Composite semi-permeable membrane

Abstract

The composite semi-permeable membrane according to the present invention is provided with: a support film including a base material and a porous support layer; and a separation function layer containing a crosslinked aromatic polyamide as a main component. The sulfo group content of the separation function layer is 7.0×10-5-5.0×10-2g / m2, and the separation function layer has a structure represented by formula 1.

Description

[Technical field]

[0001] The present invention relates to composite semipermeable membranes useful for the selective separation of liquid mixtures. [Background technology]

[0002] Regarding the separation of liquid mixtures, there are various technologies for removing substances (e.g., salts) dissolved in a solvent (e.g., water), but in recent years, the use of membrane separation methods has expanded 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, and these membranes are used, for example, to obtain drinking water from water containing salt or harmful substances, to produce ultrapure water for industrial use, to treat wastewater, and to recover valuable materials.

[0003] Most reverse osmosis and nanofiltration membranes currently on the market are composite semipermeable membranes in which a separation functional layer with salt separation performance is coated on a support membrane, and there are two types: one with an active layer in which a gel layer and a polymer are crosslinked on the support membrane, and one with an active layer in which a monomer is polycondensed on the support membrane. Composite semipermeable membranes can achieve both separation performance and strength because the separation functional layer, which is responsible for the separation function, and the support membrane, which gives strength to the separation functional layer, can be selected independently.

[0004] Various composite semipermeable membranes have been disclosed. For example, Patent Document 1 discloses a composite semipermeable membrane in which a separation functional layer made of a crosslinked aromatic polyamide obtained by polycondensation reaction of a polyfunctional amine with a polyfunctional acid halide is coated on a support membrane. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-open No. 62-121603 [Patent Document 2] Japanese Patent Application Publication No. 2-78428 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the conventional composite semipermeable membrane having a separation functional layer made of crosslinked aromatic polyamide has both separation performance and permeability, but has a problem that its separation performance is limited. In addition, there is a problem that the crosslinked aromatic polyamide constituting the separation functional layer is decomposed by contact with a certain oxidizing agent due to an operation error, etc., and the separation performance is irreversibly impaired.

[0007] Therefore, an object of the present invention is to provide a composite semipermeable membrane which combines excellent separation performance, particularly good salt separation performance, with permeation performance, and further has excellent oxidation resistance. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a support membrane including a substrate and a porous support layer, and a separation functional layer that contains a crosslinked aromatic polyamide and is disposed on the porous support layer, The separation functional layer has a sulfo group of 7.0×10 -5 ~5.0×10 -2 g / m 2 The present invention provides a composite semipermeable membrane comprising:

[0009] [ka]

[0010] (wherein R1 is a hydrogen atom or a hydrocarbon having 1 to 10 carbon atoms which may have a substituent, R2 to R5 are hydrogen atoms or a hydrocarbon having 1 to 10 carbon atoms which may have a substituent, Ar1 to Ar3 are aromatic rings having 6 to 14 carbon atoms which may have a substituent, and at least one of R1, Ar1, and Ar3 has a sulfo group.) Effect of the Invention

[0011] According to the present invention, it is possible to provide a composite semipermeable membrane having excellent salt separation performance and permeation performance, as well as excellent oxidation resistance. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a cross-sectional view showing a schematic diagram of the structure of a composite semipermeable membrane, where (a) is a cross-sectional view of the composite semipermeable membrane, (b) is an enlarged view of the separation functional layer, and (c) is an enlarged view of the pleat structure of the separation functional layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to these in any way.

[0014] 1.Composite semipermeable membrane The structure of a composite semipermeable membrane is illustrated in Figure 1. As shown in Figure 1(a), a composite semipermeable membrane 1 includes a substrate 2, a porous support layer 3, and a separation functional layer.

[0015] (1-1) Support membrane The laminate consisting of the substrate 2 and the porous support layer 3 is called the support membrane. The support membrane is intended to impart strength to the separation functional layer, and does not itself have substantial solute separation performance.

[0016] Examples of the substrate 2 include fabrics made of polyester polymers, polyamide polymers, polyolefin polymers, and mixtures or copolymers thereof. Among these, fabrics made of polyester polymers, which have high mechanical and thermal stability, are preferred. As the form of the fabric, long fiber nonwoven fabrics, short fiber nonwoven fabrics, and woven and knitted fabrics can be preferably used.

[0017] The porous support layer 3 has a large number of interconnected pores. The pore size and pore size distribution of the pores are not particularly limited, but a porous support layer having, for example, a symmetrical structure with uniform pore size, or an asymmetrical structure in which the pore size gradually increases from one surface to the other, and in which the pore size on the surface with the smaller pore size is 0.1 to 100 nm, is preferred.

[0018] As the material of the porous support layer 3, homopolymers or copolymers such as polysulfone (hereinafter, "PSf"), polyethersulfone, polyamide, polyester, cellulose-based polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, polyphenylene oxide, etc. can be used alone or in blends. Here, examples of the cellulose-based polymer include cellulose acetate and cellulose nitrate, and examples of the vinyl polymer include polyethylene, polypropylene, polyvinyl chloride, and polyacrylonitrile. Among them, 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, and PSf is particularly preferred because of its high chemical, mechanical, and thermal stability and ease of molding.

[0019] The weight average molecular weight of PSf (hereinafter, "M w The M of PSf is preferably 10,000 to 200,000, and more preferably 15,000 to 100,000. w When the M of PSf is 10,000 or more, the porous support layer can have a preferable mechanical strength and heat resistance. w When the molecular weight is 200,000 or less, the viscosity of the porous support layer stock solution falls within an appropriate range, and good moldability can be achieved.

[0020] The thicknesses of the substrate and the porous support layer affect the strength of the composite semipermeable membrane and the packing density when it is made into an element. In order to obtain good mechanical strength and packing density, the total thickness of the substrate and the porous support layer is preferably 30 to 300 μm, more preferably 100 to 220 μm. The thickness of the porous support layer is preferably 20 to 100 μm. The thicknesses of the substrate and the porous support layer can be calculated by calculating the average value of the thicknesses at 20 points measured at 20 μm intervals in a direction perpendicular to the thickness direction (membrane surface direction) by cross-sectional observation.

