Composite semipermeable membrane and method for manufacturing a composite semipermeable membrane

Abstract

The present invention relates to a composite semipermeable membrane comprising a porous support layer and a separation function layer provided on the porous support layer, wherein the separation function 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 function layer is 0.002 or more and 0.016 or less, and the boron removal rate is 90% or more when an aqueous solution with a sodium chloride concentration of 32000 mg / L and a boron concentration of 5 mg / L is permeated through the composite semipermeable membrane at an operating pressure of 5.5 MPa at 25°C and pH 6.5.

Description

Technical Field

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

Background Art

[0002] Semipermeable membranes used for separating liquid mixtures include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, and the like. These membranes are used, for example, in the production of drinking water from water containing salts or harmful substances, the production of industrial ultrapure water, wastewater treatment, or the recovery of valuable substances.

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

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

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

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

[0007] [Patent Document 1] Japanese Patent Publication No. 2003-200028 [Patent Document 2] Japanese Patent No. 6197969 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, the method described in Patent Document 1 has insufficient chlorine resistance because the separation functional layer contains many chlorine-reactive reaction sites, and it cannot be said to have excellent acid resistance because it has a certain number of amino groups at its ends as a crosslinked aromatic polyamide. Similarly, the method described in Patent Document 2 cannot be said to possess sufficient chlorine resistance and acid resistance for the same reasons as in Patent Document 1.

[0009] Therefore, the present invention aims to provide a composite semipermeable membrane that combines high chlorine resistance and acid resistance. [Means for solving the problem]

[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, 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 with a sodium chloride concentration of 32000 mg / L and a boron concentration of 5 mg / L is permeated through the composite semipermeable membrane at an operating pressure of 5.5 MPa at 25°C and pH 6.5. [2] The composite semipermeable film 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 or more and 0.016 or less. [3] The composite semipermeable film 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] A composite semipermeable membrane according to any one of [1] to [3] above, wherein the degree of yellowing of the separation functional layer before and after contact with the vanillin solution is 5 or more and 20 or less. [5] A 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] A composite semipermeable membrane according to any one of [1] to [3] above, wherein the ratio of the number of carbon atoms to which chlorine is bonded 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] A 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 a composite semipermeable membrane as described in any one of [1] to [3] above. [9] A liquid separation apparatus comprising a composite semipermeable membrane as 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, and the method comprises the steps of (a) contacting the separation functional layer with a polyfunctional amine solution and (b) contacting the separation functional layer with a polyfunctional carboxylic acid solution. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a composite semipermeable membrane that combines high chlorine resistance and acid resistance. [Modes for carrying out the invention]

[0012] The present invention will be described in more detail below.

[0013] <Composite semipermeable membrane> The present invention provides a composite semipermeable membrane comprising a porous support layer and a separation functional layer containing polyamide on the porous support layer (polyamide-based semipermeable membrane). 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] A "separation function layer" refers to a layer that has the function of separating the substances to be removed contained in the liquid being treated.

[0015] A "porous support layer" refers to a porous layer with a dense structure. The pore size on the surface of the porous support layer that forms the separation function layer is, for example, between 0.1 nm and 100 nm.

[0016] Examples of the material constituting the porous support layer include polysulfone, polyethersulfone, polyamide, polyester, cellulose polymers, vinyl polymers, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, polyphenylene oxide, etc. Examples of cellulose polymers include cellulose acetate, cellulose nitrate, etc., and examples of vinyl polymers include polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile, etc.

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

[0018] "Polyamide" means a polymer of a polyfunctional amine and a polyfunctional acid halide. Among them, polyamide is preferably an aromatic polyamide which is a polymer of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide. Further, polyamide is preferably a crosslinked polyamide in which at least one of the polyfunctional amine and the polyfunctional acid halide described later has three or more functional groups, and more preferably a crosslinked aromatic polyamide in which at least one of the polyfunctional aromatic amine and the polyfunctional aromatic acid halide has three or more functional groups.

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

[0020] A "polyfunctional aliphatic amine" refers to an aliphatic amine that has two or more amino groups in a single molecule. Examples of polyfunctional aliphatic amines include piperazine derivatives represented by the following general formula (I) and ethylenediamines.

