JPH0221856B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a gas separation membrane having excellent selective separation and permeability for gas mixtures. A gas separation membrane is required to have a high gas separation rate and a high permeation rate. In order to meet these demands, it is desirable that the thickness of the membrane exhibiting substantial separation performance be as thin as possible, and in practical use such membranes are often coated with an air-permeable porous layer (e.g. Japanese paper, non-woven fabric, synthetic paper, paper, cloth, wire mesh,
It is considered preferable to use a structure that is supported by a membrane (eg, ultrafiltration membrane, ultrafiltration membrane, etc.). Various methods have been proposed for manufacturing such structures. 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) are used. A method of forming an integral sheet body into a film at once, a method of directly polymerizing monomers on a porous film by various methods to form a thin film with separability, or a method of forming a thin film with separability on a porous film. A known method is to coat a polymer solution thereon and then evaporate the solvent to form a thin film with separation properties. Among the various methods mentioned above, there is a method in which a solution of another polymeric material is coated on an air-permeable porous membrane that serves as a support, and then the solvent is evaporated to form a separable thin film layer. , is preferable because it enables 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, and if the membrane is coated thickly to meet this requirement, the permeation rate of the material to be treated will decrease. There is a trade-off issue. In order to alleviate such inconveniences, the following two measures have been considered from the viewpoint of membrane materials. Firstly, although it is impossible to make the film thinner, it is necessary to choose a material that has relatively high gas permeability and separation performance even at the current thickness.Secondly, even if the film is made thinner, it must be possible to avoid pinholes. The key is to choose materials that do not cause this. However, at present, nothing satisfactory has been obtained in either case. For example, hydrocarbon rubbers (e.g. natural rubber, polybutadiene) have double bonds in their molecules, and gas,
In particular, it is known as one of the polymer materials with the second highest permeability coefficient for CO ₂ after organopolysiloxane, but on the other hand, it has rubber elasticity and strong cohesive force, making it difficult to form a thin film. Furthermore, 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 occur, and good gas separation performance will not be exhibited. Furthermore, since polyalkynes have conjugated double bonds in their molecules, they can be expected to have good gas permeability similar to that of carbon-hydrogen 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 good 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. The present inventors first discovered that it is possible to obtain a novel chain polymer from 2-alkynes in high yield, and that the resulting polymer has a weight average molecular weight of 10,000 or more as determined by light scattering, and in particular, 10,000 or more. It was discovered that it has an extremely high molecular weight for an acetylene compound polymer, ranging from 10,000 to 1,000,000, and is also completely soluble in hydrocarbons such as toluene and cyclohexane. No. 112108). As a result of intensive studies on separation properties using this new poly-2-alkyne, we found that when this chain polymer is used as the main membrane material, it can be used to separate gas mixtures while maintaining excellent selectivity. It was discovered that a membrane with a higher gas permeability coefficient than conventional membranes of the same type could be obtained. That is, the present invention aims to provide a membrane with a large gas permeability coefficient while maintaining excellent selectivity in the separation of gas mixtures, and the gist thereof is as follows: (In the above formula, A is an alkyl group, an aryl group,
Indicates an aralkyl group, an alkoxy group, an aryloxy group, or a halogen atom. n represents an integer of 0 to 5. ) The gas separation membrane is mainly composed of a chain polymer having a weight average molecular weight of 10,000 or more and having the compound represented by the following as a monomer. The present invention will be explained in detail below. The separation membrane of the present invention is made of a polyalkyne made of monomers represented by the above formula (). Polyalkynes made from monomers of formula () will be described. A in formula () represents an alkyl group, an ary group, an aralkyl group, an alkoxy group, an aryloxy group, or a halogen atom. Also, n is 0~
Indicates an integer of 5. In order to obtain a chain polymer having a weight average molecular weight of 10,000 or more from the monomer of the above formula (), a mixture of a group transition metal carbonyl and an organic halide or a monomer is irradiated with 2-chloro-1. -2-chloro-1 by polymerizing phenylacetylenes
- Polymers of phenylacetylenes can be produced. All of the above group transition metal carbonyls are in powder form and are stable in air, so they are easy to handle.As group transition metal carbonyls,
Examples include chromium carbonyl, molybdenum carbonyl, and tungsten carbonyl (for details, see Kyoritsu Shuppan Co., Ltd., Chemistry Dictionary, Vol. 3, p. 201, Vol. 9, p. 294,
