Method for preparing a selective permeable membrane and water treatment method

Abstract

To provide a selective permeable membrane formed with a dense layer by an interfacial polymerization method where the reduction of a permeation flux caused by membrane contaminants such as protein and the like is easily and effectively suppressed.SOLUTION: A selective permeable membrane production method has a step to form a dense layer on a porous support by the interfacial polymerization of a polyfunctional amine monomer with a polyfunctional acid halide monomer and is characterized by having a step to perform modification by a 2-methoxy ethyl acrylate monomer on the surface of the dense layer. A selective permeable membrane produced by the selective permeable membrane production method is used in a water treatment method.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a selective permeable membrane, a method for producing the same, and a water treatment method using the selective permeable membrane. [Background technology]

[0002] Reverse osmosis (RO) membranes and nanofiltration (NF) membranes are widely used as selective permeable membranes in fields such as seawater and brine desalination, industrial water and ultrapure water production, and wastewater recovery. RO membrane treatment and NF membrane treatment have the advantage of being able to remove ions and low molecular weight organic matter to a high degree, but they have the challenge that the permeate flux decreases over time due to the adsorption of membrane contaminants such as nonionic surfactants, polysaccharides, proteins, and humic substances contained in the treated water.

[0003] The most common method for fabricating RO and NF membranes involves interfacial polymerization of polyfunctional amine monomers and polyfunctional acid chloride monomers on a porous substrate to form a dense layer. Since amide bonds are formed by the reaction between the amine and acid chloride, the selective permeable membranes fabricated in this way are called polyamide membranes. Because interfacial polymerization of polyfunctional amine monomers and polyfunctional acid chloride monomers forms a very dense and thin separation layer, this method is the most frequently used film fabrication method for NF and RO membranes.

[0004] Conventionally, various attempts have been made to improve the stain resistance of polyamide films. For example, methods for introducing hydroxyl groups such as polyvinyl alcohol to the dense layer surface of a polyamide film include a method of hydrophilizing by uniformly adhering a water-insolubilized polyvinyl alcohol polymer to the surface of an aromatic polysulfone porous film (Patent Document 1), a method of coating the dense layer surface with an ethylene-vinyl alcohol copolymer layer (Patent Document 2), and a method of applying polyvinyl alcohol, which is insoluble in water at 25°C and soluble in water at 80°C, to the surface layer of an aromatic polyamide film (Patent Document 3). However, these methods had challenges in terms of the long-term stability of the coating layer.

[0005] To improve stain resistance, a method has been proposed in which a compound having at least one functional group that can react with the acid halide remaining after interfacial polymerization is reacted to form a covalent bond (Patent Document 4). In this document, the water-soluble compound having at least one reactive group that reacts with the acid halide can be an aliphatic, aromatic, or heterocyclic compound, and can be any compound that is substantially soluble in water and reacts with the acid halide group to form a covalent bond. Examples of functional groups include hydroxyl groups, amino groups, and epoxy groups. Ethylenediamine (diaminoethane) and propylenediamine (diaminopropane) are also included in the examples, but these are treated on the same level as alcohols such as m-phenylenediamine and methanol. In the examples, polyethyleneimine, 2-ethanolamine, N-(3-aminopropyl)morpholine, and N,N-dimethyl-p-phenylenediamine are used. Of these, the one using polyethyleneimine has been shown to have a smaller decrease in permeation flux. However, polyethyleneimine is likely to have a positively charged surface, and therefore is not considered effective against proteins or humic substances.

[0006] On the other hand, biocompatible polymers have been developed as materials that suppress the adsorption of proteins in living organisms, and it has been reported that membrane contamination can be suppressed when applied to selective permeable membranes. As examples, 2-methacryloyloxyethyl phosphorylcholine (Patent Document 5), a phosphobetaine-type zwitterionic monomer, N,N-dimethyl-γ-aminobutyric acid (Non-Patent Document 1), a carboxybetaine-type zwitterionic monomer, and [(2-methacryloyloxy)ethyl]dimethyl[3-sulfopropyl]ammonium hydroxide (Non-Patent Document 2), a sulfobetaine-type zwitterionic monomer, are being considered as membrane modification materials. In addition, 2-hydroxyethyl methacrylate (HEMA) and ethylene glycol methacrylate, which are not zwitteryin monomers, are also being considered for application (Non-Patent Document 2).

