JPH0339541B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing ultrathin polymer membranes. More specifically, the present invention relates to a method for producing an ultrathin polymer membrane having high permeability to mixed gases. In recent years, methods using thin polymer films have been attracting attention as a means of separating and concentrating specific gases (oxygen, nitrogen, etc.) from mixed gases (air, etc.). For example, polydimethylsiloxane, polydimethylsiloxane-polycarbonate block copolymer (U.S. Pat. No. 3,980,456,
3874986), polydimethylsiloxane copolymers (JP-A-56-26504, etc.) and olefinic polymers such as poly(4-methylpentene-1).
(Japanese Unexamined Patent Publication No. 57-4203) is known. However, these did not satisfy all of the permeability coefficient (Po ₂ ) of a specific gas (eg, oxygen), permeability coefficient ratio (separation coefficient) (Po ₂ /Pn ₂ ), and processability to form a thin film. The present inventors have arrived at the present invention as a result of extensive studies aimed at obtaining an ultra-thin polymer membrane with excellent permeability coefficients and separation coefficients. That is, the present invention provides a method for producing a thin polymer film by spreading a hydrocarbon solution of a film-forming polymer on a water surface, in which at least a portion of the polymer has the general formula (In the formula, R is a C _1-4 linear or branched alkyl group) using a 1-monoalkyldimethylsilylpropyne polymer having a repeating unit,
The present invention is also a method for producing an ultrathin polymer film, characterized in that a nonionic surfactant is present in the solution. In general formula (1), the C _1-4 straight chain or branched alkyl group of R ₁ includes straight chain alkyl groups such as methyl, ethyl, propyl, butyl groups; branched alkyl groups such as isobutyl group, tertiary alkyl group, etc. Examples include butyl group. Examples of 1-monoalkyldimethylsilylpropyne used to obtain a polymer having a repeating unit represented by general formula (1) include 1-trimethylsilylpropyne, 1-monoethyldimethylsilylpropyne, and 1-mono-n -propyldimethylsilylpropyne, 1-mono-n-butyldimethylsilylpropyne, and the like. Among these, preferred is 1-trimethylsilylpropyne. As 1-trimethylsilylpropyne, a commercially available monomer (product of Petrarch Company, USA, product T3728 of SP Development Department of Chitsuso Corporation) can be used. This polymer can be obtained in the presence of a catalyst based on group V transition metals such as niobium (Nb) and tantalum (Ta) (e.g. NbCl ₅ , TaCl ₅ , NbBr ₅ , TaBr ₅ ) and in a container. (Aromatic hydrocarbons such as benzene, toluene, xylene, alicyclic hydrocarbons such as cyclohexene, 1,2-dichloroethane, chlorinated solvents such as carbon tetrachloride, etc.), usually at 30°C.
It can be obtained by polymerizing at ~100°C for 12 to 36 hours. It can also be obtained by the method described in Japanese Patent Application No. 58-84626. The obtained polymer is a white fibrous or powdery polymer. Its number average molecular weight is usually 10,000 or more, preferably 100,000 or more, as measured by a light scattering method. In the present invention, the 1-monoalkyldimethylsilylpropyne polymer may be used in combination with other polymers, if necessary. Other polymers include 1-alkyne polymers (polymers such as tertiary-butylacetylene, neopentylacetylene, and tertiary-pentylacetylene, preferably tertiary-butylacetylene polymers), vinylorganosilane polymers (vinyltrimethylsilane, Polymers such as vinyltriethylsilane and vinyltripropylsilane, preferably vinyltrimethylsilane polymers), polyorganosiloxanes (dimethylsiloxane, polymethylphenylsiloxane, polydiphenylsiloxane, etc.), cellulose polymers (ethyl cellulose, hydroxy Ethyl cellulose, triacetyl cellulose, etc., preferably ethyl cellulose), α-olefin polymer (4
-methylpentene-1 polymer), alkyl sulfone polymer (copolymer of α-olefin and SO ₂ , preferably an alkyl group with 10 to 20 carbon atoms)
long-chain alkyl sulfone polymers), tertiary amine-containing polymers (vinylpyridine polymers, N,
N-diethylaminoethyl acrylate polymer,
Examples include N,N-dimethylaminostyrene polymers, preferably vinylpyridine polymers. When the monoalkyldimethylsilylpropyne polymer and the second component (another polymer) are used together, the content of the monoalkyldimethylsilylpropyne polymer is usually 50% by weight or more, preferably 70% by weight or more. The hydrocarbon solvent used in the preparation of the hydrocarbon solution in the present invention usually has a boiling point of 30 to 99°C;
