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

Abstract

The present application provides a composite semipermeable membrane having excellent friction resistance and good water permeability. The composite semipermeable membrane of the present application has a support membrane, a separation functional layer containing crosslinked polyamide, and a coating layer disposed on the separation functional layer, the spread area ratio Sdr of the coating layer side surface is 60 to 200%, and the static friction coefficient μs of the coating layer side surface and a polishing film abrasive material having a particle size of #2000 is 0.40 to 1.30.

Description

Technical Field

[0001] This invention relates to composite semipermeable membranes, composite semipermeable membrane assemblies, and fluid separation devices that are useful for the selective separation of liquid mixtures. Background Technology

[0002] There are various techniques for removing substances (e.g., salts) dissolved in solvents (e.g., water), but in recent years, the use of membrane separation methods using semi-permeable membranes such as reverse osmosis membranes and nanofiltration membranes has been expanding as a process to save energy and resources.

[0003] Currently commercially available reverse osmosis and nanofiltration membranes are generally composite semi-permeable membranes with a support membrane and a separation functional layer stacked on the support membrane. As the separation functional layer, cross-linked polyamides obtained through the polycondensation reaction of polyfunctional amines and polyfunctional acyl halides are known.

[0004] Such composite semi-permeable membranes, due to their thin separation functional layers, are prone to reduced separation performance due to friction within these layers. Examples of friction include contact between the composite semi-permeable membranes during post-manufacturing stacking for storage, and contact with packaging materials used for storage. Furthermore, composite semi-permeable membranes are often used as components assembled from two or more composite semi-permeable membranes and interposed flow path materials. Contact between the composite semi-permeable membranes during assembly and components of the assembly device or other components can also be cited as a cause of friction.

[0005] Various methods have been disclosed as ways to suppress the reduction in separation performance caused by such friction. For example, Patent Document 1 discloses a method to suppress friction on the separation functional layer by depositing a coating layer made of a polymer such as polyvinyl alcohol on the surface of the separation functional layer. In addition, Patent Document 2 discloses a method to suppress the generation of film defects caused by friction on the separation functional layer by ensuring that the separation functional layer has a sufficient amount of polyamide.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2003-200026

[0009] Patent Document 2: Japanese Patent Application Publication No. 2019-98329 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] While the method described in Patent Document 1 shows a certain improvement in abrasion resistance, it also suffers from a decrease in the water permeability of the composite semi-permeable membrane due to the presence of the coating layer. Furthermore, the method described in Patent Document 2 presents a trade-off between the amount of polyamide in the separation functional layer and the water permeability of the composite semi-permeable membrane.

[0012] Therefore, the purpose of this invention is to provide a composite semipermeable membrane with excellent abrasion resistance and good water permeability.

[0013] Methods for solving problems

[0014] To address the aforementioned issues, the present invention provides a composite semipermeable membrane, a composite semipermeable membrane assembly, and a fluid separation device.

[0015] [1] A composite semipermeable membrane comprising a support membrane, a separation functional layer comprising crosslinked polyamide disposed on the support membrane, and a coating layer disposed on the separation functional layer.

[0016] The unfolded area ratio (Sdr) of the coated layer side surface of the composite semi-permeable membrane is 60-200%.

[0017] The static friction coefficient μs between the coated side surface of the composite semi-permeable membrane and the polishing abrasive material with a particle size of #2000 is 0.40 to 1.30.

[0018] [2] According to the composite semipermeable membrane described in [1] above, the coefficient of dynamic friction μd between the coated side surface of the composite semipermeable membrane and the polishing abrasive material with a particle size of #2000 is 0.25 to 0.73.

[0019] [3] According to the composite semipermeable membrane described in [1] or [2] above, the root mean square height Sq of the coating layer side surface of the composite semipermeable membrane is 140 to 300 nm.

[0020] [4] The composite semipermeable membrane according to any one of [1] to [3] above, wherein the coating layer comprises at least one of a vinyl alcohol polymer and an alkylene glycol polymer.

[0021] [5] According to the composite semipermeable membrane described in [4] above, the degree of saponification of the vinyl alcohol polymer is 96 mol% or more.

[0022] [6] According to the composite semipermeable membrane described in [4] or [5] above, wherein the degree of polymerization of the vinyl alcohol polymer is 100 to 1,500.

[0023] [7] The composite semipermeable membrane according to any one of [4] to [6] above, wherein the ethylene alcohol polymer is an ethylene alcohol copolymer containing the structure represented by the following general formula (1).

[0024] [Chemical Formula 1]

[0025]

[0026] [In general formula (1), X is a divalent hydrocarbon group with 2 to 6 carbon atoms, and l, m, and n are the number of repeating units.]

[0027] [8] According to the composite semipermeable membrane described above [7], wherein X in the general formula (1) is a divalent hydrocarbon group with 2 carbon atoms.

[0028] [9] According to the composite semipermeable membrane described above [8], wherein X in the general formula (1) is 1,2-ethylene.

[0029]

[10] The composite semipermeable membrane according to any one of [7] to [9] above, wherein the copolymerization ratio of the ethylene alcohol copolymer: n / (l+m+n) is 0.035 to 0.16.

[0030]

[11] According to the composite semipermeable membrane described above [4], the molecular weight of the alkylene glycol polymer is 500 to 500,000.

[0031]

[12] A composite semipermeable membrane assembly comprising any one of [1] to

[11] a composite semipermeable membrane.

[0032]

[13] A fluid separation device comprising the composite semipermeable membrane assembly described in

[12] above.

[0033] The effects of the invention

[0034] According to the present invention, a composite semipermeable membrane with excellent abrasion resistance and good water permeability can be provided. Attached Figure Description

[0035] [ Figure 1 ] Figure 1 This is a schematic diagram showing the cross-sectional structure of the composite semipermeable membrane.

[0036] [ Figure 2 ] Figure 2 To illustrate the structure of a composite semipermeable membrane with a pleated separation functional layer and a coating layer, (a) is a partial enlarged view, and (b) is an enlarged view of the Y region in (a).

[0037] [ Figure 3 ] Figure 3 A schematic diagram illustrating a method for friction testing of a composite semipermeable membrane.

[0038] [ Figure 4 ] Figure 4Here is an example of a graph showing the static friction force Fs (N) and dynamic friction force Fd (N) obtained by friction test of a composite semipermeable membrane. Detailed Implementation

[0039] The embodiments of the present invention will be described in detail below, but the present invention is not limited to these embodiments in any way.

[0040] It should be noted that in this application specification, "mass" and "weight" have the same meaning.

[0041] 1. Composite semi-permeable membrane

[0042] Figure 1 The first embodiment shows the structure of the composite semipermeable membrane 1 in this embodiment. The composite semipermeable membrane 1 of the present invention includes a support membrane 2, a separation functional layer 3, and a coating layer 4.

[0043] (1-1) Support membrane

[0044] The composite semipermeable membrane described in this embodiment has a support membrane that has at least a porous support layer. The support membrane is used to impart strength to the composite semipermeable membrane, but it does not inherently possess solute separation properties.

[0045] The porous support layer has a large number of interconnected micropores. The pore size and pore size distribution are not particularly limited. For example, a porous support layer with a symmetrical structure obtained by uniform pore size is preferred, or an asymmetrical structure with pore size gradually increasing from one side surface to the other side surface, and the pore size of the side with smaller pore size is 0.1 to 100 nm.

[0046] As raw materials for the porous support layer, homopolymers or copolymers such as polysulfone (hereinafter also referred to as "PSf"), polyethersulfone, polyamide, polyester, cellulose polymers, vinyl polymers, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene ether can be used alone or in blends. Examples of cellulose 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, and cellulose acetate, PSf, polyphenylene sulfide sulfone, or polyphenylene sulfone are more preferred. PSf is particularly preferred due to its high chemical stability, mechanical stability, thermal stability, and ease of molding.

[0047] The weight-average molecular weight (hereinafter also referred to as "Mw") of PSf is preferably 10,000 to 200,000, more preferably 15,000 to 100,000. When the Mw of PSf is 10,000 or more, it can obtain the mechanical strength and heat resistance preferred for a porous support layer. On the other hand, when the Mw of PSf is 200,000 or less, the viscosity of the porous support layer stock solution is within an appropriate range, and good moldability can be achieved.