[0007] 2-methoxyethyl acrylate (MEA) has traditionally been used as a disinfectant, but in recent years, it has been investigated as a material that suppresses membrane contamination. For example, by blending polymerized MEA with polyvinylidene fluoride (PVDF), a contamination-resistant microfiltration (MF) membrane has been obtained (Non-Patent Literature 3). However, currently, MEA is only applied to MF membranes and is not applied to NF membranes or RO membranes that remove ions. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 8-52333 [Patent Document 2] Japanese Patent Application Publication No. 4-330924 [Patent Document 3] International Publication No. 1997 / 034686 [Patent Document 4] Japanese Patent Publication No. 2002-224546 [Patent Document 5] Japanese Patent Publication No. 2012-55870 [Non-patent literature]

[0009] [Non-Patent Document 1] Matsuno et al., Membrane, 35, 86-92 (2010) [Non-Patent Document 2] Zhe et al., J. Membrane Science, 582, 111-119(2019) [Non-Patent Document 3] Ohno et al., Abstracts of the Membrane Symposium, 32, 86 (2020) [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] The present invention aims to provide a simple and effective technique for suppressing the decrease in permeation flux caused by membrane contaminants such as proteins in a selective permeation membrane having a dense layer formed by an interfacial polymerization method.

Means for Solving the Problems

[0011] The present inventor has conducted extensive studies to solve the above problems and found that by modifying the dense layer formed by the interfacial polymerization of a polyfunctional amine monomer and a polyfunctional acid halide monomer with 2-methoxyethyl acrylate, the fouling resistance of the selective permeation membrane can be enhanced, and the decrease in permeation flux can be suppressed. That is, the gist of the present invention is as follows.

[0012] [1] A method for producing a selective permeation membrane having a step of forming a dense layer on a porous support by interfacial polymerization of a polyfunctional amine monomer and a polyfunctional acid halide monomer, characterized in that it has a step of modifying the surface of the dense layer with a 2-methoxyethyl acrylate monomer.

[0013] [2] The method for producing a selective permeation membrane according to [1], wherein the modification with 2-methoxyethyl acrylate is carried out through modification with 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, or derivatives thereof, followed by modification with 2-bromoisobutyryl bromide.

[0014] [3] In the modification with 2-methoxyethyl acrylate, 2-methoxyethyl acrylate is introduced at 0.005 to 0.1 mg / cm per membrane area of the selective permeation membrane. 2 The method for producing a selective permeation membrane according to [1] or [2].

[0015] [4] A selective permeation membrane having a dense layer formed by interfacial polymerization of a polyfunctional amine monomer and a polyfunctional acid halide monomer on a porous support, characterized in that the dense layer is surface-modified with 2-methoxyethyl acrylate.

[0016] [5] The amount of 2-methoxyethyl acrylate introduced by the surface modification is 0.005 to 0.1 mg / cm² per unit area of ​​the selective permeable membrane. 2 The selective permeable membrane described in [4].

[0017] A water treatment method using a selective permeable membrane obtained by the selective permeable membrane preparation method described in any of [1] to [3], or a selective permeable membrane described in [4] or [5].

[0018] [7] The water treatment method according to [6], wherein the water to be treated has a protein concentration of 1 mg / L or more, and is treated with the selective permeable membrane. [Effects of the Invention]

[0019] According to the present invention, by modifying the surface of a dense layer formed by interfacial polymerization of a polyfunctional amine monomer and a polyfunctional acid halide monomer with 2-methoxyethyl acrylate, the adsorption of membrane contaminants such as proteins can be prevented, the decrease in permeation flux of the selective permeable membrane caused by these membrane contaminants can be suppressed, and stable and efficient water treatment can be performed over a long period of time. [Brief explanation of the drawing]

[0020] [Figure 1] This graph shows the relationship between MEA dosage and IR peak ratio (1730 / 1660). [Figure 2] This is a diagram showing the configuration of the test apparatus used in the examples and comparative examples. [Figure 3] This graph shows the results for Examples 1 and 2 and Comparative Example 1. [Figure 4] This graph shows the results for Examples 3 and 4 and Comparative Example 2. [Modes for carrying out the invention]

[0021] The present invention will be described in detail below.

