JP2006063095A - Method for producing vinylidene fluoride-based resin porous membrane - Google Patents
Method for producing vinylidene fluoride-based resin porous membrane Download PDFInfo
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本発明は、薬剤または細菌等の精密濾過膜として使用される多孔質膜、あるいは電池用セパレータとして使用されるフッ化ビニリデン系樹脂多孔膜の製造方法に関する。 The present invention relates to a method for producing a porous membrane used as a microfiltration membrane for drugs or bacteria, or a vinylidene fluoride resin porous membrane used as a battery separator.
従来より合成樹脂系多孔質膜は気体隔膜分離、気液分離、固液分離等の分離膜として、あるいは絶縁材、保温材、遮音材、断熱材などとして多方面に利用されている。これらの内、特に分離膜として使用される場合には分離機能に影響を与える以下の特性が要求される。まず、多孔質膜の分離効率を目的とする適度な空孔率を有すること、分離精度の向上を目的とした均一な孔径分布を有すること、加えて分離対象物に最適な孔径を有することが求められる。また、膜構成素材の性質としては、分離対象物の特性に対する耐薬品性、耐候性、耐熱性、強度等が要求される。さらに、多孔質膜使用時における機械的強度として充分な破断点伸度、破断点応力などが要求される。 Synthetic resin-based porous membranes have been used in various fields as separation membranes such as gas diaphragm separation, gas-liquid separation, and solid-liquid separation, or as insulating materials, heat insulating materials, sound insulation materials, heat insulating materials, and the like. Among these, particularly when used as a separation membrane, the following characteristics that affect the separation function are required. First, it must have an appropriate porosity for separation efficiency of the porous membrane, have a uniform pore size distribution for the purpose of improving separation accuracy, and have an optimum pore size for the separation object Desired. Further, as the properties of the membrane constituent material, chemical resistance, weather resistance, heat resistance, strength and the like with respect to the characteristics of the separation object are required. Furthermore, sufficient elongation at break and stress at break are required as mechanical strength when using the porous membrane.
この点、従来から開発されているポリオレフィン樹脂系の多孔膜（例えば特許文献１）は、分離膜としての使用後の逆洗ならびにオゾン処理における耐薬品性に問題が残る。 In this respect, a polyolefin resin-based porous membrane (for example, Patent Document 1) that has been conventionally developed has a problem in chemical resistance in backwashing and ozone treatment after use as a separation membrane.
フッ化ビニリデン系樹脂は耐候性、耐薬品性、耐熱性、強度等に優れているため、これら分離用多孔質膜への応用が検討されている。しかしながら、フッ化ビニリデン系樹脂は、前記した優れた特性を有する反面、非粘着性、低相溶性であるため成形性は必ずしもよくない。また、多孔質膜の開発としては分離性能向上を目的とした高い空孔率、狭い孔径分布を追求する余り、機械的強度において満足すべきものは得られていなかった。このため強度を補充するために、濾過膜として使用する場合には多孔質膜にサポートする膜を重ね合せて機械的物性を高めて使用しているのが現状である。また、電池用セパレータに使用される場合等には、多孔質膜が芯材に巻き付けて使用されることから、電池製造時の巻付け工程に耐え得る充分な破断点伸度、破断点応力等の機械的物性を有することが望まれる。加えて電池用セパレータに使用される際には、電極に使用される活物質の微粉末を遮断できる分布幅の狭い貫通孔径と多孔質膜を芯材に巻き付けた後に行われる電解液の高効率な含浸性が望まれている。また精密濾過膜として使用される際には、長期間に亘って高い濾過性を保持することが望まれている。 Since vinylidene fluoride resin is excellent in weather resistance, chemical resistance, heat resistance, strength, etc., application to these porous membranes for separation is being studied. However, the vinylidene fluoride resin has the above-described excellent characteristics, but it is non-adhesive and has low compatibility, so that the moldability is not always good. Further, as a porous membrane development, a high porosity and narrow pore size distribution aimed at improving separation performance have been pursued, and no satisfactory mechanical strength has been obtained. For this reason, in order to supplement the strength, in the case of using as a filtration membrane, a membrane supporting it is superposed on a porous membrane and the mechanical properties are increased. In addition, when used for battery separators, etc., since the porous film is wound around the core material, sufficient elongation at break, stress at break, etc. that can withstand the winding process during battery production It is desirable to have the following mechanical properties. In addition, when used in battery separators, the high efficiency of the electrolyte performed after winding through holes with a narrow distribution width that can block the fine powder of active material used for electrodes and a porous membrane around the core material A good impregnation property is desired. When used as a microfiltration membrane, it is desired to maintain high filterability for a long period of time.
フッ化ビニリデン系樹脂多孔膜の製造方法として、ポリフッ化ビニリデン樹脂にフタル酸ジエチル等の有機液状体と無機微粉体として疎水性シリカを混合し、溶融成形後に有機液状体と疎水性シリカを抽出する方法が開示されている（特許文献２）。こうして得られる多孔質膜は比較的大きい機械的強度を有する。しかしこの方法では、疎水性シリカを抽出するためにアルカリ水溶液を用いることから、膜を構成するフッ化ビニリデン系樹脂が劣化し易い。 As a method for producing a polyvinylidene fluoride resin porous membrane, an organic liquid such as diethyl phthalate and hydrophobic silica are mixed with polyvinylidene fluoride resin as an inorganic fine powder, and the organic liquid and hydrophobic silica are extracted after melt molding. A method is disclosed (Patent Document 2). The porous membrane thus obtained has a relatively high mechanical strength. However, in this method, since an alkaline aqueous solution is used to extract hydrophobic silica, the vinylidene fluoride resin constituting the film is easily deteriorated.
これに対し、本発明等は、特定の分子量特性を有するフッ化ビニリデン系樹脂を延伸を含む多孔化工程に付す方法が適度の寸法と分布の微細孔を有し且つ機械的強度の優れたフッ化ビニリデン系樹脂多孔膜の形成に有効であることを見出して、一連の提案を行っている（特許文献３他）。しかしながら、多孔膜をろ過膜とし使用する場合に必要なろ過性能（透水量）および機械的性能等を含む総合性能に関して、一層の改善の要求は強い。 On the other hand, in the present invention, a method of subjecting a vinylidene fluoride resin having a specific molecular weight characteristic to a pore forming process including stretching has fine pores with appropriate dimensions and distribution and has excellent mechanical strength. A series of proposals have been made by finding that it is effective for forming a vinylidene fluoride resin porous membrane (Patent Document 3 and others). However, there is a strong demand for further improvement in terms of overall performance including filtration performance (water permeability) and mechanical performance required when using a porous membrane as a filtration membrane.
また、延伸されたフッ化ビニリデン系樹脂多孔膜を空気中あるいは水中で緩和処理することも提案されている(特許文献４および５)が、このような緩和処理によっては透水量の改善は得られない(後記比較例３，４および６)。
従って、本発明の主要な目的は、適度の寸法と分布の微細孔を有し且つ機械的強度が優れるとともに、透水能が一層改善されたフッ化ビニリデン系樹脂多孔膜を提供することにある。 Accordingly, a main object of the present invention is to provide a vinylidene fluoride resin porous membrane having fine pores of appropriate size and distribution, excellent mechanical strength, and further improved water permeability.
本発明者らは、上述の目的で研究した結果、延伸工程を経て得られたフッ化ビニリデン系樹脂多孔膜を、特定の液体による湿潤下に緩和処理することにより、見かけの細孔径分布は余り変らず、機械的強度も良好に維持した範囲内で、膜の透水能が著しく改善されることが見出された。 The inventors of the present invention have studied the above-mentioned purpose, and as a result of relaxing the vinylidene fluoride resin porous membrane obtained through the stretching process under the wet condition with a specific liquid, the apparent pore size distribution is not much. It was found that the water permeability of the membrane was remarkably improved within the range in which the mechanical strength was maintained well.