[0048] In addition, the support membrane may have a substrate in addition to the porous support layer.

[0049] Examples of raw materials for the base material include fabrics formed from polyester polymers, polyamide polymers, polyolefin polymers, and mixtures or copolymers thereof. Among these, fabrics made from polyester polymers with high mechanical and thermal stability are preferred. As for the form of the fabric, long-fiber nonwoven fabrics and short-fiber nonwoven fabrics are preferred, and woven or knitted fabrics are even more preferred.

[0050] The thickness of the support membrane affects the strength of the composite semi-permeable membrane and the packing density when it is fabricated into an element. To obtain good mechanical strength and packing density, the thickness of the support membrane is preferably 50–300 μm, more preferably 100–250 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 20–100 μm. It should be noted that the thickness of the support membrane can be calculated as follows: by observing a cross-section, measurements are taken at 20 μm intervals in a direction orthogonal to the thickness direction (the surface direction of the membrane), and the average thickness at 20 points is calculated.

[0051] (1-2) Separate functional layers

[0052] The separation functional layer of the composite semi-permeable membrane described in this embodiment, disposed on the support membrane, is a layer that performs the function of separating the solute and contains cross-linked polyamide. The proportion of cross-linked polyamide in the separation functional layer is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The content of cross-linked polyamide in the separation functional layer can usually be calculated by analysis using nuclear magnetic resonance (NMR).

[0053] The crosslinked polyamide is preferably a condensation polymer of a polyfunctional amine and a polyfunctional acyl chloride. Preferably, at least one of the polyfunctional amine and the polyfunctional acyl chloride comprises a compound with three or more functions. This allows for the formation of rigid molecular chains and a well-defined porous structure suitable for removing fine solutes such as hydrated ions and silica.

[0054] A polyfunctional amine is an amine having at least two primary and / or secondary amino groups in one molecule. Examples include aromatic trifunctional amines such as 1,3,5-triaminobenzene and 1,2,4-triaminobenzene; o-phenylenediamine, m-phenylenediamine (hereinafter also referred to as "m-PDA"), p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-diaminopyridine, m-diaminopyridine, p-diaminopyridine, 3,5-diaminobenzoic acid, 2,4-diaminobenzenesulfonic acid, 3-aminobenzylamine, 4-aminobenzylamine; and aliphatic difunctional amines such as ethylenediamine, propylenediamine, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, 4-aminopiperidine, and aminoethylpiperazine. These polyfunctional amines can be used alone or in combination of two or more.

[0055] From the perspective of separation performance, water permeability, and heat resistance of composite semipermeable membranes, polyfunctional amines such as m-PDA, p-phenylenediamine, or 1,3,5-triaminobenzene are preferred. Among them, m-PDA is particularly preferred from the perspective of ease of acquisition and processing.

[0056] A polyfunctional acyl chloride is an acyl chloride having at least two chlorocarbonyl groups in one molecule. Examples include aromatic trifunctional acyl chlorides such as trimesoyl chloride (hereinafter also referred to as "TMC") and trimesoyl chloride, aliphatic trifunctional acyl chlorides such as 1,3,5-cyclohexanetricarboxylate chloride, biphenyl dicarboxylate chloride, azophthaloyl chloride, terephthaloyl chloride, isophthaloyl chloride, and 2,6-naphthalenedilicate chloride, as well as aliphatic difunctional acyl chlorides such as adipyl chloride, sebacyl chloride, and 1,4-cyclohexanedicarboxylate chloride. These polyfunctional acyl chlorides can be used alone or in combination of two or more.

[0057] From the perspective of separation performance and heat resistance of composite semipermeable membranes, polyfunctional acyl chlorides are preferably polyfunctional aromatic acyl chlorides having 2 to 4 chlorocarbonyl groups in one molecule. Among them, TMC is particularly preferred from the perspective of ease of acquisition and processing.

[0058] (1-3) Covering layer

[0059] The composite semi-permeable membrane involved in this embodiment has a coating layer that serves as a protective layer for the separation functional layer and is disposed on the separation functional layer.

[0060] Regarding the composite semi-permeable membrane of the present invention, the static friction coefficient (hereinafter also referred to as "μs") between the coated layer side surface and the polishing film abrasive material with a particle size of #2000 is 0.40 to 1.30.

[0061] The coefficient of static friction is proportional to the static friction force, which prevents an object from moving from a stationary state. When μs is 1.30 or less, the static friction force experienced by the composite semipermeable membrane when it begins to slide is smaller, thus reducing damage to the separation functional layer caused by friction. On the other hand, when μs is 0.40 or more, the composite semipermeable membrane becomes less prone to sliding, thus suppressing deformation (stretching) of the wound body caused by axial displacement of the composite semipermeable membrane towards the composite semipermeable membrane element when the composite semipermeable membrane is wound into a spiral shape or when the composite semipermeable membrane element is operated. μs is preferably 0.80 to 1.30, more preferably 0.95 to 1.25, and even more preferably 1.08 to 1.20.

[0062] The static friction coefficient of the composite semipermeable membrane can be controlled, for example, by the heating temperature of the support membrane after contact with the organic solvent solution of polyfunctional acyl chloride in the polymerization process of separating the functional layers, the raw materials of the coating layer, and the concentration of water-soluble polymer in the aqueous solution used to form the coating layer.

[0063] The coefficient of dynamic friction (hereinafter also referred to as "μd") between the coated side surface of the composite semi-permeable membrane and the polishing abrasive material with a particle size of #2000 in this embodiment is preferably 0.25 to 0.73, more preferably 0.45 to 0.73, even more preferably 0.55 to 0.72, and particularly preferably 0.66 to 0.70.

[0064] The coefficient of kinetic friction is proportional to the kinetic friction force, which acts to prevent movement when an object is moving. When μd is below 0.73, the kinetic friction force experienced by the composite semipermeable membrane during sliding is reduced, thus reducing damage to the separation functional layer caused by friction. On the other hand, when μd is above 0.25, the composite semipermeable membrane is less prone to sliding, thus suppressing the stretching and contraction of the composite semipermeable membrane element.

[0065] The dynamic friction coefficient of the composite semipermeable membrane can be controlled, for example, by the heating temperature of the support membrane after contact with the organic solvent solution of polyfunctional acyl chloride in the polymerization process of separating the functional layers, the raw materials of the coating layer, and the concentration of water-soluble polymer in the aqueous solution used to form the coating layer.

[0066] The shape and thickness of the separation functional layer and the covering layer affect the separation performance and water permeability. Figure 2 A second embodiment shows the structure of the composite semi-permeable membrane 1 in this embodiment. For example... Figure 2As shown in (a) and (b), the separation functional layer 3 is preferably a pleated shape with multiple protrusions. Furthermore, it is more preferable that the interior 5 of the protrusions (between the separation functional layer 3 and the support membrane 2) is a void. The separation functional layer 3, having a pleated shape, can obtain a larger surface area than when it has a flat shape, thus achieving high water permeability while maintaining separation performance. It should be noted that the coating layer 4 can also be formed thinly on the separation functional layer 3 to form a pleated shape together with the separation functional layer, or it can have a relatively large thickness, such as when the pleated shape of the separation functional layer 3 is buried.

[0067] As an effective configuration for suppressing the performance degradation of the separation functional layer caused by friction, the shape of the coating layer side surface of the composite semipermeable membrane (the unfolded area ratio Sdr below) and the total thickness of the separation functional layer and the coating layer are described below.

