / or a vinylidene fluoride copolymer. A plurality of types of vinylidene fluoride copolymers may be contained. The vinylidene fluoride copolymer is not particularly limited as long as it is a polymer having a vinylidene fluoride residue structure, and is typically a copolymer of a vinylidene fluoride monomer and other fluorine-based monomers, for example, Examples thereof include a copolymer of at least one fluorine-based monomer selected from vinyl fluoride, tetrafluoroethylene, propylene hexafluoride, and ethylene trifluoride chloride and vinylidene fluoride. In some cases, a monomer such as ethylene other than the fluorine-based monomer may be included. The weight average molecular weight of the polyvinylidene fluoride resin may be appropriately selected depending on the required strength and water permeability of the hollow fiber membrane, but is preferably in the range of 100,000 to 1,000,000. In consideration of processability to a hollow fiber membrane, a range of 250,000 to 600,000 is preferable, and a range of 350,000 to 450,000 is more preferable.
[0008]
In the present invention, the poor solvent means that the polyvinylidene fluoride resin cannot be dissolved by 5% by weight or more at a low temperature of less than 60 ° C., but it is 60 ° C. or more and below the melting point of the polyvinylidene fluoride resin (for example, polyvinylidene fluoride resin). However, it is a solvent that can be dissolved in an amount of 5 wt% or more in a high temperature region of about 178 ° C. when the vinylidene fluoride homopolymer is constituted alone. A solvent capable of dissolving 5% by weight or more of a polyvinylidene fluoride resin at a low temperature of less than 60 ° C. with respect to a poor solvent is a good solvent, the polyvinylidene fluoride resin up to the melting point of the polyvinylidene fluoride resin or the boiling point of the liquid A solvent that does not dissolve or swell is defined as a non-solvent. Examples of the poor solvent include cyclohexanone, isophorone, γ-butyrolactone, methyl isoamyl ketone, dimethyl phthalate, propylene glycol methyl ether, propylene carbonate, diacetone alcohol, glycerol triacetate, etc., medium chain length alkyl ketone, ester, glycol ester And organic carbonates. Examples of the good solvent include N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, methyl ethyl ketone, acetone, tetrahydrofuran, tetramethylurea, lower alkyl ketones such as trimethyl phosphate, esters, amides, and the like. Non-solvents include water, hexane, pentane, benzene, toluene, methanol, ethanol, carbon tetrachloride, o-dichlorobenzene, trichloroethylene, low molecular weight polyethylene glycol and other aliphatic hydrocarbons, aromatic hydrocarbons, Examples include chlorinated hydrocarbons and other chlorinated organic liquids.
[0009]
The hydrophilic porosifying agent of the present invention is not limited in any way as long as it has hydrophilicity and has the property of promoting the porosity of the hollow fiber membrane. It is a polymer or low molecular weight substance. Specifically, water-soluble polymers such as polyethylene glycol, polypropylene glycol, polyvinyl alcohol, polyvinyl acetate, polyvinyl pyrrolidone, polyacrylic acid, ester bodies of polyhydric alcohols such as sorbitan fatty acid esters (mono, triesters, etc.) Ethylene oxide low mole adduct of sorbitan fatty acid ester, ethylene oxide low mole adduct of nonylphenol, pluronic type ethylene oxide low mole adduct, etc., polyoxyethylene alkyl ester, alkylamine salt, polyacrylic acid Surfactants such as soda, polyhydric alcohols such as glycerin, and glycols such as tetraethylene glycol and triethylene glycol. These may be used alone or in a mixture of two or more. These hydrophilic porosifiers should have a weight average molecular weight of 50,000 or less (more preferably 30,000 or less). Those having a molecular weight larger than this may be unfavorable because they have poor extractability and are difficult to uniformly dissolve in the spinning solution.
[0010]
This hydrophilic porosifying agent is considered to remain in the hollow fiber membrane for a relatively long time compared to the solvent when the hollow fiber membrane is discharged from the die and solvent is extracted in the cooling bath to cause structural aggregation. Since the hydrophilic porosizing agent is extracted after the structure aggregation accompanying the solvent extraction becomes gentle, the obtained hollow fiber membrane has high porosity. Structurally, depending on the type, molecular weight, added amount, etc. of the hydrophilic porogen, it has a structure in which spherical structures are connected, and pores are distributed at the boundary between the spherical structure and the spherical structure, or in the gaps, or The gap between the spherical structures itself becomes large, or a structure in which a large number of pores of 5 μm or less are distributed in the spherical structure itself, or a structure in which these are combined, has high porosity and high water permeability.
[0011]
The spherical structure is presumed to be exclusively spherulites. A spherulite is a crystal in which a polyvinylidene fluoride resin is precipitated and solidified into a spherical shape when a polyvinylidene fluoride resin solution is phase-separated to form a porous structure. A hollow fiber membrane having such a structure can have higher strength and higher water permeability than a hollow fiber membrane having a network structure obtained by a conventional wet solution method.
[0012]
  In the present invention, first, a polyvinylidene fluoride resin (hereinafter also simply referred to as a polymer) is used.30-50% by weightIn the concentration range of 1 to 30% by weight, preferably 1 to 20% by weight, more preferably 1 to 10% by weight of the hydrophilic porosifying agent in the poor solvent of the resin, preferably 80 to 175 ° C. Is dissolved in a temperature range of 100 to 150 ° C. to prepare the polyvinylidene fluoride resin solution.
