JPH1057783A - Reverse osmosis composite membrane - Google Patents

Abstract

(57) Abstract: A reverse osmosis composite membrane including at least a porous support membrane layer and a separation active layer, wherein a water-insoluble organic polymer having an anionic hydrophilic group on the surface of the separation active layer. By forming the coalesced layer, it has high anionicity, high salt rejection, high water permeability and chlorine resistance, and enables practical desalination at relatively low pressure. SOLUTION: On a reverse osmosis membrane such as an aromatic polyamide membrane, a logarithmic viscosity is 0.84 cm ³ / g, and an ion exchange capacity is 1.
Dissolve 23 milliequivalents / g of the sulfonated polysulfone copolymer in ethylene glycol monomethyl ether.
A 25 wt% solution is applied by a dipping method,
Dry at 3 ° C. for 3 minutes to form a thin layer. The separation active layer 12 exists on the porous polysulfone support membrane 11, and the anionic sulfonated polysulfone copolymer layer 13 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the performance stability of a reverse osmosis composite membrane for selectively separating components of a liquid mixture,
It is related to improvement of membrane performance such as stain resistance, in detail, with a hydrophilic organic polymer thin film having a specific structure on a reverse osmosis composite membrane, high salt rejection, high chlorine disinfectant resistance, And a reverse osmosis composite membrane having high contamination resistance and the like. Such a reverse osmosis composite membrane is suitable for production of ultrapure water, desalination of brackish water, and the like. The substance can be removed and collected, thereby contributing to closing of the wastewater. In addition, it is possible to operate stably for a long period of time even for water quality containing a pollutant such as an anion or a neutral surfactant which causes a decrease in the amount of permeated water. Further, according to the present invention, chlorine resistance can be improved.

[0002]

BACKGROUND ART Reverse osmosis membranes used industrially include:
As asymmetric membranes made from cellulose acetate, for example, US Pat. No. 3,133,132 and US Pat.
No. 137 describes a lob-type membrane. on the other hand,
As a reverse osmosis membrane having a different structure from an asymmetric reverse osmosis membrane, a reverse osmosis composite membrane formed by forming an active thin film having substantially selective separation on a microporous support membrane is known.

At present, many of such reverse osmosis composite membranes are known in which a thin film made of polyamide obtained by interfacial polymerization of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide is formed on a support membrane. (For example, JP-A-55-147106, JP-A-62-121603).
JP, JP-A-63-218208, JP-A-2-
187135).

[0004] Further, there has been proposed a thin film made of a polyamide obtained by interfacial polymerization of a polyfunctional aromatic amine and a polyfunctional alicyclic acid halide formed on a support film (for example, see Japanese Patent Application Laid-Open Publication No. H11-163873). No. 61-42308, etc.).

[0005] The above reverse osmosis composite membrane has high desalination performance and water permeation performance, but in recent water treatment systems, even higher membrane performance is required depending on the application. For example, in the field of ultrapure water production, operation at ultra-low pressure and high salt removal rate are required, but in desalination applications of brackish water, etc., the raw water contains various ions, so high desalination performance with various mixed ions Is required. In addition, during long-term operation of such a system, a disinfectant such as sodium hypochlorite is used to prevent water quality deterioration due to propagation of various germs and the like. Fungicidal properties are required. Further, for removing a specific substance such as anionic property, a method of further increasing the polarity of the film is required.

Various methods for sulfonating a polysulfone copolymer have been disclosed as methods for adding anionic properties. For example, the linear polysulfone copolymers represented by the formulas (Chem. 2) and (Chem. 3) themselves have already been proposed in Canadian Patent No. 847,963, and the sulfonated products of the copolymers have already been proposed. JP-A-55-57222
No. 1993. That is, according to this publication, the repeating units of the formula (Chemical Formula 2) are substantially all sulfonated by dissolving the polysulfone copolymer in concentrated sulfuric acid and sulfonating the same. It is described that a hydrophilic sulfonated polysulfone is formed in which substantially all of the repeating unit 3) remains in a non-sulfonated state. It further states that the sulfonated polysulfone copolymer is potentially useful as an ultrafiltration membrane.

