JP2018039003A - Composite semipermeable membrane and production method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite semipermeable membrane and a production method of the same where both water permeability and durability are achieved.SOLUTION: In a composite semipermeable membrane,: a porous support is provided with a dense layer being in contact with a separation function layer and a macro void layer positioning between the dense layer and a base material; the thickness of the dense layer is 0.5 μm or more and 5 μm or less; the major diameter of pores included in the dense layer is less than 0.5 μm; the macro void layer includes macro voids having a width in a surface direction of the composite semipermeable membrane of 0.5 μm or more and 5 μm or less at a position having a distance from the boundary surface between the separation function layer and the porous support of 5 μm; and the macro voids exist by 0.2 or more pieces/μm and 1.8 or less pieces/μm at a position separated from the boundary surface between the separation function layer and the porous support by 5 μm in a surface direction of the composite semipermeable membrane.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 and brine, for example.

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

  Patent Document 1 discloses a semipermeable membrane including a nonwoven fabric, a microporous layer, and a separation functional layer. In Patent Document 1, the microporous layer has two layers, an A layer having pores with a diameter of 200 nm or less and a B layer having pores with a diameter of 200 nm or more. Further, the thickness of the A layer is 2 μm or more, the thickness of the B layer is 8 μm or more, and the ratio X of the thickness of the A layer to the total thickness of the A layer and the B layer is 20% or more.

  Patent Document 2 discloses a polyimide resin semipermeable membrane comprising a homogeneous skin layer and a porous layer made of the same material as the homogeneous skin layer and having a thicker porous layer than the homogeneous skin layer. In Patent Document 2, the average thickness of the homogeneous skin layer portion is 5 nm to 1000 nm, and the average pore diameter of the void structure in the porous layer is less than 3 μm.

JP-A-8-168658 JP-A-9-122461

  With the composite semipermeable membranes that have been proposed so far, the water permeability may decrease, particularly during high pressure application operation. An object of the present invention is to provide a composite semipermeable membrane capable of maintaining water permeability even during high pressure addition operation.

To achieve the above object, the present invention has the following configuration.
(1) A composite semipermeable membrane comprising a substrate, a porous support provided on the substrate, and a separation functional layer provided on the porous support,
The porous support comprises a dense layer in contact with the separation functional layer, and a macrovoid layer located between the dense layer and the base material,
The major axis of the holes contained in the dense layer is less than 0.5 μm;
The dense layer has a thickness of 0.5 μm or more and 5 μm or less,
In the macro void layer, the number of macro voids having a width of 0.5 μm or more and 5 μm or less in the plane direction of the composite semipermeable membrane at a position 5 μm from the interface with the dense layer is 0.2 / μm or more. 1.8 pieces / μm or less,
Composite semipermeable membrane.
(2) The composite semipermeable membrane according to (1), wherein the porous support has a thickness of 10 μm or more and 100 μm or less.
(3) The porous support is made of polysulfone, polyacrylonitrile, polyamide, polyester, polyvinyl alcohol, polyphenylene sulfide sulfone, polyphenylene sulfone, polyphenylene sulfide, polyether sulfone, polyvinylidene fluoride, cellulose acetate, polyvinyl chloride or chlorinated. The composite semipermeable membrane according to (1) or (2), which contains at least one resin selected from the group consisting of vinyl chloride.
(4)
(A) placing a resin solution in which a resin is dissolved in a good solvent on a substrate;
(B) a step of obtaining a porous support by coagulating the resin in a coagulating liquid containing a non-solvent of the resin and a good solvent;
(C) A method for producing a composite semipermeable membrane comprising a step of forming a separation functional layer on the porous support.
(5) The temperature of the coagulation bath is in the range of 5 to 50 ° C., and the coagulation bath contains 0.5 to 50% by weight of a good solvent. A method for producing a permeable membrane.
(6) The composite semipermeable material according to (4) or (5), wherein the coagulation bath contains two or more solvents selected from the group consisting of amides, lower alkyl ketones, esters and lactones as the good solvent. A method for producing a membrane.
(7) The coagulation bath contains N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), tetramethylurea (THU) .N, N-dimethylacetamide (DMAc) as the good solvent. ) · N, N-dimethylformamide (DMF) · N, N-dimethylisobutyramide (DMIB), N, N-diisopropylisobutyramide, N, N-bis (2-ethylhexyl) isobutyramide; Acetone methyl ethyl ketone (MEK) A method for producing a composite semipermeable membrane according to (6), which comprises two or more solvents selected from the group consisting of: trimethyl phosphate; and γ-butyrolactone

  In the composite semipermeable membrane of the present invention, the size and number of macrovoids in the porous support are regulated within a specific range, so that the thickness change of the porous support in the high pressure addition operation is suppressed, and as a result , Water permeability is maintained.

It is sectional drawing of one embodiment of the composite semipermeable membrane of this invention.

1. Composite Semipermeable Membrane The composite semipermeable membrane 1 of the present embodiment includes a support membrane 2 and a separation functional layer 5. The support film 2 includes a base material 3 and a porous support 4 provided on the base material 3.

