JPH0378129B2 - - Google Patents

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 divided into a part that performs the separation function (separation functional layer) and a part that maintains mechanical strength (porous support). So-called composite membranes, which are composed of separate materials that are optimal for each, are attracting attention as they dramatically increase the degree of freedom in membrane design.

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 is usually formed as a thin layer (thin film) from a solution in which a separation membrane-forming substance is dissolved in an organic 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 high flow rate during use. It has problems such as easy changes over time such as deterioration.

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 investigated stabilizing a composite membrane consisting of a polysulfone porous membrane and a separation functional layer thereon by subjecting the composite membrane to a specific treatment. Normally, when a composite membrane is subjected to a specific treatment, the flow rate of the composite membrane decreases, but if the polysulfone porous membrane that makes up the composite membrane is subjected to a specific treatment in advance, then the composite membrane can be subjected to the same specific treatment. We have arrived at the present invention by discovering that the permeation flow rate through the membrane does not decrease, but increases, and that the stability of the flow rate is further improved. That is, the present invention provides a composite membrane consisting of a polysulfone-based porous membrane and a separation functional layer with a thickness of 0.5μ or less existing thereon, in which the polysulfone porous membrane is formed by wet film forming and has a surface pore size of 0.5μ or less. The water permeation rate is 1×10 ^-4 (g/cm ²・sec・atm) or more,
and treated in hot water at 50 to 130°C for 0.2 hours or more, and after forming the composite membrane, the pressure on one side of the composite membrane is lower than the other side, and the pressure on one side of the composite membrane is lower than that on the other side. 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 pressure of 0.1 to 400 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 -SO ₂ - bonding group in its molecule. The following formula (1) or (2) has excellent heat resistance. Examples include polymers having 50 mol% or more of repeating units represented by These polymers can be used alone or as 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 liquid.

Examples of such solvents include dimethylacetamide, dimethylformamide, N-methylpyrrolidone, and tetramethylurea.

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 membrane shape such as a flat membrane, tubular fiber, or hollow fiber by drooling or spinning. When forming into a flat film or a tubular film, other supports may be used as necessary. Further, after forming by drooling, spinning, etc., the solvent etc. in the resin solution may be partially dried.

In the present invention, film formation is performed by immersing the thus formed film in 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, etc. can be mentioned.

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

The porous membrane of the present invention can be obtained by immersing a membrane formed from the resin solution in these coagulating liquids, substantially coagulating the membrane, 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 film layer, the surface pore diameter of the porous membrane is 0.5 μ or less, preferably 0.2 μ or less, and more preferably 0.1 μ or less. If it is larger than 0.5μ, the membrane layer of the separation functional thin film cannot be made thinner.

The flow rate should be as large as possible, and the temperature should be 25℃.
The water permeation rate measured at 1×10 ^-5 (g/
^cm2・sec・atm) or more, preferably 1×10 ^-4 (g/
^cm2・sec・atm) or more.

In the present invention, the wet-formed polysulfone porous membrane as described above is immersed in hot water and heat-treated. Hot water temperature is 50-130℃, preferably 60-100℃
It is ℃. If the temperature is 100℃ or higher, perform under pressure. 50℃
Below this, there is almost no effect of stabilizing the porous membrane. 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 time is less than 0.2 hours, the heat treatment will not be effective. 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.

In the hot water immersion method, the polysulfone porous membrane once formed can be washed with water and then immersed again in warm water. 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 subjected to dipping treatment 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 porous polysulfone membrane is once dried and then heat-treated, polysulfone is hydrophobic, and once it dries, water cannot soak into the pores of the porous membrane sufficiently, reducing the effectiveness of the treatment. Therefore, it is preferable to process the polysulfone porous membrane in a wet state without drying it.

The separation functional layer of the composite membrane used in the present invention is a thin film made of an organic polymer compound, and such a thin film can be prepared by a method such as spreading on water, casting, or coating from an organic solvent solution containing the organic polymer. Formed by known methods. 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, poly[methycryloxypropyltris(trimethylsiloxy)silane], poly2,6-dimethyl Examples include phenylene ether.

