JP2023020053A - composite semipermeable membrane - Google Patents

Abstract

To provide a composite semipermeable membrane having improved acid resistance and base resistance while having oxidation resistance.SOLUTION: A composite semipermeable membrane has a support film, and a separation function layer containing a crosslinked aromatic polyamide, the separation function layer including a moiety represented by the formula 1.SELECTED DRAWING: None

Description

The present invention relates to composite semipermeable membranes useful for selective separation of liquid mixtures.

Regarding the separation of liquid mixtures, there are various techniques for removing substances (e.g. salts) dissolved in a solvent (e.g. water). is expanding. Membranes used in membrane separation include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, and the like. It is used for the production of industrial ultrapure water, wastewater treatment, and recovery of valuables.

Most of the reverse osmosis membranes and nanofiltration membranes currently on the market are composite semipermeable membranes in which a support membrane is coated with a separation function layer that has separation performance for salts, etc., and a gel layer and a polymer are placed on the support membrane. There are two types, one having a crosslinked active layer and the other having an active layer formed by polycondensation of monomers on a support film. In the composite semipermeable membrane, the separation function layer that performs the separation function and the support membrane that imparts strength to the separation function layer can be independently selected, so that both separation performance and strength can be achieved.

Various composite semipermeable membranes have been disclosed. For example, Patent Document 1 discloses a composite semipermeable membrane in which a support membrane is coated with a separating functional layer made of a crosslinked aromatic polyamide obtained by a polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide. It is Further, Patent Document 1 discloses introducing a sulfo group into a crosslinked aromatic polyamide using a sulfonating reagent. Patent Document 1 describes that a composite semipermeable membrane having both permeation performance and salt separation performance and excellent oxidation resistance can be obtained.

International publication WO2021/085599 pamphlet

An object of the present invention is to provide a composite semipermeable membrane having improved acid resistance and base resistance while having oxidation resistance.

In order to solve the above problems, the present invention provides a composite semipermeable membrane comprising a support membrane and a separation functional layer containing a crosslinked aromatic polyamide, wherein the separation functional layer includes a partial structure represented by the following formula 1: I will provide a.

(where R ₁ to R ₁₁ are a hydrogen atom, a halogen atom, or an aliphatic chain having 1 to 10 carbon atoms, and Ar ₁ is an optionally substituted aromatic ring having 4 to 14 carbon atoms; and R ₁₂ and R ₁₃ are a hydrogen atom, a halogen atom, an aliphatic chain having 1 to 4 carbon atoms, or a structure represented by the following formula 2, and at least one of R ₁₂ and R ₁₃ is represented by the following formula 2 It is a structure that is used.)

(where X is an aliphatic chain having 1 to 4 carbon atoms or a single bond, and Y ₁ to Y ₃ are each independently O, OH, or ^O- . In addition, the following formula 3 in formula 2 above represents a single bond or a double bond.)

ADVANTAGE OF THE INVENTION According to this invention, the composite semipermeable membrane which has the outstanding salt separation performance and permeation performance, and is excellent in chemical resistance can be provided.

1 is a cross-sectional view schematically showing the structure of a composite semipermeable membrane, (a) is a cross-sectional view of the composite semipermeable membrane, (b) is an enlarged view of a separation function layer, and (c) is a separation function. FIG. 4 is an enlarged view of the fold structure of the layers;

Embodiments of the present invention will be described in detail below, but the present invention is not limited by these.

1. Composite Semipermeable Membrane FIG. 1 shows the structure of a composite semipermeable membrane 1 in this embodiment.

(1-1) Support Membrane As shown in FIG. 1( a ), in the composite semipermeable membrane 1 , the support membrane includes a substrate 2 and a porous support layer 3 . However, the supporting film need not have such a two-layer structure, and may be composed of only one layer or three or more layers. The support membrane is for giving strength to the separation functional layer, and itself does not substantially have a solute separation performance.

Examples of the base material 2 include fabrics made of polyester-based polymers, polyamide-based polymers, polyolefin-based polymers, and mixtures or copolymers thereof. Among them, polyester-based polymer fabric having high mechanical and thermal stability is preferable. As the form of the fabric, a long-fiber nonwoven fabric, a short-fiber nonwoven fabric, and a woven or knitted fabric can be preferably used.

The porous support layer 3 has a large number of communicating pores. The pore size and pore size distribution of the pores are not particularly limited. A porous support layer having a pore size of 0.1 to 100 nm on the side surface is preferred.

Materials for the porous support layer 3 include homogenous materials such as polysulfone (hereinafter referred to as "PSf"), polyethersulfone, polyamide, polyester, cellulose polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene oxide. Polymers or copolymers can be used alone or in blends. Cellulosic polymers include cellulose acetate and cellulose nitrate, and vinyl polymers include polyethylene, polypropylene, polyvinyl chloride and polyacrylonitrile. Among them, homopolymers or copolymers such as PSf, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, polyphenylene sulfide sulfone are preferred, and cellulose acetate, PSf, polyphenylene sulfide sulfone, or polyphenylene sulfone are preferred. PSf is more preferred because it has high chemical, mechanical and thermal stability and is easy to mold.

The weight average molecular weight (hereinafter “M _w ”) of PSf is preferably 10,000 to 200,000, more preferably 15,000 to 100,000. When the _Mw of PSf is 10,000 or more, it is possible to obtain mechanical strength and heat resistance preferable for the porous support layer. On the other hand, when the _Mw of PSf is 200,000 or less, the viscosity of the undiluted solution for the porous support layer falls within an appropriate range, and good moldability can be achieved.

The thickness of the substrate and the porous support layer affect the strength of the composite semipermeable membrane and the packing density when it is made into an element. In order to obtain good mechanical strength and packing density, the total thickness of the substrate and the porous support layer is preferably 30-300 μm, more preferably 100-220 μm. Also, the thickness of the porous support layer is preferably 20 to 100 μm. The thickness of the base material and the porous support layer can be obtained by calculating the average value of 20 thicknesses measured at intervals of 20 μm in a direction perpendicular to the thickness direction (surface direction of the film) by cross-sectional observation. can.

