JPH0889770A - Production of gas separation membrane - Google Patents

Abstract

PURPOSE: To obtain a gas separation membrane which enables efficient separation of carbon dioxide from natural gas containing carbon dioxide by blowing gas for heating in a specified temp. range to the surface of a coating layer formed by applying a film forming source liquid and then irradiating the surface with IR rays. CONSTITUTION: A film forming source liquid 4 is applied by a liquid coating means 3 on the one surface of a nonwoven fabric released from a releasing roller 1 to form a coating layer. Then the coating layer is heated by blowing nitrogen gas in 100 to 300 deg.C temp. range from a blowing means 5 of the heating gas and further by an IR ray heater 8 to vaporize the main solvent and additives in the surface layer of the coating layer. Then, immediately the nonwoven fabric 2 is dipped in a solidifying soln. 10 and wound up on a winding roller 11. By this method, a gas separation membrane comprising a polyether sulfone dense layer and a polyether sulfone porous layer is formed on the one surface of the nonwoven fabric 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a gas separation membrane, and more particularly to a method for producing a gas separation membrane capable of efficiently selectively separating carbon dioxide from natural gas containing carbon dioxide.

[0002]

2. Description of the Related Art Gas separation membranes using polymer resins have been studied for many years and various kinds have been proposed. Among them, a polyethersulfone gas separation membrane that separates carbon dioxide from natural gas is highly demanded in industry and is strongly desired for practical use.

It is important that the carbon dioxide separation membrane has an excellent function of selectively separating carbon dioxide from a mixed gas such as natural gas and also an excellent function of permeating carbon dioxide. That is, it is important that the carbon dioxide separation membrane has excellent carbon dioxide selectivity and carbon dioxide permeability.

Generally, the amount of gas permeation through a gas separation membrane having a dense and homogeneous structure is inversely proportional to the thickness of the gas separation membrane. Therefore, how to obtain a thin film in a polymer resin having gas selectivity is an important point in film formation.
At the same time, the gas separation membrane is required to have sufficient mechanical strength.

Therefore, a method of adhering a polymer resin film to the surface of a porous support produced in advance is disclosed in JP-A-56-9.
It is disclosed in Japanese Patent No. 2926 and Japanese Patent Laid-Open No. 63-296822.

However, it is industrially difficult to produce an extremely thin homogeneous thin film and adhere it to the surface of the porous support, and furthermore, the gas separation performance of the thin film is easily impaired by the adhesion.

Therefore, as a useful gas separation membrane, a dense layer having high gas selection performance is integrally supported by a porous layer having columnar or sponge-like pores, that is, an asymmetric structure having a so-called anisotropic structure. A gas separation membrane is disclosed in JP-A-5
8-36617 and U.S. Pat. No. 47463.
No. 33 patent specification.

In order to manufacture such an asymmetric gas separation membrane, a polymer resin constituting the membrane body, a main solvent for dissolving the polymer resin, a coagulating solution for coagulating the polymer resin into a membrane shape, Also, an additive or the like for forming columnar or sponge-like pores in the film is required. The additive has the property that it has very low solubility in the polymer resin and high solubility in the coagulation solution.

The asymmetric gas separation membrane is manufactured as follows. That is, the polymer resin constituting the film body is dissolved in a solvent system composed of a main solvent and an additive to prepare a stock solution for film formation. Next, the film-forming stock solution thus prepared is applied onto a film-forming supporting base material such as glass or a non-woven fabric to form a coating layer on the film-forming supporting base material, and left for a short time. During this time, the main solvent and the additives evaporate from the surface layer portion of the coating layer. As a result, the polymer resin concentration in the surface layer of the coating layer is increased. Immediately thereafter, the coating layer is immersed in the coagulation solution together with the film-forming support substrate. As a result, an asymmetric membrane composed of a dense layer having a surface layer made of a polymer resin and a lower layer having a porous layer made of the same polymer resin as the surface layer having columnar or sponge-shaped pores formed therein. A gas separation membrane is formed on the supporting substrate. Here, the reason why the porous layer is formed is that the additive in the lower layer portion is eluted into the coagulation solution, and this portion remains as pores.

The following technology is disclosed in the specification of US Pat. No. 4,746,333. That is, in order to manufacture a good asymmetric gas separation membrane by the above-mentioned membrane forming method, it is necessary to evaporate the main solvent in a short time to form a thin dense layer on the surface layer portion. Because of this, the boiling point is low,
A halogenated hydrocarbon solvent such as dichloromethane or 1,1,2-trichloroethane, which has a very high evaporation rate, is used as a main solvent and left in the air for a short time. Hereinafter, this method is referred to as a conventional technique.

