WO2014133133A1 - Composite semipermeable membrane - Google Patents

Abstract

The purpose of the present invention is to provide a composite semipermeable membrane having high pressure resistance. This composite semipermeable membrane is provided with a microporous support membrane, which has a base material and a porous support layer formed on the base material, and with a separation function layer established on the porous support layer, and the weight per unit volume of the porous support layer after passing pure water through for 24 hours at a temperature of 25°C and 5.5 MPa pressure is 0.50 g/cm³ to 0.65 g/cm³.

Description

Composite semipermeable membrane

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

Regarding the separation of mixtures, there are various techniques for removing substances (eg, salts) dissolved in a solvent (eg, water), but in recent years, the use of membrane separation methods has expanded as a process for saving energy and resources. is doing. Membranes used in membrane separation methods include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes. These membranes can be used for beverages such as seawater, brine, and water containing harmful substances. It is used for obtaining water, industrial ultrapure water production, wastewater treatment, recovery of valuable materials, and the like (see Patent Documents 1 and 2).

The majority of currently marketed reverse osmosis membranes and nanofiltration membranes are composite semipermeable membranes, which have an active layer in which a gel layer and a polymer are crosslinked on a porous support membrane, and monomers on the porous support membrane. There are two types, one having an active layer obtained by polycondensation. Among these, composite semipermeable membranes obtained by coating a porous 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 have permeability and selective separation. It is widely used as a highly reliable separation membrane.

When performing separation using a reverse osmosis membrane, it is necessary to apply a pressure higher than the difference between the osmotic pressure on the supply water side and the osmotic pressure on the permeate side to the supply water side. When the pressure is high, a higher pressure is required as the operation pressure. Further, if the ratio of the amount of permeated water to the feed water (this is referred to as the yield) increases, the solute concentration of the concentrated water increases, so that a higher pressure is required as the operating pressure.
For example, in the case of seawater desalination, the osmotic pressure of seawater having a concentration of 3.5% by weight is approximately 2.5 MPa, and when desalination is performed at a yield of 40%, the concentration of concentrated water is about 6% by weight. The operating pressure is not less than the osmotic pressure (about 4.4 MPa).

In order to obtain sufficient quality and quantity of permeated water, it is actually necessary to apply a pressure about 2 MPa higher than the osmotic pressure of concentrated water (this pressure is called effective pressure) to the concentrated water side. is there.
Conventional general seawater desalination is operated under a condition of about 40% yield with a pressure of about 6 to 6.5 MPa. In the case of separation / concentration of a high concentration solution, there is an example in which a reverse osmosis membrane device is operated at a pressure of 7 MPa or more (see Patent Document 3).

In order to achieve both the pressure resistance and membrane performance of the reverse osmosis membrane, in Patent Document 4, 60% or more of the pleats having a height of 1 to 600 nm and a diameter of 1 to 500 nm existing in the separation functional membrane have a diameter of 150 nm or less. Thus, there has been proposed a composite semipermeable membrane having a separation functional membrane formed of a crosslinked aromatic polyamide that suppresses a decrease in the rejection rate and improves pressure resistance.

Patent Document 5 proposes a composite semipermeable membrane having high pressure resistance by adding an inorganic salt to a membrane forming stock solution of a microporous support membrane and strengthening the bond between polymers by electrostatic interaction. .

Japanese Unexamined Patent Publication No. 55-14706 Japanese Patent Laid-Open No. 5-76740 Japanese Unexamined Patent Publication No. 10-305216 Japanese Patent Laid-Open No. 9-141071 Japanese Unexamined Patent Publication No. 2002-177750

Despite the various proposals described above, the pressure resistance of the separation membrane was not sufficiently improved, and there was room for improvement. An object of the present invention is to provide a composite semipermeable membrane having higher pressure resistance.

In order to achieve the above object, the composite semipermeable membrane of the present invention has the following constitutions (1) to (8).
(1) A composite semipermeable membrane comprising a substrate and a microporous support membrane comprising a porous support layer formed on the substrate, and a separation functional layer provided on the porous support layer. ,
A composite half having a weight per unit volume of the porous support layer of 0.50 g / cm ³ or more and 0.65 g / cm ³ or less after passing pure water for 24 hours at a temperature of 25 ° C. and a pressure of 5.5 MPa. Permeable membrane.
(2) The average impregnation amount per unit area of the porous support layer to the substrate is 1.0 g / m ² or more and 5.0 g / m ² or less, and 1.2 times or more of the average impregnation amount The composite semipermeable membrane according to the above (1), which contains 20% or more of the portion.
(3) The above-mentioned (1) or (2), wherein the base material is a long-fiber nonwoven fabric, and the air flow rate of the base material is 0.5 ml / cm ² / sec or more and 5.0 ml / cm ² / sec or less. ) Composite semipermeable membrane.
(4) The orientation degree difference between the fiber orientation on the porous support layer side surface of the substrate and the fiber orientation on the opposite surface of the substrate to the porous support layer is 10 ° or more and 90 ° or less. The composite semipermeable membrane according to any one of (1) to (3).
(5) The composite semipermeable membrane according to any one of (1) to (4), wherein the surface of the separation functional layer is coated with a hydrophilic polymer.
(6) The composite semipermeable membrane according to (5), wherein the hydrophilic polymer has an average molecular weight of 8,000 or more.
(7) The composite semipermeable membrane according to (5) or (6), wherein the hydrophilic polymer is polyethylene glycol or a copolymer containing polyethylene glycol.
(8) The separation functional layer is a polyamide separation functional layer containing a carboxy group and an amide group, and a ratio of [molar equivalent of carboxy group / molar equivalent of amide group] in the polyamide separation functional layer is 0.40 or more. The composite semipermeable membrane according to any one of (1) to (7), wherein the average [oxygen / nitrogen] atomic ratio between the front and back sides of the polyamide separation functional layer is 0.95 or less.

By the present invention, a composite semipermeable membrane having high pressure resistance is realized.
By using this membrane in a water treatment device such as a membrane separator, it is expected to continue stable operation over a long period of time even under high-pressure operation conditions in the desalination of brine or seawater.

1. Composite semipermeable membrane The composite semipermeable membrane of the present invention comprises a substrate and a microporous support membrane comprising a porous support layer formed on the substrate, and a separation functional layer provided on the porous support layer. The weight per unit volume of the porous support layer after passing pure water for 24 hours at a temperature of 25 ° C. and a pressure of 5.5 MPa is 0.50 g / cm ³ or more and 0.65 g / cm ³ or less. It is characterized by being.

(1-1) Microporous support membrane In the present invention, the microporous support membrane comprises a base material and a porous support layer, and has substantially no separation performance of ions or the like. This is to give strength to the separation functional layer having separation performance.
The thickness of the microporous support membrane described above affects the strength of the composite semipermeable membrane and the packing density when it is used as a membrane element. In order to obtain sufficient mechanical strength and packing density, the thickness is preferably in the range of 30 to 300 μm, more preferably in the range of 50 to 250 μm.

(1-1-1) Porous support layer As the material of the porous support layer, polysulfone, polyamide, polyester, cellulose polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, polyphenylene oxide, homopolymer such as polyphenylene oxide, These copolymers can be used alone or blended.
Here, cellulose acetate, cellulose nitrate and the like 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, a homopolymer such as polysulfone, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone or a copolymer thereof is 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. Furthermore, it can be preferably used.

Specifically, it is preferable to use polysulfone composed of repeating units represented by the following chemical formula because the pore diameter is easy to control and the dimensional stability is high.

