JPS588514A - Preparation of composite separation film - Google Patents

Abstract

PURPOSE:To prepare a composite separation film having heat resistance and mechanical strength and excellent in gas permeation and gas separation capacities, by coating a dilute solution of an other heat resistant polymer is coated on an aromatic polyimide microporous film and the obtained coating film is dried. CONSTITUTION:On a microporous film prepared from aromatic polyamic acid or aromatic polyimide obtained by polymerizing an aromatic tetracarboxylic acid component and an aromatic diamine, a polymer solution obtained by dissolving a heat resistant polymer such as poly (2;6-diphenylphenylene oxide), polysulfone or silicone rubber (polydimethylsiloxane) in an aromatic polyimide insoluble solvent such as benzene is coated and the formed coating film is dried while gradually heated. By this method, a composite film having high separation capacity of H2 from CO can be stably prepared in good reproducibility.

Description

[Detailed description of the invention] This invention relates to an aromatic polyimide microporous membrane.

The present invention relates to a method for manufacturing a heat-resistant composite separation membrane by applying a dilute heat-resistant polymer solution consisting of the polyimide-insoluble organic solvent and another heat-resistant polymer and drying the solution.

The composite separation membrane having a polyimide microporous layer manufactured by the present invention has excellent heat resistance and mechanical strength, and has excellent gas permeability and gas separation performance.

In the past, various methods for producing polyimide separation membranes, which are heat-resistant and high-performance separation membranes, have been proposed9.
No. 9-45152 discloses that a homogeneous solution of aromatic polyamic acid is used as a dope solution for film formation, and a thin film of the dope solution is formed.

A thin film of the polyamic acid solution (dope solution) is wet-formed using a mixed solvent containing an imide cyclized composition consisting essentially of a lower aliphatic carboxylic acid and a 6th-class amine as a coagulating liquid for film formation. A method is described for producing an asymmetric polyimide membrane by coagulating the polymer by a membrane forming method and cyclizing the polymer with imide.

well known.

However, in the above-mentioned known film forming method, the film is formed by a wet film forming method by contacting with a coagulating liquid, and coagulation and imide cyclization are simultaneously performed in the coagulating liquid, making it difficult to control them. It is extremely difficult to manufacture polyimide separation membranes with good separation performance with good reproducibility. Therefore, the separation performance of gas components is unstable and varies widely, and the permeation rate of gas components is not fast enough. The problem is that this often happens.

The inventors conducted extensive research on a new method for producing a heat-resistant separation membrane that does not have the drawbacks mentioned above. As a result, a dilute solution of a heat-resistant polymer was applied to the surface of a pre-fabricated aromatic polyimide microporous membrane. It was discovered that a high-performance, heat-resistant composite separation membrane could be stably produced by coating the coating layer, drying the coated layer, and gradually removing the solvent, and completed the present invention.

That is, this invention relates to an aromatic polyimide microporous membrane.

A dilute solution of a heat-resistant polymer consisting of 100 parts by weight of an organic solvent insoluble in the polyimide and 0.01 to 7 parts by weight of a heat-resistant polymer other than aromatic polyimide or polyamic acid is applied.

The present invention relates to a method for producing a composite separation membrane, which is characterized by drying the coating layer and gradually removing the solvent.

The method of this invention is to apply a dilute solution of a heat-resistant polymer other than the polyimide (or polyamic acid) to the aromatic polyimide microporous membrane, dry the coated layer, and apply it to the surface of the polyimide microporous membrane. A heat-resistant composite separation membrane is manufactured through a simple process of forming an extremely thin layer of a heat-resistant polymer homogeneous layer (dense layer), so it is a new method that can stably manufacture a high-performance composite separation membrane with good reproducibility. It is.

