JP2020054997A - Composite semipermeable membrane - Google Patents

Abstract

To provide a composite semipermeable membrane using an AS resin as a material of a porous support, in which a thickness change of a support film is small.SOLUTION: A composite semipermeable membrane includes a base material, a porous support arranged on the base material and a separation function layer arranged on the porous support, in which the porous support includes a dense layer in contact with the separation function layer, a major axis of a hole included in the dense layer is less than 100 nm, a thickness of the dense layer is 300 nm or more, the porous support contains a thermoplastic resin as a main component, and a weight average molecular weight Mw of the thermoplastic resin is 140,000 or more.SELECTED DRAWING: Figure 1

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 or brackish water, for example.

With respect to separation of mixtures, there are various techniques for removing substances (eg, salts) dissolved in a solvent (eg, water). In recent years, the use of the membrane separation method as a process for energy saving and resource saving is expanding. The membrane used in the membrane separation method includes a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane, and the like. These membranes are currently commercially available, for example, used for obtaining drinking water from seawater, brackish water, water containing harmful substances, and for producing industrial ultrapure water, wastewater treatment, and collecting valuable resources. Most filtration membranes, especially reverse osmosis and nanofiltration membranes, are composite semipermeable membranes. Patent Literature 1 discloses a composite semipermeable membrane including a support membrane including a base material and a porous support, and a separation functional layer provided on the porous support. Further, as the thermoplastic resin contained in the porous support, polysulfone, polyacrylamide, polyestersulfone, cellulose ester, polyacrylonitrile, polyvinyl chloride and the like are disclosed. Patent Document 2 discloses a copolymer based on polyacrylonitrile as a material for a support.

WO2014 / 192883 US2012 / 181228

  In use, a large pressure is applied to the filtration membrane. Then, a defect may occur due to deformation of the filtration membrane due to pressurization. Therefore, strength (pressure resistance) is required for the filtration membrane.

  An object of the present invention is to provide a new porous support that realizes pressure resistance of a filtration membrane, particularly a composite semipermeable membrane.

In order to achieve the above object, the present invention has the following configurations.
[1] A composite semipermeable membrane including a base material, a porous support disposed on the base material, and a separation functional layer disposed on the porous support,
The porous support includes a dense layer in contact with the separation function layer,
The major axis of the pores contained in the dense layer is less than 100 nm,
The thickness of the dense layer is 300 nm or more,
A composite semipermeable membrane comprising a thermoplastic resin having a weight average molecular weight Mw of the porous support of 140,000 or more as a main component.
[2] The composite semipermeable membrane according to the above [1], wherein the thermoplastic resin is a polymer of a vinyl cyanide monomer and an aromatic vinyl monomer.
[3]
A thermoplastic resin having a weight average molecular weight Mw of 140,000 or more, and a good solvent thereof, having a Hansen solubility parameter having a polarity term dP of 11.0 to 17.0 and a hydrogen bond term dH of 7.0 to 12.12. Applying a resin solution containing a solvent that is 0 or less to the substrate,
The substrate coated with the solution of the thermoplastic resin, the thermoplastic resin is coagulated by immersing in a coagulation bath containing a non-solvent having a small solubility compared to the good solvent of the thermoplastic resin, the porous Forming a support,
By performing interfacial polycondensation on the surface of the porous support using an aqueous solution containing a polyfunctional amine and a water-immiscible organic solvent solution containing a polyfunctional acid halide, the separation functional layer is formed. A method for producing a composite semipermeable membrane, comprising the step of forming

  Since the composite semipermeable membrane of the present invention has a certain weight average molecular weight of the thermoplastic resin or more, even when used under a high pressure condition of 4.0 MPa or more, the composite semitransparent membrane has a small change in thickness of the support film and a pressure resistance. Can be obtained.

FIG. 3 is a schematic sectional view of a composite semipermeable membrane.

1. Composite Semipermeable Membrane The composite semipermeable membrane according to the present invention comprises a support membrane comprising a base material and a porous support disposed on the base material, and a polyamide separation functional layer disposed on the porous support ( Hereinafter, it may be simply referred to as “separation function layer”.). The separation function layer has substantially separation performance, and the support membrane has substantially no separation performance of ions and the like, and can provide strength to the separation function layer.

(1-1) Support membrane In the present invention, the support membrane includes a substrate and a porous support disposed on the substrate.

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

The substrate 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 base material is within the above range, the polymer solution serving as the porous support impregnates the base material, so that the adhesiveness with the base material is improved and the physical stability of the support film is increased. be able to.

  The air permeability can be measured by a Frazier-type tester based on JIS L1096 (2010).

  For example, a base material is cut out to a size of 200 mm × 200 mm to obtain a sample. This sample was mounted on a Frazier tester, and the suction fan and air holes were adjusted so that the pressure of the inclined barometer was 125 Pa. Based on the pressure indicated by the vertical barometer and the type of air holes used, It is possible to calculate the amount of air passing through the material, that is, the air permeability. As the Frazier-type tester, KES-F8-AP1 manufactured by Kato Tech Co., Ltd. can be used.

  The thickness of the substrate is preferably 20 μm or more and 200 μm or less, more preferably 40 μm or more, and even more preferably 120 μm or less.

  The thickness of the substrate can be measured with a dial thickness gauge or a digital thickness gauge. As the dial thickness gauge or the digital thickness gauge, products of PEACACK of Ozaki Seisakusho Co., Ltd. or Teklock Co., Ltd. can be used. When a dial thickness gauge or a digital thickness gauge is used, the thickness is measured at any 20 locations, the arithmetic average thereof is calculated, and the arithmetic average is used as the thickness of the base material.

  When it is difficult to measure the thickness of the substrate with a dial thickness gauge or digital thickness gauge, the thickness may be measured with an optical microscope or a scanning electron microscope.

(1-1-2) Porous support The porous support includes a dense layer in contact with the separation function layer, a major axis of pores included in the dense layer is less than 100 nm, and a thickness of the dense layer is 300 nm. That is all. In addition, the main component is a thermoplastic resin having a weight average molecular weight Mw of 140,000 or more or 180,000 or more contained in the porous support. "Main component" refers to a component that accounts for 50% by mass or more of the porous support.

  The present inventors have conducted intensive studies and as a result, by setting the porous support as described above, the composite semipermeable membrane having a small thickness change (high pressure resistance) of the support film even under a high pressure condition of 4.0 MPa or more. Was obtained. The reason why the pressure resistance is improved is that the toughness and rigidity near the surface of the porous support are improved by forming a dense layer having a small pore size with a certain thickness or more using a thermoplastic resin having a high weight average molecular weight. Therefore, it is considered that deformation due to pressure is suppressed.