A sulfonated polysulfone having a repeating unit represented by the following formula (Formula 4) is disclosed in US Pat. No. 3,709,709.
No. 841.

[0008]

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Japanese Patent Application Laid-Open Nos. 50-99973 and 50-146379 disclose a solution of such a sulfonated polysulfone on the surface of an anisotropic ultrafiltration membrane. There has been proposed a method for producing a reverse osmosis composite membrane in which a thin film having semi-permeability by evaporation is laminated on an ultrafiltration membrane. Similarly, the Offer of Water Researcher and Technology Development of the Interior Report (Offer of
Water Research and Technology Department of the In
terior Report) No.2001-20, an anisotropic ultrafiltration membrane consisting of a repeating unit of the above formula (Formula 4) was plugged in advance with an aqueous lactic acid solution, and then a solution of a sulfonated polysulfone was applied. A method for producing a reverse osmosis composite membrane by evaporating the solution is described.

Further, Japanese Patent Application Laid-Open Nos. 5-2364 and 5-2365 describe semi-permeable membranes of sulfonated polysulfone for the purpose of higher performance.

[0011]

However, the above-mentioned conventional membrane does not have sufficient reverse osmosis membrane performance due to, for example, a low removal rate of sodium chloride and a low water permeability.

As described above, the anionicity of the membrane is increased,
In addition, the present reverse osmosis composite membrane is insufficient to satisfy the demand for a reverse osmosis membrane having both a high salt removal rate and a high permeate flow rate, and a higher performance reverse osmosis composite membrane is required.
One of the problems of the above-mentioned polyamide reverse osmosis membrane is that it is not resistant to chlorine, cannot be sufficiently sterilized with chlorine, and cannot be efficiently washed when water permeability is reduced, and chlorine-resistant. There is a demand for improved performance.

[0013] The present invention provides a high anionic, high salt rejection,
It is an object of the present invention to provide a reverse osmosis composite membrane which has both high water permeability and further chlorine resistance and enables practical desalination at a relatively low pressure.

[0014]

In order to achieve the above-mentioned object, a first reverse osmosis composite membrane of the present invention is a reverse osmosis composite membrane including at least a porous support membrane layer and a separation active layer, An organic polymer having an anionic hydrophilic group is present in at least one layer selected from the porous support membrane layer and the separation active layer.

Next, the second reverse osmosis composite membrane of the present invention is:
A reverse osmosis composite membrane including at least a porous support membrane layer and a separation active layer, wherein a water-insoluble organic polymer layer having an anionic hydrophilic group is formed on the surface of the separation active layer. I do. In the above, the thickness of the water-insoluble organic polymer layer having an anionic hydrophilic group is 0.001 to
It is preferably in the range of 5.0 μm.

In the first and second reverse osmosis composite membranes, the fixed charge density of the reverse osmosis composite membrane is -2.5 × 10
^-3 [mol / l] or less. More preferably, −1.0 × 10 ⁻¹ [mol / l] to −2.5 ×
It is in the range of 10 ⁻³ [mol / l], particularly preferably about −7.0 × 10 ⁻³ [mol / l].

In the first and second reverse osmosis composite membranes, the water-insoluble organic polymer having an anionic hydrophilic group is preferably a polymer having a sulfonic acid group. The organic polymer having a substantially anionic hydrophilic group of the present invention is an organic polymer insoluble in water, an aqueous solution containing salts, or an aqueous solution containing a small amount of organic substances, and is a vinyl polymer. The polymer is selected from those having an anionic hydrophilic group in a coalesced polymer, a condensation polymer, or an addition polymer. Such an anionic hydrophilic group is, for example, one represented by the following formulas (Formula 5) to (Formula 8).