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

For example, an N, N-dimethylformamide (hereinafter referred to as DMF) solution of the above polysulfone is cast on a substrate to a certain thickness, and wet coagulated in water, so that most of the surface has a diameter of 1 to A microporous support membrane having fine pores of 30 nm can be obtained.

The thickness of the porous support layer is preferably in the range of 20 to 100 μm.
In the present specification, unless otherwise specified, the thickness of a layer or a film means an average value. Here, the average value represents an arithmetic average value. That is, the thickness of the layer or film is 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 (film surface direction) in cross-sectional observation of the layer or film.

When the composite semipermeable membrane is operated for the purpose of desalting or the like, the porous support layer is subjected to deformation such as compression in the thickness direction due to pressure on the porous structure. By subjecting the composite semipermeable membrane to water passage treatment at a pressure of 5.5 MPa for 24 hours or more, the film thickness becomes constant.
The porous support layer has a temperature per unit volume of 0.50 g / cm ³ or more and 0.65 g / cm ³ or less after passing pure water for 24 hours at a temperature of 25 ° C. and a pressure of 5.5 MPa.

The weight per unit volume of the porous support layer affects the strength and membrane performance of the composite semipermeable membrane and the membrane element. If it is the said range, sufficient intensity | strength and film | membrane performance can be obtained.
When the weight per unit volume is in the above range, the generation of deformation and defects is suppressed even during high-pressure load operation of the membrane separator using the composite semipermeable membrane according to the present invention, and the permeation flux and solute removal performance are improved. Stabilized. The weight per unit volume was calculated by physically peeling the substrate from the composite semipermeable membrane, measuring the weight of the porous support layer, and dividing by the volume of the porous support layer.

On the other hand, if the weight per unit volume of the porous support layer is larger than 0.65 g / cm ³ , the filtration resistance of the porous support layer portion increases, and the permeation flux of the composite semipermeable membrane may be reduced.
Further, when deformation such as crushing occurs, it causes a defect during high-pressure load operation, and the permeation flux and solute removal performance become unstable. On the other hand, when the weight per unit volume of the porous support layer is smaller than 0.5 g / cm ³ , there are many voids (defects) in the porous support layer, and the solute removal performance is lowered.

The porous support layer can have the weight per unit volume within the above range by controlling the impregnation of the porous support layer into the substrate and controlling voids in the porous support layer. Further, when the porous support layer contains polysulfone, the weight per unit volume of the porous support layer can be adjusted to the above range by adjusting the polysulfone concentration in the polymer solution to be the porous support layer. it can.
Specifically, the polysulfone concentration is preferably 18% by weight to 30% by weight, and more preferably 19% by weight to 25% by weight.

The amount of impregnation per unit volume of the substrate of the porous support layer is preferably 1.0 g / m ² or more and 5.0 g / m ² or less, more preferably 1.5 g / m ² or more and 3.0 g / m ² or less. It is. Further, it is more preferable to include 20% or more of portions that are 1.2 times or more of the average impregnation amount. When the amount of impregnation is within the above range, the adhesion with the substrate can be improved, and the physical stability of the microporous support membrane can be enhanced. In addition, when the base material is impregnated with the polymer solution, the rate of substitution of the solvent with the non-solvent is increased during the phase separation for forming the porous support as compared with the case where the polymer solution is not impregnated with the base material. . As a result, generation of macro voids can be suppressed. On the other hand, when the amount of impregnation is too large, voids in the substrate are reduced and the water permeability of the composite semipermeable membrane is lowered.
The amount of impregnation of the porous support layer into the base material per unit volume is determined by immersing the base material in a solvent in which the polymer that forms the porous support layer dissolves, and eluting the polymer before and after immersion in the solvent. It can be calculated from the weight of the substrate and the area of the substrate.

The amount of impregnation per unit volume of the porous support layer to the base material is the concentration of the polymer solution that becomes the porous support layer, the air flow rate and orientation of the base material, and the temperature and speed at which the porous support layer is formed. It can be controlled by adjusting the time.

(1-1-2) Substrate Examples of the substrate constituting the microporous support membrane include a polyester polymer, a polyamide polymer, a polyolefin polymer, or a mixture or copolymer thereof. It is done. Among them, a polyester polymer is preferable because a microporous support film that is superior in durability such as mechanical strength, heat resistance, water resistance, and chemical resistance can be obtained.

The polyester polymer is a polyester composed of an acid component and an alcohol component.
As the acid component, an aromatic carboxylic acid such as terephthalic acid, isophthalic acid or phthalic acid, an aliphatic dicarboxylic acid such as adipic acid or sebacic acid, or an alicyclic dicarboxylic acid such as cyclohexanecarboxylic acid can be used.
As the alcohol component, ethylene glycol, diethylene glycol, polyethylene glycol, or the like can be used.

Examples of the polyester polymer include polyethylene terephthalate resin, polybutylene terephthalate resin, polytrimethylene terephthalate resin, polyethylene naphthalate resin, polylactic acid resin, and polybutylene succinate resin. Examples include coalescence.

It is preferable to use a fibrous base material for the fabric used for the base material. In particular, since the base material is made of a long-fiber non-woven fabric composed of thermoplastic continuous filaments, it suppresses non-uniformity and membrane defects when casting a polymer solution caused by fuzz, which occurs when a short-fiber non-woven fabric is used. be able to. Here, the long-fiber nonwoven fabric is a nonwoven fabric having an average fiber length of 30 cm or more and an average fiber diameter of 3 to 30 μm.

In the case of continuous film formation, since a tension is applied in the film forming direction, it is preferable to use a long-fiber nonwoven fabric that is more excellent in dimensional stability for the substrate. In addition to maintaining high strength, it not only achieves a high effect of preventing membrane breakage, but also improves formability as a laminate including a porous support layer and a substrate when imparting irregularities to the separation membrane. In addition, the uneven shape on the surface of the separation membrane is stable, which is preferable.

Also, a long fiber nonwoven fabric is preferable because the base material can be sufficiently impregnated with a polymer solution containing polysulfone or the like serving as a porous support layer. By sufficiently impregnating the base material with the polymer solution, the adhesion to the base material is improved, and the physical stability of the microporous support membrane can be increased. In addition, when the base material is impregnated with the polymer solution, the rate of substitution of the solvent with the non-solvent is increased during the phase separation for forming the porous support as compared with the case where the polymer solution is not impregnated with the base material. . As a result, generation of macro voids can be suppressed. In particular, when the polymer solution serving as the porous support layer is 18% by weight or more, the impregnation of the polymer solution into the substrate is reduced, and the physical stability of the microporous support film is reduced. By increasing the impregnation, the physical stability of the microporous support membrane can be increased.

The substrate preferably has an air permeability of 0.5 ml / cm ² / sec or more and 5.0 ml / cm ² / sec or less. More preferably, it is 1.0 ml / cm ² / sec or more and 3.0 ml / cm ² / sec or less. When the air flow rate of the substrate is within the above range, the polymer solution that becomes the porous support layer is impregnated into the substrate, so that the adhesion to the substrate is improved and the physical stability of the microporous support film is improved. Can increase the sex. In addition, when the base material is impregnated with the polymer solution, the rate of substitution of the solvent with the non-solvent is increased during the phase separation for forming the porous support as compared with the case where the polymer solution is not impregnated with the base material. . As a result, generation of macro voids can be suppressed. On the other hand, if the air flow rate is too large, the polymer solution is impregnated to the back surface and the base material thickness becomes non-uniform, resulting in performance degradation. Further, the base material is deformed when a high pressure is applied. The air flow rate of the substrate can be controlled by adjusting the fiber diameter and basis weight of the long fiber nonwoven fabric.

