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

Composite semipermeable membrane

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

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

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

[0004] In order to further reduce running costs, water production plants using reverse osmosis membranes are required to have even higher water permeability. Furthermore, when composite semipermeable membranes are used as reverse osmosis membranes, they are required to be able to maintain the above membrane performance even during long-term operation at high pressure or under operating conditions in which the pressure fluctuates due to frequent operation and shutdown. To suppress performance changes during operation of composite semipermeable membranes, methods for suppressing compaction of porous support membranes have been proposed (see Patent Documents 2 and 3).

[0005] International Publication No. 2010 / 096563 Japanese Patent Application Laid-Open No. 2001-179061 Japanese Patent Application Laid-Open No. 3385824

[0006] However, conventional composite semipermeable membranes may experience a decrease in water permeability or salt rejection under conditions in which the pressure applied to the membrane fluctuates, such as when the membrane is frequently switched on and off. An object of the present invention is to provide a composite semipermeable membrane that can achieve both high salt rejection and water permeability even under conditions in which the pressure fluctuates.

[0007] To achieve the above object, the composite semipermeable membrane of the present invention has any 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 composed of a thin film containing a crosslinked aromatic polyamide, and in any 10 cross sections perpendicular to the membrane surface and measuring 2.0 μm in the membrane surface direction, the average number density of protrusions having a height relative to the support layer surface of at least one-fifth of the 10-point average surface roughness in the separation functional layer is 13.0 / 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 deformation is 1.2 nm or less. [2] The composite semipermeable membrane according to [1], wherein the average amount of deformation when the protrusions are 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 / μm or more. [4] The composite semipermeable membrane according to any one of [1] to [3], wherein the standard deviation of the deformation is 0.98 nm or less. [5] The composite semipermeable membrane according to any one of [1] to [4], wherein x+y calculated from the amounts of amino groups, carboxy groups, and amide groups in the separating functional layer is 0.70 or less, and the x and y are defined as follows: x: １３ Molar ratio y of carboxyl groups to amide groups as determined by C solid-state NMR: １３ [6] The composite semipermeable membrane according to any one of [1] to [5], wherein the thickness of the thin film on the protrusions is 10 nm or more and 20 nm or less. [7] The weight of the separating functional layer is 0.10 g / m ２ [8] The composite semipermeable membrane according to any one of [1] to [7], wherein the separating functional layer is made of a crosslinked wholly aromatic polyamide.

[0008] The method for producing a composite semipermeable membrane of the present invention has any one of the following configurations. [9] The method for producing a composite semipermeable membrane according to any one of [1] to [8] above, comprising the steps of: using a polyfunctional aromatic amine solution in which the sum a+b of the dissolved amount of oxygen a and the dissolved amount of carbon dioxide b in the solution at a solution temperature of 25°C is 9 mg / L or more; and a solution in which a polyfunctional aromatic acid halide is dissolved in an organic solvent; and then heating to form a crosslinked polyamide functional layer.

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

[0009] The water treatment system of the present invention has the following configuration:

[11] A water treatment system that separates feed water into concentrated water and fresh water using the composite semipermeable membrane according to any one of [1] to [8] above.

[0010] The present invention provides a composite semipermeable membrane that exhibits both high salt rejection and water permeability under conditions where operation and shutdown are frequently repeated and pressure fluctuates.

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

[0012] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited thereto. In this specification, "mass" has the same meaning as "weight."

[0013] 1. Composite semipermeable membrane The structure of a composite semipermeable membrane 1 in this embodiment is shown in Figure 1. As shown in Figure 1, the composite semipermeable membrane 1 according to the present invention has 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 the substrate 2, and the composite semipermeable membrane 1 according to an embodiment of the present invention may have a support membrane including the substrate 2 and the microporous support layer 3 formed on the substrate 2. The separation function layer 4 substantially has separation performance, and the microporous support layer 3 does not substantially have separation performance for ions and the like and can impart strength to the separation function layer 4.

[0015] (1-1) Support Membrane The support membrane may include a substrate 2 and a microporous support layer 3, or may be composed of only the microporous support layer 3 without the substrate 2. That is, the microporous support layer 3 may be the support membrane.

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

[0017] The microporous support layer 3 has a large number of interconnected pores. There are no particular limitations on the pore size or pore size distribution of the pores, but a preferred microporous support layer is one that has, for example, a symmetrical structure with uniform pore sizes or an asymmetrical structure in which the pore sizes gradually increase from one surface to the other, and in which the pore size on the surface with smaller pore sizes is 0.1 to 100 nm.

[0018] The material for the microporous support layer 3 may be a homopolymer or copolymer, such as polysulfone (hereinafter also referred to as "PSf"), polyethersulfone, polyamide, polyester, cellulose-based polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, or polyphenylene oxide, which may be used alone or in blends. Examples of the cellulose-based polymer include cellulose acetate and cellulose nitrate, and examples of the vinyl polymer include polyethylene, polypropylene, polyvinyl chloride, and polyacrylonitrile. Among 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. PSf is particularly preferred due to its high chemical, mechanical, and thermal stability and ease of molding.

