JPS6227025A - Composite membrane for separating gas - Google Patents

Abstract

PURPOSE:To increase permeation flow rate of a composite membrane and to stabilize the same by subjecting a porous polysulfone backing membrane to a hot water treatment then forming the membrane into the composite membrane and subjecting the membrane to a heat treatment in the gaseous phase under the reduced pressure. CONSTITUTION:The porous polysulfone membrane which has <=0.5mu surface pore size and >=10<-5>g/cm<2> sec atm as the permeation rate of water measured at 25 deg.C is used as the backing membrane. Such membrane is immersed in the hot water kept at 50-130 deg.C and is thereby heat-treated. The treatment is executed for >=0.2hr. A sepn. function layer consisting of an org. high-polymer compd. is formed on such backing membrane. The thickness of said layer is made <=0.5mu. The resulted composite membrane is treated for >=0.2hr at 60-200 deg.C in the gaseous phase under the treated for >=0.2hr at 60-200 deg.C in the gaseous phase under the reduced pressure of 0.1-400Torr. The flow rate and selectivity are stabilized and the flow rate in particular is increased by about 10% by such treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a membrane used for membrane separation of gas mixtures, and particularly to a membrane having excellent gas permeability and improved stability.

<Prior Art> In recent years, membrane separation technology has been used in many fields due to its energy saving properties. Various methods have been developed for producing membranes used in such separations, among which the membrane is separated into a part that exhibits the separation function (separation function FF2>) and a part that maintains mechanical strength (porous support). So-called composite membranes, in which each membrane is constructed from separate materials that are optimal for each, are attracting attention as they dramatically increase the degree of freedom in membrane installation.

As mentioned above, in a composite membrane, a separation functional layer is provided on a porous membrane, but it does not matter whether the functional layer is formed directly on the porous membrane or whether separately prepared layers are laminated. However, the functional layer usually contains a separation membrane forming substance.
It is formed as a 7fJ layer (thin film) from a solution dissolved in a solvent.

A porous membrane is used to support such a thin layer, but porous membranes have some degree of resistance to gas permeation, and especially composite membranes made by wet membrane formation have a reduced flow rate during use. Changes over time such as J3. It has problems such as being easily stiff.

Although polysulfone porous membranes are often used as porous membrane supports, two improvements are desired in such composite membranes: increased flow rate and stabilization.

<Structure of the Invention> The present inventors have developed a polysulfone-based porous membrane and a portion thereon!
When considering stabilizing a composite membrane consisting of an i-portal layer by applying a specific treatment to the composite membrane, it is common to use a specific treatment for the composite membrane. 2! lE'! ! However, if the polysulfone porous membrane that makes up the composite membrane is subjected to a specific treatment beforehand, the permeation flow rate of the membrane will decrease even if the composite membrane is subjected to the same specific treatment. The inventors have arrived at the present invention by discovering that the flow rate does not increase, and that the stability of the flow rate is further improved. In other words, the present invention covers the polysulfone porous membrane and the thickness of 0.5μ or less that exists on it! In a composite membrane consisting of an llIn-layer, the polysulfone porous membrane is formed by wet membrane forming, and has a surface pore diameter of 0.5μ or less and a water permeation rate of 1×10 → (g/Cm-5ec-atm) or more. , and 50
~130°C hot water for 0.2 hours or more, and after forming the composite membrane, the composite membrane has a temperature of 0.1~4
The present invention is a composite membrane for gas separation characterized in that it is produced by processing at a temperature of 60 to 200° C. for 0.2 hours or more under gas phase conditions at a reduced pressure of 0.00 Torr.

The present invention will be explained in detail below.

The polysulfone resin, which is the material of the polysulfone porous membrane used in the present invention, is composed of a polymer having a 5O2- bonding group in its molecule. The following formula (1) has excellent properties:
Alternatively, a polymer having 50 mol% or more of the repeating unit represented by (2) may be mentioned. These polymers can be used alone or in a mixture of two or more.