The long fiber nonwoven fabric has a difference in orientation degree between the fiber orientation on the porous support layer side surface (upper surface) and the fiber orientation on the surface opposite to the porous support layer (lower surface) of 10 ° or more and 90 ° or less. It is preferable that it is 20 ° or more and 90 ° or less.
Here, the fiber orientation degree is an index indicating the direction of fibers constituting the nonwoven fabric base material, 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 base material. This means the average angle of the fibers constituting the nonwoven fabric substrate when the width direction is 90 °. Accordingly, the closer to 0 ° the fiber orientation, the longer the orientation, and the closer to 90 °, the lateral orientation.

By laminating two or more long fiber nonwoven fabrics, the fiber orientation of the surface (lower surface) opposite to the fiber orientation on the porous support layer side surface (upper surface) can be controlled, and the fiber orientation degree difference Can be in the above range. Further, the fiber orientation degree can be controlled by adjusting the fiber spray angle and spray speed and the collection conveyor angle and speed.
The thickness of the substrate is preferably in the range of 10 to 200 μm, more preferably in the range of 30 to 120 μm.

When the orientation degree difference is in the above range, the groove of the permeate channel material such as tricot and the fiber orientation of the base material intersect, and deformation such as a drop in the permeate channel material groove of the composite semipermeable membrane at high pressure load. Can be suppressed, which is preferable. In addition, the said deformation | transformation becomes a cause of film | membrane performance fall. In particular, the fibers arranged on the surface (lower surface) opposite to the porous support layer are longitudinally oriented with respect to the film forming direction, so that the strength can be maintained and film breakage and the like can be prevented. The fiber orientation degree of the fibers disposed on the surface (lower surface) opposite to the porous support layer of the substrate is preferably in the range of 0 ° to 35 °.
The permeate flow channel material such as tricot is used together with the composite semipermeable membrane and generally has a groove shape in a specific direction for the purpose of collecting permeate.

The degree of fiber orientation was determined by randomly collecting 10 small sample samples from a nonwoven fabric substrate, photographing the surface of the sample with a scanning electron microscope at 100 to 1000 times, and measuring 10 fibers from each sample, for a total of 100 fibers. Measure the angle when the longitudinal direction (longitudinal direction, film forming direction) of the nonwoven fabric is 0 ° and the width direction (lateral direction) of the nonwoven fabric is 90 °, and the average value thereof is the first decimal place. Round off to obtain the fiber orientation.

(1-2) Separation Functional Layer In the present invention, the separation functional layer is preferably a polyamide separation functional layer containing polyamide.
The polyamide can be formed by interfacial polycondensation of a polyfunctional amine and a polyfunctional acid halide. Here, it is preferable that at least one of the polyfunctional amine and the polyfunctional acid halide contains a trifunctional or higher functional compound.
Moreover, the polyamide into which the aromatic ring or the heteroaromatic ring was introduce | transduced from the point which improves performance, such as a boron removal rate, is preferable.
The thickness of the polyamide separation functional layer is usually in the range of 0.01 to 1 μm, preferably in the range of 0.1 to 0.5 μm, in order to obtain sufficient separation performance and permeated water amount.

The polyfunctional amine refers to an amine containing at least one primary amino group in one molecule and further having at least one primary amino group and / or secondary amino group.
For example, phenylenediamine, xylylenediamine, 1,3,5-triaminobenzene, 1,2,4 in which two amino groups are bonded to the benzene ring in any of the ortho, meta, and para positions. Aromatic polyfunctional amines such as triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine and 4-aminobenzylamine, aliphatic amines such as ethylenediamine and propylenediamine, 1,2-diaminocyclohexane, 1 , 4-diaminocyclohexane, 4-aminopiperidine, 4-aminoethylpiperazine, and the like.

Among them, in view of the selective separation property, permeability and heat resistance of the membrane, it may be an aromatic polyfunctional amine having 2 to 4 primary amino groups and / or secondary amino groups in one molecule. Preferably, m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene are suitably used as such polyfunctional aromatic amine.
Among these, m-phenylenediamine (hereinafter referred to as m-PDA) is more preferred from the standpoint of availability and ease of handling.

These polyfunctional amines may be used alone or in combination of two or more. When using 2 or more types simultaneously, the said amines may be combined and the said amine and the amine which has at least 2 secondary amino group in 1 molecule may be combined.
Examples of the amine having at least two secondary amino groups in one molecule include piperazine and 1,3-bispiperidylpropane.

The polyfunctional acid halide refers to an acid halide having at least two carbonyl halide groups in one molecule.
For example, trifunctional acid halides include trimesic acid chloride, 1,3,5-cyclohexanetricarboxylic acid trichloride, 1,2,4-cyclobutanetricarboxylic acid trichloride, and the like. Bifunctional diacid halides such as biphenyl dicarboxylic acid dichloride, azobenzene dicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalenedicarboxylic acid chloride, and other aromatic bifunctional acid halides, adipoyl chloride, sebacoyl chloride, and the like And alicyclic bifunctional acid halides such as group difunctional acid halides, cyclopentanedicarboxylic acid dichloride, cyclohexanedicarboxylic acid dichloride, and tetrahydrofurandicarboxylic acid dichloride.

In view of reactivity with polyfunctional amines, polyfunctional acid halides are preferably polyfunctional acid chlorides, and in view of selective separation of the membrane and heat resistance, 2 to 4 per molecule are considered. The polyfunctional aromatic acid chloride having a carbonyl chloride group is preferred. Among them, it is more preferable to use trimesic acid chloride from the viewpoint of easy availability and easy handling.
These polyfunctional acid halides may be used alone or in combination of two or more.

The polyamide separation functional layer has an amide group derived from polymerization of a polyfunctional amine and a polyfunctional acid halide, an amino group and a carboxy group derived from an unreacted functional group, a polyfunctional amine or a polyfunctional acid halide. In addition, there are other functional groups and functional groups newly generated by various chemical treatments. The performance of the composite semipermeable membrane can be further improved by the chemical treatment. For example, chlorine groups can be introduced by treatment with an aqueous sodium hypochlorite solution. A halogen group can also be introduced by a Sandmeyer reaction via formation of a diazonium salt. Furthermore, an azo group can be introduced by carrying out an azo coupling reaction via diazonium salt formation.
The present inventors have found that these functional groups of the polyamide separation functional layer affect the permeation flux, solute removal rate, and stability of the membrane. For example, if the hydrophilicity of the functional group is high, the permeation flux is improved, leading to an improvement in the solute removal rate.

Also, during high pressure operation of the membrane separation apparatus provided with the composite semipermeable membrane according to the present invention, the salt concentration of the feed water in the vicinity of the polyamide separation functional layer surface increases. There is a concern that the membrane permeation flux and the solute removal rate performance may be deteriorated when the polyamide separation functional layer comes into contact with the supply water having a high salt concentration.

Thus, as a result of intensive studies, the present inventors have determined that the ratio of [mole equivalent of carboxy group / mole equivalent of amide group] in the functional group in the polyamide separation functional layer containing a carboxy group and an amide group is 0.40. When the average of the [oxygen / nitrogen] atomic ratio on the front and back of the polyamide separation functional layer is in the range of 0.95 or less, the membrane permeation flux (water production) is high and the operation pressure is increased. It was found that the decrease in the solute removal performance due to the increase in the salt concentration in the vicinity of the surface of the polyamide functional layer generated at the surface can be suppressed. The front and back sides of the polyamide separation functional layer will be described later.