[0021] [ka]

[0022] In general formula (I), R 1 , R 2 Each of these is independently either 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, and 2,5-di-n-butylpiperazine. In particular, piperazine or dimethylpiperazine is preferred.

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

[0025] A "polyfunctional acid halide" refers to an acid halide that has two or more halogenated carbonyl groups in a single molecule. Polyfunctional acid halides can form amide bonds through reaction with terminal amino groups.

[0026] Examples of polyfunctional acid halides that can be used include 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 halide is preferably a polyfunctional aromatic acid halide. Among acid halides, acid chlorides are preferred.

[0027] Specifically, "polyfunctional aromatic acid chloride" refers to an aromatic acid chloride having at least two, preferably two to four, carbonyl chloride groups in one molecule (i.e., a polyfunctional aromatic acid chloride). For example, trifunctional acid chlorides include trimesic acid chloride, and 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 individually or in combination of two or more.

[0028] In the composite semipermeable membrane of the present invention, 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 (number of halogen-bonded carbon atoms / total number of carbon atoms) is 0.002 or more and 0.016 or less.

[0029] The presence of a halogen in the polyamide constituting the separation functional layer can suppress further chlorination by free chlorine, thereby obtaining a composite semipermeable membrane with excellent chlorine resistance. When 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 within the above range, it is possible to exhibit high chlorine resistance while maintaining high removal performance. If the above ratio of carbon atoms is less than 0.002, chlorine resistance decreases, while if the ratio of carbon atoms 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 halogen-bonded carbon atoms to the total number of carbon atoms on the surface of the separation functional layer is preferably 0.004 or more and 0.016 or less, more preferably 0.010 or more and 0.016 or less, and even more preferably 0.012 or more and 0.016 or less.

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

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

[0032] Furthermore, when the halogen contains at least chlorine, it is preferable that the ratio of the number of carbon atoms to which chlorine is bonded 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.

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

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

[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 suppresses the penetration of reactive species that induce degradation into the separation functional layer, and enables the expression of high chlorine resistance and acid resistance. From the above viewpoint, a boron removal rate of 92% or higher is preferable, and 96% or higher is more preferable. The upper limit of the boron removal rate is 100%.

[0036] One method for improving the boron removal rate of a composite semipermeable membrane is to introduce a halogen into the separation functional layer and then condense a polyfunctional amine or polyfunctional carboxylic acid again. Generally, when a halogen is introduced to polyamide by chlorine treatment or the like, the amide bond is hydrolyzed, and the pore size of the separation functional layer expands. Therefore, by introducing a halogen into the polyamide and then condensing a polyfunctional amine or polyfunctional carboxylic acid again, the pore size of the separation functional layer can be reduced, improving the boron removal rate. There are no particular restrictions on the order in which the polyfunctional amine and polyfunctional carboxylic acid are condensed, but it is preferable to condense the polyfunctional amine first, and then the polyfunctional carboxylic acid.

[0037] In this embodiment, the degree of yellowing ΔYI of the separation functional layer before and after contact with the vanillin solution is preferably 5 to 20, and more preferably 10 to 17. The amino groups, such as aromatic polyamide terminals, contained in the separation functional layer form a color-developing chemical structure through a chemical reaction with vanillin. That is, the degree of yellowing 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 suppressed, 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 permeability of the separation functional layer.

[0038] The degree of yellowing ΔYI can be calculated according to the procedure described in the "Degree of Vanillin Yellowing" section of the examples below.

[0039] ΔYI can be controlled by the concentration and immersion time of the hypohalite aqueous solution when the composite semipermeable membrane is immersed in the hypohalite aqueous solution after the separation functional layer has been formed, as well as by the concentration of the polyfunctional carboxylic acid and condensing agent, contact temperature, and contact time when the polyfunctional carboxylic acid is condensed into the separation functional layer.

