JPH10330482A - Polyimide and its production, and gas separable membrane by using the same and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new polyimide having more superior permeability, high separating selectivity, excellent chemical resistance, moisture resistance, etc., by constituting the polyimide out of a tetravalent residue derived from a tetracarboxylic acid dianhydride, and a divalent residue derived from a specific diamine component. SOLUTION: This polyimide has a repeating structural unit of formula I (R is a tetravalent group). The polyimide is obtained by carrying out the condensation polymerizatino of a tetracarboxylic acid diahydride of formula II (preferably pyromellitic dianhydride, etc.), with 2-(2,4-diaminobenzyl)pyridine of formula III. The objective polyimide has 303 deg.C glass transition temperature and preferably has solubility in a polar solvent. The condensation polymerization is carried out by reacting the diamine component with the tetracarboxylic acid dianhydride in a polar solvent such as dimethylsulfoxide at 0-20 deg.C, and adding a dehydrating and cyclizing agent to the product to convert a polyamide-acid into the polyimide at 20-30 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel polyimide, a method for producing the same, a gas separation membrane using the same, and a method for producing the same. The gas separation membrane provided by the present invention not only has excellent permeation performance, but also has good moisture resistance, chemical resistance, and the like. Further, gas separation using a membrane is more energy-efficient than other separation methods, and is useful in a wide range of fields. The present invention provides, for example, the separation and recovery of hydrogen during ammonia synthesis, the recovery of carbon dioxide and the removal of sulfur oxides and nitrogen oxides from exhaust gas from thermal power plants and garbage incinerators, the recovery of carbon dioxide from oilfield offgas, Removal of hydrogen sulfide and carbon dioxide and separation of helium from natural gas, recovery of leaked gasoline from gasoline distribution stations, pervaporation separation of volatile mixture liquid, removal of gas dissolved in liquid, oxygen and air Used for separation of nitrogen.

[0002]

2. Description of the Related Art Conventionally, a cellulose acetate membrane is well known as a gas separation membrane. However, the cellulose acetate membrane is not sufficiently practical because of its low chemical resistance and heat resistance. . As a separation membrane with improved heat resistance, a polysulfone semipermeable membrane is industrially produced,
The transmission performance was insufficient and not satisfactory. Further, a silicone membrane is known as a selectively permeable membrane for oxygen. However, silicone is not industrially satisfactory because of insufficient mechanical strength.

Recently, research and development of a polyimide resin separation membrane having excellent strength and heat resistance and excellent gas permeability has been carried out. Journal Polymer Science Polymer Physics (J.polym.Scie.Polym.Phys., 28,
2291 (1990)) describe the high gas permeation and selectivity of an aromatic polyimide membrane obtained from a phenylenediamine component in which one ortho position to the amine function is substituted with an alkyl group. Further, US Pat. No. 4,717,394 and JP-B-63-111921 disclose amines,
There has been proposed an aromatic polyimide film having high gas permeability obtained from a phenylenediamine component in which all positions ortho to the functional group are substituted with an alkyl group.

[0004]

However, there is still a need for a polyimide having higher permeation performance and higher separation selectivity and a gas separation membrane using the same. The present invention is a new polyimide having more excellent permeation performance, high permeability and high separation selectivity, and also having excellent chemical resistance, moisture resistance, etc., a method for producing the same, and a gas separation membrane using the same. It is an object of the present invention to provide a manufacturing method thereof.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been intensively studied to solve the problems of the conventional gas separation, and as a result, it has been found that tetracarboxylic acid dicarboxylic acid which is a precursor of a tetravalent residue forming polyimide is obtained. 2- (2,4-diaminobenzyl) is used as the diamine component to form a divalent residue using an anhydride.
A polyimide obtained by condensation polymerization of these with pyridine and a gas separation membrane using the same have been found, and the present invention has been completed.

That is, the polyimide of the present invention has a repeating structural unit represented by the following general formula (Formula 7) (where R is a tetravalent organic group).

