JPH0468007B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a permselective composite membrane for liquid components, and more specifically, the fluidized layer within the membrane has a function of interacting with specific molecules or ions. In particular, it relates to a permselective composite membrane that selectively permeates specific molecules or ions.

(Prior Art) The essential function of a membrane is to selectively allow specific molecules or ions to permeate among many substances. The simplest of these separation functions is the "sieve" function. This type of membrane includes dialysis membranes, ultrafiltration membranes, and reverse osmosis membranes. In these membranes, molecules or ions pass through the gaps between the molecules constituting the polymer membrane, and their selectivity is determined by the size of the gaps and their interaction with the molecules. In these membranes, the gaps have a fairly wide distribution, and when there is a large difference in the size of the molecules or their interaction with the membrane constituent materials, it is easy to separate them, but it is difficult to separate them when they are of the same size.

On the other hand, as a method of imparting selective permselectivity to a membrane, it is conceivable to provide the membrane with a function of selectively interacting with the substance to be selected. For this purpose, there is a method of adding to the membrane a functional substance, that is, a carrier, which interacts with the substance to be selected. Such functional membranes include fixed membranes with fixed carriers and liquid membranes with freely movable carriers. Generally, in fixed membranes, instead of providing a stable structure, the selected substance moves through a fixed carrier, so the permeation rate is low.

On the other hand, in a liquid film, the selected substance and the carrier can move freely, making it easy to obtain a high permeation rate. However, liquid films were unstable and unsuitable for industrial use.

Therefore, as a technique for utilizing such a liquid membrane, there is an impregnated type liquid membrane in which a porous support membrane is impregnated with a liquid membrane, as shown in Japanese Patent Application Laid-Open No. 17381/1983.

That is, the above specification uses a membrane obtained by impregnating a porous support membrane of an inert polymer such as polyethylene, polypropylene, polysulfone, polytetrafluoroethylene, and polyphenylene oxide with a complexing agent. , describes an invention for transporting specific metal ions from one aqueous solution to another.

(Problems to be Solved by the Invention) The above-mentioned impregnated liquid membrane has the disadvantage that the carrier solvent of the liquid membrane easily flows out from the porous support membrane. There were some problems that made it difficult to use.

The present invention aims to solve this problem of conventional impregnated liquid membranes.

(Structure of the Invention) In order to achieve this object, the present invention has the following structure. That is, the present invention is a selectively permeable membrane for a liquid component, in which a solution or dispersion of a functional liquid or functional solid that interacts with the liquid component is soaked in a support made of a porous synthetic polymer material. This is a composite membrane characterized by coating both sides with an ultra-thin film made of a synthetic polymer compound having a thickness necessary to prevent the impregnating liquid from flowing out.

From the viewpoint of using a thin film, a porous synthetic polymer membrane of about 20 to 50 μm is desirable as the porous support. The size of the pores is preferably about 0.01 to 100 microns, preferably about 0.1 to 1 micron. Preferred materials include polyethylene, polypropylene, polytetrafluoroethylene, polysulfone, polyphenylene oxide, polyvinylidene fluoride, polyvinyl chloride, polyester, cellulose esters such as cellulose acetate, and polycarbonate. These porous supports can be selected from various commercially available products, or can be prepared by known methods using the above-mentioned materials.

Usually, a flat membrane-like porous support is used, but a hollow fiber-like porous support can also be used.

As the functional substance, ie, the carrier, that is impregnated into the porous support, a compound that has a reversible interaction with the selected substance is used. A specific example of a carrier is described below. When the substance of choice is a metal ion, metal chelating agents commonly known in the art of liquid extraction of metals can be used.
Examples of such metal chelating agents include cyclic polyethers and cyclic polyether amines known as crown ethers and cryptands, chain polyethers generally called ionophores, chain polyether amines, cyclic or chain polyesters, Examples include polyamide, polyether ester, polyether amide, etc.