[0011]

However, the above-mentioned prior art has the following problems. That is, the halogenated hydrocarbon solvent as the main solvent is highly toxic and adversely affects the human body, and it is difficult to collect the halogenated hydrocarbon solvent, which leads to destruction of the ozone layer.

[0012] Therefore, an object of the present invention is to provide a method for producing a gas separation membrane which does not adversely affect the human body and environment and is excellent in carbon dioxide selectivity and carbon dioxide permeability.

[0013]

DISCLOSURE OF THE INVENTION The present invention has a main solvent which dissolves polyether sulfone and has compatibility with water as a coagulating solution, and which does not substantially dissolve polyether sulfone, and , A solvent system consisting of the main solvent and an additive having compatibility with water as the coagulating solution, to prepare a solution for forming a film by dissolving polyether sulfone, the film forming thus prepared The stock solution for application is applied to a supporting base material to form a coating layer of the stock solution on the supporting base material, and then 100 to 300 is applied to the surface of the coating layer.
Blow a heated gas at a temperature in the range of ° C., then irradiate the surface of the coating layer with infrared rays, then immerse the coating layer together with the supporting substrate in water as the coagulating solution,
Thus, it is characterized in that the thin film of the polyether sulfone is formed on the supporting substrate.

The main solvent comprises dimethyl sulfoxide, and the additive comprises at least one selected from the group consisting of acetone and methyl ethyl ketone.

The main solvent comprises tetramethylurea and the additive comprises at least one selected from the group consisting of acetone and methyl ethyl ketone.

The main solvent comprises dimethylacetamide, and the additive comprises at least one selected from the group consisting of acetone and methyl ethyl ketone.

[0017]

The coating layer of the stock solution for film formation on the supporting substrate is sprayed with a heating gas having a temperature in the range of 100 to 300 ° C., and then is irradiated with infrared rays, whereby the main solvent of the surface layer portion of the coating layer and Since the additive can be evaporated instantly, a dense layer of polyether sulfone can be easily formed on the surface layer portion of the coating layer. By using dimethylsulfoxide, tetramethylurea or dimethylacetamide as the main solvent of the stock solution for film formation, adverse effects of the main solvent on the human body and the environment can be avoided. Further, by using water as the coagulation solution, handling of the coagulation solution and treatment of waste liquid after the treatment can be easily performed.

The present invention will be described in more detail. As the polymer resin forming the gas separation membrane used in the present invention, polyether sulfone having a high separation coefficient of 40, which is the main component of natural gas, and carbon dioxide is used.

The undiluted solution for film formation used in the present invention has a solubility not only in polyethersulfone, which is a polymer resin as a film-forming raw material, but also in a main solvent for dissolving polyethersulfone and polyethersulfone. A small one, which is soluble in the main solvent and the coagulating solution and is composed of an additive having a boiling point lower than that of the main solvent, is used. The heat treatment for evaporating the main solvent and the additive is performed so that the additive is mainly evaporated in a short time from one surface of the coating layer obtained by coating the film-forming stock solution on the film-forming supporting substrate.

The main solvent used in the present invention is preferably, for example, dimethyl sulfoxide, tetramethyl urea or dimethyl acetamide, which dissolves polyether sulfone and has compatibility with water as a coagulating solution. The reason for this is that these solvents, unlike halogenated hydrocarbon solvents such as dichloromethane used in the prior art, do not adversely affect the human body or the environment. That is, while a halogenated hydrocarbon solvent such as dichloromethane has a high evaporation rate and a low boiling point of 40.3 ° C., all of the above-mentioned solvents are
The evaporation rate is slower than that of halogenated hydrocarbon solvents, and the boiling points of dimethyl sulfoxide are 189.0 ° C, tetramethylurea is 177.5 ° C, and dimethylacetamide is 16 ° C.
Each of them has a high boiling point as compared with the halogenated hydrocarbon solvent such as 5.5 ° C.

The amount of the main solvent used is usually about 100 to 500% by weight with respect to the polyether sulfone. The amount of the main solvent used is a gas separation membrane as long as the polyether sulfone can be dissolved. It is preferable that the number is as small as possible so that the dense layer can be easily formed.

