Composite semipermeable membrane, composite semipermeable membrane element, fluid separation device, and method for manufacturing a composite semipermeable membrane element

Abstract

To provide a composite semipermeable film with excellent abrasion resistance. [Solution] A composite semipermeable membrane comprising a porous support layer, a separation functional layer containing a crosslinked polyamide provided on the porous support layer, and a coating layer containing a polymer having a structure represented by general formula (I) provided on the separation functional layer, wherein the degree of yellowing ΔVYI of the surface on the coating layer side before and after contact with vanillin solution is 5 or more and 23 or less. TIFF2026115022000017.tif21163 [In formula (I), R1 is a hydrocarbon group having 4 to 11 carbon atoms, which may be substituted, and R2 is hydrogen, a hydrocarbon group having 2 or fewer carbon atoms, or a functional group having 2 or fewer carbon atoms.]

Description

[Technical Field]

[0001] The present invention relates to a composite semipermeable membrane, a composite semipermeable membrane element, a fluid separation device, and a method for manufacturing a composite semipermeable membrane element. [Background technology]

[0002] There are various techniques for removing substances (e.g., salts) dissolved in a solvent (e.g., water), and in recent years, the use of membrane separation methods using semipermeable membranes such as reverse osmosis membranes and nanofiltration membranes has been expanding as an energy-saving and resource-saving process.

[0003] Commercially available reverse osmosis and nanofiltration membranes are generally composite semipermeable membranes having a support membrane and a separation functional layer laminated on the support membrane. As the separation functional layer, polyamides obtained by the polycondensation reaction of polyfunctional amines and polyfunctional acid halides are known.

[0004] Such composite semipermeable membranes have a thin separation layer, which makes them susceptible to a decrease in separation performance due to abrasion of the separation layer. Causes of abrasion include contact between composite semipermeable membranes when stacked for storage after manufacturing, and contact with storage packaging materials. In addition, composite semipermeable membranes are often used in an element that has two or more composite semipermeable membranes and a flow channel material inserted between them. Contact between the composite semipermeable membrane and the components of the assembly equipment or the element during the assembly of this element can also be a cause of abrasion.

[0005] As a method to suppress the decrease in separation performance due to abrasion, Patent Document 1 discloses a composite semipermeable membrane in which a coating layer made of a polymer such as polyvinyl alcohol is arranged on the surface of the separation functional layer. Furthermore, Patent Document 2 discloses a composite semipermeable membrane in which the occurrence of membrane defects due to abrasion is suppressed by increasing the amount of the separation functional layer relative to the porous support layer. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2003-200026 [Patent Document 2] Japanese Patent Publication No. 2019-098329 [Overview of the project] [Problems that the invention aims to solve]

[0007] While the composite semipermeable membranes described in Patent Documents 1 and 2 show a certain improvement in abrasion resistance, they suffer from a decrease in separation performance. Therefore, the present invention aims to provide a composite semipermeable membrane with excellent abrasion resistance. [Means for solving the problem]

[0008] To achieve the above objectives, the present invention includes the following configurations [1] to

[11] . [1] A composite semipermeable membrane comprising a porous support layer, a separation functional layer containing a crosslinked polyamide provided on the porous support layer, and a coating layer containing a polymer having a structure represented by the following general formula (I) provided on the separation functional layer, wherein the degree of yellowing ΔVYI of the surface on the coating layer side before and after contact with a vanillin solution is 5 or more and 23 or less.

[0009] [ka]

[0010] [In general formula (I), R1 is a hydrocarbon group having 4 to 11 carbon atoms, which may be substituted, and R2 is hydrogen, a hydrocarbon group having 2 or fewer carbon atoms, or a functional group having 2 or fewer carbon atoms.] [2] The composite semipermeable membrane according to [1] above, wherein the underwater elastic modulus of the surface on the coating layer side is 10 MPa or more and 45 MPa or less. [3] In the surface analysis of the coating layer side by total internal reflection infrared absorption measurement, 1642~1662 cm -1 The maximum intensity of the peak originating from amide I that appears is 1600-1610 cm. -1The composite semipermeable membrane according to [1] or [2] above, wherein the intensity ratio of the maximum intensity of the peak appearing at is 0.86 or more and 1.20 or less. [4] The composite semipermeable membrane according to any one of [1] to [3] above, wherein the degree of yellowing ΔDYI of the surface on the coating layer side before and after contact with Dragendorff reagent is 43 or more and 150 or less. [5] In the surface analysis of the coating layer side by total reflection infrared absorption measurement, 1642~1662cm -1 For the maximum intensity of the peak appearing at, the intensity ratio of the maximum intensity of the peak appearing at 2800~2900cm -1 is 0.20 or more and 0.30 or less. The composite semipermeable membrane according to any one of [1] to [4] above. [6] The composite semipermeable membrane according to any one of [1] to [5] above, wherein the polymer consists of only non-halogen atoms. [7] The composite semipermeable membrane according to any one of [1] to [6] above, wherein the polymer has a hydrophilic unit. [8] The composite semipermeable membrane according to [7] above, wherein the hydrophilic unit has a structure represented by the following general formula (II).

[0011] [Chemical formula]

[0012] [In the general formula (II), R3 and R4 in each repeating unit are each independently hydrogen or a hydrocarbon group having 2 or less carbon atoms, and n is an integer of 1 or more. ] [9] A composite semipermeable membrane element comprising the composite semipermeable membrane according to any one of [1] to [8] above.

[10] A fluid separation device comprising the composite semipermeable membrane according to any one of [1] to [8] above.

[11] A method for producing a composite semipermeable membrane, comprising the following steps (A) and (B). (A) After bringing an aqueous solution of polyfunctional amine into contact with a porous support layer, contacting a water-immiscible organic solvent solution containing a polyfunctional acid halide with the surface of the porous support layer, and forming a separation function layer containing crosslinked polyamide on the porous support layer by interfacial polymerization. (B) A step of contacting the above-mentioned separation functional layer with a solution containing a polymer having a structure represented by the following general formula (I).

[0013] [ka]

[0014] [In general formula (I), R1 is a hydrocarbon group having 4 to 11 carbon atoms, which may be substituted, and R2 is hydrogen, a hydrocarbon group having 2 or fewer carbon atoms, or a functional group having 2 or fewer carbon atoms.] [Effects of the Invention]

[0015] According to the present invention, a composite semipermeable film with high abrasion resistance can be obtained. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a schematic diagram showing the structure of a composite semipermeable membrane having a pleated separation functional layer and a coating layer according to one embodiment of the present invention, where (a) is a partially enlarged view and (b) is an enlarged view of Y in (a). [Figure 2] Figure 2 is an unfolded view of a composite semipermeable membrane element in one embodiment of the present invention. [Figure 3] Figure 3 is a schematic diagram of the abrasion test. [Figure 4] Figure 4 is a schematic diagram illustrating the method of setting up the composite semipermeable membrane in the abrasion test. [Modes for carrying out the invention]

[0017] Embodiments of the present invention will be described in detail below, but the present invention is not limited thereto.

[0018] 1. Composite semipermeable membrane The composite semipermeable membrane of this embodiment comprises a porous support layer, a separation functional layer containing polyamide provided on the porous support layer, and a coating layer provided on the separation functional layer. The composite semipermeable membrane is preferably a reverse osmosis membrane or a nanofiltration membrane in which the pore size of the separation functional layer is fine.

[0019] 1.1 Covering layer The coating layer of the composite semipermeable membrane according to this embodiment is a layer responsible for protecting the separation functional layer and is arranged on the separation functional layer. The coating layer of this embodiment is a polymer formed from one or more monomers (hereinafter also referred to as "monomer units"), where monomer units are units that can be linked together and the linked molecules form a polymer. When the polymer is a copolymer consisting of two or more monomer units, it may be a random copolymer, an alternating copolymer, or a block copolymer. Among these, random copolymers, which are widely produced industrially, are preferred.

[0020] The composite semipermeable membrane according to this embodiment comprises a coating layer containing a polymer having a structure represented by the following general formula (I).

[0021] [ka]

[0022] In general formula (I), R1 is a hydrocarbon group having 4 to 11 carbon atoms, which may be substituted, and R2 is hydrogen, a hydrocarbon group having 2 or fewer carbon atoms, or a functional group having 2 or fewer carbon atoms.

[0023] The polymer contained in the coating layer has a structure represented by general formula (I), which allows hydrogen bonds to be formed between the polymer and the amide groups, amino groups, etc., of the cross-linked polyamide contained in the separation functional layer, and also allows hydrophobic interactions originating from hydrocarbon groups to occur. Through the interaction between the polymer contained in the coating layer and the separation functional layer, the coating layer acts as a sacrificial layer, resulting in a composite semipermeable film with excellent abrasion resistance. From the above viewpoint, it is preferable that the polymer contained in the coating layer has the structure represented by general formula (I) as a repeating unit.

[0024] If the number of carbon atoms in R1 in general formula (I) is 4 or more, sufficient hydrophobic interaction is achieved, and if the number of carbon atoms is 11 or less, the decrease in membrane permeation flux due to hydrophobicity can be suppressed. The number of carbon atoms in R1 in general formula (I) is more preferably 4 to 10, even more preferably 4 to 8, and particularly preferably 4 to 6. R2 in general formula (I) is preferably hydrogen, a hydrocarbon group such as a methyl group or ethyl group, or a functional group such as a methoxymethyl group, and more preferably hydrogen. If R2 is any of the above, the interaction between the polymer contained in the coating layer and the crosslinked polyamide can be suppressed from being inhibited by steric hindrance.

[0025] In this embodiment, the degree of yellowing ΔVYI of the surface of the coating layer (hereinafter also referred to as the "coating layer surface") before and after contact with the vanillin solution is 5 to 23. The amino groups, such as the crosslinked polyamide ends, contained in the separation functional layer form a color-developing chemical structure through a chemical reaction with vanillin. That is, the degree of yellowing ΔVYI of the coating layer surface before and after contact with the vanillin solution reflects the amount of amino groups present in the separation functional layer. Here, as described above, the polymer contained in the coating layer forms hydrogen bonds with the amino groups on the surface of the separation functional layer, which reduces the number of amino groups that chemically react with vanillin and thus reduces ΔVYI. Furthermore, as the thickness of the coating layer increases, contact of vanillin with the separation functional layer is inhibited, so ΔVYI decreases.