[0068] The developed area ratio (hereinafter also referred to as "Sdr") of the coated layer side surface of the composite semi-permeable membrane of the present invention is 60% to 200%. The developed area ratio (Sdr) is a parameter representing the rate (%) of increase in the developed area (surface area) of a defined region relative to the area of ​​the defined region. The smaller this value, the closer the surface shape is to a flat surface; a completely flat surface has an Sdr of 0%. On the other hand, the larger the value, the more uneven the surface shape. When Sdr is 60% or higher, the surface area of ​​the composite semi-permeable membrane increases, thus enabling the acquisition of a composite semi-permeable membrane with good water permeability. However, when Sdr is 60% or higher, i.e., when the surface of the separation functional layer has more unevenness, the protrusions of the separation functional layer are easily damaged by abrasion, thus generally resulting in lower abrasion resistance of the composite semi-permeable membrane. Here, the inventors of this application have discovered that even when Sdr is set to 60-200%, a composite semi-permeable membrane exhibiting good abrasion resistance can be obtained by making the static friction coefficient μs between the coated layer side surface of the composite semi-permeable membrane and the polishing abrasive material with a particle size of #2000 0.40-1.30. Sdr is preferably 70-180%, and more preferably 80-150%.

[0069] Regarding the unfolded area ratio of the composite semipermeable membrane, it can be controlled, for example, by the heating temperature of the support membrane after contact with the organic solvent solution of polyfunctional acyl chloride in the polymerization process of separating the functional layers, and the concentration of the water-soluble polymer in the aqueous solution used to form the coating layer.

[0070] The root mean square height (hereinafter also referred to as "Sq") of the coated layer side surface of the composite semi-permeable membrane according to this embodiment is preferably 140-300 nm, more preferably 145-270 nm, and even more preferably 150-240 nm. When Sq is 140 nm or more, a composite semi-permeable membrane with good water permeability can be obtained in proportion to the large surface area of ​​the composite semi-permeable membrane. On the other hand, when Sq is 300 nm or less, a composite semi-permeable membrane exhibiting good abrasion resistance can be obtained.

[0071] Regarding the root mean square height of the coating layer side surface of the composite semipermeable membrane, it can be controlled, for example, by the heating temperature of the support membrane after contact with the organic solvent solution of polyfunctional acyl chloride in the polymerization process of separating the functional layer, the concentration of the water-soluble polymer in the aqueous solution used to form the coating layer, etc.

[0072] The total thickness T of the separation functional layer and the coating layer is preferably 10–100 nm, more preferably 11–70 nm, and even more preferably 11–20 nm. When the total thickness T of the separation functional layer and the coating layer is 10 nm or more, a composite semi-permeable membrane exhibiting good separation performance and abrasion resistance 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 semi-permeable membrane with good water permeability can be obtained. Figure 2 As shown in (b), the so-called "total thickness T" refers to the thickness from the inside 5 of the protrusion to the outside when the separating functional layer 3 and the covering layer 4 overlap and become one, and the separating functional layer and the covering layer form a folded shape with multiple hollow protrusions.

[0073] To prevent the target substance from penetrating into the interior of the composite semi-permeable membrane, the separation functional layer and the coating layer are preferably configured on the primary filtration side.

[0074] The coating layer of the composite semi-permeable membrane according to this embodiment preferably comprises a water-soluble polymer. Here, "water-soluble polymer" refers to a polymer that dissolves in water at 25°C at a concentration of 0.5% by mass or more. The proportion of the water-soluble polymer in the coating layer is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. By including a water-soluble polymer, in the "(2-3) coating layer formation step" described later, the coating layer can be easily formed on the separation functional layer using an aqueous solution of the water-soluble polymer. In addition, water-soluble polymers generally have excellent hydrophilicity, which can suppress the reduction in water permeability caused by the coating layer, thus enabling the acquisition of a composite semi-permeable membrane with sufficient water permeability.

[0075] It should be noted that the proportion of water-soluble polymers in the coating layer can usually be calculated using nuclear magnetic resonance analysis.

[0076] Examples of water-soluble polymers include polyacrylic acid, polymethacrylic acid, polyvinylpyrrolidone, vinyl alcohol polymers, polyethyleneimine, polyallylamine, polyacrylamide, poly(N-isopropylacrylamide), polyacrylamide morpholine, poly(2-ethyl-2-oxazoline), alkylene glycol polymers, polyvinylimidazolium, polystyrene sulfonic acid and other synthetic polymers and their copolymers, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose and other cellulose derivatives, gelatin, casein and other proteins, dextrin, etherified starch and other starches. These water-soluble polymers can be used alone or in combination of two or more.

[0077] From the viewpoints of separation performance, water permeability, and abrasion resistance of the composite semipermeable membrane, the water-soluble polymer is preferably at least one of a vinyl alcohol-based polymer and an alkylene glycol-based polymer, more preferably a vinyl alcohol-based polymer. By coating the composite semipermeable membrane with a coating layer containing at least one of a vinyl alcohol-based polymer and an alkylene glycol-based polymer, damage caused by friction of the separation functional layer can be suppressed. Furthermore, the hydroxyl groups of the vinyl alcohol-based polymer form hydrogen bonds with the crosslinked polyamide of the composite semipermeable membrane, thus the coating layer containing the vinyl alcohol-based polymer is not easily peeled off from the crosslinked polyamide, which is suitable for protecting the crosslinked polyamide from frictional damage. Therefore, the composite semipermeable membrane can be endowed with abrasion resistance.

[0078] The degree of saponification of the vinyl alcohol-based polymer included in the coating layer of this embodiment is preferably 96 mol% or more, more preferably 98 mol% or more. When the degree of saponification of the vinyl alcohol-based polymer is 96 mol% or more, the vinyl alcohol-based polymer has more hydroxyl groups, which form strong hydrogen bonds with the crosslinked polyamide of the composite semipermeable membrane, thus imparting excellent abrasion resistance to the composite semipermeable membrane.

[0079] The degree of polymerization of the vinyl alcohol-based polymer included in the coating layer according to this embodiment is preferably 100 to 1,500, more preferably 200 to 1,200. When the degree of polymerization of the vinyl alcohol-based polymer is 100 or more, a coating layer with sufficient thickness can be formed, and a composite semi-permeable membrane exhibiting excellent abrasion resistance can be obtained. On the other hand, when the degree of polymerization of the vinyl alcohol-based polymer is 1,500 or less, the permeation resistance caused by the thickness of the coating layer can be suppressed, and a composite semi-permeable membrane with sufficient water permeability can be obtained. In addition, by keeping the degree of polymerization within the above range, and ensuring that the vinyl alcohol-based polymer has sufficient water solubility, 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 later.

[0080] Furthermore, the vinyl alcohol polymer can be polyvinyl alcohol (hereinafter also referred to as "PVA") having only hydroxyl and acetic acid groups as functional groups, or it can have other functional groups besides these. Examples of vinyl alcohol polymers having functional groups other than hydroxyl and acetic acid groups include modified PVA with hydroxyl groups modified to carbonyl groups such as carboxyl or acetoacetyl groups, and vinyl alcohol copolymers copolymerized with vinylpyrrolidone, olefin units, etc. Among these, vinyl alcohol copolymers (hereinafter also simply referred to as "vinyl alcohol copolymers") containing the structure represented by the following general formula (1) are particularly preferred.

[0081] [Chemical Formula 2]

[0082]

[0083] In general formula (1), X is a divalent hydrocarbon group with 2 to 6 carbon atoms, and l, m and n are the number of repeating units.

[0084] The ethylene alcohol copolymer may also contain structures other than those represented by the above general formula (1). The proportion of the structure represented by general formula (1) in the ethylene alcohol copolymer is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably formed solely by the structure represented by the above general formula (1). The proportion of the structure represented by general formula (1) in the ethylene alcohol copolymer can usually be calculated by analysis using nuclear magnetic resonance (NMR).

[0085] For ethylene alcohol copolymers containing the structure represented by the above general formula (1), in addition to the intermolecular hydrogen bonds between hydroxyl groups as exhibited by PVA, hydrophobic interactions between hydrocarbons are also observed. Therefore, compared to PVA, the intermolecular interactions are stronger, making it less prone to changes in higher-order structures and easier to maintain hydrogen bonds with crosslinked polyamides. Furthermore, it is known that, compared to PVA, the ethylene alcohol copolymer represented by the above general formula (1) can form a film with excellent smoothness and a low coefficient of friction. Therefore, by using ethylene alcohol copolymers in the coating layer, a composite semi-permeable membrane with low risk of degradation due to friction and good abrasion resistance can be obtained.

