JP6221949B2 - Method for producing porous hollow fiber membrane and porous hollow fiber membrane - Google Patents
Method for producing porous hollow fiber membrane and porous hollow fiber membrane Download PDFInfo
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本発明は、精密濾過膜または限外濾過膜として、水処理に適した多孔質中空糸膜及びその製造方法に関する。 The present invention relates to a porous hollow fiber membrane suitable for water treatment as a microfiltration membrane or an ultrafiltration membrane and a method for producing the same.
近年、環境汚染に対する関心の高まりと規制の強化とにより、分離の完全性やコンパクト 性などに優れた濾過膜を用いた膜法による水処理が注目を集めている。このような水処理の用途において、濾過膜には優れた分離特性や透水性能、そして高い機械的強度が要求されている。 In recent years, due to increasing interest in environmental pollution and stricter regulations, water treatment by membrane methods using filtration membranes with excellent separation integrity and compactness has attracted attention. In such water treatment applications, filtration membranes are required to have excellent separation characteristics, water permeability, and high mechanical strength.
従来、透水性能に優れた濾過膜として、湿式または乾湿式紡糸法により製造される、ポリスルホン、ポリアクリロニトリル、セルロースアセテート、ポリフッ化ビニリデン製などの濾過膜が知られている。これらの濾過膜は、高分子溶液をミクロ相分離させた後、同高分子溶液を非溶媒中で凝固させて製造するものであり、高空孔率で且つ非対称な構造を持つ。 Conventionally, filtration membranes made of polysulfone, polyacrylonitrile, cellulose acetate, polyvinylidene fluoride and the like manufactured by a wet or dry wet spinning method are known as filtration membranes having excellent water permeability. These filtration membranes are manufactured by microphase-separating a polymer solution and then coagulating the polymer solution in a non-solvent, and have a high porosity and an asymmetric structure.
上記濾過膜素材の中でもポリフッ化ビニリデン樹脂（ＰＶＤＦ）は、耐薬品性、耐熱性に優れているので、分離膜の素材として好適に用いられている。しかしながらこれまでに提案されているポリフッ化ビニリデン中空糸膜からなる濾過膜は、分離特性・濾過安定性・機械的強度のいずれかが十分でないものが多く、またすべてを満たすものは製造方法が複雑であるという問題があった。 Among the above filtration membrane materials, polyvinylidene fluoride resin (PVDF) is excellent in chemical resistance and heat resistance, and thus is suitably used as a material for separation membranes. However, many of the proposed filtration membranes made of polyvinylidene fluoride hollow fiber membranes are not sufficient in any of separation characteristics, filtration stability and mechanical strength. There was a problem of being.
機械的強度を上げるために、中空状組紐を支持体とし、その表面上に多孔質中空糸膜が設けられた分離膜が提案されている（特許文献１）。しかしながら、この多孔質中空糸膜には、その製法から膜構造内部に大きなマクロボイドを有しており、外的要因による膜外表面の損傷等による分離特性の低下を招きやすいという問題があった。 In order to increase mechanical strength, a separation membrane in which a hollow braid is used as a support and a porous hollow fiber membrane is provided on the surface has been proposed (Patent Document 1). However, this porous hollow fiber membrane has a large macrovoid inside the membrane structure due to its production method, and has a problem that it tends to cause a decrease in separation characteristics due to damage to the outer surface of the membrane due to external factors. .
これに対し、製膜工程を二回繰り返して緻密層を二つ持たせることで、膜外表面の損傷に強く、分離特性の安定性に優れた複合多孔質中空糸膜が提案されている（特許文献２）。しかしながらこの多孔質中空糸膜は、透水性能を維持するために分子量分布の広いＰＶＤＦを用いた原液を両層に用いており、結果として１つ１つの層の分離特性は高くはなく、外層が外的要因によって損傷した場合に、依然として分離特性が低下する可能性があるという問題があった。 On the other hand, a composite porous hollow fiber membrane that is resistant to damage to the outer surface of the membrane and has excellent stability of separation characteristics has been proposed by repeating the membrane forming process twice to have two dense layers ( Patent Document 2). However, this porous hollow fiber membrane uses a stock solution using PVDF with a wide molecular weight distribution in both layers in order to maintain water permeability, and as a result, the separation characteristics of each layer are not high, and the outer layer is When damaged by external factors, there is still a problem that the separation characteristics may be deteriorated.
さらに、製膜工程を二回採用して緻密層を二つ持たせる上で、外層に分子量の高いＰＶＤＦを用い、内層に分子量がある程度高く且つ分子量分布の狭いＰＶＤＦを用いることにより、外層を物理的衝撃に強い保護層とし、内層を高い阻止性能を有する分画層にすることで、高い分離特性と高い耐物理損傷性を兼ね備えた複合多孔質中空糸膜が提案されている（特許文献３）。しかしながら、この多孔質中空糸膜には、その製膜条件の特徴から外層の内表面側の孔径が小さくなり易く、透水性能を高くしづらいという問題があった。 Furthermore, when the film forming process is adopted twice to have two dense layers, PVDF having a high molecular weight is used for the outer layer, and PVDF having a high molecular weight and a narrow molecular weight distribution is used for the inner layer, thereby physically changing the outer layer. A composite porous hollow fiber membrane having both high separation characteristics and high physical damage resistance has been proposed by using a protective layer that is resistant to mechanical shock and the inner layer as a fractionation layer having high blocking performance (Patent Document 3). ). However, the porous hollow fiber membrane has a problem that the pore diameter on the inner surface side of the outer layer tends to be small due to the characteristics of the film forming conditions, and it is difficult to increase the water permeability.
よって、本発明の目的は、高い分離特性・機械的強度・耐物理損傷性と、透水性能とを兼ね備えた多孔質中空糸膜を提供することにある。 Therefore, an object of the present invention is to provide a porous hollow fiber membrane having high separation characteristics, mechanical strength, physical damage resistance, and water permeability.
かかる課題を解決する本願発明の多孔質中空糸膜の製造方法は、中空多孔質支持体に膜形成用樹脂を含む第一製膜原液を塗布する工程と、前記塗布した第一製膜原液を凝固液と接触させて第一の多孔質中空糸膜前駆体を形成する工程と、前記第一の多孔質中空糸膜前駆体の表面に中間液を塗布する工程と、該中間液を塗布した第一の多孔質中空糸膜前駆体の表面に膜形成用樹脂を含む第二製膜原液を塗布する工程と、を有する多孔質中空糸膜の製造方法である。 The method for producing a porous hollow fiber membrane of the present invention that solves such problems includes a step of applying a first membrane forming stock solution containing a membrane-forming resin to a hollow porous support, and the applied first membrane forming stock solution. A step of forming a first porous hollow fiber membrane precursor by contacting with a coagulation liquid, a step of applying an intermediate liquid to the surface of the first porous hollow fiber membrane precursor, and applying the intermediate liquid Applying a second membrane-forming stock solution containing a membrane-forming resin to the surface of the first porous hollow fiber membrane precursor.
