JP2003225543A - Organic compound separation membrane and separation method for organic compound using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an innovative organic compound separation membrane having high selectivity and permeability and stable for a long duration and an organic compound separation method using the membrane. <P>SOLUTION: The organic compound separation membrane is characterized in that a film in which a macrocyclic compound identifying compound exists is formed on a base film having a polyion complexed solid film surface. The organic compound separation membrane is characterized in that charged groups exist in the base film surface and the polyion complexed solid film surface is formed on the base film by bonding a polymer electrolytic substance having the opposed charge to that of the charged groups in a thin film state based on the electrostatic mutual reaction. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an organic compound separation membrane and a method for separating organic compounds using the separation membrane.

[0002]

2. Description of the Related Art Separation or concentration operations of substances using a separation membrane are widely used in various fields such as chemical industry, food industry, pharmaceutical industry, medical field, energy field, water treatment and semiconductor manufacturing. However, the practical separation membranes that are actually used at present have a separation target because the separation principle is based on the difference in the size of the permeate and the difference in the physicochemical affinity between the membrane material and the permeate. There is a drawback that.
For example, with such a separation membrane, it is difficult to separate a compound having a similar chemical structure such as an isomer or a compound having a similar physicochemical property such as a boiling point. Certainly, by improving various conventional separation membranes, a method of separating alcohol from an alcohol / ether azeotrope or an alcohol / raffinate azeotrope using a membrane material such as cellulose acetate or polyvinyl alcohol (for example, Japanese Patent Publication No. 6-57866, Japanese Patent Laid-Open No. 2001-12937.
No. 3) has been developed, but basically, conventional membranes are not suitable for separating such substances. Therefore, attempts have been made to develop a separation membrane using a molecular recognition compound that exhibits extremely excellent selectivity for such substances, and a liquid membrane that uses a liquid in which the molecular recognition compound is dissolved as a membrane. Some polymer membranes in which pendants are bound to molecules and molecular recognition compounds have been reported (eg, Japanese Patent No. 1661020, optical isomer separation membrane, Japanese Patent No. 1935943).
No. Organic compound separation membrane). However, the former can achieve high selectivity, but lacks stability, and the latter has long-term stability, but cannot satisfy high selectivity and high flux. It has not been developed that has both high selectivity, high permeability, and long-term stability, which are required for.

[0003]

An object of the present invention is to provide a novel organic compound separation membrane having high selectivity and permeability, which is stable for a long period of time, and an organic compound separation method using this membrane. To provide.

[0004]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that the surface of the base film is subjected to plasma irradiation or chemical treatment so that the surface of the base film has a charged group. After that, the solid membrane on which the polyion complex obtained by binding the polyelectrolytes having opposite charges in a thin film form by electrostatic interaction is formed into the hydrophobic organic compound which is an undesired substance contained in the separation target substance. On the other hand, it becomes an effective permeation barrier, blocks the passage of these undesired substances, and further contains a molecular recognition compound in the polyelectrolyte, so that the target substance to be separated can be selectively transported and separated. I found that I can do it. Further, by using this membrane, it was found that a target substance can be selectively separated from a mixture containing an undesirable substance, and based on this finding, the separation method of the present invention was completed. It was

That is, according to the present invention, the following inventions are provided. (1) An organic compound separation membrane, wherein a membrane is formed by allowing a macrocyclic molecule recognizing compound to exist on a base membrane having a polyion-complexed solid membrane surface. (2) A polyion-complexed solid obtained by allowing a polyelectrolyte having a charge opposite to that of the charged group to form a thin film on the surface of the base film with electrostatic groups present on the surface of the base film. The organic compound separation membrane according to (1) above, which is a membrane surface. (3) The organic compound separation membrane as described in (2) above, wherein the surface of the base film is a film in which charged groups are present on the surface by plasma irradiation or chemical treatment. (4) A mixed solution containing a compound having a similar chemical structure or a mixture containing an organic compound forming an azeotropic compound is brought into contact with the membrane described in (1) above to separate the organic compound. Method for separating organic compounds.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The separation membrane of the present invention comprises a base membrane having a solid membrane surface on which a polyion complex (in other words, a polyion complex is formed) is allowed to contain a macrocyclic molecule recognizing compound. A film on which a film is formed.

The base membrane used as the separation membrane is an organic polymer membrane made of a cellulose derivative such as cellulose acetate, polyethylene, polytetrafluoroethylene, polyamide, polysulfone, polyvinyl alcohol, polysilicon, etc., and zeolite, silica, A porous inorganic material film selected from inorganic oxides such as alumina and alumina silicate and metals such as palladium and tungsten is used.

