JPH0636858B2 - Pervaporation separation method of organic compound mixture - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a heat-resistant asymmetric separation of an organic compound mixture solution such as an organic solvent solution in which an organic compound is dissolved, which is composed of a specific soluble aromatic polyimide. By directly contacting with the membrane, at least one organic compound in the mixture of organic compounds is selectively permeated and permeated through the asymmetric separation membrane to selectively permeate the asymmetric separation membrane. A method for pervaporation separation of an organic compound mixture liquid for separating and recovering the organic compound as vapor (pervaporation method)
Pertain to.

[Description of Prior Art]

Conventionally, a distillation method has been known as a method of separating an organic compound mixed liquid into each component. However, it has been extremely difficult to separate an azeotropic mixture, a near-boiling mixture, or an organic compound that easily undergoes a chemical change by heat by the distillation method.

In order to solve these problems, a method of separating using a separation membrane has been studied. In the method of concentrating and separating an aqueous organic solution using a separation membrane, for the concentration of some low-concentration aqueous organic solutions, contact the aqueous organic solution with the separation membrane and select a specific liquid component by the difference in osmotic pressure. Reverse osmosis has been used to selectively permeate. However, the reverse osmosis method cannot be applied to a high-concentration organic matter aqueous solution having a high osmotic pressure because it is necessary to apply a pressure equal to or higher than the osmotic pressure of the separated liquid. Therefore, the concentration range of the separable organic matter aqueous solution is limited. is there.

Recently, a pervaporation method (pervaporation method) has been attracting attention as a new separation method using a separation membrane as a separation method of an organic compound mixture different from the conventional separation method. This pervaporation method, one side of the separation membrane having selective permeability (supply side), the organic compound mixed liquid to be separated is supplied in a liquid state, and directly contact with the supply side of the separation membrane, The other side (permeation side) of the separation membrane is vacuumed or depressurized,
As a result, it is a method in which a substance that selectively permeates from the supply side to the permeate side of the separation membrane is taken out in a gaseous state to concentrate the organic compound mixed liquid or separate each organic compound.

Many proposals have been made for the above-mentioned pervaporation method.

For example, regarding separation of a benzene-cyclohexane mixed solution or a benzene-hexane mixed solution, Japanese Patent Application Laid-Open No.
No. 2-11888, a separation method using an ionomer polymer membrane, and Japanese Patent Laid-Open No. 59-30441,
A separation method using a polyamide membrane is exemplified.

However, in the known separation method of an organic compound mixed solution, the separation membrane used in the pervaporation method has a low permeation rate or selectively permeates at least one organic compound in the organic compound mixed solution. Has a problem that it has only selective separation that cannot be sufficiently, or the separation membrane used in the known pervaporation method, heat resistance, or
The solvent resistance was not sufficient, and it was extremely difficult to industrially perform separation of various organic compound mixed liquids by pervaporation for a long time.

[Problems to be solved]

An object of the present invention is to efficiently and selectively remove at least one organic compound from an organic compound mixed solution in the pervaporation method of an organic compound mixed solution using an asymmetric separation membrane without the drawbacks of known pervaporation methods. It is an object of the present invention to provide a pervaporative separation method which can be separated by the pervaporative method and can be industrially used for a long period of time.

[Means for solving problems]

This invention relates to an aromatic tetracarboxylic acid component containing at least 85 mol% of at least one aromatic tetracarboxylic acid selected from the group consisting of biphenyl tetracarboxylic acids and diphenyl ether tetracarboxylic acids;
90 aromatic diamine compounds having three benzene rings
At least one of the organic compound mixture is prepared by directly contacting the organic compound mixture with one surface of a heat-resistant asymmetric separation membrane composed of a soluble aromatic polyimide obtained from an aromatic diamine component containing at least mol%. Of the organic compound mixture permeate and permeate through the asymmetric separation membrane to separate the organic compound that has permeated the asymmetric separation membrane as a vapor, thereby pervaporating an organic compound mixture solution. Regarding separation method.