また、本願発明の多孔質中空糸膜は、中空多孔質支持体に膜形成用樹脂を含む第一製膜原液を塗布する工程と、前記塗布した第一製膜原液を凝固液と接触させて多孔質中空糸膜前駆体を形成する工程と前記多孔質中空糸膜前駆体の表面に中間液を塗布する工程と、該中間液を塗布した多孔質中空糸膜前駆体の表面に膜形成用樹脂を含む第二製膜原液を塗布する工程により得られる、多孔質中空糸膜であって、内表面孔径が0.1μｍよりも大きい多孔質中空糸膜である。 The porous hollow fiber membrane of the present invention comprises a step of applying a first membrane forming stock solution containing a film-forming resin to a hollow porous support, and contacting the applied first membrane forming stock solution with a coagulation solution. A step of forming a porous hollow fiber membrane precursor, a step of applying an intermediate liquid onto the surface of the porous hollow fiber membrane precursor, and a film forming on the surface of the porous hollow fiber membrane precursor coated with the intermediate liquid A porous hollow fiber membrane obtained by applying a second membrane-forming stock solution containing a resin, wherein the inner surface pore diameter is larger than 0.1 μm.
本発明の多孔質中空糸膜は、前記第一の多孔質中空糸膜前駆体の表面に中間液を塗布する工程を含む製造方法により製造されることにより、内表面孔径が小さくなり、分離特性・透水性能・機械的強度に優れる。 The porous hollow fiber membrane of the present invention is produced by a production method including a step of applying an intermediate liquid to the surface of the first porous hollow fiber membrane precursor, so that the inner surface pore diameter is reduced and separation characteristics are reduced.・ Excellent water permeability and mechanical strength.
以下、本発明の好適な実施の形態について説明する。
本発明の多孔質中空糸膜は、第一製膜原液の塗布と第二製膜原液の塗布の塗布工程を二回採用することで、第一製膜原液に由来する第一多孔質膜層の上に、第二製膜原液に由来する異なる第二多孔質中空糸膜層を設ける。このことにより、第二多孔質中空糸膜層の内側にある第一多孔質中空糸膜層が外的要因によって損傷する可能性が極めて低くなり、長期に渡って安定した分離特性を示すことができる。
このような構成では第一多孔質中空糸膜層が実質的に分離特性を担っており、内表面孔径も０．１μｍ以下で形成されることが多い。そのため、第二多孔質中空糸膜層が０．１μｍ以下の孔径を有しても分離特性への寄与は小さく、一方で透水性能の低下を導いてしまう。第二多孔質中空糸膜層においては、その製膜プロセス上、内表面孔径が最も小さくなり易いため、第二多孔質中空糸膜層の内表面孔径が０．１μｍ以上であることが好ましい。
Hereinafter, preferred embodiments of the present invention will be described.
The porous hollow fiber membrane of the present invention is a first porous membrane derived from the first membrane forming stock solution by adopting the coating step of applying the first membrane forming stock solution and applying the second membrane forming stock solution twice. A different second porous hollow fiber membrane layer derived from the second membrane forming stock solution is provided on the layer. This makes it extremely unlikely that the first porous hollow fiber membrane layer inside the second porous hollow fiber membrane layer will be damaged by external factors, and exhibits stable separation characteristics over a long period of time. be able to.
In such a configuration, the first porous hollow fiber membrane layer is substantially responsible for separation characteristics, and is often formed with an inner surface pore diameter of 0.1 μm or less. Therefore, even if the second porous hollow fiber membrane layer has a pore diameter of 0.1 μm or less, the contribution to the separation characteristics is small, while the water permeability performance is lowered. In the second porous hollow fiber membrane layer, the inner surface pore diameter is likely to be the smallest due to the film forming process, and therefore the inner surface pore diameter of the second porous hollow fiber membrane layer is 0.1 μm or more. preferable.
また、多孔質中空糸膜層全体の純水透過係数としては２０℃で１０ｍ３／ｍ２／ｈｒ／ＭＰａ以上であることが好ましい。この値よりも低くなると、ろ過に際して膜間差圧が高くなり、安定した運転が困難になる傾向がある。分離特性を担う第一多孔質中空糸膜層の透水性能は低くなる傾向にあるため、第二多孔質中空糸膜層の純水透過係数は２０ｍ３／ｍ２／ｈｒ／ＭＰａ以上が好ましく、３０ｍ３／ｍ２／ｈｒ／ＭＰａ以上がより好ましく、５０ｍ３／ｍ２／ｈｒ／ＭＰａ以上がさらに好ましい。 It is preferable as the pure water permeability coefficient of the entire porous hollow fiber membrane layer is 10m 3 / m 2 / hr / M Pa or more at 20 ° C.. If it is lower than this value, the transmembrane pressure difference becomes high during filtration, and stable operation tends to be difficult. Since the water permeability of the first porous hollow fiber membrane layer responsible for separating characteristic tends to decrease, pure water permeability coefficient of the second porous hollow fiber membrane layer 20m 3 / m 2 / hr / M Pa or more more preferably from 30m 3 / m 2 / hr / M Pa or more, still more preferably at least 50m 3 / m 2 / hr / M Pa.
本発明の多孔質中空糸膜層においては、第一及び第二多孔質中空糸膜層の厚さの合計を１５０μｍ以下とするのが好ましい。これは、厚さを１５０μｍ以下とすることによって、膜分離時における透過抵抗が低減され、優れた透水性能が得られるとともに、高分子樹脂溶液である製膜原液を用いて多孔質中空糸膜層を形成させる際の凝固時間を短くでき、マクロボイド（欠損部位）抑制に効果的であると共に、優れた生産性を得ることができる傾向にあるためである。より好ましくは、１００μｍ以下である。 In the porous hollow fiber membrane layer of the present invention, the total thickness of the first and second porous hollow fiber membrane layers is preferably 150 μm or less. This is because when the thickness is 150 μm or less, the permeation resistance at the time of membrane separation is reduced, and excellent water permeation performance is obtained. This is because the coagulation time during the formation of can be shortened, it is effective for suppressing macrovoids (defects), and excellent productivity tends to be obtained. More preferably, it is 100 μm or less.
また、それぞれの多孔質中空糸膜層においては、その厚さを１００μｍ以上とするのが好ましい。これは、厚さを１００μｍ以上とすることによって、実用上問題のない機械的強度を得ることができる傾向にあるためである。第一多孔質中空糸膜層については、さらに７０μｍ以下であることが好ましく、５０μｍ以下であることがより好ましい。 Moreover, in each porous hollow fiber membrane layer, it is preferable that the thickness shall be 100 micrometers or more. This is because the mechanical strength having no practical problem tends to be obtained by setting the thickness to 100 μm or more. The first porous hollow fiber membrane layer is preferably 70 μm or less and more preferably 50 μm or less.
本発明の多孔質中空糸膜は、上述の多孔質中空糸膜層のみからなるものであっても良いが、優れた機械的強度が得られることから、中空状の支持体上にこの多孔質中空糸膜層を有するものが特に好ましい。なお、ここでは多孔質中空糸膜層と支持体との位置関係を明確にするために支持体上と表現しているが、多孔質中空糸膜層が支持体の空隙を通じて支持体内部に含浸している場合もある。このような場合においても、本発明における上述の膜厚は、支持体上に露出している部分の厚さを意味するものとする。 The porous hollow fiber membrane of the present invention may be composed only of the above-described porous hollow fiber membrane layer, but since excellent mechanical strength can be obtained, the porous hollow fiber membrane is formed on a hollow support. Those having a hollow fiber membrane layer are particularly preferred. Here, in order to clarify the positional relationship between the porous hollow fiber membrane layer and the support, it is expressed on the support, but the porous hollow fiber membrane layer is impregnated inside the support through the gap of the support. Sometimes it is. Even in such a case, the above-mentioned film thickness in the present invention means the thickness of the portion exposed on the support.