The additive used in the present invention has a low solubility in polyether sulfone,
Use an organic solvent that is compatible with the main solvent and the coagulation solution. For example, at least one kind selected from ketones, aldehydes, carboxylic acids, heterocyclic compounds and the like is used. To obtain an asymmetric gas separation membrane with excellent separation performance,
It is essential to form a thin dense layer on the surface, for which purpose the solvent is evaporated from the surface layer of the coating layer, thus increasing only the concentration of polyether sulfone on the surface layer of the coating layer, and thus Need to be deposited. However, in addition to halogenated hydrocarbons, the main solvents capable of dissolving polyether sulfone are all those having a high boiling point, as described above,
As it is, almost no increase in the concentration of polyether sulfone due to evaporation can be expected.

Therefore, in the present invention, the use of an additive having a low boiling point and a high evaporation rate facilitates evaporation from the surface layer of the coating layer, which was difficult with the main solvent. The additive, together with the polyether sulfone and the main solvent, must be separated from the uniformly dissolved stock solution for film formation with a force higher than its affinity and evaporated. For this reason, the additive preferably has a boiling point lower by about 100 ° C. than the boiling point of the main solvent. For example, 56.1
Acetone having a boiling point of ° C and methyl ethyl ketone having a boiling point of 79.0 ° C are preferable. The additive is usually used in an amount of about 3 to 120% by weight with respect to the polyether sulfone, but the amount used is a large amount as long as the uniformity of the film-forming stock solution in which the polyether sulfone is dissolved is maintained. It is preferable that the amount is as large as possible so that the dense layer can be easily formed by evaporating.

As the film-forming supporting base material used in the present invention, for example, a glass plate, a thin plate such as stainless steel, aluminum, or Teflon having a smooth surface, or a nonwoven fabric such as polyester is preferable. Of these, supporting substrates other than glass plates are suitable when the present invention is applied to a continuous film forming process. The thickness of the coating film formed by applying the stock solution for film formation on the supporting substrate is 50 to 300 μm.
m, preferably 100 to 250 μm.

In the present invention, in addition to using an additive that easily evaporates, it is necessary to heat the coating layer in order to evaporate a part of the main solvent and promote the formation of a dense layer. . The heating temperature of the coating layer is 100 to 300 ° C.
It is necessary to limit it within the range. This is because below 100 ° C, the additive does not evaporate, while above 300 ° C,
This is because the polyethersulfone in the stock solution for film formation is thermally decomposed and a film is not formed.

The method of heating the coating layer on the supporting substrate in the present invention is a combination of heating gas spraying and infrared irradiation. The heating gas supplies the heat of vaporization necessary for the evaporation of the main solvent and additives in the surface layer of the coating layer, and the air flow serves as a carrier to transport the main solvent and additive molecules evaporated from the surface layer of the coating layer. As a result, the concentration of the evaporated main solvent and additive molecules in the atmosphere in the vicinity of the coating layer is constantly maintained at a low level, so that the effect of promoting evaporation of the main solvent and additive is great.

The higher the blowing speed of the heated gas, the more
The evaporation effect of the main solvent and the additive is enhanced, but if it is too fast, fine wrinkles or defects are generated on the surface of the coating layer due to the action of force due to the flow velocity, which adversely affects the formation of the dense layer. Further, if the spraying rate of the heated gas varies, a dense layer is not formed uniformly on the surface layer of the coating layer. Therefore, the heated gas flow is preferably a uniform laminar flow.

On the other hand, infrared rays have a high thermal effect, and
Ultraviolet rays have a short wavelength and therefore have a high transparency, whereas infrared rays have a long wavelength and thus a low transparency.Therefore, the main solvent and additives are selectively evaporated from the surface layer of the coating layer. Suitable to let. Further, infrared rays have the advantages that irradiation intensity and temperature can be easily controlled by electrical control, that heating efficiency is high, and that uniform heating is possible.

From the above, the combined use of the evaporation effect by the air flow by the blowing of the heated gas and the uniform heating effect by the infrared irradiation compensates for the respective disadvantages, and as a result, a dense layer excellent in separation performance is formed. To be done. Furthermore, since heat treatment increases the mechanical strength of the dense layer, it can be applied to the separation of carbon dioxide from a gas such as natural gas having a high pressure of a few to a few hundreds of kgf / cm ² · G. Become.

In the present invention, immediately after heating the surface layer portion of the coating layer so that the formed dense layer is not redissolved by the main solvent remaining in the coating layer, the coating layer is immediately immersed in the coagulating solution. Although soaking, water is used as the coagulating solution, which is compatible with the main solvent and the additive and does not dissolve the polyether sulfone. Since the coagulation solution is used in a large amount, it is preferable that the coagulation solution is easy to handle and the waste liquid can be easily treated, but water is also optimal in this respect.

