JP6508194B2 - Composite separation membrane - Google Patents

Description

  The present invention is a liquid separation membrane, particularly a nanofiltration membrane, a reverse osmosis membrane, and a long-life composite separation membrane having excellent permeability and permeability as a reverse osmosis membrane, and excellent in chlorine resistance and alkali resistance, and its production On the way.

  Liquid separation membranes subjected to separation processes such as nanofiltration, reverse osmosis, forward osmosis, etc. have a film-like structure in which the pore size of the separation functional layer is on the order of nanometer to angstrom, or has no clear pores. For this reason, the permeation resistance of the liquid tends to be large and the permeability to be low. Therefore, by forming a thin film of a separation layer having a separation function on the surface of a porous support membrane excellent in mechanical strength and water permeability as a structure of the separation membrane, a composite separation membrane that achieves both high water permeability and separation properties The structure of is preferably used. Furthermore, as a polymer constituting the separation layer, in addition to high separation selectivity, it is required to be excellent in chemical durability, in particular chlorine resistance and alkali resistance, from the viewpoint of washing properties and stability to long-term use.

  As a structure of a conventional main composite separation membrane, there is a technique of forming a thin film of a crosslinked aromatic polyamide on the surface of a porous support membrane by interfacial polymerization. For example, Patent Document 1 discloses a sheet-like composite in which a thin film of polyamide cross-linked by interfacial polymerization is formed on the surface of a porous support membrane.

  Patent Document 2 discloses a hollow fiber composite separation membrane in which a thin film of polyamide cross-linked by interfacial polymerization is formed on the surface of a hollow fiber-like porous support membrane.

  Patent Document 3 discloses a hollow fiber composite separation membrane in which a thin film of polyamide cross-linked by interfacial polymerization is formed on the surface of a porous hollow fiber-like support membrane. There is also disclosed a technique for forming a hollow fiber composite separation membrane having a more uniform separation layer by providing a step of impregnating a solution containing the same.

  As a synthetic polymer applicable to a nanofiltration membrane or a reverse osmosis membrane other than a polyamide based material, there is a polymer having an ionic functional group such as a sulfonic acid group in the molecule. For example, in Patent Document 4, a sulfonated polyarylene ether (SPAE) is dissolved in a solvent comprising formic acid, and the obtained coating solution is applied to the surface of a porous support membrane and dried to form a film. Techniques for obtaining composite separation membranes are disclosed.

  However, although the nanofiltration membrane and reverse osmosis membrane by the polyamide type composite separation membrane like patent document 1 are excellent in ion removability and water permeability, chlorine resistance is low and processing water containing sodium hypochlorite Is impossible, and chlorine cleaning is also impossible. Therefore, it is necessary to desalt the feed solution from which sodium hypochlorite has been once removed by the separation membrane, and to add the sodium hypochlorite to the filtered water obtained thereafter, and the filtration process It has the problem of being cumbersome and expensive.

  Also in Patent Document 2 and Patent Document 3, since they are polyamide-based composite separation membranes, they have a disadvantage that chlorine resistance is low, and in the process of producing hollow fiber-type composite separation membranes, structure formation by interfacial polymerization reaction The process to be carried out has the problem that it becomes complicated compared with a flat membrane or a sheet-like material.

  On the other hand, a composite separation membrane having a sulfonated polyarylene ether (SPAE) as a separation layer as in Patent Document 4 is extremely excellent in chlorine resistance due to the high chemical stability of the polyarylene ether molecular skeleton, Although it is practically preferable because it can be washed with sodium chlorate, it has a disadvantage that it has inferior permeability selectivity as a nanofiltration membrane, a reverse osmosis membrane and a forward osmosis membrane as compared with the above-mentioned polyamide-based composite separation membrane.

  Furthermore, when referring to SPAE of Patent Document 4, for example, as pointed out in Non-Patent Document 1, SPAE has similar chemical structure to polysulfone or polyethersulfone which is a polymer material of a general porous support membrane. Because of this, most solvents that can dissolve SPAE can simultaneously dissolve polysulfone or polyethersulfone. When such a solvent is used as a coating solution, the porous support membrane dissolves or swells significantly, causing a problem that a composite membrane can not be obtained.

  Therefore, as a conventional SPAE composite membrane manufacturing method, as disclosed in Patent Document 4, a limited solvent (lower carboxylic acid such as formic acid or alcohol, alkylene) which does not attack a porous support membrane made of polysulfone or polyethersulfone, is taught. Diol or triol, alkylene glycol alkyl ether) must be selected as a coating solvent.

  On the other hand, as a required property of SPAE suitable for a composite separation membrane, it is necessary to form a strong film having a high separation property and an excellent water permeability, since swelling by water does not easily occur. Such SPAE polymers are preferably those having a more rigid molecular backbone. However, the higher the rigidity of the SPAE polymer molecular skeleton, the lower the solvent solubility tends to be, and the selection range of the soluble solvent is further limited, so it is difficult to obtain the composite separation membrane by the coating method itself. Become.

JP-A-55-147106 Japanese Patent Application Laid-Open No. 62-095105 Patent No. 3250644 JP-A-63-248409

Chang Hyun Lee et al. , Journal of Membrane Science, 389 (2012), 363-371, "Disulfonated poly (arylene ether sulfone) random copolymer thin film composite membrane fabricated using a benign solvent for reverse osmosis applications"

  The present invention has been made to overcome the problems of the prior art described above, and its object is to provide a porous separation membrane and a SPAE having a separation layer of SPAE on the surface of the porous support membrane. Films (separating layer) firmly adhered to each other, the separating property and the water permeability lasting for a long time, and the separating property and the water permeability improved compared to the separating layer consisting of conventional SPAE, and its suitable production To provide a way.

  The inventor first found that, in a composite separation membrane composed of a combination of a polymer constituting a porous support membrane and an SPAE constituting a separation layer, the solvent solubility of each polymer, the compounding process, and the performance as a composite separation membrane Was examined. Polysulfone (PSU) or polyethersulfone (PES), which is a general porous support membrane material, can be selected from N-methyl-2-pyrrolidone (NMP) and N, N-dimethylacetamide DMAc) good solubility in dimethylsulfoxide (DMSO), N, N-dimethylformamide (DMF), γ-butyrolactone (GBL) and mixed solvents containing at least one of these (hereinafter referred to as solvent group 1) Show. These solvents have excellent solvency, relatively low environmental impact, high safety to the human body, and are preferable as a membrane forming solvent for obtaining a porous support membrane. On the other hand, SPAE, which constitutes the separation layer, also exhibits good solubility in solvent group 1, but when the composite film is produced by the coating method, solvent group 1 dissolves the porous support film, so coating It was impossible until now to use as a solvent. Other engineering polymers generally used for porous support membranes include polyvinylidene fluoride (PVDF) and polyetherimide (PEI), but these polymers may also be used together with the above polysulfone and polyethersulfone. The same problem occurs because it is dissolved in solvent group 1 as well.

  For this reason, in the past, a solvent has been sought which dissolves the SPAE of the separation layer but does not dissolve the polymer of the porous support membrane, but there are not necessarily many options. As such solvents, specifically, some protic polar solvents such as, for example, lower carboxylic acids or alcohols such as formic acid, alkylene diols or triols, alkylene glycol alkyl ethers (hereinafter referred to as solvent group 2) It can be mentioned.

  However, the solubility of the solvent group 2 in SPAE is often not good. In addition, in the solvent group 2 that has a somewhat good solubility in SPAE, the affinity to the porous support membrane also tends to be high, and the porous support membrane is significantly swollen even without dissolution. There is a problem that the mechanical strength is reduced. Even if an appropriate amount of solvent group 1 is added to increase the solubility of solvent group 2 in SPAE, the porous support membrane is significantly swollen, which is not preferable. When complexation is performed by a coating method using a solvent having poor solubility, the separation properties of the composite membrane may be insufficient. On the other hand, the solvent having a good solubility is more likely , Care must be taken not to cause the porous support membrane to swell excessively (excessive swelling leads to defect formation or breakage of the composite separation membrane). Therefore, the drying temperature after coating needs to be set low (for example, about 100 ° C. or less), and as a result, a dense film can not be formed, resulting in a problem that sufficient separation characteristics can not be obtained. In addition, in the solvent group 2, formic acid is relatively excellent in solubility in SPAE, but is highly toxic and corrosive, and thus it is not preferable from the viewpoint of handleability.

  Furthermore, in composite separation membrane applications, it has a rigid molecular skeleton as the chemical structure of SPAE, from the viewpoint of obtaining a SPAE film which is excellent in mechanical properties, not easily swollen by water, and which is strong and excellent in separation properties. It is more preferable that the transition temperature is high. On the other hand, it should be pointed out that the more rigid the molecular framework is aimed, the lower the solvent solubility of the SPAE will be, which further limits the choice of solvents.

In particular, block copolymers of SPAE tend to have low solvent solubility due to the high cohesion of hydrophobic blocks. For example, a hydrophobic oligomer component having a repeating structure of a hydrophobic segment represented by the following chemical formula (I), and a hydrophilic oligomer component having a repeating structure of a hydrophilic segment represented by the chemical formula (II) The SPAE constituted by the chain extender component, represented by III) or (IV), has excellent mechanical properties and low swelling due to the rigid molecular backbone and the high cohesion of the hydrophobic oligomer Although it is suitable for nanofiltration and reverse osmosis applications because it is possible to form a film, it has the problem that it is soluble in solvent group 1 but hardly soluble in solvent group 2 .
Here, two or more chain extenders are not continuously linked.
In the above formulae, m and n each represent a natural number of 1 or more, R ¹ and R ² each represent —SO ₃ M or —SO ₃ H, M represents a metal element, and a sulfonic acid in the polymer The ion exchange capacity IEC, which is an index of the group content, is in the range of 0.3 to 4.0 meq./g.

