JPS62216623A - Composite membrane for separating gas - Google Patents

Abstract

PURPOSE:To obtain a composite membrane for separating gas excellent in both gas permeability and selectivity by allowing organopolysiloxane having silanol group in a side chain to react with a silane or siloxane crosslinking agent on a supporting membrane. CONSTITUTION:The following polymer shown in a formula is used which has silanol group in an end group of one part of a side chain of polyorganosiloxane having a repeated unit bonded with siloxane in a principal chain. This polysiloxane is allowed to react with a silane crosslinking agent or a siloxane crosslinking agent on a fine porous supporting membrane. As the silane crosslinking agent, acetoxysilane, oxime silane and alkoxysilane, etc., are high in reactivity and therefore preferably used. The siloxane crosslinking agent is a hydrolyzed condensate of these silane crosslinking agents. Polysiloxane coated on the fine porous membrane is preferably regulated to 0.01-5wt%, and the crosslinking agent is regulated to 2-100 times equivalent of the number of silanol group.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention relates to a composite membrane for gas separation having good gas permeability, and more specifically to a composite membrane that is effective for obtaining oxygen-enriched air from air. Minutei! This relates to the llt film.

[Prior Art] Currently, devices that utilize combustion energy, such as home heating appliances, automobile engines, boilers, etc., are operated using air with an oxygen content of about 20% ct.

Now, when oxygen-enriched air with increased oxygen concentration is used in these devices, it is possible to not only increase the combustion efficiency but also significantly raise the combustion temperature.

Now, as a method for obtaining such oxygen-enriched air, a membrane separation method is known in which a pressure difference is created before and after a gas separation membrane and the driving force is used to condense oxygen in the atmosphere. In this membrane separation method, the cost of the oxygen-enriched air obtained is determined by the selectivity and permeability of the gas separation membrane, and therefore the development of gas force@membranes with high selectivity and high permeability is required. .

As such a gas separation membrane, a permselective composite membrane (specially permselective composite membrane) in which a polyorganosilokinane crosslinked with a tetrafunctional or higher functional silane crosslinking agent or a tetrafunctional or higher functional siloxane crosslinking agent forms a polar N membrane on a porous support. 60-257803> is known.

[Problems to be Solved by the Invention] However, the above-mentioned Japanese Patent Application Laid-Open No. 60-257803 discloses that by increasing the thickness of the silicone layer, which is the main component of the S9 film layer, and increasing the gas permeability, the thin film becomes thinner. Pinholes were formed in the layer, resulting in low selectivity, making it impossible to obtain a composite membrane for gas separation that had both sufficiently high gas permeability and selectivity.

An object of the present invention is to solve these problems and provide a composite membrane for gas separation that has both sufficiently high gas permeability and selectivity.

[Means for Solving Problem E] This defense is based on a method in which a comb-shaped organopolysiloxane having a silanol group in its side chain and a silane crosslinking agent (N agent or siloxane 4) are bonded together on a microporous support membrane. The composite membrane for gas direction 1, which is reacted to form a thin film and 1q, has 18 characteristics.

In the present invention, the organopolysiloxane having a silanol group at the end of a side chain is a polymer having a silanol group at the end of a part of the side chain of a polyorganosiloxane having a repeating unit of a siloxane bond in the main chain. It is a polymer whose structural formula is represented by the following formula. 10, but is not limited to the following Mizozo type polymer.

RI R3 R2R4 (However, in the formula, R1 and R2 are methyl group, ethyl group, propyl group, or phenyl'A, R3< is methyl group, ethyl group,
Propyl, R4 is an alkyl group having 2 to 15 carbon atoms or 0!1 (Ql, Q2. Q3 is an integer of 2 to 10), P+P"
= 3, P is an integer of 1 to 3, R1 and R2 in the formula are a methyl group, an ethyl group, a propyl group,
or a phenyl group, among which a methyl group is preferred because it has the best ability to form a thin film.

In the formula, n and m are integers, and n+m is 50 to 3000.

If n+m is less than 50, the thin film formed by the reaction on the microporous support will have many pinballs, which is not preferable. If n+m exceeds 3000,
This is not preferred because the solubility of the polymer in the solvent deteriorates and it is difficult to form a thin film on a microporous support membrane.