Specifically, dibenzo-18-crown-
6, dicyclohexyl-18-crown-6, Kryptofix 22BB, 222D (trade name), or natural ionophores such as monensin.

4,7-diphenyl-1,10-phenanthroline is an example of a chelating agent that is selective for zinc, and 4,7-diphenyl-2,9-dimethyl-1,10-phenanthroline is selective for lead. In addition, commercially available chelate extractants such as 8-hydroxyquinolines such as Cherex 100 (trade name, manufactured by Cherex),
Hydroxyoximes such as LIX63N, 65, 65N, 70 (product name, manufactured by Henkel), SME529 (product name, manufactured by Schiel), α-hydroxyoximes such as LIX63 (product name, manufactured by Henkel) β-
Metal chelate extractants such as diketones and sulfonamide quinolines such as LIX34 (trade name, manufactured by Henkel) are also effective.

For organic cations such as metal cations and quaternary ammonium cations, organic phosphoric acids such as triamyl phosphate, tributyl phosphate, tributoxyethyl phosphate, dibutoxyethyl phosphate, and dioctyl phosphate are also effective. Laun, vanadium,
Anionic metal species existing as oxidants such as tungsten, organic anions such as organic acid anions, and halogen anions include organic amines such as trioctylamine, N-octylimidazole, and alkylpyridine, and their quaternary ammoniums. Salt is effective.

Furthermore, optical resolution can be performed by using a carrier that can distinguish between optical isomers.
For example, optically active crown ethers can be used to optically resolve amino acids.

Examples of such crown ethers include optically active dibinaphtho-22-crown 6, optically active binaphtho-20-crown 6, and derivatives thereof.

Carriers are generally used as solutions. If the carrier is a liquid, it can be used as is in the membrane of the present invention. If the carrier is solid, it must be used as a solution or dispersion in a suitable solvent.

Carrier solvents include aliphatic, cycloaliphatic, aromatic, aliphatic-aromatic, and cycloaliphatic-aromatic, which dissolve the carrier and are inert liquids that do not react with other substances and are preferably immiscible with water. Group hydrocarbons and their chlorinated products are used.

Examples include diphenyl ether, diethyl-diphenyl, kerosene, and octyl alcohol. Water may be used depending on the characteristics of the carrier.

There are two methods for forming an ultra-thin film that covers both sides of an impregnated membrane: interfacial polymerization, in situ polymerization, and other methods in which a coating film is formed by polymerization on the membrane surface, and a method in which a polymer solution is applied to the membrane surface. , a method of forming a coating film by removing the solvent or making the polymer insoluble, or a method of forming a coating film by crosslinking the polymer, etc. can be considered. Hereinafter, a typical method for forming a coating film will be explained.

First, a particularly useful method for forming a coating film using an interfacial polymerization method will be explained.

The interfacial polymerization method was introduced in 1958 by PWMorgan, SL.
Published by Kwolek et al. (J.Chem.Ed., 36 , 182
(1959). ) has since been known as a method for synthesizing polyesters and polyamides. In this method, a water-soluble reactant and a fat-soluble reactant polymerize to form a polymer compound at the interface between water and an organic liquid that is essentially immiscible with water.

One of the water-soluble reactants for interfacial polymerization that forms the coating film is a compound that has at least two primary or secondary amino groups in the molecule, or a compound that has at least two or more hydroxyl groups in the molecule. be. Specifically, the former includes C ₂ to _{C 10} straight chain aliphatic diamines such as ethylenediamine, diaminopropane, diaminobutane, diaminopentane, hexamethylenediamine, diaminoheptane, diaminooctane, diaminononane, diaminodecane, Cycloaliphatic diamines, such as piperazine,
_C6 to _C20 aromatic diamines such as p-,m-phenylenediamine, 4,4'-diaminodiphenylmethane, and 4,4'-diaminodiphenyl ether.

