JPH05192552A - Polyimide gas separation membrane - Google Patents

Abstract

PURPOSE:To obtain a membrane having excellent oxygen/nitrogen selectivity and high oxygen permeation rate by introducing a carboxyl group and a sulfonic acid group into polyimide having a bisphenylfluorene skeleton to provide pseudo- crosslinking effect to polyimide. CONSTITUTION:A polyimide gas separation membrane is obtained from soluble aromatic polyimide represented by formula I [where X is a divalent org. group originating from diamine, Y is a tetravalent org. group originating from carboxylic dianhydride and n is an integer of 1 or more showing a repeating number and at least 5mol% or more of X is a divalent org. group having a bisphenylfluorene skeleton represented by formula II (wherein R1-R4 are H, CH3, C2H5, F, Cl or Br and R5 and R6 are H, SO3H or COOH) and at least a part of X and/or Y is a carboxyl group and/or a sulfonic acid group] and characterized in that the inherent viscosity of a solution of 0.5g of polyimide in 100ml of N-methyl-2-pyrrolidone at 30 deg.C is 0.2g/dl or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide gas separation membrane having a high oxygen permeation rate and a high oxygen-nitrogen selectivity which have not been hitherto obtained, and having excellent heat resistance. Due to its high oxygen-nitrogen selectivity, this polyimide gas separation membrane is used for the production of oxygen-enriched air with an oxygen concentration of 40%, which can be used for medical purposes, biotechnology, etc., or for food preservation and explosion-proof in organic solvent tanks. Concentration of nitrogen that can be used for etc. 9
It is suitable for the production of 5% or more nitrogen-enriched air. Further, since it has a highly polar functional group, high CO ₂ separation performance can be expected.

[0002]

2. Description of the Related Art In recent years, the use of nitrogen-enriched air having a nitrogen concentration of 95 to 99.5% has attracted attention. One example of the use of such nitrogen-enriched air is explosion-proof in flammable liquid storage tanks. In this case, high-purity nitrogen is not required, but it is required to be inexpensive. In order to supply inexpensive nitrogen for membrane separation, a product that produces nitrogen gas as a non-permeable component of the oxygen selective permeable membrane requires a separation membrane that has an excellent oxygen permeation rate and oxygen-nitrogen selectivity. Becomes As an oxygen selective permeable membrane, a polyacetylene separation membrane (Japanese Patent Laid-Open No. 2-59,031) is known. Further, a separation membrane of a polycarbonate-dimethylsiloxane block copolymer is disclosed in JP-A-54-40868. However, these films have insufficient selectivity, and improvement has been desired.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a solvent-soluble polyimide gas separation membrane having excellent oxygen-nitrogen selectivity and oxygen permeation rate and having excellent heat resistance. It is in.

[0004]

The present invention provides the following general formula (1):

[Chemical 3] (However, in the formula, X represents a divalent organic group derived from diamine,
Y represents a tetravalent organic group derived from carboxylic acid dianhydride, and n
Is an integer of 1 or more representing the number of repetitions), and at least 5 mol% or more of X is represented by the following general formula (2).

[Chemical 4] (However, R ₁ , R ₂ , R ₃ and R ₄ are —H, —CH ₃ ,
-C ₂ H _5, -F, indicates either -Cl or -Br,
R ₅ and R ₆ represent a divalent organic group having a bisphenylfluorene skeleton represented by —H, —SO ₃ H or —COOH), and further, the above X and / or Y A solution having a carboxyl group and / or a sulfonic acid group in at least a part thereof, 0.5 g of which is dissolved in 100 ml of N-methyl-2-pyrrolidone and having an inherent viscosity at 30 ° C. of 0.2 g / dl or more A polyimide gas separation membrane made of aromatic polyimide.

