JPH0679151A - Polyimide separation membrane - Google Patents

Abstract

(57) [Summary] [Object] The present invention is to provide an aromatic polyimide separation membrane having excellent separation performance. It is particularly suitable as a gas separation membrane. DETAILED DESCRIPTION OF THE INVENTION The present invention is a polyimide separation membrane substantially composed of an aromatic polyimide having a repeating unit represented by the general formula (1). (In the formula, R represents a tetravalent aromatic residue.)

Description

Description: BACKGROUND OF THE INVENTION The present invention has a specific repeating unit obtained by polymerizing and imidizing an aromatic tetralbonic acid component and an aromatic diamine component having a hydroxyl group. The present invention relates to a polyimide separation membrane composed of aromatic polyimide. The separation membrane of the present invention is particularly effective for gas separation, for example, methane / helium, methane / hydrogen, oxygen / nitrogen, etc., but can also be used for other purposes such as dehydration, purification and filtration. Since aromatic polyimides are excellent in heat resistance and mechanical strength, aromatic polyimides having various repeating units have already been proposed and are being used as separation membranes. . For example, Japanese Patent Publication No. 55-41802 discloses a polyimide separation membrane in which a substituent is introduced into a rigid polyimide skeleton in order to restrain free rotation around the main chain skeleton. Japanese Patent Publication 62-526
12, Japanese Patent Publication No. 63-55974, Japanese Patent Publication No. 6-6
Japanese Patent Publication No. 1-553086 discloses a polyimide separation membrane obtained from a tetracarboxylic acid component containing a biphenyltetracarboxylic acid as a main component and an aromatic diamine component. Further, in JP-A-2-2857, JP-A-3-65214 and JP-A-63-123420, various tetracarboxylic acid components and alkyl groups,
A polyimide separation membrane obtained from an aromatic diamine component having various substituents such as nitro group and halogen is disclosed. The polyimide separation membranes proposed in these publications have certain characteristics and separability. However, in general, when a separation membrane is applied to the separation of a mixed gas, a membrane having a high permeation rate tends to have a low degree of separation of a target gas, and a membrane having a high degree of separation tends to have a low permeability. It is required to properly use the separation membrane according to the purpose of use, and it is strongly desired to develop a membrane having a balance between the permeability and the degree of separation. DISCLOSURE OF THE INVENTION The present inventors have conducted earnest research for the purpose of developing a membrane capable of increasing the resolution while suppressing the permeability. as a result,
Having a hydroxyl group on the aromatic ring as a diamine component, a membrane using an aromatic diamine in which the aromatic ring is linked by a methylene group has a particularly high degree of separation between methane and helium,
Further, they have found that they also exhibit excellent degree of separation in methane and hydrogen, oxygen and nitrogen, methane and carbon dioxide, etc., leading to the present invention. [0006] The present invention relates to a polyimide separation membrane substantially composed of an aromatic polyimide having a repeating unit represented by the following general formula (1). ## STR2 ## (In the formula, R represents a tetravalent aromatic residue.) In the present invention, as a tetracarboxylic acid component of R representing a tetravalent aromatic residue, Is a biphenyltetracarboxylic acid such as 3,3 ′, 4,4′-biphenyltetracarboxylic acid or an acid anhydride or ester thereof,
Bis (dicarboxyphenyl) such as 3,3 ', 4'-biphenyltetracarboxylic acid and its acid anhydrides and esters
Propanes such as 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane and acid anhydrides thereof,
2,2-bis (3,4-dicarboxyphenyl) propane and its acid anhydrides such as esters, benzophenone tetracarboxylic acids such as esters, for example 3,3 ′, 4
4'-benzophenone tetracarboxylic acid and its acid anhydride, ester, etc., 2,3,3 ', 4'-benzophenone tetracarboxylic acid, its acid anhydride, ester, and other pyromellitic acids, such as pyromellitic acid and its acid Bis (dicarboxyphenyl) sulfones such as anhydrides and esters, for example, bis (3,4-dicarboxyphenyl) sulfone and acid anhydrides and esters thereof, bis (dicarboxyphenyl) ethers, such as bis ( Three
4-dicarboxyphenyl) ether and its acid anhydride,
Examples thereof include esters and the like, and tetracarboxylic acid components conventionally proposed in aromatic polyimide separation membranes. Among these tetracarboxylic acid components,
