WO2014133132A1

WO2014133132A1 - Composite semipermeable membrane

Info

Publication number: WO2014133132A1
Application number: PCT/JP2014/055061
Authority: WO
Inventors: 淳岡部; 宏治中▲辻▼; 佐々木　崇夫; 将弘木村
Original assignee: 東レ株式会社
Priority date: 2013-02-28
Filing date: 2014-02-28
Publication date: 2014-09-04
Also published as: CN105008031A; CN112870995A; JP6481366B2; JPWO2014133132A1; KR102172598B1; KR20150124952A

Abstract

The present invention provides a composite semipermeable membrane, which is capable of achieving a high permeate volume and has high desorption properties with respect to membrane-fouling substances. This composite semipermeable membrane is provided with a support membrane comprising a base material and a porous support layer, and a separation function layer provided on the porous support layer. The surface zeta potential (A) of the separation function layer under measurement conditions of pH 6 and 10 mM NaCl is in the range of ±15 mV, and the potential difference between the surface zeta potential (B) of the separation function layer under measurement conditions of pH 6 and 1 mM NaCl and the surface zeta potential (A) is ±10 mV or more.

Description

Composite semipermeable membrane

The present invention relates to a composite semipermeable membrane that can achieve a high amount of permeated water and that can be stably operated for a long time. The composite semipermeable membrane obtained by the present invention can be suitably used for desalination of brine, for example.

There are a variety of techniques for removing substances (eg, salts) dissolved in a solvent (eg, water) with respect to separation of the mixture. In recent years, the use of a membrane separation method as an energy saving and resource saving process has been expanded. Examples of membranes used in the membrane separation method include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes. These membranes are used, for example, in the case of obtaining drinking water from seawater, brine, water containing harmful substances, etc., in the production of industrial ultrapure water, wastewater treatment, recovery of valuable materials, and the like.
Most of the reverse osmosis membranes and nanofiltration membranes currently on the market are composite semipermeable membranes, which have an active layer in which a gel layer and a polymer are cross-linked on a support membrane, and polycondensation of monomers on the support membrane There are two types, one having an active layer formed. In particular, a composite semipermeable membrane obtained by coating a support membrane with a separation functional layer made of a crosslinked polyamide obtained by polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide has a permeated water amount and a selective separation property. Widely used as a high separation membrane.

In desalination plants that use reverse osmosis membranes, a higher permeate flow rate is required to further reduce running costs. In response to such demands, a method of bringing a composite semipermeable membrane containing a cross-linked polyamide polymer into a separation active layer into contact with an aqueous solution containing nitrous acid (see Patent Literature 1) or a method of bringing into contact with an aqueous solution containing chlorine (Patent Literature) 2) is known.

Also, one of the problems that occur in desalination plants using reverse osmosis membranes is fouling caused by membrane contaminants such as inorganic and organic substances. A reverse osmosis membrane significantly reduces the amount of permeated water due to fouling. As a method for improving this, a method of neutralizing the charged state by coating polyvinyl alcohol on the surface of the separation functional layer and suppressing fouling (see Patent Document 3) has been proposed.

In order to eliminate fouling, it is common to perform chemical cleaning with alkali or acid after a certain period of operation. For this reason, in order to continue stable operation over a long period of time, durability of the composite semipermeable membrane to alkali or acid, that is, a change in membrane performance before and after chemical contact is required to be small. In order to improve the alkali resistance of the composite semipermeable membrane, a method is disclosed in which a hydrogen ion concentration aqueous solution having a pH of 9 to 13 is brought into contact with the composite semipermeable membrane (see Patent Document 4). Moreover, in order to improve the acid resistance of a composite semipermeable membrane, a method of bringing a cyclic sulfate ester into contact with the composite semipermeable membrane (see Patent Document 5) is disclosed.

Japanese Unexamined Patent Publication No. 2011-125856 Japanese Unexamined Patent Publication No. 63-54905 International Publication No. 97/34686 Japanese Unexamined Patent Publication No. 2006-102624 Japanese Unexamined Patent Publication No. 2010-234284

Thus, the performance required for the reverse osmosis membrane is required not only to remove the salt and the amount of permeated water but also to be able to operate stably for a long period of time. The membranes described in Patent Document 1 and Patent Document 2 can increase the amount of permeated water, but have a problem of low fouling resistance. On the other hand, in the film described in Patent Document 3, the amount of permeated water may be reduced by coating. In addition, the composite semipermeable membranes described in Patent Document 4 and Patent Document 5 may have chemical resistance of the composite semipermeable membrane, but may require frequent chemical cleaning to eliminate fouling. There was room for study in terms of stable driving performance.
An object of the present invention is to provide a composite semipermeable membrane that can achieve a high amount of permeated water and that can be stably operated for a long period of time.

To achieve the above object, the present invention has the following configuration.
(1) A composite semipermeable membrane comprising a support membrane comprising a substrate and a porous support layer, and a separation functional layer provided on the porous support layer,
The surface zeta potential A of the separation functional layer under the measurement conditions of pH 6 and NaCl 10 mM is within ± 15 mV, and the potential difference between the surface zeta potential B of the separation functional layer and the surface zeta potential A under the measurement conditions of pH 6 and NaCl 1 mM. Is a composite semipermeable membrane having a value of ± 10 mV or more.
(2) The composite semipermeable membrane according to (1), wherein the root mean square roughness of the surface of the separation functional layer is 60 nm or more.
(3) The composite semipermeable membrane according to (1) or (2), wherein the separation functional layer is formed from a polyamide obtained by a polymerization reaction of a polyfunctional amine and a polyfunctional acid halide.
(4) The above (1), wherein the potential difference between the surface zeta potential C of the separation functional layer under pH 3 and NaCl 1 mM measurement conditions and the surface zeta potential D of the separation functional layer under pH 10 and NaCl 1 mM measurement conditions is 40 mV or less. (3) The composite semipermeable membrane according to any one of (1) to (3).
(5) The separation function layer according to any one of (1) to (4), wherein the separation functional layer contains an amino group and an amide group, and the ratio of the molar equivalent of the amino group to the molar equivalent of the amide group is 0.2 or more. Composite semipermeable membrane.
(6) The separation function layer according to any one of (1) to (5) above, wherein the separation functional layer has an amide group, an azo group, and a phenolic hydroxyl group, and the ratio of the phenolic hydroxyl group / amide group is 0.1 or less. Composite semipermeable membrane.
(7) The composite semipermeable membrane according to any one of (1) to (6), wherein the surface of the separation functional layer is coated with a crosslinked polymer.
(8) The composite semipermeable membrane according to (7), wherein the crosslinked polymer is a crosslinked compound of a hydrophilic compound.
(9) The composite semipermeable membrane according to (7) or (8), wherein the crosslinked polymer forms a covalent bond with the surface of the separation functional layer.
(10) Using the composite semipermeable membrane before the surface of the separation functional layer is coated with the cross-linked polymer, an aqueous solution having a pH of 6.5 and an NaCl concentration of 2,000 mg / l is 1.55 MPa. F1 / F1 is 0.80 or more when F1 is the amount of permeated water when filtered for 1 hour at a pressure of F2 and F2 is the amount of permeated water after the surface of the separation functional layer is coated with the crosslinked polymer. The composite semipermeable membrane according to any one of (7) to (9), wherein
(11) At 25 ° C., when the aqueous solution having a pH of 6.5 and a NaCl concentration of 2,000 mg / l is filtered at a pressure of 1.55 MPa for 1 hour, the amount of permeate is F3, followed by polyoxyethylene (10) octyl When phenyl ether is added to the aqueous solution to a concentration of 100 mg / l and filtered for 1 hour and then washed with an aqueous solution having a NaCl concentration of 500 mg / l for 1 hour, the amount of permeated water is F4. The composite semipermeable membrane according to any one of (1) to (10), wherein the value is 0.85 or more.

The present invention can provide a composite semipermeable membrane capable of achieving a high permeated water amount and capable of stable operation for a long period of time. By using this composite semipermeable membrane, high quality permeated water can be obtained in an energy saving and stable manner.

1. Composite Semipermeable Membrane The composite semipermeable membrane of the present invention includes a support membrane including a base material and a porous support layer, and a polyamide separation functional layer formed on the porous support layer of the support membrane. In the composite semipermeable membrane of the present invention, the surface zeta potential of the separation functional layer is controlled within ± 15 mV when measured under the conditions of pH 6 and NaCl 10 mM, and the surface when measured under the conditions of pH 6 and NaCl 1 mM. The zeta potential difference is ± 10 mV or more.

(1-1) Separation Function Layer The separation function layer is a layer that plays a role of separating the solute in the composite semipermeable membrane. The composition such as the composition and thickness of the separation functional layer is set in accordance with the intended use of the composite semipermeable membrane.
Specifically, the separation functional layer is made of a crosslinked polyamide obtained by interfacial polycondensation of a polyfunctional amine and a polyfunctional acid halide. Hereinafter, the separation functional layer in the present invention is also referred to as “polyamide separation functional layer”.

