Composite semipermeable membrane

Abstract

To provide a composite semipermeable membrane satisfying both of salt removal performance and permeable performance.SOLUTION: A composite semipermeable membrane has a porous layer composed of a particle containing layer containing particles and a particle not-containing layer containing no particle, and a polyamide separation functional layer provided on the particle not-containing layer.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Regarding the separation of 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 expanded as a process for saving energy and resources. Membranes used in membrane separation include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes, and these membranes are used, for example, to produce drinking water from seawater, brine, and water containing harmful substances, to produce industrial ultrapure water, to treat wastewater, and to recover valuable resources.

[0003] Most reverse osmosis and nanofiltration membranes currently on the market are composite semipermeable membranes, and there are two types: those with an active layer made of a gel layer and a polymer crosslinked on a porous support membrane, and those with an active layer made of a monomer polycondensed on a porous support membrane. Of these, composite semipermeable membranes, obtained by coating a support membrane with a separation functional layer made of crosslinked polyamide obtained by the polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide, are widely used as separation membranes with high water permeability and salt rejection.

[0004] In order to further reduce running costs in water production plants that use reverse osmosis membranes, there is a demand for reverse osmosis membranes with higher water permeability than currently available.

[0005] One factor that affects the water permeability of a composite semipermeable membrane is the pleated structure formed on the polyamide surface. Regarding the relationship between water permeability and pleated structure, it has been disclosed that extending the pleats can increase the effective membrane area and improve water permeability (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-19630 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-179061 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a composite semipermeable membrane that has both salt rejection performance and water permeability. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention includes the following configurations [1] to

[10] . [1] A composite semipermeable membrane having a porous layer consisting of a particle-containing layer containing particles and a particle-free layer not containing particles, and a polyamide separating function layer provided on the particle-free layer. [2] The composite semipermeable membrane according to [1] above, wherein the particles contain an organic polymer. [3] The composite semipermeable membrane according to [2] above, wherein the organic polymer is at least one organic polymer selected from the group consisting of melamine resins, urea resins, phenolic resins, epoxy resins, polyphenylene sulfide, polyether ether ketone, polyamide imides, polyether imides, and polyamides. [4] The composite semipermeable membrane according to any one of the above [1] to [3], wherein the particle content in the porous layer is 2.0% by mass or more and 20.0% by mass or less. [5] The composite semipermeable membrane according to any one of the above [1] to [4], wherein the particle-free layer provided with the polyamide separating functional layer has a thickness of 3.0 μm or more and 15.0 μm or less. [6] The composite semipermeable membrane according to any one of the above [1] to [5], wherein the particles have an average particle size of 0.10 μm or more and 5.0 μm or less. [7] The composite semipermeable membrane according to any one of the above [1] to [6], wherein the main component of the porous layer is a polysulfone-based resin. [8] The composite semipermeable membrane according to any one of the above [1] to [7], wherein in the particle-containing layer, particles are present in the flow path portion of the porous layer. [9] A separation membrane element comprising the composite semipermeable membrane according to any one of the above [1] to [8], a feed-side channel material, a permeate-side channel material, and a water collection pipe.

[10] A fluid separation device comprising the separation membrane element according to [9] above. [Effects of the Invention]

[0009] According to the present invention, a composite semipermeable membrane that combines high salt rejection performance and water permeability is realized. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view of a composite semipermeable membrane in one embodiment of the present invention. [Figure 2] FIG. 2 is a development view showing an example of a separation membrane element. [Figure 3] FIG. 3 is a combined image of two cross-sectional images of the porous layer of the composite semipermeable membrane of Example 4 observed with a scanning electron microscope at a magnification of 10,000 times. DETAILED DESCRIPTION OF THE INVENTION

[0011] 1.Composite semipermeable membrane As one embodiment of the composite semipermeable membrane of the present invention, a composite semipermeable membrane 1 having a substrate 2, a porous layer 3 provided on the substrate 2, and a separation functional layer 4 provided on the porous layer 3, as shown in Fig. 1, will be described below. However, the present invention is not limited to this description, and a composite semipermeable membrane having a configuration without a substrate may also be used.

[0012] (1-1) Base material The substrate has the function of imparting strength to the composite semipermeable membrane and increasing the adhesive strength between the porous layer and the substrate. Examples of the material for the substrate include fabrics made of polymers such as polyester, polyamide, polyolefin, mixtures thereof, or copolymers thereof.

[0013] As the fabric used for the substrate, a nonwoven fabric is preferably used from the viewpoints of strength, roughness-forming ability, and fluid permeability. As the nonwoven fabric, either a long-fiber nonwoven fabric or a short-fiber nonwoven fabric can be preferably used.

[0014] The fibers constituting the nonwoven fabric used as the substrate in the composite semipermeable membrane according to this embodiment may be fibers consisting of a single component, composite fibers consisting of multiple components, or so-called mixed fibers in which multiple types of fibers are mixed. Among these, composite fibers in which a low-melting polymer having a melting point lower than that of a high-melting polymer is arranged around the high-melting polymer are preferably used. By using composite fibers, the fibers in the nonwoven fabric are firmly bonded to each other by thermocompression bonding, so that when the nonwoven fabric is used as a substrate, non-uniformity during casting of the resin solution for forming the porous layer due to fluffing and membrane defects can be suppressed. Furthermore, when the above-mentioned composite fibers are used, the number of bonding points is increased compared to mixed fibers in which fibers consisting only of a high-melting polymer and fibers consisting only of a low-melting polymer are mixed, which leads to improved mechanical strength when used as a substrate.

[0015] The thickness of the substrate used in the composite semipermeable membrane of the present invention affects the strength of the composite semipermeable membrane and the packing density when it is made into an element. To obtain sufficient mechanical strength and packing density, the thickness of the substrate is preferably 30 μm or more and 120 μm or less, and more preferably 50 μm or more and 100 μm or less.

[0016] (1-2) Porous layer The porous layer of the composite semipermeable membrane according to this embodiment is preferably formed from a thermoplastic resin. Here, "thermoplastic resin" refers to a resin that exhibits the property of deforming or flowing when heated by an external force. The thermoplastic resin is preferably made of a chain polymer substance.