Biphenyltetracarboxylic acids have an extremely high degree of separation between methane and helium, and bis (dicarboxyphenyl) propanes have an extremely high degree of separation between methane and helium as well as methane and carbon dioxide. Since they have excellent hydrogen permeability, they are particularly suitable as the tetracarboxylic acid component. Further, these tetracarboxylic acid components may be used alone or in combination of two or more. In the present invention, the aromatic diamine component, dihydroxydiaminodiphenylmethane, is 3,
3'-dihydroxy-4,4'-diaminodiphenylmethane, 2,3'-dihydroxy-4,4, -diaminodiphenylmethane, 2,2'-dihydroxy-4,4'-
Mention may be made of diaminodiphenylmethane. In the present invention, the aromatic diamine component is substantially dihydroxydiaminodiphenylmethane, but part of it may be other aromatic diamine. When used in combination with other aromatic diamine, the amount is 20 mol%
The following is appropriate. Specific examples of other aromatic diamines include diaminodiphenyl ether-based compounds such as 4,4′-diaminodiphenyl ether, 3,3′-dimethyl-4,4′-diaminodiphenyl ether, and 3,3′-dimethoxy-diaminodiphenyl ether. Compound, 4,4'-diaminodiphenylmethane, 3,3 '
-Diaminobiphenylmethane, 3,3'-dichloro-
4,4'-diaminobiphenylmethane, 2,2'-difluoro-4,4'-diaminobiphenylmethane, 3,
Diaminobiphenylmethane-based compounds such as 3′-dimethyl-4,4′-diaminobiphenylmethane and 3,3′-dimethoxy-4,4′-diaminobiphenylmethane,
Diaminodibenzothiophene system such as 3,7-diamino-2,8-dimethyl-dibenzothiophene, 2,8-diamino-3,7-dimethyl-dibenzothiophene and 3,7-diamino-2,6-dimethyl-dibenzothiophene Compound, 3,7-diamino-2,8-dimethyl-diphenylene sulfone, 3,7-diamino-2,8-diethyl-diphenylene sulfone, 3,7-diamino-2,
Diaminodiphenylene sulfone compounds such as 8-dimethoxy-diphenylene sulfone and 2,8-diamino-3,7-dimethyl-diphenylene sulfone, 4,
Diaminobenzophenone-based compounds such as 4'-diaminobenzophenone and 3,3'-diaminobenzophenone
2,2-bis (4-aminophenyl) propane, 2,2
Examples thereof include bis (aminophenyl) propane compounds such as -bis (3-aminophenyl) propane. The polyimide separation membrane having repeating units of the present invention comprises a conventionally known method for producing a polyimide separation membrane from an aromatic tetracarboxylic acid component and an aromatic diamine component dihydroxydiaminodiphenylmethane, for example, Japanese Patent Publication No. 3-8818. It can be manufactured by a method similar to the method described in the publication. Specifically, for example, an aromatic tetracarboxylic acid component and an aromatic diamine component are dissolved in an organic polar solvent in approximately equimolar amounts and polymerized at a temperature of about 100 ° C. or less, particularly 60 ° C. or less. To a polyamic acid, and using this polyamic acid solution as a dope, a thin film is formed by coating or casting on a substrate, and the solvent is gradually removed while heating and raising the temperature, and the amide-acid bond is formed. A method of imidizing, followed by drying and heat treatment at a temperature of 150 to 350 ° C., an aromatic tetracarboxylic acid component and an aromatic diamine component are approximately equimolar in a phenolic solvent at about 140 ° C.
Polymerization and imidization in a single step at the above temperature to obtain a polyimide solution dissolved in a phenolic solvent, using this as a dope solution, to form a thin film by coating or casting on a substrate, heating, heating While gradually removing the solvent,
It can be manufactured by a method of drying and heat treatment at a temperature of 0 to 350 ° C. As the organic polar solvent used for preparing the dope, for example, N-methyl-2pyrrolidone, N, N-
Examples thereof include dimethylacetamide, N, N-dimethylformamide, dimethylsulfoxide, and tetramethylurea. Further, as the phenolic solvent,
Examples thereof include phenol, cresol, xylenol, monohalogenated phenol and monohalogenated alkylphenol. The polyimide separation membrane having a repeating unit of the present invention may be used as it is, or may be laminated or laminated with another polymer separation membrane or an inorganic porous membrane. INDUSTRIAL APPLICABILITY The polyimide separation membrane having the repeating unit of the present invention can be used for various purposes, but the separation degree between methane and helium is remarkably high, and methane and hydrogen, oxygen and nitrogen, and methane are separated. Since it also exhibits excellent separation degree in carbon dioxide, etc., for example, separation and recovery of helium and carbon dioxide from natural gas containing helium and carbon dioxide, removal of carbon dioxide from off-gas of combustion fields containing carbon dioxide and combustion exhaust gas It is particularly suitable as a gas separation membrane for refining oil, recovering hydrogen in an ammonia plant, producing oxygen- or nitrogen-rich gas from air, and the like. EXAMPLES In each example, the gas permeability was determined by measuring the membrane area 14.
