JP6155665B2 - Composite semipermeable membrane - Google Patents

Description

  The present invention relates to a composite semipermeable membrane useful for selective separation of a liquid mixture and a method for producing the same. The composite semipermeable membrane obtained by the present invention can be suitably used for desalination of seawater and brine, for example.

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

  The majority of currently marketed reverse osmosis membranes and nanofiltration membranes are composite semipermeable membranes, which have an active layer in which a gel layer and a polymer are cross-linked on a microporous support membrane, and on a microporous support membrane. And having an active layer in which monomers are polycondensed. Among them, the composite semipermeable membrane obtained by coating a separation function layer made of a crosslinked polyamide obtained by polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide on a microporous support membrane is permeable and selective. It is widely used as a separation membrane with high separability (Patent Documents 1 and 2).

  When performing separation using a reverse osmosis membrane, the membrane is required to have mechanical strength. For example, a method of flushing a reverse osmosis membrane with a high-pressure water flow when impurities contained in water are deposited on the surface of the reverse osmosis membrane, thereby causing clogging of the reverse osmosis membrane or reducing the production efficiency of pure water May be taken. At this time, if the strength of the reverse osmosis membrane is weak, the membrane peels off and is damaged, and a satisfactory salt removal rate cannot be obtained. The microporous support membrane is generally composed of a base material and a porous support layer, but peeling is likely to occur near the interface between the base material and the porous support layer.

  Patent Document 3 discloses that by using a composite fiber material as a base material, durability in the presence of a chemical is improved and peeling is prevented.

  Patent Document 4 discloses improving the ease of tearing by fusing a substrate and a porous support layer.

Japanese Patent Laid-Open No. 55-14706 Japanese Patent Laid-Open No. 5-76740 JP 2001-17842 A JP 2011-101837 A

  Despite the various proposals described above, improvement in mechanical strength and water permeability in a reverse osmosis membrane are not fully compatible. An object of the present invention is to provide a composite semipermeable membrane having both high peel resistance and water permeability.

To achieve the above object, the present invention has the following configuration.
(1) A composite semipermeable membrane comprising a substrate and a microporous support membrane comprising a porous support layer provided on the substrate, and a separation functional layer provided on the porous support layer,
The porous support layer has a first layer formed on a base material, a second layer formed on the first layer, and a third layer formed on the second layer. When the porous support layer is peeled off from the substrate at a peeling direction of 180 ° with a gripping speed of 10 mm / min using a Tensilon tensile tester at a temperature of 25 ° C. under a temperature condition of 25 ° C. A composite semipermeable membrane having a peel strength of 1.0 N / 25 mm or more, which is an average value of values obtained by measuring the maximum value of the peel force 10 times.
(2) The composite semipermeable membrane according to (1), wherein an interface between the first layer and the second layer and an interface between the second layer and the third layer are continuous structures.
(3) The porous support layer applies the polymer solution A that forms the first layer on the substrate, and simultaneously the polymer solution B that forms the second layer and the polymer solution that further forms the third layer. The composite semipermeable membrane according to the above (2), which is formed by applying C and then contacting a coagulation bath to cause phase separation.
(4) The composite semipermeable membrane according to (3), wherein the polymer solution A and the polymer solution B have different compositions, and the polymer solution C and the polymer solution B have different compositions.
(5) The solid content concentration b (wt%) of the polymer solution B is lower than the solid content concentration a (wt%) of the polymer solution A and the solid content concentration c (wt%) of the polymer solution C. The composite semipermeable membrane according to (4), which has a concentration.
(6) The solid content concentration a (wt%) of the polymer solution A, the solid content concentration b (wt%) of the polymer solution B, and the solid content concentration c (wt%) of the polymer solution C are: The composite semipermeable membrane according to the above (4) or (5), which satisfies the relational expression of a ≧ c> b.
(7) The composite semipermeable membrane according to any one of (1) to (6), wherein the base material is a long-fiber nonwoven fabric containing polyester.
(8) The amount of water produced after passing an aqueous solution having a NaCl concentration of 3.5% by weight, a temperature of 25 ° C. and a pH of 6.5 at a pressure of 5.5 MPa for 24 hours is 1.6 m ³ / m ² / The composite semipermeable membrane according to any one of (1) to (7), wherein the desalting rate is 99.85% or more for at least a day.

  According to the present invention, it is possible to achieve both high peel resistance and water permeability in the composite semipermeable membrane.

1. Composite Semipermeable Membrane The composite semipermeable membrane includes a microporous support membrane including a base material and a porous support layer, and a separation functional layer provided on the porous support layer. The composite semipermeable membrane of the present invention is characterized in that the peel strength between the substrate and the porous support layer is 1.0 N / 25 mm or more. Here, the peel strength is a peel force when the porous support layer is peeled from the substrate at a peel direction of 180 ° using a Tensilon tensile tester at a holding speed of 10 mm / min under a temperature condition of 25 ° C. It is the average value of the values obtained by measuring the maximum value of 10 times.

(1-1) Microporous support membrane In the present invention, the microporous support membrane comprises a base material and a porous support layer, has substantially no separation performance of ions or the like, and has substantially no separation performance. It is a membrane for giving strength to the separation functional layer.

For the material of the porous support layer, polysulfone, polyethersulfone, polyamide, polyester, cellulosic polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, polyphenylene oxide, and the like homopolymers or copolymers alone or blended. Can be used. Here, cellulose acetate and cellulose nitrate can be used as the cellulose polymer, and polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile and the like can be used as the vinyl polymer. Among them, homopolymers or copolymers such as polysulfone, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, and polyphenylene sulfide sulfone are preferable. More preferred is cellulose acetate, polysulfone, polyphenylene sulfide sulfone, or polyphenylene sulfone. Among these materials, polysulfone is highly stable chemically, mechanically and thermally, and is easy to mold. Can be used generally.
Specifically, it is preferable to use a polysulfone containing a repeating unit represented by the following chemical formula because the pore diameter can be easily controlled and the dimensional stability is high.

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

  The thickness of the microporous support membrane described above affects the strength of the composite semipermeable membrane and the packing density when it is used as a membrane element. In order to obtain sufficient mechanical strength and packing density, the thickness of the microporous support membrane is preferably in the range of 30 to 300 μm, more preferably in the range of 50 to 250 μm. Moreover, it is preferable that the thickness of a porous support layer exists in the range of 10-200 micrometers, More preferably, it exists in the range of 20-100 micrometers. The thickness of the substrate is preferably in the range of 10 to 250 μm, more preferably in the range of 20 to 200 μm.

  In this document, unless otherwise specified, the thickness of each layer and film means an average value. Here, the average value represents an arithmetic average value. That is, the thickness of each layer and film is determined by calculating the average value of the thicknesses of 20 points measured at intervals of 20 μm in the direction orthogonal to the thickness direction (film surface direction) by cross-sectional observation.

  In the present invention, the porous support layer has a multilayer structure. The porous support layer having a porous structure is composed of three layers: a first layer that comes into contact with the substrate, a second layer that holds and transports an aqueous monomer solution such as amine, and a third layer that comes into contact with the separation functional layer. The first layer is in close contact with the substrate to achieve high peel strength. The second layer plays a role of holding a monomer such as an amine necessary for forming the separation functional layer and transferring it to a polymerization field. The third layer serves as a field for interfacial polymerization, and holds and releases the monomer, thereby supplying the monomer to the formed separation functional layer and also serving as a starting point for the fold growth of the separation functional layer.

  The peel strength between the substrate and the porous support layer can be optimally controlled by the microphase separation structure of the support layer, the volume fraction occupied by the polymer, the strength of the polymer material, and the like. However, a strong support layer does not always function as an optimal interfacial polymerization field.

For example, a porous support layer having a high volume fraction occupied by a polymer has a high peel strength, but is not suitable as a polymerization field because a space capable of holding an aqueous monomer solution is small.
In addition, the porous support layer with a low volume fraction of the polymer increases the space in which the monomer aqueous solution can be held, but the membrane is easily peeled off, and pressure application and water flow (temperature 25 ° C., seawater at pH 6.5, operation) When the pressure is 5.5 MPa and the filtration process is performed for 24 hours, the membrane is compressed and the permeation flow rate is lowered.

