JPH0536091B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a separation membrane that has good separation properties and permeability, particularly for gases, and is suitable for selectively separating substance mixtures, especially gas mixtures. In the following description, gas mixtures will be taken as examples of substance mixtures. A separation membrane suitable for selectively separating gas mixtures is required to have a high gas separation rate and a high permeation rate. In order to meet such demands,
It is desirable that the thickness of the membrane that exhibits substantial separation performance be as thin as possible, and in practical use, such a membrane is coated with an air-permeable porous layer (e.g. Japanese paper, non-woven fabric, synthetic paper, paper, cloth, etc.). wire mesh, permeable membrane, ultrapermeable membrane, etc.)
Preferably, the structure is held by Many methods have been proposed for manufacturing structures such as those described above. For example, a method in which a separately formed thin film with separability is superimposed on a porous membrane with breathability, a skin layer (having separability) and a porous layer (having breathability and serving as a support) A method of forming a sheet body in one piece,
Direct polymerization of monomers on a porous membrane using various methods to form a thin film with separation properties, or coating a porous membrane with a polymer solution and then evaporating the solvent. A method of forming a thin film having separability is known. Among the various methods mentioned above, a method in which a solution of another polymeric material is coated on an air-permeable porous membrane serving as a support, and then the solvent is evaporated to form a separable thin film layer. However, it is preferable because it allows the application of a relatively wide variety of polymeric materials.
However, in this case, if the thickness of the membrane to be coated is made too thin, the separation performance will deteriorate, so it is necessary to coat the membrane thicker than a certain level. There is a problem of trade-offs. In order to alleviate such inconveniences, the following two measures have been considered from the viewpoint of membrane materials. First, although it is impossible to make a thin film, it is necessary to select a material that has relatively high gas permeability and separation performance even at the current thickness. The key is to choose a material that does not create holes. However, at present, nothing satisfactory has been obtained in either case. For example, hydrocarbon rubber (e.g. natural rubber, polybutadiene) has double bonds in its molecules and is known as one of the polymer materials with the second highest permeation number for gases, especially CO ₂ , after organopolysiloxane. On the other hand, it has rubber elasticity and strong cohesive force, making it difficult to form a thin film. Moreover, if the film is forced to have a thickness of several tens of microns or less, problems of non-uniformity in thickness and the occurrence of pinholes will arise, and good gas separation performance will not be exhibited. Furthermore, since acetylene compound polymers have conjugated double bonds in their molecules, they can be expected to have good gas permeability similar to hydrocarbon rubbers. However, in reality, only low-molecular-weight polymers can be obtained, or even if high-molecular-weight polymers are obtained, there are cases in which there is no suitable solvent, or even if a solvent is available, it is only soluble at high temperatures. , when melted, it may change in quality due to its thermal instability. Thus, until now, no polymer has been known that meets the demands for separation membranes and that can be made into thin films. On the other hand, it is possible to obtain novel chain polymers in high yield from monosubstituted phenylacetylenes or disubstituted acetylenes, and the resulting polymer has a weight average molecular weight of 10,000 or more as measured by light scattering method, especially
