Separation membrane, method for producing same, membrane module for degassing and / or gas injection, and device for degassing and / or gas injection

Abstract

The present invention addresses the problem of providing a separation membrane having low leakage properties while maintaining high gas permeability by using poly (4-methyl-1-pentene) having excellent solvent resistance and gas permeability. The present invention pertains to a separation membrane having poly (4-methyl-1-pentene) as the main component, having an average pore diameter of 0.10-1.00 nm in terms of the NKP curve, and a porosity of 40-70%, and having a pore diameter variation coefficient [alpha] i of 0-150% in all regions (1-5), where the regions (1-5) are divided into five regions sequentially at equal intervals in the thickness direction from one surface.

Description

TECHNICAL FIELD

[0001] The present application relates to a separation membrane, a method for producing the same, a membrane module as at least one of a degassing and a gas injection, and an apparatus as at least one of a degassing and a gas injection. BACKGROUND

[0002] As a degassing method for removing a dissolved gas from a liquid, or a gas exchange method for exchanging a dissolved gas in a liquid with a gas component in a gas phase, there is a method using a hollow fiber membrane. For the hollow fiber membrane used in these applications, solvent resistance against a liquid to be treated, and high gas permeation performance are required, and thus poly(4-methyl-1-pentene) excellent in these properties is sometimes used as a membrane material. Among them, a membrane having a thin dense layer of 2.0 μm or less is preferable in terms of being able to improve the permeability of a gas. On the other hand, such a membrane having a thin dense layer tends to easily form a through-hole called a defect in the dense layer, and a solution leaks out from the hole, and thus has a tendency to have a high leakage property.

[0003] Hitherto, in order to obtain a gas permeation membrane having both high permeability and low leakage, various methods have been proposed. For example, a dry-wet method using a polyolefin-based high molecule is disclosed in Patent Literature 1. Specifically, a polymer solution obtained by dissolving a polyolefin-based high molecule in a good solvent is cooled in a cooling medium at a temperature lower than a solidification temperature, and a heat-induced phase separation by heat-induced phase separation is performed to form an asymmetric structure having a dense layer on one surface.

[0004] However, the membrane of Patent Literature 1 has a difficulty in that a solution easily leaks out from the pores of the dense layer as long as the pore diameter of the dense layer is less than 100 nm.

[0005] A hollow fiber membrane using a melt method is disclosed in Patent Literature 2. Specifically, a polyolefin-based resin is extruded from a spinneret at a temperature above the melting point, and then cooled and solidified by bringing the inner surface and the outer surface into contact with a gas, and then cracked by stretching, thereby forming a porous structure. In this method, a membrane having high gas permeability can be obtained, but since the surface is a porous structure, there is a difficulty in that a solution easily leaks out.

[0006] A hollow fiber membrane using a melt method is disclosed in Patent Literature 3. Specifically, a polyolefin-based resin is extruded from a spinneret at a temperature above the melting point, and then cooled and solidified, and then stretched, thereby forming a structure in which the surface layer is dense and the inside is porous by partially cracking. In this method, a membrane having low leakage can be obtained, but since it is a structure with a low void ratio, there is a difficulty in that the gas permeation performance is insufficient.

[0007] PRIOR ART DOCUMENTS PATENT LITERATURE Patent Literature 1: Japanese Patent Application Laid-Open No. 2005-515061 Patent Literature 2: Japanese Patent Application Laid-Open No. H8-332359 Patent Literature 3: Japanese Patent Application Laid-Open No. H7-155569 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION According to the present inventors' insight, in the separation membrane of Patent Literatures 1 and 2, although having high gas permeability, the pore diameter of the membrane surface is large, and it is difficult to achieve low bleeding. In addition, according to the present inventors' insight, the separation membrane obtained in Patent Literature 3, although having low bleeding, is a structure with low void ratio, and thus does not have sufficient gas permeability.

[0009] In view of the problems of the above-described conventional technologies, the present inventors aimed to provide a separation membrane that maintains high gas permeability and has low bleeding, using poly(4-methyl-l-pentene).

[0010] MEANS FOR SOLVING THE PROBLEMS The present inventors conducted intensive studies in order to solve the above-described problems, and as a result, found that by making a separation membrane that uses poly(4-methyl-l-pentene) as a main component, has an average pore diameter converted from an NKP curve within a specific range, has a void ratio within a specific range, and has each region, which is divided into five in the thickness direction from one surface of the separation membrane at equal intervals, set as regions 1 to 5, has a variation coefficient a of the pore diameter in all of the aforementioned regions 1 to 5 of 0 to 150%, it is possible to have both high gas permeability and low bleeding, and thus completed the present invention. i In a specific range. Note that in this specification, "~" means to include the numerical value recited before and after it as the lower limit value and the upper limit value.

[0011] According to the present invention, the following modes are provided.

[0012] [1] A separation membrane that is a separation membrane using poly(4-methyl-l-pentene) as a main component, in which the average pore diameter converted from an NKP curve is 0.10 to 1.00 nm, the void ratio is 40 to 70%, when each region, which is divided into five in the thickness direction from one surface of the aforementioned separation membrane at equal intervals, is set as regions 1 to 5, the variation coefficient a of the pore diameter of region i in all of the aforementioned regions 1 to 5 is 0 to 150%. i

[0013] [2] The separation membrane according to the above [1], in which in the aforementioned regions 1 to 5, the average pore diameter D of region i​i meets the requirements of (a) or (b) below, (a) D1 ≥ D2 ≥ D3 ≥ D4 ≥ D5 (b) D5 ≥ D4 ≥ D3 ≥ D2 ≥ D1.

[0014] [3] The separation membrane according to the above [1] or [2], wherein the average open porosity of the cross section of the separation membrane is 25 to 50%.

[0015] [4] The separation membrane according to the above [2], wherein in the separation membrane, the average pore diameter D i When the requirement of the above (a) is met, the surface of D5 has a dense layer, the average pore diameter D i When the requirement of the above (b) is met, the surface of D1 has a dense layer.

[0016] [5] The separation membrane according to the above [4], wherein the thickness of the dense layer is in the range of 0.1 to 2.0 μm.

[0017] [6] The separation membrane according to any one of the above [1] to [5], wherein the ratio of the CO2 permeation performance to the N2 permeation performance (separation factor β (CO2 / N2)) of the separation membrane under a pressure difference of 100 kPa is 5.0 to 100.0.

[0018] [7] The separation membrane according to any one of the above [1] to [6], wherein the N2 permeation performance of the separation membrane under a pressure difference of 100 kPa at 37°C is 5 to 400 GPU.

[0019] [8] The separation membrane according to any one of the above [1] to [7], wherein the separation membrane is in a hollow fiber shape.

[0020] [9] The separation membrane according to the above [8], wherein in the regions 1 to 5, the average pore diameter D i When the requirement of the above (a) is met, the surface of D5 has a dense layer, the average pore diameter D i When the requirement of the above (b) is met, the surface of D1 has a dense layer, In the case where any one of the requirements of (a) or (b) below is met, the surface having the dense layer is the outer surface of the separation membrane in the hollow fiber shape, (a) D1 ≥ D2 ≥ D3 ≥ D4 ≥ D5 (b) D5 ≥ D4 ≥ D3 ≥ D2 ≥ D1.

[0021]

[10] The membrane assembly, which is used for at least one of degassing and gas injection, has a housing and a separation membrane as described in any one of [1] to [9] above, and the separation membrane is filled in the housing.

[0022]

[11] The device, which is used for at least one of degassing and gas injection, includes a membrane module as described above

[10] , which is used for at least one of degassing and gas injection.

[0023]

[12] A method for producing a liquid, comprising removing at least one of a dissolved gas and a gas-imposing device as described above

[11] for degassing and gas injection.

[0024]

[13] The method for manufacturing the separation membrane includes the following steps (1) to (2): (1) Preparation process: A mixture containing more than 10% by mass and less than 50% by mass of poly(4-methyl-1-pentene) and more than 50% by mass and less than 90% by mass of plasticizer is melt-blended to obtain a resin composition; (2) Molding process: The aforementioned resin composition is discharged from the spinneret, and after the volatile plasticizer is discharged at a wind speed of 8-20 m / s, it is impregnated with a distance Ra of 5.0 MPa relative to the solubility parameter of poly(4-methyl-1-pentene). 1 / 2 Above and 18MPa 1 / 2 The following range, and the distance from Rb relative to the solubility parameter of the aforementioned plasticizer, is 1.0 MPa. 1 / 2 Above and 2.9MPa 1 / 2 Below or 6.5MPa 1 / 2 Above and 10.0 MPa 1 / 2 The following range of solvents are used for winding in a cooling bath.

[0025]

[14] According to the method for manufacturing the separation membrane described above

[13] , the cooling bath in the aforementioned forming process is 15 to 45°C.