支持体としては、高い機械的強度を有し、かつ多孔質中空糸膜層と一体化できるものであれば、適宜選択して使用することができ、特に限定するものではないが、製膜時の張力による伸びを抑えられる点から、熱処理された支持体であることが好ましい。
また、製造コストが低く、柔軟性と断面の形状安定性（真円性）を両立でき、多孔質中空糸膜層との接着性にも優れることから、編紐がより好ましい。中でも、マルチフィラメントからなる１本の糸を丸編した中空状編紐であることが好ましい。
The support is not particularly limited as long as it has a high mechanical strength and can be integrated with the porous hollow fiber membrane layer, and is not particularly limited. It is preferable that the support is subjected to a heat treatment from the viewpoint of suppressing the elongation due to the tension.
In addition, a knitted string is more preferable because the manufacturing cost is low, flexibility and cross-sectional shape stability (roundness) can be achieved, and adhesion to the porous hollow fiber membrane layer is excellent. Among these, a hollow knitted string obtained by circularly knitting a single yarn made of multifilament is preferable.
多孔質中空糸膜層は、膜形成用樹脂によって形成される。膜形成用樹脂としては、例えば、ポリスルホン樹脂、ポリエーテルスルホン樹脂、スルホン化ポリスルホン樹脂、ポリフソ化ビニリデン樹脂、ポリアクリロニトリル樹脂、ポリイミド樹脂、ポリアミドイミド樹脂、ポリエステルイミド樹脂などが挙げられる。これらの中でも、耐薬品性に優れることから、ポリフッ化ビニリデン樹脂（ＰＶＤＦ）が好ましい。 The porous hollow fiber membrane layer is formed of a membrane forming resin. Examples of the film forming resin include polysulfone resins, polyether sulfone resins, sulfonated polysulfone resins, polyfluorinated vinylidene resins, polyacrylonitrile resins, polyimide resins, polyamideimide resins, and polyesterimide resins. Among these, polyvinylidene fluoride resin (PVDF) is preferable because of excellent chemical resistance.
膜形成用樹脂としてＰＶＤＦを用いる場合、第一製膜原液には質量平均分子量が５．０×１０５以上１．０×１０６以下であるポリフッ化ビニリデン樹脂を用いることが好ましい。質量平均分子量が５．０×１０５未満では、得られる第一多孔質中空糸膜層の内部構造が粗大化しやすく、分離特性が低下する傾向がある。一方、質量平均分子量が１．０×１０６を超えると、内部構造が緻密化しやすく、透水性能が低下する径化王がある。
また、第一製膜原液には、分子量分布が５．５以下であるポリフッ化ビニリデン樹脂を用い得ることが好ましい。分子量分布が５．５を超えると、内部構造が粗大化しやすく、分離特性が低下する傾向にあり好ましくない。
When PVDF is used as the film-forming resin, it is preferable to use a polyvinylidene fluoride resin having a mass average molecular weight of 5.0 × 10 5 or more and 1.0 × 10 6 or less for the first film-forming stock solution. When the mass average molecular weight is less than 5.0 × 10 5 , the internal structure of the obtained first porous hollow fiber membrane layer tends to be coarsened, and the separation characteristics tend to be lowered. On the other hand, when the mass average molecular weight exceeds 1.0 × 10 6 , there is a diameter increasing king that the internal structure is easily densified and the water permeability performance is lowered.
Moreover, it is preferable that the polyvinylidene fluoride resin whose molecular weight distribution is 5.5 or less can be used for a 1st film forming undiluted | stock solution. If the molecular weight distribution exceeds 5.5, the internal structure tends to be coarsened, and the separation characteristics tend to deteriorate, such being undesirable.
一方、第二製膜原液に用いるポリフッ化ビニリデン樹脂としては、質量平均分子量が５．０×１０５以上のものが好ましく、７．０×１０５以上のものがより好ましく、１．０×１０６以上のものがさらに好ましい。このようなポリフッ化ビニリデン樹脂を用いることにより、第二多孔質中空糸膜層の強度が向上し、第一多孔質中空糸膜層を外的要因による損傷から保護しやすくなる。
また、第二製膜原液に用いるポリフッ化ビニリデン樹脂として、質量平均分子量が５．０×１０５以上のものと１．０×１０６以上のものとのブレンドを用いると、ある程度透水性能を維持したまま強度を向上されることができ、特に好ましい。質量平均分子量１．０×１０６以上のポリフッ化ビニリデン樹脂は、比較的少量の使用であっても強度向上に対する寄与は大きいため、ブレンド比は１．０×１０６以上のポリフッ化ビニリデン樹脂が５０％以下であることが好ましく、４０％以下であることがより好ましい。
On the other hand, the polyvinylidene fluoride resin used for the second film-forming stock solution preferably has a mass average molecular weight of 5.0 × 10 5 or more, more preferably 7.0 × 10 5 or more, and 1.0 × 10 5. More preferably 6 or more. By using such a polyvinylidene fluoride resin, the strength of the second porous hollow fiber membrane layer is improved, and the first porous hollow fiber membrane layer is easily protected from damage due to external factors.
In addition, when polyvinylidene fluoride resin used for the second film-forming stock solution is a blend of those having a mass average molecular weight of 5.0 × 10 5 or more and 1.0 × 10 6 or more, water permeability is maintained to some extent. The strength can be improved as it is, which is particularly preferable. A polyvinylidene fluoride resin having a mass average molecular weight of 1.0 × 10 6 or more greatly contributes to improvement in strength even when used in a relatively small amount. Therefore, a polyvinylidene fluoride resin having a blend ratio of 1.0 × 10 6 or more is used. It is preferably 50% or less, and more preferably 40% or less.
次に、本発明の多孔質中空糸膜の製造方法について説明する。本発明の多孔質中空糸膜は、環状ノズルを用いて中空多孔質支持体に第一製膜原液を塗布し、凝固液中で凝固させて第一多孔質中空糸膜層を形成させた後、環状ノズルを用いて該第一多孔質中空糸膜層の表面に第二製膜原液を塗布し、凝固液中で凝固させて第二多孔質中空糸膜層を形成させる多孔質中空糸膜の製造方法において、第一多孔質中空糸膜層の表面に中間液を塗布した後に、該中間液の表面に第二製膜原液を塗布することにより製造することができる。
中間液を用いない場合は、第一多孔質中空糸膜層が第二製膜原液中の良溶媒により溶解され、第一多孔質中空糸膜層と第二多孔質中空糸膜層が溶着し、透水性能が著しく低下してしまう。
Next, the manufacturing method of the porous hollow fiber membrane of this invention is demonstrated. In the porous hollow fiber membrane of the present invention, the first membrane forming stock solution was applied to the hollow porous support using an annular nozzle, and solidified in the coagulation solution to form the first porous hollow fiber membrane layer. Thereafter, a second membrane forming stock solution is applied to the surface of the first porous hollow fiber membrane layer using an annular nozzle, and solidified in a coagulating solution to form a second porous hollow fiber membrane layer. In the method for producing a hollow fiber membrane, the intermediate liquid can be applied to the surface of the first porous hollow fiber membrane layer, and then the second membrane forming stock solution can be applied to the surface of the intermediate liquid.
When no intermediate solution is used, the first porous hollow fiber membrane layer is dissolved by the good solvent in the second membrane forming stock solution, and the first porous hollow fiber membrane layer and the second porous hollow fiber membrane layer Will be welded and the water permeability will be significantly reduced.
