JP2020069469A - Composite semipermeable membrane - Google Patents

Abstract

To provide a composite semipermeable membrane capable of maintaining foul resistance, even after washing under a low pH condition.SOLUTION: A composite semipermeable membrane includes a microporous support layer, a separation function layer provided on the microporous support layer, and a coating layer provided on the separation function layer. The composite semipermeable membrane has a polymer (A) of the coating layer, and the polymer (A) contains a polyalkylene oxide component (A-a), a (meth)acrylic acid component (A-b) and an ester linkage (A-c).SELECTED DRAWING: None

Description

  TECHNICAL FIELD The present invention relates to a semipermeable membrane useful for selective separation of a liquid mixture, and relates to a composite semipermeable membrane excellent in high water permeability, stain resistance and oxidation resistance.

  Membranes used for membrane separation of liquid mixtures include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, etc.These membranes are, for example, salts, water containing harmful substances, etc. It is used for obtaining water, production of industrial ultrapure water, wastewater treatment, and recovery of valuables.

  Most of the reverse osmosis membranes and nanofiltration membranes currently on the market are composite semipermeable membranes. Among them, a separation functional layer composed of a crosslinked polyamide obtained by a polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide is used. A composite semipermeable membrane obtained by coating on a microporous support membrane is widely used as a separation membrane having high permeability and high selective separation.

  However, if the composite semipermeable membrane is continuously used, there is a problem that contaminants such as organic substances, heavy metals, and microorganisms adhere to the membrane surface to reduce the permeation flux of the membrane. Further, in order to recover the permeation flow rate, chemical solution cleaning with acid, alkali, etc. may be performed after the operation for a certain period of time, but there is a problem that the membrane performance deteriorates. Therefore, in order to continue stable operation for a long period of time, there is a demand for a composite semipermeable membrane in which fouling substances are less likely to adhere and the performance of the composite semipermeable membrane is small before and after cleaning with a chemical solution such as acid or alkali.

  As a method for improving the adhesion of dirt, a method in which polyvinyl alcohol is coated on the surface of the separation functional layer to neutralize the charge state to suppress fouling (see Patent Document 1), a coating layer containing polyalkylene oxide A method of forming a film (see Patent Document 2) has been proposed.

International Publication No. 97/34686 Japanese Patent Publication No. 2003-501249

However, the membranes described in Patent Documents 1 and 2 have reduced stain resistance after severe chemical cleaning under high temperature and low pH conditions.

  An object of the present invention is to provide a composite semipermeable membrane that can maintain stain resistance even after washing under low pH conditions. It is another object of the present invention to provide a composite semipermeable membrane that can maintain stain resistance even when using oxidation-treated feed water.

In order to solve the above problems, the present invention includes any one of the following configurations (1) to (5).
(1) A composite semipermeable membrane comprising a microporous support layer, a separation functional layer provided on the microporous support layer, and a coating layer provided on the separation functional layer, wherein the polymer of the coating layer is A composite semipermeable membrane having (A), wherein the polymer (A) contains a polyalkylene oxide component (Aa), a (meth) acrylic acid component (Ab), and an ester bond (Ac).
(2) The composite semipermeable membrane according to (1), wherein the polyalkylene oxide component (Aa) in the coating layer is 50 to 95% by weight.
(3) The composite semipermeable membrane according to (1) or (2), wherein the (meth) acrylic acid component (A-b) in the coating layer is 3 to 20% by weight.
(4) The composite semipermeable membrane according to (1) to (3), wherein the polyalkylene oxide group terminal structure of the polymer (A) of the coating layer is OH and / or OMe (5) The separation functional layer and coating The composite semipermeable membrane according to (1) to (4), wherein the layers are bound by an amide bond (6) The composite according to (1) to (5), wherein the separation functional layer is made of polyamide obtained by interfacial polymerization. Semi-permeable membrane (7) When the amount of antifreeze water measured using a differential scanning calorimeter (DSC) per 1 g of the polymer (A) is W _n (g) and the amount of water with reduced melting point is W _f (g), The composite semipermeable membrane W _n + W _f ≧ 2.5 Formula (3) described in (1) to (6) that satisfies the following Formulas 3 and 4:
W _f / (W _n + W _f ) ≧ 0.5 Expression (4)
(8) A method for producing a composite semipermeable membrane, comprising a microporous support layer, a separation functional layer formed on the microporous support layer, and a coating layer provided on the separation functional layer,
A method for producing a composite semipermeable membrane, comprising a step of forming the separation functional layer by performing the following steps (a), (b) and (c) in this order.
(A) by using an aqueous solution containing a polyfunctional amine and an organic solvent containing a polyfunctional acid halide to perform interfacial polycondensation on the surface of the support film including the substrate and the porous support layer, A step of forming a crosslinked polyamide.
(B) Step (c) of applying the polymer (A) having a polyalkylene oxide group to the crosslinked polyamide obtained in the step (a) (c) Polymer having a polyalkylene oxide group (obtained in the step (b) ( Step (9) of heating the crosslinked polyamide coated with A) (9) A pretreatment device for pretreating seawater, and treated water pretreated by the pretreatment device are filtered through a composite semipermeable membrane to obtain concentrated water and fresh water. A water treatment system for separation, wherein the composite semipermeable membrane uses the composite semipermeable membrane according to (1) to (7), and the treated water has a biopolymer component of 100 μg C / L or less. ..

  According to the present invention, particularly excellent stain resistance when operated in high salt seawater, and exhibit a high amount of fresh water production and salt removal rate, and stain resistance after acid cleaning, and when using feed water after oxidation treatment. It is possible to obtain a composite semipermeable membrane having excellent stain resistance.

[1. Composite semipermeable membrane]
The composite semipermeable membrane according to the present invention comprises a microporous support membrane, a separation functional layer provided on the microporous support membrane, and a coating layer provided on the separation functional layer. The separation functional layer has substantially separation performance, and the microporous support membrane does not substantially have separation performance of ions, etc., although it permeates water, and can give strength to the separation functional layer. .. Further, the coating layer can impart stain resistance during operation.

(1) Microporous support film In the present embodiment, the microporous support film includes a base material and a microporous support layer. However, the present invention is not limited to this configuration. For example, the support film may have no base material and may be composed of only a microporous support layer.

(1-1) Substrate Examples of the substrate include polyester-based polymers, polyamide-based polymers, polyolefin-based polymers, and mixtures or copolymers thereof. Among them, a polyester polymer cloth having high mechanical and thermal stability is particularly preferable. As the form of the cloth, a long fiber non-woven fabric, a short fiber non-woven fabric, or a woven or knitted fabric can be preferably used.

(1-2) Microporous support layer In the present invention, the microporous support layer has substantially no separation performance for ions and the like, and imparts strength to the separation functional layer having substantially separation performance. Is. The pore size and distribution of the microporous support layer are not particularly limited. For example, uniform and fine pores, or gradually larger micropores from the surface on which the separation functional layer is formed to the other surface, and the size of the micropores on the surface on which the separation functional layer is formed. A microporous support layer having a thickness of 0.1 nm or more and 100 nm or less is preferable. The material used for the support layer and its shape are not particularly limited.

