JP2006224051A - Porous membrane, porous membrane element, and membrane filter apparatus - Google Patents
Porous membrane, porous membrane element, and membrane filter apparatus Download PDFInfo
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本発明は、河川や湖水、海水などの浄化、ならびに、下水（炊事、洗濯、風呂、トイレ、その他の生活環境から生ずる生活排水）や、生産工場、レストラン、水産加工場、食品加工場などから生ずる廃水の浄化、さらには、培養液のろ過など生物科学分野のろ過に用いられる多孔質膜に関する。 The present invention relates to purification of rivers, lakes, seawater, etc., as well as sewage (cooking, washing, baths, toilets, domestic wastewater from other living environments), production factories, restaurants, fishery processing plants, food processing plants, etc. The present invention relates to a porous membrane used for purification of generated wastewater and further for filtration in the biological science field such as filtration of culture solution.
精密ろ過膜や限外ろ過膜などの多孔質膜は食品工業や医療分野、用水製造、排水処理分野等をはじめとして様々な方面で利用されている。例えば飲料水製造分野すなわち浄水処理過程においては、多孔質膜を用いることによって、従来の浄水処理における殺菌技術である塩素処理で死なないクリプトスポリジウムなどの病原性微生物を完全に阻止でき、安全で水質良好な飲料水を得ることが可能になるためである。また、近年、下水や廃水の浄化にも多孔質膜が使われるようになってきている。そのような多孔質膜には、いろいろな種類、形態のものがあるが、有機重合体溶液を、織布や不織布のような多孔質基材の表面に塗布したり、多孔質基材に含浸したりした後、有機重合体を凝固させるとともに多孔質基材の表面に多孔質樹脂層を形成してなる、いわゆる精密ろ過膜や限外ろ過膜と称される平膜が注目され、従来下廃水処理技術である活性汚泥槽の中に直接精密ろ過膜や限外ろ過膜を浸漬して、高速・高効率の処理を行う膜分離活性汚泥法（メンブレンバイオリアクター法）が盛んに研究され、実用化が開始されている。 Porous membranes such as microfiltration membranes and ultrafiltration membranes are used in various fields including the food industry, medical field, water production, wastewater treatment field and the like. For example, in the drinking water manufacturing field, that is, in the water purification process, the use of a porous membrane can completely prevent pathogenic microorganisms such as Cryptosporidium that do not die by chlorination, which is a sterilization technique in conventional water purification treatment, and is safe and water quality. This is because good drinking water can be obtained. In recent years, porous membranes have been used to purify sewage and wastewater. There are various types and forms of such porous membranes, but an organic polymer solution is applied to the surface of a porous substrate such as a woven fabric or a nonwoven fabric, or impregnated into the porous substrate. After that, flat membranes called so-called microfiltration membranes and ultrafiltration membranes, which solidify the organic polymer and form a porous resin layer on the surface of the porous substrate, have attracted attention. Membrane-separated activated sludge method (membrane bioreactor method) that performs high-speed and high-efficiency treatment by immersing a microfiltration membrane or ultrafiltration membrane directly in an activated sludge tank, which is a wastewater treatment technology, has been actively studied. Practical use has begun.
精密ろ過膜や限外ろ過膜は、ろ過対象に応じた細孔径を保ちつつ透水量を多くすることが要求されている。しかるに、透水量を大きくしようとして空隙率を高くすると、細孔径が大きくなりすぎたり、表面に亀裂が入ったりして阻止率が低下する。一方、阻止率を上げようとして細孔を小さくすると、今度は透水性が低下してしまう。すなわち、阻止率の向上と透水性の向上とは相反する関係にあり、両者のバランスよく整えることは難しい。そこで、膜表面の細孔径を小さくして、いわゆる緻密層を形成し、膜内部の孔径を大きくして、阻止性の向上と透水性の向上を両立させた多孔質膜が提案された。しかし、製造した膜を用いて、膜エレメント、膜モジュール、膜ろ過装置を製作しる際に、膜に極微小な傷をつけてしまうと、阻止率が低下する問題があった。加えて、膜分離活性汚泥法においては、使用中に砂のような無機物や汚泥、その他の固形物が激しく衝突したり、活性汚泥への酸素の供給や目詰まり防止のために行うエアレーション操作による気泡が膜面に激しく衝突したりするので、膜に極微小な傷が発生することがあり、阻止率が低下する問題があった。 The microfiltration membrane and the ultrafiltration membrane are required to increase the amount of water permeation while maintaining the pore diameter according to the filtration target. However, if the porosity is increased to increase the water permeation amount, the pore size becomes too large or the surface cracks and the blocking rate decreases. On the other hand, if the pores are made small in order to increase the blocking rate, the water permeability will be lowered this time. That is, the improvement in the rejection rate and the improvement in water permeability are in a contradictory relationship, and it is difficult to arrange them in a well-balanced manner. Therefore, a porous membrane has been proposed in which the pore diameter on the membrane surface is reduced to form a so-called dense layer, and the pore diameter inside the membrane is increased to achieve both improved barrier properties and improved water permeability. However, when a membrane element, a membrane module, and a membrane filtration device are manufactured using the produced membrane, there is a problem that the blocking rate is lowered if a very minute scratch is made on the membrane. In addition, in the membrane-separated activated sludge method, inorganic substances such as sand, sludge and other solids collide violently during use, or by aeration operation to prevent oxygen supply to the activated sludge and clogging. Since bubbles violently collide with the film surface, extremely small scratches may occur on the film, resulting in a problem that the blocking rate is lowered.
