Semipermeable composite membrane, semipermeable composite membrane element, and fluid separation device

Abstract

The present invention pertains to a semipermeable composite membrane comprising: a support membrane; a separation function layer that is disposed on the support membrane and that contains a crosslinked aromatic polyamide; and a coating layer disposed on the separation function layer. The coating layer contains a vinyl alcohol-based polymer. In a surface analysis performed on the coating layer side of the composite semipermeable membrane by a time-of-flight secondary ion mass spectrometry (TOF-SIMS), when A represents the count number of peaks derived from C2H3O-, B represents the count number of peaks derived from CHO2 -, and C represents the count number of peaks derived from C6H3 -, 3.2≤A / C≤240 and 0.3≤B / C≤40 are satisfied.

Description

Composite semipermeable membrane, composite semipermeable membrane element, and fluid separation device

[0001] The present invention relates to a composite semipermeable membrane, a composite semipermeable membrane element, and a fluid separation device that are useful for selectively separating liquid mixtures.

[0002] There are various techniques for removing substances (e.g., salts) dissolved in a solvent (e.g., water). In recent years, membrane separation methods using semipermeable membranes such as reverse osmosis membranes and nanofiltration membranes have been increasingly used as processes for saving energy and resources.

[0003] Currently commercially available reverse osmosis membranes and nanofiltration membranes are generally composite semipermeable membranes that have a support membrane and a separation functional layer laminated on the support membrane. The separation functional layer is known to be a crosslinked aromatic polyamide obtained by a polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide.

[0004] One of the challenges in membrane separation is fouling. Fouling is a phenomenon in which substances contained in the water to be treated are adsorbed onto the surface or inner pores of a semipermeable membrane, inhibiting the permeation of the solution and reducing the membrane permeation flux of the composite semipermeable membrane. Fouling is classified according to the type of adsorbed substance, and includes chemical fouling caused by the adsorption of organic matter and biofouling caused by the adsorption of microorganisms.

[0005] A known method for suppressing these fouling events is to coat the surface of a composite semipermeable membrane with a hydrophilic substance. For example, Patent Documents 1 and 2 disclose a method for suppressing fouling by coating the surface of a separation functional layer with polyvinyl alcohol. Patent Document 3 discloses a method for pretreating the water to be treated with an ultrafiltration membrane or the like as a method for reducing fouling substances contained in the water to be treated. Furthermore, Patent Document 4 discloses a method for cleaning a fouled composite semipermeable membrane with a chemical such as an acid or alkali as a method for improving the decrease in membrane permeation flux due to fouling.

[0006] International Publication No. 1997 / 034686 International Publication No. 2014 / 133132 International Publication No. 2006 / 057249 Japanese Patent Application Laid-Open No. 10-066972

[0007] The methods described in Patent Documents 1 and 2 can impart a certain level of fouling resistance, but have the problem of a trade-off between fouling resistance, which depends on the amount of coating layer, and the membrane permeation flux of the composite semipermeable membrane. Furthermore, the method described in Patent Document 3 has the problem that if an oxidizing agent or the like used for cleaning an ultrafiltration membrane or the like leaks into a downstream stage, the composite semipermeable membrane is oxidized and deteriorated, resulting in a decrease in separation performance. Furthermore, the method described in Patent Document 4 has the problem that the separation performance of the composite semipermeable membrane is reduced by acids or alkalis, and the coating layer is deteriorated, resulting in a decrease in fouling resistance.

[0008] Therefore, an object of the present invention is to provide a composite semipermeable membrane that has excellent fouling resistance and sufficient membrane permeation flux, and further has good oxidation resistance, acid resistance, and alkali resistance.

[0009] In order to solve the above problems, the present invention includes the following configurations [1] to

[12] : [1] A membrane comprising a support membrane, a separation functional layer containing a crosslinked aromatic polyamide disposed on the support membrane, and a coating layer disposed on the separation functional layer, wherein the coating layer contains a vinyl alcohol-based polymer, and in a surface analysis of the coating layer side by time-of-flight secondary ion mass spectrometry (TOF-SIMS), C ２ H ３ O － The peak counts derived from A, CHO ２ － The peak counts derived from B and C ６ H ３ －[2] The composite semipermeable membrane according to the above [1], which satisfies 12 ≦ A / C ≦ 240 and 0.3 ≦ B / C ≦ 40, or 3.2 ≦ A / C ≦ 240 and 2.5 ≦ B / C ≦ 40, where C is the peak count derived from the above. [3] The composite semipermeable membrane according to the above [2], which satisfies 3.2 ≦ A / C ≦ 240 and 2.5 ≦ B / C ≦ 40, where C is the peak count derived from the above. [4] The composite semipermeable membrane according to any one of the above [1] to [3], wherein the coating layer includes a structure in which the vinyl alcohol-based polymer is crosslinked with a polyhydric aldehyde. [5] A membrane-supporting membrane, a separation functional layer containing a crosslinked aromatic polyamide disposed on the membrane-supporting membrane, and a coating layer disposed on the separation functional layer, wherein the coating layer contains a vinyl alcohol-based polymer, and a surface analysis of the coating layer side by time-of-flight secondary ion mass spectrometry (TOF-SIMS) reveals that C ２ H ３ O － The peak counts derived from A and C ６ H ３ － The peak counts derived from ５ H ７ SO ３ － [6] A composite semipermeable membrane satisfying 3.2≦A / C≦240 and 0.04≦D / C≦25, where D is the peak count derived from the above. [6] The composite semipermeable membrane according to the above [5], satisfying 12≦A / C≦240 and 0.04≦D / C≦25, or 3.2≦A / C≦240 and 0.3≦D / C≦25. [7] The composite semipermeable membrane according to the above [6], satisfying 3.2≦A / C≦240 and 0.3≦D / C≦25. [8] The composite semipermeable membrane according to any one of the above [5] to [7], wherein the coating layer contains a structure in which the vinyl alcohol-based polymer is crosslinked with polyvinyl sulfone. [9] The composite semipermeable membrane according to any one of the above [1] to [8], wherein the vinyl alcohol-based polymer is a vinyl alcohol copolymer containing a structure represented by the following general formula (I):

[0010]

[0011] [In general formula (I), X is a divalent hydrocarbon group having 2 to 6 carbon atoms, and l, m, and n represent the number of repeating units and are integers of 1 or more.]

[10] The composite semipermeable membrane according to [9] above, wherein X in general formula (I) is a divalent hydrocarbon group having 2 carbon atoms.

[11] The composite semipermeable membrane according to

[10] above, wherein X in general formula (I) is an ethylene group.

[12] The composite semipermeable membrane according to any one of [9] to

[11] above, wherein the copolymerization ratio n / (l + m + n) of the vinyl alcohol copolymer in the structure represented by general formula (I) above is 0.035 or more and 0.16 or less.

[13] A composite semipermeable membrane element comprising the composite semipermeable membrane according to any one of [1] to

[12] above.

[14] A fluid separation device comprising the composite semipermeable membrane element according to

[13] above.

[0012] According to the present invention, it is possible to provide a composite semipermeable membrane that has excellent fouling resistance and sufficient membrane permeation flux, and further has good oxidation resistance, acid resistance, and alkali resistance.

[0013] Fig. 1 is a schematic diagram showing the cross-sectional structure of a composite semipermeable membrane. Fig. 2 is a schematic diagram showing the cross-sectional structure of a composite semipermeable membrane having a pleated separation functional layer and a coating layer, where (a) is a partially enlarged view and (b) is an enlarged view of Y in (a).

[0014] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited thereto. In this specification, "mass" has the same meaning as "weight."

[0015] 1. Composite Semipermeable Membrane A schematic diagram of the cross-sectional structure of a composite semipermeable membrane 1 according to this embodiment is shown in FIG. 1. The composite semipermeable membrane 1 of the present invention comprises a support membrane 2, a separating functional layer 3, and a coating layer 4.

[0016] The composite semipermeable membrane of the present invention includes a first embodiment in which A / C and B / C, which will be described later, satisfy 3.2≦A / C≦240 and 0.3≦B / C≦40, and a second embodiment in which A / C and D / C, which will be described later, satisfy 3.2≦A / C≦240 and 0.04≦D / C≦25.

[0017] In any of the embodiments, the composite semipermeable membrane has excellent anti-fouling properties and sufficient membrane permeation flux, as well as good oxidation resistance, acid resistance, and alkali resistance, by setting the amount of the vinyl alcohol-based polymer contained in the coating layer and the degree of crosslinking of the vinyl alcohol-based polymer within appropriate ranges.

[0018] 1.1 Support Membrane The support membrane of the composite semipermeable membrane of the present invention is sufficient as long as it has at least a porous support layer, and may have a substrate in addition to the porous support layer. The support membrane is intended to impart strength to the composite semipermeable membrane, and does not itself substantially have the ability to separate solutes.

[0019] The porous support layer has a large number of interconnected pores. The pore size and pore size distribution of the pores are not particularly limited, but a preferred porous support layer is one having a symmetrical structure with uniform pore sizes or an asymmetrical structure in which the pore sizes gradually increase from one surface to the other, and in which the pore size on the surface with smaller pore sizes is 0.1 nm to 100 nm.

[0020] As the material for the porous support layer, homopolymers or copolymers such as polysulfone (hereinafter referred to as "PSf"), polyethersulfone, polyamide, polyester, cellulose-based polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene oxide can be used alone or in blends. Here, examples of cellulose-based polymers include cellulose acetate and cellulose nitrate, and examples of vinyl polymers include polyethylene, polypropylene, polyvinyl chloride, and polyacrylonitrile. Among these, homopolymers or copolymers such as PSf, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, and polyphenylene sulfide sulfone are preferred, with cellulose acetate, PSf, polyphenylene sulfide sulfone, and polyphenylene sulfone being more preferred. PSf is particularly preferred due to its high chemical, mechanical, and thermal stability and ease of molding.

