JPH0523817B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preparing an organic polymer film that can control substance selection function.

In recent years, membrane technologies that utilize permeability or permselectivity have been developed in a wide range of fields such as engineering, medicine, and agriculture, and are being put into practice, such as moisture-proof membranes, desalination membranes, dialysis membranes for artificial kidneys, and ion exchange membranes. be. Furthermore, recently, as an energy-saving technology, the development of specific and highly functional membranes such as oxygen enrichment membranes, resource separation membranes, and charge separation membranes has become increasingly important.

For example, regarding oxygen enrichment membranes, their materials include porous polymer membranes (Japanese Patent Laid-Open No. 55-8803), silicone rubber containing fluorine - porous polytetrafluoroethylene (Japanese Patent Laid-Open No. 56-5121). , crosslinked polyorganosiloxane-linear polyorganosiloxane copolymer (JP-A-56-26508), cellulose monocarboxylic acid ester (JP-A-56-26526), styrene siloxane polymer α, ω-bifunctional polysiloxane Cross-linked polymer (JP-A No. 56-28604, etc.)
Various proposals have been made. However, for both materials, gas permeability coefficient, separation coefficient,
Or, the balance of the film thickness etc. that can be manufactured is insufficient.

On the other hand, many methods for preparing organic polymer films have also been proposed. For example, a method of forming a film by casting onto a water surface or a method of forming a film on a porous support by plasma vapor phase polymerization (Japanese Patent Application Laid-open No.
50-41958 etc.). However, there is still a strong need in the art today for reliable and reproducible methods for producing thin organic polymer membranes with a practical area.

The present inventors have conducted extensive research to solve the conventional problems regarding organic polymer film materials and methods for forming the same, and have completed the present invention.

That is, the method of preparing an organic polymer film capable of controlling the substance selection function of the present invention involves copolymerization of a vinyl halide polymer and/or a monomer copolymerizable with vinyl halide and a nematic liquid crystal. A composition containing the substance is dissolved in a mixed solvent of a good solvent and a poor solvent for the (co)polymer to obtain a polymer solution, and the polymer solution is spread on a water surface to form a film. This is a characteristic feature.

Examples of the vinyl halide polymer and/or the copolymer of vinyl halide and a monomer copolymerizable with vinyl halide used in the present invention include polyvinyl chloride, polyvinyl bromide, polyvinyl fluoride, and vinyl chloride. Vinyl-vinyl acetate copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-propylene copolymer, vinyl chloride-styrene copolymer, vinyl chloride-isobutylene copolymer, vinyl chloride-vinylidene chloride copolymer, chloride Vinyl-styrene-maleic anhydride terpolymer, vinyl chloride-styrene-acrylonitrile copolymer,
Vinyl chloride-butadiene copolymer, vinyl chloride-
Isoprene copolymer, vinyl chloride-chlorinated propylene copolymer, vinyl chloride-chlorinated vinylidene-
Examples include vinyl acetate terpolymer, vinyl chloride-acrylic acid ester copolymer, vinyl chloride-maleic acid ester copolymer, vinyl chloride-acrylonitrile copolymer, and the like. The halogenated vinyl polymer referred to in the present invention also includes polytetrafluoroethylene, polytetrafluorochloroethylene, polyvinylidene fluoride, polyvinylidene chloride, and the like. These polymers can be selected from a wide range of materials depending on the purpose and usage of the membrane, as long as they are compatible with the nematic liquid crystal material. For example, for use as an oxygen enrichment membrane, polymers with suitable solvents are advantageous.

Nematic liquid crystal materials used in the present invention include, for example, methoxybenzylidene-p-n
-Butylaniline, ethoxybenzylidene-p-
n-butylaniline, n-propyloxybenzylidene-pn-butylaniline, n-butoxybenzylidene-pn-butylaniline, methoxybenzylidene-pn-amylaniline, ethoxybenzylidene-pn-amylaniline, n-
Propyloxybenzylidene-pn-amylaniline, n-butoxybenzylidene-pn-amylaniline, n-amyloxybenzylidene-p-
n-amylaniline, methoxybenzylidene-p
-n-hexylaniline, p-anicylidene-p
-aminophenyl acetate, p-anicylidene-p-aminobenzonitrile, p-azoxyanisole, p-ethoxy-p'-hexanonyloxyazobenzene, p-n-hexylbenzoic acid-p'-n-hexyl Oxyphenyl ester, butyl-(4'-ethoxyphenoxycarbonyl)-phenyl carbonate (BEPCPC), N-
4-Pentyloxycarbonyloxybenzylidene-
Examples include 4'-anisidine (PCBA), 4-n-heptyloxybenzoic acid (HBA), N,N'-bis-p-methoxybenzylidene-3,3'-dichlorobendiazine (MBDB), etc. .

The amount of the nematic liquid crystal substance to be used can be appropriately selected from the range of 5 to 95 parts by weight based on 95 to 5 parts by weight of the vinyl halide (co)polymer, depending on the intended use of the membrane.

In the present invention, a material selectivity improver can also be used in combination with the mixture of the vinyl halide (co)polymer and the nematic liquid crystal material. The substance selectivity enhancer is selected from a wide range of substances depending on the intended use of the membrane. For example, when the organic polymer membrane according to the present invention is used as an oxygen-enriching membrane, a substance with a high oxygen uptake capacity is advantageously selected as the substance selectivity improver. Examples include perfluorotributylamine, perfluorodecalin, perfluoromethyldecalin, perfluorotetrahydrofuran, perfluorobutyltetrahydrofuran, etc. Also, when crown ether is used as a substance selectivity improver, metal ions are selectively permeated. An organic polymer film is obtained. Furthermore, when using azo crown ether, it is possible to obtain, for example, an organic polymer film in which the transport of K ⁺ ions can be accelerated with light. The amount of substance selectivity improver added depends on the type of organic polymer compound used in the organic polymer membrane,
It is determined as appropriate, taking into consideration the type and amount of nematic liquid crystal material used. Furthermore, a surfactant or the like may be added to improve the dispersion of the substance selectivity improver.