It is described in Volume 5, page 710. ) Molybutene hexacarbonyl shows particularly high activity. As the organic halides used for catalyst preparation in the above method for producing a chain polymer, halogenated hydrocarbons such as carbon tetrachloride and carbon tetrabromide, and halogenated fatty acid esters such as ethyl trichloroacetate can be used. Carbon tetrachloride is preferred because it is inexpensive, easy to handle, and can also serve as a reaction solvent. Since the monomer 2-chloro-1-phenylacetylene itself has a chlorine atom, a mixed solution of the group transition metal carbonyl and the monomer can be prepared for the first time without adding an organic halogen compound separately. It is also possible to advance the polymerization simultaneously with the preparation of the catalyst by irradiating the catalyst with light for a predetermined period of time. A method in which a mixed solution of a group transition metal carbonyl and an organic halide is irradiated and then polymerized by adding a monomer in the dark is better than a method in which a mixed solution of a metal carbonyl and a monomer is polymerized simultaneously with irradiation. , producing high molecular weight polymers. The amount of the organic halogen compound to be used is equal to or more than the amount of the group transition metal carbonyl, and when used as a solvent like the above-mentioned carbon tetrachloride, a correspondingly large amount may be used. In the polymerization of 2-chloro-1-phenylacetylenes, the amount of transition metal carbonyl used is suitably in the range of 0.1 to 10 mol % based on the monomer of the above formula (). The light used for irradiation is
Although near-ultraviolet light from a 100W to 1KW high-pressure mercury lamp is most preferred, simple exposure to sunlight produces catalytic species effective for polymerization. Light irradiation time is 10 minutes ~
A temperature range of 0 to 100°C is suitable for several hours.
The intensity of the light is preferably such that it corresponds to the amount of irradiation for 10 minutes or more, preferably 30 minutes to 2 hours, at a distance of 30 cm from a 100 W to 1 KW light source. As a solvent for polymerization reaction, halogenated hydrocarbon,
It is preferable to use aromatic hydrocarbons and the like. The concentration of monomer in the polymerization reaction is 0.1 to 5 mol/
A range of is preferred. The temperature of polymerization reaction is usually 0 to 60
°C and time are selected from the range of several tens of minutes to several tens of hours. After the reaction is completed, the reaction system is diluted with the solvent used in the reaction and then poured into a large amount of methanol. Since the resulting polymer precipitates, it is separately dried. By the above method, a new chain polymer can be obtained in high yield from the 2-alkynes of the formula (), and the weight average molecular weight of the polymer as determined by light scattering method is 10,000 or more, especially 100,000. It has a molecular weight of ~1 million, which is extremely high for an acetylene polymer, and is also characterized by being completely soluble in hydrocarbons such as toluene and cyclohexane. By casting the solution of the polymer thus obtained, a homogeneous thin film can be obtained. The separation membrane may be the deuterium obtained as described above or one containing it as the main component, one formed into a copolymer with other components, or one mixed with other components as a blend product. A film formed by forming a film may also be used. The separation membrane of the present invention is mainly composed of the polyalkynes obtained as described above, and is obtained as a transparent and durable film by dissolving it in an organic solvent and casting it (solution casting method). In the casting method, raw materials are dissolved in an organic solvent or water, and if necessary, plasticity is added to obtain a viscous solution. After completely removing dust and air bubbles, the material is poured onto a flat glass plate. Alternatively, it is a method of casting onto a uniform metal support using a rotating flat plate, and removing the solvent to form a thin film.The resulting film has excellent uniformity in thickness, and has excellent flatness, transparency, and photoselectivity. Are better. Furthermore, it has the characteristic that it has no directionality and can produce an extremely high quality film free of foreign substances, and is suitable for obtaining a separation membrane from the polyalkyne of the present invention. For example, if it is attempted to form a film by a melting method, the melting point and decomposition temperature of the polyalkynes of the present invention are close to each other, so there is a risk of deterioration, which is not preferable. The organic solvent used to make the casting solution may be any solvent as long as it dissolves the polyalkyne well and evaporates easily after casting. Specifically, benzene, toluene, cyclohexane, n-hexane, etc. Hydrocarbon solvents, tetrahydrofuran, etc. are preferably used. The solution concentration for obtaining a homogeneous film from the casting solution varies depending on the molecular weight and molecular weight distribution of the polymer and the type of solvent, but is usually in the range of 1 to 50% by weight, preferably 5 to 30% by weight. Concentration is 1% by weight
If the solution concentration is less than 50% by weight, the resulting membrane will be too thick and the gas permeation rate will be high, but sufficient separation performance will not be achieved. Although separation performance can be obtained, the gas permeation rate becomes low. The thickness of the produced film is not particularly limited, but is usually in the range of 5 to 50 microns, preferably 10 to 30 microns. 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.
