JP6511808B2 - Composite semipermeable membrane - Google Patents

Description

  The present invention relates to a composite semipermeable membrane useful for selective separation of a liquid mixture, and more particularly to a composite semipermeable membrane having practical water permeability and high resistance to chlorine.

  Although there are various techniques for removing substances (eg, salts) dissolved in a solvent (eg, water) with respect to separation of mixtures, in recent years, the use of membrane separation has been expanded as a process for energy saving and resource saving. doing. Membranes used in the membrane separation method include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, etc. These membranes are, for example, beverages from seawater, brackish water, water containing harmful substances, etc. It is used in the case of obtaining water, the production of industrial ultrapure water, waste water treatment, the recovery of valuables, etc. (Patent Documents 1 and 2).

  Most of the reverse osmosis membranes and nanofiltration membranes currently on the market are composite semipermeable membranes, which have an active layer obtained by crosslinking a gel layer and a polymer on a porous support layer, and a monomer on the porous support layer There are two types, those having an active layer obtained by polycondensing. Among the latter, the composite semipermeable membrane obtained by coating the porous support layer with a separation functional layer composed of a crosslinked polyamide obtained by the polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide is It is widely used as a separation membrane with high selectivity.

  These composite semipermeable membranes are cleaned with various oxidizing agents, especially chlorine, from the pursuit of low cost due to more stable operability, simple operability and prolongation of membrane life in various water treatments such as water production plants. Durability that can endure is required. Some of the known polyamide-based semipermeable membranes described above have a certain degree of oxidation resistance, but in order to cope with a wider variety of water quality, they have a further high degree of oxidation resistance, permeability and removability. A permeable membrane is desired.

  As a method of improving the durability to chlorine, a method of improving a monomer component forming the separation functional layer and a method of forming a protective layer on the separation functional layer are known. Patent Document 3 discloses that sodium m-phenylenediamine-4-sulfonate is used as a polyfunctional amine forming a separation functional layer, and Patent Document 4 discloses a polyfunctional amine forming a separation functional layer. It is disclosed to use a compound having a hexafluoro alcohol as a side chain.

Japanese Patent Application Laid-Open No. 55-14706 Unexamined-Japanese-Patent No. 5-76740 Japanese Patent Application Laid-Open No. 63-137704 WO 2010/096563

  Although there are also membranes having chlorine resistance in the various proposals described above, membranes having both permeability and removability have not been obtained. Moreover, when the water quality of the raw water is poor, the TDS removal rate may decrease under the situation where frequent cleaning with chlorine is performed to maintain the apparatus. An object of the present invention is to provide a composite semipermeable membrane having water permeability and removability that can withstand practical use, and having a high TDS removal rate even after contact with chlorine.

The composite semipermeable membrane for solving the above-mentioned subject takes the following composition.
[1] base material,
A porous support layer formed on the substrate;
A separation functional layer provided on the porous support layer and containing a polyamide obtained by the polycondensation of a polyfunctional amine and a polyfunctional acid halide,
The composite semipermeable membrane which has the partial structure in which the said polyamide is represented by (1).

(Wherein, Ar ₁ is an aromatic ring having 6 to 14 carbon atoms having at least one substituent satisfying Hammett's substituent constant σ _m 0.40.40, σ _p 0.500.50, R ₁ and R ₂ Is a hydrogen atom or an organic chain having 1 to 10 carbon atoms.)
[2] The composite semipermeable membrane according to the above [1], wherein the polyamide further has a partial structure represented by the formula (2).

(Wherein Ar ₂ is an aromatic ring having 6 to 14 carbon atoms having at least one substituent other than a hydrogen atom satisfying Hammett's substituent constants σ _m ≦ 0.15, σ _p ≦ 0.15, R 2 ₃ and R _{4 each} is a hydrogen atom or an organic chain having 1 to 10 carbon atoms.)
[3]
The substituent possessed by the partial structure represented by the structural formula (1) is characterized in that it can be converted by an oxidation reaction from a substituent satisfying Hammett's substituent constant σ _m ≦ 0.15 and σ _p ≦ 0.15. The composite semipermeable membrane according to any one of [1] or [2].
[4] The separation functional layer containing polyamide has a fold structure, and the composite semipermeable membrane according to any one of the above [1] to [3], wherein the median value of the heights of protrusions in the fold structure is 50 nm or more. .

  According to the present invention, a composite semipermeable membrane having practicable removability and excellent in chlorine resistance can be obtained.