For the formation of the base film of the present invention, in the case of an organic polymer film, a method for producing such an organic polymer film is usually used. For example, in the case of a cellulose acetate film, a so-called phase separation method is adopted in which cellulose acetate is dissolved in a solvent such as dioxane, and the solution is poured onto the surface of a glass plate and immersed in a poor solvent to form the film. Membranes made of polyethylene, zeolite, etc. are also produced by the commonly used methods such as melt drawing and sol-gel method. The base film may be formed as long as the base film can be formed, and the present invention is not limited to this, and a conventionally known method can be appropriately adopted for production. As the film made of an inorganic oxide and the porous inorganic substance film, a film made of these substances is used.

Next, the surface of the base film is brought into a state where charged groups are present. The charged group means a cation or an anion. The state in which charged groups are present on the surface of the base film means that the surface of the base film is charged by a specific treatment. Chemical treatment and plasma treatment are performed as the treatment for bringing the charged group into the state. For the chemical treatment, surface treatment by a normal chemical reaction using a chemical substance is performed. As the chemical reaction, a functional group on the base film and a reaction reagent having an ionic group such as a carboxyl group, a sulfonic acid group, and an amino group at one end may be reacted, and all commonly used reactions can be performed. Applicable. For example, when a silanol-containing hydroxyl group is present on the surface of the base film, aminopropylsilane may be reacted, and a cation can be easily introduced onto the surface of the base film by this method. When it is desired to introduce an anion, a silane agent having a carboxyl group or a sulfonic acid group at the terminal may be used instead of aminopropylsilane. Further, in the case of cellulose acetate having no such reactive group on the surface of the base film, first, the surface is treated with a strong alkaline aqueous solution to generate a hydroxyl group, and then treated with an acid anhydride to facilitate the treatment. Carboxyl groups can be introduced on the surface. In the case of plasma treatment, oxygen plasma is used when anions are applied to the surface. In a cellulose acetate film, an anion group can be introduced into the film surface by treating the film in oxygen plasma (0.1 Torr) for 20 to 100 W for 30 to 180 seconds. Although there are some changes in the conditions of the plasma treatment depending on the substance, the conditions of the values in this range are set.
When imparting cations to the surface, ammonia can be used instead of oxygen and the treatment can be performed in the same manner. The introduction of charged groups on the surface of the film by the treatment can be confirmed by the following facts. In the untreated membrane, no polyion complex is formed, the contact angle of the membrane surface with water is decreased before and after the treatment to increase the hydrophilicity, and the functional group on the surface is increased after the treatment.
For example, in the oxygen plasma treatment, the oxygen content is increased (a specific example of this method is described later in Examples) and the CH bond is decreased and the CO bond is increased.
You can check.

Polyion complex (in other words,
The thin film (on which the polyionic complex is formed) is prepared as follows. When the surface of the base membrane is subjected to a base membrane treatment operation in a state where charged groups are present, and when the base membrane surface has cations, a polyelectrolyte having anions and also a base membrane If the surface has anions,
Contact with a polyelectrolyte having cations. For example,
When the base film has a cation, acrylic acid, alginic acid and the like can be used, and when the base film has an anion, compounds such as polyallylamine and chitosan can be used. The polyion complex thin film thus formed acts as a barrier against undesired coexisting organic compounds at the time of separation, and only the compound to be permeated interacts with the molecular recognition compound to permeate through the film and separate. Noh develops.

According to the procedure described above, a molecular recognition compound-containing polyion complex thin film is prepared by introducing and coexisting the molecular recognition compound into the film on which the polyion complex is formed. As the molecular recognition compound, a conventionally known cyclic compound such as cyclodextrin, cyclophane, calixarene (a type of cyclophane), or the like, which can form a hydrophobic molecule recognition field even with a cyclic or acyclic compound having a hydrophobic ring If it can be used. As a method of introducing the molecular recognition compound, a polyion complex may be formed by preliminarily binding it to the polymer electrolyte by a covalent bond, or may be introduced at the time of forming the polyion complex. In the former case, it may be prepared by copolymerizing a vinyl monomer having a molecular recognition compound and a monomer having an ionic group, or a polyelectrolyte may be prepared and then the molecular recognition compound may be attached to a side chain on a pendant. May be. In the latter case, for example, by allowing a molecular recognition compound to coexist in a solution at the time of forming an ion complex, it can be incorporated into the ion complex network by electrostatic interaction or hydrophobic interaction.