Here, the polyfunctional amine is preferably composed of at least one component selected from an aromatic polyfunctional amine and an aliphatic polyfunctional amine.
The aromatic polyfunctional amine is an aromatic amine having two or more amino groups in one molecule, and is not particularly limited, but includes metaphenylenediamine, paraphenylenediamine, 1,3,5-triamine. Examples include aminobenzene. Examples of the N-alkylated product include N, N-dimethylmetaphenylenediamine, N, N-diethylmetaphenylenediamine, N, N-dimethylparaphenylenediamine, and N, N-diethylparaphenylenediamine. In view of stability of performance, metaphenylenediamine or 1,3,5-triaminobenzene is particularly preferable.

Further, the aliphatic polyfunctional amine is an aliphatic amine having two or more amino groups in one molecule, preferably a piperazine-based amine or a derivative thereof. For example, piperazine, 2,5-dimethylpiperazine, 2-methylpiperazine, 2,6-dimethylpiperazine, 2,3,5-trimethylpiperazine, 2,5-diethylpiperazine, 2,3,5-triethylpiperazine, 2- Examples thereof include n-propylpiperazine, 2,5-di-n-butylpiperazine, ethylenediamine and the like. In particular, piperazine or 2,5-dimethylpiperazine is preferable from the viewpoint of stability of performance expression.

These polyfunctional amines may be used alone or in combination of two or more.

The polyfunctional acid halide is an acid halide having two or more carbonyl halide groups in one molecule, and is not particularly limited as long as it gives a polyamide by reaction with the polyfunctional amine. Examples of the polyfunctional acid halide include oxalic acid, malonic acid, maleic acid, fumaric acid, glutaric acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid. 1,3,5-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,3-benzenedicarboxylic acid, 1,4-benzenedicarboxylic acid and other halides can be used. Among acid halides, acid chlorides are preferred, and are acid halides of 1,3,5-benzenetricarboxylic acid, particularly in terms of economy, availability, ease of handling, and ease of reactivity. Trimesic acid halide is preferred. The said polyfunctional acid halide may be used individually by 1 type, or may mix and use 2 or more types.

As a result of intensive studies, the inventors of the present application have found that the surface zeta potential of the separation functional layer is closely related to the amount of permeated water of the composite semipermeable membrane and the detachability of membrane contaminants attached to the membrane surface. I found it.
The zeta potential is a measure of the net fixed charge on the surface of the ultrathin film layer, and the zeta potential on the surface of the thin film layer of the present invention is calculated from the electric mobility according to Helmholtz-Smolchowski as shown in the following formula (1). It can be calculated by the following formula.

(In Formula (1), U is an electric mobility, (epsilon) is a dielectric constant of a solution, (eta) is a viscosity of a solution. Here, the dielectric constant of a solution and a viscosity used the literature value in measurement temperature.)

The principle of measuring the zeta potential will be described. In the (water) solution in contact with the material, there exists a stationary layer that cannot flow in the vicinity of the surface due to the influence of the charge on the surface of the material. The zeta potential is the potential for the solution at the interface (slip surface) between the stationary and fluidized layers of the material.
Here, considering the aqueous solution in the quartz glass cell, since the quartz surface is normally negatively charged, positively charged ions and particles gather near the cell surface. On the other hand, negatively charged ions and particles increase in the center of the cell, and ion distribution occurs in the cell. When an electric field is applied in this state, the ion distribution is reflected in the cell, and ions move at different migration speeds at positions in the cell (referred to as electroosmotic flow). Since the migration speed reflects the charge on the cell surface, the charge (surface potential) on the cell surface can be evaluated by obtaining this migration speed distribution.

Usually, zeta potential is measured using a membrane sample having a size of 20 mm × 30 mm, and standard particles for electrophoresis are NaCl aqueous solutions in which polystyrene particles whose surface is coated with hydroxypropylcellulose (particle size: 520 nm) are adjusted to a predetermined concentration. It can be dispersed and measured. For example, an electrophoretic light scattering photometer ELS-8000 manufactured by Otsuka Electronics Co., Ltd. can be used.

In the composite semipermeable membrane of the present invention, the surface zeta potential of the separation functional layer is controlled within ± 15 mV when measured under the conditions of pH 6 and NaCl 10 mM (surface zeta potential A), and measured under the condition of NaCl 1 mM. The difference between the surface zeta potential B and the surface zeta potential A must be ± 10 mV or more.

The polyamide separation functional layer contains unreacted amino groups and carboxyl groups derived from polyfunctional amines and polyfunctional acid halides, and the value of zeta potential varies depending on the degree of dissociation of these functional groups. The zeta potential at pH 6 of the separation functional layer is related to the adsorptivity of membrane contaminants. When the zeta potential is controlled within ± 15 mV under the condition of NaCl 10 mM, the interaction between membrane contaminants and membrane surface materials is affected. Can be suppressed. If the zeta potential is controlled within ± 15 mV, it indicates that the membrane surface is electrically neutral and suppresses the electrical interaction of membrane contaminants with charged groups present in water. Because. When the zeta potential is ± 15 mV or more, an electrical bias occurs on the film surface, so that an electrical interaction of a film contaminant having a charged group is likely to occur.

On the other hand, when the degree of dissociation of the functional group is high, the salt removal performance and the amount of permeated water of the composite semipermeable membrane increase. This is presumably because the electrostatic repulsion increases or the hydrophilicity increases as the functional group amount of the separation functional layer increases. In the present invention, since the potential difference between the zeta potential A when measured with NaCl 10 mM and the surface zeta potential B when measured with NaCl 1 mM is ± 10 mV or more, desorption of membrane contaminants at a high salt concentration In addition to the properties, high salt removal performance and permeated water can be satisfied at the same time. When the potential difference is less than ± 10 mV, the amount of permeated water is greatly reduced or the interaction with membrane contaminants is strengthened.

The potential difference between the surface zeta potential C of the separation functional layer under pH 3 and NaCl 1 mM measurement conditions and the surface zeta potential D of the separation functional layer under pH 10 and NaCl 1 mM measurement conditions is related to the performance stability of the composite semipermeable membrane. It is preferable that it is 40 mV or less from the viewpoint of high releasability of contaminants when washing the composite semipermeable membrane, and more preferably 25 mV or less.

In order to satisfy the above zeta potential range, the functional group ratio “(molar equivalent of amino group) / (molar equivalent of amide group)” in the separation functional layer is preferably 0.2 or more, more preferably 0.6. That's it. If the ratio of “(mol equivalent of amino group) / (mole equivalent of amide group)” is 0.2 or more, the amount of functional groups in the polyamide separation functional layer is sufficient, so that the hydrophilicity of the membrane can be maintained and the amount of permeated water In addition, a high effect can be obtained in fixing the coating layer to the separation functional layer described later.

For the functional group amount in the polyamide separation functional layer, for example, a ¹³ C solid state NMR method can be used. Specifically, the base material is peeled from the composite semipermeable membrane to obtain a polyamide separation functional layer and a porous support layer, and then the porous support layer is dissolved and removed to obtain a polyamide separation functional layer. The obtained polyamide separation functional layer was measured by DD / MAS- ¹³ C solid state NMR method, and the ratio of each functional group was calculated from the comparison of the integrated value of the carbon peak of each functional group or the carbon peak to which each functional group was bonded. Can be calculated.

Further, 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 Adhesion Society of Japan”, Vol. 27, no. 4 (1991), X-ray photoelectron spectroscopy (XPS) can be used.

As a method of controlling the zeta potential of the separation functional layer, a method of controlling the separation functional layer so that the amount of the functional group of the separation functional layer is reduced when forming the separation functional layer, and the functional group of the separation functional layer having another structure. And a method of coating the surface of the separation functional layer with a polymer. These methods may be used alone or a plurality of methods may be used in combination. However, the method of simply coating the polymer reduces the interaction between the separation functional layer and the membrane contaminant, but is not preferable because the amount of permeated water of the membrane is reduced.

In the method of coating a polymer on the surface of the separation functional layer, the polymer is preferably a hydrophilic compound. By using the hydrophilic compound, it is possible to reduce a decrease in the amount of permeated water of the composite semipermeable membrane due to the coating treatment. It is also preferred that the polymer is a crosslinked polymer. When the polymer to be coated is a crosslinked polymer, peeling of the coating layer can be suppressed when the composite semipermeable membrane is used continuously or washed with a chemical solution, and stable performance is exhibited for a long time. be able to.

The hydrophilic compound of the present invention preferably has at least one reactive group that reacts with a functional group on the film surface. The reactive group may be any as long as it forms a covalent bond with the functional group on the film surface. Examples of the reactive group that binds to the acid halide on the film surface include a hydroxyl group, an amino group, and an epoxy group. Specific examples of hydrophilic compounds include polyvinyl alcohol, partially saponified polyvinyl acetate, polyethyleneimine, polyallylamine, polyepiaminohydrin, amine-modified polyepichlorohydrin, polyoxyethylenedipropylamine, amino group or hydroxyl group. And a partially saponified product of vinyl acetate and a methacrylate ester copolymer, a partially saponified product of vinyl acetate and 2-methacryloyloxyethyl phosphorylcholine copolymer, and the like. These may be used alone or in combination. Among these, from the viewpoint of reactivity and the performance of the obtained film, a primary or secondary amino compound or a polymer having a hydroxyl group is preferably used. When the amino group reacts with the acid halide, an amide bond is formed between the crosslinked polyamide separation functional layer and the hydrophilic compound. When the hydroxyl group reacts with the acid halide, the crosslinked polyamide separation functional layer reacts with the hydrophilic property. An ester bond is formed with the compound.

