JP5318385B2 - Porous membrane made of vinylidene fluoride resin and method for producing the same - Google Patents

Porous membrane made of vinylidene fluoride resin and method for producing the same Download PDF

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JP5318385B2
JP5318385B2 JP2007209474A JP2007209474A JP5318385B2 JP 5318385 B2 JP5318385 B2 JP 5318385B2 JP 2007209474 A JP2007209474 A JP 2007209474A JP 2007209474 A JP2007209474 A JP 2007209474A JP 5318385 B2 JP5318385 B2 JP 5318385B2
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porous membrane
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vinylidene fluoride
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fluoride resin
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JP2008062226A (en
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新 石躍
賢作 小松
晃司 山田
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Kuraray Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide porous membrane excellent in fractionation capability, permeability and physical strength that can be made easily at a low cost and is suitable for water treatment such as water purification, potable water preparation, industrial water preparation, and waste water treatment. <P>SOLUTION: The porous membrane made from a vinylidene fluoride resin is characterized by comprising circular or elliptical micropores having a mean ratio of their major axis to their minor axis not lower than 1 to 1 and lower than 5 to 1 on one surface thereof and rectangular micropores having a mean ratio of their major axis to their minor axis not lower than 5 to 1 on the other surface thereof with its cut-off particle diameter being not smaller than 0.2 &mu;m. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

本発明は、浄水処理、飲料水製造、工業用水製造、排水処理などの水処理分野、食品工業分野、荷電膜分野、燃料電池分野等に好適な透過性能や分画性能に優れ、さらに工程制御性、コスト性、良孔形成性に優れた多孔膜を製造する際に用いられる多孔膜及び多孔膜の製造方法に関する。   The present invention is excellent in permeation performance and fractionation performance suitable for water treatment fields such as water purification treatment, drinking water production, industrial water production, wastewater treatment, food industry field, charged membrane field, fuel cell field, and process control. The present invention relates to a porous membrane used when producing a porous membrane excellent in properties, cost performance, and good pore forming properties, and a method for producing the porous membrane.

近年、選択透過性を有する多孔膜を用いた分離手段の技術がめざましく進展している。このような分離操作の技術は、例えば飲料水、超純水および医薬品の製造工程、醸造製品の除菌・仕上げにおいて、分離手段、洗浄手段および殺菌手段等を含む一連の浄化システムとして実用化されている。これらの用途分野においては、水のファイン化（高度処理）や安全性向上、精度向上などが高いレベルで要求されており多孔膜の利用が進んでいる。上記のような状況を鑑み、多孔膜に求められる特性はより高度化している。膜特性の中で最も重要なものは、透過性能と分画性能である。両性能に関してはそのバランスが重要であり、より高い純水透過速度でより小さな粒子を除去できることが望ましく、この達成には膜の孔連通性と膜表面構造が大きなポイントとなる。   In recent years, the technology of separation means using a porous membrane having selective permeability has been remarkably advanced. Such separation operation technology has been put into practical use as a series of purification systems including separation means, washing means, sterilization means, etc., for example in the manufacturing process of drinking water, ultrapure water and pharmaceuticals, and sterilization and finishing of brewed products. ing. In these application fields, finer water (advanced treatment), improved safety, and improved accuracy are required at a high level, and the use of porous membranes is progressing. In view of the situation as described above, the characteristics required for the porous membrane are becoming more sophisticated. The most important membrane properties are permeation performance and fractionation performance. The balance is important for both performances, and it is desirable to be able to remove smaller particles at higher pure water permeation rates, and achieving this is a key point in membrane pore connectivity and membrane surface structure.

また、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、酸、アルカリ、塩素、界面活性剤などで膜そのものを洗浄するため、多孔膜には耐薬品性も求められる。さらに、水道水製造では、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とから、このような事故を防ぐため、多孔膜には、原水が処理水に混入しないように十分な分離特性と糸切れが起こらないように高い物理的強度が要求されている。 In addition, in the water purification treatment, a disinfectant such as sodium hypochlorite is added to the membrane module part for the purpose of sterilizing the permeated water and preventing biofouling of the membrane, or the membrane with acid, alkali, chlorine, surfactant, etc. In order to clean itself, the porous membrane is also required to have chemical resistance. Furthermore, in tap water production, pathogenic microorganisms resistant to chlorine such as Cryptosporidium derived from livestock manure cannot be treated at the water purification plant, and accidents mixed into the treated water have become apparent since the 1990s. For this reason, in order to prevent such an accident, the porous membrane is required to have sufficient separation characteristics so that the raw water is not mixed into the treated water and high physical strength so that the yarn breakage does not occur.

このように、多孔膜に求められる重要な特性としては、分離精度、透過性能、物理的強度および化学的強度（耐薬品性）が挙げられる。そこで、近年ではフッ化ビニリデン系樹脂を用いた多孔膜の開発が進められている。フッ化ビニリデン系樹脂を用いた多孔膜は、強度や伸度、耐薬品性に優れるだけでなく、耐酸化剤性にも優れるため、近年注目されているオゾンを用いた高度水処理にも利用可能である。   As described above, important characteristics required for the porous membrane include separation accuracy, permeation performance, physical strength, and chemical strength (chemical resistance). Therefore, in recent years, development of a porous film using a vinylidene fluoride resin has been advanced. Porous membranes using vinylidene fluoride resin are not only excellent in strength, elongation and chemical resistance, but also in oxidation resistance, so they can be used for advanced water treatment using ozone, which has recently been attracting attention. Is possible.

上述のように、多孔膜の物理的強度および耐薬品性に代表される化学的強度は膜素材の特性に由来するところが大きいが、多孔膜の透過性能や分画性能は、膜の製造方法に大きく依存する。   As described above, the chemical strength represented by the physical strength and chemical resistance of the porous membrane is largely derived from the characteristics of the membrane material, but the permeation performance and fractionation performance of the porous membrane depend on the method for producing the membrane. It depends heavily.

高い純水透過速度を発現する中空糸膜を製造する方法として、延伸開孔法が挙げられる。該方法は、膜素材を特定条件下でアニール処理および延伸することを特徴とし、その結果、膜全体にミクロフィブリルとスタックドラメラからなる結節部とに囲まれて形成される短冊状微小空孔を有する中空糸膜を製造することができる（例えば特許文献１参照）。しかし該方法により製造された中空糸膜は、延伸により繊維方向に配向するため円周方向に対する強度が大きく低下してしまうという問題がある。特に、孔径が大きくなると強度は低下傾向となるため、該方法により実用的な強度を有する中空糸膜を製造することは困難である。また、純水透過速度は高いものの、孔径分布が広く、かつ形成される孔の形がスリット状となるため、細長い形状の物質は透過しやすくなり分離精度が低くなりやすいなどの問題がある。   An example of a method for producing a hollow fiber membrane that exhibits a high pure water permeation rate is a stretch hole method. The method is characterized in that the film material is annealed and stretched under specific conditions, and as a result, the strip-shaped microvoids formed by the entire film surrounded by the nodules made of microfibrils and stack lamellae. Can be produced (see, for example, Patent Document 1). However, since the hollow fiber membrane produced by this method is oriented in the fiber direction by stretching, there is a problem that the strength in the circumferential direction is greatly reduced. In particular, since the strength tends to decrease as the pore diameter increases, it is difficult to produce a hollow fiber membrane having practical strength by this method. In addition, although the pure water permeation rate is high, the pore size distribution is wide and the shape of the holes formed is slit-like, so that there is a problem that elongated substances are easily transmitted and the separation accuracy tends to be low.

透過性能や分画性能に優れた分離膜を製造する方法として、相分離を利用する場合が多く知られている。そのような相分離を利用した製造方法は、非溶剤誘起相分離法と熱誘起相分離法に大きく分けることができる。 In many cases, phase separation is used as a method for producing a separation membrane having excellent permeation performance and fractionation performance. Manufacturing methods using such phase separation can be broadly divided into non-solvent induced phase separation methods and thermally induced phase separation methods.

非溶剤誘起相分離法では、ポリマーと溶剤からなる均一なポリマー溶液は、非溶剤の進入や溶剤の外部雰囲気への蒸発による濃度変化によって相分離を起こす。このような非溶剤誘起相分離法を利用した分離膜の製造方法として、ポリスルホン系樹脂をＮ，Ｎ−ジメチルアセトアミド等の溶剤に溶解後に、凝固浴中で非溶剤誘起相分離を発現させることで分離膜を形成することが知られている（例えば、特許文献２参照）。しかし、一般に非溶剤誘起相分離法は、非溶剤中での相分離制御が難しく、非溶剤が必須であるため製造コストがかかり、マクロボイド（粗大孔）が発生しやすいなど、膜物性、工程制御性およびコスト性の面で問題がある。   In the non-solvent induced phase separation method, a uniform polymer solution composed of a polymer and a solvent undergoes phase separation due to the concentration change due to the ingress of the non-solvent or evaporation of the solvent to the external atmosphere. As a method of manufacturing a separation membrane using such a non-solvent induced phase separation method, after dissolving a polysulfone resin in a solvent such as N, N-dimethylacetamide, non-solvent induced phase separation is expressed in a coagulation bath. It is known to form a separation membrane (see, for example, Patent Document 2). However, in general, the non-solvent induced phase separation method is difficult to control the phase separation in the non-solvent, and the non-solvent is essential. There are problems in terms of controllability and cost.

一方、熱誘起相分離法は通常、以下のステップよりなる。（１）ポリマーと高い沸点を持った溶剤の混合物を高温で溶融させる。（２）相分離を誘発させるために適当な速度で冷却させ，ポリマーを固化させる。（３）用いた溶剤を抽出する。   On the other hand, the thermally induced phase separation method usually comprises the following steps. (1) A mixture of a polymer and a solvent having a high boiling point is melted at a high temperature. (2) Allow the polymer to solidify by cooling at an appropriate rate to induce phase separation. (3) Extract the used solvent.

また、熱誘起相分離法が、非溶剤誘起相分離法と比較して有利な点は以下のとおりである。（ａ）膜の強度を弱める要因となるマクロボイドが発生しない。（ｂ）非溶剤誘起相分離法では、溶剤のほかに非溶剤が必要であるため、製造工程における制御が困難であり、再現性も低い。一方、熱誘起相分離法では非溶剤は必要ないため工程制御性およびコスト性に優れ、また再現性も高い。（ｃ）孔径制御が比較的容易で、孔径分布がシャープで良孔形成性に優れる。 The advantages of the thermally induced phase separation method compared to the non-solvent induced phase separation method are as follows. (A) Macrovoids that cause a decrease in film strength are not generated. (B) In the non-solvent induced phase separation method, a non-solvent is required in addition to the solvent, so that control in the production process is difficult and reproducibility is low. On the other hand, the heat-induced phase separation method does not require a non-solvent, and thus has excellent process controllability and cost, and high reproducibility. (C) The pore diameter control is relatively easy, the pore diameter distribution is sharp, and the good hole forming property is excellent.

熱誘起相分離には固−液型熱誘起相分離と液−液型熱誘起相分離が存在し、どちらを発現するかは、ポリマーと溶剤の相容性に起因する。両者の相容性が非常に高い場合は固−液型熱誘起相分離を発現するが、相容性が低くなると液−液型熱誘起相分離を発現し、ついに両者は非相容となる。一般に、液−液型熱誘起相分離ではスピノーダル分解により相分離が進行するため、固−液型熱誘起相分離と比較して共連続構造が発現し易いという特徴を持ち、その結果、孔の連通性や均一性などの良孔形成性に優れる分離膜を製造することができる。つまり、透過性能と分画性能に優れる分離膜を製造するには、液−液型熱誘起相分離を発現する適切なポリマーと溶剤の組み合わせを選択することが好ましい。しかし、一般にポリマーと溶剤が液−液型熱誘起相分離を発現する領域は狭いため、該方法により分離膜を製造する場合、ポリマーと溶剤の適切な組み合わせを選ぶことが極めて重要であることが知られている（例えば、非特許文献１参照）。   Thermally induced phase separation includes solid-liquid type thermally induced phase separation and liquid-liquid type thermally induced phase separation, and it is attributed to the compatibility between the polymer and the solvent. When the compatibility of both is very high, solid-liquid type thermally induced phase separation is developed, but when compatibility is low, liquid-liquid type thermally induced phase separation is developed, and finally both become incompatible. . In general, in liquid-liquid type thermally induced phase separation, since phase separation proceeds by spinodal decomposition, it has a feature that a co-continuous structure is easily developed compared to solid-liquid type thermally induced phase separation. A separation membrane having excellent pore forming properties such as communication and uniformity can be produced. That is, in order to produce a separation membrane excellent in permeation performance and fractionation performance, it is preferable to select an appropriate polymer and solvent combination that exhibits liquid-liquid type thermally induced phase separation. However, since a region where a polymer and a solvent exhibit liquid-liquid type thermally induced phase separation is generally narrow, it is extremely important to select an appropriate combination of a polymer and a solvent when producing a separation membrane by this method. It is known (for example, refer nonpatent literature 1).

液−液型熱誘起相分離法を利用したフッ化ビニリデン系樹脂多孔膜の製造方法は公知であるが（例えば、特許文献３参照）。しかし、該方法で作製した膜は３００００Ｌ／ｍ２／ｈｒ／９８ｋＰａ以上、分画粒子径１μｍ以上ではあるが、本発明者の検討によると、膜には連通していない孔すなわち独立孔が存在しており、また多孔膜の一表面と他表面とがほぼ同等のサイズの孔を有しているため、該多孔膜は分画粒子径に対して高い純水透過速度が発現できていないことが判明した。 Although the manufacturing method of the vinylidene fluoride resin porous membrane using the liquid-liquid type | mold thermally induced phase separation method is well-known (for example, refer patent document 3). However, although the membrane produced by this method has 30000 L / m 2 / hr / 98 kPa or more and a fractional particle diameter of 1 μm or more, according to the study of the present inventor, there are pores that do not communicate with the membrane, that is, independent pores. In addition, since one surface and the other surface of the porous membrane have pores of almost the same size, the porous membrane cannot exhibit a high pure water permeation rate with respect to the fractional particle diameter. There was found.