In addition, the composite separation membrane produced by the method of the present invention has excellent heat resistance because it is integrally formed with a porous layer made of aromatic polyimide and a homogeneous layer (dense layer) made of heat-resistant polymer. The gas separation performance is significantly improved compared to the starting material aromatic polyimide microporous membrane, which has high strength and high strength, for example, hydrogen and monoxide. The separation performance with carbon (ratio of permeability P between hydrogen and carbon monoxide; PH!/Pco) is 4 times or more, especially 5 times or more, the separation performance (PH27PCO) of the microporous membrane. The permeation rate is also high.

The method of the present invention will be explained in more detail below.

The aromatic polyimide microporous membrane used in the method of this invention has the general formula fN<::>R<::>N-R'-) (I
) (where, R is an aromatic residue related to the aromatic tetracarboxylic acid component, and pt/ is an aromatic residue related to the aromatic diamine component). In a gas permeation test, for example, hydrogen gas permeability (PH2) is about I x 10 to 5 x
10 crA/ctA ・Sec”c@Hgl Preferably 5×10 to 1×10ctVaA-eec-crnHg
, the ratio of permeability P between hydrogen and carbon monoxide (PH2
/PC! O) is 2-25. Preferably it is about 2.5 to 20.

The aromatic polyimide microporous membrane described above is made of aromatic polyamic acid or aromatic polyimide obtained by polymerizing an aromatic tetracarboxylic acid component and an aromatic diamine component.
It can be produced by a dry film forming method or a wet film forming method using a solution uniformly dissolved in an organic polar solvent as a dope liquid.

The inventors have proposed two different methods for producing aromatic polyimide microporous membranes in Japanese Patent Application No. 55-59472 and Japanese Patent Application No. 54965-1983.
A patent application was filed as No. 56-54967 and Japanese Patent Application No. 56-54967.

These inventions generally involve polyamic acids or polyimides obtained through a polymerization reaction from an aromatic tetracarboxylic acid component and an aromatic diamine component.

in a specific mixed solvent of each polymer-soluble organic polar solvent and its respective polymer-insoluble organic polar solvent.

A polymer composition uniformly dissolved at an appropriate polymer concentration is used as a dope solution for film formation.

In this method, a thin film (flat film shape, hollow fiber shape) of the dope liquid is formed, and a dry method is performed by heating and drying, and if necessary, imide cyclization is performed to produce a polyimide microporous membrane.

In addition, the aromatic polyimide microporous membrane contains an aromatic tetracarboxylic acid component and an aromatic diamine component.

A homogeneous solution of aromatic polyamic acid or aromatic polyimide obtained by polymerization at low temperature in an organic polar solvent is used as a dope solution, and a thin film (flat film shape/hollow fiber shape) of the dope solution is formed. water.

Manufactured by forming a coagulated film of siboriamic acid or polyimide using a wet method using a lower alcohol-based coagulating liquid, drying the coagulated film, and if necessary, heating the polymer to a high temperature to imide cyclize the polymer. be able to.

Aromatic residue R that will constitute the above general formula (I)
As the aromatic tetracarboxylic acid component related to p, for example, +
313',414'-biphenyltetracarboxylic acid.

2+3+314'-biphenyltetracarboxylic acid y j
3<4,4'-penzophenonetetraluponic acid j 2
, 2-bis(314-dicarboxyphenyl)propane ν bis(3,4-dicarboxyphenyl)methane, bis(3,4-dicarboxyphenyl)sulfone, bis(
3,4-dicarboxyphenyl)needle, bis(3,
Mention may be made of 4-dicarboxyphenyl)thionidel-t-pyromellitic acid, or acid anhydrides, salts, or esterified derivatives thereof.

