JPS588512A - Preparation of polyimide separation membrane - Google Patents

Abstract

PURPOSE:To make it possible to coagulate a polymide film at a high speed even by using a coagulating bath based on water by using a dihydric phenol compound as a solvent for a biphenyltetracarboxylic aromatic polymide. CONSTITUTION:An aromatic polyimide obtained from a biphenyl-tetracarboxylic acid component and an aromatic diamine component is dissolved in a dihydric compound such as pyrocatechol, resorcinol or hydroquinone in a range of 6- 30wt% and the obtained solution is heated at 80-200 deg.C to prepare a film forming dope. From the obtained dope of a polyimide composition having repeating units shown by the formula, a liquid thin film is formed and, after part of the phenol compound is evaprated from one surface thereof, the dried film is coagulated in water alone or in a coagulating bath containing 70wt% or more of water. By this method, compared to a conventional method using a monohydric phenol compound, a sufficiently developed porous layer can be formed by using water as a coagulating liquid. In the formula, R is a divalent aromatic residue derived from a aromatic diamine.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to biphenyltetracarboxylic acid components such as +3t3,4*4'-biphenyltetracarboxylic acids and t3t3'g4'-biphenyltetracarboxylic acids.

The aromatic polyimide obtained from the aromatic diamine component represented by the general formula H, N-R-NH, (R is an aromatic residue) is a phenolic compound whose main component is a divalent phenol compound. The present invention relates to a method for producing a polyimide separation membrane by using a polyimide composition dissolved in a melted liquid, forming a liquid thin film of the composition at high temperature, and coagulating the thin film with a coagulating liquid.

Conventionally, as shown in JP-A-56-21602, an aromatic polyimide obtained from a biphenyltetracarboxylic acid component and an aromatic diamine component has been used to produce a phenolic compound such as phenol or its halogenated phenol. A polyimide semipermeable membrane is produced by using a composition dissolved in a molten liquid of a compound to form a liquid thin film of the composition, and then immersing the thin film in a coagulating liquid to solidify it. The method was well known.

However, in known polyimide compositions, the specifically indicated solvent is a monohydric phenol and its -
In these compositions, when a non-polluting water-based solvent is used as a coagulation liquid, the coagulation rate is slow and a porous layer does not develop sufficiently. However, there was a tendency for a dense layer to develop, and in extreme cases, coagulation itself took a long time, and the resulting polyimide membrane did not have sufficient permeability.

The inventors have developed a method for producing an aromatic polyimide separation membrane that can solidify at a sufficiently high rate and form a well-developed porous layer even when using a coagulating liquid mainly composed of water. As a result of extensive research, we have discovered that using a polyimide composition in which a biphenyltetracarboxylic acid-based aromatic polyimide is dissolved in a phenolic solvent containing dihydric phenol as the main component, a liquid thin film of the composition was formed. If the thin film is formed and coagulated with a coagulating liquid mainly composed of water,
This invention was completed after discovering that a polyimide separation membrane with a sufficiently developed porous layer could be obtained.

In other words, this invention.

(However, R is a divalent aromatic residue excluding the amine group of an aromatic diamine.) A polyimide having 90 or more repeating units represented by the formula (R is a divalent aromatic residue excluding the amine group of an aromatic diamine) has a divalent phenol compound of 45
Using a polyimide composition that is dissolved in the melt of a phenolic compound containing more than % by weight! The present invention relates to a method for producing a polyimide separation membrane, which comprises forming a thin film of the polyimide composition at a temperature higher than that at which the composition can maintain its liquid state, and then immersing the thin film in a coagulating liquid to coagulate it.

Alternatively, it is possible to obtain a membrane with a high gas permeation rate, and use pollution-free water that has no effect on the human body, or a coagulating liquid containing 70% by weight or more of water, to create an aromatic fragrance with a sufficiently developed porous layer. Porous membrane of group polyimide,
Alternatively, asymmetric membranes can be produced.

A polyimide composition obtained by the method of this invention.

Gas separation due to the well-developed porous layer.

When used for liquid separation, etc., the permeation rate of each component is increased.

The polyimide separation membrane obtained by the method of this invention has chemical resistance,
Heat resistance 9 Mechanical properties are as good as those of conventionally known polyimide separation membranes.

This invention will be explained in more detail below.

