Composite semipermeable membranes and spiral membrane elements

Abstract

By adjusting the amount of residual functional groups on the front and back surfaces of the separation functional layer, we provide a composite semipermeable membrane with further improved alkali resistance, and a spiral-type membrane element using the same. [Solution] A composite semipermeable membrane comprising a separation functional layer, wherein the separation functional layer contains a polyamide resin, the surface functional group ratio A and the back surface functional group ratio B satisfy the relationship A / B ≤ 3.0, and the carboxyl group concentration x and the amino group concentration y satisfy the relationship x + y ≤ 0.015. The surface functional group ratio A is a value calculated as A = x / y, where x is the carboxyl group concentration relative to the total carbon amount and y is the amino group concentration relative to the total carbon amount when the surface of the separation functional layer is measured by the ESCA gas phase modification method, and the back surface functional group ratio B is a value calculated as B = X / Y when the back surface of the separation functional layer is measured in the same manner.

Description

[Technical Field]

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

[0002] The membranes used in membrane separation methods include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes. These membranes are used, for example, to obtain drinking water from seawater, brine, and water containing harmful substances, as well as for the production of industrial ultrapure water, wastewater treatment, and the recovery of valuable materials.

[0003] As a reverse osmosis membrane, a composite semipermeable membrane is widely used as a separation membrane with high permeability and selective separation properties, in which a separation functional layer containing a crosslinked polyamide obtained by a polycondensation reaction between a polyfunctional amine and a polyfunctional acid halide is formed on a porous resin layer (Patent Document 1).

[0004] When composite semipermeable membranes are used continuously in water desalination plants, fouling accumulates on the membrane surface over time, reducing the membrane's water production capacity. Therefore, cleaning with alkaline or other chemical solutions becomes necessary after a certain period of operation. For this reason, there is a need for composite semipermeable membranes that can maintain high separation performance and practical levels of water permeability even after alkaline cleaning.

[0005] As a technique to improve the durability of alkaline cleaning, for example, Patent Document 2 proposes a composite semipermeable membrane comprising a separation functional layer on a porous support membrane, wherein the separation functional layer contains a crosslinked total aromatic polyamide, and when x is the molar ratio of carboxyl groups to amide groups, x is 0.54 or less. In this document, regarding the quantification of the molar ratio x, the recovered separation functional layer is prepared as a powder sample by freeze-pulverization, sealed in a sample tube used for solid-state NMR measurement, and measured by CP / MAS method and DD / MAS method. 13The report describes how 13C solid-state NMR measurements were performed, and from the obtained spectra, peak splitting was performed for each peak originating from the carbon atom to which each functional group was attached. The ratio of functional group amounts was then quantified from the area of ​​the split peaks.

[0006] Furthermore, as an invention that quantifies the functional groups present on the surface of a separation functional layer using X-ray photoelectron spectroscopy (ESCA), Patent Document 3 describes a composite semipermeable membrane in which an ultrathin film layer of cross-linked polyamide is formed on a microporous support film, and the carboxyl group concentration in the ultrathin film layer, as analyzed using X-ray photoelectron spectroscopy (ESCA), is 0.02 to 0.07, and the water permeability at an operating pressure of 0.3 MPa is 0.5 to 3.0 m³. 3 / m 2 A composite semipermeable membrane characterized by being d has been proposed. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 5-76740 [Patent Document 2] International Publication No. WO2016 / 002819 [Patent Document 3] Patent No. 3852211 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, our investigations have shown that when a separation functional layer containing a crosslinked polyamide is formed by interfacial polymerization of a polyfunctional amine and a polyfunctional acid halide using a conventional manufacturing method, carboxyl groups may be unevenly distributed on either the front or back side of the separation functional layer. Therefore, as described in Patent Document 2, a parameter that quantifies carboxyl groups across the entire separation functional layer is insufficient as an indicator for improving alkali durability.

[0009] Furthermore, even when quantifying functional groups present on the surface of the separation functional layer using X-ray photoelectron spectroscopy (ESCA), as described in Patent Document 3, it was found that quantifying only the front side of the separation functional layer, or quantifying based on the average value of both sides, is insufficient as an indicator for improving alkali durability.

[0010] While there are known techniques for chemically modifying separation functional layers, such as analyzing functional groups on the front and back surfaces of the separation functional layer using ESCA, there has been no technique to date for determining the ratio of carboxyl groups on the front and back surfaces of an unmodified separation functional layer using ESCA.

[0011] Therefore, the object of the present invention is to provide a composite semipermeable membrane with further improved alkali resistance by adjusting the amount of residual functional groups on the surface and back surface of the separation functional layer, and a spiral-type membrane element using the same. [Means for solving the problem]

[0012] The inventors of the present invention have conducted extensive research to solve the aforementioned problems and have found that by adjusting the molar concentration ratio of the monomers used when forming the separation functional layer, the amount of solvent before heating and drying, and the rate of heating and drying, it is possible to adjust not only the amount of unreacted functional groups but also the front-to-back ratio of carboxyl groups. By setting this within a predetermined range, alkali resistance can be further improved, leading to the completion of the present invention. That is, the present invention includes the following embodiments.

[0013] [1] A composite semipermeable membrane comprising a porous support having a porous resin layer and a separation functional layer formed of a polyamide resin on the porous resin layer, The separation functional layer comprises an amino group and a carboxyl group, The separation functional layer is a composite semipermeable membrane characterized in that the ratio of surface functional groups A and the ratio of back surface functional groups B, as defined below, satisfy the relationship A / B ≤ 3.0, and the carboxyl group concentration x and the amino group concentration y, as defined below, satisfy the relationship x + y ≤ 0.015. Here, when the surface functional group ratio A is calculated, x is the carboxyl group concentration with respect to the total carbon amount when the surface of the separation functional layer is measured by the ESCA gas phase modification method, and y is the amino group concentration with respect to the total carbon amount when the surface of the separation functional layer is measured by the ESCA gas phase modification method, and A = x / y. When the back surface functional group ratio B is calculated, X is the carboxyl group concentration with respect to the total carbon amount when the back surface of the separation functional layer is measured by the ESCA gas phase modification method, and Y is the amino group concentration with respect to the total carbon amount when the back surface of the separation functional layer is measured by the ESCA gas phase modification method, and B = X / Y.

