JP2016097362A - Porous hollow fiber membrane, method for producing porous hollow fiber membrane, and water purification method - Google Patents
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Landscapes
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
Description
本発明は、多孔性中空糸膜、多孔性中空糸膜の製造方法、及び浄水方法に関する。 The present invention relates to a porous hollow fiber membrane, a method for producing a porous hollow fiber membrane, and a water purification method.
懸濁水である河川水、湖沼水及び地下水等の天然水源水から飲料水及び工業用水を得る上水処理、並びに、下水等の生活排水を処理して再生雑用水を得たり、放流可能な清澄水を得たりする下水処理には、固液分離操作(除濁操作)を行うことで懸濁物を除去(除濁)することが必須である。その除去は、上水処理に関しては、懸濁水である天然水源水由来の懸濁物(粘土、コロイド、細菌等)の除去であり、下水処理に関しては、下水中の懸濁物や、活性汚泥等により生物処理(2次処理)した処理水中の懸濁物(汚泥等)の除去である。従来は、これらの除濁操作は、主に、沈殿法、砂濾過法又は凝集沈殿砂濾過法により行われてきたが、近年は、膜濾過法が普及しつつある。膜濾過法の利点として、例えば以下の事項が挙げられる。
(1)得られる水質の除濁レベルが高く且つ安定している(得られる水の安全性が高い)。
(2)濾過装置の設置スペースが小さくてすむ。
(3)自動運転が容易である。
Clear water that can be reclaimed miscellaneous water by treating drinking water and industrial water from natural water source water such as river water, lake water, and groundwater that is suspended water, and domestic wastewater such as sewage In the sewage treatment to obtain water, it is essential to remove the suspension (turbidity) by performing a solid-liquid separation operation (turbidity removal operation). The removal is removal of suspensions (clays, colloids, bacteria, etc.) derived from natural water source water, which is suspension water for water treatment, and suspensions of activated water and activated sludge for sewage treatment. It is removal of the suspended matter (sludge etc.) in the treated water which carried out biological treatment (secondary treatment) by etc. Conventionally, these turbidity removal operations have been mainly performed by a precipitation method, a sand filtration method, or an agglomeration precipitation sand filtration method, but in recent years, a membrane filtration method has become widespread. Examples of the advantages of the membrane filtration method include the following.
(1) The turbidity level of the obtained water is high and stable (the safety of the obtained water is high).
(2) The installation space for the filtration device is small.
(3) Automatic operation is easy.
例えば、上水処理では、凝集沈殿砂濾過法の代替として、あるいは、凝集沈殿砂濾過の後段に設置して凝集沈殿砂濾過された処理水の水質をさらに向上するための手段等として膜濾過法が用いられている。下水処理に関しても、下水2次処理水からの汚泥の分離等に膜濾過法を使用することの検討が進んでいる。 For example, in clean water treatment, membrane filtration as an alternative to coagulation sedimentation sand filtration or as a means to further improve the quality of treated water that has been installed after the aggregation sedimentation sand filtration and filtered. Is used. Regarding sewage treatment, studies are underway to use a membrane filtration method to separate sludge from sewage secondary treated water.
これら膜濾過法による除濁操作には、主として、中空糸状の限外濾過膜や精密濾過膜(孔径数nmから数百nmの範囲)が用いられる。中空糸状の濾過膜を用いた濾過方式としては、膜の内表面側から外表面側に向けて濾過する内圧濾過方式と、外表面側から内表面側に向けて濾過する外圧濾過方式の2方式がある。これらのうち、原水と接触する側の膜表面積を大きくするのが可能であることから、単位膜表面積当たりの濁質負荷量を小さくできる外圧濾過方式が有利である。特許文献1〜3は中空糸及びその製造方法を開示する。 For the turbidity operation by these membrane filtration methods, a hollow-fiber ultrafiltration membrane or a microfiltration membrane (with a pore diameter of several nm to several hundred nm) is mainly used. As a filtration method using a hollow fiber filtration membrane, there are two methods, an internal pressure filtration method for filtering from the inner surface side to the outer surface side of the membrane and an external pressure filtration method for filtering from the outer surface side to the inner surface side. There is. Among these, since it is possible to increase the membrane surface area on the side in contact with the raw water, an external pressure filtration system that can reduce the turbidity load per unit membrane surface area is advantageous. Patent Documents 1 to 3 disclose a hollow fiber and a manufacturing method thereof.
また、特許文献4には、濾過用途に好適な、緻密な細孔と高い透水性能とを併せ持ち、かつ強度に優れた、熱可塑性樹脂より成る多孔性多層中空糸膜、およびその安定した製造方法を提供することを目的として、円環状吐出口を有する中空糸成型ノズルを用い、該円環状吐出口から熱可塑性樹脂と有機液体を含む溶融混練物を吐出し、得られた多層中空糸から該有機液体を抽出除去して多孔性多層中空糸膜を製造する方法において、該中空糸成型ノズルが同心円状に配置された円環状吐出口を二つ以上有し、隣り合う吐出口からは互いに異なる組成の溶融混練物が吐出され、少なくとも1つの該円環状吐出口から吐出される溶融混練物が無機微粉も含み、得られた多層中空糸状から該無機微粉も抽出除去される事を特徴とする製造方法が開示されている。さらに、特許文献5には、組紐と膜材とを具備し、膜材は組紐外表面に隣接する緻密層を 有する第一多孔質層と、第一多孔質層に隣接する緻密層を有する第二多孔質層とを具備することを特徴とする複合多孔質膜を提供することを目的として、組紐と膜材とを具備し、膜材は組紐外表面に隣接する緻密層を有する第一多孔質層と、第一多孔質層に隣接する緻密層を有する第二多孔質層とを具備する 複合多孔質膜を開示している。 Patent Document 4 discloses a porous multilayer hollow fiber membrane made of a thermoplastic resin that has both fine pores and high water permeability and is excellent in strength, suitable for filtration, and a stable production method thereof. For this purpose, a hollow fiber molding nozzle having an annular discharge port is used, and a melt-kneaded product containing a thermoplastic resin and an organic liquid is discharged from the annular discharge port. In a method for producing a porous multilayer hollow fiber membrane by extracting and removing an organic liquid, the hollow fiber molding nozzle has two or more annular discharge ports arranged concentrically, and is different from adjacent discharge ports A melt-kneaded material having a composition is discharged, the melt-kneaded material discharged from at least one annular discharge port also contains inorganic fine powder, and the inorganic fine powder is also extracted and removed from the obtained multilayer hollow fiber shape. Manufacturing method disclosed It has been. Further, Patent Document 5 includes a braid and a membrane material, and the membrane material includes a first porous layer having a dense layer adjacent to the braid outer surface and a dense layer adjacent to the first porous layer. For the purpose of providing a composite porous membrane comprising a second porous layer having a braid and a membrane material, the membrane material having a dense layer adjacent to the outer surface of the braid A composite porous membrane comprising a first porous layer and a second porous layer having a dense layer adjacent to the first porous layer is disclosed.
膜濾過法による除濁は、上述のように従来の沈殿法や砂濾過法にはない利点が多くあることから、従来法の代替技術や補完技術として上水処理や下水処理への普及が進みつつある。 As described above, turbidity removal by membrane filtration has many advantages over conventional precipitation methods and sand filtration methods, and as a result, it has become popular in water treatment and sewage treatment as an alternative and complementary technology to conventional methods. It's getting on.
ところで、多孔性膜の製法として、熱誘起相分離法が知られている。この製法では熱可塑性樹脂と有機液体を用いる。有機液体として、該熱可塑性樹脂を室温では溶解しないが、高温では溶解する溶剤、すなわち潜在的溶剤を用いる。より詳細には、熱誘起相分離法は、熱可塑性樹脂と有機液体を高温で混練し、熱可塑性樹脂を有機液体に溶解させた後、室温まで冷却することで相分離を誘発させ、さらに有機液体を除去して多孔体を製造する方法である。熱誘起相分離法は、以下の利点を持つ。
(a)汎用される溶剤中に室温で溶解可能なものがない、ポリエチレン等のポリマーでも、製膜が可能になる。
(b)高温で溶解した後、冷却固化させて製膜するので、特に熱可塑性樹脂が結晶性樹脂である場合に、製膜時に結晶化が促進されて高強度の膜が得られやすい。
Incidentally, a thermally induced phase separation method is known as a method for producing a porous membrane. In this manufacturing method, a thermoplastic resin and an organic liquid are used. As the organic liquid, a solvent that does not dissolve the thermoplastic resin at room temperature but dissolves at a high temperature, that is, a latent solvent, is used. More specifically, in the thermally induced phase separation method, a thermoplastic resin and an organic liquid are kneaded at a high temperature, the thermoplastic resin is dissolved in the organic liquid, and then cooled to room temperature to induce phase separation. This is a method for producing a porous body by removing a liquid. The thermally induced phase separation method has the following advantages.
(A) Films can be formed even with polymers such as polyethylene that do not dissolve at room temperature in commonly used solvents.
(B) Since the film is formed by cooling and solidifying after melting at a high temperature, particularly when the thermoplastic resin is a crystalline resin, crystallization is promoted during film formation, and a high-strength film is likely to be obtained.
上記の利点から、熱誘起相分離法は、多孔性膜の製造方法として多用されている(例えば、非特許文献1〜4参照)。 From the above advantages, the thermally induced phase separation method is frequently used as a method for producing a porous membrane (for example, see Non-Patent Documents 1 to 4).
しかしながら、長期にわたり安定した膜濾過法の運転を行う技術は確立されておらず、これが膜濾過法の広範囲な普及を妨げている(上記非特許文献5参照)。安定した膜濾過法の運転を妨げる原因は、主に膜表面の擦過による膜の透水性能の劣化である。透水性能の劣化は、濁質物質等による膜の目詰まり(ファウリング)(上記非特許文献5参照)と、膜表面が懸濁物の擦過を受けることが原因となる。 However, a technique for performing stable membrane filtration operation over a long period of time has not been established, and this hinders widespread use of membrane filtration methods (see Non-Patent Document 5 above). The cause of hindering the stable operation of the membrane filtration method is mainly the deterioration of the water permeability of the membrane due to abrasion of the membrane surface. The deterioration of the water permeation performance is caused by clogging (fouling) of the membrane due to turbid substances or the like (see Non-Patent Document 5 above) and the membrane surface being rubbed by the suspension.
この膜表面の擦過は、膜濾過法の運転時ではなく、外圧式濾過により膜の外表面(以下、「膜外表面」と略する場合もある。)に堆積した懸濁物を空気洗浄等により膜外表面から剥離する時に主として起こるとされている。ところが、この現象そのものがあまり知られていなかったこともあり、膜面擦過による透水性能劣化への対応技術の開発はあまりなされていない。現在、膜面擦過に対応する技術としては、特開平11−138164号公報において、エアバブリング洗浄による膜性能変化を抑制する手段として、破断強度の高い膜を用いることを開示するに過ぎない。 This abrasion on the membrane surface does not occur during the operation of the membrane filtration method, but air-washing suspensions deposited on the outer surface of the membrane (hereinafter sometimes abbreviated as “membrane outer surface”) by external pressure filtration, etc. This is mainly caused when peeling from the outer surface of the film. However, since this phenomenon itself has not been well known, development of a technique for dealing with deterioration of water permeability performance due to film surface abrasion has not been made. Currently, as a technique for dealing with film surface abrasion, Japanese Patent Application Laid-Open No. 11-138164 merely discloses the use of a film having a high breaking strength as a means for suppressing film performance change due to air bubbling cleaning.
