JPH05168879A - Composite separation membrane - Google Patents

Abstract

PURPOSE:To obtain a separation membrane excellent in durability, heat resistance, transmitting flow rate, and separation performance, which is suitable to remove water from a liquid mixture by pervaporation method. CONSTITUTION:This separation membrane is used for separation of liquid mixture by pervaporation method. The membrane has a thin film layer comprising polyvinyl alcohol on a fine porous membrane of aromatic polyimide, aromatic polyamideimide, or mixture of them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separation membrane used for separating a liquid mixture by a pervaporation method. More specifically, the present invention relates to a separation membrane using a polymer material having a high water affinity, which is used in a separation method for removing water from a liquid mixture by a pervaporation method.

[0002]

BACKGROUND OF THE INVENTION In the industrial world, it is often necessary to remove water from water-soluble liquids such as evaporation, freezing, extraction and
Separation methods such as the dialysis method and the reverse osmosis method are used properly according to the usage conditions. Water-soluble liquids include alcohols, phenols, esters, ketones, ethers, aldehydes, oxygen-containing organic compounds such as organic acids,
Nitrogen-containing organic compounds such as nitriles, inorganic compounds such as inorganic acids, and mixtures thereof.

As the method for removing water from a liquid mixture, the above-mentioned methods can be mentioned, but it cannot be said that it is necessarily suitable for the formation of an azeotropic mixture and the separation of substances having similar boiling points, and in recent years At the same time, research and development of separation by the pervaporation method have become popular due to energy requirements. Further, in actual use, heat resistance, chemical resistance, and mechanical strength are as important as the separation ability. Therefore, it is required to develop a material having a high separation ability while giving due consideration to these points.

To this end, how efficient, in many cases pinhole formation, is to obtain a practical separation ability by giving the membrane a characteristic affinity existing in the compound to be separated. A major problem is how to form a very thin film, and how to maintain durability against other compounds containing the compound to be separated.

[0005]

Conventionally, a polyimide film such as polyimide or polyamide-imide has been used for this purpose. This is because it has an imide bond and an add bond in the selective separation of water, and is considered to have an effective affinity for water. However, as described above, it is necessary to form an extremely thin polymer film without pinholes in order to bring out practical separation ability from the polymer material. If the same material is used, the thinner the film thickness is, the better the practical separation ability is, but if pinholes are present, the separation ability is fatally lowered. Therefore,
In order to form a film that is close to ideal, the polymer material that is the raw material of the film must have excellent film-forming properties. That is,
As a practical matter, it should preferably be soluble at room temperature. If so, various ideas can be easily adopted for membrane formation or hollow fiber spinning, and an extremely thin homogeneous membrane and an asymmetric membrane integral with the support can be easily produced. However, in order to satisfy this requirement, it is not limited to any polyimide or polyamide-imide, and development of a suitable material satisfying this requirement has been desired.

On the other hand, as a method for separating a liquid mixture using polyvinyl alcohol, Japanese Patent Laid-Open No. 52-47579,
JP-A-47-10549, JP-A-58-40103, JP-A-58-40104, JP-A-58-58105, JP-A-59-109204, and JP-A-2-6823 are mentioned, but they are required as a practical film. Permeation performance, separation performance, durability, high temperature use performance, etc. are not sufficient.

As a method for separating a liquid mixture using polyimide or polyamide-imide, there is disclosed in Japanese Patent Laid-Open No. 27050/1988.
No. 6, but the performance as a practical membrane is insufficient.
As described above, in the industrial field, the high-performance pervaporation film satisfying the above-mentioned various conditions has not yet been put into practical use.

[0008]

In view of the above-mentioned problems, the present inventors have found that a polymer having excellent heat resistance, chemical resistance and mechanical strength in actual use, and having a high permeation flow rate and separation ability. As a result of developing and studying the materials, a composite membrane having a thin film layer made of polyvinyl alcohol on a microporous membrane made of aromatic polyimide, aromatic polyamideimide, etc. The present invention has been achieved by finding out that it is also excellent from the above point.

That is, the gist of the present invention is a separation membrane used for separating a liquid mixture by a pervaporation method, wherein polyvinyl alcohol is provided on a microporous membrane made of aromatic polyimide, aromatic polyamideimide or a mixture thereof. A composite separation membrane having a thin film layer made of The present invention will be described in detail below.

