Separation membrane

Abstract

The present invention provides a novel separation membrane that has improved separation performance with respect to a mixed gas that includes hydrogen. This separation membrane 10 comprises: a separation functional layer 1 that includes a polyamide; and a protection layer 5 that protects the separation functional layer 1 and includes a resin R that has a water contact angle of at least 60°. The polyamide includes a structural unit A1 that is derived from a bifunctional acid halide.

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] While conventional separation membranes have room for improvement in separation performance for hydrogen-containing mixed gases, the present invention provides a novel separation membrane with improved separation performance for hydrogen-containing mixed gases.

[0006] The present invention provides a separation membrane comprising: a separation functional layer containing a polyamide; and a protective layer that protects the separation functional layer and contains a resin having a contact angle with water of 60° or more, wherein the polyamide has a structural unit A1 derived from a bifunctional acid halide.

[0007] According to the present invention, a new separation membrane having improved separation performance for a mixed gas containing hydrogen can be provided.

[0008] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.

[0009] A separation membrane according to a first aspect of the present invention comprises: a separation functional layer containing a polyamide; and a protective layer that protects the separation functional layer and contains a resin having a contact angle with water of 60° or more, wherein the polyamide has a structural unit A1 derived from a bifunctional acid halide.

[0010] In a second aspect of the present invention, for example, in the separation membrane according to the first aspect, the bifunctional acid halide has an aromatic ring.

[0011] In a third aspect of the present invention, for example, in the separation membrane according to the first or second aspect, the bifunctional acid halide includes isophthalic acid dichloride.

[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 content of the structural unit A1 in the polyamide is 1 mol % or more.

[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 polyamide further has a structural unit A2 derived from a trifunctional acid halide.

[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 polyamide further has a structural unit B derived from a polyfunctional amine.

[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 resin includes a silicone resin.

[0016] In an eighth aspect of the present invention, for example, in the separation membrane according to any one of the first to seventh aspects, the protective layer is formed from an addition type silicone resin composition or a condensation type silicone resin composition.

[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, the protective layer is in direct contact with the separation functional layer.

[0018] In a tenth aspect of the present invention, for example, the separation membrane according to any one of the first to ninth aspects further comprises a porous support that supports the separation functional layer.

[0019] In an eleventh aspect of the present invention, for example, the separation membrane according to any one of the first to tenth aspects is used to separate hydrogen from a mixed gas containing hydrogen.

[0020] 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.

[0021] 1, a separation membrane 10 of this embodiment includes a separation functional layer 1 containing polyamide P, and a protective layer 5 containing a resin R that protects the separation functional layer 1 and has a contact angle with water of 60° or more. The polyamide P contained in the separation functional layer 1 has a structural unit A1 derived from a bifunctional acid halide.

[0022] 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 methane and nitrogen.

[0023] The separation membrane 10 may further include a porous support 3 that supports the separation functional layer 1. The separation functional layer 1 is preferably located between the protective layer 5 and the porous support 3, and is in direct contact with both the protective layer 5 and the porous support 3. In particular, when the separation functional layer 1 is in direct contact with the protective layer 5, it tends to preferentially allow small molecules such as hydrogen and helium to permeate.

[0024] 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.

[0025] (Separation functional layer) The separation functional layer 1 is a layer that preferentially allows small molecules such as hydrogen and helium to permeate. As described above, the separation functional layer 1 contains polyamide P. The polyamide P has a structural unit A1 derived from a bifunctional acid halide. In detail, the polyamide P has a structural unit A derived from a polyfunctional acid halide and a structural unit B derived from a polyfunctional amine, and has the structural unit A1 as the structural unit A.

[0026] A bifunctional acid halide is a compound having two acid halide groups. Examples of the acid halide group include a carbonyl halide group (-COX) and a sulfonyl halide group (-SO2X), with a carbonyl halide group being preferred. Examples of the halogen atom (X) contained in the acid halide group include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a chlorine atom being preferred. The acid halide group is particularly preferably a carbonyl chloride group. In a bifunctional acid halide, the two acid halide groups are preferably the same. However, the two acid halide groups may be different from each other.

