JPS63264121A - Polyimide membrane for separating gas - Google Patents

Abstract

PURPOSE:To increase the CO2 separation efficiency of the title membrane by forming the membrane from the aromatic tetracarboxylic acid skeleton consisting essentially of a dephenyl ether tetracarboxylate skeleton and an aromatic polyimide consisting of an aromatic diamine skeleton. CONSTITUTION:The aromatic polyimde membrane is formed from an aromatic tetracarboxylic acid skeleton consisting of 10-100% diphenyl ether tetracarboxylate component such as 3,3',4,4'-diphenyl ether tetracarboxylate and 0-10% aromatic tetracarboxylic acid component having no hydroxyl group such as 3,3',4,4'-biphenyl tetracarboxylate and an aromatic diamine skeleton such as 4,4'-diaminodiphenyl ether. The obtained gas separation membrane has excellent permselectvity to CO2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to polyimide gaseous J11 membranes. More specifically, the present invention relates to a gas separation membrane having a homogeneous layer made of aromatic polyimide, which is useful for separating or concentrating carbon dioxide from a gas mixture containing carbon dioxide.

[Background of the Invention] Conventionally, various types of gas separation membranes made of polyimide have been known.
The publication discloses a gas separation material having a gas separation layer made of biphenyltetracarboxylic acid-based polyimide. However, when biphenyltetracarboxylic acid-based aromatic polyimide gas component gI membranes are used for separating or concentrating carbon dioxide from a gas mixture containing carbon dioxide, the carbon dioxide permeation performance is poor. Not enough.

[Object of the Invention] The present invention is useful for separating and concentrating carbon dioxide from a gas mixture containing carbon dioxide.

A new aromatic polyimide gas component with heat resistance! 1
The purpose is to provide 39.

[Summary of the Invention] The present invention provides a polyimide gas separation membrane formed from an aromatic polyimide comprising an aromatic tetracarboxylic acid skeleton and an aromatic diamine skeleton, wherein the aromatic tetracarboxylic acid skeleton is composed of diphenyl ether. A polyimide gas separation membrane is characterized in that it consists of a tetracarboxylic acid component 10 to 100 mol% and an aromatic tetracarboxylic acid component having no oxy group O to 90 mol%.

[Detailed Description of the Invention] The present invention is made of an aromatic polyimide consisting of an aromatic tetracarboxylic acid skeleton mainly consisting of a diphenyl ether tetracarboxylic acid skeleton and an aromatic diamine skeleton, and has excellent carbon dioxide permeability. This invention relates to polyimide gas separation membranes.

The above diphenyl ether tetracarboxylic acid is represented by the general formula [I]: [11]. The manufacturing method is disclosed in JP-A-55-136246, and is formed mainly from an aromatic tetracarboxylic acid skeleton consisting of diphenyl ether tetracarboxylic acid or a derivative thereof represented by the general formula [I] and an aromatic diamine skeleton. Aromatic polyimides are known.

The diphenyl ether tetracarboxylic acid component used in the aromatic polyimide of the present invention is 3.3'.

4.4°-diphenyl ether tetracarboxylic acid, or 2,3.3',4'-diphenyl ether tetracarboxylic acid, or acid dianhydrides and esters thereof,
Any diphenyl ether tetracarboxylic acid derivative such as a halide salt may be used, but an acid dianhydride can be particularly advantageously used.

The aromatic tetracarboxylic acid component used in the aromatic polyimide of undeveloped IJJ contains at least 10 mol 5 or more, more 30 mol % or more, especially 45 to 100 mol % of the diphenyl ether tetracarboxylic acid or its derivative. It is preferable.

In the above aromatic tetracarboxylic acid component, if the amount of the diphenyl ether tetracarboxylic acid component is less than 10 mol 5, practically sufficient permeation performance for carbon dioxide cannot be obtained, so I/) is preferred.

Moreover, the above-mentioned aromatic tetracarboxylic acid component may contain an aromatic tetracarboxylic acid component having no oxy group together with the diphenyl ether tetracarboxylic acid component.