[0018]

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[0019]

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[0020]

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[0021]

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It is sufficient that the organic polymer contains at least one of them, and an organic polymer having a -SO ₃ -group is preferably used. As the organic polymer having a —SO ₃ — group, sulfonated polysulfone is more preferably used.

In the first and second reverse osmosis composite membranes, the polymer having a sulfonic acid group is preferably a polymer obtained by sulfonating a polymer containing any of the units of the above formula (Formula 1). .

In the first and second reverse osmosis composite membranes, the polymer containing any one of the units of the formula (1) is at least one selected from polysulfone, polyethersulfone, and polyetherethersulfone. It is preferably one.

In the first and second reverse osmosis composite membranes, the polymer having a sulfonic acid group is obtained by partially sulfonating at least one unit selected from the above formulas (Chemical Formula 2) to (Chemical Formula 3). N-methyl-2
The logarithmic viscosity measured at 30 ° C. of a solution of 0.5 g of polymer in 100 ml of pyrrolidone is 0.5
It is preferably made of a water-insoluble partially sulfonated polysulfone having an ion exchange capacity of not more than cm ³ / g and not more than 2 meq / g.

In the first and second reverse osmosis composite membranes, the sulfonic acid group of the partially sulfonated polysulfone is -SO ₃ M (where M represents hydrogen, an alkali metal or tetraalkylammonium). Preferably it is represented.

The first and second reverse osmosis composite membranes have high anionicity, high salt rejection, and high water permeability, and enable practical desalination at a relatively low pressure. A reverse osmosis composite membrane can be realized.

[0028]

DETAILED DESCRIPTION OF THE INVENTION The sulfonated polysulfone copolymer used in the present invention may contain a small amount of an aprotic polar organic solvent. For example, it is produced by dissolving in an alkylene glycol monoalkyl ether to form a membrane-forming solution, coating the solution on the surface of the separation active layer of an appropriate reverse osmosis composite membrane, and evaporating the solvent. The sulfonated polysulfone copolymer used in the present invention is obtained by dissolving the polysulfone copolymer, the formulas (2) to (3) or a copolymer thereof in concentrated sulfuric acid and stirring at room temperature for several hours. Can be easily obtained. The degree of sulfonation is, for example, that substantially all of the repeating units of the above formula (Formula 2) are sulfonated, but substantially all of the repeating units of the above formula (Formula 3) remain in a non-sulfonated state. By using a copolymer in which the ratio of the repeating units of the formulas (Chemical Formula 2) and (Chemical Formula 3) is changed, it can be easily controlled. Further, by controlling the sulfonation conditions, the sulfonation itself of the repeating unit of the above formula (Formula 3) can be controlled.

In the present invention, when a thin film of the sulfonated polysulfone copolymer is formed on the surface of the separation active layer, the ion exchange capacity is 2 meq / g or less and the N-methyl- A solution obtained by dissolving 0.5 g of this copolymer in 100 ml of 2-pyrrolidone has a logarithmic viscosity measured at 30 ° C. (hereinafter, the method for measuring the logarithmic viscosity of sulfonated polysulfone is 0.5 cm ³ / g). Above, preferably 0.7cm
It is necessary to be at least ³ / g. When the ion exchange capacity exceeds 2 meq / g, the sulfonated polysulfone becomes water-soluble, which is unsuitable as a semipermeable membrane which often treats a liquid containing an aqueous medium, and has a logarithmic viscosity. If it is smaller than 0.7 cm ³ / g, it is difficult to produce a uniform thin film layer having no defects such as pinholes on the surface of the active separation layer. Sulfonic acid group sulfonated polysulfone copolymer has used in the present invention is represented by the formula -SO ₃ M, where M is hydrogen, an alkali metal or tetraalkylammonium. For example, after sulfonating the polysulfone copolymer, the sulfonated polysulfone copolymer is washed with water and dried to obtain a sulfonated polysulfone copolymer having free sulfonic acid groups. Further, when the sulfonated polysulfone copolymer is treated with an aqueous solution of an alkali metal hydroxide or an alkali metal alcoholate, a methanol or ethanol solution, or the like, the sulfonic acid group can be converted into an alkali metal salt. As the alkali metal hydroxide,
For example, sodium hydroxide, potassium hydroxide, lithium hydroxide and the like are used, and as the alkali metal alcoholate, for example, sodium methylate, potassium methylate, potassium ethylate and the like are used. Also, a tetraalkylammonium, for example, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide and the like, when treated with a solution similar to the above, to give the corresponding tetraalkylammonium salt be able to.

