JPH09285722A - Production of gas separating membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably produce a gas separating membrane having high separating performance while preventing the deterioration of gas permeability by firing a film of a polyimidazopyrrolone polymer at a specified temp. in an inert atmosphere. SOLUTION: A film of a polyimidazopyrrolone polymer is fired at 410-1,500 deg.C, preferably 450-900 deg.C in an inert atmosphere. The pref. firing time is about 10-120min, especially about 10-60min. The polyimidazopyrrolone polymer is preferably produced by polycondensing tetramine and tetracarboxylic acid dianhydride as essential components in a proper solvent such as N,N- dimethylacetamide or N-methylpyrrolidone optionally in the presence of a reaction assistant such as acetic anhydride, thionyl chloride, trifluoroacetic anhydride or benzoic acid, isolating the resultant precursor of polyimidazopyrrolone and bringing it into ring closure by heating at about 200-400 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a gas separation membrane having high selectivity (the gas in the present invention includes vapor).

The gas separation membrane obtained by the production method of the present invention is, for example, oxygen / nitrogen separation of air, separation and recovery of hydrogen from off-gas in the platforming method, separation and recovery of hydrogen during ammonia synthesis, thermal power generation and dust. Recovery of carbon dioxide from waste gas from incineration, removal of nitrogen oxides and sulfur oxides,
Recovery of carbon dioxide from offgas of oil field, removal of acidic gas such as hydrogen sulfide and carbon dioxide and water (water vapor) from natural gas, decarboxylation of landfill gas and recovery of methane, dehumidification of air and organic vapor, and aqueous solution of organic matter. It is used for dehydration, pervaporation separation of volatile substance mixed liquid, removal of gas dissolved in liquid, dissolution of specific gas in liquid, etc. Of course, the present invention is not limited to these applications.

[0003]

2. Description of the Related Art Gas separation using a gas separation membrane has poor selectivity (separation performance) as compared with a cryogenic separation method or an adsorption method (PSA), and these methods are costly for producing a high purity gas. Is inferior to the above, and is particularly remarkable in the application of air separation.

Therefore, the development of a membrane material having high selectivity while suppressing a decrease in permeability as much as possible has been advanced. Among the organic polymers, polyimidazopyrrolone has strength, durability,
In recent years, it has been reported that it is an extremely excellent membrane material having excellent heat resistance, oxidation resistance and solvent resistance, and having high gas permeability and high selectivity. For example, P
olymer Preprints, Japan Vol.41, No.3, P.6
44 (1992) describes excellent gas selective permeation properties of various polyimidazopyrrolone, and PCT application WO 94/12465 describes a fluid separation membrane composed of a specific polyimidazopyrrolone.

[0005]

However, when these membranes are applied to the separation of oxygen and nitrogen as, for example, an air separation membrane, they are compared with the PSA method which is a competitive technology of the conventional separation method. It was not always possible to expect sufficient separability.

An object of the present invention is to provide a method for stably producing a gas separation membrane having a high separability while preventing a decrease in gas permeability as much as possible.

[0007]

[Means for Solving the Problems] The present inventors focused their attention on polyimidazopyrrolone having excellent properties as a separation membrane material, and as a result of diligent studies aimed at further improving its gas-selective property, the result was a polyimidazopyrrolone-based compound. A film made of a polymer is heated to 410 to 1500 ° C., preferably 450 to 900 ° C. in an inert atmosphere such as an inert gas or a vacuum.
It has been found that a gas separation membrane having improved gas selectivity can be easily and stably produced by carbonizing by a production method such as firing at.

