Composite semipermeable membrane, composite semipermeable membrane element, and filtration device

Abstract

The present invention provides a composite semipermeable membrane and a composite semipermeable membrane element that exhibit excellent monovalent ion / multivalent ion permselectivity under acidic conditions. The present invention relates to a composite semipermeable membrane having a porous support layer and a separation functional layer on one face side of the porous support layer, the separation functional layer containing a semi-aromatic crosslinked polyamide, the face of the separation functional layer side of the composite semipermeable membrane being set as a first face, the face on the side opposite the first face being set as a second face, a positron beam being irradiated from the first face side of the composite semipermeable membrane, the average pore diameter R1 of the separation functional layer under conditions of a positron beam intensity of 0.1 keV and the average pore diameter R2 of the separation functional layer under conditions of a positron beam intensity of 0.5 keV derived from positron annihilation lifetime measurement being 0.30 nm or more and 2.00 nm or less, and satisfying 0.90 ≤ R1 / R2 ≤ 1.10.

Description

TECHNICAL FIELD

[0001] The present application relates to a composite semipermeable membrane, a composite semipermeable membrane element, and a filtration device. BACKGROUND

[0002] With respect to separation of a mixture, there are various techniques for removing substances (e.g., salts) dissolved in a solvent (e.g., water), and in recent years, the use of membrane separation methods as processes for energy saving and resource saving has been expanding. Membranes used in membrane separation methods include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, and the like, and these membranes are used, for example, in cases where potable water is produced from seawater, brackish water, water containing harmful substances, and the like, in cases of softening of potable water, in food applications, in production of industrial ultra-pure water, in wastewater treatment, in recovery of valuable substances, and the like.

[0003] Most of the reverse osmosis membranes and nanofiltration membranes currently on the market are composite semipermeable membranes, and there are two types: composite semipermeable membranes having a gel layer and an active layer obtained by cross-linking a polymer on a support membrane; and composite semipermeable membranes having an active layer obtained by polycondensation of a monomer on a support membrane. Among these, composite semipermeable membranes in which a separation functional layer formed of a cross-linked polyamide obtained by polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide is coated on a support membrane are widely used as separation membranes having high permeability and high selective separation properties.

[0004] In the past, nanofiltration membranes have been widely used in order to separate a specific substance from a mixed solution of monovalent ions, polyvalent ions, and organic substances, and nanofiltration membranes having a separation functional layer formed of a cross-linked polyamide obtained by reacting an aliphatic amine with an acid halide have been proposed.

[0005] For example, a nanofiltration membrane formed of a polyamide obtained by reacting a polyfunctional aromatic carboxylic acid chloride with piperazine has been disclosed (Patent Document 1). On the other hand, one problem that arises in a membrane separation plant using a nanofiltration membrane is fouling caused by inorganic substances and organic substances. The nanofiltration membrane can significantly decrease in water permeability due to fouling. As a method for improving this, a method for recovering water permeability by cleaning using an acid or a chemical has been proposed, and nanofiltration membranes having high chemical resistance are also known (Patent Document 2). In addition, as a nanofiltration membrane having high chemical resistance, a polyamide separation functional layer having a large specific surface area in a hollow-convex shape and a hydrophobic chemical composition has been known to suppress hydrolysis of the polyamide caused by an acid or a base, and thus to be able to maintain excellent polyvalent ion removal properties for a long period of time (Patent Document 3).

[0006] PRIOR ART DOCUMENTS

[0007] PATENT DOCUMENTS

[0008] Patent Document 1: Japanese Patent Application Publication No. 2007-277298

[0009] Patent Literature 2: Japanese Patent Application Laid-Open No. 2003-534422

[0010] Patent Literature 3: International Publication No. 2021 / 085600 SUMMARY

[0011] PROBLEMS TO BE SOLVED BY THE INVENTION

[0012] Thus, the performance required for a nanofiltration membrane is not only water permeability and selective separation performance, but also chemical resistance. The membrane described in Patent Literature 1 has low chemical resistance. On the other hand, the membrane described in Patent Literature 2 has high chemical resistance compared to the membrane described in Patent Literature 1, but has a problem of low selectivity between monovalent ions and multivalent ions. In addition, the membrane described in Patent Literature 3 suppresses hydrolysis caused by contact with acid or base, and maintains high multivalent ion removal performance under neutral conditions, but the pore size changes under acidic conditions, and thus there is room for improvement in the selectivity between monovalent ions and multivalent ions when the membrane is used under acidic conditions.

[0013] An object of the present application is to provide a composite semipermeable membrane, a composite semipermeable membrane element, and a filtration device that exhibit excellent monovalent ion / multivalent ion selectivity under acidic conditions.

[0014] MEANS FOR SOLVING THE PROBLEMS

[0015] To achieve the above object, the present application adopts the following configuration.

[0016] [1] A composite semipermeable membrane comprising a porous support layer, and a separation functional layer on one surface side of the porous support layer,

[0017] The separation functional layer contains a semi-aromatic crosslinked polyamide,

[0018] The surface of the composite semipermeable membrane on the side of the separation functional layer is the first surface, and the surface on the side opposite to the first surface is the second surface,

[0019] The average pore diameter R1 and the average pore diameter R2 of the separation functional layer derived from positron annihilation lifetime measurement are 0.30 nm or more and 2.00 nm or less, and satisfy 0.90 ≤ R1 / R2 ≤ 1.10, when the composite semipermeable membrane is irradiated with a positron beam from the first surface side.

[0020] R1: average pore diameter under the condition that the intensity of the positron beam is 0.1 keV

[0021] R2: average pore diameter under the condition that the intensity of the positron beam is 0.5 keV

[0022] [2] The composite semipermeable membrane according to the above [1], wherein the average pore diameter Rl is 0.55 nm or more and 1.00 nm or less.

[0023] [3] The composite semipermeable membrane according to the above [1] or [2], wherein, in a cross section of the separation functional layer perpendicular to the surface of the composite semipermeable membrane, the total number Pl of pores having a pore diameter of 0.30 nm or more and 1.20 nm or less, the total number P2 of pores having a pore diameter of 0.50 nm or more and less than 0.80 nm, the total number P3 of pores having a pore diameter of 0.80 nm or more and 1.20 nm or less, and the total number P4 of pores having a pore diameter greater than 1.20 nm satisfy 0.20 < P2 / Pl < 0.40, P3 / P2 < 0.20, and P4 / Pl < 0.01.

[0024] [4] The composite semipermeable membrane according to any one of the above [1] to [3], wherein, in a cross section of the separation functional layer perpendicular to the surface of the composite semipermeable membrane, when each region obtained by equally dividing the separation functional layer into 5 from the first surface side toward the second surface side is set as regions a to e, the amino group density Nb in the region b and the amino group density Nd in the region d satisfy Nb / Nd < 0.80.

[0025] [5] The composite semipermeable membrane according to the above [4], wherein the Nb is 1.0 x 10 -23 mol / nm 2 or more.

[0026] [6] The composite semipermeable membrane according to any one of the above [1] to [5], wherein, when a glucose permeation rate when a 1000 ppm glucose aqueous solution at 25°C and pH 6.5 is permeated at an operation pressure of 0.5 MPa is set as B and a sucrose permeation rate when a 1000 ppm sucrose aqueous solution at 25°C and pH 6.5 is permeated at an operation pressure of 0.5 MPa is set as C, B / C is 10 or more.

[0027] [7] The composite semipermeable membrane according to any one of the above [1] to [6], wherein the separation functional layer has a hollow pleated structure.

[0028] [8] A composite semipermeable membrane element comprising the composite semipermeable membrane according to any one of the above [1] to [7].

[0029] [9] A filtration device comprising the composite semipermeable membrane element according to the above [8].

[0030] Effects of the Invention

[0031] In the composite semipermeable membrane of the present application, the pore size distribution in the film thickness direction of the separation function layer is uniform, and thus the direction of diffusion of ions within the separation function layer becomes uniform, and the permeation resistance of monovalent ions, which are of a size that can move freely within the separation function layer, can be sufficiently suppressed, while multivalent ions are effectively prevented from permeating, and as a result, excellent monovalent ion / multivalent ion permselective separation performance can be achieved under acidic conditions. BRIEF DESCRIPTION OF DRAWINGS

[0032] [ Figure 1 ] Figure 1 A schematic view showing a cross section of a composite semipermeable membrane according to an embodiment of the present application.

[0033] [ Figure 2 ] Figure 2 A schematic view showing a composite semipermeable membrane element according to an embodiment of the present application.

[0034] [ Figure 3 ] Figure 3 A schematic view showing a cross section of a separation function layer in a composite semipermeable membrane according to an embodiment of the present application.

[0035] [ Figure 4 ] Figure 4 A schematic view showing a hollow pleated structure possessed by a separation function layer of a composite semipermeable membrane according to an embodiment of the present application. DETAILED DESCRIPTION

[0036] Hereinafter, an embodiment of the present application will be described in detail, but the present application is not limited to the following description, and can be arbitrarily modified without departing from the gist of the present application.

[0037] 1. Composite semipermeable membrane

[0038] The composite semipermeable membrane according to the present embodiment has a porous support layer, and a separation function layer provided on one face side of the porous support layer. In the composite semipermeable membrane, the face on the separation function layer side is referred to as a first face, and the face on the side opposite to the first face is referred to as a second face. The composite semipermeable membrane according to the present embodiment is a membrane having a region having a fractionation property positioned between a reverse osmosis membrane and an ultrafiltration membrane, and is generally defined as a nanofiltration membrane.

[0039] The reverse osmosis membrane generally has a tendency to remove most of the organic substances and ions, on the other hand, the ultrafiltration membrane generally does not remove most of the ion species, but removes organic substances of high molecular weight.

[0040] (1-1) Support membrane

[0041] ​​​​The composite semipermeable membrane according to the present embodiment can have only the porous support layer, and the porous support layer is a layer that constitutes a support membrane. The support membrane can be formed only of the porous support layer, as shown in Figure 1 As shown in Figure 1 The composite semipermeable membrane 1 can have the porous support layer 3 and the separation functional layer 4, and the support membrane constituted by the porous support layer 3 can be formed only of the porous support layer 3, or can have the base material 2 and the porous support layer 3, as shown in

[0042] The support membrane serves to provide strength to the composite semipermeable membrane by supporting the separation functional layer. The support membrane itself does not substantially have separation performance of low-molecular organic substances, ions, and the like.

[0043] The size and distribution of the pores in the support membrane are not particularly limited, and, for example, it is preferable that the pores be uniform and fine, or that the fine pores gradually increase in size from the surface on the side on which the separation functional layer is formed to the other surface, and that the fine pores on the surface on the side on which the separation functional layer is formed have a size of 0.1 nm or more and 100 nm or less.

[0044] As the material of the base material, a cloth formed of at least one selected from the group consisting of a polyester and an aromatic polyamide can be exemplified. Among them, a polyester having high mechanical stability and thermal stability is particularly preferable.

[0045] As the cloth used in the base material, a long fiber nonwoven fabric, a short fiber nonwoven fabric, or the like can be exemplified. From the viewpoint of avoiding penetration of a high-molecular solution into the back surface due to excessive penetration of the high-molecular solution when the high-molecular solution is cast on the base material, or avoiding peeling of the base material from the porous support layer, and avoiding non-uniformity of the membrane, defects such as pinholes, or the like due to fuzzing of the base material, or the like, that is, from the viewpoint of excellent film-forming properties, a long fiber nonwoven fabric is preferably used.