[0027] The bifunctional acid halide preferably has an aromatic ring. The aromatic ring may be composed only of carbon atoms, or may be a heteroaromatic ring containing a heteroatom such as an oxygen atom, a nitrogen atom, or a sulfur atom. The aromatic ring may be polycyclic or monocyclic. The number of carbon atoms in the aromatic ring is not particularly limited and is, for example, 4 to 14. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a fluorene ring, a furan ring, a pyrrole ring, a pyridine ring, and a thiophene ring, with a benzene ring being preferred. When the bifunctional acid halide has an aromatic ring, the bifunctional acid halide may have two acid halide groups as substituents on the aromatic ring.

[0028] Examples of bifunctional acid halides having an aromatic ring include terephthalic acid dichloride, isophthalic acid dichloride, biphenyldicarboxylic acid dichloride, naphthalenedicarboxylic acid dichloride, benzenedisulfonic acid dichloride, etc. The bifunctional acid halides preferably include isophthalic acid dichloride.

[0029] The bifunctional acid halide is not limited to those described above. The bifunctional acid halide may have a chain hydrocarbon group or an alicyclic hydrocarbon group. These hydrocarbon groups may contain heteroatoms. The number of carbon atoms in these hydrocarbon groups is not particularly limited and is, for example, 1 to 10.

[0030] Examples of bifunctional acid halides having a chain hydrocarbon group include propanedicarboxylic acid dichloride, butanedicarboxylic acid dichloride, pentanedicarboxylic acid dichloride, glutaryl halides (particularly glutaryl chloride), and adipoyl halides (particularly adipoyl chloride).

[0031] Examples of bifunctional acid halides having an alicyclic hydrocarbon group include cyclopentanedicarboxylic acid dichloride, cyclobutanedicarboxylic acid dichloride, cyclohexanedicarboxylic acid dichloride, and tetrahydrofurandicarboxylic acid dichloride.

[0032] In the polyamide P, the content R1 of the structural unit A1 derived from a bifunctional acid halide is, for example, 1 mol% or more, and may be 5 mol% or more, 10 mol% or more, 15 mol% or more, 18 mol% or more, or even 20 mol% or more. The upper limit of the content R1 of the structural unit A1 is, for example, 60 mol% or less, and may be 50 mol% or less, 40 mol% or less, or even 30 mol% or less.

[0033] In polyamide P, the ratio of the amount of constituent unit A1 to the amount of all constituent units A derived from polyfunctional acid halides may be, for example, 10 mol% or more, 20 mol% or more, 30 mol% or more, 35 mol% or more, 40 mol% or more, or even 45 mol% or more. The upper limit of this ratio may be, for example, 90 mol% or less, 80 mol% or less, 70 mol% or less, 60 mol% or less, or even 50 mol% or less. Note that polyamide P may contain only constituent unit A1 as the constituent unit A derived from polyfunctional acid halides.

[0034] It is preferable that the polyamide P further includes a structural unit A2 derived from a trifunctional acid halide as the structural unit A derived from a polyfunctional acid halide. It is preferable that the polyamide P has a crosslinked structure resulting from the structural unit A2. The trifunctional acid halide is a compound having three acid halide groups. Examples of the acid halide groups include those described above. In the trifunctional acid halide, it is preferable that the three acid halide groups are the same as each other. However, the three acid halide groups may be different from each other.

[0035] The trifunctional acid halide preferably has an aromatic ring. Examples of the aromatic ring include those described above. When the trifunctional acid halide has an aromatic ring, the trifunctional acid halide may have three acid halide groups as substituents on the aromatic ring.

[0036] Examples of the trifunctional acid halide having an aromatic ring include trimesic acid trichloride, benzenetrisulfonic acid trichloride, chlorosulfonylbenzenedicarboxylic acid dichloride, etc. The trifunctional acid halide preferably includes trimesic acid trichloride.