[0013]
If the polymer concentration of the polyvinylidene fluoride resin is increased, a hollow fiber membrane having high strength and elongation characteristics can be obtained. However, if the polymer concentration is too high, the porosity of the produced hollow fiber membrane is reduced, and the water permeability is lowered. Further, if the viscosity of the prepared polymer solution is not within an appropriate range, it is difficult to form a hollow fiber. In the preparation of the polymer solution, a plurality of poor solvents may be used. In addition, a good solvent or a non-solvent may be mixed in the poor solvent as long as the solubility of the polymer is not hindered. In the conventional wet solution method, the polymer concentration is about 10 to 20% by weight in order to develop the water permeability, and a film having high strength and elongation is not obtained. In the present invention, high strength and elongation characteristics are expressed by increasing the polymer concentration as described above.
[0014]
Further, in the present invention, in the polyvinylidene fluoride resin solution, the hollow fiber membrane obtained when the hydrophilic porogen is not contained or low does not have sufficient porosity, and it is difficult to obtain water permeability. If too much hydrophilic porosifying agent is contained, it cannot be uniformly dissolved in the spinning dope and cannot be formed into a hollow fiber shape. In addition, pinhole-like defects are given to the hollow fiber membrane, the separation characteristics are lowered, and the strength and elongation are weakened. In the present invention, high water permeability is expressed by setting the hydrophilic porous agent concentration in the polyvinylidene fluoride resin solution, which is a spinning stock solution, as described above.
[0015]
In addition, by using a poor solvent, a film structure having a spherical structure presumed to be composed of spherical crystals is preferentially formed over a network structure obtained by a wet solution method. When the solvent system deviates from the poor solvent-like dissolution characteristics due to excessive addition of a solvent other than the poor solvent, the following problems occur. That is, when the solvent or the solvent system is a good solvent or has good solvent characteristics, the dissolving ability of the spinning dope for the polymer is increased even at a low temperature. As a result, even when quenched to a low temperature during spinning, the spherical structure that has undergone thermal phase separation due to the temperature drop is less likely to solidify and precipitate, and the spherical spheres grow larger. As a result, the resulting film is disadvantageous in that the spherical structures are closely connected with each other in a few points, and the strength is weak. On the other hand, when it is a non-solvent or has non-solvent properties, it is difficult for the polymer to be uniformly dissolved in the spinning dope, which is disadvantageous in terms of spinning stability.
[0016]
In the present invention, the polymer solution is cooled and solidified from a temperature range of 80 to 175 ° C. using a cooling liquid or the like to obtain a hollow fiber membrane having a structure in which spherical structures are connected and there are voids therebetween. be able to.
[0017]
Furthermore, as a result of intensive studies, the inventors have found that this spherical structure can be controlled by the cooling method together with the polymer solution temperature. That is, (1) If the temperature of the polymer solution is too low, it gels and solidifies before the spherical structure develops, so that no porous structure is expressed and water permeability cannot be obtained, and (2) the polymer solution temperature is If it is too high, it takes time for cooling, gelation, and solidification, and the spherical structure develops sufficiently, so that the spherical structure becomes large, and the aggregates of polymer molecules that connect the spherical structure and the spherical structure decrease. It was found that the film structure decreases in strength.
[0018]
In the method for producing a hollow fiber membrane of the present invention, after preparing a polymer solution, the polymer solution is discharged and formed into a hollow fiber shape. For example, it is discharged from a double-tube type die for spinning a hollow fiber membrane, and after passing through a dry part having a predetermined length as necessary, it is introduced into a cooling bath and solidified. When using a double-tube type die, it is preferable to filter the polymer solution with a 5-100 μm stainless steel filter or the like before discharging from the die. The size of the base to be used may be appropriately selected according to the size of the hollow fiber membrane to be manufactured and the membrane structure, but is roughly slit outer diameter 0.7 to 10 mm, slit inner diameter 0.5 to 4 mm, injection tube inner diameter 0.25. A range of ˜2 mm is preferable. The spinning draft (take-off speed / stock solution discharge linear speed) is preferably 0.8 to 100, more preferably 0.9 to 50, still more preferably 1 to 30, and the dry length is preferably 10 to 1000 mm. More preferably, it is the range of 10-500 mm, More preferably, it is the range of 10-300 mm.
[0019]
Further, the temperature of the die, that is, the spinning temperature may be in the range of 80 to 175 ° C., preferably 100 to 170 ° C., similarly to the melting temperature, and the die temperature and the melting temperature may be different. Regarding the melting temperature, it is also possible to preferably employ a temperature higher than the die temperature from the viewpoint that the melting is performed uniformly in a short time.