[0007]

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In the above general formula (Chemical formula 7), the tetravalent organic group is represented by the following general formulas (Chemical formula 8) to (Chemical formula 10)
0), X _{-C (CF 3) 2 -,} - C (CF 3) (C 6 H 5) -,
_{-C (CH 3) (C 6} H 5) -, - CH 2 -, - C (CH 3) 2 -,
_{-CO -, - SO 2 -,} - O -, - S -, - NH -, -
COO -, - CONH -, - Si (CH 3) 2 -, - O-C
_{6 H 4 -C (CH 3)} 2 -C 6 H 4 -O -, - O-C 6 H 4 -O
_{-, - O-CH 2 -CH} 2 -O -, - CF 2 CF 2 CF
_{2 -, - CO-C 6} H 4 -CO -, - O-C 6 H 4 -S-C 6
At least one group selected from H ₄ —O—).

[0009]

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[0010] The polyimide of the present invention preferably has a glass transition temperature of about 303 ° C. The polyimide of the present invention has a gas permeability coefficient (Barrer = 10 ⁻¹⁰ cm).
³ (STP) cm / cm ² / sec / cmHg, where cm ³ (STP) is the volume of gas permeating at standard temperature and pressure (0 ° C., 1 atm), cm is the thickness of the film, cm ² is the film Area, sec is time (seconds),
cmHg indicates pressure and is a value at 25 ° C. and 1 atm. ) Is O
Preferably, ₂ is about 7.22 Barrer, CH ₄ is about 1.67 Barrer, N ₂ is about 1.34 Barrer, and CO ₂ is about 54.9 Barrer.

The polyimide of the present invention preferably has the property of dissolving in a polar solvent. The polar solvent used in the present invention is N-methyl-2-pyrrolidone,
It is preferably at least one solvent selected from N, N-dimethylacetamide, dimethylsulfoxide, and N, N-dimethylformamide.

Next, a method for producing a polyimide according to the present invention comprises a tetracarboxylic dianhydride represented by the following general formula (Chemical formula 11) (where R is a tetravalent group) and a compound represented by the following general formula (Chemical formula 12). By condensation polymerization with the diamine shown, the following general formula
A polyimide having a repeating structural unit represented by (Formula 13) (where R is a tetravalent group) is obtained.

[0013]

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In the method of the present invention, the tetravalent organic group is represented by the following general formula (Chemical Formula 14) to (Chemical Formula 16)
(Formula 16), X is _{-C (CF 3) 2 -,} - C (CF 3) (C
_{6 H 5) -, - C} (CH 3) (C 6 H 5) -, - CH 2 -, - C (C
_{H 3) 2 -, - CO} -, - SO 2 -, - O -, - S -, - N
H -, - COO -, - CONH -, - Si (CH 3) 2 -,
_{-O-C 6 H 4 -C (} CH 3) 2 -C 6 H 4 -O -, - O-C 6
H ₄ —O—, —O—CH ₂ —CH ₂ —O—, —CF ₂ CF ₂
CF ₂ —, —CO—C ₆ H ₄ —CO—, and —O—C ₆ H ₄
It is preferable at least showing the one group) selected from -S-C ₆ H ₄ -O- is at least one organic group selected.

[0015]

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In the method of the present invention, the polycondensation is preferably carried out in a polar solvent. In the method of the present invention, the polar solvent is preferably at least one solvent selected from N-methyl-2-pyrrolidone, N, N-dimethylacetamide, dimethylsulfoxide, and N, N-dimethylformamide. .

In the method of the present invention, the amount of the polar solvent used is 70 to 90% by weight based on the weight of the reaction system.
Is preferable. In the method of the present invention, the polycondensation is carried out by mixing a diamine component and a tetracarboxylic dianhydride component at room temperature or lower (in the range of 0 to 20 ° C.).
At a temperature of 5 to 50 hours to synthesize a polyamic acid, and a step of polyimideating the polyamic acid.

In the method of the present invention, it is preferable that the polycondensation is performed at a temperature of room temperature or lower (a range of 0 to 20 ° C.). In the method of the present invention,
In the polyimidization step, it is preferable to add a dehydrating ring-closing agent to the reaction solution and react at room temperature (20 to 30 ° C.) for 5 to 24 hours to polyimidate the polyamic acid.

In the method of the present invention, the dehydrating ring closing agent is preferably at least one compound selected from acetic anhydride, pyridine and triethylamine. Further, in the method of the present invention, in the polyimidization step, the polyamic acid is heated to 180 to 200 ° C., a compound capable of azeotroping with water is added, and water generated by ring closure of the amic acid is azeotropically removed from the system 5
It is preferable that the polyamic acid is made into a polyimide by reacting for 10 to 10 hours.

