JPS60257803A - Permselective composite membrane - Google Patents

Abstract

PURPOSE:To provide a permselective composite membrane having no pinhole and excellent in gas permeability, by forming polyorganosiloxane crosslinked by tetrafunctional or more silane and siloxane crosslinking agents into an extremely thin membrane. CONSTITUTION:Tetrafunctional or more condensed type silane and siloxane crosslinking agents reacting the terminal silanol group of polyorganosiloxane, for example, tetraacetoxysilane or ethyl polysilicate, polyorganosiloxane and a catalyst such as dibutyltin diacetate are dissolved in a non-aqueous solution to prepare a dilute solution. This dilute solution is thinly and uniformly applied onto a porous support and the coated support is heated and dried to obtain a composite membrane.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a permselective composite membrane.

More specifically, the present invention relates to a permselective composite membrane that is effective for obtaining oxygen-enriched air from air by membrane separation.

[Prior Art] In recent years, methods of obtaining oxygen-enriched air from air by gas separation by demethods, particularly membrane separation, have been attracting attention. What membranes can be practically used for this membrane separation?

Since the condition of high gas permeability must be met, a membrane material with gas separation properties was made into a thin film on a porous support. It is necessary to take the form of a composite membrane. Polyorganosiloxane, which has excellent gas permeability, has attracted attention as a material for this membrane, and studies on thinning the membrane have been conducted, for example, in Japanese Patent Publication No. 59-320.
As shown in No. 1, various methods have been developed, including polyorganosiloxane.

By itself, it is extremely poor in forming a thin film, and it is extremely difficult to form an extremely thin film without pin holes. For this reason, it was copolymerized with rigid polymers such as styrene, polycarbonate, and silphenylene. Polyorganosiloxane copolymers are known. However, since the gas permeability of the rigid polymer is extremely low, the gas permeability of the copolymer is also lower than that of polyorganosiloxane homopolymers. Yes, it is cross-linked with a trifunctional or less cross-linking agent, which has been known up to now as a cross-linking type.
Oh, 7. . Burnt 7 Oh, □ Oh, 8 ゛The disadvantage of permselective composite membranes is that because the crosslinking speed is slow, polyorganosiloxane agglomerates when thinning the membrane, making it difficult to obtain an ultra-thin membrane without pinholes. was there.

[Problem that the invention seeks to solve]

An object of the present invention is to eliminate the above-mentioned drawbacks and provide a composite membrane with particularly excellent gas permeability/selectivity.

[Failure to solve the problem]

In order to achieve the above object, the present invention has the following configuration, namely:
This is a permselective composite membrane formed by forming an extremely thin film of bo-1 organone loxane crosslinked on a tetrafunctional or higher functional silane and a siloxane crosslinking agent on a porous support.

In the present invention. The porous support A may be anything that supports a thin film, such as Oro paper, non-woven fabric 2 synthetic paper, etc. r:1
Paper, cloth, wire mesh, R-filter membrane, ultra-R-filter membrane, etc. can be used, but among these, ultra-F5 membrane is preferable because smoothness of the surface and smaller pores are preferable for reinforcement. Specific examples of ultrafiltration membranes include polysulfone porous support membranes, polyethersulfone porous support membranes, polypropylene porous support membranes, and polyfluoroethylene porous support membranes. The shapes of these porous supports A include sheet, tubular, and fibrous shapes, but are not particularly limited.

The term "tetrafunctional or higher functional silane and siloxane crosslinking agent" in the present invention refers to a tetrafunctional or higher functional condensed silane and siloxane crosslinking agent that reacts with the terminal silanol group of polyorganosiloxane. Among these, the types of silane crosslinking agents include alkoxy silanes typified by tetraacetoxy 7rane, oxime silanes typified by tetradimethyl oxy/mushilan, ethyl orne silica-1-, and propyl orthosilicate. Alkoxy silane,
Alkenyloxy-based silanes and amide-based silanes, such as detrakisisopropenyloxysilane.