Hereinafter, each requirement of the present invention will be described in more detail.

The soluble aromatic polyimide forming the asymmetric separation membrane used in the pervaporation separation method of the present invention is at least one aromatic tetracarboxylic acid selected from the group consisting of biphenyltetracarboxylic acids and diphenylethertetracarboxylic acids. 70 mol% or more, preferably 80 mol% of acids with respect to the wholly aromatic tetracarboxylic acid component
The aromatic tetracarboxylic acid component containing 90 mol% or more, and the aromatic diamine compound having 2 to 3 benzene rings are particularly preferably 85 mol% or more, preferably 90 mol%, based on the total aromatic diamine component. The aromatic polyimide having a high molecular weight, which is soluble in a phenolic organic solvent or the like and which is obtained by polymerization from an aromatic diamine component containing at least 1% by weight, may be used.

For the aromatic polyimide, for example, an aromatic tetracarboxylic acid component and an aromatic diamine component are uniformly dissolved in a phenolic organic solvent, and the solution is about 150-
Heat to a high temperature of 250 ° C, or about 10-10
It can be produced by polymerizing and imidizing both components in the solution by reacting at a low temperature of about 0 ° C. in the presence of an imidizing agent.

The above-mentioned biphenyltetracarboxylic acids include 2,3,
3 ′, 4′- or 3,3 ′, 4,4′-biphenyltetracarboxylic acid or an acid dianhydride thereof, or a salt of these acids or a lower alcohol esterified product, and the like, and Examples of the diphenyl ether tetracarboxylic acids include 3,3 ′, 4,4′-diphenyl ether tetracarboxylic acid or its dianhydride, or its acid salt or lower alcohol ester compound.

As the above-mentioned aromatic tetracarboxylic acids, in particular, 3,
3 ', 4,4'-biphenyltetracarboxylic dianhydride, 3,
Dianhydrides such as 3 ', 4,4'-diphenyl ether tetracarboxylic acid dianhydride are preferred for making the polyimide.

In the present invention, examples of the aromatic diamine compound having 2 to 3 benzene rings include bis (aminophenoxy) benzenes, diaminodiphenyl ethers, diaminodiphenylthioethers, diaminodiphenylsulfonic acid, diaminodiphenylmethanes, diaminodiphenylpropane. ), Diaminodibenzothiophenes and diaminothioxanthenes, and an aromatic diamine component containing 85 mol% or more, particularly 90 mol% or more of an aromatic diamine compound of two or more kinds is preferable. .

The above-mentioned bis (aminophenoxy) benzenes, which are typical examples of aromatic diamine compounds having three benzene rings, include 1,4-bis (4-aminophenoxy) benzene and 1,4-bis (4-aminophenoxy) benzene.
Examples thereof include bis (3-aminophenoxy) benzene and 1,3-bis (4-aminophenoxy) benzene.

In addition, as a typical example of an aromatic diamine compound having two benzene rings, 4,4′-diaminodiphenyl ether,
Diaminodiphenyl ethers such as 3,4′-diaminodiphenyl ether, diaminodiphenylmethanes such as 4,4′-diaminodiphenylmethane and 3,4′-diaminodiphenylmethane, 4,4′-diamino- (2,2-diphenylpropane), Diaminodiphenylpropanes such as 3,4′-diamino- (2,2-diphenylpropane), 4,
Examples thereof include diaminodiphenylsulfones such as 4′-diaminodiphenylsulfone and 3,3′-diaminodiphenylsulfone, and diaminodiphenyls such as o-anisidine.

