Composite semipermeable membrane, composite semipermeable membrane element and filtering device

Abstract

Provided are a composite semipermeable membrane and a composite semipermeable membrane element which exhibit excellent monovalent ion / multivalent ion selective separation performance under acidic conditions. The present invention pertains to a composite semipermeable membrane provided with a porous support layer and a separation function layer positioned on one surface side of the porous support layer, the separation function layer containing a semi-aromatic crosslinked polyamide, the surface of the composite semipermeable membrane on the separation function layer side being defined as a first surface, and the surface of the composite semipermeable membrane on the second surface being defined as a third surface. A surface on the opposite side of the first surface is set as a second surface, and the composite semipermeable membrane is irradiated with a positron beam from the first surface side. The average pore diameter (R1) of the separation function layer under the condition that the positron beam intensity is 0.1 keV as derived by positron annihilation lifetime measurement and the average pore diameter (R2) of the separation function layer under the condition that the positron beam intensity is 0.5 keV are 0.30 nm or more and 2.00 nm or less, and 0.90 < = R1 / R2 < = 1.10 is satisfied.

Description

Technical Field

[0001] The present invention relates to a composite semipermeable membrane, a composite semipermeable membrane element, and a filtration device. Background Art

[0002] Regarding the separation of mixtures, there are various techniques for removing substances (such as salts) dissolved in a solvent (such as water). In recent years, as a process for energy conservation and resource saving, the use of membrane separation methods has been continuously expanding. The membranes used in membrane separation methods include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, etc. These membranes are used, for example, in the production of drinking water from seawater, brackish water, water containing harmful substances, etc., softening of drinking water, food applications, production of industrial ultrapure water, wastewater treatment, recovery of valuable substances, etc.

[0003] Most of the currently commercially available reverse osmosis membranes and nanofiltration membranes are composite semipermeable membranes, and there are the following two types: a composite semipermeable membrane having a gel layer and an active layer obtained by crosslinking a polymer on a support membrane; and a composite semipermeable membrane having an active layer formed by polycondensing monomers on a support membrane. Among them, a composite semipermeable membrane obtained by coating a support membrane with a separation functional layer formed of a crosslinked polyamide obtained by the polycondensation reaction of a polyfunctional amine and a polyfunctional acyl halide is widely used as a separation membrane with high permeability and high selective separation performance.

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

[0005] For example, a nanofiltration membrane formed of a polyamide obtained by reacting a polyfunctional aromatic carboxyl chloride with piperazine has been disclosed (Patent Document 1). On the other hand, one problem that occurs in membrane separation plants using nanofiltration membranes is fouling caused by inorganic substances and organic substances. The nanofiltration membrane will cause a significant decrease in water permeability due to fouling. As a method for improving this, a method of restoring water permeability by cleaning with an acid or a chemical has also been proposed, and a nanofiltration membrane with high chemical resistance is also known (Patent Document 2). In addition, as a nanofiltration membrane with high chemical resistance, a nanofiltration membrane having a polyamide separation functional layer with a large specific surface area and a hydrophobic chemical composition formed in a hollow corrugated shape, which inhibits hydrolysis of the polyamide caused by an acid or a base, and can thus maintain excellent polyvalent ion removal performance for a long time, is also known (Patent Document 3).

[0006] Prior Art Documents

[0007] Patent Documents

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

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

[0010] Patent Document 3: WO 2021 / 085600 Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] Thus, the required properties of the nanofiltration membrane include not only water permeability and selective separation performance, but also chemical resistance. The chemical resistance of the membrane described in Patent Document 1 is low. On the other hand, the membrane described in Patent Document 2 has higher chemical resistance than the membrane described in Patent Document 1, but has a problem of low selectivity for separating monovalent ions from polyvalent ions. In addition, the membrane described in Patent Document 3 suppresses hydrolysis caused by contact with acids and alkalis and maintains high polyvalent ion removal performance under neutral conditions, but the pore size changes under acidic conditions. Therefore, when the membrane is used under acidic conditions, there is room for improvement in the selectivity for separating monovalent ions from polyvalent ions.

[0013] An object of the present invention is to provide a composite semipermeable membrane, a composite semipermeable membrane element, and a filtration device that exhibit excellent monovalent ion / polyvalent ion selective separation performance under acidic conditions.

[0014] Means for Solving the Problems

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

[0016] [1] A composite semipermeable membrane comprising a porous support layer and a separation functional layer located 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 defined as the first surface, and the surface on the side opposite to the first surface is defined as the second surface,

[0019] The composite semipermeable membrane is irradiated with a positron beam from the first surface side, and the average pore diameters R1 and 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.

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

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

[0022] [2] The composite semipermeable membrane as described in [1] above, wherein the average pore size R1 is 0.55 nm or more and 1.00 nm or less.

[0023] [3] The composite semipermeable membrane as described in [1] or [2] above, wherein in the cross-section of the separation functional layer perpendicular to the surface of the composite semipermeable membrane, the total number P1 of pores with a pore size of 0.30 nm or more and 1.20 nm or less, the total number P2 of pores with a pore size of 0.50 nm or more and less than 0.80 nm, the total number P3 of pores with a pore size of 0.80 nm or more and 1.20 nm or less, and the total number P4 of pores with a pore size greater than 1.20 nm satisfy 0.20 < P2 / P1 < 0.40, P3 / P2 < 0.20, and P4 / P1 ≤ 0.01.

[0024] [4] The composite semipermeable membrane as described in any one of [1] to [3] above, wherein in the 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 parts from the first surface side toward the second surface side is set as regions a to e, the amino group density Nb in region b and the amino group density Nd in region d satisfy Nb / Nd ≤ 0.80.

[0025] [5] The composite semipermeable membrane as described in [4] above, wherein the above Nb is 1.0×10 -23 mol / nm 2 or less.

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

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

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

[0029] [9] A filtration device comprising the composite semipermeable membrane element as described in [8] above.

[0030] Advantages of the Invention

[0031] Regarding the composite semipermeable membrane of the present invention, the pore size distribution in the film thickness direction of the separation functional layer is uniform. Therefore, the direction of ion diffusion in the separation functional layer becomes uniform, and it is possible to sufficiently suppress the permeation resistance of monovalent ions (which are of a size that can move freely within the separation functional layer), while effectively preventing the permeation of multivalent ions. As a result, excellent monovalent ion / multivalent ion selective separation performance can be achieved under acidic conditions. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0034] Figure 3 Figure 3 FIG. is a schematic view showing a cross section of a separation functional layer in a composite semipermeable membrane according to an embodiment of the present invention.

[0035] Figure 4 Figure 4 FIG. is a schematic view of a hollow corrugated structure of a separation functional layer of a composite semipermeable membrane according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following description and can be arbitrarily modified and implemented without departing from the gist of the present invention.

[0037] 1. Composite semipermeable membrane

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

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

[0040] (1-1) Support membrane

[0041] ​​​​​​​​The composite semipermeable membrane according to this embodiment only needs to have a porous support layer and a separation functional layer. The porous support layer is the layer constituting the support membrane. The support membrane can be formed only by the porous support layer. As shown in Figure 1 it can include a substrate 2 and a porous support layer 3 disposed on the substrate 2. That is, as shown in Figure 1 the composite semipermeable membrane 1 can include a porous support layer 3 and a separation functional layer 4. The support membrane formed by the porous support layer 3 can be formed only by the porous support layer 3, or can include a substrate 2 and a porous support layer 3.

[0042] The support membrane is used to provide strength to the composite semipermeable membrane by supporting the separation functional layer. The support membrane itself substantially does not have the separation performance for low molecular weight organic substances, ions, etc.

[0043] The size and distribution of the pores in the support membrane are not particularly limited. For example, it is preferably a uniform and fine pore, or a fine pore that gradually becomes larger from the surface on the side where the separation functional layer is formed to the other side, and the size of the fine pores on the surface on the side where the separation functional layer is formed is a pore of 0.1 nm or more and 100 nm or less.

[0044] As the material of the substrate, a fabric formed of at least one selected from polyester and aromatic polyamide can be exemplified. Among them, polyester with high mechanical stability and thermal stability is particularly preferably used.

[0045] As the fabric used in the substrate, long fiber non-woven fabric, short fiber non-woven fabric, etc. can be cited. Considering the requirements of avoiding excessive penetration of the polymer solution to the back surface when casting the polymer solution on the substrate, or avoiding peeling between the substrate and the porous support layer, and avoiding defects such as non-uniformity and pinholes of the membrane caused by fuzzing of the substrate, that is, considering excellent film-forming properties, long fiber non-woven fabric is preferably used.

[0046] As the long fiber non-woven fabric, a long fiber non-woven fabric composed of thermoplastic continuous filaments, etc. can be cited. By making the substrate include long fiber non-woven fabric, it is possible to suppress the non-uniformity and film defects during the casting of the polymer solution caused by fuzzing when only short fiber non-woven fabric is used. In addition, in the process of continuously forming the composite semipermeable membrane, since tension is also applied to the film-forming direction of the substrate, long fiber non-woven fabric with excellent dimensional stability is preferably used as the substrate.