It is drawing which shows about the calculation method of 10 point average surface roughness.

1. Composite Semipermeable Membrane (1-1) Base Material Examples of the base material include polyester polymers, polyamide polymers, polyolefin polymers, and mixtures or copolymers thereof. Among them, polyester polymer fabrics having high mechanical and thermal stability are particularly preferable. As the form of the fabric, a long-fiber non-woven fabric, a short-fiber non-woven fabric, and a woven or knitted fabric can be preferably used. Here, the long-fiber non-woven fabric refers to a non-woven fabric having an average fiber length of 300 mm or more and an average fiber diameter of 3 to 30 μm.

The base material preferably has an air permeability of 0.5 cc / cm ² / sec or more and 5.0 cc / cm ² / sec. When the air permeability of the substrate is in the above range, the polymer solution forming the porous support layer is impregnated into the substrate, so the adhesion to the substrate is improved, and the physical property of the microporous support membrane is improved. It can improve stability.

  The thickness of the substrate is preferably in the range of 10 to 200 μm, more preferably in the range of 30 to 120 μm. In the present specification, thickness means an average value unless otherwise noted. Here, the average value represents an arithmetic mean value. That is, the thicknesses of the substrate and the porous support layer can be determined by calculating the average value of the thickness of 20 points measured at intervals of 20 μm in the direction (plane direction of the membrane) orthogonal to the thickness direction in cross-sectional observation.

(1-2) Porous Support Layer In the present invention, the porous support layer is for imparting strength to the separation functional layer having substantially no separation performance such as ions and the like. . The size and distribution of the pores in the porous support layer are not particularly limited, but, for example, uniform fine pores or gradually large micropores from the surface on the side on which the separation functional layer is formed to the other surface, The porous support layer is preferably such that the size of the micropores is 0.1 nm or more and 100 nm or less on the surface on which the separation functional layer is formed, but the material to be used and the shape thereof are not particularly limited.

  The material of the porous support layer may be, for example, a homopolymer or copolymer of polysulfone, polyethersulfone, polyamide, polyester, cellulose polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, polyphenylene oxide, etc. alone or It can be used by blending. Here, cellulose acetate and cellulose nitrate can be used as the cellulose-based polymer, and polyethylene, polypropylene, polyvinyl chloride, polyacrylonitrile and the like can be used as the vinyl polymer. Among them, homopolymers or copolymers of polysulfone, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, polyphenylene sulfide sulfone and the like are preferable. More preferably, cellulose acetate, polysulfone, polyphenylene sulfide sulfone, or polyphenylene sulfone can be mentioned, and furthermore, among these materials, polysulfone is preferable because of high chemical, mechanical and thermal stability and easy molding. It can be used generally.

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

  The polysulfone preferably has a weight average molecular weight (Mw) of 10000 or more and 200,000 or less, more preferably, when measured by gel permeation chromatography (GPC) using N-methylpyrrolidone as a solvent and polystyrene as a standard substance. 15000 or more and 100000 or less. When Mw is 10000 or more, mechanical strength and heat resistance preferable as a porous support layer can be obtained. Moreover, the viscosity of a solution becomes an appropriate range by Mw being 200,000 or less, and favorable moldability can be implement | achieved.

  For example, by casting a solution of the above polysulfone in N, N-dimethylformamide (hereinafter referred to as DMF) to a certain thickness on a tightly woven polyester cloth or non-woven fabric and wet coagulating it in water A porous support layer can be obtained which has fine pores with a diameter of several tens of nm or less for the majority of the surface.

  The thickness of the substrate and the porous support layer affects the strength of the composite semipermeable membrane and the packing density when it is used as an element. In order to obtain sufficient mechanical strength and packing density, the total thickness of the substrate and the porous support layer is preferably 30 μm or more and 300 μm or less, and more preferably 100 μm or more and 220 μm or less. Moreover, it is preferable that the thickness of a porous support layer is 20 micrometers or more and 100 micrometers or less. In the present specification, thickness means an average value unless otherwise noted. Here, the average value represents an arithmetic mean value. That is, the thicknesses of the substrate and the porous support layer can be determined by calculating the average value of the thickness of 20 points measured at intervals of 20 μm in the direction (plane direction of the membrane) orthogonal to the thickness direction in cross-sectional observation.

  The porous support layer used in the present invention can be selected from various commercial materials such as "Millipore filter VSWP" (trade name) manufactured by Millipore, and "Ultra Filter UK10" (trade name) manufactured by Toyo Roshi Co., Ltd. No. “Office of Saline Water Research and Development Progress Report” No. It can be manufactured according to the method described in 359 (1968).