If the ratio of [Mole equivalent of carboxy group / Mole equivalent of amide group] is 0.40 or more, the hydrophilicity of the polyamide separation functional layer is maintained by the carboxy group that is ionized in water and expected to be a hydrophilic functional group. Thus, a membrane having a high membrane permeation flux can be obtained.
In addition, if the average [oxygen / nitrogen] atomic ratio is 0.95 or less, there are few oxygen atoms that are likely to interact with salt, and it is difficult to be affected even when contacted with a high salt concentration. can get. Further, if the average [oxygen / nitrogen] atomic ratio is within this range, the boron removal rate is probably improved, probably because the affinity with boron is lowered.

Moreover, the upper limit of the ratio of [mole equivalent of carboxy group / mole equivalent of amide group] is usually 0.60 or less, and the lower limit of the average [oxygen / nitrogen] atomic ratio on the front and back of the polyamide separation functional layer is usually 0.80. That's it.
The ratio of [mole equivalent of carboxy group / mole equivalent of amide group] and the average of [oxygen / nitrogen] atomic ratio can be controlled by, for example, the type and amount of functional groups introduced by chemical treatment of the polyamide separation functional layer. .

For example, a ¹³ C solid state NMR method can be used for the functional group amount including a carboxy group and an amide group in the polyamide separation functional layer.
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.

In the polyamide separation functional layer, the element ratio used in the average of the [oxygen / nitrogen] atomic ratio 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.

In the present specification, the front and back surfaces of the polyamide separation functional layer refer to the surface of the polyamide separation functional layer and the surface of the polyamide separation functional layer on the porous support layer side (back surface of the polyamide separation functional layer). That is, the atomic ratio of [oxygen / nitrogen] on the front surface and the atomic ratio of [oxygen / nitrogen] on the back surface are respectively determined, and the average value is defined as the average of the [oxygen / nitrogen] atomic ratio on the front and back of the polyamide separation functional layer.
Note that the [oxygen / nitrogen] atomic ratio on the back side of the polyamide separation functional layer is such that after peeling the substrate from the composite semipermeable membrane, the surface side of the polyamide separation functional layer is fixed to an appropriate member, and the porous support layer is dissolved. The porous support layer is dissolved and removed with a solvent to expose the back surface of the polyamide separation functional layer, and then the element ratio of the back surface can be measured using XPS.

Furthermore, the composite semipermeable membrane of the present invention can be coated with a hydrophilic polymer after the separation functional layer is formed. By coating the surface with a hydrophilic polymer, solute removal performance and pressure resistance, and performance stability under high solute concentration conditions are improved.
The hydrophilic polymer may be bonded to the separation functional layer through a covalent bond, or may be bonded through a non-covalent bond such as a hydrogen bond or intermolecular force, and may be present on the separation functional layer. The coating method is not particularly limited. The presence of a hydrophilic polymer on the separation functional layer can be used to analyze the membrane surface such as XPS or time-of-flight secondary ion mass spectrometer (TOF-SIMS) total reflection infrared spectroscopy (ATR-FTIR). It can be confirmed by the technique.

In the present invention, the hydrophilic polymer refers to a polymer that is dissolved in an amount of 0.1 g or more in 1 L of water at 25 ° C. Examples of such hydrophilic polymers include polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, polyacrylic acid, polyethyleneimine, polyoxazoline, polyallylamine, carboxymethylcellulose, and the like. Moreover, you may use the block copolymer of these hydrophilic polymers, a graft copolymer, and a random copolymer. Furthermore, block copolymers, graft copolymers, and random copolymers of these hydrophilic polymers and hydrophobic polymers can be used. These hydrophilic polymers may be used alone or in combination. Among these hydrophilic polymers, especially when the composite semipermeable membrane is coated with polyethylene glycol (hereinafter referred to as PEG) or a copolymer containing polyethylene glycol, solute removal performance and pressure resistance, under high solute concentration conditions This is preferable because the stability of the performance is improved.

The average molecular weight (number average molecular weight) of the hydrophilic polymer is preferably 2,000 or more because solute removal performance and performance stability under high solute concentration conditions are improved, and more preferably 8,000 or more.

2. Next, a method for producing a composite semipermeable membrane according to the present invention will be described. The manufacturing method includes (2-1) a microporous support membrane forming step and (2-2) a separation functional layer forming step.

(2-1) Microporous support membrane forming step The microporous support membrane forming step includes a step of applying a polymer solution, which is a component of the porous support layer, to the substrate, and a step of forming the porous support layer on the substrate. The step of impregnating the polymer solution as a component, and the solvent impregnated with the polymer solution into the base material impregnated with the polymer solution in which the solubility of the polymer is small compared to the good solvent of the polymer as a component of the porous support layer ( A step of immersing in a coagulation bath with a non-solvent) to coagulate the polymer to form a three-dimensional network structure may be included.
The step of forming the microporous support membrane may further include a step of preparing a polymer solution by dissolving a polymer that is a component of the porous support layer in a good solvent for the polymer.

In order to obtain a microporous support membrane having a predetermined structure, it is important to control the phase separation of the polymer solution, and it is necessary to control the polymer, solvent, and coagulation bath liquid that are components of the porous support layer. is important.
When polysulfone is contained as the material for the porous support layer, the polysulfone concentration in the polymer solution is preferably 18% by weight or more. When the polysulfone concentration is 18% by weight or more, the pores in the porous support layer become dense and the formation of macrovoids is suppressed, and the mechanical strength of the composite semipermeable membrane including the microporous support membrane is improved. And it comes to have excellent pressure resistance.
The concentration of polysulfone is preferably 30% by weight or less. If it exceeds 30% by weight, the porous support layer becomes dense and the filtration resistance increases, so the permeation flux of the composite semipermeable membrane decreases. Moreover, since the impregnation property to a base material falls, the pressure | voltage resistance of a composite semipermeable membrane falls from the fall of adhesiveness with a base material, or generation | occurrence | production of a void.

Note that the solvent in which the polymer is dissolved may be a good solvent for the polymer. The good solvent of the present invention dissolves a polymer material.
Although the good solvent varies depending on the polymer, it is generally a lower alkyl such as N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, methyl ethyl ketone, acetone, tetrahydrofuran, tetramethylurea, and trimethyl phosphate. Examples include ketones, esters, amides, and the like, and mixed solvents thereof.

As the non-solvent, although it varies depending on the polymer, for example, water, hexane, pentane, benzene, toluene, methanol, ethanol, carbon tetrachloride, o-dichlorobenzene, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, Aliphatic hydrocarbons such as propylene glycol, butylene glycol, pentanediol, hexanediol, low molecular weight polyethylene glycol, aromatic hydrocarbons, aliphatic polyhydric alcohols, aromatic polyhydric alcohols, chlorinated hydrocarbons, or other chlorine And organic solvents and mixed solvents thereof.

The polymer solution may contain an additive for adjusting the pore size, porosity, hydrophilicity, elastic modulus and the like of the microporous support membrane.
Additives for adjusting the pore size and porosity include water, alcohols, polyethylene glycol, polyvinyl pyrrolidone, polyvinyl alcohol, water-soluble polymers such as polyacrylic acid or salts thereof, lithium chloride, sodium chloride, calcium chloride Inorganic salts such as lithium nitrate, formaldehyde, formamide and the like are exemplified, but not limited thereto.
Examples of additives for adjusting hydrophilicity and elastic modulus include various surfactants.