[0037] The trifunctional acid halide is not limited to those described above. The trifunctional acid halide may have a chain hydrocarbon group or an alicyclic hydrocarbon group. These hydrocarbon groups may contain heteroatoms. The number of carbon atoms in these hydrocarbon groups is not particularly limited and is, for example, 1 to 10.

[0038] Examples of trifunctional acid halides having a chain hydrocarbon group include propanetricarboxylic acid trichloride, butanetricarboxylic acid trichloride, and pentanetricarboxylic acid trichloride.

[0039] Examples of the trifunctional acid halide having an alicyclic hydrocarbon group include cyclopropanetricarboxylic acid trichloride, cyclopentanetricarboxylic acid trichloride, and cyclohexanetricarboxylic acid trichloride.

[0040] In the polyamide P, the content R2 of the structural unit A2 derived from a trifunctional acid halide is, for example, 1 mol% or more, and may be 5 mol% or more, 10 mol% or more, 15 mol% or more, 18 mol% or more, or even 20 mol% or more. The upper limit of the content R2 of the structural unit A2 is, for example, 40 mol% or less, and may be 30 mol% or less. Note that the polyamide P does not necessarily have the structural unit A2.

[0041] In the polyamide P, the ratio of the amount of constituent units A2 to the amount of all constituent units A derived from the polyfunctional acid halide may be, for example, 10 mol% or more, 20 mol% or more, 30 mol% or more, 35 mol% or more, 40 mol% or more, or even 45 mol% or more. The upper limit of this ratio may be, for example, 90 mol% or less, 80 mol% or less, 70 mol% or less, or even 60 mol% or less.

[0042] The polyamide P may further have a structural unit A3 derived from a polyfunctional acid halide having tetrafunctionality or more. This polyfunctional acid halide is a compound having four or more acid halide groups. Examples of the acid halide groups include those described above. In the polyfunctional acid halide, the four or more acid halide groups are preferably the same as each other. However, the four or more acid halide groups may be different from each other.

[0043] Examples of polyfunctional acid halides having tetrafunctional or more include cyclobutanetetracarboxylic acid tetrachloride, cyclopentanetetracarboxylic acid tetrachloride, and tetrahydrofurantetracarboxylic acid tetrachloride.

[0044] In the polyamide P, the content R3 of the structural unit A3 derived from a polyfunctional acid halide having tetrafunctionality or more is, for example, 20 mol % or less, and may be 10 mol % or less, 5 mol % or less, 1 mol % or less, or even 0.5 mol % or less. The polyamide P may not have the structural unit A3.

[0045] In polyamide P, the ratio of the amount of substance of structural unit A3 to the amount of substance of all structural units A derived from polyfunctional acid halides is, for example, 20 mol% or less, and may be 10 mol% or less, 5 mol% or less, 1 mol% or less, or even 0.5 mol% or less.

[0046] As described above, polyamide P typically further contains a structural unit B derived from a polyfunctional amine. In particular, polyamide P preferably contains a structural unit B1 derived from a bifunctional amine as the structural unit B. The polyfunctional amine is a compound having two or more amino groups (particularly primary amino groups).

[0047] The polyfunctional amine preferably has an aromatic ring. Examples of the aromatic ring include those described above. When the polyfunctional amine has an aromatic ring, the polyfunctional amine may have an amino group as a substituent on the aromatic ring.

[0048] Examples of polyfunctional amines having an aromatic ring 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.

[0049] The polyfunctional amine is not limited to those described above. The polyfunctional amine may have a chain hydrocarbon group or an alicyclic hydrocarbon group. These hydrocarbon groups may contain heteroatoms. The number of carbon atoms in these hydrocarbon groups is not particularly limited and is, for example, 1 to 10.

[0050] Examples of polyfunctional amines having a chain hydrocarbon group include ethylenediamine, propylenediamine, and tris(2-aminoethyl)amine.

