JP7351623B2 - Composite hollow fiber membrane module - Google Patents

Description

The present invention relates to a composite hollow fiber membrane module.

Membrane separation technology using semipermeable membranes is attracting attention from the viewpoints of energy saving, resource saving, and environmental protection. Membrane separation techniques using semipermeable membranes include, for example, nanofiltration (NF) membranes, reverse osmosis (RO) membranes, and forward osmosis (FO) membranes. A membrane including a semipermeable membrane layer having the function of a permeable membrane is used. Examples of membranes used in membrane separation techniques using such semipermeable membranes include composite membranes that include not only a semipermeable membrane layer but also a support layer that supports the semipermeable membrane layer.

Examples of the composite membrane including a semipermeable membrane layer and a support layer include not only flat membrane-shaped composite membranes but also, for example, hollow fiber membrane-shaped composite membranes. Furthermore, when a separation membrane such as a composite membrane is used for water treatment or the like, the separation membrane may be used as a module housed in a housing. As described above, when a separation membrane such as a composite membrane is used for water treatment as a module housed in a housing, the surface area of the membrane per installation area can be increased by using a hollow fiber membrane rather than a flat membrane. For this reason, hollow fiber membranes are preferably used because they can provide a water treatment system that saves more space.

Examples of modules including such hollow fiber membranes include the modules described in Patent Document 1 and Patent Document 2.

Patent Document 1 describes a core tube connected to a supply port or a discharge port, a hollow fiber membrane group consisting of a plurality of hollow fiber membranes, and a resin wall that fixes the core tube and the hollow fiber membrane group at both ends thereof. A hollow fiber membrane element comprising: the core tube having holes only in the vicinity of a first end, which is one end of the hollow fiber membrane group; and a plurality of the hollow fiber membranes intersecting with each other. It is wound spirally around the core tube, and has a cross point group including a plurality of cross points that are intersections of the hollow fiber membranes, and at least near the first end of the hollow fiber membrane group. A hollow fiber membrane module is described that includes a hollow fiber membrane element in which the cross-point group is present and a container filled with at least one hollow fiber membrane element.

Patent Document 2 discloses a forward osmosis composite hollow fiber membrane module having a hollow fiber bundle composed of a plurality of hollow fiber membranes, in which the hollow fibers are coated with a polymer on the inner surface of a microporous hollow fiber support membrane. The hollow fiber is provided with a separation active layer made of a thin polymer film, the membrane area of the hollow fiber fiber bundle is 1 m ² or more, and in a scanning electron microscope image taken of a cross section in the thickness direction of the separation active layer. A module is described in which the coefficient of variation of the average thickness of the separation active layer in the radial direction and length direction of the hollow fiber bundle, calculated by a method of measuring the mass of the separation active layer portion, is 0 to 60%. .

International Publication No. 2015/125755 International Publication No. 2016/027869

As described above, when a composite membrane is used as a module housed in a housing for water treatment or the like, it is required that not only the composite membrane has high water permeability, but also that the water permeation rate of the module as a whole is high. However, in the case of conventional hollow fiber membrane modules, there have been cases where a sufficiently high water permeation rate cannot be obtained for the module as a whole.

For example, Patent Document 1 discloses that it is possible to provide a hollow fiber membrane module in which the flow rate of liquid passing outside the hollow fiber membrane is high and in which stagnation of liquid does not easily occur within the element. . However, in the hollow fiber membrane module described in Patent Document 1, even if a composite hollow fiber membrane including a semipermeable membrane layer containing crosslinked polyamide, which is expected to have high performance as a hollow fiber membrane, is adopted, the entire module Therefore, it is considered that a sufficiently high water permeation rate cannot be obtained. As described above, in the hollow fiber membrane module described in Patent Document 1, a plurality of hollow fiber membranes are spirally wound around a core tube so as to cross each other, and the hollow fiber membranes are wound spirally around a core tube so as to cross each other. Contains multiple intersections. It is thought that the semipermeable membrane layer peels off from the composite hollow fiber membrane at intersections where the hollow fiber membranes intersect with each other. From this, it is considered that even if the composite hollow fiber membrane is employed in the hollow fiber membrane module described in Patent Document 1, a sufficiently high water permeation rate cannot be obtained as a whole module.

According to Patent Document 2, it is disclosed that it is possible to provide a composite hollow fiber membrane module that has a separation active layer with little variation in average thickness in the radial direction and length direction and exhibits stable and high performance. There is. In the composite hollow fiber membrane module described in Patent Document 2, the hollow fibers are provided with a separation active layer of a polymer thin film on the inner surface of a microporous hollow fiber support membrane. In this way, since the separation active layer is formed on the inner surface of the support layer, the area of the separation active layer is insufficient, and it is thought that a sufficiently high water permeation rate cannot be obtained for the module as a whole. It will be done. Furthermore, Patent Document 2 states that polysulfone and polyethersulfone are preferable as materials for the microporous hollow fiber support membrane. Since polysulfone and polyether sulfone do not have sufficiently high hydrophilicity, the composite hollow fiber membrane module described in Patent Document 2 that preferably uses these is not intended to increase water permeability, but to improve water permeability. It is thought that the purpose is to reduce gender disparity.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a composite hollow fiber membrane module with excellent water permeability.

As a result of various studies, the present inventors have found that the above object can be achieved by the present invention described below.

A composite hollow fiber membrane module according to one aspect of the present invention includes a housing and a plurality of composite hollow fiber membranes housed in the housing, wherein the composite hollow fiber membranes contain a polyfunctional amine compound and a polyfunctional acid. The semipermeable membrane layer includes a crosslinked polyamide made of a halide compound, and a hollow fiber-like porous support layer, the semipermeable membrane layer is in contact with the outer peripheral surface of the support layer, and the semipermeable membrane layer is in contact with the outer peripheral surface of the support layer, and The inner diameter is 10 to 200 cm, and the effective length of the composite hollow fiber membrane is 0.3 to 3 m.

According to such a configuration, a composite hollow fiber membrane module with excellent water permeability can be provided. This is thought to be due to the following.

First, the composite hollow fiber membrane provided in the composite hollow fiber membrane module is equipped with a semipermeable membrane layer containing a crosslinked polyamide made of a polyfunctional amine compound and a polyfunctional acid halide compound on a support layer. It is considered that separation using can be suitably performed. Further, by using a hollow fiber-like support layer as the support layer, the membrane area can be made larger than when a flat membrane is used. Furthermore, since the semipermeable membrane layer is in contact with the outer peripheral surface of the support layer, the semipermeable membrane layer is in contact with the inner peripheral surface of the support layer. The area of can be increased. For these reasons, the area of the composite hollow fiber membrane provided in the composite hollow fiber membrane module, particularly the area of the semipermeable membrane layer, can be increased. Therefore, the composite hollow fiber membrane provided in the composite hollow fiber membrane module is considered to be able to achieve excellent water permeability because separation using the semipermeable membrane layer can be suitably performed.

Furthermore, a composite hollow fiber membrane module obtained by accommodating the composite hollow fiber membrane having an effective length of 0.3 to 3 m in a casing having an inner diameter of 10 to 200 cm is provided with the composite hollow fiber membrane. It is considered that separation using a semipermeable membrane layer can be suitably performed.

From the above, the composite hollow fiber membrane module can suitably perform separation using the semipermeable membrane layer provided in the composite hollow fiber membrane, and therefore has excellent water permeability that the composite hollow fiber membrane has. can be suitably demonstrated. Therefore, it is considered that a composite hollow fiber membrane module with excellent water permeability and a high water permeation rate as a whole module can be obtained. In addition, when the composite hollow fiber membrane module is used, for example, in a forward osmosis method, by bringing two solutions with different solute concentrations into contact through the composite hollow fiber membrane, the osmotic pressure difference resulting from the solute concentration difference is reduced. As a driving force, water can suitably permeate from a dilute solution with a low solute concentration to a concentrated solution with a high solute concentration. When the composite hollow fiber membrane module is used in forward osmosis, for example, it can exhibit excellent desalination performance.

Further, in the composite hollow fiber membrane module, it is preferable that the composite hollow fiber membrane has an outer diameter of 0.1 to 2 mm and an inner diameter of 0.05 to 1.5 mm.

According to such a configuration, a composite hollow fiber membrane module with superior water permeability can be obtained. This is considered to be because the composite hollow fiber membrane included in the composite hollow fiber membrane module can exhibit better water permeability.

Further, in the composite hollow fiber membrane module, the ratio of the total cross-sectional area of the plurality of composite hollow fiber membranes to the area of the cross section perpendicular to the longitudinal direction of the composite hollow fiber membrane inside the housing is 10 to 10. Preferably it is 65%.

According to such a configuration, a composite hollow fiber membrane module with superior water permeability can be obtained. This is considered to be because the excellent water permeability of the composite hollow fiber membrane provided in the composite hollow fiber membrane module can be more suitably exhibited.

Further, it is preferable that the composite hollow fiber membrane module is used in a forward osmosis method.

Since the composite hollow fiber membrane module can suitably perform separation using the semipermeable membrane layer provided in the composite hollow fiber membrane, the composite hollow fiber membrane module can be suitably used in the forward osmosis method. I can do it. When the composite hollow fiber membrane module is used in forward osmosis, for example, it can exhibit excellent desalination performance.

Further, in the composite hollow fiber membrane module, the composite hollow fiber membrane has a ratio of water permeation rate in a dry state to a water permeation rate in a wet state of 40 to 100% in a forward osmosis method. It is preferable.