In the present invention, as the aromatic diamine component, in particular, at least one aromatic diamine compound selected from the group consisting of diaminodibenzothiophenes, diaminothioxanthenes, diaminodiphenylalkanes (especially methane or propane) ( Other aromatic diamine compounds containing 20 mol% or more, particularly 25 to 100 mol%, of those having two benzene rings), and having 2 to 3 benzene rings, based on the total aromatic diamine component. For example, 4,4'-diaminodiphenyl ether, bis (aminophenoxy) benzenes, etc.] is 80 mol% or less, especially 0 to 75 mol% based on the wholly aromatic diamine component.
It is the aromatic diamine component contained, the moldability of the asymmetric separation membrane from the solution of the aromatic polyimide obtained using such an aromatic diamine component, and the asymmetry composed of the aromatic polyimide It is suitable for the separation performance of the sex separation membrane.

The diaminodibenzothiophenes have the general formula (However, R ₁ and R ₂ are hydrogen, a methyl group, or an ethyl group, and n is 0 or 2.) The benzothiophene-based diamine compound is preferable.

Examples of the diaminodibenzothiophenes represented by the general formula I include 3,7-diaminodibenzothiophene, 3,7-diaminodibenzothiophene-5,5-dioxide, and 2,8-dimethyl-3,7-diamino. Dibenzothiophene,
2,6-Dimethyl-3,7-diaminodibenzothiophene, 4,6-
Dimethyl-3,7-diaminodibenzothiophene, 2,8-dimethyl-3,7-diaminodibenzothiophene-5,5-dioxide, 2,6-dimethyl-3,7-diaminodibenzothiophene-
5,5-dioxide, 4,6-dimethyl-3,7-diaminodibenzothiophene-5,5-dioxide, 2,8-diethyl-3,7-diaminodibenzothiophene, 2,6-diethyl-3,7- Diaminodibenzothiophene, 4,6-diethyl-3,7-diaminodibenzothiophene, 2,8-diethyl-3.7-diaminodibenzothiophene-5,5-dioxide, 2,6-diethyl-3,7-diaminodibenzothiophene- Examples include dibenzothiophene-based diamine compounds such as 5,5-dioxide and 4,6-diethyl-3,7-diaminodibenzothiophene-5,5-dioxide.

The diaminothioxanthenes have the general formula shown below. (However, R ₃ and R ₄ are hydrogen or a methyl group, and n is 0 or 2.) A thioxanthene-based diamine compound is preferable.

The diaminothioxanthenes represented by the above general formula II include, for example, 3,7-diaminothioxanthene, 3,7-diaminothioxanthene-5,5-dioxide, and 2,8-dimethyl-
3,7-Diaminothioxanthene, 2,6-Dimethyl-3,7-diaminothioxanthene, 4,6-Dimethyl-3,7-diaminothioxanthene, 2,8-Dimethyl-3,7-diaminothioxanthene- 5,5-Dioxide, 2,6-Dimethyl-3,7-diaminothioxanthene-5,5-Dioxide, 4,6-Dimethyl-3,7-
Examples thereof include thioxanthene-based diamine compounds such as diaminothioxanthene-5,5-dioxide.

The above diaminodiphenylalkanes are represented by the following general formula: (However, R ₅ , R ₆ , R ₇ and R ₈ are hydrogen or a methyl group.) A diamine compound such as diaminodiphenylmethane or 2,2-bis (diaminodiphenyl) propane. Can be mentioned.

Examples of the diaminodiphenylalkanes represented by the above general formula III include 4,4′-diammodiphenylmethane, 3,
4'-diaminodiphenylmethane, 3,3'-dimethyl-4,
Diphenylmethane-based diamine compounds such as 4'-diaminodiphenylmethane, or 2,2-bis (4-aminophenyl) propane, 2,2-bis (3-aminophenyl) propane, 3,4'-diamino- (2 2,2-bis (phenyl) propane-based diamine compounds such as 1,2-diphenylpropane).

The aromatic polyimide forming the asymmetric separation membrane used in the present invention is obtained by polymerizing with an aromatic diamine component by using the aromatic tetracarboxylic acid component alone as the aromatic tetracarboxylic acid component. It may be an aromatic polyimide, or a copolymer obtained by polymerizing with an aromatic diamine component using a mixture of two or more kinds of aromatic tetracarboxylic acids.

