JPS61278307A - Preparation of gas separation membrane - Google Patents

Abstract

PURPOSE:To increase the strength of membrane remarkably and to obtain separation membrane having high durability by forming thin film comprising a permeable membrane material having reactive groups on the surface of water and crosslinking under this condition the membrane by irradiating with light or electronic energy. CONSTITUTION:Reactive groups having high photosensitivity are introduced into a polymer to be used for a permeable membrane material. Thin film is formed on the surface of water with the material. In this stage, 0.1-30wt% basing on the amt. of the membrane material of a photosensitizer is added to the membrane material. The thin film is irradiated with light energy such as ultraviolet rays while holding the thin film on the water surface. Electronic energy may be used also, but sensitizer is unnecessary for this case, and setting time can be reduced remarkably. The measure for the degree of crosslinking is defined by a degree where the irradiated film becomes insoluble in tetra hydrofuran.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a gas separation membrane for separating and concentrating 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 liquid-liquid separation or liquid-membrane separation for desalination of seawater, treatment of factory waste liquid, concentration of food (liquid substances), etc., and gas-membrane separation, that is, two types of separation. The separation and concentration of specific gases from the above-mentioned mixed gases has not yet been fully put into practical use, and is currently at the research stage.

The reason why it is difficult to put conventional gas separation membranes into practical use is mainly because the membrane material has low selective permselectivity, that is, there is no membrane that selectively allows certain gases to pass through while virtually no other gases pass through. In order to obtain high-purity gas, it is necessary to adopt a multi-stage method in which membrane separation is repeated several times, which makes the equipment too thick and the permeation flow rate is small, making it impossible to produce a large amount of gas. Can be mentioned.

However, there are many fields in which high-purity gas is not necessarily required as an end use. For example, in the case of oxygen, it can be used for blast furnace ventilation, combustion assistance, sludge treatment, and medical exhalation.

These objectives can be achieved if the oxygen concentration in the atmosphere is increased to some extent, so-called oxygen-enriched air.

Research and development is particularly active on so-called oxygen-enriching membranes that concentrate and separate oxygen, including organosiloxane-polycarbonate copolymers (see Japanese Patent Laid-Open No. 64-40868) manufactured by General Electric Company in the United States. , various polymeric materials have been synthesized. The present inventors also developed a copolymer mainly composed of silicone (Japanese Unexamined Patent Publication No.
11245γ) was synthesized. The methods for forming these membrane materials are mainly a method of overlapping separately formed thin films on a porous support, and a method of forming an anisotropic film in which a skin layer and a porous support coexist at the same time. There are methods such as forming a thin film by directly polymerizing monomers on a porous membrane by various methods, or forming a thin film by coating a polymer solution and then evaporating the solvent.

Among the above film forming methods, one of the most representative is the water surface spreading method [Langmuir-Prodgett film forming method (abbreviated as LB method)]. In this method, a polymer solution is dropped onto the water surface and allowed to spread, and as a result, the solvent used spontaneously evaporates, leaving only the polymer on the water surface. Film formation is then completed by attaching the obtained polymer thin film onto a porous support.

In the case of this method, the conditions for the polymer to be satisfied include the presence of one or more kinds of solvents that can dissolve the polymer, and the need to maintain a certain level of strength on the support after film formation. However, in order to obtain a certain degree of strength, it is necessary to significantly increase the molecular weight of the polymer used (crosslinking), but if the polymerization progresses too much, solubility decreases and it becomes difficult to select a solvent. Moreover, it is not preferable from the viewpoint of thinning the film. In other words, if polymerization is performed to improve film strength, problems arise such as the solubility of the polymer or the difficulty of forming a thin film. On the other hand, in the case of low-molecular polymers that have excellent solubility and can be made into thin films, the film strength is poor and the polymer itself hangs into the pores of the porous support, creating pinholes, making it difficult to separate the polymer. In order to obtain performance, it is necessary to increase the film thickness considerably,
In extreme cases, the polymer may pass through the porous support, making it impossible to obtain separation performance. In addition, the polymer film formed by the water surface spreading method is completely the same in physical properties as the polymer before water surface spreading, and the film strength, heat resistance, and solvent resistance have not changed, and it is naturally easy to use the solvent used. Needless to say, it is molten and has poor weather resistance. The above can be said not only to the water surface development method but also to other methods.

