JP2895133B2 - Method for producing permselective membrane - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a selectively permeable membrane, and more particularly, to a selectively permeable membrane having a separation ability suitable as a separation membrane for a liquid mixture by a pervaporation method. To provide.

(Problems to be Solved by the Prior Art and the Invention) In a pervaporation method (pervaporation method) which is effective as a separation technique for a mixture of organic liquids or a solution of an organic compound, especially for a compound having a close boiling point and an azeotropic mixture, A separation membrane having excellent durability and industrially excellent durability is required. That is, in such a pervaporation method, an organic liquid mixture is supplied to one side through a separation membrane, and the other is decompressed or evacuated to vaporize and extract a specific liquid component. In addition, a separation membrane having chemical resistance, heat resistance, mechanical strength, and the like is required.

Conventionally, as a material of the separation membrane, although it depends on its use, for example, polymers such as cellulose, polyvinyl, polyamide, polyester, polysulfone, polycarbonate, and polyimide have been proposed. Among them, polymers generally known as engineering plastics have good heat resistance, chemical resistance and the like, but are still insufficient as materials for separation membranes exhibiting sufficient separation ability in the pervaporation method as described above.

(Means for Solving the Problems) In view of the above problems, the present inventors have conducted intensive studies and as a result, have found that a separation membrane made of an aromatic imide polymer having a haloalkyl group treated with a specific solvent is particularly suitable for pervaporation. The present invention has been found to be extremely effective as a separation membrane having good permselectivity in a filtration method, and has completed the present invention.

That is, the present invention solidifies an aromatic imide polymer having a haloalkyl group dissolved in an organic solvent in a coagulation liquid to obtain a film, and then a solvent capable of shrinking the film and a film capable of shrinking the film. To shrink the film-like material by contacting the film-like material,
The present invention provides a method for producing a permselective membrane characterized by heating at 00 ° C., and further comprises solidifying an aromatic imide polymer having a haloalkyl group dissolved in an organic solvent in a coagulating liquid. Obtaining a film-like material, then contacting the film-like material with a solvent capable of shrinking the film-like material, thereby shrinking the film-like material and performing a quaternization reaction using an amine compound; and Another object of the present invention is to provide a method for producing a permselective membrane, characterized by further heating the film-like substance subjected to shrinkage and quaternization reaction by 100 to 200 ° C.

The aromatic imide polymer having a haloalkyl group that can be used in the present invention is produced by introducing a haloalkyl group into the aromatic imide polymer.

As the aromatic imide polymer, a known condensation polymer having an aromatic hydrocarbon group and an imide group in the main chain can be used without any limitation. For example, the following formula (I) (However, Ar ₁ and Ar _{2 each} represent a divalent aromatic hydrocarbon group.) Or the following formula (II) Those having a repeating unit represented by formula (1) are preferably used. In particular, in the present invention, the following formula (III) An aromatic imide polymer having a repeating unit represented by formula (1) is preferred. The average molecular weight is generally preferably 20,000 or more from the viewpoint of the mechanical strength of the obtained selectively permeable membrane.

As the haloalkyl group, a chloromethyl group, a bromomethyl group, an iodomethyl group, a chloroethyl group and the like are generally used. As a method for introducing a haloalkyl group into the aromatic imide polymer, a known method is used. For example, a halomethyl ether such as chloromethyl ether is used as a haloalkylating agent, and a catalyst such as SnCl ₄ , TiC
Friedel-craft type catalysts such as l ₄ and AlCl ₃ are used, and as a solubilizer or swelling agent for an aromatic imide polymer in order to uniformly perform haloalkylation, for example,
Halogenated hydrocarbons such as 1,2-dichloroethane and tetrachloroethane are preferably used. In general, the degree of haloalkylation in such an aromatic imide polymer is preferably from 3 to 12% by weight in terms of the halogen content measured by the Mohr method. Incidentally, the number of haloalkyl groups introduced per repeating unit of the aromatic imide polymer calculated from the halogen content described above is generally 0.5 to
2.2 pieces. The measurement of the ¹ H-nuclear magnetic resonance spectrum confirms that the haloalkyl group has been introduced into the aromatic ring of the aromatic imide polymer.

