Composite semipermeable membrane and separation membrane element provided with composite semipermeable membrane

Abstract

The present invention relates to: a composite semipermeable membrane which comprises a base material, a porous layer that is provided on one surface of the base material, and a separation function layer that is provided on the porous layer, wherein the mass of the porous layer is 3 g / m2 to 13g / m2 inclusive and the root mean square height Rq of the surface of the base material on the side where the porous layer is provided is 1.0 µm to 6.0 µm inclusive; and a separation membrane element which is provided with the composite semipermeable membrane.

Description

Composite semipermeable membrane and separation membrane element comprising a composite semipermeable membrane

[0001] The present invention relates to a composite semipermeable membrane and a separation membrane element comprising a composite semipermeable membrane.

[0002] Generally, composite semipermeable membranes, obtained by coating a porous layer with a separation functional layer made of polyamide obtained by the polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide, have high water permeability and solute removal capabilities and are used in reverse osmosis treatments to remove solutes from raw water, such as in seawater desalination.

[0003] In reverse osmosis, a pressure greater than the difference between the osmotic pressure of the feedwater and the permeate is applied to the feedwater side of the composite semipermeable membrane. In recent years, reverse osmosis has been used in Zero Liquid Discharge (ZLD) to eliminate wastewater and in the concentration of valuable materials in recovery processes, and in some cases, it is operated at higher pressures than conventional methods depending on the solute concentration.

[0004] In high-pressure operation of such reverse osmosis treatment, the permeability of the composite semipermeable membrane may decrease, i.e., the amount of water produced may decrease. In the absence of pressure history, the permeability of the porous layer is approximately 100 times or more than that of the separation functional layer, so the permeability of the composite semipermeable membrane is dominated by the separation functional layer. However, Patent Documents 1 and 2 have pointed out that the amount of water produced by the composite semipermeable membrane decreases due to the consolidation of the porous layer caused by high-pressure operation.

[0005] Patent documents 1 and 2 disclose a method for improving the water treatment efficiency of brine by reducing the water production rate of a composite semipermeable membrane and by thinning the substrate and porous layer constituting the composite membrane, thereby reducing the permeability resistance of the composite between the substrate and the porous layer. Furthermore, the methods described in patent documents 1 and 2 allow for the incorporation of more composite semipermeable membranes into the separation membrane element, thereby increasing the effective membrane area per unit volume of the separation membrane element, and thus improving water treatment efficiency without changing the size of the spiral-type separation membrane element.

[0006] Japanese Patent Publication No. 2015-089532 Japanese Patent Publication No. 2016-068019

[0007] On the other hand, the configurations in Patent Documents 1 and 2 had the problem that solute removal efficiency decreased significantly when the operating pressure was increased to treat saltwater with seawater concentration. The present invention aims to provide a composite semipermeable membrane that has high solute removal efficiency and can maintain the amount of water produced even after high-pressure operation.

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

[10] : [1] A composite semipermeable membrane comprising a substrate, a porous layer provided on one surface of the substrate, and a separation functional layer provided on the porous layer, wherein the mass of the porous layer is 3 g / m ２ 13g / m or more ２ The following composite semipermeable membrane, wherein the root mean square height Rq of the surface of the substrate on the side on which the porous layer is provided is 1.0 μm or more and 6.0 μm or less. [2] The surface of the substrate on the side on which the porous layer is provided has an uneven shape, and the number of recesses with a depth of 20 μm or more is equal to the number of recesses with a depth of 20 μm or more and an area of ​​500 μm ２ The composite semipermeable membrane according to [1] above, wherein the proportion of the number of recesses is 15% or less. [3] The surface of the substrate on the side on which the porous layer is provided has an uneven shape, and the average area of ​​the recesses is 500 μm ２ 2000 μm or more ２ The composite semipermeable membrane described in [1] or [2] above, which is as follows: [4] The surface of the substrate on the side on which the porous layer is provided has an uneven shape, and the number of recesses with a depth of 10 μm or more is equal to the number of recesses with a depth of 10 μm or more and an area of ​​500 μm ２ A composite semipermeable membrane according to any one of the above items [1] to [3], wherein the proportion of the above number of recesses is 20% or less. [5] A composite semipermeable membrane according to any one of the above items [1] to [4], wherein the root mean square height Rq of the surface of the substrate on the side on which the porous layer is provided is 2.0 μm or more and 5.0 μm or less. [6] The mass of the porous layer is 3 g / m ２ 10g / m or more ２The composite semipermeable membrane according to any one of the above [1] to [5]. [7] The composite semipermeable membrane according to any one of the above [1] to [6], wherein the root mean square height Rq of the surface of the base material on the side where the porous layer is provided is 2.0 μm or more and 4.5 μm or less. [8] The composite semipermeable membrane according to any one of the above [1] to [7], wherein the root mean square height Rq of the surface of the porous layer on the side where the separation functional layer is provided after supplying an aqueous solution having a NaCl concentration of 3.5% by mass and a pH of 6.5 at 5.5 MPa and 25 ° C. for 2 hours is 1.0 μm or more and 2.5 μm or less. [9] The composite semipermeable membrane according to any one of the above [1] to [8], wherein the polymer impregnation amount of the base material is 0.5 g / m ２ or more and 2.5 g / m ２ or less.

[10] A separation membrane element comprising the composite semipermeable membrane according to any one of the above [1] to [9].

[0009] According to the present invention, a composite semipermeable membrane having high solute removal performance and capable of maintaining the water production rate even after high-pressure operation can be obtained, and the water treatment efficiency can be improved.

[0010] FIG. 1 is a cross-sectional view of a composite semipermeable membrane according to an embodiment of the present invention. FIG. 2 is a developed view of a separation membrane element according to an embodiment of the present invention.

[0011] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited thereto. In this specification, "mass" is synonymous with "weight".

[0012] 1. Composite semipermeable membrane As an embodiment of the present invention, hereinafter, as shown in FIG. 1, a composite semipermeable membrane 1 having a base material 2, a porous layer 3 provided on the base material 2, and a separation functional layer 4 provided on the porous layer 3 will be described. In addition, a composite body in which a porous layer 3 is provided on a base material 2 is also referred to as a porous support.

[0013] 1.1 Base material The base material gives physical strength to the composite semipermeable membrane. Examples of the base material include fabrics made of polymers such as polyester, polyamide, polyolefin, or mixtures or copolymers thereof.

[0014] As the fabric used as the base material, it is preferable to use a nonwoven fabric from the viewpoint of strength, ability to form irregularities, and fluid permeability. As the nonwoven fabric, both long-fiber nonwoven fabrics and short-fiber nonwoven fabrics can be preferably used.

[0015] The fibers constituting the substrate in the composite semipermeable membrane according to this embodiment may be single-component fibers, composite fibers composed of multiple components, or so-called blended fibers made by mixing multiple types of fibers. Among these, composite fibers in which a low-melting-point polymer having a melting point lower than that of the high-melting-point polymer is arranged around the high-melting-point polymer are preferably used. By using composite fibers, the fibers in the nonwoven fabric adhere firmly to each other by heat-compression bonding. Therefore, when a nonwoven fabric is used as the substrate, it is possible to suppress non-uniformity during casting of the polymer solution for forming the porous layer (hereinafter also simply referred to as "polymer solution") due to fluffing, and to suppress membrane defects. Furthermore, when using the above-mentioned composite fibers, the number of adhesion points is increased compared to blended fibers made by mixing fibers made only of high-melting-point polymers and fibers made only of low-melting-point polymers, so the number of recessed areas in the substrate is reduced, and a composite semipermeable membrane that can withstand high-pressure operation can be produced even when the strength of the porous layer is low.

[0016] 1.1.1 Basis Weight of Substrate The basis weight of the substrate in the composite semipermeable film according to this embodiment is 30 g / m². ２ More than 100g / m ２ The following is preferable: 60 g / m ２ 80g / m or more ２ The following is more preferable: Base material weight of 30 g / m² ２ With the above conditions, excessive permeation during polymer solution casting is minimized, resulting in good film formation, high film peel strength and mechanical strength, and a highly durable separation film can be obtained. On the other hand, if the basis weight of the substrate is 100 g / m² ２ The following conditions allow for a reduction in the thickness of the composite semipermeable membrane and an increase in the membrane area per composite semipermeable membrane element.

[0017] 1.1.2 Density of the Substrate The density of the substrate in the composite semipermeable membrane according to this embodiment is 0.70 g / cm³. ３ 1.05g / cm or more ３ The following is preferable: The density of the base material is 0.70 g / cm³. ３As a result, excessive permeability during polymer solution casting is minimized, allowing for good film formation and the creation of a composite semipermeable film with high mechanical strength and excellent durability. On the other hand, if the density of the substrate is 1.05 g / cm³ ３ As described below, the polymer solution penetrates rapidly into the nonwoven fabric during porous layer formation, resulting in strong adhesion between the substrate and the porous layer, and a semipermeable film with excellent peel strength can be obtained.

[0018] 1.1.3 Substrate Thickness The thickness of the substrate in the composite semipermeable membrane according to this embodiment is preferably 50 μm or more and 120 μm or less, more preferably 50 μm or more and 110 μm or less, and even more preferably 60 μm or more and 100 μm or less. When the thickness of the substrate is within the above range, sufficient strength for pressure resistance can be maintained and the effective membrane area when used as a separation membrane element can be increased.

