WO2017110898A1

WO2017110898A1 - Composite semipermeable membrane

Info

Publication number: WO2017110898A1
Application number: PCT/JP2016/088153
Authority: WO
Inventors: 佐藤　一樹; 佐々木　崇夫
Original assignee: 東レ株式会社
Priority date: 2015-12-25
Filing date: 2016-12-21
Publication date: 2017-06-29
Also published as: JPWO2017110898A1; CN108430612A; CN108430612B

Abstract

A composite semipermeable membrane according to the present invention is provided with a support membrane and a separation function layer. In the membrane, the separation function layer contains an aromatic polyamide; the aromatic polyamide contains a nitro group as a functional group that is bound to an aromatic ring; when the total number, which is represented by A, of nitrogen atoms derived from the nitro group in the aromatic polyamide and the total number, which is represented by B, of nitrogen atoms in the aromatic polyamide are analyzed by X-ray photoelectron spectroscopy, the separation function layer satisfies the formula: C-D ≥ 0.010 wherein C represents an A/B value obtained when X-ray is emitted from one surface of the separation function layer and D represents an A/B value obtained when X-ray is emitted from the other surface of the separation function layer; and the other surface of the separation function layer is in contact with the support membrane.

Description

Composite semipermeable membrane

The present invention relates to a composite semipermeable membrane useful for selective separation of a liquid mixture, and relates to a composite semipermeable membrane having high oxidation resistance, acid resistance and alkali resistance.

Regarding the separation of mixtures, there are various techniques for removing substances (eg, salts) dissolved in a solvent (eg, water), but in recent years, the use of membrane separation methods has expanded as a process for saving energy and resources. is doing. Membranes used in membrane separation methods include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes. These membranes can be used for beverages such as seawater, brine, and water containing harmful substances. It is used to obtain water, to manufacture industrial ultrapure water, to treat wastewater, to recover valuable materials.

The majority of currently marketed reverse osmosis membranes and nanofiltration membranes are composite semipermeable membranes, which have an active layer in which a gel layer and a polymer are cross-linked on a microporous support membrane, and on a microporous support membrane. And having an active layer in which monomers are polycondensed. Among them, a composite semipermeable membrane obtained by coating a separation function layer made of a crosslinked polyamide obtained by polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide on a microporous support membrane (Patent Documents 1 to 4). ) Is widely used as a separation membrane with high permeability and selective separation.

However, if the composite semipermeable membrane is continuously used, there is a problem that the separation performance of the membrane deteriorates due to contact with an oxidizing substance such as free chlorine contained in the water to be treated. In addition, dirt adheres to the membrane surface with the elapsed time of use, and the membrane permeation flux of the membrane decreases. Therefore, chemical cleaning with acid, alkali or the like is required after a certain period of operation, but there is a problem that the separation performance of the membrane is lowered.

Therefore, in order to continue stable operation over a long period of time, it is hoped to develop a composite semipermeable membrane with high oxidation resistance and little change in membrane performance before and after cleaning with chemicals such as acids and alkalis, that is, high acid resistance. It is rare.

As means for improving oxidation resistance, Patent Documents 5 and 6 disclose a method in which a persulfate is brought into contact with a composite semipermeable membrane.

Japanese Unexamined Patent Publication No. 55-147106 Japanese Unexamined Patent Publication No. Sho 62-121603 Japanese Unexamined Patent Publication No. Sho 63-218208 Japanese Unexamined Patent Publication No. 2001-79372 Japanese Unexamined Patent Publication No. 2008-100214 Japanese Unexamined Patent Publication No. 2010-234284

Although the films disclosed in Patent Documents 5 and 6 are excellent in oxidation resistance, a film having durability against alkaline chemicals is desired.
Accordingly, an object of the present invention is to provide a composite semipermeable membrane that is excellent in acid resistance and alkali resistance, in addition to oxidation resistance, having little change in membrane performance even by chemical cleaning.

In order to achieve the above object, the composite semipermeable membrane of the present invention has the following configurations [1] to [6].
[1] A composite semipermeable membrane comprising a support membrane and a separation functional layer provided on the support membrane, wherein the separation functional layer comprises a polyfunctional aromatic amine and a polyfunctional aromatic carboxylic acid An aromatic polyamide that is a polymer with a derivative, the aromatic polyamide has a nitro group as a functional group bonded to an aromatic ring, and the separation functional layer is derived from a nitro group in the aromatic polyamide. Assuming that the number of nitrogen atoms is A, the total number of nitrogen atoms in the aromatic polyamide is B, and A and B are analyzed by X-ray photoelectron spectroscopy (XPS), X-rays are irradiated from one surface of the separation functional layer. When A / B at the time is C and A / B when X-rays are irradiated from the other surface of the separation function layer is D, CD is 0.010 or more, and the separation function layer A composite semipermeable membrane in which the other surface is in contact with the support membrane.
[2] When the X-ray photoelectron spectroscopy (XPS) is analyzed by irradiating X-rays from the one surface of the separation functional layer, when the total number of oxygen atoms in the polyamide is E, 1.00 The composite semipermeable membrane according to [1], which satisfies ≦ E / B ≦ 1.20.
[3] The composite semipermeable membrane according to [1] or [2], wherein the CD is 0.20 or less.
[4] The composite semipermeable membrane according to any one of [1] to [3], wherein the CD is 0.030 or more.
[5] The composite semipermeable membrane according to any one of [1] to [4], which is used for treating a liquid mixture having a TDS (Total Dissolved Solids) of 500 mg / L to 100 g / L.
[6] A composite semipermeable membrane element comprising the composite semipermeable membrane according to any one of [1] to [5].