In addition to having an extremely high molecular weight for an acetylene compound polymer, ranging from 100,000 to 1,000,000, it is also completely soluble in hydrocarbons such as toluene and cyclohexane. It is described in various publications such as No. 55-23565 and Japanese Unexamined Patent Publication No. 58-32608, and is well known. However, the separability of novel chain polymers obtained from these monosubstituted phenylacetylenes or disubstituted acetylenes in gas mixtures, liquid mixtures, etc. is still completely unknown. In view of the current situation, the present inventors have conducted intensive studies on the separability of substance mixtures such as gases and liquids using these novel substituted polyacetylenes, and have determined that these chain polymers can be used as the main component of membrane materials. We have found that when this method is used, it is possible to obtain a membrane with a higher gas permeability coefficient than conventional membranes of the same type while maintaining excellent selectivity in the separation of gas mixtures. That is, substituted alkynes, for example, the general formula () HC≡C-R' ... () (In the above formula, R' is a branched alkyl group, and this alkyl group has one or more hydrogen atoms in the group. A separation membrane mainly composed of a chain polymer having a weight average molecular weight of 10,000 or more and having monosubstituted acetylene as a monomer represented by the general formula (), which may be substituted with a substituent. (In the above formula, A represents a substituent such as an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, or a halogen atom,
n represents an integer of 0 to 5. ), or a separation membrane based on a chain polymer with a weight average molecular weight of 10,000 or more and containing disubstituted acetylene as a monomer, or with the general formula () CH ₃ −C≡C−R″ ...() ( In the above formula, R'' is an aryl group, and one or more of the hydrogen atoms of this aryl group may be substituted with a substituent, and some may be further substituted with a halogen atom, an aryl group, an alkoxy group, or an aryloxy group.) By using a separation membrane mainly composed of a chain polymer with a weight average molecular weight of 10,000 or more and having disubstituted acetylene as a monomer represented by It was discovered for the first time that a membrane with a gas permeability coefficient equal to or higher than that of conventional membranes of the same type could be obtained, and the patent application was filed. (Special Application No. 57-066475,
No. 57-117813 and patent application No. 57-174389. ) The present inventors, based on the above novel findings,
Considering that high polymers of acetylenes can be expected to have good separation properties for substance mixtures, we first used polymers such as monosubstituted phenylacetylenes and monosubstituted heterocyclic acetylenes to improve separation properties for substance mixtures, such as gas mixtures. As a result of further consideration,
It has been shown that when this chain polymer is used as the main membrane material, a membrane can be obtained that maintains excellent selectivity in separating gas mixtures and has a gas permeability coefficient equivalent to that of conventional membranes of the same type. Heading, we arrived at the present invention. That is, the present invention provides excellent selectivity in the separation of mixtures, especially gaseous mixtures, while
The purpose is to provide a membrane with a large gas permeability coefficient, and its gist is as follows:
General formula () HC≡C-X ...() (wherein, X is