すなわち、本発明のフッ化ビニリデン系樹脂多孔膜の製造方法は、延伸されたフッ化ビニリデン系樹脂多孔膜を、該フッ化ビニリデン系樹脂多孔膜を濡らす液体による湿潤下に緩和させることを特徴とするものである。 That is, the method for producing a vinylidene fluoride resin porous membrane of the present invention is characterized in that the stretched vinylidene fluoride resin porous membrane is relaxed by being wetted with a liquid that wets the vinylidene fluoride resin porous membrane. To do.
本発明に従い、膜の透水能が著しく向上する理由は必ずしも明らかではないが、細孔分布の数値が余り変らないことから考えて、延伸されたフッ化ビニリデン系樹脂多孔膜が濡れのよい液体の湿潤下に微細構造変化を起こし、透水機構に関与する膜の厚さ方向に連通する微細孔の割合が増大したものと推定される。 The reason why the water permeability of the membrane is remarkably improved according to the present invention is not necessarily clear, but considering that the numerical value of the pore distribution does not change so much, the stretched vinylidene fluoride resin porous membrane is a liquid with good wettability. It is presumed that the ratio of micropores communicating in the thickness direction of the membrane involved in the water permeation mechanism increased due to microstructural changes under wet conditions.
上述したように、本発明のフッ化ビニリデン系樹脂多孔膜の製造方法は、延伸されたフッ化ビニリデン系樹脂多孔膜を特定の液体による湿潤下に緩和処理することを特徴とするものである。延伸されたフッ化ビニリデン系樹脂多孔膜の形成法は、基本的には任意であるが、効果的な延伸と多孔形成を通じて特性の優れた多孔膜を得るために、所定の分子量特性を有するフッ化ビニリデン系樹脂と、可塑剤とフッ化ビニリデン系樹脂の良溶媒からなる組成物を膜状(好ましくは中空糸膜状)に溶融押出し、その片側面から（外側から）優先的に冷却して固化成膜した後、可塑剤を抽出し、更に延伸して多孔膜を形成することが好ましい。以下、この好ましい態様について、順次説明する。 As described above, the method for producing a vinylidene fluoride-based resin porous membrane of the present invention is characterized in that the stretched vinylidene fluoride-based resin porous membrane is subjected to relaxation treatment while being wetted with a specific liquid. The method of forming the stretched vinylidene fluoride resin porous membrane is basically arbitrary, but in order to obtain a porous membrane having excellent characteristics through effective stretching and pore formation, a fluoropolymer having a predetermined molecular weight characteristic is obtained. A composition comprising a vinylidene fluoride resin and a good solvent of a plasticizer and a vinylidene fluoride resin is melt-extruded into a film (preferably a hollow fiber film) and cooled preferentially from one side (from the outside). After the solidified film is formed, the plasticizer is preferably extracted and further stretched to form a porous film. Hereinafter, this preferable aspect is demonstrated one by one.
（フッ化ビニリデン系樹脂）
本発明においては、主たる膜原料として、重量平均分子量（Ｍｗ）が２０万〜６０万であるフッ化ビニリデン系樹脂を用いることが好ましい。Ｍｗが２０万以下では得られる多孔膜の機械的強度が小さくなる。またＭｗが６０万以上であるとフッ化ビニリデン系樹脂と可塑剤との相分離構造が過度に微細になり、得られた多孔膜を精密濾過膜として用いる場合の透水量が低下する。
(Vinylidene fluoride resin)
In the present invention, it is preferable to use a vinylidene fluoride resin having a weight average molecular weight (Mw) of 200,000 to 600,000 as a main film material. When the Mw is 200,000 or less, the mechanical strength of the obtained porous film becomes small. On the other hand, if Mw is 600,000 or more, the phase separation structure between the vinylidene fluoride resin and the plasticizer becomes excessively fine, and the water permeability when the obtained porous membrane is used as a microfiltration membrane is reduced.
本発明において、フッ化ビニリデン系樹脂としては、フッ化ビニリデンの単独重合体、すなわちポリフッ化ビニリデン、他の共重合可能なモノマーとの共重合体あるいはこれらの混合物が用いられる。フッ化ビニリデン系樹脂と共重合可能なモノマーとしては、四フッ化エチレン、六フッ化プロピレン、三フッ化エチレン、三フッ化塩化エチレン、フッ化ビニル等の一種又は二種以上を用いることができる。フッ化ビニリデン系樹脂は、構成単位としてフッ化ビニリデンを７０モル％以上含有することが好ましい。なかでも機械的強度の高さからフッ化ビニリデン１００モル％からなる単独重合体を用いることが好ましい。 In the present invention, as the vinylidene fluoride resin, a homopolymer of vinylidene fluoride, that is, a copolymer of polyvinylidene fluoride, another copolymerizable monomer, or a mixture thereof is used. As the monomer copolymerizable with the vinylidene fluoride resin, one or more of tetrafluoroethylene, hexafluoropropylene, ethylene trifluoride, ethylene trifluoride chloride, vinyl fluoride and the like can be used. . The vinylidene fluoride resin preferably contains 70 mol% or more of vinylidene fluoride as a structural unit. Among them, it is preferable to use a homopolymer composed of 100 mol% of vinylidene fluoride because of its high mechanical strength.
上記したような比較的高分子量のフッ化ビニリデン系樹脂は、好ましくは乳化重合あるいは懸濁重合、特に好ましくは懸濁重合により得ることができる。 The relatively high molecular weight vinylidene fluoride resin as described above can be obtained by emulsion polymerization or suspension polymerization, particularly preferably suspension polymerization.
本発明の多孔膜を形成するフッ化ビニリデン系樹脂は、上記したように重量平均分子量が２０万〜６０万と比較的大きな分子量を有することに加えて、ＤＳＣ測定による樹脂本来の融点Ｔｍ２（℃）と結晶化温度Ｔｃ（℃）との差Ｔｍ２−Ｔｃが３２℃以下、特に３０℃以下、で代表される良好な結晶特性、すなわち冷却に際しての球状結晶成長を抑制した結晶特性、を有することが好ましい。 The vinylidene fluoride resin that forms the porous film of the present invention has a relatively large molecular weight of 200,000 to 600,000 as described above, and also has an inherent melting point Tm2 (° C. ) And the crystallization temperature Tc (° C.) have good crystal characteristics represented by Tm2−Tc of 32 ° C. or less, particularly 30 ° C. or less, that is, crystal characteristics that suppress the growth of spherical crystals during cooling. Is preferred.
ここで樹脂本来の融点Ｔｍ２（℃）は、入手された試料樹脂あるいは多孔膜を形成する樹脂を、そのままＤＳＣによる昇温過程に付すことにより測定される融点Ｔｍ１（℃）とは区別されるものである。すなわち、一般に入手されたフッ化ビニリデン系樹脂は、その製造過程あるいは加熱成形過程等において受けた熱および機械的履歴により、樹脂本来の融点Ｔｍ２（℃）とは異なる融点Ｔｍ１（℃）を示すものであり、上記したフッ化ビニリデン系樹脂の融点Ｔｍ２（℃）は、入手された試料樹脂を、一旦、所定の昇降温サイクルに付して、熱および機械的履歴を除いた後に、再度ＤＳＣ昇温過程で見出される融点（結晶融解に伴なう吸熱のピーク温度）として規定されるものであり、その測定法の詳細は後述実施例の記載に先立って記載する。 Here, the original melting point Tm2 (° C.) of the resin is distinguished from the melting point Tm1 (° C.) measured by subjecting the obtained sample resin or the resin forming the porous film to the temperature rising process by DSC as it is. It is. That is, generally-available vinylidene fluoride resins exhibit a melting point Tm1 (° C.) different from the original melting point Tm2 (° C.) due to the heat and mechanical history received during the manufacturing process or thermoforming process. The melting point Tm2 (° C.) of the above-mentioned vinylidene fluoride resin is determined by subjecting the obtained sample resin to a predetermined heating / cooling cycle to remove heat and mechanical history and then increasing the DSC temperature again. It is defined as the melting point found in the temperature process (endothermic peak temperature accompanying crystal melting), and details of the measurement method will be described prior to the description of the examples described later.