According to the present invention, a composite semipermeable membrane having high oxidation resistance, acid resistance, and alkali resistance, that is, a separation membrane can be obtained. The composite semipermeable membrane of the present invention can be suitably used particularly for seawater desalination.

I. Composite Semipermeable Membrane (1) Support Membrane In this embodiment, the support membrane includes a substrate and a porous support layer. However, the present invention is not limited to this configuration.

(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 and thermal stability is particularly preferable.
As the form of the fabric, a long fiber nonwoven fabric, a short fiber nonwoven fabric, or a woven or knitted fabric can be preferably used. Here, the long-fiber nonwoven fabric refers to a nonwoven fabric having an average fiber length of 300 mm or more and an average fiber diameter of 3 to 30 μm.

The substrate preferably has an air flow rate of 0.5 cc / cm ² / sec or more and 5.0 cc / cm ² / sec or less. When the air flow rate of the base material is within the above range, the polymer solution forming the porous support layer can be easily impregnated into the base material, so that the adhesion between the base material and the porous support layer is improved. The physical stability of the porous support membrane to be formed can be enhanced.

The thickness of the substrate is preferably in the range of 10 to 200 μm, more preferably in the range of 30 to 120 μm. In this document, unless otherwise specified, the thickness means an average value. Here, the average value represents an arithmetic average value. Specifically, the thickness is obtained by calculating an average value of thicknesses at 20 points measured at intervals of 20 μm in a direction orthogonal to the thickness direction (film surface direction) by cross-sectional observation.

(1-2) Porous Support Layer The porous support layer is intended to give strength to the separation functional layer that has substantially no separation performance such as ions and substantially has separation performance. The size and distribution of the pores of the porous support layer are not particularly limited.For example, uniform and fine pores, or gradually having fine pores from the surface on the side where the separation functional layer is formed to the other surface, and A porous support layer having a fine pore size of 0.1 nm or more and 100 nm or less on the surface on the side where the separation functional layer is formed is preferred, but the material used and its shape are not particularly limited.

Examples of the material for the porous support layer include, for example, polysulfone, polyethersulfone, polyamide, polyester, cellulosic polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, polyphenylene oxide, homopolymer or copolymer alone or Can be blended and used. Here, cellulose acetate and cellulose nitrate can be used as the cellulose polymer, and polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile and the like can be used as the vinyl polymer. Among them, homopolymers or copolymers such as polysulfone, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, and polyphenylene sulfide sulfone are preferable. More preferred is cellulose acetate, polysulfone, polyphenylene sulfide sulfone, or polyphenylene sulfone. Among these materials, polysulfone is highly stable chemically, mechanically and thermally, and is easy to mold. Can be used generally.

Specifically, it is preferable to use polysulfone composed of repeating units represented by the following chemical formula because the pore diameter of the porous support layer can be easily controlled and the dimensional stability is high.

In the above formula, n represents the number of repeating units.

The polysulfone preferably has a weight average molecular weight (Mw) of 10,000 or more and 200,000 or less when measured by gel permeation chromatography (GPC) using N-methylpyrrolidone as a solvent and polystyrene as a standard substance. 15000 or more and 100000 or less. When Mw is 10,000 or more, mechanical strength and heat resistance preferable as a porous support layer can be obtained. Moreover, when Mw is 200000 or less, the viscosity of the solution falls within an appropriate range, and good moldability can be realized.

For example, a solution of the above polysulfone in N, N-dimethylformamide (hereinafter referred to as DMF) is cast on a densely woven polyester cloth or non-woven fabric as a base material to a certain thickness, By wet coagulation with, a porous support layer having most of the surface with fine pores having a diameter of 10 nm or less can be obtained. The porous support layer only needs to be formed on at least one of the two surfaces of the substrate, and can be arbitrarily selected depending on the desired film thickness and application of the composite semipermeable membrane.

The thickness of the substrate and the porous support layer affects the strength of the composite semipermeable membrane and the packing density when it is used as an element. In order to obtain sufficient mechanical strength and packing density, the total thickness of the base material and the porous support layer is preferably 30 μm or more and 300 μm or less, and more preferably 100 μm or more and 220 μm or less. The thickness of the porous support layer is preferably 20 μm or more and 100 μm or less.

(2) Separation functional layer The separation functional layer contains an aromatic polyamide. In this document, unless otherwise specified, “polyamide” means “aromatic polyamide”. The content of polyamide in the separation functional layer is preferably 80% by weight or more, and more preferably 90% by weight or more. Note that the separation functional layer may be formed substantially only of polyamide.

Polyamide is a polymer of a polyfunctional aromatic amine and a polyfunctional aromatic carboxylic acid derivative, and can be formed by interfacial polycondensation of a polyfunctional aromatic amine and a polyfunctional aromatic carboxylic acid derivative. Here, it is preferable that at least one of the polyfunctional aromatic amine or the polyfunctional aromatic carboxylic acid derivative contains a trifunctional or higher functional compound.

The polyfunctional aromatic amine refers to an amine having at least two primary and / or secondary amino groups in one molecule. As the polyfunctional aromatic amine, for example, phenylenediamine, xylylenediamine, 1,3,5-triamine having two amino groups bonded to the benzene ring in any of the ortho, meta, and para positions. Aromatic polyfunctional amines such as aminobenzene, 1,2,4-triaminobenzene, and 3,5-diaminobenzoic acid can be mentioned. Among these, considering the selective separation property, permeability, and heat resistance of the membrane, a polyfunctional aromatic amine having 2 to 4 primary and / or secondary amino groups in one molecule is preferable. As such polyfunctional aromatic amines, m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene are preferably used. Among these, m-phenylenediamine (hereinafter referred to as m-PDA) is more preferred from the standpoint of availability and ease of handling. These polyfunctional aromatic amines may be used alone or in combination of two or more.