[0026]

[15] According to the method for manufacturing the separation membrane described in

[13] or

[14] above, the winding in the aforementioned forming process has a draw ratio of 3.0 to 20.0.

[0027] Invention Effects According to the present invention, a separation membrane with high gas permeability and low leakage is provided by using poly(4-methyl-1-pentene). Attached Figure Description

[0028] Figure 1 Figure 1 is an example of an image obtained by taking a photograph of a cross section cut in the thickness direction of the separation membrane at a magnification of 10,000 times.

[0029] Figure 2 Figure 2 is an image obtained by binarizing the image of Figure 1 and removing noise.

[0030] Figure 3 Figure 3 is a figure showing the thickness of the dense layer by extracting the outline of voids larger than 10 nm from the image of Figure 2 . DETAILED DESCRIPTION

[0031] The separation membrane of the embodiment of the present application (hereinafter, also referred to as "the present embodiment") is characterized in that the average pore diameter converted from the NKP curve is 0.10 to 1.00 nm and the void fraction is 40 to 70% with poly(4-methyl-l-pentene) as the main component, and when each region obtained by dividing the separation membrane in the thickness direction from one surface into five regions at equal intervals is set as regions 1 to 5, the coefficient of variation a of the pore diameter of region i in all of the aforementioned regions 1 to 5 is 0 to 150%. i In the present specification, the proportion (percentage, parts, etc.) on a mass basis is the same as the proportion (percentage, parts, etc.) on a weight basis.

[0032] (Resin composition constituting the separation membrane) The resin composition constituting the separation membrane of the present embodiment has poly(4-methyl-l-pentene) shown in (1) below as the main component. In addition, components shown in (2) to (3) below can be contained in addition to (1).

[0033] (1) Poly(4-methyl-l-pentene) (hereinafter, shown as "PMP") The separation membrane of the present embodiment requires PMP as the main component. The main component herein means a component contained in the largest amount on a mass basis among all the components of the separation membrane.

[0034] PMP only needs to have a repeating unit derived from 4-methyl-l-pentene. PMP can be a homopolymer of 4-methyl-l-pentene or a copolymer of 4-methyl-l-pentene and a monomer copolymerizable with 4-methyl-l-pentene other than 4-methyl-l-pentene. The monomer copolymerizable with 4-methyl-l-pentene can be specifically exemplified by an olefin having 2 to 20 carbon atoms (hereinafter, referred to as "olefin having 2 to 20 carbon atoms") other than 4-methyl-l-pentene.

[0035] ​​​Examples of the olefin having 2 to 20 carbon atoms copolymerized with 4-methyl-1-pentene include ethylene, propylene, 1-butene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, and 1-eicosene, and the like.

[0036] The olefin having 2 to 20 carbon atoms copolymerized with 4-methyl-1-pentene can be one or a combination of two or more.

[0037] The density of the PMP of the present embodiment is preferably 825 to 840 (kg / m 3 ), and further preferably 830 to 835 (kg / m 3 ). When the density is less than the aforementioned range, there is a possibility that the mechanical strength of the separation membrane decreases, and the like. On the other hand, when the density is greater than the aforementioned range, there is a tendency that the gas permeability decreases.

[0038] The melt flow rate (MFR) of the PMP measured at 260°C under a load of 5 kg is not particularly limited as long as it is in a range in which the PMP is easily mixed with a plasticizer described later and co-extrusion is possible, and is preferably 1 to 200 g / 10 min, and more preferably 5 to 30 g / 10 min. When the MFR is in the aforementioned range, it is easy to extrusion-mold a film having a relatively uniform thickness.

[0039] The PMP can be directly produced by polymerizing an olefin, or can be produced by thermally decomposing a high-molecular-weight 4-methyl-1-pentene-based polymer. Furthermore, the 4-methyl-1-pentene-based polymer can be purified by a method such as solvent fractionation using a difference in solubility with respect to a solvent, or molecular distillation using a difference in boiling point.

[0040] The PMP can be a commercially available polymer such as TPX manufactured by Mitsui Chemicals, Inc. in addition to a product produced as described above.

[0041] The content of the PMP in the separation membrane is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, and further preferably 90 to 100% by mass, when the entirety of the components of the separation membrane is taken as 100% by mass. By the content of the PMP in the separation membrane being 70% by mass or more, the gas permeability becomes sufficient.

[0042] Furthermore, the content of the PMP in the raw material for producing the separation membrane is preferably 10 to 50% by mass, when the entirety of the components of the raw material is taken as 100% by mass. By the content being 10% by mass or more, the film strength of the separation membrane becomes good. On the other hand, by the content being 50% by mass or less, the permeation performance of the separation membrane becomes good. The content is more preferably 15 to 50% by mass, further preferably 20 to 45% by mass, and particularly preferably 25 to 40% by mass.

[0043] (2) Plasticizer of PMP The resin composition constituting the separation membrane of the present embodiment can contain a plasticizer of PMP. From the viewpoint of improving permeability, the content of the plasticizer in the separation membrane is preferably 1000 ppm or less, more preferably 500 ppm or less, particularly preferably 100 ppm or less, on a mass basis.

[0044] The plasticizer of PMP is not particularly limited as long as it is a compound capable of thermoplasticizing PMP. The plasticizer of PMP can use not only one plasticizer but also two or more plasticizers in combination.

[0045] As the plasticizer of PMP, for example, palm kernel oil, dibutyl phthalate, dioctyl phthalate, benzyl ether, coconut oil, or a mixture thereof can be given. Among them, from the viewpoints of compatibility and stringiness, dibutyl phthalate and benzyl ether are preferably used.

[0046] The plasticizer of PMP is preferably eluted from the separation membrane after the formation of the separation membrane. In addition, the content of the plasticizer of PMP in the raw material for manufacturing the separation membrane is preferably 50 to 90 mass% when the entirety of the components constituting the raw material is taken as 100 mass%.

[0047] By the content of 90 mass% or less, the film strength of the separation membrane becomes good. Further, by the content of 50 mass% or more, the permeability of the separation membrane becomes good. The content is more preferably 50 to 85 mass%, further preferably 55 to 80 mass%, particularly preferably 60 to 75 mass%.

[0048] (3) Additive The resin composition constituting the separation membrane of the present embodiment can also contain an additive other than those described in (2) within a range not impairing the effects of the present embodiment.

[0049] As the additive, for example, resins such as cellulose ether, polyacrylonitrile, polyolefin, polyvinyl compound, polycarbonate, poly(meth)acrylate, polysulfone, or polyethersulfone, organic lubricant, crystallization nucleating agent, organic particle, inorganic particle, end-capping agent, chain extender, ultraviolet absorber, infrared absorber, anti-coloring agent, matting agent, antibacterial agent, antistatic agent, deodorant, flame retardant, weathering agent, antistatic agent, antioxidant, ion exchanger, antifoaming agent, coloring pigment, optical brightener, or dye, and the like can be given.

[0050] (Shape of the separation membrane) As the separation membrane of the present embodiment, a separation membrane in a hollow fiber shape (hereinafter, referred to as "hollow fiber membrane") is preferably used, but the separation membrane of the present application is not limited to the hollow fiber shape. The hollow fiber membrane can be efficiently packed into the module, can increase the effective membrane area per unit volume of the module, and thus is preferred.

[0051] The shape of the separation membrane of the present embodiment, i.e., the thickness of the separation membrane, the outer diameter and the inner diameter of the hollow fiber membrane, and the hollow ratio, for example, can be observed by cutting the hollow fiber membrane, which has been sufficiently cooled in liquid nitrogen, in the thickness direction of the membrane by applying stress, and observing the cross section (hereinafter, referred to as "radial cross section") using an optical microscope or a scanning electron microscope (SEM). The specific method is described in detail in the examples.

[0052] From the viewpoint of balancing the permeation performance and the membrane strength, the thickness of the separation membrane is preferably 10 to 500 μm. Further, the thickness is more preferably 30 μm or more, and further preferably 50 μm or more. The thickness is more preferably 200 μm or less, further preferably 150 μm or less, and particularly preferably 100 μm or less.

[0053] From the viewpoint of balancing the effective membrane area when packed into the module and the membrane strength, the outer diameter of the hollow fiber membrane is preferably 50 to 2500 μm. The outer diameter of the hollow fiber membrane is more preferably 100 μm or more, further preferably 200 μm or more, and particularly preferably 300 μm or more. Further, the outer diameter is more preferably 1000 μm or less, further preferably 500 μm or less, and particularly preferably 450 μm or less.

[0054] Further, from the viewpoint of the relationship between the pressure loss of the fluid flowing in the hollow portion and the buckling pressure, the inner diameter of the hollow fiber membrane is preferably 20 to 1000 μm. The inner diameter of the hollow fiber membrane is more preferably 50 μm or more, further preferably 100 μm or more, and particularly preferably 150 μm or more. Further, the inner diameter is more preferably 500 μm or less, further preferably 300 μm or less, and particularly preferably 250 μm or less.