Polysulfone-based porous membranes are formed by a known method in which a solution of polysulfone-based resin dissolved in a solvent is coagulated in a coagulating solution.

Such solvents include, for example, dimethylacetamide,
Dimethylformamide, N-methylpyrrolidone, tetramethylurea, etc. are used.

Further, commonly used additives such as pore opening agents and stabilizers can be added to the polysulfone solution.

In the present invention, a resin solution containing the above-described polysulfone resin, its solvent, and optionally additives is used to form a film shape such as flat IQ, tubular, or hollow fiber by flow rate or spinning. When forming into a flat film or a tubular film, other supports may be used as necessary. Also the flow rate.

After shaping such as spinning, the solvent in the resin solution may be partially dried.

In the present invention, film formation is performed by immersing the film thus formed into a coagulating liquid.

The coagulating liquid used in forming the microporous membrane of the present invention is water, at least one organic liquid that is freely miscible with water, or a mixture thereof.

Examples of organic liquids that are freely miscible with water include methanol, ethanol, ethylene glycol, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and the like.

The coagulation bath of the present invention is particularly preferably a liquid consisting essentially of water.

A film formed from the resin solution is immersed in these coagulation solutions,
The porous membrane of the present invention can be obtained by substantially coagulating and, if necessary, washing with water to remove residual solvent and the like.

The porous membrane of the present invention may be formed in the form of a flat membrane, a tubular membrane, a hollow fiber membrane, etc. depending on the purpose of use.

In the case of flat membranes, tubular membranes, etc., a base material such as nonwoven fabric may be used as a reinforcing material.

When the polysulfone porous membrane thus obtained is used as a support for a separation functional thin membrane layer, the surface pore diameter of the porous membrane is 0.
It is 5μ or less, preferably 0.2μ or less, more preferably 0.1μ or less. If it is larger than 0.5μ, the membrane layer of the separation functional thin film cannot be made thinner.

It is preferable that the diversion is as large as possible, and the water permeation rate measured at 25°C is 1 x 10"5 (g/Cd-SQ
C-atm) or more, preferably 1×10→<'j/c
ti-sec-ati) or more.

In the present invention, the wet-formed polysulfone porous membrane as described above is immersed in hot water and heat-treated. The temperature of the hot water is 50-130°C, preferably 60-100°C.

When the temperature is 100°C or higher, it is carried out under pressure.

At temperatures below 50°C, there is almost no effect of stabilizing the porous membrane. The hot water treatment time is 0.2 hours or more, preferably 0.5 hours.
It is more than 1 hour, more preferably 1 hour or more. If the heating time is less than 0.2 hours, the heat treatment will not be effective. Although the processing time is not particularly limited, it is usually within 24 hours. Even if you take it for more than 24 hours, there is no difference in effectiveness than if you take it for less than 24 hours.

In the hot water immersion method, the polysulfone porous membrane that has been formed can be washed with water and then immersed in warm water again.

In this case, if it is in the form of a flat membrane, the effect will be the same whether it is immersed in a rolled form or in a sheet form. In the case of hollow fibers or tubular fibers, they can be immersed continuously or in bundles. Alternatively, a continuous treatment method can be used in which the membrane is discharged from the coagulation solution after film formation and then passed through a hot water treatment tank.

Note that when a wet-formed polysulfone-based porous membrane is once dried and then heat-treated, polysulfone is hydrophobic and once dried, water will not soak sufficiently into the pores of the porous membrane.
It is preferable to treat the polysulfone-based porous membrane in a wet state without drying it, since the effectiveness of the treatment will be reduced.

The separation functional layer of the composite membrane used in the present invention is a thin film made of an organic polymer compound. Jm is formed from an organic solvent solution containing a polymer compound by a well-known method such as a water surface spreading method, a casting method, or a coating method. As the membrane material which is an organic polymer compound, any known material having excellent selectivity to a specific gas can be used as appropriate. When the specific gas is, for example, oxygen, an addition polymer or main chain of at least one unsaturated compound selected from hydrocarbon compounds and/or silane compounds having a polymerizable double bond or triple bond between carbon and carbon. Polymers having siloxane units in their side chains, aromatic polyethers, and the like are preferably used.

