JP2019018167A - Gas separation membrane - Google Patents

Abstract

To provide a gas separation membrane in which water is hard to be condensed in a hole of a porous support.SOLUTION: A gas separation membrane has a porous support with an open hole and a gas separation active layer which is located on the porous support. In the membrane, the porous support has a water-repellent agent on at least a part of a surface of the porous support and/or at least a part of a surface of the open hole. It is preferable that the porous support has the water-repellent agent on at least a part of the surface of the porous support, and a contact angle at the time of dropping pure water of 2 μL onto the porous support is 95° to 150°.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a gas separation membrane for separating a target gas component contained in a raw material gas using membrane separation.

Gas separation / concentration with a gas separation membrane is an energy efficient and highly safe method compared to distillation, high pressure adsorption, and the like. Recently, a method for removing and recovering carbon dioxide, which is a greenhouse gas from synthesis gas, natural gas, and the like using a gas separation membrane, has been actively studied (Patent Documents 1, 2, 3, etc.). .
A general form of the gas separation membrane has a configuration in which a gas separation active layer having gas separation ability is disposed on the surface of a porous support. This configuration is effective for increasing the amount of gas permeation while giving a certain degree of strength to the membrane. The separation layer in this case is often a layer containing a non-porous polymer.

  In general, the performance of a gas separation membrane is expressed using a permeation rate and a separation coefficient as indices. The permeation rate is expressed by (gas permeability coefficient) / (separation layer thickness). As is clear from the above equation, as a measure for obtaining a membrane having a high permeation rate, the thickness of the gas separation active layer is reduced (Patent Documents 4, 5, etc.), the gas permeation coefficient is increased, and the like. Can be mentioned. That is, it is important to use a material having a large transmission coefficient and separation coefficient and to reduce the film thickness to the limit to obtain an efficient membrane process. The separation coefficient is represented by the ratio of the permeation speeds of the two gases to be separated, and is a value depending on the gas separating polymer constituting the gas separation membrane.

International Publication No. 2014/157069 JP 2011-161387 A Japanese Patent Laid-Open No. 9-898 Japanese Patent No. 5,507,079 Japanese Patent No. 5019502

  FIG. 4 is a cross-sectional view illustrating a schematic configuration of a conventional gas separation membrane. The membrane structure of the gas separation membrane 4 shown in FIG. 4 generally has an asymmetric structure in which a gas separation active layer 42 having a separation ability is laminated on a porous support 41 having through holes P. In addition, in FIG. 4 which is sectional drawing, although the through-hole P is drawn in the substantially circular shape or the substantially elliptical shape, the through-hole P is a hole penetrated from one surface of the porous support body to the other surface. The porous support does not have the ability to separate gases, and functions as a support that supports a gas separation active layer having gas separation ability. The thickness of the gas separation active layer is on the order of microns. Further reducing the thickness of the gas separation active layer is significant from the viewpoint of increasing productivity per gas separation membrane module and making separation equipment compact.

  For example, an olefin separation membrane is a membrane that separates olefin components such as ethylene, propylene, 1-butene, 2-butene, isobutene, and butadiene from two or more kinds of mixed gases. This mixed gas mainly contains paraffins such as ethane, propane, butane and isobutane in addition to olefins. Since the olefin and paraffin in the mixed gas have molecular sizes close to each other, generally, the separation coefficient in the solution diffusion separation mechanism is small. On the other hand, since olefin has an affinity for silver ions, copper ions and the like and forms a complex, it is known that the olefin can be separated from the mixed gas by a facilitated transport permeation mechanism using the complex formation.

  The facilitated transport permeation mechanism refers to a separation mechanism that utilizes the affinity between a target gas and a membrane. The main constituent material of the film itself may have an affinity for the target gas, or a component having an affinity for the target gas may be doped into the film. The facilitated transport permeation mechanism generally provides a higher separation factor than the solution diffusion separation mechanism. In an accelerated permeation mechanism for olefin separation, metals are generally used to obtain affinity for olefins. In this case, since the metal species needs to be ions, the gas separation active layer usually contains water and an ionic liquid, and therefore the gas separation active layer is usually in the form of a gel membrane.