In this invention, as the aromatic polyimide, 3,3 ', 4,
An aromatic tetracarboxylic acid component containing 4'-biphenyltetracarboxylic dianhydride as a main component and the above-mentioned general formulas I to II.
Aromatic polyimide obtained from an aromatic diamine component containing an aromatic diamine compound represented by I, the film-forming property of the asymmetric separation membrane, the separation performance of the obtained asymmetric separation membrane to the organic compound mixture, Most preferable in terms of durability, mechanical strength, heat resistance and the like.

As the aromatic tetracarboxylic acid component that can be used together with the aromatic tetracarboxylic acids in the above-mentioned aromatic polyimide production method, pyromellitic acid or its acid diacid hydrate, 2,2-bis (3,4- Dicarboxyphenyl) propane or its acid dianhydride, bis (3,4-dicarboxyphenyl) methane or its acid dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid or its acid dianhydride And so on.

In the method for producing the aromatic polyimide, if the content ratio of the biphenyltetracarboxylic acids or diphenylethertetracarboxylic acids in the tetracarboxylic acid component is too low, the resulting aromatic polyimide is soluble in a phenolic organic solvent. Is unfavorable, since it is not possible to produce an asymmetric separation membrane of stable quality, or the separation performance of the obtained asymmetric separation membrane in pervaporation is poor.

In the above-mentioned method for producing an aromatic polyimide, a small proportion of an aromatic diamine compound having two benzene rings and another aromatic diamine compound such as a phenylenediamine-based diamine compound such as m-phenylenediamine and p-phenylenediamine. You can also share it with.

The asymmetric separation membrane composed of the above-mentioned aromatic polyimide used in the present invention, a phenolic solvent solution of aromatic polyimide is used, a thin film of the solution (flat membrane shape, hollow fiber shape) is cast, It is formed by an extrusion method or the like, and then the thin film is brought into contact with a coagulating liquid at a relatively low temperature to coagulate the thin film to form a flat membrane-shaped or hollow fiber-shaped asymmetric separation membrane. Can be done, for example,
JP-A-56-21602, JP-A-56-157435
It can be produced by a conventionally known film forming method as described in Japanese Patent Publication No.

In the above-mentioned method for producing an asymmetric separation membrane, the asymmetric separation membrane produced by the wet membrane production method is a suitable organic solvent (for example, lower alcohols such as methanol, ethanol, propanol, butanol, and n-hexane). , N
After washing with an aliphatic or alicyclic hydrocarbon solvent such as heptane, octane, cyclohexane, etc., and further sufficiently drying, further under a gas atmosphere of nitrogen, air or the like, at about 150 to 350 ° C., particularly Aging treatment (heat treatment) at a temperature of 180 to 330 ° C. for about 0.1 to 5 hours is suitable.

The asymmetric separation membrane used in the present invention has a permeation rate Q of selectively permeating organic compounds of about 0.1 kg / m ² · Hr when pervaporative separation is performed using an organic compound mixture.
Above, in particular, about 0.2 to 5 kg / m ² · Hr, and the separation performance (separation coefficient α described later) between the permeated organic compound and the non-permeated organic compound is 5 or more, particularly 10 to 60.
It is preferably 00.

The pervaporative separation method of the present invention comprises: (a) supplying an organic compound mixed liquid to a separation membrane module containing an asymmetric separation membrane (flat membrane shape, hollow fiber shape) made of the aromatic polyimide described above, and , The organic compound mixture is directly contacted with the supply side of the asymmetric separation membrane in the separation membrane module, (b) the permeate side of the asymmetric separation membrane, if necessary,
The carrier gas (sweep gas) is made to flow, or it is connected to a decompression pump or the like installed outside the separation membrane module to be in a decompressed state, and the asymmetric separation membrane is separated from the supplied organic compound mixed liquid. At least one organic compound is selectively permeated and permeated to vaporize and separate (c) Finally, from the non-permeate side (supply side) of the asymmetric separation membrane to the outside of the separation membrane module. , The concentrated residual organic compound solution that did not pass through the separation membrane is taken out and recovered, and at the same time, the separation membrane is selectively permeated from the permeation side of the asymmetric separation membrane to the outside of the separation membrane module. The permeated vapor (permeate) of the organic compound is taken out, and if necessary, the permeated vapor (permeate) is cooled and condensed to be recovered.