本発明で好ましく用いられるフッ化ビニリデン系樹脂の結晶化温度を代表するＴｍ２−Ｔｃ≦３２℃の条件は、例えば共重合によるＴｍ２の低下によっても達成可能であるが、この場合には、生成する多孔膜の耐薬品性が低下する傾向が認められる場合もある。従って、より好ましい態様においては、重量平均分子量（Ｍｗ）が１５万〜６０万であるフッ化ビニリデン系樹脂７０〜９８重量％をマトリクス（主体）樹脂とし、これよりＭｗが１．８倍以上、好ましくは２倍以上であり且つ１２０万以下である結晶特性改質用の高分子量フッ化ビニリデン系樹脂を２〜３０重量％添加することにより得た、フッ化ビニリデン系樹脂混合物が用いられる。このような方法によればマトリクス樹脂単独の（好ましくは１７０〜１８０℃の範囲内のＴｍ２により代表される）結晶融点を変化させることなく、有意に結晶化温度Ｔｃを上昇させることができる。より詳しくはＴｃを上昇させることにより、膜表面に比べて冷却の遅い膜内部ならびに片側面からの優先的冷却に際しては膜内部から反対面にかけてフッ化ビニリデン系樹脂の固化を早めることが可能になり、球状粒子の成長を抑制することができる。Ｔｃは、好ましくは１４３℃以上である。 The condition of Tm2−Tc ≦ 32 ° C., which represents the crystallization temperature of the vinylidene fluoride resin preferably used in the present invention, can be achieved also by, for example, a decrease in Tm2 due to copolymerization. There is a case where the chemical resistance of the porous film tends to decrease. Therefore, in a more preferable embodiment, 70 to 98% by weight of vinylidene fluoride resin having a weight average molecular weight (Mw) of 150,000 to 600,000 is used as a matrix (main) resin, and Mw is 1.8 times or more from this. Preferably, a vinylidene fluoride resin mixture obtained by adding 2 to 30% by weight of a high molecular weight vinylidene fluoride resin for crystal property modification that is 2 times or more and 1.2 million or less is used. According to such a method, the crystallization temperature Tc can be significantly increased without changing the crystal melting point of the matrix resin alone (preferably represented by Tm2 within the range of 170 to 180 ° C.). More specifically, by increasing Tc, it becomes possible to accelerate the solidification of the vinylidene fluoride resin from the inside of the film to the opposite surface when cooling from the inside of the film, which is slower than the film surface, and from one side. The growth of spherical particles can be suppressed. Tc is preferably 143 ° C. or higher.
高分子量フッ化ビニリデン系樹脂のＭｗがマトリクス樹脂のＭｗの１．８倍未満であると球状粒子構造の形成を十分には抑制し難く、一方、１２０万以上であるとマトリックス樹脂中に均一に分散させることが困難である。 When the Mw of the high molecular weight vinylidene fluoride resin is less than 1.8 times the Mw of the matrix resin, it is difficult to sufficiently suppress the formation of the spherical particle structure. Difficult to disperse.
また、高分子量フッ化ビニリデン系樹脂の添加量が２重量％未満では球状粒子構造の形成を抑制する効果が十分でなく、一方、３０重量％を超えるとフッ化ビニリデン系樹脂と可塑剤の相分離構造が過度に微細化して、膜の透水量が低下する傾向がある。 Further, if the amount of the high molecular weight vinylidene fluoride resin is less than 2% by weight, the effect of suppressing the formation of the spherical particle structure is not sufficient, whereas if it exceeds 30% by weight, the phase of the vinylidene fluoride resin and the plasticizer is not sufficient. There is a tendency that the separation structure becomes excessively fine and the water permeability of the membrane decreases.
本発明において用いられる延伸された多孔膜の好ましい形成態様に従い、上記のフッ化ビニリデン系樹脂に、フッ化ビニリデン系樹脂の可塑剤および良溶媒を加えて膜形成用の原料組成物を形成する。 According to a preferred embodiment of the stretched porous film used in the present invention, a plasticizer of vinylidene fluoride resin and a good solvent are added to the above-mentioned vinylidene fluoride resin to form a raw material composition for film formation.
（可塑剤）
可塑剤としては、一般に、二塩基酸とグリコールからなる脂肪族系ポリエステル、例えば、アジピン酸−プロピレングリコール系、アジピン酸−１，３−ブチレングリコール系等のアジピン酸系ポリエステル；セバシン酸−プロピレングリコール系、セバシン酸系ポリエステル；アゼライン酸−プロピレングリコール系、アゼライン酸−１，３−ブチレングリコール系等のアゼライン酸系ポリエステル等が用いられる。
(Plasticizer)
The plasticizer is generally an aliphatic polyester composed of dibasic acid and glycol, for example, adipic acid-based polyester such as adipic acid-propylene glycol-based, adipic acid-1,3-butylene glycol-based; sebacic acid-propylene glycol And azelaic acid polyesters such as azelaic acid-propylene glycol and azelaic acid-1,3-butylene glycols.
（良溶媒）
また、フッ化ビニリデン系樹脂の良溶媒としては、２０〜２５０℃の温度範囲でフッ化ビニリデン系樹脂を溶解できる溶媒が用いられ、例えば、Ｎ−メチルピロリドン、ジメチルホルムアミド、ジメチルアセトアミド、ジメチルスルホキシド、メチルエチルケトン、アセトン、テトラヒドロフラン、ジオキサン、酢酸エチル、プロピレンカーボネート、シクロヘキサン、メチルイソブチルケトン、ジメチルフタレート、およびこれらの混合溶媒等が挙げられる。なかでも高温での安定性からＮ−メチルピロリドン（ＮＭＰ）が好ましい。
(Good solvent)
In addition, as a good solvent for the vinylidene fluoride resin, a solvent capable of dissolving the vinylidene fluoride resin in a temperature range of 20 to 250 ° C. is used. For example, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, Examples thereof include methyl ethyl ketone, acetone, tetrahydrofuran, dioxane, ethyl acetate, propylene carbonate, cyclohexane, methyl isobutyl ketone, dimethyl phthalate, and a mixed solvent thereof. Of these, N-methylpyrrolidone (NMP) is preferred because of its stability at high temperatures.
（組成物）
膜形成用の原料組成物は、好ましくはフッ化ビニリデン系樹脂１００重量部に対し、可塑剤７０〜２５０重量部および良溶媒５〜８０重量部を混合することにより得られる。
(Composition)
The raw material composition for forming a film is preferably obtained by mixing 70 to 250 parts by weight of a plasticizer and 5 to 80 parts by weight of a good solvent with respect to 100 parts by weight of a vinylidene fluoride resin.
