Composite semi-permeable membrane

Abstract

To provide a composite semipermeable membrane that is excellent in fouling resistance and that enables a stable desalting treatment to be executed over an extended period of time.SOLUTION: A composite semipermeable membrane comprises a porous support membrane, a separation function layer including a polyamide provided on the porous support membrane, and a coating layer provided on the separation function layer. A water contact angle of a surface of the coating layer is 40° or less. Protein adsorbability of the surface of the coating layer is 0.4 nN or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a composite semipermeable membrane. [Background technology]

[0002] A composite semipermeable membrane having a porous support membrane and a separation functional layer provided thereon is known as a separation membrane for desalination treatment used as a reverse osmosis membrane, etc. Furthermore, it is also known that the separation functional layer is treated with a hydrophilic polymer or the like in order to improve the durability and fouling resistance (resistance to contamination) of the composite semipermeable membrane. For example, Patent Document 1 describes a composite semipermeable membrane in which the separation functional layer is treated with a hydrophilic polymer that contains a functional group having a positive charge and a functional group having a negative charge and is negatively charged. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 124103 Summary of the Invention [Problem to be solved by the invention]

[0004] However, since the composite semipermeable membrane described in Patent Document 1 is constructed with consideration given to improving fouling resistance in the presence of negatively charged foulants, the composite semipermeable membrane may not have sufficient fouling resistance depending on the treatment conditions, and therefore may not be able to perform stable desalination treatment over a long period of time.

[0005] An object of one embodiment of the present invention is to provide a composite semipermeable membrane that has excellent fouling resistance and can perform stable desalination treatment for a long period of time. [Means for solving the problem]

[0006] A composite semipermeable membrane according to one embodiment of the present invention comprises a porous support membrane, a separation functional layer containing polyamide provided on the porous support membrane, and a coating layer provided on the separation functional layer, wherein the water contact angle of the surface of the coating layer is 40° or less, and the protein adsorption force of the surface of the coating layer is 0.4 nN or less. Effect of the Invention

[0007] According to one aspect of the present invention, a composite semipermeable membrane that has excellent fouling resistance and can perform stable desalination treatment for a long period of time can be provided. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 shows a schematic cross-sectional view of a composite semipermeable membrane according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiment of the present invention will be described in more detail, but the present invention is not limited to the embodiment described in this specification. Furthermore, the contents or ratios described in this specification are based on weight unless a unit is specified.

[0010] As shown in Fig. 1, a composite semipermeable membrane 10 according to one embodiment of the present invention includes a porous support membrane 5 and a separation functional layer (also referred to as an active layer or a skin layer) 2 provided on the porous support membrane 5. The separation functional layer 2 in this embodiment may be a separation functional layer mainly containing polyamide. More specifically, the separation functional layer 2 is a layer containing a crosslinked polyamide, and is preferably a layer made of a crosslinked polyamide.

[0011] In the composite semipermeable membrane 10 according to this embodiment, a coating layer 1 is provided on a separation functional layer 2. The coating layer 1 is a layer constituting the uppermost layer of the composite semipermeable membrane, and is a layer that is in direct contact with the water to be treated when the composite semipermeable membrane is in use. The coating layer 1 is a layer that at least partially covers the separation functional layer 2, and preferably covers the entire surface of the separation functional layer 2. In addition, the porous support membrane 5 may have a substrate 4 and a porous support layer 3 provided on the substrate 4, and the separation functional layer 2 is formed on the porous support layer 3.

[0012] The water contact angle of the surface of the coating layer in this embodiment may be 40° or less. This water contact angle may be preferably 35° or less, more preferably 30° or less, and even more preferably 25° or less. In this embodiment, the coating layer has high hydrophilicity corresponding to the water contact angle in the above range. Due to the high hydrophilicity of the coating layer surface, water molecules tend to preferentially adhere or bond to the surface, and a layer of hydrated water tends to form on the coating layer, making it difficult for foulants to adhere.

[0013] In addition, the protein adsorption power of the surface of the coating layer may be 0.4 nN or less, and preferably 0.38 nN or less. When the coating layer has a protein adsorption power in the above range, in particular, proteins or protein-like foulants contained in the water to be treated are less likely to adhere to the coating layer. According to this embodiment, the membrane performance of the composite semipermeable membrane can be maintained for a long period of time.