By the way, for the purpose of increasing the selectivity, which is one of the performances of the gas separation membrane, the development of a polymer membrane material having a high selectivity is under way. In a polymer membrane, gas selectivity is expressed as a gas permeability ratio, and gas permeability is expressed as a product of diffusivity and solubility. That is,
High selectivity can be achieved by developing and using a polymer material having a large diffusivity ratio and a large solubility ratio. Here, when considering the separation of oxygen and nitrogen, the solubility ratio of oxygen and nitrogen is generally about 2 in all polymer materials, so increasing the diffusivity ratio is an excellent oxygen-nitrogen selection method. The key is to obtain a separation membrane material with high efficiency. The diffusivity of gas in the polymer material is the degree of ease of passage of gas molecules in the polymer chain gap of the material. Therefore, the diffusivity can be controlled by controlling the polymer chain gap, and as a result, the diffusivity of gas molecules having different molecular sizes can be controlled. As a method of controlling the gaps between the polymer chains of the material, introduction of a crosslinked structure can be considered. As the crosslinked structure, chemical crosslinks and pseudo crosslinks are considered,
The introduction of chemical cross-linking tends to cause insolubilization of the polymer material, and it is difficult to control the degree of cross-linking. On the other hand, pseudo-crosslinking with a polar functional group hardly causes insolubilization of a polymer, and is suitable as a method for controlling the gap between polymer chains.

The polyimide of the present invention comprises a diamine compound as an X component, a carboxylic acid dianhydride as a Y component, and at least 5 mol% or more of the X component as a diamine having a bisphenylfluorene skeleton. It is a polycondensate. Here, the bisphenylfluorene skeleton suppresses thermal motion of the polymer main chain due to its bulky structure and creates many micropoids in the polymer. As a result, the polymer having a bisphenylfluorene skeleton has excellent heat resistance and excellent solvent solubility.
Here, in order to impart excellent heat resistance and excellent solvent solubility to the polymer, it is necessary that 5 mol% or more of the X component is bisphenylfluorene. Bisphenylfluorenes can be introduced up to 100 mol% of the X component, and when the mol% of bisphenylfluorenes increases, heat resistance and solvent solubility are further improved. As the diamine having a bisphenylfluorene skeleton, 9,
9 bis - (4-aminophenyl) fluorene and 3-position and / or 5-position of the hydrogen atoms of the amino phenyl group (H) is, -CH ₃ group, -C ₂ alkyl group H ₅ group or the like or -F 9, 9- substituted with one or two or more substituents selected from halogen groups such as group, -Cl group and -Br group
There is a substitution product of bis- (4-aminophenyl) fluorene.

The other diamine as the X component may be either an aromatic diamine or an aliphatic diamine. Specifically, 3,3 ′, 5,5′-tetramethylbenzidine, 3,3′-diethylbenzidine, 2-N-diethylmelamine, 3,3′-dimethylnaphthidine, amelin,
2,4-diamino-6-hydroxypyrimidine, 4,4
-Diamino-2-mercaptopyrimidine, 4,4'-diaminodiphenyl ether, 1,4-diamino-2-nitrobenzene, 2,4-diaminotoluene, p-phenylenediamine, tetrafluoro-p-phenylenediamine, 1,5- Examples thereof include diaminoanthraquinone, 1,8-naphthalenediamine, etidylenediamine, 1,4-diaminoptan, hexaethylenediamine, 1,12-diaminododecane and 1,4-cyclohexanediamine. The carboxylic acid dianhydride which is the Y component includes 3,3 ′, 4,4′-benzophenone tetracarboxylic acid dianhydride and 2,2-bis (3,4-biscarboxyphenyl) -1,1. , 1,3,3,3-hexafluoropropane dianhydride, pyromellitic dianhydride,
4,4'-biphthalic anhydride, bicyclo [2,2,2]
Octo-7-ene-2,3,5,6-tetracarboxylic dianhydride, 2,2-bis (3,4-biscarboxyphenyl) propane dianhydride and the like can be mentioned.