What about the aromatic diamine component related to group R'? For example t4
．． 4'-diaminodiphenyl ether l 3,3'-
')) 1 thyl-4,4'-diaminodiphenyl ether* 3,3'-dimethoxy-4,4'-diaminodiphenyl ether p j3'-diaminodiphenyl ether + 3.4'-Diphenyl ether diamines such as 4,4'-diaminodiphenyl ether '-Diaminodiphenylthioether* 3,3'-dimethyl-4,4'
-Diamino diphenyl thioether # Diphenyl thioether diamines such as 3,3'-diaminodiphenyl thioether 4,4'-diaminobenzophenone p 595'-dimethyl-4,4'-diaminobenzophenostone 3,3'-diaminobenzophenone, etc. benzophenone diamines such as 4,4'-diaminodipheralmethane, 3.3'-dimethoxy-4,4'-diami)diphenylmethane, and diphenylmethane diamines such as 3.3'-diaminodiphenylmethane, 2,2-
Bisphenylpropane-based cyamines such as bis-(4-amino-7ethyl)propane and 2,2-bis(6-aminophenyl)propane, 4.4'-diaminodiphenylsulfone, 3.3'-di'amino Diphenylsulfone natonosyphenylsulfone diamine, benzidine.

3.3'-dimethylbenzidine l 3,3'-dimethoxybe, thidine j 3,3'-diaminobiphenyl, or other biphenyl diamines, or 1 m + p
"-+ O-phenylenediamine, etc. can be mentioned.

In the method for producing the aromatic polyimide microporous membrane described above,
Biphenyltetracarboxylic acid or its acid anhydride as the aromatic tetracarboxylic acid component.

6 or benzophenone tetracarboxylic acid, or its acid anhydride, and a diamine compound having two benzene nuclei as the aromatic diamine component, obtained by polymerizing approximately equimolar amounts of both components. Aromatic polyimides are soluble in phenolic solvents9 such as phenolmicresol, xylenol, halogenated phenols, and non-halogenated cresols, so these solutions are used as dope solutions for film formation, and the thin film is made into a coagulating solution. Alternatively, a polyimide solution prepared by dissolving the polyimide in a mixed solvent of the above-mentioned phenolic solvent and an aromatic solvent insoluble in polyimide is used as a dope solution for film formation. A microporous membrane can be produced by a dry method.

In addition, 2. Normally, aromatic polyimides that are not substantially soluble in organic polar solvents can be obtained by uniformly dissolving polyamic acid, which is a precursor of the aromatic polyimide, in a suitable organic polar solvent. It can be used as a dope solution for solution gold film formation to produce a microporous film.

The aromatic polyimide microporous membrane used in the method of this invention does not deteriorate in permeability of gas components at a temperature of at least 200°C, and has a permeability of about 100 kg/cm.
It is preferable that the gas permeability is not deteriorated at pressures up to about rA.

The aromatic polyimide microporous membrane may have any thickness as long as it exhibits sufficient mechanical strength to withstand use, particularly from 2 to 500 μm, more preferably from 2 to 500 μm. The thickness is preferably about 5 to 300μ.

In the method of this invention, the dilute solution of heat-resistant polymer is
100 parts by weight of an organic solvent insoluble in the polyimide forming the aromatic boimide microporous membrane.

and 0 heat-resistant polymers other than aromatic polyimide or aromatic polyamic acid which is a precursor of the polyimide.
．． 0.01 to 7 parts by weight, preferably 0.05 to 5 parts by weight.

The heat-resistant polymer does not soften at temperatures below about 100'C, has gas separation performance, and is uniformly dispersed in a suitable organic solvent (a solvent in which the aromatic polyimide is insoluble) at 0.01°C. Any type of material may be used as long as it can be dissolved at a concentration of ~5N.

Examples of the heat-resistant polymer include poly(2,6-
Siphenylphenylene oxide) p poly(2,,6-dimethylphenylene oxide), polysulfone 2 silicone rubber (polydimethylsiloxane) I poly(4-vinylhyridine), 1,2-syndiocuctic polyptadiene, etc. It is possible to mention it suitably.

The organic solvent used in the heat-resistant polymer dilute solution is
A solvent that does not dissolve aromatic polyimide in an amount of 6% by weight or more, particularly 2% by weight or more.