[0021] The weight average molecular weight (hereinafter "Mw") of PSf is preferably 10,000 or more and 200,000 or less, and more preferably 15,000 or more and 100,000 or less. When the Mw of PSf is 10,000 or more, the porous support layer can have preferable mechanical strength and heat resistance. On the other hand, when the Mw of PSf is 200,000 or less, the viscosity of the porous support layer stock solution falls within an appropriate range, and good formability can be achieved.

[0022] When the support membrane has a substrate, examples of the material for the substrate include fabrics made of polyester polymers, polyamide polymers, polyolefin polymers, and mixtures or copolymers thereof. Among these, fabrics made of polyester polymers, which have high mechanical and thermal stability, are preferred. As the form of the fabric, long-fiber nonwoven fabrics, short-fiber nonwoven fabrics, and woven and knitted fabrics can be preferably used.

[0023] The thickness of the support membrane affects the strength of the composite semipermeable membrane and the packing density when the composite semipermeable membrane is used as an element. In order to obtain good mechanical strength and packing density, the thickness of the support membrane is preferably 50 μm or more and 300 μm or less, and more preferably 100 μm or more and 250 μm or less. Furthermore, when the support membrane is composed of a porous support layer and a substrate, the thickness of the porous support layer is preferably 20 μm or more and 100 μm or less. The thickness of the support membrane is calculated as the average value of thicknesses measured at 20 μm intervals in a direction perpendicular to the thickness direction (in the plane direction of the membrane) by cross-sectional observation at 20 points.

[0024] 1.2 Separation Functional Layer The separation functional layer of the composite semipermeable membrane according to this embodiment is a layer disposed on the support membrane, which performs the function of separating solutes, and contains a crosslinked aromatic polyamide. The proportion of the crosslinked aromatic polyamide in the separation functional layer is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may even be 100% by mass. The proportion of the crosslinked aromatic polyamide in the separation functional layer can generally be calculated by analysis using nuclear magnetic resonance spectroscopy.

[0025] The term "aromatic polyamide" refers to a polymer of a polyfunctional amine and a polyfunctional acid halide, at least one of which is an aromatic compound. Specific examples include a polymer of a polyfunctional aromatic amine and a polyfunctional aliphatic acid halide, a polymer of a polyfunctional aliphatic amine and a polyfunctional aromatic acid halide, and a polymer of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide. Of these, wholly aromatic polyamides, which are polymers of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide, are preferred.

[0026] "Crosslinked aromatic polyamide" means that the aromatic polyamide forms a crosslinked structure. For example, the aromatic polyamide may form a crosslinked structure via a crosslinking agent or the like, or at least one of the polyfunctional amine and the polyfunctional acid halide may be trifunctional or more, and the aromatic polyamide may form a network-like crosslinked structure. Among them, it is more preferable that at least one of the polyfunctional amine and the polyfunctional acid halide is trifunctional or more, and the aromatic polyamide forms a network-like crosslinked structure. Furthermore, from the viewpoint of forming a preferable crosslinked structure, it is more preferable that only one of the polyfunctional amine or the polyfunctional acid halide is trifunctional or more, and it is even more preferable that the polyfunctional acid halide is a trifunctional polyfunctional aromatic acid halide.

[0027] The term "polyfunctional amine" refers to an amine having at least two primary amino groups and / or secondary amino groups in one molecule. Examples include aromatic trifunctional amines such as 1,3,5-triaminobenzene and 1,2,4-triaminobenzene; aromatic bifunctional amines such as o-phenylenediamine, m-phenylenediamine (hereinafter referred to as "m-PDA"), p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m-diaminopyridine, p-diaminopyridine, 3,5-diaminobenzoic acid, 2,4-diaminobenzenesulfonic acid, 3-aminobenzylamine, and 4-aminobenzylamine; and aliphatic bifunctional amines such as ethylenediamine, propylenediamine, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, 4-aminopiperidine, and aminoethylpiperazine. These polyfunctional amines may be used alone or in combination of two or more.

[0028] From the viewpoints of the separation performance, membrane permeation flux, and heat resistance of the composite semipermeable membrane, the polyfunctional amine is preferably a polyfunctional aromatic amine such as m-PDA, p-phenylenediamine, or 1,3,5-triaminobenzene. Of these, from the viewpoints of easy availability and ease of handling, m-PDA is particularly preferred.

[0029] The term "polyfunctional acid halide" refers to an acid halide having at least two halocarbonyl groups in one molecule. Examples of polyfunctional acid halides that can be used include halides of oxalic acid, malonic acid, maleic acid, fumaric acid, glutaric acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, trimesic acid, 1,2,4-benzenetricarboxylic acid, 1,3-benzenedicarboxylic acid, and 1,4-benzenedicarboxylic acid. Polyfunctional aromatic acid halides are preferred as the polyfunctional acid halide. Furthermore, from the viewpoint of reactivity with polyfunctional amines, acid chlorides are preferred as the acid halide. Examples of polyfunctional acid chlorides include trifunctional aromatic acid chlorides such as trimesic acid chloride (hereinafter referred to as "TMC") and trimellitic acid chloride, trifunctional aliphatic acid chlorides such as 1,3,5-cyclohexanetricarboxylic acid trichloride, aromatic bifunctional acid chlorides such as biphenyldicarboxylic acid chloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, and 2,6-naphthalenedicarboxylic acid dichloride, and aliphatic bifunctional acid chlorides such as adipoyl chloride, sebacoyl chloride, and 1,4-cyclohexanedicarboxylic acid dichloride. These polyfunctional acid chlorides may be used alone or in combination of two or more.

[0030] From the viewpoints of the separation performance and heat resistance of the composite semipermeable membrane and ease of availability and handling, the polyfunctional acid chloride is preferably a polyfunctional aromatic acid chloride, more preferably a tri- or higher functional aromatic acid chloride, and particularly preferably TMC.

[0031] If necessary, the terminal amino groups or terminal carboxy groups of the crosslinked aromatic polyamide in the separation functional layer may be converted to other functional groups, such as phenolic hydroxyl groups, azo groups, amide groups, and nitro groups.

[0032] 1.3 Coating Layer The composite semipermeable membrane of the present invention has a coating layer provided on the separating functional layer. The coating layer contains a vinyl alcohol polymer and protects the separating functional layer.

[0033] By coating the separation functional layer with a coating layer containing a vinyl alcohol-based polymer, a composite semipermeable membrane that is resistant to chemical fouling can be obtained. Furthermore, by suppressing chemical fouling, the proliferation of microorganisms that feed on organic matter can be prevented, resulting in a composite semipermeable membrane that is resistant to biofouling. Furthermore, since the vinyl alcohol-based polymer is hydrophilic, the reduction in membrane permeation flux due to the coating layer is small, and a composite semipermeable membrane with sufficient membrane permeation flux can be obtained.

[0034] In the composite semipermeable membrane according to the first embodiment, in a surface analysis of the coating layer side by time-of-flight secondary ion mass spectrometry (hereinafter referred to as "TOF-SIMS"), ２ H ３ O － The peak counts derived from A, CHO ２ － The peak counts derived from B and C ６ H ３ － When the peak count number resulting from the above is defined as C, the conditions satisfy 3.2≦A / C≦240 and 0.3≦B / C≦40.

[0035] Here, C ２ H ３ O － , CHO ２ － , C ６ H ３ － are mainly derived from fragments of the structures represented by the following formulas (II), (III), and (IV), respectively.

[0036]

[0037]

[0038]

[0039] The wavy lines in the above formulas (II) to (IV) represent the bonding positions to other atoms.

[0040] The structure represented by the formula (II) is a structure (C ２ H ４The structure represented by the formula (III) is derived from an acetal structure (CHO) formed by the reaction of a hydroxyl group of a vinyl alcohol polymer with a crosslinking agent. ２ The structure represented by the formula (IV) is derived from the aromatic ring structure (C ６ H ３ For example, when the crosslinked aromatic polyamide is a polymer of m-PDA and TMC, it is derived from the aromatic ring structure of the trifunctional TMC. The structure shown in the above formula (IV) is derived from the aromatic ring structure (C ６ H ３ ) and may be bonded to other atoms at any position on the aromatic ring.

[0041] That is, A / C means the ratio of hydroxyl groups of the vinyl alcohol polymer contained in the coating layer to the crosslinked aromatic polyamide on the surface of the separating functional layer, and correlates with the amount of vinyl alcohol polymer per membrane area.

[0042] When A / C is 3.2 or more, a coating layer containing a sufficient amount of polyvinyl alcohol-based polymer is formed on the surface of the separating functional layer, thereby obtaining a composite semipermeable membrane with excellent fouling resistance. Furthermore, when A / C is 240 or less, the permeation resistance due to the vinyl alcohol-based polymer contained in the coating layer can be suppressed, and a composite semipermeable membrane with sufficient membrane permeation flux can be obtained. From the viewpoint of achieving both fouling resistance and membrane permeation flux, A / C is preferably 5.5 or more and 200 or less, more preferably 12 or more and 170 or less, and even more preferably 70 or more and 140 or less.

[0043] Since the information depth of TOF-SIMS is several nm or less, when the thickness of the coating layer increases, the structure of the crosslinked aromatic polyamide on the surface of the separation functional layer (C ６ H ３ The peak count number C, which is mainly due to the difference between the thickness of the coating layer and the thickness of the coating layer, decreases. That is, C is also affected by the thickness of the coating layer, and an A / C of 240 or less means that the thickness of the coating layer is thin and the permeation resistance, which depends on the thickness of the coating layer, is low.

