WO2018159562A1

WO2018159562A1 - Gas separation membrane, gas separation module, gas separation device, and gas separation method

Info

Publication number: WO2018159562A1
Application number: PCT/JP2018/007051
Authority: WO
Inventors: 北村　哲; 基原田
Original assignee: 富士フイルム株式会社
Priority date: 2017-02-28
Filing date: 2018-02-26
Publication date: 2018-09-07
Also published as: JP2020073249A

Abstract

A gas separation membrane which comprises a gas separation layer that contains a cellulose compound as a constituent material, and wherein the cellulose compound has a repeating unit represented by general formula (1); a gas separation module which uses this gas separation membrane; a gas separation device; and a gas separation method. In general formula (1), each of R¹-R³ moieties represents a hydrogen atom or a substituent, provided that at least one of the R¹-R³ moieties represents a substituent T that comprises an active hydrogen and a fluorine atom, while having a molecular weight of 100 or more but less than 500.

Description

Gas separation membrane, gas separation module, gas separation device, and gas separation method

The present invention relates to a gas separation membrane, a gas separation module, a gas separation device, and a gas separation method.

A material composed of a polymer compound has gas permeability specific to each material. Based on the property, a desired gas component can be selectively permeated and separated by a membrane composed of a specific polymer compound. As an industrial application of this gas separation membrane (gas separation membrane), it is related to the problem of global warming and separated from large-scale carbon dioxide generation sources in thermal power plants, cement plants, steelworks blast furnaces, etc. Recovery is under consideration. Natural gas, biogas (biological waste, organic fertilizer, biodegradable substances, sewage, garbage, gas generated by fermentation and anaerobic digestion of energy crops, etc.) are mainly mixed gases containing methane and carbon dioxide. As a means for removing impurities such as carbon dioxide, the use of gas separation membranes is being studied.

As a material for this gas separation membrane, a gas separation membrane using a polyimide compound has been actively studied. Gas separation membranes using cellulose compounds are also known. For example, Patent Document 1 mentions the use of a fluorine-containing cellulose derivative having a specific structure as a separation membrane.

In order to obtain a practical gas separation membrane, it is necessary to secure a sufficient gas permeability by making the gas separation layer thin. As a method for thinning the gas separation layer, there is a method in which a polymer compound is made into an asymmetric membrane by a phase separation method, and a portion contributing to separation is made into a thin layer called a dense layer or a skin layer. In this asymmetric membrane, a portion other than the dense layer is allowed to function as a support layer that bears the mechanical strength of the membrane.
In addition to the asymmetric membrane, a composite membrane is also known. In this composite membrane, the gas separation layer responsible for the gas separation function and the support layer responsible for the mechanical strength are made of different materials, and the gas separation layer having gas separation ability is formed in a thin layer on the gas permeable support layer. .

JP-A-2-212501

In the purification of natural gas using a membrane separation method, excellent gas permeability and gas separation selectivity are required in order to separate gases more efficiently. However, in general, gas permeability and gas separation selectivity are in a so-called trade-off relationship. Therefore, by adjusting the molecular structure of the polymer compound used in the gas separation layer, either the gas permeability or gas separation selectivity of the gas separation layer can be improved, but both characteristics are at a high level. It is difficult to achieve both.
Further, in an actual plant or the like, the membrane is plasticized due to high pressure conditions or the influence of impurities (benzene, toluene, xylene, etc.) present in natural gas, and this causes a problem of reduction in gas separation selectivity. Therefore, the gas separation membrane not only enhances gas permeability and gas separation selectivity, but also continuously exhibits good gas permeability and gas separation selectivity under high pressure conditions and in the presence of the above impurity components. A plasticizing resistance that can be produced is also required.

The present invention realizes both high gas permeability and excellent gas separation selectivity at a sufficient level even when used under high pressure conditions, and enables high-speed and high-selective gas separation. It is an object of the present invention to provide a gas separation membrane that can maintain good gas separation selectivity even when in contact with a plasticizing component. Another object of the present invention is to provide a gas separation module, a gas separation apparatus, and a gas separation method using the gas separation membrane.

As a result of intensive studies in view of the above problems, the present inventors have determined that a cellulose compound in a form in which at least a part of the hydrogen atoms constituting the hydroxyl group of cellulose is substituted with a group having active hydrogen and fluorine atoms is used as a gas. When used as a gas separation layer of a separation membrane, this gas separation membrane exhibits excellent gas separation selectivity even when used under high pressure conditions, has excellent gas permeability, and is plasticized by the influence of impurity components such as toluene. I found out that it is difficult to make it. The present invention has been completed through further studies based on these findings.

The above problems have been solved by the following means.
[1]
A gas separation membrane having a gas separation layer containing a cellulose compound as a constituent material, wherein the cellulose compound has a repeating unit represented by the following general formula (1).

In general formula (1), R ¹ to R ³ represent a hydrogen atom or a substituent. However, at least one of R ¹ to R ³ is a substituent T having an active hydrogen and a fluorine atom and having a molecular weight of 100 or more and less than 500.
[2]
The gas separation membrane according to [1], wherein the active hydrogen is a hydrogen atom constituting a hydroxyl group, a carboxy group, an amide group, an amide bond, a sulfamoyl group, —SO ₂ NH—, a urethane bond, or a boric acid group.
[3]
The gas separation membrane according to [1] or [2], wherein at least one of R ¹ to R ³ is methyl or acetyl.
[4]
The gas separation according to any one of [1] to [3], wherein at least one of R ¹ to R ³ is a group represented by the following general formulas (2-1) to (2-3): film.

In general formulas (2-1) to (2-3), R ^f represents a group having a fluorine atom. * Indicates a binding site.
[5]
[1] to [4], wherein at least one of R ¹ to R ³ is a group represented by any one of the following general formulas (3-1) to (3-3): Gas separation membrane.

In the general formulas (3-1) to (3-3), L ^f represents a divalent group having a fluorine atom. * Indicates a binding site.
[6]
The gas separation membrane according to any one of [1] to [5], wherein the degree of substitution by the substituent T of the cellulose compound is 0.5 or more and 3.0 or less.
[7]
The gas separation membrane according to any one of [1] to [6], wherein the degree of substitution of the cellulose compound exceeds 2.5.
[8]
The gas separation membrane according to any one of [1] to [7], wherein the gas separation membrane is a gas separation composite membrane having the gas separation layer above the gas-permeable support layer.
[9]
The gas separation membrane according to [8], wherein the support layer includes a porous layer on the gas separation layer side and a nonwoven fabric layer on the opposite side to the gas separation layer.
[10]
The gas separation membrane according to any one of [1] to [9], which is used for selectively permeating carbon dioxide from a gas containing carbon dioxide and methane.
[11]
In the case where the gas to be separated is a mixed gas of carbon dioxide and methane, the transmission rate of carbon dioxide under a gas supply condition of 40 ° C. and 5 MPa is 20 GPU or more, and the transmission rate of carbon dioxide relative to the transmission rate of methane The gas separation membrane according to any one of [1] to [10], wherein the ratio is 15 or more.
[12]
[1] A gas separation module comprising the gas separation membrane according to any one of [11].
[13]
[1] A gas separation apparatus comprising the gas separation membrane according to any one of [11].
[14]
[1] A gas separation method using the gas separation membrane according to any one of [11].

