JP2631253B2 - Highly selective gas separation membrane and its production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The first invention of the present application is summarized as follows.
A specific component obtained from an aromatic tetracarboxylic acid component mainly containing biphenyltetracarboxylic acids and / or 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride and an aromatic diamine component The asymmetric gas separation membrane made of the aromatic polyimide of the above is plasma-treated, and the helium gas permeation rate (PHe) is at a high level, and the helium gas permeation rate and the nitrogen gas permeation rate And the ratio (PHe / PN
_{The present invention} relates to a novel highly selective gas separation membrane having an extremely high selective permeability (gas separation performance) shown in ₂ ).

The second invention of this application is to provide an asymmetric gas separation membrane which is formed of the above-mentioned specific aromatic polyimide and which has not been subjected to plasma treatment and has a specific low gas separation performance. The present invention relates to a method for industrially producing the above-mentioned highly selective gas separation membrane by performing a chemical plasma treatment in the presence of a compound.

[0003]

2. Description of the Related Art Hitherto, many methods for improving the selective permeability of a porous heat-resistant gas separation membrane have been proposed for porous gas separation membranes made of various polymers.

For example, a porous gas separation membrane is manufactured by forming a film from a heat-resistant polymer solution by a wet film forming method or the like, and then,
Heat-treating the gas separation membrane to form a dense layer,
There is known a method for producing a gas separation membrane which is modified to improve gas permeation rate and gas separation performance (selectivity) of gas.

However, in order to improve the selective permeability of a gas separation membrane made of a heat-resistant polymer by heat treatment, the gas separation membrane is exposed to an extremely high temperature for a long time. Therefore, the porous structure of the gas separation membrane is remarkably deteriorated or non-uniformly deteriorated, and as a result, the gas permeability is reduced or the gas separation membrane with improved selectivity is improved with good reproducibility. There was a problem that it could not be manufactured.

Recently, a method of plasma-treating the surface of a porous gas separation membrane has been proposed as a method for improving the selective permeability of a porous gas separation membrane made of a heat-resistant polymer. For example, JP-A-57-94304 and JP-A-57-9
JP-A-4305 and JP-A-58-8503 disclose that a porous gas separation membrane (support) made of a heat-resistant polymer such as polysulfone or acrylonitrile can be used for the presence of a gaseous organic compound and / or an inert gas. Below, a method has been proposed in which a dense layer (separation layer) is formed by plasma treatment or a surface layer is modified to produce a gas separation membrane (hollow fiber) having improved permselectivity.

However, in the method of forming a dense layer on a porous gas separation membrane by the above-mentioned plasma treatment, the surface openings of many fine pores are closed by the plasma treatment to form a dense layer. It is extremely difficult to form a dense layer with good reproducibility on the surface of the gas separation membrane. In particular, for an aromatic polyimide porous gas separation membrane, an asymmetric gas separation membrane provided with a sufficiently high selectivity Could not be substantially obtained.

[0008] Japanese Patent Laid-Open No. 60-99323 to 993
No. 27, and JP-A No. 62-204825-2
04827, polysulfone, polyamide,
Perfluorocyclohexene, perfluoroheptene-1, on a porous film made of polyacrylonitrile, etc.
There is known a method for producing a gas separation membrane having a dense layer of a plasma-polymerized membrane by plasma-polymerizing an unsaturated fluoro compound such as tetrakis (trifluoromethyl) ethylene and tetrakis (trifluoromethyl) dithiethane.

Japanese Patent Application Laid-Open No. 61-107923 discloses a specific poly (2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] olopropane dianhydride and phenylenediamine. A polymerizable film is formed by plasma polymerizing a polymerizable monomer such as a silane-based unsaturated compound on an asymmetric porous film made of etherimide, and then a coating thin film of organopolysiloxanes is formed. There has been proposed a method for producing a composite membrane.