  Therefore, the first layer responsible for the peel strength, the second layer that plays a role in transferring monomers such as amines necessary for the formation of the separation functional layer to the polymerization field, and a place for interfacial polymerization, and holding and releasing the monomer Thus, the third layer supplying the monomer to the separation functional layer to be formed should be functionally separated.

  The 1st layer of the porous support layer in this invention plays the role which adhere | attaches a base material and a porous support layer, and supports a porous support layer. The peel strength between the substrate and the porous support layer can be optimally controlled by the volume fraction of the polymer. The second layer plays a role of transferring an aqueous polyfunctional amine solution necessary for forming the separation functional layer to the polymerization field. In order to efficiently transfer the monomer, it is preferable to have continuous pores, and the pore diameter is preferably 0.1 μm or more and 1 μm or less. The third layer serves as a polymerization field and serves to supply and supply the monomer to the formed separation functional layer by holding and releasing the monomer, and also serves as a starting point for the fold growth of the separation functional layer. The separation functional layer formed by interfacial polymerization has a pleated structure in which convex portions and concave portions are continuously repeated, and the separation performance of the composite semipermeable membrane varies depending on the structure such as the shape and height of the folds. Therefore, the separation performance can be improved by controlling the third layer that is the starting point of pleat growth. By adjusting the third layer monomer retention capacity, release rate and feed rate, and third layer structure, the height of the pleated recesses, the distance between adjacent recesses in contact with the porous support layer surface In addition, the width of the cavity inside the convex portion can be controlled.

  As a result of intensive studies by the present inventors, the first layer has a dense structure, the second layer has a sparse structure, and the third layer has a dense structure and a uniform surface. It has been found that the shape of the folds of the separation functional layer is high in strength and is a long and narrow columnar shape that is preferable for separation performance. In order to make the first layer a dense structure, for example, there is a method of increasing the concentration of the undiluted polymer solution. In order to make the second layer sparse, for example, there is a method of reducing the concentration of the undiluted polymer solution. In order to make the third layer have a dense structure and a uniform surface, for example, there is a method of increasing the concentration of the stock polymer solution.

  Further, in the porous support layer of the present invention, the interface between the first layer and the second layer formed on the first layer and the interface between the third layer formed on the second layer have a continuous structure. Is preferred. The “continuous structure” in the present invention refers to a structure in which no skin layer is formed at the interface. The skin layer here means a portion having a high density. Specifically, the surface pores of the skin layer are in the range of 1 nm to 50 nm. When a skin layer is formed at the interface between the first layer, the second layer, and the third layer, a high resistance is generated in the porous support layer, and as a result, the permeation flow rate is dramatically reduced.

  The substrate constituting the microporous support membrane is preferably porous. For example, a polymer such as a polyester polymer, a polyamide polymer, a polyolefin polymer, or a mixture or copolymer thereof can be used. The cloth used as the material can be mentioned. Polyester polymers are preferred because a microporous support membrane having better mechanical strength, heat resistance, water resistance, and the like can be obtained.

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

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

  As the fabric used for the substrate, it is preferable to use a fibrous substrate in terms of strength, unevenness forming ability, and fluid permeability. As the fibrous base material, either a long fiber nonwoven fabric or a short fiber nonwoven fabric can be preferably used. In particular, long-fiber non-woven fabrics have excellent permeability when casting a polymer solution on the base material, and the porous support layer is peeled off. Uniformity and occurrence of defects such as pinholes can be suppressed. In addition, since the base material is made of a long-fiber non-woven fabric composed of thermoplastic continuous filaments, it suppresses non-uniformity and membrane defects during casting of a polymer solution caused by fuzz that occurs when a short-fiber non-woven fabric is used. be able to. Moreover, in continuous film formation of a composite semipermeable membrane, since the tension | tensile_strength is applied with respect to the film forming direction, it is preferable to use the long-fiber nonwoven fabric which is more excellent in dimensional stability for a base material.

  In the long-fiber nonwoven fabric, the fibers in the surface layer on the side opposite to the porous support layer side are preferably longitudinally oriented compared to the fibers on the surface layer on the porous support layer side in terms of moldability and strength. According to such a structure, not only a high effect of preventing film breakage by maintaining strength is realized, but also a lamination including a porous support layer and a substrate when imparting irregularities to the separation functional layer Formability as a body is also improved, and the uneven shape on the surface of the separation functional layer is stabilized, which is preferable. More specifically, the fiber orientation degree in the surface layer opposite to the porous support layer side of the long-fiber nonwoven fabric is preferably 0 ° to 25 °, and the fiber orientation in the porous support layer side surface layer It is preferable that the orientation degree difference with the degree is 10 ° to 90 °.

  The separation membrane manufacturing process and the element manufacturing process include a heating process, but a phenomenon occurs in which the porous support layer or the separation functional layer contracts due to the heating. This is particularly noticeable in the width direction where no tension is applied in continuous film formation. Since shrinkage causes problems in dimensional stability and the like, a substrate having a small rate of thermal dimensional change is desired. In the nonwoven fabric, when the difference between the fiber orientation degree on the surface layer opposite to the porous support layer and the fiber orientation degree on the porous support layer side surface layer is 10 ° to 90 °, the change in the width direction due to heat is suppressed. Can also be preferred.

  Here, the fiber orientation degree is an index indicating the fiber direction of the nonwoven fabric base material, and the direction of film formation during continuous film formation is 0 °, and the direction perpendicular to the film formation direction, that is, the width of the nonwoven fabric base material. It means the average angle of the fibers constituting the nonwoven fabric substrate when the direction is 90 °. Accordingly, the closer to 0 ° the fiber orientation, the longer the orientation, and the closer to 90 °, the lateral orientation.

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

(1-2) Separation Functional Layer The separation functional layer is a layer that bears a solute separation function in the composite semipermeable membrane. The composition such as the composition and thickness of the separation functional layer is set in accordance with the intended use of the composite semipermeable membrane.

(Separation functional layer made of polyamide)
For example, the separation functional layer may contain polyamide as a main component. The polyamide constituting the separation functional layer can be formed by interfacial polycondensation of a polyfunctional amine and a polyfunctional acid halide. Here, it is preferable that at least one of the polyfunctional amine or the polyfunctional acid halide contains a trifunctional or higher functional compound.

  In this document, “X contains Y as a main component” means that Y occupies 60% by weight, 80% by weight, or 90% by weight of X, and X is substantially The structure containing only Y is included.

  The thickness of the polyamide separation functional layer is usually preferably in the range of 0.01 to 1 μm and more preferably in the range of 0.1 to 0.5 μm in order to obtain sufficient separation performance and permeated water amount.

  Here, the polyfunctional amine has at least two of primary amino groups and secondary amino groups in one molecule, and at least one of the amino groups is a primary amino group. Say an amine. For example, phenylenediamine, xylylenediamine, 1,3,5-triaminobenzene, 1,2,4 in which two amino groups are bonded to the benzene ring in any of the ortho, meta, and para positions. Aromatic polyfunctional amines such as triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine and 4-aminobenzylamine, aliphatic amines such as ethylenediamine and propylenediamine, 1,2-diaminocyclohexane, 1 , 4-diaminocyclohexane, 4-aminopiperidine, 4-aminoethylpiperazine, and other alicyclic polyfunctional amines. Among them, in view of selective separation, permeability, and heat resistance of the membrane, it should be an aromatic polyfunctional amine having 2 to 4 of primary amino groups and secondary amino groups in one molecule. Is preferred. As such a polyfunctional aromatic amine, m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene are preferably used. Among these, it is more preferable to use m-phenylenediamine (hereinafter referred to as m-PDA) from the standpoint of availability and ease of handling. These polyfunctional amines may be used alone or in combination of two or more. When using 2 or more types together, the said amines may be combined and the said amine and the amine which has at least 2 secondary amino group in 1 molecule may be combined. Examples of the amine having at least two secondary amino groups in one molecule include piperazine and 1,3-bispiperidylpropane.