Examples of such polymers include polymethylpentene, polymethylhexene, polybutadiene, polyvinyltrimethylsilane, polytrimethylsilylacetylene, poly(
methylhexene-allyltrimethylsilane) copolymer,
Poly-t-butylacetylene, poly(allyltrimethylsilane-allyl-t-butyldimethylsilane), polydimethylsiloxane, polysiloxane-polycarbonate copolymer, polysiloxane-polybutadiene copolymer,
Examples include poly[methycryloxybrobyl tris(trimethylsiloxy)silane], poly 2,6-dimethylphenylene ether, and the like.

Any solvent may be used as long as it dissolves the membrane material, such as benzene, toluene, xylene, cyclohexane, cyclohexene,
Hydrocarbon solvents such as hexene, octane, hexadecene, and octadecene, halogenated hydrocarbon solvents such as trichloroethylene, tetrachloroethylene, chloroform, and trichlorotrifluoroethylene, ether solvents such as tetrahydrofuran and dioxane, dimethylformamide, dimethylacetamide, N- These include aprotic solvents such as methylpyrrolidone, alcoholic solvents such as ethanol, 1so-propyl alcohol, butanol, etc., and these solvents may be used alone or in a mixture of two or more thereof. In addition to the solvent, a surfactant or a developing aid may be added to stabilize the film formation. In order to form a thin film layer, a solution of a specific polymer compound dissolved in such a solvent is prepared, and a thin film layer is formed by a conventional and well-known method. That is, for example, this organic polymer compound solution is spread on a water surface or cast on a flat solid surface to make a thin solution, then the solvent is removed to form a thin film, and then it is laminated on a porous membrane. Alternatively, there is a method in which a porous membrane is coated with an organic polymer compound solution and the solvent is removed to form a thin film.

In either case, the organic polymer compound is dissolved in a solvent, the solution is used to form a film, and then the solvent is removed to form a thin film.

Note that the separation functional layer may be a single layer (single layer) or may be a plurality of layers consisting of at least two layers. In particular, a membrane with a separation function layer made by laminating at least two thin films is preferably used because defective parts of the thin films are filled by overlapping, improving the separation characteristics, and the strength of the separation layer is also improved. . Of course, the thin films to be laminated may be made of the same material or may be made of different materials.

The thickness of the microlayer of the present invention is preferably as thin as possible from the viewpoint of gas permeability as long as no defects occur in the film, and the thickness is 0.5μ or less, preferably 0.3μ or less, and more preferably It is 0.15μ or less.

The composite membrane thus obtained is treated at a temperature of 60 to 200° C. for 0.2 hours or more under gas phase conditions at a reduced pressure of 0.1 to 400 TOrr.

The flow rate of the composite membrane of the present invention is increased by such heat treatment, and the flow rate and selectivity of the composite membrane are stabilized even during use or storage, especially the flow rate is stabilized. The flow rate increases by a maximum of 10% and an average of 5% compared to before heat treatment.

What is very interesting is that the increase in flow rate due to heat treatment of the composite membrane occurs only when a porous polysulfone membrane that has been previously treated with hot water is used, and when a similar composite membrane is used with a porous polysulfone membrane that is not treated with hot water. When it is made and heat treated, the flow rate decreases compared to before heat treatment.

There are also differences in the stability of flow rate. When a composite membrane is made using a polysulfone-based porous membrane that is not treated with hot water and then heat treated, the flow rate is significantly more stable and the heat treatment effect is obtained compared to one that is not heat-treated, but the heat treatment effect of the composite membrane is even better when a heat-treated polysulfone-based porous membrane is used. This further improves the stability of the flow rate.