  The material of the microporous support layer, for example, polysulfone, polyether sulfone, polyamide, polyester, cellulosic polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and homopolymers or copolymers such as polyphenylene oxide, They can be used alone or as a mixture. Here, cellulose acetate, cellulose nitrate and the like can be used as the cellulosic polymer, and polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile and the like can be used as the vinyl polymer.

  Of these, homopolymers or copolymers such as polysulfone, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, and polyphenylene sulfide sulfone are preferable. More preferably, cellulose acetate, polysulfone, polyphenylene sulfide sulfone, or polyphenylene sulfone is used. Furthermore, among these materials, polysulfone can be generally used because it has high chemical, mechanical and thermal stability and is easy to mold.

  The polysulfone preferably has a mass 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, and more preferably It is 15,000 or more and 100,000 or less.

  When the Mw of the polysulfone is 10,000 or more, the mechanical strength and heat resistance preferable as the microporous support layer can be obtained. Further, when the Mw is 200,000 or less, the viscosity of the solution is in an appropriate range, and good moldability can be realized.

  The thickness of the substrate and the microporous 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 microporous 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 microporous support layer is preferably 20 μm or more and 100 μm or less. In the present specification, the thickness means an average value unless otherwise specified. Here, the average value represents an arithmetic mean value. That is, the thicknesses of the base material and the microporous support layer can be obtained by calculating the average value of the thicknesses at 20 points measured at intervals of 20 μm in the direction orthogonal to the thickness direction (the surface direction of the film) by cross-sectional observation. ..

(1-3) Method for forming support film The microporous support layer used in the present invention is made of "Millipore Filter VSWP" (trade name) manufactured by Millipore or "Ultra Filter UK10" (trade name) manufactured by Toyo Roshi Kaisha, Ltd. It is possible to select from various commercially available materials such as "Office of Saline Water Research and Development Progress Report" No. 359 (1968).

(2-1) Chemical Structure of Separation 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 refers to a component that accounts for 50% by weight or more of the components of the separation functional layer. The separation functional layer can exhibit high removal performance by containing 50% by weight or more of the crosslinked aromatic polyamide. The content of the crosslinked aromatic polyamide in the separation functional layer is preferably 80% by weight or more, more preferably 90% by weight or more.

  The crosslinked aromatic polyamide can be formed by chemically reacting a polyfunctional aromatic amine and a polyfunctional aromatic acid chloride. Here, it is preferable that at least one of the polyfunctional aromatic amine and the polyfunctional aromatic acid chloride contains a trifunctional or higher functional compound. As a result, a rigid molecular chain is obtained, and a good pore structure for removing fine solutes such as hydrated ions and boron is formed.

  A polyfunctional aromatic amine has two or more amino groups of at least one of a primary amino group and a secondary amino group in one molecule, and at least one of the amino groups is a primary amino group. It means an aromatic amine that is an amino group. Examples of polyfunctional aromatic amines include o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m-. 1,3,5-Triaminobenzene, a polyfunctional aromatic amine in which two amino groups such as diaminopyridine and p-diaminopyridine are bonded to an aromatic ring in any one of the ortho, meta and para positions. , 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, and polyfunctional aromatic amines such as 4-aminobenzylamine. Particularly, considering the selective separation property, permeability and heat resistance of the membrane, m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene are preferably used. Above all, it is more preferable to use m-phenylenediamine (hereinafter, also referred to as m-PDA) from the viewpoint of easy availability and easy handling. These polyfunctional aromatic amines may be used alone or in combination of two or more.

  The polyfunctional aromatic acid chloride refers to an aromatic acid chloride having at least two chlorocarbonyl groups in one molecule. Examples of trifunctional acid chlorides include trimesic acid chloride, and examples of bifunctional acid chlorides include biphenyldicarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, and naphthalenedicarboxylic acid chloride. You can Considering the selective separation property and heat resistance of the membrane, a polyfunctional aromatic acid chloride having 2 to 4 carbonyl chloride groups in one molecule is preferable.

(3) Coating layer (3-1) Structure of coating layer The composite semipermeable membrane has a coating layer on the surface. The coating layer has a function of substantially suppressing the attachment of dirt.

  The coating layer has a polymer (A), and the polymer (A) has a polyalkylene oxide component (Aa), a (meth) acrylic acid component (Ab), components (A-a) and (A-b). It contains an ester bond (Ac) between and. The (meth) acrylic acid component (Ab) retains water in the coating layer, and the polyalkylene oxide component (Aa) improves the mobility of water, so that the coating layer exhibits excellent stain resistance. be able to.

  Furthermore, the composite semipermeable membrane of the present invention can exhibit excellent stain resistance even when the feed water is subjected to an oxidation treatment such as ozone treatment. The inventors have speculated as to the mechanism of producing this effect as follows. That is, by having the polyalkylene oxide component (A-a) in the coating layer, the alkylene oxide component (A-a) captures the active radical species generated when the feed water is subjected to an oxidation treatment such as ozone treatment, and the active radical is generated. By eliminating the seed, deterioration of the separation functional layer can be suppressed and the durability of the composite semipermeable membrane is improved.

The presence of the polyalkylene oxide component (Aa) on the separation functional layer of the crosslinked aromatic polyamide means that when the coating layer side of the composite semipermeable membrane is measured using time-of-flight secondary ion mass spectrometry. , Positive secondary ions m / z = 45.03, 59.05, 104.03, 108.07, 135.06 are a, b, c, d, and e, respectively, and can be determined by satisfying the following formula (1).
(a + b) / (c + d + e) ≧ 10… (1)
The positive secondary ions m / z = 45.03, 59.05 belong to the polyalkylene oxide component (Aa), and 104.03, 108.07, 135.06 belong to the partial structure of the aromatic polyamide.

  The polyalkylene oxide component (Aa) is a component having an ether skeleton as described in the general formula (2).

Specific examples thereof include a polyoxyethylene group (corresponding to n = 2 in the formula (2)) and a polyoxypropylene group (corresponding to n = 3 in the general formula (2)). Further, the degree of polymerization of the oxyalkylene group, that is, m in the chemical formula (2) is preferably 4 or more and 30 or less. When m is 4 or more, the composite semipermeable membrane can show a good removal rate as a reverse osmosis membrane, and when m is 30 or less, the composite semipermeable membrane has a good water permeability as a reverse osmosis membrane. Can be shown.

In the polymer (A), the polyalkylene oxide component (Aa) is contained in an amount of 50% by weight or more and 95% by weight or less, and further 80% by weight or more and 95% by weight or less, based on 100% by weight of the entire polymer (A). Preferably. When the proportion of the polyalkylene oxide component (Aa) is 50% by weight or more, excellent stain resistance can be obtained. When the content of the polyalkylene oxide component (A-a) is 95% by weight or less, the room for containing the (meth) acrylic acid component (A-b) is 5% by weight. The (meth) acrylic acid component (Ab) has an effect of retaining water and forming an amide bond between the separation functional layer and the coating layer.
In particular, when the total amount of the polymer (A) is 100% by weight, the effect becomes remarkable when the polyalkylene oxide component (Aa) is contained in an amount of 85% by weight or more and 95% by weight. Further, when the polyalkylene oxide component (Aa) is contained in an amount of 85% by weight or more and 95% by weight, some of the polyalkylene oxide component (Aa) change in structure by eliminating active radical species, but the remaining polyalkylene oxide component (Aa) remains. Since the component (Aa) can contribute to improving the mobility of the coating layer, stain resistance can also be exhibited.