The polyfunctional aromatic carboxylic acid derivative refers to an aromatic acid halide having at least two carbonyl halide groups in one molecule. Examples of multifunctional aromatic carboxylic acid derivatives include trimethic acid chloride for trifunctional acid halides, biphenyl dicarboxylic acid dichloride, azobenzene dicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalene dicarboxylic acid for difunctional acid halides. Mention may be made of aromatic bifunctional acid halides such as acid chlorides. Considering the reactivity with the polyfunctional amine, the polyfunctional aromatic carboxylic acid derivative is preferably a polyfunctional carboxylic acid chloride, and considering the selective separation property and heat resistance of the membrane, The polyfunctional aromatic acid chloride having 2 to 4 carbonyl chloride groups is preferable. Among them, it is more preferable to use trimesic acid chloride from the viewpoint of easy availability and easy handling. These polyfunctional aromatic carboxylic acid derivatives may be used alone or in combination of two or more.

An aromatic polyamide has at least one nitro group as a functional group bonded to an aromatic ring. The nitro group of the aromatic polyamide is preferably an aromatic ring terminal group derived from a polyfunctional aromatic amine. When the aromatic polyamide has at least one nitro group, the oxidation resistance and acid resistance of the aromatic polyamide are improved.

A method for giving a nitro group to an aromatic polyamide is that the polyfunctional aromatic amine of the monomer constituting the aromatic polyamide or the polyfunctional aromatic carboxylic acid itself has a nitro group. Although a method of adding a chemical action may be used, a method of adding a chemical action to an aromatic polyamide later is preferable from the viewpoint of availability of monomers and ease of handling. Examples of the method of adding a chemical action include an oxidation treatment of a terminal amino group of an aromatic polyamide. Specifically, it is preferable to bring a water-soluble oxidant into contact with the composite semipermeable membrane, and examples of the water-soluble oxidant include hydrogen peroxide, peracetic acid, sodium perborate, potassium peroxymonosulfate, and the like. .

When the number of nitrogen atoms derived from the nitro group in the aromatic polyamide is A and the total number of nitrogen atoms in the aromatic polyamide is B, when A and B are measured by X-ray photoelectron spectroscopy (XPS), the separation function The A / B values measured from one side of the layer and from the other side are different. The larger the A / B on one side, the better the oxidation resistance and acid resistance, and the smaller the A / B on the other side, the higher order structure of the polyamide is maintained, so that the alkali resistance is improved.
The inventors have realized that a film excellent in all of oxidation resistance, acid resistance, and alkali resistance can be realized when the difference in A / B between one surface and the other surface of the separation functional layer is 0.010 or more. I found it. That is, when A / B when X-rays are irradiated from one surface of the separation functional layer is C and A / B when X-rays are irradiated from the other surface of the separation functional layer is D, CD It is preferable to satisfy the relationship of ≧ 0.010. The difference (C−D) is more preferably 0.030 or more. The difference (C−D) is preferably 0.20 or less.
Here, one side is the side that forms the surface of the composite semipermeable membrane, the side that supplies the raw water of the separation functional layer, and the other side is the side that is in contact with the support membrane. , Also called “front side” and “back side” on the subject.

In addition, the ratio (A / B) of the nitrogen atom number A derived from the nitro group and the total nitrogen atom number B can be obtained by X-ray photoelectron spectroscopy (XPS) analysis of the polyamide. Specifically, “Journal of Polymer Science”, Vol. 26, 559-572 (1988) and “Journal of the Adhesion Society of Japan”, Vol. 27, no. 4 (1991), X-ray photoelectron spectroscopy (XPS) can be used. A and B on one side (surface) of the separation functional layer can be measured by irradiating X-rays from the side of the separation functional layer where raw water is supplied. A and B on the other side (back side) of the separation functional layer are peeled off from the composite semipermeable membrane and placed on a substrate wetted with an alcohol such as ethanol so that the surface of the separation functional layer is in contact with dichloromethane. It can measure by removing a porous support layer with organic solvents, such as, and irradiating X-rays in the state where the back surface of a separation functional layer becomes an upper side. The substrate used at this time is not particularly limited, and examples thereof include a silicone resin and a silicon wafer.

Furthermore, when the total number of nitrogen atoms B and the number of oxygen atoms E are measured by irradiating one surface of the separation functional layer, that is, the surface, by satisfying 1.00 ≦ E / B ≦ 1.20, A film having a better balance of oxidation resistance, acid resistance, and alkali resistance can be obtained.

The thickness of the separation functional layer is usually in the range of 0.01 to 1 μm, preferably in the range of 0.1 to 0.5 μm, in order to obtain sufficient separation performance and permeated water amount.

II. Manufacturing Method Next, the manufacturing method of the composite semipermeable membrane will be described with specific examples.
The polyamide which is the skeleton of the separation functional layer in the composite semipermeable membrane is, for example, an aqueous solution containing the above-mentioned polyfunctional aromatic amine and an organic material immiscible with water containing the polyfunctional aromatic carboxylic acid derivative. It is formed by performing interfacial polycondensation on the surface of the support membrane using a solvent solution (or on the surface of the porous support layer if the support membrane includes a substrate and a porous support layer).

