JPH02237627A - Permselective membrane for gas - Google Patents

Abstract

PURPOSE:To obtain a film having enough gas selectivity and gas permeability with little deterioration of characteristics by forming two kinds of thin films each comprising specific polymer expressed by specified formulae by spreading the polymers on water and then laminating the films on a porous supporting body. CONSTITUTION:The first polymer is expressed by formula I (wherein R1 represents a halogen atom or alkyl group with 1-3 carbons and R2 represents a phenyl group, alkyl or trialkylsilyl group with 1-6 carbons) and has excellent gas permeability. The second polymer is expressed by formula II (wherein X is a silethylene residual group or silphenylene residual group, R3 and R4 are alkyl or phenyl groups with 1-6 carbons) and has excellent gas permeability. Each of the polymers above-described is formed into a thin film by spreading the material on water. Then two films are laminated on the porous supporting body comprising aromatic polysulfone or polyethersulfone to constitute the three-layer structure in a manner that the second polymer thin film is on the first polymer thin film. Thereby, the obtd. membrane has enough selectivity and permeability for gas and shows little change in characteristics for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a selective gas permeable membrane for gas separation and concentration that selectively permeates a specific gas from a mixed gas.

Conventional technology In recent years, technology for separating and concentrating specific gases from mixed gases through polymeric membranes has begun to be put into practical use, and has already been used for the concentration of oxygen from the air, industrial hydrogen separation and concentration, and recovery of carbon dioxide gas. It is used. In particular, so-called oxygen enrichment membranes, which concentrate oxygen more than air, have a large impact on industry because of their wide range of uses.

Problems to be Solved by the Invention However, when considering the oxygen-enriching membranes currently in practical use, most of them that treat atmospheric air are polyorganosiloxane-based membranes, and the oxygen The permeation rate is approximately 0.1 cc/c+J-sec-atm. On the other hand, the oxygen/
The nitrogen separation ratio is small, not reaching 2, and the oxygen concentration in the oxygen-enriched air produced does not reach 30%.

Among oxygen-enriching membranes, those used for medical purposes have a high oxygen/nitrogen separation ratio of 3 to 4, and can obtain oxygen-enriched air of around 40%, but have a small throughput of gas. For example, the material-specific oxygen permeation rate of polyolefin membranes is
0.01~0.001 cc/ctd-sec-atm
It is extremely small.

Further, as a material having higher gas permeability than polyorganosiloxane membranes, there is a 1-monoalkylsilylpropylene polymer membrane material which is an acetylene polymer (Japanese Patent Application Laid-Open No. 154106/1986).

This membrane material has approximately an order of magnitude higher gas permeability. However, the 1-monoalkylsilylpropylene polymer membrane has poor oxygen and nitrogen separability, with a ratio of only about 1.4. Furthermore, although the initial properties of gas permeability are excellent as described above, they deteriorate significantly over time.

For example, if the film is about 0.1 .mu.m, its characteristics deteriorate over time, making it impractical and difficult to develop.

Of course, attempts have been made to improve the properties of 1-monoalkylsilylpropylene polymer membranes, but at present none has reached a practical level.

In view of the above circumstances, it is an object of the present invention to provide a high-performance selective gas permeable membrane that has both sufficient gas selectivity and gas permeability, and is less likely to deteriorate over time.

Means for Solving the Problems In order to solve the problems, the inventions according to claims 1 to 4 are as follows:
It has the following structure.

The selective gas permeable membrane according to claims 1 to 4 has the following general formula (
A first polymer represented by a) and having excellent gas permeability;
The second compound, which is represented by the following general formula (b) and has excellent gas permeability,
It is made of polymers.

(However, R1 represents an alkyl group having 1 to 3 carbon atoms or a halogen atom, R2 represents a phenyl group, an alkyl group having 1 to 6 carbon atoms, or a trialkylsilyl group, and the alkyl group of this trialkylsilyl group has 1 to 6 carbon atoms.R1 in one molecule may be the same or different, and the same applies to R2.)R. ．． (However, X represents a silethylene residue or a silphenylene residue, and R3 and 几4 represent an alkyl group or a phenyl group having 1 to 6 carbon atoms. The same applies.) In the selective gas permeable membrane according to claim 2, in addition, the first polymer and the second polymer are separately formed into thin films by a water surface development method, and the first polymer thin film is directly supported on a porous support, and the 20th polymer thin film is laminated thereon.

In addition, in the selective gas permeable membrane according to claim 3, the porous support is made of aromatic boris sulfone or polyether sulfone.