In the present specification, the numerical value range represented by “to” means that the numerical values described before and after the numerical value range are included as a lower limit value and an upper limit value.
In the present specification, when there are a plurality of substituents, linking groups, and the like (hereinafter referred to as substituents) indicated by specific symbols, or when a plurality of substituents are specified simultaneously or alternatively, It means that a substituent etc. may mutually be same or different. The same applies to the definition of the number of substituents and the like. Further, when there are repetitions of a plurality of partial structures represented by the same indication in the formula, each partial structure or repeating unit may be the same or different.

In the present specification, the term “compound” or “group” is used to mean a compound or group itself, a salt thereof, or an ion thereof. In addition, it means that a part of the structure is changed as long as the desired effect is achieved.

The gas separation membrane, gas separation module, and gas separation apparatus of the present invention achieve a high level of both excellent gas permeability and excellent gas separation selectivity even when used under high pressure gas supply conditions. This enables high-speed and highly selective gas separation.
According to the gas separation method of the present invention, the target gas can be separated with excellent gas permeability and excellent gas separation selectivity even under high-pressure gas supply conditions, and high speed and high selectivity. Gas separation is possible.

It is sectional drawing which shows typically one Embodiment of the gas separation composite membrane of this invention. It is sectional drawing which shows typically another embodiment of the gas separation composite membrane of this invention.

The gas separation membrane of the present invention contains a specific cellulose compound in the gas separation layer. A preferred embodiment of the gas separation membrane of the present invention will be described.

[Cellulose compound]
The gas separation layer of the gas separation membrane of the present invention contains a cellulose compound having a repeating unit represented by the following general formula (1).

In general formula (1), R ¹ to R ³ represent a hydrogen atom or a substituent. At least one of R ¹ to R ³ is a substituent having an active hydrogen and a fluorine atom and having a molecular weight of 100 or more and less than 500 (hereinafter referred to as “substituent T”).

In the present invention, the “active hydrogen” of the substituent T means a hydrogen atom bonded to a nitrogen atom, an oxygen atom or a sulfur atom. This active hydrogen is preferably a hydroxyl group (—OH), a carboxy group (—COOH), an amide group (—CONH ₂ ), an amide bond (—CONH—), a sulfamoyl group (—SO ₂ NH ₂ ), —SO ₂ NH—. , A hydrogen bond constituting a urethane bond (—O—CO—NH—) or a boric acid group (—B (OH) ₂ ), and a hydrogen atom constituting a hydroxyl group, a carboxy group or a urethane bond is preferably More preferably, it is a hydrogen atom which comprises a carboxy group or a urethane bond.
When the cellulose compound constituting the gas separation layer has active hydrogen in the substituent T, the interaction between the cellulose chains is effectively enhanced, and the gas separation layer is stiffened to further improve the gas separation selectivity. And the plasticization resistance can be further increased.
On the other hand, since the cellulose compound has a fluorine atom in the substituent T, the gas separation layer may also exhibit sufficient gas permeability due to the formation of minute holes in the gas separation layer due to electron repulsion. it can. Furthermore, the fluorine atom is considered to suppress the affinity for plasticizing components such as toluene and contribute to the improvement of plasticization resistance.

The molecular weight of the substituent T is 100 or more and less than 500. If the molecular weight of the substituent T is too large, the interaction between the cellulose chains may be reduced, and the plasticization resistance may be reduced. The molecular weight of the substituent T is preferably 125 or more and less than 450, more preferably 150 or more and less than 400.

In addition to the substituent T, the cellulose compound preferably has methyl or acetyl as R ¹ to R ³ . By these forms, it can be set as the form which methoxy or acetyloxy was introduce | transduced into the cellulose compound. Methoxy and acetyloxy are compact polar groups, and are preferable because they can increase the solubility of the cellulose compound in a solvent without deteriorating gas separation selectivity.

At least one of R ¹ to R ³ is a group represented by any one of the following general formulas (2-1) to (2-3) (the following general formulas (2-1) to (2-3) It is preferable that it is the substituent T) represented by either. In the present specification, * indicates a binding site (bonding hand).

In each formula, R ^f represents a group having a fluorine atom.
R ^f is preferably an alkyl group having a fluorine atom or an aryl group having a fluorine atom, and more preferably an aryl group having a fluorine atom.
The alkyl group having a fluorine atom preferably has 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and particularly preferably 1 to 3 carbon atoms.

The aryl group having a fluorine atom is preferably phenyl having a fluorine atom. R ^f is preferably an aryl group having a fluorine atom as a substituent and / or an aryl group having a fluorinated alkyl group (preferably trifluoromethyl). The aryl group preferably has active hydrogen, and the aryl group having active hydrogen is preferably an aryl group having a hydroxyl group or a carboxy group.
Preferred specific examples of R ^f are shown below.

When the substituent T is a group represented by any one of the above general formulas (2-1) to (2-3), gas permeability tends to be further improved. When the substituent T is a group represented by any one of the general formulas (2-1) to (2-3), the general formula is used from the viewpoint of membrane rigidity that affects gas separation selectivity and plasticization resistance. A group represented by (2-1) is more preferable.

Further, at least one of R ¹ to R ³ is a group represented by any one of the following general formulas (3-1) to (3-3) (the following general formulas (3-1) to (3-3) It is also preferred that it is a substituent T) represented by any one of

In each formula, L ^f represents a divalent group having a fluorine atom. L ^f is preferably an alkylene group or an arylene group having a fluorine atom, and more preferably an arylene group having a fluorine atom.
The alkylene group having a fluorine atom, which can be taken as L ^f , preferably has 1 to 8 carbon atoms, more preferably 1 to 6, still more preferably 1 to 4, and particularly preferably 1 to 3.

It can take as L ^f, arylene group having a fluorine atom is preferably a phenylene having a fluorine atom. L ^f is preferably an arylene group having a fluorine atom as a substituent and / or an arylene group having a fluorinated alkyl group (preferably trifluoromethyl) as a substituent.

Preferable specific examples of “—L ^f —COOH” in the general formulas (3-1) to (3-3) are shown below.

When the substituent T is a group represented by any one of the above general formulas (3-1) to (3-3), gas separation selectivity or plasticization resistance tends to be further improved. In the case where the substituent T is a group represented by any one of the general formulas (3-1) to (3-3), the general formula is used from the viewpoint of membrane rigidity that affects gas separation selectivity and plasticization resistance. A group represented by (3-1) is more preferable.

The cellulose compound used in the present invention is a group represented by any one of general formulas (2-1) to (2-3) and general formulas (3-1) to (3-3) as R ¹ to R ^3. May have two or more groups.
When the cellulose compounds used in the present invention have groups represented by general formulas (2-1) to (2-3) as R ¹ to R ³ , the general formulas (3-1) to (3- 3) In the case where the group represented by any one of the general formulas (3-1) to (3-3) is not present, the general formula (2-1) ) To (2-3) are preferred. By adopting such a form, a gas separation membrane having a further improved target property (gas permeability or gas separation selectivity) while realizing both desired gas permeability and gas separation selectivity is obtained. Can do.
It is represented by any one of the general formulas (2-1) to (2-3) and the general formulas (3-1) to (3-3) in the total number of substituents T included in the cellulose compound used in the present invention. The ratio of the total number of groups is preferably 25 to 100%, more preferably 50 to 100%, and further preferably 75 to 100%.

Specific examples of the substituent T are shown below, but the present invention is not limited to these forms.