  That is, when it is intended to obtain a composite separation membrane using an SPAE block copolymer having low solvent solubility although having excellent separation properties as described above, solvent group 2 may be used as a coating solvent Because it can not be done, we have to use solvent group 1 with high solvency. For that purpose, the porous support membrane insoluble in the solvent group 1 is essential, and the above-mentioned known porous support membrane could not be used.

  Therefore, the present inventors searched for a polymer which is insoluble in the solvent group 1 and suitable for the porous support membrane of the composite separation membrane, and trial manufacture of the composite separation membrane coated with the above-mentioned SPAE block copolymer. I piled up. It is preferable that the porous support membrane supports the thin film of the separation layer under pressure (0.1 to 8.0 MPa) at the time of separation operation, and can be used stably for a long time, and the polymer is excellent in mechanical strength and chemical durability It is an essential condition to use Furthermore, it is possible to easily obtain a membrane having a pore size of the order of ultrafiltration membrane, which has appropriate solvent solubility and is suitable as a porous support membrane of a composite separation membrane by a known wet or dry-wet membrane forming method preferable. Also, in order to obtain high mechanical properties, polymers having a high glass transition temperature are preferred. In addition, in order to obtain appropriate solvent solubility, it is preferable to be an amorphous polymer. That is, specifically, a porous support membrane using an amorphous aromatic polymer is preferable.

Table 1 shows the solubility of a typical known polymer in aprotic polar solvents and the like.

  In general, it is known that the solvent solubility of crystalline and semi-crystalline polymers having high crystallinity is poor, for example, polyphenylene sulfide (PPS) or crystalline polymers having excellent mechanical properties and chemical durability. Polyether ether ketone (PEEK) etc. are known. These are originally insoluble in almost all known solvents except for inorganic acids, and although melt forming is possible, they are unsuitable for wet film formation, and it is easy to obtain a porous support film suitable for composite films. Not As the non-crystalline aromatic polymer, polyetherimide (PEI), polysulfone (PSU), and polyethersulfone (PES) have appropriate solvent solubility, but are dissolved in solvent group 1. Although polyvinylidene fluoride (PVDF) is a crystalline polymer, it is a non-aromatic polymer, has a low glass transition temperature, and has appropriate solvent solubility, but it also dissolves in solvent group 1.

  Among these, the present inventors focused on the special solvent solubility exhibited by polyphenylene ether (PPE) among known non-crystalline aromatic polymers. It has been found that polyphenylene ether is insoluble in solvent group 1 or shows limited solubility, and is a polymer suitable as a porous support membrane to achieve the object of the present invention.

  Specifically, polyphenylene ether is completely insoluble in dimethyl sulfoxide (DMSO) and γ-butyrolactone (GBL) in solvent group 1 of the aprotic polar solvent. On the other hand, N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc) and N, N-dimethylformamide (DMF) are insoluble at normal temperature but can be dissolved in a high temperature region as described later As a result, it has the feature that a porous support membrane can be easily obtained. Therefore, if a porous support membrane made of polyphenylene ether is used, even if a coating solution in which the SPAE block copolymer is dissolved is applied to the solvent group 1, the porous support membrane is not attacked. Even more surprisingly, if a suitable solvent combination is selected from solvent group 1, the polyphenylene ether porous support membrane is not excessively swollen by the solvent, so that it is relatively hot in the drying step after coating. It was found that even if the solvent was dried quickly, breakage of the membrane and performance degradation were unlikely to occur. This is a great advantage in the production method of the composite separation membrane, and even if the solvent group 1 having a relatively high boiling point (150 to 210 ° C.) is rapidly dried if the solvent is rapidly dried at a high temperature (100 ° C. or more) It has been found that it is possible to stably and easily form a separation layer of a dense SPAE copolymer having separation properties.

  Furthermore, in the composite separation membrane of the present invention, a clear microphase separation structure is expressed in the separation layer of several tens to several hundreds nm of SPAE block copolymer, and hydrophilic channels penetrate in the film thickness direction. It was found to be prone to For this reason, the result that the ion separation property is improved was obtained as compared with the composite separation membrane made of the conventional SPAE random copolymer.

That is, the present invention is completed based on the above-mentioned knowledge, and has the composition of the following (1)-(5).
(1) A composite separation membrane having a separation layer with a thickness of 5 nm to 1 μm on the surface of a porous support membrane, wherein the porous support membrane is composed of polyphenylene ether, and the separation layer has a number average molecular weight of 1000 or more Comprising a multiblock copolymer of a sulfonated polyarylene ether composed of a hydrophobic oligomer component of the following, a hydrophilic oligomer component having a number average molecular weight of 1000 or more, and a chain extender component that combines the two oligomer components A separation membrane, and the copolymer is a hydrophobic oligomer component having a repeating structure of a hydrophobic segment represented by the following chemical formula (I) or (XV), and a hydrophilic segment represented by the chemical formula (II) And a hydrophilic oligomer component, which is a repeating structure of the formula (III), and a chain extender component represented by the chemical formula (III), Coalescence, nanofiltration or for composite separator for infiltration, which comprises dissolving in the solvent group 1.
Solvent group 1: N-methyl-2-pyrrolidone, N, N-dimethylacetamide, dimethylsulfoxide, N, N-dimethylformamide, γ-butyrolactone




However, two or more chain extender components are not connected in succession,
m and n each represent a natural number of 1 or more, R ¹ and R ² each represent -SO ₃ M or -SO ₃ H, M represents a metal element, and is an index of sulfonic acid group content in the polymer The multiblock copolymer of the sulfonated polyarylene ether having an ion exchange capacity IEC in the range of 0.3 to 4.0 meq./g (2) is a hydrophilic oligomer having a sulfonate group, and a sulfonate group and a sulfonate group The composite separation membrane according to (1), which is a polymer obtained by binding a hydrophobic oligomer having no oxo group by a chain extender.
(3) The composite separation membrane according to (1) or (2) , wherein the content of polyphenylene ether in the porous support membrane is 80% by mass or more.
(4) Sulfonation to an aprotic polar solvent containing at least one selected from dimethylsulfoxide, N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, and γ-butyrolactone A coating solution obtained by dissolving a multiblock copolymer of polyarylene ether is applied to the surface of a porous support membrane composed of polyphenylene ether, and then the coated surface is subjected to a drying treatment (1) The manufacturing method of the composite separation membrane in any one of-( 3 ).
(5) The method according to (4) , wherein the porous support membrane is impregnated with at least one member selected from the group consisting of alcohol, alkylene diol or triol, alkylene glycol alkyl ether, and water, and then the coating solution is applied. Method of manufacturing composite separation membrane.

  In the composite separation membrane of the present invention, since the separation layer consisting of a specific SPAE multi-block copolymer is provided on the surface of the porous support membrane mainly composed of polyphenylene ether, the adhesion between the porous support membrane and the separation layer is obtained. Is very good. Furthermore, since the continuous hydrophilic channels formed by the SPAE multi-block copolymer are connected in the film thickness direction, they have the advantages of excellent ion separation characteristics and improved water permeability. As a result, the separation characteristics and permeability suitable as a nanofiltration membrane, a reverse osmosis membrane, and a forward osmosis membrane are maintained for a long time, and excellent in chlorine resistance and alkali resistance and long life.

FIG. 1 shows a schematic view (flat membrane) of the composite separation membrane of the present invention. FIG. 2 shows a schematic view (hollow fiber membrane) of the composite separation membrane of the present invention. FIG. 3 is a SEM (Scanning Electron Microscope) image of the cross section of the composite separation membrane of Example 1. FIG. 4 is an enlarged SEM image of the membrane cross section outer layer portion of the composite separation membrane of Example 1. FIG. 5 is an enlarged SEM image of the membrane surface of the composite separation membrane of Example 1. 6 (a) and 6 (b) are TEM (Transmission Electron Microscope) images of separation layer sections of the composite separation membranes of Example 1 and Comparative Example 1, respectively. It is the graph which put together the film | membrane performance in Examples 1-5 and Comparative Examples 1-5.

  The composite separation membrane of the present invention has a separation layer on the surface of a porous support membrane, and the porous support membrane contains polyphenylene ether as a main component, and the separation layer has a sulfonated polyarylene ether having a specific repeating structure. It is characterized by comprising a copolymer.

  The composite separation membrane of the present invention is suitable as a liquid treatment membrane, particularly as a nanofiltration membrane, a reverse osmosis membrane and a forward osmosis membrane. These membranes are separation membranes having a dense film-like separation layer which is considered to have a pore diameter of several nm or less, or have no clear pores, and have low molecular weight organic molecules such as glucose or the like. , Inorganic salt solutes are used when they are separated from the solution. The nanofiltration membrane is a liquid-treated membrane that has a larger pore size than the reverse osmosis membrane and can partially remove low molecular weight organic molecules, monovalent ions and polyvalent ions, and the reverse osmosis membrane has a pore size larger than that of the nanofiltration membrane. It is a liquid-treated membrane which is small and can completely separate and remove even monovalent ions such as sodium ions.