According to such a configuration, even if the composite hollow fiber membrane provided in the composite hollow fiber membrane module is in a dry state, the composite hollow fiber membrane module can be used for the forward osmosis method. When the composite hollow fiber membrane module is used in a forward osmosis method, the composite hollow fiber membrane is often used in a wet state. However, in cases such as after transporting the composite hollow fiber membrane module without filling it with liquid, when the composite hollow fiber membrane module is started to be used for forward osmosis, the composite hollow fiber membrane is in a dry state. In some cases. Even in such a case, the composite hollow fiber membrane module can be used in the forward osmosis method. This makes it possible to transport the composite hollow fiber membrane module without filling it with liquid.

Further, in the composite hollow fiber membrane module, it is preferable that the composite hollow fiber membrane has a water permeation rate of 2 to 100 LMH in a wet state in a forward osmosis method.

According to such a configuration, a composite hollow fiber membrane module with superior water permeability can be obtained. This is considered to be because the composite hollow fiber membrane included in the composite hollow fiber membrane module can exhibit better water permeability.

Further, in the composite hollow fiber membrane module, it is preferable that the contact angle of water with respect to the outer circumferential surface of the support layer is 90° or less.

According to such a configuration, a composite hollow fiber membrane module with superior water permeability can be obtained. This is thought to be due to the following.

First, since the semipermeable membrane layer is in contact with the outer peripheral surface of the support layer that has been made hydrophilic, it is considered that the semipermeable membrane layer can suitably exist. Moreover, it is considered that the support layer is suitably made hydrophilic. From these facts, it is considered that the composite hollow fiber membrane included in the composite hollow fiber membrane module can more appropriately perform separation using a semipermeable membrane layer, and can realize better water permeability. From this, it is thought that a composite hollow fiber membrane module with superior water permeability can be obtained.

Furthermore, when the composite hollow fiber membrane is manufactured using a support layer in which the contact angle of water with respect to the outer circumferential surface is 90° or less, in the forward osmosis method, the water permeation rate in the dry state is lower than that in the wet state. It is believed that a composite hollow fiber membrane having a water permeation rate ratio of 40 to 100% can be produced. From this point of view as well, it is thought that a composite hollow fiber membrane module with superior water permeability can be obtained.

Further, it is preferable that the composite hollow fiber membrane module has a pressure resistance of 0.1 to 3 MPa.

According to such a configuration, a highly durable composite hollow fiber membrane module can be obtained. Therefore, a composite hollow fiber membrane module that not only has excellent water permeability but also excellent durability can be obtained.

According to the present invention, a composite hollow fiber membrane module with excellent water permeability can be provided.

FIG. 1 is a schematic diagram showing an example of a composite hollow fiber membrane module according to an embodiment of the present invention. FIG. 2 is a partial perspective view of a composite hollow fiber membrane provided in a composite hollow fiber membrane module according to an embodiment of the present invention. FIG. 3 is a schematic diagram showing an example of the layered structure of the composite hollow fiber membrane shown in FIG. 2. FIG. 4 is a schematic cross-sectional view of the composite hollow fiber membrane module shown in FIG. 1.

Hereinafter, embodiments according to the present invention will be described, but the present invention is not limited thereto.

[Hollow fiber membrane module]
A composite hollow fiber membrane module according to an embodiment of the present invention is a composite hollow fiber membrane module in which a plurality of composite hollow fiber membranes are housed in a housing. That is, the composite hollow fiber membrane module is a composite hollow fiber membrane module that includes the plurality of composite hollow fiber membranes and a casing that accommodates the plurality of composite hollow fiber membranes. The composite hollow fiber membrane includes a semipermeable membrane layer containing a crosslinked polyamide made of a polyfunctional amine compound and a polyfunctional acid halide compound, and a hollow fiber-like porous support layer, and the semipermeable membrane layer includes the It is in contact with the outer peripheral surface of the support layer. Such a composite hollow fiber membrane is equipped with a semipermeable membrane layer containing the crosslinked polyamide, which enables separation using the semipermeable membrane layer, and the area of this semipermeable membrane layer can be increased. . In the composite hollow fiber membrane module, by using one of the composite hollow fiber membranes having an effective length of 0.3 to 3 m, and further using the casing having an inner diameter of 10 to 200 cm, Separation can be suitably performed using the semipermeable membrane layer provided in the composite hollow fiber membrane. That is, the composite hollow fiber membrane module has excellent water permeability.

Specifically, the composite hollow fiber membrane module is a composite hollow fiber membrane module in which each of the composite hollow fiber membranes is sealed in the housing with a sealant or the like, with the hollow interior of each composite hollow fiber membrane being open. Examples include thread membrane modules. In such a composite hollow fiber membrane module, the composite hollow fiber membrane is sealed in the housing, so that the composite hollow fiber membrane is fixed to the housing in a liquid-tight manner. Further, in the composite hollow fiber membrane module, each of the composite hollow fiber membranes and the casing may be directly bonded and sealed with a sealant, or each of the composite hollow fiber membranes may be sealed with a sealant. Each of the composite hollow fiber membranes and the housing may be sealed by being adhered to a cylindrical case and fixing the cylindrical case to the housing. Further, the composite hollow fiber membrane module may include, for example, bundling a predetermined number of the plurality of hollow fiber membranes, cutting the composite hollow fiber membrane bundle into a predetermined length, and housing (filling) the composite hollow fiber membrane bundle in a casing having a predetermined shape. It is obtained by fixing the end portion to the casing with a sealant containing a thermosetting resin such as polyurethane resin or epoxy resin. Furthermore, examples of the composite hollow fiber membrane module include a composite hollow fiber membrane module 1 shown in FIG. 1, for example. Note that FIG. 1 is a schematic diagram showing an example of a composite hollow fiber membrane module according to this embodiment.

As shown in FIG. 1, the composite hollow fiber membrane module 1 includes a housing 2, a plurality of composite hollow fiber membranes 11, a lower end sealant 4, and an upper end sealant 5. The housing 2 is not particularly limited as long as it can be used as a housing for a hollow fiber membrane module. Specifically, the housing 2 may be a cylindrical body or the like. The plurality of composite hollow fiber membranes 11 are each fixed to the housing 2 by the lower end sealing agent 4 and the upper end sealing agent 5, with the lower end portion and the upper end portion opening the hollow portion. The lower end sealant 4 fixes the lower ends of the plurality of composite hollow fiber membranes 11 to the housing 2, and the upper end sealant 5 fixes the upper ends of the plurality of composite hollow fiber membranes 11 to the housing 2. Fix it to body 2. The lower end sealant 4 and the upper end sealant 5 are not particularly limited as long as they are sealants used for hollow fiber membrane modules. Specifically, the lower end sealant 4 and the upper end sealant 5 include sealants containing thermosetting resins such as polyurethane resins and epoxy resins. The housing 2 includes a shell-side inlet 6, a shell-side outlet 7, a bore-side inlet 8, and a bore-side outlet 9. The shell-side inlet 6 and the shell-side outlet 7 are provided on the circumferential surface of the casing 2. By supplying liquid into the housing 2 from the shell-side inlet 6 and discharging the liquid from the shell-side outlet 7 after passing through the housing 2, the liquid flows into the housing 2. and the plurality of composite hollow fiber membranes 11, that is, the shell side. Further, the bore side inlet 8 and the bore side outlet 9 are provided on the lower end surface and the upper end surface of the housing 2, respectively. By supplying liquid into the housing 2 from the bore-side inlet 8 and discharging the liquid from the bore-side outlet 9 after passing through the housing 2, the liquid can be It is supplied to the inside of the hollow fiber membrane 11, that is, to the bore side.

The case where the composite hollow fiber membrane module is used, for example, in the FO method, that is, the case where the composite hollow fiber membrane is used as an FO membrane will be explained. First, when a feed solution (FS) is supplied to the shell side and a driving solution (Draw Solution: DS) is supplied to the bore side, the water in the feed solution supplied to the shell side is transferred to the bore side. The supplied driving solution causes the osmotic pressure difference to be used as a driving force, and the tube is drawn toward the bore side. That is, by bringing a feed solution and a driving solution, which have different solute concentrations, into contact via a composite hollow fiber membrane, the osmotic pressure difference generated from the difference in solute concentration is used as a driving force, and the solute concentration is changed from the feed solution with a low solute concentration to the driving solution. Permeates water into the higher driving solution. The supply solution is a liquid to be treated (raw water), and specifically includes seawater and the like. The driving solution will be described later, but specific examples thereof include relatively high concentration aqueous polymer solutions. Further, in the composite hollow fiber membrane module, the driving solution may be supplied to the shell side, and the supply solution may be supplied to the bore side. Further, the membrane separation (membrane filtration) using the composite hollow fiber membrane module is preferably a cross-flow filtration method. For this reason, it is preferable that the supply solution and the driving solution are supplied in a cross-flow filtration manner.

[Composite hollow fiber membrane]
The composite hollow fiber membrane 11, as shown in FIG. 2, is a hollow fiber membrane. Further, as shown in FIG. 3, the composite hollow fiber membrane 11 includes a hollow fiber-like porous support layer 12 and a semipermeable membrane layer 13, and the semipermeable membrane layer 13 is a support layer 12 that is similar to the support layer 12. It is in contact with the outer circumferential surface. Note that FIG. 2 is a partial perspective view of a composite hollow fiber membrane provided in a composite hollow fiber membrane module according to an embodiment of the present invention. Moreover, FIG. 3 shows the layer structure of the composite hollow fiber membrane 11 by enlarging a part A of the composite hollow fiber membrane 11 shown in FIG. Note that FIG. 3 is a schematic diagram that represents the positional relationship of the layers, but does not particularly represent the relationship of the thicknesses of the layers.