[0047] In particular, on the surface of the substrate opposite to the surface in contact with the porous support layer, by making the orientation of the fibers longitudinal with respect to the film-forming direction, the strength of the substrate can be maintained, and film rupture, etc. can be prevented, so it is preferred. Here, "longitudinal orientation" means that the orientation direction of the fibers is parallel to the film-forming direction. On the contrary, when the orientation direction of the fibers is perpendicular to the film-forming direction, it is called transverse orientation.

[0048] The fiber orientation degree of the fiber is preferably 0° or more and 25° or less. Here, the "fiber orientation degree" is an index of the orientation of the non-woven fabric fibers, and refers to the average angle of the fibers constituting the non-woven fabric when the film-forming direction during continuous film formation is set to 0° and the direction perpendicular to the film-forming direction, i.e., the width direction of the non-woven fabric, is set to 90°. Therefore, the closer the fiber orientation degree is to 0°, the more it tends to be longitudinally oriented, and the closer it is to 90°, the more it tends to be transversely oriented.

[0049] The manufacturing process of the composite semi-permeable membrane and the manufacturing process of the element include a heating process, but heating causes the support membrane or the composite semi-permeable membrane to shrink. Especially in continuous film formation, since no tension is applied in the width direction, it is easy to shrink in the width direction. Problems occur in terms of dimensional stability and the like due to the shrinkage of the support membrane or the composite semi-permeable membrane. Therefore, as the substrate, a substrate with a small thermal dimensional change rate is ideal.

[0050] In the substrate using the non-woven fabric, if the difference between the fiber orientation degree of the surface opposite to the surface in contact with the porous support layer and the fiber orientation degree of the surface on the porous support layer side is 10° or more and 90° or less, it is possible to suppress the dimensional change in the width direction caused by the heat applied in the heating process or the like, so it is preferred.

[0051] The air permeability of the substrate is preferably 0.5 cc / cm 2 / s or more. When the air permeability is within this range, the water permeability of the composite semi-permeable membrane becomes high. The reason is considered that in the process of forming the support membrane, when a polymer is cast on the substrate and impregnated in the coagulation bath, the non-solvent replacement speed from the substrate side becomes faster, and thus the internal structure of the porous support layer changes, which affects the monomer retention amount and diffusion speed in the subsequent process of forming the separation functional layer.

[0052] It should be noted that the air permeability can be measured based on JIS L1096 (2010) using a Frazier-type tester. For example, the substrate is cut into a size of 200 mm × 200 mm as a sample. The sample is installed on the Frazier-type tester, and the suction fan and air holes are adjusted so that the inclined manometer becomes a pressure of 125 Pa. According to the pressure shown by the vertical manometer at this time and the type of air holes used, the amount of air passing through the substrate, that is, the air permeability, can be calculated. For example, a Frazier-type tester such as KES-F8-AP1 manufactured by KATO TECH Co., Ltd. can be used.

[0053] The thickness of the substrate is preferably 10 μm or more and 200 μm or less, 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 cited. Among them, polysulfone or polyethersulfone having high chemical stability, mechanical stability, and thermal stability is particularly preferred.

[0055] The thickness of the porous support layer affects the strength of the obtained composite semipermeable membrane and the packing density when it is made into an element. 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, etc. For example, in the case of observing using a scanning electron microscope, after peeling the porous support layer from the substrate, it is cut in a direction perpendicular to the surface of the composite semipermeable membrane by the freeze-fracture method to prepare a sample for cross-sectional observation. Platinum or platinum-palladium or ruthenium tetrachloride, preferably ruthenium tetrachloride, is thinly coated on this sample, and observation is carried out at an acceleration voltage of 3 to 15 kV using a high-resolution field emission scanning electron microscope (hereinafter referred to as "UHR-FE-SEM"). As the UHR-FE-SEM, for example, an S-900 type electron microscope manufactured by Hitachi, Ltd. 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 and "Ultra Filter UK10" (product name) manufactured by Toyo Roshi Kaisha, Ltd., or can be manufactured according to the method described in "Office of Saline Water Research and Development Progress Report" No. 359 (1968), etc.

[0058] The thickness of the substrate and the thickness of the composite semipermeable membrane can be measured using a digital thickness gauge. It should be noted 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 regarded as the thickness of the support membrane. In addition, by subtracting the thickness of the substrate from the thickness of the composite semipermeable membrane, the thickness of the porous support layer can be easily calculated. As the digital thickness gauge, for example, PEACOCK manufactured by Ozaki Seisakusho Co., Ltd. can be used. When using a digital thickness gauge, the thickness is measured at 20 different positions and the average value is calculated.

[0059] It should be noted that when it is difficult to measure the thickness of the base material and the thickness of the composite semi-permeable membrane using a thickness gauge, a scanning electron microscope can be used for measurement. In this case, for one sample, the thickness is measured from the electron microscope photographs of the cross-sections of any five parts, and the average value is calculated, thereby obtaining the thickness.

[0060] (1-2) Separation functional layer

[0061] Among the components of the composite semi-permeable membrane, the separation functional layer substantially has solute separation performance. As Figure 1 shown, the separation functional layer 4 is disposed on one surface side of the porous support layer 3.

[0062] The separation functional layer contains a semi-aromatic crosslinked polyamide obtained by interfacial polycondensation of a polyfunctional aliphatic amine and a polyfunctional aromatic acyl halide. In the composition of the separation functional layer, the proportion of the semi-aromatic crosslinked polyamide is preferably 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably formed only of the semi-aromatic crosslinked polyamide. By making the separation functional layer contain 50% by mass or more of the semi-aromatic crosslinked polyamide, excessive densification caused by π-π interaction from the aromatic rings in the polyamide is suppressed, and excellent monovalent ion permeability is easily obtained. Here, "crosslinked polyamide" refers to a compound having three or more amide bonds and a branched structure with a molecular weight of 400 or more.

[0063] The polyfunctional aliphatic amine is preferably an alicyclic diamine. Examples of the alicyclic diamine include bipiperidine derivatives and piperazine derivatives.

[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 still more preferably 110 or more. By making the molecular weight of the alicyclic diamine 90 or more, the diffusion coefficient of the amine becomes smaller, and polyamide is slowly formed during interfacial polycondensation, thereby enabling the formation of pores that inhibit the permeation resistance of monovalent ions while hindering the permeation of polyvalent ions.

[0066] In addition, the molecular weight of the alicyclic diamine is preferably 160 or less, more preferably 150 or less. Generally, in the initial stage of polycondensation, oligomers are excessively generated on the first surface side in contact with the organic layer, resulting in blockage of the pores on the first surface side. Therefore, the pore size distribution in the film thickness direction tends to become non-uniform. By making the molecular weight of the alicyclic diamine 160 or less, the molecular weight of the generated oligomers is reduced, and the interaction with the semi-aromatic crosslinked polyamide can be decreased. Thus, the oligomers can be easily removed in the drainage process and the post-treatment process immediately after film formation under high humidity conditions described below. It should be noted that by reducing the molecular weight of the oligomers, it is easy to form a separation functional layer with a uniform pore size in the film thickness direction, that is, a separation functional layer in which the average pore size R1 and the average pore size R2 described below satisfy 0.90 ≤ R1 / R2 ≤ 1.10, and a film with a high monovalent ion permeability is obtained.

[0067] Examples of the alicyclic diamine having a molecular weight of 90 or more and 160 or less include substituted piperazines in which the piperazine ring is substituted with an alkyl group having 1 to 3 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, 2,3,5,6-tetramethylpiperazine, etc.), and homopiperazine.

[0068] "Polyfunctional aromatic acyl halide" refers to an aromatic acyl halide having two or more halogenated carbonyl groups in one molecule, and any substance that can provide a semi-aromatic crosslinked polyamide through reaction with the above polyfunctional aliphatic amine is acceptable, without particular limitation. As the polyfunctional aromatic acyl halide, for example, halogenated products 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, etc. can be cited. Among the polyfunctional aromatic acyl halides, acyl chloride is preferred. Particularly from the aspects of economy, availability, ease of operation, and ease of reactivity, the acyl halide of 1,3,5-benzenetricarboxylic acid, i.e., trimesoyl chloride (hereinafter referred to as "TMC"), the acyl halide of 1,3-benzenedicarboxylic acid, i.e., isophthaloyl chloride, the acyl halide of 1,4-benzenedicarboxylic acid, i.e., terephthaloyl chloride, the acyl halide of 1,3,5-benzenetrisulfonic acid, i.e., 1,3,5-benzenetrisulfonyl chloride, and the acyl halide of 1,3,6-naphthalenetrisulfonic acid, i.e., 1,3,6-naphthalenetrisulfonyl chloride are preferred. The above polyfunctional aromatic acyl halides can be used alone or in combination of two or more. By mixing any one of the bifunctional isophthaloyl chloride and terephthaloyl chloride in the trifunctional TMC, 1,3,5-benzenetrisulfonyl chloride, and 1,3,6-naphthalenetrisulfonyl chloride, the molecular gap of the polyamide crosslinked structure is enlarged, and a membrane with a uniform pore size distribution can be controlled within a wide range. The mixing molar ratio of the trifunctional acyl chloride to the bifunctional acyl chloride is preferably 1:20 to 50:1, 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, 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 with sufficient water permeability can be easily obtained. In addition, by making the thickness of the separation functional layer 20 nm or more, the removal performance will not be reduced due to the generation of defects, and a composite semipermeable membrane with sufficient water permeability can be stably obtained. On the other hand, the thickness of the separation functional layer is preferably 50 nm or less, 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 can be obtained.