The latter include, for example, ethylene glycol, propanediol, butanediol, pentanediol,
_C2 - _{C10 aliphatic} dialcohols such as hexanediol, heptanediol, octanediol, nonanediol, decadiol, cycloaliphatic dialcohols such as cyclohexanediol, 4,4'-dihydroxydiphenylmethane,
_C6 to _C20 aromatic dialcohols such as 4,4'-dihydroxydiphenyl ether.

The other fat-soluble reactant includes functional groups that can react with the diamines and dialcohols, such as acid chloride groups, isocyanuric groups, chloroformel groups, sulfonyl chloride groups, acid anhydride groups, and thiocyanate groups. It is a compound that has two or more within.
Specifically, aliphatic acid chlorides such as oxalyl chloride, malonyl chloride, succinyl chloride, glycaryl chloride, fumaryl chloride, sebacoyl chloride, aromatic acid chlorides such as terephthaloyl chloride, isophthaloyl chloride, trimesoyl chloride, ethylene diisocyanate, Aliphatic isocyanates such as propylene diisocyanate, benzene diisocyanate, toluene diisocyanate, naphthalene diisocyanate, aromatic isocyanates such as methylene bis(4-phenyl isocyanate), aliphatic thiocyanates such as ethylene dithioisocyanate, propylene dithioisocyanate, propylene dithioisocyanate , aromatic thiocyanates such as benzene dithioisocyanate, toluene dithioisocyanate, naphthalene dithioisocyanate, aliphatic and aromatic sulfonyl chlorides such as 1,3-benzenesulfonyl chloride, 1,4-benzenesulfonyl chloride, and ethylene bischloroformate. , propylene bischloroformate, butylene bischloroformate, and the like.

When an acid halide is used in interfacial polymerization as one of the reactants in the process, it is desirable to include an acid acceptor in the reaction mixture. This is because it is necessary to remove hydrogen halide produced as a by-product in the polymerization reaction. The acid acceptor is preferably an alkali metal hydroxide or a weak acid salt; specific examples include sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium hydrogen carbonate, sodium carbonate, potassium carbonate, etc. . Organic bases such as tertiary amines such as triethylamine and pyridine can also be used.

The composite membrane of the present invention by interfacial polymerization can be obtained by the following method. A lipophilic reactant is added to the carrier liquid or carrier solution, which will be one of the reactants in the interfacial polymerization. A porous support is impregnated with this liquid. Impregnation can be performed by ultrasonic irradiation, suction, or reduced pressure. The membrane impregnated with the fluidized bed is immersed in a water-soluble reactant that will be the other reactant for interfacial polymerization. If an acid halide is used as the fat-soluble reactant, an acid acceptor is added as necessary.
The surface of the impregnated membrane is coated in this way, and the membrane is thoroughly washed with water before use.

Next, a coating film forming method using an in-situ polymerization method will be explained. In this method, a polymerizable monomer is added to a carrier liquid or solution in advance, impregnated into a porous support, and then polymerized to form a coating.

In this method, polymerizable monomers generally known in the field of polymerization, such as vinyl monomers and ring-opening polymerization type monomers, are used. Specifically, they include styrene, vinyl acetate, acrylic acid and its esters, methacrylic acid and its esters, acrylonitrile, ethylene, propylene, tetrafluoroethylene, vinyl chloride, and the like.

This law can be broadly divided into the following three laws. First, a polymerization initiator is added to a carrier solution along with a polymerizable monomer in advance, and a porous support is impregnated into the carrier solution, and the resulting polymer is polymerized by heat or light and deposited on the membrane surface to form a coating film. There is.

Next, there is a method of adding only a polymerization initiator to a carrier solution and impregnating the porous support, and then supplying a polymerizable monomer from outside the membrane to form a coating membrane. This method is particularly effective for gaseous polymerizable monomers.