- Knee is 0.001 or more and 0.20 or less.

nt... If it is less than 0.001, the reactivity with the silane crosslinking agent or siloxane crosslinking agent is low, making it difficult to form a pinhole-free thin film on the microporous support, which is not preferred. If it exceeds 0.20, the reactivity with the silane crosslinking agent or siloxane crosslinking agent is high and gelation easily occurs, making it impossible to form a 39 membrane on the microporous support membrane, which is not preferable.

An organopolysiloxane having a silanol group represented by the above formula is produced by dissolving a precursor whose side chain ends in a methoxy group in an organic solvent that is immiscible with water, and then mixing the solution with an aqueous solution containing an acid or base. It is obtained by converting a methoxy group into a silanol group using a hydrolysis reaction induced by stirring. At this time, if the concentration of the precursor dissolved in the organic solvent exceeds 20 wt%, the comb-shaped silanol group polyorganosiloxane will gel due to intramolecular condensation or intermolecular condensation when converted to silanol groups in the hydrolysis reaction. This is not desirable because it causes

Silane crosslinking agents include acetoxy silanes, oxime silanes, alkoxy silanes, which are highly reactive with silanol groups,
Examples include alkenyloxy silanes, amide silanes, and amino silanes.

The siloxane crosslinking agent is a hydrolyzed condensate of the above-mentioned silane crosslinking agent.

Regarding the number of functional groups in the silane crosslinking agent and the siloxane crosslinking agent, the more reactive the functional group is, the more reactive the WJW on the microporous support membrane.
This is preferable because it improves formability. Specific examples of such tetrafunctional or higher functional silane crosslinking agents or siloxane crosslinking agents include tetraazetoxysilane, tetradimedyyl Δxime silane, ethyl orthosilicate-1~, propyl orthosilicate, TE1~rakisisopenyl silane, and ethyl polysilicate. , pentadimethyloxime siloxane,
Examples include hexaacedimedyloxime siloxane and hexaace1-xysiloxane.

The microporous support membrane used in the present invention does not provide gas permeation resistance by itself, but functions to support a thin film formed by a reaction, and the size of the pores on the surface is approximately 10 mm. -5000 people, preferably about 10-1000 people. In addition, it is preferable to have an asymmetric structure so that gas permeation resistance is less likely to occur. As for gas permeability,
Nitrogen permeation rate is 10 (m'/7112-hr-at
m) or above are also preferred. Such microporous support membranes include glassy porous materials, sintered metals, ceramics,
Examples include cellulose ester asymmetric membranes, polyethersulfone asymmetric membranes, polysulfone asymmetric membranes, and polyimide asymmetric membranes. Among these, polysulfate asymmetric membranes are preferred because they have sufficient gas permeability and appropriate pore sizes.

The thinner the thin film obtained by reacting an organopolysiloxane having a silanol group at the end of its side chain with a silane crosslinking agent or a siloxane crosslinking agent on a microporous support membrane, the higher the gas permeability. However, if it is too young, pinholes will occur, which will reduce the selectivity of the composite membrane. In the present invention,
HD pinhole-free thin film thickness down to around 0.1μ
It is now possible to reduce If it is made thinner than that, bottle balls will occur and the selectivity of the composite membrane will decrease, which is not preferable.

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

A solution is prepared by dissolving an organopolysiloxane having a silanol group at the end of a side chain and a silane crosslinking agent (C^11 or a siloxane crosslinking agent) in a solvent.The concentration of the organopolysiloxane is 0.01wt% or more and 5°Owt%. The following is preferable.If the concentration is less than o, o'+wt%, it will be difficult to form a pinhole-free thin film, and 5.Qwt
%, it is difficult to increase the thickness of a thin film of less than 1°0 μm, which is not preferable.

Addition of silane and siloxane crosslinking agent should be at least 10 times the number of terminal silanol groups of the polyorganosiloxane.
It is preferable that the amount is 0 times m or less, and addition (2) other than that is not preferable because gelation progresses or the crosslinking rate becomes slow. The ts is added to speed up the crosslinking speed, but dibdeltin diacetate-1-, dibdeltin dioc-1-ate,
Examples include stannous octoate. The solvent must be a non-solvent that does not attack the microporous support membrane, and must be selected depending on the material of the microporous support membrane. For example, when using a polyethersulfone asymmetric membrane or a polysulfone asymmetric membrane as the microporous support membrane, the solvents may be cyclohexane, isopentane, ethyl ether, 1-dichloro-1helifluoroethane, Schiff[1-hexene, n-
Hexene and the like are preferred.