  As for the carbon dioxide separation membrane, a technique for separating carbon dioxide by a facilitated transport permeation mechanism similar to that of an olefin separation membrane is known. Carbon dioxide generally has an affinity for an amino group, and carbon dioxide can be separated using the affinity. This separation membrane usually also contains water and an ionic liquid, and the gas separation active layer is often in the form of a gel membrane.

  In general, the raw material gas of the facilitated transport membrane system contains moisture. This is because the facilitated transport permeation mechanism can be maintained by supplying moisture to the gas separation active layer. As described above, moisture is indispensable for the facilitated transport film. However, due to the presence of moisture, some of the pores of the porous support are blocked by the condensation of moisture (blocking C in FIG. 4). There is a problem that the membrane permeation rate of the target gas component is lowered. However, a gas separation membrane that hardly condenses moisture in the pores of the porous support has not been developed so far. For example, a method for avoiding moisture condensation by enlarging the pore diameter of the porous support is conceivable. However, since it is difficult to apply the gas separation active layer to the surface of the porous support without defects, there is a limit to increasing the pore diameter. Therefore, the problem to be solved by the present invention is to provide a gas separation membrane in which moisture is hardly condensed in the pores of the porous support.

In order to solve the above-mentioned problems, the present inventors have intensively studied. As a result, by hydrophobizing the pores of the porous support of the gas separation membrane having a gas separation active layer, it was found that condensation of moisture into the pores was suppressed, and excellent gas permeability was obtained. The present invention has been reached.
The present invention is summarized as follows.

[1] A gas separation membrane having a porous support having through-holes and a gas separation active layer disposed on the porous support,
The gas separation membrane in which the porous support has a water repellent agent on at least a part of the surface of the porous support and / or at least a part of the surface of the through hole.
[2] The porous support has a water repellent on at least a part of the surface of the porous support, and a contact angle when 2 μL of pure water is dropped onto the porous support is 95 ° to The gas separation membrane according to the first aspect, which is 150 °.
[3] The above porous support, wherein the porous support contains one or more materials selected from the group consisting of polyvinylidene fluoride (PVDF), polyethersulfone (PES), polysulfone (PSF), and polyacrylonitrile (PAN). The gas separation membrane according to aspect 1 or 2.
[4] The gas separation membrane according to any one of the above aspects 1 to 3, wherein the porous support has an average pore size of 0.01 μm to 2.0 μm.
[5] The gas separation according to any one of the above aspects 1 to 4, wherein the propylene / propane separation coefficient α is 50 or more and 2,000 or less under the conditions of a measurement temperature of 30 ° C. and a propylene partial pressure of 0.6 atm. film.

  According to the present invention, a gas separation membrane having a high permeation rate for a target gas and a high separation performance is provided.

It is sectional drawing explaining the porous support body of the gas separation membrane which concerns on one Embodiment of this invention. It is sectional drawing explaining schematic structure of the gas separation membrane which concerns on one Embodiment of this invention. It is sectional drawing explaining schematic structure of the gas separation membrane which concerns on one Embodiment of this invention. It is sectional drawing explaining schematic structure of the conventional gas separation membrane.

Hereinafter, exemplary embodiments of the present invention will be described, but the present invention is not limited to these embodiments. In addition, the same code | symbol provided to drawing shows the same element.
FIG. 1 is a cross-sectional view illustrating a porous support for a gas separation membrane according to an embodiment of the present invention, and FIGS. 2 and 3 illustrate a schematic configuration of the gas separation membrane according to an embodiment of the present invention. FIG. The gas separation membranes 1 and 2 have porous supports 11 and 21 having through holes P, and gas separation active layers 12 and 22 disposed on the porous supports 11 and 21. In addition, although the through-hole P is drawn in the substantially circular shape or the substantially elliptical shape in FIGS. 1-3 which are sectional drawings, the through-hole P is a hole penetrated from one surface of the porous support to the other surface. It is. The porous supports 11 and 21 have a water repellent 23 on at least a part of the surfaces of the porous supports 11 and 21 and / or at least a part of the surface of the through holes P. Such a gas separation membrane suppresses condensation of moisture in the porous support, and as a result, can provide excellent permeability. In the present disclosure, the surface of the porous support means the outer surface of the porous support. In the present disclosure, at least part of the surface is a concept including part and all of the surface.

