Separation membrane, method for manufacturing a separation membrane, separation membrane module, apparatus equipped with a separation membrane module, and method for manufacturing a liquid or gas using the apparatus.

Abstract

The objective is to provide a separation membrane using poly(4-methyl-1-pentene) that maintains high gas permeability while also possessing leakage resistance. [Solution] The present invention relates to a separation membrane mainly composed of poly(4-methyl-1-pentene), comprising a surface layer and an inner layer, wherein the pore mode diameter Dp determined by mercury intrusion measurement is 100 to 230 nm, the value of the pore diameter distribution area W, determined by the mercury intrusion measurement and calculated by the following formula, is 1.50 to 10.00, and the porosity is 40 to 65%. W = |(D90 - D10) / D50| (In the formula, D10, D50, and D90 represent the pore diameter when the pore volume is 10% of the total pore volume, the pore diameter when the pore volume is 50% of the total pore volume, and the pore diameter when the pore volume is 90% of the total pore volume, respectively.)

Description

Technical Field

[0001] The present invention relates to a separation membrane, a method for producing the separation membrane, a separation membrane module, an apparatus equipped with the separation membrane module, and a method for producing a liquid or a gas using the apparatus.

Background Art

[0002] As a method for removing dissolved gas from a liquid, a method for injecting gas into a liquid, or a method for exchanging a dissolved gas in a liquid with a gas component in a gas phase, there is a method using a separation membrane. Since the separation membrane to be used is required to have leak resistance to the liquid and high gas permeability, poly(4-methyl-1-pentene), which is a kind of polyolefin, may be used as a membrane material having excellent properties in these respects.

[0003] Among such separation membranes, a heterogeneous membrane having a dense surface layer on the surface and a porous structure inner layer inside is desirable in that it has leak resistance for suppressing the intrusion of the liquid to be treated into the separation membrane and high gas permeability.

[0004] So far, various methods have been proposed to obtain a heterogeneous membrane made of polyolefin. For example, Patent Document 1 discloses a dry-wet solution method. Specifically, a polymer solution in which polyolefin is dissolved in a good solvent is extruded from a die at a temperature higher than the melting point of polyolefin, and this polymer solution is brought into contact with a cooling solvent. By thermally induced phase separation, a dense non-porous structure is formed on the surface and a porous structure is formed inside, and an integral asymmetric membrane is obtained.

[0005] Patent Document 2 discloses a multi-component melt spinning method. Specifically, a multi-cylindrical spinning nozzle is used to melt-combine a crystalline thermoplastic polymer and a second polymer in two layers, then the material is stretched to make only the layer consisting of the crystalline thermoplastic polymer porous. In other words, two types of polyolefins with different crystalline properties are co-extruded from the die at a temperature above their melting point, cooled and solidified, and then stretched to partially cleave only the highly crystalline component, forming a non-porous structure on the surface and a porous structure inside.

[0006] Patent Document 3 discloses a single-component melt spinning method. Specifically, it is a method for producing a heterogeneous film in which a crystalline thermoplastic polymer is extruded into the gas from a hollow fiber nozzle using gas as a core to melt spin it into a hollow fiber, and then stretched to form a non-porous layer on at least one surface of the hollow fiber and a porous structure on the other parts. In this method, a gas with a higher oxygen concentration than air is brought into contact with at least one surface of the molten hollow fiber precursor extruded from the hollow fiber nozzle. This differs from Patent Document 2 in that instead of using a component with a low degree of crystallinity as the surface layer component, the molten polyolefin is oxidized and decomposed. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japan Special Publication No. 2002-535114 [Patent Document 2] Japanese Patent Publication No. 7-116483 [Patent Document 3] Japanese Patent Publication No. 7-155569 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, even when using heterogeneous membranes, there was a problem in that if the separation membrane was used for a long time, the liquid to be processed would pass through the surface layer and penetrate into the inner layer of the separation membrane, eventually leaking into the gas-side channel and degrading the performance of the separation membrane module.

[0009] According to our findings, for separation membranes used in degassing, gas injection, and gas exchange to have high leakage resistance, a dense surface layer alone is insufficient; it is important to form an inner layer with an appropriate pore size. However, if the inner layer is made dense and has a low porosity to achieve high leakage resistance, gas permeability tends to decrease.

[0010] The membrane described in Patent Document 1 has high gas permeability, but because the pore structure of the inner layer grows significantly during the phase separation process, once the liquid to be treated penetrates the inner layer, the liquid easily leaks into the gas channel through these pores, leaving room for further improvement in leak resistance. On the other hand, the separation membranes described in Patent Documents 2 and 3 have a denser inner layer structure which is advantageous for leak resistance, but they have a low porosity and insufficient gas permeability.

[0011] Thus, although poly(4-methyl-1-pentene) is a material with excellent gas permeability, conventional separation membranes have not been able to achieve both high gas permeability and leakage resistance because the pore size of the inner layer is not appropriate.

[0012] Based on the above, the problem that the present invention aims to solve is to provide a separation membrane that uses poly(4-methyl-1-pentene) to maintain high gas permeability while also being leak-resistant. [Means for solving the problem]

[0013] The present invention aims to solve the above-mentioned problems, and according to the present invention, the following invention is provided. In this specification, "~" means that the numerical values ​​written before and after it are included as the lower limit and upper limit. [1] A separation membrane mainly composed of poly(4-methyl-1-pentene), comprising a surface layer and an inner layer, wherein the pore mode diameter Dp determined by mercury intrusion measurement is 100 to 230 nm, the value of the pore diameter distribution area W, determined by the mercury intrusion measurement and calculated by the following formula, is 1.50 to 10.00, and the porosity is 40 to 65%. W = |(D90 - D10) / D50| (In the formula, D10, D50, and D90 represent the pore diameter when the pore volume is 10% of the total pore volume, the pore diameter when the pore volume is 50% of the total pore volume, and the pore diameter when the pore volume is 90% of the total pore volume, respectively.) [2] The separation membrane according to [1] above, wherein the thickness of the surface layer is 100 to 1500 nm. [3] The separation membrane according to claim 1 or 2, wherein the ratio of CO2 permeability to N2 permeability at a differential pressure of 100 kPa (separation coefficient α(CO2 / N2)) is 3.0 to 100.0. [4] The separation membrane according to any one of the above [1] to [3], wherein the separation membrane is hollow fiber in shape. [5] The separation membrane according to [4], wherein the surface layer is the outer surface of a hollow fiber-shaped separation membrane. [6] The separation membrane according to any one of [1] to [5], wherein the separation membrane has an N2 permeability of 5 to 350 GPU at a differential pressure of 100 kPa. [7] A separation membrane module for degassing and / or gas mixture separation, comprising a case and a separation membrane as described in any one of items [1] to [6] above, wherein the separation membrane is filled into the case. [8] Apparatus for degassing and / or for separating gas mixtures, comprising the separation membrane module described in [7] above. [9] A method for producing a liquid, comprising removing dissolved gas and adding gas using the apparatus described in [8] above.

[10] A method for producing a gas, comprising separating a gas mixture using the apparatus described in [8] above.

[11] A method for producing a separation membrane, comprising the steps (1) to (2) below. (1) A preparation step in which, using a twin-screw extruder or a multi-screw extruder, a plasticizer is introduced from a position (1 / 20)L to (5 / 20)L in the longitudinal direction from the introduction position to the screw tip, with respect to the screw length L, which is the length from the introduction position of poly(4-methyl-1-pentene), and 30% to 55% by mass of poly(4-methyl-1-pentene) and 45% to 70% by mass of plasticizer are melt-kneaded at 220°C to 260°C to obtain a resin composition. (2) A molding process in which the resin composition is extruded from an extrusion nozzle having a gap of 50 to 400 μm, passed through an idle section for 10 to 40 milliseconds, introduced into a cooling bath, and wound up to obtain a resin molded product.

[12] The method for producing a separation membrane according to

[11] , wherein the temperature of the cooling bath in the molding step is 5 to 30°C. [Effects of the Invention]

[0014] According to the present invention, a separation membrane is provided that uses poly(4-methyl-1-pentene) and achieves both high gas permeability and leakage resistance. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic diagram illustrating a separation membrane with a hollow fiber structure. [Figure 2] This is an example of an SEM image taken at 10,000x magnification of a cross-section of a separation membrane cut in the thickness direction. [Figure 3] The image in Figure 2 has been binarized and then the noise has been removed. [Figure 4] Figure 3 is an analytical image used to extract the contours of voids larger than 10 nm and measure the thickness of the surface layer. [Modes for carrying out the invention]

[0016] The separation membrane of this embodiment (hereinafter also referred to as "this embodiment") is a separation membrane mainly composed of poly(4-methyl-1-pentene), and is characterized by including a surface layer and an inner layer, having a pore mode diameter Dp determined from mercury intrusion measurement of 100 to 230 nm, a pore diameter distribution area W value determined from the mercury intrusion measurement and calculated by the formula W = |(D90-D10) / D50| of 1.50 to 10.00, and a porosity of 40 to 65%. In this specification, mass-based proportions (percentages, parts, etc.) are the same as weight-based proportions (percentages, parts, etc.). The separation membrane of this embodiment will be described below.

[0017] (Composition of the separation membrane) The separation membrane of this embodiment mainly consists of poly(4-methyl-1-pentene) as shown in (1) below. In addition to (1), it may also contain the components shown in (2) to (3) below.

[0018] (1) Poly(4-methyl-1-pentene) (hereinafter referred to as "PMP") The separation membrane in this embodiment must have PMP as its main component. Here, "main component" refers to the component that is present in the largest quantity by mass among all components of the separation membrane.

[0019] PMP is defined as a polymer that has repeating units derived from 4-methyl-1-pentene. PMP may be a homopolymer of 4-methyl-1-pentene or a copolymer of 4-methyl-1-pentene with other monomers copolymerizable with 4-methyl-1-pentene.

