Separation membrane

Abstract

The present invention provides a novel separation membrane suitable for separating hydrogen from a mixed gas containing hydrogen. A separation membrane 10 according to the present invention comprises a separation function layer 1, and a protection layer 5 for protecting the separation function layer 1. The ratio A2 / A1 of the thickness A2 (μm) of the protection layer 5 to the thickness A1 (μm) of the separation function layer 1 is at least 0.5 and less than 2.0.

Description

separation membrane

[0001] The present invention relates to a separation membrane.

[0002] In recent years, technologies for using hydrogen as an energy source have been developed with the aim of reducing environmental impact. Accordingly, hydrogen purification methods have also been investigated. In particular, methods such as steam reforming, in which hydrocarbons such as methane are reacted with steam, produce a mixed gas containing not only hydrogen but also the raw hydrocarbons. Therefore, there is a need for a method for efficiently separating hydrogen from such a mixed gas.

[0003] As a method for separating hydrogen from a mixed gas containing hydrogen, for example, a membrane separation method is considered. The membrane separation method has the potential to efficiently separate hydrogen from a mixed gas while suppressing operating costs. Patent Document 1 discloses a composite membrane having a crosslinked polyamide separation functional layer formed on a support membrane as a separation membrane used in the membrane separation method.

[0004] JP 2022-54573 A

[0005] There is a need for new separation membranes suitable for separating hydrogen from hydrogen-containing gas mixtures.

[0006] The present invention provides a separation membrane comprising: a separation functional layer; and a protective layer that protects the separation functional layer, wherein the ratio A2 / A1 of the thickness A2 (μm) of the protective layer to the thickness A1 (μm) of the separation functional layer is 0.5 or more and less than 2.0.

[0007] According to the present invention, a new separation membrane suitable for separating hydrogen from a hydrogen-containing mixed gas can be provided.

[0008] FIG. 1 is a cross-sectional view schematically showing a separation membrane according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a membrane separation device equipped with a separation membrane of the present invention. FIG. 3 is a perspective view schematically showing a modified example of a membrane separation device equipped with a separation membrane of the present invention. FIG. 4 is a graph showing the results of pressure test 1 performed on the separation membranes of Examples 9 to 11. FIG. 5 is a graph showing the results of pressure test 2 performed on the separation membranes of Examples 12 to 14.

[0009] A separation membrane according to a first aspect of the present invention comprises a separation functional layer and a protective layer that protects the separation functional layer, wherein the ratio A2 / A1 of the thickness A2 (μm) of the protective layer to the thickness A1 (μm) of the separation functional layer is 0.5 or more and less than 2.0.

[0010] In a second aspect of the present invention, for example, in the separation membrane according to the first aspect, the thickness A1 is 0.01 μm to 50 μm.

[0011] In a third aspect of the present invention, for example, in the separation membrane according to the first or second aspect, the thickness A2 is 0.01 μm to 50 μm.

[0012] In a fourth aspect of the present invention, for example, in the separation membrane according to any one of the first to third aspects, the separation functional layer contains at least one selected from the group consisting of polyamide, cellulose ester, polyolefin, fluorine-containing polymer, polysulfone, and ceramic.

[0013] In a fifth aspect of the present invention, for example, in the separation membrane according to any one of the first to fourth aspects, the protective layer contains a silicone resin.

[0014] In a sixth aspect of the present invention, for example, in the separation membrane according to any one of the first to fifth aspects, the protective layer is formed from an addition type silicone resin composition or a condensation type silicone resin composition.

[0015] In a seventh aspect of the present invention, for example, in the separation membrane according to any one of the first to sixth aspects, the protective layer is in direct contact with the separation functional layer.

[0016] In an eighth aspect of the present invention, for example, the separation membrane according to any one of the first to seventh aspects further comprises a porous support that supports the separation functional layer.

[0017] In a ninth aspect of the present invention, for example, in the separation membrane according to any one of the first to eighth aspects, when helium is supplied at a pressure of 0.6 MPa to a space adjacent to one surface of the separation membrane, the permeation rate T of helium that permeates the separation membrane is He is 100 GPU or more.

[0018] In a tenth aspect of the present invention, for example, in the separation membrane according to any one of the first to ninth aspects, the separation factor α of helium relative to nitrogen is He / N2 is 200 or more. He / N2 is the permeation rate T of nitrogen that permeates the separation membrane when nitrogen at a pressure of 0.6 MPa is supplied to the space adjacent to one side of the separation membrane. N2 (GPU) The permeation rate T of helium that permeates the separation membrane when helium at a pressure of 0.6 MPa is supplied to the space. He (GPU) ratio T He / T N2 means.

[0019] In an eleventh aspect of the present invention, for example, in the separation membrane according to any one of the first to tenth aspects, a separation factor α of helium relative to carbon dioxide is He / CO2 is 20 or more. He / CO2 is the permeation rate T of carbon dioxide that permeates the separation membrane when carbon dioxide at a pressure of 0.6 MPa is supplied to a space adjacent to one side of the separation membrane. CO2 (GPU) The permeation rate T of helium that permeates the separation membrane when helium at a pressure of 0.6 MPa is supplied to the space. He (GPU) ratio T He / T CO2 means.

[0020] In a twelfth aspect of the present invention, for example, the separation membrane according to any one of the first to eleventh aspects is used to separate hydrogen from a mixed gas containing hydrogen.

[0021] The present invention will be described in detail below, but the following description is not intended to limit the present invention to a specific embodiment.

[0022] 1 , a separation membrane 10 of this embodiment includes a separation functional layer 1 and a protective layer 5 that protects the separation functional layer 1. The protective layer 5 is preferably in direct contact with the separation functional layer 1. In this case, the separation functional layer 1 preferentially allows small molecules, such as hydrogen and helium, to pass through. In the separation membrane 10, the ratio A2 / A1 of the thickness A2 (μm) of the protective layer 5 to the thickness A1 (μm) of the separation functional layer 1 is 0.5 or more and less than 2.0.

[0023] According to studies by the present inventors, in separation membrane 10 having a ratio A2 / A1 of 0.5 or more, defects such as cracks that occur in separation functional layer 1 tend to be sufficiently filled by protective layer 5, and deterioration of separation performance due to defects tends to be sufficiently suppressed. The ratio A2 / A1 may be preferably 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.1 or more, 1.2 or more, 1.3 or more, or even 1.4 or more.

[0024] Furthermore, according to studies by the present inventors, in a separation membrane 10 in which the ratio A2 / A1 is less than 2.0, the decrease in permeability to small molecules such as hydrogen and helium caused by the protective layer 5 tends to be sufficiently suppressed. The ratio A2 / A1 is preferably 1.9 or less, and may be 1.8 or less, 1.7 or less, 1.6 or less, or even 1.5 or less. In some cases, the ratio A2 / A1 may be 1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1.0 or less, or even 0.9 or less. The ratio A2 / A1 is particularly preferably 0.5 to 1.5.

[0025] The thickness A1 of the separation functional layer 1 can be determined by the following method. First, the cross section of the separation membrane 10 is observed at multiple arbitrary points (at least three points) using a transmission electron microscope (TEM). The magnification at this time is, for example, 20,000 times. Next, for each of the obtained TEM images, the minimum value a1 (μm) and maximum value a2 (μm) of the thickness of the separation functional layer 1 are determined. Note that the minimum value a1 and maximum value a2 of the thickness of the separation functional layer 1 respectively refer to the minimum and maximum values ​​of the distance between a pair of opposing main surfaces of the separation functional layer 1 in the stacking direction of the separation functional layer 1 and the protective layer 5. In this specification, the main surface refers to the surface of the separation functional layer 1 having the largest area.

