Composite semipermeable membrane and method for producing composite semipermeable membrane

Abstract

The present invention pertains to a composite semipermeable membrane comprising: a porous support layer; and a separation function layer provided on the porous support layer. The separation function layer contains a polyamide including a halogen. The ratio of the number of carbon atoms to which a halogen is bonded with respect to the number of all carbon atoms on the surface of the separation function layer is 0.002-0.016. The composite semipermeable membrane exhibits a boron removal rate of at least 90% when an aqueous solution at 25°C having a pH of 6.5 and a sodium chloride concentration of 32000 mg / L and a boron concentration of 5 mg / L is caused to pass through the composite semipermeable membrane with an operation pressure of 5.5 MPa.

Description

Composite semipermeable membrane and method for producing the same

[0001] The present invention relates to a composite semipermeable membrane having a separating functional layer containing a polyamide, and a method for producing the same.

[0002] Semipermeable membranes used for separating liquid mixtures include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, etc. These membranes are used, for example, to produce drinking water from water containing salt or harmful substances, to produce ultrapure water for industrial use, to treat wastewater, or to recover valuable resources.

[0003] The majority of currently commercially available reverse osmosis membranes and nanofiltration membranes are composite semipermeable membranes. A typical composite semipermeable membrane is a polyamide semipermeable membrane having a microporous support membrane and a separation functional layer covering the microporous support membrane, the separation functional layer being made of a polyamide obtained by a polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide, and having high water permeability and selective separation properties.

[0004] However, if an oxidizing agent such as chlorine supplied for cleaning pipes or the like is mixed into the liquid supplied to the composite semipermeable membrane during use, the composite semipermeable membrane may be deteriorated by the oxidizing agent, and the removal performance may decrease. Also, when cleaning fouling such as metal compounds that are difficult to decompose with an oxidizing agent such as chlorine, an acid may be supplied, which may similarly decrease the removal performance of the composite semipermeable membrane.

[0005] Patent Document 1 discloses a composite semipermeable membrane that has both high removal performance and high chlorine resistance by adopting a structure in which the two-body center energy of the carbon-nitrogen bond of the amide bond in a polyamide resin when the hydrogen atom of the amide bond is substituted with a chlorine atom is −16.00 eV or less.

[0006] Patent Document 2 discloses a composite semipermeable membrane that has high water permeability and removal performance as well as high acid resistance, by using a structure in which the total amount of amino groups and carboxyl groups relative to amide groups in a crosslinked aromatic polyamide is 0.50 or more and the amount of amino groups is small relative to the amount of carboxyl groups.

[0007] Japanese Patent Publication No. 2003-200028 Japanese Patent No. 6197969

[0008] However, the method of Patent Document 1 has insufficient chlorine resistance because there are many chlorinable reaction sites in the separation functional layer, and since the crosslinked aromatic polyamide has a certain number of amino groups at its terminals, it cannot be said to have excellent acid resistance.The method of Patent Document 2 also cannot be said to have sufficient chlorine resistance and acid resistance for the same reasons as Patent Document 1.

[0009] Therefore, an object of the present invention is to provide a composite semipermeable membrane that has both high chlorine resistance and acid resistance.

[0010] To solve the above problems, the present invention includes the following configurations [1] to

[10] . [1] A composite semipermeable membrane comprising a porous support layer and a separation functional layer provided on the porous support layer, wherein the separation functional layer contains a halogen-containing polyamide, and the ratio of the number of halogen-bonded carbon atoms to the total number of carbon atoms on the surface of the separation functional layer is 0.002 to 0.016, and the composite semipermeable membrane has a boron rejection rate of 90% or more when an aqueous solution having a sodium chloride concentration of 32,000 mg / L, a pH of 6.5, and a boron concentration of 5 mg / L is passed through the composite semipermeable membrane at an operating pressure of 5.5 MPa at 25°C. [2] The composite semipermeable membrane according to [1] above, wherein the ratio of the number of halogen-bonded carbon atoms to the total number of carbon atoms on the surface of the separation functional layer is 0.004 to 0.016. [3] The composite semipermeable membrane according to [2] above, wherein the ratio of the number of halogen-bonded carbon atoms to the total number of carbon atoms on the surface of the separation functional layer is 0.010 or more and 0.016 or less. [4] The composite semipermeable membrane according to any one of [1] to [3] above, wherein the yellowing index of the separation functional layer before and after contact with a vanillin solution is 5 or more and 20 or less. [5] The composite semipermeable membrane according to any one of [1] to [3] above, wherein the halogen is at least one selected from the group consisting of chlorine, bromine, and iodine. [6] The composite semipermeable membrane according to any one of [1] to [3] above, wherein the ratio of the number of chlorine-bonded carbon atoms to the total number of carbon atoms on the surface of the separation functional layer is 0.010 or more and 0.016 or less. [7] The composite semipermeable membrane according to any one of [1] to [3] above, wherein the polyamide is an aromatic polyamide and has an α,β-unsaturated carbonyl structure. [8] A separation membrane element comprising the composite semipermeable membrane described in any one of [1] to [3] above. [9] A liquid separation device comprising the composite semipermeable membrane described in any one of [1] to [3] above.

[10] A method for producing a composite semipermeable membrane comprising a porous support layer and a separation functional layer provided on the porous support layer, wherein the separation functional layer contains a halogen-containing polyamide, the method comprising: a step (a) of contacting the separation functional layer with a polyfunctional amine solution; and a step (b) of contacting the separation functional layer with a polyfunctional carboxylic acid solution.