One of the effects of heat treatment on composite films is that a trace amount of the FR solvent used in the stage of forming the molecular II functional layer remains in the film even during the removal process after film formation, and this is removed by heat treatment. In addition, one of the effects of hot water treatment of polysulfone-based porous membranes is to remove minute amounts of membrane-forming solvent remaining in wet-formed polysulfone-based porous membranes, and the effect is said to be great. I think about it, but that alone doesn't explain everything.

One way of thinking is that hot water treatment of a polysulfone porous membrane brings about structural changes along with desolvation, and then heat treatment in a dry state creates the optimal structure for the support, for example, the pores on the surface expand a little and the degree of aperture increases. etc. are expected. In other words, it is thought that the hydrothermal treatment/heat treatment not only removed the film-forming solvent but also brought about a change in the structure of polysulfone, leading to stability of the film. It is thought that the structure may be stabilized by heat treatment of the mochiro/υ separated Akebono layer.

In other words, the present invention exhibits its effects only when the porous polysulfone membrane used as a support is treated with hot water under specific conditions, and the composite membrane is further heat-treated under specific conditions after being made into a composite membrane. This is what I discovered.

The treatment of the composite membrane of the present invention is carried out under gas phase conditions at a reduced pressure of 0.1 to 400 Torr. The reduced-pressure gas phase conditions here refer to cases in which the composite membrane of the present invention is placed in such a reduced-pressure container and the entire membrane is treated, and cases in which the composite membrane is assembled into a module shape that can be sucked under reduced pressure from one side of the membrane, and the membrane is treated in a vacuum container. 0.1 to one side of
Atmospheric pressure is applied to the side where the membrane is used (atmospheric pressure on the side where the membrane is used)
There are two methods: one in which air or inert gas is passed through a composite membrane; Among these, the latter method is preferably used because the gas passes through the composite membrane and the treatment effect is large. The degree of reduced pressure is 0.1 to 400 Torr
Preferably 10-300 TOrr, preferably 20-25
It is 0 TOrr. If the temperature is 400T orr or more, the effect of heat treatment is small, and even if the temperature is set to 0.1T orr or less, the effect is no different from 0.1T orr or less.

The temperature condition for this treatment is 60 to 200°C, but when assembled as a composite membrane member or module, the temperature is limited by the heat resistance of the member including the module member. That is, if the treatment is performed at a temperature higher than the allowable temperature limit of the member, the membrane or module will be deformed and damaged, resulting in inconvenience. The temperature is preferably lower than the heat resistant temperature of the member, but as high as possible. Generally preferably 65
The temperature is preferably 70 to 150°C, more preferably 70 to 150°C.

The heat treatment time is 0.2 hours or more, preferably 0.5 hours or more, and more preferably 1 hour or more. If the time is less than 0.2 hours, the heat treatment will have no effect. The length of treatment time is not particularly limited, but is usually within 24 hours.

Even if you take it for more than 24 hours, there is no difference in effectiveness than if you take it for less than 24 hours.

The composite membrane for gas separation of the present invention can be stacked if it is in the form of a flat membrane, or bundled into multiple pieces if it is in the form of a tube or hollow fiber, and then assembled into a module and further as an oxygen enrichment device to extract oxygen-enriched air from the atmosphere. Since it can be used in manufacturing, it can help improve the combustion efficiency of engines and heating equipment, it can also be useful in caring for premature babies and treating people with respiratory disorders, and it can also be used as artificial lungs and artificial gills.

