Composite semipermeable membrane, method for producing composite semipermeable membrane, and method for concentrating raw-material liquid using composite semipermeable membrane

Abstract

Provided is a composite semipermeable membrane comprising a support membrane and a polyamide separation function layer on the support membrane, the composite semipermeable membrane being characterized in that: the polyamide separation function layer includes a projecting part having a projection structure provided with a plurality of protrusions and a plurality of recesses, and a smooth part that does not have the projection structure; and, in a surface image of the polyamide separation function layer obtained at a magnification of 1000 times using a scanning electron microscope, the proportion of the projecting part occupying the surface of the support membrane is 10-90%.

Description

Composite semipermeable membrane, method for producing composite semipermeable membrane, and method for concentrating raw material liquid using composite semipermeable membrane

[0001] The present invention relates to a composite semipermeable membrane, a method for producing a composite semipermeable membrane, and a method for concentrating a raw material liquid using a composite semipermeable membrane. More specifically, the present invention relates to a composite semipermeable membrane having selective permeability, which is used to separate a solvent by removing a solid or solute from a liquid mixture, a method for producing a composite semipermeable membrane, and a method for concentrating a raw material liquid using a composite semipermeable membrane. More specifically, the present invention relates to a composite semipermeable membrane produced by forming a separation functional layer made of a thin polymer film having selective permeability on the inner surface of a microporous hollow fiber support membrane by an interfacial polymerization method, a method for producing the composite semipermeable membrane, and a method for concentrating a raw material liquid using the composite semipermeable membrane.

[0002] Forward osmosis is a known method for producing purified water (see Patent Documents 1 and 2). Forward osmosis involves contacting raw water to be purified with a draw solution containing a high concentration of water-separable solutes via a semipermeable membrane, extracting only the water in the raw water into the draw solution, and then removing the solutes from the draw solution to obtain purified water. In water purification systems using forward osmosis, the extraction of water from the raw water into the draw solution is driven by an osmotic pressure difference, eliminating the need to create an artificial pressure difference. Composite membranes typically used as forward osmosis membranes are manufactured by forming an active layer made of a thin film on the surface of a support membrane. This active layer can be formed, for example, by coating, interfacial polymerization, or plasma polymerization.

[0003] Interfacial polymerization is a technique in which two types of reactive monomers are dissolved in water and a water-immiscible organic solvent, respectively, and then the solutions are brought into contact with each other to react the monomers at the interface between the two solutions to produce a polymer. This interfacial polymerization reaction can be carried out on the surface of a microporous support membrane to produce a composite membrane for use as a forward osmosis membrane. The commonly known interfacial polymerization method for producing a composite membrane is carried out as follows: a first solution containing one reactive compound and a second solution containing the other reactive compound, which is immiscible with the first solution, are prepared. The microporous support membrane is then immersed in the first solution, and the excess first solution is removed before the membrane is immersed in the second solution. This allows interfacial polymerization of the reactive compounds on the surface of the microporous support membrane. The solvent from the second solution is then removed to form a composite membrane having a thin film on the surface of the microporous support membrane.

[0004] Methods for forming a polymer thin film on the outer surface of a microporous support membrane having a hollow fiber shape by interfacial polymerization are well known. For example, a method is known in which a guide roll is provided in a reaction solution tank and the microporous hollow fiber support membrane is continuously immersed in the reaction solution through the roll (see, for example, Patent Documents 3 and 4). The technique of forming a polymer membrane on the outer surface of a hollow fiber has the advantage that it can be performed continuously following the spinning process. However, this technique has the problem of damaging the polymer membrane that has been carefully formed due to contact with the guide roll or contact between the hollow fibers when filling the module. In contrast, when forming a polymer thin film on the inner surface of a hollow fiber, the polymer membrane can be formed after modularizing the hollow fibers, and the polymer membrane will not be damaged during subsequent handling. One known method for forming a polymer thin film on the inner surface of a hollow fiber is, for example, filling the hollow portion of the hollow fiber with a first solution to form a liquid film of the first solution on the inner surface of the hollow fiber, removing excess solution by passing high-pressure air through the hollow portion, and then passing a second solution through the hollow portion (see, for example, Patent Document 5). Furthermore, a method is known in which a prepolymer or oligomer is applied to the inner surface of a hollow fiber and then crosslinked to form a thin polymer film on the inner surface of the hollow fiber (Patent Document 6).

[0005] Patent Publication No. 2014-512951 International Publication No. 2014 / 078415 Japanese Patent Laid-Open No. 63-205108 Japanese Patent Laid-Open No. 2-6848 Chinese Patent No. 101269301 Specification of Patent Publication No. 3-35971 International Publication No. 2016 / 027869

[0006] In order for a composite semipermeable membrane to achieve both high water permeability and high rejection, it is important to form the polyamide membrane, which is the separation functional layer, thin and without defects. On the other hand, if the polyamide membrane is made too thin, there is a problem that salt rejection and back pressure resistance decrease. The surface of the thin film formed by the technology of Patent Document 6 is extremely smooth, and therefore the water permeation rate is insufficient for practical use. For example, Patent Document 7 discloses a composite semipermeable membrane having a separation active layer with little variation in average thickness in the radial and longitudinal directions, but there is room for improvement in achieving both water permeability and rejection performance.

[0007] The present invention has been made to improve the above-mentioned current situation, and an object of the present invention is to provide a composite semipermeable membrane having a separation functional layer with a predetermined ratio of thick polyamide film areas to thin polyamide film areas, and exhibiting high water permeability and high blocking properties, and a method for producing the same.

[0008] The present invention is as follows: [1] A composite semipermeable membrane comprising a support membrane and a polyamide separation function layer on the support membrane, wherein the polyamide separation function layer comprises protrusions having a protrusion structure comprising a plurality of convex portions and a plurality of concave portions, and a smooth portion without the protrusion structure, wherein in a surface image of the polyamide separation function layer at a magnification of 1000 times using a scanning electron microscope, the proportion of the protrusions to the surface of the support membrane is 10% or more and 90% or less. [2] The composite semipermeable membrane according to [1], wherein the proportion of the protrusions is 10% or more and 60% or less. [3] The composite semipermeable membrane according to [1] or [2], wherein the polyamide separation function layer is a polycondensation product of one or more first monomers selected from polyfunctional amines and one or more second monomers selected from polyfunctional acid halides. [4] The composite semipermeable membrane according to [3], wherein the polyfunctional amine is an aliphatic amine. [5] A method for producing a composite semipermeable membrane comprising a microporous hollow fiber support membrane and a polyamide separation functional layer on the microporous hollow fiber support membrane, the method comprising: forming a liquid membrane of a first solution containing one of one or more first monomers selected from polyfunctional amines and one or more second monomers selected from polyfunctional acid halides on the inner surface of the microporous hollow fiber support membrane; then creating a pressure difference between the inside and outside of the microporous hollow fiber support membrane such that (inside pressure) > (outside pressure); and then contacting the liquid membrane of the first solution with a second solution containing the other of the first monomer and the second monomer. [6] The method according to [5], in which the pressure difference is created by reducing the pressure on the outside of the microporous hollow fiber support membrane. [7] The method according to [5] or [6], in which the pressure difference is 5 to 70 kPa. [8] A method for concentrating a raw material liquid, comprising a step of concentrating a raw material liquid containing an electrolyte and one or more solutes using the composite semipermeable membrane according to any one of [1] to [4]. [9] The method for concentrating a raw material liquid according to [8], comprising carrying out the concentration by one or more methods selected from the group consisting of a reverse osmosis membrane method, a forward osmosis membrane method, a nanofiltration membrane method, a dialysis method, and a salt exchange method.