[0014] The coating layer in this embodiment preferably contains a hydrophilic polymer. The ratio of the hydrophilic polymer constituting the coating layer may be preferably 80% by weight or more, more preferably 90% by weight or more, based on the entire coating layer, and it is even more preferable that the coating layer is made of a hydrophilic polymer. Note that, although the polymer used in the coating layer in this embodiment is hydrophilic, it is preferable that it is not water-soluble or easily water-soluble.

[0015] Furthermore, the hydrophilic polymer is preferably amphoteric. An amphoteric polymer is a polymer having both cationic and anionic groups in the molecule. A cationic group is a group having a cation (a group having a positive charge) or a group that can change to have a cation depending on the surrounding environment. Specific examples of the cationic group include an amino group, an ammonium group, a sulfonium group, and a phosphonium group. An anionic group is a group having an anion (a group having a negative charge) or a group that can change to have an anion depending on the surrounding environment. Specific examples of the anionic group include a carboxyl group, a phosphonic acid group, a sulfate group, and a phosphate group.

[0016] The ratio of the zwitterionic hydrophilic polymer to the entire coating layer may be preferably 50% by weight or more, more preferably 60% by weight or more, even more preferably 80% by weight or more, and even more preferably 90% by weight or more, and the coating layer may consist of the zwitterionic hydrophilic polymer.

[0017] In this embodiment, the coating layer contains an amphoteric polymer, which increases the surface free energy of the coating layer and thus increases the hydrophilicity of the coating layer, making it even more difficult for foulants to adhere to the coating layer.

[0018] The amphoteric hydrophilic polymer used in the coating layer is represented by the formula (1): [ka] [wherein R1 represents a hydrogen atom or a methyl group, and X represents an alkoxysilyl group-containing group, a 3- to 4-membered ring ether-containing group, or an imide group-containing group], and

[0019] [ka] [in formula (2), R1 is the same as in formula (1), R2 represents an alkylene group having 1 to 6 carbon atoms, R3 and R4 each independently represent an alkyl group having 1 to 4 carbon atoms, R5 represents an alkylene group having 1 to 4 carbon atoms, and Y represents an oxygen atom or an -NH- group].

[0020] The amphoteric polymer contains the portion derived from the first monomer, so that the coating layer can be well bonded to the polyamide separation functional layer. Therefore, peeling of the coating layer is unlikely to occur, and the service life of the composite semipermeable membrane can be extended. In addition, the portion derived from the first monomer in the amphoteric polymer can be bonded to the functional group on the surface of the polyamide separation functional layer, so that a condensing agent or the like is not required when forming the coating layer on the polyamide separation functional layer, and the cost and effort required when producing the composite semipermeable membrane can be reduced.

[0021] When X in the first monomer is an alkoxysilyl group-containing group, it is represented by the formula (3):

[0022] [ka] [in formula (3), R6 represents an alkylene group having 1 to 6 carbon atoms, R7 to R9 each independently represent an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, and at least one of R7 to R9 is an alkoxy group].

[0023] In formula (3), at least one of R7 to R9 is an alkoxy group. From the viewpoint of enabling the coating layer to form a stronger bond with the polyamide separating functional layer, it is preferable that at least two of R7 to R9 are alkoxy groups, and it is more preferable that all of R7 to R9 are alkoxy groups.

[0024] More specifically, X of the first monomer may be a trimethoxysilylpropyl group, a triethoxysilylpropyl group, a methyldimethoxysilylpropyl group, a methyldiethoxysilylpropyl group, or the like. Of these, it is preferable that X is a trimethoxysilylpropyl group or a methyldiethoxylpropyl group. That is, preferred specific examples of the first monomer may be γ-(meth)acryloyloxypropyltrimethoxysilane, γ-(meth)acryloyloxypropyltriethoxysilane, γ-(meth)acryloyloxypropyltriisopropoxysilane, γ-(meth)acryloyloxypropylmethyldimethoxysilane, γ-(meth)acryloyloxypropylmethyldiethoxysilane, γ-(meth)acryloyloxypropylmethyldipropoxysilane, or the like.