Any solvent may be used as long as it dissolves the membrane material, such as hydrocarbon solvents such as benzene, toluene, xylene, cyclohexane, cyclohexene, hexene, octane, hexadecene, and octadecene;
Halogenated hydrocarbon solvents such as trichlorethylene, tetrachlorethylene, chloroform, trichlorotrifluoroethylene, ether solvents such as tetrahydrofuran and dioxane, aprotic solvents such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethanol, iso-propyl Alcohol solvents such as alcohol and butanol are used alone or in a mixture of two or more. 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 functional layer, a solution of an organic 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 casted on a flat solid surface to make a thin solution, and then the solvent is removed to form a thin film, which is then laminated onto a porous membrane. method, or 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),
Alternatively, it may be a multi-layer structure consisting of at least two layers. In particular, a membrane with a separation function layer formed by laminating at least two thin films has the advantage that defective parts of the thin films are filled by overlapping and the separation properties are improved. It is preferably used because it can also improve the strength of the functional layer. 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 separation functional layer of the present invention is preferably as thin as possible in terms of gas permeability, as long as no defects occur in the membrane, and the thickness is preferably 0.5μ or less, preferably
It is 0.3μ or less, more preferably 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 membranes is that the organic solvent used in the stage of forming the separation functional layer remains in the membrane in trace amounts 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 the removal of trace amounts of membrane-forming solvent remaining in wet-formed polysulfone-based porous membranes, and I believe that this effect is visible, but that is not all. I can't explain everything.

One way of thinking is that hot water treatment of polysulfone porous membranes brings about structural changes along with desolvation, and then heat treatment in a dry state creates a structure that is optimal for use as a support, for example, the pores on the surface expand a little and the degree of aperture increases. is expected. In other words, hot water treatment
It is thought that the heat treatment not only removed the film-forming solvent but also caused a change in the structure of the polysulfone, leading to stability of the film. Of course, it is thought that the structure may be stabilized by heat treatment of the separation functional 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. Here, the reduced pressure gas phase conditions 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. There are two methods: one in which one side of the membrane is vacuumed to a reduced pressure of 0.1 to 400 Torr (the other side of the membrane is at atmospheric pressure) and air or inert gas is passed through the composite membrane. Among these, the latter method is preferably used because a large amount of gas passes through the composite membrane and the treatment effect is large. The degree of pressure reduction is 0.1 to 400 Torr, preferably 10 to 300 Torr, preferably 20 to 250 Torr. If the temperature is 400 Torr or more, the effect of heat treatment will be small, and even if the temperature is set to 0.1 Torr or less, the effect will be the same as if it were within 0.1 Torr.

The temperature conditions for this treatment are 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 65-180℃
More preferably, the temperature is 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. Heat treatment has no effect if the time is less than 0.2 hours. The length of processing 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 a plurality of membranes if it is in the form of a tube or hollow fiber, and 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 separating carbon dioxide from a gas mixture mainly composed of carbon dioxide and air (e.g., combustion waste gas).
Separation of helium or argon from gas mixtures consisting primarily of helium or argon and nitrogen gas (e.g. liquefied helium or argon vaporized and mixed with air), helium enrichment from natural gas, or hydrogen and carbon monoxide or It can also be suitably used for the separation of hydrogen from gas mixtures containing methane and the like (for example, water gas and process gas). 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 (basis weight 180
g/m ² ) on top of polysulfone (Nissan Chemical
udelP3500) 15wt%, N-methylpyrrolidone
A solution consisting of 85 wt% was cast into a layer with a thickness of about 0.35 mm, and the polysulfone layer was immediately gelled in a water bath at 20°C to obtain a nonwoven reinforced polysulfone porous membrane.

Subsequently, the porous membrane was washed in running water for 2 days to remove residual solvent. The polysulfone porous membrane thus obtained was immersed in hot water at 100°C for 2 hours for hot water treatment.

As for the characteristics of this porous membrane, when the amount of pure water permeated at 25° C. was measured at a pressure of 1 Kg/cm ² , the water permeation rate was 1.41×10 ⁻² g/cm ² ·sec·atm.

In addition, the pore diameter of the membrane was determined by surface electron microscopy at a magnification of 100,000 times and was found to be 0.01 to 0.02μ.

A cyclohexene solution of poly-4-methylpentene (3wt% of cyclohexene hydroperoxide was added as a developing aid) on this polysulfone porous membrane.
poly-4-, which was formed by spreading it on the surface of water (with the addition of
Several thin films of methylpentene are stacked to a film thickness of approximately 0.12μ.
Then, I made a composite film.