[0020] Monomers copolymerizable with 4-methyl-1-pentene specifically include olefins having 2 to 20 carbon atoms other than 4-methyl-1-pentene (hereinafter referred to as "olefins with 2 to 20 carbon atoms"). Examples of olefins with 2 to 20 carbon atoms include ethylene, propylene, 1-butene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, and 1-eicosene. The olefins with 2 to 20 carbon atoms copolymerized with 4-methyl-1-pentene may be one type or a combination of two or more types.

[0021] The mass percentage of PMP contained in the separation membrane of this embodiment is preferably 70 to 100% by mass, when the total components of the separation membrane are considered as 100% by mass. A mass percentage of 70% by mass or more of PMP results in good gas permeability. A mass percentage of 80% by mass or more of PMP is more preferable, and 90% by mass or more is even more preferable.

[0022] The density of the PMP raw material used in the production of the separation membrane in this embodiment is 825-840 kg / m³. 3It is preferable that the density be 825 kg / m³. 3 As a result of meeting these requirements, the mechanical strength of the separation membrane is good, reaching 840 kg / m². 3 The following conditions result in good gas permeability: Density: 830 kg / m³ 3 The above is more preferable. Also, 835 kg / m 3 The following are preferable.

[0023] The melt flow rate (MFR) of the PMP raw material, measured at 260°C and a 5kg load, is not particularly specified as long as it is within the range where it can be easily mixed with the plasticizer described later and co-extruded, but it is preferably between 1 and 200 g / 10 min. If the MFR is within the above range, it is easy to extrude to a relatively uniform film thickness. An MFR of 5 g / 10 min or higher is more preferable, and 30 g / 10 min or lower is even more preferable.

[0024] PMP raw materials may be produced directly by polymerizing olefins, or by thermal decomposition of high molecular weight 4-methyl-1-pentene polymers. Furthermore, the 4-methyl-1-pentene polymer may be purified by methods such as solvent fractionation based on differences in solubility in a solvent, or molecular distillation based on differences in boiling points. PMP raw materials may also be commercially available PMP polymers, such as TPX® (trademark registered trademark) manufactured by Mitsui Chemicals, Inc.

[0025] (2) Plasticizers for PMP The separation membrane of this embodiment may contain a plasticizer of PMP.

[0026] The mass percentage of plasticizer contained in the separation membrane is preferably 0 to 1000 ppm (by mass) when the total components of the separation membrane are considered as 100% by mass. A mass percentage of 1000 ppm (by mass) or less of plasticizer results in good gas permeability. A mass percentage of 500 ppm (by mass) or less of plasticizer is more preferable, and 100 ppm (by mass) or less is particularly preferable.

[0027] The plasticizer for PMP is not particularly limited as long as it is a compound that thermoplasticizes PMP. Examples of plasticizers include palm kernel oil, dibutyl phthalate, dioctyl phthalate, dibenzyl ether, and coconut oil. Among these, dibutyl phthalate and dibenzyl ether are preferred in terms of compatibility and stringability. The plasticizer for PMP may be one type, a combination of two or more types, or a mixture of two or more plasticizers.

[0028] (3) Additives The separation membrane of this embodiment may contain additives other than those described in (2), as long as they do not impair the effects of this embodiment.

[0029] Examples of additives include resins such as cellulose ether, polyacrylonitrile, polyolefin, polyvinyl compound, polycarbonate, poly(meth)acrylate, polysulfone or polyethersulfone, elastomers, and other organic lubricants, nucleating agents, antioxidants, organic particles, inorganic particles, end-capping agents, chain extenders, ultraviolet absorbers, infrared absorbers, color inhibitors, matting agents, antibacterial agents, antistatic agents, deodorants, flame retardants, weather-resistant agents, antistatic agents, antioxidants, ion exchange agents, defoaming agents, coloring pigments, fluorescent whitening agents, or dyes.

[0030] (Shape of the separation membrane) In this embodiment, a hollow fiber-shaped separation membrane (hereinafter referred to as "hollow fiber membrane") is preferably used as the separation membrane, but the separation membrane of the present invention is not limited to a hollow fiber shape. Hollow fiber membranes are preferred because they can be efficiently packed into modules and allow for a large effective membrane area per unit volume of the module.

[0031] The shape of the separation membrane in this embodiment, that is, the thickness of the separation membrane, and in the case of a hollow fiber membrane, the outer diameter, inner diameter, and hollow ratio, is preferably determined from the viewpoint of the effective membrane area when the separation membrane is modularized, the strength of the separation membrane, gas permeability, pressure drop, etc. The shape of the separation membrane can be measured, for example, by applying stress to a separation membrane that has been sufficiently cooled in liquid nitrogen, and observing the cross-section obtained by cutting the membrane in the thickness direction using an optical microscope or a scanning electron microscope (SEM). Specific methods will be described in detail in the examples.

[0032] The separation membrane of this embodiment is composed of a dense surface layer present on the membrane surface and a porous inner layer present beneath it. The total thickness of the separation membrane, including the surface and inner layers, is preferably 10 to 500 μm. A thickness of 10 μm or more provides good mechanical strength to the separation membrane, while a thickness of 500 μm or less provides good gas permeability. A total thickness of 20 μm or more is more preferable, 30 μm or more is even more preferable, and 50 μm or more is particularly preferable. Furthermore, a thickness of 200 μm or less is more preferable, 150 μm or less is even more preferable, and 100 μm or less is particularly preferable.

[0033] When the separation membrane is in the form of a hollow fiber, the outer diameter of the hollow fiber membrane is preferably 50 to 2500 μm. An outer diameter of 50 μm or more results in good membrane strength, and an outer diameter of 2500 μm or less results in good effective membrane area when packed into a module. An outer diameter of 100 μm or more is more preferable, 200 μm or more is even more preferable, and 300 μm or more is particularly preferable. Furthermore, an outer diameter of 1000 μm or less is more preferable, 500 μm or less is even more preferable, and 450 μm or less is particularly preferable.

[0034] The inner diameter of the hollow fiber membrane is preferably 20 to 1000 μm. An inner diameter of 20 μm or more results in good pressure loss of the fluid flowing through the hollow portion, while an inner diameter of 1000 μm or less results in good buckling pressure. An inner diameter of 50 μm or more is more preferable, 100 μm or more is even more preferable, and 150 μm or more is particularly preferable. An inner diameter of 500 μm or less is more preferable, 300 μm or less is even more preferable, and 250 μm or less is particularly preferable.

[0035] The hollowness ratio of a hollow fiber membrane is a value calculated using the following formula. Hollowness ratio (%)=100×[inner diameter (μm)] 2 / [Outer diameter (μm)] 2 The hollow ratio is preferably 15-70%. A hollow ratio of 15% or more results in good pressure loss of the fluid flowing through the hollow section, while a hollow ratio of 70% or less results in good buckling pressure. A hollow ratio of 20% or more is more preferable, 23% or more is even more preferable, and 25% or more is particularly preferable. Furthermore, a hollow ratio of 60% or less is more preferable, 50% or less is even more preferable, and 40% or less is particularly preferable.

[0036] The method for setting the outer diameter, inner diameter, and hollowness ratio of the hollow fiber membrane within the above ranges is not particularly limited, but can be adjusted, for example, by changing the shape of the discharge hole of the discharge nozzle used in the molding process for manufacturing the hollow fiber membrane, or by appropriately changing the draft ratio calculated by winding speed / discharge linear speed.

[0037] (Structure of the separation membrane) In this embodiment, when the separation membrane is a hollow fiber membrane, an example of a structure is shown in Figure 1, in which an inner layer 3 is located beneath the surface layer 2 present on the membrane surface 1. The separation membrane is a heterogeneous membrane having the surface layer shown in (1) below and the inner layer shown in (2) below. Furthermore, in addition to (1) and (2), it has the structural features shown in (3) below.

[0038] (1) Surface layer The separation membrane of this embodiment has a surface layer on at least one surface. The surface layer is defined as the portion of the membrane from any point on the surface of the separation membrane to the other surface side (inner layer side) when a straight line is drawn perpendicular to the surface when the cross-section of the separation membrane cut in the thickness direction is observed at a magnification of 10,000 times using an SEM, up to the first time the straight line reaches a pore larger than 10 nm. In other words, the surface layer is a dense layer without pores larger than 10 nm, and its primary role is to suppress the penetration of the liquid to be processed into the separation membrane, thereby improving leakage resistance (hereinafter, the effect of the surface layer in suppressing the penetration of the liquid to be processed into the separation membrane will be referred to as "primary leakage resistance").

[0039] When the separation membrane is a hollow fiber membrane, the surface layer may be on the outer surface side of the hollow structure, on the inner surface side, or on both the outer and inner surfaces. When the separation membrane is a hollow fiber membrane, it is more preferable that the surface layer be on the outer surface of the separation membrane. Having the surface layer on the outer surface allows for a larger effective membrane area per unit volume of the module.

[0040] The surface layer is the functional separation layer of the separation membrane, and its thickness tends to increase gas permeability as it decreases. The separation membrane of this embodiment has a surface layer that is very thin compared to the overall thickness of the separation membrane, resulting in high gas permeability. The thickness of the surface layer can be determined, for example, by applying stress to a separation membrane that has been sufficiently cooled in liquid nitrogen (using a razor, microtome, or broad ion beam as needed), and observing a cross-section (hereinafter referred to as a "transverse section") perpendicular to the longitudinal direction of the separation membrane and parallel to the thickness direction of the membrane, or a cross-section (hereinafter referred to as a "longitudinal section") parallel to the longitudinal direction of the separation membrane and parallel to the thickness direction of the membrane, using a SEM at a magnification of 10,000 times. After binarizing the obtained image using the image analysis software "ImageJ", only pores larger than 10 nm are extracted, and the distance to those pores is measured by drawing a straight line perpendicular to the membrane surface. The specific method for measuring the thickness of the surface layer will be described in detail in the examples.