However, each composite separation membrane manufactured by the above-mentioned known plasma polymerization method has a helium gas permeation rate (PHe) of about 1.2 × 10 ^{−3 to} 6.8 × 10 ^−4.
cm ³ (STP) / cm ² · sec · cmHg, but on the other hand, their permselectivity (PHe / PN ₂ ) is on the order of 13-32, or helium. Gas permeation speed (P
He) is 1.4 × 10 ^{−5 to} 2.0 × 10 ⁻⁵ cm ³ /
cm ² · sec · cmHg, which was extremely small, and could not be sufficiently satisfied in practical use.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly practical gas having a sufficiently high helium gas permeation rate and a very high gas separation property (selective permeability) between helium and nitrogen. An object of the present invention is to provide a novel aromatic polyimide high selectivity gas separation membrane having gas separation performance, and a method for industrially producing the high selectivity gas separation membrane with good reproducibility.

[0012]

[Means for Solving the Problems] The first invention of this application is:
General formula A

[0013]

Embedded image (Wherein, R ₁ is a divalent aromatic residue based on an aromatic diamine compound) and / or a general formula (B)

[0014]

Embedded image (Wherein, R ₂ is a divalent aromatic residue based on an aromatic diamine compound).
100 mol% and the general formula (C)

[0015]

Embedded image (In the formula, R is a tetravalent aromatic residue based on an aromatic tetracarboxylic acid, and R ₃ is a divalent aromatic residue based on an aromatic diamine compound.)

The asymmetric gas separation membrane formed of an aromatic polyimide comprising 20 mol% or less of the repeating unit (C) represented by the formula (1) is used for forming an unsaturated hydrocarbon compound, an unsaturated halide, an unsaturated aliphatic alcohol and an unsaturated aliphatic alcohol. It has been plasma-treated in the presence of at least one unsaturated compound selected from the group consisting of saturated aliphatic amines, and has a helium gas permeation rate (PHe) of 1 × 10 ^{−4 at} 80 ° C.
cm ³ (STP) / cm ² · sec · cmHg or more, preferably 2 × 10 ^{−4 to} 1 × 10 ⁻³ cm ³ (STP) / c
m ² · sec · cmHg, and the ratio (PHe / PN ₂ ) of the helium gas permeation rate (PHe) to the nitrogen gas permeation rate (PN ₂ ) at 80 ° C. is 50 or more;
In particular, the present invention relates to a highly selective gas separation membrane characterized by being about 60 to 300.

The second invention of this application is characterized in that the repeating unit (A) represented by the general formula (A) and / or the repeating unit (B) represented by the general formula (B) is 80 to 100 mol%,
And an aromatic polyimide comprising 20 mol% or less of the repeating unit (C) represented by the general formula (C),
Also, the permeation rate of helium gas at 80 ° C (PHe)
Is 1 × 10 ^-4 cm ³ (STP) / cm ² · sec · cm
Hg or more, preferably 5 × 10 ^{−4 to} 5 × 10 ⁻³ cm
³ (STP) / cm ² · sec · cmHg, and the ratio (P) of the transmission rate of helium gas (PHe) to the transmission rate of nitrogen gas (PN ₂ ) at 80 ° C.
A gas separation membrane having He / PN ₂ ) of about 1.5 to 50, preferably about 2 to 20 is formed of a group consisting of an unsaturated hydrocarbon compound, an unsaturated halide, an unsaturated aliphatic alcohol and an unsaturated aliphatic amine. A plasma treatment in the presence of at least one unsaturated compound selected from the group consisting of:

The high selectivity gas separation membrane of the present invention is characterized in that a porous or asymmetric gas separation membrane made of a specific aromatic polyimide is formed by a glow discharge or corona discharge in the presence of a specific unsaturated compound. Plasma treatment, a cross-linked structure is formed on the surface layer of the gas separation membrane, a functional group is introduced, or a thin film of a plasma polymer is formed. It is a novel highly selective gas separation membrane made of aromatic polyimide to which performance is given.

