JP2020138138A - Composite semipermeable membrane - Google Patents

Abstract

To provide a composite semipermeable membrane that has water permeability and salt removability sufficient to withstand practical use and can still have salt removability even after contacting chlorine.SOLUTION: The composite semipermeable membrane according to the present invention has a microporous support layer and a separation functional layer provided on the microporous support layer, where the separation functional layer contains cross-linked aromatic polyamide and the polymide has a specific partial structure.SELECTED DRAWING: None

Description

The present invention relates to a semipermeable membrane useful for selective separation of a liquid mixture, and particularly to a composite semipermeable membrane having practical permeability and selective separability and high durability.

Membranes used for membrane separation of liquid mixtures include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, etc., and these membranes are beverages from, for example, salt and water containing harmful substances. It is used to obtain water, to produce industrial ultrapure water, to treat wastewater, and to recover valuable resources.

Most of the reverse osmosis membranes and nanofiltration membranes currently on the market are composite semipermeable membranes, and among them, a separation function composed of a crosslinked aromatic polyamide obtained by a polycondensation reaction between a polyfunctional amine and a polyfunctional acid halide. A composite semipermeable membrane (Patent Document 1-2) obtained by coating a layer on a microporous support membrane is widely used as a separation membrane having high permeability and selective separation.

Here, in various water treatments such as water production plants, the operation is designed so that the chlorine added to the pretreatment does not come into contact with the membrane in principle, but the chlorine leaked due to an operation error comes into contact with the membrane and the membrane is oxidized. There is a risk of deterioration. Therefore, in order to reduce the risk of membrane deterioration due to chlorine leakage and prolong the membrane life, studies have been conducted on these composite semipermeable membranes for improving chlorine resistance.

As a method for improving chlorine resistance, a method for improving the monomer component forming the separation functional layer and a method for forming a protective layer on the separation functional layer are known. Patent Document 1 discloses that sodium m-phenylenediamine-4-sulfonate is used as the polyfunctional amine forming the separation functional layer, and Patent Document 2 discloses the polyfunctional amine forming the separation functional layer. Disclosed as a compound having a hexafluoroalcohol as a side chain.

JP-A-63-137704 WO2010 / 096563

In the various proposals described above, some membranes have chlorine resistance, but membranes having both water permeability and removability have not been obtained. An object of the present invention is to provide a composite semipermeable membrane having water permeability and salt removing property that can withstand practical use and having high salt removing property even after contact with chlorine.

In order to achieve the above object, the composite semipermeable membrane of the present invention is a composite semipermeable membrane having a microporous support layer and a separation function layer provided on the microporous support layer, and the separation. The functional layer contains a crosslinked aromatic polyamide, and the polyamide has a partial structure represented by (1).

(Ar1 to 3 are aromatic rings having 5 to 14 carbon atoms which may have a substituent, X is a hydrocarbon having at least two substituents, and X is a carboxy group as the substituent. It has a substituent other than the carboxy group, and one or more of the substituents of X has a pKa of 2.5 or less. Further, R2 to 5 are hydrogen atoms or fats having 1 to 10 carbon atoms. It is a tribal chain.)

According to the present invention, a composite semipermeable membrane having practical water permeability and salt removability and further exhibiting high salt removability even after contact with chlorine can be obtained.

[1. Composite semipermeable membrane]
The composite semipermeable membrane according to the present invention includes a support membrane and a separation functional layer formed on the support membrane. The composite semipermeable membrane has separation performance as a reverse osmosis membrane or a nanofiltration membrane. The separation functional layer has substantially separation performance, and although the support membrane allows water to pass through, it does not substantially have separation performance of ions and the like, and can give strength to the separation functional layer.

(1) Support film In the present embodiment, the 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 not have a base material and may be composed only of a microporous support layer.

(1-1) Base material Examples of the base material include polyester-based polymers, polyamide-based polymers, polyolefin-based polymers, and mixtures or copolymers thereof. Of these, polyester-based polymer fabrics with high mechanical and thermal stability are particularly preferable. As the form of the cloth, a long fiber non-woven fabric, a short fiber non-woven fabric, and a woven or knitted fabric can be preferably used.

