Composite semipermeable membrane and spiral membrane element

Abstract

The purpose of the present invention is to provide: a composite semipermeable membrane which is capable of attaining favorable organic compound-blocking performance and waterproofness, by controlling the superficial area at the microscopic level of an isolative function layer, by using an indicator which differs from the prior art; and a spiral-type membrane element which uses the same. A composite semipermeable membrane 1 according to the present invention which is equipped with a porous support body 1b and an isolative function layer 1a formed from a polyamide resin on the porous support body 1b, said composite semipermeable membrane 1 being characterized in that the isolative function layer 1a has a surface roughness Ra1 of 90-150nm when measuring a region which is 5μm×5μm using an atomic force microscope (AFM) underwater.

Description

[Technical Field]

[0001] The present invention relates to a composite semipermeable membrane comprising a porous support and a separation functional layer, and a spiral-wound membrane element (hereinafter sometimes abbreviated as "membrane element") using the same. [Background technology]

[0002] Composite semipermeable membranes are called reverse osmosis (RO) membranes, nanofiltration (NF) membranes, forward osmosis (FO) membranes, etc. depending on their filtration performance and treatment method, and can be used for ultrapure water production, seawater desalination, brackish water desalination, wastewater recycling, etc. In recent years, particularly overseas, there has been an increasing demand for composite semipermeable membranes used in the production of drinking water that have the ability to block organic compounds (e.g., molecular weights of 150 to 250) such as herbicides and odorous components, as well as good water permeability when removing these compounds.

[0003] Currently, partial desalination loose-type NF membranes, which are more permeable to inorganic salts than RO membranes used in desalination processes, are commercially available, and their application to the production of drinking water as described above is being considered. However, commercially available partial desalination loose-type NF membranes have problems in that they either have good blocking performance for organic compounds such as herbicides and odorous components but insufficient water permeability, or they have good water permeability but insufficient blocking performance for the organic compounds.

[0004] In other words, there is a trade-off between the blocking performance against the organic compounds and water permeability. In particular, in the application of drinking water production, the processing volume is large, so energy conservation is important, but the current situation is that it is difficult to obtain a composite semipermeable membrane that combines blocking performance and water permeability.

[0005] On the other hand, as a composite semipermeable membrane that is frequently used industrially, for example, a composite semipermeable membrane in which a skin layer containing a polyamide resin obtained by reacting a polyfunctional amine component with a polyfunctional acid halide component is formed on the surface of a porous support as a separation functional layer is known. Furthermore, a method is known for improving the water permeability of such a composite semipermeable membrane while maintaining the blocking performance by providing fine irregularities in the separation functional layer to increase the surface area.

[0006] For example, in Patent Document 1, when a skin layer is formed on a microporous support by contacting a solution A containing a polyfunctional amine component with a solution B containing a polyfunctional acid halide component, a solution A or B having a solubility parameter of 8 to 14 (cal / cm 3 ) 1 / 2 The document discloses a method for producing a composite reverse osmosis membrane having an average surface roughness of the skin layer of 55 nm or more by adding a compound of the formula (1) to the membrane. In this document, the average surface roughness of the skin layer is calculated using values ​​measured in air using an atomic force microscope (AFM). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 9-85068 Summary of the Invention [Problem to be solved by the invention]

[0008] However, according to the studies of the present inventors, it has been found that the surface roughness measured in the atmosphere using an atomic force microscope (AFM) is difficult to correlate with water permeability, especially when the size of the fine irregularities in the separation functional layer is above a certain level. In other words, the size of the fine irregularities in the separation functional layer when actually used for membrane separation tends to differ from the surface roughness of the separation functional layer measured in the atmosphere, and it has been found that there are limitations to using this as an indicator to control the size of the fine irregularities in the separation functional layer (i.e., the microscopic surface area) to improve water permeability.

[0009] Therefore, an object of the present invention is to provide a composite semipermeable membrane that can improve both the blocking performance against organic compounds and water permeability by controlling the microscopic surface area of ​​the separation functional layer using an index different from conventional indicators, and a spiral membrane element using the same. [Means for solving the problem]

[0010] As a result of extensive research to solve the above-mentioned problems, the inventors have discovered that by using the surface roughness Ra1 measured in water with an atomic force microscope (AFM) as an index, the size of the fine irregularities in the separation functional layer can be accurately controlled, and that if this is within a predetermined range, both the blocking performance against organic compounds and water permeability can be improved, and have thereby completed the present invention. That is, the present invention includes the following aspects.

