JPS59183804A - Gas permselective composite membrane and its manufacture - Google Patents

Abstract

PURPOSE:To form a gas permselective composite membrane excellent in mechanical characteristics, cost effectiveness, and heat resistance, by combining a polyether-imide as a base material and a silicone compound as a composite component. CONSTITUTION:Polyether-imide of formula I is obtained by polycondensation of phenoxyphenylcarboxylic anhydride with phenylenediamine. A silicone compound of fomula II, where X is an organic group having at least one aromatic ring on its main chain or side chain, is obtained by polycondensation of an organosiloxane with an organic compound having at least one aromatic ring on its main chain or side chain. The polyether-imide is made into a membrane structure with asymmetrical pore diameters and the thin film of the silicone compound having a great gas permeability is laminated on one side having a dense and average pore diameter of the membrane, or further a glow discharge plasma-polymerized thin film is deposited thereon.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a gas-selective permselective composite membrane and a method for producing the same, and more specifically, the present invention relates to a gas-selective permselective composite membrane and a method for producing the same, and more specifically, a polyetherimide asymmetric pore membrane is used as a support and a silicone compound is laminated thereon, or Furthermore, the present invention relates to a gas-selective permselective composite membrane on which a plasma-polymerized thin film of an organosilane compound is deposited, and a method for manufacturing the same.

(Prior art and its problems) In recent years, it has become possible to separate fluid mixtures using selectively permeable membranes instead of energy-consuming processes that involve phase changes such as distillation and deep cooling. It is being actively considered.

Among membrane separation and purification processes for fluid mixtures, the ones that have been put into practical use on an industrial scale are mainly liquid-liquid separation and liquid-solid separation, such as in seawater desalination and industrial wastewater treatment. , little work has been done on gas-gas separation. The reason why membrane separation of gases is difficult to put into practical use is that the permselectivity is low, that is, there is no membrane that selectively passes a specific gas and hardly allows other gases to pass through, making it difficult to obtain a specific gas with high purity. This requires a multi-stage system in which membrane separation is repeated many times, resulting in large equipment, and the low gas permeability makes it difficult to process large amounts of gas.

In particular, when gas selectivity is increased, gas permeability worsens.
When the gas permeability is increased, the permselectivity tends to decrease, and this relationship has not been able to be improved satisfactorily.

Until now, the film forming methods to obtain a satisfactory film are as follows:
A method of pursuing an asymmetrical structure in which the thickness of the active skin layer on the surface is made as thin as possible, which has been studied as a casting process for polymer solutions, and an ultra-thin film corresponding to the active skin layer is manufactured independently and applied to other porous supports. A typical example is a method that attempts to create a composite. Although these are legitimate methods for improving gas permeability, they cannot necessarily be said to provide general practical methods. This is because commercially available polymers or copolymers alone have characteristics in at least one of permselectivity, permeability, heat resistance, chemical resistance, strength, etc., and at the same time at least one of the other properties. This is because the structure of a high molecular weight polymer that satisfies all physical properties cannot be uniquely determined.

Among these, in recent years, there has been a particular desire to develop a material that has excellent mechanical properties and heat resistance and is inexpensive to manufacture, and polysulfone is being considered as a typical example. However, the mechanical properties and heat resistance have not reached a sufficient level.

Furthermore, methods of coating and vulcanizing rubber-based solutions on asymmetric membranes have been studied, but they have various problems such as the complexity of the vulcanization process, reduced reproducibility, and energy costs required for heating. are doing.

(Structure of the Invention) The present inventor has developed polyetherimide, which is different from polysulfone, as a material that has excellent mechanical properties, cost, and heat resistance, and has further developed a rubber-based material to be used as a composite material. On the contrary, we have discovered that we can take a step forward toward this goal by using a silicon compound as a composite material, which has excellent mechanical properties, film-forming properties, and heat resistance, and does not require a vulcanization process. Polyetherimide is obtained by condensation polymerization of phenoxyphenyl dicarboxylic anhydride and phenylene diamine, and its typical structural formula has repeating structural units represented by the following formula.

On the other hand, a silicon compound is obtained by condensation polymerization of an organosiloxane and an organic substance having at least one aromatic ring in the main chain or side chain, and has a repeating structural unit represented by the following formula.