また、フッ化ビニリデン系樹脂は疎水性樹脂であるため、そのままでは水を透過させることが難しく、水を始めとする親水性液体を透過させるためには親水化処理が必要である。 Further, since vinylidene fluoride resin is a hydrophobic resin, it is difficult to permeate water as it is, and hydrophilic treatment is required to permeate hydrophilic liquids such as water.

この発明に関連する先行技術文献としては次のものがある。
特開平５−４９８７８号公報 特開平１１−１０４２３５号公報 特開２００５−１９４４６１号公報 特開２００３−１３８４２２号公報 特開２００５−２００６２３号公報 「ケミカル・エンジニヤリング」 化学工業社 １９９８年６月号４５３ページ〜４６４ページ Prior art documents related to the present invention include the following.
JP-A-5-49878 Japanese Patent Laid-Open No. 11-104235 JP 2005-194461 A JP 2003-138422 A Japanese Patent Laying-Open No. 2005-200563 “Chemical Engineering” Chemical Industry Co., Ltd. June 1998, pages 453-464

本発明は、従来技術の上述した問題点に鑑み、浄水処理、飲料水製造、工業用水製造、排水処理などの水処理に好適な透過性能、分画性能、物理的強度、化学的強度さらに工程制御性、コスト性、良孔形成性に優れた多孔膜を安価かつ容易に提供することを目的とするものである。 In view of the above-mentioned problems of the prior art, the present invention is suitable for water treatment such as water purification treatment, drinking water production, industrial water production, wastewater treatment, permeation performance, fractionation performance, physical strength, chemical strength and further steps. An object of the present invention is to easily and inexpensively provide a porous film excellent in controllability, cost, and good pore formation.

上記課題を解決するための本発明の多孔膜は、フッ化ビニリデン系樹脂よりなる多孔膜であって、該多孔膜は一表面に長径と短径の比の平均が１：１以上５：１より小さい円形または楕円形の微細孔を有し、他表面に長径と短径の比の平均が５：１以上の短冊状微細孔を有している分画粒子径が０．２μｍ以上であることを特徴とする。このとき多孔膜が９０〜９９重量％のフッ化ビニリデン系樹脂と１〜１０重量％の親水性樹脂とのブレンドポリマーで構成されることが好ましい。更には親水性樹脂がビニルピロリドン系樹脂であることが好ましく、また更には多孔膜が中空糸膜であることが好ましい。   The porous membrane of the present invention for solving the above problems is a porous membrane made of a vinylidene fluoride resin, and the porous membrane has an average ratio of the major axis to the minor axis of 1: 1 to 5: 1 on one surface. The fractional particle diameter is 0.2 μm or more, having smaller circular or elliptical micropores, and having strip-like micropores with an average ratio of major axis to minor axis of 5: 1 or more on the other surface. It is characterized by that. At this time, the porous film is preferably composed of a blend polymer of 90 to 99% by weight of vinylidene fluoride resin and 1 to 10% by weight of hydrophilic resin. Furthermore, the hydrophilic resin is preferably a vinyl pyrrolidone resin, and the porous membrane is preferably a hollow fiber membrane.

また本発明者らは、多孔膜製造原液を構成する各成分の相容性に着目し、鋭意検討した結果、溶剤と無機粒子、凝集剤を適切に組み合わせることにより、フッ化ビニリデン系樹脂と溶剤が固−液型熱誘起相分離を発現する組合せの場合でも、液−液型熱誘起相分離を発現する組合せにより得られた多孔膜と同等以上の特性を有する膜の製造が可能であることを見出した。   In addition, the inventors of the present invention paid attention to the compatibility of each component constituting the porous membrane production stock solution, and as a result of intensive studies, the vinylidene fluoride resin and the solvent were appropriately combined with a solvent, inorganic particles, and an aggregating agent. Even in the case of a combination that exhibits solid-liquid type thermally induced phase separation, it is possible to produce a membrane having characteristics equal to or better than the porous film obtained by the combination that exhibits liquid-liquid type thermally induced phase separation. I found.

本発明は、フッ化ビニリデン系樹脂、溶剤、無機粒子及び凝集剤からなる多孔膜製造原液において、該溶剤は水溶性溶剤であり、該無機粒子と該凝集剤は親和性を有し、かつ該溶剤と該凝集剤は相容しない又は上部臨界溶解温度を有する多孔膜製造原液を用い、冷却させることにより相分離を誘起させたのちに固化させ、次いで溶剤、無機粒子、凝集剤のいずれかを抽出終了する前に多孔膜を延伸する工程および７０〜１６０℃の範囲で熱処理する工程を含むことを特徴とする上記特性を有するフッ化ビニリデン系樹脂多孔膜を製造することにある。
The present invention provides a porous membrane production stock solution comprising a vinylidene fluoride resin, a solvent, inorganic particles and a flocculant , the solvent being a water-soluble solvent, the inorganic particles and the flocculant having affinity, and the The solvent and the flocculant are incompatible with each other, or a porous membrane production stock solution having an upper critical solution temperature is used. After cooling, the phase separation is induced to solidify, and then the solvent, inorganic particles, or flocculant is added. It is to produce a porous membrane of vinylidene fluoride resin having the above properties, which comprises a step of heat treatment in the range of process and 70 to 160 ° C. stretching the porous film before the extraction end.

本発明によれば、分画性能、透過性能、物理的強度に優れる多孔膜を工業的に安定に、かつ安価に製造することが可能である。本発明の多孔膜を用いることにより、高い分画性能でかつ高い純水透過速度のろ過が可能となり、造水コストの低減が可能になる。   ADVANTAGE OF THE INVENTION According to this invention, it is possible to manufacture the porous membrane which is excellent in fractionation performance, permeation | transmission performance, and physical strength industrially stably and cheaply. By using the porous membrane of the present invention, high fractionation performance and high pure water permeation rate can be filtered, and the water production cost can be reduced.

本発明のフッ化ビニリデン系樹脂多孔膜は、一表面に長径と短径の比の平均が１：１以上かつ５：１より小さい円形または楕円形の微細孔を有し、他表面に長径と短径の比の平均が５：１以上の短冊状微細孔を有している分画粒子径が０．２μｍ以上であることが特徴である。   The vinylidene fluoride resin porous membrane of the present invention has circular or elliptical micropores with an average ratio of major axis to minor axis of 1: 1 or more and smaller than 5: 1 on one surface, and a major axis on the other surface. The fractional particle diameter having strip-like micropores having an average minor axis ratio of 5: 1 or more is characterized by being 0.2 μm or more.

本発明の多孔膜は、長径と短径の比の平均が１：１以上かつ５：１より小さい円形または楕円形の微細孔を有している一表面が、粒子を通すか通さないかを決定付ける活性点として寄与するため、高い分画性能を有する。また、本発明の多孔膜は、長径と短径の比の平均が５：１以上のミクロフィブリルを含む構造により形成された短冊状微細孔を有している他表面は、高い開孔率を有する短冊状微細孔によって、高い純水透過速度を有する。これら特長を併せ持つ本発明の多孔膜は、従来膜に比して、分画粒子径に対する透過性能が格段に高いものとなる。よって、分画粒子径１μｍ以上を有する高透過性能の膜を製造することが可能である。また、孔径が大きくなることで湿潤状態でも１００ｋＰａ以下の低い圧力で空気などの気体が透過できるようになるため、気体逆洗などの物理的手段による洗浄が可能となる。   In the porous membrane of the present invention, whether one surface having circular or elliptical micropores having an average ratio of major axis to minor axis of 1: 1 or more and smaller than 5: 1 passes or does not pass through particles. Since it contributes as a determinative active point, it has a high fractionation performance. In addition, the porous membrane of the present invention has a stripping micropore formed by a structure containing microfibrils having an average ratio of major axis to minor axis of 5: 1 or more. It has a high pure water permeation rate due to the strip-shaped fine holes. The porous membrane of the present invention having these features has significantly higher permeation performance with respect to the fractional particle diameter than the conventional membrane. Therefore, it is possible to produce a highly permeable membrane having a fractional particle size of 1 μm or more. Further, since the pore diameter is increased, a gas such as air can be permeated at a low pressure of 100 kPa or less even in a wet state, so that cleaning by physical means such as gas backwashing is possible.

ここでいう長径と短径の比が平均で１：１以上かつ５：１より小さい円形または楕円形の微細孔とは、図１の表面に示すように、一表面の少なくとも２ヶ所について電子顕微鏡を用いて写真撮影（例えば倍率１０００倍）し、写真の視野範囲内に見える全ての微細孔の長径と短径の比を計測し、上記操作を計測した微細孔数が少なくとも３０個を越えるまで上記操作を繰り返した上で、上記計測値の平均が１：１以上かつ５：１より小さいものをいう。 As used herein, circular or elliptical micropores having an average ratio of major axis to minor axis of 1: 1 or more and smaller than 5: 1 are electron microscopes in at least two places on one surface as shown in FIG. Take a picture using the magnifying glass (for example, 1000 times magnification), measure the ratio of the major and minor diameters of all the micropores that can be seen in the field of view of the photograph, until the number of micropores measured in the above operation exceeds at least 30 After repeating the above operation, the average of the measurement values is 1: 1 or more and less than 5: 1.

また、ここで、長径と短径の比の平均が５：１以上の短冊状微細孔とは、図１〜５の表面に示すように、一表面の少なくとも２ヶ所について電子顕微鏡を用いて写真撮影（例えば倍率５００倍）し、写真の視野範囲内に見える、繊維長方向に配列したミクロフィブリルによって形成される短冊状の微細孔であり、この長径と短径の比を計測し、上記操作を計測した微細孔数が少なくとも３０個を越えるまで上記操作を繰り返した上で、上記計測値の平均が５：１以上のものをいう。   Here, the strip-shaped micropores having an average ratio of the major axis to the minor axis of 5: 1 or more are photographs using an electron microscope at least at two places on one surface as shown in the surface of FIGS. This is a strip-shaped micropore formed by microfibrils arranged in the fiber length direction that is photographed (for example, at a magnification of 500 times) and visible within the field of view of the photograph. The ratio of the major axis to the minor axis is measured, and the above operation is performed. The above measurement is repeated until the number of micropores measured at least exceeds 30, and the average of the measured values is 5: 1 or more.

膜断面は、円形または楕円形の微細孔を有する一表面よりも大きな孔径を有する三次元網目構造が好ましいが、対称構造や非対称構造、またはフィンガーライク構造やボイドを有していても良い。また、多孔膜内の空間の体積比である空隙率は５０〜９５％、好ましくは７０〜９０％である。空隙率が５０％よりも小さくなると十分な純水透過速度を得ることが困難であり、９０％を越えると膜の強度が低下し、膜濾過の実施中に多孔膜の破断や折れが発生し膜としての耐久性に欠ける。 The membrane cross section preferably has a three-dimensional network structure having a larger pore diameter than one surface having circular or elliptical micropores, but may have a symmetric structure, an asymmetric structure, a finger-like structure, or a void. The porosity, which is the volume ratio of the space in the porous membrane, is 50 to 95%, preferably 70 to 90%. When the porosity is less than 50%, it is difficult to obtain a sufficient pure water permeation rate. When the porosity exceeds 90%, the strength of the membrane decreases, and the porous membrane breaks or breaks during membrane filtration. It lacks durability as a film.

長径と短径の比の平均が１：１以上かつ５：１より小さい円形または楕円形の微細孔を有している面と長径と短径の比の平均が５：１以上の短冊状微細孔を有する面の上下や内外の配置は、ろ過方式によって変えることができるが、円形または楕円形の微細孔を有する面が分離機能を担い、断面構造が物理的強度を担うため、円形または楕円形の微細孔を有する面を分離対象側に配置することが好ましい。特に、汚れ物質の付着による透過性能の低下を抑制するためには、分離機能を担う円形または楕円形の微細孔を有する面を分離対象側の最表層に配置することが好ましい。   A strip-shaped fine having an average ratio of major axis and minor axis of 1: 1 or more and a circular or elliptical micropore smaller than 5: 1 and an average ratio of major axis to minor axis of 5: 1 or more. The top / bottom and inside / outside arrangement of the surface with holes can be changed depending on the filtration method, but the surface with circular or elliptical micropores has a separation function and the cross-sectional structure has physical strength. It is preferable to arrange the surface having the fine pores on the separation target side. In particular, in order to suppress a decrease in permeation performance due to adhesion of dirt substances, it is preferable to arrange a surface having circular or elliptical micropores that perform a separation function on the outermost layer on the separation target side.

本発明の多孔膜は、中空糸膜形状、平膜形状いずれの形態でも好ましく用いることができるが、中空糸膜は効率良く充填することが可能であり、単位体積当たりの有効膜面積を増大させることができるため好ましく用いられる。 The porous membrane of the present invention can be preferably used in either a hollow fiber membrane shape or a flat membrane shape, but the hollow fiber membrane can be filled efficiently and increases the effective membrane area per unit volume. Can be preferably used.

本発明におけるフッ化ビニリデン系樹脂は、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いても良い。フッ化ビニリデン共重合体としては、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る少なくとも１種とフッ化ビニリデンとの共重合体が挙げられる。また、フッ化ビニリデン系樹脂の重量平均分子量は、要求される多孔膜の強度と透水性能によって適宜選択すれば良いが、重量平均分子量が大きくなると製膜性が低下し、重量平均分子量が小さくなると強度が低下する。このため、重量平均分子量は５万以上１００万以下が好ましい。多孔膜が薬液洗浄に晒される水処理用途の場合、重量平均分子量は１０万以上７０万以下が好ましく、さらに１５万以上６０万以下が好ましい。   The vinylidene 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. Examples of the vinylidene fluoride copolymer include a copolymer of vinylidene fluoride and at least one selected from vinyl fluoride, tetrafluoroethylene, propylene hexafluoride, and ethylene trifluoride chloride. In addition, the weight average molecular weight of the vinylidene fluoride resin may be appropriately selected depending on the required strength and water permeability of the porous membrane, but when the weight average molecular weight increases, the film-forming property decreases and the weight average molecular weight decreases. Strength decreases. For this reason, the weight average molecular weight is preferably from 50,000 to 1,000,000. In the case of water treatment applications in which the porous membrane is exposed to chemical cleaning, the weight average molecular weight is preferably from 100,000 to 700,000, more preferably from 150,000 to 600,000.