(1-2) Separation Function Layer The separation function layer 4 is a layer that performs a solute separation function and contains crosslinked aromatic polyamide. The separation functional layer 4 preferably contains a crosslinked aromatic polyamide as a main component.

Having a crosslinked aromatic polyamide as a main component means that the proportion of the crosslinked aromatic polyamide in the separation functional layer is 50% by mass or more. The proportion of the crosslinked aromatic polyamide in the separation functional layer is preferably 80% by mass or more, more preferably 90% by mass or more.

The separation functional layer includes a partial structure represented by Formula 1 above. In Formula 1 above, at least one of R ₁₂ and R ₁₃ has a structure represented by Formula 2 above. Moreover, in Formula 1 above, R ₁₃ preferably has a structure represented by Formula 2 above. Examples of the structure represented by Formula 2 include a sulfo group, a sulfomethyl group, a sulfoethyl group, a sulfopropyl group, a sulfoisopropyl group, a sulfobutyl group, and a sulfoisobutyl group.

In the structure represented by the above formula 2, the substituent as a whole is negatively charged by ionizing any portion of Y ₁ to Y ₃ in neutral water. As a result, it is possible to obtain a composite semipermeable membrane that achieves both excellent water permeability due to high hydrophilicity and excellent salt separation performance due to Coulombic repulsion with anions that constitute the salt to be removed. .

In addition, as a result of intensive studies by the present inventors, the amino group of the crosslinked aromatic polyamide, particularly the terminal amino group, is the starting point of oxidative deterioration, and that the electron density of the amino group, the amide group, and the aromatic ring is reduced. It was found that oxidative deterioration can be suppressed by In the above formula 1, when at least one of R ₁₂ and R ₁₃ has an electron-withdrawing structure represented by the above formula 2, the electron density of the amino group, the amide group and the aromatic ring is reduced, and the following It is possible to obtain a composite semipermeable membrane having excellent oxidation resistance in which reactivity with oxidizing agents such as chlorous acid is suppressed.

The structure represented by Formula 2 is present at the m-position relative to at least one of R ₁₂ and R ₁₃ in Formula 1, ie, the amide group or amino group of the crosslinked aromatic polyamide.

Patent Document 1 describes a method of reacting a crosslinked aromatic polyamide after polymerization with a reagent such as 1,3-propanesultone. However, in general, amide groups and amino groups have o,p orientation, so in this method, substituents are introduced at the o,p positions relative to the amide group or amino group. Furthermore, in this method, since the reagent is allowed to react with the crosslinked aromatic polyamide after polymerization, the substituents are introduced mainly near the surface of the separation functional layer with which the reagent comes into contact, and are uniformly expressed by the above formula 2 over the entire separation functional layer. It is difficult to introduce a structure that

Further, in Patent Document 1, a polyfunctional aromatic amine having a structure represented by the above formula 2 at the o and p positions of an amino group, such as 2,4-diaminobenzenesulfonic acid, is added to a polyfunctional aromatic acid. A method for polymerizing with chloride is described. However, in this method, the structure represented by the above formula 2 is introduced at the o- and p-positions relative to the amide group or amino group due to the structure of the polyfunctional aromatic amine. Furthermore, in this method, steric hindrance of the substituent present at the o-position of the amino group reduces the reactivity of the amino group, making it difficult to obtain a crosslinked aromatic polyamide having a sufficient degree of polymerization.

On the other hand, in the present invention, by polymerizing a polyfunctional aromatic amine having a structure represented by the above formula 2 at the m-position of an amino group represented by the following formula 4 with a polyfunctional aromatic acid chloride, sufficient A composite semipermeable membrane having a degree of polymerization and having the partial structure represented by the above formula 1 distributed throughout the separation functional layer can be obtained.

(where X is an aliphatic chain having 1 to 4 carbon atoms or a single bond, Y ₁ to Y ₃ are each independently O, OH or ^O- , R ₁₄ to R ₁₈ are hydrogen atoms, halogen atom, or an aliphatic chain having 1 to 10 carbon atoms, and the above formula 3 in the above formula 4 represents a single bond or a double bond.)
When the structure represented by the above formula 2 exists at the o and p positions with respect to the amide group of the crosslinked aromatic polyamide, the adjacent group effect with the hydroxyl group in the structure represented by the above formula 2 adjacent to the amide group causes an acidic Alternatively, hydrolysis of the amide group is promoted under basic conditions. For this reason, if chemical cleaning with an acid or base is performed for the purpose of removing fouling substances and the like that adhere to the membrane surface during operation and reduce the permeation performance, a problem arises in that the separation performance deteriorates.

On the other hand, since the structure represented by the above formula 2 exists at the m-position with respect to the amide group of the crosslinked aromatic polyamide, the hydroxyl group in the structure represented by the above formula 2 is present at a position away from the amide group. , the amide group is resistant to hydrolysis even under acidic or basic conditions. As a result, it is possible to obtain a composite semipermeable membrane having excellent acid resistance and base resistance that maintains separation performance even after repeated washing with a chemical solution.

X in Formula 2 above is an aliphatic chain having 1 to 4 carbon atoms or a single bond. X in Formula 2 above is preferably an aliphatic chain having 1 to 2 carbon atoms or a single bond, more preferably an aliphatic chain having 2 carbon atoms or a single bond. When X in the above formula 2 is an aliphatic chain having 1 or more carbon atoms, the highly hydrophilic functional group can rotate freely without being bound by the aromatic ring. Semipermeable membranes can be obtained. On the other hand, when X in the formula 2 is an aliphatic chain having 4 or less carbon atoms, a composite semipermeable membrane having excellent permeation performance can be obtained without excessively increasing the ratio of the hydrophobic structure. In addition, X in the above formula 2 is a single bond, that is, the electron density of the amino group, the amide group, and the aromatic ring is further reduced by directly bonding the electron-withdrawing functional group to the aromatic ring. , it is possible to obtain a composite semipermeable membrane having excellent oxidation resistance in which reactivity with oxidizing agents such as hypochlorous acid is suppressed. X in the above formula 2 can be appropriately selected according to desired properties of the composite semipermeable membrane, such as permeation performance and oxidation resistance.

