Composite semipermeable membranes and composite semipermeable membrane elements

Abstract

The present invention relates to a composite semipermeable membrane having a porous support layer and a separation functional layer provided on the porous support layer, wherein the separation functional layer contains an aromatic polyamide having a structure represented by the following general formula (I). [Formula 1] TIFF0007845578000022.tif40166

Description

[Technical Field]

[0001] This invention relates to a composite semipermeable membrane useful for the selective separation of liquid mixtures. [Background technology]

[0002] Regarding the separation of liquid mixtures, various techniques exist for removing substances (e.g., salts) dissolved in a solvent (e.g., water). In particular, the use of membrane separation methods has been expanding in recent years as a process for saving energy and resources. Membranes used in membrane separation methods include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes. These membranes are used, for example, to obtain drinking water from water containing salts or harmful substances, to produce industrial ultrapure water, to treat wastewater, and to recover valuable materials.

[0003] Most reverse osmosis membranes and nanofiltration membranes currently on the market are composite semipermeable membranes in which a separation functional layer having the ability to separate salts and the like is coated on a support membrane. There are two types of such composite semipermeable membranes: those having an active layer formed by crosslinking a gel layer and a polymer on the support membrane, and those having an active layer formed by polycondensation of monomers on the support membrane. Among the latter type of composite semipermeable membrane, composite semipermeable membranes having a separation functional layer containing a crosslinked polyamide obtained by the polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide are widely used as separation membranes with high permeability and selective separation (Patent Document 1). These composite semipermeable membranes are required to have higher salt removal capabilities so that treated water of higher quality can be obtained from water containing salt.

[0004] As a means of improving the salt removal properties of composite semipermeable membranes, post-treatment methods are known that convert the amine ends of the crosslinked polyamide in the separation functional layer by means of a diazo coupling reaction, contact with a bromine-containing free chlorine aqueous solution, or contact with a low-temperature aqueous solution containing aldehydes or epoxides (Patent Documents 2, 3, and 4). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2010 / 096563 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-090192 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-259388 [Patent Document 4] International Publication No. 2006 / 051888 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] The salt removal property and water permeability of a composite semipermeable membrane generally have a trade-off relationship. Particularly in reverse osmosis membranes and nanofiltration membranes, when the salt removal property is increased, the water permeability is significantly impaired. When the water permeability decreases, it is necessary to increase the operating pressure, resulting in an increase in operating costs. Patent Document 2 describes a method for obtaining permeated water with a low salt concentration when treating raw water with a relatively low salt concentration of about 500 mg / L, but it cannot exhibit sufficient salt removal property in the treatment of raw water with a high salt concentration such as seawater. The composite semipermeable membranes described in Patent Document 3 or 4 have low water permeability, so it is necessary to operate at a high pressure to obtain a sufficient water production rate.

[0007] Therefore, an object of the present invention is to provide a composite semipermeable membrane that achieves both salt removal property and water permeability. [Means for Solving the Problems]

[0008] In order to achieve the above object, the present invention has any one of the following configurations [1] to

[11] . [1] A composite semipermeable membrane having a porous support layer and a separation functional layer provided on the porous support layer, wherein the separation functional layer contains an aromatic polyamide having a structure represented by the following general formula (I).

[0009] [Chemical formula]

[0010] [In general formula (I), each of Ar1 to Ar6 is independently a divalent aromatic ring group having 5 to 14 carbon atoms which may have a substituent, each of R2 to R7 is independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms which may have a substituent, and R1 has a structure represented by the following general formula (II).]

[0011] [Chemical formula]

[0012] [In general formula (II), n is an integer of 1 to 6, each of X1 and X2 is independently a carbon atom or a nitrogen atom, and each of L1 and L2 is independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 6 carbon atoms which may have a substituent, or a non-bonding electron pair. L1 and L2 may be directly or indirectly bonded to form a cyclic structure, and the total number of carbon atoms of all L1 and L2 is 12n or less.] [2] The composite semipermeable membrane according to [1] above, wherein n in the general formula (II) is 1 or 2. [3] The composite semipermeable membrane according to [1] or [2] above, wherein R1 in the general formula (I) has a structure represented by the following general formula (III).

[0013] [Chemical formula]

[0014] [In general formula (III), each of Y1 to Y4 is independently a hydrogen atom, a monovalent hydrocarbon group having 1 to 4 carbon atoms which may have a substituent, an ester group, or a halogen atom, and the total number of carbon atoms of Y1 to Y4 is 8 or less. Y1 to Y4 may be directly or indirectly bonded to form a cyclic structure.] [4] The composite semipermeable membrane according to [3] above, wherein Y1 to Y4 in the general formula (III) are hydrogen atoms. [5] Let P be the sum of the signal intensity at m / z=75.02 and the signal intensity at m / z=76.03 obtained by TOF-SIMS on the surface of the separation functional layer, and let Q be the signal intensity of the fragment with the maximum signal intensity among the fragments derived from the structure containing R1 in the general formula (I), then the ratio Q / P of the signal intensity Q to the sum P is 2.0 × 10 -2 The above 3.5 × 10 -1 The composite semipermeable membrane described in any of the above [1] to [4] is as follows: [6] Let S be the signal intensity at m / z = 75.02 obtained by TOF-SIMS on the surface of the separation functional layer, and let Q be the signal intensity of the fragment with the maximum signal intensity among the fragments derived from the structure containing R1 in the general formula (I), then the ratio Q / S of the signal intensity Q to the signal intensity S is 3.0 × 10 -2 The above 5.3 × 10 -1 The composite semipermeable membrane described in any of the above [1] to [5] is as follows: [7] A composite semipermeable membrane according to any one of [1] to [6] above, wherein the degree of yellowing ΔYI of the separation functional layer before and after contact with vanillin solution is 3.0 or more and 10.0 or less. [8] A composite semipermeable membrane according to any of [1] to [7] above, wherein the zeta potential of the surface of the separation functional layer at pH 3.0 is between -15 mV and 10 mV. [9] A composite semipermeable membrane element comprising a composite semipermeable membrane as described in any of [1] to [8] above.

[10] A water treatment system that separates the supply water into concentrated water and fresh water using the composite semipermeable membrane element described in [9] above.

[11] A method for producing a composite semipermeable membrane, comprising the following steps (a) and (b). Step (a) Step of forming a layer containing aromatic polyamide on a porous support layer. Step (b) A step of bringing the separation functional layer into contact with a processing solution containing a compound represented by the following general formula (IV) at a temperature of 45°C or higher.

[0015] [ka]

[0016] [In general formula (IV), Z1 and Z2 are each independently a formyl group, an acetal group, a hemiaminal group, or an aminal group, n is an integer from 1 to 6, X1 and X2 are each independently a carbon atom or a nitrogen atom, L1 and L2 are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 6 carbon atoms which may have substituents, or a lone pair of electrons, and L1 and L2 may be directly or indirectly bonded to form a cyclic structure, and the sum of the carbon numbers of all L1 and L2 is 12n or less.] [Effects of the Invention]

[0017] According to the present invention, a composite semipermeable membrane that achieves both salt removal properties and water permeability can be obtained. [Modes for carrying out the invention]

[0018] Embodiments of the present invention will be described in detail below, but the present invention is not limited thereto.

[0019] 1.Composite semipermeable membrane The composite semipermeable membrane according to an embodiment of the present invention comprises a porous support layer and a separation function layer provided on the porous support layer. Hereinafter, the "up and down" direction refers to the thickness direction of the composite semipermeable membrane. The separation function layer is positioned "on top" of the porous support layer.

[0020] The porous support layer of the composite semipermeable membrane according to this embodiment may be formed on a substrate. In this case, the configuration including the substrate and the porous support layer formed on the substrate is referred to as the "support membrane". Furthermore, the porous support layer only needs to be formed on at least one main surface of the substrate. The separation functional layer substantially possesses separation capabilities, while the porous support layer substantially does not possess separation capabilities for ions, etc., and can provide strength to the separation functional layer.