[0046] As the long fiber nonwoven fabric, a long fiber nonwoven fabric constituted by thermoplastic continuous filaments, or the like can be exemplified. By including a long fiber nonwoven fabric in the base material, non-uniformity in the casting of the high-molecular solution due to fuzzing, defects of the membrane, or the like, which are caused when only a short fiber nonwoven fabric is used, can be suppressed. In addition, in the process of continuously forming the composite semipermeable membrane, since a tension is also applied to the base material in the film-forming direction, a long fiber nonwoven fabric having excellent dimensional stability is preferably used as the base material.

[0047] In particular, on the side of the base material that is opposite to the side that is in contact with the porous support layer, it is preferable that the orientation of the fibers be longitudinal with respect to the film-forming direction, so that the strength of the base material can be maintained, and the membrane can be prevented from being broken or the like. Here, "longitudinal" means that the orientation direction of the fibers is parallel to the film-forming direction. Conversely, when the orientation direction of the fibers is at a right angle to the film-forming direction, it is referred to as "lateral".

[0048] The fiber orientation degree of the fiber is preferably 25° or less. Here, the "fiber orientation degree" is an index of the orientation of the fiber of the nonwoven fabric, and refers to the average angle of the fiber constituting the nonwoven fabric when the direction of film formation during continuous film formation is set to 0° and the direction at a right angle to the direction of film formation, i.e., the width direction of the nonwoven fabric, is set to 90°. Therefore, the closer the fiber orientation degree is to 0°, the more the fiber tends to be oriented in the longitudinal direction, and the closer the fiber orientation degree is to 90°, the more the fiber tends to be oriented in the lateral direction.

[0049] A heating step is included in the manufacturing step of the composite semipermeable membrane and the manufacturing step of the element, but heating can cause the supporting membrane or the composite semipermeable membrane to shrink. In particular, in continuous film formation, the width direction is not subjected to tension, and thus the width direction is easily shrunk. Therefore, a base material having a small thermal dimensional change rate is desirable as a base material.

[0050] In the base material using a nonwoven fabric, if the difference between the fiber orientation degree of the side opposite to the side in contact with the porous supporting layer and the fiber orientation degree of the side in contact with the porous supporting layer is 10° or more and 90° or less, the dimensional change in the width direction due to heat applied in the heating step or the like can be suppressed, and thus this is preferable.

[0051] The air permeability of the base material is preferably 0.5 cc / cm 2 or more. When the air permeability is in this range, the water permeation performance of the composite semipermeable membrane is improved. It is considered that the reason for this is that, in the step of forming the supporting membrane, when a high-molecular polymer is cast on the base material and immersed in a coagulation bath, the displacement speed of the non-solvent from the base material side becomes fast, and thus the internal structure of the porous supporting layer changes, and this affects the holding amount of monomers and the diffusion speed in the step of forming the separation functional layer.

[0052] Note that the air permeability can be measured based on JIS L1096 (2010) using a Frazier-type tester. For example, the base material is cut into a size of 200 mm x 200 mm, and used as a sample. The sample is installed in the Frazier-type tester, and the suction fan and the air hole are adjusted so that the pressure of the inclined manometer becomes 125 Pa. Based on the pressure indicated by the vertical manometer at this time and the type of the air hole used, the amount of air passing through the base material, i.e., the air permeability, can be calculated. The Frazier-type tester can be, for example, KES-F8-AP1 manufactured by KATO TECH Co., Ltd.

[0053] The thickness of the base material is preferably 10 μm or more and 200 μm or less, and more preferably 30 μm or more and 120 μm or less.

[0054] As the material of the porous support layer, for example, polysulfone, polyethersulfone, cellulose acetate, polyvinyl chloride, or a mixture thereof can be mentioned. Among them, polysulfone or polyethersulfone, which have high chemical stability, mechanical stability, and thermal stability, are particularly preferable.

[0055] The thickness of the porous support layer affects the strength of the resulting composite semipermeable membrane and the packing density when it is made into a device. In order to obtain sufficient mechanical strength and packing density, the thickness of the porous support layer is preferably 50 μm or more and 300 μm or less, more preferably 100 μm or more and 250 μm or less.

[0056] The morphology of the porous support layer can be observed using a scanning electron microscope, a transmission electron microscope, an atomic force microscope, or the like. For example, in the case of observation using a scanning electron microscope, the porous support layer is peeled off from the substrate, and then cut in a direction perpendicular to the surface of the composite semipermeable membrane using a freeze-fracture method to prepare a sample for cross-sectional observation. A thin layer of platinum or platinum-palladium or ruthenium tetrachloride, preferably ruthenium tetrachloride, is applied to the sample, and observation is performed using a high-resolution field emission type scanning electron microscope (hereinafter referred to as "UHR-FE-SEM") at an acceleration voltage of 3 to 15 kV. As the UHR-FE-SEM, for example, an S-900 electron microscope manufactured by Hitachi, Ltd., or the like can be used.

[0057] The support membrane can be selected from various commercially available materials such as "Millipore Filter VSWP" (product name) manufactured by Millipore Corporation, "Ultra Filter UK10" (product name) manufactured by Toyobo Filter Paper Co., Ltd., or the like, or can be manufactured according to the method described in "Office of Saline Water Research and Development Progress Report" No. 359 (1968) or the like.

[0058] The thickness of the substrate and the thickness of the composite semipermeable membrane can be measured using a digital thickness gauge. Note that since the thickness of the separation functional layer is very thin compared to the support membrane, the thickness of the composite semipermeable membrane can be regarded as the thickness of the support membrane. That is, the thickness of the composite semipermeable membrane can be measured using a digital thickness gauge, and the thickness of the support membrane can be regarded as the thickness of the composite semipermeable membrane. In addition, the thickness of the porous support layer can be easily calculated by subtracting the thickness of the substrate from the thickness of the composite semipermeable membrane. As the digital thickness gauge, for example, PEACOCK manufactured by Ozaki Mfg. Co., Ltd., or the like can be used. In the case of using a digital thickness gauge, the thickness is measured for 20 different parts, and the average value is calculated.

[0059] Note that in a case where it is difficult to measure the thickness of the base material and the thickness of the composite semipermeable membrane using a thickness gauge, a scanning electron microscope can be used for the measurement. In this case, the thickness is measured from electron microscope images of cross sections of an arbitrary 5 portions of one sample, and the average value is calculated to obtain the thickness.

[0060] (1-2) Separation function layer

[0061] Among the components of the composite semipermeable membrane, the separation function layer substantially has a solute separation function. As shown in FIG. 1, the separation function layer 4 is disposed on one face side of the porous support layer 3. Figure 1

[0062] The separation function layer contains a semi-aromatic crosslinked polyamide obtained by interfacial polycondensation of a polyfunctional aliphatic amine and a polyfunctional aromatic acid halide. The proportion of the semi-aromatic crosslinked polyamide in the components of the separation function layer is preferably 50% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, and particularly preferably consists only of the semi-aromatic crosslinked polyamide. By containing 50% by mass or more of the semi-aromatic crosslinked polyamide in the separation function layer, excessive densification due to π-π interaction from the aromatic rings in the polyamide is suppressed, and excellent monovalent ion permeability is easily obtained. Here, the "crosslinked polyamide" refers to a compound having 3 or more amide bonds and a molecular weight of 400 or more, and having a branched structure.

[0063] The polyfunctional aliphatic amine is preferably an alicyclic diamine. As the alicyclic diamine, a bispiperidine derivative, a piperazine derivative can be given.

[0064] The molecular weight of the alicyclic diamine is preferably 90 or more and 160 or less.

[0065] The molecular weight of the alicyclic diamine is preferably 90 or more, more preferably 100 or more, and further preferably 110 or more. By making the molecular weight of the alicyclic diamine 90 or more, the diffusion coefficient of the amine becomes small, and the polyamide is slowly formed during interfacial polycondensation, and thus a pore that hinders the permeation of multivalent ions while suppressing the permeation resistance of monovalent ions can be formed.

[0066] ​In addition, the molecular weight of the alicyclic diamine is preferably 160 or less, more preferably 150 or less. Generally, at the initial stage of polycondensation, oligomers are excessively produced on the 1st surface side that is in contact with the organic layer, resulting in clogging of the pores on the 1st surface side, and thus the pore size distribution in the film thickness direction tends to become uneven. By making the molecular weight of the alicyclic diamine 160 or less, the molecular weight of the produced oligomers is reduced, and thus the interaction with the semi-aromatic crosslinked polyamide is reduced, and thus the oligomers are easily removed in the liquid discharge process and the post-treatment process that are performed immediately after the film formation under the high humidity conditions described later. Note that by reducing the molecular weight of the oligomers, a separation functional layer in which the pore size in the film thickness direction is uniform, i.e., the average pore size R1 and the average pore size R2 of the separation functional layer described later satisfy 0.90 ≤ R1 / R2 ≤ 1.10, is easily formed, and a film having a high monovalent ion permeation rate is obtained.

[0067] As the alicyclic diamine having a molecular weight of 90 or more and 160 or less, for example, substituted piperazines in which a piperazine ring is substituted with an alkyl group having 1 to 3 carbon atoms (e.g., 2-methylpiperazine, 2-ethylpiperazine, 2-n-propylpiperazine, 2,2-dimethylpiperazine, 2,2-diethylpiperazine, 2,3-dimethylpiperazine, 2,3-diethylpiperazine, 2,5-dimethylpiperazine, 2,5-diethylpiperazine, 2,6-dimethylpiperazine, 2,6-diethylpiperazine, 2,3,5,6-tetramethylpiperazine, and the like), homopiperazines can be given.

[0068] The "polyfunctional aromatic acid halide" refers to an aromatic acid halide having two or more halogenated carbonyl groups in one molecule, and is not particularly limited as long as it provides a semi-aromatic crosslinked polyamide by reaction with the above-described polyfunctional aliphatic amine. As the polyfunctional aromatic acid halide, for example, halogenated compounds of 1,3,5-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,3-benzenedicarboxylic acid, 1,4-benzenedicarboxylic acid, 1,3,5-benzenetrisulfonic acid, 1,3,6-naphthalenetrisulfonic acid, and the like can be given. Among the polyfunctional aromatic acid halides, an acid chloride is preferred, and particularly from the aspects of economy, ease of handling, ease of operation, ease of reactivity, and the like, an acid halide of 1,3,5-benzenetricarboxylic acid, i.e., trimesoyl chloride (hereinafter, referred to as "TMC"), an acid halide of 1,3-benzenedicarboxylic acid, i.e., isophthaloyl chloride, an acid halide of 1,4-benzenedicarboxylic acid, i.e., terephthaloyl chloride, an acid halide of 1,3,5-benzenetrisulfonic acid, i.e., 1,3,5-benzenetrisulfonyl chloride, and an acid halide of 1,3,6-naphthalenetrisulfonic acid, i.e., 1,3,6-naphthalenetrisulfonyl chloride are preferred. The above-described polyfunctional aromatic acid halide can be used alone, or two or more kinds thereof can be used in combination, and by mixing any one of the difunctional isophthaloyl chloride and terephthaloyl chloride in the trifunctional TMC, 1,3,5-benzenetrisulfonyl chloride, and 1,3,6-naphthalenetrisulfonyl chloride, the intermolecular gap of the polyamide crosslinked structure is expanded, and the membrane having a uniform pore size distribution can be controlled in a wide range. The mixing molar ratio of the trifunctional acid chloride to the difunctional acid chloride is preferably 1:20 to 50:1, and more preferably 1:1 to 20:1.