[0086] In the above general formula (1), the divalent hydrocarbon group having 2 to 6 carbon atoms as X can be exemplified by, for example, 1,2-ethylene (-CH2CH2-), 1,1-ethylene (-CH(CH3)-), 1,2-vinylene (-CH=CH-), trimethylene (-CH2CH2CH2-), 1,2-propylene (-CH(CH3)CH2-), tetramethylene (-CH2(CH2)2CH2-), cyclopentyl, hexamethylene (-CH2(CH2(CH2)4), etc. X in the above general formula (1) is preferably a divalent hydrocarbon group having 2 carbon atoms. The above general formula... When X in (1) is a divalent hydrocarbon group with 2 carbon atoms, the ethylene alcohol copolymer has sufficient water solubility, and the coating layer can be easily formed on the separation functional layer using an aqueous solution of the ethylene alcohol copolymer in the "(2-3) coating layer formation process" described later. Furthermore, X in the above general formula (1) is preferably a divalent saturated hydrocarbon group with 2 to 6 carbon atoms. When X in the above general formula (1) is a divalent saturated hydrocarbon group with 2 to 6 carbon atoms, a coating layer that is not easily degraded by oxidation, etc., can be formed. From the viewpoint of ease of acquisition, X in the above general formula (1) is particularly preferably 1,2-ethylene.

[0087] The copolymerization ratio of the ethylene alcohol copolymer containing the structure represented by the above general formula (1), n / (l+m+n), is preferably 0.035 to 0.16, more preferably 0.040 to 0.11, and even more preferably 0.042 to 0.095. When the copolymerization ratio is 0.035 or higher, the ethylene alcohol copolymer exhibits strong intermolecular interactions through sufficient hydrophobic interactions, and a composite semipermeable membrane with good abrasion resistance can be obtained. On the other hand, when the copolymerization ratio is 0.16 or lower, the ethylene 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 ethylene alcohol copolymer in the "(2-3) coating layer formation process" described later. It should be noted that the copolymerization ratio can usually be calculated by analysis using nuclear magnetic resonance (NMR).

[0088] The degree of polymerization of the ethylene alcohol copolymer (l+m+n) is preferably 100 to 1,500, more preferably 200 to 1,200. When the degree of polymerization of the ethylene alcohol copolymer is 100 or higher, a coating layer with sufficient thickness can be formed, and a composite semipermeable membrane exhibiting excellent abrasion resistance can be obtained. On the other hand, when the degree of polymerization of the ethylene alcohol copolymer is 1,500 or lower, the permeation resistance caused by the thickness of the coating layer can be suppressed, and a composite semipermeable membrane with sufficient water permeability can be obtained. In addition, when the degree of polymerization is within the above range, the ethylene alcohol copolymer has sufficient water solubility, and the coating layer can be easily formed on the separation functional layer using an aqueous solution of the ethylene alcohol copolymer in the "(2-3) Coating Layer Formation Step" described later.

[0089] The molecular weight of the alkylene glycol polymer included in the coating layer according to this embodiment is preferably 500 to 500,000, more preferably 700 to 100,000, and even more preferably 800 to 10,000. When the degree of polymerization of the alkylene glycol polymer is 500 or more, a coating layer with sufficient thickness can be provided, and a composite semipermeable membrane exhibiting excellent abrasion resistance can be obtained. On the other hand, when the degree of polymerization of the alkylene glycol polymer is 500,000 or less, the reduction in water permeability caused by the thickness of the coating layer can be suppressed, and a composite semipermeable membrane with sufficient water permeability can be obtained.

[0090] Furthermore, the alkylene glycol polymer preferably has functional groups at its ends, such as carboxyl, amino, acetoacetyl, or glycidyl groups, which can react with the functional groups of the crosslinked polyamide. By having these functional groups at the ends of the alkylene glycol polymer, a coating layer can be easily formed on the separation functional layer using an aqueous solution of the alkylene glycol polymer.

[0091] The water-soluble polymer contained in the coating layer is preferably made insoluble to prevent leaching when the composite semipermeable membrane is used. Examples of methods for making the water-soluble polymer in the coating layer insoluble include: forming non-covalent bonds such as hydrogen bonds and ionic bonds between the water-soluble polymer and cross-linked polyamide and fixing it onto the separation functional layer; forming covalent bonds between the water-soluble polymer and cross-linked polyamide through reactions of functional groups or cross-linking based on a cross-linking agent and fixing it onto the separation functional layer; forming covalent bonds between the water-soluble polymer and cross-linked polyamide through cross-linking based on a cross-linking agent and forming a three-dimensional structure to achieve insolubility; and so on. From the viewpoint of enabling long-term, stable operation, methods that form covalent bonds between the water-soluble polymer and cross-linked polyamide through reactions of functional groups or cross-linking based on a cross-linking agent and fix it onto the separation functional layer are more preferred.

[0092] (1-4) NaCl removal rate, membrane permeation flux

[0093] The NaCl removal rate of the composite semi-permeable 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. Furthermore, the membrane permeation flux during the manufacture of the composite semi-permeable membrane is preferably 1.00 m / d or more, more preferably 1.15 m / d or more, and even more preferably 1.30 m / d or more. By ensuring the membrane performance of the composite semi-permeable membrane is within the above range, it can be preferably used as a separation membrane for separating salts and the like.

[0094] Furthermore, the NaCl removal rate of the composite semipermeable membrane after the friction test is preferably 99.25% or higher, more preferably 99.35% or higher, and even more preferably 99.40% or higher. By ensuring that the membrane performance of the composite semipermeable membrane after the friction test is within the above range, it can be preferably used as a composite semipermeable membrane with excellent friction resistance. The friction test method is as described in "(3) Friction Test and Friction Coefficient" below.

[0095] 2. Manufacturing method of composite semi-permeable membrane

[0096] Regarding the manufacturing method of the composite semipermeable membrane involved in this embodiment, there are no particular limitations as long as a composite semipermeable membrane that satisfies the above-described desired characteristics can be obtained. For example, it can be manufactured by the following method.

[0097] (2-1) Fabrication of the support membrane

[0098] As a method for fabricating a support membrane, known methods can be appropriately utilized. The following explanation will take the case where PSf is used as the raw material for the porous support layer as an example.

[0099] First, PSf is dissolved in a good solvent to prepare a porous support layer stock solution. A good solvent for PSf is preferably N,N-dimethylformamide (hereinafter also referred to as "DMF").

[0100] The concentration of PSf in the porous support layer stock solution is preferably 10-25% by mass, more preferably 12-20% by mass. By keeping the concentration of PSf in the porous support layer stock solution within the above range, both the strength and permeability of the obtained porous support layer can be considered. It should be noted that the preferred range of the concentration of raw materials in the porous support layer stock solution can be appropriately adjusted according to the raw materials, good solvents, etc. used.

[0101] Next, the obtained porous support layer solution is coated onto the substrate surface and immersed in a coagulation bath containing PSf non-solvent.

[0102] Water is preferred, for example, as a non-solvent for PSf contained in the coagulation bath. By contacting the porous support layer stock solution coated on the substrate surface with the coagulation bath containing the non-solvent PSf, the porous support layer stock solution is coagulated due to non-solvent-induced phase separation, thereby obtaining a support film with a porous support layer formed on the substrate surface.

[0103] The coagulation bath can consist of only non-solvent PSf, or it can contain a good solvent of PSf within the range that can coagulate the porous support layer stock solution.

[0104] The residual solvent in the support membrane can be removed by cleaning the obtained support membrane before forming the separation functional layer.

[0105] (2-2) Polymerization process for separating functional layers

[0106] Next, a separation functional layer containing cross-linked polyamide is formed on the support film.

[0107] Regarding the method for forming a separation functional layer containing crosslinked polyamide, an example will be described using a method of polymerizing and curing a polyfunctional amine with a polyfunctional acyl chloride on a support film obtained in "(2-1) Film Formation of Support Film". From the viewpoint of productivity and performance, interfacial polymerization is the most preferred polymerization method. The steps of interfacial polymerization will be described below.