(semi-permeable membrane layer)
The semipermeable membrane layer 13 includes a crosslinked polyamide made of a polyfunctional amine compound and a polyfunctional acid halide compound, that is, a crosslinked polyamide made by polymerizing a polyfunctional amine compound and a polyfunctional acid halide compound. It is not particularly limited as long as it is a layer that performs the function of a membrane. The content of the crosslinked polyamide in the semipermeable membrane layer 13 is preferably 90 to 100% by mass, more preferably 100%. That is, it is preferable that the semipermeable membrane layer 13 is made of only the crosslinked polyamide.

The polyfunctional amine compound is not particularly limited as long as it is a compound having two or more amino groups in the molecule. Examples of the polyfunctional amine compound include aromatic polyfunctional amine compounds, aliphatic polyfunctional amine compounds, and alicyclic polyfunctional amine compounds. Further, examples of the aromatic polyfunctional amine compound include phenylene diamines such as m-phenylene diamine, p-phenylene diamine, and o-phenylene diamine, 1,3,5-triaminobenzene, and 1,3,4- Triaminobenzene such as triaminobenzene, diaminotoluene such as 2,4-diaminotoluene and 2,6-diaminotoluene, 3,5-diaminobenzoic acid, xylylenediamine, and 2,4-diaminophenol dihydrochloride ( amidol), etc. Further, examples of the aliphatic polyfunctional amine compound include ethylenediamine, propylenediamine, and tris(2-aminoethyl)amine. Examples of the alicyclic polyfunctional amine compound include 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, and 4-aminomethylpiperazine. can be mentioned. Among these, aromatic polyfunctional amine compounds are preferred, and phenylenediamine is more preferred. Further, as the polyfunctional amine compound, the above-exemplified compounds may be used alone, or two or more types may be used in combination.

The polyfunctional acid halide compound (polyfunctional acid halide) is produced by removing two or more hydroxyl groups from an acid contained in a polyfunctional organic acid compound having two or more acids such as carboxylic acid in the molecule. There are no particular limitations on the compound as long as it is a compound in which a halogen is bound to the removed acid. The polyfunctional acid halide compound may be divalent or more, preferably trivalent or more. Examples of the polyfunctional acid halide compound include polyfunctional acid fluorides, polyfunctional acid chlorides, polyfunctional acid bromides, and polyfunctional acid iodides. Among these, polyfunctional acid chlorides (polyfunctional acid chloride compounds) are preferably used because they are most easily obtained and have high reactivity, but are not limited thereto. In addition, polyfunctional acid chlorides are illustrated below, but examples of polyfunctional acid halides other than polyfunctional acid chlorides include those obtained by replacing the chlorides illustrated below with other halides.

Examples of the polyfunctional acid chloride compound include aromatic polyfunctional acid chloride compounds, aliphatic polyfunctional acid chloride compounds, and alicyclic polyfunctional chloride compounds. Examples of the aromatic polyfunctional acid chloride compounds include trimesic acid trichloride, terephthalic acid dichloride, isophthalic acid dichloride, biphenyldicarboxylic acid dichloride, naphthalene dicarboxylic acid dichloride, benzenetrisulfonic acid trichloride, and benzenedisulfonic acid dichloride. Can be mentioned. In addition, examples of the aliphatic polyfunctional acid chloride compounds include propanedicarboxylic acid dichloride, butanedicarboxylic acid dichloride, pentanedicarboxylic acid dichloride, propanetricarboxylic acid trichloride, butanetricarboxylic acid trichloride, pentantricarboxylic acid trichloride, and glutaryl. Examples include chloride and adipoyl chloride. Examples of the alicyclic polyfunctional chloride compounds include cyclopropanetricarboxylic acid trichloride, cyclobutanetetracarboxylic acid tetrachloride, cyclopentanetricarboxylic acid trichloride, cyclopentanetricarboxylic acid tetrachloride, cyclohexanetricarboxylic acid trichloride, and tetracarboxylic acid trichloride. Examples include hydrofuran tetracarboxylic acid tetrachloride, cyclopentanedicarboxylic acid dichloride, cyclobutanedicarboxylic acid dichloride, cyclohexanedicarboxylic acid dichloride, and tetrahydrofurandicarboxylic acid dichloride. Among these, aromatic polyfunctional acid chloride compounds are preferred, and trimesic acid trichloride is more preferred. Further, as the polyfunctional acid halide compound, the above-exemplified compounds may be used alone, or two or more types may be used in combination.

(Support layer)
As described above, the support layer 12 is not particularly limited as long as it is hollow fiber-like and porous. Further, the support layer 12 may be made hydrophilic by containing a hydrophilic resin. The hydrophilic resin contained in the support layer 12 is preferably crosslinked. That is, the support layer 12 preferably includes a crosslinked hydrophilic resin in a hollow fiber-like porous base material. The crosslinked hydrophilic resin may be contained in the entire support layer 12 or in a part of the support layer 12, but in that case, the crosslinked hydrophilic resin may not be contained in the outer peripheral surface of the support layer 12. It is preferable that it is included in the outer circumferential surface of the support layer 12, and more preferably that it is also included in a portion other than the outer circumferential surface of the support layer 12.

The hollow fiber-like porous base material is not particularly limited as long as it is a base material made of a material that can constitute a hollow fiber membrane. Components included in the support layer 12 (components constituting the hollow fiber porous base material) include, for example, acrylic resin, polyacrylonitrile, polystyrene, polyamide, polyacetal, polycarbonate, polyphenylene ether, polyphenylene sulfide, polyethylene terephthalate, Polytetrafluoroethylene, polyvinylidene fluoride, polyetherimide, polyamideimide, polychloroethylene, polyethylene, polypropylene, polyketone, crystalline cellulose, polysulfone, polyphenylsulfone, polyethersulfone, acrylonitrile butadiene styrene (ABS) resin, and acrylonitrile styrene (AS) resin. Among these, polyvinylidene fluoride, polysulfone, and polyethersulfone are preferred from the viewpoint of excellent pressure resistance. Furthermore, as the component contained in the supporting layer 12 (component constituting the hollow fiber-like porous base material), the above-mentioned resins may be used alone or in combination of two or more. .

The hydrophilic resin is not particularly limited as long as it is a resin that can make the support layer 12 hydrophilic by being included in the hollow fiber-like porous base material. Examples of the hydrophilic resin include cellulose, cellulose acetate polymers such as cellulose acetate and cellulose triacetate, vinyl alcohol polymers such as polyvinyl alcohol and polyethylene vinyl alcohol, polyethylene glycol polymers such as polyethylene glycol and polyethylene oxide, and polyacrylics. Examples include acrylic acid-based polymers such as sodium chloride, and polyvinylpyrrolidone-based polymers such as polyvinylpyrrolidone. Among these, vinyl alcohol-based polymers and polyvinylpyrrolidone-based polymers are preferred, and polyvinyl alcohol and polyvinylpyrrolidone are more preferred. Moreover, as the hydrophilic resin, the above-mentioned exemplified resins may be used alone, or two or more types may be used in combination. Further, the hydrophilic resin may contain hydrophilic monomolecules such as glycerin and ethylene glycol, or may be a polymer thereof, and may contain these as a copolymerization component with the above resin. There may be.

The crosslinking of the hydrophilic resin may be carried out as long as the hydrophilic resin is crosslinked and the solubility of the hydrophilic resin in water is reduced, and examples include crosslinking to make it insolubilized so that it does not dissolve in water. When polyvinyl alcohol is used as the hydrophilic resin, examples of crosslinking of the hydrophilic resin include an acetalization reaction using formaldehyde and an acetalization reaction using glutaraldehyde. Furthermore, when polyvinylpyrrolidone is used as the hydrophilic resin, for example, it may be reacted with a hydrogen peroxide solution. It is considered that when the degree of crosslinking of the hydrophilic resin is high, elution of the hydrophilic resin from the composite hollow fiber membrane can be suppressed even if the composite hollow fiber membrane is used for a long period of time. Therefore, it is considered that peeling between the semipermeable membrane layer and the support layer can be suppressed for a long period of time.

The support layer 12 has an inclined structure in which the pores of the support layer 12 gradually become larger from the outer surface toward the inner circumferential surface, that is, have an inclined structure in which the pores gradually become smaller from the inner surface toward the outer surface. It is preferable. The slanted structure in which the pores of the support layer 12 gradually become larger from the outer surface to the inner peripheral surface means that the pores existing on the outer surface are smaller than the pores existing on the inner peripheral surface, and the pores of the support layer 12 gradually increase in size from the outer surface to the inner peripheral surface. The internal pores have a structure that is equal to or larger than the pores existing on the outer circumferential surface and equal or smaller than the pores existing on the inner circumferential surface.

In the composite hollow fiber membrane 11, the semipermeable membrane layer 13 is provided in contact with the outer peripheral surface of the support layer 12, as described above. This outer peripheral surface is a so-called dense surface.