[0025] Furthermore, when X of the first monomer is a 3- to 4-membered ring ether-containing group, it may be an epoxy group-containing group or an oxetanyl group-containing group. Among these, an oxetanyl group-containing group is preferred, and an alkyl group having 1 to 3 carbon atoms and an oxetanyl group, which is substituted with an alkyl group having 1 to 3 carbon atoms or is unsubstituted, is more preferred. In particular, X is preferably a (3-ethyloxetan-3-yl)methyl group. That is, a preferred specific example of the first monomer is (3-ethyloxetan-3-yl)methyl (meth)acrylate.

[0026] In addition, when X of the first monomer is an imide group-containing group, X is preferably a substituted or unsubstituted N-succinimidyl group. Of these, X is more preferably an N-succinimidyl group. That is, a preferred specific example of the first monomer is N-succinimidyl (meth)acrylate.

[0027] The above-mentioned first monomers may be used alone or in combination of two or more thereof. In this specification, (meth)acrylate refers to methacrylate and / or acrylate.

[0028] The second monomer represented by the above formula (2) preferably has a betaine structure. Specific examples of the second monomer include N-(meth)acryloyloxyethyl-N,N-dimethylammonium-α-N-methylcarboxybetaine, N-(meth)acryloylaminoethyl-N,N-dimethylammonium-α-N-methylcarboxybetaine, etc.

[0029] The second monomer may also be used alone or in combination of two or more kinds.

[0030] As is clear from the above description, the amphoteric nature of the amphoteric hydrophilic polymer in this embodiment is derived from the second monomer. It is preferable that the first monomer has neither a cationic group nor an anionic group.

[0031] The weight ratio of the first monomer to the second monomer used to produce the amphoteric polymer is preferably 3:97 to 95:5, more preferably 5:95 to 75:25. When the weight ratio of the first monomer to the second monomer is 3:97 or more, the coating layer containing the amphoteric hydrophilic polymer can be more firmly bonded to the separation functional layer. On the other hand, when the weight ratio of the first monomer to the second monomer is 95:5 or less, amphoteric moieties can be sufficiently present in the polymer, thereby improving the effect of preventing foulant adhesion.

[0032] The amphoteric hydrophilic polymer in this embodiment may be a copolymer of the first monomer and the second monomer, or may be a copolymer obtained by copolymerizing the first monomer, the second monomer, and a polymerizable monomer other than the first monomer and the second monomer (sometimes referred to as other polymerizable monomers). Examples of the polymerizable monomer other than the first monomer and the second monomer include monomers having a carbon-carbon unsaturated double bond, such as styrene-based monomers, carboxylate-based monomers, and amide-based monomers. The other polymerizable monomers may be used alone or in combination of two or more kinds.

[0033] When other polymerizable monomers are used to prepare the zwitterionic hydrophilic polymer, the parts by weight of the other polymerizable monomers per 100 parts by weight of total monomers may be 30 parts by weight or less, 10 parts by weight or less, or 5 parts by weight or less.

[0034] The ratio of the number of cationic groups to the number of anionic groups in the amphoteric hydrophilic polymer can be 40:60 to 60:40, preferably 55:45 to 45:55, even if the amphoteric hydrophilic polymer contains a portion derived from other polymerizable monomers. By bringing the ratio of the number of cationic groups to the number of anionic groups in the amphoteric hydrophilic polymer closer to 1:1, the number of cationic groups and the number of anionic groups in the amphoteric hydrophilic polymer can be balanced, and excellent fouling resistance can be exhibited for the water to be treated over a wide range of pH. Therefore, even if the pH of the water to be treated or the type of electrolyte contained therein fluctuates over time, stable desalination treatment can be performed for a long period of time.

[0035] When the first monomer, the second monomer, and optionally other monomers are polymerized to obtain an amphoteric hydrophilic polymer, a polymerization initiator can be used. Examples of the polymerization initiator include azobisisobutyronitrile, azoisobutyronitrile, methyl azoisobutyrate, azobisdimethylvaleronitrile, benzoyl peroxide, potassium persulfate, ammonium persulfate, benzophenone derivatives, phosphine oxide derivatives, benzoketone derivatives, phenylthioether derivatives, azide derivatives, diazo derivatives, and disulfide derivatives.

[0036] The weight-average molecular weight of the amphoteric hydrophilic polymer used in this embodiment is preferably 50,000 to 500,000, and more preferably 100,000 to 200,000. By having the weight-average molecular weight in the above range, a coating layer having a sufficient thickness for improving fouling resistance can be formed, and the polymer becomes easy to handle when forming the coating layer.