The polymerization initiators used in these methods include peroxides such as benzoyl peroxide and dicumyl peroxide, and polymerization initiators commonly used in the field of polymer synthesis such as azoisobutyronitrile.

A typical method for forming a coating film from a vinyl monomer will be described below. Suitable vinyl monomers and polymerization initiators are added to the carrier liquid or solution so that they are insoluble in the carrier solution after polymerization. In some cases, an appropriate amount of a compound having two or more vinyl groups in the molecule, such as divinylbenzene, is added. A porous support is impregnated with this solution. A coating film is formed by polymerizing with light or heat and depositing the produced polymer on the surface of the porous support.

Furthermore, there is a method in which a porous support is impregnated with only a polymerizable monomer added to a carrier liquid or solution, and the porous support is immersed in a solution of a polymerization initiator to polymerize on the membrane surface to form a coating membrane.

The procedure for forming a coating film from a vinyl monomer using this method will be described below. A suitable vinyl monomer is added to the carrier solution such that it becomes insoluble in the polymer solution after polymerization. In some cases, an appropriate amount of a compound having two or more vinyl groups in the molecule, such as divinylbenzene, is added. A porous support is impregnated with this solution. A coating film is formed by immersing it in an aqueous solution of a polymerization initiator such as a hydrogen sulfite radical generator.

Another method is to apply a polymer solution to a film impregnated with a carrier solution. Using a polymer that is insoluble in the carrier solution, the polymer solution is applied to the surface of the impregnated membrane and the polymer solvent is removed by drying, or the membrane is immersed in a polymer curing agent to form a coating.

Polymers suitable for this purpose must be selected from among the commonly used polymers and are insoluble in the carrier solution.

Also useful are methods of forming coatings by crosslinking polymers. A crosslinking agent is added to the carrier solution in advance, and the porous support is impregnated with the porous support and then immersed in the polymer solution to insolubilize the polymer by crosslinking and form a coating film. or impregnating a porous support with a polymer solution together with a carrier solution;
A coating film is formed by immersing it in a solution of a crosslinking agent.

As the polymer, polyfunctional polymers such as polyethyleneimine and polyvinyl alcohol are preferable. In this case, the crosslinking agent used is a fat-soluble reactant having two or more acid chloride groups, isocyanate groups, etc. in the molecule as mentioned in the interfacial polymerization method. The procedure for forming a coating film by crosslinking is the same as the interfacial polymerization method except that the above-mentioned polyethyleneimine, polyvinyl alcohol, etc. are used as the water-soluble reactant.

Further, according to the present invention, a method has been developed in which a porous support made of a highly reactive material is used instead of a conventional porous support and reacted with the porous support to form a polymer. This is, for example, a production method in which both sides of a porous support made of a copolymer (styrene-maleic anhydride) are coated with polyamine and polymerized;
Alternatively, a method may be used in which a porous polypropylene support is chlorinated, further aminated, and then treated with acroyl polychloride to form a coating film. In these cases, a thin coating film that can withstand long-term use is formed.

The thickness of the ultra-thin film formed in this way is approximately
It is about 0.01 to 0.1 μm.

The composite membrane of the present invention selectively permeates metal ions such as sodium, potassium, and copper, and cations such as ammonium, selectively permeates anions such as halogens and organic acids, separates water and organic solvents such as alcohol, and separates toluene and heptane. It is effectively used for applications such as separation between organic solvents and selective permeation of beneficial organic compounds such as amino acids.

Examples will be shown below using the apparatus shown in FIG. 1 equipped with the composite membrane of the present invention.

Examples 1 and 2 Comparative Example A tributyl phosphate solution of sebacoyl chloride at a concentration of 5 mmol was added to a commercially available polytetrafluoroethylene porous membrane (trade name Chloropore FP-010, manufactured by Sumitomo Electric Industries, Ltd., average diameter 0.1 μm, thickness 50 μm). ). This was immersed for 10 hours in a 1% polyvinyl alcohol solution containing 5 mmol sodium hydroxide as an acid acceptor. Polyvinyl alcohol was crosslinked with sebacoyl chloride to form a coating layer.

