JPH10309449A - Organic material separating polymer film and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic material separating polymer film for separating a water and organic mixture on an organic material to be operated at the high temperature and provided with a high permeation flux and high separation constant. SOLUTION: A polyion complex is formed on a sulfonated aromatic polymer film having the thickness of substitution of sulfonic group of 0.2 to 5 mol.% is by using a cationic group containing synthetic polymer containing annular quaternary ammonium in the repeated unit to manufacture an organic material separating polymer film. Preferably the sulfonated aromatic polymer is sulfonated polysulfone or sulfonated polyethersulfone.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic substance aqueous solution, an organic substance mixture, an organic substance / water mixture vapor or an organic substance separation polymer membrane for separating water or an organic substance from an organic substance mixture vapor, and a method for producing the same. TECHNICAL FIELD The present invention relates to a polymer membrane for organic matter separation having a high permeation rate and a high separation performance in which a polyion complex is formed at a membrane interface, which is modified with a water-soluble polymer, and a method for producing the same.

[0002]

2. Description of the Related Art With respect to concentration and separation of an aqueous solution of an organic substance using a membrane, a reverse osmosis method has been put to practical use for concentration of a part of an aqueous solution of an organic substance having a low concentration. However, the reverse osmosis method needs to apply a pressure equal to or higher than the osmotic pressure of the separation liquid to the liquid to be separated, and therefore cannot be applied to a highly concentrated aqueous solution in which the osmotic pressure is high. There is a limit. On the other hand, pervaporation and vapor permeation methods, which are not affected by osmotic pressure, have been spotlighted as new separation methods. In the pervaporation method, a separation liquid is supplied to the primary side of the membrane, and the secondary side (permeation side) of the membrane is depressurized or a carrier gas is passed to make the separated substance gaseous and pass through the membrane. It is a way to make it. The vapor permeation method is to supply a mixed vapor instead of a separation liquid to the primary side of the membrane, and to reduce the pressure on the secondary side (permeation side) of the membrane or to ventilate the carrier gas to convert the separated substance into a gaseous state. This is a method of allowing the membrane to pass through. The permeated material generated by these is collected by cooling and condensing the permeated vapor.

[0003] Many studies have been reported on the pervaporation method. For example, US Patent 3,750,
No. 735 and U.S. Pat. No. 4,067,805 propose the separation of organics / water by polymers having active anionic groups. Also in Japan, Japanese Patent Application Laid-Open No. 59-109204 proposes using a cellulose acetate film and a polyvinyl alcohol film, and Japanese Patent Application Laid-Open No. 59-55305 proposes using a polyethyleneimine crosslinked film. However, the separation performance and heat resistance exhibited by the membranes described in these patents are low, and their practicability is poor. For this reason, JP-A-63-182005 discloses an ion complex membrane in which an ion complex is formed between a carboxyl group in the membrane and a cationic polymer having a quaternary ammonium group.
JP-A-9534 and JP-A-5-301035 propose ion-complex membranes in which an ion complex is formed between a hydrolyzed polyacrylonitrile membrane and a cationic polymer having a quaternary ammonium group, respectively. It is described that high separation performance can be obtained in pervaporation separation of an alcohol mixture. However, the separation active layer of the polyion complex membrane described in JP-A-63-182005, JP-A-2-229534 and JP-A-5-301035 is composed of polyacrylic acid and hydrolyzed polyacrylonitrile. Since these polymers have a glass transition temperature of about 90 ° C., long-term operation at 80 ° C. or more causes problems such as plasticization of the membrane or irreversible deterioration of membrane performance due to swelling.

For this reason, a polymer having excellent heat resistance is required as a film material. Examples of the polymer having excellent heat resistance include polysulfone, polyethersulfone, and polyetheretherketone, which are engineering plastics having an aromatic ring in the molecule. Since polymers as engineering plastics generally have poor hydrophilicity, attempts have been made to add hydrophilicity by introducing sulfonic acid groups. For example, Japanese Patent Laid-Open No. 5-1848
No. 90 discloses separation of a water / alcohol mixture using a pervaporation membrane having polysulfone in a dense layer. In addition, Japanese Patent Publication No. 53-13679 discloses a method of providing a polymer that has been hydrophilized by introducing a sulfonic acid group into polysulfone and Japanese Unexamined Patent Publication No. 2-16126, into polyether sulfone. . Further Japanese Patent
JP-A-62-95104 describes that a sulfonated polyetheretherketone membrane obtained by sulfonating polyetheretherketone has high hydrophilicity in ultrafiltration separation. In order to increase the hydrophilicity of the membrane as described above, introduction of a sulfonic acid group is effective. However, when a large number of sulfonic acid groups are introduced, the membrane swells with water, and conversely, the membrane separation performance is reduced.