It is also a preferred aspect that the hydrophilic compound having at least one reactive group that reacts with the functional group on the film surface further has a hydrophilic group that does not react with the functional group on the film surface. Examples of hydrophilic groups include ether groups, amide groups, ester groups, tertiary amino groups, quaternary ammonium groups, cyano groups, nitro groups, alkoxy groups, carboxyl groups, carbonyl groups, keto groups, alkoxycarbonyl groups, amides. Group, cyano group, formyl group, mercapto group, imino group, alkylthio group, sulfinyl group, sulfonyl group, sulfo group, nitroso group, phosphate group, phosphorylcholine group and the like. In particular, an electrically neutral hydrophilic group such as an ether group, an amide group or an ester group is preferred. An amphoteric charged polymer containing the same amount of positively charged groups and negatively charged groups is also preferable in controlling the zeta potential of the present invention.

A hydrophilic compound having at least one reactive group that reacts with a functional group on the membrane surface reacts with a functional group on the surface of the crosslinkable polyamide separation functional layer to form a covalent bond and fix it on the membrane surface. Compared to the case of just adsorbing, stable performance can be expressed for a long time.

The functional group present in the separation functional layer can be converted into a different functional group by an appropriately selected chemical reaction. For example, an aromatic amino group causes a diazo coupling reaction via an aromatic diazonium salt by using dinitrogen tetroxide, nitrous acid, nitric acid, sodium hydrogen sulfite, sodium hypochlorite, or the like as a reagent. An amino group can also be converted to an azo group by reaction of an amino group with a nitroso compound. The zeta potential of the separation functional layer can be controlled by changing the concentration of the reagent to be reacted and the temperature and time for the reaction. In addition, when the functional group is converted, the amount of the functional group before the reaction also affects the zeta potential of the obtained separation functional layer. Therefore, by reducing the thickness of the porous support layer, the unreacted substance remains at the time of production. The zeta potential of the separation functional layer can also be controlled by a method of reducing the amount or a method of removing the compound having a functional group by hot water washing after forming the separation functional layer.

When the separation functional layer is brought into contact with a reagent that reacts with an amino group or a carboxyl group, the yellowness of the separation functional layer is preferably 15 or more and 50 or less, and more preferably 20 or more and 45 or less. The yellowness varies depending on the amount of the azo compound and azo group in the separation functional layer, and when it is within the above range, the zeta potential of the present invention and the stability of the hydrophilic compound can be obtained. When the yellowness of the separation functional layer is less than 15, the amount of the azo compound in the separation functional layer is small, so that the zeta potential of the present invention cannot be obtained. If the yellowness exceeds 50, the amount of azo compound is large and the amount of permeated water is low.

An azo compound is an organic compound having an azo group (—N═N—), and is produced and retained in the separation functional layer when the separation functional layer is brought into contact with a reagent that reacts with an amino group or a carboxyl group. Is done.

The yellowness degree is a degree defined by Japanese Industrial Standards JIS K7373 (2006), which is the degree to which the hue of the polymer is separated from colorless or white in the yellow direction, and is expressed as a positive value.
The yellowness of the separation functional layer can be measured with a color meter. For example, when measuring yellowness in a composite semipermeable membrane in which a separation functional layer is provided on a support membrane, the reflection measurement method is simple. Also, after placing the composite semipermeable membrane on the glass plate so that the separation functional layer is on the bottom, dissolve and remove the support membrane with a solvent that dissolves only the support membrane, and remove the separation functional layer sample remaining on the glass plate. It can also be measured by a transmission measurement method. In addition, when putting a composite semipermeable membrane on a glass plate, it is preferable to peel beforehand the base material of a support film. As the color meter, SM color computer SM-7 manufactured by Suga Test Instruments Co., Ltd. can be used.

In the present invention, the polyamide separation functional layer has an amide group, an azo group, and a phenolic hydroxyl group, and the ratio of the phenolic hydroxyl group / amide group is 0.10 or less, so that even after contact with acid or alkali This is preferable because a composite semipermeable membrane with high chemical resistance and a small change in the amount of permeated water and low fouling property can be obtained. Since the phenolic hydroxyl group is protonated or deprotonated as the pH of the solution changes, the charge state of the polyamide chain constituting the separation functional layer changes and the higher order structure of the polyamide chain changes. There is concern that the amount of water and salt removal performance will change. Crosslinked aromatic polyamides formed by interfacial polycondensation of polyfunctional aromatic amines and polyfunctional acid halides do not have phenolic hydroxyl groups, but dinitrogen tetroxide, nitrous acid, By reacting with a reagent such as nitric acid, sodium hydrogen sulfite or sodium hypochlorite, the aromatic amino group is converted into an aromatic diazonium salt. Then, the reaction which an aromatic diazonium salt is converted into a phenolic hydroxyl group arises by contacting with water. Further, even by a diazo coupling reaction in which a phenol is reacted with an aromatic diazonium salt, a phenolic hydroxyl group that is not present in the crosslinked aromatic polyamide immediately after interfacial polycondensation is introduced.

The lower limit of the phenolic hydroxyl group / amide group ratio is not particularly limited, but this ratio may be, for example, 0.005 or more, or 0.01 or more.

In the composite semipermeable membrane of the present invention, an aromatic diazonium salt produced by post-treatment of a crosslinked aromatic polyamide is reacted with an aromatic compound having an electron donating group or a carbon acid having a highly acidic proton. Thus, the diazo coupling reaction is preferentially generated, and the generation of phenolic hydroxyl groups caused by the reaction with water is suppressed. Examples of the electron donating group include a hydroxy group, an amino group, and an alkoxy group. However, as described above, it is not preferable to use a phenolic compound having a hydroxy group, and a compound having an aromatic amino group in consideration of water solubility. It is desirable to use

The root mean square surface roughness (Rms) of the separation functional layer is preferably 60 nm or more. When the root mean square surface roughness is 60 nm or more, the surface area of the separation functional layer is increased and the amount of permeated water is increased. On the other hand, when the coating layer is thick and the root mean square surface roughness is less than 60 nm, the amount of permeated water is greatly reduced.

The root mean square roughness of the separation functional layer can be controlled by the monomer concentration and temperature when the separation functional layer is formed by interfacial polycondensation. For example, when the temperature during interfacial polycondensation is low, the root mean square roughness decreases, and when the temperature is high, the root mean square roughness increases. In addition, when the polymer is coated on the surface of the separation functional layer, the root mean square roughness becomes small if the coating layer is thick.

The root mean square surface roughness can be measured with an atomic force microscope (AFM). The root mean square surface roughness is the square root of the value obtained by averaging the squares of deviations from the reference plane to the specified plane. Here, the measurement surface is the surface indicated by all measurement data, the specified surface is the surface that is subject to roughness measurement, the specific portion specified by the clip of the measurement surface, and the reference surface is the specified surface When the average height is Z0, it means a plane represented by Z = Z0. As the AFM, for example, NanoScope IIIa manufactured by Digital Instruments can be used.

(1-2) Support Membrane The support membrane is for imparting strength to the polyamide separation functional layer having separation performance and itself has substantially no separation performance for ions and the like. A support membrane consists of a base material and a porous support layer.

The size and distribution of pores in the support membrane are not particularly limited. For example, uniform and fine pores, or gradually having larger fine pores from the surface on the side where the separation functional layer is formed to the other surface, and separation. A support membrane in which the size of the micropores on the surface on which the functional layer is formed is 0.1 nm or more and 100 nm or less is preferable.

The support membrane can be obtained, for example, by forming a porous support layer on the base material by casting a polymer on the base material. The material used for the support membrane and its shape are not particularly limited.

Examples of the base material include a fabric made of at least one selected from polyester and aromatic polyamide. Particular preference is given to using polyesters which are highly mechanically and thermally stable.

As the fabric used for the substrate, a long fiber nonwoven fabric or a short fiber nonwoven fabric can be preferably used. When a polymer solution is cast on a substrate, it penetrates by over-penetration, the substrate and the porous support layer peel off, and the membrane is non-uniform due to fluffing of the substrate. The long fiber nonwoven fabric can be more preferably used because excellent film-forming properties that do not cause defects such as crystallization and pinholes are required. Examples of the long fiber nonwoven fabric include a long fiber nonwoven fabric composed of a thermoplastic continuous filament. When the base material is made of a long-fiber nonwoven fabric, it is possible to suppress non-uniformity and membrane defects caused by fluffing caused by fluffing, which occurs when a short-fiber nonwoven fabric is used. Further, in the step of continuously forming the composite semipermeable membrane, it is preferable to use a long-fiber non-woven fabric having excellent dimensional stability because the tension is applied in the film forming direction of the substrate. In particular, since the orientation of the fiber disposed on the side opposite to the porous support layer of the base material is the vertical orientation with respect to the film forming direction, the strength of the base material can be maintained and film breakage and the like can be prevented. Therefore, it is preferable. Here, the vertical orientation means that the orientation direction of the fibers is parallel to or close to the film forming direction. On the contrary, when the orientation direction of the fiber is perpendicular to the film forming direction or close to a right angle, the orientation is called horizontal orientation.