[0026] When ΔVYI is 5 or higher, the decrease in membrane permeation flux due to the introduction of an excessive coating layer can be suppressed. Furthermore, when ΔVYI is 23 or lower, a sufficient amount of amino groups in the separation functional layer interact with the coating layer, reducing the performance degradation due to abrasion. From the above viewpoint, ΔVYI is preferably 7 to 20, and more preferably 12 to 20. The degree of yellowing ΔVYI on the surface of the coating layer is calculated by the method described in "Coloring with Vanillin" in the examples described later.

[0027] The value of ΔVYI can be controlled, for example, by providing a coating layer containing a polymer having functional groups and molecular chains that form strong hydrogen bonds with the amino groups on the surface of the separation functional layer, or by the amount of the coating layer.

[0028] In the composite semipermeable membrane according to this embodiment, when the separation functional layer is pleated, the underwater modulus of elasticity of the surface on the coating layer side is preferably 10 MPa to 45 MPa, more preferably 12 MPa to 40 MPa, and even more preferably 15 MPa to 35 MPa. "Underwater modulus" is a value that shows the relationship between stress and strain in the initial stage of elastic deformation that occurs when stress is applied to the membrane in water after immersing the composite semipermeable membrane in a 20% by mass isopropanol aqueous solution at 25°C for 20 minutes, then immersing it in distilled water at 25°C for 1 hour, and then immersing the membrane in water. It represents the slope near the origin of the stress-strain curve. If the underwater modulus of elasticity of the coating layer surface is 10 MPa or higher, the coating layer has sufficient strength, improving the abrasion resistance of the separation functional layer. Furthermore, if the underwater modulus of elasticity of the coating layer surface is 45 MPa or lower, the coating layer does not become too hard and remains flexible, thus reducing damage due to abrasion. The underwater modulus of elasticity of the coating layer surface is calculated by the method described in "Underwater Modulus" in the examples described later.

[0029] The underwater elastic modulus of the coating layer surface can be controlled, for example, by the underwater elastic modulus of the separation functional layer surface of the composite semipermeable membrane, the structure of the polymer described in "1.1.1 Polymers forming the coating layer" below, the amount of the coating layer, etc.

[0030] When the underwater elastic modulus of the separation functional layer surface of the composite semipermeable membrane before the coating layer is formed is less than 10 MPa, it is preferable that the interaction between the polymer contained in the coating layer and the cross-linked polyamide of the separation functional layer is strong. When the polymer contained in the coating layer and the cross-linked polyamide of the separation functional layer interact strongly, the underwater elastic modulus of the coating layer surface becomes higher than that of the separation functional layer surface, thus improving abrasion resistance.

[0031] Furthermore, if the underwater elastic modulus of the separation functional layer surface of the composite semipermeable membrane before the coating layer is formed exceeds 45 MPa, it is preferable that the polymer contained in the coating layer is highly hydrophilic and interacts with the cross-linked polyamide of the separation functional layer. When the polymer contained in the coating layer is highly hydrophilic, the underwater elastic modulus of the coating layer surface becomes lower than that of the separation functional layer surface, and the coating layer functions as a sacrificial layer against stress, resulting in excellent abrasion resistance.

[0032] In surface analysis of the coating layer side of the composite semipermeable film according to this embodiment, the absorption rate was 1642-1662 cm² in total internal reflection infrared absorption spectroscopy (hereinafter referred to as "ATR-IR"). -1 The maximum intensity of the peak originating from amide I that appears is 1600-1610 cm. -1 It is preferable that the intensity ratio of the peaks appearing is between 0.86 and 1.20. Generally, this is 1642-1662 cm. -1 The peaks that appear are amide I peaks, which originate from the C=O stretching of amide groups contained in the separation functional layer and coating layer. Also, 1600-1610 cm -1 The peaks that appear originate from the benzene rings contained in the separation functional layer, coating layer, and porous support layer. Therefore, the intensity ratio of the amide I peak to the peak derived from the benzene rings is the value obtained by standardizing the absorption peaks derived from the separation functional layer and coating layer with the absorption peak derived from the composite semipermeable membrane. When the intensity ratio of the above peaks is 0.86 or higher, the separation functional layer is sufficiently protected by the coating layer, resulting in excellent abrasion resistance. Furthermore, when the intensity ratio of the above peaks is 1.20 or lower, the decrease in membrane permeation flux due to the introduction of an excessive coating layer can be suppressed. From the above viewpoint, the intensity ratio of the above peaks is more preferably 0.90 to 1.15, and even more preferably 0.95 to 1.10. The above peaks are calculated by the method described in "ATR-IR" in the examples described later. The intensity ratio of the above peaks can be controlled, for example, by the polymer concentration during coating layer formation, coating time, etc.

[0033] In this embodiment, the composite semipermeable membrane preferably has a degree of yellowing ΔDYI of 43 to 150 on the surface of the coating layer before and after contact with Dragendorff's reagent. Dragendorff's reagent reacts specifically with tertiary and quaternary amines and polyethylene glycol structures, resulting in coloration. Therefore, the degree of yellowing ΔDYI on the surface of the coating layer before and after contact with Dragendorff's reagent reflects the amount of tertiary and quaternary amines and polyethylene glycol structures contained in the polymer in the coating layer, i.e., the amount of the coating layer. This is particularly useful when the copolymer contains a structure represented by the above general formula (II).

[0034] When ΔDYI is 43 or more, a sufficient amount of the coating layer is formed, so that the performance degradation due to abrasion can be reduced. On the other hand, when ΔDYI is 150 or less, the decrease in the membrane permeation flux due to the introduction of an excessive coating layer can be suppressed. From the above viewpoints, ΔDYI is more preferably 55 or more and 140 or less, and even more preferably 60 or more and 120 or less. The yellowness degree ΔDYI of the coating layer surface is calculated by the method described in "Color Development with Dragendorff Reagent" in the examples described later. The ΔDYI of the coating layer surface can be controlled, for example, by the polymer concentration and the coating time during the formation of the coating layer.

[0035] In the surface analysis of the coating layer side by ATR-IR, the composite semipermeable membrane according to the present embodiment has a wavenumber range of 1642 - 1662 cm -1 The intensity ratio of the maximum intensity of the peak appearing at 2800 - 2900 cm -1 to the maximum intensity of the peak appearing at is preferably 0.20 or more and 0.30 or less. Usually, in a composite semipermeable membrane provided with a separation functional layer containing crosslinked polyamide on a porous support layer, the intensity of the peak appearing at 2800 - 2900 cm -1 is relatively small compared to the intensity of the peak derived from amide I, and the intensity ratio is less than 0.20. When a peak derived from a hydrocarbon group appears at 2800 - 2900 cm -1 it means that the polymer contained in the coating layer has a hydrocarbon group. When the polymer contained in the coating layer has a hydrocarbon group, a hydrophobic interaction occurs between the polymer contained in the coating layer and the crosslinked polyamide, making it difficult for the coating layer to peel off from the crosslinked polyamide during abrasion.

[0036] When the intensity ratio of the above peak is 0.20 or more, a sufficient hydrophobic interaction occurs between the polymer contained in the coating layer and the crosslinked polyamide, and the coating layer becomes a sacrificial layer, so that excellent abrasion resistance can be obtained. On the other hand, when the intensity ratio of the above peak is 0.30 or less, the decrease in the membrane permeation flux due to the introduction of an excessive coating layer can be suppressed. The above peak is calculated by the method described in "ATR-IR" in the examples described later.

[0037] The intensity ratio of the above peaks can be controlled, for example, by using a method that gives the polymer contained in the coating layer a structure with an alkyl chain which is a hydrophobic group, or by the polymer concentration during coating layer formation, coating time, etc.

[0038] 1.1.1 Polymers that form the coating layer The polymer contained in the coating layer of this embodiment preferably has a hydrophilic unit in addition to the structure represented by the general formula (I) above.

[0039] A "hydrophilic unit" is a monomer unit from which a single polymer (weight-average molecular weight: 10,000 g / mol) obtained from monomer units is water-soluble. Here, "water-soluble" means that a polymer consisting of monomer units that form a hydrophilic unit and having a molecular weight of 100,000 g / mol dissolves in water at 25°C at a concentration of 0.05% by mass or more.

[0040] Polymers having hydrophilic units are soluble in water-soluble solvents. "Soluble in water-soluble solvents" means that they dissolve in a solvent that is "water-soluble" at 25°C, at a concentration of 0.05% by mass or more. Because the polymer is water-soluble or soluble in water-soluble solvents, a coating layer containing the polymer can be formed on the composite semipermeable membrane using a solvent that does not alter the composite semipermeable membrane.

[0041] The hydrophilic polymer units contained in the coating layer of the composite semipermeable membrane according to this embodiment preferably have a structure represented by the following general formula (II).

[0042] [ka]

[0043] In general formula (II), R3 and R4 in each repeating unit are independently hydrogen or a hydrocarbon group having 2 or fewer carbon atoms, and n is an integer of 1 or more.

[0044] When the polymer has the structure represented by the above general formula (II), the polymer's affinity for water-soluble solvents is improved, and hydrophobic interactions act between the ether group and the crosslinked polyamide, strengthening the interaction between the polymer and the crosslinked polyamide, thereby adequately protecting the crosslinked polyamide and resulting in a composite semipermeable film with excellent abrasion resistance. From the viewpoint of the polymer's solubility in water-soluble solvents and the formation of hydrogen bonds between the hydrophilic units in the polymer and the polyamide, as well as the function of hydrophobic interactions, R3 and R4 are preferably hydrogen or methyl groups. Furthermore, from the viewpoint of the polymer's solubility in water-soluble solvents, n is preferably an integer between 5 and 500, more preferably between 5 and 300, and even more preferably between 10 and 250.

[0045] The hydrophilic unit preferably has a carbon chain with 4 to 11 carbon atoms in its main chain. When the carbon chain has 4 or more carbon atoms, a strong hydrophobic interaction acts between the polymer and the polyamide, causing the coating layer to act as a sacrificial layer and improving the abrasion resistance of the composite semipermeable membrane. Furthermore, when the carbon chain has 11 or fewer carbon atoms, the solubility of the polymer in water-soluble solvents increases, making it possible to form a coating layer by contacting a water-soluble solvent containing the polymer that forms the coating layer onto the separation functional layer. The carbon chain may be linear or cyclic, and may have unsaturated bonds.

[0046] Furthermore, the hydrophilic unit may also have a structure represented by the following general formula (III). Specifically, the hydrophilic unit may have a structure represented by general formula (III) and preferably have a hydrocarbon group with 4 to 11 carbon atoms as a carbon chain in the main chain.