[0055] Further, from the viewpoint of the relationship between the pressure loss of the fluid flowing in the hollow portion and the buckling pressure, the hollow ratio of the hollow fiber membrane is preferably 15 to 70%. The hollow ratio is more preferably 20% or more, and further preferably 25% or more. Further, the hollow ratio is more preferably 60% or less, further preferably 50% or less, and particularly preferably 40% or less.

[0056] Here, the hollow ratio is a value calculated by the following formula.

[0057] Hollow ratio (%) = 100 x [inner diameter (μm)] 2 / [outer diameter (μm)] 2 Figure 1 An example of an image obtained by photographing a cross section of the separation membrane cut in the thickness direction at a magnification of 10,000 times is shown in FIG. 1, and an image obtained by removing noise and binarizing the image of FIG. 1 is shown in FIG. 2. Figure 1 Figure 2 An image obtained by further extracting the outline of a void of 10 nm or more from the image of FIG. 1 to indicate the dense layer thickness is shown in FIG. 3. Figure 2 Figure 3 .

[0058] The method of adjusting the outer diameter, inner diameter, and hollow ratio of the hollow fibers in the hollow fiber membrane to the above ranges is not particularly limited, and can be adjusted, for example, by appropriately changing the draw ratio, which can be calculated by the shape of the discharge hole of the spinning nozzle for manufacturing the hollow fibers or the winding speed / discharge speed.

[0059] (Average pore diameter converted from NKP curve) The average pore diameter converted from the NKP curve in the separation membrane of the present embodiment is important and is 0.10 to 1.00 nm. By the average pore diameter converted from the NKP curve being 0.10 nm or more, the permeability becomes good, and by being 1.00 nm or less, the low bleeding becomes good. The average pore diameter converted from the NKP curve is preferably 0.30 to 0.75 nm, more preferably 0.35 to 0.60 nm, and further preferably 0.40 to 0.55 nm. The average pore diameter converted from the NKP curve can be estimated by Normalized Knudsen-based Permeance (NKP) as described in the literature (Membrane. 2011, 383, 152-158.). The formula defined in the NKP is expressed by the following formula (1) based on He in the case where there is no large difference in activation energy of each gas species, according to the molecular dependence of the gas permeation coefficient at an arbitrary temperature of a certain point.

[0060] [Equation 1] [Equation 2] Here, P i is the gas permeation coefficient of the i component shown in formula (2), J is the flux of the gas, d is the membrane thickness, P H and P L are the partial pressures of the supply side and the permeation side of the gas, respectively. In addition, M i is the molecular weight of the i component, M He is the molecular weight of He, D p is the average pore diameter converted from the NKP curve, D i is the molecular diameter of the i component, and D He ​​Where is the molecular diameter of He, P i / P He The value can be replaced by the separation coefficient β(i / He) between component i and He, as described later. The type of gas used as component i is not limited as long as the activation energy is not significantly different; preferred gases include H2, O2, N2, and CH4. It should be noted that N2 is used in this embodiment for ease of gas availability and operability. Furthermore, the formula used in this calculation is only applicable to separation membranes without large pores on their outer surface, i.e., those whose surface pores are not confirmed in surface observations such as SEM.

[0061] (Porosity) In this embodiment, the separation membrane is preferably composed of a porosity of 40% to 70%. A porosity of 40% or higher results in good permeability, while a porosity of 70% or lower results in good membrane strength. The porosity is preferably 45% to 60%, and particularly preferably 53% to 60%. To obtain a porosity within this range, it is preferable to use a structure with thermally induced phase separation, as described later. It should be noted that the porosity in this embodiment refers to the overall porosity of the separation membrane, and the specific method for measuring the porosity is detailed in the examples.

[0062] (Pore structure of the separation membrane) The most important aspect of the separation membrane in this embodiment is its average pore size D. i The coefficient of variation α i The values ​​are all between 0 and 150%. Average pore size D i This refers to the average pore size of region i when a surface of the separation membrane is divided into five equally spaced regions along its thickness direction, designated as regions 1 to 5. Average pore size D i The following method can be used: stress is applied to the separation membrane that has been fully cooled in liquid nitrogen (using a razor, slicer, or wide ion beam as needed) to expose a cross section (hereinafter referred to as "cross section") that is perpendicular to the length direction of the separation membrane and parallel to the thickness direction of the membrane, or a cross section (hereinafter referred to as "longitudinal section") that is parallel to the length direction of the separation membrane and parallel to the thickness direction of the membrane. The resulting image is then observed using a scanning electron microscope (SEM). After binarizing the image in the image analysis software "ImageJ", only pores with an average diameter greater than 10 nm are extracted.

[0063] It should be noted that when the separation membrane is a hollow fiber membrane, the cross-section and radial section of the hollow fiber membrane have the same meaning. Furthermore, the length direction of the hollow fiber membrane refers to the direction perpendicular to its width direction. Conversely, the width direction of the hollow fiber membrane refers to the direction parallel to its radial direction; the width direction can be considered as the direction parallel to the hollow surface, i.e., the in-plane direction of the hollow surface. Therefore, the length direction of the hollow fiber membrane can be considered as the direction perpendicular to the hollow surface.

[0064] The observation region is: when the cross section or longitudinal section is observed using the SEM, 5 regions obtained by dividing the thickness direction in equal intervals 5 times with each surface of the separation membrane as the end. Coefficient of variation α i is a value obtained by dividing the standard deviation of the pore diameter of the observation region i by the arithmetic mean of the pore diameter and multiplying by 100. When the coefficient of variation is 0 to 150%, the pore diameter in the region is uniform, and thus liquid leakage in a local portion due to a large pore can be suppressed, and both permeability and low leakage can be achieved. The coefficient of variation α i is preferably 0 to 120%, more preferably 0 to 100%, and further preferably 0 to 80%. Average pore diameter D i is preferably 100 to 1000 nm. By the average pore diameter D i being 100 nm or more, permeability becomes good, and by being 1000 nm or less, the strength of the separation membrane becomes good. The average pore diameter D i is preferably 120 to 800 nm, more preferably 150 to 600 nm, further preferably 170 to 400 nm, and particularly preferably 200 to 300 nm. The average pore diameter D i The measurement method of the average pore diameter D

[0065] In addition, the separation membrane of the present embodiment preferably has the aforementioned average pore diameter D i satisfies the requirements of (a) or (b) below.

[0066] (a) D1 ≥ D2 ≥ D3 ≥ D4 ≥ D5 (b) D5 ≥ D4 ≥ D3 ≥ D2 ≥ D1 by the average pore diameter D i satisfies the requirements of (a) or (b), that is, is larger or smaller in a stepwise manner toward either surface, and thus separation can be uniformly performed, liquid leakage in a local portion due to a large pore can be suppressed, and both permeability and low leakage can be achieved.

[0067] (Dense layer of separation membrane) The separation membrane of the present embodiment preferably has a dense layer in at least one surface layer. In the case of a hollow fiber membrane, the dense layer can be located on the outer surface side of the hollow fiber membrane, can be located on the inner surface side, or can be located on both the outer surface and the inner surface, but the aforementioned average pore diameter D i satisfies (a) D1 ≥ D2 ≥ D3 ≥ D4 ≥ D5, the separation membrane preferably has a dense layer on the surface of D5, and the average pore diameter D i satisfies (b) D5 ≥ D4 ≥ D3 ≥ D2 ≥ D1, the separation membrane preferably has a dense layer on the surface of D1. By the average pore diameter D iWhen (a) is satisfied, the separation membrane has a dense layer on the surface at D5, and when (b) is satisfied, the separation membrane has a dense layer on the surface at D1, whereby defects in the dense layer can be inhibited, and low leakage can be achieved. In addition, when the separation membrane is in the shape of a hollow fiber, it is more preferable to have a dense layer on the outer surface of the separation membrane. By having a dense layer on the outer surface of the separation membrane, the effective membrane area per unit volume of the module can be increased.

[0068] The dense layer refers to a portion up to the first time a hole of more than 10 nm is reached when a straight line is drawn perpendicularly to the outer surface from any point on the outer surface of the separation membrane toward the inner surface side or from the inner surface toward the outer surface, when observed at a magnification of 10,000 times using a scanning electron microscope (SEM). This can be obtained, for example, by applying stress to a separation membrane that has been sufficiently cooled in liquid nitrogen (using a razor or microtome or wide ion beam as necessary), observing the cross section or longitudinal section of the separation membrane using a scanning electron microscope (SEM), binarizing the resulting image in image analysis software "ImageJ", extracting only holes of more than 10 nm, drawing a straight line perpendicularly from the outer surface, and measuring the distance up to the hole. The specific measurement method is described in detail in the examples.

[0069] The thickness of the dense layer is preferably 0.1 to 2.0 μm. By having a thickness of the dense layer of 0.1 μm or more, the low leakage becomes good, and by having a thickness of 2.0 μm or less, the permeability becomes good.