  The porous support preferably contains, as a main component, a polymer (vinyl copolymer) of a vinyl cyanide monomer and an aromatic vinyl monomer. Here, the thermoplastic resin is a resin that is made of a chain-like polymer material and has a property of being deformed or flowed by an external force when heated.

  Examples of the vinyl cyanide-based monomer include acrylonitrile, methacrylonitrile, and ethacrylonitrile, and acrylonitrile is preferably used. The vinyl cyanide-based monomer contained in the copolymer may be one type, or two or more types may be mixed.

  Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, t-butylstyrene, o-ethylstyrene, o-chlorostyrene, and o, p-dichlorostyrene. And styrene and α-methylstyrene are particularly preferably used. The aromatic vinyl monomer contained in the copolymer may be a single kind or a mixture of two or more kinds.

  The proportion of the vinyl cyanide monomer in the vinyl monomer constituting the vinyl copolymer is preferably from 5% by weight to 60% by weight, more preferably from 10% by weight to 40% by weight. And more preferably 15% by weight or more and 30% by weight or less. When the proportion is 5% by weight or more, a porous support having high pressure resistance is realized. Further, when the proportion is 60% by weight or less, the amine release property at the time of interfacial polycondensation is increased and large folds are formed, so that the water permeability of the composite semipermeable membrane is enhanced.

  The proportion of the aromatic vinyl-based monomer in the vinyl-based monomer constituting the vinyl-based copolymer is preferably from 40 to 95% by weight, more preferably from 60 to 90% by weight, even more preferably. Is 70% by weight or more and 85% by weight or less. When the content is 40% by weight or more, the porous support and the separation functional layer are firmly adhered to each other, so that occurrence of defects is suppressed. When the content is 95% by weight or less, a porous support having high pressure resistance is realized.

  The weight average molecular weight (Mw) of the tetrahydrofuran (THF) soluble component in the porous support is 140,000 or more or 180,000 or more, and more preferably 320,000 or more. When Mw is at least 140,000, the major axis of the pores contained in the dense layer of the porous support can be reduced. Further, when Mw is 140,000 or more, the thickness of the dense layer of the porous support can be increased.

  The weight-average molecular weight (Mw) of the THF-soluble component in the porous support can be measured by the following method. First, the support membrane or the composite semipermeable membrane cut into a predetermined area is thoroughly washed with warm water and air-dried at room temperature. Next, only the porous support was dissolved by contacting with THF, and the resulting solution was filtered through a metal mesh (wire diameter 0.03 mm, mesh 300, manufactured by Kansai Wire Mesh Co., Ltd.) to obtain a substrate and a function. Remove the layer. Subsequently, the obtained filtrate was subjected to 8800 rpm. p. After centrifugation at m (10,000 G or more) for 40 minutes, the supernatant is collected. The obtained supernatant is measured by gel permeation chromatography (GPC) using THF as a solvent and polystyrene as a standard substance to determine a weight average molecular weight.

  The thickness of the porous support is preferably 10 μm or more and 100 μm or less. If the thickness is less than 10 μm, the substrate may be exposed and a defect may occur. If the thickness exceeds 100 μm, the water permeability decreases due to the resistance due to the thickness of the porous support.

  The thickness of the porous support is controlled by the type of solvent that dissolves the thermoplastic resin, the viscosity of the thermoplastic resin solution, the concentration of the thermoplastic resin solution, the coagulation bath temperature, and the thickness of the thermoplastic resin solution applied to the substrate. can do.

  The thickness of the porous support can be measured by cross-sectional observation using a scanning electron microscope (SEM) or an optical microscope. Even in the case of a composite semipermeable membrane, the thickness of the separation functional layer is extremely thin compared to the base material and the porous support. Therefore, determine the thickness of the porous support from the cross-sectional observation results of the composite semipermeable membrane. Can be. When measuring by SEM, it can be determined by the following method. The composite semipermeable membrane or the supporting membrane is cut by a freeze splitting method to prepare a section sample, and the section sample is observed with a SEM at a magnification of 100 to 500 times. From the obtained image, arbitrary 10 points of thickness (preferably measured at 10 μm intervals) are measured in a direction perpendicular to the thickness direction (plane direction of the film) using a scale or a caliper. The same operation is performed on five section samples, and the arithmetic mean of 50 pieces of data is calculated to be the thickness of the porous support. Before observation by SEM, the sample is thinly coated with platinum, platinum-palladium or ruthenium tetroxide. As the SEM, an S-5500 scanning electron microscope manufactured by Hitachi High-Technologies Corporation can be used, and observation is performed at an acceleration voltage of 3 to 6 kV.

  Further, the thickness of the support film and the porous support can also be measured with a dial thickness gauge or a digital thickness gauge as in the case of the base material. Since the thickness of the separation functional layer is very thin compared to the base material and the porous support, the thickness of the composite semipermeable membrane can be regarded as the total thickness of the base material and the porous support (the thickness of the support film). it can. Therefore, the thickness of the porous support can be easily calculated by measuring the thickness of the composite semipermeable membrane with a dial thickness gauge or digital thickness gauge and subtracting the thickness of the base material from the thickness of the composite semipermeable membrane. it can. When a dial thickness gauge or a digital thickness gauge is used, the thickness is measured at any 20 locations, and the arithmetic mean thereof is calculated.

  The dense layer 40 refers to a layer in which the major axis of the included hole 42 is less than 100 nm. Further, the major axis of the pores contained in the dense layer is preferably 2 nm or more.

  The macrovoid layer 41 is a layer including a hole 43 having a major axis of 500 nm or more (hereinafter, referred to as “macrovoid”). It is preferable that the thickness of the macrovoid layer 41 be 5 μm or more and 95 μm or less.

  Whether or not the porous support 4 satisfies the above conditions can be confirmed as follows. The composite semipermeable membrane 1 is cut at an arbitrary position perpendicularly to the membrane surface direction to obtain a cross section. The width of the cross section is 10 μm or more. Observing this cross section, if there is a layer of pores having a major axis of less than 100 nm from the interface A between the separation function layer and the porous support, a portion (apex) farthest from the separation function layer among the outer edges of the pores and the separation function The distance from the layer 5 is measured. If there is a plurality of holes 42 from the vertices, the distance between the vertices of the holes 42 farthest from the separation function layer and the separation function layer 5 may be measured. This distance (the distance between AB in FIG. 1) is the thickness of the dense layer 40.