[0037] The coating layer may contain a component other than the amphoteric hydrophilic polymer. The component other than the amphoteric hydrophilic polymer may be a non-volatile hydrophilic component, for example, a water-soluble polymer such as polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, etc. Among these, the water-soluble polymer, particularly polyvinyl alcohol, is preferred from the viewpoint that a layer of hydration water is easily formed on the coating layer and foulants are less likely to adhere.

[0038] The above-mentioned amphoteric hydrophilic polymer can react with a non-volatile hydrophilic component, so that the inclusion of a non-volatile hydrophilic component can form a strong coating layer. As a result, the chemical resistance of the resulting coating layer against acids and alkalis is improved. In particular, when polyvinyl alcohol is used as a component other than the amphoteric hydrophilic polymer, a composite semipermeable membrane having both fouling resistance and chemical resistance can be produced at low cost.

[0039] When the coating layer contains a non-volatile hydrophilic component, the amount of the non-volatile hydrophilic component may be preferably 10 to 50% by weight, more preferably 20 to 40% by weight, and even more preferably 25 to 35% by weight, based on the total amount of the coating layer (layer in a dried state). When the amount of the non-volatile hydrophilic component is 10% by weight or more, chemical resistance to acids and alkalis is improved. In addition, it is possible to produce a composite semipermeable membrane at low cost while maintaining appropriate foulant resistance and desalination treatment performance. On the other hand, from the viewpoint of further improving foulant resistance, the amount of the non-volatile hydrophilic component is preferably 50% by weight or less.

[0040] When the coating layer contains a non-volatile hydrophilic component, the ratio of the content of the non-volatile hydrophilic component, which is a component other than the amphoteric hydrophilic polymer in the coating layer, to the content of the amphoteric hydrophilic polymer ((content of non-volatile hydrophilic component) / (content of amphoteric hydrophilic polymer)) may be preferably 0.05 to 1, more preferably 0.1 to 0.8.

[0041] A method for producing a composite semipermeable membrane will be described below. The method for producing a composite semipermeable membrane can include the steps of forming a porous support membrane, forming a separation functional layer, and forming a coating layer.

[0042] First, to form a porous support membrane, a substrate is prepared, and a porous support layer is formed on the substrate. The substrate may be a fibrous planar structure, specifically, a woven fabric, a knitted fabric, a nonwoven fabric, etc., among which a nonwoven fabric is preferred. The type of fiber constituting the nonwoven fabric is not limited, but a synthetic fiber is preferred. Specific examples of the fiber include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polyglycolic acid (PGA), polylactic acid (PLA), nylon 6, polycaprolactone (PCL), polyethylene adipate (PEA), polyhydroxyalkanoate (PHA), or copolymers thereof. Among these, it is preferred to use polyester such as polyethylene terephthalate because of its high dimensional stability and moldability, as well as its high oil resistance.

[0043] Also, the material of the porous support layer may be polysulfone, polysulfone, polyethersulfone, polycarbonate, polyethylene oxide, polyimide, polyetherimide, polyetheretherketone, polypropylene, polymethylpentene, polymethylchloride, polyvinylidene fluoride, etc. The method of forming the porous support layer on the substrate is not particularly limited, but for example, the above-mentioned material is dissolved in a solvent, the resulting solution is applied to the substrate, microphase separation is caused at a predetermined temperature and a predetermined humidity, and then the polymer is solidified.

[0044] The method for forming a polyamide separation functional layer on a porous support membrane is not particularly limited, but can be carried out, for example, by immersing the surface of the porous support layer in a solution of a polyfunctional amine compound, and then contacting it with a solvent solution of an acid halide compound to cause interfacial polymerization.

[0045] The polyfunctional amine may be an aromatic polyfunctional amine, an aliphatic polyfunctional amine, or a combination thereof. The aromatic polyfunctional amine may be m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, or the like, or N-alkylated products thereof, such as N,N-dimethyl m-phenylenediamine, N,N-diethyl m-phenylenediamine, N,N-dimethyl p-phenylenediamine, and N,N-diethyl p-phenylenediamine. The aliphatic polyfunctional amine may be piperazine or a derivative thereof. Specific examples of the aliphatic polyfunctional amine include piperazine, 2,5-dimethylpiperazine, 2-methylpiperazine, 2,6-dimethylpiperazine, 2,3,5-trimethylpiperazine, 2,5-diethylpiperazine, 2,3,5-triethylpiperazine, 2-n-propylpiperazine, 2,5-di-n-butylpiperazine, and ethylenediamine. These polyfunctional amines may be used alone or in combination of two or more kinds.