[0070] The thickness of the dense layer is more preferably 0.1 to 1.5 μm. Furthermore, the thickness of the dense layer is further preferably 0.1 to 1.0 μm, and particularly preferably 0.1 to 0.4 μm.

[0071] (Large voids of more than 10 μm in the support layer) The separation membrane of the present embodiment preferably has 3 or less voids of 10 μm or more in the support layer. The support layer refers to a layer obtained by removing the dense layer from the separation membrane, and has a plurality of voids. The voids refer to recesses of 10 nm or more in diameter when the support layer in the cross section or longitudinal section of the separation membrane is observed at a magnification of 2,000 times using a scanning electron microscope (hereinafter, "SEM"). Further, the plurality of voids refer to 10 or more voids per 1 field of view when the support layer in the cross section or longitudinal section is observed at a magnification of 2,000 times using a SEM. By having 3 or less voids of 10 μm or more in the support layer, the strength of the separation membrane becomes good. The number of voids of 10 μm or more in the support layer can be obtained by applying stress to the separation membrane sufficiently cooled in liquid nitrogen (using a razor, microtome, or wide ion beam as necessary), observing the cross section or longitudinal section using a scanning electron microscope (SEM), and extracting only the pores having an average diameter of 10 μm or more after binarizing the obtained image in image analysis software "ImageJ". The voids of 10 μm or more in the support layer are more preferably 2 or less, further preferably 1 or less, and particularly preferably 0. The method for measuring the voids of 10 μm or more in the support layer is described in detail in the examples.

[0072] (Average open area ratio of cross section) The average open area ratio of cross section of the present embodiment is preferably 25 to 50%. The average open area ratio of cross section can be calculated by exposing the cross section or longitudinal section after applying stress to the separation membrane sufficiently cooled in liquid nitrogen (using a razor, microtome, or wide ion beam as necessary), observing using a scanning electron microscope (SEM), and calculating the proportion of the area of pores having an average diameter of 10 nm or more with respect to the field of view area after binarizing the obtained image in image analysis software "ImageJ". By having an average open area ratio of cross section of 25% or more, the permeability becomes good, and by having an average open area ratio of cross section of 50% or less, the strength of the separation membrane becomes good. The average open area ratio of cross section is preferably 30 to 45%, and further preferably 35 to 40%. Note that the specific method for measuring the average open area ratio of cross section is described in detail in the examples.

[0073] (Gas permeation performance) The separation membrane of the present embodiment preferably has a N2 permeation performance of 5 to 400 GPU at a pressure difference of 100 kPa and at 37°C. The pressure difference of 100 kPa means that the pressure difference between the gas supply side and the gas permeation side of the separation membrane is 100 kPa. The higher the gas permeation performance, the higher the separation efficiency per unit area, and therefore the lower limit of the N2 permeation performance is preferably 5 GPU or more, more preferably 10 GPU or more, further preferably 20 GPU or more, still further preferably 30 GPU or more, and particularly preferably 40 GPU or more. On the other hand, the upper limit of the N2 permeation performance is preferably 400 GPU or less, more preferably 300 GPU or less, further preferably 250 GPU or less, still further preferably 200 GPU or less, and particularly preferably 150 GPU or less. When the N2 permeation performance is within the above range, the pores or defects present in the dense layer are reduced, and such a separation membrane can have more excellent low bleeding properties. The method for calculating the N2 permeation performance is described in detail in the Examples.

[0074] (Separation factor β (CO2 / N2)) The dense layer of the present embodiment is non-porous, and therefore has a very long bleeding time, and since it is non-porous, the permeation of the gas occurs by the dissolution-diffusion mechanism. On the other hand, the porous structure has through-pores, and therefore has a short bleeding time, and the gas permeates by Knudsen diffusion. That is, the density of the dense layer can be evaluated by the separation factor of the gas, and the membrane having a high density tends to have a long bleeding time.

[0075] Generally, the permeation in a polymer membrane depends on the pore size in the membrane. In a membrane in which the maximum pore diameter of the dense layer is 3 nm or less, the gas permeates by the dissolution-diffusion mechanism. At this time, the separation factor β, which represents the ratio of the permeation coefficients P or the permeation flux Q of the two gases, depends only on the polymer material, and not on the thickness of the dense layer. Therefore, for example, the gas separation factor β (CO2 / N2) for CO2 and N2 can be represented by P(CO2) / P(N2) or Q(CO2) / Q(N2). In commonly used polymers, at least one or more β (CO2 / N2) values are produced.

[0076] On the other hand, in a porous membrane having pores of 3 nm to 10 μm in size, the gas permeates mainly by "Knudsen diffusion". At this time, the gas separation factor β is obtained from the square root of the ratio of the molecular weights of the gases. Therefore, β (CO2 / N2) is √28 / 44 = 0.80. If it is Knudsen diffusion, there is a risk of bleeding, and β (CO2 / N2) is preferably 1 or more, since the risk of bleeding is lower.

[0077] When a gas permeates a membrane having a dense layer with a microporous support structure and defects, the apparent permeation flow rate increases on one hand, but the gas separation factor decreases on the other hand. The defects referred to here are pores of 3 nm or more in size in the surface of the dense layer. Therefore, the presence or absence of pores and defects in the dense layer of the membrane of the present embodiment can be read by measuring the gas separation factor β (CO2 / N2) of CO2 and N2. When the gas separation factor β (CO2 / N2) is less than 1, the membrane has a plurality of pores or defects in the dense layer. When a plurality of pores or defects are present in the dense layer, premature liquid leakage or plasma leakage occurs, and the membrane is not suitable for long-term use. Also, such a membrane cannot be used for use in a gas separation region. In contrast, when the gas separation factor β (CO2 / N2) is 1.0 or more, the membrane has low leakage properties. In particular, in the case of a thin membrane in which the thickness of the dense layer is 0.1 to 2.0 μm as described above, the separation factor β (CO2 / N2) is 5.0 or more, and the low leakage properties are good.

[0078] In order to maintain high gas permeation properties and have low leakage properties, the gas separation factor β (CO2 / N2) of the membrane of the present embodiment is preferably 5.0 to 100.0. The lower limit of the gas separation factor β (CO2 / N2) is preferably 5.0 or more, more preferably 7.0 or more, further preferably 8.0 or more, still further preferably 9.0 or more, particularly preferably 10.0 or more. On the other hand, the upper limit of the gas separation factor β (CO2 / N2) is preferably 100.0 or less, more preferably 50.0 or less, further preferably 30.0 or less, still further preferably 20.0 or less, particularly preferably 15.0 or less. When the gas separation factor β (CO2 / N2) is the above upper limit or less, the dense layer has a moderate micropore, and such a separation membrane can maintain excellent low leakage properties and have high gas permeation properties. The specific measurement method of the gas separation factor β (CO2 / N2) is described in detail in the Examples.

[0079] Note that in the present specification, the gas separation factor β (CO2 / N2) is also referred to as "separation factor β (CO2 / N2)".

[0080] (Method for producing separation membrane) The method for producing a separation membrane of the present embodiment has (1) to (2) described below.

[0081] (1) Preparation step: melt-kneading a mixture containing 10 mass% or more and 50 mass% or less of poly(4-methyl-l-pentene) and 50 mass% or more and 90 mass% or less of a plasticizer, to obtain a resin composition; (2) Molding process: The aforementioned resin composition is discharged from the spinneret, and after the volatile plasticizer is discharged at a wind speed of 8-20 m / s, it is impregnated with a distance Ra of 5.0 MPa relative to the solubility parameter of poly(4-methyl-1-pentene). 1 / 2 Above and 18MPa 1 / 2 The following range, and the distance from Rb relative to the solubility parameter of the aforementioned plasticizer, is 1.0 MPa. 1 / 2 Above and 2.9MPa 1 / 2 Below or 6.5MPa 1 / 2 Above and 10.0 MPa 1 / 2 The following range of solvents are used for winding in a cooling bath.

[0082] Next, taking the case where the separation membrane is a hollow fiber membrane as an example, the method for manufacturing the separation membrane of this embodiment will be specifically described.

[0083] (Preparation process) In the preparation step of obtaining the resin composition for manufacturing the separation membrane of this embodiment, a mixture comprising 10 to 50% by mass of PMP and 50 to 90% by mass of plasticizer is melt-blended. The mixture preferably comprises 15 to 50% by mass of PMP and 50 to 85% by mass of plasticizer, more preferably 20 to 45% by mass of PMP and 55 to 80% by mass of plasticizer, and particularly preferably 25 to 40% by mass of PMP and 60 to 75% by mass of plasticizer.

[0084] For the apparatus used in the melt mixing of the mixture, kneaders, roller mills, Banbury mixers, or single-screw or twin-screw extruders can be used. Among these, a twin-screw extruder is preferred from the viewpoint of achieving good uniform dispersion of the plasticizer, and a twin-screw extruder with venting holes is more preferred from the viewpoint of removing moisture, low molecular weight substances, and other volatiles. Furthermore, a twin-screw extruder with a screw having a kneading disc is preferred from the viewpoint of improving mixing strength and achieving good uniform dispersion of the plasticizer.