In the method of the present invention, it is preferable that the solution azeotropic with water is at least one solution selected from benzene, toluene, xylene, chlorobenzene and dichlorobenzene. In the method of the present invention, the polyimide is preferably dissolved in a polar solvent. In the method of the present invention, the polar solvent is N-methyl-2-pyrrolidone, N, N-dimethylacetamide, dimethylsulfoxide, and N, N-
It is preferably at least one solvent selected from dimethylformamide.

Next, the gas separation membrane of the present invention has the following general formula:
A polyimide having a repeating structural unit represented by the following formula (where R is a tetravalent group) is contained in a gas separation layer.

[0022]

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In the gas separation membrane of the present invention, tetravalent
Of the following general formulas (Chemical Formula 18) to (Chemical Formula 20)
In the general formula (Chemical formula 20), X is -C (CF_Three)_Two−, −C (CF_Three)
(C₆H_Five)-, -C (CH_Three) (C₆H_Five)-, -CH_Two−, −C
(CH_Three)_Two-, -CO-, -SO_Two-, -O-, -S-,
-NH-, -COO-, -CONH-, -Si (CH_Three) _Two
-, -OC₆H_Four-C (CH_Three)_Two-C₆H_Four-O-, -O-
C₆H_Four-O-, -O-CH_Two-CH_Two-O-, -CF_TwoC
F_TwoCF_Two-, -CO-C₆H_Four-CO- and -OC₆
H_Four-SC₆H_FourAt least one selected from -O-
At least one organic group selected from
Is preferred.

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In the gas separation membrane of the present invention,
Preferably, the glass transition temperature of the polyimide film is about 303 ° C. In the gas separation membrane of the present invention,
Gas permeability coefficient of polyimide membrane (Barrer = 10 ^-10 cm ³ (STP)
cm / cm ² / sec / cmHg, where cm ³ (STP) is the standard temperature and pressure (0
° C, 1 atm) The volume of gas permeating, cm is the thickness of the film, cm ² is the area of the film, sec is the time (second), cmHg
Indicates a pressure, and the measured data are values at 25 ° C. and 1 atm. ), O ₂ is about 7.22 Barrer, CH ₄ is about 1.67 Barrer
Preferably, er and N ₂ are about 1.34 Barrer and CO ₂ is about 54.9 Barrer.

In the gas separation membrane of the present invention,
Gas permselective polyimide membrane, O ₂ / N ₂ of about 5.38, CH ₄
Preferably, / N ₂ is about 1.25 and CO ₂ / N ₂ is about 40.9.
In the gas separation membrane of the present invention, the thickness of the polyimide membrane is preferably in the range of 0.03 to 20 μm. In the gas separation membrane of the present invention, it is preferable that the polyimide membrane is formed on a surface layer of the support member having a smooth surface.

In the gas separation membrane of the present invention,
Preferably, the polyimide membrane is at least one membrane selected from a flat membrane and a hollow fiber membrane. In the gas separation membrane of the present invention, the polyimide is preferably dissolved in a polar solvent.

In the gas separation membrane of the present invention,
When the polar solvent is N-methyl-2-pyrrolidone, N, N-dimethylacetamide, dimethylsulfoxide, N, N-
It is preferably at least one solvent selected from dimethylformamide. Further, in the gas separation membrane of the present invention, the intrinsic viscosity of the polyimide is 0.4 to 1.5 dL / g as measured by a solution of N-methyl-2-pyrrolidone in 0.5 g per deciliter at 30 ° C. It is preferably within the range.

Next, the process for producing a gas separation membrane of the present invention is carried out by dissolving a polyimide having a repeating structural unit represented by the following general formula (Formula 21) (wherein R is a tetravalent group) in a polar solvent. It is characterized in that at least one membrane selected from a membrane and a hollow fiber membrane is formed.

Embedded image In the above method, the tetravalent organic group is represented by the following general formula (Chemical Formula 2)
2) to (Formula 24) (wherein, in the following general formula (Formula 24), X is -C
_{(CF 3) 2 -, -} C (CF 3) (C 6 H 5) -, - C (CH 3) (C 6
_{H 5) -, - CH 2} -, - C (CH 3) 2 -, - CO -, - S
O _2- , -O-, -S-, -NH-, -COO-, -C
_{ONH -, - Si (CH 3} ) 2 -, - O-C 6 H 4 -C (C
_{H 3) 2 -C 6 H 4} -O -, - O-C 6 H 4 -O -, - O-C
H ₂ —CH ₂ —O—, —CF ₂ CF ₂ CF ₂ —, —CO—C ₆
At least one group selected from H ₄ —CO— and —O—C ₆ H ₄ —S—C ₆ H ₄ —O—.