[0020]
As described above, the polymer formed into a hollow fiber shape is discharged into a cooling bath and solidified to form a hollow fiber membrane. In this case, a liquid containing a poor solvent having a temperature of 0 to 50 ° C., preferably 5 to 30 ° C. and a concentration of 60 to 100% by weight, preferably 75 to 90% by weight is used for the cooling bath. It is preferable to coagulate. When the cooling bath is in this temperature range, cooling solidification in which spherulites easily develop becomes dominant in the solidification step. A plurality of poor solvents may be used as a mixture. In addition, a solvent other than the poor solvent may be mixed with the poor solvent as long as the concentration range is not deviated. Preferably, a non-solvent is mixed, but in some cases, a good solvent may be mixed. By rapidly cooling by giving a large temperature difference from the polymer dissolution temperature, the spherical structure becomes minute, and at the same time, there are moderately aggregated polymer molecules between the spherical structures, and the membrane structure has water permeability and high strength and elongation characteristics. Is expressed. Further, by incorporating a poor solvent having a certain high concentration in the cooling liquid, non-solvent-induced phase separation can be suppressed, and a hollow fiber membrane can be formed without forming a dense layer on the membrane surface. If a liquid containing a non-solvent such as water at a high concentration is used as the cooling liquid, a dense layer is formed on the surface of the film, and even if it is stretched, water permeability is not exhibited.
[0021]
The form of the cooling bath is not particularly limited as long as the cooling liquid and the polymer solution formed into a hollow fiber shape are in sufficient contact and can be cooled, and the cooling liquid is literally stored. The liquid tank may be in the form of a liquid tank, and if necessary, the liquid tank may be circulated or updated with a liquid whose temperature and composition are adjusted. Although the liquid tank form is most suitable, depending on the case, the form in which the cooling liquid is flowing in the pipe may be used, or the form in which the cooling liquid is jetted onto the hollow fiber membrane running in the air. It may be.
[0022]
Further, in forming the hollow part of the hollow fiber membrane, gas or liquid is usually accompanied with the polymer solution. In the present invention, a liquid containing a poor solvent with a concentration in the range of 60 to 100% by weight is used for forming the hollow part. It can preferably be employed as a liquid. The concentration of the poor solvent in the hollow portion forming liquid is more preferably in the range of 70 to 100% by weight, and still more preferably in the range of 80 to 100% by weight. Similar to the cooling liquid in the cooling bath, the non-solvent-induced phase separation can be suppressed and a fine spherical structure can be formed by adding a high concentration poor solvent to the hollow portion forming liquid. In the hollow portion forming liquid, a plurality of poor solvents may be used as a mixture. In addition, a good solvent or a non-solvent may be mixed with the poor solvent as long as the concentration range is not deviated.
[0023]
  As a cooling liquid,, The concentration is 140% by weightA method of coagulating using a liquid containing a hydrophilic porosifying agent within the above range is also preferably employed. The hydrophilic porosizing agent is preferably one or more of the same type as that contained in the spinning dope, but other hydrophilic porogens may be used.. coldBy containing a hydrophilic porosifying agent in the rejection bath, the hydrophilic porosifying agent is extracted by a concentration gradient compared to the solvent extraction rate of the spinning dope when the discharged hollow fiber membrane is subjected to solvent extraction and solidification precipitation in the cooling bath. The extraction speed of is reduced. As a result, the hydrophilic porosifying agent remains in the structure for a longer period of time even when the structure contracts due to solvent extraction, and a highly porous film with high porosity is developed.
[0024]
  In addition, in forming the hollow portion of the hollow fiber membrane,further,Concentration from 140% by weightIt is preferable to use a liquid containing a hydrophilic porosifying agent in the range as described above as the liquid for forming the hollow part. The concentration of the hydrophilic porogen in the liquid for forming the hollow part is more preferable.Is 1It is in the range of ˜30% by weight. Like the cooling bath, the hollow portion forming liquid contains a hydrophilic porogen to suppress the extraction rate of the hydrophilic porogen during solidification precipitation, thereby forming a membrane with high porosity and high water permeability. It becomes possible. In the hollow portion forming liquid, a plurality of hydrophilic porosifying agents may be used as a mixture..
[0025]
The cooling liquid used for the cooling bath and the hollow portion forming liquid may be the same or different, and may be appropriately selected according to the characteristics of the target hollow fiber membrane. From the viewpoint of the production process, when the polymer solution, the liquid used for the cooling bath, and the solvent used for the liquid for forming the hollow portion are of the same type, it is highly convenient in the recovery of the solvent in the production process, but is particularly limited. It is not a thing.
[0026]
A hollow fiber membrane having sufficient water permeability and high strength and elongation characteristics as a separation membrane for water treatment can be obtained by the above production method, but a step of stretching the hollow fiber membrane is provided to further increase water permeability. May be. Specifically, it is 1.1 to 5 times (more preferably 1.1 to 4 times, still more preferably 1) in a temperature range of 50 to 140 ° C. (more preferably 50 to 120 ° C., still more preferably 50 to 100 ° C.). The desired hollow fiber membrane is obtained by stretching to a draw ratio in the range of. When stretched at a low temperature of less than 50 ° C., it is difficult to stably and uniformly stretch, and only a structurally weak portion is broken. When stretched at a temperature of 50 to 140 ° C., a part of the spherical structure and an aggregate of polymer molecules linking the spherical structure and the spherical structure are uniformly stretched to form a large number of fine and elongated pores. Water permeability performance is improved while maintaining Depending on the type and amount of the hydrophilic porogen, the pores after extraction of the hydrophilic porogen are partially torn and elongated pores grow larger. Since this partial pore enlargement has a very small scale when viewed as a whole membrane, it does not affect the separation performance even if it contributes to the improvement of water permeability. When it is stretched at a temperature exceeding 140 ° C., it becomes close to the melting point of the polyvinylidene fluoride resin, so that the spherical structure is melted and stretched without forming too many pores, so that the water permeability is not improved. Further, stretching is preferably performed in a liquid because temperature control is easy, but may be performed in a gas such as steam. As the liquid, water is convenient and preferable, but when stretching at about 90 ° C. or higher, it is also possible to preferably employ a low molecular weight polyethylene glycol or the like. Further, stretching in a mixed liquid of a plurality of liquids such as a mixed liquid of water and polyethylene glycol can also be employed.