The reverse osmosis composite membrane according to the present invention can be manufactured by various methods. Usually, the organic polymer having an anionic hydrophilic group is dissolved in an organic solvent to form a membrane forming solution. This can be manufactured by applying this to a separation active layer having appropriate reverse osmosis performance and evaporating the solvent. Examples of the organic solvent for preparing the film forming solution include aprotic polar organic solvents such as dimethylsulfoxide, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, and ethylene glycol monomethyl. Alkylene glycol monoalkyl ethers in which the alkylene group has 2 or 3 carbon atoms and the alkyl group has 1 to 4 carbon atoms, such as ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether; , Ethanol, isopropyl alcohol and the like. Depending on the organic polymer having an anionic hydrophilic group to be used, it may not dissolve in the above-mentioned alkylene glycol monoether or may only swell, but the organic polymer having such an anionic hydrophilic group may be used. It is also well dissolved in a mixed solvent obtained by adding a small amount of the above aprotic polar organic solvent to an alkylene glycol monoether. Using a mixed solvent of alkylene glycol monoalkyl ether or a small amount of the aprotic polar organic solvent as the solvent for the film forming solution can remove the solvent at room temperature or slightly by heating at the time of evaporating and removing the solvent described below. This is advantageous because a uniform thin film free from defects can be obtained on the surface of the organic active layer. The concentration of the sulfonated polysulfone copolymer in the membrane-forming solution depends on the thickness of the obtained semipermeable membrane, but is usually 0.01 to 15% by weight.
Is particularly preferable, and a range of 0.1 to 10% by weight is particularly preferable. The reverse osmosis membrane having a separation active layer to which the membrane forming solution is applied is not particularly limited, but a membrane formed by a cellulose-based wet membrane, a polyamide-based membrane, or a polyurea-based membrane formed by an interfacial polymerization method. There is. These films can be easily obtained by a conventionally known method or the like. For example, in the interfacial polymerization method, a porous polysulfone support membrane is used, and an aqueous solution of a monomer or polymer having a reactive amino group such as metaphenylenediamine, piperazine, or polyethyleneimine is applied to at least one surface of the porous polysulfone support membrane. By contacting a polyfunctional acid chloride such as acid chloride or isophthalic acid chloride, a polyfunctional isocyanate such as tolylene diisocyanate, or a mixture of these with a solvent such as hexane, interfacial polymerization is performed on the porous polysulfone support membrane. A reverse osmosis composite membrane can be formed by forming a film having desalination performance.

The separation active layer may be heated, if necessary, to impart a solvent of the organic polymer solution having an anionic hydrophilic group of the present invention to the surface of the separation active layer and evaporate the solvent. The heating temperature may be appropriately selected according to the solvent used. In order to promote the evaporation of the solvent after the application of the film forming solution, the film forming solution may be heated in advance. Next, the reverse osmosis composite membrane according to the present invention can be obtained by evaporating and removing the solvent from the applied membrane forming solution.

