Composite film and method for manufacturing the same

Abstract

The present invention aims to provide a composite membrane and a method for producing the same, which can be used to separate a fluorine compound in an organic solution containing at least one organic solvent selected from the group consisting of propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether, and a fluorine compound having a total of 1 to 6 fluorine-containing groups in its molecule, selected from the group consisting of perfluoroalkyl groups having 1 to 6 carbon atoms and perfluoroalkylene groups having 1 to 6 carbon atoms, and which achieves a high level of both permeability of the organic solvent and blocking performance of the fluorine compound. [Solution] The composite film of the present invention comprises a silicone layer, a dense layer and a support layer, and a polymer film formed of a polymer other than silicone, wherein the silicone layer is provided on the surface of the dense layer, and is used for separating fluorine compounds present in an organic solution.

Description

[Technical Field]

[0001] The present invention relates to a composite membrane used for separating fluorine compounds present in organic solutions and a method for producing the same. [Background technology]

[0002] In recent years, from the perspective of building a sustainable society and achieving carbon neutrality, the chemical industry has also been required to adopt more energy-efficient processes. In particular, since distillation processes account for a large proportion of the energy consumed by the chemical industry as a whole, there is a need to switch to more energy-efficient processes, and a shift to membrane separation processes, which are energy-efficient, is being considered.

[0003] Membrane separation processes are used in water purification and in the manufacturing processes of various industrial products that use water as a solvent, and have become an industrially established technology. Polymer membranes are the mainstream material for separation membranes used in membrane separation processes because they are relatively easy to mold and process, making it easy to establish inexpensive mass production processes, and they are lightweight, flexible, and easy to handle.

[0004] On the other hand, in the chemical industry, organic solvents are mainly used as solvents, so solvent resistance is required for the material of the separation membrane. For example, in the manufacture of semiconductors and liquid crystal panels, glycol ether solvents such as propylene glycol monomethyl ether, 3-methoxybutanol, propylene glycol monomethyl ether acetate, 3-methoxybutyl acetate, dipropylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether; cyclic ketones such as cyclohexanone; and aprotic polar solvents such as dimethyl sulfoxide and N-methylpyrrolidone are used in the photoresist chemicals, cleaning solutions, and stripping solutions used to form wiring patterns. In order to use a membrane separation process as an alternative to a distillation process, the material of the separation membrane needs to be resistant to these organic solvents.

[0005] Furthermore, in order to use membrane separation processes as an alternative to distillation processes, separation membranes with nanofiltration-level separation capabilities are required that can separate solutes in organic solvent-based liquids, particularly solutes with a molecular weight of approximately 200 to 1000.

[0006] Under these circumstances, it is being considered to obtain nanofiltration membranes using polyamide resins that have high resistance to the aforementioned various organic solvents, employing a method called thermally induced phase separation (TIPS). The TIPS method is a relatively new method in which a solvent that does not dissolve in a polymer material at low temperatures but dissolves at high temperatures is selected, and a homogeneous polymer solution dissolved at high temperatures is cooled to a temperature below the binodal line, which is the boundary between the one-phase and two-phase regions, thereby inducing phase separation and fixing the structure through polymer crystallization or glass transition. The TIPS method can be applied to polymers for which there are no solvents that dissolve at low temperatures, making it applicable to resins with high solvent resistance. Furthermore, because it tends to produce a sponge-like homogeneous structure and yields a high-strength separation membrane, it is possible to apply high pressure, which is the driving force for liquid permeation, in nanofiltration membranes where the liquid permeability is low due to the small pore size, making it a suitable method for obtaining solvent-resistant nanofiltration membranes.

[0007] For example, Patent Document 1 describes a product produced by the TIPS method, with a fractional molecular weight of 200 to 1000 and a methanol permeate rate of 0.03 L / (m³). 2 A nanofiltration hollow fiber membrane formed using polyamide resin has been proposed, with a density of (bar·h) or higher.

[0008] Furthermore, Patent Document 2 proposes a polyamide hollow fiber membrane, manufactured using the TIPS method, which has a dense layer formed on at least one surface and has unidirectional striated recesses on the surface of the dense layer, and which can be used as an ultrafiltration membrane or nanofiltration membrane.

[0009] In order to use a membrane separation process as an alternative to a distillation process, a separation membrane that has excellent permeation performance for organic solvents and excellent solute rejection performance in an organic solvent-based liquid to be treated is required. However, since the permeation performance and the rejection performance are conflicting performances, it is very difficult to achieve both the permeation performance and the rejection performance at a high level. <9000079> Further, for example, in the photoresist chemical solution or the like, an onium salt having a fluorine compound having a perfluoroalkyl group or a perfluoroalkylene group as an anion part as a photoacid generator is used. Since the fluorine compound constituting the photoacid generator is a chemically stable substance, it is difficult to be decomposed by microorganisms and the decomposition in the ecosystem does not proceed, so the residue in the environment has become a major problem. Therefore, the development of a separation membrane that can efficiently and effectively remove specific fluorine compounds from industrial waste liquids and the like is strongly desired.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0012] Generally, when separating a solute from an organic solution using a separation membrane, in order to improve the rejection rate of the solute without reducing the permeation amount of the organic solvent, (1) the separation functional layer of the separation membrane has a high affinity for the organic solvent and a low affinity for the solute; (2) there is a large difference in molecular weight between the organic solvent and the solute; and (3) the viscosity of the organic solvent is low.

[0013] ]>For example, the fluorine compound in the anionic portion of a photoacid generator is typically a fluorine compound having a total of 1 to 6 perfluoroalkyl or perfluoroalkylene groups with 1 to 6 carbon atoms in its molecule, and the molecular weight of the fluorine compound is approximately 150 to 1500. To separate the fluorine compound from an organic solution using a separation membrane, it is conceivable to use a nanofiltration membrane (NF membrane) or reverse osmosis membrane (RO membrane) with a fractional molecular weight of several hundred. Furthermore, if the organic solvent in the organic solution has a molecular weight sufficiently smaller than that of the fluorine compound and has sufficiently low viscosity, it is considered possible to achieve a high level of both the permeability of the organic solvent and the blocking performance of the fluorine compound using the separation membrane.

[0014] However, propylene glycol monomethyl ether acetate or propylene glycol monomethyl ether is generally used as the organic solvent for photoresist solutions, and since the difference in molecular weight between this organic solvent and the fluorine compound is small and the viscosity is high (around 1.0 to 2.0 mPa·s), the separation membrane was unable to achieve a high level of both permeability of the organic solvent and blocking performance of the fluorine compound.

[0015] The present invention aims to provide a composite membrane and a method for producing the same, which can be used to separate a fluorine compound in an organic solution containing at least one organic solvent selected from the group consisting of propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether, and a fluorine compound having a total of 1 to 6 fluorine-containing groups in its molecule, selected from the group consisting of perfluoroalkyl groups having 1 to 6 carbon atoms and perfluoroalkylene groups having 1 to 6 carbon atoms, and which achieves a high level of both permeability of the organic solvent and blocking performance of the fluorine compound. [Means for solving the problem]

[0016] The inventors of the present invention conducted diligent studies to solve the above problems and found that a composite film comprising a silicone layer, a dense layer and a support layer, and a polymer film formed of a polymer other than silicone, wherein the silicone layer is provided on the surface of the dense layer, can achieve a high level of both permeability of the specific organic solvent and blocking performance of the specific fluorine compound when used to separate a specific fluorine compound in an organic solution containing at least one organic solvent selected from the group consisting of propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether (hereinafter also referred to as "specific organic solvent") and a fluorine compound having a total of 1 to 6 fluorine-containing groups in its molecule selected from the group consisting of perfluoroalkyl groups having 1 to 6 carbon atoms and perfluoroalkylene groups having 1 to 6 carbon atoms (hereinafter also referred to as "specific fluorine compound"). The present invention was completed by further studies based on this finding.

[0017] In other words, the present invention provides inventions in the following embodiments. <1> A composite film comprising a silicone layer, a dense layer and a support layer, and a polymer film formed of a polymer other than silicone, wherein the silicone layer is provided on the surface of the dense layer, The aforementioned composite membrane is used to separate fluorine compounds present in an organic solution. The organic solvent of the aforementioned organic solution contains at least one selected from the group consisting of propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether. The fluorine compound is a composite film having a total of 1 to 6 fluorine-containing groups in its molecule, selected from the group consisting of perfluoroalkyl groups having 1 to 6 carbon atoms and perfluoroalkylene groups having 1 to 6 carbon atoms. <2> The polymer membrane is formed of polyamide or polyacrylonitrile. <1> The composite film described above. <3> Polymer membranes are hollow fiber membranes. <1> or <2> The composite film described above. <4> The dense layer is located on the inner surface side of the hollow fiber membrane. <3> The composite film described above. <5> The supporting layer has a porosity of 60-80%. <1> ~ <4> A composite film as described in any of the following. <6> The dense layer has a thickness of 0.1 μm or more. <1> ~ <5> A composite film as described in any of the following. <7> The silicone layer has a thickness of 0.05 to 10 μm. <1> ~ <6> A composite film as described in any of the following. <8> The silicone layer is made of silicone rubber. <1> ~ <7> A composite film as described in any of the following. <9> <1> ~ <8> A filtration method for filtering a liquid to be treated containing an organic solvent and a fluorine compound using a composite membrane as described in any of the following, The organic solvent contains at least one selected from the group consisting of propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether, The fluorine compound is a fluorine compound having a total of 1 to 6 fluorine-containing groups in its molecule, selected from the group consisting of perfluoroalkyl groups having 1 to 6 carbon atoms and perfluoroalkylene groups having 1 to 6 carbon atoms. <10> In the module case, <1> ~ <8> A membrane module comprising a composite membrane described in any of the following, The aforementioned membrane module is used to separate fluorine compounds present in an organic solution. The organic solvent of the aforementioned organic solution contains at least one selected from the group consisting of propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether. The fluorine compound is a membrane module having a total of 1 to 6 fluorine-containing groups in its molecule, selected from the group consisting of perfluoroalkyl groups having 1 to 6 carbon atoms and perfluoroalkylene groups having 1 to 6 carbon atoms. [Effects of the Invention]

[0018] The composite membrane of the present invention comprises a silicone layer and a polymer membrane formed of a polymer other than silicone, having a dense layer and a support layer, and having a characteristic structure in which the silicone layer is provided on the surface of the dense layer. Therefore, when used to separate a specific fluorine compound in an organic solution containing a specific organic solvent and a specific fluorine compound, it is possible to achieve a high level of both permeability of the specific organic solvent and blocking performance of the specific fluorine compound. [Brief explanation of the drawing]

[0019] [Figure 1] This is a schematic diagram of an apparatus used to measure the molecular weight cutoff, permeability (Flux), and rejection rate of composite hollow fiber membranes or hollow fiber membranes. [Figure 2] This is a schematic diagram illustrating an example of calculating the porosity of the support layer of a hollow fiber membrane, and is a schematic cross-sectional view of the hollow fiber membrane cut perpendicular to its longitudinal direction. [Figure 3] This is a magnified view of the area enclosed by the dotted line in Figure 2. [Figure 4] This is a magnified view of the area enclosed by the dotted line in Figure 2. [Modes for carrying out the invention]

[0020] 1.Definition In the present invention, when "ultrafiltration" or "ultrafiltration membrane" is used, it means filtration in which the molecular weight cutoff is set in the range of 1,000 to 1,000,000, or a filtration membrane in which the molecular weight cutoff is set in the range of 1,000 to 1,000,000. When "nanofiltration" or "nanofiltration membrane" is used, it means filtration in which the molecular weight cutoff is set in the range of 200 to 1,000, or a filtration membrane in which the molecular weight cutoff is set in the range of 200 to 1,000.

[0021] In the present invention, "dense layer" refers to a region in a polymer film where dense micropores are aggregated, and where the presence of pores is substantially absent in a scanning electron microscope (SEM) image at a magnification of 10,000x.

[0022] In the present invention, the term "support layer" refers to a porous region in a polymer film other than the dense layer, which has a continuous porous structure and in which the presence of substantially fine pores can be observed in a scanning electron microscope (SEM) image at a magnification of 2000x.

[0023] In the present invention, "silicone layer" means a layer provided on the surface of a dense layer of a polymer film and formed using silicone.

[0024] In the present invention, "hollow fiber membrane" means a hollow fiber-shaped polymer membrane formed of a polymer other than silicone, having a dense layer and a support layer.

[0025] 2.Composite membrane The composite film of the present invention comprises a silicone layer and a polymer film having a dense layer and a support layer, and formed of a polymer other than silicone, wherein the silicone layer is provided on the surface of the dense layer. The composite film of the present invention will be described in detail below.

[0026] [Polymer membrane] The polymer film, which is the main component of the composite film of the present invention, has a dense layer and a support layer, and is formed of a polymer other than silicone.

[0027] The polymers constituting the polymer membrane are not particularly limited and include polyamides, polyacrylonitriles, polyethylenes, polypropylenes, polytetrafluoroethylenes, polyvinylidene fluoride, polyethersulfones, polyarylates, polyetheretherketones, sulfonated polyetherketones, polyphenylene sulfide, polyvinyl chloride, polyesters, cellulose acetate, cellulose, polybenzimidazoles, polyamideimides, polyimides, and polyetherimides. These may be used individually or in combination of two or more. Of these, polyamides and polyacrylonitriles are preferred, and polyamides are more preferred, from the viewpoint of conferring resistance to specific organic solvents and other organic solvents to the composite membrane.