[0026] As will be described later, the separation functional layer 1 may have a pleated microstructure, and the pleats of this microstructure may penetrate into the protective layer 5. In this case, the area where the pleats exist is also considered to be part of the separation functional layer 1, and the minimum value a1 and maximum value a2 of the thickness of the separation functional layer 1 are specified.

[0027] Next, the average value a1 of the minimum values ​​a1 identified from each TEM image ave (μm) and the average value a2 of the maximum values ​​a2 identified from each TEM image ave (μm) and calculate the average value a1 ave and a2 ave Based on the formula: (average value a1 ave (μm) + average value a2 ave The value calculated by the formula (μm) / 2 can be regarded as the thickness A1 of the separation functional layer 1.

[0028] The thickness A1 of the separation functional layer 1 is, for example, 50 μm or less, and may be 25 μm or less, 15 μm or less, 10 μm or less, 5 μm or less, 2 μm or less, 1 μm or less, 0.8 μm or less, or even 0.5 μm or less. The smaller the thickness A1 of the separation functional layer 1, the more the permeation rate of the permeating fluid that permeates the separation membrane 10 tends to improve. The lower limit of the thickness A1 of the separation functional layer 1 is, for example, 0.01 μm or more, and may be 0.03 μm or more, 0.05 μm or more, 0.08 μm or more, 0.1 μm or more, or even 0.3 μm or more. The thickness A1 of the separation functional layer 1 is preferably 0.01 μm to 50 μm.

[0029] When the separation functional layer 1 has a pleated microstructure, the pleat height A3 is not particularly limited and may be, for example, 50 μm or less, 25 μm or less, 15 μm or less, 10 μm or less, 5 μm or less, 2 μm or less, 1 μm or less, 0.8 μm or less, or even 0.5 μm or less. The lower limit of the pleat height A3 is, for example, 0.01 μm or more, 0.03 μm or more, 0.05 μm or more, 0.08 μm or more, 0.1 μm or more, or even 0.3 μm or more. The ratio A2 / A3 of the thickness A2 (μm) of the protective layer 5 to the pleat height A3 (μm) may be 0.40 to 1.00, or 0.45 to 0.95.

[0030] The height A3 of the pleats of the separation functional layer 1 can be determined by the following method. First, the average value a1 ave (μm) and the average value a2 ave (μm) and calculate the average value a1 ave and a2 ave Based on the formula: (average value a2 ave (μm)-average value a1 ave The value calculated by the above equation (μm) can be regarded as the height A3 of the pleats of the separation functional layer 1.

[0031] The thickness A2 of the protective layer 5 can be determined by the following method. First, elemental analysis is performed on the protective layer 5 to determine the weight m (g / m) of a specific element per unit area of ​​the main surface of the protective layer 5. 2 ) is identified. For example, an X-ray fluorescence (XRF) analysis can be used as the elemental analysis. Next, from the weight m, the weight M (g / m) of the material of the protective layer 5 per unit area of ​​the main surface of the protective layer 5 is determined. 2 The density (g / m) of the material of the protective layer 5 is determined from the weight M. 3 ) and convert the unit to calculate the thickness A2 of the protective layer 5. The density (true density) of the material of the protective layer 5 can be determined, for example, in accordance with the balance method defined in Japanese Industrial Standards (JIS) K0061:2001.

[0032] For example, when the material of the protective layer 5 is polydimethylsiloxane (PDMS), the thickness A2 of the protective layer 5 can be determined by the following method. First, the weight m of silicon (Si) per unit area of ​​the main surface of the protective layer 5 is determined by elemental analysis. Si (g / m 2 ) to determine the weight m Si Based on the atomic weight of silicon (28.09) and the molecular weight per one PDMS structural unit (composition formula: C2H6OSi) (74.15), the weight M of PDMS per unit area of ​​the main surface of the protective layer 5 was calculated by the following formula: PDMS (g / m 2 ) is calculated. PDMS (g / m 2 )=weight m Si (g / m 2 ) x 74.15 / 28.09

[0033] Next, the weight M of PDMS per unit area of ​​the main surface of the protective layer 5 PDMS (g / m 2 ), and the density of PDMS (980000 g / m 3 ) and the thickness A2 of the protective layer 5 can be calculated by the following formula: Thickness A2 (μm) = Weight M PDMS (g / m 2 ) / 980000(g / m 3 ) x 10 6

[0034] The thickness A2 of the protective layer 5 is, for example, 50 μm or less, and may be 25 μm or less, 15 μm or less, 10 μm or less, 5 μm or less, 2 μm or less, 1 μm or less, 0.8 μm or less, 0.5 μm or less, 0.4 μm or less, or even 0.3 μm or less. The smaller the thickness A2 of the protective layer 5, the more likely it is that the permeation rate of the permeating fluid that permeates the separation membrane 10 will be improved. From the viewpoint of suppressing a decrease in separation performance, the lower limit of the thickness A2 of the protective layer 5 is, for example, 0.01 μm or more, and may be 0.03 μm or more, 0.05 μm or more, 0.08 μm or more, 0.1 μm or more, 0.15 μm or more, or even 0.2 μm or more. In some cases, the thickness A2 of the protective layer 5 may be 0.3 μm (300 nm) or more, 0.4 μm (400 nm) or more, 0.5 μm (500 nm) or more, 0.6 μm (600 nm) or more, or even 0.7 μm (700 nm) or more. When the thickness A2 of the protective layer 5 is 0.3 μm or more (preferably 0.6 μm or more), the pressure resistance of the separation membrane 10 tends to be high. The thickness A2 of the protective layer 5 is preferably 0.01 μm to 50 μm.

[0035] In another aspect, the present invention provides a separation membrane comprising: a separation functional layer; and a protective layer protecting the separation functional layer, wherein the protective layer has a thickness of 600 nm to 5000 nm. This separation membrane tends to have particularly excellent pressure resistance. The thickness of the protective layer may be 650 nm to 2500 nm, or 700 nm to 1000 nm. In the separation membrane, the ratio A2 / A1 of the thickness A2 (μm) of the protective layer to the thickness A1 (μm) of the separation functional layer does not necessarily have to be 0.5 or more and less than 2.0, and may be, for example, 2.0 or more, or 3.0 to 10.0.

[0036] (Separation Functional Layer) The separation functional layer 1 is a layer that preferentially allows small molecules such as hydrogen and helium to permeate. Materials for the separation functional layer 1 include polymers such as polyamide, cellulose ester, polyolefin, fluorine-containing polymer, and polysulfone; and inorganic materials such as ceramic. In the separation functional layer 1, the above polymers and inorganic materials may form a three-dimensional network skeleton. The separation functional layer 1 preferably contains at least one selected from the group consisting of polyamide, cellulose ester, polyolefin, fluorine-containing polymer, polysulfone, and ceramic, and particularly preferably contains polyamide.

[0037] The polyamide contained in the separation functional layer 1 is preferably a polymer of a polyfunctional amine and a polyfunctional acid halide.

[0038] The polyfunctional amine is a compound having two or more reactive amino groups, and examples thereof include aromatic, aliphatic and alicyclic polyfunctional amines.