  In the composite separation membrane of the present invention, the size of the target fractionation substance is on the surface of the porous support membrane made of a hydrophobic polymer having pores (diameter of about 10 nm to several hundreds nm) sufficiently larger than the size of the target fractionation substance. And a film formed of a polymer having a separation property of at least two kinds of polymers, wherein the separation layer and the porous support membrane are clearly distinguished from each other. it can. In the case of a flat membrane as shown in FIG. 1, the porous support membrane 2 is placed on the nonwoven fabric 3 such as polyester, and the thin film of the separation layer 1 is formed on the surface of the porous support membrane 2. Further, in the case of a hollow fiber membrane as shown in FIG. 2, a thin film of the separation layer 1 is formed on a hollow fiber porous support membrane 2. Here, the thin film refers to a film having a thickness of about 5 nm or more and 1 μm or less. The thickness of the porous support membrane is at least 5 μm or more, which is sufficiently thicker than the thin film.

  On the other hand, an asymmetric membrane exists as a membrane structure different from the composite separation membrane of the present invention. The asymmetric membrane is a membrane obtained by solidifying the membrane-forming stock solution by the phase separation method, and is controlled so that the surface layer of the membrane is dense and the inner layer side of the membrane is porous. The asymmetric membrane may be composed of one or more types of polymer components using a polymer blend method or the like, but basically it is a membrane obtained only by controlling the gradient of the polymer density in the membrane The polymer components of the separating layer and the porous support layer are identical. In general, the composite separation membrane can control the structure and thickness of the porous support membrane and the structure and thickness of the separation layer independently, so it is easier to control the water permeability, the salt removal rate, and the balance thereof.

  Next, preferred embodiments of the porous support membrane, the SPAE block copolymer and the composite separation membrane in the composite separation membrane of the present invention and the method for producing the same will be described in order.

(Porous support membrane)
The polyphenylene ether used for the porous support membrane of the composite separation membrane of the present invention is represented by the following chemical formula (XIV).
In the above formula, k represents a natural number of 1 or more.

  The number average molecular weight of the polyphenylene ether is preferably 5,000 or more and 500,000 or less. Within this range, it is possible to dissolve at a high temperature in a part of the aprotic polar solvent shown in the above-mentioned solvent group 1, and the viscosity of the membrane forming solution becomes sufficient, and a porous support membrane of sufficient strength. Can be made.

  From the viewpoint of improving the strength of the porous support membrane or optimizing the membrane performance, the above polyphenylene ether is blended with various polymers including polystyrene which is known to be completely compatible with the polyphenylene ether. May be Alternatively, the polyphenylene ether may contain a filler. Furthermore, from the viewpoint of imparting hydrophilicity, the porous film of the polyphenylene ether which is a hydrophobic polymer may contain an ionic surfactant, a nonionic surfactant, or a hydrophilic polymer such as polyethylene glycol or polyvinyl pyrrolidone. Good. However, the proportion of polyphenylene ether constituting the porous support membrane is preferably 50% by mass or more. More preferably, it is 80 mass% or more. Within this range, the polyphenylene ether porous support membrane is not attacked against the solvent group 1, and the characteristics of the polyphenylene ether having higher mechanical strength and chemical resistance are also maintained. It is advantageous in the manufacturing process.

  As a membrane-forming solvent for obtaining a porous support membrane using polyphenylene ether, N-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide (DMAc) among aprotic polar solvents of solvent group 1 can be used. ), N, N-dimethylformamide (DMF) is a so-called “latent solvent”, for example, at which temperatures of about 60 ° C. and higher give a uniform film-forming solution and is insoluble at temperatures lower than that. Preferred. However, in this latent solvent, the temperature range in which polyphenylene ether can be dissolved varies depending on the molecular weight of polyphenylene ether, the polymer concentration of the membrane forming solution, and the interaction between the separately added substance and the polymer and latent solvent. It should be adjusted as appropriate. Among these, N-methyl-2-pyrrolidone is particularly preferable because the solution stability of the membrane forming solution is good. On the other hand, in the solvent group 1, for example, dimethyl sulfoxide and γ-butyrolactone are non-solvents which do not dissolve polyphenylene ether even under high temperature conditions of 100 ° C. or higher, and therefore less preferable as a membrane forming solvent for obtaining a porous support film. Absent.

  Here, in the present invention, “a latent solvent” refers to a solvent-specific Flory's theta temperature (polymer chain with respect to a polymer (which is a polyphenylene ether in the present invention) which is a solute in the membrane-forming stock solution of the porous support membrane. It refers to a solvent where there is a temperature at which the interaction acting between the segments of A becomes an apparent zero, ie, a temperature at which the second virial coefficient becomes a zero), and the theta temperature is below normal temperature or the boiling point of the solvent. Above the theta temperature, a uniform film-forming stock solution is obtained, and below the theta temperature, the polymer is insoluble in the solvent. In fact, the apparent theta temperature of the membrane forming solution in the present invention changes to some extent depending on the polymer concentration and the solvent composition. The term "good solvent" refers to a solvent that produces a film-forming solution that is uniform at room temperature regardless of the temperature at which the repulsive force acting between the polymer chain segments exceeds the attractive force in the film-forming solution. "Non-solvent" refers to a solvent that does not have a theta temperature, or because the theta temperature is so high, that the polymer is totally insoluble regardless of temperature.

  As a solvent for polyphenylene ether, in addition to the above-mentioned latent solvent, it is known that a good solvent which can be dissolved even at normal temperature is also present. Chowdhury, B .; Kruczek, T. Nonpolar solvents such as carbon tetrachloride, carbon disulfide, benzene, toluene, chlorobenzene, dichloromethane, chloroform, etc. as summarized in Matsuura, Polyphenylene Oxide and Modified Polyphenylene Oxide Molecules Gas, Vapor and Liquid Separation, 2001, Springer Hereinafter, solvent group 3 is known. However, unlike the solvent group 1 described above, these solvents can dissolve polyphenylene ether at normal temperature, but have a large environmental impact and also have high harmfulness to the human body. Not desirable.

  A wet film forming method and a dry / wet film forming method are preferably used as a film forming method for obtaining a porous support film from a film forming solution prepared by dissolving polyphenylene ether in the latent solvent. In the wet film forming method, a uniform solution-like film forming solution is mixed with a good solvent in the film forming solution, and the polymer is immersed in a coagulation bath consisting of a nonsolvent so as to be insoluble and the polymer becomes a phase It is a method of forming a membrane structure by separating and depositing. In addition, the dry-wet film forming method is an asymmetric structure in which the polymer density of the film surface layer is further reduced by partially evaporating the solvent from the surface of the film forming solution immediately before immersing the film forming solution in the coagulation bath. How to get In the present invention, it is more preferable to select a dry-wet film forming method.

  The shape of the membrane of the composite separation membrane of the present invention is not particularly limited, and a flat membrane or a hollow fiber membrane is preferable. All these membranes can be manufactured by methods conventionally known to those skilled in the art. For example, in the case of a flat membrane, it can be produced by casting a film-forming stock solution on a substrate and optionally immersing in a coagulation bath after giving a drying period for a fixed period. In the case of the hollow fiber membrane, the membrane forming solution is discharged from the outer peripheral slit of the double cylindrical spinning nozzle so as to become a hollow cylindrical shape, and the non-solvent, latent solvent, good from the inner nozzle inner hole. A fluid selected from a solvent or a mixed solvent thereof, a liquid incompatible with a membrane forming solvent, or a gas such as nitrogen, air, etc. is extruded together with a membrane forming solution, and if desired, constant After giving the evaporation period of (1), it can manufacture by immersing in a coagulation bath.

  The concentration of polyphenylene ether in the membrane forming solution is 5% by mass or more and 60% by mass from the viewpoint of making the water permeability of the porous support membrane and the surface pore diameter appropriate while the mechanical strength of the obtained porous support membrane is sufficient. It is preferable that it is the following. Furthermore, it is more preferable that it is 10 to 50 mass%.

  Moreover, it is preferable that the temperature of a film forming undiluted | stock solution is at least 40 degreeC or more. More preferably, the temperature is 60 ° C. or higher. The upper limit of the temperature is equal to or lower than the boiling point of the above-mentioned film-forming solvent, more preferably, 150 ° C. or lower, and even more preferably, less than 100 ° C. When the temperature of the membrane-forming solution becomes lower than the above range, the membrane-forming solution becomes less than the above-mentioned theta temperature, which is not preferable because the polymer is precipitated. From the experience of the present inventor, the polyphenylene ether solid obtained by leaving the above-mentioned stock solution at a temperature lower than the theta temperature is not preferable as a separation layer because it is brittle. Non-solvent-induced phase separation is caused by immersing in a coagulation bath filled with a non-solvent from the state of the film-forming stock solution in a uniform state above the theta temperature to form a membrane structure. Preferred membrane structures are obtained. On the other hand, when the temperature of the membrane-forming solution is made higher than the above range, the viscosity of the membrane-forming solution decreases, which makes molding difficult, which is not preferable. In addition, since the evaporation rate of the good solvent in the stock solution for membrane formation and the solvent exchange rate in the coagulation bath become too high, the polymer density on the membrane surface becomes too dense, and the water permeability as the supporting membrane decreases remarkably. Is not preferable because problems such as

  In the dry-wet film forming method, a constant solvent evaporation time is given before the step of immersing the film forming solution in the coagulation bath. The evaporation time and temperature are not particularly limited, and the asymmetric structure of the finally obtained porous support membrane should be adjusted to be as desired, for example, at an atmosphere temperature of 5 to 200 ° C. It is preferred to partially evaporate the solvent for 0.1 to 600 seconds.