The concentration of the polyfunctional aromatic amine in the polyfunctional aromatic amine aqueous solution is preferably in the range of 0.1 to 20% by weight, more preferably in the range of 0.5 to 15% by weight. In this range, sufficient salt removal performance and water permeability can be obtained. As long as the polyfunctional aromatic amine aqueous solution does not interfere with the reaction between the polyfunctional aromatic amine and the polyfunctional aromatic carboxylic acid derivative, a surfactant, organic solvent, alkaline compound, antioxidant, etc. May be included. The surfactant has the effect of improving the wettability of the support membrane surface and reducing the interfacial tension between the aqueous amine solution and the nonpolar solvent. The organic solvent may act as a catalyst for the interfacial polycondensation reaction, and when added, the interfacial polycondensation reaction may be efficiently performed.

The concentration of the polyfunctional aromatic carboxylic acid derivative in the organic solvent solution is preferably in the range of 0.01 to 10% by weight, and more preferably in the range of 0.02 to 2.0% by weight. A sufficient reaction rate can be obtained by setting the concentration of the polyfunctional aromatic carboxylic acid derivative to 0.01% by weight or more, and the occurrence of side reactions can be suppressed by setting the concentration to 10% by weight or less. It is. Further, it is more preferable to include an acylation catalyst such as DMF in the organic solvent solution, since interfacial polycondensation is promoted.

It is desirable that the organic solvent is immiscible with water and dissolves the polyfunctional aromatic carboxylic acid derivative and does not break the porous support membrane. The polyfunctional aromatic amine compound and the polyfunctional aromatic carboxylic acid are desirable. Any material that is inert to the acid derivative may be used. Preferable examples include hydrocarbon compounds such as n-hexane, n-octane, isooctane and n-decane.

In order to perform interfacial polycondensation on the porous support membrane, first, the above-mentioned polyfunctional aromatic amine aqueous solution is brought into contact with the support membrane. The contact is preferably performed uniformly and continuously on the support membrane surface. Specific examples include a method of coating a polyfunctional aromatic amine aqueous solution on a support membrane and a method of immersing the support membrane in a polyfunctional aromatic amine aqueous solution. The contact time between the support membrane and the polyfunctional aromatic amine aqueous solution is preferably in the range of 1 to 10 minutes, and more preferably in the range of 1 to 3 minutes.

After the polyfunctional aromatic amine aqueous solution is brought into contact with the support membrane, the solution is sufficiently drained so that no droplets remain on the membrane. By sufficiently draining the liquid, it is possible to prevent the remaining portion of the liquid droplet from becoming a film defect after the film is formed and deteriorating the film performance. As a method for draining, for example, as described in Japanese Patent Application Laid-Open No. 2-78428, the support film after contact with the polyfunctional aromatic amine aqueous solution is vertically gripped to remove excess aqueous solution. The method of making it flow down, the method of blowing off air currents, such as nitrogen from an air nozzle, and forcibly draining can be used. In addition, after draining, the membrane surface can be dried to partially remove water from the aqueous solution.

The organic solvent solution containing the polyfunctional aromatic carboxylic acid derivative is brought into contact with the polyfunctional aromatic amine aqueous solution phase thus obtained, and the skeleton of the crosslinked polyamide separation functional layer is formed by interfacial polycondensation.

The method for contacting the organic solvent solution containing the polyfunctional aromatic carboxylic acid derivative with the polyfunctional aromatic amine aqueous solution phase may be the same as the method for coating the support film with the polyfunctional aromatic amine aqueous solution.

At this time, the support membrane in contact with the organic solvent solution of the polyfunctional aromatic acid halide may be heated. The temperature for the heat treatment is 50 ° C. or higher and 180 ° C. or lower, preferably 60 ° C. or higher and 160 ° C. or lower. By heating at 50 ° C. or higher, it is possible to compensate for the decrease in reactivity associated with monomer consumption in the interfacial polymerization reaction by the effect of promoting the reaction by heat. By heating at 180 ° C. or lower, it is possible to prevent the solvent from being completely volatilized and the reaction efficiency from being significantly lowered. The heat treatment time is preferably 5 seconds or more and 180 seconds or less. The reaction promoting effect can be obtained by setting it to 5 seconds or longer, and the solvent can be prevented from completely volatilizing by setting it to 180 seconds or shorter.

As described above, after the interfacial polycondensation is performed by bringing the organic solvent solution containing the polyfunctional aromatic carboxylic acid derivative into contact with each other and the separation functional layer containing the crosslinked polyamide is formed on the support membrane, the excess solvent is liquidized. Cut it off. As a method for draining, for example, a method in which a film is held in a vertical direction and excess organic solvent is allowed to flow down and removed can be used. In this case, the holding time in the vertical direction is preferably between 1 and 5 minutes, more preferably between 1 and 3 minutes. If it is too short, the separation functional layer will not be completely formed, and if it is too long, the organic solvent will be overdried and defects will easily occur and performance will be deteriorated.

The composite semipermeable membrane obtained by the above method is subjected to a hydrothermal treatment step in the range of 40 to 100 ° C., preferably in the range of 60 to 100 ° C. for 1 to 10 minutes, more preferably 2 to 8 minutes. By adding, the solute blocking performance and water permeability of the composite semipermeable membrane can be further improved.

Next, a method for adding a nitro group on an aromatic ring derived from a functional aromatic amine by applying a chemical action to the aromatic polyamide later will be described.

There are two methods for giving a nitro group as a terminal group of polyamide, one is a method for converting a terminal amino group, and the other is a method for substitution on an unsubstituted aromatic ring. From the viewpoint of ease of control, a method of converting the terminal amino group is preferred.

An oxidation reaction is used as a method for converting the terminal amino group to a nitro group. A general oxidizing agent such as a water-soluble peroxide can be used for the oxidation reaction, but the oxidizing agent is preferably a persulfate compound from the viewpoint of reactivity with the aromatic polyamide and ease of handling. More preferably, it is potassium peroxymonosulfate.