(1-3) Separated Functional Layer The separated functional layer has a thin film whose main component is polyamide obtained by the polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide. In other words, the separation functional layer contains the crosslinked wholly aromatic polyamide as a main component. The main component refers to a component that occupies 50% or more of the components of the separation functional layer. When the separation functional layer contains 50% or more of the crosslinked wholly aromatic polyamide, high performance membrane performance is easily exhibited.

  Moreover, a polyfunctional amine is specifically a polyfunctional aromatic amine, and a polyfunctional acid halide is a polyfunctional aromatic acid halide. The polycondensation reaction is interfacial polycondensation.

  Here, it is preferable that at least one of the polyfunctional aromatic amine and the polyfunctional aromatic acid halide contains a trifunctional or higher functional compound.

  Further, the thickness of the separation functional layer is usually in the range of 0.01 to 1 μm, preferably in the range of 0.1 to 0.5 μm, in order to obtain sufficient separation performance and the amount of permeated water. The separation functional layer in the present invention is hereinafter also referred to as a polyamide separation functional layer.

  The separation functional layer formed of the crosslinked wholly aromatic polyamide forms a fold shape in which the concave and the convex are repeated. The higher the convexity, the larger the surface area, so the effective membrane area becomes larger, and the water permeability is improved. Moreover, although the water permeability is lowered as the film thickness of the convex portion is larger, the chemical resistance is improved.

The inventors of the present invention have intensively studied and found that a multifunctional aromatic having an aromatic ring having at least one substituent other than a hydrogen atom satisfying Hammett's substituent constants σ _m ≦ 0.15 and σ _p ≦ 0.15. An interfacial polymerization reaction is carried out using an amine followed by chemical conversion to convert this functional group into an electron-withdrawing group satisfying Hammett's substituent constant σ _m 0.40.40, σ _p 0.500.50. It has been found that, by forming a large fold, a composite semipermeable membrane having improved oxidation resistance can be obtained.

  The crosslinked wholly aromatic polyamide functional layer constituting the composite semipermeable membrane of the present invention has a partial structure represented by the structural formula (1) at least one place on an aromatic ring derived from a polyfunctional aromatic amine. It features.

  Specifically, the crosslinked wholly aromatic polyamide functional layer constituting the composite semipermeable membrane of the present invention is a portion represented by the structural formula (1) at least one place on an aromatic ring derived from a polyfunctional aromatic amine It is characterized by having a structure.

Here, Ar ₁ is an aromatic ring having 6 to 14 carbon atoms having at least one substituent that satisfies Hammett's substituent constant σ _m 0.40.40, σ _p 0.500.50, and R ₁ and R ₂ are It is a hydrogen atom or an organic chain having 1 to 10 carbon atoms. The substituent that satisfies Hammett's substituent constant σ _m 0.40.40 and σ _p 0.500.50 that Ar ₁ has and is represented by the structural formula (1) is introduced by chemical treatment after interfacial polycondensation reaction.

The Hammett's substituent constant is, for example, L.I. P. It is the value which quantified the electronic property of the substituent on an aromatic ring which Hammett proposed based on an experimental value. The substituent constant of Hammett sets the reference hydrogen atom to 0, and the larger the value is, the more electron-withdrawing the substituent, and the smaller the value is, the more electron-donating. The symbol σ _m indicates the effect when the substituent is present at the meta position, and the symbol σ _p indicates the effect when present at the para position. The substituent constant of Hammett is, for example, C.I. Hansch, et al., 'Chemical Reviews' 91, 1991, p. Reference can be made at 165-195. In the present specification, the substituent is limited by the Hammett's substituent constant, but the case where the experimentally obtained Hammett's substituent constant is included within the indicated range is also applicable even if there is no description in the literature.

Examples of the substituent satisfying Hammett's substituent constant σ _m 0.40.40 and σ _p 0.500.50 include a cyano group, a nitroso group, a nitro group, a dimethylsulfonyl group and a dimethylphosphinyl group. The presence of substituents of Hammett's substituent constant σ _m 0.40.40 and σ _p 0.500.50 lowers the electron density of the amide group of the polyamide and the aromatic ring, and chlorine and other oxidizing agents The reactivity of the polyamide is suppressed and the oxidation resistance of the polyamide is improved.

  Furthermore, the crosslinked wholly aromatic polyamide in the present invention can also contain a partial structure represented by Formula (2).

