CN118414203A

CN118414203A - Composite semipermeable membrane

Info

Publication number: CN118414203A
Application number: CN202280084492.XA
Authority: CN
Inventors: 三井伸也; 小川久美子; 永野泉; 志村晴季
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 2021-12-28
Filing date: 2022-12-26
Publication date: 2024-07-30

Abstract

The present invention relates to a composite semipermeable membrane comprising a microporous support layer and a separation functional layer provided on the microporous support layer, wherein the separation functional layer comprises a crosslinked aromatic polyamide having a specific partial structure.

Description

Composite semipermeable membrane

Technical Field

The present invention relates to a composite semipermeable membrane for filtering a liquid or the like.

Background

Examples of membranes used for membrane separation of the liquid mixture include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, and the like, and these membranes are used in cases where drinking water is obtained from water containing salts, hazardous substances, and the like, in the production of industrial ultrapure water, wastewater treatment, recovery of valuable materials, and the like.

Most of the reverse osmosis membranes and nanofiltration membranes sold in the market at present are composite semipermeable membranes. The composite semipermeable membrane is a membrane having a plurality of layers, and particularly a composite semipermeable membrane that has a microporous support layer and a separation functional layer containing a crosslinked aromatic polyamide obtained by polycondensation of a polyfunctional aromatic amine and a polyfunctional aromatic acyl halide is widely used. In order to improve the water quality obtained during use, these composite semipermeable membranes are required to have high salt removal properties.

As a method for improving the salt removal property of a film, for example, a post-treatment method of converting the amine end of a crosslinked aromatic polyamide by bringing the film into contact with a bromine-containing free chlorine aqueous solution by a diazonium coupling reaction is known (patent documents 1 and 2).

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2007-090192

Patent document 2: japanese patent laid-open No. 2001-259388.

Disclosure of Invention

Problems to be solved by the invention

The desalination property and water permeability of the membrane are in a trade-off relationship, and particularly, when the desalination property is increased in a reverse osmosis membrane or a nanofiltration membrane, the water permeability is greatly impaired. If the water permeability is reduced, the operating pressure needs to be increased, and the operating cost increases.

Accordingly, an object of the present invention is to provide a composite semipermeable membrane which has improved salt removal properties and which does not impair water permeability.

Means for solving the problems

In order to achieve the above object, the present invention has any one of the following configurations [1] to [8 ].

[1] A composite semipermeable membrane comprising a microporous support layer and a separation functional layer provided on the microporous support layer, wherein the separation functional layer comprises a crosslinked aromatic polyamide having a partial structure represented by the following formula (1).

[ Chemical formula 1]

[ The symbols in the above formula (1) have the following meanings:

Ar ₁～Ar₃ is an aromatic ring having 5 to 14 carbon atoms which may have a substituent.

R ₁ represents a structure represented by any one of the following formulas (2) to (4).

R ₂～R₅ is independently a hydrogen atom or an aliphatic chain having 1 to 10 carbon atoms. A kind of electronic device

[ Chemical formula 2]

[ The symbols in the above formulae (2) to (4) have the following meanings:

L ₁ is a single bond or an aliphatic chain having 1 to 6 carbon atoms.

Each of W ₁～W₃ is independently a hydrogen atom or an aliphatic chain having 1 to 6 carbon atoms which may contain a heteroatom or a branched chain, and at least one of W ₁～W₃ is an aliphatic chain having 1 to 6 carbon atoms which may contain a heteroatom or a branched chain.

Wherein when W ₃ is a hydrogen atom, the total number of carbon atoms of W ₁ and W ₂ is 2 to 12. In addition, W ₁～W₃ does not contain a carbonyl group. A kind of electronic device

[2] The composite semipermeable membrane according to [1], wherein the separation functional layer has a ratio of (molar equivalent of amino group+molar equivalent of carboxyl group)/(molar equivalent of amide group) of 0.56 or less as measured by DD-MAS- ¹³ C solid state NMR.

[3] The composite semipermeable membrane according to [1] or [2], wherein L ₁ in the formulae (2) to (4) is a single bond.

[4] The composite semipermeable membrane according to [1] or [2], wherein W ₃ in the formulae (2) to (4) is an aliphatic chain having 1 to 6 carbon atoms which may contain a heteroatom or a branched chain.

[5] The composite semipermeable membrane according to [1] or [2], wherein R ₁ in the formula (1) is represented by any one of the following formulas (5) to (8).

[ Chemical formula 3]

[6] A method for producing a composite semipermeable membrane, comprising:

(a) A step of forming a layer containing a crosslinked aromatic polyamide having a partial structure represented by the following formula (9) on a microporous support layer; and

(B) And (3) a step of modifying the terminal amino group of the crosslinked aromatic polyamide with an amino group-containing aliphatic carboxylic acid represented by any one of the following formulas (10) to (12).

[ Chemical formula 4]

[ The symbols in the above formula (9) have the following meanings:

[ Chemical formula 5]

[ The symbols in the above formulae (10) to (12) have the following meanings:

L ₁ is a single bond or an aliphatic chain having 1 to 6 carbon atoms.

[7] The method for producing a composite semipermeable membrane according to [6], wherein L ₁ in the formulae (10) to (12) is a single bond.

[8] The method for producing a composite semipermeable membrane according to [6] or [7], wherein the aliphatic carboxylic acid having an amino group is at least one compound selected from the group consisting of proline, sarcosine, 2-aminoisobutyric acid and threonine.

ADVANTAGEOUS EFFECTS OF INVENTION

The composite semipermeable membrane has high desalting performance and practical water permeability.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these examples. In the present specification, "weight" and "mass" and "wt%" and "mass%" are synonymous, respectively.

<1. Composite semipermeable Membrane >

The composite semipermeable membrane according to the present embodiment includes a microporous support layer and a separation functional layer provided on the microporous support layer. The composite semipermeable membrane according to an embodiment of the present invention includes a support membrane including a base material and a microporous support layer, and a separation functional layer formed on the microporous support layer.

