Composite semipermeable membrane

Abstract

The present invention provides a composite semipermeable membrane which can achieve both of high salt removal performance and water permeability under a condition where the pressure is variable. The composite semipermeable membrane according to the present invention is provided with a microporous support membrane and a separation functioning layer containing a crosslinked aromatic polyamide, in which, when cross-sectional surfaces of arbitrarily selected ten areas each having a length of 2.0 μm in the direction along the film surface of the composite semipermeable membrane are observed, the average number density of protrusions each having a height of 1 / 5 or more of the 10-point average surface roughness in the separation functioning layer on each of the cross-sectional surfaces is 13.0 protrusions / μm or more, the average value of the amounts of deformation of the protrusions when the protrusions are pressed in at a force of 5 nN is 2.2 nm or less, and the standard deviation of the amounts of deformation is 1.2 nm or less.

Description

[Technical Field]

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

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

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

[0004] In water desalination plants using reverse osmosis membranes, even higher water permeability is required to further reduce running costs. Furthermore, when using composite semipermeable membranes as reverse osmosis membranes, it is necessary that the above membrane performance can be maintained even under operating conditions such as long-term operation at high pressure or frequent operation and shutdown, which causes pressure fluctuations. To suppress performance changes when operating composite semipermeable membranes, methods have been proposed to suppress the consolidation of porous support membranes (see Patent Documents 2 and 3). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2010 / 096563 [Patent Document 2] Japanese Patent Publication No. 2001-179061 [Patent Document 3] Japanese Patent No. 3385824 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, with conventional composite semipermeable membranes, the water permeability or salt removal performance may decrease under conditions where the pressure on the membrane fluctuates, such as when the system is frequently turned on and off. The object of the present invention is to provide a composite semipermeable membrane that can achieve both high salt removal performance and water permeability even under conditions of fluctuating pressure. [Means for solving the problem]

[0007] To achieve the above objective, the composite semipermeable membrane of the present invention comprises one of the following configurations. [1] A composite semipermeable membrane having a microporous support layer and a separation functional layer provided on the microporous support layer, wherein the separation functional layer has a plurality of protrusions made of a thin film containing a crosslinked aromatic polyamide, and in any 10 cross-sections perpendicular to the membrane surface direction and with a length of 2.0 μm in the membrane surface direction, the average number density of the protrusions, whose height relative to the surface of the support layer is 1 / 5 or more of the 10-point average surface roughness in the separation functional layer, is 13.0 protrusions / μm or more, and the average amount of deformation when the protrusions are pressed with a force of 5 nN is 2.2 nm or less, and the standard deviation of the amount of deformation is 1.2 nm or less. [2] The composite semipermeable membrane according to [1], wherein the average value of the deformation when the protrusion is pressed with a force of 5 nN is 1.7 nm or less. [3] The composite semipermeable membrane according to [1] or [2], wherein the average number density of the protrusions is 15.0 or more per μm. [4] The composite semipermeable film according to any one of [1] to [3], wherein the standard deviation of the amount of deformation is 0.98 nm or less. [5] A composite semipermeable membrane according to any one of [1] to [4], wherein x + y calculated from the amounts of amino groups, carboxyl groups and amide groups in the separation functional layer is 0.70 or less, and x and y are defined as follows. x: 13 The molar ratio of carboxyl groups to amide groups, as measured by 13C solid-state NMR. y: 13 The molar ratio of amino groups to amide groups, as measured by 13C solid-state NMR. [6] The composite semipermeable film according to any one of [1] to [5], wherein the thickness of the thin film in the protrusion is 10 nm or more and 20 nm or less. [7] The weight of the separation functional layer is 0.10 g / m 2 The above describes any one of the composite semipermeable membranes described in [1] to [6]. [8] The composite semipermeable membrane according to any one of [1] to [7], wherein the separation functional layer is a crosslinked whole aromatic polyamide.

[0008] Furthermore, the method for producing a composite semipermeable membrane according to the present invention comprises any of the following configurations. [9] A method for producing a composite semipermeable membrane according to any one of [1] to [8] above, comprising the step of forming a crosslinked polyamide functional layer by heating after performing interfacial polycondensation on the surface of a support film containing a microporous support layer, using a polyfunctional aromatic amine solution in which the sum of the dissolved amount of oxygen a and the dissolved amount of carbon dioxide b in the solution, a+b, is 9 mg / L or more when the solution temperature is 25°C, and a solution in which a polyfunctional aromatic acid halide is dissolved in an organic solvent.

[10] The method for producing a composite semipermeable membrane according to [9], wherein the ratio of the amount of dissolved material b to the amount of dissolved material a, b / a, is 0.90 or more.

[0009] Furthermore, the water treatment system of the present invention comprises the following configurations.

[11] A water treatment system that separates supply water into concentrated water and fresh water using a composite semipermeable membrane described in any one of [1] to [8] above. [Effects of the Invention]

[0010] According to the present invention, a composite semipermeable membrane that achieves both high salt removal performance and water permeability under conditions where operation and stoppage are frequently repeated and pressure fluctuates is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] [Figure 1] Fig. 1 is a cross-sectional view schematically showing the structure of a composite semipermeable membrane, where (a) of Fig. 1 is a schematic cross-sectional view of the composite semipermeable membrane, (b) of Fig. 1 is an enlarged schematic view of a separation functional layer, and (c) of Fig. 1 is an enlarged cross-sectional view schematically showing the pleated structure of the separation functional layer. [Figure 2] Fig. 2 is a schematic view showing the pleated structure of a thin film in a separation functional layer. [Figure 3] Fig. 3 is a diagram schematically showing a method for measuring the amount of deformation of a convex portion of a separation functional layer. MODE FOR CARRYING OUT THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited thereto in any way. In this specification, "mass" is synonymous with "weight".

[0013] 1. Composite Semipermeable Membrane Fig. 1 shows the structure of a composite semipermeable membrane 1 according to the present embodiment. As shown in Fig. 1, the composite semipermeable membrane 1 according to the present invention comprises a microporous support layer 3 and a separation functional layer 4 provided on the microporous support layer 3.

[0014] The microporous support layer 3 may be formed on a base material 2, and the composite semipermeable membrane 1 according to the embodiment of the present invention may have a support membrane comprising the base material 2 and the microporous support layer 3 formed on the base material 2. The separation functional layer 4 substantially has separation performance, while the microporous support layer 3 substantially has no separation performance for ions or the like, and can impart strength to the separation functional layer 4.

[0015] (1-1) Support Membrane The support film may comprise a base material 2 and a microporous support layer 3, or it may not have a base material 2 and consist only of the microporous support layer 3. In other words, the microporous support layer 3 may be the support film.