特許文献１には、平均孔径０．０１μｍから１μｍの微多孔を有する透過層を少なくとも３層と、該透過層との間に巨大ボイドを有する支持層が介在された、少なくとも５層からなる多孔性膜が開示されている。これは、３層の透過層があるため、使用中に被処理液の側の透過層に欠陥が生じても残りの２層の透過層で、優れた阻止性能を発揮するというものである。中空糸膜の内表面と外表面が透過層であり、膜内部にも透過層があるとしているが、膜内部の透過層は断面の電子顕微鏡写真でそのように見えているだけであり、実際に膜内部に透過層が存在するものではない。従って、膜エレメント作製時に極微小な傷をつけた場合や、長期間運転をして極微小な傷が発生した場合には、阻止率が低下する問題がある。 Patent Document 1 discloses a porous structure composed of at least five layers in which a permeable layer having a micropore with an average pore diameter of 0.01 μm to 1 μm is interposed and a support layer having a giant void is interposed between the permeable layers. A functional membrane is disclosed. Since there are three transmission layers, even if a defect occurs in the transmission layer on the side of the liquid to be treated during use, the remaining two transmission layers exhibit excellent blocking performance. The inner surface and the outer surface of the hollow fiber membrane are permeable layers, and there is a permeable layer inside the membrane, but the permeable layer inside the membrane just looks like that in the cross-sectional electron micrograph, actually In addition, a permeable layer does not exist inside the membrane. Therefore, there is a problem that the blocking rate is lowered when a very small scratch is made during the fabrication of the membrane element or when a very small scratch is generated after long-term operation.
特許文献２には、微孔質膜（精密ろ過膜に相当）の上に限外ろ過膜を形成するものであり、限外ろ過膜形成時に微孔質膜の細孔を詰まらせて透水性を損なわないように微孔質膜の表面に特定の物質を保持させるものである。微孔質膜と限外ろ過膜はある程度密着しており短期間の使用において剥がれることはないが、水処理分野、特に下廃水処理における膜分離活性汚泥法においては剥がれが発生することがある。
本発明は、上述した従来の技術の問題点を解決し、膜エレメント作製時に傷をつけた場合や、長期間運転をした後でも阻止率を低下させることのない、極めて高い安全性を有する透過水が得られる多孔質膜を提供することである。 The present invention solves the above-mentioned problems of the prior art, and has a very high safety permeation that does not lower the rejection even when the membrane element is damaged or after a long period of operation. It is to provide a porous membrane from which water is obtained.
発明者らは上記課題を解決するために鋭意検討した結果、阻止率を低下させることのない多孔質膜を発明するに至った。すなわち本発明は、
（１）多孔を有した層状の樹脂からなる、または、基材に多孔を有した層状の樹脂が担持されて形成されてなる多孔質膜であって、前記多孔質膜の表面の少なくとも一方の表面および前記多孔質膜内部に緻密層を有し、かつ、前記多孔質膜の少なくとも一方の表面にある緻密層の平均孔径が１０ｎｍから５００ｎｍであることを特徴とする多孔質膜。
As a result of intensive studies to solve the above-mentioned problems, the inventors have invented a porous film that does not reduce the blocking rate. That is, the present invention
(1) A porous film made of a layered resin having porosity, or formed by supporting a layered resin having porosity on a base material, and at least one of the surfaces of the porous film A porous membrane having a dense layer on the surface and inside the porous membrane, and having an average pore diameter of 10 nm to 500 nm in the dense layer on at least one surface of the porous membrane.
（２）ＡＳＴＭ Ｄ６７３に記載の落砂式摩耗試験装置を用いて落砂式摩耗試験を行った後の平均孔径が１０ｎｍから５００ｎｍであることを特徴とする多孔質膜。 (2) A porous membrane having an average pore diameter of 10 nm to 500 nm after a sandfall wear test using the sandfall wear test apparatus described in ASTM D673.
（３）多孔質膜がポリフッ化ビニリデンを主成分とする樹脂からなる（１）または（２）に記載の多孔質膜。 (3) The porous film according to (1) or (2), wherein the porous film is made of a resin mainly composed of polyvinylidene fluoride.
（４）（１）から（３）のいずれかに記載の多孔質膜を有する多孔質膜エレメント。 (4) A porous membrane element having the porous membrane according to any one of (1) to (3).
（５）（１）から（３）のいずれかに記載の多孔質膜を有する多孔質膜ろ過装置。 (5) A porous membrane filtration apparatus having the porous membrane according to any one of (1) to (3).
（６）（４）に記載の多孔質膜エレメントを有する膜ろ過装置。
からなるものである。
(6) A membrane filtration apparatus having the porous membrane element according to (4).
It consists of
本発明は、多孔質膜において、少なくとも一方の表面が平均孔径１０ｎｍから５００ｎｍの緻密層であり、膜内部に緻密層を有することによって、例えば膜エレメント作製時に生じる極微小な傷、使用中の砂のような無機物や汚泥、その他の固形物が激しく衝突することによって生じる極微小な傷によって阻止率を低下させることなく、極めて安全性の高い透過水を提供することができる。また、長期間使用しても内部の緻密層を境に剥離することのない、耐久性に優れた多孔質膜を提供できる。 The present invention is a porous membrane in which at least one surface is a dense layer having an average pore diameter of 10 nm to 500 nm, and has a dense layer inside the membrane. Thus, it is possible to provide permeated water with extremely high safety without reducing the blocking rate due to extremely small scratches caused by intense collision of inorganic substances, sludge, and other solid substances. In addition, it is possible to provide a porous membrane having excellent durability that does not peel off at the inner dense layer even when used for a long time.
本発明の多孔質膜は、図１に示すとおり、少なくとも一方の表面に緻密層を有し、かつ、膜内部にも緻密層を有することを特徴とする。すなわち、該一方の表面にある緻密層が極微小の傷の発生によって、除去対象物質の阻止率が低下するような状態になっても、膜内部にあって該表面とほぼ平行に広がる緻密層が該除去対象物質の透過を阻止し、極めて安全性の高い透過水を提供する。 As shown in FIG. 1, the porous membrane of the present invention is characterized by having a dense layer on at least one surface and also having a dense layer inside the membrane. That is, even if the dense layer on the one surface is in a state in which the rejection rate of the substance to be removed is reduced due to the occurrence of extremely small scratches, the dense layer that is inside the film and extends almost parallel to the surface Prevents permeation of the substance to be removed and provides permeated water with extremely high safety.