  From the interface A between the separation function layer 5 and the dense layer 40, the major axis of the hole 42 is measured at the interface B between the dense layer 41 and the macrovoid layer. It is sufficient that the major axis is less than 100 nm and the thickness of the dense layer is 300 nm or more.

  Further, it is preferable that the dense layer and the macrovoid layer have a continuous structure. The “continuous structure” refers to a structure in which no skin layer is formed at the interface between the dense layer and the macrovoid layer. Here, the skin layer means a portion having a high density. Specifically, the surface pores of the skin layer are in the range of 2 nm or more and less than 100 nm.

  The thickness of the support membrane (the sum of the thickness of the base material and the thickness of the porous support) affects the strength of the composite semipermeable membrane and the packing density when the composite semipermeable membrane is used as an element. In order to obtain sufficient mechanical strength and packing density, the total thickness of the support film is preferably 30 μm or more and 300 μm or less, more preferably 80 μm or more and 200 μm or less.

The pure water permeability coefficient of the support membrane at 25 ° C. is preferably 1.0 × 10 ⁻⁹ m ³ / (m ² · s · Pa) or more.

The pure water permeability coefficient of the support membrane can be determined by the following method. First, the supporting membrane is thoroughly washed with pure water. Next, the sample is cut into a circle having a diameter of 4.3 cm, and the cut sample is set in a stirring-type ultra holder (UHP-43K manufactured by Advantech Toyo Co., Ltd.). Subsequently, pure water at 25 ° C. is put into the cell, a cap is attached, and the pressure is increased to 100 kPa with nitrogen or compressed air. Finally, the pure water permeation amount in a certain time is measured, and the pure water permeation coefficient (m ³ / (m ² · s · Pa), 25 ° C.) is calculated from the following equation.

Pure water permeability coefficient = Pure water permeability ÷ (membrane area x water sampling time x supply pressure)
(1-2) Polyamide Separation Function Layer The polyamide separation function layer has a thin film mainly composed of polyamide obtained by a polycondensation reaction between a polyfunctional amine and a polyfunctional acid halide. That is, the polyamide occupies 50% by mass or more in the separation function layer.

  The polyamide separation functional layer can be formed by interfacial polycondensation between a polyfunctional amine and a polyfunctional acid halide.

  Here, it is preferable that at least one of the polyfunctional amine and the polyfunctional acid halide contains a compound having three or more functional groups.

  The polyfunctional amine means an amine having at least two amino groups of at least one of a primary amino group and a secondary amino group in one molecule.

  For example, piperazine, 2,5-dimethylpiperazine, 2-methylpiperazine, 2,6-dimethylpiperazine, 2,3,5-trimethylpiperazine, 2,5-diethylpiperazine, 2,3,5-triethylpiperazine, 2- aliphatic polyfunctional amines such as n-propylpiperazine, 2,5-di-n-butylpiperazine, ethylenediamine; o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-xylylenediamine, m-xylylenediamine Two amino groups such as amine, p-xylylenediamine, o-diaminopyridine, m-diaminopyridine, and p-diaminopyridine are bonded to an aromatic ring in any of ortho, meta, and para positions. Polyfunctional aromatic amine; 1,3,5-triaminobenzene, 1,2,4-triaminoben Emissions, 3,5-diaminobenzoic acid, 3-amino-benzylamine, such a polyfunctional aromatic amines such as 4-aminobenzyl amine.

  Among them, piperazine, m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, and 2-methylpiperazine are preferably used in consideration of the selective separation property, permeability and heat resistance of the membrane. These polyfunctional amines may be used alone or in combination of two or more.

  The polyfunctional acid halide refers to an acid halide having at least two carbonyl halide groups in one molecule.

  For example, trifunctional acid halides include trimesic acid chloride, 1,3,5-cyclohexanetricarboxylic acid trichloride, 1,2,4-cyclobutanetricarboxylic acid trichloride and the like. Bifunctional dicarboxylic acid halides include biphenyldicarboxylic acid. Aromatic difunctional acid halides such as acid dichloride, azobenzene dicarboxylic dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalene dicarboxylic acid chloride, etc., aliphatic bifunctional acid halides such as adipoyl chloride, sebacoyl chloride, cyclopentane Alicyclic difunctional acid halides such as dicarboxylic acid dichloride, cyclohexanedicarboxylic acid dichloride, tetrahydrofurandicarboxylic acid dichloride and the like can be mentioned.

  In consideration of the reactivity with the polyfunctional amine, the polyfunctional acid halide is preferably a polyfunctional aromatic acid chloride. It is preferably a polyfunctional aromatic acid chloride having 2 to 4 carbonyl chloride groups. Among these, trimesic acid chloride, terephthalic acid chloride, and isophthalic acid chloride are more preferable from the viewpoint of availability and ease of handling. These polyfunctional aromatic acid halides may be used alone or in combination of two or more.

  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.

2. Method for Manufacturing Composite Semipermeable Membrane A method for manufacturing a composite semipermeable membrane will be described. The manufacturing method includes a step of forming a support film and a step of forming a separation functional layer. The composite semipermeable membrane of the present invention is not limited to the manufacturing method and the method for forming each layer described in this document.

(2-1) Step of Forming Support Film The step of forming the support film includes, for example, (i) a step of applying a solution of a thermoplastic resin to a substrate, and (ii) a step of applying the solution of the thermoplastic resin. A step of immersing the substrate in a coagulation bath containing a non-solvent having a lower solubility than the good solvent of the thermoplastic resin to solidify the thermoplastic resin and form a porous support. In the step of forming the support film, before the step (i), the thermoplastic resin as a component of the porous support is dissolved in a good solvent of the thermoplastic resin to prepare a solution of the thermoplastic resin. The method may further include a step, or may include a step of impregnating the substrate with the solution of the thermoplastic resin after the step (i). (I) a step of applying a solution of the thermoplastic resin to the substrate For example, a spin coater, flow coater, roll coater, spray, comma coater, bar coater, gravure coater, slit die coater and the like can be used.

  The solution of the thermoplastic resin can be adjusted by using a thermoplastic resin composition obtained by melt-mixing the thermoplastic resin, or adding and mixing the thermoplastic resin at the time of melting. The method of melt mixing is not particularly limited, and a method of melt mixing using a single screw or a twin screw with a heating device and a cylinder having a vent can be used.