[0021] (1-1) Support membrane The support film includes a substrate and a porous support layer. Examples of materials for the base material include fabrics made from polyester polymers, polyamide polymers, polyolefin polymers, mixtures thereof, or copolymers. 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 long-fiber nonwoven fabrics, short-fiber nonwoven fabrics, or woven or knitted fabrics. The base material should have an air permeability of 0.5 cc / cm³. 2 / s or more 5.0cc / cm 2 It is preferable that the value be less than or equal to / s.

[0022] The porous support layer has a large number of interconnected pores. The pore diameter and pore diameter distribution are not particularly limited, but for example, a porous support layer with a symmetrical structure consisting of uniform pore diameters, or an asymmetrical structure in which the pore diameter gradually increases from one surface to the other, and in which the pore diameter on the surface with smaller pore diameters is 0.1 nm or more and 100 nm or less, is preferred.

[0023] As the material for the porous support layer, homopolymers or copolymers such as polysulfone (hereinafter referred to as "PSf"), polyethersulfone, polyamide, polyester, cellulose polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene oxide 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 such as PSf, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, and polyphenylene sulfide sulfone are preferred, and cellulose acetate, PSf, polyphenylene sulfide sulfone, or polyphenylene sulfone are more preferred. Among these, PSf is particularly preferred because it has high chemical, mechanical, and thermal stability and is easy to mold.

[0024] The weight-average molecular weight (hereinafter referred to as "Mw") of PSf is preferably between 10,000 and 200,000, and more preferably between 15,000 and 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.

[0025] The sum of the thickness of the substrate and the porous support layer, i.e., the thickness of the support film, affects the strength of the composite semipermeable membrane and the packing density when the composite semipermeable membrane is used as an element. To obtain good mechanical strength and packing density, the thickness of the support film is preferably 30 μm to 300 μm, and more preferably 100 μm to 220 μm. The thickness of the porous support layer is preferably 20 μm to 100 μm. The thickness of the support film and the porous support layer can be determined by calculating the average value of 20 thicknesses measured at 20 μm intervals in a direction perpendicular to the thickness direction (the surface direction of the film) during cross-sectional observation.

[0026] (1-2) Separation functional layer In the composite semipermeable membrane according to this embodiment, the separation functional layer is responsible for the solute separation function and contains an aromatic polyamide having a structure represented by the following general formula (I). Furthermore, it is preferable that the separation functional layer has an aromatic polyamide as its main component. "Mainly composed of aromatic polyamide" means that aromatic polyamide accounts for 50% by mass or more in the separation functional layer. Preferably, the proportion of aromatic polyamide in the separation functional layer is 80% by mass or more, more preferably 90% by mass or more, and even more preferably the separation functional layer is substantially composed solely of aromatic polyamide. "The separation functional layer is substantially composed solely of aromatic polyamide" means that aromatic polyamide accounts for 99% by mass or more in the separation functional layer. Note that the above proportions are values ​​measured using the separation functional layer in a dry state.

[0027] [ka]

[0028] In the above general formula (I), Ar1 to Ar6 are each independently a divalent aromatic ring group having 5 to 14 carbon atoms which may have substituents, R2 to R7 are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms which may have substituents, and R1 has a structure represented by the following general formula (II). In other words, the structure represented by general formula (I) means a structure in which the polyamide termini are crosslinked by R1.

[0029] [ka]

[0030] In the above general formula (II), n is an integer from 1 to 6, X1 and X2 are each independently a carbon atom or a nitrogen atom, and the cis-trans isomers of the double bond between X1 and X2 are not limited. In each repeating unit, L1 and L2 are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 6 carbon atoms which may have substituents, or a lone pair of electrons, and L1 and L2 may be directly or indirectly bonded to form a cyclic structure, and the sum of the carbon atoms of all L1 and L2 is 12n or less. The separation functional layer in the composite semipermeable membrane has a structure represented by the above general formula (II), which improves the salt removal performance.

[0031] In the above general formula (I), Ar1 to Ar6 are preferably C6 divalent aromatic ring groups, i.e., phenylene groups, from the viewpoint of securing an appropriate free volume for water permeation in the separation functional layer. The phenylene group may be unsubstituted or may have substituents. Examples of substituents on the phenylene group include amino groups, carboxyl groups, methyl groups, chloro groups, and bromo groups, and substituents other than those listed above may also be present as long as they do not hinder the effects of the present invention.

[0032] In the above general formula (I), R2 to R7 are preferably hydrogen atoms, from the viewpoint of forming hydrogen bonds between aromatic polyamides constituting the separation functional layer and contributing to improved selective permeability.

[0033] In the above general formula (II), n is preferably 1 or 2, and more preferably 1, from the viewpoint of easily forming a pore structure in the separation functional layer that prevents salt from permeating and allows water to permeate selectively.

[0034] The two nitrogen atoms in the structure of general formula (II) above (not the nitrogen atoms that are options for X1 and X2) originate from the amino groups at the aromatic polyamide termini. In other words, the structure of general formula (II) is obtained by crosslinking the two amino groups at the polyamide termini with the compound described later, and contributes to improved salt removal properties.

[0035] In the structure of the above general formula (II), when X1 and X2 are carbon atoms, L1 and L2 are each preferably a hydrogen atom, a halogen atom, or a monovalent hydrocarbon group having 1 to 6 carbon atoms, which may have substituents. In the structure of the above general formula (II), when X1 and X2 are nitrogen atoms, L1 and L2 are each preferably a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 6 carbon atoms which may have substituents, or a lone pair of electrons.

[0036] X1 and X2 are preferably carbon atoms. Examples of halogen atoms in L1 and L2 include chlorine and bromine atoms. In L1 and L2, linear or branched C1-C6 monovalent hydrocarbon groups are preferred. Furthermore, when the C1-C6 monovalent hydrocarbon group has substituents, hydroxymethyl, 1-hydroxyethyl, 2-hydroxyethyl, 1-hydroxypropyl, 2-hydroxypropyl, 3-hydroxypropyl, 1-hydroxybutyl, 2-hydroxybutyl, 3-hydroxybutyl, 4-hydroxybutyl, 1-hydroxypentyl, 2-hydroxypentyl, 3-hydroxypentyl, 4-hydroxypentyl, 5-hydroxypentyl, 1-hydroxyhexyl, 2-hydroxyhexyl, 3-hydroxyhexyl, 4-hydroxyhexyl, 5-hydroxyhexyl, 6-hydroxyhexyl, 1- Examples include hydroxypropan-2-yl group, 2-hydroxypropan-2-yl group, aminomethyl group, 1-aminoethyl group, 2-aminoethyl group, 1-aminopropyl group, 2-aminopropyl group, 3-aminopropyl group, 1-aminobutyl group, 2-aminobutyl group, 3-aminobutyl group, 4-aminobutyl group, 1-aminopentyl group, 2-aminopentyl group, 3-aminopentyl group, 4-aminopentyl group, 5-aminopentyl group, 1-aminohexyl group, 2-aminohexyl group, 3-aminohexyl group, 4-aminohexyl group, 5-aminohexyl group, 6-aminohexyl group, 1-aminopropan-2-yl group, and 2-aminopropan-2-yl group.

[0037] In the structure of general formula (II) above, the cyclic structure formed by the direct or indirect bonding of L1 and L2 may be an aromatic ring, such as a benzene ring or a naphthalene ring. The inclusion of an aromatic ring in the structure of general formula (II) allows for the introduction of a rigid and chemically stable cyclic structure into the separation functional layer, thereby suppressing the decrease in water permeability associated with the reaction. If multiple L1 and L2 atoms are present, any of the L1 and L2 atoms may be directly or indirectly bonded to each other.

[0038] Furthermore, it is preferable that R1 in the above general formula (I) has a structure represented by the following general formula (III).

[0039] [ka]

[0040] In the above general formula (III), Y1 to Y4 are each independently a hydrogen atom, a monovalent hydrocarbon group having 1 to 4 carbon atoms which may have substituents, an ester group, or a halogen atom, and the total number of carbon atoms of Y1 to Y4 is 8 or less. Y1 to Y4 may be directly or indirectly bonded together to form a cyclic structure.

