JPH09896A - Fluorine-containing polyimide-based gas separation membrane, its manufacturing method and module - Google Patents

Abstract

(57) [Summary] [Object] To provide a fluorine-containing polyimide gas separation membrane which is homogeneous over a wide membrane area, has no defects such as pinholes, and has a high permeation flux and a separation coefficient α. [Structure] A polyimide-based resin containing a solution of an organic solvent (A) having a dielectric constant of 30 or less and a dipole moment of 3.0D or less and an organic solvent having at least one ether bond in a molecular structural unit as a main component. Organic solvent (B)
Which is dissolved in at least one solvent selected from the following solutions, and which does not dissolve the fluorine-containing polyimide resin, but which is dissolved in the solvent (C) having compatibility with the organic solvent (A) or (B) to remove the solvent. By using a solvent, an asymmetric gas separation membrane is formed. Fluorine-containing polyimide resin layer 3
Is a skin layer 1 (thickness L ₁ : about 40 nm) and a sponge layer 2
(Thickness L ₂ : about 30 μm). 4 is a support such as a non-woven fabric.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorine-containing polyimide gas separation membrane which is homogeneous over a wide area and has a high permeation flux and a separation coefficient α, and a method for producing the same. More specifically, it relates to the production of a fluorine-containing polyimide-based gas separation membrane for gas separation by a wet phase inversion method using a specific solvent, and a specific component such as hydrogen, methane, carbon dioxide gas from an industrial mixed gas, The present invention relates to an asymmetric-containing fluoropolyimide gas separation membrane used in the form of an asymmetric membrane or a composite membrane used for separating and concentrating oxygen, nitrogen, water vapor and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Polyimide is known as a membrane separation material having excellent heat resistance and chemical resistance because it has a high glass transition temperature and a rigid molecular chain structure. Separation membranes using various polyimides are known. Is being considered. For example, in U.S. Pat. No. 4,378,400 and U.S. Pat. No. 4,959,151, aromatic polyimides using biphenyltetracarboxylic dianhydride are disclosed in JP-A-5-7749, U.S. Pat. No. 3,822,202, and U.S. Pat. No. 3,899,309.
U.S. Pat. No. 4532041, U.S. Pat. No. 46
45824, U.S. Pat. No. 4,705,540.
U.S. Pat. No. 4,717,393, U.S. Pat. No. 4,717.
394, US Pat. No. 483900, US Pat. No. 4,897,092, US Pat. No. 4,932,982.
U.S. Pat. No. 4,929,405, U.S. Pat. No. 4,981,497, U.S. Pat. No. 5,042,992 and the like disclose fluorine-containing aromatic polyimides.

Further, a polyimide system using an aliphatic or alicyclic tetracarboxylic acid dianhydride is also disclosed in US Pat. No. 4,964,887 and US Pat. No. 4,988,371.

Considering that the separation membrane has practical mechanical strength, thinning and asymmetrical membranes are also being studied.
When a polymer having a high-performance separation coefficient is formed as a thin film on a suitable porous support membrane, the thickness of the thin film is preferably 0.1 μm in order to increase the gas permeation rate to a practical degree. In order to industrially produce the film having the following film thickness, the number of manufacturing steps is plural, the yield is poor, and the cost is high, which is not suitable for industrial implementation. Further, the asymmetric film formation is also described in the above-mentioned publication, but the required 0.1
It is difficult to industrially form a film having a thickness of less than or equal to μm without pinholes. U.S. Pat. No. 4,929,405 discloses controlling the film thickness of a fluorine-containing aromatic polyimide-based homogeneous film to a required film thickness of 0.1 μm or less and 40 nm or less by a water surface development method. It has no practical mechanical strength due to the lack of layers. Therefore, film formation on an industrial scale is difficult.

In order to form a pinhole-free asymmetric film, post-treatment (Japanese Patent Application Laid-Open Nos. 5-049882 and 5-1998).
No. 146651) and pretreatment (JP-A-5-184887).
No.), improvement of manufacturing process (US Pat. No. 4,902,422, US Pat. No. 5,085,676, US Pat. No. 516).
No. 5963) is disclosed.

However, these methods have problems that the number of working steps is increased and complicated, cost is high, and stable film formation on an industrial level is difficult.

[0007]

SUMMARY OF THE INVENTION Since the polyimide separation membrane is manufactured at a practical industrial level and an efficient separation operation is performed, the above-mentioned conventional techniques are not satisfactory. Specifically, firstly, a pinhole is formed during film formation,
Due to the pinholes, the performance of the separation membrane deteriorates, and the dispersion and instability become unstable, so that an efficient separation operation cannot be performed. Secondly, in case of compensating the first drawback, the film forming process becomes complicated and the cost becomes high. Thirdly, it is difficult to control the film-forming conditions in order to reduce pinholes as much as possible, and as a result, it is not possible to manufacture a film having a stable separation performance and well-balanced permeability.