[0014] According to the composite semipermeable membrane of the present invention, by satisfying the relational expressions of A / B ≤ 3.0 and x + y ≤ 0.015, a composite semipermeable membrane with further improved alkali durability can be obtained. Although the details of the reason are unclear, it is considered as follows. That is, in the conventional manufacturing method, due to the charged monomer concentration when forming the separation functional layer, the amount of solvent before heat drying, and the rate of heat drying, the surface functional group ratio A tends to exceed three times the back surface functional group ratio B, which has been an obstacle to improving alkali durability. In the present invention, by adjusting the molar concentration ratio of the charged monomers, the amount of solvent before heat drying, the rate of heat drying, etc. when forming the separation functional layer, while reducing the sum x + y of the carboxyl group concentration x and the amino group concentration y on the surface, and making A / B ≤ 3.0, the concentration of carboxyl groups with respect to amino groups throughout the thickness direction of the separation functional layer is made uniform, and by reducing the amount of residual functional groups on the back surface, it is considered that a composite semipermeable membrane with further improved alkali durability can be obtained.

[0015] [2] The composite semipermeable membrane according to [1], wherein when the absorption peak intensity (around 1665 cm -1 -1) derived from the amide group and the absorption peak intensity (around 1710 cm -1 -1) derived from the carboxyl group of the separation functional layer are measured by the FT-IR method, the absorption peak intensity ratio of the carboxyl group to the amide group is 0.08 or less.

[0016] According to the FT-IR method, since the relative amount of the carboxy group to the amide group can be quantified for the entire thickness direction of the separation functional layer, it is considered that by making this below a certain level, the alkali durability can be more reliably improved.

[0017] [3] The composite semipermeable membrane according to [1] or [2], wherein the polyamide resin contains a constituent component obtained by polymerizing a polyfunctional amine component and a polyfunctional acid halogen component.

[0018] When including a constituent component obtained by polymerizing a polyfunctional amine component and a polyfunctional acid halogen component, the separation functional layer contains a polyamide resin having an amino group and a carboxy group, and in order to improve the alkali durability as described above, it is particularly important to satisfy the relational expressions of A / B ≦ 3.0 and x + y ≦ 0.015.

[0019] [4] The composite semipermeable membrane according to any one of [1] to [3], wherein the polyamide resin contains a constituent component obtained by polymerizing m-phenylenediamine and trimesic acid chloride.

[0020] When the polyamide resin contains a constituent component obtained by polymerizing m-phenylenediamine and trimesic acid chloride, since there is a tendency for the surface functional group ratio A to exceed three times the back surface functional group ratio B particularly by the conventional production method, it is important to satisfy the relational expressions of A / B ≦ 3.0 and x + y ≦ 0.015.

[0021] [5] A spiral membrane element having the composite semipermeable membrane according to any one of [1] to [4].

[0022] According to the spiral membrane element of the present invention, since it has the composite semipermeable membrane of the present invention as described above, a spiral membrane element with further improved alkali durability can be provided.

Effects of the Invention

[0023] According to the present invention, by adjusting the amount of residual functional groups on the front and back surfaces of the separation functional layer, it is possible to provide a composite semipermeable membrane with further improved alkali resistance, and a spiral-type membrane element using the same. [Brief explanation of the drawing]

[0024] [Figure 1] This is a partially disassembled perspective view showing an example of a spiral-type membrane element. [Modes for carrying out the invention]

[0025] Embodiments of the present invention will be described below.

[0026] (composite semipermeable membrane) The composite semipermeable membrane of the present invention comprises a porous support having a porous resin layer and a separation functional layer formed of a polyamide resin on the porous resin layer. The separation functional layer contains amino groups and carboxyl groups derived from unreacted functional groups of the monomer components of the polyamide resin.

[0027] The separation functional layer can be formed by interfacial polymerization of a polyamide resin, and it is particularly preferable that the separation functional layer contains a polyamide resin obtained by polymerizing a polyfunctional amine component and a polyfunctional acid halogen component. In other words, it is preferable that the polyamide resin contains components obtained by polymerizing a polyfunctional amine component and a polyfunctional acid halogen component.

[0028] A polyfunctional amine component is a polyfunctional amine having two or more reactive amino groups, and examples include aromatic, aliphatic, and alicyclic polyfunctional amines. In this invention, at least a divalent polyfunctional amine is used as the polyfunctional amine component.

[0029] Examples of aromatic polyfunctional amines include m-phenylenediamine (MPD), 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.

[0030] Examples of aliphatic polyfunctional amines include ethylenediamine, propylenediamine, tris(2-aminoethyl)amine, and n-phenylethylenediamine.

[0031] Examples of alicyclic polyfunctional amines include 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, and 4-aminomethylpiperazine.

[0032] These polyfunctional amines may be used individually or in combination of two or more. To obtain a separation functional layer with the desired inhibitory performance, it is preferable to use an aromatic polyfunctional amine, and more preferably to use m-phenylenediamine.

[0033] In particular, from the viewpoint of easily obtaining the desired inhibitory performance, it is preferable to use 70 to 100 mol% of m-phenylenediamine in the polyfunctional amine component, more preferably 90 to 100 mol%, and most preferably 100 mol%. This makes it possible to form a separation functional layer using a polyamide resin containing components derived from m-phenylenediamine.

[0034] A polyfunctional acid halide component is a polyfunctional acid halide having two or more reactive carbonyl groups. Examples of polyfunctional acid halides include aromatic, aliphatic, and alicyclic polyfunctional acid halides. In this invention, a polyfunctional acid halide with at least trivalent or higher is used as the polyfunctional acid halide component.

[0035] Examples of aromatic polyfunctional acid halides include trimesic acid chloride (TMC) (trimesic acid trichloride), terephthalic acid dichloride, isophthalic acid dichloride, biphenyl dicarboxylic acid dichloride, naphthalenedicarboxylic acid dichloride, benzenetrisulfonic acid trichloride, benzenedisulfonic acid dichloride, and chlorosulfonylbenzenedicarboxylic acid dichloride.

[0036] Examples of 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.

[0037] 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 tetrahydrofrancolamine carboxylic acid dichloride.

[0038] These polyfunctional acid halides may be used individually or in combination of two or more. To obtain a separation functional layer with high salt blocking performance, it is preferable to use aromatic polyfunctional acid halides. Furthermore, it is preferable to use a polyfunctional acid halide of trivalent or higher in at least a portion of the polyfunctional acid halide component to form a crosslinked structure, and it is more preferable to use trimesic acid chloride (TMC).