[0029]

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In the above method, it is preferable to produce a gas separation membrane by applying a solution containing polyimide to a surface layer of a support member having a smooth surface and casting it, and then removing the solvent. Further, in the above method, the removal of the solvent is heat drying treatment, reduced pressure drying treatment,
And at least one treatment selected from the group consisting of dissolving the solvent and immersing the polyimide in an organic solvent which is a poor solvent for the polyimide.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION The compound of the above general formula (Formula 7)
It can be produced by equimolar polycondensation of a diamine represented by the following formulas (11) and (12). The polymerization method is not particularly limited, and polymerization can be performed by a method generally used as a polymerization method for polyimide. Examples of the polymerization solvent include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, dimethylsulfoxide, N, N-dimethylformamide, and the like.
Used as a mixture. The amount of the solvent to be used with respect to the raw materials is not particularly limited, but is usually a concentration of 70 to 90% by weight.
The diamine component and the tetracarboxylic dianhydride component are mixed and reacted at a temperature of room temperature or lower, usually for 5 to 50 hours, to synthesize a polyamic acid. Next, a dehydrating ring-closing agent such as acetic anhydride, pyridine or triethylamine is added to the reaction solution, and the mixture is further reacted at room temperature for usually 5 to 24 hours to polyimide the polyamic acid. Alternatively, the polyamic acid is heated to 180 to 200 ° C., and a hydrocarbon or a chlorinated solution such as benzene, toluene, xylene, chlorobenzene, and dichlorobenzene, which is azeotropic with water, is added thereto, and water generated by cyclizing the amic acid Is removed from the system by azeotropic distillation, and the polyamide acid is converted into a polyimide by reacting for 5 to 10 hours. The polyimide obtained from this is N-methyl-
It is soluble in 2-pyrrolidone, N, N-dimethylacetamide, dimethylsulfoxide, N, N-dimethylformamide and the like.

Next, a gas separation membrane made of the polyimide of the present invention comprises a tetracarboxylic dianhydride represented by the above general formula (Chemical Formula 11) (where R is a tetravalent group) and a general formula (Chemical Formula 12) Is a polyimide gas separation membrane obtained by condensation polymerization of a diamine represented by the following formula: Hereinafter, the polyimide forming the gas separation membrane will be described in detail. The polyimide of the present invention has the general formula
Any polymer may be used as long as it is a polymer obtained by polycondensation as a main component of a tetracarboxylic dianhydride represented by the following formula (where R is a tetravalent group) and a diamine represented by the following general formula (Formula 12).

Here, as the compound of the general formula (Formula 11), for example, 4,4 '-(hexafluoroisopropylidene)
Diphthalic dianhydride, 3,3 ′)-biphenyltetracarboxylic dianhydride or pyrrolimic dianhydride are preferred. The diamine represented by the general formula (Formula 12) is 2
-(2,4-diaminobenzyl) pyridine.

As described above, the polyimide of the present invention is a polymer obtained by random polycondensation of tetracarboxylic dianhydride and a diamine component as raw materials. Have In the present invention, as a polyimide having both heat resistance and aromatic aromatic tetracarboxylic dianhydride and diamine, pyromellitic dianhydride can be mentioned as a basic substance of tetracarboxylic dianhydride, Examples of the diamine include 2- (2,4-diaminobenzyl) pyridine. The weight ratio of the tetracarboxylic dianhydride and the diamine component of the random polycondensation polyimide produced using these is 5% each.
4.2 (wt%) and 45.8 (wt%).

As another example, pyromellitic dianhydride and 4,4'-tetracarboxylic dianhydride are used.
A mixture of the same amount of (hexafluoroisopropylidene) diphthalic dianhydride can be given, and 2- (2,4-diaminobenzyl) pyridine can be given as a diamine. In the random polycondensation polyimide produced using these, the weight ratio of each of the tetracarboxylic dianhydride and the diamine component is 64.3 (wt).
%) And 35.7 (wt%).