可塑剤が７０重量部未満であると、空孔率が低くなるため電池セパレータにおいては電解液の含浸性が劣り、あるいは電気抵抗が増し、精密ろ過膜においてはろ過性能（透水量）に劣る。また、２５０重量部を超えると空孔率が大きくなり過ぎるため、機械的強度が低下する。 If the plasticizer is less than 70 parts by weight, the porosity will be low, so that the battery separator will have poor electrolyte impregnation properties, or electrical resistance will increase, and the microfiltration membrane will have poor filtration performance (water permeability). Moreover, since a porosity will become large when it exceeds 250 weight part, mechanical strength falls.
良溶媒が５重量部未満ではポリフッ化ビニリデン系樹脂と可塑剤を均一に混合できなかったり、あるいは混合に時間を要する。また、８０重量部を超えると可塑剤の添加量に見合った空孔率が得られない。すなわち可塑剤の抽出による効率的な空孔形成が阻害される。 If the good solvent is less than 5 parts by weight, the polyvinylidene fluoride resin and the plasticizer cannot be mixed uniformly, or mixing takes time. On the other hand, if it exceeds 80 parts by weight, the porosity corresponding to the amount of plasticizer added cannot be obtained. That is, efficient pore formation due to extraction of the plasticizer is hindered.
可塑剤と良溶媒の合計量は１００〜２５０重量部の範囲が好ましい。両者はいずれも溶融押出し組成物の粘度低減効果があり、ある程度代替的に作用する。そのうち良溶媒は、５〜３０重量％の割合が好ましい。 The total amount of the plasticizer and the good solvent is preferably in the range of 100 to 250 parts by weight. Both have the effect of reducing the viscosity of the melt-extruded composition and act to some extent as an alternative. Of these, the proportion of the good solvent is preferably 5 to 30% by weight.
（混合・溶融押出し）
溶融押出組成物は、一般に１４０〜２７０℃、好ましくは１５０〜２００℃、の温度で、中空ノズルあるいはＴ−ダイから押出されて膜状化される。従って、最終的に、上記温度範囲の均質組成物が得られる限りにおいて、フッ化ビニリデン系樹脂、可塑剤および良溶媒の混合並びに溶融形態は任意である。このような組成物を得るための好ましい態様の一つによれば、二軸混練押出機が用いられ、（好ましくは主体樹脂と結晶特性改質用樹脂の混合物からなる）フッ化ビニリデン系樹脂は、該押出機の上流側から供給され、可塑剤と良溶媒の混合物が、下流で供給され、押出機を通過して吐出されるまでに均質混合物とされる。この二軸押出機は、その長手軸方向に沿って、複数のブロックに分けて独立の温度制御が可能であり、それぞれの部位の通過物の内容により適切な温度調節がなされる。
(Mixing / melt extrusion)
The melt-extruded composition is generally formed into a film by being extruded from a hollow nozzle or a T-die at a temperature of 140 to 270 ° C, preferably 150 to 200 ° C. Therefore, as long as a homogeneous composition in the above temperature range is finally obtained, the mixing of the vinylidene fluoride resin, the plasticizer and the good solvent and the molten form are arbitrary. According to one preferred embodiment for obtaining such a composition, a biaxial kneading extruder is used, and the vinylidene fluoride resin (preferably comprising a mixture of a main resin and a crystal characteristic modifying resin) is The mixture of the plasticizer and the good solvent is supplied from the upstream side of the extruder, is supplied downstream, and is made into a homogeneous mixture before being discharged through the extruder. This twin-screw extruder can be controlled independently by dividing it into a plurality of blocks along its longitudinal axis direction, and appropriate temperature adjustment is made according to the contents of the passing material at each site.
（冷却）
延伸された多孔膜の好ましい形成法に従い、溶融押出された膜状物は、その片面側から冷却・固化される。冷却は、Ｔ−ダイから押出された平坦シート状物が、表面温度調節された冷却ドラムないしローラと接触させることにより行われ、ノズルから押出された中空糸膜の場合は、水等の冷却媒体中を通過させることにより行われる。冷却ドラム等あるいは冷却媒体の温度は５〜１２０℃と、かなり広い温度範囲から選択可能であるが、好ましくは１０〜１００℃、特に好ましくは３０〜８０℃の範囲である。
(cooling)
In accordance with a preferred method for forming a stretched porous film, the melt-extruded film-like product is cooled and solidified from one side thereof. Cooling is performed by bringing a flat sheet extruded from a T-die into contact with a cooling drum or roller whose surface temperature is adjusted. In the case of a hollow fiber membrane extruded from a nozzle, a cooling medium such as water is used. This is done by passing through. The temperature of the cooling drum or the like or the cooling medium can be selected from a fairly wide temperature range of 5 to 120 ° C., preferably 10 to 100 ° C., particularly preferably 30 to 80 ° C.
（抽出）
冷却・固化された膜状物は、次いで抽出液浴中に導入され、可塑剤および良溶媒の抽出除去を受ける。抽出液としては、ポリフッ化ビニリデン系樹脂を溶解せず、可塑剤や良溶媒を溶解できるものであれば特に限定されない。例えばアルコール類ではメタノール、イソプロピルアルコールなど、塩素化炭化水素類ではジクロロメタン、１，１，１−トリクロロエタンなど、の沸点が３０〜１００℃程度の極性溶媒が適当である。
(Extraction)
The cooled and solidified film-like material is then introduced into the extract bath and subjected to extraction and removal of the plasticizer and good solvent. The extract is not particularly limited as long as it does not dissolve the polyvinylidene fluoride resin and can dissolve the plasticizer and good solvent. For example, polar solvents having a boiling point of about 30 to 100 ° C. such as methanol and isopropyl alcohol for alcohols and dichloromethane and 1,1,1-trichloroethane for chlorinated hydrocarbons are suitable.
（熱処理）
抽出後の膜状物は、次いで引き続く延伸操作性の向上のために、８０〜１６０℃、好ましくは１００〜１４０℃の範囲で、１秒〜３６００秒、好ましくは３秒〜９００秒、熱処理して、結晶化度を増大させることが好ましい。
(Heat treatment)
The extracted film-like material is then heat-treated at 80 to 160 ° C., preferably 100 to 140 ° C. for 1 second to 3600 seconds, preferably 3 seconds to 900 seconds, in order to improve the subsequent stretching operability. Thus, it is preferable to increase the crystallinity.
（延伸）
膜状物は、次いで延伸に付され、空孔率および孔径の増大並びに強伸度の改善を受ける。延伸は、例えばテンター法による二軸延伸も可能であるが、一般に、周速度の異なるローラ対等による膜状物の長手方向への一軸延伸を行うことが好ましい。これは、本発明のフッ化ビニリデン系樹脂多孔膜の多孔率と強伸度を調和させるためには、延伸方向に沿って延伸フィブリル（繊維）部と未延伸ノード（節）部が交互に現われる微細構造が好ましいことが知見されているからである。延伸倍率は、１．２〜４．０倍、特に１．４〜３．０倍程度が適当である。
(Stretching)
The film is then subjected to stretching and undergoes an increase in porosity and pore size and an improvement in strength. The stretching may be biaxial stretching by, for example, a tenter method, but generally it is preferable to perform uniaxial stretching in the longitudinal direction of the film-like material by a pair of rollers having different peripheral speeds. This is because, in order to harmonize the porosity and the strong elongation of the vinylidene fluoride resin porous membrane of the present invention, stretched fibril (fiber) portions and unstretched node (node) portions appear alternately along the stretching direction. This is because it has been found that a fine structure is preferable. The draw ratio is suitably about 1.2 to 4.0 times, particularly about 1.4 to 3.0 times.