[0041] The structure of general formula (III) above corresponds to the structure in general formula (II) above, where n is 1, X1 and X2 are carbon atoms, and L1 and L2 are directly bonded to form a benzene ring. Thus, the inclusion of a benzene ring in R1 ensures the chemical stability of the structure, and at the same time, a rigid ring structure like a benzene ring is preferable because it contributes to the formation of a pore structure that allows water to selectively permeate.

[0042] As the monovalent hydrocarbon group having 1 to 4 carbon atoms, linear or branched alkyl groups having 1 to 4 carbon atoms are preferred. When the monovalent hydrocarbon group having 1 to 4 carbon atoms has substituents, examples include hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group, 1-hydroxypropyl group, 2-hydroxypropyl group, 3-hydroxypropyl group, 1-hydroxybutyl group, 2-hydroxybutyl group, 3-hydroxybutyl group, 4-hydroxybutyl group, 1-hydroxypropan-2-yl group, 2-hydroxypropan-2-yl group, aminomethyl group, 1-aminoethyl group, 2-aminoethyl group, 1-aminopropyl group, 2-aminopropyl group, 3-aminopropyl group, 1-aminobutyl group, 2-aminobutyl group, 3-aminobutyl group, 4-aminobutyl group, 1-aminopropan-2-yl group, and 2-aminopropan-2-yl group.

[0043] As the ester group, ROC(=O)-(where R is an alkyl group having 1 to 6 carbon atoms) is preferred.

[0044] Examples of halogen atoms include chlorine and bromine atoms.

[0045] In the structure of the general formula (III) described above, the cyclic structure formed by the direct or indirect bonding of Y1 to Y4 is preferably a cyclic structure formed by the bonding of Y1 and Y2, Y2 and Y3, or Y3 and Y4. Examples include a cyclopentane ring, a cyclohexane ring, a pyrrolidine ring, a tetrahydrofuran ring, a dioxol ring, a dioxolane ring, a benzene ring, and the like.

[0046] In the above general formula (III), it is preferable that Y1 to Y4 are all hydrogen atoms. When Y1 to Y4 are all hydrogen atoms, the polyamide constituting the separation functional layer fills the space more densely, resulting in higher salt removal performance.

[0047] The presence or absence and abundance of R1 in the above general formula (I), i.e., the structure represented by general formula (II), can be evaluated by surface analysis of the separation functional layer side by TOF-SIMS. In TOF-SIMS, Bi3 is used as the primary ion beam on the separation functional layer side of the film sample under vacuum. ++ When irradiated, secondary ions are emitted from a few nanometers of the sample surface. By introducing these secondary ions into a time-of-flight (TOF) mass spectrometer, information about the chemical structure of the sample surface can be obtained. Mass spectrometry is performed in positive secondary ion mode.

[0048] Specifically, Bi3 is placed on the surface of the separation functional layer of the composite semipermeable membrane. ++ When irradiated, some of the covalent bonds of the aromatic polyamide constituting the separation functional layer are cleaved, yielding fragments. Here, from the structure derived from the structure containing R1 of general formula (I), that is, the structure containing the structure of general formula (II), fragments represented by the following general formulas (V) or (VI) can be obtained.

[0049] [ka]

[0050] [ka]

[0051] In the above general formulas (V) and (VI), Ar1 and Ar4 are each independently substituted divalent aromatic ring groups having 5 to 14 carbon atoms, n is an integer from 1 to 6, X1 and X2 in each repeating unit are each independently a carbon atom or a nitrogen atom, and the cis-trans isomers of the double bond between X1 and X2 are not limited. In each repeating unit, L1 and L2 are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 6 carbon atoms which may have substituents, or a lone pair of electrons, and L1 and L2 may be directly or indirectly bonded to form a cyclic structure, and the sum of the carbon atoms of all L1 and L2 is 12n or less. The "·" in the upper right corner means a radical. For example, "··" indicates that there are two radicals in the general formula.

[0052] The presence of the R1 structure in the aromatic polyamide of the separation functional layer can be confirmed by the presence or absence of a signal from a fragment derived from the R1 structure. For example, if Ar1 in general formula (I) is an unsubstituted phenylene group, and the R1 structure is derived from o-phthalaldehyde, the m / z is 207.09; from malealdehyde, it is 157.08; from 3-methylphthalaldehyde, it is 221.11; from 4-bromophthalaldehyde, it is 285.00; and from 3,4-diformylmethyl benzoate, it is 265 At 0.10, signals are obtained at m / z=335.13 if derived from benzene-1,2,4,5-tetracarbaldehyde, at m / z=251.08 if derived from benzo[d][1,3]dioxol-4,5-dicarbaldehyde, at m / z=257.11 if derived from naphthalene-2,3-dicarbaldehyde, and at m / z=283.12 if derived from [1,1'-biphenyl]-2,2'-dicarbaldehyde.

[0053] In the composite semipermeable membrane according to this embodiment, when the sum of the signal intensities at m / z = 75.02 and the signal intensity at m / z = 76.03 obtained by TOF-SIMS on the surface of the separation functional layer is defined as P, and the signal intensity of the fragment with the maximum signal intensity among the fragments derived from the structure containing R1 is defined as Q, the ratio Q / P of the signal intensity Q to the sum P is 2.0×10 -2 or more and 3.5×10 -1 or less, preferably 2.5×10 -2 or more and 3.0×10 -1 or less, more preferably 2.9×10 -2 or more and 2.0×10 -1 or less, even more preferably 3.3×10 -2 or more and 7.5×10 -2 or less, particularly preferably.

[0054] Also, in the composite semipermeable membrane according to this embodiment, when the signal intensity at m / z = 75.02 obtained by TOF-SIMS on the surface of the separation functional layer is defined as S, and the signal intensity of the fragment with the maximum signal intensity among the fragments derived from the structure containing R1 is defined as Q, the ratio Q / S of the signal intensity Q to the signal intensity S is 3.0×10 -2 or more and 5.3×10 -1 or less, preferably 3.8×10 -2 or more and 4.5×10 -1 or less, more preferably 4.4×10 -2 or more and 3.0×10 -1 or less, even more preferably 5.0×10 -2 or more and 1.1×10 -1 or less, particularly preferably.

[0055] In TOF-SIMS on the surface of the separation functional layer of a composite semipermeable membrane having a separation functional layer containing an aromatic polyamide, fragments derived from Ar2, Ar3, Ar5, and Ar6 of the general formula (I) are obtained. When Ar2, Ar3, Ar5, or Ar6 is a phenylene group having no substituent, the ion formula of the main fragment obtained is C6H4 +This is obtained as a signal with m / z = 76.03. When Ar2, Ar3, Ar5, or Ar6 is a phenylene group (trisubstituted benzene ring) with one substituent, the main fragment obtained is C6H3 + and C6H4 + This is obtained as signals at m / z = 75.02 and m / z = 76.03. That is, Q / P reflects the ratio of the structure represented by general formula (II) to the aromatic ring groups constituting the aromatic polyamide in the separation functional layer. Q / P is 2.0 × 10 -2 As described above, the composite semipermeable membrane exhibits good salt removal properties because it contains a sufficient cross-linking structure to achieve high salt removal. Furthermore, the Q / P ratio is 3.5 × 10⁻⁶. -1 The following conditions can suppress the reduction in water permeability caused by the introduction of excessive cross-linking structures.

[0056] In particular, when a trisubstituted benzene ring is used as a polyfunctional aromatic amine and / or polyfunctional aromatic acid halide to form a crosslinked structure, the main fragment derived from the trisubstituted benzene ring among Ar2, Ar3, Ar5, and Ar6 of general formula (I) is C6H3. + This is obtained as a signal with m / z = 75.02. That is, Q / S reflects the ratio of the structure represented by general formula (II) to the aromatic ring group that contributes to the formation of the crosslinked structure in the aromatic polyamide. Q / S is 3.0 × 10 -2 As described above, the composite semipermeable membrane exhibits good salt removal properties because it contains a sufficient cross-linking structure to achieve high salt removal. Furthermore, the Q / S is 5.3 × 10⁻⁶. -1 The following conditions can suppress the reduction in water permeability caused by the introduction of excessive cross-linking structures.