[0047] [ka]

[0048] In general formula (III), R5 is a hydrocarbon group having 4 to 11 carbon atoms, which may be substituted.

[0049] The hydrophilic unit has a structure represented by the above general formula (III), which allows for the formation of strong hydrogen bonds between the polymer having highly polarizable carbonyl groups and the polyamide.

[0050] The number of carbon atoms in the hydrocarbon group R5 is preferably 4 to 10, more preferably 4 to 8, and even more preferably 4 to 6. When R5 is a hydrocarbon group with 4 to 11 carbon atoms, hydrophobic interactions occur between the hydrophilic units in the polymer and the polyamide.

[0051] Preferred structures for R5 include, for example, a butylene group (-C4H8-) and a pentylene group (-C5H8-). 10 -), hexylene group (-C6H 12 -), heptylene group (-C7H 14 -), octylene group (-C8H 16 -), nonylene group (-C9H 18 -), decilen group (-C 10 H 20 Hydrocarbon groups such as -), butenylene group (-C4H6-), pentenylene group (-C5H8-), hexenylene group (-C6H 10 Hydrocarbons having unsaturated structures such as -), cyclobutylene group (-C4H6-), cyclopentylene group (-C5H8-), cyclohexylene group (-C6H 10 Examples include cyclic hydrocarbons such as (-) and aromatic hydrocarbons such as phenylene groups (-C6H4-). These carbon chains may be substituted with any functional group, such as a hydroxyl group. In particular, R5 can be a butylene group (-C4H8-) or a pentylene group (-C5H 10 -), hexylene group (-C6H 12 -), a phenylene group (-C6H4-) is more preferred.

[0052] Furthermore, it is even more preferable that the hydrophilic unit has a structure represented by the following general formula (IV).

[0053] [ka]

[0054] In general formula (IV), X is a structure containing general formula (II), R5 is a hydrocarbon group having 4 to 11 carbon atoms, which may be substituted, and R6 and R7 are each independently hydrogen, a hydrocarbon group having 2 or fewer carbon atoms, or a functional group having 2 or fewer carbon atoms.

[0055] When the hydrophilic unit has the structure represented by the general formula (IV) above, a strong hydrogen bond is formed between the polymer and the polyamide, and a strong hydrophobic interaction is at work, and the coating layer acts as a sacrificial layer, resulting in a composite semipermeable film with excellent abrasion resistance. If the polymer contained in the coating layer has two or more different hydrophilic units, it is sufficient that at least one hydrophilic unit has the structure of the general formula (IV), and it is more preferable that all hydrophilic units have the structure of the general formula (IV).

[0056] The preferred number of carbon atoms and specific examples of the hydrocarbon group R5 are as described above for general formula (III). R6 and R7 are preferably hydrogen or a hydrocarbon group with 1 carbon atom, and more preferably hydrogen, because they have good interaction with the amide group of the crosslinked polyamide of the separation functional layer and thus have less steric hindrance.

[0057] The polymer contained in the coating layer of the composite semipermeable membrane according to this embodiment preferably has a structure represented by the following general formula (V).

[0058] [ka]

[0059] In general formula (V), R1 and R5 are each independently substituted hydrocarbon groups having 4 to 11 carbon atoms, R2, R6, and R7 are each independently hydrogen or hydrocarbon groups having 2 or fewer carbon atoms or functional groups having 2 or fewer carbon atoms, X is a structure containing the above general formula (II), and r and q are each independently integers of 1 or more.

[0060] In other words, the above general formula (V) is a copolymer of a hydrophilic unit having the structure represented by the above general formula (IV) and a unit having the structure represented by the above general formula (I). When the polymer contained in the coating layer has the structure represented by general formula (V), it forms strong hydrogen bonds with the crosslinked polyamide and hydrophobic interactions occur, making it difficult for the coating layer to peel off from the crosslinked polyamide, resulting in a composite semipermeable film with high abrasion resistance. The preferred forms of R1 and R2 are as described above with respect to the general formula (I). The preferred form of R5 is as described above with respect to the general formula (III). The preferred forms of R6 and R7 are as described above with respect to the general formula (IV).

[0061] In this embodiment, the coating layer of the composite semipermeable membrane is preferably immobilized so that it does not leach out when the composite semipermeable membrane is used. Examples of methods for immobilizing the coating layer include forming non-covalent bonds such as hydrogen bonds and ionic bonds between the coating layer and the polyamide and immobilizing it on the separation functional layer, forming covalent bonds between the polyamide and a crosslinking agent and immobilizing it on the separation functional layer, and forming covalent bonds between the coating layers and a crosslinking agent and immobilizing them as a three-dimensional structure. Among these, from the viewpoint of being able to continue stable operation over a long period of time, the method of forming covalent bonds between the coating layer and a crosslinking agent and immobilizing it on the separation functional layer is more preferable.

[0062] The copolymer contained in the coating layer of the composite semipermeable membrane according to this embodiment preferably consists only of non-halogen atoms. Halogen atoms typically act as electron-withdrawing groups and therefore affect the degree of polarization of the functional group. Furthermore, halogen atoms hydrolyze in water, releasing halogen atoms into the water, which raises concerns about water pollution.

[0063] The polymer contained in the coating layer of the composite semipermeable membrane according to this embodiment is preferably water-soluble or soluble in water-soluble solvents. By the polymer being water-soluble or soluble in water-soluble solvents, a coating layer containing the polymer can be formed on the composite semipermeable membrane using a solvent that does not alter the composite semipermeable membrane. Examples of water-soluble solvents include acetic acid, acetone, acetonitrile, N,N-dimethylformamide (hereinafter referred to as "DMF"), dimethyl sulfoxide, dioxane, methanol, ethanol, propanol, tetrahydrofuran, dimethylacetamide, and N-methylpyrrolidone.

[0064] In the composite semipermeable membrane according to this embodiment, 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 50 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 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 semipermeable membrane with good membrane permeation flux can be obtained. The total thickness T of the separation functional layer and the coating layer can be measured by observing the composite semipermeable membrane with a scanning transmission electron microscope.

[0065] The presence of the aforementioned polymer in the coating layer of a composite semipermeable membrane can be confirmed, for example, by analyzing the surface of the separation functional layer side of the composite semipermeable membrane using time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy, Raman spectroscopy, or infrared spectroscopy. This allows for the detection of characteristic peaks such as amide groups present in the polymer contained in the coating layer. Furthermore, the structure of the polymer can be identified by extracting only the coating layer and analyzing it using nuclear magnetic resonance spectroscopy, liquid chromatography-mass spectrometry, or gas chromatography-mass spectrometry.

[0066] 1.2 Porous support layer The composite semipermeable membrane according to this embodiment includes a porous support layer. The porous support layer may be formed on a substrate, and the composite of the substrate and the porous support layer is also referred to as the support membrane. The porous support layer and the substrate may each consist of one layer or two or more layers. The porous support layer and the substrate are for providing strength to the separation functional layer and do not substantially possess solute separation performance themselves.

[0067] Examples of base materials include fabrics made from polyester polymers, polyamide polymers, polyolefin polymers, and mixtures or copolymers thereof. Among these, fabrics made from polyester polymers, which have high mechanical and thermal stability, are preferred. The fabric can preferably be in the form of a long-fiber nonwoven fabric, a short-fiber nonwoven fabric, or a woven or knitted fabric.

[0068] The porous support layer has numerous interconnected pores. The pore diameter and pore diameter distribution are not particularly limited, but a porous support layer is preferred in which, for example, there is a symmetric structure with uniform pore diameters, or an asymmetric structure in which the pore diameter gradually increases from one surface to the other, and the pore diameter on the surface with smaller pore diameters is 0.1 to 100 nm.

[0069] As the material for the porous support layer, homopolymers (homopolymers) or copolymers of polysulfone (hereinafter referred to as "PSf"), polyethersulfone, polyamide, polyester, cellulose polymers, vinyl polymers, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, polyphenylene oxide, etc., can be used alone or in blends. Here, 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 of PSf, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, polyphenylene sulfide sulfone, and polyphenylene sulfone are preferred, with PSf, cellulose acetate, polyphenylene sulfide sulfone, or polyphenylene sulfone being more preferred. PSf is particularly preferred because it has high chemical, mechanical, and thermal stability and is easy to mold.

[0070] The weight-average molecular weight (hereinafter referred to as "Mw") of PSf is preferably 10,000 to 200,000, and more preferably 15,000 to 100,000. When the Mw of PSf is 10,000 or more, desirable mechanical strength and heat resistance can be obtained as 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.

[0071] The thickness of the substrate and the porous support layer affects the strength of the composite semipermeable membrane and the packing density when it is used as a composite semipermeable membrane element. To obtain good mechanical strength and packing density, the total thickness of the substrate and the porous support layer is preferably 50 μm to 300 μm, and more preferably 100 μm to 250 μm. Furthermore, the thickness of the porous support layer is preferably 20 μm to 100 μm. The thickness of the substrate and the porous support layer is the average value of 20 thicknesses measured at 20 μm intervals in a direction perpendicular to the thickness direction (the surface direction of the membrane) during cross-sectional observation.

[0072] 1.3 Separation functional layer The separation functional layer of the composite semipermeable membrane according to this embodiment is a layer responsible for solute separation and contains cross-linked polyamide. It is more preferable that the separation functional layer is mainly composed of cross-linked polyamide. "Mainly composed of cross-linked polyamide" means that the proportion of cross-linked polyamide in the separation functional layer is 50% by mass or more. It is more preferable that the proportion of cross-linked polyamide in the separation functional layer is 80% by mass or more, and even more preferable that it is 90% by mass or more.

[0073] The crosslinked polyamide contained in the separation functional layer is a polycondensate of a polyfunctional amine and a polyfunctional acid halide. In particular, the crosslinked polyamide is preferably a crosslinked aromatic polyamide.

[0074] "Cross-linked polyamide" means that the polyamide forms a cross-linked structure. For example, the polyamide may form a cross-linked structure via a cross-linking agent, or at least one of the polyfunctional amine and polyfunctional acid halide may be trifunctional or more, and the polyamide may form a network-like cross-linked structure. In particular, it is more preferable that at least one of the polyfunctional amine and polyfunctional acid halide is trifunctional or more, and the polyamide forms a network-like cross-linked structure. This results in a rigid molecular chain and a cross-linked polyamide having a good pore structure for removing fine solutes such as hydrated ions and silica.