  The concentration of the thermoplastic resin in the thermoplastic resin solution is preferably from 10% by weight to 40% by weight, more preferably from 15% by weight to 30% by weight. When the concentration of the thermoplastic resin is 15% by weight or more and 30% by weight or less, a support film having a strength that can withstand practical use can be obtained.

  The solvent that dissolves the thermoplastic resin is a good solvent for the thermoplastic resin, and has a polarity parameter dP of the Hansen solubility parameter of 11.0 or more and 17.0 or less, and a hydrogen bond term dH of 7.0 or more and 12.0 or less. Is preferred. The good solvent for the thermoplastic resin is one that dissolves the thermoplastic resin. As the solvent, for example, at least one solvent selected from the group consisting of sulfoxides, amides, lower alkyl ketones, esters and lactones is preferable. More specifically, examples of good solvents include N-methyl-2-pyrrolidone (NMP), dimethylsulfoxide (DMSO), dimethylacetamide (DMAC), dimethylformamide (DMF), and γ-butyrolactone (GBL). Further, a solvent in which the polarity term dP of the Hansen solubility parameter is 11.0 or more and 17.0 or less and the hydrogen bond term dH is 7.0 or more and 12.0 or less by mixing may be used. In particular, dimethyl sulfoxide (DMSO) or a mixed solvent of DMSO and the above-mentioned other solvents is preferable.

  In particular, by using dimethyl sulfoxide (DMSO) or a mixed solvent containing dimethyl sulfoxide (DMSO) and another solvent and having dP and dH in the above-described range, the dense layer in the porous support can be formed. The thickness can be 300 nm or more. Further, it is also effective to make the difference between the melting point of the good solvent contained in the resin solution and the temperature of the coagulation bath solution within ± 20 ° C. to make the thickness of the dense layer 300 nm.

  The thermoplastic resin solution may contain an additive for adjusting the pore size, porosity, hydrophilicity, elastic modulus and the like of the porous support. Examples of additives for adjusting the pore size and porosity include water, alcohols, water-soluble polymers such as polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid or salts thereof, and further include lithium chloride, sodium chloride, and chloride. Examples thereof include inorganic salts such as calcium and lithium nitrate, and formamide, but are not limited thereto. Various surfactants can be used as additives for adjusting hydrophilicity and elastic modulus.

  By applying the thermoplastic resin solution to the base material as described above, the thermoplastic resin solution is impregnated in the base material, but in order to obtain a support film without defects, the thermoplastic resin solution is applied to the base material. It is necessary to control the impregnation. In order to control the amount of impregnation of the thermoplastic resin solution into the substrate, for example, a method of controlling the time until the substrate is immersed in a coagulation bath after applying the thermoplastic resin solution on the substrate, or There is a method of adjusting the viscosity by controlling the temperature or concentration of the solution, and these methods can be combined.

  The temperature of the solution at the time of applying the thermoplastic resin solution is preferably in the range of 5 to 60C, more preferably in the range of 10 to 40C. Within this range, the thermoplastic resin solution does not precipitate, and the organic solvent solution of the thermoplastic resin is sufficiently impregnated between the fibers of the base material and then easily solidified. As a result, it is possible to obtain a support film in which the porous support is firmly bonded to the substrate by the anchor effect.

  The time from application of the thermoplastic resin solution on the substrate to immersion in the coagulation bath is usually preferably in the range of 0.1 to 5 seconds. If the time until immersion in the coagulation bath is within this range, the thermoplastic resin solution is sufficiently impregnated between the fibers of the base material and then solidified. The preferred range of the time until immersion in the coagulation bath may be appropriately adjusted depending on the viscosity of the thermoplastic resin solution used.

  The coagulation bath contains a good solvent for the thermoplastic resin described above and a non-solvent having a lower solubility than the good solvent. Non-solvents include, for example, water, hexane, pentane, benzene, toluene, methanol, ethanol, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol, low molecular weight polyethylene glycol, and the like. Aliphatic hydrocarbons, aromatic hydrocarbons, aliphatic alcohols, and mixed solvents thereof. Generally, water is used.

  The temperature of the coagulation bath is preferably from -20C to 50C. More preferably, it is 5 to 40C. If the temperature exceeds 50 ° C., the vibration of the coagulation bath surface becomes intense due to thermal motion, and the smoothness of the film surface after film formation tends to decrease. If the temperature is lower than −20 ° C., the coagulation rate becomes slow, and the film forming property may be deteriorated.

  Further, the difference between the melting point of the good solvent contained in the resin solution and the temperature of the coagulation bath solution is preferably within ± 20 ° C.

  Next, the support film obtained above is washed with pure water in order to remove the solvent remaining in the support film. The temperature of the pure water at this time is preferably 25 to 80C.

  As the method for producing the vinyl copolymer constituting the porous support, any of polymerization methods such as emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization can be used. Two or more of these may be combined. There are no particular restrictions on the method of charging each monomer.Initial batch charging, or continuous or divided charging and polymerization of part or all of the charged monomers in order to know the composition distribution of the copolymer. You may. The suspension polymerization method or the bulk polymerization method is preferred, and the suspension polymerization method is most preferred in view of the ease of polymerization control and the ease of post-treatment.

  Examples of the suspension stabilizer used for suspension polymerization include inorganic suspension stabilizers such as clay, barium sulfate, and magnesium hydroxide, and organic solvents such as polyvinyl alcohol, carboxymethyl cellulose, polyacrylamide, and methyl methacrylate / acrylamide copolymer. And a suspension stabilizer. Two or more of these may be used. Among these, an organic suspension stabilizer is preferable in terms of thermal coloring stability at the time of melting, and a methyl methacrylate / acrylamide copolymer is more preferable.

  The initiator used for the polymerization is not particularly limited, and a peroxide, an azo compound or a persulfate is used.

  Specific examples of the peroxide include benzoyl peroxide, cumene hydroperoxide, dicumyl peroxide, diisopropylbenzene hydroperoxide, t-butyl hydroperoxide, t-butylperoxyacetate, t-butylperoxybenzoate, t-butyl isopropyl carbonate, di-t-butyl peroxide, t-butyl peroctate, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t -Butylperoxy) cyclohexane, t-butylperoxy-2-ethylhexanoate and the like.

  Specific examples of the azo compound include azobisisobutyronitrile, azobis (2,4-dimethylvaleronitrile, 2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile, 2-cyano-2-propylazo Formamide, 1,1'-azobiscyclohexane-1-carbonitrile, azobis (4-methoxy-2,4-dimethylvaleronitrile), dimethyl 2,2'-azobisisobutyrate, 1-t-butylazo-2 -Cyanobutane, 2-t-butylazo-2-cyano-4-methoxy-4-methylpentane and the like.