In the polymer comprising random polycondensation according to the present invention, when a plurality of tetracarboxylic dianhydrides are used, the kind and the mixing ratio of these tetracarboxylic dianhydrides are not particularly limited. It is sufficient that the total mole of the tetracarboxylic dianhydride and the total mole of the diamine component are equimolar.

In the present invention, pyromellitic dianhydride, which is preferably used as tetracarboxylic dianhydride, is a substance having the minimum molecular weight as tetracarboxylic dianhydride. On the other hand, in the present invention, 2- (2,4-diaminobenzyl) pyridine is preferably used as the diamine. Therefore, in the present invention, as long as 2- (2,4-diaminobenzyl) pyridine is used as the diamine, a random combination of tetracarboxylic dianhydride and 2- (2,4-diaminobenzyl) pyridine as the diamine is used. The weight ratio of the components in the polymer formed by the condensation polymerization is equimolar, and is 54.2 (wt.
%) Or more and 45.8 (wt%) or less.

The polyimide used in the second invention is N-
Methyl-2-pyrrolidone has an intrinsic viscosity of 0.4 to 1 as measured with a 30 ° C. solution of 0.5 g dissolved in 1 deciliter.
5 preferably in the range of 0.5 to 1.0. If the intrinsic viscosity is too small, the self-supporting property of the gas separation membrane is poor, and the mechanical strength is insufficient. On the other hand, if the intrinsic viscosity is too large, it is difficult to obtain a uniform film-forming solution, and it becomes difficult to form a film.

The gas separation membrane of the present invention can be manufactured by various methods. The polyimide represented by the general formula (Chemical Formula 1) is dissolved in a film forming solution solvent to form a uniform film forming solution, which is cast and applied to a suitable supporting substrate, and then subjected to heat treatment or heat treatment under reduced pressure. To evaporate the solvent to form a homogeneous film. A sufficiently thin film is required to achieve a practical gas permeation performance, that is, a high permeation rate, but from the viewpoint of mechanical strength and generation of pinholes, the film thickness is in the range of 0.03 μm to 20 μm. Is desirable. The film-forming solution solution is N-methyl-2-pyrrolidone, like the polymerization reactant.
Organic solvents such as N, N-dimethylacetamide, dimethylsulfoxide and N, N-dimethylformamide are preferred. There is no particular limitation on the support substrate for applying the film forming solution. A member having a smooth surface made of a material exemplified by a heat-resistant polymer, glass, metal, ceramic or the like is exemplified. After applying the film-forming solution to the supporting substrate, the heating temperature depends on the film-forming solution solvent.
00 ° C, preferably 100 to 150 ° C. Particularly preferably, most of the solvent is evaporated in such a temperature range, and then the temperature is raised to 200 to 300 ° C. to completely evaporate.
Further, after coating the film-forming solution on the supporting substrate, after immersing in water or an organic solvent (poor solvent for polyimide) mixed with the organic solvent, dried at the above temperature to form a heterogeneous film. It is also possible. There is no limitation on the film formation and film form, and a composite film may be used. The membrane shape can be a flat membrane or a hollow fiber membrane.

The terms used to describe the membrane performance of the present invention are defined as follows. (1) Gas permeation coefficient: an index indicating a gas permeation rate through a semipermeable membrane, and a unit is represented by the following equation (Equation 1).

Barrer = 10 ⁻¹⁰ cm ³ (STP) cm / cm ² / sec / cmHg (where cm ³ (STP) is the volume of gas permeating at standard temperature and pressure (0 ° C., 1 atm)) , Cm indicates the thickness of the film, cm ² indicates the area of the film, sec indicates the time (second), and cmHg indicates the pressure.)
The measurement data is a value at 25 ° C. and 1 atm. (2) Selectivity: The gas selectivity of a semipermeable membrane is represented by the ratio of the permeability coefficient measured for each gas alone on the same membrane. For example, CO ₂ / N ₂ = 50 indicates that the film permeates CO ₂ gas at 50 times the speed of N ₂ gas. Measurement data is 25
° C, 1 atm.

Hereinafter, the present invention will be described in more detail with reference to Examples, but it should not be construed that the invention is limited thereto.