  The polyfunctional acid halide refers to an acid halide having at least two carbonyl halide groups in one molecule. For example, examples of the trifunctional acid halide include trimesic acid chloride, 1,3,5-cyclohexane tricarboxylic acid trichloride, 1,2,4-cyclobutane tricarboxylic acid trichloride, and the like. Aromatic difunctional acid halides such as biphenyl dicarboxylic acid dichloride, azobenzene dicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalenedicarboxylic acid chloride, aliphatic bifunctional acid halides such as adipoyl chloride, sebacoyl chloride, Mention may be made of alicyclic bifunctional acid halides such as cyclopentanedicarboxylic acid dichloride, cyclohexanedicarboxylic acid dichloride, and tetrahydrofurandicarboxylic acid dichloride. In consideration of the reactivity with the polyfunctional amine, the polyfunctional acid halide is preferably a polyfunctional acid chloride. In view of selective separation of the membrane and heat resistance, the polyfunctional acid chloride is more preferably a polyfunctional aromatic acid chloride having 2 to 4 carbonyl chloride groups in one molecule. Among these, it is more preferable to use trimesic acid chloride from the viewpoint of easy availability and easy handling. These polyfunctional acid halides may be used alone or in combination of two or more.

(Organic-inorganic hybrid separation functional layer)
The separation functional layer may have an organic-inorganic hybrid structure containing Si element or the like. Such a separation functional layer is also referred to as an organic-inorganic hybrid membrane. The organic-inorganic hybrid film is excellent in terms of moldability and chemical resistance. The composition of the separation functional layer having an organic-inorganic hybrid structure is not particularly limited. For example, the separation functional layer has (A) a reactive group having an ethylenically unsaturated group and a hydrolyzable group directly bonded to a silicon atom. A silicon compound and (B) a compound other than the compound (A) and having an ethylenically unsaturated group can be contained. Specifically, the separation functional layer may contain a condensate of the hydrolyzable group of the compound (A) and a polymer of the ethylenically unsaturated group of the compounds (A) and / or (B). That is, the separation functional layer is
-The polymer of only a compound (A)-The polymer of only a compound (B) and-The copolymer of a compound (A) and a compound (B) can be contained at least 1 sort (s). The polymer includes a condensate. In the copolymer of the compound (A) and the compound (B), the compound (A) may be condensed via a hydrolyzable group.

  In the separation functional layer, the content of the compound (A) is preferably 10% by weight or more, more preferably 20% by weight to 50% by weight. Moreover, the content rate of the compound (B) in a separation function layer becomes like this. Preferably it is 90 weight% or less, More preferably, it is 50 weight%-80 weight%. The weight ratio of compound (A): compound (B) may be 1: 9 to 1: 1. Within these ranges, a relatively high degree of crosslinking is obtained in the condensation polymer contained in the separation functional layer, so that elution of components from the separation functional layer is suppressed during membrane filtration, resulting in stable filtration performance. Is done.

  In addition, a compound (A), a compound (B), and another compound may form compounds, such as a polymer (a condensate is included). Therefore, for example, when discussing the “content ratio of the compound (A) in the separation functional layer”, the compound (A) includes the amount of the component derived from the compound (A) in the polycondensation product. The same applies to the compound (B) and other compounds.

  In addition to the compound (A), the separation functional layer may contain a silicon compound (C) having no hydrolyzable group but not having a reactive group having an ethylenically unsaturated group. Examples of such a compound (C) will be described later. The compound (C) may be included as a condensate of only the compound (C), or may be included as a condensate of the polymer of the compound (A) and the compound (B).

First, the compound (A) will be described.
In the compound (A), the reactive group having an ethylenically unsaturated group is directly bonded to the silicon atom. Examples of such reactive groups include vinyl groups, allyl groups, methacryloxyethyl groups, methacryloxypropyl groups, acryloxyethyl groups, acryloxypropyl groups, and styryl groups. From the viewpoint of polymerizability, a methacryloxypropyl group, an acryloxypropyl group, and a styryl group are preferable.

  The condensate of the compound (A) is obtained by bonding the compounds (A) to each other by a siloxane bond through a process in which the hydrolyzable group directly bonded to the silicon atom in the compound (A) is changed to a hydroxyl group. It may be formed.

  Examples of the hydrolyzable group in the compound (A) include functional groups such as alkoxy group, alkenyloxy group, carboxy group, ketoxime group, aminohydroxy group, halogen atom and isocyanate group. As an alkoxy group, a C1-C10 thing is preferable, More preferably, it is a C1-C2 thing. The alkenyloxy group preferably has 2 to 10 carbon atoms, more preferably 2 to 4 carbon atoms, and particularly preferably 3 carbon atoms. The carboxy group is preferably one having 2 to 10 carbon atoms, more preferably one having 2 carbon atoms, that is, an acetoxy group. Examples of the ketoxime group include a methyl ethyl ketoxime group, a dimethyl ketoxime group, and a diethyl ketoxime group. An aminohydroxy group is one in which an amino group is bonded to a silicon atom via an oxygen atom. Examples of such include dimethylaminohydroxy group, diethylaminohydroxy group, and methylethylaminohydroxy group. As the halogen atom, a chlorine atom is preferably used.

  In forming the separation functional layer, a silicon compound in which a part of the hydrolyzable group is hydrolyzed and has a silanol structure can be used. In addition, two or more silicon compounds having a high molecular weight such that a part of the hydrolyzable group is not hydrolyzed, condensed, or crosslinked can be used.

The silicon compound (A) is preferably represented by the following general formula (a).
Si (R1) _m (R2) _n (R3) _4-mn (a)
(R1 represents a reactive group containing an ethylenically unsaturated group. R2 represents an alkoxy group, an alkenyloxy group, a carboxy group, a ketoxime group, a halogen atom or an isocyanate group. R3 represents H or an alkyl group. M and n are integers satisfying m ≧ 1, n ≧ 1, and m + n ≦ 4 When two or more functional groups are bonded to a silicon atom in each of R1, R2, and R3, they may be the same or different. May be.)

R1 is a reactive group containing an ethylenically unsaturated group, as described above.
R2 is a hydrolyzable group, and these are as described above. The alkyl group applicable to R3 preferably has 1 to 10 carbon atoms, more preferably 1 to 2 carbon atoms.
As the hydrolyzable group, an alkoxy group is preferable. It is because the reaction liquid prepared in the formation of the separation functional layer has high viscosity because the hydrolyzable group is an alkoxy group.
Examples of the silicon compound (A) include vinyltrimethoxysilane, vinyltriethoxysilane, styryltrimethoxysilane, methacryloxypropylmethyldimethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, and methacryloxy. Examples are propyltriethoxysilane and acryloxypropyltrimethoxysilane.

  In addition to the compound (A), as described above, a silicon compound (C) having no hydrolyzable group, which does not have a reactive group having an ethylenically unsaturated group, can also be used. As such a compound (C), the compound whose m is zero in General formula (a) is illustrated. Examples of such compounds include tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, and methyltriethoxysilane.

Next, the compound (B) will be described. The compound (B) is a compound having an ethylenically unsaturated group other than the compound (A).
The ethylenically unsaturated group has addition polymerizability. Examples of the compound (B) having such a group include ethylene, propylene, methacrylic acid, acrylic acid, styrene, and derivatives thereof.
In addition, this compound (B) is an alkali-soluble compound having an acid group in order to increase the selective permeability of water and increase the salt rejection when a composite semipermeable membrane is used for separation of an aqueous solution. Preferably there is.

  Preferred acid groups include carboxylic acid groups, phosphonic acid groups, phosphoric acid groups, and sulfonic acid groups, and the structure of these acid groups is any of acid forms, ester compounds, and metal salts. May be present. These compounds having one or more ethylenically unsaturated groups can contain two or more acid groups, and among them, compounds containing 1 to 2 acid groups are preferred.

  Examples of the compound having a carboxylic acid group among the compounds having one or more ethylenically unsaturated groups include the following. Maleic acid, maleic anhydride, acrylic acid, methacrylic acid, 2- (hydroxymethyl) acrylic acid, 4- (meth) acryloyloxyethyl trimellitic acid and the corresponding anhydride, 10-methacryloyloxydecylmalonic acid, N- ( 2-hydroxy-3-methacryloyloxypropyl) -N-phenylglycine and 4-vinylbenzoic acid.

  Among the compounds having at least one ethylenically unsaturated group, compounds having a phosphonic acid group include vinylphosphonic acid, 4-vinylphenylphosphonic acid, 4-vinylbenzylphosphonic acid, 2-methacryloyloxyethylphosphonic acid. 2-methacrylamidoethylphosphonic acid, 4-methacrylamido-4-methyl-phenyl-phosphonic acid, 2- [4- (dihydroxyphosphoryl) -2-oxa-butyl] -acrylic acid and 2- [2-dihydroxyphosphoryl] ) -Ethoxymethyl] -acrylic acid-2,4,6-trimethyl-phenyl ester.