そこで、本発明は、高いろ過性能を長期にわたって維持可能な多孔性中空糸膜を提供することを目的とする。 Then, an object of this invention is to provide the porous hollow fiber membrane which can maintain high filtration performance over a long period of time.
本発明者らは、上記従来技術の課題を解決するために鋭意努力した結果、粘度平均分子量が特定値以上であるポリエチレンと溶剤とを加熱し、溶融混練して作製した多孔質膜層を備えた多孔性中空糸膜が耐擦過性に優れ、透水性の劣化を抑制できることを見出し、本発明を完成させるに至った。 As a result of diligent efforts to solve the above-mentioned problems of the prior art, the present inventors include a porous membrane layer prepared by heating, melting and kneading polyethylene and a solvent having a viscosity average molecular weight of a specific value or more. The present inventors have found that the porous hollow fiber membrane has excellent scratch resistance and can suppress deterioration of water permeability, thereby completing the present invention.
すなわち、本発明は以下のとおりである。
[1]粘度平均分子量が100万以上のポリエチレンを含む多孔質膜層を備え、
前記多孔質膜層は、孔径が0.3μm以上1.0μm以下、細孔のアスペクト比が10以下、空孔率が70%以上であり、
純水フラックスが5000LMH以上であり、
耐膜面擦過率が80%以上である多孔性中空糸膜。
[2]外表面側に位置する前記多孔質膜層と、内表面側に位置する中空状の支持体とを備える、[1]に記載の多孔性中空糸膜。
[3]前記支持体が編紐である、[2]に記載の多孔性中空糸膜。
[4]前記編紐がポリエチレンテレフタレートを含む、[3]に記載の多孔性中空糸膜。
[5][1]〜[4]のいずれか一に記載の多孔性中空糸膜の製造方法であって、
粘度平均分子量が100万以上のポリエチレンと溶剤とを220℃以上に加熱し、シリンダー径Dに対するシリンダー長さLの比(L/D)が10以上の押出機を用いて溶融混練して、製膜原液を作製する溶融混練工程と、
前記製膜原液を、冷却凝固して熱誘起相分離法により製膜させて多孔質膜層を形成する冷却凝固工程と、
を有する多孔性中空糸膜の製造方法。
[6]前記ポリエチレンと前記溶剤とを、前記製膜原液100質量%に対し、90質量%以上含有する、[5]に記載の多孔性中空糸膜の製造方法。
[7]前記ポリエチレンを、前記製膜原液100質量%に対し、5質量%以上20質量%以下含有する、[5]又は[6]に記載の多孔性中空糸膜の製造方法。
[8]前記ポリエチレンの粘度平均分子量の大きさにより、前記多孔性中空糸膜の孔径の大きさを制御する、[5]〜[7]のいずれか一に記載の多孔性中空糸膜の製造方法。
[9]前記製膜原液を二重管ノズルの内管と外管との間の流路から吐出し、前記溶剤を前記内管内の流路から吐出する吐出工程をさらに有し、
前記冷却凝固工程において、前記吐出工程を経た前記製膜原液を製膜させる、[5]〜[8]のいずれか一に記載の多孔性中空糸膜の製造方法。
[10]前記多孔性中空糸膜は、外表面側に位置する前記多孔質膜層と、内表面側に位置する中空状の支持体とを備え、
前記製膜原液を二重管ノズルの内管と外管との間の流路から吐出し、前記支持体を内管から排出し、前記支持体に前記製膜原液を積層する積層工程をさらに有し、
前記冷却凝固工程において、前記積層工程を経た前記製膜原液を製膜させる、[5]〜[8]のいずれか一に記載の多孔性中空糸膜の製造方法。
[11][1]〜[4]のいずれか一に記載の多孔性中空糸膜を用いてろ過をする浄水方法。
That is, the present invention is as follows.
[1] A porous membrane layer containing polyethylene having a viscosity average molecular weight of 1,000,000 or more,
The porous membrane layer has a pore diameter of 0.3 μm or more and 1.0 μm or less, a pore aspect ratio of 10 or less, and a porosity of 70% or more,
Pure water flux is 5000 LMH or more,
A porous hollow fiber membrane having a membrane scratch resistance of 80% or more.
[2] The porous hollow fiber membrane according to [1], comprising the porous membrane layer located on the outer surface side and a hollow support located on the inner surface side.
[3] The porous hollow fiber membrane according to [2], wherein the support is a knitted string.
[4] The porous hollow fiber membrane according to [3], wherein the knitted string includes polyethylene terephthalate.
[5] A method for producing a porous hollow fiber membrane according to any one of [1] to [4],
Polyethylene having a viscosity average molecular weight of 1 million or more and a solvent are heated to 220 ° C. or more, and melt-kneaded using an extruder having a cylinder length L to cylinder diameter D of 10 or more (L / D). A melt-kneading step for producing a membrane stock solution;
A cooling and solidification step in which the film-forming stock solution is cooled and solidified to form a porous membrane layer by heat-induced phase separation; and
A method for producing a porous hollow fiber membrane having
[6] The method for producing a porous hollow fiber membrane according to [5], comprising 90% by mass or more of the polyethylene and the solvent with respect to 100% by mass of the membrane-forming stock solution.
[7] The method for producing a porous hollow fiber membrane according to [5] or [6], wherein the polyethylene is contained in an amount of 5% by mass to 20% by mass with respect to 100% by mass of the membrane-forming stock solution.
[8] The production of the porous hollow fiber membrane according to any one of [5] to [7], wherein the pore size of the porous hollow fiber membrane is controlled by the viscosity average molecular weight of the polyethylene. Method.
[9] The film-forming stock solution is further discharged from a flow path between an inner pipe and an outer pipe of a double-tube nozzle, and further includes a discharge step of discharging the solvent from the flow path in the inner pipe.
The method for producing a porous hollow fiber membrane according to any one of [5] to [8], wherein in the cooling and solidifying step, the membrane-forming stock solution that has passed through the discharging step is formed.
[10] The porous hollow fiber membrane includes the porous membrane layer located on the outer surface side, and a hollow support located on the inner surface side,
A stacking step of discharging the film-forming stock solution from a flow path between an inner tube and an outer tube of a double-tube nozzle, discharging the support from the inner tube, and laminating the film-forming stock solution on the support; Have
The method for producing a porous hollow fiber membrane according to any one of [5] to [8], wherein in the cooling and solidifying step, the membrane-forming stock solution that has undergone the laminating step is formed.
[11] A water purification method for filtration using the porous hollow fiber membrane according to any one of [1] to [4].
本発明の多孔性中空糸膜によれば、高いろ過性能を長期にわたって維持することができる。 According to the porous hollow fiber membrane of the present invention, high filtration performance can be maintained over a long period of time.
以下、本発明を実施するための形態(以下、「本実施形態」という。)について詳細に説明する。以下の本実施形態は、本発明を説明するための例示であり、本発明を以下の内容に限定する趣旨ではない。本発明は、その要旨の範囲内で適宜に変更して実施できる。 Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be implemented with appropriate modifications within the scope of the gist.
[多孔性中空糸膜]
本実施形態に係る多孔性中空糸膜は、粘度平均分子量が100万以上のポリエチレンを含む多孔質膜層を備え、純水フラックスが5000LMH以上であり、耐膜面擦過率が80%以上である。当該多孔質膜層は、孔径が0.3μm以上1.0μm以下、細孔のアスペクト比が10以下、空孔率が70%以上である。
[Porous hollow fiber membrane]
The porous hollow fiber membrane according to the present embodiment includes a porous membrane layer containing polyethylene having a viscosity average molecular weight of 1,000,000 or more, a pure water flux is 5,000 LMH or more, and a membrane scratch resistance is 80% or more. . The porous membrane layer has a pore diameter of 0.3 μm or more and 1.0 μm or less, a pore aspect ratio of 10 or less, and a porosity of 70% or more.
図1は、本実施形態に係る多孔性中空糸膜の一例である多孔性中空糸膜の断面を模式的に示したものである。図1に示す多孔性中空糸膜は、二層構造を有し、一方の多孔質膜層として、外表面FAを有する多孔質膜層1aと、他方の中空状の支持体として、中空部1cに対して内表面FBを有する編紐1bとを備える。この多孔質膜層1aは熱可塑性樹脂からなり、編紐1bは中空状の編紐からなる。なお、多孔質膜層1aは熱可塑性樹脂以外の成分(不純物等)を5質量%程度まで含んでいてもよい。 FIG. 1 schematically shows a cross section of a porous hollow fiber membrane which is an example of a porous hollow fiber membrane according to the present embodiment. The porous hollow fiber membrane shown in FIG. 1 has a two-layer structure. One porous membrane layer is a porous membrane layer 1a having an outer surface FA, and the other hollow support is a hollow portion 1c. And a braided string 1b having an inner surface FB. The porous membrane layer 1a is made of a thermoplastic resin, and the knitted string 1b is made of a hollow knitted string. In addition, the porous membrane layer 1a may contain up to about 5% by mass of components (impurities and the like) other than the thermoplastic resin.
なお、ここでは二層構造の多孔性中空糸膜を例示したが、多孔性中空糸膜は多孔質膜層の単層構造であってもよい。また、図1に示す多孔性中空糸膜は外圧濾過方式を採用することを前提としているが、本実施形態では内圧濾過方式を採用するものであってもよく、内圧濾過方式を採用する場合は、多孔質膜層の単層構造であることが、製造上の観点から好ましい。 In addition, although the porous hollow fiber membrane of the two-layer structure was illustrated here, the porous hollow fiber membrane may be a single layer structure of the porous membrane layer. Further, the porous hollow fiber membrane shown in FIG. 1 is premised on the adoption of an external pressure filtration method, but in the present embodiment, an internal pressure filtration method may be adopted. When the internal pressure filtration method is adopted, A single layer structure of the porous membrane layer is preferable from the viewpoint of production.
図2は、図1に示す断面の一部を拡大したものであり、図1に示す分離膜部分1aと組紐1bの一部を示す。図2に示す分離膜は、多孔質膜層1aとしてスキン層と多孔質膜層とを備え、編紐1bとして縦紐として組まれている編紐フィラメントと横紐として組まれている編紐フィラメントとから構成される。 FIG. 2 is an enlarged view of a part of the cross section shown in FIG. 1, and shows a part of the separation membrane portion 1a and the braid 1b shown in FIG. The separation membrane shown in FIG. 2 includes a skin layer and a porous membrane layer as the porous membrane layer 1a, and a braided filament that is assembled as a vertical cord and a braided filament as a braided cord 1b. It consists of.