本発明における親水化処理は、公知の技術を適用することが可能である（例えば特許文献４参照）。   A known technique can be applied to the hydrophilic treatment in the present invention (see, for example, Patent Document 4).

本発明における親水性樹脂とは、水との親和性が非常に強い樹脂であり、ビニルピロリドン系樹脂、ポリビニルアルコール、エチレン‐酢酸ビニル共重合体のケン化物、ポリエチレングリコール、ポリグリコールモノエステル、ポリエチレングリコールとポリプロピレングリコールとの共重合体、ポリアクリル酸、ポリメタクリル酸、ポリスチレンスルホン酸、セルロース誘導体およびポリソルベート等である。好ましくはビニルピロリドン系樹脂である。 The hydrophilic resin in the present invention is a resin having a very strong affinity with water, such as vinyl pyrrolidone resin, polyvinyl alcohol, saponified ethylene-vinyl acetate copolymer, polyethylene glycol, polyglycol monoester, polyethylene. Copolymers of glycol and polypropylene glycol, polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, cellulose derivatives and polysorbate. A vinyl pyrrolidone resin is preferable.

本発明におけるビニルピロリドン系樹脂とは、ビニルピロリドン単独重合体、他の共重合可能なビニル系モノマーとの共重合体を示す。その中でも、ポリビニルピロリドン単独重合体が好ましい。   The vinyl pyrrolidone resin in the present invention refers to a vinyl pyrrolidone homopolymer and a copolymer with other copolymerizable vinyl monomers. Among these, polyvinylpyrrolidone homopolymer is preferable.

またこれらの樹脂の重量平均分子量は、特に限定はない。要求される膜の強度と透水性能によって適宜選択すれば良いが、多孔質膜への加工性を考慮すると、５千〜２００万の範囲内であることが好ましい。また、ビニルピロリドン系樹脂の内、ポリビニルピロリドンのような水溶性樹脂では、水系で使用すると徐々に溶解する可能性が高い。溶出した水溶性樹脂が処理液側へ混入することが問題となる場合には、水溶性樹脂の不溶化処理を行うことが好ましい。ポリビニルピロリドンの不溶化処理は、ガンマー線によるポリビニルピロリドンの架橋、ＵＶ照射による架橋、強アルカリや過硫酸塩の存在下に加熱処理することで得られる化学架橋などが挙げられる。その中でも、本発明においては過硫酸塩を用いる化学架橋を行うことが好ましい。   The weight average molecular weight of these resins is not particularly limited. Although it may be appropriately selected depending on the required strength and water permeability of the membrane, it is preferably in the range of 5,000 to 2,000,000 in consideration of processability to the porous membrane. Of vinyl pyrrolidone resins, water-soluble resins such as polyvinyl pyrrolidone are likely to dissolve gradually when used in an aqueous system. When it is a problem that the eluted water-soluble resin is mixed into the treatment liquid, it is preferable to perform insolubilization treatment of the water-soluble resin. Examples of the insolubilization treatment of polyvinyl pyrrolidone include crosslinking of polyvinyl pyrrolidone with gamma rays, crosslinking with UV irradiation, and chemical crosslinking obtained by heat treatment in the presence of a strong alkali or persulfate. Among them, in the present invention, it is preferable to perform chemical crosslinking using persulfate.

本発明における溶剤は、熱誘起相分離を起こすものが用いられる。熱誘起相分離の形態には固−液相分離、液−液相分離が存在し、ポリフッ化ビニリデンと固−液相分離状態を取りうる溶剤としては、γ−ブチロラクトン、ε−カプロラクトンなどが挙げられる。本発明では、γ−ブチロラクトン、ε−カプロラクトンのような水溶性溶剤を使用することが好ましい。水溶性溶剤を用いると製膜後、多孔膜から溶剤を抽出する際に、水を使用することが可能であり、抽出した溶剤は生物処理等によって処分することが可能となる。一方、非水溶性の溶剤を用いると、製膜後、多孔膜から溶剤を抽出する際に、アセトンなどの有機溶剤を用いる必要があり、有機溶剤の性状によっては防爆設備が必要となる。また、抽出した溶剤は産業廃棄物として処分が必要となる。抽出した溶剤を回収する場合もあるが、そのためには、別途回収設備が必要となる。以上の理由により、安全面、設備面、コスト面の観点から工業的には水溶性溶剤を用いることが好ましい。
As the solvent in the present invention, a solvent that causes thermally induced phase separation is used. Solid-liquid phase separation and liquid-liquid phase separation exist in the form of thermally induced phase separation , and γ -butyrolactone, ε-caprolactone, etc. are listed as solvents that can take a solid-liquid phase separation state with polyvinylidene fluoride. It is done . In the present invention, it is preferable to use a water-soluble solvent such as γ-butyrolactone and ε-caprolactone. When a water-soluble solvent is used, it is possible to use water when extracting the solvent from the porous membrane after film formation, and the extracted solvent can be disposed of by biological treatment or the like. On the other hand, when a water-insoluble solvent is used, it is necessary to use an organic solvent such as acetone when extracting the solvent from the porous film after film formation, and an explosion-proof facility is required depending on the properties of the organic solvent. The extracted solvent must be disposed of as industrial waste. In some cases, the extracted solvent is recovered, but in order to do so, a separate recovery facility is required. For the above reasons, it is preferable to use a water-soluble solvent industrially from the viewpoints of safety, equipment, and cost.

本発明における無機粒子は、多孔膜の孔の核となるものであり、薬品などによる抽出が容易で粒径分布の比較的狭い微粒子が望ましい。その例として、シリカ、珪酸カルシウム、珪酸アルミニウム、珪酸マグネシウム、炭酸カルシウム、炭酸マグネシウム、リン酸カルシウム、鉄、亜鉛などの金属酸化物または水酸化物、ナトリウム、カリウム、カルシウム等の塩類などを例示することができる。特に、凝集性を有する無機粒子は、通常であればフッ化ビニリデン系樹脂と溶剤とが相分離してしまうような組成に添加することでフッ化ビニリデン系樹脂と溶剤とが相容状態にあるときの安定性が向上する結果、均質な多孔膜を製造することが可能となり、より大きな孔径を有する多孔膜を製造するときに好適である。このような凝集性の点から無機粒子としてはシリカが好適である。無機粒子の粒子径（凝集性を有する無機粒子では凝集粒子径のことである）は目的とする多孔膜の孔径により適宜選択することができ、限外ろ過膜であれば０．０１μｍ以下を、分画粒子径が１μｍ未満の精密濾過膜であれば０．０１〜１μｍ、更に分画粒子径が１μｍ以上の大孔径膜であれば１μｍ以上の凝集粒子径を持つ無機粒子を選択する。また多孔膜の孔径制御、特に孔の連通性を向上させることを目的として、異なる凝集粒子径を有する無機粒子を混合することもできる。本発明の多孔膜が発現する効果一つである高い透過性能に関しては、本発明の多孔膜の分画粒子径が大きいほど、その効果の程度が従来技術と比較して顕著である。その点においては、本発明の多孔膜の分画粒子径は０．２μｍ以上であり、好ましくは１μｍ以上より好ましくは１．５μｍ、さらに好適には２．０μｍであることが好ましい。   The inorganic particles in the present invention are the cores of the pores of the porous membrane, and are desirably fine particles that can be easily extracted with chemicals and have a relatively narrow particle size distribution. Examples thereof include metal oxides or hydroxides such as silica, calcium silicate, aluminum silicate, magnesium silicate, calcium carbonate, magnesium carbonate, calcium phosphate, iron and zinc, and salts such as sodium, potassium and calcium. it can. In particular, the inorganic particles having a cohesive property are usually compatible with each other by adding to a composition in which the vinylidene fluoride resin and the solvent are phase-separated. As a result of the improved stability, it is possible to produce a homogeneous porous membrane, which is suitable when producing a porous membrane having a larger pore size. From such a cohesive point, silica is suitable as the inorganic particles. The particle diameter of the inorganic particles (in the case of inorganic particles having aggregating properties, the agglomerated particle diameter) can be appropriately selected depending on the pore diameter of the target porous membrane, and 0.01 μm or less for an ultrafiltration membrane, In the case of a microfiltration membrane having a fractional particle diameter of less than 1 μm, inorganic particles having an aggregate particle diameter of 1 μm or more are selected in the case of a 0.01 to 1 μm or larger pore diameter membrane having a fractional particle diameter of 1 μm or more. In addition, inorganic particles having different agglomerated particle diameters can be mixed for the purpose of improving the pore diameter control of the porous membrane, in particular, improving the pore connectivity. Regarding the high permeation performance, which is one of the effects exhibited by the porous membrane of the present invention, the greater the fractional particle diameter of the porous membrane of the present invention, the more remarkable the effect compared to the prior art. In that respect, the fractional particle diameter of the porous membrane of the present invention is 0.2 μm or more, preferably 1 μm or more, more preferably 1.5 μm, and even more preferably 2.0 μm.

本発明における凝集剤とは、（１）無機粒子と親和性がある、好適には無機粒子の凝集性を向上させる。（２）溶剤とは相容しない、又は上部臨界溶解温度を有する、という（１）および（２）の特性を有する化合物であり、さらに、（３）フッ化ビニリデン系樹脂とは相容しない、（４）フッ化ビニリデン系樹脂と溶剤とが相容する温度以上の沸点を有する、（５）親水基を有する、以上（３）〜（５）の特性を有する化合物が好ましい。（１）、（３）〜（５）の特性を有する凝集剤の例としては、エチレングリコール、プロピレングリコール、トリエチレングリコール、ポリエチレングリコール、グリセリンなどの多価アルコール類、モノラウリン酸デカグリセリルのようなポリグリセリン脂肪酸エステル類、モノステアリン酸ポリオキシエチレングリセリンのようなポリオキシエチレングリセリン脂肪酸エステル類、ポリオキシエチレンラウリルエーテルやポリオキシエチレンセチルエーテルのようなポリオキシエチレンアルキルエーテル類、ポリオキシエチレンポリオキシプロピレンセチルエーテルのようなポリオキシエチレンポリオキシプロピレンアルキルエーテル類、ポリオキシエチレンノニルフェニルエーテルのようなポリオキシエチレンアルキルフェニルエーテル類、モノパルミチン酸ポリオキシエチレンソルビタンのようなポリオキシエチレンソルビタン脂肪酸エステル類などが挙げられる。
これらの中から（２）の特性を有するものを選定することが好ましい。 The flocculant in the present invention has (1) affinity with inorganic particles, and preferably improves the aggregability of inorganic particles. (2) It is a compound having the characteristics of (1) and (2) that is incompatible with a solvent or has an upper critical solution temperature, and (3) incompatible with a vinylidene fluoride resin. (4) A compound having a boiling point equal to or higher than the temperature at which the vinylidene fluoride resin and the solvent are compatible, (5) having a hydrophilic group, and having the above characteristics (3) to (5) is preferable. Examples of the flocculant having the characteristics (1) and (3) to (5) include polyhydric alcohols such as ethylene glycol, propylene glycol, triethylene glycol, polyethylene glycol, and glycerin, and decaglyceryl monolaurate. Polyglycerol fatty acid esters, polyoxyethylene glycerol fatty acid esters such as polyoxyethylene glycerol monostearate, polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene cetyl ether, polyoxyethylene polyoxy Polyoxyethylene polyoxypropylene alkyl ethers such as propylene cetyl ether, polyoxyethylene alkylphenyl ethers such as polyoxyethylene nonylphenyl ether S, and the like, polyoxyethylene sorbitan fatty acid esters such as monopalmitate polyoxyethylene sorbitan.
Among these, it is preferable to select one having the characteristic (2).

上記した（２）の上部臨界溶解温度とは、溶剤と凝集剤の相容性が温度によって変化する組合せの場合、相分離が起こる上限温度をいう。ここでいう相容とは、溶剤と凝集剤とが混和可能であることを示す。ここでいう上部臨界溶解温度の測定は、例えば以下に述べる方法で実施される。所定の重量分率になるように秤量した溶剤と凝集剤の分散液をサンプル管に封入し、シリコンオイルを満たした高温恒温槽中で加熱して溶液を調製した。加熱温度は、溶剤または凝集剤の沸点の内、低い方の沸点−１０℃を設定温度とした。加熱温度で５分間保持した後、サンプル管内を目視し、二相分離していればそれら溶剤と凝集剤の組み合わせは相容しないと定義した。また、均一な一相状態である場合、高温恒温槽からサンプル管を引き上げ冷却し、均一な一相溶液が曇り始める温度を上部臨界溶解温度と定義した。   The upper critical solution temperature of (2) mentioned above refers to the upper limit temperature at which phase separation occurs in a combination in which the compatibility of the solvent and the flocculant varies with temperature. The term “compatibility” here means that the solvent and the flocculant are miscible. The measurement of upper critical solution temperature here is implemented by the method described below, for example. A solvent and a coagulant dispersion weighed to a predetermined weight fraction were sealed in a sample tube and heated in a high-temperature thermostatic bath filled with silicon oil to prepare a solution. The heating temperature was set to the lower boiling point of −10 ° C. among the boiling points of the solvent or the flocculant. After holding at the heating temperature for 5 minutes, the inside of the sample tube was visually observed, and it was defined that the combination of the solvent and the flocculant was incompatible if two-phase separation was performed. Moreover, when it was a uniform one-phase state, the sample tube was pulled up and cooled from the high-temperature thermostat, and the temperature at which the uniform one-phase solution began to cloud was defined as the upper critical dissolution temperature.