[0051] Examples of polyfunctional amines having an alicyclic hydrocarbon group include 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, and 4-aminomethylpiperazine.

[0052] In the polyamide P, the content R4 of the structural unit B derived from a polyfunctional amine (particularly, the structural unit B1 derived from a bifunctional amine) is, for example, 30 mol % to 70 mol %, and may be 40 mol % to 60 mol %.

[0053] The polyamide P may further contain a structural unit C derived from a monomer other than the above-mentioned monomer. Examples of the other monomer include polyhydric alcohols such as sorbitol and glycerin. In the polyamide P, the content R5 of the structural unit C derived from the other monomer is, for example, 10 mol% or less, and may be 5 mol% or less, 1 mol% or less, or even 0.1 mol% or less. The polyamide P may not contain the structural unit C.

[0054] The separation functional layer 1 may contain polyamide P as a main component, or may be composed essentially of polyamide P. 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 components other than polyamide P.

[0055] The separation functional layer 1 may have a pleated microstructure. The pleats of this microstructure may penetrate into the protective layer 5.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] The thickness 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, 500 nm or less, or even 300 nm or less. The smaller the thickness of the separation functional layer 1, the more likely it is that the permeation rate of the permeating fluid that permeates the separation membrane 10 will increase. The lower limit of the thickness of the separation functional layer 1 is not particularly limited and may be, for example, 10 nm or more, 30 nm or more, 50 nm or more, or even 100 nm or more.

[0060] (Protective Layer) The protective layer 5 is a layer for protecting the separation functional layer 1. As described above, the protective layer 5 contains a resin R having a contact angle with water of 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.

[0061] Resin R is preferably a hydrogen-permeable resin having high hydrogen permeability. The hydrogen-permeable resin has a hydrogen permeability coefficient of 300 Barrers or more, preferably 500 Barrers or more, and more preferably 1000 Barrers or more. The hydrogen permeability coefficient can be calculated by measuring the hydrogen permeation rate (GPU) by the gas chromatography method specified in JIS K7126-1:2006 using a sheet made of the resin to be evaluated, and multiplying the measured permeation rate by the thickness (μm) of the sheet. In this specification, Barrer is defined as 10 -10 ·cm 3 (STP)·cm / (sec·cm 2 ・cmHg). GPU is 10 -6 ·cm 3 (STP) / (sec cm 2 cm 3 (STP) means the volume of gas at 1 atmosphere and 0°C. The thickness of the sheet can be measured, for example, using a commercially available dial gauge. Dial gauges are suitable for measuring the thickness of sheets ranging from several tens of microns to several mm.

[0062] The resin R preferably contains a silicone resin (a silicone-based polymer). That is, the protective layer 5 preferably contains a silicone resin. In another aspect, the present invention provides a separation membrane 10 comprising: a separation functional layer 1 containing a polyamide; and a protective layer 5 protecting the separation functional layer 1 and containing a silicone resin, wherein the polyamide has a structural unit A1 derived from a bifunctional acid halide.

[0063] 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 an addition type silicone resin composition.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] Examples of the polyorganosiloxane P2 include polymethylhydrogensiloxane, poly(dimethylsiloxane-methylhydrogensiloxane), and hydrosilyl-terminated polydimethylsiloxane.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] The polyorganosiloxane P3 is, for example, a polyorganosiloxane in which silanol groups have been introduced into the polyorganosiloxane described above for the polyorganosiloxane P1.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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 described 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 include acetylacetone.

[0085] 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.

[0086] 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.

[0087] 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).

[0088] The thickness of the protective layer 5 is, for example, 0.1 μm or more, and may be 0.5 μm or more, 1.0 μm or more, 5 μm or more, 10 μm or more, or even 15 μm or more. The thicker the protective layer 5, the more likely it is that the separation membrane 10 will suppress the permeation of relatively large molecules such as methane and nitrogen. From the viewpoint of the permeation rate of the permeating fluid passing through the separation membrane 10, the upper limit of the thickness of the protective layer 5 is preferably 50 μm or less, and may be 40 μm or less, 30 μm or less, or even 20 μm or less. The thickness of the protective layer 5 can be determined, for example, by X-ray fluorescence (XRF) measurement. XRF measurement is suitable for determining the thickness of a protective layer 5 having a thickness of 2 μm or less. XRF measurement can be performed, for example, under the conditions described below in the examples.