多孔性中空糸膜の内径は、0.4mm以上5mm以下が好ましい。内径が0.4mm以上であれば多孔性中空糸膜内を流れる液体の圧損が大きくなるのを防ぐことができ、5mm以下であれば比較的薄い膜厚で十分な圧縮強度や破裂強度を発現しやすい。この内径は、より好ましくは0.5mm以上3.0mm以下であり、さらに好ましくは0.6mm以上1.0mm以下である。 The inner diameter of the porous hollow fiber membrane is preferably 0.4 mm or more and 5 mm or less. If the inner diameter is 0.4 mm or more, the pressure loss of the liquid flowing in the porous hollow fiber membrane can be prevented, and if it is 5 mm or less, sufficient compressive strength and bursting strength are expressed with a relatively thin film thickness. It's easy to do. This inner diameter is more preferably 0.5 mm or more and 3.0 mm or less, and further preferably 0.6 mm or more and 1.0 mm or less.
本実施形態の多孔性中空糸膜の厚さは、好ましくは100μm以上500μm以下であり、より好ましくは200μm以上300μm以下である。厚さが100μm以上であると圧縮に対する強度がより高くなり、他方、500μm以下であると膜抵抗による圧損をより小さくすることができる。 The thickness of the porous hollow fiber membrane of this embodiment is preferably 100 μm or more and 500 μm or less, more preferably 200 μm or more and 300 μm or less. When the thickness is 100 μm or more, the strength against compression becomes higher, and when the thickness is 500 μm or less, the pressure loss due to the membrane resistance can be further reduced.
多孔性中空糸膜の透水性に対する指標である純水フラックス(透水量)は、多孔性中空糸膜の中空部に純水を注入し、中空部から外表面に透過する純水量を測定することで決定できる。詳細には下記実施例に記載した方法に準じて測定できる。 The pure water flux (water permeability), which is an index for the water permeability of the porous hollow fiber membrane, is to inject pure water into the hollow portion of the porous hollow fiber membrane and measure the amount of pure water that permeates from the hollow portion to the outer surface. Can be determined. In detail, it can measure according to the method described in the following Example.
本実施形態の多孔性中空糸膜の純水フラックスは、5000LMH以上であり、好ましくは5,000LMH以上30,000LMH以下、より好ましくは5,000LMH以上20,000LMH以下である。純水フラックスが5000LMH以上であると実際のろ過時の透水性を維持しやすくなり、他方、30,000LMH以下であると大腸菌などの菌群を阻止できる。純水フラックスがこのような範囲にある多孔性中空糸膜を得るには、例えば、ポリマー濃度を調整や紡糸温度の調整など紡糸条件を調整すればよい。 The pure water flux of the porous hollow fiber membrane of this embodiment is 5000 LMH or more, preferably 5,000 LMH or more and 30,000 LMH or less, more preferably 5,000 LMH or more and 20,000 LMH or less. When the pure water flux is 5000 LMH or more, water permeability during actual filtration can be easily maintained, and when it is 30,000 LMH or less, bacterial groups such as Escherichia coli can be blocked. In order to obtain a porous hollow fiber membrane having a pure water flux in such a range, for example, the spinning conditions such as adjusting the polymer concentration and adjusting the spinning temperature may be adjusted.
多孔性中空糸膜の擦過性に対する指標である耐膜面擦過率は、多孔性中空糸膜をサンドブラストの中に置き、10分経過後の純水透水量を測定して、その初期に対する保持率によって測定できる。詳細には下記実施例に記載した方法に準じて測定できる。 The membrane surface scratch resistance, which is an index for the scratch resistance of the porous hollow fiber membrane, is measured by placing the porous hollow fiber membrane in sandblast and measuring the amount of pure water permeation after 10 minutes. Can be measured by. In detail, it can measure according to the method described in the following Example.
本実施形態の多孔性中空糸膜の耐膜面擦過率は、80%以上であり、好ましくは80%以上100%以下、より好ましくは90%以上100%以下である。耐膜面擦過率が80%以上であると耐擦過性としては十分良好である。 The abrasion resistance surface abrasion rate of the porous hollow fiber membrane of this embodiment is 80% or more, preferably 80% or more and 100% or less, more preferably 90% or more and 100% or less. When the film scratch resistance is 80% or more, the scratch resistance is sufficiently good.
擦過による透水性能の低下の原因は、隣り合う多孔性中空糸膜の膜同士が擦れることにより、膜表面の細孔が潰れることが主因と考えられる。多孔性中空糸膜の主成分を粘度平均分子量100万以上のポリエチレンとすることで、その素材としての摺動性及び耐摩耗性から、隣り合う膜同士が擦れあっても、細孔が潰れるのを抑制して膜表面の細孔形状を維持することができる。 The main cause of the decrease in water permeability due to rubbing is that the pores on the membrane surface are crushed by rubbing between adjacent porous hollow fiber membranes. By using polyethylene having a viscosity average molecular weight of 1 million or more as the main component of the porous hollow fiber membrane, the pores are crushed even if the adjacent membranes rub against each other due to the slidability and wear resistance of the material. Can be suppressed and the pore shape of the membrane surface can be maintained.
<多孔質膜層>
本実施形態の多孔質膜層は、粘度平均分子量が100万以上のポリエチレンを含み、表面に多数の孔を有している。また、多孔質膜層は網目構造であることが好ましい。通常、多孔質層の構造としては網目構造と球状構造が挙げられ、構造上、連結している熱可塑性樹脂の体積が少ない球状構造よりも連結部分の体積が多い網目構造の方が一般的に高い伸度を有する。したがって、組紐部が寸法変化して多孔構造が伸長されてもポリマー連結部のミクロな破断等が起こり難い網目構造の方が好ましい。
<Porous membrane layer>
The porous membrane layer of this embodiment contains polyethylene having a viscosity average molecular weight of 1,000,000 or more, and has a large number of pores on the surface. The porous membrane layer preferably has a network structure. Usually, the structure of the porous layer includes a network structure and a spherical structure, and the network structure having a larger volume of the connected portion is generally more than the spherical structure having a smaller volume of the connected thermoplastic resin. Has high elongation. Therefore, even if the braid portion changes in size and the porous structure is elongated, a network structure in which micro breakage or the like of the polymer connecting portion hardly occurs is preferable.
<ポリエチレン>
本実施形態の多孔質膜層は、粘度平均分子量が100万以上のポリエチレンを含む。粘度平均分子量100万以上のポリエチレンは、特に限定されないが、例えば、メタロセン系触媒を用いて懸濁重合等することにより、調製することができる。
<Polyethylene>
The porous membrane layer of this embodiment includes polyethylene having a viscosity average molecular weight of 1 million or more. The polyethylene having a viscosity average molecular weight of 1 million or more is not particularly limited, but can be prepared by, for example, suspension polymerization using a metallocene catalyst.
本実施形態のポリエチレンは、粘度平均分子量が100万以上であり、好ましくは150万以上700万以下であり、より好ましくは200万以上400万以下である。この粘度平均分子量が100万以上であると耐摩耗性が向上し、他方、700万以下であると粘度が低く紡糸しやすい。 The polyethylene of this embodiment has a viscosity average molecular weight of 1 million or more, preferably 1.5 to 7 million, and more preferably 2 to 4 million. When the viscosity average molecular weight is 1,000,000 or more, the wear resistance is improved. On the other hand, when the viscosity average molecular weight is 7 million or less, the viscosity is low and spinning is easy.
<粘度平均分子量(Mv)>
本実施形態のポリエチレンの粘度平均分子量については、ISO1628−3(2010)従って、以下に示す方法によって求めた。まず、溶融管にパウダー状のポリエチレン20mgを秤量し、溶融管を窒素置換した後、20mLのデカヒドロナフタレン(2,6−ジ−t−ブチル−4−メチルフェノールを1g/L加えたもの)を加え、150℃で2時間攪拌してパウダー状のポリエチレンを溶解させた。その溶液を135℃の恒温槽で、キャノン−フェンスケの粘度計(柴田科学器械工業社製:製品番号−100)を用いて、標線間の落下時間(ts)を測定した。同様に、パウダー状のポリエチレン量を10mg、5mg、2.5mgと変えたサンプルついても同様に標線間の落下時間(ts)を測定した。ブランクとしてパウダー状のポリエチレンを入れていない、デカヒドロナフタレンのみの落下時間(tb)を測定した。以下の式(1)に従って求めたパウダー状のポリエチレンの還元粘度(ηsp/C)をそれぞれプロットして濃度(C)(単位:g/dL)と超高分子量エチレン系共重合体パウダーの還元粘度(ηsp/C)の直線式を導き、濃度0に外挿した極限粘度([η])を求めた。
ηsp/C=(ts/tb−1)/0.1 (単位:dL/g) ・・・(1)
次に、下記式(2)を用いて、上記極限粘度[η]の値を用い、粘度平均分子量(Mv)を算出した。
Mv=(5.34×104)×[η]1.49 ・・・(2)
<Viscosity average molecular weight (Mv)>
About the viscosity average molecular weight of the polyethylene of this embodiment, it calculated | required by the method shown below according to ISO1628-3 (2010). First, 20 mg of powdered polyethylene was weighed in a melting tube, and the melting tube was replaced with nitrogen, and then 20 mL of decahydronaphthalene (with 1 g / L of 2,6-di-t-butyl-4-methylphenol added) And stirred at 150 ° C. for 2 hours to dissolve the powdered polyethylene. The solution was measured in a thermostatic bath at 135 ° C. using a Canon-Fenske viscometer (manufactured by Shibata Kagaku Kikai Kogyo Co., Ltd .: product number-100) for the drop time (ts) between the marked lines. Similarly, the drop time (ts) between the marked lines was measured in the same manner for samples in which the amount of polyethylene powder was changed to 10 mg, 5 mg, and 2.5 mg. The dropping time (tb) of only decahydronaphthalene without powdered polyethylene as a blank was measured. The reduced viscosity (ηsp / C) of the powdered polyethylene determined according to the following formula (1) is plotted, and the concentration (C) (unit: g / dL) and the reduced viscosity of the ultrahigh molecular weight ethylene copolymer powder are plotted. A linear equation of (ηsp / C) was derived, and the intrinsic viscosity ([η]) extrapolated to a concentration of 0 was determined.
ηsp / C = (ts / tb−1) /0.1 (unit: dL / g) (1)
Next, the viscosity average molecular weight (Mv) was calculated using the value of the intrinsic viscosity [η] using the following formula (2).
Mv = (5.34 × 104) × [η] 1.49 (2)
本実施形態の多孔質膜層の孔径、細孔のアスペクト比、空孔率は、例えば、電子顕微鏡を用いて多孔質膜層のSEM画像を撮影し、その画像解析を行うことで求めることができる。詳細には下記実施例に記載した方法に準じて測定できる。 The pore diameter, pore aspect ratio, and porosity of the porous membrane layer of the present embodiment can be obtained by, for example, taking an SEM image of the porous membrane layer using an electron microscope and analyzing the image. it can. In detail, it can measure according to the method described in the following Example.