  The non-solvent of the coagulation bath used in the wet film forming method or the dry / wet film forming method is not particularly limited, and water, alcohol, polyhydric alcohol (ethylene glycol, diethylene glycol, triethylene glycol, glycerin etc.) is preferable. It may be a mixed liquid. From the viewpoint of simplicity and economy, water is preferably contained as a component.

  Also, other substances may be added to the coagulation bath. For example, from the viewpoint of controlling the rate of solvent exchange in the coagulation process and making the membrane structure preferable, solvents of solvent group 1 and, in particular, N-methyl-2-pyrrolidone and N, N-dimethylacetamide are preferably used in the coagulation bath. A latent solvent can be preferably added. Also, polysaccharides, water-soluble polymers, etc. may be added to control the viscosity of the coagulation bath.

  The temperature of the coagulation bath is not particularly limited, and may be appropriately selected from the viewpoint of controlling the pore diameter of the porous support membrane, or from the viewpoint of economy and work safety. Specifically, 0 ° C. or more and less than 100 ° C. are preferable, and 10 ° C. or more and 80 ° C. or less are preferable. If the temperature is lower than this range, the viscosity of the coagulating liquid becomes too high, and as a result, the demixing process proceeds more slowly, and as a result, the membrane structure tends to be densified and the water permeability of the membrane tends to decrease. . Further, if the temperature is higher than this range, the demixing process proceeds more instantaneously, and as a result, the membrane structure tends to be sparse and the membrane strength tends to decrease, which is not preferable.

  The time for immersing in the coagulation bath may be adjusted to the time when the structure of the porous support membrane is sufficiently formed. It is preferably in the range of 0.1 to 1000 seconds, and more preferably in the range of 1 to 600 seconds from the viewpoint of sufficiently advancing solidification and phase separation, and not unnecessarily lengthening the process. preferable.

  The porous support membrane obtained by completing the membrane structure formation in the coagulation bath is preferably washed with water. The method for washing with water is not particularly limited, and the porous support membrane may be immersed in water for a sufficient time or may be washed with running water for a certain period while being transported.

  The porous support membrane washed with water is preferably post-treated so as to be in a preferable state for the composite membrane formation step described later. For example, it is preferable to impregnate the porous support membrane with an alcohol, an alkylene diol or triol, an alkylene glycol alkyl ether, a hydrophilic solvent such as water, or a mixed solvent thereof, and treat the pores in the support membrane by plugging. It will be. This filling process solves the problem of excessive permeability of the SPAE molecules into the porous support membrane when the coating solution is applied in the compounding step, thereby reducing the water permeability. In addition, the liquid used for the plugging treatment acts as a pore diameter retention agent, and the drying shrinkage of the porous support membrane can be suppressed. In addition, the porous support membrane, which is hydrophobic, can be made hydrophilic.

  It is preferable that the porous support membrane subjected to the above-mentioned plugging treatment be dried to a suitable excess of water and solvent. The drying conditions should be suitably adjusted in order to make the performance as a composite separation membrane appropriate, and specifically, it is dried at a temperature of 20 to 300 ° C. for about 0.01 seconds to overnight. Is preferred.

  The obtained porous support membrane may be taken up and stored by a winding device, and may be subsequently rewound as a separate step and subjected to a compounding step, or continuously transported without passing through the winding device. However, the compounding process may be performed.

  The thickness of the porous support membrane used for the composite separation membrane is preferably 5 μm or more and 500 μm or less. If the thickness is smaller than this range, a problem that pressure resistance can not be sufficiently obtained tends to occur, and if the thickness is larger than this range, it is not preferable because the permeation resistance becomes large. A more preferable range is 10 μm to 100 μm. In addition, in the case of a hollow fiber porous support membrane, the outer diameter of the membrane is preferably 50 μm or more and 2000 μm or less. If it is smaller than this range, the flow pressure loss of the permeated liquid or the feed liquid flowing inside the hollow becomes too large, and the operating pressure becomes undesirably large. Moreover, since the pressure resistance of a film | membrane will fall when larger than this range, it is unpreferable. A more preferable range is 80 μm or more and 1500 μm or less.

(SPAE block copolymer)
The SPAE block copolymer used in the separation layer of the composite separation membrane of the present invention is obtained by combining a hydrophilic oligomer having a sulfonic acid group with a hydrophobic oligomer having no sulfonic acid group by a chain extender. Preferred polymers. It is possible to suitably select the chemical structure of each monomer unit of these hydrophilic oligomers and hydrophobic oligomers. Specifically, by selecting a highly rigid chemical structure, it is possible to form a film of a strong SPAE block copolymer that is difficult to swell. Furthermore, in the copolymerization reaction, by adjusting the molecular weight of each oligomer, the introduction amount of the sulfonic acid group in the block copolymer can be reproducibly and precisely controlled.

As a specific structure of the SPAE block copolymer, those composed of a hydrophobic oligomer component represented by the following chemical formula (V) and a hydrophilic oligomer component represented by the chemical formula (VI) are excellent It is preferable in order to develop chemical durability. Furthermore, in the chemical formulas (V) and (VI), in particular when X, Y, Z and W are selected from the following combinations, the whole molecular structure becomes more rigid and a polymer having a high glass transition temperature is obtained. And preferable because it can maintain good chemical durability.
However, two or more chain extender components are not connected in succession,
In the above formula, X is either of chemical formula (VII) or (VIII),
Y is a single bond or any one of chemical formulas (IX) to (XII),
Z is any one of chemical formulas (IX), (XIII) and (XII),
W is any one of chemical formulas (IX), (XIII) and (XII),
The same chemical structure is not selected at the same time for Y and W, and
a and b each represent one or more natural numbers,
R ¹ and R ^{2 each} represent —SO ₃ M or —SO ₃ H, M represents a metal element, and the ion exchange capacity IEC which is an index of the content of the sulfonic acid group in the polymer is 0.3-4. It is in the range of 0 meq./g.

More preferably, the SPAE used in the separation layer of the present invention comprises a repeating structure of a hydrophobic oligomer component represented by the following chemical formula (I) and a hydrophilic oligomer component represented by the chemical formula (II) is there. By the presence of the benzonitrile structure in the chemical formula (I), a strong cohesive force acts on the hydrophobic oligomer component, so that a stronger and less peelable separation layer can be formed.
However, two or more chain extender components are not connected in series.
In the above formulas, m and n each represent a natural number of 1 or more, R ¹ and R ² each represent —SO ₃ M or —SO ₃ H, and M represents a cation, and the content of sulfonic acid group in the polymer The ion exchange capacity IEC which is an index of is in the range of 0.3 to 4.0 meq./g.

  The preferred ion exchange capacity IEC (ie, the milliequivalent of sulfonic acid group per gram of sulfonated polymer) of the SPAE block copolymer having the chemical structure as described above is 0.3 to 4.0 meq. It is / g. When the IEC is lower than the above range, the amount of sulfonic acid groups is too small to sufficiently express ion separation. Moreover, when IEC is higher than the said range, the hydrophilicity of a polymer becomes large too much and it is unpreferable in order that a SPAE isolation | separation layer may swell excessively. The more preferable range of IEC is 0.5 to 3.0 meq. It is / g.

When R ¹ and R ^{2 in the} above chemical formula (VI) and the chemical formula (II) are —SO ₃ M, the cation M is not particularly limited, and metal ions such as potassium, sodium, magnesium, aluminum and cesium, or ammonium ions Nonmetallic ions such as are preferred. More preferably, it is potassium and sodium.

  It is known that the chain length of the oligomer component of the SPAE block copolymer represented by the above-mentioned chemical formula (V), (VI) and chemical formulas (I), (II) is appropriately adjusted during polymerization of each oligomer. It is possible based on the polymerization method. The preferable number average molecular weight is preferably 1,000 or more for each of the hydrophilic oligomer and the hydrophobic oligomer, and more preferably 2,000 or more. When the molecular weight is smaller than this range, it is difficult to express a clear microphase separation structure. The upper limit of the molecular weight of the oligomer is not particularly limited but is preferably 20,000 or less.

  There is no particular limitation on the method for obtaining a block copolymer by combining hydrophilic and hydrophobic oligomers with a chain extender. For example, Hae-Seung Lee et al. , Polymer, 49 (2008), 715-723, "Hydrophilic-hydrophobic mutiblock copolymer based on poly (arylene ether sulfone) via low-temperature coupling reactions for proton exchange membrane fuel cells", hydrophobic oligomers Both ends of the molecule are modified with a chain extender of formula (III) or (IV). What refine | purified this and another which superposed | polymerized and refine | purified the hydrophilic oligomer separately are mixed again, and a block copolymer can be obtained on 60-130 degreeC temperature conditions.

  As another method, the solution in which the polymerization reaction of the hydrophilic oligomer is completed and the solution in which the polymerization reaction of the hydrophobic oligomer is completed are not purified, or only byproducts such as inorganic salts are removed from the solution The block copolymers can be obtained by mixing in the state and adding the above-mentioned chain extender.