The reaction means of the oxidizing agent and polyamide has a high introduction rate of nitro groups on the surface of the separation functional layer, and in order to have a distribution in the depth direction, for example, an aqueous solution of an oxidizing agent is applied to a composite semipermeable membrane of polyamide. A method of covering the film with the film and a method of standing still or a method of applying an aqueous solution of an oxidizing agent by spraying are preferable.

The concentration of the oxidizing agent is preferably 0.1 to 10% by weight, more preferably 0.5 to 3% by weight.

The pH of the oxidizing agent aqueous solution is not particularly limited as long as the oxidizing power of the oxidizing agent can be sufficiently exhibited, but is preferably in the range of 1.5 to 7.0.

The contact time between the aqueous oxidizing agent solution and the polyamide is preferably from 30 seconds to 20 minutes, more preferably from 1 minute to 10 minutes, in order to increase the surface nitro groups and keep the nitro groups on the back surface in contact with the support film.

The contact temperature between the oxidizing agent aqueous solution and the polyamide is preferably 10 ° C to 90 ° C, more preferably 40 ° C to 60 ° C. By carrying out the treatment at this temperature, it is possible to have many nitro groups on the surface in a short period of time, and to reduce the number of nitro groups on the inside and back surface, which is excellent in oxidation resistance, acid resistance, and alkali resistance A film can be obtained.

In order to stop the oxidation reaction after contact with the oxidizing agent, the polyamide composite membrane is brought into contact with the reducing agent. Here, the reducing agent is not particularly limited as long as it causes an oxidation-reduction reaction with the oxidizing agent to be used, but it is preferable to use any one of sodium bisulfite, sodium sulfite and sodium thiosulfate from the viewpoint of availability and handling. . They are preferably used as 0.01 to 1% by weight aqueous solutions.

The contact time with the reducing agent may be such that the oxidation reaction is stopped and the structure of the polyamide is not changed, and an immersion time of 30 seconds to 20 minutes is usually preferable.

After contact with the reducing agent, it is preferable to rinse with water in order to wash away the reducing agent remaining in the polyamide composite membrane.

The composite semipermeable membrane of the present invention formed in this way has a large number of pores together with a raw water channel material such as a plastic net, a permeate channel material such as tricot, and a film for increasing pressure resistance if necessary. Is wound around a cylindrical water collecting pipe and is suitably used as a spiral composite semipermeable membrane element. Furthermore, a composite semipermeable membrane module in which these elements are connected in series or in parallel and accommodated in a pressure vessel can be obtained.

Also, the above-described composite semipermeable membrane, its elements, and modules can be combined with a pump for supplying raw water to them, a device for pretreating the raw water, and the like to constitute a fluid separation device. By using this separation device, raw water can be separated into permeated water such as drinking water and concentrated water that has not permeated through the membrane, and water suitable for the purpose can be obtained.

The higher the operating pressure of the fluid separation device, the better the salt removal rate, but in consideration of the increased energy required for operation and the durability of the composite semipermeable membrane, the water to be treated passes through the composite semipermeable membrane. The operating pressure at that time is preferably 1.0 MPa or more and 10 MPa or less. As the feed water temperature rises, the salt removal rate decreases, but as the feed water temperature decreases, the membrane permeation flux also decreases. When the supply water pH is high, such as seawater, there is a risk that scales such as magnesium may occur and membrane deterioration due to high pH operation is a concern. preferable.

Examples of the raw water treated by the composite semipermeable membrane according to the present invention include liquid mixtures containing 500 mg / L to 100 g / L TDS (Total Dissolved Solids) such as seawater, brine, and wastewater. TDS is the total dissolved solid content, and is expressed by “weight per volume” or “weight ratio”. According to the definition, the solution filtered with a 0.45 micron filter can be calculated from the weight of the residue by evaporating at a temperature of 39.5 to 40.5 ° C, but more simply converted from practical salt (S) To do.

The composite semipermeable membrane of the present invention is characterized by having high oxidation resistance and acid resistance. Regarding the oxidation resistance index, for example, the pH is in the vicinity of neutrality, more specifically, pH 6.0-8. It is appropriate to use the resistance to a sodium hypochlorite aqueous solution adjusted to 0.0 as an index. This is because free chlorine generated from hypochlorous acid is a typical oxidizing substance contained in the raw water described above.

As for the indexes of acid resistance and alkali resistance, it is appropriate to use the resistance to a pH 1 sulfuric acid aqueous solution and a pH 13 sodium hydroxide aqueous solution, respectively. The conditions of pH 1 and pH 13 are conditions stronger than the pH during acid washing and alkali washing in membrane filtration operation. Therefore, if resistance to pH 1 sulfuric acid aqueous solution and pH 13 sodium hydroxide aqueous solution is demonstrated, acid washing and alkali washing are performed. This is because it is ensured that the film is hardly deteriorated even if it is performed a plurality of times.

Hereinafter, the present invention will be described in more detail with reference to examples.