The position represented by [formula] substituted phenyl group or

【formula】

【formula】

【formula】

[Formula] or

[Formula] represents a heterocyclic group, and R represents a nitro group, an alkoxy group having 1 to 6 carbon atoms, a phenoxy group, a phenylsulfonyl group, a phenylthio group, or -CH=N-N(C ₆ H ₅ ) ₃ and n is 1,
The separation membrane is mainly composed of a chain polymer having a number average molecular weight of 1000 or more and having -substituted acetylene as a monomer represented by the number 2 or 3. The present invention will be explained in detail below. The main component of the separation membrane of the present invention is a polymer obtained by addition polymerization of a monosubstituted acetylene monomer represented by the general formula (). That is,

A polymer containing the structural unit of [Formula] with a content of 20 to 100 mol%, preferably 50 to 100 mol%, and the number average molecular weight of the polymer depends on the type of monomer and polymerization conditions. It varies depending on the time, but it is approximately between 10 million and 300,000. The chain polymer forming the main body of the separation membrane of the present invention is 1
It is obtained by catalytically polymerizing one or more monosubstituted acetylene compounds in a solvent. In this case, solvents include aromatic hydrocarbons such as benzene, toluene, and tetralin, ethers such as dioxane, dibutyl ether, and anisole, esters such as methyl benzoate, and ethyl acetate, carbon tetrachloride, orthodichlorobenzene, ，
Chlorinated hydrocarbons such as 2-dichloroethane can be used alone or in combination. As a catalyst, (1) tungsten hexachloride WCl ₆ ,
(2) Molybdenum pentachloride MoCl ₅ , (3) W(CO) ₆ or Mo
Group transition metal carbonyl of the periodic table represented by (CO) ₆ and organic halokene compounds such as CCl ₄ ,
A photoreaction product with CBr ₄ or CCl ₃ COOEt is used. As a co-catalyst used in conjunction with this catalyst, water, alcohols or organic tin compounds may be used. Particularly preferred are organic tin compounds, and among these, tetraphenyltin is preferred. The ratio of monomer to (main) catalyst is the former in terms of molar ratio.
100, the latter range is suitably in the range of 5 to 0.2, and the molar ratio of the promoter to the main catalyst is preferably in the range of 0.3 to 3. The catalyst is used in the form of a solution, and the main catalyst and co-catalyst are preferably dissolved in a solvent and left at 30-60°C for 10-60 minutes before use. The monomer concentration in the polymerization reaction is preferably in the range of 0.1 to 5 mol/mol. The temperature of the polymerization reaction is usually selected from 0 to 60°C, and the reaction time is selected from the range of several tens of minutes to several hours. After the reaction is completed and diluted with the solvent used for the reaction,
If it is poured into a large amount of methanol, the resulting polymer will precipitate, so this is separated and dried. The thus obtained monosubstituted acetylene polymer can be cast into a homogeneous thin film by casting the solution. The separation membrane may be the polymer obtained as described above or a product containing this as the main component, a copolymer with other components, or a blend product mixed with other components. A film formed by forming a film may also be used. The separation membrane of the present invention is mainly composed of the polymer obtained as described above, and is produced by a known membrane forming method, such as a dry-wet film forming method (a method for producing a homogeneous membrane or an asymmetric membrane by a solution casting method). ), liquid surface film forming method (water surface development method), solution coating method (polymer coating method), vacuum evaporation method, etc. can be used as the separation membrane. In addition, the solution coating method is
A solution of another polymeric material is coated onto an air-permeable porous membrane that serves as a support, such as a flat membrane, a tubular membrane, or a hollow fiber membrane, and then the solvent is evaporated to form a thin membrane layer with separation properties. This method is applicable to a relatively wide variety of polymer materials, and is also suitable as a method for forming the separation membrane of the present invention. Due to its excellent properties, the separation membrane of the present invention can be used in the form of homogeneous membranes, asymmetric membranes and composite membranes for the separation of specific substances in substance mixtures.
The target substance can be used to separate gases from each other, in particular gas mixtures containing at least one of the following gases: oxygen, nitrogen, carbon dioxide, carbon monoxide, hydrogen, helium, methane, argon. For example, separation of nitrogen and oxygen in the production of oxygen-enriched air, separation of methane and helium in the recovery of helium from natural gas, argon and hydrogen, methane and hydrogen, nitrogen and hydrogen in the recovery of hydrogen from hydrogenation reaction waste gas. It can be applied to the separation of carbon monoxide and hydrogen in the recovery of hydrogen from cracking gas, the separation of carbon dioxide and nitrogen in the recovery of carbon dioxide from combustion gas, etc. Next, the present invention will be explained in more detail with reference to Examples and production examples of polymers used in the Examples. In this specification, "%" is by weight unless otherwise specified. Production Example 1 A slurry liquid of tungsten hexachloride-toluene and a slurry liquid of tetraphenyltin-toluene were prepared separately and then mixed so that the concentration of each was 0.1M. The slurry liquid after mixing was initially dark gray, but after stirring at room temperature for 30 minutes, it turned dark and colored. The catalyst slurry liquid obtained in this way was
2.12 g of 4-ethynyl phenyl phenyl ether [HC≡C-X,X:

[Formula]] (hereinafter referred to as "monomer") in toluene solution,
Each catalyst was added in an amount of 3.8 mol % based on the monomer and stirred at room temperature for 24 hours to obtain 2.00 g (yield = 94%) of a brick-colored polymer powder. The IR spectrum of the resulting polymer product showed the disappearance of the absorption at 3300 cm ^-1 inherent to the terminal acetylene present in the monomer. In addition, the elemental analysis values of the product are based on the structural units of the polymer, as shown in the table below. It was in good agreement with the calculated value.