[0027]
These hydrophilic porogens may be extracted in a cooling bath, but a special extraction step such as extraction of polyvinyl alcohol in a glycerin bath at 100 ° C. may be added. During stretching, extraction may be performed before and after stretching. For extraction, a solvent that is soluble in a hydrophilic porogen and has low solubility in a polyvinylidene fluoride resin, such as water, higher alcohol, glycol, glycerin, benzene, toluene, and the above poor solvent alone Alternatively, it is preferable to use a mixed solvent to adjust the liquid temperature in the temperature range of 0 to 140 ° C. and soak, but the invention is not limited to this. Further, the hydrophilic porosifying agent may remain in the hollow fiber for the purpose of improving the hydrophilicity of the surface of the polyvinylidene fluoride resin.
[0028]
The outer diameter and the film thickness of the hollow fiber membrane may be determined so that the water permeability of the membrane module becomes the target value in consideration of the pressure loss in the longitudinal direction inside the hollow fiber membrane within a range that does not impair the strength of the membrane. That is, if the outer diameter is thick, it is advantageous in terms of pressure loss, but the number of fillings is reduced, which is disadvantageous in terms of membrane area. On the other hand, when the outer diameter is small, the number of fillings can be increased, which is advantageous in terms of membrane area, but disadvantageous in terms of pressure loss. The film thickness is preferably thin as long as the strength is not impaired. Therefore, if an approximate standard is shown, the outer diameter of the hollow fiber membrane is preferably about 0.3 to 3 mm, more preferably 0.4 to 2.5 mm, and still more preferably 0.5 to 2 mm. The film thickness is preferably 0.08 to 0.4 times the outer diameter, more preferably 0.1 to 0.35 times, and still more preferably 0.12 to 0.3 times.
[0029]
Furthermore, the hollow fiber membrane manufactured with the said manufacturing method can be used as a hollow fiber membrane module. A module is a bundle of a plurality of hollow fiber membranes that is placed in a cylindrical container and fixed at both ends or one end with polyurethane or epoxy resin so that permeate can be collected. It is what fixed the both ends of so that permeated water could be collected. Water separation device for membrane filtration of raw water by providing a pressure means such as a pump or a water level difference on the raw water side of this hollow fiber membrane module, or a suction means such as a pump or siphon on the permeate side Can be used as Using this water separator, purified permeate can be produced from raw water. Raw water includes river water, lake water, ground water, seawater, sewage, drainage, and treated water thereof.
[0030]
The present invention will be described below with reference to specific examples, but the present invention is not limited to these examples.
[0031]
【Example】
In the following examples, the water permeation performance is such that reverse osmosis membrane treated water is fed to a small module (length: about 20 cm, number of hollow fiber membranes: about 1 to 10) with a water level difference of 1.5 m at 25 ° C. The value obtained by measuring the amount of permeated water for a certain time was calculated by converting per 100 kPa. However, the water permeation performance may be obtained by converting a value obtained by pressurizing to a constant pressure with a pump or the like per 100 kPa. The water temperature may also be measured at a temperature other than 25 ° C. and converted to a value at 25 ° C. from the viscosity of the evaluation liquid. The tensile strength at break was determined by measuring a load of 2000 g full scale at a test length of 50 mm at a crosshead speed of 50 mm / min using a tensile tester. The porosity is a ratio of the pore volume to the hollow fiber membrane wall volume, and is calculated from the weight of the hollow fiber in the wet state and the dry state.
[0032]
Example 1
A vinylidene fluoride homopolymer having a molecular weight of 284,000 and a molecular weight of 4,000 polyethylene glycol and isophorone were mixed at a ratio of 55% by weight, 5% by weight, and 40% by weight, respectively, and dissolved at a temperature of 160 ° C. A polymer solution was prepared. A cooling bath having a cooling liquid composed of a 90% by weight aqueous solution of isophorone at a temperature of 30 ° C., which is discharged in a hollow fiber shape from a base at 160 ° C. with 100% isophorone accompanying the hollow portion as a liquid for forming a hollow portion. After solidifying in, it was stretched 2.0 times in 90 ° C. water. The obtained hollow fiber membrane has an outer diameter of 1.55 mm, an inner diameter of 0.95 mm, and a water permeability of 2.7 m.^Three/ (M²Hr) (conditions of differential pressure of 100 kPa and 25 ° C.), the breaking strength was 730 g / piece, and the breaking elongation was 53%.