[0011] [1] A composite semipermeable membrane comprising a porous support and a separation functional layer formed of a polyamide resin on the porous support, The separating functional layer is a composite semipermeable membrane having a surface roughness Ra1 of 90 to 150 nm when measured in a 5 μm×5 μm area in water with an atomic force microscope (AFM).

[0012] According to the composite semipermeable membrane of the present invention, by using the surface roughness Ra1 measured in water as an index, it is possible to measure the magnitude of the fine irregularities of the separation functional layer under conditions similar to those actually used in membrane separation, and by controlling this within a predetermined range, it is possible to increase the microscopic surface area and improve water permeability without reducing the blocking performance against organic compounds. That is, as shown in Figure 1, the separation functional layer 1a formed on the porous support 1b of the composite semipermeable membrane 1 in the atmosphere tends to be observed as having the fine irregularities of the separation functional layer 1a in a collapsed or crushed state compared to the state when actually used in membrane separation, and by using the surface roughness Ra1 measured in water as an index, it is possible to more accurately measure the magnitude of the fine irregularities of the separation functional layer under conditions similar to those actually used in membrane separation.

[0013] [2] The composite semipermeable membrane according to [1], wherein the polyamide resin contains a component derived from m-phenylenediamine.

[0014] When the polyamide resin contains a constituent component derived from m-phenylenediamine, it tends to have a structure in which benzene rings are densely arranged, making it easier to adjust the rejection rate for organic compounds to a certain level or higher.

[0015] [3] The composite semipermeable membrane according to [1] or [2], wherein the ratio of the surface roughness Ra1 to the surface roughness Ra2 measured in an area of ​​5 μm × 5 μm in air using an atomic force microscope (AFM): R = Ra1 / Ra2 is 1.6 or more.

[0016] When the ratio R=Ra1 / Ra2 is 1.6 or more, the difference from the value measured in air becomes large to some extent, so it becomes more effective to use the surface roughness Ra1 as an index. In other words, by using the surface roughness Ra1 measured in water as an index, it becomes possible to more appropriately measure the magnitude of the fine irregularities of the separation functional layer under conditions closer to those actually used in membrane separation, compared to measurements in air.

[0017] [4] The composite semipermeable membrane according to any one of [1] to [3], which has an atrazine rejection rate of 95.0% or more.

[0018] By achieving such a rejection rate of atrazine, it is possible to achieve sufficient blocking performance against organic compounds (for example, molecular weight of 150 to 250) such as herbicides and odorous components.

[0019] [5] The composite semipermeable membrane according to any one of [1] to [4], which has a water permeability of 9.0 LMH / bar or more when evaluated using simulated water modeled after river water.

[0020] When the water permeability to the simulated water is within this range, it becomes easier to achieve both the blocking performance against organic compounds and the water permeability, which are in a trade-off relationship.

[0021] [6] A spiral membrane element having the composite semipermeable membrane according to any one of [1] to [5].

[0022] The spiral-wound membrane element of the present invention has the composite semipermeable membrane of the present invention as described above, and therefore can provide a spiral-wound membrane element that can improve both the blocking performance for organic compounds and the water permeability by controlling the microscopic surface area of ​​the separation functional layer using an index different from conventional ones. [Effects of the Invention]

[0023] According to the present invention, by controlling the microscopic surface area of ​​the separation functional layer using an index different from conventional ones, it is possible to provide a composite semipermeable membrane and a spiral membrane element that can improve both the blocking performance against organic compounds and the water permeability. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a conceptual diagram schematically illustrating the difference between a separation functional layer of a composite semipermeable membrane in the atmosphere and a separation functional layer of a composite semipermeable membrane in water. [Figure 2] FIG. 1 is a partially cutaway perspective view showing an example of a spiral membrane element. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, an embodiment of the present invention will be described.

[0026] (composite semipermeable membrane) The composite semipermeable membrane of the present invention is a composite semipermeable membrane comprising a porous support and a separation functional layer formed of a polyamide resin on the porous support, wherein the separation functional layer has a surface roughness Ra1 of 90 to 150 nm when measured in a 5 μm × 5 μm area in water with an atomic force microscope (AFM).

[0027] Examples of the separation functional layer include those capable of separating monovalent inorganic ions, monovalent organic ions, divalent inorganic ions, divalent organic ions, organic compounds with a molecular weight of 100 to 150, organic compounds with a molecular weight of 150 to 250, and organic compounds with a molecular weight of more than 250, depending on the size of the solute to be separated. For all of these, the surface roughness Ra1 measured in water can be used as an index to measure the size of the fine irregularities on the separation functional layer under conditions close to those actually used in membrane separation. By controlling this within a predetermined range, the microscopic surface area can be increased and water permeability can be improved without reducing the rejection performance.