That is, according to the present invention, (1) a film made of a polyimidazopyrrolone-based polymer is used in an inert atmosphere at 410-410.
A method for producing a gas separation membrane, which comprises calcination at 1500 ° C., (2) calcination at 450 to 900 ° C. (1)
The method for producing a gas separation membrane according to (1) or (2) above, wherein the polyimidazopyrrolone-based polymer is a polymer obtained mainly from aromatic tetraamines and aromatic tetracarboxylic acids. A method for producing a gas separation membrane,
(4) A solvent-soluble precursor of a polyimidazopyrrolone-based polymer obtained by polycondensation of aromatic tetraamines and aromatic tetracarboxylic dianhydrides as main components is formed into a film and then heated. The method for producing a gas separation membrane according to the above (1), (2) or (3), which comprises forming a membrane made of a polyimidazopyrrolone-based polymer, and subsequently heating the membrane at elevated temperature, and (5) poly The method for producing a gas separation membrane according to (4) above, wherein the solvent-soluble precursor of the imidazopyrrolone-based polymer is a polyamic acid having an amino residue and / or a polyimide having an amino residue.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polyimidazopyrrolone polymer used in the present invention is a polymer having a stereoisomer structure of the following general formula (1) and / or general formula (1) as a repeating unit, and Those containing 50 mol% or more of repeating units can be mentioned.

[0010]

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(Wherein Z ₁ and Z ₂ are tetravalent groups,
It is preferable that Z ₁ and Z ₂ are aromatic, and among them, Z ₁ is

[0012]

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More preferably, the structure is
₂ is

[0014]

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More preferably, the structure is

The method for producing the polyimidazopyrrolone-based polymer is arbitrary and, for example, N, N-dimethylacetamide,
In a suitable solvent such as N-methylpyrrolidone, acetic anhydride, thionyl chloride, trifluoroacetic anhydride, if necessary,
A reaction aid such as dicyclohexylcarbodiimide, pyridine, triethylamine, or benzoic acid is added, and polyamine is condensed with tetraamine and tetracarboxylic acid dianhydride as a main component to form a polyimidazopyrrolone precursor. A polyimidazopyrrolone precursor is obtained by a method such as polycondensation as a component to form a polyimidazopyrrolone precursor, and polycondensation of tetraamine and tetracarboxylic acid dichloride as a main component to form a polyimidazopyrrolone precursor. Release, then 200-400
A method of ring closure by heating at 0 ° C, etc. can be mentioned. Among them, a polyimidazopyrrolone precursor is obtained by polycondensation with tetraamine and tetracarboxylic acid dianhydride as main components, and this is isolated,
Then, a method of heating and ring-closing at 200 to 400 ° C. is preferable. The term “main component” means that the content is 50 mol% or more.

Here, the polyimidazopyrrolone precursor may be, for example, polyamic acid having an amino residue, polyimide having an amino residue, or polyisoimide having an amino residue. The polyimidazopyrrolone formation of the polyimidazopyrrolone precursor can be confirmed by, for example, an infrared absorption spectrum.

The above tetraamine is not particularly limited, and any one can be used alone or in combination of two or more kinds, but it is aromatic, heterocyclic or alicyclic having a pair of amino groups adjacent to each other in ortho positions. The tetraamines of the formula and derivatives thereof are preferred. Among these, aromatic tetraamines are more preferable, and the following tetraamines are still more preferable.

[0019]

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Specific examples of the above tetraamine include:
3,3 ', 4,4'-tetraaminodiphenyl ether, 3,3', 4,4'-tetraaminodiphenylmethane, 3,3 ', 4,4'-tetraaminobiphenyl,
1,2,4,5-tetraaminobenzene, 3,3 ',
4,4'-tetraaminodiphenylisopropylidene,
Aromatic tetraamines such as 1,4,5,8-tetraaminonaphthalene, 3,3 ', 4,4'-tetraaminopyridine, 3,3', 4,4'-tetraaminopyridine, dibenzothiophene-2, 3,7,8-Tetraamine-
Examples of heterocyclic tetraamines such as 5,5-dioxide, 2,3,7,8-tetraaminobenzoquinone and 1,2,4,5-tetraaminoanthraquinone, among which 3,3 ′, 4,4 ′ -Tetraaminodiphenyl ether, 3,3 ′, 4,4′-tetraaminodiphenylmethane, 3,3 ′, 4,4′-tetraaminobiphenyl (hereinafter abbreviated as diaminobenzidine), 1,2,
4,5-tetraaminobenzene, 3,3 ', 4,4'-
Tetraaminodiphenylisopropylidene is preferred,
Diaminobenzidine and 1,2,4,5-tetraaminobenzene are particularly preferred.