[0041] Note that the longitudinal direction of the separation membrane is the direction perpendicular to the transverse direction of the separation membrane. If the separation membrane is a hollow fiber membrane, the transverse direction is the direction parallel to the radial direction of the hollow fiber membrane, and the transverse direction can be rephrased as the direction parallel to the hollow surface, that is, the in-plane direction of the hollow surface. Therefore, the longitudinal direction of a hollow fiber membrane can be rephrased as the direction parallel to the radial direction, or the direction perpendicular to the hollow surface. From this, when the separation membrane is a hollow fiber membrane, "radial cross-section" is used synonymously with "cross-section".

[0042] The surface layer thickness is preferably 100 to 1500 nm. A surface layer thickness of 100 nm or more provides good leakage resistance, while a thickness of 1500 nm or less provides good gas permeability. A surface layer thickness of 120 nm or more is more preferable, 140 nm or more is even more preferable, and 150 nm or more is particularly preferable. Furthermore, a thickness of 1000 nm or less is more preferable, 500 nm or less is even more preferable, and 250 nm or less is particularly preferable.

[0043] The density of the surface layer can be evaluated by the gas separation coefficient α(CO2 / N2), which will be described later. A larger value of the separation coefficient α(CO2 / N2) indicates a denser surface layer, and tends to result in higher primary leakage resistance. A separation coefficient α(CO2 / N2) of 3.0 or higher is preferable. On the other hand, in separation membranes with a large separation coefficient α(CO2 / N2), i.e., a dense surface layer, gas permeability tends to decrease. To maintain high gas permeability, a separation coefficient α(CO2 / N2) of 100.0 or less is preferable. A separation coefficient α(CO2 / N2) of 5.0 or higher is more preferable, 7.0 or higher is even more preferable, and 8.0 or higher is particularly preferable. Furthermore, a value of 50.0 or less is more preferable, 25.0 or less is even more preferable, and 15.0 or less is particularly preferable.

[0044] (2) Inner layer The separation membrane of this embodiment has an inner layer beneath the surface layer present on the membrane surface. The inner layer refers to the portion of the separation membrane excluding the surface layer. The inner layer is a porous structure with multiple pores resulting from thermally induced phase separation, and since it accounts for most of the total thickness of the separation membrane, the separation membrane has high gas permeability. Pores refer to pores with a diameter of 4 nm or more, as determined by the mercury intrusion method described later.

[0045] The inner layer has a porous structure, but the presence of coarse pores tends to reduce the strength of the separation membrane. Coarse pores are defined as pores with a diameter of 10 μm or more, and are often found in the inner layer. The number of pores with a diameter of 10 μm or more in the inner layer (hereinafter referred to as "coarse pores") can be determined, for example, by observing the cross-section or longitudinal section of the separation membrane with a SEM at 2,000x magnification, and the resulting image with an observation field of view of 2,400 μm. 2It can be obtained by trimming to a size of (40 μm in length and 60 μm in width), binarizing in the image analysis software "ImageJ", and extracting only pores with an average diameter greater than 10 μm. The specific method for measuring the number of large pores in the inner layer will be described in detail in the examples.

[0046] The number of large pores is 3 per 2400 μm 2 It is preferably as follows. The number of large pores is 3 per 2400 μm 2 When it is as follows, the strength of the separation membrane becomes good. The number of large pores is 2 per 2400 μm 2 More preferably, it is 1 per 2400 μm 2 Even more preferably, it is 0 per 2400 μm 2 is particularly preferred.

[0047] In addition to the dense surface layer, the separation membrane of the present embodiment has an inner layer with an appropriate pore diameter, so that it has high gas permeability while having excellent leakage resistance. The inner layer with an appropriate pore diameter suppresses the progress of the liquid to be treated further inside after it has passed through the surface layer, and plays a role in enhancing the leakage resistance secondarily (hereinafter, the effect of suppressing the progress of the liquid to be treated by the inner layer is referred to as "secondary leakage resistance"). The inventors have found that by having both the primary leakage resistance due to the very thin surface layer with a non-porous structure and the secondary leakage resistance due to the inner layer with a porous structure but with appropriately controlled pore diameters, a separation membrane having high gas permeability and more excellent leakage resistance than conventional ones can be obtained.

[0048] As parameters representing the characteristics of the pores present in the inner layer, it is important that the mode diameter Dp of the pores obtained from the mercury intrusion method and the value of the pore diameter distribution width W calculated by the following formula are within a specific range.

[0049] W = |(D90 - D10) / D50| Here, D10, D50, and D90 are pore diameters D (nm) such that the pore volume ΣV in the integrated pore volume distribution is 10%, 50%, and 90% of the total pore volume ΣVp, respectively. As will be explained in detail below, the pore diameter and pore size distribution of the inner layer are desirable when the values ​​of the mode diameter Dp and the distribution width W are within a specific range.

[0050] The mercury intrusion method is a technique in which pressure is applied to mercury, which has high surface tension, and it is injected into the pores of a sample. The pore size distribution is then determined from the relationship between the applied pressure and the amount of mercury injected, and pore sizes in the range of mesopores to macropores (approximately 3 nm to 500 μm) can be evaluated. In the separation membrane of this embodiment, the pores have an unspecified shape, but in the mercury intrusion method, the pores are assumed to be cylindrical and the pore diameter is assumed to be the diameter of the cylinder, and the pore diameter is calculated using the following equation (1).

[0051] D = (-4σ × cosθ / P) × 10 9 ...Formula (1) Here, D is the pore size (nm), σ is the surface tension of mercury (N / m), θ is the contact angle of mercury (°), and P is the pressure (Pa). In this specification, calculations are performed using σ = 0.484 N / m and θ = 141.3°. The pore size D and pressure P are inversely proportional; the smaller the pore size D, the greater the pressure required for mercury injection.

[0052] This specification describes a mercury injection method for the pressurization process. The amount of mercury injected, i.e., the pore volume ΣV(cm), is increased stepwise while the pressure P is gradually increased. 3 By calculating ( / g) and plotting the pore diameter D on the horizontal axis (common logarithmic axis) and the pore volume ΣV on the vertical axis of the graph, the integrated pore volume distribution can be obtained.

[0053] Furthermore, the difference in pore volume ΣV between measurement points can be used to determine the difference in pore volume dV(cm²). 3 The pressure P(g) can be determined. That is, if a certain measurement point is i(pressure P i ), the next measurement point is i+1 (pressure P i+1 Assuming this is the case, the difference pore volume dV is expressed by the following formula.

[0054] dV = ΣVi+1 -ΣV i Here, ΣV i+1 sigma i These are the measurement points i (pressure P) respectively. i ), measurement point i+1 (pressure P i+1 This is the pore volume in ). The differential pore volume dV is P i <P≦P i+1 Corresponding pore size D i+1 ≤D <D i This can be said to be the pore volume. Here, if we plot the arithmetic mean of the pore diameter D between measurement points on the horizontal axis (common logarithmic axis) and the value of dV / d(logD) expressed by the following formula on the vertical axis (common logarithmic axis), we can obtain the log differential pore volume distribution.

[0055] dV / d(logD) = dV / (logD i -logD i+1 ) dV / d(logD) (unit: cm) 3 The value obtained by dividing the differential pore volume dV by the difference d(logD) between the pore diameters D between measurement points, which are treated on a common logarithmic scale.

[0056] From the cumulative pore volume distribution and log differential pore volume distribution obtained above, the pore mode diameter Dp and the pore diameter distribution width W can be determined as parameters representing the pore characteristics of the separation membrane of this embodiment. In this embodiment, since the thickness of the surface layer is very small, the evaluation results of the mercury intrusion method mainly reflect the characteristics of the inner layer.

[0057] The log differential pore volume distribution is close to the differential form of the integrated pore volume distribution, and the frequency of each pore size can be evaluated. The mode diameter Dp is the pore size D for which the vertical axis dV / d(logD) is maximized in the range of 4 nm to 10 μm on the horizontal axis of the log differential pore volume distribution, i.e., the most frequent value of the pore size D. From equation (1), the smaller the diameter of the pores in the inner layer, the greater the pressure required for liquid passage, and therefore the higher the secondary leakage resistance of the separation membrane tends to be.

[0058] A mode diameter Dp of 230 nm (equivalent to a pressure of P6.57 MPa) or less is desirable for good secondary leakage resistance of the separation membrane. On the other hand, if the pore size of the inner layer becomes too small, the gas permeability of the separation membrane tends to decrease, so a mode diameter Dp of 100 nm (equivalent to a pressure of P15.1 MPa) or more is preferable. A mode diameter Dp of 220 nm (equivalent to a pressure of P6.87 MPa) or less is more preferable, 200 nm (equivalent to a pressure of P7.55 MPa) or less is even more preferable, and 190 nm (equivalent to a pressure of P7.95 MPa) or less is particularly preferable. Furthermore, 130 nm (equivalent to a pressure of P11.6 MPa) or more is more preferable, 150 nm (equivalent to a pressure of P10.1 MPa) or more is even more preferable, and 170 nm (equivalent to a pressure of P8.89 MPa) or more is particularly preferable.

[0059] The cumulative pore volume distribution is the pore diameter distribution that most closely matches the information obtained from measurements, and from this, the variability of the pore diameter distribution can be evaluated. The pore diameter distribution width W is a value calculated by the following formula, and a smaller value indicates less variability in pore diameter.