（湿潤緩和処理）
本発明に従い、上記のようにして延伸されたフッ化ビニリデン系樹脂多孔膜を、該フッ化ビニリデン系樹脂多孔膜を濡らす液体による湿潤下に緩和させる。
(Wet relaxation treatment)
According to the present invention, the vinylidene fluoride resin porous membrane stretched as described above is relaxed under wetting with a liquid that wets the vinylidene fluoride resin porous membrane.
フッ化ビニリデン系樹脂の濡れ張力よりも小さな表面張力（ＪＩＳ Ｋ６７６８）を有する液体がフッ化ビニリデン系樹脂多孔膜の湿潤液として用いられ、より具体的には、メタノール、エタノール、イソプロパノール等のアルコール類、ジクロロメタン、１，１，１−トリクロロエタン等の塩素化炭素類で、好ましくは沸点が３０〜１００℃程度の特性溶媒から選択される。 A liquid having a surface tension (JIS K6768) smaller than the wetting tension of the vinylidene fluoride resin is used as a wetting liquid for the vinylidene fluoride resin porous film, and more specifically, alcohols such as methanol, ethanol, isopropanol, etc. , Chlorinated carbons such as dichloromethane and 1,1,1-trichloroethane, preferably selected from characteristic solvents having a boiling point of about 30 to 100 ° C.
これら湿潤液による湿潤下での多孔膜の緩和は、好ましくは、湿潤液で湿潤された多孔膜を、周速が次第に低減する上流ローラと下流ローラ間に湿潤された多孔膜を送通することによって行われる。 The relaxation of the porous film under the wet condition by the wetting liquid is preferably performed by passing the porous film wetted with the wetting liquid through the wet porous film between the upstream roller and the downstream roller where the peripheral speed is gradually reduced. Is done by.
（１−（下流ローラ周速／上流ローラ周速））×１００（％）で定まる緩和率は、極く小さくても透水量の増大効果はあるが、より効果的にするため、２〜１５％、特に５〜１０％の範囲とすることが好ましい。２％未満では緩和による効果が顕著でなく、１５％を超える緩和は、緩和されるべき多孔膜が受けた延伸倍率にもよるが、実現困難であり、所定の緩和倍率を経た多孔膜を得ることが困難である。 The relaxation rate determined by (1− (downstream roller circumferential speed / upstream roller circumferential speed)) × 100 (%) has an effect of increasing the water permeation amount even if it is extremely small. %, Particularly in the range of 5 to 10%. If less than 2%, the effect of relaxation is not significant, and relaxation exceeding 15% is difficult to achieve, depending on the stretch ratio received by the porous film to be relaxed, and a porous film having a predetermined relaxation ratio is obtained. Is difficult.
上記において、延伸された多孔膜の緩和処理を行う環境としての湿潤液による湿潤状態は、多孔膜の湿潤液への浸漬状態により形成するのが簡便であるが、多孔膜を湿潤液に一旦浸漬して、多孔膜中に湿潤液を含浸させた後に、フッ化ビニリデン系樹脂に対して濡れ性を示さない液体（例えば水）あるいは空気等の気体中に導入して緩和を起こさせてもよい。 In the above, the wet state by the wetting liquid as the environment for relaxing the stretched porous film is easy to form by immersing the porous film in the wetting liquid, but the porous film is once immersed in the wetting liquid. Then, after impregnating the porous film with the wetting liquid, it may be introduced into a liquid (for example, water) or a gas such as air that does not show wettability with respect to the vinylidene fluoride resin to cause relaxation. .
緩和温度は、０〜１００℃、特に５〜８０℃が好ましい。緩和処理時間は、所望の緩和率が得られる限り、短時間でも、長時間でもよい。一般には５秒〜１分程度であるが、この範囲内である必要はない。 The relaxation temperature is preferably 0 to 100 ° C, particularly 5 to 80 ° C. The relaxation treatment time may be short or long as long as a desired relaxation rate is obtained. Generally, it is about 5 seconds to 1 minute, but it is not necessary to be within this range.
上記した湿潤下での緩和処理による効果は、得られる多孔膜の透水量が増大することが顕著な効果であるが、孔径分布は余り変らず、空孔率はやや低下する傾向を示す。多孔膜の肉厚は余り変らないが、中空糸膜としたときの内径および外径は増大傾向を示す。 The effect of the relaxation treatment under the above-described wetness is a remarkable effect that the water permeability of the obtained porous membrane increases, but the pore size distribution does not change so much and the porosity tends to slightly decrease. Although the thickness of the porous membrane does not change much, the inner and outer diameters of the hollow fiber membrane tend to increase.
上記した湿潤緩和処理の前および／または後、特に後に、空気等の気体中での乾熱緩和処理を行うことも好ましい。乾熱緩和処理によっては、透水量の増大効果は期待し難い（殆ど変化はない）が、孔径が若干小さくなり、均一化するために、多孔膜による被処理流体中の微粒子の分離性能が向上する効果が得られる。ただし、湿潤緩和の直後の空気中緩和は、多孔膜中に残存する湿潤液の存在により、湿潤緩和の効果も示す(後記実施例２との対比における実施例１)。 It is also preferable to perform dry heat relaxation treatment in a gas such as air before and / or after the above-described wet relaxation treatment. Depending on the dry heat relaxation treatment, it is difficult to expect the effect of increasing the water permeation amount (almost no change), but the pore size becomes slightly smaller and uniform, so that the separation performance of fine particles in the fluid to be treated by the porous membrane is improved. Effect is obtained. However, the relaxation in the air immediately after the moisture relaxation also shows the effect of the moisture relaxation due to the presence of the wetting liquid remaining in the porous membrane (Example 1 in comparison with Example 2 described later).
乾熱緩和処理は、温度８０〜１６０℃、特に１２０〜１４０℃で、０〜１０％、特に２〜１０％程度の緩和率が得られる程度が好ましい。緩和率０％は、例えば、湿潤緩和後の熱固定に相当する（後記実施例２）。 The dry heat relaxation treatment is preferably performed at a temperature of 80 to 160 ° C., particularly 120 to 140 ° C., and a relaxation rate of about 0 to 10%, particularly about 2 to 10%. The relaxation rate of 0% corresponds to, for example, heat fixation after wet relaxation (Example 2 described later).
（フッ化ビニリデン系樹脂多孔膜）
上記のようにして得られる本発明のフッ化ビニリデン系樹脂多孔膜によれば、一般に空孔率が５５〜９０％、好ましくは６０〜８５％、特に好ましくは６５〜８０％、引張り強度が５ＭＰａ以上、破断伸度が５％以上の特性が得られ、これを透水処理膜として使用する場合には５ｍ３／ｍ２・ｄａｙ・１００ｋＰａ以上の透水量が得られる。また厚さは、５〜８００μｍ程度の範囲が通常であり、好ましくは５０〜６００μｍ、特に好ましくは１５０〜５００μｍである。中空糸の場合、その外径は０．３〜３ｍｍ程度、特に１〜３ｍｍ程度が適当である。
(Vinylidene fluoride resin porous membrane)
According to the vinylidene fluoride resin porous membrane of the present invention obtained as described above, the porosity is generally 55 to 90%, preferably 60 to 85%, particularly preferably 65 to 80%, and the tensile strength is 5 MPa. As described above, a characteristic having a breaking elongation of 5% or more is obtained, and when this is used as a water permeable membrane, a water permeability of 5 m 3 / m 2 · day · 100 kPa or more is obtained. The thickness is usually in the range of about 5 to 800 μm, preferably 50 to 600 μm, particularly preferably 150 to 500 μm. In the case of a hollow fiber, the outer diameter is suitably about 0.3 to 3 mm, particularly about 1 to 3 mm.