In the formula (2), Ar ₂ is an aromatic ring having 6 to 14 carbon atoms which has at least one substituent other than a hydrogen atom satisfying Hammett's substituent constant σ _m ≦ 0.15, σ _p ≦ 0.15. And R ₃ and R _{4 each} represent a hydrogen atom or an organic chain having 1 to 10 carbon atoms. As a substituent other than a hydrogen atom satisfying σ _m ≦ 0.15, σ _p ≦ 0.15, dimethyl phosphino group, methyl sulfide group, methyl group, hydroxyamino group, 1-hydroxyethyl group and the like can be mentioned.

The substituent that satisfies the Hammett substituent constant σ _m m0.40 and σ _p 0.500.50 possessed by Ar ₁ of the structural formula (1) contained in the above-mentioned polyamide is a substituent having the Hammett substituent constant σ _m ≦ 0. It is obtained by chemical conversion from the substituent which satisfy | fills 15 and (sigma) _p <= 0.15. Examples of substituents obtained by chemical conversion include dimethylsulfonyl group, dimethylphosphinyl group, nitroso group, nitro group and the like. These substituents are obtained after the interfacial polycondensation reaction of a polyfunctional aromatic amine having a substituent satisfying the Hammett substituent constants σ _m ≦ 0.15 and σ _p ≦ 0.15 with a polyfunctional acid halide. , Can be induced by performing a chemical transformation.

  In the present specification, the term "polyfunctional aromatic amine" refers to one having at least one amino group of at least one of a primary amino group and a secondary amino group in one molecule, and at least one of the amino groups. One means an aromatic amine which is a primary amino group.

For example, polyfunctional aromatic amines such as o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m-diamino A multifunctional aromatic amine in which two amino groups such as pyridine and p-diaminopyridine are bonded to an aromatic ring at any of an ortho position, a meta position and a para position; 1,3,5-triaminobenzene; 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, 4-aminobenzylamine, 2,4-diaminothioanisole, 1,3-diaminothioanisole, 1,3- Diamino-5- (dimethylphosphino) benzene, (3,5-diaminophenyl) dimethylphosphine oxide, (2,4- Aminophenyl) dimethyl phosphine oxide, 1,3-diamino-5- (methylsulfonyl) benzene, 1,3-diamino-4- (methylsulfonyl) benzene, 1,3-diamino-5-nitrosobenzene, 1,3- Polyfunctional aromatic amines such as diamino-4-nitrosobenzene, 1,3-diamino-5- (hydroxyamino) benzene, 1,3-diamino-4- (hydroxyamino) benzene and the like can be mentioned. These polyfunctional aromatic amines may be used alone or in combination of two or more. However, it is always necessary that at least one polyfunctional aromatic amine has a substituent satisfying the Hammett's substituent constant σ _m ≦ 0.15 and σ _p ≦ 0.15. For example, 4-aminobenzylamine, 2,4-diaminothioanisole, 1,3-diaminothioanisole, 1,3-diamino-5- (dimethylphosphino) benzene, 1,3-diamino-5- (hydroxyamino) And benzene), 1,3-diamino-4- (hydroxyamino) benzene. The polyfunctional aromatic acid halide is also referred to as a polyfunctional aromatic carboxylic acid derivative, and refers to an aromatic acid halide having at least two halogenated carbonyl groups in one molecule. For example, in trifunctional acid halides, trimesic acid chloride and the like can be mentioned, and in bifunctional acid halides, biphenyldicarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalenedicarboxylic acid chloride and the like It can be mentioned. In view of reactivity with polyfunctional aromatic amines, the polyfunctional aromatic acid halide is preferably a polyfunctional aromatic acid chloride, and in view of the selective separation of the membrane and heat resistance, It is preferable that it is a polyfunctional aromatic acid chloride having 2 to 4 carbonyl chloride groups in it. Among them, trimesic acid chloride is more preferably used from the viewpoint of easy availability and handling. These polyfunctional aromatic acid halides may be used alone or in combination of two or more.

The convex part of the separation functional layer in the present invention means a convex part having a height of not less than one-fifth of the 10-point average surface roughness. The 10-point average surface roughness is a value obtained by the following calculation method. First, the cross section in the direction perpendicular to the film surface is observed with the following magnification by an electron microscope. In the obtained cross-sectional image, the surface of the separation functional layer (indicated by symbol “1” in FIG. 1) appears as a curve of a pleated structure in which the convex portions and the concave portions are continuously repeated. For this curve, a roughness curve defined according to ISO 4287: 1997 is determined. A cross-sectional image is extracted with a width of 2.0 μm in the direction of the mean line of the roughness curve (FIG. 1).