本発明における溶剤と凝集剤は、熱誘起相分離を起こす温度で相容しないことが好ましく、工程性の点から、上部臨界溶解温度が３０℃以上、好ましくは０℃以上、さらに好ましくはいずれの温度領域においても相容しない組合せを選定する。一般的な製膜技術においては、均質な多孔膜を製造するのが困難になるため、原液成分として上記（２）に該当する性状を示すものは選定されない傾向にある。しかし、本発明では、上記性状を示す無機粒子を用いることにより、上記（２）の性状を示すものの選択が可能となる。 The solvent and the flocculant in the present invention are preferably incompatible with each other at a temperature causing thermally induced phase separation. From the viewpoint of processability, the upper critical solution temperature is 30 ° C. or higher, preferably 0 ° C. or higher, more preferably any Select a combination that is compatible with the temperature range. In a general film forming technique, it becomes difficult to produce a homogeneous porous film, and therefore, a raw material component that exhibits properties corresponding to the above (2) tends not to be selected. However, in the present invention, by using inorganic particles having the above properties, it is possible to select those having the properties (2).

上記（２）の性状を示す溶剤−凝集剤の組合せを用いることにより、高い分離性能と高い透水性能を併せもつ多孔膜を工業的に容易に、かつ、安価に作製することが可能となる。高い分離性能と高い透水性能を併せ持つ多孔膜の製造方法として、液−液型熱誘起相分離を発現させるフッ化ビニリデン系樹脂と溶剤の組合せを選択する方法が記載されているが（例えば特許文献３参照）、一般に液−液相分離の領域は狭く、制御が困難である。また、液−液相分離を発現する適切な組合せを選択することが極めて重要であり、容易ではない。一方、本発明における溶剤は、凝集剤と上記（２）の性状を示すものであれば、フッ化ビニリデン系樹脂と液−液相分離、固−液相分離のいずれを発現するものであっても良い。本発明の製造方法においては、固−液相分離の溶剤を用いた場合でも、従来技術である液−液相分離を用いる方法によって製造された多孔膜と同等以上の分離性能、透過性能を有する多孔膜を得ることができる。これによって、多孔膜製造原液を構成する成分の選択の幅が広がり、分離性能、透過性能に優れる多孔膜の製造が容易になった。具体的には、γ−ブチロラクトン（水溶性）−グリセリン（水溶性）、ε−カプロラクトン（水溶性）−グリセリン（水溶性）などが挙げられる。本発明では、水溶性の溶剤、水溶性の凝集剤の組み合わせを用いることが好ましい。
By using the solvent-flocculant combination exhibiting the property (2) above, it is possible to industrially easily and inexpensively produce a porous membrane having both high separation performance and high water permeability. As a method for producing a porous membrane having both high separation performance and high water permeation performance, a method of selecting a combination of a vinylidene fluoride resin and a solvent that develops liquid-liquid type thermally induced phase separation is described (for example, Patent Documents) 3), in general, the region of liquid-liquid phase separation is narrow and difficult to control. In addition, it is extremely important and difficult to select an appropriate combination that exhibits liquid-liquid phase separation. On the other hand, as long as the solvent in the present invention exhibits the properties of the flocculant and the above (2), any of the vinylidene fluoride resin, liquid-liquid phase separation, and solid-liquid phase separation is developed. Also good. In the production method of the present invention, even when a solid-liquid phase separation solvent is used, the separation performance and permeation performance are equal to or better than the porous membrane produced by the conventional method using liquid-liquid phase separation. A porous membrane can be obtained. As a result, the range of selection of components constituting the porous membrane production stock solution has been expanded, and the production of a porous membrane having excellent separation performance and permeation performance has become easier. Specific examples include γ -butyrolactone (water-soluble) -glycerin (water-soluble) and ε-caprolactone (water-soluble) -glycerin (water-soluble) . In the present invention, it is preferable to use a combination of a water-soluble solvent and a water-soluble flocculant.

上記したフッ化ビニリデン系樹脂、溶剤、無機粒子および凝集剤からなる多孔膜製造原液の組成は、製造された多孔膜が実用に耐える強度を持ち、所望の孔径および多孔膜の一表面から他表面までを連通する連通孔が所望の性能を満たす程度に存在し得る範囲内で自由に設定することができる。多孔膜製造原液の組成は上記した各構成成分の化学構造等により異なるが、フッ化ビニリデン系樹脂、溶剤、無機粒子および凝集剤の組成比の合計を１２０とした場合に（以下も同様）、フッ化ビニリデン系樹脂：溶剤：無機粒子：凝集剤＝２０〜４０：２５〜６０：１０〜３０：２０〜５０の範囲内にあることが望ましい。多孔膜製造原液の組成がこの範囲を外れると、多孔膜製造原液を中空糸状に紡糸するときの安定性が低下して均質な中空糸状物を紡糸することが困難となり、また、フッ化ビニリデン系樹脂の量が上記した量より多いときには、均質な中空糸状物を紡糸することは可能であっても得られる中空糸膜の透水性と分画性のバランスが悪くなる傾向になる。   The composition of the porous membrane production stock solution composed of the above-mentioned vinylidene fluoride resin, solvent, inorganic particles, and aggregating agent has the strength that the produced porous membrane can withstand practical use. It can be freely set within a range in which the communication holes communicating with the above can exist to the extent that the desired performance is satisfied. The composition of the porous membrane production stock solution varies depending on the chemical structure of each component described above, but when the total composition ratio of the vinylidene fluoride resin, the solvent, the inorganic particles, and the flocculant is 120 (and so on), It is desirable that the vinylidene fluoride resin: solvent: inorganic particles: flocculant = 20-40: 25-60: 10-30: 20-50. If the composition of the porous membrane production stock solution is out of this range, the stability when spinning the porous membrane production stock solution into a hollow fiber shape is lowered, making it difficult to spin a homogeneous hollow fiber product. When the amount of the resin is larger than the above-mentioned amount, even if it is possible to spin a homogeneous hollow fiber-like product, the balance between water permeability and fractionation of the obtained hollow fiber membrane tends to deteriorate.

上記したフッ化ビニリデン系樹脂、溶剤、無機粒子および凝集剤からなる多孔膜製造原液には、必要に応じて、酸化防止剤、紫外線吸収剤、滑剤、アンチブロッキング剤、染料などの各種添加剤を本発明の目的を損なわない範囲で添加することができる。   Various additives such as antioxidants, ultraviolet absorbers, lubricants, anti-blocking agents, dyes, etc. are added to the porous membrane manufacturing stock solution comprising the above-mentioned vinylidene fluoride resin, solvent, inorganic particles and aggregating agent as necessary. It can add in the range which does not impair the objective of this invention.

上記したフッ化ビニリデン系樹脂、溶剤、無機粒子および凝集剤からなる多孔膜製造原液は、二軸混練設備、プラストミル、ミキサーなどの中で混練される。混練温度はフッ化ビニリデン系樹脂と溶剤とが相容しかつ上記混合物の各成分が分解しない範囲で設定する。多孔膜製造原液は混練された後、十分に気泡が除去され、ギヤポンプなどの計量ポンプで計量した後、シートダイや二重環構造のノズルより押出し、所望の形状に成形される。中空糸状にするときは、二重環構造のノズルの中心部から、空気、窒素などの気体、または上記製膜原液の押出し温度以上の沸点を有する液体が同時に押出される。上記二重環構造のノズルの中心部から押出すのに用いられる液体としては、フッ化ビニリデン系樹脂に対して非溶剤又は貧溶剤を用いることが好ましい。例えばテトラエチレングリコールやプロピレングリコール、グリセリンなどの多価アルコール類を例示することができる。これらの選択により、得られる中空糸の内表面側の熱誘起相分離が進行し、最内表面における構造が粗大化し大きな孔径を得るうえでより効果的になる場合がある。粗大化した孔は、表面に長径と短径の比の平均が５：１以上の短冊状微細孔を形成させる上で、極めて重要である。   The porous membrane production stock solution comprising the above-mentioned vinylidene fluoride resin, solvent, inorganic particles and aggregating agent is kneaded in a biaxial kneading equipment, a plast mill, a mixer or the like. The kneading temperature is set in such a range that the vinylidene fluoride resin and the solvent are compatible with each other and each component of the mixture is not decomposed. After the porous membrane production stock solution is kneaded, the bubbles are sufficiently removed, measured by a metering pump such as a gear pump, and then extruded from a sheet die or a nozzle having a double ring structure to be formed into a desired shape. When forming into a hollow fiber shape, a gas such as air or nitrogen or a liquid having a boiling point equal to or higher than the extrusion temperature of the film-forming stock solution is extruded simultaneously from the center of the nozzle having a double ring structure. It is preferable to use a non-solvent or a poor solvent for the vinylidene fluoride resin as the liquid used for extrusion from the center of the double-ring nozzle. For example, polyhydric alcohols such as tetraethylene glycol, propylene glycol, and glycerin can be exemplified. By these selections, thermally induced phase separation on the inner surface side of the obtained hollow fiber proceeds, and the structure on the innermost surface may become coarse and more effective in obtaining a large pore diameter. The coarse pores are extremely important in forming strip-like micropores having an average ratio of major axis to minor axis of 5: 1 or more on the surface.

シートダイやノズルより押出された押出成形物は、例えば冷却といった温度の変化によりフッ化ビニリデン系樹脂と溶剤とが相分離を起こしてフッ化ビニリデン系樹脂が固化する。フッ化ビニリデン系樹脂とフッ化ビニリデン系樹脂が相容する溶媒との混合物がフッ化ビニリデン系樹脂の貧溶媒中との接触により固化するときには、上記混合物と非溶媒の界面にあたる部分が緻密な層を形成し、得られる多孔膜が不均一な構造となり、高い分離精度が得られないおそれがある。冷却の方法は、空気中で行なう方法、液体中に導入する方法、一旦空気中を通した後に液体中に導入する方法などがありいずれの方法を用いても良いが、冷却の速度が多孔膜の強度や伸度、さらに孔径制御に大きく影響するので冷却速度をコントロールできるように雰囲気温度を温風で制御したり、冷却に用いられる液体の温度を制御することが望ましい。冷却に用いられる液体として、水または有機液体が挙げられる。それらは、少なくとも1種以上の成分を溶解させた複数の成分からなる冷却液体であっても構わない。環境面、生産コスト面を考慮すると、水を用いることが好ましい。なお、水溶性溶剤を用い、冷却浴に水を用いる場合には、少なくとも1種以上の塩を溶解させたものや、複数の塩からなる混合液を好ましく用いることができる。凝固する工程に塩水溶液を用いることにより、水（非溶剤）と水溶性溶剤の交換速度を低下させることが可能となり、急速な構造固定による膜表面への緻密層形成を抑制した多孔膜の成形が可能となる。塩濃度が高くなるほど、水と水溶性溶剤との交換速度は低くなり、得られる膜の表面細孔数及び表面細孔径は大きくなる。ここでいう塩とは、ハロゲン化物、硫酸塩、硝酸塩、塩素酸塩、乳酸塩及び酢酸塩などのような１価又は多価のものであって、無水塩または含水塩を使用することができる。例えば、硫酸ナトリウム、硫酸カリウム等の塩を例示することができる。塩水溶液の濃度は、重量濃度３０ｇ／Ｌ以上でかつ、飽和水溶液濃度に対して１０〜１００％の範囲にすることが好ましく、１０〜６０％の範囲にすることがより好ましい。飽和溶液濃度に対して６０％を超えると取扱い性の面で好ましくない。   In the extruded product extruded from the sheet die or nozzle, for example, the vinylidene fluoride resin and the solvent undergo phase separation due to a temperature change such as cooling, and the vinylidene fluoride resin is solidified. When the mixture of the vinylidene fluoride resin and the solvent compatible with the vinylidene fluoride resin is solidified by contact with the poor solvent of the vinylidene fluoride resin, the portion corresponding to the interface between the mixture and the non-solvent is a dense layer. The resulting porous membrane has a non-uniform structure, and high separation accuracy may not be obtained. The cooling method includes a method of performing in air, a method of introducing into the liquid, a method of once passing through the air and then introducing into the liquid, and any method may be used. Therefore, it is desirable to control the ambient temperature with warm air so that the cooling rate can be controlled, or to control the temperature of the liquid used for cooling. The liquid used for cooling includes water or an organic liquid. They may be a cooling liquid composed of a plurality of components in which at least one component is dissolved. In consideration of the environment and production cost, it is preferable to use water. In the case where a water-soluble solvent is used and water is used for the cooling bath, a solution in which at least one salt is dissolved or a mixed solution composed of a plurality of salts can be preferably used. By using an aqueous salt solution in the solidification process, the exchange rate of water (non-solvent) and water-soluble solvent can be reduced, and the formation of a porous membrane that suppresses the formation of a dense layer on the membrane surface due to rapid structural fixation Is possible. The higher the salt concentration, the lower the exchange rate between water and the water-soluble solvent, and the larger the number of surface pores and the surface pore diameter of the resulting membrane. The salt here is a monovalent or polyvalent salt such as halide, sulfate, nitrate, chlorate, lactate and acetate, and an anhydrous salt or a hydrated salt can be used. . For example, salts such as sodium sulfate and potassium sulfate can be exemplified. The concentration of the aqueous salt solution is preferably at least 30 g / L in weight concentration and in the range of 10 to 100%, more preferably in the range of 10 to 60% with respect to the saturated aqueous solution concentration. If it exceeds 60% with respect to the saturated solution concentration, it is not preferable in terms of handleability.