[0039] In particular, from the viewpoint of easily obtaining the desired inhibitory performance, it is preferable to use 30 to 100 mol% of trimesinate chloride (TMC) in the polyfunctional acid halide component, more preferably 80 to 100 mol%, and most preferably 100 mol%. This makes it possible to form a separation functional layer using a polyamide resin containing components derived from trimesinate chloride.

[0040] The separation functional layer satisfies the relationship A / B ≤ 3.0 between the surface functional group ratio A and the back functional group ratio B, as defined below. From the viewpoint of improving alkali durability by reducing the surface functional group ratio A, it is more preferable that A / B ≤ 2.5 is satisfied, even more preferably that A / B ≤ 2.0 is satisfied, and particularly preferably that A / B ≤ 1.5 is satisfied. Furthermore, from the viewpoint of improving alkali durability by balancing the surface functional group ratio A and the back functional group ratio B, it is preferable that the relationship between the surface functional group ratio A and the back functional group ratio B satisfies the relationship 0.3 ≤ A / B, more preferably that 0.5 ≤ A / B is satisfied, and even more preferably that 0.7 ≤ A / B is satisfied.

[0041] Here, the surface functional group ratio A is calculated as A = x / y, where x is the carboxyl group concentration relative to the total carbon content when the surface of the separation functional layer is measured by the ESCA gas phase modification method, and y is the amino group concentration relative to the total carbon content when the surface of the separation functional layer is measured by the ESCA gas phase modification method. The back surface functional group ratio B is calculated as B = X / Y, where X is the carboxyl group concentration relative to the total carbon content when the back surface of the separation functional layer is measured by the ESCA gas phase modification method, and Y is the amino group concentration relative to the total carbon content when the back surface of the separation functional layer is measured by the ESCA gas phase modification method.

[0042] Furthermore, the separation functional layer satisfies the relationship x+y≦0.015 between the carboxyl group concentration x and the amino group concentration y as defined below. From the viewpoint of reducing the total amount of unreacted functional groups on the surface and improving alkali durability, it is more preferable that x+y≦0.014 is satisfied, even more preferably x+y≦0.014 is satisfied, and particularly preferably x+y≦0.010 is satisfied. From the viewpoint of improving alkali durability, the sum of the carboxyl group concentration x and the amino group concentration y, x+y, is preferable as small as possible, but from the viewpoint of ensuring sufficient water permeability, it is more preferable that 0.007≦x+y is satisfied, and even more preferably 0.009≦x+y is satisfied.

[0043] In this invention, the absorption peak intensity (1665 cm) originating from the amide group of the separation functional layer is determined by FT-IR. -1 (Near) and absorption peak intensity (1710 cm) originating from the carboxyl group. -1 When measuring the absorption peak intensity of the carboxyl group relative to the amide group, it is preferable that the absorption peak intensity ratio of the carboxyl group to the amide group is 0.08 or less. From the viewpoint of reducing the relative amount of carboxyl groups over the entire thickness direction of the separation functional layer and improving alkali durability, it is more preferable that the absorption peak intensity ratio is 0.075 or less, and even more preferable that it is 0.070 or less. From the viewpoint of reducing the relative amount of carboxyl groups over the entire thickness direction of the separation functional layer, a smaller absorption peak intensity ratio of carboxyl groups to amide groups is preferable, but the absorption peak intensity ratio may be 0.01 or more, 0.02 or more, or 0.03 or more, etc.

[0044] Furthermore, in order to improve the performance of the separation functional layer containing polyamide resin, polymers such as polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylic acid, and polyhydric alcohols such as sorbitol and glycerin may be copolymerized.

[0045] The porous support that supports the separation functional layer may have a porous resin layer, or may be formed solely from a porous resin layer, but it is preferable that it is reinforced with a base material such as woven fabric or nonwoven fabric. The porous support having a porous resin layer may be such that it can support the separation functional layer on its upper surface, but the average surface pore size of the porous resin layer is preferably 1 to 300 nm, and more preferably 5 to 100 nm, from the viewpoint of maintaining the permeability of the resulting composite semipermeable membrane while making it difficult for the polymerization reaction of the separation functional layer to proceed inside the porous resin layer.

[0046] Various materials can be used to form the porous resin layer, such as polysulfone-based resins like polysulfone, polyethersulfone, and polyphenylsulfone, as well as polyimide, polyetherimide, and polyvinylidene fluoride. However, polysulfone-based resins are particularly preferred due to their chemical, mechanical, and thermal stability.

[0047] The overall thickness of the porous support having a porous resin layer is, for example, about 50 to 200 μm, preferably about 80 to 150 μm. The thickness of the porous resin layer is, for example, 10 to 50 μm, preferably 20 to 40 μm. The porosity of the porous resin layer is, for example, 50 to 80%, preferably 60 to 70%.

[0048] (Method for producing composite semipermeable membranes) Preferred methods for forming a separation functional layer containing a polyamide resin on the surface of a porous support include interfacial polymerization. Specifically, interfacial polymerization involves forming a separation functional layer by bringing an aqueous amine solution containing a polyfunctional amine component into contact with an organic solution containing a polyfunctional acid halide component and performing interfacial polymerization, and then placing the separation functional layer on a porous support, or directly forming a separation functional layer of polyamide resin on a porous support by the aforementioned interfacial polymerization on the porous support. Details of the conditions for such interfacial polymerization are described in Japanese Patent Publication No. 58-24303, Japanese Patent Publication No. 1-180208, etc., and these known technologies can be appropriately adopted.

[0049] In the method for producing the composite semipermeable membrane of the present invention, in which a separation functional layer containing a polyamide resin is directly formed on a porous support by interfacial polymerization on the porous support, it is preferable to adjust the molar concentration ratio of the monomers used in forming the separation functional layer, the amount of solvent before heating and drying, and the rate of heating and drying to form a separation functional layer that satisfies the relationships A / B ≤ 3.0 and x + y ≤ 0.015. Specifically, it is preferable to employ the following method.

[0050] The molar concentration ratio of the monomers used in interfacial polymerization is the value obtained by dividing the molar concentration of the polyfunctional acid halide component in the organic solution used for interfacial polymerization by the molar concentration of the polyfunctional amine component in the amine solution used, when equal masses of the organic solution and the amine aqueous solution are prepared. For example, when using trimesic acid chloride (TMC) and m-phenylenediamine (MPD), the molar concentration ratio of the monomers used can be calculated using the following formula. Molar concentration ratio of the monomers used in the preparation (-) = Molar concentration of MPD in solution ÷ Molar concentration of TMC in solution The molar concentration ratio of such monomers is preferably 35 to 75, and more preferably 37 to 68, such that the carboxyl group concentration x and the amino group concentration y satisfy the relationship x + y ≤ 0.015.