  Specific examples of the persulfate include potassium persulfate, sodium persulfate, and ammonium persulfate.

  Two or more of these initiators may be used. The initiator can also be used in a redox system.

In addition, a chain transfer agent can be used for the purpose of adjusting the degree of polymerization of the suspension polymerization of the vinyl copolymer.
Specific examples of the chain transfer agent include mercaptans such as n-octyl mercaptan, t-dodecyl mercaptan, n-dodecyl mercaptan, n-tetradecyl mercaptan, n-octadecyl mercaptan, and terpenes such as terpinolene. Two or more of these may be used. Of these, n-octyl mercaptan and t-dodecyl mercaptan are preferably used.

  When the vinyl copolymer is produced by suspension polymerization, the polymerization temperature is not particularly limited, but from the viewpoint that the weight average molecular weight of the vinyl copolymer is easily adjusted to the above range, from the viewpoint of suspension stability. It is preferable that the polymerization is started at 60 to 80 ° C, and the temperature is raised when the conversion reaches 50 to 70%, and finally the temperature is raised to 100 to 120 ° C.

  The weight-average molecular weight of the vinyl copolymer can be easily adjusted by using the above-mentioned initiator or chain transfer agent, and setting the polymerization temperature in the above-mentioned preferable range.

(2-2) Step of Forming Polyamide Separation Function Layer Next, the step of forming the polyamide separation function layer constituting the composite semipermeable membrane will be described. The polyamide separation function layer is a layer containing polyamide as a main component.

  In the step of forming the polyamide separation functional layer, an aqueous solution containing the above-mentioned polyfunctional amine and a water-immiscible organic solvent solution containing the polyfunctional acid halide are used to form an interface weight on the surface of the support membrane. By performing the condensation, a polyamide skeleton can be formed.

  The concentration of the polyfunctional amine in the aqueous solution of the polyfunctional amine is preferably in the range of 0.1% by weight to 15% by weight, and more preferably in the range of 0.5% by weight to 10% by weight. . Within this range, sufficient water permeability and solute removal performance can be obtained.

  If the polyfunctional amine aqueous solution does not hinder the reaction between the polyfunctional amine and the polyfunctional acid halide, additives such as a surfactant, an alkaline compound, an acylation catalyst, and an antioxidant are added. be able to.

  Examples of the surfactant include sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium lauryl sulfate, and the like.

  Examples of the alkaline compound include sodium hydroxide, trisodium phosphate, triethylamine and the like.

  In order to perform interfacial polycondensation on the support membrane, first, the above-mentioned aqueous solution of a polyfunctional amine is brought into contact with the support membrane. The contact is preferably performed uniformly and continuously on the surface of the support film.

  Specifically, for example, a method of coating a polyfunctional amine aqueous solution on a support film or a method of dipping the support film in a polyfunctional amine aqueous solution can be used.

  The contact time between the support membrane and the aqueous solution of polyfunctional amine is preferably in the range of 1 second to 10 minutes, more preferably in the range of 5 seconds to 3 minutes.

  After the aqueous solution of the polyfunctional amine is brought into contact with the support film, the solution is sufficiently drained so that no droplet remains on the film. By sufficiently draining the liquid, it is possible to prevent the remaining portion of the liquid droplet from becoming a defect after the formation of the composite semipermeable membrane, thereby preventing the removal performance of the composite semipermeable membrane from deteriorating.

  Examples of the draining method include a method in which the support film after contact with the polyfunctional amine aqueous solution is vertically held and an excessive aqueous solution flows naturally, or a gas stream such as nitrogen is blown from an air nozzle to forcibly remove the liquid. A cutting method or the like can be used. After draining, the film surface may be dried to partially remove the water content of the aqueous solution.

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

  The concentration of the polyfunctional acid halide in the water-immiscible organic solvent solution is preferably in the range of 0.01% by weight to 3% by weight, and in the range of 0.05% by weight to 2% by weight. It is more preferable that it is within. When the concentration of the polyfunctional acid halide is 0.01% by weight or more, a sufficient reaction rate can be obtained. When the concentration is 3% by weight or less, generation of a side reaction can be sufficiently suppressed.

  The organic solvent that is immiscible with water is preferably one that 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 just need. For example, a hydrocarbon solvent may be mentioned, and it may be a simple substance or a mixture. Examples of the organic solvent include saturated hydrocarbons such as hexane, heptane, octane, nonane, and decane; IP Solvent 1620, IP Clean LXIP Solvent 2028, and isoparaffins such as ISOPAR E, ISOPAR G, ISOPAR H, ISOPAR L manufactured by ExxonMobil. Naphthene solvents such as Exol D30, Exol D40, Exol D60 and Exol D80 manufactured by ExxonMobil.

  The organic solvent solution may contain other polyfunctional amine-reactive monomers, organic solvents, acylation catalysts, surfactants, solubilizing agents, complexing agents, and the like. For example, other polyfunctional amine-reactive monomers include compounds containing at least one, preferably 2 to 4 amine-reactive functional groups selected from sulfonyl halides and acid anhydrides, at least one carboxy group and Compounds containing at least one acyl halide are included. Examples of the organic solvent include benzene, toluene, acetone, ethyl acetate and the like. Examples of the acylation catalyst include DMF.

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

  In the interfacial polycondensation step of the present invention, the support film is sufficiently covered with a crosslinked polyamide thin film, and a water-immiscible organic solvent solution containing a polyfunctional acid halide contacted with the support film remains on the support film. It is important to keep it. For this reason, the time for performing the interfacial polycondensation is preferably 0.1 seconds or more and 3 minutes or less, and more preferably 0.1 seconds or more and 1 minute or less. Since the time for performing the interfacial polycondensation is 0.1 seconds or more and 3 minutes or less, the support film can be sufficiently covered with the crosslinked polyamide thin film and supports the organic solvent solution containing the polyfunctional acid halide. It can be held on a membrane.

  After forming the polyamide separation function layer on the support membrane by interfacial polycondensation, the excess solvent is drained. The method of draining includes, for example, a method of vertically removing the excess organic solvent by grasping the membrane in a vertical direction, a method of drying and removing the organic solvent by blowing air with a blower, a mixed fluid of water and air A method of removing excess organic solvent with (two fluids) can be used.