  The (meth) acrylic acid component (Ab) of the present application is a component having the structure represented by the general formula (3). The presence of the (meth) acrylic acid component (A-b) in the polymer (A) can be determined by using a time-of-flight secondary ion mass spectrometry method described later.

  The (meth) acrylic acid component (A-b) is preferably 3% by weight or more and 20% by weight or less, more preferably 5% by weight or more and 15% by weight or less, based on 100% by weight of the entire polymer (A). The carboxy group contained in the (meth) acrylic acid component (Ab) can form a covalent bond with the functional group in the separation functional layer, while it is complexed with a biopolymer such as protein and sugar in seawater. Has the property of being easy to form. Therefore, when the amount of the (meth) acrylic acid component (A-b) is 3% by weight or more, the bond between the separation functional layer and the coating layer becomes strong, and durability and stain resistance after acid-proof cleaning are achieved. A film having excellent properties is realized. Further, when the content is 20% by weight or less, the biopolymer is less likely to adhere, and the film has excellent stain resistance.

The ester bond (A-c) is a structure represented by R ₁ -C (= O) -O-R ₂ .

  Whether the polymer (A) has an ester bond (A-c) can be determined by an X-ray photoelectron spectroscopy analyzer (ESCA) and a Fourier infrared spectrophotometer (FT-IR) ATR method analysis. Since the polymer (A) has an ester bond (A-c), a film having excellent stain resistance after acid treatment can be obtained.

When the polymer (A) of the present invention has an amount of antifreeze water measured using a differential scanning calorimeter (DSC) per 1 g of the resin as W _n (g) and a melting point reduced water amount as W _f (g), It is preferable to satisfy the following Expressions 3 and 4.
W _n + W _f ≧ 2.5 Formula (3)
W _f / (W _n + W _f ) ≧ 0.5 Expression (4)
Although the mechanism for exhibiting excellent stain resistance by satisfying the above formula has not been clarified in detail, it is presumed to be due to the amount of water of hydration and the mobility of the polymer (A). When the polymer (A) of the present invention satisfies the formula 3, the polymer (A) has a sufficient amount of hydration water to form a hydration water layer that suppresses the approach of contaminants. By filling, the hydration water of the polymer (A) and the surrounding free water can be exchanged at a sufficiently fast rate. Therefore, it is thought that the hydration water layer can be restored when the soil component destroys the hydration water layer of the coating layer containing the polymer (A) and approaches the separation functional membrane surface.
Particularly in the present invention, it is more preferable that the formula (4) W _f / (W _n + W _f ) is 0.7 or more because the mobility is improved and the stain resistance is excellent. In order for the formula (4) W _f / (W _n + W _f ) to be 0.7 or more, for example, by containing the polyalkylene oxide component (Aa) in the polymer (A) in an amount of 80% by weight or more, Can be achieved.

Amount of unfrozen water W _n and a melting point lowering amount of water W _f described above can be measured using a differential scanning calorimeter (DSC). The measuring method will be described later.

(3-4) Chemical bond between the coating layer and the separation functional layer In the present application, it is preferable that the coating layer and the separation functional layer are bonded by an amide bond. When the coating layer and the separation functional layer are bound to each other by an amide bond, the coating layer can exist more stably, which is more preferable in terms of durability.

  Specifically, an amide bond may be formed between the carboxy group of the polymer (A) forming the coating layer and the amino group of the crosslinked aromatic polyamide forming the separation functional layer.

[2. Manufacturing method of composite semipermeable membrane]
(1) Outline An example of the method for producing the composite semipermeable membrane of the present invention will be described below. However, the composite semipermeable membrane of the present invention is not limited to the one manufactured by the following manufacturing method.

  The following production method has a step of forming a coating layer on the surface of a separation functional layer of a composite membrane having a substrate, a microporous support layer, and a separation functional layer.

(2) Method for producing composite membrane As a method for producing a composite membrane, a conventionally known method can be applied. The method for producing the composite membrane is specifically as follows.

(2-1) Method for Forming Separation Functional Layer The method for producing a composite membrane has at least a step for forming a separation functional layer. The separation functional layer is obtained by chemically reacting a polyfunctional aromatic amine and a polyfunctional aromatic acid chloride to form a crosslinked aromatic polyamide. As a chemical reaction method, the interfacial polymerization method is most preferable from the viewpoint of productivity and performance. That is, the separation functional layer uses an aqueous solution containing a polyfunctional amine and an organic solvent containing a polyfunctional acid halide to cause interfacial polycondensation on the surface of the support film including the substrate and the porous support layer. It is formed by performing. By this step, a crosslinked polyamide is formed.

  More specifically, in the step of interfacial polymerization, (a) a step of bringing an aqueous solution containing a polyfunctional aromatic amine into contact with the porous support layer and (b) bringing an aqueous solution containing a polyfunctional aromatic amine into contact with each other. Contacting a solution A having a polyfunctional aromatic acid chloride dissolved therein with the porous support layer, and (c) heating an organic solvent solution B having a polyfunctional aromatic acid chloride dissolved therein. (D) a step of draining the organic solvent solution after the reaction.

  In this column, the case where the support film comprises a substrate and a microporous support layer is taken as an example, but when the support film has another structure, the “microporous support layer” is replaced with “support film”. Should be read as

  In the step (a), the concentration of the polyfunctional aromatic amine in the polyfunctional aromatic amine aqueous solution is preferably in the range of 0.1% by weight or more and 20% by weight or less, more preferably 0.5% by weight or more and 15% by weight or more. It is within the range of not more than wt%. When the concentration of the polyfunctional aromatic amine is within this range, sufficient solute removal performance and water permeability can be obtained.

  The contact with the polyfunctional aromatic amine aqueous solution is preferably carried out uniformly and continuously on the microporous support layer. Specifically, for example, a method of coating a polyfunctional aromatic amine aqueous solution on a microporous support layer, a method of immersing the microporous support layer in a polyfunctional aromatic amine aqueous solution, and the like can be mentioned. The contact time between the microporous support layer and the polyfunctional aromatic amine aqueous solution is preferably 1 second or more and 10 minutes or less, and more preferably 10 seconds or more and 3 minutes or less.

  After bringing the polyfunctional aromatic amine aqueous solution into contact with the microporous support layer, it 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 droplets from becoming a film defect after the formation of the microporous support layer and deteriorating the removal performance. As a method of draining, for example, as described in JP-A-2-78428, a method of vertically holding the support membrane after contact with the polyfunctional aromatic amine aqueous solution and allowing the excess aqueous solution to flow down naturally Alternatively, a method of blowing a stream of nitrogen or the like from an air nozzle to forcibly drain the liquid can be used. Further, after draining, the film surface may be dried to partially remove the water content of the aqueous solution.