Gases can be used as target substances, 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 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 cracking gas, and the separation of carbon dioxide and nitrogen in the recovery of carbon dioxide from combustion gas. Examples of the present invention and production examples of polyalkynes used in these examples will be described below. Production example Under a dry nitrogen atmosphere, 30 mmol of molybdenum hexacarbonyl and 1.0 mole of 2-chloro-1-phenylacetylene in 1 part of purified carbon tetrachloride and 25% by volume of tetralin based on the monomer as an internal standard for gas chromatography. and 30 minutes at 30℃
Irradiation was performed using a 300W high-pressure mercury lamp. after that
Polymerization was carried out in the dark at 30°C for 23.5 hours. When the amount of residual monomer was determined by gas chromatography, the reaction rate was 83%. The resulting polymer was precipitated by pouring the reaction solution into a large amount of methanol, and then dried separately. The amount of methanol-insoluble polymer produced was 72% of the amount of monomer charged. The resulting polymer is a yellowish white solid;
It was soluble in toluene, carbon tetrachloride, ethylene dichloride, etc., and insoluble in n-hexane, ether, alcohol, etc. No softening point was observed below 300°C. It was confirmed by the following analysis that the product was a polymer with the expected structure. Elemental analysis value [(C ₈ H ₆ Cl)
_o ] Calculated values C70.35%, H3.69%, Cl25.96%, actual values C70.86%, H3.67%, Cl25.30%. Infrared absorption spectrum 3100-3000 (m), 1650-1550 (W), 1495
(S), 1445 (S), 1090 (m), 825 (m), 755 (S)
),
690 (S), 545 (m) cm ^-1 . According to the light scattering method, the weight average molecular weight of the resulting polymer was 980,000, and the intrinsic viscosity measured at 30°C in toluene was:
It was 2.58 dl/g. Furthermore, the relationship between the weight average molecular weight Mw determined by the light scattering method and the intrinsic recognition [η] was as follows. [η] = KM ^a _w (K = 10 ^-6.06 a = 1.07) Example 1 Poly(2-chloro-1-phenylacetylene) obtained in the above production was dissolved in toluene to give a concentration of 5% by weight.
This solution was applied to one side and both sides of a porous membrane (Millipore Filter VSWP (manufactured by Nippon Millipore Amit)). After drying, the coating thickness of the solid content was determined by gravimetric method and was 2.0 g/m ² and 8.0 g/m ² (total on both sides). This composite membrane was attached to a permeation test device, and the permeation characteristics of various gases were measured. The measuring device used was an ultraviolet device (Model 52, manufactured by Amicon, USA). After the membrane was attached, a specified gas was pressurized to the top of the membrane at a pressure of 1.0 kg/cm ² G, and the measurement was performed. Connect the bottom surface of the membrane to a gas filter and measure the amount of gas passing through the membrane over a certain period of time at 25°C to determine gas permeability. The results are shown in Table 1 below. The unit of gas permeability coefficient for various gases is cc (STP)・cm/cm ²・sec・
cmHg. Comparative Example 1 The same procedure as in Example 1 was performed except that poly(2-chloro-1-phenylacetylene) was not used (ie, a 0% by weight polymer solution in toluene). Gas permeability results are shown in Table 1. Example 2 Poly(2-chloro-1-
Dissolve phenylacetylene) in toluene and add 3%
(wt) concentration and kept at 34 °C. One drop of this polymer solution is added with a micropipette to water that has been filled in a container and maintained at 10°C. The weight of the droplet at this time was 13.7 mg. The dropped liquid immediately spread on the water surface, and an extremely thin circular film was obtained. The membrane area at this time was 18.8 cm ² , and the membrane thickness determined from this by the gravimetric method was 0.38 μ. The ultrathin membrane obtained here was taken out onto a polysulfone porous membrane to produce a composite membrane. The amount of gas permeation through this composite membrane was measured in the same manner as in Example 1. The results are shown in Table 1. Comparative Example 2 In Example 2, poly(2-chloro-1-phenylacetylene) was not used (i.e., polymer 0
Gas permeability was measured using the same procedure except for using a toluene solution (wt%). The results are shown in Table 1.

[Table] The above explanation and examples are related to typical examples to help the understanding of the present invention, and the present invention is not limited to these examples.
Other modifications may be made within the spirit of the invention.

Claims (1)

[Claims] 1. General formula (In the above formula, A is an alkyl group, an aryl group,
Indicates an aralkyl group, an alkoxy group, an aryloxy group, or a halogen atom. n represents an integer of 0 to 5. ) A gas separation membrane mainly composed of a chain polymer having a weight average molecular weight of 10,000 or more and containing a compound represented by the following as a monomer.