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

Abstract

The present invention provides a method for producing a polymeric material 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, the coating layer containing a vinyl alcohol-based polymer, and a method for producing a polymeric material comprising: - The peak counts derived from A, CHO2 - The peak counts derived from B, C6H3 - When the peak count resulting from the above is defined as C, the composite semipermeable membrane satisfies 3.2≦A / C≦240 and 0.3≦B / C≦40.

Description

[Technical Field]

[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. [Background technology]

[0002] There are various technologies for removing substances (e.g., salts) dissolved in solvents (e.g., water). In recent years, membrane separation methods using semipermeable membranes such as reverse osmosis 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 occurs when substances contained in the water being treated are adsorbed onto the surface or inner pores of the 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 substance being adsorbed, 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. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 1997 / 034686 [Patent Document 2] International Publication No. 2014 / 133132 [Patent Document 3] International Publication No. 2006 / 057249 [Patent Document 4] Japanese Patent Publication No. 10-066972 Summary of the Invention [Problem to be solved by the invention]

[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 decline 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 decline 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. [Means for solving the problem]

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

[12] . [1] 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; the coating layer contains a vinyl alcohol-based polymer, In the surface analysis of the above coating layer side by time-of-flight secondary ion mass spectrometry (TOF-SIMS), C2H3O - The peak counts derived from A, CHO2 - The peak counts derived from B, C6H3 - 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 [1] above, 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 [2] above, which satisfies 3.2≦A / C≦240 and 2.5≦B / C≦40. [4] The composite semipermeable membrane according to any one of the above [1] to [3], wherein the coating layer contains 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; the coating layer contains a vinyl alcohol-based polymer, In the surface analysis of the above coating layer side by time-of-flight secondary ion mass spectrometry (TOF-SIMS), C2H3O - The peak counts derived from A, C6H3 - The peak counts derived from C, C5H7SO3 - A composite semipermeable membrane satisfying the conditions of 3.2≦A / C≦240 and 0.04≦D / C≦25, where D is the peak count resulting from the above. [6] The composite semipermeable membrane according to [5] above, 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 [6] above, which satisfies 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 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 polymer is a vinyl alcohol copolymer containing a structure represented by the following general formula (I):

[0010] [ka]

[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 the above [9], wherein X in the above general formula (I) is a divalent hydrocarbon group having 2 carbon atoms.

[11] The composite semipermeable membrane according to the above

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

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

[11] , wherein the copolymerization ratio n / (l+m+n) in the structure represented by the above 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 the above [1] to

[12] .

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

[13] above. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing the cross-sectional structure of a composite semipermeable membrane. [Figure 2] FIG. 2 is a schematic diagram showing the cross-sectional structure of a composite semipermeable membrane having a pleated separating functional layer and a coating layer, where (a) is a partially enlarged view and (b) is an enlarged view of Y in (a). DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these in any way. In this specification, "mass" is synonymous with "weight."

[0015] 1.Composite semipermeable membrane 1 is a schematic diagram showing the cross-sectional structure of a composite semipermeable membrane 1 according to this embodiment. 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 size or an asymmetrical structure in which the pore size gradually increases from one surface to the other, and in which the pore size on the surface with smaller pore size 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 favorable 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. To obtain good mechanical strength and packing density, the thickness of the support membrane is preferably 50 μm to 300 μm, more preferably 100 μm to 250 μm. 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 to 100 μm. 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 a 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 these, 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] "Multifunctional amine" refers to an amine having at least two primary amino groups and / or secondary amino groups per 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 multifunctional amines may be used alone or in combination.

[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. Among 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 carbonyl halide groups per 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, acid chlorides are preferred as the acid halide from the viewpoint of reactivity with polyfunctional amines. 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 trifunctional or higher 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 Covering layer The composite semipermeable membrane of the present invention comprises 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 a surface analysis of the coating layer side by time-of-flight secondary ion mass spectrometry (hereinafter referred to as "TOF-SIMS"), the composite semipermeable membrane according to the first embodiment was found to contain C2H3O - The peak counts derived from A, CHO2 - The peak counts derived from B, C6H3 - When the peak count resulting from the above is defined as C, the conditions satisfy 3.2≦A / C≦240 and 0.3≦B / C≦40.