  Among the compounds having one or more ethylenically unsaturated groups, the phosphate ester compounds include 2-methacryloyloxypropyl monohydrogen phosphate, 2-methacryloyloxypropyl dihydrogen phosphate, and 2-methacryloyloxyethyl monoester. Hydrogen phosphate and 2-methacryloyloxyethyl dihydrogen phosphate, 2-methacryloyloxyethyl-phenyl-hydrogen phosphate, dipentaerythritol-pentamethacryloyloxyphosphate, 10-methacryloyloxydecyl-dihydrogen phosphate, dipentaerythritol penta Methacryloyloxyphosphate, phosphoric acid mono- (1-acryloyl-piperidin-4-yl) -ester, 6- (methacrylamide) hexyl dihydrogen phosphate and 1,3-bis- (N-acryloyl-N-pro Le - amino) - propan-2-yl - dihydrogen phosphate are exemplified.

  Among the compounds having one or more ethylenically unsaturated groups, examples of the compound having a sulfonic acid group include vinylsulfonic acid, 4-vinylphenylsulfonic acid, and 3- (methacrylamide) propylsulfonic acid.

2. Next, a method for manufacturing the composite semipermeable membrane will be described. The manufacturing method includes a microporous support membrane forming step and a separation functional layer forming step. In addition, the composite semipermeable membrane of the present invention is not limited to the manufacturing method and the method of forming each layer described in this document.

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

  In the present invention, the porous support layer has a multilayer structure in which the first layer, the second layer, and the third layer are laminated from the substrate side. In order to form such a structure, in the step of applying the polymer solution to the substrate, the polymer solution that forms the second layer at the same time as applying the polymer solution A that forms the first layer on the substrate. It is preferable to apply the polymer solution C that forms B and the third layer. When a curing time is provided after applying the polymer solution A or the polymer solution B, the surface of the first layer or the second layer formed by phase separation of the polymer solution A or the polymer solution B has a high density. A skin layer is formed and the permeation flow rate is greatly reduced. Therefore, it is important to simultaneously apply the polymer solution B and the polymer solution C to such an extent that the polymer solution A does not form a dense skin layer by phase separation. For example, “applied simultaneously” means that the polymer solution B and the polymer solution C are in contact with each other before the polymer solution A reaches the substrate, that is, the polymer solution A is the substrate. When applied to the polymer solution B, the polymer solution B and the polymer solution C are applied on the polymer solution A.

  Application of the polymer solution onto the substrate can be carried out by various coating methods, but pre-metering coating methods such as die coating, slide coating, curtain coating and the like that can supply an accurate amount of the coating solution are preferably applied. Further, in the formation of the porous support layer having a multilayer structure of the present invention, the polymer solution forming the first layer, the polymer solution forming the second layer, and the polymer solution forming the third layer are simultaneously applied. The triple slit die method is more preferably used.

  When the polymer solution A forming the first layer contains polysulfone as the material of the porous support layer, the polysulfone concentration (that is, the solid content concentration a) of the polymer solution A is preferably 15% by weight or more. Preferably it is 17 weight% or more. The polysulfone concentration of the polymer solution A is preferably 30% by weight or less, and more preferably 25% by weight or less. The required peel strength can be obtained when the polymer concentration is 16% by weight or more.

  When the polymer solution B forming the second layer also contains polysulfone, the polysulfone concentration (that is, the solid content concentration b) of the polymer solution B is preferably 12% by weight or more, more preferably 13% by weight. That's it. The polysulfone concentration of the polymer solution B is preferably 20% by weight or less, more preferably 17% by weight or less. Within this range, when forming the polyamide separation functional layer, the aqueous amine solution can be supplied from the pores formed by phase separation.

  When the polymer solution C forming the third layer contains polysulfone as the material of the porous support layer, the polysulfone concentration (that is, the solid content concentration c) of the polymer solution C is preferably 15% by weight or more. Preferably it is 17 weight% or more. The polysulfone concentration of the polymer solution C is preferably 30% by weight or less, more preferably 25% by weight or less. The required peel strength can be obtained when the polymer concentration is 16% by weight or more. Moreover, the structure which has water permeability can be obtained because polymer concentration is 30 weight% or less.

Here, it is preferable from the viewpoints of the performance and durability of the composite semipermeable membrane that the polymer solution A and the polymer solution B have different compositions and the polymer solution C and the polymer solution B have different compositions. Here, the difference in composition means that at least the concentration of solid content is different. That is, it is preferable that the solid content concentration a (wt%) and the solid content concentration b (wt%) are different, and the solid content concentration b (wt%) and the solid content concentration c (wt%) are different. Thereby, in the formed first layer to third layer, adjacent layers, that is, the first layer and the second layer, and the second layer and the third layer can have different densities, and the composite semi-transparent It is preferable from the viewpoint of the performance and durability of the membrane.
In this case, the difference between the solid content concentration a and the solid content concentration b is preferably greater than 0% by weight and 10% by weight or less, and the difference between the solid content concentration b and the solid content concentration c is greater than 0% by weight and 10% by weight or less. preferable.

Further, the solid content concentration b (% by weight) of the polymer solution B is lower than the solid content concentration a (% by weight) of the polymer solution A and the solid content concentration c (% by weight) of the polymer solution C. Is preferred. That is, it is preferable that the solid content concentrations a to c satisfy the relational expressions of a> b and b <c. Porousness whose first layer has a dense structure, the second layer has a sparse structure, and the third layer has a dense structure due to the lowest solid content concentration b among the solid content concentrations a to c. A support layer can be obtained.
In this case, the difference between the solid content concentration a and the solid content concentration b is preferably 0.5% by weight to 10% by weight, and the difference between the solid content concentration b and the solid content concentration c is 0.5% by weight to 10% by weight. preferable.

  The solid content concentration a (wt%) of the polymer solution A, the solid content concentration b (wt%) of the polymer solution B, and the solid content concentration c (wt%) of the polymer solution C are a It is preferable to satisfy the relational expression of ≧ c> b. Further, it is more preferable that the solid content concentration a, the solid content concentration b, and the solid content concentration c satisfy the above-mentioned relational expressions while satisfying the respective preferable numerical ranges described above.

  When using a polysulfone, the temperature of the polymer solution at the time of applying the polymer solution is usually within a range of 10 to 60 ° C. Within this range, the polymer solution does not precipitate and is solidified after sufficiently impregnating the organic solvent solution containing the polymer between the fibers of the substrate. As a result, the microporous support membrane is firmly bonded to the substrate by the anchor effect, and the microporous support membrane of the present invention can be obtained. The preferable temperature range of the polymer solution may be adjusted as appropriate depending on the viscosity of the polymer solution used.

  The polymers contained in the polymer solution A, the polymer solution B, and the polymer solution C may be the same compound or different compounds. It can be adjusted as appropriate in consideration of various properties such as strength properties, permeability properties, and surface properties of the microporous support membrane to be produced.

  The solvent contained in the polymer solution A, the polymer solution B, and the polymer solution C may be the same solvent or different solvents as long as they are good polymers. It can be adjusted as appropriate by taking into consideration the strength characteristics of the microporous support membrane to be produced and the impregnation of the polymer solution into the substrate.

  The good solvent of the present invention dissolves a polymer material. Examples of the good solvent include N-methyl-2-pyrrolidone (NMP), tetrahydrofuran, dimethyl sulfoxide, amides such as tetramethylurea, dimethylacetamide, and dimethylformamide, lower alkyl ketones such as acetone and methylethylketone, trimethyl phosphate, γ- Examples thereof include esters such as butyrolactone, lactones, and mixed solvents thereof.

  Examples of the polymer non-solvent include water, hexane, pentane, benzene, toluene, methanol, ethanol, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol, and low Examples thereof include aliphatic hydrocarbons such as polyethylene glycol having a molecular weight, aromatic hydrocarbons, aliphatic alcohols, and mixed solvents thereof.

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

  By applying the polymer solution to the base material as described above, the base material is impregnated with the polymer solution. In order to obtain a microporous support film having a predetermined structure, the base material of the polymer solution is used. It is necessary to control the impregnation of the resin. In order to control the impregnation of the polymer solution into the substrate, for example, a method of controlling the time until the polymer solution is immersed on the coagulation bath after coating the polymer solution on the substrate, or the temperature of the polymer solution or The method of adjusting a viscosity by controlling a density | concentration is mentioned, These methods are also combinable.