The polymer material forming the highly selective gas separation membrane of the present invention comprises a repeating unit (A) represented by the aforementioned general formula (A) and / or a repeating unit represented by the following general formula (B): B) 80 to 100 mol%, preferably 90 to 10
0 mol% and the repeating unit (C) represented by the general formula (C)
It is an aromatic polyimide comprising 20 mol% or less, preferably 0 to 18 mol%.

In the present invention, the aromatic polyimide may be, for example, (a) 90 to 100 mol% of a repeating unit (A) represented by the above-mentioned general formula (A); A soluble aromatic polyimide comprising 0 to 10 mol% of repeating units (C),
(B) a repeating unit (A) 5 represented by the aforementioned general formula (A)
-70 mol%, especially 10-60 mol%, 20-90 mol%, especially 30-90 mol% of the repeating unit (B) represented by the general formula (B)
It is suitable to be a soluble aromatic polyimide comprising 80 mol% and 20 mol% or less, preferably 0 to 18 mol% of the repeating unit (C) represented by the general formula (C).

That is, the aromatic polyimide (a)
Is biphenyltetracarboxylic acid or its acid dianhydride 8
An aromatic tetracarboxylic acid component composed of 0 to 100 mol% and other aromatic tetracarboxylic acids of 20 mol% or less, and an aromatic diamine component are polymerized and imidized in an organic polar solvent in substantially equimolar amounts of both components. And the resulting soluble aromatic polyimide.

The aromatic polyimide (b) may be a biphenyltetracarboxylic acid or its dianhydride in an amount of 5 to 70 mol%, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane or its dianhydride. 20 to 90 mol% of the product and, if necessary, 20 mol% or less of pyromellitic acid, benzophenone tetracarboxylic acid, diphenyl ether tetracarboxylic acid, or other aromatic tetracarboxylic acids composed of diacids of these acids Is a soluble aromatic polyimide obtained by polymerizing and imidizing an aromatic tetracarboxylic acid component and an aromatic diamine component in substantially equimolar amounts of both components in an organic polar solvent.

The repeating unit (A) is preferably represented by the general formula (AA)

Embedded image (Wherein, R ₁ is a divalent aromatic residue based on an aromatic diamine compound).

That is, the aromatic polyimide forming the highly selective gas separation membrane of the present invention is 3,3 ′, 4,4
Other than using 4'-biphenyltetracarboxylic acid or its acid dianhydride as biphenyltetracarboxylic acids, the fragrance obtained by polymerization and imidization reaction as in the polymerization method (a) or (b) described above. It is preferably a group III polyimide having a repeating unit (AA) represented by the general formula (AA).

In the above general formula (C), R
Is preferably a tetravalent aromatic residue based on aromatic tetrarubonic acids such as pyromellitic acid, benzophenonetetracarboxylic acid, biphenylethertetracarboxylic acid or their acid dianhydrides, and in particular, pyromellitic acid or Acid dianhydrides are preferred.

The aromatic diamine which forms a divalent aromatic residue of R ₁ , R ₂ or R ₃ in the general formulas (A), (AA), (B) and (C) is All may be the same or may be different, for example,

(A) 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether,
Diphenyl ether diamine compounds such as 3′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 3,
Diphenylmethane diamine compounds such as 3'-diaminodiphenylmethane, 2,2-bis (3-aminophenyl) propane, 2,2-bis (4-aminophenyl) propane, and 2,2-bis (4-aminophenyl) hexa Bis (phenyl) propane-based diamine compounds such as fluoropropane, 4,4′-diaminodiphenylsulfone,
Diphenylsulfone diamine compounds such as 3,4'-diaminodiphenylsulfone; benzophenone diamine compounds such as 4,4'-diaminobenzophenone and 3,4'-diaminobenzophenone; 3,7-diamino-2,
8-dimethyl-diphenylene sulfone, 3,7-diamino-2,8-diethyl-diphenylene sulfone, 3,7
Diphenylene sulfone diamine compounds such as -diamino-4,8-dimethyl-diphenylene sulfone;