本実施形態の多孔質膜層の孔径は、0.3μm以上1.0μm以下であり、好ましくは0.1μm以上2.0μm以下であり、より好ましくは0.3μm以上1.0μm以下である。この孔径が0.3μm以上であるとより優れた透水性能が得られ、他方、1.0μm以下であると懸濁水中に含まれる濁質成分の素抜けが起こりにくい。孔径がこのような範囲にある多孔質膜層を得るには、例えば、ポリマー濃度を調整や紡糸温度の調整など紡糸条件を調整すればよい。 The pore diameter of the porous membrane layer of this embodiment is 0.3 μm or more and 1.0 μm or less, preferably 0.1 μm or more and 2.0 μm or less, more preferably 0.3 μm or more and 1.0 μm or less. When this pore diameter is 0.3 μm or more, more excellent water permeability can be obtained, and when it is 1.0 μm or less, turbid components contained in the suspended water are not easily removed. In order to obtain a porous membrane layer having a pore diameter in such a range, for example, the spinning conditions such as adjusting the polymer concentration and adjusting the spinning temperature may be adjusted.
本実施形態の多孔質膜層の細孔のアスペクト比は、10以下であり、好ましくは2以上20以下であり、より好ましくは4以上10以下である。この細孔のアスペクト比が10以下であると孔径分布が狭まりやすく、他方、2以上であると耐圧縮強度が強くなりやすい。なお、細孔のアスペクト比は、孔の長径と短径の比(長径/短径)であるため、下限は1.0である。アスペクト比がこのような範囲にある多孔性中空糸膜を得るには、例えば、ポリマー濃度を調整や紡糸温度の調整など紡糸条件を調整すればよい。 The aspect ratio of the pores of the porous membrane layer of this embodiment is 10 or less, preferably 2 or more and 20 or less, more preferably 4 or more and 10 or less. When the aspect ratio of the pores is 10 or less, the pore diameter distribution tends to be narrowed, and when the aspect ratio is 2 or more, the compression resistance strength tends to increase. The aspect ratio of the pore is the ratio of the major axis to the minor axis of the pore (major axis / minor axis), so the lower limit is 1.0. In order to obtain a porous hollow fiber membrane having an aspect ratio in such a range, for example, the spinning conditions such as adjusting the polymer concentration and adjusting the spinning temperature may be adjusted.
本実施形態の多孔質膜層の空孔率は、70%以上であり、好ましくは70%以上90%以下であり、より好ましくは70%以上80%以下である。この空孔率が70%以上であると透水性能が得られやすく、他方、90%以下であると機械的強度が得られやすい。空孔率がこのような範囲にある多孔性中空糸膜を得るには、例えば、ポリマー濃度を調整や紡糸温度の調整など紡糸条件を調整すればよい。 The porosity of the porous membrane layer of this embodiment is 70% or more, preferably 70% or more and 90% or less, more preferably 70% or more and 80% or less. When the porosity is 70% or more, water permeability is easily obtained, and when it is 90% or less, mechanical strength is easily obtained. In order to obtain a porous hollow fiber membrane having a porosity in such a range, for example, the spinning conditions such as adjusting the polymer concentration and adjusting the spinning temperature may be adjusted.
<支持体>
本実施形態に係る多孔性中空糸膜としては、外圧ろ過の観点から、外表面側に位置する上記の多孔質膜層と、内表面側に位置する中空状の支持体とを備えるものが好ましい。
<Support>
As the porous hollow fiber membrane according to this embodiment, from the viewpoint of external pressure filtration, it is preferable to include the porous membrane layer located on the outer surface side and the hollow support located on the inner surface side. .
中空状の支持体としては、特に限定されないが、例えば、編紐(組紐)及び不織布等を管状に構成したものが挙げられる。編紐による支持体は、一本の繊維又は二本以上の繊維が束ねられて形成された複数本の糸(マルチフィラメント糸)を管状に組むことにより形成されたものである。支持体が編紐であると、耐圧が高いため好ましい。 Although it does not specifically limit as a hollow support body, For example, what comprised the braided string (braid), the nonwoven fabric, etc. in the tubular shape is mentioned. The support made of knitted string is formed by assembling a plurality of yarns (multifilament yarns) formed by bundling one fiber or two or more fibers into a tubular shape. It is preferable that the support is a braided string because the pressure resistance is high.
中空状の支持体に含まれる素材として、具体的には、ナイロン6、ナイロン66、芳香族ポリアミド等のポリアミド系、ポリエチレンテレフタレート、ポリ乳酸、ポリグリコール等のポリエステル系、ポリエチレン及びポリプロピレン等のポリオレフィン系、ポリ塩化ビニル及びポリ塩化ビニリデン等のポリ塩化ビニル系、ポリテトラフルオロエチレン及びポリフッ化ビニリデン等のポリフッ素系、ポリビニルアルコール系、ポリアクリロニトリル系、ポリ尿酸系、ポリアルキレンパラオキシベンゾエート系、並びにポリウレタン系等の合成高分子素材;セルロース系、タンパク質系、種子毛繊維及び石綿等の天然高分子素材;金属繊維、炭素繊維及びケイ酸塩繊維等の無機素材;並びに、上記素材を組み合わせたものが挙げられる。これらは、用途に応じて適切なものを選ぶことが可能である。水処理等の用途においては、コストや繊維形状の自由度の高さから合成高分子素材が好ましく、ポリエチレンテレフタラートがより好ましい。 Specific examples of materials contained in the hollow support include nylons, nylon 66, polyamides such as aromatic polyamide, polyesters such as polyethylene terephthalate, polylactic acid, and polyglycol, and polyolefins such as polyethylene and polypropylene. , Polyvinyl chloride such as polyvinyl chloride and polyvinylidene chloride, polyfluorine such as polytetrafluoroethylene and polyvinylidene fluoride, polyvinyl alcohol, polyacrylonitrile, polyuric acid, polyalkylene paraoxybenzoate, and polyurethane Synthetic polymer materials such as cellulose, protein, natural polymer materials such as seed wool fibers and asbestos; inorganic materials such as metal fibers, carbon fibers and silicate fibers; and combinations of the above materials It is done. These can be selected appropriately depending on the application. In applications such as water treatment, synthetic polymer materials are preferred, and polyethylene terephthalate is more preferred because of its high cost and flexibility in fiber shape.
繊維の太さは特に限定されないが、直径1μm以上100μm以下が好ましい。直径が1μm以上であれば、表面の毛羽立ち等をより抑制し、多孔質層とのより高い接着性を発揮でき、100μm以下であれば得られる組紐がしっかりと組まれ、一層高い圧縮強度を発揮できる。マルチフィラメント糸の場合、糸1本における繊維の本数は、10本以上1000本以下であることが好ましい。10本以上であれば、マルチフィラメント糸及びこれからなる組紐の柔軟性がより高くなり、結果としてエアースクラビング等で揺れやすい洗浄効果の高い多孔性中空糸膜が得られる。一方、1000本以下であれば、マルチフィラメント糸が太くなりすぎず、より高い圧縮強度を有する組紐を得ることができる。組紐の打ち数は、5以上100以下であることが好ましい。5以上であれば得られる組紐が更に高い圧縮強度を発現でき、100以下であれば収縮による構造変化をより好ましい範囲に抑えることができる。 The thickness of the fiber is not particularly limited, but is preferably 1 μm or more and 100 μm or less in diameter. If the diameter is 1 μm or more, the surface fluffing can be further suppressed and higher adhesiveness with the porous layer can be exhibited. If the diameter is 100 μm or less, the resulting braid is firmly assembled and exhibits higher compressive strength. it can. In the case of a multifilament yarn, the number of fibers in one yarn is preferably 10 or more and 1000 or less. If the number is 10 or more, the flexibility of the multifilament yarn and the braid made of the yarn becomes higher, and as a result, a porous hollow fiber membrane having a high cleaning effect that is easily shaken by air scrubbing or the like is obtained. On the other hand, if it is 1000 or less, the multifilament yarn does not become too thick, and a braid having higher compressive strength can be obtained. The number of braids is preferably 5 or more and 100 or less. If it is 5 or more, the resulting braid can exhibit higher compressive strength, and if it is 100 or less, the structural change due to shrinkage can be suppressed to a more preferable range.
本実施形態における支持体の断面形状は、図1に示すような円形に限定されず、三角形状、四角形状、その他の異形形状等、様々な形状において効果を発揮することができる。生産性や中空部の潰れへの耐久性の観点からは、円形が好ましい。 The cross-sectional shape of the support in the present embodiment is not limited to the circular shape as shown in FIG. 1, and the effect can be exhibited in various shapes such as a triangular shape, a quadrangular shape, and other irregular shapes. From the viewpoint of productivity and durability against crushing of the hollow portion, a circular shape is preferable.
[多孔性中空糸膜の製造方法]
本実施形態の多孔性中空糸膜の製造方法について説明する。本実施形態に係る多孔性中空糸膜の製造方法は、ポリエチレンと溶剤とを溶融混練して製膜原液を作製する溶融混練工程と、この製膜原液を冷却凝固して多孔質膜層を形成する冷却凝固工程とを有する。具体例としては、粘度平均分子量が100万以上のポリエチレンと溶剤とを220℃以上に加熱し、径Dに対する長さLの比(L/D)が10以上のシリンダーを備える押出機を用いて溶融混練して、製膜原液を作製する溶融混練工程と、上記製膜原液を、冷却凝固して熱誘起相分離法により製膜させて多孔質膜層を形成する冷却凝固工程とを有する製造方法により、多孔性中空糸膜を製造することができる。
[Method for producing porous hollow fiber membrane]
The manufacturing method of the porous hollow fiber membrane of this embodiment is demonstrated. The method for producing a porous hollow fiber membrane according to the present embodiment includes a melt-kneading step in which polyethylene and a solvent are melt-kneaded to produce a membrane-forming stock solution, and the membrane-forming stock solution is cooled and solidified to form a porous membrane layer. Cooling and solidifying step. As a specific example, using an extruder equipped with a cylinder having a viscosity average molecular weight of 1,000,000 or more and a solvent heated to 220 ° C. or more and a ratio of length L to diameter D (L / D) of 10 or more. Manufacturing comprising a melt-kneading step in which a film-forming stock solution is prepared by melt-kneading, and a cooling-solidifying step in which the film-forming stock solution is cooled and solidified to form a film by a heat-induced phase separation method to form a porous membrane layer By the method, a porous hollow fiber membrane can be produced.