[0022] [mechanism] As mentioned above, a polyamide film is obtained by interfacial polymerization of polyfunctional amine monomers and polyfunctional acid halide monomers on a porous support. Because this interfacial polymerization layer is a very dense and thin separation layer, it is the most commonly used film-forming method for creating NF films and RO films. In this invention, the base performance of NF membranes and RO membranes fabricated by this method is utilized, and 2-methoxyethyl acrylate (MEA) is introduced through post-modification. The amount of MEA introduced is 0.5 mg / cm² per membrane area. 2 Preferably, 0.1 mg / cm³ 2 By doing so, the modification can be performed while maintaining almost the performance of the base NF membrane and RO membrane. Furthermore, if the amount of MEA introduced increases, the modified layer becomes thicker, creating a risk that membrane contaminants will undergo concentration polarization and be adsorbed at high concentrations. This risk can be reduced by decreasing the amount of MEA introduced.

[0023] One example of a modification method is the ATRP method. The inventors improved the method described in Non-Patent Document 2 and introduced MEA into the polyamide RO film using the following method.

[0024] The polyamide RO membrane to be used was cut into a square of approximately 90 mm x 90 mm. It was then stored in a 300 mL beaker of pure water for 1 hour. 0.5 mL of APTES (3-aminopropyltriethoxysilane) and 50 mL of pure water were stirred and mixed. The membrane was sandwiched between polytetrafluoroethylene (PTFE) plates, and the prepared APTES solution was poured into the liquid-holding area between the PTFE plates and the membrane to add amino groups. Ten minutes after the start of the reaction, the membrane substrate was washed with pure water. APTMS can be used instead of APTES, and even derivatives such as N-(2-aminoethyl)-3-aminopropyltriethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane can also be used. 0.3 g of BIBB (2-bromoisobutyryl bromide) was added to 10 g of hexane and stirred. The prepared BIBB-hexane solution was poured into a PTFE plate and membrane to start bromination. After immersion for 1 minute, the membrane substrate was washed with pure water. A solvent was prepared in a 100 mL graduated cylinder by mixing 18 mL of pure water and 20 mL of methanol. 0.65 g (5 mmol) of MEA, 0.070 g of ascorbic acid, and 0.017 g of EBIB (ethyl-2-bromoisobutyrate) were added and stirred. 2 mL of reagent aqueous solution (containing 0.004 g of CuBr2 (copper(II) bromide) and 0.012 g of TPMA (tris(2-pyridylmethyl)amine)) was added, and the cut membrane was placed in the solution to initiate the polymerization reaction of MEA. After the reaction was allowed to proceed for a predetermined time, the membrane was removed from the solution to stop the polymerization. The reaction time was 10 seconds to 1 hour, with 10 seconds to 10 minutes being preferred. The introduction of MEA can be confirmed by drying the prepared membrane in a vacuum constant-temperature drying oven (DRV320DA, ADVANTEC, Japan) for 30 minutes, followed by measurement using FT-IR (FT / IR-4200, JASCO, Japan).

[0025] Figure 1 shows the relationship between MEA introduction rate and IR peak ratio (1730 / 1660). 1730cm -1 The peak is at ether bonding, 1660 cm. -1 The peak represents the absorption of the carbon-oxygen double bond that constitutes the amide bond, and thus evaluates the ratio of methoxy groups of the MEA to the base polyamide film. As shown in Figure 1, it can be seen that the amount of methoxy groups increases with the amount of MEA introduced. MEA introduced: 0 mg / cm 2 and 0.02 mg / cm³ 2 The peak ratio is 0.02, and it can be said that a peak ratio of 0.02 or higher is acceptable for the introduction of MEA.