[0051] The molar concentration ratio of the monomers used in the preparation can be determined by adjusting the molar concentration of the polyfunctional acid halide component in the organic solution and the molar concentration of the polyfunctional amine component in the amine aqueous solution. Furthermore, the molar concentration of the monomers used in the preparation tends to affect desalination performance and water permeability.

[0052] Therefore, the molar concentration of the polyfunctional acid halide component in the organic solution is preferably 0.0003 to 0.146 mol / L, more preferably 0.0015 to 0.0876 mol / L, and even more preferably 0.002 to 0.058 mol / L. These preferred molar concentrations can be converted to the mass concentration of TMC, which is preferably 0.01 to 5% by mass, more preferably 0.05 to 3% by mass, and even more preferably 0.08 to 2% by mass.

[0053] Furthermore, the molar concentration of the polyfunctional amine component in the amine aqueous solution is preferably 0.009 to 0.648 mol / L, and more preferably 0.093 to 0.463 mol / L. These preferred molar concentrations can be converted to the mass concentration of MPD, which is preferably 0.1 to 7% by mass, and more preferably 1 to 5% by mass.

[0054] Furthermore, in interfacial polymerization, an amine aqueous solution containing a polyfunctional amine component, which is usually present on a porous support, is brought into contact with an organic solution containing a polyfunctional acid halide component. However, immediately after contact, it is preferable to allow contact with a large amount of the organic solution for at least 2 seconds to ensure the initial reaction of interfacial polymerization. For example, a large amount of organic solution can be brought into contact with the porous support coated with the amine aqueous solution by immersing it in an organic solution containing a polyfunctional acid halide component.

[0055] In this process, if the temperature of the organic solution is too low, the reaction will not proceed easily, and if the temperature is too high, there will be an excess of polyfunctional acid halide components that contribute to the reaction, disrupting the balance of the reaction, which is undesirable. For these reasons, the temperature of the organic solution containing polyfunctional acid halide components is preferably around 10 to 35°C.

[0056] In the interfacial polymerization method, a separation functional layer is typically formed by contacting an amine aqueous solution containing a polyfunctional amine component present on a porous support with an organic solution containing a polyfunctional acid halide component, and then proceeding with interfacial polymerization while heating and drying.

[0057] In this process, the amount of solvent immediately before heating and drying is important for satisfying the relationships A / B ≤ 3.0 and / or x + y ≤ 0.015. The amount of solvent before heating and drying is calculated by dividing the volume of the organic solution containing polyfunctional acid halide components present on the surface of the porous support by the coating area on the porous support. Since the concentration is dilute, this is calculated as the amount of solvent per unit area (cc / m²). 2) It is such. The amount of solvent immediately before such heat drying affects the molar amount of the polyfunctional acid halide component used in the reaction in relation to the molar concentration of the polyfunctional acid halide component, and this affects the value of A / B and / or the value of x + y.

[0058] Therefore, as the amount of solvent immediately before heat drying, 95 cc / m 2 or less is preferable, 80 cc / m 2 or less is more preferable, and 50 cc / m 2 is even more preferable.

[0059] Furthermore, the solvent residual rate 10 seconds after the start of heat drying, which is an index of the heat drying rate, is important for satisfying the relational expressions of A / B ≤ 3.0 and / or x + y ≤ 0.015. The solvent residual rate 10 seconds after the start of heat drying is calculated by dividing the mass immediately before the start of heat drying of the organic solution containing the polyfunctional acid halide component present on the surface of the porous support by the mass 10 seconds after the start of heat drying. Since the concentration is dilute, this is defined as the solvent residual rate (%). Such a solvent residual rate 10 seconds after the start of heat drying affects the reaction rate and reaction time between the polyfunctional amine component and the polyfunctional acid halide component, and this affects the value of A / B and / or the value of x + y.

[0060] Therefore, as the solvent residual rate 10 seconds after the start of heat drying, 60% or more is preferable, 70% or more is more preferable, and 90% is even more preferable. The solvent residual rate 10 seconds after the start of heat drying can be adjusted, for example, by the heating temperature in the oven, the air flow rate, the air flow direction, etc.

[0061] The heating temperature in the oven is preferably within the range of 100°C to 170°C. Although production is possible even when the overheating temperature is less than 100°C, since the time until solvent drying is too long, the solvent may flow on the film during drying and the film surface may become non-uniform. Also, it is hard to say that a heating temperature higher than 170°C is desirable from an environmental aspect.

[0062] In this invention, when an aqueous amine solution containing a polyfunctional amine component is present on a porous support, it is preferable to first allow at least a portion of the aqueous amine solution to impregnate and adhere to the porous resin layer, and then remove the excess aqueous amine solution on the porous support to adjust the amount of aqueous amine solution impregnated and adhered to the porous resin layer to a certain level or less. This stabilizes the amount of aqueous amine solution that actually contributes to the reaction. Furthermore, when in contact with an organic solution containing a polyfunctional acid halide component, the aqueous amine solution remaining on the surface is less likely to interfere with the reaction.

[0063] The coating method for the amine aqueous solution may be immersion, contact with a cloth soaked in the amine aqueous solution, or other coating methods, but it is preferable to adjust the time during which the amine aqueous solution is impregnated into the porous resin layer. For example, when using the immersion method, it is preferable to adjust the immersion time to between 1 second and 5 minutes.

[0064] Furthermore, in order to adjust the amount of amine aqueous solution impregnating and adhering to the porous resin layer to a certain level or lower, it is preferable to remove excess amine aqueous solution from the porous support. For example, when employing an immersion method, it is preferable to remove the porous support after the immersion time has elapsed and remove the excess amine aqueous solution from the surface of the porous support using a wiper or the like.

[0065] In this way, the amount of amine aqueous solution impregnating and adhering to the porous resin layer is 500 mg / m². 2 It is preferable that the amount be less than 450 mg / m². 2 The less the better.

[0066] The liquid temperature when impregnating and adhering the amine aqueous solution to the porous resin layer is correlated with the amount of amine impregnated. If the amount of amine impregnated is too high, it becomes amine-rich, making it difficult to form a suitable separation functional layer. For this reason, the liquid temperature of the amine aqueous solution is preferably 10 to 30°C.