[溶融混練工程]
本実施形態の溶融混練工程では、径Dに対する長さLの比(L/D)が10以上であるシリンダーを備える押出機により、ポリエチレンと溶剤とを溶融混練して、製膜原液を作製する。押出機は、シリンダーの径Dに対するシリンダーの長さの比(L/D)が10以上であるものであれば特に限定されないが、L/Dが10以上100以下であると好ましく、10以上50以下であるとより好ましい。また、押出機は、混練を強めるため、シリンダーが二軸である押出機が好ましい。
[Melting and kneading process]
In the melt-kneading step of this embodiment, polyethylene and a solvent are melt-kneaded by an extruder equipped with a cylinder having a length L to diameter D ratio (L / D) of 10 or more to produce a film-forming stock solution. . The extruder is not particularly limited as long as the ratio of the cylinder length to the cylinder diameter D (L / D) is 10 or more, but L / D is preferably 10 or more and 100 or less, and preferably 10 or more and 50. The following is more preferable. Moreover, since an extruder strengthens kneading | mixing, the extruder whose cylinder is biaxial is preferable.
例えば、特許文献4は、超高分子量ポリエチレンを原料とした平膜の製造方法が開示されている。分離膜として好適に使用するためには、平膜よりも多孔性中空糸膜の方が同じフットプリントでも膜面積を広くできることから好ましい。多孔性中空糸膜を成形するためには、特許文献4に記載のような中庸のせん断(二軸押出機のL(シリンダー長さ)/D(シリンダー径)が6程度)では、中空糸膜に成形する用途としては溶剤と超高分子量ポリエチレンとの相溶が十分でない。そこで、L/Dが10以上のシリンダーおけるせん断を経て、押出機に備えられる二重管ノズルから製膜原液を吐出することが好ましい。 For example, Patent Document 4 discloses a method for producing a flat film using ultrahigh molecular weight polyethylene as a raw material. In order to be suitably used as a separation membrane, a porous hollow fiber membrane is preferable to a flat membrane because the membrane area can be increased even with the same footprint. In order to form a porous hollow fiber membrane, the hollow fiber membrane is obtained by using a medium shear as described in Patent Document 4 (L (cylinder length) / D (cylinder diameter) of the twin screw extruder is about 6). For use in molding, the compatibility between the solvent and the ultra high molecular weight polyethylene is not sufficient. Therefore, it is preferable to discharge the film forming stock solution from a double tube nozzle provided in the extruder through shearing in a cylinder having an L / D of 10 or more.
<溶剤>
本実施形態の溶剤の三次元溶解性パラメーターP(下記式(3)に従い求める。)は、好ましくは3.0未満であり、より好ましくは2.0未満であり、さらに好ましくは1.8未満であり、特に好ましくは1.5未満である。この値が3.0未満であるとポリエチレンが溶剤により十分に溶解又は分散した製膜原液を得ることができる。
P=((σdm−σdp)2+(σpm−σpp)2+(σhm−σhp)2)1/2 ・・・(3)
(式(3)中、σdm及びσdpは溶剤及びポリエチレンの分散力項をそれぞれ示し、σpm及びσppは溶剤及びポリエチレンの双極子結合力項をそれぞれ示し、σhm及びσhpは溶剤及びポリエチレンの水素結合項をそれぞれ示す。)
<Solvent>
The three-dimensional solubility parameter P (determined according to the following formula (3)) of the solvent of this embodiment is preferably less than 3.0, more preferably less than 2.0, and even more preferably less than 1.8. And particularly preferably less than 1.5. When this value is less than 3.0, a film-forming stock solution in which polyethylene is sufficiently dissolved or dispersed in a solvent can be obtained.
P = ((σ dm −σ dp ) 2 + (σ pm −σ pp ) 2 + (σ hm −σ hp ) 2 ) 1/2 (3)
(In formula (3), σ dm and σ dp represent the dispersion force terms of the solvent and polyethylene, σ pm and σ pp represent the dipole binding force terms of the solvent and polyethylene, respectively, and σ hm and σ hp represent the solvent. And hydrogen bond terms of polyethylene respectively.)
例えば、フタル酸ジ2−エチルヘキシル(DOP)、フタル酸ジイソノニル(DINP)及びフタル酸ジイソデシル(DIDP)など、溶剤は上記式で表される三次元溶解性パラメーターPが3.0未満のものを好適に用いることができる。 For example, a solvent having a three-dimensional solubility parameter P represented by the above formula of less than 3.0, such as di-2-ethylhexyl phthalate (DOP), diisononyl phthalate (DINP), and diisodecyl phthalate (DIDP) is suitable. Can be used.
製膜原液に含まれるポリエチレン及び溶剤の合計の含有率は、製膜原液100質量%に対し、好ましくは90質量%以上であり、より好ましくは80質量%以上100質量%以下であり、さらに好ましくは90質量%以上100質量%以下である。この含有率が90質量%以上であるとポリマー本来の性質が得られやすい。 The total content of polyethylene and the solvent contained in the film-forming stock solution is preferably 90% by weight or more, more preferably 80% by weight or more and 100% by weight or less, more preferably 100% by weight of the film-forming stock solution. Is 90% by mass or more and 100% by mass or less. When the content is 90% by mass or more, the original properties of the polymer are easily obtained.
製膜原液に含まれるポリエチレンの含有率は、製膜原液100質量%に対し、好ましくは5質量%以上20質量%以下であり、より好ましくは10質量%以上20質量%以下であり、さらに好ましくは10質量%以上18質量%以下である。この値が5質量%以上であるとより高い機械的強度が得られやすく、他方、20質量%以下であると溶融混練物の粘度がより低くなるので多孔質膜層を成形しやすい。 The content of polyethylene contained in the film-forming stock solution is preferably 5% by mass or more and 20% by mass or less, more preferably 10% by mass or more and 20% by mass or less, and still more preferably, with respect to 100% by mass of the film-forming stock solution. Is 10 mass% or more and 18 mass% or less. When this value is 5% by mass or more, higher mechanical strength is easily obtained. On the other hand, when it is 20% by mass or less, the viscosity of the melt-kneaded product becomes lower, so that the porous membrane layer can be easily formed.
ポリエチレンの粘度平均分子量の大きさにより、多孔性中空糸膜の孔径の大きさを制御することができる。例えば、ポリエチレンの粘度平均分子量を大きくすることにより、空孔率を大きく変えずに、孔径を大きくすることができる。 The size of the pore diameter of the porous hollow fiber membrane can be controlled by the size of the viscosity average molecular weight of polyethylene. For example, by increasing the viscosity average molecular weight of polyethylene, the pore diameter can be increased without greatly changing the porosity.
製膜原液は、ポリエチレン及び溶剤の二成分からなるものであって、ポリエチレン、溶剤及び無機微粉の三成分からなるものであってもよく、本発明の作用効果を阻害しない範囲において、その他の各種成分を含んでもよい。無機微粉を使用する場合には、製膜原液に含まれる無機微粉の一次粒径は、好ましくは50nm以下であり、より好ましくは5nm以上20nm以下である。なお、無機微粉を含む製膜原液を使用して多孔性膜層を製造する場合には、多孔性中空糸膜の製造方法が、冷却凝固工程後に、無機微粉を抽出除去する工程をさらに有することが好ましい。 The film-forming stock solution is composed of two components of polyethylene and a solvent, and may be composed of three components of polyethylene, a solvent and an inorganic fine powder. Ingredients may be included. When inorganic fine powder is used, the primary particle size of the inorganic fine powder contained in the film-forming stock solution is preferably 50 nm or less, more preferably 5 nm or more and 20 nm or less. In addition, when manufacturing a porous membrane layer using the membrane forming stock solution containing inorganic fine powder, the manufacturing method of a porous hollow fiber membrane further has the process of extracting and removing inorganic fine powder after a cooling solidification process. Is preferred.
無機微粉の具体例としては、シリカ微粉、酸化チタン及び塩化リチウムが挙げられ、これらのうち、コストの観点からシリカ微粉が好ましい。上述の「無機微粉の一次粒径」は電子顕微鏡写真の解析から求めた値を意味する。すなわち、まず無機微粉の一群をASTM D3849の方法によって前処理を行う。その後、透過型電子顕微鏡写真に写された3000〜5000個の無機微粉の粒子直径を測定し、これらの値を算術平均することで無機微粉の一次粒径を算出する。 Specific examples of the inorganic fine powder include silica fine powder, titanium oxide, and lithium chloride. Among these, silica fine powder is preferable from the viewpoint of cost. The above-mentioned “primary particle size of inorganic fine powder” means a value obtained from analysis of an electron micrograph. That is, a group of inorganic fine powder is first pretreated by the method of ASTM D3849. Then, the particle diameter of 3000-5000 inorganic fine powders copied to the transmission electron micrograph is measured, and the primary particle diameter of the inorganic fine powders is calculated by arithmetically averaging these values.
溶融混練工程において、ポリエチレンと溶剤とを220℃以上に加熱し、溶融混練する。その際、好ましくは200℃以上300℃以下、より好ましくは200℃以上250℃以下である。220℃以上に加熱することにより、より混練が強まりであり、他方、300℃以下に加熱することにより、ポリマーの分解を抑制できる。加熱は、押出機に対して、電気ヒーターを用いることにより行うことができる。 In the melt-kneading step, the polyethylene and the solvent are heated to 220 ° C. or higher and melt-kneaded. In that case, it is preferably 200 ° C. or higher and 300 ° C. or lower, more preferably 200 ° C. or higher and 250 ° C. or lower. By heating to 220 ° C. or higher, kneading is further strengthened. On the other hand, heating to 300 ° C. or lower can suppress decomposition of the polymer. Heating can be performed by using an electric heater for the extruder.
[吐出工程]
本実施形態の多孔性中空糸膜の製造方法では、例えば、製膜原液をノズルから吐出する吐出工程により中空状に多孔質膜層を形成することができる。また、上記のノズルは二重管ノズルであることが、品質向上の観点から好ましい。二重管ノズルを用いた吐出工程としては、例えば、製膜原液を二重管ノズルの内管と外管との間の流路から吐出し、溶剤を内管内の流路から吐出するもの、及び気体を内管内の流路から吐出するもの挙げられるが、溶剤を内管内の流路から吐出するものが、塗膜不良を少なくする観点からより好ましい。この吐出工程を経た製膜原液は、後述する冷却凝固工程により、製膜される。
[Discharge process]
In the method for producing a porous hollow fiber membrane of the present embodiment, for example, the porous membrane layer can be formed in a hollow shape by a discharge step of discharging a film-forming stock solution from a nozzle. Moreover, it is preferable from a viewpoint of quality improvement that said nozzle is a double tube nozzle. As a discharge process using a double tube nozzle, for example, a film forming stock solution is discharged from a flow channel between an inner tube and an outer tube of a double tube nozzle, and a solvent is discharged from a flow channel in the inner tube, And those that discharge gas from the flow path in the inner pipe, but those that discharge the solvent from the flow path in the inner pipe are more preferable from the viewpoint of reducing coating film defects. The film-forming stock solution that has undergone this discharge step is formed by a cooling and solidification step that will be described later.