[0035] where C2H3O - , CHO2 - , C6H3 - are mainly derived from fragments of the structures represented by the following formulas (II), (III), and (IV), respectively.

[0036] [ka]

[0037] [ka]

[0038] [ka]

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

[0040] The structure represented by formula (II) above is derived from a structure (C2H4O) containing a hydroxyl group of the vinyl alcohol polymer contained in the coating layer. The structure represented by formula (III) above is derived from an acetal structure (CHO2) formed by the reaction of a hydroxyl group of the vinyl alcohol polymer with a crosslinking agent. The structure represented by formula (IV) above is derived from an aromatic ring structure (C6H3) forming a crosslinked structure in the crosslinked aromatic polyamide contained on the surface of the separation functional layer. 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. Note that the structure shown in formula (IV) above is an example of an aromatic ring structure (C6H3), and the aromatic ring 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, resulting in 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, resulting in a composite semipermeable membrane with sufficient membrane permeation flux. 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] Because the information depth of TOF-SIMS is a few nanometers or less, as the thickness of the coating layer increases, the peak count C, which is mainly due to the crosslinked aromatic polyamide structure (C6H3) on the surface of the separation functional layer, decreases. In other words, C is also affected by the thickness of the coating layer, and an A / C of 240 or less means that 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 higher, 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, sustained 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 more preferable that 5.5≦A / C≦200 and 2.5≦B / C≦40 are satisfied, it is even more preferable that 12≦A / C≦170 and 2.5≦B / C≦26 are satisfied, and it is particularly preferable that 70≦A / C≦140 and 4.5≦B / C≦22 are satisfied.

[0047] In the composite semipermeable membrane according to the second embodiment, a surface analysis of the coating layer side by TOF-SIMS revealed that the - The peak counts derived from A, C6H3 - The peak counts derived from C, C5H7SO3 - When the peak count number resulting from the above is defined as D, the conditions satisfy 3.2≦A / C≦240 and 0.04≦D / C≦25.

[0048] where C5H7SO3 - is mainly derived from a fragment of the structure represented by the following formula (V).

[0049] [ka]

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

[0051] The structure represented by the above formula (V) is derived from the structure (C5H9SO3) generated by the reaction of the hydroxyl group of the vinyl alcohol polymer with the crosslinking agent.

[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 the D / C is 0.04 or higher, 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 makes the coating layer less susceptible to deterioration even after acid cleaning, resulting in a composite semipermeable membrane with better, sustained fouling resistance.

[0055] Furthermore, if the vinyl alcohol polymer in the coating layer is not excessively crosslinked by the crosslinking agent, i.e., if the D / C is 25 or less, a sufficient number of hydroxyl groups of the vinyl alcohol polymer in the coating layer will be 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 the 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, the 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 both excellent fouling resistance, sustained fouling resistance, acid resistance, alkali resistance, and oxidation resistance, 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 more preferable that 5.5≦A / C≦200 and 0.3≦D / C≦25 are satisfied, it is even more preferable that 12≦A / C≦170 and 0.3≦D / C≦16 are satisfied, and it is particularly preferable that 70≦A / C≦140 and 1.0≦D / C≦12 are satisfied.

[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-based polymer used in the coating layer is preferably 82.0 mol% to 99.8 mol%, more preferably 86.0 mol% to 99.5 mol%. When the saponification degree of the vinyl alcohol-based polymer is 82.0 mol% or more, i.e., when the vinyl alcohol-based polymer has more hydroxyl groups, the intermolecular hydrogen bonds of the vinyl alcohol-based polymer and the hydrogen bonds with the crosslinked aromatic polyamide are stronger, resulting in 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-based polymer is 99.8 mol% or less, the vinyl alcohol-based polymer has sufficient water solubility, and the coating layer can be easily formed on the separation functional layer using an aqueous solution of the vinyl alcohol-based polymer 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 degree of polymerization of the vinyl alcohol polymer is 100 or more, it is easy to provide a coating layer with a sufficient thickness, and a composite semipermeable membrane exhibiting excellent fouling resistance can be obtained. On the other hand, when the degree of polymerization of the vinyl alcohol polymer is 1,500 or less, it is possible to suppress the permeation resistance due to the thickness of the coating layer, and a composite semipermeable membrane with sufficient membrane permeation flux can be obtained.