[0039] Examples of aromatic polyfunctional amines include m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 2,4-diaminotoluene, 2,6-diaminotoluene, N,N'-dimethyl-m-phenylenediamine, 2,4-diaminoanisole, amideol, xylylenediamine, and n-phenylethylenediamine.

[0040] Examples of the aliphatic polyfunctional amine include ethylenediamine, propylenediamine, and tris(2-aminoethyl)amine.

[0041] Examples of the alicyclic polyfunctional amine include 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, and 4-aminomethylpiperazine.

[0042] These polyfunctional amines may be used alone or in combination of two or more. It is preferable to use an aromatic polyfunctional amine as the polyfunctional amine.

[0043] The polyfunctional acid halide is a compound having two or more reactive carbonyl groups, and examples thereof include aromatic, aliphatic and alicyclic polyfunctional acid halides.

[0044] Examples of aromatic polyfunctional acid halides include trimesic acid trichloride, terephthalic acid dichloride, isophthalic acid dichloride, biphenyldicarboxylic acid dichloride, naphthalenedicarboxylic acid dichloride, benzenetrisulfonic acid trichloride, benzenedisulfonic acid dichloride, and chlorosulfonylbenzenedicarboxylic acid dichloride.

[0045] Examples of the aliphatic polyfunctional acid halides include propanedicarboxylic acid dichloride, butanedicarboxylic acid dichloride, pentanedicarboxylic acid dichloride, propanetricarboxylic acid trichloride, butanetricarboxylic acid trichloride, pentanetricarboxylic acid trichloride, glutaryl halide, and adipoyl halide.

[0046] Examples of alicyclic polyfunctional acid halides include cyclopropanetricarboxylic acid trichloride, cyclobutanetetracarboxylic acid tetrachloride, cyclopentanetricarboxylic acid trichloride, cyclopentanetetracarboxylic acid tetrachloride, cyclohexanetricarboxylic acid trichloride, tetrahydrofurantetracarboxylic acid tetrachloride, cyclopentanedicarboxylic acid dichloride, cyclobutanedicarboxylic acid dichloride, cyclohexanedicarboxylic acid dichloride, and tetrahydrofurandicarboxylic acid dichloride.

[0047] These polyfunctional acid halides may be used alone or in combination of two or more. It is preferable to use an aromatic polyfunctional acid halide as the polyfunctional acid halide. It is also preferable to form a crosslinked structure by using a trivalent or higher polyfunctional acid halide.

[0048] Furthermore, in order to improve the performance of the separation functional layer 1 containing polyamide, polymers such as polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylic acid; and polyhydric alcohols such as sorbitol and glycerin may be copolymerized.

[0049] Examples of cellulose esters include cellulose acetate, etc. Examples of polyolefins include polypropylene, etc. Examples of fluorine-containing polymers include polytetrafluoroethylene (Teflon (registered trademark)).

[0050] In a preferred embodiment, the separation functional layer 1 may contain a polymer such as polyamide as a main component, or may be composed substantially of polymer alone. In this specification, the term "main component" refers to the component that is contained in the largest amount by weight in the separation functional layer 1. The separation functional layer 1 may further contain other components in addition to the polymer.

[0051] In another preferred embodiment, the separation functional layer 1 may contain an inorganic material such as ceramic as a main component, or may be composed substantially of only inorganic materials. The separation functional layer 1 may further contain components other than inorganic materials.

[0052] The separation functional layer 1 may have a pleated microstructure. The pleats of this microstructure may penetrate into the protective layer 5. In some cases, the pleats of the microstructure may penetrate the protective layer 5 in the thickness direction. The pleated microstructure tends to be formed when the separation functional layer 1 contains polyamide.

[0053] The separation functional layer 1 typically has pores (fine pores), and preferably has a porous structure. The pores contained in this porous structure may be continuous pores formed in a three-dimensional manner. The separation functional layer 1 preferably has through-holes that penetrate the separation functional layer 1. However, the separation functional layer 1 may also have closed pores.

[0054] The average pore diameter of the separation functional layer 1 having a porous structure is preferably less than 10 nm, and may be 5 nm or less, 2 nm or less, or even 1 nm or less. The lower limit of the average pore diameter of the separation functional layer 1 is not particularly limited, and may be, for example, 0.1 nm or more. The average pore diameter of the separation functional layer 1 can be determined by the following method. First, the surface of the separation functional layer 1 is observed with a transmission electron microscope (TEM). Next, the area of ​​a specific pore present in the obtained electron microscope image is calculated by image processing. The diameter of a circle having the same area as the calculated area is regarded as the diameter of that specific pore. The diameters of an arbitrary number of pores (at least 20) are calculated, and the average of the calculated values ​​is regarded as the average pore diameter.

[0055] The pores of the separation functional layer 1 may be filled with the material of the protective layer 5 (e.g., a silicone-based polymer). In this case, the pores of the separation functional layer 1 may be filled entirely or partially with this material. Inside the pores, between the above materials (e.g., between silicone-based polymers), minute paths through which small molecules (e.g., hydrogen) can pass may be formed. When the pores of the separation functional layer 1 are filled with the material of the protective layer 5, the separation performance of the separation membrane 10 tends to be further improved.

[0056] (Protective Layer) The protective layer 5 is a layer for protecting the separation functional layer 1. The protective layer 5 preferably contains a resin R. The contact angle of the resin R with water is, for example, 60° or more. The contact angle with water can be evaluated by the sessile drop method specified in Japanese Industrial Standards (JIS) R3257:1999 using a sheet made of the resin to be evaluated. The contact angle with water of the resin R is preferably 70° or more, and may be 80° or more, 90° or more, or even 100° or more. In this specification, a resin having a contact angle with water of 90° or more may be referred to as a hydrophobic resin. The upper limit of the contact angle with water of the resin R is not particularly limited and may be, for example, 150° or less, or 120° or less.

[0057] The protective layer 5 preferably contains a silicone resin (silicone-based polymer) as the resin R. The protective layer 5 containing a silicone resin can be formed from a silicone resin composition. Examples of the silicone resin composition include an addition type silicone resin composition and a condensation type silicone resin composition. The protective layer 5 is preferably formed from an addition type silicone resin composition or a condensation type silicone resin composition, and is particularly preferably formed from a condensation type silicone resin composition.

[0058] The addition type silicone resin composition is a type of silicone resin composition that cures by an addition reaction. The addition type silicone resin composition contains, for example, a polyorganosiloxane P1 having an alkenyl group and a polyorganosiloxane P2 having a hydrosilyl (SiH) group. The addition type silicone resin composition preferably further contains a curing catalyst (hydrosilylation catalyst). The addition type silicone resin composition may be a commercially available silicone resin composition to which a curing catalyst has been added. However, the addition type silicone resin composition does not necessarily need to contain a curing catalyst.

[0059] The addition-type silicone resin composition can be formed by, for example, heat treatment, whereby the alkenyl groups of the polyorganosiloxane P1 react with the hydrosilyl groups of the polyorganosiloxane P2 (hydrosilylation reaction) to form a silicone resin. In this hydrosilylation reaction, the polyorganosiloxane P2 functions as a crosslinking agent.

[0060] Examples of the alkenyl group of the polyorganosiloxane P1 include a vinyl group and a hexenyl group. The number of alkenyl groups in the polyorganosiloxane P1 is, for example, 2 or more. The alkenyl groups are located, for example, at the terminals of the polyorganosiloxane P1.