The separation functional layer is a layer having substantially separation performance, and the support film has substantially no separation performance such as ion although it transmits water, and can impart strength to the separation functional layer.

(1) Support film

The composite semipermeable membrane according to the present embodiment may be provided with a microporous support layer and a separation functional layer, and the microporous support layer is a layer constituting the support membrane. The support film includes a substrate and a microporous support layer. However, the present invention is not limited to this configuration. For example, the support film may be composed of only a microporous support layer without a base material.

(1.1) Substrate

Examples of the substrate include polyester polymers, polyamide polymers, polyolefin polymers, and mixtures and copolymers thereof. Among them, a polyester polymer fabric having high mechanical stability and thermal stability is particularly preferable. As the form of the fabric, a long fiber nonwoven fabric, a short fiber nonwoven fabric, and a woven and knitted fabric can be preferably used.

(1.2) Microporous support layer

In the present embodiment, the microporous support layer has substantially no separation performance such as ions, and is used to impart strength to the separation functional layer having substantially separation performance. The size and distribution of pores of the microporous support layer are not particularly limited. The microporous support layer is preferably a microporous support layer having uniform and fine pores or fine pores gradually increasing in size from the surface on the side where the separation functional layer is formed to the other surface, and the size of the fine pores on the surface on the side where the separation functional layer is formed is from 0.1nm to 100 nm. The material used for the microporous support layer and the shape thereof are not particularly limited.

Examples of the material of the microporous support layer include homopolymers and copolymers such as polysulfone, polyethersulfone, polyamide, polyester, cellulose-based polymer, vinyl polymer, polyphenylene sulfide sulfone, polyphenylene sulfone and polyphenylene oxide, alone or in combination. Here, cellulose acetate, nitrocellulose, and the like can be used as the cellulose-based polymer, and polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile, and the like can be used as the vinyl polymer.

Among them, as the material of the microporous support layer, homopolymers or copolymers of polysulfone, polyamide, polyester, cellulose acetate, nitrocellulose, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide sulfone, and the like are preferable, and cellulose acetate, polysulfone, polyphenylene sulfide sulfone, or polyphenylene sulfone is more preferable. Further, polysulfone is particularly preferable as a material for the microporous support layer because of its high chemical stability, mechanical stability, thermal stability, and ease of molding.

The polysulfone preferably has a weight average molecular weight (Mw) of 10000 to 200000, more preferably 15000 to 100000, when measured by Gel Permeation Chromatography (GPC) using N-methylpyrrolidone as a solvent and polystyrene as a standard substance.

When the Mw of polysulfone is 10000 or more, mechanical strength and heat resistance preferable as the microporous support layer can be obtained. Further, by setting the Mw to 200000 or less, the viscosity of the solution is in an appropriate range, and good moldability can be achieved.

For example, in the case of forming a microporous support layer using polysulfone, an N, N-dimethylformamide (hereinafter referred to as DMF) solution of polysulfone is poured onto a densely woven polyester cloth or nonwoven fabric at a certain thickness and wet-coagulated in water. According to this method, a microporous support layer having fine pores with a diameter of 10nm or less on the surface can be obtained.

The thickness of the substrate and the microporous support layer will have an effect on the strength of the composite semipermeable membrane and the packing density when it is formed into a device. In order to obtain sufficient mechanical strength and packing density, the total thickness of the substrate and the microporous support layer is preferably 30 μm to 300 μm, more preferably 100 μm to 220 μm.

In addition, from the viewpoint of minimizing the resistance to water passing through the membrane and imparting mechanical strength to the separation functional layer, the thickness of the microporous support layer is preferably 20 μm to 100 μm, more preferably 25 μm to 50 μm.

In the present specification, unless otherwise specified, thickness refers to an average value. Here, the average value means an arithmetic average value. That is, the thicknesses of the substrate and the microporous support layer can be determined as follows: the thickness at 20 was measured at 20 μm intervals in a direction perpendicular to the thickness direction (in the plane direction of the film) by cross-sectional observation, and the average value was calculated.

(2) Separating functional layer

The separation functional layer contains a crosslinked aromatic polyamide. In particular, the separation functional layer preferably contains a crosslinked aromatic polyamide as a main component. The main component is a component constituting 50 mass% or more of the components of the separation functional layer. By including 50 mass% or more of the crosslinked aromatic polyamide in the separation functional layer, high salt removal performance can be exhibited. The content of the crosslinked aromatic polyamide in the separation functional layer is more preferably 80 mass% or more, and still more preferably 90 mass% or more.

In this embodiment, the crosslinked aromatic polyamide has a partial structure represented by the following formula (1) through an amide bond of its terminal amino group.

[ Chemical formula 6]

The symbols in the above formula (1) have the following meanings:

R ₂～R₅ is independently a hydrogen atom or an aliphatic chain having 1 to 10 carbon atoms.

[ Chemical formula 7]

The symbols in the above formulas (2) to (4) have the following meanings:

L ₁ is a single bond or an aliphatic chain having 1 to 6 carbon atoms.

Wherein when W ₃ is a hydrogen atom, the total number of carbon atoms of W ₁ and W ₂ is 2 to 12. In addition, W ₁～W₃ does not contain a carbonyl group.

Ar ₁～Ar₃ in the above formula (1) is preferably a benzene ring which may have a substituent from the viewpoint of ensuring an appropriate free volume for water permeation in the separation functional layer. Examples of the substituent that the benzene ring may have include an amino group, a carboxyl group, and a methyl group, and other substituents may be used. Furthermore, the benzene ring may also be unsubstituted.

R ₂～R₅ in the above formula (1) is preferably a hydrogen atom from the viewpoint of forming hydrogen bonds between the crosslinked aromatic polyamides constituting the separation functional layer and contributing to improvement of the permselectivity.