The fiber orientation degree of the nonwoven fabric substrate is preferably such that the fiber orientation degree on the side opposite to the porous support layer is in the range of 0 ° to 25 °. Here, the degree of fiber orientation is an index indicating the direction of the fibers of the nonwoven fabric substrate constituting the support membrane, and the direction of film formation during continuous film formation is 0 °, that is, the direction perpendicular to the film formation direction, that is, the nonwoven fabric. The average angle of the fibers constituting the nonwoven fabric substrate when the width direction of the substrate is 90 °. Accordingly, the fiber orientation degree is closer to 0 °, and the fiber orientation is closer to 90 °.

The manufacturing process of the composite semipermeable membrane and the manufacturing process of the element include a heating step, but a phenomenon occurs in which the support membrane or the composite semipermeable membrane contracts due to heating. In particular, in continuous film formation, since no tension is applied in the width direction, the film tends to shrink in the width direction. Since the support membrane or the composite semipermeable membrane shrinks, a problem arises in dimensional stability and the like, and therefore, a substrate having a low rate of thermal dimensional change is desired.

In the nonwoven fabric substrate, if the orientation degree difference between the fiber arranged on the opposite side of the porous support layer and the fiber arranged on the porous support layer side is 10 ° to 90 °, the change in the width direction due to heat is suppressed. This is preferable.

The air permeability of the substrate is preferably 2.0 cc / cm ² / sec or more. When the air permeability is within this range, the amount of permeated water of the composite semipermeable membrane increases. This is a process of forming a support film. When a high molecular weight polymer is cast on a base material and immersed in a coagulation bath, the non-solvent replacement rate from the base material side is increased, thereby increasing the porous support layer. This is thought to be because the internal structure of the resin changes and affects the retention amount and diffusion rate of the monomer in the subsequent step of forming the separation functional layer.

The air permeability can be measured by a Frazier type tester based on JIS L1096 (2010). For example, a base material is cut out to a size of 200 mm × 200 mm and used as a sample. This sample is attached to the Frazier type tester, and the suction fan and air hole are adjusted so that the inclined barometer has a pressure of 125 Pa. Based on the pressure indicated by the vertical barometer and the type of air hole used, The amount of air passing through the material, that is, the air permeability can be calculated. As the Frazier type tester, KES-F8-AP1 manufactured by Kato Tech Co., Ltd. can be used.

The thickness of the substrate is preferably in the range of 10 μm to 200 μm, more preferably in the range of 30 μm to 120 μm.

In the present invention, the support membrane includes a base material and a porous support layer, and has substantially no separation performance for ions or the like, and gives strength to the separation functional layer having separation performance substantially. Is.

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

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

For example, the N, N-dimethylformamide (DMF) solution of the above polysulfone is cast on a densely woven polyester fabric or polyester nonwoven fabric to a certain thickness, and wet coagulated in water, so that the surface It is possible to obtain a support membrane having fine pores mostly having a diameter of several tens of nm or less.

The thickness of the above support membrane affects the strength of the resulting 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 thickness of the support film is preferably in the range of 30 μm to 300 μm, more preferably in the range of 100 μm to 220 μm.

The morphology of the porous support layer can be observed with a scanning electron microscope, a transmission electron microscope, or an atomic microscope. For example, when observing with a scanning electron microscope, after peeling off the porous support layer from the substrate, it is cut by the freeze cleaving method to obtain a sample for cross-sectional observation. The sample is thinly coated with platinum or platinum-palladium or ruthenium tetrachloride, preferably ruthenium tetrachloride, and observed with a high resolution field emission scanning electron microscope (UHR-FE-SEM) at an acceleration voltage of 3 to 15 kV. As the high resolution field emission scanning electron microscope, an S-900 electron microscope manufactured by Hitachi, Ltd. can be used.

The support membrane used in the present invention can be selected from various commercially available materials such as “Millipore Filter VSWP” (trade name) manufactured by Millipore, and “Ultra Filter UK10” (trade name) manufactured by Toyo Roshi Kaisha, “Office of Saleen Water Research and Development Progress Report” No. 359 (1968).

The thickness of the porous support layer is preferably in the range of 20 μm to 100 μm. Since the porous support layer has a thickness of 20 μm or more, good pressure resistance can be obtained and a uniform support film having no defects can be obtained. Therefore, a composite semipermeable membrane provided with such a porous support layer Can exhibit good salt removal performance. When the thickness of the porous support layer exceeds 100 μm, the remaining amount of unreacted substances at the time of production increases, thereby reducing the amount of permeated water and chemical resistance.

The thickness of the base material and the thickness of the composite semipermeable membrane can be measured with a digital thickness gauge. Moreover, since the thickness of the separation functional layer is very thin compared with the support membrane, the thickness of the composite semipermeable membrane can be regarded as the thickness of the support membrane. Therefore, the thickness of the porous support layer can be easily calculated by measuring the thickness of the composite semipermeable membrane with a digital thickness gauge and subtracting the thickness of the substrate from the thickness of the composite semipermeable membrane. As the digital thickness gauge, PEACOCK manufactured by Ozaki Manufacturing Co., Ltd. can be used. When a digital thickness gauge is used, the average value is calculated by measuring the thickness at 20 locations.

In addition, when it is difficult to measure the thickness of the substrate or the thickness of the composite semipermeable membrane with a thickness gauge, the thickness may be measured with a scanning electron microscope. Thickness is calculated | required by measuring thickness from the electron micrograph of the cross-sectional observation in arbitrary five places about one sample, and calculating an average value.

2. Manufacturing method Next, the manufacturing method of the said composite semipermeable membrane is demonstrated. The manufacturing method includes a support film forming step and a separation functional layer forming step.

(2-1) Support film forming step The support film forming step includes a step of applying a polymer solution to a substrate and a step of immersing the substrate coated with the solution in a coagulation bath to coagulate the polymer. .
In the step of applying the polymer solution to the substrate, the polymer solution is prepared by dissolving a polymer that is a component of the porous support layer in a good solvent for the polymer.

The temperature of the polymer solution during application of the polymer solution is preferably in the range of 10 ° C. to 60 ° C. when polysulfone is used as the polymer. If the temperature of the polymer solution is within this range, the polymer does not precipitate, and the polymer solution is sufficiently impregnated between the fibers of the base material and then solidified. As a result, the porous support layer is firmly bonded to the substrate by the anchor effect, and a good support film can be obtained. The preferred temperature range of the polymer solution can be adjusted as appropriate depending on the type of polymer used, the desired solution viscosity, and the like.

The time from application of the polymer solution on the substrate to immersion in the coagulation bath is preferably in the range of 0.1 to 5 seconds. If the time until dipping in the coagulation bath is within this range, the organic solvent solution containing the polymer is sufficiently impregnated between the fibers of the base material and then solidified. In addition, the preferable range of time until it immerses in a coagulation bath can be suitably adjusted with the kind of polymer solution to be used, desired solution viscosity, etc.

As the coagulation bath, water is usually used, but any solid can be used as long as it does not dissolve the polymer that is a component of the porous support layer. The membrane form of the support membrane obtained by the composition of the coagulation bath changes, and the resulting composite semipermeable membrane also changes. The temperature of the coagulation bath is preferably −20 ° C. to 100 ° C. More preferably, it is 10 ° C to 50 ° C. When the temperature of the coagulation bath is higher than this range, the vibration of the coagulation bath surface becomes intense due to thermal motion, and the smoothness of the film surface after film formation tends to decrease. On the other hand, if the temperature is too low, the coagulation rate becomes slow and the film-forming property is lowered.

Next, the support membrane thus obtained is washed with hot water in order to remove the solvent remaining in the membrane. The temperature of the hot water at this time is preferably 40 ° C. to 100 ° C., more preferably 60 ° C. to 95 ° C. Within this range, the shrinkage of the support membrane does not increase and the amount of permeated water is good. Conversely, if the temperature is too low, the cleaning effect is small.

(2-2) Formation Process of Separation Function Layer Next, the formation process of the separation function layer constituting the composite semipermeable membrane will be described. In the formation process of the polyamide separation functional layer, by performing interfacial polycondensation on the surface of the support membrane using the aqueous solution containing the polyfunctional amine described above and the organic solvent solution containing the polyfunctional acid halide described above, A polyamide separation functional layer is formed.

Any organic solvent that dissolves the polyfunctional acid halide can be used as long as it is immiscible with water, does not destroy the support membrane, and does not inhibit the formation reaction of the crosslinked polyamide. May be. Typical examples include liquid hydrocarbons and halogenated hydrocarbons such as trichlorotrifluoroethane. In consideration of being a substance that does not destroy the ozone layer, availability, ease of handling, and safety in handling, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, heptadecane, A simple substance such as hexadecane, cyclooctane, ethylcyclohexane, 1-octene, 1-decene or a mixture thereof is preferably used.