[10] The method for concentrating a raw material liquid according to [8] or [9], wherein the solute is one or more compounds selected from the group consisting of nucleic acids, proteins, peptides, amino acids, antibiotics, small molecule drugs, and vitamins.

[11] The method for concentrating a raw material liquid according to any one of [8] to

[10] , wherein the composite semipermeable membrane is in the form of a hollow fiber membrane.

[12] The method for concentrating a raw material liquid according to any one of [8] to

[11] , wherein the electrolyte is an organic or inorganic compound having a molecular weight of 50 to 200.

[13] The method for concentrating a raw material liquid according to any one of [8] to

[12] , wherein the pKa of the electrolyte is -2 to 4.

[14] The method for concentrating a raw material liquid according to any one of [8] to

[13] , wherein the molecular weight of the solute is 300 to 3,000.

[15] The method for concentrating a raw material liquid according to any one of [8] to

[14] , wherein the raw material liquid contains one or more organic solvents.

[0009] The composite semipermeable membrane of the present invention has a separation functional layer having a predetermined ratio of thick polyamide membrane areas to thin polyamide membrane areas, thereby achieving a thin composite semipermeable membrane. Therefore, the composite hollow fiber membrane has high water permeability and rejection, and exhibits stable performance without a decrease in salt rejection or back pressure resistance. Therefore, the composite hollow fiber membrane can be suitably applied to the concentration of raw material liquids, and can be used, for example, to concentrate valuable materials.

[0010] 1 is a cross-sectional view showing an example of the structure of a composite hollow fiber membrane module of the present invention. 2 is a schematic diagram showing an example of the configuration of an apparatus for forming a separation function layer on a microporous hollow fiber support membrane module by the method of the present invention. 3 is a scanning electron microscope image of the separation function layer of a composite semipermeable membrane constituting the module of Example 1.

[0011] An example of an embodiment of the present invention will be described in detail below. This embodiment provides a composite semipermeable membrane comprising a polyamide separation function layer on a support membrane. In one aspect, the polyamide separation function layer of the composite semipermeable membrane of this embodiment includes a protruding portion having a protruding structure comprising a plurality of convex portions and a plurality of concave portions, and a smooth portion without a protruding structure. In one aspect, the polyamide separation function layer of the composite semipermeable membrane of this embodiment has a proportion of the protruding portions occupying 10% to 90% of the support membrane surface in a surface image at 1000x magnification using a scanning electron microscope. In one aspect, the composite semipermeable membrane is composed of hollow fibers. In one aspect, this embodiment provides a method for producing the composite semipermeable membrane of this embodiment. In one aspect, this embodiment provides a method for concentrating a feedstock liquid using the composite semipermeable membrane of this embodiment. In one aspect, the composite hollow fiber membrane module of this embodiment is a module including a plurality of composite semipermeable membranes composed of hollow fibers. In one embodiment, a composite hollow fiber membrane module can be produced by forming a polyamide separation functional layer on a microporous hollow fiber support membrane of a microporous hollow fiber support membrane module containing a plurality of microporous hollow fiber support membranes.

[0012] <Polyamide Separation Functional Layer> The polyamide separation functional layer of this embodiment includes a protrusion having a protrusion structure with multiple convex portions and multiple concave portions, and a smooth portion without a protrusion structure. When an image of the polyamide separation functional layer is captured using a scanning electron microscope, the amount of secondary electrons generated varies depending on the unevenness of the layer. Therefore, in areas with many protrusions, the amount of secondary electrons is high, resulting in a white image, while in areas with few protrusions, the amount of secondary electrons is low, resulting in a black image. In this disclosure, the white and black portions of an image obtained by binarizing an image of the polyamide separation functional layer captured using a scanning electron microscope are referred to as the protrusions and smooth portion, respectively. The conditions for capturing an image of the polyamide separation functional layer using a scanning electron microscope are the same as those described in the examples.

[0013] In the polyamide separation function layer of this embodiment, in a surface image taken at 1000x magnification using a scanning electron microscope, the proportion of protrusions on the support membrane surface is preferably 10% to 90%, more preferably 10% to 60%, and even more preferably 10% to 50%. In the surface image, the area of ​​the support membrane surface corresponds to the area of ​​the polyamide separation function layer. The inventors have demonstrated that as the proportion of thick protrusions increases in the polyamide separation function layer of a composite semipermeable membrane, water permeability decreases, but salt rejection, salt rejection after application of back pressure, and durability increase. On the other hand, the inventors have demonstrated that as the proportion of thin smooth portions increases in the polyamide separation function layer of a composite semipermeable membrane, water permeability increases. In the composite semipermeable membrane of this embodiment, the polyamide separation function layer has an appropriate proportion of thick protrusions and thin smooth portions, thereby achieving a balanced increase in water permeability, salt rejection, and durability. The thickness of the polyamide separating functional layer is preferably 0.1 to 3 μm, more preferably 0.2 to 2 μm.

[0014] The microporous hollow fiber support membrane (hereinafter also referred to as the support membrane) in this embodiment is a membrane for supporting the polyamide separation function layer made of the above-mentioned polymer thin film, and preferably does not itself exhibit substantial separation performance for the substance to be separated. Any microporous hollow fiber support membrane can be used as this microporous hollow fiber support membrane, including known microporous hollow fiber support membranes. The microporous hollow fiber support membrane in this embodiment preferably has micropores on its inner surface, with a pore size of preferably 0.001 μm to 0.1 μm, more preferably 0.005 μm to 0.05 μm. Meanwhile, the structure of the microporous hollow fiber support membrane from the inner surface to the outer surface, other than the inner surface, is preferably as sparse as possible while maintaining strength, in order to reduce the permeation resistance of the permeating fluid. The sparse structure in this portion is preferably, for example, a mesh-like structure, a finger-like void structure, or a mixture thereof.

[0015] In this embodiment, the permeation performance, which is expressed as the amount of pure water that permeates a certain membrane area (internal surface area) in a certain time when a certain pressure is applied to the microporous hollow fiber support membrane, is preferably 100 kg / m ２ / hr / 100 kPa or more, more preferably 200 kg / m ２ / hr / 100 kPa or more. If the permeability of the support membrane is too low, the permeability of the resulting composite hollow fiber membrane module is likely to be low as well. The permeability of the support membrane is preferably as high as possible within a range that does not impair the mechanical strength of the support membrane. Generally, as the permeability increases, the mechanical strength decreases. Therefore, the permeability of the microporous hollow fiber support membrane in this embodiment is preferably 50,000 kg / m ２ / hr / 100kPa or less, more preferably 10,000kg / m ２ / hr / 100kPa or less is the guideline.