The separation membrane was installed in a 65 cm ² stainless steel cell, and carbon dioxide gas, methane gas, nitrogen gas, oxygen gas, helium gas, or hydrogen gas was pressurized to 1.5 kg / cm ² each and the separation membrane was formed at 50 ° C. The amount of permeating gas was measured with a flow meter, and the permeability (P) of each gas was calculated by the following formula. [Formula 1] The degree of separation (α) is indicated by the ratio of the permeability of each gas. Example 1 65.5 g of N-methyl-2-pyrrolidone was placed in a separable flask equipped with a stirrer and a nitrogen gas introducing tube.
1.1 g of 3,3′-dihydroxy-4,4′-diaminodiphenylmethane was added and dissolved, and 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane was added with stirring while introducing nitrogen gas. 2.0 g was added over 30 minutes, and the mixture was kept at 25 ° C. for 3 hours for polymerization. The resulting polyamic acid solution was cast on a glass plate, and 100
After imidization was performed at 5 ° C. for 5 hours and then heat treatment was performed at 300 ° C. for 1 hour to form a polyimide film, a 9.83 μm-thick polyimide separation film was taken out from the glass plate. The permeability and separation of each gas of this membrane are shown in Table 1. Example 2 64.9 g of N-methyl-2-pyrrolidone was placed in a separable flask equipped with a stirrer and a nitrogen gas introducing tube.
2.9 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was dissolved and suspended. To this, 3,3'-
2.3 g of dihydroxy-4,4′-diaminodiphenylmethane was added over 30 minutes, and the mixture was maintained at 25 ° C. for 1 hour for polymerization. The obtained polyamic acid solution was cast on a glass plate, imidized at 100 ° C. for 3 hours, then 3 times.
After heat treatment was performed at 00 ° C. for 1 hour to form a polyimide film, a 28.45 μm-thick polyimide separation film was taken out from the glass plate. The permeability and separation of each gas of this membrane are shown in Table 1. Comparative Example 1 86.1 g of N-methyl-2-pyrrolidone was placed in a separable flask equipped with a stirrer and a nitrogen gas inlet tube.
With stirring, 11.8 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was dissolved and suspended. to this,
9.8 g of 3,3′-dimethoxy-4,4′-diaminobiphenyl was added, and the mixture was maintained at 25 ° C. for 5 hours while introducing nitrogen gas to carry out polymerization. The obtained polyamic acid solution is
A film was formed from this in the same manner as in Example 1, and the thickness was 18.3 μm.
A polyimide separation membrane of was obtained. The permeability and separation of each gas of this membrane are shown in Table 1. Comparative Example 2 25.7 g of parachlorophenol was placed in a separable flask equipped with a stirrer and a nitrogen gas introducing tube, and while stirring, while introducing nitrogen gas, 3,3 ', 4,4'- 2.9 g of biphenyl tetracarboxylic dianhydride and 4,
Add 2.0 g of 4'-diaminodiphenylmethane, add 18
It was kept at 0 ° C. for 3 hours for polymerization and imidization. The resulting polyimide solution is cast on a glass plate and kept at 100 ° C for 3 hours.
After heat treatment for 1 hour at 300 ° C. for 1 hour to form a polyimide film, the thickness of the glass plate is 12.5 μm.
The polyimide separation membrane of was taken out. The permeability and separation of each gas of this membrane are shown in Table 1. Comparative Example 3 138.4 g of parachlorophenol was placed in a separable flask equipped with a stirrer and a nitrogen gas introducing tube, and 2,2 bis (3,4-di-diene) was introduced while introducing nitrogen gas under stirring. Carboxyphenyl) hexafluoropropane 17.8
g and 8.1 g of 4,4′-diaminodiphenylmethane were added, and the mixture was held at 180 ° C. for 4 hours for polymerization and imidization. The obtained polyimide solution was formed into a film in the same manner as in Comparative Example 2 to obtain a polyimide separation film having a thickness of 15.2 μm. The permeability and separation of each gas of this membrane are shown in Table 1. Comparative Example 4 52.4 g of N-methyl-2-pyrrolidone was placed in a separable flask equipped with a stirrer and a nitrogen gas introducing tube.
While stirring and introducing nitrogen gas, 6.5 g of pyromellitic dianhydride and 6.1 g of 4,4′-diaminodiphenyl ether were added, and the mixture was maintained at 25 ° C. for 6 hours for polymerization. The obtained polyamic acid solution was formed into a film in the same manner as in Example 1 to obtain a polyimide separation film having a thickness of 13.4 μm. The permeability and separation of each gas of this membrane is
Shown in the table. [Table 1]

Claims (1)

What is claimed is: 1. A polyimide separation membrane, which is substantially composed of an aromatic polyimide having a repeating unit represented by the following general formula (1). [Chemical 1] (However, R in the formula represents a tetravalent aromatic residue.)