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

[0071] The inventors of the present application conducted in-depth research and found that a composite semipermeable membrane satisfying the following requirements exhibits excellent monovalent ion / multivalent ion selective separation performance under acidic conditions.

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

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

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

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

[0076] The "positron annihilation lifetime measurement method" is a method for measuring the time from when a positron enters a sample until it annihilates (at the level of several hundred picoseconds to several tens of nanoseconds) and non-destructively evaluating information such as the size, number density, and size distribution of pores in the range of 0.1 to 10 nm based on its annihilation lifetime.

[0077] It should be noted that the measurement region in the depth direction from the sample surface can be adjusted by the energy of the positron beam incident on the sample. The higher the energy, the deeper the part from the sample surface is included in the measurement region, but its depth is affected by the sample density. For example, when measuring the separation functional layer of the composite semipermeable membrane, if a positron beam with an energy of about 0.1 keV is irradiated from the first surface side of the composite semipermeable membrane, the region with a depth of 0 to 5 nm from the sample surface can usually be measured. If it is a positron beam with an energy of about 0.5 keV, the region with a depth of 0 to 50 nm from the sample surface can usually be measured. It should be noted that in this embodiment, when other layers such as a protective layer are provided on the separation functional layer, the average pore diameters R1 and R2 of the separation functional layer can be measured by removing other layers such as the protective layer in advance.

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

[0079] Although the detailed content of the above mechanism has not been fully elucidated, it is speculated that by making the pore diameters uniform in the film thickness direction, the diffusion direction of ions in the separation functional layer becomes uniform, and the permeation resistance of monovalent ions (which are of a size capable of freely moving in the separation functional layer) is suppressed. As a result, it is considered that excellent monovalent ion / multivalent ion selective separation performance is achieved. Therefore, it is more preferable that the average pore diameters R1 and R2 of the separation functional layer satisfy 0.95 ≤ R1 / R2 ≤ 1.05, and it is further preferable that they 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, the function as a substantial 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, still 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 permeation resistance of monovalent ions is suppressed and the effect of hindering the permeation of multivalent ions becomes remarkable. In addition, from the viewpoint of exhibiting the 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, still 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: interfacial polycondensation under high humidity conditions; the molecular weight of the polyfunctional aliphatic amine used in the interfacial polycondensation; the temperature of the organic solvent solution containing the polyfunctional aromatic acyl halide during the interfacial polycondensation; and so on. Specifically, when the polyfunctional aliphatic amine is an alicyclic diamine having a molecular weight of 90 or more and 160 or less, in the drainage process and the post-treatment process immediately following the film formation under the high humidity conditions described below, it is easy to remove the oligomers, and R1 / R2 can be controlled within a particularly preferred range.

[0082] Regarding the composite semipermeable membrane according to the present embodiment, in the cross-section of the separation functional layer perpendicular to the surface of the composite semipermeable membrane, the total number P1 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 preferably satisfy 0.20 < P2 / P1 < 0.40, P3 / P2 < 0.20, and P4 / P1 ≤ 0.01.

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

[0084] In the case of a composite semipermeable membrane that 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 only water and monovalent ions pass with a pore diameter of 0.50 nm or more and 0.80 nm or less have a higher existence ratio compared to the pores through which only water passes with a pore diameter of 0.30 nm or more and less than 0.50 nm and the large pores through which polyvalent ions and water pass with a pore diameter of 0.80 nm or more and 1.20 nm or less. The effect of suppressing the permeation resistance of monovalent ions and hindering the permeation of polyvalent ions becomes significant, and excellent monovalent ion / polyvalent ion selective separation performance is obtained under acidic conditions. P1 and P2 more preferably satisfy 0.26 ≤ P2 / P1 ≤ 0.35, and further preferably satisfy 0.31 ≤ P2 / P1 ≤ 0.35. By making P1 and P2 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 making P2 and P3 satisfy the above range, the effect of hindering the permeation of polyvalent ions becomes more significant.

[0085] In addition, when P4 / P1 ≤ 0.01, more excellent monovalent ion / polyvalent ion selective separation is exhibited. When P4 / P1 > 0.01, there are a large number of large pores through which polyvalent ions easily permeate, and the monovalent ion / polyvalent ion selective separation property decreases. Therefore, P4 / P1 is more preferably P4 / P1 ≤ 0.007, further preferably P4 / P1 ≤ 0.005, and particularly preferably P4 does not exist.

[0086] P1, P2, P3, and P4 can be controlled, for example, by the molecular weight of the polyfunctional aliphatic amine used in interfacial polycondensation, the temperature of coating the organic solvent solution containing the polyfunctional aromatic acyl halide during interfacial polycondensation, hydrophilic solvent treatment, etc. More specifically, in the case of using an alicyclic diamine with a molecular weight of 100 or more and 160 or less as the polyfunctional aliphatic amine, in the drainage step and the post-treatment step immediately following film formation under the high humidity conditions described later, the oligomers can be easily removed, and P2 / P1 can be controlled within a particularly preferred range.

[0087] As Figure 3 shown, with respect to the separation functional layer in the composite semipermeable membrane according to this 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 equally dividing the separation functional layer and the like into five parts from the first surface side toward the second surface side is set as regions a to e, the amino group density Nb in region b and the amino group density Nd in region d preferably satisfy Nb / Nd ≤ 0.80.

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

[0089] In the separation functional layer of the composite semipermeable membrane according to this embodiment, when the amino group density Nb in region b and the amino group density Nd in region d satisfy Nb / Nd ≤ 0.80, that is, in the case of a separation functional layer containing semi-aromatic crosslinked polyamide having the above-mentioned density difference in the thickness direction of the separation functional layer, a composite semipermeable membrane with 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, it is more preferable that the amino group density Nb and the amino group density Nd 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 caused by an excessive amino group density difference and the accompanying significant performance fluctuations, it is preferable that the amino group density Nb and the amino group density Nd satisfy Nb / Nd ≥ 0.10. In order to control the amino group distribution within the above range, the atmospheric humidity needs to be controlled at 80% or more, more preferably 90% or more, and further preferably 95% or more. The reason is that it suppresses the evaporation of water from the formed polyamide and suppresses the insolubilization of oligomers with a large number of amino groups generated in excess due to intermolecular hydrogen bonds, thereby enabling efficient removal of oligomers in the drainage process and the solvent treatment process. In addition, it is also possible to use a method of forming a separation functional layer by coating an aqueous solution containing a polyfunctional aliphatic amine on the surface of a porous support layer to reduce the terminal amino group density on the first surface side compared to the amino group density on the second surface side.

[0090] In addition, regarding the separation functional layer of the composite semipermeable membrane according to this embodiment, the amino group density Nb in region b is preferably 1.0×10 -23 mol / nm 2 or less. By making Nb 1.0×10 -23 mol / nm 2 or less, excellent monovalent ion permeability can be achieved. Nb is more preferably 0.9×10 -23 mol / nm 2 or less, and further preferably 0.8×10 -23 mol / nm 2 or less. In addition, from the viewpoint of suppressing a decrease in water permeability associated with the hydrophobization of the polyamide forming the separation functional layer, Nb is preferably 0.1×10 -23 mol / nm 2As described above, by increasing the concentration of the polyfunctional acyl halide during interfacial polymerization, the amino density Nb can be controlled to be low. However, when the monomer balance during interfacial polymerization is disrupted due to an increase in the concentration of the polyfunctional acyl halide, since the degree of polymerization cannot be increased, a large number of thick pores are likely to be formed, and the removal performance of multivalent ions is reduced. In addition, although the amino density Nb can be reduced by reacting the amino groups on the first surface side of the separation functional layer with an acid anhydride after interfacial polymerization, this results in a decrease in the permeability of monovalent ions and water permeability, so it is not preferred. Therefore, in order to control the amino distribution Nb within the above range, as described above, the atmospheric humidity needs to be controlled at 80% or more, more preferably 90% or more, and further preferably 95% or more. In addition, by performing the treatment process using a hydrophilic solvent described later together, the amino distribution Nb can be further reduced.