(1-1) Base material The base material plays a role of giving strength to the separation membrane. The substrate is preferably porous so that water can pass through. Specifically, examples of the base material include a fabric made of a polymer such as a polyester polymer, a polyamide polymer, a polyolefin polymer, or a mixture or copolymer thereof. A polyester-based polymer is preferable because a porous support having better mechanical strength, heat resistance, water resistance, and the like can be obtained.

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

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

  Nonwoven fabric is preferably used as the fabric. Nonwoven fabrics include long fiber nonwoven fabrics and short fiber nonwoven fabrics. The long fiber nonwoven fabric has excellent permeability when casting a polymer solution on the base material, the porous support peels off, and the composite semipermeable membrane becomes non-uniform due to fluffing of the base material. And the occurrence of defects such as pinholes can be suppressed. In addition, since the base material is made of a long-fiber nonwoven fabric composed of thermoplastic continuous filaments, it suppresses non-uniformity and film defects when casting thermoplastic resin solutions caused by fuzz, which occurs when short-fiber nonwoven fabrics are used. can do. Moreover, in continuous film formation of a composite semipermeable membrane, since the tension | tensile_strength is applied with respect to the film forming direction, it is preferable to use the long-fiber nonwoven fabric which is more excellent in dimensional stability for a base material.

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

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

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

  The degree of fiber orientation was obtained by randomly collecting 10 small sample pieces from a nonwoven fabric as a base material, photographing the surface of the sample with a scanning electron microscope at a magnification of 100 to 1000 times, 10 pieces from each sample, a total of 100 pieces. For the fibers, the angles when the longitudinal direction (longitudinal direction, film forming direction) of the nonwoven fabric that is the base material is 0 ° and the width direction (lateral direction) of the nonwoven fabric that is the base material is 90 ° are measured. The average value is calculated as the fiber orientation by rounding off the first decimal place.

  The thickness of the substrate is preferably in the range of 10 to 200 μm, more preferably in the range of 30 to 150 μm.

(1-2) Porous Support The porous support 4 has substantially no separation performance for ions and the like, and gives strength to the separation functional layer having substantially the separation performance.

  The composition of the porous support 4 is not particularly limited, but the porous support 4 is formed of a resin, and is particularly preferably thermoplastic. Here, the thermoplastic resin refers to a resin that is made of a chain polymer substance and exhibits a property of being deformed or fluidized by an external force when heated.

  Examples of thermoplastic resins include polysulfones, polyether sulfones, polyamides, polyesters, cellulosic polymers, vinyl polymers, polyphenylene sulfide, polyphenylene sulfide sulfones, polyphenylene sulfones, polyphenylene oxides, homopolymers or copolymers, alone or in combination. Can be used. Here, cellulose acetate and cellulose nitrate can be used as the cellulose polymer, and polyethylene, polypropylene, polyvinyl chloride, chlorinated vinyl chloride, polyacrylonitrile and the like can be used as the vinyl polymer. Among these, polysulfone, polyacrylonitrile, polyamide, polyester, polyvinyl alcohol, polyphenylene sulfide sulfone, polyphenyle sulfone, polyphenylene sulfide, polyether sulfone, polyvinylidene fluoride, cellulose acetate, polyvinyl chloride or chlorinated vinyl chloride are preferable.

  More preferably, cellulose acetate, polyvinyl chloride or chlorinated vinyl chloride, polysulfone, polyphenylene sulfide sulfone, or polyphenylene sulfone can be mentioned, and among these materials, chemical, mechanical, and thermal stability is high, Polysulfone can generally be used because it is easy to mold. The porous support preferably contains these listed compounds as a main component.

  Specifically, it is preferable that the porous support contains polysulfone containing a repeating unit represented by the following chemical formula because the pore diameter is easy to control and the dimensional stability is high.

  The thickness of the porous support is preferably in the range of 10 μm to 100 μm.

  The porous support 4 preferably includes a dense layer 40 and a macrovoid layer 41.

  The dense layer 40 plays a role of transferring a polyfunctional amine aqueous solution necessary for the formation of the separation functional layer 5 to a polyamide polymerization field (an interface between the amine aqueous solution and the polyfunctional acid halide solution). In order to efficiently transfer the polyfunctional amine aqueous solution, the dense layer 40 preferably has continuous pores. The surface layer of the porous support (surface opposite to the base material) is a place for polymerization, and the polyfunctional amine aqueous solution is supplied to the separation functional layer formed by holding and releasing the polyfunctional amine aqueous solution. As well as serving as a starting point for the fold growth of the separation functional layer.

  The dense layer 40 refers to a layer in which the major axis of the contained holes is less than 0.5 μm. Moreover, it is preferable that the long diameter of the hole contained in a dense layer is 0.05 micrometer or more. The dense layer preferably has a thickness of 0.5 μm or more and 5 μm or less.