[0046] The acid halide compound is not particularly limited as long as it can give a polyamide by reacting with the polyfunctional amine, but it is preferable that the acid halide has two or more halide carbonyl groups in one molecule.As the acid halide compound, a halide compound of fatty acid such as oxalic acid, malonic acid, maleic acid, fumaric acid, glutaric acid, 1,3,5-cyclohexane tricarboxylic acid, 1,3-cyclohexane dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, etc., an acid halide compound of aromatic acid such as phthalic acid, isophthalic acid, 1,3,5-benzene tricarboxylic acid, 1,2,4-benzene tricarboxylic acid, 1,3-benzene dicarboxylic acid, 1,4-benzene dicarboxylic acid, etc. can be used.These acid halide compounds can be used alone or in combination of two or more kinds.

[0047] To form a coating layer on the separation functional layer, a solution containing the above-mentioned amphoteric hydrophilic polymer, for example, an aqueous solution, is prepared in advance. The surface of the separation functional layer is then immersed in the aqueous polymer solution, and then dried to form the coating layer. Heat may be applied during drying.

[0048] The polymer solution (coating solution) used to form the coating layer, for example, the polymer concentration of the aqueous polymer solution, can be preferably 0.01 to 5% by weight, more preferably 0.05 to 3% by weight. The concentration of the amphoteric hydrophilic polymer in the coating solution can be preferably 0.01 to 5% by weight, more preferably 0.05 to 3% by weight. The time for immersing the surface of the separation functional layer in the polymer solution can be, for example, 1 second to 10 minutes, preferably 5 seconds to 5 minutes.

[0049] The polymer solution (coating solution) used for forming the coating layer may contain, for example, the above-mentioned non-volatile hydrophilic component. When the non-volatile hydrophilic component is added, the concentration of the non-volatile hydrophilic component in the coating solution may be preferably 0.025 to 1% by weight, more preferably 0.05 to 0.5% by weight.

[0050] The composite semipermeable membrane is preferably configured in a flat membrane shape. The flat composite semipermeable membrane according to the present embodiment can be suitably used in a spiral-type membrane module configured by winding the composite semipermeable membrane in a spiral shape around the outside of a water collection pipe.

[0051] In this way, the composite semipermeable membrane of this embodiment has a coating layer covering the separation functional layer, and the surface of the coating layer has a predetermined water contact angle and a predetermined protein adsorption power, which can effectively prevent the adhesion of foulants contained in the treated water, particularly proteinaceous foulants, and can be used continuously for a long period of time.

[0052] The composite semipermeable membrane of this embodiment can effectively prevent adhesion of foulants, and can be widely used in the production of pure water, desalination of seawater, and desalination treatment for reuse of wastewater for industrial, agricultural, or domestic use. In particular, in industrial wastewater treatment, water to be treated that has a high salt concentration and a high COD concentration is often required to be treated, and the composite semipermeable membrane of this embodiment can treat such water at a high permeate rate for a long period of time. Therefore, stable operation for a long period of time is possible even in a zero-discharge (ZLD) system, and the maintenance work and cost for removing foulants from the separation membrane can be reduced. EXAMPLES

[0053] Hereinafter, the embodiments of the present invention will be described based on examples, but the present invention is not limited to these examples.