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

[0092] The composite semipermeable membrane is immersed in an aqueous tungstic acid solution multiple times. In this composite semipermeable membrane, a cross-section of the separation functional layer perpendicular to the thickness direction of the separation functional layer is photographed at a magnification of 100,000 using a field emission scanning transmission electron microscope (hereinafter referred to as "STEM"). In the obtained image, as Figure 3 shown, a reference point P is set at an arbitrary position on the outer surface of the separation functional layer (the surface opposite to the porous support layer side), and with the normal line Y0 passing through the reference point P as the center, straight lines Y1 and Y2 parallel to the normal line are drawn at an arbitrary interval of 3 to 10 nm on both sides in the direction orthogonal to the normal line Y0.

[0093] In addition, a tangent line X1 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 on the porous support layer side) parallel thereto are drawn. Four straight lines that divide the interval between X1 and X2 into five equal parts are drawn. The regions surrounded by Y1 and Y2 and surrounded by X1, X2, and the four straight lines in between are sequentially designated as regions a to e from the outer surface of the separation functional layer.

[0094] It should be noted that when multiple wrinkled structures are formed in the separation functional layer, a cross-sectional image is photographed using the same method as above, and with the wrinkled structure having the highest wrinkled height among the obtained wrinkled structures as the reference, 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 vertex of the convex portion, Y1 and Y2 are drawn using the same procedure. Then, using the same procedure as above, the regions a to e are obtained. It should be noted that the area of each of the regions a to e is set to be 5 nm 2 above 30 nm 2 below.

[0095] The amino group density in each of the regions a to e obtained by equally dividing the separation functional layer into five parts at equal intervals is determined by the following method.

[0096] For each of the above regions surrounded by the four straight lines between X1, X2 or them and Y1, Y2 (each region composed of regions a to e), the brightness is measured using STEM. The minimum brightness Lmin and the maximum brightness Lmax are determined for each region. Among the obtained minimum brightness Lmin and maximum brightness Lmax, the area of the portion showing a brightness of {Lmin + (Lmax - Lmin) / 3} or more in each region is integrated. This integrated value corresponds to the area (nm 2 ) of the portion having amino groups labeled with tungsten (W). The obtained integrated value is divided by the area per molecule of amino group (0.04 nm 2 ), Avogadro's constant (6.0×10 23 molecules / mol), and the area of each region, whereby the amino group density (mol / nm 2 ) can be calculated. For each region of five randomly selected wrinkled structures, the average value of the obtained amino group density is taken as the amino group density of each region.

[0097] In the composite semipermeable membrane according to the present embodiment, the monovalent ion removal rate is preferably 75% or less, more preferably 60% or less, and still more preferably 50% or less. By setting the monovalent ion removal rate within the above range, the concentration of monovalent ions in the permeated water becomes high, enabling the concentration step of monovalent ions in the purification process of monovalent ions to be made efficient or the step to be saved, contributing to shortening of the purification time and reduction of the purification cost. The polyvalent ion removal rate is preferably 99.4% or more, more preferably 99.6% or more, and still more preferably 99.8% or more. By setting the polyvalent ion removability within the above range, the concentration of polyvalent ions in the permeated water is reduced, enabling the purification process of monovalent ions to be made efficient or the step to be saved. In addition, since the concentration of polyvalent ions in the non-permeated water is increased, polyvalent ions can be effectively purified.

[0098] The following "selectivity of monovalent ions / polyvalent ions" means: an aqueous solution containing monovalent ions and polyvalent ions is used as the feed water, and membrane filtration treatment is performed using a separation membrane. Based on the ion concentrations contained in the permeated water obtained at this time, the monovalent ion removal rate and the polyvalent ion removal rate are calculated, and the value calculated using the following formula based on the monovalent ion removal rate and the polyvalent ion removal rate. It should be noted that in the present specification, the ions used in the calculation of the selectivity of monovalent ions / polyvalent ions refer to cations.

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

[0100] The selectivity of monovalent ions to polyvalent ions is preferably 70 or more, more preferably 80 or more, and still more preferably 100 or more. By making the selectivity of monovalent ions to polyvalent ions within the above range, the purification efficiency of both monovalent and polyvalent ions is improved, contributing to shortening the purification time and reducing 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 apparent pore number per unit membrane area increases. As a result, the pressure required for treating a solution using the composite semipermeable membrane can be reduced, and the heat discharge amount and power consumption of the operating device can be reduced.

[0102] Regarding the wrinkled structure of the separation functional layer, 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), regarding Figure 4 the separation functional layer 4 on the porous support layer 3 shown, the wrinkling height 201 and the thickness 202 of the separation functional layer are measured, and the ratio of the wrinkling height to the thickness of the separation functional layer (wrinkling height / thickness of the separation functional layer) is obtained. When the wrinkling height / thickness of the separation functional layer is 1.2 or more, it is considered that the separation functional layer has a wrinkled structure, and when it is less than 1.2, it is considered that the separation functional layer does not have wrinkles.

[0103] The "thickness of the separation functional layer" refers to the length of a line segment that connects two points on the supply water side and the permeated water side of the separation functional layer in the shortest way in the cross-sectional image of the separation functional layer, corresponding to Figure 4 the length of the thickness 202 of the separation functional layer shown. The cross-sectional image of the separation functional layer is divided into 10 intervals, and the point farthest from the support membrane in each interval is used as the measurement point on the supply water side. When the separation functional layer forms a wrinkled structure and the wrinkled structure forms across the above intervals, the interval farther from the support membrane is used as the measurement point.

[0104] The so-called "wrinkling height" refers to the length of a line segment that connects the point on the supply water side when measuring the thickness of the separation functional layer and the intersection point of the perpendicular line dropped from this point to the surface of the support membrane with the surface of the support membrane, corresponding to Figure 4 the length of the wrinkling height 201 shown. Regarding the wrinkling height, 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), 100 randomly selected wrinkles are measured, and the average value is calculated.

[0105] From the viewpoint of water permeability, the corrugation height is preferably 20 nm or more and 500 nm or less, more preferably 50 nm or more and 300 nm or less. By setting it to 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 a low pressure. In addition, by setting it to 500 nm or less, clogging of the water flow path and concentration polarization at the membrane surface caused by the overlap of adjacent corrugations can be suppressed, and thus high water permeability can be obtained at a low pressure. Regarding the control of the corrugation height, it can be controlled by the lipophilicity and molecular weight of the polyfunctional amine and the temperature during interfacial polymerization.

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

[0107] "logP" refers to the value obtained by calculating the octanol-water partition coefficient of a compound based on the octanol-water partition coefficients of each functional group contained in the compound according to Non-Patent Document 1. In the specification of this application, it is set to the value calculated using Chem Draw, a structural formula drawing software.

[0108] It has long been known (Non-Patent Document 2) that the interfacial polymerization of polyamide proceeds by the distribution and diffusion of amine in the organic phase and the reaction with polyfunctional acyl halide in the organic phase. By setting logP to -0.5 or more and 2.0 or less, the distribution and diffusion of the polyfunctional aliphatic amine in the organic solvent during interfacial polycondensation are optimized, and it is easy to form a separation functional layer having a hollow corrugated structure.

[0109] Examples of the polyfunctional aliphatic amine having logP of -0.5 or more and 2.0 or less include substituted piperazines in which the piperazine ring is substituted with an alkyl group having a total carbon atom number of 1 to 4 (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, etc.), bipiperidine derivatives (for example, 2,2'-bipiperidine, 3,3'-bipiperidine, 4,4'-bipiperidine, etc.).

[0110] The composite semipermeable membrane according to this embodiment is suitable not only for the separation of lithium plasma solutes but also for the separation of nonionic solutes, and is characterized in terms of the ratio of the permeability of each solute. For example, as nonionic solutes, glucose and sucrose can be mentioned. When the glucose permeability when a 1000 ppm glucose aqueous solution at 25°C and pH 6.5 is passed through at an operating pressure of 0.5 MPa is defined as B, and the sucrose permeability when a 1000 ppm sucrose aqueous solution at 25°C and pH 6.5 is passed through at an operating pressure of 0.5 MPa is defined as C, B / C is preferably 10 or more, more preferably 30 or more, and further preferably 50 or more. The upper limit of B / C is not particularly limited, for example, it is 1000 or less. Here, the permeability of each solute is represented by 100×(solute concentration in the permeated water / solute concentration in the feed water). By making B / C high, for example, it helps to shorten the separation and purification time of monosaccharides and polysaccharides in sugar purification and reduce the cost of purification.

[0111] 2. Method for manufacturing the composite semipermeable membrane

[0112] Next, the method for manufacturing the above composite semipermeable membrane will be described. The method for manufacturing the 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 the support membrane

[0114] The step of forming the support membrane can also be referred to as the step of forming a porous support layer in other words. This step includes, for example, a step of coating a polymer solution on a substrate and a step of immersing the substrate coated with the polymer solution in a coagulation bath to solidify the polymer.