[0108] The interfacial polymerization process includes: (a) contacting an aqueous solution containing a polyfunctional amine with a support membrane; (b) contacting an organic solvent solution containing a polyfunctional acyl chloride with the support membrane after contacting the aqueous solution containing the polyfunctional amine; (c) dehydrating the organic solvent solution after contact; and (d) cleaning the composite semipermeable membrane after dehydrating the organic solvent solution with hot water.

[0109] In step (a), the aqueous solution contains at least a polyfunctional amine. Examples of polyfunctional amines include those exemplified in “(1-2) Separation of functional layers”.

[0110] The concentration of the polyfunctional amine in the aqueous solution is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, and even more preferably 1.0 to 10% by mass. When the concentration of the polyfunctional amine is 0.1% by mass or more, a separation functional layer with solute separation properties can be formed. On the other hand, when the concentration of the polyfunctional amine is 20% by mass or less, a separation functional layer with good water permeability can be formed.

[0111] In addition, aqueous solutions can contain compounds such as surfactants and antioxidants as needed, provided that they do not hinder polymerization.

[0112] The aqueous solution preferably comes into uniform and continuous contact with the supporting membrane. Specifically, for example, methods such as coating the supporting membrane with a polyfunctional amine aqueous solution or immersing the supporting membrane in an aqueous solution can be used. The contact time between the supporting membrane and the aqueous solution is preferably 1 second to 10 minutes, more preferably 3 seconds to 3 minutes.

[0113] After the aqueous solution comes into contact with the supporting membrane, it is preferable to perform thorough dehydration to prevent droplets from remaining on the supporting membrane. Thorough dehydration prevents residual droplets from becoming membrane defects after the formation of the separation functional layer, thus avoiding a decrease in separation performance. Examples of dehydration methods include holding the supporting membrane vertically after contact with the aqueous solution and allowing excess aqueous solution to flow down naturally; or forcibly dehydrating by blowing an airflow such as nitrogen through an air nozzle. Alternatively, drying the membrane surface after dehydration can remove some of the water from the aqueous solution.

[0114] In step (b), as a polyfunctional acyl chloride, for example, the polyfunctional acyl chloride exemplified in "(1-2) Separation of functional layer" can be cited.

[0115] The organic solvent is preferably immiscible with water, capable of dissolving polyfunctional acyl chlorides, does not corrode the supporting film, and is inactive with respect to polyfunctional amines and polyfunctional acyl chlorides. Examples of organic solvents include hydrocarbon compounds such as n-nonane, n-decane, n-undecane, n-dodecane, isooctane, isodecane, and isododecane, as well as mixtures thereof.

[0116] The concentration of the polyfunctional acyl chloride in the organic solvent solution is preferably 0.01 to 10% by mass, more preferably 0.02 to 4% by mass, and even more preferably 0.03 to 2% by mass. When the concentration of the polyfunctional acyl chloride is 0.01% by mass or more, polymerization can proceed at a sufficient reaction rate. On the other hand, when the concentration of the polyfunctional acyl chloride is 10% by mass or less, the occurrence of side reactions in polymerization can be suppressed. In addition, compounds such as surfactants can be included in the organic solvent solution as needed, provided that they do not hinder polymerization.

[0117] The organic solvent solution of polyfunctional acyl chloride is preferably in uniform and continuous contact with the support film after contact with the aqueous solution of polyfunctional amine. Specifically, for example, a method of coating the support film after contact with the aqueous solution of polyfunctional amine with the organic solvent solution of polyfunctional acyl chloride can be described. The contact time between the support film after contact with the aqueous solution of polyfunctional amine and the organic solvent solution of polyfunctional acyl chloride is preferably 3 seconds to 10 minutes, more preferably 5 seconds to 3 minutes.

[0118] Alternatively, the support film after contact with the organic solvent solution of the polyfunctional acyl chloride can be subjected to heat treatment as needed. When heat treatment is performed, the heating temperature is preferably 35–180°C, more preferably 50–160°C, and even more preferably 60–150°C. Regarding the heating time, the optimal time varies depending on the temperature of the film surface serving as the reaction zone, but is preferably 5 seconds or more, more preferably 10 seconds or more.

[0119] In step (c), the organic solvent solution on the composite semipermeable membrane after the polymerization reaction is dehydrated and removed. Examples of dehydration methods include holding the membrane vertically to allow excess organic solvent solution to flow down naturally; drying the organic solvent by blowing air with a blower; and removing excess organic solvent solution using a mixture of water and air.

[0120] In step (d), the composite semi-permeable membrane, from which the organic solvent has been removed, is cleaned with hot water. The temperature of the hot water is preferably 40–95°C, more preferably 60–95°C. When the hot water temperature is above 40°C, residual unreacted substances and oligomers in the membrane can be thoroughly removed. On the other hand, when the hot water temperature is below 95°C, the shrinkage of the composite semi-permeable membrane does not increase, maintaining good water permeability. It should be noted that the preferred range of hot water temperature can be appropriately adjusted depending on the polyfunctional amine or polyfunctional acyl chloride used.

[0121] (2-3) Formation process of the coating layer

[0122] Next, a coating layer is formed on the separation functional layer.

[0123] Regarding the method of forming a coating layer on the separation functional layer, an example will be given of a method in which a water-soluble polymer is crosslinked with the crosslinked polyamide contained in the separation functional layer obtained in the "(2-2) polymerization process of the separation functional layer" so that the water-soluble polymer becomes insoluble.

[0124] The coating formation process includes: (e) a process of contacting an aqueous solution containing a water-soluble polymer and a crosslinking agent with the separation functional layer; (f) a process of crosslinking the water-soluble polymer with a crosslinked polyamide and fixing it onto the separation functional layer; (g) a process of removing excess aqueous solution; and (h) a process of cleaning the composite semipermeable membrane.

[0125] In step (e), the aqueous solution contains a water-soluble polymer and a crosslinking agent. Examples of water-soluble polymers include those exemplified in "(1-3) Coating Layer".

[0126] The concentration of the water-soluble polymer in the aqueous solution is preferably 0.3 to 10% by mass, more preferably 0.35 to 8% by mass, and even more preferably 0.4 to 5% by mass. When the concentration of the water-soluble polymer is 0.3% by mass or more, a coating layer with sufficient thickness can be formed, and a composite semi-permeable membrane exhibiting excellent abrasion resistance can be obtained. On the other hand, when the concentration of the water-soluble polymer is 10% by mass or less, the thickness of the coating layer will not be too thick, and a composite semi-permeable membrane with sufficient water permeability can be obtained.

[0127] "Crosslinking agent" refers to a compound that reacts with the functional groups of a water-soluble polymer and the functional groups of a crosslinked polyamide to form covalent bonds. When using vinyl alcohol-based polymers as the water-soluble polymer, examples of crosslinking agents include poly(aldehydes) such as succinaldehyde, glutaraldehyde, and terephthalaldehyde.

[0128] The concentration of the crosslinking agent in the aqueous solution is preferably 0.01 to 5% by mass, more preferably 0.02 to 1% by mass, and even more preferably 0.05 to 0.5% by mass. When the concentration of the crosslinking agent is 0.01% by mass or more, the water-soluble polymer and the crosslinked polyamide form covalent bonds, making the water-soluble polymer insoluble. On the other hand, when the concentration of the crosslinking agent is 5% by mass or less, it is possible to suppress rapid crosslinking reactions and form a uniform coating layer.

[0129] In addition, aqueous solutions may contain compounds such as catalysts, depending on the need. When using vinyl alcohol-based polymers as water-soluble polymers and polyaldehydes as crosslinking agents, inorganic acids such as hydrochloric acid and sulfuric acid can be used as catalysts.

[0130] For aqueous solutions, it is preferable to ensure uniform and continuous contact with the separation functional layer. Specifically, a method of coating the separation functional layer with an aqueous solution can be cited as an example. The contact time between the separation functional layer and the aqueous solution is preferably 5 seconds to 10 hours, more preferably 10 seconds to 1 hour.