The cellulose compound preferably has a degree of substitution with a substituent T of 0.5 or more and 3.0 or less from the viewpoint of solubility in a solvent necessary for film formation and gas permeability.
Here, the substitution degree of the cellulose compound will be described. The β-1,4-bonded glucose unit constituting cellulose has a total of three hydroxyl groups at the 2nd, 3rd and 6th positions. The degree of substitution of the cellulose compound indicates the degree of substitution of hydrogen atoms in these hydroxyl groups with other groups. For example, when all of the hydrogen atoms constituting the 2nd, 3rd, and 6th hydroxyl groups of all glucose units are substituted with other groups, the degree of substitution is 3. Further, for example, in all glucose units, all the hydrogen atoms constituting the hydroxyl group at the 6-position are substituted with other groups, and the hydrogen atoms constituting the hydroxyl groups at the 2-position and the 3-position are both substituted with other groups. When there is no hydroxyl group (when the 2-position and 3-position hydroxyl groups remain in the hydroxyl state), the degree of substitution is 1.
The kind of functional group substituted with the hydrogen atom constituting the hydroxyl group of cellulose and the degree of substitution of the cellulose compound are described in Cellulose Communication 1999, Vol. 6, p. It can be determined by ¹ H-NMR based on the method described in 73-79.
The cellulose compound has a degree of substitution by a substituent T of 1.0 or more and 2.75 or less from the viewpoint of enhancing solubility in a solvent while imparting desired gas separation selectivity and gas permeability to the gas separation layer. It is preferable that it is 1.5 or more and 2.5 or less. The degree of substitution with the substituent T is preferably 1.0 to 2.5, and more preferably 1.0 to 2.0.

The cellulose compound preferably has a degree of substitution (including substitution with a substituent T) of more than 2.5, preferably more than 2.8, more preferably more than 2.9. That is, it is preferable that the cellulose compound has a smaller amount of hydroxyl groups. When the amount of hydroxyl groups is large, gas permeability tends to decrease.

The molecular weight of the cellulose compound is preferably a number average molecular weight (Mn) in the range of 5 × 10 ³ to 1000 × 10 ³ , more preferably in the range of 10 × 10 ³ to 500 × 10 ³ , and 10 × 10 ³ to 200 ×. 10 ³ ranges are most preferred. The weight average molecular weight (Mw) is preferably in the range of 7 × 10 ³ to 10000 × 10 ³ , more preferably in the range of 15 × 10 ³ to 5000 × 10 ³ , and in the range of 100 × 10 ³ to 3000 × 10 ³ . Is most preferred.
In the present invention, the number average molecular weight (Mn) and the weight average molecular weight (Mw) can be measured using gel permeation chromatography (GPC). Specifically, N-methylpyrrolidone is used as a solvent, a polystyrene gel is used, and the molecular weight can be determined using a conversion molecular weight calibration curve obtained in advance from a standard monodisperse polystyrene constituent curve.

(Preparation of cellulose compound)
The manufacturing method of the cellulose compound used for this invention is not specifically limited, It can obtain by introduce | transducing the target substituent by etherification reaction or esterification reaction with respect to raw material cellulose by a conventional method. As the etherification reaction, for example, by reacting cellulose with various alkyl halides, various aryl halides, various epoxies and the like in the presence of a base, a target cellulose compound can be obtained. Moreover, as an esterification reaction, the target cellulose compound can be obtained by making a cellulose react with various acid chlorides, various acid anhydrides, etc., for example. The raw material cellulose is not particularly limited. For example, methyl cellulose, ethyl cellulose, cellulose acetate, hydroxymethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose, hydroxypropyl in which the hydroxyl group of cellulose is partially substituted in advance in addition to cotton, linter, pulp, etc. Various substituted celluloses such as ethyl cellulose can also be used. Details of these raw material celluloses can be found in, for example, Marusawa and Uda, “Plastic Materials Course (17) Fibrous Resin”, Nikkan Kogyo Shimbun (published in 1970), and Japan Institute of Invention and Technology Publication No. 2001-2001. 1745 (pages 7 to 8).

[Gas separation membrane]
In the gas separation composite membrane which is a preferred embodiment of the gas separation membrane of the present invention, a gas separation layer containing a specific cellulose compound is formed on the upper side of the gas permeable support layer. A porous support layer is used as the gas permeable support layer.
FIG. 1 is a longitudinal sectional view schematically showing a gas separation composite membrane 10 which is a preferred embodiment of the present invention. 1 is a gas separation layer, 2 is a support layer. FIG. 2 is a cross-sectional view schematically showing a gas separation composite membrane 20 which is another preferred embodiment of the present invention. In this embodiment, in addition to the gas separation layer 1 and the support layer 2, the nonwoven fabric layer 3 is added as a further support body.
1 and 2 show a mode in which carbon dioxide is selectively permeated from a mixed gas of carbon dioxide and methane.

In the present specification, “upper support layer” means that another layer may be interposed between the support layer and the gas separation layer. For the upper and lower expressions, unless otherwise specified, the side on which the gas to be separated is supplied is “upper”, and the side on which the separated gas (permeate gas) is emitted is “lower”.

In the gas separation composite membrane of the present invention, a gas separation layer is formed on at least the surface of the gas permeable support layer. By forming a gas separation layer on the surface of the support layer, a composite membrane having both gas separation selectivity and gas permeability and mechanical strength can be obtained. The layer thickness of the gas separation layer is preferably a thin film as much as possible within the range showing high gas permeability while having desired mechanical strength and separation selectivity.

In the gas separation composite membrane of the present invention, the thickness of the gas separation layer is preferably 0.01 to 5.0 μm, and more preferably 0.05 to 2.0 μm.

The support layer is not particularly limited as long as it has the purpose of meeting mechanical strength and high gas permeability, and may be either organic or inorganic material. An organic polymer porous film is preferable, and the thickness thereof is 1 to 3000 μm, preferably 5 to 500 μm, and more preferably 5 to 150 μm. The pore structure of this porous membrane usually has an average pore diameter of 10 μm or less, preferably 0.5 μm or less, more preferably 0.2 μm or less. The porosity is preferably 20 to 90%, more preferably 30 to 80%.
Here, the support layer has “gas permeability” means that carbon dioxide is supplied to the support layer (a film composed of only the support layer) at a temperature of 40 ° C. with the total pressure on the gas supply side being 4 MPa. This means that the permeation rate of carbon dioxide is 1 × 10 ⁻⁵ cm ³ (STP) / cm ² · sec · cmHg (10 GPU) or more. Further, the gas permeability of the support layer is such that when carbon dioxide is supplied at a temperature of 40 ° C. and the total pressure on the gas supply side is 4 MPa, the carbon dioxide permeation rate is 3 × 10 ⁻⁵ cm ³ (STP) / It is preferably cm ² · sec · cmHg (30 GPU) or more, more preferably 100 GPU or more, further preferably 200 GPU or more, and further preferably 500 GPU or more.
Examples of the material for the support layer include conventionally known polymers such as polyolefin resins such as polyethylene and polypropylene, fluorine-containing resins such as polytetrafluoroethylene, polyvinyl fluoride, and polyvinylidene fluoride, polystyrene, cellulose acetate, polyurethane, Polyacrylonitrile, polyphenylene oxide, polysulfone, polyethersulfone, polyimide, polyaramid and the like can be mentioned. The shape of the support layer can be any shape such as a flat plate shape, a spiral shape, a tubular shape, and a hollow fiber shape.