[0069] The thickness of the separation functional layer is preferably 15 nm or more and 50 nm or less, and more preferably 20 nm or more and 40 nm or less. By making the thickness of the separation functional layer 15 nm or more, a composite semipermeable membrane having sufficient water permeability can be easily obtained, and by making the thickness of the separation functional layer 20 nm or more, the removal property is not reduced due to the generation of defects, and a composite semipermeable membrane having sufficient water permeability can be stably obtained. On the other hand, the thickness of the separation functional layer is preferably 50 nm or less, and more preferably 40 nm or less. By making the thickness of the separation functional layer 50 nm or less, stable membrane performance can be obtained, and by making the thickness of the separation functional layer 40 nm or less, further sufficient water permeability is obtained.

[0070] The thickness of the separation functional layer can be analyzed using observation methods such as a transmission electron microscope, TEM tomography, a focused ion beam / scanning electron microscope (FIB / SEM), and the like.

[0071] The inventors of the present application have conducted intensive studies, and as a result, have found that a composite semipermeable membrane satisfying the following requirements exhibits excellent monovalent ion / multivalent ion selective separation performance under acidic conditions.

[0072] The composite semipermeable membrane, wherein the average pore diameter R1 and the average pore diameter R2 of the separation functional layer derived by positron annihilation lifetime measurement are 0.30 nm or more and 2.00 nm or less, and satisfy 0.90 ≤ R1 / R2 ≤ 1.10, when a positron beam is irradiated from the first surface side of the composite semipermeable membrane of the embodiment.

[0073] Here, R1 and R2 are defined as follows.

[0074] R1: average pore diameter under the condition that the intensity of the positron beam is 0.1 keV

[0075] R2: average pore diameter under the condition that the intensity of the positron beam is 0.5 keV

[0076] "Positron annihilation lifetime measurement" is a method of measuring the time (on the order of several hundred picoseconds to several tens of nanoseconds) from the incidence of a positron to the annihilation and non-destructively evaluating information on the size of pores of 0.1 to 10 nm, the number density thereof, and the distribution of the size thereof, based on the annihilation lifetime thereof.

[0077] Note that the measurement region in the depth direction from the surface of the sample can be adjusted by the energy of the positron beam incident into the sample. The higher the energy, the deeper the portion from the surface of the sample included in the measurement region, but the depth is influenced by the density of the sample. For example, when the separation functional layer of the composite semipermeable membrane is measured, if a positron beam of energy of around 0.1 keV is irradiated from the first surface side of the composite semipermeable membrane, a region of a depth of 0 to 5 nm from the surface of the sample can be generally measured, and if a positron beam of energy of around 0.5 keV is irradiated, a region of a depth of 0 to 50 nm from the surface of the sample can be generally measured. Note that in the present embodiment, in the case where other layers such as a protective layer are provided on the separation functional layer, the average pore diameter R1 and the average pore diameter R2 of the separation functional layer can be measured by previously removing the other layers such as the protective layer.

[0078] As described above, the weaker the intensity of the positron beam, the more the pore diameter on the first surface side is reflected, and the stronger the intensity of the positron beam, the more the pore diameter on the second surface side is reflected, and the closer R1 / R2 is to 1, the more uniform the pore diameter in the thickness direction of the membrane is. In the present embodiment, by satisfying 0.90 ≤ R1 / R2 ≤ 1.10, excellent monovalent ion / multivalent ion selective separation performance can be achieved.

[0079] Although the details of the above mechanism have not been fully elucidated, it is presumed that by making the pore diameter uniform in the film thickness direction, the direction in which ions diffuse within the separation functional layer becomes uniform, and the permeation resistance of monovalent ions, which are of a size that can move freely within the separation functional layer, is suppressed. As a result, it is believed that excellent monovalent ion / multivalent ion permselective separation performance is achieved. Therefore, the average pore diameters R1 and R2 of the separation functional layer more preferably satisfy 0.95 ≤ R1 / R2 ≤ 1.05, and further preferably satisfy 0.97 ≤ R1 / R2 ≤ 1.03.

[0080] The average pore diameters R1 and R2 of the separation functional layer in the composite semipermeable membrane according to the present embodiment are 0.30 nm or more and 2.00 nm or less. By making the average pore diameters R1 and R2 within the above range, a function as a substantially nanofiltration membrane is exhibited. R1 is preferably 0.55 nm or more and 1.00 nm or less, more preferably 0.55 nm or more and 0.80 nm or less, more preferably 0.55 nm or more and 0.70 nm or less, further preferably 0.57 nm or more and 0.68 nm or less, and particularly preferably 0.60 nm or more and 0.65 nm or less. By making R1 within the above range, the effect of suppressing the permeation resistance of monovalent ions and hindering the permeation of multivalent ions becomes significant. In addition, from the viewpoint of exhibiting a function as a nanofiltration membrane, R2 is preferably 0.50 nm or more and 1.10 nm or less, more preferably 0.50 nm or more and 0.80 nm or less, more preferably 0.50 nm or more and 0.77 nm or less, further preferably 0.55 nm or more and 0.70 nm or less, and particularly preferably 0.60 nm or more and 0.65 nm or less.

[0081] The average pore diameters R1 and R2 can be controlled, for example, by the following factors: performing interfacial polycondensation under high humidity conditions; the molecular weight of the polyfunctional aliphatic amine used in the interfacial polycondensation; the temperature at which the organic solvent solution containing the polyfunctional aromatic acid halide is applied at the time of interfacial polycondensation; and the like. Specifically, in the case where the polyfunctional aliphatic amine is a cycloaliphatic diamine having a molecular weight of 90 or more and 160 or less, oligomers are easily removed in the liquid discharge process and the post-treatment process that are performed immediately after the film formation under the high humidity conditions described later, and it is possible to control R1 / R2 within the particularly preferable range.

[0082] In the case of the composite semipermeable membrane according to the present embodiment, in a cross section of the separation functional layer perpendicular to the surface of the composite semipermeable membrane, the total number of pores having a pore diameter of 0.30 nm or more and 1.20 nm or less P1, the total number of pores having a pore diameter of 0.50 nm or more and less than 0.80 nm P2, the total number of pores having a pore diameter of 0.80 nm or more and 1.20 nm or less P3, and the total number of pores having a pore diameter greater than 1.20 nm P4 preferably satisfy 0.20 < P2 / P1 < 0.40, P3 / P2 < 0.20, and P4 / P1 ≤ 0.01.

[0083] Here, the pores having a pore diameter of 0.30 nm or more and less than 0.50 nm are water-only passing pores, the pores having a pore diameter of 0.50 nm or more and 0.80 nm or less are effective pores through which water and monovalent ions pass, the pores having a pore diameter of 0.80 nm or more and 1.20 nm or less are large pores through which water, monovalent ions, and multivalent ions pass, and the pores having a pore diameter of more than 1.20 nm are large pores through which multivalent ions pass. That is, P2 / P1 refers to the proportion of the effective pores through which water and monovalent ions pass, with respect to the total number of pores having a pore diameter of 0.30 nm or more and 1.20 nm or less, P3 / P2 refers to the proportion of the large pores through which multivalent ions and water pass, with respect to the effective pores through which water and monovalent ions pass, and P4 / P1 refers to the proportion of the large pores through which multivalent ions more easily pass, with respect to the total number of pores having a pore diameter of 0.30 nm or more and 1.20 nm or less.

[0084] In the case where the composite semipermeable membrane satisfies 0.20 < P2 / P1 < 0.40 and P3 / P2 < 0.20 in the cross section of the separation functional layer perpendicular to the surface of the composite semipermeable membrane, the effective pores through which water and monovalent ions pass, having a pore diameter of 0.50 nm or more and 0.80 nm or less, are present in a high proportion with respect to the water-only passing pores having a pore diameter of 0.30 nm or more and less than 0.50 nm, and the large pores through which multivalent ions and water pass, having a pore diameter of 0.80 nm or more and 1.20 nm or less, the resistance to the permeation of monovalent ions is suppressed and the effect of hindering the permeation of multivalent ions becomes significant, and excellent monovalent ion / multivalent ion permselective separation performance is obtained under an acidic condition. P1 and P2 more preferably satisfy 0.26 ≤ P2 / P1 ≤ 0.35, and further preferably satisfy 0.31 ≤ P2 / P1 ≤ 0.35. By causing P1 and P2 to satisfy the above range, excellent permeability of monovalent ions is easily exhibited. In addition, P2 and P3 preferably satisfy P3 / P2 ≤ 0.12, more preferably satisfy P3 / P2 ≤ 0.09, and further preferably satisfy P3 / P2 ≤ 0.05. By causing P2 and P3 to satisfy the above range, the effect of hindering the permeation of multivalent ions becomes more significant.

[0085] Further, in the case where P4 / P1 ≤ 0.01, more excellent monovalent ion / multivalent ion permselective separation is exhibited. In the case where P4 / P1 > 0.01, a large number of large pores through which multivalent ions easily pass are present, and the monovalent ion / multivalent ion permselective separation is reduced. Therefore, P4 / P1 is more preferably P4 / P1 ≤ 0.007, further preferably P4 / P1 ≤ 0.005, and particularly preferably P4 is not present.

[0086] P1, P2, P3 and P4 can be controlled, for example, by the molecular weight of the polyfunctional aliphatic amine used in the interfacial polycondensation, the temperature at which the organic solvent solution containing the polyfunctional aromatic acid halide is applied during the interfacial polycondensation, the hydrophilic solvent treatment, and the like. More specifically, in the case where an alicyclic diamine having a molecular weight of 100 or more and 160 or less is used as the polyfunctional aliphatic amine, the oligomer is easily removed in the liquid discharge process and the post-treatment process immediately after the film formation under the high humidity conditions described later, and P2 / P1 can be controlled within the particularly preferable range.

[0087] As shown in Figure 3 With respect to the separation functional layer in the composite semipermeable membrane according to the present embodiment, in a cross section perpendicular to the surface of the composite semipermeable membrane (a cross section perpendicular to the first surface), when each region obtained by dividing the above separation functional layer into five at equal intervals from the first surface side toward the second surface side is set as regions a to e, the amino group density Nb in the region b and the amino group density Nd in the region d preferably satisfy Nb / Nd < 0.80.

[0088] The separation functional layer having the semi-aromatic crosslinked polyamide formed by the interfacial polycondensation as the main component has an amino group and a carboxyl group as the terminal functional groups. In particular, the separation functional layer having a high amino group density becomes a loose structure under acidic conditions, and the permeability of monovalent ions is also high, whereas the blocking property of large-sized multivalent ions decreases. On the other hand, in the separation functional layer having a low amino group density, the separation functional layer becomes a dense structure under acidic conditions, and the permeability of monovalent ions decreases, whereas the blocking property of multivalent ions increases. Thus, there is a trade-off relationship between the permeability of monovalent ions and the blocking property of multivalent ions, and by forming a separation functional layer having a uniform distribution of the amino group density, the following performance can be obtained: the balance between the permeability of monovalent ions and the blocking property of multivalent ions is maintained.

[0089] In the case where the amino group density Nb in the region b and the amino group density Nd in the region d satisfy Nb / Nd ≤ 0.80 in the separation functional layer in the composite semipermeable membrane according to the present embodiment, that is, in the case of the separation functional layer containing a semi-aromatic crosslinked polyamide having the density difference in the thickness direction of the separation functional layer as described above, a composite semipermeable membrane having more excellent monovalent ion permeability and multivalent ion blocking performance can be obtained. From the viewpoint of simultaneously achieving monovalent ion permeability and multivalent ion blocking performance, the amino group density Nb and the amino group density Nd more preferably satisfy Nb / Nd ≤ 0.70, further preferably satisfy Nb / Nd ≤ 0.65, and particularly preferably satisfy Nb / Nd ≤ 0.60. In addition, from the viewpoint of suppressing changes in the polyamide structure and significant changes in performance accompanying the changes, the amino group density Nb and the amino group density Nd preferably satisfy Nb / Nd ≥ 0.10. In order to control the amino group distribution within the above range, the atmospheric humidity needs to be controlled to 80% or more, more preferably 90% or more, and further preferably 95% or more. The reason for this is that evaporation of water from the formed polyamide is suppressed, and the excess generated amino group-rich oligomer is prevented from being insolubilized due to intermolecular hydrogen bonding, whereby the oligomer can be efficiently removed in the liquid discharge process and the solvent treatment process. In addition, the method of forming the separation functional layer by applying an aqueous solution containing a multifunctional aliphatic amine to the surface of the porous support layer can be used to reduce the terminal amino group density on the 1st surface side compared to the amino group density on the 2nd surface side.