In this specification, the imidization rate is a value used to quantitatively indicate the degree of imidization of aromatic polyimide, and refers to all bonding moieties (monomeric The imidization rate is 100 when the bonding part (bonding part between bodies) becomes an imide bond, and when there is no imide bond at all (for example, when there is only an amide-acid bond), the imidization rate is 0. This is the value for which it is assumed that In other words, the imidization rate is the percentage of imide bonds present in all bonds ψ between monomers of a polyimide polymer. Measurement of imidization rate.

This is done using infrared absorption spectroscopy.

The repeating unit represented by the polyimide used in the method of this invention (wherein R is a divalent residue of an aromatic diamine excluding the amine group represented by the general formula H, NR-NH) , a melt of an aromatic polyimide having dihydric phenol as its main component in the main chain of the polymer at a ratio of 90% or more, preferably 95% or more to the total structural units. It can be dissolved in

The above aromatic polyimide is heated at 30°C2 concentration 0.5f/
The logarithmic viscosity measured with a 100% solvent (a mixed solvent of 4 volumes of parachlorophenol and 1 volume of orthochlorophenol) is 0.3 to 7.0. Especially from 0.4. 5.0. 0 more
．． A wide range of values from about 5 to 4.0 can be used.

The aromatic polyimide has 3.3?4.4'-biphenyltetracarboxylic acid component + 2@3t314'
- Obtained from a biphenyltetracarboxylic acid component such as a biphenyltetracarboxylic acid component and an aromatic diamine component represented by the general atmosphere H, N -R-NH2 by a polycondensation reaction and an imidization reaction (imide cyclization reaction) Any aromatic polyimide produced by any known method may be used.

The method for producing the aromatic polyimide used in the method of the present invention is, for example, by combining the biphenyltetracarboxylic acid component and the aromatic di,amine component with N-methylpyrrolidone, pyridine, N,N-dimethylacetamide, Approximately equimolar amounts of about 8
Condensation polymerization occurs at a temperature of 0°C or lower, especially 0 to 60°C, and the logarithmic viscosity (IN-methylpyrrolidone at 30°C9 concentration of 0.5f/100) is 0.3 or higher, especially 0.5 to 7. Manufacture a certain polyamic acid.

Add a tertiary amine compound such as trimethylamine, triethylamine, or pyridine, or an imidization accelerator such as acetic anhydride, sulfone dichloride, or carbodiimide to a solution of the polyamic acid in an organic polar solvent (the reaction solution may be used as is). and imidize at 5-150°C, or without adding an imidization accelerator, the polyamic acid solution at 100-300°C, preferably 120-150°C.
When heated to 250°C, the imidization rate of the polymer was 90
A method in which the aromatic polyimide powder is precipitated and isolated by imidization to obtain a polyimide of 100% or higher is very suitable.

In addition, as a method for producing aromatic polyimide, logarithmic viscosity (30°C90,5+710
0ml solvent) to a solution of polyamic acid of 0.5 or more,
Add a large amount of acetone or alcohol to precipitate the polyamic acid powder, or add a precipitant while removing the solvent from the polyamic acid solution to precipitate the polyamic acid powder. isolated.

This polyamic acid powder was heated at 150 to 300°C, especially at 1
Heat to 60-250°C and imidize the polymer until the imidization rate reaches 90 degrees or higher.

Mention may be made of methods for producing polyimide.

Furthermore, as a method for producing aromatic polyimide, 9 e.g.
2 +3 t3'4'- and/or 3. Showa 4, 4
'-biphenyltetracarboxylic acid component and the general formula H2N
and an aromatic diamine represented by -R-NH2.

In the melt of phenolic compound, 120-400°C
2.T polyimide can also be produced by polycondensation and imidization in one stage, especially at 150 to 300°C. In this one-stage method, a polyimide composition of polyimide and a phenolic compound containing 9 divalent or phenol as a main component, which can be used in the method of the present invention, is directly obtained, and the reaction mixture is directly produced. It is optimal because it can be used as a dope solution for membranes.

2. Reel used in each of the above-mentioned aromatic polyimide manufacturing methods.
3.3',4'-biphenyltetracarboxylic acid component.