In the gas separation composite membrane of the present invention, it is preferable that a support is formed to further impart mechanical strength to the lower part of the support layer forming the gas separation layer. Examples of such a support include woven fabrics, nonwoven fabrics, nets, and the like, but nonwoven fabrics are preferably used in terms of film forming properties and cost. As the nonwoven fabric, fibers made of polyester, polypropylene, polyacrylonitrile, polyethylene, polyamide or the like may be used alone or in combination. The nonwoven fabric can be produced, for example, by making a main fiber and a binder fiber uniformly dispersed in water using a circular net or a long net, and drying with a dryer. Moreover, it is also preferable to apply a heat treatment by sandwiching a non-woven fabric between two rolls for the purpose of removing fluff and improving mechanical properties.

The gas separation membrane of the present invention is not limited to the above-described composite membrane, but is preferably an asymmetric membrane as described later.

<Manufacture of gas separation membrane>
Next, production of the gas separation membrane of the present invention will be described.
As described above, the gas separation membrane of the present invention is preferably in the form of a composite membrane in which a gas separation layer is provided on a gas-permeable support layer (porous support layer). In addition, the gas separation membrane of the present invention can be in the form of an asymmetric membrane in which the support and the gas separation layer are integrally formed of the same cellulose compound.

(Manufacture of gas separation composite membrane)
The composite membrane of the present invention preferably includes forming a gas separation layer by applying a coating liquid containing the cellulose compound on a gas permeable support layer and drying the coating membrane. The cellulose compound content in the coating solution is not particularly limited, but is preferably 0.1 to 30% by mass, more preferably 0.5 to 15% by mass. When the content of the cellulose compound is too small, when the film is formed on the porous support, it easily penetrates into the lower layer, and there is a high possibility that defects will occur in the surface layer that contributes to separation. On the other hand, if the cellulose compound content is too high, the pores are filled at a high concentration when a film is formed on the porous support, and sufficient permeability may not be obtained.

The organic solvent used as a medium for the coating solution is not particularly limited, but hydrocarbons such as n-hexane and n-heptane, esters such as methyl acetate, ethyl acetate and butyl acetate; methanol, ethanol, n- Alcohols such as propanol, isopropanol, n-butanol, isobutanol, tert-butanol, ethylene glycol, diethylene glycol, triethylene glycol, glycerin, propylene glycol; acetone, methyl ethyl ketone, methyl isobutyl ketone, diacetone alcohol, cyclopentanone, cyclohexanone, etc. Aliphatic ketones; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol methyl ether, dipropylene glycol methyl ether, tri Lopylene glycol methyl ether, ethylene glycol phenyl ether, propylene glycol phenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, dibutyl ether, tetrahydrofuran, methylcyclopentyl ether, Examples include ethers such as dioxane; N-methylpyrrolidone, 2-pyrrolidone, dimethylformamide, dimethylimidazolidinone, dimethyl sulfoxide, and dimethylacetamide, and one or more of these can be used.

In the gas separation composite membrane of the present invention, another layer may exist between the support layer and the gas separation layer. A preferred example of the other layer is a siloxane compound layer. By providing the siloxane compound layer, the unevenness on the outermost surface of the support can be smoothed, and the separation layer can be easily thinned. Examples of the siloxane compound forming the siloxane compound layer include those having a main chain made of polysiloxane and compounds having a siloxane structure and a non-siloxane structure in the main chain.
In the present specification, the term “siloxane compound” means an organopolysiloxane compound unless otherwise specified.

-Siloxane compounds whose main chain consists of polysiloxane-
Examples of the siloxane compound having a main chain made of polysiloxane that can be used in the siloxane compound layer include one or more polyorganosiloxanes represented by the following formula (1) or (2). Moreover, these polyorganosiloxanes may form a crosslinking reaction product. As the cross-linking reaction, for example, a compound represented by the following formula (1) is crosslinked by a polysiloxane compound having a group capable of linking by reacting with the reactive group X ^S of the formula (1) at both ends The compound of the form is mentioned.

In the formula (1), R ^S is a non-reactive group and is an alkyl group (preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 12 carbon atoms) or an aryl group (preferably having 6 to 6 carbon atoms). 15, more preferably an aryl group having 6 to 12 carbon atoms, and still more preferably phenyl).
X ^S is a reactive group selected from a hydrogen atom, a halogen atom, a vinyl group, a hydroxyl group, and a substituted alkyl group (preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 12 carbon atoms). It is preferably a group.
Y ^S and Z ^S are the above R ^S or X ^S.
m is a number of 1 or more, preferably 1 to 100,000.
n is a number of 0 or more, preferably 0 to 100,000.

Wherein ^{^{^{(2), X S, Y}}} S, Z S, R S, m and n are ^X S of each formula ^{^{(1), Y S, Z}} S, R S, and m and n synonymous.

In the above formulas (1) and (2), when the non-reactive group R ^S is an alkyl group, examples of the alkyl group include methyl, ethyl, hexyl, octyl, decyl, and octadecyl. . When the non-reactive group R is a fluoroalkyl group, examples of the fluoroalkyl group include —CH ₂ CH ₂ CF ₃ and —CH ₂ CH ₂ C ₆ F ₁₃ .

In the above formulas (1) and (2), when the reactive group ^XS is a substituted alkyl group, examples of the alkyl group include a hydroxyalkyl group having 1 to 18 carbon atoms and an aminoalkyl group having 1 to 18 carbon atoms. A carboxyalkyl group having 1 to 18 carbon atoms, a chloroalkyl group having 1 to 18 carbon atoms, a glycidoxyalkyl group having 1 to 18 carbon atoms, a glycidyl group, an epoxycyclohexylalkyl group having 7 to 16 carbon atoms, Examples thereof include a (1-oxacyclobutan-3-yl) alkyl group having 4 to 18 carbon atoms, a methacryloxyalkyl group, and a mercaptoalkyl group.
The number of carbon atoms of the alkyl group constituting the hydroxyalkyl group is preferably an integer of 1 to 10, for example, —CH ₂ CH ₂ CH ₂ OH.
The number of carbon atoms of the alkyl group constituting the aminoalkyl group is preferably an integer of 1 to 10, and examples thereof include —CH ₂ CH ₂ CH ₂ NH ₂ .
The number of carbon atoms of the alkyl group constituting the carboxyalkyl group is preferably an integer of 1 to 10, and examples thereof include —CH ₂ CH ₂ CH ₂ COOH.
The number of carbon atoms of the alkyl group constituting the chloroalkyl group is preferably an integer of 1 to 10, and a preferred example is —CH ₂ Cl.
A preferable carbon number of the alkyl group constituting the glycidoxyalkyl group is an integer of 1 to 10, and a preferred example is 3-glycidyloxypropyl.
The preferable number of carbon atoms of the epoxy cyclohexyl alkyl group having 7 to 16 carbon atoms is an integer of 8 to 12.
A preferable carbon number of the (1-oxacyclobutan-3-yl) alkyl group having 4 to 18 carbon atoms is an integer of 4 to 10.
A preferable carbon number of the alkyl group constituting the methacryloxyalkyl group is an integer of 1 to 10, and examples thereof include —CH ₂ CH ₂ CH ₂ —OOC—C (CH ₃ ) ═CH ₂ .
A preferable carbon number of the alkyl group constituting the mercaptoalkyl group is an integer of 1 to 10, and examples thereof include —CH ₂ CH ₂ CH ₂ SH.
m and n are preferably numbers that give a molecular weight of 5,000 to 1,000,000.