[0089] (Porous Support) As described above, the porous support 3 is a member that supports the separation function layer 1. 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, it is preferable that the microporous layer is 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.

[0090] 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 or polyarylethersulfone. The thickness of the microporous layer is not particularly limited and is, for example, 10 μm to 35 μm.

[0091] 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.

[0092] (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.

[0093] (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). The separation function layer 1 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 such as a bifunctional acid halide to form a separation function layer 1 by interfacial polymerization, 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 P 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, and the like.

[0094] Next, a protective layer 5 is formed on the separation functional layer 1, thereby producing the separation membrane 10. 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. Next, the 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 examples that can be used include spin coating, dip coating, slot die coating, gravure coating, and comma coating. The coating liquid may be applied to the separation functional layer 1 using an applicator or a wire bar.

[0095] 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.

[0096] 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.

[0097] (Characteristics of Separation Membrane) As described above, the separation membrane 10 allows hydrogen to preferentially permeate from a hydrogen-containing mixed gas. For example, the separation membrane 10 tends to have a high separation coefficient α for hydrogen relative to methane.

[0098] In the separation membrane 10, the separation factor α of hydrogen relative to methane is, for example, 600 or more, and may be 700 or more, 800 or more, 900 or more, 1000 or more, 1300 or more, or even 1500 or more. The upper limit of the separation factor α is not particularly limited and may be, for example, 3000 or less, or 2000 or less.

[0099] The separation coefficient α is the permeation rate T of methane permeating through the separation membrane 10. CH4 (GPU) vs. the hydrogen permeation rate T H2 (GPU) ratio T H2 / T CH4 means.

[0100] Hydrogen permeation rate T H2Specifically, can be measured by the following method. First, hydrogen at 30°C is supplied to a space (supply 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). At this time, the space (permeation space) adjacent to the other surface of the separation membrane 10 (for example, the main surface 12 of the separation membrane 10 on the porous support side) is depressurized, and the pressure difference between the supply space and the permeation space (supply pressure - permeation pressure) is adjusted to 0.1 MPa. The permeation space is preferably depressurized so that the pressure within the space is 0.1 MPa lower than the atmospheric pressure in the measurement environment. As a result, a permeated fluid (hydrogen) that has permeated the separation membrane 10 is obtained from the other surface of the separation membrane 10. The flow rate of this permeated fluid is measured by a gas chromatograph, and the hydrogen permeation rate T H2 The above method corresponds to the gas chromatography method specified in JIS K7126-1:2006.

[0101] Hydrogen permeation rate T H2 is, for example, 10 GPU or more, and may be 20 GPU or more, 30 GPU or more, 40 GPU or more, 50 GPU or more, 60 GPU or more, 70 GPU or more, 80 GPU or more, or even 90 GPU or more. H2 The upper limit is not particularly limited, and is, for example, 500 GPU or less.

[0102] Methane permeation rate T CH4 The hydrogen permeation rate T H2 The methane permeation rate T can be measured by the method described above. CH4 is, for example, 0.01 GPU to 1.0 GPU.

[0103] (Uses of Separation Membrane) The separation membrane 10 of this embodiment may be used to separate hydrogen from a gas mixture containing hydrogen. In particular, the separation membrane 10 is suitable for separating hydrogen from a gas mixture containing hydrogen and methane. However, the use of the separation membrane 10 is not limited to separating hydrogen from the above-mentioned gas mixture. For example, the separation membrane 10 may be used to separate helium from a gas mixture containing helium.

[0104] <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.

[0105] 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.

[0106] 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%.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] <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.

[0113] 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.