[0031]

EXAMPLES Next, the present invention will be described in more detail by way of examples. Example 1 A gas separation membrane was produced using a continuous membrane forming apparatus as shown in FIG. This continuous film forming apparatus will be described.

In FIG. 1, 1 is a feeding roller around which a nonwoven fabric 2 made of polyester is wound, and 3 is one surface of the nonwoven fabric 2 which is continuously fed from the feeding roller 1, and a stock solution 4 for film formation, which will be described later, is provided on one surface thereof. The stock solution applying means 5 for applying is a heating gas spraying means for heating the surface layer portion of the film forming stock solution 4 applied to the surface of the nonwoven fabric 2. The heating gas spraying means 5 is composed of a heater 6 for heating the nitrogen gas and a rectifier 7 having a function of rectifying the nitrogen gas heated by the heater 6 and uniformly spraying the nitrogen gas onto the surface of the nonwoven fabric 2. . 8 is an infrared heater provided downstream of the heating gas blowing means 5 in the moving direction of the nonwoven fabric 2, 9 is a tank containing the coagulation solution 10, and 11 is provided in the tank 9. And a take-up roller for the nonwoven fabric 2 on which the gas separation membrane is formed.

The stock solution 4 for film formation is a polyether sulfone commercially available as a polymer resin (trade name: VICTREX PE manufactured by ICI, product name).
S 4800P) 30% by weight, dimethylfoxide 35% by weight as an additive, and acetone 35% by weight as an additive. This composition is a combination in which the main solvent is as small as possible and the additive is as large as possible, based on the weight of the polyether sulfone. The boiling point difference between the main solvent and the additive is 132.9.
° C.

On one surface of the nonwoven fabric 2 continuously fed from the feeding roller 1 at a speed of 2 cm / sec, the film forming stock solution 4 is continuously applied by the stock solution applying means 3 to a thickness of 250 μm, and the non-woven cloth is obtained. A coating layer was uniformly formed on one surface of No. 2. In addition, when the heat treatment is not performed, immediately after the coating layer is formed, the nonwoven fabric 2 on which the coating layer is formed is formed.
Was immersed in coagulation solution 10. On the other hand, when heat treatment is performed, the coating layer on the polyester non-woven fabric is blown with nitrogen gas heated from the heating gas blowing means 5 for 1 second, and then the coating layer is further heated for 2 seconds by the infrared heater 8. Then, the main solvent and the additive in the surface layer portion of the coating layer were evaporated in a short time, and immediately, the nonwoven fabric 2 on which the coating layer was formed was immersed in the coagulating solution 10. The nonwoven fabric 2 dipped in the coagulation solution 10 was wound by the winding roller 11. In this way, a gas separation membrane composed of a dense layer of polyether sulfone and a porous layer of polyether sulfone was produced on one surface of the nonwoven fabric 2.

The heating temperature control by the heating gas spraying means 5 is performed so that the nitrogen gas temperature is maintained at a predetermined temperature.
The heater 6 was controlled by PID. The heating temperature control by the infrared heater 8 was performed by the load current control.

The permeation rates of carbon dioxide gas and methane gas of the gas separation membrane thus produced were determined as follows. That is, the front side of the film (the side where the dense layer is formed) is maintained at 1 kgf / cm ² · G by methane gas, and the back side of the film is maintained at a vacuum of 2 kgf / cm ² ·.
The permeation rate was determined from the rate of increase in pressure due to the methane gas permeating to the back side of the membrane, using the operating pressure of G. Further, using carbon dioxide, the permeation rate was determined as in methane gas. The separation coefficient was determined by the ratio of the permeation rate of carbon dioxide to the permeation rate of methane gas.

Tables 1 and 2 show the performance of the gas separation membrane produced according to the above-mentioned method. The temperature of the heat treatment at this time was set as follows. That is, the heating temperature gas is set to 100, 200, 300 ° C. (infrared irradiation temperature condition is fixed at 200 ° C .: Table 1), and the temperature by infrared irradiation is 100, 200, 300 ° C. (heating gas temperature condition is: Fixed at 200 ° C .: set to Table 2). The surface temperature of the coating layer by infrared irradiation was measured with an infrared radiation thermometer.