(B) bis (phenoxy) benzene diamine compounds such as 1,4-bis (3-aminophenoxy) benzene and 1,4-bis (4-aminophenoxy) benzene; Bis (phenyl) benzene-based diamine compounds such as aminophenyl) benzene and 1,4-bis (3-aminophenyl) benzene;

(C) 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4-
(4-aminophenoxy) phenyl] propane, 2,2
Bis [(phenoxy) phenyl] propane-based diamine compounds such as -bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis [4-
(4-aminophenoxy) phenyl] sulfone, 2,2
Bis [(phenoxy) phenyl] sulfone-based diamine compounds such as -bis [4- (3-aminophenoxy) phenyl] sulfone;

(D) Phenylene diamine compounds such as o-, m- or p-phenylenediamine and 3,5-diaminobenzoic acid.

The aromatic diamine component is mainly an aromatic diamine compound having a plurality of benzene rings, particularly a monocyclic or condensed ring of 2 to 4 benzenes (about 80 to about 80).
Mol% or more, especially 90 to 100 mol%), and particularly preferably mainly contains a diphenylene sulfone diamine compound, a diphenyl ether diamine compound, a diphenylmethane diamine compound, and a bis (phenoxy) benzene diamine compound. It is suitable.

The highly selective gas separation membrane of the present invention may be in the form of a flat membrane or a hollow fiber, and preferably has a thickness of about 10 to 500 μm, especially about 20 to 300 μm. .

The production method of the present invention is characterized in that the aforementioned repeating unit (A)
And helium gas permeation rate (PHe) at 80 ° C. is 1 × 10 ⁻⁴ cm ³ (STP) / cm.
² sec · cmHg or more, and the ratio of the transmission speed of helium gas to that of nitrogen gas at 80 ° C. (PH
e / PN ₂ ) is provided with a porous or asymmetric gas separation membrane of 1.5 to 50, and the gas separation membrane is prepared in the presence of the aforementioned unsaturated compound (preferably the unsaturated compound). about 0.01~100cm ³ (STP) while circulating in / min feed rate), 0.01~10torr, especially about the pressure and gas temperature 0.05～5Torr 200
C. or lower, high-frequency plasma processing such as glow discharge and corona discharge [preferably low-frequency plasma processing at a frequency of 1 to 50 MHz and high-frequency power of 1 to 100 W: non-equilibrium plasma processing. "Ultra LSI Plasma Chemistry" (Publisher: Industrial Research Institute Co., Ltd., Editor: "Electronic Materials" Editorial Department, Publication Date:
1983.9.10. )) For about 0.1-30 minutes,
In particular, it is preferable to produce a highly selective gas separation membrane by performing the treatment for 0.3 to 10 minutes.

The hydrocarbon compound which is an unsaturated compound used in the above-mentioned plasma treatment includes ethylene, propylene, 1-butene, 2-butene, isobutene, 1-butene and the like.
Pentene, 2-pentene, 2-methyl-1-butene, 2
-Olefin-based hydrocarbons such as -methyl-2-butene, butadiene, 1,3-pentadiene, 1,4-pentadiene, 1-methylbutadiene, 2,3-dimethylbutadiene, diene-based hydrocarbons such as arene, acetylene and the like Derivatives are preferred.

Examples of the unsaturated compound halide include olefinic hydrocarbons such as 1,1-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, vinyl chloride, vinylidene chloride and 1,2-dibromoethylene. Alternatively, a halide of a diene hydrocarbon can be preferably exemplified.