For organic solvent solution containing polyfunctional amine aqueous solution or polyfunctional acid halide, acylation catalyst, polar solvent, acid scavenger, surface activity, if necessary, as long as they do not interfere with the reaction between both components A compound such as an agent and an antioxidant may be contained.

In order to perform interfacial polycondensation on the support membrane, first, the surface of the support membrane is coated with a polyfunctional amine aqueous solution. Here, the concentration of the aqueous solution containing the polyfunctional amine is preferably 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 less.

As a method for coating the surface of the supporting membrane with the polyfunctional amine aqueous solution, the surface of the supporting membrane may be uniformly and continuously coated with this aqueous solution, and a known coating means, for example, an aqueous solution is coated on the surface of the supporting membrane. A method, a method of immersing the support film in an aqueous solution, or the like may be performed. The contact time between the support membrane and the polyfunctional amine aqueous solution is preferably in the range of 5 seconds to 10 minutes, and more preferably in the range of 10 seconds to 3 minutes. Next, it is preferable to remove the excessively applied aqueous solution by a liquid draining step. As a method for draining liquid, for example, there is a method in which the film surface is allowed to flow naturally while being held in a vertical direction. After draining, the membrane surface may be dried to remove all or part of the water in the aqueous solution.

Thereafter, an organic solvent solution containing the above-mentioned polyfunctional acid halide is applied to a support film coated with an aqueous polyfunctional amine solution, and a separation functional layer of crosslinked polyamide is formed by interfacial polycondensation. The time for performing the interfacial polycondensation is preferably from 0.1 second to 3 minutes, and more preferably from 0.1 second to 1 minute.

The concentration of the polyfunctional acid halide in the organic solvent solution is not particularly limited. However, if it is too low, formation of the separation functional layer as an active layer may be insufficient, which may be a disadvantage. Therefore, it is preferably about 0.01% by weight or more and 1.0% by weight or less.

Next, it is preferable to remove the organic solvent solution after the reaction by a liquid draining step. For removing the organic solvent, for example, a method of removing the excess organic solvent by naturally flowing it by holding the film in the vertical direction can be used. In this case, the time for gripping in the vertical direction is preferably between 1 minute and 5 minutes, and more preferably between 1 minute and 3 minutes. When the holding time is 1 minute or longer, it is easy to obtain a separation functional layer having the desired function, and when it is 3 minutes or shorter, generation of defects due to over-drying of the organic solvent can be suppressed, thereby suppressing deterioration in performance. Can do.

The composite semipermeable membrane obtained by the above-described method is further added with a process of washing with hot water for 1 minute to 60 minutes within the range of 25 ° C to 90 ° C, so that the solute blocking performance of the composite semipermeable membrane is added. And the amount of permeated water can be further improved. However, if the temperature of the hot water is too high, the chemical resistance decreases if it is cooled rapidly after the hot water washing treatment. Therefore, the hot water cleaning is preferably performed within the range of 25 ° C to 60 ° C. In addition, when the hot water cleaning process is performed at a high temperature exceeding 60 ° C. and not higher than 90 ° C., it is preferable to cool slowly after the hot water cleaning process. For example, there is a method of cooling to room temperature by contacting with low temperature hot water stepwise.

In the hot water washing step, acid or alcohol may be contained in the hot water. By containing an acid or alcohol, it becomes easier to control the formation of hydrogen bonds in the separation functional layer. Examples of the acid include inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid, and organic acids such as citric acid and oxalic acid. The acid concentration is preferably adjusted to be pH 2 or less, more preferably pH 1 or less. Examples of the alcohol include monohydric alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, and polyhydric alcohols such as ethylene glycol and glycerin. The concentration of the alcohol is preferably 10 to 100% by weight, more preferably 10 to 50% by weight.

When the zeta potential of the separation functional layer is controlled by a method for converting the functional group of the separation functional layer, the reagent that reacts the separation functional layer with an unreacted functional group contained in the separation functional layer. Contact. The reagent to be reacted is not particularly limited, and examples thereof include aqueous solutions of nitrous acid and salts thereof, nitrosyl compounds, etc. that react with primary amino groups in the separation functional layer to form a diazonium salt or a derivative thereof. It is done. Since an aqueous solution of nitrous acid or a nitrosyl compound easily generates gas and decomposes, it is preferable to sequentially generate nitrous acid by, for example, a reaction between nitrite and an acidic solution. In general, nitrite reacts with hydrogen ions to produce nitrous acid (HNO ₂ ), but is efficiently produced when the aqueous solution has a pH of 7 or less, preferably pH 5 or less, more preferably pH 4 or less. Among these, an aqueous solution of sodium nitrite reacted with hydrochloric acid or sulfuric acid in an aqueous solution is particularly preferable because of easy handling.

The concentration of nitrous acid or nitrite in the reagent that reacts with the primary amino group to produce a diazonium salt or a derivative thereof is preferably in the range of 0.01 to 1% by weight. When the concentration is 0.01% by weight or more, it is easy to obtain a sufficient effect. When the concentration of nitrous acid or nitrite is 1% by weight or less, handling of the solution becomes easy.

The temperature of the nitrous acid aqueous solution is preferably 15 ° C to 45 ° C. When the temperature of the solution is lower than 15 ° C, the reaction takes time, and when it exceeds 45 ° C, decomposition of nitrous acid is quick and difficult to handle.

The contact time with the nitrous acid aqueous solution may be a time for forming a diazonium salt and / or a derivative thereof, and can be processed in a short time at a high concentration, but a long time is required at a low concentration. Therefore, in the solution having the above concentration, the contact time is preferably within 10 minutes, and more preferably within 3 minutes. The contacting method is not particularly limited, and the composite semipermeable membrane may be immersed in the reagent solution even if the reagent solution is applied. As the solvent for dissolving the reagent, any solvent may be used as long as the reagent can be dissolved and the composite semipermeable membrane is not eroded. The solution may contain a surfactant, an acidic compound, an alkaline compound, or the like as long as it does not interfere with the reaction between the primary amino group and the reagent.

A part of the diazonium salt produced by contact or a derivative thereof is converted into a phenolic hydroxyl group by reacting with water. Moreover, it reacts with the aromatic ring in the material forming the support membrane or the separation functional layer or the aromatic ring of the compound contained in the separation functional layer to form an azo group.

Next, the composite semipermeable membrane formed with the diazonium salt or derivative thereof may be further contacted with a reagent that reacts with the diazonium salt or derivative thereof. Reagents used here are chloride ion, bromide ion, cyanide ion, iodide ion, boron fluoride, hypophosphorous acid, sodium bisulfite, sulfite ion, aromatic amine, phenols, hydrogen sulfide, thiocyanate. An acid etc. are mentioned.
For example, halogen can be introduced by reacting with copper (I) chloride, copper (I) bromide, potassium iodide, or the like. Moreover, a diazo coupling reaction occurs by making it contact with an aromatic amine and phenols, and it becomes possible to introduce | transduce an aromatic into a film surface. In addition, these reagents may be used alone, may be used by mixing a plurality, or may be brought into contact with different reagents a plurality of times. Among these reagents, a reagent that causes a diazo coupling reaction is preferably used because it effectively works to improve the boron removal rate of the composite semipermeable membrane. This is presumably because the substituent introduced instead of the amino group by the diazo coupling reaction is bulky, and the effect of closing the pores existing in the separation functional layer was obtained.
Examples of the reagent that causes the diazo coupling reaction include compounds having an electron-rich aromatic ring or heteroaromatic ring. Examples of the compound having an electron-rich aromatic ring or heteroaromatic ring include aromatic amine derivatives, heteroaromatic amine derivatives, phenol derivatives, and hydroxyheteroaromatic ring derivatives. Specific examples of the above compounds include, for example, aniline, methoxyaniline bonded to the benzene ring in any positional relationship of ortho position, meta position, and para position, and two amino groups in the ortho position, meta position, and para position. Phenylenediamine bonded to the benzene ring in any position of the position, aminophenol in which the amino group and hydroxy group are bonded to the benzene ring in any position of the ortho, meta, or para positions, 1, 3, 5 -Triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, 4-aminobenzylamine, sulfanilic acid, 3,3'-dihydroxybenzidine, 1-aminonaphthalene 2-aminonaphthalene, 1-amino-2-naphthol-4-sulfonic acid, 2-amino-8-naphthol-6-sulfonic acid, 2-amino-5-naphthol-7-sulfonic acid, or an N-alkylated product thereof, and salts thereof, phenol, cresol in any of ortho, meta, and para positions, catechol, resorcinol, hydroquinone, phloroglucinol, Examples thereof include hydroxyquinol, pyrogallol, tyrosine, 1-naphthol, 2-naphthol and salts thereof.