[0016] Any material can be used for such a microporous hollow fiber support membrane as long as it can be used to form a microporous hollow fiber support membrane. However, when producing a composite semipermeable membrane by the preferred production method of this embodiment, it is necessary that the material is not chemically damaged by the monomer solution used. Therefore, from the viewpoints of chemical resistance, membrane formability, durability, etc., the material for the microporous hollow fiber support membrane is preferably composed primarily of at least one selected from polysulfone, polyethersulfone, polyacrylonitrile, polyethylene, polypropylene, polyamide, polyvinylidene fluoride, and cellulose acetate, more preferably at least one selected from polysulfone and polyethersulfone, and even more preferably polyethersulfone.

[0017] The fiber diameter size of the microporous hollow fiber support membrane used in this embodiment is not particularly limited. Considering the membrane production stability, ease of handling, membrane area when made into a module, etc., the outer diameter is preferably in the range of 100 μm to 3,000 μm and the inner diameter is 30 μm to 2,500 μm, and more preferably the outer diameter is 200 μm to 1,500 μm and the inner diameter is 50 μm to 1,000 μm. Such a microporous hollow fiber support membrane can be produced using a material selected from the above materials by a known dry / wet membrane production method, melt membrane production method, wet membrane production method, or the like.

[0018] The microporous hollow fiber support membrane module used in this embodiment is obtained by modularizing the microporous hollow fiber support membrane. A cylindrical housing with a diameter of 2 to 20 inches can be used as the module housing, and the module can be formed using, for example, a urethane-based or epoxy-based adhesive. The microporous hollow fiber support membrane has a structure in which a hollow fiber bundle is housed within the module and the fiber bundle ends are fixed with the adhesive. The adhesive is solidified so as not to clog the pores of each hollow fiber. This ensures the flowability of the hollow fibers. Furthermore, the module preferably includes a conduit that communicates with the inside (hollow portion) of the hollow fiber bundle but not with the outside, and a conduit that communicates with the outside of the hollow fiber bundle but not with the inside. This configuration allows the inside and outside of the hollow fiber bundle to be subjected to different pressures, making it suitable for use in forming the polyamide separation function layer (described below) in this embodiment. In this embodiment, the polyamide separating function layer made of a high molecular weight polymer thin film can be formed by an interfacial polymerization reaction and has substantial separating performance.

[0019] The thinner the polymer thin film, the more preferable it is if there are no pinholes. However, to maintain mechanical strength and chemical resistance, an appropriate thickness is required. Therefore, taking into consideration the membrane formation stability, permeability, etc., the thickness of the polymer thin film is preferably 0.1 to 3 μm, more preferably 0.2 to 2 μm. In this embodiment, the membrane area is a value defined by the following mathematical formula (3) using the length, inner diameter, and number of hollow fibers excluding adhesive portions in the module. Here, a is the membrane area (m ２ a = c × π × b × n (3) From the viewpoint of practical use, the membrane area of ​​the module is 1 m ２ Preferably, it is 1.5 m or more. ２ More preferably, it is equal to or greater than this.

[0020] The polymer in the high molecular weight polymer thin film is preferably a polycondensation product of, for example, one or more first monomers selected from polyfunctional amines and one or more second monomers selected from polyfunctional acid halides. More specifically, for example, polyamides obtained by interfacial polycondensation reaction of polyfunctional amines and polyfunctional acid halides can be mentioned. When these polymer thin films are used as the polyamide separation functional layer of the present disclosure, the separation performance refers to the ability to separate pure water from solutes such as ions dissolved therein.

[0021] The types and combinations of the first and second monomers, and the type of solvent (described below) used are not particularly limited as long as the two monomers undergo a polymerization reaction immediately at the interface to form a polymer thin film. However, it is preferable that at least one of the first and second monomers contains a reactive compound having three or more reactive groups. This allows the formation of a thin film made of a three-dimensional polymer, which is more preferable in terms of film strength.

[0022] Examples of the polyfunctional amine include polyfunctional aromatic amines, polyfunctional aliphatic amines, monomers having a plurality of reactive amino groups, and prepolymers thereof.

[0023] The polyfunctional aromatic amine is an aromatic amino compound having two or more amino groups in one molecule, and more specific examples thereof include m-phenylenediamine, p-phenylenediamine, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenylamine, 3,5-diaminobenzoic acid, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 1,3,5-triaminobenzene, and 1,5-diaminonaphthalene, and these can be used alone or in combination.

[0024] The polyfunctional aliphatic amine is an aliphatic amino compound having two or more amino groups in one molecule, and more specifically, for example, primary amines having a cyclohexane ring, such as 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 4,4'-bis(paraaminocyclohexyl)methane, 1,3-bis(aminomethyl)cyclohexane, 2,4-bis(aminomethyl)cyclohexane, and 1,3,5-triaminocyclohexane; secondary amines having a piperazine ring, such as piperazine, 2-methylpiperazine, ethylpiperazine, and 2,5-dimethylpiperazine; secondary amines having a piperidine ring, such as 1,3-bis(4-piperidyl)methane, 1,3-bis(4-piperidyl)propane, and 4,4'-bipiperidine; and amines having both primary and secondary amino groups, such as 4-(aminomethyl)piperidine. Examples of suitable polyfunctional aliphatic amines include ethylenediamine, propylenediamine, 1,2-propanediamine, 1,2-diamino-2-methylpropane, 2,2-dimethyl-1,3-propanediamine, tris(2-aminoethyl)amine, N,N'-dimethylethylenediamine, and N,N'-dimethylpropanediamine, and these can be used alone or in mixtures. In this embodiment, 2,5-dimethylpiperazine is particularly preferred as the polyfunctional aliphatic amine. Mixtures of these polyfunctional aliphatic amines with the above-mentioned polyfunctional aromatic amines can also be used.

[0025] Examples of the monomer having multiple reactive amino groups include polyethyleneimine, amine-modified polyepichlorohydrin, aminated polystyrene, etc. Suitable examples of the prepolymer include prepolymers made of one or more compounds selected from piperazine, 4-(aminomethyl)piperidine, ethylenediamine, and 1,2-diamino-2-methylpropane.

[0026] Examples of the polyfunctional acid halide include polyfunctional aromatic acid halides and polyfunctional aliphatic acid halides, etc. These may be bifunctional or higher so as to react with the polyfunctional amine to form a polymer.

[0027] The polyfunctional aromatic acid halide is an aromatic acid halide compound having two or more acid halide groups in one molecule.Specific examples include trimesic acid halide, trimellitic acid halide, isophthalic acid halide, terephthalic acid halide, pyromellitic acid halide, benzophenonetetracarboxylic acid halide, biphenyldicarboxylic acid halide, naphthalenedicarboxylic acid halide, pyridinedicarboxylic acid halide, benzenedisulfonic acid halide, etc., and these can be used alone or in mixture.In this embodiment, trimesic acid chloride alone, a mixture of trimesic acid chloride and isophthalic acid chloride, or a mixture of trimesic acid chloride and terephthalic acid chloride is particularly preferably used.