Examples of polar functional groups effective for improving gas separation performance include a carboxyl group and a sulfonic acid group. These functional groups have the effect of creating pseudo-crosslinks by hydrogen bonding between the functional groups, and as a result, controlling the gaps between polymer chains. The degree of its effect is influenced by the amount of introduced functional groups. That is, a carboxyl group,
By increasing the amount of sulfonic acid group present in the polymeric material,
It becomes possible to form stronger pseudo-crosslinks. Introducing 0.05 carboxyl groups and sulfonic acid groups into the gas separation membrane per 1 unit of the polymer of the material shows the effect of pseudo-crosslinking, and as a result, the oxygen selectivity is improved. Here, the content of the carboxyl group and the sulfonic acid group is represented by the amount per unit of polymer. That is, 0.05 per polymer unit means that one polymer has 20 carboxyl units and / or sulfonic acid groups. The amount of the carboxyl group and the sulfonic acid group has no upper limit if it is possible in the synthesis, but if the content of the carboxyl group and the sulfonic acid group becomes too large, the permeation rate decreases more than the improvement of the selectivity. Therefore, it is preferable that the content of carboxyl groups and sulfonic acid groups is 2.0 or less per unit of polymer. In addition, a carboxyl group, a sulfonic acid group alone or both can be introduced into the polymer.

To introduce a carboxyl group or a sulfonic acid group into the polyimide of the present invention, it is desirable to use a monomer having a carboxyl group or a sulfonic acid group. As long as it is a diamine having a carboxyl group or a sulfonic acid group, or a carboxylic acid dianhydride, any monomer having a carboxyl group and / or a sulfonic acid group can be used alone or in combination. As an example of a desirable monomer, the diamine as the X component is 9,9-bis-
(4-aminophenyl) fluorene-4-carboxylic acid,
3,3'-dimethyl-4,4'-diaminobiphenyl-
6,6′-disulfonic acid, m-phenylenediamine-4
-Sulfonic acid, m-phenylenediamine-4-carboxylic acid, 4,4'-diaminostilbene-2,2'-disulfonic acid and the like can be mentioned. Another method for introducing the functional group is to directly introduce the functional group into the polyimide. For example, it is possible to introduce a sulfonic acid group by using thionyl chloride, but in this case, compared to the method using a monomer having a functional group, the amount of introduced functional group is small and the site for introducing the functional group is reduced. It is difficult to identify.

In the gas separation membrane of the present invention, the degree of polymerization has no significant effect on the separation performance, but from the viewpoint of the mechanical strength of the obtained membrane, 0.5 g of polyimide is 100 m.
30 of the solution dissolved in 1 N-methyl-2-pyrrolidone
The inherent viscosity at 0 ° C. must be 0.2 g / dl or more. More desirably in terms of film strength, the above-mentioned inherent viscosity is 0.4 g / dl or more. Further, considering workability in filtering the solution of the polymer material of the present invention, if the inherent viscosity is too high, the solution viscosity becomes too high. Therefore, the upper limit of the inherent viscosity is 1.5 g / It is preferably dl or less.

In order to improve the gas permeation amount, it is necessary to thin the separation functional layer. If the polymer is soluble in the solvent, thinning of the separation functional layer can be easily achieved by, for example, forming an asymmetric membrane by a phase inversion method. However, generally known polyimide has low solvent solubility due to its rigid structure,
It was extremely difficult to thin the separation functional layer. However, the polyimide of the present invention shows excellent solvent solubility even though it is a polyimide because it has a bisphenylfluorene skeleton, which is a bulky structure in the main chain of the polymer material, and exhibits a thin separation function layer. Is extremely easy. Solvent solubility that facilitates thinning of the separation functional layer in the polyimide of the present invention is obtained by setting the content of the bisphenylfluorene skeleton in the divalent organic group X derived from diamine to 5 mol% or more. Further, from the viewpoint of the stability of the polyimide solution, the content of the bisphenylfluorene skeleton is preferably 15 mol% or more. More preferably, the content of the bisphenylfluorene skeleton is 25 mol% or more.

[0012]

EXAMPLES The present invention will be specifically described below based on Examples and Comparative Examples. In addition, in the following examples and comparative examples, the inherent viscosity is 10
It is the value measured at 30 ° C. in a solution dissolved in 0 ml of N-methyl-2-pyrrolidone. The gas permeation coefficient was measured using a differential pressure type gas permeation rate measuring device using a gas chromatograph as a detector. The unit of gas permeability coefficient is barrrer = 1
It is shown by 0 ^-10 cm ³ · cm / cm ² · sec · cmHg. The selectivity is indicated by the ratio of gas permeability coefficients.