[0011] According to the present invention, a composite semipermeable membrane having both high chlorine resistance and acid resistance can be provided.

[0012] The present invention will now be described in further detail.

[0013] <Composite semipermeable membrane> The composite semipermeable membrane of the present invention is a composite semipermeable membrane (polyamide-based semipermeable membrane) comprising a porous support layer and a separation functional layer containing polyamide on the porous support layer. From the viewpoint of increasing the strength of the composite semipermeable membrane, the porous support layer may be formed on a substrate. In this specification, a form in which a porous support layer is formed on a substrate is also referred to as a support membrane.

[0014] The term "separation functional layer" refers to a layer having the function of separating the substances to be removed contained in the liquid to be treated.

[0015] The term "porous support layer" refers to a porous layer having a dense structure. The pore size of the surface of the porous support layer on the side where the separation function layer is formed is, for example, 0.1 nm or more and 100 nm or less.

[0016] Examples of materials that can be used to form the porous support layer include polysulfone, polyethersulfone, polyamide, polyester, cellulose-based polymers, vinyl polymers, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, polyphenylene oxide, etc. Cellulose-based polymers include cellulose acetate and cellulose nitrate, and vinyl polymers include polyethylene, polypropylene, polyvinyl chloride, and polyacrylonitrile.

[0017] The separating functional layer of the polyamide-based semipermeable membrane preferably contains polyamide as a main component. The main component means a component that accounts for 50% by mass or more of the components constituting the separating functional layer. The polyamide content in the separating functional layer is preferably 80% by mass or more, more preferably 90% by mass or more.

[0018] "Polyamide" refers to a polymer of a polyfunctional amine and a polyfunctional acid halide. Among these, the polyamide is preferably an aromatic polyamide, which is a polymer of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide. Furthermore, the polyamide is preferably a crosslinked polyamide in which at least one of the polyfunctional amine and the polyfunctional acid halide described below is trifunctional or higher, and more preferably a crosslinked aromatic polyamide in which at least one of the polyfunctional aromatic amine and the polyfunctional aromatic acid halide is trifunctional or higher.

[0019] Examples of polyfunctional amines include polyfunctional aromatic amines and polyfunctional aliphatic amines. The term "polyfunctional aromatic amine" refers to an aromatic amine having two or more primary and / or secondary amino groups in one molecule, with at least one of the amino groups being a primary amino group. Examples of polyfunctional aromatic amines include compounds in which two amino groups are bonded to an aromatic ring at the ortho, meta, or para positions, such as o-phenylenediamine, m-phenylenediamine (hereinafter referred to as "m-PDA"), p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m-diaminopyridine, and p-diaminopyridine; 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, and 4-aminobenzylamine. In particular, m-PDA, p-phenylenediamine, or 1,3,5-triaminobenzene is preferably used from the viewpoint of obtaining a semipermeable membrane having excellent selective separation properties, permeability, and heat resistance.

[0020] The term "polyfunctional aliphatic amine" refers to an aliphatic amine having two or more amino groups in one molecule. Examples of polyfunctional aliphatic amines include piperazine derivatives represented by the following general formula (I) and ethylenediamine.

[0021]

[0022] In general formula (I), R １ , R ２are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[0023] Specific examples of piperazine derivatives include piperazine, 2,5-dimethylpiperazine, 2-methylpiperazine, 2,5-diethylpiperazine, 2-n-propylpiperazine, 2,5-di-n-butylpiperazine, etc. In particular, piperazine or dimethylpiperazine is preferably used.

[0024] When forming the separation functional layer, at least one polyfunctional amine may be used, and two or more compounds may be selected from polyfunctional aromatic amines and polyfunctional aliphatic amines. Among them, it is preferable to use a polyfunctional aromatic amine as the polyfunctional amine, from the viewpoint of easily improving the performance of the polyamide-based semipermeable membrane.

[0025] The term "polyfunctional acid halide" refers to an acid halide having two or more halocarbonyl groups in one molecule. The polyfunctional acid halide can form an amide bond by reacting with a terminal amino group.

[0026] Examples of polyfunctional acid halides that can be used include halides of oxalic acid, malonic acid, maleic acid, fumaric acid, glutaric acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, trimesic acid, 1,2,4-benzenetricarboxylic acid, 1,3-benzenedicarboxylic acid, and 1,4-benzenedicarboxylic acid. The polyfunctional acid halides are preferably polyfunctional aromatic acid halides. Among acid halides, acid chlorides are preferred.

[0027] Specifically, the term "polyfunctional aromatic acid chloride" refers to an aromatic acid chloride having at least two, and preferably two to four, carbonyl chloride groups in one molecule (i.e., a polyfunctional aromatic acid chloride). For example, an example of a trifunctional acid chloride is trimesic acid chloride, and examples of difunctional acid chlorides include biphenyldicarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, and naphthalenedicarboxylic acid chloride. These polyfunctional aromatic acid halides may be used alone or in combination of two or more.

[0028] In the composite semipermeable membrane of the present invention, the separating functional layer contains a halogen-containing polyamide, and the ratio of the number of halogen-bonded carbon atoms to the total number of carbon atoms on the surface of the separating functional layer (number of halogen-bonded carbon atoms / total number of carbon atoms) is 0.002 or more and 0.016 or less.