[0131] In step (f), the water-soluble polymer is crosslinked with the crosslinked polyamide separating the functional layer to make it insoluble. The crosslinking method can be appropriately selected depending on the water-soluble polymer and crosslinking agent used. When using a vinyl alcohol-based polymer as the water-soluble polymer and a polyaldehyde as the crosslinking agent, thermal crosslinking is preferred as the crosslinking method. Examples of thermal crosslinking methods include heating the aqueous solution and the composite semipermeable membrane by blowing hot air with a blower. The temperature of the hot air is preferably 30 to 120°C, more preferably 40 to 80°C. When the temperature of the hot air is above 30°C, the water-soluble polymer and the crosslinked polyamide form covalent bonds, making the water-soluble polymer insoluble. On the other hand, when the temperature of the hot air is below 120°C, the rapid crosslinking reaction can be suppressed, a uniform coating layer can be formed, and the shrinkage of the composite semipermeable membrane will not increase, thus maintaining good water permeability.

[0132] In step (g), the aqueous solution on the composite semipermeable membrane after the crosslinking reaction is dehydrated to remove it. Examples of dehydration methods include holding the membrane vertically to allow excess aqueous solution to flow down naturally; drying the aqueous solvent by blowing air with a blower; etc.

[0133] In step (h), the composite semi-permeable membrane, after the aqueous solution has been removed, is cleaned with water. The temperature of the water used for cleaning is preferably 15–70°C, more preferably 20–50°C. When the water temperature is above 15°C, unreacted substances, catalysts, and other residues remaining in the composite semi-permeable membrane can be sufficiently removed. On the other hand, when the water temperature is below 70°C, the shrinkage of the composite semi-permeable membrane does not increase, and good water permeability can be maintained. It should be noted that the preferred range of water temperature can be appropriately adjusted according to the type of water-soluble polymer and crosslinking agent used.

[0134] Additionally, the composite semipermeable membrane can be hydrophilized as needed. Examples of hydrophilization methods include contacting the composite semipermeable membrane with aqueous solutions of surfactants such as polyoxyethylene octylphenyl ether and sodium dodecylbenzenesulfonate, or aqueous solutions of alcohols such as methanol, ethanol, and isopropanol.

[0135] 3. Applications of composite semi-permeable membranes

[0136] The composite semi-permeable membrane described in this embodiment is suitable for use as a spiral composite semi-permeable membrane element, wound around a cylindrical water collection pipe having multiple holes, together with a water supply channel material such as a plastic mesh, a water permeable channel material such as tricot knitted fabric, and a membrane used to improve pressure resistance as needed. Furthermore, it is also possible to manufacture a composite semi-permeable membrane assembly in which the element is connected in series or parallel and housed in a pressure vessel.

[0137] Furthermore, the aforementioned composite semi-permeable membrane, its elements, and components can be combined with a pump supplying water to it, a device for pre-treating the supplied water, etc., to form a fluid separation device. By using this fluid separation device, the supplied water can be separated into permeable water such as drinking water and concentrated water that has not permeated the membrane, thereby obtaining the target water.

[0138] Examples of liquid mixtures containing 500 mg / L to 100 g / L of total dissolved solids (TDS) can be used as supply water for treatment using the composite semi-permeable membrane described in this embodiment. These mixtures include seawater, brackish water, and wastewater. TDS is typically expressed as mass / volume or mass ratio. By definition, it is calculated based on the weight of the residue after evaporation of a solution filtered through a 0.45-micron filter at 39.5–40.5°C, but a simpler method is to convert it based on practical salinity (S).

[0139] Higher operating pressures in fluid separation devices increase solute removal rates, but also increase energy requirements. Furthermore, considering the durability of the composite semi-permeable membrane, the operating pressure for the treated water to pass through it is preferably 0.5–10 MPa. Higher supply water temperatures decrease solute removal rates, but lower supply water temperatures decrease permeability. Therefore, a supply water temperature of 5–45°C is preferred. Additionally, in the case of supply water with high solute concentrations, such as seawater, higher pH levels may lead to the formation of scale, such as magnesium. Moreover, since operation under high pH conditions can degrade the composite semi-permeable membrane, operation in a neutral pH range is preferable.

[0140] Example

[0141] The present invention is illustrated by specific embodiments described below, but the present invention is not limited to these embodiments in any way.

[0142] The physical properties related to the composite semipermeable membrane of the present invention were measured using the following method.

[0143] (1) Membrane permeation flux

[0144] For a 75 mm diameter composite semi-permeable membrane, evaluation water (hereinafter referred to as "evaluation water") prepared with a NaCl concentration of 2,000 mg / L, at 25 °C and pH 7 was supplied at an operating pressure of 1.55 MPa. After 2 hours of operation, permeate was collected over 15 minutes. The permeate flow rate (m³) was measured. 3 And convert it to membrane area per unit (m²) 2 The membrane permeation flux (m / d) is calculated by taking the values ​​of m / d and unit time (d).

[0145] (2) NaCl removal rate

[0146] In the membrane filtration test for “(1) Membrane permeate flux”, the conductivity of the evaluation water and the permeate water was measured using a multi-functional water quality meter (manufactured by Toa DKK Corporation; MM-60R), and the NaCl concentration (practical salinity) of each was measured. Based on the obtained NaCl concentration, the NaCl removal rate (%) was calculated according to the following formula (1). It should be noted that the value obtained by rounding to the third decimal place is used.

[0147] NaCl removal rate (%) = 100 × {1 - (NaCl concentration in permeated water / NaCl concentration in evaluation water)} ... Equation (1)

[0148] (3) Friction test and friction coefficient

[0149] The friction test was conducted as follows.

[0150] The composite semi-permeable membrane was cut into 10cm x 10cm squares and washed with distilled water at 70°C for 5 minutes. The washed composite semi-permeable membrane was then attached to a 2.09kg (20.5N) cuboid (12cm x 13cm square base) with the coating layer or separation functional layer as the surface side. Nitrogen was blown onto the membrane surface to remove liquid. Additionally, a polishing abrasive material (TRUSCO Nakayama Co., Ltd.; TLF-2000, grit #2000) was attached to a flat metal plate with the polishing surface as the surface side. Figure 3 As shown, a weight 8 is placed on the abrasive surface of the polishing film abrasive material 10 attached to the metal plate 11, in such a way that it is in complete contact with the coating layer or separation functional layer of the composite semi-permeable membrane 9. A rope is attached to one side of the weight 8 in the axial (horizontal) direction, and the other side of the rope is connected to a tensile testing machine 6 (manufactured by A&D Corporation; RTG-1210). A pulley 7 is positioned between the weight 8 and the tensile testing machine 6 with the rope bent vertically. The weight 8 and the composite semi-permeable membrane 9 are stretched together using the tensile testing machine 6 under the following conditions.

[0151] Stretching speed: 100mm / min

[0152] Extension distance: 120mm

[0153] Measurement room temperature: 25℃

[0154] like Figure 4 As shown, the maximum load in the friction test is set as the static friction force Fs (N), and the average load from the start of the relative offset motion between the contact surfaces to the initial 60 mm is set as the dynamic friction force Fd (N).

[0155] Replace the composite semipermeable membrane and repeat the same measurement 5 times. Based on the average values ​​of static friction force Fs (N) and dynamic friction force Fd (N) and the load Fp (N) of the weight, calculate the static friction coefficient μs and dynamic friction coefficient μd based on the following formulas (2) and (3).

[0156] μs=Fs / Fp···Equation (2)

[0157] μd=Fd / Fp···Equation (3)

[0158] In addition, using the composite semipermeable membranes that underwent the friction test, the NaCl removal rate (%) after the friction test was calculated using the method described in "(2) NaCl Removal Rate". All five composite semipermeable membranes that underwent the friction test were measured, and their average value was taken as the NaCl removal rate after the friction test.