[0038]

[Table 1]

[0039]

[Table 2]

In Comparative Example 1, Oya et al., Membrane, vol. Thirteen
(3) is a performance value of the asymmetric gas separation membrane using the polyether sulfone of p165-170 (1988).
Oya et al., Polyethersulfone 20% by weight, 153.
An undiluted solution for film formation of dimethylformamide having a boiling point of 0 ° C. of 80% by weight is used, no additive is added, and water is used as a coagulating solution. In addition, the heat treatment,
After film formation, the film is left to stand in an atmosphere of 90 ° C. for 5 minutes.

As is clear from Table 1, the gas temperature is 300
As for the gas separation performance of the produced asymmetric gas separation membrane, the separation performance was 2.7 times and the carbon dioxide permeation rate was 1.3 times better than those of Comparative Example 1. Turned out to show. Gas temperature from 100 ℃ to 2
When the temperature was raised to 00 ° C, the separation factor increased more than twice. However, even if the temperature was raised to 300 ° C, the separation coefficient was not increased. This is because the gas temperature rises,
It is considered that the formation of the dense layer progressed and the separation coefficient increased. The carbon dioxide permeation rate did not change significantly even when the gas temperature changed.

As is clear from Table 2, the gas temperature of 200
As for the gas separation performance of the produced asymmetric gas separation membrane, the separation performance was 4.3 times and the carbon dioxide permeation rate was 3.0 times better than those of Comparative Example 1. Turned out to show. In particular, in terms of separation factor, it is the ideal separation factor of polyethersulfone 4
The result was equivalent to 0. The separation factor increased with increasing temperature condition by infrared irradiation. this is,
It is considered that the dense layer formation progressed as the heating temperature by infrared rays increased, and the separation coefficient increased. The carbon dioxide permeation rate did not change significantly even when the gas temperature changed.

Example 2 30% by weight of the same polyether sulfone as in Example 1 was uniformly dissolved in a mixed solution of 35% by weight of dimethyl sulfoxide as a main solvent and 35% by weight of methyl ethyl ketone as an additive to form a film. An undiluted solution was prepared. This composition is a combination in which the main solvent is as small as possible and the additive is as large as possible, based on the weight of the polyether sulfone. Also, the boiling point difference between the main solvent and the additive,
It was 110.0 ° C. Thereafter, a film was formed in the same manner as in Example 1 and a film performance test was conducted.

Tables 3 and 4 show performance values of the asymmetric gas separation membranes produced by the above method. The temperature of the heat treatment at this time was set as follows. That is, the heating temperature gas is set to 100, 200, 250 ° C. (infrared irradiation temperature condition is fixed at 200 ° C .: Table 3),
The temperature by infrared irradiation was set to 200 and 300 ° C. (heating gas temperature condition fixed at 200 ° C .: Table 4). In addition,
The surface temperature of the coating layer by infrared irradiation was measured by an infrared radiation thermometer.

[0045]

[Table 3]

[0046]

[Table 4]

As is apparent from Table 3, the gas temperature is 250
The gas separation performance of the asymmetric gas separation membrane produced under the temperature heating conditions of 200 ° C. and infrared irradiation of 200 ° C. was 3.2 times in separation performance and 8.6 times in carbon dioxide permeation rate as compared with Comparative Example 1. Was found to show. When the gas temperature was raised from 100 ° C. to 200 ° C., the separation coefficient increased, and when the gas temperature was raised to 250 ° C., the separation coefficient further increased to 30.0. It is considered that this is because the formation of the dense layer progressed as the gas temperature increased and the separation coefficient increased. Moreover, the permeation rate of carbon dioxide tended to decrease as the gas temperature increased. It is considered that this is because the dense layer was gradually thickened and the gas permeation resistance was increased.

As is clear from Table 4, the gas temperature is 200
As for the gas separation performance of the produced asymmetric gas separation membrane, the separation performance was 2.2 times and the carbon dioxide permeation rate was 12.9 times better than those of Comparative Example 1. Turned out to show. Even when the temperature by infrared irradiation increased from 200 ° C. to 300 ° C., the separation coefficient remained at about 20 and did not increase any further. In addition, the carbon dioxide permeation rate showed a slight tendency to decrease as the temperature increased from 200 to 300 ° C.

Example 3 30% by weight of the same polyether sulfone as in Example 1 was uniformly dissolved in a mixed solution of 35% by weight of tetramethylurea as a main solvent and 35% by weight of acetone as an additive to prepare a mixture. A stock solution for the membrane was prepared. This composition is a combination in which the main solvent is as small as possible and the additive is as large as possible, based on the weight of the polyether sulfone. The boiling point difference between the main solvent and the additive was 121.4 ° C. Thereafter, a film was formed in the same manner as in Example 1 and a film performance test was conducted.