[Raw material gas]
The gas separation membrane according to the present invention can be used for separating a target gas component from a mixed gas containing the target gas component (also referred to as a source gas in the present disclosure). Examples of the target gas component include carbon dioxide, methane, ethane, ethylene, propane, propylene, butane, 1 butene, 2 butene, isobutane, isobutene, and butadiene.

  The gas separation membrane is, for example, a composite hollow fiber membrane having a gas separation active layer on the surface of a porous hollow fiber support, or a composite flat membrane having a gas separation active layer on the surface of a porous flat membrane support. Good.

[Porous support]
With reference to FIG. 1, the porous support 11 in the gas separation membrane of the present embodiment is a membrane having a large number of through holes P (that is, holes penetrating from one surface of the support to the other surface). This porous support has substantially no gas separation performance, but can give mechanical strength to the gas separation membrane of this embodiment.

  The material of the porous support is not particularly limited as long as it has sufficient corrosion resistance against the raw material gas and durability at the operation temperature and operation pressure, but as an organic material, polyvinylidene fluoride (PVDF), polyethersulfone ( A homopolymer or copolymer such as PES), polysulfone (PSF), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyimide, polybenzoxazole, and polybenzimidazole is preferable. Preferred examples of the copolymer include a polymer having a homopolymer moiety in a part of the main chain. A porous support can be formed of any of these homopolymers and copolymers alone or a mixture thereof. In a preferred embodiment, the porous support contains one or more materials selected from the group consisting of polyvinylidene fluoride (PVDF), polyethersulfone (PES), polysulfone (PSF), and polyacrylonitrile (PAN).

  When the porous support is a hollow fiber, the inner diameter of the hollow fiber is appropriately selected depending on the processing amount of the raw material gas, but is generally selected between 0.1 mm and 20 mm. In order to improve the contact between the target gas component contained in the raw material gas and the absorbing liquid (for example, an aqueous silver nitrate solution), the inner diameter of the hollow fiber is preferably 0.2 mm to 15 mm. The outer diameter of the hollow fiber is not particularly limited, but is appropriately selected according to the inner diameter of the hollow fiber so that the hollow fiber has a thickness that can withstand the pressure difference between the inside and outside of the hollow fiber. The outer diameter of the hollow fiber is preferably 0.11 mm or more and 30 mm or less, more preferably 0.13 mm or more and 25 mm or less from the viewpoint of obtaining good durability against a pressure difference between the inside and outside of the hollow fiber.

  When the porous support is a flat membrane, the thickness of the flat membrane is appropriately selected depending on the throughput of the raw material gas, but is preferably 0.1 mm or more and 2 mm or less from the viewpoint of obtaining good durability and separation performance. More preferably, it is 0.15 mm or more and 1.5 mm or less.