  The time until the polymer solution is applied on the substrate and then immersed in the coagulation bath is preferably in the range of usually 0.1 to 5 seconds. If the time until dipping in the coagulation bath is within this range, the polymer solution is sufficiently impregnated between the fibers of the base material and then solidified. In addition, the preferable range of the time until dipping in the coagulation bath may be appropriately adjusted depending on the viscosity of the polymer solution to be used.

  As the coagulation bath, water is usually used, but any water that does not dissolve the polymer may be used. Depending on the composition, the membrane form of the microporous support membrane changes, and thereby the membrane-forming property of the composite semipermeable membrane also changes. The temperature of the coagulation bath is preferably -20 ° C to 100 ° C, more preferably 10 to 30 ° C. If it is below the above upper limit, the vibration of the coagulation bath surface due to thermal motion does not intensify, and the smoothness of the film surface after formation is good. Moreover, if it is more than the said minimum, sufficient coagulation | solidification rate will be obtained and film forming property will be favorable.

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

(2-2) Formation process of separation functional layer (polyamide separation functional layer)
Next, as an example of the formation process of the separation functional layer constituting the composite semipermeable membrane, the formation of the separation functional layer mainly composed of polyamide will be described. In the step of forming the polyamide separation functional layer, an aqueous solution containing the above-mentioned polyfunctional amine and an organic solvent solution immiscible with water containing the polyfunctional acid halide are used, and the interface is formed on the surface of the microporous support membrane. By performing polycondensation, a polyamide skeleton can be formed.

  The concentration of the polyfunctional amine in the polyfunctional amine aqueous solution is preferably in the range of 0.1% by weight to 20% by weight, and more preferably in the range of 0.5% by weight to 15% by weight. Within this range, sufficient water permeability and salt and boron removal performance can be obtained. As long as the polyfunctional amine aqueous solution does not interfere with the reaction between the polyfunctional amine and the polyfunctional acid halide, a surfactant, an organic solvent, an alkaline compound, an antioxidant, or the like may be contained. The surfactant has the effect of improving the wettability of the microporous support membrane surface and reducing the interfacial tension between the aqueous amine solution and the nonpolar solvent. The organic solvent may act as a catalyst for the interfacial polycondensation reaction, and when added, the interfacial polycondensation reaction may be efficiently performed.

  In order to perform interfacial polycondensation on the microporous support membrane, first, the above-mentioned polyfunctional amine aqueous solution is brought into contact with the microporous support membrane. The contact is preferably performed uniformly and continuously on the surface of the microporous support membrane. Specific examples include a method of coating a polyfunctional amine aqueous solution on a microporous support membrane and a method of immersing the microporous support membrane in a polyfunctional amine aqueous solution. The contact time between the microporous support membrane and the polyfunctional amine aqueous solution is preferably in the range of 5 seconds to 10 minutes, and more preferably in the range of 10 seconds to 3 minutes.

  After bringing the polyfunctional amine aqueous solution into contact with the microporous support membrane, the solution is sufficiently drained so that no droplets remain on the membrane. By sufficiently draining the liquid, it is possible to prevent the removal performance of the composite semipermeable membrane from being deteriorated due to the remaining portion of the droplet after the formation of the composite semipermeable membrane. As a method for draining, for example, as described in JP-A-2-78428, the microporous support membrane after contacting with the polyfunctional amine aqueous solution is vertically gripped to allow the excess aqueous solution to flow down naturally. A method or a method of forcibly draining an air stream such as nitrogen from an air nozzle can be used. In addition, after draining, the membrane surface can be dried to partially remove water from the aqueous solution.

  Next, a water-immiscible organic solvent solution containing a polyfunctional acid halide is brought into contact with the microporous support membrane after contact with the polyfunctional amine aqueous solution, and a crosslinked polyamide separation functional layer is formed by interfacial polycondensation.

  The concentration of the polyfunctional acid halide in the organic solvent solution immiscible with water is preferably in the range of 0.01 wt% to 10 wt%, and preferably 0.02 wt% to 2.0 wt%. More preferably within the range. When the polyfunctional acid halide concentration is 0.01% by weight or more, a sufficient reaction rate can be obtained, and when it is 10% by weight or less, the occurrence of side reactions can be suppressed. Further, it is more preferable to include an acylation catalyst such as DMF in the organic solvent solution, since interfacial polycondensation is promoted.

  The organic solvent immiscible with water is preferably one that dissolves the polyfunctional acid halide and does not destroy the microporous support membrane, and is inert to the polyfunctional amine compound and polyfunctional acid halide. I just need it. Preferable examples include hydrocarbon compounds such as hexane, heptane, octane, nonane and decane.

  The method of bringing the organic solvent solution containing the polyfunctional acid halide into contact with the microporous support membrane may be performed in the same manner as the method of coating the microporous support membrane with the polyfunctional amine aqueous solution.

  In the interfacial polycondensation step, the microporous support membrane is sufficiently covered with a crosslinked polyamide thin film, and a water-immiscible organic solvent solution containing a polyfunctional acid halide is brought into contact with the microporous support membrane. It is important to leave them in the water. For this reason, the time for performing the interfacial polycondensation is preferably from 0.1 second to 3 minutes, and more preferably from 0.1 second to 1 minute. By performing the interfacial polycondensation for 0.1 second or more and 3 minutes or less, the microporous support membrane can be sufficiently covered with a crosslinked polyamide thin film, and an organic solvent solution containing a polyfunctional acid halide Can be held on the microporous support membrane.

  After the polyamide separation functional layer is formed on the microporous support membrane by interfacial polycondensation, excess solvent is drained. As a method for draining, for example, a method in which a film is held in a vertical direction and excess organic solvent is allowed to flow down and removed can be used. In this case, the time for gripping in the vertical direction is preferably 1 minute or more and 5 minutes or less, and more preferably 1 minute or more and 3 minutes or less. Within such a range, the separation functional layer is sufficiently formed and the organic solvent is not overdried, so that no defective portion is generated in the polyamide separation functional layer, and sufficiently high membrane performance is obtained.

(Organic / inorganic hybrid separation functional layer)
Next, a method for forming the organic / inorganic hybrid separation functional layer on the porous support layer will be described.
In order to form the separation functional layer, in addition to the above-described compound (A), a reaction liquid containing the above-described compound (B) having one or more ethylenically unsaturated groups and a polymerization initiator can be used. Specifically, the separation functional layer applies these reaction liquids on the porous support layer, and in addition to condensing the hydrolyzable groups, the compounds are polymerized by ethylenically unsaturated groups. Can be formed. When the compound (A) is condensed alone, the bonding of the crosslinking chain concentrates on the silicon atom, and the density difference between the periphery of the silicon atom and the part away from the silicon atom increases, so that the pore size in the separation functional layer is not large. It may be uniform. On the other hand, in addition to increasing the molecular weight of the compound (A) itself and crosslinking, the compound (B) is copolymerized so that the crosslinking point due to condensation of hydrolyzable groups and the crosslinking point due to polymerization of ethylenically unsaturated groups are moderately increased. Distributed. By appropriately dispersing the crosslinking points in this manner, a separation functional layer having a uniform pore diameter is formed, and a composite semipermeable membrane having a balance between water permeability and removal performance can be obtained. Moreover, since the compound which has 1 or more of ethylenically unsaturated groups is high molecular weight, it becomes difficult to elute at the time of use of a composite semipermeable membrane, Therefore It is hard to cause a membrane performance fall.

  In the separation functional layer, the content of the compound (A) is preferably 10 parts by weight or more, more preferably 20 parts by weight to 50 parts by weight with respect to 100 parts by weight of the solid content contained in the reaction solution. Here, the solid content contained in the reaction liquid is a composite semipermeable membrane obtained by removing the solvent and distilled components such as water and alcohol produced by the condensation reaction from all components contained in the reaction liquid Refers to a component finally contained as a separation functional layer. When the amount of the compound (A) is small, the degree of crosslinking tends to be insufficient, so that there is a possibility that problems such as elution of the separation functional layer during membrane filtration and deterioration of separation performance may occur.