[0063] The vinyl alcohol 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 polymers having functional groups other than hydroxyl groups and acetate groups include modified PVA in which hydroxyl groups are modified to carbonyl groups such as carboxyl groups and acetoacetyl groups, vinylpyrrolidone, and vinyl alcohol copolymers copolymerized with olefin units, etc. 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] [ka]

[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] Vinyl alcohol copolymers containing the structure represented by the general formula (I) exhibit not only the intermolecular hydrogen bonding between hydroxyl groups exhibited by PVA, but also hydrophobic interactions between hydrocarbons. Therefore, compared with PVA, vinyl alcohol copolymers have stronger intermolecular interactions, are less susceptible to changes in their higher-order structure, and are 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 general formula (I), examples of the divalent hydrocarbon group having 2 to 6 carbon atoms represented by X include an ethylene group (-CHCH-), an ethylidene group (-CH(CH)-), a vinylene group (-CH=CH-), a trimethylene group (-CHCHCH-), a propylene group (-CH(CH)CH-), a tetramethylene group (-CH(CH)CH-), a cyclopentylene group, and a hexamethylene group (-CH(CH)CH-). X in the general formula (I) is preferably a divalent hydrocarbon group having 2 carbon atoms. When X in the 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 general formula (I) is preferably a divalent saturated hydrocarbon group having 2 to 6 carbon atoms. When X in the 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 or the like can be formed. Of these, from the viewpoint of ease of availability, it is particularly preferable that X in the general formula (I) is an ethylene group.

[0069] In the vinyl alcohol copolymer containing the structure represented by the general formula (I), the copolymerization ratio (n / (l+m+n)) in 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, making it possible to easily form a coating layer on the separation functional layer using an aqueous solution of the vinyl alcohol copolymer 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 polyaldehyde. Examples of polyaldehydes 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 the polyaldehyde. Therefore, vinyl alcohol-based polymers can be crosslinked with each other with the polyaldehyde. Furthermore, the polyaldehyde can crosslink the terminal amino groups of the vinyl alcohol-based polymer and the crosslinked aromatic polyamide, thereby fixing the coating layer to the crosslinked polyamide. Among these, glutaraldehyde is particularly preferred as the polyaldehyde due to its good reactivity with the 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 the above formula (V) 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 good reactivity with the vinyl alcohol polymer.

[0073] The presence of a structure crosslinked by a polyaldehyde or a polyvinyl sulfone in a vinyl alcohol polymer can be confirmed by confirming fragments 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 a 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 inside 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 pleated shapes 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 the slightest protrusions are observed in the separating functional layer during TEM observation, it is determined that the separating functional layer has pleated shapes.

[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 is 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 is 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 removal 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. The membrane permeation flux F0 of the composite semipermeable membrane is preferably 1.10 m / d or more, more preferably 1.15 m / d or more, and even more preferably 1.30 m / d or more. 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] Furthermore, the membrane permeation flux F1 after fouling of the composite semipermeable membrane 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. Furthermore, the ratio of the membrane permeation flux F1 after fouling to the membrane permeation flux F0 of the composite semipermeable membrane (hereinafter referred to as "F1 / F0") is preferably 0.6 or more, more preferably 0.7 or more, and even more preferably 0.8 or more. When the membrane performance of the composite semipermeable membrane after fouling is within the above range, it can be preferably used as a composite semipermeable membrane with excellent fouling resistance. The fouling conditions are as described in the "Membrane permeation flux after fouling" section of the Examples described below.

[0080] The NaCl rejection rate of the composite semipermeable membrane according to this embodiment after contact with an oxidant 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 oxidant is within the above range, it can be preferably used as a composite semipermeable membrane with a low risk of oxidative degradation due to oxidant leakage. The conditions for contact with an oxidant are as described in the "Oxidant 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 later.