The aromatic tetracarboxylic acid component without an oxy group that can be used with the diphenyl ether tetracarboxylic acid component includes 3.3", 4,4"-biphenyltetracarboxylic acid, or 2,3,3° ,4
Biphenyltetracarboxylic acids such as °-biphenyltetracarboxylic acid, acid dianhydrides and lower alcohol esters thereof; 3,3°,4,4"-benzophenonetetracarboxylic acid, or 2,3.

Benzophenonetetracarboxylic acids such as 3°, 4°-benzophenonetetracarboxylic acid, or their acid dianhydrides and lower alcohol esters: In addition, pyromellitic acids, such as pyromellitic acid, its acid dianhydrides, and esterified products, etc. can be mentioned.

In undeveloped II, 3.3',4 as an aromatic tetracarboxylic acid component without oxino, (.

It is preferable to use 4'-biphenyltetracarboxylic acid, 2,3,3°,4'-biphenyltetracarboxylic acid, or acid dianhydrides thereof. By using the above-mentioned biphenyltetracarboxes m, after producing aromatic polyamic acid or aromatic polyimide in an organic polar solvent as described later, a stable dope solution can be obtained and the product quality can be improved. Therefore, it is suitable.

-L oxy group as described in 1. The solid aromatic tetracarboxylic acid component is 90 mol% of the total aromatic tetracarboxylic acid component.
Below, it is further preferably 70 mol% or less, particularly 55 mol% or less.

The aromatic diamine component forming the aromatic polyimide of the present invention includes 4,4°-diaminodiphenyl ether,
Diphenyl ether compounds such as 3,3'-dimethyl-4,4'-diaminodiphenyl ether, 3,3'-dimethoxy-4,4''-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane , 3. Diphenylmethane compounds such as 3'-diaminodiphenylmethane, 3.

Diaminodiphenylsulfide compounds such as 3°-diaminodiphenylsulfide, 4.4″-diaminodiphenylsulfide, 3.3°-diaminodiphenylsulfone, 4.4°-diaminodiphenylsulfone, 4.4
'-Diaminobibenzyl, 4,4'-diamino-2,2
Bibenzyl compounds such as °-dimethylbenzidine, 4.
Benzophenone compounds such as 4'-diaminobenzophenone and 3,3'-diaminobenzophenone, 2,2-
Bis(3-aminophenyl)propane.

2,2-his(4-aminophenyl)propane, 2,2-bis[4-(4'-aminophenoxy)
2,2-bis(phenyl)propane compounds such as phenyl]propane, 3,3'-dimethylbenzidine, 3,
Benzidine-based compounds such as 3'-dimethoxybenzidine, O-dianisidine, O-, m-, p-phenylenediamine, 3.

Examples include 5-diaminobenzoic acid and 2,6-dinemitubiridine.

As the aromatic diamine component used in the present invention, aromatic diamines selected from the following groups can be used alone or in combination, including 4,4'-diaminodiphenyl ether or 0-dianisidine. It is preferable to use alone.

The aromatic polyamic acid (polyimide precursor) or aromatic polyimide used in the production of the gas separation membrane of the present invention is obtained from the above-mentioned aromatic tetracarboxylic acid component and the above-mentioned aromatic diamine component in approximately equal moles. It may be manufactured by any known method.

The above aromatic polyamic acid has a logarithmic viscosity (measurement temperature: 30°C, concentration: 0.5 g/100 mfL melt, solvent 2N-methyl-2-pyrrolidone) of 0.1 to 7, especially 0.
．． It is preferable that the aromatic polyimide is a polymer whose logarithmic viscosity (measurement temperature = 30°C, concentration: 0.5 g 7100 ml solvent, solvent:
p-chlorophenol 4 volumes 1 + o-chlorophenol 1
It is preferable to use a polymer having a capacitance of about 0.1 to 7, particularly about 0.2 to 5.