In order to solve the above conventional problems, the present invention is a fluorine-containing polyimide gas separation membrane which is homogeneous in a wide membrane area, has no defects such as pinholes, and has a high permeation flux and a separation coefficient α. Another object of the present invention is to provide a production method for obtaining a gas separation membrane which has a high gas permeation flux and is practically satisfactory in terms of cost by a simple membrane production method.

[0009]

In order to achieve the above object, the fluorine-containing polyimide gas separation membrane of the present invention comprises at least a sponge layer composed of a solvent-soluble fluorine-containing polyimide resin and a skin layer on the surface thereof. A gas separation membrane having a membrane area of 0.5 m ² or more, wherein the skin layer has an average thickness in the range of 1 to 100 nm and a CO ₂ gas permeation rate of 0.01 to 50 Nm ³ / m ² / It is characterized in that the h / atm range and the CO ₂ / methane separation coefficient α are in the range of 2 to 60.

In the above structure, the gas separation membrane is preferably at least one separation membrane formed in the shape of a tube, a hollow fiber, or a gas permeable support.
This is because such a separation membrane is practically useful as a module.

Next, the method for producing a fluorine-containing polyimide gas separation membrane of the present invention is a method for producing a gas separation membrane having at least a sponge layer made of a solvent-soluble fluorine-containing polyimide resin and a skin layer on the surface thereof. The polyimide-based resin is mainly a solution containing an organic solvent (A) having a dielectric constant of 30 or less and a dipole moment of 3.0D or less, and an organic solvent having at least one ether bond in a molecular structural unit. A solvent that dissolves in at least one solvent selected from the solution consisting of the organic solvent (B) as a component and then does not dissolve the fluorine-containing polyimide resin, but has compatibility with the above organic solvent (A) or (B) ( It is characterized in that it is immersed in C) to remove the solvent.

Next, the gas separation membrane module of the present invention comprises a gas separation membrane having a membrane area of 0.5 m ² or more, which is provided with at least a sponge layer made of a solvent-soluble fluorine-containing polyimide resin and a skin layer on the surface thereof. In the module used, the skin layer has an average thickness in the range of 1 to 100 nm and a CO ₂ gas permeation rate of 0.01 to 50 Nm ³ /
m ² / h / atm range, CO ₂ / methane separation factor α
Is in the range of 2 to 60.

In the invention of the module, it is preferable that the module is at least one selected from a tubular shape, a hollow fiber shape, and a flat membrane formed on the surface of the gas permeable support. This is because the module is practically useful.

In the gas separation membrane and the manufacturing method of the present invention, the solvent-soluble fluorine-containing polyimide resin is contained in the repeating molecular structural unit constituting the polyimide resin layer,
At least 3 fluorine atoms and at least 1 (-S
It is preferably at least one resin selected from fluorine-containing polyimide resins having an O ₂ −) moiety. This is because such a resin has a high gas separation ability.

Further, in the gas separation membrane and the production method of the present invention, it is preferable that at least one --CF ₃ group is contained in the repeating molecular structural unit constituting the fluorine-containing polyimide resin. This is because such resins also have high gas separation ability.

In the gas separation membrane and the production method of the present invention, the fluorine-containing polyimide resin is substantially the same as the compound represented by the formula (1) (wherein A _{1 to} A _n are aromatic, alicyclic and aliphatic). Represents at least one tetravalent organic group selected from group hydrocarbon groups, and R _{1 to} R _n are divalent aromatic, alicyclic or aliphatic hydrocarbon groups, or these hydrocarbon groups are 2
A divalent organic group bonded by a valent organic bonding group, wherein at least one organic group among A _{1 to} A _n is an organic group having three or more fluorine atoms, and among R _{1 to} R _n at least one organic group - has a site (-SO _2). )
It is preferable that the repeating unit represented by This is because such resins also have high gas separation ability.

Further, in the gas separation membrane and the production method of the present invention, it is preferable that the fluorine-containing polyimide resin substantially contains a repeating unit represented by the above formula (Formula 2) as a main component. This is because such resins also have high gas separation ability.

In the method for producing a gas separation membrane of the present invention, it is preferable that the organic solvent (A) has a dielectric constant of 10 or less and a dipole moment of 3.0D or less. Such a solvent has a property that it is difficult to be compatibilized with water, for example, but it will be compatibilized with time. Therefore, the polyimide resin is dissolved in the organic solvent (A) and cast-formed into, for example, a film, and then desolvated in water. When the solvent is used, the solvent is gradually removed, so that the skin layer and the sponge layer inside can be in a homogeneous state.

Further, in the gas separation membrane and the manufacturing method of the present invention, the main component of the organic solvent (A) or (C) is at least one solvent selected from diethylene glycol dimethyl ether, diethylene glycol diethyl ether and a mixed solvent thereof. It is preferable. Similarly to the above, when the solvent is removed in water, the solvent is gradually removed, so that the skin layer and the internal sponge layer are in a homogeneous state.

In the method for producing a gas separation membrane of the present invention, it is preferable that the solvent (B) is at least one liquid selected from water, alcohols and a mixture thereof. Similarly to the above, when the solvent is removed in the liquid, the solvent is gradually removed, so that the skin layer and the internal sponge layer are in a homogeneous state.