[0017] Examples of thermoplastic resins that can be used include polysulfone-based resins having aromatic rings and sulfonyl groups in the main chain, such as polysulfone (hereinafter referred to as "Psf"), polyethersulfone, polyphenylene sulfide sulfone, and polyphenylene sulfone; homopolymers or copolymers of polyamide, polyester, cellulose-based polymers, vinyl polymers, polyphenylene sulfide (hereinafter referred to as "PPS"), and polyphenylene oxide, either alone or in blends. Examples of cellulose-based polymers that can be used include cellulose acetate and cellulose nitrate, and examples of vinyl polymers that can be used include polyethylene, polypropylene, polyvinyl chloride, chlorinated vinyl chloride, and polyacrylonitrile. Among these, Psf, polyacrylonitrile, polyamide, polyester, polyvinyl alcohol, polyphenylene sulfide sulfone, polyphenylene sulfone, PPS, polyether sulfone, polyvinylidene fluoride, cellulose acetate, polyvinyl chloride, or chlorinated vinyl chloride are preferred, and cellulose acetate, polyvinyl chloride, chlorinated vinyl chloride, Psf, polyether sulfone, polyphenylene sulfide sulfone, or polyphenylene sulfone are more preferred. Furthermore, among these materials, Psf is preferred because of its high chemical, mechanical, and thermal stability and ease of molding.

[0018] The porous layer preferably contains these listed compounds as its main component, where "main component" means a component that accounts for 50% by mass or more of the components that make up the porous layer.

[0019] The thickness of the porous layer of the composite semipermeable membrane of the present invention is preferably 20 μm or more and 80 μm or less, more preferably 20 μm or more and 60 μm or less.

[0020] Furthermore, the thickness of the composite of the substrate and the porous layer (hereinafter also referred to as the "porous support") affects the strength of the composite semipermeable membrane and the packing density when it is made into an element. To obtain sufficient mechanical strength and packing density, the thickness of the porous support is preferably 50 μm or more and 200 μm or less, and more preferably 70 μm or more and 160 μm or less.

[0021] The thicknesses of the substrate, porous layer, and porous support can be measured using a dial thickness gauge or digital thickness gauge. In this specification, the thickness of the separation functional layer is much thinner than the substrate or porous layer, so the total thickness of the substrate and porous layer, i.e., the thickness of the porous support, is considered to be the thickness of the composite semipermeable membrane. Therefore, the thicknesses of the composite semipermeable membrane and the substrate are measured separately, and the thickness of the porous layer can be calculated by subtracting the thickness of the substrate from the thickness of the composite semipermeable membrane. When using a dial thickness gauge or digital thickness gauge, the thickness is measured at any 20 locations, and the arithmetic average is calculated.

[0022] The composite semipermeable membrane of the present invention has a porous layer consisting of a particle-containing layer (hereinafter simply referred to as the "particle-containing layer") that contains particles and a particle-free layer (hereinafter simply referred to as the "particle-free layer") that does not contain particles, and a polyamide separating function layer provided on the particle-free layer. Here, the "particle-free layer" refers to a porous layer that substantially does not contain particles. Specifically, it refers to a layer in which no particles are observed in a 0.5 μm-wide region parallel to the composite semipermeable membrane surface as shown in FIG. 3 in a cross-sectional image of the composite semipermeable membrane taken at a magnification of 10,000 times, obtained by the method described below in "(1) Thickness of the particle-free layer." When a region at the same position from the composite semipermeable membrane surface is observed in five different cross-sectional images, and no particles are observed in the region in four or more cross-sectional images, that region is considered to be a particle-free layer.

[0023] As a result of extensive research, the inventors have found that the water permeability of a composite semipermeable membrane having a polyamide separation functional layer formed by interfacial polymerization can be improved by forming a porous layer including a particle-containing layer containing particles and a particle-free layer not containing particles. The particle-containing layer transports monomers, such as amines, necessary for the formation of the separation functional layer to the polymerization site. It is believed that the interaction between the particle-constituting components and the monomer increases the monomer concentration in the particle-containing layer, thereby improving the rate of monomer transport to the particle-free layer, thereby contributing to the improved water permeability of the composite semipermeable membrane. Examples of the type of interaction include hydrogen bonding, hydrophobic interaction, and π-π interaction. The particle-free layer serves as a polymerization site, retaining and releasing the monomer to supply the formed separation functional layer with the monomer and supporting the formed separation functional layer. Furthermore, providing a separation functional layer on the particle-free layer prevents particles from being exposed to the surface of the porous layer, suppressing the occurrence of defects in the separation functional layer and achieving high removal performance.

[0024] Furthermore, the porous layer of the composite semipermeable membrane according to this embodiment preferably has a continuous structure at the interface between the particle-containing layer and the particle-free layer. Here, "continuous structure" refers to a structure in which no skin layer is present at the interface between the particle-containing layer and the particle-free layer. The "skin layer" refers to a portion of the porous layer that has a high density, specifically, a layer with a pore diameter of 1 nm or more and 50 nm or less. If a skin layer is present at the interface between the particle-containing layer and the particle-free layer, high resistance occurs in the porous layer, resulting in a decrease in the water permeability of the composite semipermeable membrane. The pore diameter of the skin layer can be calculated by image analysis of a cross-sectional image of the composite semipermeable membrane, similar to the method described below in "(1) Thickness of the particle-free layer." The pore diameter is calculated as a circle-equivalent diameter.

[0025] The particles contained in the particle-containing layer of the composite semipermeable membrane according to this embodiment preferably contain an organic polymer, and more preferably consist solely of an organic polymer. Furthermore, the particles preferably have affinity, i.e., interaction, with polyfunctional amines. Furthermore, when the porous layer is formed by non-solvent-induced phase separation, the particles preferably do not dissolve in a good solvent that dissolves the thermoplastic resin in order to maintain their shape. Examples of organic polymers that satisfy the above conditions include melamine-based resins containing a condensate of melamine and formaldehyde, urea resins containing a condensate of urea and formaldehyde, phenol-based resins containing a condensate of phenol and formaldehyde, epoxy resins, PPS, polyether ether ketone, polyamideimide, polyetherimide, and polyamide. Among these, the particles preferably contain melamine-based resins, PPS, or polyamide as organic polymers.