[0067] Furthermore, in the present invention, when forming a separation functional layer by interfacial polymerization, it is possible to increase the effective film area and improve water permeability by creating fine irregularities. In particular, in a method for producing a composite semipermeable membrane by forming a polyamide-based skin layer (separation functional layer) by means including the steps of coating a porous support with solution A containing a polyfunctional amine component and contacting solution B containing a polyfunctional acid halogen component with the solution A phase, it is preferable to add an interfacial modifier such as an alkanolamine compound, alkyl ketone compound, or alkyl ester compound to solution A.

[0068] Examples of alkanolamine compounds include ethanolamine, methanolamine, propanolamine, and butanolamine, and any of monoalkanolamine, dialkanolamine, or trialkanolamine may be used. Furthermore, the hydrogen atom bonded to the nitrogen atom of the alkanolamine compound may be substituted with an alkyl group, alkenyl group, alkynyl group, phenyl group, etc. Among these, trialkanolamine is preferred, and triethanolamine, tri(t-butanol)amine, and tri(isopropanol)amine are more preferred.

[0069] Examples of alkyl ketone compounds include acetone, diisopropyl ketone, and cyclohexanone, while examples of alkyl ester compounds include ethyl acetate, propyl acetate, and butyl acetate.

[0070] From the viewpoint of improving the water permeability of the composite semipermeable membrane, the concentration of the interface modifier is preferably 0.01 to 10.0% by mass, and more preferably 0.1 to 5.0% by mass, in solution A.

[0071] Furthermore, when forming a separation functional layer by interfacial polymerization, if the effective film area is increased by creating fine irregularities, at least one of the solutions A, B, and microporous support must have a solubility parameter of 8-17 (cal / cm³). 3 ) 1 / 2 It is preferable to have the compound present.

[0072] Examples of solubility parameter adjusters include alcohols such as ethanol, propanol, butanol, and pentanol, as well as nitrogen compounds such as ethylamine, triethylamine, and n-butylamine. Furthermore, the solubility parameter can be adjusted by the type and concentration of the polyfunctional amine component or polyfunctional acid halogen component used.

[0073] Furthermore, various conventionally known treatments may be applied to improve the salt-blocking properties, water permeability, and oxidation resistance of the composite semipermeable membrane.

[0074] (Spiral-type membrane element) The spiral membrane element of the present invention is characterized by having a 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.

[0075] The spiral membrane element of the present invention comprises, for example, a perforated central tube 5 and a wound body R containing a separation membrane 1 wound around the central tube 5, as shown in Figure 1.

[0076] In the example shown in Figure 1, the system comprises a plurality of membrane leaves L with permeation-side channel material 3 interposed between opposing separation membranes 1, a supply-side channel material 2 interposed between the membrane leaves L, a perforated central tube 5 around which the membrane leaves L and the supply-side channel material 2 are wound, and a sealing portion 12 to prevent mixing of the supply-side channel and the permeation-side channel. In this case, the permeation-side channel within the membrane leaves L can be formed by the permeation-side channel material 3 (also called a permeation-side spacer).

[0077] It is also possible to create irregularities or grooves on the surface of the separation membrane 1 to form the supply channel and / or permeate channel on the separation membrane 1 itself, in which case the supply channel material 2 and / or permeate channel material 3 can be omitted.

[0078] Figure 1 shows an example in which the sealing portion includes both end sealing portions and an outer peripheral sealing portion 12. Of the sealing portions, the both end sealing portions are formed by sealing the two end surfaces on both sides of the membrane leaf L in the axial direction A1 with adhesive. The outer peripheral sealing portion 12 is formed by sealing the end surface of the outer peripheral tip of the membrane leaf L with adhesive. The region enclosed by the opposing separation membrane 1, the both end sealing portions, and the outer peripheral sealing portion 12 becomes the permeate channel, which is in communication with the opening 5a of the central tube 5.

[0079] Furthermore, it is preferable to have a central sealing portion formed by sealing the perforated central tube 5 and the base end of the sealing portions at both ends of the membrane leaf L with an adhesive. The membrane leaf L and the supply-side flow channel material 2 are wound around the central tube 5 via such a central sealing portion, forming a wound body R. The adhesive is not particularly limited, and any conventionally known adhesive such as urethane-based adhesive or epoxy-based adhesive can be used.

[0080] A first end member 10 having a function such as a seal carrier may be provided on the upstream side of the wound body R of the membrane element, and a second end member 20 having a function such as an anti-telescopic material may be provided on the downstream side.

[0081] In a typical 8-inch diameter spiral membrane element, approximately 15 to 30 membrane leaves L are wound around it. When the membrane element is in use, it is housed in a pressure vessel (vessel), and the feed liquid 7 is supplied from one end face of the membrane element. The supplied feed liquid 7 flows along the supply-side flow channel material 2 in a direction parallel to the axial direction A1 of the central tube 5, and is discharged as concentrated liquid 9 from the other end face of the membrane element. In addition, the permeate 8 that has permeated the separation membrane 1 as the feed liquid 7 flows along the supply-side flow channel material 2 flows along the permeate-side flow channel material 3, then flows into the interior of the central tube 5 through the opening 5a, and is discharged from the end of the central tube 5.

[0082] The supply-side channel material 2 generally serves to ensure gaps for evenly supplying fluid to the membrane surface. Such a supply-side channel material 2 can be made of, for example, a net, knitted fabric, or a textured sheet, and can be used as needed with a maximum thickness of approximately 0.1 to 3 mm. Furthermore, when channel materials are installed on both sides of the separation membrane 1, it is common to use different channel materials, with the supply-side channel material 2 on the supply liquid side and the permeate-side channel material 3 on the permeate liquid side. It is preferable to use a coarse, thick net-like channel material for the supply-side channel material 2, while using a fine-mesh woven or knitted channel material for the permeate-side channel material 3.

[0083] The permeate channel material 3 is installed between opposing separation membranes 1 in a membrane reef L when RO membranes or NF membranes are used in applications such as seawater desalination and wastewater treatment. This permeate channel material 3 is required to support the pressure on the membrane from the back of the membrane and to ensure a flow path for the permeate 8.

[0084] To ensure such functionality, it is preferable that the permeable channel material 3 is formed from a tricot knitted fabric, and more preferably that the tricot knitted fabric is reinforced with resin impregnation or fused after knitting.