中間液に膜形成用樹脂の非溶媒を用いた場合は、第二多孔質中空糸膜層の内表面が即座に凝固され、内表面孔径が小さくなり、透水性能が低下してしまう。一方、中間液に膜形成用樹脂の良溶媒を用いた場合は、第一多孔質中空糸膜層が溶解されて第一多孔質中空糸膜層と第二多孔質中空糸膜層が溶着し、同様に透水性能が著しく低下してしまう。
そのため、中間液としては、良溶媒と非溶媒の混合液が好ましく、良溶媒が７０％以上含まれる中間液がより好ましい。このことにより第二多孔質中空糸膜層の内表面の凝固が遅くなり、平均孔径を大きくできると共に、透水性能の低下を抑制することができる。良溶媒が９０％以上含まれることがさらに好ましい。
When a non-solvent for the film-forming resin is used for the intermediate liquid, the inner surface of the second porous hollow fiber membrane layer is immediately solidified, the inner surface pore diameter is reduced, and the water permeability is deteriorated. On the other hand, when a good solvent for the film-forming resin is used for the intermediate liquid, the first porous hollow fiber membrane layer and the second porous hollow fiber membrane layer are dissolved by dissolving the first porous hollow fiber membrane layer. Will be welded and the water permeability will be significantly reduced.
Therefore, the intermediate solution is preferably a mixed solution of a good solvent and a non-solvent, and more preferably an intermediate solution containing 70% or more of the good solvent. This slows the solidification of the inner surface of the second porous hollow fiber membrane layer, can increase the average pore diameter, and can suppress a decrease in water permeability. More preferably, 90% or more of the good solvent is contained.
また、中間液としては、膜形成用樹脂の良溶媒と、貧溶媒又は非溶媒の高粘度流体との混合液であることが好ましい。高粘度流体を含まない場合、中間液の粘度が低いため、第一多孔質中空糸膜層に塗布された後に重力等により変形しやすく、均一に存在することが難しくなり、中間液が存在しない部分が発生する可能性がある。
なお、本発明の高粘度流体の粘度は、２０℃における粘度が１×１０３ｍＰａ・ｓ以上である。より好ましくは２×１０３ｍＰａ・ｓ以上であることがより好ましい。
粘度が高く、かつ水に溶けやすく洗浄しやすいという点で、貧溶媒又は非溶媒としてはグリセリンを用いて良溶媒との混合液とすることが好ましい。
The intermediate liquid is preferably a mixed liquid of a good solvent for the film-forming resin and a high-viscosity fluid such as a poor solvent or a non-solvent. When high viscosity fluid is not included, since the viscosity of the intermediate liquid is low, it is easily deformed by gravity after being applied to the first porous hollow fiber membrane layer, making it difficult to exist uniformly, and there is an intermediate liquid. There is a possibility that a part not to occur.
The viscosity of the high viscosity fluid of the present invention is 1 × 10 3 mPa · s or more at 20 ° C. More preferably, it is more preferably 2 × 10 3 mPa · s or more.
It is preferable to use glycerin as a poor solvent or a non-solvent to make a mixed solution with a good solvent because it has a high viscosity and is easily dissolved in water and easy to wash.
第一多孔質中空糸膜層に中間液を塗布する方法としては、第一多孔質中空糸膜層に中間液を均一に塗布できる方法であれば、特に限定するものではないが、粘度の低い中間液を第一多孔質中空糸膜層の全周に確実に塗布できる点から、中間液槽に第一多孔質中空糸膜層を浸漬させて塗布することが好ましい。
中間液槽は、深さ５ｍｍ以上溜められていることが好ましい。5ｍｍより浅いと、中間液が第一多孔質中空糸膜に随伴して中間液が無くなり、中間液が塗布されない部分が発生する可能性がある。
中間液は、中間液槽に一定量を供給し続けられることが好ましい。また中間液槽には、オーバーフロー配管によって溜めた場所から抜くことで常に一定量溜めることが好ましい。中間液槽の貯液量が変化すると、第一多孔質中空糸膜層への塗布状態も変化し、第二多孔質中空糸膜層の内表面の凝固状態が均一にならない可能性がある。
The method for applying the intermediate liquid to the first porous hollow fiber membrane layer is not particularly limited as long as the intermediate liquid can be uniformly applied to the first porous hollow fiber membrane layer. It is preferable to immerse the first porous hollow fiber membrane layer in the intermediate liquid tank so that a low intermediate solution can be reliably applied to the entire circumference of the first porous hollow fiber membrane layer.
The intermediate liquid tank is preferably stored at a depth of 5 mm or more. If it is shallower than 5 mm, the intermediate liquid is lost along with the first porous hollow fiber membrane, and there is a possibility that a portion where the intermediate liquid is not applied is generated.
It is preferable that a constant amount of the intermediate liquid can be continuously supplied to the intermediate liquid tank. Further, it is preferable to always store a certain amount in the intermediate liquid tank by removing it from the place where it is stored by the overflow pipe. When the amount of liquid stored in the intermediate liquid tank changes, the state of application to the first porous hollow fiber membrane layer also changes, and the solidification state of the inner surface of the second porous hollow fiber membrane layer may not be uniform. is there.
中間液槽を通過させた第一多孔質中空糸膜前駆体は、続けて中間液槽の下流側に配置された筒状通路を通過させ、余分に付着した中間液を取り除くことが好ましい。過剰の中間液が塗布されていると、その中間液が層となって、第一多孔質中空糸膜層と第二多孔質中空糸膜層の間に隙間ができ、第二多孔質中空糸膜層が剥離しやすくなるため好ましくない。
該筒状通路の幅Ａ（ｍｍ）は、第一多孔質中空糸膜前駆体の外径Ｂ（ｍｍ）に対し、Ｂ＜Ａ≦Ｂ＋０．１より好ましくは、Ｂ＜Ａ≦Ｂ＋０．０５を満たすことが好ましい。幅がＢ＋０．１（ ｍｍ）より大きくなると、多量の中間液が前駆体に随伴しやすくなり、得られる第一多孔質中空糸膜層と第二多孔質中空糸膜層の間に隙間ができやすくなる。
ここで、筒状通路の幅Ａは、筒状通路の断面形状が円である場合はその断面の直径を、それ以外の場合は、断面の中心を通り、筒上通路の外周で切り取られる線分のうちも短いものの長さとする。
It is preferable that the first porous hollow fiber membrane precursor passed through the intermediate liquid tank is subsequently passed through a cylindrical passage disposed on the downstream side of the intermediate liquid tank to remove the excessively adhered intermediate liquid. If an excess of the intermediate liquid is applied, the intermediate liquid becomes a layer, and a gap is formed between the first porous hollow fiber membrane layer and the second porous hollow fiber membrane layer. This is not preferable because the hollow fiber membrane layer is easily peeled off.
The width A (mm) of the cylindrical passage is B <A ≦ B + 0.1, more preferably B <A ≦ B + 0.05 with respect to the outer diameter B (mm) of the first porous hollow fiber membrane precursor. It is preferable to satisfy. When the width is larger than B + 0.1 (mm), a large amount of intermediate liquid is likely to accompany the precursor, and there is a gap between the obtained first porous hollow fiber membrane layer and the second porous hollow fiber membrane layer. It becomes easy to do.
Here, the width A of the cylindrical passage is a line that is cut off at the outer periphery of the on-cylinder passage through the diameter of the cross section when the cross sectional shape of the cylindrical passage is a circle, and otherwise through the center of the cross section. It is the length of the short part of the minutes.