As a tetracarboxylic acid component such as L3't4,4'-biphenyltetracarboxylic acid component, + 3 + 3'
+ 414'-biphenyltetracarboxylic dianhydride (
(hereinafter sometimes abbreviated as 5-BPDA), and 2
・334-biphenyltetracarboxylic dianhydride (hereinafter sometimes abbreviated as ta-BPDA) is preferable, but t
2,3.3ζ4'-also ii 3+314,4'-
Biphenyltetracarboxylic acid, or * 2+3+
It may also be a salt of 3', 4'- or 3+3r414'-biphenyltetracarboxylic acid or an esterified derivative thereof. The biphenyltetracarboxylic acid component may be a mixture of the above-mentioned tetracarboxylic acids.

In addition, the above biphenyltetracarboxylic acid component is the above-mentioned 2.3.3ζ4'- or 3 +3't4 +4'-
In addition to biphenyltetracarboxylic acids, pyromellitic acid *'y3'+41
4'-benzophenonetetracarboxylic acid? 212-
his(3,4-dicarboxyphenyl)propane, bis(3,4-dicarboxyphenyl)sulfone, bis(3
ν4-dicarboxyphenyl)ether, bis(3,4
-Contains tetracarboxylic acids such as (dicarboxyphenyl)thioether, butanetetracarboxylic acid, or its acid anhydride, salt, or esterified derivative in a proportion of 10 molti or less, especially 5 molti or less, based on the total tetracarboxylic acid component. You may do so.

The aromatic diamine component represented by the general formula H, NR, -NH, used in the above-mentioned method for producing an aromatic polyimide resin is 2, for example, the general formula (however, in each of the above general formulas, l R3 or R4 is a substituent such as hydrogen, lower alkyl, or lower alkoxy, and A is -o-, -s
-, -cO, -5O2+.

Aromatic diamine compounds represented by divalent groups such as -S O-, -Cj R2-, -C(OR3)2-, etc.) are preferred.

There are two examples of aromatic diamine compounds represented by
4+4'-diaminodiphenyl ether, 3,3'-
Dimethyl-4,4'-diaminodiphenyl ether.

3.3'-dimethoxy-494'-diaminodiphenyl ether + 3.3'-diaminodiphenyl ether + 3 + diphenyl ether diamine I such as 4'-diaminodiphenyl ether 414'-diaminodiphenylthioether + 313'-dimethyl-4,4'-
Diaminodiphenylthioether j313'-dimethoxy-44'-diaminodiphenylthioether? 3
．． Diphenylthioether compounds such as 3'-diaminodiphenylthioether, 4,4'-diaminobenzophenone t 3+benzophenone compounds such as 3'-dimethyl-4,4'-diaminobenzophenone + 3t
3'-diaminodiphenylmethane + 4+4'-diaminodiphenylmethane I 3+3'-dimethoxy-4
, 4'-diaminodiphenylmethane, 3'-dimethyl-4,4'-diaminodiphenylmethane and other diphenylmethane compounds.

2,'-His(4-aminophenyl)propane.

2. Bisphenylpropane compound of 2-his(3-aminophenyl)propanato + 4+4'-diaminodiphenyl sulfoxide? Examples include 4'-diaminodiphe=IL;s/l/phone+3+3'') aminodiphenyl sulfone.

Examples of the aromatic diamine compound represented by the general formula include 9, for example, pentidine + 313'-dimethylbenzidine.

Examples include 3.3'-dimethoxybenzidine and 3.3'-diaminobiphenyl.

As the aromatic diamine compound represented by the aforementioned general formula) 12N-R1-NR2, in particular, ta, 4/-diaminodiphenyl ether + 4t4'-diaminodiphenylthioether, 4,4'-diaminodiphenylmethane.

Bentidine, 3.3'-dimethoxypentidine 1
One or more aromatic diamines selected from the group consisting of 3j3'-dimethylbenzidine are preferred.

However, as an aromatic diamine, 414'-diaminodiphenyl ether alone or 4,4'-diaminodiphenyl ether and other aromatic diamines (e.g., para-phenylene diamine, meta-phenylene diamine m
4t4'-diaminodiphenylthioether t 41
4'-diaminodiphenylmethane e 3t3'-dimethyl-4,4'-diaminodiphenyl ether t3.3
'-dimethylpentidine, pentidine t-pentidine sulfone, etc.) (at least 4,4'-diaminodiphenyl ether is added to the fully aromatic diamine component).
The optimum content is 0 molti or more, particularly preferably 50 molti or more.