[0026] The average particle size of the particles contained in the particle-containing layer of the composite semipermeable membrane according to this embodiment is preferably 0.10 μm or more and 10 μm or less, more preferably 0.10 μm or more and 5 μm or less, even more preferably 0.10 μm or more and 2.0 μm or less, and most preferably 0.10 μm or more and 1.2 μm or less. By using particles having an average particle size within the above range, the particles can be uniformly dispersed in the resin solution that forms the porous layer, making it easy to form a porous layer containing the particles.

[0027] The average particle size can be measured by observation using a scanning electron microscope (hereinafter referred to as "SEM"). The area of ​​each particle is determined from the image obtained by observation using image analysis software such as ImageJ, and the area is converted to a circle-equivalent diameter. The average value is then used as the average particle size. Note that the significant digits are two.

[0028] The particle content of the porous layer in the composite semipermeable membrane according to this embodiment is preferably 2.0% by mass or more and 20.0% by mass or less, and more preferably 4.0% by mass or more and 18.0% by mass or less. By setting the particle content of the porous layer to 2.0% by mass or more, the water permeability of the composite semipermeable membrane can be improved. By setting the particle content of the porous layer to 20.0% by mass or less, the formability of the particle-containing layer can be maintained, the occurrence of defects can be suppressed, and the strength of the porous layer can be maintained.

[0029] The particle content in the porous layer can be measured by dissolving the porous layer in a solvent that dissolves the thermoplastic resin that forms the porous layer but not the particles, and then centrifuging the resulting solution to precipitate the particles in the porous layer. For example, when the porous layer is PSf, N,N-dimethylformamide (hereinafter referred to as "DMF") can be used as a solvent that dissolves the thermoplastic resin. Furthermore, the polyamide separation functional layer of the composite semipermeable membrane is removed before dissolving the porous layer. One method for removing the polyamide separation functional layer is to immerse the composite semipermeable membrane in a sodium hypochlorite aqueous solution. Furthermore, when the composite semipermeable membrane contains a substrate, the substrate is peeled off and removed from the porous layer, and then the porous layer is dissolved. Specifically, the particle content can be measured by the method described below in "(3) Particle Content."

[0030] The particle content of the porous layer can be controlled by adjusting the concentration of particles added to the resin solution A described in "(2-1) Porous layer forming step" below.

[0031] The thickness of the particle-free layer provided with the separating functional layer of the composite semipermeable membrane according to this embodiment is preferably 3.0 μm or more and 15.0 μm or less, more preferably 3.0 μm or more and 10.0 μm or less. By making the thickness of the particle-free layer 3.0 μm or more, particle exposure to the surface can be prevented. By making the thickness of the particle-free layer 15.0 μm or less, permeation resistance can be suppressed and the water permeability performance of the composite semipermeable membrane can be improved. The thickness of the particle-free layer can be measured by observing the cross section of a sliced ​​sample obtained by cutting the composite semipermeable membrane in a direction perpendicular to the membrane surface using an SEM. Specifically, it can be measured by the method described below in "(1) Thickness of the particle-free layer." Figure 3 shows an example of an observed image. An SEM such as the S-5500 scanning electron microscope manufactured by Hitachi High-Technologies Corporation can be used, and observation is performed at an accelerating voltage of 2 to 5 kV.

[0032] The thickness of the particle-free layer can be controlled by adjusting the coating thickness of the resin solution B described in "(2-1) Porous layer forming step" below.

[0033] Furthermore, the composite semipermeable membrane of the present invention may have any structure as long as it includes a particle-free layer provided with a separation functional layer, and may have, for example, a three-layer structure such as particle-free layer-particle-containing layer-particle-free layer, or the particle-free layer may exist in the particle-containing layer in the form of islands.

[0034] In the particle-containing layer, the particles are preferably present in the flow path portion of the porous layer. Here, "flow path portion of the porous layer" means the portion of the porous layer that contacts and passes through the fluid. The presence of the particles in the flow path portion of the porous layer allows the particles to adsorb monomer, increasing the monomer concentration in the particle-containing layer and facilitating an improvement in the rate of monomer transfer to the particle-free layer during the polymerization reaction.

[0035] (1-3) Separation functional layer The polyamide separating functional layer in the composite semipermeable membrane of the present invention preferably contains a crosslinked polyamide, more preferably contains a crosslinked polyamide as a main component. The separating functional layer can exhibit high removal performance by containing 50% by mass or more of crosslinked polyamide. The content of crosslinked polyamide in the separating functional layer is preferably 80% by mass or more, more preferably 90% by mass or more.

[0036] "Crosslinked polyamide" refers to a polyamide having a crosslinked structure. Examples include a form in which the crosslinked structure is formed via a crosslinking agent, and a form in which at least one of a polyfunctional amine and a polyfunctional acid halide is trifunctional or higher, and the polyamide forms a network-like crosslinked structure. Of these, it is preferable that at least one of the polyfunctional amine and the polyfunctional acid halide contains a trifunctional or higher compound. This results in a rigid molecular chain and a good pore structure for removing fine solutes such as hydrated ions and boron.

[0037] The term "polyfunctional amine" refers to an amine having at least two primary and / or secondary amino groups in one molecule. Examples of polyfunctional amines include polyfunctional aromatic amines in which two amino groups are bonded to an aromatic ring at the ortho, meta, or para positions, such as o-phenylenediamine, m-phenylenediamine (hereinafter referred to as "m-PDA"), p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m-diaminopyridine, and p-diaminopyridine; 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, and 4-aminobenzylamine. Examples of suitable polyfunctional amines include polyfunctional aromatic amines, polyfunctional aliphatic amines such as ethylenediamine and propylenediamine, and alicyclic polyfunctional amines such as 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, 2-methylpiperazine, 2,6-dimethylpiperazine, 2,3,5-trimethylpiperazine, 2-ethylpiperazine, 2,5-diethylpiperazine, 2,3,5-triethylpiperazine, 2-n-propylpiperazine, 2,5-di-n-butylpiperazine, 1,3-bispiperidylpropane, and 4-aminomethylpiperazine. These polyfunctional amines may be used alone or in combination.

[0038] When the purpose is to remove NaCl, such as in seawater desalination, it is preferable to use a polyfunctional aromatic amine, and among these, m-PDA and 1,3,5-triaminobenzene are more preferable.