[0021] (1-2) Separation functional layer The separating functional layer 4 is a layer that performs the function of separating solutes, and contains a crosslinked aromatic polyamide. The separating functional layer 4 preferably contains a crosslinked aromatic polyamide as a main component.

[0022] The term "mainly composed of crosslinked aromatic polyamide" means that the proportion of crosslinked aromatic polyamide in the separation functional layer is 50% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more.

[0023] The separation functional layer has a structure represented by the above formula 1. In the above formula 1, at least one of R1, Ar1, Ar2, and Ar3 has a sulfo group. In the above formula 1, R1 is preferably a hydrocarbon having 1 or 2 carbon atoms and having at least one sulfo group, and Ar2 is more preferably an aromatic ring having 6 to 14 carbon atoms and having at least one sulfo group. In the above formula 1, at least one of R1, Ar1, Ar2, and Ar3 has a sulfo group means that a structure having a sulfo group is bonded to a terminal amino group or aromatic ring of the crosslinked aromatic polyamide.

[0024] As a result of intensive research, the present inventors have found that the amino group, especially the terminal amino group, of the crosslinked aromatic polyamide is the starting point of oxidative degradation, and that oxidative degradation can be suppressed by lowering the electron density of the amino group, amide group, or aromatic ring. In the above formula 1, by having at least one of R1, Ar1, Ar2, and Ar3 having a sulfo group, which is an electron-withdrawing substituent, the electron density of the amino group, amide group, or aromatic ring is lowered, and a composite semipermeable membrane having excellent oxidation resistance and suppressed reactivity with oxidizing agents such as hypochlorous acid can be obtained.

[0025] In addition, the sulfo group is a hydrophilic substituent and exists in an ionized state when in contact with neutral water. In the above formula 1, by having at least one of R1, Ar1, Ar2, and Ar3 have a hydrophilic and negatively charged sulfo group, a composite semipermeable membrane can be obtained that has both excellent permeability due to hydrophilicity and excellent salt separation performance due to Coulomb repulsion with anions constituting the salt to be removed.

[0026] The separation functional layer has a sulfo group of 7.0 × 10 -5 ~5.0×10 -2 g / m 2 Contains sulfo groups of 7.0×10 -5 g / m 2 When the content of sulfo groups is 5.0×10 or more, oxidation resistance due to the electron density reduction of amino groups, amide groups, and aromatic rings, permeability due to hydrophilicity, and salt separation performance due to Coulomb repulsion can be fully exhibited. -2 g / m 2 By keeping the sulfo group content in the separation functional layer at 1.0×10 or less, it is possible to prevent a decrease in the separation performance of the composite semipermeable membrane due to the enlargement of the pore size of the separation functional layer caused by the Coulomb repulsion between the negatively charged sulfo groups in contact with neutral water. -4 ~3.0×10 -2 g / m 2 Preferably, it is 2.0×10 -4 ~1.0×10 -2 g / m 2 More preferably, it is 5.0×10 -4 ~7.0×10 -3 g / m 2It is even more preferable that:

[0027] The distribution of sulfo groups in the thickness direction of the separating functional layer affects the separation performance and permeation performance. The distribution of sulfo groups in the separating functional layer is determined by the following values ​​C and D. A: the number of sulfur atoms derived from sulfo groups in the separation functional layer measured by X-ray photoelectron spectroscopy (hereinafter referred to as "XPS"); B: Total number of nitrogen atoms in the separation functional layer measured by XPS C: A / B value measured on the surface of the separation functional layer in the composite semipermeable membrane D: A / B measured on a solid obtained by molding the powder of the separation functional layer extracted from the composite semipermeable membrane C / D is preferably 3 or more, more preferably 4 or more. Here, C represents the density of sulfo groups near the surface of the separation functional layer, and D represents the density of sulfo groups in the entire separation functional layer. C / D of 3 or more means that sulfo groups are present at a high density near the surface of the separation functional layer. A composite semipermeable membrane having such a separation functional layer has excellent oxidation resistance, salt separation performance, and permeation performance. There is no particular upper limit for C / D, but C / D is, for example, 10 or less.

[0028] The zeta potential of the separation functional layer at pH 3 is preferably -5 mV or less, more preferably -10 mV or less. The zeta potential is a measure of the net fixed charge on the surface of a flat sample. The crosslinked aromatic polyamide contained in the separation functional layer has amino groups, carboxyl groups, and sulfo groups as terminal functional groups, and the degree of dissociation of these groups depends on the pH. At pH 3, the amino groups are mainly positively charged, the carboxyl groups are mainly neutral, and the sulfo groups are mainly negatively charged. In other words, the zeta potential of the separation functional layer at pH 3 is considered to depend mainly on the amount of amino groups and sulfo groups. By having the zeta potential of the separation functional layer at pH 3 be -5 mV or less, the sulfo groups are present at a high density near the surface of the separation functional layer, and a composite semipermeable membrane having excellent oxidation resistance, salt separation performance, and permeability can be obtained.

[0029] The surface density of nitrogen atoms in the separation functional layer was determined by Rutherford backscattering spectroscopy (hereinafter referred to as "RBS") to be 4.0 × 10 20 ~1.2×10 21 pieces / m 2 It is preferable that the ratio is 6.0×10 20 ~1.2×10 21 pieces / m 2 More preferably, it is 8.0×10 20 ~1.2×10 21 pieces / m 2 The nitrogen atom surface density determined by RBS corresponds to the density of the crosslinked aromatic polyamide, which is the main component of the separation functional layer. The nitrogen atom surface density determined by RBS is more preferably 4.0×10 20 pieces / m 2 With this, the crosslinked aromatic polyamide is present at a high density, and therefore a composite semipermeable membrane having excellent separation performance due to the dense pore size can be obtained, and the decrease in separation performance of the composite semipermeable membrane caused by the Coulomb repulsion between negatively charged sulfo groups in contact with neutral water can be prevented, which is caused by the enlargement of the pore size of the separation functional layer. On the other hand, when the surface density of nitrogen atoms obtained by RBS is 1.2×10 21 pieces / m 2 When the density of the crosslinked aromatic polyamide is not too high, a composite semipermeable membrane having appropriate permeability can be obtained.

[0030] In addition, the separation functional layer preferably contains a compound having a structure represented by the following formula 2.