The phenolic compound for dissolving the aromatic polyimide in the method of this invention is a divalent phenol compound 9, for example, 1,2-dihydroxybenzene (pyrocatechol), 1t3-dihydroxybenzene (resorcinol).
91y4-dihydroxybenzene (hydroquinone),
Or the mixture thereof is 45% by weight or more, especially 50% to
It is a phenolic compound containing 100% by weight.

Among the phenolic compounds, other phenolic compounds used together with the divalent phenol compound include 1, for example, phenol, 0-.

monohydric phenolic compounds such as m- or p-cresol, 3.5-xylenol carvacrol, thymol;
Or halogenated phenols in which hydrogen in the benzene nucleus of these -valent phenol compounds is replaced with halogen, such as P-chlorophenol, 0-chlorophenol,
m-Chlorphenol*P, fromphenol go
-Bromphenol t 2-chloro-4-hydroxytoluene, 3-chloro-6-hydroxytoluene, etc. can be mentioned.

In the method of this invention, the dihydric phenol compounds include pyrocatechol and resorcinol! A mixture of pyrocatechol and resorcinol.

A mixture of pyrocatechol and hydroquinone, etc.
Polyimide composition (solution) stable at temperatures above 00°C
It is suitable because it can obtain the following.

In the method of the present invention, as described above in the production of polyimide, a biphenyltetracarboxylic acid component and an aromatic diamine component are added to a melt of a phenolic compound containing 45% by weight or more of the dihydric phenol compound. When producing polyimide by polymerizing and imidizing in one stage at about 120 to 400°C, the mixed liquid obtained by the polymerization reaction is adjusted to adjust the polyimide concentration or solution viscosity as necessary. After adjustment, it can be used immediately as a polyimide composition for film formation.

However, when polyimide is isolated as a powder in the production of polyimide, the polyimide composition used in the present invention contains 45% of the dihydric phenol compound.
Polyimide powder is mixed and dispersed in a melted solution of a phenolic compound containing at least % by weight, and the mixed dispersion is sufficiently heated to completely and uniformly dissolve the polyimide powder.

It can be prepared.

In the method of this invention, ν is used as the polyimide composition.
A composition containing two or more types of polyimides represented by the above general formula can be used.

Furthermore, it is also possible to use a composition containing the polyimide represented by the above general formula and other aromatic polyimides.

In the method of this invention, the concentration of the total polyimide contained in the polyimide composition is 5% by weight based on the total composition.
Above, especially 6 to 30% by weight, more preferably 8 to 25% by weight
It is preferably within the range of % by weight. Further, the temperature of the polyimide composition during film formation is within the range of about 50 to 200°C.

Especially when the rotational viscosity is 1000 centipoise or more.

It is preferable that the composition becomes a uniform liquid composition of about 100 to 100,000 poise, more preferably about 500 to 10,000 poise, and can be used as a dope solution for film formation.

In the method of this invention, the above-mentioned polyimide composition is
At least the temperature at which the composition becomes liquid, preferably 50°
C or above, especially 80 to 200°C, and use it as a dope solution for film formation, and form a liquid thin film (for example, a flat film, hollow fiber, or tubular thin film) from the dope solution of the polyimide composition. , at least the temperature at which the composition becomes liquid, preferably at least 50°C.

In particular, it is formed at a temperature of 100 to 200°C.

The thin film is immersed in a coagulating solution and coagulated to produce a polyimide separation membrane.

In the method of the present invention, it is preferable to use a suitable known filter to remove solid matter from the liquid polyimide composition or to sufficiently degas it to obtain a dope solution for film formation.