[0039] When the purpose is to separate monovalent ions from polyvalent ions, it is preferable to use a polyfunctional aliphatic amine or an alicyclic polyfunctional amine, it is more preferable to use an alicyclic polyfunctional amine, and it is even more preferable to use piperazine and a substituted piperazine.

[0040] The term "polyfunctional acid halide" refers to an acid halide or polyfunctional acid anhydride halide having at least two halocarbonyl groups in one molecule, and is not particularly limited as long as it forms a crosslinked polyamide separation layer upon reaction with the polyfunctional amine. For example, trifunctional acid halides include trimesoyl chloride (hereinafter referred to as "TMC"), 1,3,5-cyclohexanetricarboxylic acid trichloride, and 1,2,4-cyclobutanetricarboxylic acid trichloride. Examples of the bifunctional acid halides include aromatic bifunctional acid halides such as biphenyldicarboxylic acid dichloride, biphenylenecarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, and naphthalenedicarboxylic acid chloride, aliphatic bifunctional acid halides such as adipoyl chloride and sebacoyl chloride, and alicyclic bifunctional acid halides such as cyclopentanedicarboxylic acid dichloride, cyclohexanedicarboxylic acid dichloride, and tetrahydrofurandicarboxylic acid dichloride. These polyfunctional acid halides may be used alone or in combination.

[0041] (1-4) Separation membrane element The separation membrane element according to this embodiment comprises a composite semipermeable membrane according to an embodiment of the present invention. An example of the configuration of the separation membrane element will be described with reference to FIG.

[0042] As shown in FIG. 2, the separation membrane element 5 includes a feed-side channel material 8 , a composite semipermeable membrane 1 , a permeate-side channel material 9 , a water collection pipe 10 , and end plates 6 and 7 .

[0043] The feed-side channel material 8 is disposed so as to face the feed side of the composite semipermeable membrane 1, and is wrapped around the water collection pipe 10 together with the composite semipermeable membrane 1. The feed-side channel material 8 is preferably, for example, a net.

[0044] The permeate-side channel material 9 is disposed so as to face the permeate side of the composite semipermeable membrane 1, and is wrapped around the water collection pipe 10 together with the composite semipermeable membrane 1. As the permeate-side channel material 9, for example, tricot or a projection-fixed sheet or the like can be used.

[0045] The water collection pipe 10 is a hollow cylindrical member with a plurality of holes on the side surface, and the end plates 6 and 7 are disk-shaped members with a plurality of supply ports (or discharge ports).

[0046] Fluid separation by the separation membrane element 5 will now be described. Feed water 11 is supplied to the separation membrane element 5 through multiple supply ports in the end plate 6. The feed water 11 moves through the feed-side flow path formed by the feed-side flow path material 8 on the supply side of the composite semipermeable membrane 1. The fluid that has permeated the composite semipermeable membrane 1 (shown as permeate 12 in the figure) moves through the permeate-side flow path formed by the permeate-side flow path material 9. The permeate 12 that has reached the water collection pipe 10 passes through the holes in the water collection pipe 10 and enters the interior of the water collection pipe 10. The permeate 12 that has flowed through the water collection pipe 10 is discharged to the outside from the end plate 7. On the other hand, the fluid that has not permeated the composite semipermeable membrane 1 (shown as concentrate 13 in the figure) moves through the feed-side flow path and is discharged to the outside from the end plate 7. In this way, the feed water 11 is separated into the permeate 12 and the concentrate 13.

[0047] 2. Manufacturing method of composite semipermeable membrane (2-1) Porous layer formation process The process for forming the porous layer of the composite semipermeable membrane according to this embodiment comprises the following steps (a) to (c). Step (a) is a step of dissolving a thermoplastic resin (hereinafter also referred to as "resin") in a good solvent, adding particles to the resin solution A, and placing the resin solution A on the surface of a substrate. Step (b) is a step of disposing a resin solution B, prepared by dissolving a resin in a good solvent, on the surface of the resin solution A disposed on the surface of the substrate. Step (c) is a step of contacting the resin solutions A and B placed on the substrate with a coagulation liquid containing a non-solvent and a good solvent for the resin, thereby coagulating the resin.

[0048] The step of forming the porous layer may further include a step of preparing a resin solution by dissolving a resin, which is a component of the porous layer, in a good solvent for the resin.

[0049] The term "resin" refers to the thermoplastic resin that is the main component of the porous layer, and is specifically as described above. The following conditions are particularly preferably applied when the resin is Psf.

[0050] The term "good solvent" refers to a solvent that dissolves the resin. The speed at which the good solvent flows out of the resin solution in step (c) can be adjusted by selecting the good solvent. The good solvent is preferably at least one solvent selected from the group consisting of amides such as N-methyl-2-pyrrolidone, tetrahydrofuran, dimethyl sulfoxide (hereinafter "DMSO"), tetramethylurea, N,N-dimethylacetamide, DMF, N,N-dimethylisobutyramide, N,N-diisopropylisobutyramide, and N,N-bis(2-ethylhexyl)isobutyramide; lower alkyl ketones such as acetone and methyl ethyl ketone; esters such as trimethyl phosphate; and lactones such as γ-butyrolactone. DMSO or DMF is more preferred as the good solvent.

[0051] The solvents contained in the resin solutions may be the same or different as long as they are good solvents for the resins. The solvent content can be adjusted appropriately taking into consideration the strength characteristics of the porous layer to be produced or the impregnation of the base material with the resin solution.

[0052] The resin solution may also contain additives for adjusting the dense layer, void layer, pore size, porosity, hydrophilicity, elastic modulus, etc. of the porous layer. Examples of additives for adjusting the pore size and porosity include, but are not limited to, water, alcohols, water-soluble polymers such as polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid, or salts thereof, inorganic salts such as lithium chloride, sodium chloride, calcium chloride, and lithium nitrate, formaldehyde, and formamide. Examples of additives for adjusting the hydrophilicity and elastic modulus include various surfactants.

[0053] Steps (a) and (b) can be carried out by applying a resin solution.

[0054] The step of applying the resin solution can be carried out using various coaters, such as a spin coater, flow coater, roll coater, comma coater, bar coater, gravure coater, slit die coater, etc. The application methods in steps (a) and (b) may be the same or different.