[0085] As the separation membrane 1, the composite semipermeable membrane of the present invention described above is used. That is, the spiral membrane element of the present invention is a composite semipermeable membrane comprising a porous support having a porous resin layer and a separation functional layer formed of a polyamide resin on the porous resin layer, wherein the separation functional layer contains amino groups and carboxyl groups, and the separation functional layer satisfies the relationship A / B ≤ 3.0 between the surface functional group ratio A and the back surface functional group ratio B, and satisfies the relationship x + y ≤ 0.015 between the carboxyl group concentration x and the amino group concentration y.

[0086] In the case of a typical spiral membrane element, the outer circumference of the wound body R is provided with an outer covering material 15. The outer covering material 15 is not particularly limited and can be various sheets, films, tapes, etc., and if necessary, fiber-reinforced plastic (FRP) or the like is used for reinforcement. As a method for forming the fiber-reinforced plastic, it is preferable to use roving in which fibers are impregnated with a curable resin and wrap this around the outer circumference of the wound body R.

[0087] (Application) The composite semipermeable membrane and spiral membrane element of the present invention can be used, for example, to obtain drinking water from seawater, brine, or water containing harmful substances, as well as for the production of industrial ultrapure water, wastewater treatment, and the recovery of valuable materials. [Examples]

[0088] The present invention will be described below with reference to examples, but the present invention is not limited in any way by these examples. In the examples, the physical properties, etc., were measured or evaluated by the following methods. Specifically, the physical property values, etc., in the present invention are values ​​measured by the following methods.

[0089] (1) Molar concentration ratio of the starter (MPD / TMC) The molar concentration ratio of the monomers used (MPD / TMC) was calculated using the following formula. The molar concentration ratio at the start of the preparation is calculated as follows: (-) = molar concentration of m-phenylenediamine (MPD) in the solution ÷ molar concentration of trimesinate chloride (TMC) in the solution

[0090] (2) Amount of solvent before heating and drying Immediately before heating and drying, the mass of the TMC solution (B) present on the surface of the porous support was measured, and the amount of solvent per unit area (cc / m²) was determined. 2 The solvent volume (cc / m³) was calculated. Specifically, the mass of the TMC solution (B) present on the surface of the porous support was measured from the difference in mass before and after immersion in the TMC solution (B). The volume of the solution per unit area was calculated by dividing the mass of the solution (B) by the density of the solution (B) and the surface area of ​​the porous support. Since the concentration is dilute, this was calculated as the solvent volume per unit area (cc / m³). 2 )

[0091] (3) Solvent remaining rate 10 seconds after the start of heating and drying Ten seconds after the start of heating and drying, the porous support was removed from the oven, and the mass of the TMC solution (B) present on the surface of the porous support was measured to calculate the solvent retention rate (%). Because the concentration was dilute, the solvent retention rate (%) was calculated using the following formula.

[0092] Solvent retention rate (%) = Mass of solution (B) 10 seconds after the start of heating and drying / Mass of solution (B) immediately before heating and drying × 100

[0093] (4) Measurement of x, y, X, Y by ESCA vapor phase modification method The composite semipermeable membrane was immersed in cyclohexanone to dissolve the polysulfone layer, and the amount of functional groups present on the front and back surfaces of the separated functional layer, which consisted only of the skin layer, was analyzed by X-ray photoelectron spectroscopy (ESCA) using a scanning X-ray photoelectron spectrometer (ULVAC-PHI QUANTUM2000) with an X-ray output of 15kV and a detector angle of 45°.

[0094] First, the amount of amino groups and carboxyl groups present on the surface and back surface of the separation functional layer was modified using a labeling reagent in the gas phase. Pentafluorobenzaldehyde was used as the labeling reagent for the amino groups, and 2,2,2-trifluoroethanol was used for the carboxyl groups.

[0095] To measure the carboxyl group concentration relative to the total carbon content, the sample was chemically modified in the gas phase using a labeling reagent, and the reaction rate (r) of the labeling reagent was determined from the ESCA spectrum of the polyacrylic acid standard sample that had also been chemically modified in the gas phase. Next, the area intensity [F1s] of the F1s peak (the peak of the fluorine 1s orbital) formed by the reaction between the sample and the labeling reagent was determined. Furthermore, the area intensity [C1s] of the C1s peak (the peak of the carbon 1s orbital) was determined by elemental analysis. In this way, the area intensities [F1s] and [C1s] obtained when measuring the surface of the separation functional layer were substituted into the following formula to determine the carboxyl group concentration x(-) relative to the total carbon content.

[0096] Carboxylate group concentration x(-) = [F1s] / (3[C1s]-2[F1s]r) Similarly, the number of carboxyl groups X(-) relative to the total carbon content was determined from the area intensity [F1s] and [C1s] measured on the back surface of the separation functional layer.

[0097] To measure the amino group concentration relative to the total carbon content, the sample was chemically modified in the gas phase using a labeling reagent, and the reaction rate (r) of the labeling reagent was determined from the ESCA spectrum of a 4,4'-diaminodiphenyl ether standard sample that had also been chemically modified in the gas phase. Next, the area intensity [F1s] of the F1s peak (the peak of the fluorine 1s orbital) formed by the reaction between the sample and the labeling reagent was determined. Furthermore, the area intensity [C1s] of the C1s peak (the peak of the carbon 1s orbital) was determined by elemental analysis. In this way, the area intensities [F1s] and [C1s] obtained when measuring the surface of the separation functional layer were substituted into the following formula to determine the amino group concentration y(-) relative to the total carbon content.

[0098] Amino group concentration y(-) = [F1s] / (5[C1s]-7[F1s]r) Similarly, the amino group concentration Y(-) relative to the total carbon content was determined from the area intensity [F1s] and [C1s] measured on the back surface of the separation functional layer.

[0099] (5) Measurement of carboxyl group concentration by FT-IR method FT-IR analysis revealed the absorption peak intensity (1665 cm²) originating from the amide group across the entire thickness direction of the separation functional layer. -1 (Near) and the absorption peak intensity (1710 cm) derived from the carboxyl group -1 The absorption peak intensity ratio of the carboxyl group to the amide group was calculated by measuring the vicinity of the amide group.