In the gas separation membrane and manufacturing method of the present invention, the fluorine-containing polyimide-based gas separation membrane is
Further, it is preferable to form a protective film of an elastomer polymer. Further, it is possible to prevent pinhole defects and the like.

Further, in the gas separation membrane and the manufacturing method of the present invention, it is preferable that the protective membrane of the elastomer polymer is a membrane obtained by crosslinking a crosslinkable silicone resin. Similarly, it is possible to prevent pinhole defects and the like.

Further, in the gas separation membrane of the present invention,
It is preferable that the sponge layer has no void portion having a diameter of more than 1 μm. This is because if the sponge layer is also homogeneous, the defects are reduced.

[0024]

[Function] The above-mentioned fluorine-containing polyimide-based gas of the present invention
According to the separation membrane, solvent-soluble fluorine-containing polyimide resin
Less sponge layer made of fat and skin layer on the surface
Membrane area with 0.5m²The above gas separation membrane
The average thickness of the skin layer is in the range of 1 to 100 nm.
Yes, CO₂Gas permeation rate is 0.01 to 50 Nm ^Three/
m²/ H / atm range, CO₂/ Separation coefficient of methane α
Is in the range of 2 to 60, so that a large film area
High homogeneity, no defects such as pinholes, and high permeation flow
Fluorine-Containing Polyimide Gas Separation with Bundle and Separation Factor α
A membrane can be realized. Next, the fluorine-containing polyimide of the present invention
According to the method for producing a gas separation membrane, solvent-soluble fluorine-containing
Sponge layer made of polyimide resin and its surface layer
A method for producing a gas separation membrane, comprising at least a Kin layer.
The above-mentioned polyimide resin has a dielectric constant of 30 or less and is bipolar.
From an organic solvent (A) having a child moment of 3.0D or less
Solution and at least one ether in the molecular structural unit
Organic solvent containing an organic solvent having a hydrogen bond as a main component (B)
Dissolved in at least one solvent selected from
And then does not dissolve the fluorine-containing polyimide resin
Has compatibility with the above organic solvent (A) or (B)
By immersing in solvent (C) and removing the solvent,
Practical in terms of cost with high gas permeation flux due to film formation method
The gas separation membrane that satisfies
You.

Next, according to the gas separation membrane module of the present invention, a gas separation membrane having a membrane area of 0.5 m ² or more, which is provided with at least a sponge layer composed of a solvent-soluble fluorine-containing polyimide resin and a skin layer on the surface thereof. A module using a membrane, wherein the skin layer has an average thickness in the range of 1 to 100 nm and a CO ₂ gas permeation rate of 0.01 to 50 Nm.
³ / m ² / h / atm range and CO ₂ / methane separation coefficient α in the range of 2 to 60 make the membrane uniform over a wide membrane area, have no defects such as pinholes, and have high permeation flux. A gas separation membrane module having a separation coefficient α can be realized.

[0026]

The present invention will be described more specifically with reference to the following examples. INDUSTRIAL APPLICABILITY According to the present invention, by using a specific solvent for preparing a dope, the thickness of a homogeneous skin layer is set to a certain value or less by a wet phase conversion film forming method, and a pinhole that greatly reduces the separation performance is not formed over a wide range. The present invention has been accomplished by finding a film forming method for an asymmetric film. The asymmetric membrane is a membrane whose surface is covered with a skin layer and whose inside is formed with a sponge layer.

The fluorine-containing polyimide resin layer used in the present invention is a layer that contributes to gas separation performance, and contains at least 3 fluorine atoms and at least 1 (-SO _2- ) in the repeating molecular structural unit constituting the polyimide. Although it is composed of a fluorine-containing polyimide resin having a moiety, it is preferable to have at least one —CF ₃ in the repeating molecular structural unit that constitutes the polyimide resin layer. Furthermore,
The fluorine content in the fluorine-containing polyimide thin film is 6 to 1
Two (the number of fluorine atoms in the repeating molecular structural unit) is preferable for obtaining a gas separation membrane having substantially stable and high quality.

The fluorine-containing polyimide resin used in the present invention is represented by the following general formula (Formula 3) (wherein A ₁ to
A _n represents a tetravalent organic group consisting of an aromatic, alicyclic or aliphatic hydrocarbon group, and R _{1 to} R _n represent a divalent aromatic, alicyclic or aliphatic hydrocarbon group, or a hydrocarbon thereof. It represents a divalent organic group in which a hydrogen group bonded with a divalent organic linking group, at least one organic group among a ₁ to a _n is an organic group having a fluorine atom 3 or more, R ₁ to R at least one organic group of _n is - having the moiety (-SO _2). It is preferable that the main component is a repeating molecular structural unit represented by).

[0029]

Embedded image

4 having at least 3 or more fluorine atoms
As the valent organic group, A₁Or A ₂Of the tetravalent organic group
Place the pronto on a fluorine atom or a group containing a fluorine atom.
There is no particular limitation as long as it is strange, but more preferable
Ku A₁Or A₂At least one of the tetravalent organic groups of
CF has one proton_ThreeThe thing that was replaced is used
And, for example, a tetravalent organic group represented by the following formula (Formula 4)
And the like are preferably used.