The coating method is not particularly limited, but a dipping method, a transfer method, a spray method and the like are preferably used. The thickness of the resulting organic polymer thin film having an anionic hydrophilic group is preferably small in order to increase the water permeability of the film. Therefore, although not particularly limited, the film thickness is usually 0.1.
It is in the range of 001 to 5 μm. The method for controlling the film thickness is not particularly limited, but can be controlled by a solution concentration or the like.

The reverse osmosis composite membrane according to the present invention thus obtained has a high salt removal rate and a high water permeability, and is excellent in chlorine resistance, oil resistance, heat resistance and the like, and can be used as a reverse osmosis composite membrane. It is suitable. In particular, it is preferable to form a water-insoluble organic polymer layer having an anionic hydrophilic group on the surface of the separation active layer in order to improve chlorine resistance, oil resistance, and heat resistance.

When the organic polymer having an anionic hydrophilic group is soluble in water, a reactive amino group such as metaphenylenediamine, piperazine, polyethyleneimine or the like described in the above-mentioned method for forming a reverse osmosis membrane is used. After previously dissolving it in an aqueous solution of a monomer or polymer having the same and applying it to at least one surface of a porous polysulfone support membrane, a polyfunctional acid chloride such as trimesic acid chloride and isophthalic acid chloride, or a polyfunctional acid such as tolylene diisocyanate It is possible to form a reverse osmosis composite membrane by forming in a separation active layer having desalination performance by performing interfacial polymerization on a porous polysulfone support membrane by contacting with a solvent such as hexane of isocyanate or a mixture thereof. it can.

The fixed charge density is used as one of the indicators of anionicity of the obtained membrane. The fixed charge density of the membrane was measured using the cell shown in FIG. 1 for measuring the membrane potential. In FIG.
1 is a reverse osmosis composite membrane, 2 is a salt bridge, 3 is a standard calomel electrode,
4 is a stirrer (stirrer). In this apparatus, the separation active layer of the membrane (the same applies to those containing an organic polymer having an anionic hydrophilic group in and on the membrane surface) is set in contact with the concentrated solution, and the liquid on the membrane surface is stirred by the stirrer. I was doing it. The solution uses potassium chloride and the concentration ratio is C
₁ / C ₂ = 2/1, and the measurement temperature was 25 ° C.

It is assumed that the membrane potential is determined by the solution concentration and the membrane fixed ion concentration, and the cation / anion mobility ratio.
Using the S model ["Membranes and ions-Theory and calculation of mass transfer-" by Tetsuya Hanai (Chemical Doujin Inc.)], the fixed charge density was obtained by performing curve fitting of the experimental value and the theoretical value. The fixed charge density is desirably, for example, -2.5 × 10 ³ [mol / l] or less in order to increase anionic solutes and improve stain resistance to anionic substances.

The reverse osmosis composite membrane having the obtained water-insoluble organic polymer having an anionic hydrophilic group in the surface layer and / or in the separation active layer has a water permeability of 15 kg.
/ Cm ² , temperature 25 ° C, feed solution 1500ppm NaC
It is suitable for actual operation that the water permeability is 0.1 [m ³ / m ² / day] or more, preferably 0.5 [m ³ / m ² / day] or more under the condition of 1 above.

[0038]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these examples. In Examples, the salt removal rate and the water permeation rate of the obtained reverse osmosis composite membrane were measured using a sodium chloride aqueous solution having a concentration of 1500 ppm as a stock solution at a temperature of 25 ° C. and a pressure of 15%.
A permeation experiment was performed at kg / cm ² to find the value.

[0039]

Example 1 m-phenylenediamine: 3.0% by weight,
Sodium lauryl sulfate: 0.15% by weight, triethylamine: 3.0% by weight, camphorsulfonic acid: 6.0
An aqueous solution containing 5% by weight of isopropyl alcohol and 5% by weight of isopropyl alcohol was brought into contact with the porous polysulfone support membrane for several seconds to remove the excess solution and form a layer of the solution on the support membrane.