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

[0020] The thicknesses of the substrate and the microporous support layer affect the strength of the composite semipermeable membrane and the packing density when it is made into 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, more preferably 100 to 220 μm. 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 the thicknesses measured at 20 μm intervals in a direction perpendicular to the thickness direction (in the plane direction of the membrane) by cross-sectional observation.

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

[0022] "Containing crosslinked aromatic polyamide as the main component" means that the proportion of crosslinked aromatic polyamide in the separation functional layer is 50% by mass or more. The proportion of crosslinked aromatic polyamide in the separation functional layer is preferably 80% by mass or more, more preferably 90% by mass or more, and it is even more preferable that the separation functional layer is formed substantially only from crosslinked aromatic polyamide. "The separation functional layer is formed substantially only from crosslinked aromatic polyamide" means that the separation functional layer is formed of 99% by mass or more from crosslinked aromatic polyamide.

[0023] Examples of crosslinked aromatic polyamides include aramid-based compounds, but they may contain non-aromatic moieties in their molecular structure. However, crosslinked fully aromatic polyamides are more preferred in terms of rigidity, chemical stability, and durability against 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 be referred to as a polyamide separation functional layer hereinafter.

[0024] The polyfunctional aromatic amine refers to an aromatic amine having two or more primary amino groups and / or secondary amino groups in one molecule, and at least one of the amino groups being a primary amino group.

[0025] Examples of polyfunctional aromatic amines include polyfunctional aromatic amines in which two amino groups are bonded to an aromatic ring at the ortho, meta, or para positions, such as o-phenylenediamine, m-phenylenediamine, 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, m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene are preferably used in consideration of the selective separation property, permeability, and heat resistance of the membrane. Among these, m-phenylenediamine (hereinafter also referred to as "m-PDA") is more preferably used in view of its ease of availability and ease of handling. These polyfunctional aromatic amines may be used alone or in combination of two or more kinds.

[0027] The polyfunctional aromatic acid halide refers to an aromatic acid halide having at least two halocarbonyl groups in one molecule. For example, a trifunctional acid halide may be trimesoyl chloride, and a bifunctional acid halide may be biphenyldicarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, and naphthalenedicarboxylic acid chloride.

[0028] In consideration of the reactivity with the polyfunctional aromatic amine, the polyfunctional aromatic acid halide is preferably a polyfunctional aromatic acid chloride, and in consideration of the selective separation property and heat resistance of the membrane, it is more preferably a polyfunctional aromatic acid chloride having 2 to 4 carbonyl chloride groups in one molecule.

[0029] The shape and thickness of the separation functional layer affect its separation and permeation performance. As shown in FIG. 1B, the separation functional layer 4 includes a thin film 41 that is pleated with multiple convex portions 42 and concave portions 43. In the layer made of the thin film 41, adjacent convex portions 42 and concave portions 43 form protrusions. The pleated thin film in the separation functional layer significantly increases the specific surface area of ​​the separation functional layer compared to a planar structure. As a result, the permeation performance can be improved in proportion to the surface area of ​​the separation functional layer while maintaining separation performance. As shown in FIG. 1C, the interior of the convex portion 42 (between the thin film 41 and the microporous support layer 3) is a void. Convex portions and concave portions are explained using FIG. 2. "Convex portion" and "concave portion" refer to relatively protruding and concave portions in the thin film. In particular, the portion above the reference line A described below is referred to as a convex portion, and the portion below is referred to as a concave portion. A "protrusion" refers to the area from the bottom of a concave portion to the bottom of the adjacent concave portion, i.e., from one convex portion to the bottoms of the concave portions on both sides. In the following description, the term "protrusion" refers to a protrusion whose height from the surface of the support layer is equal to or greater than one-fifth of the 10-point average surface roughness of the thin film.

[0030] The inventors have found that when the protrusions, specifically the convex portions forming the protrusions, are pressed with a force of 5 nN in pure water at 25°C, the average amount of deformation is 2.2 nm or less and the standard deviation of the amount of deformation is 1.2 nm or less, and stable membrane performance can be obtained even under conditions of pressure fluctuations, such as frequent repetition of operation and shutdown.

[0031] The deformation amount of the protrusions can be calculated as follows. The surface of the separation functional layer is observed in pure water at 25°C using an atomic force microscope (AFM), and two arbitrary regions within a 2 μm square area are selected. Ten protrusions, specifically convex portions, are selected from each of 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 apex of the selected protrusion (convex portion) is pressed with a force of 5 nN to obtain the deformation amount. The arithmetic mean of the deformation amounts obtained at the 20 points is taken as the average deformation amount.