(1-2) Microporous Support Layer In the present invention, the microporous support layer is intended to give strength to a separation functional layer that does not substantially have separation performance such as ions and has substantially separation performance. Is. The size and distribution of the pores in the microporous support layer are not particularly limited. For example, it has uniform and fine pores or gradually large fine pores from the surface on the side where the separation function layer is formed to the other surface, and the size of the fine pores on the surface on the side where the separation function layer is formed. A microporous support layer having a size 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 includes, for example, homopolymers or copolymers such as polysulfone, polyether sulfone, polyamide, polyester, cellulose-based polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene oxide. It can be used alone or in combination. Here, as the cellulosic polymer, cellulose acetate, cellulose nitrate and the like can be used, and as the vinyl polymer, polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile and the like can be used.

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 can be mentioned. Further, among these materials, polysulfone can be generally used because of its high chemical, mechanical and thermal stability and easy molding.

The mass average molecular weight (Mw) of polysulfone measured by gel permeation chromatography (GPC) using N-methylpyrrolidone as a solvent and polystyrene as a standard substance is preferably 10,000 or more and 200,000 or less, more preferably. It is 15,000 or more and 100,000 or less.

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

For example, a solution of polysulfone in N, N-dimethylformamide (hereinafter referred to as DMF) is cast on a densely woven polyester cloth or non-woven fabric to a certain thickness and wet-coagulated in water. A microporous support layer can be obtained in which most of the surface has fine pores having a diameter of several tens of nm or less.

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 this document, unless otherwise specified, the thickness means an average value. Here, the average value represents an arithmetic mean value. That is, the thickness of the base material and the microporous support layer can be obtained by calculating the average value of the thicknesses of 20 points measured at intervals of 20 μm in the direction orthogonal to the thickness direction (plane direction of the film) in the cross-sectional observation. ..

(2) Separation function layer (2-1) Chemical structure of separation function layer The separation function layer contains 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 aromatic polyamide in the present invention has a partial structure represented by (1) by an amide bond via its terminal amino group.

(Ar1 to 3 are aromatic rings having 5 to 14 carbon atoms which may have a substituent, X is a hydrocarbon having at least two substituents, and X is a carboxy group as the substituent. It has a substituent other than the carboxy group, and one or more of the substituents of X has a pKa of 2.5 or less. Further, R2 to 5 are hydrogen atoms or fats having 1 to 10 carbon atoms. It is a tribal chain.)
The repeating unit (structure in parentheses) in the formula (1) is preferably a polymer of a polyfunctional aromatic amine and a polyfunctional aromatic acid chloride.

By having the structure (1) at the terminal instead of the amino group, the energy level is lowered as compared with the terminal amino group, so that the oxidation resistance is improved and the structure is less likely to change even after chlorine contact. Further, due to the presence of the hydrophilic carbonyl group, the water permeability is unlikely to decrease even if the terminal functional group becomes bulky. Further, by setting the pKa to 2.5 or less, the proportion of the terminal groups having a charge in the neutral region increases, and the electrostatic field formed by the charge improves the salt removal performance.

The carbon number of X in the partial structure (1) is preferably 6 or less, more preferably 5 or less, still more preferably 4 or less. When the number of carbon atoms is 6 or less, the ratio of the hydrophobic site to the hydrophilic group becomes small, so that the water permeability of the membrane becomes large.

The number of substituents other than the carboxy group of X can be appropriately selected, but from the viewpoint of steric hindrance during the reaction, it is preferably 3 or less, more preferably 2 or less.