[0100] Composite semipermeable membranes are used as cells in a cross-flow test system for flat membrane evaluation (effective membrane surface area: 44.2 cm²). 2The sample was set in a 3D printer and washed with RO water under pressure at 1.5 MPa for 30 minutes. After that, the composite semipermeable membrane was dried at room temperature for 12 hours to prepare the sample for measurement. The sample for measurement was then attached to a Fourier transform infrared spectrophotometer (PerkinElmer Spectrum TWO), and a germanium ATR crystal was used as an accessory for total internal reflection measurement. The ATR-IR method was used to scan the sample under conditions of an incident angle of 45° and 25 reflections. The absorption peak intensity (1665 cm²) originating from the C=O stretching vibration of the amide group in the polyamide resin, which is the material forming the separation functional layer, was measured. -1 (Near) and the absorption peak intensity (1710 cm) originating from the stretching vibration of the C=O group of the polyfunctional acid halide component. -1 The values ​​(in the vicinity) were measured (16 scans). From these results, the amount of carboxyl groups relative to the amide groups in the separation functional layer was calculated using the following formula. Carboxylic group amount (-) = Absorption peak intensity (1710 cm) -1 (Nearby) / Absorption peak intensity (1665cm) -1 (Nearby)

[0101] (6) Initial NaCl rejection rate As an aqueous NaCl solution, an aqueous solution was prepared by dissolving NaCl at a concentration of 1500 ppm in RO water. A flat composite semipermeable membrane was cut into predetermined shapes and sizes, and used as a cell for a cross-flow test system for flat membrane evaluation (effective membrane surface area: 44.2 cm²). 2 The apparatus was set up as follows: An aqueous NaCl solution (at 25°C) was permeated through the composite semipermeable membrane at an operating pressure of 1.55 MPa for 30 minutes. After 30 minutes, the conductivity of the permeate, concentrate, and feed solution was measured using a conductivity measuring device, and the initial NaCl rejection rate was calculated from the results and the calibration curve (concentration-conductivity) based on the following formula. NaCl rejection rate (%) = (1 - (NaCl concentration in permeate / (NaCl concentration in supply solution + NaCl concentration in concentrate) / 2)) × 100

[0102] (7) Evaluation of alkali resistance The fabricated flat composite semipermeable membrane was cut into pieces of the same shape and size, and then placed in the cell of a cross-flow test system for flat membrane evaluation. A pH 12.5 NaOH aqueous solution (temperature 25°C) was permeated through the composite semipermeable membrane at an operating pressure of 0.3 MPa for 8 hours. After 8 hours of permeation, a pH 2 citric acid aqueous solution (temperature 25°C) was permeated through the composite semipermeable membrane at an operating pressure of 0.3 MPa for 2 hours. The permeation of the two types of aqueous solutions was repeated alternately until the total permeation time reached 200 hours. After 200 hours of permeation, the NaCl rejection rate after alkali contact was calculated in the same manner as in (6) above. Alkali durability was evaluated by calculating the rate of change (-) from the NaCl rejection rate before and after 200 hours of immersion using the following formula. Change rate (-) = (100 - NaCl rejection rate after alkaline immersion) / (100 - initial NaCl rejection rate)

[0103] (Example 1) A porous support, on which a polysulfone porous resin layer (average surface pore size 20 nm) was formed on a polyester nonwoven fabric, was coated with an aqueous solution (A) containing 2.0% by mass of m-phenylenediamine (MPD), 0.15% by mass of sodium lauryl sulfate, 3% by mass of triethylamine, 6% by mass of p-toluenesulfonic acid, and 4% by mass of isopropyl alcohol. The excess aqueous solution (A) was then removed to form an aqueous coating layer.

[0104] Subsequently, the surface coated with aqueous solution (A) was immersed for 4 seconds in a 25°C solution (B) containing 0.1% by mass of trimesinate chloride (TMC) dissolved in isooctane. Then, the porous support was lifted vertically from the solution (B), and 90 cc / m² of material was applied to the porous support. 2 The solvent was maintained in the oven at 130°C while heating and drying was initiated. Heating and drying was carried out for 3 minutes under conditions where the solvent retention rate was 85% 10 seconds after the start of heating and drying, and a composite semipermeable membrane having a separation functional layer containing polyamide resin was obtained. The evaluation results, along with the manufacturing conditions, are shown in Table 1.

[0105] (Example 2) In Example 1, a composite semipermeable membrane was prepared under the same conditions as in Example 1, except that the amount of solvent before heating and drying and the solvent remaining percentage after 10 seconds were changed as shown in Table 1 by altering the time for flowing and removing solution (B) and the wind speed and wind direction during heating and drying. The evaluation results, along with the manufacturing conditions, are shown in Table 1.

[0106] (Example 3) In Example 1, a composite semipermeable membrane was prepared under the same conditions as in Example 1, except that the amount of solvent before heating and drying and the solvent remaining percentage after 10 seconds were changed as shown in Table 1 by altering the time for flowing and removing solution (B) and the wind speed and wind direction during heating and drying. The evaluation results, along with the manufacturing conditions, are shown in Table 1.

[0107] (Example 4) In Example 1, a composite semipermeable membrane was prepared under the same conditions as in Example 1, except that the amount of TMC was changed to 0.08% by mass, and the time for flowing and removing solution (B) was changed, as well as the wind speed and wind direction during heating and drying, resulting in changes to the amount of solvent before heating and drying and the solvent remaining percentage after 10 seconds, as shown in Table 1. The evaluation results, along with the manufacturing conditions, are shown in Table 1.

[0108] (Example 5) In Example 1, a composite semipermeable membrane was prepared under the same conditions as in Example 1, except that the amount of TMC was changed to 0.12% by mass, and the time for flowing and removing solution (B) and the wind speed and wind direction during heating and drying were changed, resulting in the solvent amount before heating and drying and the solvent remaining percentage after 10 seconds being changed as shown in Table 1. The evaluation results, along with the manufacturing conditions, are shown in Table 1.

[0109] (Example 6) In Example 1, a composite semipermeable film was prepared under the same conditions as in Example 1, except that the MPD was changed to 1.75% by mass and the TMC to 0.07% by mass, and the airflow velocity and direction during heating and drying were changed to alter the solvent residue rate after 10 seconds as shown in Table 1. The evaluation results, along with the manufacturing conditions, are shown in Table 1.

[0110] (Example 7) In Example 1, a composite semipermeable membrane was prepared under the same conditions as in Example 1, except that the amount of TMC was changed to 0.07% by mass, and the time for flowing and removing solution (B) and the air velocity and direction during heating and drying were changed, resulting in the solvent amount before heating and drying and the solvent remaining percentage after 10 seconds being changed as shown in Table 1. The evaluation results, along with the manufacturing conditions, are shown in Table 1.