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

[0116] When using polysulfone as the polymer, the temperature of the polymer solution during coating is preferably 10°C or more and 60°C or less. If the temperature of the polymer solution is within this range, the polymer will not precipitate, and the polymer solution will solidify after sufficiently impregnating between the fibers of the substrate. As a result, a porous support layer firmly bonded to the substrate by the anchoring effect can be obtained. It should be noted that the preferred temperature range of the polymer solution can be appropriately adjusted according to the type of polymer used, the desired solution viscosity, etc.

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

[0118] The time from coating the polymer solution on the substrate to dipping it into the coagulation bath is preferably 0.1 second or more and 5 seconds or less. If the time until dipping into the coagulation bath is within this range, the polymer solution cures after being sufficiently impregnated between the fibers of the substrate. It should be noted that the preferred range of the time until dipping into the coagulation bath can be appropriately adjusted according to the type of the polymer solution used, the desired solution viscosity, etc.

[0119] As the coagulation bath, water is usually used, but as long as it does not dissolve the polymer, which is the component of the porous support layer. The temperature of the coagulation bath is preferably -20°C or more and 100°C or less, more preferably 10°C or more and 50°C or less. When the temperature of the coagulation bath is 100°C or less, oscillation of the coagulation bath surface caused by thermal motion can be suppressed, and the smoothness of the film surface after film formation can be maintained. In addition, when the temperature is -20°C or more, the coagulation rate can be maintained, so the film-forming property 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 washed with hot water. The temperature of the hot water at this time is preferably 40°C or more and 100°C or less, more preferably 60°C or more and 95°C or less. When the washing temperature is 100°C or less, the shrinkage degree of the support film will not become too large, and a decrease in water permeability can be suppressed. In addition, when the washing temperature is 40°C or more, a high washing effect can be obtained.

[0121] (2-2) Formation process of the separation functional layer

[0122] Next, an example of the formation process of the separation functional layer constituting the composite semipermeable membrane will be described. In the formation process of the separation functional layer, an aqueous solution containing a polyfunctional aliphatic amine compound and an organic solvent solution containing a polyfunctional 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 functional layer includes:

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

[0125] (b) After the above (a), a step of further contacting with a solution containing a polyfunctional aromatic acyl halide at 10°C or more and 38°C or less.

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

[0127] The aqueous solution containing a polyfunctional aliphatic amine may contain alcohols. Examples of the alcohols include ethanol, 1-propanol, 2-propanol, butanol, and the like. By including alcohols in the aqueous solution containing a polyfunctional aliphatic amine, the same effects as those of the above surfactants can be obtained.

[0128] The aqueous solution containing a polyfunctional aliphatic amine may contain a basic compound. Examples of the basic compound include sodium hydroxide, trisodium phosphate, triethylamine, and the like. By including a basic compound, hydrogen halide generated in the interfacial polycondensation reaction is removed, the decrease in the reactivity of the polyfunctional aliphatic amine can be inhibited, and thus the polyamidation reaction is promoted. In addition to the separation selectivity, the durability against acids and bases can also be improved.

[0129] The solvent in the solution containing a polyfunctional aromatic acyl halide is an organic solvent. As the organic solvent, the following organic solvents are preferably used: those that are immiscible with water, do not damage the support membrane, and do not hinder the formation reaction of the semi-aromatic crosslinked polyamide, and the solubility parameter (hereinafter "SP value") is 15.2 (MPa) 1 / 2 or more, and logP is 3.2 or more. By making the SP value 15.2 (MPa) 1 / 2 or more, and logP is 3.2 or more, the distribution and diffusion of the polyfunctional aliphatic amine during interfacial polycondensation can be optimized, and the amount of functional groups can be increased.

[0130] As the organic solvent with an SP value of 15.2 (MPa) 1 / 2 or more, and logP is 3.2 or more, for example, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, heptadecane, hexadecane, cyclooctane, ethylcyclohexane, 1-octene, 1-decene and other monomers or their mixtures can be preferably used.

[0131] The aqueous solution containing a polyfunctional aliphatic amine compound may contain a surfactant. Examples of the surfactant include sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium dodecyl diphenyl ether disulfonate, styrene bis(naphthalenesulfonate), sodium polyoxyethylene alkyl ether sulfate, and the like. By including a surfactant, the surface of the porous support layer can be uniformly coated with the above aqueous solution, so that the separation functional layer is uniformly formed, and the effects of stable membrane performance and improved adhesion between the separation functional layer and the porous support layer can be obtained.

[0132] In the aqueous solution containing a polyfunctional aliphatic amine compound and the organic solvent solution containing a polyfunctional aromatic acyl halide, compounds such as an acylation catalyst, a polar solvent, an acid scavenger, and an antioxidant can be included as needed.

[0133] In order to conduct interfacial polycondensation of a polyfunctional aliphatic amine and a polyfunctional aromatic acyl halide on a 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 a method of coating the surface of the porous support layer with the above-mentioned aqueous solution containing the polyfunctional aliphatic amine, it is sufficient that the surface of the porous support layer is uniformly and continuously coated with the aqueous solution. For example, there can be mentioned a method of coating the aqueous solution on the surface of the porous support layer, a method of immersing the support membrane in the aqueous solution, etc. Among them, a method of coating the aqueous solution on the surface of the porous support layer is preferred. By coating the aqueous solution containing the polyfunctional aliphatic amine on the surface of the porous support layer, compared with the method of immersion, the amount of water contained in the porous support layer becomes less, that is, the amount of amine contained in the support membrane becomes less. Therefore, at the initial stage of interfacial polycondensation after coating the polyfunctional aromatic acyl halide, an excessive supply of amine to the reaction site can be suppressed, which helps to form pores that inhibit the permeation resistance of monovalent ions and impede the permeation of polyvalent ions. At the same time, it is possible to reduce the terminal amino group density on the first surface side of the formed separation functional layer compared to the amino group density on the second surface side.

[0134] Next, it is preferred to remove the excessively coated aqueous solution by a drainage process. As a method of drainage, for example, there is a method of allowing it to flow down naturally while keeping the membrane surface in the vertical direction. After drainage, the membrane surface can be dried to remove all or part of the water in the aqueous solution on the membrane surface.

[0135] Then, an organic solvent solution containing the above-mentioned polyfunctional aromatic acyl halide is coated on the porous support layer containing the above-mentioned aqueous solution containing the polyfunctional aliphatic amine. The coating temperature is preferably carried out at 10°C or higher and 38°C or lower, more preferably 20°C or higher and 35°C or lower. By making the coating temperature 10°C or higher, the diffusion rate of the amine in the organic solvent becomes sufficient, and it is easy to form a polyamide with a pore diameter required for polyvalent ion selective removal. In addition, if the temperature during coating is 38°C or lower, the hindrance to diffusion caused by the increase in the reaction rate is suppressed, so the pore structure becomes uniform and the selective separation performance is improved.

[0136] When trimesoyl chloride is contained as the polyfunctional aromatic acyl 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, 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 performance, and acid durability can be obtained. When using other trifunctional acyl chlorides or bifunctional acyl chlorides, after adjusting according to the molecular weight ratio of the above-mentioned trimesoyl chloride so that the molar concentration of the acyl chloride becomes the same level, it is used.

[0137] By bringing the polyfunctional aliphatic amine into contact with the polyfunctional aromatic halide in this manner, the two are subjected to interfacial polycondensation. The interfacial polycondensation is preferably carried out at a temperature of 10°C or above, more preferably at a temperature of 80°C or above, and further preferably at a temperature above the melting point of the polyfunctional aliphatic amine. In addition, the interfacial polycondensation is preferably carried out at a temperature of 120°C or below. By carrying out the interfacial polycondensation at a temperature of 10°C or above, the reduction in the mobility of the oligomers can be suppressed during the interfacial polycondensation reaction, the polyfunctional aliphatic amine can maintain high mobility in the reaction system, an efficient cross-linking reaction can be carried out, and excellent selective removal of polyvalent ions can be achieved. In addition, by carrying out the interfacial polycondensation at a temperature of 120°C or below, excessive drying of the porous support layer can be prevented, and practical water permeability can be ensured.

[0138] The inventor of the present application has conducted in-depth research and found that by controlling the atmospheric humidity (relative humidity) during the implementation of the interfacial polycondensation to more than 80%, it is easy to obtain the composite semipermeable membrane involved in the present embodiment. By making the atmospheric humidity during the interfacial polycondensation to be more than 80%, the evaporation of the water of the formed polyamide can be suppressed, and the insolubilization caused by the intermolecular hydrogen bond of the oligomer with many amino groups generated in excess can be suppressed. It is believed that the oligomer can be efficiently removed in the drainage process and solvent treatment process described later, so the pore size expansion accompanied by the swelling of the semi-aromatic cross-linked polyamide can be suppressed when the membrane is used under acidic conditions, and the amino density of the first side of the separation functional layer is reduced. The gradient of the amino density in the film thickness direction becomes larger, and when the membrane is used under acidic conditions, the swelling of the polyamide on the first side contacted by the high concentration of acid and the excessive pore size expansion accompanied therewith can be suppressed, and excellent monovalent ion permeability and excellent multivalent ion removal can be achieved simultaneously. Therefore, the atmospheric humidity during the implementation of the interfacial polycondensation is preferably more than 80%, more preferably more than 90%, and further preferably more than 95%. It should be noted that the atmospheric humidity can be adjusted by using a precision air conditioning device or the like.