[0029] By having a halogen in the polyamide constituting the separation functional layer, further chlorination by free chlorine can be suppressed, and a composite semipermeable membrane with excellent chlorine resistance can be obtained. When the ratio of the number of carbon atoms bonded to halogen to the total number of carbon atoms on the surface of the separation functional layer is within the above range, it is possible to exhibit high chlorine resistance while maintaining high removal performance. If the carbon number ratio is less than 0.002, chlorine resistance decreases, while if the carbon number ratio is greater than 0.016, the removal performance of the separation functional layer decreases significantly. From the viewpoint of achieving both removal performance and chlorine resistance of the composite semipermeable membrane, the ratio of the number of carbon atoms bonded to halogen to the total number of carbon atoms on the surface of the separation functional layer is preferably 0.004 to 0.016, more preferably 0.010 to 0.016, and even more preferably 0.012 to 0.016.

[0030] The ratio of the number of halogen-bonded carbon atoms to the total number of carbon atoms on the surface of the separation functional layer can be measured by X-ray photoelectron spectroscopy (XPS). Specifically, it can be calculated by the method described in the "Ratio of the number of halogen-bonded carbon atoms to the total number of carbon atoms" section of the Examples below. If a coating layer is formed on the surface of the separation functional layer, the ratio can be measured by extracting elemental information on the surface of the separation functional layer using XPS (GCIB-XPS) measurement by gas cluster ion beam (GCIB) etching.

[0031] From the viewpoint of forming pores in the separation functional layer that selectively allow water to pass through, the halogen on the surface of the separation functional layer of the composite semipermeable membrane of this embodiment is preferably at least one selected from the group consisting of chlorine, bromine, and iodine, and chlorine is more preferred.

[0032] When at least chlorine is contained as the halogen, the ratio of the number of carbon atoms bonded to chlorine to the total number of carbon atoms on the surface of the separation functional layer is preferably 0.010 or more and 0.016 or less.

[0033] Methods for introducing halogen into the polyamide contained in the separation functional layer include, for example, a method of forming a crosslinked polyamide using a pre-halogenated polyfunctional amine or polyfunctional acid halide, and a method of forming a separation functional layer and then immersing the composite semipermeable membrane in an aqueous solution of a hypohalite, etc. Among these, the method of introducing halogen after forming a separation functional layer is preferred.

[0034] Furthermore, the composite semipermeable membrane of the present invention has a boron rejection rate of 90% or more when an aqueous solution having a pH of 6.5, a sodium chloride concentration of 32,000 mg / L, and a boron concentration of 5 mg / L is passed through it at an operating pressure of 5.5 MPa at 25°C.

[0035] Since boron is a neutral molecule, the boron removal rate can be used as an indicator of the pore size of the separation functional layer. When the boron removal rate is within the above range, the separation functional layer has a small pore size and a sufficiently dense structure, which can prevent active species that induce deterioration from penetrating into the separation functional layer, thereby enabling the layer to exhibit high chlorine resistance and acid resistance. From the above perspective, the boron removal rate is preferably 92% or more, more preferably 96% or more. The upper limit of the boron removal rate is 100%.

[0036] One method for improving the boron rejection rate of a composite semipermeable membrane is, for example, to introduce a halogen into the separation functional layer and then condense a polyfunctional amine or a polyfunctional carboxylic acid again. Generally, when a halogen is introduced into a polyamide by chlorination or the like, the amide bond is hydrolyzed, and the pore size of the separation functional layer increases. Therefore, by introducing a halogen into the polyamide and then condensing a polyfunctional amine or a polyfunctional carboxylic acid again, the pore size of the separation functional layer can be reduced, thereby improving the boron rejection rate. The order in which the polyfunctional amine and the polyfunctional carboxylic acid are condensed is not particularly limited, but it is preferable to condense the polyfunctional amine first and then the polyfunctional carboxylic acid.

[0037] In the composite semipermeable membrane according to this embodiment, the yellowing index ΔYI of the separation functional layer before and after contact with the vanillin solution is preferably 5 or more and 20 or less, more preferably 10 or more and 17 or less. Amino groups, such as those at the aromatic polyamide terminals, contained in the separation functional layer form a color-developing chemical structure upon chemical reaction with vanillin. That is, the yellowing index ΔYI before and after contact with the vanillin solution reflects the amount of amino groups on the surface of the separation functional layer. When ΔYI is 20 or less, the amount of amino groups on the surface of the separation functional layer is reduced, achieving both chlorine resistance and acid resistance. On the other hand, when ΔYI is 5 or more, it is possible to impart a certain degree of hydrophilicity to the separation functional layer, thereby suppressing a decrease in the water permeability of the separation functional layer.

[0038] The yellowing index ΔYI can be calculated according to the procedure described in the "Vanillin Yellowing Index" section of the Examples below.

[0039] ΔYI can be controlled by the concentration of the hypohalite aqueous solution and the immersion time when the composite semipermeable membrane is immersed in a hypohalite aqueous solution or the like after forming the separation functional layer, and also by the concentrations, contact temperature, and contact time of the polyfunctional carboxylic acid and condensing agent when the polyfunctional carboxylic acid is condensed on the separation functional layer.

[0040] In the composite semipermeable membrane according to this embodiment, the polyamide contained in the separation functional layer is preferably an aromatic polyamide and has an α,β-unsaturated carbonyl structure. When the aromatic polyamide contained in the separation functional layer has an α,β-unsaturated carbonyl structure, the chlorine resistance of the separation functional layer is improved. In particular, it is more preferable that the aromatic polyamide has an α,β-unsaturated carbonyl structure in which the aromatic ring is oxidized.