[0019] 1.1.4 Pure water permeability coefficient of the substrate The pure water permeability coefficient of the substrate in the composite semipermeable membrane according to this embodiment at 25°C is 50 × 10 －９ I understand ３ / (m ２ ・s・Pa) or more 1500×10 －９ I understand ３ / (m ２ Preferably less than s・Pa, and 100 × 10 －９ I understand ３ / (m ２ ・s・Pa) or more 1000×10 －９ I understand ３ / (m ２ A value of less than or equal to s・Pa is more preferable. When the pure water permeability coefficient is within the above range, it does not affect the permeability resistance which would lead to a decrease in the amount of water produced by the composite semipermeable membrane. Furthermore, because the polymer solution penetrates quickly into the nonwoven fabric when the porous layer is formed, the substrate and the porous layer adhere strongly, and a semipermeable membrane with excellent membrane peel strength can be obtained.

[0020] The pure water permeability coefficient of the substrate can be determined by the following method. Cut out a circle of the substrate with a diameter of 4.3 cm, and set the cut-out sample in a stirring-type ultra-holder (UHP-43K, manufactured by Advantec Toyo Co., Ltd.). Next, fill the cell with pure water at 25°C, attach the cap, and then increase the pressure to a constant level using nitrogen or compressed air. Finally, measure the amount of pure water permeate over a certain period of time, and calculate the pure water permeability coefficient from the following formula (1). Pure water permeability coefficient [m ３ / (m ２ (s・Pa) = Pure water permeability / (Effective filtration area of ​​substrate × Sampling time × Supply pressure) ... Equation (1)

[0021] 1.1.5 Root Mean Square Height Rq of the Substrate The composite semipermeable membrane of the present invention has a root mean square height Rq (hereinafter also simply referred to as "substrate Rq") of 1.0 μm or more and 6.0 μm or less on the surface of the substrate on the side where the porous layer is provided. The substrate Rq is more preferably 2.0 μm or more and 5.5 μm or less, even more preferably 2.0 μm or more and 5.0 μm or less, and particularly preferably 2.0 μm or more and 4.5 μm or less. When the substrate Rq is 6.0 μm or less, deformation of the porous layer and the separation function layer due to irregularities in the substrate when the composite semipermeable membrane is operated under high pressure can be prevented, and a composite semipermeable membrane with high solute removal performance can be obtained regardless of the strength of the porous layer. Furthermore, when the substrate Rq is 1.0 μm or more, the adhesive strength between the substrate and the porous layer is increased, and a decrease in the performance of the separation membrane element due to peeling that occurs near the interface between the substrate and the porous layer is less likely to occur.

[0022] The Rq of the substrate can be calculated by observing the surface of the substrate on the side where the porous layer is provided using a laser microscope. Specifically, it is calculated by the method described in "Root Mean Square Height Rq of Substrate" in the examples described later. If the substrate already has a porous layer, it can be observed by immersing it in a good solvent that can dissolve the porous layer, leaving only the substrate. The Rq of the substrate can be controlled, for example, by the number of times, temperature, and linear pressure of the heat-compression bonding with a flat roll as described in "2.1 Substrate Formation Process" described later.

[0023] 1.1.6 Average Area of ​​Recesses in the Substrate The surface of the substrate on the side where the porous layer is provided in the composite semipermeable membrane according to this embodiment has an uneven shape, and the average area of ​​the recesses is 500 μm². ２ 2000 μm or more ２ Preferably, the following: 500 μm ２ 1500 μm or more ２ It is more preferable that the average area of ​​the recesses is 2000 μm². ２ The following conditions prevent deformation of the porous layer and separation function layer caused by irregularities in the substrate when the composite semipermeable membrane is operated under high pressure. Furthermore, the average area of ​​the recesses is 500 μm². ２ As a result, the adhesive strength between the substrate and the porous layer is increased, and the performance degradation of the separation membrane element due to delamination occurring near the interface between the substrate and the porous layer is less likely to occur.

[0024] The number of recesses on the surface of the substrate is preferably 100 to 600 per 1224 μm square of substrate, more preferably 200 to 600, and even more preferably 200 to 550. When the number of recesses on the surface of the substrate is 100 or more, the adhesive strength between the substrate and the porous layer is increased, and the performance degradation of the separation membrane element due to delamination occurring near the interface between the substrate and the porous layer is less likely to occur. Furthermore, when the number of recesses on the surface of the substrate is 600 or less, deformation of the porous layer and the separation functional layer due to the unevenness of the substrate can be prevented when the composite semipermeable membrane is operated under high pressure, and a composite semipermeable membrane with high solute removal performance can be obtained regardless of the strength of the porous layer.

[0025] The average area of ​​the recesses in the substrate can be calculated by observing the surface of the substrate on the side where the porous layer is provided using a laser microscope. Specifically, it is calculated using the method described in "Average Area of ​​Recesses in the Substrate" in the examples described later. If the substrate already has a porous layer, it can be observed by immersing it in a good solvent that can dissolve the porous layer, leaving only the substrate. The average area of ​​the recesses in the substrate can be controlled, for example, by using a composite fiber in which a low-melting-point polymer having a lower melting point than the high-melting-point polymer is arranged around the high-melting-point polymer, or by the number of times, temperature, and linear pressure of the heat-compression bonding with a flat roll as described in "2.1 Substrate Formation Process" described later.

[0026] 1.1.7 Ratio of the number of recesses on the substrate The surface of the substrate on the side where the porous layer is provided in the composite semipermeable membrane according to this embodiment has an uneven shape, and the ratio of the number of recesses with a depth of 10 μm or more to the ratio of recesses with a depth of 10 μm or more and an area of ​​500 μm ２ The ratio of the number of recesses (hereinafter also referred to as the "ratio of 10 μm recesses") is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. Depth 10 μm or more and area 500 μm ２ If more than 20% of the substrate has the above-mentioned recesses, deformation of the porous layer and separation functional layer due to the recesses in the substrate will occur when the composite semipermeable membrane is operated at high pressure, and the solute removal performance is likely to decrease. When the proportion of 10 μm recesses is within the above range, high solute removal performance can be obtained even when the composite semipermeable membrane is operated at high pressure. From the viewpoint of minimizing deformation of the porous layer and separation functional layer due to the recesses in the substrate, it is most desirable that there are no recesses with a depth of 10 μm or more, and the lower limit of the proportion of 10 μm recesses is 0%.

[0027] Furthermore, the surface of the substrate on the side where the porous layer is provided in the composite semipermeable membrane according to this embodiment has a depth of 20 μm or more and an area of ​​500 μm, relative to the number of recesses with a depth of 20 μm or more. ２ The ratio of the number of recesses (hereinafter also referred to as the "ratio of 20 μm recesses") is preferably 15% or less, more preferably 10% or less, and even more preferably 5% or less. When the ratio of 20 μm recesses is within the above range, deformation of the porous layer and separation functional layer caused by recesses in the substrate can be suppressed when the composite semipermeable membrane is operated under high pressure, and a decrease in solute removal performance can be prevented. From the viewpoint of minimizing deformation of the porous layer and separation functional layer caused by recesses in the substrate, it is most desirable that there are no recesses with a depth of 20 μm or more, and the lower limit of the ratio of 20 μm recesses is 0%.

[0028] The ratio of recesses in the substrate can be calculated by observing the surface of the substrate on the side where the porous layer is provided using a laser microscope. Specifically, it is calculated using the method described in "Ratio of Recesses in the Substrate" in the examples described later. If the substrate already has a porous layer, it can be observed by immersing it in a good solvent that can dissolve the porous layer, leaving only the substrate. The ratio of recesses in the substrate can be controlled, for example, by using a composite fiber in which a low-melting-point polymer having a lower melting point than the high-melting-point polymer is arranged around the high-melting-point polymer, or by the number of times, temperature, and linear pressure of thermocompression bonding with a flat roll as described in "2.1 Substrate Formation Process" described later.

[0029] 1.1.8 Polymer Impregnation Amount of Substrate The polymer impregnation amount of the substrate in the composite semipermeable membrane according to this embodiment is 0.5 g / m² ２ 2.5g / m or more ２ The following is preferred: 1.0 g / m ２ 2.3g / m or more ２ The following is more preferable: 1.2 g / m ２ 2.1g / m or more ２ The following is even more preferable: The polymer impregnation amount of the substrate is 2.5 g / m². ２ The following conditions allow for suppression of the penetration of the sealing material by the polymer impregnated in the substrate when impregnating the sealing portion of the separation membrane element with the sealing material, thereby obtaining a separation membrane element that is sufficiently impregnated with the sealing material. Furthermore, the amount of polymer impregnated in the substrate is 0.5 g / m². ２ As a result, the adhesive strength between the substrate and the porous layer is increased, and performance degradation of the composite semipermeable membrane and separation membrane element due to delamination occurring near the interface between the substrate and the porous layer is less likely to occur. Polymer impregnation amount refers to the amount of polymer that forms the porous layer contained in the substrate after the porous layer has been peeled off, and is measured by the method described in "Polymer Impregnation Amount of Substrate" in the examples described later.

[0030] The amount of polymer impregnation into the substrate can be controlled, for example, by conditions such as the coating thickness of the polymer solution on the substrate and the polymer solution temperature in "2.2 Formation of Porous Layer" described later, or by the number of times, temperature, and linear pressure of the heat-compression bonding with a flat roll as described in "2.1 Formation of Substrate" described later.