The supporting layer 12 preferably has a contact angle of water with respect to the outer circumferential surface (dense surface) of 90° or less, more preferably 65° or less, and even more preferably 10 to 65°. By adjusting the contact angle of water with respect to the outer peripheral surface of the support layer 12, the water permeability of the composite hollow fiber membrane 11, particularly the water permeability in a dry state, can be adjusted. When the composite hollow fiber membrane is manufactured using a support layer in which the contact angle of water with respect to the outer peripheral surface is 90° or less, in the forward osmosis method, the water permeation rate in the wet state is lower than that in the dry state. It is believed that a composite hollow fiber membrane with a permeation rate ratio of 40 to 100% can be produced. From this point of view as well, it is thought that a composite hollow fiber membrane module with superior water permeability can be obtained. Furthermore, if the contact angle is too large, the support layer will not be sufficiently hydrophilized, and the semipermeable membrane layer will tend not to be suitably formed on the support layer. This is thought to be due to the following. When forming the semipermeable membrane layer, first, the dense surface side of the support layer is brought into contact with an aqueous solution of a polyfunctional amine compound, which is a raw material for the crosslinked polyamide polymer constituting the semipermeable membrane layer. At this time, if the contact angle of water with respect to the outer circumferential surface (dense surface) is 90° or less, the aqueous solution of the polyfunctional amine compound sufficiently permeates into the dense surface side of the support layer. In this state, the dense surface side of the support layer is brought into contact with an organic solvent of a polyfunctional acid halide compound, which is a raw material for the crosslinked polyamide polymer, and then dried. A semipermeable membrane layer containing the crosslinked polyamide polymer is formed so as to be in contact with the dense surface of the support layer through interfacial polymerization with the acid halide compound. On the other hand, if the contact angle of water with respect to the outer circumferential surface (dense surface) is too large, the aqueous solution of the polyfunctional amine compound will not be able to sufficiently penetrate into the dense surface side of the support layer, making it difficult to carry out the interfacial polymerization. tend not to be able to do so. For this reason, there is a tendency that the semipermeable membrane layer cannot be suitably formed on the support layer. Furthermore, if the contact angle of water with respect to the outer circumferential surface (dense surface) is too large, even if the semipermeable membrane layer is formed, the semipermeable membrane layer may peel off from the support layer. There is also a tendency to be easy.

The support layer 12 is preferably made hydrophilic so that the contact angle of water with respect to the outer peripheral surface is 90° or less, as described above, but the support layer 12 is preferably made hydrophilic as a whole so that the contact angle of water with respect to the outer peripheral surface is 90° or less. It is more preferable to be present.

Note that whether or not the support layer is made hydrophilic can be determined by subjecting the support layer to IR (Infrared Spectroscopy) analysis, XPS (X-ray Photoelectron Spectroscopy) analysis, and the like. For example, by performing the above analysis on each of the inner surface, outer surface, and inner surface of the support layer, it can be determined whether or not the hydrophilic resin is present at each position. . If the hydrophilic resin is present throughout the support layer, it can be seen that the entire support layer has been made hydrophilic. That is, if the presence of the hydrophilic resin can be confirmed on all of the inner surface, outer surface, and inside of the support layer, it can be seen that the entire support layer has been made hydrophilic.

The support layer 12 preferably has a fractional particle diameter of 0.001 to 0.3 μm, more preferably 0.001 to 0.2 μm, and more preferably 0.001 to 0.1 μm. is even more preferable. That is, it is preferable that the pores existing on the outer circumferential surface (dense surface) are such that the fractional particle diameter of the support layer is within the above range. If the fractional particle size is too large, the pores present on the dense surface will be large, and the semipermeable membrane layer will tend not to be suitably formed on the dense surface. That is, the entire dense surface cannot be covered with the semipermeable membrane layer, and there is a tendency that separation by the semipermeable membrane layer cannot be performed appropriately. When the composite hollow fiber membrane is used, for example, as a forward osmosis (FO) membrane, it tends to be difficult to obtain sufficient desalination performance. On the other hand, if the fractional particle size is too small, separation using a semipermeable membrane layer can be performed appropriately and, for example, desalination performance can be sufficiently exhibited, but the permeation flux tends to decrease. Therefore, when the fractional particle diameter is within the above range, separation by the semipermeable membrane layer and permeability can be achieved at the same time. Note that the fractional particle size refers to the particle size of the smallest particle that can prevent passage through the support layer, and specifically, for example, when the rate at which permeation is blocked by the support layer (blocking rate by the support layer) is 90%. Examples include the diameter of the particles when .

In the support layer 12, the average diameter of pores formed on the inner peripheral surface is preferably 1 to 50 μm, more preferably 1 to 30 μm, and even more preferably 1 to 20 μm. If this average diameter is too small, the degree of enlargement of the pores of the support layer from the outer peripheral surface toward the inner peripheral surface in the inclined structure of the support layer will be too low, and the permeability will tend to be insufficient. . Moreover, if this average diameter is too large, the strength of the support layer tends to be insufficient.

The support layer 12 preferably has a compressive strength of 0.3 MPa or more and less than 5 MPa, more preferably 0.3 MPa or more and less than 4 MPa, and even more preferably 0.3 MPa or more and less than 3 MPa. This compressive strength is the maximum pressure that can maintain the shape of the support layer when pressure is applied from the outside of the support layer, and the maximum pressure that can maintain the shape of the support layer when pressure is applied from the inside of the support layer. This is the lower pressure. Note that the maximum pressure at which the shape of the support layer can be maintained when pressure is applied from the outside of the support layer is, for example, the pressure at which the support layer collapses when pressure is applied from the outside of the support layer. Further, the maximum pressure at which the shape of the support layer can be maintained when pressure is applied from inside the support layer is, for example, the pressure at which the support layer ruptures when pressure is applied from the inside of the support layer. If the compressive strength is too low, the durability of the composite hollow fiber membrane tends to be insufficient in practical operation using the composite hollow fiber membrane. The higher the pressure resistance is, the more preferable it is, but an excessively high pressure resistance may be unnecessary in practice.

Note that the method for manufacturing the support layer 12 is not particularly limited as long as a hollow fiber membrane having the above structure can be manufactured. Examples of the method for manufacturing the hollow fiber membrane include a method for manufacturing a porous hollow fiber membrane. As a method for manufacturing such a porous hollow fiber membrane, a method using phase separation is known. Examples of methods for manufacturing hollow fiber membranes that utilize this phase separation include nonsolvent induced phase separation (NIPS method) and thermally induced phase separation (TIPS method). Can be mentioned.

The NIPS method is a method in which a uniform polymer stock solution in which a polymer is dissolved in a solvent is brought into contact with a non-solvent that does not dissolve the polymer. This is a method of causing a phase separation phenomenon by replacing the solvent with a non-solvent. In the NIPS method, the diameter of the pores formed generally changes depending on the solvent exchange rate. Specifically, the slower the solvent exchange rate, the larger the pores tend to become. Furthermore, in the production of hollow fiber membranes, the solvent exchange rate is fastest at the contact surface with the non-solvent, and becomes slower toward the inside of the membrane. Therefore, the hollow fiber membrane produced by the NIPS method has an asymmetric structure in which the vicinity of the contact surface with the non-solvent is dense and the pores gradually become coarser toward the inside of the membrane.

In addition, the TIPS method involves dissolving polymers at high temperatures in a poor solvent that can dissolve them at high temperatures but not when the temperature drops, and by cooling the solution, a phase separation phenomenon occurs. This is the way to do it. The heat exchange rate is generally faster than the solvent exchange rate in the NIPS method, and it is difficult to control the rate. Therefore, in the TIPS method, uniform pores are likely to be formed in the film thickness direction.

Moreover, the method for manufacturing the hollow fiber membrane (the support layer) is not particularly limited as long as the hollow fiber membrane can be manufactured. Specifically, examples of this manufacturing method include the following manufacturing methods. This manufacturing method includes a step of preparing a membrane-forming stock solution containing a resin and a solvent constituting the hollow fiber membrane (preparation step), a step of extruding the membrane-forming stock solution into a hollow fiber shape (extrusion step), and a step of extruding the membrane-forming stock solution into a hollow fiber shape. Examples include a method comprising a step of solidifying a hollow fiber membrane forming stock solution to form a hollow fiber membrane (forming step).

(Composite hollow fiber membrane)
The composite hollow fiber membrane has a support layer that supports the semipermeable membrane layer and does not inhibit separation by the semipermeable membrane layer, Not particularly limited. That is, the composite hollow fiber membrane includes a semipermeable membrane layer containing a crosslinked polyamide made of a polyfunctional amine compound and a polyfunctional acid halide compound, and a support layer, and the support layer has a function suitable for the semipermeable membrane layer. Any support layer may be used as long as it provides the desired effect. Further, the support layer does not have to be a semipermeable membrane layer containing crosslinked polyamide described in the following examples, but may be any support layer that suitably performs the function of each semipermeable membrane layer.