The above-mentioned aromatic imide polymer having a haloalkyl group is dissolved in an organic solvent to prepare a solution called a dope solution. As the organic solvent for dissolving the aromatic imide polymer having a haloalkyl group, those having compatibility with a coagulation solution described later are preferably used. For example, dimethylacetamide, N-methyl-2-pyrrolidone, dimethylformamide, 2-pyrrolidone , Tetrachloroethane and the like. In addition, the dope solution is prepared so that the concentration of the aromatic imide polymer having a haloalkyl group is generally 10 to 30% by weight, particularly 15 to 25% by weight, in order to facilitate molding into a film-like material described later. Is preferred.

In the present invention, as a method of forming a film from the above-mentioned dope solution, a known method can be adopted without any limitation.

When a flat film is obtained as a film, a method is employed in which the above-mentioned dope is cast on a flat plate and then immersed in a coagulation liquid to be solidified. When the membrane is a hollow fiber membrane,
In general, a known means for extruding and forming a dope from an annular nozzle for producing a hollow fiber is employed. For example, when using a tube-in-orifice type nozzle in which a tube projects at the center of an orifice that opens at the center of the nozzle bed, the annular gap between the inner peripheral surface of the opening of the orifice and the outer peripheral surface of the tube is used. In this method, a dope solution is extruded, and at the same time, a core solution is supplied from an inner hole of a tube to form a hollow fiber. The core liquid may be any liquid that does not coagulate the dope liquid from the inside of the hollow fiber and that does not dissolve the aromatic imide polymer having a haloalkyl group in the dope liquid, and water is generally used. . Next, the unsolidified hollow fiber membrane thus formed is quickly immersed in a predetermined coagulation liquid, and solidified from outside the hollow fiber,
A solidified hollow fiber membrane can be obtained.

When solidifying in the coagulating liquid, a solvent capable of contracting the film-like material described below is used as the coagulating liquid, and when conditions for contracting the film-like material are employed, a dense layer is formed on the surface of the film-like material. This makes it impossible to impart selective permeability to the film. Further, there is a fear that the film-like material cannot be shrunk due to contact between the film-like material and a solvent capable of shrinking the film-like material described below. Therefore, the type of the coagulating liquid and the conditions for solidification with the coagulating liquid are selected so that the film-like material contracts when the film-like material is brought into contact with a solvent capable of contracting the film-like material described below. Examples of the type of coagulation liquid include water; alcohols such as methanol, ethanol, and isopropyl alcohol; ethers such as tetrahydrofuran and dioxane; glycols such as ethylene glycol; and a mixture of two or more of these. Particularly, water, an aqueous methanol solution (50% by weight or more of water), and an aqueous solution of isopropanol (50% by weight or more of water) can be suitably used. Some of the examples of the coagulating liquid may cause the film to shrink depending on the temperature conditions.If such a coagulating liquid is used, a temperature condition that does not cause the film to shrink may be determined in advance. good. As a temperature condition which does not shrink the film-like material, a range of 0 to 50 ° C. is generally adopted.

The film thus obtained is then brought into contact with a solvent capable of shrinking the film. In the present invention, good selective permeability can be imparted to the film by bringing the film into contact with such a specific solvent. When the selectively permeable membrane obtained in the present invention is used as a separation membrane for a pervaporation method, the selectivity of the separation membrane is improved as the contraction rate of the membrane is increased, but, on the other hand,
It shows a tendency that the amount of transmission decreases. Therefore, an appropriate solvent may be selected in consideration of the balance between the selectivity and the permeation amount. In general, the linear shrinkage rate of the solidified film obtained above (when the film is a hollow fiber membrane, the shrinkage in the longitudinal direction of the hollow fiber membrane, the same applies hereinafter) is 3 to 30%. Preferably 5 to 25%
It is preferable to use a solvent that can be converted into a solvent.