[0044] B / C means the ratio of the acetal structure formed by the reaction of the hydroxyl groups of the vinyl alcohol-based polymer contained in the coating layer with the crosslinking agent to the crosslinked aromatic polyamide on the surface of the separation functional layer, and correlates with the degree of crosslinking of the vinyl alcohol-based polymer per membrane area.

[0045] The degree of crosslinking of the vinyl alcohol-based polymer in the coating layer affects the durability of fouling resistance, acid resistance, alkali resistance, and oxidation resistance. When the vinyl alcohol-based polymer in the coating layer is sufficiently crosslinked by the crosslinking agent, i.e., when B / C is 0.3 or more, the crosslinking is maintained even after repeated chemical cleaning. This reduces the risk of the vinyl alcohol-based polymer eluting during membrane use, resulting in a composite semipermeable membrane with good acid resistance, alkali resistance, and oxidation resistance, as well as excellent sustained fouling resistance. Furthermore, when the vinyl alcohol-based polymer in the coating layer is not excessively crosslinked by the crosslinking agent, i.e., when B / C is 40 or less, a sufficient number of hydroxyl groups of the vinyl alcohol-based polymer are present in the coating layer. This strengthens the intermolecular hydrogen bonds of the vinyl alcohol-based polymer and the hydrogen bonds between the vinyl alcohol-based polymer and the crosslinked aromatic polyamide, resulting in a composite semipermeable membrane with good oxidation resistance, acid resistance, and alkali resistance. Therefore, by setting B / C within the above range, a composite semipermeable membrane with sustained fouling resistance, acid resistance, alkali resistance, and oxidation resistance can be obtained. From the above viewpoints, B / C is preferably 0.7 or more and 32 or less, more preferably 2.5 or more and 26 or less, and even more preferably 4.5 or more and 22 or less.

[0046] From the viewpoint of achieving both excellent fouling resistance, durability of fouling resistance, acid resistance, alkali resistance, and oxidation resistance, the composite semipermeable membrane according to the first embodiment preferably satisfies 12≦A / C≦240 and 0.3≦B / C≦40, or 3.2≦A / C≦240 and 2.5≦B / C≦40, and more preferably satisfies 3.2≦A / C≦240 and 2.5≦B / C≦40. Furthermore, it is even more preferable to satisfy 5.5≦A / C≦200 and 2.5≦B / C≦40, and it is even more preferable to satisfy 12≦A / C≦170 and 2.5≦B / C≦26, and it is particularly preferable to satisfy 70≦A / C≦140 and 4.5≦B / C≦22.

[0047] In the composite semipermeable membrane according to the second embodiment, in a surface analysis of the coating layer side by TOF-SIMS, ２ H ３ O － The peak counts derived from A and C ６ H ３ － The peak counts derived from ５ H ７ SO ３ － When the number of peak counts resulting from the above is defined as D, the conditions satisfy 3.2≦A / C≦240 and 0.04≦D / C≦25.

[0048] Here, C ５ H ７ SO ３ － is mainly derived from a fragment of the structure represented by the following formula (V).

[0049]

[0050] The wavy lines in the above formula (V) represent the bonding positions to other atoms.

[0051] The structure represented by the formula (V) is a structure (C ５ H ９ SO ３ ) comes from

[0052] In the second embodiment, A / C, like A / C in the first embodiment, means the ratio of hydroxyl groups of the vinyl alcohol polymer contained in the coating layer to the crosslinked aromatic polyamide on the surface of the separation functional layer, and correlates with the amount of vinyl alcohol polymer per membrane area. The preferred range of A / C in the second embodiment is the same as that described above for A / C in the first embodiment.

[0053] D / C means the ratio of the structure represented by the above formula (V) formed by the reaction of the hydroxyl groups of the vinyl alcohol-based polymer contained in the coating layer with the crosslinking agent to the crosslinked aromatic polyamide on the surface of the separation functional layer, and correlates with the degree of crosslinking of the vinyl alcohol-based polymer per membrane area.

[0054] As described above, the degree of crosslinking of the vinyl alcohol-based polymer in the coating layer affects the durability of fouling resistance, acid resistance, alkali resistance, and oxidation resistance. When the vinyl alcohol-based polymer in the coating layer is sufficiently crosslinked by the crosslinking agent, i.e., when D / C is 0.04 or more, the crosslinking is maintained even after repeated chemical cleaning. This reduces the risk of the vinyl alcohol-based polymer eluting during membrane use, resulting in a composite semipermeable membrane with good acid resistance, alkali resistance, and oxidation resistance, as well as excellent, sustained fouling resistance. In addition, since the crosslinks containing the structure represented by formula (V) above are composed of ether structures, they have superior acid resistance compared to crosslinks composed of acetal structures. This results in a composite semipermeable membrane that is less susceptible to deterioration of the coating layer even after acid cleaning, and has superior, sustained fouling resistance.

[0055] Furthermore, when the vinyl alcohol polymer in the coating layer is not excessively crosslinked by the crosslinking agent, i.e., when D / C is 25 or less, a sufficient number of hydroxyl groups of the vinyl alcohol polymer in the coating layer are present. This strengthens the intermolecular hydrogen bonds of the vinyl alcohol polymer and the hydrogen bonds between the vinyl alcohol polymer and the crosslinked aromatic polyamide, resulting in a composite semipermeable membrane with good oxidation resistance, acid resistance, and alkali resistance. Therefore, by setting D / C within the above range, a composite semipermeable membrane with sustained fouling resistance, acid resistance, alkali resistance, and oxidation resistance can be obtained. From the above viewpoints, D / C is preferably 0.1 or more and 20 or less, more preferably 0.3 or more and 16 or less, and even more preferably 1.0 or more and 12 or less.

[0056] From the viewpoint of achieving excellent fouling resistance, durability of fouling resistance, acid resistance, alkali resistance, and oxidation resistance at the same time, the composite semipermeable membrane according to the second embodiment preferably satisfies 12≦A / C≦240 and 0.04≦D / C≦25, or 3.2≦A / C≦240 and 0.3≦D / C≦25, and more preferably satisfies 3.2≦A / C≦240 and 0.3≦D / C≦25. Furthermore, it is even more preferable to satisfy 5.5≦A / C≦200 and 0.3≦D / C≦25, and it is even more preferable to satisfy 12≦A / C≦170 and 0.3≦D / C≦16, and it is particularly preferable to satisfy 70≦A / C≦140 and 1.0≦D / C≦12.

[0057] As described below in "2.3 Coating layer formation process," A / C, B / C, and D / C in the surface analysis of the coating layer side can be controlled, for example, by the concentration of the vinyl alcohol polymer in the solution to be brought into contact with the separation functional layer, the concentration of the crosslinking agent in the solution, the amount of solution to be brought into contact, the contact time between the separation functional layer and the solution, the temperature of the hot air, etc.

[0058] Vinyl alcohol-based polymers exhibit intermolecular hydrogen bonds between hydroxyl groups. This makes it difficult for the higher-order structure formed by the vinyl alcohol-based polymer due to intermolecular interactions, etc., to change during cleaning with acid or alkali. Therefore, by providing a coating layer containing a vinyl alcohol-based polymer, a composite semipermeable membrane with good acid and alkali resistance can be obtained. Furthermore, the hydroxyl groups of the vinyl alcohol-based polymer form hydrogen bonds with the amino groups at the terminals of the crosslinked aromatic polyamide in the separation functional layer and the amide groups in the backbone, thereby suppressing oxidation of the crosslinked aromatic polyamide. Therefore, by using a vinyl alcohol-based polymer in the coating layer, a composite semipermeable membrane with good oxidation resistance and a low risk of oxidative degradation due to contact with oxidizing agents leaked during chemical cleaning can be obtained.

[0059] The proportion of the vinyl alcohol-based polymer in the coating layer of the composite semipermeable membrane according to this embodiment is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and most preferably 100% by mass, i.e., the coating layer is composed solely of the vinyl alcohol-based polymer. When the proportion of the vinyl alcohol-based polymer in the coating layer is 50% by mass or more, a composite semipermeable membrane having good oxidation resistance, acid resistance, and alkali resistance can be obtained.

[0060] The proportion of the vinyl alcohol polymer in the coating layer can generally be calculated by analysis using nuclear magnetic resonance spectroscopy.

[0061] The saponification degree of the vinyl alcohol polymer used for the coating layer is preferably 82.0 mol% or more and 99.8 mol% or less, more preferably 86.0 mol% or more and 99.5 mol% or less. When the saponification degree of the vinyl alcohol polymer is 82.0 mol% or more, that is, when the vinyl alcohol polymer has more hydroxyl groups, the intermolecular hydrogen bonds of the vinyl alcohol polymer and the hydrogen bonds with the crosslinked aromatic polyamide are strengthened, thereby obtaining a composite semipermeable membrane with good oxidation resistance, acid resistance, and alkali resistance. On the other hand, when the saponification degree of the vinyl alcohol polymer is 99.8 mol% or less, the vinyl alcohol polymer has sufficient water solubility, and the coating layer can be easily formed on the separation functional layer using an aqueous vinyl alcohol polymer solution in the "2.3 Coating layer formation step" described below.

[0062] The degree of polymerization of the vinyl alcohol polymer used in the coating layer is preferably 100 or more and 1,500 or less, more preferably 200 or more and 1,200 or less. When the polymerization degree of the vinyl alcohol polymer is 100 or more, a coating layer having a sufficient thickness can be easily provided, and a composite semipermeable membrane exhibiting excellent fouling resistance can be obtained. On the other hand, when the polymerization degree of the vinyl alcohol polymer is 1,500 or less, permeation resistance due to the thickness of the coating layer can be suppressed, and a composite semipermeable membrane having sufficient membrane permeation flux can be obtained.