The outer diameter R1 of the composite hollow fiber membrane is preferably 0.1 to 2 mm, more preferably 0.2 to 1.5 mm, and even more preferably 0.3 to 1.5 mm. If the outer diameter is too small, the inner diameter of the composite hollow fiber membrane may also be too small, and in this case, the liquid passage resistance in the hollow portion becomes large and there is a tendency that a sufficient flow rate cannot be secured. When the composite hollow fiber membrane is used as a forward osmosis membrane or the like, there is a tendency that the driving solution cannot flow at a sufficient flow rate. Furthermore, if the outer diameter is too small, the pressure resistance against pressure applied to the outside tends to decrease. Furthermore, if the outer diameter is too small, the thickness of the composite hollow fiber membrane may become too thin, and in this case, the strength of the composite hollow fiber membrane tends to be insufficient. That is, there is a tendency that suitable compressive strength cannot be achieved. Furthermore, if the outer diameter is too large, when a hollow fiber membrane module is constructed in which a plurality of composite hollow fiber membranes are housed in a housing, the number of hollow fiber membranes housed in the housing will be reduced. The membrane area decreases, and there is a tendency that a sufficient flow rate cannot be secured for practical use as a hollow fiber membrane module. If the outer diameter is too large, the pressure resistance against pressure applied from the inside tends to decrease. Therefore, if the outer diameter of the composite hollow fiber membrane is within the above range, the composite hollow fiber membrane has sufficient strength and can suitably perform separation using a semipermeable membrane with excellent permeability.

The inner diameter R2 of the composite hollow fiber membrane is preferably 0.05 to 1.5 mm, preferably 0.1 to 1 mm, and more preferably 0.2 to 1 mm. If the inner diameter is too small, the liquid passage resistance in the hollow portion becomes large, and there is a tendency that a sufficient flow rate cannot be secured. When the composite hollow fiber membrane is used as a forward osmosis membrane or the like, there is a tendency that the driving solution cannot flow at a sufficient flow rate. Furthermore, if the inner diameter is too small, the outer diameter of the composite hollow fiber membrane may also be too small, and in this case, the pressure resistance strength against pressure applied to the outside tends to decrease. Furthermore, if the inner diameter is too large, the outer diameter of the composite hollow fiber membrane may also become too large. Since the number of hollow fiber membranes accommodated in the body is not small, the membrane area of the hollow fiber membranes decreases, and there is a tendency that a sufficient flow rate cannot be ensured for practical use as a hollow fiber membrane module. If the inner diameter is too large, the outer diameter of the composite hollow fiber membrane may also become too large, and in this case, the pressure resistance against pressure applied from the inside tends to decrease. Furthermore, if the inner diameter is too large, the thickness of the composite hollow fiber membrane may become too thin, and in this case, the strength of the composite hollow fiber membrane tends to be insufficient. That is, there is a tendency that suitable compressive strength cannot be achieved. Therefore, if the inner diameter of the composite hollow fiber membrane is within the above range, the composite hollow fiber membrane has sufficient strength and can suitably perform separation using a semipermeable membrane with excellent permeability.

Further, the membrane thickness T of the composite hollow fiber membrane is preferably 0.02 to 0.3 mm, more preferably 0.05 to 0.3 mm, and more preferably 0.05 to 0.25 mm. is even more preferable. If the membrane thickness is too thin, the composite hollow fiber membrane tends to have insufficient strength. That is, there is a tendency that suitable compressive strength cannot be achieved. Moreover, if the film thickness is too thick, the permeability tends to decrease. Furthermore, if the membrane thickness is too thick, internal concentration polarization in the support layer tends to occur, which tends to inhibit separation by the semipermeable membrane. That is, when the composite hollow fiber membrane is used as a forward osmosis membrane or the like, the contact resistance between the driving solution and the supply solution increases, so that the permeability tends to decrease. Therefore, if the membrane thickness of the composite hollow fiber membrane is within the above range, the composite hollow fiber membrane has sufficient strength, has excellent permeability, and can suitably perform separation using a semipermeable membrane.

The thickness of the semipermeable membrane layer 13 is the thickness formed by interfacial polymerization described below. Specifically, the thickness of the semipermeable membrane layer is 1 to 10,000 nm, more preferably 1 to 5,000 nm, and even more preferably 1 to 3,000 nm. If the membrane thickness is too thin, there is a tendency that separation by the semipermeable membrane layer cannot be performed appropriately. When the composite hollow fiber membrane is used as a forward osmosis membrane, etc., sufficient desalination performance cannot be exhibited, and separation by the semipermeable membrane layer cannot be performed properly, such as an increase in the salt backflow rate. Tend. This is thought to be due to the fact that the semipermeable membrane layer is too thin and cannot fully perform its function, or that the semipermeable membrane layer cannot sufficiently cover the support layer. . Moreover, if the film thickness is too thick, the permeability tends to decrease. This is thought to be because the semipermeable membrane layer is too thick and has a high water permeation resistance, making it difficult for water to permeate.

The thickness of the support layer 12 is the difference between the thickness of the composite hollow fiber membrane and the thickness of the semipermeable membrane layer 13, and specifically, it is 0.02 to 0.3 mm, and 0.02 to 0.3 mm. It is more preferably 0.05 to 0.3 mm, and even more preferably 0.05 to 0.25 mm. The thickness of the support layer is approximately the same as the thickness of the composite hollow fiber membrane because the semipermeable membrane layer is very thin compared to the support layer. If the membrane thickness is too thin, the composite hollow fiber membrane tends to have insufficient strength. That is, there is a tendency that suitable compressive strength cannot be achieved. Moreover, if the film thickness is too thick, the permeability tends to decrease. Furthermore, if the membrane thickness is too thick, internal concentration polarization in the support layer tends to occur, which tends to inhibit separation by the semipermeable membrane. That is, when the composite hollow fiber membrane is used as a forward osmosis membrane or the like, the contact resistance between the driving solution and the supply solution increases, so that the permeability tends to decrease. Therefore, if the membrane thickness of the composite hollow fiber membrane is within the above range, the composite hollow fiber membrane has sufficient strength, has excellent permeability, and can suitably perform separation using a semipermeable membrane.

The composite hollow fiber membrane is applicable to membrane separation technology using semipermeable membranes. That is, the composite hollow fiber membrane can be used as, for example, an NF membrane, an RO membrane, an FO membrane, and the like. Among these, it is preferable that the composite hollow fiber membrane is an FO membrane used in the FO method.

In the forward osmosis method, the composite hollow fiber membrane preferably has a high ratio of the water permeation rate in a dry state to the water permeation rate in a wet state. Specifically, this ratio is preferably 40% or more, more preferably 50% or more, and even more preferably 60% or more. The higher the ratio, the better, but basically, the upper limit is 100%, excluding errors. That is, the ratio is preferably 40 to 100%, more preferably 50 to 100%, and even more preferably 60 to 100%. If the ratio is too low, it indicates that the hydrophobicity of the composite hollow fiber membrane is relatively high, and the water permeation performance tends to be low in the forward osmosis method. This is considered to be because at least one of the feed solution (FS) and the driving solution (DS) has low affinity with the support layer and is difficult to penetrate to the semipermeable membrane layer. Furthermore, from this, when manufacturing or transporting a composite hollow fiber membrane module, it is better not to dry the composite hollow fiber membrane, that is, it is better to keep the composite hollow fiber membrane in a moist state. It is required to fill the hollow fiber membrane module with liquid. This increases transportation costs. As long as the ratio of the composite hollow fiber membranes included in the composite hollow fiber membrane module is within the above range, the composite hollow fiber membrane module can be used in a forward osmosis method even in a dry state. When the composite hollow fiber membrane module is used in a forward osmosis method, the composite hollow fiber membrane is often used in a wet state. However, in cases such as after transporting the composite hollow fiber membrane module without filling it with liquid, when the composite hollow fiber membrane module is started to be used for forward osmosis, the composite hollow fiber membrane is in a dry state. In some cases. Even in such a case, the composite hollow fiber membrane module can be used in the forward osmosis method. This makes it possible to transport the composite hollow fiber membrane module without filling it with liquid.

The ratio can be adjusted in various ways, for example, by making the support layer hydrophilic so that the contact angle of water with the outer peripheral surface of the support layer provided in the composite hollow fiber membrane module is 90° or less. For example, the method of

In the forward osmosis method, the water permeation rate in a wet state and the water permeation rate in a dry state include the water permeation rate at 25°C.

Examples of the water permeation rate in a dry state include the permeation rate measured by the following method. First, the composite hollow fiber membrane that is the object to be measured is dried. This drying is not particularly limited as long as the composite hollow fiber membrane can be dried, but examples include drying in a constant temperature air blower dryer at 60° C. for 24 hours or more. Using this dry composite hollow fiber membrane, the amount of water that permeates through the composite hollow fiber membrane per minute is measured using a forward osmosis method. For example, through a composite hollow fiber membrane, ion-exchanged water is placed on one side as a feed solution (FS) and 0.6M NaCl aqueous solution is placed on the other side as a driving solution (DS), and filtration is performed. The amount of water that permeates through the hollow fiber membrane per minute is measured. From this measured water permeation amount, the water permeation rate (L/m ² /hour: LMH) is obtained by converting the water permeation amount per unit membrane area, unit time, and unit pressure.

Examples of the water permeation rate in a wet state include the permeation rate measured by the following method. First, the composite hollow fiber membrane to be measured is brought into a wet state. This wet state treatment (wet treatment) is not particularly limited as long as it can suitably bring the composite hollow fiber membrane into a wet state. Specifically, the composite hollow fiber membrane is subjected to a wet treatment of being immersed in a 50% by mass ethanol aqueous solution for 20 minutes, and then washed with pure water for 20 minutes. The water permeation rate in the wet state ( L/m ² /hour: LMH) is obtained.