It is also possible to use triamine instead of tetraamine. In this case, it is considered that 1/2 of the triamine used constitutes the polyimidazopyrrolone repeating unit. If necessary, a triamine component, a diamine component, and other copolymerization components may be mixed with these tetraamine components before use.

The tetracarboxylic acid dianhydride is not particularly limited, and any one can be used alone or in combination of two or more kinds. Among them, aromatic, heterocyclic or alicyclic tetracarboxylic acid can be used. An acid dianhydride is preferable, and the following tetracarboxylic acid dianhydride is particularly preferable.

[0023]

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Specific examples of the above-mentioned tetracarboxylic acid dianhydride include naphthalenetetracarboxylic acid dianhydride, biphenyltetracarboxylic acid dianhydride, pyromellitic acid dianhydride, benzophenonetetracarboxylic acid dianhydride, diphenylethertetraanhydride. Carboxylic dianhydride, hexafluoroisopropylidene diphthalic dianhydride, diphenyl sulfone tetracarboxylic dianhydride, perylene tetracarboxylic dianhydride, bis (dicarboxyphenyl)
Methane acid dianhydride, bis (dicarboxyphenyl) ethanoic acid dianhydride, bis (dicarboxyphenyl) propanoic acid dianhydride, anthracene tetracarboxylic acid dianhydride,
Aromatic tetracarboxylic dianhydrides such as azobenzene tetracarboxylic dianhydride, cyclobutane tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydrides such as cyclohexane tetracarboxylic dianhydride, thiophene tetracarboxylic dianhydride Heterocyclic tetracarboxylic acid dianhydrides such as anhydrides, furan tetracarboxylic acid dianhydrides, pyridine tetracarboxylic acid dianhydrides and the like can be mentioned, among which 4,
4 ′-(hexafluoroisopropylidene) diphthalic acid dianhydride (hereinafter abbreviated as 6FDA), pyromellitic dianhydride (hereinafter abbreviated as PMDA), 3, 3 ′,
4,4'-biphenyltetracarboxylic dianhydride, 3,
3 ', 4,4'-benzophenone tetracarboxylic dianhydride, 3,3', 4,4'-diphenylsulfone tetracarboxylic dianhydride, 3,3 ', 4,4'-diphenyl ether tetracarboxylic dianhydride Anhydrous, naphthalene-
1,2,4,5-tetracarboxylic dianhydride, 3,4
9,10-Perylenetetracarboxylic dianhydride is preferred, and 6FDA is particularly preferred.

Instead of these tetracarboxylic acid dianhydrides, tetracarboxylic acid or tetracarboxylic acid dichloride having the same structure as these dianhydrides can also be preferably used.

The polyimidazopyrrolone-based polymer used in the present invention may be a copolymer containing another structure as long as it has a polyimidazopyrrolone structure as a main component, and examples of the other structure include , Polyimide, polyamide, polyhydrazide, polyoxazole, polyimidazole, polythiazole and the like. It may be a polymer obtained by polymerizing a triamine component and tetracarboxylic acid dianhydride, in which a polyimide portion and a polyimidazopyrrolone portion are alternately polymerized.

In order to produce a film comprising a polyimidazopyrrolone-based polymer, for example, a polyimidazopyrrolone precursor obtained as described above, for example, a polyamic acid having an amino residue, a polyimide having an amino residue, and an amino residue are used. A method in which a polyisoimide having a group is dissolved in a solvent to form a film in an arbitrary shape, the solvent is removed, and then polyimidazopyrrolone is formed by heating can be used.