[0031] [ka]

[0032] (wherein X and Y are either a nitrogen atom, an oxygen atom, or a hydrocarbon; R6 is a hydrogen atom or a hydrocarbon having 1 to 10 carbon atoms; and R7 is a hydrocarbon having 2 to 4 carbon atoms). The compound having this cyclic structure contains an imine structure in the ring, and the nitrogen atom of the imine portion exhibits basicity in water. Therefore, when the separation functional layer is in contact with water, the portion represented by the above formula 2 forms an ion pair with the sulfo group on the crosslinked aromatic polyamide contained in the separation functional layer. This is thought to prevent the hydrogen ion from being ionized when in contact with water, and the electrostatic repulsion between the negatively charged sulfo groups and the resulting increase in the pore size of the separation functional layer. As a result, a composite semipermeable membrane having good permeability and excellent separation performance is obtained.

[0033] The shape and thickness of the separation functional layer affect the separation performance and permeation performance. As shown in FIG. 1(b), the separation functional layer preferably includes a pleated thin film 41 having a plurality of convex portions 42 and concave portions 43. By having the separation functional layer have a pleated thin film, the specific surface area of ​​the separation functional layer can be significantly improved compared to a planar structure. As a result, the permeation performance can be improved in proportion to the surface area of ​​the separation functional layer while maintaining the separation performance. The inside of the convex portions 42 (between the thin film 41 and the porous support layer 3) is a gap.

[0034] The average value of the thickness T of the thin film is preferably 10 to 20 nm, more preferably 10 to 16 nm. When the average value of the thickness T of the thin film is within the above range, a composite semipermeable membrane having both separation performance and permeation performance can be obtained.

[0035] In order to prevent the substance to be separated from penetrating into the composite semipermeable membrane, the separation functional layer is preferably arranged on the surface side of the composite semipermeable membrane, and more preferably arranged on the primary filtration side.

[0036] (1-3) NaCl rejection rate, boron rejection rate, membrane permeation flux The composite semipermeable membrane preferably has a NaCl rejection rate of 99.75% or more, more preferably 99.80% or more, and even more preferably 99.85% or more. The boron rejection rate is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. Furthermore, the membrane permeation flux is 0.50 m3 / m 2 / day or more is preferable, and 0.60m 3 / m 2 / day or more is preferable, and 0.70m 3 / m 2 When the membrane performance of the composite semipermeable membrane is within these ranges, it can be preferably used as a separation membrane for seawater desalination.

[0037] In addition, the composite semipermeable membrane preferably has a NaCl removal rate of 99.60% or more after contact with chlorine, more preferably 99.70% or more, and even more preferably 99.75% or more. In addition, the boron removal rate of 70% or more after contact with chlorine is preferably 75% or more, and even more preferably 80% or more. When the membrane performance of the composite semipermeable membrane after contact with chlorine is within these ranges, it can be preferably used as a composite semipermeable membrane with a low risk of oxidative deterioration due to chlorine leakage. The conditions for contact with chlorine will be described in the Examples.

[0038] 2. Manufacturing method of composite semipermeable membrane 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 above-mentioned desired characteristics can be obtained. For example, the composite semipermeable membrane can be produced by the following method.

[0039] (2-1) Preparation of the support film The method for producing the support membrane will be described by taking as an example the case where PSf is used as the material for the porous support layer.

[0040] First, PSf is dissolved in a good solvent for PSf to prepare a porous support layer stock solution. As a good solvent for PSf, for example, N,N-dimethylformamide (hereinafter, "DMF") is preferable.

[0041] The concentration of PSf in the porous support layer stock solution is preferably 10 to 25% by mass, more preferably 12 to 20% by mass. By keeping the concentration of PSf in the porous support layer stock solution within this range, the strength and permeability of the resulting porous support layer can be compatible. The preferred range of the concentration of the material in the porous support layer stock solution can be appropriately adjusted depending on the material, good solvent, etc. used.

[0042] Next, the obtained porous support layer stock solution is applied to the surface of a substrate, and the substrate is immersed in a coagulation bath containing a non-solvent for PSf.

[0043] The temperature of the porous support layer stock solution when applied is preferably 10 to 60°C. When the temperature of the porous support layer stock solution is within this range, PSf does not precipitate, and the porous support layer stock solution is sufficiently impregnated into the spaces between the fibers of the substrate and then solidifies. As a result, the porous support layer is firmly bonded to the substrate due to the anchor effect, and a support film with excellent strength can be obtained. The preferred temperature range of the porous support layer stock solution can be appropriately adjusted depending on the material, good solvent, concentration, etc. used.

[0044] After applying the porous support layer stock solution, the time until immersion in the coagulation bath is preferably 0.1 to 5.0 seconds. When the time until immersion in the coagulation bath is 0.1 seconds or more, the porous support layer stock solution is sufficiently impregnated into the spaces between the fibers of the substrate and then coagulated. On the other hand, when the time until immersion in the coagulation bath is 5.0 seconds or less, the porous support layer stock solution can be immersed in the coagulation bath before it is coagulated by water vapor in the air. The preferred range of the time until immersion in the coagulation bath can be appropriately adjusted depending on the material, good solvent, concentration, etc. used.

[0045] The non-solvent for PSf contained in the coagulation bath is preferably water, for example. By contacting the porous support layer stock solution applied to the substrate surface with a coagulation bath containing a non-solvent for PSf, the porous support layer stock solution is coagulated by non-solvent-induced phase separation, and a support membrane in which a porous support layer is formed on the substrate surface can be obtained.

[0046] The coagulation bath may be composed of only a non-solvent for PSf, but may also contain a good solvent for PSf within the range in which the porous support layer stock solution can be coagulated. When the support membrane is continuously produced, the good solvent for PSf derived from the porous support layer stock solution is mixed into the coagulation bath, and the concentration of the good solvent for PSf in the coagulation bath gradually increases. For this reason, it is preferable to replace the coagulation bath as appropriate so that the composition of the coagulation bath is kept within a certain range. The lower the concentration of the good solvent for PSf in the coagulation bath, the faster the coagulation of the porous support layer stock solution, so that the structure of the porous support layer is homogenized and excellent strength can be expressed. In addition, since the coagulation of the porous support layer stock solution is faster, the membrane production speed can be increased to improve the productivity of the support membrane. For this reason, the concentration of the good solvent for PSf in the coagulation bath is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less.