The macro void layer 41 is a layer including a hole 42 (hereinafter referred to as “macro void”) having a long diameter of 0.5 μm or more. The thickness of the macrovoid layer 41 is preferably not less than 5 μm and not more than 95 μm. Further, the macrovoid layer 41 is positioned at a depth of 0.1 μm from the interface B between the dense layer and the macrovoid layer in the lateral direction (film In the direction parallel to the surface direction) having a macro void with a width of 0.5 μm or more and 5 μm or less, and the number of these macro voids is 0.3 / μm or more and 1.8 / μm or less in the same direction. Preferably it is present. When the macrovoid layer satisfies these specific numerical ranges, the thickness of the porous support is maintained even during high-pressure addition operation, so that the permeation flow rate is stabilized. Further, by maintaining the thickness of the porous support, the occurrence of channeling in which a member such as a membrane jumps out from the end of the element is suppressed.

  Whether the porous support satisfies the above-described conditions can be confirmed as follows. The composite semipermeable membrane 1 is cut perpendicularly to the film surface direction at an arbitrary position to obtain a cross section. The width of the cross section is 10 μm or more. By observing this cross section, if there is a void having a major axis of 0.5 μm or more (that is, macro void), the distance between the portion (vertex) closest to the separation functional layer and the separation functional layer 5 on the outer edge of the macro void is determined. taking measurement. When there are a plurality of voids, the distance between the apex of the macro void 42 closest to the separation functional layer 5 and the separation functional layer 5 may be measured. This distance (the distance between A and B in FIG. 1) is the thickness of the dense layer 40. The distance from the apex of the macrovoid 42 closest to the separation function layer 5 to the base material 3 (the distance between B and C in FIG. 1) is the thickness of the macrovoid layer 41.

  From the interface B between the macrovoid layer 41 and the dense layer 40, the width of the macrovoid 42 is measured at a position D that is 0.1 μm inside the macrovoid layer 41. Macrovoids of 0.5 μm or more and 5 μm or less are selected, and the number of these macrovoids may be 0.2 / μm or more and 1.8 / μm or less with respect to the width of the film.

  Furthermore, 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. The skin layer here means a portion having a high density. Specifically, the surface pores of the skin layer are in the range of 1 nm to 50 nm.

The density of the porous support 4 is preferably 0.3 g / cm ³ or more and 0.7 g / cm ³ or less, and the porosity is preferably 30% or more and 70% or less. When the density of the porous support layer on the substrate is 0.3 g / cm ³ or more or the porosity is 30% or more, suitable strength can be obtained and suitable for the fold growth of the polyamide separation functional layer Surface structure can be obtained. Moreover, favorable water permeability can be obtained because the density of the porous support on the substrate is 0.7 g / cm ³ or less or the porosity is 70% or less.

  The thickness of the support membrane 2 is preferably in the range of 50 to 300 μm, and more preferably in the range of 60 to 250 μm.

(1-2) Separation Functional Layer The separation functional layer 5 is a layer that bears a solute separation function in the composite semipermeable membrane. The composition such as the composition and thickness of the separation functional layer is set in accordance with the intended use of the composite semipermeable membrane.

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

  The thickness of the polyamide separation functional layer is usually preferably in the range of 0.01 to 1 μm and more preferably in the range of 0.1 to 0.5 μm in order to obtain sufficient separation performance and permeated water amount. The thickness of the separation functional layer can be based on the conventional method for measuring the thickness of the separation membrane. For example, the separation membrane is embedded with resin, and an ultrathin section is prepared by cutting the separation membrane, and the obtained section is subjected to processing such as staining. Thereafter, the thickness can be measured by observing with a transmission electron microscope. Further, when the separation functional layer has a pleat structure, it can be measured at intervals of 50 nm in the cross-sectional length direction of the pleat structure located above the porous support, and the number of pleats can be measured to obtain 20 from the average. it can.

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

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

(Organic-inorganic hybrid separation functional layer)
Further, the separation functional layer may have an organic-inorganic hybrid structure containing Si element or the like. Examples of the separation functional layer having an organic-inorganic hybrid structure include the following compounds (A) and (B):
(A) a silicon compound in which a reactive group and a hydrolyzable group having an ethylenically unsaturated group are directly bonded to a silicon atom, and (B) a compound other than the compound (A) and having an ethylenically unsaturated group Compounds can be included. Specifically, the separation functional layer may contain a condensate of the hydrolyzable group of the compound (A) and a polymer of the ethylenically unsaturated group of the compounds (A) and / or (B). That is, the separation functional layer is
A polymer formed by condensation and / or polymerization of only the compound (A),
-The polymer formed by superposing | polymerizing only a compound (B), and-At least 1 sort (s) of polymer of the copolymer of a compound (A) and a compound (B) can be contained. The polymer includes a condensate. In the copolymer of the compound (A) and the compound (B), the compound (A) may be condensed through a hydrolyzable group.

2. Next, a method for manufacturing the composite semipermeable membrane will be described. The manufacturing method includes a porous support forming step and a separation functional layer forming step.