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

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

[0018] As the material for the microporous support layer 3, homopolymers or copolymers such as polysulfone (hereinafter also referred to as "PSf"), polyethersulfone, polyamide, polyester, cellulose polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene oxide can be used alone or in blends. Here, examples of cellulose polymers include cellulose acetate and cellulose nitrate, and examples of vinyl polymers include polyethylene, polypropylene, polyvinyl chloride, and polyacrylonitrile. Among these, homopolymers or copolymers such as PSf, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, and polyphenylene sulfide sulfone are preferred, with cellulose acetate, PSf, polyphenylene sulfide sulfone, or polyphenylene sulfone being more preferred, and PSf being particularly preferred because it has high chemical, mechanical, and thermal stability and is easy to mold.

[0019] Weight-average molecular weight of PSf (hereinafter referred to as "M") w It is also called ". ) is preferably 10,000 to 200,000, and more preferably 15,000 to 100,000. PSf's M w When the ratio is 10000 or more, desirable mechanical strength and heat resistance can be obtained as a microporous support layer. On the other hand, the M of PSf w By keeping the value below 200,000, the viscosity of the microporous support layer stock solution falls within an appropriate range, enabling good moldability.

[0020] The thickness of the substrate and the microporous support layer affects the strength of the composite semipermeable membrane and the packing density when it is used as an element. To obtain good mechanical strength and packing density, the total thickness of the substrate and the microporous support layer is preferably 30 to 300 μm, and more preferably 100 to 220 μm. Furthermore, the thickness of the microporous support layer is preferably 20 to 100 μm. The thickness of the substrate and the microporous support layer can be determined by calculating the average value of 20 thicknesses measured at 20 μm intervals in a direction perpendicular to the thickness direction (the surface direction of the membrane) during cross-sectional observation.

[0021] (1-2) Separation functional layer The separation function layer 4 is responsible for the solute separation function and contains a cross-linked aromatic polyamide. It is preferable that the separation function layer 4 has a cross-linked aromatic polyamide as its main component.

[0022] "Mainly composed of cross-linked aromatic polyamide" means that the proportion of cross-linked aromatic polyamide in the separation functional layer is 50% by mass or more. Preferably, the proportion of cross-linked aromatic polyamide in the separation functional layer is 80% by mass or more, more preferably 90% by mass or more, and even more preferably the separation functional layer is formed substantially solely of cross-linked aromatic polyamide. "Formally formed solely of cross-linked aromatic polyamide" means that cross-linked aromatic polyamide accounts for 99% by mass or more of the separation functional layer.

[0023] Examples of crosslinked aromatic polyamides include aramid compounds, but they may also contain non-aromatic moieties within their molecular structure. However, crosslinked whole aromatic polyamides are more preferred in terms of rigidity, chemical stability, and resistance to operating pressure. Crosslinked aromatic polyamides can be formed by interfacial polycondensation of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide. Here, it is preferable that at least one of the polyfunctional aromatic amine and the polyfunctional aromatic acid halide contains a trifunctional or higher compound. The separation functional layer in the present invention may hereinafter be referred to as the polyamide separation functional layer.

[0024] A polyfunctional aromatic amine is an aromatic amine that has two or more amino groups of at least one type (primary amino group and secondary amino group) in a single molecule, and at least one of these amino groups is a primary amino group.

[0025] Examples of polyfunctional aromatic amines include polyfunctional aromatic amines in which two amino groups are bonded to the aromatic ring in an ortho, meta, or para position, such as o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m-diaminopyridine, and p-diaminopyridine; and polyfunctional aromatic amines such as 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, and 4-aminobenzylamine.

[0026] In particular, considering the selective separation, permeability, and heat resistance of the membrane, m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene are preferably used. Among these, m-phenylenediamine (hereinafter also referred to as "m-PDA") is more preferable due to its availability and ease of handling. These polyfunctional aromatic amines may be used individually or in combination of two or more.

[0027] A polyfunctional aromatic acid halide is an aromatic acid halide having at least two halogenated carbonyl groups in one molecule. For example, trifunctional acid halides include trimesic acid chloride, and difunctional acid halides include biphenyl dicarboxylic acid dichloride, azobenzene dicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, and naphthalenedicarboxylic acid chloride.

[0028] Considering the reactivity with polyfunctional aromatic amines, polyfunctional aromatic acid halides are preferably polyfunctional aromatic acid chlorides, and considering the selective separation properties and heat resistance of the film, polyfunctional aromatic acid chlorides having 2 to 4 carbonyl chloride groups in one molecule are more preferable.

[0029] The shape and thickness of the separation functional layer affect the separation and permeation performance. As shown in Figure 1(b), the separation functional layer 4 includes a thin film 41 that forms a pleated shape with multiple protrusions 42 and recesses 43, and in the layer made of the thin film 41, protrusions are formed by adjacent protrusions 42 and recesses 43. By having a pleated thin film in the separation functional layer, the specific surface area of ​​the separation functional layer can be significantly improved compared to a planar structure. As a result, while maintaining separation performance, the permeation performance can be improved in proportion to the surface area of ​​the separation functional layer. As shown in Figure 1(c), the inside of the protrusions 42 (between the thin film 41 and the microporous support layer 3) is a void. Protrusions and recesses will be explained using Figure 2. "Protrusions" and "recesses" refer to the parts that are relatively protruding and recessed in the thin film, and in particular, the part above the reference line A described later is called a protrusion, and the part below is called a recess. "Protrusion" refers to the distance from the bottom of a recess to the bottom of the adjacent recess, that is, from one protrusion to the bottoms of the recesses on both sides of it. Furthermore, in the following, a protrusion refers to a projection whose height, relative to the surface of the support layer, is one-fifth or more of the 10-point average surface roughness of the thin film.

[0030] The inventors have found that when the average value of the deformation amount when the protrusion, specifically the convex portion forming the protrusion, is pressed with a force of 5 nN in pure water at 25°C is 2.2 nm or less, and the standard deviation of the deformation amount is 1.2 nm or less, stable film performance can be obtained even under conditions where the pressure fluctuates due to frequent operation and stopping.

[0031] The deformation of the aforementioned protrusions can be calculated as follows: The surface of the separation functional layer is observed using an atomic force microscope (AFM) in pure water at 25°C, and any two regions within a 2 μm square area are selected. Ten protrusions, specifically convex parts, are selected from these two regions, for a total of 20 points. Furthermore, a point within a circular region with a diameter of 100 nm centered on the vertex of each selected protrusion (convex part) is pressed with a force of 5 nN to obtain the deformation amount. The arithmetic mean of the deformation amounts obtained for the 20 points is taken as the average deformation amount.

[0032] The deformation of the protrusion (convex part) can be measured using the tapping mode of an atomic force microscope (AFM). Specifically, as shown in Figure 3, on a force curve with the distance between the tip and sample (separation) on the horizontal axis and the load on the vertical axis, point A is the point before the cantilever is brought close to the sample, point B is the moment the load rises, point C is the point where the load is 90% of the maximum load, and point D is the point of maximum load. The deformation is defined as the distance between C and D. Note that the force curve used is the one taken when the cantilever is brought close to the sample.