[0031] 1.2 Porous Layer The porous layer in the composite semipermeable membrane according to this embodiment is preferably made of a thermoplastic polymer. Here, "thermoplastic polymer" means a polymer made of chain polymers that exhibits the property of deforming or flowing when heated by an external force.

[0032] Examples of thermoplastic polymers include homopolymers of polysulfone, polyethersulfone, polyamide, polyester, cellulose polymers, vinyl polymers, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene oxide, as well as copolymers thereof. One type may be used alone, or two or more types may be used in combination.

[0033] Examples of cellulosic polymers include cellulose acetate and cellulose nitrate, while examples of vinyl polymers include polyethylene, polypropylene, polyvinyl chloride, chlorinated vinyl chloride, and polyacrylonitrile. Among these, polysulfone (hereinafter referred to as "Psf"), polyacrylonitrile, polyamide, polyester, polyvinyl alcohol, polyphenylene sulfide sulfone, polyphenylene sulfone, polyphenylene sulfide, polyethersulfone, polyvinylidene fluoride, cellulose acetate, polyvinyl chloride, or chlorinated vinyl chloride are preferred. Among these, Psf is more preferred because it has high chemical, mechanical, and thermal stability and is easy to mold. The porous layer preferably contains these listed compounds as its main components.

[0034] The mass-average molecular weight (hereinafter referred to as "Mw") of Psf, measured by gel permeation chromatography (GPC) with N-methylpyrrolidone as the solvent and polystyrene as the standard substance, is preferably between 10,000 and 200,000, and more preferably between 15,000 and 100,000. When the Mw of Psf is 10,000 or higher, desirable mechanical strength and heat resistance can be obtained as a porous layer. Furthermore, when the Mw is 200,000 or lower, the viscosity of the solution is within an appropriate range, and good moldability can be achieved.

[0035] 1.2.1 Mass of the porous layer The mass of the porous layer in the composite semipermeable membrane of the present invention is 3 g / m ２ 13g / m or more ２ The following applies: 3 g / m ２ 10g / m or more ２ The following is preferable: 4 g / m ２ 8g / m or more ２ The following is more preferable: The mass of the porous layer is 3 g / m ２ The above conditions provide the necessary strength and surface morphology for a porous layer. On the other hand, the higher the mass of the porous layer, the less it is affected by deformation due to the shape of the substrate, and solute removal performance is maintained, but water production capacity tends to decrease. ２ The following conditions result in a composite semipermeable membrane with high water production capacity retention. Furthermore, the effective membrane area of ​​the separation membrane element can also be increased. The mass of the porous layer can be controlled by, for example, the polymer concentration in the polymer solution, the coating thickness of the polymer solution on the substrate, and the temperature of the coagulation solution. Note that the mass of the porous layer (g / m²) ２ This refers more specifically to the mass of the porous layer per unit area, and is calculated by the method described in the "Mass of the Porous Layer" section of the examples described later.

[0036] The performance of composite semipermeable membranes is important not only for water production volume retention but also for high solute removal performance. The inventors of this invention found that when the mass of the porous layer in a composite semipermeable membrane is controlled within the above range, the porous layer and separation functional layer deform, reducing solute removal performance. As a result of diligent research to address this issue, they discovered that the unevenness of the substrate, represented by Rq, is important among the indicators of substrate smoothness. Conventionally, indicators for the surface smoothness of the substrate forming the porous layer have focused on macroscopic areas such as Beck smoothness, core level difference (Sk), and 75-degree specular gloss. However, controlling these indicators has not been able to suppress deformation of the porous layer and separation functional layer by the substrate. In other words, the present invention has found that by setting the Rq of the substrate forming the porous layer to 1.0 μm or more and 6.0 μm or less, deformation of the porous layer and separation functional layer by the substrate is suppressed even when the mass of the porous layer is within the above range, thereby achieving both water production volume retention and high solute removal performance.

[0037] 1.2.2 Thickness of the Porous Layer The thickness of the porous layer in the composite semipermeable membrane according to this embodiment is preferably 4 μm or more and 25 μm or less, more preferably 4 μm or more and 18 μm or less, and even more preferably 4 μm or more and 12 μm or less. When the thickness of the porous layer is 4 μm or more, the polymer solution for forming the porous layer can be applied without causing surface defects, and it can function as a scaffold for interfacial polycondensation to form a separation functional layer. Furthermore, when the thickness of the porous layer is 25 μm or less, a composite semipermeable membrane with high water production capacity can be obtained.

[0038] Furthermore, the thickness of the porous layer after supplying the composite semipermeable membrane according to this embodiment with an aqueous solution of 3.5% by mass and pH 6.5 under conditions of 7.0 MPa and 45°C for 24 hours (hereinafter also simply referred to as "thickness of the porous layer after pressurization") is preferably 3 μm to 12 μm, and more preferably 3 μm to 7 μm. When the thickness of the porous layer after pressurization is within the above range, sufficient strength for pressure resistance can be maintained, and the effective membrane area of ​​the separation membrane element can be increased. The thickness of the porous layer can be controlled, for example, by the thickness of the polymer solution applied to the substrate, the temperature of the coagulation solution, etc.

[0039] 1.2.3 Root Mean Square Height Rq of the Porous Layer After supplying an aqueous solution with a NaCl concentration of 3.5% by mass and a pH of 6.5 to the composite semipermeable membrane according to this embodiment at 5.5 MPa and 25°C for 2 hours, the root mean square height Rq of the surface of the porous layer on the side where the separation functional layer is provided (hereinafter also simply referred to as "Rq of the porous layer after pressurization") is preferably 1.0 μm or more and 2.5 μm or less, and more preferably 1.0 μm or more and 2.0 μm or less. The fact that the Rq of the porous layer after pressurization is within the above range means that the deformation of the porous layer is small during high-pressure operation, and a composite semipermeable membrane with high solute removal capacity and water production capacity retention can be obtained even during high-pressure operation.

[0040] The Rq of the porous layer after pressurization can be calculated by observing the surface of the porous layer on the side where the separation functional layer is provided using a laser microscope after pressurization. Specifically, it is calculated using the method described in "Root Mean Square Height Rq of Porous Layer" in the examples described later. If a separation functional layer is already provided in the porous layer, the measurement may be taken with the separation functional layer formed, or the measurement may be taken after the separation functional layer has been decomposed and removed with sodium hypochlorite.

[0041] The mass of the porous layer is 3 g / m ２ 13g / m or more ２ The following applies, and the Rq of the porous layer after pressurization can be controlled within the above range by, for example, the number of times, temperature, and linear pressure of thermocompression bonding with a flat roll as described in "2.1 Formation Process of Substrate" below. Another method is to improve the strength of the porous layer by using a high-strength thermoplastic polymer.

[0042] 1.3 Separation Functional Layer The separation functional layer of the composite semipermeable membrane according to this embodiment preferably contains polyamide, and more preferably contains polyamide as the main component. "Main component" means a component that accounts for 50% by mass or more of the components of the separation functional layer. Furthermore, the polyamide contained in the separation functional layer is preferably a crosslinked polyamide, and more preferably a crosslinked aromatic polyamide.

[0043] "Polyamide" refers to a polycondensate formed by polycondensing a polyfunctional amine and a polyfunctional acid halide.

[0044] "Cross-linked polyamide" refers to a polyamide having a cross-linked structure. Examples include a form in which a cross-linked structure is formed via a cross-linking agent, and a form in which at least one of a polyfunctional amine and a polyfunctional acid halide is trifunctional or more, and the polyamide forms a network-like cross-linked structure. Examples of cross-linked polyamides include cross-linked aromatic polyamides and cross-linked aliphatic polyamides.

[0045] "Cross-linked aromatic polyamide" refers to a cross-linked polyamide composed of polyfunctional aromatic amines and polyfunctional aromatic acid halides.

[0046] "Cross-linked aliphatic polyamide" refers to a cross-linked polyamide composed of a polyfunctional aliphatic amine and a polyfunctional aromatic acid halide.

[0047] The presence of polyamide in the separation functional layer can be confirmed, for example, by ATR-FTIR (total internal reflection measurement-Fourier transform infrared spectroscopy).

[0048] In particular, the separation functional layer preferably contains 50% by mass or more of cross-linked polyamide, more preferably 80% by mass or more, and even more preferably 90% by mass or more, from the viewpoint of being able to exhibit high solute removal performance.

[0049] From the viewpoint of obtaining rigid molecular chains and forming a pore structure suitable for the removal of fine solutes such as hydrated ions and boron, it is preferable that the crosslinked polyamide contains at least one of a polyfunctional amine and a polyfunctional acid halide that is trifunctional or more. In particular, the separation functional layer preferably contains a crosslinked aromatic polyamide obtained by polycondensation of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide.

[0050] A "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 the aromatic ring in an ortho, meta, or para position, 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; and polyfunctional aromatic amines such as 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, and 4-aminobenzylamine. Furthermore, examples of polyfunctional amines include aliphatic amines such as ethylenediamine and propylenediamine, and polyfunctional aliphatic amines such as alicyclic polyfunctional amines such as 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, 2-methylpiperazine, 2,6-dimethylpiperazine, 2,3,5-trimethylpiperazine, 2,5-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 individually or in combination of two or more.