[0031]

Embedded image

In the above formula (Formula 3), at least one (-
Examples of the divalent organic group having a SO ₂ −) moiety include R ₁ to
There is no particular limitation as long as it has a (—SO ₂ —) moiety in at least one of R _n , but more preferably a divalent organic group represented by the following formula (Formula 5) is used. .

[0033]

Embedded image

Further, it is more preferable that the fluorine-containing polyimide resin used in the present invention substantially contains a repeating unit represented by the following formula (Formula 6) as a main component.

[0035]

[Chemical 6]

Further, even if all of the imide ring moieties in the above formula (Formula 6) remain partially in the amic acid state, the abundance ratio is 30% or less, that is, the imidization ratio is 70%. If it is above%, there is no problem. The abundance ratio is a value obtained by quantifying and calculating the amount of residual —COOH with respect to all imide ring moieties using ¹ H-NMR. If the abundance ratio exceeds 30%, the affinity between the organic solvent (A) and the solvent (B) (due to an increase in —COOH) increases, which causes pinhole formation, and the original fluorine-containing polyimide-based gas. The separation performance of the separation membrane decreases.

The fluorine-containing polyimide resin used in the present invention may be used alone, but may also be used as a mixture of two or more kinds. Further, if it is 50 mol% or less, it may be a copolymer or a mixture with a polymer such as polysulfone or polyethersulfone other than the fluorine-containing polyimide resin.

The fluorine-containing polyimide resin used in the present invention can be obtained by using a tetracarboxylic dianhydride and a diamine component by a known polymerization method as described in, for example, US Pat. No. 3,959,350. For example,
Tetracarboxylic acid dianhydride and diamine compound are used in approximately equimolar amounts in a polar solvent at a temperature of about 80 ° C. or lower, preferably 0 to 60 ° C. (however, polyamic acid is polymerized.
The polar solvent used here is not particularly limited, but N-
Methylpyrrolidone, pyridine, dimethylacetamide,
Dimethylformamide, dimethylsulfoxide, tetrameethylurea, phenol, cresol and the like are preferably used.

A solution of the obtained polyamic acid in a polar solvent was added to a third solution of trimethylamine, triethylami, pyridine or the like.
An imidization promoter such as a primary amine compound, acetic anhydride, thionyl chloride or carbodiimide is added, and the mixture is stirred at a temperature of 5 to 150 ° C. to imidize so that the imidization ratio becomes 70% or more. When carrying out the imidization reaction, 100 to 40 of the polyamic acid solution was added without adding an imidization accelerator.
It may be imidized by heating at 0 ° C., preferably 120 to 300 ° C.

After the imidization reaction, in order to remove the polar solvent and the imide accelerator during the polymerization, the purified polyimide is dried by dropping it in a large amount of a solution of acetone, alcohol, water or the like, and the dielectric constant used in the present invention. Of 30 or less and a dipole moment of 3.0 D or less and redissolved in an organic solvent (A) to be used as a dope for film formation.

When the imidization reaction is carried out without adding an imidization promoter, a polyamic acid powder or a polyamic acid solution obtained by dropping the polyamic acid solution into a large amount of a solution of acetone, alcohol or the like. The solid of the polyamic acid obtained by evaporating the solvent from (from which a precipitating agent or the like may be added during evaporation to form a polyamic acid powder, which may be separated by filtration) is imidized by heating at 100 to 400 ° C. An organic solvent having a dielectric constant of 30 or less and a dipole moment of 3.0D or less (A), or an organic solvent containing an organic solvent having at least one ether bond in a molecular structural unit as a main component (C) To be used as a dope for film formation.

The dielectric constant used in the present invention is 30 or less,
Use of an organic solvent (A) having a dipole moment of 3.0D or less or an organic solvent (C) containing as a main component an organic solvent having at least one ether bond in a molecular structural unit as a solvent during synthesis. You can also At this time, even if the step of removing the imidization accelerator is not performed, the element performance is not affected at all, which is suitable for reducing the dope adjusting step.

The dielectric constant used in the present invention is 30 or less,
The dope for film formation is re-dissolved in an organic solvent (A) having a dipole moment of 3.0 D or less or an organic solvent (C) containing an organic solvent having at least one ether bond in the molecular structural unit as a main component. When adjusting, the concentration of the polyimide solution is 3 to 40% by weight, preferably 10 to 30% by weight. When adjusting the dope for film formation, a swelling agent, a dispersant, a thickener, and the like may be added as necessary.

The organic solvent (A) used in the present invention has a dielectric constant of 30 or less and a dipole moment of 3.0D or less, but the dielectric constant is preferably 10 or less. Since the organic solvent (A) used in the present invention has a small polarity, its affinity with the solvent used as the coagulating liquid, that is, the solvent (C) becomes weak. Therefore, the rate of leaching of the dope solvent into the solvent used as the coagulating liquid is sufficiently slower than the formation of the skin layer at the time of wet phase conversion film formation, so that pinholes are not formed in a wide range of homogeneous skin layers and industrial Can be formed on a dynamic scale.