From the viewpoint of suppressing the decrease in hydrophilicity of the crosslinked aromatic polyamide constituting the separation functional layer, L ₁ in the above formulas (2) to (4) is preferably a single bond.

From the viewpoint of improving the water permeability of the composite semipermeable membrane, W ₃ in the above formulas (2) to (4) is preferably an aliphatic chain having 1 to 6 carbon atoms which may contain a heteroatom or a branched chain.

The crosslinked aromatic polyamide preferably contains a polyfunctional aromatic amine and a polyfunctional aromatic acyl chloride as monomer components. That is, a polycondensate of a polyfunctional aromatic amine and a polyfunctional aromatic acyl chloride is preferable. Specific examples of the polyfunctional aromatic amine and polyfunctional aromatic acid chloride are described in the column of the production process.

As shown in the above formula (1), R ₁ contains an amino group in the structure. The hydrogen atom contained in the amino group is a hydrogen bond donor, and has high affinity with a hydrogen bond acceptor such as a carbonyl group and a permeated water oxygen atom in the crosslinked aromatic polyamide, thereby contributing to the formation of continuous hydrogen bonds between the crosslinked aromatic polyamide and the permeated water. This increases the water permeability of the separation functional layer containing the crosslinked aromatic polyamide.

On the other hand, in the case where the interaction between the hydrogen atom of the amino group in the structure of R ₁ in the above formula (1) and the carbonyl group in the crosslinked aromatic polyamide is strong, there is a possibility that the pores as the passage of the permeated water in the separation functional layer containing the crosslinked aromatic polyamide are blocked. However, by setting the amino group in the structure of R ₁ in the above formula (1) to be a secondary amino group or to be a primary amino group having a tertiary or quaternary carbon adjacent to the amino group, the interaction between the amino group and the carbonyl group in the crosslinked aromatic polyamide is not dense, and the distance can be ensured. This can suppress clogging of the holes due to the interaction, and can ensure water permeability.

The amino group in the structure of R ₁ in the above formula (1) is more preferably a secondary amino group from the viewpoint of further suppressing the above interaction and further improving the water permeability. Specifically, W ₃ in the structure of R ₁ in the above formula (1) is preferably an aliphatic chain having 1 to 6 carbon atoms which may contain a heteroatom or a branched chain.

In addition, W ₁～W₃ in the structures of R ₁ in the above formula (1), that is, the above formulas (2) to (4), does not contain a carbonyl group from the viewpoint of suppressing clogging of the hole due to the above interaction.

Further, since an aliphatic chain exists around the amino group, if the number of carbon atoms of the aliphatic chain becomes large, the formation of the continuous hydrogen bond is hindered. Accordingly, in the above formulae (2) to (4), when L ₁ or W ₁～W₃ is an aliphatic chain, the number of carbon atoms is 1 to 6, preferably 1 to 2, and more preferably 1.

In the formulae (2) to (4), when W ₃ is a hydrogen atom, the total number of carbon atoms of W ₁ and W ₂ is 2 to 12, preferably 2 to 4, and more preferably 2.

Specific examples of R ₁ in the above formula (1) include the following formulas (5) to (8). From the viewpoint of the formation of continuous hydrogen bonds, R ₁ in the above formula (1) is preferably represented by any one of the following formulas (5) to (8).

[ Chemical formula 8]

The ratio of (molar equivalent of amino group+molar equivalent of carboxyl group)/(molar equivalent of amide group) of the separation functional layer measured by DD-MAS- ¹³ C solid state NMR method is preferably 0.56 or less. When the ratio is 0.56 or less, the polyamide in the separation functional layer has a dense network structure, and the salt removal rate is improved. The ratio is more preferably 0.50 or less, still more preferably 0.45 or less, and particularly preferably 0.42 or less. From the viewpoint of ensuring a water-permeable passage in the separation functional layer, the ratio is preferably 0.30 or more, more preferably 0.35 or more.

As a method for adjusting the ratio of (molar equivalent of amino group + molar equivalent of carboxyl group)/(molar equivalent of amide group) of the separation functional layer, there is a method of polycondensing a polyfunctional aromatic amine with a polyfunctional aromatic acyl chloride and then drying, and a method of polymerizing a high-concentration polyfunctional aromatic amine aqueous solution and a high-concentration polyfunctional aromatic acyl chloride solution in the polymerization step.

The measurement of the functional group in the separation functional layer by DD-MAS- ¹³ C solid NMR can be performed as follows.

When the composite semipermeable membrane includes a base material, the base material is peeled off to obtain a separation functional layer and a microporous support layer, and then the microporous support layer is dissolved and removed to obtain the separation functional layer. The resulting separated functional layer was measured by DD/MAS- ¹³ C solid-state NMR, and the ratio of the amounts of the functional groups was calculated from the comparison of the integrated values of the carbon peaks of the functional groups or the carbon peaks to which the functional groups were bonded. For the DD-MAS- ¹³ C solid state NMR measurement, CMX-300 manufactured by CHEMAGNETICS, for example, can be used.

<2 > Method for producing composite semipermeable Membrane

The method for producing a composite semipermeable membrane according to the present embodiment includes a polymerization step and a modification step described below.

(1) Polymerization process: step of forming layer containing crosslinked aromatic polyamide

The polymerization step is a step of forming a layer containing a crosslinked aromatic polyamide having a partial structure represented by the following formula (9) on a microporous support layer.

[ Chemical formula 9]

The symbols in the above formula (9) have the following meanings:

The preferable mode of each group represented by Ar ₁～Ar₃ and R ₂～R₅ in the formula (9) is the same as that of the formula (1).