[0051] In particular, from the viewpoint of solute removal, water permeability, and heat resistance of the composite semipermeable membrane, it is preferable to use m-PDA, p-phenylenediamine, and 1,3,5-triaminobenzene as the polyfunctional amine. Among these, it is more preferable to use m-PDA due to its availability and ease of handling. These polyfunctional aromatic amines may be used individually or in combination of two or more.

[0052] "Polyfunctional acid halides" refer to acid halides or polyfunctional acid anhydride halides having at least two halogenated carbonyl groups in one molecule, and are not particularly limited as long as they form a separation functional layer of polyamide through polycondensation with the above-mentioned polyfunctional amine. For example, trifunctional acid halides include trimesic acid chloride (hereinafter referred to as "TMC"), 1,3,5-cyclohexanetricarboxylic acid trichloride, and 1,2,4-cyclobutanetricarboxylic acid trichloride. Examples of difunctional acid halides include aromatic difunctional acid halides such as biphenyldicarboxylic acid dichloride, biphenylenecarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, and naphthalenedicarboxylic acid chloride; aliphatic difunctional acid halides such as adipoyl chloride and sebacoyl chloride; and alicyclic difunctional acid halides such as cyclopentanedicarboxylic acid dichloride, cyclohexanedicarboxylic acid dichloride, and tetrahydrofrancicarboxylic acid dichloride. These polyfunctional acid halides may be used individually or in combination of two or more.

[0053] From the viewpoint of solute removal and heat resistance of the composite semipermeable membrane, the polyfunctional acid halide is more preferably a polyfunctional aromatic acid chloride having 2 to 4 carbonyl chloride groups in one molecule.

[0054] 1.4 Separation Membrane Element An example of the configuration of a separation membrane element comprising a composite semipermeable membrane according to this embodiment will be described with reference to Figure 2.

[0055] As shown in Figure 2, the separation membrane element 5 comprises a composite semipermeable membrane 1, a supply-side channel material 8, a permeable-side channel material 9, a water collection pipe 10, and end plates 6 and 7. The supply-side channel material 8 is positioned opposite the supply side of the composite semipermeable membrane 1 and is wound around the water collection pipe 10 together with the composite semipermeable membrane 1. For the supply-side channel material 8, a net is preferred, for example. By using a supply-side channel material 8 with a thickness of 0.3 mm to 1.0 mm, the water treatment efficiency of the separation membrane element using the composite semipermeable membrane of the present invention can be further improved. The permeable-side channel material 9 is positioned opposite the permeable side of the composite semipermeable membrane 1 and is wound spirally around the water collection pipe 10 together with the composite semipermeable membrane 1. When using the composite semipermeable membrane according to this embodiment, it can withstand the winding pressure, thereby suppressing deformation of the porous layer and the separation functional layer, and improving the initial treatment efficiency of the separation membrane element. For the permeable-side channel material 9, for example, tricot, a protrusion fixing sheet, etc., can be used. By using a permeable channel material 9 with a thickness of 0.1 mm to 0.5 mm, the processing efficiency of the separation membrane element using the composite semipermeable membrane according to this embodiment can be further improved. The water collection pipe 10 is a hollow cylindrical member having multiple holes on its side. The end plates 6 and 7 are disc-shaped members equipped with multiple supply ports (or discharge ports).

[0056] The separation of fluids by the separation membrane element 5 will now be explained. The supply water 11 is supplied to the separation membrane element 5 from multiple supply ports on the end plate 6. The supply water 11 moves within the supply-side flow channel formed by the supply-side flow channel material 8 on the supply side of the composite semipermeable membrane 1. The fluid that permeates through the composite semipermeable membrane 1 (shown as permeate water 12 in the figure) moves within the permeate-side flow channel formed by the permeate-side flow channel material 9. The permeate water 12 that reaches the collection pipe 10 enters the inside of the collection pipe 10 through the holes in the collection pipe 10. The permeate water 12 that has flowed inside the collection pipe 10 is discharged to the outside from the end plate 7. On the other hand, the fluid that did not permeate through the composite semipermeable membrane 1 (shown as concentrated water 13 in the figure) moves within the supply-side flow channel and is discharged to the outside from the end plate 7. In this way, the supply water 11 is separated into permeate water 12 and concentrated water 13.

[0057] 2.1 Formation Process of Substrate In the composite semipermeable film according to this embodiment, the substrate is preferably a laminate of multiple layers of nonwoven fabric or the like, formed by applying heat and pressure to obtain sufficient strength and smoothness, and it is more preferable to apply heat and pressure multiple times. If the number of layers is two or more, the texture is improved compared to a single layer, and sufficient uniformity can be obtained. Furthermore, if the number of layers is five or less, it is possible to suppress wrinkle formation during lamination and to suppress delamination between layers.

[0058] The base material is obtained by heat-pressing, for example, using two or more sets of flat rolls, either continuously or discontinuously, in a two-roll x two-set system, a two-roll x three-set system, or a three-roll system such as elastic / metal / elastic, elastic / metal / metal, or metal / elastic / metal, during the manufacturing process.

[0059] A "flat roll" refers to a roll with no irregularities on its surface. For example, by using a combination of a metal roll and an elastic roll, it is possible to suppress the fusion of fibers on the surface of a nonwoven fabric and maintain its shape.

[0060] Examples of elastic rolls include so-called paper rolls such as paper, cotton, and aramid paper, and resin rolls such as urethane resin, epoxy resin, silicone resin, polyester resin, and hard rubber.

[0061] The surface temperature of the metal roll is preferably 20 to 90°C lower than the melting point of the polymer constituting at least the surface of the fibers constituting the base material, and more preferably 30 to 70°C lower. If the surface temperature of the metal roll is 20°C or more lower than the melting point of the polymer constituting at least the surface of the fibers constituting the base material, excessive fusion of the surface fibers of the base material can be suppressed, the polymer solution for forming the porous layer can penetrate more easily, and a porous support with excellent adhesive strength can be obtained. On the other hand, if the difference between the surface temperature of the metal roll and the melting point of the polymer constituting at least the surface of the fibers constituting the nonwoven fabric is 90°C or less, the fibers constituting the base material can be firmly bonded to each other, and the unevenness and recess area of ​​the base material can be controlled.

[0062] Furthermore, it is also preferable to create a temperature difference between the metal roll and the elastic roll, so that the surface temperature of the elastic roll is 10 to 120°C lower than the surface temperature of the metal roll.

[0063] Furthermore, the linear pressure of the flat roll is preferably 196 N / cm or more and 4900 N / cm or less, more preferably 490 N / cm or more and 4900 N / cm or less, and even more preferably 980 N / cm or more and 4900 N / cm or less. When the linear pressure of the flat roll is 196 N / cm or more, the fibers constituting the base material are firmly bonded to each other, and the unevenness and recess area of ​​the base material can be controlled. Also, when the linear pressure of the flat roll is 4900 N / cm or less, excessive fusion of the surface fibers of the base material can be suppressed, and the penetration of the polymer solution for forming the porous layer into the base material is not hindered, and a porous support with excellent film adhesion strength can be obtained.

[0064] 2.2 Process for Forming a Porous Layer The process for forming a porous layer in the composite semipermeable membrane according to this embodiment comprises: (a) forming a polymer solution for forming a porous layer, which is obtained by dissolving a thermoplastic polymer in a good solvent, into a flat film; and (b) obtaining a porous layer by solidifying the thermoplastic polymer in a solidification solution containing a non-solvent and a good solvent for the thermoplastic polymer.

[0065] The process for forming a porous layer may further include a step of preparing a polymer solution by dissolving a thermoplastic polymer, which is a component of forming the porous layer, in a good solvent for the thermoplastic polymer.

[0066] The preferred material for the thermoplastic polymer that forms the main component of the porous layer is as described above. The following conditions are particularly preferred when the thermoplastic polymer is Psf.

[0067] A "good solvent" is one that dissolves thermoplastic polymers. By selecting a good solvent, the rate at which the good solvent flows out of the polymer solution in step (b) above can be adjusted. As a result, the surface properties of the porous layer, the density layer thickness, and the surface roughness can be controlled. As a good solvent, at least one solvent selected from the group consisting of amides such as N-methylpyrrolidone, tetrahydrofuran, dimethyl sulfoxide, tetramethylurea, N,N-dimethylacetamide, N,N-dimethylformamide (hereinafter referred to as "DMF"), N,N-dimethylisobutylamide, N,N-diisopropylisobutylamide, and N,N-bis(2-ethylhexyl)isobutylamide, lower alkyl ketones such as acetone and methyl ethyl ketone, esters such as trimethyl phosphate, and lactones such as γ-butyrolactone is preferably used. Among these, dimethyl sulfoxide and DMF are preferably used as good solvents.

[0068] Step (a) can be carried out by applying a polymer solution to the substrate or by immersing the substrate in a polymer solution.

[0069] The application of polymer solutions to substrates can be carried out by various coating methods. Among these, pre-metering coating methods such as die coating, slide coating, and curtain coating, which allow for the application of precise amounts of solution, are preferred. Furthermore, in the formation of porous layers, the slit die method for applying polymer solutions is even more preferably used.

[0070] The polymer concentration (i.e., solid content concentration) in the polymer solution is preferably 15% by mass or more and 30% by mass or less, more preferably 16% by mass or more and 25% by mass or less, and even more preferably 17% by mass or more and 20% by mass or less.

[0071] If the polymer concentration is 15% by mass or more, the mass of the porous layer is 3 g / m ２ 13g / m or more ２ Sufficient porous layer strength can be obtained even under the following conditions. Furthermore, when the polymer concentration is 30% by mass or less, the viscosity of the polymer solution falls within an appropriate range, allowing for the application of an accurate amount of solution using various coating methods.