[0060] W = |(D90 - D10) / D50| Here, D10, D50, and D90 are pore diameters D such that, when the horizontal axis of the cumulative pore volume distribution, with pore diameter D ranging from 4 nm to 10 μm, represents the total pores of the separation membrane, the pore volume ΣV is 10%, 50%, and 90% of the total pore volume ΣVp, respectively. The total pore volume ΣVp is the sum of the pore volumes in the range of pore diameter D from 4 nm to 10 μm. It is important that the pore diameter distribution area W is between 1.50 and 10.00. Having the pore diameter distribution area W within this range increases the probability of finding desirable pore diameters, resulting in good secondary leakage resistance and gas permeability. A pore diameter distribution area W of 5.00 or less is more preferable, and 2.50 or less is even more preferable.

[0061] (3) Porosity The separation membrane of this embodiment has a high porosity derived from the porous structure of the inner layer. Porosity refers to the porosity of the entire separation membrane, including the surface layer and the inner layer, and is calculated using the following formula with the total pore volume ΣVp obtained from the mercury intrusion method.

[0062] ε = (ΣVp / ΣVp+1 / ρ) × 100 Here, ε is the porosity (%), and ΣV is the pore volume (cm³) obtained from the mercury intrusion method. 3 ( / g), ρ is the density of PMP (cm³) 3 The ratio is ( / g). The separation membrane has high gas permeability due to its large porosity, that is, a high proportion of the pore volume ΣV within the separation membrane.

[0063] It is important that the porosity is between 40% and 65%. A porosity of 40% or more results in good gas permeability, while a porosity of 65% or less results in good film strength. A porosity of 45% or more is more preferable, and 50% or more is even more preferable. Furthermore, a porosity of 60% or less is preferable, and 55% or less is even more preferable. As a method for achieving a porosity within the above range, structure formation using thermally induced phase separation, as described later, is preferably used.

[0064] Based on (1) to (3) above, the separation membrane of this embodiment includes a surface layer and an inner layer, has a pore mode diameter Dp determined from mercury intrusion measurement of 100 to 230 nm, a pore diameter distribution area W value determined from the mercury intrusion measurement and calculated by the following formula of 1.50 to 10.0, and a porosity of 40 to 65%, thereby providing a separation membrane that maintains high gas permeability while also being leak-resistant.

[0065] W = |(D90 - D10) / D50| (In the formula, D10, D50, and D90 represent the pore diameter when the pore volume is 10% of the total pore volume, the pore diameter when the pore volume is 50% of the total pore volume, and the pore diameter when the pore volume is 90% of the total pore volume, respectively.) (Gas permeability) The separation membrane of this embodiment has an N2 permeability of 5 to 350 GPU (1 GPU = 1 × 10¹⁶) at a differential pressure of 100 kPa and 37°C. -6 cm 3 (STP) / (s·cm 2 ·cmHg, ), [cm 3(STP) is preferably the volume of the gas at 1 atmosphere and 0°C. A differential pressure of 100 kPa means that the pressure difference between the gas supply side and the permeate side across the separation membrane is 100 kPa. Since a higher gas permeability can increase the separation efficiency per unit area of ​​the separation membrane, an N2 permeability of 5 GPU or more is preferable. On the other hand, an N2 permeability of 350 GPU or less reduces the pores or defects present on the surface, and such a separation membrane has better primary leakage resistance. The method for calculating N2 permeability will be described in detail in the examples. An N2 permeability of 30 GPU or more is more preferable, 40 GPU or more is even more preferable, and 50 GPU or more is particularly preferable. Furthermore, 250 GPU or less is more preferable, 200 GPU or less is even more preferable, and 150 GPU or less is particularly preferable.

[0066] (Separation coefficient α(CO2 / N2)) The separation membrane of this embodiment has a dense surface layer, and this surface layer serves as the effective separation layer of the separation membrane. From this, the density of the surface layer can be evaluated by the separation coefficient α, which is the ratio of the permeability of two types of gases. For example, the separation coefficient α(CO2 / N2) for CO2 and N2 is calculated by the following formula.

[0067] α(CO2 / N2)=Q(CO2) / Q(N2) Here, Q(CO2) is the CO2 permeation velocity, and Q(N2) is the N2 permeation flow rate. In commonly used polymer materials, α(CO2 / N2) is at least 1.0. In the separation membrane of this embodiment, a larger separation coefficient α(CO2 / N2) indicates a denser surface layer. In particular, since the surface layer has a thin structure of 100 to 1500 nm, a separation coefficient α(CO2 / N2) of 3.0 or higher is preferable for good leakage resistance. On the other hand, separation membranes with a large separation coefficient α(CO2 / N2) tend to have reduced gas permeability. To maintain high gas permeability, a separation coefficient α(CO2 / N2) of 100.0 or less is preferable. A separation coefficient α(CO2 / N2) of 5.0 or more is more preferable, 7.0 or more is even more preferable, and 8.0 or more is particularly preferable. Furthermore, 50.0 or less is more preferable, 25.0 or less is even more preferable, and 15.0 or less is particularly preferable. Furthermore, a separation membrane whose separation coefficient α(CO2 / N2) satisfies the preferred range in this embodiment can also be suitably used for separating gaseous mixtures.

[0068] (Method for manufacturing separation membranes) The separation membrane of this embodiment can be manufactured by a method comprising the following (1) to (2). Furthermore, if necessary, steps other than (1) and (2) shown in (3) to (4) below may also be performed. (1) A preparation step in which a plasticizer is introduced from a position of (1 / 20)L to (5 / 20)L relative to the screw length L using a twin-screw or multi-screw extruder, and a mixture containing 30% to 55% by mass of poly(4-methyl-1-pentene) and 45% to 70% by mass of plasticizer is melt-kneaded at 220°C to 260°C to obtain a resin composition. (2) A molding process in which the resin composition is extruded from an extrusion nozzle having a gap of 50 to 400 μm, passed through an idle section for 10 to 40 milliseconds, introduced into a cooling bath, and wound up to obtain a resin molded product.

[0069] The following describes each step.

[0070] (1) Preparation process In the molding process (2), which is a preparation process in which a mixture containing 30-55% by mass of PMP and 45-70% by mass of plasticizer is melt-kneaded to obtain a uniform resin composition, it is necessary to suppress the excessive growth of the phase separation structure in the molding process (1) by performing the preparation process (1) at the lowest possible temperature to suppress the generation of foreign matter due to heat. The resin composition preferably contains 30-55% by mass of PMP and 45-70% by mass of plasticizer when the total components of the resin composition are considered as 100% by mass. Having 30% by mass or more of PMP suppresses the formation of large pores in the inner layer of the separation membrane by preventing the pore volume ΣV from becoming too large, resulting in good leakage resistance. On the other hand, having a content of 55% by mass or less results in good gas permeability of the separation membrane. The resin composition more preferably contains 35% by mass or more of PMP and 65% or less of plasticizer, and even more preferably contains 37% by mass or more of PMP and 63% or less of plasticizer. Furthermore, it is more preferable to contain 50% by mass or less of PMP and 50% by mass or more of a plasticizer, and even more preferable to contain 43% by mass or less of PMP and 57% or more of a plasticizer.

[0071] In the production of the separation membrane of this embodiment, it is important that the apparatus used for melt kneading is a twin-screw extruder or a multi-screw extruder. A multi-screw extruder is an extruder equipped with three or more screw shafts and has a greater distribution action than a twin-screw extruder. Distribution action refers to the action of stirring the kneaded material to suppress variations in composition and physical properties. If the apparatus used for melt kneading is anything other than these, such as a kneader, roll mill, Banbury mixer, or single-screw extruder, the distribution action will be insufficient, making it difficult to obtain a resin composition with sufficient uniform dispersion at the preferred kneading temperature described later. Among twin-screw extruders and multi-screw extruders, it is preferable to use an extruder with vent holes from the viewpoint of being able to remove volatile substances derived from moisture and low molecular weight components. Furthermore, from the viewpoint of enhancing the distribution action, it is preferable to use an extruder equipped with a screw that includes a kneading disc. In addition, in order to suppress thermal oxidative degradation during kneading, it is preferable to use an extruder equipped with a mechanism that replaces the raw material input section and kneading section with an inert gas such as N2.

[0072] In the manufacturing of the separation membrane of this embodiment, it is important that the kneading temperature is 220 to 260°C. If the kneading temperature is too high, side reactions such as the decomposition or carbonization of PMP and plasticizers will occur during kneading, and foreign matter is likely to be generated in the resin composition. Such foreign matter becomes a nucleus when heat-induced phase separation proceeds in the (2) molding process, causing the pores in the inner layer of the separation membrane to grow too large, and thus it has been difficult to appropriately control the pore size of the inner layer with conventional technology. The inventors have found that by setting the melt kneading temperature to 260°C or lower, which is lower than conventional methods, the generation of foreign matter in the resin composition can be suppressed, and furthermore, by combining this with the rapid cooling process described later, that is, a method in which the resin composition is discharged from a discharge nozzle with a gap of 50 to 400 μm, passed through an air-running section for 10 to 40 milliseconds, and then introduced into a cooling bath, it is possible to form a porous structure in the inner layer of the separation membrane that can achieve both high gas permeability and leakage resistance.

[0073] However, with PMP having a melting point of approximately 220-235°C, simply setting the mixing temperature to 260°C or lower makes it difficult to obtain a uniform resin composition due to insufficient mixing, and furthermore, it is easy for the equipment to be overloaded (torque overloaded) by unmelted resin. The inventors achieved the mixing temperature of this embodiment by using a twin-screw or multi-screw extruder to enhance the distribution action, and by adding a plasticizer immediately after the PMP is introduced to quickly lower the melting temperature.

[0074] The kneading temperature is more preferably 255°C or lower, and even more preferably 250°C or lower. On the other hand, since the kneading temperature must be above the melting point of the PMP raw material, it is preferable that it be 220°C or higher.