How to form a liquid thin film from a dope solution of a polyimide composition! It can be carried out by a method similar to a conventionally known casting film forming method.9 For example, the dope solution of the polyimide composition is cast on the surface of a planographic base material (glass plate, copper plate, etc.) with a smooth surface9. Next, a method of forming a liquid thin film with a uniform thickness using a doctor blade, or - supplying the dope solution of the polyimide composition onto the surface of a roll with a smooth outer peripheral surface and uniformly forming it with a doctor knife provided close to the roll surface. A continuous film forming method can be employed, such as forming a thin film by casting to a certain thickness, or extruding the polyimide composition into a thin film from a T-die and winding it around the surface of a roll to form a thin film. In the method of this invention, the temperature of the dope solution of the polyimide composition during film formation should be set to a temperature that provides an appropriate rotational viscosity for film formation, depending on the relationship between the rotational viscosity of the polyimide composition and temperature. Yes, but preferably at 80°C
As mentioned above, it is particularly preferable that the temperature is within the range of about 100 to 200°C, and the temperature range of 105°C to 180°C is optimal. Furthermore, the thickness of the liquid thin film formed as described above is 10 to 500μ, particularly 20 to 300μ.
It is preferable that it be about the same level.

The liquid thin film formed as described above can be obtained by partially evaporating the phenolic compound from one side of the liquid thin film while forming the liquid thin film or after forming the liquid thin film. This is preferred because an asymmetric thin film is effectively formed by solidification.

The method of partially evaporating the phenolic compound from one side of a liquid thin film is to evaporate a portion of the phenolic compound from one side of the liquid thin film on the lithographic plate or roll circumferential surface.
A method of spraying a gas at 80°C or higher, especially 100 to 200°C for 5 seconds to 200 minutes, especially 10 seconds to 100 minutes is preferable, but it is preferable to heat the liquid thin film on the lithographic plate or roll circumference ( 50 to 120°C) and left in a reduced pressure atmosphere for 0.5 to 100 minutes, particularly 1 to 50 minutes.

In the method of this invention, the coagulating liquid used to coagulate the polyimide liquid thin film formed as described above may be any liquid as long as it is freely mixed and compatible with the divalent phenol compound. 2 For example, water, lower alcohols such as methanol, ethanol, and propatool, aromatic hydrocarbons such as benzene, toluene, and xylene,
Saturated hydrocarbons such as n-hexane, n-hefrotane, and n-octane; ketones such as acetone, methyl ethyl ketone, diethyl ketone, and methyl propyl ketone.

Ethers such as tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, amides such as dimethylacetamide and dimethylformamide, dimethyl sulfoxide, etc., or mixtures thereof;
In particular, a mixture of water and the above-mentioned alcohols, ketones, ethers, and amides can be mentioned.

In the present invention, the coagulating liquid may be, in particular, water alone or a solution containing 70% by weight or more, particularly 80% by weight or more of water.

In the method of this invention, a solution containing 70 to 100% by weight of water can be used as a coagulating liquid to coagulate a thin film of a polyimide composition.

In particular, a composition of parachlorophenol solvent and polyimide could not be coagulated in a short time using a coagulating solution of water, and the resulting polyimide separation membrane did not have sufficient permeation performance. In this invention, a thin film of a polyimide composition is used.

It is a coagulating liquid mainly composed of water, which can be coagulated in a short time, and the resulting polyimide separation membrane has excellent permeability.

Therefore, in the method of the present invention, a polyimide film can be coagulated without using a large amount of an organic solvent such as alcohol, ketone, or ether as a coagulating liquid, making it extremely safe.

In the method of the present invention, a liquid thin film of a polyimide composition is coagulated with the above-mentioned coagulating liquid.

Any known method may be used to form a thin film (
It is preferable that the liquid thin film of the composition is immersed in the coagulating liquid together with the base material being cast (casting), and that the temperature of the coagulating liquid is about 0 to 150°C, especially about 0 to 100°C. is preferable, and the thin film immersed in the coagulation liquid is preferably 0 to 0.
The temperature is preferably about 150°C, particularly about 0 to 100°C. The time for which the thin film is immersed in the coagulation solution as described above varies depending on the type of polyimide composition, the type of coagulation solution, and other conditions, but generally +-o, o 5 to 20 hours, It is sufficient if it is about 0.1 to 10 o'clock.

The membrane solidified from the liquid thin film as described above already has a porous layer with sufficient properties as a semipermeable membrane, but it is further coated with methylalcohol, -ruethylalcohol, fluorocarbon, etc. Soak in lower alcohol such as pill alcohol at 0 to 50°C for about 0.5 to 10 hours,
and/or in ion-exchanged water at 0-50°C.
It is preferable to carry out a post-treatment of soaking for ~10 hours and washing and removing residual phenolic compounds in the coagulated membrane.