次いで、上記により形成された成形物から、溶剤、無機粒子および凝集剤を抽出終了する前に多孔膜を延伸する工程を含むことを特徴としている。抽出終了前の多孔膜を延伸することにより、最終的に得られる多孔膜の高透過性化が期待できる。延伸は、空間温度０℃以上１６０℃以下で行うことが望ましい。１６０℃より高い場合には延伸斑が大きいうえに破断伸度の低下及び透水性能が低くなり好ましくなく、０℃以下では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。より好ましくは３０〜１２０℃、更に好ましくは３０〜１００℃の温度範囲で１．１〜４倍、より好ましくは１．１〜３．５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、目的の多孔膜が得られる。ここでいう延伸倍率とは、延伸工程中で最も伸ばされる時の多孔膜の長さから求められる倍率のことである。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、９５℃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。本発明においては、溶剤および凝集剤を含んだ多孔膜を延伸することが好ましい。溶剤および凝集剤を含んだ多孔膜の方が、溶剤および凝集剤を含んでいない多孔膜よりも、延伸時の破断が少ない。また、無機粒子を含んだ多孔膜を延伸することが好ましい。無機粒子を含んだ多孔膜の方が、膜断面に存在する独立孔が無機粒子を起点に開裂し、連通孔へと変わり、膜断面の連通性が高まる。また、多孔膜の一表面に存在する粗大化した孔を短冊状微細孔へと変化させることが可能となり、多孔膜の透過性能を著しく向上させることができる。本発明においては、溶剤、無機粒子および凝集剤を含む多孔膜を延伸することがより望ましい。また、延伸した多孔膜を抽出する方法は、延伸により多孔膜の表面及び内部に空隙が増加しているため、抽出溶剤が多孔膜内部に浸透し易いという利点がある。   Next, the method includes a step of stretching the porous film before the extraction of the solvent, the inorganic particles, and the flocculant is completed from the molded product formed as described above. By stretching the porous membrane before the end of extraction, it is possible to expect high permeability of the finally obtained porous membrane. The stretching is desirably performed at a space temperature of 0 ° C. or higher and 160 ° C. or lower. If the temperature is higher than 160 ° C, the stretched spots are large, and the elongation at break and the water permeability are lowered, which is not preferable. Breaks. More preferably, it is 1.1 to 4 times, more preferably 1.1 to 3.5 times, and still more preferably 1.1 to 3 times in the temperature range of 30 to 120 ° C, more preferably 30 to 100 ° C. The target porous film is obtained by stretching at a stretching ratio. The stretching ratio here is a ratio determined from the length of the porous film when stretched most during the stretching process. 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 95 ° C. or higher, it is also possible to preferably employ 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. In the present invention, it is preferable to stretch a porous film containing a solvent and a flocculant. A porous membrane containing a solvent and a flocculant has less breakage during stretching than a porous membrane containing no solvent and a flocculant. Further, it is preferable to stretch a porous film containing inorganic particles. In the porous film containing inorganic particles, the independent pores existing in the cross section of the membrane are cleaved starting from the inorganic particles and changed to communication holes, and the connectivity of the cross section of the membrane is enhanced. Moreover, it becomes possible to change the coarse hole which exists in one surface of a porous membrane into a strip-shaped micropore, and can improve the permeation | transmission performance of a porous membrane remarkably. In the present invention, it is more desirable to stretch a porous film containing a solvent, inorganic particles, and an aggregating agent. Further, the method of extracting the stretched porous membrane has an advantage that the extraction solvent easily penetrates into the porous membrane because the voids increase on the surface and inside of the porous membrane due to stretching.

次いで、上記により形成された成形物から、溶剤、無機粒子および凝集剤を抽出して多孔膜を得る。これらの成分の抽出は、押出、固化などの操作と共に工程中で連続的に行なうことができるし、成形物を一旦枠やカセなどに巻き取った後に行なっても、あるいは成形物を所定の形状のケースに収納してモジュール化した後に行なっても良い。各成分の抽出に用いる溶剤は、抽出温度においてフッ化ビニリデン系樹脂の非溶剤であることが必要である。抽出溶剤は抽出成分の化学構造等によっても異なるが、例えば水溶性溶剤の場合は水が挙げられる。また無機粒子がシリカの場合は、アルカリ溶液による抽出が好適である。さらに凝集剤が難水溶性の場合は、ヘキサン、アセトン、メタノールなど、水溶性の場合は水が挙げられる。多孔膜は、これらの処理を行なった後に、例えば枠やカセに巻き取った状態で乾燥される。
Next, a solvent, inorganic particles, and an aggregating agent are extracted from the molded product formed as described above to obtain a porous film. The extraction of these components can be carried out continuously in the process together with operations such as extrusion and solidification, and can be carried out after the molded product is once wound up on a frame or a cassette, or the molded product can be formed into a predetermined shape. You may carry out after storing in the case and modularizing. The solvent used for extraction of each component must be a non-solvent of vinylidene fluoride resin at the extraction temperature. Extraction solvent varies depending the chemical structure or the like of the extracted components, in the case of water-soluble solvents For example include water. In addition, when the inorganic particles are silica, extraction with an alkaline solution is preferable. Furthermore, when the flocculant is poorly water-soluble, hexane, acetone, methanol, etc., and when it is water-soluble, water is exemplified. The porous film is dried after being subjected to these treatments, for example, in a state of being wound around a frame or a cassette.

また、本発明の多孔膜は、熱処理等を適宜行ってもよい。熱処理は、フッ化ビニリデン系樹脂多孔膜のα型結晶構造の比率を高めるためである。本発明者らは、フッ化ビニリデン系樹脂多孔膜の耐薬品性について検討した結果、結晶化度のみならず、結晶構造も大きく寄与していることを見出した。更に鋭意検討した結果、α型結晶構造がβ型結晶構造よりも高い比率で存在することで耐薬品性が向上することを見出した。α型結晶構造がβ型結晶構造よりも高い比率で存在することで耐薬品性が向上するのは、次の理由によると考えられる。α型結晶構造は、β型結晶構造に比べて、水素原子とフッ素原子が非局在化しており、電荷の偏りが少ないことに基因すると推定される。すなわち、水素原子とフッ素原子が局在化し、分子内分極しているβ型結晶構造より、非極性であるα型結晶構造の存在比率が高いために、本発明のポリフッ化ビニリデン多孔膜は優れた耐薬品性を有すると推定される。そこで、本発明の多孔膜においては、多孔膜が固定されていないフリーの状態で熱処理されることが好ましい。例えば、延伸処理後、一旦枠やカセに巻取り、その後、多孔膜をフリー状態にすることで、溶剤、凝集剤を抽出すると同時に、熱処理を行うことが可能である。固定された状態で熱処理を行うと、熱収縮等が起こって歪が生じ、多孔膜のミクロ環境における結晶構造の変化が起こる。具体的にはα型結晶構造からβ型結晶構造への転移が起こり、多孔膜中のβ型結晶構造の比率が高まり、所望の効果が得られない場合が生じる。   Moreover, the porous film of the present invention may be appropriately subjected to heat treatment or the like. The heat treatment is to increase the ratio of the α-type crystal structure of the vinylidene fluoride resin porous membrane. As a result of examining the chemical resistance of the vinylidene fluoride resin porous membrane, the present inventors have found that not only the crystallinity but also the crystal structure contributes greatly. As a result of further intensive studies, it has been found that the chemical resistance is improved when the α-type crystal structure is present at a higher ratio than the β-type crystal structure. The reason why the chemical resistance is improved when the α-type crystal structure is higher than the β-type crystal structure is considered to be as follows. The α-type crystal structure is presumed to be caused by the fact that the hydrogen atom and the fluorine atom are delocalized compared to the β-type crystal structure and there is less charge bias. That is, the polyvinylidene fluoride porous membrane of the present invention is superior because the non-polar α-type crystal structure is present in a higher proportion than the β-type crystal structure in which hydrogen atoms and fluorine atoms are localized and polarized intramolecularly. It is estimated to have high chemical resistance. Therefore, in the porous membrane of the present invention, it is preferable to perform heat treatment in a free state in which the porous membrane is not fixed. For example, after the stretching treatment, it is possible to perform the heat treatment at the same time as extracting the solvent and the flocculant by winding the porous film once in a frame or a cassette and then setting the porous film in a free state. When heat treatment is performed in a fixed state, thermal shrinkage or the like occurs and distortion occurs, and the crystal structure in the microenvironment of the porous film changes. Specifically, the transition from the α-type crystal structure to the β-type crystal structure occurs, and the ratio of the β-type crystal structure in the porous film increases, and a desired effect may not be obtained.

本発明におけるポリフッ化ビニリデン多孔膜中の結晶構造の比率の測定は、例えば以下に述べる方法によって行われる。ＩＲ測定により得られる７６３ｃｍ−１の吸光度（Ａ７６３）及び８４０ｃｍ−１の吸光度（Ａ８４０）から下式（１）によって計算されるＲ１の値である。
Ｒ１＝Ａ７６３／Ａ８４０（１）
ここで、Ａ７６３はα型結晶構造に帰属する吸光度であり、Ａ８４０はβ型結晶構造に帰属する吸光度である（例えば、特許文献５参照）。Ｒ１の値は、ポリフッ化ビニリデンの結晶領域におけるα型とβ型の割合を示している。図６に示されるような多孔膜のＩＲチャートから、６９５および７８０ｃｍ−１近傍のＩＲチャートの極小値の間に線を引き、７６３ｃｍ−１近傍のα型結晶構造に帰属される特性吸収ピーク高さを読み取る。併せて、８１０および９２５ｃｍ−１近傍のＩＲチャートの極小値の間に線を引き８４０ｃｍ−１近傍のβ型結晶構造に帰属される特性吸収ピーク高さを読み取り、Ｒ１を求める。本発明におけるＲ１は１．５以上が好ましい。 The ratio of the crystal structure in the polyvinylidene fluoride porous film in the present invention is measured, for example, by the method described below. It is the value of R 1 calculated by the following formula (1) from the absorbance (A 763 ) of 763 cm −1 and the absorbance (A 840 ) of 840 cm −1 obtained by IR measurement.
R 1 = A 763 / A 840 (1)
Here, A 763 is an absorbance attributed to the α-type crystal structure, and A 840 is an absorbance attributed to the β-type crystal structure (see, for example, Patent Document 5). The value of R 1 indicates the ratio of α-type and β-type in the crystalline region of polyvinylidene fluoride. From the IR chart of the porous film as shown in FIG. 6, a line is drawn between the minimum values of the IR chart in the vicinity of 695 and 780 cm −1 , and the characteristic absorption peak height attributed to the α-type crystal structure in the vicinity of 763 cm −1. Read. In addition, a line is drawn between the minimum values of the IR chart in the vicinity of 810 and 925 cm −1 to read the characteristic absorption peak height attributed to the β-type crystal structure in the vicinity of 840 cm −1 to obtain R 1 . In the present invention, R 1 is preferably 1.5 or more.

ポリフッ化ビニリデン樹脂のα型結晶構造とは、重合体分子中のある１つの主鎖炭素に結合するフッ素原子（または水素原子）に対し、一方の隣接する炭素原子に結合した水素原子（またはフッ素原子）がトランスの位置にあり、なおかつもう一方（逆側）に隣接する炭素原子に結合する水素原子（またはフッ素原子）がゴーシュの位置（６０度の位置）にあり、その立体構造の連鎖が２つ以上連続して有することを特徴とするものであって、分子鎖がＴＧ＋ＴＧ−型でＣ−Ｆ２、Ｃ−Ｈ２結合の双極子能率が分子鎖に垂直方向と平行方向とにそれぞれ成分を有している。α型結晶構造を有するポリフッ化ビニリデン樹脂についてＩＲ分析を行なうと、１２１２ｃｍ−１、１１８３ｃｍ−１および７６３ｃｍ−１付近に特徴的なピーク（特性吸収）を有し、粉末Ｘ線回折分析においては２θ＝１７.７度、１８．３度および１９．９度付近に特徴的なピークを有する。 The α-type crystal structure of the polyvinylidene fluoride resin refers to a fluorine atom (or hydrogen atom) bonded to one main chain carbon in a polymer molecule, and a hydrogen atom (or fluorine atom) bonded to one adjacent carbon atom. Atom) is in the trans position, and the hydrogen atom (or fluorine atom) bonded to the carbon atom adjacent to the other (reverse side) is in the Gauche position (60 degree position), The molecular chain is a TG + TG − type, and the dipole efficiency of C—F 2 and C—H 2 bonds is perpendicular to and parallel to the molecular chain. Each has a component. When performing IR analysis polyvinylidene fluoride resin having an α-type crystal structure, 1212cm -1, has characteristic peaks (characteristic absorptions) around 1183 cm -1 and 763cm -1, 2θ in the powder X-ray diffraction analysis = 17.7 degrees, 18.3 degrees, and 19.9 degrees have characteristic peaks.

ポリフッ化ビニリデン樹脂のβ型結晶構造とは、重合体分子中の１つの主鎖炭素に隣り合う炭素原子に結合したフッ素原子と水素原子がそれぞれトランスの立体配位（ＴＴ型構造）、つまり隣り合う炭素原子に結合するフッ素原子と水素原子が炭素−炭素結合の方向から見て１８０度の位置に存在することを特徴とする。ＴＴ型構造の部分がＴＴ型の主鎖を構成する炭素−炭素結合は平面ジグザグ構造をもち、Ｃ−Ｆ２、Ｃ−Ｈ２結合の双極子能率が分子鎖に対して垂直方向の成分を有している。β型結晶構造についてＩＲ分析を行なうと、１２７４ｃｍ−１、１１６３ｃｍ−１および８４０ｃｍ−１付近に特徴的なピーク（特性吸収）を有し、粉末Ｘ線回折分析においては２θ＝２１度付近に特徴的なピークを有する。 The β-type crystal structure of the polyvinylidene fluoride resin is that the fluorine atom and the hydrogen atom bonded to the carbon atom adjacent to one main chain carbon in the polymer molecule are each in the trans configuration (TT-type structure), that is, adjacent to each other. A fluorine atom and a hydrogen atom bonded to a matching carbon atom are present at a position of 180 degrees when viewed from the direction of the carbon-carbon bond. The carbon-carbon bond in which the TT-type structure part constitutes the TT-type main chain has a planar zigzag structure, and the dipole efficiency of the C—F 2 and C—H 2 bonds has a component perpendicular to the molecular chain. Have. When performing IR analysis β-type crystal structure, 1274Cm -1, has a 1163Cm -1 and 840 cm -1 near the characteristic peaks (characteristic absorptions), characterized in the vicinity of degrees 2 [Theta] = 21 in the powder X-ray diffraction analysis Has a typical peak.