[0139] The time for carrying out the interfacial polycondensation is preferably from 0.1 second to 3 minutes, and more preferably from 1 second to 1 minute.

[0140] Next, the organic solvent solution after the reaction is preferably removed by a drainage step. The organic solvent can be removed by, for example, a method in which the film is held vertically to allow the excess organic solvent to flow down naturally and be removed, a method in which the organic solvent is dried by blowing air with a blower, or a method in which the excess organic solvent is removed by a mixed fluid of water and air. Among them, the method in which the organic solvent is removed by a mixed fluid of water and air is particularly preferred.

[0141] When a mixed fluid of water and air is used, swelling occurs due to the inclusion of water in the separation functional layer, and the water permeability becomes high. In the case of natural flow-down, as the holding time in the vertical direction, it is preferably between 1 minute and 5 minutes, more preferably between 1 minute and 3 minutes. By making the holding time 1 minute or more, it is easy to obtain a separation functional layer having the target function. By making the holding time 5 minutes or less, the generation of defects due to excessive drying of the organic solvent can be suppressed, and thus the performance degradation can be suppressed.

[0142] The composite semipermeable membrane obtained by the above method is further subjected to a step 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 excess amide oligomers with a large number of amino groups on the first surface side and making the pore size distribution in the film thickness direction of the separation functional layer uniform. As a result, the monovalent ion / multivalent ion selective separation performance of the composite semipermeable membrane can be further improved. Here, the "hydrophilic solvent" means a solvent that can be dissolved in water by 10 mass% or more and can be used as an aqueous solution of 10 mass% or more. The solubility of the hydrophilic solvent in water is preferably 50 mass% or more, more preferably 80 mass% or more, further preferably 90 mass% or more, and particularly preferably an undiluted hydrophilic solvent.

[0143] As the hydrophilic solvent, a solvent that does not corrode the support membrane is suitable, and alcohols are particularly preferred. As alcohols, for example, monohydric alcohols such as methanol, ethanol, or 2-propanol, diols such as ethylene glycol, 1,3-butanediol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, or polybutylene glycol, glycerol, diglycerol derivatives, glycerol fatty acid esters, etc. can be cited. Among them, from the viewpoints of being easily removed by water washing and having a high effect of improving the monovalent ion / multivalent ion selective separation performance, 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. In particular, from the viewpoints of removing excess oligomers and the pore size uniformizing effect brought about by the reconstruction of the polyamide structure, the hydrophilic solvent is particularly preferably a diol having a molecular weight of 200 or less with high permeability to polyamide.

[0144] 3. Composite semipermeable membrane element

[0145] The composite semipermeable membrane element according to the present embodiment is characterized by including the composite semipermeable membrane according to the present embodiment. Since the composite semipermeable membrane element according to the present embodiment includes the composite semipermeable membrane according to the present embodiment, it exhibits excellent monovalent ion / multivalent ion selective separation performance. Refer 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 this embodiment, as Figure 2 shown, the composite semipermeable membrane element 100 includes a composite semipermeable membrane 1, a supply-side flow path material 11, a permeate-side flow path material 12, a header pipe 6, a first end plate 7, and a second end plate 8. The composite semipermeable membrane 1 forms a cylindrical membrane 20 by laminating. The cylindrical membrane 20 is wound around the header pipe 6 in a spiral shape, thereby forming a wound body 26. In order to protect the wound body 26, other components such as a film and filaments can be wound around the outer periphery of the wound body 26.

[0147] The supply-side flow path material 11 is arranged so as to face the supply side of the composite semipermeable membrane 1, and is wound around the header pipe 6 together with the composite semipermeable membrane 1. As the supply-side flow path material 11, for example, a net can be preferably used. The permeate-side flow path material 12 is arranged so as to face the permeate side of the composite semipermeable membrane 1, and is wound around the header pipe 6 together with the composite semipermeable membrane 1. As the permeate-side flow path material 12, for example, a tricot woven fabric or a sheet with protrusions fixed thereto can be used. It should be noted that when protrusions (equivalent to the permeate-side flow path material) are directly fixed to the surface on the substrate side of the composite semipermeable membrane, the permeate-side flow path material 12 can be omitted. The header pipe 6 is a hollow cylindrical member and has a plurality of holes on the side surface. The first end plate 7 is a disk-shaped member having a plurality of supply ports. The first end plate 7 is arranged at the first end of the wound body 26. The second end plate 8 is a disk-shaped member having a concentrated water discharge port and a permeate water discharge port. The second end plate 8 is arranged at the second end of the wound body 26.

[0148] The separation of the fluid based on the composite semipermeable membrane element 100 will be described. The supply water 101 is supplied from the plurality of supply ports of the first end plate 7 to the wound body 26. The supply water 101 moves in the supply-side flow path formed by the supply-side flow path material 11 on the supply side of the composite semipermeable membrane 1. The fluid that permeates through the composite semipermeable membrane 1 ( Figure 2 shown as permeate water 102 in the figure) moves in the permeate-side flow path formed by the permeate-side flow path material 12. The permeate water 102 that reaches the header pipe 6 passes through the holes of the header pipe 6 and enters the inside of the header pipe 6. The permeate water 102 flowing in the header pipe 6 is discharged to the outside from the second end plate 8. On the other hand, the fluid that does not permeate through the composite semipermeable membrane 1 ( Figure 2 shown as concentrated water 103 in the figure) 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 permeate water 102 and concentrated water 103.

[0149] 4. Manufacturing method of the composite semipermeable membrane element

[0150] As a method for manufacturing a composite semipermeable membrane element, a method disclosed in, for example, Japanese Patent Publication No. Sho 44-14216, Japanese Patent Publication No. Hei 4-11928, or Japanese Patent Publication No. Hei 11-226366 can be used.

[0151] 5. Use of the composite semipermeable membrane and the 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 separating monovalent ions and polyvalent ions. The composite semipermeable membrane and the composite semipermeable membrane element according to the present embodiment can be used, for example, for removing salts or adjusting minerals from brackish water or seawater, removing salts or adjusting minerals in the food field, recovering acids from industrial uses such as electroplating and refining, and recovering metals in acid solutions.

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

[0154] In addition, the above-mentioned composite semipermeable membrane, composite semipermeable membrane element, and composite semipermeable membrane module can be combined with a pump for supplying raw water to them, a device for pre-treating the raw water, etc. to form a fluid separation device. By using this separation device, raw water can be separated into permeated water such as drinking water and concentrated water that does not pass through the membrane, thereby obtaining water that meets the purpose.

[0155] 6. Filtration device

[0156] The filtration device according to the present embodiment includes a separation device and a flow control device. The separation device includes the above-mentioned composite semipermeable membrane element, and in the flow control device, the flow rates of the permeated water and the concentrated water of the separation device are controlled.

[0157] The separation device preferably has a structure including a pressure vessel (vessel) filled with the composite semipermeable membrane element and capable of supplying a solution to the vessel using a high-pressure pump.

[0158] In order to control the flow rates of the permeated water and the concentrated water of the composite semipermeable membrane element, the flow rate control device for the permeated water and the concentrated water preferably has an instrument (flowmeter) capable of measuring the flow rates of the permeated water and the concentrated water of the composite semipermeable membrane element. In the control of the flow rate of the permeated water, the high-pressure pump preferably has a mechanism for receiving the data of the permeated water flowmeter at any time and controlling the output power of the high-pressure pump so as to achieve a constant permeated water flow rate. In terms of the control of the concentrated water flow rate, it is preferable to have a solenoid valve near the concentrated water flowmeter, and the solenoid valve preferably has a mechanism for receiving the data of the concentrated water flowmeter at any time and controlling the concentrated water flow rate to a certain amount.

[0159] Regarding the filtration device according to this embodiment, in addition to the above, pumps, pipes, valves, tanks, containers, temperature control instruments, meters (pH meters, conductivity meters, flow meters, pressure gauges, etc.), etc. can be selected and arbitrarily combined.