本発明の多孔質膜は、一般に精密ろ過膜や限外ろ過膜と呼ばれる多孔質膜であれば特に限定はされないが、少なくとも一方の表面および内部に緻密層を有し、そのうち、少なくとも一方の表面にある緻密層の平均孔径が１０ｎｍから５００ｎｍであることを特徴とする。ここで言う緻密層とは、平均孔径が１０ｎｍから５００ｎｍであるとともに、膜の断面を見た場合に実質的に１μｍ以上の大きな空孔の無い層を示す。膜内部の緻密層は、具体的には、図１に示すように実質的に１μｍ以上の大きな空孔の無い薄い層であり、明らかに構造の変化がある部分である。その厚みは、膜の製法によって異なるが、あまり厚いと透水性が低くなり薄いと阻止率が低くなるため、通常１０ｎｍから１０μｍ、好ましくは５０ｎｍから５μｍの範囲である。膜内部の緻密層の平均孔径は膜の製法に依存し特に規定しないが、１０ｎｍから５００ｎｍの範囲が好ましい。そうすることで、ろ過における分離性能と透水性能のバランスを保つことが可能になり、且つ、一方の表面の緻密層が極微小の傷の発生によって、除去対象物質の阻止率が低下するような状態になっても、多孔質膜全体として阻止率を維持することが可能になるので好ましい。 The porous membrane of the present invention is not particularly limited as long as it is a porous membrane generally called a microfiltration membrane or an ultrafiltration membrane, but has at least one surface and a dense layer on the inside, and of these, at least one surface In the dense layer, the average pore size is 10 nm to 500 nm. The dense layer here refers to a layer having an average pore diameter of 10 nm to 500 nm and substantially free of large pores of 1 μm or more when the cross section of the film is viewed. Specifically, the dense layer inside the film is a thin layer substantially free of large pores of 1 μm or more, as shown in FIG. The thickness varies depending on the film production method, but if it is too thick, the water permeability is low, and if it is thin, the rejection is low. Therefore, it is usually in the range of 10 nm to 10 μm, preferably 50 nm to 5 μm. The average pore size of the dense layer inside the membrane depends on the production method of the membrane and is not particularly defined, but is preferably in the range of 10 nm to 500 nm. By doing so, it becomes possible to maintain the balance between the separation performance and the water permeation performance in filtration, and the rejection rate of the substance to be removed is reduced due to the occurrence of a very small scratch on the dense layer on one surface. Even in such a state, it is possible to maintain the blocking rate as the entire porous membrane, which is preferable.
ここで平均孔径は、次のように求める。逆浸透膜透過水、蒸留水などの精製水に任意の平均粒径のポリスチレンラテックス微粒子を１０ｐｐｍ程度の濃度になるように分散させてなる原液を用い、原液を撹拌しながら温度２５℃、１０ｋＰａ程度のろ過差圧を駆動力に多孔質膜を透過させ、原液と透過液についてそれぞれの濃度から、式（１）によって阻止率を求める。 Here, the average pore diameter is determined as follows. Using a stock solution in which polystyrene latex fine particles having an arbitrary average particle diameter are dispersed in purified water such as reverse osmosis membrane permeated water and distilled water to a concentration of about 10 ppm, the temperature is about 25 ° C. and about 10 kPa while stirring the stock solution. The rejection rate is obtained by the equation (1) from the respective concentrations of the stock solution and the permeated solution.
阻止率＝［（原液濃度−透過液濃度）／原液濃度］×１００ ・・・式（１）
異なる４種類以上の平均粒径のポリスチレンラテックス微粒子について阻止率を求め、ポリスチレンラテックス微粒子平均粒径と阻止率の関係をプロットしてなめらかに結び、阻止率が９０％となるポリスチレンラテックス微粒子の平均粒径を平均孔径とする。
Rejection rate = [(stock solution concentration−permeate concentration) / stock solution concentration] × 100 (1)
Obtain the blocking rate for four or more different types of polystyrene latex fine particles having an average particle diameter, and plot the relationship between the polystyrene latex fine particle average particle diameter and the blocking rate to smoothly connect the average particle size of the polystyrene latex fine particles with a blocking rate of 90%. Let the diameter be the average pore diameter.
本発明の多孔質膜は、落砂式摩耗試験後の平均孔径が１０ｎｍから５００ｎｍであることを特徴とする。落砂式摩耗試験は、落砂式摩耗試験装置（ＡＳＴＭ Ｄ６７３、東洋精機製作所製）を用いて行なう。直径４４ｍｍの円に切り出した多孔質膜サンプルを、水平面と４５°の角度に保持した受台に多孔質膜サンプルの表面が表に出るように膜の両端を押さえ板で動かないように固定して、直径２ｍｍの穴が中心に１箇所、周りに６箇所あいている補給タンクに４００ｇのＳｉＣ（４５＃）を入れ、補給タンクを回転しながら、高さ６５０ｍｍから直径（内径）２３ｍｍの筒を介して４００ｇのＳｉＣ（４５＃）がセットした多孔質膜の中心に落ちるようにして、落下させる。その後、水平面と４５°の角度に保持した落砂式摩耗試験膜の膜表面に付着したＳｉＣを除き、前述の阻止率の測定を行い、平均孔径を求める。 The porous membrane of the present invention is characterized in that the average pore diameter after a sandfall type abrasion test is 10 nm to 500 nm. The sand fall type wear test is performed using a sand fall type wear test apparatus (ASTM D673, manufactured by Toyo Seiki Seisakusho). A porous membrane sample cut into a circle with a diameter of 44 mm is fixed to a pedestal held at an angle of 45 ° with the horizontal plane so that the surface of the porous membrane sample is exposed to the surface so that the both ends of the membrane are not moved by the holding plate. Then, put 400 g of SiC (45 #) into a replenishment tank with a hole with a diameter of 2 mm at the center and 6 places around it, and rotate the replenishment tank while turning the replenishment tank to a cylinder with a diameter (inner diameter) of 23 mm Then, 400 g of SiC (45 #) is dropped to the center of the set porous film. Then, the above-mentioned blocking rate is measured except for SiC adhering to the film surface of the sand-falling type abrasion test film held at an angle of 45 ° with the horizontal plane, and the average pore diameter is obtained.
