JPS6115718A - Composite membrane for gas separation - Google Patents

Abstract

PURPOSE:To obtain a gas separation composite membrane having high separation capacity and showing high and stable permeability over a long period of time, by forming a polymer membrane having a high gas separation property onto a porous support of which the surface openings are sealed by polyorganosilylacetylene. CONSTITUTION:A polymer membrane having a high gas separation property is formed onto the surface of a porous support of which the surface openings are sealed with polyorganosilylacetylene represented by formula. The transmission coefficient of oxygen of polyorganosilylacetylene is 6-8X10<-7>cm<2>(STP)cm/cm. Hg.sec.cm<2> and the MW thereof is 200,000 or more. As the porous support, one comprising polystyrene with a pore size of 50-500Angstrom is used and one, wherein parts as near as possible to the surfaces of fine pores are sealed by the aforementioned polyacetylene, is used. As the polymer having the high gas separation property, poly(4-methylpentene-1) is used and formed into a membrane with a thickness of 0.3mum or less.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a composite membrane for gas separation. More specifically, the present invention relates to a composite membrane for gas separation that is effective for obtaining oxygen-enriched air from air by a membrane separation method.

[Conventional technology]

In recent years, gas separation by demethods, particularly methods for obtaining oxygen-enriched air by membrane separation, have attracted attention. A membrane that can be practically used for this membrane separation must satisfy the conditions of high gas separation performance and high gas permeation performance. Therefore, the form of the membrane is a thin membrane made of membrane material with high gas separation performance.
It is necessary to form a composite membrane on a porous support.

The composite membrane can be produced by a coating method in which a porous support is coated with a coating solution of a membrane material having high gas separation properties, or by polymerizing a reactive monomer using low-temperature plasma to form a thin film on a porous support. Plasma polymerization method to form (low-temperature plasma chemistry (area of chemistry, special edition 1)
11, edited by Keiichi Hozumi)) or a thin film on the water surface that is formed after a dilute solution of a polymer with high gas separation properties is dropped onto the water surface and the solvent evaporates from the dilute solution that spreads on the water/surface. A water surface cleavage method, in which a porous support is supported on a porous support, is known. However, conventionally known porous supports, such as polysulfone porous support membranes, ethyl cellulose porous support membranes, and polypropylene porous support membranes, have low gas permeation resistance, but have pore sizes of about 50 Å or more. Because of their large size, in composite membranes created using the coating method, the coating solution impregnates into the pores, increasing the thickness of the thin film.

In addition, even in composite membranes created by the plasma polymerization method, the polymer obtained at the initial stage of polymerization falls into the pores and then forms a thin film on the porous support, so it is similar to the coating method described above. The drawback was that the film was thick and its gas permeability was low. In addition, composite membranes obtained by the water surface casting method can be made thinner because the thin membrane is supported on a porous support in a solid state, but if the composite membrane is used for a long time, the porous Since the thin film on the support has large pores, it has the drawback that it falls into the pores and breaks, and gas permeation performance deteriorates.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION An object of the present invention is to provide a composite membrane for gas separation which has high gas separation performance and whose high gas permeation performance is stable for a long period of time, in order to eliminate the above-mentioned drawbacks.

[Means for solving problems]

The present invention has the following configuration to achieve the above objective. That is, by polyacetylene whose structural formula is represented by CH3 (n-0 to 2),
This is a composite membrane for gas separation, in which a thin Il@ made of a polymer having high gas separation properties is formed on a porous support whose pore surface openings are closed.

H3 In the present invention, the polyacetylene represented by the structural formula +C-C←1-1s C-8i -CHs (R is (CH2)n C1-13 (n = 0 to 2)) is CI- 1s Cl-13-C:EC-8i-CH5 (R is (CI-
12) It is a product obtained by polymerizing disubstituted acetylene represented by Cl-1s (n-〇~2〉), and as a polymerization catalyst,
It can be obtained by polymerizing by heating at about 50 to 80°C in an inert gas using chloride, NbCl5, or the like. The alkyl group R is preferably n-0 to n-2. n=3
In the above, we will discuss the gas permeability of polyacetylene, especially the oxygen permeability coefficient Po 2 (a+t <STP')・cm, 'c
Since the mHg-sec-al) is low, the gas permeation resistance of the porous support plugged with polyacetylene becomes large, which is not preferable. Polyacetylene having an alkyl group R of 7I-0 to 2 has an oxygen permeability coefficient Po 2 (cJ
(STP)-cm/cml-1g-sec -cffl
) is 6 to Bxio-z, and has a significantly higher gas permeability coefficient than conventionally known polymers, so even if the pores of the porous support are blocked, the This is preferable because it does not significantly increase gas permeation resistance. The molecular weight is
A number average molecular weight of 200,000 or more is preferred. If it is less than 200,000, the film-forming property decreases, and when the openings on the pore surface of the porous support are closed, a film is not formed in the pores, which is not preferable.