  The content of the compound (B) is preferably 90 parts by weight or less, and more preferably 50 parts by weight to 80 parts by weight with respect to 100 parts by weight of the solid content contained in the reaction solution. When the content of the compound (B) is within these ranges, the resulting separation functional layer has a high degree of crosslinking, and thus membrane filtration can be performed stably without the separation functional layer eluting.

Next, the process of forming the separation functional layer on the porous support layer will be described.
The separation functional layer includes a step of applying a reaction liquid containing the compound (A) and the compound (B), a step of removing the solvent, a step of polymerizing the ethylenically unsaturated group, and a step of condensing the hydrolyzable group. It can be formed by performing in order. In the step of polymerizing the ethylenically unsaturated group, the hydrolyzable group may condense at the same time.

  First, the reaction liquid containing the compound (A) and the compound (B) is brought into contact with the porous support layer. Such a reaction solution is usually a solution containing a solvent, but such a solvent does not destroy the porous support layer and dissolves the compound (A) and the compound (B), and a polymerization initiator added as necessary. If it does, it will not specifically limit. To this reaction solution, 1 to 10 times, preferably 1 to 5 times, the amount of water with respect to the number of moles of the compound (A) is added together with an inorganic acid or an organic acid to It is preferable to promote decomposition.

  As the solvent for the reaction solution, water, an alcohol-based organic solvent, an ether-based organic solvent, a ketone-based organic solvent, and a mixture thereof are preferable. For example, as an alcohol organic solvent, methanol, ethoxymethanol, ethanol, propanol, butanol, amyl alcohol, cyclohexanol, methylcyclohexanol, ethylene glycol monomethyl ether (2-methoxyethanol), ethylene glycol monoacetate, diethylene glycol monomethyl ether, Examples include diethylene glycol monoacetate, propylene glycol monoethyl ether, propylene glycol monoacetate, dipropylene glycol monoethyl ether, and methoxybutanol. Examples of ether organic solvents include methylal, diethyl ether, dipropyl ether, dibutyl ether, diamyl ether, diethyl acetal, dihexyl ether, trioxane, dioxane and the like. In addition, as ketone organic solvents, acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, methyl cyclohexyl ketone, diethyl ketone, ethyl butyl ketone, trimethylnonanone, acetonitrile acetone, dimethyl oxide, phorone, cyclohexanone, di Acetone alcohol etc. are mentioned. Moreover, as an addition amount of a solvent, 50-99 weight part is preferable with respect to 100 weight part of solid content contained in a reaction liquid, Furthermore, 80-99 weight part is preferable. If the amount of the solvent added is too large, defects tend to occur in the membrane, and if it is too small, the water permeability of the resulting composite semipermeable membrane tends to be low.

  The contact between the porous support layer and the reaction solution is preferably performed uniformly and continuously on the surface of the porous support layer. Specifically, for example, a method of coating the porous support layer with the reaction solution using a coating device such as a spin coater, a wire bar, a flow coater, a die coater, a roll coater, or a spray. Moreover, the method of immersing a porous support layer in a reaction liquid can be mentioned.

  When immersed, the contact time between the porous support layer and the reaction solution is preferably within a range of 0.5 to 10 minutes, and more preferably within a range of 1 to 3 minutes. After the reaction solution is brought into contact with the porous support layer, it is preferable to sufficiently drain the liquid so that no droplets remain on the membrane. By sufficiently draining the liquid, it is possible to prevent the remaining portion of the liquid droplet from becoming a film defect after the film is formed and deteriorating the film performance. As a method for draining, the porous support layer after contact with the reaction solution is vertically gripped and the excess reaction solution is allowed to flow naturally, or air such as nitrogen is blown from an air nozzle to forcibly drain the solution. A method or the like can be used. In addition, after draining, the membrane surface can be dried to remove a part of the solvent in the reaction solution.

  The step of condensing the hydrolyzable group of silicon is carried out by bringing the reaction liquid into contact with the porous support layer and then heat-treating it. The heating temperature at this time is required to be lower than the temperature at which the porous support layer melts and the performance as a composite semipermeable membrane is lowered. In order to allow the condensation reaction to proceed rapidly, it is usually preferred to heat at 0 ° C. or higher, more preferably 20 ° C. or higher. Further, the reaction temperature is preferably 150 ° C. or lower, and more preferably 100 ° C. or lower. If the reaction temperature is 0 ° C. or higher, the hydrolysis and condensation reaction proceed rapidly, and if it is 150 ° C. or lower, the hydrolysis and condensation reaction are easily controlled. Further, by adding a catalyst that promotes hydrolysis or condensation, the reaction can proceed even at a lower temperature. Furthermore, heating conditions and humidity conditions can be selected so that the separation functional layer has pores when the condensation reaction proceeds appropriately.

  As a polymerization method of the ethylenically unsaturated group of the compound (A) and the compound (B), heat treatment, electromagnetic wave irradiation, electron beam irradiation, and plasma irradiation can be performed. Here, the electromagnetic wave includes infrared rays, ultraviolet rays, X-rays, γ rays and the like. The polymerization method may be appropriately selected as appropriate, but polymerization by electromagnetic wave irradiation is preferred from the viewpoint of running cost, productivity and the like. Among electromagnetic waves, infrared irradiation and ultraviolet irradiation are more preferable from the viewpoint of simplicity. When the polymerization is actually performed using infrared rays or ultraviolet rays, these light sources do not need to selectively generate only light in this wavelength range, and any light source containing electromagnetic waves in these wavelength ranges may be used. However, from the viewpoint of ease of shortening the polymerization time and controlling the polymerization conditions, it is preferable that the intensity of these electromagnetic waves is higher than electromagnetic waves in other wavelength regions.

  Electromagnetic waves can be generated from halogen lamps, xenon lamps, UV lamps, excimer lamps, metal halide lamps, rare gas fluorescent lamps, mercury lamps, and the like. The energy of the electromagnetic wave is not particularly limited as long as it can be polymerized, but particularly high efficiency and low wavelength ultraviolet rays have a high thin film forming property. Such ultraviolet rays can be generated by a low-pressure mercury lamp or an excimer laser lamp. The thickness and form of the separation functional layer may vary greatly depending on the respective polymerization conditions. In the case of polymerization using electromagnetic waves, the thickness and form of the separation functional layer may vary greatly depending on the wavelength and intensity of the electromagnetic waves, the distance to the irradiated object, and the treatment time. Therefore, these conditions may be optimized as appropriate.

  For the purpose of increasing the polymerization rate, it is preferable to add a polymerization initiator, a polymerization accelerator or the like during the formation of the separation functional layer. Here, the polymerization initiator and the polymerization accelerator are not particularly limited, and are appropriately selected according to the structure of the compound to be used, the polymerization technique, and the like.

  The polymerization initiator is exemplified below. As an initiator for polymerization by electromagnetic waves, benzoin ether, dialkylbenzyl ketal, dialkoxyacetophenone, acylphosphine oxide or bisacylphosphine oxide, α-diketone (for example, 9,10-phenanthrenequinone), diacetylquinone, furylquinone, anisylquinone, 4,4′-dichlorobenzylquinone and 4,4′-dialkoxybenzylquinone, and camphorquinone are exemplified. Initiators for thermal polymerization include azo compounds (eg, 2,2′-azobis (isobutyronitrile) (AIBN) or azobis- (4-cyanovaleric acid)), or peroxides (eg, peroxidation). Dibenzoyl, dilauroyl peroxide, tert-butyl peroctanoate, tert-butyl perbenzoate or di- (tert-butyl) peroxide), aromatic diazonium salts, bissulfonium salts, aromatic iodonium salts, aromatic sulfonium salts, Examples include potassium persulfate, ammonium persulfate, alkyl lithium, cumyl potassium, sodium naphthalene, and distyryl dianion. Of these, benzopinacol and 2,2'-dialkylbenzopinacol are particularly preferred as initiators for radical polymerization.

  Peroxides and α-diketones are preferably used in combination with aromatic amines to accelerate initiation. This combination is also called a redox system. Examples of such systems include benzoyl peroxide or camphorquinone and amines (eg, N, N-dimethyl-p-toluidine, N, N-dihydroxyethyl-p-toluidine, ethyl p-dimethyl-aminobenzoate). Ester or a derivative thereof). Furthermore, a system containing a peroxide in combination with ascorbic acid, barbiturate or sulfinic acid as a reducing agent is also preferred.