[0028] In particular, in recent years overseas, there has been an increasing demand for composite semipermeable membranes used in the production of drinking water that have good blocking performance against organic compounds (e.g., molecular weights of 150 to 250) such as herbicides and odorous components, and good water permeability when removing these compounds, and the composite semipermeable membrane of the present invention is particularly effective as a separation membrane for removing such organic compounds.

[0029] As a material for forming the separation functional layer, a polyamide-based resin is used, which can form the separation functional layer by interfacial polymerization and can control the size of the fine irregularities of the separation functional layer during this process. As a separation functional layer formed from a polyamide-based resin, a separation functional layer containing a polyamide-based resin obtained by polymerizing a polyfunctional amine component and a polyfunctional acid halogen component is particularly preferred.

[0030] The polyfunctional amine component is a polyfunctional amine having two or more reactive amino groups, and examples thereof include aromatic, aliphatic, and alicyclic polyfunctional amines.

[0031] Examples of aromatic polyfunctional amines include m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 2,4-diaminotoluene, 2,6-diaminotoluene, N,N'-dimethyl-m-phenylenediamine, 2,4-diaminoanisole, amidol, and xylylenediamine.

[0032] Examples of the aliphatic polyfunctional amine include ethylenediamine, propylenediamine, tris(2-aminoethyl)amine, and n-phenyl-ethylenediamine.

[0033] Examples of the alicyclic polyfunctional amine include 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, and 4-aminomethylpiperazine.

[0034] These polyfunctional amines may be used alone or in combination of two or more. In order to obtain a separating functional layer with high salt rejection performance, it is preferable to use an aromatic polyfunctional amine.

[0035] In particular, from the viewpoint of facilitating adjustment to a certain level or higher of rejection rate for organic compounds with a molecular weight of 150 to 250, it is preferable to use m-phenylenediamine as the polyfunctional amine component, preferably at 20 to 100 mol %, more preferably at 50 to 100 mol %, and most preferably at 100 mol % in the polyfunctional amine component. This allows the separation functional layer to be formed from a polyamide resin containing a component derived from m-phenylenediamine.

[0036] The polyfunctional acid halide component is a polyfunctional acid halide having two or more reactive carbonyl groups, and examples of the polyfunctional acid halide include aromatic, aliphatic, and alicyclic polyfunctional acid halides.

[0037] Examples of aromatic polyfunctional acid halides include trimesic acid trichloride, terephthalic acid dichloride, isophthalic acid dichloride, biphenyldicarboxylic acid dichloride, naphthalenedicarboxylic acid dichloride, benzenetrisulfonic acid trichloride, benzenedisulfonic acid dichloride, and chlorosulfonylbenzenedicarboxylic acid dichloride.

[0038] Examples of the aliphatic polyfunctional acid halides include propanedicarboxylic acid dichloride, butanedicarboxylic acid dichloride, pentanedicarboxylic acid dichloride, propanetricarboxylic acid trichloride, butanetricarboxylic acid trichloride, pentanetricarboxylic acid trichloride, glutaryl halide, and adipoyl halide.

[0039] Examples of alicyclic polyfunctional acid halides include cyclopropanetricarboxylic acid trichloride, cyclobutanetetracarboxylic acid tetrachloride, cyclopentanetricarboxylic acid trichloride, cyclopentanetetracarboxylic acid tetrachloride, cyclohexanetricarboxylic acid trichloride, tetrahydrofurantetracarboxylic acid tetrachloride, cyclopentanedicarboxylic acid dichloride, cyclobutanedicarboxylic acid dichloride, cyclohexanedicarboxylic acid dichloride, and tetrahydrofurandicarboxylic acid dichloride.

[0040] These polyfunctional acid halides may be used alone or in combination of two or more. To obtain a separation functional layer with high salt-rejecting performance, it is preferable to use an aromatic polyfunctional acid halide. It is also preferable to use a trivalent or higher polyfunctional acid halide as at least a part of the polyfunctional acid halide component to form a crosslinked structure.

[0041] In particular, from the viewpoint of facilitating adjustment to a certain level or higher of rejection rate for organic compounds having a molecular weight of 150 to 250, it is preferable to use trimesic acid trichloride as the polyfunctional acid halide component, preferably at 20 to 100 mol %, more preferably at 50 to 100 mol %, and most preferably at 100 mol % in the polyfunctional acid halide component. This allows the separation functional layer to be formed from a polyamide resin containing a constituent component derived from trimesic acid trichloride.

[0042] In order to improve the performance of the separating functional layer containing a polyamide resin, the layer may be copolymerized with a polymer such as polyvinyl alcohol, polyvinylpyrrolidone, or polyacrylic acid, or a polyhydric alcohol such as sorbitol or glycerin.