In the forward osmosis method, the composite hollow fiber membrane preferably has a water permeation rate in a wet state of 2 to 100 LMH, more preferably 3 to 100 LMH, and even more preferably 3 to 80 LMH. . If the permeation rate is too low, when the composite hollow fiber membrane is used to form a composite hollow fiber membrane module, the water permeation performance as a module tends to be insufficient. On the other hand, if the permeation rate is too high, separation by the semipermeable membrane layer will be insufficient, and for example, desalination performance will tend to be insufficient.

(Method for manufacturing composite hollow fiber membrane)
The method for producing the composite hollow fiber membrane is not particularly limited as long as the composite hollow fiber membrane described above can be produced. Examples of the manufacturing method include the following manufacturing methods. The manufacturing method includes a step (first contact step) of bringing an aqueous solution of the polyfunctional amine compound into contact with the outer peripheral surface (dense surface) side of the support layer; A step of further contacting the outer peripheral surface (dense surface) side of the support layer with an organic solvent solution of the polyfunctional acid halide compound (second contact step), and a step of contacting the aqueous solution of the polyfunctional amine compound and the polyfunctional acid halide compound. and a step of drying the support layer that has been brought into contact with the organic solvent solution (drying step).

In the first contact step, the aqueous solution of the polyfunctional amine compound is brought into contact with the outer peripheral surface (dense surface) side of the support layer. By doing so, the aqueous solution of the polyfunctional amine compound permeates into the support layer from the outer peripheral surface (dense surface) side.

In the aqueous solution of the polyfunctional amine compound, the concentration of the polyfunctional amine compound is preferably 0.1 to 5% by mass, more preferably 0.1% by mass or more and less than 3% by mass. If the concentration of the polyfunctional amine compound is too low, a suitable semipermeable membrane layer tends to not be formed, such as pinholes being formed in the formed semipermeable membrane layer. For this reason, separation by the semipermeable membrane layer tends to be insufficient. Furthermore, if the concentration of the polyfunctional amine compound is too high, the semipermeable membrane layer tends to become too thick. If the semipermeable membrane layer becomes too thick, the permeability of the resulting composite hollow fiber membrane tends to decrease.

The aqueous solution of the polyfunctional amine compound is a solution in which the polyfunctional amine compound is dissolved in water, and additives such as salts, surfactants, and polymers may be added as necessary.

In the second contact step, an organic solvent solution of the polyfunctional acid halide compound is further brought into contact with the outer peripheral surface (dense surface) side of the support layer that has been contacted with the aqueous solution of the polyfunctional amine compound. By doing so, an interface is formed between the aqueous solution of the polyfunctional amine compound infiltrated into the outer peripheral surface (dense surface) of the support layer and the organic solvent solution of the polyfunctional acid halide compound. Then, at the interface, the reaction between the polyfunctional amine compound and the polyfunctional acid halide compound proceeds. That is, interfacial polymerization between the polyfunctional amine compound and the polyfunctional acid halide compound occurs. This interfacial polymerization forms a crosslinked polyamide.

The organic solvent solution of the polyfunctional acid halide compound preferably has a concentration of 0.01 to 5% by mass, more preferably 0.01 to 3% by mass. If the concentration of the polyfunctional acid halide compound is too low, a suitable semipermeable membrane layer tends to not be formed, such as pinholes being formed in the formed semipermeable membrane layer. For this reason, separation by the semipermeable membrane layer, such as desalting performance, tends to be insufficient. Furthermore, if the concentration of the polyfunctional acid halide compound is too high, the semipermeable membrane layer tends to become too thick. If the semipermeable membrane layer becomes too thick, the permeability of the resulting composite hollow fiber membrane tends to decrease.

The organic solvent solution of the polyfunctional acid halide compound is a solution in which the polyfunctional acid halide compound is dissolved in an organic solvent. The organic solvent is not particularly limited as long as it dissolves the polyfunctional acid halide compound and does not dissolve in water. Examples of the organic solvent include alkane-based saturated hydrocarbons such as n-hexane, cyclohexane, heptane, octane, nonane, decane, and dodecane. As the organic solvent, the above-mentioned exemplified solvents may be used alone, or two or more types may be used in combination. As the organic solvent, when used alone, examples include n-hexane, and when used in combination of two or more types, examples include a mixed solvent of nonane, decane, and dodecane. Additives such as salts, surfactants, and polymers may be added to the organic solvent as necessary.

In the drying step, the support layer that has been brought into contact with the aqueous solution of the polyfunctional amine compound and the organic solvent solution of the polyfunctional acid halide compound is dried. In the second contacting step, the crosslinked polyamide polymer obtained by interfacial polymerization by contacting the aqueous solution of the polyfunctional amine compound with the organic solvent solution of the polyfunctional acid halide compound spreads over the dense surface of the support layer. It is formed to cover. By drying this support layer, the formed crosslinked polyamide polymer is dried, and a semipermeable membrane layer containing the crosslinked polyamide polymer is formed.

The drying temperature is not particularly limited as long as the formed crosslinked polyamide polymer is dried. The drying temperature is, for example, preferably 50 to 150°C, more preferably 80 to 130°C. If the drying temperature is too low, not only will drying tend to be insufficient, but the drying time will also tend to be too long, leading to a decrease in production efficiency. Furthermore, if the drying temperature is too high, the formed semipermeable membrane layer tends to be thermally degraded, making it difficult to perform separation using the semipermeable membrane. For example, there is a tendency for desalination performance to decrease or water permeability to decrease. Further, the drying time is preferably, for example, 1 to 30 minutes, more preferably 1 to 20 minutes. If the drying time is too short, drying tends to be insufficient. Furthermore, if the drying time is too long, production efficiency tends to decrease. In addition, the formed semipermeable membrane layer tends to deteriorate due to heat, making it difficult to perform separation using the semipermeable membrane. For example, there is a tendency for desalination performance to decrease or water permeability to decrease.

According to the manufacturing method described above, separation using the semipermeable membrane layer can be suitably performed, and furthermore, a composite hollow fiber membrane with excellent durability can be suitably produced.

(Case)
The housing is not particularly limited as long as it can be used as a housing for a hollow fiber membrane module. Further, the inner diameter of the housing is preferably 10 to 200 cm, more preferably 10 to 100 cm, and even more preferably 10 to 50 cm. Further, the height of the casing is preferably 0.3 to 3 m, more preferably 0.3 to 2 m, and even more preferably 0.5 to 1.5 m. If this casing is too large, it tends to be difficult to handle and increase maintenance costs. Furthermore, if the housing is too large, the residence time of the driving solution (DS) becomes long, and the driving solution (DS) tends to be diluted by water permeated from the feed solution (FS), resulting in a decrease in water permeability. be. Furthermore, if the casing is too small, it will not be possible to ensure a sufficient flow rate for practical purposes, and as a result, a large number of hollow fiber membrane modules will have to be prepared, resulting in increased equipment and operational costs. Tend. Further, the effective length of the composite hollow fiber membrane accommodated in the housing is preferably 0.3 to 3 m, more preferably 0.3 to 2 m, and more preferably 0.5 to 1.5 m. It is even more preferable.

In the composite hollow fiber membrane module, the filling rate of the composite hollow fiber membrane is preferably 10 to 65%, more preferably 10 to 60%, and even more preferably 20 to 55%. If the filling rate is too low, the composite hollow fiber membrane module tends to have insufficient water permeability. On the other hand, if the filling rate is too high, the excellent water permeability of the composite hollow fiber membrane module tends to be difficult to maintain over a long period of time. This is considered to be because the contact between the composite hollow fiber membranes increases during operation, which damages the semipermeable membrane layer provided on the outer peripheral surface of the composite hollow fiber membrane. Therefore, when the filling rate is within the above range, the composite hollow fiber membrane module has excellent water permeability, and this excellent water permeability can be maintained for a long period of time.

The filling rate of the composite hollow fiber membrane is the ratio of the total cross-sectional area of the plurality of composite hollow fiber membranes to the area of the cross section perpendicular to the longitudinal direction (fiber direction) of the composite hollow fiber membrane inside the casing. Specifically, as shown in FIG. 4, the total area of the plurality of composite hollow fiber membranes 11 with respect to the area of the cross section perpendicular to the longitudinal direction (fiber direction) of the composite hollow fiber membranes 11 in the hollow portion of the casing 2 It is the ratio of cross-sectional areas. Note that the cross-sectional area of the composite hollow fiber membrane 11 is a cross-sectional area including not only the cross-sectional area of the hollow portion but also the membrane itself, and is a cross-sectional area calculated from the outer diameter of the composite hollow fiber membrane 11. The filling rate can be calculated using, for example, the number of composite hollow fiber membranes housed in the housing 2 (pieces) and the cross-sectional area (m ² /piece) of one composite hollow fiber membrane 11. By dividing the product of , that is, the area occupied by the hollow fiber membrane 11 in the casing 2 by the area calculated from the inner diameter of the casing 2, that is, the inner area of the casing 2, The filling rate can be calculated. Note that FIG. 4 is a schematic cross-sectional view of the hollow fiber membrane module shown in FIG. 1.