  Subsequently, when this is heat-processed at about 100-200 degreeC, a polycondensation reaction will occur and the composite semipermeable membrane in which the separation functional layer derived from the silane coupling agent was formed in the porous support layer surface can be obtained. Although the heating temperature depends on the material of the porous support layer, if it is too high, dissolution occurs and the pores of the porous support layer are blocked, resulting in a decrease in the amount of water produced in the composite semipermeable membrane. On the other hand, if it is too low, the polycondensation reaction becomes insufficient, and the removal rate decreases due to elution of the functional layer.

  In the above production method, the step of increasing the molecular weight of the silane coupling agent and the compound having at least one ethylenically unsaturated group may be performed before the polycondensation step of the silane coupling agent, or after You may go. Moreover, you may carry out simultaneously.

Furthermore, in the present invention, the formed polyamide separation functional layer may be brought into contact with an amine reactive reagent. This process can further improve the chemical resistance of the composite semipermeable membrane by reducing the amount of amino groups in the polyamide. Examples of amine-reactive reagents include acid halides, acid anhydrides, esters, nitrosyl compounds, nitrous acid and its salts, hypochlorite, and the like. In particular, it is preferable to contact with a nitrosyl compound, nitrous acid, or a salt thereof that reacts with a primary amino group in the polyamide separation functional layer to form a diazonium salt or a derivative thereof.
The method of bringing the compound that reacts with the primary amino group into a diazonium salt or a derivative thereof into contact with the polyamide separation functional layer is not particularly limited as long as the surface of the separation functional layer and the compound are in contact with each other. Can be used.
In the present invention, the compound that reacts with a primary amino group to produce a diazonium salt or a derivative thereof is preferably used as an aqueous solution. Since an aqueous solution of a nitrosyl compound or nitrous acid tends to generate gas and decompose easily, it is preferable to sequentially generate nitrous acid by, for example, a reaction between nitrite and an acidic solution. In general, nitrite reacts with hydrogen ions to produce nitrous acid, but it is efficiently produced at 20 ° C. when the pH of the aqueous solution is 7 or less, preferably 5 or less, more preferably 4 or less. Among these, an aqueous solution of sodium nitrite reacted with hydrochloric acid or sulfuric acid in an aqueous solution is particularly preferable because of easy handling.
The concentration of nitrous acid or nitrite in a compound solution that reacts with a primary amino group to form a diazonium salt or a derivative thereof is preferably in the range of 0.01 to 1% by weight at 20 ° C. If the concentration is lower than 0.01% by weight, a sufficient effect cannot be obtained. If the concentration of nitrous acid and nitrite is higher than 1% by weight, handling of the solution becomes difficult.
The temperature of the nitrous acid aqueous solution is preferably 15 ° C to 45 ° C. If it is less than 15 ° C., the reaction takes time, and if it exceeds 45 ° C., decomposition of nitrous acid is quick and difficult to handle. The contact time between the aqueous nitrous acid solution and the primary amino group may be a time for forming a diazonium salt. A high concentration allows treatment in a short time, but a low concentration requires a long time contact. When the diazonium salt is produced at a low concentration over a long period of time, the diazonium salt reacts with water before reacting with the reactive compound, so it is desirable to perform treatment at a high concentration for a short time. For example, it is preferable to perform treatment for 30 seconds to 10 minutes with a 2,000 mg / liter nitrous acid aqueous solution.

  The composite semipermeable membrane thus obtained can be used as it is, but before use, it is preferable to hydrophilize the surface of the membrane with, for example, an alcohol-containing aqueous solution or an alkaline aqueous solution.

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

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

  The higher the operating pressure of the fluid separator, the higher the salt removal rate, but the energy required for operation also increases, and considering the durability of the composite semipermeable membrane, water to be treated is added to the composite semipermeable membrane. The operating pressure at the time of permeation is preferably 1.0 MPa or more and 10 MPa or less. As the feed water temperature rises, the salt removal rate decreases, but as the feed water temperature decreases, the membrane permeation flux also decreases. In addition, when the pH of the feed water becomes high, scales such as magnesium may be generated in the case of feed water with a high salt concentration such as seawater, and there is a concern about deterioration of the membrane due to high pH operation. Is preferred.

  Examples of raw water to be treated by the composite semipermeable membrane include liquid mixtures containing TDS (Total Dissolved Solids) of 500 mg / L to 100 g / L such as seawater, brine, and drainage. In general, TDS indicates the total dissolved solid content, and is expressed by “mass / volume”, but 1 L may be expressed as 1 kg and may be expressed by “weight ratio”. According to the definition, the solution filtered with a 0.45 micron filter can be calculated from the weight of the residue by evaporating at a temperature of 39.5 to 40.5 ° C., but more simply converted from practical salt content.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples.

<Production of composite semipermeable membrane>
In the following Examples and Comparative Examples, polysulfone UDEL p-3500 manufactured by Solvay Advanced Polymers Co., Ltd. was used as the polysulfone.

Example 1
Polysulfone 17 wt% DMF solution (Polymer solution A), Polysulfone 20 wt% DMF solution (Polymer solution B) and Polysulfone 18 wt% DMF solution (Polymer solution C) were mixed with each solvent and solute mixture. It was prepared by heating and holding at 90 ° C. for 2 hours while stirring.
Each of the prepared polymer solutions was cooled to room temperature, supplied to a separate extruder, and filtered with high precision. Thereafter, the filtered polymer solution is passed through a triple slit die on a non-woven fabric made of polyethylene terephthalate fiber (yarn diameter: 1 dtex, thickness: about 90 μm, air permeability: 1 cc / cm ² / sec), polymer solution A, The polymer solution B and the polymer solution C were simultaneously cast in this order, and immediately immersed in pure water and washed for 5 minutes to obtain a microporous support membrane. Each polymer solution was cast so that the first layer had a thickness of 50 μm, the second layer had a thickness of 60 μm, and the third layer had a thickness of 50 μm.
The obtained microporous support membrane was immersed in a 4.0 wt% aqueous solution of m-PDA for 2 minutes, and then slowly pulled up so that the membrane surface was vertical. Nitrogen was blown from the air nozzle to remove excess aqueous solution from the surface of the support membrane, and then an n-decane solution at 25 ° C. containing 0.12% by weight of trimesic acid chloride was applied so that the membrane surface was completely wetted. After leaving still for 1 minute, in order to remove excess solution from the film, the film surface was held vertically for 1 minute to drain the liquid. Then, the composite semipermeable membrane provided with a base material, a porous support layer, and a polyamide separation functional layer was obtained by washing with water at 45 ° C. for 2 minutes.

(Example 2)
In Example 1, a 20% by weight polysulfone DMF solution was used as the polymer solution A, a 17% by weight polysulfone DMF solution was used as the polymer solution B, and a 15% polysulfone DMF solution was used as the polymer solution C. In the same manner as in Example 1, a composite semipermeable membrane of Example 2 was obtained.

(Example 3)
In Example 1, a DMF solution containing 20% by weight of polysulfone was used as the polymer solution A, a DMF solution containing 15% by weight polysulfone was used as the polymer solution B, and a DMF solution containing 20% by weight polysulfone was used as the polymer solution C. In the same manner as in Example 1, a composite semipermeable membrane of Example 3 was obtained.

Example 4
In Example 1, a DMF solution containing 20% by weight of polysulfone was used as the polymer solution A, a DMF solution containing 13% by weight polysulfone was used as the polymer solution B, and a DMF solution containing 20% by weight polysulfone was used as the polymer solution C. The composite semipermeable membrane of Example 4 was obtained in the same manner as in Example 1.

(Example 5)
In Example 1, a DMF solution containing 20% by weight of polysulfone was used as the polymer solution A, a DMF solution containing 13% by weight polysulfone was used as the polymer solution B, and a DMF solution containing 20% by weight polysulfone was used as the polymer solution C. A composite semipermeable membrane was obtained in the same manner as in Example 1. Further, this composite semipermeable membrane was immersed in a 0.3 wt% sodium nitrite aqueous solution adjusted to pH 3.0 with sulfuric acid at 35 ° C. for 30 seconds, and then immediately immersed in a water bath, so that the composite semipermeable membrane of Example 5 was used. A permeable membrane was obtained.

(Example 6)
In Example 1, a DMF solution of 22% by weight of polysulfone was used as the polymer solution A, a DMF solution of 13% by weight of polysulfone was used as the polymer solution B, and a DMF solution of 20% by weight of polysulfone was used as the polymer solution C. In the same manner as in Example 1, a composite semipermeable membrane of Example 6 was obtained.