In addition, an average line is a straight line defined based on ISO4287: 1997, and it is drawn so that the sum of the area of the field surrounded by an average line and a roughness curve becomes equal above and below an average line in measurement length. Is a straight line.

In the extracted image having a width of 2.0 μm, the height of the convex portion and the depth of the concave portion in the separation functional layer are measured using the above average line as a reference line. The average value is calculated for the absolute values of the heights H1 to H5 of the five protrusions from the highest protrusion to the fifth height, and the depth gradually decreases from the deepest recess. Depth D1 of five depressions up to the fifth depth
The average value is calculated for the absolute values of to D5, and the sum of the absolute values of the two obtained average values is further calculated. The sum thus obtained is the 10-point average surface roughness.

The height intermediate value of the convex portion can be measured by a transmission electron microscope. First, the sample is embedded in a water-soluble polymer to prepare an ultrathin section for transmission electron microscopy (TEM). As the water-soluble polymer, any polymer that can maintain the shape of the sample may be used, and for example, PVA or the like can be used. Next, it is stained with OsO ₄ to facilitate cross-sectional observation, and this is cut with an ultramicrotome to make ultrathin sections. The ultra-thin section thus obtained is taken a cross-sectional photograph using a TEM. The height of the convex portion can be analyzed by reading a cross-sectional photograph into image analysis software. The height of the convex portion is a value measured for a convex portion having a height of 1⁄5 or more of the 10-point average surface roughness. The height intermediate value of the convex portion is measured as follows. In the composite semipermeable membrane, when observing cross sections at any 10 locations, the height of a convex portion which is at least one fifth of the above-mentioned 10-point average surface roughness is measured in each cross section. Further, by calculating the intermediate value based on the calculation results for the cross sections at ten locations, the convex portion height intermediate value can be obtained. Here, each cross section has a width of 2.0 μm in the direction of the mean line of the roughness curve.

The height of the convex portion of the separation functional layer in the present invention is preferably 50 nm or more, more preferably 70 nm or more. Further, the height of the convex portion of the separation functional layer is preferably 1000 nm or less, more preferably 800 nm or less. When the height of the convex portion is 50 m or more, a composite semipermeable membrane with sufficient water permeability can be easily obtained. In addition, when the height of the convex portion is 1000 nm or less, stable membrane performance can be obtained without the convex portion being crushed even when the composite semipermeable membrane is operated and used at high pressure.

2. Method for Producing Composite Semipermeable Membrane Next, a method for producing the composite semipermeable membrane will be described.

(2-1) Method of Producing Separation Functional Layer Next, the process of forming the separation functional layer constituting the composite semipermeable membrane will be described. The formation process of the separation functional layer is
(A) contacting an aqueous solution containing a polyfunctional aromatic amine on the porous support layer;
(B) contacting a porous support layer contacted with an aqueous solution containing a polyfunctional aromatic amine with an organic solvent solution containing a polyfunctional aromatic acid halide.

  In the step (a), the concentration of the polyfunctional aromatic amine in the polyfunctional aromatic amine aqueous solution is preferably in the range of 0.1% by weight to 20% by weight, more preferably 0.5% by weight to 15%. It is in the range of weight% or less. When the concentration of the polyfunctional aromatic amine is in this range, sufficient solute removal performance and water permeability can be obtained. The polyfunctional aromatic amine aqueous solution contains a surfactant, an organic solvent, an alkaline compound, an antioxidant, etc. as long as it does not disturb the reaction between the polyfunctional aromatic amine and the polyfunctional aromatic acid halide. It may be Surfactants have the effect of improving the wettability of the support membrane surface and reducing the interfacial tension between the polyfunctional aromatic amine aqueous solution and the nonpolar solvent. The organic solvent may act as a catalyst for the interfacial polycondensation reaction, and the addition may result in efficient interfacial polycondensation reaction.

  The contact of the polyfunctional aromatic amine aqueous solution is preferably carried out uniformly and continuously on the porous support layer. Specifically, for example, a method of coating a porous support layer with a polyfunctional aromatic amine aqueous solution, and a method of immersing a porous support layer in a polyfunctional aromatic amine aqueous solution can be mentioned. The contact time between the porous support layer and the aqueous polyfunctional amine solution is preferably 1 second or more and 10 minutes or less, and more preferably 10 seconds or more and 3 minutes or less.