In the above formulas (1) and (2), a reactive group-containing siloxane unit (wherein the number is a structural unit represented by n) and a siloxane unit having no reactive group (wherein the number is m The distribution of the structural unit represented by That is, in the formulas (1) and (2), the (Si (R ^S ) (R ^S ) —O) units and the (Si (R ^S ) (X ^S ) —O) units may be randomly distributed. .

-Compounds with siloxane and non-siloxane structures in the main chain-
Examples of the compound having a siloxane structure and a non-siloxane structure in the main chain that can be used in the siloxane compound layer include compounds represented by the following formulas (3) to (7).

Wherein ^{(3), R} S, m and n are respectively the same as ^R S, m and n in formula (1). R ^L is —O— or —CH ₂ —, and R ^S1 is a hydrogen atom or methyl. Both ends of the formula (3) are preferably an amino group, a hydroxyl group, a carboxy group, a trimethylsilyl group, an epoxy group, a vinyl group, a hydrogen atom, or a substituted alkyl group.

In Formula (4), m and n are synonymous with m and n in Formula (1), respectively.

In formula (5), m and n have the same meanings as m and n in formula (1), respectively.

In Formula (6), m and n are synonymous with m and n in Formula (1), respectively. It is preferable that the both ends of Formula (6) have an amino group, a hydroxyl group, a carboxy group, a trimethylsilyl group, an epoxy group, a vinyl group, a hydrogen atom, or a substituted alkyl group bonded thereto.

In formula (7), m and n are synonymous with m and n in formula (1), respectively. It is preferable that an amino group, a hydroxyl group, a carboxy group, a trimethylsilyl group, an epoxy, a vinyl group, a hydrogen atom, or a substituted alkyl group is bonded to both ends of the formula (7).

In the above formulas (3) to (7), the siloxane structural unit and the non-siloxane structural unit may be randomly distributed.

The compound having a siloxane structure and a non-siloxane structure in the main chain preferably contains 50 mol% or more of siloxane structural units, more preferably 70 mol% or more, based on the total number of moles of all repeating structural units. .

The weight average molecular weight of the siloxane compound used in the siloxane compound layer is preferably 5,000 to 1,000,000 from the viewpoint of achieving both a thin film and durability. The method for measuring the weight average molecular weight is as described above.

Furthermore, the preferable example of the siloxane compound which comprises a siloxane compound layer is enumerated below.
Polydimethylsiloxane, polymethylphenylsiloxane, polydiphenylsiloxane, polysulfone / polyhydroxystyrene / polydimethylsiloxane copolymer, dimethylsiloxane / methylvinylsiloxane copolymer, dimethylsiloxane / diphenylsiloxane / methylvinylsiloxane copolymer, methyl -3,3,3-trifluoropropylsiloxane / methylvinylsiloxane copolymer, dimethylsiloxane / methylphenylsiloxane / methylvinylsiloxane copolymer, diphenylsiloxane / dimethylsiloxane copolymer terminal vinyl, polydimethylsiloxane terminal vinyl, One or more selected from polydimethylsiloxane terminal H and dimethylsiloxane-methylhydrosiloxane copolymer. In addition, these include the form which forms the cross-linking reaction product.

In the composite film of the present invention, the thickness of the siloxane compound layer is preferably 0.01 to 5 μm, and more preferably 0.05 to 1 μm, from the viewpoint of smoothness and gas permeability.
Further, the gas permeability at 40 ° C. and 4 MPa of the siloxane compound layer is preferably 100 GPU or more, more preferably 300 GPU or more, and further preferably 1000 GPU or more in terms of carbon dioxide transmission rate.

(Manufacture of gas separation asymmetric membrane)
The gas separation membrane of the present invention may be an asymmetric membrane. The asymmetric membrane can be formed by a phase change method using a solution containing a cellulose compound. The phase inversion method is a known method for forming a film while bringing a polymer solution into contact with a coagulation liquid to cause phase conversion. In the present invention, a so-called dry / wet method is suitably used. The dry and wet method evaporates the solution on the surface of the polymer solution in the form of a film to form a thin dense layer, and then immerses it in a coagulation liquid (solvent that is compatible with the solvent of the polymer solution and the polymer is insoluble), This is a method of forming a porous layer by forming micropores using the phase separation phenomenon that occurs at that time, and proposed by Rob Thrillerjan et al. (For example, US Pat. No. 3,133,132) It is.

In the gas separation asymmetric membrane of the present invention, the thickness of the surface layer contributing to gas separation called a dense layer or skin layer is not particularly limited. The thickness of the surface layer is preferably 0.01 to 5.0 μm and more preferably 0.05 to 1.0 μm from the viewpoint of imparting practical gas permeability. On the other hand, the porous layer below the dense layer lowers the gas permeability resistance and at the same time plays a role of imparting mechanical strength, and its thickness is particularly limited as long as it is self-supporting as an asymmetric membrane. It is not limited. This thickness is preferably 5 to 500 μm, more preferably 5 to 200 μm, and even more preferably 5 to 100 μm.

The gas separation asymmetric membrane of the present invention may be a flat membrane or a hollow fiber membrane. The asymmetric hollow fiber membrane can be produced by a dry and wet spinning method. The dry-wet spinning method is a method for producing an asymmetric hollow fiber membrane by applying a dry-wet method to a polymer solution that is discharged from a spinning nozzle to have a hollow fiber-shaped target shape. More specifically, the polymer solution is discharged from a nozzle into a hollow fiber-shaped target shape, and after passing through an air or nitrogen gas atmosphere immediately after discharge, the polymer is not substantially dissolved and is compatible with the solvent of the polymer solution. In this method, an asymmetric structure is formed by dipping in a coagulating liquid having a gas, then dried, and further heat-treated as necessary to produce a gas separation asymmetric membrane.

The solution viscosity of the solution containing the cellulose compound discharged from the nozzle is 2 to 17000 Pa · s, preferably 10 to 1500 Pa · s, particularly 20 to 1000 Pa · s at the discharge temperature (for example, 10 ° C.). This is preferable because the shape after discharge can be stably obtained. For immersion in the coagulation liquid, the film is immersed in the primary coagulation liquid and solidified to such an extent that the shape of the hollow fiber or the like can be maintained, wound on a guide roll, and then immersed in the secondary coagulation liquid to fully saturate the entire film. It is preferable to solidify. It is efficient to dry the coagulated film after replacing the coagulating liquid with a solvent such as hydrocarbon. The heat treatment for drying is preferably performed at a temperature lower than the softening point or secondary transition point of the cellulose compound used.

In the gas separation membrane of the present invention, a siloxane compound layer may be provided on the gas separation layer as a protective layer in contact with the gas separation layer.

(Other components in the gas separation layer)
Various polymer compounds can be added to the gas separation layer of the gas separation membrane of the present invention in order to adjust the membrane properties. High molecular compounds include acrylic polymers, polyurethane resins, polyamide resins, polyester resins, epoxy resins, phenol resins, polycarbonate resins, polyvinyl butyral resins, polyvinyl formal resins, shellac, vinyl resins, acrylic resins, rubber resins. Waxes and other natural resins can be used. Two or more of these may be used in combination.
In addition, nonionic surfactants, cationic surfactants, organic fluoro compounds, and the like can be added to adjust liquid properties.