[0041] One method for forming an α,β-unsaturated carbonyl structure in the aromatic polyamide contained in the separation functional layer is, for example, to immerse the composite semipermeable membrane in a hypohalite aqueous solution after forming the separation functional layer. Specifically, by immersing the composite semipermeable membrane in a hypochlorite aqueous solution under conditions where the product of the concentration (ppm) and contact time (h) is 3000 or more, oxidation of the amide bond adjacent to the aromatic ring of the aromatic polyamide is promoted, thereby converting the aromatic ring into an α,β-unsaturated carbonyl structure, and an aromatic polyamide having an α,β-unsaturated carbonyl structure can be obtained. The presence of an α,β-unsaturated carbonyl structure in an aromatic polyamide can be measured, for example, by time-of-flight secondary ion mass spectrometry.

[0042] <Separation membrane element> The composite semipermeable membrane according to this embodiment is wound around a cylindrical water collection pipe having a large number of holes, together with a feed-side channel material such as a plastic net, a permeate-side channel material such as a tricot, and, if necessary, a film for increasing pressure resistance, and is suitably used as a spiral separation membrane element (hereinafter also simply referred to as "element"). Furthermore, this element can be connected in series or in parallel and housed in a pressure vessel to form a separation membrane module.

[0043] Furthermore, the composite semipermeable membrane, the element, and the separation membrane module can be combined with a pump that supplies feed water to them, a device that pretreats the feed water, etc. to form a liquid separation device. By using this liquid separation device, the feed water can be separated into permeated water such as drinking water and concentrated water that did not permeate the membrane, thereby obtaining water suitable for the intended purpose.

[0044] <Liquid Separation Device> A liquid separation device using an element according to this embodiment includes, in order to perform a liquid passing treatment through the element, a tank for storing water to be treated, an element mounting part for mounting an element incorporating a composite semipermeable membrane according to this embodiment, piping connecting the tank and the element mounting part, and a pump running between the tank and the element mounting part.

[0045] More specifically, a liquid separation device using the element of this embodiment is configured to include an element mounting section including a container in which the element is mounted, piping connecting the element mounting section to the tank, and a pump connected to the piping.

[0046] The liquid separation device may further include a tank for the cleaning solution, a pump, piping, etc.

[0047] <Method for producing composite semipermeable membrane> The method for producing a composite semipermeable membrane of the present invention is a method for producing a composite semipermeable membrane comprising a porous support layer and a separation functional layer containing a halogen-containing polyamide on the porous support layer, and comprises a step (a) of contacting the separation functional layer with a polyfunctional amine solution, and a step (b) of contacting the separation functional layer with a polyfunctional carboxylic acid solution.

[0048] The separation functional layer of the composite semipermeable membrane according to this embodiment is preferably formed by interfacial polymerization using an aqueous solution containing a polyfunctional amine and an organic solvent solution containing a polyfunctional acid halide. In particular, it is preferable to use a polyfunctional aromatic amine as the polyfunctional amine and a polyfunctional aromatic acid halide as the polyfunctional acid halide, and form a crosslinked aromatic polyamide as the separation functional layer. Below, an example using a polyfunctional aromatic amine and a polyfunctional aromatic acid halide will be described.

[0049] The interfacial polymerization step includes (i) applying an aqueous solution containing a polyfunctional aromatic amine to a porous support layer, and (ii) applying an organic solvent solution containing a polyfunctional aromatic acid halide to the porous support layer after step (i).

[0050] In the steps (i) and (ii), examples of the means for applying the solution include immersion, showering, and coating.

[0051] The organic solvent in which the polyfunctional aromatic acid halide is dissolved in step (ii) is immiscible with water and has a solubility parameter of 15.2 (MPa) or less. １／２ It is preferable to use an organic solvent having an octanol / water partition coefficient of 3.2 or more. It is also preferable that the organic solvent does not destroy the support, particularly the porous support layer.

[0052] Representative examples of organic solvents that satisfy the above conditions include octane, nonane, decane, undecane, dodecane, isododecane, tridecane, tetradecane, heptadecane, hexadecane, isodecane, cyclooctane, isooctane, ethylcyclohexane, 1-octene, 1-decene, and the like, either alone or in combination.

[0053] Methods for obtaining a separation functional layer containing a halogen-containing polyamide include a method of forming a polyamide using a pre-halogenated polyfunctional amine or polyfunctional acid halide, and a method of forming a separation functional layer and then immersing a composite semipermeable membrane in an aqueous solution of a hypohalite salt. Among these, the method of immersing a composite semipermeable membrane in an aqueous solution of a hypohalite salt is preferred. Examples of hypohalite salts include sodium hypochlorite, sodium hypobromite, and potassium hypoiodite.

[0054] When using a method of immersing a composite semipermeable membrane in an aqueous hypohalite solution, the amount of halogen introduced into the polyamide can be controlled by the concentration (ppm) of the solution containing hypohalous acid and the time (h) for which the separation functional layer is contacted with the solution containing hypohalous acid (hereinafter also simply referred to as "contact time"). From the viewpoint of achieving both the removal performance and chlorine resistance of the composite semipermeable membrane, the product of the concentration (ppm) of the aqueous hypohalite solution and the contact time (h) is preferably 3 or more and 15,000 or less, more preferably 10 or more and 4,500 or less.