[0026] The mechanism by which the introduction of MEA into a polyamide membrane suppresses the adsorption of membrane contaminants such as proteins is thought to be as follows. Charged materials have strong interactions with the opposite charge, making it difficult to suppress the adsorption of substances with both positive and negative charges, such as proteins. On the other hand, uncharged materials have weaker electrostatic interactions with proteins, and those containing intermediate water also have weaker hydrophobic interactions, thus suppressing protein adsorption. MEA is also uncharged and contains intermediate water, making it a material that proteins are less likely to adsorb. For example, in "Abstracts of the Autumn Meeting of the Society of Chemical Engineers, Japan, Nakata et al., VK209 (2021)," the miscibility of several uncharged materials, including MEA and HEMA, with the hydrocarbon pentane was investigated. Among those investigated, MEA was shown to be the least miscible with pentane, meaning that fouling due to hydrophobic interactions was less likely to occur.

[0027] [Method for fabricating selective permeable membranes] The present invention relates to a method for producing a selective permeable membrane, comprising the step of forming a dense layer on a porous support by interfacial polymerization of a polyfunctional amine monomer and a polyfunctional acid halide monomer, characterized in that the method further comprises the step of modifying the surface of the dense layer with a 2-methoxyethyl acrylate (MEA) monomer.

[0028] <Porous support> In the present invention, the porous support is a layer that does not substantially possess separation properties and is used to provide strength to a dense layer (separation functional layer) that substantially possesses separation properties.

[0029] The porous support has a structure in which fine pores of uniform diameter extend from one surface to the other, or an asymmetrical structure in which dense, fine pores are present on one surface and the pore diameter gradually increases from that surface to the other surface, preferably with a fine pore size of 100 nm or less. The thickness of the porous support is 1 μm to several mm, preferably 10 μm or more from the viewpoint of strength, and several hundred μm or less from the viewpoint of ease of handling and ease of modular processing. The porous support material can be a homopolymer or copolymer of polysulfone, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, or polyphenylene sulfide sulfone, either alone or in blends thereof. Among these materials, polysulfone is preferred because it has high chemical, mechanical, and thermal stability and is easy to mold.

[0030] <Polyfunctional amine monomers> The polyfunctional amine monomer used in the present invention may be any aliphatic or aromatic compound having two or more amino groups. Generally, aromatic amines such as m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, para-xylylenediamine, and diaminopyridine, and aliphatic amines such as ethylenediamine, propylenediamine, dimethylethylenediamine, piperazine, and aminomethylpiperidine are used. Among these, aromatic amines, particularly m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene, are preferred in terms of reactivity and the performance of the resulting film. These polyfunctional amine compounds can be used individually or in combination.

[0031] As polyfunctional acid halide monomers, aromatic acid halides such as trimesic acid halide, benzophenone tetracarboxylic acid halide, trimellitic acid halide, pyromellitic acid halide, isophthalic acid halide, terephthalic acid halide, naphthalenedicarboxylic acid halide, diphenyl dicarboxylic acid halide, pyridine dicarboxylic acid halide, benzene disulfonic acid halide, and chlorosulfonyl isophthalic acid halide can be used. Aliphatic acid halides such as cyclohexanetricarboxylic acid halide and cyclohexanedicarboxylic acid halide can also be used. Among these, isophthalic acid chloride, terephthalic acid chloride, trimesic acid chloride, and mixtures thereof are preferred, considering their solubility in the film-forming solvent and the properties of the resulting selective permeable film.

[0032] <Interface overlap> The interfacial polymerization between a polyfunctional amine monomer and a polyfunctional acid halide monomer can be carried out according to a conventional method. That is, an aqueous solution of a polyfunctional amine monomer and a solution of a polyfunctional acid halide monomer are sequentially applied onto a porous support to cause an in-situ interfacial polycondensation reaction, thereby forming a polyamide dense layer having substantially separation performance.