多孔質膜の材質は、被処理水の水質や用途に応じた分離性能と透水性能が得られれば特に限定はされないが、阻止性能、透水性能や耐汚れ性といった分離性能の点からは多孔質樹脂層を含む多孔質膜であることが好ましく採用できる。また、セルロース繊維、セルローストリアセテート繊維、ポリエステル繊維、ポリプロピレン繊維、ポリエチレン繊維などの有機繊維を用いてなる織布や不織布や、無機材料からなる基材と多孔質樹脂層とから形成されたものでも良い。多孔質樹脂層の材質としてはポリエチレン系樹脂、ポリプロピレン系樹脂、ポリ塩化ビニル系樹脂、ポリフッ化ビニリデン系樹脂、ポリスルホン系樹脂、ポリエーテルスルホン系樹脂、ポリアクリロニトリル系樹脂、セルロース系樹脂、セルローストリアセテート系樹脂などからなれば良く、これらの樹脂を主成分とする樹脂の混合物であってもよい。中でも、溶液による製膜が容易で、物理的耐久性や耐薬品性にも優れているポリ塩化ビニル系樹脂、ポリフッ化ビニリデン系樹脂、ポリスルホン系樹脂、ポリエーテルスルホン系樹脂、ポリアクリロニトリル系樹脂が好ましい。ポリフッ化ビニリデン系樹脂またはそれを主成分とするものが最も好ましい。ここで、ポリフッ化ビニリデン系樹脂とは、フッ化ビニリデンの単独重合体が好ましく用いられるが、フッ化ビニリデンの単独重合体の他、フッ化ビニリデンと共重合可能なビニル系単量体との共重合体も好ましく用いられる。かかるビニル系単量体としては、テトラフルオロエチレン、ヘキサフルオロプロピレン、三塩化フッ化エチレンなどが例示される。本発明の多孔質膜は、少なくとも一方の表面と膜内部に緻密層を有するが、一方の緻密層から内部の緻密層の直前まで（図１の４）と内部の緻密層から他方の表面まで（図１の３）とが異なる材質であっても、多孔を有した層状の樹脂で構成された多孔質樹脂層（ａ）と多孔質樹脂層（ｂ）とが剥がれることが無ければ良い。その組み合わせは任意であるが、ポリスルホン系樹脂とポリエーテルスルホン系樹脂、ポリフッ化ビニリデン系樹脂とセルロース系樹脂、ポリフッ化ビニリデン系樹脂とセルローストリアセテート系樹脂、ポリフッ化ビニリデン系樹脂とポリ酢酸ビニル系樹脂、フッ化ビニリデン単独重合体とフッ化ビニリデンとビニル系単量体との共重合体が好ましい。この中でも、フッ化ビニリデン単独重合体とフッ化ビニリデンとビニル系単量体との共重合体が特に好ましい。多孔質樹脂層（ｂ）の厚みは、あまり薄いと十分な物理的強度が無く、厚いと透水性が低くなるため、通常５μｍから２００μｍ、好ましくは１０μｍから１００μｍの範囲で選択される。 The material of the porous membrane is not particularly limited as long as the separation performance and water permeation performance according to the quality of the water to be treated and the application can be obtained, but it is porous from the viewpoint of separation performance such as blocking performance, water permeation performance and dirt resistance. A porous film including a resin layer can be preferably employed. Moreover, it may be formed from a woven fabric or nonwoven fabric using organic fibers such as cellulose fiber, cellulose triacetate fiber, polyester fiber, polypropylene fiber, polyethylene fiber, or a substrate made of an inorganic material and a porous resin layer. . The material of the porous resin layer is polyethylene resin, polypropylene resin, polyvinyl chloride resin, polyvinylidene fluoride resin, polysulfone resin, polyethersulfone resin, polyacrylonitrile resin, cellulose resin, cellulose triacetate resin. It may be made of a resin or the like, and may be a mixture of resins mainly composed of these resins. Among these, polyvinyl chloride resin, polyvinylidene fluoride resin, polysulfone resin, polyethersulfone resin, and polyacrylonitrile resin, which are easy to form a film by solution and have excellent physical durability and chemical resistance, are available. preferable. A polyvinylidene fluoride-based resin or one having a main component thereof is most preferable. Here, as the polyvinylidene fluoride resin, a homopolymer of vinylidene fluoride is preferably used. In addition to a homopolymer of vinylidene fluoride, a copolymer of a vinyl monomer copolymerizable with vinylidene fluoride is used. A polymer is also preferably used. Examples of such vinyl monomers include tetrafluoroethylene, hexafluoropropylene, and trichlorofluoroethylene. The porous membrane of the present invention has a dense layer on at least one surface and inside the membrane, from one dense layer to immediately before the inside dense layer (4 in FIG. 1) and from the inside dense layer to the other surface. Even if the material is different from (3 in FIG. 1), it is sufficient that the porous resin layer (a) and the porous resin layer (b) made of a layered resin having porosity are not peeled off. The combination is arbitrary, but a polysulfone resin and a polyethersulfone resin, a polyvinylidene fluoride resin and a cellulose resin, a polyvinylidene fluoride resin and a cellulose triacetate resin, a polyvinylidene fluoride resin and a polyvinyl acetate resin A vinylidene fluoride homopolymer and a copolymer of vinylidene fluoride and a vinyl monomer are preferred. Among these, a vinylidene fluoride homopolymer and a copolymer of vinylidene fluoride and a vinyl monomer are particularly preferable. When the thickness of the porous resin layer (b) is too thin, sufficient physical strength is not obtained, and when it is thick, the water permeability becomes low. Therefore, the thickness is usually selected in the range of 5 μm to 200 μm, preferably 10 μm to 100 μm.