[Table] The number average molecular weight of the monosubstituted acetylene polymer obtained was 9,900. Note that the number average molecular weight was measured by gel permeation chromatography. In this case, the polystyrene calibration curve used and the conditions are as follows. Column: TSK G5432mix Solvent: Tetrahydrofuran Detection: Using refractive index Flow rate: 10 ml/min Temperature: 40°C Solution concentration: 0.5 Wt% Injection amount: 100μ Production examples 2 to 6 Production example 1 of 4-ethynyl phenyl phenyl ether Instead, X denoted by HC≡C−X

[Formula] (Production Example 2),

[Formula] (Production Example 3),

[Formula] (Production Example 4),

[Formula] (Production Example 5) or

[Formula] (Production Example 6) A polymer of five monosubstituted acetylenes having a red color to black and a solid color was obtained in exactly the same manner as in Production Example 1, except that five types of monosubstituted acetylenes having the formula (Production Example 6) were used. Ta. The yields of the five types of polymers obtained in Production Examples 2 to 6 were 100%, 38%, 63%, 96%, and 63%, respectively.
The number average molecular weights of the polymers are 7800 and 7800, respectively.
They were 10300, 2200, 11200, and 2500. Example 1 The polymer obtained from 4-ethynyl phenyl phenyl ether in Production Example 1 was dissolved in toluene to obtain 1
% solution, and a porous membrane [Millipore Filter VSWP (manufactured by Nippon Millipore Limited)] was immersed in this solution and applied. After drying, the coating thickness of the solid content in the obtained composite film was determined by gravimetric method and was found to be 1.6 g/m ² . The obtained composite membrane was installed in a permeation test device, and the permeation characteristics of various gases were measured. The measuring device is an ultraviolet device [manufactured by Amicon, USA;
Model 52], after installing the above composite membrane,
A specified gas was applied to the upper surface of the membrane at a pressure of 1.0 kg/cm ² G, and the lower surface of the membrane was connected to a gas burette.
The gas permeation rate was determined by measuring the amount of gas permeating through the membrane over a certain period of time at ℃. These results are shown in Table 1 below.
Shown below. In the table, the units of gas permeation rate for various gases are
cm ³ (STP)/cm ²・sec・cmHg. Examples 2 to 6 In Example 1, each polymer obtained in Production Examples 2 to 6 was used instead of the polymer from 4-ethynyl phenyl phenyl ether obtained in Production Example 1, and the solvent The same procedure as in Example 1 was carried out, except for some changes (chloroform was used when the polymer was insoluble in toluene). The gas permeation rates of various gases were measured in the same manner as in Example 1 for each composite membrane of Examples 2 to 6 obtained using each of the five types of polymers of Production Examples 2 to 6. These results are summarized in Table 1 below. Comparative Example 1 A membrane obtained by performing exactly the same procedure as in Example 1 except that the polymer obtained from 4-ethynyl phenyl phenyl ether of Production Example 1 was not used was used. Gas permeation rates of various gases were measured in the same manner. The results are shown in Table 1 below. From the results in Table 1, it can be seen that the composite membrane of the present invention has a much higher ratio of gas permeation rates for various gases than the conventional membrane of Comparative Example 1, and is particularly excellent as a separation membrane for gas mixtures. .

【table】

Claims (1)

[Claims] 1 General formula () HC≡C-X ... () (wherein, X is a substituted phenyl group represented by [formula] or [formula] [formula] [formula] [formula] or [formula] represents a heterocyclic group of the formula], and R represents a nitro group, an alkoxy group having 1 to 6 carbon atoms, a phenoxy group, a phenylsulfonyl group, a phenylthio group, or -CH≡N-N(C ₆ H ₅ ) ₃ , and n is 1,
A separation membrane mainly composed of a chain polymer having a number average molecular weight of 1000 or more and having a -substituted acetylene monomer represented by the number 2 or 3. 2. The separation membrane according to claim 1, wherein the separation membrane is a gas separation membrane.