[0075] As mentioned above, the plasticizer should be added to the extruder immediately after the PMP is added, and it is preferable that the length of the plasticizer added from the PMP addition point is between (1 / 20)L and (5 / 20)L relative to the screw length L. The screw length L refers to the length from the PMP addition point to the tip of the screw. The plasticizer addition point is more preferably (4 / 20)L or less, even more preferably (3 / 20)L or less, and particularly preferably (2 / 20)L or less.

[0076] The resin composition obtained in the preparation process may be pelletized and then remelted for use in melt film formation, or it may be directly introduced into the die and used in melt film formation.

[0077] When introducing the resin composition to the die, it is preferable to appropriately control the temperature of the melt spinning pack (spin block) that houses the die. Hereinafter, the set temperature of this melt spinning pack will be referred to as the "discharge temperature." In PMP with a melting point of approximately 220 to 235°C, the discharge temperature is preferably 220 to 255°C, from the viewpoint of ensuring the fluidity of the resin composition and suppressing thermal degradation. More preferably, it is 220 to 240°C. Furthermore, the discharge temperature can be controlled independently of the mixing temperature. For example, by setting the discharge temperature lower than the mixing temperature, the thermal history of the resin composition can be reduced. If the mixing temperature is approximately the same as the melting point of the resin composition, setting the discharge temperature to approximately the same as the mixing temperature can maintain high fluidity of the resin composition and improve discharge stability.

[0078] When forming pellets, it is preferable to use a resin composition in which the pellets are dried to a moisture content of 200 ppm (by mass) or less. By keeping the moisture content at 200 ppm (by mass) or less, the deterioration of the resin during film formation can be suppressed.

[0079] (2) Molding process (1) This molding process involves extruding the resin composition obtained in the preparation process from the discharge nozzle, passing it through the idle section, introducing it into a cooling bath, and winding it to obtain a molded resin product. The discharge temperature is as described in the preparation process above. In this process, the molten resin composition containing at least PMP and a plasticizer becomes a molded resin product having a heterogeneous structure due to phase separation. As mentioned above, (2) the molding process must be a rapid cooling process. By suppressing the generation of foreign matter in the preparation process (1) and combining it with the rapid cooling process, the growth of pores in the inner layer of the separation membrane due to phase separation is suppressed, resulting in a separation membrane with a desirable pore size.

[0080] In the manufacturing of the separation membrane of this embodiment, it is important that the gap between the discharge nozzles (the flow path width of the resin composition) is 50 to 400 μm. When the gap between the discharge nozzles is 400 μm or less, the difference in cooling rate between the inside and outside of the resin composition is reduced, resulting in a rapid cooling process. On the other hand, if the gap between the discharge nozzles is small, the pressure loss of the resin composition at the discharge nozzle increases, and the pressure required for discharge increases. Therefore, the lower limit of the gap between the discharge nozzles is preferably 50 μm. The gap between the discharge nozzles is more preferably 250 μm or less, and even more preferably 150 μm or less. Furthermore, it is more preferably 60 μm or more, and even more preferably 70 μm or more.

[0081] If the separation membrane to be manufactured is a hollow fiber membrane, (2) the molding process is, as an example, a process in which a molten resin composition is discharged from the outer tube of a double annular nozzle for spinning, while a hollow-forming gas is discharged from the inner ring of a double-tube type nozzle and introduced into a cooling bath to separate the phases of the resin composition and obtain a resin molded product in the shape of a hollow fiber.

[0082] The type of gas used to form the hollow space is not particularly limited, but examples include air, vaporized substances, and inert gases such as N2, CO2, and Ar. Among these, N2, CO2, and Ar are preferred as inert gases that have the effect of suppressing thermal oxidative degradation. The gas used to form the hollow space may be one type or a mixture of two or more gases.

[0083] The resin composition discharged from the discharge nozzle is preferably exposed to a gaseous atmosphere that promotes the evaporation of plasticizers, i.e., an atmosphere in which the evaporation of plasticizers can occur, before being cooled by a cooling bath, at least one of its surfaces, preferably the surface where a surface layer should form. The gas used for the gaseous atmosphere is not particularly limited, but is preferably air or N2. The gaseous atmosphere is generally at a temperature lower than the discharge temperature of the resin composition. This results in a separation film with a dense surface layer on its surface.

[0084] However, in order to immediately introduce the resin composition into the cooling bath and carry out a rapid cooling process, it is important that the passage time through the gaseous atmosphere is 10 to 40 milliseconds. In this specification, the "passage time through the gaseous atmosphere" is referred to as the "free-run time." A free-run time of 10 milliseconds or more results in a surface layer thickness within a desirable range, while a free-run time of 40 milliseconds or less provides a sufficient rapid cooling effect. A free-run time of 15 milliseconds or more is more preferable, and 20 milliseconds or more is even more preferable. Furthermore, 30 milliseconds or less is more preferable, and 25 milliseconds or less is even more preferable.

[0085] The resin composition passes through a gaseous atmosphere and then enters a cooling bath. The refrigerant in the cooling bath is preferably a liquid with better thermal conductivity than the gaseous atmosphere, and the type of liquid used in the cooling bath (hereinafter referred to as the "cooling bath solvent") is preferably selected based on its affinity with the PMP and the plasticizer.

[0086] The cooling bath solvent has a solubility parameter distance Ra of 5.0 to 18.0 MPa for PMP. 1 / 2 The range is such that the solubility parameter distance Rb for the plasticizer is 1.0 to 2.9 MPa. 1 / 2 Alternatively, 6.5-10.0 MPa 1 / 2 It is preferable to use materials within the specified range. When Ra and Rb are within the aforementioned range, a dense surface layer without defects is formed, resulting in a leakage-resistant separation membrane. The reason for this is that Ra is between 5.0 and 18.0 MPa. 1 / 2 Within this range, aggregation and solidification occur before crystallization of PMP, and furthermore, Rb is 1.0-2.9 or 6.5-10.0 MPa. 1 / 2 It is hypothesized that being within this range allows for the exchange of the cooling bath solvent and plasticizer at an appropriate rate, resulting in the formation of micropores through which only gas can pass. Ra is 5.0~7.0 MPa. 1 / 2 and Rb is 6.5~10.0 MPa 1 / 2 It is more preferable that it be within that range.

[0087] The solubility parameter distance is a value that can be used as an indicator of the affinity between two materials. As described in the literature (Ind.Eng.Chem.Res.2011,50,3798-3817.), it can be estimated using the three-dimensional Hansen solubility parameter. For example, when considering the affinity between PMP and a cooling bath solvent, the solubility parameter distance Ra is calculated using the following equation (2), and a smaller Ra indicates a higher affinity of the cooling bath solvent to the PMP.

[0088]

number

[0089] The affinity between the plasticizer and the cooling bath solvent can be estimated in a similar manner. Specifically, a smaller solubility parameter distance Rb in equation (3) below indicates a higher affinity of the cooling bath solvent to the plasticizer.

[0090]

number

[0091] If the solvent is a mixed solvent, the solubility parameter δ of the mixed solvent Mixture This can be calculated using the following formula (4).

[0092]

number

[0093] In the production of the separation membrane of this embodiment, the cooling bath solvent in the molding process may be cyclohexanone, diethyl phthalate, isophorone, dihexyl phthalate, Benzoflex (registered trademark) manufactured by Eastman, diisoheptyl phthalate, dimethyl phthalate, fatty acid methyl ester, n-butyl acetate, n-amyl 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, ethyl 3-ethoxypropionate, propylene glycol monomethyl ether acetate, diacetone alcohol, isopentyl acetate, Tri-N-butyl citrate, Solvesso® 100 manufactured by ExxonMobil, isobutyl isobutyrate, ε-caprolactone, propylene glycol phenyl ether, isopropyl acetate, sec-butyl acetate, propylene glycol monobutyl ether, Texanol, Solvesso 150, ethylbenzene, γ-butyrolactone, tetrahydrofurfuryl alcohol, N,N-dimethylformamide, dipropylene glycol methyl ether, dipropylene glycol methyl ether, propylene glycol monomethyl ether, triethyl citrate, methyl carbitol, ethyl lactate, ethylene glycol monobutyl ether, cyclohexane, methylcyclohexane, dimethylcyclohexane, benzyl alcohol, dimethyl sulfoxide, etc. are preferred. Among these, triacetin is more preferred because its Ra and Rb values ​​are within the more preferred ranges mentioned above. The cooling bath solvent may be one type or a mixture of two or more cooling bath solvents.

[0094] The temperature of the cooling bath is preferably 5 to 30°C. A cooling bath temperature of 5°C or higher allows the resin composition to reach its glass transition temperature, stabilizing the winding process. A temperature of 30°C or lower provides sufficient rapid cooling, resulting in a separation membrane with a desirable pore structure in the inner layer. A cooling bath temperature of 10°C or higher is more preferable, and 15°C or higher is even more preferable. Furthermore, a temperature of 30°C or lower is even more preferable, and 25°C or lower is even more preferable.

[0095] (3) Washing process (2) By removing the plasticizer from the resin molded product obtained in the preparation step, a separation membrane mainly composed of PMP is obtained. The method for removing the plasticizer from the resin molded product is not particularly limited, but this step can be performed as needed.

[0096] This process involves (2) the resin molded product obtained in the preparation process, with a solubility parameter distance Ra of 8.0 to 35.0 MPa relative to PMP. 1 / 2 The range is such that the solubility parameter distance Rb for the plasticizer is 5.0 to 35.0 MPa. 1 / 2 This is a washing process in which the plasticizer is introduced into a washing solvent within a specified range, and the plasticizer is extracted to obtain a separation membrane. The plasticizer is removed from the resin molded product, increasing its porosity and resulting in a separation membrane with high gas permeability.