[0047] The temperature of the coagulation bath is preferably -20 to 100°C, more preferably 10 to 50°C. When the temperature of the coagulation bath is -20°C or higher, the coagulation speed is appropriate and the membrane formability is good. On the other hand, when the temperature of the coagulation bath is 100°C or lower, the vibration of the coagulation bath surface due to thermal motion is not intense, and the smoothness of the support membrane surface after the formation of the porous support layer is maintained. The preferred range of the temperature of the coagulation bath can be appropriately adjusted depending on the material, good solvent, concentration, etc. used.

[0048] Finally, the obtained support membrane is washed with hot water to remove the solvent remaining in the membrane. The temperature of the hot water is preferably 40 to 95°C, more preferably 60 to 95°C. When the temperature of the hot water is 40°C or higher, the solvent remaining in the membrane can be sufficiently removed. On the other hand, when the temperature of the hot water is 95°C or lower, the shrinkage degree of the support membrane does not increase, and good permeability performance can be maintained. The preferred range of the temperature of the hot water can be appropriately adjusted depending on the material, good solvent, concentration, etc. used.

[0049] (2-2) Polymerization process of the separation functional layer The method for forming a separation functional layer containing a crosslinked aromatic polyamide will be described by taking as an example a method in which a polyfunctional aromatic amine and a polyfunctional aromatic acid chloride are polymerized and solidified on the support membrane obtained in "(2-1) Formation of support membrane". As the polymerization method, the interfacial polymerization method is the most preferable from the viewpoints of productivity and performance. The interfacial polymerization process will be described below.

[0050] The interfacial polymerization process includes the steps of: (a) contacting an aqueous solution containing a polyfunctional aromatic amine with a support membrane; (b) contacting an organic solvent solution containing a polyfunctional aromatic acid chloride with the support membrane that has been contacted with the aqueous solution containing a polyfunctional aromatic amine; (c) draining the organic solvent solution after the contact; and (d) washing the composite semipermeable membrane from which the organic solvent solution has been drained with hot water.

[0051] In step (a), examples of polyfunctional aromatic amines include polyfunctional aromatic amines in which two amino groups are bonded to an aromatic ring at the ortho, meta, or para positions, such as o-phenylenediamine, m-phenylenediamine (hereinafter referred to as "m-PDA"), p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m-diaminopyridine, and p-diaminopyridine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, 4-aminobenzylamine, and 2,4-diaminobenzenesulfonic acid. In particular, m-PDA, p-phenylenediamine, and 1,3,5-triaminobenzene are preferably used in consideration of the separation performance, permeation performance, and heat resistance of the membrane. Among them, m-PDA is more preferably used because of its ease of availability and ease of handling. In addition, by using 2,4-diaminobenzenesulfonic acid, a sulfo group can be introduced into the aromatic ring of the crosslinked aromatic polyamide, forming a separation functional layer including the structure represented by the above formula 1. These polyfunctional aromatic amines may be used alone or in combination of two or more kinds.

[0052] The concentration of the polyfunctional aromatic amine in the polyfunctional aromatic amine aqueous solution is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, and even more preferably 1.0 to 10% by mass. When the concentration of the polyfunctional aromatic amine is 0.1% by mass or more, a separation functional layer having a solute separation performance can be formed. On the other hand, when the concentration of the polyfunctional aromatic amine is 20% by mass or less, a separation functional layer having good permeability can be formed. In addition, the polyfunctional aromatic amine aqueous solution may contain compounds such as surfactants and antioxidants as necessary, as long as they do not inhibit polymerization.

[0053] The polyfunctional aromatic amine aqueous solution is preferably uniformly and continuously brought into contact with the support membrane.Specific examples of the method include a method of coating the polyfunctional aromatic amine aqueous solution on the support membrane, and a method of immersing the support membrane in the polyfunctional aromatic amine aqueous solution.The contact time between the support membrane and the polyfunctional aromatic amine aqueous solution is preferably 1 second to 10 minutes, and more preferably 10 seconds to 3 minutes.

[0054] After the polyfunctional aromatic amine aqueous solution is brought into contact with the support membrane, it is preferable to thoroughly drain the solution so that no droplets remain on the support membrane. By thoroughly draining the solution, it is possible to prevent the remaining droplets from becoming membrane defects after the composite semipermeable membrane is formed, which leads to a decrease in separation performance. As a method of draining the solution, for example, as described in Patent Document 2, a method of vertically holding the support membrane after contact with the polyfunctional aromatic amine aqueous solution to allow the excess aqueous solution to flow naturally down, or a method of blowing an air flow such as nitrogen from an air nozzle to forcibly drain the solution, can be mentioned. In addition, after draining, the membrane surface can be dried to remove some of the water content of the aqueous solution.

[0055] In step (b), examples of the polyfunctional aromatic acid chloride include trimesic acid chloride (hereinafter, "TMC"), biphenyldicarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalenedicarboxylic acid chloride, and 2,5-furandicarboxylic acid chloride. These polyfunctional aromatic acid chlorides may be used alone or in combination of two or more.

[0056] The organic solvent is preferably immiscible with water, dissolves the polyfunctional aromatic acid chloride, does not damage the support membrane, and is inactive against the polyfunctional aromatic amine and the polyfunctional aromatic acid chloride. Examples of the organic solvent include hydrocarbon compounds such as n-nonane, n-decane, n-undecane, n-dodecane, isooctane, isodecane, and isododecane, and mixtures thereof.

[0057] The concentration of the polyfunctional aromatic acid chloride in the organic solvent solution is preferably 0.01 to 10% by mass, more preferably 0.02 to 4% by mass, and even more preferably 0.03 to 2% by mass. When the concentration of the polyfunctional aromatic acid chloride is 0.01% by mass or more, the polymerization can proceed at a sufficient reaction rate. On the other hand, when the concentration of the polyfunctional aromatic acid chloride is 10% by mass or less, the occurrence of side reactions during the polymerization can be suppressed. In addition, the organic solvent solution may contain a compound such as a surfactant as necessary, as long as it does not inhibit the polymerization.