Specific examples of the surfactant include alkylbenzene sulfonate, alkylnaphthalene sulfonate, higher fatty acid salt, sulfonate of higher fatty acid ester, sulfate ester of higher alcohol ether, sulfonate of higher alcohol ether, higher alkyl Anionic surfactants such as alkyl carboxylates of sulfonamides, alkyl phosphates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, ethylene oxide adducts of acetylene glycol, Nonionic surfactants such as ethylene oxide adducts of glycerin and polyoxyethylene sorbitan fatty acid esters, and other amphoteric boundaries such as alkyl betaines and amide betaines Active agents, silicone surface active agent, including a fluorine-based surfactant, can be appropriately selected from surfactants and derivatives thereof are known.

In addition, a polymer dispersant may be included, and specific examples of the polymer dispersant include polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl methyl ether, polyethylene oxide, polyethylene glycol, polypropylene glycol, and polyacrylamide. Of these, polyvinylpyrrolidone is preferably used.

The conditions for forming the gas separation membrane of the present invention are not particularly limited, but the temperature is preferably −30 to 100 ° C., more preferably −10 to 80 ° C., and particularly preferably 5 to 50 ° C.

In the present invention, a gas such as air or oxygen may coexist at the time of forming the film, but it is preferably in an inert gas atmosphere.
In the gas separation membrane of the present invention, the content of the cellulose compound in the gas separation layer is not particularly limited as long as desired gas separation performance can be obtained. From the viewpoint of further improving the gas separation performance, the content of the cellulose compound in the gas separation layer is preferably 20% by mass or more, more preferably 40% by mass or more, and 60% by mass or more. Is preferable, and it is more preferable that it is 70 mass% or more. The content of the polyimide compound in the gas separation layer may be 100% by mass, but is usually 99% by mass or less.

<Applications and characteristics of gas separation membranes>
The gas separation membrane (composite membrane and asymmetric membrane) of the present invention can be suitably used as a gas separation recovery method and gas separation purification method. For example, hydrogen, helium, carbon monoxide, carbon dioxide, hydrogen sulfide, oxygen, nitrogen, ammonia, sulfur oxides, nitrogen oxides, saturated hydrocarbons such as methane and ethane, unsaturated hydrocarbons such as propylene, and tetrafluoroethane A gas separation membrane capable of efficiently separating a specific gas from a gas mixture containing a gas such as perfluorohydrocarbon. In particular, a gas separation membrane that selectively permeates carbon dioxide from a gas mixture containing carbon dioxide and hydrocarbon (preferably methane) is preferable.

In the gas separation membrane of the present invention, when the gas to be separated is a mixed gas of carbon dioxide and methane, the permeation rate of carbon dioxide at 40 ° C. and 5 MPa is preferably 20 GPU or more, and 30 GPU or more. More preferably, it is 35 to 500 GPU. The permeation rate ratio between carbon dioxide and methane (R _CO2 / R _CH4 ) is preferably 15 or more, and more preferably 20 or more. R _CO2 represents the permeation rate of carbon dioxide, and R _CH4 represents the permeation rate of methane.
1 GPU is 1 × 10 ⁻⁶ cm ³ (STP) / (cm ² · sec · cmHg).

[Gas separation method]
The gas separation method of the present invention is a method for separating a specific gas from a mixed gas of two or more components using the gas separation membrane of the present invention. The gas separation method of the present invention preferably includes selectively allowing carbon dioxide to permeate from a mixed gas containing carbon dioxide and methane. The pressure during gas separation is preferably 0.5 to 10 MPa, more preferably 1 to 10 MPa, and further preferably 2 to 7 MPa. The gas separation temperature is preferably −30 to 90 ° C., more preferably 15 to 70 ° C. In the mixed gas containing carbon dioxide and methane gas, the mixing ratio of carbon dioxide and methane gas is not particularly limited, but is preferably carbon dioxide: methane gas = 1: 99 to 99: 1 (volume ratio). More preferably, methane gas = 5: 95 to 90:10.

[Gas separation module and gas separation device]
A gas separation membrane module can be prepared using the gas separation membrane of the present invention. Examples of modules include spiral type, hollow fiber type, pleated type, tubular type, plate & frame type and the like.
In addition, a gas separation apparatus having means for separating and recovering or purifying gas can be obtained using the gas separation membrane or gas separation membrane module of the present invention. The gas separation composite membrane of the present invention may be applied to, for example, a gas separation and recovery device as a membrane / absorption hybrid method used in combination with an absorbing solution as described in JP-A-2007-297605.

The present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[Synthesis example]
<Synthesis of Cellulose Compound 1>
As raw material cellulose, 2.0 g of hydroxypropylmethylcellulose (trade name Metroze 90SH-100; manufactured by Shin-Etsu Chemical Co., Ltd.) and 50 mL of pyridine were mixed and stirred at 80 ° C. for 1 hour. Next, 9.36 g (50 mmol) of 4- (trifluoromethyl) phenyl isocyanate was added, and the mixture was further stirred at 80 ° C. for 3 hours. After cooling the reaction solution to room temperature, 20 mL of isopropanol and 180 mL of hexane were added, and the precipitated solid was filtered and washed with hexane. This solid was reslurried four times with a mixed solution of isopropanol (40 mL) / hexane (160 mL), and vacuum dried to obtain 3.10 g of cellulose compound 1 as a white powder.
The obtained cellulose compound 1, the type of functional groups substituting for the hydrogen atom constituting a hydroxyl group contained in the cellulose raw material (R ¹ in the general formula ^(1), R ^2, and R ^3), as well as cellulose compound 1 The degree of substitution was observed and determined by ¹ H-NMR using the method described in Cellulose Communication 6, 73-79 (1999).
Moreover, the weight average molecular weight Mw of the cellulose compound 1 was measured using the gel permeation chromatography (GPC). Specifically, N-methylpyrrolidone was used as a solvent, a polystyrene gel was used, and a molecular weight calibration curve obtained in advance from a constituent curve of standard monodisperse polystyrene was used. As the GPC apparatus, HLC-8220 GPC (manufactured by Tosoh Corporation) was used.
The weight average molecular weight of the cellulose compound 1 was 406000.

<Synthesis of Cellulose Compound 2>
In the synthesis of cellulose compound 1, methyl cellulose (methyl substitution degree 1.8, manufactured by Wako Pure Chemical Industries) was substituted for hydroxypropylmethylcellulose, and 3,5-bis (trifluoro) was substituted for 4- (trifluoromethyl) phenyl isocyanate. Cellulose compound 2 was obtained in the same manner as in the synthesis of cellulose compound 1 except that methyl) phenyl isocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.) was used.
The weight average molecular weight of the cellulose compound 1 was 621000.

<Synthesis of Cellulose Compound 3>
Cellulose compound 1 was synthesized in the same manner as cellulose compound 1 except that 4,5-difluorophthalic anhydride (manufactured by Tokyo Chemical Industry) was used in place of 4- (trifluoromethyl) phenyl isocyanate in the synthesis of cellulose compound 1. 3 was obtained.
The weight average molecular weight of the cellulose compound 3 was 281000.

<Synthesis of Cellulose Compound 4>
In the synthesis of the cellulose compound 1, methylcellulose (methyl substitution degree 1.8, manufactured by Wako Pure Chemical Industries) was substituted for hydroxypropylmethylcellulose, and 4-trifluoromethylphthalic acid was substituted for 4- (trifluoromethyl) phenyl isocyanate. (Manufactured by Tokyo Chemical Industry), Organic Letters, 2010, Vol. 12, p. Cellulose compound 4 was synthesized in the same manner as cellulose compound 1 except that 4-trifluoromethylphthalic anhydride synthesized by the method described in 4796-4799 was used.
The weight average molecular weight of the cellulose compound 4 was 597,000.