In the present invention, the organic compound mixed liquid supplied to the separation membrane module is about 0 to 120 ° C., particularly preferably 20 to 1 ° C.
The temperature is preferably about 00 ° C.

In the separation method of the present invention, the pressure applied to the separation method is
Usually, the pressure on the permeate side of the separation membrane is set to be lower than the pressure on the feed side, and the pressure on the feed side is set to atmospheric pressure to 60 kg / cm ² , preferably atmospheric pressure to 30 kg / cm ² .

The permeate side of the asymmetric separation membrane in the separation membrane module, when performing pervaporative separation of the organic compound mixture, may be swept gas, or may be under reduced pressure,
The reduced pressure may be lower than atmospheric pressure, particularly preferably about 200 torr or less, and more preferably 100 torr or less.
It is preferable that the pressure is reduced to less than or equal to torr.

As the organic compound mixed liquid to which the pervaporation method of the organic compound mixed liquid in the present invention can be applied, there are combinations of various organic compounds. For example, ordinary distillation is performed because each organic compound has an azeotropic point. It is particularly effective in the case of a mixture of organic compounds which cannot be separated by the method, or a mixture of organic compounds which is very difficult to separate by distillation because the boiling points of the organic compounds are close to each other.

Further, all of the organic compound mixed liquids may be uniformly dissolved in each other, or some of them may exceed the solubility and be separated to be in a suspended state. However, the mixed liquid containing the organic compound needs to be liquid under the conditions of temperature and pressure when performing pervaporation separation in the mixed state.

Examples of the mixed liquid of organic compounds having an azeotropic point include benzene / cyclohexane, benzene / normal hexane, methanol / acetone, benzene / methanol, acetone / chloroform, ethanol / cyclohexane, butanol / cyclohexane, chloroform / normal hexane, and ethanol. / Benzene, ethanol /
Examples thereof include toluene and xylene isomer mixed liquid.

Examples of the organic compound mixed liquid having a boiling point difference of about 20 ° C. or less, particularly 10 ° C. or less and boiling points close to each other include, for example, ethylbenzene / styrene, parachloroethylbenzene / parachlorostyrene, toluene / methyl. Cyclohexane, butadiene / butenes, butadiene /
Examples thereof include butanes and normal butene-1 / isobutene. The above-mentioned organic compound mixed solution can be applied not only to the above-mentioned two-component mixed solution but also to a three-component or more multi-component mixed solution.

In the pervaporation separation method of the present invention, the composition ratio of the above-mentioned organic compound mixed liquid is not particularly limited, and a mixed liquid of organic compounds in an arbitrary ratio can be separated or concentrated.

The structure, form, etc. of the separation membrane module are not particularly limited, and examples thereof include, but are not particularly limited to, plate-and-frame type modules, spiral type modules, and hollow fiber membrane type modules. It is preferable.

〔Example〕

Hereinafter, examples and comparative examples relating to the pervaporative separation method of the present invention will be shown to explain the present invention in more detail.

In Examples and Comparative Examples, the permeation rate Q and the separation coefficient α were measured by cooling and condensing the vaporized component that permeated the membrane, collecting the weight, measuring the weight of the vaporized component, adding an internal standard solution to the condensate, and measuring TCD. -The weight ratio of the organic compounds X and Y was measured by gas chromatography and calculated by the following formula.

The abbreviations of the compounds used for the aromatic tetracarboxylic acid component and the aromatic diamine component in the reference example are shown below.