[0063] The vinyl alcohol-based polymer contained in the coating layer of the composite semipermeable membrane according to this embodiment may be polyvinyl alcohol (hereinafter referred to as "PVA") having only hydroxyl groups and acetate groups as functional groups, or may have other functional groups. Examples of vinyl alcohol-based polymers having functional groups other than hydroxyl groups and acetate groups include modified PVA in which hydroxyl groups have been modified to carbonyl groups such as carboxyl groups and acetoacetyl groups, vinylpyrrolidone, and vinyl alcohol copolymers in which olefin units and the like are copolymerized. Among these, vinyl alcohol copolymers containing a structure represented by the following general formula (I) (hereinafter simply referred to as "vinyl alcohol copolymers") are particularly preferred.

[0064]

[0065] In general formula (I), X is a divalent hydrocarbon group having 2 to 6 carbon atoms, and l, m, and n are the numbers of repeating units and are integers of 1 or more. The repeating units are not limited to block units having l, m, and n, but may be random units in which the respective units are linked randomly.

[0066] The proportion of the structure represented by the general formula (I) in the vinyl alcohol polymer contained in the coating layer is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and may be 100% by mass. The proportion of the structure represented by the general formula (I) in the vinyl alcohol polymer can generally be calculated by analysis using a nuclear magnetic resonance spectroscopy.

[0067] A vinyl alcohol copolymer containing the structure represented by the general formula (I) exhibits hydrophobic interactions between hydrocarbons in addition to the intermolecular hydrogen bonds between hydroxyl groups exhibited by PVA. Therefore, the vinyl alcohol copolymer has stronger intermolecular interactions than PVA, is less susceptible to changes in its higher-order structure, and is more likely to maintain hydrogen bonds with crosslinked aromatic polyamides. Therefore, by using a vinyl alcohol copolymer in the coating layer, a composite semipermeable membrane with better acid resistance, alkali resistance, and oxidation resistance can be obtained.

[0068] In the above general formula (I), examples of the divalent hydrocarbon group having 2 to 6 carbon atoms represented by X include an ethylene group (—CH２ CH ２ -), ethylidene group (-CH(CH ３ )-), vinylene group (-CH=CH-), trimethylene group (-CH ２ CH ２ CH ２ -), propylene group (-CH(CH ３ ) CH ２ -), tetramethylene group (-CH ２ (CH ２ ) ２ CH ２ -), cyclopentylene group, hexamethylene group (-CH ２ (CH ２ ) ４ CH ２ -), etc. X in the above general formula (I) is preferably a divalent hydrocarbon group having 2 carbon atoms. When X in the above general formula (I) is a divalent hydrocarbon group having 2 carbon atoms, the vinyl alcohol copolymer has sufficient water solubility, and a coating layer can be easily formed on the separation functional layer using an aqueous solution of the vinyl alcohol copolymer in the "2.3 Coating Layer Formation Step" described below. Furthermore, X in the above general formula (I) is preferably a divalent saturated hydrocarbon group having 2 to 6 carbon atoms. When X in the above general formula (I) is a divalent saturated hydrocarbon group having 2 to 6 carbon atoms, a coating layer that is resistant to deterioration due to oxidation, etc. can be formed. Among these, from the viewpoint of ease of availability, it is particularly preferable that X in the above general formula (I) is an ethylene group.

[0069] The copolymerization ratio n / (l + m + n) in the structure represented by the general formula (I) of the vinyl alcohol copolymer containing the structure represented by the general formula (I) is preferably 0.035 or more and 0.16 or less, more preferably 0.040 or more and 0.11 or less, and even more preferably 0.042 or more and 0.095 or less. When the copolymerization ratio is 0.035 or more, the vinyl alcohol copolymer exhibits strong intermolecular interactions due to sufficient hydrophobic interactions, resulting in a composite semipermeable membrane with good oxidation resistance. On the other hand, when the copolymerization ratio is 0.16 or less, the vinyl alcohol copolymer has sufficient water solubility, and a coating layer can be easily formed on the separation functional layer using a vinyl alcohol copolymer aqueous solution in the "2.3 Coating Layer Formation Step" described below. The copolymerization ratio can generally be calculated by analysis using nuclear magnetic resonance spectroscopy.

[0070] The coating layer is preferably insolubilized so as not to be eluted when the composite semipermeable membrane is used. Examples of methods for insolubilizing the coating layer include a method in which a non-covalent bond such as a hydrogen bond or an ionic bond is formed between the coating layer and the crosslinked aromatic polyamide, and the coating layer is immobilized on the separation functional layer; a method in which a covalent bond is formed between the coating layer and the crosslinked aromatic polyamide using a crosslinking agent or the like, and the coating layer is immobilized on the separation functional layer; and a method in which a covalent bond is formed between the coating layers using a crosslinking agent or the like, and the coating layer is insolubilized as a three-dimensional structure. Among these, from the viewpoint of being able to continue stable operation for a long period of time, a method in which a covalent bond is formed between the coating layer and the crosslinked aromatic polyamide using a crosslinking agent or the like, and the coating layer is immobilized on the separation functional layer is more preferred.

[0071] The coating layer of the composite semipermeable membrane according to the first embodiment preferably includes a structure in which a vinyl alcohol-based polymer is crosslinked with a polyhydric aldehyde. Examples of polyhydric aldehydes include succinaldehyde, glutaraldehyde, o-phthalaldehyde, and terephthalaldehyde. An acetal structure is formed when two adjacent hydroxyl groups of a vinyl alcohol-based polymer react with a polyhydric aldehyde. Therefore, vinyl alcohol-based polymers can be crosslinked with each other with a polyhydric aldehyde. Furthermore, a polyhydric aldehyde can crosslink the terminal amino groups of a vinyl alcohol-based polymer and a crosslinked aromatic polyamide, thereby fixing the coating layer to the crosslinked polyamide. Among these, glutaraldehyde is particularly preferred as the polyhydric aldehyde due to its favorable reactivity with a vinyl alcohol-based polymer.

[0072] The coating layer of the composite semipermeable membrane according to the second embodiment preferably includes a structure in which a vinyl alcohol polymer is crosslinked with a polyvinyl sulfone. Examples of polyvinyl sulfone include divinyl sulfone, 1,3-bis(vinylsulfonyl)-2-propanol, N,N'-ethylenebis[2-(vinylsulfonyl)acetamide], and N,N'-trimethylenebis[2-(vinylsulfonyl)acetamide]. The structure represented by formula (V) above is formed by the reaction of the hydroxyl groups of the vinyl alcohol polymer with the polyvinyl sulfone. Therefore, vinyl alcohol polymers can be crosslinked with each other with the polyvinyl sulfone. Furthermore, the polyvinyl sulfone can crosslink the terminal amino groups of the vinyl alcohol polymer and the crosslinked aromatic polyamide, thereby immobilizing the coating layer on the crosslinked polyamide. Among these, N,N'-trimethylenebis[2-(vinylsulfonyl)acetamide] is particularly preferred as the polyvinyl sulfone due to its favorable reactivity with the vinyl alcohol polymer.

[0073] The presence of a structure crosslinked with a polyaldehyde or a polyvinyl sulfone in a vinyl alcohol polymer can be confirmed by confirming a fragment derived from an acetal structure or the structure represented by formula (V) above using the above-mentioned TOF-SIMS, and by combining various analyses such as NMR and mass spectrometry to identify a substance obtained by hydrolyzing the acetal structure of the coating layer or cleaving the ether structure of the structure represented by formula (V) above.

[0074] The shapes and thicknesses of the separation functional layer and coating layer affect the separation performance and membrane permeation flux. Figure 2 shows an example of the cross-sectional structure of the composite semipermeable membrane 1 in this embodiment. As shown in Figures 2(a) and 2(b), the separation functional layer 3 preferably has a pleated shape with multiple convex portions. It is more preferable that the interior 5 of the convex portions (between the separation functional layer 3 and the support membrane 2) is a void. A pleated shape of the separation functional layer 3 is larger than a flat shape, and therefore a high membrane permeation flux can be achieved while maintaining separation performance. The coating layer 4 may be formed thinly on the separation functional layer 3 to form a pleated shape together with the separation functional layer 3, or may have a relatively large thickness that fills the pleated shape of the separation functional layer 3.

[0075] The presence of a pleated shape in the separating functional layer can be confirmed by observing a cross section of the separating functional layer perpendicular to the surface of the composite semipermeable membrane with a transmission electron microscope (TEM). If even a small amount of convexity is observed in the separating functional layer during TEM observation, the separating functional layer is deemed to have a pleated shape.

[0076] The total thickness T of the separation functional layer and the coating layer is preferably 10 nm or more and 100 nm or less, more preferably 11 nm or more and 70 nm or less, and even more preferably 11 nm or more and 20 nm or less. When the total thickness T of the separation functional layer and the coating layer is 10 nm or more, a composite semipermeable membrane with good separation performance can be obtained. On the other hand, when the total thickness T of the separation functional layer and the coating layer is 100 nm or less, a composite semipermeable membrane with good membrane permeation flux can be obtained. As shown in Figure 2 (b), the "total thickness T" means the thickness from the inside 5 of the convex portion to the outside when the separation functional layer 3 and the coating layer 4 are overlapped and integrated, and the separation functional layer and the coating layer have a pleated shape with multiple hollow convex portions.

[0077] In order to prevent the substance to be separated from penetrating into the composite semipermeable membrane, it is preferable that the separation functional layer and coating layer are arranged on the surface side of the composite semipermeable membrane, and it is preferable to use the surface on the separation functional layer and coating layer side as the primary filtration side.

[0078] 1.4 NaCl rejection rate, membrane permeation flux The NaCl rejection rate of the composite semipermeable membrane according to this embodiment is preferably 99.55% or more, more preferably 99.65% or more, and even more preferably 99.75% or more. ０ When the membrane performance of the composite semipermeable membrane is within the above range, it can be preferably used as a separation membrane for separating salts and the like.