[0057] The Q / P and Q / S values ​​can be controlled, for example, by the conditions of step (b) described in "(2-3) Modification process of the separation function layer" described later.

[0058] In this embodiment, the composite semipermeable membrane preferably has a degree of yellowing ΔYI of 3.0 or more and 10.0 or less before and after contact of the separation functional layer with the vanillin solution. The amino groups, such as aromatic polyamide terminals, contained in the separation functional layer form a color-developing chemical structure through a chemical reaction with vanillin. That is, the degree of yellowing ΔYI before and after contact with the vanillin solution reflects the amount of amino groups on the surface of the separation functional layer.

[0059] A ΔYI of 10.0 or less is preferable because it improves salt removal performance, as more amino groups form a cross-linked structure represented by general formula (II). On the other hand, a ΔYI of 3.0 or more is preferable because it suppresses the decrease in water permeability due to the introduction of excessive cross-linked structures. From the above viewpoint, a yellowing degree ΔYI of 5.0 or more and 10.0 or less is more preferable.

[0060] The degree of yellowing ΔYI can be controlled by adjusting the amount of amino groups at the two aromatic polyamide terminals in the separation functional layer. This can be done, for example, by converting the amino groups at the aromatic polyamide terminals to a cross-linked structure represented by general formula (II) or to other functional groups. The value of ΔYI can be controlled more specifically by the conditions of step (b) described in "(2-3) Modification of the Separation Functional Layer" below.

[0061] In this embodiment, it is preferable that the zeta potential of the separation functional layer of the composite semipermeable membrane at pH 3.0 is between -15 mV and 10 mV.

[0062] Zeta potential is a measure of the net fixed charge on the surface of a plate-shaped sample. The aromatic polyamide contained in the separation functional layer mainly has amino groups and carboxyl groups as terminal functional groups, and the degree of dissociation of these depends on pH. Under conditions of pH 3.0, the amino groups are mainly positively charged and the carboxyl groups are mainly neutral, so the zeta potential of the separation functional layer at pH 3.0 is thought to depend mainly on the amount of amino groups. Since R1 in general formula (I) is introduced in a way that modifies the amino groups, the amount of amino groups decreases as the amount of R1 introduced increases, that is, the zeta potential of the separation functional layer at pH 3.0 can be controlled by the amount of R1 introduced. Therefore, a zeta potential of 10mV or less at pH 3.0 is preferable because it indicates that R1 has been sufficiently introduced into the separation functional layer, and the salt removal rate is further improved. On the other hand, a zeta potential of -15mV or higher at pH 3.0 is preferable because it can suppress the decrease in water permeability caused by the excessive introduction of R1. From the above perspective, a zeta potential of 0mV to 5mV at pH 3.0 is more preferable.

[0063] The zeta potential can be controlled, for example, by the conditions of step (b) described in "(2-3) Modification of the separation functional layer" below.

[0064] The aromatic polyamide contained in the separation functional layer of the composite semipermeable membrane according to this embodiment may be an aramid compound, but it may also contain non-aromatic moieties in its molecular structure. From the viewpoint of rigidity, chemical stability, and durability against operating pressure, the aromatic polyamide is more preferably a crosslinked aromatic polyamide, and even more preferably a crosslinked total aromatic polyamide consisting only of aromatic polyamides.

[0065] "Cross-linked aromatic polyamide" means that the aromatic polyamide has formed a cross-linked structure. For example, the aromatic polyamide may form a cross-linked structure via a cross-linking agent, or the compound that serves as the raw material for the aromatic polyamide may itself have three or more functionalities, and the aromatic polyamide may form a network-like cross-linked structure by polymerizing such a compound. In particular, it is preferable that the compound that serves as the raw material for the aromatic polyamide has three or more functionalities, thereby forming a network-like cross-linked structure. Furthermore, the crosslinking structure in aromatic polyamides includes the R1 structure represented by the general formula (II) above.

[0066] The crosslinked aromatic polyamide is preferably a polymer of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide, and in this case, from the viewpoint of obtaining the crosslinked structure described above, it is preferable that at least one of the polyfunctional aromatic amine and the polyfunctional aromatic acid halide is trifunctional or more.

[0067] A "polyfunctional aromatic amine" refers to an aromatic amine that has two or more amino groups, at least one of either primary or secondary amino groups, in a single molecule, and at least one of these amino groups is a primary amino group. The aromatic rings derived from polyfunctional aromatic amines correspond to Ar1, Ar3, Ar4, and Ar6 in general formula (I).

[0068] Examples of polyfunctional aromatic amines include o-phenylenediamine, m-phenylenediamine (hereinafter referred to as "m-PDA"), p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m-diaminopyridine, p-diaminopyridine, and other polyfunctional aromatic amines in which two amino groups are bonded to the aromatic ring in an ortho, meta, or para position; 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, and 4-aminobenzylamine. These may be used individually or in combination of two or more. In particular, considering the selective separation, permeability, and heat resistance of the membrane, m-PDA, p-phenylenediamine, and 1,3,5-triaminobenzene are preferred.

[0069] A "polyfunctional aromatic acid halide" refers to an aromatic acid halide that has at least two halogenated carbonyl groups in one molecule. The aromatic rings derived from polyfunctional aromatic acid halides correspond to Ar2 and Ar5 in general formula (I).

[0070] Among polyfunctional aromatic acid halides, trifunctional acid halides include, for example, trimesic acid chloride, and difunctional acid halides include, for example, biphenyldicarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalenedicarboxylic acid chloride, and 2,5-franj carboxylic acid chloride. These may be used individually or in combination of two or more. Among polyfunctional aromatic acid halides, polyfunctional aromatic acid chlorides are preferred, and in particular, TMC, an acid chloride of 1,3,5-benzenetricarboxylic acid, isophthalic acid chloride, an acid chloride of 1,3-benzenedicarboxylic acid, and terephthalic acid chloride, an acid chloride of 1,4-benzenetricarboxylic acid, are preferred in terms of economy, availability, ease of handling, and reactivity.

[0071] To prevent the substance to be separated from penetrating into the interior of the composite semipermeable membrane, the separation functional layer is preferably located on the surface side of the composite semipermeable membrane, and more preferably on the primary side of filtration.

[0072] 2. Method for manufacturing composite semipermeable membranes The method for producing the composite semipermeable membrane 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 produced by the following method.

[0073] (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. First, PSf is dissolved in a suitable solvent to prepare a porous support layer stock solution. For example, N,N-dimethylformamide (hereinafter referred to as "DMF") is preferred as a suitable solvent for PSf.

[0074] The PSf concentration in the porous support layer stock solution is preferably 12% to 25% by mass, and more preferably 14% to 23% by mass. The higher the polymer concentration (i.e., solid content concentration) in the porous support layer stock solution, the higher the number density of particles on the surface of the porous support layer that can be obtained. As a result, the number density of protrusions in the separation function layer also increases, enabling the realization of a protrusion structure that can withstand pressure fluctuations. Furthermore, by lowering the polymer concentration, the surface pore diameter of the porous support layer is adjusted to such an extent that the monomer supply rate during separation function layer formation does not become too low, and protrusions of appropriate height are formed during separation function layer formation. When the PSf concentration in the porous support layer stock solution is within the above range, both the strength and permeability of the resulting porous support layer can be achieved. The preferred range of polymer concentration in the porous support layer stock solution can be appropriately adjusted depending on the materials used, good solvents, etc.

[0075] Next, the obtained porous support layer stock solution is applied to the substrate surface and immersed in a coagulation bath containing a non-solvent of PSf. Water is preferred as the non-solvent of PSf in the coagulation bath. By bringing the porous support layer stock solution applied to the substrate surface into contact with the coagulation bath containing a non-solvent of PSf, the porous support layer stock solution coagulates through non-solvent-induced phase separation, and a support film with a porous support layer formed on the substrate surface can be obtained. The coagulation bath may consist only of a non-solvent of PSf, or it may contain a good solvent for PSf within a range that allows the porous support layer stock solution to coagulate. The obtained support film may be washed before the formation of the separation functional layer to remove any remaining solvent in the film.