The organic solvent (A) used in the present invention is not particularly limited as long as the above conditions are satisfied, but diethylene glycol dimethyl ether (having a dielectric constant of 5.9).
7, the dipole moment is preferably 1.97D, and other examples include 1,2-dimethoxyethane (dielectric constant: 5.50, dipole moment: 1.79D). Besides being used alone, they are also used as a mixed solvent of two or more kinds. Further, in order to adjust the solubility of the fluorine-containing polyimide used and the viscosity of the dope, an aprotic solvent having a dielectric constant of more than 30 and / or a dipole moment of more than 3.0 D within a range not exceeding 30% by weight. May be added. When the aprotic solvent is added,
The organic solvent (A) particularly preferably used in the present invention is an organic solvent containing 60% by weight or more and 100% by weight or less of diethylene glycol dimethyl ether, although it is appropriately selected depending on the solvent used. For example, a mixed solution of 67 wt% diethylene glycol dimethyl ether and 33 wt% N-methylpyrrolidone (NMP) is exemplified.

N which has been conventionally used as a solvent for dope
-Methyl-2-pyrrolidone (dielectric constant 320 (25
℃)), the dipole moment is 4.00D (30 ℃),
N, N-dimethylacetamide (dielectric constant 37.8 (2
5 ° C)), the dipole moment is 3.72D), N, N-
Dimethylformad (dielectric constant 36.7 (25 ℃)),
Dipole moment is 3.86D (25 ° C)), dimethyl sulfoxide (dielectric constant is 48.9 (20 ° C)), dipole moment is 4.30D). With the above, the dipole moment is 3.
It is 7D or more and is considered to have a strong affinity with a solvent used as a coagulating liquid, for example, water. Due to the strength of this affinity, the rate of leaching of the dope solvent into the solvent used as the coagulating liquid is higher than that of the skin layer during wet phase conversion film formation, so that a wide range of homogeneous skin layers can be obtained. A pinhole is formed in the. Furthermore, in the case of the aprotic polar solvent that has been conventionally used, during the wet phase conversion film formation, the dope for film formation is cast or spun on a gas permeable support, and then left at a predetermined temperature for a predetermined time. However, a part of the solvent is evaporated, but since the affinity with water is too strong, it absorbs moisture in the air, and the surface becomes cloudy to promote pinhole formation.

The organic solvent (C) used in the present invention is not particularly limited as long as it is an organic solvent containing an organic solvent having at least one ether bond in the molecular structural unit as a main component, but diethylene glycol dimethyl ether, diethylene glycol. Diethyl ether, diethylene glycol dibutyl ether, triethylene glycol diethyl ether, 1,2-dimethoxyethane,
1,2-diethoxyethane, 1,2-dibutoxyethane and the like can be mentioned. Preferably, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, or a mixed solvent thereof is used. Besides being used alone, they are also used as a mixed solvent of two or more kinds. In order to adjust the solubility of the fluorine-containing polyimide used and the viscosity of the dope, an aprotic solvent having no ether bond in the molecular structural unit may be added within a range not exceeding 30% by weight.

The wet phase conversion film forming method using the above dope will be described below. The method of forming the gas separation membrane and the form of the membrane in the present invention are not particularly limited, but the coagulating liquid or solvent (B A), an asymmetric membrane such as a tubular shape (including hollow fiber shape) or a flat membrane shape can be obtained.

In the case of a flat membrane, a dope is coated on a gas permeable support by a method such as casting or dipping, and immersed in a coagulating liquid, that is, a solvent (B) to obtain an asymmetric membrane in a composite form. Is also suitable in terms of increasing mechanical strength. Examples of suitable supports used in the present invention include a glass plate having a smooth surface and the following gas-permeable supports. Examples of the gas-permeable support include organic, inorganic, and metal porous materials having a smooth surface, woven cloth, non-woven cloth, and the like. The dope on the gas-permeable support and the coating thickness are 25 to 400 μm, preferably 30 to 2
It is 00 μm.

The dope using the organic solvent (A) used in the present invention is formed into a film at a temperature range of -80 to 80 ° C, preferably -20 to 40 ° C. As long as it does not dissolve the fluorine-containing polyimide resin used as the coagulating liquid used when the organic solvent (A) is removed by immersion, that is, the solvent (B), it is compatible with the organic solvent (A), Although not limited, water, alcohols such as methanol, ethanol and isopropyl alcohol, and a mixed solution thereof are used, and water is particularly preferably used. The temperature of the coagulant when the organic solvent (A) is removed by immersion, that is, the temperature of the solvent (B) is not particularly limited, but is preferably 0 to 50 ° C.