Furthermore, the composite membrane for gas separation of the present invention is suitable not only for producing oxygen-enriched air from the atmosphere, but also for producing gas mixtures mainly composed of carbon dioxide and air (e.g., combustion waste gas).
separation of helium or argon from gas mixtures consisting mainly of helium or argon and nitrogen gas (e.g. liquefied helium or argon vaporized and mixed with air); helium enrichment from natural gas; Alternatively, it can also be suitably used to separate hydrogen from a gas mixture (for example, water gas or process gas) containing hydrogen and carbon monoxide or methane. The present invention will be further explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 Densely woven polyester nonwoven fabric (fabric weight ffl 180
Polysulfone (account chemistry ud
elP3500) A solution consisting of 15 wt% of N-methylpyrrolidone and 85 wt% of N-methylpyrrolidone was cast into a layer with a thickness of about 0.35 rrs, and the polysulfone layer was immediately gelled in a water bath at 20°C to form a nonwoven reinforced polysulfone porous membrane. Obtained.

Subsequently, the porous membrane was washed in running water for 2 days to remove residual solvent. The polysulfone porous membrane thus obtained was
The sample was immersed in hot water at 00°C for 2 hours for hot water treatment.

As a characteristic of this porous membrane, when the amount of permeation of pure water at 25°C at a pressure of 1'J/l:i was measured, the water permeation rate was T 1.41 x 10-' 9 / ci
・See-ajm.

Further, the pore diameter of the membrane was determined by photographing the surface of the membrane with an electron microscope at a magnification of 100,000 times, and was found to be 0.01 to 0.02 .mu.m.

A thin film of poly-4-methylpentene was formed on this porous polysulfone membrane by spreading a cyclohexene solution of poly-4-methylpentene (3 wt% of cyclohexene hydroperoxide was added as a developing aid) on the water surface. A composite film was made by stacking several layers to a film thickness of approximately 0.12 μm.

This composite membrane was cut into a size of 25c1R x 50cIR, the aluminum plate, the net, and the composite membrane were stacked in this order, a nozzle opening was attached, and the four sides were solidified with epoxy resin to form a separation membrane element (module).

After drying the membrane, air was separated by suction at 160 Torr from the nozzle opening, and 217 CG/min of oxygen-enriched air with an oxygen concentration of 40.5% was obtained.

Next, this element was placed in a hot air oven at 80° C., and the pressure was reduced to 130 Torr from the nozzle opening for treatment for 3 hours. After treatment, air separation was performed under the same conditions as the rabbit, and the oxygen concentration was 40.6% and the amount of oxygen-enriched air was 228cc.
/minute.

Next, suck this element from the nozzle opening and apply 160T.
Although suction was carried out continuously for 500 hours in a clean air atmosphere at a reduced pressure of orr and a temperature of 23°C, the oxygen concentration did not change and the flow rate remained stable at 226 cc for 7 minutes (retention rate 99%). A composite membrane was prepared in the same manner as in Example 1 except that a non-treated polysulfone porous membrane was used. The air separation performance of this composite membrane before hydrothermal treatment is as follows:
．． 6%, enriched air signature 208cc, 7 minutes. The performance of this composite membrane after heat treatment is as follows:
Iti98cc decreased to 7 minutes. Further, in the same durability test as in Example 1, the flow rate retention rate after 5000 hours was 95%.

Example 2 Poly-2,6-dimethylphenyllene oxide 2.0I
A solution consisting of parts ffi ffi, 1.5 parts by weight of cyclohexenyl hydroperoxide, and 97 parts by weight of trichlorethylene was maintained at 50°C and injected with 6.0 parts by weight from the tip of an O, aSφ syringe needle. A thin film of poly-2,6-dimethylphenylene oxide was formed on the water surface by continuously supplying the needle tip onto the water surface maintained at 5° C. at a flow rate of Occ/min while in contact with the water surface. The formed thin film is 00 (ml1) from the needle tip.
At the second stage, the first layer was formed by pressing onto the polysulfone porous membrane used in Example 1 and pulling it up onto the polysulfone porous membrane. Film thickness is 0.015
It was calculated as 81 μm.

Next, the polydimethylsiloxane-polybutadiene copolymer had a tensile modulus of 318 kg/ci, P O2
1,5x 10' CG-cm/cm-3eC-ct
nHg, α: 2.0) A solution consisting of 7 parts by weight, 5 parts by weight of cyclohexenyl hydroperoxide and 88 parts by weight of benzene was similarly continuously supplied onto the water surface, and polydimethylsiloxane-polybutadiene was deposited on the water surface. A thin film of the copolymer was formed. Two thin films of this copolymer were laminated on top of the first layer to form an intermediate layer.