The concentration and time of the reagent reacted with these diazonium salts or derivatives thereof can be adjusted as appropriate in order to obtain the desired effect. The contacting temperature is preferably 10 to 90 ° C, more preferably 20 to 60 ° C. When the contact temperature is less than 10 ° C, the reaction is difficult to proceed, and the desired effect may not be obtained, and may be converted to a phenolic hydroxyl group by reaction with water. At temperatures higher than 90 ° C, the polymer shrinks and permeates. The amount of water may decrease. The concentration of the reagent is preferably 0.01 to 10% by weight, more preferably 0.05 to 1% by weight. When the concentration is lower than 0.01% by weight, the reaction with the diazonium salt or a derivative thereof may take a long time. When the concentration is higher than 10% by weight, it is difficult to control the reaction with the diazonium salt or the derivative thereof. It may become.

Next, the process of providing a hydrophilic compound on the separation functional layer will be described. The hydrophilic compound is formed by coating a solution containing a compound having a hydrophilic group on the separation functional layer and then heating.

The hydrophilic compounds may be used alone or in combination. The hydrophilic compound is preferably used as a solution having a weight concentration of 10 ppm to 1%. If the concentration of the hydrophilic compound is less than 10 ppm, the separation functional layer is not sufficiently coated, and the adhesion of the membrane contaminants becomes remarkable, so that it is difficult to desorb the membrane contaminants during the cleaning. Since the coating layer becomes thicker than 1%, the surface zeta potential A that reflects the potential of the outermost surface of the membrane and the surface zeta potential B that is considered to reflect the potential of the separation functional layer with little influence of ions liberated in water. The potential difference of ± 10 mV or more cannot be achieved.
As the solvent used in the solution containing the hydrophilic compound, water, lower alcohol, halogenated hydrocarbon, acetone, acetonitrile, or the like is preferably used. These may be used alone or in combination of two or more.
Other compounds may be mixed in the solution as necessary. For example, to accelerate the reaction, an alkaline metal compound such as sodium carbonate, sodium hydroxide, or sodium phosphate may be added, or the remaining water-immiscible solvent, free polyfunctional acid halide and amine In order to remove the reaction product with the compound, it is also preferable to add a surfactant such as sodium dodecyl sulfate or sodium benzenesulfonate.

The method for crosslinking the hydrophilic compound is not particularly limited, but preferably thermal crosslinking is performed. As a heating method when performing thermal crosslinking, for example, a method of blowing hot air can be used. In this case, the heating temperature is preferably within the range of 30 to 150 ° C., more preferably within the range of 30 to 130 ° C., and even more preferably within the range of 60 to 100 ° C. When the heating temperature is lower than 30 ° C, sufficient heating is not performed and the crosslinking reaction rate tends to decrease. When the heating temperature is higher than 150 ° C, the side reaction tends to proceed. Moreover, when thermal crosslinking is performed at a temperature exceeding 150 ° C., the thermal shrinkage of the composite semipermeable membrane may increase, and the amount of permeated water tends to decrease.

It is preferable to use a crosslinking agent for crosslinking of the hydrophilic compound. Examples of the crosslinking agent include the aldehydes having at least two functional groups in one molecule, such as the acid or alkali, glyoxal, and glutaraldehyde described above. In particular, the raw material of the crosslinked polymer is preferably polyvinyl alcohol, the crosslinking agent is glutaraldehyde, and the crosslinked polymer preferably contains a reaction product of polyvinyl alcohol and glutaraldehyde.

The addition concentration of the crosslinking agent is preferably in the range of 0.01 to 5.0% by weight, more preferably in the range of 0.01 to 1.0% by weight, and 0.01 to 0.00%. More preferably, it is in the range of 5% by weight. When the concentration is less than 0.01% by weight, the crosslinking density is lowered and the water insolubility of the crosslinked polymer tends to be insufficient. When the concentration is more than 5.0% by weight, the crosslinking density is increased and the amount of permeated water tends to decrease. Furthermore, there is a tendency that the cross-linking reaction rate is increased, gelation is likely to occur, and uniform coating becomes difficult. The reaction time for the crosslinking reaction is preferably 10 seconds to 3 minutes. If it is less than 10 seconds, the reaction may not proceed sufficiently, and if it exceeds 3 minutes, it is difficult to adjust to the zeta potential of the present invention.

Here, even if the composite semipermeable membrane of the present invention is coated with a cross-linked polymer, it is preferable that the amount of permeated water hardly decreases before and after that. That is, using a composite semipermeable membrane before the surface of the separation functional layer is coated with a cross-linked polymer, an aqueous solution having a pH of 6.5 mg and a NaCl concentration of 2,000 mg / l at a pressure of 1.55 MPa is 1 When the permeated water amount after time filtration is F1, and the permeated water amount after coating the surface of the separation functional layer with a crosslinked polymer is F2, the value of F2 / F1 is preferably 0.80 or more. More preferably, it is 0.90 or more. By using such a composite semipermeable membrane, it is possible to impart high detachability to membrane contaminants on the membrane surface without greatly reducing the amount of permeated water of the membrane.

3. Utilization of Composite Semipermeable Membrane The composite semipermeable membrane of the present invention comprises a plurality of pores together with a raw water channel material such as a plastic net, a permeate channel material such as tricot, and a film for increasing pressure resistance as required. Is wound around a cylindrical water collecting pipe and is suitably used as a spiral composite semipermeable membrane element. Furthermore, a composite semipermeable membrane module in which these elements are connected in series or in parallel and accommodated in a pressure vessel can be obtained.

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

By using the composite semipermeable membrane of the present invention, for example, a high permeated water amount can be maintained in a low pressure region such as an operating pressure within a range of 0.1 to 3 MPa, more preferably within a range of 0.1 to 1.5 MPa. However, a composite semipermeable membrane or a fluid separation element can be used. Since the operating pressure can be lowered, the capacity of a pump to be used can be reduced, power consumption can be reduced, and the cost of water production can be reduced. When the operating pressure is less than 0.1 MPa, the amount of permeated water tends to decrease, and when it exceeds 3 MPa, the power consumption of the pump and the like increases and the membrane is easily clogged by fouling.

The composite semipermeable membrane of the present invention uses a sodium chloride aqueous solution having a pH of 6.5 and a concentration of 2,000 mg / l, and the permeated water amount when filtered at 25 ° C. with an operating pressure of 1.0 MPa for 1 hour is 0.5 to 0.5%. It is preferable that it is 3m < ³ > / m < ² > / d. Such a composite semipermeable membrane can be produced, for example, by appropriately selecting the production method described above. By setting the amount of water permeation in the range of 0.5 to 3 m ³ / m ² / d, generation of fouling can be moderately suppressed and water can be formed stably.

In the sewage treated with the composite semipermeable membrane of the present invention, a hardly biodegradable organic substance such as a surfactant may be contained without being completely decomposed by biological treatment. When the treatment is performed with a conventional composite semipermeable membrane, the surfactant is adsorbed on the membrane surface, and the amount of permeated water is reduced. However, since the composite semipermeable membrane of the present invention has a high amount of permeated water and a high detachability with respect to membrane contaminants, it can exhibit stable performance.

Here, the composite semipermeable membrane of the present invention is highly detachable from membrane contaminants. That is, the amount of permeated water when an aqueous solution having a pH of 6.5 mg and a NaCl concentration of 2,000 mg / l was filtered at a pressure of 1.55 MPa for 1 hour was defined as F3, followed by polyoxyethylene (10) octylphenyl ether Is added to the aqueous solution to a concentration of 100 mg / l, filtered for 1 hour, and washed with an aqueous solution having a NaCl concentration of 500 mg / l for 1 hour, where the amount of permeate is F4, the value of F4 / F3 is It is preferably 0.85 or more. More preferably, it is 0.90 or more. By using such a composite semipermeable membrane, even when fouling occurs on the surface of the membrane, the interaction between the membrane and the contaminant is suppressed by washing with an aqueous solution having a NaCl concentration of 500 mg / l or more. Since it has the effect to do, it can detach | desorb easily. Therefore, even when used for advanced treatment of sewage, it is possible to operate stably for a long period of time.
In addition, when the surface of the separation functional layer of the composite semipermeable membrane of the present invention is coated with a crosslinked polymer, the permeated water amount F3 is the same as the aforementioned permeated water amount F2.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

(NaCl removal rate)
The composite semipermeable membrane was subjected to membrane filtration by supplying evaluation water adjusted to a temperature of 25 ° C., pH 7, and a sodium chloride concentration of 2,000 ppm at an operating pressure of 1.55 MPa. The electric conductivity of the supplied water and the permeated water was measured with an electric conductivity meter manufactured by Toa Denpa Kogyo Co., Ltd. to obtain the respective practical salinities, that is, NaCl concentrations. Based on the NaCl concentration thus obtained and the following equation, the NaCl removal rate was calculated.
NaCl removal rate (%) = 100 × {1− (NaCl concentration in permeated water / NaCl concentration in feed water)}

(Permeate amount)
In the test of the preceding paragraph, the amount of the permeated water of the supply water (NaCl aqueous solution) was measured, and the value converted into the daily permeated amount (cubic meter) per square meter of the membrane surface was the membrane permeation flux (m ³ / m ² / d ).
In the evaluation of the amount of permeated water at the time of membrane formation, when the separation functional layer surface is coated with a crosslinked polymer, the composite semipermeable membrane before coating is used at 25 ° C., pH 6.5, NaCl concentration. The amount of permeated water when an aqueous solution of 2,000 mg / l was filtered at a pressure of 1.55 MPa for 1 hour was defined as F1, the amount of permeated water after being coated with the crosslinked polymer was defined as F2, and the value of F2 / F1 was calculated. .
In the evaluation of the amount of permeated water after washing, the amount of permeated water when an aqueous solution having a pH of 6.5 and a NaCl concentration of 2,000 mg / l at 25 ° C. was filtered at a pressure of 1.55 MPa for 1 hour was defined as F3. Oxyethylene (10) octylphenyl ether was added to the aqueous solution to a concentration of 100 mg / l, filtered for 1 hour, and then washed with an aqueous solution having a NaCl concentration of 500 mg / l for 1 hour. The value of / F3 was calculated.