[0043] The porous support for supporting the separation functional layer is not particularly limited as long as it can support the separation functional layer, and typically, an ultrafiltration membrane having micropores with an average pore size of about 10 to 500 Å is preferably used. Examples of materials for forming the porous support include various materials such as polysulfone, polyarylethersulfone such as polyethersulfone, polyimide, polyetherimide, and polyvinylidene fluoride, but polysulfone and polyarylethersulfone are preferably used in view of their chemical, mechanical, and thermal stability.

[0044] The thickness of such a porous support is usually about 25 to 125 μm, preferably about 40 to 75 μm, but is not necessarily limited to these. Preferably, the porous support is reinforced by a backing made of a substrate such as a woven fabric or nonwoven fabric.

[0045] The method for forming a separation functional layer containing a polyamide resin on the surface of a porous support is not particularly limited, and any known method can be used. Examples include interfacial condensation, phase separation, and thin film coating. The interfacial condensation method specifically involves contacting an aqueous amine solution containing a polyfunctional amine component with an organic solution containing a polyfunctional acid halide component to form a separation functional layer by interfacial polymerization, and then placing the separation functional layer on a porous support. Alternatively, the interfacial polymerization on the porous support directly forms a separation functional layer of a polyamide resin on the porous support. Details of the conditions for such interfacial condensation methods are described in JP-A-58-24303 and JP-A-1-180208, and these known techniques can be appropriately adopted.

[0046] The separation functional layer formed on the porous support has fine irregularities, and the size of the irregularities can be measured using the surface roughness Ra1 as an indicator when measuring an area of ​​5 μm x 5 μm in water using an atomic force microscope (AFM).

[0047] In the present invention, from the viewpoint of improving water permeability while maintaining blocking performance, the surface roughness Ra1 is preferably 90 nm or more, more preferably 95 nm or more, even more preferably 100 nm or more, and particularly preferably 105 nm or more.

[0048] Furthermore, from the viewpoint of preventing defects and durability, the surface roughness Ra1 is preferably 150 nm or less, more preferably 140 nm or less, even more preferably 130 nm or less, and particularly preferably 125 nm or less.

[0049] In addition, the size of the fine irregularities in the separation functional layer can be determined to some extent by the surface roughness Ra2 measured in an area of ​​5 μm x 5 μm in air using an atomic force microscope (AFM). However, using the surface roughness Ra1 measured in water as an indicator allows for a more appropriate measurement of the size of the fine irregularities in the separation functional layer under conditions closer to those actually used in membrane separation.

[0050] Therefore, the larger the ratio R = Ra1 / Ra2, the greater the difference between the value Ra1 measured in water and the value Ra2 measured in air. Therefore, when the ratio R = Ra1 / Ra2 is preferably 1.6 or more, more preferably 1.7 or more, and even more preferably 1.8 or more, it becomes more effective to control the surface roughness using the surface roughness Ra1 as an index in the present invention. Note that if the ratio R = Ra1 / Ra2 is too large, the deformation of the asperities in water and air becomes too large, so the ratio R = Ra1 / Ra2 is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less.

[0051] In this specification, the surface roughness Ra1 measured in water and the surface roughness Ra2 measured in air refer to the planar surface roughness Ra defined by the following formula (Mathematical Formula 1).

[0052]

number

[0053] Planar surface roughness can be calculated using values ​​measured using an atomic force microscope (AFM). Average surface roughness (Ra) is a three-dimensional extension of the centerline average roughness Ra defined in JIS B0601 so that it can be applied to measurement surfaces, and is the average of the absolute values ​​of the deviation from the reference surface to the specified surface. Here, the measurement surface refers to the surface indicated by all measurement data, the specified surface refers to the surface targeted for roughness measurement, a specific portion of the measurement surface designated with a clip (designated area is 5 μm x 5 μm), and the reference surface refers to the plane represented by Z=Z0, where Z0 is the average height of the designated surface.

[0054] Methods for manufacturing composite semipermeable membranes that can adjust the surface roughness Ra2 measured in air are described in, for example, Japanese Patent Application Laid-Open Nos. 9-85068 and 7-8770. In accordance with such manufacturing methods, the present invention also makes it possible to adjust the surface roughness Ra1 while checking the surface roughness Ra1 measured in water.

[0055] In particular, in a method for producing a composite semipermeable membrane by forming a polyamide-based skin layer (separation functional layer) by a means including a step of coating a porous support with a solution A containing a polyfunctional amine component and a step of contacting the solution A phase with a solution B containing a polyfunctional acid halide component, it is preferable to add an interfacial conditioner such as an alkanolamine compound, an alkyl ketone compound, or an alkyl ester compound to the solution A.