The film formation of the polyimidazopyrrolone precursor may be carried out by any method, for example, wet spinning method, dry wet spinning method, wet coextrusion method, water surface spreading method, solvent casting method,
It can be performed by applying a coating method, an interfacial polymerization method, or the like. As an example, a solution of a polyimidazopyrrolone precursor is extruded into a gas phase from a circular nozzle by using a fluid such as air, a gas such as nitrogen or a liquid such as water or alcohol as a core material, and a gas phase. A heterogeneous film composed of the polyimidazopyrrolone precursor can be produced by a so-called dry-wet method, in which the film is soaked in a coagulating liquid after traveling for a certain distance to coagulate the film.

Further, as another example, a composite membrane is produced by applying a solution of the polyimidazopyrrolone precursor to a heat-resistant porous hollow fiber (including capillaries) and immersing it in a coagulant or drying it. You can do it. Examples of the heat-resistant porous hollow fiber include ceramics such as alumina, inorganic materials such as glass and carbon, and organic materials such as ladder-type silicon resin.

As a method of ring-closing a film made of a polyimidazopyrrolone precursor to form a film made of a polyimidazopyrrolone type polymer, for example, in an inert gas such as nitrogen, argon or helium, or in an inert atmosphere such as a vacuum. 200-4
The method of heating at 00 degreeC is mentioned. Heating time is 10
It is preferably 480 minutes, more preferably 10 to 150 minutes. Moreover, it is preferable to heat while raising the temperature in the temperature range of 200 to 400 ° C. because the treatment time can be shortened.

In order to form a gas separation membrane of the present invention by firing a membrane made of polyimidazopyrrolone polymer, the membrane made of polyimidazopyrrolone polymer is placed in an inert gas such as nitrogen, argon or helium. Or in a vacuum or the like in an inert atmosphere, as it is, at 410 to 1500 ° C., preferably 4
It may be heated to 50 to 900 ° C., more preferably 500 to 800 ° C., and fired until the gas selectivity of the film made of the polyimidazopyrrolone-based polymer is improved, so that the surface or the whole of the film is appropriately carbonized. It does not necessarily have to be performed until the entire film is completely carbonized. The firing time is preferably 10 to 120 minutes, more preferably 10 to 60 minutes. In order to obtain a film having excellent gas selectivity and gas permeability, for example, firing may be appropriately performed under the conditions of 450 to 750 ° C. and 40 to 140 minutes. It is also possible to carry out firing at 800 to 1500 ° C., preferably 800 to 1200 ° C., for a short period of time of 1 second to 10 minutes. Above all, it is preferable to perform firing while raising the temperature in the firing temperature range, since the firing time can be shortened from the viewpoint of improving productivity.

The polyimidazopyrrolone-based polymer used in the present invention may be treated with an oxidative crosslinking treatment prior to firing in the same manner as in the case of firing other ordinary organic polymers, and may also be used as a firing precursor. It is not brittle and difficult to handle like the organic polymer of, and can be easily fired after that, but due to the ladder structure of this polymer, even if it is fired as it is, sufficient strength and flexibility during firing are obtained. Easy to hold and handle,
It is preferable to calcination and carbonize as it is, without performing oxidative crosslinking treatment, because it is easily and stably carbonized.

In the present invention, the polyimidazopyrrolone precursor may be converted into a polyimidazopyrrolone and the obtained polyimidazopyrrolone polymer may be baked continuously. It is preferable in terms of reduction. That is, a film made of a polyimidazopyrrolone precursor is heat-treated at 200 to 400 ° C., and subsequently 410 to 1
It can be fired at 500 ° C. When a film made of a polyimidazopyrrolone precursor is heated while being heated to a firing temperature range of the present invention from a temperature of 400 ° C. or lower, a polyimidazopyrrolone-based polymer is produced during the temperature increase, and the polyimidazopyrrolone is subjected to a subsequent heat treatment. Since the membrane made of the system polymer is fired, the gas separation membrane of the present invention can be obtained by one step in appearance.