[0032] The deformation of the protrusion (convex portion) 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 tip-sample distance (separation) on the horizontal axis and the load on the vertical axis, the point before the cantilever is brought close to the sample is Point A, the moment the load rises is Point B, the point where the load is 90% of the maximum load is Point C, and the maximum load point is Point D, and the distance between C and D is the deformation. Note that the force curve used is that when the cantilever is brought close to the sample.

[0033] The atomic force microscope can be, for example, a Dimension FastScan manufactured by Bruker AXS. By using the included attachment, observations can be made underwater. The cantilever used has a conical (pyramidal) tip. Before using the cantilever, calibration is performed. First, the deflection sensitivity of the cantilever is measured using a material with sufficient hardness. Examples of materials with sufficient hardness include silicon wafers and sapphire. Next, the spring constant of the cantilever is measured using thermal tune. Calibration improves measurement accuracy.

[0034] The deformation amount of the protrusions (convex portions) of the separation functional layer reflects the density of the pore structure of the separation functional layer. Specifically, the coarser the pore structure of the separation functional layer, the greater the deformation amount, and the denser the pore structure, the smaller the deformation amount. It is presumed that when the average deformation amount is 2.2 nm or less, the separation functional layer has a sufficiently dense structure, so that even if high pressure is applied locally during changes in operating pressure, compaction is unlikely to occur. It is more preferable that the average deformation amount is 1.7 nm or less. On the other hand, if the deformation amount is too small, the functional layer is too dense to obtain sufficient water permeability, and the flexibility is low, so the physical structural stability is reduced when the membrane is subjected to impacts such as bending, folding, or shaking, making pinhole defects more likely to occur. Therefore, it is preferable that the average deformation amount is 0.5 nm or more.

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

[0036] The protrusions on the thin film can be observed using an electron microscope such as a scanning electron microscope (SEM, FE-SEM) or a transmission electron microscope (TEM). First, to prepare ultrathin sections for TEM, the sample is embedded in a water-soluble polymer. Any water-soluble polymer can be used as long as it can maintain the shape of the sample, and an example of this is polyvinyl alcohol (PVA). Next, to facilitate cross-sectional observation, osmium tetroxide (OsO ４ The sample is stained with fluorine and cut with an ultramicrotome to prepare ultrathin sections. The resulting ultrathin sections are photographed using an electron microscope. The observation magnification can be determined appropriately depending on the film thickness of the separation functional layer. However, in order to be able to observe the cross-sectional shape of the separation functional layer and to avoid localized measurement, if the thickness of the separation functional layer is about 10 to 100 nm, the observation magnification should be set to 50,000 to 100,000 times.

[0037] The 10-point average surface roughness of a thin film is obtained by the following method. A cross section perpendicular to the membrane surface is observed using an electron microscope. The observation magnification is preferably 10,000 to 100,000 times. In the obtained cross-sectional image, the surface of the composite semipermeable membrane (indicated by the symbol "1" in Figure 1) appears as a curve, as shown in Figures 1(a) and 1(b). A roughness curve defined in accordance with ISO 4287:1997 is obtained for this curve. Also in accordance with ISO 4287:1997, the average line of the roughness curve is obtained. The average line is a straight line drawn so that the total area of ​​the region enclosed by the average line and the roughness curve is equal above and below the average line.

[0038] In the image thus obtained, which is parallel to the mean line and has a width of 2.0 μm, as shown in FIG. 2, the mean line is set as reference line A, and heights H1 to H5 from the reference line A (distances from reference line A to the apex of the convexity) are measured for the five convexities from the highest to the fifth highest, and the average value is calculated. In addition, depths D1 to D5 (distances from reference line A to the apex of the concaveity) are measured for the five concaveities from the deepest to the fifth deepest, and the average value is calculated. The sum of the two average values ​​obtained is the 10-point average surface roughness. The apex is the point on the convexity or concaveity that is the greatest distance from the reference line.

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

[0040] The height of the protrusions is preferably 70 nm or more. Furthermore, the height of the protrusions is preferably 1000 nm or less, more preferably 800 nm or less. When the height of the protrusions is 70 nm or more, a composite semipermeable membrane with sufficient water permeability can be easily obtained. Furthermore, when the height of the protrusions is 1000 nm or less, the protrusions are not crushed even when the composite semipermeable membrane is operated and used at high pressure, and stable membrane performance can be obtained.

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

[0042] The average value of the thickness T of the thin film is preferably 10 nm or more and 20 nm or less. When the average value of T is 10 nm or more, good separation performance is obtained and durability against physical external forces is improved. Furthermore, when the average value of T is 20 nm or less, a composite semipermeable membrane with good permeability performance can be obtained. The average value of the thickness T is more preferably 15 nm or less.

[0043] The average number density of the protrusions of the separation functional layer is 13.0 / μm or more, more preferably 15.0 / μm or more. The average number density of the protrusions of the separation functional layer is preferably 50 / μm or less, more preferably 40 / μm or less. When the average number density of the protrusions is 13.0 / μm or more, the composite semipermeable membrane can obtain sufficient water permeability, and deformation of the protrusions when pressurized can be suppressed, resulting in stable membrane performance. When the number density of the protrusions is 50 / μm or less, the growth of the pleated structure occurs sufficiently, making it easy to obtain a composite semipermeable membrane with the desired water permeability. The average number density of the protrusions can be measured by observing 10 cross sections with a width of 2.0 μm as described above, and counting the number of protrusions that are at least one-fifth of the 10-point average surface roughness on each cross section.