The main chain portion of X may be a ring type or a chain type, and may be formed only by a saturated bond or may contain an unsaturated bond, and may be appropriately selected depending on the desired performance. it can. Since methylene hydrogen adjacent to an unsaturated bond is easily attacked by chlorine radicals and its structure after chlorine contact is likely to change, its durability is further improved when it is formed only by a saturated bond. On the other hand, when it has an unsaturated bond, entanglement in the partial structure is less likely to occur and the viscosity is lowered, so that the mobility is improved and the water permeability is improved.
The amount of functional groups in these polyamides can be determined, for example, by 13C solid-state NMR measurement. Specifically, the base material is peeled from the composite semipermeable membrane to obtain a separation function layer and a porous support layer, and then the porous support layer is dissolved and removed to obtain a separation function layer. The obtained separation functional layer is subjected to DD / MAS-13C solid-state NMR measurement, and the integrated value of the peak of the carbon atom to which each functional group is bonded is calculated. Each functional group amount can be identified from this integrated value. As the functional group measured by 13C solid-state NMR, specifically, a carboxy group, an amino group, and an aliphatic chain portion in X are assumed.
X is a cyclic acid anhydride having a substituent such as a sulfo group, a fluoro group, a chloro group, a bromo group, an iodo group or a hydroxyterephthalic acid group, a sulfo group, a fluoro group, a chloro group, a bromo group, an iodo group or a hydroxyterephthalate group. It is preferably derived from at least one compound selected from the group consisting of dicarboxylic acids or dicarboxylic acid salts having substituents such as acid groups. These compounds will be described later.
In the present invention, the oxygen atom / nitrogen atom is preferably 1.15 or more, and more preferably 1.20 or more. Since the oxygen atom / nitrogen atom is 1.15 or more, X containing a carboxy group is sufficiently contained, so that the salt removal property is expected to be improved by the electrostatic field formed by the electric charge and the water permeability is expected to be improved by the hydrophilicity of the carboxy group. ..
The element ratio of the polyamide separation functional layer can be analyzed using, for example, X-ray photoelectron spectroscopy (XPS). Specifically, "Journal of Polymer Science", Vol. 26,559-572 (1988) and "Journal of the Japan Society of Adhesion", Vol. 27, No. It can be obtained by using the X-ray photoelectron spectroscopy (XPS) illustrated in 4 (1991).

2. 2. Method for producing composite semipermeable membrane (1) Method for forming separation functional layer The above separation functional layer is obtained by chemically reacting a polyfunctional aromatic amine, a polyfunctional aromatic acid chloride, and an aliphatic carboxylic acid derivative. The crosslinked aromatic polyamide, which is the main skeleton, is constructed by a polymerization reaction of a polyfunctional aromatic amine and a polyfunctional aromatic acid chloride.

The 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 primary. It means an aromatic amine which is an amino group. Examples of the polyfunctional aromatic amine include o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-xylylene diamine, m-xylylene diamine, p-xylylene diamine, o-diaminopyridine, and m-. A polyfunctional aromatic amine in which two amino groups such as diaminopyridine and p-diaminopyridine are bonded to an aromatic ring at any of the ortho-position, meta-position, and para-position, 1,3,5-triaminobenzene. , 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, 4-aminobenzylamine and other polyfunctional aromatic amines. In particular, m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene are preferably used in consideration of selective separability, permeability, and heat resistance of the membrane. Above all, it is more preferable to use m-phenylenediamine from the viewpoint of easy availability and ease of 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. For example, the trifunctional acid chloride includes trimesic acid chloride and the like, and the bifunctional acid chloride includes biphenyldicarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalenedicarboxylic acid chloride and the like. Can be done. Considering the selective separability and heat resistance of the membrane, a polyfunctional aromatic acid chloride having 2 to 4 carbonyl chloride groups in one molecule is preferable. Trimesic acid chloride is more preferable in consideration of selective separability, permeability and heat resistance of the membrane. These polyfunctional aromatic acid chlorides may be used alone or in combination of two or more.

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.
As a method of chemical reaction, the interfacial polymerization method is most preferable from the viewpoint of productivity and performance. Hereinafter, the step of interfacial polymerization will be described.