[0005]

As described above, if a sulfonic acid group is introduced into a heat-resistant polymer, the heat resistance and the hydrophilicity can be improved. However, a large amount of sulfonic acid groups are introduced to enhance the hydrophilicity. This does not necessarily enhance the separation performance of the membrane.

The present invention has a high permeation rate and a high separation performance suitable for separating an organic substance aqueous solution, an organic substance mixture, an organic substance / water mixture vapor or an organic substance mixture vapor by a pervaporation method and a vapor permeation method. Another object of the present invention is to obtain a polymer membrane for separating organic substances having heat resistance.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies on the above points, and as a result, have found that an aromatic polymer having a sulfonic acid group can be ion-complexed with a cationic polymer having a cyclic structure to obtain an 80% polymer. It has been found that a high permeation rate and a high separation performance are maintained even at a temperature of not less than ℃, and a polymer membrane for organic matter separation having excellent heat resistance can be obtained.

That is, the present invention relates to a polymer membrane for separating a water / organic substance or an organic mixture by a pervaporation method or a vapor permeation method, wherein the surface of the sulfonated aromatic polymer membrane has a cyclic quaternary ammonium base. For separating organic substances, characterized in that the aromatic polymer and the cationic polymer having a cyclic structure at the interface are modified by a cationic polymer containing a repeating unit in a repeating unit to form a polyion complex by ionic bonding. It is intended to provide a polymer film.

According to the present invention, the molecules of the sulfonated aromatic polymer and the specific cationic polymer are associated with each other through many ionic bonds to form a polyion complex, thereby providing excellent heat resistance and high permeation rate. And a polymer membrane for organic matter separation having high separation performance can be obtained. In addition, the polyion complex generally shows solvent insolubility because molecular chains are associated with each other by ionic bonds, and as a result, the polymer membrane for organic matter separation of the present invention has good solvent resistance.

In preparing the polymer membrane for organic matter separation of the present invention, a membrane composed of a sulfonated aromatic polymer is formed in advance, and a cyclic quaternary ammonium base is contained in a repeating unit on the membrane surface. A polyion complex is formed by casting the cationic polymer or immersing the membrane in a cationic polymer solution containing a cyclic quaternary ammonium base in a repeating unit. In general, as a method for producing a polyion complex membrane, a method in which an anionic polymer and a cationic polymer are previously dissolved in a solvent, cast on a smooth surface such as glass, and then a film is formed together with the evaporation or solvent replacement of the solvent, an anionic polymer or a cation. Casting a membrane consisting of only one of the reactive polymers in advance, forming a membrane, and casting a counter-ionic polymer solution on the membrane surface to form a polyion complex near the interface between both polymer layers, A method of forming a polyion complex on the membrane surface by immersing a membrane made of only one of an anionic polymer and a cationic polymer formed in advance in a counterionic polymer solution and adsorbing the counterionic polymer in the solution. Etc. are known. However, in a general production method, swelling and gelation occur in a solvent, so that film formation is difficult. On the other hand, membrane formation is easy according to the above-mentioned production method, and it is considered that the polyion complex produced by the particular production method is present in an extremely thin layer at the interface or surface, whereby a sufficiently high separation performance is exhibited.

In the present invention, sulfonated aromatic polymers which can be used as an anionic polymer having excellent heat resistance include sulfonated polysulfone,
Sulfonated polyether sulfone, sulfonated polyether ether ketone, sulfonated polyphenylene oxide, sulfonated polystyrene and the like can be mentioned.
However, sulfonated polysulfone or sulfonated polyethersulfone is particularly preferred because it can form a film having excellent heat resistance and good hydrophilicity. Further, the molecular weight of the sulfonated polysulfone and the sulfonated polyether sulfone is desirably 15,000 to 200,000.