As the coagulation bath, water is usually used, but any non-solvent that does not dissolve the polymer may be used.
Depending on the composition, the membrane form of the microporous support membrane changes, and the membrane-forming property of the composite membrane also changes accordingly.
The temperature of the coagulation bath is preferably −20 ° C. to 100 ° C. More preferably, it is 10 to 30 ° C. If it 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 it is too low, the coagulation rate will be slow, causing a problem in film forming properties.

It is also important to control the impregnation of the polymer solution into the substrate. In order to control the impregnation of the polymer solution into the base material, for example, there is a method of controlling the time until the polymer solution is immersed on the base material after being applied on the base material.

The time from application of the polymer solution on the substrate to immersion in the coagulation bath is preferably in the range of usually 0.1 to 5 seconds, more preferably in the range of 0.1 to 4 seconds. is there.
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. As a result, the porous support layer is firmly bonded to the substrate by the anchor effect, and the microporous support film of the present invention can be obtained.
Moreover, since the impregnation property to the base material of a polymer solution improves by using a long-fiber nonwoven fabric as a base material, time until it is immersed in a coagulation bath can be shortened. When the time until immersion is long, the separation functional layer side surface (upper surface) becomes dense and the filtration resistance increases, so that the membrane permeation flux of the composite semipermeable membrane decreases. In addition, what is necessary is just to adjust the preferable range of time until it immerses in a coagulation bath suitably with the viscosity etc. of the polymer solution to be used.

Next, the microporous support membrane obtained under such preferable conditions is washed with hot water in order to remove the membrane-forming solvent remaining in the membrane. The temperature of the hot water at this time is preferably 50 to 100 ° C, more preferably 60 to 95 ° C. When it is higher than this range, the degree of shrinkage of the microporous support membrane increases, and the water permeability decreases. Conversely, if it is low, the cleaning effect is small.

(2-2) Separation Function Layer Formation Step Next, as an example of the separation function layer formation step constituting the composite semipermeable membrane, formation of a polyamide separation function layer mainly composed of polyamide will be described. In the present specification, the main component means a state containing 50% by weight or more of the components of the separation functional layer.
In the step of forming the polyamide separation functional layer, interfacial polycondensation is performed on the surface of the support membrane using the aqueous solution containing the polyfunctional aromatic amine and the organic solvent solution containing the polyfunctional aromatic acid halide. Can form the skeleton. As the organic solvent, a solvent immiscible with water is used.

Here, the concentration of the polyfunctional amine in the polyfunctional amine aqueous solution is preferably in the range of 0.1 to 20% by weight, more preferably in the range of 0.5 to 15% by weight. When the concentration of the polyfunctional amine is within this range, sufficient salt removal performance and water permeability can be obtained.
As long as the polyfunctional amine aqueous solution does not interfere with the reaction between the polyfunctional amine and the polyfunctional acid halide, a surfactant, an organic solvent, an alkaline compound, an antioxidant, or the like may be contained.

The surfactant has the effect of improving the wettability of the microporous support membrane surface and reducing the interfacial tension between the aqueous amine solution and the nonpolar solvent. The organic solvent may act as a catalyst for the interfacial polycondensation reaction, and when added, the interfacial polycondensation reaction may be efficiently performed.

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

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

Next, an organic solvent solution containing a polyfunctional acid halide is brought into contact with the microporous support membrane after contact with the polyfunctional amine aqueous solution, and a polyamide skeleton of the polyamide separation functional layer is formed by interfacial polycondensation.
The concentration of the polyfunctional acid halide in the organic solvent solution is preferably in the range of 0.01 to 10% by weight, and more preferably in the range of 0.02 to 2.0% by weight. 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. Further, it is more preferable to include an acylation catalyst such as DMF in the organic solvent solution, since interfacial polycondensation is promoted.

The organic solvent is preferably immiscible with water and dissolves the polyfunctional acid halide and does not break the microporous support membrane, and is inert to the polyfunctional amine compound and the polyfunctional acid halide. If there is something. Preferable examples include hydrocarbon solvents such as n-hexane, n-octane, and n-decane.

The method for contacting the polyfunctional acid halide organic solvent solution with the polyfunctional amine compound aqueous solution phase may be the same as the method for coating the polyfunctional amine aqueous solution on the microporous support membrane.
After interfacial polycondensation is performed by contacting an organic solvent solution of a polyfunctional acid halide to form a separation functional layer containing a crosslinked polyamide on the microporous support membrane, excess solvent may be drained.

As a method for draining, for example, a method in which a film is held in a vertical direction and excess organic solvent is allowed to flow down and removed can be used. In this case, the holding time in the vertical direction is preferably 1 to 5 minutes, and more preferably 1 to 3 minutes. If it is too short, the separation functional layer will not be completely formed, and if it is too long, the organic solvent will be overdried and defects will easily occur and performance will be deteriorated.

Further, the separation membrane in which the polyamide separation functional layer is formed on the microporous support membrane is within the range of 40 to 100 ° C., preferably within the range of 60 to 100 ° C., for 1 to 10 minutes, more preferably 2 to By performing the hydrothermal treatment for 8 minutes, the solute blocking performance and water permeability of the composite semipermeable membrane can be further improved.

Furthermore, in order to improve the permeation flux and solute removal rate of the membrane, various chemical treatments can be performed on the polyamide separation functional layer. The chemical treatment is preferably a diazonium salt or a derivative thereof followed by a contact treatment with a compound that reacts with the diazonium salt or a derivative thereof from the viewpoint of diversity of functional group conversion by the chemical treatment and operational simplicity.

The amino group of the polyamide separation functional layer is converted into a diazonium salt and reacted with water to produce a phenolic hydroxyl group. As a result, the hydrophilicity of the polyamide separation functional layer can be improved and the membrane permeation flux can be improved, but a decrease in the boron removal rate is probably due to an increase in affinity with boron. Furthermore, the average [oxygen / nitrogen] atomic ratio of the polyamide separation functional layer increases, and a decrease in boron removal rate when the operating pressure is increased is observed.

As a result of intensive studies, the present inventors have converted the amino group of the polyamide separation functional layer into a diazonium salt and brought it into contact with an aromatic compound or heteroaromatic ring compound, thereby improving permeation flux and solute removal rate, and high pressure. It has been found that a decrease in boron removal rate during operation can be suppressed. Details will be described below.

The polyamide separation functional layer is contacted with a reagent that reacts with a primary amino group to form a diazonium salt or a derivative thereof. Examples of the reagent that reacts with the primary amino group to be contacted to produce a diazonium salt or a derivative thereof include aqueous solutions of nitrous acid and salts thereof, nitrosyl compounds, and the like.
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 it is efficiently produced when the pH of the aqueous solution is 7 or less, preferably 5 or less, more preferably 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 it is 0.01% by weight or more, a sufficient effect such as improvement of the membrane permeation flux can be obtained, and when the concentration of nitrous acid and nitrite is 1% by weight or less, handling of the solution becomes easy. .

The temperature of the aqueous nitrous acid solution is preferably 15 ° C to 45 ° C. By being 15 degreeC or more, the time required for a chemical reaction is short, and when it is 45 degreeC or less, decomposition | disassembly of nitrous acid is not too early, and handling becomes easy.
The contact time between the composite semipermeable membrane and 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 at a low concentration. is necessary. Therefore, the solution having the above concentration is preferably within 10 minutes, more preferably within 3 minutes.