The calculated thickness of this intermediate layer was 0.10 μm.

Furthermore, a layer of poly-2,6-dimethylphenylene oxide (thickness 0.015 μTrL) is placed on top of this, and a separation functional layer is formed by laminating polyphenylene oxide, polydimethylraloxane, polybutadiene, and polyphenylene oxide. We created a composite membrane with

When air separation was carried out using this composite in the same manner as in Example 1 (reduced pressure: 160 Torr), oxygen-enriched air with an oxygen concentration of 40.2% and a flow rate of 412 cc for 7 minutes was obtained. This was suctioned from the nozzle opening, the pressure was reduced to 180 Torr, and heat treatment was performed in an atmosphere at a temperature of 80° C. for 3 hours.

Air separation after heat treatment (reduced pressure 160T)
orr ) Oxygen-enriched air with a flow rate of 428 CC7 minutes was obtained with an oxygen concentration of 40.1%.

Example 3 A solution consisting of 3 fflflfft parts of poly-4-methylpentene-1 (manufactured by San4 Petrochemical Company Ltd., grade DX 845) and 3 parts of cyclohexenyl hydroperoxylide was maintained at 30°C, and 0. 60 from the tip of an 8Mφ syringe needle
C and C were continuously supplied onto the water surface maintained at 5° C. with the needle tip in contact with the water surface at a flow rate of 7 minutes. The polymer solution formed a thin film on the water surface. The formed thin film is removed from the needle tip for 60 minutes.
At a distance of cm, the polysulfone porous membrane used in Example 1 was pulled onto the polysulfone porous membrane by continuously pressing it from above. Next, polydimethylsiloxane-polycarbonate copolymer (siloxane content: 6
0 mol%.

P○22 X 10-” cc-ctn/cri-se
a-cmHo, α: 2.2. Tensile modulus 26O
A solution consisting of 8 parts by weight of cyclohexenyl hydroperoxide, 5 parts by weight of cyclohexenyl hydroperoxide, and 8 parts of benzene fluoride was spread on the water surface to form a thin film of the copolymer. Penten's? This layer was laminated on top of the J layer, and an intermediate layer having a thickness of 0.108 μm was formed again.

Next, a thin film of poly-4-methylpentene-1 having a thickness of 0.01 γμ, which had been formed in the same manner as before, was laminated on the outside of this intermediate layer to obtain a composite membrane having a laminated separation functional layer.

When we conducted an air separation test using this composite membrane by sending air to the ventral side and reducing the pressure to 160 Torr on the opposite side of the porous support, we found that oxygen-enriched air with an oxygen concentration of 41.3% was -Amount of rIL (qare 7CQ this is 80
At 3 o'clock while suctioning at a reduced pressure of 130T orr from the nozzle opening in a temperature atmosphere of ℃! ! ] Processed.

After 98 hours, air separation was performed in the same manner, and oxygen-enriched air with an oxygen concentration of 41.3% was obtained at a maximum rate of 4.5 cycles/minute. Further, when this treated membrane was subjected to a continuous suction test under the same conditions as in Example 1, the flow rate retention rate after 500 hours was 99% or more, and the oxygen concentration remained stable.

Example 4 Densely woven polyester nonwoven fabric (basis weight 1357/T
polysulfone (Sumitomo Chemical, PE5300P)
) A nonwoven reinforced polysulfone porous membrane was obtained by casting a solution consisting of 15 wt% and 85 wt% of N-methylpyrrolidone into a layer with a thickness of approximately 0.3 m, and immediately gelling the polysulfone layer in a water bath at 15°C. Obtained.