[0033]
Example 2
A vinylidene fluoride homopolymer having a molecular weight of 47,000, polyvinyl alcohol having a molecular weight of 21,000, and γ-butyrolactone were mixed at a ratio of 40% by weight and 10% by weight and 50% by weight, respectively, and dissolved at a temperature of 140 ° C. This polymer solution was discharged as a hollow fiber from a base at 110 ° C. with 100% γ-butyrolactone as a hollow portion forming liquid accompanying the hollow portion, and had a cooling liquid consisting of an 85 wt% cyclohexanone aqueous solution at a temperature of 25 ° C. After solidifying in a cooling bath, polyvinyl alcohol was extracted in hot water at 80 ° C. and stretched twice in polyethylene glycol (molecular weight 400) at 110 ° C. The obtained hollow fiber membrane has an outer diameter of 1.45 mm, an inner diameter of 0.95 mm, and a water permeability of 2.8 m.^Three/ (M²Hr) (differential pressure 100 kPa, conditions of 25 ° C.), the breaking strength was 1130 g / piece, the breaking elongation was 52%, and the porosity was 70%.
The structure was a structure in which spherical structures having a particle diameter of about 1 μm were connected.
[0034]
Comparative Example 1
A vinylidene fluoride homopolymer having a molecular weight of 41,000 and γ-butyrolactone were mixed at a ratio of 40 wt% and 60 wt%, respectively, and dissolved at a temperature of 140 ° C. This polymer solution was discharged as a hollow fiber from a base at 110 ° C. with 100% γ-butyrolactone as a hollow portion forming liquid accompanying the hollow portion, and had a cooling liquid consisting of an 85 wt% cyclohexanone aqueous solution at a temperature of 25 ° C. After solidifying in a cooling bath, the film was stretched twice in polyethylene glycol (molecular weight 400) at 110 ° C. The obtained hollow fiber membrane has an outer diameter of 1.42 mm, an inner diameter of 0.95 mm, and a water permeability of 1.5 m.^Three/ (M²Hr) (conditions of differential pressure of 100 kPa and 25 ° C.), the breaking strength was 1130 g / piece, the breaking elongation was 52%, and the porosity was 65%. The structure was a structure in which spherical structures having a particle diameter of about 1 μm were connected, but the gap ratio between the spherical structures was smaller than that in Example 2.
[0035]
Comparative Example 2
A vinylidene fluoride homopolymer having a molecular weight of 47,000, polyvinyl alcohol having a molecular weight of 21,000, and γ-butyrolactone were mixed at a ratio of 40% by weight, 0.5% by weight, and 59.5% by weight, respectively, and 120 ° C. At a temperature of A cooling bath having a cooling liquid composed of an 85 wt% aqueous solution of cyclohexanone at a temperature of 25 ° C., in which the polymer solution is discharged as a hollow fiber from a base at 120 ° C. with 100% γ-butyrolactone as a hollow portion forming liquid accompanying the hollow portion. After solidifying in, it was stretched twice in polyethylene glycol (molecular weight 400) at 110 ° C. The obtained hollow fiber membrane has an outer diameter of 1.44 mm, an inner diameter of 0.96 mm, and a water permeability of 1.6 m.^Three/ (M²Hr) (conditions of differential pressure of 100 kPa and 25 ° C.), the breaking strength was 1050 g / piece, the breaking elongation was 51%, and the porosity was 51%.
[0036]
Example 3
A vinylidene fluoride homopolymer having a molecular weight of 3580 thousand, polyvinylpyrrolidone and cyclohexanone having a molecular weight of 35,000 were mixed at a ratio of 40% by weight, 10% by weight and 50% by weight, respectively, and dissolved at a temperature of 130 ° C. A cooling bath having a cooling liquid composed of an 80% by weight aqueous solution of cyclohexanone at a temperature of 20 ° C., which is discharged into a hollow fiber shape from a base at 130 ° C. with 100% cyclohexanone accompanying the hollow portion as a liquid for forming a hollow portion. After solidifying in the film, the film was stretched 3.0 times in 85 ° C. water. The obtained hollow fiber membrane has an outer diameter of 1.02 mm, an inner diameter of 0.65 mm, and a water permeability of 3.8 m.^Three/ (M²Hr) (conditions of differential pressure of 100 kPa and 25 ° C.), the breaking strength was 880 g / piece, and the breaking elongation was 44%.
[0037]
  Comparative Example 3
  A vinylidene fluoride homopolymer having a molecular weight of 417,000 was mixed with tetraethylene glycol and cyclohexanone in proportions of 20 wt%, 30 wt%, and 50 wt%, respectively, and dissolved at a temperature of 100 ° C. The polymer solution was discharged in the form of a hollow fiber from a base at 100 ° C. with a 95 wt% cyclohexanone aqueous solution as a hollow portion forming liquid accompanying the hollow portion, and a cooling liquid consisting of an 80 wt% cyclohexanone aqueous solution at a temperature of 10 ° C. After solidifying in the cooling bath having, it was stretched 3.5 times in 85 ° C. water. The obtained hollow fiber membrane has an outer diameter of 1.10 mm, an inner diameter of 0.73 mm, and a water permeability of 5.2 m.³/ (M²Hr) (conditions of differential pressure of 100 kPa and 25 ° C.), the breaking strength was 600 g / piece, and the breaking elongation was 30%.
[0038]
  Example4
  A vinylidene fluoride homopolymer having a molecular weight of 572,000, polyoxyethylene sorbitan monooleate (Tween 80), and cyclohexanone were mixed at a ratio of 35% by weight, 1% by weight, and 64% by weight, respectively, and dissolved at a temperature of 155 ° C. . A cooling bath having a cooling liquid composed of an 80% by weight aqueous solution of cyclohexanone at a temperature of 15 ° C., in which the polymer solution is discharged as a hollow fiber from a base at 155 ° C. with 100% cyclohexanone as a hollow portion forming liquid accompanying the hollow portion. After solidifying in the film, the film was stretched 4.0 times in 85 ° C. water. The obtained hollow fiber membrane has an outer diameter of 1.38 mm, an inner diameter of 0.86 mm, and a water permeability of 2.5 m.³/ (M²Hr) (conditions of differential pressure 100 kPa and 25 ° C.), the breaking strength was 1420 g / piece, and the breaking elongation was 47%.