Preferably, the temperature is 35 to 70°C. Specifically, linear or branched saturated or unsaturated aliphatic hydrocarbon solvents (n-pentane, n-hexane, isohexane, n-heptane, n-octane, isooctane, 1-hexene, 1-heptene, petroleum ether (preferably n-hexane and petroleum ether), alicyclic hydrocarbon solvents (cyclohexane, cyclohexene, methylcyclohexane, ethylcyclohexane, etc., preferably cyclohexene), aromatic hydrocarbon solvents (benzene,
toluene, o-, m-, or p-xylene, styrene, ethylbenzene, naphthalene, preferably benzene and toluene), halogenated hydrocarbon solvents (carbon tetrachloride, 1,2,3-trichloropropane, trichloroethylene, chloroform, chlorobenzene) , chloroethylbenzene, preferably 1,2,3-trichloropropane), and mixtures of two or more thereof. The concentration of the 1-monoalkyldimethylsilylpropyne polymer and optionally other polymers in the solution in the present invention is usually 0.01 to 5.0% by weight, preferably
It is 0.5-2.0% by weight. If the concentration is less than 0.01% by weight, it takes a long time to develop and form a thin film on the water surface, which is disadvantageous for continuous film production. Also, the concentration is 5.0% by weight
If it is larger, the clay of the polymer solution will be higher and it will be difficult to spread it uniformly into a thin film. In the present invention, the nonionic surfactant to be present in the hydrocarbon solution is preferably a nonionic surfactant having an HLB in the range of 1 to 10. H.L.B.
Known methods for determining , such as Griffin's method, Davis' method, and Mr. Kawakami's method, can be used as long as the HLB is 1 to 10, but Griffin's method is generally used. Examples of such nonionic surfactants include the following. [1] Polyoxyalkylene nonionic surfactants These are compounds in which alkylene oxide [ethylene oxide (abbreviated as EO), propylene oxide (abbreviated as PO), etc.] is added to an active hydrogen-containing compound. Examples of active hydrogen-containing compounds include phenols, alcohols, carboxylic acids, amines, mercaptans, amides, and the like. Phenols include alkylphenols or alkylnaphthols having an alkyl group usually having 8 to 12 carbon atoms; styrenated phenols (reaction products of phenols such as phenols, alkylphenols, alkylnaphthols, and phenols with 1 to 20 moles of styrene) ) etc. Alcohols include linear or branched natural or synthetic aliphatic alcohols with 8 to 20 carbon atoms, preferably 12 to 18 carbon atoms, polyhydric alcohols with 2 to 8 hydroxyl groups, or their intramolecular anhydrides (glycerin, pentaerythritol, Examples include partial esters of polyhydric alcohols (sorbitol, sorbitan, etc.) and the following fatty acids. Examples of carboxylic acids include saturated or unsaturated fatty acids having 8 to 20 carbon atoms, preferably 12 to 18 carbon atoms, and polycarboxylic acids having 2 to 4 carboxyl groups. Amines include alkylamines having 8 to 20 carbon atoms, alkylene diamines having 2 to 6 carbon atoms, and polyalkylene ( _C2-6 ) polyamines; mercaptans include alkyl mercaptans having 8 to 20 carbon atoms; amides include alkylols; Amides (such as reaction products of fatty acids having 5 to 20 carbon atoms and mono- or diethanolamine, etc.) Specific examples of polyoxyalkylene nonionic surfactants are as follows: (1) Polyoxyethylene alkylaryl ether alkyl EO adducts of phenols or alkylnaphthols, such as nonylphenol EO(2). (2) Polyoxyethylene polyhydric alcohol fatty acid esters EO adducts of esters of polyhydric alcohols or intramolecular anhydrides and fatty acids, such as sorbitan monostearate. EO(4). (3) Polyoxyethylene fatty acid ester Esters (mono or diester) of fatty acids and polyethylene glycol or esters of fatty acids
EO adducts, such as polyethylene glycol (molecular weight 200) stearic acid monoester,
Polyethylene glycol (molecular weight 200) lauric acid diester, etc. (4) Polyoxyethylene alkyl ether EO adducts of higher alcohols, such as oleyl alcohol EO(2). (5) Polyoxyethylene polyoxypropylene polyol Pluronic type nonionic surfactant such as polypropylene glycol (abbreviated as PPG) (average molecular weight () 900~
2900); Tetronik type nonionic surfactants such as EO adducts of polyoxypropylene alkylene diamine [Tetronik (manufactured by Wyandot)], etc. [2] Polyhydric alcohol type nonionic surfactants (1) Polyhydric alcohol fatty acid ester Esters of polyhydric alcohols or intramolecular anhydrides and fatty acids, such as oleic acid ester of sorbitan, stearic acid ester of sorbitan, palmitic acid ester of sorbitan Ester, lauric acid ester of sorbitan; esters include mono, sesqui, and triacetate, respectively. Among these, preferred are polyoxyethylene alkylaryl ethers,
Particularly preferred is nonylphenol.