本発明の多孔質膜は、平膜であっても中空糸膜であっても良い。平膜の場合、その厚みは用途に応じて選択されるが、例えば、２０μｍから５０００μｍ、好ましくは５０μｍから２０００μｍの範囲で選択される。上述したように、本発明の多孔質膜は基材と多孔質樹脂層とから形成されていても良い。その際、基材に多孔質樹脂層が浸透していても、基材に多孔質樹脂層が浸透していなくてもどちらでも良く、用途に応じて選択される。基材の厚みは、５０μｍから３０００μｍの範囲で選択される。中空糸膜の場合、内径は１００μｍから５０００μｍの範囲で選択され、膜厚は２０μｍから２０００μｍの範囲で選択される。また、有機繊維又は無機繊維を筒状にした織物や編み物を含んでいても良い。 The porous membrane of the present invention may be a flat membrane or a hollow fiber membrane. In the case of a flat membrane, the thickness is selected according to the application, but is selected in the range of, for example, 20 μm to 5000 μm, preferably 50 μm to 2000 μm. As described above, the porous film of the present invention may be formed of a base material and a porous resin layer. At that time, either the porous resin layer permeates the base material or the porous resin layer does not permeate the base material, and it is selected depending on the application. The thickness of the substrate is selected in the range of 50 μm to 3000 μm. In the case of a hollow fiber membrane, the inner diameter is selected in the range of 100 μm to 5000 μm, and the film thickness is selected in the range of 20 μm to 2000 μm. Moreover, the textile fabric and knitting which made the organic fiber or the inorganic fiber the cylinder shape may be included.
以下、ポリフッ化ビニリデン系樹脂を多孔質樹脂層として形成する平膜の場合の製造方法を例に挙げて、本発明をより詳細に述べる。 Hereinafter, the present invention will be described in more detail by taking as an example a production method in the case of a flat film in which a polyvinylidene fluoride resin is formed as a porous resin layer.
本発明において製法上の特徴は、まず重合体溶液（ａ）から少なくとも一方の表面に緻密層を有する多孔質樹脂層（ａ）を公知の方法で作製し、その上に重合体溶液（ｂ）を塗布して多孔質樹脂層（ｂ）を作製することである。この場合、重合体溶液（ｂ）の溶媒の多孔質樹脂層（ａ）に対する溶解性が低いものを選択することが極めて重要な要件である。溶解性が高い場合、得られた多孔質膜内部に緻密層が形成されなかったり、透水性能が大きく低下したりしてしまう。ポリフッ化ビニリデン系樹脂多孔質膜の場合、重合体溶液（ａ）における溶媒は、Ｎ，Ｎ−ジメチルアセトアミド（ＤＭＡｃ）、Ｎ，Ｎ−ジメチルホルムアミド（ＤＭＦ）、Ｎ−メチルピロリドン（ＮＭＰ）、ヘキサメチルホスホリックトリアミド（ＨＭＰＴ）等を例示することができる。 In the present invention, the production method is characterized in that a porous resin layer (a) having a dense layer on at least one surface is first prepared from the polymer solution (a) by a known method, and the polymer solution (b) is formed thereon. Is applied to produce a porous resin layer (b). In this case, it is a very important requirement to select a polymer solution (b) having a low solubility in the porous resin layer (a) of the solvent. When the solubility is high, a dense layer is not formed inside the obtained porous membrane, or the water permeability performance is greatly reduced. In the case of the polyvinylidene fluoride resin porous membrane, the solvent in the polymer solution (a) is N, N-dimethylacetamide (DMAc), N, N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), hexa Examples thereof include methylphosphoric triamide (HMPT).
一方、重合体溶液（ｂ）における溶媒としては、ポリフッ化ビニリデン系樹脂の溶解性が相対的に低い、ジメチルスルホキシド（ＤＭＳＯ）、アセトン、メチルエチルケトンなどを例示することができる。その中でも、ＤＭＳＯが好ましく用いられる。さらに、重合体溶液（ｂ）を塗布する際の温度も重要である。高すぎると重合体溶液（ｂ）を塗布する際に多孔質樹脂層（ａ）に損傷を与えて多孔質膜内部に緻密層を形成できなかったり透水性能を大きく低下させてしまったりしてしまう。低すぎると重合体溶液（ｂ）中で樹脂成分が析出して塗布しにくく、また、得られた多孔質膜の透水性能や阻止性能が悪化してしまう。そのため、通常２０℃から６０℃、好ましくは２５℃から５０℃の範囲で選択される。重合体溶液（ｂ）を塗布した後は、ポリフッ化ビニリデン系樹脂の非溶媒を含む溶液で凝固させ、脱溶媒を行う。非溶媒は、特に限定しないが、通常、水、メタノールなどのアルコール類であり、好ましくは水である。非溶媒単独でも良いが、他の非溶媒や重合体溶液（ａ）や重合体溶液（ｂ）の溶媒を含んでいても良い。本発明においては、透水性能や阻止性能を制御するために、重合体溶液（ａ）および／または重合体溶液（ｂ）に、凝固に用いる非溶媒に溶解する有機化合物を含んでいてもよい。たとえば、水、グリセリン、エチレングリコールなどの低分子化合物や、ポリエチレングリコール、ポリビニルアルコール、ポリビニルピロリドン、ポリエチレンイミンなどの水溶性高分子、ポリエチレングリコールの脂肪酸エステル、ポリエチレングリコールソルビタン脂肪酸エステルなどの界面活性剤をあげることができる。さらには、シリカ、塩化カルシウム、炭酸カルシウム、塩化リチウムなどの無機化合物を含んでいてもよい。 On the other hand, examples of the solvent in the polymer solution (b) include dimethyl sulfoxide (DMSO), acetone, and methyl ethyl ketone, which have relatively low solubility of the polyvinylidene fluoride resin. Among these, DMSO is preferably used. Furthermore, the temperature at which the polymer solution (b) is applied is also important. If it is too high, the porous resin layer (a) may be damaged when the polymer solution (b) is applied, and a dense layer cannot be formed inside the porous membrane, or the water permeability performance may be greatly reduced. . If it is too low, the resin component will precipitate in the polymer solution (b) and it will be difficult to apply, and the water permeability and blocking performance of the resulting porous membrane will deteriorate. Therefore, it is selected in the range of usually 20 ° C to 60 ° C, preferably 25 ° C to 50 ° C. After the polymer solution (b) is applied, it is coagulated with a solution containing a non-solvent of polyvinylidene fluoride resin, and the solvent is removed. The non-solvent is not particularly limited, but is usually alcohol such as water or methanol, preferably water. Although the non-solvent may be used alone, it may contain other non-solvents or the solvent of the polymer solution (a) or the polymer solution (b). In the present invention, the polymer solution (a) and / or the polymer solution (b) may contain an organic compound that dissolves in a non-solvent used for coagulation in order to control the water permeation performance and blocking performance. For example, low molecular weight compounds such as water, glycerin, and ethylene glycol; water-soluble polymers such as polyethylene glycol, polyvinyl alcohol, polyvinyl pyrrolidone, and polyethyleneimine; and surfactants such as polyethylene glycol fatty acid esters and polyethylene glycol sorbitan fatty acid esters. I can give you. Furthermore, inorganic compounds such as silica, calcium chloride, calcium carbonate, and lithium chloride may be included.