Note that the logarithmic viscosity has a considerable correlation with the degree of polymerization or the molecular weight, and is a value calculated using the formula shown in the first order.

Logarithmic viscosity = (natural logarithm (solution viscosity / solvent viscosity)) /
Concentration of Polymer in Solution The polyimide gas separation membrane of the present invention uses an organic solvent solution of aromatic polyamic acid or aromatic polyimide formed from the above-mentioned aromatic tetracarboxylic acid skeleton and aromatic diamine skeleton for membrane formation. A dry process in which a thin film is formed from the dope by using it as a dope, and the film is formed mainly through a drying process in which the solvent is removed and solidified, or a thin film formed from the dope is coagulated by contact with a coagulation solution. Polyimide membranes with various structures such as flat membranes and hollow fibers can be obtained by the wet membrane-forming method.

For example, as a method for manufacturing the polyimide gas separation membrane of the present invention, the following dry method 11) ff method can be mentioned.

(A) Film forming method from a solution of polyamic acid The above-mentioned aromatic tetracarboxylic acid component and aromatic diamine component are mixed in approximately equal moles in an organic polar solvent.

The aromatic polyamic acid is produced by polymerizing at a temperature of about 100°C or less, particularly 60°C or less.

A solution of the aromatic polyamic acid in an organic polar solvent (polymer concentration: about 3 to 30% by weight) was used as a dope solution for film formation, and was applied or cast onto a Omura surface at a temperature of about 10 to 100°C. A thin film is formed from the dope liquid, and then the solvent is gradually removed by evaporation from the thin film, and the temperature is gradually heated to imide-cyclize the amide-acid bond of the aromatic polyamic acid to obtain an aromatic polyimide. .

Finally, heat it sufficiently to a temperature of about 150 to 350 degrees Celsius and dry it.
Dry process I to form a homogeneous film of aromatic polyimide by heat treatment
III Membrane Method.

(B) Film forming method from polyimide organic solvent solution The above-mentioned aromatic tetracarboxylic acid component and aromatic diamine component are mixed in approximately equal moles, about 140% in an organic solvent of a phenolic compound.
It is polymerized and imidized in one step at temperatures above 0.degree. C. to form an aromatic polyimide.

A solution of this aromatic polyimide in an organic polar solvent (concentration: about 3
~30% by weight) is used as the dope, and approximately 30-15
A thin film is formed from the dope solution by coating or casting on the Omura at a temperature of 0°C, and then.

The solvent is gradually evaporated and removed from the thin film.

Finally, a dry film forming method in which a homogeneous film of aromatic polyimide is formed by sufficiently drying and heat-treating at a temperature of 150 to 400°C, particularly 170 to 350°C.

In the production of the above-mentioned homogeneous membrane, it goes without saying that the final high-temperature drying and heat treatment is carried out at a temperature at which the aromatic polyimide used does not melt. It is optimal to carry out for about 0.5 to 10 hours within a temperature range of ~350°C,
This high-temperature heat treatment significantly improves the gas separation properties of the homogeneous membrane.

In the production of the above-mentioned homogeneous film, after forming a homogeneous film by using a material with a smooth surface as the base material (for example, a glass plate, a flat smooth copper plate, a fully curved roll or belt with a smooth surface, etc.), from the base material. When the membrane is peeled off, a highly uniform film-like membrane is obtained. This extremely thin film-like homogeneous membrane can be used as it is as a gas separation material, but it can also be used by tajF or bonding with other porous membranes.

Furthermore, if a porous membrane is used as the base material in the above-described homogeneous membrane manufacturing method, a composite gas separation material in which the homogeneous membrane is integrally formed on the surface of the porous membrane as described above can be obtained.

The organic polar solvents used in the production of the aromatic polyamic acid and the preparation of its dope solution include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone.
, N-dimethylformamide, dimethyl sulfoxide,
Examples include tetramethylurea.