First, with the intention of improving membrane strength, weather resistance, and performance in life tests, a transparent membrane material having a photosensitive group was attached to a porous support, and then irradiated with ultraviolet rays, electron beams, etc. We have previously filed a patent application for polymerization (crosslinking), but in this case, there is no problem with relatively high-molecular permeable membrane materials, but in the case of low-molecular weight materials, they tend to sag into the porous support, making it impossible to create ultra-thin membranes. As a result, it was necessary to increase the film thickness. In particular, the present invention is the result of repeated studies on a relatively low-molecular permeable membrane material that can be made into an ultra-thin film.

Problems to be Solved by the Invention As mentioned earlier, in the conventional film forming method using the water surface spreading method, in the case of low-molecular polymers that have excellent solubility and can be formed into ultra-thin films on the water surface, the polymer itself Due to lack of strength,
Separation membranes cannot exhibit sufficient performance on porous supports, and even if separation membrane performance is achieved, the membrane strength is weak, heat resistance and solvent resistance are poor, making handling difficult and environmentally friendly. It has the disadvantage that it is sensitive to changes in the film and shows severe film deterioration even in life tests.

In view of the above-mentioned drawbacks, the present invention forms a thin film of a transparent film material having a reactive group on the water surface, and in this state is irradiated with light energy or electron energy to form a polymerized (crosslinked) film. By significantly improving strength, maintaining separation membrane performance as an ultra-thin membrane on a porous support, and improving heat resistance and solvent resistance, we have created a separation membrane that is easy to handle and has excellent durability. A manufacturing method is provided.

Means for Solving the Problems In order to achieve this objective, the method for producing a separation membrane of the present invention involves forming a thin film of a permeable membrane material having reactive groups on the liquid surface, particularly on the water surface, and in this state. It consists of forming a polymerized (crosslinked) film by irradiating light energy or electron energy.

Basically, the reactive group is preferably one that has excellent photosensitivity, such as a vinyl group, an allyl group, a cinnamoyl group, an α-cyanocinnamoyl group, a cinnamylideneacetyl group, an α-cyanocinnamylideneacetyl group, and a benzyl group. Acetophenone (
chalcone group), phenyl azide group, α-7 enylmaleimide group, furyl acroyl group, etc. Among them, ethylene-based ones such as vinyl group and allyl group are particularly suitable. As the base material of the membrane material, 4-
Methylpentene-1, polystyrene, polyvinyl alcohol, phenoxy resin (condensation resin of epoxy resin and bisphenol compound), polyether having a hydroxyl group, polyester having a hydroxyl group, polyamide having a hydroxyl group, polyallyl alcohol, styrene-maleic acid,
Examples include silicone lid composites typified by polysimethylsiloxane, but a copolymer may be obtained by using one or more of these as a mixture.

Among these, copolymerization with silicone polymers is particularly effective in bringing out the characteristics of both transparency and separation.Next, when using ultraviolet rays as light energy, a sensitizer such as the one described below is added to the reactive group. By adding it to a permeable membrane material having the following properties, the curing time can be significantly shortened.

Peroxides such as benzoyl peroxide, azo compounds such as azobisin butyronitrile, carbonyl compounds such as diacetyl and dibenzyl, sulfur compounds such as diphenyl mono- and disulfide, dibenzoyl mono- and disphite, and halogen compounds such as carbon tetrachloride. , metal salts such as ferric chloride, ether compounds such as penzoin isobutylene ether, etc. These sensitizers are usually used in an amount of 0.1 to 30% by weight, and practically 0.5 to 6% by weight based on the membrane material.