The composite hollow fiber membrane module preferably has a pressure strength of 0.1 to 3 MPa, more preferably 0.1 to 2.5 MPa, and even more preferably 0.1 to 2.3 MPa. . This pressure resistance is the maximum pressure that can maintain operation when pressure is applied from the outside or inside of the composite hollow fiber membrane module. For example, the maximum pressure that can maintain the shape of a composite hollow fiber membrane when pressure is applied from the outside of the composite hollow fiber membrane, and the maximum pressure that can maintain the shape of the composite hollow fiber membrane when pressure is applied from the inside of the composite hollow fiber membrane. This is the lower of the pressures. Note that the maximum pressure at which the shape of the composite hollow fiber membrane can be maintained when pressure is applied from the outside of the composite hollow fiber membrane is, for example, the maximum pressure that can maintain the shape of the composite hollow fiber membrane when pressure is applied from the outside of the composite hollow fiber membrane. This is the pressure when Also, the maximum pressure that can maintain the shape of a composite hollow fiber membrane when pressure is applied from the inside of the composite hollow fiber membrane is, for example, when pressure is applied from the inside of the composite hollow fiber membrane, the composite hollow fiber membrane ruptures. This is the pressure when If the pressure resistance strength is too low, the housing or composite hollow fiber membrane provided in the composite hollow fiber membrane module tends to be easily damaged when the feed solution (FS) and driving solution (DS) are circulated. A compressive strength that is too high may be unnecessary in practice. Furthermore, if the pressure resistance is too high, not only will the cost increase due to the excessive pressure resistance, but also the pressure resistance will be given too much priority and the water permeability will tend to decrease.

The composite hollow fiber membrane module is applicable to membrane separation technology using semipermeable membranes. That is, the composite hollow fiber membrane module can be used in, for example, the NF method, the RO method, the FO method, and the like. Among these, the composite hollow fiber membrane module is preferably used for the FO method. Examples of the feed solution (FS) and driving solution (DS) when the composite hollow fiber membrane module is used in the FO method include the following solutions.

The feed solution (FS) is not particularly limited as long as it is a feed solution used for forward osmosis. Specifically, the feed solution (FS) includes a dilute solution having an osmotic pressure lower than that of the driving solution (DS). More specifically, water, solutions in which salts such as sodium chloride, ammonium carbonate, and calcium carbonate are dissolved, solutions in which sugars such as sucrose and dextrose are dissolved, and polymeric compounds such as polypropylene glycol and polyethylene glycol. Examples include solutions in which . From a more practical point of view, feed solutions (FS) include, for example, seawater, industrial wastewater, sewage water, food liquids, etc., which can be used as feed solutions (FS) and water extracted from them. Conceivable.

The driving solution (DS) is not particularly limited as long as it is a driving solution used for forward osmosis. Specifically, the driving solution (DS) includes a concentrated solution having a higher osmotic pressure than that of the feed solution (FS). More specifically, the driving solution (DS) includes a solution in which salts such as sodium chloride, ammonium carbonate, and calcium carbonate are dissolved, a solution in which sugars such as sucrose and dextrose are dissolved, and polypropylene glycol and polyethylene glycol. Examples include solutions in which polymeric compounds such as the like are dissolved, magnetic dispersion liquids, and ionic liquids. Among these, the driving solution (DS) used in the composite hollow fiber membrane module according to the present embodiment has high hydrophilicity (high compatibility with water), and has a high compatibility with water due to some external stimulus. It is preferable to use a material that has the property of decreasing and separating. Specific examples of this external stimulus include temperature, pH, magnetic force, and light. Among these, a driving solution whose compatibility with water changes depending on temperature is preferred.

As described above, the composite hollow fiber membrane module can be used in the forward osmosis method, and specifically, can be used in water generation treatment methods, energy production methods, and the like.

The water generation method includes, for example, a step of drawing water from the supply solution to the driving solution using the driving solution, and a step of separating and regenerating the driving solution and the drawn water. Water is obtained from these steps by separating the water drawn from the feed solution into the driving solution from the driving solution. Further, in this case, by using the above-mentioned driving solution whose compatibility with water decreases due to external stimulation, separation of water in the separation/regeneration step is facilitated. Furthermore, by using a driving solution whose compatibility with water decreases depending on temperature, separation of water in the separation/regeneration step becomes easier.

The energy production method includes, for example, a step of drawing water from the supply solution to the driving solution in a space where the driving solution is pressurized, and increasing the volume by the drawn water on the driving solution side; and extracting energy by rotating a turbine in minutes.

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the scope of the present invention is not limited thereto.

[Example 1]
(Preparation of composite hollow fiber membrane)
As the support layer of the composite hollow fiber membrane, a hollow fiber membrane provided in an external pressure hollow fiber membrane module (Puria GS manufactured by Kuraray Co., Ltd.) was used.

Note that the contact angle of water with respect to the outer peripheral surface of this support layer was measured as follows.

A water droplet was dropped on the outer peripheral surface of the support layer, and an image was taken at that moment. Then, the angle between the water droplet surface and the outer circumferential surface was measured at a location where the water droplet surface touched the outer circumferential surface. This angle is the contact angle of water. As a measuring device, Drop Master 700 manufactured by Kyowa Interface Science Co., Ltd. was used. The contact angle of water with respect to the outer peripheral surface obtained by the above measurement method was 45°.

A semipermeable membrane layer was formed on the outer surface side of the support layer.

Specifically, the support layer was first immersed in a 50% by mass ethanol aqueous solution for 20 minutes, and then immersed in pure water for 30 minutes to perform the wet treatment. The wet support layer subjected to this wet treatment was fixed to a frame so as not to come into contact with other support layers. Then, this support layer is immersed for 2 minutes in a 2% by mass aqueous solution of m-phenylenediamine, which is an aromatic polyfunctional amine compound, so that the 2% by mass aqueous solution of m-phenylenediamine contacts the outer peripheral surface side of the support layer. I let it happen. By doing so, a 2% by mass aqueous solution of m-phenylenediamine was impregnated from the outer peripheral surface side of the support layer. Thereafter, the excess 2% by mass aqueous solution of m-phenylenediamine that did not penetrate into the support layer was removed.

Then, this support layer was heated in a 0.2% by mass hexane solution of trimesic acid trichloride, which is an aromatic acid halide compound, so that a 0.2% by mass hexane solution of trimesic acid trichloride, which is an aromatic acid halide compound, came into contact with the outer peripheral surface side of the support layer. It was immersed in the solution for 1 minute. By doing so, an interface is formed between the aqueous m-phenylenediamine solution that has soaked into the outer peripheral surface of the support layer and the hexane solution of trimesic acid trichloride. At this interface, interfacial polymerization between m-phenylenediamine and trimesic acid trichloride proceeds to form a crosslinked polyamide.

Thereafter, the support layer formed of crosslinked polyamide was dried for 10 minutes in a dryer at 90°C. By doing so, a semipermeable membrane layer was formed on the outer peripheral surface side of the support layer so as to be in contact with the outer peripheral surface. The formation of this semipermeable membrane layer was also confirmed by observation with a scanning electron microscope. Specifically, the outer surface of the composite hollow fiber membrane in which the semipermeable membrane layer was formed on the support layer was observed using a scanning electron microscope (S-3000N manufactured by Hitachi, Ltd.). The obtained image revealed that a semipermeable membrane layer was suitably formed on the outer surface side of the composite hollow fiber membrane. Note that the formed semipermeable membrane layer had a thickness of 300 nm. Further, the thickness of the support layer was 0.2 mm.

(Composite hollow fiber membrane)
By the above manufacturing method, a composite hollow fiber membrane including a support layer and a semipermeable membrane layer was obtained. This composite hollow fiber membrane had an outer diameter of 1.0 mm, an inner diameter of 0.6 mm, and a membrane thickness of 0.2 mm. Note that the thickness of the composite hollow fiber membrane and the thickness of the support layer are approximately the same. This is because the semipermeable membrane layer is very thin compared to the support layer, so its thickness is within the error range.

[evaluation]
The composite hollow fiber membrane obtained as described above was evaluated by the method shown below.

(Water permeability of composite hollow fiber membrane in dry state: water permeation rate in dry state)
The obtained composite hollow fiber membrane was dried in a hot air dryer at 60° C. for 24 hours to completely dry the moisture inside the composite hollow fiber membrane.

Thereafter, this dry composite hollow fiber membrane was used in a forward osmosis (FO) method to measure the water permeation rate. Specifically, a 0.6M NaCl aqueous solution as a simulated driving solution (simulated DS) and ion-exchanged water as a simulated feed solution (simulated FS) were introduced through the obtained dry composite hollow fiber membrane. and filtered. At that time, the simulated DS was flowed on the semipermeable membrane layer side of the composite hollow fiber membrane, and the simulated FS was flowed on the support layer side of the composite hollow fiber membrane. The amount of water permeation from the simulated FS to the simulated DS was calculated from the weight changes of the simulated FS and the simulated DS. Then, from the calculated water permeation amount, the water permeation rate (JwFOdry) (L/m ² /hour: LMH) was obtained by converting the water permeation amount per unit membrane area, unit time, and unit pressure. This permeation rate was evaluated as the water permeability of the composite hollow fiber membrane in a dry state.

(Water permeability of composite hollow fiber membrane in wet state: permeation rate of pure water in wet state)
The obtained composite hollow fiber membrane was immersed in a 50% by mass ethanol aqueous solution for 1 minute, and then in pure water for 30 minutes. Using this swollen composite hollow fiber membrane in the forward osmosis (FO) method, the pure water permeation rate in the wet state (JwFOwet) (L/m ² /hour: LMH) was measured. This permeation rate was evaluated as the water permeability of the composite hollow fiber membrane in a wet state.

(Ratio of water permeation rate in dry state to water permeation rate in wet state in composite hollow fiber membrane: water permeation rate in dry state/water permeation rate in wet state)
By dividing the water permeation rate in the dry state calculated as above by the water permeation rate in the wet state, the water permeation rate in the dry state is compared to the water permeation rate in the wet state. The rate ratio (water permeation rate in dry state/water permeation rate in wet state: JwFOdry/JwFOwet) was calculated.