[0079] In addition, the membrane permeation flux F after fouling of the composite semipermeable membrane １ is preferably 0.80 m / d or more, more preferably 0.90 m / d or more, and even more preferably 1.00 m / d or more. ０ Membrane permeation flux F after fouling １ The ratio of (hereinafter referred to as "F １ / F ０ ") is preferably 0.6 or more, more preferably 0.7 or more, and even more preferably 0.8 or more. When the membrane performance after fouling of the composite semipermeable membrane is within the above range, it can be preferably used as a composite semipermeable membrane excellent in anti-fouling properties. The fouling conditions are as described in "Membrane permeation flux after fouling" in the Examples described later.

[0080] The NaCl rejection rate of the composite semipermeable membrane according to this embodiment after contact with an oxidizing agent is preferably 99.50% or more, more preferably 99.60% or more, and even more preferably 99.70% or more. When the membrane performance of the composite semipermeable membrane after contact with an oxidizing agent is within the above range, it can be preferably used as a composite semipermeable membrane with a low risk of oxidative degradation due to oxidizing agent leakage. The conditions for oxidizing agent contact are as described in the "Oxidizing Agent Contact" section of the Examples below.

[0081] The NaCl rejection rate of the composite semipermeable membrane according to this embodiment after contact with an acid or alkali is preferably 99.40% or more, more preferably 99.50% or more, and even more preferably 99.60% or more. When the membrane performance of the composite semipermeable membrane after contact with an acid or alkali is within the above range, it can be preferably used as a composite semipermeable membrane that maintains its separation performance even after repeated chemical washing. The conditions for acid or alkali contact are as described in the "Alkali Contact" or "Acid Contact" sections of the Examples below.

[0082] Furthermore, the NaCl rejection rate of the composite semipermeable membrane according to this embodiment after the membrane deterioration test is preferably 99.15% or more, more preferably 99.30% or more, and even more preferably 99.40% or more. When the membrane performance of the composite semipermeable membrane after the membrane deterioration test is within the above range, it can be preferably used as a composite semipermeable membrane with a low risk of combined deterioration due to alkalis, acids, and oxidizing agents. The conditions for the membrane deterioration test are as described in the "Membrane Deterioration Test" in the Examples described below.

[0083] In addition, the composite semipermeable membrane according to this embodiment has a membrane permeation flux F ２ Membrane permeation flux F after fouling in the composite semipermeable membrane after membrane deterioration test ３ (Membrane permeation flux F after subjecting the composite semipermeable membrane to a membrane deterioration test and then further subjecting it to fouling ３ ) ratio (hereinafter referred to as "F ３ / F ２ ") is preferably 0.5 or more, more preferably 0.55 or more, and even more preferably 0.6 or more. When the membrane performance after fouling in the composite semipermeable membrane after the membrane deterioration test is within the above range, it can be preferably used as a composite semipermeable membrane that maintains excellent anti-fouling properties.

[0084] 2. Method for Producing Composite Semipermeable Membrane The method for producing the composite semipermeable membrane according to this embodiment is not particularly limited as long as it can produce a composite semipermeable membrane that satisfies the above-described desired characteristics. For example, the membrane can be produced by the following method.

[0085] 2.1 Formation of Support Membrane As a method for forming the support membrane, a known method can be suitably used. Hereinafter, an example will be described in which the support membrane has a porous support layer and a substrate, and PSf is used as the material for the porous support layer.

[0086] First, a stock solution of the porous support layer is prepared by dissolving PSf in a good solvent for PSf, such as N,N-dimethylformamide (hereinafter referred to as "DMF").

[0087] The concentration of PSf in the stock solution of the porous support layer is preferably 10% by mass or more and 25% by mass or less, more preferably 12% by mass or less and 20% by mass or less. When the concentration of PSf in the stock solution of the porous support layer is within the above range, both the strength of the obtained porous support layer and the membrane permeation flux can be achieved. Note that the preferred range of the concentration of the material in the stock solution of the porous support layer can be appropriately adjusted depending on the material used, good solvent, etc.

[0088] Next, the obtained stock solution of the porous support layer is applied to the surface of the substrate, which is then immersed in a coagulation bath containing a non-solvent for PSf.

[0089] The non-solvent for PSf contained in the coagulation bath is preferably water, for example. By contacting the stock solution of the porous support layer applied to the surface of the substrate with a coagulation bath containing a non-solvent for PSf, the stock solution of the porous support layer is coagulated by non-solvent-induced phase separation, thereby obtaining a support membrane in which the porous support layer is formed on the surface of the substrate.

[0090] The coagulation bath may be composed of only a non-solvent for PSf, or may contain a good solvent for PSf to the extent that the stock solution of the porous support layer can be coagulated.

[0091] The resulting support membrane may be washed before forming the separation functional layer to remove the solvent remaining in the support membrane.

[0092] 2.2 Formation of Separation Functional Layer The method for forming a separation functional layer containing a crosslinked aromatic polyamide will be described using as an example a method in which a polyfunctional aromatic amine and a polyfunctional aromatic acid halide, one of which is trifunctional or higher, are polymerized and solidified on the support membrane obtained in "2.1 Formation of Support Membrane." As the polymerization method, interfacial polymerization is the most preferable from the viewpoints of productivity and performance. The interfacial polymerization process will be described below.

[0093] The interfacial polymerization process includes the steps of: (a) contacting an aqueous solution containing a polyfunctional aromatic amine with a support membrane; (b) contacting an organic solvent solution containing a polyfunctional aromatic acid halide with the support membrane that has been contacted with the aqueous solution containing a polyfunctional aromatic amine; (c) draining the organic solvent solution after the contact; and (d) washing the composite semipermeable membrane from which the organic solvent solution has been drained with hot water.

[0094] In step (a), the aqueous solution contains at least a polyfunctional aromatic amine. Examples of the polyfunctional aromatic amine include the polyfunctional aromatic amines exemplified in "1.2 Separation functional layer."

[0095] The concentration of the polyfunctional aromatic amine in the aqueous solution is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 15% by mass or less, and even more preferably 1.0% by mass or more and 10% by mass or less. When the concentration of the polyfunctional aromatic amine is 0.1% by mass or more, a separation functional layer having solute separation performance can be formed. On the other hand, when the concentration of the polyfunctional aromatic amine is 20% by mass or less, a separation functional layer having good membrane permeation flux can be formed.

[0096] Furthermore, the aqueous solution may contain compounds such as surfactants and antioxidants, if necessary, as long as the amount does not inhibit polymerization.

[0097] The aqueous solution is preferably brought into uniform and continuous contact with the support membrane. Specific examples include a method of coating the support membrane with the polyfunctional aromatic amine aqueous solution and a method of immersing the support membrane in the aqueous solution. The contact time between the support membrane and the aqueous solution is preferably 1 second to 10 minutes, more preferably 3 seconds to 3 minutes.

[0098] After contacting the aqueous solution with the support membrane, it is preferable to thoroughly drain the solution so that no droplets remain on the support membrane. By thoroughly draining the solution, it is possible to prevent remaining droplets from becoming membrane defects after the formation of the separation functional layer, which would result in a decrease in separation performance. Methods for draining the solution include, for example, holding the support membrane vertically after contact with the aqueous solution to allow excess aqueous solution to flow naturally, and spraying an air current such as nitrogen from an air nozzle to forcibly drain the solution. Furthermore, after draining the solution, the membrane surface can be dried to remove some of the water content of the aqueous solution.

[0099] In the step (b), examples of the polyfunctional aromatic acid halide include the polyfunctional aromatic acid halides exemplified in "1.2 Separation functional layer."

[0100] The organic solvent is preferably immiscible with water, dissolves the polyfunctional aromatic acid halide, does not attack the support film, and is inert to the polyfunctional aromatic amine and the polyfunctional aromatic acid halide. Examples of the organic solvent include hydrocarbon compounds such as n-nonane, n-decane, n-undecane, n-dodecane, isooctane, isodecane, and isododecane, and mixtures thereof.

[0101] The concentration of the polyfunctional aromatic acid halide in the organic solvent solution is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.02% by mass or more and 4% by mass or less, and even more preferably 0.03% by mass or more and 2% by mass or less. When the concentration of the polyfunctional aromatic acid halide is 0.01% by mass or more, the polymerization can proceed at a sufficient reaction rate. On the other hand, when the concentration of the polyfunctional aromatic acid halide is 10% by mass or less, the occurrence of side reactions during polymerization can be suppressed. Furthermore, the organic solvent solution may contain compounds such as surfactants as needed, as long as they do not inhibit the polymerization.

[0102] The organic solvent solution of polyfunctional aromatic acid halide is preferably uniformly and continuously brought into contact with the support film that has been contacted with the aqueous polyfunctional aromatic amine solution.Specifically, for example, a method of coating the organic solvent solution of polyfunctional aromatic acid halide on the support film that has been contacted with the aqueous polyfunctional aromatic amine solution can be mentioned.The contact time between the support film that has been contacted with the aqueous polyfunctional aromatic amine solution and the organic solvent solution of polyfunctional aromatic acid halide is preferably 3 seconds to 10 minutes, more preferably 5 seconds to 3 minutes.

[0103] If necessary, the support membrane contacted with the organic solvent solution of the polyfunctional aromatic acid halide may be heat-treated. When heat-treated, the heating temperature is preferably 35°C or higher and 180°C or lower, more preferably 50°C or higher and 160°C or lower, and even more preferably 60°C or higher and 150°C or lower. The optimal heating time varies depending on the temperature of the membrane surface, which is the reaction site, but is preferably 5 seconds or longer, more preferably 10 seconds or longer.

[0104] In step (c), the organic solvent solution on the composite semipermeable membrane after the polymerization reaction is removed by draining. Examples of draining methods include a method in which the membrane is held vertically and excess organic solvent solution is removed by gravity flow, a method in which the organic solvent is dried and removed by blowing air onto the membrane with a blower, and a method in which excess organic solvent solution is removed with a mixed fluid of water and air.