The solvent prepared in this way is then coated on the top of the microporous support, and this coating method can be applied using a roll coater such as a conventional sleeve coater, reverse coater, or gravure coater.
Application methods include coating by dipping, wick coating, spray coating, and the like. At this time, by pre-impregnating the pores of the microporous support membrane with a non-solvent of the solution, such as water or ethylene glycol, it is possible to prevent the solution from impregnating into the pores and to ensure pinhole-free production. This is preferable because a thin film can be formed.

It is preferable that the solvent is dried after application at a temperature that does not cause thermal deformation of the microporous support membrane. Usually 50℃~2
It is 00℃. Also, apply UJ1 barley for 0.5 seconds to 10 seconds.
Preferably, drying for 0.5 seconds to 5 seconds reduces pinholes in the 1q thin film.

In the manner described above, 1 q of composite membranes for gas separation of the present invention can be produced.

The thus obtained composite membrane for gas separation of the present invention is generally used for gas separation to obtain oxygen-enriched air from air, and for separating specific gases such as carbon dioxide, hydrogen, carbon oxide, and helium. However, it is particularly preferable to use it for the separation of oxygen-enriched gases.

[Example] The method of measuring the characteristic value and the method of evaluating the effect of the present invention are as follows.

(1) Gas permeability The selectively permeable composite membrane for gas separation of the present invention is separated, and the pressure on the downstream side is set to 2 atm and the pressure on the downstream side is set to 1 atm. ) The permeation rate was measured with a precision Maki flowmeter 5F-101 (Standard Technology Formal Attire), and this oxygen permeation rate was used as a scale for evaluating gas permeability.

(2) Gas separability The separation coefficient, which is the ratio of the oxygen permeation rate and nitrogen permeation rate determined above, is used as a measure for evaluating gas separability.

The present invention will be explained based on examples.

Example 1 aHtsu CH+ Sh.

A methoxy-modified siloxane represented by (CH2) 2 OH2 Cl-1-OH OH2 (CH2) 3 Si (OCH3) 3 is dissolved in 1 to 1-lichlorofluoroethane and adjusted to 1 wt%.

This was hydrolyzed with a 10 wt% aqueous hydrochloric acid solution to obtain a silanol-modified siloxane solution in which methoxy was changed to silanol.
5'Iru. This solution is roughly diluted with trichlorotrifluoroethane to give a 0.1 wt% solution.

To this solution were added 1 wt % of Te1-roxime silane Q and 0.01 w 1 % of Stanus 2-ethylhexoe-1, and the mixture was thoroughly crushed. Pre-impregnate the hole with water.
This solution was applied to the surface of the polysulfone microporous support membrane with a wet thickness of 25 μm.
Dry with hot air at °C. Once again, wet thickness 20
Apply the solution with μ and dry under the same conditions. The oxygen permeation rate of the composite membrane for gas separation thus obtained was 9 (m'
/1712-br-atm), and the oxygen/nitrogen separation property was 2.1.

Examples 2 to 4 Methoxy-modified siloxanes, which are necessary precursors shown in Table 1, were hydrolyzed in the same manner as in Example 1 to obtain silanol-modified siloxanes corresponding to the precursors. Using the silane crosslinking agent or siloxane crosslinking agent shown in Table 1 in this solution, a composite membrane for gas separation was prepared in the same manner as in Example 1.

The results are shown in Table 1.

Table 1 (1) Middle 2 Oxygen/Nitrogen Separation Factor Table 1 (2) As is clear from the above, the composite membrane for gas separation of the present invention has both high gas permeability and selectivity.

[Effects of the Invention] The present invention provides a gas separation material obtained by reacting an organopolysiloxane having a silanol group at the end of a side chain with a silane crosslinking agent or a siloxane crosslinking agent on the crotch of a microporous support to form a thin film. Since it was a composite membrane, it was possible to achieve the effect of having excellent gas permeability and selectivity.

Claims (1)

[Claims] (1) A composite membrane for gas separation obtained by reacting an organopolysiloxane having a silanol group at the end of a side chain with a silane crosslinking agent or a siloxane crosslinking agent on a microporous support membrane to form a thin film.