The interfacial polymerization steps include (a) a step of contacting an aqueous solution containing a polyfunctional aromatic amine on the porous support layer and (b) a porous support layer in which an aqueous solution containing a polyfunctional aromatic amine is brought into contact. The step of contacting with the polyfunctional aromatic acid chloride solution, (c) the step of draining the organic solvent solution after contact, and (d) washing the composite semipermeable membrane obtained by draining the organic solvent solution with hot water. Has a process.

In this column, the case where the support film includes the base material and the microporous support layer is given as an example, but when the support film has a different configuration, the "microporous support layer" is referred to as "support film". It should be read as.

In the step (a), the concentration of the polyfunctional aromatic amine in the aqueous solution of the polyfunctional aromatic amine 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. It is within the range of weight% or less. When the concentration of the polyfunctional aromatic amine is in this range, sufficient solute removal performance and water permeability can be obtained.

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

After the polyfunctional aromatic amine aqueous solution is brought into contact with the microporous support layer, the liquid is sufficiently drained so that no droplets remain on the membrane. By draining the liquid sufficiently, it is possible to prevent the residual portion of the droplet from becoming a film defect and deteriorating the removal performance after the formation of the microporous support layer. As a method of draining the liquid, for example, as described in JP-A-2-78428, a method of vertically grasping 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 forcibly draining the liquid by blowing an air flow such as nitrogen from an air nozzle can be used. Further, after draining the liquid, the film surface can be dried to remove a part of the water content of the aqueous solution.

In the step (b), the concentration of the polyfunctional aromatic acid chloride in the organic solvent solution is preferably in the range of 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. It is more preferably within the following range. This is because a sufficient reaction rate can be obtained when the content is 0.01% by weight or more, and the occurrence of side reactions can be suppressed when the content is 10% by weight or less.

The organic solvent is preferably immiscible with water, dissolves the polyfunctional aromatic acid chloride, and does not destroy the support film, and is inactive against the polyfunctional aromatic amine and the polyfunctional aromatic acid chloride. Anything is fine. Preferred examples include hydrocarbon compounds such as n-nonane, n-decane, n-undecane, n-dodecane, isooctane, isodecan, isododecane and mixed solvents.

The method of contacting the microporous support layer in which the organic solvent solution of the polyfunctional aromatic acid chloride is brought into contact with the polyfunctional aromatic amine aqueous solution is the method of coating the microporous support layer of the polyfunctional aromatic amine aqueous solution. You can do the same.

In step (c), the organic solvent is removed by the step of draining the organic solvent solution after the reaction. To remove the organic solvent, for example, a method of grasping the membrane in the vertical direction and naturally flowing down the excess organic solvent to remove the organic solvent, a method of drying and removing the organic solvent by blowing wind with a blower, a mixed fluid of water and air. A method of removing excess organic solvent can be used.

In step (d), the composite semipermeable membrane from which the organic solvent has been removed is washed with hot water. The temperature of the hot water is 40 ° C. or higher and 100 ° C. or lower, preferably 60 ° C. or higher and 100 ° C. or lower.

In this way, a layer containing a crosslinked aromatic polyamide having a terminal amino group (formula (2) below) is formed.

(Ar1 to 3 are aromatic rings having 5 to 14 carbon atoms which may have substituents, and R2 to 5 are aliphatic chains having 1 to 10 hydrogen atoms or carbon atoms.)
Next, the partial structure represented by (1) above is imparted to the crosslinked aromatic polyamide. Examples of X having a pKa of 2.5 or less include an SO3H group and a SeO3H group. Examples of the substituent other than the carboxy group in which the pKa of the carboxy group of X is 2.5 or less include a fluoro group, a chloro group, a bromo group, an iodo group and a hydroxyterephthalic acid group. As a method for introducing a substituent other than the carboxy group and the carboxy group, a method in which a cyclic acid anhydride having a substituent other than the carboxy group such as a sulfo group or a fluoro group is allowed to act on the amino group terminal of the aromatic polyamide, sulfo. Examples thereof include a method of reacting a dicarboxylic acid or a dicarboxylic acid salt having a substituent other than the carboxy group such as dicarboxylic acid and fluorodicarboxylic acid.