[0044] The polyamide separating functional layer contains amide groups derived from the polymerization of polyfunctional aromatic amines and polyfunctional aromatic acid halides, and amino and carboxy groups derived from unreacted functional groups.

[0045] When the molar ratio of carboxy groups to amide groups in the separation functional layer (carboxy groups / amide groups) is x and the molar ratio of amino groups to amide groups (amino groups / amide groups) is y, it is preferable that x + y is 0.70 or less. More preferably, x + y is 0.60 or less. 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 it is presumed that compaction is less likely to occur even when high pressure is applied locally during changes in operating pressure.

[0046] The molar ratio of the carboxyl group, the amino group, and the amide group in the separating functional layer is １３ It can be determined by C solid state NMR measurement. ２The substrate is peeled off from the substrate to obtain a polyamide separation functional layer and a microporous support layer, and then the microporous support layer is dissolved and removed to obtain a polyamide separation functional layer. １３ Measurement is carried out by C solid state NMR, and each ratio can be calculated by comparing the integrated values ​​of the carbon peaks of each functional group or the carbon peaks to which each functional group is bonded.

[0047] The weight of the separation functional layer of the present invention is 0.10 g / m ２ It is preferable that the content is 0.11 g / m or more, and more preferably 0.11 g / m ２ More preferably, 0.12 g / m ２ The weight of the separation functional layer is 0.10 g / m ２ If the amount of polyamide constituting the separation functional layer is above this, the durability against external physical forces is improved, and stable membrane performance can be obtained even under conditions of fluctuating pressure.

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

[0049] 2. Method for Producing Composite Semipermeable Membrane The method for producing the composite semipermeable membrane of the present invention is not particularly limited as long as it can produce a composite semipermeable membrane that satisfies the above-mentioned desired characteristics. For example, the membrane can be produced by the following method.

[0050] (2-1) Formation of Support Membrane As a method for forming the support membrane, a known method can be suitably used. Hereinafter, an example will be described in which PSf is used as the material for the microporous support layer.

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

[0052] The PSf concentration in the microporous support layer stock solution is preferably 10 to 25% by mass, and more preferably 14 to 23% by mass. The higher the polymer concentration (i.e., solids concentration) in the polymer solution, the greater 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 protrusions in the separation functional layer, enabling the realization 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 functional layer formation is not too slow, the surface pore size of the microporous support layer is adjusted, and protrusions of an appropriate height are formed during separation functional layer formation. By keeping the PSf concentration in the microporous support layer stock solution within this range, the strength and permeability of the resulting microporous support layer can be achieved at the same time. The preferred range of the material concentration in the microporous support layer stock solution can be adjusted as appropriate depending on the materials used, good solvents, etc.

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

[0054] The non-solvent for PSf contained in the coagulation bath is preferably water, for example. By contacting the microporous support layer stock solution applied to the substrate surface with a coagulation bath containing a non-solvent for PSf, the microporous support layer stock solution is coagulated by non-solvent-induced phase separation, thereby obtaining a support membrane in which a microporous support layer is formed on the substrate surface.

[0055] The coagulation bath may be composed only of a non-solvent for PSf, or may contain a good solvent for PSf to the extent that the stock solution for the microporous support layer can be coagulated. The resulting support membrane may be washed before the formation of the separation functional layer to remove any solvent remaining in the membrane.

[0056] (2-2) Polymerization step for separation functional layer The method for forming a separation functional layer containing a crosslinked aromatic polyamide will be described using as an example a method in which a polyfunctional aromatic amine and a polyfunctional aromatic acid halide are polymerized and solidified on the support membrane obtained in "(2-1) Formation of support membrane". As the polymerization method, an interfacial polymerization method is used from the viewpoints of productivity and performance. The interfacial polymerization step will be described below.

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

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

[0059] Examples of the microporous support layer, polyfunctional aromatic amine, and polyfunctional aromatic acid halide include those described above, and the preferred examples are also the same.

[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 to 20% by weight, more preferably in the range of 0.5% by weight to 15% by weight. When the concentration of the polyfunctional aromatic amine is in this range, sufficient solute removal performance and water permeability can be obtained. Two or more types of polyfunctional aromatic amines may be used.

[0061] The polyfunctional aromatic amine solution may contain surfactants, organic solvents, alkaline compounds, antioxidants, etc., as long as they do not interfere with the reaction between the polyfunctional aromatic amine and the polyfunctional aromatic acid halide. The surfactant has the effect of improving the wettability of the support membrane surface and reducing the interfacial tension between the polyfunctional aromatic amine solution and the nonpolar solvent. The organic solvent may act as a catalyst for the interfacial polycondensation reaction, and its addition may sometimes make the interfacial polycondensation reaction more efficient.