When used, it is important to select the sensitizer that is most compatible with the membrane material or the solvent used.

In addition, there are no particular limitations on the irradiation light source, and the purpose can be achieved by using those used in general chemical reactions as they are; however, especially in the case of ultraviolet irradiation, the intensity varies depending on the light source, so it is difficult to polymerize the film. The degree is determined by the extent to which the irradiated film becomes insoluble in tetrahydrofuran.

Furthermore, when an electron beam device is used for electron energy irradiation, compared to an ultraviolet lamp or the like, a sensitizer is not required and the curing time can be significantly shortened, but the disadvantage is that the equipment is quite large.

Function Using the above-described configuration, first, a stock solution or a solution of a permeable membrane material having a reactive group is dropped onto the water surface, and a thin film of the permeable membrane material is spread on the water surface.

In this state, the membrane material is simply a chain polymer or oligomer, so for example, tetrahydrofuran,
Easily soluble in solvents such as dimethylformamide. Furthermore, when a low-molecular membrane material is used, almost no membrane strength is obtained, and the membrane simply floats on the water surface. Next, when the membrane material is spread out on the water surface to form a thin film and irradiated with ultraviolet rays or electron beams, polymerization (crosslinking) proceeds due to the reactive groups in the membrane material, and the basic structure until then is chain-like. What used to be a structure changes into a mesh structure. Along with this, the strength of the membrane is greatly improved, and even when it is deposited on a porous support, it does not sag and has enough strength to exhibit sufficient separation membrane performance. Therefore, it becomes insolubilized in solvents such as tetrahydrofuran and dimethylformamide, which were previously soluble, and its solvent resistance is improved. At the same time, heat resistance is also improved, making it possible to produce a separation membrane that has excellent weather resistance and is easy to handle.

In addition, in the case of ultraviolet irradiation, a sensitizer is often used as mentioned above, but in this case, the sensitizer is cleaved by the ultraviolet rays, and a reaction on the membrane material side begins accordingly. Eventually, it will exhibit a sufficient network structure. However, depending on the type of membrane material, the proportion of reactive groups included, the type and amount of sensitizer added, etc., some membranes may swell significantly and exhibit a gel-like appearance, although they become insolubilized. However, even in such a case, the membrane strength is sufficient to exhibit separation performance, and most membranes are sufficiently insolubilized in solvents such as methanol and acetate, and do not show any swelling.

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

(Example 1) Gum-like 5H-410 (manufactured by Toshi Silicone Co., Ltd.), which is a vinyl-based material at both ends of polydimethyl 7-loxane, is dissolved in benzene to form a solution having a weight of about 20%. 5 for this
Add 1 part by weight of benzoin isopropyl ether (hereinafter abbreviated as BIPE) to the weight of H-410, and stir thoroughly to make the mixture uniform. Develop this on the water surface, evaporate the solvent sufficiently, and place 5H-41 on the water surface.
0 to form a continuous ultra-thin film. Next, as a light source, a mercury lamp [mercury lamp 5HLS for physical and chemical use manufactured by Toshiba Corporation] was used.
-1002A type (Lamp S! (L -100OA.

1 ooV, soC/S, 2A) ] i, with an irradiation intensity of 6.6 mW/(yj
Irradiation was carried out for about 20 seconds. Next, the obtained polymer film is attached to DURAGUARD 2400 [porous support made of polypropylene, manufactured by Polyplastics Co., Ltd.]. When we investigated the characteristics using a bubble flowmeter (a device that pressurizes at -atmosphere, passes the same volume of oxygen and nitrogen through the membrane, and evaluates the characteristics based on the number of seconds), we found the results shown in Figure 1. was gotten. As a result, it can be seen that the number of seconds of oxygen permeation per 10CC of oxygen is about 8.5 seconds, and that the separation coefficient α clears 2.0. Note that when the obtained membrane was immersed in tetrahydrofuran and benzene for 24 hours and its properties were examined again, it was found that there was no change and no pinholes were generated.