As the base film, one having a large permeability to a hydrophobic substance is used. Further, the polymer electrolyte forming the ion complex is suitably hydrophilic. In the membrane prepared under such conditions, the polyion complex thin film acts as a barrier against undesired coexisting organic compounds, and only the compound to be permeated permeates the membrane through the ring of the molecular recognition compound. It will be. As a membrane separation method using this membrane, various conventional membrane separation methods such as pervaporation, dialysis, gas separation, pressure filtration, electrodialysis, etc. can be used according to the characteristics of the substance to be separated.

The mixture of organic compounds which can be separated in the present invention is a mixed solution containing a compound having a similar chemical structure or a mixed solution containing a compound having a similar physicochemical property such as boiling point. Specifically, various azeotropic mixtures, structural isomer mixtures such as n-alkyl alcohols, i-alkyl alcohols and t-alkyl alcohols, o
-Xylene, m-xylene, p-xylene, a mixture of positional isomers of 2,6-dimethylnaphthalene and 2,7-dimethylnaphthalene, and a mixture of optical isomers such as amino acids.

[0014]

EXAMPLES The present invention will be described in more detail based on examples. However, it is not limited to this embodiment. Example 1 [Water / Ethanol Separation by Polyion Complex Membrane] A 2% dioxane solution of acetyl cellulose (average molecular weight: 50,000) was poured on a glass plate and air-dried for 1 day to obtain a transparent film. This film in oxygen plasma (0.1 Tor
In step r), an anionic group was introduced into the membrane surface by treating it for 20-100 W for 30-180 seconds. Then, this membrane was treated with a cationic polyelectrolyte polyallylamine (average molecular weight 6000).
A polyion complex was formed on the surface of the film by immersing it in the aqueous solution of (0). The introduction of anionic groups on the surface of the film by plasma treatment means that no polioion complex is formed in the untreated film,
The contact angle of water on the membrane surface is 67 ° to 24 ° before and after treatment.
It was proved from a sharp decrease and an increase in hydrophilicity, and an increase in oxygen content on the surface and a decrease in CH bonds and an increase in CO bonds after plasma treatment, as shown in ESCA measurement in Table 1. The formation of the polyion complex was confirmed by a total reflection infrared spectrophotometer (ATR / FT-IR) by the decrease or disappearance of the C = O absorption (around 1750 cm ^-1 ) of the acetyl group of the base film.

[0015]

[Table-1]

The permeation inhibiting ability of the hydrophobic compound by this membrane was measured by a pervaporation experiment of a water / ethanol mixed solution. Table 2 shows the results of measuring a 90% ethanol aqueous solution.

[Table-2]

The experimental temperature was 25 ° C., the pressure on the permeate side was 25 Pa, and the analysis of the permeate was carried out using a GC chromatograph. The selectivity α in the table is α = (water concentration in permeate / ethanol concentration in permeate) / (water concentration in stock solution / ethanol concentration in stock solution). From this table, it was found that in the membrane having the polyion complex thin film formed on the surface, the selectivity of the membrane for water was remarkably improved, and the polyion complex became an effective barrier for the hydrophobic organic compound. Further, it was found that the selectivity was increased by repeating the operation of immersing the polyion complex thin film in a polyacrylic acid aqueous solution having a negative charge opposite to that of allylamine, then washing and immersing the polyallylamine aqueous solution again. For example, in a membrane in which this lamination operation was repeated twice and three layers of polyion complex layers were formed, the water flux was slightly reduced to half that of the single layer membrane, but the selectivity increased markedly, and It's quadrupled to 80. This means that stacking the polyion complex thin film increases the effect of a barrier against undesired hydrophobic organic substances without significantly impairing the water flux, and significantly improves the membrane performance. This is an important finding for developing.

Example 2 [Separation of butanol isomers by cyclodextrin-containing polyion complex membrane] The cyclodextrin-containing cationic polyelectrolyte was 2-hydroxy-3-methacryloyl-
It was prepared by copolymerizing β-cyclodextrin and allylamine by the following method. 4g 2-hydroxy-3-metha
After cryloyl-β-cyclodextrin and 1 g of allylamine were dissolved in 10 ml of water and degassed for 30 minutes, 0.05 g of ammonium persulfate was added and reacted at 50 ° C. for 24 hours under a nitrogen atmosphere. Then, the produced copolymer was precipitated with ethanol, washed, and then vacuum dried. Hereinafter, this copolymer will be referred to as PALA-β-CD. Polyion complex membrane has a thickness of 17
The membrane was prepared by immersing the Nafion 117 (manufactured by DuPont) membrane of 8 μm as a base membrane in an aqueous solution of PALA-β-CD at room temperature for 24 hours. The formation of polyion complex thin film was confirmed by ATR-FTIR and ESCA. Original Nafion and PALA-β-CD treated Nafion (Nafion / PALA
The results of ESCA of -β-CD) are shown in Table 3.