  The target block copolymer can be obtained by any of the above synthesis methods. The condensation reaction of the respective oligomers and the chain extension reaction between the oligomers can be reacted at appropriate temperature conditions in the presence of a basic compound such as cesium carbonate, potassium carbonate or sodium carbonate.

  As for the chain extender represented by the above chemical formula (III) or (IV), if the halogen is fluorine, the reactivity is high and the side reaction such as the decrease in segment length can be suppressed, so that an aromatic system containing fluorine Chain extenders are preferred. Perfluoro compounds are preferable because they are more reactive. Specifically, it is preferable to use either decafluorobiphenyl or hexafluorobenzene, or a mixture of these.

  The molecular weight of the finally obtained SPAE block copolymer is 0.5 or more in logarithmic viscosity when measured at 30 ° C. for a solution of 0.5 g / dL of N-methyl-2-pyrrolidone Is preferable from the viewpoint of exhibiting separation performance, more preferably 0.9 or more, and still more preferably 1.2 or more. If the ratio is less than 0.5, the coating property is likely to be poor in a compounding step with a coating described later, which is not preferable.

(Composite separation membrane)
As a coating solvent for dissolving the above-mentioned SPAE block copolymer, dimethylsulfoxide, N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, which is an aprotic polar solvent of solvent group 1 Among γ-butyrolactone, a solvent containing at least one component is preferred. Furthermore, among the solvents of the solvent group 1, dimethyl sulfoxide and γ-butyrolactone are more preferable because the above-mentioned polyphenylene ether porous support membrane is not attacked even at high temperature. Moreover, the solvent which mixed any one of N, N- dimethylacetamide, N, N- dimethylformamide, N-methyl- 2-Pyrrolidone with dimethylsulfoxide and (gamma) -butyrolactone is preferable. Furthermore, in the composite separation membrane, a solvent having a lower solubility or a solvent having a different vapor pressure is added to the solvent of the solvent group 1 to change the evaporation rate of the coating solution or to change the solution stability. The structure of the separation layer may be controlled. For example, the solvent of solvent group 2 may be contained in the solvent of solvent group 1.

  In addition, known hydrophilic polymers such as polyethylene glycol and polyvinyl pyrrolidone may be added in order to change the viscosity and hydrophilicity of the coating solution of SPAE. The use of these additives is to apply the coating solution to the surface of the porous support membrane by an appropriate amount in the coating step, and / or control the separation layer structure of the composite separation membrane, to thereby perform the performance of the composite separation membrane It should just be carried out as a device of the usual range for optimizing.

  The polymer concentration of SPAE in the coating solution is not particularly limited, and should be appropriately adjusted to control the thickness of the separation layer in the composite separation membrane. The final thickness of the separation layer is influenced by the speed at which the coating solution is applied to the surface of the porous support membrane, the temperature, etc., but the concentration of SPAE is preferably 0.01 to 20% by mass. And more preferably 0.1 to 10% by mass. If the concentration of SPAE is less than this range, the thickness of the separation layer is too thin, which tends to cause defects, which is not preferable. Moreover, when it is larger than this range, the thickness of the separation layer is too thick, and the filtration resistance becomes large, so that sufficient water permeability as a composite separation membrane can not be obtained, which is not preferable. The final thickness of the SPAE separation layer is preferably about 30 nm or more and 1 μm or less, and more preferably 50 nm or more and 500 nm or less.

  The method for applying the coating solution to the surface of the porous support membrane is not particularly limited, and any known means may be used. For example, in the case of a flat membrane, a method is preferred in which the coating solution is applied to the surface of the porous support membrane by brushing, conveniently by hand. As a more industrial method, a method in which a coating solution is applied by a slide bead coater to the surface of a continuously transported porous support membrane is preferably used. In the case of a hollow fiber membrane, a dip-coating method in which the hollow fiber membrane transported continuously is immersed in a bath filled with a coating solution and then pulled up to coat the outer surface of the hollow fiber membrane It is preferably used. Alternatively, after inserting the coating solution into the hollow fiber membrane from the cross section of the module in which the hollow fiber membranes are bundled, hollow fiber can be obtained by extruding the coating solution with gas or drawing out from one side of the module with vacuum. The method of coating on the inner surface of the film is also preferably used.

  The coating solution applied to the surface of the porous support membrane is dried to form a thin film of SPAE. Although the drying method is not particularly limited, for example, a method is adopted in which drying is performed by passing the porous support membrane coated in a forced convection drying oven for a certain period of time. Or heat drying by infrared rays may be performed. The drying temperature, the drying time, or the air flow rate in the forced convection drying oven is a condition that should be appropriately adjusted in order to bring the performance of the composite separation membrane to a specific desired value, and the solvent is dried rapidly. The temperature may be appropriately adjusted so as to obtain a composite separation membrane having excellent separability without damaging the porous support membrane by excessive high temperature.

  As the membrane performance of the final composite separation membrane, values required from a practical viewpoint are the size of the fractionation target, the affinity with the membrane, the operating pressure condition, the salt concentration condition, the fouling of the membrane (soiling tendency The nanofiltration membrane preferably has a NaCl removal rate of about 10 to 90%, although it may change depending on the nature and is not necessarily clear. The water permeability is preferably as high as possible within the range in which the pressure resistance and the performance stability of the composite separation membrane are ensured. The NaCl removal rate is more preferably about 20 to 80%. Moreover, as a reverse osmosis membrane, it is preferable that a NaCl removal rate is 95% or more for the separation use of a salt water whose comparatively low salt concentration is about 1500 ppm of NaCl concentration. More preferably, it is 98% or more. The water permeability is preferably as high as possible, as long as the pressure resistance of the composite separation membrane and the stability of the salt removal performance are ensured. The composite separation membrane of the present invention is suitable as a nanofiltration membrane, a reverse osmosis membrane, and a forward osmosis membrane in that the above-mentioned conditions for removing NaCl and permeability can be satisfied for a long time.

Example 1
(Preparation of porous support membrane)
As a polymer of the porous support membrane, polyphenylene ether PX100L (hereinafter abbreviated as PPE) manufactured by Mitsubishi Engineering Plastics Co., Ltd. was prepared. The mixture was dissolved at 130 ° C. while adding and kneading N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) so that PPE would be 20% by mass, and a uniform film-forming stock solution was obtained.

  Subsequently, while extruding the membrane-forming solution into a hollow shape from a double cylindrical tube nozzle, a 20 mass% NMP aqueous solution is simultaneously extruded as an inner liquid and allowed to travel in the air for evaporation, and then a 10 mass% NMP aqueous solution is filled. The film was immersed in a coagulation bath at 25 ° C. to prepare a PPE porous support membrane, and then washed with water.

  The water-washed PPE porous support membrane was impregnated with a 50% by mass aqueous glycerin solution, and then dried overnight at 50 ° C. to obtain a clogged membrane.

The outer diameter of the obtained PPE porous support membrane was 270 μm, and the film thickness was 54 μm. When the pure water permeation test was performed, the pure water permeation amount FR was 11,000 L / m ² / day at a test pressure of 0.5 MPa.

(Preparation of SPAE block copolymer)
An SPAE block copolymer having a repeating structure of the hydrophobic oligomer component represented by the chemical formula (I) and the hydrophilic oligomer component represented by the chemical formula (II) was prepared as follows.

  The polymerization of the hydrophobic oligomer and the chain extender modification of the end of the oligomer molecule were carried out by the following method. 9.600 g of 2,6-dichlorobenzonitrile (hereinafter abbreviated as DCBN), 10.568 g of 4,4'-biphenol (hereinafter abbreviated as BP), 8.620 g of potassium carbonate, 140 mL of NMP, 30 mL of toluene, nitrogen inlet tube, stirring It was placed in a 300 mL branched flask fitted with wings, Dean Stark trap, thermometer and heated in a stream of nitrogen with stirring in an oil bath. After dehydration by azeotropic distillation with toluene at 140 ° C., all the toluene was removed. Thereafter, the temperature was raised to 160 ° C., and heating was carried out for 5 hours. At this time, the number average molecular weight by 1 H-NMR measurement was 14,500. 80mL NMP and 3.574g decafluorobiphenyl (hereinafter abbreviated as DFB) are placed in another 500mL branched flask equipped with a nitrogen introduction tube, a stirring blade, a cooling reflux tube, and a thermometer, and the oil is stirred under nitrogen stream while stirring. It was heated to 110 ° C. in a bath. Thereto, a reaction solution of DCBN and BP was charged with stirring using a dropping funnel over 2 hours, and after the addition was completed, the mixture was further stirred for 2 hours. The reaction solution was filtered to remove inorganic salts, and then poured into 3000 mL of acetone to solidify the oligomer, and then washed three times with acetone to remove NMP and DFB. The obtained oligomer was dried at 100 ° C. for 2 hours and then dried under reduced pressure at 120 ° C. for 24 hours to obtain a DFB end-modified hydrophobic oligomer.

