JPS62125825A - Gas separation membrane - Google Patents

Abstract

PURPOSE:To enable polymerization in the atmosphere wherein polymerization inhibition due to oxydation is easily caused by performing ultraviolet rays irradiation for a substance which is made to a thin membrane by adding a polymerization initiator to a membrane material having >=3 functionality as a photoreactive group in one molecular and polymerizing and curing it. CONSTITUTION:A membrane material having >=3 functionality as a photoreactive functional group such as acryloyl group, methacryloyl group and vinyl group is used. A silicone compd. is suitable as the membrane material when considering high permeability and stability. As a polymerization initiator, either of a radical reaction type and an ion reaction type may be used and benzoins such as a structure of 1-(4-alkylphenyl)-2-hydroxy-2-methylpropane-1-one is high in polymerization starting efficiency and preferably used and the loadings are 0.1-30wt%. A soln. of this mixture is made to a membrane having <=10mum thickness and polymerization is performed by irradiating ultraviolet rays thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a gas separation membrane for separating and condensing gases.

BACKGROUND OF THE INVENTION In recent years, separation technologies using polymers such as ultrafiltration membranes, reverse osmosis membranes, and gas permeation membranes have made remarkable progress, and some of them have been put into practical use on an industrial scale. However, what has actually been put into practical use is seawater desalination,
Processing of factory waste liquid 9 Liquid-liquid separation or liquid-surface separation, such as concentration of food (liquid substances), and gas-gas separation, that is, separation and concentration of a specific gas from a mixture of two or more gases, is completely practical. Currently, it has not yet reached the stage of development and is only at the research stage.

The reason why conventional gas permeable membranes are difficult to put into practical use is that
The main reason is that the selectivity of the membrane material is low, that is, there are no membranes that selectively allow certain gases to pass through while hardly allowing other gases to pass through. To obtain highly pure gases, membrane separation is repeated several times. It is necessary to adopt a multi-stage method, which may make the device too harsh. Another problem is that a large amount of gas cannot be produced because the permeation flow rate is small.

However, there are many fields in which high-purity gases are not necessarily required as end-uses, such as oxygen, blast furnace ventilation, combustion assistance, and sludge treatment.

For medical exhalation, etc., the purpose can be achieved if the oxygen concentration in the atmosphere is increased to some extent, so-called oxygen-enriched air.

Particularly active research and development is being carried out on so-called oxygen enrichment membranes that concentrate and separate oxygen, with the leading research being on organosiloxane-polycarbonate copolymer C (see Japanese Patent Application Laid-open No. 40868/1986) from General Electric Company in the United States. Various polymeric materials have been synthesized, and research is currently underway in Japan, focusing on copolymers containing silicone as the main component (see Japanese Patent Application Laid-Open No. 112457/1983). The film-forming methods used were mainly a method of overlapping separately formed thin films on a porous support, a method of forming an anisotropic film in which a skin layer and a porous support coexist, and a method of forming an anisotropic film in which a skin layer and a porous support coexist. Monomers can be directly polymerized on the membrane by various methods to form a thin film, or the membrane material can be dropped onto the water surface as it is or diluted with a solvent, and monomers can be formed on the water surface by surface active action. The so-called [Langmuir-Prodgett film forming method], which forms a film, can be considered.

A possible application of this ``Langmuir-Prodgett film forming method'' is the ``water surface spreading method.'' In this method, a solution of the membrane material is dropped onto the water surface, the solution is spread on the water surface, and the solvent used spontaneously evaporates, leaving only the membrane material on the water surface. Next, the film formation is completed by attaching a thin film of the obtained film material onto a porous support. In the case of this method, generally a highly polymerized membrane material is often used, which determines the membrane thickness, membrane strength, and life characteristics. However, when using a polymerized material, it is difficult to develop it on the water surface.
Since it is a necessary condition that it can be dissolved in some kind of solvent,
There is a limit to further increasing polymerization for the purpose of improving membrane strength. Furthermore, since it has already been made into a polymer, there is a limit in terms of making it an ultra-thin film.