[0061] The polyorganosiloxane P1 is, for example, a polyalkylalkylsiloxane such as polydimethylsiloxane, polydiethylsiloxane, or polymethylethylsiloxane; a polyalkylarylsiloxane; or a polyorganosiloxane such as poly(dimethylsiloxane-diethylsiloxane) to which an alkenyl group has been introduced.

[0062] The weight average molecular weight of polyorganosiloxane P1 is, for example, 1000 or more, and may be 10,000 or more, 100,000 or more, 200,000 or more, 300,000 or more, or even 400,000 or more. The upper limit of the weight average molecular weight of polyorganosiloxane P1 is not particularly limited and is, for example, 1,000,000.

[0063] The number of hydrosilyl groups in the polyorganosiloxane P2 is, for example, at least 2. The hydrosilyl groups may be located at the terminals of the polyorganosiloxane P2 or may be contained in the main chain of the polyorganosiloxane P2.

[0064] Examples of the polyorganosiloxane P2 include polymethylhydrogensiloxane, poly(dimethylsiloxane-methylhydrogensiloxane), and hydrosilyl-terminated polydimethylsiloxane.

[0065] The weight average molecular weight of the polyorganosiloxane P2 is, for example, not less than 100, and may be not less than 10,000. The upper limit of the weight average molecular weight of the polyorganosiloxane P2 is not particularly limited, and is, for example, 1,000,000.

[0066] The weight ratio P2 / P1 of polyorganosiloxane P2 to polyorganosiloxane P1 is, for example, 500 wt% or less, 100 wt% or less, 50 wt% or less, 20 wt% or less, 10 wt% or less, or even 5 wt% or less. The lower limit of the weight ratio P2 / P1 is, for example, 0.01 wt% or more.

[0067] Examples of the curing catalyst contained in the addition-type silicone resin composition include platinum-based catalysts, such as chloroplatinic acid, platinum olefin complexes, and chloroplatinic acid olefin complexes.

[0068] The addition-type silicone resin composition may contain a compound that generates catalytically active species that catalyze the addition reaction when irradiated with active energy rays such as ultraviolet (UV) rays. With an addition-type silicone resin composition containing this compound, the addition reaction can be promoted by, for example, UV irradiation.

[0069] The addition type silicone resin composition may further contain an organic solvent, a cure retarder, etc. in addition to the above-mentioned components. Examples of organic solvents include hydrocarbon solvents such as cyclohexane, n-hexane, and n-heptane; aromatic solvents such as toluene and xylene; ester solvents such as ethyl acetate and methyl acetate; ketone solvents such as acetone and methyl ethyl ketone; and alcohol solvents such as methanol, ethanol, and butanol. The organic solvents may be used alone or in combination of two or more. The addition type silicone resin composition may be a solventless type that does not contain a solvent such as an organic solvent.

[0070] The condensation type silicone resin composition is a type of silicone resin composition that cures by a condensation reaction. The condensation type silicone resin composition preferably contains a polyorganosiloxane P3 having a silanol (SiOH) group. The condensation type silicone resin composition may or may not contain a silane compound P4 having a functional group such as an alkoxy group, an alkenyloxy group, an acyloxy group, an amino group, a ketoxime group, or an amide group, together with the polyorganosiloxane P3. The condensation type silicone resin composition may or may not further contain a curing catalyst. The condensation type silicone resin composition may be a commercially available silicone resin composition to which a curing catalyst has been added.

[0071] For example, in a condensation type silicone resin composition, a reaction (condensation reaction) between the silanol groups of the polyorganosiloxane P3 and the functional groups of the silane compound P4 is promoted by heat treatment to form a silicone resin. In this condensation reaction, the silane compound P4 functions as a crosslinking agent. Note that, by the heat treatment, multiple molecules of the polyorganosiloxane P3 may be condensed via the silanol groups.

[0072] The number of silanol groups in polyorganosiloxane P3 is, for example, 2 or more. The silanol groups are located, for example, at the terminals of polyorganosiloxane P3. Polyorganosiloxane P3 may have an alkyl group such as a methyl group or an ethyl group, or a phenyl group introduced as a substituent on the side chain.

[0073] The polyorganosiloxane P3 is, for example, a polyorganosiloxane in which silanol groups have been introduced into the polyorganosiloxane described above for the polyorganosiloxane P1.

[0074] The weight average molecular weight of polyorganosiloxane P3 is, for example, 1000 or more, and may be 10,000 or more, 100,000 or more, 200,000 or more, 300,000 or more, or even 400,000 or more. The upper limit of the weight average molecular weight of polyorganosiloxane P3 is not particularly limited and is, for example, 1,000,000.

[0075] As described above, the silane compound P4 has functional groups such as alkoxy groups, alkenyloxy groups, acyloxy groups, amino groups, ketoxime groups, and amide groups. Examples of alkoxy groups include methoxy groups and ethoxy groups. Examples of alkenyloxy groups include isopropenyloxy groups. Examples of acyloxy groups include acetoxy groups. Examples of amino groups include dimethylamino groups, diethylamino groups, and ethylmethylamino groups. Examples of ketoxime groups include acetoxime groups and methylethylketoxime groups. Examples of amide groups include acetamide groups, N-methylacetamide groups, and N-ethylacetamide groups. The number of functional groups in the silane compound P4 is, for example, two or more. In particular, it is preferable that the silane compound P4 contains an alkoxysilyl group as the alkoxy group.

[0076] The silane compound P4 may be a low molecular weight compound having a molecular weight of about 1000 or less, or may be a high molecular weight compound having a polysiloxane skeleton.

[0077] Examples of the curing catalyst contained in the condensation type silicone resin composition include tin-based catalysts, such as organotin catalysts such as dibutyltin dilaurate, dibutyltin diacetate, and dibutyltin dioctate.

[0078] The condensation type silicone resin composition may further contain an organic solvent, a cure retarder, etc. in addition to the above-mentioned components. Examples of the organic solvent include those mentioned above for the addition type silicone resin composition. The condensation type silicone resin composition may be a solventless type that does not contain a solvent such as an organic solvent. Examples of the cure retarder for the condensation type silicone resin composition include acetylacetone.

[0079] The total free volume parameter of the silicone resin contained in the protective layer 5 is preferably 10 or more. In this case, the permeation rate of the permeating fluid that permeates the separation membrane 10 tends to be improved. The upper limit of the total free volume parameter of the silicone resin is not particularly limited, and is, for example, 20 or less.

[0080] The total free volume parameter is the free volume V (nm 3 ) multiplied by the relative signal intensity I (%) (free volume V × relative signal intensity I). The free volume V and the relative signal intensity I can be calculated from the measurement results of the positron lifetime spectrum of the silicone resin.

[0081] The protective layer 5 may contain the resin R as a main component, or may be composed substantially of only the resin R. The protective layer 5 may further contain components other than the resin R (for example, the above-mentioned curing catalyst).

[0082] (Porous Support) The separation membrane 10 may further include a porous support 3 that supports the separation functional layer 1. In this case, in the separation membrane 10, the separation functional layer 1 is preferably located between the protective layer 5 and the porous support 3 and in direct contact with both the protective layer 5 and the porous support 3.

[0083] The porous support 3 may be an ultrafiltration membrane in which a microporous layer having an average pore size of 0.01 to 0.4 μm is formed on a nonwoven fabric. In this case, the microporous layer is preferably in direct contact with the separation function layer 1. The average pore size of the microporous layer can be determined by the method described above for the separation function layer 1.