In the present invention, the cationic polymer containing a cyclic quaternary ammonium base in a repeating unit which can be used as a cationic polymer having excellent heat resistance is, for example, a compound represented by the following structural formula:

[0013]

Embedded image

(Wherein X represents an anionic group, and n represents the degree of polymerization.) R ₁ is H, and R ₂ is CH ₃ , C ₂ H ₅ , CH ₂ CH ₂ OH, CH ₂ Ph, CH ₂ CH = C
H ₂ or CH (OH) CH ₂ Cl, R ₁ is CH ₃ and R ₂ is CH ₃ , CH ₂ CH ₂ O
H, CH ₂ Ph or CH (OH) CH ₂ Cl, R ₁ is C ₂ H ₅ , R ₂ is C ₂ H ₅ and R ₁ is CH ₂ CH ₂ OH, and R ₂ is CH ₂ CH ₂ OH And those in which X is Cl. Among them, those in which R ₁ and R ₂ are a hydrocarbon group having 1 to ₂ carbon atoms or a benzyl group are particularly preferable because the properties of a polyion complex formed by ionic bonding with a sulfonated aromatic polymer are good. . The molecular weight of such a cationic polymer is preferably from 2000 to 500,000.

The sulfonated aromatic polymer used in the present invention preferably has a degree of sulfonic acid group substitution of 5 mol% or less. Specifically, it is desirable that the content be 0.2 mol% or more and 5 mol% or less. More preferably, the content is 0.3 mol% or more and 3.5 mol% or less. If the amount is less than 0.2 mol%, the formed polyion complex membrane does not have sufficient hydrophilicity and thus does not show good separation performance. If it exceeds 5 mol%, the membrane swells with water and the separation performance is rather deteriorated. Would. The degree of sulfonic acid group substitution in the present invention is the number of sulfonic acid groups introduced per unit unit constituting the polymer, and is expressed in mol%.

The polymer membrane for separating organic substances of the present invention can further improve the durability and solvent resistance of the membrane by providing a crosslinked structure consisting of a covalent bond in addition to an ionic bond. In the case of a material having a very high hydrophilicity, such as the membrane of the present invention, by having both the polyion complex structure and the cross-linking structure by covalent bond, the swelling of the membrane due to the aqueous solution of the organic substance to be separated is further reduced. , Separation performance is kept high. The crosslink by covalent bond described here may be a method using an electrolytic group such as a sulfonic acid group or an amino group. However, all or most of the electrolytic group is consumed and the ability to form a polyion complex is lost. It must not be so advanced that it can cause it to fall. The crosslinking is preferably carried out by dissolving a crosslinking agent in a solution of a polymer to be a film material and, after forming the film, performing a reaction with heating or a suitable catalyst. Examples of the crosslinking agent include methylolated melamine and diamine.

When the polymer membrane for separating organic substances according to the present invention takes the form of, for example, a flat membrane, the membrane is preferably as thin as possible. However, in general, a film having a film thickness of 10 μm or less has insufficient mechanical strength, and it is difficult to apply a high pressure difference on both sides of the film to use it as a separation film.
4040 μm is appropriate. Obtaining an asymmetric membrane by a phase transformation method after adding a cross-linking agent to a solution comprising a sulfonated aromatic polymer as a membrane material as necessary is a point that the skin layer can be thinned and the mechanical strength of the membrane is supplemented. Desirable. In addition, after adding a crosslinking agent to a solution comprising a sulfonated aromatic polymer as a membrane material on a porous support as necessary, the solution is cast using an applicator such as a doctor blade or a wire bar, and then heated and dried. Alternatively, it is also desirable to obtain a composite film or a reinforcing film by performing an ion complexing treatment after forming the film by phase conversion. Here, the porous support has, on the surface thereof, fine pores of several tens to several thousand square meters, and the material is polysulfone,
It is a known sheet material such as a porous film such as polyether sulfone, cellulose ester, polycarbonate or polyvinylidene fluoride, and a nonwoven fabric or woven fabric. Further, it is preferable to reduce the thickness of the skin layer of the composite film or the reinforcing film,
Therefore, lowering the solid content concentration of the solution comprising the sulfonated aromatic polymer applied on the porous support,
Alternatively, it is desirable to reduce the thickness to which the solution is applied.

The polymer membrane for separating organic substances according to the present invention can be in any form such as a known flat membrane, tube membrane or hollow fiber membrane. For example, a module can be formed by laminating a flat membrane of a polymer membrane for separating organic substances as it is, or by forming it into a pleated or spiral shape.

The polymer membrane for separating organic substances of the present invention is used for separating a water / organic substance mixture. Organic substances include, for example, alcohols such as methanol, ethanol, 1-propanol, 2-propanol and n-butanol, acetone, ketones such as methyl ethyl ketone, tetrahydrofuran,
Ethers such as dioxane, organic acids such as formic acid and acetic acid,
Aldehydes such as aldehyde and propionaldehyde,
Amines such as pyridine and picoline;
The polymer membrane for organic matter separation of the present invention is used for separating an aqueous solution containing one or more of these or a vapor mixture with water. It can also be used for separating an organic mixed solution or an organic vapor mixture containing two or more of the above organic substances.