The membrane thus prepared was attached to an acrylic permeation cell, and 40 ml of a 0.1 mmol tryptophan, 1 mmol hydrochloric acid, and 0.1 molar sodium perchlorate aqueous solution were placed on one side of the membrane, and 0.1 mmol on the other side. 40 ml of an aqueous solution of tryptophan at a concentration of 1 mmol and hydrochloric acid at a concentration of 1 mmol were added. Tryptophan was actively transported from the side with sodium perchlorate to the side without sodium perchlorate. The initial transport speed is
It was 1.33×10 ⁻⁷ mol/cm ² , hr.

As shown in Example 1 in FIG. 2, this membrane continued to actively transport tryptophan even after 10 hours, and deterioration was slow.

The same polytetrafluoroethylene porous membrane as above was then impregnated with a 25 mmolar sebacoyl chloride and tributyl phosphate solution. This was immersed for 5 hours in a 25 mmol concentration phenylenediamine aqueous solution to which 25 mmol concentration sodium hydrogen carbonate was added as an acid acceptor. At the interface, sebacoyl chloride and phenylene diamine undergo polycondensation to form a coating film of polyphenylene sebaamide.

The membrane thus prepared was mounted in a permeation cell, and 0.1 mmolar tryptophan was added to one side of the membrane.
1 mmolar hydrochloric acid, 0.1 molar sodium perchlorate in an aqueous solution of 40 ml, and 0.1 molar on the other side.
Millimolar tryptophan and 40 ml of a 1 millimolar hydrochloric acid aqueous solution were added. Tryptophan was actively transported from the side with sodium perchlorate to the side without sodium perchlorate. The initial rate of transport was 1.33×10 ^-7 mol/cm ² , hr. This is shown as Example 2 in FIG.

For comparison, an experiment was conducted using an impregnated membrane without an adhesion layer. That is, a membrane prepared by impregnating the same polytetrafluoroethylene porous membrane with tributyl phosphate was attached to a permeation cell, and the other conditions were as in Example 2.
Active transport of tryptophan was carried out in exactly the same manner.

The initial rate of transport was similar to that in the example, but active transport stopped after 5 hours due to membrane deterioration. This is shown as a comparative example in FIG.

Example 3 Dibenzo-18 at 25 mmolar concentration as carrier
The same polytetrafluoroethylene porous membrane of Example 1 was impregnated with a diphenyl ether solution of -Crown-6 and sebacoyl chloride at a concentration of 25 mmolar as a lipophilic reactant for interfacial polymerization. The impregnated membrane was immersed for 3 hours in a 25 mmol concentration of phenylene diamine and a 25 mmol concentration of sodium bicarbonate aqueous solution as an acid acceptor. At the interface, sebacoyl chloride and phenylene diamine undergo polycondensation to form a coating film of polyphenylene sebacoamide.

The prepared membrane was attached to a permeation cell, 100 ml of a 0.1 molar potassium chloride aqueous solution was placed on one side of the membrane, and distilled water was placed on the other side to examine the permeation rate of potassium chloride, which was 5.9 x 10 ^-6. It was mol/cm ² , hr.

A similarly prepared membrane was attached to a permeation cell, 100 ml of 0.1 molar sodium chloride was placed on one side of the membrane, and distilled water was placed on the other side to examine the permeation rate of sodium chloride. Ta. This state is shown in FIG.

Example 4 Commercially available polypropylene porous membrane (trade name Jyuraguard 2500, maximum diameter 0.04 x 0.4 μm, thickness 25 μm)
dibenzo-18 at a concentration of 5 mmolar as a carrier.
-Crown-6 was impregnated with a diphenyl ether solution of terephthaloyl chloride at a concentration of 5 mmol as one of the reactants for interfacial polymerization. This was immersed in an aqueous solution of hexamethylene diamine at a concentration of 5 mmol as the other interfacial polymerization reactant and sodium bicarbonate at a concentration of 5 mmol as the acid acceptor, and coated with polyhexamethylene phthalamide by interfacial polymerization.