[0084] Examples of materials for the microporous layer include polyarylethersulfones such as polysulfone and polyethersulfone, polyimide, polyetherimide, and polyvinylidene fluoride. From the viewpoints of chemical stability, mechanical stability, and thermal stability, the microporous layer preferably contains polysulfone. The thickness of the microporous layer is not particularly limited and is, for example, 10 μm to 35 μm.

[0085] Examples of materials for the nonwoven fabric include polyolefin, polyester, and cellulose. From the viewpoint of formability, the nonwoven fabric preferably contains polyester. The nonwoven fabric may be a long-fiber nonwoven fabric or a short-fiber nonwoven fabric. The thickness of the nonwoven fabric is not particularly limited and is, for example, 50 μm to 90 μm.

[0086] The laminate of the separation functional layer 1 and the porous support 3 may function as a filtration membrane such as a reverse osmosis membrane (RO membrane) or a nanofiltration membrane (NF membrane). In this specification, an RO membrane refers to a membrane that has a sodium chloride removal rate of 93% or more when filtering a test solution with a sodium chloride concentration of 2000 mg / L at an operating pressure of 1.5 MPa. An NF membrane refers to a membrane that has a sodium chloride removal rate of 5% or more but less than 93% when filtering a test solution with a sodium chloride concentration of 2000 mg / L at an operating pressure of 1.5 MPa.

[0087] (Shape of Separation Membrane) In this embodiment, the separation membrane 10 is typically a flat membrane. However, the separation membrane 10 may have a shape other than a flat membrane, and may also be a hollow fiber membrane.

[0088] (Method for manufacturing separation membrane) The separation membrane 10 can be produced, for example, by the following method. First, a separation function layer 1 is formed on a porous support 3 (more specifically, the microporous layer of the porous support 3). As an example, a separation function layer 1 containing polyamide can be produced using an interfacial condensation method, a phase separation method, a thin film coating method, or the like. Examples of the interfacial condensation method include a method in which an aqueous amine solution containing a polyfunctional amine is contacted with an organic solution containing a polyfunctional acid halide to cause interfacial polymerization to form a separation function layer 1, and then the separation function layer 1 is disposed on the porous support 3, and a method in which a separation function layer 1 containing polyamide is directly formed on the porous support 3 by interfacial polymerization on the porous support 3. Details of the interfacial condensation method are described in JP-A-58-24303, JP-A-1-180208, etc.

[0089] Next, the separation membrane 10 can be produced by forming the protective layer 5 on the separation functional layer 1. The protective layer 5 can be formed, for example, by the following method. First, a coating liquid (e.g., a silicone resin composition) containing the material for the protective layer 5 is prepared. The viscosity and solid content of the coating liquid can be adjusted appropriately depending on the desired thickness of the protective layer 5. The solid content of the coating liquid is, for example, 0.1 wt % to 30 wt %, and may be 1 wt % to 5 wt %.

[0090] Next, a coating liquid is applied onto the separation functional layer 1 to form a coating film. The method for applying the coating liquid is not particularly limited, and for example, spin coating, dip coating, slot die coating, gravure coating, comma coating, etc. can be used. The coating liquid may be applied to the separation functional layer 1 using an applicator or a wire bar. The application conditions for the coating liquid can be adjusted appropriately depending on the desired thickness of the protective layer 5. As an example, when applying the coating liquid by spin coating, the rotation speed of the spin coater is, for example, 100 to 5000 rpm, and may be 1000 to 2000 rpm.

[0091] Next, the protective layer 5 is formed by curing the coating film. Curing of the coating film can be carried out at room temperature or in a heated environment. When curing the coating film by heating, the heating conditions for the coating film are not particularly limited. For example, the heating temperature of the coating film may be 80°C or higher, 90°C or higher, 100°C or higher, or even 120°C or higher. The upper limit of the heating temperature of the coating film is not particularly limited, and is, for example, 200°C. The heating time of the coating film can be adjusted appropriately depending on the composition of the coating film.

[0092] The separation membrane 10 may be produced by a roll-to-roll method. That is, a long porous support 3 may be unwound from a wound porous support 3, and the separation function layer 1 and the protective layer 5 may be formed while the porous support 3 is being transported. The formation of the separation function layer 1 and the formation of the protective layer 5 are preferably carried out continuously. However, after the formation of the separation function layer 1, the long laminate including the porous support and the separation function layer may be temporarily wound up. In this case, the separation membrane 10 can be produced by unwounding the long laminate again and forming the protective layer 5 while transporting the laminate. The resulting separation membrane 10 may be wound up to produce a wound separation membrane 10. The roll-to-roll method is suitable for mass production of the separation membrane 10.

[0093] In addition, when the separation functional layer 1 has pores, applying a coating liquid (e.g., a silicone resin composition) onto the separation functional layer 1 may cause a portion of the coating liquid to fill the interior of the pores of the separation functional layer 1. As the coating liquid hardens inside the pores, the interior of the pores of the separation functional layer 1 is filled with the material of the protective layer 5 (e.g., a silicone-based polymer). In this case, minute paths through which small molecules (e.g., hydrogen) can pass tend to be formed between the above-mentioned materials (e.g., between silicone-based polymers) inside the pores.

[0094] (Characteristics of Separation Membrane) The separation membrane 10 of this embodiment is typically a membrane that preferentially allows hydrogen to permeate from a hydrogen-containing mixed gas. Specifically, the separation membrane 10 preferentially allows small molecules such as hydrogen and helium to permeate, while suppressing the permeation of relatively large molecules such as carbon dioxide, nitrogen, and methane.

[0095] For example, the separation membrane 10 tends to have a high separation factor for hydrogen relative to methane. The separation factor for hydrogen relative to methane is calculated by multiplying the separation factor α He / N2 Therefore, the separation factor α of helium relative to nitrogen He / N2 From this, it is possible to predict to some extent the separation factor of hydrogen relative to methane.

[0096] In the separation membrane 10, the separation factor α of helium relative to nitrogen He / N2 is, for example, 200 or more, and may be 300 or more, 400 or more, 500 or more, or even 600 or more. He / N2 The upper limit of is not particularly limited, and is, for example, 1000 or less.

[0097] Separation factor α He / N2 is the permeation rate T of nitrogen that permeates the separation membrane 10 when nitrogen at a pressure of 0.6 MPa is supplied to the space adjacent to one side of the separation membrane 10. N2 (GPU) is the permeation rate T of helium that permeates the separation membrane 10 when helium is supplied to the space at a pressure of 0.6 MPa. He (GPU) ratio T He / T N2 In this specification, unless otherwise specified, "pressure" means absolute pressure.

[0098] Helium permeation rate T He Specifically, the separation membrane 10 to be measured is prepared. The membrane area of ​​the separation membrane 10 to be measured is, for example, 0.43 cm 2Next, helium at a pressure of 0.6 MPa and a temperature of 25° C. is supplied to a space adjacent to one surface of the separation membrane 10 (for example, the main surface 11 of the separation membrane 10 on the protective layer side). As a result, a permeated fluid (helium) that has permeated the separation membrane 10 is obtained from the other main surface of the separation membrane 10 (for example, the main surface 12 of the separation membrane 10 on the porous support side). The flow rate of this permeated fluid is measured with a mass flow meter, and from the obtained results, the permeation rate T of helium is calculated. He Depending on the flow rate of the permeating fluid, a soap film flow meter may be used instead of the mass flow meter.