(Porous support layer thickness)
The thickness of the base material before the porous support layer was formed and the thickness of the completed composite semipermeable membrane were measured with a PEACOCK digital thickness gauge manufactured by Ozaki Seisakusho Co., Ltd., and the difference was defined as the thickness of the porous support layer. The thickness of the base material and the thickness of the composite semipermeable membrane were measured at 20 points in the width direction, and average values were calculated.
Porous support layer thickness (μm) = support film thickness (μm) −substrate thickness (μm)

(Zeta potential)
The composite semipermeable membrane is washed with ultrapure water, set in a flat sample cell so that the separation functional layer surface of the composite semipermeable membrane is in contact with the monitor particle solution, and an electrophoretic light scattering photometer (ELS) manufactured by Otsuka Electronics Co., Ltd. -8000). As the monitor particle solution, a measurement solution in which polystyrene latex monitor particles were dispersed in an aqueous NaCl solution adjusted to pH 6, pH 10, or pH 3, respectively was used.
Using each measurement solution, the surface zeta potential A (pH 6, NaCl 10 mM), surface zeta potential B (pH 6, NaCl 1 mM), surface zeta potential C (pH 3, NaCl 1 mM), surface zeta potential D (pH 10, NaCl 1 mM) of the separation function layer are used. Each was measured.

(Functional group amount)
The amount of functional groups in the polyamide separation functional layer is determined by separating the substrate from the composite semipermeable membrane, obtaining the polyamide separation functional layer and the porous support layer, and then dissolving and removing the porous support layer with dichloromethane to separate the polyamide. A functional layer was obtained. The obtained polyamide separation functional layer was measured by DD / MAS- ^13C solid state NMR method, and the amount of each functional group was determined by comparing the carbon peak of each functional group or the integrated value of the carbon peak to which each functional group was bonded. Calculated.

(Root mean square roughness)
A composite semipermeable membrane washed with ultrapure water and air-dried is cut into 1 cm squares, attached to a slide glass with double-sided tape, and the root mean square roughness (RMS) of the separation functional layer is measured with an atomic force microscope. (Nanoscope IIIa: Digital Instruments Co., Ltd.) was used for measurement in the tapping mode. As the cantilever, Veeco Instruments NCHV-1 was used, and measurement was performed at normal temperature and pressure. The scan speed was 1 Hz, and the number of sampling points was 512 pixels square. Gwydion was used as the analysis software. The measurement results were subjected to one-dimensional baseline correction (tilt correction) for both the X axis and the Y axis.

(Air permeability)
The air permeability was measured by a fragile type tester based on JIS L1096 (2010). The base material is cut into a size of 200 mm × 200 mm, attached to a Frazier type tester, the suction fan and air hole are adjusted so that the inclined barometer has a pressure of 125 Pa, and the pressure indicated by the vertical barometer at this time The air permeability was determined from the type of air holes used. As the Frazier type tester, KES-F8-AP1 manufactured by Kato Tech Co., Ltd. was used.

(Production of composite semipermeable membrane)
(Comparative Example 1)
Immediately after casting a 15.0 wt% dimethylformamide (DMF) solution of polysulfone on a non-woven fabric (air permeability 1.0 cc / cm ² / sec) made of polyester fiber produced by the papermaking method at room temperature (25 ° C.) By immersing in pure water for 5 minutes, a support membrane having a porous support layer thickness of 40 μm was produced.
Next, this support membrane was immersed in a 3.5% by weight aqueous solution of metaphenylenediamine, and then the excess aqueous solution was removed, and further, trimesic acid halide was dissolved in n-decane to a concentration of 0.14% by weight. The solution was applied so that the surface of the porous support layer was completely wetted. Next, in order to remove excess solution from the membrane, the membrane was vertically drained and dried by blowing air at 20 ° C. using a blower. Then, it wash | cleaned with the pure water of 40 degreeC, and obtained the composite semipermeable membrane. When the composite semipermeable membrane obtained in this way was evaluated, the membrane performance was the value shown in Table 1.

(Example 1)
The composite semipermeable membrane obtained in Comparative Example 1 was used as an acid catalyst in an aqueous solution containing 0.5% by weight of polyvinyl alcohol (degree of saponification 88%, weight average molecular weight 2,000) and 0.2% by weight of glutaraldehyde. It was immersed for 1 minute in the aqueous solution which added hydrochloric acid so that it might become 0.1 mol / l. After holding for 1 minute vertically and cutting off excess liquid, it was dried in a hot air dryer at 90 ° C. for 30 seconds to obtain a composite semipermeable membrane having a separation functional layer coated with polyvinyl alcohol. The composite semipermeable membrane was hydrophilized by immersing in a 10% aqueous isopropanol solution for 10 minutes before evaluation. The composite semipermeable membrane thus obtained was evaluated. The membrane performance was as shown in Table 1.

(Example 2)
The composite semipermeable membrane obtained in Comparative Example 1 was used as an acid catalyst in an aqueous solution containing 0.5% by weight of polyvinyl alcohol (degree of saponification 88%, weight average molecular weight 2,000) and 0.2% by weight of glutaraldehyde. It was immersed for 1 minute in the aqueous solution which added hydrochloric acid so that it might become 0.1 mol / l. After maintaining for 1 minute vertically and cutting off excess liquid, it was dried in a hot air dryer at 90 ° C. for 1 minute to obtain a composite semipermeable membrane having a separation functional layer coated with polyvinyl alcohol. The composite semipermeable membrane was hydrophilized by immersing in a 10% aqueous isopropanol solution for 10 minutes before evaluation. The composite semipermeable membrane thus obtained was evaluated. The membrane performance was as shown in Table 1.

(Comparative Example 2)
The composite semipermeable membrane obtained in Comparative Example 1 was used as an acid catalyst in an aqueous solution containing 0.5% by weight of polyvinyl alcohol (degree of saponification 88%, weight average molecular weight 2,000) and 0.2% by weight of glutaraldehyde. It was immersed for 2 minutes in an aqueous solution to which hydrochloric acid was added to a concentration of 0.1 mol / liter. After maintaining for 1 minute vertically and cutting off excess liquid, it was dried in a hot air dryer at 90 ° C. for 4 minutes to obtain a composite semipermeable membrane having a separation functional layer coated with polyvinyl alcohol. The composite semipermeable membrane was hydrophilized by immersing in a 10% aqueous isopropanol solution for 10 minutes before evaluation. The composite semipermeable membrane thus obtained was evaluated. The membrane performance was as shown in Table 1.

(Comparative Example 3)
The composite semipermeable membrane obtained in Comparative Example 1 was immersed in an aqueous solution containing 0.5% by weight of polyvinyl alcohol (degree of saponification 99%, average degree of polymerization 500) for 2 minutes. After maintaining for 1 minute vertically and cutting off excess liquid, it was dried in a hot air dryer at 90 ° C. for 4 minutes to obtain a composite semipermeable membrane having a separation functional layer coated with polyvinyl alcohol. The composite semipermeable membrane was hydrophilized by immersing in a 10% aqueous isopropanol solution for 10 minutes before evaluation. The composite semipermeable membrane thus obtained was evaluated. The membrane performance was as shown in Table 1.

(Comparative Example 4)
The composite semipermeable membrane obtained in Comparative Example 1 was treated with a 0.3 wt% aqueous sodium nitrite solution adjusted to pH 3 with sulfuric acid at 30 ° C. for 1 minute. The composite semipermeable membrane was taken out from the nitrous acid aqueous solution and then washed with pure water at 20 ° C. to obtain a composite semipermeable membrane. The composite semipermeable membrane thus obtained was evaluated. The membrane performance was as shown in Table 1.

(Example 3)
The composite semipermeable membrane obtained in Comparative Example 4 was used as an acid catalyst in an aqueous solution containing 0.5% by weight of polyvinyl alcohol (degree of saponification 88%, weight average molecular weight 2,000) and 0.2% by weight of glutaraldehyde. It was immersed for 1 minute in the aqueous solution which added hydrochloric acid so that it might become 0.1 mol / l. After maintaining for 1 minute vertically and cutting off excess liquid, it was dried in a hot air dryer at 90 ° C. for 45 seconds to obtain a composite semipermeable membrane having a separation functional layer coated with polyvinyl alcohol. The composite semipermeable membrane was hydrophilized by immersing in a 10% aqueous isopropanol solution for 10 minutes before evaluation. The composite semipermeable membrane thus obtained was evaluated. The membrane performance was as shown in Table 1.