(2-1) Porous Support Forming Step The porous support forming step is:
(A) placing a resin solution in which a resin is dissolved in a good solvent on a substrate;
(B) a step of obtaining a porous support by coagulating the resin in a coagulating liquid containing a non-solvent of the resin and a good solvent;
Is provided. The “resin” is a material that is a main component of the porous support, and is specifically as described above.

The forming step of the porous support may further include a step of preparing a resin solution by dissolving a resin that is a component of the porous support in a good solvent for the resin.

The good solvent of the present invention dissolves the resin. Examples of the good solvent include N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), tetramethylurea (THU), N, N-dimethylacetamide (DMAc) · N, N— Amides such as dimethylformamide (DMF), N, N-dimethylisobutyramide (DMIB), N, N-diisopropylisobutyramide, N, N-bis (2-ethylhexyl) isobutyramide; lower grades such as acetone and methyl ethyl ketone (MEK) At least one solvent selected from the group consisting of alkyl ketones; esters such as trimethyl phosphate; and lactones such as γ-butyrolactone is preferably used. More preferably, N-methyl-2-pyrrolidone (NMP) is used as a good solvent. , Methyl sulfoxide (DMSO , N, N-dimethylacetamide (DMAc), N, N-dimethylformamide (DMF) · N, N-dimethylisobutyramide (DMIB) is fried and the rate of the solvent flowing out when forming the porous support is increased. By appropriately adjusting, the dense layer and the void layer of the porous support can be adjusted to a desired range.

  For example, a porous support in which most of the surface has fine pores having a diameter of 1 to 30 nm is formed by casting the polysulfone solution on a substrate to a certain thickness and wet coagulating it in water. You can get a body.

  Step (a) can be performed by applying a resin solution to the substrate or immersing the substrate in the resin solution.

  Application of the resin solution onto the substrate can be carried out by various coating methods, but pre-metering coating methods such as die coating, slide coating, curtain coating and the like that can supply an accurate amount of the coating solution are preferably applied. Furthermore, in the formation of the porous support of the present invention, the slit die method of applying a resin solution is more preferably used.

When the resin solution forming the porous support contains polysulfone as the material of the porous support, the polysulfone concentration (that is, the solid content concentration) of the resin solution is preferably 15% by weight or more, more preferably It is 17% by weight or more. The polysulfone concentration of the resin solution is preferably 30% by weight or less, and more preferably 25% by weight or less. When the polysulfone concentration is 16% by weight or more, the aqueous amine solution can be supplied from the pores formed by phase separation when the polyamide separation functional layer is formed. Moreover, when the polysulfone concentration is 30% by weight or less, a structure having water permeability can be obtained, and if it is within this range, it is preferable from the viewpoint of the performance and durability of the composite semipermeable membrane.
When using polysulfone, the temperature of the resin solution at the time of application of the resin solution is usually preferably within a range of 10 to 60 ° C. Within this range, the resin solution does not precipitate and is solidified after sufficiently impregnating the organic solvent solution containing the resin between the fibers of the base material. As a result, the porous support is firmly bonded to the substrate by impregnation, and the porous support of the present invention can be obtained. In addition, what is necessary is just to adjust the preferable temperature range of a resin solution suitably with the viscosity etc. of the resin solution to be used.

  The polymer contained in the resin solution can be appropriately adjusted in consideration of various characteristics such as strength characteristics, permeability characteristics, and surface characteristics of the porous support to be produced.

  The solvent contained in the resin solution may be the same solvent or a different solvent as long as it is a good solvent for the resin. It can be adjusted as appropriate in consideration of the strength characteristics of the porous support to be produced and the impregnation of the resin solution into the substrate.

  As the resin solvent, a mixed solvent of two or more good solvents is preferable.

  The mixing ratio of the good solvent of the resin is that N, N-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) are mixed at a ratio of 95: 5 to 50:50 or 85:15 to 70:30. N, N-dimethylformamide (DMF) and N, N-dimethylisobutyramide (DMIB) are preferably mixed at a ratio of 90:10 to 50:50 or 80:20 to 60:40. The mixing ratio of N, N-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) or the mixing ratio of N, N-dimethylformamide (DMF) and N, N-dimethylisobutyramide (DMIB) is the above numerical value. When the range is satisfied, the thickness of the dense layer and the void layer formed on the porous support is adjusted by using the difference in the rate of the solvent flowing out from the porous support during the phase separation that forms the porous support layer. can do.

  Examples of the non-solvent for the resin include water, hexane, pentane, benzene, toluene, methanol, ethanol, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol, and low molecular weight. And an aliphatic hydrocarbon such as polyethylene glycol, an aromatic hydrocarbon, an aliphatic alcohol, or a mixed solvent thereof.

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

  By applying the resin solution to the base material as described above, the resin solution is impregnated into the base material. In order to obtain a porous support having a predetermined structure, the base material is impregnated with the resin solution. Need to control. In order to control the impregnation of the resin solution into the base material, for example, a method of controlling the time until the resin solution is applied on the base material and then immersed in the coagulation bath, or the temperature or concentration of the resin solution is controlled. The method of adjusting a viscosity by doing is mentioned, It is also possible to combine these methods.