The pervaporation method in the present invention is a method of separating a specific component from a liquid mixture by using a polymer film or a ceramic film. Among a large number of separation methods, it is effective for separation of those forming an azeotropic mixture, separation of components having close boiling points, or separation of a mixture containing components having low thermal stability, and research and development have been actively conducted in recent years.
In the present invention, the object to be separated is not particularly limited, but its purpose is mainly to remove water from a substantially homogeneous liquid mixture as follows. That is, the liquid mixture is mainly a mixture of various liquid components and water, and the ratio thereof is not limited as long as it is homogeneous.

Particularly, the liquid mixture is an oxygen-containing organic compound such as alcohols, phenols, esters, ketones, ethers, aldehydes and organic acids, a nitrogen-containing organic compound such as nitriles, an inorganic compound such as inorganic acids, And in the case of aqueous solutions of these mixtures, they are preferably separated. As alcohols, methanol, ethanol, iso and normal propanol, butanol, octanol,
In addition to benzyl alcohol, examples of polyhydric alcohols include ethylene glycol, polyethylene glycol and glycerin.

Examples of phenols include cresol, phenol and catechol. Examples of the esters include water-soluble esters such as ethyl acetate, methyl acetate, ethyl formate and methyl propionate. Examples of the ketones include acetone, methyl ethyl ketone, acetophenone and the like.

As the ethers, diethyl ether,
Examples thereof include dibutyl ether, dioctyl ether, diphenyl ether, dioxane, trioxane and tetrahydrofuran. Examples of aldehydes include formaldehyde and acetaldehyde. Examples of organic acids include formic acid, acetic acid, oxalic acid, and propionic acid. Examples of nitriles include acetonitrile and acrylonitrile. As the inorganic acids, hydrochloric acid,
Examples thereof include sulfuric acid, nitric acid, phosphoric acid and boric acid.

As the aromatic polyimide used in the present invention, generally, an aromatic diamine represented by the following general formula (1), an aromatic tetracarboxylic acid anhydride represented by the general formula (2) and degenerate They are united and have a repeating unit represented by the general formula (3).

[0015]

[Chemical 1]

(In the formula, Ar 'is a divalent aromatic residue, preferably a phenyl group which may be substituted, an aryl group, a biphenyl group, a naphthyl group, a bisphenol residue and the like. Ar represents a tetravalent aromatic tetracarboxylic acid residue.) The aromatic polyimide particularly preferably used in the present invention is
An aromatic copolyimide characterized by the presence of a repeating unit represented by the following general formula (4), more preferably 10 to 30 mol% of the repeating unit, wherein R is a residue represented by the following formula (5): Represents 90 to 70 mol% of the repeating unit
R represents a residue represented by the following formulas (6) and / or (7).

[0017]

[Chemical 2]

This copolyimide is, for example, USP 3,7
08,458, 3,3 ', 4,
4'-benzophenone tetracarboxylic dianhydride in an appropriate molar ratio of 4,4'-methylenebisphenyl isocyanate (4,4'-diphenylmethane diisocyanate)
And tolylene diisocyanate (2,4-isomer,
It can be easily obtained by reacting with a 2,6-isomer or a mixture thereof in the presence of a polar solvent. At this time, it is possible to use a small amount of another diisocyanate compound or another tetracarboxylic acid compound.

The aromatic polyamideimide used in the present invention generally has a repeating unit represented by the following general formula (8). The aromatic polyamideimide used particularly preferably in the present invention has a structure in which 10 to 90 mol%, preferably 70 to 90 mol%, of the repeating unit has a structure represented by the following formula (9), and 90 to 10% of the repeating unit. Mol%, preferably 30 to 10 mol%, is an aromatic copolyamideimide having a structure represented by the following formula (10).

[0020]

[Chemical 3]

This copolyamide imide is available in USP 3,9
29,691, using about 10
A mixture of trimellitic anhydride and isophthalic acid in a proportion of from about 90 mol% to about 90 mol% to about 10 mol% and about 100 mol% of 4,4'-methylenebisphenylisocyanate in approximately equal amounts. It can be easily obtained by reacting a nato in the presence of a polar solvent. At this time, a small amount of another diisocyanate compound can be used.

The solvent used for polymerizing and dissolving these copolyimides and copolyamideimides is a polar organic solvent and is dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, dimethyl sulfone, hexamethylphosphoramide. ,
Examples thereof include tetramethylurea and pyridine, but they are not particularly limited. Further, these may be mixed and used. Preferably dimethylformamide,
Dimethylacetamide and N-methylpyrrolidone are used, more preferably dimethylformamide.