[0105] In step (d), the composite semipermeable membrane from which the organic solvent has been removed is washed with hot water. The temperature of the hot water is preferably 40°C or higher and 95°C or lower, more preferably 60°C or higher and 95°C or lower. When the temperature of the hot water is 40°C or higher, unreacted substances and oligomers remaining in the membrane can be sufficiently removed. On the other hand, when the temperature of the hot water is 95°C or lower, the degree of shrinkage of the composite semipermeable membrane does not increase, and a good membrane permeation flux can be maintained. The preferred range of the temperature of the hot water can be appropriately adjusted depending on the polyfunctional aromatic amine or polyfunctional aromatic acid halide used.

[0106] 2.3 Formation of coating layer The method for forming the coating layer will be described using as an example a method in which a solution containing a vinyl alcohol polymer and a crosslinking agent is brought into contact with the separation functional layer obtained in "2.2 Formation of separation functional layer" to insolubilize the vinyl alcohol polymer.

[0107] The coating layer formation process includes the steps of (e) contacting the separation functional layer with a solution containing a vinyl alcohol-based polymer and a crosslinking agent, (f) bonding the vinyl alcohol-based polymer to the crosslinked aromatic polyamide via the crosslinking agent to immobilize it on the separation functional layer, (g) draining off excess solution, and (h) washing the composite semipermeable membrane.

[0108] In step (e), the solution brought into contact with the separation functional layer contains at least a vinyl alcohol polymer and a crosslinking agent. Examples of the vinyl alcohol polymer and crosslinking agent that can be used include those exemplified in "1.3 Coating layer." From the viewpoint of suppressing deterioration of the separation functional layer and the support membrane during contact with the solution, it is preferable to use water as a solvent for dissolving the vinyl alcohol polymer and the crosslinking agent. An additive may also be used to improve the solubility of the vinyl alcohol polymer.

[0109] The concentration of the vinyl alcohol-based polymer in the solution is preferably 0.05% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 8% by mass or less, and even more preferably 0.2% by mass or more and 5% by mass or less. When the concentration of the vinyl alcohol-based polymer is 0.05% by mass or more, a coating layer having a sufficient thickness can be provided, and a composite semipermeable membrane exhibiting excellent fouling resistance can be obtained. On the other hand, when the concentration of the vinyl alcohol-based polymer is 10% by mass or less, a decrease in membrane permeation flux due to the coating layer can be suppressed, and a composite semipermeable membrane having sufficient membrane permeation flux can be obtained.

[0110] The concentration of the crosslinking agent in the solution is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.02% by mass or more and 3% by mass or less, and even more preferably 0.05% by mass or more and 2% by mass or less. When the concentration of the crosslinking agent is 0.01% by mass or more, covalent bonds are formed between the vinyl alcohol polymer and the crosslinked aromatic polyamide, and between the vinyl alcohol polymers, thereby making the vinyl alcohol polymer insoluble. On the other hand, when the concentration of the crosslinking agent is 5% by mass or less, rapid progress of the crosslinking reaction is suppressed, and a uniform coating layer can be formed.

[0111] Furthermore, the solution may contain, as necessary, components for forming a coating layer other than the vinyl alcohol polymer and the crosslinking agent, compounds such as a catalyst for promoting the crosslinking reaction, etc. Examples of catalysts for promoting the crosslinking reaction include inorganic acids such as hydrochloric acid and sulfuric acid, and inorganic alkalis such as aqueous sodium hydroxide and aqueous sodium carbonate solutions. When a polyaldehyde is used as the crosslinking agent, the catalyst for promoting the crosslinking reaction is preferably an inorganic acid such as hydrochloric acid and sulfuric acid. When a polyvinyl sulfone is used as the crosslinking agent, the catalyst for promoting the crosslinking reaction is preferably an inorganic alkali such as aqueous sodium hydroxide and aqueous sodium carbonate solution.

[0112] The solution is preferably brought into uniform and continuous contact with the separation functional layer. Specifically, for example, a method of immersing a laminate of a support membrane and a separation functional layer in the solution, or a method of coating the solution on the separation functional layer can be mentioned. When the solution is coated on the separation functional layer, the amount of the solution is 15 ml / m ２ 120ml / m or more ２ Preferably, 35 ml / m or less ２ More than 100ml / m ２ The contact time between the separation functional layer and the solution is preferably from 1 second to 10 minutes, more preferably from 3 seconds to 3 minutes.

[0113] In step (f), the vinyl alcohol polymer is bonded to the crosslinked aromatic polyamide of the separating functional layer via a crosslinking agent and fixed. In step (f), although fixation of the vinyl alcohol polymer may proceed naturally after the contact in step (e) without any special operation, heating is preferred. Examples of heating methods include a method of heating the solution and the composite semipermeable membrane by blowing hot air with a blower. The hot air temperature is preferably 45°C or higher and 100°C or lower, more preferably 50°C or higher and 75°C or lower. When the hot air temperature is 45°C or higher, the vinyl alcohol polymer and the crosslinked aromatic polyamide form a bond via the crosslinking agent, and the vinyl alcohol polymer can be fixed to the separating functional layer. On the other hand, when the hot air temperature is 100°C or lower, rapid progress of the crosslinking reaction is suppressed, a uniform coating layer can be formed, and the degree of shrinkage of the composite semipermeable membrane is not increased, allowing good membrane permeation flux to be maintained.

[0114] In step (g), the solution on the composite semipermeable membrane after the crosslinking reaction is removed by draining. Examples of draining methods include a method in which the membrane is held vertically to remove excess solution by gravity flow, and a method in which the solvent is dried and removed by blowing air onto the membrane with a fan.

[0115] In step (h), the composite semipermeable membrane from which the solution has been removed is washed with water. The temperature of the water used for washing is preferably 15°C or higher and 70°C or lower, more preferably 20°C or higher and 50°C or lower. When the water temperature is 15°C or higher, unreacted substances, catalysts, etc. remaining in the composite semipermeable membrane can be sufficiently removed. On the other hand, when the water temperature is 70°C or lower, the degree of shrinkage of the composite semipermeable membrane does not increase, and a good membrane permeation flux can be maintained. The preferred range of the water temperature can be appropriately adjusted depending on the types of vinyl alcohol polymer and crosslinking agent used.

[0116] Furthermore, if necessary, the composite semipermeable membrane may be subjected to hydrophilization treatment. Examples of the hydrophilization treatment method include a method of contacting the composite semipermeable membrane with an aqueous solution of a surfactant such as polyoxyethylene octylphenyl ether or sodium normal dodecylbenzenesulfonate, or an aqueous solution of an alcohol such as methanol, ethanol, isopropanol, or glycerin.

[0117] 3. Use of the composite semipermeable membrane The composite semipermeable membrane according to this embodiment is suitably used as a spiral composite semipermeable membrane element by being wound around a cylindrical water collection pipe having many holes, together with a feed water flow path material such as a plastic net, a permeate water flow path material such as tricot, and, if necessary, a film for increasing pressure resistance. Furthermore, this element can also be connected in series or in parallel and housed in a pressure vessel to form a composite semipermeable membrane module.

[0118] Furthermore, the composite semipermeable membranes, their elements, and modules can be combined with a pump that supplies feed water to them, a device that pretreats the feed water, etc. to form a fluid separation device. By using this fluid separation device, feed water can be separated into permeated water such as drinking water and concentrated water that did not permeate the membrane, thereby obtaining water suitable for the intended purpose.

[0119] The feed water to be treated by the composite semipermeable membrane according to this embodiment includes liquid mixtures containing 500 mg / L or more and 100 g / L or less of total dissolved solids (hereinafter referred to as "TDS"), such as seawater, brine, and wastewater. Generally, TDS refers to the amount of total dissolved solids and is expressed as "mass / volume" or "mass ratio." In this specification, it is converted from practical salinity (S).

[0120] The higher the operating pressure of the fluid separation device, the better the solute removal rate. However, considering the increased energy required for operation and the durability of the composite semipermeable membrane, the operating pressure when permeating the water to be treated through the composite semipermeable membrane is preferably 0.5 MPa or more and 10 MPa or less. As the feed water temperature increases, the solute removal rate decreases, but as the temperature decreases, the membrane permeation flux also decreases. Therefore, the feed water temperature is preferably 5 to 45°C. Furthermore, in the case of feed water with a high solute concentration, such as seawater, increasing the pH of the feed water may cause the formation of scale such as magnesium. Furthermore, since there is a concern that operation under high pH conditions may deteriorate the composite semipermeable membrane, it is preferable to operate in the neutral range.

[0121] The present invention will be described below with reference to specific examples, but the present invention is not limited to these examples in any way.

[0122] The physical properties of the composite semipermeable membrane of the present invention were measured by the following methods.

[0123] <Membrane permeation flux> Evaluation water (hereinafter referred to as "evaluation water") adjusted to a NaCl concentration of 2,000 mg / L, 25°C, and pH 7 was supplied to a composite semipermeable membrane having a diameter of 75 mm at an operating pressure of 1.55 MPa, and cross-flow filtration was carried out for 2 hours. After that, the permeated water was collected for 15 minutes. ３ ) and the unit membrane area (m ２ ), converted into a value per unit time (d), and the membrane permeation flux F ０ (m / d) or the membrane permeation flux F of the composite semipermeable membrane after the membrane deterioration test ２ (m / d) was calculated.