The number of sulfur atoms/the number of nitrogen atoms A on the surface of the separation functional layer is preferably 0.005≦A≦0.55, more preferably 0.01≦A≦0.4, and 0.05≦ More preferably, A≦0.33. When A is 0.005 or more, the partial structure represented by the above formula 1 is sufficiently present on the surface of the separation functional layer, and water permeability due to hydrophilicity, salt separation performance due to Coulomb repulsion, amino groups, amide groups, and A composite semipermeable membrane having both oxidation resistance, acid resistance, and base resistance can be obtained by reducing the electron density of the aromatic ring. On the other hand, when only the polyfunctional aromatic amine having the structure represented by the above formula 2 at the m-position of the amino group is used as the polyfunctional aromatic amine, A is about 0.5, but under neutral water contact. In order to prevent the deterioration of the separation performance of the composite semipermeable membrane due to the expansion of the pore size of the separation functional layer due to Coulomb repulsion between the negatively charged substituents in the polyfunctional aromatic not having the structure represented by the above formula 2 It is more preferable to blend an amine and adjust the value of A as appropriate.

Further, the number of sulfur atoms/number of nitrogen atoms B in the entire separation functional layer is preferably 0.5≦B/A≦2.0, more preferably 0.6≦B/A≦1.7. Preferably, 0.8≤B/A≤1.3 is more preferable. When B/A is in the above range, the partial structure represented by the above formula 1 is uniformly distributed throughout the separation functional layer. Composite that exhibits excellent water permeability performance, salt separation performance, oxidation resistance, acid resistance, and base resistance while suppressing the deterioration of the separation performance of the composite semipermeable membrane due to the expansion of the pore size of the separation function layer due to Coulomb repulsion. Semipermeable membranes can be obtained.

The shape and thickness of the separation functional layer affect separation performance and permeation performance. As shown in FIG. 1B, the separation functional layer preferably includes a pleated thin film 41 having a plurality of protrusions 42 and recesses 43 . Since the separation functional layer has a pleated thin film, the surface area of the separation functional layer can be greatly increased compared to a planar structure. As a result, the permeation performance can be improved in proportion to the surface area of the separation functional layer while maintaining the separation performance. The inside of the convex portion 42 (between the thin film 41 and the porous support layer 3) is a void.

The root mean square height R _q of the separation functional layer is preferably 60 to 300 nm, more preferably 80 to 280 nm, even more preferably 100 to 260 nm. When _Rq is 60 nm or more, it is possible to obtain a composite semipermeable membrane having good permeation performance in proportion to the large surface area of the separation functional layer. On the other hand, when R _q is 300 nm or less, it is possible to obtain a composite semipermeable membrane that maintains the shape of a pleated thin film even under high-pressure operating conditions in seawater desalination applications.

The average thickness T of the thin film is preferably 10 to 20 nm, more preferably 11 to 16 nm. When the average value of T is 10 nm or more, a composite semipermeable membrane having good separation performance can be obtained. On the other hand, when the average value of T is 20 nm or less, a composite semipermeable membrane having good permeability can be obtained.

In order to prevent the substance to be separated from penetrating into the composite semipermeable membrane, the separation functional layer is preferably arranged on the surface side of the composite semipermeable membrane and is arranged on the primary filtration side. more preferred.

(1-3) NaCl removal rate, boron removal rate, membrane permeation flux The composite semipermeable membrane preferably has an NaCl removal rate of 99.70% or more, more preferably 99.75% or more, More preferably, it is 99.80% or more. Also, the boron removal rate is preferably 80% or more, more preferably 85% or more. Furthermore, the membrane permeation flux is preferably 0.70 m ³ /m ² /day or more, more preferably 0.90 m ³ /m ² /day or more, and 1.10 m ³ /m ² /day or more. is more preferable. When the membrane performance of the composite semipermeable membrane is within these ranges, it can be preferably used as a separation membrane for seawater desalination.

In addition, the composite semipermeable membrane preferably has a NaCl removal rate after contact with chlorine of 99.40% or more, more preferably 99.50% or more, and even more preferably 99.60% or more. . Further, the boron removal rate after contact with chlorine is preferably 70% or more, more preferably 75% or more, and even more preferably 80% or more. When the membrane performance of the composite semipermeable membrane after contact with chlorine is within these ranges, it can be preferably used as a composite semipermeable membrane with a low risk of oxidation deterioration due to leakage of chlorine. Conditions for chlorine contact are described in the Examples.

In addition, the composite semipermeable membrane preferably has a NaCl removal rate of 99.50% or higher, more preferably 99.60% or higher, and more preferably 99.75% or higher after being contacted with an acid or base. More preferred. Also, the boron removal rate after contact with acid or base is preferably 70% or more, more preferably 75% or more, and even more preferably 80% or more. When the membrane performance of the composite semipermeable membrane after contact with acid or base is within these ranges, it can be preferably used as a composite semipermeable membrane that maintains separation performance even after repeated washing with a chemical solution. Conditions for acid or base contact are described in the Examples.

2. Method for Producing Composite Semipermeable Membrane The method for producing the composite semipermeable membrane of the present invention is not particularly limited as long as the composite semipermeable membrane satisfying the desired characteristics described above can be obtained. .

(2-1) Formation of Supporting Membrane As a method for forming the supporting membrane, a known method can be suitably used. An example of using PSf as the material of the porous support layer will be described below.

First, PSf is dissolved in a good solvent for PSf to prepare a porous support layer undiluted solution. As a good solvent for PSf, for example, N,N-dimethylformamide (hereinafter “DMF”) is preferable.

The concentration of PSf in the undiluted solution for the porous support layer is preferably 10 to 25% by mass, more preferably 12 to 20% by mass. When the concentration of PSf in the undiluted solution for the porous support layer is within this range, both strength and permeability of the resulting porous support layer can be achieved. The preferable range of the concentration of the material in the undiluted solution for the porous support layer can be appropriately adjusted depending on the material used, the good solvent, and the like.

Next, the obtained undiluted solution for the porous support layer is applied to the substrate surface and immersed in a coagulation bath containing a PSf non-solvent.