[0085] The resin composition obtained in the preparation process can be temporarily granulated and then remelted for melt film formation, or it can be directly introduced into the spinneret for melt film formation. When temporarily granulating, it is preferable to use a resin composition in which the granules are dried to a moisture content of 200 ppm (by mass) or less. By keeping the moisture content below 200 ppm (by mass), resin degradation can be suppressed.

[0086] (Forming process) In the forming process of the hollow fiber membrane, a hollow fiber membrane is obtained from a molten mixture of the PMP and the plasticizer, i.e., the resin composition, by phase separation. Specifically, it is a process of discharging the resin composition obtained in the preparation process from a discharge spinneret having, for example, a double ring-shaped nozzle having a gas flow path provided in the central portion to a gas atmosphere, introducing into a cooling bath to cause phase separation of the resin composition, and obtaining a resin formed product.

[0087] As a specific method, the above-described resin composition in a molten state is discharged from a tube outside a double ring-shaped nozzle for spinning, and a hollow portion forming gas is discharged from a ring inside the double tube spinneret. Then, the discharged resin composition is moved in a gas atmosphere and then cooled and solidified in a cooling bath, whereby a resin formed product is obtained.

[0088] Here, the cooling bath for cooling the resin composition discharged from the discharge spinneret is described. The solvent of the cooling bath is important in terms of the affinity to the PMP and the plasticizer. As the solvent of the cooling bath, it is important to use a solvent having a solubility parameter distance Ra of 5.0 to 18.0 MPa 1 / 2 and a solubility parameter distance Rb of 1.0 to 2.9 MPa 1 / 2 or 6.5 to 10.0 MPa 1 / 2 with respect to the PMP and the plasticizer, respectively, in the cooling bath. By Ra and Rb being in the aforementioned ranges, the size of the micropores in the dense layer can be controlled, and high permeability and low bleeding can be taken into account. As a reason therefor, it is presumed that by making Ra be in the range of 5.0 to 18.0 MPa 1 / 2 , solidification occurs before crystallization of the PMP, and by making Rb be in the range of 1.0 to 2.9 or 6.5 to 10.0 MPa 1 / 2 , exchange of the solvent with the plasticizer proceeds at an appropriate speed, whereby a coarse pore, which is a main cause of bleeding as a liquid, can be suppressed, and a micropore through which only a gas can pass is formed. More preferably, a solvent having Ra in the range of 5.0 to 7.0 MPa 1 / 2 and Rb in the range of 6.5 to 10.0 MPa 1 / 2 is used in the cooling bath.

[0089] The affinity of the PMP to the solvent can be estimated by the three-dimensional Hansen solubility parameter as described in the literature (Ind. Eng. Chem. Res. 2011, 50, 3798-3817.). Specifically, the smaller the solubility parameter distance (Ra) of the following formula (3), the higher the affinity of the solvent to the PMP.

[0090] [Formula 3] Here, δ Ad , δAp and δ Ah are the dispersion term, the polar term and the hydrogen bond term of the solubility parameter of the PMP, δ Cd , δ Cp and δ Ch are the dispersion term, the polar term and the hydrogen bond term of the solubility parameter of the solvent.

[0091] The affinity of the plasticizer to the cooling solvent can also be estimated in the same manner. Specifically, the smaller the solubility parameter distance (Rb) of the following formula (4) is, the higher the affinity of the solvent to the plasticizer is.

[0092] [Num 4] Here, δ Bd , δ Bp and δ Bh are the dispersion term, the polar term and the hydrogen bond term of the solubility parameter of the PMP, δ Cd , δ Cp and δ Ch are the dispersion term, the polar term and the hydrogen bond term of the solubility parameter of the solvent.

[0093] When the solvent is a mixed solvent, the solubility parameter (δ Mixture ) of the mixed solvent can be obtained by the following formula (5).

[0094] [Num 5] Here, φ i , δ i are the volume fraction and the solubility parameter of the component i, respectively, in the dispersion term, the polar term and the hydrogen bond term. Here, the "volume fraction of the component i" means the ratio of the volume of the component i before mixing to the sum of the volumes of all the components before mixing. The three-dimensional Hansen solubility parameter of the solvent was used as the value described in the literature (Ind. Eng. Chem. Res. 2011, 50, 3798-3817.). For the solvents for which the solubility parameter was not described, the value described in the software "Hansen Solubility Parameter in Practice" developed by Charls Hansen et al. was used. The three-dimensional Hansen solubility parameter of the solvents and the polymers for which the solubility parameter was not described in the above software can be calculated by using the Hansen sphere method of the above software.

[0095] In the production method of the separation membrane of the present embodiment, as the solvent in the cooling bath used in the shaping step, when dibutyl phthalate is used as the plasticizer, cyclohexanone, diethyl phthalate, isophorone, dihexyl phthalate, Benzoflex (Benzoflex (registered trademark)) manufactured by Eastman, diisopropyl phthalate, dimethyl phthalate, fatty acid methyl ester, n-butyl acetate, n-pentyl acetate, triacetin, N,N-dimethylacetamide, butyl diglycol acetate, acetyl triethyl citrate, n-propyl acetate, dipropylene glycol mono-n-butyl ether, diethylene glycol mono-butyl ether, t-butyl acetate, 3-ethoxypropyl acetate, propylene glycol mono-methyl ether acetate, diacetone alcohol, isoamyl acetate, tri-n-butyl citrate, Solvesso (registered trademark) 100 manufactured by Exxon Mobil, isobutyl isobutyrate, ε-caprolactone, propylene glycol phenyl ether, isopropyl acetate, sec-butyl acetate, propylene glycol mono-butyl ether, TEXANOL, Solvesso 150, ethyl benzene, γ-butyrolactone, tetrahydrofurfuryl alcohol, N,N-dimethylformamide, dipropylene glycol methyl ether, dipropylene glycol methyl ether, propylene glycol mono-methyl ether, triethyl citrate, methyl carbitol, ethyl lactate, ethylene glycol mono-butyl ether, cyclohexane, methylcyclohexane, dimethylcyclohexane, benzyl alcohol, dimethyl sulfoxide are preferable, and triacetin is more preferable because Raand Rbare in the more preferable range described above.

[0096] Further, the cooling bath used is preferably 15 to 45°C. By being 15°C or higher, a sharp change in temperature is inhibited, winding is stabilized, and variation in fiber shape is reduced. On the other hand, by being 45°C or lower, excessive crystallization is inhibited, and permeability becomes good. The temperature of the cooling bath is preferably 15 to 40°C, and more preferably 25 to 35°C.

[0097] Further, the resin composition discharged from the discharge spinneret is important in that at least one of its surfaces, preferably the surface on which the dense layer is to be formed, is subjected to air blowing at a wind speed of 8 to 20 m / s to promote evaporation of the plasticizer before cooling in the cooling bath. By air blowing at a wind speed of 8 m / s or higher, the plasticizer that has evaporated is rapidly air blown, so that the plasticizer can be inhibited from liquefying to become a cause of defects in the case of adhering to the surface of the membrane, and a dense layer having moderate micropores can be formed when cooled in the aforementioned cooling bath. On the other hand, by being 20 m / s or lower, yarn breakage caused by shaking of the resin composition is inhibited. The air blowing wind speed is preferably 8 to 17 m / s, and more preferably 10 to 14 m / s. Further, the gas used in the gaseous atmosphere of the air blowing portion is not particularly limited, and air or nitrogen is preferably used. The gaseous atmosphere generally has a temperature lower than the temperature of the discharge spinneret.

[0098] Further, the resin composition discharged from the discharge spinneret is preferably introduced into the cooling bath after passing through a dead space of 30 to 80 mm in distance from the spinneret plane to the solvent plane. By passing through the dead space of 30 to 80 mm, the dense layer thickness becomes good. Note that the dead space refers to the space from the spinneret plane to the solvent plane of the cooling bath. Note that the "distance from the spinneret plane to the solvent plane" is sometimes referred to as "dead space distance" in this specification.

[0099] The dead space distance is preferably 30 to 70 mm, more preferably 35 to 60 mm, and particularly preferably 40 to 50 mm.

[0100] In the forming step for producing the separation membrane of the present embodiment, the resin composition discharged from the discharge spinneret is wound by a winding device. At this time, the value of the draw ratio calculated based on the winding device (winding speed) / (discharge speed from the discharge spinneret) is preferably 3.0 to 20.0. By the draw ratio being 3.0 or more, the winding is stabilized, and the variation in fiber shape becomes small. By setting the draw ratio to 20.0 or less, excessive stretching of the resin composition discharged from the spinneret can be suppressed, and leakage due to defects in the dense layer can be suppressed. The draw ratio is preferably 3.0 to 10.0, and more preferably 4.5 to 8.0.