<Synthesis of Cellulose Compound 5>
In the synthesis of cellulose compound 1, acetyl cellulose (acetyl substitution degree 2.2, manufactured by Daicel) was substituted for hydroxypropylmethylcellulose, and 3-hydroxy-5- (trimethyl) was substituted for 4- (trifluoromethyl) phenyl isocyanate. Fluoromethyl) benzoic acid from Journal of Medicinal Chemistry, 2016, Vol. 59, p. Cellulose compound 5 was synthesized in the same manner as cellulose compound 1 except that 3-hydroxy-5- (trifluoromethyl) benzoic acid chloride synthesized by the method described in 2478-2496 was used.
The weight average molecular weight of the cellulose compound 5 was 273,000.

<Synthesis of Cellulose Compound 6>
In the synthesis of cellulose compound 1, cellulose compound 6 was synthesized in the same manner as in the synthesis of cellulose compound 1 except that tetrafluorosuccinic anhydride (manufactured by Tokyo Chemical Industry) was used instead of 4- (trifluoromethyl) phenyl isocyanate. did.
The weight average molecular weight of the cellulose compound 6 was 255000.

<Synthesis of Cellulose Compound 7>
In the synthesis of cellulose compound 1, methyl cellulose (methyl substitution degree 1.8, manufactured by Wako Pure Chemical Industries) was substituted for hydroxypropylmethylcellulose, and 3, 3, 3,-instead of 4- (trifluoromethyl) phenyl isocyanate. From trifluoro-2-hydroxy-2-methylpropionic acid, Journal of Medicinal Chemistry, 1996, Vol. 39, p. Cellulose compound 7 was synthesized in the same manner as cellulose compound 1 except that 3,3,3, -trifluoro-2-hydroxy-2-methylpropionic acid chloride synthesized by the method described in 4592-4601 was used. did.
The weight average molecular weight of the cellulose compound 7 was 575000.

<Synthesis of Cellulose Compound 8>
In the synthesis of cellulose compound 1, ethylcellulose (ethoxy substitution degree 2.4, manufactured by Aldrich) was substituted for hydroxypropylmethylcellulose, and 3,5-difluorophenylisocyanate (manufactured by Aldrich) instead of 4- (trifluoromethyl) phenylisocyanate. The cellulose compound 8 was synthesized in the same manner as the synthesis of the cellulose compound 1 except that.
The weight average molecular weight of the cellulose compound 8 was 599000.

<Synthesis of Cellulose Compound 9>
In the synthesis of cellulose compound 1, methylcellulose (methyl substitution degree 1.8, manufactured by Wako Pure Chemical Industries) was substituted for hydroxypropylmethylcellulose, and 3,6-difluoro was substituted for 4- (trifluoromethyl) phenyl isocyanate (50 mmol). Cellulose compound 9 was synthesized in the same manner as cellulose compound 1 except that phthalic anhydride (manufactured by Aldrich) (20 mmol) was used.
The weight average molecular weight of the cellulose compound 9 was 571,000.

In the cellulose compounds 1 to 9 obtained in the above synthesis examples, the structures of substituents corresponding to R ¹ to R ³ in the general formula (1) are shown below. The numerical value attached below each substituent indicates the degree of substitution, and the parenthesis indicates the molecular weight. Me represents methyl, and Et represents ethyl.

[Comparative synthesis example]
Comparative compound 1 is acetylcellulose (acetyl substitution degree 2.4, manufactured by Daicel), comparative compound 2 is a cellulose compound described in Example 1 of JP-A-59-55307, and comparative compound 3 is Japanese Patent Publication No. 58-24161. The cellulose compound described in Example 1 of the gazette, the cellulose compound described in Example 2 of JP-A-2-227401 as the comparative compound 4 and the compound described in Example 6 of JP-A-2-212501 as the comparative compound 5 A cellulose compound was used.
The structure of the substituent corresponding to R ¹ to R ³ in the general formula (1) and the degree of substitution thereof for each comparative compound (cellulose compound) are shown below. The parenthesis indicates the molecular weight.

[Example 1] Production of composite membrane <Production of PAN porous membrane with smooth layer>
(Preparation of radiation curable polymer having dialkylsiloxane group)
In a 150 mL three-necked flask, 39 g of UV9300 (manufactured by Momentive), 10 g of X-22-162C (manufactured by Shin-Etsu Chemical), DBU (1,8-diazabicyclo [5.4.0] undec-7-ene). 007 g was added and dissolved in 50 g of n-heptane. This was maintained at 95 ° C. for 168 hours to obtain a radiation curable polymer solution having a poly (siloxane) group (viscosity of 22.8 mPa · s at 25 ° C.).

(Preparation of polymerizable radiation curable composition)
5 g of the radiation curable polymer solution was cooled to 20 ° C. and diluted with 95 g of n-heptane. To the obtained solution, 0.5 g of UV9380C (manufactured by Momentive) as a photopolymerization initiator and 0.1 g of organics TA-10 (manufactured by Matsumoto Fine Chemical) are added to obtain a polymerizable radiation-curable composition. Prepared.

(Application of polymerizable radiation curable composition to porous support, formation of smooth layer)
PAN (polyacrylonitrile) porous membrane (polyacrylonitrile porous membrane is present on the nonwoven fabric, including the nonwoven fabric, the film thickness is about 180 μm) After spin coating the above polymerizable radiation curable composition as a support, After UV treatment (Fusion UV System, Light Hammer 10, D-bulb) under UV treatment conditions with a UV intensity of 24 kW / m and a treatment time of 10 seconds, it was dried. In this way, a smooth layer having a thickness of 1 μm and having a dialkylsiloxane group was formed on the porous support.

<Production of composite membrane>
The gas separation composite membrane shown in FIG. 2 was produced (the smooth layer is not shown in FIG. 2).
In a 30 ml brown vial, 0.08 g of cellulose compound 1 and 9.92 g of tetrahydrofuran were mixed and stirred for 30 minutes, and then spin coated on the PAN porous membrane provided with the above smooth layer to form a gas separation layer. A composite membrane of Example 1 was obtained. The thickness of the layer of the cellulose compound 1 was about 70 nm, and the thickness of the PAN porous film was about 180 μm including the nonwoven fabric.
These polyacrylonitrile porous membranes had a molecular weight cut-off of 100,000 or less. Further, the permeability of carbon dioxide at 40 ° C. and 5 MPa of this porous membrane was 25000 GPU.