The amount of polar organic solvent used in the polymerizations described above is preferably at least sufficient to initially dissolve all the reactants. The amount of solvent used is adjusted according to the desired viscosity of the copolyimide, and the weight% of the copolyimide is not so important, but normally 5 wt% to about 35 wt% is preferable. Aromatic copolyimides or copolyamideimides are quite good, but not universal, in terms of chemical resistance to other organic compounds present in the liquid mixture to be separated. It is practically effective to insolubilize the already produced separation membrane by crosslinking it by heating, electron beam irradiation or other methods, and thus it is possible to crosslink and insolubilize it after membrane formation. This is also included in the polymer material as referred to in the present invention.
Furthermore, with respect to the polymer, other polymer materials that do not interfere with film formation, heat resistance stabilizers, film formation stabilizers, post-crosslinking reaction reagents,
5 for separation membranes manufactured with anti-oxidation stabilizers, simple plasticizers, etc.
If it is 0% by weight or less, it may be added. Various stabilizers for improving durability may give good results.

The copolyimide and copolyamideimide used in the present invention have a logarithmic viscosity (ηinh) of 0.1 dl /
g or more, and more preferably 0.3 to 4 dl / g (measured in N-methylpyrrolidone at 0.5% at 30 ° C.). In the present invention, a mixture of the above aromatic polyimide and aromatic polyamideimide can also be used.

The polyvinyl alcohol used in the present invention preferably has an average degree of polymerization of 500 to 350.
0, polyvinyl alcohol having a saponification degree of 80 to 100 mol%, or a copolymer thereof. As the copolymer, an unsaturated carboxylic acid such as acrylic acid, crotonic acid, maleic acid or itaconic acid or an ester thereof is vinyl. Carboxyl group-modified polyvinyl alcohol copolymerized with acetic acid and introduced with COONa group as a functional group, cation-modified polyvinyl alcohol copolymerized with vinyl acetate and aminoalkyl methacrylamide-based monomer, Si
Polyvinyl alcohol copolymers such as Si-modified polyvinyl alcohol obtained by copolymerizing a vinyl polymer containing a group with vinyl acetate and acetoacetyl-modified polyvinyl alcohol having a highly reactive function in the molecule (block copolymers, graft copolymers (Including coalescence).

The above-mentioned aromatic polyimide, aromatic polyamide-imide of the present invention, or a mixture thereof (hereinafter referred to as "aromatic polyimide of the present invention") can be produced by a dry film forming method or a wet method. A film forming method, which can be easily produced by a known film forming method such as an extrusion method, preferably a wet film forming method is used, for example, a thin film is formed from a polymer dope, and in a poor solvent such as water. An asymmetric microporous membrane having a skin layer on the surface, which is obtained by solidifying, thoroughly washing, and further drying, is particularly preferable.

The microporous membrane used in the present invention includes
Pore size is 5 Å ~ 1μ, and water vapor transmission rate is 10 ^-4
cm ³ / cm ² · sec. It is preferably cmHg or more and the permeation rate ratio of hydrogen and nitrogen gas is 2.5 or more, and usually the film thickness is preferably 10 to 500 μm. In the case of hollow fibers, the outer diameter is particularly preferably 100 to 3000 μ.

Regarding the method for producing the microporous membrane, for example,
JP-A-62-231017 and 63-175116.
And the production method of the separation membrane described in JP-A-63-175115. The form of the microporous membrane is preferably an asymmetric membrane having a dense layer on the outer surface or inner surface of the separation membrane or on both outer and inner surfaces.

Further, an asymmetric membrane having finger-shaped voids inside the sorting membrane sandwiched between the outer surface and the inner surface is also preferable. The holes of the finger type structure are formed inside the hollow fiber between the inner surface and the outer surface, and are formed in one or a plurality of rows in the circumferential direction. For example, when the holes are formed in one row in the circumferential direction, the length of the holes may be smaller than the wall thickness of the hollow fiber, and preferably 99 of the wall thickness.
˜1%, more preferably 99-50%. Further, for example, when the holes are formed in two or more rows in the circumferential direction, the sum of the long diameters of the holes on the same diameter may be less than the wall thickness, preferably 99 to 1% of the wall thickness. Preferably 9
It may be 9 to 50%. The minor axis size of the pores may be equal to or shorter than the major axis.