When considering ultra-thin films, low-molecular materials are of course more advantageous than high-molecular materials in terms of spread and film thickness. Monomers, oligomers, and relatively low molecular weight polymeric materials with photoreactive groups are deployed on the water surface.

The present inventors have already proposed a method of polymerizing the film by irradiating it with ultraviolet rays or electron beams after forming a thin film. The ultrathin film obtained by this method has particularly high solvent resistance K
There were very few deviations and pinholes, and good results were obtained in terms of reliability. However, the problem with this method is that when irradiated with ultraviolet rays or electron beams in the atmosphere, the photoreactive groups in the film material react with oxygen in the atmosphere, hindering the polymerization reaction and reducing the film strength. difficult to obtain. Therefore, when performing light irradiation,
Polymerization in a thin film state is only possible by replacing the atmosphere with an inert gas such as nitrogen, but this requires complicated packaging and
It is troublesome to handle.

In order to make the film thinner, it is more advantageous to lower the molecular weight of the film material, and ultimately a monomolecular film with one unit of monomer can be considered. However, in general, as the molecular weight decreases, the influence of air inhibition tends to increase, and the thinner the film, the more attention must be paid to air inhibition.

Problems to be Solved by the Invention As mentioned earlier, in the conventional film forming method, the molecular weight of the membrane material used for water surface development is relatively high in order to obtain membrane strength, which causes However, thin films naturally had their limits.

It also had the disadvantage of poor solvent resistance.

Therefore, in order to solve these drawbacks, the present inventors developed a monomer having a photoreactive group.

A film-forming method (water surface UV curing method) has already been proposed in which oligomers and relatively low-molecular-weight polymeric materials are spread on the water surface to form a thin film, and in this state are irradiated with ultraviolet rays or electron beams to polymerize. However, although this method is extremely effective in an atmosphere of an inert gas such as nitrogen, it has the disadvantage that it is inhibited by air in an atmospheric environment, and polymerization does not proceed and film strength cannot be obtained. .

In view of the above-mentioned drawbacks, the present invention has been made after repeated careful studies on film materials.The present invention has been developed by forming a thin film of a material with less than two functionalities per molecule in the air, and polymerization does not proceed even when irradiated with light, but with trifunctional materials. It was discovered that when the above conditions were used, photopolymerization occurred even in the atmosphere. Therefore, by increasing the number of photoreactive groups per molecule of monomers, oligomers, and relatively low molecular weight polymer materials used as membrane materials, the influence of air inhibition per unit area can be reduced, and even in the atmosphere, the so-called " water surface U
This led to an invention that enables film formation using the "V curing method". Specifically, a polymerization initiator is added to a film material having three or more functional photoreactive groups, the film is formed into a thin film by a water surface spreading method, etc., and then polymerized and cured by ultraviolet irradiation, resulting in excellent film strength. This provides an ultra-thin membrane for gas separation with a large permeation flow rate.

Means for Solving the Problems In order to achieve this objective, the gas separation membrane of the present invention has the following features:
It consists of adding a polymerization initiator to a film material having trifunctional or higher functional groups as photoreactive groups in the molecule, and polymerizing and curing the thin film by irradiating it with ultraviolet rays.

Examples of photoreactive groups include acryloyl group, methacryloyl group, vinyl group, allyl group, and nannamoyl group.

α-anocinnamylideneacetyl group, nonnamylideneacetyl group + a-cyanocinnamylideneacetyl group.

Examples include benzalacetophenone (chalcone group), phenyl azide group, α-phenylmaleimide group, furyl acroyl group, etc. Among them, acryloyl group, methacryloyl group, vinyl group, etc. are particularly suitable, but photoreactive functional groups If so, there is no problem.

Second, membrane materials include styrene, vinyl alcohol,
Phenoxys (condensation product of Epoquin and bisphenol compound) 2 ethers, esters.

Amides, allyl alcohol, styrene-maleic acid, maleic esters, and fumaric esters.