Further, it is preferable to add a step of performing a washing treatment with pure water at 25 ° C. or more and 80 ° C. or less for 1 minute or more.
3. Use of composite semipermeable membrane The composite semipermeable membrane of the present invention is suitably used as a spiral composite semipermeable membrane element. Further, a composite semipermeable membrane module in which these elements are connected in series or in parallel and housed in a pressure vessel can be provided.

  In addition, the above-described composite semipermeable membrane, its elements and modules can be combined with a pump for supplying raw water thereto, a device for pre-treating the raw water, and the like to constitute a fluid separation device. By using this separation device, raw water can be separated into permeated water intended for drinking water and the like and concentrated water not permeated through the membrane to obtain water suitable for the purpose.

  The higher the operating pressure of the fluid separation device, the higher the salt removal performance, but the energy required for operation also increases, and in consideration of the durability of the composite semipermeable membrane of the present invention, the composite semipermeable membrane is covered with The operating pressure when permeating the treated water is preferably 0.2 MPa or more and 5.5 MPa or less.

  As the temperature of the feed water increases, the salt removal property decreases, but as the temperature decreases, the membrane permeation flux also decreases. Therefore, the temperature is preferably 5 ° C. or more and 35 ° C. or less.

  In addition, if the feedwater pH becomes high, in the case of feedwater having a high salt concentration such as seawater, scale such as magnesium may be generated, and the membrane may be deteriorated due to the high pH operation. Operation at is preferred.

  Examples of raw water treated by the composite semipermeable membrane include a liquid mixture containing 500 mg / L to 100 g / L of TDS (Total Dissolved Solids: total dissolved solids) such as seawater, brackish water, and wastewater. Generally, TDS refers to the total amount of dissolved solids, and is expressed as "mass / volume" or as "weight ratio" when 1 L is regarded as 1 kg. According to the definition, the solution filtered through a 0.45 μm filter can be evaporated at a temperature of 39.5 to 40.5 ° C. and can be calculated from the weight of the residue.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<1. Measurement of long diameter and thickness of dense layer>
For the measurement of the major axis and the thickness of the dense layer, a porous support was randomly cut out from 10 small sample pieces.

  By observing the sample section from the surface layer of the cross section of the porous support to the boundary with the substrate using a scanning electron microscope or a transmission electron microscope, it is possible to determine the major axis and the thickness of the dense layer of the porous support. it can. For example, in the case of a cross-sectional photograph of a scanning electron microscope, a sample obtained by immersing a membrane sample in liquid nitrogen and freezing it is cut perpendicularly to the direction in which the stock solution was cast, dried, and then dried. A thin section is coated with platinum / palladium or ruthenium tetroxide, preferably ruthenium tetroxide, and applied to a high-resolution field emission scanning electron microscope (S-5500 scanning electron microscope manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 1 to 6 kV. To observe. The optimum observation magnification may be any magnification at which the entire cross section of the film from the surface of the porous support to the surface of the substrate can be observed. For example, if the long diameter of the dense layer of the porous support is 100 nm, 10,000. ~ 200,000 is preferred. From the obtained electron micrograph, the thickness of the porous support can be directly measured on a scale or the like in consideration of the observation magnification.

<2. Measurement of Support Film Thickness>
The support membrane washed with pure water at 70 ° C. for 5 minutes was air-dried at 25 ° C. The thickness of the dried sample was measured at an arbitrary 20 points using a digital thickness gauge (SMD-565J-L manufactured by TECLOCK Co., Ltd.), and the arithmetic average thereof was calculated to obtain the thickness of the support film.

<3. Measurement of thickness of porous support>
The support membrane washed with pure water at 70 ° C. for 5 minutes was cut by a freeze-fracture method to obtain five sections. From each section, 10 small sample pieces were collected, coated with a thin platinum film, and accelerated at 5 kV using a high-resolution field emission scanning electron microscope (S-5500 scanning electron microscope manufactured by Hitachi High-Technologies Corporation). Cross-sectional photographs were taken at a voltage of 100 to 500 times. In each image obtained by photographing, the thickness of the porous support was measured on a scale. The arithmetic mean was calculated from the 50 values obtained for one support membrane, and this was defined as the thickness of the porous support.

<4. Measurement of Pure Water Permeability Coefficient of Supporting Membrane>
First, the produced supporting film was washed with pure water at 70 ° C. for 5 minutes. Next, the sample was cut into a circle having a diameter of 4.3 cm, and the cut sample was set on a stirring-type ultra holder (UHP-43K manufactured by Advantech Toyo Co., Ltd.) (effective filtration area: 10.9 cm 2). Subsequently, pure water at 25 ° C. was put into the cell, a cap was attached, and the pressure was increased to 100 kPa with nitrogen. Finally, the amount of pure water permeation for a certain time was measured, and the pure water permeation coefficient (× 10 ⁻⁹ m ³ / (m ² · s · Pa), 25 ° C.) was calculated from the following equation.

Pure water permeability coefficient = Pure water permeability ÷ (membrane area x water sampling time x supply pressure)
<5. Measurement of Weight-Average Molecular Weight Mw of THF Soluble in Porous Support>
The support membrane or composite semipermeable membrane (area 0.1 m2) washed with pure water at 70 ° C. for 1 hour or more is air-dried and immersed in THF (200 ml) at 25 ° C. for 4 hours to dissolve the porous support portion Thus, a thermoplastic resin solution was obtained (at the time of immersion, a 250 ml container was used). Next, the obtained solution was filtered through a metal mesh (wire diameter 0.03 mm, mesh 300, manufactured by Kansai Wire Mesh Co., Ltd.) to remove the base material and the functional layer. Subsequently, the obtained filtrate was centrifuged at 8800 rpm (KUBOTA 6900). p. m (12,300 G), and centrifuged at 5 ° C. for 40 minutes, and the supernatant was collected. The obtained supernatant was measured using GPC under the following conditions, and the weight average molecular weight (Mw) was calculated. In addition, polystyrene was used for the calibration curve.

Solvent: Tetrahydrofuran Equipment: Waters 2695 Separation Module Column: Tosoh TSKgel Super IIZM-M, Super II ZM-N, SuperHZ-L (3 in total)
Column temperature: 40 ° C
Solvent flow rate: 0.35 ml / min Detector: Waters 2414 differential refractive index detector <6. Evaluation of membrane performance>
The performance of the composite semipermeable membrane was evaluated by the following method.