[0039]
  Example5
  Homopolymer with a molecular weight of 3580 thousand, copolymer of ethylene tetrafluoride and vinylidene fluoride, and glycerin and cyclohexanone were mixed at a ratio of 30% by weight, 10% by weight, 2% by weight and 58% by weight, respectively. And dissolved at a temperature of 165 ° C. A cooling bath having a cooling liquid composed of a 90% by weight aqueous solution of cyclohexanone at a temperature of 30 ° C., which is discharged in a hollow fiber shape from a base at 160 ° C. while allowing the polymer solution to follow the hollow portion as 100% cyclohexanone as a liquid for forming a hollow portion. After solidifying in, it was stretched 1.5 times in water at 80 ° C. The obtained hollow fiber membrane has an outer diameter of 1.52 mm, an inner diameter of 0.90 mm, and a water permeability of 1.5 m.³/ (M²Hr) (conditions of differential pressure of 100 kPa and 25 ° C.), the breaking strength was 1600 g / piece, and the breaking elongation was 58%.
[0040]
  Comparative example4
  A vinylidene fluoride homopolymer having a molecular weight of 41.7 million, polyvinyl alcohol having a molecular weight of 21,000, and γ-butyrolactone were mixed in proportions of 20% by weight, 32% by weight, and 48% by weight, respectively, at a temperature of 170 ° C. for 12 hours. Although stirred, it did not dissolve uniformly.
[0041]
  Comparative example5
  A vinylidene fluoride homopolymer having a molecular weight of 41,000, a polyethylene glycol having a molecular weight of 400, and cyclohexanone were mixed at a ratio of 18% by weight, 5% by weight, and 77% by weight, respectively, and dissolved at a temperature of 90 ° C. When this polymer solution was discharged in a hollow fiber shape from a 90 ° C. mouthpiece with a 90% by weight cyclohexanone aqueous solution as a hollow portion forming liquid accompanying the hollow portion, the viscosity of the polymer solution was too low to be molded into a hollow fiber shape. There wasn't.
[0042]
  Comparative example6
  A vinylidene fluoride homopolymer having a molecular weight of 41,000, a polyethylene glycol having a molecular weight of 400, and cyclohexanone were mixed at a ratio of 61% by weight, 1% by weight, and 38% by weight, respectively, and dissolved at a temperature of 165 ° C. When this polymer solution was discharged in a hollow fiber shape from a die at 165 ° C. while allowing 100% cyclohexanone to follow the hollow portion as a liquid for forming a hollow portion, the polymer solution was too viscous to be molded into a hollow fiber shape. .
[0044]
Comparative Example 7
A vinylidene fluoride homopolymer having a molecular weight of 284,000 and a polyvinyl alcohol and cyclohexanone having a molecular weight of 21,000 were mixed at a ratio of 20% by weight, 10% by weight, and 80% by weight, respectively, and dissolved at a temperature of 150 ° C. An attempt was made to spin at a die temperature of 78 ° C., but gelation occurred in the hopper of the spinning machine and spinning was impossible.
[0048]
  Example6
  A vinylidene fluoride homopolymer having a molecular weight of 284,000, a polyvinyl alcohol having a molecular weight of 21,000, and γ-butyrolactone were mixed at a ratio of 45% by weight, 10% by weight, and 45% by weight, respectively, and dissolved at a temperature of 155 ° C. . This polymer solution was discharged as a hollow fiber from a base at 155 ° C. with 100% γ-butyrolactone as a hollow portion forming liquid accompanying the hollow portion, and a cooling liquid consisting of an 80% by weight aqueous solution of γ-butyrolactone at a temperature of 30 ° C. After solidifying in a cooling bath having, the film was stretched 1.8 times in 88 ° C. water. After stretching, it was immersed in a 100 ° C. polyethylene glycol bath and replaced with water. The obtained hollow fiber membrane has an outer diameter of 1.36 mm, an inner diameter of 1.03 mm, and a water permeability of 2.8 m.³/ (M²Hr) (under conditions of differential pressure of 100 kPa and 25 ° C.), the breaking strength was 980 g / piece, the breaking elongation was 50%, and the porosity was 54%. The structure was a spherical structure with pores that appear to be after the extraction of polyvinyl alcohol.
[0049]
  Example7
  A vinylidene fluoride homopolymer having a molecular weight of 3580 thousand, polypropylene glycol having a molecular weight of 3,000, and γ-butyrolactone were mixed at a ratio of 45% by weight, 10% by weight, and 45% by weight, respectively, and dissolved at a temperature of 140 ° C. . This polymer solution was discharged in the form of a hollow fiber from a base at 140 ° C. with 100% γ-butyrolactone as a hollow portion forming liquid accompanying the hollow portion, and a cooling liquid consisting of an 85 wt% aqueous solution of γ-butyrolactone at a temperature of 25 ° C. After solidifying in a cooling bath having a temperature of 150 ° C., the polymer was stretched 1.5 times in polyethylene glycol (molecular weight 400). The obtained hollow fiber membrane has an outer diameter of 1.34 mm, an inner diameter of 0.83 mm, and a water permeability of 4.0 m.³/ (M²Hr) At 100 kPa and 25 ° C., the breaking strength was 980 g / piece, and the breaking elongation was 52%.