[0033] For atomic force microscopy, for example, the Dimension FastScan manufactured by Bruker AXS can be used. With the included attachment, observation underwater is possible. In this case, a conical (pyramid-shaped) cantilever probe should be used. Calibration must be performed before using the cantilever. First, the deflection sensitivity of the cantilever is measured using a material with sufficient hardness. Silicon wafers or sapphire can be used as materials with sufficient hardness. Next, the spring constant of the cantilever is measured using thermal tuning. Calibration improves the accuracy of the measurement.

[0034] The amount of deformation of the protrusions (bumps) in the separation functional layer reflects the density of the pore structure of the separation functional layer. Specifically, the more coarse the pore structure of the separation functional layer, the greater the deformation, and the denser the pore structure, the smaller the deformation. An average deformation of 2.2 nm or less indicates that the separation functional layer has a sufficiently dense structure, making it less likely for compaction to occur even when localized high pressure is applied during changes in operating pressure. An average deformation of 1.7 nm or less is more preferable. On the other hand, if the deformation is too small, the functional layer is too dense, resulting in insufficient water permeability, and the low flexibility reduces the physical structural stability when the membrane is subjected to impacts such as bending, folding, or shaking, making it more susceptible to pinhole defects. Therefore, an average deformation of 0.5 nm or more is preferable.

[0035] Furthermore, even if the average value of the deformation is 2.2 nm or less, if some parts are coarse and some parts are dense, defects will occur in the coarse parts when high pressure is applied locally, and the salt removal rate is likely to decrease. It is preferable that the standard deviation of the deformation is 1.2 nm or less, as this reduces excessively coarse and dense parts. More preferably, the standard deviation of the deformation is 0.98 nm or less. On the other hand, in order to achieve both mechanical strength and elasticity in the separation functional layer, it is preferable that the standard deviation of the deformation is 0.1 nm or more.

[0036] Thin film protrusions can be observed using electron microscopes such as scanning electron microscopes (SEM, FE-SEM) and transmission electron microscopes (TEM). First, to prepare ultrathin sections for TEM, the sample is embedded in a water-soluble polymer. Any water-soluble polymer that can maintain the shape of the sample is acceptable, such as polyvinyl alcohol (PVA). Next, to facilitate cross-sectional observation, the sample is stained with osmium tetroxide (OsO4), and then cut with an ultramicrotome to prepare ultrathin sections. Cross-sectional images of the obtained ultrathin sections are taken using an electron microscope. The observation magnification can be appropriately determined depending on the thickness of the separation functional layer, but to observe the cross-sectional shape of the separation functional layer and to avoid localized measurements, an observation magnification of 50,000 to 100,000 times is recommended when the thickness of the separation functional layer is about 10 to 100 nm.

[0037] The 10-point average surface roughness of a thin film can be obtained by the following method. An electron microscope is used to observe a cross-section perpendicular to the film surface. A magnification of 10,000 to 100,000 times is preferred. As shown in Figures 1(a) and (b), the surface of the composite semipermeable film (indicated by the symbol "1" in Figure 1) appears as a curve in the obtained cross-sectional image. A roughness curve is determined from this curve according to ISO 4287:1997. Similarly, an average line of the above roughness curve is obtained according to ISO 4287:1997. The average line is a straight line drawn such that the sum of the areas enclosed by the average line and the roughness curve is equal above and below the average line.

[0038] In the resulting 2.0 μm wide image parallel to the mean line, as shown in Figure 2, the mean line is used as the reference line A. For the five convex areas from the highest to the fifth highest point, the heights H1 to H5 from the reference line A (distance from the reference line A to the apex of the convex area) are measured, and the average value is calculated. Similarly, for the five concave areas from the deepest to the fifth deepest point, the depths D1 to D5 (distance from the reference line A to the apex of the concave area) are measured, and the average value is calculated. The sum of these two average values ​​is the 10-point average surface roughness. The apex is defined as the point in a convex or concave area where the distance from the reference line is maximum.

[0039] The protrusion height is calculated as follows: For protrusions that are at least one-fifth of the average surface roughness of the 10 points in 10 cross-sections with a width of 2.0 μm parallel to the average line mentioned above, the protrusion height Ph is calculated as the sum of the average d of the depths d1 and d2 at both ends of the protrusion (distance from the reference line to the apex of the concave part) and the height h of the convex part (distance from the reference line to the apex of the convex part).

[0040] The height of the protrusions is preferably 70 nm or more. Furthermore, the height of the protrusions is preferably 1000 nm or less, and more preferably 800 nm or less. A protrusion height of 70 nm or more allows for easy acquisition of a composite semipermeable membrane with sufficient water permeability. Additionally, a protrusion height of 1000 nm or less ensures that the protrusions do not collapse even when the composite semipermeable membrane is operated under high pressure, resulting in stable membrane performance.

[0041] The average thickness of the thin film in the protrusions can be measured by TEM. The preparation of ultrathin sections for TEM is as described above. The cross-sections of the obtained ultrathin sections are photographed by TEM. The observation magnification can be appropriately determined based on the thickness of the separation functional layer. The obtained cross-sectional images can be analyzed using image analysis software.

[0042] The average thickness T of the thin film described above is preferably between 10 nm and 20 nm. An average T of 10 nm or more provides good separation performance and improved resistance to physical forces. Furthermore, an average T of 20 nm or less allows for the creation of a composite semipermeable film with good transmission performance. An average thickness T of 15 nm or less is more preferable.

[0043] The average number density of protrusions on the separation functional layer is 13.0 protrusions / μm or more, more preferably 15.0 protrusions / μm or more. Further, the average number density of protrusions on the separation functional layer is preferably 50 protrusions / μm or less, more preferably 40 protrusions / μm or less. When the average number density of protrusions is 13.0 protrusions / μm or more, the composite semipermeable membrane can obtain sufficient water permeability, furthermore, deformation of the protrusions during pressurization can be suppressed, and stable membrane performance can be obtained. In addition, when the number density of protrusions is 50 protrusions / μm or less, the fold structure can grow sufficiently, and a composite semipermeable membrane having desired water permeability can be easily obtained. The average number density of protrusions can be measured from the number of protrusions having a height of 1 / 5 or more of the 10-point average surface roughness described above in each cross-section when observing 10 cross-sections each having a width of 2.0 μm described above.

[0044] The polyamide separation functional layer has amide groups derived from polymerization of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide, and amino groups and carboxy groups derived from unreacted functional groups.

[0045] When x represents the molar ratio of carboxy groups to amide groups in the separation functional layer (carboxy groups / amide groups), and y represents the molar ratio of amino groups to amide groups in the separation functional layer (amino groups / amide groups), x+y is preferably 0.70 or less. More preferably, x+y is 0.60 or less. It is presumed that when x+y is small, the molar ratio of amide groups to the total amount of amino groups and carboxy groups is large, and the polymer has a dense structure, so that compaction is less likely to occur even when a local high pressure is applied during a change in operating pressure.