[0099] Helium permeation rate T He is, for example, 100 GPU or more, and may be 105 GPU or more, 110 GPU or more, 115 GPU or more, 120 GPU or more, or even 125 GPU or more. He The upper limit of is not particularly limited, and is, for example, 500 GPU or less. The permeation rate of hydrogen permeating through the separation membrane 10 is higher than the permeation rate T He Therefore, the helium permeation rate T He From this, the hydrogen permeation rate can be predicted to some extent. -6 ·cm 3 (STP) / (sec cm 2 cm 3 (STP) means the volume of a gas at 1 atmosphere and 0°C.

[0100] Nitrogen permeation rate T N2 is the helium permeation rate T except that nitrogen at a pressure of 0.6 MPa and a temperature of 25°C is used instead of helium. He The nitrogen permeation rate T can be measured by the method described above. N2 is, for example, 0.01 GPU to 1.0 GPU.

[0101] Furthermore, the separation membrane 10 tends to have a high separation factor for hydrogen relative to carbon dioxide. The separation factor for hydrogen relative to carbon dioxide is calculated by multiplying the separation factor α He / CO2 Therefore, the separation factor α of helium for carbon dioxide is He / CO2From this, it is possible to predict to some extent the separation factor of hydrogen from carbon dioxide.

[0102] In the separation membrane 10, the separation factor α of helium relative to carbon dioxide He / CO2 is, for example, 20 or more, and may be 25 or more, 30 or more, or even 35 or more. He / CO2 The upper limit of is not particularly limited, and is, for example, 100 or less.

[0103] Separation factor α He / CO2 is the permeation rate T of carbon dioxide that permeates the separation membrane 10 when carbon dioxide at a pressure of 0.6 MPa is supplied to the space adjacent to one side of the separation membrane 10. CO2 (GPU) is the permeation rate T of helium that permeates the separation membrane 10 when helium is supplied to the space at a pressure of 0.6 MPa. He (GPU) ratio T He / T CO2 means.

[0104] Carbon dioxide permeation rate T CO2 is the helium permeation rate T except that carbon dioxide at a pressure of 0.6 MPa and a temperature of 25°C is used instead of helium. He The carbon dioxide transmission rate T CO2 is, for example, 0.1 GPU to 5.0 GPU.

[0105] (Applications of Separation Membrane) The separation membrane 10 of this embodiment may be used to separate hydrogen from a mixed gas containing hydrogen. In particular, the separation membrane 10 is suitable for separating hydrogen from a mixed gas containing hydrogen and methane or a mixed gas containing hydrogen and carbon dioxide. However, the application of the separation membrane 10 is not limited to separating hydrogen from the above-mentioned mixed gas. For example, the separation membrane 10 may be used to separate helium from a mixed gas containing helium.

[0106] <Embodiment of Membrane Separation Apparatus> As shown in Fig. 2, a membrane separation apparatus 100 of this embodiment includes a separation membrane 10 and a tank 20. The tank 20 includes a first chamber 21 and a second chamber 22. The separation membrane 10 is disposed inside the tank 20. Inside the tank 20, the separation membrane 10 separates the first chamber 21 from the second chamber 22. The separation membrane 10 extends from one to the other of a pair of wall surfaces of the tank 20.

[0107] The first chamber 21 has an inlet 21 a and an outlet 21 b. The second chamber 22 has an outlet 22 a. The inlet 21 a, the outlet 21 b, and the outlet 22 a are preferably openings formed in the wall surface of the tank 20.

[0108] Membrane separation using the membrane separation device 100 is performed, for example, by the following method. First, a hydrogen-containing gas mixture 30 is supplied to the first chamber 21 through the inlet 21a. The concentration of hydrogen in the gas mixture 30 is not particularly limited, and under standard conditions, it is, for example, 0.01 vol% (100 ppm) or more, preferably 1 vol% or more, more preferably 10 vol% or more, even more preferably 30 vol% or more, and particularly preferably 50 vol% or more. The upper limit of the hydrogen concentration in the gas mixture 30 is not particularly limited, and under standard conditions, it is, for example, 90 vol%.

[0109] The pressure inside the first chamber 21 may be increased by the supply of the mixed gas 30. The membrane separation apparatus 100 may further include a pump (not shown) for increasing the pressure of the mixed gas 30. The pressure of the mixed gas 30 supplied to the first chamber 21 is, for example, 0.1 MPa or more, preferably 0.3 MPa or more.

[0110] The second chamber 22 may be depressurized while the gas mixture 30 is supplied to the first chamber 21. The membrane separation apparatus 100 may further include a pump (not shown) for depressurizing the second chamber 22. The second chamber 22 may be depressurized so that the space within the second chamber 22 is reduced in pressure by, for example, 10 kPa or more, preferably 50 kPa or more, and more preferably 100 kPa or more relative to the atmospheric pressure in the measurement environment.

[0111] By supplying the gas mixture 30 into the first chamber 21, a permeated fluid 35 having a higher hydrogen content than the gas mixture 30 can be obtained on the other side of the separation membrane 10. That is, the permeated fluid 35 is supplied to the second chamber 22. The permeated fluid 35 preferably contains hydrogen as a main component. However, the permeated fluid 35 may also contain small amounts of gases other than hydrogen. The permeated fluid 35 is discharged to the outside of the tank 20 through the outlet 22a.

[0112] The concentration of hydrogen in the gas mixture 30 gradually decreases from the inlet 21a to the outlet 21b of the first chamber 21. The gas mixture 30 (non-permeated fluid 36) treated in the first chamber 21 is discharged to the outside of the tank 20 through the outlet 21b.

[0113] The membrane separation apparatus 100 of this embodiment is suitable for a continuous membrane separation method, but may also be used for a batch-type membrane separation method.

[0114] <Modifications of Membrane Separation Device> The membrane separation device 100 may be a spiral membrane element, a hollow fiber membrane element, or the like. Fig. 3 shows a spiral membrane element. The membrane separation device 110 of Fig. 3 includes a central tube 41 and a stack 42. The stack 42 includes the separation membrane 10.

[0115] The central tube 41 has a cylindrical shape. A plurality of holes are formed on the surface of the central tube 41 to allow the permeating fluid 35 to flow into the interior of the central tube 41. Examples of materials for the central tube 41 include resins such as acrylonitrile-butadiene-styrene copolymer resin (ABS resin), polyphenylene ether resin (PPE resin), and polysulfone resin (PSF resin); and metals such as stainless steel and titanium. The inner diameter of the central tube 41 is, for example, in the range of 20 to 100 mm.

[0116] The laminate 42 further includes a feed-side channel material 43 and a permeate-side channel material 44 in addition to the separation membrane 10. The laminate 42 is wound around a central tube 41. The membrane separation device 110 may further include an exterior material (not shown).

[0117] The feed-side channel material 43 and the permeate-side channel material 44 may be, for example, a resin net made of polyphenylene sulfide (PPS) or ethylene-chlorotrifluoroethylene copolymer (ECTFE).

[0118] Membrane separation using the membrane separation device 110 is performed in the following manner. First, the gas mixture 30 is supplied to one end of the wound stack 42. The permeated fluid 35 that has permeated the separation membrane 10 of the stack 42 moves into the interior of the central tube 41. The permeated fluid 35 is discharged to the outside through the central tube 41. The gas mixture 30 (non-permeated fluid 36) that has been treated in the membrane separation device 110 is discharged to the outside from the other end of the wound stack 42. This allows hydrogen to be separated from the gas mixture 30.