[0072] The temperature of the polymer solution when applied to the substrate is preferably between 10°C and 60°C. When the polymer solution temperature is within this range, the polymer does not precipitate, and the polymer solution is sufficiently impregnated into the spaces between the fibers of the substrate before solidifying. As a result, a porous support can be obtained in which the porous layer is firmly bonded to the substrate by impregnation. The preferred temperature range of the polymer solution can be appropriately adjusted depending on the viscosity of the polymer solution used.

[0073] Furthermore, the thermoplastic polymer contained in the polymer solution can be selected as appropriate, taking into consideration various properties such as the strength characteristics, permeability characteristics, and surface characteristics of the porous layer to be manufactured. For example, by pouring the polymer solution onto a substrate to a certain thickness and wet solidifying it in a solidification bath, a porous layer having fine pores with a diameter of several 1 to 30 nm on most of its surface can be obtained.

[0074] The solvent contained in the polymer solution may be the same solvent as the polymer solution or a different solvent, as long as it is a good solvent for thermoplastic polymers. It can be adjusted as appropriate, taking into account the strength characteristics of the porous layer to be manufactured and the impregnation of the polymer solution into the substrate.

[0075] As described above, applying a polymer solution to a substrate causes the polymer solution to impregnate the substrate. To control the impregnation of the polymer solution into the substrate, methods include controlling the time between applying the polymer solution to the substrate and immersing it in a solidification solution (solidification bath), or adjusting the viscosity by controlling the temperature or concentration of the polymer solution. It is also possible to combine these methods.

[0076] In step (b), a polymer solution placed on a substrate is immersed in a coagulation solution having a polymer solubility lower than that of a good solvent in the polymer solution, thereby solidifying the polymer and forming a three-dimensional network structure.

[0077] Furthermore, by including a non-solvent such as water and a good solvent in the coagulation solution, it becomes possible to form a dense layer on the film surface through non-solvent-induced phase separation.

[0078] Examples of non-solvents include aliphatic hydrocarbons such as water, hexane, pentane, benzene, toluene, methanol, ethanol, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol, and low molecular weight polyethylene glycol, as well as aromatic hydrocarbons, aliphatic alcohols, or mixtures thereof. These may be used individually or in combination of two or more.

[0079] The temperature of the coagulation solution is preferably between 5°C and 50°C, and more preferably between 5°C and 30°C. When the temperature of the coagulation solution is 50°C or lower, the vibration of the coagulation bath surface due to thermal motion does not become excessive, and the surface smoothness of the porous layer is improved. Furthermore, when the temperature of the coagulation solution is 5°C or higher, a sufficient coagulation rate is obtained, and film formation is good. In addition, when the temperature of the coagulation solution is within the above range, a porous layer with a surface pore size of 3 nm to 10 nm is easily obtained.

[0080] Next, it is preferable to wash the porous support with hot water to remove any remaining film-forming solvent from the resulting porous support. The temperature of the hot water at this time is preferably 50°C to 100°C, and more preferably 60°C to 95°C. If the temperature of the hot water is 100°C or lower, the degree of shrinkage of the porous support can be kept to a minimum. Also, if the temperature of the hot water is 50°C or higher, a high cleaning effect can be obtained.

[0081] 2.3 Formation Process of the Separation Functional Layer The separation functional layer is obtained, for example, by forming a polyamide by polycondensation of a polyfunctional amine and a polyfunctional acid halide, as described above. Interfacial polymerization is the most preferred method of polycondensation from the viewpoint of productivity and performance. That is, the separation functional layer is preferably formed by performing interfacial polycondensation on the surface of the porous layer using an aqueous solution containing a polyfunctional amine and an organic solvent containing a polyfunctional acid halide. A polyamide is formed by this process. The following describes a process for forming a crosslinked aromatic polyamide using a polyfunctional aromatic amine as the polyfunctional amine and a polyfunctional aromatic acid chloride as the polyfunctional acid halide, but the present invention is not limited thereto.

[0082] Interfacial polymerization includes the following steps (c) and (d): Step (c) A step of contacting a porous layer with an aqueous solution containing a polyfunctional aromatic amine. Step (d) After step (c), a step of contacting the porous layer with a solution in which a polyfunctional aromatic acid chloride has been dissolved.

[0083] In step (c), the concentration of the polyfunctional aromatic amine in the aqueous solution of the polyfunctional aromatic amine is preferably 0.1% by mass or more and 20% by mass or less, and preferably 0.5% by mass or more and 15% by mass or less. When the concentration of the polyfunctional aromatic amine is within the above range, sufficient solute removal performance and water permeability can be obtained.

[0084] It is preferable to apply the polyfunctional aromatic amine aqueous solution uniformly and continuously to the porous layer. Specifically, examples include coating the porous layer with the polyfunctional aromatic amine aqueous solution or immersing the porous layer in the polyfunctional aromatic amine aqueous solution. The contact time between the porous layer and the polyfunctional aromatic amine aqueous solution is preferably 1 second to 10 minutes, and more preferably 10 seconds to 3 minutes.

[0085] After contacting the porous layer with the polyfunctional aromatic amine aqueous solution, it is preferable to remove any remaining liquid droplets from the surface of the porous support. Removing the liquid can suppress the occurrence of defects in the separation functional layer. Methods for removing the liquid include, for example, holding the porous support vertically after contact with the polyfunctional aromatic amine aqueous solution to allow excess solution to flow naturally, or forcibly removing the liquid by blowing a stream of air such as nitrogen from an air nozzle. After removing the liquid, the film surface can also be dried to remove some of the water from the aqueous solution.

[0086] In step (d), the concentration of polyfunctional aromatic acid chloride in the solution is preferably 0.01% by mass or more and 10% by mass or less, and more preferably 0.02% by mass or more and 2.0% by mass or less. A sufficient reaction rate can be obtained when the concentration of polyfunctional aromatic acid chloride in the solution is 0.01% by mass or more. Furthermore, the occurrence of side reactions can be suppressed when the concentration of polyfunctional aromatic acid chloride in the solution is 10% by mass or less.

[0087] The solvent used in the solution for dissolving the polyfunctional aromatic acid chloride is preferably an organic solvent that is immiscible with water, dissolves the polyfunctional aromatic acid chloride without destroying the porous support, and is inert to the polyfunctional aromatic amine and the polyfunctional aromatic acid chloride. Preferred examples of organic solvents include hydrocarbon compounds such as n-nonane, n-decane, n-undecane, n-dodecane, isooctane, isodecane, and isododecane, or mixtures thereof.

[0088] The method for contacting a porous layer containing a polyfunctional aromatic acid chloride solution with an aqueous polyfunctional aromatic amine solution can be carried out in the same manner as the method for coating the porous layer with the aqueous polyfunctional aromatic amine solution.

[0089] After the reaction, the organic solvent is removed from the film surface. Methods for removing the organic solvent include, for example, vertically gripping the porous support and allowing excess organic solvent to drain naturally; drying the organic solvent by blowing air with a fan; or removing excess organic solvent with a water-air mixture.

[0090] 3. Method of Using the Composite Semipermeable Membrane As described above, the composite semipermeable membrane according to this embodiment is suitably used as a spiral-type separation membrane element. Furthermore, these elements can be connected in series or parallel and housed in a pressure vessel to form a separation membrane module.

[0091] Furthermore, the above-mentioned composite semipermeable membranes, separation membrane elements, and separation membrane modules can be combined with pumps that supply water to them, and devices that pre-treat the supply water to constitute a fluid separation system. By using this separation system, for example, gas separation or separation of supply water into permeate water such as drinking water and concentrated water that did not permeate the membrane can be performed to obtain water suitable for the purpose.

[0092] Examples of feedwater treated by the composite semipermeable membrane according to this embodiment include liquid mixtures containing 500 mg / L to 100 g / L of TDS (Total Dissolved Solids), such as seawater, brine, and wastewater. Generally, TDS is expressed as "mass / volume" or "mass ratio". According to the definition, it can be calculated from the mass of the residue after evaporating a solution filtered through a 0.45 micron filter at a temperature of 39.5 to 40.5°C, but a simpler method is to convert it from the practical salinity (S).

[0093] A higher operating pressure when permeating feedwater through the composite semipermeable membrane improves the solute removal rate. However, considering the increased energy required for operation and the durability of the composite semipermeable membrane, the operating pressure when permeating feedwater through the composite semipermeable membrane is preferably between 0.5 MPa and 12 MPa. As the feedwater temperature increases, the solute removal rate decreases, and as it decreases, the amount of water produced decreases. Therefore, the feedwater temperature is preferably between 5°C and 55°C.

[0094] The composite semipermeable membrane according to this embodiment allows for appropriate modification of the separation functional layer according to the solute to be removed. For example, by providing a separation functional layer containing a crosslinked aromatic polyamide in the composite semipermeable membrane, it can be used as a reverse osmosis membrane for treating seawater or brine. In this case, the water production capacity retention rate of the composite semipermeable membrane, calculated by the method described in the "NaCl high pressure test" of the examples described later, is preferably 90% or higher, more preferably 93% or higher, and even more preferably 95% or higher. Furthermore, the NaCl removal rate of the composite semipermeable membrane, calculated by the method described in the "NaCl removal rate and water production capacity of the composite semipermeable membrane" of the examples described later, is preferably 99.70% or higher, more preferably 99.80% or higher, and even more preferably 99.83% or higher. Moreover, it is preferable that the water production capacity retention rate and the NaCl removal rate simultaneously satisfy the above ranges.