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

[0041] One method for forming an α,β-unsaturated carbonyl structure in the aromatic polyamide contained in the separation functional layer is to immerse the composite semipermeable membrane in an aqueous hypohalite solution after forming the separation functional layer. Specifically, by immersing the composite semipermeable membrane under conditions where the product of the concentration (ppm) and contact time (h) of the aqueous hypochlorite solution is 3000 or more, the oxidation of the amide bond adjacent to the aromatic ring of the aromatic polyamide is promoted, thereby causing the aromatic ring to become 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 aromatic polyamides 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 preferably used as a spiral-type separation membrane element (hereinafter also simply referred to as "element"), wound around a cylindrical water collection pipe with numerous holes, together with a supply-side flow channel material such as a plastic net, a permeable-side flow channel material such as tricot, and a film to enhance pressure resistance as needed. Furthermore, these elements can be connected in series or parallel and housed in a pressure vessel to form a separation membrane module.

[0043] Furthermore, the composite semipermeable membrane, elements, and separation membrane modules can be combined with a pump to supply water to them, and a device to pre-treat the supply water, to constitute a liquid separation apparatus. By using this liquid separation apparatus, the supply water can be separated into permeate (such as drinking water) and concentrated water that did not permeate the membrane, thereby obtaining water suitable for the purpose.

[0044] <Liquid separation device> The liquid separation apparatus using the element according to this embodiment comprises a tank for storing water to be treated, an element mounting section for mounting the element incorporating the composite semipermeable membrane according to this embodiment, piping connecting the tank and the element mounting section, and a pump between the tank and the element mounting section for performing liquid flow treatment on the element.

[0045] More specifically, the liquid separation apparatus using the element according to this embodiment comprises an element mounting section including a container for mounting the element, piping connecting the element mounting section and a tank, and a pump connected to the piping.

[0046] The liquid separation apparatus may also include a tank for a cleaning solution, a pump, piping, and the like.

[0047] <Method for manufacturing composite semipermeable membranes> The present invention provides a method for producing a composite semipermeable membrane comprising a porous support layer and a separation functional layer containing a halogenated polyamide on the porous support layer, the method comprising: (a) contacting the separation functional layer with a polyfunctional amine solution and (b) contacting the separation functional layer with a polyfunctional carboxylic acid solution.

[0048] In this embodiment, the separation functional layer of the composite semipermeable membrane 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 halogen as the polyfunctional acid halogen, and to form a crosslinked aromatic polyamide as the separation functional layer. An example using a polyfunctional aromatic amine and a polyfunctional aromatic acid halogen will be described below.

[0049] The interfacial polymerization step comprises (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 halogen to the porous support layer after step (i).

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

[0051] The organic solvent used to dissolve the polyfunctional aromatic acid halide in step (ii) is one that is immiscible with water and has a solubility parameter of 15.2 (MPa).1 / 2 It is preferable to use an organic solvent that meets the above criteria and has an octanol / water partition coefficient of 3.2 or higher. Furthermore, it is preferable that the organic solvent does not damage the support, especially the porous support layer.

[0052] Typical examples of organic solvents that satisfy the above requirements include octane, nonane, decane, undecane, dodecane, isododecane, tridecane, tetradecane, heptadecane, hexadecane, isodecane, cyclooctane, isooctane, ethylcyclohexane, 1-octene, and 1-decene, either individually or in mixtures thereof.

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

[0054] When using a method in which a composite semipermeable membrane is immersed in an aqueous hypohalite solution, the amount of halogen introduced into the polyamide can be controlled by the concentration (ppm) of the hypohalite solution and the contact time (h) of the separation functional layer with the hypohalite solution (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 hypohalite solution and the contact time (h) is preferably 3 or more and 15000 or less, and more preferably 10 or more and 4500 or less.

[0055] In the method for producing a composite semipermeable membrane of the present invention, steps (a) and (b) may be performed in any order, or steps (a) and (b) may be performed simultaneously, i.e., contact with a solution containing both a polyfunctional amine and a polyfunctional carboxylic acid may be performed. In particular, from the viewpoint of efficiently condensing the polyfunctional amine and polyfunctional carboxylic acid with the polyamide, it is preferable to perform steps (a) and then (b). Furthermore, steps (a) and (b) may be performed multiple times.

[0056] The polyfunctional amine solution and the polyfunctional carboxylic acid solution are preferably aqueous solutions from the viewpoint of not causing swelling, decomposition, or dissolution of the polyamide in the separation functional layer.

[0057] In steps (a) and (b), methods for bringing the solution into contact with the separation functional layer include, for example, coating each solution onto 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 1 minute to 72 hours, more preferably 30 minutes to 48 hours, and even more preferably 1 hour to 24 hours.