[Examples 2 to 9] Production of composite membranes In Example 1 above, composites of Examples 2 to 9 were used in the same manner as Example 1 except that cellulose compounds 2 to 9 were used instead of cellulose compound 1. A membrane was prepared. The cellulose compounds used in Examples 2 to 9 are as follows.
Example 2: Cellulose Compound 2, Example 3: Cellulose Compound 3, Example 4: Cellulose Compound 4, Example 5: Cellulose Compound 5, Example 6: Cellulose Compound 6, Example 7: Cellulose Compound 7, Example 8: Cellulose compound 8, Example 9: Cellulose compound 9

[Comparative Examples 1 to 5] Preparation of Composite Membrane Composite membranes of Comparative Examples 1 to 5 in the same manner as in Example 1 except that Comparative Compound 1 to 5 was used instead of Cellulose Compound 1 in Example 1 above. Was made. The comparative compounds used in Comparative Examples 1 to 5 are as follows.
Comparative Example 1: Comparative Compound 1, Comparative Example 2: Comparative Compound 2, Comparative Example 3: Comparative Compound 3, Comparative Example 4: Comparative Compound 4, Comparative Example 5: Comparative Compound 5

Test Example 1 Evaluation of CO ₂ Permeation Rate and Gas Separation Selectivity of Gas Separation Membrane Gas separation performance was evaluated as follows using the gas separation membranes (composite membranes) of the above Examples and Comparative Examples.
The gas separation membrane was cut to a diameter of 5 cm together with the porous support (support layer) to prepare a permeation test sample. Using a gas permeability measuring device manufactured by GTR Tech Co., Ltd., a mixed gas of carbon dioxide (CO ₂ ): methane (CH ₄ ) of 13:87 (volume ratio) is used, and the total pressure on the gas supply side is 5 MPa (minus CO ₂ The pressure was adjusted to 0.65 MPa), the flow rate was 500 mL / min, and 40 ° C., and the gas was supplied from the gas separation layer side. The permeated gas was analyzed by gas chromatography. The gas permeability of the membrane was compared by calculating the gas permeation rate as gas permeability (Permeance). The unit of gas permeability (gas permeation rate) was expressed by GPU (Gas Permeation Unit) unit [1 GPU = 1 × 10 ⁻⁶ cm ³ (STP) / (cm ² · sec · cmHg)]. Note that STP is Standard Temperature and pressure, and 1 × 10 ⁻⁶ cm ³ (STP) is the volume of gas at 1 atm and 0 ° C. The gas separation selectivity was calculated as the ratio of the CO ₂ permeation rate R _{CO2 to} the CH ₄ permeation rate R _CH4 of this membrane (R _CO2 / R _CH4 ). The evaluation criteria of gas permeability and gas separation selectivity were as follows.

-Gas permeability evaluation criteria-
A: R _CO2 is 60 or more B: R _CO2 is 45 or more and less than 60 C: R _CO2 is 30 or more and less than 45 D: R _CO2 is less than 30

-Gas separation selectivity evaluation criteria-
A: R _CO2 / R _CH4 is 20 or more B: R _CO2 / R _CH4 is 17 or more and less than 20 C: R _CO2 / R _CH4 is 14 or more and less than 17 D: R _CO2 / R _CH4 is less than 14

[Test Example 2] Evaluation of resistance to plasticization The gas separation membrane used in Test Example 1 was placed in a stainless steel container containing a petri dish filled with a toluene solvent, and the gas separation membranes prepared in Examples and Comparative Examples were placed. , A closed system. Then, after storing for 20 minutes at 25 ° C. and exposing the composite membrane to toluene vapor, gas separation selectivity was evaluated in the same manner as in [Test Example 1]. Calculate the ratio of gas separation selectivity (Q) after exposure to toluene to the gas separation selectivity (P) before exposure to toluene (Q / P, retention rate of gas separation selectivity after exposure to toluene vapor). Plasticization resistance was evaluated.
By exposure to toluene, it is possible to evaluate the plasticization resistance of the gas separation membrane against impurity components such as benzene, toluene and xylene.

-Plasticization resistance evaluation criteria-
A: Gas separation selectivity maintenance ratio after exposure to toluene vapor is 0.9 or more B: Gas separation selectivity maintenance ratio after exposure to toluene vapor is 0.8 or more and less than 0.9 C: Gas separation selection after exposure to toluene vapor Maintenance ratio is 0.7 or more and less than 0.8 D: Gas separation selectivity maintenance ratio after exposure to toluene vapor is less than 0.7

The results of the above test examples are shown in the table below.

As shown in the above table, when the cellulose compound constituting the gas separation layer does not have active hydrogen in the substituent, the gas permeability is greatly reduced, resulting in poor gas separation selectivity and plasticization resistance. (Comparative Examples 1 to 4). This did not improve even when a fluorine atom was introduced into the substituent (Comparative Examples 2 to 4). Even if the cellulose compound constituting the gas separation layer has a form having a substituent having active hydrogen and a fluorine atom, if the molecular weight of the substituent is larger than that defined in the present invention, the gas permeation is still necessary. The results were inferior to all of the properties, gas separation selectivity and plasticization resistance (Comparative Example 5).
In contrast, any of the gas separation membranes of Examples 1 to 9 using a cellulose compound having a substituent T in the gas separation layer has both high gas permeability and high gas separation selectivity and is resistant to plasticization. It was also excellent.

While this invention has been described in conjunction with its embodiments, we do not intend to limit our invention in any detail of the description unless otherwise specified and are contrary to the spirit and scope of the invention as set forth in the appended claims. I think it should be interpreted widely.

This application claims priority based on Japanese Patent Application No. 2017-037647 filed in Japan on February 28, 2017, which is hereby incorporated herein by reference. Capture as part.

DESCRIPTION OF SYMBOLS 1 Gas separation layer 2 Porous layer 3

Nonwoven fabric layer

10, 20 Gas separation composite membrane

Claims

A gas separation membrane having a gas separation layer containing a cellulose compound as a constituent material, wherein the cellulose compound has a repeating unit represented by the following general formula (1).

In general formula (1), R 1 to R 3 represent a hydrogen atom or a substituent. However, at least one of R 1 to R 3 is a substituent T having an active hydrogen and a fluorine atom and having a molecular weight of 100 or more and less than 500.
2. The gas separation membrane according to claim 1, wherein the active hydrogen is a hydrogen atom constituting a hydroxyl group, a carboxy group, an amide group, an amide bond, a sulfamoyl group, —SO 2 NH—, a urethane bond, or a boric acid group.
The gas separation membrane according to claim 1 or 2, wherein at least one of R 1 to R 3 is methyl or acetyl.
The gas separation membrane according to any one of claims 1 to 3, wherein at least one of R 1 to R 3 is a group represented by the following general formulas (2-1) to (2-3).

In general formulas (2-1) to (2-3), R f represents a group having a fluorine atom. * Indicates a binding site.
The gas according to any one of claims 1 to 4, wherein at least one of R 1 to R 3 is a group represented by any one of the following general formulas (3-1) to (3-3): Separation membrane.

In the general formulas (3-1) to (3-3), L f represents a divalent group having a fluorine atom. * Indicates a binding site.
The gas separation membrane according to any one of claims 1 to 5, wherein the degree of substitution with the substituent T of the cellulose compound is 0.5 or more and 3.0 or less.
The gas separation membrane according to any one of claims 1 to 6, wherein the substitution degree of the cellulose compound exceeds 2.5.
The gas separation membrane according to any one of claims 1 to 7, wherein the gas separation membrane is a gas separation composite membrane having the gas separation layer on the gas permeable support layer.
The gas separation membrane according to claim 8, wherein the support layer comprises a porous layer on the gas separation layer side and a nonwoven fabric layer on the opposite side to the gas separation layer.
The gas separation membrane according to any one of claims 1 to 9, which is used for selectively permeating carbon dioxide from a gas containing carbon dioxide and methane.
In the case where the gas to be separated is a mixed gas of carbon dioxide and methane, the transmission rate of carbon dioxide under a gas supply condition of 40 ° C. and 5 MPa is 20 GPU or more, and the transmission rate of carbon dioxide relative to the transmission rate of methane The gas separation membrane according to any one of claims 1 to 10, wherein the ratio is 15 or more.
A gas separation module comprising the gas separation membrane according to any one of claims 1 to 11.
A gas separation apparatus comprising the gas separation membrane according to any one of claims 1 to 11.
A gas separation method using the gas separation membrane according to any one of claims 1 to 11.