[0033] The concentration of the polyfunctional amine monomer aqueous solution is preferably within the range of 0.1 to 20% by weight, and more preferably within the range of 0.5 to 15% by weight. When the concentration of the polyfunctional amine monomer is less than 0.1% by weight, the progress of the interfacial polycondensation reaction becomes slow, and when it exceeds 20% by weight, the film thickness of the dense layer increases and the water permeability tends to decrease.

[0034] The solvent for dissolving the polyfunctional acid halide monomer may be any one that is immiscible with water, dissolves the polyfunctional acid halide monomer, does not destroy the porous support, and can form a crosslinked polymer by interfacial polycondensation. For example, hydrocarbon compounds, cyclohexane, 1,1,2-trichloro-1,2,2-trifluoroethane, etc. may be mentioned. From the reaction rate and the volatility of the solvent, preferably n-hexane, heptane, octane, nonane, decane, undecane, dodecane, 1,1,2-trichloro-1,2,2-trifluoroethane, etc.

[0035] The concentration of the polyfunctional acid halide monomer in the above organic solvent is preferably within the range of 0.01 to 1% by weight. When the concentration of the polyfunctional acid halide monomer is less than 0.01% by weight, the formation of the dense layer tends to be insufficient. When it exceeds 1% by weight, the carboxyl group concentration on the surface of the dense layer becomes high, and when the raw water contains a cationic organic substance (for example, a cationic surfactant), the water permeability decreases, and the cost also increases.

[0036] <Modification by MEA> To modify the surface of a dense layer formed by interfacial polymerization of polyfunctional amine monomers and polyfunctional acid halide monomers with MEA, the surface is first modified with 3-aminopropyltriethoxysilane (APTE), 3-aminopropyltrimethoxysilane (APTMS), or their derivatives N-(2-aminoethyl)-3-aminopropyltriethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, followed by modification with 2-bromoisobutyryl bromide (BIBB), and then MEA is introduced. In other words, since it is necessary to introduce a radical polymerization initiation site that reacts with the double bond of MEA, MEA cannot be directly introduced into the dense layer. Therefore, first, amino groups are added to the carboxyl groups of the dense layer using APTES or the like, and then these amino groups are brominated using BIBB, and MEA is introduced using this as an initiator.

[0037] Modification with APTES, etc., can be carried out by bringing an aqueous solution of APTES, etc., with a concentration of about 0.01 to 1% by weight into contact with the surface of the dense layer. Furthermore, modification with BIBB can be carried out by contacting a BIBB solution with a concentration of approximately 0.1 to 10% by weight with the dense layer after modification with APTES or the like. The solvent used for the BIBB solution can be the same solvent used for the polyfunctional acid halide monomer solution mentioned above.

[0038] Next, MEA modification can be performed by bringing the MEA solution into contact with the dense layer after BIBB modification and holding it for a predetermined time. The MEA concentration in the MEA solution is preferably 0.1 to 10% by weight. Furthermore, it is preferable that the MEA solution contains 0.05 to 0.5% by weight of a reducing agent such as ascorbic acid to reduce Cu(II) to Cu(I), 0 to 0.1% by weight of a reaction control agent such as ethyl-2-bromoisobutyrate, 0.005 to 0.05% by weight of a catalyst such as copper bromide, and 0.01 to 0.1% by weight of a ligand such as tris(2-pyridylmethyl)amine. In addition, as the solvent used in the MEA solution, a mixed solvent of water and an alcohol such as methanol is preferable, and the water content in this mixed solvent is preferably about 20 to 80% by weight.

[0039] <MEA introduction amount> The amount of MEA introduced into the dense layer by the above MEA modification is 0.005 mg / cm per membrane area 2 or more, particularly 0.01 mg / cm 2 or more, especially 0.02 mg / cm 2 or more is preferable, and 0.5 mg / cm 2 or less, particularly 0.1 mg / cm 2 or less is preferable. If the MEA introduction amount is above the above lower limit, the anti-fouling effect by MEA modification can be sufficiently obtained. If the MEA introduction amount is below the above upper limit, as described above, the modification can be performed while substantially maintaining the performance of the base NF membrane and RO membrane. Also, by reducing the introduction amount of MEA, the modified layer becomes thinner, and the risk that membrane contaminants cause concentration polarization and adsorb at high concentrations can be reduced. This MEA introduction amount can be adjusted by the reaction time of MEA modification, the MEA concentration of the MEA solution used for MEA modification, etc.