[0055] In the method for producing a composite semipermeable membrane of the present invention, either step (a) or step (b) may be carried out first, or step (a) and step (b) may be carried out simultaneously, i.e., by contacting with a solution containing both a polyfunctional amine and a polyfunctional carboxylic acid. From the viewpoint of efficiently condensing a polyfunctional amine and a polyfunctional carboxylic acid with a polyamide, it is preferable to carry out step (a) and step (b) in that order. Furthermore, step (a) and step (b) may be carried out multiple times.

[0056] The polyfunctional amine solution and the polyfunctional carboxylic acid solution are preferably aqueous solutions from the viewpoint of not swelling, decomposing, or dissolving the polyamide of the separating functional layer.

[0057] In steps (a) and (b), methods for contacting the separation functional layer with the solution include, for example, applying each solution to the surface of the separation functional layer, or immersing the separation functional layer or composite semipermeable membrane in each solution.

[0058] In step (a), the time for contacting the separation functional layer with the polyfunctional amine solution is preferably from 1 minute to 72 hours, more preferably from 30 minutes to 48 hours, and even more preferably from 1 hour to 24 hours.

[0059] The polyfunctional amine concentration in the polyfunctional amine solution is preferably 50 ppm to 5000 ppm, more preferably 100 ppm to 3000 ppm. When the polyfunctional amine concentration in the polyfunctional amine solution is 50 ppm or more, bonding between the carboxy group and the polyfunctional amine is likely to be promoted, and when it is 5000 ppm or less, a decrease in the water permeability of the separation functional layer due to excessive polyfunctional amine adsorption to the separation functional layer can be suppressed.

[0060] The polyfunctional amine solution may contain a condensing agent to improve condensation efficiency. When a condensing agent is contained, the concentration of the condensing agent in the polyfunctional amine solution is preferably 10 ppm or more and 10,000 ppm or less, more preferably 50 ppm or more and 3,000 ppm or less. When the concentration of the condensing agent is 10 ppm or more, the terminal carboxyl group of the polyamide contained in the separation functional layer can be sufficiently bonded to the polyfunctional amine. The type of condensing agent will be described later.

[0061] The temperature of the polyfunctional amine solution is preferably 10° C. or higher and 50° C. or lower, and more preferably 20° C. or higher and 45° C. or lower. When the temperature of the polyfunctional amine solution is 10° C. or higher, the bonding between the carboxy group and the polyfunctional amine is easily promoted, and when the temperature is 50° C. or lower, the effects of heat, such as denaturation of the separation functional layer, can be suppressed.

[0062] In addition, in order to promote bonding between the carboxy group and the polyfunctional amine, the pH of the polyfunctional amine aqueous solution may be 10 or more and 13 or less.

[0063] A "polyfunctional carboxylic acid" is a carboxylic acid having two or more carboxy groups in one molecule. Examples of polyfunctional carboxylic acids include oxalic acid, malonic acid, maleic acid, fumaric acid, glutaric acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3,5-benzenetricarboxylic acid (hereinafter referred to as "trimesic acid"), 1,2,4-benzenetricarboxylic acid, 1,3-benzenedicarboxylic acid, and 1,4-benzenedicarboxylic acid. Among polyfunctional carboxylic acids, 1,3,5-benzenetricarboxylic acid is preferred. As the polyfunctional carboxylic acid, only one type of compound may be used, or two or more types of compounds may be combined.

[0064] In step (b), the time for which the separation functional layer is brought into contact with the polyfunctional carboxylic acid solution is preferably from 1 minute to 6 hours, and more preferably from 10 minutes to 3 hours. When the separation functional layer is brought into contact with the polyfunctional carboxylic acid solution for 1 minute or more, bonding between the amino group and the polyfunctional carboxylic acid is likely to be promoted, and when the time is 6 hours or less, a decrease in the water permeability of the separation functional layer due to adsorption of excess polyfunctional carboxylic acid onto the separation functional layer can be suppressed, which is preferable.

[0065] The polyfunctional carboxylic acid concentration in the polyfunctional carboxylic acid solution is preferably 50 ppm to 5000 ppm, more preferably 100 ppm to 3000 ppm. When the polyfunctional carboxylic acid concentration in the polyfunctional carboxylic acid solution is 50 ppm or more, bonding between the amino group and the polyfunctional carboxylic acid is easily promoted, and when it is 5000 ppm or less, a decrease in the water permeability of the separation functional layer due to excessive polyfunctional carboxylic acid adsorption on the separation functional layer can be suppressed.

[0066] The polyfunctional carboxylic acid solution may contain a condensing agent to improve condensation efficiency. When the condensing agent is contained, the concentration of the condensing agent in the polyfunctional carboxylic acid solution is preferably 10 ppm or more and 10,000 ppm or less, more preferably 50 ppm or more and 3,000 ppm or less. When the concentration of the condensing agent is 10 ppm or more, the terminal amino group of the polyamide contained in the separation functional layer and the polyfunctional carboxylic acid can be sufficiently bonded.

[0067] The temperature of the polyfunctional carboxylic acid solution is preferably 10° C. or higher and 50° C. or lower, and more preferably 20° C. or higher and 45° C. or lower. When the temperature of the polyfunctional carboxylic acid solution is 10° C. or higher, the bonding between the amino group and the polyfunctional carboxylic acid is promoted, and when the temperature is 50° C. or lower, the effects of heat, such as denaturation of the separation functional layer, can be suppressed.

[0068] In order to promote bonding between the amino group and the polyfunctional carboxylic acid, the pH of the polyfunctional carboxylic acid aqueous solution may be 10 or more and 13 or less.