  The polymerization of the hydrophilic oligomer was carried out by the following method. 10.000 g of 3,3'-disulfonic acid-4,4'-dichlorodiphenyl sulfone disodium salt (hereinafter abbreviated as SDCDPS), 3.9438 g of BP, 3.22 g of sodium carbonate, 30 mL of NMP, 6 mL of toluene, nitrogen inlet tube, stirring It was placed in a 200 mL branched flask fitted with a wing, Dean Stark trap, thermometer and heated in a stream of nitrogen with stirring in an oil bath. After dehydration by azeotropic distillation with toluene at 140 ° C., all the toluene was removed. Then, it heated up to 210 degreeC and heated for 24 hours. The resulting solution was filtered to remove inorganic salts. The resulting solution was dropped into 2000 mL of acetone to solidify the oligomer. The oligomer was further washed three times with acetone, followed by filtration and drying under reduced pressure to obtain a hydrophilic oligomer. The number average molecular weight by 1 H-NMR measurement was 10,300.

  Block copolymerization with a chain extender was carried out by the following method. 6.26 g of hydrophilic oligomer, 8.48 g of hydrophobic oligomer, 0.18 g of sodium carbonate, 130 mL of NMP, put into a 300 mL branched flask equipped with a nitrogen introducing pipe, a stirring blade, a Dean Stark trap, a thermometer and under nitrogen stream 50 Stir and dissolve in an oil bath at ° C. Then, it heated to 110 degreeC and made it react for 5 hours. Thereafter, it was cooled to room temperature and dropped into 2000 mL of 2-propanol to solidify the polymer. After washing three times with 2-propanol, washing was repeated with pure water at 80 ° C. Thereafter, the obtained polymer was dried under reduced pressure at 120 ° C. for 12 hours to finally obtain a SPAE block copolymer. IEC = 1.3 meq. / G, logarithmic viscosity was 1.90 dL / g.

  Although the solubility to 2-methoxyethanol, a formic acid, and diethylene glycol was examined as a solvent of the solvent group 2 with respect to the obtained SPAE polymer, it did not melt | dissolve. The solvent group 1 showed good solubility.

(Preparation of composite membrane)
An NMP / DMSO mixed solvent (30/70 weight ratio) was selected as a coating solvent, and was dissolved with stirring at 80 ° C. to obtain a uniformly clear 1.0 wt% concentration coating solution.

  A dip-coated bath equipped with a guide roller is filled with the above-mentioned SPAE coating solution, the PPE porous support membrane is passed through it, coating is performed while pulling up at a speed of 3 m / min, and then vertical forced convection It was dried at a temperature of 150 ° C. in a drying oven. The composite separation membrane obtained after sufficient drying was wound on a winder.

The obtained composite separation membrane was immersed in a 50% by mass aqueous ethanol solution for 30 minutes to perform a hydrophilization treatment, and then a performance evaluation test was performed. Under the conditions of a test pressure of 0.5 MPa and a sodium chloride concentration of 1500 mg / L, the water permeability was 72 L / m ² / day, and the salt removal rate was 92.0%.

  As a result of SEM observation, the thickness of the SPAE separation layer in the obtained composite separation membrane was about 300 nm. As a result of TEM observation, it was confirmed that a microphase separation structure was developed in the separation layer cross section. The SEM image of the cross section of the obtained composite separation membrane, the enlarged SEM image of the outer layer portion of the membrane cross section, and the enlarged SEM image of the membrane surface are respectively shown in FIGS. A TEM image of the microphase separation structure formed in the separation layer cross section is shown in FIG. 6 (a).

Example 2
(Preparation of porous support membrane)
The porous support membrane was the same as in Example 1.

(Preparation of SPAE block copolymer)
An SPAE block copolymer was obtained by the same method as Example 1, except that the raw material preparation amount at the time of polymerization was changed, and the molecular weight of the hydrophilic oligomer was 3,000 and the molecular weight of the hydrophobic oligomer was 3,000. . IEC = 2.0 meq. / G, logarithmic viscosity was 1.92 dL / g.

  The solubility of the obtained SPAE polymer was the same as in Example 1, and showed no solubility in the solvents of solvent group 2. On the other hand, the solubility in NMP / DMSO mixed solvent (weight ratio 30/70) was good, and this was used as a coating solvent.

(Preparation of composite membrane)
A composite separation membrane was produced in the same manner as in Example 1. A performance evaluation test was conducted. Under the conditions of a test pressure of 0.5 MPa and a sodium chloride concentration of 1500 mg / L, the water permeability was 620 L / m ² / day, and the salt removal rate was 54.0%.

  As a result of SEM observation, the thickness of the SPAE separation layer in the obtained composite separation membrane was about 250 nm. Moreover, as a result of TEM observation, it could be confirmed that the microphase separation structure was expressed in the separation layer.

Example 3
(Preparation of porous support membrane)
The porous support membrane was the same as in Example 1.

(Preparation of SPAE block copolymer)
An SPAE block copolymer was obtained by the same method as Example 1, except that the raw material preparation amount at the time of polymerization was changed, and the molecular weight of the hydrophilic oligomer was 15,000 and the molecular weight of the hydrophobic oligomer was 13,000. . IEC = 1.9 meq. / G, logarithmic viscosity was 2.03 dL / g.

  The solubility of the obtained SPAE polymer was the same as in Example 1, and showed no solubility in the solvents of solvent group 2. On the other hand, the solubility in NMP / DMSO mixed solvent (weight ratio 30/70) was good, and this was used as a coating solvent.

(Preparation of composite membrane)
A composite separation membrane was produced in the same manner as in Example 1. A performance evaluation test was conducted. Under the conditions of a test pressure of 0.5 MPa and a sodium chloride concentration of 1500 mg / L, the water permeability was 280 L / m ² / day, and the salt removal rate was 73.0%.

  As a result of SEM observation, the thickness of the SPAE separation layer in the obtained composite separation membrane was about 300 nm. Moreover, as a result of TEM observation, it could be confirmed that the microphase separation structure was expressed in the separation layer.

Example 4
(Preparation of porous support membrane)
As a polymer of the porous support membrane, a polyphenylene ether PX100L (hereinafter abbreviated as PPE) manufactured by Mitsubishi Engineering Plastics Co., Ltd. was prepared in the same manner as in Example 1. The mixture was dissolved at 130 ° C. while adding and kneading N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) so that PPE would be 18% by mass, and a uniform film-forming stock solution was obtained.

  Subsequently, on a glass substrate kept at 70 ° C., a polyester paper sheet (05 TH-60, manufactured by Ayase Paper Co., Ltd.) appropriately impregnated with 50% by mass glycerin aqueous solution is placed, and from above, the film forming solution at 70 ° C. is made uniform. Was coated with a hand coater. After drying treatment for about 10 seconds, it was immersed in a coagulation bath of 10% by mass NMP aqueous solution at 25 ° C. to obtain a flat porous support membrane. Thereafter, water washing treatment was performed. The thickness of the PPE porous support membrane excluding the polyester papermaking portion of the obtained membrane was 40 μm.

The water-washed PPE porous support membrane was impregnated with a 50% by mass aqueous glycerin solution, and then dried overnight at 50 ° C. to obtain a clogged membrane. The pure water permeation performance at 0.5 MPa was 12,000 L / m ² / day.

(Preparation of SPAE block copolymer)
A SPAE block copolymer was obtained in the same manner as in Example 1. The molecular weight of the hydrophilic oligomer was 10,300, and the molecular weight of the hydrophobic oligomer was 14,500. IEC = 1.3 meq. / G, logarithmic viscosity was 1.90 L / g.

(Preparation of composite membrane)
An NMP / DMSO mixed solvent (weight ratio 30/70) was selected as a coating solvent and dissolved while stirring at 80 ° C. to obtain a 1.0% by mass concentration coating solution. The complexing was performed by brushing on the surface of a flat membrane-like PPE porous support membrane of 30 cm square. After applying the coating solution, hot air drying was performed at 90 ° C. for 30 minutes.

The obtained composite separation membrane was subjected to a hydrophilization treatment by being immersed in a 50% by mass aqueous ethanol solution for 30 minutes, and then a performance evaluation test was performed. As with the other examples except that the flat membrane evaluation apparatus was used, when the evaluation conditions of test pressure 0.5 MPa and sodium chloride concentration 1500 mg / L were used, the water permeability was 100 L / m ² / day, salt The removal rate was 90.0%.

  As a result of SEM observation, the thickness of the SPAE separation layer in the obtained composite separation membrane was about 200 nm. Moreover, as a result of TEM observation, it could be confirmed that the microphase separation structure was expressed in the separation layer.

Example 5
(Preparation of porous support membrane)
The porous support membrane was the same as in Example 1.

(Preparation of SPAE block copolymer)
Using the same method as in Example 1, except that the DCBN monomer in the hydrophobic oligomers of Examples 1 to 4 was changed to 4,4′-dichlorodiphenyl sulfone (hereinafter abbreviated as DCDPS), the following chemical formula (XV) A hydrophobic oligomer represented by the formula (II) and a hydrophilic oligomer represented by the formula (II) were prepared. Among the chain extenders of formula (III) or (IV), DFB was used to prepare a block copolymer having these oligomers linked. The molecular weight of the hydrophilic oligomer was 11,000, and the molecular weight of the hydrophobic oligomer was 15,000. IEC = 1.2 meq. / G, logarithmic viscosity was 1.70 L / g.

  The solubility of the obtained SPAE polymer tended to be better in the solvent group 1 as compared with the polymers of Examples 1 to 4. On the other hand, the solubility of the solvent group 2 in the solvent was not good, and although there was a tendency to be partially dissolved in diethylene glycol etc., it became cloudy and could not obtain good solubility. DMSO solvent was used as a coating solvent.