(1) Ratio A / B of the number of nitrogen atoms derived from nitro groups and the total number of nitrogen atoms in aromatic polyamide
The number of nitrogen atoms derived from the nitro group (A) and the total number of nitrogen atoms (B) on one surface (front surface) and the other surface (back surface) of the separation functional layer of the composite semipermeable membrane in Comparative Examples and Examples are It calculated from the measurement result by a line photoelectron spectroscopy (XPS).
Measuring device: Quantera SXM (manufactured by PHI)
Excitation X-ray: monochromatic Al Kα1,2 line (1486.6 eV)
X-ray diameter: 0.2mm
The N1s peak obtained by XPS is attributed to the inner electron of the nitrogen atom. In the following example, since the N1s peak was considered to be composed of a component derived from N—C and a component derived from NOx (x ≧ 2), the N1s peak was divided into two components. A component derived from N—C appears in the vicinity of 400 eV, and a component derived from NO x (x ≧ 2) appears in the vicinity of 406 eV. The peak area ratio of each component was calculated by rounding off the first decimal place. A / B was determined by dividing the peak area ratio derived from NOx (x ≧ 2) groups by the peak area ratio derived from N—C. In addition, if it was 0.1% or less as a result of peak division, it was set as below the detection limit. Surfaces A and B were analyzed by irradiating X-rays from the raw water supply side of the composite semipermeable membrane. The surface A / B was determined from the obtained results.
Backside A and B were analyzed as follows. The base material is peeled off from the composite semipermeable membrane and placed on a 2 cm square silicon wafer on which one drop of ethanol is placed so that the surface of the separation functional layer is in contact with it, and dichloromethane is allowed to flow through the porous support layer in the dichloromethane solution. The elution of the polymer to form was repeated until it could not be detected by thin layer chromatography. A and B on the back surface of the separation functional layer were calculated by irradiating X-rays from the upper side of the sample thus obtained. A / B on the back surface was determined from the obtained results.
Then, assuming that A / B on the front surface is C and A / B on the back surface is D, the difference between A / B of each surface, that is, CD is calculated.

(2) Ratio E / B of total nitrogen atom number B to total oxygen atom number E in aromatic polyamide
Measurement by X-ray photoelectron spectroscopy (XPS) is performed by irradiating X-rays under the same conditions as described in (1) from one surface (surface) of the separation functional layer of the composite semipermeable membrane in Comparative Examples and Examples. From the results, the total number of nitrogen atoms B and the total number of oxygen atoms E were calculated. E / B was calculated based on the intensity ratio of the N1s peak and O1s peak obtained by XPS.

Hereinafter, various characteristics of the composite semipermeable membranes in the comparative examples and examples are as follows. Seawater (TDS concentration of about 3.5%) adjusted to a temperature of 25 ° C. and pH 6.5 is applied to the composite semipermeable membranes at an operating pressure of 5.5 MPa. The membrane was subjected to membrane filtration treatment, and the water quality was determined by measuring the quality of the permeated water and the feed water.

(3) Membrane permeation flux Membrane permeation flux (m ³ / m ² / day) is calculated by converting the permeate flow rate of the supplied water (seawater) to the permeation rate per cubic meter of membrane surface per day (cubic meter). Expressed.

(4) Boron removal rate The boron concentration in the feed water and the permeated water was analyzed with an ICP emission analyzer (“P-4010” (trade name) manufactured by Hitachi, Ltd.), and obtained from the following formula.
Boron removal rate (%) = 100 × {1− (boron concentration in permeated water / boron concentration in feed water)}

(5) Oxidation resistance test The composite semipermeable membrane was immersed in a 100 mg / L sodium hypochlorite aqueous solution adjusted to pH 6.5 in an atmosphere at 25 ° C for 20 hours. Then, it calculated | required by immersing in 100 mg / L sodium hydrogensulfite aqueous solution for 10 minutes, wash | cleaning sufficiently with water, and evaluating the boron removal rate of a composite semipermeable membrane.

(6) Acid resistance test The composite semipermeable membrane was immersed in an aqueous sulfuric acid solution adjusted to pH 1 for 20 hours in an atmosphere at 25 ° C. Thereafter, it was thoroughly washed with water and evaluated by evaluating the boron removal rate of the composite semipermeable membrane.

(7) Alkali resistance test The composite semipermeable membrane was immersed in an aqueous sodium hydroxide solution adjusted to pH 13 in an atmosphere of 25 ° C for 20 hours. Thereafter, it was thoroughly washed with water and evaluated by evaluating the boron removal rate of the composite semipermeable membrane.

(Reference Example 1)
A 16.0 wt% DMF solution of polysulfone (PSf) was cast at a thickness of 200 μm at 25 ° C. on a polyester non-woven fabric (aeration rate 2.0 cc / cm ² / sec) and immediately immersed in pure water. A porous support membrane was prepared by leaving for 5 minutes.

(Examples 1 and 2)
The porous support membrane obtained in Reference Example 1 was immersed in a 3% by weight aqueous solution of m-phenylenediamine (m-PDA) for 2 minutes, the support membrane was slowly pulled up in the vertical direction, and nitrogen was blown from an air nozzle. After removing excess aqueous solution from the surface of the support membrane, 25 ° C. Isoper M (manufactured by ExxonMobil) containing 0.165% by weight of trimesic acid chloride (TMC) was applied so that the surface was completely wetted, and the surface was allowed to stand still for 1 minute. After placing, the composite semipermeable membrane was obtained by making the membrane vertical and draining and removing excess solution.
On the membrane surface of the obtained composite semipermeable membrane, 0.33 L / m ^{2 of} a 3 wt% potassium peroxymonosulfate aqueous solution having a predetermined pH (Example 1: pH 3, Example 2: pH 2) was applied at 60 ° C., The film was covered and left in an oven at 60 ° C. for a predetermined time (Example 1: 10 minutes, Example 2: 2 minutes) (see Table 1). Thereafter, the film was immersed in a 0.1 wt% aqueous sodium hydrogen sulfite solution for 10 minutes, and then washed with water to obtain a composite semipermeable membrane.
For the obtained composite semipermeable membrane, the difference (CD) between the front and back surfaces of the separation functional layer (CD) was calculated according to the method of (1) above, and the entire separation functional layer according to the method of (2) above was calculated. The ratio E / B of the number of nitrogen atoms B and the total number of oxygen atoms E was calculated. Further, the membrane permeation flux and the boron removal rate of the obtained composite semipermeable membrane were measured according to the methods (3) and (4) above, and the composite semipermeable membrane was measured according to the methods (5) to (7) above. Oxidation resistance, acid resistance, and alkali resistance tests of the permeable membrane were performed, and the boron removal rate was measured. The results are shown in Table 2.