[0095] Furthermore, for example, by providing a separation functional layer containing a cross-linked aliphatic polyamide in a composite semipermeable membrane, it can be used as an NF membrane that separates monovalent and divalent ions. In this case, the "MgSO" example described later can be used. ４The water production capacity retention rate of the composite semipermeable membrane, calculated by the method described in "High Pressure Test," is preferably 90% or higher, more preferably 93% or higher, and even more preferably 95% or higher. The MgSO4 of the composite semipermeable membrane, calculated by the method described in "Removal Rate and Water Production Capacity of Composite Semipermeable Membrane" in the Examples described later, is also preferable. ４ A removal rate of 95.0% or higher is preferable, 96.0% or higher is more preferable, and 97.0% or higher is even more preferable. Furthermore, the water production volume retention rate and MgSO4 are also important. ４ It is preferable that the removal rate simultaneously satisfies the above range.

[0096] Furthermore, if the pH of the supply water is high, there is a risk of scale formation, such as magnesium, in the case of supply water with high solute concentrations, such as seawater. Also, since there is a concern about membrane deterioration due to filtering high pH supply water, it is preferable that the pH of the supply water be neutral.

[0097] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited thereto. Unless otherwise specified, the porous support was obtained by immersing a composite semipermeable membrane in a 2% by mass sodium hypochlorite aqueous solution for 48 hours and removing the separation functional layer. The substrate may be measured before the porous layer is formed, or if a porous layer is already provided on the substrate, the porous support may be immersed in a good solvent (DMF) at 60°C for 24 hours to dissolve the porous layer, replaced with pure water, dried at 120°C for 2 hours, and the substrate from which the porous layer has been removed may be measured.

[0098] <Mass of the Porous Layer> A 0.11 m x 0.19 m rectangle was cut from the porous support and dried at 120°C for 2 hours. The mass of the porous support was measured. In addition, masking tape (Teraoka Seisakusho P-Cut Tape No. 4140, 100 mm wide) was applied to the porous layer side of the porous support, and the porous layer was removed from the substrate by peeling it off twice in the longitudinal (MD) direction. The mass of the substrate from which the porous layer had been removed was measured, and the mass of the porous layer was calculated using the following formula (2). The same procedure was performed on five different samples, the arithmetic mean of the obtained values ​​was calculated, and the value rounded to the first decimal place was taken as the mass of the porous layer. Mass of the Porous Layer [g / m ２ ] = (mass of porous support - mass of substrate) / (0.11 × 0.19) ... Equation (2)

[0099] <Root Mean Square Height Rq of Substrate> The surface of the substrate forming the porous layer was observed with a laser microscope (OLYMPUS OLS4100) using a standard lens at 20x magnification. The lowest concave point was set as the lower height limit, and the highest convex point as the upper height limit, and the surface shape was measured. The observation size of the substrate was 1224 μm square. Next, the data obtained from the measurement was processed using the analysis software (application version: 3.1.1.296) included with the OLYMPUS LEXT OLS5100. Noise was removed by automatic noise reduction and tilt correction was performed. After that, "surface roughness" was selected, and "Rq" was calculated under the analysis conditions shown below. The same operation was performed on five different substrates, and the arithmetic mean of the obtained values ​​was calculated and rounded to the second decimal place to obtain the Rq of the substrate. [Analysis Conditions] Measurement range: Entire area (1224 μm square) Filter type: Gaussian Parameter: Height / Composite histogram class division method: 200 divisions Load area ratio for V parameter: p = 10%, q = 80% Load area ratio for Sxp parameter: p = 2.5%, q = 50% Correlation threshold: s = 0.2 Peak / valley discrimination limit: Szx = 5% Smoothing setting: Smoothing is performed as a preprocessing step before calculating shape parameters Missing point interpolation setting: Roughness parameters are calculated by interpolating non-measured points

[0100] <Percentage of Recesses in the Substrate> The data observed using the "Root Mean Square Height Rq of the Substrate" described above was processed using the analysis software (application version: 3.1.1.296) included with the OLYMPUS LEXT OLS5100. Automatic noise reduction and tilt correction were performed. The entire corrected image area was selected. Then, "Area / Volume" was selected, and the following analysis conditions were used: "Depth 10 μm or more and area 500 μm". ２ The number of recesses above 10 μm and the number of recesses with a depth of 10 μm or more were calculated. From the obtained data, the percentage of 10 μm recesses in the substrate was calculated using the following formula (3). The same procedure was performed on five different samples, the arithmetic mean of the obtained values ​​was calculated, and the value rounded to the first decimal place was taken as the percentage of 10 μm recesses in the substrate. Percentage of 10 μm recesses [%] = (depth of 10 μm or more and area of ​​500 μm) ２(Number of recesses above / Number of recesses with a depth of 10 μm or more) × 100 ... Equation (3) [Analysis conditions] Measurement range: entire area (1224 μm square) Threshold 1: -10 μm Measure the lower limit from threshold 1 (100 μm) ２ (Exclude areas smaller than the following size from calculations)

[0101] Also, by selecting "Area / Volume" and using the analysis conditions shown below, "Depth 20 μm or more and area 500 μm" ２ The number of recesses above and below, and the number of recesses with a depth of 20 μm or more were calculated. From the obtained data, the area of ​​500 μm ２ The number of recesses was calculated, and the percentage of 20 μm recesses in the substrate was calculated using the following formula (4). The same procedure was performed on five different samples, the arithmetic mean of the obtained values ​​was calculated, and the value rounded to the first decimal place was taken as the percentage of 20 μm recesses in the substrate. Percentage of 20 μm recesses [%] = (depth 20 μm or more and area 500 μm) ２ (Number of recesses above / Number of recesses with a depth of 20 μm or more) × 100 ... Equation (4) [Analysis conditions] Measurement range: entire area (1224 μm square) Threshold 1: -20 μm Measure the lower limit from threshold 1 (100 μm) ２ (Exclude areas smaller than the following size from calculations)

[0102] <Average Area of ​​Recesses in the Substrate> The data observed using the "root mean square height Rq of the substrate" described above was processed using the analysis software (application version: 3.1.1.296) included with the OLYMPUS LEXT OLS5100. Automatic noise reduction and tilt correction were performed using image processing. Then, "Area / Volume" was selected, and the "area of ​​recesses" and "number of recesses" were calculated under the analysis conditions shown below. The average area of ​​recesses in the substrate was calculated using the following formula (5). The same operation was performed on five different samples, and the arithmetic mean of the obtained values ​​was calculated and rounded to the first decimal place to obtain the average area of ​​recesses in the substrate. Average area of ​​recesses [μm²] ２ ] = Total area of ​​recesses / Number of recesses ... Equation (5) [Analysis conditions] Measurement range: Entire area (1224 μm square) Threshold 1: 0 μm Measure the lower limit from threshold 1 (100 μm) ２ (Exclude areas below the following size from calculations)

[0103] <Root Mean Square Height Rq of the Porous Layer After Pressurization> A composite semipermeable membrane was subjected to a 5.5 MPa operation under conditions of 5.5 MPa and 25°C, in which an aqueous solution with a NaCl concentration of 3.5 mass% and a pH of 6.5 was supplied for 2 hours. After the 5.5 MPa operation, the composite semipermeable membrane was immersed in a 2 mass% sodium hypochlorite aqueous solution for 48 hours to remove the separation functional layer and obtain a porous support. The surface of the porous layer of the obtained porous support was observed with a laser microscope (OLYMPUS OLS4100) at 20x magnification with a standard lens. The lowest concave part was set as the lower height limit and the highest convex part as the upper height limit, and the surface shape was measured. Next, the data obtained from the measurement was processed using image processing software (application version: 3.1.1.296) attached to the OLYMPUS LEXT OLS5100, to remove noise using automatic noise reduction and correct the tilt. Next, "surface roughness" was selected, and "Rq" was calculated under the analysis conditions shown below. The same operation was performed on five different substrates, and the arithmetic mean of the obtained values ​​was calculated and rounded to the second decimal place to obtain the Rq of the porous layer after pressurization. [Analysis conditions] Measurement range: entire area (1224 μm square) Filter type: Gaussian Parameter: height / Composite histogram class division method: 200 divisions Load area ratio for V parameter: p = 10%, q = 80% Load area ratio for Sxp parameter: p = 2.5%, q = 50% Correlation threshold: s = 0.2 Peak and valley discrimination limit: Szx = 5% Smoothing setting: smoothing is performed as a preprocessing step before calculating shape parameters Missing point interpolation setting: roughness parameters are calculated by interpolating non-measured points

[0104] <Amount of Polymer Impregnation in Substrate> The mass of the substrate was measured by peeling off the porous layer with tape using the same method as described above for "mass of porous layer". Then, the substrate was immersed in a good solvent (DMF) at 60°C for 24 hours to dissolve the polymer impregnated in the substrate. The substrate was removed from the good solvent, replaced with pure water, dried at 120°C for 2 hours, and the mass of the substrate after immersion in the good solvent was measured. The amount of polymer impregnation in the substrate was calculated using the following formula (6). The same procedure was performed on five different samples, the arithmetic mean of the obtained values ​​was calculated, and the value rounded to the second decimal place was taken as the amount of polymer impregnation in the substrate. Amount of polymer impregnation in the substrate [g / m ２] = (Mass of substrate - Mass of substrate after immersion in good solvent) / (0.11 × 0.19) ... Equation (6)

[0105] <Thickness of the substrate and the porous layer after pressurization> After supplying an aqueous solution with a NaCl concentration of 3.5 mass% and pH 6.5 to the composite semipermeable membrane under conditions of 7.0 MPa and 45°C for 24 hours, the thickness of the composite semipermeable membrane was measured using a dial thickness gauge G-7C (manufactured by Ozaki Seisakusho Co., Ltd.). At this time, since the separation functional layer was very thin, the thickness of the composite semipermeable membrane was considered to be the sum of the thicknesses of the substrate and the porous layer. Subsequently, the porous layer was peeled off from the substrate with tape using the method described in "Mass of the Porous Layer" above, and the thickness of the obtained substrate was measured with a dial thickness gauge G-7C. The difference between the thickness of the composite semipermeable membrane and the thickness of the substrate was taken as the thickness of the porous layer after pressurization. For each thickness, 20 points were measured at randomly selected locations on the same membrane surface, and the arithmetic mean value was rounded to the first decimal place. The thickness of the substrate of the composite semipermeable membrane was measured using the same method with the composite semipermeable membrane before operation under the conditions described above.