  The concentration of the polyfunctional aromatic acid chloride in the organic solvent solution (Solution A and Solution B) is preferably 0.01% by weight or more and 10% by weight or less, and 0.02% by weight or more and 2.0% by weight or less. % Or less is more preferable. This is because a sufficient reaction rate can be obtained with an amount of 0.01% by weight or more, and the occurrence of side reactions can be suppressed with an amount of 10% by weight or less.

  The organic solvent is preferably immiscible with water, dissolves the polyfunctional aromatic acid chloride, and does not destroy the supporting film, and is inert to the polyfunctional aromatic amine and the polyfunctional aromatic acid chloride. Anything will do. Preferred examples include hydrocarbon compounds such as n-nonane, n-decane, n-undecane, n-dodecane, isooctane, isodecane, isododecane, and mixed solvents.

  The method for contacting the microporous support layer in which the solution of the polyfunctional aromatic acid chloride in the organic solvent is contacted with the aqueous solution of the polyfunctional aromatic amine is a method for coating the microporous support layer with the aqueous solution of the polyfunctional aromatic amine. Do the same.

  In the step (c), the solution B in which the polyfunctional aromatic acid chloride is dissolved is brought into contact and heated. The heat treatment temperature is 50 ° C. or higher and 180 ° C. or lower, preferably 60 ° C. or higher and 160 ° C. or lower. By heating in this range, a synergistic effect of promoting the interfacial polymerization reaction by heat and concentration of the solution can be obtained.

  In step (d), the organic solvent is removed by the step of draining the organic solvent solution after the reaction. The organic solvent can be removed by, for example, holding the film in a vertical direction to naturally remove excess organic solvent, removing the organic solvent by blowing air with a blower, or a mixed fluid of water and air. The method of removing the excess organic solvent can be used.

(2-2) Formation of Microporous Support Layer The method for producing the composite membrane may include a step of forming a microporous support layer.

  The microporous support layer can be formed by applying a solution containing a polymer and a solvent onto a substrate and wet coagulating the polymer in a coagulation bath. In the case of polysulfone, N, N-dimethylformamide (hereinafter referred to as DMF) may be used as a solvent and water may be used as a coagulation bath.

(3) Method for forming coating layer (3-1) Synthesis of polymer (A) The polymer (A) can be synthesized by using an existing polycondensation reaction. In the polymer (A), the polyalkylene oxide component (A-a) and the (meth) acrylic acid are formed in the polymer (A) by forming the polymer (A) by block polymerization using the polyalkylene oxide component (A-a) generated in advance. Since the component (A-b) is uniformly dispersed, the effect of improving the stain resistance of the composite semipermeable membrane is high, which is particularly preferable. Among these, it is preferable to use a radical copolymer of a polyalkylene oxide component-containing (meth) acrylate monomer and a carboxy group-containing (meth) acrylate monomer. Thereby, the content of the polyalkylene oxide component in the polymer (A) can be increased, the hydration water mobility of the coating layer can be improved, and the stain resistance can be improved.

  As the polyalkylene oxide component-containing (meth) acrylate monomer, commercially available methoxy polyethylene glycol # 400 acrylate, methoxy polyethylene glycol # 800 acrylate and the like can be used. It can also be obtained by a method of esterifying an arbitrary polyalkylene oxide diol and acrylic acid. Among these, when the polyalkylene oxide component-containing (meth) acrylate monomer has an alkylene oxide component (A-a) and an ester bond (A-c), it is hydrophilic with the alkylene oxide component (A-a) which is a hydrophobic moiety. Since the ester bond, which is a sex site, is finely dispersed in the polymer, the water dispersibility of the polymer is improved, which is preferable.

  Examples of the (meth) acrylate monomer having a carboxy group include maleic acid, maleic anhydride, acrylic acid, methacrylic acid, 2- (hydroxymethyl) acrylic acid, 4- (meth) acryloyloxyethyltrimethic acid and corresponding anhydrides. Among them, acrylic acid, methacrylic acid and maleic acid are preferable from the viewpoints of versatility and copolymerizability.

(3-2) Formation of coating layer The coating layer is formed by applying a solution containing the polymer (A) onto the surface of the separation functional layer. The application may be coating, or may be immersing the membrane containing the separation functional layer in a solution containing the polymer (A), or the composite semipermeable membrane element described below may be prepared before the polymer (A). It is also possible to pass a solution containing By passing the solution, that is, by supplying the solution to the element and filtering, the solvent passes through the membrane and the polymer (A) remains on the separation functional layer, so that the coating layer is formed.

  Specifically, as described above, an amide bond can be formed between the carboxy group of the polymer (A) forming the coating layer and the amino group of the crosslinked aromatic polyamide forming the separation functional layer. The carboxy group of the polymer (A) is specifically derived from the (meth) acrylic acid component (Ab).

  The formation of the amide bond is carried out when the crosslinked aromatic polyamide constituting the separation functional layer is brought into contact with the polymer (A). Specifically, when the separation functional layer is coated with a solution containing the polymer (A) to form a coating layer, a chemical reaction may be performed between the coating layer and the separation functional layer. Alternatively, when the membrane containing the separation functional layer is immersed in the solution containing the polymer (A) to form the coating layer, a chemical reaction may be performed between the coating layer and the separation functional layer. Further, when a composite semipermeable membrane element described below is prepared and a solution containing the polymer (A) is passed through to form a coating layer, a chemical reaction is performed between the coating layer and the separation functional layer. Good.

  When forming an amide bond between the coating layer and the separation functional layer, the carboxy group is preferably kept in a state of high reaction activity, if necessary. For example, it is also preferable to use various reaction aids (condensation accelerators) in the reaction between the carboxy group and the amino group for highly efficient and short-time amide bond formation. As the condensation accelerator, sulfuric acid, 4- (4,6-dimethoxy-1,3,5-triazin-2-yl) -4-methylmorpholinium chloride (DMT-MM), 1- (3-dimethylamino Propyl) -3-ethylcarbodiimide hydrochloride, N, N'-dicyclohexylcarbodiimide, N, N'-diisopropylcarbodiimide, N, N'-carbonyldiimidazole, 1,1'-carbonyldi (1,2,4-triazole ), 1H-benzotriazol-1-yloxytris (dimethylamino) phosphonium hexafluorophosphate, 1H-benzotriazol-1-yloxytris (dimethylamino) phosphonium hexafluorophosphate, (7-azabenzotriazole -1-yloxy) tripyrrolidinophosphonium hexafluorophosphate, chlorotripyrrolidinophosphonium hexafluorophosphate, bromotris (dimethylamino) phosphonium hexafluoro Phosphate, 3- (diethoxyphosphoryloxy) -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 hexafluorophosphate, 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-octoxy-2-oxoethyl) dimethylammonium, S- (1-oxide-2-pyridyl) -N, N, N ', N'-tetramethylthiuronium Tetrafluoroborate, O- [2-oxo-1 (2H) -pyridyl] -N, N, N ', N'-tetramethyluronium tetrafluoroborate, {{[(1-cyano-2-ethoxy -2-Oxoethylidene) amino] oxy} -4-morpholinomethylene} dimethylammonium hexafluorophosphate, 2-chloro-1,3-dimethylimidazolinium hexafluorophosphate, 1- (chloro-1-pyrrolid (Dinylmethylene) pyrrolidinium hexafluorophosphate, 2-fluoro-1,3-dimethylimidazolinium hexafluorophosphate, fluoro-N, N, N ', N'-tetramethylformamidinium hexafluoro Phosphate, etc. are mentioned as an example.