[0069] Steps (a) and (b) may be performed in a state where the composite semipermeable membrane is incorporated into an element. When steps (a) and (b) are performed in the state of an element, the polyfunctional amine solution and the polyfunctional carboxylic acid solution may be continuously supplied to the element, or the composite semipermeable membrane may be immersed in these solutions by supplying each solution to the element and then leaving it to stand, or the element may be immersed in each solution. Each solution can be brought into contact with the separation functional layer by flowing each solution through the supply side flow path of the composite semipermeable membrane in the element.

[0070] Furthermore, since the total treatment time can be shortened, it is preferable that the time for which the separating functional layer is in contact with the polyfunctional amine solution is longer than the time for which the separating functional layer is in contact with the polyfunctional carboxylic acid solution.

[0071] Examples of the condensing agent used in the above-mentioned steps (a) and (b) include carbodiimide-based condensing agents, imidazole-based condensing agents, triazine-based condensing agents, phosphonium-based condensing agents, uronium-based condensing agents, sulfuric acid, and the like.

[0072] Among the above, carbodiimide-based condensing agents or triazine-based condensing agents are preferred, and as a carbodiimide-based condensing agent, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (hereinafter referred to as "EDC-HCl") can be preferably used, and as a triazine-based condensing agent, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (hereinafter referred to as "DMT-MM") can be preferably used, in that they are preferred for condensation in a water-containing system.

[0073] The polyfunctional amine solution and the polyfunctional carboxylic acid solution may contain compounds such as an acylation catalyst, a polar solvent, an acid scavenger, and an antioxidant, if necessary.

[0074] The present invention will be described in more detail below with reference to examples, although the present invention is not limited thereto.

[0075] (Membrane permeation flux) Evaluation water (NaCl concentration 3.5 mass%, boron concentration approximately 5 ppm) adjusted to pH 6.5 was supplied to the element at an operating pressure of 5.5 MPa and a recovery rate of 8%, and the amount of water permeated through the membrane after membrane filtration treatment for 24 hours was measured. This was converted into the amount of water permeated (cubic meters) per square meter of membrane surface per day, and was used as the membrane permeation flux (m ３ / m ２ / day) was calculated.

[0076] (Boron Removal Rate) Evaluation water (NaCl concentration 3.5% by mass, boron concentration approximately 5 ppm) adjusted to pH 6.5 was supplied to the element at an operating pressure of 5.5 MPa and a recovery rate of 8%, and the boron concentrations of the supply water and permeate after 24 hours of membrane filtration treatment were determined using an ICP optical emission analyzer (5110 ICP-OES manufactured by Agilent Technologies), and the boron removal rate was calculated using the following formula: Boron Removal Rate (%) = 100 × {1 - (boron concentration in permeate water / boron concentration in evaluation water)}

[0077] (Chlorine Degradation Treatment) An aqueous solution of sodium hypochlorite (25 ppm) adjusted to pH 8 using monopotassium phosphate and added with NaCl so that the NaCl concentration was 3.4% was supplied to the element at 25°C, and chlorine degradation treatment was performed by static immersion for 24 hours (chemical solution changed every 8 hours). For the element after chlorine degradation treatment, the membrane permeation flux and boron removal rate were measured by the methods described above in "Membrane Permeation Flux" and "Boron Removal Rate", and the membrane permeation flux ratio and boron permeability ratio were calculated from the following formulas. Membrane permeation flux ratio = (membrane permeation flux after chlorine degradation treatment) / (membrane permeation flux before degradation treatment) Boron permeability ratio = {100 - (boron removal rate after chlorine degradation treatment)} / {100 - (boron removal rate before degradation treatment)}

[0078] (Oxidation Deterioration Treatment) An acid deterioration treatment was performed by supplying sulfuric acid of pH 1.0 to the element at 25°C and leaving it to immerse for 20 hours. For the element after the acid deterioration treatment, the membrane permeation flux and boron rejection rate were measured by the methods described in the above-mentioned "Membrane Permeation Flux" and "Boron Rejection Rate", and the membrane permeation flux ratio and boron permeability ratio were calculated from the following formulas. Membrane permeation flux ratio = (Membrane permeation flux after acid deterioration treatment) / (Membrane permeation flux before degradation treatment) Boron permeability ratio = {100 - (Boron rejection rate after acid deterioration treatment)} / {100 - (Boron rejection rate before degradation treatment)}

[0079] (Ratio of the number of halogen-bonded carbon atoms to the total number of carbon atoms) The ratio of the number of halogen-bonded carbon atoms to the total number of carbon atoms on the surface of the separation functional layer was measured by X-ray photoelectron spectroscopy (XPS). A composite semipermeable membrane was vacuum-dried at 25 ° C for at least 1 hour to serve as a measurement sample. Soft X-rays were irradiated onto the surface of the separation functional layer in an ultra-high vacuum using an analyzer (Quantera SXM, manufactured by PHI Corporation), and photoelectrons emitted from the surface were detected with an analyzer. The peaks derived from halogen atoms in the obtained spectrum were divided to determine the area of ​​the peak derived from halogen atoms bonded to carbon atoms. This area was divided by the area of ​​the peak derived from carbon atoms to calculate the ratio of the number of halogen-bonded carbon atoms to the total number of carbon atoms. The XPS measurement conditions were as follows. The peaks used in the analysis were C1s for carbon (the horizontal axis was corrected with the main peak at 284.6 eV), Cl2p for chlorine, Br3d for bromine, and I3d for iodine. ５／２ Excitation X-ray: monochromatic Al Kα １，２ ray (1486.6 eV) X-ray diameter: 200 μm Photoelectron detection angle: 90° (inclination of the detector relative to the sample surface)