Any type of organic solvent may be used as long as it is capable of dissolving 0.01 to 5x the above-mentioned heat-resistant polymer. In this invention, the organic solvent has a melting point of 100°C or less, particularly 80°C or less, and a boiling point (normal pressure) of 600°C.
C or less, especially 250°C or less, more preferably 200°C or less
The temperature is preferably below °C.

Examples of the solvent include aromatic hydrocarbons or their halides such as benzene, toluene, xylene, halogenated benzene, halogenated toluene, halogenated xylene, and halogenated naphthalene, methyl alcohol,
Ethyl alcohol, furoyl alcohol, methyl alcohol) L/, lower alcohols such as ethylene glycol and propylene glycol, acetone, methyl ethyl ketone, methyl isobutyl keto/, ethyl isobutyl keto/, and ketone compounds such as cyclohexane -n- xane, n-pentane, n-octane, n-
Saturated hydrocarbons such as nonane and cyclohexane + N,
N-dimethylacetamide e N,N-diethylacetamide r N+N-dimethylformamide, N,N
-Amide compounds such as diethylformamide; sulfoxide compounds such as dimethyl sulfoxide and diethyl sulfoxide; and the like.

In this inventive method, the heat-resistant polymer dilute solution may not form a stable leak-proof polymer homogeneous layer on the entire surface of the aromatic polyimide microporous membrane when the heat-resistant polymer concentration becomes too small. This is not appropriate because the gas separation performance of the separation membrane ultimately obtained will not be improved.

On the other hand, if the needle thermophilic polymer concentration becomes too large,
This is not suitable because the polymer homogeneous layer becomes thick and the ultimately obtained separation membrane has poor gas permeability.

The above-mentioned dilute solution of the heat-resistant polymer is preferably not very viscous, as long as its rotational viscosity (at 30° C.) is about 1 to 500,000 centipoise, particularly about 50,000 to 10,000 centipoise.

In this invention, the temperature at which the dilute solution of the heat-resistant polymer is applied to the surface of the aromatic polyimide microporous membrane is: - A temperature at which the solvent of the dilute solution does not evaporate and disappear rapidly; For example, 0 to 1 may be used as long as the temperature does not precipitate the partially solidified polymer.
00°C9, especially about 5 to 80°C.

The dilute solution of the heat-resistant polymer can be applied to the microporous membrane in two different ways, for example:
A method of casting a dilute solution onto the surface of a microporous membrane to coat it with a uniform thickness, and a method of spraying a dilute solution onto the surface of a microporous membrane (
Examples include a method of applying by spraying), a method of applying by contacting a microporous membrane with a roll wetted with a dilute polymer solution, and a method of applying by immersing the microporous membrane in a dilute solution. .

The thickness of the dilute solution coating layer applied to the surface of the microporous membrane as described above is about 0.1 to 200 μm.

In particular, it is preferably about 1 to 100μ, more preferably about 2 to 80μ.

In addition, prior to applying the dilute solution mentioned above, the aromatic polyimide microporous membrane was coated with lower alcohol and low molecular weight ketone p.
After immersing the membrane in a solvent such as a benzene solvent, a low molecular weight fatty acid ester, an aliphatic hydrocarbon, or an alicyclic hydrocarbon to remove the solvent only from the surface of the membrane and impregnating the inside with the solvent, The above-described coating operation is preferred because the dilute solution of the heat-resistant polymer can be applied thinly only to the surface layer of the microporous membrane.

In the method of this invention, as described above.

A heat-resistant composite separation membrane is manufactured by applying a dilute solution of a heat-resistant polymer to the surface of a microporous aromatic polyimide membrane, drying the applied layer, and gradually removing the solvent.

The above-mentioned coating layer is dried at 26-600°C2, especially at 25-200°C.
It is preferable to carry out the heating at 50°C or under heating under the flow of an inert gas, and it is not necessary to completely remove the solvent by drying the coating layer as described above. Even if a small amount remains, it is acceptable as long as the coating layer is solidified or solidified and can be used as a gas separation membrane.