  After applying the resin solution on the substrate, the time until the substrate is immersed in the coagulation bath is preferably in the range of usually 0.1 to 5 seconds. If the time until dipping in the coagulation bath is within this range, the resin solution is sufficiently impregnated between the fibers of the base material and then solidified. In addition, what is necessary is just to adjust the preferable range of time until it immerses in a coagulation bath suitably with the viscosity etc. of the resin solution to be used.

  The liquid temperature of the coagulation bath is preferably in the range of 5-50 ° C, more preferably 10-30 ° C. If it is below the above upper limit, the vibration of the coagulation bath surface due to thermal motion does not intensify, and the smoothness of the film surface after formation is good. Moreover, if it is more than the said minimum, sufficient coagulation | solidification rate will be obtained and film forming property will be favorable.

  In step (b), the resin solution placed on the substrate is immersed in a coagulation bath having a lower resin solubility than the good solvent in the solution to solidify the resin, thereby forming a three-dimensional network structure. Can be made.

  Further, by incorporating a non-solvent such as water and a good solvent into the liquid in the coagulation bath, a dense layer can be formed on the membrane surface by non-solvent induced phase separation.

  The concentration of the good solvent in the coagulation bath is preferably 0.5% by weight or more, 5% by weight or more, or 10% by weight or more, and 50% by weight or less, or 30% by weight or less.

  The concentration of the non-solvent in the coagulation bath is preferably 50% by weight or more or 70% by weight or more, and preferably 95% by weight or less or 90% by weight or less.

  The mixing ratio of the liquid good solvent in the coagulation bath is 95: 5 to 50:50 or 85:15 to 70: N, N-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP). Mix in a ratio of 30 or mix N, N-dimethylformamide (DMF) and N, N-dimethylisobutyramide (DMIB) in a ratio of 90:10 to 50:50 or 80:20 to 60:40. Is preferred. The mixing ratio of N, N-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) or the mixing ratio of N, N-dimethylformamide (DMF) and N, N-dimethylisobutyramide (DMIB) is the above numerical value. When the range is satisfied, the thicknesses of the dense layer and the void layer formed on the porous support can be adjusted using the difference in the rate at which the solvent flows out of the porous support during the phase separation.

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

(2-2) Formation process of separation functional layer Next, as an example of the formation process of the separation functional layer constituting the composite semipermeable membrane, formation of a layer mainly composed of polyamide (that is, a polyamide separation functional layer) is given. explain. The step of forming the polyamide separation functional layer uses an aqueous solution containing the above-mentioned polyfunctional amine and an organic solvent solution immiscible with water containing the polyfunctional acid halide, and the interface weight on the surface of the porous support. It includes forming a polyamide skeleton by performing condensation.

  The concentration of the polyfunctional amine in the polyfunctional amine aqueous solution is preferably in the range of 0.1 wt% to 20 wt%, and more preferably in the range of 0.5 wt% to 15 wt%. . Within this range, sufficient water permeability and sufficient removal performance of salt and boron can be obtained.

  The polyfunctional amine aqueous solution may contain a surfactant, an organic solvent, an alkaline compound, an antioxidant, or the like as long as it does not interfere with the reaction between the polyfunctional amine and the polyfunctional acid halide. The surfactant has the effect of improving the wettability of the porous support surface and reducing the interfacial tension between the aqueous amine solution and the nonpolar solvent. Since the organic solvent may act as a catalyst for the interfacial polycondensation reaction, the interfacial polycondensation reaction may be efficiently performed by adding the organic solvent.

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

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

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

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

  The water-immiscible organic solvent preferably dissolves the polyfunctional acid halide and does not destroy the microporous porous support, and is inert to the polyfunctional amine compound and polyfunctional acid halide. Anything is acceptable. Preferable examples include hydrocarbon compounds such as hexane, heptane, octane, nonane and decane.

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

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

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

  The composite semipermeable membrane thus obtained is washed with hot water in order to remove the polyfunctional amine aqueous solution remaining in the membrane. The temperature of the hot water at this time is preferably 30 to 100 ° C, more preferably 45 to 95 ° C. When it is higher than this range, the degree of shrinkage of the porous support increases, and the water permeability decreases. Conversely, if it is low, the cleaning effect is small. Furthermore, chemical treatment with chlorine, acid, alkali, nitrous acid, or the like may be performed as necessary to improve separation performance and permeation performance.

  The hybrid structure described above can be formed by a known method. An example of a method for forming a hybrid structure is as follows. A reaction solution containing the compound (A) and the compound (B) is applied to the porous support. In order to condense the hydrolyzable group after removing the excess reaction solution, heat treatment may be performed. As a polymerization method of the ethylenically unsaturated groups of the compound (A) and the compound (B), heat treatment, electromagnetic wave irradiation, electron beam irradiation, and plasma irradiation may be performed. For the purpose of increasing the polymerization rate, a polymerization initiator, a polymerization accelerator and the like can be added during the formation of the separation functional layer.