Attach the above membrane to a permeation cell, with 1
When 100 ml of a millimolar concentration lead nitrate aqueous solution was poured into one and 100 ml of distilled water was poured into the other, the permeation rate of lead nitrate was examined, and it was found to be 1.6×10 ^-7 /cm ² , hr.

A similarly prepared membrane was attached to a permeation cell, and 100 ml of 1 mmol calcium nitrate was added to one side, and 100 ml of distilled water was added to the other side, and the permeation rate of calcium nitrate was examined. Ta.

Example 5 50 mmolar concentration of (R)-3 as carrier,
A nitrophenyl phenyl ether solution of toluene diisocyanate at a concentration of 50 mmol was used as one of the reactants for interfacial polymerization with 3'-dibenzobinaphtho-20-crown-6, and a commercially available polypropylene porous membrane (trade name: Jyuragard 2400, maximum diameter 0.02 × 0.2μ
25 μm thick). This was immersed for 3 hours in an aqueous solution of hexamethylene diamine at a concentration of 50 mmol as the other reactant for interfacial polymerization, and coated with polyurethane by interfacial polymerization.

Attach the above membrane to the permeation cell and place it on one side of the membrane.
40 ml of an aqueous solution of D- or L-phenylglycine perchlorate at a concentration of 50 millimolar was added, and 40 ml of distilled water was added to the other side, and the permeation rate of phenylglycine was examined. The permeation rate of D-phenylglycine is
It was 6.24×10 ⁻⁷ mol/cm ² , hr. On the other hand, the permeation rate of L-phenylglycine is 6.52×10 ^-8 mol/
It was cm ² , hr.

Example 6 10% in the same polypropylene porous membrane as Example 5
Kerosene solution of LIX64N (product name: Henkel)
It was impregnated with 30 parts of styrene, 1 part of divinylbenzene, and 5 parts of benzoyl peroxide per 100 parts. This was heated to 60°C in a water bath under a nitrogen stream and polymerized for 8 hours.

The prepared membrane was attached to a permeation cell, and one side of the membrane was filled with a 3 mmolar copper sulfate sulfuric acid solution (PH2.5).
100 ml and on the other side 100 ml of 1N sulfuric acid. When the permeation rate of copper ions was investigated, it was 2.83×
It was 10 ^-6 mol/cm ² , hr.

A similarly prepared membrane was attached to a permeation cell, and a 3 mmolar ferrous sulfate solution (PH 2.5) was placed on one side of the membrane, and 100 ml of 1N sulfuric acid was placed on the other side. When we investigated the permeation rate of iron ions, it was 1.07×
It was 10 ^-8 mol/cm ² , hr.

Example 7 The same polytetrafluoroethylene porous membrane as in Example 1 was impregnated with a diethyl diphenyl solution containing 5 mmolar concentration of dibenzo-18-crown-6, 30% acrylonitrile, and 0.3% divinylbenzene. This membrane was immersed in 150 ml of 0.3% polyoxyethylene nonyl ether aqueous solution at 50°C under a nitrogen stream.
It was heated to A 10 ml aqueous solution of 0.45 g potassium peroxodisulfate and 0.45 g sodium bisulfite were added in 1 ml portions over 2 hours. The treated membrane was further polymerized for 1 hour and washed with water.

This membrane is attached to a permeation cell and one side of the membrane is
100 ml of potassium chloride with a concentration of 0.1 mol was added to the other side, and 100 ml of distilled water was added to the other side to check the permeation rate of potassium chloride, which was found to be 1.3 x 10 ^-6 mol/cm ² , hr. A similarly prepared membrane was attached to a permeation cell, and sodium chloride at a concentration of 0.1 mmol was placed on one side of the membrane, and distilled water was placed on the other side to examine the permeation rate of sodium chloride. Ta.