These include amino-based silanes. Preferred are ace).oxy-based silanes, ogynom-based silanes, alkoxy-based silanes, and alkenyloxy-based silanes because of their high crosslinking speeds. Among them, particularly preferred are tetra-a-toxosilane, tetra-sidimethyloxysilane, and ethyl ortho-silica=1.
It is. In addition, as a tetrafunctional or higher functional nosiloxane crosslinking agent,
Cohydrolysis condensates of trifunctional silanes and tetrafunctional silanes, partial hydrolysis condensates of each tetrafunctional silane, cohydrolysis condensates of trifunctional silanes and tri-functional plans, and cohydrolysis condensates of trifunctional silanes and tetrafunctional solanes. There are tetrafunctional or higher functional condensates produced by hydrolysis of polyfunctional silanes, such as co-hydrolyzed condensates.

Among these, preferred are cohydrolyzed condensates of trifunctional silanes and tetrafunctional silanes, and partial hydrolyzed condensates of various tetrafunctional silanes. Other siloxanes are not preferred due to their slow crosslinking speeds. Preferred specific siloxane crosslinking agents include:

Ethyl polysilicate, pentadimethyloxime siloxane, hexadimethyloxime soloxane.

Examples include hexane-toxysiloxane.

In addition, the composition ratio of the silane crosslinking agent and the polyorganosiloxane is also important;
Twice the number of moles of silane crosslinker is used. If the amount of the silane crosslinking agent is less than equimolar to the silanol groups, it is not preferable because the reaction becomes extremely slow, occurs only partially, or unreacted silanol groups remain. Also.

When the number of moles exceeds 20 times, the curing reaction becomes slow and unnecessary crosslinking agent remains, which is not preferable for forming a thin film.

The polyorganonoloxane in the present invention is at least 50 mo1% or more of the number of end groups, preferably 80 mo1% or more of the number of end groups.
o 1% or more, more preferably a polymer in which all terminal groups are silanol groups. 50 mo1% of the number of end groups
When less than 7 ranol groups are present, the crosslinking rate decreases significantly due to the presence of uncrosslinked polyorganosiloxane, resulting in poor thin film forming properties and is unsophisticated.

The molecular weight of polyorganosiloxane is i, oo.

300,000 or more, preferably 10,000 or more
-100,000 or less is desirable. Molecular weight is 1,0
If it is less than 00, the crosslinking density is too high and it becomes brittle.

This is not a good opportunity because it is difficult to obtain an ultra-thin film without pinholes. If the molecular weight exceeds 300,000, it is not preferable because thin film forming properties are significantly impaired due to a decrease in crosslinking density and crosslinking rate.

The chemical structure of polyorgan and nosiloxane is shown by the 9th formula.

R2 (However, R1 and R2 are -OH3, -C!2H5, -N
H2゜--C! H = selected from 0H2-06H5)
However, preferred is -OH for both R and R2.

Other substituents are not preferred because they have low gas permeability and poor thin film forming properties.

The thickness of the ultra-thin film is preferably 0.01 μm or more and 1.0 μm or less. If the film thickness is less than 0.001 μm, pinholes are likely to occur, which is not preferable. Moreover, if the film thickness exceeds 11.0 μm, the gas permeability of the composite film will be significantly reduced, which is not preferable.

In the method for producing a permselective composite membrane of the present invention, an ultrathin crosslinked membrane of polyorganosiloxane crosslinked with a tetrafunctional or higher functional silane and a siloxane crosslinking agent is formed on a porous support as follows. Namely.

and tetrafunctional or higher functional silane and siloxane crosslinking agents.

Polyorganosiloxane and catalyst are dissolved in a non-aqueous solution to form a dilute solution. A method is adopted in which this dilute solution is thinly and uniformly applied onto a porous support and then heated and dried to form a composite film. At this time, depending on the type of crosslinking agent, the crosslinking reaction may proceed even without a catalyst, but since it is almost impossible to increase the crosslinking rate, a catalyst is essential. The catalyst selected at this time is

Diptyltin diacetate, Diptyltin dioctoate,
Examples include stanas ethylhexoate.

Further, the solvent used here not only dissolves the silane crosslinking agent, polyorganosiloxane, catalyst, etc., but also desirably does not attack the surface of the porous support. These solvents include hexane, cyclohexane, dioxane,
Pentane, ether.

Examples include chloroform, Freon, and hexamethyldisiloxane. The concentration of the dilute solution is preferably 0.001 to 5.0% by weight. If the concentration is less than 0.01% by weight, it becomes very difficult to form an extremely thin film without pinholes.