[0075] "Aromatic polyamide" refers to a polymer of a polyfunctional amine and a polyfunctional aromatic acid halide. Specifically, examples include polymers of polyfunctional aliphatic amines and polyfunctional aromatic acid halides, and polymers of polyfunctional aromatic amines and polyfunctional aromatic acid halides. Aromatic polyamides may contain non-aromatic moieties in their molecular structure. From the viewpoint of rigidity, chemical stability, and chemical resistance to operating pressure, crosslinked aromatic polyamides are more preferable, and crosslinked total aromatic polyamides consisting solely of aromatic polyamides are even more preferable.

[0076] A "polyfunctional amine" refers to an amine having at least two primary amino groups and / or secondary amino groups in a single molecule. Examples of polyfunctional amines include aromatic trifunctional amines such as 1,3,5-triaminobenzene and 1,2,4-triaminobenzene; aromatic difunctional 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 difunctional amines such as ethylenediamine, propylenediamine, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, 4-aminopiperidine, and aminoethylpiperazine. These polyfunctional amines may be used individually or in combination of two or more.

[0077] From the viewpoint of the separation performance, membrane permeation flux, and heat resistance of the composite semipermeable membrane, the polyfunctional amines are preferably m-PDA, p-phenylenediamine, and 1,3,5-triaminobenzene. Among these, m-PDA is particularly preferred from the viewpoint of ease of availability and ease of handling.

[0078] A "polyfunctional acid halide" refers to an acid halide having at least two halogenated carbonyl groups in one molecule. Examples of polyfunctional acid halides 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, bifunctional aromatic acid chlorides such as biphenyldicarboxylic acid chloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, and 2,6-naphthalenedicarboxylic acid dichloride, and bifunctional aliphatic acid chlorides such as adipoyl chloride, sebacoyl chloride, and 1,4-cyclohexanedicarboxylic acid dichloride. These polyfunctional acid halides may be used individually or in combination of two or more.

[0079] From the viewpoint of the separation performance and heat resistance of the composite semipermeable membrane, polyfunctional aromatic acid chlorides having 2 to 4 chlorocarbonyl groups in one molecule are preferred as the polyfunctional acid halide. Among these, TMC is particularly preferred from the viewpoint of ease of availability and ease of handling.

[0080] The shape and thickness of the separation functional layer and the coating layer affect the separation performance and membrane permeation flux. As shown in Figures 1(a) and (b), the separation functional layer 3 is preferably pleated, having multiple protrusions. Furthermore, it is more preferable that the inside of the protrusions 5 (between the separation functional layer 3 and the support membrane 2) be voids. The separation functional layer 3 can have a larger surface area if it has a pleated shape rather than a flat shape, thus enabling a high membrane permeation flux 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, or it may have a relatively large thickness that fills the pleated shape of the separation functional layer 3.

[0081] The presence of a pleated shape in the separation functional layer can be confirmed by observing a cross-section of the separation functional layer perpendicular to the surface of the composite semipermeable membrane using a transmission electron microscope (TEM). If even a slight protrusion is observed in the separation functional layer during TEM observation, it is considered to have a pleated shape.

[0082] Generally, composite semipermeable membranes are subjected to cleaning with acidic and alkaline chemicals in water treatment facilities, so it is desirable that they possess acid and alkali resistance. Furthermore, if pretreatment using an ultrafiltration membrane or the like is performed before the composite semipermeable membrane, oxidizing agents such as chlorine used to clean the pretreatment membrane may leak and come into contact with the composite semipermeable membrane, causing oxidative degradation. Therefore, it is preferable that composite semipermeable membranes also possess chlorine resistance.

[0083] In this embodiment, the composite semipermeable membrane stabilizes the crosslinked aromatic polyamide by forming hydrogen bonds and hydrophobic interactions between the polymer contained in the coating layer and the crosslinked aromatic polyamide contained in the separation functional layer. Therefore, the composite semipermeable membrane exhibits excellent abrasion resistance as well as high acid resistance, alkali resistance, and chlorine resistance. Due to these properties, the composite semipermeable membrane according to this embodiment can maintain good performance before and after chemical cleaning and oxidizing agent cleaning.

[0084] 1.4 Composite semipermeable membrane elements The composite semipermeable membrane element according to this embodiment comprises the composite semipermeable membrane according to this embodiment. An example of the configuration of the composite semipermeable membrane element will be described with reference to Figure 2.

[0085] As shown in Figure 2, the composite semipermeable membrane element 6 comprises a composite semipermeable membrane 1, a supply-side channel material 9, a permeable-side channel material 10, a water collection pipe 11, and end plates 7 and 8. The supply-side channel material 9 is positioned opposite the supply side of the composite semipermeable membrane 1 and is wrapped around the water collection pipe 11 together with the composite semipermeable membrane 1. A net is preferred as the supply-side channel material 9. The permeable channel material 10 is positioned opposite the permeable side of the composite semipermeable membrane 1 and is wrapped around the water collection pipe 11 together with the composite semipermeable membrane 1. For example, tricot or a protrusion-fixing sheet can be used as the permeable channel material 10. The water collection pipe 11 is a hollow cylindrical member having multiple holes on its side. The end plates 7 and 8 are disc-shaped members equipped with multiple supply ports (or discharge ports).

[0086] The separation of fluids by the composite semipermeable membrane element 6 will now be explained. The supply water 12 is supplied to the composite semipermeable membrane element 6 from multiple supply ports on the end plate 7. The supply water 12 moves within the supply-side channel formed by the supply-side channel material 9 on the supply side of the composite semipermeable membrane 1. The fluid that permeates through the composite semipermeable membrane 1 (shown as permeate water 13 in the figure) moves within the permeate-side channel formed by the permeate-side channel material 10. The permeate water 13 that reaches the collection pipe 11 enters the inside of the collection pipe 11 through the holes in the collection pipe 11. The permeate water 13 that has flowed inside the collection pipe 11 is discharged to the outside from the end plate 8. On the other hand, the fluid that did not permeate through the composite semipermeable membrane 1 (shown as concentrated water 14 in the figure) moves within the supply-side channel and is discharged to the outside from the end plate 8. In this way, the supply water 12 is separated into permeate water 13 and concentrated water 14.

[0087] 2. Method for manufacturing composite semipermeable membranes The method for manufacturing a composite semipermeable membrane according to one embodiment of the present invention is not particularly limited as long as a composite semipermeable membrane satisfying the desired characteristics described above can be obtained, but for example, it can be manufactured by the following method.

[0088] 2.1 Formation of the support film For the method of forming the support film, known methods can be suitably used. The following description will take the case where PSf is used as the material for the porous support layer as an example.

[0089] First, PSf is dissolved in a suitable solvent to prepare a porous support layer stock solution. DMF is a preferred solvent for PSf.

[0090] The concentration of PSf in the porous support layer stock solution is preferably 10% to 25% by mass, and more preferably 12% to 20% by mass. When the concentration of PSf in the porous support layer stock solution is within the above range, both the strength and membrane permeation flux of the resulting porous support layer can be achieved. The preferred range of material concentration in the porous support layer stock solution can be appropriately adjusted depending on the material used, the good solvent, etc.

[0091] Next, the obtained porous support layer stock solution is applied to the substrate surface and immersed in a solidification solution containing a non-solvent of PSf. Water is preferred as the non-solvent of PSf in the solidification solution. By bringing the porous support layer stock solution applied to the substrate surface into contact with the solidification solution containing a non-solvent of PSf, the porous support layer stock solution solidifies through non-solvent-induced phase separation, and a support film with a porous support layer is obtained on the substrate surface.

[0092] The coagulation solution may consist solely of non-solvent PSf, but it may also contain a good solvent for PSf to the extent that it can coagulate the porous support layer stock solution.

[0093] The resulting support film may be washed before the formation of the separation functional layer to remove any remaining solvent in the film.

[0094] 2.2 Process for forming the separation functional layer Regarding the formation method of a separation functional layer containing polyamide, we will describe, as an example, a method in which a polyfunctional amine and a polyfunctional acid halide are polymerized and solidified on the porous support layer of the 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 interfacial polymerization process will be described below.

[0095] The interfacial polymerization process comprises (a) contacting an aqueous solution containing a polyfunctional amine with a porous support layer, (b) contacting an organic solvent solution containing a polyfunctional acid halide with the surface of the porous support layer that has been contacted with the aqueous solution containing the polyfunctional 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.

[0096] In step (a), the aqueous solution contains at least a polyfunctional amine. As the polyfunctional amine, for example, the polyfunctional amines described in "1.3 Separation Functional Layer" above can be used.

[0097] The concentration of the polyfunctional amine in the aqueous solution is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 15% by mass or less, and even more preferably 1.0% by mass or more and 10% by mass or less. When the concentration of the polyfunctional amine is 0.1% by mass or more, a separation functional layer having solute separation performance can be formed. On the other hand, when the concentration of the polyfunctional amine is 20% by mass or less, a separation functional layer having good membrane permeation flux can be formed. Furthermore, the aqueous solution may contain compounds such as surfactants and antioxidants as needed, as long as they do not inhibit polymerization.

[0098] It is preferable to bring the polyfunctional amine aqueous solution into uniform and continuous contact with the porous support layer. Specifically, examples include coating the porous support layer with the polyfunctional amine aqueous solution, or immersing the porous support layer or support film in the aqueous solution. The contact time between the porous support layer and the aqueous solution is preferably 1 second to 10 minutes, and more preferably 3 seconds to 3 minutes.

[0099] After bringing the polyfunctional amine aqueous solution into contact with the porous support layer, it is preferable to thoroughly drain the liquid so that no droplets remain on the porous support layer. Thorough draining prevents residual droplets from becoming membrane defects and reducing separation performance after the formation of the composite semipermeable membrane. Methods for draining include, for example, holding the porous support layer or support membrane vertically after contact with the aqueous solution to allow excess aqueous solution to flow naturally, or forcibly draining the liquid by blowing a stream of air such as nitrogen from an air nozzle. Alternatively, after draining, the membrane surface can be dried to remove some of the water from the aqueous solution.

[0100] In step (b), as the polyfunctional acid halide, for example, the polyfunctional acid halide described in "1.3 Separation Functional Layer" above can be used.