[0050]
  Example8
  A vinylidene fluoride homopolymer having a molecular weight of 41.7 million, polyethylene glycol, polyoxyethylene sorbita monooleate (Tween 80), and γ-butyrolactone in proportions of 40% by weight, 9% by weight, 1% by weight, and 50% by weight, respectively. Mixed and dissolved at a temperature of 130 ° C. This polymer solution was discharged as a hollow fiber from a base at 130 ° C. with 100% γ-butyrolactone as a hollow portion forming liquid accompanying the hollow portion, and a cooling liquid consisting of an 80% by weight aqueous solution of γ-butyrolactone at a temperature of 20 ° C. After solidifying in the cooling bath having, it was stretched 2.0 times in 85 ° C. water. The obtained hollow fiber membrane has an outer diameter of 1.35 mm, an inner diameter of 0.82 mm, and a water permeability of 4.4 m.³/ (M²Hr) (conditions of differential pressure of 100 kPa and 25 ° C.), the breaking strength was 1420 g / piece, and the breaking elongation was 41%.
[0051]
  Comparative Example 8
  A vinylidene fluoride homopolymer having a molecular weight of 47,000, a polyethylene glycol having a molecular weight of 4,000, and γ-butyrolactone were mixed at a ratio of 25% by weight, 10% by weight, and 65% by weight, respectively, and dissolved at a temperature of 100 ° C. . From this polymer solution, a 95% by weight γ-butyrolactone aqueous solution was discharged in the form of a hollow fiber from a base at 95 ° C. as a hollow part forming liquid accompanying the hollow part, and from an 80% by weight γ-butyrolactone aqueous solution at a temperature of 10 ° C. After solidifying in a cooling bath having a cooling liquid, the film was stretched 4.0 times in 85 ° C. water. The obtained hollow fiber membrane has an outer diameter of 1.08 mm, an inner diameter of 0.73 mm, and a water permeability of 4.4 m.³/ (M²Hr) (conditions of differential pressure of 100 kPa and 25 ° C.), the breaking strength was 470 g / piece, and the breaking elongation was 30%.
[0053]
  Comparative example9
  A vinylidene fluoride homopolymer having a molecular weight of 47,000, polypropylene glycol having a molecular weight of 3,000, and γ-butyrolactone were mixed at a ratio of 18% by weight, 3% by weight, and 79% by weight, respectively, and dissolved at a temperature of 90 ° C. . When this polymer solution was discharged into a hollow fiber shape from a 90 ° C. mouthpiece while adhering 90% by weight of a γ-butyrolactone aqueous solution as a hollow portion forming liquid to the hollow portion, the viscosity of the polymer solution was too low to form a hollow fiber shape. Could not mold.
[0054]
  Comparative example10
  A vinylidene fluoride homopolymer having a molecular weight of 47,000, polyethylene glycol having a molecular weight of 4,000, and γ-butyrolactone were mixed at a ratio of 65% by weight, 1% by weight, and 34% by weight, respectively, and dissolved at a temperature of 170 ° C. . The viscosity of the polymer solution was too high to be molded into a hollow fiber.
[0058]
  ImplementationExample 9
  A vinylidene fluoride homopolymer having a molecular weight of 41,000, a polyethylene glycol having a molecular weight of 400, and γ-butyrolactone were mixed at a ratio of 38% by weight, 5% by weight, and 57% by weight, respectively, and dissolved at a temperature of 140 ° C. This polymer solution is discharged as a hollow fiber from a base at 100 ° C. with 100% γ-butyrolactone as a hollow portion forming liquid accompanying the hollow portion, and a cooling liquid comprising an 80% by weight aqueous solution of γ-butyrolactone at a temperature of 20 ° C. After solidifying in a cooling bath having a thickness of 1.3, the film was stretched 1.3 times in water at 85 ° C. The obtained hollow fiber membrane has an outer diameter of 1.85 mm, an inner diameter of 1.15 mm, and a water permeability of 1.6 m.³/ (M²Hr) (conditions of differential pressure of 100 kPa and 25 ° C.), the breaking strength was 1310 g / piece, and the breaking elongation was 54%.
[0059]
  Example10
  Example9When the cooling liquid in the cooling bath was changed to an aqueous solution containing 80% by weight of γ-butyrolactone and 5% by weight of polyethylene glycol having a molecular weight of 400 at a temperature of 20 ° C., the resulting hollow fiber membrane had an outer diameter of 1.86 mm and an inner diameter of 1 .15mm, water permeability is 1.8m³/ (M²Hr) (conditions of differential pressure of 100 kPa and 25 ° C.), the breaking strength was 1180 g / piece, and the breaking elongation was 54%. Moreover, when the hollow part forming liquid was changed to a 95 wt% γ-butyrolactone, 5 wt% molecular weight 400 polyethylene glycol mixture, the resulting hollow fiber membrane had an outer diameter of 1.86 mm, an inner diameter of 1.15 mm, Water permeability is 1.9m³/ (M²Hr) (conditions of differential pressure of 100 kPa and 25 ° C.), the breaking strength was 1160 g / piece, and the breaking elongation was 53%.