[0101] (Washing Step) By immersing the resin composition thus obtained in a solvent that does not dissolve the polymer but can mix with the plasticizer, the porosity can be improved by a process of dissolving out the plasticizer. At this time, by using a solvent or a mixed solvent that has moderate affinity with the plasticizer, good solvent exchange can be performed, and the washing efficiency can be improved. The solvent that does not dissolve the polymer but can mix with the plasticizer is not particularly limited, and as specific examples, methanol, ethanol, isopropanol, and acetone can be preferably used.

[0102] (Drying Step) In order to remove the adhering solvent by the washing step, the resin composition after the washing step is preferably subjected to a drying step. Drying is preferably performed at a temperature at which the above solvent that does not dissolve the polymer but can mix with the plasticizer can be vaporized and removed, and is particularly preferably performed at room temperature to 150°C.

[0103] In this way, the separation membrane of the present embodiment, which has PMP as the main component, can be produced.

[0104] (Assembly) The separation membrane of the present embodiment obtained as described above can be made into a membrane module as at least one of a degassing and a gas injection by a method known in the art. For example, a hollow fiber membrane module has a plurality of hollow fiber membranes and a cylindrical housing. The plurality of hollow fiber membranes are bundled and inserted into the cylindrical housing, and then the end portions thereof are fixed to the housing and sealed with a thermosetting resin such as polyurethane or epoxy resin. The end portions of the hollow fiber membranes cured with the thermosetting resin are cut, whereby the opening faces of the hollow fiber membranes are obtained, and thus the module is produced.

[0105] It should be noted that the liquid as a processing target of the "membrane module as at least one of a degassing and a gas injection" of the present embodiment is water, an organic solvent, and a mixture thereof, and blood is not a target. The liquid can contain a hydrocarbon solvent.

[0106] The liquid can be at least one selected from the group consisting of glycols, glycol monoalkyl ethers, glycol dialkyl ethers, glycol monoacetates, glycol diacetates, alcohols, ketones, acetates, lactates, saturated hydrocarbons, unsaturated hydrocarbons, cyclic saturated hydrocarbons, cyclic unsaturated hydrocarbons, aromatic hydrocarbons, terpenes, ethers, cyclic imides, 3-alkyl-2-oxazolidinones, N-alkylpyrrolidinones, lactones, and nitrogen-containing solvents.

[0107] The liquid can also be a UV ink or a ceramic ink.

[0108] (An apparatus as at least one of a degassing and a gas injection) Using the separation membrane of the present embodiment, it is also possible to provide an apparatus as at least one of a degassing and a gas injection, which is provided with the membrane module as at least one of a degassing and a gas injection of the present embodiment using the separation membrane of the present embodiment.

[0109] (A method for producing a liquid) It is also possible to provide a method for producing a liquid, which includes at least one of removing a dissolved gas and imparting a gas using an apparatus as at least one of a degassing and a gas injection, the apparatus being provided with the membrane module as at least one of a degassing and a gas injection of the present embodiment using the separation membrane of the present embodiment. Examples

[0110] The following examples further illustrate the present application, but the present application is not limited to any of them.

[0111] [Measurement and evaluation method] Each property value in the examples was obtained by the following method.

[0112] (1) Outer diameter and inner diameter of the hollow fiber membrane (μm) After the hollow fiber membrane was frozen with liquid nitrogen, stress was applied (a razor or microtome was used as needed), the exposed radial cross section was observed with an optical microscope, and the average of the outer diameter and inner diameter of 10 randomly selected locations were set as the outer diameter and inner diameter of the hollow fiber membrane, respectively.

[0113] (2) Hollow ratio (%) of the hollow fiber membrane The hollow ratio of the hollow fiber membrane was calculated from the outer diameter and inner diameter obtained from the above (1) by the following equation.

[0114] Hollow ratio (%) = 100 x [inner diameter (μm)] 2 / [outer diameter (μm)] 2 .

[0115] (3) Gas permeation performance (GPU) A small module including 3 hollow fiber membranes with an effective length of 100 mm was prepared. Specifically, 3 hollow fiber membranes were bundled, inserted into a plastic tube as a cylindrical housing, and then, in the end portions of the bundle of hollow fiber membranes, the gaps between the membranes and the gaps with the tube were cured and sealed with a thermosetting resin. An opening surface of the hollow fiber membrane was obtained by cutting the end portions of the sealed hollow fiber membranes, thereby preparing a small module for evaluation. Using this small module, the gas permeation flow rate was measured. As the measurement gas, carbon dioxide, nitrogen, and helium were used individually for evaluation, and according to the pressure sensor method of JIS K7126-1 (2006), the pressure change on the permeation side per unit time of carbon dioxide or nitrogen or helium was measured by the outside pressure method. Here, the pressure difference between the supply side and the permeation side was set to 100 kPa. A pressure difference (pressure differential) of 100 kPa indicates that the pressure difference between the gas supply side and the gas permeation side of the separation membrane is 100 kPa. The temperature of the gas was set to 37°C.

[0116] Next, the gas permeation flow rate Q was calculated by the following equation (6), and the value was set as the gas permeation performance. Here, as described above, J is the flow of the gas, P H and P L are the partial pressures of the supply side and the permeation side of the gas, respectively. GPU is a general unit indicating the gas permeation flow rate Q, 1 GPU = 3.35 x 10 -10 mol / m 2 ・s・Pa. In addition, the ratio of the gas permeation flow rate Q of each component was set as the separation coefficient β. The membrane area was calculated from the outer diameter and length of the region contributing to gas permeation.

[0117] [Equation 6] .

[0118] (4) Average pore diameter (nm) converted from the NKP curve The gas permeation properties of N2and He were calculated by the method of the above (3), and the separation factor β (N2 / He) as a ratio thereof was calculated. This value was substituted into the above formula (1) to calculate the average pore diameter. Note that in the formula used in this calculation, when the separation factor β (N2 / He) is low, specifically when β (N2 / He) is 2.7 or less, the solution does not converge, and thus it was determined that the average pore diameter could not be measured.

[0119] (5) Dense layer thickness (μm) The separation membrane was frozen with liquid nitrogen, and then cut to expose the radial cross section by applying stress (using a razor or a microtome or a wide ion beam as necessary). Next, the radial cross section was subjected to pretreatment by sputtering with platinum under the following conditions, and then observed at a magnification of 10,000 times using an SEM. In this case, when a straight line perpendicular to the outer surface was drawn from an arbitrary point on the outer surface of the separation membrane toward the inner surface side, the length until the first pore of 10 nm or more was reached was defined as the dense layer thickness. The extraction of the pores was performed after binarizing the analysis image in the image analysis software "ImageJ". Binarization was performed as follows. That is, when a pixel number distribution in which the horizontal axis represents the brightness in the analysis image and the vertical axis represents the number of pixels for the corresponding brightness was obtained, the number of pixels for the highest brightness was defined as A, and binarization was performed using the point with a lower brightness among the two points of brightness corresponding to (1 / 2) x A. Further, for the obtained binarized image, noise removal (corresponding to Despeckle in ImageJ) was performed once by replacing all the pixels with the central value of 3 x 3 pixels around the pixels, and the obtained image was used as the analysis image. A line perpendicular to the outer surface was drawn from an arbitrary point on the outer surface of the obtained image toward the inner surface side, and the length until the first pore of 10 nm or more was reached was calculated. Note that the measurement was performed for 10 arbitrary points, and the average value was used as the dense layer thickness.

[0120] (Sputtering) Apparatus: Hitachi High-Technology Co., Ltd. (E-1010) Deposition time: 40 seconds Current value: 20 mA.

[0121] (SEM) Apparatus: Hitachi High-Technology Co., Ltd. (SU1510) Acceleration voltage: 5 kV Probe current: 30 pA.

[0122] (6) Void of 10 μm or more in the support layer The separation membrane was frozen with liquid nitrogen and then cut to expose the radial cross section by applying stress (using a razor or microtome or wide ion beam as needed). Next, the radial cross section was subjected to pretreatment by sputtering with platinum, and then the pores having a diameter of 10 μm or more, i.e., the area of the pores being 78.5 μm or more, were all extracted when the diameter was observed at a magnification of 2,000 times using SEM under the following conditions, and the number thereof was calculated to be the average pore diameter of the support layer. The extraction of the pores was performed after the analysis image was binarized (Huang's binarization) in the image analysis software "ImageJ". Further, for the obtained binarized image, noise removal was performed once by replacing all pixels with the central value of 3 x 3 pixels around the pixel (corresponding to Despeckle in ImageJ), and the obtained image was used as the analysis image. The extraction of the pores was performed by the Analyze Particles command of ImageJ, and the number of the obtained pores was calculated. It should be noted that the measurement was performed on any 5 places, and the average value thereof was used as the void of 10 μm or more in the support layer. 2

[0123] (Sputtering) Apparatus: Hitachi High-Technology Co., Ltd. (E-1010) Deposition time: 40 seconds Current value: 20 mA

[0124] (SEM) Apparatus: Hitachi High-Technology Co., Ltd. (SU1510) Acceleration voltage: 5 kV Probe current: 30 pA

[0125] (7) Void fraction (%) The fiber length L (mm) and the mass M (g) of the hollow fiber membrane which was vacuum-dried at 25°C for 8 hours were measured. The density p1 (g / mm 3 ) of the hollow fiber membrane was calculated using the values of the outer diameter (mm) and the inner diameter (mm) measured in the above (1) by the following equation.