[0046] The molar ratio of carboxy groups, amino groups, and amide groups in the separation functional layer is determined by the 13 13C solid-state NMR measurement. Specifically, 5 m of the composite semipermeable membrane 2 is peeled off from the substrate to obtain a polyamide separation functional layer and a microporous support layer, then the microporous support layer is dissolved and removed to obtain the polyamide separation functional layer. The obtained polyamide separation functional layer is subjected to DD / MAS- 13By performing measurements using 1C solid-state NMR, the ratios can be calculated by comparing the integral values ​​of the carbon peaks of each functional group or the carbon peaks to which each functional group is attached.

[0047] The weight of the separation functional layer of the present invention is 0.10 g / m². 2 Preferably, it is 0.11 g / m² or more. 2 More preferably 0.12 g / m 2 That's all. The weight of the separation layer is 0.10 g / m². 2 If the above conditions are met, there will be a sufficient amount of polyamide constituting the separation functional layer, improving durability against physical external forces and enabling stable membrane performance even under conditions of fluctuating pressure.

[0048] To prevent the substance to be separated from penetrating into the interior of the composite semipermeable membrane, the separation functional layer is preferably located on the surface side of the composite semipermeable membrane, and more preferably on the primary side of filtration.

[0049] 2. Method for manufacturing composite semipermeable membranes The method for producing the composite semipermeable membrane of the present invention is not particularly limited as long as a composite semipermeable membrane satisfying the desired characteristics described above can be obtained, but for example, it can be produced by the following method.

[0050] (2-1) Formation of the support film For the method of forming the support film, known methods can be suitably used. The following description will take the case where PSf is used as the material for the microporous support layer as an example.

[0051] First, PSf is dissolved in a suitable solvent to prepare a microporous support layer stock solution. A suitable solvent for PSf is, for example, N,N-dimethylformamide (hereinafter referred to as "DMF").

[0052] The concentration of PSf in the microporous support layer stock solution is preferably 10-25% by mass, and more preferably 14-23% by mass. The higher the polymer concentration (i.e., solid content concentration) in the polymer solution, the higher the number density of particles on the surface of the microporous support layer, resulting in a microporous support layer with a higher number density of particles. As a result, the number density of protrusions in the separation function layer also increases, enabling the creation of a protrusion structure that can withstand pressure fluctuations. Furthermore, by keeping the polymer concentration low enough so that the monomer supply rate during separation function layer formation does not become too low, the surface pore diameter of the microporous support layer is adjusted, and protrusions of appropriate height are formed during separation function layer formation. By keeping the concentration of PSf in the microporous support layer stock solution within this range, it is possible to achieve both strength and permeability in the resulting microporous support layer. The preferred range of material concentration in the microporous support layer stock solution can be appropriately adjusted depending on the material used, the good solvent, etc.

[0053] Next, the resulting microporous support layer stock solution is applied to the substrate surface and immersed in a solidification bath containing a non-solvent of PSf.

[0054] As a non-solvent for PSf included in the coagulation bath, water is preferred, for example. By bringing the microporous support layer stock solution applied to the substrate surface into contact with a coagulation bath containing a non-solvent for PSf, the microporous support layer stock solution coagulates due to non-solvent-induced phase separation, and a support film with a microporous support layer formed on the substrate surface can be obtained.

[0055] The coagulation bath may consist solely of non-solvent PSf, but it may also contain a good solvent of PSf to the extent that it can coagulate the microporous support layer stock solution. The resulting support film may be washed before the formation of the separation functional layer to remove any remaining solvent in the film.

[0056] (2-2) Polymerization process of the separation functional layer Regarding the formation method of a separation functional layer containing crosslinked aromatic polyamide, we will describe, as an example, a method in which a polyfunctional aromatic amine and a polyfunctional aromatic acid halide are polymerized and solidified on the support film obtained in "(2-1) Film Formation of Support Film". From the viewpoint of productivity and performance, the polymerization method will be performed by interfacial polymerization. The interfacial polymerization process will be described below.

[0057] The present invention provides a method for producing a composite semipermeable membrane, comprising the steps of using a polyfunctional aromatic amine solution in which the sum of dissolved oxygen a and dissolved carbon dioxide b in the solution, a+b, is 9 mg / L or more when the solution temperature is 25°C, and a solution in which a polyfunctional aromatic acid halide is dissolved in an organic solvent, performing interfacial polycondensation on the surface of a support film containing a microporous support layer, and then heating to form a crosslinked polyamide functional layer.

[0058] More specifically, the interfacial polymerization step comprises: (a) contacting a support film with an amine solution containing a polyfunctional aromatic amine, wherein the sum of the dissolved oxygen amount a and the dissolved carbon dioxide amount b in the solution, a+b, at a solution temperature of 25°C is 9 mg / L or more; (b) contacting the support film that has been contacted with the amine solution containing the polyfunctional aromatic amine with an organic solvent solution containing a polyfunctional aromatic acid halide; (c) heating the film after contact with the amine and the acid halide; and (d) washing the composite semipermeable film formed in step (c), which has a crosslinked polyamide functional layer on the support film, with hot water.

[0059] Examples of microporous support layers, polyfunctional aromatic amines, and polyfunctional aromatic acid halides include those mentioned above, and the same applies to preferred materials.

[0060] In step (a), the concentration of the polyfunctional aromatic amine in the polyfunctional aromatic amine solution is preferably in the range of 0.1% by weight or more and 20% by weight or less, and more preferably in the range of 0.5% by weight or more and 15% by weight or less. A concentration of the polyfunctional aromatic amine within this range allows for sufficient solute removal performance and water permeability. Two or more types of polyfunctional aromatic amines may be used.

[0061] The polyfunctional aromatic amine solution may contain surfactants, organic solvents, alkaline compounds, and antioxidants, as long as they do not interfere with the reaction between the polyfunctional aromatic amine and the polyfunctional aromatic acid halide. Surfactants improve the wettability of the support film surface and reduce the interfacial tension between the polyfunctional aromatic amine solution and the nonpolar solvent. Organic solvents can act as catalysts for interfacial polycondensation reactions, and their addition may allow the reaction to proceed more efficiently.

[0062] The polyfunctional aromatic amine solution should be used with a gas content of 9 mg / L or more, where a (mg / L) is the dissolved oxygen content and b (mg / L) is the dissolved carbon dioxide content at a solution temperature of 25°C. Preferably, a+b is 15 mg / L or more, more preferably 32 mg / L or more, and even more preferably 100 mg / L or more. Methods for adjusting the amount of dissolved gas include contacting the solution with a gas in a predetermined mixing ratio, dissolving the gas by pressurization, and using a commercially available solution (e.g., carbonated water) in which the gas has been pre-dissolved. If the reaction between the polyfunctional aromatic amine and the polyfunctional aromatic acid halide is not interfered with, the gas may be generated using a chemical reaction. When using a commercially available solution in which the gas has been pre-dissolved, the dissolved amount may be reduced to a predetermined amount by degassing using ultrasound or a vacuum pump. These methods can be arbitrarily selected.