Tables 5 and 6 show performance values of the asymmetric gas separation membrane produced by the above method. The temperature of the heat treatment at this time was set as follows. That is, the heating temperature gas is set to 100, 200, 250 ° C. (the temperature condition of infrared irradiation is fixed at 200 ° C .: Table 5),
The temperature by infrared irradiation was set to 200 and 300 ° C. (heating gas temperature condition fixed at 200 ° C .: Table 6). In addition,
The surface temperature of the coating layer by infrared irradiation was measured by an infrared radiation thermometer.

[0051]

[Table 5]

[0052]

[Table 6]

As is clear from Table 5, the gas temperature is 250
The gas separation performance of the asymmetric gas separation membrane manufactured under the temperature heating conditions of 200 ° C. and infrared irradiation of 200 ° C. is 4.6 times as good as that of Comparative Example 1 and 2.1 times as high as the carbon dioxide permeation rate. Was found to show. In particular, in terms of separation factor, it is the ideal separation factor of polyethersulfone 4
The result was equivalent to 0. Gas temperature from 100 ℃ to 20
When the temperature was raised to 0 ° C, the separation coefficient hardly increased, but when the temperature was raised to 250 ° C, the separation coefficient increased sharply. It is considered that this is because the formation of the dense layer rapidly progressed when the gas temperature became 200 ° C. or higher. The carbon dioxide permeation rate tended to decrease rapidly in response to an increase in the separation coefficient.

As is clear from Table 6, the gas temperature is 200
As for the gas separation performance of the asymmetric gas separation membrane manufactured under the temperature heating conditions of 300 ° C. and infrared irradiation of 300 ° C., the separation performance was 2.0 times that of Comparative Example 1 and the carbon dioxide permeation rate was 13.5, which was excellent results. Turned out to show. Even if the temperature condition by infrared irradiation rises from 200 ℃ to 300 ℃, the separation coefficient,
No significant change was observed in the carbon dioxide permeation rate.

Example 4 30% by weight of the same polyether sulfone as in Example 1 was homogeneously dissolved in a mixed solution of 35% by weight of tetramethylurea as a main solvent and 35% by weight of methyl ethyl ketone as an additive to prepare a mixture. A stock solution for the membrane was prepared. This composition is a combination in which the main solvent is as small as possible and the additive is as large as possible, based on the weight of the polyether sulfone. The boiling point difference between the main solvent and the additive is 98.5 ° C.
Met. Thereafter, a film was formed in the same manner as in Example 1 and a film performance test was conducted.

Tables 7 and 8 show performance values of the asymmetric gas separation membranes produced by the above method. The temperature of the heat treatment at this time was set as follows. That is, the heating temperature gas is set to 100, 200, 300 ° C. (infrared irradiation temperature condition is fixed at 200 ° C .: Table 7),
The temperature by infrared irradiation was set to 100, 200, 300 ° C. (heating gas temperature condition fixed at 200 ° C .: Table 8). The surface temperature of the coating layer by infrared irradiation was measured with an infrared radiation thermometer.

[0057]

[Table 7]

[0058]

[Table 8]

As is apparent from Table 7, the gas temperature is 250
The gas separation performance of the asymmetric gas separation membrane produced under the temperature heating conditions of 200 ° C. and infrared irradiation of 200 ° C. was 2.8 times as high as the separation performance and 28.4 times as high as the carbon dioxide permeation rate as compared with Comparative Example 1. Was found to show. When the gas temperature was raised from 100 ° C to 200 ° C, the separation factor increased, but
Even if the temperature was raised to 0 ° C, no further remarkable increase tendency was observed. It is considered that this is because the formation of the dense layer was almost completed under the gas temperature up to 200 ° C. Also,
The carbon dioxide permeation rate did not decrease significantly when the gas temperature was 200 ° C. or higher, like the behavior of the separation coefficient.

As is clear from Table 8, the gas temperature of 200
As for the gas separation performance of the asymmetric gas separation membrane produced under the temperature heating conditions of 300 ° C. and infrared irradiation of 300 ° C., the separation performance was 3.2 times that of Comparative Example 1 and the carbon dioxide permeation rate was 30.4. Turned out to show. No significant increase in the separation coefficient was observed even when the temperature condition by infrared irradiation increased from 200 ° C to 300 ° C. Further, the carbon dioxide permeation rate tended to decrease from 100 ° C to 200 ° C, but no significant change was observed from 200 ° C to 300 ° C.