RyR: monovalent functional group m r n i natural number Another feature of the present invention is that polyetherimide, which has a relatively high gas permselectivity but a low permeability, has an asymmetric pore membrane structure, and its asymmetry Alternatively, a thin film of a silicon compound with high gas permeability may be laminated on one surface having a dense average pore size using the method, or a thin film polymerized by glow discharge may be further deposited thereon.

Although polyetherimide has excellent heat resistance, chemical resistance, and architivity, it has a decisive drawback of insufficient gas permeability. In order to overcome these drawbacks, the present inventors either laminated a thin polymer film with high gas permeability made of a silicon compound on polyetherimide of an asymmetric pore size membrane, or created a composite membrane with even higher permselectivity. In order to obtain ultra-thin traps (less than 1 μm), we adopted a method of laminating a polymer thin film of a silicon compound on polyetherimide and then depositing the polymer thin film using a plasma polymerization method under glow discharge. It has been found that it is possible to maintain high permeability by processing 5), and at the same time, it is possible to freely select from a wide range of materials with high gas selective permeability as the material itself used for polymerization.

Another feature of the present invention is that a silicone compound is selected as the material when laminating a highly gas permeable polymer thin film on one surface of a polyetherimide asymmetric pore size membrane having a dense average pore size. In addition to satisfying mechanical properties and heat resistance, the addition of cross-linking agents, which are essential for rubber materials, and the complicated processes of mixing and heat vulcanization, which affect membrane performance and can lead to lack of uniformity in performance, are required. This makes it possible to eliminate many steps.

The polyetherimide used in the present invention is a polymer consisting of repeating units represented by 2 + 2 b+s
[4(3,4-dicarboxyphpuri-2o]oxy)phenyl]propane anhydride obtained by condensation reaction with tometaphenylenediamine, of course the carboxy and phenoxy positions are a + 3'; 4 t4, /; 31
4. / or a mixture thereof. Propane has the most preferred structure of -C(CHa)2-, but other pg -CHg-CHg-CH21-, -CH2-CH-te It is good to have a good atmosphere, and n=1 to 8 among -CnH21 other than propane may also be used.

These polyetherimides can be used in chlorine-based solvents such as trichlorethylene, amide-based solvents such as dimethylformamide, etc.
-Solubility in cyclic nitrogen-containing solvents such as methyl 2-pyrrolidone. Further, since cyclic ethers such as tetrahydrofuran and dioxane exhibit considerable solubility, it is also possible to add a second solvent with a low boiling point to the first solvent with high solubility. Further, the pore diameter of the asymmetric pore membrane can be changed by adding polyhydric alcohol, inorganic salt, etc. as an additive to the first solvent having a large solubility. These additives are sometimes called swelling agents.

Next, use a doctor knife to spread these solutions onto the support plate.
The asymmetric pore size of polyetherimide is achieved by uniformly casting the polyetherimide and then gelling it by immersing it in a non-solvent, usually water, or by partially evaporating the solvent in the cast solution and then gelling it. Obtain a membrane. Of course, it is also possible to create a hollow body using a tubular nozzle.

The properties of an asymmetric pore membrane are affected by the concentration of the solution, the type of solvent, the amount of additives, etc. Generally, the higher the concentration, the higher the selective gas permeability, but the lower the gas permeability. Furthermore, as the amount of additive increases, gas permeability increases, but gas selective permeability decreases. For example, when the average pore diameter is 0.001μ or less, it shows gas selective permselectivity as it is, but sufficiently stable permselective properties can be obtained with 7J, Ir, etc.
However, if the thickness exceeds 0.01μ, selective permeability may be lost.

Therefore, a membrane having stable permselectivity can be obtained by impregnating a different type of polymer solution and further laminating a thin film thereon by plasma polymerization.

When the pore size ranges from 11μ to 0.5μ, it is necessary to increase the coating thickness and concentration of the polymer to make a somewhat thicker film, but it is still possible to laminate the film so that it exhibits gas selective permeability. When the pore diameter range exceeds 0.5μ, it becomes difficult to form a polymer having high gas permeability.

The silicon compound used in the present invention is a polymer consisting of repeating units represented by the structural formula; It may be.

R9R' is, for example, -HI GH3+BeD, -CH
= CH2.