In the present invention, it is also possible to heat the polyimidazopyrrolone polymer and then heat it in a gas atmosphere containing an oxidizing gas such as oxygen or chlorine. Further, it is also possible to heat-treat a film obtained by firing a polyimidazopyrrolone-based polymer after contacting it with an oxidizing agent such as nitric acid or sulfuric acid. The temperature of these heat treatments is 200
The temperature is preferably 400 to 400 ° C. and the treatment time is preferably 1 to 120 minutes.

Further, when the separation active layer of the gas separation membrane produced by the method of the present invention has a communication hole or a pinhole and the separation coefficient is lowered, it is sealed with a silicone resin or the like. Is also possible.

The gas separation membrane produced by the method of the present invention is not limited in its shape and can be formed in any shape, but an asymmetric membrane or a composite membrane which can obtain a high permeation rate is preferable. Further, as the membrane shape, a hollow fiber membrane which can obtain a large membrane area with a small occupied area is preferable. The thickness of the separation active layer (dense layer) of the gas separation membrane is preferably as thin as possible, preferably 0.02 to 10 μm,
More preferably 0.02 to 1 μm, most preferably 0.
It is from 02 to 0.3 μm. The thickness of the separation active layer can be measured by observing the cross section of the film with an electron microscope. However, the separation active layer in the membrane of the present invention may have a fine porous structure that cannot be observed by an electron microscope by firing.

[0037]

The present invention will be described more specifically below with reference to examples and comparative examples.

Example 1 (Preparation of polyimidazopyrrolone) 3,3 ', in a polymerization vessel heated and dehydrated for 1 hour using a dryer under a nitrogen atmosphere.
10 mmol (2.143 g) of 4,4′-tetraaminobiphenyl (DABZ) and 25 g of the solvent N, N-dimethylacetamide (DMAC) were added, and the mixture was stirred until DABZ was completely dissolved. Then, while immersing the polymerization vessel in an ice water bath with stirring and cooling, 40 g of a DMAC solution in which 10 mmol (4.442 g) of 4,4 ′-(hexafluoroisopropylidene) diphthalic acid dianhydride (6FDA) was completely dissolved was added. Dropping into the polymerization vessel at a rate of 10 to 15 drops per minute,
After completion of dropping, the mixture was stirred for 12 hours in an ice water bath. The obtained reaction solution was filtered by suction to obtain a polyamic acid solution having an amino group. The obtained polyamic acid solution having amino groups is cast on a glass plate and dried at 60 ° C. for 6 hours to obtain a polyamic acid film having amino groups, and the film is heat-treated in a nitrogen stream at 150 ° C. for 8 hours. Thus, a polyimide film having an amino group was obtained. Further, the same film was heat-treated in a nitrogen stream at 300 ° C. for 2 hours to obtain a red polyimidazopyrrolone film. The production of polyimidazopyrrolone and its precursor was separately confirmed by infrared absorption spectrum.

(Calcination of Polyimidazopyrrolone Membrane and Gas Permeation Measurement) The obtained polyimidazopyrrolone membrane was continuously heated in a nitrogen stream at 7 ° C./min without removing from the heating furnace, and after reaching 500 ° C. When baked at the same temperature for 1 hour and carbonized, a film-like film having a thickness of 48 μm and made of a black polyimidazopyrrolone fired product having a golden metallic luster was obtained.

The gas permeation measurement results (gas permeation coefficient and gas separation coefficient) of this membrane by the ASTM-D1434 pressure method are shown in Tables 1 and 2. In addition, the measurement is the primary pressure 1
It was carried out under the conditions of atmospheric pressure and temperature of 35 ° C.