[0101] The organic solvent is preferably immiscible with water, dissolves polyfunctional acid halides, does not damage the support film, and is inert to polyfunctional amines and polyfunctional acid halides. Examples of organic solvents include hydrocarbon compounds such as n-nonane, n-decane, n-undecane, n-dodecane, isooctane, isodecane, and isododecane, as well as mixed solvents thereof.

[0102] The concentration of the polyfunctional 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 acid halide 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 acid halide is 10% by mass or less, the occurrence of side reactions during polymerization can be suppressed. Furthermore, the organic solvent solution may contain compounds such as surfactants as needed, as long as they do not inhibit polymerization.

[0103] It is preferable to uniformly and continuously bring the organic solvent solution of the polyfunctional acid halide into contact with a porous support layer that has been brought into contact with an aqueous solution of a polyfunctional amine. Specifically, for example, one method is to coat the porous support layer that has been brought into contact with an aqueous solution of a polyfunctional amine with the organic solvent solution of the polyfunctional acid halide. The contact time between the porous support layer that has been brought into contact with the aqueous solution of a polyfunctional amine and the organic solvent solution of the polyfunctional acid halide is preferably 3 seconds to 10 minutes, and more preferably 5 seconds to 3 minutes.

[0104] Furthermore, if necessary, the porous support layer, which has been contacted with an organic solvent solution of a polyfunctional 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 film surface, which is the reaction field, but is preferably 5 seconds or more, and more preferably 10 seconds or more.

[0105] In step (c), the organic solvent solution on the composite semipermeable membrane after the polymerization reaction is removed by dewatering. Methods for dewatering include, for example, holding the membrane vertically and allowing the excess organic solvent solution to flow down naturally; blowing air with a fan to dry and remove the organic solvent; or removing the excess organic solvent solution with a mixed fluid of water and air.

[0106] 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 to 95°C, and more preferably 60°C to 95°C. If 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, if 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 amine or polyfunctional acid halide used.

[0107] 2.3 Process for forming the coating layer The composite semipermeable membrane processed in this process may be an unused membrane or a membrane that has deteriorated due to use or other factors. Furthermore, this process can be considered one of the manufacturing processes for composite semipermeable membranes.

[0108] The coating layer formation step comprises (e) bringing a solution containing a polymer having a structure represented by the following general formula (I) into contact with the separation functional layer, (f) draining off excess solution, and (g) washing the composite semipermeable membrane.

[0109] [ka]

[0110] In general formula (I), R1 is a hydrocarbon group having 4 to 11 carbon atoms, which may be substituted, and R2 is hydrogen, a hydrocarbon group having 2 or fewer carbon atoms, or a functional group having 2 or fewer carbon atoms.

[0111] In step (e), the solution containing the polymer forming the coating layer may optionally contain compounds such as a crosslinking agent. The crosslinking agent may crosslink the polymers forming the coating layer, or it may crosslink the polymers forming the coating layer with the crosslinked polyamide in the separation functional layer. When the polymers forming the coating layer are fixed to the crosslinked polyamide in the separation functional layer by the crosslinking agent, further improvement in abrasion resistance can be expected. Examples of crosslinking agents include molecules having multiple glycidyl groups in the molecule, such as ethylene glycol diglycidyl ether, and methyl vinyl ether / maleic anhydride copolymer.

[0112] The solution contains water and at least one solvent selected from the water-soluble solvents mentioned above. In other words, the solution may contain two or more solvents.

[0113] The concentration of the polymer forming the coating layer in the solution is preferably 0.0002% by mass or more and 10% by mass or less, more preferably 0.0002% by mass or more and 2% by mass or less, and even more preferably 0.005% by mass or more and 1% by mass or less. When the concentration of the polymer forming the coating layer is 0.0002% by mass or more, a sufficient amount of the polymer forming the coating layer comes into contact with the surface of the separation functional layer, so the coating layer acts as a sacrificial layer and excellent abrasion resistance can be obtained. On the other hand, when the concentration of the polymer forming the coating layer is 10% by mass or less, a composite semipermeable membrane with sufficient water permeability can be obtained.

[0114] It is preferable that the contact between the solution containing the polymer that forms the coating layer and the composite semipermeable membrane be uniform and continuous on the separation functional layer. Specifically, for example, one method is to coat the separation functional layer with the solution containing the polymer that forms the coating layer. The contact time with the solution containing the polymer that forms the coating layer is preferably 5 seconds to 24 hours, and more preferably 10 seconds to 24 hours.

[0115] In step (f), the solution on the composite semipermeable membrane is removed by dewatering. Methods of dewatering include, for example, gripping the membrane vertically and allowing the excess solution to flow down naturally, or blowing air with a fan to dry and remove the solvent.

[0116] In step (g), the composite semipermeable membrane from which the solution has been removed is washed with water. The water temperature is preferably 15°C to 95°C, and more preferably 20°C to 90°C. If the water temperature is 15°C or higher, unreacted substances and catalysts remaining in the membrane can be sufficiently removed. On the other hand, if the water temperature 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 water temperature can be appropriately adjusted depending on the water-soluble polymer and crosslinking agent used.

[0117] Furthermore, the composite semipermeable membrane may be hydrophilized if necessary. Examples of hydrophilization methods include contacting the composite semipermeable membrane with aqueous solutions of surfactants such as polyoxyethylene octylphenyl ether and sodium n-decylbenzenesulfonate, or aqueous solutions of alcohols such as methanol, ethanol, isopropanol, and glycerin.

[0118] 3. Use of composite semipermeable membranes The composite semipermeable membrane according to this embodiment is preferably used as a spiral-type composite semipermeable membrane element, wound around a cylindrical water collection pipe with numerous holes, together with a water supply channel material such as a plastic net, a permeable water channel material such as tricot, and a film to enhance pressure resistance as needed. Furthermore, a composite semipermeable membrane module can be formed by connecting these elements in series or parallel and housing them in a pressure vessel.

[0119] Furthermore, the composite semipermeable membranes, their elements, and modules can be combined with pumps that supply water to them, and devices that pre-treat the supply water to constitute a fluid separation system. By using this separation system, the supply water can be separated into permeate (such as drinking water) and concentrated water that did not permeate the membrane, thereby obtaining water suitable for the purpose.

[0120] From the viewpoint of reducing environmental impact and effectively utilizing water resources, it is preferable that the fluid separation device be applicable to zero-liquid discharge systems (hereinafter referred to as "ZLD") and resource recovery applications. In ZLD, wastewater is concentrated using membrane separation technology, and then subjected to evaporation and drying treatment. Because the wastewater is concentrated to the extreme, foulants in the feedwater are concentrated, making fouling likely to occur. Fouling is a phenomenon in which substances contained in the water to be treated are adsorbed onto the surface or pores of a semipermeable membrane, inhibiting the permeation of the solution and reducing the membrane permeation flux of the composite semipermeable membrane. To eliminate the fouling phenomenon, frequent chemical cleaning is performed, so it is preferable to use a composite semipermeable membrane with excellent chemical resistance in ZLD. In ZLD, it is preferable to equip the preceding stage with a UF membrane device, as this allows for efficient removal of foulants. Industries in which ZLD is introduced include, for example, semiconductor and electronic component manufacturing, chemical industry, thermal power plants, and dyeing and textile factories. Since the wastewater from these industries may have a temperature of 35°C or higher, it is preferable that the fluid separation device used in ZLD can be used under conditions where the feedwater temperature is 35°C or higher. When using water at temperatures above 35°C as the supply water, a problem arises in that the deterioration of the composite semipermeable membrane in the fluid separation device is accelerated. On the other hand, in resource recovery applications, useful components are concentrated from factory wastewater using membrane separation technology and then recovered by sedimentation or adsorption. In this case, since the treated water may contain acidic or alkaline substances and oxidizing agents, the composite semipermeable membrane is prone to deterioration, and it is preferable to use a composite semipermeable membrane with excellent chemical resistance.

[0121] The composite semipermeable membrane according to this embodiment has excellent acid resistance, alkali resistance, and oxidation resistance, and can suppress degradation by chemicals that are a concern in ZLD and resource recovery applications, and is therefore preferably used in fluid separation devices for ZLD and resource recovery.

[0122] Furthermore, from the viewpoint of improving yield and reliability in the manufacturing process, fluid separation devices are preferably applicable to precision industries that use high-purity water and chemicals, such as semiconductor manufacturing. Examples of precision industries include the pharmaceutical and biopharmaceutical manufacturing field, where high purity of raw materials and solvents is required; the electronic and optical materials manufacturing field, where impurity control is required to maintain optical and electrical properties; the nuclear-related field, where the purity of chemicals and water affects the behavior of radioactive materials; and high-precision analytical fields, such as mass spectrometry and chromatography, where the purity of reagents and solvents directly impacts analytical accuracy. For example, hydrogen peroxide, one of the chemicals used for cleaning in the semiconductor manufacturing process, is generally synthesized and then purified using a method that utilizes the oxidation-reduction reaction of anthraquinones in an organic solvent. Impurities remaining in these manufacturing processes cause a decrease in semiconductor manufacturing yield, so it is preferable that they be removed in the purification process.

[0123] The composite semipermeable membrane according to this embodiment has excellent acid resistance, alkali resistance, and oxidation resistance, making it less susceptible to degradation caused by chemicals present in the liquid supplied to the composite semipermeable membrane. Therefore, it can effectively separate water, hydrogen peroxide, and other chemicals from impurities, and the quality of the permeate remains stable during operation. As a result, it can be preferably used in fluid separation devices for the purification of water and chemicals used in precision industries.

[0124] Examples of feedwater treated by the composite semipermeable membrane according to this embodiment include liquid mixtures containing 500 mg / L to 100 g / L of TDS (Total Dissolved Solids), such as seawater, brine, and wastewater. Generally, TDS refers to the total amount of dissolved solids and is expressed as "mass / volume" or "mass ratio". According to the definition, it can be calculated from the weight of the residue after evaporating a solution filtered through a 0.45 μm filter at a temperature of 39.5 to 40.5°C, but a simpler method is to convert it from the practical salinity (S).

[0125] While a higher operating pressure for the fluid separation device improves the solute removal rate, it also increases the energy required for operation. Considering the durability of the composite semipermeable membrane, the operating pressure when the treated water is permeated through the composite semipermeable membrane is preferably between 0.5 MPa and 10 MPa. Although a higher feedwater temperature reduces the solute removal rate, a lower temperature reduces the membrane permeation flux, so a temperature between 5°C and 45°C is preferable. Furthermore, if the feedwater pH is high, there is a risk of scale formation, such as magnesium, in the case of feedwater with high solute concentrations, such as seawater, and there is a concern about membrane deterioration due to high pH operation. Therefore, operation in the neutral range is preferable.