  The reaction time and concentration of the amide bond formation between the coating layer and the separation functional layer can be appropriately adjusted depending on the solvent used, the condensing agent and the aliphatic polyamide, and the chemical structure of the crosslinked aromatic polyamide. From the viewpoint, the reaction time is preferably within 24 hours, more preferably within 1 hour, further preferably within 10 minutes, particularly preferably within 3 minutes. After completion of the reaction, it is preferable to wash the obtained composite semipermeable membrane with water, hot water or a suitable organic solvent to remove the reactive compound.

  The coating layer forming step preferably includes a step of heating the composite film coated with the solution containing the polymer (A) in order to promote the formation of an amide bond between the coating layer and the separation functional layer. The heating here includes a step of drying the composite film coated with the solution by a dryer, a step of bathing the composite film coated with the solution in a hot water, and the like. The heating temperature is preferably 50 ° C or higher and 150 ° C or lower, more preferably 60 ° C or higher and 100 ° C or lower. Although the heating time can be adjusted as appropriate, it is preferably 10 seconds or more and 5 minutes or less from the viewpoint of productivity.

[3. Use of composite semipermeable membranes]
A composite semi-permeable membrane is a tubular water collection pipe with a large number of holes, along with a feed water flow path material such as a plastic net, a permeate water flow path material such as a tricot, and a film for enhancing pressure resistance if necessary. It is wound around and is suitably used as a spiral type composite semipermeable membrane element. Furthermore, a composite semipermeable membrane module in which these elements are connected in series or in parallel and housed in a pressure vessel can be used.
The above-mentioned composite semipermeable membrane, its element, and module can be combined with a pump for supplying feed water to them, a device for pretreating the feed water, and the like to form a fluid separation device. By using this separator, the feed water can be separated into permeated water such as drinking water and concentrated water that has not permeated through the membrane to obtain water suitable for the purpose.

  As the feed water treated by the composite semipermeable membrane according to the present invention, a liquid mixture containing 500 mg / L or more and 100 g / L or less of TDS (Total Dissolved Solids: total dissolved solids) such as seawater, brackish water, and drainage water. Can be mentioned. Generally, TDS refers to the total amount of dissolved solids, and is represented by "mass / volume" or "weight ratio". According to the definition, the solution filtered through a 0.45 micron filter can be evaporated from a temperature of 39.5 ° C or higher and 40.5 ° C or lower to calculate the weight of the residue. Convert from

  The higher the operating pressure of the fluid separation device, the higher the solute removal rate, but the energy required for operation also increases, and considering the durability of the composite semipermeable membrane, the water to be treated is placed in the composite semipermeable membrane. The operating pressure for permeation is preferably 0.5 MPa or more and 10 MPa or less. The solute removal rate decreases as the supply water temperature increases, but the membrane permeation flux decreases as the supply water temperature decreases, so 5 ° C or higher and 45 ° C or lower is preferable. Further, when the pH of the feed water becomes high, scales such as magnesium may be generated in the case of feed water having a high solute concentration such as seawater, and there is a concern that the membrane may deteriorate due to high pH operation. Driving is preferred.

  On the other hand, there is a case where low-pH feed water is used as the chemical liquid cleaning after the operation for a long period of time. At that time, if the acid resistance of the coating layer is insufficient, there is a concern that the film may deteriorate. The coating layer of the present invention has a resin (A) containing an alkylene oxide group, and the polyalkylene oxide component (A-a) and the (meth) acrylic acid component (A-b) have an ester bond (A-c). It is preferable that the bond is less likely to be broken than other chemical bonds and the durability under low pH conditions is excellent because the bond is bonded via (4).

  In addition, the composite semipermeable membrane provided with the coating layer of the present invention can exhibit stain resistance by improving the hydration water mobility of the coating layer. This is because the biopolymer component of the feed water is 100 μgC / It is particularly useful in water treatment systems below L. When the biopolymer component of the feed water is 100 μg C / L or less, proteins and sugars having a lower molecular weight than the biopolymer are the main causes of stains, so the stain resistance effect due to the improvement of hydration water mobility is likely to appear. Is.

  Further, the composite semipermeable membrane provided with the coating layer of the present invention can capture the active radical species by having the polyalkylene oxide component (Aa). Even when it is a target, it is preferable because it can be operated without impairing the stain resistance performance.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to this.

(1) Time-of-flight secondary ion mass spectrometry (1-1) Polyalkylene oxide component (Aa)
The composite semipermeable membrane was dried at room temperature under vacuum, and a time-of-flight secondary ion mass spectrometry measurement was performed using a TOF SIMS 5 (manufactured by ION TOF) (secondary ion polarity: positive, mass range ( m / z) = 0-200, raster size: 300 μm, number of scans: 16, number of pixels (one side) = 256, measurement vacuum degree = 4 × 10 ⁻⁷ Pa or less, primary ion species: Bi ₃ ⁺⁺ , (Primary ion acceleration voltage = 25 kV, pulse width = 12.5, 13.3 ns, bunching: Yes, charge neutralization: Yes, second-stage acceleration: 10 kV). On the surface of the composite semipermeable membrane on the coating layer side, positive secondary ions m / z = 45.03, 59.05, 104.03, 108.07, 135.06 were obtained, and the positive secondary ions m /Z=45.03, 59.05, 104.03, 108.07, and 135.06 were set as a, b, c, d, and e, and the value of (a + b) / (c + d + e) was calculated. When (a + b) / (c + d + e) ≧ 10, it was judged to have a polyalkylene oxide component.

(1-2) Polyacrylic acid component (Ab)
In the same manner as in (1-1), the secondary ion polarity was set to be negative and measurement was performed, and the count numbers of negative secondary ions m / z = 71.02, 103.02, 107.06, and 133.04 were obtained. Then, the values of f / (g + h + i) were calculated with f, g, h, and i, respectively. When f / (g + h + i) ≧ 1, it was judged to have a polyacrylic acid component (Ab).

(2) Performance evaluation of composite semipermeable membrane Seawater (TDS concentration 3.5%) (Total Dissolved Solids: total dissolved solids) adjusted to a temperature of 25 ° C and pH 7 was applied to the obtained composite semipermeable membrane at an operating pressure of 5 A membrane water permeation test was carried out by supplying at 0.5 MPa. Based on the obtained results, the salt removal rate was calculated from the following formula.

Salt removal rate (%) = 100 × {1- (TDS concentration in permeated water / TDS concentration in feed water)}
Further, the permeated water amount (m ³ / m ² / day) was obtained from the permeated water amount (cubic meter) per square meter of the membrane surface obtained under the above-mentioned conditions.

(3) Fouling resistance test After the evaluation of the production performance in (2) above, seawater added with 200 ppm of skim milk (manufactured by Morinaga & Co., Ltd.) was supplied for 2 hours at an operating pressure of 5.5 MPa to conduct a membrane water permeation test, and then permeation The amount of water was measured, the ratio with the amount of permeated water at the time of production was calculated, and four-level evaluation of ⊚, ◯, Δ, and × was performed. Δ is a level with no problem in practical use, and ◯ and ◎ are good.