[0019]

[Table-3] From this table, it can be seen that in the Nafion film treated with PALA-β-CD, the fluorine atom of Nafion disappeared and the nitrogen atom of allylamine newly appeared. Also, the relative concentration of sulfonic acid groups on Nafion is significantly reduced. This is PA
In the LA-β-CD treated Nafion membrane, it means that the thin PALA-β-CD polyelectrolyte covers the Nafion surface and forms an ion complex thin film. Since it is clear that the polyion complex membrane effectively blocks hydrophobic organic compounds as shown in Experimental Example 1, isomer separation, which is a higher degree of separation in this membrane, can be used for tertiary butanol (t-butanol) and primary butanol. Separation of (n-butanol) was examined by a pervaporation experiment. The results are shown in Table 4.

[0020]

[Table-4]

The experimental conditions are temperature: 25 ° C., pressure on the permeate side:
25Pa, undiluted composition: t-butanol / n-butanol = 45
/ 55, and the analysis of the permeate was performed using a Gaku chromatograph. The selectivity α in the table is α = (n-butanol concentration in the permeate / t in the permeate
-Butanol concentration) / (n-butanol concentration in stock solution /
T-butanol concentration in the stock solution). The table also shows the results for a membrane in which only polyallylamine containing no cyclodextrin was polyion-complexed with Nafion. From this table, the effect of CD is clear, and there is almost no selectivity in the membrane in which the polyion complex is formed only by Nafion or polyallylamine not containing Nafion and CD, but the polyallylamine containing CD forms a polyion complex thin film on the surface. The selected Nafion membrane clearly shows the selectivity for n-butanol. from this result,
It can be seen that not only the polyion complex acts as an effective barrier of the hydrophobic organic compound, but also the molecular recognition compound contained therein effectively acts as a fixed carrier. Further, since the film thickness of this polyion complex film is small, it can be said that the reduction of the flux is small and the high flux and high selectivity which are the aims of the present invention can be realized.

[0022]

According to the membrane of the present invention, the surface of the base film is subjected to plasma irradiation or chemical treatment to make it have a charged group on the surface of the base film, and then a polyelectrolyte having an opposite charge is electrostatically interacted with the polymer electrolyte. The solid membrane on which a polyion complex obtained by binding in a thin film by the action is an effective permeation barrier against a hydrophobic organic compound or a hydrophilic organic compound which is an undesirable substance contained in the substance to be separated, By blocking the passage of these undesired substances and further incorporating a molecular recognition compound in the polyelectrolyte, it is possible to selectively transport the target substance to be separated. can get. Further, by using this membrane, the target substance can be selectively separated from the mixture containing the undesirable substance.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C07C 31/12 C07C 31/12 C08J 7/00 306 C08J 7/00 306 CEP CEP 7/12 7/12 Z // C08L 1:12 C08L 1:12 (72) Inventor Takashi Iwatsubo 1-1-1 East, Tsukuba City, Ibaraki Prefecture Independent Administrative Law Inside the National Institute of Advanced Industrial Science and Technology Tsukuba Center (72) Kimio Sumaru, East Tsukuba City, Ibaraki Prefecture 1-1-1 Independent Administrative Law F-Term in Tsukuba Center, National Institute of Advanced Industrial Science and Technology (Reference) 4D006 GA25 MA03 MA07 MA08 MB01 MB09 MC02 MC03 MC18X MC22 MC30 MC33 MC54 MC60X MC62 MC65 MC71 NA40 NA43 NA45 NA54 PA04 PA05 PB12 PB32 4F073 AA11 BA03 BB01 CA01 EA62 EA71 4H006 AA02 AD19 FE11

Claims (4)

[Claims] 1. An organic compound separation membrane, characterized in that a membrane is formed by allowing a macrocyclic molecule recognizing compound to exist on a base membrane having a polyion-complexed solid membrane surface. 2. A polyion complex obtained by bringing a charged group on the surface of a base film and binding a polyelectrolyte having an opposite charge to the charged group on the base film in a thin film form by electrostatic interaction. The organic compound separation membrane according to claim 1, which is a solid membrane surface. 3. The organic compound separation membrane according to claim 2, wherein the surface of the base film is plasma-irradiated or chemically treated so that charged groups are present on the surface. 4. A mixed solution containing a compound having a similar chemical structure or a mixture containing an organic compound forming an azeotropic compound is contacted with the membrane according to claim 1 to separate the organic compound. A method for separating an organic compound.