The method of bringing the composite semipermeable membrane into contact with a reagent such as a nitrous acid aqueous solution is not particularly limited, and the composite semipermeable membrane may be immersed in the reagent solution or by applying the reagent solution. . As the solvent for dissolving the reagent, any solvent may be used as long as the reagent is 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.

Subsequently, the composite semipermeable membrane is brought into contact with a reagent that reacts with a diazonium salt or a derivative thereof. Examples of the reagent used here include chloride ion, bromide ion, cyanide ion, iodide ion, boron fluoride, hypophosphorous acid, sodium hydrogen sulfite, sulfite ion, aromatic compound, hydrogen sulfide, thiocyanic acid and the like. It is done. In the previous step, a part of the diazonium salt or derivative thereof generated on the composite semipermeable membrane is converted into a phenolic hydroxyl group by reacting with water. In this case, the conversion to a phenolic hydroxyl group can be suppressed by contacting with an aqueous solution containing a reagent that reacts with a diazonium salt or a derivative thereof.

For example, a corresponding halogen atom is introduced by contacting with an aqueous solution containing copper (I) chloride, copper (I) bromide or potassium iodide. Moreover, a diazo coupling reaction arises by making it contact with an aromatic compound, and an aromatic ring is introduce | transduced through an azo bond. In addition, these reagents may be used alone, or may be used by mixing a plurality of them, or may be brought into contact with different reagents a plurality of times. Among these reagents, it is particularly preferable to use an aromatic compound that causes a diazo coupling reaction because the boron removal rate of the composite semipermeable membrane is greatly improved. This is considered to be because the aromatic ring introduced in place of the amino group by the diazo coupling reaction is bulky and has a high effect of closing the pores existing in the separation functional layer.

Examples of the aromatic compound that undergoes 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 an unsubstituted heteroaromatic ring compound, an aromatic compound having an electron donating substituent, and a heteroaromatic ring compound having an electron donating substituent. Examples of the electron-donating substituent include an amino group, an ether group, a thioether group, an alkyl group, an alkenyl group, an alkynyl group, and an aryl group. Specific examples of the above compounds include, for example, methoxyaniline bonded to a benzene ring in any positional relationship of aniline, ortho-position, meta-position, and para-position, and two amino groups are ortho-position, meta-position, para-position, and the like. Phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine bonded to the benzene ring in any positional relationship Examples include 4-aminobenzylamine, sulfanilic acid, 3,3′-dihydroxybenzidine, 1-aminonaphthalene, 2-aminonaphthalene, or N-alkylated products of these compounds.

The concentration and time for contacting the reagent to be reacted with these diazonium salts or derivatives thereof can be appropriately adjusted in order to obtain the desired effect. The contact temperature is preferably 15 ° C. or higher and 45 ° C. or lower. When the temperature is less than 15 ° C., the diazo coupling reaction proceeds slowly and a phenolic hydroxyl group is generated by a side reaction with water, which is not preferable. On the other hand, when the temperature is higher than 45 ° C., the polyamide separation functional layer shrinks and the amount of permeated water decreases, which is not preferable.

Next, the composite semipermeable membrane is brought into contact with a solution containing a hydrophilic polymer, and the polyamide separation functional layer can be coated with the hydrophilic polymer. As the hydrophilic polymer, those described above can be used. In particular, it is preferable to bring the composite semipermeable membrane into contact with an aqueous solution containing polyethylene glycol (PEG) because the salt removal rate and the boron removal rate are improved.

The concentration of the hydrophilic polymer is preferably 1 ppm or more and 1000 ppm or less. Less than 1 ppm is not preferable because the effect of improving the salt removal rate and boron removal rate of the composite semipermeable membrane is low. On the other hand, if it exceeds 1000 ppm, the water permeability of the composite semipermeable membrane is lowered, which is not preferable.

The temperature of the solution containing the hydrophilic polymer is preferably 15 ° C. or higher and 45 ° C. or lower. If it is less than 15 ° C., the solubility of the hydrophilic polymer may decrease, which is not preferable. If it exceeds 45 ° C., the separation functional layer contracts, and the water permeability of the composite semipermeable membrane decreases.

The time for bringing the composite semipermeable membrane into contact with the solution containing the hydrophilic polymer is preferably 1 second or more and 24 hours or less, but can be appropriately adjusted according to the concentration of the hydrophilic polymer. Less than 1 second is not preferable because the effect of improving the salt removal rate and boron removal rate of the composite semipermeable membrane is low. On the other hand, if it exceeds 24 hours, the water permeability of the composite semipermeable membrane is lowered, which is not preferable.

The method of bringing the composite semipermeable membrane into contact with the solution containing the hydrophilic polymer is not particularly limited, and the solution containing the hydrophilic polymer may be applied using a bar coater, a die coater, a gravure coater, a spray, or the like. It may be immersed in a solution containing a hydrophilic polymer. In addition to the hydrophilic polymer, an acidic compound, an alkaline compound, a surfactant, an antioxidant, and the like may be included.

3. Others The composite semipermeable membrane of the present invention is a cylinder in which a large number of holes are formed together with a raw water channel material such as a plastic net, a permeate channel material such as tricot, and a film for enhancing pressure resistance as required. It is wound around a cylindrical water collecting pipe and is suitably used as a spiral type composite semipermeable membrane element.
Furthermore, a composite semipermeable membrane module in which these elements are connected in series or in parallel and accommodated in a pressure vessel can be obtained.

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

The higher the operating pressure of the fluid separator, the higher the salt removal rate, but the energy required for operation also increases, and considering the durability of the composite semipermeable membrane, water to be treated is added to the composite semipermeable membrane. The operating pressure at the time of permeation is preferably 0.5 MPa or more and 10 MPa or less.
As the feed water temperature rises, the salt removal rate decreases, but as the feed water temperature decreases, the membrane permeation flux also decreases.

In addition, when the supply water pH becomes high, scales such as magnesium may be generated in the case of high salt concentration supply water such as seawater, brine, and drainage, and there is a concern about membrane deterioration due to high pH operation. The operation in a neutral region is preferable.

Examples of raw water to be treated by the composite semipermeable membrane according to the present invention include liquid mixtures containing TDS (Total Dissolved Solids) of 500 mg / L or more and 100 g / L or less, such as seawater, brine, and drainage. It is done.
In general, TDS refers to the total dissolved solid content, and is expressed as “mass ÷ volume” or “weight ratio”. According to the definition, it can be calculated from the weight of the residue by evaporating the solution filtered with a 0.45 μm filter at a temperature of 39.5 ° C. or higher and 40.5 ° C. or lower, but more simply converted from the practical salt content.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples.
Various characteristics of the composite semipermeable membrane in Examples and Comparative Examples were as follows. Seawater adjusted to a temperature of 25 ° C. and pH 6.5 (TDS concentration: about 3.5%, boron concentration: about 5 ppm) Was supplied at an operating pressure of 5.5 MPa, and membrane filtration treatment was performed for 24 hours.
The following shows how to obtain various characteristics.

(Desalination rate (TDS removal rate))
TDS removal rate (%) = 100 × {1− (TDS concentration in permeated water / TDS concentration in feed water)}

(Membrane permeation flux)
Membrane permeation flux (m ³ / m ² / day) was expressed based on the permeation amount per day (m ³ ) per square meter of the membrane surface of the feed water (seawater).