⊚: Ratio with permeated water during manufacturing 0.95 or more ◯: Ratio with permeated water during manufacturing 0.80 or more and less than 0.95 Δ: Ratio with permeated water during manufacturing 0.70 or more. Less than 0.80 x: Ratio with the amount of permeated water during production less than 0.70 (4) Stain resistance after acid cleaning The composite semipermeable membrane after the stain resistance test of (3) above was subjected to a temperature of 50 ° C. and a pH of 1. The RO water adjusted to 1. was supplied at an operating pressure of 5.5 MPa, acid cleaning was performed for 20 hours, and then the stain resistance test described in (3) was performed again. A four-level evaluation of ⊚, ◯, Δ, and × was performed, and Δ was a level at which there was no problem in practical use, and ◯ and ⊚ were good.

⊚: Ratio with permeated water during manufacturing 0.95 or more ◯: Ratio with permeated water during manufacturing 0.80 or more and less than 0.95 Δ: Ratio with permeated water during manufacturing 0.70 or more. Less than 0.80 ×: Ratio with the amount of permeated water during production Less than 0.70 (5) Presence or absence of ester bond The following IR spectrum was measured on the surface of the composite semipermeable membrane on the coating layer side, and a peak derived from ester (1750) was obtained. .About.1700 cm.sup.- ^1, and / or 1300 to 1000 cm.sup.- ¹ ). When it had an ester bond, it was Y, and when it did not have it, it was N.

An Avatar 360 FT-IR measuring instrument manufactured by Nocolet Co., Ltd. was used as a measuring machine, and the sample surface was measured using a single-reflection horizontal upper ATR measuring device (OMNI-Sampler) and an ATR crystal made of germanium. The measurement conditions are a resolution of 4 cm ⁻¹ and a scan count of 256 times.

(6) Method of measuring biopolymer The concentration of biopolymer is measured by LC-OCD (manufactured by DOC-Labor) in which a wet total organic carbon measuring instrument (OCD measuring instrument) is connected to high performance liquid chromatography (HPLC). The measurement is conducted by Stefan A. Huber et al. “Characterisation of aquatic humic and non-humic matter with size-exclusion chromatography -organic carbon detection -organic nitrogen detection (LC-OCD-OND)” Water Research 45 (2011) pp879-885. The method was performed under the following conditions according to the method described in 1.
・ Flow rate: 1.1 mL / min
・ Sample injection volume: 1 mL
・ Column: 250 mm x 20 mm, TSK HW50S
・ UV wavelength: 254 nm
・ OCD meter: Acid injection rate 0.2mL / min
- Hold Time: 25 to 38 min (7) antifreeze water _(W n), melting point lowering amount of water _(W f)
(7-1) Preparation of sample A sample (polymer) was dissolved in ion-exchanged water so as to be 5,000 ppm, and a hydrolysis reaction was allowed to proceed at 70 ° C for 2 hours while stirring. After cooling, purification by dialysis was performed using a dialysis membrane (BIOTECH RC molecular weight cutoff 3.5-5 kD, Spectrum), and freeze-dried to obtain a hydrolyzed sample. Ion-exchanged water was added to the obtained hydrolyzed sample so as to be 16.7% by weight (water content: 500%) to prepare a DSC measurement sample.

(7-2) Measurement of DSC Using DSC6200 (EXSTAR6000 manufactured by SII), measurement was performed under the condition of nitrogen flow rate of 40 mL / min. The temperature program includes (i) cooling from 25 ° C. to −100 ° C. at a cooling rate of 20 ° C./min, (ii) holding at −100 ° C. for 5 minutes, and (iii) heating rate of 5 ° C./min from −100 ° C. to 25 ° C. The temperature was raised to ° C. In the above (iii), the endothermic peak due to the melting of water was measured.

(7-3) antifreeze water _{(W n)} and the melting point lowering amount of water _{(W f)} Calculation 0 melting point lowering water from endotherm below ° C. _(W h), the free water (Wf from endotherm at 0 ℃ or higher ) Was calculated, and the amount of antifreeze water (Wn) was calculated by the following equation (5). The melting enthalpy of water was calculated using the equation (6).
_{W n = W 0 -W f -W} h (5)
ΔH (T) = 334.1 + 2.119 (T-273.15)-0.00783 (T-273.15) ² (6)
_{(W 0:} total water content, _{W n:} amount of unfrozen water, _{W h:} mp decrease water amount, _{W f:} free water)
(8) Oxidation resistance and dirt resistance in oxidation-treated supply water Seawater (TDS concentration 3.5%) (Total Dissolved Solids: total dissolved solids) adjusted to pH 7 is equipped with an ozone generator (produced by Ebara Jitsugyo, capacity 10 g). / H) and an ozone reaction tank (batch type, capacity 2.5 L, ozone absorption amount 20 mg / L) are used for ozone treatment to obtain feed water with an ozone concentration of 5 ppm, and then to the composite semipermeable membrane obtained by the present invention. Then, the membrane water permeation test (initial characteristics) was performed by supplying at a temperature of 25 ° C. and an operating pressure of 5.5 MPa.
Next, RO water adjusted to a temperature of 50 ° C. and pH 1 was supplied at an operating pressure of 5.5 MPa, acid cleaning was performed for 20 hours, and then the stain resistance test described in (3) was performed again. A four-level evaluation of ⊚, ◯, Δ, and × was performed, and Δ was a level at which there was no problem in practical use, and ◯ and ⊚ were good.

⊚: Percentage of permeated water of initial characteristics 0.95 or more ◯: Percentage of permeated water of initial characteristics 0.80 or more and less than 0.95 Δ: Ratio of permeated water of initial characteristics 0.70 or more. Less than 0.80 x: Ratio of permeated water of initial characteristics less than 0.70 (9) Preparation of composite semipermeable membrane (Reference Example 1)
A 16.0 mass% DMF solution of polysulfone (PSf) was cast on a polyester non-woven fabric (air permeability of 2.0 cc / cm2 / sec) at a temperature of 25 ° C. to a thickness of 200 μm, and immediately immersed in pure water for 5 minutes. A porous support membrane was prepared by leaving it for a minute.
The obtained porous support membrane was immersed in a 3 mass% 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 to blow the support membrane from the surface. After removing the excess aqueous solution, a decane solution containing 0.165% by mass of trimesic acid chloride (TMC) was applied so that the surface was completely wet and allowed to stand for 1 minute, and then the membrane was made vertical to remove the excess solution. A composite membrane having a crosslinked aromatic polyamide separation functional layer was obtained by draining, removing, and washing with pure water.

Reference Example 2 Synthesis of Polymer (A-1) A gas inlet tube and a cooling tube were attached to a reaction vessel containing a stirrer, water was used as a solvent, 5100 parts by weight of acrylic acid, methoxy polyethylene glycol # 400 acrylate (new An aqueous solution containing 490 parts by weight of Nakamura Chemical Co., Ltd., AM-90G) and 1 part by weight of 2,2′-azobis (2-methylpropionamidine) dihydrochloride (V-50 manufactured by Wako Pure Chemical Industries, Ltd.). Added and dissolved uniformly. The mixture was stirred while flowing a nitrogen gas, heated to 60 ° C., kept at 60 ° C. in the reaction vessel for 5 hours with stirring and polymerized, and then cooled to room temperature to obtain a solution of the polymer (A-1). The composition ratio of the resin (A-1) is a resin containing a polyalkylene oxide component (Aa) / (meth) acrylic component (Ab) = 49/51 and an ester bond (Ac).