Portions of the finger-shaped structure other than the pores are connected to both surfaces, and have an inclined porous structure in which the average pore diameter changes in the thickness direction. Due to the existence of the holes, the permeation resistance of the hole portion can be substantially ignored, and a sufficient permeation rate and mechanical strength can be obtained. Examples of the method of forming the thin film layer of polyvinyl alcohol of the present invention on the microporous film include a method of applying a dilute solution of polyvinyl alcohol dissolved in a solvent to the microporous film, a method of plasma polymerization, and the like. As a coating method, known methods such as a dipping method, a doctor blade, a bar coater, a roll transfer method, and a spray method are used, and the dipping method is particularly preferable for the coating on the hollow fiber microporous membrane. The application can be performed on both the inner surface and the outer surface of the hollow fiber or on either one of the surfaces.

The preparation of a dilute solution of polyvinyl alcohol is not particularly limited as long as it is a solvent that dissolves the polyvinyl alcohol and is a poor solvent for the microporous membrane, but as a particularly preferred solvent, water or water / water / An alcohol mixed solvent may be used. The polymer concentration can be appropriately adjusted depending on the pore structure or permeation performance of the microporous membrane used, but it is preferably 0.05% by weight to 10% by weight.

In order to use the composite separation membrane of the present invention in a field requiring chemical resistance such as dehydration of an organic solvent by a pervaporation membrane, it is preferable to use soluble polyvinyl alcohol crosslinked with a crosslinking agent. As a method of crosslinking the polyvinyl alcohol, for example, a dilute solution of polyvinyl alcohol is allowed to contain a crosslinking agent, and the solution is applied to a microporous membrane and dried, and then 50 ° C to 300 ° C, preferably 100 ° C to 200 ° C. It can be performed by heat treatment at ℃. The crosslinking agent used is not particularly limited, but preferred examples include formalin, organic acids, dialdehydes, melamine resins, block isocyanates and the like.

As a method of crosslinking, the composite membrane
The heat treatment may be performed at 50 ° C. or higher, preferably 180 to 225 ° C. That is, this makes it possible to make polyvinyl alcohol insoluble in hot water. If the temperature of this heat treatment is too low, insolubilization is not sufficient, and if it is too high, thermal deterioration occurs, which is not preferable.

The degree of cross-linking is adjusted according to the chemical resistance of the organic solvent used for pervaporation. The thickness of the thin film layer obtained by using polyvinyl alcohol is usually 100 Å to 50 μm, preferably 500 Å
It is 5 μm. In the combination of polyvinyl alcohol and the microporous film, it is preferable to treat the surface of the microporous film with a silane coupling agent in order to enhance the adhesion between the polyvinyl alcohol and the microporous film.

As the silane coupling agent, γ-
Ureidopropyl triethoxysilane, γ-aminopropyl triethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane and the like are particularly preferable.

As a treatment method of the silane coupling agent in the composite formation, the microporous membrane is immersed or sprayed in an alcohol solution or a water bath of the silane coupling agent, and then the microporous membrane is applied. A polyvinyl alcohol solution is applied to the mixture and the temperature is 100 ° C. or higher, preferably 1
The heat treatment is performed at a temperature of 50 ° C. or higher, particularly preferably 180 ° C. or higher.

In the present invention, it is also possible to add a silane coupling agent to the polyvinyl alcohol solution and apply it to the surface of the microporous membrane. In this case, the concentration of the silane coupling agent is adjusted to 0.001 to 5% by weight of water, water / alcohol or polyvinyl alcohol solution before use. The heat treatment temperature of the composite film was 15
When the temperature is 0 ° C. or lower, the adhesion treatment effect of the silane coupling agent may be insufficient. In the composite separation membrane composed of polyvinyl alcohol and the aromatic polyimide of the present invention,
In order to increase the separation ratio, the separation coefficient of the microporous membrane such as aromatic polyimide is water / isopropyl alcohol = 13 /
87 (weight ratio) and a temperature of 80 ° C. are at least 1.0 or more and preferably 1.8 or more at a vacuum degree of 5 Torr.

On the other hand, if the separation coefficient of polyvinyl alcohol is too high, the permeation flow rate becomes low, and the permeation flow rate extremely decreases depending on the thickness of the polyvinyl alcohol thin film layer, which is not preferable. Therefore, in order to obtain a permeation performance in which both the separation ratio and the permeation flow rate are balanced, the separation coefficient of the film when the homogenous film is composed of only the aromatic polyimide or the like is a homogenous film composed of only polyvinyl alcohol. It is preferable to select and use the aromatic polyimide or the like and polyvinyl alcohol of the present invention so as to be 10% or more higher than the separation coefficient in the case of, especially 2
It is preferable that the number is double or more.