Acetylene derivatives, monomers such as silicone compounds mainly containing dimethane loxane, oligomers, and relatively low-molecular polymer materials can be considered, but silicone compounds are the most suitable, especially when considering high permeability and stability. Ori,
It is desirable to use silicone alone or, if high separation is also considered, a combination of silicone and the above membrane material.

In addition, the polymerization initiators used include radical reaction type,
Any ionic reaction type can be used, such as acetophenones such as jetoxyacetophenone, di- and trichloroacetophenone, benzoin ethers such as benzophenone, Michler's ketone, benzyl, benzoins, benzoin methyl ether, and penzoin isoglobil ether.

Benzyl dimethyl ketal, benzoyl benzoate,
Examples include a-aziroxime ester, tetramethylthiuram monosulfide, azo compounds, among others 1-(4-alkylphenyl)-2-hydroxy-2-
Benzoins having an alkyl group such as a methylpropan-1-one structure have extremely high initiation efficiency and are most suitable as polymerization initiators for use in the present invention. The amount added is
Normally 0.1 to 30 weight factor for membrane material, practically 0
．． It is effective to use a weight of 2 to 6.0.

The method of thinning the film of the present invention may basically be any method, including the LB method (water surface spreading method) described above, a dipping method, a casting method, a spray method, etc., and is not limited to any particular method. do not have. In addition, if the molecular weight of the membrane material is high and it is difficult to make it into a thin film as it is, a solvent may be added as necessary. Especially in the case of a thin film of 1107 u or less, the air-obstructed area on the membrane surface can be reduced. , surface hardness can be increased. Further, ultraviolet rays are irradiated after the thin film is formed. In this case, the irradiation means may be a discharge lamp method, a flash lamp method, a single laser method, an electrodeless lamp method, etc., and any method may be used. Furthermore, it is of course possible to use an electron beam as the irradiation source. In this case, there is no need to add a polymerization initiator, which is simpler, but the equipment becomes complicated and the cost increases, so it is simpler and more practical to use ultraviolet light.

It should be noted that in order to check whether a thin film is polymerized by ultraviolet irradiation, it is obvious that the irradiated thin film is wound up on a porous support and then the separation coefficient is determined using a bubble flow meter.
As a precaution, we checked whether it was insoluble in tetrahydrofuran and evaluated whether it was polymerized. The porous support of the gas separation membrane of the present invention may be made of any material such as polypropylene, polyester, polysulfone, polyethylene, polyethersulfone, polycarbonate, etc., and the resin used is not limited.

Effect With the above structure, first, add an appropriate amount of a polymerization initiator to a membrane material having trifunctional or higher functional groups as photoreactive groups in one molecule, add an appropriate amount of solvent or no solvent, and form a membrane using a water surface development method or the like. Form a thin film of material.

Next, in this state, ultraviolet rays are irradiated in the atmosphere, and the polymerization initiator added to the thin film becomes radicals, and a reaction is initiated. On the surface of the thin film, after the initiation reaction of the polymerization initiator, the radically cleaved photoreactive groups of the film material react with oxygen in the atmosphere, and a partial polymerization termination reaction occurs, but one molecule of the film material used When there are three or more photoreactive groups, the photoreactive groups that did not participate in the reaction with oxygen in the atmosphere proceed with the reaction between the film materials after radical cleavage, resulting in polymerization even on the thin film surface. It progresses.

Because it has many photoreactive groups, it minimizes the oxidative polymerization termination on the thin film surface even in the air, making it possible to perform polymerization in ultra-thin films.

EXAMPLES Next, the present invention will be explained in more detail based on examples.
The content of the present invention is not limited only to the examples.