(Production of composite hollow fiber membrane module)
A composite hollow fiber membrane module shown in FIG. 1 was produced using the composite hollow fiber membrane. The composite hollow fiber membrane provided in the composite hollow fiber membrane module has hollow portions at its upper and lower ends opened, and both the upper and lower portions other than the hollow fiber openings are sealed with epoxy resin. . The hollow fiber membrane had an effective length of 1 m. Further, the inner diameter of the casing of the hollow fiber membrane module was 20 cm. Then, this hollow fiber membrane was housed in the casing of the hollow fiber membrane module so that the filling rate was 40%.

[evaluation]
(Pressure strength of composite hollow fiber membrane module)
To the obtained composite hollow fiber membrane module, water was added alternately to the bore side and the share side so that the pressure inside the housing increased by 0.1 MPa, and the water was added to the housing of the composite hollow fiber membrane module. This was continued until water leakage occurred due to breakage or water leakage between shell and bore occurred due to breakage of the composite hollow fiber membrane. The pressure immediately before these water leaks occurred was defined as the pressure strength of the composite hollow fiber membrane module.

(Water permeability of composite hollow fiber membrane module in dry state: Water permeation rate in dry state)
The obtained composite hollow fiber membrane module was dried in a hot air dryer at 60° C. for 24 hours to completely dry the moisture inside the composite hollow fiber membrane.

Thereafter, this dry composite hollow fiber membrane module was used in a forward osmosis (FO) method to measure the water permeation rate. Specifically, a 0.6M NaCl aqueous solution as a simulated driving solution (simulated DS) and ion-exchanged water as a simulated feed solution (simulated FS) were introduced through the obtained dry composite hollow fiber membrane. and filtered. At that time, the simulated DS was flowed on the share side of the composite hollow fiber membrane module, and the simulated FS was flowed on the bore side of the composite hollow fiber membrane module. The amount of water permeation from the simulated FS to the simulated DS was calculated from the weight changes of the simulated FS and the simulated DS. Then, from the calculated water permeation amount, the water permeation rate (JwmodFOdry) (L/m ² /hour: LMH) was obtained by converting the water permeation amount per unit membrane area, unit time, and unit pressure. This permeation rate was evaluated as the water permeability of the composite hollow fiber membrane module in a dry state.

(Water permeability of composite hollow fiber membrane module in wet state: permeation rate of pure water in wet state)
The obtained composite hollow fiber membrane was immersed in a 50% by mass ethanol aqueous solution for 1 minute, and then in pure water for 30 minutes. Using this swollen composite hollow fiber membrane in the forward osmosis (FO) method, the pure water permeation rate in the wet state (JwmodFOwet) (L/m ² /hour: LMH) was measured. This permeation rate was evaluated as the water permeability of the composite hollow fiber membrane module in a wet state.

(Ratio of water permeation rate in a dry state to water permeation rate in a wet state in a composite hollow fiber membrane module: water permeation rate in a dry state/water permeation rate in a wet state)
By dividing the water permeation rate in the dry state calculated as above by the water permeation rate in the wet state, the water permeation rate in the dry state is compared to the water permeation rate in the wet state. The rate ratio (water permeation rate in dry state/water permeation rate in wet state: JwmodFOdry/JwmodFOwet) was calculated.

The evaluation results are shown in Table 1.

[Example 2]
As a support layer for the composite hollow fiber membrane, an external pressure hollow fiber membrane module (Puria GL manufactured by Kuraray Co., Ltd.) was used instead of the hollow fiber membrane provided in the external pressure hollow fiber membrane module (Puria GS manufactured by Kuraray Co., Ltd.). A composite hollow fiber membrane module was obtained in the same manner as in Example 1 except that the hollow fiber membrane provided in ) was used.

Note that the contact angle of water with respect to the outer peripheral surface of this support layer was 45°. Further, the formed semipermeable membrane layer had a thickness of 280 nm. Further, the thickness of the support layer was 0.25 mm. Moreover, the obtained composite hollow fiber membrane had an outer diameter of 1.25 mm, an inner diameter of 0.75 mm, and a membrane thickness of 0.25 mm. Note that the thickness of the composite hollow fiber membrane and the thickness of the support layer are approximately the same. This is because the semipermeable membrane layer is very thin compared to the support layer, so its thickness is within the error range.

The evaluation results are shown in Table 1.

[Example 3]
A composite hollow fiber membrane module was obtained in the same manner as in Example 1, except that the inner diameter of the housing of the composite hollow fiber module was 28 cm, the effective length of the composite hollow fiber membrane was 0.6 m, and the filling rate was 25%. .

The evaluation results are shown in Table 1.

[Example 4]
A composite hollow fiber membrane module was obtained in the same manner as in Example 1, except that the inner diameter of the housing of the composite hollow fiber module was 18 cm, the effective length of the composite hollow fiber membrane was 1.8 m, and the filling rate was 49%. .

The evaluation results are shown in Table 1.

[Comparative example 1]
A composite hollow fiber membrane module was obtained in the same manner as in Example 1, except that a composite hollow fiber membrane was used in which the surface on which the semipermeable membrane layer was formed was changed from the outer surface of the support layer to the inner surface of the support layer.

The evaluation results are shown in Table 1.

[Comparative example 2]
A composite hollow fiber membrane module was obtained in the same manner as in Example 1, except that the inner diameter of the composite hollow fiber module was 9 cm and the effective length of the composite hollow fiber membrane was 3.3 m.

The evaluation results are shown in Table 1.

Table 1 shows that a composite hollow fiber membrane is provided with a semipermeable membrane layer containing a crosslinked polyamide made of a polyfunctional amine compound and a polyfunctional acid halide compound so as to be in contact with the outer peripheral surface of a hollow fiber-shaped porous support layer. In the case of a composite hollow fiber membrane module housed in a case with an inner diameter of 10 to 200 cm so that the effective length is 0.3 to 3 m (Examples 1 to 4), other than such composite hollow fiber membrane module Compared to the case of (Comparative Examples 1 and 2), the water permeation rate in the wet state of the module was high. In addition, the ratio of the water permeation rate in the dry state to the water permeation rate in the swollen state of the module was not particularly low compared to Comparative Examples 1 and 2. The permeation rate was also found to be high. That is, it was found that the composite hollow fiber membrane modules according to Examples 1 to 4 were able to maintain a high water permeation rate (water permeation rate) even in a dry state.

From the above, it was found that the composite hollow fiber membrane modules according to Examples 1 to 4 were composite hollow fiber membrane modules with excellent water permeability.

On the other hand, when using a composite hollow fiber membrane in which the semipermeable membrane layer is in contact with the inner circumferential surface of the support layer (Comparative Example 1), the water permeation rate in the wet state as a module is sufficiently reduced. I couldn't raise it.

In addition, when using a narrow housing with an inner diameter of 10 cm or less, even if the effective length of the composite hollow fiber membrane is increased to 3.3 m and the filling rate is set to 40% (Comparative Example 2), the wet state as a module is It was not possible to sufficiently increase the water permeation rate.

1 Composite hollow fiber membrane module 2 Housing 4 Lower end sealant 5 Upper end sealant 6 Shell side inlet 7 Shell side outlet 8 Bore side inlet 9 Bore side outlet 11 Composite hollow fiber membrane 12 Support layer 13 semipermeable membrane layer

Claims (8)

comprising a housing and a plurality of composite hollow fiber membranes housed within the housing,
The composite hollow fiber membrane is
A semipermeable membrane layer containing a crosslinked polyamide made of a polyfunctional amine compound and a polyfunctional acid halide compound, and a hollow fiber-like porous support layer,
the semipermeable membrane layer is in contact with the outer peripheral surface of the support layer,
the polyfunctional amine compound is phenylenediamine,
The polyfunctional acid halide compound is trimesic acid trichloride,
The support layer contains polyvinylidene fluoride and a hydrophilic resin,
The inner diameter of the housing is 18 to 50 cm,
A composite hollow fiber membrane module characterized in that the effective length of the composite hollow fiber membrane is 1 to 2 m. The composite hollow fiber membrane module according to claim 1, wherein the composite hollow fiber membrane has an outer diameter of 0.1 to 2 mm and an inner diameter of 0.05 to 1.5 mm. 1 or 2, wherein the ratio of the total cross-sectional area of the plurality of composite hollow fiber membranes to the cross-sectional area perpendicular to the longitudinal direction of the composite hollow fiber membranes inside the housing is 10 to 65%. 2. The composite hollow fiber membrane module according to 2. The composite hollow fiber membrane module according to any one of claims 1 to 3, which is used in a forward osmosis method. The composite hollow fiber membrane according to claim 4, wherein the composite hollow fiber membrane has a ratio of water permeation rate in a dry state to a water permeation rate in a wet state of 40 to 100% in a forward osmosis method. module. 6. The composite hollow fiber membrane module according to claim 4, wherein the composite hollow fiber membrane has a water permeation rate of 2 to 100 LMH in a wet state in a forward osmosis method. The composite hollow fiber membrane module according to any one of claims 1 to 6, wherein the contact angle of water with respect to the outer peripheral surface of the support layer is 90° or less. The composite hollow fiber membrane module according to any one of claims 1 to 7, having a compressive strength of 0.1 to 3 MPa.