[0059] The concentration of the polyfunctional amine in the polyfunctional amine solution is preferably 50 ppm to 5000 ppm, and more preferably 100 ppm to 3000 ppm. When the concentration of the polyfunctional amine in the polyfunctional amine solution is 50 ppm or higher, the binding of the carboxyl group and the polyfunctional amine is easily promoted, and when it is 5000 ppm or lower, the decrease in the water permeability of the separation functional layer due to excessive adsorption of the polyfunctional amine to the separation functional layer can be suppressed.

[0060] The polyfunctional amine solution may contain a condensing agent to improve condensation efficiency. If a condensing agent is present, the concentration of the condensing agent in the polyfunctional amine solution is preferably 10 ppm to 10,000 ppm, and more preferably 50 ppm to 3,000 ppm. A concentration of 10 ppm or higher allows for sufficient bonding between the terminal carboxyl groups of the polyamide contained in the separation functional layer and the polyfunctional amine. The types of condensing agents will be described later.

[0061] The temperature of the polyfunctional amine solution is preferably between 10°C and 50°C, and more preferably between 20°C and 45°C. A temperature of 10°C or higher promotes the bonding of the carboxyl group to the polyfunctional amine, while a temperature of 50°C or lower suppresses the effects of heat, such as the denaturation of the separation functional layer.

[0062] Furthermore, in order to promote the bonding between the carboxyl group and the polyfunctional amine, the pH of the polyfunctional amine aqueous solution may be between 10 and 13.

[0063] A "polyfunctional carboxylic acid" is a carboxylic acid having two or more carboxyl 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. A single compound may be used as the polyfunctional carboxylic acid, or two or more compounds may be combined.

[0064] In step (b), the contact time of the separation functional layer with the polyfunctional carboxylic acid solution is preferably 1 minute to 6 hours, and more preferably 10 minutes to 3 hours. A contact time of 1 minute or more is preferable because it promotes the bonding of amino groups with polyfunctional carboxylic acids, while a contact time of 6 hours or less is preferable because it suppresses the decrease in the water permeability of the separation functional layer due to excessive adsorption of polyfunctional carboxylic acid onto the separation functional layer.

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

[0066] The polyfunctional carboxylic acid solution may contain a condensing agent to improve condensation efficiency. If a condensing agent is included, the concentration of the condensing agent in the polyfunctional carboxylic acid solution is preferably 10 ppm to 10,000 ppm, and more preferably 50 ppm to 3,000 ppm. A concentration of 10 ppm or higher of the condensing agent allows for sufficient bonding between the terminal amino groups of the polyamide contained in the separation functional layer and the polyfunctional carboxylic acid.

[0067] The temperature of the polyfunctional carboxylic acid solution is preferably between 10°C and 50°C, and more preferably between 20°C and 45°C. A temperature of 10°C or higher promotes the bonding of the amino group to the polyfunctional carboxylic acid, while a temperature of 50°C or lower suppresses the effects of heat, such as the denaturation of the separation functional layer.

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

[0069] Steps (a) and (b) may be performed with the composite semipermeable membrane incorporated into the element. When steps (a) and (b) are performed with the 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 allowing the element to stand after supplying each solution, 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 channel of the composite semipermeable membrane in the element.

[0070] Furthermore, since the total processing time can be shortened, it is preferable that the contact time of the separation functional layer with the polyfunctional amine solution is longer than the contact time of the separation functional layer with the polyfunctional carboxylic acid solution.

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

[0072] Among the above, carbodiimide-based condensing agents or triazine-based condensing agents are preferred. In terms of suitability for condensation in a hydrated system, if a carbodiimide-based condensing agent is used, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (hereinafter referred to as "EDC-HCl") is preferred, and if a triazine-based condensing agent is used, 4-(4,6-dimethoxy-1,3,5-triazine-2-yl)-4-methylmorpholinium chloride (hereinafter referred to as "DMT-MM") is preferred.