In addition, the selective gas permeable membrane according to claim 4 uses a second polymer having a siloxane content of 80% or more and a weight average molecular weight of 10,000 or more.

Function: Since the selective gas permeable membrane of the present invention is a composite membrane consisting of both the first and second polymers, that is, an acetylene polymer and a silicone-modified polymer, it has good gas permeability and gas selectivity. , its deterioration over time is small.

Regarding gas permeability, for example, the oxygen permeation flow rate (Fo1) of the membrane of the present invention is 0.4 to 1. 2 cc/
1.sec-atm and 0.0.sec-atm of conventional polyorganosiloxane membranes. This is considerably higher than 1 cc/ad-see-atm.

Regarding gas selectivity, for example, the flow rate ratio of oxygen and nitrogen of the membrane of the present invention: α=F 02 /F N2 is 2.
The flow rate ratio is about 6 to 3.0, which is considerably higher than the flow rate ratio of 2 for conventional membranes.

In other words, by using the membrane of the present invention, the flow rate of oxygen increases and at the same time the oxygen concentration in the resulting oxygen-enriched gas increases.

The film has the following characteristics and is highly reliable with little deterioration over time.

As shown by curve (a) in FIG. 1, the membrane of the present invention (for example, the selective gas permeable membrane shown in FIG. 2) has a flow rate of 96% of the initial flow rate (100%) even after 600 hours of continuous operation. %
maintain the flow rate. The oxygen concentration of the obtained oxygen-enriched gas also remains almost unchanged.

In contrast, with the conventional acetylene polymer membrane shown in Figure 3, as shown by curve (b) in Figure 1, after 600 hours of continuous operation, the flow rate is approximately 10% of the initial flow rate (100%). The flow rate decreases to .

A three-layer structure in which a first polymer and a second polymer are each made into thin films by a water surface spreading method, and the second polymer thin film is laminated on a porous support via the first polymer film, It is easy to make and easy to exhibit the specified performance.

A porous support made of aromatic polysulfone or polyethersulfone has good gas permeability and is therefore suitable for supporting the membrane.

The second polymer is suitably one whose siloxane content is 80% or more and whose weight average molecular weight is 10ooo or more, and in particular, the higher the siloxane content, the more
Good gas permeability. Furthermore, the second polymer is suitable because it is easy to make a film that can be spread on the water surface and forms a film.

EXAMPLE Hereinafter, an example of the selective gas permeable membrane according to the present invention will be explained from the stage of its manufacture.

Example 1 As a first polymer with excellent gas permeability, poly(1-(trimethylsilyl)-1-propyne) (hereinafter referred to as l'-FM) having a weight average molecular weight of 950,000, which is an acetylene polymer, was used as a first polymer with excellent gas permeability.
S P j) was used.

As a second polymer with excellent gas permeability, we used polydimethylsiloxane-silphenylene copolymer (PS manufactured by Chinoso Corporation), which is a silicone-modified polymer and has a weight average molecular weight of 400,000.
O95) was used. The siloxane content of this copolymer was found to be 92% by elemental analysis.

Next, a first benzene solution containing 1 wt% of the above PMSP and a second benzene solution containing 3 wt% of the above PSO95 were prepared.

Next, the first benzene solution is dropped onto the water surface to reveal an ultra-thin water surface film to form a PMSP thin film (first polymer thin film).
At the same time, drop a second benzene solution onto the water surface,
An ultra-thin water surface spreading film was revealed to obtain a PSO95 thin film (second polymer thin film).

Both membranes developed and exposed on the water surface were coated on a porous support made of polyethersulfone material (Kl-12 manufactured by Toyo Cross ■).
) First, a PMSP thin film is laminated on the surface, and then PSO9
Five thin films were laminated to complete the selective gas permeable membrane shown in FIG.

Therefore, as shown in FIG. 2, the completed selective gas permeable membrane consists of a first polymer membrane (acetylene polymer layer) 2 on a porous support 1, and then a second polymer membrane 3. are stacked in order. Of course, both films 2 and 3 are films formed by the water surface development method.

Next, a module of about 250 cd was fabricated using this membrane, and its membrane properties were measured. As a result of transmitting the atmosphere (oxygen concentration 21%) under a pressure difference of 60 cmHg and room temperature, 2.
Oxygen-enriched air with an oxygen concentration of 32.3% was obtained at a flow rate of 20 l/min. Even after continuous operation for 600 hours, the flow rate remained almost unchanged at 2.11/min, and the oxygen concentration in the obtained oxygen-enriched air was also approximately the same.