Comparative Example 1 Material with vinyl terminals at both ends of bifunctional polydimethylsiloxane per molecule [manufactured by Chinon Co., Ltd., trade name: PS441,
PS445, PS448, etc.] and benzoin isopropyl ether as a polymerization initiator. A thin film was formed on the water surface using an end strip with a weight factor of ○ to 6.0. In this state, it was irradiated with ultraviolet light (intensity 6.6 mw/CJ) for 30 minutes, but it did not polymerize at all, and was wound up on a polypropylene porous support [manufactured by Polyplastics Co., Ltd., trade name: DURAGUARD]. When we investigated the characteristics on the bubble flow rate side (a device that evaluates the characteristics based on the number of seconds it takes for 10cc to pass when 1 atm pressure is applied to each of oxygen and nitrogen), we found that it could not withstand 1 atm pressure because it had not polymerized. It becomes a pinhole ff1
I couldn't determine l+. In addition, as a polymerization initiator, Darocure 953 [manufactured by Merck Co., Ltd., 1-(4-
The results were the same even when 2-hydroxy-2-methylpropan-1-one] was used.

PS441.445,448 Darocure 953 Example 1 A 5H-410C bundle (manufactured by Silicone Co., Ltd.) having the following structure was dissolved in benzene to form a solution with approximately 20 stacks of ends.

H-410 Next, as a polymerization initiator, benzoin isopropyl ether was added to 5H-410 in a proportion of 0.5 to 4. ○In addition, a thin film was created using the water surface spreading method. 6.6 in this state
Ultraviolet irradiation was carried out at an intensity of mw/crA, and polymerization was carried out to a degree of about 6 minutes. It was wound up using Duraguard, and its characteristics were examined using a bubble flow meter, and the results are shown in Figure 1. Comparative example 1
However, it was bifunctional and thin film properties could not be obtained.
It can be seen that in the case of polyfunctionality as in this example, polymerization occurs in a thin film. As a result of examining polymerization initiators, it was found that most of them were capable of polymerization in about 5 minutes, but Darocure 95 was particularly effective.
When No. 3 was used, the polymerization rate was extremely fast, and the polymerization took about 6 to 16 seconds. Note that the obtained polymer film was insoluble in tetrahydrofuran, benzene, and the like.

Similarly, Darocure 963 was added as a polymerization initiator to a polydimethyl-methylvinylsiloxane copolymer having a vinyl terminal group (manufactured by Chisso Corporation, trade name, PS493).
Added 0.5 to 6.0 heavy weights to the membrane material, made it into a thin film using the water surface spreading method, and irradiated it with an irradiation intensity of 6.6 mw/c4C.
When the thin film properties were examined by winding it around Duraguard, which had been polymerized for ~2Q seconds, the same results as shown in Figure 1 were obtained, and after polymerization, a solvent resistance test was carried out using solvents such as tetrahydrofuran and benzene. and confirmed that it was insoluble.

Comparative Example 2 0.5 to 7.0 of Darocure 963 was added as a polymerization initiator to polydimethylsiloxane having methacroyl groups at both ends.
A large amount of the polymer was added, spread on the water surface as in the example, made into a thin film, and then irradiated with ultraviolet rays at an intensity of 6.6 mw/crl for about 30 minutes, but no polymerization occurred, and the film was rolled up on Duraguard and the thin film properties were evaluated. I looked into it, but it was impossible to measure because of a pinhole. Furthermore, the results were the same even when other polymerization initiators were used.

Example 2 Polydimethyl-methacryloquine probylmethylronloxane [manufactured by Chisso Corporation, trade name: PS4291, 0.5 to 6.0% by weight of Darocure 963 was added as a polymerization initiator, and a thin film was formed on the water surface. The polymer was irradiated with ultraviolet light at an intensity of 6.6 m W /Ci and polymerized for 10 to 30 seconds. Next, when it was wound around Duraguard and measured using a bubble flowmeter, results almost the same as those in FIG. 1 of Example 1 were obtained. still,
Polymerization was possible using other polymerization initiators, but required ultraviolet irradiation for 5 to 10 minutes. Furthermore, the obtained membrane was insoluble in tetrahydrofuran, benzene, and toluene.

Comparative Example 3 Niricone alkyl diol manufactured by Chisso Corporation (trade name,
Using F M 4411, M, W=1ooo) as a starting material, a difunctional urethane acrylate of phosphoricone diol as shown below was synthesized by reacting a difunctional incyanate and β-hydroxyethyl acrylate.