[0126] p1 = M / [π x {(outer diameter / 2) 2 - (inner diameter / 2) 2} x L] Further, the void fraction ε (%) was calculated by the following equation.

[0127] ε = 1 - p1 / p2 Here, p2 is the density of the polymer.

[0128] (8) Average open porosity (%) of cross section ​The separation membrane was frozen with liquid nitrogen, and then cut to expose the radial cross section by applying stress (using a razor blade or a microtome or a wide ion beam as necessary). Next, in the case where the radial cross section was observed at a magnification of 10,000 times using SEM after pretreatment by sputtering with platinum, the proportion of the area of pores having an average diameter of more than 10 nm with respect to the field of view was calculated. The extraction of pores was performed after binarizing the analysis image (Huang's binarization) in the image analysis software "ImageJ". Further, for the resulting binarized image, noise removal (equivalent to Despeckle in ImageJ) was performed once by replacing all pixels with the central value of 3 x 3 pixels around the pixel, and the resulting image was used as the analysis image. The extraction of pores was performed by the Analyze Particles command of ImageJ, and the proportion of the total area of the resulting pores with respect to the field of view was calculated as the open porosity. Note that the measurement was performed on five arbitrary places, and the average value thereof was set as the average open porosity of the cross section.

[0129] (9) Average pore diameter D i (nm) The separation membrane was frozen with liquid nitrogen, and then cut to expose the radial cross section by applying stress (using a razor blade or a microtome or a wide ion beam as necessary). Next, in the case where the radial cross section was observed at a magnification of 10,000 times using SEM after pretreatment by sputtering with platinum under the following conditions, the average pore diameter was calculated from the average area of the resulting pores with respect to the field of view. The extraction of pores was performed after binarizing the analysis image (Huang's binarization) in the image analysis software "ImageJ". Further, for the resulting binarized image, noise removal (equivalent to Despeckle in ImageJ) was performed once by replacing all pixels with the central value of 3 x 3 pixels around the pixel, and the resulting image was used as the analysis image. The extraction of pores was performed by the Analyze Particles command of ImageJ, and the average pore diameter was calculated from the average area of the resulting pores. Note that the measurement was performed on five regions obtained by dividing the separation membrane into five equal intervals in the thickness direction with the respective surfaces of the separation membrane as the end portions, and the average pore diameter of each region was set as D1 to D5 in order from one side surface. In addition, for the above five regions, the coefficient of variation was calculated by dividing the standard deviation of the pore diameter by the arithmetic mean of the pore diameter and multiplying by 100.

[0130] [PMP] As the PMP, the following material was prepared.

[0131] PMP: TPX DX845 (density: 833 kg / m 3 , MFR: 9.0 g / 10 min).

[0132] [Other raw materials] Plasticizer: dibutyl phthalate

[0133] (Example 1) PMP 35 mass% and dibutyl phthalate 65 mass% were supplied to a twin-screw extruder, melt-kneaded at 290°C, and then introduced into a melt spinning set with a spinning temperature set to 245°C, and spun downward from the outer annular portion of a discharge spinneret having one spinneret hole (double circular tube type, discharge hole diameter 2.0 mm). The spun hollow fibers were introduced into a triacetin cooling bath at 30°C, and wound with a winder at a draw ratio of 5.0. At this time, the free span was set to 20 mm, and the period from discharge to the cooling bath was degassed at an air volume of 11 m / s. Here, as a filter within the melt spinning set, a metal filter with a diameter of 200 μm was used. The wound hollow fibers were immersed in isopropyl alcohol for 24 hours, and further vacuum-dried at room temperature to remove the isopropyl alcohol, and a hollow fiber membrane was obtained. The physical properties of the obtained hollow fiber membrane are shown in Tables 1 and 2. The average pore diameter converted from the NKP curve was 0.50 nm, the void fraction was 55%, the pore diameter variation coefficient α1 was 78%, α2 was 76%, α3 was 80%, α4 was 73%, and α5 was 96% in each region, and was 150% or less in all regions. In addition, the N2 permeation performance was 42 GPU, and the separation factor β (CO2 / N2) was 10.3, and the permeation performance was excellent and had low leakage.

[0134] (Example 2) A triacetin cooling bath was used, and otherwise the same as Example 1, and a hollow fiber membrane was obtained. As a result, as shown in Tables 1 and 2, the average pore diameter converted from the NKP curve was 0.90 nm, the void fraction was 42%, the pore diameter variation coefficient α1 was 122%, α2 was 128%, α3 was 112%, α4 was 133%, and α5 was 142% in each region, and was 150% or less in all regions. In addition, the N2 permeation performance was 38 GPU, and the separation factor β (CO2 / N2) was 5.2.

[0135] (Example 3) A γ-butyrolactone cooling bath was used, and otherwise the same as Example 1, and a hollow fiber membrane was obtained. As a result, as shown in Tables 1 and 2, the average pore diameter converted from the NKP curve was 0.56 nm, the void fraction was 48%, the pore diameter variation coefficient α1 was 63%, α2 was 75%, α3 was 75%, α4 was 91%, and α5 was 80% in each region, and was 150% or less in all regions. In addition, the N2 permeation performance was 47 GPU, and the separation factor β (CO2 / N2) was 7.7.

[0136] (Example 4) The cooling bath temperature was set to 41°C, and otherwise, the same as in Example 1 was performed to obtain a hollow fiber membrane. As a result, as described in Tables 1 and 2, the average pore diameter converted from the NKP curve was 0.36 nm, the void fraction was 47%, the pore diameter variation coefficients of the respective regions were 99% for al, 87% for a2, 84% for a3, 88% for a4, and 76% for a5, and were all 150% or less in all regions. In addition, the N2 permeance was 22 GPU, and the separation factor β (CO2 / N2) was 12.1.

[0137] (Example 5) The cooling bath temperature was set to 17°C, and otherwise, the same as in Example 1 was performed to obtain a hollow fiber membrane. As a result, as described in Tables 1 and 2, the average pore diameter converted from the NKP curve was 0.54 nm, the void fraction was 54%, the pore diameter variation coefficients of the respective regions were 92% for al, 76% for a2, 87% for a3, 96% for a4, and 85% for a5, and were all 150% or less in all regions. In addition, the N2 permeance was 39 GPU, and the separation factor β (CO2 / N2) was 10.2.

[0138] (Example 6) The PMP was set to 48 mass%, the dibutyl phthalate was set to 52 mass%, and the draw ratio was set to 18.0, and otherwise, the same as in Example 1 was performed to obtain a hollow fiber membrane. As a result, as described in Tables 1 and 2, the average pore diameter converted from the NKP curve was 0.29 nm, the void fraction was 42%, the pore diameter variation coefficients of the respective regions were 121% for al, 139% for a2, 102% for a3, 98% for a4, and 101% for a5, and were all 150% or less in all regions. In addition, the N2 permeance was 7 GPU, and the separation factor β (CO2 / N2) was 9.7.

[0139] (Example 7) The draw ratio was set to 3.5, and otherwise, the same as in Example 1 was performed to obtain a hollow fiber membrane. As a result, as described in Tables 1 and 2, the average pore diameter converted from the NKP curve was 0.59 nm, the void fraction was 47%, the pore diameter variation coefficients of the respective regions were 101% for al, 79% for a2, 108% for a3, 99% for a4, and 96% for a5, and were all 150% or less in all regions. In addition, the N2 permeance was 60 GPU, and the separation factor β (CO2 / N2) was 8.6.

[0140] (Example 8) The exhaust air volume was set to 18 m / s, and otherwise, the same as in Example 1 was performed to obtain a hollow fiber membrane. As a result, as described in Tables 3 and 4, the average pore diameter converted from the NKP curve was 0.47 nm, the void fraction was 54%, the pore diameter variation coefficient al was 78%, a2 was 66%, a3 was 106%, a4 was 86%, and a5 was 70% in each region, and was 150% or less in all regions. In addition, the N2 permeation performance was 31 GPU, and the separation factor β (CO2 / N2) was 10.4.