It is an adduct of 1 to 5 moles of EO. Nonionic surfactants are described in "New Introduction to Surfactants" (written by Takehiko Fujimoto, published by Sanyo Chemical Industries, Ltd. in 1972). When adding a nonionic surfactant to a hydrocarbon solution of a 1-monoalkyldimethylsilylpropyne polymer, the amount added is usually 0.0001 to 0.1% by weight, preferably 0.001 to 0.01% by weight, based on the hydrocarbon solution. . Addition amount is 0.0001
If it is less than 0.1%, the spreadability of the polymer solution on the water surface is poor, and if it is more than 0.1%, the uniformity of the formed thin film will be impaired. Further, the amount of the nonionic surfactant is preferably 50% by weight or less based on the weight of the polymer. Examples of methods for spreading the polymer solution on the water surface include adding or dropping the solution onto the water surface. When a polymer solution is added or dropped onto the water surface, it immediately spreads over the water surface to form an extremely thin film. When a hydrocarbon solution of a polymer is spread on a water surface to form an ultra-thin film of the polymer, it is preferable to maintain the temperature of the polymer solution and the water within a certain temperature range in advance. The temperature of the polymer solution is preferably 20 to 50°C; if this temperature is lower than 20°C, the viscosity of the polymer solution increases and it is difficult to spread into a thin film. When the temperature of the polymer solution is higher than 50°C, the solvent tends to volatilize and wrinkles easily when spread on the water surface. On the other hand, the temperature of the water is preferably 5 to 30°C, particularly preferably 10 to 25°C. This temperature is 5
If the temperature is lower than ℃, the viscosity of the polymer solution will increase and it will be difficult to spread into a thin film.
If the temperature is higher than 30°C, the solvent tends to evaporate, and the polymer solution dropped onto the water surface is difficult to spread independently. In the present invention, when obtaining an ultrathin film by using the 1-monoalkyldimethylsilylbropine polymer and other polymers in combination, the method is (1) from a solution of the mixture of the two components in the same manner as in the present invention. Can be formed into a film. The thickness of the film formed by casting on the water surface and drying can be varied depending on the molecular weight of the polymer used and the concentration of the polymer solution, but is usually 1 μm or less (for example, 0.01 to 1 μm). easily by using a polymer with a large molecular weight at a low concentration.
Ultra-thin films of about 0.1μ can be created.
It is also possible to form thicker films using highly concentrated solutions. Since the ultrathin membrane obtained by the present invention has little self-supporting properties, a support is usually required when it is used as a gas separation membrane. Porous materials such as Japanese paper, nonwoven fabric,
Examples include synthetic paper, paper, cloth, porous ceramics, porous metals, precision membranes, ultrafiltrates, etc. By combining with these supports, it can be used satisfactorily as a membrane for gas separation.
The compositing method can be a known method, for example, by pressing a film formed on the water surface onto a support, scooping it up, or suctioning it through the support to create a composite with the support. . An adhesive or the like can be present between these supports and the membrane for support.