[積層工程]
本実施形態の多孔性中空糸膜の製造方法では、例えば、製膜原液を支持体に吐出して積層する積層工程により支持体に多孔質膜層を形成することができる。また、二重管ノズルから製膜原液と支持体とを吐出して積層する積層工程であることが、品質向上の観点から好ましい。二重管ノズルを用いた積層工程としては、多孔性中空糸膜が外表面側に位置する多孔質膜層と内表面側に位置する中空状の支持体とを備える場合、例えば、製膜原液を二重管ノズルの内管と外管との間の流路から吐出し、支持体を内管から排出し、支持体に製膜原液を積層するものがあり、塗膜不良が低下するため好ましい。この積層工程を経た製膜原液は、後述する冷却凝固工程により、製膜される。
[Lamination process]
In the method for producing a porous hollow fiber membrane of the present embodiment, for example, the porous membrane layer can be formed on the support by a laminating process in which a membrane-forming stock solution is discharged and laminated on the support. Moreover, it is preferable from a viewpoint of a quality improvement that it is the lamination process which discharges | stacks a film forming undiluted solution and a support body from a double tube nozzle, and laminates | stacks. When the porous hollow fiber membrane includes a porous membrane layer located on the outer surface side and a hollow support located on the inner surface side, for example, as a laminating step using a double tube nozzle, for example, a membrane-forming stock solution Is discharged from the flow path between the inner tube and the outer tube of the double tube nozzle, the support is discharged from the inner tube, and the film-forming stock solution is laminated on the support, resulting in a decrease in coating film defects. preferable. The film-forming stock solution that has undergone this laminating process is formed into a film by a cooling and solidification process that will be described later.
例えば、特許文献5は、組紐上に多孔質膜層をコーティングする方法を開示する。この方法を採用する場合、二重管ノズルの内管と外管との間の流路から製膜原液を吐出し、内管から組紐を吐出して紡糸する。製膜原液の吐出に合わせて、組紐を引き取れば、多孔質膜層を組紐にコーティングされた多孔性中空糸膜を得ることができる。こうして得られた多孔性中空糸膜は、より高い開口率とより高い強度を両立することができる。 For example, Patent Document 5 discloses a method of coating a porous membrane layer on a braid. When this method is adopted, the film-forming stock solution is discharged from the flow path between the inner tube and the outer tube of the double tube nozzle, and the braid is discharged from the inner tube to perform spinning. If the braid is taken out in accordance with the discharge of the membrane-forming stock solution, a porous hollow fiber membrane in which the porous membrane layer is coated on the braid can be obtained. The porous hollow fiber membrane thus obtained can achieve both higher opening ratio and higher strength.
[冷却凝固工程]
本実施形態の冷却凝固工程では、製膜原液を冷却凝固して熱誘起相分離法により製膜させて多孔質膜層を形成することができる。多孔質膜層の製膜法としては、非溶剤と接触させることで相分離を起こし多孔質層を形成させる乾湿式法(非溶媒相分離法)、並びに、冷却することにより相分離を起こし多孔質層を形成させる熱誘起相分離法が挙げられる。これらの中では、均質膜が得られるため、熱誘起相分離法が好ましい。熱誘起相分離法は、例えば、製膜原液を約30℃程度の水に浸すことにより、相分離を起こさせることができる。
[Cooling and solidification process]
In the cooling and solidification step of the present embodiment, the porous membrane layer can be formed by cooling and solidifying the film-forming stock solution to form a film by a thermally induced phase separation method. As a method for forming a porous membrane layer, a dry / wet method (non-solvent phase separation method) in which a phase separation is caused by contact with a non-solvent to form a porous layer, and a phase separation is caused by cooling to produce a porous layer. There is a heat-induced phase separation method for forming a porous layer. Among these, a thermally induced phase separation method is preferable because a homogeneous membrane can be obtained. In the thermally induced phase separation method, for example, phase separation can be caused by immersing the membrane forming stock solution in water at about 30 ° C.
こうして、多孔質膜層を備える本実施形態の多孔性中空糸膜を得ることができる。なお、本実施形態の製造方法は、本発明の作用効果を阻害しない限り、上記以外に、多孔性中空糸膜の製造方法が有し得る他の工程を有していてもよい。 In this way, the porous hollow fiber membrane of this embodiment provided with a porous membrane layer can be obtained. In addition, the manufacturing method of this embodiment may have the other process which the manufacturing method of a porous hollow fiber membrane can have besides the above, unless the effect of this invention is inhibited.
[浄水方法]
本実施形態の浄水方法は、上述の多孔性中空糸膜を用いてろ過をする。ろ過する懸濁水としては、例えば、天然水、生活排水、及びこれらの処理水が挙げられる。天然水としては、河川水、湖沼水、地下水及び海水が例として挙げられる。これら天然水に対し沈降処理、砂濾過処理、凝集沈殿砂濾過処理、オゾン処理及び活性炭処理などの処理を施した処理水も、処理対象の懸濁水に含まれる。生活排水の例としては、例えば下水が挙げられる。下水に対してスクリーン濾過や沈降処理を施した下水1次処理水や、生物処理を施した下水2次処理水、さらには凝集沈殿砂濾過、活性炭処理及びオゾン処理などの処理を施した3次処理(高度処理)水も、処理対象の懸濁水に含まれる。処理対象の懸濁水には、μmオーダー以下の微細な有機物、無機物及び有機無機混合物からなる濁質(腐植コロイド、有機質コロイド、粘土、細菌など)が含まれ得る。また、研磨廃水など比較的堅い粒子を含んだ原水を濃縮、精製する用途にも使用できる
[Water purification method]
The water purification method of the present embodiment performs filtration using the porous hollow fiber membrane described above. Examples of the suspended water to be filtered include natural water, domestic wastewater, and treated water thereof. Examples of natural water include river water, lake water, groundwater, and seawater. Treated water obtained by subjecting these natural waters to sedimentation treatment, sand filtration treatment, coagulation sedimentation sand filtration treatment, ozone treatment, activated carbon treatment, and the like is also included in the suspension water to be treated. An example of domestic wastewater is sewage, for example. Sewage primary treated water that has been subjected to screen filtration and sedimentation treatment, sewage secondary treated water that has been subjected to biological treatment, and tertiary that has undergone treatment such as coagulation sedimentation sand filtration, activated carbon treatment and ozone treatment. Treated (highly treated) water is also included in the suspension water to be treated. Suspended water to be treated can include turbidity (humic colloid, organic colloid, clay, bacteria, etc.) composed of fine organic substances, inorganic substances, and organic-inorganic mixtures of the order of μm or less. It can also be used to concentrate and purify raw water containing relatively hard particles such as polishing wastewater.
懸濁水(上述の天然水、生活排水、及びこれらの処理水など)の水質は、一般に、代表的な水質指標である濁度及び有機物濃度の単独又は組み合わせにより表現できる。濁度(瞬時の濁度ではなく平均濁度)で水質を区分すると、大きくは、濁度1未満の低濁水、濁度1以上10未満の中濁水、濁度10以上50未満の高濁水、濁度50以上の超高濁水などに区分できる。また、有機物濃度(全有機炭素濃度(Total Organic Carbon(TOC)):mg/L)(瞬時の値ではなく平均値)で水質を区分すると、大きくは、1未満の低TOC水、1以上4未満の中TOC水、4以上8未満の高TOC水、8以上の超高TOC水などに区分できる。基本的には、濁度又はTOCの高い水ほど濾過膜を目詰まりさせやすいため、濁度又はTOCの高い水ほど、本実施形態の多孔性中空糸膜(例えば図1に示す多孔性中空糸膜10,20)を使用する効果が大きくなる。
より具体的には、本発明は、膜濾過法により天然水、生活排水、及びこれらの処理水である懸濁水を除濁する方法において、膜の目詰まりによる透水性能劣化が少なく、また膜表面の擦過による透水性能劣化も少ない多孔性中空糸膜を提供することを目的とする。
The water quality of suspended water (such as the above-mentioned natural water, domestic wastewater, and treated water thereof) can be generally expressed by turbidity and organic substance concentration, which are representative water quality indicators, alone or in combination. When water quality is classified by turbidity (average turbidity, not instantaneous turbidity), it is roughly divided into low turbid water with turbidity less than 1, turbid water with turbidity of 1 to less than 10, high turbidity with turbidity of 10 to less than 50, It can be classified into ultra-turbid water with turbidity of 50 or more. Moreover, when water quality is classified by organic substance concentration (total organic carbon (TOC): mg / L) (average value, not instantaneous value), it is roughly less than 1 low TOC water, 1 or more 4 It can be classified into less than medium TOC water, 4 or more and less than 8 high TOC water, and 8 or more ultra-high TOC water. Basically, the higher the turbidity or TOC, the easier it is to clog the filtration membrane. Therefore, the higher the turbidity or TOC, the higher the turbidity or TOC, the porous hollow fiber membrane of this embodiment (for example, the porous hollow fiber shown in FIG. The effect of using the membrane 10, 20) is increased.
More specifically, the present invention provides a method for removing turbidity of natural water, domestic wastewater, and suspension water, which is treated water, by membrane filtration, and has little deterioration in water permeability due to membrane clogging. An object of the present invention is to provide a porous hollow fiber membrane with little deterioration in water permeability due to rubbing.
以下、実施例を挙げて本実施形態を詳細に説明するが、本実施形態はその要旨を超えない限り、これらによって何ら限定されるものではない。実施例、比較例における各物性値は以下の方法で各々測定及び評価を行った。 Hereinafter, although an Example is given and this embodiment is described in detail, this embodiment is not limited at all unless it exceeds the summary. Each physical property value in Examples and Comparative Examples was measured and evaluated by the following methods.
(1)開口率、空孔率、孔径及びアスペクト比
HITACHI製の電子顕微鏡(製品名「SU8000シリーズ」)を使用し、加速電圧3kVで膜の表面及び断面の走査型電子顕微鏡(SEM)画像を5000倍で撮影した。電子顕微鏡用の断面サンプルは、エタノール中で凍結した膜サンプルを輪切りに割断して得た。次に、画像解析ソフトWinroof6.1.3(Mitani社製製品名)を用いて、100mm×100mmの領域におけるSEM画像の「ノイズ除去」を数値「6」によって行い、更に単一しきい値による二値化により、「しきい値:105」によって二値化を行った。こうして得た膜の表面の二値化画像の占有面積率を求めることにより開口率を、膜の断面の二値化画像の占有面積率を求めることにより空孔率を、それぞれ求めた。以上の測定はSEM画像10枚について実施し、その平均値を用いた。
孔径は、表面の100mm×100mmの領域におけるSEM画像において、表面に存在した各孔に対し、孔径の小さい方から順に各孔の孔面積を加算していき、その和が、各孔の孔面積の総和の50%に達するところの孔の孔径で決定した。
細孔のアスペクト比は、孔径を測定する際、孔の長径と短径を測定し、(長径)/(短径)でアスペクト比を算出する。100個程度の外表面孔について測定し、算術相加平均を求め、その値を外表面孔のアスペクト比とした。
(1) Aperture ratio, porosity, hole diameter and aspect ratio Using an electron microscope (product name “SU8000 series”) manufactured by HITACHI, scanning electron microscope (SEM) images of the surface and cross section of the film at an acceleration voltage of 3 kV The photo was taken at 5000x. A cross-sectional sample for an electron microscope was obtained by cutting a membrane sample frozen in ethanol into round slices. Next, using the image analysis software Winroof 6.1.3 (product name, manufactured by Mitani), “noise removal” of the SEM image in the area of 100 mm × 100 mm is performed by the numerical value “6”, and further by a single threshold value. By binarization, binarization was performed using “threshold value: 105”. The aperture ratio was determined by determining the occupied area ratio of the binarized image on the surface of the film thus obtained, and the porosity was determined by determining the occupied area ratio of the binarized image of the cross section of the film. The above measurement was performed on 10 SEM images, and the average value was used.