Example 8 The same polypropylene porous membrane as in Example 4 was impregnated with a 5 mmolar solution of terephthaloyl chloride in trioctyl phosphate. It was immersed for 10 hours in a 1% polyvinyl alcohol aqueous solution containing 5 mmol sodium hydroxide as an acid acceptor. Polyvinyl alcohol was crosslinked with terephthaloyl chloride to form a coating.

The membrane thus prepared was mounted in a permeation cell, and 0.1 mmolar concentration of phenylalanine was added to one side of the membrane.
Add 40 ml of an aqueous solution of 1 mmolar hydrochloric acid and 1 mmolar sodium perchlorate to the other side.
40 ml of an aqueous solution of phenylalanine at a concentration of 0.1 mmol and hydrochloric acid at a concentration of 1 mmol were added. Phenylalanine was transported from the side with sodium perchlorate to the side without sodium perchlorate. Transport speed is 4.53×10 ^-8 /
It was cm ² , hr.

Example 9 The same polypropylene porous membrane as in Example 5 was chlorinated (chlorination rate: 10.7%) by a known method, and then azidized, followed by reduction and amination by a known method. The amination rate was 0.38%.

This aminated polypropylene porous membrane was impregnated with a 5 mmolar solution of dibenzo-18-crown-6 in diethyl diphenyl. A 5% solution of acroyl polychloride in chloroform was casted on both sides of the membrane, sandwiched between glass plates, and reacted for 12 hours. Next, it was immersed in sodium hydrogen carbonate water, thoroughly washed with water, and then treated with diazomethane to convert the carboxyl group into methyl ester.

The prepared membrane was attached to a permeation cell, and one side was
Add 100ml of millimolar potassium perchlorate,
When we put 100ml of distilled water on the other side and checked the permeation rate of potassium perchlorate, it was 4.3×10 ^-7 /cm ² ,
When the permeation rate of potassium chloride at a concentration of 1 mmol was investigated in the same manner, it was 1.7×10 ^-7 /cm ² ,
It was hr.

(Effect of the invention) The ultra-thin film covering the impregnated membrane in the liquid permselective composite membrane of the present invention has a minimum thickness necessary and sufficient to prevent the carrier and solvent in the impregnated membrane material from flowing out. Ultra-thin films meeting these conditions cannot be obtained by conventional bonding or coating methods. Although the film thickness varies depending on the raw material for forming the ultra-thin film and the formation conditions, it is possible to easily obtain an ultra-thin film layer that satisfies the above conditions.

Therefore, the ultra-thin film formed integrally on the surface of the impregnated membrane prevents the carrier and solvent in the liquid film from flowing out. It becomes possible to maintain good transmission performance for a long time.

As described above, the composite membrane of the present invention dramatically improves the permeation performance, which has been problematic in conventional composite membranes, and also has the excellent selectivity of a carrier liquid layer membrane.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a permeation cell used in Examples of the present invention, Figure 2 is a graph showing the relationship between permeate concentration and elapsed time in Examples 1 and 2, and the comparison column;
The figure is a graph showing the above relationship in Example 3. In FIG. 1, 1... selectively permeable membrane, 2...
Permeation cell, 3... Permeated liquid, 4... Permeated liquid, 5...
...Daytector, 6...Bung, 7...Magnetic stirrer.

Claims (1)

[Claims] 1. A selectively permeable membrane for a liquid component, in which a support made of a porous synthetic polymer material is impregnated with a solution or dispersion of a functional liquid or functional solid that interacts with the liquid component, and impregnated on both sides. A composite membrane characterized by being coated with an ultra-thin film made of a synthetic polymer compound having a thickness necessary to prevent liquid outflow.