Example 2 A film having a thickness of 56 μm was obtained in the same manner as in Example 1 except that a slightly thicker polyimidazopyrrolone film was obtained in the same manner as in Example 1 and the film was baked at 500 ° C. for 2 hours. To obtain a film made of a black polyimidazopyrrolone fired body having a golden metallic luster.

Tables 1 and 2 show the gas permeation measurement results (gas permeation coefficient and gas separation coefficient) of this membrane performed in the same manner as in Example 1.

Example 3 A film having a thickness of 40 μm was obtained in the same manner as in Example 1 except that a slightly thin polyimidazopyrrolone film was obtained in the same manner as in Example 1 and the film was baked at 700 ° C. for 1 hour. To obtain a film made of a black polyimidazopyrrolone fired body having a golden metallic luster.

The gas permeation measurement results (gas permeation coefficient and gas separation coefficient) of this membrane performed in the same manner as in Example 1 are shown in Tables 1 and 2.

Example 4 A film having a thickness of 53 μm was obtained in the same manner as in Example 1 except that a slightly thicker polyimidazopyrrolone film was obtained in the same manner as in Example 1 and the film was baked at 800 ° C. for 1 hour. To obtain a film made of a black polyimidazopyrrolone fired body having a golden metallic luster.

Tables 1 and 2 show the gas permeation measurement results (gas permeation coefficient and gas separation coefficient) of this membrane performed in the same manner as in Example 1. From Table 2, it can be seen that the one treated at a high temperature is effective for separating a gas such as hydrogen having a small molecular diameter.

Comparative Example 1 In the same manner as in Example 1, a red polyimidazopyrrolone film having a thickness of 32 μm was obtained. The gas permeation measurement results (gas permeation coefficient and gas separation coefficient) of this membrane performed in the same manner as in Example 1 are shown in Tables 1 and 2 for comparison.

Comparative Example 2 A polyimidazopyrrolone film was obtained in the same manner as in Example 1, and the same procedure as in Example 1 was carried out except that this film was subjected to heat treatment at 400 ° C. for 10 hours. Almost the same red film was obtained.

Tables 1 and 2 show the gas permeation measurement results (gas permeation coefficient and gas separation coefficient) of this membrane performed in the same manner as in Example 1. For all measured gases, the permeability coefficient increased, but the separation coefficient decreased. At the heat treatment temperature of 400 ° C., no improvement in the separation coefficient is observed even after the treatment for 10 hours.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

EFFECT OF THE INVENTION A gas separation membrane having improved gas selectivity can be easily and stably manufactured.

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[Procedure amendment]

[Submission date] May 16, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

In the formula, Z ₁ and Z ₂ are tetravalent groups, and Z 1
₁ and Z ₂ are preferably aromatic, and especially Z
₁ is

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0050

[Correction method] Change

[Correction contents]

[0050]

[Table 1]

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0051

[Correction method] Change

[Correction contents]

[0051]

[Table 2]

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Claims (5)

[Claims] 1. A method for producing a gas separation membrane, which comprises firing a membrane made of a polyimidazopyrrolone-based polymer at 410 to 1500 ° C. in an inert atmosphere. 2. The method for producing a gas separation membrane according to claim 1, which is fired at 450 to 900 ° C. 3. The method for producing a gas separation membrane according to claim 1, wherein the polyimidazopyrrolone-based polymer is a polymer obtained mainly from aromatic tetraamines and aromatic tetracarboxylic acids. 4. A solvent-soluble precursor of a polyimidazopyrrolone polymer obtained by polycondensation of aromatic tetraamines and aromatic tetracarboxylic acid dianhydrides as main components is formed into a film and then heated. The method for producing a gas separation membrane according to claim 1, 2 or 3, wherein after the membrane is made of a polyimidazopyrrolone-based polymer, the temperature is subsequently raised and the membrane is fired. 5. A solvent-soluble precursor of a polyimidazopyrrolone-based polymer is a polyamic acid having an amino residue and / or
The method for producing a gas separation membrane according to claim 4, which is a polyimide having an amino residue.