Example 1 9,9-bis (4-aminophenyl) fluorene 5.2
3 g (0.015 mol), 9,9-bis (4-aminophenyl) fluorene-4-carboxylic acid 5.89 g (0.
015 mol), 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride 9.67 g (0.03 mol) and N-methyl-2-pyrrolidone 200 g in a four-necked flask equipped with a stirrer. After charging, the temperature of the solvent was kept at 180 ° C. and the reaction was carried out while removing the produced water. After completion of the reaction, the reaction solution was filtered with a glass filter, reprecipitated in methanol, washed, and then vacuum dried to obtain a polyimide.

The polyimide obtained had 0.5 carboxyl groups per polymer unit, and its inherent viscosity was 0.76 g / dl. Also, a 15 wt% N-methyl-2-pyrrolidone solution of this polyimide was uniformly applied onto a glass substrate, and the solvent was dried and removed to obtain a uniform film. The oxygen permeability coefficient, the nitrogen permeability coefficient and the oxygen-nitrogen selectivity of the obtained uniform film were as shown below. Oxygen permeability coefficient: 1.8 barrer Nitrogen permeability coefficient: 0.27 barrer Oxygen nitrogen selectivity: 6.7

Comparative Example 1 9,9-bis (4-aminophenyl) fluorene 10.
5 g (0.03 mol), 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride 9.67 g (0.03 mol)
Mol) and 200 g of N-methyl-2-pyrrolidone were charged into a four-necked flask equipped with a stirrer, and the solvent temperature was adjusted to 18
The temperature was maintained at 0 ° C., and the reaction was carried out while removing the produced water.
After completion of the reaction, the reaction solution was filtered with a glass filter, reprecipitated in methanol, washed, and then vacuum dried to obtain a polyimide. The obtained polyimide was a carboxyl-free polyimide and had an inherent viscosity of 0.72 g / dl. The oxygen permeation coefficient, the nitrogen permeation coefficient and the oxygen-nitrogen selectivity of the obtained uniform film of polyimide were as shown below. Oxygen Permeability Coefficient: 2.2 barrer Nitrogen Permeability Coefficient: 0.35 barrer Oxygen Nitrogen Selectivity: 6.2 In the case of this comparative example, it was confirmed that the oxygen nitrogen selectivity was smaller than that of Example 1. Was done.

Example 2 9,9-bis (4-aminophenyl) fluorene-4-
Carboxylic acid 11.8 g (0.03 mol), 3,3 ',
Charge 9,67 g (0.03 mol) of 4,4′-benzophenone tetracarboxylic dianhydride and 200 g of N-methyl-2-pyrrolidone into a four-necked flask equipped with a stirrer, and keep the solvent temperature at 180 ° C. Then, the reaction was carried out while removing the produced water. After completion of the reaction, the reaction solution was filtered with a glass filter, reprecipitated in methanol, washed, and then vacuum dried to obtain a polyimide.

The polymer of the obtained polyimide had one carboxyl group per unit of polymer, and its inherent viscosity was 0.67 g / dl. Also, a 15 wt% N-methyl-2-pyrrolidone solution of this polyimide was uniformly applied onto a glass substrate, and the solvent was dried and removed to obtain a uniform film. The oxygen permeability coefficient, the nitrogen permeability coefficient and the oxygen-nitrogen selectivity of the obtained uniform film were as shown below. Oxygen permeability coefficient: 0.82 barrer Nitrogen permeability coefficient: 0.11 barrer Oxygen nitrogen selectivity: 7.3

Example 3 9,9-Bis (4-aminophenyl) fluorene 5.2
3 g (0.015 mol), 3,3'-dimethyl-4,
5.59 g (0.015 mol) of 4'-diaminobiphenyl-6,6'-disulfonic acid, 3,3 ', 4,4'-
Benzophenone tetracarboxylic dianhydride 9.67g
(0.03 mol) and N-methyl-2-pyrrolidone 20
0 g was placed in a four-necked flask equipped with a stirrer, the temperature of the solvent was kept at 180 ° C., and the reaction was carried out while removing the produced water. After completion of the reaction, the reaction solution was filtered with a glass filter, reprecipitated in methanol, washed, and then vacuum dried to obtain a polyimide.