[0058] The method of contacting the organic solvent solution of the polyfunctional aromatic acid chloride with the support membrane which has been brought into contact with the aqueous polyfunctional aromatic amine solution may be carried out in the same manner as in the method of coating the aqueous polyfunctional aromatic amine solution on the support membrane.

[0059] If necessary, the support membrane contacted with the organic solvent solution of the polyfunctional aromatic acid chloride may be heat-treated. When heat-treated, the heating temperature is preferably 50 to 180° C., more preferably 60 to 160° C., and even more preferably 80 to 150° C. The optimal heating time varies depending on the temperature of the membrane surface, which is the reaction site, but is preferably 10 seconds or more, and more preferably 20 seconds or more.

[0060] In step (c), the organic solvent solution on the composite semipermeable membrane after the polymerization reaction is drained and removed. Examples of the draining method include a method in which the membrane is held vertically and the excess organic solvent solution is removed by gravity flow, a method in which the organic solvent is dried and removed by blowing air with a blower, and a method in which the excess organic solvent solution is removed with a mixed fluid of water and air.

[0061] 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 to 95°C, more preferably 60 to 95°C. When the temperature of the hot water is 40°C or higher, unreacted substances and oligomers remaining in the membrane can be sufficiently removed. On the other hand, when the temperature of the hot water is 95°C or lower, the degree of shrinkage of the composite semipermeable membrane does not increase, and good permeability performance can be maintained. The preferred range of the temperature of the hot water can be appropriately adjusted depending on the polyfunctional aromatic amine or polyfunctional aromatic acid chloride used.

[0062] In addition, the composite semipermeable membrane may be further washed as necessary. Examples of the washing method include a method of contacting the composite semipermeable membrane surface with radicals. Examples of the radicals include hydroxyl radicals, hydroperoxy radicals, peroxy radicals, alkoxy radicals, thiyl radicals, and sulfite radicals. Among them, sulfite radicals are preferred in terms of ease of control of the radical strength and concentration. In addition, chlorine radicals and persulfate radicals, which react with aromatic rings of crosslinked aromatic polyamides and cause chemical deterioration, are not preferred. By contacting the composite semipermeable membrane surface with radicals, unreacted substances and oligomers remaining in the membrane can be further removed, and the thickness of the thin film can also be adjusted. The preferred ranges of the radical strength, concentration, temperature, pH, etc. can be appropriately adjusted depending on the activity of the radicals used.

[0063] (2-3) Modification process of separation functional layer A method for forming a separation functional layer containing a structure represented by the above formula 1 will be described using as an example a method in which a sulfonating reagent is reacted with a separation functional layer containing a crosslinked aromatic polyamide obtained in "(2-2) Polymerization step of the separation functional layer."

[0064] Examples of sulfonating reagents include chlorosulfonic acid, 1,3-propane sultone, 1,4-butane sultone, sodium 2-bromoethanesulfonate, methylsulfonyloxymethanesulfonic acid, sulfur trioxide pyridine complex, N-sulfomaleimide, 1,3-disulfoimidazolium chloride, and dimethyl sulfomalonate. By contacting and reacting these sulfonating reagents with the separation functional layer in a solution dissolved in a solvent that does not alter the support membrane, or in the form of the reagent alone without using a solvent, a sulfo group is introduced into the crosslinked aromatic polyamide, and a separation functional layer including the structure represented by the above formula 1 can be formed.

[0065] Examples of the solvent for the sulfonating reagent include water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, formic acid, acetic acid, propionic acid, methyl acetate, ethyl acetate, and butyl acetate.

[0066] When used as a sulfonating reagent solution, the concentration of the sulfonating reagent is preferably 0.05 to 20 mass%, more preferably 0.2 to 10 mass%, and even more preferably 0.5 to 7 mass%. When the concentration of the sulfonating reagent is 0.05 mass% or more, sulfo groups can be sufficiently introduced into the crosslinked aromatic polyamide. On the other hand, when the concentration of the sulfonating reagent is 20 mass% or less, deterioration of the composite semipermeable membrane due to the solvent or reaction by-products can be suppressed.

[0067] The sulfonating reagent or the sulfonating reagent solution is preferably uniformly and continuously brought into contact with the separation functional layer. Specifically, for example, a method of coating the separation functional layer with the sulfonating reagent or the sulfonating reagent solution, or a method of immersing the composite semipermeable membrane in the sulfonating reagent or the sulfonating reagent solution can be mentioned. In addition, after preparing a composite semipermeable membrane element described later, the sulfonating reagent or the sulfonating reagent solution may be passed through the element to cause a reaction. The contact time between the separation functional layer and the sulfonating reagent or the sulfonating reagent solution is preferably 1 second to 24 hours, more preferably 10 seconds to 2 hours, and even more preferably 20 seconds to 30 minutes.

[0068] Next, the composite semipermeable membrane after the modification reaction is washed with water. The temperature of the water is preferably 15 to 95°C, more preferably 40 to 95°C. By keeping the temperature of the water at 15°C or higher, unreacted substances and by-products remaining in the membrane can be removed. On the other hand, by keeping the temperature of the water at 95°C or lower, the degree of contraction of the composite semipermeable membrane does not increase, and good permeability performance can be maintained. The preferred range of the water temperature can be appropriately adjusted depending on the sulfonation reagent used.

[0069] The composite semipermeable membrane obtained by the above-mentioned production method has a NaCl rejection rate of preferably 99.60% or more, more preferably 99.70% or more. The composite semipermeable membrane obtained has a boron rejection rate of preferably 80% or more, more preferably 85% or more. Furthermore, the membrane permeation flux during production is preferably 0.50 m 3 / m 2 / day or more is preferable, and 0.70m 3 / m 2 When the membrane performance during production of the composite semipermeable membrane is within these ranges, the composite semipermeable membrane can be preferably used as a separation membrane for seawater desalination.

[0070] 3. Use of composite semipermeable membranes The composite semipermeable membrane is preferably used as a spiral-type composite semipermeable membrane element by winding it around a cylindrical water collection pipe having a large number of holes, together with a feed water flow path material such as a plastic net, a permeate water flow path material such as tricot, and, if necessary, a film for increasing pressure resistance. Furthermore, this element can be connected in series or in parallel and housed in a pressure vessel to form a composite semipermeable membrane module.