熱処理を行う手順としては、製膜後、抽出成分を洗浄等で除去する前に行っても良いし、除去した後に行っても良い。また、膜が束ねられた糸束状態、乾燥処理後に行っても良いし、モジュール化した後に熱処理を行っても構わない。なお、モジュール化後に熱処理する場合には熱処理による収縮を見越し、膜が引っ張られないように予めゆとりを持たせておくことが好ましい。   As a procedure for performing the heat treatment, it may be performed after the film formation and before the extraction component is removed by washing or the like, or after the removal. Moreover, the yarn bundle state in which the membranes are bundled may be performed after the drying process, or may be heat-treated after being modularized. When heat treatment is performed after modularization, it is preferable to allow for a space in advance so as to prevent shrinkage due to heat treatment.

熱処理方法としては、熱風による乾式方法、液体に浸漬して行う湿式方法、加熱変調した金属製のロール等に多孔膜を接触させて行う方法、スチーム等の気体で行う方法又は電磁波を放射する方法などが例示でき、多孔膜が湿潤状態でも乾燥状態でもどちらでも可能である。中でも、水中で行う方法が温度制御が容易であり簡便である。低分子量のポリエチレングリコ−ル、などのようなポリフッ化ビニリデン樹脂の非溶剤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、界面活性剤水溶液など、複数成分の混合液体中で熱処理することも採用できる。 As a heat treatment method, a dry method using hot air, a wet method performed by immersing in a liquid, a method performed by contacting a porous film with a heat-modulated metal roll, a method performed using a gas such as steam, or a method of emitting electromagnetic waves The porous film can be either wet or dry. Among them, the method carried out in water is easy because temperature control is easy. It is also possible to preferably employ a non-solvent of polyvinylidene fluoride resin such as low molecular weight polyethylene glycol. Furthermore, heat treatment in a mixed liquid of a plurality of components such as a mixed liquid of water and polyethylene glycol or a surfactant aqueous solution can also be employed.

湿式方式における浸漬液体の選定によっては、製膜原液中の抽出成分の抽出除去と熱処理を同時に行うことも可能となる。 Depending on the selection of the immersion liquid in the wet method, it is possible to simultaneously perform the extraction and removal of the extracted components in the film-forming stock solution and the heat treatment.

熱処理温度は、熱処理の効果が得られ、かつ化学的強度以外の多孔膜の要求特性を損なわないという観点から、７０℃〜１６０℃の範囲で行うことが好適である。
The heat treatment temperature is preferably in the range of 70 ° C. to 160 ° C. from the viewpoint that the effect of the heat treatment is obtained and the required characteristics of the porous film other than the chemical strength are not impaired .

熱処理時間は、特に制限はないが、工程性の観点から１〜５時間の範囲が好ましい。熱処理温度を高温にすることで、処理時間を短縮することが可能である。   The heat treatment time is not particularly limited, but is preferably in the range of 1 to 5 hours from the viewpoint of processability. By increasing the heat treatment temperature, the treatment time can be shortened.

熱処理後は、室温などで放置し、ゆっくり放冷するのが好ましい。   After the heat treatment, it is preferably left at room temperature or the like and allowed to cool slowly.

上述のフッ化ビニリデン系樹脂多孔膜は、原液流入口や透過液流入口などを備えたケーシングに収容され膜モジュールとして使用される。膜モジュールは、膜が中空糸膜である場合には、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て、透過液を回収できるようにしたり、平板状に中空糸膜を固定して透過液を回収できるようにする。膜が平膜状である場合には、平膜を集液管の周りに封筒状に折り畳みながらスパイラル状に巻き取り、円筒状の容器に納め、透過液を回収できるようにしたり、集液管の両面に平膜を配置して周囲を密に固定し、透過液を回収できるようにする。   The above-mentioned vinylidene fluoride resin porous membrane is housed in a casing having a raw solution inlet, a permeate inlet, and the like and used as a membrane module. When the membrane module is a hollow fiber membrane, the permeate can be collected by bundling a plurality of hollow fiber membranes and placing them in a cylindrical container and fixing both ends or one end with polyurethane, epoxy resin or the like. Or by fixing the hollow fiber membrane in a flat plate shape so that the permeate can be collected. When the membrane is a flat membrane, the flat membrane is wound around in an envelope shape around the collecting tube and wound into a spiral shape and placed in a cylindrical container so that the permeate can be collected. Flat membranes are arranged on both sides of the plate so that the perimeter is fixed tightly so that the permeate can be collected.

そして、膜モジュールは、少なくとも原液側に加圧手段または透過液側に吸引手段を設け、水などを分離する分離装置として用いられる。加圧手段としてはポンプを用いても良いし、水位差による圧力を利用してもよい。また、吸引手段としては、ポンプやサイフォンを利用すればよい。   The membrane module is used as a separation device for separating water and the like by providing a pressurizing means at least on the stock solution side or a suction means on the permeate side. A pump may be used as the pressurizing means, or a pressure due to a water level difference may be used. Moreover, what is necessary is just to utilize a pump and a siphon as a suction means.

この分離装置は、水処理分野であれば浄水処理、上水処理、排水処理、工業用水製造などで利用でき、河川水、湖沼水、地下水、海水、下水、排水などを被処理水とする。   This separation device can be used for water purification, clean water treatment, wastewater treatment, industrial water production, etc. in the field of water treatment, and uses river water, lake water, groundwater, seawater, sewage, wastewater, etc. as treated water.

また、上記フッ化ビニリデン系樹脂多孔膜は、電池の内部で正極と負極とを分離する電池用セパレーターに用いることもでき、この場合、イオンの透過性が高いことによる電池性能の向上や、破断強度が高いことによる電池の耐久性向上などの効果が期待できる。   The vinylidene fluoride-based resin porous membrane can also be used for a battery separator that separates the positive electrode and the negative electrode inside the battery. In this case, the battery performance is improved due to high ion permeability or breakage. Effects such as improved battery durability due to high strength can be expected.

さらに、上記の製造方法により作製したフッ化ビニリデン系樹脂多孔膜は、荷電基（イオン交換基）を導入して荷電膜とすると、イオンの認識性向上や、破断強度が高いことによる荷電膜の耐久性向上などの効果が期待できる。   Furthermore, when a charged group (ion exchange group) is introduced into a charged membrane by introducing a charged group (ion exchange group) into a vinylidene fluoride resin porous membrane produced by the above-described production method, the ion recognition performance is improved, and the charged membrane due to high breaking strength is used. Effects such as improved durability can be expected.

さらにまた、上記のフッ化ビニリデン系樹脂多孔膜にイオン交換樹脂を含浸し、イオン交換膜として燃料電池に用いると、特に燃料にメタノールを用いる場合、イオン交換膜のメタノールによる膨潤が抑えられるので、燃料電池性能の向上が期待できる。さらに、破断強度が高いことによる燃料電池の耐久性向上なども期待できる。   Furthermore, when the above-mentioned vinylidene fluoride resin porous membrane is impregnated with an ion exchange resin and used as a fuel cell as an ion exchange membrane, particularly when methanol is used as a fuel, swelling of the ion exchange membrane due to methanol can be suppressed. Improvement of fuel cell performance can be expected. Furthermore, improvement in the durability of the fuel cell due to high breaking strength can be expected.

以下、実施例により本発明を具体的に説明する。なお、本発明はこれによってなんら限定を受けるものではない。   Hereinafter, the present invention will be described specifically by way of examples. In addition, this invention does not receive any limitation by this.

フッ化ビニリデン系樹脂としてポリフッ化ビニリデン（以下、ＰＶＤＦと略記することがある）（ソルベイ ソレクシス株式会社製、ＳＯＬＥＦ６０１０）と、溶剤としてγ−ブチロラクトンと、無機粒子としてシリカ（株式会社トクヤマ製、ファインシールＸ−４５）と、凝集剤としてグリセリン（花王株式会社製、精製グリセリン）とを、重量比で３６：４７：１８：１９の割合となるように製膜原液を調製した。この製膜原液の組成を表１に示す。該組成比のγ−ブチロラクトンとグリセリンの上部臨界溶解温度は、４０．６℃であった。 Polyvinylidene fluoride (hereinafter sometimes abbreviated as PVDF) (Solvay Solexis, Solef 6010) as a vinylidene fluoride resin, γ-butyrolactone as a solvent, and silica (manufactured by Tokuyama, Fine Seal) as inorganic particles X-45) and glycerin (purified glycerin, manufactured by Kao Corporation) as a flocculant were prepared so as to have a weight ratio of 36: 47: 18: 19. The composition of this film forming stock solution is shown in Table 1. The upper critical solution temperature of γ-butyrolactone and glycerin with this composition ratio was 40.6 ° C.

上記した製膜原液を、二軸混練押出機中で加熱混練（温度１５０℃）して、押出したストランドをペレタイザーに通すことでチップ化した。このチップを、外径１．６ｍｍ、内径０．８ｍｍの二重環構造のノズルを装着した押出機（１５０℃）を用いて押出した。このときテトラエチレングリコールを押出物の中空部内に注入した。   The film-forming stock solution described above was heated and kneaded (temperature: 150 ° C.) in a twin-screw kneading extruder, and the extruded strand was passed through a pelletizer to form chips. This chip was extruded using an extruder (150 ° C.) equipped with a double ring nozzle having an outer diameter of 1.6 mm and an inner diameter of 0.8 mm. At this time, tetraethylene glycol was injected into the hollow portion of the extrudate.

紡口から空気中に押し出した押出成形物を、３ｃｍの空中走行距離を経て、重量パーセント濃度２０％硫酸ナトリウム水溶液からなる水浴中（温度６０℃）に入れ、約１００ｃｍ水浴中を通過させて冷却固化させた。次いで、溶剤、凝集剤および無機粒子の大部分が中空糸状物中に残存している状態で、９０℃の熱水中で繊維方向に原長の約１．５倍長となるよう延伸処理をした後、次いで、得られた中空糸状物を９５℃の流水中で１８０分間熱処理と溶剤（γ−ブチロラクトン）、凝集剤（グリセリン）、注入液（テトラエチレングリコール）の抽出除去を行った。   The extruded product extruded into the air from the nozzle is placed in a water bath (temperature: 60 ° C.) consisting of a 20% aqueous solution of sodium sulfate by weight over a distance of 3 cm and cooled by passing through a water bath of about 100 cm. Solidified. Next, in a state where most of the solvent, the flocculant and the inorganic particles remain in the hollow fiber-like material, the drawing treatment is performed in hot water at 90 ° C. so as to be about 1.5 times the original length in the fiber direction. Then, the obtained hollow fiber-like material was heat-treated in flowing water at 95 ° C. for 180 minutes, and the solvent (γ-butyrolactone), the flocculant (glycerin), and the injection solution (tetraethylene glycol) were extracted and removed.

このようにして得られた中空糸状物を４０℃の重量パーセント濃度５％水酸化ナトリウム水溶液中で１２０分浸漬して無機粒子（シリカ）を抽出除去した後に、水洗工程を経て中空糸膜を得た。製造した中空糸膜の試験結果を表２に示す。製造した中空糸膜のＩＲ測定により求めたＲ１は２．５であった。 The hollow fiber obtained in this manner is immersed in an aqueous solution of sodium hydroxide at a weight percent concentration of 5% at 40 ° C. for 120 minutes to extract and remove inorganic particles (silica), and then a hollow fiber membrane is obtained through a washing step. It was. The test results of the manufactured hollow fiber membrane are shown in Table 2. R 1 obtained by IR measurement of the produced hollow fiber membrane was 2.5.

得られた中空糸膜の耐酸化剤性を評価するため、次亜塩素酸ナトリウム水溶液（有効塩素濃度：５０００ｐｐｍ）に６０℃で７日間浸漬し、その物性評価（引張破断強度）を測定し、結果を表３に記載した。 In order to evaluate the oxidation resistance of the obtained hollow fiber membrane, it was immersed in an aqueous sodium hypochlorite solution (effective chlorine concentration: 5000 ppm) at 60 ° C. for 7 days, and its physical property evaluation (tensile breaking strength) was measured. The results are shown in Table 3.

各種の測定（分析）方法および装置
（１）分画粒子径
異なる粒子径を有する少なくとも２種類の粒子の阻止率を測定し、その測定値を元にして下記の近似式（１）において、Ｒが９０となるＳの値を求め、これを分画粒子径とした。
Ｒ＝１００／（１−ｍ×ｅｘｐ（−ａ×ｌｏｇ（ｓ））） ・・・（１）
（１）式中、ａおよびｍは中空糸膜によって定まる定数であって、２種類以上の阻止率の測定値をもとに算出される。ただし、０．１μｍ径の粒子の阻止率が９０％以上の場合の分画粒子径は、＜０．１μｍと表記される。 Various Measurement (Analysis) Methods and Apparatuses (1) Fractionated particle diameter The blocking rate of at least two kinds of particles having different particle diameters is measured, and R in the following approximate expression (1) based on the measured values, R Was obtained as a fractional particle size.
R = 100 / (1−m × exp (−a × log (s))) (1)
In the formula (1), a and m are constants determined by the hollow fiber membrane, and are calculated based on measured values of two or more types of rejection. However, the fractional particle size in the case where the rejection rate of 0.1 μm diameter particles is 90% or more is expressed as <0.1 μm.