[0073] The polyfunctional amine solution and the polyfunctional carboxylic acid solution may optionally contain compounds such as acylation catalysts, polar solvents, acid scavengers, and antioxidants. [Examples]

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

[0075] (membrane flux) 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%. After 24 hours of membrane filtration treatment, the amount of water permeated through the membrane was measured and converted to the permeable flow rate (cubic meters) per square meter of membrane surface per day. The membrane permeation flux (m³) was then calculated. 3 / m 2 The calculation (per day) was performed.

[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%. After 24 hours of membrane filtration, the boron concentration of the supplied water and permeate was determined using an ICP emission spectrometer (Agilent Technologies 5110 ICP-OES), 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) A chlorine degradation treatment was performed by supplying an aqueous solution of sodium hypochlorite (25 ppm), prepared by adding NaCl to a 3.4% NaCl concentration using monopotassium phosphate, to the element at 25°C and allowing it to stand and immerse for 24 hours (chemical solution replacement every 8 hours). After the chlorine degradation treatment, the membrane permeation flux and boron removal rate were measured for the element using the methods described above for "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 transmission ratio = {100 - (boron removal rate after chlorine degradation treatment)} / {100 - (boron removal rate before degradation treatment)}

[0078] (Oxidative degradation treatment) Acid degradation treatment was performed by supplying sulfuric acid at pH 1.0 to the element at 25°C and allowing it to stand for 20 hours. After the acid degradation treatment, the membrane permeation flux and boron removal rate were measured for the element using the methods described above for "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 acid degradation treatment) / (Membrane permeation flux before degradation treatment) Boron transmission ratio = {100 - (boron removal rate after acid degradation treatment)} / {100 - (boron removal rate before degradation treatment)}

[0079] (The ratio of the number of carbon atoms bonded to halogens to the total number of carbon atoms) The ratio of halogen-bonded carbon atoms to the total number of carbon atoms on the separation functional layer surface was determined by X-ray photoelectron spectroscopy (XPS). A composite semipermeable film was vacuum-dried at 25°C for more than one hour to prepare the sample. Using an analyzer (PHI Quantera SXM), soft X-rays were irradiated onto the separation functional layer surface in an ultra-high vacuum, and photoelectrons emitted from the surface were detected by the analyzer. The peaks originating from halogen atoms in the obtained spectrum were separated, and the area of ​​the peak originating from halogen atoms bonded to carbon atoms was determined. By dividing this area by the area of ​​the peak originating from carbon atoms, the ratio of halogen-bonded carbon atoms to the total number of carbon atoms was calculated. The XPS measurement conditions were as follows. The peaks used for analysis were C1s for carbon (horizontal axis correction performed with the main peak set at 284.6 eV), Cl2p for chlorine, Br3d for bromine, and I3d for iodine. 5 / 2 I used it. ·Excited X-ray: monochromatic Al Kα 1,2 Line (1486.6eV) • X-ray diameter: 200 μm • Photoelectron detection angle: 90° (inclination of the detector relative to the sample surface)

[0080] <Degree of vanillin yellowing> The composite semipermeable membrane was washed with 90°C hot water for 2 minutes, and the surface moisture was removed by air drying. After drying, the 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 from the membrane surface, and the ethanol on the membrane surface was removed by air drying. Furthermore, the membrane was heated in a 150°C oven for 15 minutes to obtain a vanillin-treated membrane sample. In addition, an untreated membrane sample was obtained by washing the composite semipermeable membrane with 90°C hot water for 2 minutes and then air drying the surface moisture. The yellowness of the membrane samples was measured using an SM-7 color computer (manufactured by Suga Test Instruments Co., Ltd.), in accordance with JIS standards (JIS K 7373), using a standard illuminant D65 light source, and the yellowness YI of the vanillin-treated membrane sample and the yellowness YI0 of the untreated membrane sample were measured from the tristimulus values ​​of the XYZ color system, and the degree of yellowing ΔYI was calculated using the following formula. ΔYI=YI-YI0 Note that the yellowing degree ΔYI was rounded to the first decimal place.

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

[0082] [Example 2] The solution contact process was carried out in the same manner as in Example 1, except that the sodium hypochlorite aqueous solution was replaced with a sodium hypobromite aqueous solution. The performance evaluation results are shown in Table 1. Although the chlorine resistance and acid resistance of the element were sufficiently improved by treatment with the sodium hypobromite aqueous solution, the acid resistance was lower than in Example 1.