In the present invention, the opening portion of the pore surface is closed.
The purpose is to close the portions of the pores penetrating through the porous support that open to the surface, and it is preferable to close the portions as close to the surface of the pores as possible. If the pores are deeply blocked, the gas permeation resistance of the blocked polyacetylene portion increases, which is undesirable. As long as the polyacetylene closes the part close to the surface of the pores, it may cover the porous support thinly, but in this case, the thinner the polyacetylene film covering the porous support, the better the gas permeation. This is preferable because the resistance is small.

The porous support in the present invention is defined as having a pore size of 50
There is no particular limitation as long as the support has a diameter of Å or more and 500 or less. If the pore size is less than 50, the gas permeation resistance will be large, making it undesirable as a porous support for a composite membrane for gas separation. If the number exceeds 500, if the pores are completely blocked with the polyacetylene described above, the polyacetylene will be impregnated deep into the pores, making gas permeation resistance too large, which is not preferable. As porous supports having the above-mentioned pores, ultra-permeable membranes such as polysulfone porous support membranes, ethyl cellulose porous support membranes, and polyacrylonitrile porous support membranes can be used. In this respect, polysulfone porous support membranes are preferred.

The polymer having high gas separation properties in the present invention may be any polymer as long as it has a high gas content (11f) and relatively good gas permeability.
The following polymers are preferred in terms of gas permeability balance.

Vinyl polymers of poly(4-methylpentene-1), polyethylene/propylene technology polymers, and polyvinyltrimethylsilane. The general formula is (however, m is an integer of 1, 2.3, R1 is 10H3, -C
21" 5, - C3 to 1, = 04
1-19, -Cs 1-1u. ), or if the general formula is 1← OC-N l-1-Rs -N
C-0-R4-1-=π-C3H6-1-04 t-
1a-1-CsH+a-1R2 is -02114,0-1
Responsibility C2H40su7, +Cs H6o-y-1+ C4I
”a Orl (Cs Hlo O). ) or whose general formula is 〇=Cl-12, -C2H4-1-C31-1e-1-C
4hl a-1. Here m is 1
An integer of ゜2.3. ) is a typical example of polysulfone, but it is not limited thereto.

Among these, particularly preferred are poly(4methylpentene-1) and polyvinyltrimethylsilane. The thickness of the thin film of the polymer is usually preferably 0.3 μm or less since this does not reduce gas permeation performance.

As long as the film thickness is 0.3 μm or less, the thinner the film is, the more preferable it is. Since a porous support whose pores are closed with the aforementioned boriahytylene, which is a feature of the present invention, is used, there is no possibility that the film will become too thin and lack mechanical strength and break.

□ Next, a method for manufacturing the composite membrane for gas separation of the present invention will be explained.

Prepare a dilute solution of polyacetylene in advance. Good solvents include cyclohexane, toluene, chloroform, carbon tetrachloride, etc., but among these good solvents, it is necessary to select one that does not attack the porous support. For example, if a polysulfone porous support membrane is used as the porous support, cyclohexane, which is a non-solvent for the support membrane, is optimal.

The temperature was adjusted to 0.01 wt% to 1. The porous support membrane is coated with the solution prepared to 0 wt % at a wet thickness of 10 μm to 30 μm; and dried with hot air at 50° C. to 150° C. In this way, a porous support membrane 19 whose pores are plugged with polyacetylene is obtained. The method of the present invention is achieved by coating this porous support membrane with a solution of a polymer having high gas separation properties dissolved in a solvent such as benzene, toluene, xylene, dichloromethane, cyclohexane, cyclohexene, or tetrachloroethane to form a thin film. A composite membrane for gas separation is obtained. At this time, 1 g of polymer having high gas separation property c) 0.01 to 1. Owt%, particularly preferable L<=, 0.03 to 0.5wt% is suitable.

In addition, there is a plasma polymerization method as a method for forming a thin film of a polymer having high gas separation properties. In order to create a composite membrane for gas separation using this method, a thin film is formed by plasma polymerizing a reactive hexamer using a commercially available plasma device on a porous support whose pores are closed with polyacetylene as described above. You can get a lot.

The evaluation criteria for the characteristics used in the present invention are as follows.

(1) Gas permeability and gas separation property The composite membrane for gas separation of the present invention is separated so that the pressure on the next side can be reduced to 2
The pressure on the ATM secondary side was set to 1 atm, and the permeation rate of gas (oxygen or nitrogen) passing through the composite membrane was measured using a precision membrane flow hanger 5F-101 (manufactured by Standard Technology).