Solvents preferably used in the present invention include, for example, alcohols such as methanol, ethanol and isopropyl alcohol; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as toluene and xylene; nitromethane, nitroethane, 1- Nitroalkanes such as nitropropane and 2-nitropropane; and mixtures of these solvents with each other, or aqueous solutions of these solvents.

As a method for contacting the film-like material with a solvent for shrinking the film-like material, a known solid-liquid contact method is employed without any limitation.
For example, a method of immersing the film in a solvent that shrinks the film, a method of applying a solvent to the film, and the like can be used. In addition, since the contraction rate of the film-like material often changes depending on the contact temperature and time, the temperature and time may be determined in advance so as to obtain an appropriate contraction rate. In order to impart good selectivity and good permeation amount to the film, the linear shrinkage of the film is preferably 3 to 30%, more preferably 5 to 25%. In order to obtain such a linear shrinkage, the contact temperature is selected from the range of room temperature to the boiling point of the solvent, and the contact time is selected from the range of 10 minutes to several hours.

In this way, a film having excellent permselectivity can be obtained.

The present invention also provides a method for performing quaternization by reacting an amine compound with a haloalkyl group of the aromatic imide polymer. By performing the quaternization reaction, the selective permeability can be further improved.

The quaternization reaction is carried out simultaneously with the shrinkage of the film of the aromatic imide polymer having a haloalkyl group.
That is, the amine compound is dissolved in a solvent that shrinks the film of the aromatic imide polymer having a haloalkyl group described above, and the haloalkyl group of the film is formed with the tertiary amino group of the amine compound. By the reaction, it is converted to a quaternary ammonium base, and a crosslinked structure is formed as required. Examples of the amine compound used in the present invention include aliphatic tertiary amines such as trimethylamine, triethylamine, triethanolamine and tributylamine, as well as primary, secondary amines, aliphatic polyamines and aromatic polyamines. Either may be used. In particular, amine compounds and polyamine compounds having a vinyl group are preferable because a crosslinked structure can be easily formed together with the conversion of the quaternary ammonium base in the present invention. Examples of the amine compound having such a vinyl group include N-vinyldimethylamine, N-vinyldiethylamine, N-vinyldiphenylamine, vinylpyridine, N-vinylpyrrole, N-vinylindole, vinylquinoline, vinylpiperidine, vinylpyrazine, Examples thereof include N-vinylimidazole, vinylbenzylamine, N, N-dimethylvinylbenzylamine, and methacryloylaminopropyldimethylamine. Among these, vinylpyridine and vinylbenzylamine can be particularly preferably used. When these amine compounds having a vinyl group are used, polymerization is performed if necessary. Examples of the polyamine compound include ethylenediamine, triethylenediamine, tetraethylenepentamine, polyethyleneimine, NNN'N'-
Tetramethyldiaminomethane, NNN'N'-tetramethylethylenediamine, NNN'N'-tetramethyl-1,3-propanediamine, NNN'N'-tetramethyl1,6-hexanediamine, NNN'N'-tetramethyl -1,4-phenylenediamine, NNN'N'-tetramethylbenzidine, NNN '
N'-tetramethyl-1,3-diamino-2-propanol and the like. Among these, when it is not a tertiary amine, it may be reacted with a haloalkyl group and then quaternized by a known method. Such amination and quaternization are also included in the quaternization reaction of the present invention. Generally, it is preferable to use the amine compound at a concentration of 0.1 to 3.0 mol / l. In the present invention, the reaction conditions for simultaneously performing the shrinkage of the film-like material and the quaternization reaction of the haloalkyl group with the amine compound are generally achieved by immersion treatment at room temperature to 80 ° C. for 30 seconds to 100 hours. .