[0071] Furthermore, the above-mentioned composite semipermeable membrane, its element, and module can be combined with a pump for supplying feed water thereto, a device for pretreating the feed water, etc. to form a fluid separation device. By using this separation device, the feed water can be separated into permeated water such as drinking water and concentrated water that did not permeate the membrane, thereby obtaining water suitable for the purpose.

[0072] The feed water to be treated by the composite semipermeable membrane according to the present invention includes liquid mixtures containing 500 mg / L to 100 g / L of TDS (Total Dissolved Solids), such as seawater, brackish water, and wastewater. In general, TDS refers to the amount of total dissolved solids, and is expressed as "mass / volume" or "weight ratio." According to the definition, it can be calculated from the weight of the residue obtained by evaporating a solution filtered through a 0.45 micron filter at a temperature of 39.5 to 40.5°C, but it is more convenient to convert it from the practical salinity (S).

[0073] The higher the operating pressure of the fluid separation device, the higher the solute removal rate, but the energy required for operation also increases. In addition, taking into consideration the durability of the composite semipermeable membrane, the operating pressure when the treated water is permeated through the composite semipermeable membrane is preferably 0.5 to 10 MPa. The higher the feed water temperature, the lower the membrane permeation flux decreases, so a temperature of 5 to 45°C is preferable. In addition, if the pH of the feed water is high, there is a risk of magnesium scale formation in the case of feed water with a high solute concentration such as seawater, and there is also concern about membrane deterioration due to high pH operation, so operation in the neutral region is preferable. EXAMPLES

[0074] The present invention will be described below with reference to specific examples, but the present invention is not limited to these examples in any way.

[0075] The physical properties of the composite semipermeable membrane of the present invention were measured by the following methods.

[0076] (1) Sulfo group content, C / D (i) Near the surface of the separation functional layer The composite semipermeable membrane was cut into a 3 cm x 3 cm square, washed with distilled water at 90°C for 10 minutes, and dried. The composite semipermeable membrane after drying was measured with XPS (Quantera SXM, manufactured by PHI) with the separation functional layer as the measurement surface, and the number of sulfur atoms derived from sulfo groups (A) and the total number of nitrogen atoms (B) were calculated, and the value of A / B was defined as C. The specific measurement conditions were as follows:

[0077] (ii) The entire separation functional layer Composite semipermeable membrane total 1m 2The membrane was cut out, washed with distilled water at 90°C for 10 minutes, and dried. The substrate was peeled off from the dried composite semipermeable membrane, and the peeled off body consisting of two layers, the porous support layer and the separation functional layer, was put into dichloromethane to elute the polymer forming the porous support layer. The precipitate mainly composed of the separation functional layer was repeatedly washed with dichloromethane until the polymer forming the porous support layer could not be detected by thin layer chromatography. The precipitate after washing was freeze-dried to obtain a powder of the separation functional layer. The obtained powder was molded into pellets. The molded sample was subjected to XPS measurement, and the number of sulfur atoms derived from sulfo groups (A) and the total number of nitrogen atoms (B) were calculated, and the value of A / B was taken as D. In addition, the amount of sulfo groups per unit area in the separation functional layer was calculated from A. The specific measurement conditions were as follows. Excitation X-ray: monochromatic Al Kα1, 2 line (1486.6 eV) X-ray diameter: 0.2 mm The S2p peak obtained by XPS is due to the inner shell electrons of sulfur atoms. The N1s peak is due to the inner shell electrons of nitrogen atoms. The components derived from SC appear at 169 eV, and the components derived from NC appear at around 400 eV. A was calculated from the peak area derived from SC, and B was calculated from the peak area derived from NC.

[0078] (2) Average thickness T of the thin film The composite semipermeable membrane was cut into a 3 cm x 3 cm square and washed with distilled water at 25°C for 24 hours. The washed composite semipermeable membrane was embedded in epoxy resin and then stained with osmium tetroxide to prepare a measurement sample. The obtained sample was observed with a scanning transmission electron microscope (Hitachi; HD2700) with the thin film cross section as the observation surface. Using an image acquired at a magnification of 1 million times, the shortest distance from a point on the thin film outer surface to the inner surface was determined as the thin film thickness T. For 10 randomly selected convex parts, analysis was performed at five points per convex part, and the average of these was determined as the average thickness of the thin film.

[0079] (3) Nitrogen atom surface density The composite semipermeable membrane was cut into a 10 cm x 10 cm square and washed with distilled water at 25 ° C. for 24 hours. The composite semipermeable membrane after washing was measured with RBS (Pelletron 3SDH manufactured by National Electrostatics Corporation) with the separation functional layer as the measurement surface, and the nitrogen atom surface density was calculated. The specific measurement conditions were as follows. Measurement mode: RBS only measurement Incident ions: 4 He 2+ Incident energy: 2300keV Incident angle: 0° Scattering angle: 160° Specimen current: 4nA Beam diameter: 2mmφ Irradiation dose: 0.8μC x 126 points = 100.8μC (4) Zeta potential The composite semipermeable membrane was washed with distilled water. The washed composite semipermeable membrane was set in a flat sample cell, and the separation functional layer was used as the measurement surface and measured using an electrophoretic light scattering photometer (Otsuka Electronics; ELS-8000) to obtain the zeta potential of the separation functional layer at pH 3. Five measurement points were randomly selected, and the average of these was taken as the zeta potential. The specific measurement conditions were as follows:

[0080] Monitor particles: Polystyrene latex (hydroxypropyl cellulose coated) Measurement solution: NaCl aqueous solution (10mM) pH: 3 Temperature: 25℃ Light source: He-Ne laser (5) Weight average molecular weight The weight-average molecular weight (polystyrene equivalent) of PSf was measured using gel permeation chromatography (Tosoh Corporation; HLC-8022) under the following specific measurement conditions.

[0081] Column: TSK gel SuperHM-H (Tosoh; inner diameter 6.0 mm, length 15 cm) x 2 Eluent: LiBr / N-methylpyrrolidone solution (10 mM) Sample concentration: 0.1% by mass Flow rate: 0.5mL / min Temperature: 40℃ (6)NaCl removal rate A membrane filtration test was conducted by supplying evaluation water adjusted to a NaCl concentration of 35,000 ppm, a boron concentration of 5 ppm, 25°C, and pH of 7 to the composite semipermeable membrane at an operating pressure of 5.5 MPa. The electrical conductivity of the evaluation water and the permeated water was measured using a multi-water quality meter (MM-60R, manufactured by DKK-TOA) to obtain the respective NaCl concentrations (practical salinity). From the NaCl concentrations thus obtained, the NaCl removal rate (%) was calculated based on the following formula 3.