[0080] <Vanillin Yellowing Index> The composite semipermeable membrane was washed with hot water at 90 ° C. for 2 minutes, and then the surface moisture was removed by air-drying. The dried composite semipermeable membrane was immersed in a 2% by mass ethanol solution of vanillin at 25 ° C. for 15 seconds, the membrane was tilted to remove excess vanillin solution on the membrane surface, and the ethanol on the membrane surface was removed by air-drying. Further, a vanillin-treated membrane sample was obtained by heating in an oven at 150 ° C. for 15 minutes. In addition, the composite semipermeable membrane was washed with hot water at 90 ° C. for 2 minutes, and then the surface moisture was air-dried to obtain an untreated membrane sample. The yellowness index of the membrane sample was measured using an SM Color Computer SM-7 (manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS standards (JIS K 7373), using a standard illuminant D65 light source as the light source, and the yellowness index YI of the vanillin-treated membrane sample and the yellowness index YI of the untreated membrane sample were calculated from the tristimulus values ​​of the XYZ color system. ０ The yellowing index ΔYI was calculated by the following formula: ΔYI=YI−YI ０ The yellowing index ΔYI was rounded off to the first decimal place.

[0081] Example 1 A sodium hypochlorite aqueous solution (100 ppm) was supplied at 25°C to a TM800M reverse osmosis membrane element for seawater desalination, manufactured by Toray Industries, Inc., equipped with a polyamide semipermeable membrane, and the element was left to stand for 24 hours. The interior of the element was then replaced with pure water. Next, a sodium hydroxide aqueous solution with a pH of 13.0 was supplied at 25°C, and the element was left to stand for 24 hours. The interior of the element was then replaced with pure water. Furthermore, a solution containing sulfuric acid with a pH of 1.0 was supplied at 25°C, and the element was left to stand for 24 hours. The interior of the element was then replaced with pure water. Subsequently, an aqueous solution containing 500 ppm of m-PDA and 1000 ppm of DMT-MM was supplied at 40°C, and the element was left to stand for 22 hours. After replacing the inside of the element with pure water, a solution contact step was carried out in which an aqueous solution containing 1000 ppm of trimesic acid and 2000 ppm of DMT-MM was supplied at 40°C, and the element was left to stand for 2 hours. The performance evaluation results are shown in Table 1.

[0082] [Example 2] A solution contact step was carried out in the same manner as in Example 1, except that the aqueous sodium hypochlorite solution was changed to an aqueous sodium hypobromite solution. The performance evaluation results are shown in Table 1. By treating with the aqueous sodium hypobromite solution, the chlorine resistance and acid resistance of the element were sufficiently improved, but the acid resistance was lower than in Example 1.

[0083] [Example 3] A solution contact step was carried out in the same manner as in Example 1, except that the aqueous solution of sodium hypochlorite was changed to an aqueous solution of potassium hypoiodite. The performance evaluation results are shown in Table 1. By treating with the aqueous solution of potassium hypoiodite, the chlorine resistance and acid resistance of the element were sufficiently improved, but the acid resistance was lower than in Example 2.

[0084] Example 4 A solution contact step was carried out in the same manner as in Example 1, except that the concentration of the aqueous sodium hypochlorite solution was changed to 150 ppm. The performance evaluation results are shown in Table 1. The chlorine resistance of the element was improved compared to Example 1 because the product of the concentration (ppm) of the aqueous sodium hypochlorite solution and the contact time (h) exceeded 3,000 and the aromatic polyamide of the separating functional layer had an α,β-unsaturated carbonyl structure.

[0085] Example 5 A solution contact step was carried out in the same manner as in Example 1, except that the concentration of the aqueous sodium hypochlorite solution was 5 ppm, the static immersion time was 1 hour, and the static immersion time for the aqueous solution containing m-PDA and DMT-MM was changed to 8 hours. The performance evaluation results are shown in Table 1. The ratio of the number of carbon atoms bonded to chlorine to the total number of carbon atoms on the surface of the separation functional layer was below 0.004, and therefore the chlorine resistance of the element was lower than in Example 1.

[0086] [Example 6] A solution contact step was carried out in the same manner as in Example 1, except that the concentration of the aqueous sodium hypochlorite solution was changed to 200 ppm. The performance evaluation results are shown in Table 1. Because the ratio of the number of carbon atoms bonded to chlorine to the total number of carbon atoms on the surface of the separation functional layer exceeded 0.014, the acid resistance of the element was lower than in Example 1.

[0087] Example 7 The solution contact step was carried out in the same manner as in Example 1, except that the concentration of the aqueous sodium hypochlorite solution was changed to 10 ppm, and the element was further immersed in a 10 ppm aqueous sodium hypobromite solution and a 10 ppm aqueous potassium hypoiodite solution for 1 hour each. The performance evaluation results are shown in Table 1. The ratio of the number of halogen-bonded carbon atoms to the total number of carbon atoms on the surface of the separation functional layer was the same as in Example 1, but the acid resistance of the element was slightly lower than in Example 1 due to the mixed presence of chlorine, bromine, and iodine.

[0088] Example 8 A solution contact step was carried out in the same manner as in Example 1, except that the static immersion time in the aqueous solution containing m-PDA and DMT-MM was changed to 30 hours. The performance evaluation results are shown in Table 1. The boron removal rate was improved compared to Example 1, and therefore the acid resistance of the element was improved compared to Example 1.