また、本発明法により得られるフッ化ビニリデン系樹脂多孔膜は、微細構造として、Ｘ線回折法により結晶配向部と、結晶非配向部（ランダム配向部）が認められることが特徴であり、これはそれぞれ延伸フィブリル部と未延伸ノード部に対応するものと解される。 In addition, the vinylidene fluoride resin porous membrane obtained by the method of the present invention is characterized in that a crystal orientation part and a crystal non-orientation part (random orientation part) are recognized by an X-ray diffraction method as a fine structure. Are considered to correspond to the stretched fibril part and the unstretched node part, respectively.
［実施例］
以下、実施例、比較例により、本発明を更に具体的に説明する。以下の記載を含め、本明細書に記載の特性は、以下の方法による測定値に基くものである。
[Example]
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The characteristics described in this specification, including the following description, are based on measured values by the following method.
（重量平均分子量（Ｍｗ））
日本分光社製のＧＰＣ装置「ＧＰＣ−９００」を用い、カラムに昭和電工社製の「Shodex ＫＤ−８０６Ｍ」、プレカラムに「Shodex ＫＤ−Ｇ」、溶媒にＮＭＰを使用し、温度４０℃、流量１０ｍｌ／分にて、ゲルパーミエーションクロマトグラフィー（ＧＰＣ）法によりポリスチレン換算分子量として測定した。
(Weight average molecular weight (Mw))
Using a GPC device “GPC-900” manufactured by JASCO Corporation, using “Shodex KD-806M” manufactured by Showa Denko Co., Ltd. as a column, “Shodex KD-G” used as a precolumn, NMP as a solvent, temperature 40 ° C., flow rate The molecular weight was measured in terms of polystyrene by gel permeation chromatography (GPC) at 10 ml / min.
（結晶融点Ｔｍ１，Ｔｍ２および結晶化温度Ｔｃ）
パーキンエルマー社製の示差走査熱量計ＤＳＣ７を用いて、試料樹脂１０ｍｇを測定セルにセットし、窒素ガス雰囲気中で、温度３０℃から１０℃／分の昇温速度で２５０℃まで一旦昇温し、ついで２５０℃で１分間保持した後、２５０℃から１０℃／分の降温速度で３０℃まで降温してＤＳＣ曲線を求めた。このＤＳＣ曲線における昇温過程における吸熱ピーク速度を融点Ｔｍ１（℃）とし、降温過程における発熱ピーク温度を結晶化温度Ｔｃ（℃）とした。引き続いて、温度３０℃で１分間保持した後、再び３０℃から１０℃／分の昇温速度で２５０℃まで昇温してＤＳＣ曲線を測定した。この再昇温ＤＳＣ曲線における吸熱ピーク温度を本発明のフッ化ビニリデン系樹脂の結晶特性を規定する本来の樹脂融点Ｔｍ２（℃）とした。
(Crystal melting point Tm1, Tm2 and crystallization temperature Tc)
Using a differential scanning calorimeter DSC7 manufactured by PerkinElmer, 10 mg of the sample resin was set in the measurement cell, and the temperature was once raised from a temperature of 30 ° C. to 250 ° C. at a rate of 10 ° C./min in a nitrogen gas atmosphere. Then, after holding at 250 ° C. for 1 minute, the temperature was lowered from 250 ° C. to 30 ° C. at a temperature lowering rate of 10 ° C./min to obtain a DSC curve. In the DSC curve, the endothermic peak speed in the temperature rising process was the melting point Tm1 (° C.), and the exothermic peak temperature in the temperature lowering process was the crystallization temperature Tc (° C.). Subsequently, after maintaining at a temperature of 30 ° C. for 1 minute, the temperature was raised again from 30 ° C. to 250 ° C. at a rate of 10 ° C./min, and the DSC curve was measured. The endothermic peak temperature in this reheated DSC curve was the original resin melting point Tm2 (° C.) that defines the crystal characteristics of the vinylidene fluoride resin of the present invention.
（空孔率）
多孔膜の長さ、並びに幅および厚さ（中空糸の場合は外径および内径）を測定して多孔膜の見掛け体積Ｖ（ｃｍ２）を算出し、更に多孔膜の重量Ｗ（ｇ）を測定して次式より空孔率を求めた。
［数１］
空孔率（％）＝（１−Ｗ／（Ｖ×ρ））×１００
ρ：ＰＶＤＦの比重（＝１．７８ｇ／ｃｍ２）
(Porosity)
The apparent volume V (cm 2 ) of the porous membrane was calculated by measuring the length, width and thickness of the porous membrane (in the case of hollow fibers, the outer diameter and the inner diameter), and the weight W (g) of the porous membrane was further calculated. The porosity was calculated from the following equation after measurement.
[Equation 1]
Porosity (%) = (1−W / (V × ρ)) × 100
ρ: Specific gravity of PVDF (= 1.78 g / cm 2 )
（透水量（ＰＷＦ＝純水フラックス））
多孔膜をエタノールに１５分間浸漬し、次いで水に１５分間浸漬して親水化した後、水温２５℃、差圧１００ｋＰａにて測定した。多孔膜が中空糸形状の場合、試長（ろ過が行われる部分の長さ）を８００ｍｍとし、膜面積は外径に基いて次式により算出した。
［数２］
膜面積（ｍ２）＝外径×π×試長
(Water permeability (PWF = pure water flux))
The porous membrane was immersed in ethanol for 15 minutes and then hydrophilized by immersion in water for 15 minutes, and then measured at a water temperature of 25 ° C. and a differential pressure of 100 kPa. When the porous membrane had a hollow fiber shape, the test length (the length of the portion where filtration was performed) was set to 800 mm, and the membrane area was calculated by the following formula based on the outer diameter.
[Equation 2]
Membrane area (m 2 ) = Outer diameter × π × Test length
（平均孔径）
ＡＳＴＭ Ｆ３１６−８６およびＡＳＴＭ Ｅ１２９４−８９に準拠し、Porous Materials, Inc.社製「パームポロメータＣＦＰ−２００ＡＥＸ」を用いてハーフドライ法により平均孔径を測定した。試液はパーフルオロポリエステル（商品名「Galwick」）を用いた。
(Average pore diameter)
Based on ASTM F316-86 and ASTM E1294-89, the average pore diameter was measured by a half dry method using “Palm Porometer CFP-200AEX” manufactured by Porous Materials, Inc. Perfluoropolyester (trade name “Galwick”) was used as a test solution.
（最大孔径）
ＡＳＴＭ Ｆ３１６−８６およびＡＳＴＭ Ｅ１２９４−８９に準拠し、Porous Materials, Inc.社製「パームポロメータＣＦＰ−２００ＡＥＸ」を用いてバブルポイント法により最大孔径を測定した。試液はパーフルオロポリエステル（商品名「Galwick」）を用いた。
(Maximum hole diameter)
Based on ASTM F316-86 and ASTM E1294-89, the maximum pore size was measured by the bubble point method using “Palm Porometer CFP-200AEX” manufactured by Porous Materials, Inc. Perfluoropolyester (trade name “Galwick”) was used as a test solution.
（引張り強度および破断伸度）
引張り試験機（東洋ボールドウィン社製「ＲＴＭ−１００」）を使用して、温度２３℃、相対湿度５０％の雰囲気中で初期試料長１００ｍｍ、クロスヘッド速度２００ｍｍ／分の条件下で測定した。
(Tensile strength and elongation at break)
Using a tensile tester (“RTM-100” manufactured by Toyo Baldwin Co., Ltd.), measurement was performed under the conditions of an initial sample length of 100 mm and a crosshead speed of 200 mm / min in an atmosphere at a temperature of 23 ° C. and a relative humidity of 50%.