Water, for example, is preferable as a non-solvent for PSf contained in the coagulation bath. The undiluted solution of the porous support layer applied to the substrate surface is brought into contact with a coagulation bath containing a PSf non-solvent, whereby the undiluted porous support layer is coagulated by non-solvent-induced phase separation, forming a porous support layer on the substrate surface. can obtain a support film formed by

The coagulation bath may be composed only of a non-solvent for PSf, but may contain a good solvent for PSf to the extent that the undiluted solution of the porous support layer can be coagulated.

The obtained support membrane may be washed before forming the separation functional layer to remove the solvent remaining in the membrane.

(2-2) Polymerization step of separation functional layer Regarding the method of forming a separation functional layer containing a crosslinked aromatic polyamide, a polyfunctional aromatic A method of polymerizing and solidifying a group amine and a polyfunctional aromatic acid chloride will be described as an example. As the polymerization method, the interfacial polymerization method is most preferable from the viewpoint of productivity and performance. The process of interfacial polymerization will be described below.

The step of interfacial polymerization includes (a) a step of bringing an aqueous solution containing a polyfunctional aromatic amine into contact with a support membrane, and (b) an organic solvent solution containing a polyfunctional aromatic acid chloride, and (c) draining the organic solvent solution after contact; (d) washing the composite semipermeable membrane with hot water after draining the organic solvent solution; and a step of performing.

In step (a), the aqueous solution contains at least the first polyfunctional aromatic amine having the structure represented by Formula 2 above at the m-position of the amino group represented by Formula 4 above. Examples of the first polyfunctional aromatic amine include 3,5-diaminobenzenesulfonic acid, 3,5-diamino-2,4,6-trimethylbenzenesulfonic acid, 3,5-diaminophenylmethanesulfonic acid, 3 ,5-diaminophenylethanesulfonic acid, 3,5-diaminophenylpropanesulfonic acid, and 3,5-diaminophenylbutanesulfonic acid. By using these polyfunctional aromatic amines, it is possible to obtain a composite semipermeable membrane in which the separation functional layer includes the partial structure represented by Formula 1 above.

In addition, the aqueous solution may further contain a second polyfunctional aromatic amine that does not have the structure represented by Formula 2 above at the m-position of the amino group. The second polyfunctional aromatic amine may have a substituent other than the structure represented by Formula 2 at the m-position of the amino group, or hydrogen may be at the m-position. Examples of the second polyfunctional aromatic amine include o-phenylenediamine, m-phenylenediamine (hereinafter referred to as "m-PDA"), p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p - Polyfunctional in which two amino groups such as xylylenediamine, o-diaminopyridine, m-diaminopyridine, and p-diaminopyridine are bonded to an aromatic ring at the ortho, meta, or para position. aromatic amines, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, 4-aminobenzylamine;

By using the second polyfunctional aromatic amine together with the first polyfunctional aromatic amine, the ratio of the number of sulfur atoms/the number of nitrogen atoms A on the surface of the separation functional layer can be appropriately adjusted. As a result, the deterioration of the separation performance of the composite semipermeable membrane due to the expansion of the pore size of the separation functional layer due to Coulomb repulsion between the negatively charged substituents under contact with neutral water is suppressed, and excellent water permeability and salt A composite semipermeable membrane exhibiting separation performance, oxidation resistance, acid resistance, and base resistance can be obtained.

The total concentration of the first and second polyfunctional aromatic amines in the aqueous solution is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, and 1.0 More preferably, it is up to 10% by mass. When the total concentration of the first and second polyfunctional aromatic amines is 0.1% by mass or more, a separation functional layer having solute separation performance can be formed. On the other hand, when the total concentration of the first and second polyfunctional aromatic amines is 20% by mass or less, a separation functional layer having good permeability can be formed.

Further, the ratio of the concentration of the first polyfunctional aromatic amine to the sum of the concentrations of the first and second polyfunctional aromatic amines in the aqueous solution is preferably 10 to 100%, more preferably 20 to 90%. and more preferably 30 to 80%. A composite semipermeable membrane exhibiting excellent water permeability, salt separation performance, oxidation resistance, acid resistance, and base resistance is obtained by setting the concentration ratio of the first polyfunctional aromatic amine to 10% or more. be able to. In addition, the aqueous solution may contain compounds such as surfactants and antioxidants, if necessary, as long as they do not inhibit the polymerization.

It is preferable that the aqueous solution is brought into uniform and continuous contact with the support membrane. Specifically, for example, a method of coating the supporting membrane with an aqueous solution of phosphorus and a method of immersing the supporting membrane in an aqueous solution can be used. The contact time between the supporting membrane and the aqueous solution is preferably 1 second to 10 minutes, more preferably 3 seconds to 3 minutes.

After bringing the aqueous solution into contact with the support film, it is preferable to drain the solution sufficiently so that no droplets remain on the support film. By sufficiently draining the liquid, it is possible to prevent the drop remaining portion from becoming a membrane defect after forming the composite semipermeable membrane and lowering the separation performance. As a method for removing the liquid, for example, as described in Patent Document 1, the support film after contact with the aqueous solution is gripped in the vertical direction and the excess aqueous solution is allowed to flow naturally, or an air flow of nitrogen or the like from an air nozzle. and forcibly draining the liquid. Also, after draining, the film surface can be dried to partially remove water from the aqueous solution.

Examples of the polyfunctional aromatic acid chloride in step (b) include trimesic acid chloride (hereinafter referred to as "TMC"), biphenyldicarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, and naphthalenedicarboxylic acid chloride. , 2,5-furandicarboxylic acid chloride. These polyfunctional aromatic acid chlorides may be used alone or in combination of two or more.

The organic solvent is immiscible with water, dissolves the polyfunctional aromatic acid chloride, does not attack the supporting membrane, and is inert to the polyfunctional aromatic amine and the polyfunctional aromatic acid chloride. is preferred. Examples of organic solvents include hydrocarbon compounds such as n-nonane, n-decane, n-undecane, n-dodecane, isooctane, isodecane, and isododecane, and mixed solvents thereof.