Specifically, the polymerization step is a step of forming a crosslinked aromatic polyamide by polycondensing a polyfunctional aromatic amine and a polyfunctional aromatic acid chloride, and more specifically, comprises: a step of bringing an aqueous solution containing a polyfunctional aromatic amine (hereinafter also simply referred to as a polyfunctional aromatic amine aqueous solution) into contact with the microporous support layer; and thereafter bringing an organic solvent solution containing a polyfunctional aromatic acid chloride (hereinafter also simply referred to as a polyfunctional aromatic acid chloride solution) into contact with the microporous support layer.

Preferably, at least one of the polyfunctional aromatic amine and the polyfunctional aromatic acyl chloride is 3 or more functions. Thus, a rigid molecular chain can be obtained, and a good pore structure for removing fine solutes such as hydrated ions and boron can be formed.

The polyfunctional aromatic amine is an aromatic amine having at least 2 primary amino groups and at least 1 secondary amino group in one molecule, and at least 1 amino group in the amino groups is a primary amino group. Examples of the polyfunctional aromatic amine include compounds having 2 amino groups bonded to the aromatic ring in any of the ortho, meta and para positions, such as o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m-diaminopyridine and p-diaminopyridine, and 1,3, 5-triaminobenzene, 1,2, 4-triaminobenzene, 3, 5-diaminobenzoic acid, 3-aminobenzylamine and 4-aminobenzylamine. Of these polyfunctional aromatic amines, 1 may be used, or a plurality of these polyfunctional aromatic amines may be used in combination. In particular, from the viewpoint of obtaining a film excellent in selective separation property, permeability and heat resistance, it is preferable to use at least 1 compound selected from m-phenylenediamine, p-phenylenediamine and 1,3, 5-triaminobenzene as the polyfunctional aromatic amine. Among them, m-phenylenediamine is preferable from the viewpoints of easiness of obtaining and easiness of handling.

The polyfunctional aromatic acyl chloride is an aromatic acyl chloride having at least 2 chlorocarbonyl groups in one molecule. Examples of the 3-functional acid chloride include trimesoyl chloride, and examples of the 2-functional acid chloride include biphenyl dicarboxylic acid chloride, azobenzene dicarboxylic acid chloride, terephthaloyl chloride, isophthaloyl chloride, and naphthalene dicarboxylic acid chloride. The polyfunctional aromatic acid chloride may be used in an amount of 1 or in combination of two or more thereof. In particular, from the viewpoint of obtaining a film excellent in selective separation property, permeability and heat resistance, polyfunctional aromatic acid chlorides having 2 to 4 chlorocarbonyl groups in one molecule are preferable, and trimesoyl chloride is more preferable.

That is, the polyfunctional aromatic amine and the polyfunctional aromatic acid chloride are preferably m-phenylenediamine and trimesoyl chloride, respectively.

The concentration of the polyfunctional aromatic amine in the polyfunctional aromatic amine aqueous solution is preferably in the range of 0.1 mass% to 20 mass%, more preferably in the range of 0.5 mass% to 15 mass%. When the concentration of the polyfunctional aromatic amine is within this range, sufficient desalting performance and water permeability can be obtained.

The contacting of the aqueous polyfunctional aromatic amine solution with the microporous support layer is preferably performed uniformly and continuously on the microporous support layer. Specifically, for example, a method of applying an aqueous polyfunctional aromatic amine solution to the microporous support layer, a method of immersing the microporous support layer in an aqueous polyfunctional aromatic amine solution, and the like are mentioned. The contact time between the microporous support layer and the aqueous polyfunctional aromatic amine solution is preferably 1 second to 10 minutes, more preferably 10 seconds to 3 minutes.

After bringing the aqueous polyfunctional aromatic amine solution into contact with the microporous support layer, it is preferable to drain the liquid so that no droplets remain on the film. By draining the liquid, it is possible to prevent the residual liquid droplet portion from becoming a film defect after the formation of the microporous support layer, and thus to reduce the salt removal performance. As a method of draining liquid, a method of holding a support film in which an aqueous polyfunctional aromatic amine solution is contacted in a vertical direction and naturally flowing down an excessive amount of the aqueous solution, a method of forcibly draining liquid by blowing a flow of nitrogen gas or the like from an air nozzle, and the like can be used. After the liquid discharge, the film surface may be dried to remove a part of the water content of the aqueous solution.

The concentration of the polyfunctional aromatic acyl chloride in the polyfunctional aromatic acyl chloride solution is preferably in the range of 0.01 mass% to 10 mass%, more preferably in the range of 0.02 mass% to 2.0 mass%. By setting the concentration of the polyfunctional aromatic acid chloride to 0.01 mass% or more, a sufficient reaction rate can be obtained, and by setting the concentration to 10 mass% or less, the occurrence of side reactions can be suppressed.

The organic solvent in the polyfunctional aromatic acid chloride solution is preferably a solvent which is not miscible with water and which dissolves the polyfunctional aromatic acid chloride without damaging the support film, as long as it is inactive to the polyfunctional aromatic amine and the polyfunctional aromatic acid chloride.

Preferable examples of the organic solvent include hydrocarbon compounds such as n-nonane, n-decane, n-undecane, n-dodecane, isooctane, isodecane, isododecane, and mixed solvents thereof.

The contact of the polyfunctional aromatic acid chloride solution with the microporous support layer may be performed in the same manner as the method for coating the microporous support layer with the polyfunctional aromatic amine aqueous solution.

The membrane may be dried after the polyfunctional aromatic acid chloride solution is brought into contact with the microporous support layer. By drying, the separation functional layer can be adjusted by (molar equivalent of amino group+molar equivalent of carboxyl group)/(molar equivalent of amide group).

The drying method is not particularly limited, and may be performed using, for example, an oven, a heat gun, a heat generating device, or the like.