[Gas separation active layer]
2 and 3, the gas separation active layers 12 and 22 are layers that give the gas separation membranes 1 and 2 substantial gas separation ability. The thickness of the gas separation active layer is preferably thin, and is generally selected between 0.01 μm and 100 μm. In order to improve the recovery rate of the target gas component contained in the source gas, the thickness of the gas separation active layer is preferably 0.01 μm to 10 μm. The film thickness can be determined, for example, by combining a transmission electron microscope (TEM) or a gas cluster ion gun mounted X-ray photoelectron spectroscopic analysis (GCIB-XPS) and a scanning electron microscope (SEM). . Specifically, for example, the following method can be used.
(I) The thickness of the gas separation active layer is measured.
[When using TEM]
When using TEM, for example, the film thickness of the gas separation active layer is evaluated under the following conditions.
(Preprocessing)
A gas separation membrane, for example, freeze-fractured is used as a measurement sample, and the outer surface of the sample is coated with Pt and embedded in an epoxy resin. And after producing an ultra-thin section by cutting with an ultramicrotome (for example, type “UC-6” manufactured by LEICA), phosphotungstic acid staining is performed, and this is used as a sample for microscopic examination.
(Measurement)
The measurement can be performed using, for example, Hitachi TEM, format “S-5500”, at an acceleration voltage of 30 kV.
[When using GCIB-XPS]
In the case of using GCIB-XPS, the film thickness of the gas separation active layer can be known from the obtained distribution curve of relative element concentration.
GCIB-XPS can be performed under the following conditions using, for example, the format “VersaProbeII” manufactured by ULVAC-PHI.
(GCIB conditions)
Acceleration voltage: 15 kV
Cluster size: Ar ₂₅₀₀
Cluster range: 3mm x 3mm
Sample rotation during etching: Exist Etching interval: 3 minutes / level Sample current: 23 nA
Total etching time: 69 minutes (XPS conditions)
X-ray: 15kV, 25W
Beam size: 100 μm
(Ii) The thickness of the dense layer is evaluated.
From the thickness of the separation active layer determined in (i) above and the SEM image, the thickness of the dense layer can be evaluated. For example, the SEM is evaluated under the following conditions.
(Preprocessing)
A gas separation membrane obtained by freezing and crushing the gas separation membrane on a surface substantially perpendicular to the boundary surface between the base material membrane and the separation active layer is used as a measurement sample, and a platinum coating is applied to the cross section of the sample to obtain a sample for speculum.
(Measurement)
The measurement is performed at an accelerating voltage of 20 kV using, for example, an SEM manufactured by JEOL, “Carry Scope (JCM-5100)”.
On the observation screen with a magnification of 10,000, the pore diameters other than the separation active layer determined in (i) are observed, and the thickness of the layer composed of pores less than 0.01 μm is determined.

  The material of the gas separation active layer is selected according to the type of the source gas and the target gas component. A typical material for the gas separation active layer is a polymer having a hydrophilic group in that it easily forms a gel film containing water. In a typical embodiment, the gas separation active layer is a gel membrane containing water. In a preferred embodiment, the material of the gas separation active layer is polyvinyl alcohol, polyacrylic acid, poly 1-hydroxy-2-propyl acrylate, polyethylene oxide modified phosphoric acid methacrylate, polyallyl sulfonic acid, polyvinyl sulfonic acid, polyacrylamide methyl propane sulfone. Examples thereof include acids, polyethyleneimine, polyallylamine, gelatin, polylysine, polyglutamic acid, polyarginine, polyglycidyl methacrylate, poly 1-hydroxy-2-propyl acrylate, polyethylene oxide-modified phosphate methacrylate, and polysaccharides. In addition, the polysaccharide in this indication means the polymer | macromolecule which has the structure which a monosaccharide couple | bonds with a glycosidic bond, and is a concept including an oligosaccharide. The number of repeating units of the polysaccharide is preferably 100 to 10,000, more preferably 300 to 7,000, and still more preferably 500 to 4,000.

  Examples of the polysaccharide include chitosan, alginic acid, pectin, chondroitin, hyaluronic acid, xanthan gum, cellulose, chitin, pullulan, oligoglucosamine, oligofructose, and derivatives thereof. These polysaccharides may be used alone or as a mixture.

The gas separation membrane preferably further contains a metal salt in order to improve the gas separation performance. The metal salt can be included in the porous support, the gas separation active layer, or both. Examples of the metal salt include a cation selected from the group consisting of monovalent silver ions, monovalent copper ions, and complex ions thereof, and F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , CN ⁻ , NO ₃ ⁻ , Preference is given to salts consisting of SCN ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , BF ₄ ⁻ and PF ₆ ⁻ , and anions selected from the group consisting of these. Of these, Ag (NO ₃ ) is particularly preferable from the viewpoint of availability and product cost. The content of the metal salt is preferably 5 wt% to 90 wt%, more preferably 10 wt%, based on the total weight of the metal salt and the water of the gas separation membrane (typically the water of the gas separation active layer). % To 80 wt%.

[Water repellent]
2 and 3, the porous support 11 has a water repellent 23 on at least a part of the surface of the porous support 11 and / or at least a part of the surface of the through hole P. The water repellent imparts hydrophobicity to the porous support having through-holes and contributes to good gas separation ability. Although not wishing to be bound by theory, in the case of a porous and hydrophobic membrane having a through-hole, condensation of moisture in the pores of the porous support is suppressed during separation of the source gas containing moisture. It is thought that it is done.