In addition, if it exceeds 50% by weight, it is difficult to obtain a uniform ultra-thin film of 0.5μ or less:
i□1, which is not preferable.

Note that the evaluation criteria for characteristics in the present invention are as follows.

(1) Gas permeability, gas separation properties Across the composite membrane, set the pressure on the downstream side to 2 atm and the pressure on the secondary side to 1 atm, and measure the permeation rate of gas (oxygen or nitrogen) that has passed through the composite membrane. Precision membrane flowmeter 5y-101 (
(manufactured by Standard Technology). The oxygen permeation rate is considered gas permeation performance.

The separation coefficient, which is the ratio of oxygen permeation rate to nitrogen permeation rate, was used as an evaluation criterion for gas separation performance.

〔Example〕

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

Example 1 Polydimethylsiloxane with silanol groups at both ends (
95 parts by weight of number average molecular weight of approximately 50,000), 0.4 parts by weight of ethyl orthosilicate, and 01 parts by weight of S31f7.2-ethylhexoate were dissolved in cyclohexane to obtain a solid content of 0.5.
Adjust to % by weight. This dilute solution was coated on a polysulfone porous support, dried by heating at 120° C. for 1 minute, and then dried at room temperature for 10 minutes to obtain a composite membrane. Note that the film thickness of polydimethylsiloxane was approximately 0.1 μm. Table 1 shows the membrane performance of the obtained composite membrane. It is clear from Table 1 that the gas permeability is very good.

Example 2 A composite membrane was obtained in the same manner as in Example 1 except that ethyl polysilicate was used in the same amount instead of ethyl orthosilicate. Note that the film thickness of polydimethylsiloxane was 01 μm. Table 1 shows the membrane performance of the obtained composite membrane.

Example 6 Polydimethyl 70xane with 7ranol groups at both ends (
95 parts by weight (number average molecular weight approximately 50,000), 0.4 parts by weight of tetradimethyloxime silane, 01 parts by weight of dibutyltin diacetate
Dissolve part by weight in cyclohexane, solid content 0.5% by weight
Prepare to. This dilute solution was coated on a polysulfone porous support, dried by heating at 120° C. for 1 minute, and then dried at room temperature for 10 minutes to obtain a composite membrane. Note that the film thickness of polydimethylsiloxane was 0.1 μm. Table 1 shows the membrane performance of the obtained composite membrane.

Example 4 A composite membrane was obtained in the same manner as in Example B except that the same amount of tetraacetoxysilane was used instead of tetradimethyloximsilane. Note that the film thickness of polydimethylsiloxane was 01 μm. Table 1 shows the membrane performance of the obtained composite membrane. It can be seen that, like Example 1, Examples 2 to 4 also have very excellent gas permeation performance.

Comparative Example 1 Polyorganosiloxane phenylene copolymer ps0
95 (copolymerization ratio of silphenylene/dimethylsiloxane manufactured by Chisso Co., Ltd. -115, number average molecular weight of about 300,000) was dissolved in cyclohexane.

0.01% by weight. This diluted solution was coated on a polysulfone porous support, dried by heating at 120° C. for 1 minute, and then dried at room temperature for 10 minutes to obtain a composite membrane. Note that the film thickness of the polyorganosiloxane phenylene copolymer was 01 μm.

Table 1 shows the membrane performance of the obtained composite membrane. It can be seen that the gas separation performance of this composite membrane is at the same level as Examples 1 to 4, but the gas permeability is considerably low.

Comparative Example 2 95 parts by weight of polydimethylsiloxane, 04 parts by weight of methyltrioxime silane, dibutyltin dioxane) x -1-
Dissolve 0.1 part by weight of W4 in chlorohexane.

The solid content was adjusted to 05% by weight. This diluted solution.

Coated onto polysulfone porous support.

After drying by heating at 120° C. for 1 minute, drying was performed at room temperature for 10 minutes to obtain a composite membrane. Note that the film thickness of polydimethylsiloxane was 0.4 μm. Table 1 shows the membrane performance of the obtained composite membrane. Also in the case of Example 1 using a tetrafunctional silane crosslinking agent
It is clear that the gas permeability is considerably lower compared to ~4.