Further, the unsaturated compounds include allyl alcohol, 2-buten-1-ol, 3-buten-1-ol, 3-buten-2-ol, 2-penten-1-ol, and 2-penten-1-ol. Penten-2-ol, 4-penten-1-ol, 4-penten-2-ol, 1-hexen-3-ol, 2-hexen-1-ol, 3-hexen-1-ol, 4-hexen- 1-ol, 5-
Unsaturated aliphatic alcohols such as hexen-1-ol, 2-butene-1,4-diol, 2-cyclohexen-1-ol, propargyl alcohol, and

Allylamine, diallylamine, triallylamine, N, N-dimethylallylamine, N-methyldiallylamine, 1-dimethylamino-2-propylene,
Examples thereof include unsaturated aliphatic amines such as 3- (dimethylamino) acrolein, 3- (dimethylamino) acrylonitrile, and propargylamine. An unsaturated alcohol having a carbon-carbon double bond is most preferable.

The unsaturated compound used in the plasma treatment in the production method of the present invention may be other organic compounds or inorganic gases such as oxygen, hydrogen, nitrogen, air, helium, argon, carbon dioxide, carbon monoxide, and ammonia. It may be supplied to the plasma treatment step in a state where it is contained up to 70 mol%.

The gas separation membrane made of aromatic polyimide used in the production method of the present invention is obtained by uniformly dissolving a soluble aromatic polyimide having the above-mentioned repeating units (A) and (B) in an organic polar solvent. Using a polymer solution as a spinning dope, for example, JP-B-61-352
No. 82, Japanese Patent Publication No. 1-44484, a spinning nozzle discharge temperature (about 60 to 150 ° C.,
Especially the rotational viscosity at 70 to 120 ° C) is 10 to 20,000.
The dope solution having a poise, in particular, about 50 to 10,000 poise is extruded from a hollow fiber spinning nozzle to form a hollow fiber body, dried for a short time, and immediately coagulated (about -10 to 10).
60 ° C.) to solidify the hollow fiber and form a hollow fiber gas separation membrane by the “semi-dry / wet spinning method”.
It can be produced at a spinning speed of about 2 to 80 m / min.

[0040] The hollow fiber gas separation membrane produced as described above is finally made of, for example, isopentane, n-hexane,
After replacing the coagulating solvent in the hollow fiber membrane with an aliphatic hydrocarbon solvent such as isooctane or n-heptane, the aliphatic hydrocarbon solvent is evaporated to dryness at a temperature of about 50 to 150 ° C. and dried. It is preferable to use a hollow fiber gas separation membrane.
The heat treatment may be performed at a temperature of about 300 ° C. for a short time.

The soluble aromatic polyamide is 30
Logarithmic viscosity at 0 ° C (measured concentration: 0.5 g / 100 ml solvent, solvent: mixed solvent of 4 parts by volume of parachlorophenol and 1 part by volume of orthochlorophenol) is 0.1 to
7, particularly preferably about 0.2 to 5.

The organic polar solvent used in the polymer solution is an organic solvent which is used as a polymerization solvent for the aromatic polyimide and can uniformly dissolve the aromatic polyimide, and has a melting point of 200 ° C. or lower. Especially 150 ° C
The following are preferable, for example, phenols such as phenol, cresol and xylenol, catechols having two hydroxyl groups directly bonded to a benzene ring,
3-chlorophenol (hereinafter also referred to as PCP), 4
Phenolic solvents such as halogenated phenols such as -bromophenol and 2-chloro-5-hydroxytoluene, or N-methyl-2-pyrrolidone, N, N-
Examples thereof include amide solvents such as dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, and N, N-diethylformamide, and mixed solvents containing these as main components.

[0043]

The present invention will now be described in more detail with reference to Reference Examples, Examples and Comparative Examples.

The permeation performance of the hollow fiber gas separation membranes obtained in Reference Examples, Examples and Comparative Examples was measured by the following method.
First, using each sample hollow fiber of the hollow fiber gas separation membrane, a stainless steel pipe, and an epoxy resin-based adhesive, a yarn bundle element of a hollow fiber for permeation performance evaluation was prepared, and
The permeation performance was measured by mounting the yarn bundle element on a stainless steel container for a gas permeation test, using a mixed gas of helium gas and nitrogen gas at a temperature of 80 ° C. and 10 kg / cm.
^A gas permeation test was performed at a differential pressure of ² , and the gas permeation rate of each gas and the gas permeation rate ratio (indicating the selective permeability and the degree of gas separation) were analyzed by gas chromatography of the permeated gas and the unpermeated gas. Was calculated from the measured values.