（２）純水透過速度
有効長が３ｃｍの片端開放型の中空糸膜モジュールを用いて、原水として純水を利用し、濾過圧力が５０ｋＰａ、温度が２５℃の条件で中空糸膜の外側から内側に濾過（外圧濾過）して時間当たりの透水量を測定し、単位膜面積、単位時間、単位圧力当たりの透水量に換算した数値で算出した。 (2) Pure water permeation rate Using a single-end open type hollow fiber membrane module with an effective length of 3 cm, pure water is used as raw water, the filtration pressure is 50 kPa, and the temperature is 25 ° C., from the outside of the hollow fiber membrane. The amount of permeation per hour was measured by filtering inside (filtering with external pressure), and calculated by a numerical value converted into the amount of permeation per unit membrane area, unit time, and unit pressure.

溶剤としてε-カプロラクトンを用いた以外は実施例１と同様にして中空糸膜を得た。該組成比のε-カプロラクトンとグリセリンの上部臨界溶解温度は、４７．３℃であった。製造した中空糸膜の試験結果を表２に示す。 A hollow fiber membrane was obtained in the same manner as in Example 1 except that ε-caprolactone was used as a solvent. The upper critical solution temperature of ε-caprolactone and glycerin with this composition ratio was 47.3 ° C. The test results of the manufactured hollow fiber membrane are shown in Table 2.

比較例１
ポリフッ化ビニリデン（ソルベイ ソレクシス株式会社製、ＳＯＬＥＦ６０１０）と、γ−ブチロラクトンと、無機粒子としてシリカ、凝集剤としてポリオキシエチレンノニルフェニルエーテル（日光ケミカルズ株式会社製：ＮＰ−５）とを、重量比でそれぞれ３６：４７：１８：１９の割合となるように製膜原液を調製した以外は、実施例１と同様にして中空糸膜を得た。該組成比のγ−ブチロラクトンとポリオキシエチレンノニルフェニルエーテルにおいて、上部臨界溶解温度は観察されず、いずれの温度においても相容した。製造した中空糸膜の試験結果を表２に示す。 Comparative Example 1
Polyvinylidene fluoride (Solef 6010, manufactured by Solvay Solexis Co., Ltd.), γ-butyrolactone, silica as inorganic particles, and polyoxyethylene nonylphenyl ether (manufactured by Nikko Chemicals: NP-5) as an aggregating agent in a weight ratio. A hollow fiber membrane was obtained in the same manner as in Example 1 except that the membrane forming stock solution was prepared so as to have a ratio of 36: 47: 18: 19, respectively. In the composition ratio of γ-butyrolactone and polyoxyethylene nonylphenyl ether, the upper critical solution temperature was not observed, and they were compatible at any temperature. The test results of the manufactured hollow fiber membrane are shown in Table 2.

ポリフッ化ビニリデン（ソルベイ ソレクシス株式会社製、ＳＯＬＥＦ６０１０）と、溶剤としてγ−ブチロラクトンと、無機粒子としてシリカ（株式会社トクヤマ製、ファインシールＦ−８０）と、凝集剤としてグリセリン（花王株式会社製、精製グリセリン）と、親水性樹脂としてポリビニルピロリドン（ＢＡＳＦ社製、Ｋ−９０）を、重量比で３５：４３：２０：１９：３の割合となるように製膜原液を調製した。この製膜原液の組成を表１に示す。該組成比のγ−ブチロラクトンとグリセリンの上部臨界溶解温度は、４１．６℃であった。 Polyvinylidene fluoride (Solef 6010, manufactured by Solvay Solexis Co., Ltd.), γ-butyrolactone as a solvent, silica (manufactured by Tokuyama Co., Ltd., Fine Seal F-80), and glycerin (produced by Kao Corporation, purified) as an aggregating agent Glycerin) and polyvinylpyrrolidone (manufactured by BASF, K-90) as a hydrophilic resin were prepared so as to have a weight ratio of 35: 43: 20: 19: 3. The composition of this film forming stock solution is shown in Table 1. The upper critical dissolution temperature of γ-butyrolactone and glycerin having this composition ratio was 41.6 ° C.

上記した製膜原液を、二軸混練押出機中で加熱混練（温度１５０℃）して、押出したストランドをペレタイザーに通すことでチップ化した。このチップを、外径１．６ｍｍ、内径０．８ｍｍの二重環構造のノズルを装着した押出機（１５０℃）を用いて押出した。このときテトラエチレングリコールを押出物の中空部内に注入した。   The film-forming stock solution described above was heated and kneaded (temperature: 150 ° C.) in a twin-screw kneading extruder, and the extruded strand was passed through a pelletizer to form chips. This chip was extruded using an extruder (150 ° C.) equipped with a double ring nozzle having an outer diameter of 1.6 mm and an inner diameter of 0.8 mm. At this time, tetraethylene glycol was injected into the hollow portion of the extrudate.

紡口から空気中に押し出した押出成形物を、３ｃｍの空中走行距離を経て、重量パーセント濃度１０％硫酸ナトリウム水溶液からなる水浴中（温度３０℃）に入れ、約１００ｃｍ水浴中を通過させて冷却固化させた。次いで、溶剤、凝集剤および無機粒子の大部分が中空糸状物中に残存している状態で、９０℃の熱水中で繊維方向に原長の約１．８倍長となるよう延伸処理をした後、次いで、得られた中空糸状物を９５℃の流水中で１８０分間熱処理と溶剤（ガンマ-ブチロラクトン）、凝集剤（グリセリン）、注入液（テトラエチレングリコール）の抽出除去を行った。   The extruded product extruded into the air from the nozzle is placed in a water bath (temperature: 30 ° C.) consisting of a 10% sodium sulfate aqueous solution by weight over a distance of 3 cm and cooled by passing through a water bath of about 100 cm. Solidified. Next, in a state where most of the solvent, the flocculant and the inorganic particles remain in the hollow fiber-like material, the drawing treatment is performed in hot water at 90 ° C. so as to be about 1.8 times the original length in the fiber direction. Then, the obtained hollow fiber-like material was heat-treated in flowing water at 95 ° C. for 180 minutes, and the solvent (gamma-butyrolactone), the flocculant (glycerin), and the injection solution (tetraethylene glycol) were extracted and removed.

このようにして得られた中空糸状物を４０℃の重量パーセント濃度５％水酸化ナトリウム水溶液中で１２０分浸漬して無機粒子（シリカ）を抽出除去した後に、水洗工程を経て中空糸膜を得た。 The hollow fiber obtained in this manner is immersed in an aqueous solution of sodium hydroxide at a weight percent concentration of 5% at 40 ° C. for 120 minutes to extract and remove inorganic particles (silica), and then a hollow fiber membrane is obtained through a washing step. It was.

次いで、得られた中空状物を５重量パーセントのぺルオキソニ硫酸水溶液（３０℃）に３０分浸漬した後、水溶液中から取り出して中空状物に付着した余分な溶液を除去し、その後、反応槽に入れた。該反応槽内に約１２０℃のスチームを吹き込んで、槽内を９０℃以上に保つようにして３０分間加熱処理した。次に加熱処理された中空状物を９０℃の熱水で３０分洗浄した後に中空糸膜を得た。製造した中空糸膜の試験結果を表２に示す。次いで、製造した中空糸膜を４０℃に設定した送風乾燥機内で１２時間乾燥させた。乾燥前後における透水性能保持率を表３に示す。また膜構造を観察するにあたって撮影した走査型電子顕微鏡写真を図１〜４に示す。 Next, the obtained hollow product was immersed in a 5 weight percent aqueous solution of peroxodisulfuric acid (30 ° C.) for 30 minutes, and then removed from the aqueous solution to remove excess solution adhering to the hollow product. Put in. About 120 ° C. steam was blown into the reaction vessel, and heat treatment was performed for 30 minutes so as to keep the inside of the vessel at 90 ° C. or higher. Next, after the heat-treated hollow material was washed with hot water at 90 ° C. for 30 minutes, a hollow fiber membrane was obtained. The test results of the manufactured hollow fiber membrane are shown in Table 2. Next, the produced hollow fiber membrane was dried for 12 hours in a blow dryer set at 40 ° C. Table 3 shows water permeability retention ratios before and after drying. Scanning electron micrographs taken for observing the film structure are shown in FIGS.

比較例２
ポリフッ化ビニリデン（ソルベイ ソレクシス株式会社製、ＳＯＬＥＦ６０１０）と、溶剤として安息香酸ヘキシル（和光純薬株式会社製、試薬１級）と、無機粒子としてシリカ（株式会社トクヤマ製、ファインシールＸ−４５）と、凝集剤としてモノラウリン酸ヘキサグリセリル（日光ケミカルズ株式会社製、Ｈｅｘａｇｌｙｎ １−Ｌ）とを、重量比で２０：８０：１０：１０の割合となるように製膜原液を調製した。この製膜原液の組成を表１に示す。該組成比の安息香酸ヘキシルとモノラウリン酸ヘキサグリセリルにおいて、上部臨界溶解温度は観察されず、いずれの温度においても非相容であった。 Comparative Example 2
Polyvinylidene fluoride (Solef 6010 manufactured by Solvay Solexis Co., Ltd.), hexyl benzoate (manufactured by Wako Pure Chemical Industries, Ltd., reagent grade 1) as a solvent, silica (manufactured by Tokuyama Co., Ltd., Fine Seal X-45) as inorganic particles, A film-forming stock solution was prepared so that hexaglyceryl monolaurate (manufactured by Nikko Chemicals Co., Ltd., Hexaglyn 1-L) as a flocculant was in a weight ratio of 20: 80: 10: 10. The composition of this film forming stock solution is shown in Table 1. In this composition ratio of hexyl benzoate and hexaglyceryl monolaurate, the upper critical solution temperature was not observed and was incompatible at any temperature.

上記した製膜原液を、二軸混練押出機中で加熱混練（温度２４０℃）して、押出したストランドをペレタイザーに通すことでチップ化した。このチップを、外径１．６ｍｍ、内径０．８ｍｍの二重環構造のノズルを装着した押出機（２３０℃）を用いて押出した。このときテトラエチレングリコールを押出物の中空部内に注入した。   The film-forming stock solution described above was heated and kneaded (temperature 240 ° C.) in a twin-screw kneading extruder, and the extruded strand was passed through a pelletizer to form chips. This chip was extruded using an extruder (230 ° C.) equipped with a double ring nozzle having an outer diameter of 1.6 mm and an inner diameter of 0.8 mm. At this time, tetraethylene glycol was injected into the hollow portion of the extrudate.

紡口から空気中に押し出した押出成形物を、３ｃｍの空中走行距離を経て、水浴中（温度３０℃）に入れ、約１００ｃｍ水浴中を通過させて冷却固化させた。次いで、得られた中空糸を５０℃のメタノール中で６０分の浸漬を２回繰り返して溶剤（安息香酸ヘキシル）と凝集剤（モノラウリン酸ヘキサグリセリル）、さらに注入液（テトラエチレングリコール）を抽出除去した。   The extruded product extruded into the air from the spinning nozzle was placed in a water bath (temperature 30 ° C.) through an air travel distance of 3 cm, and allowed to cool and solidify by passing through a water bath of about 100 cm. Next, the obtained hollow fiber was immersed in methanol at 50 ° C. for 60 minutes twice to extract and remove the solvent (hexyl benzoate), the flocculant (hexaglyceryl monolaurate), and the injection solution (tetraethylene glycol). did.

このようにして得られた中空糸状物を８０℃の熱水中で繊維方向に原長の約２倍長となるよう延伸処理をした後に、１００℃の熱水中で熱固定を行ない、次いで４０℃の重量パーセント濃度５％水酸化ナトリウム水溶液中で１２０分浸漬して無機粒子（シリカ）を抽出除去した後に、水洗工程を経て中空糸膜を得た。試験結果を表２に示す。次いで、製造した中空糸膜を４０℃に設定した送風乾燥機内で１２時間乾燥させた。乾燥前後における透水性能保持率を表３に示す。また膜構造を観察するにあたって撮影した走査型電子顕微鏡写真を図５に示す。   The hollow fiber-like material thus obtained was stretched in hot water at 80 ° C. so as to be about twice as long as the original length in the fiber direction, and then heat-set in hot water at 100 ° C., After immersing in an aqueous solution of sodium hydroxide at a weight percent concentration of 5% at 40 ° C. for 120 minutes to extract and remove inorganic particles (silica), a hollow fiber membrane was obtained through a water washing step. The test results are shown in Table 2. Next, the produced hollow fiber membrane was dried for 12 hours in a blow dryer set at 40 ° C. Table 3 shows water permeability retention ratios before and after drying. A scanning electron micrograph taken for observing the film structure is shown in FIG.

ポリフッ化ビニリデン（ソルベイ ソレクシス株式会社製、ＳＯＬＥＦ６０１０）と、溶剤としてε−カプロラクトンと、無機粒子として疎水性シリカ（日本アエロジル株式会社製、Ｒ−９７２）と、凝集剤としてグリセリンとを、重量比で３６：５４：１８：１２の割合となるように混合液を調製した。該組成比のε−カプロラクトンとグリセリンの上部臨界溶解温度は、３５．８℃であった。   Polyvinylidene fluoride (Solef 6010, Solvay Solexis Co., Ltd.), ε-caprolactone as a solvent, hydrophobic silica (N-Aerosil Co., Ltd., R-972) as inorganic particles, and glycerin as a flocculant in weight ratio A mixed solution was prepared so as to have a ratio of 36: 54: 18: 12. The upper critical dissolution temperature of ε-caprolactone and glycerin having the composition ratio was 35.8 ° C.

上記した混合液を、二軸混練押出機中で加熱混練（温度１６５℃）して、押出したストランドをペレタイザーに通すことでチップ化した。このチップを、外径１．６ｍｍ、内径０．８ｍｍの二重環構造のノズルを装着した押出機（１５０℃）を用いて押出した。このときテトラエチレングリコールを押出物の中空部内に注入した。   The above mixed solution was heated and kneaded (temperature: 165 ° C.) in a twin-screw kneading extruder, and the extruded strand was passed through a pelletizer to form chips. This chip was extruded using an extruder (150 ° C.) equipped with a double ring nozzle having an outer diameter of 1.6 mm and an inner diameter of 0.8 mm. At this time, tetraethylene glycol was injected into the hollow portion of the extrudate.