Furthermore, the membrane supported on the support may be heat-treated. The ultrathin polymer membrane obtained in this way usually has an oxygen permeability coefficient of 10 ^-2 to 10 ^-4 (CC(STP)/
cm ² , sec, cmHg). Further, the ratio of oxygen to nitrogen permeability is usually in the range of 1.5 to 3.0. The ultra-thin film obtained by the present invention is epoch-making superior to the oxygen-enriching films known up to now, and exhibits satisfactory performance when put into practical use. Moreover, the separation coefficient can be increased by using other polymers in combination. The ultrathin polymer membrane obtained by the present invention has excellent gas permeability, separation coefficient, and thinning properties. That is, it has a separation property comparable to that of polydimethylsiloxane, a gas permeability coefficient that is far superior to polydimethylsiloxane, is equal to or higher than that of olefinic polymers, and can be easily formed into a thin film. In addition, the production method of the present invention can be carried out at a relatively high polymer concentration (1% by weight or more) compared to the case where a nonionic surfactant is not used. (2) A suitable thin film can be formed in a relatively short time (usually within 1 minute). Therefore, productivity is high and it is suitable for continuous film formation. (3) Even if the polymer concentration is set to a relatively high concentration (1% by weight or more), the ultrathin film is uniform and pinholes do not occur. If nonionic surfactants are not used, the ultrathin films are somewhat heterogeneous when carried out at relatively high concentrations;
Therefore, pinholes and the like are likely to occur in the produced ultra-thin film. (4) A wide variety of solvents can be used as solvents for the polymer, including not only aliphatic hydrocarbons but also cycloaliphatic and aromatic hydrocarbons. It is excellent in such respects. Ultrathin membranes obtained by the method of the invention are useful for gas separation. In other words, it is suitable for producing oxygen-enriched air from air, and is expected to have an energy-saving effect when applied to boilers, various heating furnaces (calcination furnaces, glass melting furnaces, etc.), and various engines. Since this oxygen-enriched air is clean, it can be used as an incubator for premature babies, a treatment device for patients with respiratory diseases, an artificial lung, and as dust-free air in clean rooms for ultra-LSIs. Can be used. Furthermore, as a gas separation membrane, it can be used for recovering hydrogen from ammonia purge gas in ammonia plants, separating H2 _and CO in _C1 chemistry, recovering helium from natural gas, etc. On the other hand, it can also be used to selectively separate alcohol from a water-alcohol mixture produced from biomass by pervaporation. The present invention will be further explained below with reference to Examples, but the present invention is not limited thereto. Examples 1 to 7 1-trimethylsilylpropyne polymer (hereinafter referred to as
PMSP) (The intrinsic viscosity of PMSP is toluene 30
PMSP alone or mixed with other polymers using the hydrocarbon solvent shown in Table 1.
A 1.5% by weight solution was prepared. Furthermore, a developing solution was prepared by adding a nonionic surfactant (indicated by HLB) shown in Table 1 to the hydrocarbon solution of the polymer at a concentration of 0.005% by weight, and the temperature was maintained at 20°C. 0.4 g of the developing solution was gently added to a stainless steel water bath (ion-exchanged water was used; the water temperature was fixed at 15° C.) with a base area of 30 cm square on each side. The polymer solution spontaneously spread into a circular shape, and an extremely thin film was formed after about 5 seconds. The average film thickness based on the film area of the obtained ultra-thin film is shown in Table 1.

[Table] Example 8 The ultra-thin film created in Example 1 was coated with Jyuragard 2400.
(polypropylene porous membrane) and dried to create a composite membrane. The gas permeation rate of the obtained composite membrane is (CC(STP)/
^The oxygen permeation amount was 3.2×10 ⁻² and the nitrogen permeation amount was 1.8×10 ⁻² .

Claims (1)

[Scope of Claims] 1. In a method for producing an ultra-thin polymer film by spreading a hydrocarbon solution of a film-forming polymer on a water surface, at least a portion of the polymer has the general formula (In the formula, R is a C _1-4 linear or branched alkyl group) using a 1-monoalkyldimethylsilylpropyne polymer having a repeating unit,
A method for producing an ultra-thin polymer film, characterized in that a nonionic surfactant is present in the solution. 2. Claim 1, wherein the amount of nonionic surfactant in the hydrocarbon solution is 0.0001 to 0.1% by weight.
Manufacturing method described in section. 3 The concentration of the polymer in the hydrocarbon solution is 0.01 to 5.0.
The manufacturing method according to claim 1 or 2, which is % by weight. 4. The manufacturing method according to any one of claims 1 to 3, wherein the nonionic surfactant has an HLB of 1 to 10.