(Reference Example 3) Synthesis of polymer (A-2)
A reaction vessel containing a stirrer is equipped with a gas introduction tube and a cooling tube, water is used as a solvent, and acrylic acid is used 500 parts by weight, methoxypolyethylene glycol # 400 acrylate (Shin-Nakamura Chemical Co., Ltd., AM-90G) 500 parts by weight. Part, 2,2′-azobis (2-methylpropionamidine) dihydrochloride (V-50 manufactured by Wako Pure Chemical Industries, Ltd.) 1 part by weight was added and the solution was uniformly dissolved. The mixture was stirred while flowing a nitrogen gas, heated to 60 ° C., kept at 60 ° C. in the reaction vessel for 5 hours with stirring and polymerized, and then cooled to room temperature to obtain a solution of the polymer (A-2). The composition ratio of the resin (A-2) is a resin containing a polyalkylene oxide component (Aa) / (meth) acrylic component (Ab) = 50/50 and an ester bond (Ac).

(Reference Example 4) Synthesis of polymer (A-3)
A reaction vessel containing a stirrer is equipped with a gas introduction tube and a cooling tube, water is used as a solvent, acrylic acid 250 parts by weight, methoxypolyethylene glycol # 400 acrylate (Shin-Nakamura Chemical Co., Ltd., AM-90G) 750 parts by weight. Part, 2,2′-azobis (2-methylpropionamidine) dihydrochloride (V-50 manufactured by Wako Pure Chemical Industries, Ltd.) 1 part by weight was added and the solution was uniformly dissolved. The mixture was stirred while flowing nitrogen gas, the temperature was raised to 60 ° C., the reaction vessel was kept at 60 ° C., the mixture was stirred and polymerized for 5 hours, and then cooled to room temperature to obtain a polymer (A-3) solution. The composition ratio of the resin (A-3) is a resin containing a polyalkylene oxide component (Aa) / (meth) acrylic component (Ab) = 75/25 and an ester bond (Ac).

Reference Example 5 Synthesis of Polymer (A-4) A reaction vessel equipped with a stirrer was equipped with a gas introduction tube and a cooling tube, water was used as a solvent, and 200 parts by weight of acrylic acid and methoxy polyethylene glycol # 400 acrylate (new An aqueous solution containing 800 parts by weight of Nakamura Chemical Co., Ltd., AM-90G) and 1 part by weight of 2,2′-azobis (2-methylpropionamidine) dihydrochloride (V-50 manufactured by Wako Pure Chemical Industries, Ltd.) Added and dissolved uniformly. The mixture was stirred while flowing a nitrogen gas, heated to 60 ° C., kept at 60 ° C. in the reaction vessel, stirred and polymerized for 5 hours, and then cooled to room temperature to obtain a solution of the polymer (A-4). The composition ratio of the resin (A-4) is a resin containing a polyalkylene oxide component (Aa) / (meth) acrylic component (Ab) = 80/20 and an ester bond (Ac).

(Reference Example 6) Synthesis of polymer (A-5)
A reaction vessel containing a stirrer is equipped with a gas introduction tube and a cooling tube, water is used as a solvent, acrylic acid 50 parts by weight, methoxypolyethylene glycol # 400 acrylate (Shin-Nakamura Chemical Co., Ltd., AM-90G) 950 parts by weight. Part, 2,2′-azobis (2-methylpropionamidine) dihydrochloride (V-50 manufactured by Wako Pure Chemical Industries, Ltd.) 1 part by weight was added and the solution was uniformly dissolved. The mixture was stirred while flowing a nitrogen gas, heated to 60 ° C., kept at 60 ° C. in the reaction vessel, stirred and polymerized for 5 hours, and then cooled to room temperature to obtain a polymer (A-5) solution. The composition ratio of the resin (A-5) is a resin containing a polyalkylene oxide component (Aa) / (meth) acrylic component (Ab) = 95/5 and an ester bond (Ac).

(Reference Example 7) Synthesis of polymer (A-6)
A gas inlet tube and a cooling tube were attached to a reaction vessel containing a stirrer, water was used as a solvent, acrylic acid 20 parts by weight, methoxypolyethylene glycol # 400 acrylate (Shin-Nakamura Chemical Co., Ltd., AM-90G) 980 parts by weight. Part, 2,2′-azobis (2-methylpropionamidine) dihydrochloride (V-50 manufactured by Wako Pure Chemical Industries, Ltd.) 1 part by weight was added and the solution was uniformly dissolved. The mixture was stirred while flowing a nitrogen gas, the temperature was raised to 60 ° C., the reaction vessel was kept at 60 ° C., the mixture was stirred and polymerized for 5 hours, and then cooled to room temperature to obtain a polymer (A-6) solution. The composition ratio of the resin (A-6) is a resin containing a polyalkylene oxide component (Aa) / (meth) acrylic component (Ab) = 98/2 and an ester bond (Ac).

(Reference Example 8) Synthesis of polymer (A-7)
In a nitrogen-substituted glove box, 2.05 g (15.8 mmol) of polyacrylic acid, 22.9 μl (0.10 mmol) of ethyl-2-methyl-2-n-butylteranyl-propionate (hereinafter referred to as “BTEE”), 1,1′-Azobis (1-cyclohexanecarbonitrile) (hereinafter referred to as “ACHN”) 4.9 mg (0.020 mmol) was added, and the mixture was reacted at 90 ° C. for 21 hours. Next, 0.90 g (8.64 mmol) of methoxypolyethylene glycol # 400 acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., AM-90G) and ACHN 12.2 mg (0.050 mmol) were added to the obtained solution, and 90 ° C was added. And reacted for 46 hours. After completion of the reaction, the polymer (A-7) was obtained by reprecipitation treatment with heptane and drying. The composition ratio of the resin (A-7) is a resin containing a polyalkylene oxide component (Aa) / (meth) acrylic component (Ab) = 95/5 and an ester bond (Ac).

(Reference Example 9) Synthesis of polymer (A-8) 500 parts by weight of polyacrylic acid and 500 parts by weight of aliphatic amine of the following formula 5 were dissolved in pure water and stirred at 25 ° C for 12 hours to cause a condensation reaction, A solution of polymer (A-8) was obtained. The composition ratio of the resin (A-8) is a resin having no polyalkylene oxide component (Aa) / (meth) acrylic component (Ab) = 50/50 and no ester bond (Ac).