The polyimide obtained had one sulfonic acid group per polymer unit, and the polyimide had an inherent viscosity of 0.73 g / dl. Also, a 15 wt% N-methyl-2-pyrrolidone solution of this polyimide was uniformly applied onto a glass substrate, and the solvent was dried and removed to obtain a uniform film. The oxygen permeability coefficient, the nitrogen permeability coefficient and the oxygen-nitrogen selectivity of the obtained uniform film were as shown below. Oxygen permeability coefficient: 0.67 barrer Nitrogen permeability coefficient: 0.089 barrer Oxygen-nitrogen selectivity: 7.5

Example 4 9,9-bis (4-aminophenyl) fluorene-4-
Carboxylic acid 5.89 g (0.015 mol), hexaethylenediamine 1.74 g (0.015 mol), 3,
9.67 g (0.03 mol) of 3 ', 4,4'-benzophenone tetracarboxylic dianhydride and N-methyl-2-
Pyrrolidone (200 g) was charged into a four-necked flask equipped with a stirrer, the solvent temperature was kept at 180 ° C., and the reaction was carried out while removing water produced. After completion of the reaction, the reaction solution was filtered with a glass filter, reprecipitated in methanol, washed, and then vacuum dried to obtain a polyimide.

The polyimide obtained had 0.5 carboxylic acid groups per polymer unit, and its inherent viscosity was 0.78 g / dl. A 15 wt% N-methyl-2-pyrrolidone solution of this polyimide was uniformly applied onto a glass substrate, and the solvent was dried and removed to obtain a uniform film. The oxygen permeability coefficient, the nitrogen permeability coefficient and the oxygen-nitrogen selectivity of the obtained uniform film were as shown below. Oxygen Permeability Coefficient: 0.14 barrer Nitrogen Permeability Coefficient: 0.017 barrer Oxygen Nitrogen Selectivity: 8.1

[0022]

INDUSTRIAL APPLICABILITY The polar group-containing polyimide gas separation membrane of the present invention has an excellent oxygen permeability coefficient and oxygen-nitrogen selectivity, and also has excellent heat resistance, and is used for medical purposes. It is possible to produce a large amount of oxygen-enriched air having an oxygen concentration of 40% or a nitrogen-enriched air having a nitrogen concentration of 95% or more at a low cost. As a result, gas separation membrane technology using membranes is widely spread.

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[Procedure amendment]

[Submission date] April 17, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

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[0002]

2. Description of the Related Art In recent years, the use of nitrogen-enriched air having a nitrogen concentration of 95 to 99.5% has attracted attention. One example of the use of such nitrogen-enriched air is explosion protection in flammable liquid storage tanks. In this case, high-purity nitrogen is not required, but it is required to be inexpensive. In order to supply inexpensive nitrogen by membrane separation, the product nitrogen gas is obtained as a non-permeation component of the oxygen permselective membrane, resulting in an excellent oxygen permeation rate.
And a separation membrane having both oxygen and nitrogen selectivity are required. As an oxygen selective permeable membrane, a polyacetylene separation membrane (Japanese Patent Laid-Open No. 2-59,031) is known. Further, a separation membrane of a polycarbonate-dimethylsiloxane block copolymer is disclosed in JP-A-54-40868. However, these films have insufficient selectivity, and improvement has been desired.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