[0055] The interval between steps (a) and (b) is preferably 3 seconds or less, which can prevent the formation of a skin layer at the interface between the particle-containing layer and the particle-free layer.

[0056] When the resin solution contains Psf, the Psf concentration (ie, solid content concentration) is preferably 15% by mass or more and 25% by mass or less.

[0057] The concentration of the particles added to the resin solution A is preferably 2% by mass or more and 25% by mass or less with respect to the resin concentration.

[0058] The thickness of the particle-containing layer and particle-free layer to be obtained can be controlled, for example, by controlling the coating thickness of the resin solutions A and B.

[0059] When using PSF, the temperature of the resin solution during application is preferably within the range of 10°C to 50°C. Within this range, the resin solution is highly stable and has good applicability. The preferred temperature range of the resin solution can be adjusted appropriately depending on the viscosity of the resin solution used.

[0060] The interval between steps (b) and (c) is preferably 0.1 seconds to 5 seconds. If the time until contact with the coagulating liquid is within this range, the resin solution will be sufficiently impregnated into the spaces between the fibers of the substrate before coagulation.

[0061] In step (c), the resin solution placed on the substrate is brought into contact with a solidifying liquid (non-solvent) in which the resin has a lower solubility than the good solvent in the solution, thereby solidifying the resin, thereby forming a porous structure. Preferred methods for bringing the resin solution into contact with the solidifying liquid include, for example, applying the solidifying liquid to the resin solution and immersing the resin solution in the solidifying liquid.

[0062] Examples of the non-solvent include aliphatic hydrocarbons such as water, hexane, pentane, benzene, toluene, methanol, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol, and low-molecular-weight polyethylene glycol, aromatic hydrocarbons, aliphatic alcohols, and mixed solvents thereof.

[0063] The temperature of the coagulation liquid is preferably from 5° C. to 50° C., more preferably from 5° C. to 30° C. Within this range, a sufficient coagulation rate can be obtained, and film-forming properties are good.

[0064] Next, the obtained porous support is preferably washed with hot water to remove any remaining good solvent etc. The temperature of the hot water at this time is preferably 50°C or higher and 90°C or lower.

[0065] (2-2) Separation functional layer formation process Next, a method for forming the separation functional layer will be described.

[0066] The separation functional layer can be obtained, for example, by chemically reacting a polyfunctional amine with a polyfunctional acid halide to form a polyamide, as described above. From the viewpoints of productivity and performance, the chemical reaction method is preferably interfacial polymerization. That is, the separation functional layer is preferably formed by performing interfacial polycondensation on the surface of a porous layer using an aqueous solution containing a polyfunctional amine and an organic solvent solution containing a polyfunctional acid halide. This process results in the formation of a polyamide separation functional layer.

[0067] More specifically, the interfacial polymerization step preferably comprises the following steps (d) to (g). Step (d) contacting the porous layer with an aqueous solution containing a polyfunctional amine. Step (e) removing the excess polyfunctional amine-containing aqueous solution from the porous layer. Step (f) A step of contacting the porous layer that has been contacted with the aqueous solution containing the polyfunctional amine with an organic solvent solution in which a polyfunctional acid halide is dissolved. Step (g): A step of removing the organic solvent solution after the reaction.

[0068] In step (d), the concentration of the polyfunctional amine in the aqueous polyfunctional amine solution is preferably 0.1% by mass to 15% by mass, more preferably 0.5% by mass to 10% by mass, which allows for sufficient solute removal performance and water permeability.

[0069] The contact of the aqueous polyfunctional amine solution with the porous layer is preferably carried out uniformly and continuously. Specific examples include a method of applying the aqueous polyfunctional amine solution to the porous layer and a method of immersing the porous layer in the aqueous polyfunctional amine solution. The contact time between the porous layer and the aqueous polyfunctional amine solution is preferably 1 second to 2 minutes, more preferably 3 seconds to 1 minute.

[0070] In step (e), after contacting the polyfunctional amine aqueous solution with the porous layer, the polyfunctional amine aqueous solution is removed so that no droplets remain on the porous layer. Removing the polyfunctional amine aqueous solution prevents residual droplets from becoming membrane defects after the separation function layer is formed, which could reduce removal performance. Methods for removing the polyfunctional amine aqueous solution include, for example, vertically holding the porous layer after contact with the polyfunctional amine aqueous solution to allow the excess aqueous solution to flow naturally, blowing a stream of air such as nitrogen from an air nozzle to drain and dry the layer, or removing the aqueous solution using paper or other materials that can absorb the aqueous solution.

[0071] In step (f), the concentration of the polyfunctional acid halide in the organic solvent solution is preferably 0.01% by mass or more and 2.0% by mass or less, more preferably 0.02% by mass or more and 1.0% by mass or less, because a sufficient reaction rate can be obtained by setting the concentration of the polyfunctional acid halide to 0.01% by mass or more, and the occurrence of side reactions can be suppressed by setting the concentration of the polyfunctional acid halide to 2.0% by mass or less.

[0072] The organic solvent for dissolving the polyfunctional acid halide is preferably immiscible with water, dissolves the polyfunctional acid halide, and does not destroy the porous support, and may be inactive to the polyfunctional amine and the polyfunctional acid halide. Examples of the organic solvent for dissolving the polyfunctional acid halide include saturated hydrocarbons such as hexane, heptane, octane, nonane, and decane, isoparaffinic solvents such as IP Solvent 1620, IP Clean LX IP Solvent 2028, ISOPAR E, ISOPAR G, ISOPAR H, and ISOPAR L manufactured by ExxonMobil, and naphthenic solvents such as ExxonMobil Exxol D30, Exxol D40, Exxol D60, and Exxol D80, and these can be used alone or in combination.

[0073] The organic solvent solution may contain other polyfunctional amine-reactive monomers, organic solvents, acylation catalysts, surfactants, solubilizers, complexing agents, etc. Examples of other polyfunctional amine-reactive monomers include compounds containing at least one, preferably 2 to 4, amine-reactive functional groups selected from sulfonyl halides and acid anhydrides, and compounds containing at least one carboxy group and at least one acyl halide. Examples of organic solvents include benzene, toluene, acetone, and ethyl acetate. Examples of acylation catalysts include DMF.