[0119] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0120] Example 1 First, a porous support was prepared, which had a polysulfone microporous layer formed on a polyester nonwoven fabric. Next, an amine aqueous solution containing 3.0 wt% m-phenylenediamine (MPD), 0.15 wt% sodium dodecyl sulfate, 2.15 wt% triethylamine, 0.31 wt% sodium hydroxide, 6 wt% camphorsulfonic acid, and 1 wt% isopropyl alcohol was applied to the microporous layer of the porous support, and excess amine aqueous solution was removed to produce a coating film.

[0121] Next, 0.075 wt% of trimesic acid trichloride (TMC) and 0.113 wt% of isophthalic acid dichloride (IPC) were dissolved in a naphthenic solvent (Exxsol D40, manufactured by ExxonMobil Corporation) to prepare an acid chloride solution. The surface of the above-mentioned coating film was immersed in this acid chloride solution for 7 seconds. Excess solution was removed from the surface of the coating film, which was then air-dried for 20 seconds and then placed in a hot air dryer at 140°C for 3 minutes. This resulted in the formation of a separation functional layer containing polyamide on the porous support.

[0122] Next, 4.00 g of a condensation type silicone resin composition (manufactured by Momentive Performance Materials Japan, YSR3022, toluene-MEK solution, solid content 30 wt%) was diluted with 55.84 g of normal heptane (manufactured by Sankyo Chemical Co., Ltd.) as a dilution solvent, 0.040 g of a tin-based catalyst (manufactured by Momentive Performance Materials Japan, YC6831) as a curing catalyst, and 0.120 g of acetylacetone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a curing retarder, to prepare a coating liquid (condensation type silicone resin composition). The solid content concentration of this coating liquid was 2 wt%.

[0123] Next, a spin coater was used to apply 8 mL of the above coating solution onto the separation function layer to obtain a coating film. The operating conditions of the spin coater were a set rotation speed of 2000 rpm, a time to reach the set rotation speed of 20 seconds, and a time to maintain the set rotation speed of 10 seconds. Next, the coating film was heated at 120 ° C for 5 minutes and cured to form a protective layer. This resulted in the separation membrane of Example 1.

[0124] (Examples 2 to 8) Separation membranes of Examples 2 to 8 were obtained in the same manner as in Example 1, except that the composition of the coating solution applied onto the separation functional layer and the rotation speed of the spin coater were changed as shown in Table 1.

[0125] [Thickness of Separation Functional Layer and Height of Folds] The cross section of the produced separation membrane was observed at three points using a transmission electron microscope (TEM) (Hitachi High-Tech Corporation, "HT-7820"), and the thickness A1 of the separation functional layer and the height A3 of the folds were determined by the method described above. Note that the TEM observation was performed at a magnification of 20,000 times.

[0126] [Thickness of Protective Layer] The protective layer of the prepared separation membrane was subjected to X-ray fluorescence (XRF) analysis using an X-ray fluorescence analyzer (Rigaku Corporation, "ZSX Primus III+"). In each example, the protective layer was substantially composed of only polydimethylsiloxane (PDMS), so in the XRF analysis, the weight m of silicon (Si) per unit area of ​​the main surface of the protective layer was Si (g / m 2 ) was determined. Weight m SiBased on the atomic weight of silicon (28.09) and the molecular weight per unit of PDMS (composition formula: C2H6OSi) (74.15), the weight M of PDMS per unit area of ​​the main surface of the protective layer was calculated using the above-mentioned formula. PDMS (g / m 2 ) was calculated. PDMS (g / m 2 ), and the density of PDMS (980000 g / m 3 ) and the thickness A2 of the protective layer was calculated using the above-mentioned calculation formula.

[0127] [Evaluation of Separation Membrane Properties] The helium permeation rate T He First, the separation membrane (membrane area 0.43 cm 2 ) was set in a metal cell and sealed with an O-ring to prevent leakage. Next, helium was injected into the metal cell at a pressure of 0.6 MPa and a temperature of 25°C so that the helium contacted the main surface of the separation membrane on the protective layer side. As a result, a permeated fluid (helium) was obtained from the main surface of the separation membrane on the porous support side. The flow rate of the obtained permeated fluid was measured, and the helium permeation rate T He was calculated.

[0128] Furthermore, the nitrogen permeation rate T N2 and the carbon dioxide permeation rate T CO2 The nitrogen permeation rate T N2 is the helium permeation rate T He was measured by the method described above. Similarly, the carbon dioxide permeation rate T CO2 is the helium permeation rate T He was measured by the method described above.

[0129] Based on the results obtained, the nitrogen permeation rate T N2 Helium permeation rate T He (GPU) ratio T He / T N2 The calculated value is used as the separation factor α of helium relative to nitrogen.He / N2 Furthermore, the carbon dioxide permeation rate T CO2 Helium permeation rate T He (GPU) ratio T He / T CO2 The calculated value is used as the separation factor α of helium for carbon dioxide. He / CO2 It was considered that.

[0130]

[0131]

[0132] The abbreviations in Table 1 are as follows: YSR3022: Condensation type silicone resin composition (manufactured by Momentive Performance Materials Japan, Inc., YSR3022) SD7328: Addition type silicone resin composition (manufactured by Dow-Toray, Inc., SD7328) BY24-489: Addition type silicone resin composition (manufactured by Dow-Toray, Inc., BY24-489) YC6831: Tin-based catalyst (manufactured by Momentive Performance Materials Japan, Inc., YC6831) SRX212: Curing catalyst (manufactured by Dow-Toray, Inc., SRX212)

[0133] As can be seen from Table 2, the separation membranes of Examples 1 to 3, in which the ratio A2 / A1 of the thickness A2 (μm) of the protective layer to the thickness A1 (μm) of the separation functional layer was 0.5 or more and less than 2.0, exhibited a helium permeation rate T He , the separation factor α of helium relative to nitrogen He / N2 , and the separation factor α of helium relative to carbon dioxide He / CO2 were all high values. As mentioned above, the helium permeation rate and separation factor tend to be correlated with the hydrogen permeation rate and separation factor. Therefore, it is presumed that the separation membranes of Examples 1 to 3 have high hydrogen permeability and separation performance for hydrogen. It can be said that the separation membranes of Examples 1 to 3 are suitable for separating hydrogen from a hydrogen-containing mixed gas.

[0134] As can be seen from Table 2, the separation membranes of Examples 4 to 6, in which the ratio A2 / A1 was less than 0.5, had a separation factor α He / N2 and separation factor α He / CO2 The separation membranes of Examples 7 and 8, in which the ratio A2 / A1 was greater than 2.0, exhibited a helium permeation rate THe and separation factor α He / CO2 was smaller than those in Examples 1 to 3.

[0135] <Pressure Test> Separation membranes of Examples 9 to 14 were prepared and pressure tests 1 and 2 were carried out on these separation membranes.

[0136] (Examples 9 to 11) Separation membranes of Examples 9 to 11 were produced by the same method as Example 1, except that the protective layer was formed under the conditions shown in Table 3. The thickness A2 of the protective layer was determined by the method described above for Examples 1 to 8.

[0137]

[0138] The abbreviations in Table 3 are as follows: YSR3022: Condensation type silicone resin composition (manufactured by Momentive Performance Materials Japan, Inc., YSR3022) YC6831: Tin-based catalyst (manufactured by Momentive Performance Materials Japan, Inc., YC6831)

[0139] Example 12 The separation membrane of Example 12 was produced by the following method. First, except that a long porous support was used, a separation functional layer containing polyamide was formed on the porous support by the same method as in Example 1. This resulted in a long laminate including the porous support and the separation functional layer.