  For any separation functional layer of polyamide and hybrid, the surface of the membrane may be hydrophilized with, for example, an alcohol-containing aqueous solution or an alkaline aqueous solution before use.

3. Utilization of composite semipermeable membrane The composite semipermeable membrane manufactured in this way is combined with raw water flow path materials such as plastic nets, permeate flow path materials such as tricot, and a film for enhancing pressure resistance as required. The spiral semi-permeable membrane element can be formed by being wound around a cylindrical water collecting pipe having a large number of holes. Further, this element can be connected in series or in parallel and housed in a pressure vessel to constitute a composite semipermeable membrane module.

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

  The higher the operating pressure of the fluid separator, the better the salt removal, but the energy required for operation also increases, and considering the durability of the composite semipermeable membrane, water to be treated is added to the composite semipermeable membrane. The operating pressure at the time of permeation is preferably 1.0 MPa or more and 10 MPa or less. The operation pressure is a so-called transmembrane pressure. As the feed water temperature increases, the salt removability decreases, but the membrane permeation flux decreases as the supply water temperature decreases, so that the feed water temperature is preferably 5 ° C. or higher and 45 ° C. or lower. In addition, when the pH of the feed water becomes high, scales such as magnesium may be generated in the case of feed water with a high salt concentration such as seawater, and there is a concern about deterioration of the membrane due to high pH operation. Is preferred.

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

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples.
<Measurement of dense layer thickness and void size>
To measure the thickness of the dense layer and the size of the voids, 10 pieces of small piece samples were cut out at random from the porous support.

  By observing the sample section from the surface layer of the cross section of the porous support to the boundary with the substrate with a scanning electron microscope or transmission electron microscope, the size of the dense layer, void layer and void of the porous support can be determined. Can be sought. For example, in the case of a cross-sectional photograph of a scanning electron microscope, a membrane sample immersed in liquid nitrogen and frozen is cleaved perpendicularly to the direction in which the film-forming stock solution is cast and dried, and then the membrane The cross section is thinly coated with platinum / palladium or ruthenium tetroxide, preferably ruthenium tetroxide, and observed with a high resolution field emission scanning electron microscope (UHR-FE-SEM) at an acceleration voltage of 1 to 6 kV. A Hitachi S-900 electron microscope or the like can be used as the high-resolution field emission scanning electron microscope. The optimum observation magnification may be any magnification that allows observation of the entire membrane cross section from the surface of the porous support to the surface of the substrate. For example, when the thickness of the porous support is 50 μm, 1,000 to 10 is used. 1,000 is preferred. The thickness of the porous support can be directly measured with a scale or the like in consideration of the observation magnification from the obtained electron micrograph.

<Porous support thickness and change rate before and after operation pressure 5.5 MPa evaluation>
For 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 obtained by observing the sample section from the boundary with the separation functional layer in the cross section of the porous support to the boundary with the substrate with a scanning electron microscope or a transmission electron microscope. For example, in the case of a cross-sectional photograph of a scanning electron microscope, a membrane sample immersed in liquid nitrogen and frozen is cleaved perpendicularly to the direction in which the film-forming stock solution is cast and dried, and then the membrane The cross section is thinly coated with platinum / palladium or ruthenium tetroxide, preferably ruthenium tetroxide, and observed with a high resolution field emission scanning electron microscope (UHR-FE-SEM) at an acceleration voltage of 1 to 6 kV. A Hitachi S-900 electron microscope or the like can be used as the high-resolution field emission scanning electron microscope. The optimum observation magnification may be any magnification that allows observation of the entire membrane cross section from the surface of the porous support to the surface of the substrate. For example, when the thickness of the porous support is 50 μm, 1,000 to 10 is used. 1,000 is preferred. The thickness of the porous support can be directly measured with a scale or the like in consideration of the observation magnification from the obtained electron micrograph.
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. The results are shown in Table 3.

<Desalination rate (TDS removal rate)>
Filtration was performed for 24 hours by supplying seawater (corresponding to feed water) at a temperature of 25 ° C. and a pH of 6.5 to the composite semipermeable membrane at an operating pressure of 5.5 MPa. The obtained permeated water was used for measuring the TDS removal rate.

  Practical salinity was obtained by measuring the electrical conductivity of the supplied water and the permeated water with an electric conductivity meter manufactured by Toa Radio Industry Co., Ltd. From the TDS concentration obtained by converting this practical salinity, the desalting rate, that is, the TDS removal rate was determined by the following equation.

TDS removal rate (%) = 100 × {1− (TDS concentration in permeated water / TDS concentration in feed water)}
<Membrane permeation flux>
The amount of permeated water obtained by the above filtration treatment for 24 hours was converted to the amount of water per day (cubic meter) per square meter of the membrane surface and expressed as the membrane permeation flux (m ³ / m ² / day).

Example 1
The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples.

<Production of composite semipermeable membrane>
Example 1
a. Porous support 17 wt% polysulfone was added to a mixed solvent in which DMF and NMP were mixed at a ratio of 75:25, and the mixture was stirred at 90 ° C. for 2 hours or more to prepare a uniform solution.