[0074] The method of bringing the organic solvent solution containing the polyfunctional acid halide into contact with the porous layer may be carried out in the same manner as the method of bringing the aqueous polyfunctional amine solution into contact with the porous layer.

[0075] Step (f) may include a step of heating the organic solvent solution in which the polyfunctional acid halide has been dissolved. The temperature at which the organic solvent solution is heated is preferably from 50° C. to 180° C., more preferably from 60° C. to 160° C. Heating within this range can promote the interfacial polymerization reaction.

[0076] In step (g), the organic solvent solution after the reaction is drained to remove the organic solvent. For example, the organic solvent can be removed by holding the porous support vertically and allowing the excess organic solvent to flow down by gravity, by blowing air onto the support with a fan to dry the organic solvent, or by using a water-air mixture to remove the excess organic solvent.

[0077] 3. How to use composite semipermeable membranes The composite semipermeable membrane according to the embodiment of the present invention is preferably used as a spiral separation membrane element by being wound around a feed-side channel material such as a net, a permeate-side channel material such as a tricot, and a cylindrical water collection pipe having a large number of holes. Furthermore, such elements can be connected in series or in parallel and housed in a pressure vessel to form a composite semipermeable membrane module.

[0078] Furthermore, the above-mentioned composite semipermeable membranes, composite semipermeable membrane elements, and composite semipermeable membrane 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 has not permeated the membrane, thereby obtaining water that meets the intended purpose.

[0079] The feed water to be treated by the composite semipermeable membrane according to an embodiment of the present invention can be a liquid mixture containing a total dissolved solids (hereinafter "TDS") of 500 mg / L or more and 100 g / L or less, such as seawater, brine, or wastewater. Generally, TDS is expressed as "mass / volume" or "mass ratio." By definition, TDS can be calculated from the mass of the residue obtained by evaporating a solution filtered through a 0.45 μm filter at a temperature of 39.5°C or more and 40.5°C or less, or more simply, it can be converted from the practical salinity (S).

[0080] 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 the water to be treated passes through the composite semipermeable membrane is preferably 0.4 MPa or more and 8 MPa or less. As the supply water temperature increases, the solute removal rate decreases, but as the temperature decreases, the water permeability also decreases, so the temperature is preferably 5°C or more and 45°C or less.

[0081] Furthermore, if the pH of the feed water becomes high, there is a risk of scale formation such as from magnesium in the case of feed water with a high solute concentration, such as seawater, and there is also concern that membrane deterioration may occur due to operation at a high pH, ​​so operation in the neutral range is preferable. [Example]

[0082] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited thereto.

[0083] (1) Thickness of the particle-free layer on which the separation functional layer is provided The thickness of the particle-free layer was measured by cross-sectional observation using an SEM. Specifically, the composite semipermeable membrane was washed with pure water at 70 ° C for 10 minutes, and then cut perpendicular to the composite semipermeable membrane surface using the freeze-fracturing method to obtain five slices. Each slice sample was thinly coated with platinum, and then a cross-sectional image was taken using a high-resolution field emission scanning electron microscope (S-5500, manufactured by Hitachi High-Technologies Corporation) at an accelerating voltage of 5 kV and a magnification of 10,000 times. In the obtained image, as shown in Figure 3, the composite semipermeable membrane surface on the side where the separation functional layer is present was divided into regions parallel to the composite semipermeable membrane surface every 0.5 μm in the direction perpendicular to the composite semipermeable membrane surface. The presence of particles was visually confirmed in each divided region from the composite semipermeable membrane surface side, such as region 14 with a width of 0.5 μm parallel to the first composite semipermeable membrane surface from the composite semipermeable membrane surface, and region 15 with a width of 0.5 μm parallel to the second composite semipermeable membrane surface from the composite semipermeable membrane surface. Five different cross-sectional images were checked, and if particles were not observed in four or more images in the same region from the composite semipermeable membrane surface, that region was designated as a particle-free layer. The above observation was repeated, and the number of regions in which particles were not observed in four or more of the five different cross-sectional images was multiplied by 0.5 μm to determine the thickness of the particle-free layer provided with a separation functional layer. For example, if particles were observed in one of five different cross-sectional images in the third 0.5 μm-wide region from the composite semipermeable membrane surface, and particles were observed in two of five different cross-sectional images in the fourth 0.5 μm-wide region from the composite semipermeable membrane surface, the region from the composite semipermeable membrane surface to the third 0.5 μm-wide region was the particle-free layer, and the thickness of the particle-free layer provided with a separation functional layer was determined to be 1.5 μm. Note that thicknesses other than the particle-free layer provided with a separation functional layer can also be measured using the same method.

[0084] (2) Thickness of the porous layer The thickness of the composite semipermeable membrane air-dried at room temperature was measured using a dial thickness gauge (constant pressure thickness gauge PG-01A, manufactured by Teclock Corporation). Next, the substrate was peeled from the porous layer in a 180-degree direction at a peeling speed of 50 mm / min, and the thickness of the resulting substrate was measured using a dial thickness gauge. Finally, the thickness of the porous layer was calculated by subtracting the thickness of the substrate from the thickness of the composite semipermeable membrane. The thickness was measured at 20 random locations, and the arithmetic mean was calculated to determine the thickness of the substrate and composite semipermeable membrane. In addition, decimal points were rounded off.

[0085] (3) Particle content The composite semipermeable membrane was immersed in a 2% by mass aqueous solution of sodium hypochlorite at 25°C for 48 hours to remove the polyamide separation function layer and obtain a porous support. The porous support was then washed with pure water at 70°C for 10 minutes and then dried at room temperature. After drying, the substrate was removed from the porous support by peeling in a 180° direction at a peeling speed of 50 mm / min, and the mass of the porous layer was measured. The porous layer was then dissolved in DMF at 70°C for 2 hours, and the resulting solution was centrifuged at 10,000 G or higher for 40 minutes, the supernatant was removed, and the precipitate at the bottom was obtained. The resulting precipitate was then washed by contacting it with DMF at 70°C for 1 hour, and the washed precipitate was obtained by the above centrifugation. The washed precipitate was vacuum-dried at 60°C for 8 hours, and the amount of precipitated material after drying was measured. The particle content was calculated using the following formula: Particle content (mass%) = mass of precipitate after drying / mass of porous layer × 100.