[0076] (2-2) Fabrication of the separation function layer The present invention provides a method for producing a composite semipermeable membrane, comprising the following steps (a) and (b). Step (a) Step of forming a separation functional layer containing aromatic polyamide on a porous support layer. Step (b) A step of bringing the separation functional layer into contact with a processing solution containing a compound represented by the following general formula (IV) at a temperature of 45°C or higher.

[0077] [ka]

[0078] In the above general formula (IV), Z1 and Z2 are each independently a formyl group, an acetal group, a hemiacetal group, a hemiaminal group, or an aminal group, n is an integer from 1 to 6, X1 and X2 in each repeating unit are each independently a carbon atom or a nitrogen atom, and the cis-trans isomers of the double bond between X1 and X2 are not limited. L1 and L2 in each repeating unit are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 6 carbon atoms which may have substituents, or a lone pair of electrons, L1 and L2 may be directly or indirectly bonded to form a cyclic structure, and the sum of the carbon numbers of all L1 and L2 is 12n or less.

[0079] (2-2-1) Process for forming the separation functional layer Regarding the process of forming a separation functional layer containing aromatic polyamide, we will describe, as an example, a method in which a polyfunctional aromatic amine and a polyfunctional aromatic acid halide are polymerized on the support film obtained in "(2-1) Formation of support film" to form a separation functional layer containing aromatic polyamide. From the viewpoint of productivity and performance, interfacial polymerization is the most preferred polymerization method. The interfacial polymerization process will be described below.

[0080] The separation function layer formation step (a) preferably includes step (a1) contacting an aqueous solution containing a polyfunctional aromatic amine with a support film, step (a2) contacting an organic solvent solution containing a polyfunctional aromatic acid halide with the support film that has been contacted with the aqueous solution containing the polyfunctional aromatic amine, step (a3) ​​draining the organic solvent solution after contact, and step (a4) washing the composite semipermeable membrane. Even before carrying out step (b) described later, the layer containing aromatic polyamide may also be referred to as the separation function layer. Furthermore, a composite membrane having a substrate, a porous support layer, and a layer containing aromatic polyamide may also be referred to as a composite semipermeable membrane.

[0081] Examples of porous support layers, polyfunctional aromatic amines, and polyfunctional aromatic acid halides include those mentioned above, and the same applies to preferred materials. In particular, from the viewpoint of easily forming crosslinked aromatic polyamides, it is preferable to use mPDA as the polyfunctional aromatic amine and TMC as the polyfunctional aromatic acid halide.

[0082] In step (a1), the concentration of the polyfunctional aromatic amine in the aqueous solution of the polyfunctional aromatic amine is preferably 0.1% by mass or more and 20% by mass or less, and more preferably 0.5% by mass or more and 15% by mass or less. When the concentration of the polyfunctional aromatic amine is within the above range, sufficient solute removal performance and water permeability can be obtained. Two or more types of polyfunctional aromatic amines may be used.

[0083] In step (a1), it is preferable that the aqueous solution be brought into uniform and continuous contact with the support film. Specifically, examples include coating the support film with an aqueous amine solution or immersing the support film in the aqueous solution. The contact time between the support film and the aqueous solution is preferably 1 second to 10 minutes, and more preferably 3 seconds to 3 minutes.

[0084] After the aqueous solution has come into contact with the support film, it is preferable to remove any remaining droplets from the film. Removing the liquid helps to suppress the occurrence of defects in the separation layer. Methods for removing the liquid include, for example, holding the support film vertically after contact with the aqueous solution to allow excess solution to flow naturally, or forcibly removing the liquid by blowing a stream of air such as nitrogen from an air nozzle. After removing the liquid, the film surface can also be dried to remove some of the water from the aqueous solution.

[0085] The organic solvent is preferably immiscible with water, dissolves polyfunctional aromatic acid halides, does not damage the support film, and is inert to polyfunctional aromatic amines and polyfunctional aromatic 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.

[0086] The concentration of the polyfunctional aromatic acid halide in the organic solvent solution is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.02% by mass or more and 4% by mass or less, and even more preferably 0.03% by mass or more and 2% by mass or less. When the concentration of the polyfunctional aromatic acid halide is 0.01% by mass or more, polymerization can proceed at a sufficient reaction rate. On the other hand, when the concentration of the polyfunctional aromatic acid halide is 10% by mass or less, the occurrence of side reactions during polymerization can be suppressed.

[0087] The aqueous solutions of polyfunctional aromatic amines and polyfunctional aromatic acid halides may contain, if necessary, compounds such as surfactants, antioxidants, and metal salts, as long as they do not inhibit polymerization.

[0088] The method for contacting a support film containing a polyfunctional aromatic acid halide solution in an organic solvent with a polyfunctional aromatic amine aqueous solution can be carried out in the same manner as the method for contacting the support film with the polyfunctional aromatic amine aqueous solution.

[0089] In step (a2), it is preferable to contact the support film, which has been contacted with an aqueous solution containing a polyfunctional aromatic amine, with an organic solvent solution of a polyfunctional aromatic acid halide, and then heat-treat the film. By accelerating the reaction through heat treatment and promoting high molecular weight, low molecular weight components can be reduced, and changes in performance during acid contact can be suppressed. Furthermore, the hydrolysis of the halocarbonyl groups of the aromatic acid halides due to the above-mentioned additives and the hydrolysis of the aromatic acid halides can be hydrolyzed, suppressing the reaction with the aromatic amine, and this can be compensated for by accelerating the reaction through heat treatment. The temperature for heat-treating the film is preferably 50°C to 180°C, more preferably 60°C to 160°C, and even more preferably 80°C to 150°C. If the heating temperature is 180°C or lower, the decrease in water permeability due to the thickening of the separation functional layer can be suppressed.

[0090] In step (a3), the organic solvent is removed by draining the reaction-induced organic solvent solution. For example, the removal of the organic solvent can be done by grasping the membrane vertically and allowing the excess organic solvent to flow down naturally, by blowing air with a blower to dry out the organic solvent, or by using a mixed fluid of water and air to remove the excess organic solvent.

[0091] In step (a4), the composite semipermeable membrane is washed with hot water. Washing with hot water removes unreacted monomers and oligomers. The temperature of the hot water used for washing is preferably 40°C to 100°C, and more preferably 60°C to 100°C. By going through these steps (a1) to (a4), a separation functional layer containing an aromatic polyamide having the substructure of the following general formula (VII) is formed.

[0092] [ka]

[0093] In formula (VII) above, Ar1 to Ar3 are each independently a divalent aromatic ring group having 5 to 14 carbon atoms, which may have substituents, and R2 to R4 are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms, which may have substituents. Preferred embodiments of Ar1 to Ar3 and R2 to R4 in general formula (VII) are the same as preferred embodiments of Ar1 to Ar3 and R2 to R4 in general formula (I).

[0094] (2-3) Modification process of the separation functional layer (process (b)) The present invention provides a method for producing a composite semipermeable membrane comprising a separation functional layer containing an aromatic polyamide on a porous support layer, wherein the method comprises, following a step (a) of forming the separation functional layer, a step (b) of contacting the separation functional layer with a treatment solution containing the compound represented by the general formula (IV) at a temperature of 45°C or higher. This step (b) causes the terminal amino groups in the aromatic polyamide substructure represented by the general formula (VII) to be crosslinked, thereby forming the structure of the general formula (I).

[0095] In general formula (IV), formyl groups are preferred as Z1 and Z2 from the viewpoint of reactivity with the terminal amino groups of aromatic polyamides. The preferred embodiments of n, X1, X2, L1, and L2 in general formula (IV) are the same as the preferred embodiments of n, X1, X2, L1, and L2 in general formula (II).