Examples of the cyclic acid anhydride used include 2-sulfosuccinic anhydride, 4-sulfomaleic anhydride, sulfomaleic anhydride, tetrafluorosuccinic anhydride, tetrafluoromalic anhydride, tetrafluoromaleic anhydride, and tetra. Chlorosuccinic anhydride, tetrachlorosuccinic anhydride, tetrachloromaleic anhydride, tetrabromosuccinic anhydride, tetrabromosphthalic anhydride, tetrabromosuccinic anhydride, tetraiodosuccinic anhydride, tetraiodomalic anhydride, tetraiodomale anhydride Acid and the like can be mentioned.
Examples of the sulfodicarboxylic acid or sulfodicarboxylate include sulfosuccinic acid, sulfomaronic acid, sulfoglutaric acid, sulfoadipic acid, sulfoisophthalic acid, sulfoterephthalic acid and salts thereof [metal salts such as alkali metals (lithium, sodium, (Potass, etc.), salts of alkaline earth metals (calcium, magnesium, etc.) and Group IIB metals (zinc, etc.); ammonium salts; and amine salts, quaternary ammonium salts, etc.] and the like.
The cyclic anhydride or dicarboxylic acid used preferably has 7 or less carbon atoms, more preferably 6 or less, and further preferably 5 or less. When the cyclic acid anhydride has 7 or less carbon atoms, it easily approaches the amino group at the end of the polyamide, so that the reaction proceeds sufficiently and the effect of improving the chlorine resistance of the separation functional layer can be obtained. Further, when the number of carbon atoms in the cyclic acid anhydride is 7 or less, the total number of carbon atoms in X is 6 or less, so that the ratio of the hydrophobic site to the hydrophilic group becomes small and the water permeability of the membrane is improved. ..

The step (A) of reacting the cyclic acid anhydride and the step (B) of reacting the dicarboxylic acid or the dicarboxylic acid salt will be described below, but any of the steps (A) and (B) can be used as the method for imparting the partial structure (1). You may use it. In the step (A), since the cyclic acid anhydride is likely to undergo a hydrolysis reaction due to its ring strain, it is preferable to perform the reaction after draining the excess water. As a method of draining the liquid, a method of forcibly draining the liquid by blowing an air flow such as nitrogen from an air nozzle, a method of drying the film surface by raising the ambient temperature, and the like can be used.
The cyclic acid anhydride may be contacted as it is, or may be dissolved in a solvent that does not deteriorate the support membrane and brought into contact with the composite semipermeable membrane. The solvent is not particularly limited as long as it can dissolve or suspend the cyclic acid anhydride, but it is preferable that the water content in the solvent is 2% or less because the reaction inhibition due to hydrolysis is small.

As a method of contacting the cyclic acid anhydride, the reaction may be carried out by coating on the separation functional layer of the composite semipermeable membrane, or a membrane containing the separation functional layer is added to the cyclic acid anhydride or a solution containing the same. It may be immersed and reacted. Alternatively, a composite semipermeable membrane element, which will be described later, may be prepared and then a solution containing a cyclic acid anhydride may be passed through and reacted.

The reaction time and temperature when the cyclic acid anhydride is applied as a solution or as it is to the composite semipermeable membrane can be appropriately adjusted depending on the type and application method of the cyclic acid anhydride. When the cyclic acid anhydride is applied as a solution, the concentration of the solution is preferably 10 mmol / L or more. When it is 10 mmol / L or more, the amino group at the polyamide terminal of the functional layer reacts sufficiently with the cyclic acid anhydride, and the effect of improving the chlorine resistance of the separation functional layer can be obtained.

In the step (B), a solution prepared by dissolving N, N'-dicyclohexylcarbodiimide and a dicarboxylic acid in an alcohol such as ethanol is coated on the separation functional layer of the composite semipermeable membrane to bring them into contact with each other for reaction. The reaction time and temperature at the time of coating can be appropriately adjusted depending on the type of dicarboxylic acid and the coating method. The concentration of the solution is preferably 10 mmol / L or more. When it is 10 mmol / L or more, it sufficiently reacts with the amino group at the polyamide terminal of the functional layer, and the effect of improving the chlorine resistance of the separated functional layer can be obtained.