This porous membrane was washed in running water for 2 days to remove residual solvent, and then heat-treated in 90° C. hot water for 10 hours. The water permeation rate of this porous membrane is 3. lX10-3<g/cr
i-sec-atm) and the surface pore diameter is 0.01μ
It was below.

On this polysulfone porous membrane, 0% of poly(allyl-butyldimethylsilane-allyltrimethylsilane) copolymer (allyl-℃-butyldimethylsilane 30 mol%) was applied.
．． 0.024μ thin film, then a 0.10μ thin film of polymethylsiloxane-borivinyltrimedylsilane copolymer (dimethylsiloxane content 70 mol%), and then a 0.10μ thin film of poly(allyl-℃-butyldimedylsilane-allyltrimethyl). Silane) copolymer thin films of 0.024 μm were laminated in this order to obtain a composite film.

In order to investigate the performance of this composite membrane, air separation was performed (reduced pressure 50 TOrr) 'Pli concentration 3 concentration 2
%.

The enriched air ffi was 1.5017 min.

This composite film was heated at 120℃ from the nozzle opening in a temperature atmosphere of 70℃.
The mixture was vacuumed to a vacuum of Torr and heat-treated for 5 hours. When air separation was performed under the same conditions as before, the oxygen temperature was 38.
．． 2%, enriched air l 1,53 fi/min.

Example 5 Polysulfone (Nizho Kagaku, udelP3500) 2
0wt%.

N~Methylpyrrolidone 57wt%, lithium chloride 3wt
A solution consisting of 20 wt% of xyethanol was discharged from an annular slit at 30°C using water as the core liquid, and immersed in water at 25°C to coagulate. A polysulfone hollow fiber porous membrane was obtained. Next, bundle this hollow porous membrane and make 100
It was immersed in hot water at ℃ for 4 hours for hot water treatment.

The water passing rate through this polysulfone hollow porous membrane is 4, OX
10'('j/cm-see-arm)
Met. The inner and outer surface pore diameters of the hollow fibers were both 0.01 to 0.02 μ. Moreover, this hollow fiber porous membrane had a dense structure on the inside and outside, and a hollow finger structure on the inside.

This hollow porous membrane was packed into a pipe made of polycarbonate 1~, and both ends were secured with adhesive to form a hollow fiber membrane module 19.

Next, while the hollow fiber porous membrane of this module is impregnated with water, a 4wt% cyclohexene solution of polymethylpentene (grade MX-002 manufactured by Mitsui Petrochemical ■) is poured inside the hollow fiber while the module is intact. . After pouring, train and air dry, and repeat the process of pouring the polymer solution three times.

The separation membrane thus obtained was dried and then subjected to a heat treatment for 5 hours under vacuum of 160 Torr from the outside suction port of the module in an atmosphere of 75°C. When air was separated under reduced pressure of 160T orr, the oxygen concentration was 38.8%.

The enriched air amount was 159 cc/rd·min. A durability test was conducted by continuously suctioning in the same atmosphere as in Example 1, and the flow rate retention rate after 5000 hours was 98%.
Above all, performance was stable.

Patent applicant: Teijin Ltd.
Patent attorney former 1) Jun 1 7.
/1(゛

Claims (2)

[Claims] (1) A polysulfone-based porous membrane and a 0.
In a composite membrane consisting of a separation functional layer with a thickness of 5μ or less,
The polysulfone-based porous membrane is formed by wet film forming, and has a surface pore diameter of 0.5μ or less and a water permeation rate of 1×10^-^.
4 (g/cm^2・sec・atm) or more, and 5
The composite membrane is treated in hot water at 0 to 130°C for 0.2 hours or more, and after forming the composite membrane,
1. A composite membrane for gas separation, characterized in that it is treated under gas phase conditions at a reduced pressure of 400 Torr at a temperature of 60 to 200°C for 0.2 hours or more. (2) The composite membrane for gas separation according to claim 1, wherein the separation functional layer is a membrane layer formed from an organic solvent solution containing an organic polymer compound.