For the hole diameter, in the SEM image in the 100 mm × 100 mm region of the surface, the hole area of each hole is added in order from the smallest hole diameter to each hole existing on the surface, and the sum is the hole area of each hole. Was determined by the hole diameter at which the hole reached 50% of the total sum.
As for the aspect ratio of the pore, when measuring the pore diameter, the major axis and minor axis of the pore are measured, and the aspect ratio is calculated by (major axis) / (minor axis). About 100 outer surface holes were measured, an arithmetic arithmetic average was obtained, and the value was taken as the aspect ratio of the outer surface holes.
(2)純水フラックス
エタノールに浸漬した後、数回純水への浸漬を繰り返した約10cm長の湿潤中空糸膜の一端を封止し、他端から中空部内に注射針を挿入し、25℃の環境下にて注射針から0.1MPaの圧力で25℃の純水を中空部内に注入し、外表面に透過してくる純水量を測定し、下記式(4)により純水フラックスを決定した。
純水フラックス[L/m2/h(LMH)]=60×(透過水量[L])/{π×(膜外径[m])×(膜有効長[m])×(測定時間[min])} ・・・(4)
なお、ここに膜有効長とは、注射針が挿入されている部分を除いた、正味の膜長を指す。
(2) Pure water flux After being immersed in ethanol, one end of a wet hollow fiber membrane having a length of about 10 cm, which was repeatedly immersed in pure water several times, was sealed, and an injection needle was inserted into the hollow portion from the other end. Pure water at 25 ° C. is injected into the hollow portion from the injection needle at a pressure of 0.1 MPa in an environment of ° C., the amount of pure water permeating through the outer surface is measured, and the pure water flux is expressed by the following equation (4). Were determined.
Pure water flux [L / m 2 / h (LMH)] = 60 × (permeated water amount [L]) / {π × (membrane outer diameter [m]) × (membrane effective length [m]) × (measurement time [ min])} (4)
Here, the membrane effective length refers to the net membrane length excluding the portion where the injection needle is inserted.
(3)耐膜面擦過率
耐膜面擦過率は、膜面擦過による透水性能劣化の程度を判断するための1指標である。エタノールに浸漬した後、数回純水への浸漬を繰り返した湿潤中空糸膜(約10cm長)を金属板の上に並べ、微小な砂(粒径130μm、製品名「Fuji Brown FRR#120」)20質量%を水に懸濁させた懸濁水を、膜の上方70cmにセットしたノズルから0.07MPaの圧力で噴射し、膜外表面に吹き付けた。10分間吹き付けを行った後、膜を裏返して、同じ条件で10分間、懸濁水の吹き付けを行った。吹き付けの前後において、上記「(2)純水フラックス」において湿潤中空糸膜の一端を封止する以降と同様の操作をして純水フラックスを測定し、下記式(5)から耐膜面擦過率を求めた。
耐膜面擦過率[%]=100×(吹き付け後純水フラックス[LMH])/(吹き付け前純水フラックス[LMH]) ・・・(5)
(3) Film Surface Abrasion Rate The film surface abrasion rate is an index for judging the degree of water permeability performance deterioration due to film surface abrasion. After dipping in ethanol, wet hollow fiber membranes (approximately 10 cm long) that have been dipped in pure water several times are arranged on a metal plate and fine sand (particle size 130 μm, product name “Fuji Brown FRR # 120”). ) Suspended water in which 20% by mass was suspended in water was sprayed at a pressure of 0.07 MPa from a nozzle set 70 cm above the membrane and sprayed on the outer surface of the membrane. After spraying for 10 minutes, the membrane was turned over and suspended water was sprayed for 10 minutes under the same conditions. Before and after spraying, the pure water flux was measured by performing the same operation as that after sealing one end of the wet hollow fiber membrane in “(2) Pure water flux”. The rate was determined.
Scratch resistance [%] = 100 × (pure water flux after spraying [LMH]) / (pure water flux before spraying [LMH]) (5)
(4)懸濁水濾過時の透水性能保持率
懸濁水濾過時の透水性能保持率は、目詰まり(ファウリング)による透水性能劣化の程度を判断するための1指標である。エタノールに浸漬した後、数回純水への浸漬を繰り返した湿潤中空糸膜を用いて、膜有効長11cmにて外圧方式により濾過を行った。初めに純水を、膜外表面積1m2当たり1日当たり10m3透過する濾過圧力にて濾過し、透過水を2分間採取し、採取した水の量を初期純水透水量とした。次いで、天然の懸濁水である河川表流水(富士川表流水:濁度2.2、TOC濃度0.8ppm)を、初期純水透水量を測定したときと同じ濾過圧力にて10分間濾過し、濾過を開始してから8分後から10分後までの2分間透過水を採取し、採取した水の量を懸濁水濾過時透水量とした。それらの透水量から、懸濁水濾過時の透水性能保持率を、下記式(6)により算出した。操作は全て25℃、膜面線速0.5m/秒で行った。
懸濁水濾過時の透水性能保持率[%]=100×(懸濁水濾過時透水量[g])/(初期純水透水量[g]) ・・・(6)
なお、式(6)中の各パラメーターは下記式(7)、(8)、(9)から算出される。
濾過圧力={(入圧[MPa])+(出圧[MPa])}/2 ・・・(7)
膜外表面積[m2]=π×(中空糸膜外径[m])×(中空糸膜有効長[m]) ・・・(8)
膜面線速[m/s]=4×(濾過水量[m3/s])/{π×(中空糸膜内径[m])2−π×(膜外径[m])2} ・・・(9)
(4) Permeability performance retention rate during suspension water filtration The permeation performance retention rate during suspension water filtration is an index for judging the degree of water permeation performance degradation due to clogging (fouling). After dipping in ethanol, filtration was performed by an external pressure method with a membrane effective length of 11 cm using a wet hollow fiber membrane that was repeatedly dipped in pure water several times. First, pure water was filtered at a filtration pressure of 10 m 3 per day per 1 m 2 of the outer membrane surface area, the permeated water was collected for 2 minutes, and the amount of the collected water was defined as the initial pure water permeability. Next, the river surface water (Fuji River surface water: turbidity 2.2, TOC concentration 0.8 ppm), which is a natural suspension water, is filtered for 10 minutes at the same filtration pressure as when the initial pure water permeability was measured, The permeated water was collected for 2 minutes from 8 minutes to 10 minutes after the start of filtration, and the amount of the collected water was taken as the water permeation amount during suspension water filtration. From the water permeability, the water permeability retention rate during suspension water filtration was calculated by the following formula (6). All operations were performed at 25 ° C. and a film surface linear velocity of 0.5 m / sec.
Permeability retention ratio during suspension water filtration [%] = 100 × (water permeability during suspension water filtration [g]) / (initial pure water permeability [g]) (6)
In addition, each parameter in Formula (6) is computed from following formula (7), (8), (9).
Filtration pressure = {(input pressure [MPa]) + (output pressure [MPa])} / 2 (7)
Surface area outside membrane [m 2 ] = π × (outer diameter of hollow fiber membrane [m]) × (effective length of hollow fiber membrane [m]) (8)
Membrane surface linear velocity [m / s] = 4 × (filtered water amount [m 3 / s]) / {π × (hollow fiber membrane inner diameter [m]) 2 −π × (membrane outer diameter [m]) 2 } (9)
本測定においては懸濁水の濾過圧力を各膜同一ではなく、初期純水透水性能(懸濁水濾過開始時点での透水性能でもある)が膜外表面積1m2当たり1日当たり10m3透過する濾過圧力に設定した。これは、実際の上水処理や下水処理において、膜は定量濾過運転(一定時間内に一定の濾過水量が得られるよう濾過圧力を調整して濾過運転する方式)で使用されるのが通常であるため、本測定においても中空糸膜1本を用いた測定という範囲内で、定量濾過運転の条件に極力近い条件での透水性能劣化の比較ができるようにしたためである。 In this measurement, the filtration pressure of the suspended water is not the same for each membrane, but the initial pure water permeability (also the permeability at the time of suspension water filtration start) is the filtration pressure that permeates 10 m 3 per day per 1 m 2 of the membrane surface area. Set. This is because in actual water treatment and sewage treatment, the membrane is usually used in quantitative filtration operation (a method in which the filtration pressure is adjusted so that a constant amount of filtered water is obtained within a certain period of time). Therefore, in this measurement, the deterioration of water permeability performance can be compared under conditions as close as possible to the conditions of quantitative filtration operation within the range of measurement using one hollow fiber membrane.
(5)HSP距離(三次元溶解性パラメーター)
HSP距離[dPVDF−d溶媒]は、「Hansen, Charles(2007) Hansen Solubility Parameters: A user‘s handbook, Second Edition. Boca Raton, Fla:CRC Press(ISBN 978−0−8493 7248−3)」に記載する方法により求めた。
(5) HSP distance (three-dimensional solubility parameter)
The HSP distance [dPVDF-d solvent] is “Hansen, Charles (2007) Hansen Solubility Parameters: A user's handbook, Second Edition. It was determined by the method described.
[実施例1]
2重構造の紡糸ノズル(二重管ノズル)を用いて、実施例1の多孔質膜を得た。具体的には、まず、熱可塑性樹脂として超高分子量ポリエチレン(旭化成ケミカルズ社製、製品名「UH−900」、粘度平均分子量:3.3×106)12.5質量%と、フタル酸ビス(2−エチルヘキシル)(DEHP)87.5質量%とを準備した。
[Example 1]
A porous membrane of Example 1 was obtained using a double-structure spinning nozzle (double tube nozzle). Specifically, first, as a thermoplastic resin, 12.5% by mass of ultra high molecular weight polyethylene (manufactured by Asahi Kasei Chemicals, product name “UH-900”, viscosity average molecular weight: 3.3 × 10 6 ), and bisphthalate (2-ethylhexyl) (DEHP) 87.5 mass% was prepared.