[0096] Specific examples of compounds represented by general formula (IV) include, for example, malealdehyde, (2Z,4Z)-hexa-2,4-dienedial, o-phthalaldehyde, p-phthalaldehyde, m-phthalaldehyde, 3-methylphthalaldehyde, 4-bromophthalaldehyde, 3,4-diformylmethyl benzoate, benzene-1,2,4,5-tetracarbaldehyde, benzo[d][1,3]dioxol-4,5-dicarbaldehyde, naphthalene-2,3-dicarbaldehyde, and [1,1'-biphenyl]-2,2'-dicarbaldehyde. Dehyde, (Z)-1,1,4,4-tetramethoxy-2-butene, (3Z,5Z)-2,7-dimethylocta-3,5-diene, 1,2-bis(dimethoxymethyl)benzene, 1,2-bis(dimethoxymethyl)-3-methylbenzene, 4-bromo-1,2-bis(dimethoxymethyl)benzene, 3,4-bis(dimethoxymethyl)methyl benzoate, 1,2,4,5-tetrakis(dimethoxymethyl)benzene, 4,5-bis(dimethoxymethyl)benzo[d][1,3]dioxol, 2,3-bis(dimethoxymethyl) Phthalene, 2,2'-bis(dimethoxymethyl)-1,1'-biphenyl, (Z)-1,2-di(1,3-dioxolan-2-yl)ethene, (1Z,3Z)-1,4-di(1,3-dioxolan-2-yl)-1,3-butadiene, 1,2-di(1,3-dioxolan-2-yl)benzene, 1,2-di(1,3-dioxolan-2-yl)-3-methylbenzene, 4-bromo-1,2-di(1,3-dioxolan-2-yl)benzene, 3,4-di(1,3-dioxolan-2-yl)methyl benzoate, 1,2,4,5 Examples include -tetra(1,3-dioxolan-2-yl)benzene, 4,5-di(1,3-dioxolan-2-yl)benzo[d][1,3]dioxol, 2,3-di(1,3-dioxolan-2-yl)naphthalene, 2,2'-di(1,3-dioxolan-2-yl)-1,1'-biphenyl, 1,1'-(1,2-phenylene)bis(1-methoxy-N,N-dimethylmethaneamine), 1,2-bis(1,3-dimethylimidazolidined-2-yl)benzene, and (Z)-N-(2-oxoethyridine)formamide.

[0097] In general formula (IV), X1 and X2 are preferably carbon atoms, and Z1 and Z2 are preferably formyl groups. When X1 and X2 are carbon atoms and Z1 and Z2 are formyl groups, the structure represented by general formula (I) can be obtained without side reactions. Furthermore, n is preferably 1. When n is 1, a rigid five-membered ring structure is obtained by the reaction. In addition, L1 and L2 preferably form an aromatic ring containing X1 and X2 as the backbone, and more preferably form a benzene ring or a naphthalene ring. By L1 and L2 forming an aromatic ring containing X1 and X2 as the backbone, a rigid and chemically stable ring structure can be introduced into the separation functional layer, and the decrease in water permeability associated with the reaction can be suppressed.

[0098] If the reaction temperature in step (b) is below 45°C, the reaction to crosslink the amino group terminals does not proceed sufficiently, and a structure like the one shown in general formula (VIII) below is mainly formed, in which only one amino group reacts with the molecule represented by the general formula (IV) above.

[0099] [ka]

[0100] The definitions of Ar1~Ar3, R2~R4, n, X1, X2, L1, and L2 in the above general formula (VIII) are the same as in general formula (I).

[0101] The structure of general formula (VIII) is obtained during the formation process of the structure of general formula (I), and heating to 45°C or higher is necessary to allow the reaction to proceed to the structure of general formula (I).

[0102] The structure represented by the general formula (VIII) also contributes to improved salt removal, but its effect on improving salt removal is lower than that of the structure represented by general formula (I), requiring a larger amount to be introduced. On the other hand, increasing the amount of the structure represented by general formula (VIII) leads to a decrease in water permeability. In other words, to achieve both high water permeability and high salt removal, it is essential to react the terminal amino group of the aromatic polyamide with the compound represented by general formula (VII) at 45°C or higher, and introduce the structure represented by general formula (I) in an appropriate amount.

[0103] To obtain the cross-linked structure of general formula (I), the bond between X1 and X2 in general formula (IV) must be a double bond. That is, the compound of general formula (IV) must have a structure in which X1 and X2, located at both ends of the double bond or at both ends of the π-conjugated system, react with amino groups, Z1 and Z2, respectively. In this case, the carbonyl group in general formula (VIII) is conjugated to the double bond between X1 and X2, causing further reaction of the amino group and resulting in the structure of general formula (II). On the other hand, if the bond between X1 and X2 is a single bond, a structure like general formula (VIII) cannot be obtained regardless of the reaction temperature, and as a result, a structure like general formula (I) with cross-linked terminal amino groups cannot be obtained either. For this reason, a large reaction amount is required to achieve a sufficient high salt removal effect, which reduces the water permeability of the composite semipermeable membrane.

[0104] The treatment solution containing the compound represented by general formula (IV) may be a solution obtained by dissolving the compound in a solvent, or a liquid obtained by melting the compound. When using a solution, water is preferably used as the solvent. When the treatment solution is a solution, the appropriate reaction time depends on the concentration of the compound in the solution and the temperature, but is preferably 10 seconds to 30 minutes, more preferably 10 seconds to 10 minutes, and even more preferably 10 seconds to 2 minutes. The concentration of the compound represented by general formula (IV) in the solution is preferably 0.001% by mass to 0.5% by mass, and more preferably 0.001% by mass to 0.05% by mass. The concentration of the compound in the solution is preferably 0.1 mM to 10 mM, and more preferably 0.1 mM to 1 mM. The temperature at which the treatment solution is brought into contact with the material is preferably 60°C to 100°C, and more preferably 80°C to 100°C. The pH of the treatment solution may be adjusted using any acid or base, and is preferably in the range of 0.5 to 9.0, and more preferably in the range of 1.5 to 7.5.

[0105] By performing step (b) under the conditions within the preferred range described above, Q / P, Q / S, ΔYI, and zeta potential can be controlled to a preferred range.

[0106] Furthermore, various processes may be performed after process (b) or between process (a) and process (b).

[0107] 3. Use of composite semipermeable membranes The composite semipermeable membrane according to this embodiment is suitably used as a composite semipermeable membrane element. More preferably, it is suitably 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, these composite semipermeable membrane elements can be connected in series or parallel and housed in a pressure vessel to form a composite semipermeable membrane module.

[0108] Furthermore, the composite semipermeable membrane, composite semipermeable membrane element, and composite semipermeable membrane module described above can be combined with a pump to supply water to them, a device to pre-treat the supply water, etc., to constitute a fluid separation device. By using this fluid separation device, the supply water can be separated into permeate water such as drinking water and concentrated water that did not permeate the membrane, thereby obtaining water suitable for the purpose.

[0109] In other words, the above-mentioned composite semipermeable membrane can be used in a water treatment system that separates supply water into concentrated water and fresh water using a composite semipermeable membrane element incorporating it.

[0110] Examples of feedwater treated by the composite semipermeable membrane according to this embodiment include liquid mixtures containing a total dissolved solids content (hereinafter referred to as "TDS") of 500 mg / L to 100 g / L, such as seawater, brine, and wastewater. Generally, TDS refers to the total dissolved solids content and is expressed as "mass / volume" or "mass ratio". According to the definition, TDS is calculated from the mass of the residue after evaporating a solution filtered through a 0.45 micron filter at a temperature of 39.5 to 40.5°C, but in this specification, it is calculated more simply by converting it from the practical salinity (S).

[0111] A higher operating pressure for the fluid separation device improves the solute removal rate. Considering the increased energy required for operation and the durability of the composite semipermeable membrane, the operating pressure when supplying feedwater to the composite semipermeable membrane is preferably between 0.5 MPa and 10 MPa. Since a high feedwater temperature reduces the solute removal rate and a low feedwater temperature reduces the permeability, the feedwater temperature is preferably between 5°C and 45°C. Furthermore, if the pH of the feedwater is high, in the case of feedwater with high solute concentrations such as seawater, scale such as magnesium is more likely to form, and deterioration of the composite semipermeable membrane is a concern, so the pH of the feedwater is preferably in the neutral range. [Examples]

[0112] The present invention will be described below with reference to specific examples, but the present invention is not limited in any way by these examples.