(Examples 3 to 5)
The porous support membrane obtained in Reference Example 1 was immersed in a 3% by weight aqueous solution of m-phenylenediamine (m-PDA) for 2 minutes, the support membrane was slowly pulled up in the vertical direction, and nitrogen was blown from an air nozzle. After removing the excess aqueous solution from the surface of the support membrane, 25 ° C. isooctane containing 0.165% by weight of trimesic acid chloride (TMC) was applied so that the surface was completely wetted and allowed to stand for 10 seconds. The composite semipermeable membrane was obtained by leaving still in an oven for 15 seconds. An aqueous solution of potassium peroxymonosulfate having a predetermined pH 3 concentration (Example 3: 3 wt%, Examples 4 and 5: 1 wt%) was applied to the membrane surface of the obtained composite semipermeable membrane at a predetermined temperature (Example 3). : 90 ° C., Example 4 and Example 5: 60 ° C.) and applied at a rate of 0.33 L / m ² , and a film is placed over the oven at the same temperature as the application (Example 3 and Example 4). : 5 minutes, Example 5: 2 minutes) and allowed to stand (see Table 1). Thereafter, the film was immersed in a 0.1 wt% aqueous sodium hydrogen sulfite solution for 10 minutes, and then washed with water to obtain a composite semipermeable membrane.
For the obtained composite semipermeable membrane, the CD and E / B of the separation functional layer were calculated, the membrane permeation flux and boron removal rate of the obtained composite semipermeable membrane were measured, and the composite semipermeable membrane was further measured. The film was subjected to oxidation resistance, acid resistance, and alkali resistance tests, and the boron removal rate was measured. The results are shown in Table 2.

(Examples 6 to 8)
The porous support membrane obtained in Reference Example 1 was immersed in a 3% by weight aqueous solution of m-phenylenediamine (m-PDA) for 2 minutes, the support membrane was slowly pulled up in the vertical direction, and nitrogen was blown from an air nozzle. After removing the excess aqueous solution from the surface of the supporting membrane, 25 ° C. decane containing 0.165% by weight of trimesic acid chloride (TMC) was applied so that the surface was completely wetted, and allowed to stand for 10 seconds. The composite semipermeable membrane was obtained by leaving still in an oven for 15 seconds.
The obtained composite semipermeable membrane was mixed with a 1 wt% aqueous solution of potassium peroxymonosulfate having a predetermined pH (Example 6: pH 6, Example 7 and Example 8: pH 2) at a predetermined temperature (Example 6 and Example 7: 60 ° C., Example 8: 40 ° C.) is applied to the film surface at a rate of 0.33 L / m ² , and the film is placed on the oven at the same temperature as the application for a predetermined time (Examples 6 and 7: 2 minutes, Example 8: 5 minutes) was allowed to stand (see Table 1). Thereafter, the film was immersed in a 0.1 wt% aqueous sodium hydrogen sulfite solution for 10 minutes, and then washed with water to obtain a composite semipermeable membrane.
For the obtained composite semipermeable membrane, the CD and E / B of the separation functional layer were calculated, the membrane permeation flux and boron removal rate of the obtained composite semipermeable membrane were measured, and the composite semipermeable membrane was further measured. The film was subjected to oxidation resistance, acid resistance, and alkali resistance tests, and the boron removal rate was measured. The results are shown in Table 2.

(Comparative Examples 1 and 2)
Following the method described in International Publication No. 2011/105278, the porous support membrane obtained in Reference Example 1 was immersed in a 3% by weight aqueous solution of m-phenylenediamine (m-PDA) for 2 minutes, and the support membrane Is slowly pulled up in the vertical direction, nitrogen is blown from the air nozzle to remove excess aqueous solution from the surface of the support membrane, and then Isoper M (produced by ExxonMobil) at 25 ° C. containing 0.165% by weight of trimesic acid chloride (TMC) is used. Was applied so that the surface was completely wetted and allowed to stand for 1 minute, and then the membrane was made vertical to drain off and remove the excess solution to obtain a composite semipermeable membrane.
The obtained composite semipermeable membrane was immersed in a 1% by weight potassium peroxymonosulfate aqueous solution having a predetermined pH (Comparative Example 1: pH 6, Comparative Example 2: pH 2) at 25 ° C. for 30 minutes (see Table 1). Then, after being immersed in a 0.1 wt% sodium hydrogen sulfite aqueous solution for 10 minutes, it was washed away with water to obtain a composite semipermeable membrane.
For the obtained composite semipermeable membrane, the CD and E / B of the separation functional layer were calculated, the membrane permeation flux and boron removal rate of the obtained composite semipermeable membrane were measured, and the oxidation resistance Then, acid resistance and alkali resistance tests were carried out, and the boron removal rate was measured. The results are shown in Table 2.