[0028] The type of polyamide is not particularly limited, but examples include polyamide homopolymers, polyamide copolymers, or mixtures thereof. Specific examples of polyamide homopolymers include polyamide 6, polyamide 66, polyamide 46, polyamide 610, polyamide 612, polyamide 11, polyamide 12, polyamide MXD6, polyamide 4T, polyamide 6T, polyamide 9T, and polyamide 10T. Specific examples of polyamide copolymers include copolymers of polyamide with polyethers such as polytetramethylene glycol or polyethylene glycol. The ratio of the polyamide component in the polyamide copolymer is not particularly limited, but for example, the proportion of the polyamide component is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and particularly preferably 95 mol% or more. By satisfying the above range for the ratio of the polyamide component in the polyamide copolymer, the polymer film can be provided with even better organic solvent resistance. Polyamides may be used individually or in combination of two or more types.

[0029] Among these polyamides, polyamide 6 is preferred as a polymer film-forming resin because it readily achieves a suitable balance of pressure resistance and solvent resistance, and also readily improves the permeability of specific organic solvents.

[0030] While the presence or absence of crosslinking is not a requirement for polyamide, non-crosslinked polyamide is preferred from the standpoint of reducing manufacturing costs.

[0031] The relative viscosity of the polyamide is not particularly limited, but for example, it can be 2.0 to 7.0, preferably 2.5 to 6.0, and more preferably 3.0 to 5.0. Having such a relative viscosity improves moldability and controllability of phase separation during the production of polymer films, and makes it possible to provide the polymer film with excellent dimensional stability. Here, relative viscosity refers to the value measured using an Ubbelohde viscometer at 25°C with a solution prepared by dissolving 1 g of polyamide in 100 mL of 96% sulfuric acid.

[0032] Polyacrylonitrile is not particularly limited and may be a homopolymer of acrylonitrile or a copolymer of acrylonitrile and a copolymer monomer, but is preferably a homopolymer of acrylonitrile. The copolymer monomer is not particularly limited and monomers used in the production of polyacrylonitrile can be used. If it is a copolymer, the acrylonitrile content is preferably 70% by weight or more, more preferably 85% by weight or more, and the copolymer monomer content is preferably 30% by weight or less, more preferably 15% by weight or less. The copolymer monomer may be used alone or in combination of two or more. Polyacrylonitrile may also be used alone or in combination of two or more.

[0033] The intrinsic viscosity of polyacrylonitrile is not particularly limited, but from the viewpoint of ensuring good strength of the polymer film and good solubility of polyacrylonitrile when preparing the film-forming stock solution, it is preferably 0.4 or more and less than 3.5, more preferably 1.0 or more and 3.0 or less, and even more preferably 2.0 or more and 3.0 or less. Here, intrinsic viscosity refers to the value measured by an Ostwald viscometer at 25°C using a solution prepared by dissolving 150 mg of polyacrylonitrile in 50 mL of N,N-dimethylformamide with 0.1 mol / liter sodium thiocyanate.

[0034] The polymer membrane may, in addition to the polymer, optionally contain fillers, provided that they do not impair the effects of the present invention. The inclusion of fillers can improve the strength, elongation, and modulus of elasticity of the polymer membrane. In particular, the inclusion of fillers also provides the effect of making the polymer membrane less prone to deformation even when high pressure is applied during filtration. There are no particular restrictions on the types of fillers to be added, but examples include fibrous fillers such as glass fibers, carbon fibers, potassium titanate whiskers, zinc oxide whiskers, calcium carbonate whiskers, wollastonite whiskers, aluminum borate whiskers, aramid fibers, alumina fibers, silicon carbide fibers, ceramic fibers, asbestos fibers, gypsum fibers, and metal fibers; silicates such as talc, hydrotalcite, wollastonite, zeolite, sericite, mica, kaolin, pyrophyllite, bentonite, and asbestos; metal compounds such as silicon oxide, magnesium oxide, alumina, zirconium oxide, titanium oxide, and iron oxide; carbonates such as calcium carbonate, magnesium carbonate, and dolomite; sulfates such as calcium sulfate and barium sulfate; metal hydroxides such as calcium hydroxide, magnesium hydroxide, and aluminum hydroxide; and inorganic materials such as non-fibrous fillers such as glass beads, glass flakes, glass powder, ceramic beads, boron nitride, silicon carbide, carbon black, silica, and graphite. These fillers may be used individually or in combination of two or more. Among these fillers, mica, talc, hydrotalcite, silica, titanium dioxide, and more preferably mica and talc are used. The filler content is not particularly limited, but for example, per 100 parts by weight of polymer, the filler may be 0.1 to 100 parts by weight, preferably 10 to 75 parts by weight, and more preferably 25 to 50 parts by weight. By including fillers in such a content, the strength, elongation, and elastic modulus of the polymer film can be improved.

[0035] Polymer films may contain additives such as thickeners, antioxidants, surface modifiers, lubricants, and surfactants, as needed, to control pore size and improve film performance.

[0036] The shape of the polymer membrane is not particularly limited and can be selected from any shape such as hollow fiber membranes or flat membranes. Hollow fiber membranes are preferred in the present invention because they have a large filtration area per unit volume of module and can perform filtration efficiently. In other words, the composite membrane of the present invention is preferably a composite hollow fiber membrane.

[0037] The thickness of the polymer membrane is appropriately set according to the thickness of the dense layer and support layer, the permeability and blocking performance to be provided, etc., but for example, 50 to 600 μm, preferably 100 to 350 μm is used. If the polymer membrane is a hollow fiber membrane, the thickness of the hollow fiber membrane is calculated by dividing the value obtained by subtracting the inner diameter from the outer diameter by 2.

[0038] When the polymer membrane is a hollow fiber membrane, the outer diameter of the hollow fiber membrane is appropriately set according to the thickness of the dense layer and support layer, the permeability and blocking performance to be provided, etc. However, considering the relationship between the effective membrane area when filled into a module, the membrane strength, the pressure loss of the fluid flowing through the hollow part, and the buckling pressure, the outer diameter of the hollow fiber membrane can be 400 μm or more, preferably 450 to 4000 μm, and more preferably 500 to 3500 μm. The inner diameter of the hollow fiber membrane is not particularly limited, but for example, it can be 100 to 3000 μm, preferably 200 to 2500 μm, more preferably 300 to 2000 μm, and even more preferably 300 to 1500 μm. In this invention, the outer and inner diameters of the hollow fiber membranes are determined by observing five composite hollow fiber membranes with an optical microscope at a magnification of 200x, measuring the outer and inner diameters (both at the point of maximum diameter) of the hollow fiber membranes constituting each composite hollow fiber membrane, and calculating the average value of each.

[0039] Here, filtration membranes (separation membranes) are classified in order of the size of the substances they separate, from largest to smallest: microfiltration (MF) membranes, ultrafiltration (UF) membranes, nanofiltration (NF) membranes, and reverse osmosis (RO) membranes. For filtration membranes smaller than UF membranes, the molecular weight cutoff is used as an indicator of the size of the substance to be captured. The molecular weight cutoff is determined by a permeation test using a standard substance with a known molecular weight. The molecular weight cutoff is determined by the lower limit of molecular size (Dalton units: Da) at which 90% or more is retained by the permeation test. In this invention, the molecular weight cutoff of ultrafiltration membranes is 1,000 to 1,000,000, and the molecular weight cutoff of nanofiltration membranes is 200 to 1,000,000.

[0040] From the viewpoint of obtaining the composite membrane of the present invention that can achieve a high level of both permeability to specific organic solvents and blocking performance of specific fluorine compounds, the polymer membrane is preferably an ultrafiltration membrane or a nanofiltration membrane. Furthermore, the molecular weight cutoff of the polymer membrane is not particularly limited and can be adjusted to the desired value by appropriately adjusting the thickness of the dense layer and the pore size of the support layer. However, from the viewpoint of obtaining the composite membrane of the present invention that can achieve a higher level of both permeability to specific organic solvents and blocking performance of specific fluorine compounds, if it is an ultrafiltration membrane, it is preferably 1000 to 120000, more preferably 1000 to 100000, even more preferably 1000 to 80000, and even more preferably 1000 to 70000. If it is a nanofiltration membrane, it is preferably 200 to 1000, more preferably 400 to 1000, and even more preferably 600 to 1000.

[0041] In this invention, the molecular weight cutoff of the polymer membrane is determined when dextran is used as a standard substance and water as the solvent, if it is greater than 3000. Specifically, the molecular weight cutoff of the polymer membrane (if greater than 3000) is determined when a module is prepared using the polymer membrane and an aqueous solution containing multiple known molecular weights of dextran at predetermined concentrations is used as the stock solution for a filtration operation. The dextran concentration in the permeate is measured by high-performance liquid chromatography, and the solute rejection rate at each molecular weight is calculated according to the following formula. The results are then plotted on a graph with molecular weight on the x-axis and rejection rate on the y-axis, and the molecular weight at the intersection of the resulting approximation curve and the 90% rejection rate is used. Solute rejection rate (%) = {(Dextran concentration in stock solution - Dextran concentration in permeate) / Dextran concentration in stock solution} × 100

[0042] Furthermore, in the present invention, the molecular weight cutoff of the polymer membrane is a value determined when monodisperse polystyrene is used as a standard substance and N-methyl-2-pyrrolidone (hereinafter also referred to as "NMP") is used as the solvent, if the molecular weight cutoff of the polymer membrane is 3000 or less. Specifically, the molecular weight cutoff of the polymer membrane (if the molecular weight cutoff is 3000 or less) is a value determined when a module is made using the polymer membrane and a filtration operation is performed using an NMP solution containing multiple polystyrenes of known molecular weights at predetermined concentrations as the stock solution. The polystyrene concentration in the permeate is measured by high-performance liquid chromatography, and the solute rejection rate at each molecular weight is calculated according to the following formula. Then, each result is plotted on a graph with molecular weight on the x-axis and rejection rate on the y-axis, and the molecular weight at the intersection of the resulting approximation curve and the rejection rate of 90% is the molecular weight. Solute rejection rate (%) = {(Polystyrene concentration in stock solution - Polystyrene concentration in permeate) / Polystyrene concentration in stock solution} × 100

[0043] [Dense layer] The dense layer is a region in a polymer film where dense micropores are clustered together, and where the presence of pores is substantially absent in a scanning electron microscope (SEM) image at a magnification of 10,000x. The dense layer may be formed on one side of the polymer film or on both sides.

[0044] When the polymer membrane is a hollow fiber membrane, the dense layer may be formed on the inner surface of the hollow fiber membrane, on the outer surface, or on both surfaces. However, from the viewpoint of achieving a higher level of both permeability to specific organic solvents and blocking performance of specific fluorine compounds, it is preferable that the dense layer be formed on the inner surface. When observing the dense layer with a scanning electron microscope (SEM), if the dense layer is located on the outer surface of the hollow fiber membrane, the hollow fiber membrane can be cut to an appropriate size, placed on a sample stage, and then observed after vapor deposition of Pt, Au, Pd, etc. If the dense layer is located on the inner surface of the hollow fiber membrane, the hollow fiber membrane can be cut longitudinally with a sharp blade such as a scalpel to expose the inner surface, then cut to an appropriate size, placed on a sample stage, and then observed after vapor deposition of Pt, Au, Pd, etc.

[0045] The thickness of the dense layer is not particularly limited and can be adjusted to the desired value by appropriately adjusting the solvent, concentration, and temperature of the film-forming stock solution, the type and temperature of the coagulation solution, etc. However, from the viewpoint of improving the blocking performance of specific fluorine compounds, it is preferably 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.3 μm or more. Furthermore, from the viewpoint of improving the permeability of specific organic solvents, it is preferably 2.0 μm or less, more preferably 1.8 μm or less, even more preferably 1.5 μm or less, even more preferably 1.2 μm or less, and even more preferably 1.0 μm or less. In the present invention, the thickness of the dense layer is a value obtained by measuring the distance (thickness) of the region in which substantially no pores are observed in the polymer film constituting the composite film at regular intervals in a scanning electron microscope (SEM) image of the composite film cross-section at a magnification of 10,000x, and calculating the average value.

[0046] [Support layer] The support layer is a porous region in the polymer film, other than the dense layer, that has a continuous porous structure in which the presence of substantially fine pores can be observed in scanning electron microscope (SEM) images at a magnification of 2000x.

[0047] The pore size of the support layer is not particularly limited, as long as it does not significantly hinder the strength required to hold the dense layer and the permeability of fluids.

[0048] The porosity of the support layer is not particularly limited and can be adjusted to the desired value by appropriately adjusting the solvent, concentration, and temperature of the film-forming stock solution, the type and temperature of the coagulation solution, etc., during the production of the polymer film. However, from the viewpoint of ease of film formation and from the viewpoint of increasing the film strength so that the permeability can be increased by raising the operating pressure during film filtration, it is preferably 60-85%, more preferably 63-83%, even more preferably 65-80%, and even more preferably 66-77%.

[0049] In this invention, the porosity of the support layer is a value obtained by calculating the area ratio (%) of the total pore area to the area of ​​the analysis region in scanning electron microscope (SEM) images of the composite film cross-section, which are taken at five equally spaced locations in the thickness direction of the cross-section of the support layer, and then calculating the average value. Specifically, the porosity of the support layer is a value obtained by the following method: For a cross-section of the support layer cut perpendicular to the longitudinal direction, scanning electron microscope (SEM) images are taken at five equally spaced locations in the thickness direction so that only the support layer is captured. The magnification is set so that an analysis region with 30 to 300 pores can be set in the captured image. Image analysis of the analysis region is performed using image analysis software (ImageJ) on the five captured SEM images, and the pore portion is distinguished from the polymer portion by binarization processing. Then, the area ratio (%) of the total pore area to the area of ​​the analysis region is calculated for each, and the average value is calculated.