In this invention, in order to gradually remove the solvent by drying the coating layer, it is preferable to dry the cicada in stages from a low temperature to a high temperature.
At a temperature of about 0°C, inert gas (e.g. dry air,
dry nitrogen gas, etc.) for 0.1 to 50 hours, especially 0.5 to 30 hours.

Air dry at 80-150°C, especially at 85-1
0.1 to 10 hours, especially 0.2 to 10 hours at a temperature of about 40°C
Heat and dry for 5 hours, if needed.

at a temperature of 150 to 600°C, especially 160 to 250°C, for about 1 to 20 hours, especially about 0.2 to 10 hours.

It is preferable to dry by heating. In the method of the present invention, the coating layer can be dried while increasing the temperature in more steps than described above.

The polyimide composite separation membrane produced by the method of this invention is an aromatic polyimide porous membrane (thickness 2 to 500 μ9
% to 500μ) and a polyimide homogeneous layer (thickness 5μ
This is a composite separation membrane in which the membranes (hereinafter referred to as 1μ or less) are integrally joined together, and the entire one-coat separation membrane is made of a heat-resistant material called aromatic polyimide, so the operating temperature when used for gas separation is It has a wide range from room temperature to about 200°C.

On the other hand, the aromatic polyimide composite separation membrane produced by the method of the present invention showed excellent results in gas permeation tests.

It has excellent gas permeation rate and gas separation performance at the same time.For example, hydrogen gas permeability (PHZ) is 5 x 1.
0-' ah/crll ・BeC・cmHg or more, and the separation performance between hydrogen and carbon monoxide (PH2/POO
) is high at 25 or more.

Reference examples and examples will be shown below.

In the example, the gas permeation test was performed on two areas 14.65-
A separation membrane is installed in a stainless steel cell to remove hydrogen.

- Carbon oxide is pressurized to 065 to 1/cIA, respectively, to 2
The amount of gas passing through the separation membrane was measured with a flowmeter.

The permeability of each gas was calculated using the following equation.

2 The separation performance of the separation membrane is determined by the ratio of hydrogen permeability (PHz) to -carbon oxide permeability (pco) (PH2/POO
).

Reference Example 1 3; 3', 4'-Pifue megatetracarboxylic dianhydride 40 mmotl a, 4'-diaminodiphenyl ether 40 mm0L and parachlorophenol 1
65 tons was placed in a rubber flask equipped with a stirrer and a nitrogen gas inlet pipe, and the mixture was heated for 1 hour while flowing nitrogen gas.
The reaction solution was heated from room temperature to 180°C in about 50 minutes,
Further, the reaction solution was held at 180°C for 8 hours to perform 9 polymerization and imide cyclization in one stage to obtain a viscous polyimide solution.

The polyimide solution has a polymer concentration of 10% by weight, a polymer imidization rate of 95% or more, and a polymer logarithmic viscosity (50°C 20,5f/100% parachlorophenol) of 2.2. there were.

Polyimide solution prepared as described above.

A thin liquid film with a thickness of 0.2 cm was formed by casting on a glass plate at 25°C, and the liquid thin film was immersed in a methanol coagulation solution at room temperature (25°C) for about 20 hours to solidify it. Form a coagulated film, remove the coagulated film from the methanol coagulation solution,
Further, the coagulated film was immersed in n-hexane at 25°C for 20 hours, and then air-dried for 5 hours at 25°C under air circulation.
Next, dry at 100°C for 1 hour, and then dry at 200°C for 6 hours.
Heat treated for some time.

A polyimide porous membrane was obtained.

The polyimide porous membrane has a thickness of about 25 μm and 2
Hydrogen permeability (P) by gas permeation test at 5°C
H2) is 7.1 sentences 10′″” ” / m” 8 e
Q, c@11 g, and the hydrogen to carbon monoxide permeability ratio (PHa/pao) was 2.8.