[Aromatic tetracarboxylic acid component]

s-BPDA; 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride BTDA; 3,3', 4,4'-benzophenone tetracarboxylic dianhydride ETDA; 3,3 ', 4,4 ′ -Biphenyl ether tetracarboxylic dianhydride PMDA; pyromellitic dianhydride [aromatic diamine compound] TSN; 2,8-dimethyl-3,7-diaminodibenzothiophene-5,
Isomeric mixture of 5-dioxide, 2,6-dimethyl-3,7-diaminodibenzothiophene-5,5-dioxide and 4,6-dimethyl-3,7-diaminodibenzothiophene-5,5-dioxide DMTX; 2 , 8-Dimethyl-3,7-diaminothioxanthene-5,5-dioxide, 2,6-dimethyl-3,7-diaminothioxanthene-5,5-dioxide, 4,6-dimethyl-3,7 -Diaminothioxanthene-5,5-dioxide isomer mixture DADE; 4,4'-diaminodiphenyl ether DADM; 4,4'-diaminodiphenylmethane TPE-Q; 1,4-bis (4-aminophenoxy) benzene 34IP 3,4'-diamino- (2,2-diphenylpropane) DABA; 3,5-diaminobenzoic acid DAN; o-dianisidine Reference Examples 1 to 17 Acid component and diamine component having the charging ratios shown in Table 1; In an organic polar solvent of parachlorophenol using approximately equimolar amount of At the polymerization temperature and the polymerization time was producing an aromatic polyimide solution by polymerization and imidization.

Table 1 shows the polymer concentration and solution viscosity (rotational viscosity at 100 ° C .; poise) of each aromatic polyimide solution produced as described above.

Using the aromatic polyimide solution obtained as described above, a coagulation liquid (ethanol aqueous solution) having a composition shown in Table 1 and a wet film-forming method at a hollow fiber take-off speed of 10 m / min. After forming a hollow fiber membrane with, washed with alcohol and aliphatic hydrocarbon, dried and heat-treated at the heat treatment temperature shown in Table 1 for 30 minutes to obtain the shape shown in Table 1 (inner diameter of hollow fiber and Asymmetric hollow fiber separation membranes made of aromatic polyimide having a film thickness) were produced.

Examples 1 to 32 Four 7.5 cm long asymmetric hollow fiber separation membranes produced in each reference example are bundled to form a yarn bundle, and one end of the yarn bundle is sealed with an epoxy resin. , A hollow fiber bundle element is prepared, and the hollow fiber bundle element is internally provided in a container having an inlet for supplying an organic compound mixed liquid, an outlet for a non-permeate and an outlet for a permeate, and a separation membrane. The module was manufactured.

The organic compound mixture having the composition and temperature shown in Table 2 was supplied to the separation membrane module, and the inside of the hollow fiber of the hollow fiber element in the separation membrane module was pervaporated under a reduced pressure of 3 Torr or less, The permeate vapor was cooled and recovered.

Table 2 shows the permeation rate Q in pervaporation and the separation coefficient α of each organic compound.

Examples 33 to 35 The asymmetric hollow fiber separation membranes produced in Reference Example 1 were treated with benzene (Example 33), a mixed solution of benzene and cyclohexane (weight ratio 1: 1) (Example 34), or Mixture of benzene and n-hexane (weight ratio 1: 1)
50 at 150 ° C. in the treatment solvent consisting of (Example 35)
A treatment of dipping for a time was performed.

After drying each asymmetric hollow fiber separation membrane that had been subjected to the above-mentioned treatment at 30 ° C. for 20 hours, a separation membrane module was manufactured in the same manner as in Example 1, and the organic compounds shown in Table 2 for each separation membrane module were produced. The separation performance of the compound mixture was measured.

The results are shown in Table 2.