Comparative Examples 3 and 4 Comparative Examples 3 and 4 were obtained by using the same amounts of vinyltrioxy'/mushilan and methyl i-lyacetoxysilane as silane crosslinking agents in Comparative Example 2 and Comparative Examples 4, respectively, to obtain composite membranes under the same conditions. The film thickness of polydimethylsiloxane was 0 to 71 in both cases. Table 1 shows the membrane performance of the obtained composite membrane.
Shown below. From Table 1.

It is clear that Comparative Example No. 4 also has low gas permeability.

Table 1 *1) θo2- Oxygen permeation rate ('m7rr+21qr
-atm) *2) θN2- Nitrogen permeation rate (〃) *6) α - Separation coefficient [Effects of the invention] The permselective composite membrane of the present invention is capable of reducing polyorganosiloxane by using a tetrafunctional or higher functional silane and a siloxane crosslinking agent. Since the crosslinking reaction is completed quickly, a crosslinked thin film of polyorganosiloxane is formed on the porous support without pinholes. This material has very good gas permeability.

In addition, the crosslinking density is improved compared to films obtained with less than three functional groups, and the mechanical strength is also excellent.

Furthermore, because the ultra-thin film is made of silicone.

The resulting composite membrane has excellent long-term durability including four-heat resistance, cold resistance, lil' weather resistance, etc., and has great practical advantages.

Patent applicant Higashi Shi Co., Ltd. Procedural amendments Manabu Shiga, Commissioner of the Japan Patent Office 1, Indication of the case: 1982 Patent Application No. I: 1' 31165 2, Name of the invention: Selectively permeable composite membrane 3, Amendment Relationship with the case filed by the person who filed the patent application Daisaku Office 2-2-5 Nihonbashi Muromachi, Chuo-ku, Tokyo Number of inventions increased by the amendment None 6, 1 claim of the specification subject to the amendment Column 7 of ``Detailed Description of the Invention'', Contents of the Amendment in the Specification <1) The scope of the claims is amended as shown in the attached sheet.

(2) On page 3, line 6, "and" is corrected to "crosslinking agent or tetrafunctional or higher functional".

(3) Page 3, line 6 Delete "top".

(4) Page 3, lines 9 and 18 Delete "A".

(5) On page 4, line 1, ``and'' is corrected to read [crosslinking agent or tetrafunctional or higher functional].

(6) The 4th line of the 4th sentence, “and”, is corrected to read “crosslinking agent or condensed type with four or more functional functions.”

(7) Page 4, line 5 "Silane" is supplemented with [tetrafunctional or higher functional silane 1].

(8) Page 4, lines 16-17 ryh5, 1-f) Lt□, tsu>, l? j”
j-f-uhhhhh, patyloxime silane,” he corrected.

(9) Page 5, line 1 Correct "and" to "or".

(10) On page 5, line 8, "siloxane" is corrected to "siloxane with four or more functional functions."

11) On page 5, lines 12, 14, and 15, "silane" is corrected to "silane with four or more functional functions."

(12) Page 5, line 17 ``Does it happen?'' is corrected as ``Does gelation occur?''.

(13) On page 7, line 15, ``and'' is corrected to read ``one crosslinking agent or tetrafunctional or more functional.''

(14) On page 7, lines 15 and 18, ``and'' is corrected to [crosslinking agent or tetrafunctional or higher functional].

(15) Page 8, line 7, [Stannas ethylhexoate] is corrected to ``Stannas 2-ethylhexoate.''

(16) On page 14, line 3, "and" is corrected to "crosslinking agent or tetrafunctional or higher functional".

(17) Page 5, line 7 Correct "Siloxane J" with "Siloxane Crosslinker J".

Attachment Claim 1 Porous support 1-, a tetrafunctional or more dinone crosslinking agent J
A permselective composite membrane formed by poly(A-kanosyloquiline) crosslinked with a penta- or tetrafunctional or more functional siloxane crosslinking agent to form a membrane. ”

Claims (1)

[Claims] A permselective composite membrane formed by forming an ultrathin membrane of polyorganosiloxane crosslinked with a tetrafunctional or higher functional silane and a siwaxane crosslinking agent on a porous support.