This composite membrane was cut to a size of 25 cm x 50 cm, the aluminum plate, the net, and the composite membrane were stacked in that order, a nozzle opening was attached that communicated with the nonwoven fabric side, and the four sides were solidified with epoxy resin to form a separation membrane element (module).

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

Next, put this element in a hot air oven at 80℃,
The pressure was reduced to 130 Torr from the nozzle opening and the treatment was carried out for 3 hours. When air separation was performed under the same conditions as before after treatment, the oxygen concentration was 40.6% and the amount of oxygen-enriched air was
It was 228c.c./min.

Next, suck this elelent from the nozzle opening.
Although suction was carried out continuously for 5,000 hours under a vacuum of 160 Torr and a clean air atmosphere at a temperature of 23°C, the oxygen concentration did not change and the flow rate remained stable at 226 c.c./min (retention rate 99%). If the composite membrane is not heat treated,
In a similar durability test, its flow retention rate was 93%.

Comparative Example 1 A composite membrane was prepared in the same manner as in Example 1, except that a porous polysulfone membrane that was not subjected to hot water treatment was used. The air separation performance of this composite membrane before hydrothermal treatment was an oxygen concentration of 40.6% and an enriched air amount of 208 c.c./min. The performance of this composite membrane after heat treatment is determined by the oxygen concentration
The amount of enriched air decreased by 40.5% to 198 c.c./min. Further, in the same durability test as in Example 1, the flow rate retention rate after 5000 hours was 95%.

Example 2 A solution consisting of 2.0 parts by weight of poly-2,6-dimethylphenylene oxide, 1.58 parts by weight of cyclohexenyl hydroperoxide and 97 parts by weight of trichlorethylene was maintained at 50°C, and 6.0 parts by weight was injected from the tip of a 0.8 mmφ injection 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 cc/min. The formed thin film was pulled up onto the polysulfone porous membrane used in Example 1 by pressing it from above the polysulfone porous membrane used in Example 1 at a distance of 60 cm from the needle tip.
formed a layer. The film thickness was calculated to be 0.015 μm.

Next, polydimethylsiloxane-polybutadiene copolymer (tensile modulus 318 Kg/cm ² , PO ₂ 1.5
×10 ^-8 cc・cm/cm ²・sec・cmHg, α: 2.0) 7 parts by weight, cyclohexenyl hydroperoxide 5
Similarly, a solution consisting of 88 parts by weight of benzene and 88 parts by weight of benzene was continuously supplied onto the water surface to form a thin film of polydimethylsiloxane-polybutadiene copolymer on the water surface. 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 μm) was applied on top of this, and polyphenylene oxide-polydimethyl raloxane layer was formed.
We created a composite membrane with a separation function layer made of polybutadiene-polyphenylene oxide.

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 c.c./min was obtained. This was suctioned through 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)
160 Torr), oxygen enriched air with a flow rate of 428 c.c./min at an oxygen concentration of 40.1% was obtained.

Example 3 Poly-4-methylpentene-1 (Mitsui Petrochemical
Co., Ltd., grade DX845) and 3 parts by weight of cyclohexenyl hydroperoxide was maintained at 30°C and injected into the tip of a 0.8 mmφ syringe needle.
The needle tip was continuously supplied onto the water surface maintained at 5° C. at a flow rate of 60 c.c./min while being in contact with the water surface. The polymer solution formed a thin film on the water surface. The formed thin film was pulled onto the polysulfone porous membrane by continuously pressing the polysulfone porous membrane used in Example 1 from above at a distance of 60 cm from the needle tip. Next, polydimethylsiloxane-polycarbonate copolymer (siloxane content 60 mol%,
PO ₂ 2×10 ^-8 cc・cm/cm ²・sec・cmHg, α: 2.2,
A solution consisting of 8 parts by weight of tensile modulus (260 kg/cm ² ), 5 parts by weight of cyclohexenyl hydroperoxide, and 87 parts by weight of benzene was spread on the water surface to form a thin film of the copolymer, and the poly4 - layered on top of a thin layer of methylpentene and layered once again to form an interlayer with a thickness of 0.108μ. Next, a thin film of poly4-methylpentene-1 having a thickness of 0.017 μm, 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.

Using this composite membrane, we conducted an air separation test by sending air to the separation functional layer side and reducing the pressure to 160 Torr on the opposite side, the porous support side.
An amount of 4.2/m ² of oxygen-enriched air with an oxygen concentration of 41.3% was obtained. This was treated in a temperature atmosphere of 80° C. for 3 hours while suctioning under a reduced pressure of 130 Torr from the nozzle opening.