[0040] The amount of MEA introduced into the dense layer is measured and calculated by the method described in the Examples section below.

[0041] Also, as described above, the modification by MEA can be confirmed by FT-IR measurement, and as described above, when the IR peak ratio (1730 / 1660) is 0.02 or more, preferably 0.04 to 0.2, it can be analyzed that the MEA modification has been performed with an effective amount of MEA introduced.

[0042] [Water treatment method] The water treatment method of the present invention is a method of performing water treatment using the selective permeation membrane of the present invention in which MEA modification is applied to the surface of the dense layer by interfacial polymerization of a polyfunctional amine monomer and a polyfunctional acid halide monomer, prepared as described above. Here, the selective permeable membrane may be an RO membrane or an NF membrane.

[0043] There are no particular restrictions on the water to be treated using the selective permeable membrane of the present invention. However, because the selective permeable membrane of the present invention has excellent resistance to contaminants such as proteins, it is particularly effective for treating water with a protein concentration of 1 mg / L or more, for example, 1 to 20 mg / L. Examples of treated water include industrial wastewater and biologically treated sewage, but the treatment is not limited to these types of water. [Examples]

[0044] The present invention will be described in more detail below with reference to examples.

[0045] [Fabrication of selective permeable membranes] 1) Base membrane The following materials were used as selective permeable films in which a dense interfacial polymerization layer was formed. Ultra-low pressure polyamide RO membrane "ES-20" (manufactured by Nitto Denko Corporation)

[0046] 2) Reagents The reagents used in the examples are as follows: • Ethanol: Reagent grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. • 3-Aminopropyltrimethoxysilane (APTES): Fujifilm Wako Pure Chemical Industries, Ltd., Reagent Grade Hexane: Reagent grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. • α-Bromoisobutyryl bromide (BIBB): Manufactured by Sigma-Aldrich. Methanol: Reagent grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. • 2-Methoxyethyl Acrylate (MEA): Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako Grade 1 L(+)-Ascorbic Acid: Reagent grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. · Ethyl 2-Bromo-2-methylpropionate (EBIB) (2-bromo-2-methylpropionate ethyl (=ethyl 2-bromoisobutyrate)): Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Wako Grade 1 Tris(2-pyridylmethyl)amine (TPMA): Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. for organic synthesis. • Copper(II) Bromide: Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako Grade 1

[0047] 3) Manufacturing procedure 3-1) Amino group introduction (APTES treatment) The base polyamide RO membrane was cut into a square of approximately 90mm x 90mm. It was then stored in a 300mL beaker filled with pure water for 1 hour. Two frames made of 5mm thick polytetrafluoroethylene (PTFE) plates and eight binder clips were prepared, and the PTFE plates were washed in ethanol and then with pure water. An APTES solution was prepared by stirring and mixing 0.5 mL of APTES (3-aminopropyltriethoxysilane) with 50 mL of pure water. A polyamide RO film was sandwiched between PTFE plates, and two double clips were attached to each side. The bromination process was carried out using the same procedure, sandwiching the film in the same locations. The prepared APTES solution was poured into a liquid-holding chamber formed by a PTFE plate and a polyamide RO membrane, and amino groups were added to the dense layer of the polyamide RO membrane. Ten minutes after the start of the reaction, the polyamide RO membrane was washed with pure water. After washing, the polyamide RO membrane was placed in a 300 mL beaker containing pure water and stored in a refrigerator.

[0048] 3-2) Br modification (bromination) Similar to the APTES treatment, two frames made of 5mm thick PTFE plates and eight binder clips were prepared, and the PTFE plates were washed in ethanol and then with pure water. A BIBB-hexane solution was prepared by adding 0.3 g of BIBB to 10 g of hexane and stirring. A polyamide RO membrane treated with APTES was sandwiched between PTFE plates, and two double clips were attached to each side. Bromination was initiated by pouring a prepared BIBB-hexane solution into the liquid-holding chamber formed by the PTFE plate and polyamide RO membrane. After immersion for 1 minute, the polyamide RO membrane was washed with pure water. After washing, the polyamide RO membrane was placed in a 300 mL beaker containing pure water and stored in a refrigerator.