(Example 7)
In Example 1, a DMF solution containing 20% by weight of polysulfone was used as the polymer solution A, a DMF solution containing 13% by weight polysulfone was used as the polymer solution B, and a DMF solution containing 22% by weight polysulfone was used as the polymer solution C. In the same manner as in Example 1, a composite semipermeable membrane of Example 7 was obtained.

(Example 8)
In Example 1, a DMF solution containing 17% by weight of polysulfone was used as the polymer solution A, a DMF solution containing 17% by weight polysulfone was used as the polymer solution B, and a DMF solution containing 17% by weight polysulfone was used as the polymer solution C. In the same manner as in Example 1, a composite semipermeable membrane of Example 8 was obtained.

(Comparative Example 1)
In Example 1, the same procedure as in Example 1 except that only 13% by weight of polysulfone in DMF was applied on the nonwoven fabric to a thickness of 220 μm using a single slit die coater instead of a triple slit die. A microporous support membrane was obtained.
On the obtained microporous support membrane, a separation functional layer was formed by the same procedure as in Example 1 to obtain a composite semipermeable membrane of Comparative Example 1.

(Comparative Example 2)
A composite semipermeable membrane of Comparative Example 2 was obtained in the same manner as Comparative Example 1 except that a DMF solution containing 15% by weight of polysulfone was used as the polymer solution.

(Comparative Example 3)
A composite semipermeable membrane of Comparative Example 3 was obtained in the same manner as Comparative Example 1 except that a 20% by weight polysulfone DMF solution was used as the polymer solution.

(Comparative Example 4)
The polymer solution A was a 13% by weight polysulfone DMF solution, the polymer solution B was a 20% polysulfone DMF solution, the polymer solution C was not used, and a double slit die was used instead of a triple slit die. In the same manner as in Example 1, a composite semipermeable membrane of Comparative Example 4 was obtained.

(Comparative Example 5)
The polymer solution A is a 15% by weight polysulfone DMF solution, the polymer solution B is a 20% polysulfone DMF solution, the polymer solution C is not used, and a double slit die is used instead of a triple slit die. In the same manner as in Example 1, a composite semipermeable membrane of Comparative Example 5 was obtained.

(Comparative Example 6)
The polymer solution A is a 15% by weight polysulfone DMF solution, the polymer solution B is a 20% polysulfone DMF solution, the polymer solution C is not used, and a double slit die is used instead of a triple slit die. Obtained a composite semipermeable membrane in the same manner as in Example 1. The composite semipermeable membrane was immersed in a 0.3 wt% aqueous sodium nitrite solution adjusted to pH 3.0 with sulfuric acid at 35 ° C. for 30 seconds, and then immediately immersed in a water bath, so that the composite semipermeable membrane of Comparative Example 6 was used. A membrane was obtained.

(Comparative Example 7)
The polymer solution A is a 20% by weight polysulfone DMF solution, the polymer solution B is a 15% polysulfone DMF solution, the polymer solution C is not used, and a double slit die is used instead of a triple slit die. In the same manner as in Example 1, a composite semipermeable membrane of Comparative Example 7 was obtained.

<Measurement of peel resistance>
The peel resistance of the composite semipermeable membranes in Examples and Comparative Examples was measured using a Tensilon tester (RTG-1210). The maximum value of the peeling force was determined by peeling a new film sample that had not been subjected to pressure application and water passage at 25 ° C. with a gripping movement speed of 10 mm / min and a peeling direction of 180 °. This operation was performed 10 times for one sample, and the average of the obtained values was calculated to obtain the peel strength.

<Desalination rate (TDS removal rate)>
Filtration was performed for 24 hours by supplying seawater (corresponding to feed water) at a temperature of 25 ° C. and a pH of 6.5 to the composite semipermeable membrane at an operating pressure of 5.5 MPa. The obtained permeated water was used for measuring the TDS removal rate.
Practical salinity was obtained by measuring the electrical conductivity of the supplied water and the permeated water with an electric conductivity meter manufactured by Toa Radio Industry Co., Ltd. From the TDS concentration obtained by converting this practical salinity, the desalting rate, that is, the TDS removal rate was determined by the following equation.
TDS removal rate (%) = 100 × {1− (TDS concentration in permeated water / TDS concentration in feed water)}

<Membrane permeation flux>
The amount of permeated water obtained by the above filtration treatment for 24 hours was converted to the amount of water per day (cubic meter) per square meter of the membrane surface and expressed as the membrane permeation flux (m ³ / m ² / day).

<Measurement of compressibility of semipermeable membrane after evaluation>
The thickness of the semipermeable membrane in Examples and Comparative Examples was measured using a micrometer (Mitutoyo. Corp ID-C112XBS). A new membrane sample that has not been subjected to pressure application and water passage, and a membrane sample that has been subjected to pressure application and water passage (temperature 25 ° C., seawater at pH 6.5, operating pressure 5.5 MPa, filtration treatment for 24 hours) The thickness was determined under a room temperature atmosphere. In this operation, the thickness of 10 locations was measured for one sample, the average value of the obtained values was calculated, and the compression ratio of the film thickness after evaluation was determined by the following formula.
Compression rate of film thickness after evaluation = 100 × (thickness after applying pressure ÷ thickness before applying pressure)

  The results are shown in Table 1. In the semipermeable membranes of Comparative Examples 1 to 7, it was found that, although the high peel strength was obtained due to the high concentration of the polymer solution, the membrane having a high peel strength has low water permeability. On the other hand, from Examples 1-8, it turns out that the composite semipermeable membrane which balanced high peeling resistance of 1.1 N / 25mm or more and high water permeability is obtained by this invention. Moreover, it turns out that all the semipermeable membranes of Examples 1-8 have a high compression rate of the film after evaluation, and can maintain the film thickness after operation.

  The composite semipermeable membrane of the present invention can be particularly suitably used for brine or seawater desalination.

Claims (6)

A composite semipermeable membrane comprising a substrate and a microporous support membrane comprising a porous support layer provided on the substrate, and a separation functional layer provided on the porous support layer,
The porous support layer has a first layer formed on a base material, a second layer formed on the first layer, and a third layer formed on the second layer. Multi-layer structure,
The first layer has a dense structure, the second layer has a sparse structure, the third layer has a dense structure, and
Using a Tensilon tensile tester, the maximum value of the peeling force when the porous support layer was peeled off from the substrate at a peeling direction of 180 ° at a holding speed of 10 mm / min under a temperature condition of 25 ° C. was 10 A composite semipermeable membrane having a peel strength of 1.0 N / 25 mm or more, which is an average value of values obtained by repeated measurements.   2. The composite semipermeable membrane according to claim 1, wherein an interface between the first layer and the second layer and an interface between the second layer and the third layer have a continuous structure. A method for producing a composite semipermeable membrane comprising a substrate and a microporous support membrane comprising a porous support layer provided on the substrate, and a separation functional layer provided on the porous support layer,
The porous support layer has a first layer formed on a base material, a second layer formed on the first layer, and a third layer formed on the second layer. Multi-layer structure,
The polymer solution A for forming the first layer is applied on the base material, and simultaneously the polymer solution B for forming the second layer and the polymer solution C for forming the third layer are applied to the coagulation bath. Including contacting and phase-separating ,
The solid content concentration b (wt%) of the polymer solution B is lower than the solid content concentration a (wt%) of the polymer solution A and the solid content concentration c (wt%) of the polymer solution C. A method for producing a composite semipermeable membrane. The solid content concentration a (wt%) of the polymer solution A, the solid content concentration b (wt%) of the polymer solution B, and the solid content concentration c (wt%) of the polymer solution C are a ≧ c The manufacturing method of the composite semipermeable membrane of Claim 3 which satisfy | fills the relational expression of> b . The composite semipermeable membrane according to claim 1 or 2 , wherein the base material is a long-fiber nonwoven fabric containing polyester. The amount of water produced after passing an aqueous solution having a NaCl concentration of 3.5% by weight, a temperature of 25 ° C. and a pH of 6.5 at a pressure of 5.5 MPa for 24 hours is 1.6 m ³ / m ² / day or more, And the desalination rate is 99.85% or more, The composite semipermeable membrane according to any one of claims 1, 2, and 5 .