[0126] When a composite semipermeable membrane is used as a reverse osmosis membrane, the NaCl removal rate is preferably 99.0% or higher, more preferably 99.30% or higher, and even more preferably 99.50% or higher. The membrane permeation flux is preferably 0.5 m / d or more and 1.8 m / d or less, more preferably 0.7 m / d or more and 1.8 m / d or less, and even more preferably 1.0 m / d or more and 1.8 m / d or less. In this specification, the abrasion resistance of a composite semipermeable membrane refers to a small difference in membrane performance before and after the abrasion test described in the examples. Specifically, the difference in NaCl removal rate, which is the value obtained by subtracting the NaCl removal rate after the abrasion test from the initial performance NaCl removal rate, is preferably 0.4% or less, more preferably 0.2% or less, and even more preferably 0.1% or less. Furthermore, the membrane permeation flux ratio, which is the value obtained by dividing the membrane permeation flux after the abrasion test by the membrane permeation flux before the abrasion test, is preferably 1.5 or less, more preferably 1.3 or less, and even more preferably 1.1 or less.

[0127] The chemical resistance of the composite semi-permeable membrane in this specification means that in the "immersion treatment" described in the examples, the difference in membrane performance before and after the immersion treatment is small. Specifically, the SP ratio, which is the ratio of the NaCl permeability before and after the immersion treatment, is preferably 5.0 or less, more preferably 4.5 or less, and even more preferably 4.0 or less. Also, the membrane permeation flux ratio, which is the value obtained by dividing the membrane permeation flux after the immersion treatment by the membrane permeation flux before the immersion treatment, is preferably 1.7 or less, more preferably 1.6 or less, and even more preferably 1.5 or less. Further, it shows that the smaller the difference in membrane performance before and after the immersion treatment described in the "immersion treatment in hydrogen peroxide solution" in the examples, the higher the chemical resistance. Specifically, the SP ratio, which is the ratio of the NaCl permeability before and after the immersion treatment in hydrogen peroxide solution, is preferably 7.0 or less, more preferably 6.5 or less, and even more preferably 5.0 or less. Also, the membrane permeation flux ratio, which is the value obtained by dividing the membrane permeation flux after the immersion treatment in hydrogen peroxide solution by the membrane permeation flux before the immersion treatment in hydrogen peroxide solution, is preferably 1.7 or less, more preferably 1.6 or less, and even more preferably 1.5 or less.

[0128] 4. Treatment Agent for Composite Semi-Permeable Membrane As described above, since the polymer having the structures represented by general formulas (I) and (II) forms a hydrogen bond with crosslinked polyamide and hydrophobic interaction occurs, it can be used as a coating agent for improving the abrasion resistance of a composite semi-permeable membrane containing polyamide in the separation functional layer. The coating agent may contain other components such as a crosslinking agent within a range that does not interfere with the effects of the present invention.

Examples

[0129] The present invention will be described below with specific examples, but the present invention is not limited to these examples. In the table, "-" means not measured.

[0130] <NaCl Removal Rate> A composite semipermeable membrane was used as the supply water for evaluation, with the water adjusted to a temperature of 25°C, pH 7.0, and NaCl concentration of 34,000 ppm, and the membrane permeation flux was 1.0 m. 3 / m 2 The operating pressure was adjusted to achieve a ratio of / d, and the water was supplied and membrane filtration was performed for 1 hour. Subsequently, the electrical conductivity of the supplied water and permeate was measured using a multi-water quality meter MM60R (manufactured by Toa DKK Co., Ltd.) to obtain the practical salinity, i.e., the NaCl concentration, for each. From the obtained NaCl concentration, the NaCl removal rate was calculated using the following formula (1). Here, the NaCl concentration (ppm) refers to the concentration on a mass basis. The value was rounded to the third decimal place. NaCl removal rate (%) = 100 × {1 - (NaCl concentration in permeate / NaCl concentration in feedwater)} ... Equation (1)

[0131] <Membrane permeation flux> Evaluation water, adjusted to a temperature of 25°C, pH 7.0, and sodium chloride concentration of 34,000 ppm, was supplied to a composite semipermeable membrane at a pressure of 5.50 MPa, and membrane filtration was performed for 1 hour. Subsequently, the permeate volume (m³) over 20 minutes was measured. 3 ) was measured, and the unit membrane area (m²) was measured. 2 The membrane permeation flux (m / d) was calculated by converting the values ​​to values ​​per unit time (d). Two significant figures were used.

[0132] <Immersion treatment> The composite semipermeable membrane was immersed in a sodium hypochlorite aqueous solution prepared at 25°C, 100 ppm, and pH 7.0 for 20 hours and washed with distilled water. Next, it was immersed in a sodium hydroxide aqueous solution prepared at 25°C and pH 13.0 for 20 hours, then immersed in sulfuric acid prepared at 25°C and pH 1.0 for 20 hours and washed with distilled water. For the resulting composite semipermeable membrane after immersion treatment, the NaCl removal rate and membrane permeation flux were calculated using the methods described above for "NaCl removal rate" and "membrane permeation flux". Chemical resistance was evaluated by the membrane permeation flux ratio and SP ratio before and after immersion treatment, and calculated using the following formulas (2) to (4). Membrane permeation flux ratio = Membrane permeation flux after immersion treatment / Membrane permeation flux before immersion treatment ... Equation (2) NaCl transmittance (%)=100-NaCl removal rate...Equation (3) SP ratio = NaCl permeability after immersion treatment / NaCl permeability before immersion treatment ... Equation (4) A membrane permeation flux ratio of 1.7 or less before and after immersion treatment is considered good. Furthermore, an SP ratio of 5.0 or less before and after immersion treatment is also considered good. Furthermore, the composite semipermeable membranes of Reference Example 3, Example 10, and Comparative Example 7, described later, were subjected to immersion treatment, and the membrane performance before and after the immersion treatment was evaluated.

[0133] <Immersion treatment in hydrogen peroxide solution> The composite semipermeable membrane was immersed in a 35% by mass aqueous solution of hydrogen peroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako Grade 1, product code 080-01186) at 25°C for 72 hours, and then washed with distilled water. The NaCl removal rate and membrane permeation flux were calculated for the resulting composite semipermeable membrane after the immersion treatment using the methods described in "NaCl Removal Rate" and "Membrane Permeation Flux" above. Chemical resistance was evaluated by the membrane permeation flux ratio and SP ratio before and after immersion treatment in hydrogen peroxide, as described in "Immersion Treatment" above. A membrane permeation flux ratio of 1.7 or less before and after immersion in hydrogen peroxide solution is considered good. Furthermore, an SP ratio of 7.0 or less before and after immersion in hydrogen peroxide solution is also considered good. Furthermore, the composite semipermeable membranes of Reference Example 3, Example 10, and Comparative Example 7, described later, were subjected to immersion treatment in hydrogen peroxide solution, and the membrane performance before and after the treatment was evaluated.

[0134] <Coloring due to vanillin> A composite semipermeable membrane was washed with 85°C hot water for 2 minutes, and then the moisture on the surface of the coating layer or separation functional layer was removed by air drying. After drying, the composite semipermeable membrane was immersed in a 2% by mass ethanol solution containing vanillin at 25°C for 15 seconds, the membrane was tilted to remove excess ethanol solution from the membrane surface, and the ethanol on the membrane surface was removed by air drying. Furthermore, a vanillin-treated membrane sample was obtained by heating in a 150°C oven for 15 minutes. Alternatively, a composite semipermeable membrane was washed with 85°C hot water for 2 minutes, and then the moisture on the surface was removed by air drying. After drying, the composite semipermeable membrane was immersed in an ethanol solution for 15 seconds, the membrane was tilted to remove excess ethanol solution from the membrane surface, and the ethanol on the membrane surface was removed by air drying. Furthermore, an untreated membrane sample was obtained by heating in a 150°C oven for 15 minutes. The yellowness of the surface of the coating layer or separation functional layer was measured using a portable colorimeter (TCS-100, Time Technology Co., Ltd.) in accordance with JIS K 7373, using a standard illuminant D65 light source. The yellowness VYI of the vanillin-treated film sample and the yellowness VYI0 of the untreated film sample were measured from the tristimulus values ​​of the XYZ color system, and the degree of yellowing ΔVYI was calculated using the following formula (5). The degree of yellowing ΔVYI was measured three times using different samples, and the average value obtained was rounded to the first decimal place. ΔVYI = VYI - VYI0 ... Equation (5)

[0135] <Elastic modulus underwater> Under the following conditions, the deformation of the coating layer surface was measured using an atomic force microscope (AFM). The elastic modulus in water was then measured based on the deformation. Ten different folds and protrusions were measured within each sample. Furthermore, three measurements were performed using different samples, and the average value obtained was rounded to the first decimal place. Observation equipment: BRUKER FastScan scanning probe microscope Probe: Cantilever (made of silicon, spring constant: 0.7 N / m, shape: conical) Scanning mode: Nanomechanical Mapping in Fluid Scanning area: 2 μm square

[0136] The cantilever's bending sensitivity was measured using sapphire, and the cantilever's spring constant was determined by thermal vibration. The composite semipermeable membrane was immersed in a 20% by mass aqueous solution of isopropanol at 25°C for 20 minutes, and then immersed in distilled water at 25°C for 1 hour. Subsequently, a 1 cm square piece of the composite semipermeable membrane was fixed to a sample stage, and 0.3 mL of distilled water was added dropwise. The cantilever was then pressed against the convex folds on the separation functional layer side and then released, and a curve plotting the force acting on the cantilever against the distance between the cantilever and the composite semipermeable membrane was obtained. In this specification, this curve is referred to as the force curve.