(Comparative Example 3)
The porous support membrane obtained in Reference Example 1 was immersed in a 3% by weight aqueous solution of m-phenylenediamine (m-PDA) for 2 minutes, the support membrane was slowly pulled up in the vertical direction, and nitrogen was blown from an air nozzle. After removing the excess aqueous solution from the surface of the support membrane, 25 ° C Isoper M (ExxonMobil Corp.) containing 0.165% by weight of trimesic acid chloride (TMC) was applied so that the surface was completely wetted and allowed to stand for 10 seconds. After placing, the composite semipermeable membrane was obtained by leaving still in a 25 degreeC oven for 1 minute.
A 1% by weight aqueous solution of peracetic acid was applied to the surface of the composite semipermeable membrane at a rate of 0.33 L / m ² at 25 ° C., covered with a film, and left in an oven at 25 ° C. for 60 minutes. Thereafter, the film was immersed in a 0.1 wt% aqueous sodium hydrogen sulfite solution for 10 minutes, and then washed with water to obtain a composite semipermeable membrane.
For the obtained composite semipermeable membrane, the CD and E / B of the separation functional layer were calculated, the membrane permeation flux and boron removal rate of the obtained composite semipermeable membrane were measured, and the composite semipermeable membrane was further measured. The film was subjected to oxidation resistance, acid resistance, and alkali resistance tests, and the boron removal rate was measured. The results are shown in Table 2.

(Comparative Examples 4 and 5)
The porous support membrane obtained in Reference Example 1 was immersed in a 3% by weight aqueous solution of m-phenylenediamine (m-PDA) for 2 minutes, the support membrane was slowly pulled up in the vertical direction, and nitrogen was blown from an air nozzle. After removing the excess aqueous solution from the surface of the support membrane, 40 ° C. isooctane containing 0.165% by weight of trimesic acid chloride (TMC) was applied so that the surface was completely wetted and allowed to stand for 10 seconds. The composite semipermeable membrane was obtained by leaving still in an oven for 1 minute.
The obtained composite semipermeable membrane was placed in a 1 wt% potassium peroxymonosulfate aqueous solution having a predetermined pH (Example 4: pH 8, Example 5: pH 6) at 25 ° C. for a predetermined time (Comparative Example 4:30 minutes, Comparative Example 5). : 2 minutes) soaking (see Table 1). Then, after being immersed in a 0.1 wt% sodium hydrogen sulfite aqueous solution for 10 minutes, it was washed away with water to obtain a composite semipermeable membrane.
For the obtained composite semipermeable membrane, the CD and E / B of the separation functional layer were calculated, the membrane permeation flux and boron removal rate of the obtained composite semipermeable membrane were measured, and the oxidation resistance Then, acid resistance and alkali resistance tests were carried out, and the boron removal rate was measured. The results are shown in Table 2.

(Comparative Example 6)
The porous support membrane obtained in Reference Example 1 was immersed in a 3% by weight aqueous solution of m-phenylenediamine (m-PDA) for 2 minutes, the support membrane was slowly pulled up in the vertical direction, and nitrogen was blown from an air nozzle. After removing the excess aqueous solution from the surface of the support membrane, 40 ° C. decane containing 0.165% by weight of trimesic acid chloride (TMC) was applied so that the surface was completely wetted, and allowed to stand for 10 seconds. The composite semipermeable membrane was obtained by leaving still in an oven for 15 seconds.
The obtained composite semipermeable membrane was immersed in a 1 wt% potassium peroxymonosulfate aqueous solution having a pH of 3 at 60 ° C. for 2 minutes (see Table 1). Thereafter, the film was immersed in a 0.1 wt% aqueous sodium hydrogen sulfite solution for 10 minutes, and then washed with water to obtain a composite semipermeable membrane.
For the obtained composite semipermeable membrane, the CD and E / B of the separation functional layer were calculated, the membrane permeation flux and boron removal rate of the obtained composite semipermeable membrane were measured, and the composite semipermeable membrane was further measured. The film was subjected to oxidation resistance, acid resistance, and alkali resistance tests, and the boron removal rate was measured. The results are shown in Table 2.

As can be seen from the results in Table 2, in Examples 1 to 8, CD was 0.010 or more. These composite semipermeable membranes maintain a boron removal rate of 85% or more after a forced deterioration test with chlorine and maintain a boron removal rate of 90% or more after a forced deterioration test with acid or alkali. It was found to have suitable high chemical resistance.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application filed on December 25, 2015 (Japanese Patent Application No. 2015-254749), the contents of which are incorporated herein by reference.

The composite semipermeable membrane of the present invention can be particularly suitably used for seawater desalination.

Claims

A composite semipermeable membrane comprising a support membrane and a separation functional layer provided on the support membrane,
The separation functional layer contains an aromatic polyamide which is a polymer of a polyfunctional aromatic amine and a polyfunctional aromatic carboxylic acid derivative, and the aromatic polyamide has a nitro group as a functional group bonded to an aromatic ring. Having a group,
The separation functional layer is obtained by analyzing A and B by X-ray photoelectron spectroscopy (XPS), where A is the number of nitrogen atoms derived from the nitro group in the aromatic polyamide and B is the total number of nitrogen atoms in the aromatic polyamide. When A / B when X-rays are irradiated from one surface of the separation functional layer is C and A / B when X-rays are irradiated from the other surface of the separation functional layer is D, C− D is 0.010 or more,
A composite semipermeable membrane in which the other surface of the separation functional layer is in contact with the support membrane.
When X-ray photoelectron spectroscopy (XPS) is used for analysis by irradiating X-rays from the one surface of the separation functional layer, where E is the total number of oxygen atoms in the polyamide, 1.00 ≦ E / The composite semipermeable membrane according to claim 1, wherein B ≦ 1.20.
The composite semipermeable membrane according to claim 1 or 2, wherein the CD is 0.20 or less.
The composite semipermeable membrane according to any one of claims 1 to 3, wherein the CD is 0.030 or more.
The composite semipermeable membrane according to any one of claims 1 to 4, which is used for treating a liquid mixture having a TDS (Total Dissolved Solids) of 500 mg / L to 100 g / L.
A composite semipermeable membrane element comprising the composite semipermeable membrane according to any one of claims 1 to 5.