The temperature at the time of drying, that is, the temperature at the time of polycondensation of the polyfunctional amino group and the polyfunctional aromatic acid chloride is preferably in the range of 50 to 100 ℃, more preferably in the range of 60 to 90 ℃, even more preferably in the range of 65 to 90 ℃, from the viewpoint of appropriately adjusting (molar equivalent of amino group+molar equivalent of carboxyl group)/(molar equivalent of amide group) of the separation functional layer.

In addition, in order to remove excess solution remaining on the film surface of the dried film, liquid may be discharged in the same manner as the aqueous polyfunctional aromatic amine solution. As a method of draining the liquid, a mixed fluid of water and air may be used in addition to the methods exemplified for the aqueous polyfunctional aromatic amine solution.

At the interface between the aqueous polyfunctional aromatic amine solution and the polyfunctional aromatic acid chloride solution, the polyfunctional amino group as a monomer is polycondensed with the polyfunctional aromatic acid chloride to thereby produce the crosslinked aromatic polyamide represented by the above formula (9).

By washing the thus obtained film with hot water, unreacted monomers can be removed. The temperature of the hot water is preferably 40 ℃ to 100 ℃, more preferably 60 ℃ to 100 ℃.

Since the crosslinked aromatic polyamide-containing layer has a separation function even before the modification step described later, the layer may be referred to as a separation function layer, and the composite membrane including the base material, the microporous support layer, and the crosslinked aromatic polyamide-containing layer may be referred to as a composite semipermeable membrane.

(2) Modification step

The modification step is a step of modifying the terminal amino group of the crosslinked aromatic polyamide represented by the above formula (9) with an amino group-containing aliphatic carboxylic acid represented by any one of the following formulas (10) to (12). Through this step, the structure of the above formula (1) is formed.

The term "terminal amino group of the crosslinked aromatic polyamide represented by the formula (9)" means "-NHR ₂" in the formula (9).

[ Chemical formula 10]

The symbols in the formulae (10) to (12) have the following meanings:

L ₁ is a single bond or an aliphatic chain having 1 to 6 carbon atoms.

L ₁ in the formulae (10) to (12) is preferably a single bond in view of suppressing the decrease in hydrophilicity of the crosslinked aromatic polyamide constituting the separation functional layer.

The preferable mode of each group represented by W ₁～W₃ in the formulas (10) to (12) is the same as that of the formula (1).

The compounds represented by the formulas (10) to (12) are amino group-containing aliphatic carboxylic acids. Specific examples of the amino group-containing aliphatic carboxylic acid include sarcosine, guanidinoacetic acid, N-methylalanine, N-ethylglycine, proline, azetidine-2-carboxylic acid, hydroxyproline, 3, 4-dehydroproline, homoproline, serine, threonine, allothreonine, lysine, arginine, cysteine, 2-aminoisobutyric acid, 2-aminobutyric acid, valine, leucine, isoleucine, methionine, and glucosamine.

Among them, from the viewpoint of the formation of continuous hydrogen bonds, at least 1 compound selected from the group consisting of proline, sarcosine, 2-aminoisobutyric acid and threonine is preferable as the amino group-containing aliphatic carboxylic acid.

In the condensation reaction (modification step) with the terminal amino group of the crosslinked aromatic polyamide represented by the above formula (9), at least 1 compound selected from the compounds represented by the above formulas (10) to (12) is used. These compounds may be used alone or in combination of 2 or more.

As a method for condensing (modifying) the amino group-containing aliphatic carboxylic acid represented by any one of the formulas (10) to (12) (hereinafter, also referred to as "amino group-containing aliphatic carboxylic acid") to the crosslinked aromatic polyamide represented by the above formula (9), the amino group-containing aliphatic carboxylic acid may be applied to the separation functional layer of the composite semipermeable membrane to react the same, or the composite semipermeable membrane including the separation functional layer may be immersed in the amino group-containing aliphatic carboxylic acid or a solution including the same to react the same. After the production of the composite semipermeable membrane element described later, a solution containing an aliphatic carboxylic acid having an amino group may be subjected to a liquid passing treatment to react the solution.

The reaction time, temperature and concentration of the above-mentioned amino group-containing aliphatic carboxylic acid in the form of an aqueous solution or directly applied to the composite semipermeable membrane can be appropriately adjusted according to the type of amino group-containing aliphatic carboxylic acid and the application method. For example, when the concentration of the amino group-containing aliphatic carboxylic acid is 0.1mmol/L, the reaction time is preferably 30 minutes or longer and the reaction temperature is preferably 10℃or longer.

In the modification step, a solution containing the above-mentioned amino group-containing aliphatic carboxylic acid may be used, or a solvent-free liquid containing the amino group-containing aliphatic carboxylic acid may be used. In the case of using a solution, the solvent may be changed depending on the kind of the amino group-containing aliphatic carboxylic acid, and water or isopropyl alcohol may be exemplified.