[0159] (4) The total thickness T of the separation functional layer and the coating layer

[0160] The composite semi-permeable membrane was cut into 3cm × 3cm squares and immersed in distilled water at 25°C for 24 hours. After immersion, the composite semi-permeable membrane was embedded in epoxy resin, stained with osmium tetroxide, and then cut into extremely thin sections using a microtome as the test samples. For the obtained samples, the cross-section of the composite semi-permeable membrane was used as the observation surface, and observation was performed using a scanning transmission electron microscope (Hitachi, Ltd.; HD2700). Using images acquired at 1,000,000x magnification, the shortest distance from a point on the outer surface of the separating functional layer or coating layer to the inner surface was measured. For 10 randomly selected protrusions, 5 points were measured at each protrusion, and the average value was taken as the total thickness T (nm) of the separating functional layer and the coating layer.

[0161] (5) Surface area ratio Sdr, root mean square height Sq

[0162] The composite semipermeable membrane was cut into 3cm × 3cm squares and immersed in distilled water at 25°C for 24 hours. After immersion, the composite semipermeable membrane was observed using an atomic force microscope (Bruker; Dimension FastScan), with the coating layer or separation functional layer on the surface as the measurement surface, under the following conditions while wetted with distilled water. For 10 randomly selected locations, the developed area ratio and root mean square height were calculated according to ISO 25178:2014 surface properties (measurement of surface roughness), and their average values ​​were used as the developed area ratio Sdr (%) and root mean square height Sq (nm).

[0163] Scanning mode: Nanomechanical mapping in water

[0164] Probe: Silicon cantilever (manufactured by Bruker; Scan Asyst-Fluid)

[0165] Maximum load: 5nN

[0166] Scan range: 10μm × 10μm

[0167] Scan speed: 1Hz

[0168] Pixel count: 512×512

[0169] Test environment: Distilled water

[0170] Measurement temperature: 25℃

[0171] (6) Weight-average molecular weight

[0172] The weight-average molecular weight (converted to polystyrene) of PSf was determined using gel permeation chromatography (manufactured by Tosoh Corporation; HLC-8022). Specific determination conditions are as follows.

[0173] Chromatographic column: 2 TSK gel SuperHM-H columns (manufactured by Tosoh Corporation; inner diameter 6.0 mm, length 15 cm).

[0174] Eluent: LiBr / N-methylpyrrolidone solution (10mM)

[0175] Sample concentration: 0.1% by mass

[0176] Flow rate: 0.5 mL / min

[0177] Temperature: 40℃

[0178] The raw materials of the composite semipermeable membranes used in the examples and comparative examples are summarized below.

[0179] PSf (made by Solvay Specialty Polymers Japan Co., Ltd.; UdelP-3500, Mw80,000)

[0180] DMF (manufactured by Fujifilm and Wako Pure Chemical Industries, Ltd.)

[0181] Polyester long fiber nonwoven fabric (thickness 90μm; density 0.42g / cm³) 3 )

[0182] m-PDA (manufactured by Fujifilm and Wako Pure Chemical Industries, Ltd.)

[0183] TMC (manufactured by Fujifilm and Wako Pure Chemical Industries, Ltd.)

[0184] n-Decane (manufactured by Fujifilm and Wako Pure Chemical Industries, Ltd.)

[0185] Sodium nitrite (manufactured by Fujifilm and Wako Pure Chemical Industries, Ltd.)

[0186] Sodium sulfite (manufactured by Fujifilm and Wako Pure Chemical Industries, Ltd.)

[0187] Sulfuric acid (manufactured by Fujifilm and Kazumitsu Chemical Co., Ltd.)

[0188] Polyacrylic acid (manufactured by Fujifilm and Kazumitsu Chemical Co., Ltd.; Mw25,000)

[0189] 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholine chloride (hereinafter also known as "DMT-MM") (manufactured by Fujifilm and Koko Pure Chemical Industries, Ltd.)

[0190] PVA1 (manufactured by Sigma-Aldrich; degree of saponification 99.5 mol%, degree of polymerization 2,600)

[0191] PVA2 (manufactured by Sigma-Aldrich; saponification degree 98.0-99.0 mol%, degree of polymerization 900)

[0192] Vinyl alcohol copolymer 1 (manufactured by Kuraray Co., Ltd.; EXCEVAL RS-2117, degree of saponification 97.5-99.0 mol%, degree of polymerization 1,700, ethylene copolymerization ratio 0.030)

[0193] Vinyl alcohol copolymer 2 (manufactured by Kuraray Co., Ltd.; EXCEVAL AQ-4104, saponification degree 98.0-99.0 mol%, degree of polymerization 400, ethylene copolymerization ratio 0.059)

[0194] Vinyl alcohol copolymer 3 (manufactured by Kuraray Co., Ltd.; EXCEVAL HR-3010, saponification degree 99.0-99.4 mol%, degree of polymerization 1,000, ethylene copolymerization ratio 0.045)

[0195] Vinyl alcohol copolymer 4 (manufactured by Kuraray Co., Ltd.; EXCEVAL RS-1717, degree of saponification 92.0-94.0 mol%, degree of polymerization 1,700, ethylene copolymerization ratio 0.028)

[0196] Glutaraldehyde (manufactured by Fujifilm and Wako Pure Chemical Industries, Ltd.)

[0197] Isopropyl alcohol (manufactured by Fujifilm and Wako Pure Chemical Industries, Ltd.)

[0198] Alkyl glycol polymer 1 (manufactured by Nagase Chemtex Co., Ltd.; DENACOL EX-171, molecular weight 900)

[0199] Alkyl glycol polymer 2 (manufactured by Nagase Chemtex Co., Ltd.; DENACOL EX-861, molecular weight 1100)

[0200] [Comparative Example 1]

[0201] A porous support layer stock solution was prepared by dissolving 15% by mass of PSf and 85% by mass of DMF at 100°C. This porous support layer stock solution was coated onto 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 allow it to solidify. It was then washed with hot water at 80°C for 2 minutes, thereby obtaining a support film with a porous support layer formed of PSf on the surface of the polyester long-fiber nonwoven fabric as the substrate. The thickness of the porous support layer in the obtained support film was 30 μm.

[0202] Next, the obtained support membrane was immersed in a 3% by mass aqueous solution of m-PDA for 2 minutes. The support membrane was then slowly pulled vertically, and nitrogen was blown from an air nozzle to remove excess aqueous solution from the surface of the support membrane. Under controlled conditions of 25°C, 20 ml of a 25°C n-decane solution containing 0.12% by mass of TMC was applied to completely wet the surface of the support membrane, and the membrane was allowed to stand for 1 minute to form a separation functional layer through interfacial polymerization. The obtained membrane was then held vertically for 30 seconds to remove excess solution, and then washed with hot water at 80°C for 2 minutes. Subsequently, the washed membrane was 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 semi-permeable membrane.

[0203] [Comparative Example 2]

[0204] The composite semipermeable membrane obtained in Comparative Example 1 was immersed in an aqueous solution containing 0.01% by mass of polyacrylic acid and 0.1% by mass of DMT-MM for 6 hours at a controlled temperature of 20°C, thereby forming a coating layer on the separation functional layer. Then, the composite semipermeable membrane was held vertically to remove excess aqueous solution and washed with water at 40°C for 2 minutes.

[0205] [Comparative Example 3]

[0206] On the surface of the separation functional layer of the composite semipermeable membrane obtained in Comparative Example 1, a solution (isopropanol / water = 3 / 7) containing 0.25% by mass of PVA1 (99.5 mol% saponification degree, 2,600 degree of polymerization) was brought into complete contact with the surface at a controlled temperature of 20°C. With the aqueous solution remaining on the surface of the separation functional layer, the membrane was kept at 100°C for 5 minutes, then brought into contact with the solution again, and kept at 130°C for 5 minutes, thereby forming a coating layer on the separation functional layer. Then, it 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 for hydrophilization treatment.

[0207] [Comparative Example 4]

[0208] On the surface of the separation functional layer of the composite semipermeable membrane obtained in Comparative Example 1, an aqueous solution containing 0.15% by mass of vinyl alcohol copolymer 1 (EXCEVAL RS-2117), 0.1% by mass of glutaraldehyde, and 0.1% by mass of sulfuric acid was brought into contact with the overall surface at a controlled temperature of 20°C. With the aqueous solution remaining on the surface of the separation functional layer, hot air at 70°C was blown onto the composite semipermeable membrane for 1 minute, thereby forming a coating layer on the separation functional layer. Then, the composite semipermeable membrane was held 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 14% by mass aqueous solution of isopropanol at 20°C for 5 minutes for hydrophilication treatment.