[0028] The polyfunctional aliphatic acid halide is an aliphatic acid halide compound having two or more acid halide groups in one molecule.Specific examples include alicyclic polyfunctional acid halide compounds such as cyclobutanedicarboxylic acid halide, cyclopentanedicarboxylic acid halide, cyclopentanetricarboxylic acid halide, cyclopentanetetracarboxylic acid halide, cyclohexanedicarboxylic acid halide, and cyclohexanetricarboxylic acid halide; as well as propanetricarboxylic acid halide, butanetricarboxylic acid halide, pentanetricarboxylic acid halide, succinic acid halide, and glutaric acid halide.These compounds can be used alone or in combination, and mixtures of these polyfunctional aliphatic halides with the above-mentioned polyfunctional aromatic acid halides can also be used.The first and second monomers described above are each dissolved in a suitable solvent and subjected to interfacial polymerization as a solution.

[0029] In this specification, the term "first solution" refers to a solution containing a monomer that will first come into contact with the microporous hollow fiber support membrane, and the term "second solution" refers to a solution containing a monomer that will come into contact with the support membrane after the first solution has come into contact with the support membrane and react with the monomer in the first solution to form a polymer. One of the first monomer and the second monomer will be contained in the first solution, and the other will be contained in the second solution. Either monomer may be contained in either solution, but an embodiment in which both monomers are contained in one solution is not preferred.

[0030] The solvents for the first and second solutions are not particularly limited, as long as they dissolve the monomers contained therein, form a liquid-liquid interface when the two solutions come into contact, and do not damage the microporous hollow fiber support membrane. Examples of such solvents include water and alcohols, either alone or in combination, for the first solution, and hydrocarbon solvents such as n-hexane, cyclohexane, n-heptane, n-octane, n-nonane, and n-decane, either alone or in combination, for the second solution. By selecting such solvents, the first and second solutions become immiscible, allowing the interfacial polymerization to proceed as expected. It is preferable to select the first monomer as the monomer contained in the first solution, and the second monomer as the monomer contained in the second solution. The concentrations of these reactive compounds contained in the first and second solutions vary depending on the type of monomer, the partition coefficient relative to the solvent, and other factors, and are not particularly limited and can be appropriately determined by one skilled in the art.

[0031] For example, the following example shows a case where an aqueous 2,5-dimethylpiperazine solution is used as the first solution and an n-hexane solution of trimesoyl chloride is used as the second solution: The concentration of 2,5-dimethylpiperazine is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass. The concentration of trimesoyl chloride is preferably 0.01 to 10% by mass, more preferably 0.1 to 5% by mass. If the concentrations of these solutions are too low, the formation of a thin film by interfacial polymerization may be incomplete, leading to defects and reduced separation performance. Conversely, if the concentrations are too high, the thin film formed may be too thick, resulting in reduced permeability. In addition, the amount of residual unreacted material in the membrane may increase, adversely affecting membrane performance. If acid is generated during the interfacial polymerization reaction, an alkali may be added as an acid scavenger to the first or second solution. Furthermore, surfactants for improving wettability with the microporous hollow fiber support membrane, catalysts for accelerating the reaction, and the like may be added as needed.

[0032] Examples of the acid scavenger include, for example, caustic alkalis such as sodium hydroxide; sodium phosphates such as trisodium phosphate; sodium carbonates such as sodium carbonate; and tertiary amines such as trimethylamine, triethylamine, and triethylenediamine. Examples of the surfactant include, for example, sodium lauryl sulfonate and sodium laurylbenzene sulfonate. Examples of the catalyst include, for example, dimethylformamide. These can be added in advance to the first solution or the second solution.

[0033] In one aspect, the composite semipermeable membrane of this embodiment may be manufactured as a plurality of composite hollow fiber membranes contained in a composite hollow fiber membrane module. The following describes the manufacture of a composite hollow fiber membrane module as an example of a method for manufacturing a composite semipermeable membrane. The composite hollow fiber membrane module of this embodiment can be manufactured by providing a polyamide separation function layer to the aforementioned microporous hollow fiber support membrane module containing a plurality of microporous hollow fiber support membranes, i.e., a membrane module supporting a polyamide separation function layer made of a thin polymer film.

[0034] An example of the structure of a composite hollow fiber membrane module according to this embodiment is shown in FIG. 1 . The composite hollow fiber membrane module 1 has a cylindrical body filled with a fiber bundle consisting of a plurality of hollow fibers 4, and both ends of the hollow fiber bundle are fixed to the cylinder with adhesive fixing portions 5 and 6. The cylindrical body has shell-side conduits 2 and 3 on its side and is sealed by headers 7 and 8. The adhesive fixing portions 5 and 6 are solidified so as not to clog the pores of the hollow fibers. The headers 7 and 8 have core-side conduits 9 and 10, respectively, which communicate with the inside (hollow portion) of the hollow fibers 4 but not with the outside. These conduits allow liquid to be introduced into or removed from the hollow fibers 4. The shell-side conduits 2 and 3 communicate with the outside of the hollow fibers 4 but not with the inside.

[0035] In this specification, the inside of the hollow fiber is referred to as the core side, and the space between the outside of the hollow fiber and the tube is referred to as the shell side. In the composite hollow fiber membrane module of this embodiment, the liquid flowing through the core side and the liquid flowing through the shell side are in contact only via the hollow fiber membrane. Furthermore, a pressure difference can be created between the inside and outside of the hollow fiber by applying different pressures to the shell-side conduits 2 and 3 and the core-side conduits 9 and 10, respectively. In this embodiment, the core side of the microporous hollow fiber support membrane module is filled with a first solution containing one of the first and second monomers, and then a pressure difference is created between the core and shell sides. Then, a second solution containing the other of the first and second monomers and immiscible with the first solution is passed through the module, causing a reaction between the first and second monomers on the inner surface of the microporous hollow fiber support membrane to form a polymer thin film, thereby forming the desired composite semipermeable membrane, thereby producing a composite hollow fiber membrane module.

[0036] The method for creating a pressure difference between the core side and the shell side is arbitrary. For example, any of the following methods can be selected: a method of reducing the pressure on both the core side and the shell side; a method of reducing the pressure on the shell side and setting the core side to atmospheric pressure; a method of setting the shell side to atmospheric pressure and pressurizing the core side; a method of pressurizing both the core side and the shell side. However, in this embodiment, it is preferable to set the pressure on the shell side lower than that on the core side.

[0037] By establishing the above-mentioned pressure difference (core-side pressure > shell-side pressure) after filling the core side with the first solution, excess first solution is believed to penetrate into the micropores of the support membrane, forming a liquid membrane of the first solution with a relatively uniform thickness on the inner surface of the support membrane throughout the module. In this embodiment, the protrusions and smooth portions of the polyamide separation function layer made of a thin polymer film formed on the inner surface of the microporous hollow fiber support membrane of the composite hollow fiber membrane module are closely related to the thickness of the liquid membrane of the first solution. The thickness of this liquid membrane can be adjusted by the pressure difference between the core side and the shell side applied to the module, the time for which the pressure difference is maintained, the amount of surfactant added to the first solution, and other factors. To form a polyamide separation function layer with protrusions and smooth portions in a predetermined ratio, the pressure difference between the core side and the shell side is preferably 5 to 70 kPa. The time for which the pressure difference is maintained is preferably 1 to 100 minutes, more preferably 10 to 50 minutes. The amount of the surfactant added to the first solution is preferably 0.01 to 1% by mass, more preferably 0.05 to 0.5% by mass, based on the total amount of the first solution.