[0062] The polyfunctional aromatic amine solution is used with a gas dissolved amount a+b of 9 mg / L or more, where a (mg / L) is the dissolved amount of oxygen in the solution and b (mg / L) is the dissolved amount of carbon dioxide in the solution at a solution temperature of 25°C. Preferably, a+b is 15 mg / L or more, more preferably a+b is 32 mg / L or more, and even more preferably a+b is 100 mg / L or more. Methods for adjusting the dissolved amount of gas include contacting the solution with a gas at a predetermined mixture ratio, injecting the gas into the solution, and using a commercially available liquid (e.g., carbonated water) in which the gas has been pre-dissolved. Gas may be generated using a chemical reaction, provided that it does not interfere with the reaction between the polyfunctional aromatic amine and the polyfunctional aromatic acid halide. When using a commercially available liquid 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 selected arbitrarily.

[0063] Typically, the heating step (c) described below causes the functional layer to densify, reducing the average deformation amount of the protrusions (convex portions), and the average deformation amount is 2.2 nm or less. However, at the same time, the protrusions also become more integrated, reducing the number density of the protrusions, and the average number density of the protrusions is no longer 13.0 / μm or more. On the other hand, as the dissolved gas amount a + b increases, the number of starting points for forming protrusions increases due to the generation of microbubbles described below, and even after the heating step, the average number density of the protrusions remains 13.0 / μm or more. As the dissolved gas amount a + b increases, molecules enter the dense areas during interfacial polymerization, inhibiting aggregation and preventing the reaction from proceeding locally, thereby suppressing the generation of coarse and dense portions. This reduces the variation in the deformation amount, and the standard deviation is 1.2 nm or less. On the other hand, by injecting gas, it is possible to make the dissolved gas amount excessive, but if the dissolved gas amount is too large, defects are likely to occur in the protrusions and the removal rate will decrease, so it is preferable that the dissolved gas amount a+b is 10,000 or less.

[0064] In step (a), the polyfunctional aromatic amine solution is preferably brought into uniform and continuous contact with the support membrane. Specific examples include a method of coating the polyfunctional aromatic amine solution on the support membrane, and a method of immersing the support membrane in the polyfunctional aromatic amine solution. The contact time between the support membrane 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 membrane, it is preferable to thoroughly drain the solution so that no droplets remain on the support membrane. By thoroughly draining the solution, it is possible to prevent the remaining droplets from becoming membrane defects after the composite semipermeable membrane is formed, which would result in a decrease in separation performance. Examples of draining methods include, as described in Japanese Patent Application Laid-Open No. 2-78428, a method in which the support membrane after contact with the aqueous solution is held vertically to allow excess aqueous solution to flow naturally, and a method in which an air current such as nitrogen is blown from an air nozzle to forcibly drain the solution. Furthermore, after draining the solution, the membrane surface can be dried to remove some of the water content of the aqueous solution.

[0066] In step (b), examples of the polyfunctional aromatic acid halide include polyfunctional aromatic acid chlorides such as 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-furandicarboxylic acid chloride. The polyfunctional aromatic acid halides may be used alone or in combination of two or more.

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

[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. When the concentration of the polyfunctional aromatic acid halide is 0.01% by mass or more, the polymerization can proceed at a sufficient reaction rate. On the other hand, when the concentration of the polyfunctional aromatic acid halide is 10% by mass or less, the occurrence of side reactions during the polymerization can be suppressed. Furthermore, the organic solvent solution may contain a compound such as a surfactant, as long as it does not inhibit the polymerization.

[0069] The method of contacting the organic solvent solution of the polyfunctional aromatic acid halide with the support membrane that has been brought into contact with the polyfunctional aromatic amine solution may be carried out in the same manner as the method of coating the support membrane with the polyfunctional aromatic amine solution.

[0070] The temperature at which the microporous support layer contacted with an aqueous solution containing a polyfunctional aromatic amine and the solution containing a polyfunctional aromatic acid halide are contacted is preferably 25 to 60°C, more preferably 30 to 55°C. Temperatures below 25°C may result in insufficient protrusion height. As the temperature increases, the solubility of gas decreases, and the remaining gas generates microbubbles, increasing the number of protrusion-forming starting points. However, at temperatures above 60°C, the reaction proceeds too quickly, resulting in an increase in the thickness of the protrusion film and the progression of protrusion coalescence, both of which result in insufficient water permeability. A contact temperature of 25 to 60°C increases the number of protrusions and substantially increases the surface area of ​​the reaction interface, thereby increasing the amount of polyamide and suppressing the expansion of the film thickness T. The temperature can be applied by heating the support film or by contacting a heated organic solvent solution of a polyfunctional acid halide. The temperature of the film surface immediately after contacting the polyfunctional aromatic amine solution with the polyfunctional acid halide solution can be measured using a non-contact thermometer such as a radiation thermometer.