The oxygen permeation rate was defined as the gas permeation performance, and the separation coefficient, which is the ratio of the oxygen permeation rate to the nitrogen permeation j* degree, was used as the evaluation standard for the gas separation performance.

(Example) Next, embodiments of the present invention will be described based on Examples.

Example 1 Polysulfone (trade name: P-1700, manufactured by Union Carpaiton 1) was dissolved in dimethylformamide, and 14
Prepare a 1% W solution. Add this solution to polyester 433
Wet thickness of coating liquid on 4ft non-woven fabric 200mm
Coat with μ and immerse in a coagulation bath of water. In this way, a polysulfone porous support membrane is created. As a result of electron microscopic observation, the diameter of the pores opening on the surface was approximately 75. It was bae.

As a catalyst, 20mM of TaCl5 was dissolved in toluene and polymerized at 80°C for 24 hours under a nitrogen atmosphere. The number average molecular weight of the obtained trimethylsilylpropyne was 500,000. This polymer was prepared as a 0.1 wt% solution of cyclohexane, and applied to the polysulfone porous support crotch prepared in advance at a wet thickness of 20 μm as a coating liquid.
It was dried with hot air at 140°C.

Next, poly(4-methylpentene-1) (product name TP
X-MXOO1 (manufactured by Mitsui Petrochemicals, Inc.) was prepared in a 0.1 wt% solution of cyclohexane, and the coating solution was wetted onto a polysulfone porous support membrane whose openings on the pore surface were closed with the previously prepared trimethylsilylpropyne. Thickness 2
A composite membrane for gas separation was prepared by coating at 0μ and drying with hot air at 140°C.

The thickness of poly(4-methylpentene-1) was 0.02μ. Table 1 shows the gas permeation performance of the obtained composite membrane for gas separation.

Comparative Example 1 On the polysulfone porous support membrane prepared in Example 1'c,
A 0.1 wt % solution of 4-phosphorus to the cyclocyclohexane of poly(4-methylpentene-1) prepared in Example 1 was applied to a wet thickness of 20 μm of the coating liquid, and dried with hot air at 140° C. The thickness of poly(4-methylpentene-1) is 0.02 μm when the wet thickness is reduced to 0.02 μm. Table 1 shows the gas permeation performance of the composite membrane for gas separation that was not obtained. Example 1,
Although the coating thickness of poly(4-methylpentene-1) was the same in both Comparative Example 1, high gas separation performance was obtained in Example 1.
l Bamboo power has not been obtained. This shows that the composite membrane for gas separation of the present invention has excellent high gas separation performance and excellent high gas permeation performance.

Table 1 *IQo,: Oxygen permeation rate (m"/1712-hr-
atm ) *2 Qui: Nitrogen permeation rate (Tl+”/
T11'-hr-atm)*3 α: Separation coefficient Example 2 The polysulfone porous support membrane prepared in Example 1 and having pores blocked with trimethylsilylpropyne is prepared. Poly(4-methylpentene-1) was dissolved in cyclohexene to prepare a 0.1 wt% solution. One drop of this solution was dropped on the water surface to form a thin film on the water surface. This thin film
A composite membrane for gas separation is prepared by supporting the polysulfone porous support membrane prepared earlier with the openings on the pore surface closed with trimethylsilylpropyne. The gas permeation performance of this composite membrane for gas separation was measured, and the primary pressure was then adjusted to 10at.
Table 2 shows the measurement results of the gas permeation performance after setting the sample to m and leaving it for -week.

Comparative Example 2 A thin film of poly(4-methylbeni/thene-1) prepared using the same strip 1 as in Example 2 was placed on a polysulfone porous support membrane made using the same strip 1 as in Example 1. A composite membrane for gas separation was prepared by supporting the membrane. The gas permeation performance of this composite membrane for gas valve H was measured, and the gas permeation performance was set at a primary temperature of 10 atm and left for - weeks. Table 1 shows the measurement results of gas permeation performance. As can be seen from Comparative Example 2, the composite membrane for gas separation of the present invention is found to have excellent long-term performance stability.

Table 2 [Effects of the Invention] The composite membrane for gas separation of the present invention has a structural formula of CI-1s ■ TO=Cj7+ (R is (CH2)nCH3H2O-8i
-CI-13 A thin film made of a polymer having a high gas content mt property was formed on a porous support whose pore surface openings were closed with polyacetylene represented by (x=O~2>). , the following excellent effects can be obtained.

(1) Both gas separation performance and gas permeation performance are extremely excellent.

(2) Excellent long-term performance stability.

Patent applicant: Higashishi Co., Ltd. Showa
time

Claims (1)

[Claims] (1) A thin film made of a polymer with high gas separation properties is placed on a porous support whose pore surface openings are closed with polyacetylene whose structural formula is represented by ▲mathematical formula, chemical formula, table, etc.▼ A composite membrane for gas separation formed by