本発明の多孔質膜は、透過水の取出口を有する枠体などの支持体の両面に、流路材、たとえばプラスチックネットを介して貼り合わせることによって多孔質膜エレメントとすることができる。さらに、この多孔質膜エレメント複数枚をユニット化して水槽に沈め、多孔質膜エレメントの下部から多孔質膜の表面に空気を供給できる散気管を設け、複数の多孔質膜エレメントの透過水を集水できる配管と吸引ろ過するためのポンプ等を有する膜ろ過装置とすることもできる。また、上述の多孔質膜、多孔質膜エレメント、膜ろ過装置を下廃水の処理に用いることも好ましく、下廃水処理方法として採用できる。 The porous membrane of the present invention can be made into a porous membrane element by adhering to both surfaces of a support such as a frame having a permeated water outlet through a flow path material such as a plastic net. Furthermore, a plurality of porous membrane elements are unitized and submerged in a water tank, and a diffuser pipe is provided to supply air from the lower part of the porous membrane element to the surface of the porous membrane, collecting the permeated water of the plurality of porous membrane elements. It can also be set as the membrane filtration apparatus which has the pipe | tube which can be watered, and the pump for suction filtration. Moreover, it is also preferable to use the above-mentioned porous membrane, porous membrane element, and membrane filtration apparatus for the treatment of sewage wastewater, which can be employed as a method for treating sewage wastewater.
以下に実施例を挙げて本発明を具体的に説明するが、本発明は、これら実施例によって何ら限定されるものではない。 EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
［透水性能の測定方法］
多孔質膜の透水量の測定は、多孔質膜を直径４４ｍｍの円形に切り出し円筒型のろ過ホルダーにセットし、飲料水を透析膜（東レ（株）製 フィルトライザー Ｂ２−１．５Ｈ）でろ過したものを原水とし、２５℃で、水頭高さ１ｍで５分間予備透過させた後、続けて透過させて透過水を５分間採取して求めた。なお、ポンプ等で加圧や吸引して得た値を換算して求めても良いし、水温についても、水の粘性で換算しても良い。評価に際し、多孔質膜はエタノールに１５分浸漬後水中に２時間以上浸漬置換し評価に用いた。
[Measurement method of water permeability]
The water permeability of the porous membrane was measured by cutting the porous membrane into a circular shape with a diameter of 44 mm and setting it in a cylindrical filter holder, and drinking water with a dialysis membrane (Filtizer B2-1.5H manufactured by Toray Industries, Inc.). The filtered water was used as raw water, preliminarily permeated at 25 ° C. with a head height of 1 m for 5 minutes, and then continuously permeated to collect permeated water for 5 minutes. The value obtained by pressurization or suction with a pump or the like may be obtained by conversion, and the water temperature may also be converted by the viscosity of water. In the evaluation, the porous membrane was immersed in ethanol for 15 minutes and then immersed in water for 2 hours or more and used for evaluation.
［平均孔径の測定方法］
平均孔径は、ポリスチレンラテックスの阻止曲線から求める。すなわち、逆浸透膜透過水、蒸留水などの精製水に任意の平均粒径のポリスチレンラテックス微粒子を１０ｐｐｍ程度の濃度になるように分散させてなる原液を用い、原液を撹拌しながら温度２５℃、１０ｋＰａ程度のろ過差圧を駆動力に多孔質膜を透過させ、原液と透過液についてそれぞれの濃度から、式（１）によって阻止率を求める。濃度の測定には例えば波長２４０ｎｍの紫外線の吸光度などを使うことができる。
[Measurement method of average pore size]
The average pore diameter is determined from the inhibition curve of polystyrene latex. That is, using a stock solution in which polystyrene latex fine particles having an arbitrary average particle diameter are dispersed in purified water such as reverse osmosis membrane permeated water and distilled water so as to have a concentration of about 10 ppm, while stirring the stock solution, the temperature is 25 ° C., The porous membrane is permeated with a filtration differential pressure of about 10 kPa as a driving force, and the blocking rate is obtained from the respective concentrations of the stock solution and the permeated solution according to Equation (1). For the measurement of the concentration, for example, the absorbance of ultraviolet light having a wavelength of 240 nm can be used.
阻止率＝［（原液濃度−透過液濃度）／原液濃度］×１００・・・式（１）。 Blocking rate = [(stock solution concentration−permeate concentration) / stock solution concentration] × 100 (1).
異なる４種類以上の平均粒径のポリスチレンラテックス微粒子について阻止率を求め、ポリスチレンラテックス微粒子平均粒径と阻止率の関係をプロットしてなめらかに結び、阻止率が９０％となるポリスチレンラテックス微粒子の平均粒径を平均孔径とする。 Obtain the blocking rate for four or more different types of polystyrene latex fine particles having an average particle diameter, and plot the relationship between the polystyrene latex fine particle average particle diameter and the blocking rate to smoothly connect the average particle size of the polystyrene latex fine particles with a blocking rate of 90%. Let the diameter be the average pore diameter.