[0071] In step (c), after contacting the support membrane with the organic solvent solution of the polyfunctional aromatic acid chloride, the support membrane is heat-treated. When heat-treated, the heating temperature is preferably 50 to 180°C, more preferably 60 to 160°C, and even more preferably 80 to 150°C. A synergistic effect is obtained between the promotion of the interfacial polymerization reaction due to an increase in surface area caused by heating and microbubbles generated by heating, the promotion of interfacial polymerization due to the concentration of the polyfunctional aromatic acid halide during the interfacial polymerization, and the improvement of reaction efficiency due to the improvement of the mobility of the monomers and oligomers, so that the amount of polyamide in the separation functional layer is 0.10 g / m ２ As the temperature rises, the amount of amide groups increases and x + y becomes 0.70 or less. The functional layer becomes more densified, and the average value of the deformation amount becomes 2.2 nm or less. If the heating temperature is too high, the protrusions become more unified, the number density decreases, and the film becomes thicker, so good water permeability cannot be obtained. When the microbubbles generated by heating rise, they entrain the surrounding liquid, causing a flow, dispersing the monomer in the liquid and promoting the reaction, which increases the densification of the functional layer and prevents localized reaction from progressing, so the average value of the deformation amount becomes even smaller and the variation in the deformation amount also becomes even smaller.

[0072] In this case, the greater the amount of gas dissolved (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 temperature at the time of contact, thereby enhancing this effect.

[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 carbon dioxide dissolved in the amine solution b to the amount of oxygen dissolved in the amine solution a) be 0.9 or more, since this will enhance the above-mentioned effects. The ratio b / a is more preferably 1.0 or more.

[0074] After the reaction and heating, the organic solvent is preferably removed by a step of draining the organic solvent solution. For example, the organic solvent can be removed by a method of holding the membrane vertically and removing excess organic solvent by gravity flow, a method of blowing air onto the membrane with a blower to dry and remove the organic solvent, or a method of removing excess organic solvent with a mixed fluid of water and air.

[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, more preferably 60 to 95°C. When the hot water temperature is 40°C or higher, unreacted substances and oligomers remaining in the membrane can be sufficiently removed. On the other hand, when the hot water temperature is 95°C or lower, the degree of shrinkage of the composite semipermeable membrane does not increase, and good permeability performance can be maintained. The preferred range of the 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 feed water into permeate (freshwater) and concentrated water using a composite semipermeable membrane. Specifically, the composite semipermeable membrane is wound around a cylindrical water collection pipe with multiple holes, together with a feed water flow path material such as a plastic net, a permeate water flow path material such as tricot, and, if necessary, a film for increasing pressure resistance, and is suitably used as a spiral composite semipermeable membrane element. Furthermore, this element can be connected in series or in 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 a pump that supplies feed water to them, a device that pretreats the feed water, etc. to form a fluid separation device. By using this separation device, feed water can be separated into permeated water such as drinking water and concentrated water that did not permeate the membrane, thereby obtaining water suitable for the intended purpose.

[0078] The feed water to be treated by the composite semipermeable membrane of the present invention includes 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 amount of total dissolved solids and is expressed as "mass / volume" or "weight ratio." By definition, it can be calculated from the weight of the residue obtained by evaporating a solution filtered through a 0.45 micron filter at a temperature of 39.5 to 40.5°C, but it can be more simply calculated from the practical salinity (S).

[0079] The higher the operating pressure of the fluid separation device, the higher the solute removal rate, but the more energy required for operation. Also, taking into consideration the durability of the composite semipermeable membrane, the operating pressure when permeating the water to be treated through the composite semipermeable membrane is preferably 0.5 to 10 MPa. The solute removal rate decreases as the supply water temperature increases, but the membrane permeation flux also decreases as the supply water temperature decreases, so a temperature of 5 to 45°C is preferred. Furthermore, if the supply water pH increases, there is a risk of magnesium scale formation in the case of supply water with a high solute concentration, such as seawater, and there is also concern about membrane degradation due to high pH operation. Therefore, operation in the neutral range is preferred.

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

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

[0082] (Deformation amount and standard deviation of protrusions (convex portions)) A composite semipermeable membrane wetted with pure water was cut into 1 cm squares and fixed to a sample stand using an adhesive with the separation functional layer surface facing up to prepare a 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 with an atomic force microscope (AFM). Ten force curves of the convex portions were extracted from the obtained image and the deformation amount was analyzed. This operation was performed for two fields of view, and the deformation amount of a total of 20 points was analyzed, and the average, maximum, and standard deviation were calculated. The specific measurement conditions are as follows. - Apparatus: Dimension FastScan manufactured by Bruker AXS - Scanning mode: Underwater nanomechanical mapping - Probe: Silicon cantilever (ScanAsyst-Fluid manufactured by Bruker AXS). The cantilever was calibrated before measurement. Maximum load: 5.0 nN Scanning range: 2 μm x 2 μm Scanning speed: 0.5 Hz Number of pixels: 256 x 256 Measurement conditions: in pure water Measurement temperature: 25°C