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

(Weight per unit volume of support layer)
The composite semipermeable membrane was cut out to a geometric area of 44.2 cm ² , pure water was passed through it at a temperature of 25 ° C. and a pressure of 5.5 MPa for 24 hours, and then the composite semipermeable membrane was dried under vacuum. Thereafter, the weight and film thickness of the composite semipermeable membrane were measured, and the substrate was further peeled from the composite semipermeable membrane. The weight and film thickness of the substrate were measured, and the weight per unit volume of the porous support layer was calculated from the following formula.
Weight per unit volume of porous support layer (g / cm ³ ) = (weight of composite semipermeable membrane−weight of substrate) / (area of composite semipermeable membrane × (film thickness of composite semipermeable membrane−substrate) Film thickness))

(Average amount of impregnation per unit area of the porous support layer to the substrate)
The composite semipermeable membrane at an arbitrary 50 points of 5 cm × 5 cm was dried under vacuum, and then the substrate was peeled off. The substrate was immersed in a DMF solution for 24 hours, washed and dried under vacuum, and the average impregnation amount per unit area was calculated from the following formula.
Average impregnation amount (g / m ² ) = Substrate weight before DMF immersion−Substrate weight after DMF immersion Further, out of 50 arbitrary points, the following points were calculated for 1.2 times or more of the calculated average impregnation amount: The ratio was calculated by the following formula.
Locations where the average impregnation amount is 1.2 times or more (%) = (Number of locations where the average impregnation amount is 1.2 times or more / 50) × 100

(Aeration rate of substrate (ml / cm ² / sec))
Based on the JIS L 1906: 2000 4.8 (1) Frazier method, measurement was performed on any 45 points in a 30 cm × 50 cm non-woven fabric with a pressure gauge of 125 Pa. However, the average value was rounded off to the second decimal place.

(Fiber orientation of the substrate)
Ten small sample samples are taken at random from the nonwoven fabric, taken with a scanning electron microscope at a magnification of 100 to 1000 times, and the longitudinal direction (longitudinal direction) of the nonwoven fabric is measured for a total of 100 fibers, 10 from each sample. The angle when the width direction (lateral direction) of the non-woven fabric was 90 ° was measured, and the average value thereof was rounded off to the first decimal place to obtain the fiber orientation degree.

(Pressure resistance)
Permeate channel material (Tricot (thickness: 300 μm, groove width: 200 μm, ridge width: 300 μm, groove depth: 105 μm)) was installed on the permeate side, and seawater (TDS concentration adjusted to a temperature of 25 ° C. and pH 6.5) 3.5%) at a pressure of 7.0 MPa for 1 minute × 200 times, and the change in film thickness before and after that was measured. Moreover, the performance change before and behind was calculated | required from the permeation | transmission flux ratio and the boron SP ratio.
Moreover, the amount of drop of the separation membrane into the permeate channel material was measured. The amount of sagging is measured by taking 500-3000 times photographs with a scanning electron microscope (unit: μm) for any three cross-sections of the separation membrane, and rounding off the first decimal place of those average values. Asked.
The direction in which the separation membrane support and the permeate flow path material overlap each other was such that the nonwoven fabric width direction (lateral direction) of the separation membrane support was orthogonal to the groove direction of the permeate flow path material.
Film thickness change = film thickness after water flow / film thickness before water flow membrane permeation flux ratio = membrane permeation flux after water flow / membrane permeation flux before water flow Boron SP ratio = (100−after water flow) Boron removal rate) / (100-Boron removal rate before passing water)
Note that SP is an abbreviation for “Substance Permeation”.

(Stability under high salt concentration conditions)
The composite semipermeable membrane was immersed in concentrated seawater adjusted to a concentration of 7.0%, a temperature of 25 ° C., and a pH of 8 at room temperature for 100 hours. From the membrane permeation flux and boron removal rate before and after immersion, the membrane permeation flux ratio and boron Each SP ratio was determined.

(TOF-SIMS measurement)
The composite semipermeable membrane was washed by immersing it in ultrapure water for 1 day. This membrane was dried with a vacuum dryer and subjected to TOF-SIMS measurement. The measurement is performed by TOF. Manufactured by ION-TOF. Using SIMS ⁵ , secondary ions generated when irradiated with Bi ₃ ⁺⁺ as a primary ion species and a primary acceleration voltage of 30 kV were measured with a time-of-flight mass spectrometer to obtain a mass spectrum.

(Example 1)
A composite semipermeable membrane was produced according to the conditions shown in Table 1.
A 18% by weight polysulfone DMF solution of polysulfone was prepared by heating and holding a mixture of each solvent and solute at 90 ° C. for 2 hours. A polysulfone solution was cast at a room temperature (25 ° C.) with a thickness of 200 μm on a polyester nonwoven fabric composed of long fibers, and immediately immersed in pure water and allowed to stand for 5 minutes to prepare a microporous support membrane.
The obtained microporous support membrane was immersed in a 5.5 wt% aqueous solution of m-PDA for 2 minutes, the support membrane was slowly pulled up in the vertical direction, and nitrogen was blown from an air nozzle to surface the microporous support membrane. After removing the excess aqueous solution, an n-decane solution at 25 ° C. containing 0.165% by weight of trimesic acid chloride was applied so that the surface was completely wetted and allowed to stand for 1 minute. Next, in order to remove excess solution from the membrane, the membrane was held vertically for 1 minute to drain, and then washed with hot water at 90 ° C. for 2 minutes.
The composite semipermeable membrane thus obtained was evaluated for pressure resistance, TDS removal rate, membrane permeation flux, boron removal rate, and stability under high salt concentration conditions, and the values shown in Table 2 were obtained. Further, with respect to this composite semipermeable membrane, the weight per unit volume of the porous support layer after passing pure water for 24 hours at a temperature of 25 ° C. and a pressure of 5.5 MPa was as shown in Table 2.

(Example 2)
The membrane obtained in Example 1 was treated with a 0.3 wt% aqueous sodium nitrite solution adjusted to pH 3 with sulfuric acid at room temperature (35 ° C.) for 1 minute. The composite semipermeable membrane was removed from the nitrous acid aqueous solution and then immersed in a 0.3 wt% m-PDA aqueous solution for 2 minutes.
The composite semipermeable membrane thus obtained was evaluated for pressure resistance, TDS removal rate, membrane permeation flux, boron removal rate, and stability under high salt concentration conditions, and the values shown in Table 2 were obtained. Further, with respect to this composite semipermeable membrane, the weight per unit volume of the porous support layer after passing pure water for 24 hours at a temperature of 25 ° C. and a pressure of 5.5 MPa was as shown in Table 2.

(Examples 3 to 18)
Except for changing the conditions used in Table 1 except that the base material used, the air flow rate of the base material, the difference in orientation of the base material, the polysulfone concentration, the amount of polysulfone impregnated into the base material, the reagent and concentration reacted after the nitrous acid treatment Produced and processed a composite semipermeable membrane in the same manner as in Example 2.
The composite semipermeable membrane thus obtained was evaluated for pressure resistance, TDS removal rate, membrane permeation flux, boron removal rate, and stability under high salt concentration conditions, and the values shown in Table 2 were obtained. Further, the weight per unit volume of the porous support layer after passing pure water for 24 hours at a temperature of 25 ° C. and a pressure of 5.5 MPa was as shown in Table 2.