[0038] The greater the pressure difference and the longer the pressure difference is maintained, the thinner the thickness of the liquid membrane of the first solution becomes; conversely, the thicker it becomes. If the liquid membrane thickness is too small, even slight variations in membrane thickness can result in areas where the liquid membrane is not formed, causing defects in the separation function layer. Furthermore, if the liquid membrane thickness is too large, sufficient permeation performance may not be achieved. In the manufacturing method for the composite hollow fiber membrane module of this embodiment, the pressure difference between the core side and the shell side is uniform from the outermost portion to the center of the hollow fibers in the module, and is also uniform from one end to the other end of the hollow fibers in the module. This results in a uniform thickness of the liquid membrane of the first solution formed at each location, and the thickness of the separation function layer formed based on this is also uniform. Therefore, variation in the liquid permeation rate at each location is reduced, allowing the composite hollow fiber membrane module to exhibit stable, high performance.

[0039] In conventional methods in which a liquid membrane of the first solution is formed inside the hollow fibers by passing high-pressure air through the module, the longer the module length and the larger the diameter of the module, the greater the variation in the average thickness of the separation function layer at each location. However, in the manufacturing method of the composite hollow fiber membrane module of this embodiment, the thickness is substantially uniform at each location. The larger the module size, the more pronounced the effects of this embodiment. However, in practice, it is convenient for the module to have a length of 50 cm to 300 cm and a diameter of 2 inches to 20 inches. Of course, the effects of this embodiment can also be achieved with modules with lengths and diameters shorter or longer than these.

[0040] The present inventors speculate as follows about the mechanism by which the surface of the separation functional layer in the composite hollow fiber membrane module of this embodiment has a protrusion structure comprising a plurality of convex portions and a plurality of concave portions. However, this embodiment is not bound by the following theory. The separation functional layer in the composite hollow fiber membrane module of this embodiment is preferably formed by interfacial polymerization. In interfacial polymerization, it is thought that when a liquid film of a first monomer solution formed on the hollow fiber surface comes into contact with a second monomer solution, the two are incompatible, and polymerization proceeds at the interface to form a polymerized layer. As a result, it is thought that the formed separation functional layer has a shape with a protrusion structure on its surface. It is speculated that if a separation functional layer is formed by a method other than interfacial polymerization, it will not be possible to form a separation functional layer with a protrusion structure on its surface.

[0041] A method for producing a composite hollow fiber membrane module of this embodiment will be described below with reference to Figure 2. In the apparatus of Figure 2, a microporous hollow fiber support membrane module 11, in which the inside (core side) of the microporous hollow fiber support membrane is filled with a first solution, has a piping 15 connected to a second solution storage tank 14 at the core side inlet, and a pump 16 connected midway for pressure-feeding the second solution. A piping 18 from a reaction wastewater storage tank 17 is connected to the core side outlet, and a core-side pressure regulator 12 is connected from this tank to control the pressure inside the hollow fibers of the microporous hollow fiber support membrane module 11. An end cap 19 is fitted to the lower conduit on the shell side of the microporous hollow fiber support membrane module 11, and a shell-side pressure regulator 13 for controlling the shell pressure is connected to the upper conduit.

[0042] The composite hollow fiber membrane module of this embodiment is manufactured, for example, by the following procedure: First, each pipe is connected to a microporous hollow fiber support membrane module 11 whose core side (inside the microporous hollow fiber support membrane) is filled with a first solution. Next, a pressure difference is established between the core side and the shell side using the core side pressure regulator 12 and the shell side pressure regulator 13 (core side pressure > shell side pressure). At this time, excess first solution in the core side hollow fibers enters the micropores due to the pressure difference (and may seep into the shell side), forming a liquid membrane of uniform thickness inside the hollow fibers. Next, the second solution in the storage tank 14 is pumped inside the hollow fibers and brought into contact with the liquid membrane of the first solution. This contact causes interfacial polymerization of both monomers, forming a separation functional layer consisting of a thin polymer film inside the microporous hollow fiber support membrane. While the pressure on the core side may fluctuate when the second solution is delivered, this pressure fluctuation is suppressed by the function of the core side pressure control device 12. In this way, when carrying out interfacial polymerization, it is preferable to maintain a preset pressure difference between the core side and the shell side.

[0043] In this way, a thin polymer film is formed on the inside of the microporous hollow fiber support membrane by interfacial polymerization of the first monomer and the second monomer, thereby producing the composite hollow fiber membrane module of this embodiment. In the method for producing a composite hollow fiber membrane module of this embodiment, the thickness of the liquid film of the first monomer solution used to form the polymer by interfacial polymerization is uniform at the outer periphery and center of the module, and at the top and bottom of the module. Therefore, the composite hollow fiber membrane module has a uniform polymer layer throughout its entirety. Because the interfacial polymerization proceeds at the interface between the first monomer solution and the second monomer solution, the surface of the polymer layer formed has a protruding structure with multiple convex and concave portions.

[0044] The performance of the composite semipermeable membrane of this embodiment includes water permeability and rejection, which can be evaluated by the water permeation rate and rejection rate, respectively. These membrane performances are basically evaluated at room temperature (25°C). Here, the water permeation rate (Flux) refers to the amount of solution (unit: kg m) that permeates the membrane per membrane area during pressure filtration. -2 ・hr -1・bar -1 ) and is the amount of solution (unit: kg m) that permeates the membrane per membrane area for various solutions pressurized in the range of 0.1 to 5 bar. -2 ・hr -1 ・bar -1 ) The permeability indicated by the amount of water permeated and the rejection indicated by the rejection rate are usually in a trade-off relationship, and it is difficult to achieve both performances at the same time. However, the composite semipermeable membrane of this embodiment can achieve a good balance between the permeability and the rejection rate, and is therefore excellent in processes such as the separation, purification, and concentration of valuable substances in the raw material solution. The flux and rejection rate are measured by the methods described in the Examples.

[0045] [Flux] In the method for concentrating a raw material liquid according to the present embodiment, the flux, which is the water permeation rate per membrane area of ​​the composite hollow fiber membrane module according to the present embodiment, is preferably as large as possible. However, in order to ensure a water permeation rate equivalent to or greater than that of currently commercially available membranes using a module with a space-occupying volume equivalent to that of the membranes, a flux of 3 kg / (m ２ The water permeability of a composite hollow fiber membrane module in this specification means the amount of water that moves from raw water to a draw solution due to osmotic pressure when raw water to be treated and a draw solution with a higher concentration are placed across a composite semipermeable membrane, and is defined by the following formula (1): Flux = L / (M × H × bar) (1) Here, Flux is the water permeability (kg / (m ２ × hr × bar), L is the amount of water permeated (kg), M is the internal surface area of ​​the membrane (m ２ ), H is time (hr) and bar is back pressure.