中間液を塗布した後は、第二製膜原液をできるだけ早く塗布することが好ましい。塗布までに時間がかかると、中間液の塗布状態が重力等によって変化し、第二多孔質中空糸膜層の内表面の凝固状態が均一にならない可能性がある。
第一多孔質中空糸膜層が、中間液を溜めた場所の下方にある通路を抜けてから、第二製膜原液が塗布されるまでの時間は０．３秒以下であることが好ましく、０．２秒以下がより好ましく、０．１秒以下がさらに好ましい。
After applying the intermediate solution, it is preferable to apply the second film-forming stock solution as soon as possible. If it takes time to apply, the application state of the intermediate liquid may change due to gravity or the like, and the solidification state of the inner surface of the second porous hollow fiber membrane layer may not be uniform.
It is preferred that the time from when the first porous hollow fiber membrane layer passes through the passage below the place where the intermediate solution is stored until the second membrane forming stock solution is applied is 0.3 seconds or less. 0.2 seconds or less is more preferable, and 0.1 seconds or less is more preferable.
製膜原液は、通常、膜形成用樹脂と親水性樹脂とこれらを溶解する溶媒とを含む。製膜原液は、必要に応じてその他の添加成分を含んでもよい。
親水性樹脂は、製膜原液の粘度を多孔質中空糸膜層の形成に好適な範囲に調整し、製膜状態の安定化を図るために添加されるものであって、ポリエチレングリコールやポリビニルピロリドンなどが好ましく使用される。これらの中でも、得られる多孔質中空糸膜の孔径の制御や強度制御の点から、ポリビニルピロリドンやポリビニルピロリドンに他の単量体が共重合した共重合体が好ましい。
また、親水性樹脂は、２種以上の樹脂を混合して使用することもできる。例えば親水性樹脂として、より高分子量のものを用いると、膜構造の良好な多孔質中空糸膜を形成しやすい傾向がある。一方、低分子量の親水性樹脂は、多孔質中空糸膜からより除去されやすい点で好適である。よって、目的に応じて、分子量が異なる同種の親水性樹脂を適宜ブレンドして用いてもよい。
The film-forming stock solution usually contains a film-forming resin, a hydrophilic resin, and a solvent for dissolving them. The film-forming stock solution may contain other additive components as necessary.
The hydrophilic resin is added to adjust the viscosity of the membrane-forming stock solution to a range suitable for the formation of the porous hollow fiber membrane layer and to stabilize the membrane-forming state. Polyethylene glycol or polyvinylpyrrolidone Etc. are preferably used. Among these, polyvinylpyrrolidone and a copolymer obtained by copolymerizing other monomers with polyvinylpyrrolidone are preferable from the viewpoint of controlling the pore size and strength of the porous hollow fiber membrane to be obtained.
Moreover, 2 or more types of hydrophilic resin can also be mixed and used. For example, when a higher molecular weight hydrophilic resin is used, a porous hollow fiber membrane having a good membrane structure tends to be formed. On the other hand, a low molecular weight hydrophilic resin is preferable in that it is more easily removed from the porous hollow fiber membrane. Therefore, the same kind of hydrophilic resins having different molecular weights may be appropriately blended depending on the purpose.
良溶媒としては、Ｎ,Ｎ―ジメチルホルムアミド、Ｎ,Ｎ―ジメチルアセトアミド、ジメチルスルホキシド、Ｎ―メチル―２―ピロリドン、Ｎ―メチルモルホリン―Ｎ一オキンドなどが挙げられ、これらを1種以上使用できる。また、溶媒への膜形成用樹脂や親水性樹脂の溶解性を損なわない範囲で、膜形成用樹脂や親水性樹脂の貧溶媒や非溶媒を混合して使用してもよい。 Examples of the good solvent include N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, N-methylmorpholine-N monooxide, and one or more of these can be used. . In addition, a poor solvent or a non-solvent of the film forming resin or the hydrophilic resin may be mixed and used within a range that does not impair the solubility of the film forming resin or the hydrophilic resin in the solvent.
第一製膜原液の４０℃ における粘度は、１０００〜２００，０００ｍＰａ・秒であることが好ましく、５０００〜１，０００，０００ｍＰａ・秒であることがより好ましく、１０，０００〜５０，０００ｍＰａ・秒であることがさらに好ましい。第二製膜原液の40℃ における粘度は、１０，０００〜５００，０００ｍＰａ・秒であることが好ましく、２０，０００〜３００，０００ｍＰａ・秒であることがより好ましく、４０，０００〜２００，０００ｍＰａ・秒であることがさらに好ましい。粘度が低すぎると均一塗布が難しくなる。一方、粘度が高すぎると相分離の速度が低下し、透水性能が低下する傾向がある。保護層となる第二多孔質中空糸膜層の製膜原液の粘度が、第一製膜原液の粘度より高いことが好ましい。 The viscosity of the first film-forming stock solution at 40 ° C. is preferably 1000 to 200,000 mPa · s, more preferably 5000 to 1,000,000 mPa · s, and 10,000 to 50,000 mPa · s. More preferably. The viscosity at 40 ° C. of the second film-forming stock solution is preferably 10,000 to 500,000 mPa · sec, more preferably 20,000 to 300,000 mPa · sec, and 40,000 to 200,000 mPa · s. More preferably, it is seconds. If the viscosity is too low, uniform application becomes difficult. On the other hand, if the viscosity is too high, the speed of phase separation decreases, and the water permeability tends to decrease. It is preferable that the viscosity of the film-forming stock solution of the second porous hollow fiber membrane layer serving as the protective layer is higher than the viscosity of the first film-forming stock solution.
親水性樹脂の濃度の上限は、粘度が高すぎると製膜が困難となり目的の多孔質中空糸膜が得られにくくなる傾向にあるため、下限は１０質量％が好ましく、１２質量％がより好ましい。また、上限は３０質量%が好ましく、２５質量％がより好ましい。
一方、親水性樹脂の濃度の下限は、多孔質中空糸膜をより形成しやすいものとするために1質量%が好ましく、５質量％がより好ましい。親水性樹脂の濃度の上限は、製膜原液の取扱性の点から２０質量％以下が好ましく、１５質量％以下がより好ましい。
The upper limit of the concentration of the hydrophilic resin is that if the viscosity is too high, film formation tends to be difficult and the desired porous hollow fiber membrane tends to be difficult to obtain. Therefore, the lower limit is preferably 10% by mass, more preferably 12% by mass. . The upper limit is preferably 30% by mass, and more preferably 25% by mass.
On the other hand, the lower limit of the concentration of the hydrophilic resin is preferably 1% by mass and more preferably 5% by mass in order to make the porous hollow fiber membrane easier to form. The upper limit of the concentration of the hydrophilic resin is preferably 20% by mass or less, and more preferably 15% by mass or less from the viewpoint of the handleability of the film-forming stock solution.
製膜原液に接触させる凝固液は、膜形成用樹脂の非溶媒で、親水性樹脂の良溶媒を用いる。例えば、水、工タノール、メタノール等やこれらの混合物が挙げられるが、中でも製膜原液に用いた溶媒と水との混合液が安全性、運転管理の面から好ましい。
製膜原液に用いた溶媒と水との混合液を用いる場合は、溶媒の濃度が５〜５０質量％の範囲であることが好ましく、１０〜４０質量％の範囲であることがより好ましい。この範囲を下回ると非溶媒の増加速度が速まり、内部の構造が緻密になりすぎることがある。また、この範囲を上回ると、十分な量の非溶媒が浸入できず、凝固槽内で凝固が完了しないことがある。
The coagulating liquid to be brought into contact with the film-forming stock solution is a non-solvent for the film-forming resin and a good solvent for the hydrophilic resin. For example, water, techanol, methanol and the like, and a mixture thereof can be mentioned. Among them, a mixed solution of a solvent and water used for the film forming stock solution is preferable from the viewpoint of safety and operation management.