[0113] The physical properties of the composite semipermeable membrane of the present invention were measured by the following method.

[0114] <Salt removal rate> Seawater (TDS concentration 3.5%) adjusted to a temperature of 25°C and pH 6.5 was supplied at an operating pressure of 5.5 MPa to obtain permeate. The salt removal rate was determined from the TDS of the obtained permeate using the following formula. Salt removal rate (%) = 100 × {1 - (TDS concentration in permeate water / TDS concentration in supply water)}

[0115] <Membrane permeation flux> The amount of permeate obtained under the conditions described in "Salt Removal Rate" above is converted to permeable flow rate (cubic meters) per square meter of membrane surface per day, and the membrane permeation flux (m³) is used as an indicator of permeability. 3 / m 2 It was expressed as / day).

[0116] <tof-sims> The composite semipermeable membrane was immersed in ethanol for one day, the surface on the separation function layer side was washed with ultrapure water, and then the composite semipermeable membrane was washed again by immersion in ultrapure water for one day. The washed composite semipermeable membrane was dried in a vacuum dryer for 24 hours. The surface on the separation function layer side of the dried composite semipermeable membrane was analyzed under the following conditions. Measurement device: TOF.SIMS 5 (Manufactured by ION-TOF) Secondary ion polarity: Negative Mass range (m / z): 0~1500 Raster size: 300 μm Number of scans: 32 Pixel count (per side): 256 pixels Vacuum level measured (before sample introduction): 4 × 10 -7 Pa or less Primary ion species: Bi3 ++ Primary ion acceleration voltage: 30kV Pulse width: 10.9 ns Bunching: Yes Neutralization of static charge: Yes Rear acceleration: 9.5kV

[0117] <Degree of vanillin yellowing> The composite semipermeable membrane was washed with 90°C hot water for 2 minutes, and the surface moisture was removed by air drying. After drying, the composite semipermeable membrane was immersed in a 2% by mass ethanol solution of vanillin at 25°C for 15 seconds, the membrane was tilted to remove excess vanillin solution from the membrane surface, and the ethanol on the membrane surface was removed by air drying. Furthermore, the membrane was heated in a 150°C oven for 15 minutes to obtain a vanillin-treated membrane sample. In addition, an untreated membrane sample was obtained by washing the composite semipermeable membrane with 90°C hot water for 2 minutes and then air drying the surface moisture. The yellowness of the membrane samples was measured using an SM-7 color computer (manufactured by Suga Test Instruments Co., Ltd.), in accordance with JIS standards (JIS K 7373), using a standard illuminant D65 light source, and the yellowness YI of the vanillin-treated membrane sample and the yellowness YI0 of the untreated membrane sample were measured from the tristimulus values ​​of the XYZ color system, and the degree of yellowing ΔYI was calculated using the following formula. ΔYI=YI-YI0 Note that the yellowing degree ΔYI was rounded to two decimal places.

[0118] <Zeta potential> A composite semipermeable membrane was cut into 10 cm x 10 cm squares, and the surface on the separation function layer side was washed with distilled water. After washing, the composite semipermeable membrane was set in a plate sample cell, and the zeta potential of the separation function layer surface at pH 3.0 was measured using an electrophoretic light scattering spectrometer ELSZneo (manufactured by Otsuka Electronics Co., Ltd.), with the separation function layer side as the measurement surface. Five measurement points were randomly selected, and the average of these values ​​was taken as the zeta potential. The specific measurement conditions were as follows. Monitor particles: Polystyrene latex (hydroxypropyl cellulose coated) Measurement solution: NaCl aqueous solution (10mmоl / L) pH: 3.0 Particle concentration: 0.1% by mass Average particle size: 500nm Temperature: 25℃ Light source: Charge-Ne laser

[0119] [Comparative Example 1] Base material (polyester nonwoven fabric, air permeability 2.0 cc / cm²) 2 A support film comprising a substrate and a porous support layer was fabricated by casting an 18.0 mass% DMF solution of PSf to a thickness of 200 μm onto one main surface of the substrate ( / s) and immediately immersing it in pure water for 5 minutes. This support film was immersed in a 3.0 mass% m-PDA aqueous solution for 2 minutes. The support film was slowly pulled up vertically, and excess aqueous solution was removed from the surface of the support film by blowing nitrogen from an air nozzle. In a controlled environment of 40°C, a 40°C n-decane solution containing 0.16 mass% TMC was applied onto the porous support layer so that the surface was completely wetted. Next, the support film was heated in a 120°C oven, and then the film was drained vertically to remove excess solution from the film. The resulting film was washed with 85°C hot water for 2 minutes to fabricate a separation functional layer on the porous support layer of the support film. A composite semipermeable film was obtained as described above.

[0120] [Comparative Example 2] An aqueous solution with a pH of 7.0 containing 0.1% by mass of o-phthalaldehyde was prepared as the treatment solution. The composite semipermeable membrane obtained in Comparative Example 1 was immersed in this treatment solution at 25°C for 30 minutes, and then the membrane was washed with pure water to obtain a composite semipermeable membrane.

[0121] [Comparative Example 3] A composite semipermeable membrane was obtained using the same method as in Comparative Example 2, except that the immersion time of the composite semipermeable membrane in the treatment solution was set to 60 minutes.

[0122] [Comparative Example 4] A composite semipermeable membrane was obtained using the same method as in Comparative Example 2, except that the concentration of the treatment solution was set to 0.01% by mass, the temperature to 40°C, and the immersion time of the composite semipermeable membrane in the treatment solution was 10 minutes.

[0123] [Comparative Example 5] A composite semipermeable membrane was obtained using the same method as in Comparative Example 4, except that the immersion time of the composite semipermeable membrane in the treatment solution was set to 20 minutes.

[0124] [Comparative Example 6] A composite semipermeable membrane was obtained by the same method as in Comparative Example 4, except that succinaldehyde was used as the reaction reagent, the concentration of the treatment solution was 0.01% by mass, the temperature was 85°C, and the immersion time of the composite semipermeable membrane in the treatment solution was 1 minute.

[0125] [Comparative Example 7] A composite semipermeable membrane was obtained using the same method as in Comparative Example 3, except that glutaraldehyde was used as the reaction reagent.

[0126] [Comparative Example 8] A composite semipermeable membrane was obtained using the same method as in Comparative Example 6, except that glutaraldehyde was used as the reaction reagent.

[0127] [Comparative Example 9] A composite semipermeable membrane was obtained by the same method as in Comparative Example 6, except that the reaction reagent was cyclopentane-1,3-dicarbaldehyde.

[0128] [Comparative Example 10] Base material (polyester nonwoven fabric, air permeability 2.0 cc / cm²) 2 A support film comprising a substrate and a porous support layer was prepared by casting a 15.3 mass% DMF solution of PSf to a thickness of 200 μm onto one main surface of the substrate ( / s), and immediately immersing it in pure water and letting it stand for 5 minutes. This support film was immersed in a 3.4 mass% m-PDA aqueous solution for 2 minutes. The support film was slowly pulled up vertically, and excess aqueous solution was removed from the surface of the support film by blowing nitrogen from an air nozzle. In a controlled environment of 25°C, a 25°C n-decane solution containing 0.15 mass% TMC and 0.014 mass% oxalyl chloride was applied onto the porous support layer so that the surface was completely wet, and it was left to stand for 1 minute. After that, the film was tilted vertically and drained to remove excess solution from the film. Subsequently, it was washed with 90°C hot water for 2 minutes and immersed in a sodium hypochlorite aqueous solution adjusted to pH 7.0 and chlorine concentration of 200 mg / L for 2 minutes. Next, the membrane was immersed in a 1000 mg / L sodium bisulfite aqueous solution to reduce and remove excess sodium hypochlorite. Furthermore, the membrane was washed again with hot water at 95°C for 2 minutes, immersed in a 0.1 mass% aqueous solution of o-phthalaldehyde at pH 7.0 at 25°C for 60 minutes, and then washed with pure water to obtain a composite semipermeable membrane.

[0129] [Comparative Example 11] A composite semipermeable membrane was obtained using the same method as in Comparative Example 2, except that the concentration of the processing solution was set to 0.01% by mass.