[0114] 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).

[0115] 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).

[0116] 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.

[0117] 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.

[0118] Example 1: First, a porous support was prepared, comprising 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 the excess amine aqueous solution was removed to produce a coating film. Next, an acid halide solution was prepared by dissolving isophthalic acid dichloride (IPC), a bifunctional acid halide, and trimesic acid trichloride (TMC), a trifunctional acid halide, in a naphthenic solvent (Exxsol D40, manufactured by ExxonMobil). The acid halide solution contained 0.113 wt% IPC and 0.075 wt% TMC. The surface of the coating film was immersed in this acid halide 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 (thickness 100 nm) containing polyamide on the porous support.

[0119] Next, 100 g of a condensation type silicone resin composition (manufactured by Momentive Performance Materials Japan, YSR3022, toluene-MEK solution, solids content 30 wt%) was diluted with 400 g of normal heptane (manufactured by Sankyo Chemical Co., Ltd.) as a dilution solvent, 1 g of a tin-based catalyst (manufactured by Momentive Performance Materials Japan, YC6831) as a curing catalyst, and 3 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). This coating liquid was applied onto the separation function layer to obtain a coating film. Next, the coating film was heated at 130 ° C. for 5 minutes and cured to prepare a protective layer. This resulted in the separation membrane of Example 1.

[0120] (Example 2) The separation membrane of Example 2 was obtained by the same method as in Example 1, except that the acid halide solution was prepared without using IPC, and the separation functional layer containing polyamide was formed using this acid halide solution.

[0121] (Example 3) A separation membrane of Example 3 was obtained by the same method as in Example 1, except that the coating liquid applied to the separation functional layer was changed from a condensation type silicone resin composition to an addition type silicone resin composition. The coating liquid was prepared by adding 400 g of normal heptane (manufactured by Sankyo Chemical Co., Ltd.) as a dilution solvent and 0.6 g of a curing catalyst (manufactured by Dow-Toray Industries, Inc., SRX212) to 100 g of an addition type silicone resin composition (manufactured by Dow-Toray Industries, Inc., SD7328, toluene solution, solids content 30 wt %).

[0122] (Example 4) The separation membrane of Example 4 was obtained by the same method as in Example 1, except that the acid halide solution was prepared without using IPC, and the separation functional layer containing polyamide was formed using this acid halide solution.

[0123] [Polyamide Composition] The polyamides contained in the separation functional layers of Examples 1 to 4 were prepared by the following method. 1H NMR measurement was performed. First, a laminate of the porous support and the separation function layer was immersed in cyclohexanone overnight to dissolve the microporous layer of polysulfone contained in the porous support in cyclohexanone. This allowed the separation function layer to be removed from the porous support. The separation function layer was air-dried and then subjected to high-temperature methanol decomposition treatment under alkaline conditions. The treated sample was analyzed under the following conditions. 1 H NMR measurement was carried out. 1 H NMR measurement Apparatus: Bruker Biospin, AVANCE NEO-600 with CryoProbe Observation frequency: 600 MHz (1H) Measurement solvent: DMSO-d6 (1H) Temperature: 300 K Chemical shift standard: DMSO-d6 (1H: 2.50 ppm)

[0124] The above 1 From the results of H NMR measurement, the ratio of the amounts of substance of the structural unit A2 derived from a trifunctional acid halide (TMC), the structural unit A1 derived from a difunctional acid halide (IPC), and the structural unit B derived from a polyfunctional amine (MPD) in the polyamide contained in the separation functional layer was identified.