[0106] <NaCl Removal Rate and Water Production Volume of Composite Semipermeable Membrane> Raw water (NaCl concentration 3.2 mass%) adjusted to 25°C and pH 6.5 was supplied to a composite semipermeable membrane at an operating pressure of 5.5 MPa, and membrane filtration treatment was performed for 2 hours. After that, the electrical conductivity of the supply water and permeate was measured using a multi-water quality meter (MM60R) manufactured by Toa DKK Co., Ltd. Next, the NaCl concentration was calculated by converting this conductivity using a calibration curve prepared in advance. From the obtained NaCl concentration, the NaCl removal rate, which is the solute removal performance, was determined by the following formula (7). An NaCl removal rate of 99.70% or higher is considered good. NaCl removal rate [%] = 100 × {1 - (NaCl concentration in permeate / NaCl concentration in supply water)} ... Equation (7) Furthermore, after performing the above membrane filtration treatment for 2 hours, the amount of permeate water over 30 minutes was measured and converted to the amount of water produced per day (cubic meters) per square meter of membrane surface, and the amount of water produced [m³] was calculated. ３ / m ２ The value per day was calculated.

[0107] <NaCl High-Pressure Test>For the composite semipermeable membrane on which the performance evaluation was carried out in the above-mentioned "NaCl removal rate and water production of the composite semipermeable membrane", raw water adjusted to 45°C and pH 6.5 (NaCl concentration 3.2% by mass) was supplied at an operating pressure of 7.0 MPa, and membrane filtration treatment was carried out for 6 hours. Then, membrane performance evaluation was carried out in the same method as "NaCl removal rate and water production of the composite semipermeable membrane", and the water production after high-pressure operation was obtained. Also, whether the membrane performance was good or not was judged to be good when the water production retention rate calculated by the following formula (8) was 90% or more.Water production retention rate [%] = Water production after high-pressure operation / Water production before high-pressure operation × 100 ··· Formula (8)

[0108] <Removal Rate and Water Production of MgSO₄ in Composite Semipermeable Membrane> ４ For the composite semipermeable membrane, salt water adjusted to a temperature of 25°C, pH 6.5, and a MgSO₄ concentration of 4000 mg / L was supplied at an operating pressure of 1.55 MPa, and membrane filtration treatment was carried out for 2 hours. Then, the electrical conductivities of the supply water and the permeated water were measured with a multi-water quality meter (MM60R) manufactured by Toa DKK Corporation. Next, using the calibration curve created in advance, this conductivity was converted to calculate the MgSO₄ concentration. From the obtained MgSO₄ concentration, the MgSO₄ removal rate, which is the solute removal performance, was obtained by the following formula (9). It is good when the MgSO₄ removal rate is 95.0% or more.MgSO₄ removal rate (%) = 100 × {1 - (MgSO₄ concentration in permeated water / MgSO₄ concentration in supply water)} ··· Formula (9)Also, after the above-mentioned membrane filtration treatment was carried out for 2 hours, the membrane permeation water volume for 30 minutes was measured and converted to the water production per square meter of the membrane surface per day (cubic meters), and the water production [m³ / m² / day] was calculated. ４ ４ ４ ４ ４ ４ ４ ４ ３ ２

[0109] <MgSO₄ High-Pressure Test> ４ For the composite semipermeable membrane on which the performance evaluation was carried out in the above-mentioned "Removal rate and water production of MgSO₄ in composite semipermeable membrane", raw water adjusted to 25°C and pH 6.5 (MgSO₄ ４ ４ ​​​​​​​A concentration of 4.0% by mass was supplied at an operating pressure of 7.0 MPa, and membrane filtration was performed for 6 hours. Subsequently, the composite semipermeable membrane was subjected to MgSO4. ４ The membrane performance was evaluated using the same method as for "removal rate and water production volume," and the water production volume after high-pressure operation was determined. Furthermore, the membrane performance was judged to be good if the water production volume retention rate calculated by the above formula (8) was 90% or higher.

[0110] <Manufacturing of Polyester Nonwoven Fabric> [Reference Example 1] Polyester Nonwoven Fabric A The core component was polyethylene terephthalate resin with an intrinsic viscosity (IV value) of 0.65, a melting point of 260°C, and a titanium dioxide content of 0.3% by mass. The sheath component was copolymerized polyethylene terephthalate resin with an intrinsic viscosity (IV value) of 0.66, an isophthalic acid copolymerization rate of 11 mol%, a melting point of 230°C, and a titanium dioxide content of 0.2% by mass. The core component and sheath component were melted in an extruder, weighed to a mass ratio of 80:20, and core-sheath type composite fibers were spun. The spun core-sheath type composite fibers were cooled and solidified in an atmosphere at room temperature of 20°C, passed through a rectangular ejector, the yarn was pulled and stretched, and collected on a moving net to form a nonwoven web. Next, it was temporarily bonded using a pair of upper and lower metal calender rolls, and the basis weight was 36 g / m². ２ A spunbond nonwoven web (a) was obtained. Two of the obtained spunbond nonwoven webs (a) in a temporarily bonded state were stacked on top of each other, and the laminated nonwoven web was passed between the middle and bottom of a set of three flat rolls, with the top being a resin elastic roll, the middle a metal roll, and the bottom a resin elastic roll, and heat-pressed. The laminated nonwoven web was then folded back and passed between the top and middle, and heat-pressed again. After that, the back side of the obtained laminated composite nonwoven fabric that had been in contact with the elastic rolls was brought into contact with a metal cold roll with a surface temperature of 45°C for 0.6 seconds to produce a polyester nonwoven fabric A with a thickness of 90 μm and Rq = 5.8 μm. At this time, the surface temperatures of the three flat rolls were 140°C for the top, 180°C for the middle, and 140°C for the bottom, and the linear pressure was 1715 N / cm.

[0111] [Reference Example 2] Polyester Nonwoven Fabric B A polyester nonwoven fabric B with a thickness of 90 μm was manufactured in the same manner as in Reference Example 1, except that the heat-sealing conditions were adjusted so that the Rq of the nonwoven fabric base material after heat-sealing was 5.6 μm, using the spunbond nonwoven web (a) described in Reference Example 1.

[0112] [Reference Example 3] Polyester non-woven fabric C A polyester non-woven fabric C with a thickness of 90 μm was produced in the same manner as in Reference Example 1, except that the thermal bonding conditions were adjusted so that the Rq of the non-woven fabric base material after thermal bonding was 5.1 μm, using the spunbond non-woven web (a) described in Reference Example 1.

[0113] [Reference Example 4] Polyester non-woven fabric D In the spinning, non-woven web formation, and temporary adhesion steps described in Reference Example 1, a spunbond non-woven web (c) in a temporarily adhered state with a basis weight of 40 g / m ２ and the spunbond non-woven web (a) described in Reference Example 1 were laminated, and a polyester non-woven fabric D with a thickness of 90 μm was produced in the same manner as in Reference Example 1, except that the thermal bonding conditions were adjusted so that the Rq of the non-woven fabric base material after thermal bonding was 4.2 μm.

[0114] [Reference Example 5] Polyester non-woven fabric E In the spinning, non-woven web formation, and temporary adhesion steps described in Reference Example 1, a spunbond non-woven web (d) in a temporarily adhered state with a basis weight of 50 g / m ２ and the spunbond non-woven web (a) described in Reference Example 1 were laminated, and a polyester non-woven fabric E with a thickness of 90 μm was produced in the same manner as in Reference Example 1, except that the thermal bonding conditions were adjusted so that the Rq of the non-woven fabric base material after thermal bonding was 2.8 μm.

[0115] [Reference Example 6] Polyester non-woven fabric F A polyester non-woven fabric F with a thickness of 90 μm was produced in the same manner as in Reference Example 1, except that the thermal bonding conditions were adjusted so that the Rq of the non-woven fabric base material after thermal bonding was 1.0 μm, by laminating the spunbond non-woven web (d) described in Reference Example 5 and the spunbond non-woven web (a) described in Reference Example 1.