[0086] (4) Performance evaluation of composite semipermeable membranes under high pressure conditions Raw water (NaCl concentration 3.2% by mass) adjusted to a temperature of 25°C and pH 7 was supplied to the composite semipermeable membrane at an operating pressure of 5.5 MPa, and membrane filtration was performed for 2 hours. After that, the electrical conductivity of the supply water and permeate was measured using a multi-purpose water quality meter (MM60R) manufactured by DKK-TOA Corporation. Next, this electrical conductivity was converted using a previously prepared calibration curve to calculate the NaCl concentration. From the calculated NaCl concentration, the salt rejection performance, i.e., the NaCl rejection rate, was calculated using the following formula. NaCl removal rate (%) = 100 × {1 - (NaCl concentration in permeate water / NaCl concentration in feed water)} In addition, in the above test, the amount of water permeating the membrane for 30 minutes after 2 hours of membrane filtration treatment was measured, and converted into the amount of water permeating (cubic meters) per day per square meter of membrane surface, and the amount of water produced (m 3 / m 2 / day) was calculated.

[0087] (5) Performance evaluation of composite semipermeable membranes under medium pressure conditions The NaCl rejection rate was determined in the same manner as in "(4) Performance evaluation of composite semipermeable membrane under high-pressure conditions" above, except that raw water (NaCl concentration 0.2% by mass) adjusted to a temperature of 25°C and pH 7 was supplied to the composite semipermeable membrane at an operating pressure of 1.55 MPa and membrane filtration treatment was carried out for 2 hours.

[0088] In addition, in the above test, the amount of water permeating the membrane for 30 minutes after 2 hours of membrane filtration treatment was measured, and converted into the amount of water permeating (cubic meters) per day per square meter of membrane surface, and the amount of water produced (m 3 / m 2 / day) was calculated.

[0089] (6) Performance evaluation of composite semipermeable membranes under low pressure conditions The MgSO4 removal rate was determined in the same manner as in "(4) Performance evaluation of composite semipermeable membrane under high-pressure conditions" above, except that raw water (MgSO4 concentration 0.2 mass%) adjusted to a temperature of 25°C and pH 7 was supplied to the composite semipermeable membrane at an operating pressure of 0.48 MPa and membrane filtration treatment was carried out for 2 hours.

[0090] In addition, in the above test, the amount of water permeating the membrane for 30 minutes after 2 hours of membrane filtration treatment was measured, and converted into the amount of water permeating (cubic meters) per day per square meter of membrane surface, and the amount of water produced (m 3 / m 2 / day) was calculated.

[0091] [Example 1] Resin solution A was prepared by adding 18% by mass of PSF and 3% by mass of melamine-based resin particles (Eposter S, manufactured by Nippon Shokubai Co., Ltd., average particle size 0.20 μm) to DMF. Resin solution B was also prepared by dissolving PSF in DMF to a concentration of 18% by mass. Resin solution A at 25°C was applied to a polyester nonwoven fabric (thickness 90 μm) substrate, followed by application of resin solution B at 25°C within 3 seconds. Two seconds after application of resin solution B, the substrate was immersed in pure water at 20°C. The substrate was left to stand in pure water for 1 minute to prepare a porous support with a porous layer formed on the substrate. The resulting porous support was then immersed in pure water at 60°C for 10 minutes to remove the DMF and washed. Cross-sectional images taken with an SEM revealed that the resulting porous layer had a continuous structure without a skin layer.

[0092] The washed porous support was immersed in a 3% by mass aqueous solution of m-PDA for 60 seconds, and the support was slowly pulled up vertically, and nitrogen was sprayed from an air nozzle to remove excess aqueous solution from the porous layer surface. Next, a 25°C n-decane solution containing 0.16% by mass of TMC was applied to the porous layer surface so that it was completely wet, and the surface was left standing for 30 seconds. Then, the porous support was vertically placed, and excess solution was drained and removed, and air at 25°C was blown onto the n-decane solution using a blower to dry it. Finally, the porous support was immersed in 80°C pure water for 10 minutes for washing, thereby obtaining a composite semipermeable membrane with a polyamide separation functional layer.

[0093] [Examples 2 to 5] A composite semipermeable membrane having a polyamide separation function layer was obtained in the same manner as in Example 1, except that the amount of melamine-based resin particles added to resin solution A was 6 mass% in Example 2, 11 mass% in Example 3, 17 mass% in Example 4, 22 mass% in Example 5, and 25 mass% in Example 6.

[0094] [Examples 7 to 10] A composite semipermeable membrane having a polyamide separating function layer was obtained in the same manner as in Example 4, except that the thickness of the particle-free layer was adjusted to 1 μm in Example 7, 3 μm in Example 8, 10 μm in Example 9, and 15 μm in Example 10 by adjusting the coating thickness of resin solution B.

[0095] [Examples 11 to 13] A composite semipermeable membrane having a polyamide separation function layer was obtained in the same manner as in Example 1, except that in Example 11, melamine-based resin particles (Eposter SS manufactured by Nippon Shokubai Co., Ltd., average particle diameter 0.10 μm) were used as the melamine-based resin particles added to resin solution A, in Example 12, melamine-based resin particles (Eposter S6 manufactured by Nippon Shokubai Co., Ltd., average particle diameter 0.40 μm) were used, and in Example 13, melamine-based resin particles (Eposter S12 manufactured by Nippon Shokubai Co., Ltd., average particle diameter 1.2 μm) were used.

[0096] [Comparative Example 1] Using a polyester nonwoven fabric (thickness 90 μm) as a substrate, resin solution B at 25°C was applied to the substrate, and 2 seconds after applying resin solution B, the substrate was immersed in pure water at 20°C. The substrate was left to stand in the pure water for 1 minute to produce a porous support having a porous layer formed on the substrate. Using the obtained porous support, a composite semipermeable membrane having a polyamide separating function layer was obtained in the same manner as in Example 1.