Next, an IP1016 (isoparaffinic hydrocarbon oil manufactured by Idemitsu Chemical Co., Ltd.) solution containing trimesic acid chloride: 0.20% by weight and isopropyl alcohol: 0.05% by weight was brought into contact with the surface of the supporting membrane, Then, it was kept in a hot air dryer at 120 ° C. for 3 minutes to form a polymer thin film on the support film to obtain a reverse osmosis membrane.

On the other hand, a sulfonated polysulfone copolymer having a logarithmic viscosity of 0.84 cm ³ / g and an ion exchange capacity of 1.23 meq / g (the above formula (Chem. 2): (Chem. 3) = 57: 43)
(Molar ratio)) was dissolved in ethylene glycol monomethyl ether to obtain a 0.25 wt% solution. This solution was applied on the reverse osmosis membrane by a dipping method.
After drying for a minute, a thin layer (average thickness: 0.2 μm) was formed. FIG. 2 shows a schematic cross-sectional view of the obtained film. In FIG. 2, 11 is a porous polysulfone support membrane, 12 is a separation active layer, and 13 is an anionic sulfonated polysulfone copolymer layer.

The membrane obtained as described above was immersed in a solution of an anionic surfactant (500 ppm) for 46 hours, and remeasured under the above conditions. Table 1 shows the measurement results. In addition, according to the method described with reference to FIG. 1, the fixed charge density of the film after washing with an aqueous solution of sodium hypochlorite (20 ppm, pH = 7.0) for 30 minutes and with ultrapure water for 30 minutes was measured. Table 3 shows the results. The membrane was set in a measuring cell, and a 100 ppm aqueous solution of sodium hypochlorite was circulated over the membrane surface for 48 hours. Then, measurement was performed with a 1500 ppm aqueous solution of sodium chloride as shown in Table 1, and the results were shown in Table 2. Show.

[0043]

Comparative Example 1 m-phenylenediamine: 2.0% by weight
Sodium dodecyl sulfate: 0.3% by weight, camphorsulfonic acid: 4.0% by weight and triethyleneamine: 2.
An aqueous solution containing 0% by weight is applied to a microporous polysulfone support membrane, and then contacted with a 0.5% by weight solution of n-hexane composed of a mixture of trimesic acid chloride / isophthalic acid chloride (= 2/3: weight ratio). And then at 120 ° C
And dried with hot air for 5 minutes to obtain a reverse osmosis composite membrane. The same evaluation as in Example 1 was performed on the obtained reverse osmosis composite membrane. The results are summarized in Tables 1 and 2. Table 3 shows the fixed charge density.

[0044]

[Table 1] Sample No. Initial performance After immersion in an anionic surfactant (500 ppm) solution for 46 hours, NaCl, 1500 ppm Flux NaCl, 1500 ppm Flux Retention rate Rej. (%) M ³ / m ² / d Rej. (%) m ³ / m ² / d Flux / Flux2 Example 1 99.11 0.58 98.53 0.56 97% Comparative Example 1 99.47 0.70 98.80 0.47 67%

[0045]

[Table 2] Sample No. Initial performance After circulation of 100 ppm sodium hypochlorite aqueous solution (48 hr) NaCl, 1500 ppm Flux NaCl, 1500 ppm Flux Retention rate Rej. (%) M ³ / m ² / d Rej. (%) m ³ / m ² / d Flux / Flux2 Example 1 99.11 0.58 98.90 0.60-Comparative example 1 99.47 0.70 88.12 2.12-

[0046]

Table 3 Sample No. Fixed charge density A × 10 ³ [mol / l] Example 1-7.0 Comparative Example 2-2.3

As is evident from the results of Tables 1 to 3, the reverse osmosis composite membrane of this example has high anionicity, high salt rejection, high water permeability, and chlorine resistance. It was confirmed that practical desalination was possible at low pressure. On the other hand, in the reverse osmosis composite membrane of Comparative Example 1, although the initial flux (Flux) was relatively high, the flux (Flux) after immersion in the anionic surfactant solution was greatly reduced (Table 1). ). In Comparative Example 1, the flux was reduced because rejection (Rej.) Was reduced due to damage to the film by chlorine.
(Flux) increased, but in Example 1, there was almost no decrease in rejection (Rej.) Since the film was not damaged by chlorine, and the flux (Flux) maintained the initial performance (Table 2). ).