The concentration of the polyfunctional aromatic acid chloride in the organic solvent solution is preferably 0.01 to 10% by mass, more preferably 0.02 to 4% by mass, and 0.03 to 2% by mass. It is even more preferable to have When the concentration of the polyfunctional aromatic acid chloride is 0.01% by mass or more, polymerization can proceed at a sufficient reaction rate. On the other hand, when the concentration of the polyfunctional aromatic acid chloride is 10% by mass or less, the occurrence of side reactions during polymerization can be suppressed. In addition, the organic solvent solution may contain a compound such as a surfactant, if necessary, as long as it does not inhibit the polymerization.

The method of contacting the organic solvent solution of the polyfunctional aromatic acid chloride with the support film contacted with the polyfunctional aromatic amine aqueous solution may be carried out in the same manner as the method of coating the support film with the polyfunctional aromatic amine aqueous solution. .

Moreover, if necessary, the support film contacted with the organic solvent solution of the polyfunctional aromatic acid chloride may be heat-treated. In the case of heat treatment, the heating temperature is preferably 50 to 180°C, more preferably 60 to 160°C, even more preferably 80 to 150°C. The optimum heating time varies depending on the temperature of the film surface, which is the reaction field, but is preferably 10 seconds or longer, more preferably 20 seconds or longer.

In step (c), the organic solvent solution on the composite semipermeable membrane after the polymerization reaction is drained and removed. As a method for removing the liquid, for example, a method of removing the excessive organic solvent solution by holding the membrane vertically and allowing it to naturally flow down, a method of drying and removing the organic solvent by blowing air with an air blower, and a method of removing water and air. A method of removing an excess organic solvent solution with a mixed fluid, and the like.

In step (d), the composite semipermeable membrane from which the organic solvent has been removed is washed with hot water. The temperature of the hot water is preferably 40-95°C, more preferably 60-95°C. When the temperature of the hot water is 40° C. or higher, unreacted substances and oligomers remaining in the film can be sufficiently removed. On the other hand, when the temperature of the hot water is 95° C. or lower, the degree of contraction of the composite semipermeable membrane does not increase, and good permeation performance can be maintained. The preferred temperature range of the hot water can be appropriately adjusted depending on the polyfunctional aromatic amine or polyfunctional aromatic acid chloride used.

The NaCl removal rate of the composite semipermeable membrane obtained by the above manufacturing method is preferably 99.60% or more, more preferably 99.70% or more. Moreover, the boron removal rate of the obtained composite semipermeable membrane is preferably 80% or more, more preferably 85% or more. Furthermore, the membrane permeation flux during production is preferably 0.50 m ³ /m ² /day or more, more preferably 0.70 m ³ /m ² /day or more. When the membrane performance at the time of production of the composite semipermeable membrane is within these ranges, it can be preferably used as a separation membrane for seawater desalination.

3. Use of composite semipermeable membranes Composite semipermeable membranes are composed of feed water channel materials such as plastic nets, permeate water channel materials such as tricot, films to increase pressure resistance as necessary, and a large number of holes. The composite semipermeable membrane element is preferably used as a spiral type composite semipermeable membrane element. Furthermore, a composite semipermeable membrane module in which these elements are connected in series or in parallel and housed in a pressure vessel can also be formed.

Further, the composite semipermeable membranes, elements thereof, and modules described above can be combined with a pump for supplying water to them, a device for pretreating the water, and the like to constitute a fluid separation device. By using this separator, it is possible to separate feed water into permeated water such as drinking water and concentrated water that has not permeated the membrane, thereby obtaining desired water.

Examples of the feed water to be treated by the composite semipermeable membrane according to the present invention include liquid mixtures containing 500 mg/L to 100 g/L of TDS (Total Dissolved Solids) such as seawater, brackish water, and waste water. be done. In general, TDS refers to total dissolved solids and is expressed as "mass/volume" or "weight ratio". According to the definition, it can be calculated from the weight of the residue after evaporating the solution filtered through a 0.45 micron filter at a temperature of 39.5 to 40.5 ° C, but more easily converted from the practical salinity (S) do.

The higher the operating pressure of the fluid separation device, the higher the solute removal rate, but the energy required for operation also increases, and considering the durability of the composite semipermeable membrane, The operating pressure during permeation is preferably 0.5 to 10 MPa. The higher the feed water temperature, the lower the solute removal rate, but the lower the feed water temperature, the lower the membrane permeation flux. In addition, when the pH of the feed water increases, scale such as magnesium may occur in the case of feed water with a high solute concentration such as seawater, and there is concern about deterioration of the membrane due to high pH operation. It is preferable to drive at

EXAMPLES The present invention will be described below with specific examples, but the present invention is not limited to these examples.

Physical properties of the composite semipermeable membrane of the present invention were measured by the following methods.

(1) Number of Sulfur Atoms/Number of Nitrogen Atoms (i) Separation Functional Layer Surface The composite semipermeable membrane was cut into 3 cm×3 cm squares, washed with distilled water at 90° C. for 10 minutes, and dried. The composite semipermeable membrane after drying is measured by X-ray photoelectron spectroscopy (hereinafter “XPS”) (manufactured by PHI; Quantera SXM) using the separation function layer as a measurement surface, and sulfur atomic composition (atomic%) and nitrogen The atomic composition (atomic %) was calculated, and the ratio of these was defined as the number of sulfur atoms/the number of nitrogen atoms A. Specific measurement conditions were as follows.

(ii) Entire Separation Functional Layer A total of 1 m ² of the composite semipermeable membrane was cut out, washed with distilled water at 90° C. for 10 minutes, and dried. When the composite semipermeable membrane had a substrate, the substrate was peeled off from the composite semipermeable membrane after drying. The polymer forming the porous support layer was eluted by putting the obtained membrane comprising two layers of the porous support layer and the separation functional layer into dichloromethane. The precipitate containing the separation functional layer as a main component was repeatedly washed with dichloromethane until the polymer forming the porous support layer could no longer be detected by thin layer chromatography. The separated functional layer powder was obtained by freeze-drying the precipitate after washing. The obtained powder was molded into pellets. The sample after molding was subjected to XPS measurement to calculate the sulfur atomic composition (atomic %) and the nitrogen atomic composition (atomic %), and the ratio of these was defined as the number of sulfur atoms/number of nitrogen atoms B. Specific measurement conditions were as follows.
Excitation X-ray: monochromatic Al Kα1, 2 rays (1486.6 eV)
X-ray diameter: 0.2mm
The S2p peak obtained by XPS is attributed to core electrons of sulfur atoms. In addition, the N1s peak originates from inner-shell electrons of nitrogen atoms. The SC-derived component appears at 169 eV, and the NC-derived component appears at around 400 eV. The sulfur atom composition was determined from the SC-derived peak area, and the nitrogen atom composition was determined from the NC-derived peak area.