[0046] <Method for Concentrating a Raw Material Liquid> The method for concentrating a raw material liquid according to this embodiment includes a step of concentrating a raw material liquid containing an electrolyte and one or more solutes using the composite semipermeable membrane according to this embodiment. Examples of such methods include evaporation, thin-film distillation, evaporation, membrane distillation, pervaporation, vapor permeation, reverse osmosis, nanofiltration, forward osmosis, dialysis, and salt exchange. The evaporation method involves circulating a gas through a container containing the raw material liquid to vaporize the first solvent in the raw material liquid and remove it from the container. In the method for concentrating a raw material liquid according to this embodiment, concentration is preferably performed by one or more methods selected from the group consisting of reverse osmosis, forward osmosis, nanofiltration, dialysis, and salt exchange. However, concentration may also be performed by combining other methods. Among these methods, dialysis, salt exchange, reverse osmosis, nanofiltration, and forward osmosis are effective because they can remove solvent from the raw material liquid without heating, resulting in less thermal denaturation of valuable materials.

[0047] The composite semipermeable membrane may have any of the following structures: a hollow fiber membrane, a tubular membrane, and a flat membrane. A hollow fiber composite semipermeable membrane is preferred because it can form flow paths for the raw material solution and the draw solution without using a spacer or the like, and can perform uniform concentration.

[0048] <Feedstock Liquid> The feedstock liquid targeted by the concentration method of this embodiment contains one or more solutes and an electrolyte. In one aspect, the feedstock liquid may contain one or more solvents (e.g., one or more organic solvents). Examples of feedstock liquids applicable to the concentration method of this embodiment include food products; pharmaceuticals; seawater; and produced water discharged from gas fields, oil fields, and the like. However, considering the advantage of this embodiment that concentration can be performed without the need for heating, the concentration method of this embodiment is effective when applied to feedstock liquids containing substances that are likely to be decomposed by heating, particularly raw materials for pharmaceuticals, functional chemical species, and the like, as valuable resources.

[0049] The temperature of the raw material liquid to be subjected to the method for concentrating the raw material liquid of this embodiment is preferably adjusted to a range of 1°C or higher and 50°C or lower.

[0050] <Solute> In the present disclosure, the solute refers to a pharmaceutical ingredient, a functional chemical species, etc. Examples of the pharmaceutical ingredient include one or more compounds selected from the group consisting of amino acids, peptides, proteins, sugars, vaccines, nucleic acids, antibiotics, antibody-drug conjugates (ADCs), yeast, small molecule drugs, and vitamins.

[0051] An amino acid is a compound having a single amino acid backbone consisting of a carboxyl group, an amino group, and a moiety connecting them. In the present disclosure, the term "amino acid" encompasses essential amino acids, non-essential amino acids, and unnatural amino acids. Essential amino acids include, for example, tryptophan, lysine, methionine, phenylalanine, threonine, valine, leucine, and isoleucine. Non-essential amino acids include, for example, arginine, glycine, alanine, serine, tyrosine, cysteine, asparagine, glutamine, proline, aspartic acid, and glutamic acid. Unnatural amino acids are artificial compounds that do not occur in nature and have a single amino acid backbone within the molecule. Examples of unnatural amino acids used as pharmaceutical raw materials in the present disclosure include labeled amino acids and functionalized amino acids. Labeled amino acids are compounds in which a desired labeling compound is bound to the amino acid backbone. Examples of labeling compounds include dyes, fluorescent substances, luminescent substances, enzyme substrates, coenzymes, antigenic substances, and protein-binding substances. Examples of functionalized amino acids include photoresponsive amino acids, photoswitch amino acids, fluorescent probe amino acids, and fluorescently labeled amino acids.

[0052] A peptide refers to a compound in which 2 or more but less than 70 amino acid residues are bonded, and may be linear or cyclic. Examples of peptides in the present disclosure include L-alanyl-L-glutamine, β-alanyl-L-histidine cyclosporine, glutathione disulfide, and neotame. A protein generally refers to a compound in which amino acid residues are bonded that has a longer chain than a peptide. Examples of proteins in the present disclosure include interferon α, interferon β, interleukins 1 to 12, growth hormone, erythropoietin, insulin, granulocyte-colony stimulating factor (G-CSF), tissue plasminogen activator (TPA), natriuretic peptide, blood coagulation factor VIII, somatomedin, glucagon, growth hormone-releasing factor, serum albumin, calcitonin, and lipase G Amano 50.

[0053] Examples of sugars include monosaccharides, disaccharides, sugar chains (excluding disaccharides), and sugar chain derivatives. Examples of monosaccharides include glucose, fructose, galactose, mannose, ribose, and deoxyribose. Examples of disaccharides include maltose, sucrose, and lactose. The sugar chain in this disclosure is a concept excluding disaccharides, and includes, for example, cellulose, glycosaminoglycan, starch, saccharin, dextran, dextrin, inulin, curdlan, fucoidan, fructan, pullulan, pectin, polydextrose, maltodextrin, lignin, xylan, mannan, glucomannan, glucuronoxylan, and xylose. Examples of sugar chain derivatives include sugar derivatives such as N-acetylglucosamine, N-acetylgalactosamine, and N-acetylneuraminic acid.

[0054] Examples of vaccines include hepatitis A vaccine, hepatitis B vaccine, and hepatitis C vaccine; examples of nucleic acids include oligonucleotides, RNA, aptamers, and decoys; examples of antibiotics include streptomycin and vancomycin; examples of antibody-drug conjugates (ADCs) include brentuximab vedotin (Adcetris), trastuzumab emtansine (Kadcyla), and gemtuzumab ozogamicin (Mylotarg). Examples of yeast include Saccharomyces cerevisiae, Pichiastipitis, Candida shehatae, and Pachysolentannophilus, including mutant strains thereof. Examples of small molecule drugs include aspirin. Examples of vitamins include vitamin A, vitamin B, and vitamin C, as well as derivatives and salts thereof. Vitamin B includes, for example, vitamin B6 and vitamin B12.

[0055] The term "functional chemical species" refers to various chemical species used as functional chemical products, as well as their modified products, precursors, raw materials, etc. Examples of functional chemical species include metal nanoparticles, semiconductor nanoparticles, metal colloids, nanodiamonds, porous nanoclays, metal organic frameworks (MOFs), carbon nanotubes, fullerenes, graphene, graphene oxide, carbon nanohorns, and cellulose nanofibers, as well as their modified products, precursors, raw materials, etc.

[0056] The molecular weight, in terms of number average molecular weight, of the solute contained in the raw material liquid subjected to the raw material liquid concentrating method of this embodiment is preferably in the range of 300 to 3000. The molecular weight of the solute can be determined by calculation from the chemical formula of the solute.

[0057] <Solvent> In the present disclosure, a solvent is a compound capable of dissolving or dispersing a solute and an electrolyte. The solvent typically includes water and / or one or more organic solvents. The organic solvent is an organic compound having one or more carbon atoms, and in one embodiment, is a compound that exists in a liquid state at a temperature of 0°C or higher and lower than 50°C under normal pressure. However, carboxylic acids are excluded from the solvents in the present disclosure. Examples of organic solvents include alcohols, esters, ethers, aprotic polar compounds, aromatic compounds, aliphatic compounds, chlorinated hydrocarbon ketones, and aldehydes.