When using the liquid mixture of the solvent and water used for the film forming undiluted | stock solution, it is preferable that the density | concentration of a solvent is the range of 5-50 mass%, and it is more preferable that it is the range of 10-40 mass%. Below this range, the rate of increase of the non-solvent increases and the internal structure may become too dense. Moreover, if it exceeds this range, a sufficient amount of non-solvent cannot enter and solidification may not be completed in the coagulation tank.
凝固液の温度は２０℃以上９５℃以下の範囲にすることが好ましく、２５以上８５℃以下にすることがさらに好ましい。凝固液の温度を前記下限値以上とすることにより、得られる多孔質中空糸膜の透水性能が高くなり、前記上限値以下とすることにより、得られる多孔質中空糸膜の分離特性が向上する。親水性樹脂として、ポリビニルピロリドン等の高分子を用いた場合は、多孔質中空糸膜を熱水で洗浄した後、酸化剤含有液で処理して親水性樹脂を分解し、除去することが好ましい。 The temperature of the coagulation liquid is preferably in the range of 20 ° C. or higher and 95 ° C. or lower, more preferably 25 or higher and 85 ° C. or lower. By setting the temperature of the coagulation liquid to the lower limit value or more, the water permeability of the obtained porous hollow fiber membrane is increased, and by setting the temperature to the upper limit value or less, the separation characteristics of the obtained porous hollow fiber membrane are improved. . When a polymer such as polyvinylpyrrolidone is used as the hydrophilic resin, it is preferable that the porous hollow fiber membrane is washed with hot water and then treated with an oxidant-containing liquid to decompose and remove the hydrophilic resin. .
（多孔質中空糸膜の外径）
多孔質中空糸膜の外径は、以下の方法で測定した。
測定するサンプルを約１０ｃｍに切断し、数本を束ねて、全体をポリウレタン樹脂で覆った。ポリウレタン樹脂は支持体の中空部にも入るようにした。
ポリウレタン樹脂硬化後、カミソリ刃を用いて厚さ（膜の長手方向）約０．５ｍｍの薄片をサンプリングした。
次に、サンプリングした多孔質中空糸膜の断面を、投影機（ニコン社製、ＰＲＯＦＩＬＥ ＰＲＯＪＥＣＴＯＲ Ｖ−１２）を用い、対物レンズ１００倍にて観察した。
観察している多孔質中空糸膜の断面の中心を通り互いに垂直な直線を引き、これら直線との外表面の交点の位置から外径を読み取った。これを３回測定して外径の平均値を求めた。
(Outer diameter of porous hollow fiber membrane)
The outer diameter of the porous hollow fiber membrane was measured by the following method.
The sample to be measured was cut into about 10 cm, several pieces were bundled, and the whole was covered with polyurethane resin. The polyurethane resin also entered the hollow part of the support.
After the polyurethane resin was cured, a thin piece having a thickness (longitudinal direction of the film) of about 0.5 mm was sampled using a razor blade.
Next, the cross section of the sampled porous hollow fiber membrane was observed with a projector (Nikon Corporation, PROFILE PROJECTOR V-12) at an objective lens of 100 times.
Straight lines passing through the center of the cross section of the observed porous hollow fiber membrane were drawn, and the outer diameter was read from the position of the intersection of the outer surface with these straight lines. This was measured three times to determine the average value of the outer diameter.
（多孔質中空糸膜層の膜厚）
実施例における多孔質中空糸膜層の膜厚は、支持体の表面から多孔質中空糸膜の表面までの厚さであり、以下の方法で測定した。
測定するサンプルは外径を測定したサンプルと同様の方法でサンプリングした。
次に、サンプリングした多孔質中空糸膜の断面を、投影機（ニコン社製、ＰＲＯＦＩＬＥ ＰＲＯＪＥＣＴＯＲ Ｖ−１２）を用い、対物レンズ１００倍にて観察した。
観察している多孔質中空糸膜断面の３時方向位置の膜厚の外表面と内表面の位置にマーク（ライン）をあわせて膜厚を読み取った。同様に、９時方向、１２時方向、６時方向の順で膜厚を読み取った。これを３回測定して内径の平均値を求めた。
(Thickness of porous hollow fiber membrane layer)
The film thickness of the porous hollow fiber membrane layer in the examples is the thickness from the surface of the support to the surface of the porous hollow fiber membrane, and was measured by the following method.
The sample to be measured was sampled in the same manner as the sample whose outer diameter was measured.
Next, the cross section of the sampled porous hollow fiber membrane was observed with a projector (Nikon Corporation, PROFILE PROJECTOR V-12) at an objective lens of 100 times.
The film thickness was read by aligning marks (lines) at the positions of the outer surface and inner surface of the film at the 3 o'clock position on the cross section of the porous hollow fiber membrane being observed. Similarly, the film thickness was read in the order of 9 o'clock, 12 o'clock, and 6 o'clock. This was measured three times to determine the average inner diameter.
（多孔質中空糸膜の各層の孔径）
実施例における多孔質中空糸膜各層の外表面孔径及び内表面孔径は、以下の方法で測定した。
得られた多孔質中空糸膜の第一多孔質中空糸膜層と第二多孔質中空糸膜層との界面に沿ってカミソリ刃を当て、第一多孔質中空糸膜層と第二多孔質中空糸膜層に分離した。その後、さらに剃刀場で、第一多孔質中空糸膜層と第二多孔質中空糸膜層を切り開いて平面状として側転サンプルを得た。このサンプルを用いて、ＳＥＭで３００００倍に拡大観察し、撮影した写真について、（株）プラネトロン製Ｉｍａｇｅ−Ｐｒｏ Ｐｌｕｓを用いて画像解析を行い、各層の平均孔径を算出した。
(Pore diameter of each layer of porous hollow fiber membrane)
The outer surface pore diameter and inner surface pore diameter of each porous hollow fiber membrane layer in the examples were measured by the following methods.
A razor blade is applied along the interface between the first porous hollow fiber membrane layer and the second porous hollow fiber membrane layer of the obtained porous hollow fiber membrane, and the first porous hollow fiber membrane layer and the first porous hollow fiber membrane layer Separated into two porous hollow fiber membrane layers. Thereafter, the first porous hollow fiber membrane layer and the second porous hollow fiber membrane layer were further cut open at a razor blade to obtain a roll sample in a planar shape. Using this sample, the image was magnified 30000 times with SEM, and the photographed photograph was subjected to image analysis using Image-Pro Plus manufactured by Planetron Co., Ltd., and the average pore size of each layer was calculated.
（純水透過係数） 純水透過係数は、濾過有効長が４ｃｍとなる１本の中空糸多孔質中空糸膜からなるミニモジュールを作製し、エタノールに浸漬して親水化処理を行った後、加圧１００ｋＰａの条件にて多孔質中空糸膜の外側から内側へ純水を送液して一定時間の透水量（ｍ３）を測定して得られた値から単位有効膜面積（ｍ２）、単位時間（ｈｒ）、単位圧力（ＭＰａ）における値に換算して算出した。 (Pure water permeability coefficient) The pure water permeability coefficient is obtained by preparing a mini-module composed of one hollow fiber porous hollow fiber membrane having an effective filtration length of 4 cm, and immersing it in ethanol for hydrophilization treatment. Unit effective membrane area (m 2 ) from the value obtained by feeding pure water from the outside to the inside of the porous hollow fiber membrane under pressure of 100 kPa and measuring the amount of water permeation (m 3 ) for a certain period of time , the unit time (hr), was calculated in terms of the values in the unit pressure (M Pa).