[0049] The amount of MEA introduced was calculated from the weight of a 10 mm diameter polyamide RO membrane before and after polymerization using the following formula.

[0050] 3-3) MEA modification The Br-modified polyamide RO film was cut into 10mm diameter circles for FT-IR measurement and MEA introduction amount measurement, and 37mm diameter circles for transmission testing. A 37mm and 10mm diameter belt punch, hammer, and cutting mat were used for cutting. Both belt punches and the cutting mat were cleaned with ethanol and pure water before use. Furthermore, it was confirmed that the size and number of polyamide RO films to be cut fit within the PTFE plate frame before cutting. A 10mm diameter polyamide RO film was dried in a vacuum constant-temperature dryer for 30 minutes. After drying, the weight of the film was measured using a precision electronic balance to compare the weight of the film before and after polymerization. A solvent was prepared in a 100 mL graduated cylinder by mixing 18 mL of pure water and 20 mL of methanol. 0.65 g (5 mmol) of MEA (2-methoxyethyl acrylate), 0.070 g of ascorbic acid, and 0.017 g of EBIB (ethyl-2-bromoisobutyrate) were added and stirred. 2 mL of reagent solution (containing 0.004 g of CuBr2 (copper(II) bromide) and 0.012 g of TPMA (tris(2-pyridylmethyl)amine)) was added, and two cut polyamide RO membranes (a 10 mm diameter polyamide RO membrane and a 37 mm diameter polyamide RO membrane) were added to start polymerization. Polymerization was carried out at a temperature of 25°C (room temperature) and, after the reaction time, the polyamide RO membranes were removed from the solution to stop polymerization. The removed polyamide RO membranes were washed with pure water. After washing, the 37 mm diameter polyamide RO membrane was placed in pure water and stored in a refrigerator.

[0051]

number

[0052] [Performance evaluation equipment] Figure 2 shows the performance evaluation apparatus for the fabricated polyamide RO film. In this test apparatus, RO membrane supply water is supplied from piping 11 by a high-pressure pump 4 to the raw water chamber 1A below the flat membrane cell 2 in which the RO membrane is set in the sealed container 1. As shown in Figure 2(b), the sealed container 1 consists of a lower case 1a on the raw water chamber 1A side and an upper case 1b on the permeate chamber 1B side, and the flat membrane cell 2 is fixed between the lower case 1a and the upper case 1b via an O-ring 8. The flat membrane cell 2 is configured such that the permeate side of the RO membrane 2A is supported by a porous support plate 2B. The raw water chamber 1A below the flat membrane cell 2 is stirred by rotating the agitator 5 with a stirrer 3. The RO membrane permeate water is taken out from piping 12 after passing through the permeate chamber 1B above the flat membrane cell 2. Concentrated water is taken out from piping 13. The pressure inside the sealed container 1 is adjusted by a pressure gauge 6 installed in the water supply piping 11 and a pressure adjustment valve 7 installed in the concentrated water take-out piping 13.

[0053] [Performance Evaluation 1] Using pure water as the feedwater, the permeate flux at a temperature of 25°C was evaluated, and the operating pressure was adjusted to obtain a permeate flux of 1.0 m / d. At the same temperature and permeate flux, the change in operating pressure over time was measured using a 10 mg / L lysozyme aqueous solution (pH 7) as the feedwater. The normalized permeate flux was calculated using the following formula. Normalized permeate flux [m / d] = 1.0 [m / d] × 0.75 [MPa] / operating pressure [MPa]

[0054] <Comparative Example 1> Performance evaluation 1 was performed using the base film.

[0055] <Example 1> Film deposition was performed with a MEA modification reaction time of 5 minutes, and performance evaluation 1 was conducted. The amount of MEA introduced into the film used was 0.033 mg / cm³. 2 That was the case.