［耐久性の評価方法］
多孔質膜の耐久性評価は、落砂式摩耗試験によって行った。落砂式摩耗試験は、落砂式摩耗試験装置（ＡＳＴＭ Ｄ６７３、東洋精機製作所製）を用いて行った。直径４４ｍｍの円に切り出した多孔質膜サンプルを、水平面と４５°の角度に保持した受台に多孔質膜サンプルの表面が表に出るように膜の両端を押さえ板で動かないように固定して、直径２ｍｍの穴が中心に１箇所、周りに６箇所あいている補給タンクに４００ｇのＳｉＣ（４５＃）を入れ、補給タンクを回転しながら、高さ６５０ｍｍから直径（内径）２３ｍｍの筒を介して４００ｇのＳｉＣ（４５＃）がセットした多孔質膜の中心に落ちるようにして、落下させた。その後、水平面と４５°の角度に保持した落砂式摩耗試験膜の膜表面に付着したＳｉＣを除き、上述の阻止率の測定を行い、平均孔径を求めた。
[Durability evaluation method]
Durability evaluation of the porous membrane was performed by a sandfall type abrasion test. The falling sand wear test was performed using a fall sand wear test apparatus (ASTM D673, manufactured by Toyo Seiki Seisakusho). A porous membrane sample cut into a circle with a diameter of 44 mm is fixed to a pedestal held at an angle of 45 ° with the horizontal plane so that the surface of the porous membrane sample is exposed to the surface so that the both ends of the membrane are not moved by the holding plate. Then, put 400 g of SiC (45 #) into a replenishment tank with a hole with a diameter of 2 mm at the center and 6 places around it, and rotate the replenishment tank while turning the replenishment tank to a cylinder with a diameter (inner diameter) of 23 mm And then dropped to the center of the porous film in which 400 g of SiC (45 #) was set. Then, the above-mentioned blocking rate was measured by removing the SiC adhering to the film surface of the sand-falling type abrasion test film held at an angle of 45 ° with the horizontal plane, and the average pore diameter was obtained.
表１に実施例１，２、比較例１から３の多孔質膜の透水性と平均孔径、落砂式磨耗試験後の透水性と平均孔径を整理した。 Table 1 shows the water permeability and average pore diameter of the porous membranes of Examples 1 and 2 and Comparative Examples 1 to 3, and the water permeability and average pore diameter after the falling sand type wear test.
（実施例１）
重量平均分子量約２５万のポリフッ化ビニリデン樹脂１３重量％、数平均分子量約４００のポリエチレングリコール５重量％とＤＭＡｃ８２重量％からなる４０℃の重合体溶液（ａ）をポリエステル不織布（密度０．４８ｇ／ｃｍ３、厚み約２００μｍ）に塗布し、３０℃の水で凝固せしめた後、水洗しＤＭＡｃを脱溶媒して多孔質樹脂層（ａ）を作製した。透水性は５５（×１０−９ｍ３／ｍ２・ｓ・Ｐａ）、平均孔径は１００ｎｍであった。多孔質樹脂層（ａ）を４０℃のオーブン中４時間乾燥させた後、ポリフッ化ビニリデン樹脂７重量％、ＤＭＳＯ９３重量％からなる４０℃の重合体溶液（ｂ）を塗布し、３０℃の水で凝固せしめた後、水洗しＤＭＳＯを脱溶媒して多孔質樹脂層（ｂ）を作製し、多孔質膜を得た。透水性は４１（×１０−９ｍ３／ｍ２・ｓ・Ｐａ）、平均孔径は８０ｎｍであった。落砂式磨耗試験後、透水性は５０（×１０−９ｍ３／ｍ２・ｓ・Ｐａ）、平均孔径は１００ｎｍであった。
Example 1
A polymer solution (a) composed of 13% by weight of a polyvinylidene fluoride resin having a weight average molecular weight of about 250,000, 5% by weight of polyethylene glycol having a number average molecular weight of about 400 and 82% by weight of DMAc was added to a polyester nonwoven fabric (density 0.48 g / cm 3, was applied to about 200 [mu] m) thick, after coagulate at 30 ° C. water to prepare porous resin layer (a) and washed with water DMAc by desolvation. The water permeability was 55 (× 10 −9 m 3 / m 2 · s · Pa), and the average pore diameter was 100 nm. After the porous resin layer (a) was dried in an oven at 40 ° C. for 4 hours, a polymer solution (b) at 40 ° C. consisting of 7% by weight of polyvinylidene fluoride resin and 93% by weight of DMSO was applied, and water at 30 ° C. was applied. After solidifying with DM, the porous resin layer (b) was produced by washing with water and removing DMSO to obtain a porous film. The water permeability was 41 (× 10 −9 m 3 / m 2 · s · Pa), and the average pore diameter was 80 nm. After the falling sand type abrasion test, the water permeability was 50 (× 10 −9 m 3 / m 2 · s · Pa), and the average pore diameter was 100 nm.
（実施例２）
実施例１で得た乾燥した多孔質樹脂層（ａ）に、フッ化ビニリデンと六フッ化プロピレンの共重合体（ソルベイアドバンストケミカル社製、ＳＯＬＥＦ１１０００）７重量部、ＤＭＳＯ９３重量部からなる４０℃の重合体溶液（ｂ）を塗布し、３０℃の水で凝固せしめた後、水洗しＤＭＳＯを脱溶媒して多孔質樹脂層（ｂ）を作製し、多孔質膜を得た。透水性は３０（×１０−９ｍ３／ｍ２・ｓ・Ｐａ）、平均孔径は８０ｎｍであった。落砂式磨耗試験後、透水性は４０（×１０−９ｍ３／ｍ２・ｓ・Ｐａ）、平均孔径は１００ｎｍであった。
(Example 2)
The dried porous resin layer (a) obtained in Example 1 was subjected to 40 ° C. consisting of 7 parts by weight of a vinylidene fluoride / propylene hexafluoride copolymer (SOLEF11000, manufactured by Solvay Advanced Chemical Co.) and 93 parts by weight of DMSO. After the polymer solution (b) was applied and coagulated with water at 30 ° C., it was washed with water and DMSO was removed to prepare a porous resin layer (b) to obtain a porous film. The water permeability was 30 (× 10 −9 m 3 / m 2 · s · Pa), and the average pore diameter was 80 nm. After the falling sand type abrasion test, the water permeability was 40 (× 10 −9 m 3 / m 2 · s · Pa), and the average pore diameter was 100 nm.