[0082] NaCl removal rate (%) = 100 × {1 - (NaCl concentration in permeated water / NaCl concentration in evaluation water)} (Equation 3) (7) Boron removal rate In the membrane filtration test of “(6) NaCl removal rate”, the boron concentration in the evaluation water and the permeated water was measured using an ICP emission spectrometer (Agilent Technologies; Agilent 5110), and the boron removal rate (%) was calculated based on the following formula 4. Boron removal rate (%) = 100 × {1 - (boron concentration in permeated water / boron concentration in evaluation water)} (Equation 4) (8) Membrane permeation flux In the membrane filtration test of "(6) NaCl removal rate", the permeate volume (m 3 ) and the unit membrane area (m 2 ) and converted to a value per unit time (day), and the membrane permeation flux (m 3 / m 2 / day).

[0083] (9) Chlorine Contact The composite semipermeable membrane was immersed in a 25 mg / L aqueous solution of sodium hypochlorite adjusted to pH 7.0 at 25° C. for 24 hours, then immersed in a 1000 mg / L aqueous solution of sodium hydrogen sulfite for 10 minutes and washed with distilled water.

[0084] The raw materials of the composite semipermeable membranes used in the examples and comparative examples are summarized below. PSf (Solvay Specialty Polymers; Udel P-3500, M w 80000) DMF (Fujifilm Wako Pure Chemical Industries, Ltd.) Polyester long fiber nonwoven fabric (thickness 90 μm, density 0.42 g / cm 3 ) m-PDA (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) TMC (FUJIFILM Wako Pure Chemical Industries, Ltd.) Decane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Sodium hypochlorite (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Sodium hydrogen sulfite (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Isopropyl alcohol (Fujifilm Wako Pure Chemical Industries, Ltd.) Sulfanilic acid (Fujifilm Wako Pure Chemical Industries, Ltd.) 1,3-Propane sultone (Fujifilm Wako Pure Chemical Industries, Ltd.) Chlorosulfonic acid (Fujifilm Wako Pure Chemical Industries, Ltd.) Butyl acetate (Fujifilm Wako Pure Chemical Industries, Ltd.) Comparative Example 1 15% by mass of PSf and 85% by mass of DMF were dissolved at 100°C to prepare a porous support layer stock solution. This porous support layer stock solution was applied to the surface of a polyester long fiber nonwoven fabric at 25°C, and after 3 seconds, it was immersed in a coagulation bath of distilled water at 25°C for 30 seconds to coagulate, and washed with hot water at 80°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 50 μm.

[0085] Next, the obtained support membrane was immersed in a 3% by mass aqueous solution of m-PDA for 2 minutes, and the support membrane was slowly pulled up vertically, and nitrogen was sprayed from an air nozzle to remove excess aqueous solution from the support membrane surface. In an environment controlled at 40°C, a decane solution containing 0.18% by mass of TMC at 40°C was applied so that the surface was completely wet and left to stand for 1 minute, and then the support membrane was vertically turned to drain off excess solution and removed. In this way, a layer containing a crosslinked aromatic polyamide was formed on the support membrane to obtain a composite semipermeable membrane. Finally, the composite semipermeable membrane was washed with hot water at 80°C for 2 minutes. The results of evaluating the obtained composite semipermeable membrane are shown in Table 2.

[0086] Comparative Example 2 The support membrane obtained in Comparative Example 1 was immersed in a 3% by mass aqueous solution of m-PDA for 2 minutes, the support membrane was slowly pulled up vertically, and nitrogen was sprayed from an air nozzle to remove excess aqueous solution from the support membrane surface. In an environment controlled at 45°C, a 45°C decane solution containing 0.2% by mass of TMC was applied so that the surface was completely wet, and the solution was left to stand for 10 seconds, and then heated in a 120°C oven for 10 minutes, and the support membrane was then turned vertically to drain off excess solution and remove it. In this way, a layer containing a crosslinked aromatic polyamide was formed on the support membrane, and a composite semipermeable membrane was obtained. Thereafter, the composite semipermeable membrane was washed with hot water at 80°C for 2 minutes. Furthermore, oxygen was bubbled into the sodium hydrogen sulfite aqueous solution to remove 1.0×10 -3 An aqueous solution containing 1.0 mol / L of sulfite radicals at 25°C and pH 3 was prepared, and the composite semipermeable membrane was immersed for 1 hour. Finally, it was immersed for 1 hour in a 10% by mass aqueous solution of isopropyl alcohol at 25°C, and then immersed for 1 hour in distilled water at 25°C. The results of evaluation of the obtained composite semipermeable membrane are shown in Table 2.

[0087] Comparative Example 3 The composite semipermeable membrane obtained in Comparative Example 1 was immersed in an aqueous solution of pH 7 containing 1% by mass of polyacrylic acid / vinyl sulfonic acid copolymer and 0.1% by mass of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride at 25° C. for 24 hours. The composite semipermeable membrane was washed with distilled water at 45° C. for 10 minutes to obtain a composite semipermeable membrane modified with a separation functional layer. The evaluation results of the obtained composite semipermeable membrane are shown in Table 2.

[0088] Comparative Example 4 The composite semipermeable membrane obtained in Comparative Example 1 was immersed in an aqueous solution of pH 7 containing 1% by mass of polyacrylic acid / 4-vinylphenylsulfonic acid copolymer and 0.1% by mass of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride at 25° C. for 24 hours. The composite semipermeable membrane was washed with distilled water at 45° C. for 10 minutes to obtain a composite semipermeable membrane modified with a separation functional layer. The evaluation results of the obtained composite semipermeable membrane are shown in Table 2.

[0089] Comparative Example 5 The composite semipermeable membrane obtained in Comparative Example 2 was immersed in an aqueous solution of pH 7 containing 1% by mass of polyacrylic acid / 3-(methacrylamide)propylsulfonic acid copolymer and 0.1% by mass of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride at 25° C. for 24 hours. The composite semipermeable membrane was washed with distilled water at 45° C. for 10 minutes to obtain a composite semipermeable membrane modified with a separation functional layer. The evaluation results of the obtained composite semipermeable membrane are shown in Table 2.