[0125] [Contact Angle of Silicone Resin with Water] The contact angle of water for the silicone resin contained in the protective layer of Examples 1 to 4 was measured by the following method. First, sheets having the same composition as the protective layer of Examples 1 to 4 were prepared. Specifically, using the coating liquid (condensation type silicone resin composition) prepared in Examples 1 and 2, sheet S1 (freestanding film: thickness 254.6 μm) was prepared under the same curing conditions. Using the coating liquid (addition type silicone resin composition) prepared in Examples 3 and 4, sheet S2 (freestanding film: thickness 442.7 μm) was prepared under the same curing conditions. The thicknesses of sheets S1 and S2 were measured using a dial gauge (R1N-255, manufactured by Ozaki Seisakusho Co., Ltd.). The contact angle of water for sheets S1 and S2 was measured using the sessile drop method specified in JIS R3257:1999. The obtained measured value was considered to be the contact angle of the silicone resin with water.

[0126] [Hydrogen Permeability Coefficient of Silicone Resin] The hydrogen permeability coefficient of the silicone resin contained in the protective layer of Examples 1 to 4 was measured by the following method. First, sheets (the above-mentioned sheets S1 and S2) having the same composition as the protective layer of Examples 1 to 4 were prepared. Next, the hydrogen permeability rate (GPU) of sheets S1 and S2 was measured by the gas chromatography method specified in JIS K7126-1:2006. As a result, the hydrogen permeability rate of sheet S1 was 5.318 GPU, and the hydrogen permeability rate of sheet S2 was 3.274 GPU. The value obtained by multiplying the obtained permeability rate by the sheet thickness (μm) was regarded as the hydrogen permeability coefficient of the silicone resin.

[0127] [Thickness of Protective Layer] The thickness of the protective layer provided in the separation membranes of Examples 1 to 4 was measured by the following method. First, the separation membrane was cut into 35 mm squares to prepare test pieces. The test pieces were fixed to a measurement holder, and X-ray fluorescence (XRF) measurement was performed under the following conditions. XRF Measurement Analysis equipment: ZSX Primus IV manufactured by Rigaku Target element: Si X-ray source: Vertical Rh tube Analysis area: 30 mmφ Analyzing crystal: RX4 Output: 50 kV, 46 mA

[0128] In the above measurements, all of the detected Si components were assumed to be derived from the silicone resin, and the signal intensity of the Si components was converted to the thickness of the protective layer using a calibration curve created from data on silicone resin films of known thickness.

[0129] [Evaluation of Separation Membrane Properties] The hydrogen permeation rate T H2 , and methane permeation rate T CH4 Based on the results obtained, the methane permeation rate T CH4 Hydrogen permeation rate T H2 (GPU) ratio T H2 / T CH4 was calculated, and the calculated value was regarded as the separation factor α of hydrogen relative to methane.

[0130]

[0131] The abbreviations in Table 1 are as follows: TMC: trimesic acid trichloride IPC: isophthalic acid dichloride MPD: m-phenylenediamine 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)

[0132] As can be seen from Table 1, when the resin R contained in the protective layer is the same, the separation membranes of Examples 1 and 3, which have a separation functional layer containing a polyamide having a structural unit A1 derived from a bifunctional acid halide, have a higher separation coefficient α than the separation membranes of Examples 2 and 4, respectively, and have improved separation performance for hydrogen.

[0133] In the separation membranes of Examples 1 and 3, the hydrogen permeation rate T H2 was 20 GPU or more, which were all sufficient values ​​for practical use.

[0134] 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 containing a polyamide; and a protective layer that protects the separation functional layer and contains a resin having a contact angle with water of 60° or more, wherein the polyamide has a structural unit A1 derived from a bifunctional acid halide.

2. The separation membrane according to claim 1, wherein the bifunctional acid halide has an aromatic ring.

3. The separation membrane of claim 1, wherein the bifunctional acid halide comprises isophthalic acid dichloride.

4. The separation membrane according to claim 1, wherein the content of the structural unit A1 in the polyamide is 1 mol % or more.

5. The separation membrane according to claim 1, wherein the polyamide further comprises a structural unit A2 derived from a trifunctional acid halide.

6. The separation membrane according to claim 1, wherein the polyamide further comprises a structural unit B derived from a polyfunctional amine.

7. The separation membrane of claim 1, wherein the resin comprises a silicone resin.

8. 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.

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

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

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

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