[0054] <Examples of composite semipermeable membrane manufacturing> An amine aqueous solution containing 3.0% by weight of m-phenylenediamine (MPD), 0.15% by weight of sodium dodecyl sulfate, 2.15% by weight of triethylamine, 0.31% by weight of sodium hydroxide, 6% by weight of camphorsulfonic acid, and 1% by weight of isopropyl alcohol was applied onto a polysulfone porous support layer formed on a polyester nonwoven fabric, and then the excess amine aqueous solution was removed to form an aqueous solution coating layer. Next, the surface of the aqueous solution coating layer was immersed for 7 seconds in an acid chloride solution in which 0.075% by weight of trimesic acid chloride (TMC) and 0.113% by weight of isophthalic acid chloride (IPC) were dissolved in a naphthenic solvent (Exxsol D40, manufactured by ExxonMobil Corporation). Thereafter, excess solution on the surface of the aqueous solution coating layer was removed, the layer was air-dried for 20 seconds, and then the layer was placed in a hot air dryer at 140°C for 3 minutes to form a separation functional layer containing a polyamide resin on the porous polysulfone support layer, thereby forming a composite semipermeable membrane having a nonwoven fabric substrate, a polysulfone porous support layer, and a polyamide separation functional layer arranged in that order.

[0055] Example 1 25.0 g of N-methacryloyloxyethyl-N,N-dimethylammonium-α-N-methylcarboxybetaine monohydrate, 4.4 g of γ-methacryloyloxypropyltrimethoxysilane, and 500.3 g of ethanol were charged into a 1 L container and stirred with a stirrer. After degassing by reducing the pressure inside the container, nitrogen gas was introduced into the container to return it to normal pressure. Next, 2.8 g of azobisisobutyronitrile was added, and the temperature of the contents was kept at 70°C while maturing for 8 hours, and then cooled to 30°C in a water bath to obtain a polymer solution (a solution of amphoteric hydrophilic polymer).

[0056] Furthermore, water and isopropyl alcohol (IPA) were added to the obtained polymer solution to prepare a coating solution with an IPA concentration of 10% by weight and an amphoteric hydrophilic polymer concentration of 0.2% by weight. The surface of the separation functional layer of the composite semipermeable membrane produced in the above production example was immersed in this coating solution for 10 seconds. Thereafter, the separation functional layer was air-dried for 30 seconds and further held in a hot air dryer at 120°C for 2 minutes to form a coating layer.

[0057] Example 2 A polymer solution was obtained in the same manner as in Example 1, except that 4.6 g of γ-methacryloyloxypropyltrimethoxysilane was used instead of γ-methacryloyloxypropylmethyldiethoxysilane.

[0058] A coating solution was obtained from the obtained polymer solution in the same manner as in Example 1, and a coating layer was formed on the separating functional layer of the composite semipermeable membrane produced in the above Production Example.

[0059] Example 3 A polymer solution was obtained in the same manner as in Example 1, except that γ-methacryloyloxypropyltrimethoxysilane was changed to 3.3 g of (3-ethyloxetan-3-yl)methyl methacrylate.

[0060] A coating solution was obtained from the obtained polymer solution in the same manner as in Example 1, and a coating layer was formed on the separating functional layer of the composite semipermeable membrane produced in the above Production Example.

[0061] Example 4 A polymer solution was obtained in the same manner as in Example 1, except that γ-methacryloyloxypropyltrimethoxysilane was changed to 3.2 g of N-methacryloxysuccinimide.

[0062] A coating solution was obtained from the obtained polymer solution in the same manner as in Example 1, and a coating layer was formed on the separating functional layer of the composite semipermeable membrane produced in the above Production Example.

[0063] Example 5 A coating solution was prepared in the same manner as in Example 1, except that water, isopropyl alcohol (IPA), and polyvinyl alcohol (PVA) were added to the obtained polymer solution. The IPA concentration of the coating solution in this example was 10% by weight, the amphoteric hydrophilic polymer concentration was 0.2% by weight, and the polyvinyl alcohol concentration was 0.1% by weight. A coating layer was formed on the separation functional layer of the composite semipermeable membrane produced in the above production example using the coating solution.

[0064] Comparative Example 1 The composite semipermeable membrane before the formation of the coating layer was used as Comparative Example 1.

[0065] The composite semipermeable membranes of Examples 1 to 4 and Comparative Example 1 were measured for the water contact angle and protein adsorptive power of the coating layer surface. Furthermore, the membrane performance was evaluated. The results are shown in Table 1.

[0066] <Measurement and Evaluation> (Contact angle measurement) The static contact angle was automatically calculated by computer image analysis using the θ / 2 method using a Drop Master DM500 manufactured by Kyowa Interface Science Co., Ltd. The droplet volume was 1.5 μL, and the contact angle was measured 10 seconds after the start of droplet application of distilled water onto the separation functional layer.