[0090] In addition, in the separation functional layer in the composite semipermeable membrane according to the present embodiment, the amino group density Nb in the region b is preferably 1.0 x 10 -23 mol / nm 2 or more, and more preferably 1.5 x 10 -23 mol / nm 2 or more. By making Nb 1.0 x 10 -23 mol / nm 2 or more, and more preferably 1.5 x 10 -23 mol / nm 2 or more, excellent monovalent ion permeability can be achieved. In addition, from the viewpoint of suppressing a decrease in water permeability accompanying the hydrophobization of the polyamide forming the separation functional layer, Nb is preferably 0.1 x 10 -23 mol / nm 2The above. By increasing the concentration of the polyfunctional acyl halide at the time of interfacial polymerization, the amino group density Nb can be controlled to be low. However, in the case where the monomer balance at the time of interfacial polymerization is destroyed due to the increase in the concentration of the polyfunctional acyl halide, the degree of polymerization cannot be increased, and thus a large number of coarse pores are easily formed, and the removal of polyvalent ions decreases. In addition, although the amino group density Nb can be decreased by reacting the amino groups on the first surface side of the separation functional layer with an anhydride after interfacial polymerization, this leads to a decrease in the permeability of monovalent ions and water permeability, and thus is not preferable. Therefore, in order to control the amino group distribution Nb within the above range, the atmospheric humidity needs to be controlled to be 80% or more, more preferably 90% or more, and further preferably 95% or more, as described above. Furthermore, by performing the treatment process using a hydrophilic solvent described later in combination, the amino group distribution Nb can be further decreased.

[0091] Each of the regions a to e obtained by dividing the separation functional layer at intervals into five was determined using the following method.

[0092] The composite semipermeable membrane was immersed in a tungstic acid aqueous solution multiple times. In the composite semipermeable membrane, a cross section of the separation functional layer perpendicular to the thickness direction of the separation functional layer was photographed at a magnification of 100,000 times using a field emission type scanning transmission electron microscope (hereinafter referred to as "STEM"). In the obtained image, as shown in FIG. 1, a reference point P was set at an arbitrary position on the outer surface of the separation functional layer (the surface on the opposite side from the surface of the porous support layer), a normal line Y0 passing through the reference point P was taken as the center, and straight lines Yl and Y2 parallel to the normal line were drawn at an arbitrary interval of 3 to 10 nm on both sides in the direction orthogonal to the normal line Y0. Figure 3

[0093] In addition, a tangent line Xl of the outer surface of the separation functional layer passing through the reference point P, and a tangent line X2 of the inner surface (the surface of the porous support layer side) of the separation functional layer parallel to the same were drawn. Four straight lines dividing the space between Xl and X2 at intervals into five were drawn. The regions surrounded by Yl and Y2, and the four straight lines between Xl, X2, and were set as regions a to e in order from the outer surface of the separation functional layer.

[0094] Note that, in the case where the separation functional layer forms a plurality of wrinkle-like structures, a cross-sectional image was photographed using the same method as described above, the wrinkle having the highest wrinkle height among the wrinkle-like structures in the obtained image was taken as a reference, and Yl and Y2 were drawn in an arbitrary region included within 50 to 100% of the height from the surface on the second surface side of the separation functional layer (the surface of the support membrane) to the apex of the convex portion using the same procedure. Subsequently, regions a to e were obtained using the same procedure as described above. Note that the area of each of regions a to e was set to 5 nm 2 30 nm 2 The above. By increasing the concentration of the polyfunctional acyl halide at the time of interfacial polymerization, the amino group density Nb can be controlled to be low. However, in the case where the monomer balance at the time of interfacial polymerization is destroyed due to the increase in the concentration of the polyfunctional acyl halide, the degree of polymerization cannot be increased, and thus a large number of coarse pores are easily formed, and the removal of polyvalent ions decreases. In addition, although the amino group density Nb can be decreased by reacting the amino groups on the first surface side of the separation functional layer with an anhydride after interfacial polymerization, this leads to a decrease in the permeability of monovalent ions and water permeability, and thus is not preferable. Therefore, in order to control the amino group distribution Nb within the above range, the atmospheric humidity needs to be controlled to be 80% or more, more preferably 90% or more, and further preferably 95% or more, as described above. Furthermore, by performing the treatment process using a hydrophilic solvent described later in combination, the amino group distribution Nb can be further decreased.​

[0095] The amino group density in each region a to e obtained by dividing the functional layer into 5 equal parts is determined using the following method.

[0096] For each region (regions a to e) enclosed by the four lines X1, X2, or those between them, and Y1, Y2, STEM was used to measure the brightness. The minimum brightness Lmin and maximum brightness Lmax were determined for each region. The area of ​​the region exhibiting a brightness greater than {Lmin + (Lmax - Lmin) / 3} was integrated from the obtained minimum brightness Lmin and maximum brightness Lmax. This integrated value corresponds to the area (nm) of the portion containing tungsten (W)-labeled amino groups. 2 The obtained integral value is divided by the area of ​​one amino group (0.04 nm). 2 ), Avogadro's constant (6.0 × 10⁻⁶) 23 The amino density (mol / nm) can be calculated by considering the amino groups per mol and the area of ​​each region. 2 For each region of five randomly selected wrinkled structures, the average amino density obtained is taken as the amino density of each region.

[0097] In the composite semi-permeable membrane of this embodiment, the removal rate of monovalent ions is preferably 75% or less, more preferably 60% or less, and even more preferably 50% or less. By keeping the removal rate of monovalent ions within the above range, the concentration of monovalent ions in the permeate water increases, which can improve the efficiency of the concentration step in the purification process of monovalent ions or save this step, thus contributing to the reduction of purification time and the reduction of purification cost. The removal rate of polyvalent ions is preferably 99.4% or more, more preferably 99.6% or more, and even more preferably 99.8% or more. By keeping the removal rate of polyvalent ions within the above range, the concentration of polyvalent ions in the permeate water decreases, which can improve the efficiency of the purification process of monovalent ions or save this step. In addition, since the concentration of polyvalent ions in the non-permeate water is increased, polyvalent ions can be effectively purified.

[0098] The following "selectivity of monovalent ions / polyvalent ions" refers to: using an aqueous solution containing both monovalent and polyvalent ions as the feed water, performing membrane filtration using a separation membrane, and calculating the removal rates of monovalent and polyvalent ions based on the ion concentrations in the resulting permeate. The values ​​of these removal rates are then calculated using the following formula. It should be noted that, in this application specification, the ions used in the calculation of the selectivity of monovalent and polyvalent ions refer to cations.

[0099] Selectivity for monovalent ions / polyvalent ions = (100 - removal rate of monovalent ions) / (100 - removal rate of polyvalent ions)

[0100] The selectivity of monovalent ions to polyvalent ions is preferably 70 or higher, more preferably 80 or higher, and even more preferably 100 or higher. By ensuring that the selectivity of monovalent ions to polyvalent ions is within the above range, the purification efficiency of both monovalent and polyvalent ions is improved, which helps to shorten the purification time and reduce the cost of purification.

[0101] The separation functional layer of the composite semipermeable membrane according to this embodiment preferably has a hollow, wrinkled structure. When the separation functional layer of the composite semipermeable membrane has a hollow, wrinkled structure, the number of apparent pores per unit membrane area increases. As a result, the pressure required to treat solutions using the composite semipermeable membrane can be reduced, and the heat dissipation and power consumption of the operating device can be decreased.

[0102] Regarding the wrinkled structure of the separated functional layer, in images obtained by observing a cross-section of the separated functional layer perpendicular to the surface of the composite semipermeable membrane using transmission electron microscopy (TEM), regarding... Figure 4 The separation functional layer 4 on the porous support layer 3 is shown. The fold height 201 and the thickness 202 of the separation functional layer are measured, and the ratio of the fold height to the thickness of the separation functional layer (fold height / thickness of the separation functional layer) is calculated. When the fold height / thickness of the separation functional layer is 1.2 or more, the separation functional layer is considered to have a folded structure; when it is less than 1.2, the separation functional layer is considered not to have folds.

[0103] "Thickness of the separation functional layer" refers to the length of the line segment connecting the supply water side and the permeate water side of the separation functional layer in the shortest possible way in a cross-sectional image of the separation functional layer, equivalent to... Figure 4 The thickness 202 of the separation functional layer is shown as the length. The cross-sectional image of the separation functional layer is divided into 10 intervals, and the point in each interval that is farthest from the support membrane is taken as the measurement point on the water supply side. In the case where the separation functional layer forms a wrinkled structure and the wrinkled structure is formed in a manner that spans the above intervals, the interval that is farther from the support membrane is taken as the measurement point.

[0104] The term "wrinkle height" refers to the length of the line segment connecting the point on the water supply side when measuring the thickness of the separation functional layer, and the intersection of the perpendicular line drawn from that point to the surface of the support membrane and the surface of the support membrane. It is equivalent to... Figure 4 The length of the fold height 201 is shown. Regarding the fold height, the average value was calculated by measuring 100 randomly selected folds in an image obtained by observing a cross-section of the separation functional layer perpendicular to the surface of the composite semipermeable membrane using a transmission electron microscope (TEM).

[0105] From the viewpoint of water permeability, the pleat height is preferably 20 nm or more and 500 nm or less, and more preferably 50 nm or more and 300 nm or less. By being 20 nm or more, the specific surface area of the separation functional layer can be sufficiently increased, and high water permeability can be obtained at low pressure. In addition, by being 500 nm or less, clogging of the water flow path due to overlapping of adjacent pleats, concentration polarization at the membrane surface can be suppressed, and thus high water permeability can be obtained at low pressure. In terms of control of the pleat height, the liposolubility and the molecular weight of the polyfunctional amine, and the temperature at the time of interfacial polymerization can be controlled.

[0106] In order to form a separation functional layer having a pleated structure with a hollow shape, the logP of the polyfunctional aliphatic amine used in the interfacial polycondensation is preferably -0.5 or more and 2.0 or less, and more preferably -0.5 or more and 1.5 or less.

[0107] The "logP" is a value obtained by calculating the octanol-water partition coefficient of a compound based on the octanol-water partition coefficient of each functional group contained in the compound according to Non-Patent Document 1, and in the present application, is the value calculated using Chem Draw as a structural formula drawing software.

[0108] It has long been known that interfacial polymerization of polyamide is performed by distribution and diffusion of an amine in an organic phase, and reaction with a polyfunctional acid halide in the organic phase (Non-Patent Document 2), and by making the logP -0.5 or more and 2.0 or less, the distribution and diffusion of the polyfunctional aliphatic amine in the organic solvent at the time of interfacial polycondensation is optimized, and a separation functional layer having a pleated structure with a hollow shape is easily formed.