(Comparative Example 1) 5H-410, which is the same material as Example 1, was used in the same <2
A 0% by weight benzene solution was used to form a thin film on the water surface. When this was attached to DURAGUARD 2400 and its characteristics were examined in the same manner as in Example 1, the results shown in FIG. 2 were obtained. As a result, in order to clear the separation coefficient α of 2.0, the number of seconds per 10 cc of oxygen required to pass through is 15.5 SeC or more, and when compared with Example 1,
It can be said that the properties are improved by about twice when the polymer film is formed on the water surface. In addition, if a polymer film is not formed, the 5H-410 on the porous support may not be able to withstand the pressure during pressurization of one atmosphere using a bubble flowmeter, and may sag and gradually become pinholes. A lot, especially 10cc of oxygen
It was noticeable when the permeation time was within 15 seconds.

(Example 2) Silicon diol urethane acrylate (hereinafter abbreviated as SDUA) having a viscosity of about 100 cs and a molecular weight of 6000.

) was dissolved in benzene to 60% by weight, then 5DU
Add 2 parts by weight of Darocure 963 (manufactured by Merck Japan Co., Ltd.) to the weight of A, and stir thoroughly to make the mixture uniform. This is spread on the water surface and the solvent is sufficiently evaporated to form an ultra-thin film of 5DUA on the water surface. Next, we used a mercury lamp as a light source [Mercury lamp 5 for physical and chemical use manufactured by Toshiba Corporation.
HLS-1002A type (lamp 5HL-1oooA,
1ooV.

50C/S, 2A)], irradiation was performed for about 6 seconds at an irradiation intensity of 6.6 rnw/i with a thin film formed on the water surface. Next, the obtained polymer film was attached to DURAGUARD 2400, and its characteristics were examined using a bubble flow meter as in Example 1, and the results shown in FIG. 3 were obtained.

From this, the number of seconds per 10cc of oxygen is approximately 6.05
It can be seen that the separation coefficient of 2° or more is cleared in the region of ee or more. The obtained membrane 'ff was immersed in tetrahydrofuran and benzene for 24 hours and then measured again, and it was found that the properties remained almost unchanged and no pinholes were formed.

(Comparative Example 2) The material adjusted in Example 2 was spread on the water surface in the same manner and was adhered to Duraguard in that state without irradiating with ultraviolet rays.

Next, when we investigated the characteristics using a bubble flow meter, we found that it was a pinhole, and there was no change even if the film thickness was increased considerably.
Separation performance could not be obtained. After the measurement, we examined the condition of the membrane and found that the membrane material that had adhered to the primary side of DuraGuard was found on the secondary side, and it is thought that the membrane material had passed through the pores of DuraGuard due to its poor strength. .

(Example 3) 5DUA1oy used in Example 2 and viscosity of about 20C3
0.4y of jetoxyacetophenone was added as a sensitizer to the 4-methylpentene-1 monomer 102, and the mixture was thoroughly stirred and mixed. Thereafter, it was dropped onto the water surface to form a thin film. Next, with the mercury lamp used in Examples 1 and 2,
Ultraviolet irradiation was performed for 0 seconds to form a polymerized (crosslinked) film on the water surface. Next, it was attached to DURAGUARD 2400, and its characteristics were determined using a bubble flow meter in the same manner as in the previous example. The results are shown in Figure 4.

According to Figure 4, the number of seconds per 10 cc of oxygen is approximately 8.
．． Separation coefficient α clears 2.0 at around 6SeC, 1
At 6 ki or higher, it shows a constant value of about 2.36, and it can be said that the pinhole property is extremely low. The obtained membrane was immersed in tetrahydrofuran and benzene for 24 hours, and then measured using a bubble flow meter, and the results were the same as those shown in FIG. 4.