[0058] Specific examples of organic solvents include: alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-propyl alcohol, isopropanol, normal butanol, sec-butanol, t-butanol, and hexafluoroisopropyl alcohol; esters such as methyl formate, ethyl formate, methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, and isobutyl acetate; ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, cyclopentyl methyl ether, t-butyl methyl ether, anisole, and 1,2-dimethoxyethane; aprotic polar compounds such as acetonitrile, dimethylacetamide, N-methylpyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide, nitromethane, and sulfolane; aromatic compounds such as benzene, toluene, xylene, cumene, and pyridine; and aliphatic compounds such as heptane, hexane, cyclohexane, methylcyclohexane, and tetralin. Examples of chlorinated hydrocarbons include dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,2-dichloroethene, 1,1,1-trichloroethane, 1,1,2-trichloroethene, and chlorobenzene; examples of ketones include acetone, methyl butyl ketone, methyl ethyl ketone, and methyl isobutyl ketone; and examples of aldehydes include formaldehyde, acetaldehyde, propionaldehyde, butanal, acrolein, benzaldehyde, furfural, and vanillin.

[0059] <Electrolyte> In the present disclosure, the electrolyte refers to an organic or inorganic compound contained in the raw material solution. In one embodiment, the electrolyte is an organic compound having a molecular weight of 50 to 200. In one embodiment, the electrolyte is an inorganic compound such as magnesium sulfate or sodium chloride having a molecular weight of 50 to 200. The molecular weight of the electrolyte can be determined by calculation from the chemical formula of the electrolyte. In one embodiment, the acid dissociation constant (pKa) of the electrolyte is -2 to 4. The acid dissociation constant (pKa) of the electrolyte is measured by neutralization titration using methyl orange or the like as an indicator and titrating with sodium hydroxide or the like. Examples of the electrolyte in the present disclosure include organic acids. Examples of organic acids include formic acid, acetic acid, propionic acid, citric acid, fluoroacetic acid, difluoroacetic acid, trifluoroacetic acid (TFA), oxalic acid, gluconic acid, lactic acid, hexafluoroisopanol, glycolic acid, and glyceric acid.

[0060] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0061] <Water permeability (Flux) of composite hollow fiber membrane module> Water as solvent, 0.05 mass% MgSO as electrolyte ４ A sample solution containing 120 Mg (molecular weight) was used. The sample solution at 25°C was passed through the primary side of the modules of Examples 1 to 7 and Comparative Examples 1 to 3 described below at a flow rate of 120 mL / min, a back pressure of 2 bar, and an operation time of 10 minutes, and then filtered. The weight (kg) of the filtrate after 10 minutes was applied to the following formula (1) to calculate the flux. Flux = L / (M × H × bar) Formula (1) Here, flux is the water permeation rate (kg / (m ２ × hr × bar), L is the weight of the permeated filtrate (kg), M is the internal surface area of ​​the membrane (m ２ ), H is time (hr) and bar is back pressure. The water permeability (flux) of the composite hollow fiber membrane module is 3.0 (kg / (m ２ × hr × bar) or more, it can be suitably used for concentrating the raw material liquid.

[0062] MgSO4 in composite hollow fiber membrane modules ４ From the conductivity of the sample solution after the above filtration and the filtrate, the rejection rate of MgSO４ and the concentration of MgSO in the filtrate ４ The concentration of MgSO in the sample solution was measured. ４ and the concentration of MgSO in the filtrate ４ By applying the concentration of MgSO to the following equation (2), ４ The conductivity of the sample solution and the filtrate was measured using a conductivity meter (Horiba Ltd., product name: HE-960). ４ Rejection rate (%) = 100 × (1 - MgSO in the filtrate that permeated the membrane) ４ Concentration (wt%) / MgSO in sample solution ４ Concentration (wt%) of the composite hollow fiber membrane module ４ If the rejection rate is 97% or more, it can be suitably used for concentrating the raw material liquid.

[0063] <Scanning Electron Microscope Observation of the Separation Functional Layer and Measurement of the Protrusion and Smooth Portions of the Separation Functional Layer> - Preparation of Observation Sample As an observation sample, a composite semipermeable membrane was immersed in pure water, frozen using liquid nitrogen, and then dried by freeze-drying. The dried sample was then cut or subjected to Broad Ion Beam (BIB) processing, preferably BIB processing, to prepare a cross section perpendicular to the membrane surface. The obtained cross section was thinly coated with platinum, platinum / palladium, osmium tetroxide, or osmium to prepare an observation sample. The cross section of this observation sample was observed at an acceleration voltage of 1 to 6 kV, preferably 1 kV. The observation magnification may be any magnification that allows observation of the contact interface between the support membrane and the separation functional layer or the surface of the support membrane. For example, 5,000 to 100,000x is preferred, and 50,000x is more preferred.

[0064] Image processing Using a scanning electron microscope (acceleration voltage 1.0 kV, model: SU8000 manufactured by Hitachi High-Technologies Corporation), the surface of the polyamide separation function layer was observed at a magnification of 1000x, with three locations extracted per 10 cm of the membrane: the top, middle, and bottom. Secondary electron images were then taken. The obtained images were smoothed using a 55 x 55 Gaussian filter. The smoothed images were binarized using a known binarization method (Otsu's binarization), and the ratio of white to black areas was calculated to determine the ratio of protruding and smooth areas of the polyamide separation function layer.

[0065] [Example 1] The forward osmosis membrane (as a composite semipermeable membrane) housed in the composite hollow fiber forward osmosis membrane module (as a composite hollow fiber membrane module) in Example 1 was a forward osmosis membrane that used a hollow fiber membrane made of polysulfone (PSf) as a microporous hollow fiber support membrane and had a separation functional layer made of polyamide on the inner surface of the hollow fiber membrane. The composite hollow fiber forward osmosis membrane module of Example 1 was produced as follows.

[0066] <Production of Microporous Hollow Fiber Support Membrane> A homogeneous polymer solution (spinning dope) consisting of 19% by mass of polysulfone (Udel-P3500, manufactured by Solvay Specialty Polymers), 61% by mass of N-methyl-2-pyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 20% by mass of tetraethylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd.) was prepared as a spinning dope. The spinning dope was filled into a wet hollow fiber spinning machine equipped with a double spinneret. The spinning dope was discharged from the outer spinneret of the double spinneret, and the internal coagulation liquid (water) was discharged from the inner spinneret. The resulting mixture was introduced into a coagulation bath filled with water as the external coagulation liquid, resulting in a microporous hollow fiber support membrane. The resulting microporous hollow fiber support membrane had an outer diameter of 1.00 mm, an inner diameter of 0.60 mm, and a membrane thickness of 0.20 mm.

[0067] <Production of Support Membrane Module> One hundred and thirty of the above-mentioned microporous hollow fiber support membranes cut to a length of 120 mm were placed in a cylindrical housing made of synthetic resin with a diameter of 20 mm, and both ends were fixed with an adhesive so as not to block the hollow portions of the hollow fibers. This resulted in a module with an effective length of 80 mm and an effective membrane inner surface area of ​​0.02 m. ２A supported membrane module (a microporous hollow fiber supported membrane module) was manufactured. The internal space of this supported membrane module was divided into two by the membrane wall of the hollow fiber, and the two spaces were fluidically isolated except for allowing liquid to pass through the membrane wall. The housing had liquid inlets and outlets (liquid inlet and liquid outlet) communicating with the space inside the hollow fiber and liquid inlets and outlets (liquid inlet and liquid outlet) communicating with the space outside the hollow fiber.