  From the viewpoint of obtaining good gas separation performance due to the hydrophobicity of the gas separation membrane, the porous support has a water repellent on at least a part of the surface of the porous support, and 2 μL of the porous support is provided on the porous support. The contact angle when pure water is dropped is preferably 95 ° or more and 150 ° or less. The contact angle is more preferably 100 ° or more and 150 ° or less. The contact angle is a value when 2 μL of pure water is dropped onto the porous support at a temperature of 23 ° C. and a relative humidity of 50% using the droplet method.

  The hydrophobicity of the porous support can be adjusted by controlling the presence of the water repellent agent on at least a part of the surface of the porous support and / or at least a part of the surface of the through-hole. In addition to this, the hydrophobicity of the porous support can also be adjusted by selecting or refining the porous support material.

  The water repellent can be formed as a hydrophobic coating on the surface or inside of the porous support (specifically, the surface of the through-hole), thereby imparting or improving the water repellency to the porous support. . Preferred examples of the water repellent include a compound having a siloxane bond, a compound having a silyl group and / or a fluoro group. Examples of the compound having a siloxane bond include silicone oil. Silicone oils include straight silicone oil (dimethyl silicone oil, methylphenyl silicone oil, etc.), reactive modified silicone oil (eg, silicone oil introduced with an organic functional group such as amino group), non-functional silicone oil (eg, fluoroalkyl). Examples include modified silicone oil, etc. Examples of the compound having a silyl group and / or a fluoro group include a polymer having a fluoroalkyl group, an alkylsilyl group, and / or a fluorosilyl group.

Examples of a method for applying a water repellent to the porous support include the following methods:
(A) Water repellent having a siloxane bond, for example, straight silicone oil such as dimethyl silicone oil and methylphenyl silicone oil, reactive modified silicone oil (for example, an organic functional group such as an amino group), non-functional silicone oil (For example, a fluoroalkyl-modified one) or the like applied to the surface of the porous support;
(A) A polymer having a fluoroalkyl group, an alkylsilyl group, a fluorosilyl group or the like is used as a water repellent, and the water repellent is a main component, which is dispersed in a solvent such as a carbon-based solvent or a fluorine-based solvent. Applying to a porous support in the form of an emulsion;
(C) A method of obtaining a strong film by crosslinking the water repellent film with a blocked isocyanate crosslinking agent when performing the method (a) or (b);
(D) After reacting the silane coupling agent with the porous support, a polymer having a fluoroalkyl group, an alkylsilyl group, and / or a fluorosilyl group is bonded to form the silane coupling agent and the polymer. A method of forming a water repellent; and (e) after reacting alkoxysilane with the porous support, as in method (d), having a fluoroalkyl group, an alkylsilyl group, and / or a fluorosilyl group A method of forming a water repellent comprising the alkoxysilane and the polymer by bonding the polymer.

[Confirmation of presence of water repellent]
The presence of the water-repellent agent in the gas separation membrane can be confirmed by measuring the contact angle before and after the water-repellent treatment or by using the following X-ray light spectroscopy (XPS).

[Quantification of water repellent]
The abundance of the water repellent in the gas separation membrane is determined by the relative element concentration determined from X-ray light spectroscopy (XPS). For example, if the water repellent is a fluorine-based water repellent, CF ₃ within the XPS of 295～291EV - and CF ₂ C1s spectrum of -CF ₂ bonding state was observed, and CF ₃ in all elements - The element ratio of carbon in the CF ₂ —CF ₂ bonding state is preferably 0.5% or more and less than 15.0%, more preferably 1.0% or more and less than 10%. Further, when the water repellent is a fluorine-based water repellent, the O1s spectrum is observed within the XPS range of 530 to 538 eV, and the element ratio of oxygen in the total elements is preferably 1.0% or more and 15. It is less than 0%, more preferably 2.0% or more and 10% or less.