The organic polar solvent used in the production of the above-mentioned aromatic polyimide and the preparation of the dope solution for forming the polyimide film may include phenolic solvents such as phenol, cresol, monohalogenated phenol, monohalogenated monoalkylphenol, etc. , N-methyl-2-pyrrolidone, and N,N-dimethylacetamide.

Outside the polyimide gas of the present invention! Since the gas permeation rate of the membrane decreases as the membrane thickness increases, it is practically preferable that the membrane thickness is 20 uLm or less.

[9. Effect of light] The polyimide gas separation membrane of the present invention is a gas separation membrane that has particularly excellent permselectivity for carbon dioxide compared to conventional gas separation membranes.

Therefore, the polyimide gas separation membrane of the present invention can be suitably used for separating, purifying, and concentrating carbon dioxide from a gas mixture containing carbon dioxide.

Furthermore, the polyimide gas separation membrane of the present invention has heat resistance, chemical resistance, and mechanical strength equivalent to those of known aromatic polyimide gas separation membranes.

Next, Examples and Comparative Examples will be shown. In the Examples and Comparative Examples, a gas permeation test was conducted by installing a gas separation membrane in a stainless steel cell with an area of 14.65 Crn', and passing a mixed gas of hydrogen, carbon dioxide, and methane. , 50℃, 0.5-2
The mixture of permeate gases is applied to the vacuum side by applying pressure to one side of the membrane and keeping the other side of the membrane at vacuum. ), the components of the gas mixture and the volume of each component were measured by gas chromatographic analysis, and the permeability coefficient of each gas component and the mutual separation coefficient of each gas component were calculated.

In the present invention, the gas permeability coefficient (cm" * cm / c tn
' msec·cmHg) is calculated according to the formula shown below.

Gas permeation coefficient = (gas permeation amount x membrane thickness) / (membrane area x permeation time x pressure difference) [Example 1] In a separable flask equipped with a stirrer and a nitrogen introduction tube, 3.3', 4. 20 mmol of 4'-diphenyl ether tetracarboxylic dianhydride (hereinafter abbreviated as ETDA), 20 mmol of 4,4°-diaminodiphenyl ether (hereinafter abbreviated as DA)
20 mmol (abbreviated as DE) and 85 g of p-chlorophenol were added, and the temperature was raised from room temperature (25°C) to 180°C in about 60 minutes while stirring the reaction solution under a nitrogen atmosphere.
Further, the reaction solution was maintained at 180° C. for about 20 hours to carry out polymerization and imidization in one step to obtain a viscous polyimide solution. This polyimide solution had a polymer concentration of about 10% by weight.

This polyimide solution was filtered and defoamed under pressure to obtain a dope solution for film formation. This dope solution is cast onto a glass plate,
An I8I film of the dope solution was formed using a doctor blade to a uniform thickness of approximately 0.2 mm, and the thin film was maintained at approximately 100°C for 3 hours in a nitrogen stream to gradually evaporate and remove the solvent. 1. Next, the temperature was raised from room temperature to 300°C in about 1 hour, and then dried and heat-treated at 300°C for 1 hour to form a homogeneous membrane with a thickness of 7 pm. This homogeneous membrane was used as a gas separation membrane, and the above-mentioned A gas permeation test was conducted using the method described below.

The results are shown in Table 1.

[Example 2] As the aromatic tetracarboxylic acid component, instead of 20 mmol of ETDA, 16 mmol of ETDA and 3.3°
, Example 1 except that 4 mmol of 4,4°-biphenyltetracarboxylic dianhydride (hereinafter abbreviated as BPDA) was used.
A homogeneous aromatic polyimide film having a thickness of 71 Lm was formed in the same manner as above, and a gas permeation test was conducted using this homogeneous film as a gas molecule a film.

The results are shown in Table 1.

[Example 3] As the aromatic tetracarboxylic acid component, 10 mmol of ETDA and BPD were used instead of 20 mmol of ETDA.
A homogeneous aromatic polyimide membrane having a thickness of 7 μLm was formed in the same manner as in Example 1 except that mmol of AIO was used, and a gas permeation test was conducted using this homogeneous membrane as a gas separation membrane. The results are shown in Table 1.