[0056] Examples of the alkanolamine compound include ethanolamine, methanolamine, propanolamine, butanolamine, etc., and may be any of monoalkanolamine, dialkanolamine, and trialkanolamine. In addition, the hydrogen atom bonded to the nitrogen atom of the alkanolamine compound may be substituted with an alkyl group, an alkenyl group, an alkynyl group, a phenyl group, etc. Among these, monoethanolamine, diethanolamine, and triethanolamine are preferred, and monoethanolamine and triethanolamine are more preferred.

[0057] Examples of the alkyl ketone compound include acetone, diisopropyl ketone, and cyclohexanone, and examples of the alkyl ester compound include ethyl acetate, propyl acetate, and butyl acetate.

[0058] The concentration of the interfacial conditioner in the solution A is preferably 0.1 to 10.0% by mass, more preferably 1.0 to 5.0% by mass, from the viewpoint of producing a composite semipermeable membrane having the above-mentioned surface roughness Ra1.

[0059] The surface roughness Ra1 can also be adjusted by the difference in solubility parameter between the solution A and the solution B, or the solubility parameter of a compound added to the solution A and / or the solution B. When producing a composite semipermeable membrane having the above-mentioned surface roughness Ra1, it is necessary to add a compound having a solubility parameter of 8 to 17 (cal / cm) to at least one selected from the solution A, the solution B, and the microporous support. 3 ) 1 / 2 It is preferred that a compound of the formula:

[0060] Examples of the solubility parameter adjuster include alcohols such as ethanol, propanol, butanol, and pentanol, and nitrogen compounds such as ethylamine, triethylamine, and n-butylamine. The solubility parameter can also be adjusted by the type and concentration of the polyfunctional amine component or polyfunctional acid halogen component used.

[0061] In order to improve the salt blocking property, water permeability, oxidation resistance, etc. of the composite semipermeable membrane, various conventionally known treatments may be applied.

[0062] (Spiral membrane element) The spiral membrane element of the present invention is characterized by having the composite semipermeable membrane as described above, and any of the conventional membrane element configurations can be adopted for the parts other than the composite semipermeable membrane.

[0063] The spiral membrane element of the present invention comprises, for example, a perforated central tube 5 and a wound body R wound around the central tube 5 and including a separation membrane 1, as shown in FIG.

[0064] 2, the device includes a plurality of membrane leaves L, each having a permeate-side channel material 3 interposed between opposing separation membranes 1, a feed-side channel material 2 interposed between the membrane leaves L, a perforated central tube 5 around which the membrane leaves L and the feed-side channel material 2 are wound, and a sealing portion 12 that prevents mixing of the feed-side channel and the permeate-side channel. In this case, the permeate-side channel in the membrane leaf L can be formed by the permeate-side channel material 3 (also referred to as the permeate-side spacer).

[0065] It is also possible to form the feed-side flow path and / or the permeation-side flow path in the separation membrane 1 itself by providing irregularities or grooves on the surface of the separation membrane 1, in which case the feed-side flow path material 2 and / or the permeation-side flow path material 3 can be omitted.

[0066] 2 shows an example in which the sealed portion includes both end sealed portions and an outer peripheral sealed portion 12. Of the sealed portions, the both end sealed portions are formed by sealing two edge portions on both sides of the membrane leaf L in the axial direction A1 with an adhesive. The outer peripheral sealed portion 12 is formed by sealing the edge portion at the outer peripheral tip of the membrane leaf L with an adhesive. The area surrounded by the opposing separation membrane 1, the both end sealed portions, and the outer peripheral sealed portion 12 forms a permeate-side flow path, which is structured to communicate with the opening 5a of the central tube 5.

[0067] It is also preferable to have a central sealing portion in which the perforated central tube 5 and the base end sides of both end sealing portions of the membrane leaf L are sealed with an adhesive. The membrane leaf L and the feed-side channel material 2 are wound around the central tube 5 via such a central sealing portion to form a wound body R. The adhesive is not particularly limited, and any conventionally known adhesive such as a urethane adhesive or an epoxy adhesive can be used.

[0068] A first end member 10 having a function such as a seal carrier may be provided on the upstream side of the membrane element wound body R, and a second end member 20 having a function such as an anti-telescope material may be provided on the downstream side.