[0111] (Comparative Example 1) In Example 1, a composite semipermeable membrane was prepared under the same conditions as in Example 1, except that the amount of solvent before heating and drying was changed as shown in Table 1 by changing the MPD to 2.25% by mass and the TMC to 0.07% by mass, and by changing the time for flowing and removing solution (B). The evaluation results, along with the manufacturing conditions, are shown in Table 1.

[0112] (Comparative Example 2) A composite semipermeable membrane was prepared under the same conditions as in Example 1, except that the MPD was changed to 2.25% by mass and the TMC to 0.2% by mass. The evaluation results, along with the manufacturing conditions, are shown in Table 1.

[0113] (Comparative Example 3) In Example 1, a composite semipermeable film was prepared under the same conditions as in Example 1, except that the amount of solvent before heating and drying was changed as shown in Table 1 by adding spray coating of solution (B). The evaluation results, along with the manufacturing conditions, are shown in Table 1.

[0114] (Comparative Example 4) In Example 1, a composite semipermeable membrane was prepared under the same conditions as in Example 1, except that the amount of solvent before heating and drying was changed as shown in Table 1 by changing the TMC to 0.05% by mass, extending the immersion time in solution (B), and adding spray coating. The evaluation results, along with the manufacturing conditions, are shown in Table 1.

[0115] (Comparative Example 5) In Example 1, a composite semipermeable membrane was prepared under the same conditions as in Example 1, except that the amount of solvent before heating and drying and the solvent remaining percentage after 10 seconds were changed as shown in Table 1 by changing the MPD to 2.2% by mass and the TMC to 0.1% by mass, and by changing the time for flowing and removing solution (B) and the air velocity and air direction during heating and drying. The evaluation results are shown in Table 1 along with the manufacturing conditions.

[0116] (Comparative Example 6) In Example 1, a composite semipermeable membrane was fabricated under the same conditions as in Example 1, except that the solvent retention rate after 10 seconds was changed as shown in Table 1 by increasing the circulating airflow rate and adjusting the airflow direction in the oven during heating and drying. The evaluation results, along with the manufacturing conditions, are shown in Table 1.

[0117] (Comparative Example 7) In Example 1, a composite semipermeable membrane was fabricated under the same conditions as in Example 1, except that the solvent retention rate after 10 seconds was changed as shown in Table 1 by increasing the circulating airflow rate and adjusting the airflow direction in the oven during heating and drying. The evaluation results, along with the manufacturing conditions, are shown in Table 1.

[0118] (Comparative Example 8) In accordance with the conventional manufacturing method for general RO membranes, the concentrations of each solution, coating conditions, and heating and drying conditions were adjusted, and the amount of solvent before heating and drying and the solvent retention rate after 10 seconds were confirmed. Specifically, in Example 1, the MPD was changed to 3% by mass and the TMC to 0.2% by mass, and the time for flowing and removing solution (B) was changed, as well as the wind speed and wind direction during heating and drying, resulting in the amount of solvent before heating and drying and the solvent retention rate after 10 seconds as shown in Table 1. Otherwise, a composite semipermeable membrane was manufactured under the same conditions as in Example 1. The evaluation results, along with the manufacturing conditions, are shown in Table 1.

[0119] [Table 1]

[0120] As shown in Table 1, Examples 1 to 7 satisfied the relationships A / B ≤ 3.0 and x + y ≤ 0.015, indicating good alkali resistance.

[0121] In contrast, Comparative Examples 1, 2, and 5, which did not satisfy only the relationship x+y≦0.015, showed reduced alkali durability. Furthermore, Comparative Examples 3, 6, 7, and 8, which did not satisfy only the relationship A / B≦3.0, also showed reduced alkali durability. Comparative Example 4, which did not satisfy both the relationship A / B≦3.0 and x+y≦0.015, showed a significant decrease in alkali durability. [Industrial applicability]

[0122] According to the present invention, it is possible to provide a composite semipermeable membrane with particularly good alkali resistance, and a spiral-type membrane element using the same, making it useful as a composite semipermeable membrane that can maintain high separation performance even after alkaline cleaning. [Explanation of Symbols]

[0123] 1: Separation membrane 5: Central tube A1: Axial direction R: Coiled body

Claims

1. A composite semipermeable membrane comprising a porous support having a porous resin layer and a separation functional layer formed of a polyamide resin on the porous resin layer, The separation functional layer comprises an amino group and a carboxyl group, The separation functional layer is a composite semipermeable membrane characterized in that the ratio of surface functional groups A and the ratio of back surface functional groups B, as defined below, satisfy the relationship A / B ≤ 3.0, and the carboxyl group concentration x and the amino group concentration y, as defined below, satisfy the relationship x + y ≤ 0.

015. Here, the surface functional group ratio A is calculated as A = x / y, where x is the carboxyl group concentration relative to the total carbon amount when the surface of the separation functional layer is measured by the ESCA gas phase modification method, and y is the amino group concentration relative to the total carbon amount when the surface of the separation functional layer is measured by the ESCA gas phase modification method. The back surface functional group ratio B is calculated as B = X / Y, where X is the carboxyl group concentration relative to the total carbon amount when the back surface of the separation functional layer is measured by the ESCA gas phase modification method, and Y is the amino group concentration relative to the total carbon amount when the back surface of the separation functional layer is measured by the ESCA gas phase modification method.

2. The absorption peak intensity (1665 cm⁻¹) originating from the amide group in the separation functional layer was determined by the FT-IR method. －１ (Near) and the absorption peak intensity (1710 cm) originating from the carboxyl group. －１ The composite semipermeable membrane according to claim 1, wherein when the absorption peak intensity ratio of the carboxyl group to the amide group is measured (in the vicinity), the ratio of the absorption peak intensity of the carboxyl group to the amide group is 0.08 or less.

3. The composite semipermeable film according to claim 1, wherein the polyamide resin comprises a component obtained by polymerizing a polyfunctional amine component and a polyfunctional acid halogen component.

4. The composite semipermeable film according to claim 1, wherein the polyamide resin comprises a component obtained by polymerizing m-phenylenediamine and trimesinate chloride.

5. A spiral membrane element having a composite semipermeable membrane according to any one of claims 1 to 4.

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