By forming an asymmetric membrane under the above conditions, a separation membrane having an average thickness of the skin layer in the range of 1 to 100 nm can be formed in a membrane area of 0.5 m ² or more. It is possible to manufacture a gas separation membrane in which the thickness of the skin layer is substantially constant, and pinholes that greatly reduce the separation performance are not present over a wide range. As a result, even create a large module membrane area, the flux for example CO ₂ gas 0.1~50Nm ^3/2 / hr. / Atm range, CO ₂ / methanol separation coefficient α can be prepared a module of 2 to 60 range.

In the gas separation membrane obtained in the present invention, it is preferable that the surface of the fluorine-containing polyimide thin film is further coated with an elastomer polymer. Forming and laminating a thin film of an elastomer polymer is suitable for blocking defects on the surface of the gas separation membrane and at the same time preventing the surface from being scratched. The elastomer polymer refers to a polymer having a flexible film-forming ability, and specific examples include:
Polypropylene, polyvinyl chloride, ethylene-propylene copolymer, ethylene-pyropyrene-diene copolymer,
Polybutadiene, polyisoprene, chloroprene rubber,
Homopolymers or copolymers of ethylenic monomers or conjugated diene-based monomers such as poly (4-methyl-pentene-1), ptadiene-styrene copolymer, isoprene-isobutylene copolymer, or polyisobutylene. Polymer, in addition to the above monomer components, acrylonitrile, (meth)
A copolymer containing a monomer component having a functional group such as acrylic acid ester or (meth) acrylic acid, or a place such as polyether polyol, polyurethane polyether, polyurene polyester, or polyamide polyether. Examples thereof include a copolymer having a soft segment and a hard segment. further,
In addition to the above, epoxy resin and ethyl cellulose, butoxy resin, etc., which are cured by a linear long-chain curing agent,
In the present invention, it can be used as the elastomer polymer.

In the present invention, a crosslinkable silicone resin is particularly preferably used as the elastomer polymer.
Such a crosslinkable silicone resin is a silicone resin that is soluble in an organic solvent before crosslinking but becomes an insoluble resin in the organic solvent after crosslinking, and is disclosed in, for example, JP-A-59-22.
The film can be formed according to the method described in Japanese Patent No. 5705.

The form of the element using the above gas separation membrane is not particularly limited, and it is a hollow fiber type element when extruded into a tubular shape, and a spiral type or flat membrane type when applied on an appropriate support. It can be modularized as a tubular element.

Next, description will be made with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a flat membrane type separation membrane 10 coated on a support according to an embodiment of the present invention. In FIG. 1, 3 is a fluorine-containing polyimide resin layer, which is a skin layer 1 and a sponge layer 2.
It is formed with. The polyimide resin layer 3 is formed on the surface of the gas permeable support 4 which is a polyester nonwoven fabric having a thickness of about 100 μm. FIG. 2 is a traced enlarged SEM photograph of the skin layer 1 and the sponge layer 2 of FIG. The thickness L ₁ of the skin layer 1 is about 40 nm, the thickness L ₂ of the shows only partially in Figure 2 the sponge layer 2 was approximately 30 [mu] m. In FIG. 2, the white portion indicates the polyimide resin portion and the black portion indicates the shadow due to the void.

Next, FIGS. 3A and 3B are reduced views of FIG. 2 and show that the structure of the sponge layer 2 is relatively uniform both in the thickness direction and in the plane direction. FIG. 4A is a trace SEM photograph of a cross section of a gas separation membrane made of a conventional fluorine-containing polyimide resin layer, and FIG. 4B is an enlarged view of part A of FIG. 4A. This asymmetric membrane is formed by using N-methylpyrrolidone (NMP) as a solvent and removing the solvent in water. In FIG. 4A, 2
1 is a skin layer, 22 is a sponge layer, 23 is a finger void portion (cylindrical void portion) formed in the sponge layer in the vertical direction, and 24 is a finger void portion formed in the lateral direction (depth direction). . Compared with FIG. 3 (a) of an embodiment of the present invention, which is an enlarged view of the same magnification, the asymmetric membrane of the prior art has a large finger void portion with a diameter of about 10 μm. The product of the present invention does not have this and has a uniform sponge layer.

The present invention will be described below with reference to specific examples, but the present invention is not limited to these examples. Example 1 A fluorine-containing polyimide having a repeating unit represented by the above formula (Formula 6) was synthesized by the following method in a solvent of diethylene glycol methyl ether.

Bis [4- (4-aminophenoxy) phenyl] sulfone (0.75 mol) was added to the organic solvent (A).
Alternatively, in a solution of 1842 g of diethylene glycol dimethyl ether as (C), under nitrogen atmosphere, 5,5'-2,2,2-trifluoro-1- (trifluoromethyl) ethylidene-bis-1,3- 0.75 mol of isobenzofurandione (6FDA) was added, and the mixture was stirred at room temperature for 8 hours to carry out polymerization to obtain a polyamic acid. Then, diethylene glycol dimethyl ether 4
After adding 06 g and the solution became uniform, 2.25 mol of pyridine, which is an imidizing agent substance, and 2.25 mo of acetic anhydride.
1 was added, and the mixture was stirred at room temperature for 12 hours to carry out an imidization reaction. After the reaction, the obtained solution was filtered as a film forming solution,
It was left to stand to be sufficiently defoamed and adjusted.