[0083] Furthermore, in the composite semipermeable membrane according to this embodiment, the ratio (hereinafter referred to as "F3 / F2") of the membrane permeation flux F3 after fouling in the composite semipermeable membrane after the membrane deterioration test (the membrane permeation flux F3 after the composite semipermeable membrane is subjected to a membrane deterioration test and then further subjected to fouling) to the membrane permeation flux F2 of the composite semipermeable membrane after the membrane deterioration test 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 with sustained excellent anti-fouling properties.

[0084] 2. Manufacturing method of composite semipermeable membrane The method for producing the composite semipermeable membrane according to this embodiment is not particularly limited as long as a composite semipermeable membrane satisfying the above-mentioned desired characteristics can be obtained, but for example, it can be produced by the following method.

[0085] 2.1 Preparation of the support film The support membrane can be formed by any known method. 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, PSf is dissolved in a good solvent for PSf to prepare a stock solution for the porous support layer, such as N,N-dimethylformamide (hereinafter, "DMF").

[0087] The concentration of PSf in the stock solution for 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 for 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 for 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 for the porous support layer applied to the surface of the substrate with a coagulation bath containing a non-solvent for PSf, the stock solution for the porous support layer is coagulated by non-solvent-induced phase separation, resulting in 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." From the standpoints of productivity and performance, interfacial polymerization is the most preferable polymerization method. 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 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 to 20% by mass, more preferably 0.5% by mass to 15% by mass, and even more preferably 1.0% by mass to 10% by mass. When the concentration of the polyfunctional aromatic amine is 0.1% by mass or more, a separation functional layer having good 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 the polymerization can be suppressed. Furthermore, the organic solvent solution may contain compounds such as surfactants 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 membrane that has been contacted with the aqueous polyfunctional aromatic amine solution. Specifically, for example, a method can be used in which the organic solvent solution of polyfunctional aromatic acid halide is coated on the support membrane that has been contacted with the aqueous polyfunctional aromatic amine solution. The contact time between the support membrane 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 or more and 10 minutes or less, more preferably 5 seconds or more and 3 minutes or less.

[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 to 180°C, more preferably 50°C to 160°C, and even more preferably 60°C to 150°C. The optimal heating time varies depending on the temperature of the membrane surface, which is the reaction site, but is preferably 5 seconds or more, more preferably 10 seconds or more.

[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 fan, 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 hot water temperature can be appropriately adjusted depending on the polyfunctional aromatic amine or polyfunctional aromatic acid halide used.

[0106] 2.3 Formation of the coating layer As an example of a method for forming a coating layer, a method in which a solution containing a vinyl alcohol-based 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-based polymer will be described.

[0107] The coating layer formation process includes the steps of (e) contacting the separation functional layer with a solution containing a vinyl alcohol polymer and a crosslinking agent, (f) bonding the vinyl alcohol 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 upon contact with the solution, it is preferable to use water as a solvent for dissolving the vinyl alcohol polymer and the crosslinking agent. Furthermore, an additive may be used to improve the solubility of the vinyl alcohol polymer.

[0109] The concentration of the vinyl alcohol 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 polymer is 0.05% by mass or more, a coating layer with 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 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 with 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. Specific examples include a method of immersing a laminate of a support membrane and a separation functional layer in the solution, and a method of coating the solution onto the separation functional layer. When coating the solution onto the separation functional layer, the amount of the solution is 15 ml / m. 2More than 120ml / m 2 Less than 35 ml / m is preferred 2 More than 100ml / m 2 The contact time between the separation functional layer and the solution is preferably 1 second or more and 10 minutes or less, and more preferably 3 seconds or more and 3 minutes or less.