[0124] <NaCl Rejection Rate> In the membrane filtration test for "Membrane Permeation Flux" described above, the electrical conductivity of the evaluation water and the permeated water was measured using a multi-water quality meter (MM-60R, manufactured by DKK-TOA Corporation), and the NaCl concentration (practical salinity) of each was measured. From the obtained NaCl concentrations, the NaCl rejection rate (%) was calculated based on the following formula. Note that the value used was rounded to two decimal places. NaCl rejection rate (%) = 100 × {1 - (NaCl concentration in permeated water / NaCl concentration in evaluation water)}

[0125] <Membrane permeation flux after fouling> Evaluation water to which polyoxyethylene (10) octylphenyl ether was added to a concentration of 50 mg / L was supplied to the composite semipermeable membrane under the conditions described in the above "Membrane permeation flux". After 30 minutes of operation, permeated water was collected for 15 minutes. The membrane permeation flux F after fouling was calculated from the obtained permeated water by the same calculation method as the above "Membrane permeation flux". １ (m / d) or membrane permeation flux F after fouling in the composite semipermeable membrane after membrane deterioration test ３ (m / d) was calculated.

[0126] <Alkali Contact> The composite semipermeable membrane was immersed in an aqueous sodium hydroxide solution adjusted to pH 12.5 at 25° C. for 72 hours, and then washed with distilled water.

[0127] <Acid Contact> The composite semipermeable membrane was immersed in sulfuric acid adjusted to pH 2.0 at 25° C. for 3 hours, and then washed with distilled water.

[0128] <Oxidizing Agent Contact> The composite semipermeable membrane was immersed in a 5 mg / L aqueous sodium hypochlorite solution adjusted to pH 7.0 at 25° C. for a total of 96 hours while changing the solution every 24 hours. Thereafter, the composite semipermeable membrane was immersed in a 1000 mg / L aqueous sodium hydrogen sulfite solution for 10 minutes and washed with distilled water.

[0129] <Membrane Deterioration Test> The composite semipermeable membrane was subjected to the above-mentioned "alkali contact," "acid contact," "oxidant contact," "alkali contact," and "acid contact" in this order, and the NaCl rejection rate (%) was calculated at each stage by the method described in the above-mentioned "NaCl rejection rate."

[0130] <TOF-SIMS Measurement> The composite semipermeable membrane was cut into a 3 cm x 3 cm square and immersed in distilled water at 25°C for 24 hours. After immersion, the composite semipermeable membrane was dried to a water content of 0.1% or less. TOF-SIMS was measured under the following conditions, with the surface of the coating layer side of the obtained composite semipermeable membrane as the measurement surface. ２ H ３ O － , CHO ２ － , C ６ H ３ － , C ５ H ７ SO ３ － The peak counts derived from the above were designated as A, B, C, and D, respectively, and A / C, B / C, and D / C were calculated. Note that for B and D, the peak count was 1.0 × 10 ３ If the value was less than 1 / 3 of the original value, it was determined to be noise, and no further calculations were performed. The calculated value had two significant digits. Measurement device: TOF.SIMS5 manufactured by ION-TOF Corporation. Raster size: 300 μm. Number of scans: 12. Number of pixels (per side): 256. Measurement vacuum level: 4×10 －７ Pa or less Primary ions: Bi ３ ＋＋ Primary ion acceleration voltage: 30 kV Pulse width: 11.7 ns Punching: Yes Charge neutralization: Yes Post-acceleration: 9.5 kV Secondary ion polarity: Negative

[0131] <Total Thickness T of Separation Functional Layer and Coating Layer> The composite semipermeable membrane was cut into a 3 cm x 3 cm square and immersed in distilled water at 25 ° C. for 24 hours. After immersion, the composite semipermeable membrane was embedded in epoxy resin, stained with osmium tetroxide, and an ultrathin section was cut using a microtome to obtain a measurement sample. The obtained sample was observed using a scanning transmission electron microscope (HD2700, manufactured by Hitachi, Ltd.) with the cross section of the composite semipermeable membrane as the observation surface. Using an image acquired at 1,000,000 times magnification, the shortest distance from a point on the outer surface of the coating layer to the inner surface was measured. However, for examples in which a coating layer was not formed, the shortest distance from a point on the outer surface of the separation functional layer to the inner surface was measured. For 10 randomly selected convex portions, five points were measured per convex portion, and the average value of a total of 50 points was taken as the total thickness T (nm) of the separation functional layer and the coating layer.

[0132] <Weight-average molecular weight> The weight-average molecular weight (polystyrene equivalent) of PSf was measured by gel permeation chromatography. Specific measurement conditions were as follows: Measurement device: HLC-8022 manufactured by Tosoh Corporation; Column: Two TSKgel (registered trademark) Super HM-H columns (manufactured by Tosoh Corporation, inner diameter 6.0 mm, length 15 cm); Eluent: LiBr / N-methylpyrrolidone solution (10 mmol / L); Sample concentration: 0.1% by mass; Flow rate: 0.5 mL / min; Temperature: 40°C.

[0133] The raw materials of the composite semipermeable membranes used in the examples and comparative examples are summarized below: PSf (Udel (registered trademark) P-3500, Mw 80,000, manufactured by Solvay Specialty Polymers Japan Co., Ltd.), DMF (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), polyester long-fiber nonwoven fabric (thickness 90 μm, density 0.42 g / cm ３) m-PDA (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) TMC (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) n-Decane (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) Sodium nitrite (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) Sodium sulfite (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) Polyoxyethylene (10) octylphenyl ether (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) Sodium hypochlorite (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) Sodium hydrogen sulfite (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) Sulfuric acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) Sodium hydroxide aqueous solution (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) PVA1 (manufactured by Sigma-Aldrich, saponification degree 99.5 mol%, polymerization degree 2,600) PVA2 (manufactured by Sigma-Aldrich, saponification degree 99.5 mol%, polymerization degree 2,000) PVA3 (manufactured by Sigma-Aldrich, degree of saponification 87.0-89.0 mol%, degree of polymerization 900) Vinyl alcohol copolymer 1 (manufactured by Kuraray Co., Ltd., Exeval (registered trademark) AQ-4104, degree of saponification 98.0-99.0 mol%, degree of polymerization 400, ethylene copolymerization ratio 0.059) Vinyl alcohol copolymer 2 (manufactured by Kuraray Co., Ltd., Exeval (registered trademark) HR-3010, degree of saponification 99.0-99.4 mol%, degree of polymerization 1,000, ethylene copolymerization ratio 0.045) Glutaraldehyde (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Isopropanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Hydrochloric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Divinyl sulfone (manufactured by Tokyo Chemical Industry Co., Ltd.) N,N'-trimethylenebis[2-(vinylsulfonyl)acetamide] (Fujifilm Wako Pure Chemical Industries, Ltd.)

[0134] [Comparative Example 1] 15% by mass of PSf and 85% by mass of DMF were dissolved at 100 ° C to prepare a stock solution for a porous support layer. This stock solution for a porous support layer was applied to the surface of a polyester long-fiber nonwoven fabric at 25 ° C. After 3 seconds, it was immersed in a coagulation bath of distilled water at 25 ° C. for 30 seconds to coagulate, and then washed with hot water at 80 ° C. for 2 minutes to obtain a support membrane in which a porous support layer made of PSf was formed on the surface of the polyester long-fiber nonwoven fabric substrate. The thickness of the porous support layer in the obtained support membrane was 30 μm. Next, the obtained support membrane was immersed in a 3% by mass aqueous solution of m-PDA for 2 minutes, and the support membrane was slowly pulled up vertically. Excess aqueous solution was removed from the support membrane surface by spraying nitrogen from an air nozzle. In an environment controlled at 25 ° C, 20 ml of a 25 ° C n-decane solution containing 0.12% by mass of TMC was applied so that the surface of the support membrane was completely wet, and the mixture was left to stand for 1 minute, and a separation functional layer was formed by interfacial polymerization. Next, the obtained membrane was held vertically for 30 seconds to drain off excess solution, and then washed with hot water at 80°C for 2 minutes. The washed membrane was then immersed in a 0.3% by mass aqueous solution of sodium nitrite at 35°C and pH 3 for 1 minute, and then in a 0.1% by mass aqueous solution of sodium sulfite for 2 minutes to obtain a composite semipermeable membrane consisting of a support membrane and a separation functional layer. The separation functional layer of the composite semipermeable membrane had a pleated shape.

[0135] [Comparative Example 2] The entire surface of the separation functional layer of the composite semipermeable membrane obtained in Comparative Example 1 was contacted with a solution (isopropanol / water = 3 / 7) containing 0.25% by mass of PVA1 (saponification degree 99.5 mol%, polymerization degree 2,600) in an environment controlled at 20 ° C. The solution was held at 100 ° C. for 5 minutes while the aqueous solution remained on the surface of the separation functional layer, and then the solution was again brought into contact with the surface and held at 130 ° C. for 5 minutes to form a coating layer on the separation functional layer. Then, the membrane was washed with water at 20 ° C. for 2 minutes. Finally, the composite semipermeable membrane was immersed in a 14% by mass aqueous solution of isopropanol at 20 ° C. for 5 minutes to obtain a hydrophilic composite semipermeable membrane.

[0136] [Comparative Example 3] The composite semipermeable membrane obtained in Comparative Example 1 was immersed for 2 minutes in an aqueous solution containing 0.5% by mass of PVA2 (saponification degree 99.5 mol%, polymerization degree 2,000), 0.2% by mass of glutaraldehyde, and 0.1 mol / L of hydrochloric acid in an environment controlled at 20 ° C. The composite semipermeable membrane was held vertically and the excess aqueous solution was drained off and removed, and hot air at 80 ° C was blown onto the membrane for 2 minutes to form a coating layer on the separation functional layer. Then, the membrane was washed with hot water at 90 ° C. for 2 minutes. Finally, the composite semipermeable membrane was immersed for 10 minutes in a 10% by mass aqueous solution of isopropanol at 20 ° C. to obtain a hydrophilic composite semipermeable membrane.