After the treatment, air separation was performed in the same manner, and an amount of oxygen-enriched air with an oxygen concentration of 41.3% was obtained in an amount of 4.5/ ^m2 . In addition, when the treated membrane was subjected to a continuous suction test under the same conditions as in Example 1,
The flow rate retention rate after 5000 hours was over 99%, and the oxygen concentration remained stable.

Example 4 Densely woven polyester nonwoven fabric (basis weight 135
g/m ² ) on top of polysulfone (Sumitomo Chemical,
PES300P) 15wt%, N-methylpyrrolidone 85wt
A nonwoven fabric-reinforced polysulfone porous membrane was obtained by casting a solution consisting of 100% of the polysulfone into a layer with a thickness of about 0.3 mm, and immediately gelling the polysulfone layer in a 15°C water bath.

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 3.1×10 ^-3
(g/cm ² ·sec · atm), and the surface pore diameter was 0.01μ or less.

On this polysulfone porous membrane, poly(allyl)
A 0.024μ thin film of t-butyldimethylsilane-allyltrimethylsilane) copolymer (allyl-t-butyldimethylsilane 30 mol%), followed by a 0.024μ thin film of polymethylsiloxane-polyvinyltrimethylsilane copolymer (dimethylsiloxane content 70 mol%) )of
0.10μ thin film, then poly(allyl-t-
A composite film was obtained by laminating 0.024μ thin films of butyldimethylsilane-allyltrimethylsilane copolymer in this order.

In order to investigate the performance of this composite membrane, air separation was performed (at reduced pressure of 50 Torr), and the oxygen concentration was 38.2%.
The enriched air amount was 1.50/m ² ·min.

This composite film was applied through the nozzle opening in a temperature atmosphere of 70℃.
The mixture was vacuumed to a reduced pressure of 120 Torr and heat-treated for 5 hours. When air separation was performed under the same conditions as before, the oxygen concentration was 38.2% and the enriched air amount was 1.53/m ² ·min.

Example 5 Polysulfone (Nissan Chemical, udelP3500) 20wt
%, N-methylpyrrolidone 57wt%, lithium chloride 3wt%, and 2-methoxyethanol 20wt% is discharged from an annular slit at 30°C using water as the core liquid, and immersed in water at 25°C to solidify. A polysulfone hollow fiber porous membrane with an outer diameter of 800 μm and an inner diameter of 500 μm was obtained. The hollow porous membranes were then bundled and immersed in hot water at 100°C for 4 hours for hot water treatment.

The water permeation rate of this polysulfone hollow porous membrane is
It was 4.0×10 ^-3 (g/cm ² sec atm). The inner and outer surface pore diameters of the hollow fibers are both 0.01~
It was 0.02μ. 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 polycarbonate pipe, and both ends were hardened with adhesive to obtain a hollow fiber membrane module.

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 Petrochemicals Co., Ltd.) is poured inside the hollow fiber while the module is intact. . After flushing, drain and air dry, and flush the polymer solution again three times.

The separation membrane thus obtained was dried and then heated to 75°C.
In an atmosphere, suction was applied from the outer suction port of the hollow fiber in the module at a reduced pressure of 160 Torr, and heat treatment was performed for 5 hours. When air was separated at a reduced pressure of 160 Torr, the oxygen concentration was 38.8% and the enriched air amount was 159 c.c./m ² ·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% or more, indicating stable performance.

Claims (1)

[Claims] 1. A polysulfone-based porous membrane and
In a composite membrane consisting of a separation functional layer with a thickness of 0.5μ or less, the polysulfone porous membrane is formed by wet film forming, and has a surface pore size of 0.5μ or less and a water permeation rate of 1×10 ^-4 (g/ ^cm2・sec・atm) or more and 50
The composite membrane is treated in hot water at ~130°C for 0.2 hours or more, and after the composite membrane is formed, the pressure on one side of the composite membrane is lower than the pressure on the other side, and A composite membrane for gas separation, characterized in that it has been heat-treated at a temperature of 60 to 200°C for 0.2 hours or more under gas phase conditions at a pressure of 0.1 to 400 Torr. 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. 3. The composite membrane for gas separation according to claim 1, wherein the other surface side is the separation functional layer side.