（実施例１）
重量平均分子量（Ｍｗ）が４．１２×１０５の主体ポリフッ化ビニリデン（ＰＶＤＦ）（粉体）とＭｗが９．３６×１０５の結晶特性改質用ポリフッ化ビニリデン（ＰＶＤＦ）（粉体）を、それぞれ９５重量％および５重量％となる割合で、ヘンシェルミキサーを用いて混合して、Ｍｗが４．３８×１０５である混合物Ａを得た。
Example 1
Main polyvinylidene fluoride (PVDF) (powder) having a weight average molecular weight (Mw) of 4.12 × 10 5 and polyvinylidene fluoride (PVDF) (powder) for crystal property modification having an Mw of 9.36 × 10 5 Were mixed using a Henschel mixer in proportions of 95% by weight and 5% by weight, respectively, to obtain a mixture A having an Mw of 4.38 × 10 5 .
脂肪族系ポリエステルとしてアジピン酸系ポリエステル可塑剤（旭電化工業株式会社社製「ＰＮ−１５０」）と、溶媒としてＮ−メチルピロリドン（ＮＭＰ）を、８２．５重量％／１７．５重量％の割合で、常温にて撹拌混合して、混合物Ｂを得た。 Adipic acid polyester plasticizer ("PN-150" manufactured by Asahi Denka Kogyo Co., Ltd.) as aliphatic polyester and N-methylpyrrolidone (NMP) as a solvent, 82.5 wt% / 17.5 wt% The mixture B was stirred and mixed at room temperature to obtain a mixture B.
同方向回転噛み合い型二軸押出機（プラスチック工学研究所社製「ＢＴ−３０」、スクリュー直径３０ｍｍ、Ｌ／Ｄ＝４８）を使用し、シリンダ最上流部から８０ｍｍの位置に設けられた粉体供給部から混合物Ａを供給し、シリンダ最上流部から４８０ｍｍの位置に設けられた液体供給部から温度１６０℃に加熱された混合物Ｂを、混合物Ａ／混合物Ｂ＝３５．７／６４．３（重量％）の割合で供給して、バレル温度２２０℃で混練し、混練物を外径５ｍｍ、内径３．５ｍｍの円形スリットを有するノズルから吐出量９．８ｇ／ｍｉｎで中空糸状に押し出した。この際、ノズル中心部に設けた通気孔から空気を流量６．２ｍｌ／ｍｉｎで糸の中空部に注入した。 Using a co-rotating meshing twin screw extruder (“BT-30” manufactured by Plastics Engineering Laboratory Co., Ltd., screw diameter 30 mm, L / D = 48), powder provided at a position 80 mm from the most upstream part of the cylinder The mixture A is supplied from the supply unit, and the mixture B heated to a temperature of 160 ° C. from the liquid supply unit provided at a position 480 mm from the most upstream part of the cylinder is mixed A / mixture B = 35.7 / 64.3 ( The mixture was kneaded at a barrel temperature of 220 ° C., and the kneaded product was extruded into a hollow fiber form at a discharge rate of 9.8 g / min from a nozzle having a circular slit having an outer diameter of 5 mm and an inner diameter of 3.5 mm. At this time, air was injected into the hollow portion of the yarn at a flow rate of 6.2 ml / min from a vent provided in the center of the nozzle.
押し出された混合物を溶融状態のまま６０℃の温度に維持され、且つノズルから１７０ｍｍ離れた位置に水面を有する（すなわちエアギャップが１７０ｍｍの）水浴中に導き冷却・固化させ（水浴中の滞留時間：約１０秒）、５ｍ／分の引取速度で引き取った後、これを周長約１ｍのカセに巻き取って第１中間成形体を得た。 The extruded mixture is maintained in a molten state at a temperature of 60 ° C., and is led to a water bath having a water surface at a position 170 mm away from the nozzle (that is, an air gap is 170 mm) and cooled and solidified (residence time in the water bath). : About 10 seconds) After being taken up at a take-up speed of 5 m / min, this was wound around a case having a circumference of about 1 m to obtain a first intermediate molded body.
次に、この第１中間成形体をジクロロメタン中に振動を与えながら室温で３０分間浸漬し、次いでジクロロメタンを新しいものに取り替えて再び同条件にて浸漬して、脂肪族系ポリエステルと溶媒を抽出し、次いで温度１２０℃のオーブン内で１時間加熱してジクロロメタンを除去するとともに熱処理を行い第２中間成形体を得た。 Next, the first intermediate molded body is immersed in dichloromethane at room temperature for 30 minutes while being vibrated, and then the dichloromethane is replaced with a new one and immersed again under the same conditions to extract the aliphatic polyester and the solvent. Subsequently, heating was performed in an oven at a temperature of 120 ° C. for 1 hour to remove dichloromethane and heat treatment was performed to obtain a second intermediate molded body.
次に、この第２中間成形体を第一のロール速度を１２．５ｍ／分にして、４５℃の水浴中を通過させ、第二のロール速度を２２．５ｍ／分にすることで長手方向に１．８倍に延伸した。次いで温度５℃に制御したジクロロメタン液中を通過させ、第三のロール速度を２１．４ｍ／分まで落とすことで、ジクロロメタン液中で５％緩和処理を行った。さらに空間温度１４０℃に制御した乾熱槽（２．０ｍ長さ）を通過させ、第四のロール速度を２．３ｍ／分まで落とすことで乾熱槽中で５％緩和処理を行った。これを巻き取って本発明法によるポリフッ化ビニリデン系多孔質中空糸（第３成形体）を得た。 Next, the second intermediate formed body is passed through a 45 ° C. water bath at a first roll speed of 12.5 m / min, and the second roll speed is set to 22.5 m / min in the longitudinal direction. The film was stretched 1.8 times. Next, 5% relaxation treatment was performed in the dichloromethane solution by passing through a dichloromethane solution controlled to a temperature of 5 ° C. and dropping the third roll speed to 21.4 m / min. Further, a 5% relaxation treatment was performed in the dry heat bath by passing it through a dry heat bath (2.0 m length) controlled at a space temperature of 140 ° C. and dropping the fourth roll speed to 2.3 m / min. This was wound up to obtain a polyvinylidene fluoride porous hollow fiber (third molded body) according to the method of the present invention.
得られたポリフッ化ビニリデン系多孔質中空糸は、外径が１．５８４ｍｍで、内径が１．０６９ｍｍ、膜厚が０．２５８ｍｍ、空孔率が７１．１％、透水量が８４．５１ｍ３／ｍ２・ｄａｙ・１００ｋＰａ、平均孔径０．１２５μｍ、最大孔径０．２５９μｍ、引張り強度１０．５ＭＰａ、破断伸度４６％、引張り弾性率１２２ＭＰａの物性を示した。 The obtained polyvinylidene fluoride porous hollow fiber has an outer diameter of 1.584 mm, an inner diameter of 1.069 mm, a film thickness of 0.258 mm, a porosity of 71.1%, and a water permeability of 84.51 m 3. / M 2 · day · 100 kPa, an average pore size of 0.125 μm, a maximum pore size of 0.259 μm, a tensile strength of 10.5 MPa, a breaking elongation of 46%, and a tensile modulus of 122 MPa.
製造条件および得られたポリフッ化ビニリデン系多孔質中空糸の物性を、以下の実施例および比較例の結果と併せてまとめて後記表１に記す。 The production conditions and the physical properties of the obtained polyvinylidene fluoride porous hollow fiber are shown in Table 1 below together with the results of the following examples and comparative examples.