(2) Method for Forming Support Film The microporous support layer used in the present invention is such as "Millipore Filter VSWP" (trade name) manufactured by Millipore Co., Ltd. or "Ultrafilter UK10" (trade name) manufactured by Toyo Filter Paper Co., Ltd. You can choose from a variety of commercially available materials, but the "Office of Saline Water Research and Development Progress Report" No. It can be produced according to the method described in 359 (1968).

Specifically, the method for forming the microporous support layer includes the following steps.
-A solution is obtained by dissolving the resin forming the microporous support layer in a solvent.
-Apply the obtained solution to the substrate.
-Immerse in a coagulating solution containing the non-solvent of the above resin.

3. 3. Utilization of composite semipermeable membrane The composite semipermeable membrane is provided with a large number of holes together with a supply water flow path material such as a plastic net, a permeation water flow path material such as a tricot, and a film for increasing pressure resistance as needed. It is wound around a cylindrical water collecting pipe, and is suitably used as a spiral type composite semipermeable membrane element. Further, the elements can be connected in series or in parallel to form a composite semipermeable membrane module housed in a pressure vessel.

Further, the composite semipermeable membrane, its elements, and modules can be combined with a pump for supplying supply water to them, a device for pretreating the supplied water, and the like to form a fluid separation device. By using this separation device, the supplied water can be separated into permeated water such as drinking water and concentrated water that has not permeated the membrane, and water suitable for the purpose can be obtained.

As the supply 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) such as seawater, brackish water, and wastewater is used. Can be mentioned. Generally, TDS refers to the total amount of dissolved solids and is expressed as "mass ÷ volume" or "weight ratio". According to the definition, a solution filtered through a 0.45 micron filter is evaporated at a temperature of 39.5 ° C. or higher and 40.5 ° C. or lower and can be calculated from the weight of the residue, but more simply, the practical salinity (S). Convert from.

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

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited thereto.
(Ratio of oxygen atom / nitrogen atom)
The total number of oxygen atoms and the total number of nitrogen atoms of the separation functional layer of the composite semipermeable membrane in Comparative Examples and Examples were calculated from the measurement results by X-ray photoelectron spectroscopy (XPS).
Measuring device: Quantera SXM (manufactured by PHI)
Excited X-rays: monochromatic Al Kα1, 2 lines (1486.6 eV)
X-ray diameter: 0.2 mm
(Identification of functional group of X)
The base material was physically peeled off from the composite semipermeable membrane 5 m2, and the porous support layer and the separating functional layer were recovered. After drying by allowing to stand at 25 ° C. for 24 hours, it was added little by little to a beaker containing dichloromethane and stirred to dissolve the polymer constituting the porous support layer. The insoluble matter in the beaker was collected with filter paper. This insoluble matter was placed in a beaker containing dichloromethane and stirred to recover the insoluble matter in the beaker. This process was repeated until the elution of the polymer forming the porous support layer in the dichloromethane solution could not be detected. The recovered separation functional layer was dried in a vacuum dryer to remove residual dichloromethane. The obtained separation functional layer was made into a powdery sample by freeze-grinding, sealed in a sample tube used for solid-state NMR measurement, and 13C solid-state NMR measurement was performed by CP / MAS method and DD / MAS method. For 13C solid-state NMR measurement, for example, CMX-300 manufactured by Chemagnetics can be used. An example of measurement conditions is shown below.
Reference substance: Polydimethylsiloxane (internal standard: 1.56 ppm)
Sample rotation speed: 10.5 kHz
Pulse repetition time: 100s
From the obtained spectrum, peak division was performed for each peak derived from the carbon atom to which each functional group was bonded, and the functional group amount ratio was quantified from the area of the divided peak.