[0097] In the washing process, using a washing solvent with appropriate affinity for both PMP and plasticizer improves washing efficiency. Among these, a washing solvent that does not dissolve PMP but is miscible with the plasticizer is preferable; specifically, one with a solubility parameter distance Ra for PMP of 8.0 to 35.0 MPa. 1 / 2 The range is such that the solubility parameter distance Rb for the plasticizer is 5.0 to 35.0 MPa. 1 / 2 Washing solvents in the range of Ra = 8.0 MPa are preferred. 1 / 2 The above conditions result in good shape stability of the resin molded product, and the pressure is 35.0 MPa. 1 / 2 The following conditions allow the resin molded product to swell appropriately, improving cleaning efficiency: Rb = 35.0 MPa 1 / 2 The following conditions ensure good solvent exchange and high cleaning efficiency: Ra is 10.0-25.0 MPa. 1 / 2 More preferably, 12.0 to 22.0 MPa 1 / 2 This is particularly preferable. Rb is more preferably 10.0 to 25.0, and particularly preferably 12.0 to 22.0.

[0098] In the manufacturing of the separation membrane of this embodiment, when dibutyl phthalate is used as the plasticizer, the washing solvent in the washing step may be methyl isobutyl ketone, acetone, butyl glycol acetate, methyl acetate, propylene glycol monoethyl ether acetate, Benzoflex (registered trademark) manufactured by Eastman, N,N-dimethylacetamide, dipropylene glycol monobutyl ether, diethylene glycol monobutyl ether, t-butyl acetate, propylene glycol monomethyl ether acetate, diacetone alcohol, ε-caprolactone, isopropyl acetate, sec-butyl acetate, propylene glycol monobutyl ether, texanol, γ-butyrolactone, tetrahydrofurfuryl alcohol, N,N-dimethylformamide, dipropylene glycol methyl ether, propylene glycol Preferred solvents include monomethyl ether, triethyl citrate, methyl carbitol, ethyl lactate, ethylene glycol monobutyl ether, dimethylcyclohexane, benzyl alcohol, dimethyl sulfoxide, propylene carbonate, cyclohexanol, glycerol diacetate, isopentyl alcohol, 2-phenoxyethanol, heptane, acetonitrile, n-amyl alcohol, methyl isobutyl carbinol, tetramethylene sulfone, hexane, VM&P naphtha, hexylene glycol, ethylene glycol monomethyl ether, 2-butanol, t-butyl alcohol, 1-butanol, ethylene carbonate, isopropyl alcohol, isobutanol, 1-propanol, dipropylene glycol, ethanol, propylene glycol, methanol, glycerol carbonate, and ethylene glycol. Among these, methanol, ethanol, and isopropyl alcohol are more preferred because their Ra and Rb values ​​are within the aforementioned particularly preferred range. The washing solvent may be one type, a combination of two or more types, or a mixture of two or more washing solvents.

[0099] (4)Drying process This step involves applying heat to a separation membrane, which is mainly composed of PMP, and drying it. For example, it is often carried out at a temperature that can remove the washing solvent used in step (3) washing, and does not impair the shape of the separation membrane, and the drying temperature is preferably 25 to 120°C.

[0100] In this way, the separation membrane of this embodiment, which has PMP as its main component, can be manufactured.

[0101] (Separation membrane module) The separation membrane of this embodiment can be filled into a case by a known method to form a separation membrane module for at least one of degassing and / or gas injection, or for separating gas mixtures. A degassing module is a component unit that separates gas from a liquid. A gas injection module is a component unit that imparts gaseous components from the gas phase to a liquid. A module for applications that perform degassing and gas injection simultaneously is a gas exchange module, which is a component unit that separates gas from a liquid and simultaneously imparts gaseous components from the gas phase to the liquid. A gas mixture separation module is a component unit that separates specific gaseous components from the gas phase.

[0102] For example, if the separation membrane is a hollow fiber membrane, the separation membrane module comprises multiple hollow fiber membranes and a cylindrical case. The multiple hollow fiber membranes are bundled together and inserted into the cylindrical case, and then their ends are fixed to the case using a thermosetting resin such as polyurethane or epoxy resin. The separation membrane module is obtained by cutting the ends of the hollow fiber membranes that have been cured with the thermosetting resin.

[0103] In addition, among the separation membrane modules equipped with the separation membrane of this embodiment, in the separation membrane module that includes a liquid as the object to be separated, i.e., at least one of the separation membrane modules for degassing and aeration, the liquid to be separated is water, organic solvents, and mixtures thereof, but blood is not included.

[0104] The liquid may contain a hydrocarbon solvent. The liquid may be at least one selected from the group consisting of glycols, glycol monoalkyl ethers, glycol dialkyl ethers, glycol monoacetates, glycol diacetates, alcohols, ketones, acetate esters, lactic acid esters, saturated hydrocarbons, unsaturated hydrocarbons, cyclic saturated hydrocarbons, cyclic unsaturated hydrocarbons, aromatic hydrocarbons, terpenes, ethers, cyclic imides, 3-alkyl-2-oxazolidinone, N-alkylpyrrolidone, lactones, and nitrogen-containing solvents. The liquid may be a UV ink or a ceramic ink.

[0105] (Device equipped with a separation membrane module) Using the separation membrane of this embodiment, an apparatus for degassing and / or gas mixture separation can also be provided, which includes at least one of the separation membrane modules for degassing and / or gas injection, or for gas mixture separation, according to this embodiment.

[0106] (Method of manufacturing liquids) A method for producing a liquid can also be provided, which includes removing dissolved gas and adding gas using an apparatus that is at least one of the degassing and injecting devices, equipped with a separation membrane module that is at least one of the degassing and injecting devices of this embodiment, and using the separation membrane of this embodiment.

[0107] (Method of producing gases) A method for producing a gas can also be provided, which involves separating a gas mixture using an apparatus for separating gas mixtures equipped with a gas mixture separation module of this embodiment, which uses the separation membrane of this embodiment. [Examples]

[0108] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way thereto. [Measurement and evaluation methods] Each characteristic value in the examples is determined by the following method.

[0109] (1) Film thickness The separation membrane was frozen with liquid nitrogen, and then stress was applied (using a razor or microtome as needed) to cleave it so that the cross-section or longitudinal section was exposed. The cross-section or longitudinal section was observed with an optical microscope, and the average of the film thickness at 10 randomly selected locations was taken as the film thickness.

[0110] (2) Outer diameter and inner diameter (μm) of the hollow fiber membrane After freezing the hollow fiber membrane with liquid nitrogen, stress was applied (using a razor or microtome as needed) to expose the diameter cross-section. The diameter cross-section was then observed with an optical microscope, and the average values ​​of the outer and inner diameters at 10 randomly selected locations were taken as the outer and inner diameters of the hollow fiber membrane, respectively.

[0111] (3) Hollow fraction of hollow fiber membrane (%) The hollow ratio was calculated from the outer and inner diameters obtained in (2) above using the following formula. Hollowness ratio (%)=100×[inner diameter (μm)] 2 / [Outer diameter (μm)] 2 .

[0112] (4) Thickness of the surface layer (nm) The cross-section or longitudinal section of the exposed separation membrane, as described in (1) above, was pre-treated by sputtering with platinum, and an observation image was obtained by observing it at a magnification of 10,000x using an SEM. After extracting the pores of the inner layer from the observation image as described below to obtain an analysis image, a straight line was drawn perpendicular to the membrane surface from an arbitrary point on the membrane surface on the side with the surface layer of the analysis image toward the inner layer, and the length until the first pore with a diameter of 10 nm or more was reached was measured. Measurements were performed at 10 arbitrary locations, and the average value was taken as the thickness of the surface layer.

[0113] The extraction of pores in the inner layer is performed using the image analysis software "ImageJ" after binarizing the observed image. This will be explained using Figures 2 to 4. Figure 2 is an example of an observed image obtained when observing a cross-section or longitudinal section of the separation membrane at a magnification of 10,000x using an SEM. Figure 3 is a processed image obtained by binarizing Figure 2 and removing noise. Binarization is performed by matching the smaller of two brightness points where the number of pixels is (1 / 2) × A relative to the maximum number of pixels A, in a distribution where the horizontal axis is brightness and the vertical axis is the number of pixels for each brightness. Following the above binarization operation, noise reduction (equivalent to Despeckle in ImageJ) is performed once, replacing all pixels with the median value of the neighboring 3 × 3 pixels of that pixel, to obtain a processed image like Figure 3. Figure 4 is an analysis image obtained by extracting pores with a diameter of 10 nm or more from Figure 3. Pore extraction is performed using the Analyze Particles command in ImageJ, and the target of extraction is a pore with an area of ​​78.5 nm. 2 This is equivalent to a pore size of 10 nm or larger in terms of a perfectly circular shape. (Sputtering) Equipment: Hitachi High-Technologies Corporation E-1010 Evaporation time: 40 seconds Current value: 20mA (SEM) Device: Hitachi High-Technologies Corporation SU1510 Acceleration voltage: 5kV, Probe current: 30pA.

[0114] (5) Number of coarse pores in the inner layer Except for setting the observation magnification to 2,000x, the same procedure as in (4) above was used to obtain observation images of the cross-section or longitudinal section of the separation membrane. The observation field of the said observation image was 2400 μm. 2 The image was trimmed to a size of 40 μm vertically and 60 μm horizontally, and then pores with a diameter of 10 μm or larger were extracted and analyzed. The number of pores was then counted. The area of ​​the extraction target was 78.5 μm. 2 Except for the above (equivalent to a pore diameter of 10 μm or more in terms of a perfect circle), the procedure was the same as in (4) above. Measurements were taken at five arbitrary locations, and the average value was taken as the number of coarse pores in the inner layer.