[0141] (Example 9) The cooling bath was set to benzyl alcohol, and otherwise, the same as in Example 1 was performed to obtain a hollow fiber membrane. As a result, as described in Tables 3 and 4, the average pore diameter converted from the NKP curve was 0.72 nm, the void fraction was 49%, the pore diameter variation coefficient al was 131%, a2 was 109%, a3 was 111%, a4 was 97%, and a5 was 86% in each region, and was 150% or less in all regions. In addition, the N2 permeation performance was 55 GPU, and the separation factor β (CO2 / N2) was 6.1.

[0142] (Example 10) The exhaust air volume was set to 8 m / s, and otherwise, the same as in Example 1 was performed to obtain a hollow fiber membrane. As a result, as described in Tables 3 and 4, the average pore diameter converted from the NKP curve was 0.76 nm, the void fraction was 56%, the pore diameter variation coefficient al was 75%, a2 was 77%, a3 was 82%, a4 was 81%, and a5 was 102% in each region, and was 150% or less in all regions. In addition, the N2 permeation performance was 128 GPU, and the separation factor β (CO2 / N2) was 5.3.

[0143] (Comparative Example 1) The exhaust air volume was set to 0 m / s, and the draw ratio was set to 231.0, and otherwise, the same as in Example 1 was performed to obtain a hollow fiber membrane. As a result, as described in Tables 3 and 4, the pore diameter variation coefficient al was 228%, and a4 was 178% in each region, and was 150% or more, and the separation factor β (CO2 / N2) was 1.2, which showed a low value.

[0144] (Comparative Example 2) The cooling bath was set to N-methylpyrrolidone, and otherwise, the same as in Example 1 was performed to obtain a hollow fiber membrane. As a result, as described in Tables 3 and 4, an open hole was confirmed on the membrane surface in the SEM, the pore diameter in the NKP curve could not be measured, and the separation factor β (CO2 / N2) was 0.8, which showed a low value.

[0145] (Comparative Example 3) The PMP was set to 100 mass%, the draw ratio was set to 700.0, spinning was performed, air cooling was performed at an exhaust air volume of 30 m / s, and otherwise, the same as in Example 1 was performed to obtain a hollow fiber membrane. As a result, as described in Tables 3 and 4, the void fraction was 18%, the N2 permeation performance was 3 GPU, and a low value was shown.

[0146] (Comparative Example 4) The PMP was set to 100 mass%, the draw ratio was set to 1000.0, spinning was performed, air cooling was performed at an exhaust air volume of 0 m / s, and otherwise, the same as in Example 1 was performed to obtain a hollow fiber membrane. As a result, as described in Tables 3 and 4, an opening was confirmed on the membrane surface in the SEM, the pore diameter in the NKP curve could not be measured, the separation factor β (CO2 / N2) was 0.9, and a low value was shown.

[0147] (Comparative Example 5) The PMP was set to 8 mass%, dibutyl phthalate was set to 92 mass%, and otherwise, the same as in Example 1 was performed, and as a result, spinning was not possible due to breakage of the yarn.

[0148] (Comparative Example 6) The exhaust air volume was set to 6 m / s, and otherwise, the same as in Example 1 was performed to obtain a hollow fiber membrane. As a result, as described in Tables 3 and 4, the average pore diameter converted from the NKP curve was 2.50 nm, which was 1.00 nm or more, the separation factor β (CO2 / N2) was 3.0, and a low value was shown.

[0149] [Table 1] .

[0150] [Table 2] .

[0151] [Table 3] .

[0152] [Table 4] .

[0153] The separation membranes obtained in Examples 1 to 10 had an average pore diameter converted from the NKP curve, a void fraction, and a pore diameter variation coefficient in each region that satisfied the requirements of the present application, the N2 permeation performance was 5 to 400 GPU, and the separation factor β (CO2 / N2) was 5.0 to 100.0, and both high permeation performance and low leakage were exhibited. On the other hand, the N2 permeation performance or the separation factor β (CO2 / N2) of the separation membranes of Comparative Examples 1 to 6, any one of which had an average pore diameter converted from the NKP curve, a void fraction, and a pore diameter variation coefficient in each region that did not satisfy the requirements of the present application, showed a value outside the above range.

[0154] It should be noted that in any one of Examples 1 to 10, the number of voids greater than 10 μm in the support layer is 0.

[0155] The application has been described in detail with particular reference to certain embodiments thereof, but it will be understood that variations and modifications will be evident to a person of ordinary skill in the art without departing from the spirit and scope of the application. It should be noted that the present application is based on Japanese Patent Application (Japanese Patent Application No. 2023-061160) filed on April 5, 2023, the entire contents of which are hereby incorporated by reference. In addition, all the references cited are incorporated herein by reference in their entirety.

[0156] Industrial applicability The separation membrane of the present application can be suitably used for the purpose of separating a gas from a liquid or imparting a gas to a liquid. For example, in a semiconductor production line, a liquid crystal color filter production line, and an ink manufacturing for an inkjet printer, etc., a degassing membrane for reducing the amount of dissolved gas in water, an aqueous solution, an organic solvent, a resist liquid, or the like, or a gas exchange membrane for a medical use such as an artificial lung, etc. can be suitably used. In particular, as a degassing membrane, it is very useful in the degassing of a photoresist liquid, a developer liquid, ultrapure water, etc. used in photolithography in a semiconductor production line.

Claims

1. A separation membrane, which is a separation membrane with poly(4-methyl-1-pentene) as the main component, wherein, The average pore size calculated from the NKP curve is 0.10–1.00 nm. The porosity is 40-70%. When the surface of the separation membrane is divided into five equally spaced regions along the thickness direction, designated as regions 1 to 5, the coefficient of variation α of the pore size of region i in all regions 1 to 5 is... i It ranges from 0% to 150%.

2. The separation membrane according to claim 1, wherein, In regions 1 to 5, the average aperture D of region i is... i If either (a) or (b) below is met, (a) D1≥D2≥D3≥D4≥D5 (b) D5≥D4≥D3≥D2≥D1.

3. The separation membrane according to claim 1 or 2, wherein, The average porosity of the cross-section of the separation membrane is 25-50%.

4. The separation membrane according to claim 2, wherein, In the separation membrane, the average pore size D i When requirement (a) is met, the surface of D5 has a dense layer, and the average pore size D i When the requirement of (b) is met, the surface of D1 has a dense layer.

5. The separation membrane according to claim 4, wherein, The thickness of the dense layer is in the range of 0.1 to 2.0 μm.

6. The separation membrane according to any one of claims 1 to 5, wherein, The ratio of CO2 permeation performance to N2 permeation performance (separation coefficient β(CO2 / N2)) of the separation membrane at a pressure difference of 100 kPa is 5.0 to 100.

0.

7. The separation membrane according to any one of claims 1 to 6, wherein, The separation membrane has an N2 permeability of 5–400 GPUs at a pressure difference of 100 kPa and a temperature of 37°C.

8. The separation membrane according to any one of claims 1 to 7, wherein, The separation membrane is in the shape of a hollow fiber.

9. The separation membrane according to claim 8, wherein, In regions 1 to 5, the average aperture D of region i is... i The surface of D5 has a dense layer when the following condition (a) is met, wherein the average pore size D i The surface of D1 has a dense layer when the following condition (b) is met. In the case that either (a) or (b) below is satisfied, the surface having the dense layer is the outer surface of the separation membrane in the shape of the hollow fiber. (a) D1≥D2≥D3≥D4≥D5 (b) D5≥D4≥D3≥D2≥D1.

10. A membrane assembly for at least one of degassing and gas injection, comprising a housing and a separation membrane according to any one of claims 1 to 9, wherein the separation membrane is filled in the housing.

11. An apparatus for at least one of degassing and gas injection, comprising a membrane module as described in claim 10 for at least one of degassing and gas injection.

12. A method of producing a liquid, comprising removing at least one of a dissolved gas and a gas-imposing device as described in claim 11 for degassing and gas injection.

13. A method for manufacturing a separation membrane, comprising the steps of (1) to (2) below, (1) Preparation process: A mixture containing more than 10% by mass and less than 50% by mass of poly(4-methyl-1-pentene) and more than 50% by mass and less than 90% by mass of plasticizer is melt-blended to obtain a resin composition; (2) Molding process: The resin composition is discharged from the spinneret, and after the volatile plasticizer is discharged at a wind speed of 8-20 m / s, it is impregnated with a distance Ra of 5.0 MPa relative to the solubility parameter of poly(4-methyl-1-pentene). 1 / 2 Above and 18MPa 1 / 2 The following range, and the distance from Rb relative to the solubility parameter of the plasticizer, is 1.0 MPa. 1 / 2 Above and 2.9MPa 1 / 2 Below or 6.5MPa 1 / 2 Above and 10.0 MPa 1 / 2 The following range of solvents are used for winding in a cooling bath.

14. The method for manufacturing the separation membrane according to claim 13, wherein, The cooling bath in the forming process is 15–45°C.

15. The method for manufacturing the separation membrane according to claim 13 or 14, wherein, The winding in the forming process has a draw ratio of 3.0 to 20.0.

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