[0083] (Quantitative determination of carboxyl group, amino group and amide group, and weight of polyamide) Composite semipermeable membrane 5m ２The substrate was physically peeled off from the substrate, and the microporous support layer and separation functional layer were recovered. After leaving it to dry for 24 hours, it was added little by little to a beaker containing dichloromethane and stirred to dissolve the polymer that constitutes the microporous support layer. The insoluble matter in the beaker was recovered with filter paper. This insoluble matter was placed in a beaker containing dichloromethane and stirred, and the insoluble matter in the beaker was recovered again. This process was repeated until no elution of the polymer that forms 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 calculated based on the weight of the area of ​​5 m used. ２ The polyamide weight per unit area was obtained by dividing the weight by the formula (2). The separation functional layer was then freeze-pulverized to prepare a powder sample, which was then sealed in a sample tube used for solid-state NMR measurement. １３ C solid state NMR measurement was carried out. １３ For the C solid state NMR measurement, a CMX-300 manufactured by Chemagnetics was used. Example measurement conditions are shown below. Reference substance: polydimethylsiloxane (internal reference: 1.56 ppm) Sample rotation speed: 10.5 kHz Pulse repetition time: 100 s From the obtained spectrum, peak division was performed for each peak derived from the carbon atom to which each functional group was bonded, and the functional group amount ratio was quantified from the area of ​​the divided peaks.

[0084] (Average value of protrusion thickness T, number density of protrusions) The composite semipermeable membrane was cut into a 3 cm x 3 cm square and washed with distilled water at 25°C for 24 hours. The washed composite semipermeable membrane was embedded in epoxy resin and then stained with osmium tetroxide to prepare a measurement sample. The obtained sample was observed using a scanning transmission electron microscope (HD2700, manufactured by Hitachi, Ltd.) with the thin film cross section as the observation surface. Using an image acquired at 1,000,000 times magnification, the shortest distance from a point on the outer surface of the thin film to the inner surface was taken as the thin film thickness T. For 10 randomly selected protrusions, analysis was performed at five points per protrusion, and the average value was taken as the average thin film thickness T. Furthermore, the number of pleated protrusions was counted to determine the average number density.

[0085] (Method of Calculating Amount of Dissolved Gas) After preparing the aqueous amine solution, oxygen and carbon dioxide were measured immediately using a commercially available DO meter and a dissolved carbon dioxide concentration meter.

[0086] (Start-stop operation under high temperature and high pressure) A start-stop test was performed 1000 times by supplying raw water for evaluation (NaCl concentration 3.2%) adjusted to a temperature of 40°C and a pH of 6.5 to a composite semipermeable membrane at an operating pressure of 7.0 MPa, and operating for 5 minutes and then stopping for 5 minutes. Then, the performance of the composite semipermeable membrane was evaluated by the method shown below.

[0087] (NaCl Permeability) 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 was performed for 24 hours. The electrical conductivity of the feed water and permeated water was then measured using an electrical conductivity meter manufactured by Toa Denpa Kogyo Co., Ltd. to obtain the respective NaCl concentrations. The NaCl permeability was calculated from the NaCl concentrations in the permeated water and feed water according to the following formula: NaCl permeability (%) = 100 x (NaCl concentration in permeated water / NaCl concentration in feed water)

[0088] (Membrane permeation flux) In the test in the preceding paragraph, the amount of water permeating the membrane of the feed water (evaluation raw water) was measured as the membrane permeation flux (m 3 ) in terms of the amount of water permeating per square meter of membrane surface per day (cubic meters). ３ / m ２ / day).

[0089] (Reference Example 1) Polyester nonwoven fabric (air permeability 2.0 cc / cm ２ A 18.0 mass % DMF solution of polysulfone (PSf) was cast onto the support membrane (1000 nm / sec) to a thickness of 200 μm, and the support membrane was immediately immersed in pure water and left for 5 minutes to prepare a support membrane.

[0090] (Reference Example 2) Polyester nonwoven fabric (air permeability 2.0 cc / cm ２ A 15% by mass solution of polysulfone (PSf) in DMF was cast onto the support (1000 nm / sec) to a thickness of 110 μm, and a 25% by mass solution of polysulfone in DMF was cast onto the support (1000 nm / sec) to a thickness of 50 μm. The support was then immediately immersed in pure water at 25° C. and allowed to stand for 5 minutes to prepare a support membrane.

[0091] Reference Example 3 A support membrane 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 mass %.