[0059] Using an applicator of the above film-forming solution as 25 ° C., width 1 m, length 15 m, thickness of about 200 [mu] m, on a polyester nonwoven fabric having a basis weight of 85 g / m ^2, thickness 200
It was cast at a thickness of μm and immersed in 20 ° C. water for 5 minutes and 20 ° C. water for 1 hour as a coagulating liquid. In this way
An asymmetric film as shown in ~ 3 was formed. After that, a cross-linkable silicone resin solution (GESilicones RTV615 hexane 3 wt% solution) which is an elastomer polymer is applied to the obtained gas separation surface and heat-treated at 110 ° C. for 15 minutes to obtain a thin film of the elastomer polymer ( A film thickness of about 1-3 μm) was formed and laminated. The obtained separation membrane was assembled into a cylindrical module (effective membrane area 1.4
m ² ), permeation rate and separation performance were measured.

The following pure gases (CO ₂ , CH ₄ , N ₂ ) were measured.
Was carried out at atmospheric pressure on the permeation side. Measurement time is 25
° C. The results are shown in Table 1.

[0061]

[Table 1]

Example 2 Example 1 was repeated except that the diamine component was changed to 3,3'-diaminodiphenyl sulfone. Table 2 shows the results.

[0063]

[Table 2]

As described in the above examples, in the asymmetric separation membrane of the present invention, the average thickness of the skin layer is uniform in the range of 1 to 100 nm in a wide membrane area required for a practical module. It was confirmed that the permeation rate and the separation performance were excellent. In addition, the film was homogeneous over a wide film area and had no defects such as pinholes.

(Example 3) Of the separation membrane obtained in Example 1, a width of 0.33 m and a length of 2.0 m were assembled into a cylindrical module (effective area 0.54 m ² ), the permeation rate and the separation performance. Was measured. The results are shown in Table 3.

[0066]

[Table 3]

As is clear from Table 3, the effective area is 0.54
It was confirmed that the module of m ² also has practically sufficient permeation rate and separation performance.

[0068]

The fluorine-containing polyimide-based gas separation membrane of the present invention has a gas membrane area of 0.5 m ² or more including at least a sponge layer composed of a solvent-soluble fluorine-containing polyimide-based resin and a surface skin layer thereof. The separation membrane, wherein the skin layer has an average thickness in the range of 1 to 100 nm,
₂ Gas permeation rate of 0.01 to 50 Nm ³ / m ² / h /
Atm range, separation factor α of CO ₂ / methane is 2 to 60
Within the range, it is possible to realize a fluorine-containing polyimide-based gas separation membrane that is homogeneous over a wide membrane area, has no defects such as pinholes, and has a high permeation flux and a separation coefficient α.

Next, the method for producing a fluorine-containing polyimide gas separation membrane of the present invention is a method for producing a gas separation membrane having at least a sponge layer made of a solvent-soluble fluorine-containing polyimide resin and a skin layer on the surface thereof. The polyimide-based resin is mainly a solution containing an organic solvent (A) having a dielectric constant of 30 or less and a dipole moment of 3.0D or less, and an organic solvent having at least one ether bond in a molecular structural unit. A solvent that dissolves in at least one solvent selected from the solution consisting of the organic solvent (B) as a component and then does not dissolve the fluorine-containing polyimide resin, but has compatibility with the above organic solvent (A) or (B) ( By immersing in C) and removing the solvent, a gas separation membrane that has a high gas permeation flux with a simple membrane forming method and is practically satisfactory in terms of cost can be obtained. Ku can reasonably be produced. Next, according to the gas separation membrane module of the present invention, a gas separation membrane having a membrane area of 0.5 m ² or more, which comprises at least a sponge layer made of a solvent-soluble fluorine-containing polyimide resin and a skin layer on the surface thereof is used. The average thickness of the skin layer is in the range of 1 to 100 nm, the permeation rate of CO ₂ gas is in the range of 0.01 to 50 Nm ³ / m ² / h / atm, and the range of CO ₂ / methane is When the separation coefficient α is in the range of 2 to 60, it is possible to realize a gas separation membrane module that is homogeneous over a wide membrane area, has no defects such as pinholes, and has a high permeation flux and a separation coefficient α.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a flat membrane type separation membrane coated on a support according to an embodiment of the present invention.

FIG. 2 is a trace diagram of an enlarged cross-sectional SEM photograph of FIG.

3A and 3B are reduced views of FIG.

4A is a traced SEM photograph of a cross section of a gas separation membrane made of a fluorine-containing polyimide resin layer according to the prior art, and FIG. 4B is an enlarged view of part A of FIG. 4A.