（実施例1）
中空多孔質支持体として、図１の支持体製造装置を用いて、捲縮加工がされていないポリエステル繊維（繊度１１１ｄｔｅｘ、フィラメント数４８）のマルチフィラメントを円筒状に丸編みし、１９０℃で熱処理したものを使用した。使用した編紐支持体の外径は１．４ｍｍであり、内径は０．８４ｍｍであった。
ポリフッ化ビニリデン（アルケマ社製、商品名カイナー７６１Ａ、質量平均分子量６．０×１０５）１３質量％、及びポリビニルピロリドン（日本触媒社製、商品名Ｋ−３０）１２質量％を、Ｎ―メチル―２―ピロリドン７５質量％に撹拌しながら溶解させて第１製膜原液を調製した。この第一製膜原液の４０℃での粘度は２×１０４ｍＰａ・ｓであった。
続いて、ポリフッ化ビニリデン（アルケマ社製、商品名カイナーＨＳＶ９００、質量平均分子量１．１×１０６）５質量％、ポリフッ化ビニリデン（アルケマ社製、商品名カイナー７６１Ａ）１２質量％及びポリビニルピロリドン（日本触媒社製、商品名Ｋ−３０）１４質量％を、Ｎ―メチル―２―ピロリドン６９質量％に撹拌しながら溶解させて第二製膜原液を調製した。この第２製膜原液の４０℃での粘度は９×１０４ｍＰａ・ｓであった。
(Example 1)
As the hollow porous support, a multifilament of polyester fibers (fineness: 111 dtex, filament number: 48) that has not been crimped is circularly knitted into a cylindrical shape and heat treated at 190 ° C. using the support manufacturing apparatus of FIG. We used what we did. The outer diameter of the used braid support was 1.4 mm, and the inner diameter was 0.84 mm.
Polyvinylidene fluoride (manufactured by Arkema, trade name Kyner 761A, mass average molecular weight 6.0 × 10 5 ) 13% by mass, and polyvinyl pyrrolidone (manufactured by Nippon Shokubai Co., Ltd., trade name K-30), 12% by mass, N-methyl -2-Pyrrolidone was dissolved in 75% by mass with stirring to prepare a first film-forming stock solution. The viscosity of this first film-forming stock solution at 40 ° C. was 2 × 10 4 mPa · s.
Subsequently, 5% by mass of polyvinylidene fluoride (trade name Kyner HSV900, mass average molecular weight 1.1 × 10 6 ) manufactured by Arkema Co., Ltd., 12% by mass of polyvinylidene fluoride (trade name Kyner 761A, manufactured by Arkema Co.) 14% by mass of Nippon Shokubai Co., Ltd., trade name K-30) was dissolved in 69% by mass of N-methyl-2-pyrrolidone with stirring to prepare a second membrane forming stock solution. The viscosity of this second film-forming stock solution at 40 ° C. was 9 × 10 4 mPa · s.
（多孔質中空糸膜の製造）
第一製膜原液を、孔径５μｍのフィルタ（図示略）を介して第一環状ノズルへ３．２ｃｃ／分の速度で送液した。また、第一製膜原液の送液と同時に編紐支持体を１０ｍ／分の速度で第一環状ノズル２０へ導いた。中空編紐を第一環状ノズル２０の上部から下部へ向けて通しながら、第一製膜原液を中空編紐の外周部に塗布した後、第一環状ノズルから１０ｍｍ離れた位置に水面を有し、２５℃の温度を有し、Ｎ−メチル−２−ピロリドンの４０質量％水溶液（凝固液）で満たされている第一凝固浴４０へ導き、固化させて、１０ｍ／分の速度で引き取って第一多孔質中空糸膜前駆体を製造した。
得られた前駆体の第一多孔質中空糸膜層の外径は１．５３ｍｍであり、厚みは４０μｍであった。
(Manufacture of porous hollow fiber membrane)
The first film-forming stock solution was fed at a rate of 3.2 cc / min to the first annular nozzle through a filter (not shown) having a pore size of 5 μm. The knitted string support was guided to the first annular nozzle 20 at a speed of 10 m / min simultaneously with the feeding of the first film-forming solution. While applying the hollow knitted string from the upper part to the lower part of the first annular nozzle 20, the first film-forming solution is applied to the outer periphery of the hollow knitted string, and then has a water surface at a position 10 mm away from the first annular nozzle. To a first coagulation bath 40 having a temperature of 25 ° C. and filled with a 40 mass% aqueous solution (coagulation liquid) of N-methyl-2-pyrrolidone, solidified and taken up at a rate of 10 m / min. A first porous hollow fiber membrane precursor was produced.
The outer diameter of the obtained first porous hollow fiber membrane layer of the precursor was 1.53 mm, and the thickness was 40 μm.
次に、第二製膜原液を、孔径５μｍのフィルタ（図示略）を介して二重環状ノズルの外層部へ７．５ｃｃ／分の速度で送液した。また、Ｎ−メチル−２−ピロリドン９０質量％とグリセリン１０質量％から成る中間液を、第二環状ノズル２２の上半部に設けた空間に３．０ｃｃ／分の速度で送液した。さらに、第二製膜原液の送液と同時に第一多孔質中空糸膜前駆体を１０ｍ／分の速度で第二環状ノズル２２の中心部へ導いた。
第一多孔質中空糸膜層を第二環状ノズルの上部から下部へ向けて通しながら、深さ８ｍｍの中間液槽を通過させ、直後に、幅１．６０ｍｍ長さ１ｍｍの通路を通過させた。そしてその後２６ｍｍ下方で第二製膜原液１２を中間液の外周部に塗布し、第二環状ノズル２２から６７ｍｍ離れた位置に水面を有し、６２℃の温度を有し、Ｎ−メチルピロリドンの３０質量％水溶液（凝固液）で満たされている第二凝固浴４２へ導き、固化させて、１０ｍ／分の速度で引き取って多孔質中空糸膜を製膜した。
Next, the second film-forming stock solution was fed at a rate of 7.5 cc / min to the outer layer portion of the double annular nozzle through a filter (not shown) having a pore diameter of 5 μm. Further, an intermediate liquid consisting of 90% by mass of N-methyl-2-pyrrolidone and 10% by mass of glycerin was fed into the space provided in the upper half of the second annular nozzle 22 at a rate of 3.0 cc / min. Further, the first porous hollow fiber membrane precursor was introduced to the center of the second annular nozzle 22 at a speed of 10 m / min simultaneously with the feeding of the second membrane forming raw solution.
While passing the first porous hollow fiber membrane layer from the upper part to the lower part of the second annular nozzle, the intermediate liquid tank having a depth of 8 mm is passed, and immediately thereafter, the passage having a width of 1.60 mm and a length of 1 mm is passed. It was. And after that, the second film-forming stock solution 12 is applied to the outer periphery of the intermediate solution 26 mm below, has a water surface at a position 67 mm away from the second annular nozzle 22, has a temperature of 62 ° C., and N-methylpyrrolidone It led to the 2nd coagulation bath 42 filled with 30 mass% aqueous solution (coagulation liquid), it was made to solidify, and it picked up at the speed | rate of 10 m / min, and formed the porous hollow fiber membrane.