Example 4
The composite semipermeable membrane obtained in Comparative Example 4 was used as an acid catalyst in an aqueous solution containing 0.5% by weight of polyvinyl alcohol (degree of saponification 88%, weight average molecular weight 2,000) and 0.2% by weight of glutaraldehyde. It was immersed for 1 minute in the aqueous solution which added hydrochloric acid so that it might become 0.1 mol / l. After maintaining for 1 minute vertically and cutting off excess liquid, it was dried in a hot air dryer at 90 ° C. for 1 minute to obtain a composite semipermeable membrane having a separation functional layer coated with polyvinyl alcohol. The composite semipermeable membrane was hydrophilized by immersing in a 10% aqueous isopropanol solution for 10 minutes before evaluation. The composite semipermeable membrane thus obtained was evaluated. The membrane performance was as shown in Table 1.

(Comparative Example 5)
The composite semipermeable membrane obtained in Comparative Example 4 was used as an acid catalyst in an aqueous solution containing 0.5% by weight of polyvinyl alcohol (degree of saponification 88%, weight average molecular weight 2,000) and 0.2% by weight of glutaraldehyde. It was immersed for 2 minutes in an aqueous solution to which hydrochloric acid was added to a concentration of 0.1 mol / liter. After holding for 1 minute vertically and cutting off excess liquid, it was dried in a hot air dryer at 90 ° C. for 3 minutes to obtain a composite semipermeable membrane having a separation functional layer coated with polyvinyl alcohol. The composite semipermeable membrane was hydrophilized by immersing in a 10% aqueous isopropanol solution for 10 minutes before evaluation. The composite semipermeable membrane thus obtained was evaluated. The membrane performance was as shown in Table 1.

(Example 5)
The composite semipermeable membrane obtained in Comparative Example 4 was immersed in an 80 ° C. aqueous solution containing 1% by weight of polyvinyl alcohol (degree of saponification 88%, weight average molecular weight 2,000) for 2 minutes. After maintaining for 1 minute vertically and cutting off excess liquid, it was dried in a hot air dryer at 90 ° C. for 1 minute to obtain a composite semipermeable membrane having a separation functional layer coated with polyvinyl alcohol. The composite semipermeable membrane was hydrophilized by immersing in a 10% aqueous isopropanol solution for 10 minutes before evaluation. The composite semipermeable membrane thus obtained was evaluated. The membrane performance was as shown in Table 1.

(Comparative Example 6)
The composite semipermeable membrane obtained in Comparative Example 1 was treated with a 0.4 wt% sodium nitrite aqueous solution adjusted to pH 3 with sulfuric acid at 30 ° C. for 1 minute. After removing the composite semipermeable membrane from the nitrous acid aqueous solution, it was immersed in a 0.1% aniline aqueous solution at 30 ° C. for 1 minute. Subsequently, it was immersed in a 0.1 wt% aqueous sodium sulfite solution for 2 minutes. The composite semipermeable membrane thus obtained was evaluated. The membrane performance was as shown in Table 1.

(Example 6)
The composite semipermeable membrane obtained in Comparative Example 6 was immersed in an aqueous solution containing 0.5% by weight of polyvinyl alcohol (degree of saponification 88%, weight average molecular weight 2,000) and 0.2% by weight of glutaraldehyde for 1 minute. . After holding for 1 minute vertically and cutting off excess liquid, it was dried in a hot air dryer at 90 ° C. for 30 seconds to obtain a composite semipermeable membrane having a separation functional layer coated with polyvinyl alcohol. The composite semipermeable membrane was hydrophilized by immersing in a 10% aqueous isopropanol solution for 10 minutes before evaluation. The composite semipermeable membrane thus obtained was evaluated. The membrane performance was as shown in Table 1.

(Example 7)
The composite semipermeable membrane obtained in Comparative Example 6 was used as an acid catalyst in an aqueous solution containing 0.5% by weight of polyvinyl alcohol (degree of saponification 88%, weight average molecular weight 2,000) and 0.2% by weight of glutaraldehyde. It was immersed for 1 minute in the aqueous solution which added hydrochloric acid so that it might become 0.1 mol / l. After holding for 1 minute vertically and cutting off excess liquid, it was dried in a hot air dryer at 90 ° C. for 30 seconds to obtain a composite semipermeable membrane having a separation functional layer coated with polyvinyl alcohol. The composite semipermeable membrane was hydrophilized by immersing in a 10% aqueous isopropanol solution for 10 minutes before evaluation. The composite semipermeable membrane thus obtained was evaluated. The membrane performance was as shown in Table 1.

(Comparative Example 7)
The composite semipermeable membrane obtained in Comparative Example 6 was used as an acid catalyst in an aqueous solution containing 0.5% by weight of polyvinyl alcohol (degree of saponification 88%, weight average molecular weight 2,000) and 0.2% by weight of glutaraldehyde. It was immersed for 2 minutes in an aqueous solution to which hydrochloric acid was added to a concentration of 0.1 mol / liter. After holding for 1 minute vertically and cutting off excess liquid, it was dried in a hot air dryer at 90 ° C. for 3 minutes to obtain a composite semipermeable membrane having a separation functional layer coated with polyvinyl alcohol. The composite semipermeable membrane was hydrophilized by immersing in a 10% aqueous isopropanol solution for 10 minutes before evaluation. The composite semipermeable membrane thus obtained was evaluated. The membrane performance was as shown in Table 1.

As described above, the composite semipermeable membrane of the present invention has a high amount of permeated water and a high detachability with respect to membrane contaminants, and can maintain stable performance for a long period of time.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application filed on February 28, 2013 (Japanese Patent Application No. 2013-39605) and a Japanese patent application filed on February 28, 2013 (Japanese Patent Application No. 2013-39648). Incorporated herein by reference.

If the composite semipermeable membrane of the present invention is used, raw water can be separated into permeated water such as drinking water and concentrated water that has not permeated through the membrane, and water suitable for the purpose can be obtained. The composite semipermeable membrane of the present invention can be particularly suitably used for brine or seawater desalination.

Claims

A composite semipermeable membrane comprising a support membrane comprising a substrate and a porous support layer, and a separation functional layer provided on the porous support layer,
The surface zeta potential A of the separation functional layer under the measurement conditions of pH 6 and NaCl 10 mM is within ± 15 mV, and the potential difference between the surface zeta potential B of the separation functional layer and the surface zeta potential A under the measurement conditions of pH 6 and NaCl 1 mM. Is a composite semipermeable membrane having a value of ± 10 mV or more.
The composite semipermeable membrane according to claim 1, wherein the root mean square roughness of the surface of the separation functional layer is 60 nm or more.
The composite semipermeable membrane according to claim 1 or 2, wherein the separation functional layer is formed from a polyamide obtained by a polymerization reaction of a polyfunctional amine and a polyfunctional acid halide.
The potential difference between the surface zeta potential C of the separation functional layer under pH 3 and NaCl 1 mM measurement conditions and the surface zeta potential D of the separation functional layer under pH 10 and NaCl 1 mM measurement conditions is 40 mV or less. The composite semipermeable membrane according to any one of the above.
The composite half layer according to any one of claims 1 to 4, wherein the separation functional layer includes an amino group and an amide group, and a ratio of a molar equivalent of the amino group to a molar equivalent of the amide group is 0.2 or more. Permeable membrane.
The composite half layer according to any one of claims 1 to 5, wherein the separation functional layer has an amide group, an azo group, and a phenolic hydroxyl group, and the ratio of the phenolic hydroxyl group / amide group is 0.1 or less. Permeable membrane.
The composite semipermeable membrane according to any one of claims 1 to 6, wherein a surface of the separation functional layer is coated with a crosslinked polymer.
The composite semipermeable membrane according to claim 7, wherein the crosslinked polymer is a crosslinked product of a hydrophilic compound.
The composite semipermeable membrane according to claim 7 or 8, wherein the cross-linked polymer forms a covalent bond with the surface of the separation functional layer.
Using the composite semipermeable membrane before the surface of the separation functional layer is coated with the crosslinked polymer, an aqueous solution having a pH of 6.5 mg and a NaCl concentration of 2,000 mg / l at a pressure of 1.55 MPa is used. The value of F2 / F1 is 0.80 or more, where F1 is the amount of permeated water when filtered for 1 hour, and F2 is the amount of permeated water after the surface of the separation functional layer is coated with the crosslinked polymer. Item 10. The composite semipermeable membrane according to any one of Items 7 to 9.
At 25 ° C., when the aqueous solution having a pH of 6.5 and a NaCl concentration of 2,000 mg / l was filtered at a pressure of 1.55 MPa for 1 hour, the amount of permeated water was F3, followed by polyoxyethylene (10) octylphenyl ether. In addition to the aqueous solution so as to have a concentration of 100 mg / l, after filtration for 1 hour, when the permeated water amount when washed with an aqueous solution having a NaCl concentration of 500 mg / l for 1 hour is F4, the value of F4 / F3 is 0. The composite semipermeable membrane according to any one of claims 1 to 10, which is 0.85 or more.