[0109] As the polyfunctional aliphatic amine having a logP of -0.5 or more and 2.0 or less, for example, substituted piperazines in which a piperazine ring is substituted with an alkyl group having a total of 1 to 4 carbon atoms (for example, 2-methylpiperazine, 2-ethylpiperazine, 2-n-propylpiperazine, 2,2-dimethylpiperazine, 2,2-diethylpiperazine, 2,3-dimethylpiperazine, 2,3-diethylpiperazine, 2,5-dimethylpiperazine, 2,5-diethylpiperazine, 2,6-dimethylpiperazine, 2,6-diethylpiperazine, 2-ethyl-3-methylpiperazine, 2-ethyl-5-methylpiperazine, 2-ethyl-6-methylpiperazine, 2-methyl-3-propylpiperazine, 2-methyl-5-propylpiperazine, 2-methyl-6-propylpiperazine, 2,5-diethylpiperazine, 2,3,5,6-tetramethylpiperazine, and the like), dipiperidine derivatives (for example, 2,2'-dipiperidine, 3,3'-dipiperidine, 4,4'-dipiperidine, and the like), and the like can be given.

[0110] The composite semipermeable membrane according to the present embodiment is suitable for separation of nonionic solutes in addition to lithium and the like ionic solutes, and has a characteristic in the ratio of permeabilities of the respective solutes. For example, as the nonionic solutes, glucose, sucrose can be given. In a case where the glucose permeability when permeating a 1000 ppm glucose aqueous solution at 25°C, pH 6.5 at an operation pressure of 0.5 MPa is set as B, and the sucrose permeability when permeating a 1000 ppm sucrose aqueous solution at 25°C, pH 6.5 at an operation pressure of 0.5 MPa is set as C, B / C is preferably 10 or greater, more preferably 30 or greater, and further preferably 50 or greater. The upper limit of B / C is not particularly limited, and for example, is 1000 or less. Here, the permeability of each solute is represented by 100 x (concentration of the solute in the permeated water / concentration of the solute in the supplied water). By making B / C high, for example, separation and purification time of monosaccharides from polysaccharides in sugar purification is shortened, and the purification is made low cost.

[0111] 2. Method for producing a composite semipermeable membrane

[0112] Next, the method for producing the above composite semipermeable membrane will be described. The method for producing the above composite semipermeable membrane includes a step of forming a support membrane and a step of forming a separation functional layer.

[0113] (2-1) Step of forming a support membrane

[0114] The step of forming a support membrane can also be referred to as a step of forming a porous support layer. This step includes, for example, a step of applying a polymer solution to a substrate, and a step of immersing the aforementioned substrate on which the polymer solution is applied in a coagulation bath to coagulate the polymer.

[0115] In the step of applying a polymer solution to a substrate, for example, a polymer solution is prepared by dissolving a component of the porous support layer, i.e., a polymer, in a good solvent for the polymer.

[0116] In a case where a polysulfone is used as the polymer, the temperature of the polymer solution at the time of application of the polymer solution is preferably 10°C or greater and 60°C or less. If the temperature of the polymer solution is within this range, the polymer does not precipitate, and the polymer solution solidifies after being sufficiently impregnated between the fibers of the substrate. As a result, a porous support layer that is firmly bonded to the substrate by anchoring effect can be obtained. Note that the preferable temperature range of the polymer solution can be appropriately adjusted depending on the kind of polymer used, the desired viscosity of the solution, and the like.

[0117] As the solvent of the polymer solution, N,N-dimethylformamide (hereinafter "DMF") is preferable.

[0118] The time from the application of the polymer solution to the substrate to the immersion in the coagulation bath is preferably 0.1 seconds or more and 5 seconds or less. If the time from the application to the immersion in the coagulation bath is within this range, the polymer solution is solidified after being sufficiently impregnated between the fibers of the substrate. Note that the preferable range of the time from the application to the immersion in the coagulation bath can be appropriately adjusted depending on the kind of the polymer solution used, the desired viscosity of the solution, and the like.

[0119] As the coagulation bath, water is generally used, but it is only necessary to not dissolve the components of the porous support layer, i.e., the polymers. The temperature of the coagulation bath is preferably -20°C or higher and 100°C or lower, and more preferably 10°C or higher and 50°C or lower. When the temperature of the coagulation bath is 100°C or lower, the oscillation of the surface of the coagulation bath due to thermal motion can be suppressed, and the smoothness of the surface of the film after the film formation can be maintained. In addition, when the temperature is -20°C or higher, the coagulation speed can be maintained, and thus the film formation properties can be improved.

[0120] Next, in order to remove the solvent remaining in the film, the support film obtained in the above manner can be subjected to hot water washing. The temperature of the hot water at this time is preferably 40°C or higher and 100°C or lower, and more preferably 60°C or higher and 95°C or lower. When the washing temperature is 100°C or lower, the shrinkage of the support film does not become excessively large, and the decrease in the water permeability can be suppressed. In addition, when the washing temperature is 40°C or higher, a high washing effect can be obtained.

[0121] (2-2) Formation Process of Separation Function Layer

[0122] Next, an example of the formation process of the separation function layer constituting the composite semipermeable membrane will be described. In the formation process of the separation function layer, an aqueous solution containing a multifunctional aliphatic amine compound and an organic solvent solution containing a multifunctional aromatic acyl halide are used, and a semi-aromatic crosslinked polyamide is formed on the surface of the support film by interfacial polycondensation.

[0123] Specifically, the process of forming the separation function layer includes:

[0124] (a) a step of coating the surface of the above porous support layer with an aqueous solution of a multifunctional aliphatic amine; and

[0125] (b) a step of further contacting the solution containing a multifunctional aromatic acyl halide at 10°C or higher and 38°C or lower after the above (a).

[0126] The concentration of the multifunctional aliphatic amine in the aqueous solution containing a multifunctional aliphatic amine compound is preferably 0.1% by mass or more and 10% by mass or less.

[0127] The aqueous solution containing the polyfunctional aliphatic amine can contain an alcohol. As the alcohol, for example, ethanol, 1-propanol, 2-propanol, butanol, and the like can be given. By containing an alcohol in the aqueous solution containing the polyfunctional aliphatic amine, the same effects as the above-described surfactant can be obtained.

[0128] The aqueous solution containing the polyfunctional aliphatic amine can contain a basic compound. As the basic compound, for example, sodium hydroxide, trisodium phosphate, triethylamine, and the like can be given. By containing a basic compound, the hydrogen halide generated in the interfacial polycondensation reaction is removed, the reactivity of the polyfunctional aliphatic amine can be inhibited from decreasing, and thus the polyamidation reaction is promoted, and in addition to the selectivity, the durability to acids and bases can be improved.

[0129] The solvent in the solution containing the polyfunctional aromatic acid halide is an organic solvent. As the organic solvent, an organic solvent which is non-miscible with water, does not damage the support film, and does not hinder the generation reaction of the semi-aromatic crosslinked polyamide, and has a solubility parameter (hereinafter "SP value") of 15.2 (MPa) 1 / 2 and has a logP of 3.2 or more. By having an SP value of 15.2 (MPa) 1 / 2 and has a logP of 3.2 or more, the distribution and diffusion of the polyfunctional aliphatic amine at the time of the interfacial polycondensation are optimized, and the amount of functional groups can be increased.

[0130] As the organic solvent having an SP value of 15.2 (MPa) 1 / 2 and has a logP of 3.2 or more, for example, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, heptadecane, hexadecane, cyclooctane, ethylcyclohexane, 1-octene, 1-decene, and the like, or a mixture thereof can be preferably used.

[0131] The aqueous solution containing the polyfunctional aliphatic amine compound can contain a surfactant. As the surfactant, for example, sodium dodecylbenzenesulfonate, sodium dodecylsulfate, sodium dodecyldiphenyl ether disulfate, styrene bis(naphthalene sodium sulfonate), sodium polyoxyethylene alkyl ether sulfate, and the like can be given. By containing a surfactant, the surface of the porous support layer can be uniformly coated with the above-described aqueous solution, and thus the separation function layer can be uniformly formed, and the effects of stabilizing the film performance and improving the adhesion of the separation function layer to the porous support layer can be obtained.

[0132] In the aqueous solution containing the polyfunctional aliphatic amine compound and the organic solvent solution containing the polyfunctional aromatic acid halide, each can contain, as needed, an acylation catalyst, a polar solvent, an acid trapping agent, an antioxidant, and the like.

[0133] In order to perform interfacial polycondensation of the polyfunctional aliphatic amine and the polyfunctional aromatic acid halide on the porous support layer, first, the surface of the porous support layer is coated with an aqueous solution containing the polyfunctional aliphatic amine to form a coating layer. As the method of coating the surface of the porous support layer with the above-described aqueous solution containing the polyfunctional aliphatic amine, any method can be used as long as the surface of the porous support layer is uniformly and continuously coated with the aqueous solution, such as a method of applying the aqueous solution to the surface of the porous support layer, a method of immersing the support film in the aqueous solution, and the like. Among them, the method of applying the aqueous solution to the surface of the porous support layer is preferred. By applying the aqueous solution containing the polyfunctional aliphatic amine to the surface of the porous support layer, the amount of water contained in the porous support layer, that is, the amount of amine contained in the support film, becomes less than in the case of the method of immersion, and thus at the initial stage of interfacial polycondensation after the polyfunctional aromatic acid halide is applied, the excessive supply of amine to the reaction site can be suppressed, which is helpful in forming pores that inhibit the permeation of monovalent ions and hinder the permeation of polyvalent ions, and at the same time, the density of terminal amino groups on the first surface side of the separation functional layer formed can be reduced as compared with the density of amino groups on the second surface side.

[0134] Next, the excess applied aqueous solution is preferably removed by a draining process. As the method of draining, for example, there is a method of allowing the film surface to flow down naturally while the film surface is kept in the vertical direction, and the like. After draining, the film surface can be dried to remove all or a part of the water in the aqueous solution on the film surface.

[0135] Then, the above-described organic solvent solution containing the polyfunctional aromatic acid halide is applied to the porous support layer containing the above-described aqueous solution containing the polyfunctional aliphatic amine. The application temperature is preferably 10°C or higher and 38°C or lower, and more preferably 20°C or higher and 35°C or lower. By setting the application temperature to 10°C or higher, the diffusion speed of the amine in the organic solvent becomes sufficient, and a polyamide having a pore diameter required for polyvalent ion selective removal can be easily formed. In addition, if the temperature at the time of application is 38°C or lower, the hindrance to diffusion due to the increase in the reaction speed is suppressed, and thus the pore structure becomes uniform, and the selective separation property is improved.

[0136] In the case where trimesoyl chloride is contained as the polyfunctional aromatic acid halide, the concentration of trimesoyl chloride in the organic solvent solution is preferably 0.05% by mass or more and 0.7% by mass or less, and more preferably 0.08% by mass or more and 0.3% by mass or less. When the concentration of trimesoyl chloride is within this range, sufficient water permeability, selective separation property, and durability to acid can be obtained. In the case where other 3-functional acid halides or 2-functional acid halides are used, adjustment is made so that the molar concentration of the acid halide becomes the same degree as the above-described trimesoyl chloride in terms of the molecular weight ratio.

[0137] The multifunctional aliphatic amine and the multifunctional aromatic acid halide are brought into contact in such a manner that interfacial polycondensation is performed therebetween. The interfacial polycondensation is preferably performed at a temperature of 10°C or higher, more preferably at a temperature of 80°C or higher, and further preferably at a temperature of higher than the melting point of the multifunctional aliphatic amine. In addition, the interfacial polycondensation is preferably performed at a temperature of 120°C or lower. By performing the interfacial polycondensation at 10°C or higher, the mobility of the oligomers can be suppressed from decreasing in the interfacial polycondensation reaction, the multifunctional aliphatic amine can maintain a high mobility in the reaction system, an efficient cross-linking reaction can be performed, and excellent multivalent ion selective removal can be achieved. In addition, by performing the interfacial polycondensation at 120°C or lower, excessive drying of the porous support layer can be prevented, and a practical water permeability can be ensured.