[0137] At this time, let Z be the displacement of the cantilever (Z=Z0 at the moment the cantilever and the composite semipermeable membrane come into contact, and Z=0 at the point furthest from the sample), and let Δ be the curvature of the cantilever. The amount of deformation δ when the composite semipermeable membrane, which is the sample, is deformed due to contact with the cantilever is given by the following equation (6). δ[nm]=(Z-Z0)-Δ ···Equation (6) Here, with respect to the displacement Zt of the cantilever where the composite semipermeable membrane and the cantilever are in contact, Z, δ, and Δ take their maximum values ​​Zt, δt, and Δt. Here, by considering Δ with respect to the cantilever displacement Z, the horizontal axis is transformed into the distance between the cantilever and the composite semipermeable membrane. At this time, the distance between the cantilever and the composite semipermeable membrane is a parameter that satisfies the following equation (7). Distance between the cantilever and the composite semipermeable membrane [nm] = Δ - Z + Zt - Δt ... Equation (7)

[0138] The distance between the cantilever and the composite semipermeable membrane at the point on the force curve where the load is zero, i.e., Δ=0 and Z=Z0, is given by equation (7) as Zt-Z0-Δt, while the deformation δt at the point of maximum interaction is given by equation (6) as Zt-Z0-Δt. Therefore, the distance between the cantilever and the composite semipermeable membrane at the point on the force curve where the load is zero was read, and the deformation δt when a certain load was applied was determined.

[0139] When the cantilever was brought close to the composite semipermeable membrane, the amount of deformation measured with the distance between the cantilever and the composite semipermeable membrane on the horizontal axis and the load on the vertical axis was used to measure the modulus of elasticity in water using the following equation (8). At that time, the curves in the load range of 3 to 21 nN were approximated to straight lines by fitting.

[0140] In the Hertz model, which assumes that the cantilever and composite semipermeable membrane are spherical, the following relationship holds between load and modulus of elasticity. Using this equation, the modulus of elasticity underwater was calculated from the resulting force curve. F=(4 / 3){E / (1-ν)}(√R)δ 3 / 2 ...Equation (8) Here, F is the load (nN), E is the modulus of elasticity in water (MPa), ν is Poisson's ratio, R is the radius of the cantilever (nm), and δ is the deformation of the composite semipermeable membrane (nm). In this specification, the load F was set to 30 nN, the cantilever radius R to 20 nm, and the Poisson's ratio ν to 0.3.

[0141] <Color development using Dragendorff's reagent> Solution A was prepared by dissolving bismuth subnitrate in 1 mol / L hydrochloric acid to a concentration of 56 mmol / L. Next, solution B was prepared by dissolving potassium iodide in water to a concentration of 2.4 mol / L. Solution A and solution B were mixed in a 1:1 ratio, and then diluted 2.5 times with water to prepare Dragendorff's reagent. The composite semipermeable membrane was immersed in 0.05 mol / L hydrochloric acid for 15 minutes, then immersed in Dragendorff's reagent for 45 minutes, and then immersed in 0.05 mol / L hydrochloric acid for 10 minutes to remove any remaining Dragendorff's reagent from the membrane surface. After air drying overnight, a Dragendorff's reagent-treated membrane sample was obtained. Alternatively, the composite semipermeable membrane was immersed in 0.05 mol / L hydrochloric acid for 15 minutes, then immersed in 0.2 mol / L hydrochloric acid for 45 minutes, and then immersed in 0.05 mol / L hydrochloric acid for 10 minutes. The untreated film samples were then air-dried overnight to obtain the untreated film samples. The yellowness of the film samples was measured using a portable colorimeter (TCS-100, Time Technology Co., Ltd.), in accordance with JIS K 7373, with a standard illuminant D65 light source. The yellowness DYI of the Dragendorff reagent-treated film samples and the yellowness DYI0 of the untreated film samples were measured from the tristimulus values ​​of the XYZ color system, and the degree of yellowing ΔDYI was calculated using the following formula (9). The degree of yellowing ΔDYI was measured three times using different samples, and the average value obtained was rounded to the first decimal place. ΔDYI = DYI - DYI0 ... Equation (9)

[0142] <Abrasion Test> As shown in Figures 3 and 4, the composite semipermeable membrane 1 was cut into a 12cm x 13cm square and attached to a 5.0kg rectangular parallelepiped (base 12cm x 13cm square) weight 15 with the coating layer or separation functional layer facing outwards. The membrane surface was then de-liquidated by blowing a nitrogen stream from an air nozzle. A polypropylene net 16 (thickness 0.7mm, pitch width: 5.6mm x 4.5mm) was attached to a flat metal plate 17. As shown in Figure 3, the weight 15 was placed on the polypropylene net 16 attached to the metal plate 17 so that the entire coating layer or separation functional layer of the composite semipermeable membrane 1 was in contact with it. A string was attached to one end of the weight 15 in the axial direction (horizontal direction), and the other end of the string was connected to a tensile testing machine 18 (RTG-1210, manufactured by A&D Co., Ltd.). A pulley 19 was interposed between the weight 15 and the tensile testing machine 18 so that the string bent vertically. The weight 15, along with the composite semipermeable membrane 1, was pulled using a tensile testing machine 18 under the following conditions. Afterwards, the weight 15 was returned to its initial position before movement, and the weight 15, along with the composite semipermeable membrane 1, was pulled again using the same procedure. Tensile speed: 100 mm / min Tensile distance: 240mm total (120mm x 2 times) Measurement room temperature: 25℃ Using the composite semipermeable membranes that underwent the abrasion test, the NaCl removal rate of the composite semipermeable membranes after the abrasion test was measured using the method described in "NaCl Removal Rate" above. The NaCl removal rate was measured for all eight membranes that underwent the abrasion test, and the average value was taken as the NaCl removal rate after the abrasion test. In addition, the difference in NaCl removal rate and the membrane permeation flux ratio were calculated from the following equations (10) and (11). A difference in NaCl removal rate, calculated by subtracting the NaCl removal rate after the abrasion test from the initial performance NaCl removal rate, is considered good if it is 0.4% or less. Furthermore, a membrane permeation flux ratio, calculated by dividing the membrane permeation flux after the abrasion test by the membrane permeation flux before the abrasion test, is considered good if it is 1.5 or less. NaCl removal rate difference (%) = NaCl removal rate before the abrasion test (initial performance) - NaCl removal rate after the abrasion test ... Equation (10) Membrane permeation flux ratio (-) = Membrane permeation flux after abrasion test / Membrane permeation flux before abrasion test (initial performance) ... Equation (11)

[0143] <atr-ir> Under an atmosphere adjusted to 20°C and 50% RH, an ATR-IR spectrum was obtained by irradiating the surface of the separation functional layer of a composite semipermeable film with infrared light using a Shimadzu IRTracer-100 and a Shimadzu IRXross / IRAffinity-1 series single-reflection diamond ATR attachment (QATR10) as an accessory for total internal reflection measurement. The measurement conditions were set to a resolution of 4 cm. -1 The settings were adjusted, and the number of scans was set to 64. The composite semipermeable membrane was air-dried beforehand, and ATR-IR measurements were performed. The obtained spectra were expressed as absorbance, and auto-baseline correction was performed. A Shimadzu LabSolutions IR was used for the analysis. Also, for example, 1600~1610 cm⁻¹ -1 Or 2800~2900cm -1 If multiple peaks were present, the intensity of the peak with the highest intensity among the detected peaks was used. Measurements were taken at two different points for each sample, and the average value was calculated. Similar measurements were performed on three different samples, and the average value obtained was rounded to the third decimal place.

[0144] <Synthesis of polymers> [Synthesis Example 1] 30 g of ε-caprolactam, 100 g of a salt consisting of polyethylene glycol with a number-average molecular weight of 600 and amino groups at both ends (hereinafter referred to as "α,ω-diaminopolyoxyethylene") and adipic acid, and 130 g of water were heated to 200°C in a heat-resistant and pressure-resistant container under a nitrogen atmosphere and reacted for 2 hours to obtain copolymer polyamide 1.

[0145] [Synthesis Example 2] 10 g of p-aminobenzoic acid, 100 g of a salt consisting of α,ω-diaminopolyoxyethylene with a number-average molecular weight of 600 and adipic acid, and 200 g of water were heated to 200°C in a heat-resistant and pressure-resistant container under a nitrogen atmosphere and reacted for 2 hours to obtain copolymer polyamide 2.

[0146] [Synthesis Example 3] 10 g of ε-caprolactam, 100 g of a salt consisting of α,ω-diaminopolyoxyethylene with a number average molecular weight of 600 and terephthalic acid, and 200 g of water were heated to 200°C in a heat-resistant and pressure-resistant container under a nitrogen atmosphere and reacted for 2 hours to obtain copolymer polyamide 3.

[0147] [Synthesis Example 4] 20 g of ε-caprolactam, 100 g of a salt consisting of α,ω-diaminopolyoxyethylene with a number average molecular weight of 4,000 and oxalic acid, and 120 g of water were heated to 200°C in a heat-resistant and pressure-resistant container under a nitrogen atmosphere and reacted for 2 hours to obtain copolymer polyamide 4.

[0148] [Synthesis Example 5] 20 g of ε-caprolactam, 100 g of a salt consisting of Jeffamine (ED-2003, manufactured by Sigma-Aldrich) and adipic acid, and 120 g of water were heated to 200°C in a heat-resistant and pressure-resistant container under a nitrogen atmosphere and reacted for 2 hours to obtain copolymer polyamide 5.

[0149] [Synthesis Example 6] 50 g of ε-caprolactam, 100 g of a salt consisting of N-(2-aminoethyl)piperazine and adipic acid, and 150 g of water were heated to 200°C in a heat-resistant and pressure-resistant vessel under a nitrogen atmosphere and reacted for 2 hours to obtain copolymer polyamide 6.

[0150] [Synthesis Example 7] 100 g of a salt consisting of α,ω-diaminopolyoxyethylene with a number-average molecular weight of 600, having amino groups at both ends, and adipic acid, and 100 g of water were heated to 200°C in a heat-resistant and pressure-resistant container under a nitrogen atmosphere and reacted for 2 hours to obtain copolymer polyamide 7.

[0151] <Fabrication of composite semipermeable membrane 1> A porous support layer stock solution was prepared by dissolving 15% by mass of PSf (Udel P-3500, Mw: 80,000, manufactured by Solvay Specialty Polymers Japan Ltd.) and 85% by mass of DMF at 100°C. This porous support layer stock solution was then mixed with a polyester long-fiber nonwoven fabric (thickness 90 μm, density 0.42 g / cm³). 3 The material was applied to the surface of the substrate at 25°C, and after 3 seconds, it was immersed in a solidification solution consisting of distilled water at 25°C for 30 seconds to solidify. The material was then washed with hot water at 90°C for 2 minutes to obtain a support film in which a porous support layer was formed on the substrate surface. The thickness of the porous support layer in the obtained support film was 40 μm.