Various characteristics of the composite semipermeable membrane are such that seawater adjusted to pH 7.0 (TDS concentration 3.5%, boron concentration about 5 ppm) is supplied to the composite semipermeable membrane at an operating pressure of 5.5 MPa to perform membrane filtration treatment 24. It was determined by measuring the quality of the permeated water and the supplied water after that.

(Membrane permeation flux)
The amount of permeated membrane of the supply water (seawater) was expressed as the permeated membrane flux (m3 / m2 / day) by the amount of permeation per day (cubic meter) per square meter of the membrane surface.

(Solute removal rate)
(Solute removal rate (TDS removal rate)) TDS removal rate (%) = 100 × {1- (TDS concentration in permeated water / TDS concentration in feed water)}
(Chlorine resistance test)
The composite semipermeable membrane was immersed in a 100 mg / L sodium hypochlorite aqueous solution adjusted to pH 7.0 under an atmosphere of 25 ° C. for 24 hours. Then, it was immersed in a 1000 mg / L sodium hydrogen sulfite aqueous solution for 10 minutes, and subsequently washed thoroughly with water.
The chemical resistance was determined from the membrane permeation flux ratio and the TDSSP ratio before and after immersion.

Membrane permeation flux ratio = Membrane permeation flux after immersion / Membrane permeation flux TDSSP ratio before immersion = (100-TDS removal rate after immersion) / (TDS removal rate after 100-immersion)
(Preparation of membrane)
(Reference example 1)
A 16.0% by mass DMF solution of polysulfone (PSf) was cast on a polyester non-woven fabric (air volume 2.0 cc / cm2 / sec) to a thickness of 200 μm under the condition of 25 ° C., and immediately immersed in pure water 5 A porous support membrane was prepared by leaving it for a minute.
(Comparative Example 1)
The porous support membrane obtained in Reference Example 1 is immersed in a 3% by mass aqueous solution of m-phenylenediamine (m-PDA) for 2 minutes, the support membrane is slowly pulled up in the vertical direction, and nitrogen is blown from an air nozzle. After removing excess aqueous solution from the surface of the support membrane, a decan solution at 40 ° C. containing 0.165% by mass of trimesic acid chloride (TMC) was applied so that the surface was completely wet in an environment controlled at room temperature of 40 ° C. After allowing to stand for 1 minute, the membrane was made vertical and the excess solution was drained and removed to obtain a composite semipermeable membrane having a crosslinked aromatic polyamide separation functional layer.

(Comparative Example 2)
The porous support membrane obtained in Reference Example 1 is immersed in a 3% by mass aqueous solution of m-phenylenediamine (m-PDA) for 2 minutes, the support membrane is slowly pulled up in the vertical direction, and nitrogen is blown from an air nozzle. After removing excess aqueous solution from the surface of the support membrane, a decan at 40 ° C. containing 0.165% by mass of trimesic acid chloride (TMC) and 0.05% by mass of 2-sulfosuccinic anhydride in an environment controlled at room temperature of 40 ° C. After applying the solution so that the surface is completely wet and allowing it to stand for 1 minute, the excess solution is drained and removed by making the membrane vertical to obtain a composite semipermeable membrane having a crosslinked aromatic polyamide separation functional layer. It was.

(Comparative Example 3)
The composite semipermeable membrane obtained in Comparative Example 1 was washed with water at 50 ° C. for 2 minutes and immersed in an aqueous solution containing 500 ppm m-PDA for 60 minutes. The membrane was then immersed in an aqueous solution at 35 ° C. containing 0.3 wt% sodium nitrite, adjusted to pH 3 with sulfuric acid, for 1 minute and then washed with water. Finally, the composite semipermeable membrane of Comparative Example 3 was obtained by immersing in a 0.1 wt% sodium sulfite aqueous solution for 2 minutes.

(Comparative Example 4)
The composite semipermeable membrane obtained in Comparative Example 1 was coated with an isopropanol solution containing 100 mmol / L succinic anhydride so that the surface was completely wet, and contacted at 25 ° C. for 2 minutes. The obtained composite semipermeable membrane was immersed in RO water for 10 minutes to obtain the composite semipermeable membrane of Comparative Example 4.