[0090] Comparative Example 6 The composite semipermeable membrane obtained in Comparative Example 2 was immersed in a 2750 mg / L aqueous sodium nitrite solution adjusted to pH 3 with sulfuric acid at 35° C. for 45 seconds. Then, it was immersed in a mixed solution of 0.01% by mass sulfanilic acid and 0.1% by mass sodium sulfite for 2 minutes. The composite semipermeable membrane was washed with distilled water at 45° C. for 10 minutes to obtain a composite semipermeable membrane modified with a separation functional layer. The evaluation results of the obtained composite semipermeable membrane are shown in Table 2.

[0091] Example 1 The composite semipermeable membrane obtained in Comparative Example 1 was immersed in a 1% by mass aqueous solution of 1,3-propane sultone at 25° C. for 24 hours. The composite semipermeable membrane was washed with distilled water at 45° C. for 10 minutes to obtain a composite semipermeable membrane modified with a separation functional layer. The evaluation results of the obtained composite semipermeable membrane are shown in Table 2.

[0092] Example 2 A butyl acetate solution containing 1% by mass of chlorosulfonic acid was coated on the separation functional layer of the composite semipermeable membrane obtained in Comparative Example 1, and the mixture was allowed to contact for 2 minutes at 25° C. The composite semipermeable membrane was washed with distilled water at 45° C. for 10 minutes to obtain a composite semipermeable membrane with a modified separation functional layer. The evaluation results of the obtained composite semipermeable membrane are shown in Table 2.

[0093] Example 3 The composite semipermeable membrane obtained in Comparative Example 2 was immersed in a 1% by mass aqueous solution of 1,3-propane sultone at 25° C. for 24 hours. The composite semipermeable membrane was washed with distilled water at 45° C. for 10 minutes to obtain a composite semipermeable membrane modified with a separation functional layer. The evaluation results of the obtained composite semipermeable membrane are shown in Table 2.

[0094] Example 4 A butyl acetate solution containing 1% by mass of chlorosulfonic acid was coated on the separation functional layer of the composite semipermeable membrane obtained in Comparative Example 2 and contacted for 10 minutes at 25° C. The composite semipermeable membrane was washed with distilled water at 45° C. for 10 minutes to obtain a composite semipermeable membrane with a modified separation functional layer. The evaluation results of the obtained composite semipermeable membrane are shown in Table 2.

[0095] Example 5 A 1% by mass aqueous solution of 1,3-disulfoimidazolium chloride was coated on the separation functional layer of the composite semipermeable membrane obtained in Comparative Example 2 and contacted at 25° C. for 1 hour. The composite semipermeable membrane was washed with distilled water at 45° C. for 10 minutes to obtain a composite semipermeable membrane with a modified separation functional layer. The evaluation results of the obtained composite semipermeable membrane are shown in Table 2.

[0096] Example 6 A composite semipermeable membrane element was prepared by the above-mentioned method using the composite semipermeable membrane obtained in Comparative Example 2, and a 1% by mass aqueous solution of 1,3-disulfoimidazolium chloride was passed through it for 2 hours at 25°C so that all the composite semipermeable membranes in the element were wetted. Thereafter, a sufficient amount of distilled water was passed through the composite semipermeable membrane element to wash it, and a composite semipermeable membrane modified with a separation functional layer was cut out from the washed composite semipermeable membrane element. The evaluation results of the obtained composite semipermeable membrane are shown in Table 2.

[0097] [Table 1]

[0098] [Table 2]

[0099] In addition, since no sulfo group was introduced in Comparative Examples 1 and 2, C / D is left blank.

Claims

1. A support membrane including a substrate and a porous support layer, and a separation functional layer containing a crosslinked aromatic polyamide and disposed on the porous support layer, The separation functional layer has a sulfo group of 7.0×10 －５ ~5.0 x 10 －２ g / m ２ and a structure represented by the following formula 1: Composite semipermeable membrane. 【Chemistry 1】 (However, R １ is a hydrogen atom or a hydrocarbon having 1 to 10 carbon atoms which may have a substituent; R ２ ~R ５ is a hydrogen atom or a hydrocarbon having 1 to 10 carbon atoms, and Ar １ ~Ar ３ is an aromatic ring having 6 to 14 carbon atoms which may have a substituent, R １ , Ar １ , Ar2, Ar ３ At least one of the groups has a sulfo group.

2. The separation functional layer has a pleated thin film, The average thickness of the thin film is 10 to 20 nm; The nitrogen atom surface density of the separation functional layer measured by Rutherford backscattering spectroscopy (RBS) is 4.0 × 10 ２０ ~1.2 x 10 ２１ pieces / m ２ That is, The composite semipermeable membrane according to claim 1.

3. A compound having a structure represented by the following formula 2 is present in the separation functional layer: The composite semipermeable membrane according to claim 1 or 2. 【Chemistry 2】 (wherein X is a hydrocarbon having one carbon atom, Y is a nitrogen atom, R 6 is a hydrogen atom, and R ７ is a hydrocarbon having 2 to 4 carbon atoms.

4. R in Formula 1 １ The composite semipermeable membrane according to any one of claims 1 to 3, wherein is a hydrocarbon having 1 or 2 carbon atoms and having at least one sulfo group.

5. Ar in Formula 1 ２ The composite semipermeable membrane according to any one of claims 1 to 4, wherein is an aromatic ring having 6 to 14 carbon atoms and having at least one sulfo group.

6. The C / D in the separation functional layer is 3 to 10. The composite semipermeable membrane according to any one of claims 1 to 5. A: The number of sulfur atoms derived from sulfo groups measured by X-ray photoelectron spectroscopy (XPS) B: Total number of nitrogen atoms measured by XPS C: A / B measured on the surface of the separation functional layer in the composite semipermeable membrane D: A / B measured on a solid obtained by molding the powder of the separation functional layer extracted from the composite semipermeable membrane

7. The separation functional layer has a zeta potential of -5 mV or less at pH 3. The composite semipermeable membrane according to any one of claims 1 to 6.

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