[0097] Comparative Example 2 Using a polyester nonwoven fabric (thickness 90 μm) as a substrate, resin solution A at 25°C was applied to the substrate, and 2 seconds after applying resin solution A, the substrate was immersed in pure water at 20°C. The substrate was left to stand in the pure water for 1 minute to produce a porous support having a porous layer formed on the substrate. Using the obtained porous support, a composite semipermeable membrane having a polyamide separating function layer was obtained in the same manner as in Example 1.

[0098] [Example 14] A composite semipermeable membrane having a polyamide separating functional layer was obtained in the same manner as in Example 1, except that the concentration of m-PDA was 2% by mass and the concentration of TMC was 0.12% by mass.

[0099] [Examples 15 to 19] A composite semipermeable membrane having a polyamide separation functional layer was obtained in the same manner as in Example 14, except that in Example 15, the porous support of Example 3 was used, in Example 16, the porous support of Example 5 was used, in Example 17, the porous support of Example 8, in Example 18, the porous support of Example 10, and in Example 19, the porous support of Example 11 was used.

[0100] [Examples 20 and 21] A porous support was prepared in the same manner as in Example 2, except that polyamide particles (Nylon 12 microparticles manufactured by Toray Industries, Inc., average particle diameter 5.0 μm) were used in Example 20, and PPS particles (Tremill manufactured by Toray Industries, Inc., average particle diameter 10 μm) were used in Example 21 as particles added to resin solution A, and a composite semipermeable membrane having a polyamide separation function layer was obtained in the same manner as in Example 14.

[0101] Comparative Example 3 A composite semipermeable membrane having a polyamide separating function layer was obtained in the same manner as in Example 14, except that the porous support of Comparative Example 1 was used.

[0102] [Example 22] The porous support of Example 1 was immersed in an aqueous solution of 2% by mass of 2-methylpiperazine, 0.01% by mass of sodium dodecyldiphenyletherdisulfonate, and 1% by mass of trisodium phosphate for 60 seconds, and the support was slowly pulled up vertically. Nitrogen was sprayed from an air nozzle to remove excess aqueous solution from the porous layer surface. Next, a 25 ° C n-decane solution containing 0.2% by mass of TMC was applied so that the porous layer surface was completely wet, and the mixture was left standing for 30 seconds. After that, the porous support was vertically turned to drain off excess solution and remove it, and air at 25 ° C was blown onto it using a blower to dry the n-decane solution. Finally, the mixture was immersed in 80 ° C pure water for 10 minutes and washed to obtain a composite semipermeable membrane with a polyamide separation functional layer.

[0103] Comparative Example 4 A composite semipermeable membrane having a polyamide separating function layer was obtained in the same manner as in Example 22, except that the porous support of Comparative Example 1 was used.

[0104] [Table 1]

[0105] [Table 2]

[0106] [Table 3]

[0107] The properties of each of the obtained composite semipermeable membranes are shown in Tables 1 to 3. An SEM image (magnification 10,000 times) of the cross section of the porous layer of the composite semipermeable membrane of Example 4 is shown in Figure 3. As can be seen from Figure 3, the porous layer obtained in Example 4 had a continuous structure without a skin layer.

[0108] The composite semipermeable membranes of Examples 1 to 13, which have porous layers made of a particle-containing layer containing particles and a particle-free layer not containing particles, have water production capacities under high pressure conditions that are 5 to 24% higher than the water production capacity of the composite semipermeable membrane of Comparative Example 1, demonstrating improved water permeability. When no particle-free layer was present, as in Comparative Example 2, the NaCl rejection rate was low at less than 99%, demonstrating that the composite semipermeable membranes formed with a particle-free layer have excellent salt rejection performance.

[0109] Furthermore, even under medium-pressure and low-pressure conditions, the water production capacities of the composite semipermeable membranes of Examples 14 to 22, which have a porous layer consisting of a particle-containing layer containing particles and a particle-free layer not containing particles, are 5 to 28% higher than the water production capacities of the composite semipermeable membranes of Comparative Examples 3 and 4, demonstrating that the water permeability is improved while maintaining high salt rejection performance. [Industrial Applicability]

[0110] The composite semipermeable membrane according to the embodiment of the present invention is used, for example, for seawater desalination, brackish water desalination, drinking water production, industrial ultrapure water production, wastewater treatment, and valuable resource recovery. [Explanation of symbols]

[0111] 1 Composite semipermeable membrane 2 Base material 3 Porous layer 4 Separation functional layer 5 Separation membrane element 6 End plate 7 End plate 8 Supply side channel material 9 Permeate side channel material 10 Water collection pipe 11 Supply water 12 Permeated water 13 Concentrated water 14 A region of 0.5 μm width parallel to the first composite semipermeable membrane surface from the composite semipermeable membrane surface 15 A region with a width of 0.5 μm parallel to the second composite semipermeable membrane surface from the composite semipermeable membrane surface

Claims

1. A composite semipermeable membrane comprising a porous layer consisting of a particle-containing layer containing particles and a particle-free layer not containing particles, and a polyamide separating function layer provided on the particle-free layer.

2. The composite semipermeable membrane according to claim 1 , wherein the particles comprise an organic polymer.

3. 3. The composite semipermeable membrane according to claim 2, wherein the organic polymer is at least one organic polymer selected from the group consisting of melamine resins, urea resins, phenolic resins, epoxy resins, polyphenylene sulfide, polyether ether ketone, polyamide imides, polyether imides, and polyamides.

4. 3. The composite semipermeable membrane according to claim 1, wherein the particle content in the porous layer is 2.0% by mass or more and 20.0% by mass or less.

5. 3. The composite semipermeable membrane according to claim 1, wherein the particle-free layer provided with the polyamide separating function layer has a thickness of 3.0 μm or more and 15.0 μm or less.

6. 3. The composite semipermeable membrane according to claim 1, wherein the particles have an average particle size of 0.10 μm or more and 5.0 μm or less.

7. 3. The composite semipermeable membrane according to claim 1, wherein the porous layer is mainly composed of a polysulfone-based resin.

8. 3. The composite semipermeable membrane according to claim 1, wherein in the particle-containing layer, the particles are present in the flow path portion of the porous layer.

9. A separation membrane element comprising the composite semipermeable membrane according to claim 1 or 2, a feed-side channel material, a permeate-side channel material, and a water collection pipe.

10. A fluid separation device comprising the separation membrane element according to claim 9.

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