[0068] <Production of a hollow fiber forward osmosis membrane module (formation of a separation functional layer)> An aqueous solution containing 0.5% by mass of 2,5-dimethylpiperazine and 0.3% by mass of sodium lauryl sulfate (first solution) was passed through the space inside the hollow fibers of the support membrane module obtained above at a flow rate of 120 mL / min for 20 minutes. After completion of the liquid passage, the support membrane module was held so that the axial direction of the support membrane module was approximately vertical, and the first solution was drained by gravity through the liquid inlet / outlet at the bottom of the module. Next, with the inner surface of the hollow fibers wetted with the first solution, the space outside the hollow fibers of the support membrane module was reduced in pressure to 5 kPaA, and this reduced pressure state was maintained for 1 minute. Air was then circulated through the space inside the hollow fibers for 1 minute to remove excess first solution.

[0069] Next, an n-hexane solution (second solution) containing 0.20% by mass of trimesoyl chloride (TMC) was passed through the space inside the hollow fibers of the support membrane module at a flow rate of 40 mL / min for 2 minutes to carry out interfacial polymerization, forming a separation functional layer containing polyamide on the inner surface of the hollow fibers. Next, nitrogen was passed through the space inside the hollow fibers for 1 minute to remove excess second solution, and then water at 70°C was passed through the space inside the hollow fibers for 20 minutes to wash the inner surface of the hollow fibers, thereby producing a composite hollow fiber forward osmosis membrane module. A scanning electron microscope image of the separation functional layer of the composite semipermeable membrane constituting the module of Example 1 is shown in Figure 3 (magnification: 1000x).

[0070] The module of Example 1 was disassembled and the ratios of the protruding portions and the smooth portions of the separating functional layer were measured to be 54% and 46%, respectively. The water permeability of the composite forward osmosis hollow fiber membrane module of Example 1 was 3.1 kg / (m ２ × hr × bar), and the rejection rate was 98.4(%).

[0071] Examples 2 to 7 and Comparative Examples 1 and 2 Composite forward osmosis hollow fiber membrane modules (Examples 2 to 7 and Comparative Examples 1 and 2) were prepared in the same manner as in Example 1, except that the pressure in the space outside the hollow fibers of the support membrane module (shell side) during interfacial polymerization was reduced to the values ​​shown in Table 1. The water permeability and rejection of the modules of Examples 2 to 7 and Comparative Examples 1 and 2 are shown in Table 1. These modules were disassembled to measure the proportions of protruding portions and smooth portions of the separating functional layer, and these results are also shown in Table 1.

[0072] A composite forward osmosis hollow fiber membrane module (Comparative Example 3) was produced in the same manner as in Example 2, except that the polymerized amine species was changed to metaphenylenediamine. The water permeation rate and rejection rate of the module of Comparative Example 3 are shown in Table 1. The module of Comparative Example 3 was disassembled and measured to find the proportions of protruding portions and smooth portions of the separating functional layer. These proportions are also shown in Table 1.

[0073]

[0074] As is clear from Table 1, in Examples 1 to 7, in which the separation functional layer was formed by interfacial polymerization under reduced pressure within a predetermined pressure difference, high water permeability and high blocking properties were achieved by the separation functional layer having a predetermined ratio of protrusions and smooth portions. On the other hand, in Comparative Examples 1 and 2, in which the separation functional layer was formed under reduced pressure within a range outside the predetermined pressure difference, and in Comparative Example 3, in which the polyfunctional amine forming the separation functional layer was changed to metaphenylenediamine, high water permeability and high blocking properties could not be achieved at the same time because the separation functional layer did not have the predetermined ratio of protrusions and smooth portions.

[0075] The composite semipermeable membrane of the present invention can be used to concentrate raw material solutions, and is suitably used, for example, for concentrating various valuable substances.

[0076] REFERENCE SIGNS LIST 1 Composite hollow fiber membrane module 2, 3 Shell side conduit 4 Hollow fibers 5, 6 Adhesive fixing portion 7, 8 Header 9, 10 Core side conduit 11 Hollow fiber membrane module 12 Core side pressure adjusting device 13 Shell side pressure adjusting device 14 Second solution storage tank 15 Second solution feed piping 16 Second solution feed pump 17 Second solution drain tank 18 Second solution drain piping 19 End cap

Claims

1. A composite semipermeable membrane comprising a support membrane and a polyamide separation function layer on the support membrane, wherein the polyamide separation function layer comprises protrusions having a protrusion structure with a plurality of convex portions and a plurality of concave portions, and a smooth portion without the protrusion structure, and wherein in a surface image of the polyamide separation function layer taken with a scanning electron microscope at 1000x magnification, the proportion of the protrusions occupying the surface of the support membrane is 10% or more and 90% or less.

2. The composite semipermeable membrane according to claim 1, wherein the proportion of said protrusions is 10% or more and 60% or less.

3. The composite semipermeable membrane according to claim 1 or 2, wherein the polyamide separation functional layer is a polycondensation product of one or more first monomers selected from polyfunctional amines and one or more second monomers selected from polyfunctional acid halides.

4. The composite semipermeable membrane according to claim 3, wherein the polyfunctional amine is an aliphatic amine.

5. A method for producing a composite semipermeable membrane comprising a microporous hollow fiber support membrane and a polyamide separation functional layer on the microporous hollow fiber support membrane, the method comprising: forming a liquid membrane of a first solution containing one or more first monomers selected from polyfunctional amines and one or more second monomers selected from polyfunctional acid halides on the inner surface of the microporous hollow fiber support membrane; then creating a pressure difference between the inside and outside of the microporous hollow fiber support membrane so that (inside pressure) > (outside pressure); and then contacting the liquid membrane of the first solution with a second solution containing the other of the first monomer and the second monomer.

6. The method of claim 5, wherein the pressure differential is created by applying a vacuum to the exterior of the microporous hollow fiber support membrane.

7. The method according to claim 5 or 6, wherein the pressure difference is 5 to 70 kPa.

8. A method for concentrating a raw material liquid, comprising the step of concentrating a raw material liquid containing an electrolyte and one or more solutes using the composite semipermeable membrane according to claim 1 or 2.

9. The method for concentrating a raw material liquid according to claim 8, wherein the concentration is carried out by one or more methods selected from the group consisting of a reverse osmosis membrane method, a forward osmosis membrane method, a nanofiltration membrane method, a dialysis method, and a salt exchange method.

10. The method for concentrating a raw material liquid according to claim 8, wherein the solute is one or more compounds selected from the group consisting of nucleic acids, proteins, peptides, amino acids, antibiotics, low-molecular-weight drugs, and vitamins.

11. The method for concentrating a raw material liquid according to claim 8, wherein the composite semipermeable membrane is in the form of a hollow fiber membrane.

12. The method for concentrating a raw material liquid according to claim 8, wherein the electrolyte is an organic or inorganic compound having a molecular weight of 50 or more and 200 or less.

13. The method for concentrating a raw material liquid according to claim 8, wherein the pKa of the electrolyte is -2 or more and 4 or less.

14. The method for concentrating a raw material liquid according to claim 8, wherein the molecular weight of the solute is 300 or more and 3,000 or less.

15. The method for concentrating a raw material liquid according to claim 8, wherein the raw material liquid contains one or more organic solvents.

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