The permselective membrane obtained by shrinking the aromatic imide polymer having a haloalkyl group obtained as described above, or the permselective membrane subjected to a quaternization reaction together with shrinkage is selectively permeated by further heating. Can be improved, the strength of the film can be increased, and expansion and contraction of the film can be prevented. The heating temperature is in the range of 100-200 ° C. When the heating temperature is lower than 100 ° C., the above-mentioned effect of the heating cannot be obtained. On the other hand, when the heating temperature is higher than 200 ° C., the temperature approaches the glass transition point of the film. As the heating temperature increases, the selectivity improves but the amount of permeation tends to decrease. Therefore, the heating temperature may be determined so as to obtain the selectivity and the amount of permeation according to the purpose.

The heating may be performed in any of a dry state and a wet state of the film, but when the film is heated in the wet state, the liquid impregnated in the film is vaporized by heating. As a result, pores are formed inside the film-like material, and the amount of permeation may increase.

The heating atmosphere may be any atmosphere, but depending on the composition of the film-like material, there is a case where an atmosphere without oxygen is better. Heat treatment may be performed on such a film-like material in an atmosphere of an inert gas such as nitrogen or argon.

(Effect of the Invention) The permselective membrane made of an aromatic imide polymer having a haloalkyl group provided in the present invention shows excellent selectivity when used as a separation membrane in a pervaporation method. In particular, the effect is remarkable in the case of alcohol-water separation. In addition, the selectively permeable membrane that has undergone a quaternization reaction with shrinkage exhibits higher selectivity and a higher permeation amount. In addition, since the permselective membrane obtained in the present invention is made of an aromatic imide polymer, heat resistance,
Good durability in chemical (solvent) resistance and mechanical strength.

Therefore, the permselective membrane obtained by the present invention is suitable for separation, concentration, and purification of a mixture containing an organic liquid or a mixture containing a non-aqueous liquid such as a solution of an organic compound, and is widely used in electronics, biochemistry, pharmaceuticals, foods, and the like. Available in the field.

(Example) Example 1 Repeating unit represented by the following formula Aromatic imide polymer having the following (trade name: Ultem 1000,
100 g of General Electric Company (molecular weight: 40,000) was uniformly dissolved in 832 g of dichloroethane while stirring at 50 ° C. under a nitrogen atmosphere at 67 ° C., 67 g of chloromethyl ether and 11 g of zinc chloride were added, and the mixture was stirred at 50 ° C. for 8 hours with stirring. Reacted. Next, the reaction solution was cooled to 30 ° C., precipitated in a large excess of methanol, dried under reduced pressure, dissolved in a chloroform-methanol system, and purified again. The obtained chloromethylated aromatic imide polymer had a chlorine content of 6.6% by weight as measured by the Mohr method, and the number of introduced chloromethyl groups per repeating unit of the polymer calculated from the chlorine content was 1.2. Individual. Further, the chloromethylated aromatic imide polymer was evaluated by ¹ H-nuclear magnetic resonance spectrum, and as a result, it was confirmed that the chloromethylated aromatic imide polymer was chloromethylated, which coincided with the methylene group concentration appearing at 4.56 ppm.

The above chloromethylated aromatic imide polymer was dissolved in a solvent of N-methylpyrrolidone to prepare a dope solution of a uniform solution having a concentration of about 20% by weight. Using this dope solution, a hollow fiber membrane is extruded from a hollow nozzle for producing a hollow fiber, and water is coagulated from the inside and the outside of the hollow fiber membrane as a coagulating liquid, and an inner diameter of 0.79 mm x an outer diameter of chloromethylated aromatic imide 1.
A 3 mm hollow fiber membrane was obtained.

Then, the hollow fiber membrane was immersed in a solvent for shrinking under the conditions shown in Table 1.