(Reference Example 10) Synthesis of polymer (A-9)
In a nitrogen-substituted glove box, 1.83 g (14.1 mmol) of polyacrylic acid, 22.9 μl (0.10 mmol) of ethyl-2-methyl-2-n-butylteranyl-propionate (hereinafter referred to as “BTEE”), 1,1′-Azobis (1-cyclohexanecarbonitrile) (hereinafter referred to as “ACHN”) 4.9 mg (0.020 mmol) was added, and the mixture was reacted at 90 ° C. for 21 hours. Next, to the resulting solution, 1.80 g (17.2 mmol) of methoxypolyethylene glycol # 400 acrylate (AM-90G, manufactured by Shin-Nakamura Chemical Co., Ltd.) and 12.2 mg (0.050 mmol) of ACHN were added, and the temperature was 90 ° C. And reacted for 46 hours. After completion of the reaction, the polymer (A-9) was obtained by reprecipitation treatment with heptane and drying. The composition ratio of the resin (A-7) is a resin containing a polyalkylene oxide component (Aa) / (meth) acrylic component (Ab) = 85/15 and an ester bond (Ac).

(Example 1)
The composite membrane obtained in Reference Example 1 was brought into contact with an aqueous solution containing 0.5% of polymer (A-1) and 0.1% of DMT-MM at 20 ° C. for 1 minute, and then washed at 60 ° C. for 1 minute in a hot water bath. Then, a composite semipermeable membrane provided with a coating layer was obtained.
The characteristics of the obtained composite semipermeable membrane are shown in Table 2. The result was not only high water permeability and removal rate, but also excellent stain resistance.

(Examples 2 to 6 and 8)
A composite semipermeable membrane was obtained in the same manner as in Example 1 except that the polymer (A-1) was changed to the polymer (A) shown in Table 1. The characteristics of the obtained composite semipermeable membrane are shown in Table 2. The result was not only high water permeability and removal rate, but also excellent stain resistance.

(Example 7)
The composite semipermeable membrane obtained in Reference Example 1 was brought into contact with an aqueous solution containing 0.5% of the polymer (A-3) at 20 ° C for 1 minute, and then washed with a hot water bath at 60 ° C for 1 minute to form a coating layer. The composite semipermeable membrane provided was obtained.
The characteristics of the obtained composite semipermeable membrane are shown in Table 2. It has high water permeability and removal rate, but the stain resistance and the stain resistance after acid treatment were at a practical level.

(Example 9)
A composite semipermeable membrane was obtained in the same manner as in Example 1 except that the polymer (A-1) was changed to the polymer (A-9). The characteristics of the obtained composite semipermeable membrane are shown in Table 2. The result was not only high water permeability and removal rate, but also excellent stain resistance.

(Comparative Example 1)
The composite semipermeable membrane obtained in Reference Example 1 was brought into contact with an aqueous solution containing 0.5% of polyethylene glycol (Sigma Aldrich, molecular weight 1000) at 20 ° C. for 1 minute, and then washed at 60 ° C. for 1 minute in a hot water bath. Then, a composite semipermeable membrane provided with a coating layer was obtained.

  The characteristics of the obtained composite semipermeable membrane are shown in Table 2. Although it had high water permeability and removal rate, it was inferior in stain resistance.

(Comparative example 2)
The composite semipermeable membrane obtained in Reference Example 1 was brought into contact with an aqueous solution containing 0.5% of polyacrylic acid (manufactured by Sigma-Aldrich, molecular weight 5000) and DMT-MM 0.1% at 20 ° C. for 1 minute, It was washed in a hot water bath at 60 ° C. for 1 minute to obtain a composite semipermeable membrane provided with a coating layer.

  The characteristics of the obtained composite semipermeable membrane are shown in Table 2. Although it had high water permeability and removal rate, it was inferior in stain resistance.

(Comparative example 3)
A composite semipermeable membrane was obtained in the same manner as in Example 1 except that the polymer (A-8) shown in Table 1 was used instead of the polymer (A-1). The characteristics of the obtained composite semipermeable membrane are shown in Table 2. Although it had a high water permeability and a high removal rate, it was inferior in stain resistance after acid treatment.

(Comparative example 4)
The composite semipermeable membrane obtained in Reference Example 1 was contacted with an aqueous solution containing 0.5% of polyvinyl alcohol (“Gohsenol” (registered trademark) Z100 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) at 20 ° C. for 1 minute, and then, It was washed in a hot water bath at 60 ° C. for 1 minute to obtain a composite semipermeable membrane provided with a coating layer.
The characteristics of the obtained composite semipermeable membrane are shown in Table 2. The result was inferior in stain resistance.

(Comparative example 5)
The composite semipermeable membrane obtained in Reference Example 1 was brought into contact with an aqueous solution containing 0.5% of poly-2-ethyl-2-oxazoline (molecular weight 5000) at 20 ° C for 1 minute, and then washed at 60 ° C for 1 minute in a hot water bath. Then, a composite semipermeable membrane provided with a coating layer was obtained.
The characteristics of the obtained composite semipermeable membrane are shown in Table 2. The result was inferior in stain resistance.

Claims (10)

A composite semipermeable membrane comprising a microporous support layer, a separation functional layer provided on the microporous support layer, and a coating layer provided on the separation functional layer,
The separation functional layer contains a polyamide, and the coating layer includes a polyalkylene oxide component (Aa), a (meth) acrylic acid component (Ab), a component (A-a) and a component (Ab). A composite semipermeable membrane containing a polymer (A) having an ester bond (Ac) of. The composite semipermeable membrane according to claim 1, wherein a proportion of the polyalkylene oxide component (A-a) in the polymer (A) is 50 to 95% by weight. The composite semipermeable membrane according to claim 1 or 2, wherein the proportion of the (meth) acrylic acid component (A-b) in the polymer (A) is 3 to 20% by weight. The composite semipermeable membrane according to any one of claims 1 to 3, wherein the polyalkylene oxide group terminal structure of the polymer (A) of the coating layer is OH and / or OMe. The composite semipermeable membrane according to any one of claims 1 to 4, wherein the separation functional layer contains polyamide, and the polyamide and the polymer (A) are bound to each other by an amide bond. When the amount of antifreeze water measured using a differential scanning calorimeter (DSC) per 1 g of the polymer (A) is W _n (g) and the amount of water with lowered melting point is W _f (g), the following formulas 3 and 4 are given. composite semipermeable membrane _{W n} + _{W f} ≧ 2.5 formula according to claim 1, satisfying (3)
W _f / (W _n + W _f ) ≧ 0.5 Expression (4) A microporous support layer, and a separation functional layer on the microporous support layer, on the separation functional layer of the composite membrane, a polyalkylene oxide component (Aa), and (meth) acrylic acid component (Ab) A method for producing a composite semipermeable membrane, comprising the step of applying a solution containing a polymer (A) having an ester bond (Ac) between the component (A-a) and the component (A-b). The method for producing a composite semipermeable membrane according to claim 7, further comprising heating the composite membrane coated with the solution. The method further comprises the step of forming a separation functional layer that forms a crosslinked polyamide by interfacial polycondensation on the surface of the microporous support layer using an aqueous solution containing a polyfunctional amine and an organic solvent containing a polyfunctional acid halide. The manufacturing method according to claim 7. A pretreatment device for pretreating seawater, and a water treatment system in which treated water pretreated by the pretreatment device is filtered by a composite semipermeable membrane to separate concentrated water and fresh water, wherein the composite semipermeable membrane is the A water treatment system which is the composite semipermeable membrane according to any one of claims 1 to 6 and in which the biopolymer component of the treated water is 100 µg C / L or less.