This separation is a characteristic value evaluated in a homogeneous film (non-porous film) of 20 to 30 μm at a water / isopropyl alcohol = 13/87 (important ratio), a temperature of 80 ° C. and a vacuum degree of 5 Torr. .. The separation membrane used for pervaporation is a membrane that separates the treatment liquid chamber and the permeation vapor chamber, and is mainly composed of the above-mentioned aromatic polyimide or aromatic polyamide-imide coated with polyvinyl alcohol. If there is a shape,
Various materials such as a sheet shape, a spiral shape, a tubular shape, and a hollow fiber shape can be adopted according to the application.

Among the shapes of such a separation membrane, particularly the hollow fiber shape can increase the effective membrane area per unit volume, and when pressure is applied from the outer peripheral side of the hollow fiber,
Advantages such as high mechanical strength against high pressure, despite the small thickness of the tube wall. In the composite separation membrane of the present invention, the mechanism by which the improvement of liquid separation performance is expressed is not clear, but the aromatic polyimide which originally has high separation ability, a finely packed layer generated in the process of producing a microporous membrane of aromatic polyamideimide. It has been found that by repairing the defects of (1) with polyvinyl alcohol, which has a certain degree of separation ability and a high permeation rate, the permeation performance (separation ratio, permeation flow rate) is dramatically improved. is there.

As a treatment for improving the adhesion between the microporous film and polyvinyl alcohol, the surface of the microporous film is treated with a silane coupling agent,
The durability is further improved, and the liquid mixture can be separated economically advantageously.

[0042]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Evaluation of various permeation performances in the following examples was performed by the following method using a module obtained by binding 12 hollow fibers with an epoxy resin.

(1) Permeation performance test of a mixed solution of water and isopropyl alcohol (hereinafter abbreviated as IPA) by pervaporation method (permeation test) Water / IPA on primary side = 13/87 (weight ratio) The mixed solution was set to 80 ° C., the secondary side was set to 2-3 mmHg, and the dehydration performance of the mixed solution was evaluated. The permeated gas is collected by liquid nitrogen, and the permeation flow rate (g / m ² · H
r) was determined.

(2) The separation coefficient α (water / IPA) is a value obtained by the following equation. Separation coefficient α (water / IPA) = [water on permeate side / IPA (weight ratio)] / [water on raw material side / IPA (weight ratio)]

Comparative Example-1 According to the procedure described in Example-4 of US Pat. No. 3,708,458, 3,3 ',
4,4'-benzophenone tetracarboxylic acid anhydride and 80 mol% of toluene diisocyanate and 2% thereof
A polymer solution obtained by polymerizing in a DMF solution containing 0 mol% 4,4'-diphenylmethane diisocyanate was extruded from a hollow fiber producing nozzle at a constant flow rate, and at the same time, air was flown into the hollow fiber at a constant flow rate. .. It was then introduced directly into a coagulation bath of water, drawn at a constant rate and wound up in water. After air-drying this for one day and night, it was dried at 100 ° C. for 30 minutes and dried and heat-treated under conditions of 310 ° C. to 30 minutes to obtain a microporous membrane hollow fiber. The outer diameter of this hollow fiber was 750 μ, and the inner diameter was 350 μ. Table 1 shows the results of the permeation performance tests of the obtained microporous membrane.

Comparative Examples-2 and 3 Heat treatment was conducted at 300 ° C. for 30 minutes (Comparative Example-2) and 325 respectively.
A microporous membrane hollow fiber membrane was produced in the same manner as in Comparative Example 1 except that the treatment was carried out under the conditions of ° C to 30 minutes (Comparative Example-3). Table 1 shows the permeation performance of the water / IPA mixed solution by the pervaporation method of this separation membrane.

[0047]

[Table 1]

Comparative Example-4 In the production of a microporous hollow fiber, ascent was poured into the hollow fiber to coagulate in water, and the hollow fiber obtained by treating in hot water at 100 ° C. for 5 minutes was treated at 300 ° C. for 30 minutes. A hollow fiber was produced in the same manner as in Comparative Example-1 except for the above. The results are shown in Table 2 below.
Shown in.

Comparative Example 5 Polyvinyl alcohol (Kuraray Co., Ltd., KM-11)
A 15 wt% solution of 8) was cast on a glass plate to form a film, which was then heat-treated at 180 ° C. for 30 minutes. Using this homogeneous film (22μ), water / IPA pervaporation evaluation was performed. The permeation velocity of water is 446 g / m ² ·
The Hr and the separation coefficient were 1280.