In addition, if UV rays are not irradiated after development on the water surface, the film formation ability is poor, and pinholes will occur due to hanging when adhering to DuraGuard, and as in Comparative Example 2, separation will occur even if the film thickness is increased. No performance was obtained.

(Example 4) 5H-410, 10f used in the previous example and 5DU
A, 10y was dissolved in sop benzene. After dropping this onto the water surface and spreading it to sufficiently evaporate the solvent, use an area beam electron beam irradiation device [Curetron for research, manufactured by Nissin High Voltage Co., Ltd.] to create a thin film on the water surface. Electron beam irradiation was performed on the After irradiation for 0.1 seconds at an irradiation intensity of 2 megarads, the formed polymerized (crosslinked) film was deposited on DURAGUARD 24oO, and its characteristics were determined using a bubble flow meter. The results are shown in Figure 5. From this oxygen 10C
When the transmission seconds per C is 7.05eC or more, the separation coefficient α2
Cleared 2.0 or higher. For comparison, we investigated the characteristics of the sample without electron beam irradiation, but even if the film thickness on the water surface was increased, the film did not have sufficient strength, resulting in pinholes and it was not possible to determine the separation performance.

As described above, according to this example, a thin film of a transparent film material having reactive groups is formed on the water surface, and a polymerized (crosslinked) film is formed by irradiating light energy or electronic energy in this state. This greatly improves membrane strength and maintains separation performance as an ultra-thin membrane on a porous support.In addition, improved heat resistance and solvent resistance result in excellent separation properties, easy handling, and durability. It becomes possible to manufacture excellent separation membranes.

Effects of the Invention As described above, the present invention forms a thin film of a transparent film material having reactive groups on the water surface, and in this state, irradiates with light energy or electron energy to form a polymerized (crosslinked) film. This greatly improves the membrane strength of the ultra-thin membrane developed on the water surface, brings out the separation performance as an ultra-thin membrane on a porous support, and also improves heat resistance and solvent resistance as the membrane strength increases. By improving this, it is possible to manufacture a separation membrane that has excellent separation characteristics, is easy to handle, and has excellent durability, and its practical effects are significant.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the number of seconds per 10 cc of oxygen permeated and the separation coefficient α determined by the bubble flowmeter in the first embodiment of the present invention, and FIG. Oxygen 10C determined by bubble flow meter in comparative example
Diagram showing the relationship between the number of seconds of transmission per C and the separation coefficient a, 3rd
4 and 6 are diagrams showing the relationship between the number of seconds per 10 cc of oxygen and the separation coefficient α for Example 2, Example 3, and Example 4 of the present invention, respectively. . Name of agent Patent attorney Toshi Nakao (a) 1st person
Figure 9 t foccXs ri/) *a##,
, L (Jjec/Boocc) Figure 2 #t fOcc'zI)i! 4 ke 41 (iec
/ 10Co) Figure 3 #t fDcc%+) AMA#P1 (a/fOo
o) Male 4 Figure it ヂOcc per ntt, age 9-k (wec/
yoct-) Fig. 5

Claims (3)

[Claims] (1) Gas separation characterized by forming a thin film of a permeable membrane material having reactive groups on the liquid surface and irradiating this state with light energy or electronic energy to form a polymerized (crosslinked) film. Membrane manufacturing method. (2) The method for producing a gas separation membrane according to claim 1, wherein the liquid is water. (3) The reactive group is a vinyl group, an allyl group, a cinnamoyl group,
One of α-cyanocinnamoyl group, cinnamylideneacetyl group, α-cyanocinnamylideneacetyl group, benzalacetophenone (chalcone) group, phenylazide group, α-phenylmaleimide group, furyl acroyl group, or 2. The method for producing a gas separation membrane according to claim 1, wherein the gas separation membrane is a mixture of more than the above.