If necessary, the above-mentioned coagulated film is placed in hot water heated to 50-150°C2, especially 60-120°C, for 1-120°C.
The heat treatment may be carried out by immersion for 5 to LO minutes. Generally, when the above-mentioned heat treatment with hot water is performed, the salt rejection rate of the resulting semipermeable membrane is improved.

Thermal stability is also improved.

The polyimide separation membrane obtained by this invention can be produced as described above! A thin film of the polyimide composition is coagulated with a coagulating liquid,
After washing, heat treatment, etc.

Dry the wet separation membrane using an appropriate method.

Dried polyimide separation membrane (porous membrane, asymmetric membrane,
Hollow fibers, flat membranes, etc.) are obtained, and the dried separation membrane can be used as a gas separation membrane for separating and concentrating gas mixtures.

Next, examples and comparative examples will be shown.

Reference Example 1 40 mmol of 313?414'-biphenyltetracarboxylic dianhydride and 40 mmol of 4,4'-diaminodiphenyl ether were combined with 70 mmol of dimethylacetamide.
The mixture was placed in a separable flask equipped with a stirrer and a nitrogen gas inlet tube, and nitrogen gas was passed through it. Polyamic acid was polymerized at a temperature of 20°C for 5 hours while stirring. , the polymerization solution was cooled to below 10°C, and dimethylacetamide 7011 was added to the polymerization solution. /l Add 240 mmol of acetic anhydride and 240 mmol of pyridine and stir thoroughly to make the polymerization solution uniform. 2. Gently raise the temperature of the polymerization solution and hold at about 30°C for 20 minutes to separate polyimide from the polymerization solution. was precipitated in powder form, and the polymerization solution was further heated to 70 to 80°C and maintained at that temperature for 30 minutes or more to complete imidization.

The polyimide powder of the polyimide composition obtained as described above was collected by filtration, thoroughly washed with methanol, and then dried under reduced pressure to obtain polyimide powder.

The polyimide powder has an imidization rate of 95 degrees or more and a logarithmic viscosity (30°C, 0.5?/1'OOmA! solvent.

Reference Example 2 where the solvent (mixture of 4 volumes of parachlorophenol and 1 volume of orthochlorophenol) is 1.9.
~19 Polyimide obtained in Reference Example 1 0.459. and phenolic compounds of the types shown in Table 1.4. As a result of heating Of above the melting point of each phenolic compound, a homogeneous solution was prepared. Table 1 shows the temperature at which each solution stably exhibits a liquid state, and the temperature at which each solution solidifies when left alone.

Each of the polyimide compositions obtained as described above has a solution viscosity of approximately 1,000 to 50,000 poise at a stable temperature at which solidification does not occur as shown in Table 1, and is suitable for use as a dope for film formation. It could be used as a liquid. Cast each dope solution onto a glass plate at a temperature higher than that at which it becomes a uniform solution,
A homogeneous transparent imide film was obtained by heating at 200°C for 5 hours.

Table 1/117) Examples 1 to 3 The polyimide solution composition obtained in Reference Example 12 was
'(:') to form a thin film of 0.1 thickness on a glass plate.The liquid thin film was heated with hot air (air) at the temperature shown in Table 2 for the time shown in Table 2. Dry the surface with hot air9
Next, the coagulated membrane (semipermeable membrane) was immersed in a coagulating solution of water at the temperature shown in Table 2 for 1 hour to coagulate it, and the coagulated membrane (semipermeable membrane) was washed with methanol and further purified with water to form a polyimide separation membrane (wet membrane). state) was manufactured.

The polyimide membrane was subjected to the following solution permeation test. The solution permeation test.

Two separation membranes were installed in a reverse osmosis membrane testing device, and an aqueous sodium chloride solution with a concentration of 0.5% by weight was supplied.

Reverse osmosis operation was performed at 20°C under a pressure of 40 kg/lfl, and the water transport overrate Flux was determined in the unit -/rr? - Shown in days.

In addition, the salt rejection rate Rj in the above reverse osmosis operation is
It is expressed as the rejection rate of IJum chloride calculated from the ratio (C/CO) of the sodium chloride concentration C in the permeated water to the sodium chloride concentration CO in the raw water using the following formula.

Rj = (1--) x 1o ochiC〇 The results of the above solution permeation test are shown in Table 2.