[0138] The inventors of the present application have conducted intensive studies, and as a result, have found that the composite semipermeable membrane according to the present embodiment can be easily obtained by controlling the humidity (relative humidity) of the atmosphere during the interfacial polycondensation to be 80% or higher. By setting the humidity of the atmosphere during the interfacial polycondensation to be 80% or higher, the evaporation of water from the polyamide formed can be suppressed, and the insolubilization of the excess generated amino-rich oligomers due to intermolecular hydrogen bonding can be suppressed. It is considered that this enables the efficient removal of the oligomers in the subsequent liquid discharge step and the solvent treatment step, and thus the pore size enlargement accompanying the swelling of the semiaromatic cross-linked polyamide in the acidic conditions, the decrease in the amino group density on the first surface side of the separation function layer, and the increase in the gradient of the amino group density in the film thickness direction can be suppressed, and the swelling of the polyamide on the first surface side contacted with the high concentration acid and the excessive pore size enlargement accompanying the swelling can be suppressed in the membrane use under the acidic conditions, and thus excellent monovalent ion permeability and excellent multivalent ion removal can be simultaneously achieved. Therefore, the humidity of the atmosphere during the interfacial polycondensation is preferably 80% or higher, more preferably 90% or higher, and further preferably 95% or higher. Note that the humidity of the atmosphere can be adjusted by using a precision air conditioning device or the like.

[0139] The time for which the interfacial polycondensation is performed is preferably 0.1 seconds or longer and 3 minutes or shorter, and more preferably 1 second or longer and 1 minute or shorter.

[0140] Next, the organic solvent solution after the reaction is preferably removed by a liquid discharge step. The removal of the organic solvent can be performed, for example, by a method in which the membrane is held in the vertical direction and the excess organic solvent is allowed to naturally flow down and removed, a method in which the organic solvent is dried by blowing air with a blower, a method in which the excess organic solvent is removed using a mixed fluid of water and air, or the like. Among these, the method in which the organic solvent is removed using a mixed fluid of water and air is particularly preferable.

[0141] If a mixed fluid of water and air is used, the water permeability increases due to swelling caused by the inclusion of water in the separation functional layer. In the case of natural flow, the holding time in the vertical direction is preferably 1 minute or more and 5 minutes or less, and more preferably 1 minute or more and 3 minutes or less. By setting the holding time to 1 minute or more, the separation functional layer having the target function is easily obtained, and by setting the holding time to 5 minutes or less, the generation of defects caused by excessive drying of the organic solvent is suppressed, and thus the decrease in performance is suppressed.

[0142] The composite semipermeable membrane obtained by the above method is further subjected to a process of treating with a hydrophilic solvent at 25°C or higher and 90°C or lower for 1 minute or more, thereby promoting the removal of the excessive amino polyamide oligomer on the first surface side and homogenizing the pore size distribution in the film thickness direction of the separation functional layer, and thus the monovalent ion / multivalent ion selective separation property of the composite semipermeable membrane can be further improved. Here, the "hydrophilic solvent" refers to a solvent that is soluble in water at 10% by mass or more, and can be used as a 10% by mass or more aqueous solution. The solubility of the hydrophilic solvent in water is preferably 50% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, and particularly preferably the hydrophilic solvent without dilution.

[0143] As the hydrophilic solvent, a solvent that does not erode the support film is suitable, and an alcohol is particularly preferred. As the alcohol, for example, monohydric alcohols such as methanol, ethanol, or 2-propanol, diols such as ethylene glycol, 1,3-butanediole, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, or polybutylene glycol, glycerol, diglycerol derivatives, glycerol fatty acid esters, and the like can be given. From the viewpoints that the removal is easy by washing with water and the monovalent ion / multivalent ion selective separation property is improved, it is preferable to use at least one alcohol selected from the group consisting of alcohols, diols, and glycerol having a molecular weight of 500 or less as the hydrophilic solvent. From the viewpoints of the removal of the excessive oligomer and the pore homogenization effect due to the reconstruction of the polyamide structure, the hydrophilic solvent is particularly preferably a diol having a molecular weight of 200 or less, which has high permeability to polyamide.

[0144] 3. Composite semipermeable membrane element

[0145] The composite semipermeable membrane element according to the present embodiment is characterized by comprising the composite semipermeable membrane according to the present embodiment. The composite semipermeable membrane element according to the present embodiment comprises the composite semipermeable membrane according to the present embodiment, and thus exhibits excellent monovalent ion / multivalent ion selective separation performance. Reference should be made to Figure 2 An embodiment of the configuration of the composite semipermeable membrane element according to the present embodiment will be described.

[0146] In one embodiment of the composite semipermeable membrane element according to the present embodiment, as shown in FIG. 1, a composite semipermeable membrane element 100 is provided with a composite semipermeable membrane 1, a supply-side flow path material 11, a permeation-side flow path material 12, a header 6, a first end plate 7, and a second end plate 8. The composite semipermeable membrane 1 is formed into an envelope-shaped membrane 20 by lamination. The envelope-shaped membrane 20 is wound around the header 6 in a spiral shape, thereby forming a winding body 26. In order to protect the winding body 26, other members such as a film and a filament can be wound around the outer periphery of the winding body 26. Figure 2

[0147] The supply-side flow path material 11 is disposed so as to oppose the supply-side surface of the composite semipermeable membrane 1, and is wound around the header 6 together with the composite semipermeable membrane 1. As the supply-side flow path material 11, for example, a mesh can be preferably used. The permeation-side flow path material 12 is disposed so as to oppose the permeation-side surface of the composite semipermeable membrane 1, and is wound around the header 6 together with the composite semipermeable membrane 1. As the permeation-side flow path material 12, for example, a tricot or a sheet having protrusions fixed thereto can be used. Note that in the case where protrusions are directly fixed to the surface of the base material in the composite semipermeable membrane (equivalent to the permeation-side flow path material), the permeation-side flow path material 12 can be omitted. The header 6 is a hollow cylindrical member having a plurality of holes in the side surface. The first end plate 7 is a disc-shaped member provided with a plurality of supply ports. The first end plate 7 is disposed at the first end of the winding body 26. The second end plate 8 is a disc-shaped member provided with a concentrated water discharge port and a permeated water discharge port. The second end plate 8 is disposed at the second end of the winding body 26.

[0148] The separation of fluid based on the composite semipermeable membrane element 100 will be described. The supply water 101 is supplied to the winding body 26 from the plurality of supply ports of the first end plate 7. The supply water 101 moves in the supply-side flow path formed by the supply-side flow path material 11 on the supply-side surface of the composite semipermeable membrane 1. The fluid that has permeated the composite semipermeable membrane 1 (indicated as the permeated water 102 in the drawing) moves in the permeation-side flow path formed by the permeation-side flow path material 12. The permeated water 102 that has reached the header 6 passes through the holes of the header 6 to enter the inside of the header 6. The permeated water 102 flowing in the header 6 is discharged to the outside from the second end plate 8. On the other hand, the fluid that has not permeated the composite semipermeable membrane 1 (indicated as the concentrated water 103 in the drawing) moves in the supply-side flow path and is discharged to the outside from the second end plate 8. In this way, the supply water 101 is separated into the permeated water 102 and the concentrated water 103. Figure 2 Figure 2

[0149] 4. Method for manufacturing a composite semipermeable membrane element

[0150] ​​​As a method for producing a composite semipermeable membrane element, a method disclosed in Japanese Patent Application Publication No. 44-14216, Japanese Patent Application Publication No. 04-11928, Japanese Patent Application Publication No. 11-226366, or the like can be used.

[0151] 5. Use of a composite semipermeable membrane and a composite semipermeable membrane element

[0152] The composite semipermeable membrane and the composite semipermeable membrane element according to the present embodiment can be suitably used as a nanofiltration membrane and a nanofiltration membrane element for a separation purpose of monovalent ions and multivalent ions. The composite semipermeable membrane and the composite semipermeable membrane element according to the present embodiment can be used, for example, for removing salt from salt water or sea water or for mineral adjustment, for salt removal or mineral adjustment in the food field, for recovering acid from industrial uses such as plating or refining, and for recovering metals in an acid solution, and the like.

[0153] The composite semipermeable membrane element according to the present embodiment can also be connected in series or in parallel to produce a composite semipermeable membrane module housed in a pressure vessel.

[0154] In addition, the composite semipermeable membrane, the composite semipermeable membrane element, and the composite semipermeable membrane module described above can be combined with a pump that supplies raw water thereto, a device that performs pretreatment on the raw water, or the like to constitute a fluid separation device. By using this separation device, it is possible to separate raw water into permeated water such as drinking water and concentrated water that does not permeate the membrane, and thus to obtain water that meets the purpose.

[0155] 6. Filtration device

[0156] The filtration device according to the present embodiment is provided with a separation device provided with the composite semipermeable membrane element described above and a flow rate control apparatus that controls the flow rates of permeated water and concentrated water of the separation device.

[0157] The separation device is preferably configured to have a pressure vessel (vessel) in which the composite semipermeable membrane element is filled and to supply a solution to the vessel using a high-pressure pump.

[0158] In order to control the flow rates of permeated water and concentrated water of the composite semipermeable membrane element, the flow rate control apparatus of permeated water and concentrated water preferably has an instrument (flow meter) that can measure the flow rates of permeated water and concentrated water of the composite semipermeable membrane element. In the flow rate control of permeated water, the high-pressure pump preferably has a mechanism that receives data of the permeated water flow meter at all times and controls the output power of the high-pressure pump in such a manner that the flow rate of permeated water becomes constant. In the flow rate control of concentrated water, it is preferable to have a solenoid valve in the vicinity of the concentrated water flow meter, and the solenoid valve preferably has a mechanism that receives data of the concentrated water flow meter at all times and controls the flow rate of concentrated water to a constant amount.

[0159] In addition to the above, a pump, a pipe, a valve, a tank, a container, a temperature adjusting instrument, a meter (pH meter, conductivity meter, flow meter, pressure gauge, etc.), and the like can be arbitrarily combined.

[0160] Example

[0161] Hereinafter, the present application will be described in more detail by examples, but the present application is not limited by these examples.

[0162] <Positron annihilation lifetime measurement based on positron beam method>

[0163] The positron annihilation lifetime measurement of the separation functional layer was performed as follows using the positron beam method. The composite semipermeable membrane was washed with pure water at 70°C for 1 hour, and then left to stand in pure water at 25°C for 30 minutes. Then, the composite semipermeable membrane was freeze-dried under reduced pressure at -30°C, and cut into 1.5 cm x 1.5 cm squares as a test sample. Using a positron annihilation lifetime measurement device for thin films equipped with a positron beam generating device (the device is described in detail in Radiation Physics and Chemistry, 58, 603, Pergamon (2000)), the separation functional layer side of the test sample was measured at a beam intensity of 0.1 and 0.5 keV under room temperature vacuum using a photomultiplier and a barium difluoride scintillation counter with a total count of 5 million, and analyzed by POSITRONFIT. From the average lifetime τ of the 3rd component obtained by the analysis, the average pore diameter at a beam intensity of 0.1 keV was calculated as Rl, and the average pore diameter at a beam intensity of 0.5 keV was calculated as R2.