[0020]

Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Examples 1 and 2 (1) Film formation Polysulfone having a molecular weight of about 100,000 was prepared by the method of Johnson et al.
According to Polym. Sci. Polym. Chem. Ed. (1984)), a sulfonation treatment was carried out in a dichloroethane solution using a sulfur trioxide-triethyl phosphate complex to prepare a sulfonated polysulfone shown below. The degree of substitution of sulfonic acid groups in the obtained polymer is 0.4, 0.6, and 2.5 mol%, respectively.
Met. The degree of substitution of the sulfonic acid group was determined by dissolving 0.5 g of the sample in 50 ml of N-methyl-2-pyrrolidone and calculating the ion exchange capacity by potentiometric titration using an aqueous 0.1 N-KOH solution.
Then I asked.

[0022]

Embedded image

(Wherein m ₁ represents 0.002 to 0.05, and n represents an integer).

The obtained polymer was dissolved in N, N-dimethylformamide at a concentration of 18% by weight to prepare a dope solution. The dope solution was cast on a glass plate, dried at 80 ° C. for 12 hours, and desolvated to prepare a flat film having a thickness of 25 μm. The sulfonated polysulfone membrane obtained at room temperature was immersed in a 2 wt% aqueous solution of the following cationic polymer (PAS-A, molecular weight: about 100,000; manufactured by Nitto Boseki Co., Ltd.) for 24 hours to obtain an ion complex membrane. .

[0025]

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(In the formula, n represents an integer.)

(2) Evaluation of separation performance The membrane obtained in the above (1) was previously immersed in hot water at 100 ° C for 4 hours. Next, on the primary side of the membrane, ethanol / water at a temperature of 60 ° C. (= 95/5 weight ratio) or 2-propanol / 80 ° C.
A mixed solution of water (= 95/5 weight ratio) was supplied, and the secondary side of the membrane was maintained at 10 mmHg by a vacuum pump. After reaching the steady state, the permeated mixed vapor was trapped by liquid nitrogen, and the total number of moles of the permeated mixed vapor was calculated from the weight measurement and the composition analysis by gas chromatography.

(3) Evaluation Results Table 1 shows the results of using a sulfonated polysulfone membrane having a sulfonic acid group substitution degree of 0.6 mol%. FIG. 1 shows the relationship between the specific permeation rate and the separation coefficient of a sulfonated polysulfone membrane and the degree of sulfonic acid group substitution. The specific transmission speed (Q) is obtained by multiplying the amount of the permeated mixture per unit film area by the film thickness, and is expressed in units of kg · m ⁻¹ · h ⁻¹ . The separation coefficient (α) is a ratio of the component 1 and the component 2 in the permeated gas to the ratio of the component 1 and the component 2 in the supply liquid or the supply vapor. That is, α = (x / y) p / (x / y) f. Where x
And y represent the respective compositions of component 1 and component 2 in a binary system, and p and f represent the permeation and feed.

Examples 3 and 4 (1) Film formation Polyether sulfone having a molecular weight of about 80,000 was subjected to a sulfonation treatment in the same manner as in Examples 1 and 2 (1) to give the following sulfonated polyether sulfone. Was adjusted.
The degree of substitution of the sulfonic acid groups of the obtained polymer was each 0.1.
6, 1.6, and 3.1 mol%. N, N
-A dope solution was prepared by dissolving in dimethylformamide at a concentration of 30 wt%. Dope solution was cast on a glass plate, and 80
Drying at 12 ° C. for 12 hours and desolvation were performed to produce a flat film having a thickness of 34 μm. The resulting sulfonated polyether sulfonic acid was ion-complexed under the same conditions as in Examples 1 and 2 (1).

[0030]

Embedded image

(Wherein m ₂ represents 0.002-0.05, and n represents an integer).

(2) Evaluation of Separation Performance The evaluation was performed under the same method and conditions as in (2) of Examples 1 and 2.

(3) Evaluation Results Table 1 shows the results obtained by using a sulfonated polyethersulfone membrane having a sulfonic acid group substitution degree of 0.6 mol%. FIG. 2 shows the relationship between the specific permeation rate and the separation coefficient of the sulfonated polyether sulfone membrane and the degree of substitution of the sulfonic acid group.