[0050] [Silicone layer] The silicone layer is a layer that has the function of separating specific fluorine compounds in an organic solution containing a specific organic solvent and a specific fluorine compound, and is a non-porous region layer provided on the surface of the dense layer of the polymer membrane. The composite membrane of the present invention, which has a silicone layer on the surface of the dense layer of the polymer membrane, has significantly improved performance in blocking specific fluorine compounds in the organic solution compared to conventional ultrafiltration membranes and nanofiltration membranes that do not have a silicone layer, and can achieve a high level of both permeability of specific organic solvents and blocking performance of specific fluorine compounds.

[0051] The reason why a silicone layer can be provided on the surface of a dense polymer film to achieve both high levels of permeability to specific organic solvents and high levels of blocking performance for specific fluorine compounds is not limited by theory, but can be considered as follows.

[0052] In reverse osmosis (RO) membranes, the separation functional layer, which is made of highly polar polymers such as polyamide and is commonly used, has low affinity for specific organic solvents, making it difficult for these solvents to permeate the separation functional layer. Conversely, the separation functional layer, which is made of a less polar polymer, has high affinity for specific organic solvents, making it easy for the polymer to dissolve. As a result, it is not possible to maintain its function as a separation functional layer, and the blocking performance of specific fluorine compounds is thought to decrease. On the other hand, silicone is a less polar polymer and therefore has high affinity for specific organic solvents. Furthermore, because it forms a cross-linked structure, it can maintain its function as a separation functional layer without dissolving in specific organic solvents. In addition, fluorine compounds are generally highly polar and have low affinity for silicone. Therefore, by providing a silicone layer on the surface of the dense layer of the polymer membrane, specific organic solvents with high affinity for the silicone layer will permeate easily, while specific fluorine compounds with low affinity for the silicone layer will not permeate easily. This makes it possible to achieve a high level of both the permeability of specific organic solvents and the blocking performance of specific fluorine compounds.

[0053] When the polymer membrane is a hollow fiber membrane, the silicone layer may be provided on the surface of the dense layer on the inner surface of the hollow fiber membrane, or on the surface of the dense layer on the outer surface of the hollow fiber membrane, but it is preferable that it be provided on the surface of the dense layer on the inner surface of the hollow fiber membrane. This is because if the silicone layer is provided on the surface of the dense layer on the outer surface of the hollow fiber membrane, peeling of the silicone layer due to contact between the hollow fiber membranes during filtration, or peeling at the interface between both ends of the module and the sealant during module fabrication, may occur. Furthermore, when the hollow fiber membrane has dense layers on both sides, the silicone layer may be provided on the surface of only one of the dense layers, or on both dense layers, but for the reasons mentioned above, it is preferable that it be provided only on the surface of the dense layer on the inner surface.

[0054] The silicone used as the material for forming the silicone layer is not particularly limited as long as it does not hinder the permeability of specific organic solvents and can improve the blocking performance of specific fluorine compounds. It may be a silicone resin or a silicone rubber, but from the viewpoint of imparting elasticity and flexibility to the silicone layer and obtaining a silicone layer with excellent shape stability, silicone rubber is preferred.

[0055] Silicone rubber is a rubbery cured product having a polyorganosiloxane structure, obtained by curing polyorganosiloxane. Polyorganosiloxane is a linear, branched, or network compound having Si-O bonds (siloxane bonds). The substituents bonded to the silicon atom are not particularly limited and include, for example, C1-C10 alkyl groups such as methyl, ethyl, propyl, and butyl groups; C2-C10 alkenyl groups such as vinyl, allyl, and butenyl groups; C6-C20 aryl groups such as phenyl, tolyl, and naphthyl groups; and C3-C10 cycloalkyl groups such as cyclopentyl and cyclohexyl groups. These substituents may be present individually or in combination of two or more.

[0056] Examples of the polyorganosiloxane include polydialkylsiloxane (e.g., polydiC 1-10 alkylsiloxane such as polydimethylsiloxane), polyalkylalkenylsiloxane (e.g., polyC 1-10 alkylC 2-10 alkenylsiloxane such as polymethylvinylsiloxane), polyalkylarylsiloxane (e.g., polyC 1-10 alkylC 6-20 arylsiloxane such as polymethylphenylsiloxane), polydiarylsiloxane (e.g., polydiC 6-20 arylsiloxane such as polydiphenylsiloxane), dialkylsiloxane-alkylalkenylsiloxane copolymer (e.g., diC 1-10 alkylsiloxane-C 1-10 alkylC 2-10 alkenylsiloxane copolymer such as dimethylsiloxane-methylvinylsiloxane copolymer), dialkylsiloxane-alkylarylsiloxane copolymer (e.g., diC 1-10 alkylsiloxane-C 1-10 alkylC 6-20 arylsiloxane copolymer such as dimethylsiloxane-methylphenylsiloxane copolymer), dialkylsiloxane-alkylalkenylsiloxane-alkylarylsiloxane copolymer (e.g., diC 1-10 alkylsiloxane-C 1-10 alkylC 2-10 alkenylsiloxane-C 1-10 alkylC 6-20 arylsiloxane copolymer such as dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer). The alkyl group of the polyorganosiloxane may be a fluorinated alkyl group. The polyorganosiloxane may be used alone or in combination of two or more. Among these polyorganosiloxanes, from the viewpoint of obtaining a silicone layer that does not inhibit the liquid permeation performance of a specific organic solvent and has excellent blocking performance against a specific fluorine compound, preferably polydialkylsiloxane (e.g., polydiC 1-10Alkylsiloxanes), polyalkylalkenylsiloxanes (e.g., polymethylvinylsiloxane, etc.) 1-10 Alkyl C 2-10 Alkenylsiloxanes), dialkylsiloxane-alkylalkenylsiloxane copolymers (e.g., dimethylsiloxane-methylvinylsiloxane copolymers, etc.) 1-10 Alkylsiloxane-C 1-10 Alkyl C 2-10 Alkenylsiloxane copolymers, and dialkylsiloxane-alkylalkenylsiloxane-alkylarylsiloxane copolymers (for example, diC such as dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers) 1-10 Alkylsiloxane-C 1-10 Alkyl C 2-10 Alkenylsiloxane-C 1-10 Alkyl C 6-20 It is at least one selected from the group consisting of arylsiloxane copolymers.

[0057] Polyorganosiloxanes may have substituents such as epoxy groups, hydroxyl groups, alkoxy groups, carboxyl groups, amino groups, ether groups, acryloyl groups, and methacryloyl groups at their molecular ends or main chain. Furthermore, the ends of polyorganosiloxanes are not particularly limited and may include, for example, trialkylsilyl groups (e.g., trimethylsilyl groups). 1-10 Alkylsilyl group), dialkylalkenylsilyl group (for example, diC such as dimethylvinylsilyl group) 1-10 Alkyl C 2-10 Alkenylsilyl groups, silanol groups, trialkoxysilyl groups (for example, trimethoxysilyl groups such as triC) 1-10 It may also be an alkoxysilyl group.

[0058] The polyorganosiloxane structure forming the silicone rubber may be linear, branched, or networked, but from the viewpoint of elasticity and flexibility, it is preferably linear.

[0059] The silicone rubber may be either a one-component curing type (cures by reacting with moisture in the air) or a two-component curing type (cures by mixing with a crosslinking agent), but the two-component curing type is preferred from the viewpoint of easier control of reaction time and excellent storage stability. Furthermore, the silicone rubber may be either a room-temperature curing type (condensation type) or a thermosetting type (addition type), but the thermosetting type (addition type) is preferred from the viewpoint of easy reaction control.

[0060] The thermosetting (addition-type) two-component curing silicone rubber is not particularly limited, but from the viewpoint of obtaining a silicone layer that does not inhibit the permeability of specific organic solvents and has superior inhibitory performance against specific fluorine compounds, it is preferably a two-component curing silicone rubber utilizing a hydrosilylation reaction, more preferably a cured product of a polyorganosiloxane having alkenyl groups as a base polymer and an organohydrogenpolysiloxane as a crosslinking agent (for example, polydialkylsiloxane, polyalkylarylsiloxane, and polydiarylsiloxane having multiple hydrogen atoms bonded to silicon atoms), and even more preferably a polyalkylalkenylsiloxane (for example, polymethylvinylsiloxane, etc.). 1-10 Alkyl C 2-10 Alkenylsiloxanes), dialkylsiloxane-alkylalkenylsiloxane copolymers (e.g., dimethylsiloxane-methylvinylsiloxane copolymers, etc.) 1-10 Alkylsiloxane-C 1-10 Alkyl C 2-10 Alkenylsiloxane copolymers, and dialkylsiloxane-alkylalkenylsiloxane-alkylarylsiloxane copolymers (for example, diC such as dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers) 1-10 Alkylsiloxane-C 1-10 Alkyl C 2-10 Alkenylsiloxane-C 1-10 Alkyl C 6-20 The cured product is a mixture of at least one base polymer selected from the group consisting of arylsiloxane copolymers and the organohydrogenpolysiloxane.

[0061] Silicone rubber may contain a curing catalyst. The curing catalyst should be appropriately selected depending on the type of silicone rubber, but examples include organic peroxides (e.g., diacyl peroxide, peroxyester, dialkyl peroxide, etc.), tin salts (e.g., tin soap, etc.), platinum group metal compounds (e.g., platinum-based catalysts such as platinum powder, platinum black, chloroplatinic acid, alcoholic solutions of chloroplatinic acid, platinum-olefin complexes, platinum-alkenylsiloxane complexes, platinum-phosphorus complexes, etc.; palladium-based catalysts and rhodium-based catalysts corresponding to these platinum-based catalysts, etc.).

[0062] The silicone layer may contain additives such as curing retarders, thickeners, antioxidants, surface modifiers, lubricants, and surfactants, as needed.

[0063] The thickness of the silicone layer is not particularly limited, but from the viewpoint of suppressing the occurrence of defects and improving the blocking performance of specific fluorine compounds, and from the viewpoint of suppressing the decrease in the permeability of specific organic solvents, it is preferably 0.05 to 10 μm, more preferably 0.1 to 8 μm, even more preferably 0.8 to 5 μm, even more preferably 1 to 5 μm, even more preferably 1.5 to 5 μm, and even more preferably 2 to 5 μm. In the present invention, the thickness of the silicone layer is a value obtained by measuring the distance (thickness) of the non-porous region present on the surface of the dense layer at 10 regular intervals in a scanning electron microscope (SEM) image of the composite film cross-section at a magnification of 10,000x, and calculating the average value.

[0064] [Application] The composite membrane of the present invention is used to separate specific fluorinated compounds from an organic solution containing a specific organic solvent and a specific fluorinated compound.

[0065] The organic solvent in the aforementioned organic solution may contain organic solvents other than the specified organic solvent. When other organic solvents are included, the content of the other organic solvents is usually 90% by weight or less, but may be 70% by weight or less, 50% by weight or less, 40% by weight or less, 30% by weight or less, 20% by weight or less, 10% by weight or less, or 5% by weight or less, relative to the total amount of organic solvents.

[0066] Other organic solvents are not particularly limited and include, for example, alcohols, ketones, ethers, aprotic polar solvents, esters, and hydrocarbons. Specifically, these organic solvents include the following. The other organic solvents may be present individually or in groups of two or more. Alcohols: Primary alcohols such as methanol, ethanol, n-propanol, n-butanol, and benzyl alcohol; secondary alcohols such as isopropyl alcohol and isobutanol; tertiary alcohols such as tertiary butyl alcohol; and polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, 1,3-butanediol, and glycerin. Ketones: Acetone, methyl ethyl ketone, cyclohexanone, diisopropyl ketone, etc. Ethers: 3-methoxybutanol, 3-methoxybutyl acetate, tetrahydrofuran, diethyl ether, diisopropyl ether, 1,4-dioxane, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monomethyl ether acetate, etc. Aprotic polar solvents: N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, sulfolane, etc. Esters: Ethyl acetate, butyl acetate, isobutyl acetate, ethyl lactate, dimethyl phthalate, diethyl phthalate, ethylene carbonate, propylene carbonate, etc. Hydrocarbons: Petroleum ether, pentane, hexane, heptane, benzene, toluene, xylene, liquid paraffin, gasoline, and mineral oil.

[0067] The specific fluorine compound has a total of 1 to 6 fluorine-containing groups in its molecule, selected from the group consisting of perfluoroalkyl groups having 1 to 6 carbon atoms and perfluoroalkylene groups having 1 to 6 carbon atoms. The specific fluorine compound may be present as one type or as two or more types in the organic solution. The number of carbon atoms in the fluorine-containing group is preferably 1 to 5, more preferably 1 to 4. The total number of fluorine-containing groups is preferably 1 to 5, more preferably 1 to 4, and even more preferably 1 to 3.

[0068] Examples of specific fluorine compounds having a perfluoroalkyl group with 1 to 6 carbon atoms include trifluoromethanesulfonic acid, perfluoroethanesulfonic acid, perfluoropropanesulfonic acid, perfluorobutanesulfonic acid, perfluoropentanesulfonic acid, perfluorohexanesulfonic acid, pentafluoropropionic acid, perfluorobutanoic acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, difluorotris(pentafluoroethyl)phosphoran, difluorotris(n-heptafluoropropyl)phosphoran, and difluorotris(n-nonafluoropropyl)phosphoran. Examples include butyl phosphorane, trifluorobis(pentafluoroethyl)phosphoran, trifluorobis(n-heptafluoropropyl)phosphoran, trifluorobis(n-nonafluorobutyl)phosphoran, tris(trifluoromethyl)borane, tris(perfluoroethyl)borane, tris(perfluoropropyl)borane, tris(perfluorobutyl)borane, tris(perfluoropentyl)borane, tris(perfluorohexyl)borane, bis(trifluoromethanesulfonyl)imide, tris(trifluoromethanesulfonyl)methide, and metal salts thereof.