[0164] <Number of pores and pore diameter of separation functional layer cross section>

[0165] The number and the pore diameter of the pores in the cross section of the separation functional layer were measured as follows using a field emission transmission electron microscope (hereinafter "STEM"). The composite semipermeable membrane was freeze-dried under reduced pressure at -30°C, and cut into a 1.5 cm x 1.5 cm square as an observation sample. Using a STEM (Hitachi HF5000) using GMS3 (Gatan Corporation) as software and DeConv. HAADF (HREM Company) as a plug-in, an image was taken of the cross section of the separation functional layer in the composite semipermeable membrane under the conditions of a pressurized power of 200 kV, a spherical aberration (Cs) of 1 μm, an aperture of 22 mrad, and an observation magnification of 100,000 times. With respect to the obtained image, using ImageJ (Fiji), the equivalent circle diameter of the pore area converted to a true circle was calculated, and the value obtained by rounding off the third decimal place was used as the pore diameter. Based on the obtained pore diameter, the total number of pores P1 having a pore diameter of 0.30 nm or more and 1.20 nm or less, the total number of pores P2 having a pore diameter of 0.50 nm or more and less than 0.80 nm, the total number of pores P3 having a pore diameter of 0.80 nm or more and 1.20 nm or less, and the total number of pores P4 having a pore diameter of more than 1.20 nm were measured. With respect to the cross sections of three different parts selected at random, three images were analyzed respectively, and the average of the obtained values was calculated.

[0166] <Measurement of Amino Density>

[0167] A 5 cm x 5 cm composite semipermeable membrane from which the substrate had been physically peeled off was treated by a freeze-ultrathin sectioning method, placed on a grid, immersed in pure water for 4 hours, and then immersed in a 10 mass% 2-propanol aqueous solution for 1 hour, and washed, and used as a sample. The obtained sample was immersed in a 1.0 x 10 -3 mol / L aqueous solution of Na2WO4 2H2O adjusted to pH 3.8 at 25°C for 10 minutes, and this operation was performed a total of three times, and then the sample was immersed in a 1.0 x 10 -7The sample was immersed in a 0.1 mol / L aqueous solution of NaOH for 7 minutes, and this operation was performed a total of 4 times. Then, the water of the sample was removed with filter paper, and then the sample was subjected to freeze drying at -30°C as an amino group density measurement sample. A cross-sectional image of the obtained amino group density measurement sample was captured at an acceleration voltage of 200 kV using a STEM (HF5000 manufactured by Hitachi High-Tech), and a STEM image at a magnification of 100,000 times was obtained. The obtained image was analyzed using image processing software, and the amino group density was calculated from the brightness value for each region a to e in the cross section perpendicular to the surface of the composite semipermeable membrane (cross section perpendicular to the first surface) from the first surface side toward the second surface side by dividing the above separation function layer and the like into 5 equal parts. The amino group density in the region b was set as Nb, the amino group density in the region d was set as Nd, and Nb / Nd was calculated.

[0168] <Mg removal rate, Li removal rate>

[0169] An aqueous solution adjusted to a temperature of 25°C, a pH of 1, a sulfuric acid concentration of 100 mmol / L, a lithium sulfate concentration of 45 mmol / L, and a magnesium sulfate concentration of 115 mmol / L was supplied to the composite semipermeable membrane at a flow rate of 3.5 L / min, and the pressure was adjusted so that the permeate flux became 0.4 m 3 / m 2 / day in terms of the water permeation amount (cubic meters) per 1 square meter of membrane surface per 1 day, and the membrane filtration treatment was performed. The concentrations of magnesium ions (hereinafter, "Mg 2+ ") and lithium ions (hereinafter, "Li + ") in the feed water and the permeate water were measured using a P-4010 type ICP (inductively coupled plasma emission spectrometer) device manufactured by Hitachi, Ltd., and the Mg removal rate and the Li removal rate were calculated based on the following formulas.

[0170] Mg removal rate (%) = {1 - (Mg 2+ concentration in the permeate water) / (Mg 2+ concentration of the feed water)} x 100

[0171] Li removal rate (%) = {1 - (Li + concentration in the permeate water) / (Li + concentration of the feed water)} x 100

[0172] <Monovalent ion / divalent ion selectivity>

[0173] The monovalent ion / divalent ion selectivity was calculated based on the following formula using the values of the Mg removal rate and the Li removal rate calculated by the measurement of "Mg removal rate, Li removal rate" described above.

[0174] Monovalent ion / divalent ion selectivity = (100 - Li removal rate) / (100 - Mg removal rate)

[0175] Note that in the above evaluation, the Mg 2+ removal rate was evaluated, and as long as the Mg 2+ permeation can be blocked, it can be considered that the permeation of other multivalent ions can also be blocked. The reason for this is that Mg 2+ is a representative divalent ion, and generally the ionic size of multivalent ions of three or more valences is larger than that of divalent ions.

[0176] <Glucose permeation rate, sucrose permeation rate>

[0177] The glucose permeation rate B when a 1000 ppm glucose aqueous solution at 25°C and pH 6.5 is permeated through the composite semipermeable membrane at an operating pressure of 0.5 MPa, and the sucrose permeation rate C when a 1000 ppm sucrose aqueous solution at 25°C and pH 6.5 is permeated through the composite semipermeable membrane at an operating pressure of 0.5 MPa were each calculated using the following formula, and the glucose permeation rate relative to the sucrose permeation rate (B / C) was calculated. Note that the glucose concentration and the sucrose concentration were calculated using a refractometer (RID-6A, manufactured by Shimadzu Corporation).

[0178] Glucose permeation rate B = (glucose concentration in permeated water / glucose concentration in supplied water) x 100

[0179] Sucrose permeation rate C = (sucrose concentration in permeated water / sucrose concentration in supplied water) x 100

[0180] <Production of support membrane>

[0181] An 18 mass% dimethylformamide (DMF) solution of polysulfone was cast on a nonwoven fabric (air permeability 1.0 cc / cm 2 / s, thickness 42 μm) formed of polyester fibers, which was produced by a papermaking method, at a casting thickness of 180 μm at room temperature (25°C), and immediately immersed in pure water for 5 minutes, thereby forming a porous support layer on the substrate, and a support membrane was produced.

[0182] <Production of composite semipermeable membrane>

[0183] (Example 1)

[0184] For the support membrane obtained above, air at 25°C was blown to remove excess water while adjusting the membrane surface temperature of the support membrane to 25°C. After dipping for 15 seconds in a 30°C aqueous solution in which 2.0 mass% of logP: -0.65) and 250 ppm of sodium dodecyl diphenyl ether disulfonate and 1.0 mass% of trisodium phosphate were dissolved, nitrogen was blown from an air nozzle to remove excess aqueous solution, whereby a coated layer of the aqueous amine solution was formed on the support membrane. Further dipping in a 38°C n-decane solution containing 0.2 mass% of TMC was followed by standing for 1 minute under conditions of an atmospheric humidity (relative humidity) of 80% and 25°C, and the surface solution was removed by blowing two kinds of fluids (pure water and air) to the membrane surface. Then, washing was performed with 80°C pure water to obtain a composite semipermeable membrane.

[0185] (Example 2)

[0186] After the same operation as in Example 1, further dipping in glycerol at 80°C for 2 minutes and then dipping in pure water at 25°C for 24 hours were performed, whereby a composite semipermeable membrane was produced.

[0187] (Example 3)

[0188] After the same operation as in Example 1, further dipping in triethylene glycol at 80°C for 2 minutes and then dipping in pure water at 25°C for 24 hours were performed, whereby a composite semipermeable membrane was produced.

[0189] (Example 4)

[0190] An aqueous amine solution was applied to the support membrane and left to stand for 15 seconds, whereby a coated layer was formed, and a composite semipermeable membrane was produced by the same method as in Example 1, except for this.

[0191] (Example 5)

[0192] An aqueous amine solution was applied to the support membrane and left to stand for 15 seconds, whereby a coated layer was formed, and a composite semipermeable membrane was produced by the same method as in Example 3, except for this.

[0193] (Example 6)

[0194] A composite semipermeable membrane was produced by the same method as in Example 4, except that the polyfunctional aliphatic amine was changed to 2-methylpiperazine (logP: -0.44).

[0195] (Example 7)

[0196] A composite semipermeable membrane was produced by the same method as in Example 6, except that the atmospheric humidity was changed to 90%.

[0197] (Example 8)

[0198] A composite semipermeable membrane was produced in the same manner as in Example 6, except that the atmospheric humidity was changed to 95%.

[0199] (Example 9)

[0200] After the same operation as in Example 8, the support film was further dipped in 1,3-butanediol at 80°C for 2 minutes, and then dipped in pure water at 25°C for 24 hours, whereby a composite semipermeable membrane was produced.

[0201] (Example 10)

[0202] A composite semipermeable membrane was produced in the same manner as in Example 1, except that the polyfunctional aliphatic amine was changed to 2,5-dimethylpiperazine (logP: -0.12).

[0203] (Example 11)

[0204] A composite semipermeable membrane was produced in the same manner as in Example 10, except that the atmospheric humidity was changed to 90%.

[0205] (Example 12)

[0206] A composite semipermeable membrane was produced in the same manner as in Example 11, except that the aqueous amine solution was applied to the support film and left to stand for 15 seconds, whereby a coating layer was formed.

[0207] (Example 13)

[0208] After the same operation as in Example 12, the support film was further dipped in diethylene glycol at 80°C for 2 minutes, and then dipped in pure water at 25°C for 24 hours, whereby a composite semipermeable membrane was produced.

[0209] (Example 14)

[0210] A composite semipermeable membrane was produced in the same manner as in Example 1, except that the polyfunctional aliphatic amine was changed to 2,5-diethylpiperazine (logP: 0.85).

[0211] (Example 15)

[0212] A composite semipermeable membrane was produced in the same manner as in Example 13, except that the polyfunctional aliphatic amine was changed to 2,5-diethylpiperazine, and diethylene glycol was changed to ethylene glycol.

[0213] (Example 16)

[0214] A composite semipermeable membrane was produced in the same manner as in Example 8, except that the polyfunctional aliphatic amine was changed to 2,5-diethylpiperazine.

[0215] (Example 17)

[0216] After the same operation as in Example 16, further dipping in ethylene glycol at 80°C for 2 minutes, followed by dipping in pure water at 25°C for 24 hours, a composite semipermeable membrane was produced.

[0217] (Comparative Example 1)

[0218] A polyfunctional aliphatic amine was piperazine, the atmospheric humidity was changed to 75%, and otherwise, a composite semipermeable membrane was produced by the same method as in Example 1.

[0219] (Comparative Example 2)

[0220] After the same operation as in Example 1, further dipping in glycerol at 80°C for 2 minutes, followed by dipping in pure water at 25°C for 24 hours, a composite semipermeable membrane was produced.

[0221] (Comparative Example 3)

[0222] An amine aqueous solution was applied to the support film and left to stand for 15 seconds, whereby a coating layer was formed, and otherwise, a composite semipermeable membrane was produced by the same method as in Comparative Example 1.

[0223] (Comparative Example 4)

[0224] After the same operation as in Comparative Example 3, dipping in ethylene glycol at 80°C for 2 minutes, followed by dipping in pure water at 25°C for 24 hours, a composite semipermeable membrane was produced.

[0225] (Comparative Example 5)

[0226] A composite semipermeable membrane was produced by the same method as in Comparative Example 3, except that the polyfunctional acid chloride concentration was changed to 0.4 mass%.

[0227] (Comparative Example 6)

[0228] A composite semipermeable membrane was produced by the same method as in Comparative Example 3, except that the temperature at the time of interfacial polycondensation was changed to 80°C.

[0229] (Comparative Example 7)

[0230] After the same operation as in Comparative Example 3, further dipping in a 1.0 mass% propionic anhydride aqueous solution at 25°C for 10 minutes, followed by dipping in pure water at 25°C for 24 hours, a composite semipermeable membrane was produced.

[0231] (Comparative Example 8)

[0232] A composite semipermeable membrane was produced by the same method as in Example 1, except that the polyfunctional aliphatic amine was changed to 4,4'-dipiperidine (logP: -0.17).