  For example, when the water repellent is a silicone water repellent, the Si2p spectrum is observed within the range of 100 to 102 eV of XPS, and the element ratio of silicon in all elements is preferably 3.0% or more and 20. It is less than 0%, more preferably 5.0% or more and less than 15%. Further, when the water repellent is a silicone water repellent, an O1s spectrum is observed in the XPS range of 530 to 538 eV, and the element ratio of oxygen in all elements is preferably 5.0% or more and 25.0%. And more preferably 10.0% or more and less than 20.0%.

[Aperture ratio, average pore diameter, pore diameter distribution and porosity]
The opening ratio of the porous support in the state of being a gas separation membrane (that is, the opening ratio of the surface of the porous support) is preferably in the range of 20% to 50%, more preferably 22% to 49%. Within the range, more preferably within the range of 25% to 45%.

  The average pore diameter of the porous support in the state of being a gas separation membrane is preferably in the range of 0.01 μm to 2.0 μm, more preferably 0.1 to 2.0 μm from the viewpoint of suppressing moisture condensation. It is in the range of 1.0 μm. If the average pore diameter is 0.01 μm or more, moisture is difficult to condense, and if it is 2.0 μm or less, coating of the gas separation active layer with substantially no defects is easy.

  The ratio of the maximum pore diameter to the average pore diameter of the porous support in the gas separation membrane (also referred to as pore diameter distribution in the present disclosure) is preferably in the range of 1.2 to 2.5. The ratio of the maximum pore diameter to the average pore diameter (pore diameter distribution) being in the range of 1.2 to 2.5 means that the pore diameter is relatively uniform. When the pore size distribution is widened, moisture concentrates on the pores having a large diameter and the moisture is condensed in the small pores. From such a viewpoint, the ratio of the maximum pore diameter to the average pore diameter of the porous support is preferably 1.2 to 2.5, more preferably 1.3 to 2.3.

  The porosity of the porous support in the state of being a gas separation membrane is preferably in the range of 50% to 85%, more preferably in the range of 52% to 82%, still more preferably 55% to 75%. Is within the range.

The aperture ratio, average pore diameter, pore diameter distribution, and porosity of the porous support can be determined by a scanning electron microscope (SEM). Specifically, for example, the following method can be used.
(Preprocessing)
A gas separation membrane obtained by freezing and crushing a gas separation membrane on a surface substantially perpendicular to the boundary surface between the base material membrane and the gas separation active layer is used as a measurement sample, and a platinum coating is applied to the cross section of the sample to obtain a sample for speculum.
(Measurement)
The measurement is performed at an accelerating voltage of 20 kV using, for example, an SEM manufactured by JEOL, “Carry Scope (JCM-5100)”.
(Opening ratio of support)
In the observation screen with a magnification of 10,000, the ratio of the aperture ratio on the film surface is determined. Specifically, the observation screen is printed, the opening is cut out, and determined from the weight ratio.
(Average pore size / pore size distribution)
On the observation screen with a magnification of 10,000 times, the pore diameters at 20 locations are measured by SEM, and the average value and distribution are obtained.
(Porosity)
In the observation screen with a magnification of 10,000 times, the ratio of the voids in the film cross section is determined. Specifically, the observation screen is printed, the void is cut out, and determined from the weight ratio.

The porous support having the aperture ratio, the average pore diameter, the pore diameter distribution, and the porosity described above can be produced, for example, by the following method:
(A) obtaining a porous support having a sharp pore size distribution;
(A) A so-called large pore diameter cutting method, for example, a method for controlling the extraction amount or extraction behavior of a plasticizer when a membrane formed from a raw material resin is made porous, a large pore size by pressing silicon powder against a porous support. How to fill the part.

  The gas separation membrane of this embodiment has a propylene gas permeability coefficient of preferably 100 Barrer to 2,000 Barrer, propylene / propane separation factor α under the conditions of a measurement temperature of 30 ° C. and a propylene partial pressure of 0.6 atm. Is 50 or more and 2,000 or less.

  Hereinafter, exemplary embodiments of the present invention will be described more specifically using examples. However, the present invention is not limited to these examples.