[0069] In a typical 8-inch diameter spiral membrane element, about 15 to 30 sets of membrane leaves L are wound. When the membrane element is in use, it is housed in a pressure vessel, and a feed liquid 7 is supplied from one end face of the membrane element. The supplied feed liquid 7 flows along the feed-side flow path material 2 in a direction parallel to the axial direction A1 of the central tube 5 and is discharged from the other end face of the membrane element as a concentrated liquid 9. In addition, permeated liquid 8, which permeates the separation membrane 1 as the feed liquid 7 flows along the permeation-side flow path material 3, flows through the permeation-side flow path material 3, and then flows into the central tube 5 through the openings 5a and is discharged from the end of the central tube 5.

[0070] The feed-side channel material 2 generally serves to ensure gaps for uniformly supplying the fluid to the membrane surface. For example, nets, knitted fabrics, textured sheets, etc. can be used as this feed-side channel material 2, and materials with a maximum thickness of approximately 0.1 to 3 mm can be used as needed. Furthermore, when channel materials are placed on both sides of the separation membrane 1, different channel materials are generally used: the feed-side channel material 2 on the feed liquid side and the permeate-side channel material 3 on the permeate side. It is preferable to use a thick, coarse-mesh net-like channel material for the feed-side channel material 2, while using a fine-mesh woven or knitted channel material for the permeate-side channel material 3.

[0071] When RO membranes or NF membranes are used in applications such as seawater desalination and wastewater treatment, the permeate-side channel material 3 is provided so as to be interposed between opposing separation membranes 1 in the membrane leaf L. This permeate-side channel material 3 is required to support the pressure applied to the membrane from the backside of the membrane and to ensure a channel for the permeate 8.

[0072] In order to ensure such a function, the permeate-side channel material 3 is preferably formed of a tricot knit fabric, and more preferably, the tricot knit fabric is subjected to resin impregnation reinforcement or fusion treatment after the knit fabric is formed.

[0073] The composite semipermeable membrane of the present invention described above is used as the separation membrane 1. That is, the spiral membrane element of the present invention is a composite semipermeable membrane comprising a porous support and a separation functional layer formed of a polyamide resin on the porous support, wherein the separation functional layer has a composite semipermeable membrane having a surface roughness Ra1 of 90 to 150 nm when measured in a 5 μm × 5 μm area in water with an atomic force microscope (AFM).

[0074] In the case of a typical spiral membrane element, an outer periphery of the wound body R is provided with an exterior material 15. The exterior material 15 is not particularly limited, and examples thereof include various sheets, films, tapes, etc., and, if necessary, a fiber-reinforced resin (FRP) or the like is used for reinforcement. A preferred method for forming the fiber-reinforced resin is to use roving, in which fibers are impregnated with a curable resin, and wrap this around the outer periphery of the wound body R.

[0075] (Application) Composite semipermeable membranes are sometimes called RO (reverse osmosis) membranes, NF (nanofiltration) membranes, partial desalination loose-type NF membranes, and selective separation NF membranes depending on the size of the solutes to be separated, and the composite semipermeable membrane of the present invention can be applied to any type of separation membrane. In particular, in recent years overseas, there has been an increasing demand for composite semipermeable membranes used in the production of drinking water that have the ability to block organic compounds (e.g., molecular weights of 150 to 250) such as herbicides and odorous components, and that have good water permeability when removing these compounds, and the composite semipermeable membrane of the present invention is particularly effective as a separation membrane for removing such organic compounds.

[0076] The spiral-wound separation membrane element can be used for other purposes as well. For example, it is suitable for producing ultrapure water and desalinating brine or seawater. It can also contribute to the closure of wastewater by removing and recovering pollutants or effective substances contained in pollutants that cause pollution, such as dye wastewater and electrodeposition paint wastewater. It can also be used for advanced treatments such as concentrating effective ingredients in food applications and removing harmful substances in water purification and sewage treatment. It can also be used for wastewater treatment in oil fields and shale gas fields. [Example]

[0077] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the examples, physical properties were measured or evaluated by the following methods. The physical properties in the present invention are specifically values ​​measured by the following methods.

[0078] (1) Surface roughness Ra2 measured by AFM in air For the prepared composite semipermeable membranes, the composite semipermeable membranes obtained after the drying process were used for the measurements. For the commercially available products, the element was washed with water, the composite semipermeable membrane was removed from the element, and then the composite semipermeable membrane was dried at 25°C for 12 hours or more for the measurements.