Also! The wet polyimide separation membrane obtained as described above was immersed in methanol at 25°C for 2 hours, and then immersed in cyclohexane at 25°C for 3 hours.
The separation membrane was dried at 100''C for 1 hour, and then heated at 200''C for 2 hours to obtain a dry polyimide separation membrane.

The dry separation membrane was subjected to the following gas permeation test. The gas permeation test shows that the membrane area is 14.65-
The aforementioned separation membrane was installed in a stainless steel gas permeation cell, and hydrogen and carbon oxide were supplied under pressure of 0.5~/cIA, and the amount of gas passing through the separation membrane at 30°C was adjusted to The permeability of each gas was calculated using the following formula.

The permeation separation performance is determined by the ratio of permeability between hydrogen and carbon monoxide (
PH2/Pco).

The results of the gas permeation test are shown in Table 2.

Table 2 Comparative Examples 1-2! 0.45 f of the polyimide obtained in Example 1 and parachlorophenol 4. Of was heated above 8°0°C to prepare a homogeneous solution of the polyimide composition. The polyimide composition was capable of stably maintaining a uniform solution at 30°C or higher.

Except for using the above polyimide composition, the same procedure as in Example 1 (Comparative Example 1) or Example 2 (Comparative Example 2) was carried out.
Film formation was carried out in the same manner as above.

The liquid thin film of the polyimide composition was hardly solidified, and a solidified film could not be formed.

Examples 4-5 Polyimide was dried in the same manner as in Example 1, except that the polyimide composition of Reference Example 2 (Example 4) or the polyimide composition of Reference Example 19 (Example 5) was used. A separation membrane was manufactured. Table 6 shows the results of the gas permeation test for the 9 separation membranes.

Comparative Example 3 Polyimide obtained in Reference Example 1 0.45 f+ pyrocatechol 1.52 and balachlorfe/-ol 2,
52 was heated to prepare a homogeneous solution of the polyimide composition. A dried polyimide film was produced in the same manner as in Example 1 except that the polyimide composition was used. The results of the gas permeation test are shown in Table 5. Table 3 Examples 6 to 8 Polyimide solution composition obtained in Reference Example 2.

It was cast onto a glass plate at 120°C to form a liquid thin film with a thickness of 0.2B. The liquid thin film was dried with hot air (air) at 120°C for 3 minutes on the film surface.

Next, the coagulated membrane (semipermeable membrane) was immersed at 0°C for 1 hour in a coagulating solution of the type shown in Table 4 to coagulate, and the coagulated membrane (semi-permeable membrane) was heated at 25°C.
A polyimide separation membrane (wet state) was prepared by washing with methanol and then with water.

Table 4 shows the results of the solution permeation test for the separation membrane.

Comparative Example 4 The same polyimide composition as in Comparative Example 1 was used, but
Film formation was performed in the same manner as in Example 7.

With the coagulation time (1 hour) of Example 7, a sufficiently coagulated film could not be obtained.

Table 4 Examples 9 to 10 As a coagulation liquid, a mixture of 0°C methanol and water (water:methanol=so:5o) (Example 9) or Oo
A dried polyimide separation membrane was produced in the same manner as in Example 1, except that methanol C (Example 10) was used. Table 5 shows the results of the gas permeation test for the separation membrane.

Example 11 The polyimide composition of Reference Example 4 was cast on a glass plate at 170°C to form a liquid thin film.

Example 6 except that 80°C water was used as the coagulation liquid.
A dried polyimide separation membrane was produced in the same manner as above. Table 5 shows the results of the gas permeation test for the separation membrane.

In addition, in the same manner as in Example 1, using any of the polyimide compositions of Reference Examples 3, 5 to 11, and 13 to 18,
Film formation is performed to obtain polyimide separation membranes, which are
It had the same transmission performance as Example 1.

Claims (1)

[Scope of Claims] (However, R is a divalent aromatic residue excluding the amide group of an aromatic diamine.) Polyimide having 90% or more of repeating units represented by: Using a polyimide composition dissolved in a melt of a phenolic compound containing at least % by weight, a thin film of the polyimide composition is formed at a temperature higher than that at which the composition can maintain its liquid state. A method for producing a polyimide separation membrane, which comprises then immersing the thin film in a coagulating solution and coagulating it.