Example 1
The gas separation membrane shown in FIGS. 1 and 2 was produced.
The surface of a hollow fiber membrane made of polyvinylidene fluoride (PVDF) having an inner diameter of 0.7 mm, an outer diameter of 1.2 mm, an average pore diameter of 0.2 μm, and a length of 12 cm is immersed in a 0.8 wt% chitosan aqueous solution. A chitosan layer as a gas separation active layer was applied to the surface of the hollow fiber membrane by drying at 7 ° C. for 7 minutes.
Ten of these hollow fibers were put into a cylindrical container having an inner diameter of 2 cm, and both ends of the container were adhesively sealed with an acid anhydride epoxy adhesive. After the adhesive was cured, both ends of the cylinder were cut 1 cm each.
As a water repellent, a solution prepared by diluting Teflon (registered trademark) AF2400 manufactured by Mitsui DuPont Fluorochemical Co., Ltd. with Novec7300 manufactured by 3M to a polymer concentration of 0.5 wt% is prepared, and the solution is passed through the end of the cylinder. The inner surface (that is, the surface of the porous support) and at least part of the through holes of the porous support were coated. This state was maintained for 5 hours, the solution was taken out, and dried at 80 ° C. for 120 minutes.
A 7M silver nitrate aqueous solution was introduced into the container from the raw material gas insertion line on the side surface of the cylindrical container to produce a gas separation device.

The permeation rate of propane and propylene was measured using this gas separator.
For the measurement, a mixed gas composed of propane and propylene (propane: propylene = 40: 60 (mass ratio)) was used, the supply side gas flow rate was 50 cc / min, and the nitrogen flow rate into the absorption gas was 50 cc / min. Nitrogen gas was supplied in a humidified atmosphere that was bubbled in water before being supplied to the gas separator. The measurement temperature was 30 ° C. The pressure is 0 KPaG for both the first gas and the second gas.
Permeated propylene was analyzed using gas chromatography (GC) 3 hours after supplying the raw material gas. The measurement results are shown in Table 1.
Further, after coating the water repellent, the module was disassembled, the hollow fiber was cut out, and the contact angle of the inner surface of the hollow fiber was measured by a liquid method. The measurement results are shown in Table 1.

Example 2
In Example 1, the measurement was performed in the same manner except that the water repellent and the solution thereof were ethanol solutions of dimethylpolysiloxane. The measurement results are shown in Table 1.

Example 3
In the said Example 1, it measured by the same method except having made the water repellent and its solution into the water repellent FS-392B by Fluoro Technology Co., Ltd. The results are shown in Table 1.

Comparative Example 1
The porous support obtained in Example 1 was measured without a hydrophobic coating with a water repellent.

  As can be seen from the results in Table 1, the propylene permeability of the film not coated with the water repellent was 210 GPU, whereas the permeability of the film coated with the water repellent showed high values. . The permeability tended to increase with increasing contact angle. This is considered to be the result of the moisture becoming less likely to condense inside the porous support as the contact angle increases.

DESCRIPTION OF SYMBOLS 1, 2, Gas separation membrane 11,21 Porous support body 12,22 Gas separation active layer 23 Water repellent agent 24 Non-water-repellent treatment part P Through-hole C Clogging

Claims (5)

A gas separation membrane having a porous support having through-holes and a gas separation active layer disposed on the porous support,
The gas separation membrane in which the porous support has a water repellent agent on at least a part of the surface of the porous support and / or at least a part of the surface of the through hole.   The porous support has a water repellent agent on at least a part of the surface of the porous support, and a contact angle when 2 μL of pure water is dropped onto the porous support is 95 ° to 150 °. The gas separation membrane according to claim 1.   The porous support contains at least one material selected from the group consisting of polyvinylidene fluoride (PVDF), polyethersulfone (PES), polysulfone (PSF), and polyacrylonitrile (PAN). 2. The gas separation membrane according to 2.   The gas separation membrane according to any one of claims 1 to 3, wherein an average pore diameter of the porous support is 0.01 µm to 2.0 µm.   The gas separation membrane according to any one of claims 1 to 4, wherein a separation factor α of propylene / propane is 50 or more and 2,000 or less under conditions of a measurement temperature of 30 ° C and a propylene partial pressure of 0.6 atm. .