[0056] <Example 2> Film deposition was performed with a MEA modification reaction time of 0.5 min, and performance evaluation 1 was conducted. The amount of MEA introduced into the film used was 0.018 mg / cm³. 2 That was the case.

[0057] The evaluation results for Examples 1 and 2 and Comparative Example 1 are shown in Figure 3. In Comparative Example 1, the decrease in permeate flux after 48 hours was 27.3%, while in Examples 1 and 2, it was 14.8% and 23.9%, respectively, indicating that membrane contamination was suppressed.

[0058] [Performance Evaluation 2] The pure water permeate flux of a polyamide RO membrane was measured at a temperature of 25°C and an operating pressure of 0.75 MPa, and the membrane was immersed in a protein aqueous solution for 48 hours. Subsequently, the pure water permeate flux was measured again under the same conditions. The rate of decrease in pure water permeate flux was calculated using the following formula. Pure water permeation flux reduction rate [%] = (1 - pure water permeation flux after immersion [m / d] / pure water permeation flux before immersion [m / d]) × 100

[0059] <Comparative Example 2> Using the base membrane, performance evaluation 2 was performed with a protein aqueous solution of 120 mg / L lysozyme.

[0060] <Example 3> A film was fabricated with a MEA modification reaction time of 5 minutes, and performance evaluation 2 was performed using a 120 mg / L lysozyme aqueous solution as the protein aqueous solution. The amount of MEA introduced into the film used was 0.034 mg / cm³. 2 That was the case.

[0061] <Example 4> A film was fabricated with a MEA modification reaction time of 0.5 min, and performance evaluation 2 was performed using a 120 mg / L lysozyme aqueous solution as the protein aqueous solution. The amount of MEA introduced into the film used was 0.018 mg / cm³. 2 That was the case.

[0062] Figure 4 shows the change in permeate flux over time when pure water is passed through the samples after immersion in a lysozyme aqueous solution. It can be seen that the permeate flux in Examples 3 and 4 is greater than that in Comparative Example 2. The decrease in pure water permeate flux was 22.3% for Comparative Example 2, and 6.5% and 15.5% for Examples 3 and 4, respectively, demonstrating that the MEA modification improved the resistance to contamination.

[0063] <Comparative Example 3> Using the base membrane, performance evaluation 2 was performed with a protein aqueous solution of 140 mg / L bovine serum albumin aqueous solution.

[0064] <Example 5> The film was fabricated with a MEA modification reaction time of 10 min, and performance evaluation 2 was performed using a 140 mg / L bovine serum albumin aqueous solution as the protein aqueous solution. The amount of MEA introduced into the film used was 0.061 mg / cm³. 2 That was the case.

[0065] The reduction rate of pure water permeate flux was 16.3% for Comparative Example 3 and 0% for Example 5, demonstrating that MEA modification improved stain resistance. [Explanation of Symbols]

[0066] 1 container 2 Flat membrane cells 2A RO membrane 2B Porous support plate 3 Stirrers 4. High-pressure pump 5 Stirring bar 6. Pressure gauge 7. Pressure regulating valve 8 O-rings

Claims

1. A method for producing a selective permeable film, comprising the step of forming a dense layer on a porous support by interfacial polymerization of a polyfunctional amine monomer and a polyfunctional acid halide monomer, The process involves modifying the surface of the dense layer with a 2-methoxyethyl acrylate monomer. A method for producing a selective permeable membrane, characterized in that the modification with 2-methoxyethyl acrylate is carried out via modification with 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, or derivatives thereof, followed by modification with 2-bromoisobutyryl bromide.

2. In the modification with 2-methoxyethyl acrylate, the amount of 2-methoxyethyl acrylate per unit area of ​​the selective permeable membrane is 0.005 to 0.1 mg / cm². ２ A method for producing a selective permeable membrane according to claim 1, to be introduced.

3. A water treatment method using a selective permeable membrane obtained by the selective permeable membrane manufacturing method described in claim 1 or 2.

4. The water treatment method according to claim 3, wherein the selective permeable membrane is used to treat water having a protein concentration of 1 mg / L or more.

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