[0069] Furthermore, the specific fluorine compound having a perfluoroalkyl group with 1 to 6 carbon atoms may be an onium salt having an anion moiety corresponding to the fluorine compound. The cation moiety of the onium salt is not particularly limited and examples include ammonium, sulfonium, phosphonium, and iodonium. Examples of such onium salts include onium salts used as photoacid generators, and specifically, the following onium salts are mentioned. [ka]

[0070] Furthermore, the specific fluorine compound having a perfluoroalkyl group with 1 to 6 carbon atoms may be an onium salt having the following anionic moiety used as a photoacid generator. The cation moiety of the onium salt is not particularly limited and includes the above-mentioned examples. [ka]

[0071] Examples of specific fluorine compounds having a perfluoroalkylene group with 1 to 6 carbon atoms include onium salts having the anionic moiety described below, which are used as photoacid generators, as well as sulfonic acids and their metal salts corresponding to the compounds described below. The cation moiety of the onium salt is not particularly limited and the above examples are given. [ka]

[0072] The content of the specific fluorine compound in the organic solution is not particularly limited, but is usually around 0.00001 to 5.0% by weight, and may be 0.00005 to 2.0% by weight, 0.0001 to 1.0% by weight, 0.0005 to 0.5% by weight, or 0.001 to 0.2% by weight. The organic solution may also contain other compounds besides the specific fluorine compound.

[0073] Examples of the organic solution include photoresist chemicals, developers, cleaning solutions, stripping solutions, and mixtures thereof used when forming wiring patterns.

[0074] 3. Method for manufacturing composite films The present invention provides a method for producing a composite film, comprising at least the following first and second steps. Step 1: Prepare a polymer film having a dense layer and a support layer, and formed from a polymer other than silicone. Step 2: A silicone layer is formed on the surface of at least one of the dense layers of the polymer film.

[0075] [1st step] In the first step, a polymer film having a dense layer and a support layer, and formed of a polymer other than silicone, is prepared. The method for preparing the polymer film is not particularly limited; a commercially available polymer film may be prepared, or the polymer film may be manufactured by the TIPS method or the non-solvent-induced phase separation method (NIPS method). The TIPS method is a method in which a homogeneous polymer solution is prepared at high temperature, and after forming the film in the form of a flat film or hollow fiber film, phase separation is induced by cooling to form a porous structure. The NIPS method is a method in which a homogeneous polymer solution is prepared using a good solvent, and after similar molding, phase separation is induced by the incorporation of a non-solvent.

[0076] The following describes a method for producing a polyamide hollow fiber membrane, using the case where the polymer membrane is a polyamide hollow fiber membrane as an example. For example, a method for forming a polyamide hollow fiber membrane by the TIPS method includes the following (1) to (3). (1) Prepare a film-forming stock solution by dissolving the polyamide resin at a concentration of 20% by weight or more in an organic solvent having a boiling point of 150°C or higher and being immiscible with the polyamide resin at temperatures below 100°C at a temperature of 100°C or higher. (2) A step of solidifying a polyamide resin into a film by extruding the film-forming stock solution in a predetermined shape into a solidification bath at 100°C or lower, wherein in this step, a solidification solution that is compatible with the organic solvent used in the film-forming stock solution and has low affinity for the polyamide resin is brought into contact with at least one surface of the film-forming stock solution extruded in the predetermined shape to form a polyamide hollow fiber film having a dense layer on at least one surface. (3) Remove the film-forming solvent and coagulation solution from the polyamide hollow fiber membrane formed in (2).

[0077] The following describes in detail the steps (1) to (3) above for forming a polyamide hollow fiber membrane by the TIPS method.

[0078] [Step (1)] In step (1), a film-forming stock solution is prepared by dissolving a polyamide resin at a concentration of 20% by weight or more in an organic solvent having a boiling point of 150°C or higher and being immiscible with the polyamide resin at temperatures below 100°C at a temperature of 100°C or higher.

[0079] Organic solvents having a boiling point of 150°C or higher and being immiscible with polyamide resin at temperatures below 100°C include, for example, aprotic polar solvents, glycerin ethers, polyhydric alcohols, organic acids and organic acid esters, and higher alcohols. Specific examples of aprotic polar solvents include sulfolane, dimethyl sulfone, dimethyl sulfoxide, γ-butyrolactone, δ-valerolactone, ε-caprolactone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, ethylene carbonate, and propylene carbonate. Specific examples of glycerin ethers include diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, diethylene glycol dibutyl ether, and tetraethylene glycol dimethyl ether. Examples of polyhydric alcohols include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, hexylene glycol, 1,3-butanediol, and polyethylene glycol (molecular weight 100 to 10000). Examples of organic acids and organic acid esters include dimethyl phthalate, diethyl phthalate, diisopropyl phthalate, dibutyl phthalate, butyl benzyl phthalate, methyl salicylate, oleic acid, palmitic acid, stearic acid, and lauric acid. Among these organic solvents, from the viewpoint of obtaining polyamide hollow fiber membranes with higher strength, preferred are aprotic polar solvents and polyhydric alcohols; more preferably sulfolane, dimethyl sulfone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, propylene glycol, hexylene glycol, 1,3-butanediol, and polyethylene glycol (molecular weight 100-600); even more preferably sulfolane, dimethyl sulfone, γ-butyrolactone, δ-valerolactone, and ε-caprolactone; and even more preferably dimethyl sulfone. These organic solvents may be used individually or in combination of two or more.While sufficient effects can be obtained by using one of these organic solvents individually, mixing two or more can sometimes lead to the creation of even more effective polyamide hollow fiber membranes due to differences in the order and structure of phase separation.

[0080] The concentration of the polyamide resin in the film-forming stock solution should be 20% by weight or more, preferably 23-50% by weight, more preferably 23-40% by weight, and even more preferably 25-38% by weight. By satisfying the above range for the concentration of the polyamide resin in the film-forming stock solution, a support layer with a porosity of 60-80% can be obtained, providing the polyamide hollow fiber membrane with excellent pressure resistance. As a result, the composite membrane of the present invention can be provided with excellent pressure resistance and permeability to specific organic solvents.

[0081] Furthermore, in step (1), when dissolving the polyamide resin in the organic solvent, it is necessary to keep the solvent temperature at 100°C or higher. Specifically, it is desirable to dissolve the resin at a temperature 10 to 50°C higher, preferably 20 to 40°C higher, than the phase separation temperature of the prepared film-forming stock solution. The phase separation temperature of the film-forming stock solution refers to the temperature at which liquid-liquid phase separation or solid-liquid phase separation by crystal precipitation occurs when a mixture of the polyamide resin and the organic solvent at a sufficiently high temperature is gradually cooled. The phase separation temperature can be measured using a microscope equipped with a hot stage or the like.

[0082] In step (1), the temperature conditions for dissolving the polyamide resin in the organic solvent can be appropriately set in a temperature range of 100°C or higher according to the indicators described above, depending on the type of polyamide resin and organic solvent used, but preferably 120 to 250°C, more preferably 140 to 220°C, and even more preferably 160 to 200°C.

[0083] Furthermore, fillers, thickeners, antioxidants, surface modifiers, lubricants, surfactants, etc., may be added to the film-forming stock solution as needed to control the pore size of the polymer film and improve its performance.

[0084] The film-forming stock solution prepared in step (1) is subjected to step (2) at the same temperature (i.e., at 100°C or higher).

[0085] [Step (2)] In step (2), the film-forming stock solution prepared in step (1) is extruded in a predetermined shape into a solidification bath at 100°C or lower to solidify the polyamide resin into a film, wherein in this step, a solidification solution (hereinafter sometimes referred to as "solidification solution for forming a dense layer") which is compatible with the organic solvent used in the film-forming stock solution and has low affinity for the polyamide resin is brought into contact with at least one surface of the film-forming stock solution extruded in the predetermined shape to form a polyamide hollow fiber film having a dense layer on at least one surface.

[0086] In step (2), the film-forming stock extruded in a predetermined shape in the coagulation bath forms a dense layer on the surface that comes into contact with the coagulation liquid for forming a dense layer. Near the surface where the film-forming stock comes into contact with the coagulation liquid for forming a dense layer, non-solvent phase separation due to solvent exchange proceeds more favorably than thermally induced phase separation due to cooling, resulting in the formation of a denser structure on the surface than in the conventional TIPS method, and as a result, a polyamide hollow fiber film having the aforementioned molecular weight cutoff is obtained.

[0087] When forming a dense layer on only one surface of a polyamide hollow fiber membrane, in step (2), one surface of the film-forming stock extruded in a predetermined shape may be brought into contact with the dense layer-forming coagulation solution, and the other surface may be brought into contact with a coagulation solution that is compatible with the organic solvent used in the film-forming stock and has high affinity for the polyamide resin (hereinafter sometimes referred to as the "support layer-forming coagulation solution"). Alternatively, when forming a dense layer on both surfaces of a polyamide hollow fiber membrane, in step (2), both surfaces of the film-forming stock extruded in a predetermined shape may be brought into contact with the dense layer-forming coagulation solution.

[0088] The solidifying solution for forming a dense layer is specifically a solvent that is compatible with the organic solvent used in the film-forming stock solution at a temperature of 25°C or lower, but does not dissolve the polyamide resin at a temperature below its boiling point or below 200°C. Specific examples of solidifying solutions for forming a dense layer include aqueous solvents such as water and aqueous solutions with a water content of 80% by weight or more; monohydric alcohols such as 1-propanol, 2-propanol, and isobutanol; glycol ethers such as polyethylene glycol with an average molecular weight of 300 or more, polypropylene glycol with an average molecular weight of 400 or more, diethylene glycol diethyl ether, triethylene glycol monomethyl ether, and propylene glycol monoethyl ether; and glycol acetates such as triacetin and propylene glycol monoethyl ether acetate. Among these, polyethylene glycol, triacetin, and triethylene glycol monomethyl ether with an average molecular weight of 300 to 600 are preferred; more preferably polyethylene glycol 300, polyethylene glycol 400, and polyethylene glycol 600; and even more preferably polyethylene glycol 300 and polyethylene glycol 400. These solvents may be used individually or in combination of two or more. In the present invention, the average molecular weights of polyethylene glycol and polypropylene glycol are number-average molecular weights calculated based on the hydroxyl value measured in accordance with JIS K 1557-6:2009 "Plastics - Polyurethane raw material polyols - Test methods - Part 6: Method for determining hydroxyl value by near-infrared (NIR) spectroscopy".

[0089] Furthermore, the solidifying solution for forming the dense layer may contain a solvent used in the solidifying solution for forming the support layer (a solvent that is compatible with the organic solvent used in the film-forming stock solution at temperatures below 25°C but does not dissolve the polyamide resin, and dissolves the polyamide resin at temperatures below its boiling point, or an aqueous solution thereof), to the extent that it is capable of forming a dense layer. When the solidifying solution for forming the dense layer contains a solvent used in the solidifying solution for forming the support layer, the content of the solvent is preferably 5 to 38% by weight, more preferably 10 to 35% by weight, even more preferably 15 to 32% by weight, and even more preferably 15 to 30% by weight, from the viewpoint of forming a dense layer of a suitable thickness and obtaining a polyamide hollow fiber film having the molecular weight cutoff.

[0090] The coagulation solution for forming the support layer may be any solvent or aqueous solution thereof that is compatible with the organic solvent used in the film-forming stock solution at a temperature of 25°C or lower, but does not dissolve the polyamide resin, and dissolves the polyamide resin at a temperature below its boiling point. Specific examples of the coagulation solution for forming the support layer include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol 200, propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, sulfolane, N-methyl-2-pyrrolidone, γ-butyrolactone, δ-valerolactone, and aqueous solutions containing 20% ​​or more of these by weight. Among these, from the viewpoint of obtaining a support layer having the aforementioned porosity, preferably, is an aqueous solution containing at least one selected from the group consisting of 1,4-butylene glycol, 1,3-butylene glycol, glycerin, propylene glycol, diethylene glycol, tetraethylene glycol, and polyethylene glycol 200, and at least one of these in a proportion of 25 to 75% by weight; more preferably, is an aqueous solution containing at least one selected from the group consisting of 1,4-butylene glycol, glycerin, propylene glycol, diethylene glycol, and tetraethylene glycol, and at least one of these in a proportion of 40 to 80% by weight (preferably 40 to 60% by weight).

[0091] If a polyamide hollow fiber membrane is to be formed as a polymer membrane, step (2) can be carried out by using a double-tube nozzle for hollow fiber production, discharging the film-forming raw material from the outer annular nozzle and the internal coagulation solution from the inner nozzle, and immersing the film in a coagulation bath. In this case, a coagulation solution for forming a dense layer should be used in at least one of the internal coagulation solution and the coagulation bath. If a coagulation solution for forming a dense layer is used in both the internal coagulation solution and the coagulation bath, a dense layer will be formed on both the inner and outer surfaces, and a polyamide hollow fiber membrane with a support layer inside will be obtained. Furthermore, if a coagulation solution for forming a dense layer is used as the internal coagulation solution and a coagulation solution for forming a support layer is used as the coagulation bath, a polyamide hollow fiber membrane will be obtained in which a dense layer is formed on the inner surface and the inner and outer surfaces are support layers. Furthermore, when a coagulation solution for forming a support layer is used as the internal coagulation solution, and a coagulation solution for forming a dense layer is used as the coagulation bath, a polyamide hollow fiber membrane is obtained in which a dense layer is formed on the outer surface and the inner surface and interior are support layers. It is preferable that the internal coagulation solution used when forming the polyamide hollow fiber membrane does not contain water, whose boiling point is below the temperature of the double annular nozzle, since it passes through the double annular nozzle.