Examples of good solvents for the halogenated vinyl (co)polymer used in the present invention include cyclohexanone, tetrahydrofuran, and butanone. In addition, as the poor solvent, a solvent such as benzene, toluene, and tetrachloroethylene is selected that is a poor solvent and is easily spreadable on the water surface. The ratio of good and poor solvents should be determined so that the polymer solution spreads easily on the water surface and controls the material selection function when forming a film on the water surface. This is determined as appropriate depending on the type of polymer and the type of good/poor solvent in order to obtain a porous membrane that can be used as a porous membrane. , a larger amount of toluene gives better results.

A polymer solution prepared by dissolving a composition containing a halogenated (co)polymer and a nematic liquid crystal substance in a mixed solvent of good and poor solvents is spread on the water surface by a conventional method, and the film is taken out from the water surface. By drying and removing the solvent, it is possible to obtain an organic polymer thin film that can control the substance selection function. According to the method of the present invention, by changing the ratio of good and poor solvents, it is possible to freely produce membranes with different ability to control substance selection functions, so these can be laminated according to the purpose. By doing so, it can be applied for a variety of purposes.

Therefore, the organic polymer membrane produced according to the present invention can specifically control the selection function of various substances, and can be widely applied as an oxygen enrichment membrane, resource separation membrane, charge separation membrane, etc. It has a range. Furthermore, since it contains a nematic liquid crystal material, the liquid crystal alignment can be controlled by applying an electric field, thereby making it possible to specifically control the membrane permeability of gases and other various substances.

The present invention will be specifically explained below using examples.

Example Polyvinyl chloride (degree of polymerization 1050) (PVC) powder,
A mixture of N-(4-ethoxybenzylidene)-4'-n-butylaniline (EBBA) and azocrown in a weight ratio of 40:60:5.2 was mixed with a mixed solvent of tetrahydrofuran (THF) and toluene (weight ratio Two types, 1/1 and 1/2, were prepared) to obtain a 10% by weight polymer solution.

A drop of this polymer solution was gently dropped on the wall of the water surface in a water tank kept at 283K to form a thin film on the water surface, which was immediately scooped up and dried under vacuum at room temperature to form a film with a thickness of about 70 nm (developed on the water surface). membrane) (approximately 400cm ² )
I got it.

After laminating 20 sheets of this water-surface-deployable membrane on a Teflon plate, the membrane was fixed to a ring-shaped frame, peeled off from the frame, and heat-treated at 333K in a nitrogen atmosphere for several minutes to prevent wrinkles or sag (cast membrane). was prepared.

In addition, the film developed on the water surface was scooped onto a specimen stage for electron microscope observation (copper mesh coated with carbon), and the copper mesh was immersed in 100 ml of methanol at about 333 K for about 12 hours to remove the liquid crystal and azo crown from the film developed on the water surface. After extraction, it was observed using a transmission electron microscope.

Figure 1 shows that tetrahydrofuran/toluene =
This is an electron micrograph of a water surface developed film when a mixed solvent of 1/1 (weight ratio) is used, and Figure 2 is an electron micrograph of a film developed on a water surface when a mixed solvent of tetrahydrofuran/toluene = 1/2 (weight ratio) is used. It's a photo.

As shown in the figure, the polymer film produced according to the present invention has a network structure, and the liquid crystal is a continuous phase in the laminated film.

The oxygen permeation rate of a thin film developed using a mixed solvent of PVC/EBBA=40/60 (weight ratio) and THF/toluene=1/2 (weight ratio) was measured. FIG. 3 is an Arrhenius plot of the oxygen permeation rate RO ₂ . For comparison, the Arrhenius equation for a film with a thickness of approximately 400 μm obtained by casting a mixture of PVC/EBBA = 40/60 (weight ratio) on a glass surface.
The plot is also shown in FIG.

[Brief explanation of drawings]

Figure 1 shows THF/toluene = 1/1 (weight ratio)
This is an electron micrograph showing the surface structure of a thin film developed on a water surface after liquid crystals and azo crowns were extracted and removed from the thin film developed on a water surface using a mixed solvent. Second
The figure is an electron micrograph showing the surface structure of a thin film developed on a water surface after liquid crystals and azo crowns were extracted and removed from the thin film obtained by developing it on a water surface using a mixed solvent of THF/toluene = 1/2 (weight ratio). . Figure 3 shows
This is an Arrhenius plot of the oxygen permeation rate of a cast film obtained by developing PVC/EBBA = 40/60 (weight ratio) on the water surface using a mixed solvent of THF/toluene = 1/2 (weight ratio). In the figure, 1 shows the one developed on the water surface, and 2 shows the one casted on the glass surface.

Claims (1)

[Claims] 1. A composition containing a halogenated vinyl polymer and/or a monomer copolymerizable with vinyl halide, a copolymer of vinyl halide, and a nematic liquid crystal substance is mixed with a good solvent and a poor solvent for the (co)polymer. A polymer solution is obtained by dissolving it in a mixed solvent with
A method for preparing an organic polymer film capable of controlling a substance selection function, which comprises spreading the polymer solution on a water surface to form a film.