[0160] Example

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

[0162] <Positron Annihilation Lifetime Measurement Method Based on Positron Beam Method>

[0163] The positron annihilation lifetime of the separation functional layer is measured using the positron beam method as follows. The composite semipermeable membrane is washed with pure water at 70 °C for 1 hour, and then left standing in pure water at 25 °C for 30 minutes. Then, the composite semipermeable membrane is freeze-dried under reduced pressure at -30 °C and cut into squares of 1.5 cm × 1.5 cm to be used as test specimens. Using a positron annihilation lifetime measurement device suitable for thin films equipped with a positron beam generation device (this device is described in detail, for example, in Radiation Physics and Chemistry, 58, 603, Pergamon (2000)), at beam intensities of 0.1 and 0.5 keV and at room temperature in vacuum, using a photomultiplier tube, the separation functional layer side of the test specimen is measured with a barium fluoride scintillation counter with a total count of 5 million, and analyzed by POSITRONFIT. Based on the average lifetime τ of the third component obtained from the analysis, the average pore diameter at a beam intensity of 0.1 keV is calculated as R1, and the average pore diameter at a beam intensity of 0.5 keV is calculated as R2.

[0164] <Number and Pore Diameter of the Cross-Section of the Separation Functional Layer>

[0165] The number and diameter of pores in the cross-section of the separation functional layer were measured as follows using a field emission type transmission electron microscope (hereinafter referred to as "STEM"). The composite semipermeable membrane was freeze-dried under reduced pressure at -30 °C and cut into a square of 1.5 cm × 1.5 cm as an observation sample. Using STEM (Hitachi HF5000) with GMS3 (manufactured by Gatana Co., Ltd.) as the software and DeConv.HAADF (manufactured by HREM Co., Ltd.) as a plug-in, an image of the cross-section of the separation functional layer in the composite semipermeable membrane was taken under the conditions of a high voltage power supply of 200 kV, a spherical aberration (Cs) of 1 μm, an aperture of 22 mrad, and an observation magnification of 100,000 times. For the obtained image, using ImageJ (Fiji), the equivalent circle diameter obtained by converting the pore area into a perfect 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 diameters, the total number P1 of pores with a pore diameter of 0.30 nm or more and 1.20 nm or less, the total number P2 of pores with a pore diameter of 0.50 nm or more and less than 0.80 nm, the total number P3 of pores with a pore diameter of 0.80 nm or more and 1.20 nm or less, and the total number P4 of pores with a pore diameter greater than 1.20 nm were measured. For cross-sections of three different randomly selected sites, three images were analyzed respectively, and the average value of the obtained values was calculated.

[0166] <Measurement of amino group density>

[0167] After treating a 5 cm × 5 cm composite semipermeable membrane from which the substrate had been physically peeled off by the cryoultramicrotomy method, it was placed on a grid, immersed in pure water for 4 hours, then immersed in a 10 mass% aqueous solution of 2-propanol for 1 hour for cleaning, and used as a sample. The obtained sample was immersed in a 1.0×10 -3 mol / L aqueous solution of Na2WO4·2H2O adjusted to pH 3.8 and 25 °C for 10 minutes, and this operation was carried out a total of 3 times. Then the sample was immersed in a 1.0×10 -7Immerse in an aqueous solution of [[mol / L]] for 7 minutes, and perform this operation a total of 4 times. Then, remove the moisture of the sample with filter paper, and then perform freeze-drying at -30 °C to obtain a sample for amino density measurement. Using STEM (HF5000 manufactured by Hitachi High-Tech), take a cross-sectional image of the obtained sample for amino density measurement under the condition of an acceleration voltage of 200 kV to obtain a STEM image at a magnification of 100,000. Analyze the obtained image with image processing software. Using the above method, in the cross-section perpendicular to the surface of the composite semipermeable membrane (the cross-section perpendicular to the first surface), divide the above separation functional layer into 5 equal parts at equal intervals from the first surface side to the second surface side, and set the obtained regions as regions a to e. Calculate the amino density for each of the regions a to e based on the brightness value. Let the amino density in region b be Nb, and the amino density in region d be Nd, and calculate Nb / Nd.

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

[0169] Supply an aqueous solution adjusted to a temperature of 25 °C, pH 1, sulfuric acid concentration of 100 mmol / L, lithium sulfate concentration of 45 mmol / L, and magnesium sulfate concentration of 115 mmol / L to the composite semipermeable membrane at a flow rate of 3.5 L / min, and adjust the pressure so that the membrane permeation flux, which is the value of the water permeation amount (cubic meters) per 1 square meter of the membrane surface per day, becomes 0.4 m 3 / m 2 / day, and perform membrane filtration treatment. Use an ICP (high-frequency inductively coupled plasma emission analysis) device of model P-4010 manufactured by Hitachi, Ltd. to measure the concentrations of magnesium ions (hereinafter "Mg 2+ ") and lithium ions (hereinafter "Li + ") in the feed water and the permeate water, and calculate the Mg removal rate and the Li removal rate based on the following formula.

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

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

[0172] <Monovalent ion / divalent ion selectivity>

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

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

[0175] It should be noted that in the above evaluation, Mg 2+ removal rate was used for evaluation. As long as the permeation of Mg 2+ can be hindered, it can be regarded as also being able to hinder the permeation of other polyvalent ions. The reason is that Mg 2+ is a representative divalent ion. Generally speaking, the ionic size of polyvalent ions with a valence of 3 or more is larger than that of divalent ions.

[0176] <Glucose permeability, sucrose permeability>

[0177] The glucose permeability B when a 1000 ppm glucose aqueous solution at a temperature of 25°C and a pH of 6.5 permeates through the composite semipermeable membrane under an operating pressure of 0.5 MPa and the sucrose permeability C when a 1000 ppm sucrose aqueous solution at a temperature of 25°C and a pH of 6.5 permeates through the composite semipermeable membrane under an operating pressure of 0.5 MPa are respectively calculated using the following formulas, and the glucose permeability (B / C) relative to the sucrose permeability is calculated. It should be noted that the glucose concentration and the sucrose concentration are determined using a refractometer (RID-6A manufactured by Shimadzu Corporation).

[0178] Glucose permeability B = (Glucose concentration in permeated water / Glucose concentration in feed water) × 100

[0179] Sucrose permeability C = (Sucrose concentration in permeated water / Sucrose concentration in feed water) × 100

[0180] <Production of support membrane>

[0181] An 18 mass% dimethylformamide (DMF) solution of polysulfone was cast at a coating thickness of 180 μm at room temperature (25°C) onto a non-woven fabric made of polyester fibers (air permeability 1.0 cc / cm 2 / s, thickness 42 μm) manufactured by the papermaking method, and then immediately immersed in pure water for 5 minutes to form a porous support layer on the substrate and produce a support membrane.

[0182] <Production of composite semipermeable membrane>

[0183] (Example 1)

[0184] For the support film obtained above, air adjusted to 25°C was blown to remove excess moisture, and at the same time, the film surface temperature of the support film was adjusted to 25°C. After impregnating in an aqueous solution at 30°C containing 2.0% by mass of homopiperazine (logP: -0.65), 250 ppm of sodium dodecyl diphenyl ether disulfonate, and 1.0% by mass of trisodium phosphate for 15 seconds, nitrogen gas was blown from an air nozzle to remove the excess aqueous solution, thereby forming a coating layer of an amine aqueous solution on the support film. Further impregnated in a 38°C n-decane solution containing 0.2% by mass of TMC, and then left standing for 1 minute under conditions of an atmospheric humidity (relative humidity) of 80% and 25°C, and two fluids (pure water and air) were blown onto the film surface to remove the surface solution. Then, it was washed with pure water at 80°C to obtain a composite semipermeable membrane.

[0185] (Example 2)

[0186] After performing the same operations as in Example 1, it was further impregnated in glycerol at 80°C for 2 minutes, and then impregnated in pure water at 25°C for 24 hours, thereby fabricating a composite semipermeable membrane.

[0187] (Example 3)

[0188] After performing the same operations as in Example 1, it was further impregnated in triethylene glycol at 80°C for 2 minutes, and then impregnated in pure water at 25°C for 24 hours, thereby fabricating a composite semipermeable membrane.

[0189] (Example 4)

[0190] An amine aqueous solution was coated on the support film and left standing for 15 seconds to form a coating layer. Otherwise, a composite semipermeable membrane was fabricated using the same method as in Example 1.

[0191] (Example 5)

[0192] An amine aqueous solution was coated on the support film and left standing for 15 seconds to form a coating layer. Otherwise, a composite semipermeable membrane was fabricated using the same method as in Example 3.

[0193] (Example 6)

[0194] A composite semipermeable membrane was fabricated using 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 fabricated using 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 performing the same operations as in Example 8, the membrane was further immersed in 1,3-butanediol at 80°C for 2 minutes, and then in pure water at 25°C for 24 hours to produce a composite semipermeable membrane.

[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] An aqueous amine solution was coated on the support membrane and allowed to stand for 15 seconds to form a coating layer, and then a composite semipermeable membrane was produced in the same manner as in Example 11.

[0207] (Example 13)

[0208] After performing the same operations as in Example 12, the membrane was further immersed in diethylene glycol at 80°C for 2 minutes, and then in pure water at 25°C for 24 hours to produce a composite semipermeable membrane.