(Salt removal)
Feed water (NaCl concentration: 500 ppm) adjusted to a temperature of 25 ° C. and a pH of 7 is supplied to the composite semipermeable membrane at an operating pressure of 0.5 MPa, and a membrane filtration treatment is performed for 3 hours. Was measured with a multi-water quality meter (MM60R) manufactured by Toa DKK Corporation. Next, using a calibration curve created in advance, the conductivity was converted to calculate the NaCl concentration. From this NaCl concentration, the salt removal property, that is, the NaCl removal rate was determined by the following equation.
NaCl removal rate (%) = 100 × {1- (NaCl concentration in permeated water / NaCl concentration in feed water)}
(Membrane permeation flux (Flux))
In the test described in the preceding paragraph, the amount of water permeated through the membrane over a certain period of time was measured, converted to the amount of water permeated per cubic meter per square meter (cubic meters), and expressed as a membrane permeation flux (m ³ / m ² / day). did.

<7. Pressurization test>
Raw water (NaCl concentration: 500 ppm) adjusted to a temperature of 25 ° C. and a pH of 7 is supplied to the composite semipermeable membrane at an operating pressure of 5.5 MPa to perform a membrane filtration treatment for 1 hour, and then supplied at an operating pressure of 0.5 MPa to the membrane. The filtration treatment was performed for 2 hours, and the NaCl removal rate was determined in the same manner as in the evaluation of the membrane performance.

<8. Thickness and change rate of porous support before and after pressure test>
In the measurement of the thickness of the porous support, five sample sections were cut out from the composite semipermeable membrane before and after the evaluation at an operating pressure of 5.5 MPa.

The thickness can be determined by observing the sample section from the boundary between the cross section of the porous support and the separation functional layer to the boundary with the substrate using a scanning electron microscope or a transmission electron microscope. For example, in the case of a cross-sectional photograph of a scanning electron microscope, the membrane sample is immersed in liquid nitrogen and frozen, then cut perpendicularly to the direction in which the stock solution is cast, dried, and then dried. The cross section is coated with platinum / palladium or ruthenium tetroxide, preferably ruthenium tetroxide, and applied to a high-resolution field emission scanning electron microscope (S-5500 scanning electron microscope manufactured by Hitachi High-Technologies) at an accelerating voltage of 1 to 6 kV. To observe. The optimal observation magnification may be any magnification at which the entire film cross section from the surface of the porous support to the surface of the substrate can be observed. For example, if the film thickness of the porous support is 50 μm, 1,000 to 10 Is preferred. From the obtained electron micrograph, the thickness of the porous support can be directly measured on a scale or the like in consideration of the observation magnification.
The rate of change of the thickness of the porous support before and after the evaluation is calculated as (1- (B / A)) × 100 from the thickness A of the porous support before the evaluation and the thickness B of the porous support after the evaluation. did. Table 3 shows the results.

  The materials used in each example and comparative example are shown below.

(Production Example 1) Medium for suspension polymerization (methyl methacrylate / acrylamide copolymer)
20 parts by weight of methyl methacrylate, 80 parts by weight of acrylamide, 0.3 parts by weight of potassium persulfate, and 1800 parts by weight of ion-exchanged water were charged into a reactor, and the gas phase in the reactor was replaced with nitrogen gas. The temperature was maintained at 70 ° C. with good stirring, and when the conversion reached 99%, the polymerization was terminated to obtain an aqueous solution of a copolymer of methyl methacrylate and acrylamide. To this aqueous solution, 35 parts by weight of sodium hydroxide and 15,000 parts by weight of ion-exchanged water were added to obtain a 0.6% by weight aqueous solution of a copolymer of methyl methacrylate and acrylamide. After stirring at 70 ° C. for 2 hours for saponification, the mixture was cooled to room temperature to obtain an aqueous solution of a medium for suspension polymerization.

(Production Example 2) Vinyl copolymer (A)
A 20 L stainless steel autoclave was charged with 6 parts by weight of the aqueous solution of methyl methacrylate / acrylamide copolymer prepared in Production Example 2 and 150 parts by weight of pure water, and the mixture was stirred at 400 rpm, and the system was replaced with nitrogen gas. Next, a mixed solution of a total of 100 parts by weight of 72 parts by weight of styrene and 28 parts by weight of acrylonitrile, 0.10 part by weight of t-dodecylmercaptan, and 0.4 part by weight of 2,2′-azobisisobutyronitrile was stirred. And the temperature was raised to 60 ° C. to initiate polymerization. After the polymerization was started, the reaction temperature was raised to 65 ° C. over 30 minutes, and then to 100 ° C. over 3 hours. Thereafter, the inside of the system was cooled to room temperature, and the polymer was separated, washed and dried to obtain a vinyl copolymer A. The weight average molecular weight Mw of this vinyl copolymer A was 320,000.

(Production Example 3) Vinyl copolymer (B)
A vinyl copolymer B was obtained in the same manner as in Production Example 2, except that t-dodecyl mercaptan was changed to 0.20 parts by weight. The weight average molecular weight Mw of this vinyl copolymer B was 180,000.

(Production Example 4) Vinyl copolymer (C)
A vinyl copolymer C was obtained in the same manner as in Production Example 2, except that the amount of t-dodecyl mercaptan was changed to 0.27 parts by weight. The weight average molecular weight Mw of this vinyl copolymer C was 140,000.

(Production Example 5) Vinyl copolymer (D)
A vinyl copolymer D was obtained in the same manner as in Production Example 2, except that the amount of t-dodecyl mercaptan was changed to 0.40 part by weight. The weight average molecular weight Mw of this vinyl copolymer D was 100,000.

<Example 1>
The vinyl copolymer A obtained in Production Example 2 was added to DMSO so as to have a resin concentration of 17% by weight shown in Table 1, and heated and maintained at 90 ° C. for 3 hours with stirring to prepare a resin solution.

  The prepared resin solution was cooled to 25 ° C. and filtered using a metal mesh (wire diameter 0.03 mm, mesh 400, manufactured by Kansai Wire Mesh Co., Ltd.). Thereafter, a resin solution was applied at a thickness of 100 μm on a nonwoven fabric (thickness: about 90 μm, air permeability: 1.0 cc / cm2 / sec) made of polyester fiber manufactured by a papermaking method. Immediately after the coating, the support was immersed in pure water adjusted to a coagulation bath temperature of 5 ° C. to separate phases, and then washed with pure water at 70 ° C. for 5 minutes to obtain a support film.