[0089] Example 9 A solution contact step was carried out in the same manner as in Example 1, except that the concentration of the aqueous sodium hypochlorite solution was 25 ppm, the static immersion time was 2 hours, and the static immersion time for the aqueous solution containing m-PDA and DMT-MM was changed to 12 hours. The performance evaluation results are shown in Table 1. Compared to Example 1, the ratio of the number of carbon atoms bonded to halogen to the total number of carbon atoms on the surface of the separation functional layer was lower, and therefore the chlorine resistance of the element was lower than in Example 1.

[0090] Example 10 A solution contact step was carried out in the same manner as in Example 1, except that the concentration of the aqueous sodium hypochlorite solution was changed to 62.5 ppm. The performance evaluation results are shown in Table 1. Compared to Example 1, the yellowing index ΔYI of the separating functional layer before and after contact with the vanillin solution increased, and therefore the chlorine resistance and acid resistance of the element were lower than those of Example 1.

[0091] Comparative Example 1 A solution contact step was carried out in the same manner as in Example 1, except that the concentration of the aqueous sodium hypochlorite solution was changed to 0.200 mass %. The performance evaluation results are shown in Table 2. Because the ratio of the number of carbon atoms bonded to chlorine to the total number of carbon atoms on the surface of the separation functional layer exceeded 0.016, the acid resistance of the element was significantly lower than in Example 1.

[0092] Comparative Example 2 A solution contact step was carried out in the same manner as in Example 1, except that the concentration of the aqueous sodium hypochlorite solution was 0.0002% by mass, the static immersion time was 1 hour, and the static immersion time for the aqueous solution containing m-PDA and DMT-MM was changed to 2 hours. The performance evaluation results are shown in Table 2. Because the ratio of the number of carbon atoms bonded to chlorine to the total number of carbon atoms on the surface of the separation functional layer was below 0.002, the chlorine resistance of the element was significantly lower than in Example 1.

[0093] Comparative Example 3 A solution contact step was carried out in the same manner as in Example 1, except that the static immersion time in the aqueous solution containing m-PDA and DMT-MM was changed to 0.5 hours. The performance evaluation results are shown in Table 2. Because the boron removal rate was below 90%, the acid resistance of the element was significantly lower than in Example 1.

[0094] Comparative Example 4 The solution contact step was carried out in the same manner as in Example 1, except that an immersion step in a sodium hypobromite aqueous solution and a potassium hypoiodite aqueous solution was added. The performance evaluation results are shown in Table 2. Because the ratio of the number of halogen-bonded carbon atoms to the total number of carbon atoms on the surface of the separation functional layer exceeded 0.016, the acid resistance of the element was significantly lower than in Example 1.

[0095] Reference Example 1 Table 2 shows the performance evaluation results of a reverse osmosis membrane element for seawater desalination, TM800M, manufactured by Toray Industries, Inc.

[0096]

[0097]

[0098] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2024-088580) filed on May 31, 2024, the contents of which are incorporated herein by reference.

[0099] The composite semipermeable membrane of the present invention can be suitably used in desalinizing and purifying devices for brine and seawater, in particular.

Claims

1. A composite semipermeable membrane comprising a porous support layer and a separation functional layer provided on the porous support layer, wherein the separation functional layer contains a halogen-containing polyamide, the ratio of the number of halogen-bonded carbon atoms to the total number of carbon atoms on the surface of the separation functional layer is 0.002 or more and 0.016 or less, and the boron removal rate is 90% or more when an aqueous solution having a sodium chloride concentration of 32,000 mg / L, a pH of 6.5, and a boron concentration of 5 mg / L is passed through the composite semipermeable membrane at an operating pressure of 5.5 MPa at 25°C.

2. The composite semipermeable membrane according to claim 1, wherein the ratio of the number of halogen-bonded carbon atoms to the total number of carbon atoms on the surface of said separating functional layer is 0.004 or more and 0.016 or less.

3. The composite semipermeable membrane according to claim 2, wherein the ratio of the number of halogen-bonded carbon atoms to the total number of carbon atoms on the surface of said separating functional layer is 0.010 or more and 0.016 or less.

4. The composite semipermeable membrane according to any one of claims 1 to 3, wherein the yellowing index of the separating functional layer before and after contact with the vanillin solution is 5 or more and 20 or less.

5. The composite semipermeable membrane according to any one of claims 1 to 3, wherein the halogen is at least one selected from the group consisting of chlorine, bromine and iodine.

6. The composite semipermeable membrane according to any one of claims 1 to 3, wherein the ratio of the number of carbon atoms bonded to chlorine to the total number of carbon atoms on the surface of the separating functional layer is 0.010 or more and 0.016 or less.

7. The composite semipermeable membrane according to any one of claims 1 to 3, wherein the polyamide is an aromatic polyamide and has an α,β-unsaturated carbonyl structure.

8. A separation membrane element comprising the composite semipermeable membrane according to any one of claims 1 to 3.

9. A liquid separation device comprising the composite semipermeable membrane according to any one of claims 1 to 3.

10. A method for producing a composite semipermeable membrane comprising a porous support layer and a separation functional layer provided on the porous support layer, wherein the separation functional layer contains a halogen-containing polyamide, the method comprising: a step (a) of contacting the separation functional layer with a polyfunctional amine solution; and a step (b) of contacting the separation functional layer with a polyfunctional carboxylic acid solution.

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