[0092] As a double-tubular nozzle for hollow fiber production, a nozzle having a double-tubular structure, similar to those used in melt spinning to produce core-sheath type composite fibers, can be used. The diameters of the outer annular nozzle and the inner nozzle of the double-tubular nozzle for hollow fiber production can be appropriately set according to the inner and outer diameters of the hollow fiber membrane.

[0093] Furthermore, the flow rate when discharging the film-forming stock solution from the annular nozzle on the outside of the double-tubular nozzle for hollow fiber production is not particularly limited as it depends on the slit width, but for example, it can be 2 to 30 g / min, preferably 3 to 20 g / min, and more preferably 5 to 15 g / min. The flow rate of the internal coagulation solution is set appropriately considering the diameter of the inner nozzle of the double-tubular nozzle for hollow fiber production, the type of internal solution used, the flow rate of the film-forming stock solution, etc., but it can be 0.1 to 2 times, preferably 0.2 to 1 time, and more preferably 0.4 to 0.7 times the flow rate of the film-forming stock solution.

[0094] Furthermore, if a flat film containing polyamide resin is to be formed as a polymer film, step (2) can be performed by using a solidifying solution for forming a dense layer as a solidifying bath, and extruding the film-forming raw material in a predetermined shape into the solidifying bath and immersing it.

[0095] In step (2), the temperature of the coagulation bath should be 100°C or lower, but preferably -20 to 100°C, more preferably 0 to 60°C, even more preferably 2 to 20°C, and particularly preferably 2 to 10°C. The suitable temperature of the coagulation bath may vary depending on the organic solvent used in the film-forming stock solution, the composition of the coagulation solution, etc. Generally, lower temperatures tend to favor thermally induced phase separation, while higher temperatures tend to favor non-solvent phase separation. That is, when producing a hollow fiber membrane in which a dense layer is formed on the luminal surface, it is preferable to set the coagulation bath to a low temperature in order to increase the pore size of the dense layer on the luminal surface, and it is preferable to set the coagulation bath to a high temperature in order to make the dense layer on the luminal surface denser and to make the internal structure coarser.

[0096] Furthermore, if a polyamide hollow fiber membrane is formed as the polymer membrane, the temperature of the internal coagulation solution should be around the set temperature of the double-tube nozzle, for example, 120 to 250°C, preferably 160 to 230°C, and more preferably 180 to 220°C.

[0097] Thus, by carrying out step (2), the film-forming stock solidifies in the solidification bath, and a polyamide hollow fiber film is formed with a dense layer on at least one surface.

[0098] [Step (3)] In step (3), the film-forming solvent and coagulation solution are removed from the polyamide hollow fiber membrane formed in step (2).

[0099] There are no particular limitations on the method for removing the film-forming solvent and coagulation solution from the polyamide hollow fiber membrane, but a method of immersing the polyamide hollow fiber membrane formed in step (2) above in an extraction solvent for extraction and removal is preferred.

[0100] The extraction solvent used for extraction and removal is preferably inexpensive, has a low boiling point, and can be easily separated after extraction by the difference in boiling point, etc. Examples include water, glycerin, methanol, ethanol, isopropanol, acetone, diethyl ether, hexane, petroleum ether, and toluene. Among these, water, methanol, ethanol, isopropanol, and acetone are preferred; more preferably, water, methanol, and isopropanol. In particular, when extracting film-forming stock solvents and coagulation solutions that are soluble in water, winding while showering with water allows for simultaneous solvent extraction, which is efficient. Furthermore, when extracting water-insoluble organic solvents such as phthalates and fatty acids, isopropyl alcohol, petroleum ether, etc., can be suitably used.

[0101] When extracting and removing the film-forming solvent and coagulation solution by immersing a polyamide hollow fiber membrane in an extraction solvent, there are no particular restrictions on the immersion time of the polyamide hollow fiber membrane in the extraction solvent, but examples include 0.2 hours to 2 months, preferably 0.5 hours to 1 month, and more preferably 2 hours to 10 days. To effectively extract and remove the coagulation solution and other substances remaining on the polyamide hollow fiber membrane, the extraction solvent may be replaced or stirred.

[0102] Thus, by carrying out step (3), a polyamide hollow fiber film having a dense layer on at least one surface is obtained from which the film-forming solvent and coagulation solution have been removed.

[0103] After step (3), it is preferable to dry out and remove the extraction solvent from the polyamide hollow fiber membrane. The extraction solvent can be dried out by known drying methods such as natural drying, hot air drying, reduced pressure drying, or vacuum drying.

[0104] Furthermore, in order to increase the strength of the polyamide hollow fiber membrane and provide it with excellent pressure resistance, the polyamide hollow fiber membrane may be stretched uniaxially (longitudinally) at the same time as drying or after drying.

[0105] To perform uniaxial stretching simultaneously with drying, the polyamide hollow fiber membrane should be dried while tension for stretching is applied. The temperature conditions for uniaxial stretching simultaneously with drying are not particularly limited, as long as both drying and stretching are possible, but examples include 40°C or higher, preferably 40 to 160°C, more preferably 50 to 140°C, and even more preferably 120 to 140°C.

[0106] Furthermore, when stretching uniaxially after drying, the temperature conditions during drying are not particularly limited, as long as the adhering extraction solvent can be volatilized. For example, temperatures of 40°C or higher, preferably 40 to 160°C, more preferably 50 to 140°C, and even more preferably 120 to 140°C are recommended. Also, when stretching uniaxially after drying, the temperature conditions during stretching are not particularly limited, and -10 to 140°C, preferably 0 to 120°C is acceptable. However, from the viewpoint of further improving liquid permeability, it is desirable that the temperature be above the glass transition temperature of the polyamide resin used (more preferably 50 to 120°C, and even more preferably 60 to 100°C).

[0107] Uniaxial stretching can be performed by known methods, for example, by winding from a low-speed roll to a high-speed roll continuously. Alternatively, the polyamide hollow fiber membrane may be cut to a certain length, and stretched using a tensile testing machine or the like by grasping both ends, or manual stretching may be used.

[0108] Examples of stretching ratios include 1.2 to 5 times, preferably 1.2 to 3 times. From the viewpoint of increasing the strength of the polymer film and providing excellent pressure resistance, the stretching ratio is preferably 1.2 to 2.4 times, more preferably 1.2 to 2.0 times.

[0109] The following describes the manufacturing method, using the case where the polymer membrane is a polyacrylonitrile hollow fiber membrane as an example. For example, a manufacturing method for forming a polyacrylonitrile hollow fiber membrane by the NIPS method includes the following (1) to (3). (1) Prepare a film-forming stock solution by dissolving polyacrylonitrile resin in an organic solvent. (2) A step of solidifying a polyacrylonitrile resin into a film by extruding the film-forming stock solution into a solidification bath in a predetermined shape, wherein in this step, a solidification solution that is compatible with the organic solvent used in the film-forming stock solution and is a non-solvent for the polyacrylonitrile resin is brought into contact with at least one surface of the film-forming stock solution extruded in a predetermined shape to form a polyacrylonitrile hollow fiber film having a dense layer on at least one surface. (3) Remove the film-forming solvent and coagulation solution from the polyacrylonitrile hollow fiber membrane formed in (2) above.

[0110] The following describes in detail the steps (1) to (3) above for forming a polyacrylonitrile hollow fiber membrane by the NIPS method.

[0111] [Step (1)] In step (1), a film-forming stock solution is prepared by dissolving polyacrylonitrile resin.

[0112] Examples of organic solvents for dissolving polyacrylonitrile resins include ethylene carbonate, propylene carbonate, γ-butyrolactone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, 2-pyrrolidone, and N-methylpyrrolidone. Among these, γ-butyrolactone and dimethyl sulfoxide are preferred from the viewpoint of solubility. These organic solvents may be used individually or in combination of two or more. While sufficient effects can be obtained by using one of these organic solvents individually, using a mixture of two or more can sometimes produce even more effective polyacrylonitrile hollow fiber membranes due to differences in the order and structure of phase separation.

[0113] The concentration of polyacrylonitrile resin in the film-forming stock solution should be 15% by weight or more, preferably 15-40% by weight, more preferably 17-38% by weight, and even more preferably 20-35% by weight. By satisfying the above range for the concentration of polyacrylonitrile resin in the film-forming stock solution, a support layer with a porosity of 60-85% can be obtained, providing the polyacrylonitrile hollow fiber membrane with excellent pressure resistance. As a result, the composite membrane of the present invention can be provided with excellent pressure resistance and permeability to specific organic solvents.

[0114] Furthermore, pore-forming agents, thickeners, surface modifiers, fillers, lubricants, surfactants, etc., may be added to the film-forming stock solution as needed to control the pore size and improve the performance of the polyacrylonitrile hollow fiber membrane.

[0115] The temperature of the film-forming solution is usually within the range of 20 to 60°C. Within this range, the polyacrylonitrile resin can solidify without precipitation.

[0116] The film-forming stock solution prepared in step (1) is used in step (2) at the same temperature.

[0117] [Step (2)] In step (2), the film-forming stock solution prepared in step (1) is extruded into a solidification bath in a predetermined shape to solidify the polyacrylonitrile resin into a film, wherein in this step, a solidification solution (hereinafter sometimes referred to as "solidification solution for forming a dense layer") which is compatible with the organic solvent used in the film-forming stock solution and is a non-solvent for the polyacrylonitrile resin is brought into contact with at least one surface of the film-forming stock solution extruded in a predetermined shape to form a polyacrylonitrile hollow fiber film having a dense layer on at least one surface.

[0118] In step (2), the film-forming stock extruded in a predetermined shape in the coagulation bath forms a dense layer on the surface that comes into contact with the coagulation liquid for forming a dense layer. Near the surface where the film-forming stock comes into contact with the coagulation liquid for forming a dense layer, non-solvent phase separation due to solvent exchange proceeds, forming a dense structure on the surface, and as a result, a polyacrylonitrile hollow fiber film having the molecular weight cutoff is obtained.

[0119] When forming a dense layer on only one surface of a polyacrylonitrile hollow fiber membrane, in step (2), the dense layer-forming coagulation solution is brought into contact with one surface of the film-forming stock solution extruded in a predetermined shape, and the other surface is brought into contact with a coagulation solution that is compatible with the organic solvent used in the film-forming stock solution and has high affinity for the polyacrylonitrile resin (hereinafter sometimes referred to as the "support layer-forming coagulation solution"). Alternatively, when forming a dense layer on both surfaces of a polyacrylonitrile hollow fiber membrane, the dense layer-forming coagulation solution is brought into contact with both surfaces of the film-forming stock solution extruded in a predetermined shape in step (2).

[0120] Examples of coagulation solutions for forming a dense layer include water; aliphatic hydrocarbons such as hexane and pentane; aromatic hydrocarbons such as benzene and toluene; halogenated hydrocarbons such as trichloroethylene; aliphatic alcohols such as methanol, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol, and low molecular weight polyethylene glycol; and mixed solvents thereof.

[0121] Furthermore, the solidifying solution for forming the dense layer may contain a solvent used in the solidifying solution for forming the support layer, to the extent that it is capable of forming a dense layer. When the solidifying solution for forming the dense layer contains a solvent used in the solidifying solution for forming the support layer, the solvent content is preferably 5 to 38% by weight, more preferably 10 to 35% by weight, even more preferably 15 to 32% by weight, and even more preferably 15 to 30% by weight, from the viewpoint of forming a dense layer of a suitable thickness and obtaining a polyacrylonitrile hollow fiber membrane having the aforementioned molecular weight cutoff.

[0122] The coagulation solution for forming the support layer can be any solvent that is compatible with the organic solvent used in the film-forming stock solution and has lower coagulation properties for the spinning stock solution than the coagulation solution for forming the dense layer. A homogeneous mixed solvent of an organic solvent that dissolves the polyacrylonitrile resin and a non-solvent that does not dissolve the polyacrylonitrile resin is preferred. Examples of organic solvents that dissolve the polyacrylonitrile resin include ethylene carbonate, propylene carbonate, γ-butyrolactone, dimethylformamide, dimethylacetamide, dimethyl sulfosoxide, 2-pyrrolidone, and N-methylpyrrolidone. Examples of non-solvents that do not dissolve the polyacrylonitrile resin include water; aliphatic hydrocarbons such as hexane and pentane; aromatic hydrocarbons such as benzene and toluene; halogenated hydrocarbons such as trichloroethylene; aliphatic alcohols such as methanol, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol, and low molecular weight polyethylene glycol; and mixed solvents thereof. The coagulation solution for forming the support layer preferably contains an organic solvent that dissolves the polyacrylonitrile resin in a proportion of 70% by weight or more.