The concentration of isopropyl alcohol as a liquid to be treated was determined using a pervaporation separation device prepared by modularizing the 20 hollow fiber membranes having a length of 150 mm obtained above into a module.
85% by weight of isopropyl alcohol (IPA) and water (H
It was performed separated tested ₂ O) and a mixture of. The liquid to be treated was supplied to the inside of the hollow fiber membrane at a liquid temperature of 60 ° C., and the degree of vacuum on the external permeated gas chamber side was set at 3 Torr. From the results of the separation, Table 1 shows the permeate volume Q (g / m ² · hr) of the hollow fiber membrane and the separation coefficient α = (P _H2O × F _IPA / P _IPA × F _H2O , where P _H2O. = Water concentration on the permeated gas side (wt%) P _IPA = Concentration of isopropyl alcohol on the permeated gas side (wt%) F _H2O = Water concentration of the liquid to be treated (wt%) F _IPA = Isopropyl alcohol concentration of the liquid to be treated (weight) %) Further, the hollow fiber membrane comprising the aromatic imide polymer was modularized in the same manner as described above without being treated with a solvent, and subjected to a separation test of an IPA-H ₂ O mixed solution. The results are shown in Table 1.

Example 2 A hollow fiber membrane made of a chloromethylated aromatic imide polymer was prepared in the same manner as in Example 1 No. 5, except that in the immersion treatment of Example 1 No. 5, the treatment time was changed as shown in Table 2. Obtained. For each of the resulting hollow fiber membrane, a module in the same manner as in Example 1, showed the results were subjected to separation test of IPA-H ₂ O mixture in Table 2.

Example 1 No. 5 immersion-treated hollow fiber membrane was air-dried, and then heat-treated in the air under the conditions shown in Table 3. The resulting modularized in the same manner as in Example 1 for each of the hollow fiber membrane showed results were subjected to the separation test and the tensile strength test of the IPA-H ₂ O mixture in Table 3.

Example 4 A hollow fiber membrane obtained by contacting with a coagulating liquid in the same manner as in Example 1 was treated with 4-vinylpyridine (hereinafter referred to as 4V) at a concentration shown in Table 4.
Abbreviated as P. ) Was immersed in a methyl ethyl ketone solution and subjected to a reaction treatment at the temperature and time shown in Table 4 to obtain a hollow fiber membrane made of a crosslinked charged type modified aromatic imide polymer. In each case, the linear shrinkage when immersed in methyl ethyl ketone was 10.3%.

For each of the resulting hollow fiber membrane, similarly modularized as in Example 1, it showed the results were subjected to separation test of IPA-H ₂ O mixture in Table 4.

In addition, a hollow fiber membrane that had been subjected to a quaternization reaction in an aqueous solution of 4VP, which is a solvent that does not shrink the hollow fiber membrane, was modularized in the same manner as described above, and subjected to a separation test of an IPA-H ₂ O mixed solution. The results are shown in Table 4.

Example 5 The quaternized hollow fiber membrane of Example 4 No. 2 was air-dried and then heat-treated under a nitrogen atmosphere under the conditions shown in Table 5. The resulting modularized in the same manner as in Example 1 for each of the hollow fiber membrane showed. The results are strength test and tensile separation test of IPA-H ₂ O mixture in Table 5.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B01D 71/64 B01D 67/00 B01D 61/36

Claims (4)

(57) [Claims] An aromatic imide polymer having a haloalkyl group dissolved in an organic solvent is solidified in a coagulation liquid to obtain a film, and then a solvent capable of shrinking the film and a solvent capable of shrinking the film. A method for producing a selectively permeable membrane, wherein the membrane is contracted by contacting the membrane. 2. An aromatic imide polymer having a haloalkyl group dissolved in an organic solvent is solidified in a coagulation liquid to obtain a film, and then a solvent capable of shrinking the film and a film capable of shrinking the film. And shrinking the film-like material by contacting the film, and then heating the film at 100 to 200 ° C. 3. A film-like substance obtained by solidifying an aromatic imide polymer having a haloalkyl group dissolved in an organic solvent in a coagulation liquid, and then a solvent capable of shrinking the film-like substance and a film-like substance. And a quaternization reaction using an amine compound to cause contraction of the film-like material by contacting the film with the compound. 4. An aromatic imide polymer having a haloalkyl group dissolved in an organic solvent is solidified in a coagulating liquid to obtain a film, and then a solvent capable of shrinking the film and a solvent capable of shrinking the film. , The film-like material is contracted, and a quaternization reaction is carried out using an amine compound.
A method for producing a permselective membrane, characterized by heating at -200 ° C.