これらを二軸混練押出機(東芝機械製TEM−37、L/D:32)により240℃で溶融混練して押出機内で製膜原液を得た。次いで、240℃で、押出機出口に設置した二重管ノズル(外層最外径2.0mm、中空部形成層最外径0.9mm)の内管と外管との間の流路から上記製膜原液を吐出すると共に、内管内の流路から空気を吐出することで、中空糸状成型物を得た。この時、製膜原液の吐出流量を二重管ノズルの製膜原液通過断面積で割ったせん断速度を、500〜5,000s-1に設定した。 These were melt-kneaded at 240 ° C. with a twin-screw kneading extruder (TEM-37, Toshiba Machine, L / D: 32) to obtain a film forming stock solution in the extruder. Next, at 240 ° C., the above-described flow path between the inner tube and the outer tube of the double tube nozzle (outer layer outermost diameter 2.0 mm, hollow portion forming layer outermost diameter 0.9 mm) installed at the exit of the extruder A hollow fiber-shaped molded product was obtained by discharging the film-forming stock solution and discharging air from the flow path in the inner tube. At this time, the shear rate obtained by dividing the discharge flow rate of the film forming solution by the film forming solution passing cross-sectional area of the double tube nozzle was set to 500 to 5,000 s −1 .
吐出した(押し出した)中空糸状成型物を、50mmの距離で空走させた後、30℃の水中で熱誘起相分離を進行させた。熱誘起相分離後の中空糸状成型物を30m/分の速度で引き取り、かせに巻き取った。巻き取った後の中空糸状成型物をイソプロピルアルコール中に浸漬させてフタル酸ビス(2−エチルヘキシル)を抽出除去し、多孔性中空糸膜を得た。 The discharged (extruded) hollow fiber-shaped molded article was idled at a distance of 50 mm, and then thermally induced phase separation was allowed to proceed in water at 30 ° C. The hollow fiber-like molded product after the heat-induced phase separation was taken up at a speed of 30 m / min and wound up in a skein. The hollow fiber-shaped molding after winding was immersed in isopropyl alcohol to extract and remove bis (2-ethylhexyl) phthalate to obtain a porous hollow fiber membrane.
表1に、得られた多孔性中空糸膜の配合組成及び製造条件並びに各種性能を示す。 Table 1 shows the blending composition, production conditions, and various performances of the obtained porous hollow fiber membrane.
[実施例2]
溶剤として、フタル酸ビス(2−エチルヘキシル)に代えてフタル酸ジイソデシル(DIDP)を用いた以外は、実施例1と同様に製膜し、実施例2の多孔性中空糸膜を得た。表1に、得られた多孔性中空糸膜の配合組成及び製造条件並びに各種性能を示す。
[Example 2]
A porous hollow fiber membrane of Example 2 was obtained in the same manner as in Example 1 except that diisodecyl phthalate (DIDP) was used in place of bis (2-ethylhexyl) phthalate as a solvent. Table 1 shows the blending composition, production conditions, and various performances of the obtained porous hollow fiber membrane.
[実施例3]
二重管ノズルの内管に内層としてポリエステル製編紐(Bonsing社製BO00B 内径:1.2mm、外径:1.9mm)を用いた以外は、実施例1と同様に製膜し、実施例3の多孔性中空糸膜を得た。表1に、得られた実施例3の多孔性中空糸膜の配合組成及び製造条件並びに各種性能を示す。
[Example 3]
A film was formed in the same manner as in Example 1 except that a polyester braided string (BO00B manufactured by Bonsing, inner diameter: 1.2 mm, outer diameter: 1.9 mm) was used for the inner pipe of the double pipe nozzle. 3 porous hollow fiber membranes were obtained. Table 1 shows the composition, production conditions, and various performances of the porous hollow fiber membrane of Example 3 obtained.
[実施例4]
内層にステンレス製メッシュパイプ(40メッシュの金網を内径:1.0mm、外径:2.0mmに成形)を用いた以外は、実施例1と同様に製膜し、実施例4の多孔性中空糸膜を得た。表1に、得られた実施例4の多孔性中空糸膜の配合組成及び製造条件並びに各種性能を示す。
[Example 4]
The porous hollow of Example 4 was formed in the same manner as in Example 1 except that a stainless steel mesh pipe (40 mesh wire mesh formed into an inner diameter of 1.0 mm and an outer diameter of 2.0 mm) was used for the inner layer. A yarn membrane was obtained. Table 1 shows the composition, production conditions, and various performances of the porous hollow fiber membrane of Example 4 obtained.
[実施例5〜8]
超高分子量ポリエチレンとして、粘度平均分子量3.3×106のものに代えて、粘度平均分子量1.0×106のもの(旭化成ケミカルズ社製、製品名「UH650」)、粘度平均分子量2.0×106のもの(旭化成ケミカルズ社製、製品名「UH850」)、粘度平均分子量4.3×106のもの(旭化成ケミカルズ社製、製品名「UH950」)、又は粘度平均分子量6.0×106のもの(旭化成ケミカルズ社製、製品名「UH970」)を用いた以外は、実施例1と同様に製膜し、それぞれ実施例5、6及び7の多孔性中空糸膜を得た。表1に、得られた実施例5〜7の多孔性中空糸膜の配合組成及び製造条件並びに各種性能を示す。このように原料に用いた超高分子量ポリエチレンの粘度平均分子量を調整することで、耐擦過性を変えずに孔径サイズを制御することができた。
[Examples 5 to 8]
As ultra-high molecular weight polyethylene, instead of the one having a viscosity average molecular weight of 3.3 × 10 6 , one having a viscosity average molecular weight of 1.0 × 10 6 (manufactured by Asahi Kasei Chemicals Co., Ltd., product name “UH650”), viscosity average molecular weight 0 × 10 6 (Asahi Kasei Chemicals, product name “UH850”), viscosity average molecular weight 4.3 × 10 6 (Asahi Kasei Chemicals, product name “UH950”), or viscosity average molecular weight 6.0 A porous hollow fiber membrane of Examples 5, 6 and 7 was obtained in the same manner as in Example 1 except that the x10 6 product (product name “UH970” manufactured by Asahi Kasei Chemicals Corporation) was used. . In Table 1, the compounding composition of the porous hollow fiber membrane of obtained Examples 5-7, manufacturing conditions, and various performance are shown. Thus, by adjusting the viscosity average molecular weight of the ultra-high molecular weight polyethylene used as the raw material, the pore size could be controlled without changing the scratch resistance.
[比較例1]
熱可塑性樹脂として、超高分子量ポリエチレンに代えて高密度ポリエチレン(旭化成ケミカルズ社製、製品名「SH−800」、粘度平均分子量:2.4×105)を用いた以外は、実施例1と同様に製膜し、比較例1の多孔性中空糸膜を得た。表1に、得られた多孔性中空糸膜の配合組成及び製造条件並びに各種性能を示す。
[Comparative Example 1]
Example 1 except that high density polyethylene (manufactured by Asahi Kasei Chemicals Corporation, product name “SH-800”, viscosity average molecular weight: 2.4 × 10 5 ) was used as the thermoplastic resin instead of ultrahigh molecular weight polyethylene. In the same manner, a porous hollow fiber membrane of Comparative Example 1 was obtained. Table 1 shows the blending composition, production conditions, and various performances of the obtained porous hollow fiber membrane.
以上のように、耐膜面擦過率が80%以上である多孔性中空糸膜は、耐擦過性に優れ、透水性保持率が高いことがわかる。 As described above, it can be seen that the porous hollow fiber membrane having a membrane scratch resistance of 80% or more has excellent scratch resistance and high water permeability retention.
本発明の多孔性中空糸膜によれば、高いろ過性能を長期にわたって維持可能な多孔性中空糸膜、その製造方法、及びこの多孔性中空糸膜を用いた浄水方法を得ることができる。本発明は、水処理等の分野において産業上の利用可能性がある。 According to the porous hollow fiber membrane of the present invention, a porous hollow fiber membrane that can maintain high filtration performance over a long period of time, a method for producing the same, and a water purification method using the porous hollow fiber membrane can be obtained. The present invention has industrial applicability in fields such as water treatment.
1…多孔性中空糸膜、1a…多孔質膜層、1b…編紐、1c…中空部、FA…外表面、FB…内表面 DESCRIPTION OF SYMBOLS 1 ... Porous hollow fiber membrane, 1a ... Porous membrane layer, 1b ... Knitted string, 1c ... Hollow part, FA ... Outer surface, FB ... Inner surface
Claims (11)
前記多孔質膜層は、孔径が0.3μm以上1.0μm以下、細孔のアスペクト比が10以下、空孔率が70%以上であり、
純水フラックスが5000LMH以上であり、
耐膜面擦過率が80%以上である多孔性中空糸膜。 A porous membrane layer containing polyethylene having a viscosity average molecular weight of 1,000,000 or more,
The porous membrane layer has a pore diameter of 0.3 μm or more and 1.0 μm or less, a pore aspect ratio of 10 or less, and a porosity of 70% or more,
Pure water flux is 5000 LMH or more,
A porous hollow fiber membrane having a membrane scratch resistance of 80% or more.
粘度平均分子量が100万以上のポリエチレンと溶剤とを220℃以上に加熱し、シリンダー径Dに対するシリンダー長さLの比(L/D)が10以上の押出機を用いて溶融混練して、製膜原液を作製する溶融混練工程と、
前記製膜原液を、冷却凝固して熱誘起相分離法により製膜させて多孔質膜層を形成する冷却凝固工程と、
を有する多孔性中空糸膜の製造方法。 It is a manufacturing method of the porous hollow fiber membrane according to any one of claims 1 to 4,
Polyethylene having a viscosity average molecular weight of 1 million or more and a solvent are heated to 220 ° C. or more, and melt-kneaded using an extruder having a cylinder length L to cylinder diameter D of 10 or more (L / D). A melt-kneading step for producing a membrane stock solution;
A cooling and solidification step in which the film-forming stock solution is cooled and solidified to form a porous membrane layer by heat-induced phase separation; and
A method for producing a porous hollow fiber membrane having
前記冷却凝固工程において、前記吐出工程を経た前記製膜原液を製膜させる、請求項5〜8のいずれか一項に記載の多孔性中空糸膜の製造方法。 Discharging the film-forming stock solution from the flow path between the inner pipe and the outer pipe of the double-tube nozzle, and further discharging the solvent from the flow path in the inner pipe,
In the said cooling solidification process, the manufacturing method of the porous hollow fiber membrane as described in any one of Claims 5-8 which forms the said film forming undiluted solution which passed through the said discharge process.
前記製膜原液を二重管ノズルの内管と外管との間の流路から吐出し、前記支持体を内管から排出し、前記支持体に前記製膜原液を積層する積層工程をさらに有し、
前記冷却凝固工程において、前記積層工程を経た前記製膜原液を製膜させる、請求項5〜8のいずれか一項に記載の多孔性中空糸膜の製造方法。 The porous hollow fiber membrane comprises the porous membrane layer located on the outer surface side, and a hollow support located on the inner surface side,
A stacking step of discharging the film-forming stock solution from a flow path between an inner tube and an outer tube of a double-tube nozzle, discharging the support from the inner tube, and laminating the film-forming stock solution on the support; Have
In the said cooling solidification process, the manufacturing method of the porous hollow fiber membrane as described in any one of Claims 5-8 which forms the said film forming undiluted solution which passed through the said lamination process.
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