[0130] [Example 1] A composite semipermeable membrane was obtained using the same method as in Comparative Example 6, except that o-phthalaldehyde was used as the reaction reagent and the pH of the treatment solution was adjusted to 2.0 using dilute sulfuric acid.

[0131] [Example 2] A composite semipermeable membrane was obtained using the same method as in Example 1, except that the pH of the treatment solution was set to 7.0.

[0132] [Example 3] A composite semipermeable membrane was obtained using the same method as in Example 2, except that the temperature of the processing solution was set to 50°C and the immersion time of the composite semipermeable membrane in the processing solution was set to 5 minutes.

[0133] [Example 4] A composite semipermeable membrane was obtained using the same method as in Example 3, except that the immersion time of the composite semipermeable membrane in the treatment solution was set to 10 minutes.

[0134] [Example 5] A composite semipermeable membrane was obtained using the same method as in Example 2, except that the temperature of the processing solution was set to 70°C and the immersion time of the composite semipermeable membrane in the processing solution was set to 3 minutes.

[0135] [Example 6] A composite semipermeable membrane was obtained in the same manner as in Example 5, except that the immersion time of the composite semipermeable membrane in the treatment solution was set to 6 minutes.

[0136] [Example 7] A composite semipermeable membrane was obtained by the same method as in Example 2, except that malealdehyde was used as the reaction reagent.

[0137] [Example 8] A composite semipermeable membrane was obtained by the same method as in Example 2, except that 3-methylphthalaldehyde was used as the reaction reagent and 10% by mass of isopropanol (hereinafter referred to as "IPA") was added to the solvent.

[0138] [Example 9] A composite semipermeable membrane was obtained by the same method as in Example 8, except that 4-bromophthalaldehyde was used as the reaction reagent.

[0139] [Example 10] A composite semipermeable membrane was obtained by the same method as in Example 2, except that the reaction reagent was methyl 3,4-diformylbenzoate.

[0140] [Example 11] A composite semipermeable membrane was obtained by the same method as in Example 8, except that the reaction reagent was benzene-1,2,4,5-tetracarbaldehyde.

[0141] [Example 12] A composite semipermeable membrane was obtained by the same method as in Example 2, except that the reaction reagent was benzo[d][1,3]dioxol-4,5-dicarbadehyde.

[0142] [Example 13] A composite semipermeable membrane was obtained by the same method as in Example 8, except that naphthalene-2,3-dicarbaldehyde was used as the reaction reagent.

[0143] [Example 14] A composite semipermeable membrane was obtained by the same method as in Example 8, except that the reaction reagent was [1,1'-biphenyl]-2,2'-dicarboxylase.

[0144] [Example 15] A composite semipermeable membrane was obtained using the same method as in Example 2, except that the concentration of the treatment solution was 0.1% by mass and the immersion time in the treatment solution was 15 seconds.

[0145] [Example 16] A composite semipermeable membrane was obtained using the same method as in Example 15, except that the immersion time in the processing solution was set to 1 minute.

[0146] The processing conditions in the comparative examples and examples are shown in Tables 1 and 2, and the results are shown in Tables 3 and 5.

[0147] [Table 1]

[0148] [Table 2]

[0149] [Table 3]

[0150] [Table 4]

[0151] [Table 5]

[0152] The composite semipermeable membranes of Examples 1 to 16 according to this embodiment have a membrane permeation flux of 0.5 m 3 / m 2 The salt removal rate is over 99.90% per day, indicating that it achieves both high water permeability and high salt removal performance.

[0153] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2024-079143, filed on 15 May 2024, the contents of which are incorporated herein by reference.

Claims

1. A composite semipermeable membrane having a porous support layer and a separation functional layer provided on the porous support layer, The separation functional layer is a composite semipermeable membrane containing an aromatic polyamide having a structure represented by the following general formula (I). 【Chemistry 1】 [In general formula (I), Ar １ ~Ar ６ Each is independently a divalent aromatic ring group having 5 to 14 carbon atoms, which may have substituents, and R ２ ~R ７ Each is independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms which may have substituents, and R １ This structure is represented by the following general formula (II). 【Chemistry 2】 In general formula (II), n is an integer of 1 to 6, and X １ , X ２ are each independently a carbon atom or a nitrogen atom, and L １ , L ２ are each independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 6 carbon atoms which may have a substituent, or a non-bonding electron pair. L １ and L ２ may be directly or indirectly bonded to form a cyclic structure, and the total number of carbon atoms of all L １ and L ２ is 12n or less.]

2. The composite semipermeable membrane according to claim 1, wherein n in the general formula (II) is 1 or 2.

3. In the above general formula (I), R １ The composite semipermeable membrane according to claim 2, wherein the structure is represented by the following general formula (III). 【Transformation 3】 [In general formula (III), Y １ ~Y ４ Each of these is independently a hydrogen atom, a C1-C4 monovalent hydrocarbon group which may have substituents, an ester group, or a halogen atom, Y １ ~Y ４ The total number of carbon atoms is 8 or less. １ ~Y ４ These may be directly or indirectly bonded to form a ring structure.

4. In the above general formula (III), Y １ ~Y ４ The composite semipermeable membrane according to claim 3, wherein is a hydrogen atom.

5. Let P be the sum of the signal intensity at m / z = 75.02 and the signal intensity at m / z = 76.03 obtained by TOF-SIMS on the surface of the separation functional layer. In the above general formula (I), R １ When Q is the signal intensity of the fragment with the highest signal intensity among the fragments derived from the structure containing the structure, The ratio of the signal intensity Q to the sum P, Q / P, is 2.0 × 10⁻⁶. －２ The above 3.5 x 10 －１ The composite semipermeable membrane according to claim 1 or 2, which is as follows:

6. Let S be the signal intensity at m / z = 75.02 obtained by TOF-SIMS on the surface of the separation functional layer. In the above general formula (I), R １ When Q is the signal intensity of the fragment with the highest signal intensity among the fragments derived from the structure containing the structure, The ratio Q / S of the signal intensity Q to the signal intensity S is 3.0 × 10 －２ The above 5.3 x 10 －１ The composite semipermeable membrane according to claim 1 or 2, which is as follows:

7. The composite semipermeable membrane according to claim 1 or 2, wherein the degree of yellowing ΔYI of the separation functional layer before and after contact with vanillin solution, calculated under the following conditions, is 3.0 or more and 10.0 or less. <Conditions for calculating vanillin yellowing degree> A composite semipermeable membrane is immersed in a 2% by mass ethanol solution of vanillin at 25°C for 15 seconds, the ethanol on the membrane surface is air-dried, and the vanillin-treated membrane sample is heated at 150°C for 15 minutes. The degree of yellowing ΔYI is calculated from the yellowing degree YI of the vanillin-treated membrane sample and the yellowing degree YI 0 of the untreated membrane sample using the following formula. ΔYI=YI-YI 0

8. The composite semipermeable membrane according to claim 1 or 2, wherein the zeta potential of the surface of the separation functional layer at pH 3.0 is -15 mV or more and 10 mV or less.

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

10. A water treatment system for separating supply water into concentrated water and fresh water using a composite semipermeable membrane element as described in claim 9.

11. A method for producing a composite semipermeable membrane, comprising the following steps (a) and (b). Step (a) Step of forming a separation functional layer containing aromatic polyamide on a porous support layer. Step (b) A step of bringing the separation functional layer into contact with a processing solution containing a compound represented by the following general formula (IV) at a temperature of 45°C or higher. 【Chemistry 4】 [In general formula (IV), Z １ Z ２ Each of these is independently a formyl group, an acetal group, a hemiaminal group, or an aminal group, and n is an integer from 1 to 6, X １ , X ２ Each is independently a carbon atom or a nitrogen atom, L １ , L ２ Each is independently a hydrogen atom, a halogen atom, a monovalent hydrocarbon group having 1 to 6 carbon atoms which may have substituents, or a lone pair of electrons, L １ and L ２ They may be directly or indirectly connected to form a ring structure, and all L １ and L ２ The total number of carbon atoms is 12n or less.

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