Comparative Example-6 A film was formed in the same manner as Comparative Example-5 except that GH-20 (manufactured by Nippon Gosei Co., Ltd.) was used as polyvinyl alcohol (2).
0 μ) and evaluated. Permeation velocity of water is 31480g
/ M ² · Hr, the separation factor was 27.

Comparative Example-7 A film was formed in the same manner as in Comparative Example-5 except that NH-17Q (manufactured by Nihon Gosei Co., Ltd.) was used as polyvinyl alcohol (25 μ), and pervaporation was evaluated. The water permeation flow rate was 62 g / m ² · Hr, and the separation coefficient was 4,450.

Comparative Example-8 The solution of the aromatic polyimide prepared in Comparative Example-1 was cast on a glass plate, dried and heat-treated at 300 ° C. for 30 minutes to form a homogeneous film. This homogeneous film (35
μ / was used to evaluate water / IPA pervaporation. The water permeation flow rate was 35 g / m ² · Hr, and the separation coefficient was 750000.

Example-1 Polyvinyl alcohol (Kuraray Co., Ltd., KM-11)
The solution obtained by filtering the 3% by weight aqueous solution of 8) with a 3μ filter was mixed with the silane coupling agent (manufactured by Nippon Unicar, A-1120) containing the microporous hollow fiber membrane obtained in Comparative Example-4.
The surface-treated product with a wt% ethanol solution was immersed for 1 minute, air-dried, and then heat-treated at 200 ° C. for 30 minutes. Using the composite membrane, water / IPA pervaporation evaluation was performed. (Table-2)

Examples-2 to 6 Composite membranes were prepared in the same manner as in Example 1 except that the concentration of the polyvinyl alcohol aqueous solution was changed to 4 to 10% by weight. The results are shown in Table-2.

[0055]

[Table 2]

Examples -7, 8 Polyvinyl alcohol (PVOH) was added to GH-20 (Nippon Gosei Co., Ltd.) and HN-17Q (Nippon Gosei Co., Ltd.).
A composite film was prepared in the same manner as in Example 1 except that the composite film was manufactured. The results are shown in Table-3.

[0057]

[Table 3]

Examples-9, 10, 11 and 12 Table 4 shows ethanol, acetone, methyl ethyl ketone and methylene chloride (MC) using the membrane of Example-1. The evaluation was carried out under pervaporation conditions. The results are shown in Table-4.

[0059]

[Table 4]

Example 13 Polyamideimide having a composition of trimellitic anhydride (3.2 mol), isophthalic acid (0.8 mol), and'4.4 'methylenebisphenylene isocyanate (4.0 mol). Then, a composite membrane was produced in the same manner as in Example-4 on the microporous hollow fiber produced by using the composition prepared by mixing equal amounts of the polyimide produced in Comparative Example-1. Water / IPA = 13 /
The evaluation by the perveation method was performed under the conditions of 87 wt% and 80 ° C. Separation factor> 50000 and permeation velocity 1
It was 550 g / m ² · Hr.

Examples-14 to 19 Pervaporation of water / isopropyl alcohol was carried out at 110 ° C. using the module of Example-3, and the composition of the feed solution shown in Table 5 below was evaluated.

[0062]

[Table 5]

[0063]

INDUSTRIAL APPLICABILITY The composite classification membrane of the present invention has excellent durability, heat resistance, permeation flow rate and classification performance, and is suitable for separating a liquid mixture by a pervaporation method.

Claims (2)

[Claims] 1. A separation membrane used for separating a liquid mixture by a pervaporation method, wherein a thin film layer made of polyvinyl alcohol is formed on a microporous membrane made of aromatic polyimide, aromatic polyamideimide or a mixture thereof. A composite separation membrane having. 2. Separation of an aromatic polyimide, an aromatic polyamide-imide or a mixture thereof and polyvinyl alcohol when the aromatic polyimide, the aromatic polyamide-imide or a mixture thereof forms a homogenous film. A value measured for a liquid mixture having a coefficient (water / isopropyl alcohol = 13/87 (weight ratio)) at a temperature of 80 ° C. and a vacuum degree of 5 Torr.
same as below. ) Is selected so that it is 10% or more higher than the separation coefficient of the film when a homogeneous film is formed using the polyvinyl alcohol.