(2) Average value of thickness T of thin film The composite semipermeable membrane was cut into 3 cm x 3 cm squares and washed with distilled water at 25°C for 24 hours. After the washed composite semipermeable membrane was embedded in an epoxy resin, it was stained with osmium tetroxide to obtain a measurement sample. The obtained sample was observed using a scanning transmission electron microscope (manufactured by Hitachi, Ltd.; HD2700) using the thin film cross section as an observation surface. The thickness T of the thin film was defined as the shortest distance from a point on the outer surface of the thin film to the inner surface, using an image acquired at a magnification of 1,000,000. Ten randomly selected convex portions were analyzed at five points per convex portion, and the average value thereof was taken as the average value of the thickness T of the thin film.

(3) Root-mean-square height _Rq of separation functional layer
The composite semipermeable membrane was cut into 3 cm×3 cm squares and washed with distilled water at 25° C. for 24 hours. The washed composite semipermeable membrane was observed using an atomic force microscope (Bruker; Dimension FastScan) while still wet with distilled water, using the separation function layer as the measurement surface. The root mean square height _Rq was calculated from the obtained height information of the unevenness of the separation functional layer.

Scanning mode: Underwater nanomechanical mapping Probe: Silicon cantilever (manufactured by Bruker; Scan Asyst-Fluid)
Maximum load: 5nN
Scanning range: 10 μm×10 μm
Scanning speed: 1Hz
Number of pixels: 512 x 512
Measurement environment: Distilled water Measurement temperature: 25°C
(4) Weight average molecular weight The weight average molecular weight (polystyrene equivalent) of PSf was measured using gel permeation chromatography (manufactured by Tosoh; HLC-8022). Specific measurement conditions were as follows.

Column: TSK gel SuperHM-H (manufactured by Tosoh; inner diameter 6.0 mm, length 15 cm) 2 Eluent: LiBr/N-methylpyrrolidone solution (10 mM)
Sample concentration: 0.1% by mass
Flow rate: 0.5mL/min
Temperature: 40°C
(5) Partial Structure Represented by Formula 1 Above, Structure Represented by Formula 2 Above A total of 1 m ² of the composite semipermeable membrane was cut out, washed with distilled water at 90° C. for 10 minutes, and dried. When the composite semipermeable membrane had a substrate, the substrate was peeled off from the composite semipermeable membrane after drying. The polymer forming the porous support layer was eluted by putting the obtained membrane comprising two layers of the porous support layer and the separation functional layer into dichloromethane. The precipitate containing the separation functional layer as a main component was repeatedly washed with dichloromethane until the polymer forming the porous support layer could no longer be detected by thin layer chromatography. The separated functional layer powder was obtained by freeze-drying the precipitate after washing.

The obtained powder of the separation functional layer was dissolved in a 6M heavy NaOH aqueous solution and heated at 120° C. for 2 hours to hydrolyze ^the amide bond. ECZ400R) was measured. From the obtained peak, the presence or absence of the partial structure represented by Formula 1 above and the structure represented by Formula 2 above were analyzed.

Further, the hydrolyzed solution was neutralized with HCl, the solvent was volatilized, and GC-MS (manufactured by Shimadzu Corporation; GCMS-QP2010) was measured. From the obtained peak, the presence or absence of the partial structure represented by Formula 1 above and the structure represented by Formula 2 above were analyzed.

(6) NaCl Removal Rate A membrane filtration test was performed by supplying evaluation water prepared to a NaCl concentration of 32,000 ppm, a boron concentration of 5 ppm, 25° C. and pH 7 to the composite semipermeable membrane at an operating pressure of 5.5 MPa. The electrical conductivities of the evaluation water and the permeated water were measured with a multi-water quality meter (manufactured by DKK Toa; MM-60R) to obtain NaCl concentration (practical salinity) for each. From the NaCl concentration thus obtained, the NaCl removal rate (%) was calculated based on Equation 5 below.

NaCl removal rate (%)=100×{1−(NaCl concentration in permeated water/NaCl concentration in evaluation water)} (Formula 5)
(7) Boron removal rate In the membrane filtration test of "(6) NaCl removal rate", the boron concentration in the evaluation water and permeated water was measured by an ICP emission spectrometer (manufactured by Agilent Technologies; Agilent 5110). Based on this, the boron removal rate (%) was calculated.
Boron removal rate (%) = 100 × {1-(boron concentration in permeated water/boron concentration in evaluation water)} (Formula 6)
(8) Membrane permeation flux In the membrane filtration test of "(6) NaCl removal rate", the amount of permeated water (m ³ ) was measured and converted into values per unit membrane area (m ² ) and per unit time (day). , membrane permeation flux (m ³ /m ² /day).

(9) Chlorine Contact The composite semipermeable membrane was immersed in a 25 mg/L sodium hypochlorite aqueous solution adjusted to pH 7.0 at 25° C. for 24 hours. After that, it was immersed in a 1000 mg/L sodium hydrogen sulfite aqueous solution for 10 minutes and washed with distilled water.

(10) Acid contact The composite semipermeable membrane was immersed in sulfuric acid adjusted to pH 1.0 at 25°C for 24 hours. After that, it was washed with distilled water.

(11) Base contact The composite semipermeable membrane was immersed in an aqueous sodium hydroxide solution adjusted to pH 13.0 at 25°C for 24 hours. After that, it was washed with distilled water.