(Preparation of composite membrane)
A composite separation membrane was produced in the same manner as in Example 1. A performance evaluation test was conducted. Under the conditions of a test pressure of 0.5 MPa and a sodium chloride concentration of 1500 mg / L, the water permeability was 86 L / m ² / day, and the salt removal rate was 90.0%.

  As a result of SEM observation, the thickness of the SPAE separation layer in the obtained composite separation membrane was about 300 nm. Moreover, as a result of TEM observation, it could be confirmed that the microphase separation structure was expressed in the separation layer.

Comparative Example 1
(Preparation of porous support membrane)
The porous support membrane was the same as in Example 1.

(Preparation of SPAE random copolymer)
A SPAE random copolymerization consisting of a hydrophobic segment represented by the following chemical formula (XVI) and a hydrophilic segment represented by the following chemical formula (XVII) was prepared as follows. 3,3'-disulfo-4,4'-dichlorodiphenyl sulfone disodium salt (S-DCDPS), 2,6-dichlorobenzonitrile (DCBN), 4,4'-biphenol (BP), potassium carbonate, and molecular The sieve was weighed into a four-necked flask and flushed with nitrogen. After adding NMP and stirring at 150 ° C. for 50 minutes, the reaction temperature was raised to 195 ° C. to 200 ° C., and the reaction was continued with the viscosity of the system sufficiently rising as a standard. Thereafter, the resultant was allowed to cool, allowed to cool, and then precipitated in water except for the settling molecular sieve. The obtained polymer was washed in boiling water for 1 hour, and then carefully washed with pure water to completely remove remaining potassium carbonate. Thereafter, the polymer after removing potassium carbonate was dried to obtain a target SPAE random copolymer. IEC = 1.00 meq. / G, logarithmic viscosity was 1.40 dL / g.

  The solubility of the obtained SPAE random copolymer tended to be better than the block copolymer of Example 1. The solvent of the solvent group 2 showed no solubility. DMSO was used as a coating solvent.

(Preparation of composite membrane)
A composite separation membrane was produced in the same manner as in Example 1. A performance evaluation test was conducted. Under the conditions of a test pressure of 0.5 MPa and a sodium chloride concentration of 1500 mg / L, the water permeability was 39 L / m ² / day, and the salt removal rate was 89.0%.

  As a result of SEM observation, the thickness of the SPAE separation layer in the obtained composite separation membrane was about 250 nm. Moreover, as a result of TEM observation, microphase separation did not occur in the separation layer. An example of TEM observation is shown in FIG.

Comparative Example 2
(Preparation of porous support membrane)
The porous support membrane was the same as in Example 1.

(Preparation of SPAE random copolymer)
In the same manner as in Comparative Example 1, SPAE random copolymerization was obtained by changing the monomer feed ratio. IEC = 1.48 meq. / G, logarithmic viscosity was 1.42 dL / g.

  The solubility of the obtained SPAE random copolymer tended to be better than the block copolymer of Example 1. The solvent of the solvent group 2 showed no solubility. DMSO was used as a coating solvent.

(Preparation of composite membrane)
A composite separation membrane was produced in the same manner as in Example 1. A performance evaluation test was conducted. Under the conditions of a test pressure of 0.5 MPa and a sodium chloride concentration of 1500 mg / L, the water permeability was 230 L / m ² / day, and the salt removal rate was 63.0%.

  As a result of SEM observation, the thickness of the SPAE separation layer in the obtained composite separation membrane was about 300 nm. Moreover, as a result of TEM observation, microphase separation did not occur in the separation layer.

Comparative Example 3
(Preparation of porous support membrane)
The porous support membrane was the same as in Example 1.

(Preparation of SPAE random copolymer)
A SPAE random copolymer was obtained by changing the monomer feed ratio in the same manner as in Comparative Example 1. IEC = 1.95 meq. / G, logarithmic viscosity was 1.32 dL / g.

  The solubility of the obtained SPAE random copolymer tended to be better than the block copolymer of Example 1. The solvent of the solvent group 2 showed no solubility. DMSO was used as a coating solvent.

(Preparation of composite membrane)
A composite separation membrane was produced in the same manner as in Example 1. A performance evaluation test was conducted. Under the conditions of a test pressure of 0.5 MPa and a sodium chloride concentration of 1500 mg / L, the water permeability was 500 L / m ² / day, and the salt removal rate was 51.0%.

  As a result of SEM observation, the thickness of the SPAE separation layer in the obtained composite separation membrane was about 300 nm. Moreover, as a result of TEM observation, microphase separation did not occur in the separation layer.

Comparative Example 4
(Preparation of porous support membrane)
The same flat membrane as in Example 4 was used as a support membrane.

(Preparation of SPAE random copolymer)
The same SPAE random copolymerization as in Comparative Example 1 was used. IEC = 1.00 meq. / G, logarithmic viscosity was 1.40 dL / g.

(Preparation of composite membrane)
A composite separation membrane was produced in the same manner as in Example 4. A performance evaluation test was conducted. Under the conditions of a test pressure of 0.5 MPa and a sodium chloride concentration of 1500 mg / L, the water permeability was 54 L / m ² / day, and the salt removal rate was 84.0%.

  As a result of SEM observation, the thickness of the SPAE separation layer in the obtained composite separation membrane was about 300 nm. Moreover, as a result of TEM observation, microphase separation did not occur in the separation layer.

Comparative Example 5
(Preparation of porous support membrane)
As a polymer of the porous support membrane, polyethersulfone 5200P (hereinafter abbreviated as PES) manufactured by Sumitomo Chemical Co., Ltd. was prepared. The PES was dissolved at 120 ° C. with 20% by mass of NMP added and kneaded to obtain a uniform film-forming solution.

  Subsequently, while maintaining the film-forming stock solution at a temperature of 60 ° C., while extruding into a hollow fiber membrane shape from a double cylindrical tube nozzle, a 70 mass% NMP aqueous solution as an inner liquid is simultaneously extruded and molded, After free running and evaporation treatment, the film was immersed in a 30 ° C. coagulation bath filled with a 30% by mass aqueous NMP solution to prepare a PES porous support membrane, followed by water washing treatment.

  The water-washed PES porous support membrane was impregnated with a 50% by mass aqueous glycerin solution, and then dried overnight at 50 ° C. to obtain a clogged membrane.

The outer diameter of the obtained PES porous support membrane was 250 μm, and the film thickness was 55 μm. When the pure water permeation test was performed, the pure water property was 9200 L / m ² / day at a test pressure of 0.5 MPa.

(Preparation of SPAE block copolymer)
The same SPAE block copolymer as in Example 1 was used. IEC = 1.30 meq. / G, logarithmic viscosity was 1.90 dL / g.

  An NMP / DMSO mixed solvent (weight ratio 30/70) was used as a coating solvent for the above-mentioned SPAE polymer.

(Preparation of composite membrane)
The composite separation membrane was prepared in the same manner as in Example 1. However, when the coating solution was applied to the PES support membrane and heated, the support membrane dissolved and thread breakage occurred, so that the composite separation membrane could not be obtained. .

Comparative Example 6
(Preparation of porous support membrane)
As a polymer of the porous support membrane, polyvinylidene fluoride kynar 301F (hereinafter abbreviated as PVDF) manufactured by Arkema Co., Ltd. was prepared. PVDF was made into 20 mass%, and NMP was added and it knead | mixed, it was made to melt | dissolve at 120 degreeC, and the uniform film forming undiluted | stock solution was obtained.

  Subsequently, while maintaining the film-forming solution at a temperature of 80 ° C., a 70% by mass aqueous solution of NMP as an inner liquid is simultaneously extruded and molded while being extruded from a double cylindrical tube nozzle into a hollow fiber membrane shape. After free running and evaporation treatment, it was immersed in a 30 ° C. coagulation bath filled with a 30% by mass aqueous NMP solution to prepare a PVDF porous support membrane, followed by water washing treatment.

  The water-washed PVDF porous support membrane was impregnated with a 50% by mass aqueous glycerin solution, and then dried overnight at 50 ° C. to obtain a clogged membrane.

The outer diameter of the obtained PVDF porous support membrane was 260 μm, and the film thickness was 50 μm. When the pure water permeation test was conducted, the pure water property was 5000 L / m ² / day at a test pressure of 0.5 MPa.

(Preparation of SPAE block copolymer)
The same SPAE block copolymer as in Example 1 was used. IEC = 1.30 meq. / G, logarithmic viscosity was 1.90 dL / g.

  An NMP / DMSO mixed solvent (weight ratio 30/70) was used as a coating solvent for the above-mentioned SPAE polymer.

(Preparation of composite membrane)
The composite separation membrane was prepared in the same manner as in Example 1. However, when the coating solution was applied to the PVDF support membrane and heated, the composite membrane significantly swelled to cause thread breakage, similarly to the PES support membrane of Comparative Example 4. A separation membrane could not be obtained.

<Evaluation method of SPAE block copolymer>
For SPAE block copolymers, molecular weight evaluation of oligomers, evaluation of end modification with chain extender, ion exchange capacity (IEC) and logarithmic viscosity were evaluated as follows.

(Logarithmic viscosity)
The sufficiently vacuum-dried polymer powder is dissolved in N-methyl-2-pyrrolidone at a concentration of 0.5 g / dL, viscosity is measured using a Ubbelohde viscometer in a thermostat at 30 ° C., and logarithmic viscosity (ln Evaluation was made using ta / tb]) / c (where ta represents the number of seconds of drop of the sample solution, tb represents the number of seconds of drop of the solvent alone, and c represents the polymer concentration).