[0115] (6) Mode diameter of pores Dp (nm) A 0.1g sample of the separation membrane was taken, cut with scissors to a size of 1 x 0.3cm (1cm in length if the separation membrane was a hollow fiber membrane), sealed in a glass measuring cell, and mercury intrusion measurement was performed under the following conditions. (Mercury intrusion measurement) Equipment: Micromeristics Autopore V9620 Mercury injection pressure: 193.1 kPa to 482.8 MPa (equivalent to pore size of 4 nm to 10 μm) Measurement mode: Pressure boosting (pressure injection) process Measurement cell volume: approximately 5 cm³ 3 The obtained pore volume ΣV(cm) 3 From the results of ( / g) and pore diameter D, a log differential pore volume distribution (dV / d(logD) - D graph) was created, and the pore diameter D that yielded the maximum value of dV / d(logD) was determined. Two measurements were performed, and the average value was taken as the pore mode diameter Dp.

[0116] (7) Distribution area of ​​pore size W The pore volume ΣV(cm) obtained by the mercury intrusion measurement described in (6) above 3 From the results of ( / g) and pore diameter D, a cumulative pore volume distribution (ΣV-D graph) was created. The pore diameters D that result in pore volume ΣV being 10%, 50%, and 90% of the total pore diameter volume ΣVp were determined, i.e., D10, D50, and D90, and the distribution area W of the pore diameter was calculated using the following formula. W = |(D90 - D10) / D50| Two measurements were taken, and the average value was adopted as the pore size distribution area W.

[0117] (8) Porosity From the pore volume ΣVp obtained by the mercury intrusion measurement described in (6) above, the porosity ε was determined by the following formula. ε = (ΣVp / ΣVp+1 / ρ) × 100 The measurement was performed twice, and the average value was adopted as the porosity ε of the pore size.

[0118] (9) Leakage resistance If a surface layer exists on the separation membrane and the mode diameter Dp of the pores obtained by the mercury intrusion measurement in (6) above is 4 to 230 nm (corresponding to a liquid mercury pressure P of 8.4 to 482.8 MPa), the leakage resistance was considered "good". On the other hand, if the thickness of the surface layer in (4) above is not measurable (if there are pores of 10 nm or more that penetrate to the membrane surface), or if the mode diameter Dp of the pores obtained by the mercury intrusion measurement in (6) above is greater than 230 nm (corresponding to a liquid mercury pressure P of 8.4 MPa), the leakage resistance was considered "poor".

[0119] (10) Gas permeability (GPU) A small module with an effective length of 100 mm, consisting of three hollow fiber membranes, was fabricated. Specifically, three hollow fiber membranes were bundled together and inserted into a cylindrical plastic pipe. The ends of the bundle were then sealed by curing a thermosetting resin to seal the gaps between the hollow fiber membranes and the pipe. The ends of the sealed hollow fiber membranes were cut to expose the hollow portions of the membranes, creating a small evaluation module. This small module was used to measure the gas permeation rate. Carbon dioxide and nitrogen were used individually as the target gases, and the pressure change on the permeation side per unit time was measured using an external pressure method in accordance with the pressure sensor method of JIS K7126-1 (2006). The pressure difference between the supply side and the permeation side was set to 100 kPa. A pressure difference (differential pressure) 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 gas temperature was set to 37°C.

[0120] Next, the gas permeation rate Q was calculated using the following formula, and this value was defined as the gas permeability. GPU is a common unit for gas permeation rate Q, with 1 GPU = 3.35 × 10⁻¹⁰ mol / m²·s·Pa.

[0121] Permeation flow rate Q(GPU)=10 -6 ×[Gas permeation rate (cm 3 )] / [Membrane area (cm 2 () × Time (s) × Pressure difference (cmHg)) (11) Separation coefficient α (CO2 / N2) From the gas permeation flow rates Q of carbon dioxide and nitrogen obtained in the measurement described in (10) above, the separation coefficient α(CO2 / N2) was determined by the following formula. α(CO2 / N2)=Q(CO2) / Q(N2) [Raw materials] The following raw materials were used in the examples. (1) PMP TPX DX845 (density: 833kg / m 3 (MFR: 9.0g / 10min) (2) Plasticizers Dibutyl phthalate.

[0122] (Example 1) 40% by mass of PMP and 60% by mass of dibutyl phthalate were supplied to a twin-screw extruder and melt-kneaded at 250°C. The dibutyl phthalate was added from a position (2 / 20)L relative to the screw length L. The resin composition was directly introduced into a melt-spinning pack with an extrusion temperature of 240°C and spun downward from the outer annular portion of an extrusion nozzle having one nozzle hole (double circular tube type, extrusion gap 100 μm). At this time, N2 was supplied to the inner annular portion as a hollow-forming gas. A metal filter with a diameter of 100 μm was used as a filter in the melt-spinning pack. The spun resin composition was introduced into a triacetin cooling bath at 20°C and wound up with a winder so that the draft ratio was 5.0. The free running time was 20 milliseconds. The wound hollow fiber-shaped resin molded product was immersed in isopropyl alcohol for 24 hours, then dried at 25°C to remove the isopropyl alcohol and obtain a hollow fiber film. The physical properties of the obtained hollow fiber membranes are shown in Tables 1 and 2.

[0123] The resulting hollow fiber membrane had a dense surface layer on its outer surface with a thickness of 203 nm. The pore mode diameter Dp, determined by the mercury intrusion method, was 180 nm (equivalent to a pressure of 8.4 MPa), the pore size distribution area W was 2.18, and the porosity was 55%. Furthermore, the N2 permeability was 66 GPU and the separation coefficient α(CO2 / N2) was 8.1, indicating leakage resistance and excellent gas permeability.

[0124] (Example 2) A hollow fiber membrane was obtained in the same manner as in Example 1, except that the kneading temperature was set to 260°C. The physical properties are as shown in Tables 1 and 2. The surface had a dense surface layer with a thickness of 210 nm. The pore mode diameter Dp, determined by the mercury intrusion method, was 215 nm (corresponding to a pressure P of 7.0 MPa), the pore size distribution area W was 4.17, and the porosity was 55%. Furthermore, the N2 permeability was 89 GPU and the separation coefficient α(CO2 / N2) was 5.8.

[0125] (Example 3) A hollow fiber membrane was obtained in the same manner as in Example 1, except that the gap between the discharge nozzles was set to 360 μm. As shown in Tables 1 and 2, the physical properties included a dense surface layer with a thickness of 215 nm. The pore mode diameter Dp, determined by the mercury intrusion method, was 228 nm (corresponding to a pressure of P6.6 MPa), the pore size distribution area W was 8.51, and the porosity was 55%. Furthermore, the N2 permeability was 46 GPU, and the separation coefficient α(CO2 / N2) was 10.0.

[0126] (Example 4) A hollow fiber membrane was obtained in the same manner as in Example 1, except that the free run time was set to 35 milliseconds. The physical properties are as shown in Tables 1 and 2. The surface had a dense surface layer with a thickness of 270 nm. The pore mode diameter Dp determined by the mercury intrusion method was 225 nm (corresponding to a pressure P of 6.7 MPa), the pore size distribution area W was 7.76, and the porosity was 55%. Furthermore, the N2 permeability was 29 GPU and the separation coefficient α(CO2 / N2) was 12.1.

[0127] (Example 5) A hollow fiber membrane was obtained in the same manner as in Example 1, except that the solidification bath temperature was set to 29°C. As shown in Tables 1 and 2, the membrane had a dense surface layer with a thickness of 212 nm. The pore mode diameter Dp, determined by the mercury intrusion method, was 220 nm (corresponding to a pressure P of 6.9 MPa), the pore size distribution area W was 6.36, and the porosity was 55%. Furthermore, the N2 permeability was 75 GPU, and the separation coefficient α(CO2 / N2) was 6.6.

[0128] (Example 6) A hollow fiber membrane was obtained in the same manner as in Example 1, except that the solidification bath temperature was set to 9°C. As shown in Tables 1 and 2, the membrane had a dense surface layer with a thickness of 148 nm. The pore mode diameter Dp, determined by the mercury intrusion method, was 177 nm (corresponding to a pressure of 8.5 MPa), the pore size distribution area W was 3.77, and the porosity was 55%. The N2 permeability was 252 GPU, and the separation coefficient α(CO2 / N2) was 3.1.

[0129] (Example 7) A hollow fiber membrane was obtained in the same manner as in Example 1, except that the composition of the melt-mixed mixture was 32% by mass of PMP and 68% by mass of dibutyl phthalate. The physical properties are as shown in Tables 1 and 2. The surface had a dense surface layer with a thickness of 175 nm. The pore mode diameter Dp determined by the mercury intrusion method was 230 nm (corresponding to a pressure of P6.6 MPa), the pore size distribution area W was 9.23, and the porosity was 63%. Furthermore, the N2 permeability was 223 GPU and the separation coefficient α(CO2 / N2) was 3.0.

[0130] (Example 8) A hollow fiber membrane was obtained in the same manner as in Example 1, except that the mixing temperature was 220°C, the discharge temperature was 220°C, and the plasticizer was added at (1.5 / 20)L. The physical properties are as shown in Tables 1 and 2. The surface had a dense surface layer with a thickness of 182 nm. The pore mode diameter Dp determined by the mercury intrusion method was 136 nm (corresponding to a pressure P of 11.1 MPa), the pore size distribution area W was 1.72, and the porosity was 55%. In addition, the N2 permeability was 152 GPU and the separation coefficient α(CO2 / N2) was 3.9.

[0131] (Example 9) A hollow fiber membrane was obtained in the same manner as in Example 1, except that the mixing temperature and discharge temperature were set to 230°C. The physical properties are as shown in Tables 1 and 2. The surface had a dense surface layer with a thickness of 189 nm. The pore mode diameter Dp determined by the mercury intrusion method was 154 nm (corresponding to a pressure P of 9.8 MPa), the pore size distribution area W was 1.95, and the porosity was 55%. Furthermore, the N2 permeability was 113 GPU and the separation coefficient α(CO2 / N2) was 5.1.