(Comparative Example 5)
A composite semipermeable membrane of Comparative Example 5 was obtained in the same manner as in Comparative Example 4 except that an isopropanol solution containing 100 mmol / L phthalic anhydride was used as the cyclic acid anhydride.

(Comparative Example 6)
The composite semipermeable membrane obtained in Comparative Example 1 is coated with a solution of 100 mmol / L of 2,5-dichloroterephthalic acid and N, N'-dicyclohexylcarbodiimide so that the surface is completely wet. Then, they were contacted at 25 ° C. for 2 minutes. The obtained composite semipermeable membrane was immersed in RO water for 10 minutes to obtain the composite semipermeable membrane of Comparative Example 6.

(Example 1)
A composite semipermeable membrane of Example 1 was obtained in the same manner as in Comparative Example 6 except that 100 mmol / L sulfomaronic acid was used as the dicarboxylic acid.

(Example 2)
A composite semipermeable membrane of Example 2 was obtained in the same manner as in Comparative Example 6 except that 100 mmol / L sulfosuccinic acid was used as the dicarboxylic acid.

(Example 3)
A composite semipermeable membrane of Example 3 was obtained in the same manner as in Comparative Example 6 except that 10 mmol / L sulfosuccinic acid was used as the dicarboxylic acid.

(Example 4)
A composite semipermeable membrane of Example 4 was obtained in the same manner as in Comparative Example 6 except that 100 mmol / L sulfopimelic acid was used as the dicarboxylic acid.

(Example 5)
A composite semipermeable membrane of Example 5 was obtained in the same manner as in Comparative Example 6 except that 100 mmol / L sulfosveric acid was used as the dicarboxylic acid.

(Example 6)
A composite semipermeable membrane of Example 6 was obtained in the same manner as in Comparative Example 6 except that 100 mmol / L hydroxyterephthalic acid was used as the dicarboxylic acid.

(Example 7)
A composite semipermeable membrane of Example 7 was obtained in the same manner as in Comparative Example 6 except that 100 mmol / L tetrafluorosuccinic acid was used as the dicarboxylic acid.

(Example 8)
The composite semipermeable membrane of Example 8 was obtained in the same manner as in Comparative Example 4 except that 100 mmol / L tetrachlorophthalic anhydride was used as the cyclic acid anhydride. Table 1 shows the number of carbon atoms of X in the composite semipermeable membrane, the oxygen / nitrogen atoms detected by the XPS method, the performance during production, and the performance after chlorine deterioration. As shown in Examples, it can be seen that the composite semipermeable membrane of the present invention has high water permeability and removal performance, and also has high chlorine resistance.

Claims (5)

A composite semipermeable membrane having a microporous support layer and a separation functional layer provided on the microporous support layer, the separation functional layer containing a crosslinked aromatic polyamide, and the polyamide (1). A composite semipermeable membrane characterized by having a partial structure represented by).

(Ar1 to 3 are aromatic rings having 5 to 14 carbon atoms which may have a substituent, X is a hydrocarbon having at least two substituents, and X is a carboxy group as the substituent. It has a substituent other than the carboxy group, and one or more of the substituents of X has a pKa of 2.5 or less. Further, R2 to 5 are hydrogen atoms or fats having 1 to 10 carbon atoms. It is a tribal chain.) The composite semipermeable membrane according to claim 1, wherein R2 to 5 of the crosslinked aromatic polyamide structure (1) of the composite semipermeable membrane is a benzene ring in which Ar1 to 3 may have a substituent. film. The composite semipermeable membrane according to claim 1 or 2, wherein the oxygen atom / nitrogen atom ≥ 1.15 detected by the XPS method in the composite semipermeable membrane. The composite semipermeable membrane according to any one of claims 1 to 3, wherein the carbon number of X in the structure (1) of the crosslinked aromatic polyamide of the composite semipermeable membrane is 2 to 6. The composite semipermeable membrane according to any one of claims 1 to 4, wherein the substituent other than the carboxy group is a sulfo group.