[0048]

As described above, the first reverse osmosis composite membrane of the present invention according to the present invention is a reverse osmosis composite membrane including at least a porous support membrane layer and a separation active layer. By the presence of an organic polymer having an anionic hydrophilic group in at least one layer selected from the support membrane layer and the separation active layer, high anionicity, high salt rejection, high water permeability, and even resistance Combined with chlorination, it is possible to achieve practical desalination at relatively low pressure.

Next, the second reverse osmosis composite membrane of the present invention comprises:
A reverse osmosis composite membrane including at least a porous support membrane layer and a separation active layer, wherein a water-insoluble organic polymer layer having an anionic hydrophilic group is formed on the surface of the separation active layer, thereby increasing the It has both anionicity, high salt rejection, high water permeability and chlorine resistance, and can enable practical desalination at relatively low pressure.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a fixed charge density measuring device used in Example 1 of the present invention.

FIG. 2 is a schematic cross-sectional view of the reverse osmosis composite membrane obtained in Example 1 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reverse osmosis composite membrane 2 Salt bridge 3 Standard calomel electrode 4 Stirrer (stirrer) 11 Porous polysulfone support membrane 12 Separation active layer 13 Anionic sulfonated polysulfone copolymer layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location // C08J 5/22 CEZ C08J 5/22 CEZ

Claims (8)

[Claims] 1. A reverse osmosis composite membrane comprising at least a porous support membrane layer and a separation active layer, wherein at least one layer selected from the porous support membrane layer and the separation active layer has an anionic hydrophilic property. A reverse osmosis composite membrane comprising an organic polymer having a group. 2. A reverse osmosis composite membrane comprising at least a porous support membrane layer and a separation active layer, wherein a water-insoluble organic polymer layer having an anionic hydrophilic group is formed on the surface of the separation active layer. A reverse osmosis composite membrane characterized by the following. 3. The fixed charge density of the reverse osmosis composite membrane is -2.5.
The reverse osmosis composite membrane according to claim 1, wherein the concentration is not more than × 10 ^-3 [mol / l]. 4. The reverse osmosis composite membrane according to claim 1, wherein the water-insoluble organic polymer having an anionic hydrophilic group is a polymer having a sulfonic acid group. 5. The reverse osmosis composite membrane according to claim 4, wherein the polymer having a sulfonic acid group is obtained by sulfonating a polymer containing a unit represented by the following formula (1). Embedded image 6. The reverse osmosis composite membrane according to claim 5, wherein the polymer containing any of the units of the formula (1) is at least one selected from polysulfone, polyethersulfone, and polyetherethersulfone. . 7. A polymer having a sulfonic acid group, which is obtained by partially sulfonating at least one unit selected from the following formulas (Chemical Formula 2) to (Chemical Formula 3), and forming a polymer on 100 ml of N-methyl-2-pyrrolidone. From a solution in which 0.5 g of the combined liquid is dissolved, a water-insoluble partially sulfonated polysulfone having a logarithmic viscosity measured at 30 ° C. of 0.5 cm ³ / g or more and an ion exchange capacity of 2 meq / g or less is used. The reverse osmosis composite membrane according to claim 4. Embedded image Embedded image 8. The reverse osmosis composite membrane according to claim 7, wherein the sulfonic acid group of the partially sulfonated polysulfone is represented by —SO ₃ M (where M represents hydrogen, alkali metal or tetraalkylammonium).