Reference Example 1 [Preparation of aromatic polyimide solution (a)] 3,3 ', 4
An aromatic tetracarboxylic acid component comprising 99 mmol of 4'-biphenyltetracarboxylic dianhydride; and 4,4'-
40 mmol of diaminodiphenyl ether and 1,4-
An aromatic diamine component composed of 60 mmol of bis (4-aminophenoxy) benzene, an aromatic diamine component composed of paraphenylenediamine, 218 g of parachlorophenol, and a separable device provided with a stirrer and a nitrogen gas inlet tube. In a flask, while stirring the reaction solution, at a polymerization temperature of 180 ° C., both monomer components were polymerized for 16 hours, and the concentration of the aromatic polyimide was 19% by weight.
(A) was prepared.

This aromatic polyimide solution (a) is
The solution viscosity (rotational viscosity) at 0 ° C. was 2000 poise, and the solution viscosity at 90 ° C. (rotational viscosity) was 2800 poise. Logarithmic viscosity of polymer in aromatic polyimide solution (a) (measurement temperature: 0.5 g / 100 ml solvent, solvent: mixed solvent of 4 parts by volume of parachlorophenol and 1 part by volume of orthochlorophenol, measurement temperature: 30 ℃)
Was 1.6.

Reference Example 2 [Preparation of aromatic polyimide solution (b)] 55 mmol of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride and 3,3 ′, 4,4 ′ An aromatic tetracarboxylic acid component consisting of 30 mmol of biphenyltetracarboxylic dianhydride and 14 mmol of pyromellitic dianhydride, 90 mmol of 3,7-diamino-2,8-dimethyldiphenylene sulfone and 4,4 ′
-An aromatic diamine component consisting of 10 mmol of diaminodiphenylmethane and 312 g of parachlorophenol were put into a separable flask equipped with a stirrer and a nitrogen gas inlet tube, and the reaction solution was stirred at 180 ° C.
At 16 ° C. for 16 hours to prepare an aromatic polyimide solution (a) having an aromatic polyimide concentration of 16% by weight.

This aromatic polyimide solution (b) is 10
The solution viscosity (rotational viscosity) at 0 ° C. was 1079 poise, and the solution viscosity at 90 ° C. (rotational viscosity) was 1507 poise. Logarithmic viscosity of polymer in aromatic polyimide solution (b) (measurement temperature: 0.5 g / 100 ml solvent, solvent: mixed solvent of 4 parts by volume of parachlorophenol and 1 part by volume of orthochlorophenol, measurement temperature: 30 ℃)
Was 1.1.

Reference Examples 3 and 4 [Production of Gas Separation Membrane (a) and (b)] The aromatic polyimide solution [(a): Reference Example 1] and the aromatic polyimide solution [(b): Reference Example 2] ]
The solution was filtered through a 400-mesh stainless steel wire mesh to prepare spinning dope solutions.

Using these spinning dope solutions, a hollow fiber spinning nozzle (outer diameter of circular opening: 1000 μm, slit width of circular opening: 200 μm, and outer diameter of core opening: 400 μm) Spinning device equipped with
No. 4804), each of the spinning dopes is charged, and the spinning dope is discharged in a hollow fiber form from the spinning nozzle, and the hollow fiber is passed through a dried nitrogen atmosphere for a short time. Immersed in a primary coagulation liquid (about 0 ° C.) composed of a 65% by weight ethanol aqueous solution, and further immersed in a secondary coagulation liquid (about 0 ° C.) in a secondary coagulation apparatus having a pair of guide rolls. Is reciprocated to complete the solidification of the hollow fiber-shaped body, and the aromatic polyimide hollow fiber gas separation membrane is taken up by a take-up roll (at a take-up speed of 15 m / min).
Each spinning was performed while taking over.