[0063] Normally, the heating process in step (c) described later causes the functional layer to become denser, reducing the average deformation amount of the protrusions (bumps) and satisfying the requirement of an average deformation amount of 2.2 nm or less. However, at the same time, the coalescence of the protrusions also progresses, reducing the number density of the protrusions and failing to satisfy the requirement of an average number density of 13.0 particles / μm or more. On the other hand, as the dissolved gas amount a+b increases, the number of starting points for protrusion formation increases due to the generation of microbubbles described later, and the average number density of protrusions remains 13.0 particles / μm or more even after the heating process. As the dissolved gas amount a+b increases, it enters areas where molecules become dense during interfacial polymerization, inhibiting aggregation and preventing localized reaction progression, thereby suppressing the formation of coarse and overcrowded areas. As a result, the variation in the deformation amount decreases and the standard deviation becomes 1.2 nm or less. On the other hand, while it is possible to increase the dissolved gas amount by injecting gas under pressure, if the dissolved gas amount is too high, defects are more likely to occur in the protrusions and the removal rate will decrease. Therefore, it is preferable that the dissolved gas amount a + b is 10,000 or less.

[0064] In step (a), it is preferable to bring the polyfunctional aromatic amine solution into uniform and continuous contact with the support film. Specifically, examples include coating the support film with the polyfunctional aromatic amine solution or immersing the support film in the polyfunctional aromatic amine solution. The contact time between the support film and the polyfunctional aromatic amine solution is preferably 1 second to 10 minutes, and more preferably 3 seconds to 3 minutes.

[0065] After contacting the polyfunctional aromatic amine solution with the support film, it is preferable to thoroughly drain the liquid so that no droplets remain on the support film. Thorough draining prevents residual droplets from becoming membrane defects and reducing separation performance after the formation of the composite semipermeable membrane. Methods for draining include, for example, the method described in Japanese Patent Publication No. 2-78428, which involves grasping the support film vertically after contact with the aqueous solution to allow excess aqueous solution to flow naturally, or the method of forcibly draining the liquid by blowing a stream of air such as nitrogen from an air nozzle. Alternatively, after draining, the film surface can be dried to remove some of the water from the aqueous solution.

[0066] In step (b), examples of polyfunctional aromatic acid halides include trimesic acid chloride (hereinafter referred to as "TMC"), biphenyldicarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalenedicarboxylic acid chloride, and 2,5-franzicarboxylic acid chloride. The polyfunctional aromatic acid halides may be used individually or in combination of two or more types.

[0067] The organic solvent is preferably immiscible with water, dissolves polyfunctional aromatic acid halides, does not damage the support film, and is inert to polyfunctional aromatic amines and polyfunctional aromatic acid halides. Examples of organic solvents include hydrocarbon compounds such as n-nonane, n-decane, n-undecane, n-dodecane, isooctane, isodecane, and isododecane, as well as mixed solvents thereof.

[0068] The concentration of the polyfunctional aromatic acid halide in the organic solvent solution is preferably 0.01 to 10% by mass, more preferably 0.02 to 4% by mass, and even more preferably 0.03 to 2% by mass. A concentration of 0.01% by mass or higher allows polymerization to proceed at a sufficient reaction rate. On the other hand, a concentration of 10% by mass or lower can suppress the occurrence of side reactions during polymerization. Furthermore, the organic solvent solution may contain compounds such as surfactants as needed, as long as they do not inhibit polymerization.

[0069] The method for contacting the support film, which is in contact with the polyfunctional aromatic amine solution, with the organic solvent solution of the polyfunctional aromatic acid halide can be the same as the method for coating the support film with the polyfunctional aromatic amine solution.

[0070] The temperature at which the microporous support layer, which has been contacted with an aqueous solution containing a polyfunctional aromatic amine, is brought into contact with the solution containing a polyfunctional aromatic acid halide is preferably 25 to 60°C, and more preferably 30 to 55°C. Below 25°C, there is a risk that sufficient protrusion height cannot be obtained. As the temperature increases, the solubility of the gas decreases, and the gas that cannot be dissolved is generated as microbubbles, increasing the number of starting points for protrusion formation. However, above 60°C, the reaction is too fast, leading to an increase in the thin film thickness of the protrusions and the unification of the protrusions, in which case sufficient water permeability cannot be obtained. By bringing the contact temperature to 25 to 60°C, the number of protrusions increases and the surface area of ​​the reaction interface increases substantially, so the amount of polyamide can be increased and the increase in film thickness T can be suppressed. The method of applying temperature may be to heat the support film, or to contact it with a heated organic solvent solution of the polyfunctional acid halide. The temperature of the film surface immediately after contact between the polyfunctional aromatic amine solution and the polyfunctional acid halide solution can be measured with a non-contact thermometer such as a radiation thermometer.

[0071] In step (c), after contacting the support film with an organic solvent solution of polyfunctional aromatic acid chloride, the support film is heat-treated. When heat-treating, the heating temperature is preferably 50 to 180°C, more preferably 60 to 160°C, and even more preferably 80 to 150°C. A synergistic effect is obtained in which the interfacial polymerization reaction is promoted by the increase in surface area due to heating and the microbubbles generated by heating, the interfacial polymerization is promoted by the concentration of polyfunctional aromatic acid halides during interfacial polymerization, and the reaction efficiency is improved by the improved mobility of monomers and oligomers. Therefore, the amount of polyamide in the separation functional layer is 0.10 g / m². 2 As the above occurs, the amount of amide groups increases and x+y becomes 0.70 or less. The functional layer becomes denser, and the average value of the above deformation amount becomes 2.2 nm or less. If the heating temperature is too high, the protrusions coalesce, the number density decreases and the film becomes thicker, so good water permeability cannot be obtained. When microbubbles generated by heating rise to the surface, flow occurs in order to carry the surrounding liquid, dispersing monomers in the liquid and promoting the reaction, which further densifies the functional layer and prevents the progress of localized reactions, so the average value of the above deformation amount becomes even smaller and the variation in the deformation amount also becomes even smaller.

[0072] In this case, the larger the amount of dissolved gas a+b in the amine solution at a solution temperature of 25°C, the greater the amount of gas that cannot be dissolved at the contact temperature, and this effect is amplified.

[0073] Furthermore, since the difference in gas solubility between 25°C and high temperatures is greater for carbon dioxide than for oxygen, it is preferable that the ratio b / a (the amount of dissolved carbon dioxide b to the amount of dissolved oxygen a in the amine solution) is 0.9 or higher, as this further enhances the above-mentioned effects. The ratio b / a is more preferably 1.0 or higher.