Example 5 30% by weight of the same polyether sulfone as in Example 1 was uniformly dissolved in a mixed solution of 35% by weight of dimethylacetamide as a main solvent and 35% by weight of acetone as an additive to form a film. An undiluted solution was prepared. This composition is a combination in which the main solvent is as small as possible and the additive is as large as possible, based on the weight of the polyether sulfone. Also, the boiling point difference between the main solvent and the additive is 109.4 ° C.
Met. Thereafter, a film was formed in the same manner as in Example 1 and a film performance test was conducted.

Tables 9 and 10 show performance values of the asymmetric gas separation membranes produced by the above method. The temperature of the heat treatment at this time was set as follows. That is, the heating temperature gas is set to 100, 200, 250 ° C. (the temperature condition of infrared irradiation is fixed at 200 ° C .: Table 9),
The temperature by infrared irradiation was set to 200 and 300 ° C. (heating gas temperature condition fixed at 200 ° C .: Table 10). The surface temperature of the coating layer by infrared irradiation was measured with an infrared radiation thermometer.

[0063]

[Table 9]

[0064]

[Table 10] As is clear from Table 9, the gas separation performance of the asymmetric gas separation membrane manufactured under the temperature heating conditions of the gas temperature of 250 ° C. and the infrared irradiation of 200 ° C. was 2.5 in the separation performance as compared with Comparative Example 1.
It was found that good results were obtained with a carbon dioxide permeation rate of 10.8 times. The gas temperature is 100 ° C to 200 ° C,
When the temperature was further increased to 300 ° C, the separation coefficient tended to gradually increase. This is due to the increase in gas temperature,
It is considered that the formation of the dense layer progressed and the separation coefficient increased. In addition, the carbon dioxide permeation rate tended to gradually decrease with increasing gas temperature. It is considered that this is because the dense layer was gradually thickened and the gas permeation resistance was increased.

As is clear from Table 10, the gas temperature is 20
The gas separation performance of the asymmetric gas separation membrane manufactured under the temperature heating conditions of 0 ° C. and infrared irradiation of 300 ° C. was 1.3 times as high as that of Comparative Example 1, and the carbon dioxide permeation rate was 14.4, which is a good result. Was found to show. When the temperature condition by infrared irradiation increased from 200 ° C. to 300 ° C., both the separation coefficient and the carbon dioxide permeation rate tended to decrease slightly.

Example 6 30% by weight of the same polyether sulfone as in Example 1 was uniformly dissolved in a mixed solution of 35% by weight of dimethylacetamide as a main solvent and 35% by weight of methyl ethyl ketone as an additive to form a film. An undiluted solution was prepared. This composition is a combination in which the main solvent is as small as possible and the additive is as large as possible, based on the weight of the polyether sulfone. Also, the boiling point difference between the main solvent and the additive,
It was 86.5 ° C. Thereafter, a film was formed in the same manner as in Example 1 and a film performance test was conducted.

Tables 11 and 12 show performance values of the asymmetric gas separation membranes produced by the above method. The temperature of the heat treatment at this time was set as follows.
That is, the heating temperature gas is set to 100, 200, 250 ° C. (infrared irradiation temperature condition is fixed at 200 ° C .: Table 11), and the temperature by infrared irradiation is 200, 300 ° C. (heating gas temperature condition is 200 ° C. Fixed to: set to Table 12).
The surface temperature of the coating layer by infrared irradiation was measured with an infrared radiation thermometer.

[0068]

[Table 11]

[0069]

[Table 12]

As is clear from Table 11, the gas temperature is 25
The gas separation performance of the asymmetric gas separation membrane manufactured under the temperature heating conditions of 0 ° C. and infrared irradiation of 200 ° C. is 1.9 times as good as that of Comparative Example 1 in terms of separation performance and 55.8 times as high as carbon dioxide permeation rate. It turned out to show a result. Gas temperature 100 ℃
, The separation factor gradually increased, and thereafter, at 200 ° C. and 250 ° C., no significant change was observed. This is because the gas temperature is 100 ℃ to 200 ℃
The formation of the dense layer gradually progresses to
This is probably because there was almost no change. In addition, the carbon dioxide permeation rate is similarly the gas temperature from 100 ℃ to 20
It gradually decreased when the temperature increased to 0 ° C., and thereafter, hardly changed.