[0233] (Comparative Example 9)

[0234] An aqueous amine solution was applied to the support film and left for 15 seconds, thereby forming a coating layer, and a composite semipermeable membrane was produced in the same manner as in Comparative Example 8, except that the atmospheric humidity was changed to 90%.

[0235] (Comparative Example 10)

[0236] A composite semipermeable membrane was produced in the same manner as in Comparative Example 9, except that the atmospheric humidity was changed to 75%.

[0237] (Comparative Example 11)

[0238] A composite semipermeable membrane was produced in the same manner as in Example 4, except that the atmospheric humidity was changed to 75%.

[0239] (Comparative Example 12)

[0240] A composite semipermeable membrane was produced in the same manner as in Comparative Example 11, except that the concentration of the polyfunctional acid chloride was changed to 0.4 mass%.

[0241] (Comparative Example 13)

[0242] A composite semipermeable membrane was produced in the same manner as in Comparative Example 11, except that the temperature at the time of interfacial polycondensation was changed to 80°C.

[0243] (Comparative Example 14)

[0244] A composite semipermeable membrane was produced in the same manner as in Comparative Example 11, except that, after the same operation as in Comparative Example 11 was performed, further immersion in triethylene glycol at 80°C was performed for 2 minutes, followed by immersion in pure water at 25°C for 24 hours.

[0245] (Comparative Example 15)

[0246] A composite semipermeable membrane was produced in the same manner as in Comparative Example 11, except that, after the same operation as in Comparative Example 11 was performed, further immersion in an aqueous 1.0 mass% acetic anhydride solution at 25°C was performed for 10 minutes, followed by immersion in pure water at 25°C for 24 hours.

[0247] (Comparative Example 16)

[0248] A composite semipermeable membrane was produced in the same manner as in Example 6, except that the atmospheric humidity was changed to 75%.

[0249] (Comparative Example 17)

[0250] A composite semipermeable membrane was produced in the same manner as in Comparative Example 16, except that the concentration of the polyfunctional acid chloride was changed to 0.4 mass%.

[0251] (Comparative Example 18)

[0252] A composite semipermeable membrane was produced in the same manner as in Comparative Example 16, except that the temperature at the time of interfacial condensation was changed to 80°C.

[0253] (Comparative Example 19)

[0254] After the same operation as in Comparative Example 16 was performed, further dipping in 1,3-butanediol at 80°C for 2 minutes, followed by dipping in pure water at 25°C for 24 hours, thereby a composite semipermeable membrane was produced.

[0255] (Comparative Example 20)

[0256] After the same operation as in Comparative Example 16 was performed, further dipping in 1.0 mass% propionic anhydride aqueous solution at 25°C for 10 minutes, followed by dipping in pure water at 25°C for 24 hours, thereby a composite semipermeable membrane was produced.

[0257] (Comparative Example 21)

[0258] A composite semipermeable membrane was produced in the same manner as in Example 12, except that the atmospheric humidity was changed to 75%.

[0259] (Comparative Example 22)

[0260] A composite semipermeable membrane was produced in the same manner as in Comparative Example 21, except that the polyfunctional acid chloride concentration was changed to 0.4 mass%.

[0261] (Comparative Example 23)

[0262] A composite semipermeable membrane was produced in the same manner as in Comparative Example 21, except that the temperature at the time of interfacial condensation was changed to 80°C.

[0263] (Comparative Example 24)

[0264] After the same operation as in Comparative Example 21 was performed, further dipping in diethylene glycol at 80°C for 2 minutes, followed by dipping in pure water at 25°C for 24 hours, thereby a composite semipermeable membrane was produced.

[0265] (Comparative Example 25)

[0266] After the same operation as in Comparative Example 21 was performed, further dipping in 1.0 mass% acetic anhydride aqueous solution at 25°C for 10 minutes, followed by dipping in pure water at 25°C for 24 hours, thereby a composite semipermeable membrane was produced.

[0267] (Comparative Example 26)

[0268] A composite semipermeable membrane was produced in the same manner as in Example 16, except that the atmospheric humidity was changed to 75%.

[0269] (Comparative Example 27)

[0270] A composite semipermeable membrane was produced in the same manner as in Comparative Example 26, except that the concentration of the polyfunctional acid chloride was changed to 0.4 mass%.

[0271] (Comparative Example 28)

[0272] A composite semipermeable membrane was produced in the same manner as in Comparative Example 26, except that the temperature at the time of interfacial polycondensation was changed to 80°C.

[0273] (Comparative Example 29)

[0274] A composite semipermeable membrane was produced in the same manner as in Comparative Example 26, except that, after the same operation as in Comparative Example 26 was performed, further dipping in ethylene glycol at 80°C for 2 minutes, followed by dipping in pure water at 25°C for 24 hours.

[0275] (Comparative Example 30)

[0276] A composite semipermeable membrane was produced in the same manner as in Comparative Example 26, except that, after the same operation as in Comparative Example 26 was performed, further dipping in a 1.0 mass% aqueous solution of acetic anhydride at 25°C for 10 minutes, followed by dipping in pure water at 25°C for 24 hours.

[0277] (Comparative Example 31)

[0278] A composite semipermeable membrane was produced in the same manner as in Comparative Example 1, except that the polyfunctional aliphatic amine was changed to 2,5-diisopropylpiperazine (logP: 1.65).

[0279] (Comparative Example 32)

[0280] A composite semipermeable membrane was produced in the same manner as in Comparative Example 31, except that the atmosphere humidity was changed to 95%, the amine aqueous solution was applied to the support film and left to stand for 15 seconds, thereby forming a coating layer, and then dipping in ethylene glycol at 80°C for 2 minutes, followed by dipping in pure water at 25°C for 24 hours.

[0281] (Comparative Example 33)

[0282] A composite semipermeable membrane was produced in the same manner as in Comparative Example 32, except that the polyfunctional aliphatic amine was changed to m-phenylenediamine (logP: 0.43).

[0283] [Table 1]

[0284]

[0285] [Table 2]

[0286]

[0287] [Table 3]

[0288]

[0289] [Table 4]

[0290]

[0291] [Table 5]

[0292]

[0293] [Table 6]

[0294]

[0295] As shown in Tables 1 to 6, the composite semipermeable membrane of Examples 1 to 17 in which R1 and R2 are 0.30 nm or more and 2.00 nm or less, and 0.90 ≤ R1 / R2 ≤ 1.10 is satisfied, showed high monovalent ion / divalent ion selectivity under acidic conditions compared to the composite semipermeable membranes of Comparative Examples 1 to 33.

[0296] As shown in the comparison between Examples 4 and 5 and Examples 11 and 12, the composite semipermeable membrane in which 0.31 ≤ P2 / P1 ≤ 0.35, P3 / P2 ≤ 0.09, and P4 / P1 ≤ 0.005 are satisfied showed more excellent monovalent ion / divalent ion selectivity.

[0297] As shown in the comparison between Example 1 and Example 3, by satisfying Nb / Nd ≤ 0.80, the monovalent ion / multivalent ion selectivity was improved.

[0298] In addition, as shown in the comparison between Example 8 and Example 9, by making Nb 1.0 x 10 -23 mol / nm 2 In the following, the monovalent ion / multivalent ion selectivity was improved.

[0299] As shown in Examples 6 to 17 in which the separation function layer has a corrugated structure, it was found that the operation can be performed at a lower pressure compared to Examples 1 to 5 which do not have a corrugated structure.

[0300] The present application has been described in detail with reference to specific embodiments, but it is apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present application. Note that this application was completed based on Japanese Patent Application (Japanese Patent Application No. 2022-192377) filed on November 30, 2022, Japanese Patent Application (Japanese Patent Application No. 2022-192378) filed on November 30, 2022, and Japanese Patent Application (Japanese Patent Application No. 2023-169359) filed on September 29, 2023, the entire contents of which are hereby incorporated by reference. In addition, all the contents cited herein are incorporated by reference in their entirety.

[0301] Explanation of Reference Signs

[0302] 1 composite semipermeable membrane

[0303] 2 base material

[0304] 3 porous support layer

[0305] 4 separation function layer

[0306] 6 header

[0307] 7 first end plate

[0308] 8 second end plate

[0309] 11 supply-side flow path material

[0310] 12 permeation-side flow path material

[0311] 20 envelope-shaped membrane

[0312] 26 wound body

[0313] 100 composite semipermeable membrane element

[0314] 101 feed water

[0315] 102 permeate water

[0316] 103 concentrated water

[0317] 201 wrinkle height

[0318] 202 thickness of separation function layer

[0319] P reference point

[0320] X1 tangent line to outer surface of membrane passing through reference point P

[0321] X2 tangent line to inner surface of membrane parallel to tangent line X1

[0322] Y0 normal line passing through reference point P

[0323] Y1, Y2 straight lines parallel to normal line Y0

[0324] a, b, c, d, e each region obtained by dividing separation function layer into 5

Claims

1. A composite semipermeable membrane having a porous support layer, and a separation functional layer on one surface side of the porous support layer, the separation functional layer containing a semi-aromatic crosslinked polyamide, a surface of the separation functional layer side of the composite semipermeable membrane is set as a first surface, and a surface on the side opposite to the first surface is set as a second surface, the composite semipermeable membrane is irradiated with a positron beam from the first surface side, and average pore diameters R1 and R2 of the separation functional layer derived from positron annihilation lifetime measurement are 0.30 nm or more and 2.00 nm or less, and satisfy 0.90 ≤ R1 / R2 ≤ 1.10, R1: average pore diameter under a condition that a positron beam intensity is 0.1 keV; R2: average pore diameter under a condition that a positron beam intensity is 0.5 keV.

2. The composite semipermeable membrane of claim 1, wherein, the average pore diameter R1 is 0.55 nm or more and 1.00 nm or less.

3. The composite semipermeable membrane of claim 1 or 2, wherein, In a cross section of the separation functional layer perpendicular to a surface of the composite semipermeable membrane, a total number of pores having a pore diameter of 0.30 nm or more and 1.20 nm or less, P1, a total number of pores having a pore diameter of 0.50 nm or more and less than 0.80 nm, P2, a total number of pores having a pore diameter of 0.80 nm or more and 1.20 nm or less, P3, and a total number of pores having a pore diameter greater than 1.20 nm, P4, satisfy 0.20 < P2 / P1 < 0.40, P3 / P2 < 0.20, and P4 / P1 ≤ 0.

01.

4. The composite semipermeable membrane of claim 1 or 2, wherein, In a cross section of the separation functional layer perpendicular to a surface of the composite semipermeable membrane, when each region obtained by equally dividing the separation functional layer into 5 from the first surface side toward the second surface side is set as regions a to e, an amino group density Nb in the region b and an amino group density Nd in the region d satisfy Nb / Nd ≤ 0.

80.

5. The composite semipermeable membrane of claim 4, wherein, The Nb is 1.0 x 10 -23 mol / nm 2 Below.

6. The composite semipermeable membrane of claim 1 or 2, wherein, When a glucose permeation rate when a 1000 ppm glucose aqueous solution at 25°C, pH 6.5 is permeated at an operation pressure of 0.5 MPa is set as B, and a sucrose permeation rate when a 1000 ppm sucrose aqueous solution at 25°C, pH 6.5 is permeated at an operation pressure of 0.5 MPa is set as C, B / C is 10 or more.

7. The composite semipermeable membrane of claim 1 or 2, wherein, the separation functional layer has a hollow pleated structure.

8. A composite semipermeable membrane element having the composite semipermeable membrane according to claim 1 or 2.

9. A filtration device having the composite semipermeable membrane element according to claim 8.

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