[0123] If a polyacrylonitrile hollow fiber membrane is to be formed as a polymer membrane, step (2) can be carried out by using a double-tube nozzle for hollow fiber production, discharging the film-forming raw material from the outer annular nozzle and the internal coagulation solution from the inner nozzle, and immersing the film in a coagulation bath. In this case, a coagulation solution for forming a dense layer should be used in at least one of the internal coagulation solution and the coagulation bath. If a coagulation solution for forming a dense layer is used in both the internal coagulation solution and the coagulation bath, a dense layer will be formed on both the inner and outer surfaces, and a polyacrylonitrile hollow fiber membrane with a support layer inside will be obtained. Furthermore, if a coagulation solution for forming a dense layer is used as the internal coagulation solution and a coagulation solution for forming a support layer is used as the coagulation bath, a polyacrylonitrile hollow fiber membrane will be obtained in which a dense layer is formed on the inner surface and the inner and outer surfaces are support layers. Furthermore, when a coagulation solution for forming a support layer is used as the internal coagulation solution, and a coagulation solution for forming a dense layer is used as the coagulation bath, a polyacrylonitrile hollow fiber membrane is obtained in which a dense layer is formed on the outer surface and the inner surface and interior are support layers.

[0124] As a double-tubular nozzle for hollow fiber production, a nozzle having a double-tubular structure, similar to those used in melt spinning to produce core-sheath type composite fibers, can be used. The diameters of the outer annular nozzle and the inner nozzle of the double-tubular nozzle for hollow fiber production can be appropriately set according to the inner and outer diameters of the polyacrylonitrile hollow fiber membrane.

[0125] Furthermore, the flow rate when discharging the film-forming stock solution from the annular nozzle on the outside of the double-tubular nozzle for hollow fiber production is not particularly limited as it depends on the slit width, but for example, it can be 2 to 30 g / min, preferably 3 to 20 g / min, and more preferably 5 to 15 g / min. The flow rate of the internal coagulation solution is set appropriately considering the diameter of the inner nozzle of the double-tubular nozzle for hollow fiber production, the type of internal solution used, the flow rate of the film-forming stock solution, etc., but it can be 0.1 to 2 times, preferably 0.2 to 1 time, and more preferably 0.4 to 0.7 times the flow rate of the film-forming stock solution.

[0126] Furthermore, if a flat film containing polyacrylonitrile resin is to be formed as a polymer film, step (2) can be performed by using a solidification solution for forming a dense layer as a solidification bath, and extruding the film-forming raw material in a predetermined shape into the solidification bath and immersing it.

[0127] In step (2), the temperature of the coagulation bath should be 100°C or lower, preferably -20 to 100°C, more preferably 0 to 60°C, and even more preferably 10 to 40°C. The suitable temperature of the coagulation bath may vary depending on the organic solvent used in the film-forming stock solution, the composition of the coagulation solution, etc., but generally, lower temperatures tend to improve the smoothness of the dense layer, while higher temperatures tend to increase the coagulation rate.

[0128] Thus, by carrying out step (2), the film-forming stock solidifies in the solidification bath, and a polyacrylonitrile hollow fiber film is formed with a dense layer on at least one surface.

[0129] [Step (3)] In step (3), the film-forming solvent and coagulation solution are removed from the polyacrylonitrile hollow fiber membrane formed in step (2).

[0130] There are no particular limitations on the method for removing the film-forming solvent and coagulation solution from the polyacrylonitrile hollow fiber membrane, but a method of immersing the polyacrylonitrile hollow fiber membrane formed in step (2) above in an extraction solvent for extraction and removal is preferred.

[0131] The extraction solvent used for extraction and removal is preferably inexpensive, has a low boiling point, and can be easily separated after extraction by the difference in boiling point, etc. Examples include water, glycerin, methanol, ethanol, isopropanol, acetone, diethyl ether, hexane, petroleum ether, and toluene. Among these, water, methanol, ethanol, isopropanol, and acetone are preferred; more preferably, water, methanol, and isopropanol. In particular, when extracting film-forming stock solvents and coagulation solutions that dissolve in water, winding the material while showering it with water allows for simultaneous solvent extraction, which is efficient.

[0132] When extracting and removing the film-forming solvent and coagulation solution by immersing a polyacrylonitrile hollow fiber membrane in an extraction solvent, there are no particular restrictions on the immersion time of the polyacrylonitrile hollow fiber membrane in the extraction solvent, but examples include 0.2 hours to 2 months, preferably 0.5 hours to 1 month, and more preferably 2 hours to 10 days. To effectively extract and remove the coagulation solution and other substances remaining on the polyacrylonitrile hollow fiber membrane, the extraction solvent may be replaced or stirred.

[0133] The temperature of the extraction solvent during extraction and removal is preferably 50 to 100°C, and more preferably 60 to 95°C, when the extraction solvent is water. By keeping the water temperature below 100°C, the degree of shrinkage of the polyacrylonitrile hollow fiber membrane can be kept low, thereby suppressing a decrease in liquid permeability. Furthermore, by keeping the water temperature above 50°C, a high cleaning effect can be obtained, allowing the film-forming solvent to be sufficiently removed from the polyacrylonitrile hollow fiber membrane.

[0134] Thus, by carrying out step (3), a polyacrylonitrile hollow fiber membrane is obtained from which the film-forming solvent and coagulation solution have been removed, and which has a dense layer on at least one surface.

[0135] After step (3), it is preferable to dry and remove the extraction solvent from the polyacrylonitrile hollow fiber membrane. The extraction solvent can be dried and removed by known drying treatments such as natural drying, hot air drying, reduced pressure drying, or vacuum drying.

[0136] Furthermore, in order to increase the strength of the polyacrylonitrile hollow fiber membrane and provide it with excellent pressure resistance, the polyacrylonitrile hollow fiber membrane may be stretched uniaxially (longitudinally) at the same time as drying or after drying.

[0137] To perform uniaxial stretching simultaneously with drying, the polyacrylonitrile hollow fiber membrane should be dried while tension for stretching is applied. The temperature conditions for uniaxial stretching simultaneously with drying are not particularly limited, as long as both drying and stretching are possible, but examples include 40°C or higher, preferably 40 to 160°C, more preferably 50 to 140°C, and even more preferably 120 to 140°C.

[0138] Furthermore, when stretching uniaxially after drying, the temperature conditions during drying are not particularly limited, as long as the adhering extraction solvent can be volatilized. For example, temperatures of 40°C or higher, preferably 40 to 160°C, more preferably 50 to 140°C, and even more preferably 120 to 140°C are recommended. Also, when stretching uniaxially after drying, the temperature conditions during stretching are not particularly limited, and temperatures of -10 to 140°C, preferably 0 to 120°C are acceptable. However, from the viewpoint of further improving liquid permeability, it is desirable that the temperature be above the glass transition temperature of the polyacrylonitrile resin being used.

[0139] Uniaxial stretching can be performed by known methods, for example, by winding from a low-speed roll to a high-speed roll continuously. Alternatively, the polyacrylonitrile hollow fiber membrane may be cut to a certain length, and stretched using a tensile testing machine or the like by grasping both ends, or manual stretching may be used.

[0140] Examples of stretching ratios include 1.2 to 5 times, preferably 1.2 to 3 times. From the viewpoint of increasing the strength of the polymer film and providing excellent pressure resistance, the stretching ratio is preferably 1.2 to 2.4 times, more preferably 1.2 to 2.0 times.

[0141] The above explanation has described the manufacturing method using polyamide hollow fiber membranes or flat membranes, and polyacrylonitrile hollow fiber membranes or flat membranes as examples. However, hollow fiber membranes or flat membranes can be manufactured using the same method as described above even when other polymers are used.

[0142] [Second process] In the second step, a silicone layer is formed on the surface of at least one of the dense layers of the polymer film prepared in the first step.

[0143] The method for forming the silicone layer is not particularly limited as long as a silicone layer with the above structure and properties can be obtained, but a preferred example is the following formation method.

[0144] One method for forming a silicone layer on the surface of a dense layer of a flat polymer film is to apply a silicone coating liquid to the surface of the dense layer to form a silicone coating film, and then cure the silicone coating film to form a silicone layer.

[0145] One method for forming a silicone layer on the surface of the dense layer on the inner surface of a hollow fiber membrane is to inject a silicone coating liquid into the hollow portion of the hollow fiber membrane to form a silicone coating film on the surface of the dense layer, and then cure the silicone coating film to form a silicone layer.

[0146] The silicone coating liquid is a liquid composition containing a precursor (uncured material) of silicone (e.g., silicone rubber) as described in the "Silicone Layer" section of "2. Composite Film" above. Below, as a representative example, we will describe the case where the silicone material forming the silicone layer is a two-component curing type silicone rubber.

[0147] The silicone coating liquid contains at least a precursor of two-component curing silicone rubber (a polyorganosiloxane, which is the base polymer, and a crosslinking agent). For example, it can be prepared by mixing a first liquid (main component) containing polyorganosiloxane and a curing catalyst with a second liquid (curing agent) containing a crosslinking agent. A commercially available two-component curing silicone rubber kit combining the main component and curing agent is, for example, SYLGARD from Toray Dow Ltd. TM 184, 527, DOWSIL TMExamples include EG-3100, CY52-276, YE5822, TSE3032, 3033, and 3070 from Momentive Performance Materials Japan LLC, and KE-109E, KE-106F, KE-1012, KE-1051, and FE-77 from Shin-Etsu Chemical Co., Ltd.

[0148] The silicone coating liquid preferably contains a diluent solvent from the viewpoints of forming a thin and uniform silicone layer on the surface of the dense layer, facilitating control of the addition reaction, and ease of workability. The diluent solvent may be added to either or both of the main component and the curing agent before mixing them, or it may be added to the mixture obtained by mixing the main component and the curing agent.

[0149] The diluent is not particularly limited as long as it is a solvent that dissolves the polyorganosiloxane and the crosslinking agent, and examples include linear alkanes such as hexane and pentane; aromatic hydrocarbons such as toluene and xylene; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; and cyclic ethers such as tetrahydrofuran.

[0150] The amount of diluent solvent needs to be adjusted appropriately depending on the viscosity of the polyorganosiloxane. However, from the viewpoint of maintaining a silicone coating film of the desired thickness on the surface of the dense layer, preventing the silicone layer from becoming too thin and causing defects, suppressing unevenness in the thickness of the silicone layer, and workability, it is preferable that the concentration of polyorganosiloxane in the silicone coating solution is 2 to 40% by weight, more preferably 5 to 30% by weight, and even more preferably 10 to 20% by weight.

[0151] In the silicone coating liquid, the proportion of the crosslinking agent needs to be adjusted appropriately depending on the type of polyorganosiloxane and crosslinking agent, but it is usually 1 to 30 parts by weight, preferably 3 to 25 parts by weight, and more preferably 5 to 20 parts by weight, in terms of solid content, per 100 parts by weight of polyorganosiloxane.

[0152] The method for injecting silicone coating liquid into the hollow portion of a hollow fiber membrane is not particularly limited as long as a silicone coating film of the desired thickness can be formed on the surface of the dense layer. However, a preferred method is to form a module using hollow fiber membranes and inject silicone coating liquid into the hollow portion of the hollow fiber membrane of the module. Specifically, this injection method is carried out by the following procedure. First, prepare a bundle of hollow fiber membranes of the desired length and number. Next, prepare a rigid tube and insert a rubber stopper of appropriate length into the opening at one end of the tube to seal the opening. Next, inject a two-component thermosetting resin from the opening at the end opposite to the stoppered end of the tube to fill the space inside the tube with the resin. After that, heat-seal one end of the bundled hollow fiber membrane prepared and insert it into the tube filled with the thermosetting resin until the tip of the end touches the stopper, and allow the thermosetting resin to harden in that state. Then, cut the area of ​​the hardened resin portion on the stopper side of the tube together with the tube to open the hollow portion of the hollow fiber membrane. Next, attach the appropriate jig to the opening end of the tube and inject the silicone coating liquid.

[0153] The injection method is not particularly limited and includes, for example, injection methods using a syringe, pumping methods using pressurized gas, and injection methods using pumps such as peristaltic pumps, plunger pumps, diaphragm pumps, and gear pumps.

[0154] The injection speed of the silicone coating liquid is not particularly limited, but as a linear velocity, it is, for example, about 0.04 to 2.5 m / sec. From the viewpoint of suppressing defects in the silicone layer, suppressing thickness unevenness of the silicone layer, and manufacturing efficiency, it is preferably 0.1 to 1.0 m / sec, and more preferably 0.1 to 0.5 m / sec.

[0155] To form a silicone coating film of uniform thickness on the surface of the dense layer, it is preferable to blow gas into the hollow portion of the hollow fiber membrane after injecting the silicone coating liquid. The gas used for blowing is not particularly limited, but dry air or nitrogen is preferred from the viewpoint of preventing reaction with the silicone coating liquid and from the viewpoint of safety.

[0156] The blowing speed is not particularly limited, but as a linear speed, it is, for example, about 1 to 50 m / s, and from the viewpoint of suppressing the occurrence of defects in the silicone layer, suppressing thickness unevenness of the silicone layer, and manufacturing efficiency, it is preferably 2.5 to 20 m / s, more preferably 5 to 10 m / s.

[0157] To promote the curing (addition reaction) of the silicone coating film formed on the surface of the dense layer, it is preferable to heat-treat the silicone coating film. The heating temperature is not particularly limited, but from the viewpoint of further promoting curing (addition reaction) and suppressing the deterioration of the physical properties of the hollow fiber film due to heat, it is preferably 40 to 160°C, more preferably 60 to 140°C, and even more preferably 80 to 120°C. The heating time is not particularly limited, but from the above viewpoint, it is preferably 10 minutes to 24 hours, more preferably 15 minutes to 16 hours, even more preferably 30 minutes to 8 hours, and even more preferably 1 to 5 hours.