  The obtained support film was immersed in a 2.0% by weight aqueous solution of m-phenylenediamine (m-PDA) prepared with pure water for 10 seconds, and then slowly pulled up so that the film surface became vertical. After removing excess aqueous solution from the surface of the support film by blowing nitrogen from an air nozzle, the support film is placed so that the film surface is horizontal, and a 25 ° C. n-decane solution containing trimesic acid chloride (0.07% by weight) is applied to the film. It was applied so that the surface was completely wetted.

  After allowing to stand for 30 seconds, the membrane surface was held vertically for 1 minute to remove excess solution from the membrane, drained, and dried by blowing air at 25 ° C. using a blower. Thereafter, by washing with pure water at 70 ° C. for 5 minutes, a composite semipermeable membrane was obtained. Table 1 shows the membrane performance of the obtained composite semipermeable membrane.

<Examples 2 to 4>
In Example 1, the composite semipermeable membranes of Examples 2 to 4 were obtained in the same manner as in Example 1 except that the resin concentration of the vinyl copolymer A was changed as shown in Table 1. Table 1 shows the membrane performance of the obtained composite semipermeable membrane.

<Examples 5 to 7>
The composite semipermeable membranes of Examples 5 to 5 were prepared in the same manner as in Example 1 except that the resin concentration of the vinyl copolymer B obtained in Production Example 3 and the coagulation bath temperature were changed as shown in Table 1. Was obtained respectively. Table 1 shows the membrane performance of the obtained composite semipermeable membrane.

<Examples 8 to 9>
Except that the resin concentration and the coagulation bath temperature of the vinyl copolymer C obtained in Production Example 4 were changed as shown in Table 1, the composite semi-permeable composites of Examples 8 and 9 were prepared in the same manner as in Example 1. Each of the films was obtained. Table 1 shows the membrane performance of the obtained composite semipermeable membrane.

<Comparative Example 1>
The composite semipermeable membrane of Comparative Example 1 was prepared in the same manner as in Example 1 except that the resin concentration of the vinyl copolymer C obtained in Production Example 4 and the coagulation bath temperature were changed as shown in Table 1. Got each. Table 1 shows the membrane performance of the obtained composite semipermeable membrane.

<Comparative Example 2>
Comparative Example 2 Comparative Example 2 was carried out in the same manner as in Example 1 except that the vinyl copolymer D obtained in Production Example 5 was immersed in pure water adjusted to a coagulation bath temperature of 15 ° C. to perform phase separation. Was obtained. Table 1 shows the membrane performance of the obtained composite semipermeable membrane.

<Comparative Example 3>
In Comparative Example 2, a composite semipermeable membrane of Comparative Example 3 was obtained in the same manner as in Example 1 except that the solvent was changed to DMF, using the vinyl copolymer D obtained in Production Example 5. Table 1 shows the membrane performance of the obtained composite semipermeable membrane.

<Comparative Example 4>
A composite semipermeable membrane of Comparative Example 4 was obtained in the same manner as in Example 5, except that the solvent was changed to NMP. Table 1 shows the membrane performance of the obtained composite semipermeable membrane.

<Comparative Example 5>
A composite semipermeable membrane of Comparative Example 4 was obtained in the same manner as in Example 5, except that the solvent was changed to DMAc. Table 1 shows the membrane performance of the obtained composite semipermeable membrane.

<Comparative Example 6>
A composite semipermeable membrane of Comparative Example 4 was obtained in the same manner as in Example 5, except that the solvent was changed to DMF. Table 1 shows the membrane performance of the obtained composite semipermeable membrane.

<Comparative Example 7>
A composite semipermeable membrane of Comparative Example 7 was obtained in the same manner as in Example 8, except that the solvent was changed to DMF in Example 8. Table 1 shows the membrane performance of the obtained composite semipermeable membrane.

<Comparative Example 8>
In Example 5, the thermoplastic resin was polyethersulfone (Ultrason E 6020P manufactured by BASF).
And a composite semipermeable membrane of Comparative Example 7 was obtained in the same manner as in Example 5 except that the solvent was changed to DMF. Table 1 shows the membrane performance of the obtained composite semipermeable membrane.
From Examples 1 to 4, by using the DMSO solvent and the vinyl copolymer A having a weight average molecular weight Mw of 320,000, a composite semipermeable membrane having a small change in the thickness of the porous support before and after the evaluation of 5.5 MPa was obtained. I have. In Examples 5 to 7, the use of the DMSO solvent and the vinyl copolymer B having a weight average molecular weight Mw of 180,000 provided a composite semipermeable membrane having a small change in the thickness of the porous support. In Examples 8 and 9, a composite semipermeable membrane having a small thickness change of the porous support was obtained by using the DMSO solvent and the vinyl copolymer C having a weight average molecular weight Mw of 140,000. According to the present invention, a composite semipermeable membrane having a small change in the thickness of the support film (high pressure resistance) even when used under high pressure conditions can be obtained.

The composite semipermeable membrane of the present invention can be suitably used particularly for desalination of brine and purification of tap water.

1: Composite semipermeable membrane 2: Supporting membrane 3: Substrate 4: Porous support 40 outside the substrate: Dense layer 41 of porous support 41: Void layer 42 of porous support: Within dense layer Existing hole 43: void existing in void layer 5: separation functional layer

Claims (3)

A composite semipermeable membrane comprising a base material, a porous support disposed on the base material, and a separation functional layer disposed on the porous support,
The porous support includes a dense layer in contact with the separation function layer,
The major axis of the pores contained in the dense layer is less than 100 nm,
The thickness of the dense layer is 300 nm or more,
A composite semipermeable membrane characterized in that the porous support mainly comprises a thermoplastic resin having a weight average molecular weight Mw of 140,000 or more. The composite semipermeable membrane according to claim 1, wherein the thermoplastic resin is a copolymer of a vinyl cyanide-based monomer and an aromatic vinyl-based monomer. A thermoplastic resin having a weight average molecular weight Mw of 140,000 or more, and a good solvent thereof, having a Hansen solubility parameter having a polarity term dP of 11.0 to 17.0 and a hydrogen bond term dH of 7.0 to 12.12. Applying a resin solution containing a solvent that is 0 or less to the substrate,
The substrate coated with the solution of the thermoplastic resin, the thermoplastic resin is coagulated by immersing in a coagulation bath containing a non-solvent having a small solubility compared to the good solvent of the thermoplastic resin, the porous Step of forming a support, and interfacial polycondensation on the surface of the porous support using an aqueous solution containing a polyfunctional amine and a water-immiscible organic solvent solution containing a polyfunctional acid halide A method for producing a composite semipermeable membrane including a step of forming a separation functional layer.

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