In the case of condensing the above amino group-containing aliphatic carboxylic acid, various reaction auxiliaries (condensation accelerators) are preferably used as needed for efficient and short-time reaction. Examples of the condensation accelerator include sulfuric acid, 4- (4, 6-dimethoxy-1, 3, 5-triazin-2-yl) -4-methylmorpholine chloride (hereinafter referred to as DMT-MM), 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride, N '-dicyclohexylcarbodiimide, N' -diisopropylcarbodiimide, N, N '-carbonyldiimidazole, 1' -carbonylbis (1, 2, 4-triazole), 1H-benzotriazol-1-yloxytris (dimethylamino) phosphonium hexafluorophosphate, (7-azabenzotriazol-1-yloxy) tripyrrolidinylphosphinium hexafluorophosphate, chlorotriazolylphosphinium hexafluorophosphate, bromotris (dimethylamino) phosphonium hexafluorophosphate, 3- (diethoxyphosphino) -1,2, 3-benzotriazin-4 (3H) -one, O- (benzotriazol-1-yl) -N, N, N ', N' -tetramethyluronium hexafluorophosphate, O- (7-azabenzotriazol-1-yl) -N, N, N ', N' -tetramethyluronium hexafluorophosphate, O- (N-succinimidyl) -N, N, N ', N' -tetramethyluronium tetrafluoroborate, O- (N-succinimidyl) -N, N, N ', N ' -tetramethyluronium tetrafluoroborate, O- (3, 4-dihydro-4-oxo-1, 2, 3-benzotriazin-3-yl) -N, N, N ', N ' -tetramethyluronium tetrafluoroborate, trifluoromethanesulfonic acid (4, 6-dimethoxy-1, 3, 5-triazin-2-yl) - (2-octyloxy-2-oxoethyl) dimethylammonium, S- (1-oxide-2-pyridinyl) -N, N, N ', N ' -tetramethylthiourea uronium tetrafluoroborate, O- [ 2-oxo-1 (2H) -pyridinyl ] -N, N, N ', N ' -tetramethyluronium tetrafluoroborate, { [ (1-cyano-2-ethoxy-2-oxoethylidene) amino ] oxy } -4-morpholinomethylene } dimethylammonium hexafluorophosphate, 2-chloro-1, 3-dimethylimidazolium hexafluorophosphate, 1- (chloro-1-pyrrolidinylmethylene) hexafluorophosphate, N, N ' -tetramethyluronium hexafluorophosphate, and the like.

The method for producing a composite semipermeable membrane may be one comprising a step of forming a microporous support layer on a substrate before the step of forming the separation functional layer.

In addition, various post-treatments may be performed after the separation functional layer is formed.

<3 > Utilization of composite semipermeable Membrane

The composite semipermeable membrane is suitably used as a spiral composite semipermeable membrane element, in which a water supply passage material such as a plastic net, a water permeable passage material such as tricot, and a membrane for improving pressure resistance as required are wound around a cylindrical water collecting pipe perforated with a plurality of holes. Further, the components may be connected in series or in parallel and stored in a pressure vessel to produce a composite semipermeable membrane module.

The composite semipermeable membrane, or the elements and components thereof, may be combined with a pump for supplying water to the composite semipermeable membrane, a device for pretreating the water, or the like, to thereby constitute a fluid separation device. By using this separator, the supplied water can be separated into the permeate water such as drinking water and the concentrate water that does not permeate the membrane, and water that meets the purpose can be obtained.

The feed water treated by the composite semipermeable membrane includes a liquid mixture containing 500mg/L to 100g/L of TDS (Total Dissolved Solids: total dissolved solid content) such as seawater, salt water, and waste water. In general, TDS refers to the total dissolved solid component amount, expressed as "mass/volume" or "weight ratio". By definition, the solution obtained by filtration through a 0.45 μm filter can be evaporated at a temperature of 39.5 ℃ to 40.5 ℃ and calculated from the weight of the residue, and converted from the practical salinity (S) more easily.

When the operating pressure of the fluid separation device is high, the solute removal rate increases, but the energy required for operation also increases, and when considering the durability of the composite semipermeable membrane, the operating pressure at which the water to be treated permeates the composite semipermeable membrane is preferably 0.5MPa to 10 MPa. When the feed water temperature is high, the solute removal rate decreases, but as the feed water temperature decreases, the membrane permeation flux also decreases, so the feed water temperature is preferably 5 ℃ or higher and 45 ℃ or lower. In addition, if the pH of the feed water is high, scaling of magnesium or the like may occur when the feed water is of a high solute concentration such as seawater, and further, the membrane may be deteriorated by operating at a high pH, so that the operation in the neutral region is preferable.

As described above, the present specification discloses the following constitution.

<1> A composite semipermeable membrane comprising a microporous support layer and a separation functional layer provided on the microporous support layer, wherein the separation functional layer comprises a crosslinked aromatic polyamide comprising a partial structure represented by the following formula (1).

[ Chemical formula 11]

[ The symbols in the above formula (1) have the following meanings:

[ Chemical formula 12]

[ The symbols in the above formulae (2) to (4) have the following meanings:

L ₁ is a single bond or an aliphatic chain having 1 to 6 carbon atoms.

<2> The composite semipermeable membrane according to <1>, wherein the separation functional layer has a ratio of (molar equivalent of amino group + molar equivalent of carboxyl group)/(molar equivalent of amide group) of 0.56 or less as measured by DD-MAS- ¹³ C solid state NMR method.

<3> The composite semipermeable membrane according to <1> or <2>, wherein L ₁ in the formulae (2) to (4) is a single bond.

The composite semipermeable membrane according to any of <1> to <3>, wherein W ₃ in formulae (2) to (4) is an aliphatic chain having 1 to 6 carbon atoms which may contain a heteroatom or a branched chain.

The composite semipermeable membrane according to any one of <1> to <4>, wherein R ₁ in the formula (1) is represented by any one of the following formulas (5) to (8).

[ Chemical formula 13]

<6> A method for producing a composite semipermeable membrane, comprising:

[ Chemical formula 14]

[ The symbols in the above formula (9) have the following meanings:

[ Chemical formula 15]

[ The symbols in the above formulae (10) to (12) have the following meanings:

L ₁ is a single bond or an aliphatic chain having 1 to 6 carbon atoms.

<7> The method for producing a composite semipermeable membrane according to <6>, wherein L ₁ in the formulae (10) to (12) is a single bond.

<8> The method for producing a composite semipermeable membrane according to <6> or <7>, wherein said aliphatic carboxylic acid having an amino group is at least one compound selected from the group consisting of proline, sarcosine, 2-aminoisobutyric acid and threonine.

Examples

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. Hereinafter, the term "composite semipermeable membrane" may be used regardless of the time and place of the modification step.

The performance of the composite semipermeable membrane obtained below was evaluated as follows.

< Evaluation of Performance of composite semipermeable Membrane >

(Salt removal rate)

Seawater (TDS concentration 3.5%) adjusted to a temperature of 25 ℃ and a ph of 6.5 was supplied at an operating pressure of 5.5MPa to obtain permeate water.