（実施例２）
ジクロロメタン液中での緩和倍率を５％、乾熱槽中での緩和倍率を０％（定長下）に変更する以外は実施例１と同様にして多孔質中空糸を得た。
(Example 2)
A porous hollow fiber was obtained in the same manner as in Example 1 except that the relaxation ratio in the dichloromethane liquid was changed to 5% and the relaxation ratio in the dry heat bath was changed to 0% (under constant length).
（実施例３）
ジクロロメタン液中での緩和倍率を１０％、乾熱槽中での緩和倍率を０％（定長下）に変更する以外は実施例１と同様にして多孔質中空糸を得た。
(Example 3)
A porous hollow fiber was obtained in the same manner as in Example 1 except that the relaxation rate in the dichloromethane liquid was changed to 10% and the relaxation rate in the dry heat bath was changed to 0% (under constant length).
（比較例１）
延伸後のジクロロメタン液通過処理を行わず、乾熱槽中での緩和倍率を０％（定長下）に変更する以外は実施例１と同様にして多孔質中空糸を得た。
(Comparative Example 1)
A porous hollow fiber was obtained in the same manner as in Example 1, except that the dichloromethane solution passage treatment after stretching was not performed and the relaxation ratio in the dry heat bath was changed to 0% (under constant length).
（比較例２）
延伸倍率を２．２倍にし、延伸後のジクロロメタン液通過処理を行わず、乾熱槽中での緩和倍率を０％（定長下）に変更する以外は実施例１と同様にして多孔質中空糸を得た。
(Comparative Example 2)
Porous in the same manner as in Example 1 except that the stretching ratio is 2.2 times, the dichloromethane solution passage treatment after stretching is not performed, and the relaxation ratio in the dry heat bath is changed to 0% (under constant length). A hollow fiber was obtained.
（比較例３）
延伸後のジクロロメタン液通過処理を行わず、乾熱槽中での緩和倍率を５％に変更する以外は実施例１と同様にして多孔質中空糸を得た。
(Comparative Example 3)
A porous hollow fiber was obtained in the same manner as in Example 1 except that the dichloromethane solution passage treatment after stretching was not performed and the relaxation ratio in the dry heat bath was changed to 5%.
（比較例４）
延伸後のジクロロメタン液通過処理を行わず、乾熱槽中での緩和倍率を１０％に変更する以外は実施例１と同様にして多孔質中空糸を得た。
(Comparative Example 4)
A porous hollow fiber was obtained in the same manner as in Example 1 except that the dichloromethane solution passage treatment after stretching was not performed and the relaxation ratio in the dry heat bath was changed to 10%.
（比較例５）
ジクロロメタン液中での緩和倍率を０％（定長下）、乾熱槽中での緩和倍率を０％（定長下）に変更する以外は実施例１と同様にして多孔質中空糸を得た。
(Comparative Example 5)
A porous hollow fiber was obtained in the same manner as in Example 1 except that the relaxation ratio in the dichloromethane solution was changed to 0% (under constant length) and the relaxation ratio in the dry heat bath was changed to 0% (under constant length). It was.
（比較例６）
５℃のジクロロメタン液を８５℃の水に変更する以外は実施例１と同様にして多孔質中空糸を得た。
(Comparative Example 6)
A porous hollow fiber was obtained in the same manner as in Example 1 except that the 5 ° C. dichloromethane solution was changed to 85 ° C. water.
（参考例１）
ジクロロメタン液中での緩和倍率を２０％、乾熱槽中での緩和倍率を１５％に変更する以外は実施例１と同様の方法を用いて多孔質中空糸の作製を試みたが、糸がたるむため設定緩和倍率での緩和を行うことができなかったため、多孔質中空糸を得ることができなかった。
(Reference Example 1)
An attempt was made to produce a porous hollow fiber using the same method as in Example 1 except that the relaxation ratio in the dichloromethane liquid was changed to 20% and the relaxation ratio in the dry heat bath to 15%. Since the slack was not able to be relaxed at the set relaxation magnification, a porous hollow fiber could not be obtained.
（参考例２）
乾熱槽の空間温度を１７０℃に変更した以外は実施例１と同様の方法を用いて多孔質中空糸の作製を試みたが、緩和処理中にメルトして破断したため、多孔質中空糸を得ることができなかった。
Except for changing the space temperature of the dry heat bath to 170 ° C., an attempt was made to produce a porous hollow fiber using the same method as in Example 1. However, since the melt was broken during the relaxation treatment, the porous hollow fiber was Couldn't get.
上記表１の結果を見れば分かる通り、本発明の方法によれば、延伸後のフッ化ビニリデン系樹脂を、フッ化ビニリデン系樹脂を濡らす液体による湿潤下に緩和させることにより、機械特性、孔径分布等を本質的に変化させることなく、透水量が顕著に向上したフッ化ビニリデン系樹脂多孔膜が製造される。 As can be seen from the results of Table 1 above, according to the method of the present invention, the vinylidene fluoride resin after stretching is relaxed under the wet condition of the liquid that wets the vinylidene fluoride resin, so that the mechanical properties, the pore diameter are reduced. A vinylidene fluoride resin porous membrane having a significantly improved water permeability is produced without essentially changing the distribution and the like.
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| WO2007032331A1 (en) * | 2005-09-14 | 2007-03-22 | Kureha Corporation | Vinylidene fluoride resin hollow fiber porous membrane and method for production thereof |
| WO2007123004A1 (en) * | 2006-04-18 | 2007-11-01 | Kureha Corporation | Porous hollow-fiber membrane of vinylidene fluoride resin and process for producing the same |
| JP2008105016A (en) * | 2006-09-26 | 2008-05-08 | Toray Ind Inc | Hollow fiber membrane made of polyvinylidene fluoride resin, and its manufacturing method |
| JP2011074346A (en) * | 2009-09-04 | 2011-04-14 | Kureha Corp | Method for producing vinylidene fluoride-based resin porous membrane |
| CN110885522A (en) * | 2018-09-11 | 2020-03-17 | 北京化工大学 | Preparation method of PVDF (polyvinylidene fluoride) composite chitosan aerogel and induction of PVDF crystallization process |
| CN114345136A (en) * | 2021-12-03 | 2022-04-15 | 山东东岳高分子材料有限公司 | Preparation method of fluorine-containing ion exchange membrane for chlor-alkali industry |
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2007032331A1 (en) * | 2005-09-14 | 2007-03-22 | Kureha Corporation | Vinylidene fluoride resin hollow fiber porous membrane and method for production thereof |
| WO2007123004A1 (en) * | 2006-04-18 | 2007-11-01 | Kureha Corporation | Porous hollow-fiber membrane of vinylidene fluoride resin and process for producing the same |
| JP2007283232A (en) * | 2006-04-18 | 2007-11-01 | Kureha Corp | Vinylidene fluoride type resin hollow filament porous membrane and its manufacturing method |
| JP2008105016A (en) * | 2006-09-26 | 2008-05-08 | Toray Ind Inc | Hollow fiber membrane made of polyvinylidene fluoride resin, and its manufacturing method |
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| CN110885522A (en) * | 2018-09-11 | 2020-03-17 | 北京化工大学 | Preparation method of PVDF (polyvinylidene fluoride) composite chitosan aerogel and induction of PVDF crystallization process |
| CN114345136A (en) * | 2021-12-03 | 2022-04-15 | 山东东岳高分子材料有限公司 | Preparation method of fluorine-containing ion exchange membrane for chlor-alkali industry |
| CN114345136B (en) * | 2021-12-03 | 2022-10-11 | 山东东岳高分子材料有限公司 | Preparation method of fluorine-containing ion exchange membrane for chlor-alkali industry |
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