[0116] [Reference Example 7] Polyester non-woven fabric G A polyester non-woven fabric G with a thickness of 90 μm was produced in the same manner as in Reference Example 1, except that the thermal bonding conditions were adjusted so that the Rq of the non-woven fabric base material after thermal bonding was 7.2 μm, using the spunbond non-woven web (a) described in Reference Example 1.

[0117] [Reference Example 8] Polyester nonwoven fabric H A polyester nonwoven fabric H with a thickness of 90 μm was manufactured in the same manner as in Reference Example 1, except that the heat-sealing conditions were adjusted so that the Rq of the nonwoven fabric base material after heat-sealing was 7.5 μm, using the spunbond nonwoven web (b) described in Reference Example 2.

[0118] [Reference Example 9] Polyester Nonwoven Fabric I A polyester nonwoven fabric I with a thickness of 90 μm was manufactured in the same manner as in Reference Example 1, except that the heat-sealing conditions were adjusted so that the Rq of the nonwoven fabric base material after heat-sealing was 0.1 μm, using the spunbond nonwoven web (d) described in Reference Example 5.

[0119] [Example 1] Using the polyester nonwoven fabric A obtained in Reference Example 1 as the base material, an 18% by mass DMF solution of PSf as a polymer solution was placed on the base material at 25°C until the mass of the porous layer was 10 g / m². ２ The polymer solution was applied in this manner. Subsequently, the substrate coated with the polymer solution was immersed in pure water for 15 seconds to create a porous support with a porous layer formed on the substrate. The porous layer was immersed in pure water and left for 5 minutes, then washed with 90°C hot water for 2 minutes. The washed porous support was immersed in a 3 mass% aqueous solution of m-PDA for 2 minutes. The support was slowly lifted vertically, and excess aqueous solution was removed from the surface of the porous support by blowing nitrogen with an air nozzle. Subsequently, a decane solution containing 0.165 mass% TMC was applied so that the surface of the porous layer was completely wetted, and it was left to stand for 1 minute. Furthermore, the film was made vertical to drain and remove excess solution, and washed with pure water to obtain a composite semipermeable membrane having a cross-linked polyamide separation functional layer. Various measurement results are shown in Table 1.

[0120] [Example 2] A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 1, except that polyester nonwoven fabric B obtained in Reference Example 2 was used as the base material. The results of various measurements are shown in Table 1.

[0121] [Example 3] The mass of the porous layer is 8 g / m ２ A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 2, except that a polymer solution was applied to achieve the desired result. The various measurement results are shown in Table 1.

[0122] [Example 4] Using the polyester nonwoven fabric C obtained in Reference Example 3 as the base material, the mass of the porous layer is 7 g / m². ２ A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 1, except that a polymer solution was applied to achieve the desired result. The various measurement results are shown in Table 1.

[0123] [Example 5] The mass of the porous layer is 5 g / m ２ A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 1, except that a polymer solution was applied to achieve the desired result. The various measurement results are shown in Table 1.

[0124] [Example 6] A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 5, except that polyester nonwoven fabric C obtained in Reference Example 1 was used as the base material. The results of various measurements are shown in Table 2.

[0125] [Example 7] A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 5, except that polyester nonwoven fabric D obtained in Reference Example 4 was used as the base material. The results of various measurements are shown in Table 2.

[0126] [Example 8] Using the polyester nonwoven fabric E obtained in Reference Example 5 as the base material, the mass of the porous layer is 3 g / m². ２ A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 1, except that a polymer solution was applied to achieve the desired result. The various measurement results are shown in Table 2.

[0127] [Example 9] A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 8, except that the polyester nonwoven fabric F obtained in Reference Example 6 was used as the base material. The results of various measurements are shown in Table 2.

[0128] [Example 10] The mass of the porous layer is 13 g / m². ２ A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 1, except that a polymer solution was applied to achieve the desired result. The various measurement results are shown in Table 2.

[0129] [Comparative Example 1] The mass of the porous layer is 17 g / m². ２A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 1, except that a polymer solution was applied to achieve the desired result. The various measurement results are shown in Table 3.

[0130] [Comparative Example 2] The mass of the porous layer is 14 g / m ２ A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 1, except that a polymer solution was applied to achieve the desired result. The various measurement results are shown in Table 3.

[0131] [Comparative Example 3] A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Comparative Example 2, except that the polyester nonwoven fabric G obtained in Reference Example 7 was used as the base material. The results of various measurements are shown in Table 3.

[0132] [Comparative Example 4] A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Comparative Example 2, except that polyester nonwoven fabric H obtained in Reference Example 8 was used as the base material. The results of various measurements are shown in Table 3.

[0133] [Comparative Example 5] The mass of the porous layer is 2 g / m ２ A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 8, except that a polymer solution was applied to achieve the desired result. The various measurement results are shown in Table 3.

[0134] [Comparative Example 6] A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 5, except that polyester nonwoven fabric I obtained in Reference Example 9 was used as the base material. The results of various measurements are shown in Table 3.

[0135] [Comparative Example 7] A composite semipermeable membrane having a crosslinked polyamide separation functional layer was obtained in the same manner as in Example 5, except that polyester nonwoven fabric H obtained in Reference Example 8 was used as the base material. The results of various measurements are shown in Table 3.

[0136] [Example 11] A porous support was prepared in the same manner as in Example 1. The obtained porous support was immersed for 30 seconds in an aqueous solution containing 1.0% by mass of piperazine and 100 ppm of sodium dodecyldiphenyl ether disulfonate. The porous support was then slowly lifted vertically, and nitrogen was blown from an air nozzle to remove excess aqueous solution from the surface of the porous layer. Next, a decane solution containing 0.40% by mass of TMC was applied to the surface of the porous layer so that it was completely wet, and it was left to stand for 30 seconds. Then, the film was held vertically, and the excess solution was drained off. The decane solution was dried by blowing 25°C air using a blower. Finally, a composite semipermeable membrane having a crosslinked aliphatic polyamide separation functional layer was obtained by washing with pure water at 80°C. The results of various measurements are shown in Table 4.

[0137] [Example 12] A composite semipermeable membrane having a crosslinked aliphatic polyamide separation functional layer was obtained in the same manner as in Example 11, except that a porous support was prepared in the same manner as in Example 7. The results of various measurements are shown in Table 4.

[0138] [Comparative Example 8] A composite semipermeable membrane having a crosslinked aliphatic polyamide separation functional layer was obtained in the same manner as in Example 11, except that a porous support was prepared in the same manner as in Comparative Example 7. The results of various measurements are shown in Table 4.

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[0143] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2024-168175, filed on 27 September 2024, the contents of which are incorporated herein by reference.

[0144] The composite semipermeable membrane of the present invention can be used for seawater desalination, brine desalination, drinking water production, industrial ultrapure water production, wastewater treatment, and recovery of valuable materials.

[0145] 1. Composite semipermeable membrane 2. Substrate 3. Porous layer 4. Separation function layer 5. Separation membrane element 6. End plate 7. End plate 8. Supply side channel material 9. Permeation side channel material 10. Water collection pipe 11. Supply water 12. Permeate water 13. Concentrated water

Claims

1. A composite semipermeable membrane comprising a substrate, a porous layer provided on one surface of the substrate, and a separation functional layer provided on the porous layer, wherein the mass of the porous layer is 3 g / m². ２ 13g / m or more ２ A composite semipermeable membrane, wherein the root mean square height Rq of the surface of the substrate on the side where the porous layer is provided is 1.0 μm or more and 6.0 μm or less.

2. The surface of the substrate on the side where the porous layer is provided has an uneven shape, and the number of recesses with a depth of 20 μm or more is equal to the area of ​​500 μm with a depth of 20 μm or more. ２ The composite semipermeable membrane according to claim 1, wherein the proportion of the number of recesses is 15% or less.

3. The surface of the substrate on the side where the porous layer is provided has an uneven shape, with an average area of ​​500 μm². ２ 2000 μm or more ２ The composite semipermeable membrane according to claim 1 or 2, which is as follows:

4. The surface of the substrate on the side where the porous layer is provided has an uneven shape, and the number of recesses with a depth of 10 μm or more corresponds to a depth of 10 μm or more and an area of ​​500 μm. ２ The composite semipermeable membrane according to claim 1 or 2, wherein the proportion of the number of recesses is 20% or less.

5. The composite semipermeable membrane according to claim 1 or 2, wherein the root mean square height Rq of the surface of the substrate on the side where the porous layer is provided is 2.0 μm or more and 5.0 μm or less.

6. The mass of the porous layer is 3 g / m ２ 10g / m or more ２ The composite semipermeable membrane according to claim 1 or 2, wherein the following applies:

7. The composite semipermeable membrane according to claim 1 or 2, wherein the root mean square height Rq of the surface of the substrate on the side where the porous layer is provided is 2.0 μm or more and 4.5 μm or less.

8. The composite semipermeable membrane according to claim 1 or 2, wherein, after supplying an aqueous solution with a NaCl concentration of 3.5% by mass and a pH of 6.5 for 2 hours under conditions of 5.5 MPa and 25°C, the root mean square height Rq of the surface of the porous layer on the side where the separation functional layer is provided is 1.0 μm or more and 2.5 μm or less.

9. The polymer impregnation amount of the base material is 0.5 g / m ２ or more and 2.5 g / m ２ or less. The composite semipermeable membrane according to claim 1 or 2.

10. A separation membrane element comprising a composite semipermeable membrane according to claim 1 or 2.

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