[0209] [Example 1]

[0210] On the surface of the separation functional layer of the composite semipermeable membrane obtained in Comparative Example 1, an aqueous solution containing 2.0 wt% PVA2 (98.0-99.0 mol% saponification, 900 degree of polymerization), 0.5 wt% glutaraldehyde, and 0.1 wt% sulfuric acid was brought into contact with the overall surface at a controlled temperature of 20°C. With the aqueous solution remaining on the surface of the separation functional layer, hot air at 70°C was blown onto the composite semipermeable membrane for 3 minutes, thereby forming a coating layer on the separation functional layer. Then, the composite semipermeable membrane was held 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 14 wt% isopropanol aqueous solution at 20°C for 5 minutes for hydrophilication treatment.

[0211] [Example 2]

[0212] Using an aqueous solution containing 0.5% by mass of vinyl alcohol copolymer 2 (EXCEVAL AQ-4104), 0.3% by mass of glutaraldehyde, and 0.1% by mass of sulfuric acid, hot air at 70°C was blown for 1 minute. Otherwise, a coating layer was formed on the separation functional layer by the same method as in Example 1, and hydrophilization treatment was performed.

[0213] [Example 3]

[0214] An aqueous solution containing 0.8% by mass of vinyl alcohol copolymer 3 (EXCEVAL HR-3010), 0.4% by mass of glutaraldehyde, and 0.1% by mass of sulfuric acid was used. In addition, a coating layer was formed on the separation functional layer by the same method as in Example 2, and hydrophilization treatment was performed.

[0215] [Example 4]

[0216] An aqueous solution containing 1.1 wt% ethylene alcohol copolymer 1 (EXCEVAL RS-2117), 0.4 wt% glutaraldehyde, and 0.1 wt% sulfuric acid was used, except that a coating layer was formed on the separation functional layer by the same method as in Example 2, and hydrophilization treatment was performed.

[0217] [Example 5]

[0218] An aqueous solution containing 0.4% by mass of vinyl alcohol copolymer 4 (EXCEVAL RS-1717), 0.2% by mass of glutaraldehyde, and 0.1% by mass of sulfuric acid was used. In addition, a coating layer was formed on the separation functional layer by the same method as in Example 2, and hydrophilization treatment was performed.

[0219] [Example 6]

[0220] An aqueous solution containing 0.7% by mass of PVA2 (98.0-99.0 mol% saponification, 900% polymerization), 0.3% by mass of ethylene alcohol copolymer 3 (EXCEVAL HR-3010), 0.4% by mass of glutaraldehyde, and 0.1% by mass of sulfuric acid was used. In addition, a coating layer was formed on the separation functional layer by the same method as in Example 2, and hydrophilization treatment was performed.

[0221] [Example 7]

[0222] The composite semipermeable membrane obtained in Comparative Example 2 and an aqueous solution containing 0.3% by mass of vinyl alcohol copolymer 3 (EXCEVAL HR-3010), 0.2% by mass of glutaraldehyde, and 0.1% by mass of sulfuric acid were used, except that a coating layer was formed on the separation functional layer by the same method as in Example 1, and hydrophilization treatment was performed.

[0223] [Example 8]

[0224] On the surface of the separation functional layer of the composite semipermeable membrane obtained in Comparative Example 1, an aqueous solution containing 1.2 mass of alkylene glycol polymer 1 (DENACOL EX-171) was contacted for 15 minutes at a controlled temperature of 20°C, thereby forming a coating layer on the separation functional layer. Then, the composite semipermeable membrane was held vertically, and excess aqueous solution was removed by dehydration, followed by washing with water at 20°C for 2 minutes.

[0225] [Example 9]

[0226] An aqueous solution containing 0.8% by mass of alkylene glycol polymer 2 (DENACOL EX-861) was used. Otherwise, a coating layer was formed on the separation functional layer by the same method as in Example 6, followed by dehydration and washing.

[0227] The structures of the composite semipermeable membranes obtained by comparing Examples 1-4 and Examples 1-9 are shown in Table 1, and their properties are shown in Table 2.

[0228] [Table 1]

[0229] Table 1

[0230] [Table 2]

[0231] Table 2

[0232]

[0233] As shown in Table 2, the composite semipermeable membranes of Examples 1-9 exhibited superior abrasion resistance and water permeability compared to the composite semipermeable membranes of Comparative Examples 1-4.

[0234] Furthermore, a comparison of Examples 2-3, 6, and 9 with Example 8 shows that better abrasion resistance is achieved by setting μs to 1.08-1.20.

[0235] The present invention has been described in detail using specific embodiments, but it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the intent and scope of the invention. It should be noted that this application is based on Japanese Patent Application No. 2023-015305, filed on February 3, 2023, the entirety of which is incorporated herein by reference.

[0236] Explanation of reference numerals in the attached figures

[0237] 1. Composite semi-permeable membrane

[0238] 2 Support membrane

[0239] 3. Separate functional layers

[0240] 4. Covering layer

[0241] 5 Inside the convex part

[0242] 6 Tensile testing machine

[0243] 7. Pulleys

[0244] 8 weights

[0245] 9. Composite semi-permeable membrane

[0246] 10 Polishing film abrasive material (grit size #2000)

[0247] 11 Metal Plate

Claims

1. A composite semi-permeable membrane, comprising a support membrane, a separation functional layer comprising cross-linked polyamide disposed on the support membrane, and a coating layer disposed on the separation functional layer. in, The crosslinked polyamide is a condensation polymer of a polyfunctional amine and a polyfunctional acyl chloride, wherein the polyfunctional amine is an aromatic difunctional amine or an aromatic trifunctional amine. The unfolded area ratio (Sdr) of the coated layer side surface of the composite semi-permeable membrane is 60-200%. The static friction coefficient μs between the coated side surface of the composite semi-permeable membrane and the polishing abrasive material with a particle size of #2000 is 0.40 to 1.

30.

2. The composite semi-permeable membrane according to claim 1, wherein, The coefficient of dynamic friction μd between the coated side surface of the composite semi-permeable membrane and the polishing abrasive material with a particle size of #2000 is 0.25 to 0.

73.

3. The composite semi-permeable membrane according to claim 1 or 2, wherein, The root mean square height Sq of the coating layer side surface of the composite semipermeable membrane is 140–300 nm.

4. The composite semi-permeable membrane according to claim 1 or 2, wherein, The coating layer comprises at least one of a vinyl alcohol polymer and an alkylene glycol polymer.

5. The composite semi-permeable membrane according to claim 4, wherein, The degree of saponification of the vinyl alcohol polymer is above 96 mol%.

6. The composite semi-permeable membrane according to claim 4, wherein, The degree of polymerization of the vinyl alcohol-based polymer is 100 to 1,500.

7. The composite semi-permeable membrane according to claim 4, wherein, The vinyl alcohol polymer is a vinyl alcohol copolymer containing the structure represented by the following general formula (1). [Chemical Formula 1] In general formula (1), X is a divalent hydrocarbon group with 2 to 6 carbon atoms, and l, m and n are the number of repeating units.

8. The composite semi-permeable membrane according to claim 7, wherein, In the general formula (1), X is a divalent hydrocarbon group with 2 carbon atoms.

9. The composite semi-permeable membrane according to claim 8, wherein, In the general formula (1), X is 1,2-ethylene.

10. The composite semi-permeable membrane according to claim 7, wherein, The copolymerization ratio of the ethylene alcohol copolymer, n / (l+m+n), is 0.035 to 0.

16.

11. The composite semi-permeable membrane according to claim 4, wherein, The molecular weight of the alkylene glycol polymer is 500 to 500,000.

12. A composite semi-permeable membrane assembly comprising the composite semi-permeable membrane as described in claim 1 or 2.

13. A fluid separation device comprising the composite semi-permeable membrane assembly of claim 12.

Images