[Explanation of symbols]

 1 Skin Layer 2 Sponge Layer 3 Fluorine-Containing Polyimide Resin Layer 4 Gas Permeable Support 10 Flat Membrane Gas Separation Membrane 21 Skin Layer 22 Sponge Layer 23, 24 Finger Void (Cylindrical Void)

Claims (15)

[Claims] 1. A gas separation membrane having a membrane area of 0.5 m ² or more, comprising at least a sponge layer made of a solvent-soluble fluorine-containing polyimide resin and a skin layer on the surface thereof.
The skin layer has an average thickness in the range of 1 to 100 nm and a CO ₂ gas permeation rate of 0.01 to 50 Nm ³ / m.
A fluorine-containing polyimide-based gas separation membrane having a ² / h / atm range and a CO ₂ / methane separation coefficient α of 2 to 60. 2. The gas separation membrane has a tubular shape, a hollow fiber shape,
The fluorine-containing polyimide gas separation membrane according to claim 1, which is at least one separation membrane formed on the surface of the gas-permeable support. 3. A method for producing a gas separation membrane, comprising at least a sponge layer composed of a solvent-soluble fluorine-containing polyimide resin and a skin layer on the surface thereof, wherein the polyimide resin has a dielectric constant of 30 or less. Dipole moment is 3.
It is dissolved in at least one solvent selected from a solution consisting of an organic solvent (A) of 0D or less and a solution consisting of an organic solvent (B) containing an organic solvent having at least one ether bond in a molecular structural unit as a main component. Then, the fluorine-containing polyimide-based gas separation is characterized in that the fluorine-containing polyimide resin is not dissolved but is immersed in a solvent (C) having compatibility with the organic solvent (A) or (B) to remove the solvent. Membrane manufacturing method. 4. A module using a gas separation membrane having a membrane area of 0.5 m ² or more, which is provided with at least a sponge layer made of a solvent-soluble fluorine-containing polyimide resin and a skin layer on the surface of the sponge layer. The average thickness of the layer is 1-10
It is in the range of 0 nm and has a CO ₂ gas permeation rate of 0.01
A gas separation membrane module having a range of ˜50 Nm ³ / m ² / h / atm and a separation coefficient α of CO ₂ / methane of 2 to 60. 5. The module is tubular, hollow fiber,
The gas separation membrane module according to claim 4, wherein the gas separation membrane module is at least one selected from the group consisting of a flat membrane formed on the surface of the gas permeable support. 6. A solvent-soluble fluorine-containing polyimide resin, wherein the repeating molecular structural unit constituting the polyimide resin layer has at least three fluorine atoms and at least one (—SO ₂ —) moiety. 4. At least one resin selected from contained polyimide resins.
Alternatively, the fluorine-containing polyimide-based gas separation membrane according to 4 above, a method for producing the same, and a module. 7. The fluorine-containing polyimide-based gas separation membrane according to claim 1, 3 or 4, which has at least one —CF ₃ group in the repeating molecular structural unit constituting the fluorine-containing polyimide resin, and a method and module for producing the same. . 8. A fluorine-containing polyimide resin has substantially the following formula (Formula 1) (wherein A _{1 to} A _{n in} (Formula 1) are at least selected from aromatic, alicyclic and aliphatic hydrocarbon groups). One tetravalent organic group is shown, and R _{1 to} R _n are divalent aromatic, alicyclic or aliphatic hydrocarbon groups, or divalent ones in which these hydrocarbon groups are bound by a divalent organic bonding group. And an organic group of at least one of A _{1 to} A _n is an organic group having 3 or more fluorine atoms, and R _{1 to} R
at least one organic group of _n is - having the moiety (-SO _2). ) The fluorine-containing polyimide gas separation membrane according to claim 1, 3 or 4, which comprises a repeating unit represented by the formula (4) as a main component, a method for producing the same, and a module. Embedded image 9. The fluorine-containing polyimide-based gas separation membrane according to claim 1, 3 or 4, wherein the fluorine-containing polyimide resin essentially contains a repeating unit represented by the following formula (Formula 2). Manufacturing method and module. Embedded image 10. The method for producing a fluorine-containing polyimide gas separation membrane according to claim 3, wherein the organic solvent (A) has a dielectric constant of 10 or less and a dipole moment of 3.0D or less. 11. The fluorine-containing polyimide-based gas separation according to claim 3, wherein the main component of the organic solvent (A) or (C) is at least one solvent selected from diethylene glycol dimethyl ether, diethylene glycol diethyl ether and a mixed solvent thereof. Membrane manufacturing method. 12. The method for producing a fluorine-containing polyimide gas separation membrane according to claim 3, wherein the solvent (B) is at least one liquid selected from water, alcohols and a mixture thereof. 13. The fluorine-containing polyimide gas separation membrane according to claim 1, 3 or 4, further comprising a protective film of an elastomer polymer formed on the fluorine-containing polyimide gas separation membrane, and a method and module for producing the same. 14. The method for producing a fluorine-containing polyimide gas separation membrane according to claim 13, wherein the protective film of the elastomer polymer is a film obtained by crosslinking a crosslinkable silicone resin. 15. The fluorine-containing polyimide-based gas separation membrane and module according to claim 1, wherein the sponge layer has no void portion having a diameter of more than 1 μm.