  After bringing the aqueous solution of polyfunctional amine into contact with the porous support layer, the solution is sufficiently drained so that no droplets remain on the membrane. By sufficiently draining the solution, it is possible to prevent the drop in film performance due to the film defect due to the remaining portion of the droplet after the formation of the porous support layer. As a method of draining, for example, as described in JP-A-2-78428, there is a method in which a support film after contacting with a polyfunctional amine aqueous solution is held vertically and an excess aqueous solution is allowed to flow naturally, It is possible to use a method such as blowing a stream of nitrogen or the like from the air nozzle to forcibly remove the liquid. Also, after draining, the film surface can be dried to partially remove the water content of the aqueous solution.

  In the step (b), the concentration of the polyfunctional acid halide in the organic solvent solution is preferably in the range of 0.01% by weight or more and 10% by weight or less, and is 0.02% by weight or more and 2.0% by weight or less It is further preferable to be within the range of When the content is 0.01% by weight or more, a sufficient reaction rate can be obtained, and when the content is 10% by weight or less, the occurrence of side reactions can be suppressed. Furthermore, it is more preferable to include an acylation catalyst such as DMF in this organic solvent solution, which promotes interfacial polycondensation, which is more preferable.

  The organic solvent is preferably one which is immiscible with water and dissolves the polyfunctional acid halide and does not destroy the support film, and is inert to the polyfunctional amine compound and the polyfunctional acid halide. I hope there is. Preferred examples include hydrocarbon compounds such as n-hexane, n-octane, n-decane and isooctane.

  The method of contacting an organic solvent solution of a polyfunctional aromatic acid halide with a porous support layer in contact with an aqueous solution of a polyfunctional aromatic amine compound is a method of coating a porous support layer with an aqueous solution of polyfunctional aromatic amine and You can do it in the same way.

  At this time, the porous support layer contacted with the organic solvent solution of the polyfunctional aromatic acid halide may be heated. The temperature for the heat treatment is 50 ° C. or more and 180 ° C. or less, preferably 60 ° C. or more and 160 ° C. or less. By heating at 60 ° C. or higher, the decrease in reactivity accompanying monomer consumption in the interfacial polymerization reaction can be compensated by the effect of promoting the reaction by heat. Heating at 160 ° C. or lower can prevent the solvent from completely volatilizing and the reaction efficiency from being significantly reduced.

  In addition, the heat treatment time of each time is preferably 5 seconds or more and 180 seconds or less. The effect of accelerating the reaction can be obtained by setting it to 5 seconds or more, and the solvent can be prevented from completely volatilizing by setting it to 180 seconds or less.

Furthermore, the composite semipermeable membrane obtained is subjected to a chemical treatment, and a substituent having a Hammett's substituent constant σ _m ≦ 0.15 and a σ _p ≦ 0.15 possessed by the polyamide is a Hammett's substituent constant σ _m ≧ Convert into a substituent satisfying 0.40, σ _p 0.50 0.50. Examples of such chemical treatment include oxidation treatment. Specifically, a water-soluble oxidizing agent is preferably brought into contact with the composite semipermeable membrane, and examples of the water-soluble oxidizing agent include hydrogen peroxide, peracetic acid, sodium perborate, potassium peroxymonosulfate and the like. Can.

3. Use of Composite Semipermeable Membrane The composite semipermeable membrane of the present invention comprises a large number of pores together with a feed water flow path material such as a plastic net, a permeate flow flow path material such as tricot, and a film for enhancing pressure resistance as needed. It is wound around a cylindrical water collection tube formed by drilling and is suitably used as a spiral type composite semipermeable membrane element. Furthermore, the elements may be connected in series or in parallel to form a composite semipermeable membrane module housed in a pressure vessel.

  In addition, the composite semipermeable membrane described above, its elements and modules can be combined with a pump for supplying supply water thereto, an apparatus for pretreating the supply water, or the like to constitute a fluid separation apparatus. By using this separation device, it is possible to separate the feed water into the permeate water such as drinking water and the concentrated water which has not permeated through the membrane, and to obtain the intended water.