[0074] After the reaction and heating, it is preferable to remove the organic solvent by draining the organic solvent solution. For example, the removal of the organic solvent can be done by grasping the film vertically and allowing the excess organic solvent to flow down naturally, by blowing air with a blower to dry out the organic solvent, or by using a mixed fluid of water and air to remove the excess organic solvent.

[0075] In step (d), the composite semipermeable membrane from which the organic solvent has been removed is washed with hot water. The temperature of the hot water is preferably 40 to 95°C, and more preferably 60 to 95°C. A hot water temperature of 40°C or higher allows for sufficient removal of unreacted substances and oligomers remaining in the membrane. On the other hand, a hot water temperature of 95°C or lower prevents excessive shrinkage of the composite semipermeable membrane, thus maintaining good permeability. The preferred range of the hot water temperature can be appropriately adjusted depending on the polyfunctional aromatic amine or polyfunctional aromatic acid chloride used.

[0076] 3. Use of composite semipermeable membranes Composite semipermeable membranes can be used in water treatment systems that separate feedwater into permeate (freshwater) and concentrated water. Specifically, the composite semipermeable membrane is wound around a cylindrical water collection pipe with numerous perforations, along with a water supply channel material such as a plastic net, a permeable water channel material such as tricot, and a film to enhance pressure resistance as needed, and is suitably used as a spiral-type composite semipermeable membrane element. Furthermore, these elements can be connected in series or parallel and housed in a pressure vessel to form a composite semipermeable membrane module.

[0077] Furthermore, the composite semipermeable membranes, their elements, and modules can be combined with pumps that supply water to them, and devices that pre-treat the supply water to constitute a fluid separation system. By using this separation system, the supply water can be separated into permeate (such as drinking water) and concentrated water that did not permeate the membrane, thereby obtaining water suitable for the purpose.

[0078] Examples of feedwater treated by the composite semipermeable membrane according to the present invention include liquid mixtures containing 500 mg / L to 100 g / L of TDS (Total Dissolved Solids), such as seawater, brine, and wastewater. Generally, TDS refers to the total amount of dissolved solids and is expressed as "mass ÷ volume" or "weight ratio". According to the definition, it can be calculated from the weight of the residue after evaporating a solution filtered through a 0.45 micron filter at a temperature of 39.5 to 40.5°C, but a simpler method is to convert it from the practical salinity (S).

[0079] While a higher operating pressure for the fluid separation device improves the solute removal rate, it also increases the energy required for operation. Considering the durability of the composite semipermeable membrane, the operating pressure when the treated water is permeated through the composite semipermeable membrane is preferably 0.5 to 10 MPa. As the feedwater temperature increases, the solute removal rate decreases, but as it decreases, the membrane permeation flux also decreases, so a temperature of 5 to 45°C is preferable. Furthermore, if the feedwater pH is high, there is a risk of scale formation, such as magnesium, in the case of feedwater with high solute concentrations such as seawater, and there is a concern about membrane deterioration due to high pH operation, so operation in the neutral range is preferable. [Examples]

[0080] The present invention will be described below with reference to specific examples, but the present invention is not limited in any way by these examples.

[0081] The physical properties of the composite semipermeable membrane of the present invention were measured by the following method.

[0082] (Deformation of protrusions (convex parts), standard deviation) A composite semipermeable membrane, wet with pure water, was cut into 1 cm squares and fixed to a sample stage using adhesive so that the separation functional layer surface was facing upwards to prepare the measurement sample. Next, the measurement sample was fixed to the measurement stage using a magnet, pure water was dropped onto the separation functional layer, and the surface was observed using an atomic force microscope (AFM). Ten force curves of the convex parts were extracted from the obtained images, and the amount of deformation was analyzed. This operation was performed for two fields of view, and the deformation amounts of a total of 20 points were analyzed, and the mean, maximum, and standard deviation were calculated. The specific measurement conditions are as follows. • Equipment: Bruker AXS Dimension FastScan • Scanning mode: Underwater nanomechanical mapping • Probe: Silicon cantilever (Bruker AXS ScanAsyst-Fluid). The cantilever was calibrated before measurement. • Maximum load: 5.0 nN Scanning area: 2μm × 2μm • Scanning speed: 0.5Hz • Pixel count: 256 x 256 • Measurement conditions: in pure water ·Measurement temperature: 25℃

[0083] (Quantitative determination of carboxyl groups, amino groups, and amide groups, and weight of polyamide) Composite semipermeable membrane 5m 2The substrate was physically peeled off, and the microporous support layer and separation functional layer were recovered. After drying by standing for 24 hours, the layers were added in small amounts to a beaker containing dichloromethane and stirred to dissolve the polymer constituting the microporous support layer. Insoluble matter in the beaker was collected using filter paper. This insoluble matter was added to the beaker containing dichloromethane and stirred, and the insoluble matter in the beaker was collected again. This process was repeated until no elution of the polymer forming the microporous support layer could be detected in the dichloromethane solution. The recovered separation functional layer was dried in a vacuum dryer to remove any remaining dichloromethane. The weight of the obtained separation functional layer was measured for the area used (5 m²). 2 By dividing by , the polyamide weight per unit area was obtained. Furthermore, the separation functional layer was converted into a powder sample by freeze-grinding, sealed in a sample tube used for solid-state NMR measurement, and subjected to CP / MAS and DD / MAS methods. 13 Solid-state NMR measurements were performed. 13 For 13C solid-state NMR measurements, a Chemagnetics CMX-300 was used. An example of the measurement conditions is shown below. Reference substance: Polydimethylsiloxane (Internal standard: 1.56 ppm) Sample rotation speed: 10.5 kHz Pulse repetition time: 100s From the obtained spectrum, peak splitting was performed for each peak originating from the carbon atom to which each functional group is bonded, and the functional group ratio was quantified from the area of ​​the split peaks.

[0084] (Average value of protrusion thickness T, number density of protrusions) A composite semipermeable membrane was cut into 3cm x 3cm squares and washed with distilled water at 25°C for 24 hours. After washing, the composite semipermeable membrane was embedded in epoxy resin and stained with osmium tetroxide to prepare the measurement sample. The obtained sample was observed using a scanning transmission electron microscope (Hitachi, Ltd.; HD2700) with the thin film cross-section as the observation plane. Using images acquired at a magnification of 1,000,000x, the shortest distance from a point on the outer surface of the thin film to the inner surface was defined as the thickness T of the thin film. For 10 randomly selected protrusions, analysis was performed on 5 points for each protrusion, and the average value of these analyses was taken as the average thickness T of the thin film. Furthermore, the number of folds and protrusions was counted, and the average number density was calculated.

[0085] (Method for calculating dissolved gas volume) Oxygen and carbon dioxide were measured immediately after the preparation of the amine aqueous solution using a commercially available DO meter and dissolved carbon dioxide concentration meter.