  In the examples of this document, Polysulfone UDEL p-3500 manufactured by Solvay Advanced Polymers Co., Ltd. was used as the polysulfone.

The prepared stock solution was cooled to room temperature, supplied to an extruder and filtered with high precision. Thereafter, the filtered lower value is passed through a slit die on a non-woven fabric made of polyethylene terephthalate fiber (yarn diameter: 1 dtex, thickness: about 90 μm, air permeability: 1 cc / cm ² / sec), and the total thickness becomes 140 μm. Immediately after casting, a porous support was obtained by immersing a mixed solvent of 10% by weight of DMF and NMP mixed at a ratio of 75:25 in a coagulation bath adjusted to 25 ° C. and washing for 5 minutes.

b. Formation of Separation Function Layer The obtained porous support was immersed in a 4.0 wt% aqueous solution of m-PDA for 2 minutes, and then slowly pulled up so that the membrane surface was vertical. Nitrogen was blown from the air nozzle to remove excess aqueous solution from the surface of the support membrane, and then an n-decane solution at 25 ° C. containing 0.12% by weight of trimesic acid chloride was applied so that the membrane surface was completely wetted. After leaving still for 1 minute, in order to remove excess solution from the film, the film surface was held vertically for 1 minute to drain the liquid. Then, the composite semipermeable membrane provided with a base material, a porous support body, and the polyamide separation function layer was obtained by wash | cleaning for 2 minutes with 70 degreeC water.

(Example 2)
A composite semipermeable membrane in Example 2 was produced in the same manner as in Example 1 except that the concentration of the mixed solvent in the coagulation bath (the ratio of DMF and NMP was 75:25) in the porous support membrane was 20% by weight.

(Example 3)
A composite semipermeable membrane in Example 3 was prepared in the same manner as in Example 1 except that the concentration of the mixed solvent in the coagulation bath (the ratio of DMF and NMP was 75:25) in the porous support membrane was 45% by weight.

Example 4
A composite semipermeable membrane in Example 4 was prepared in the same manner as in Example 1 except that the temperature of the coagulation bath was 10 ° C. in the formation of the porous support.

(Example 5)
A composite semipermeable membrane in Example 5 was produced in the same manner as in Example 1 except that the polysulfone concentration was 20% by weight in the production of the porous support.

(Example 6)
In the film formation of the porous support, the solvent of the film forming stock solution is a mixed solvent in which DMF and NMP are mixed in an 85:15 ratio, and the solvent in the coagulation bath is a mixed solvent in which DMF and NMP are mixed in an 85:15 ratio. The composite semipermeable membrane in Example 6 was produced in the same manner as in Example 1 except that.

(Example 7)
A composite semipermeable membrane in Example 7 was produced in the same manner as in Example 1 except that the concentration of the mixed solvent in the coagulation bath (the ratio of DMF and NMP was 75:25) in the porous support membrane was 5% by weight.

(Example 8)
A composite semipermeable membrane in Example 8 was prepared in the same manner as in Example 1 except that the concentration of the mixed solvent in the coagulation bath (the ratio of DMF and NMP was 75:25) in the porous support film formation was 0.6% by weight. .

Example 9
A composite semipermeable membrane in Example 7 was prepared in the same manner as in Example 1 except that the temperature of the coagulation bath was 40 ° C. in the formation of the porous support.

(Example 10)
The composite semipermeable membrane of Example 8 is the same as Example 1 except that the solvent for the membrane forming solution and the coagulation bath is a mixed solvent in which DMF and NMP are mixed at a ratio of 60:40 in the formation of the porous support. A membrane was prepared.

(Example 11)
The composite semipermeable material in Example 9 is the same as Example 1 except that the solvent for the film forming stock solution and the coagulation bath is a mixed solvent in which DMF and DMIB are mixed at a ratio of 75:25 in forming the porous support. A membrane was prepared.

(Comparative Example 1)
The composite semipermeable material in Comparative Example 1 was the same as Example 1 except that the solvent for the film forming solution and the coagulation bath was a mixed solvent in which DMF and NMP were mixed at a ratio of 25:75. A membrane was prepared.

(Comparative Example 2)
A composite semipermeable membrane in Comparative Example 2 was prepared in the same manner as in Example 1 except that the membrane forming stock solution and the coagulation bath solvent were a single solvent of NMP alone in the formation of the porous support.

(Comparative Example 3)
A composite semipermeable membrane in Comparative Example 3 was produced in the same manner as in Example 1 except that the membrane forming stock solution and the coagulation bath solvent were only DMAc alone in forming the porous support.

(Comparative Example 4)
A composite semipermeable membrane in Comparative Example 3 was prepared in the same manner as in Example 1 except that the membrane forming stock solution and the solvent of the coagulation bath were a single solvent containing only DMIB in the formation of the porous support.

(Comparative Example 5)
A composite semipermeable membrane in Comparative Example 5 was prepared in the same manner as in Example 1 except that the temperature of the coagulation bath was 3 ° C. in the formation of the porous support.