【Example】

(Example 1) 15.0 g (0.0754 mol) of diaminobenzylpyridine, N
200 ml of -methyl-2-pyrrolidone was colored and dissolved under stirring in an argon gas atmosphere. This flask is
After immersion in a 5 ° C. water bath, 33.4 g (0.075) of 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride was obtained.
4 mol) was added in four portions over 1 hour. After the addition, the flask was returned to room temperature and reacted with stirring for 20 hours to obtain a polyamic acid. Acetic anhydride 2 was added to this polymerization solution.
6.9 g (0.264 mol) and triethylamine 2
After adding 6.7 g (0.264 mol) and reacting at room temperature for 20 hours, the mixture was poured into a water-alcohol mixture to obtain a polyimide resin precipitate. Further, it was washed several times with alcohol. The intrinsic viscosity of the polyimide resin is 0.72 (dL
/ G) (0.5 g / dL, NMP, 30 ° C). The above chemical reaction process is shown in the following formula (Formula 25).

[0042]

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The identification data of the polymer thus obtained is shown in FIGS. FIG. 1 is an analysis chart of the polyimide of this example by nuclear magnetic resonance (NMR). The number of each peak indicates each bond of the polymer structural formula shown in the upper left. The analyzer used was FT-NMR: LA400 (manufactured by JEOL Ltd.). Measurement conditions, solvent: DMSO-d _6,
Concentration: 50 mg / 0.5 ml, number of accumulation: 16
0 times, ¹ H resonance frequency: 400 MHz, pulse width: 6.
4 μsec (45 ° pulse), internal reference: DMSO-d ₆
(2.5 ppm), observation center frequency: 399.778457419 MHz,
Observation range: 8 KHz.

FIG. 2 is an analysis chart based on infrared analysis (IR). The analyzer was a microscope FT-IR: FTS-
40, UMA300A (manufactured by Bio-Rad) was used. For the sample preparation and the method, a sample washed with hexane was subjected to a microscope FT-IR measurement using a compression cell. Measurement conditions are: measurement mode: transmission, resolution:
8 cm ^-1 , loading frequency: 128 times, measuring range: 4000 to 7
000 cm ^-1 . 9 of the polyimide resin obtained above
dissolved in N-methyl-2-pyrrolidone at a concentration of wt%,
After casting and coating on a glass plate and removing the solvent with a vacuum heating drier, a heat treatment was performed at 200 ° C. to 300 ° C. for 5 hours in an N ₂ gas atmosphere. Glass transition temperature and gas permeability coefficient were measured. The results are shown in Table 1.

(Comparative Example 1) In Example 1, 4,4 '-(hexafluoroisopropylidene) diphthalic dianhydride was used as tetracarboxylic dianhydride, 44.5 g (0.10 m
ol) as the diamine, 2,4-diaminotoluene, 1
A polyimide having an intrinsic viscosity of 0.53 (dL / g) was obtained in exactly the same manner except that 2.5 g (0.100 mol) was used.
Glass transition temperature and gas permeability coefficient were measured. The results are shown in Table 1.

[0046]

[Table 1]

As is clear from Table 1, the gas separation membrane of the example of the present invention had much higher gas permeation performance and selectivity than the comparative example.

[0048]

As described above, the polyimide gas separation membrane of the present invention has high gas permeation performance and selectivity, and is excellent in weather resistance and chemical resistance, and can be used as a gas separation membrane in a wide range of fields.

[Brief description of the drawings]

FIG. 1 is an analysis chart of a polyimide of Example 1 of the present invention by nuclear magnetic resonance (NMR).

FIG. 2 is an analysis chart by infrared analysis (IR) of the polyimide of Example 1 of the present invention.

Claims (4)

[Claims] 1. The following general formula (1) (where R is a tetravalent group)
The polyimide which has a repeating structural unit shown by these. Embedded image 2. The following general formula (2) (where R is a tetravalent group)
And a tetracarboxylic dianhydride represented by the following general formula
A polyimide characterized by obtaining a polyimide having a repeating structural unit represented by the following general formula (Formula 4) (where R is a tetravalent group) by polycondensing a diamine represented by the following formula (3). Manufacturing method. Embedded image Embedded image Embedded image 3. The following general formula (5) (where R is a tetravalent group)
The gas separation membrane which contains the polyimide which has a repeating structural unit shown by these in a gas separation layer. Embedded image 4. The following general formula (Formula 6) (where R is a tetravalent group)
A method for producing a gas separation membrane, comprising: dissolving a polyimide having a repeating structural unit represented by formula (1) in a polar solvent to form at least one membrane selected from a flat membrane and a hollow fiber membrane. Embedded image