  A liquid mixture containing 500 mg / L or more and 100 g / L or less of TDS (Total Dissolved Solids: total dissolved solids) such as seawater, brackish water, waste water, etc. as feed water to be treated by the composite semipermeable membrane according to the present invention It can be mentioned. In general, TDS refers to the total dissolved solids, expressed as "mass to volume" or "weight ratio". According to the definition, it can be calculated from the weight of the residue by evaporating the solution filtered with a 0.45 micron filter at a temperature of 39.5 ° C. or more and 40.5 ° C. or less, but more simply the practical salt content (S) Convert from

  The higher the operating pressure of the fluid separation device, the higher the solute removal rate, but the energy required for operation also increases, and in view of the durability of the composite semipermeable membrane, the composite semipermeable membrane is treated with treated water. The operating pressure at the time of permeation is preferably 0.5 MPa or more and 10 MPa or less. In addition, if the pH of the feed water is high, in the case of feed water with high solute concentration such as seawater, there is a risk that scales such as magnesium may be generated, and there is a concern that the membrane may be degraded by high pH operation. Driving at is preferred.

EXAMPLES The present invention will be described in more detail by the following examples, but the present invention is not limited by these examples.

  The various properties of the composite semipermeable membrane were carried out by supplying a 2000 mg / L NaCl aqueous solution adjusted to a temperature of 25 ° C. and pH 7 to the composite semipermeable membrane at an operating pressure of 1.55 MPa and performing membrane filtration treatment for 24 hours, , By measuring the quality of the water supply.

(Solute removal rate (TDS removal rate)) TDS removal rate (%) = 100 × {1- (TDS concentration in permeate water / TDS concentration in feed water)}
(Membrane permeation flux)
The membrane permeation flux (m ³ / m ² / day) was expressed by the permeating water flow rate of the feed water (seawater) in terms of the water permeation rate (cubic meter) per day per square meter of membrane surface.

(Chlorine resistance)
The composite semipermeable membrane is immersed in a 500 mg / L sodium hypochlorite aqueous solution adjusted to pH 6.5 under an atmosphere of 25 ° C. for 20 hours. Then, after immersing in a 1000 mg / L sodium bisulfite aqueous solution for 10 minutes, after thoroughly washing with water, it was determined by evaluating the boron removal rate of the composite semipermeable membrane.

(Preparation of support film)
A 16.0 wt% DMF solution of polysulfone (PSf) is cast on a polyester non-woven fabric (air flow rate 2.0 cc / cm ² / sec) at a thickness of 200 μm under conditions of 25 ° C. and immediately immersed in pure water A porous support membrane was made by standing for 5 minutes.

(Comparative example 1)
According to the method described in WO2011 / 1057278, the porous support membrane obtained by the above-mentioned operation has a concentration of 0.2 mol / L of sodium hydroxide and 0.2 mol / L of 1,3-diamino-4-sulfonic acid. For 2 minutes in a solution of water / acetonitrile mixed solvent (1: 1, v / v) contained in After that, the support film was slowly pulled up vertically, nitrogen was blown from an air nozzle, and excess aqueous solution was removed from the surface of the support film. Furthermore, a decane solution at 25 ° C. containing 0.165% by weight of trimesic acid chloride (TMC) is applied so that the surface becomes completely wet and allowed to stand for 10 seconds, and then allowed to stand for 120 seconds in an oven at 25 ° C. , To obtain a composite semipermeable membrane. The water production amount at the time of production of the obtained composite semipermeable membrane, the NaCl removal rate, and the NaCl removal rate after the evaluation of chlorine resistance are shown in Table 1. In addition, the clear convex part and the recessed part were not seen in the polyamide functional layer.

(Comparative example 2)
The porous support membrane obtained by the above-mentioned operation is prepared by mixing 1: 1 water / acetonitrile mixed solvent (1: 1, v / 1) containing 1,3-diamino-4-thioanisole at a concentration of 0.2 mol / L. Soak the solution of v) for 2 minutes. After that, the support film was slowly pulled up vertically, nitrogen was blown from an air nozzle, and excess aqueous solution was removed from the surface of the support film. Furthermore, a decane solution at 25 ° C. containing 0.165% by weight of trimesic acid chloride (TMC) is applied so that the surface becomes completely wet and allowed to stand for 10 seconds, and then allowed to stand for 120 seconds in an oven at 25 ° C. A composite semipermeable membrane was obtained. The water production amount at the time of production of the obtained composite semipermeable membrane, the NaCl removal rate, and the NaCl removal rate after the evaluation of chlorine resistance are shown in Table 1.