Finally, each of the hollow fiber gas separation membranes is wound around a bobbin, and after sufficiently washing the coagulating solvent with ethanol, the ethanol is replaced with isooctane (substitution solvent).
Further, the asymmetric hollow fiber gas separation membrane is heated to 100 ° C. to evaporate and dry isooctane, and the hollow fiber gas separation membrane (a) (using the aromatic polyimide solution (a) of Reference Example 1) and the hollow fiber A gas separation membrane (b) [using the aromatic polyimide solution (b) of Reference Example 2] was produced.

The hollow fiber gas separation membrane (a) had an outer diameter of 480 μm and a thickness of 90 μm. Also,
The hollow fiber gas separation membrane (b) had an outer diameter of 420 μm and a thickness of 70 μm. Further, a gas permeation test was performed on each of the hollow fiber gas separation membranes (a) and (b). The results are shown in Tables 1 and 2, respectively.

Example 1 A hollow fiber gas separation membrane (a) made of aromatic polyimide obtained in Reference Example 3 was wound around a “casing” and placed in a bell jar, and a high frequency power of 20 W and a pressure of 1 in the bell jar were set. .3t
orr and ethylene gas flow rate of 50 cm ³ (ST
The hollow fiber gas separation membrane (a) was subjected to ethylene-plasma treatment for 3 minutes under the plasma treatment conditions of P) / min. A gas permeation test was conducted on the plasma-treated hollow fiber gas separation membrane (a), and the resulting gas permeation rate and permselectivity are shown in Table 1.

Examples 2 to 5 The types of unsaturated compounds used in the plasma treatment and the gas flow rates thereof are shown in Table 1, and the pressure in the bell jar, the high frequency power and the plasma treatment time are shown in Table 1.
Except as shown in the table, each unsaturated compound-plasma treatment of the hollow fiber gas separation membrane (a) was performed in the same manner as in Example 1. A gas permeation test was conducted on the plasma-treated hollow fiber gas separation membrane (a), and the resulting gas permeation rate and permselectivity are shown in Table 1.

Comparative Examples 1 to 3 The hollow fiber gas separation membrane (a) made of aromatic polyimide obtained in Reference Example 3 was wound around a cassette and subjected to only heat treatment at the temperature shown in Table 1 for 30 minutes. Then, the hollow fiber gas separation membrane (a) subjected to only the heat treatment was manufactured. A gas permeation test was performed on the hollow fiber gas separation membrane (a) subjected to only the heat treatment, and the resulting gas permeation rate and permselectivity are shown in Table 1.

Example 6 The procedure of Example 1 was repeated, except that the aromatic polyimide hollow fiber gas separation membrane (b) obtained in Reference Example 4 was used, and allyl alcohol was used as the unsaturated compound. Allyl alcohol-plasma treatment of the hollow fiber gas separation membrane (b) was performed. A gas permeation test was conducted on the plasma-treated hollow fiber gas separation membrane (b), and the resulting gas permeation rate and permselectivity are shown in Table 2.

Examples 7 to 11 The aromatic polyimide hollow fiber gas separation membrane (b) obtained in Reference Example 4 was used as it is, or was subjected to a preliminary heat treatment shown in Table 2 for plasma treatment. Same as Example 1 except that the type of unsaturated compound used and the gas flow rate were as shown in Table 2, and the pressure in the bell jar, high frequency power and plasma treatment time were as shown in Table 2. And an asymmetric hollow fiber gas separation membrane (b)
Of each unsaturated compound-plasma treatment. A gas permeation test was conducted on the plasma-treated hollow fiber gas separation membrane (b), and the resulting gas permeation rate and permselectivity are shown in Table 2.