Comparative Reference Example 1 60 mmol of pyromellitic dianhydride, 60 mmol of 4,4′-diaminodiphenyl ether, and 200 g of N-methylpyrrolidone were placed in a three-necked separable flask, and nitrogen gas was circulated and stirred. While at 10 ℃ 10
Polymerization reaction is carried out for a period of time to generate polyamic acid, and 200 g of N-methylpyrrolidone is further added to the reaction solution.
Pyridine (27 g) and acetic anhydride (35 g) were added, the temperature was gradually raised to 80 ° C with strong stirring, and the temperature was maintained at 80 ° C for 1 hour.
The polymer was imidized and polyimide was broken out.
Furthermore, ethanol was added to this reaction solution to completely precipitate the polymer, which was separated by filtration, washed with ethanol, and finally dried under reduced pressure to obtain a polyimide powder.

This polyimide powder was added to p-chlorophenol, N-methyl-2-pyrrolidone, or N, N-dimethylacetamide, respectively, and the mixture was heated,
I tried to dissolve the polyimide powder in the solvent,
Substantially, the polyimide solution could not be prepared.

Therefore, it was not possible to produce an asymmetric separation membrane from the aromatic polyimide obtained by using the pyromellitic dianhydride.

Comparative Reference Examples 2 to 4, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, paraphenylenediamine (Comparative Reference Example 2), and 2,4-dimethyl-metaphenylenediamine (Comparative Reference Example 3) Alternatively, 2,6-diaminopyridine (Comparative Reference Example 3) was used in an equimolar manner, and polymerized in an organic polar solvent of parachlorophenol at a polymerization temperature of 180 ° C. for 6 hours in the same manner as in Example 1. , And aromatic polyimide was projected. These aromatic polyimide powders were not substantially dissolved in any organic solvent, and a uniform polymer solution could not be prepared.

Comparative Example 1 10 parts by weight of an aromatic polyimide (General Electric Co., trade name; Ultem), 40 parts by weight of N-methyl-2-pyrrolidone, and 50 parts by weight of tetrahydrofuran were placed in a separable flask and stirred to obtain a uniform mixture. A polymer solution was prepared.

The above polymer solution was cast on a smooth glass plate with a doctor knife to a thickness of 0.2 mm, and the glass plate and 1
It was immersed for a time to form an asymmetric separation membrane, and finally, the asymmetric separation membrane was peeled off from the glass plate and then dried at 30 ° C. to manufacture an asymmetric separation membrane.

The asymmetric separation membrane was separated by a pervaporation method into an organic compound mixture containing chloroform and n-hexane in equivalent amounts.

The asymmetric separation membrane swelled with the organic compound mixed solution, and the safe separation performance could not be measured.

[Operation and effect of the present invention]

Since the separation method of the present invention is a separation method relating to a pervaporation method using an asymmetric separation membrane made of a specific aromatic polyimide, it can be used for separation and concentration of a mixed liquid of various organic compounds, and , Which can be used for a wide range of concentrations of organic compound mixtures, and has sufficient heat resistance, water resistance, solvent resistance and durability, and is made of a specific polyimide with high separation performance. Since the asymmetric membrane is used, stable separation by pervaporation can be performed for a long time.

Claims (2)

[Claims] 1. An aromatic tetracarboxylic acid component containing at least 85 mol% of at least one aromatic tetracarboxylic acid selected from the group consisting of biphenyl tetracarboxylic acids and diphenyl ether tetracarboxylic acids;
90 aromatic diamine compounds having three benzene rings
At least one of the organic compound mixture is prepared by directly contacting the organic compound mixture with one surface of a heat-resistant asymmetric separation membrane composed of a soluble aromatic polyimide obtained from an aromatic diamine component containing at least mol%. Of the organic compound mixture permeate and permeate through the asymmetric separation membrane to separate the organic compound that has permeated the asymmetric separation membrane as a vapor, thereby pervaporating an organic compound mixture solution. Separation method. 2. An aromatic diamine component containing 20 mol% or more of at least one aromatic diamine compound selected from the group consisting of diaminodibenzothiophenes, diaminothioxanthenes and diaminodiphenylalkanes. The method for pervaporative separation of an organic compound mixture according to claim 1, wherein