[0086] (Starting and stopping operations under high temperature and pressure) A composite semipermeable membrane was supplied with evaluation raw water (NaCl concentration 3.2%) adjusted to a temperature of 40°C and pH 6.5 at an operating pressure of 7.0 MPa. This was followed by 1000 on / off tests, each involving 5 minutes of operation followed by 5 minutes of shutdown. After this, the membrane was filtered. Subsequently, the performance of the composite semipermeable membrane was evaluated using the method described below.

[0087] (NaCl transmittance) Evaluation raw water (NaCl concentration 3.2%) adjusted to a temperature of 25°C and pH 6.5 was supplied to a composite semipermeable membrane at an operating pressure of 5.5 MPa, and membrane filtration treatment was performed for 24 hours. The electrical conductivity of the feedwater and permeate was then measured using an electrical conductivity meter manufactured by Toa Denpa Kogyo Co., Ltd., and the respective NaCl concentrations were obtained. From the NaCl concentrations in the permeate and feedwater, the NaCl transmittance was calculated according to the following formula. NaCl transmittance (%) = 100 × (NaCl concentration in permeate water / NaCl concentration in feed water)

[0088] (membrane flux) In the test described above, the membrane permeation rate of the supply water (evaluation raw water) was expressed as the permeation flux (m³) per square meter of membrane surface per day. 3 / m 2 This represented / day.

[0089] (Reference example 1) Polyester nonwoven fabric (air permeability 2.0 cc / cm²) 2 A support film was fabricated by casting an 18.0 mass% DMF solution of polysulfone (PSf) to a thickness of 200 μm onto the surface ( / sec) and immediately immersing it in pure water for 5 minutes.

[0090] (Reference example 2) Polyester nonwoven fabric (air permeability 2.0 cc / cm²)2 A support film was fabricated by simultaneously casting a 110 μm thick DMF solution containing 15% by mass of polysulfone (PSf) and a 50 μm thick DMF solution containing 25% by mass of polysulfone onto a surface (at / sec), and then immediately immersing it in pure water at 25°C for 5 minutes.

[0091] (Reference example 3) A support film was prepared in the same manner as in Reference Example 1, except that the concentration of polysulfone (PSf) in the DMF solution was set to 20% by mass.

[0092] (Comparative Example 1) The support film obtained in Reference Example 1 was immersed for 2 minutes in a 6.0 mass% m-phenylenediamine aqueous solution (an example of a polyfunctional aromatic amine solution) with the gas dissolved amounts (a+b, b / a) shown in Table 1. Note that a+b is the sum of the dissolved oxygen amount a and the dissolved carbon dioxide amount b in the amine aqueous solution at a solution temperature of 25°C, and b / a is the ratio of the dissolved carbon dioxide amount b to the dissolved oxygen amount a in the amine solution. The support film was slowly lifted vertically, and excess aqueous solution was removed from the surface of the support film by blowing nitrogen from an air nozzle. In a controlled environment of 40°C, a 40°C decane solution (an example of a polyfunctional aromatic acid halide solution) containing 0.16% by mass of trimesic acid chloride (TMC) was applied to completely wet the surface. Next, the support film was heated in a 120°C oven, and then the film was drained vertically to remove excess solution, and dried by blowing 20°C air using a blower. Finally, a composite semipermeable film was obtained by washing with 90°C pure water.

[0093] (Comparative Example 2) The amount of dissolved gas in the amine aqueous solution was set to the amount shown in Table 1. Using a 3.0 mass% m-phenylenediamine aqueous solution, a TMC solution was applied to the support film with a 0.165 mass% TMC Isopar M (manufactured by ExxonMobil) solution at 45°C in an environment controlled at 45°C. The composite semipermeable film of Comparative Example 2 was obtained in the same manner as in Comparative Example 1, except that the oven temperature was changed to 150°C.

[0094] (Comparative Example 3) A composite semipermeable film of Comparative Example 3 was obtained in the same manner as in Comparative Example 1, except that the amount of dissolved gas in the amine aqueous solution was set to the amount shown in Table 1, the step of placing it in a 120°C oven was omitted, the temperature of the TMC solution was set to 25°C, and the coating was performed in an environment controlled at 25°C.

[0095] (Comparative Example 4) The amount of dissolved gas in the amine aqueous solution was set to the amount shown in Table 1, and the m-phenylenediamine aqueous solution was made to 3.0% by mass. Air was blown into the aqueous solution for 30 minutes to dissolve the gas from the air. The support film obtained in Reference Example 1 was immersed in the amine aqueous solution for 2 minutes, and the support film was slowly pulled up vertically. Excess aqueous solution was removed from the surface of the support film by blowing nitrogen from an air nozzle. In an environment controlled at 25°C, a decane solution containing 0.16% by mass of TMC at 25°C was applied so that the surface was completely wet. After standing for 1 minute, the film was drained vertically to remove excess solution, and dried by blowing 20°C air using a blower. Finally, the composite semipermeable film of Comparative Example 4 was obtained by washing with pure water at 90°C.

[0096] (Comparative Example 5) A composite semipermeable film of Comparative Example 5 was obtained in the same manner as in Comparative Example 1, except that the amount of dissolved gas in the amine aqueous solution was set to the amount shown in Table 1, a decane solution containing 0.16% by mass of TMC was applied at 40°C so that the surface was completely wet, and then a decane solution containing 0.32% by mass of TMC was applied, followed by heating in an oven at 120°C.

[0097] (Comparative Example 6) A composite semipermeable membrane of Comparative Example 6 was obtained in the same manner as Comparative Example 3, except that the amount of dissolved gas in the amine aqueous solution was as shown in Table 1, the support membrane obtained in Reference Example 2 was used, the m-phenylenediamine concentration was set to 4.0% by mass, the TMC concentration was set to 0.12% by mass, and the final washing temperature with pure water was set to 45°C.

[0098] (Comparative Example 7) A composite semipermeable film of Comparative Example 7 was obtained in the same manner as in Comparative Example 1, except that the amount of dissolved gas in the amine aqueous solution was set to the amount shown in Table 1, the solvent for the TMC solution was isooctane, the solution temperature was set to 25°C, the coating was performed in an environment controlled to 25°C, and the oven temperature was further set to 150°C.

[0099] (Comparative Example 8) A composite semipermeable membrane of Comparative Example 8 was obtained in the same manner as in Comparative Example 1, except that the amount of dissolved gas in the amine aqueous solution was as shown in Table 1.

[0100] (Comparative Example 9) A composite semipermeable membrane of Comparative Example 9 was obtained in the same manner as in Comparative Example 1, except that the amount of dissolved gas in the amine aqueous solution was as shown in Table 1, the m-phenylenediamine concentration was 2.0% by mass, and the TMC concentration was 0.10% by mass.

[0101] (Comparative Example 10) A composite semipermeable membrane of Comparative Example 10 was obtained in the same manner as in Comparative Example 1, except that the amount of dissolved gas in the amine aqueous solution was set to the amount shown in Table 1. The amount of dissolved gas was adjusted by degassing.