R-Urethane binding capacity: 1 Add Darocure 953 as a polymerization initiator to 0.2~
After adding 3.0 heavy end strips and forming a thin film using the water surface spreading method, 6.6
Ultraviolet irradiation was performed at an intensity of mW/6rJ for 30 minutes, but no polymerization occurred.Next, when the irradiation atmosphere was changed from air to nitrogen atmosphere and UV irradiation was performed in the same way, 3
Polymerization occurred in about 0 seconds. When it was wound up on a Duraguard and measured using a bubble flowmeter, the results shown in Figure 2 were obtained. Due to this grana, it can be said that there are no pinholes on the thick film side and good 7Z characteristics, but it can be seen that there are pinholes on the thin film side.

Example 3 In the same manner as in Comparative Example 3, using FM4411 as a starting material, this time a trifunctional isocyanate and β-hydroquine ethyl acrylate were reacted to prepare a tetrafunctional urethane acrylate of an silicone diol as shown below. Synthesis was performed.

R′: urethane bond, etc. Next, 0.2 to 6.0 weight of Darocure 953 is added to the membrane material as a polymerization initiator to this acrylate,
It was made into a thin film using the water surface development method. Next, in the atmospheric atmosphere, 6
．． Ultraviolet irradiation is performed at an intensity of 6 mw/cJ, and approximately 1 to 3
It polymerized within seconds. When this was wound up using Duraguard and measured using a bubble flowmeter, the results shown in Figure 3 were obtained. In addition, when UV irradiation was performed in a nitrogen atmosphere as in Comparative Example 3, polymerization occurred in about 1 to 3 seconds, the same as in the case of an air atmosphere, and no difference was observed in the polymerization rate due to the difference in the atmosphere. The increased number of groups suggests that thin film polymerization in the atmosphere is possible. Polymerization can also be carried out using other polymerization initiators, but the polymerization time takes about 3 to 5 minutes, and Darocure 953
is clearly an excellent initiator.

Although the present invention has been explained above with reference to the embodiments, focusing on the water surface spreading method, it is obvious that similar effects can be obtained by other methods such as the casting method and the dipping method.

Effects of the Invention As described above, according to the present invention, by using a film material having trifunctionality or more as a photoreactive group in one molecule, ultraviolet polymerization can be carried out in a thin film state even in an atmospheric atmosphere where polymerization inhibition due to oxidation is likely to occur. is possible, and 1-
When (4-alkylphenyl)-2-hydroxy-2-methylpropan-1-one is used, it exhibits excellent curability. This eliminates the need for forming a thin film in an inert atmosphere and cures it. Since the process is quick, it is possible to produce a gas separation membrane with a simple device and excellent productivity, and its thin film properties, membrane strength, solvent resistance, etc. are also good.

[Brief explanation of drawings]

, ■ Figure 1 shows 5f (-410
Figure 2 shows the characteristics of a thin film obtained by adding benzoin isopropyl ether as a polymerization initiator to the material and irradiating it with ultraviolet light after spreading on the water surface. FIG. 3 is a thin film characteristic diagram when a thin film of the silicone diol tetrafunctional urethane acrylate of Example 3 is formed in an atmospheric atmosphere and is irradiated with ultraviolet rays. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 5)
0CCC 1, (l K3/CTn2 near) at lEj3 1 Darocure%3 concentration 40 direct quantity/・21st silicone siol? Palace officials and ministers.

Claims (4)

[Claims] (1) A gas separation membrane characterized in that it is constructed by polymerizing and curing a thin film in which a polymerization initiator is added to a membrane material having three or more functional groups as photoreactive groups in one molecule, by irradiating ultraviolet rays. (2) The gas separation membrane according to claim 1, wherein the membrane material contains a siloxane structure. (3) The gas separation membrane according to claim 1, wherein the thin membrane has a thickness of 10 μm or less. (4) The polymerization initiator is 1-(4-alkylphenyl)-2-hydroxy-2-methylpropane-1 of the following structural formula.
The gas separation membrane according to claim 1, characterized in that it has a -on structure. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