[0158] The tubing used during the injection of the silicone coating liquid should be cut and removed at the appropriate time, for example, before or after the heat treatment of the silicone coating film.

[0159] Furthermore, as a method for forming a silicone layer on the surface of the dense layer on the outer surface of the hollow fiber membrane, for example, one can immerse the hollow fiber membrane in a bath of the silicone coating liquid or apply the silicone coating liquid to the outer surface of the hollow fiber membrane to form a silicone coating film on the surface of the dense layer, and then cure the silicone coating film to form a silicone layer. In addition, to form a silicone coating film of uniform thickness on the surface of the dense layer, the gas may be blown onto the outer surface of the hollow fiber membrane. Furthermore, in order to promote the curing (addition reaction) of the silicone coating film formed on the surface of the dense layer, the silicone coating film may be heat-treated under the above conditions.

[0160] Furthermore, as a method for forming silicone layers on the dense layers of the inner and outer surfaces of the hollow fiber membrane, for example, a method of forming a silicone layer on the dense layer of the inner surface of the hollow fiber membrane and a method of forming a silicone layer on the dense layer of the outer surface of the hollow fiber membrane can be performed in any order or in combination.

[0161] Thus, by carrying out the second step, a composite film of the present invention is obtained having a silicone layer on the surface of at least one dense layer of the polymer film.

[0162] 4. Membrane Module The composite membrane of the present invention is housed in a module case equipped with a liquid to be treated inlet, a permeate outlet, etc., and is used as a membrane module.

[0163] When the composite membrane of the present invention is in the shape of a hollow fiber, it is used as a hollow fiber membrane module.

[0164] Specifically, the hollow fiber membrane module may have a structure in which the composite hollow fiber membranes of the present invention are bundled together, housed in a module case, and one or both ends of the composite hollow fiber membranes are sealed and fixed with a potting agent. The hollow fiber membrane module may have an opening connected to a flow path passing through the outer wall surface of the composite hollow fiber membrane, and an opening connected to the hollow portion of the composite hollow fiber membrane, which serve as an inlet for the liquid to be treated or an outlet for the filtrate.

[0165] The shape of the hollow fiber membrane module is not particularly limited and may be a dead-end type module or a cross-flow type module. Specifically, examples include: a dead-end type module in which a bundle of hollow fiber membranes is bent into a U-shape and packed, and the ends of the bundle are sealed and then cut to create an opening; a dead-end type module in which a bundle of hollow fiber membranes with one end of the hollow opening sealed by heat sealing or the like is packed straight, and the end of the open end of the bundle is sealed and then cut to create an opening; a dead-end module in which a bundle of hollow fiber membranes is packed straight, both ends of the bundle are sealed, and only one end is cut to expose the opening; and a cross-flow type module in which a bundle of hollow fiber membranes is packed straight, both ends of the bundle are sealed, the sealed parts at both ends of the bundle are cut, and two flow paths are created on the side of the filter case.

[0166] The packing ratio of the composite hollow fiber membrane inserted into the module case is not particularly limited, but for example, the volume of the composite hollow fiber membrane including the volume of the hollow portion relative to the volume inside the module case is preferably 15 to 75 volume%, more preferably 25 to 65 volume%, and even more preferably 35 to 55 volume%. By satisfying such a packing ratio, a sufficient filtration area can be secured, the packing work of the composite hollow fiber membrane into the module case can be facilitated, and the potting agent can be easily flowed between the composite hollow fiber membranes.

[0167] The potting agent used in the manufacture of hollow fiber membrane modules is not particularly limited, but if the hollow fiber membrane modules are to be treated with organic solvents, it is desirable that the potting agent has resistance to organic solvents. Examples of such potting agents include polyamide, silicone resin, epoxy resin, melamine resin, polyethylene, polypropylene, phenolic resin, polyimide, and polyurea resin. Among these potting agents, those that exhibit little shrinkage or swelling upon curing and are not excessively hard are preferred, and suitable examples include polyamide, silicone resin, epoxy resin, and polyethylene. These potting agents may be used individually or in combination of two or more.

[0168] The material of the module case used in the hollow fiber membrane module is not particularly limited as long as it has resistance to the organic solvent used, and examples include polyamide, polyester, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, polysulfone, polyethersulfone, polycarbonate, polyarylate, and polyphenylene sulfide. Among these, polyamide, polyethylene, polypropylene, polytetrafluoroethylene, polycarbonate, polysulfone, and polyethersulfone are preferred, and more preferably polyamide, polyethylene, polypropylene, and polytetrafluoroethylene.

[0169] Furthermore, when the composite film of the present invention is in a flat film shape, it can be used as a plate-and-frame type, stack-type or similar sheet module, spiral-type module, rotating flat film type module, etc.

[0170] The membrane module of the present invention is used to separate specific fluorinated compounds from organic solutions containing specific organic solvents and specific fluorinated compounds, and can achieve a high level of both permeability to specific organic solvents and blocking performance of specific fluorinated compounds. [Examples]

[0171] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0172] 1.Measurement method [Outer and inner diameters of hollow fiber membranes] Five hollow fiber membranes were observed under an optical microscope at a magnification of 200x. The outer and inner diameters (at the point of maximum diameter) of each hollow fiber membrane were measured, and their average values ​​were calculated.

[0173] [Void ratio of the supporting layer] In a cross-section of a hollow fiber membrane cut perpendicular to its longitudinal direction, scanning electron microscope (SEM) images were taken at five equally spaced locations in the thickness direction of the support layer of the hollow fiber membrane. Specifically, the images were taken as follows: Figure 2 is a schematic cross-sectional view of a hollow fiber membrane cut perpendicular to its longitudinal direction, and Figures 3 and 4 are magnified views of the area enclosed by the dotted line in Figure 2, showing an example of a hollow fiber membrane 8 having a dense layer 9 and a support layer 10. As shown in Figure 3, a straight line was drawn from the center of the lumen of the hollow fiber membrane 8 toward the outer surface, and this line was divided into five equal parts from the lumen side surface to the outer surface of the support layer 10. Then, as shown in Figure 3, the midpoint of the five divided line segments was determined. Then, as shown in Figure 4, the midpoint was set so that only the support layer 10 portion was included in the image, and the number of pores was between 30 and 300, and the images were taken at a uniform magnification at five locations, so that the midpoint was at the center of the captured image. In the five SEM images taken, image analysis was performed on the aforementioned regions using image analysis software (ImageJ). After distinguishing between the pore regions and the polymer regions by binarization, the area ratio (%) of the total pore area to the area of ​​the analysis region was calculated for each region, and the average value was calculated. The specific operations in ImageJ are as follows: The image to be analyzed was imported into ImageJ, the analysis range was specified, and the brightness value at which the peak of the histogram obtained by the operation "Analyze>Histogram" was set as the threshold (i.e., the Lower threshold level was set to the brightness value at which the peak of the histogram was highest, and the Upper threshold level was set to 255). The image was then binarized using "Image>Adjust>Threshold". Next, "Analyze>Set measurements" was used to check "Area", and the total area of ​​the analysis range was obtained by the operation "Analyze>Measure". After that, "Analyze>Set measurements" was used again to check "Area" and "Limit to threshold", and the operation "Analyze>Measure" was performed again to calculate the area of ​​the polymer portion and the pore portion, and the area ratio (%) of the total pore area to the area of ​​the analysis region was calculated.

[0174] [Thickness of the dense layer] A cross-section of a hollow fiber membrane, cut perpendicular to its longitudinal direction, was observed at a magnification of 10,000x using a scanning electron microscope (SEM). In the resulting SEM image, the distance (thickness) of the region where virtually no pores were observed was measured at 10 equally spaced locations, and the average value was calculated.

[0175] [Fractional molecular weight of hollow fiber membranes (if greater than 3000)] Ten hollow fiber membranes were cut to a length of 30 cm and bundled together. Next, a rigid nylon tube with an outer diameter of 8 mm, an inner diameter of 6 mm, and a length of 50 mm was prepared. A rubber stopper approximately 20 mm long was inserted into the opening at one end of the tube to seal the end. Next, a two-part epoxy resin was injected into the opening of the connecting tube opposite to the rubber stoppered end to fill the space inside the tube with the epoxy resin. After that, one end of the bundle of hollow fiber membranes was heat-sealed to prevent epoxy resin from entering the hollow section, and this end was inserted into the epoxy resin-filled tube until the tip touched the rubber stopper. The epoxy resin was then allowed to harden in this state. Next, the rubber stoppered portion of the hardened epoxy resin was cut along with the tube to open the hollow section. The same procedure was performed on the other end to create a cross-flow module 6 with hollow sections at both ends of the hollow fiber membrane. The fabricated cross-flow module 6 was connected to the internal pressure separation line shown in Figure 1, and a fluid (undiluted solution) was continuously permeated through the cross-flow module 6 by the fluid circulation pump 2. The fluid was an aqueous solution containing 0.5% by weight, 0.5% by weight, 0.2% by weight, 0.2% by weight, and 0.4% by weight of five types of dextran with molecular weights of 5000, 10000, 40000, 70000, and 500000, respectively. The pressure of the primary pressure gauge 3 and the secondary pressure gauge 4 were adjusted by the regulator 5 so that the arithmetic mean of the pressures of the primary pressure gauge 3 and the secondary pressure gauge 4 was 1 to 3 bar. Of the fluid permeating through the module, the portion that permeated through the pores of the hollow fiber membrane was collected as a permeate separated from the fluid, and the remainder was circulated back to the separation line. Two hours after the start of circulation, the permeate flowing out of the cross-flow module 6 was collected in a tray 7, and the dextran concentration in the permeate was measured by high-performance liquid chromatography. The rejection rate for each molecular weight was calculated according to the following formula. Based on the rejection rate results for each molecular weight of dextran, a graph was created with the molecular weight of the dextran used on the x-axis and the rejection rate on the y-axis. The molecular weight at the intersection of the resulting approximation curve and the point where the rejection rate was 90% was defined as the fractional molecular weight. Solute rejection rate (%) = {(Dextran concentration in stock solution - Dextran concentration in permeate) / Dextran concentration in stock solution} × 100

[0176] [Fractional molecular weight of hollow fiber membranes (for values ​​of 3000 or less)] As the fluid, an NMP solution containing 0.05 wt% each of four types of polystyrene with molecular weights of 370, 1000, 2000, or 3000 was used. The arithmetic mean of the pressures on the primary pressure gauge 3 and the secondary pressure gauge 4 was set to 15 bar, and the fractional molecular weight was determined in the same manner as described above, except that the rejection rate was calculated according to the following formula. Solute rejection rate (%) = {(Polystyrene concentration in stock solution - Polystyrene concentration in permeate) / Polystyrene concentration in stock solution} × 100

[0177] [Thickness of the silicone layer] A cross-section of a composite hollow fiber membrane, cut perpendicular to its longitudinal direction, was observed at a magnification of 10,000x using a scanning electron microscope (SEM). In the resulting SEM images, the distance (thickness) of the non-porous region on the surface of the dense layer was measured at 10 equally spaced locations, and the average value was calculated.

[0178] [solvent permeation rate] The internal pressure separation treatment line described later is used for circulation treatment, and the permeate flowing out of the cross-flow module 6 4 hours after the start of circulation is collected in the receiving tray 7. From the amount of collected permeate, the solvent permeate (L / (m³)) is calculated using the following formula. 2 We calculated h). Solvent permeation rate = Volume of solvent that permeates to the outside of the composite hollow fiber membrane (L) / [Inner diameter of composite hollow fiber membrane (m) × 3.14 × Effective filtration length of composite hollow fiber membrane (m) × 40 (fibers) × Time (h)] Effective filtration length of composite hollow fiber membrane: In a cross-flow module, this is the length of the portion of the outer surface of the composite hollow fiber membrane that is not coated with epoxy resin.