[0137] Comparative Example 4 A composite semipermeable membrane was obtained in the same manner as in Comparative Example 3, except that the amount of PVA2 was 0.2% by mass and the amount of glutaraldehyde was 0.3% by mass.

[0138] Comparative Example 5 The surface of the separating functional layer of the composite semipermeable membrane obtained in Comparative Example 1 was coated with 30 ml / m of an aqueous solution containing 0.5 mass % of PVA3 (saponification degree 87.0-89.0 mol %, polymerization degree 900), 0.2 mass % of glutaraldehyde, and 0.1 mass % of sulfuric acid in an environment controlled at 20°C. ２ was contacted for 5 seconds. With the aqueous solution remaining on the surface of the separation functional layer, hot air at 40°C was blown onto the composite semipermeable membrane for 45 seconds to form a coating layer on the separation functional layer. Thereafter, the composite semipermeable membrane was vertically held to drain off excess aqueous solution and washed with water at 20°C for 2 minutes. Finally, the composite semipermeable membrane was immersed in a 10% by mass aqueous solution of isopropanol at 20°C for 10 seconds to obtain a hydrophilized composite semipermeable membrane.

[0139] Comparative Example 6 A composite semipermeable membrane was obtained in the same manner as in Comparative Example 5, except that the amount of PVA3 was 0.2% by mass and the amount of glutaraldehyde was 0.4% by mass.

[0140] [Comparative Example 7] The composite semipermeable membrane obtained in Comparative Example 1 was immersed for 5 seconds in an aqueous solution containing 0.5% by mass of PVA3, 0.1% by mass of divinyl sulfone, and 0.1 mol / L of sodium hydroxide aqueous solution in an environment controlled at 20 ° C. The composite semipermeable membrane was held vertically and excess aqueous solution was drained off and removed, and hot air at 80 ° C was blown onto the membrane for 2 minutes to form a coating layer on the separation functional layer. Then, the membrane was washed with hot water at 90 ° C for 2 minutes. Finally, the composite semipermeable membrane was immersed in a 10% by mass aqueous solution of isopropanol at 20 ° C. for 10 minutes to obtain a hydrophilic composite semipermeable membrane.

[0141] [Example 1] The aqueous solution brought into contact with the surface of the separation functional layer was 80 ml / m ２ A composite semipermeable membrane was obtained in the same manner as in Comparative Example 5, except that the hot air temperature was set to 65°C.

[0142] Example 2 A composite semipermeable membrane was obtained in the same manner as in Example 1, except that the hot air blown was set to 85°C.

[0143] Example 3 A composite semipermeable membrane was obtained in the same manner as in Example 1, except that the hot air blown was set to 95°C.

[0144] Example 4 A composite semipermeable membrane was obtained in the same manner as in Example 1, except that the time for blowing hot air was set to 1.5 minutes.

[0145] Example 5 A composite semipermeable membrane was obtained in the same manner as in Example 1, except that the amount of PVA3 was 1.4% by mass and the amount of glutaraldehyde was 0.7% by mass.

[0146] Example 6 A composite semipermeable membrane was obtained in the same manner as in Example 1, except that the amount of PVA3 was 1.6% by mass and the amount of glutaraldehyde was 0.15% by mass.

[0147] Example 7 A composite semipermeable membrane was obtained in the same manner as in Example 2, except that the amount of PVA3 was 0.2% by mass and the amount of glutaraldehyde was 1.5% by mass.

[0148] Example 8 A composite semipermeable membrane was obtained in the same manner as in Example 2, except that vinyl alcohol copolymer 1 was used instead of PVA3.

[0149] Example 9 A composite semipermeable membrane was obtained in the same manner as in Example 2, except that vinyl alcohol copolymer 2 was used instead of PVA3.

[0150] [Example 10] The surface of the separating functional layer of the composite semipermeable membrane obtained in Comparative Example 1 was coated with 80 ml / m of an aqueous solution containing 0.5 mass % of PVA3, 0.3 mass % of divinyl sulfone, and 0.1 mol / L of an aqueous sodium hydroxide solution in an environment controlled at 20°C. ２ The composite semipermeable membrane was then vertically held in contact with the aqueous solution for 5 minutes to form a coating layer on the separation functional layer. The excess aqueous solution was then drained off and washed with water at 20°C for 2 minutes. Finally, the composite semipermeable membrane was immersed in a 10% by mass aqueous solution of isopropanol at 20°C for 10 seconds to obtain a hydrophilic composite semipermeable membrane.

[0151] [Example 11] A composite semipermeable membrane was obtained in the same manner as in Example 10, except that after contacting the aqueous solution with the surface of the separation functional layer, hot air at 65°C was blown onto the composite semipermeable membrane for 45 seconds while the aqueous solution remained on the surface of the separation functional layer, thereby forming a coating layer on the separation functional layer.

[0152] Example 12 A composite semipermeable membrane was obtained in the same manner as in Example 11, except that the hot air blown was set to 95°C.

[0153] Example 13 A composite semipermeable membrane was obtained in the same manner as in Example 11, except that the amount of PVA3 was 1.5% by mass and the amount of divinyl sulfone was 0.1% by mass.

[0154] Example 14 A composite semipermeable membrane was obtained in the same manner as in Example 11, except that the amount of PVA3 was 0.2% by mass and the amount of divinyl sulfone was 1.5% by mass.

[0155] Example 15 A composite semipermeable membrane was obtained in the same manner as in Example 11, except that divinyl sulfone was replaced with N,N'-trimethylenebis[2-(vinylsulfonyl)acetamide].

[0156] Example 16 A composite semipermeable membrane was obtained in the same manner as in Example 15, except that vinyl alcohol copolymer 1 was used instead of PVA3.

[0157] Example 17 A composite semipermeable membrane was obtained in the same manner as in Example 15, except that vinyl alcohol copolymer 2 was used instead of PVA3.

[0158] The structures of the composite semipermeable membranes obtained in Comparative Examples 1 to 7 and Examples 1 to 17 are shown in Table 1, and their performances are shown in Tables 2 and 3. In the tables, "-" indicates that the data was judged to be noise and was not subjected to calculation.

[0159]

[0160]

[0161]

[0162] As shown in Tables 2 and 3, the composite semipermeable membranes having a coating layer containing a vinyl alcohol polymer of Examples 1 to 17 had high chemical resistance and showed sufficient membrane permeation flux even after fouling.

[0163] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2024-126511) filed on August 2, 2024, the entirety of which is incorporated by reference.

[0164] 1 Composite semipermeable membrane 2 Support membrane 3 Separation functional layer 4 Coating layer 5 Inside of convex portion T Total thickness of separation functional layer and coating layer

Claims

1. A membrane comprising a support membrane, a separation functional layer containing a crosslinked aromatic polyamide disposed on the support membrane, and a coating layer disposed on the separation functional layer, wherein the coating layer contains a vinyl alcohol-based polymer, and a surface analysis of the coating layer side by time-of-flight secondary ion mass spectrometry (TOF-SIMS) reveals that C ２ H ３ O － The peak counts derived from A, CHO ２ － The peak counts derived from B and C ６ H ３ － When the peak count number resulting from the above is defined as C, a composite semipermeable membrane satisfying 3.2≦A / C≦240 and 0.3≦B / C≦40 is provided.

2. The composite semipermeable membrane according to claim 1, which satisfies 12≦A / C≦240 and 0.3≦B / C≦40, or 3.2≦A / C≦240 and 2.5≦B / C≦40.

3. The composite semipermeable membrane according to claim 2, which satisfies 3.2≦A / C≦240 and 2.5≦B / C≦40.

4. The composite semipermeable membrane according to any one of claims 1 to 3, wherein the coating layer comprises a structure in which the vinyl alcohol polymer is crosslinked with a polyhydric aldehyde.

5. A membrane separator comprising a support membrane, a separation functional layer containing a crosslinked aromatic polyamide disposed on the support membrane, and a coating layer disposed on the separation functional layer, wherein the coating layer contains a vinyl alcohol-based polymer, and a surface analysis of the coating layer side by time-of-flight secondary ion mass spectrometry (TOF-SIMS) reveals that C ２ H ３ O － The peak counts derived from A and C ６ H ３ － The peak counts derived from ５ H ７ SO ３ － When the peak count number derived from the above is D, a composite semipermeable membrane satisfying 3.2≦A / C≦240 and 0.04≦D / C≦25 is provided.

6. The composite semipermeable membrane according to claim 5, which satisfies 12≦A / C≦240 and 0.04≦D / C≦25, or 3.2≦A / C≦240 and 0.3≦D / C≦25.

7. The composite semipermeable membrane according to claim 6, which satisfies 3.2≦A / C≦240 and 0.3≦D / C≦25.

8. The composite semipermeable membrane according to any one of claims 5 to 7, wherein the coating layer comprises a structure in which the vinyl alcohol polymer is crosslinked with polyvinyl sulfone.

9. The composite semipermeable membrane according to any one of claims 1 to 3 and 5 to 7, wherein the vinyl alcohol polymer is a vinyl alcohol copolymer containing a structure represented by the following general formula (I): [In general formula (I), X represents a divalent hydrocarbon group having 2 to 6 carbon atoms, and l, m, and n represent the number of repeating units and are integers of 1 or more.] 10. The composite semipermeable membrane according to claim 9, wherein X in said general formula (I) is a divalent hydrocarbon group having two carbon atoms.

11. The composite semipermeable membrane according to claim 10, wherein X in the general formula (I) is an ethylene group.

12. The composite semipermeable membrane according to claim 9, wherein the copolymerization ratio n / (l+m+n) in the structure represented by general formula (I) of the vinyl alcohol copolymer is 0.035 or more and 0.16 or less.

13. A composite semipermeable membrane element comprising the composite semipermeable membrane according to any one of claims 1 to 3 and 5 to 7.

14. A fluid separation device comprising the composite semipermeable membrane element according to claim 13.

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