[0152] Next, the obtained support membrane was immersed in a 1.5% by mass aqueous solution of m-PDA for 1 minute, and the support membrane was slowly pulled up vertically. Excess aqueous solution was removed from the surface of the support membrane by blowing nitrogen from an air nozzle. In an environment controlled at 25°C, 20 mL of decane solution at 25°C containing 0.1% by mass of TMC was applied to the surface of the support membrane so that it was completely wetted, and it was left to stand for 30 seconds. Next, the membrane was held vertically for 30 seconds to drain and remove the excess solution, and then washed with hot water at 90°C for 2 minutes to obtain composite semipermeable membrane 1. The separation functional layer of composite semipermeable membrane 1 had a pleated shape.

[0153] <Fabrication of composite semipermeable membrane 2> Composite semipermeable membrane 2 was obtained in the same manner as composite semipermeable membrane 1, except that the m-PDA concentration was changed to 1.2 mass% and the TMC concentration to 0.08 mass%. The separation functional layer of composite semipermeable membrane 2 had a pleated shape.

[0154] [Reference example 1] The evaluation results for composite semipermeable membrane 1 are shown in Table 1.

[0155] [Example 1] A composite semipermeable membrane 1 was brought into contact with an aqueous solution containing 10% by mass of copolymerized polyamide 1. The membrane was kept in contact with the aqueous solution at 20°C for 1 hour. After that, the composite semipermeable membrane was held vertically to drain off the excess aqueous solution, and washed with 20°C water for 10 minutes to prepare a composite semipermeable membrane with copolymerized polyamide 1 as a coating layer.

[0156] [Example 2] A composite semipermeable membrane was prepared in the same manner as in Example 1, except that the concentration of copolymerized polyamide 1 was changed to 1% by mass and the holding time to 17 hours.

[0157] [Example 3] A composite semipermeable membrane was prepared in the same manner as in Example 1, except that the concentration of copolymerized polyamide 1 was changed to 0.01% by mass and the holding time was changed to 30 seconds.

[0158] [Example 4] A composite semipermeable membrane was prepared in the same manner as in Example 2, except that copolymerized polyamide 1 was replaced with copolymerized polyamide 2.

[0159] [Example 5] A composite semipermeable membrane was prepared in the same manner as in Example 2, except that copolymerized polyamide 1 was replaced with copolymerized polyamide 3.

[0160] [Example 6] A composite semipermeable membrane was prepared in the same manner as in Example 2, except that copolymerized polyamide 1 was replaced with copolymerized polyamide 4.

[0161] [Example 7] A composite semipermeable membrane was prepared in the same manner as in Example 2, except that copolymerized polyamide 1 was replaced with copolymerized polyamide 5.

[0162] [Example 8] A composite semipermeable membrane was prepared in the same manner as in Example 2, except that copolymerized polyamide 1 was replaced with copolymerized polyamide 6.

[0163] [Comparative Example 1] Composite semipermeable membrane 1 was brought into contact with an aqueous solution containing 1% by mass of polyethylene glycol (weight-average molecular weight: 8,000,000). The membrane was kept in contact with the aqueous solution at 20°C for 24 hours. After that, the composite semipermeable membrane was held vertically to drain off excess aqueous solution, and the membrane was washed with 20°C water for 10 minutes to prepare the composite semipermeable membrane.

[0164] [Comparative Example 2] A formic acid solution containing 0.01% by mass of 6-nylon (weight-average molecular weight: 100,000) was brought into contact with composite semipermeable membrane 1. After contact with the solution, the crosslinked polyamide of the composite semipermeable membrane decomposed, and it did not exhibit salt removal properties.

[0165] [Comparative Example 3] An aqueous solution containing 2.0% by mass of fully saponified polyvinyl alcohol (molecular weight: 100,000), 0.5% by mass of glutaraldehyde, and 0.1% by mass of sulfuric acid was brought into contact with the entire surface of the separation functional layer of composite semipermeable membrane 1 in an environment controlled at 20°C. With the aqueous solution remaining on the surface of the separation functional layer, a coating layer was formed on the separation functional layer by blowing 70°C hot air onto the composite semipermeable membrane for 3 minutes. After that, the composite semipermeable membrane was held vertically to drain off the excess aqueous solution and washed with 20°C water for 2 minutes. Finally, the composite semipermeable membrane was immersed in a 14% by mass aqueous solution of isopropanol at 20°C for 5 minutes to hydrophilize it and prepare the composite semipermeable membrane.

[0166] [Comparative Example 4] A composite semipermeable membrane was prepared in the same manner as in Example 1, except that the concentration of copolymerized polyamide 1 was changed to 0.001% by mass and the holding time to 30 seconds.

[0167] [Comparative Example 5] A composite semipermeable membrane was prepared in the same manner as in Example 2, except that copolymerized polyamide 1 was replaced with copolymerized polyamide 7, and the holding time was changed to 10 hours.

[0168] Table 1 shows the performance evaluation results of the composite semipermeable membranes of Examples 1-8 and Comparative Examples 1-5.

[0169] [Table 1]

[0170] [Reference example 2] The evaluation results for composite semipermeable membrane 2 are shown in Table 2.

[0171] [Example 9] A composite semipermeable membrane was prepared in the same manner as in Example 3, except that composite semipermeable membrane 1 was converted to composite semipermeable membrane 2, and the holding time was changed to 17 hours.

[0172] [Comparative Example 6] A composite semipermeable membrane was prepared in the same manner as in Example 1, except that composite semipermeable membrane 1 was replaced with composite semipermeable membrane 2, and the holding time was changed to 17 hours.

[0173] Table 2 shows the performance evaluation results of the composite semipermeable membranes of Reference Example 2, Example 9, and Comparative Example 6.

[0174] [Table 2]

[0175] [Reference example 3] Using composite semipermeable membrane 1, immersion treatment and immersion treatment in hydrogen peroxide solution were performed, respectively.

[0176] [Example 10] The composite semipermeable membrane obtained in Example 2 was used for immersion treatment and immersion treatment in hydrogen peroxide solution, respectively.

[0177] [Comparative Example 7] The composite semipermeable membrane obtained in Comparative Example 1 was used for immersion treatment and immersion treatment in hydrogen peroxide solution, respectively.

[0178] Table 3 shows the performance evaluation results for Reference Example 3, Example 10, and Comparative Example 7.

[0179] [Table 3]

[0180] Table 4 shows the structure of the polymer contained in the coating layer of each example and comparative example.

[0181] [Table 4]

[0182] As shown in Tables 1 and 2, the composite semipermeable membrane according to this embodiment exhibited high abrasion resistance. Furthermore, as shown in Table 3, the composite semipermeable membrane according to this embodiment exhibited high chemical resistance. [Industrial applicability]

[0183] The composite semipermeable membrane according to this embodiment can be used for seawater desalination, brine desalination, drinking water production, industrial ultrapure water production, wastewater treatment, and recovery of valuable materials. [Explanation of symbols]

[0184] 1 Composite semipermeable membrane 2 Support membrane 3 Separation functional layer 4 Covering layer 5 Inside the protruding part 6. Composite semipermeable membrane element 7 End plate 8 End plate 9 Supply side channel material 10 Permeate side channel material 11 Water collection pipe 12 Supply water 13 Permeated water 14 Concentrated water 15 weights 16 Polypropylene net 17 Metal plate 18 Tensile testing machine 19 Pulley

Claims

1. A porous support layer, A separation functional layer containing crosslinked polyamide is provided on the porous support layer, The separation functional layer comprises a coating layer provided on the separation functional layer, which contains a polymer having a structure represented by the following general formula (I), A composite semipermeable membrane in which the degree of yellowing ΔVYI of the surface on the coating layer side before and after contact with vanillin solution is 5 or more and 23 or less. 【Chemistry 1】 [In general formula (I), R １ R is a hydrocarbon group having 4 to 11 carbon atoms, which may be substituted. ２ This is hydrogen, a hydrocarbon group having 2 or fewer carbon atoms, or a functional group having 2 or fewer carbon atoms.

2. The composite semipermeable membrane according to claim 1, wherein the underwater elastic modulus of the surface on the coating layer side is 10 MPa or more and 45 MPa or less.

3. In the surface analysis of the coating layer by total internal reflection infrared absorption measurement, 1642–1662 cm －１ The peak intensity derived from amide I that appears is 1600–1610 cm². －１ The composite semipermeable membrane according to claim 1 or 2, wherein the intensity ratio of the maximum intensity of the peaks appearing is 0.86 or more and 1.20 or less.

4. The composite semipermeable membrane according to claim 1 or 2, wherein the degree of yellowing ΔDYI of the surface on the coating layer side before and after contact with Dragendorff's reagent is 43 or more and 150 or less.

5. In the surface analysis of the coating layer by total internal reflection infrared absorption measurement, 1642–1662 cm －１ The maximum intensity of the peak originating from amide I that appears is 2800–2900 cm. －１ The composite semipermeable membrane according to claim 3, wherein the intensity ratio of the maximum intensity of the peaks appearing is 0.20 or more and 0.30 or less.

6. The composite semipermeable film according to claim 1 or 2, wherein the polymer consists only of non-halogen atoms.

7. The composite semipermeable membrane according to claim 1 or 2, wherein the polymer has hydrophilic units.

8. The composite semipermeable membrane according to claim 7, wherein the hydrophilic unit has a structure represented by the following general formula (II). 【Chemistry 2】 [In general formula (II), R in each repeating unit ３ and R ４ Each of these is independently a hydrogen atom or a hydrocarbon group having 2 or fewer carbon atoms, and n is an integer of 1 or more.

9. A composite semipermeable membrane element comprising a composite semipermeable membrane according to claim 1 or 2.

10. A fluid separation apparatus comprising a composite semipermeable membrane according to claim 1 or 2.

11. A method for producing a composite semipermeable membrane, comprising the following steps (A) and (B). (A) A step of contacting a porous support layer with a polyfunctional amine aqueous solution, and then contacting the surface of the porous support layer with a water- and immiscible organic solvent solution containing a polyfunctional acid halide, thereby forming a separation functional layer containing a crosslinked polyamide on the porous support layer by interfacial polymerization. (B) A step of bringing the separation functional layer into contact with a solution containing a polymer having a structure represented by the following general formula (I). 【Transformation 3】 In general formula (I), R １ is an optionally substituted hydrocarbon group having 4 to 11 carbon atoms, and R ２ is hydrogen, a hydrocarbon group having 2 or fewer carbon atoms, or a functional group having 2 or fewer carbon atoms.

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