The raw materials for the composite semipermeable membranes used in Examples and Comparative Examples are summarized below.
Concentrated sulfuric acid (manufactured by FUJIFILM Wako Pure Chemical Industries)
Fuming nitric acid (manufactured by FUJIFILM Wako Pure Chemical Industries)
Sodium m-nitrobenzenesulfonate (manufactured by Fujifilm Wako Pure Chemical Industries)
Calcium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries)
Methanol (manufactured by FUJIFILM Wako Pure Chemical Industries)
Palladium/carbon (10% Pd, about 55% water wet product) (manufactured by Tokyo Kasei Kogyo)
N-methyl-2-pyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries)
Sodium acetate (manufactured by FUJIFILM Wako Pure Chemical Industries)
Ethanol (manufactured by FUJIFILM Wako Pure Chemical Industries)
Sodium vinyl sulfonate (2.3M aqueous solution) (manufactured by Tokyo Kasei Kogyo)
Sodium allylsulfonate (manufactured by FUJIFILM Wako Pure Chemical Industries)
PSf (manufactured by Solvay Specialty Polymers; Udel P-3500, M _w 80000)
DMF (manufactured by Fujifilm Wako Pure Chemical Industries)
Polyester long fiber nonwoven fabric (thickness 90 μm, density 0.42 g/cm ³ )
TMC (manufactured by Fujifilm Wako Pure Chemical Industries)
Decane (manufactured by Fujifilm Wako Pure Chemical Industries)
m-PDA (manufactured by Fujifilm Wako Pure Chemical Industries)
1,3-propane sultone (manufactured by Fujifilm Wako Pure Chemical Industries)
Chlorosulfonic acid (manufactured by FUJIFILM Wako Pure Chemical Industries)
Butyl acetate (manufactured by FUJIFILM Wako Pure Chemical Industries)
Sodium hypochlorite (manufactured by Fujifilm Wako Pure Chemical Industries)
Sodium bisulfite (manufactured by Fujifilm Wako Pure Chemical Industries)
Sulfuric acid (manufactured by FUJIFILM Wako Pure Chemical Industries)
Sodium hydroxide aqueous solution (manufactured by FUJIFILM Wako Pure Chemical Industries)
A polyfunctional aromatic amine having a structure represented by Formula 4 above was synthesized by the procedure shown below.
(Synthesis Example 1: Synthesis of sodium 3,5-diaminobenzenesulfonate)
10 mL of fuming nitric acid was added dropwise to 20 mL of concentrated sulfuric acid at 0° C., 5 g of sodium m-nitrobenzenesulfonate was added, and the mixture was refluxed at 120° C. for 5 hours. After cooling, the mixture was diluted with 100 mL of pure water, added with 33 g of calcium hydroxide, and stirred for 1 hour. The solvent was removed by a rotary evaporator, and the resulting solid was washed with 150 mL of methanol at 60° C. and filtered while hot. 1.2 g of palladium/carbon (Pd 10%, about 55% wet with water) was added, the gas in the flask was replaced with hydrogen, and the mixture was stirred at 20° C. for 20 hours. Palladium/carbon was removed by celite filtration and the solvent was removed by rotary evaporation. The resulting residue was dissolved in 25 mL of water, 5 g of sodium carbonate was added, and the mixture was stirred at room temperature for 1 hour. The precipitate was filtered and the filtrate was concentrated under reduced pressure. The residue was dissolved in methanol and the precipitate was filtered. The filtrate was concentrated under reduced pressure to obtain sodium 3,5-diaminobenzenesulfonate.
(Synthesis Example 2: Synthesis of 3,5-diaminophenylethanesulfonic acid)
A solution of 242 mg of trans-bis(acetato)bis o-(di-o-toluylphosphino)benzyldipalladium(II) in 10 mL of DMF and 10 mL of N-methyl-2-pyrrolidone was stirred at 100° C. for 10 minutes. 1.00 g of di-tert-butyl (5-bromo-1,3-phenylene)dicarbamate and 444 mg of sodium acetate were added to the reaction solution, and the mixture was further stirred for 10 minutes. 1.68 mL of sodium vinylsulfonate (2.3 M aqueous solution) was added to the reaction solution, and the mixture was stirred at 100° C. for 12 hours. The reaction solution was cooled and the precipitated solid was filtered. 10 mL of ethanol and 1.37 g of palladium/carbon (10% Pd, approximately 55% wet with water) were added to the filtrate, the gas in the flask was replaced with hydrogen, and the mixture was refluxed for 12 hours. Palladium/carbon was removed by Celite filtration, and the solvent was removed by heating and drying under reduced pressure at 130° C. to obtain 3,5-diaminophenylethanesulfonic acid.
(Synthesis Example 3: Synthesis of 3,5-diaminophenylpropanesulfonic acid)
3,5-Diaminophenylpropanesulfonic acid was obtained in the same manner as in Synthesis Example 2 except that sodium vinylsulfonate in Synthesis Example 2 was changed to sodium allylsulfonate.

(Example 1)
15% by mass of PSf and 85% by mass of DMF were dissolved at 100° C. to prepare a stock solution for the porous support layer. This undiluted solution for the porous support layer is applied to the surface of the polyester long fiber nonwoven fabric at 25° C. After 3 seconds, it is immersed in a coagulation bath consisting of distilled water at 25° C. for 30 seconds to solidify, followed by hot water at 80° C. for 2 minutes. By washing, a support film having a porous support layer formed on the substrate surface was obtained. The thickness of the porous support layer in the obtained support film was 50 µm.

Next, the obtained support film was immersed in a 6% by mass aqueous solution of sodium 3,5-diaminobenzenesulfonate for 2 minutes, then slowly pulled up in the vertical direction, and nitrogen was blown from an air nozzle to remove the support film. Excess aqueous solution was removed from the surface. In an environment controlled at 40°C, a 40°C decane solution containing 0.18% by mass of TMC was applied so that the surface was completely wetted and allowed to stand for 1 minute. Cut and removed. Thus, a layer containing the crosslinked aromatic polyamide was formed on the support membrane to obtain a composite semipermeable membrane. Finally, the composite semipermeable membrane was washed with hot water at 80°C for 2 minutes. Tables 1 and 2 show the evaluation results of the obtained composite semipermeable membranes.