Example 1 The aromatic polyimide microporous membrane obtained in Reference Example 1 was made of poly(2,6°-biphenylphenylene oxide [logarithmic viscosity (25°C, 0.5r/100 dichloroform) of 0.93]. The microporous membrane was immersed in a dilute solution of a heat-resistant polymer dissolved in benzene at a concentration of 1% by weight at 25°C for 20 minutes, the dilute solution was applied to the microporous membrane, and the coated membrane was exposed to air. A composite separation membrane was manufactured by air drying at 25° C. for 15 hours under continuous flow.

Table 1 shows the results of a gas permeation test conducted on the composite separation membrane at the temperatures shown in Table 1.

Note that after continuing to flow carbon oxide through the composite separation membrane at 100° C. for 10 hours, a gas permeation test was conducted again, and there was no decrease in gas separation performance.

Example 2 Same as Example 1 except that a dilute solution in which silicone rubber (manufactured by Dow Corning, trade name: Sylgard 184) was dissolved in benzene at a concentration of 1.1% by weight was used as the dilute solution. A composite separation membrane was manufactured.

Table 1 shows the results of the gas permeation test for the composite separation membrane.

In addition, the composite separation membrane was heated to 98°C with 10% carbon monoxide.
I did a gas permeation test after running it for a while.

There is no decrease in gas separation performance.

Reference Example 2 A 25% by weight dimethylformamide solution of polysulfone (manufactured by NCC Co., Ltd., Bo!j Sulfone P-35-00) was cast onto a glass plate at 25°C to a thickness of 0.211 mm.
1II was formed, and the liquid thin film was added to a coagulating solution of an aqueous solution containing dimethylformamide at a concentration of 2% by weight and diuryl sulfate sodium salt at a concentration of 0.5% by weight at 25°C for 20 hours. After soaking for an hour, coagulating, and washing the coagulated film with water.

Air dry at 25°C for 20 hours under air circulation, then dry for another 10 hours.
A p-polysulfone porous membrane was prepared by heat treatment at 0°C for 30 minutes.

The polysulfone porous membrane has a hydrogen permeability PH of 6J x 10 cIA/crA・ee at 25°C.
c・3Hg, and the ratio of permeability between hydrogen and carbon monoxide (
paw/PCO) was 3.7 Comparative Example 1 The polysulfone porous membrane (Reference Example 2) was prepared in a dilute solution in which the silicone rubber used in the example was uniformly dissolved in erigroin at a concentration of 1% by weight. To.

The dilute solution is applied to the porous membrane by soaking at 25°C for 20 minutes, and the coated film is soaked at 25°C for about 15 minutes under air circulation.
A composite separation membrane was prepared by air drying for 1 minute.

Table 1 shows the results of the gas permeation test for the composite separation membrane.

In addition, after continuing to flow carbon oxide through the composite separation membrane at 98°C for 10 hours, a gas permeation test was conducted again, and as a result, the hydrogen permeability PH was 2. IX 10cIA/-
・sec"cm)Ig, and the hydrogen to carbon monoxide permeability ratio (P)l,/PCO) was 9.5.

Table 1 Example 3 Example 3 except that a dilute solution in which poly-4-vinylpyridine (average molecular weight approximately 100,000) was uniformly dissolved in methanol at a concentration of 4.7% by weight was used. A composite separation membrane was manufactured in the same manner as in Example 1. As a result of the 25° CO gas permeation test, the composite separation membrane showed a hydrogen permeability of i,
ox 1o-'aA/-・sec'm)Ig, hydrogen to carbon monoxide permeability ratio (PH2/PO
O) was 23, and its performance remained almost unchanged up to 100°C.

Patent applicant Ube Industries Co., Ltd.

Claims (1)

[Claims] A microporous aromatic polyimide membrane. 100 parts by weight of the polyimide-insoluble organic solvent;
A dilute solution of a heat-resistant polymer consisting of 0.01 to 7 parts by weight of a heat-resistant polymer other than aromatic polyimide or polyamic acid is applied. A method for producing a composite separation membrane characterized by drying the coating layer and gradually removing the solvent.