Comparative Examples 4 to 8 The hollow fiber gas separation membrane (b) made of aromatic polyimide obtained in Reference Example 4 was wound around a cassette and subjected to only heat treatment at the temperature shown in Table 2 for 30 minutes. Then, the hollow fiber gas separation membrane (b) subjected to only the heat treatment was manufactured. A gas permeation test was performed on the hollow fiber gas separation membrane (b) subjected to only the heat treatment, and the resulting gas permeation rate and permselectivity are shown in Table 2.

[0059]

[Table 1]

[0060]

[Table 2]

[0061]

[Operation and effect of the present invention] The highly selective gas separation membrane of the present invention comprises a biphenyltetracarboxylic acid and / or 2,2-
It is formed of a soluble aromatic polyimide obtained by substantially equimolar polymerization and imidization of an aromatic tetracarboxylic acid component having bis (3,4-dicarboxyphenyl) hexafluoropropane as a main component and an aromatic diamine component. The porous or asymmetric gas separation membrane is treated with an unsaturated compound-plasma, has a sufficiently high helium gas permeation rate, and has a gas separation property (selective permeability) between helium and nitrogen. This is a novel aromatic polyimide gas separation membrane having extremely high gas separation performance that is highly practical.

According to the production method of the present invention, the aromatic polyimide gas separation membrane is subjected to plasma treatment in the presence of an unsaturated compound, and the gas separation membrane (hollow fiber gas (Separation membrane) can be produced industrially with good reproducibility.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-111921 (JP, A) JP-A-3-127616 (JP, A) JP-A-3-65214 (JP, A) JP-A-63-111 123420 (JP, A) JP-A-3-106426 (JP, A) JP-A-59-127603 (JP, A) JP-A-61-107923 (JP, A) JP-A-61-103521 (JP, A)

Claims (2)

(57) [Claims] 1. A compound of the general formula A (Wherein, R ₁ is a divalent aromatic residue based on an aromatic diamine compound) and / or a general formula (B) (Wherein R ₂ is a divalent aromatic residue based on an aromatic diamine compound).
100 mol% and the general formula (C) (Wherein, R is a tetravalent aromatic residue based on an aromatic tetracarboxylic acid, and R ₃ is a divalent aromatic residue based on an aromatic diamine compound.) An asymmetric gas separation membrane formed of an aromatic polyimide having a repeating unit (C) of 20 mol% or less comprises an unsaturated hydrocarbon compound, an unsaturated halide, an unsaturated aliphatic alcohol, and an unsaturated aliphatic amine. Plasma-treated in the presence of at least one unsaturated compound selected from the group, and a helium gas transmission rate (PHe) at 80 ° C. of 1 × 10 ⁻⁴ cm ³ (STP) / cm.
² · sec · cmHg or more, and the ratio (PHe / PN ₂ ) of the permeation rate of helium gas (PHe) to the permeation rate of nitrogen gas (PN ₂ ) at 80 ° C. is 50 or more. Selective gas separation membrane. 2. A compound of the general formula A (Wherein, R ₁ is a divalent aromatic residue based on an aromatic diamine compound) and / or a general formula (B) (Wherein R ₂ is a divalent aromatic residue based on an aromatic diamine compound).
100 mol% and the general formula (C) (Wherein, R is a tetravalent aromatic residue based on an aromatic tetracarboxylic acid, and R ₃ is a divalent aromatic residue based on an aromatic diamine compound.) It is formed of an aromatic polyimide comprising 20 mol% or less of the repeating unit (C), and has a helium gas permeation rate (PHe) of 1 × 10 ⁻⁴ cm ^{3 at} 80 ° C. (ST
P) / cm ² · sec · cmHg or more and 80 ° C
Permeation rate of the permeation rate (PHe) and nitrogen gas fart helium gas in the ratio of _{(PN 2) (PHe / PN} 2) is 1.
The asymmetric gas separation membrane of 5 to 50 in the presence of at least one unsaturated compound selected from the group consisting of unsaturated hydrocarbon compounds, unsaturated halides, unsaturated aliphatic alcohols and unsaturated aliphatic amines. And a plasma processing method for producing a highly selective gas separation membrane.