The salt removal rate was determined from the TDS of the obtained permeate water by the following formula.

Salt removal rate (%) =100× {1- (TDS concentration in permeate water/TDS concentration in feed water) }

(Membrane permeation flux)

The membrane permeation flux (m ³/m²/day) was determined from the water permeation amount (m ³) per 1 square meter of the membrane surface obtained under the above conditions.

< Quantification of carboxyl amino amide group >

The substrate was physically peeled off from the 5m ² composite semipermeable membrane, and the microporous support layer and the separation functional layer were recovered. After the mixture was allowed to stand for 24 hours and dried, the microporous support layer and the separation functional layer were added to a beaker containing methylene chloride in small amounts and stirred to dissolve the polymer constituting the microporous support layer. The insoluble material in the beaker was recovered with filter paper. The insoluble matter was placed in a beaker containing methylene chloride and stirred, and the insoluble matter in the beaker was recovered. This operation was repeated until no elution of the polymer forming the microporous support layer was detected in the methylene chloride solution. The recovered separation functional layer was dried with a vacuum dryer to remove residual methylene chloride. The obtained separation functional layer was frozen and pulverized to prepare a powdery sample, which was sealed in a sample tube for measurement by a solid-state NMR method, and measured by a DD-MAS- ¹³ C solid-state NMR method.

DD-MAS- ¹³ C solid state NMR was measured using CMX-300 manufactured by CHEMAGNETICS.

The measurement conditions are as follows.

Reference substance: polydimethylsiloxane (internal standard: 1.56 ppm)

Sample rotation speed: 10.5kHz

Pulse repetition time: 100s

Based on the obtained spectrum, peak segmentation is performed for each peak from the carbon atom to which each functional group is bonded, and the functional group amount ratio is determined based on the area of the segmented peak.

(Production of support film)

A16.0% by mass DMF solution of polysulfone UDELp-3500, manufactured by Solvay Advanced Polymers Co., ltd was cast at 25℃in a thickness of 200 μm onto a polyester nonwoven fabric (aeration rate 2.0cc/cm ²/sec) as a base material. It was immediately immersed in pure water, and left for 5 minutes, thereby allowing it to solidify. Thus, a support film having a substrate and a microporous support layer was produced. The total thickness of the substrate and the microporous support layer was 150. Mu.m.

Reference example 1

The support film thus obtained was immersed in a3 mass% aqueous solution of m-phenylenediamine (m-PDA) for 2 minutes. The support film was slowly lifted in the vertical direction, and nitrogen was blown by a gas nozzle, whereby excess aqueous solution was removed from the surface of the support film. A decane solution at 40℃containing trimesic chloride (TMC) in an amount of 0.165% by mass was applied in such a manner that the surface was completely wetted in an environment controlled at 40℃and then dried in an oven at 75℃for 1 minute. Then, the support film was made vertical, and the excess solution was drained and removed. Thus, a composite semipermeable membrane of reference example 1 having a layer of crosslinked aromatic polyamide on a support membrane was obtained.

Reference example 2

The support film thus obtained was immersed in a 3 mass% aqueous solution of m-phenylenediamine (m-PDA) for 2 minutes. The support film was slowly lifted in the vertical direction, and nitrogen was blown by a gas nozzle, whereby excess aqueous solution was removed from the surface of the support film. A decane solution containing 0.165 mass% of trimesoyl chloride (TMC) at 40℃was applied in an atmosphere controlled at 40℃so that the surface was completely wetted, allowed to stand for 1 minute, and then the support film was made to stand upright, and the excess solution was drained and removed. Thus, a composite semipermeable membrane of reference example 2 having a layer of crosslinked aromatic polyamide on a support membrane was obtained.

Comparative example 1

The composite semipermeable membrane obtained in referential example 1 was immersed in an aqueous solution of pH8 containing acetic acid and DMT-MM at a concentration of 100mmol/L, respectively, at 25℃for 1 hour. The composite semipermeable membrane obtained was immersed in RO water, whereby the composite semipermeable membrane of comparative example 1 was obtained.

Comparative example 2

The composite semipermeable membrane obtained in referential example 1 was immersed in an aqueous solution of pH8 containing glycine and DMT-MM at a concentration of 100mmol/L, respectively, at 25℃for 1 hour. The composite semipermeable membrane obtained was immersed in RO water, whereby a composite semipermeable membrane of comparative example 2 was obtained.

Comparative example 3

The composite semipermeable membrane obtained in referential example 1 was immersed in an aqueous solution of pH8 containing N, N-dimethylglycine and DMT-MM at a concentration of 100mmol/L, respectively, at 25℃for 1 hour. The composite semipermeable membrane obtained was immersed in RO water, whereby a composite semipermeable membrane of comparative example 3 was obtained.

Comparative example 4

The composite semipermeable membrane obtained in referential example 1 was immersed in an aqueous solution of pH8 containing acetic uric acid and DMT-MM at a concentration of 100mmol/L, respectively, at 25℃for 1 hour. The composite semipermeable membrane obtained was immersed in RO water, whereby a composite semipermeable membrane of comparative example 4 was obtained.

Example 1

The composite semipermeable membrane obtained in referential example 1 was immersed in an aqueous solution of pH8 containing sarcosine and DMT-MM at a concentration of 100mmol/L, respectively, at 25℃for 1 hour. The composite semipermeable membrane obtained was immersed in RO water, whereby the composite semipermeable membrane of example 1 was obtained.

Example 2

The composite semipermeable membrane obtained in referential example 1 was immersed in an aqueous solution of pH8 containing proline and DMT-MM at a concentration of 100mmol/L, respectively, at 25℃for 1 hour. The obtained composite semipermeable membrane was immersed in RO water, whereby the composite semipermeable membrane of example 2 was obtained.