Comparative Examples 1 and 2 Polyacrylonitrile film (manufactured by Daicel Chemical Industries, Ltd .;
DUY-L) to 1kmol · m ^-3 aqueous sodium hydroxide solution
Hydrolysis was performed at 80 ° C. for 50 minutes. The obtained membrane was washed with water and ion-complexed by the method described in (1) of Examples 1 and 2. The obtained film was directly evaluated by the method described in Examples 1 and 2 (2). Table 1 shows the results. Compared with the sulfonated polysulfone membrane of Example 1 and the membrane obtained by ion-complexing the sulfonated polyethersulfone membrane of Example 2, the separation coefficient was extremely small and the specific permeation rate was low.

[0035]

[Table 1]

[0036]

According to the present invention, an ion complex is formed with a cationic polymer containing a sulfone group and a cyclic quaternary ammonium base in a repeating unit, particularly on a membrane comprising a sulfonated aromatic polymer containing a sulfone group. The membrane has a high water permeation rate and a high separation performance, and is more excellent in solvent resistance, heat resistance and durability than a membrane in which an ion complex is formed by a conventional carboxyl group-containing polymer and a cationic polymer.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the specific permeation rate and the separation coefficient of a polyion complex membrane comprising a sulfonated polysulfone membrane and the degree of substitution of a sulfonic acid group.

FIG. 2 is a graph showing the relationship between the specific permeation rate and the separation coefficient of a polyion complex membrane comprising a sulfonated polyether sulfone membrane and the degree of substitution of a sulfonic acid group.

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[Procedure amendment]

[Submission date] February 5, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

Examples 3 and 4 (1) Film formation Polyether sulfone having a molecular weight of about 80,000 was subjected to a sulfonation treatment in the same manner as in Examples 1 and 2 (1) to give the following sulfonated polyether sulfone. Was adjusted.
The degree of substitution of the sulfonic acid groups of the obtained polymer was each 0.1.
6, 1.6, and 3.1 mol%. N, N
-A dope solution was prepared by dissolving in dimethylformamide at a concentration of 30 wt%. Dope solution was cast on a glass plate, and 80
Drying at 12 ° C. for 12 hours and desolvation were performed to produce a flat film having a thickness of 34 μm. The resulting sulfonated polyether sulfone
The membrane was ion-complexed under the same conditions as in Examples 1 and 2 (1).

Claims (8)

[Claims] 1. A polymer membrane for separating a water / organic substance or an organic mixture by a pervaporation method or a vapor permeation method, wherein the surface of the membrane of a sulfonated aromatic polymer is formed by repeating cyclic quaternary ammonium bases. A polymer membrane for separating organic matter, wherein the polymer is modified by a cationic polymer contained therein, and the aromatic polymer and the cationic polymer associate at the interface by ionic bond to form a polyion complex. 2. The polymer membrane for separating organic matter according to claim 1, wherein the aromatic polymer is sulfonated polysulfone or sulfonated polyether sulfone. 3. The cationic polymer according to claim 1, wherein the cationic polymer is represented by the following structural formula.
Or the polymer membrane for organic matter separation according to 2. Embedded image (In the formula, R ₁ and R ₂ represent a hydrocarbon group having 1 to ₂ carbon atoms or a benzyl group, X represents an anionic group, and n represents a degree of polymerization.) 4. The aromatic polymer according to claim 1, wherein the degree of substitution of sulfonic acid groups is 0.2 mol% or more and 5 mol% or less.
4. The polymer membrane for separating an organic substance according to any one of items 3 to 3. 5. After forming a membrane of a sulfonated aromatic polymer, a cationic polymer containing a cyclic quaternary ammonium base in a repeating unit is adhered onto the membrane surface, and the aromatic polymer and the cationic polymer are mixed. A method for producing a polymer membrane for separating organic substances, comprising forming a polyion complex by associating polymers by ionic bonding. 6. The method according to claim 5, wherein the aromatic polymer is a sulfonated polysulfone or a sulfonated polyether sulfone. 7. The cationic polymer according to claim 5, wherein the cationic polymer is represented by the following structural formula.
Or the method for producing a polymer membrane for separating an organic substance according to item 6. Embedded image (In the formula, R ₁ and R ₂ represent a hydrocarbon group having 1 to ₂ carbon atoms or a benzyl group, X represents an anionic group, and n represents a degree of polymerization.) 8. The aromatic polymer according to claim 5, wherein the degree of substitution of sulfonic acid groups is from 0.2 mol% to 5 mol%.
8. The method for producing a polymer membrane for organic matter separation according to any one of claims 7 to 7.