As is clear from Table 12, the gas temperature is 20
The gas separation performance of the asymmetric gas separation membrane produced under the temperature heating conditions of 0 ° C. and infrared irradiation of 300 ° C. was 3.1 times that of Comparative Example 1 in terms of separation performance and 24.2 in terms of carbon dioxide permeation rate. Was found to show. When the heating temperature by infrared irradiation increased from 200 ° C. to 300 ° C., the separation coefficient increased, and the carbon dioxide permeation rate tended to decrease slightly.

From the results of Examples 1 to 6 described above, it is shown that the separation coefficient tends to increase as the heating temperature by spraying the heating gas and the heating temperature by infrared irradiation both increase.
On the contrary, the carbon dioxide permeation rate tended to decrease.
This is because the heat treatment has the effect of promoting the formation of a dense layer.

FIG. 2 shows the separation of the membranes shown in Examples 1 and 4 under high pressure with respect to the membranes produced under the heating conditions of a heating gas temperature of 200 ° C. and an infrared irradiation temperature of 300 ° C. FIG. 4 is a graph showing coefficient performance, and FIG. 3 is a graph showing carbon dioxide permeation rate performance for similar membranes. Comparative Example 2 is an evaluation of a cellulose acetate membrane. Comparative Examples 3 and 4
Is the International Congress o held in 1993
IWAKAM at n Membrane and Membrane Processes
I got “CO ₂ Removal, Field Test Using Cellulose Aseta
This is the separation factor value for high-pressure natural gas separation of polyimide and cellulose acetate, which was announced under the theme name "te and PolyimideMembrane".

As is clear from FIGS. 2 and 3, the polyethersulfone gas separation membrane of the present invention maintains a high separation coefficient even under high-pressure operation as compared with the separation coefficients of cellulose acetate and polyimide. In terms of speed, it is rather rising. Therefore, it was found that the gas separation membrane produced according to the present invention is extremely effective in separating carbon dioxide from high pressure natural gas.

[0075]

As described above, according to the present invention, the use of a main solvent which replaces a halogenated hydrocarbon solvent which has a bad influence on the environment such as ozone depletion and cannot be used industrially, and a main solvent. Use of additives with lower boiling points,
By carrying out heat treatment by spraying heated gas and using infrared irradiation together, it is possible to obtain an asymmetric gas separation membrane with a good separation coefficient and gas permeation rate, and also to separate carbon dioxide from natural gas under high pressure. It is possible to obtain industrially useful effects.

[Brief description of drawings]

FIG. 1 is a schematic view showing a continuous film forming apparatus.

FIG. 2 is a graph showing the relationship between the separation coefficient and the operating pressure.

FIG. 3 is a graph showing a relationship between a permeability coefficient and an operating pressure.

[Explanation of symbols]

 1: Feeding roller, 2: Nonwoven fabric, 3: Undiluted solution applying means, 4: Undiluted solution for film formation, 5: Gas blowing means for heating, 6: Heater-7: Rectifier, 8: Infrared heating heater, 9: Tank, 10 : Coagulation solution, 11: winding roller.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Ogawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (4)

[Claims] 1. A polyether sulfone is dissolved, and
A main solvent having compatibility with water as a coagulating solution,
A stock solution for film formation by dissolving polyether sulfone in a solvent system which does not substantially dissolve polyether sulfone and which is composed of the main solvent and an additive having compatibility with water as the coagulating solution. Is prepared, and the stock solution for film formation thus prepared is applied to a supporting base material to form a coating layer of the stock solution on the supporting base material, and then 100 to 300 is applied to the surface of the coating layer. Blow a heated gas at a temperature in the range of ° C., then irradiate the surface of the coating layer with infrared rays, then immerse the coating layer together with the supporting substrate in water as the coagulating solution, thus supporting A method for producing a gas separation membrane, comprising forming a thin film of the polyether sulfone on a base material. 2. The method of claim 1, wherein the main solvent comprises dimethyl sulfoxide and the additive comprises at least one selected from the group consisting of acetone and methyl ethyl ketone. . 3. The main solvent according to claim 1, wherein the main solvent is tetramethyl urea, and the additive is at least one selected from the group consisting of acetone and methyl ethyl ketone. Method. 4. The method according to claim 1, wherein the main solvent comprises dimethylacetamide, and the additive comprises at least one selected from the group consisting of acetone and methyl ethyl ketone. .