[Comparative Example 1] A product with a thickness of 7 was prepared in the same manner as in Example 1, except that BPDA was used instead of ETDA as the aromatic tetracarboxylic acid component.
A micrometer-thick aromatic polyimide homogeneous membrane was formed, and a gas permeation test was conducted using this homogeneous membrane as a gas separation membrane. The results are shown in Table 1.

[Example 4] A product with a thickness of 7 μm was prepared in the same manner as in Example 1 except that 0-dianisidine was used instead of DADE as the aromatic diamine component.
A homogeneous aromatic polyimide membrane of m was formed, and a gas permeation test was conducted using this homogeneous membrane as a gas separation membrane. The results are shown in Table 1.

[Comparative Example 2] The thickness was determined in the same manner as in Example 4, except that BPDA was used instead of ETDA as the aromatic tetracarboxylic acid component.
A homogeneous aromatic polyimide membrane of #Lm was formed, and a gas permeation test was conducted using this homogeneous membrane as a gas separation membrane. The results are shown in Table 1.

Table 1 Gas permeation coefficient for methane (XIO-”
) Separation coefficient H, Co2 CH, co2 Example 1 5.1 1.2 0.0097 12
4 Example 2 4.2 1.0 0.0077 1
30 Example 3 3.0 G, 8 0.0063
128 Comparative Example 1 1.8 G, 22 0.0024
92 Example 4 7.2 1.6 0.0145
110 Comparative Example 2 3.6 (1,600,009
861 Gas permeability coefficient: cm″m cm/c ni
'm seconds * cmHg Separation factor for methane = (CO
, gas permeability coefficient)/(gas permeability coefficient of methane) From Table 1, the polyimide gas separation membrane of the present invention has a lower carbon dioxide It is clear that the carbon permeability coefficient is high and the separation coefficient of carbon dioxide with respect to methane is large, so that it has excellent carbon dioxide permeation performance.

Claims (1)

[Scope of Claims] 1. A polyimide gas separation membrane formed from an aromatic polyimide consisting of an aromatic tetracarboxylic acid skeleton and an aromatic diamine skeleton, wherein the aromatic tetracarboxylic acid skeleton is a diphenyl ether tetracarboxylic acid skeleton. A polyimide gas separation membrane formed from 10 to 100 mol% of an acid component and 0 to 90 mol% of an aromatic tetracarboxylic acid component having no oxy group. 2. The aromatic tetracarboxylic acid skeleton is formed from 30 to 100 mol% of a diphenyl ether tetracarboxylic acid component and 0 to 70 mol% of an aromatic tetracarboxylic acid component that does not have an oxy group. A polyimide gas separation membrane according to claim 1. 3. The aromatic tetracarboxylic acid skeleton is formed from 45 to 100 mol% of a diphenyl ether tetracarboxylic acid component and 0 to 55 mol% of an aromatic tetracarboxylic acid component that does not have an oxy group. A polyimide gas separation membrane according to claim 1. 4. The diphenyl ether tetracarboxylic acid component is 3.
The polyimide gas separation membrane according to claim 1, characterized in that it is 3',4,4'-diphenyl ether tetracarboxylic dianhydride. 5. The diphenyl ether tetracarboxylic acid component is 2.
The polyimide gas separation membrane according to claim 1, characterized in that it is 3,3',4'-diphenyl ether tetracarboxylic dianhydride. 6. The polyimide gas according to claim 1, wherein the aromatic tetracarboxylic acid component having no oxy group is 3,3',4,4'-biphenyltetracarboxylic dianhydride. Separation membrane. 7. The polyimide gas according to claim 1, wherein the aromatic tetracarboxylic acid component having no oxy group is 2,3,3',4'-biphenyltetracarboxylic dianhydride. Separation membrane. 8. The polyimide gas separation membrane according to claim 1, wherein the membrane thickness is 20 μm or less.