[0083] [Example 3] The solution contact process was carried out in the same manner as in Example 1, except that the sodium hypochlorite aqueous solution was replaced with a potassium hypoiodate aqueous solution. The performance evaluation results are shown in Table 1. Although the chlorine resistance and acid resistance of the element were sufficiently improved by treatment with potassium hypoiodate aqueous solution, the acid resistance was lower than in Example 2.

[0084] [Example 4] The solution contact process was carried out in the same manner as in Example 1, except that the concentration of the sodium hypochlorite aqueous solution was changed to 150 ppm. The performance evaluation results are shown in Table 1. The product of the concentration (ppm) of the hypochlorite aqueous solution and the contact time (h) exceeded 3000, and the aromatic polyamide in the separation functional layer had an α,β-unsaturated carbonyl structure, resulting in improved chlorine resistance of the element compared to Example 1.

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

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

[0087] [Example 7] The solution contact process was carried out in the same manner as in Example 1, except that the concentration of the sodium hypochlorite aqueous solution was changed to 10 ppm, and the samples were further immersed for 1 hour each in a 10 ppm sodium hypobromite aqueous solution and a 10 ppm potassium hypoiodate aqueous solution. 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 separation functional layer surface was the same as in Example 1, but the acid resistance of the element was slightly lower than in Example 1 due to the presence of chlorine, bromine, and iodine.

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

[0089] [Example 9] The solution contact process was carried out in the same manner as in Example 1, except that the concentration of the sodium hypochlorite aqueous solution was set to 25 ppm, the standing immersion time was changed to 2 hours, and the standing immersion time of 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 halogen-bonded carbon atoms to the total number of carbon atoms on the separation functional layer surface decreased, resulting in a decrease in the chlorine resistance of the element compared to Example 1.

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

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

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

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

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

[0095] [Reference example 1] Table 2 shows the performance evaluation results for the Toray Industries TM800M reverse osmosis membrane element for seawater desalination.

[0096] [Table 1]

[0097] [Table 2]

[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 invention. This application is based on Japanese Patent Application No. 2024-088580, filed on 31 May 2024, the contents of which are incorporated herein by reference. [Industrial applicability]

[0099] The composite semipermeable membrane of the present invention can be particularly suitable for use in desalination of brine and seawater, and as a water purifier.

Claims

1. A composite semipermeable membrane comprising a porous support layer and a separation functional layer provided on the porous support layer, The separation functional layer contains an aromatic polyamide having a halogen, The ratio of the number of carbon atoms to which halogens are bonded 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 A composite semipermeable membrane in which, when an aqueous solution with a sodium chloride concentration of 32,000 mg / L and a boron concentration of 5 mg / L is permeated through the composite semipermeable membrane at an operating pressure of 5.5 MPa at 25°C and pH 6.5, the boron removal rate is 90% or more.

2. The composite semipermeable film 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 the separation functional layer is 0.004 or more and 0.016 or less.

3. The composite semipermeable film 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 the separation 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 degree of yellowing ΔYI of the separation functional layer before and after contact with vanillin solution, calculated under the following conditions, is 5 or more and 20 or less. Conditions for calculating the degree of vanillin yellowing: A composite semipermeable membrane is immersed in a 2% by mass ethanol solution of vanillin at 25°C for 15 seconds, the ethanol on the membrane surface is air-dried, and the vanillin-treated membrane sample is heated at 150°C for 15 minutes. The degree of yellowing ΔYI is calculated from the yellowing degree YI of the vanillin-treated membrane sample and the yellowing degree YI 0 of the untreated membrane sample using the following formula. ΔYI=YI-YI 0

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. A composite semipermeable membrane according to any one of claims 1 to 3, wherein the ratio of the number of carbon atoms to which chlorine is bonded 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 claims 1 to 3, wherein the aromatic polyamide has an α,β-unsaturated carbonyl structure.

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

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

10. A method for manufacturing a composite semipermeable membrane according to claim 1 or 2, comprising a porous support layer and a separation functional layer provided on the porous support layer, A method for producing a composite semipermeable membrane, comprising the steps of (a) contacting the separation functional layer with a polyfunctional amine solution and (b) contacting the separation functional layer with a polyfunctional carboxylic acid solution.

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