Example 3

The composite semipermeable membrane obtained in referential example 1 was immersed in an aqueous solution of pH8 containing threonine and DMT-MM at a concentration of 100mmol/L, respectively, at 25℃for 1 hour. The obtained composite semipermeable membrane was immersed in RO water, whereby the composite semipermeable membrane of example 3 was obtained.

Example 4

The composite semipermeable membrane obtained in referential example 1 was immersed in an aqueous solution of pH8 containing 2-aminoisobutyric acid and DMT-MM at a concentration of 100mmol/L, respectively, at 25℃for 1 hour. The obtained composite semipermeable membrane was immersed in RO water, whereby the composite semipermeable membrane of example 4 was obtained.

Example 5

The composite semipermeable membrane obtained in referential example 1 was immersed in an aqueous solution of pH8 containing 2-aminobutyric acid and DMT-MM at a concentration of 100mmol/L, respectively, at 25℃for 1 hour. The obtained composite semipermeable membrane was immersed in RO water, whereby the composite semipermeable membrane of example 5 was obtained.

Example 6

The composite semipermeable membrane obtained in referential example 1 was immersed in an aqueous solution of pH8 containing 3-aminobutyric acid and DMT-MM at a concentration of 100mmol/L, respectively, at 25℃for 1 hour. The composite semipermeable membrane obtained was immersed in RO water, whereby the composite semipermeable membrane of example 6 was obtained.

Example 7

The composite semipermeable membrane obtained in referential example 2 was immersed in an aqueous solution of pH8 containing sarcosine and DMT-MM at a concentration of 100mmol/L, respectively, at 25℃for 1 hour. The obtained composite semipermeable membrane was immersed in RO water, whereby the composite semipermeable membrane of example 7 was obtained.

TABLE 1

As is clear from the results of table 1, examples 1 to 7, which are composite semipermeable membranes according to an embodiment of the present invention, exhibited excellent salt removal properties while maintaining water permeability, as compared with comparative examples 1 to 4.

While the preferred embodiments of the present application have been described above, the present application is not limited to the above embodiments, and various modifications and substitutions may be made to the above embodiments without departing from the scope of the present application. The present application is based on Japanese patent application No. 2021-213663 filed on 12 months at 2021, japanese patent application No. 2022-030301 filed on 2 months at 2022, and Japanese patent application No. 2022-030302 filed on 28 months at 2022, the contents of which are incorporated herein by reference.

Industrial applicability

According to the present invention, a composite semipermeable membrane having high desalination performance and water permeability with practical use can be provided.

Claims

1. A composite semipermeable membrane comprising a microporous supporting layer and a separation functional layer provided on the microporous supporting layer, wherein the separation functional layer contains a cross-linked aromatic polyamide having a partial structure represented by the following formula (1):

[Chemical formula 1]

The symbols in the above formula (1) have the following meanings:

Ar ₁ to Ar ₃ are each independently an aromatic ring having 5 to 14 carbon atoms which may have a substituent;

R ₁ represents a structure represented by any one of the following formulae (2) to (4);

R ₂ to R ₅ are each independently a hydrogen atom or an aliphatic chain having 1 to 10 carbon atoms,

[Chemical formula 2]

The symbols in the above formulas (2) to (4) have the following meanings:

_L1 is a single bond or an aliphatic chain having 1 to 6 carbon atoms;

W ₁ to W ₃ are each independently a hydrogen atom, or an aliphatic chain having 1 to 6 carbon atoms which may contain a heteroatom or a branch, and at least one of W ₁ to W ₃ is an aliphatic chain having 1 to 6 carbon atoms which may contain a heteroatom or a branch,

When _W3 is a hydrogen atom, the total number of carbon atoms of _W1 and _W2 is 2 or more and 12 or less, and _W1 to _W3 do not contain a carbonyl group.

2 . The composite semipermeable membrane according to claim 1 , wherein the ratio of (molar equivalent of amino group+molar equivalent of carboxyl group)/(molar equivalent of amide group) of the separation functional layer measured by DD-MAS- ¹³ C solid NMR method is 0.56 or less.

3. The composite semipermeable membrane according to claim 1 or 2, wherein _L1 in the formula (2) to (4) is a single bond.

4. The composite semipermeable membrane according to claim 1 or 2, wherein _W3 in the formulae (2) to (4) is an aliphatic chain having 1 to 6 carbon atoms which may contain a heteroatom or a branch.

5. The composite semipermeable membrane according to claim 1 or 2, wherein _R1 in the formula (1) is represented by any one of the following formulas (5) to (8):

[Chemical formula 3]

6. A method for producing a composite semipermeable membrane, comprising:

(a) forming a layer containing a cross-linked aromatic polyamide having a partial structure of the following formula (9) on the microporous supporting layer; and

(b) a step of modifying the terminal amino group of the crosslinked aromatic polyamide with an amino group-containing aliphatic carboxylic acid represented by any one of the following formulas (10) to (12),

[Chemical formula 4]

The symbols in the above formula (9) have the following meanings:

[Chemical formula 5]

The symbols in the above formulas (10) to (12) have the following meanings:

_L1 is a single bond or an aliphatic chain having 1 to 6 carbon atoms;

W ₁ to W ₃ are each independently a hydrogen atom, or an aliphatic chain having 1 to 6 carbon atoms which may contain a heteroatom or a branch, and at least one of W ₁ to W ₃ is an aliphatic chain having 1 to 6 carbon atoms which may contain a heteroatom or a branch;

7 . The method for producing a composite semipermeable membrane according to claim 6 , wherein L ₁ in the formulas (10) to (12) is a single bond.

8 . The method for producing a composite semipermeable membrane according to claim 6 , wherein the amino group-containing aliphatic carboxylic acid is at least one compound selected from the group consisting of proline, sarcosine, 2-aminoisobutyric acid, and threonine.