The polyimide of the present invention comprises a diamine compound as an X component, a carboxylic acid dianhydride as a Y component, and at least 5 mol% or more of the X component as a diamine having a bisphenylfluorene skeleton. It is a polycondensate. Here, the bisphenylfluorene skeleton suppresses thermal motion of the polymer main chain due to its bulky structure and creates many microvoids in the polymer. As a result, the polymer having a bisphenylfluorene skeleton has excellent heat resistance and excellent solvent solubility.
Here, in order to impart excellent heat resistance and excellent solvent solubility to the polymer, it is necessary that 5 mol% or more of the X component is bisphenylfluorene. Bisphenylfluorenes can be introduced up to 100 mol% of the X component, and when the mol% of bisphenylfluorenes increases, heat resistance and solvent solubility are further improved. As the diamine having a bisphenylfluorene skeleton, 9,
9 bis - (4-aminophenyl) fluorene and 3-position and / or 5-position of the hydrogen atoms of the amino phenyl group (H) is, -CH ₃ group, -C ₂ alkyl group H ₅ group or the like or -F 9, 9- substituted with one or two or more substituents selected from halogen groups such as group, -Cl group and -Br group
There is a substitution product of bis- (4-aminophenyl) fluorene.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

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The other diamine as the X component may be either an aromatic diamine or an aliphatic diamine. Specifically, 3,3 ′, 5,5′-tetramethylbenzidine, 3,3′-diethylbenzidine, 2-N-diethylmelamine, 3,3′-dimethylnaphthidine, amelin,
2,4-diamino-6-hydroxypyrimidine, 4,4
-Diamino-2-mercaptopyrimidine, 4,4'-diaminodiphenyl ether, 1,4-diamino-2-nitrobenzene, 2,4-diaminotoluene, p-phenylenediamine, tetrafluoro-p-phenylenediamine, 1,5- Diaminoanthraquinone, 1,8-naphthalenediamine, etidylenediamine, 1,4 -diamino
Butane , hexaethylenediamine, 1,12-diaminododecane, 1,4-cyclohexanediamine and the like can be mentioned. The carboxylic acid dianhydride which is the Y component includes 3,3 ′, 4,4′-benzophenone tetracarboxylic acid dianhydride and 2,2-bis (3,4-biscarboxyphenyl) -1,1. , 1,3,3,3-hexafluoropropane dianhydride, pyromellitic dianhydride,
4,4'-biphthalic anhydride, bicyclo [2,2,2]
Octo-7-ene-2,3,5,6-tetracarboxylic dianhydride, 2,2-bis (3,4-biscarboxyphenyl) propane dianhydride and the like can be mentioned.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

[0012]

EXAMPLES The present invention will be specifically described below based on Examples and Comparative Examples. In addition, in the following examples and comparative examples, the inherent viscosity is 10
It is the value measured at 30 ° C. in a solution dissolved in 0 ml of N-methyl-2-pyrrolidone. The gas permeation coefficient was measured at 25 ° C. using a differential pressure type gas permeation rate measuring device using a gas chromatograph as a detector. The unit of gas permeability coefficient is barr
er = 10 ⁻¹⁰ cm ³ · cm / cm ² · sec · cmH
Indicated by g. The selectivity is indicated by the ratio of gas permeability coefficients.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Hironobu Kawasato 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa, Nippon Steel Corporation Advanced Technology Research Laboratories

Claims (1)

[Claims] 1. The following general formula (1): (However, in the formula, X represents a divalent organic group derived from diamine,
Y represents a tetravalent organic group derived from carboxylic acid dianhydride, and n
Is an integer of 1 or more representing the number of repetitions), and at least 5 mol% or more of X is represented by the following general formula (2): (However, R ₁ , R ₂ , R ₃ and R ₄ are —H, —CH ₃ ,
-C ₂ H _5, -F, indicates either -Cl or -Br,
R ₅ and R ₆ represent a divalent organic group having a bisphenylfluorene skeleton represented by —H, —SO ₃ H or —COOH), and further, the above X and / or Y A solution having a carboxyl group and / or a sulfonic acid group in at least a part thereof, 0.5 g of which is dissolved in 100 ml of N-methyl-2-pyrrolidone and having an inherent viscosity at 30 ° C. of 0.2 g / dl or more A polyimide gas separation membrane made of aromatic polyimide.