[0092] Comparative Example 1 The support membrane 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) in which the amount of dissolved gas (a + b, b / a) in the amine aqueous solution was set to the amount 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 when the solution temperature was 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 membrane was slowly pulled up vertically, and excess aqueous solution was removed from the support membrane surface by spraying nitrogen from an air nozzle. In an environment controlled at 40°C, a 40°C decane solution (an example of a polyfunctional aromatic acid halide solution) containing 0.16 mass% trimesoyl chloride (TMC) was applied so that the surface was completely wet. Next, the support membrane was heated in an oven at 120°C, and then the membrane was placed vertically to drain the excess solution from the membrane, and dried by blowing air at 20°C onto it using a fan. Finally, the membrane was washed with pure water at 90°C to obtain a composite semipermeable membrane.

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

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

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

[0096] Comparative Example 5 The composite semipermeable membrane of Comparative Example 5 was obtained in the same manner as in Comparative Example 1, except that the amount of gas dissolved in the aqueous amine solution was set to the amount shown in Table 1, a decane solution containing 0.16 mass% of TMC at 40°C was applied to the surface so that it was completely wet, and then a decane solution containing 0.32 mass% of TMC was further 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 in Comparative Example 3, except that the amount of gas dissolved in the aqueous amine solution was set to the amount 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 membrane of Comparative Example 7 was obtained in the same manner as in Comparative Example 1, except that the amount of gas dissolved in the aqueous amine 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, coating was performed in an environment controlled at 25°C, and the oven temperature was 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 gas dissolved in the aqueous amine solution was set to the amount 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 gas dissolved in the aqueous amine solution was set to the amount shown in Table 1, the m-phenylenediamine concentration was set to 2.0 mass%, and the TMC concentration was set to 0.10 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 aqueous amine solution was set to the amount shown in Table 1. The amount of dissolved gas was adjusted by degassing.

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

[0103] Example 2 A composite semipermeable membrane 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 A composite semipermeable membrane 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 A composite semipermeable membrane of Example 4 was obtained in the same manner as in Example 1, except that the amount of gas dissolved in the aqueous amine solution was set to the amount shown in Table 1.

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

[0107] Example 6 A composite semipermeable membrane of Example 6 was obtained in the same manner as in Example 1, except that a decane solution containing 0.16 mass% of TMC at 55°C was applied to the surface so as to completely wet the surface in an environment controlled at 55°C.

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

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

[0110] Example 9 A composite semipermeable membrane 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 A composite semipermeable membrane of Example 10 was obtained in the same manner as in Example 8, except that the TMC concentration was 0.10% by mass.

[0112] (Example 11) A composite semipermeable membrane of Example 11 was obtained in the same manner as in Example 1, except that the amount of gas dissolved in the aqueous amine solution was set to the amount shown in Table 1, and that the membrane was heated in an oven at 150°C while being heated while supplying water vapor at 100°C from a nozzle provided on the back side of the membrane.

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

[0114] The results are shown in Table 1. Examples 1 to 17 show that the composite semipermeable membrane of the present invention has excellent water permeability and little salt permeation even after frequent cycles of operation and stoppage at high temperature and high pressure.

[0115]

[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 spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2021-156465) filed on September 27, 2021, the entire contents of which are incorporated by reference.

[0117] REFERENCE SIGNS LIST 1 Composite semipermeable membrane 2 Substrate 3 Microporous support layer 4 Separation function layer 41 Thin film 42 Convex portion 43 Concave portion A Reference line H1 to H5 Height from reference line D1 to D5 Depth from reference line

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 formed of a thin film containing a crosslinked aromatic polyamide, In any 10 cross sections perpendicular to the film surface direction and having a length of 2.0 μm in the film surface direction, the average number density of protrusions whose height based on the support layer surface is 1 / 5 or more of the 10-point average surface roughness in the separation functional layer is 13.0 pieces / μm or more, and A composite semipermeable membrane, wherein 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 0.98 nm or less.

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

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

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

5. 4. The composite semipermeable membrane according to claim 1, wherein the thickness of the thin film on the protrusions is 10 nm or more and 20 nm or less.

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

7. The composite semipermeable membrane according to claim 1 or 3, wherein the separating functional layer comprises a crosslinked wholly 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 formed of a thin film containing a crosslinked aromatic polyamide, In any 10 cross sections perpendicular to the film surface direction and having a length of 2.0 μm in the film surface direction, the average number density of protrusions whose height based on the support layer surface is 1 / 5 or more of the 10-point average surface roughness in the separation functional layer is 13.0 pieces / μm or more, and A method for producing a composite semipermeable membrane, wherein an average amount of deformation when the protrusions are pressed with a force of 5 nN is 2.2 nm or less and a standard deviation of the amount of deformation is 1.2 nm or less, A method for producing a composite semipermeable membrane, comprising the steps of: using a polyfunctional aromatic amine solution in which the sum a+b of the dissolved amount of oxygen a and the dissolved amount of carbon dioxide b in the solution 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; and then performing interfacial polycondensation on the surface of a support membrane including a microporous support layer; and then heating the resulting mixture to form a crosslinked polyamide functional layer.

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

10. A water treatment system, comprising: a composite semipermeable membrane according to claim 1 or 3, for separating feed water into concentrated water and fresh water.