[0113] In step (f), the vinyl alcohol polymer is bonded to the crosslinked aromatic polyamide of the separating functional layer via a crosslinking agent, thereby immobilizing the polymer. Although the immobilization of the vinyl alcohol polymer may proceed naturally after the contact in step (e) without any special operation, heating is preferred for step (f). For example, heating may be performed by blowing hot air onto the solution and the composite semipermeable membrane 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, thereby immobilizing the vinyl alcohol polymer in the separating functional layer. On the other hand, when the hot air temperature is 100°C or lower, rapid crosslinking reaction is suppressed, a uniform coating layer can be formed, and the degree of shrinkage of the composite semipermeable membrane is not increased, maintaining a good membrane permeation flux.

[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 composite semipermeable membranes 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 formed therein 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 higher the solute removal rate. However, considering the increased energy required for operation and the durability of the composite semipermeable membrane, the operating pressure when the water to be treated passes 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, when using 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, because operation under high pH conditions may cause deterioration of the composite semipermeable membrane, it is preferable to operate in the neutral range. [Example]

[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") prepared at a NaCl concentration of 2,000 mg / L, 25°C, and pH 7 was supplied to a composite semipermeable membrane with a diameter of 75 mm at an operating pressure of 1.55 MPa. Cross-flow filtration was carried out for 2 hours, and then the permeated water was collected for 15 minutes. The amount of permeated water (m 3 ) and the unit membrane area (m 2 ) was converted to a value per unit time (d), and the membrane permeation flux F0 (m / d) or the membrane permeation flux F2 (m / d) of the composite semipermeable membrane after the membrane deterioration test was calculated.

[0124] <NaCl Removal Rate> In the membrane filtration test of the above-mentioned "membrane permeation flux", the electrical conductivity of the evaluation water and the permeated water was measured using a multi-water quality meter (manufactured by Toa DKK Corporation, MM-60R), and the respective NaCl concentrations (practical salinity) were measured. From the obtained NaCl concentrations, the NaCl removal rate (%) was calculated based on the following formula. The value rounded to the third decimal place was used. NaCl removal rate (%) = 100 × {1 - (NaCl concentration in permeated water / NaCl concentration in evaluation water)}

[0125] <Membrane Permeation Flux after Fouling> For the composite semi-permeable membrane, the evaluation water added with polyoxyethylene (10) octyl phenyl ether at a concentration of 50 mg / L was supplied under the conditions described in the above-mentioned "membrane permeation flux" and operated for 30 minutes. Then, the permeated water was collected for 15 minutes. From the obtained permeated water, the membrane permeation flux F1 (m / d) after fouling or the membrane permeation flux F3 (m / d) after fouling in the composite semi-permeable membrane after the membrane deterioration test was calculated by the same calculation method as in the above-mentioned "membrane permeation flux".

[0126] <Alkali Contact>​​​​​​​​​​​​​​​​​​​For the composite semipermeable membrane, the above-mentioned "alkali contact", "acid contact", "oxidizing agent contact", "alkali contact", and "acid contact" were carried out in this order, and the NaCl removal rate (%) was calculated by the method described in the above-mentioned "NaCl removal rate" at each stage.

[0130] <TOF-SIMS measurement> The composite semipermeable membrane was cut out into a 3 cm × 3 cm square and immersed in distilled water at 25°C for 24 hours. The immersed composite semipermeable membrane was dried to a water content of 0.1% or less. Using the surface on the coating layer side of the obtained composite semipermeable membrane as the measurement surface, TOF-SIMS was measured under the following conditions. The obtained C2H3O - , CHO2 - , C6H3 - , C5H7SO3 - The peak counts derived from were designated as A, B, C, and D, respectively, and A / C, B / C, and D / C were calculated. For B and D, when the peak count was 1.0×10 3 or less, they were judged as noise respectively, and the subsequent calculations were not performed. Also, the significant figures of the calculated values were taken as two digits. Measuring device: TOF.SIMS5 manufactured by ION-TOF Raster size: 300 μm Number of scans: 12 Number of pixels (one side): 256 Measurement vacuum degree: 4×10 -7 Pa or less Primary ion: Bi3 ++ Primary ion acceleration voltage: 30 kV Pulse width: 11.7 ns Punching: Yes Charge neutralization: Yes Post-stage acceleration: 9.5 kV Secondary ion polarity: Negative

[0131] <Total thickness T of the separation functional layer and the 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 ultrathin sections were cut using a microtome to prepare measurement samples. The obtained samples were 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 images 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. Ten randomly selected convex portions were measured at five points per convex portion, and the average value of a total of 50 points was used as the total thickness T (nm) of the separation functional layer and coating layer.