紡口から空気中に押し出した押出成形物を、３ｃｍの空中走行距離を経て、重量パーセント濃度２０％硫酸ナトリウム水溶液からなる水浴中（温度４０℃）に入れ、約１００ｃｍ水浴中を通過させて凝固させた。次いで、溶剤、凝集剤および無機粒子の大部分が中空糸状物中に残存している状態で、９０℃の熱水中で繊維方向に原長の約２．０倍長となるよう延伸処理をした後、次いで、得られた中空糸状物を９５℃の流水中で１８０分間熱処理と溶剤（ガンマ-ブチロラクトン）、凝集剤（グリセリン）、注入液（テトラエチレングリコール）の抽出除去を行った。
The extruded product extruded into the air from the nozzle is placed in a water bath (temperature: 40 ° C.) consisting of a 20% aqueous solution of sodium sulfate by weight over a distance of 3 cm and solidified by passing through an approximately 100 cm water bath. I let you. Next, in a state where most of the solvent, the flocculant and the inorganic particles remain in the hollow fiber-like material, the drawing treatment is performed so that the length becomes about 2.0 times the original length in the fiber direction in hot water at 90 ° C. Then, the obtained hollow fiber-like material was heat-treated in flowing water at 95 ° C. for 180 minutes, and the solvent (gamma-butyrolactone), the flocculant (glycerin), and the injection solution (tetraethylene glycol) were extracted and removed.

このようにして得られた中空糸状物を４０℃の重量パーセント濃度５％水酸化ナトリウム水溶液中で１２０分浸漬して無機粒子（シリカ）を抽出除去した後に、水洗工程を経て中空糸膜を得た。製造した中空糸膜の試験結果を表２に示す。   The hollow fiber obtained in this manner is immersed in an aqueous solution of sodium hydroxide at a weight percent concentration of 5% at 40 ° C. for 120 minutes to extract and remove inorganic particles (silica), and then a hollow fiber membrane is obtained through a washing step. It was. The test results of the manufactured hollow fiber membrane are shown in Table 2.

９５℃の流水中で１２０分間熱処理と溶剤、凝集剤、注入液の抽出除去を行った以外は、実施例１と同様にして中空糸膜を得た。製造した中空糸膜のＩＲ測定により求めたＲ１は２．１であった。 A hollow fiber membrane was obtained in the same manner as in Example 1, except that heat treatment was performed for 120 minutes in flowing water at 95 ° C., and the solvent, flocculant, and injection solution were extracted and removed. R 1 obtained by IR measurement of the produced hollow fiber membrane was 2.1.

得られた中空糸膜の耐酸化剤性を評価するため、次亜塩素酸ナトリウム水溶液（有効塩素濃度：５０００ｐｐｍ）に６０℃で７日間浸漬し、その物性評価（引張破断強度）を測定し、結果を表３に記載した。 In order to evaluate the oxidation resistance of the obtained hollow fiber membrane, it was immersed in an aqueous sodium hypochlorite solution (effective chlorine concentration: 5000 ppm) at 60 ° C. for 7 days, and its physical property evaluation (tensile breaking strength) was measured. The results are shown in Table 3.

８５℃の流水中で１８０分間熱処理と溶剤、凝集剤、注入液の抽出除去を行った以外は、実施例１と同様にして中空糸膜を得た。製造した中空糸膜のＩＲ測定により求めたＲ１は１．９であった。 A hollow fiber membrane was obtained in the same manner as in Example 1 except that the heat treatment was performed for 180 minutes in flowing water at 85 ° C., and the solvent, the flocculant, and the injection solution were extracted and removed. R 1 obtained by IR measurement of the produced hollow fiber membrane was 1.9.

得られた中空糸膜の耐酸化剤性を評価するため、次亜塩素酸ナトリウム水溶液（有効塩素濃度：５０００ｐｐｍ）に６０℃で７日間浸漬し、その物性評価（引張破断強度）を測定し、結果を表３に記載した。 In order to evaluate the oxidation resistance of the obtained hollow fiber membrane, it was immersed in an aqueous sodium hypochlorite solution (effective chlorine concentration: 5000 ppm) at 60 ° C. for 7 days, and its physical property evaluation (tensile breaking strength) was measured. The results are shown in Table 3.

比較例３
４５℃の流水中で１８０分間熱処理と溶剤、凝集剤、注入液の抽出除去を行った以外は、実施例１と同様にして中空糸膜を得た。製造した中空糸膜のＩＲ測定により求めたＲ１は０．９であった。 Comparative Example 3
A hollow fiber membrane was obtained in the same manner as in Example 1 except that the heat treatment was performed for 180 minutes in flowing water at 45 ° C. and the solvent, the flocculant, and the injection solution were extracted and removed. R 1 obtained by IR measurement of the produced hollow fiber membrane was 0.9.

得られた中空糸膜の耐酸化剤性を評価するため、次亜塩素酸ナトリウム水溶液（有効塩素濃度：５０００ｐｐｍ）に６０℃で７日間浸漬し、その物性評価（引張破断強度）を測定し、結果を表３に記載した。 In order to evaluate the oxidation resistance of the obtained hollow fiber membrane, it was immersed in an aqueous sodium hypochlorite solution (effective chlorine concentration: 5000 ppm) at 60 ° C. for 7 days, and its physical property evaluation (tensile breaking strength) was measured. The results are shown in Table 3.

Figure 0005318385
Figure 0005318385

Figure 0005318385
Figure 0005318385

Figure 0005318385
Figure 0005318385

Figure 0005318385
Figure 0005318385

実施例３の方法により製造したフッ化ビニリデン系樹脂多孔膜の外表面の走査型電子顕微鏡写真である。4 is a scanning electron micrograph of the outer surface of a vinylidene fluoride resin porous membrane produced by the method of Example 3. FIG. 実施例３の方法により製造したフッ化ビニリデン系樹脂多孔膜の内表面の走査型電子顕微鏡写真である。4 is a scanning electron micrograph of the inner surface of a vinylidene fluoride resin porous membrane produced by the method of Example 3. FIG. 実施例３の方法により製造したフッ化ビニリデン系樹脂多孔膜の内表面の走査型電子顕微鏡写真である。4 is a scanning electron micrograph of the inner surface of a vinylidene fluoride resin porous membrane produced by the method of Example 3. FIG. 実施例３の方法により製造したフッ化ビニリデン系樹脂多孔膜の断面の走査型電子顕微鏡写真である。4 is a scanning electron micrograph of a cross section of a vinylidene fluoride resin porous membrane produced by the method of Example 3. FIG. 比較例２の方法により製造したフッ化ビニリデン系樹脂多孔膜の内表面の走査型電子顕微鏡写真である。4 is a scanning electron micrograph of the inner surface of a vinylidene fluoride resin porous membrane produced by the method of Comparative Example 2. FIG. 実施例１の方法により製造した中空糸膜のＩＲチャートである。2 is an IR chart of a hollow fiber membrane manufactured by the method of Example 1. FIG.

Claims (10)

フッ化ビニリデン系樹脂、溶剤、無機粒子及び凝集剤で構成され、該溶剤は水溶性溶剤であり、該無機粒子と該凝集剤は親和性を有し、かつ該溶剤と該凝集剤は相容しない又は上部臨界溶解温度を有する多孔膜製造原液を冷却させることにより相分離を誘起させたのちに固化させ、次いで溶剤、無機粒子、凝集剤のいずれかを抽出終了する前に多孔膜を延伸する工程および７０〜１６０℃の範囲で熱処理する工程を含む製造方法により得られる、フッ化ビニリデン系樹脂よりなる多孔膜であって、一表面に長径と短径の比の平均が１：１以上かつ５：１より小さい円形または楕円形の微細孔を有し、他表面に長径と短径の比の平均が５．５：１以上かつ６．３：１以下の短冊状微細孔を有している分画粒子径が０．２μｍ以上であることを特徴とするフッ化ビニリデン系樹脂多孔膜。 It is composed of a vinylidene fluoride resin, a solvent, inorganic particles and a flocculant, the solvent is a water-soluble solvent, the inorganic particles and the flocculant have affinity, and the solvent and the flocculant are compatible. Or by allowing the porous membrane production stock solution having the upper critical dissolution temperature to cool, inducing phase separation to solidify, and then stretching the porous membrane before completion of extraction of any of the solvent, inorganic particles, and flocculant A porous film made of a vinylidene fluoride-based resin , obtained by a manufacturing method including a step and a step of heat-treating in a range of 70 to 160 ° C., wherein an average ratio of a major axis to a minor axis is 1: 1 or more on one surface; It has circular or elliptical micropores smaller than 5: 1, and other surfaces have strip-like micropores with an average ratio of major axis to minor axis of 5.5: 1 or more and 6.3: 1 or less. The fractional particle size is 0.2 μm or more. Porous membrane of vinylidene fluoride resin to. 多孔膜が９０〜９９重量％のフッ化ビニリデン系樹脂と１〜１０重量％の親水性樹脂とのブレンドポリマーで構成されることを特徴とする請求項１に記載のフッ化ビニリデン系樹脂多孔膜。   2. The vinylidene fluoride resin porous membrane according to claim 1, wherein the porous membrane is composed of a blend polymer of 90 to 99% by weight of vinylidene fluoride resin and 1 to 10% by weight of hydrophilic resin. . 親水性樹脂がビニルピロリドン系樹脂である請求項１または２に記載のフッ化ビニリデン系樹脂多孔膜。   The vinylidene fluoride resin porous membrane according to claim 1 or 2, wherein the hydrophilic resin is a vinylpyrrolidone resin. 多孔膜が中空糸膜であることを特徴とする請求項１〜３のいずれか１項に記載のフッ化ビニリデン系樹脂多孔膜。   The vinylidene fluoride-based resin porous membrane according to any one of claims 1 to 3, wherein the porous membrane is a hollow fiber membrane. 多孔膜の長径と短径の比の平均が１：１以上かつ５：１より小さい円形または楕円形の微細孔を有する一表面が中空糸膜の外表面であり、多孔膜の長径と短径の比の平均が５．５：１以上かつ６．３：１以下の短冊状微細孔を有している他表面が中空糸膜の内表面であることを特徴とする請求項４に記載のフッ化ビニリデン系樹脂多孔中空糸膜。 One surface having circular or elliptical micropores with an average ratio of major axis to minor axis of the porous membrane of 1: 1 or more and smaller than 5: 1 is the outer surface of the hollow fiber membrane, and the major axis and minor axis of the porous membrane 5. The other surface having strip-shaped micropores having an average ratio of 5.5: 1 to 6.3: 1 is the inner surface of the hollow fiber membrane. Vinylidene fluoride resin porous hollow fiber membrane. フッ化ビニリデン系樹脂、溶剤、無機粒子及び凝集剤で構成され、該溶剤は水溶性溶剤であり、該無機粒子と該凝集剤は親和性を有し、かつ該溶剤と該凝集剤は相容しない又は上部臨界溶解温度を有する多孔膜製造原液を冷却させることにより相分離を誘起させたのちに固化させ、次いで溶剤、無機粒子、凝集剤のいずれかを抽出終了する前に多孔膜を延伸する工程および７０〜１６０℃の範囲で熱処理する工程を含むことを特徴とする請求項１に記載のフッ化ビニリデン系樹脂多孔膜の製造方法。   It is composed of a vinylidene fluoride resin, a solvent, inorganic particles and a flocculant, the solvent is a water-soluble solvent, the inorganic particles and the flocculant have affinity, and the solvent and the flocculant are compatible. Or by allowing the porous membrane production stock solution having the upper critical dissolution temperature to cool, inducing phase separation to solidify, and then stretching the porous membrane before completion of extraction of any of the solvent, inorganic particles, and flocculant 2. The method for producing a vinylidene fluoride resin porous membrane according to claim 1, comprising a step and a heat treatment in a range of 70 to 160 ° C. 3. 多孔膜が９０〜９９重量％のフッ化ビニリデン系樹脂と１〜１０重量％の親水性樹脂とのブレンドポリマーで構成されることを特徴とする請求項６に記載のフッ化ビニリデン系樹脂多孔膜の製造方法。   7. The vinylidene fluoride resin porous membrane according to claim 6, wherein the porous membrane is composed of a blend polymer of 90 to 99% by weight of vinylidene fluoride resin and 1 to 10% by weight of hydrophilic resin. Manufacturing method. 親水性樹脂がビニルピロリドン系樹脂である請求項６または７に記載のフッ化ビニリデン系樹脂多孔膜の製造方法。   The method for producing a vinylidene fluoride resin porous membrane according to claim 6 or 7, wherein the hydrophilic resin is a vinylpyrrolidone resin. 多孔膜が中空糸膜であることを特徴とする請求項６〜８のいずれか１項に記載のフッ化ビニリデン系樹脂多孔膜の製造方法。   The method for producing a vinylidene fluoride resin porous membrane according to any one of claims 6 to 8, wherein the porous membrane is a hollow fiber membrane. 多孔膜の長径と短径の比の平均が１：１以上かつ５：１より小さい円形または楕円形の微細孔を有する一表面が中空糸膜の外表面であり、多孔膜の長径と短径の比の平均が５．５：１以上かつ６．３：１以下の短冊状微細孔を有している他表面が中空糸膜の内表面であることを特徴とする請求項９に記載のフッ化ビニリデン系樹脂多孔中空糸膜の製造方法。 One surface having circular or elliptical micropores with an average ratio of major axis to minor axis of the porous membrane of 1: 1 or more and smaller than 5: 1 is the outer surface of the hollow fiber membrane, and the major axis and minor axis of the porous membrane The other surface having strip-shaped micropores having an average ratio of 5.5: 1 to 6.3: 1 is the inner surface of the hollow fiber membrane. A method for producing a vinylidene fluoride resin porous hollow fiber membrane.
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