(Comparative Example 6)
A composite semipermeable membrane in Comparative Example 6 was produced in the same manner as in Example 1 except that the temperature of the coagulation bath was 55 ° C. in the production of the porous support.

(Comparative Example 7)
A composite semipermeable membrane in Comparative Example 7 was produced in the same manner as in Example 1 except that the concentration of the mixed solvent in the coagulation bath (the ratio of DMF and NMP was 75:25) in the porous support membrane was 55% by weight.

<Result>
The above results are shown in Table 3. In Examples 1 to 9, composite semipermeable membranes having both high durability with a small change in the thickness of the porous support of 30% or less and high water permeability were obtained.

  On the other hand, in the composite semipermeable membrane of Comparative Example 1, the dense layer was thick and a void of 0.5 μm or more was not seen at a position of 5 μm from the surface of the porous support, but a large void was seen in the vicinity of the substrate. It is considered that the permeation flow rate was lowered due to the void being crushed by the operation pressure of 5.5 MPa. Further, in the composite semipermeable membranes of Comparative Examples 2 to 4, the dense layer of the porous support layer is thin, 0.4 μm or less, and there are many voids at a position of 5 μm from the surface of the porous support. A large void is observed, and it is considered that the permeation flow rate is lowered due to the void being crushed by the operation pressure of 5.5 MPa.

  Furthermore, the composite semipermeable membrane of Comparative Example 6 has a thick dense layer and a small void at a position of 5 μm inside from the surface layer. In the composite semipermeable membrane of Comparative Example 7, the dense layer is thick and both have a permeation flow rate. Although it was large, the TDS removal rate was also low. This is because when the concentration of the solvent in the coagulation bath is high, the pore diameter of the surface of the porous support that becomes the polymerization field becomes large, so that the polyfunctional amine aqueous solution is transferred to the polymerization field and polymerized in the formation of the separation functional layer. This is thought to be because the balance with the speed was lost and sufficient pleats were not formed.

  As shown in Table 3, the composite semipermeable membranes of the present invention of Examples 1 to 9 have high water permeability and salt removal performance, and the rate of change in the thickness of the porous support is small. It can be seen that excellent membrane performance and desalination rate can be maintained even under operating conditions where physical external force is applied.

  In particular, the separation membrane element of the present invention can be suitably used for desalting seawater and brine.

1: Composite semipermeable membrane 2: Support membrane 3: Substrate 4: Porous support 40 present outside the substrate: Dense layer 41 of the porous support: Void layer 42 of the porous support 42: In the void layer Void 5 present: separation functional layer

Claims (7)

A composite semipermeable membrane comprising a substrate, a porous support provided on the substrate, and a separation functional layer provided on the porous support,
The porous support comprises a dense layer in contact with the separation functional layer, and a macrovoid layer located between the dense layer and the base material,
The major axis of the holes contained in the dense layer is less than 0.5 μm;
The dense layer has a thickness of 0.5 μm or more and 5 μm or less,
In the macro void layer, the number of macro voids having a width of 0.5 μm or more and 5 μm or less in the plane direction of the composite semipermeable membrane at a position 5 μm from the interface with the dense layer is 0.2 / μm or more. 1.8 pieces / μm or less,
Composite semipermeable membrane.   The composite semipermeable membrane according to claim 1, wherein the porous support has a thickness of 10 μm or more and 100 μm or less. The porous support is made of polysulfone, polyacrylonitrile, polyamide, polyester, polyvinyl alcohol, polyphenylene sulfide sulfone, polyphenylene sulfone, polyphenylene sulfide, polyether sulfone, polyvinylidene fluoride, cellulose acetate, polyvinyl chloride, or chlorinated vinyl chloride. The composite semipermeable membrane according to claim 1 or 2, comprising at least one resin selected from the group consisting of: (A) placing a resin solution in which a resin is dissolved in a good solvent on a substrate;
(B) a step of obtaining a porous support by coagulating the resin in a coagulating liquid containing a non-solvent of the resin and a good solvent;
(C) A method for producing a composite semipermeable membrane comprising a step of forming a separation functional layer on the porous support.   The temperature of the said coagulation bath is in the range of 5-50 degreeC, and the said coagulation bath contains 0.5-50 weight% of good solvents, The composite semipermeable membrane of Claim 4 characterized by the above-mentioned. Production method. The method for producing a composite semipermeable membrane according to claim 4 or 5, wherein the coagulation bath contains two or more solvents selected from the group consisting of amides, lower alkyl ketones, esters and lactones as the good solvent.   The coagulation bath contains N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), tetramethylurea (THU) .N, N-dimethylacetamide (DMAc) .N as the good solvent. , N-dimethylformamide (DMF) · N, N-dimethylisobutyramide (DMIB), N, N-diisopropylisobutyramide, N, N-bis (2-ethylhexyl) isobutyramide; acetone methyl ethyl ketone (MEK); phosphoric acid The method for producing a composite semipermeable membrane according to claim 6, comprising two or more solvents selected from the group consisting of trimethyl; and γ-butyrolactone.

Images