[0062]
  Example11
  A vinylidene fluoride homopolymer having a molecular weight of 41,000, a polyethylene glycol having a molecular weight of 20,000, and isophorone were mixed at a ratio of 40% by weight, 10% by weight, and 50% by weight, respectively, and dissolved at a temperature of 155 ° C. This polymer solution was discharged in a hollow fiber shape from a base at 155 ° C. with 100% isophorone as a hollow portion forming liquid, and cooled with a cooling liquid consisting of an 80% by weight aqueous solution of isophorone at a temperature of 30 ° C. After solidifying in the bath, the film was stretched 2.0 times in 85 ° C. water. The obtained hollow fiber membrane has an outer diameter of 1.60 mm, an inner diameter of 1.00 mm, and a water permeability of 2.9 m.³/ (M²Hr) (conditions of differential pressure of 100 kPa and 25 ° C.), the breaking strength was 970 g / piece, and the breaking elongation was 52%.
[0063]
  Example12
  A vinylidene fluoride homopolymer having a molecular weight of 47,000, a polyethylene glycol having a molecular weight of 20,000, and dimethyl phthalate were mixed at a ratio of 40% by weight, 5% by weight, and 55% by weight, respectively, and dissolved at a temperature of 165 ° C. . The polymer solution was discharged in the form of hollow fibers from a die at 165 ° C., with a solution consisting of 70% by weight of dimethyl phthalate and 30% by weight of polyethylene glycol (molecular weight 400) accompanying the hollow part as a hollow part forming liquid, After solidifying in a cooling bath having a cooling liquid having a temperature of 40 ° C. consisting of 60% by weight of dimethyl phthalate and 40% by weight of polyethylene glycol (molecular weight 400), it is 2.0 times in ethylene glycol (molecular weight 400) at 120 ° C. Stretched. The obtained hollow fiber membrane has an outer diameter of 1.35 mm, an inner diameter of 0.75 mm, and a water permeability of 2.0 m.³/ (M²Hr) (conditions of differential pressure of 100 kPa and 25 ° C.), the breaking strength was 1250 g / piece, and the breaking elongation was 31%.
[0064]
  Example13
  A vinylidene fluoride homopolymer having a molecular weight of 47,000, polyethylene glycol having a molecular weight of 3,000, and γ-butyrolactone were mixed at a ratio of 38% by weight, 5% by weight, and 57% by weight, respectively, and dissolved at a temperature of 120 ° C. . The polymer solution was discharged as a hollow fiber from a base at 120 ° C. with 100% by weight of γ-butyrolactone as a hollow part forming liquid accompanying the hollow part, and cooled with an 80% by weight aqueous solution of γ-butyrolactone at a temperature of 0 ° C. After solidifying in a cooling bath with liquid, it was washed with water. The obtained hollow fiber membrane has an outer diameter of 1.32 mm, an inner diameter of 0.86 mm, and a water permeability of 1.6 m.³/ (M²Hr) (conditions of differential pressure of 100 kPa and 25 ° C.), the breaking strength was 1620 g / piece, and the breaking elongation was 68%.
[0065]
【The invention's effect】
The present invention provides a method for producing a hollow fiber membrane that can produce a hollow fiber membrane having high strength and high water permeability at low cost by using a polyvinylidene fluoride resin having high chemical resistance. The

Claims

Polyvinylidene fluoride resin containing at least 30 to 50 % by weight of a polyvinylidene fluoride resin, 1 to 30% by weight of a hydrophilic porogen, and a poor solvent for the resin, and having a spinning temperature in the range of 80 to 175 ° C. the resin solution method for manufacturing a hollow fiber membrane Ru was discharged solidified in a cooling bath, cooling liquid of the cooling bath, the temperature is in the range of 0 to 50 ° C., and the cooling liquid concentration 60 A method for producing a hollow fiber membrane, which is a liquid containing a poor solvent in a range of ˜100% by weight .

The method for producing a hollow fiber membrane according to claim 1, wherein a liquid containing a poor solvent in a concentration range of 60 to 100% by weight is used as the hollow portion forming liquid used for forming the hollow portion of the hollow fiber membrane.

The hollow according to claim 1 or 2 , wherein the cooling liquid further contains a hydrophilic porogen, and the concentration of the hydrophilic porogen in the cooling liquid is in the range of 1 to 40 % by weight. Yarn membrane manufacturing method.

The hollow part forming liquid used for forming the hollow part of the hollow fiber membrane further contains a hydrophilic porogen, and the concentration of the hydrophilic porogen in the cooling liquid is 1 to 40 % by weight. The method for producing a hollow fiber membrane according to claim 2 or 3, wherein the hollow fiber membrane is in the range of .

The method for producing a hollow fiber membrane according to any one of claims 1 to 4 , wherein the solidified hollow fiber membrane is stretched in a range of 1.1 to 5 times in a temperature range of 50 to 140 ° C.

The method for producing a hollow fiber membrane according to any one of claims 1 to 5 , comprising a step of extracting the hydrophilic porosifying agent.

The hollow fiber membrane module which has a hollow fiber membrane manufactured with the manufacturing method in any one of Claims 1-6 .

A water separator comprising the hollow fiber membrane module according to claim 7 .