[0079] The surface roughness Ra defined by the above formula (Equation 1) was calculated using values ​​measured using an atomic force microscope (AFM) (Hitachi High-Tech Science Corporation, AFM5300E). The average surface roughness (Ra) is a three-dimensional extension of the centerline average roughness Ra defined in JIS B0601 so that it can be applied to the measurement surface. It is the average of the absolute values ​​of the deviations from the reference surface to the specified surface. Here, the measurement surface refers to the surface indicated by all measurement data, the specified surface refers to the surface targeted for roughness measurement, a specific portion of the measurement surface designated by a clip (designated area 5 μm × 5 μm), and the reference surface refers to the plane represented by Z = Z0, where Z0 is the average height of the designated surface. AFM measurements in air were performed on three samples each, and the average surface roughness Ra2 was calculated.

[0080] (2) Surface roughness Ra1 measured by AFM in water For the prepared composite semipermeable membranes, the composite semipermeable membranes obtained after the drying process were hydrophilized, and then the membranes were immersed in ultrapure water for measurement. For commercially available products, the elements were washed with water, the composite semipermeable membranes were removed from the elements, and then the composite semipermeable membranes were immersed in ultrapure water for measurement.

[0081] The surface profile was measured using an atomic force microscope (AFM) (Hitachi High-Tech Science Corporation, AFM5300E) in the same manner as above, except that instead of performing the AFM measurement in air as described in (1) above, the AFM measurement was performed in water as follows.

[0082] The samples were immersed in ultrapure water, and while still wet, they were placed in a holder for liquid measurements. The holder was filled with ultrapure water and AFM measurements were performed. Three samples were measured in water, and the average surface roughness Ra1 was calculated.

[0083] The ratio R of the surface roughness Ra1 to the surface roughness Ra2 measured in the atmosphere was calculated by R=Ra1 / Ra2.

[0084] (3) Evaluation of atrazine rejection rate The flat composite semipermeable membrane was cut to the specified shape and size and placed in a cell (effective membrane surface area: 44.2 cm) of a cross-flow test system for flat membrane evaluation. 2 ) and then set at 0.5 MPa, 25°C, and pH 6.5. An aqueous solution of atrazine with a concentration of 1 ppm was allowed to pass through the composite semipermeable membrane for 30 minutes, and the atrazine rejection was measured. The concentrations of the feed solution and the permeate were measured using a GC / MS analyzer (Agilent, Agilent 5975MSD), and the atrazine rejection was calculated from the measurement results using the following formula. <Atrazine Rejection Rate> Rejection rate (%) = (1 - (atrazine concentration in membrane permeate / atrazine concentration in feed solution)) x 100

[0085] (4) Evaluation of permeability using simulated water The flat composite semipermeable membrane was cut to the specified shape and size and placed in a cell (effective membrane surface area: 44.2 cm) of a cross-flow test system for flat membrane evaluation. 2 ) and the water permeability was set to 25LMH (Lm -2 h -1 The pressure was adjusted to 1 / 3 of the pressure at 25°C and pH 6.5, and simulated water, modeled on river water with the following composition and a concentration of 500 ppm, was allowed to pass through the composite semipermeable membrane for 30 minutes. The pressure after 30 minutes (pressure after 30 minutes) was used to calculate the water permeability using the following formula. <Water permeability> Permeability (LMH / bar) = 25LMH / (pressure required to produce 25LMH) <Composition of simulated water modeled on river water> A 500 ppm concentration composition containing 2.50 g of sodium chloride (NaCl), 0.27 g of sodium nitrate (NaNO3), 0.73 g of sodium silicate (SiO2Na2O), 9.10 g of sodium sulfate (Na2SO4), 5.33 g of magnesium chloride hexahydrate (MgCl2·6H2O), 5.83 g of magnesium sulfate heptahydrate (MgSO4·7H2O), 7.33 g of calcium chloride (CaCl2), and 0.33 g of potassium chloride (KCl) in 50 L of purified water.

[0086] Example 1 An aqueous amine solution containing 2.5% by mass of m-phenylenediamine (MPD), 0.1% by mass of sodium dodecyl sulfate, 2.6% by mass of triethylamine, 1.7% by mass of monoethanolamine as an interfacial modifier, 0.03% by mass of sodium hydroxide, 6% by mass of camphorsulfonic acid, 1.5% by mass of magnesium nitrate, and 4% by mass of isopropyl alcohol was applied to a polysulfone porous support formed on a polyester nonwoven fabric, and then excess amine aqueous solution was removed to form an aqueous solution coating layer.

[0087] Next, the surface of the aqueous solution coating layer was immersed for 7 seconds in an acid chloride solution prepared by dissolving 0.2% by mass of trimesoyl chloride (TMC) and 0.2% by mass of 2-methyl-2-butanol in a naphthenic solvent (Exxsol D40, manufactured by ExxonMobil). Afterwards, excess solution was removed from the surface of the aqueous solution coating layer, and the layer was air-dried for 20 seconds. The layer was then placed in a hot air dryer at 140°C for 3 minutes to form a separating functional layer containing a polyamide resin on the porous polysulfone support layer. This produced a composite semipermeable membrane consisting of a nonwoven fabric substrate, a polysulfone porous support, and a polyamide separating functional layer arranged in this order. The evaluation results are shown in Table 1.