[0132] (Example 10) A hollow fiber membrane was obtained in the same manner as in Example 1, except that the mixing temperature was set to 240°C. The physical properties are as shown in Tables 1 and 2. The surface had a dense surface layer with a thickness of 196 nm. The pore mode diameter Dp determined by the mercury intrusion method was 170 nm (corresponding to a pressure P of 8.9 MPa), the pore size distribution area W was 2.17, and the porosity was 55%. Furthermore, the N2 permeability was 90 GPU and the separation coefficient α(CO2 / N2) was 6.1.

[0133] (Example 11) A hollow fiber membrane was obtained in the same manner as in Example 1, except that the composition of the melt-mixed mixture was 55% by mass of PMP and 45% by mass of dibutyl phthalate. The physical properties are as shown in Tables 1 and 2. The surface had a dense surface layer with a thickness of 256 nm. The pore mode diameter Dp determined by the mercury intrusion method was 120 nm (corresponding to a pressure P of 12.6 MPa), the pore size distribution area W was 1.55, and the porosity was 40%. Furthermore, the N2 permeability was 32 GPU and the separation coefficient α(CO2 / N2) was 8.8.

[0134] (Example 12) A hollow fiber membrane was obtained in the same manner as in Example 1, except that the composition of the melt-mixed mixture was 50% by mass of PMP and 50% by mass of dibutyl phthalate. The physical properties are as shown in Tables 1 and 2. The surface had a dense surface layer with a thickness of 238 nm. The pore mode diameter Dp determined by the mercury intrusion method was 130 nm (corresponding to a pressure P of 11.6 MPa), the pore size distribution area W was 1.80, and the porosity was 45%. Furthermore, the N2 permeability was 30 GPU and the separation coefficient α(CO2 / N2) was 12.2.

[0135] (Comparative Example 1) A hollow fiber film was obtained in the same manner as in Example 1, except that the composition of the melt-mixed material was 35% by mass of PMP and 65% by mass of dibutyl phthalate, the mixing temperature was 290°C, and the discharge gap of the discharge nozzle was 425 μm. As shown in Tables 1 and 2, the pore mode diameter Dp determined by the mercury intrusion method was a large value of 260 nm (equivalent to a pressure of P5.8 MPa).

[0136] (Comparative Example 2) A hollow fiber membrane was obtained in the same manner as in Example 1, except that the mixing temperature was set to 290°C. As shown in Tables 1 and 2, the pore mode diameter Dp, determined by the mercury intrusion method, was a large value of 245 nm (equivalent to a pressure of P6.2 MPa).

[0137] (Comparative Example 3) Except for setting the mixing temperature to 210°C, the process was carried out in the same manner as in Example 1. As a result, the PMP inside the twin-screw kneader remained unmelted, and the resin composition could not be extruded from the discharge nozzle.

[0138] (Comparative Example 4) The process was carried out in the same manner as in Example 1, except that the dibutyl phthalate was added at (6 / 20)L. As a result, some of the PMP remained unmelted, causing thread breakage and making it impossible to wind up the resin molded product.

[0139] (Comparative Example 5) Except for using a single-screw extruder for the melt-mixing process, the procedure was the same as in Example 1. However, some of the PMP remained unmelted, causing torque overload, and the resin composition could not be extruded from the discharge nozzle.

[0140] (Comparative Example 6) PMP 100% by mass was supplied to a twin-screw extruder, melted and kneaded at 285°C, and then introduced into a melt-spinning pack with the discharge temperature set to 280°C. The molten resin was spun downwards from the outer annular portion of a discharge nozzle with one nozzle hole (double circular tube type, discharge gap 500 μm). The spun molten resin was cooled in oxygen-enriched air with an oxygen concentration of 40% without using a cooling bath, and wound up with a winder to a draft ratio of 700. At this time, N2 was supplied to the inner annular portion as a hollow-forming gas. Since there was no cooling bath, the free-running distance was considered negligible. Also, since no plasticizer was used in the raw material, immersion in isopropyl alcohol was not performed. The wound hollow fiber-like resin was heat-treated in air at 195°C for 1 minute, then stretched to 1.4 times its original size at 25°C, and then to 1.6 times its original size at 130°C, and finally heat-set in air at 195°C for 1 minute to obtain a hollow fiber film.

[0141] As shown in Tables 1 and 2, the pore mode diameter Dp determined by the mercury intrusion method was 35 nm (equivalent to a pressure of P43.2 MPa), the porosity was 20%, and the N2 permeability was low at 4 GPU.

[0142] (Comparative Example 7) A hollow fiber film was obtained in the same manner as in Comparative Example 6, except that the molten resin was cooled in air and the stretching conditions were changed to 2.3 times at 130°C. As shown in Tables 1 and 2, the physical properties showed no dense surface layer and a low separation coefficient α(CO2 / N2) of 0.9.

[0143] [Table 1]

[0144] [Table 2] In all of Examples 1 to 12, the outer diameter of the hollow membrane was 300 to 450 μm, the inner diameter was 150 to 250 μm, the hollowness was in the range of 25 to 40%, and the number of coarse pores in the inner layer was 0 per 2400 μm. 2 That was the case.

[0145] The separation membranes obtained in Examples 1 to 12 included a surface layer and an inner layer, and all of them had a structure with leakage resistance (having a surface layer that suppresses the intrusion of liquid into the separation membrane, and the mercury intrusion pressure P corresponding to the mode diameter Dp of the inner layer's pores being within the range of 6.5 to 19.3 MPa) while maintaining high gas permeability with N2 permeability of 5 to 350 GPU. On the other hand, the separation membranes of Comparative Examples 1 and 2 did not have a mode diameter Dp of pores that met the requirements of the present invention, resulting in a structure with insufficient secondary leakage resistance. Furthermore, the separation membrane of Comparative Example 6 did not have a mode diameter Dp of pores that met the requirements of the present invention, resulting in insufficient gas permeability with N2 permeability outside the above range (below the lower limit). In addition, the separation membrane of Comparative Example 7 did not have a surface layer and had a structure with insufficient primary leakage resistance.

[0146] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications are possible without departing from the spirit and scope of the invention. [Industrial applicability]

[0147] The separation membrane of the present invention can be suitably used for applications that separate gas from a liquid or add gas to a liquid. For example, it can be suitably used as a degassing membrane to reduce the amount of dissolved gas in water, aqueous solutions, organic solvents, and resist solutions in semiconductor manufacturing lines, liquid crystal color filter manufacturing lines, and inkjet printer ink manufacturing, and as a gas exchange membrane in artificial lungs for medical applications. In particular, as a degassing membrane, it is extremely useful for degassing photoresist solutions, developers, and ultrapure water used in lithography in semiconductor manufacturing lines.

[0148] Furthermore, the separation membrane of the present invention can also be suitably used for separating gaseous mixtures. [Explanation of symbols]

[0149] 1 Membrane surface 2 Surface layer 3. Inner layer 4 pores 5. Surface thickness

Claims

1. A separation membrane mainly composed of poly(4-methyl-1-pentene), Including the surface and inner layers, The mode diameter Dp of the pores determined from mercury intrusion measurements is 100 to 230 nm. The value of the pore diameter distribution area W, obtained from the mercury intrusion measurement and calculated by the following formula, is between 1.50 and 10.

00. The porosity is 40-65%. Separation membrane. W=|(D90-D10) / D50| (In the formula, D10, D50, and D90 represent the pore diameter when the pore volume is 10% of the total pore volume, the pore diameter when the pore volume is 50% of the total pore volume, and the pore diameter when the pore volume is 90% of the total pore volume, respectively.)

2. The separation membrane according to claim 1, wherein the thickness of the surface layer is 100 to 1500 nm.

3. The separation membrane is used when CO is in a differential pressure of 100 kPa. ２ Transmission performance and N ２ Ratio of transmission performance (separation coefficient α (CO) ２ / N ２ A separation membrane according to claim 1 or 2, wherein the ratio is 3.0 to 100.

0.

4. The separation membrane according to any one of claims 1 to 3, wherein the separation membrane has a hollow fiber shape.

5. The separation membrane according to claim 4, wherein the surface layer is the outer surface of a hollow fiber-shaped separation membrane.

6. The separation membrane is N at a differential pressure of 100 kPa. ２ A separation membrane according to any one of claims 1 to 5, wherein the permeability is 5 to 350 GPU.

7. A separation membrane module for degassing and / or gas mixture separation, comprising a case and a separation membrane according to any one of claims 1 to 6, wherein the separation membrane is filled into the case.

8. An apparatus for degassing and / or for separating gas mixtures, comprising the separation membrane module described in claim 7.

9. A method for producing a liquid, comprising at least one of removing dissolved gas and adding gas using the apparatus described in claim 8.

10. A method for producing a gas, comprising separating a gaseous mixture using the apparatus described in claim 8.

11. A method for producing a separation membrane, comprising the following steps (1) to (2). (1) Using a twin-screw extruder or a multi-screw extruder, With respect to the screw length L, which is the length from the point where poly(4-methyl-1-pentene) is introduced to the screw tip, the plasticizer is introduced from a position (1 / 20)L to (5 / 20)L in the longitudinal direction from the introduction point. Preparation step: A resin composition is obtained by melt-kneading 30% to 55% by mass of poly(4-methyl-1-pentene) and 45% to 70% by mass of a plasticizer at 220°C to 260°C. (2) The resin composition is discharged from a discharge nozzle having a gap of 50 to 400 μm. A molding process in which the material passes through a free-running section for 10 to 40 milliseconds, is then introduced into a cooling bath, and the material is wound up to obtain a resin molded product.

12. The method for producing a separation membrane according to claim 11, wherein the temperature of the cooling bath in the molding step is 5 to 30°C.

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