[0132] <Weight average molecular weight> The weight-average molecular weight (in terms of polystyrene) of PSf was measured by gel permeation chromatography under the following specific measurement conditions: Measuring device: Tosoh Corporation HLC-8022 Column: TSKgel (registered trademark) SuperHM-H (manufactured by Tosoh Corporation, inner diameter 6.0 mm, length 15 cm) x 2 Eluent: LiBr / N-methylpyrrolidone solution (10 mmol / L) Sample concentration: 0.1% by mass Flow rate: 0.5mL / min Temperature: 40℃

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

[0134] [Comparative Example 1] A stock solution for the porous support layer was prepared by dissolving 15% by mass of PSf and 85% by mass of DMF at 100°C. This stock solution for the porous support layer was applied to the surface of a polyester long-fiber nonwoven fabric at 25°C. After 3 seconds, the fabric 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 resulting support membrane was 30 μm. The resulting support membrane was then immersed in a 3% by mass aqueous solution of m-PDA for 2 minutes, slowly lifted vertically, and nitrogen was sprayed from an air nozzle to remove excess aqueous solution from the support membrane surface. In a controlled environment at 25°C, 20 ml of a 25°C n-decane solution containing 0.12% by mass of TMC was applied to the support membrane surface so that it was completely wet, and the membrane was left standing for 1 minute to form a separation functional layer by interfacial polymerization. The resulting membrane was then held vertically for 30 seconds to drain and remove excess solution, and then washed with 80°C hot water 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, followed by immersion 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 mass% of PVA1 (saponification degree 99.5 mol%, polymerization degree 2,600) in an environment controlled at 20°C. With the aqueous solution remaining on the surface of the separation functional layer, the membrane was held at 100°C for 5 minutes, and then the solution was again brought into contact with the membrane and held at 130°C for 5 minutes, forming a coating layer on the separation functional layer. The membrane was then washed with water at 20°C for 2 minutes. Finally, the composite semipermeable membrane was immersed in a 14 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 excess aqueous solution was drained off, and hot air at 80°C was blown onto it for 2 minutes to form a coating layer on the separation functional layer. It was then 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 The composite semipermeable membrane was contacted with the solution for 5 seconds. While the aqueous solution remained 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. The composite semipermeable membrane was then held vertically 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 hot air at 80°C was blown onto it for 2 minutes to form a coating layer on the separation functional layer. It was then 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.

[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 temperature 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 was blown at 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 2 of an aqueous solution containing 0.5 mass % of PVA3, 0.3 mass % of divinyl sulfone, and 0.1 mol / L of sodium hydroxide solution in an environment controlled at 20°C. 2 The composite semipermeable membrane was then placed vertically to remove 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 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 temperature 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 calculations.

[0159] [Table 1]

[0160] [Table 2]

[0161] [Table 3]

[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 entire contents of which are incorporated by reference. [Explanation of symbols]

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

Claims

1. a support membrane; a separation functional layer including a crosslinked aromatic polyamide disposed on the support membrane; and a coating layer disposed on the separation functional layer; the coating layer contains a vinyl alcohol-based polymer, 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 － 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, wherein 3.2≦A / C≦240 and 2.5≦B / C≦40 are satisfied.

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

5. a support membrane; a separation functional layer including a crosslinked aromatic polyamide disposed on the support membrane; and a coating layer disposed on the separation functional layer; the coating layer contains a vinyl alcohol-based polymer, 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 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, wherein 3.2≦A / C≦240 and 0.3≦D / C≦25 are satisfied.

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): 【Chemistry 1】 [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. 10. The composite semipermeable membrane according to claim 9, wherein X in the general formula (I) is a divalent hydrocarbon group having 2 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 the 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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