Example 1
1: 1 water / acetonitrile mixed solvent (1: 1, v / 1) containing the porous support membrane obtained by the above operation at a concentration of 0.2 mol / L of 1,3-diamino-4-thioanisole Soak the solution of v) for 2 minutes. After that, the support film was slowly pulled up vertically, nitrogen was blown from an air nozzle, and excess aqueous solution was removed from the surface of the support film. Furthermore, a decane solution at 25 ° C. containing 0.165% by weight of trimesic acid chloride (TMC) was applied so that the surface was completely wet, and allowed to stand for 10 seconds, and then allowed to stand for 120 seconds in an oven at 25 ° C. The obtained composite semipermeable membrane was subjected to oxidation treatment by being immersed in 1% by weight, hydrogen peroxide solution of pH 3 for 30 minutes to convert a thiomethyl group into a dimethylsulfonyl group. Then, the composite semipermeable membrane was obtained by immersing in an aqueous solution of 0.1% by weight sodium bisulfite for 10 minutes and further immersing in RO water for 10 minutes.

  The water production amount at the time of production of the obtained composite semipermeable membrane, the NaCl removal rate, and the NaCl removal rate after the evaluation of chlorine resistance are shown in Table 1. The median value of the heights of the protrusions of the polyamide functional layer was 70 nm.

(Example 2)
A composite semipermeable membrane was obtained by the same operation as in Example 1 except that the treatment with hydrogen peroxide solution was performed for 24 hours. The water production amount at the time of production of the obtained composite semipermeable membrane, the NaCl removal rate, and the NaCl removal rate after the evaluation of chlorine resistance are shown in Table 1.

(Example 3)
The porous support membrane obtained by the above-mentioned operation is prepared by mixing 3% by weight of 1,3-diamino-4- (dimethylphosphino) -benzene with 1: 1 water / acetonitrile mixed solvent (1: 1, v / v) The solution was immersed for 2 minutes. After that, the support film was slowly pulled up vertically, nitrogen was blown from an air nozzle, and excess aqueous solution was removed from the surface of the support film. Furthermore, a decane solution at 25 ° C. containing 0.165% by weight of trimesic acid chloride (TMC) was applied so that the surface was completely wet, and allowed to stand for 10 seconds, and then allowed to stand for 120 seconds in an oven at 25 ° C. The obtained composite semipermeable membrane was subjected to oxidation treatment by being immersed in 1% by weight, hydrogen peroxide solution of pH 3 for 30 minutes to convert dimethyl phosphino group into dimethyl phosphinyl group. Then, the composite semipermeable membrane was obtained by immersing in an aqueous solution of 0.1% by weight sodium bisulfite for 10 minutes and further immersing in RO water for 10 minutes.

  The water production amount at the time of production of the obtained composite semipermeable membrane, the NaCl removal rate, and the NaCl removal rate after the evaluation of chlorine resistance are shown in Table 1. The median value of the heights of the projections of the polyamide functional layer was 80 nm.

Thus, in Example 1 using a polyfunctional aromatic amine having a substituent satisfying Hammett's substituent constant σ _m = 0.15, σ _p = 0.00, a fold larger than Comparative Example 1 can be obtained. As a result, the water production amount is increased, and the oxidation resistance is further improved compared to Comparative Example 2 in which conversion is not performed by conversion to a substituent of σ _m = 0.60, σ _p = 0.72 by oxidation treatment. Know that It is understood that Example 2 in which the oxidation reaction is performed for a longer time and the conversion rate is improved is higher in oxidation resistance.

The composite semipermeable membrane of the present invention can be particularly suitably used for desalination of brackish water and seawater.

Claims (3)

A substrate,
A porous support layer formed on the substrate;
A separation functional layer provided on the porous support layer and containing a polyamide obtained by the polycondensation of a polyfunctional amine and a polyfunctional acid halide,
The composite semipermeable membrane which has the partial structure in which the said polyamide is represented by (1).

(Wherein, Ar ₁ is an aromatic ring having 6 to 14 carbon atoms having at least one of a methylsulfonyl group or a dimethylphosphinyl group as a substituent , and R ₁ and R _{2 each} represent a hydrogen atom or a carbon atom 10 organic chains.) The composite semipermeable membrane according to claim 1, wherein the polyamide further has a partial structure represented by Formula (2).

(Here, Ar ₂ is an aromatic ring having 6 to 14 carbon atoms having at least one of a methyl sulfide group or a dimethyl phosphino group as a substituent , and R ₃ and R _{4 each} represent a hydrogen atom or a carbon atom of 1 to 10) Organic chains of The composite semipermeable membrane according to claim 1 or 2 , wherein the separation functional layer containing a polyamide has a pleated structure, and the median value of the heights of protrusions in the pleated structure is 50 nm or more.

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