Example 2 After obtaining a selective gas permeable membrane in the same manner as in Example 1 except that polytetramethyldisiloxane-ethylene copolymer (PSO93 manufactured by Chinoso Corporation) was used as the second polymer, the module was and investigated its characteristics. The polytetramethyldisiloxane-ethylene copolymer had a siloxane content of 86% and a weight average molecular weight of 10,000.

The initial characteristics of the module are that the flow rate is 2. The oxygen concentration in the oxygen-enriched air was 33.0%. 600
The characteristics of the module after continuous operation for hours are that the flow rate is 1.92.
The oxygen concentration in the oxygen-enriched air was approximately the same.

Example 3 A selective gas permeable membrane was obtained in the same manner as in Example 1 except that poly t-butylacetylene (weight average molecular weight: 450,000) was used as the first polymer, and then it was made into a module and its properties were investigated.

The initial characteristics of the module are that the flow rate is 1.1; l! /min, and the oxygen concentration in the oxygen-enriched air was 36.0%. 5
The characteristics of the module after continuous operation for 00 hours are that the flow rate is 1.
The oxygen concentration in the oxygen-enriched air was approximately the same.

This invention is not limited to the above embodiments. It goes without saying that the first polymer may be an acetylene polymer other than those exemplified above. It goes without saying that the second polymer may also be a silicon-modified polymer other than those exemplified above.

The above example had a composite film structure in which the second polymer thin film was laminated on the first polymer thin film. A composite membrane structure may also be used.

Furthermore, an overcoat may be applied to the surface of the selective gas permeable membrane to improve reliability. Specifically, for example, Japanese Patent Application Laid-Open No. 59-20340 filed by the present inventors
The membrane surface is made hydrophobic as disclosed in Japanese Patent No. 8.

The porous support may also be made of materials other than those exemplified above.

Furthermore, if the support has an asymmetrical shape (asymmetrical membrane structure), the permeability will be even better.

Effects of the Invention As described above, the invention according to claims 1 to 3 has the first,
Since it is composed of a composite membrane of a second polymer, it has both sufficient gas selectivity and gas permeability, and is a high-performance selection that maintains these excellent properties over a long period of time with extremely little change over time. It is a gas permeable membrane.

Since the invention according to claim 2 has a three-layer structure of the porous support, the first thin polymer film, and the second thin polymer film, it is easy to manufacture and exhibit a predetermined performance.

The invention as claimed in claim 3 provides the selectivity of the three-layer structure without impairing the excellent gas permeability of the membrane, since the porous support is an aromatic polysulfone or polyether sulfone support with excellent gas permeability. It is a gas permeable membrane.

According to the fourth aspect of the invention, since the second polymer has a siloxane content of 80% or more and a weight average molecular weight of 10000 or more, it has even better gas permeability.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the change over time in the flow rate of an example of the selective gas permeable membrane according to the present invention and the change over time in the flow rate of a conventional selective gas permeable membrane. A schematic sectional view showing the structure of an example of a gas permeable membrane. FIG. 3 is a schematic sectional view showing an example of a conventional selective gas permeable membrane. 1... Porous support, 2... First polymer thin film, 3
...Second polymer thin film.

Claims (4)

[Claims] (1) A selective gas consisting of a first polymer represented by the following general formula (a) with excellent gas permeability and a second polymer represented by the following general formula (b) with excellent gas permeability. Transparent membrane. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(a) (However, R_1 represents an alkyl group with 1 to 3 carbon atoms or a halogen atom, R_2 is a phenyl group, or a halogen atom with 1 to 3 carbon atoms.)
6 alkyl group or trialkylsilyl group, and the alkyl group of this trialkylsilyl group has 1 to 6 carbon atoms.
It is. R_1 within one molecule may be the same or different, and the same applies to R_2. ) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(b) (However, X represents a silethylene residue or a silphenylene residue, and R_3 and R_4 represent an alkyl group or a phenyl group having 1 to 6 carbon atoms. X in one molecule may be the same or different, and the same applies to R_3 and R_4.) (2) The first polymer and the second polymer are separately formed into thin films by a water surface spreading method, and the first polymer thin film is directly supported on a porous support, and the second polymer is placed on top of the first polymer thin film. The selective gas permeable membrane according to claim 1, comprising laminated polymer thin films. (3) The selective gas permeable membrane according to claim 2, wherein the porous support is aromatic polysulfone or polyethersulfone. (4) The selective gas permeable membrane according to claim 1 or 2, wherein the second polymer has a siloxane content of 80% or more and a weight average molecular weight of 10,000 or more.