得られた多孔質中空糸膜を、７０℃の温水に３５秒間通して脱溶剤させた。次いで、濃度１００，０００ｍｇ／Ｌの次亜塩素酸ナトリウム水溶液に浸漬させた後、１００℃のスチーム槽中で４分間加熱処理した。その次に９０℃の熱水中に４０秒間通す、というこれら一連の工程を３回繰り返した後、１０５℃に熱した乾燥炉に４分間通して乾燥した後、巻き取って、多孔質中空糸膜を得た。
得られた多孔質中空糸膜の評価結果を表１に示す。
The obtained porous hollow fiber membrane was passed through warm water at 70 ° C. for 35 seconds to remove the solvent. Subsequently, after being immersed in a sodium hypochlorite aqueous solution having a concentration of 100,000 mg / L, it was heat-treated in a steam bath at 100 ° C. for 4 minutes. Next, the series of steps of passing in hot water of 90 ° C. for 40 seconds was repeated three times, then passing through a drying furnace heated to 105 ° C. for 4 minutes, drying, winding up, and porous hollow fiber A membrane was obtained.
The evaluation results of the obtained porous hollow fiber membrane are shown in Table 1.
〔比較例１〕
中間液として、グリセリン１００質量％から成る中間液を用いた以外は、実施例１と同様にして多孔質中空糸膜を得た。評価結果を表１に示す。
[Comparative Example 1]
A porous hollow fiber membrane was obtained in the same manner as in Example 1 except that an intermediate liquid consisting of 100% by mass of glycerin was used as the intermediate liquid. The evaluation results are shown in Table 1.
〔実施例２〕
第二製膜原液として、ポリフッ化ビニリデン（アルケマ社製、商品名カイナーＨＳＶ９００、質量平均分子量１．１×１０６）５質量％、ポリフッ化ビニリデン（アルケマ社製、商品名カイナー７６１Ａ）１１質量％及びポリビニルピロリドン（日本触媒社製、商品名Ｋ−３０）１３質量％を、Ｎ―メチル―２―ピロリドン７１質量％に撹拌しながら溶解させて調製した第二製膜原液を用いた以外は、実施例１と同様にして多孔質中空糸膜を得た。評価結果を表１に示す。
[Example 2]
Polyvinylidene fluoride (trade name Kyner HSV900, mass average molecular weight 1.1 × 10 6 ) 5% by mass, polyvinylidene fluoride (Arkema Co., trade name Kyner 761A) 11% by mass as the second film-forming stock solution And polyvinylpyrrolidone (Nippon Shokubai Co., Ltd., trade name K-30) 13% by mass was dissolved in 71% by mass of N-methyl-2-pyrrolidone with stirring, and the second membrane forming stock solution was used. A porous hollow fiber membrane was obtained in the same manner as in Example 1. The evaluation results are shown in Table 1.
〔実施例３〕
中間液として、Ｎ−メチル−２−ピロリドン８０質量％とグリセリン２０質量％から成る中間液を用いた以外は、実施例１と同様にして多孔質中空糸膜を得た。評価結果を表１に示す。
Example 3
A porous hollow fiber membrane was obtained in the same manner as in Example 1 except that an intermediate liquid consisting of 80% by mass of N-methyl-2-pyrrolidone and 20% by mass of glycerin was used as the intermediate liquid. The evaluation results are shown in Table 1.
〔比較例２〕
中間液として、Ｎ−メチル−２−ピロリドン６０質量％とグリセリン４０質量％から成る中間液を用いた以外は、実施例１と同様にして多孔質中空糸膜を得た。評価結果を表１に示す。
[Comparative Example 2]
A porous hollow fiber membrane was obtained in the same manner as in Example 1 except that an intermediate liquid consisting of 60% by mass of N-methyl-2-pyrrolidone and 40% by mass of glycerin was used as the intermediate liquid. The evaluation results are shown in Table 1.
〔比較例３〕
中間液の供給方法として、溜めた場所に第一多孔質中空糸膜層を通過させるのではなく、通路の壁面から中間液を供給して第一多孔質中空糸膜層に塗布した以外は、比較例２と同様にして多孔質中空糸膜を得た。評価結果を表１に示す。
[Comparative Example 3]
As a method for supplying the intermediate liquid, the first porous hollow fiber membrane layer is not applied to the first porous hollow fiber membrane layer by supplying the intermediate liquid from the wall surface of the passage, instead of passing the first porous hollow fiber membrane layer through the accumulated place. Obtained a porous hollow fiber membrane in the same manner as in Comparative Example 2. The evaluation results are shown in Table 1.
〔実施例４〕
第二製膜原液として、ポリフッ化ビニリデン（アルケマ社製、商品名カイナーＨＳＶ９００、質量平均分子量１．１×１０６）１５質量％及びポリビニルピロリドン（日本触媒社製、商品名Ｋ−３０）９質量％を、Ｎ―メチル―２―ピロリドン７６質量％に撹拌しながら溶解させて調製した第二製膜原液を用いた以外は、実施例１と同様にして多孔質中空糸膜を得た。評価結果を表１に示す。
Example 4
Polyvinylidene fluoride (trade name Kyner HSV900, mass average molecular weight 1.1 × 10 6 ) 15% by mass and polyvinyl pyrrolidone (manufactured by Nippon Shokubai Co., Ltd., trade name K-30) 9 mass as the second membrane forming stock solution % Was obtained in the same manner as in Example 1 except that a second membrane-forming stock solution prepared by dissolving in 76% by mass of N-methyl-2-pyrrolidone with stirring was used. The evaluation results are shown in Table 1.
〔比較例４〕
通路の幅Ａを１．７０ｍｍにした以外は、実施例１と同様にして製膜を行った。しかし、中間液の第一多孔質中空糸膜層への随伴が多く、第二製膜原液の第一多孔質中空糸膜層への塗布ムラが生じ、多孔質中空糸膜を安定して得ることができなかった。
[Comparative Example 4]
A film was formed in the same manner as in Example 1 except that the width A of the passage was 1.70 mm. However, the intermediate liquid is often accompanied by the first porous hollow fiber membrane layer, resulting in uneven coating of the second membrane forming solution on the first porous hollow fiber membrane layer, which stabilizes the porous hollow fiber membrane. I couldn't get it.
本発明の多孔質中空糸膜は、その構成から高い分離特性・機械的強度・耐物理損傷性を有するに加え、従来では孔径が小さくなり易かった第二多孔質中空糸膜層の内表面孔径も大きくなり、結果、透水性能も兼ね備えた膜となっている。
よって、本発明の多孔質中空糸膜は、精密濾過、限外濾過等による水処理に用いる濾過膜として好適である。
The porous hollow fiber membrane of the present invention has high separation characteristics, mechanical strength, and physical damage resistance due to its structure, and in addition, the inner surface of the second porous hollow fiber membrane layer that has been easy to reduce the pore diameter in the past. As a result, the pore diameter is increased, and as a result, the membrane has water permeability.
Therefore, the porous hollow fiber membrane of the present invention is suitable as a filtration membrane used for water treatment by microfiltration, ultrafiltration or the like.
１０ 第１の製膜原液
１２ 第２の製膜原液
２０ 第一環状ノズル
２２ 第二環状ノズル
３０ 中空支持体（編紐）
４０ 第一凝固浴
４２ 第二凝固浴
DESCRIPTION OF SYMBOLS 10 1st film forming undiluted solution 12 2nd film forming undiluted solution 20 1st annular nozzle 22 2nd annular nozzle 30 Hollow support body (knitted string)
40 First coagulation bath 42 Second coagulation bath
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