(Example 2)
In the same manner as in Example 1, except that the 6% by mass aqueous solution of sodium 3,5-diaminobenzenesulfonate in Example 1 was changed to an aqueous solution of 4% by mass of sodium 3,5-diaminobenzenesulfonate and 2% by mass of m-PDA, A composite semipermeable membrane was obtained. Tables 1 and 2 show the evaluation results of the obtained composite semipermeable membranes.

(Example 3)
A composite semipermeable membrane was obtained in the same manner as in Example 1, except that the 6% by mass aqueous solution of sodium 3,5-diaminobenzenesulfonate in Example 1 was changed to a 6% by mass aqueous solution of 3,5-diaminophenylethanesulfonic acid. rice field. Tables 1 and 2 show the evaluation results of the obtained composite semipermeable membranes.

(Example 4)
In the same manner as in Example 1, except that the 6% by mass aqueous solution of sodium 3,5-diaminobenzenesulfonate in Example 1 was changed to an aqueous solution of 4% by mass of 3,5-diaminophenylethanesulfonic acid and 2% by mass of m-PDA, A composite semipermeable membrane was obtained. Tables 1 and 2 show the evaluation results of the obtained composite semipermeable membranes.

(Example 5)
A composite semipermeable membrane was obtained in the same manner as in Example 1, except that the 6% by mass aqueous solution of sodium 3,5-diaminobenzenesulfonate in Example 1 was changed to a 6% by mass aqueous solution of 3,5-diaminophenylpropanesulfonic acid. rice field. Tables 1 and 2 show the evaluation results of the obtained composite semipermeable membranes.

(Example 6)
In the same manner as in Example 1 except that the 6% by mass aqueous solution of sodium 3,5-diaminobenzenesulfonate in Example 1 was changed to 4% by mass of 3,5-diaminophenylpropanesulfonic acid and 2% by mass of m-PDA aqueous solution, A composite semipermeable membrane was obtained. Tables 1 and 2 show the evaluation results of the obtained composite semipermeable membranes.

(Comparative example 1)
A composite semipermeable membrane was obtained in the same manner as in Example 1, except that the 6% by mass aqueous solution of sodium 3,5-diaminobenzenesulfonate in Example 1 was changed to a 3% by mass aqueous solution of m-PDA. Tables 1 and 2 show the evaluation results of the obtained composite semipermeable membranes.

(Comparative example 2)
The composite semipermeable membrane obtained in Comparative Example 1 was immersed in a 1% by mass aqueous solution of 1,3-propanesultone at 25° C. for 24 hours. The composite semipermeable membrane was washed with distilled water at 45° C. for 10 minutes to obtain a composite semipermeable membrane with a modified separation function layer. Tables 1 and 2 show the evaluation results of the obtained composite semipermeable membranes.

(Comparative Example 3)
The separation function layer of the composite semipermeable membrane obtained in Comparative Example 1 was coated with a butyl acetate solution containing 1% by mass of chlorosulfonic acid and brought into contact at 25° C. for 2 minutes. The composite semipermeable membrane was washed with distilled water at 45° C. for 10 minutes to obtain a composite semipermeable membrane with a modified separation function layer. Tables 1 and 2 show the evaluation results of the obtained composite semipermeable membranes.

(Comparative Example 4)
A composite semipermeable membrane was obtained in the same manner as in Example 1, except that the 6% by mass aqueous solution of sodium 3,5-diaminobenzenesulfonate in Example 1 was changed to a 6% by mass aqueous solution of 2,4-diaminobenzenesulfonic acid. . Tables 1 and 2 show the evaluation results of the obtained composite semipermeable membranes.

(Comparative Example 5)
Composite was prepared in the same manner as in Example 1 except that the 6% by mass aqueous solution of sodium 3,5-diaminobenzenesulfonate in Example 1 was changed to 4% by mass of 2,4-diaminobenzenesulfonic acid and 2% by mass of m-PDA aqueous solution. A semipermeable membrane was obtained. Tables 1 and 2 show the evaluation results of the obtained composite semipermeable membranes.

Claims (7)

Equipped with a support membrane and a separation functional layer containing a crosslinked aromatic polyamide,
A composite semipermeable membrane, wherein the separation function layer includes a partial structure represented by Formula 1 below.

(where R ₁ to R ₁₁ are a hydrogen atom, a halogen atom, or an aliphatic chain having 1 to 10 carbon atoms, and Ar ₁ is an optionally substituted aromatic ring having 4 to 14 carbon atoms; and R ₁₂ and R ₁₃ are a hydrogen atom, a halogen atom, an aliphatic chain having 1 to 4 carbon atoms, or a structure represented by the following formula 2, and at least one of R ₁₂ and R ₁₃ is represented by the following formula 2 It is a structure that is used.)

(where X is an aliphatic chain having 1 to 4 carbon atoms or a single bond, and Y ₁ to Y ₃ are each independently O, OH, or ^O- . In addition, the following formula 3 in formula 2 represents a single bond or a double bond.)

2. The composite semipermeable membrane according to claim 1, wherein _R13 in Formula 1 is a structure represented by Formula 2. 3. The composite semipermeable membrane according to claim 1 or 2, wherein _R13 in Formula 1 is a sulfo group. The composite semipermeable membrane according to claim 1 or 2, wherein X in formula 2 is an aliphatic chain having 1 to 4 carbon atoms. The composite semipermeable membrane according to any one of claims 1 to 4, wherein the number of sulfur atoms/the number of nitrogen atoms A on the separation functional layer surface satisfies 0.005 ≤ A ≤ 0.55. The composite semipermeable membrane according to any one of claims 1 to 5, wherein the number of sulfur atoms/number of nitrogen atoms B in the entire separation function layer satisfies 0.5 ≤ B/A ≤ 2.0. The separation function layer includes a pleated thin film having a plurality of protrusions and recesses, the average value of the thickness T of the thin film is 10 to 20 nm, and the root mean square height R _q of the separation function layer is 60. The composite semipermeable membrane according to any one of claims 1 to 6, which is ~300 nm.

Images