（比較例１）
実施例１で得た乾燥した多孔質樹脂層（ａ）の落砂式磨耗試験を実施し透水性と平均孔径を測定した。透水性は７０（×１０−９ｍ３／ｍ２・ｓ・Ｐａ）、平均孔径は８０ｎｍであった。
(Comparative Example 1)
A dried sand type abrasion test of the dried porous resin layer (a) obtained in Example 1 was performed to measure water permeability and average pore diameter. The water permeability was 70 (× 10 −9 m 3 / m 2 · s · Pa), and the average pore diameter was 80 nm.
（比較例２）
特許文献１に習い、ポリフッ化ビニリデン樹脂（アトフィナ社、Ｋｙｎａｒ４６０）２０重量部、ＤＭＳＯ１００重量部からなる４０℃の重合体溶液を、実施例１のポリエステル不織布に塗布し、ＤＭＳＯを１０重量％含む５０℃の水溶液で凝固せしめた後、水洗しＤＭＳＯを脱溶媒して多孔質膜を作製した。透水性は１（×１０−９ｍ３／ｍ２・ｓ・Ｐａ）、平均孔径は２０ｎｍであった。落砂式磨耗試験後、透水性は２０（×１０−９ｍ３／ｍ２・ｓ・Ｐａ）、平均孔径は８０ｎｍであった。
(Comparative Example 2)
According to Patent Document 1, a polymer solution at 40 ° C. composed of 20 parts by weight of a polyvinylidene fluoride resin (Atfina, Kynar 460) and 100 parts by weight of DMSO was applied to the polyester nonwoven fabric of Example 1, and 50% containing 10% by weight of DMSO. After coagulating with an aqueous solution at 0 ° C., it was washed with water and DMSO was removed from the solvent to prepare a porous membrane. The water permeability was 1 (× 10 −9 m 3 / m 2 · s · Pa), and the average pore diameter was 20 nm. After the falling sand type abrasion test, the water permeability was 20 (× 10 −9 m 3 / m 2 · s · Pa), and the average pore diameter was 80 nm.
（比較例３）
実施例１で得た乾燥した多孔質樹脂層（ａ）に、ポリフッ化ビニリデン樹脂７重量％、ＤＭＦ９３重量％からなる４０℃の重合体溶液（ｂ）を塗布し、３０℃の水で凝固せしめた後、水洗しＤＭＳＯを脱溶媒して多孔質樹脂層（ｂ）を作製し多孔質膜を得た。透水性は２（×１０−９ｍ３／ｍ２・ｓ・Ｐａ）、平均孔径は８０ｎｍであった。落砂式磨耗試験後、透水性は１０（×１０−９ｍ３／ｍ２・ｓ・Ｐａ）、平均孔径は７０ｎｍであった。
(Comparative Example 3)
The dried porous resin layer (a) obtained in Example 1 was coated with a polymer solution (b) of 40 ° C. composed of 7% by weight of polyvinylidene fluoride resin and 93% by weight of DMF, and solidified with water at 30 ° C. After washing with water and removing DMSO, a porous resin layer (b) was produced to obtain a porous membrane. The water permeability was 2 (× 10 −9 m 3 / m 2 · s · Pa), and the average pore diameter was 80 nm. After the falling sand type abrasion test, the water permeability was 10 (× 10 −9 m 3 / m 2 · s · Pa), and the average pore diameter was 70 nm.
本発明の多孔質膜、多孔質膜エレメント、および膜ろ過装置は、膜エレメント作製時に傷をつけた場合や、長期間運転をした後でも阻止率を低下させることのない、極めて高い安全性を有する透過水が得られる技術であり、産業上の利用の可能性は高い。 The porous membrane, the porous membrane element, and the membrane filtration device of the present invention have extremely high safety that does not reduce the blocking rate even when the membrane element is damaged or after a long period of operation. This is a technology that can be used to obtain the permeated water and has high industrial applicability.
１ 多孔質膜表面の緻密層（平均孔径は１０ｎｍから５００ｎｍ）
２ 多孔質膜内部の緻密層
３ 多孔質樹脂層（ａ）
４ 多孔質樹脂層（ｂ）
1 Dense layer on the surface of the porous membrane (average pore size is 10 nm to 500 nm)
2 Dense layer inside porous membrane 3 Porous resin layer (a)
4 Porous resin layer (b)
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2008117740A1 (en) * | 2007-03-23 | 2008-10-02 | Kureha Corporation | Vinylidene fluoride resin hollow-fiber porous membrane and process for production of the same |
| WO2013180272A1 (en) | 2012-06-01 | 2013-12-05 | 三菱レイヨン株式会社 | Hollow porous film |
| WO2015053366A1 (en) | 2013-10-11 | 2015-04-16 | 三菱レイヨン株式会社 | Hollow porous membrane |
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2005
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2008117740A1 (en) * | 2007-03-23 | 2008-10-02 | Kureha Corporation | Vinylidene fluoride resin hollow-fiber porous membrane and process for production of the same |
| WO2013180272A1 (en) | 2012-06-01 | 2013-12-05 | 三菱レイヨン株式会社 | Hollow porous film |
| US9694327B2 (en) | 2012-06-01 | 2017-07-04 | Mitsubishi Rayon Co., Ltd. | Hollow porous membrane |
| WO2015053366A1 (en) | 2013-10-11 | 2015-04-16 | 三菱レイヨン株式会社 | Hollow porous membrane |
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