[0102] (Example 1) The support film obtained in Reference Example 1 was immersed for 2 minutes in a 3.0 mass% m-phenylenediamine aqueous solution with the amount of dissolved gas shown in Table 1. The support film was slowly lifted vertically, and excess aqueous solution was removed from the surface of the support film by blowing nitrogen from an air nozzle. In a controlled environment of 40°C, a 40°C decane solution containing 0.16 mass% TMC was applied to the surface until it was completely wet. Next, it was heated in a 150°C oven, and then the film was drained vertically to remove excess solution, and dried by blowing 20°C air using a blower. Finally, a composite semipermeable film was obtained by washing with 90°C pure water.

[0103] (Example 2) The composite semipermeable film of Example 2 was obtained in the same manner as in Example 1, except that the oven temperature was set to 120°C.

[0104] (Example 3) The composite semipermeable film of Example 3 was obtained in the same manner as in Example 1, except that the oven temperature was set to 80°C.

[0105] (Example 4) The composite semipermeable membrane of Example 4 was obtained in the same manner as in Example 1, except that the amount of dissolved gas in the amine aqueous solution was as shown in Table 1.

[0106] (Example 5) The composite semipermeable film of Example 5 was obtained in the same manner as in Example 2, except that the support film obtained in Reference Example 3 was used.

[0107] (Example 6) The composite semipermeable film of Example 6 was obtained in the same manner as in Example 1, except that a decane solution containing 0.16% by mass of TMC was applied at 55°C in a controlled environment of 55°C so that the surface was completely wetted.

[0108] (Example 7) The composite semipermeable membrane of Example 7 was obtained in the same manner as in Example 1, except that the amount of dissolved gas in the amine aqueous solution was set to the amount shown in Table 1, and the concentration of the m-phenylenediamine aqueous solution was set to 8.0% by mass.

[0109] (Example 8) The composite semipermeable membrane of Example 8 was obtained in the same manner as in Example 1, except that the amount of dissolved gas in the amine aqueous solution was set to the amount shown in Table 1, and the concentration of the m-phenylenediamine aqueous solution was set to 2.0% by mass.

[0110] (Example 9) The composite semipermeable film of Example 9 was obtained in the same manner as in Example 1, except that the TMC concentration was set to 0.10% by mass.

[0111] (Example 10) The composite semipermeable film of Example 10 was obtained in the same manner as in Example 8, except that the TMC concentration was set to 0.10% by mass.

[0112] (Example 11) The composite semipermeable membrane of Example 11 was obtained in the same manner as in Example 1, except that the amount of dissolved gas in the amine aqueous solution was set to the amount shown in Table 1, and 100°C steam was supplied from a nozzle on the back side of the membrane while heating in a 150°C oven.

[0113] (Examples 12-17) Composite semipermeable membranes of Examples 12 to 17 were obtained in the same manner as in Example 2, except that the amount of dissolved gas in the amine aqueous solution was as shown in Table 1.

[0114] The results are shown in Table 1. From Examples 1 to 17, it can be seen that the composite semipermeable membrane of the present invention exhibits excellent water permeability and low salt permeation even after frequent operation and shutdown at high temperature and high pressure.

[0115] [Table 1]

[0116] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible without departing from the intent and scope of the invention. This application is based on Japanese Patent Application No. 2021-156465, filed on September 27, 2021, which is incorporated herein by reference in its entirety. [Explanation of Symbols]

[0117] 1 Composite semipermeable membrane 2 Base material 3 Microporous support layer 4 Separation functional layer 41 Thin film 42 Convex part 43 Recess A reference line H1~H5 Height from the reference line D1~D5 Depth from the baseline

Claims

1. A composite semipermeable membrane having a microporous support layer and a separation functional layer provided on the microporous support layer, The separation functional layer has a plurality of protrusions, which are made of a thin film containing a crosslinked aromatic polyamide. In any 10 cross-sections perpendicular to the film surface direction and with a length of 2.0 μm in the film surface direction, the average number density of protrusions whose height relative to the support layer surface is 1 / 5 or more of the 10-point average surface roughness in the separation functional layer is 13.0 protrusions / μm or more, and A composite semipermeable membrane in which the average value of the deformation amount when the aforementioned protrusion is pressed with a force of 5 nN is 2.2 nm or less, and the standard deviation of the deformation amount is 0.98 nm or less.

2. The composite semipermeable membrane according to claim 1, wherein the average value of the deformation when the projection is pressed with a force of 5 nN is 1.7 nm or less.

3. The composite semipermeable membrane according to claim 1, wherein the average number density of the protrusions is 15.0 or more per μm.

4. The composite semipermeable membrane according to claim 1 or 3, wherein x + y calculated from the amounts of amino groups, carboxyl groups, and amide groups in the separation functional layer is 0.70 or less, and x and y are defined as follows. x: １３ The molar ratio of carboxyl groups to amide groups, as measured by 13C solid-state NMR. y: １３ Molar ratio of amino groups to amide groups, measured by 13C solid-state NMR.

5. The composite semipermeable film according to claim 1 or 3, wherein the thickness of the thin film in the protrusion is 10 nm or more and 20 nm or less.

6. The weight of the separation functional layer is 0.10 g / m². ２ The composite semipermeable membrane according to claim 1 or 3.

7. The composite semipermeable membrane according to claim 1 or 3, wherein the separation functional layer is made of a crosslinked total aromatic polyamide.

8. A composite semipermeable membrane having a microporous support layer and a separation functional layer provided on the microporous support layer, The separation functional layer has a plurality of protrusions, which are made of a thin film containing a crosslinked aromatic polyamide. In any 10 cross-sections perpendicular to the film surface direction and with a length of 2.0 μm in the film surface direction, the average number density of protrusions whose height relative to the support layer surface is 1 / 5 or more of the 10-point average surface roughness in the separation functional layer is 13.0 protrusions / μm or more, and A method for manufacturing a composite semipermeable membrane, wherein the average value of the deformation amount when the protrusion is pressed with a force of 5 nN is 2.2 nm or less, and the standard deviation of the deformation amount is 1.2 nm or less, A method for producing a composite semipermeable membrane, comprising the steps of forming a crosslinked polyamide functional layer by using a polyfunctional aromatic amine solution in which the sum of dissolved oxygen a and dissolved carbon dioxide b in the solution, a+b, is 9 mg / L or more when the solution temperature is 25°C, and a solution in which a polyfunctional aromatic acid halide is dissolved in an organic solvent, performing interfacial polycondensation on the surface of a support film containing a microporous support layer, and then heating.

9. A method for producing a composite semipermeable membrane according to claim 8, wherein the ratio of the amount of dissolved material b to the amount of dissolved material a, b / a, is 0.90 or more.

10. A water treatment system that separates feedwater into concentrated water and fresh water using a composite semipermeable membrane as described in claim 1 or 3.

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