(Ion exchange capacity, IEC)
100 mg of the sufficiently dried micronized polymer was allowed to stir overnight in 300 mL of 2 M aqueous sulfuric acid to replace the counter ion of the sulfonic acid group with a proton. Thereafter, 100 mg of the polymer obtained by sufficient washing with water and vacuum drying was immersed in 50 ml of 0.01 N aqueous NaOH solution and stirred overnight at 25 ° C. Thereafter, neutralization titration was performed with a 0.05 N aqueous HCl solution. A potentiometric titrator COMTITE-980 manufactured by Hiranuma Sangyo Co., Ltd. was used for neutralization titration. The ion exchange equivalent was calculated by the following equation.
Ion exchange capacity [meq / g] = (10-titrated quantity [ml]) / 2

(1H-NMR measurement)
The polymer (counter ion of sulfonic acid group is Na or K salt) was dissolved in a solvent, and 1 H-NMR was performed at room temperature using UNITY-500 manufactured by VARIAN. As a solvent, a mixed solvent of N-methyl-2-pyrrolidone and heavy dimethyl sulfoxide (volume ratio 80 to 20) was used. The molecular weight of the hydrophilic oligomer and the hydrophobic oligomer was obtained by calculating the number average molecular weight from the integral ratio of the peak derived from the end group and the peak of the backbone portion. For example, in the hydrophobic oligomer of Example 1 above, the peak of the proton at the ortho position of the ether bond in the biphenyl structure is detected at 6.8 to 6.9 ppm from the end group and in the skeleton is 7. Since it was detected at 3 ppm, the number average molecular weight was determined from the integral ratio of these peaks. The fact that both ends of the hydrophobic oligomer molecule were modified with DFB was confirmed from the fact that the peaks derived from the end groups of the unmodified hydrophobic oligomer completely disappeared. On the other hand, in the hydrophilic oligomer of Example 1, the peak of the proton at the ortho position of the ether bond in the biphenyl structure is 6.8 ppm in the skeleton derived from the end group (the ortho position of the phenolic hydroxyl group) Since the meta position is detected at 7.7 ppm, respectively, the number average molecular weight was determined from the integral ratio of these peaks.

<Evaluation method of composite separation membrane>
With respect to the composite separation membranes of Examples 1 to 5 and Comparative Examples 1 to 4 prepared as described above, the evaluation of the membrane shape, the thickness evaluation of the separation layer, the separation performance and the permeation performance are performed by the following method. The

(Shape of porous support membrane)
Shape evaluation of the porous support membrane sample (hollow fiber) of Examples 1-3, 5 and Comparative Examples 1-3, 5 was performed by the following method. An appropriate amount of hollow fiber bundle is packed in a hole of a 2 mm thick SUS plate with a hole of 3 mm diameter, cut with a razor blade to expose a cross section, and then Nikon microscope (ECLIPSE LV100) and Nikon image processing Using a device (DIGITAL SIGHT DS-U2) and a CCD camera (DS-Ri1), capture the shape of the cross section, and use the image analysis software (NIS Element D3.00 SP6) to measure the outer diameter and the inner diameter of the hollow fiber cross section. The outer diameter, the inner diameter and the thickness of the hollow fiber membrane were calculated by measurement using the measurement function of the analysis software. The shape evaluation of the porous support membrane sample (flat membrane) of Example 4 and Comparative Example 4 was carried out by freezing the water-containing sample with liquid nitrogen, cleaving it, and air-drying it to sputter Pt on its fractured surface. Using a scanning electron microscope S-4500 manufactured by Hitachi, Ltd., observation was performed at an acceleration voltage of 5 kV, and the thickness of the porous support film was measured excluding the polyester non-woven fabric portion.

(Thickness of separation layer of composite separation membrane sample)
After subjecting the composite separation membranes of Examples 1 to 5 and Comparative Examples 1 to 4 to a hydrophilization treatment with a 50% by mass ethanol aqueous solution, those immersed in water are frozen with liquid nitrogen, cut, and air dried. Pt was sputtered onto the substrate, and observation was performed at an acceleration voltage of 5 kV using a scanning electron microscope S-4500 manufactured by Hitachi, Ltd. (SEM observation).

(Observation of micro phase separation structure in separated layer)
The composite separation membranes of Examples 1 to 5 and Comparative Examples 1 to 4 were electrostained in a liquid phase containing a metal salt, and then embedded in an epoxy resin. The embedded samples were made into ultra-thin sections using an ultramicrotome and subjected to carbon deposition. For TEM observation, a JEM-2100 transmission electron microscope manufactured by Nippon Denshi Co., Ltd. was used, and the observation conditions were: acceleration voltage: 200 kV, direct magnification: 20,000 times.

(Separation performance and permeation performance of composite separation membrane)
After bundling the hollow fiber membranes of Examples 1 to 3 and 5 and Comparative Examples 1 to 3 and inserting them into a plastic sleeve, a thermosetting resin was injected into the sleeve, cured and sealed. The open end of the hollow fiber membrane was obtained by cutting the end of the hollow fiber membrane cured with a thermosetting resin, and a module for evaluation was produced. This evaluation module was connected to a hollow fiber membrane performance test device consisting of a feed water tank and a pump, and the performance was evaluated. The flat membranes of Example 4 and Comparative Example 4 were installed in the flat membrane performance evaluation device having the constitution of the feed water tank and the pump in the same manner as described above, and the performance was evaluated. As the evaluation conditions, a feed aqueous solution having a sodium chloride concentration of 1500 mg / L is operated at 25 ° C. and a pressure of 0.5 MPa for about 30 to 1 hour, and then the permeated water from the membrane is collected and an electronic balance (Shimadzu LIBROR EB The permeated water weight was measured at -3200D). The permeated water weight was converted to a permeated water amount of 25 ° C. according to the following equation.
Permeate flow rate (L) = Permeate water weight (kg) / 0.99704 (kg / L)
Permeability (FR) was calculated from the following equation.
FR [L / m ² / day] = amount of permeated water [L] / membrane area [m ² ] / collection time [minutes] × (60 [minutes] × 24 [hours])

The sodium chloride concentration was measured using an electric conductivity meter (CM-25R manufactured by Toa DK Co., Ltd.) and the sodium chloride concentration 1500 mg / L supplied aqueous solution similarly used in the measurement of water permeability and the permeated water collected by the water permeability measurement. .
The salt removal rate was calculated by the following equation.
Salt removal rate [%] = (1− permeating water salt concentration [mg / L] / supply aqueous solution salt concentration [mg / L]) × 100

  The composite separation membrane of the present invention is extremely useful for nanofiltration treatment and reverse osmosis treatment because it can maintain salt removal property and water permeability at a high level for a long time while using a material having excellent chemical resistance.

1 Separated layer 2 made of SPAE block copolymer 2 Porous support film made of PPE 3 Non-woven fabric 4 Microphase separated structure in separated layer

Claims (5)

A composite separation membrane having a separation layer with a thickness of 5 nm or more and 1 μm or less on the surface of a porous support membrane, wherein the porous support membrane is composed of polyphenylene ether, and the separation layer has a number average molecular weight of 1,000 or more. A composite separation membrane comprising a multiblock copolymer of a sulfonated polyarylene ether composed of an oligomer component, a hydrophilic oligomer component having a number average molecular weight of 1000 or more, and a chain extender component that combines the two oligomer components. And the copolymer is a hydrophobic oligomer component which is a repeating structure of a hydrophobic segment represented by the following chemical formula (I) or (XV), and a repeating structure of a hydrophilic segment represented by a chemical formula (II) in a hydrophilic oligomer component, it is coupled by a chain extender component, of formula (III) the capital, the copolymer , Nanofiltration or for composite separator for infiltration, which comprises dissolving in the solvent group 1.
Solvent group 1: N-methyl-2-pyrrolidone, N, N-dimethylacetamide, dimethylsulfoxide, N, N-dimethylformamide, γ-butyrolactone




However, two or more chain extender components are not connected in succession,
m and n each represent a natural number of 1 or more, R ¹ and R ² each represent -SO ₃ M or -SO ₃ H, M represents a metal element, and is an index of sulfonic acid group content in the polymer An ion exchange capacity IEC is in the range of 0.3 to 4.0 meq./g The multiblock copolymer of the sulfonated polyarylene ether is a polymer obtained by combining a hydrophilic oligomer having a sulfonic acid group with a hydrophobic oligomer having no sulfonic acid group by a chain extender. The composite separation membrane according to Item 1. The composite separation membrane according to claim 1 or 2 , wherein the content of polyphenylene ether in the porous support membrane is 80% by mass or more. A sulfonated polyarylene ether in an aprotic polar solvent containing at least one selected from dimethyl sulfoxide, N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, and γ-butyrolactone of the coating solution obtained by dissolving the multiblock copolymer was applied to the surface of the formed porous support membrane polyphenylene ether according to claim 1 to 3, characterized in that the drying process the coating surface The manufacturing method of the composite separation membrane in any one. The composite separation membrane according to claim 4, wherein the coating solution is applied after the porous support membrane is impregnated with one or more selected from the group consisting of alcohol, alkylene diol or triol, alkylene glycol alkyl ether, and water. Manufacturing method.