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

[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 performing the same operations as in Example 16, it was further immersed in ethylene glycol at 80 °C for 2 minutes, and then immersed in pure water at 25 °C for 24 hours to fabricate a composite semipermeable membrane.

[0217] (Comparative Example 1)

[0218] A composite semipermeable membrane was fabricated in the same manner as in Example 1, except that the polyfunctional aliphatic amine was piperazine and the atmosphere humidity was changed to 75%.

[0219] (Comparative Example 2)

[0220] After performing the same operations as in Example 1, it was further immersed in glycerol at 80 °C for 2 minutes, and then immersed in pure water at 25 °C for 24 hours to fabricate a composite semipermeable membrane.

[0221] (Comparative Example 3)

[0222] A composite semipermeable membrane was fabricated in the same manner as in Comparative Example 1, except that an aqueous amine solution was coated on the support membrane and allowed to stand for 15 seconds to form a coating layer.

[0223] (Comparative Example 4)

[0224] After performing the same operations as in Comparative Example 3, it was immersed in ethylene glycol at 80 °C for 2 minutes, and then immersed in pure water at 25 °C for 24 hours to fabricate a composite semipermeable membrane.

[0225] (Comparative Example 5)

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

[0227] (Comparative Example 6)

[0228] A composite semipermeable membrane was fabricated in the same manner as in Comparative Example 3, except that the temperature during interfacial polycondensation was changed to 80 °C.

[0229] (Comparative Example 7)

[0230] After performing the same operations as in Comparative Example 3, it was further immersed in a 1.0% by mass aqueous solution of propionic anhydride at 25 °C for 10 minutes, and then immersed in pure water at 25 °C for 24 hours to fabricate a composite semipermeable membrane.

[0231] (Comparative Example 8)

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

[0233] (Comparative Example 9)

[0234] An amine aqueous solution was coated on the support film and allowed to stand for 15 seconds to form a coating layer. Except for this, a composite semipermeable membrane was produced in the same manner as in Comparative Example 8.

[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 90%.

[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 polyfunctional acyl chloride concentration was changed to 0.4% by 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 during interfacial polycondensation was changed to 80°C.

[0243] (Comparative Example 14)

[0244] After performing the same operations as in Comparative Example 11, it was further immersed in triethylene glycol at 80°C for 2 minutes, and then immersed in pure water at 25°C for 24 hours to produce a composite semipermeable membrane.

[0245] (Comparative Example 15)

[0246] After performing the same operations as in Comparative Example 11, it was further immersed in a 1.0% by mass aqueous solution of acetic anhydride at 25°C for 10 minutes, and then immersed in pure water at 25°C for 24 hours to produce a composite semipermeable membrane.

[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 polyfunctional acyl chloride concentration was changed to 0.4% by mass.

[0251] (Comparative Example 18)

[0252] A composite semipermeable membrane was produced using the same method as in Comparative Example 16, except that the temperature during interfacial polycondensation was changed to 80°C.

[0253] (Comparative Example 19)

[0254] After performing the same operations as in Comparative Example 16, it was further immersed in 1,3-butanediol at 80°C for 2 minutes, and then immersed in pure water at 25°C for 24 hours to produce a composite semipermeable membrane.

[0255] (Comparative Example 20)

[0256] After performing the same operations as in Comparative Example 16, it was further immersed in an aqueous solution of 1.0 mass% propionic anhydride at 25°C for 10 minutes, and then immersed in pure water at 25°C for 24 hours to produce a composite semipermeable membrane.

[0257] (Comparative Example 21)

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

[0259] (Comparative Example 22)

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

[0261] (Comparative Example 23)

[0262] A composite semipermeable membrane was produced using the same method as in Comparative Example 21, except that the temperature during interfacial polycondensation was changed to 80°C.

[0263] (Comparative Example 24)

[0264] After performing the same operations as in Comparative Example 21, it was further immersed in diethylene glycol at 80°C for 2 minutes, and then immersed in pure water at 25°C for 24 hours to produce a composite semipermeable membrane.

[0265] (Comparative Example 25)

[0266] After performing the same operations as in Comparative Example 21, it was further immersed in an aqueous solution of 1.0 mass% acetic anhydride at 25°C for 10 minutes, and then immersed in pure water at 25°C for 24 hours to produce a composite semipermeable membrane.

[0267] (Comparative Example 26)

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

[0269] (Comparative Example 27)

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

[0271] (Comparative Example 28)

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

[0273] (Comparative Example 29)

[0274] After performing the same operations as in Comparative Example 26, the composite semipermeable membrane was further immersed in ethylene glycol at 80°C for 2 minutes, and then immersed in pure water at 25°C for 24 hours.

[0275] (Comparative Example 30)

[0276] After performing the same operations as in Comparative Example 26, the composite semipermeable membrane was further immersed in a 1.0% by mass aqueous solution of acetic anhydride at 25°C for 10 minutes, and then immersed in pure water at 25°C for 24 hours.

[0277] (Comparative Example 31)

[0278] A composite semipermeable membrane was prepared 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] The atmosphere humidity was changed to 95%. An amine aqueous solution was coated on the support membrane and allowed to stand for 15 seconds to form a coating layer. Then, it was immersed in ethylene glycol at 80°C for 2 minutes, and then immersed in pure water at 25°C for 24 hours. Otherwise, a composite semipermeable membrane was prepared in the same manner as in Comparative Example 31.

[0281] (Comparative Example 33)

[0282] A composite semipermeable membrane was prepared 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, for the composite semipermeable membranes of Examples 1 to 17 where R1 and R2 are 0.30 nm or more and 2.00 nm or less and satisfy 0.90 ≤ R1 / R2 ≤ 1.10, compared with the composite semipermeable membranes of Comparative Examples 1 to 33, they show high monovalent ion / divalent ion selectivity under acidic conditions.

[0296] From the comparison between Example 4 and 5 and between Example 11 and 12, it can be seen that the composite semipermeable membranes satisfying 0.31 ≤ P2 / P1 ≤ 0.35, P3 / P2 ≤ 0.09, and P4 / P1 ≤ 0.005 show more excellent monovalent ion / divalent ion selectivity.

[0297] From the comparison between Example 1 and Example 3, it can be seen that by satisfying Nb / Nd ≤ 0.80, the monovalent ion / multivalent ion selectivity is improved.

[0298] In addition, from the comparison between Example 8 and Example 9, it can be seen that by making Nb -23 mol / nm 2 or less, the monovalent ion / multivalent ion selectivity is improved.

[0299] For Examples 6 to 17 in which the separation functional layer has a wrinkled structure, it can be seen that compared with Examples 1 to 5 that do not have a wrinkled structure, it can operate at a lower pressure.

[0300] The present invention has been described in detail with reference to a specific mode, but it is obvious that those skilled in the art can make various changes and modifications without departing from the gist and scope of the present invention. It should be noted that this application is based on Japanese Patent Application No. 2022-192377 filed on November 30, 2022, Japanese Patent Application No. 2022-192378 filed on November 30, 2022, and Japanese Patent Application No. 2023-169359 filed on September 29, 2023, and the entire content thereof is incorporated by reference. In addition, all the content cited herein is incorporated by reference as a whole.

[0301] Explanation of Reference Numerals

[0302] 1 Composite semipermeable membrane

[0303] 2 Substrate

[0304] 3 Porous support layer

[0305] 4 Separation functional layer

[0306] 6 Water collecting pipe

[0307] 7 First end plate

[0308] 8 Second end plate

[0309] 11 Feed side flow path material

[0310] 12 Permeate side flow path material

[0311] 20 Cylindrical 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 Fold height

[0318] 202 Thickness of the separation functional layer

[0319] P reference point

[0320] X1 Tangent line to the outer surface of the film passing through the reference point P

[0321] X2 Tangent line to the inner surface of the film parallel to the tangent line X1

[0322] Y0 Normal line passing through the reference point P

[0323] Y1, Y2 Lines parallel to the normal line Y0

[0324] a, b, c, d, e Each region obtained by dividing the separation functional layer into 5 parts

Claims

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

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

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

01.

4. The composite semipermeable membrane according to claim 1 or 2, wherein In the 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 parts from the first surface side toward the second surface side is defined as regions a to e, the amino group density Nb in region b and the amino group density Nd in region d satisfy Nb / Nd ≤ 0.

80.

5. The composite semipermeable membrane according to claim 4, wherein, The Nb is 1.0×10 -23 mol / nm 2 or less.

6. The composite semipermeable membrane according to claim 1 or 2, wherein, When the glucose permeability when a 1000 ppm glucose aqueous solution at 25°C and pH 6.5 permeates under an operating pressure of 0.5 MPa is defined as B, and the sucrose permeability when a 1000 ppm sucrose aqueous solution at 25°C and pH 6.5 permeates under an operating pressure of 0.5 MPa is defined as C, B / C is 10 or more.

7. The composite semipermeable membrane according to claim 1 or 2, wherein, The separation functional layer has a hollow wrinkled structure.

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

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

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