(Example 19)
The composite semipermeable membrane obtained in Example 1 was immersed in an aqueous solution of 1 ppm polyethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., number average molecular weight 8,000) for 1 hour, whereby the composite semipermeable membrane in Example 19 was used. Got. The composite semipermeable membrane thus obtained was evaluated for pressure resistance, TDS removal rate, membrane permeation flux, boron removal rate, and stability under high salt concentration conditions, and the values shown in Table 2 were obtained. Further, the weight per unit volume of the porous support layer after passing pure water for 24 hours at a temperature of 25 ° C. and a pressure of 5.5 MPa was as shown in Table 2. After measuring the stability under high solute concentration conditions, the surface of the separation functional layer was analyzed by TOF-SIMS. As a result, in addition to the benzene ring peak ( ⁷⁵ C ₆ H ₃ ⁺ ) derived from the crosslinked wholly aromatic polyamide, A peak derived from polyethylene glycol ( ⁴⁵ C ₂ H ₅ O ⁺ ) was detected.

(Example 20)
The composite semipermeable membrane obtained in Example 1 was immersed in an aqueous solution of 1000 ppm polyethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., number average molecular weight 8,000) for 1 hour, whereby the composite semipermeable membrane in Example 20 was used. Got. The composite semipermeable membrane thus obtained was evaluated for pressure resistance, TDS removal rate, membrane permeation flux, boron removal rate, and stability under high salt concentration conditions, and the values shown in Table 2 were obtained. Further, the weight per unit volume of the porous support layer after passing pure water for 24 hours at a temperature of 25 ° C. and a pressure of 5.5 MPa was as shown in Table 2. After measuring the stability under high solute concentration conditions, the surface of the separation functional layer was analyzed by TOF-SIMS. As a result, in addition to the benzene ring peak ( ⁷⁵ C ₆ H ₃ ⁺ ) derived from the crosslinked wholly aromatic polyamide, A peak derived from polyethylene glycol ( ⁴⁵ C ₂ H ₅ O ⁺ ) was detected.

(Example 21)
The composite semipermeable membrane obtained in Example 1 was immersed in an aqueous solution of 1 ppm polyethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., number average molecular weight 2,000) for 1 hour, so that the composite semipermeable membrane in Example 21 was used. Got. The composite semipermeable membrane thus obtained was evaluated for pressure resistance, TDS removal rate, membrane permeation flux, boron removal rate, and stability under high salt concentration conditions, and the values shown in Table 2 were obtained. Further, the weight per unit volume of the porous support layer after passing pure water for 24 hours at a temperature of 25 ° C. and a pressure of 5.5 MPa was as shown in Table 2. After measuring the stability under high solute concentration conditions, the surface of the separation functional layer was analyzed by TOF-SIMS. As a result, in addition to the benzene ring peak ( ⁷⁵ C ₆ H ₃ ⁺ ) derived from the crosslinked wholly aromatic polyamide, A peak derived from polyethylene glycol ( ⁴⁵ C ₂ H ₅ O ⁺ ) was detected.

(Example 22)
The composite semipermeable membrane obtained in Example 1 was immersed in a 1 ppm aqueous solution of Pluronic F-127 (manufactured by Sigma-Aldrich) for 1 hour to obtain a composite semipermeable membrane in Example 22. The composite semipermeable membrane thus obtained was evaluated for pressure resistance, TDS removal rate, membrane permeation flux, boron removal rate, and stability under high salt concentration conditions, and the values shown in Table 2 were obtained. Further, the weight per unit volume of the porous support layer after passing pure water for 24 hours at a temperature of 25 ° C. and a pressure of 5.5 MPa was as shown in Table 2. After measuring the stability under high solute concentration conditions, the surface of the separation functional layer was analyzed by TOF-SIMS. As a result, in addition to the benzene ring peak ( ⁷⁵ C ₆ H ₃ ⁺ ) derived from the crosslinked wholly aromatic polyamide, A peak derived from polyethylene glycol ( ⁴⁵ C ₂ H ₅ O ⁺ ) was detected.

(Example 23)
The composite semipermeable membrane obtained in Example 1 was immersed in an aqueous solution of 1 ppm polyacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., number average molecular weight 25,000) for 1 hour, whereby the composite semipermeable membrane in Example 23 was used. A membrane was obtained. The composite semipermeable membrane thus obtained was evaluated for pressure resistance, TDS removal rate, membrane permeation flux, boron removal rate, and stability under high salt concentration conditions, and the values shown in Table 2 were obtained. Further, the weight per unit volume of the porous support layer after passing pure water for 24 hours at a temperature of 25 ° C. and a pressure of 5.5 MPa was as shown in Table 2.

(Comparative Examples 1 to 6)
Except for changing the conditions used in Table 1 except that the base material used, the air flow rate of the base material, the difference in orientation of the base material, the polysulfone concentration, the amount of polysulfone impregnated into the base material, the reagent and concentration reacted after the nitrous acid treatment Produced and processed a composite semipermeable membrane in the same manner as in Example 2.
The composite semipermeable membrane thus obtained was evaluated for pressure resistance, TDS removal rate, membrane permeation flux, boron removal rate, and stability under high salt concentration conditions, and the values shown in Table 2 were obtained. Further, the weight per unit volume of the porous support layer after passing pure water for 24 hours at a temperature of 25 ° C. and a pressure of 5.5 MPa was as shown in Table 2.

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 Feb. 28, 2013 (Japanese Patent Application No. 2013-39553), the contents of which are incorporated herein by reference.

The composite semipermeable membrane of the present invention can be suitably used particularly for demineralization of brine or seawater under high-pressure operation when used in a membrane separation apparatus.

Claims (8)

1. A composite semipermeable membrane comprising a substrate and a microporous support membrane comprising a porous support layer formed on the substrate, and a separation functional layer provided on the porous support layer,
   A composite half having a weight per unit volume of the porous support layer of 0.50 g / cm ³ or more and 0.65 g / cm ³ or less after passing pure water for 24 hours at a temperature of 25 ° C. and a pressure of 5.5 MPa. Permeable membrane.
2. Location where the average impregnation amount per unit area of the porous support layer to the substrate is 1.0 g / m ² or more and 5.0 g / m ² or less and 1.2 times or more the average impregnation amount The composite semipermeable membrane according to claim 1, comprising 20% or more.
3. Wherein a substrate is the long-fiber nonwoven fabric, and an aeration rate of the substrate is not more than 0.5 ml ^/ cm 2 / sec or more 5.0 ml ^/ cm 2 / sec, as claimed in claim 1 or claim 2 Composite semipermeable membrane.
4. The difference in orientation between the fiber orientation on the porous support layer side surface of the substrate and the fiber orientation on the opposite surface of the substrate to the porous support layer is 10 ° or more and 90 ° or less, The composite semipermeable membrane according to any one of claims 1 to 3.
5. The composite semipermeable membrane according to any one of claims 1 to 4, wherein a surface of the separation functional layer is coated with a hydrophilic polymer.
6. The composite semipermeable membrane according to claim 5, wherein the hydrophilic polymer has an average molecular weight of 8,000 or more.
7. The composite semipermeable membrane according to claim 5 or 6, wherein the hydrophilic polymer is polyethylene glycol or a copolymer containing polyethylene glycol.
8. The separation functional layer is a polyamide separation functional layer containing a carboxy group and an amide group, and a ratio of [molar equivalent of carboxy group / molar equivalent of amide group] in the polyamide separation functional layer is 0.40 or more, The composite semipermeable membrane according to any one of claims 1 to 7, wherein an average of the [oxygen / nitrogen] atomic ratio between the front and back sides of the polyamide separation functional layer is 0.95 or less.