[0067] (Protein adsorption measurement) The spring constant and sensitivity coefficient were determined by the force curve method using a cantilever modified with bovine serum albumin (BSA) from the Oxford Instruments MFP-3D-SA, using the software that came with the device. The adhesive force was calculated using the following formula. F=kx F: Adsorption force, k: Spring constant of the cantilever, x: Sensitivity coefficient (= Distance traveled)

[0068] (Evaluation of permeation flux) RO water (water filtered through a reverse osmosis membrane) at a temperature of 25°C was allowed to pass through the resulting composite semipermeable membrane for 30 minutes at a constant operating pressure of 1.5 MPa. The evaluation device used for the evaluation was equipped with a flat plate-shaped permeation cell, and permeation was performed using a cross-flow method. The amount of permeated water was measured, and the amount of permeated water (cubic meters) converted per square meter of membrane surface per day was calculated as the permeation flux F1 (m 3 / m 2 / day).

[0069] As an example for confirming the effect of preventing biofouling by organic substances, after the above-mentioned measurement of the permeation flux, a casein aqueous solution having a concentration of 300 mg / L at a temperature of 25° C. was contacted with the composite semipermeable membrane for 30 minutes at a constant operation pressure of 1.5 MPa. Then, RO water at a temperature of 25° C. was permeated for 30 minutes at a constant operation pressure of 1.5 MPa. The amount of the permeated water obtained by this operation was measured, and the permeation flux F2 was calculated in the same manner as above.

[0070] The value of F2 / F1×100 was calculated from the permeation flux (initial permeation flux) F1 before contact with the casein aqueous solution and the permeation flux F2 after contact with the casein aqueous solution. This value can be said to be the rate of change in permeation flux.

[0071] [Table 1] [Explanation of symbols]

[0072] 1 Coating layer 2 Separation functional layer 3 Porous support layer 4 Base material 5 Porous support membrane 10 Composite semipermeable membrane

Claims

1. A porous support membrane; a separation functional layer including a polyamide provided on the porous support membrane; A coating layer provided on the separation functional layer, the water contact angle of the surface of the coating layer is 40° or less; the protein adsorptive strength of the surface of the coating layer is 0.4 nN or less; the coating layer comprises a zwitterionic hydrophilic polymer; The amphoteric hydrophilic polymer is represented by the formula (1): 【Chemistry 1】 and a first monomer represented by formula (2): 【Chemistry 2】 and a second monomer represented by In formulas (1) and (2), R1 represents a hydrogen atom or a methyl group, R2 represents an alkylene group having 1 to 6 carbon atoms, R3 and R4 each independently represent an alkyl group having 1 to 4 carbon atoms, R5 represents an alkylene group having 1 to 4 carbon atoms, X represents an alkoxysilyl group-containing group, a 3- to 4-membered ring ether-containing group, or an imido group-containing group, and Y represents an oxygen atom or an -NH- group.

2. The composite semipermeable membrane according to claim 1, wherein X in the formula (1) represents a trimethoxysilylpropyl group, a methyldimethoxysilylpropyl group, a methyldiethoxysilylpropyl group, a triethoxysilylpropyl group, a (3-ethyloxetan-3-yl)methyl group, or an N-succinimidyl group.

3. 3. The composite semipermeable membrane according to claim 1, wherein the weight ratio of the first monomer to the second monomer is from 3:97 to 95:

5.

4. forming a porous support membrane; forming a separation functional layer containing polyamide on the porous support membrane; forming a coating layer on the separation functional layer; the water contact angle of the surface of the coating layer is 40° or less; the protein adsorptive strength of the surface of the coating layer is 0.4 nN or less; the coating layer comprises a zwitterionic hydrophilic polymer; The amphoteric hydrophilic polymer is represented by the formula (1): 【Chemistry 3】 and a first monomer represented by formula (2): 【Chemistry 4】 and a second monomer represented by In formulas (1) and (2), R1 represents a hydrogen atom or a methyl group, R2 represents an alkylene group having 1 to 6 carbon atoms, R3 and R4 each independently represent an alkyl group having 1 to 4 carbon atoms, R5 represents an alkylene group having 1 to 4 carbon atoms, X represents an alkoxysilyl group-containing group, a 3- to 4-membered ring ether-containing group, or an imido group-containing group, and Y represents an oxygen atom or an -NH- group.

Images