[0179] [Fluorine compound rejection rate] 2-5 ml of permeate and fluid obtained by the internal pressure separation treatment line described later were accurately weighed into test tubes, the solvent was removed by nitrogen blowing, and then the samples were completely dried by vacuum drying. Then, approximately 0.7 ml of deuterated chloroform was added and completely dissolved. Furthermore, 2-8 drops of a deuterated chloroform solution of 1,4-bis(trimethylsilyl)-2,3,5,6-tetrafluorobenzene of known concentration were added dropwise as an internal standard substance and accurately weighed to prepare the NMR measurement solution. The 19F-NMR spectrum of NMR measurement solutions prepared using a JEOL-ECA500 NMR spectrometer manufactured by JEOL Ltd. was measured. From the resulting charts, the concentrations of fluorine compounds in the permeate and fluid were calculated from the integrated intensity of the peaks originating from the fluorine compounds, using the integrated intensity of the peaks originating from the internal standard as a reference. The rejection rate (%) of fluorine compounds was then calculated using the following formula. Rejection rate of fluorine compounds = 100 - (Concentration of fluorine compounds in permeate / Concentration of fluorine compounds in fluid) × 100

[0180] 2. Example Test [Manufacturing Example 1] 350g of polyamide 6 chips (manufactured by Unitika Ltd., A1030BRT, relative viscosity 3.53) and 650g of dimethyl sulfone (manufactured by Tokyo Chemical Industry Co., Ltd.) were stirred at 190°C for 1.5 hours to dissolve, and the stirring speed was reduced and degassed for 1 hour to prepare a film-forming stock solution. The film-forming stock solution was delivered via a metering pump to a spinneret kept warm at 200°C, and a mixture of 70% by weight polyethylene glycol 300 (PEG300) and 30% by weight glycerin was passed through as an internal coagulation solution. The extruded film-forming stock solution was placed in a coagulation bath consisting of a 60% by weight 1,4-butylene glycol (1,4BG) aqueous solution at 5°C and cooled and solidified to form a porous polyamide film. The wound polyamide porous membrane was immersed in water for 24 hours for solvent extraction (washing), and then dried by passing it through a hot air dryer (internal temperature 130°C) without stretching to obtain a polyamide hollow fiber membrane with a dense layer formed on the inner surface. The obtained polyamide hollow fiber membrane had an outer diameter of 780 μm, an inner diameter of 440 μm, a porosity of 68% in the support layer, a density layer thickness of 0.78 μm, and a molecular weight cutoff of 60,000 Da. A bundle of polyamide hollow fiber membranes was prepared, consisting of 20 membranes, each 40 cm long. A nylon rigid tube with an inner diameter of 8 mm and a length of 50 mm was prepared, and a rubber stopper approximately 20 mm long was inserted into the opening at one end of the tube to seal the end. Next, a two-part epoxy resin was injected into the tube from the opening opposite the rubber stopper, filling the internal space of the tube with the epoxy resin. After that, one end of the prepared polyamide hollow fiber membrane was heat-sealed to seal it, and the end was inserted into the tube filled with epoxy resin until it touched the rubber stopper, and the epoxy resin was allowed to harden in that state. Then, the rubber stopper side of the hardened epoxy resin portion was cut along with the tube to open the hollow part of the polyamide hollow fiber membrane, obtaining a module for injecting silicone coating liquid. A commercially available two-component silicone (Momentive, product name: TSE3033) was prepared by diluting the main component with ethyl acetate 10 times, then mixing it with an equal amount of curing agent, and filling a plastic syringe with the resulting silicone coating solution. The syringe and the silicone coating solution injection module were connected with a silicone tube, and the silicone coating solution was extruded into the hollow portion of the polyamide hollow fiber membrane at a linear velocity of 0.16 m / sec and a flow rate of 0.25 L / min. Next, the syringe was removed, nitrogen blowing was performed at a linear velocity of 6.6 m / sec and a flow rate of 10 L / min, followed by curing at 120°C for 3 hours. After that, the hollow fiber membrane was cut on the epoxy resin side of the injection module, and a composite hollow fiber membrane was obtained in which a silicone layer was formed on the surface of the dense layer on the inner surface.

[0181] [Manufacturing Example 2] 200 g of polyacrylonitrile (Sigma-Aldrich, weight-average molecular weight 150,000, intrinsic viscosity 2.7) and 800 g of γ-butyrolactone (Tokyo Chemical Industries, Ltd.) were stirred overnight at 40°C to dissolve, and then degassed for 1 hour to prepare a film-forming stock solution. The film-forming stock solution was delivered via a metering pump to a spinneret kept at 40°C, and water was flowed through it as an internal coagulation solution. The extruded film-forming stock solution was placed in a coagulation bath consisting of an 80 wt% aqueous solution of γ-butyrolactone at 40°C to solidify and form a polyacrylonitrile porous membrane. The wound polyacrylonitrile porous membrane was immersed in warm water for 24 hours for solvent extraction (washing), and then dried by passing it through a hot air dryer (internal temperature 60°C) without stretching to obtain a polyacrylonitrile hollow fiber membrane with a dense layer formed on the inner surface. The obtained polyacrylonitrile hollow fiber membrane had an outer diameter of 690 μm, an inner diameter of 460 μm, a porosity of 83% in the support layer, a density layer thickness of 0.4 μm, and a molecular weight cutoff of 20,000 Da. The obtained polyacrylonitrile hollow fiber membrane was injected with a silicone coating solution in the same manner as in Production Example 1, thereby obtaining a composite hollow fiber membrane in which a silicone layer was formed on the surface of the dense layer on the luminal surface.

[0182] [Manufacturing Example 3] In preparing the film-forming stock solution, 280g of polyamide 6 tips (manufactured by Unitika Ltd., A1030BRT, relative viscosity 3.53) and 720g of dimethyl sulfone (manufactured by Tokyo Chemical Industry Co., Ltd.) were stirred at 180°C for 1.5 hours to dissolve, and then the stirring speed was reduced and degassed for 1 hour to prepare the film-forming stock solution. Polyethylene glycol 400 (PEG400) was used as the internal coagulation solution, and the obtained polyamide hollow fiber membrane was stretched 1.3 times by passing it between rolls at different speeds. Except for these differences, a polyamide hollow fiber membrane with a dense layer formed on the inner surface was produced in the same manner as in Production Example 1. The obtained polyamide hollow fiber membrane had an outer diameter of 820 μm, an inner diameter of 370 μm, a porosity of 72% in the support layer, a density layer thickness of 1 μm, and a molecular weight cutoff of 1,000 Da.

[0183] [Manufacturing Example 4] In preparing the film-forming stock solution, 280 g of polyamide 6 tips (manufactured by Unitika Ltd., A1030BRT, relative viscosity 3.53) and 720 g of dimethyl sulfone (manufactured by Tokyo Chemical Industry Co., Ltd.) were stirred at 180°C for 1.5 hours to dissolve, and then the stirring speed was reduced and degassed for 1 hour to prepare the film-forming stock solution. Polyethylene glycol 400 (PEG400) was used as the internal coagulation solution, and the obtained polyamide hollow fiber membrane was stretched 1.8 times by passing it between rolls at different speeds. Except for these differences, a polyamide hollow fiber membrane with a dense layer formed on the inner surface was produced in the same manner as in Production Example 1. The obtained polyamide hollow fiber membrane had an outer diameter of 780 μm, an inner diameter of 355 μm, a porosity of 71% in the support layer, a density layer thickness of 0.8 μm, and a molecular weight cutoff of 3,000 Da.

[0184] [Example 1] Forty composite hollow fiber membranes obtained in Manufacturing Example 1 were cut to a length of 30 cm, and these were prepared by aligning and bundling them together. Next, a polybutylene terephthalate (PBT) tube with an outer diameter of 12.7 mm, an inner diameter of 9.5 mm, and a length of 53 mm was prepared. A silicone tube with an inner diameter of 12 mm and a length of approximately 50 mm was inserted about 15 mm into the opening at one end of the PBT tube to connect them. A rubber stopper about 20 mm in length was inserted into the opposite end of the silicone tube from the side inserted into the PBT tube, sealing the opening at that end. Next, a two-part epoxy resin was injected into the opening of the connected tube on the opposite side from the rubber stopper to fill the space inside the tube with the epoxy resin. After that, one end of the bundle of composite hollow fiber membranes prepared was heat-sealed to prevent epoxy resin from entering the hollow part, and this end was inserted into the tube filled with epoxy resin until the tip touched the rubber stopper, and the epoxy resin was allowed to harden in that state. Next, the rubber stopper side of the hardened epoxy resin portion was cut along with the tube to create a hollow opening. The same procedure was performed on the other end, creating a cross-flow module with hollow openings at both ends of the composite hollow fiber membrane. The fabricated cross-flow module 6 was connected to the internal pressure separation treatment line shown in Figure 1, and a fluid was continuously permeated through the cross-flow module 6 by the fluid circulation pump 2. The fluid used was an organic solution containing organic solvents and fluorine compounds as shown in Table 1. In the module, the pressure of the primary pressure gauge 3 and the secondary pressure gauge 4 were adjusted by the regulator 5 so that the arithmetic mean of the pressures of the primary pressure gauge 3 and the secondary pressure gauge 4 was the pressure shown in Table 1. Of the fluid permeating through the module, the portion that permeated through the composite hollow fiber membrane was collected as a permeate separated from the fluid, and the remainder was circulated back into the separation treatment line. Four hours after the start of circulation, the permeate that flowed out of the cross-flow module 6 was collected in a tray 7. Then, the amount of solvent permeation and the rejection rate of fluorine compounds were measured using the method described above. The measurement results are shown in Table 1.

[0185] [Examples 2-11] The solvent permeation rate and the rejection rate of the fluorine compound were measured using the same method as in Example 1, except that the type of solvent used in the fluid, the type and concentration of the fluorine compound were changed as shown in Table 1. The measurement results are shown in Table 1.

[0186] [Example 12] The solvent permeability and the rejection rate of fluorine compounds were measured using the same method as in Example 5, except that the composite hollow fiber membrane obtained in Production Example 2 was used. The measurement results are shown in Table 1.

[0187] [Comparative Example 1] When a commercially available RO membrane for water (FilmTec, TW30-1812-50HR, support material: polyester, base material: polysulfone, separation functional layer: aromatic polyamide) was cut from the membrane module and immersed in the fluid shown in Table 1, the separation functional layer immediately peeled off, making it impossible to use the membrane for separation treatment tests.

[0188] [Comparative Example 2] The solvent permeability and the rejection rate of fluorine compounds were measured using the same method as in Example 5, except that the polyamide hollow fiber membrane obtained in Production Example 3 was used. The measurement results are shown in Table 1.

[0189] [Comparative Example 3] Using the polyamide hollow fiber membrane obtained in Production Example 4, the solvent permeation rate and the rejection rate of fluorine compounds were measured in the same manner as in Example 5, except that the pressure in the separation treatment test was changed to 1.0 MPa. The measurement results are shown in Table 1.

[0190] [Comparative Examples 4-7] The solvent permeation rate and the rejection rate of fluorine compounds were measured using the same method as in Example 3, except that the solvent of the fluid was changed as shown in Table 1. The measurement results are shown in Table 1.

[0191] [Table 1]

[0192] The organic solvents and fluorine compounds in Table 1 are as follows: • PGMEA: Propylene glycol monomethyl ether acetate • PGME: Propylene glycol monomethyl ether THF: Tetrahydrofuran IPA: Isopropyl alcohol • PFBS: Perfluorobutanesulfonic acid • TFMS: Trifluoromethanesulfonic acid • TPS-PFBS: Sulfonium salt (photoacid generator) represented by the following formula [ka] [ka] [ka]

[0193] The composite hollow fiber membranes of Examples 1-12 have a silicone layer on the surface of the dense layer of the hollow fiber membrane, resulting in a high rejection rate of fluorine compounds of 90% or more, and a permeation rate of PGMEA and / or PGME solvent of 1.7 L / (m³). 2 The level was high (h) or higher, and it was possible to achieve a high level of both permeability and blocking performance.

[0194] On the other hand, the commercially available RO membrane in Comparative Example 1 had poor solvent resistance to PGMEA / PGME solvent and could not be used for membrane separation of organic solutions containing PGMEA / PGME solvent. The polyamide hollow fiber membranes in Comparative Examples 2 and 3 did not have a silicone layer, resulting in low rejection rates of fluorine compounds and very low permeability of PGMEA / PGME solvent. In Comparative Example 4, when THF was used as the solvent for the fluid, the silicone layer on the surface of the dense layer of the composite hollow fiber membrane swelled and peeled off during the separation treatment test, resulting in a low rejection rate of fluorine compounds. In Comparative Examples 5 or 6, when IPA or cyclohexane was used as the solvent for the fluid, the solvent permeability was low. In Comparative Example 7, when butyl acetate was used as the solvent for the fluid, the rejection rate of fluorine compounds was low. [Explanation of symbols]

[0195] 1. Fluidized liquid tank 2. Liquid transfer pump 3. Primary pressure gauge 4. Secondary pressure gauge 5. Regulator 6. Cross-flow module 7. Drip tray 8 Hollow fiber membrane 9 Layer compacta 10 Support layer

Claims

1. A composite film comprising a silicone layer, a dense layer and a support layer, and a polymer film formed of a polymer other than silicone, wherein the silicone layer is provided on the surface of the dense layer, The aforementioned composite membrane is used to separate fluorine compounds present in an organic solution. The organic solvent of the aforementioned organic solution contains at least one selected from the group consisting of propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether. The fluorine compound is a composite film having a total of 1 to 6 fluorine-containing groups in its molecule, selected from the group consisting of perfluoroalkyl groups having 1 to 6 carbon atoms and perfluoroalkylene groups having 1 to 6 carbon atoms.

2. The composite membrane according to claim 1, wherein the polymer membrane is formed of polyamide or polyacrylonitrile.

3. The composite membrane according to claim 1, wherein the polymer membrane is a hollow fiber membrane.

4. The composite membrane according to claim 3, wherein the dense layer is located on the inner surface side of the hollow fiber membrane.

5. The composite film according to claim 1, wherein the support layer has a porosity of 60 to 80%.

6. The composite film according to claim 1, wherein the dense layer has a thickness of 0.1 μm or more.

7. The composite film according to claim 1, wherein the silicone layer has a thickness of 0.05 to 10 μm.

8. The composite film according to claim 1, wherein the silicone layer is made of silicone rubber.

9. A filtration method for filtering a liquid to be treated containing an organic solvent and a fluorine compound using a composite membrane according to any one of claims 1 to 8, The organic solvent contains at least one selected from the group consisting of propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether, The fluorine compound is a fluorine compound having a total of 1 to 6 fluorine-containing groups in its molecule, selected from the group consisting of perfluoroalkyl groups having 1 to 6 carbon atoms and perfluoroalkylene groups having 1 to 6 carbon atoms.

10. A membrane module comprising a module case containing a composite membrane according to any one of claims 1 to 8, The aforementioned membrane module is used to separate fluorine compounds present in an organic solution. The organic solvent of the aforementioned organic solution contains at least one selected from the group consisting of propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether. The fluorine compound is a membrane module having a total of 1 to 6 fluorine-containing groups in its molecule, selected from the group consisting of perfluoroalkyl groups having 1 to 6 carbon atoms and perfluoroalkylene groups having 1 to 6 carbon atoms.

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