[0088] Example 2 A composite semipermeable membrane was produced under the same conditions as in Example 1, except that diethanolamine was used instead of monoethanolamine as the interface conditioner in Example 1. The evaluation results are shown in Table 1.

[0089] Example 3 A composite semipermeable membrane was produced under the same conditions as in Example 1, except that the interfacial conditioner in Example 1 was changed from monoethanolamine to triethanolamine. The evaluation results are shown in Table 1.

[0090] Example 4 A composite semipermeable membrane was produced under the same conditions as in Example 1, except that the content of monoethanolamine as an interface conditioner was changed to 2.0 mass %. The evaluation results are shown in Table 1.

[0091] (Comparative Example 1) A composite semipermeable membrane was produced under the same conditions as in Example 1, except that monoethanolamine was not used as an interfacial modifier and an amine aqueous solution was prepared so that the other components had the same concentrations. The evaluation results are shown in Table 1.

[0092] (Comparative Example 2) The composite semipermeable membrane was taken out by disassembling a commercially available NF membrane element (manufactured by DuPont, NF90-400). The evaluation results are shown in Table 1.

[0093] (Comparative Example 3) The composite semipermeable membrane was taken out by disassembling a commercially available NF membrane element (manufactured by DuPont, NF270-400). The evaluation results are shown in Table 1.

[0094] [Table 1]

[0095] As the results in Table 1 show, the surface roughness Ra1 measured with an atomic force microscope (AFM) in water and the surface roughness Ra2 measured in air do not match, and the ratio between the two fluctuates greatly.

[0096] In Examples 1 to 4, where the surface roughness Ra1 was at a certain level or higher, high water permeability was obtained while maintaining an atrazine rejection rate of 95.0% or higher. In particular, when comparing Comparative Example 1 and Example 2, it was found that Example 2, where the surface roughness Ra1 measured in water was larger, achieved higher water permeability than Comparative Example 1, where the surface roughness Ra2 measured in air was larger.

[0097] In contrast, in Comparative Example 1, which did not use an interfacial modifier, the surface roughness Ra1 was less than a certain value, and although the atrazine rejection rate was high, the water permeability was insufficient.Furthermore, in Comparative Examples 2 and 3, which used a commercially available product, the surface roughness Ra1 was small, and the atrazine rejection rate or water permeability was insufficient. [Industrial Applicability]

[0098] According to the present invention, by controlling the microscopic surface area of ​​the separation functional layer using an index different from conventional ones, it is possible to provide a composite semipermeable membrane and a spiral membrane element that can improve both the blocking performance against organic compounds and the water permeability.

[0099] For this reason, particularly in recent years overseas, there has been an increasing demand for composite semipermeable membranes used in the production of drinking water that have the ability to block organic compounds (e.g., molecular weights of 150 to 250) such as herbicides and odorous components, and that have good water permeability when removing these compounds, and the composite semipermeable membrane of the present invention is particularly effective as a separation membrane for removing such organic compounds. [Explanation of symbols]

[0100] 1: Separation membrane 1a: Separation functional layer 1b: Porous support 5: Central tube A1: Axial direction R: Rolled body

Claims

1. A composite semipermeable membrane comprising a porous support and a separation functional layer formed of a polyamide resin on the porous support, the separation functional layer has a surface roughness Ra1 of 90 to 150 nm when measured in a 5 μm×5 μm area in water with an atomic force microscope (AFM); A composite semipermeable membrane having a water permeability of 9.0 LMH / bar or more when evaluated using simulated water modeled after river water.

2. The composite semipermeable membrane according to claim 1, wherein the polyamide resin contains a component derived from m-phenylenediamine.

3. 2. The composite semipermeable membrane according to claim 1, wherein the ratio of the surface roughness Ra1 of the separation functional layer to the surface roughness Ra2 measured in an area of ​​5 μm × 5 μm in air with an atomic force microscope (AFM): R = Ra1 / Ra2 is 1.6 or more.

4. 2. The composite semipermeable membrane according to claim 1, wherein the atrazine rejection rate is 95.0% or more.

5. The composite semipermeable membrane according to claim 1, wherein the surface roughness Ra1 is 95 to 150 nm.

6. A spiral membrane element comprising the composite semipermeable membrane according to any one of claims 1 to 5.

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