[0140] Next, 8618 g of normal heptane (manufactured by Sankyo Chemical Co., Ltd.) as a dilution solvent and 12.9 g of a curing catalyst (manufactured by Dow Toray Industries, Inc., SRX212) were added to 2154 g of an addition-type silicone resin composition (manufactured by Dow Toray Industries, Inc., SD7328) to prepare a coating liquid (addition-type silicone resin composition). The solids concentration of this coating liquid was 6 wt %.

[0141] Next, the long laminate was unwound, and while the laminate was being conveyed, the coating solution was applied onto the laminate by gravure coating. The cell volume of the gravure coater used was 9.1 cm. 3 / m 2Next, the coating film was heated and cured to form a protective layer. This resulted in the separation membrane of Example 12. The thickness A2 of the protective layer was determined by the method described above for Examples 1 to 8.

[0142] (Examples 13 and 14) Separation membranes of Examples 13 and 14 were obtained by the same method as Example 12, except that the composition of the coating solution to be applied onto the separation functional layer and the cell volume of the gravure coater were changed as shown in Table 4. The thickness A2 of the protective layer was determined by the method described above for Examples 1 to 8.

[0143]

[0144] The abbreviations in Table 4 are as follows: SD7328: Addition type silicone resin composition (manufactured by Dow-Toray Industries, Inc., SD7328) SRX212: Curing catalyst (manufactured by Dow-Toray Industries, Inc., SRX212)

[0145] [Pressure Test 1] Pressure test 1 was carried out in the following manner. First, a separation membrane (membrane area 0.43 cm 2 ) was set in a metal cell and sealed with an O-ring to prevent leakage. Next, nitrogen was injected into the metal cell so that nitrogen at a temperature of 25°C came into contact with the main surface of the separation membrane on the protective layer side. At this time, the amount of nitrogen injected and the like were adjusted so that the pressure (gauge pressure) in the supply space was 1.0 MPa. As a result, a permeated fluid (nitrogen) was obtained from the main surface of the separation membrane on the porous support side. The flow rate of the obtained permeated fluid was measured, and the nitrogen permeation rate was calculated.

[0146] Next, the pressure (gauge pressure) in the supply space of the metal cell was increased by about 1.0 MPa, and the nitrogen permeation rate was determined each time. Furthermore, after the pressure in the supply space increased to 6.0 MPa, the pressure was decreased by about 1.0 MPa, and the nitrogen permeation rate was determined each time. The results are shown in Figures 4 and 5. In Figures 4 and 5, circles (◯) indicate results when the pressure in the supply space was increased, and squares (□) indicate results when the pressure in the supply space was decreased.

[0147] 4 and 5, in Examples 9 to 14, the nitrogen permeation rate returned to its original value when the pressure in the supply space was reduced from 6.0 MPa. This result shows that in Examples 9 to 14, no defects were caused in the separation membranes by Pressure Test 1.

[0148] [Pressure Test 2] Pressure test 2 was carried out in the following manner. First, a separation membrane (membrane area 0.43 cm 2 ) was set in a metal cell and sealed with an O-ring to prevent leakage. Next, carbon dioxide at a temperature of 25°C was injected into the metal cell so that the carbon dioxide came into contact with the main surface of the separation membrane on the protective layer side. At this time, the amount of carbon dioxide injected and other factors were adjusted so that the pressure (gauge pressure) in the supply space was 1.0 MPa. As a result, a permeated fluid (carbon dioxide) was obtained from the main surface of the separation membrane on the porous support side. The flow rate of the obtained permeated fluid was measured, and the carbon dioxide permeation rate was calculated.

[0149] Next, the pressure (gauge pressure) in the supply space of the metal cell was increased by approximately 1.0 MPa, and the carbon dioxide permeation rate was determined each time. Furthermore, after the pressure in the supply space increased to approximately 3.0 MPa, the pressure was decreased by approximately 1.0 MPa, and the carbon dioxide permeation rate was determined each time. The results are shown in Figures 6 and 7. In Figures 6 and 7, circles (◯) indicate results when the pressure in the supply space was increased, and squares (□) indicate results when the pressure in the supply space was decreased.

[0150] As can be seen from the results of Figures 6 and 7, in Examples 9 and 12, in which the protective layer was relatively thin, less than 0.3 µm thick, the carbon dioxide permeation rate increased as the pressure in the supply space of the metal cell increased. These results show that the separation membranes of Examples 9 and 12 have low pressure resistance. On the other hand, in Examples 10, 11, 13, and 14, in which the protective layer was 0.3 µm or thicker, the increase in the carbon dioxide permeation rate was suppressed even when the pressure in the supply space of the metal cell increased, resulting in high pressure resistance. In Examples 9 to 14, the carbon dioxide permeation rate returned to its original value when the pressure in the supply space was reduced from 3.0 MPa. These results show that in Examples 9 to 14, pressure test 2 did not cause any defects in the separation membranes.

[0151] The separation membrane of this embodiment is suitable for separating hydrogen from a mixed gas containing hydrogen.

Claims

1. A separation membrane comprising a separation functional layer and a protective layer that protects the separation functional layer, wherein the ratio A2 / A1 of the thickness A2 (μm) of the protective layer to the thickness A1 (μm) of the separation functional layer is 0.5 or more and less than 2.

0.

2. The separation membrane according to claim 1, wherein the thickness A1 is 0.01 μm to 50 μm.

3. The separation membrane according to claim 1, wherein the thickness A2 is 0.01 μm to 50 μm.

4. The separation membrane according to claim 1, wherein the separation functional layer comprises at least one selected from the group consisting of polyamide, cellulose ester, polyolefin, fluorine-containing polymer, polysulfone and ceramic.

5. The separation membrane according to claim 1, wherein the protective layer comprises a silicone resin.

6. The separation membrane according to claim 1, wherein the protective layer is formed from an addition type silicone resin composition or a condensation type silicone resin composition.

7. The separation membrane according to claim 1, wherein the protective layer is in direct contact with the separation functional layer.

8. The separation membrane according to claim 1, further comprising a porous support that supports the separation functional layer.

9. When helium is supplied at a pressure of 0.6 MPa to a space adjacent to one side of the separation membrane, what is the permeation rate T of helium that permeates the separation membrane? He The separation membrane according to claim 1, wherein the pore size is 100 GPU or more.

10. Separation factor α of helium relative to nitrogen He / N2 The separation membrane according to claim 1, wherein the separation factor α is 200 or more. He / N2 is the permeation rate T of nitrogen that permeates the separation membrane when nitrogen at a pressure of 0.6 MPa is supplied to the space adjacent to one side of the separation membrane. N2 (GPU) The permeation rate T of helium that permeates the separation membrane when helium at a pressure of 0.6 MPa is supplied to the space. He (GPU) ratio T He / T N2 means.

11. Separation factor α of helium relative to carbon dioxide He / CO2 The separation membrane according to claim 1, wherein the separation factor α is 20 or more. He / CO2 is the permeation rate T of carbon dioxide that permeates the separation membrane when carbon dioxide at a pressure of 0.6 MPa is supplied to a space adjacent to one side of the separation membrane. CO2 (GPU) The permeation rate T of helium that permeates the separation membrane when helium at a pressure of 0.6 MPa is supplied to the space. He (GPU) ratio T He / T CO2 means.

12. The separation membrane according to claim 1, which is used to separate hydrogen from a hydrogen-containing gas mixture.

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