Examples include -CH=CH-CH, -C:CH, and the like. Of course, it may be other than this.

The silicon compounds used in this product include dichloromethane, chloroform, carbon 1 chloride, chlorine solvents such as trichlene, amide solvents such as dimethylacetamide, cyclic ethers such as tetrahydrofuran, aromatic hydrocarbons such as benzene and toluene, methyl ethyl ketone, acetone, etc. Soluble in ketones. Furthermore, since it exhibits solubility in cyclic nitrogen-containing solvents such as N-methyl-2-pyrrolidone, a solvent with high solubility and a solvent with low solubility can be mixed and used.

The viscosity of the solution is adjusted by adjusting the concentration of the solution, the type of solvent, the combination of solvents, etc., and the degree of penetration into the pores of the asymmetric pore membrane can be adjusted.
The actual film thickness can also be changed.

The important point here is that by using such silicon compounds, it is possible to omit the steps such as mastication, addition and mixing of cross-linking agents, vulcanization, and secondary vulcanization, which are essential for rubber-based materials. ° Improve uniformity and reproducibility of performance
This is because we were able to improve.

This is because mastication, addition and mixing of crosslinking agents, vulcanization, and
This is because the process of secondary vulcanization includes elements that are extremely difficult to control precisely.

This will be explained below.

Normally, in silicone rubber, a phenomenon called plasticity recovery occurs due to the filler mixed in to maintain the strength of the rubber compound cross-linking over time.

Rubber that has undergone plastic recovery has significantly reduced solubility in solvents, which has a negative impact on film-forming properties. For this reason, mastication is performed to plasticize it again. However, excessive mastication may lead to molecular chain scission, and at present, the optimal conditions for mastication have not been quantitatively understood.

Next, the optimum amount of the vulcanizing agent to be added varies depending on the solution concentration, coating thickness, etc., which may lead to unvulcanized or overvulcanized states.

If the vulcanizing agent remains in the film, it will cause accelerated deterioration of the film. Therefore, in order to remove the vulcanizing agent remaining in the film, it is necessary to perform secondary vulcanization. Secondary vulcanization is
Generally, vulcanization (primary vulcanization) is performed at a temperature higher than that of vulcanization (primary vulcanization) and takes a long time, which imposes a large burden on production efficiency and energy costs.

Next, the monomer to be plasma polymerized will be explained.

Although it is known that various monomers, such as ethylene and acetylene, undergo plasma polymerization in a glow discharge atmosphere, organosilane compounds are preferably used for the purposes of the present invention.

Examples of organic silane compounds include tetramethylsilane, hexamethyldisilazane, methyldichlorosilane,
Examples include silanes such as methyltrichlorosilane. Furthermore, organic silane compounds having unsaturated bonds, such as trimethylvinylsilane, dimethylvinylchlorosilane, vinyltrichlorosilane, methylvinyldichlorosilane, methyltrivinylsilane, allyltrimethylsilane, and ethynyltrimethylsilane, are more preferably used.

For a gas selectively permeable membrane, not only must the material itself have excellent properties, but the 41 components that govern its permeability must be as thin as possible. The reason for this is as follows. Evaluation of material properties is performed using the unit of gas permeability coefficient: P = cm8-tx/cmz ・sec-crrL
It is expressed using Hg, which is converted into a material thickness of 14 m. On the other hand, in the case of a composite membrane, the permeation rate is expressed in the unit of Q-crn8/crrL2+SeC g due to the thickness of the material itself, and for membrane thicknesses of lOμ and 1μ, even though the permeation coefficient is the same value, the permeation rate is There is a difference of 10 times. Therefore, the properties that are actually required are the permeation rate and the membrane thickness.

In the present invention, after drying the asymmetric pore size membrane of polyetherimide having the pore size range described above, a silicon compound is laminated on the surface of the dense layer, or a plasma polymerized layer is further applied thereon to 1μ or less, preferably 0.8μ or less. Deposit thickness. For example, the pressure within the system is 5 torr or less, preferably 2 t.
The pressure is reduced below orr, a mixed gas of non-polymerizable gas and polymerizable gas is introduced into the system, and a predetermined output, e.g.
When a high-frequency glow discharge is applied to the system at 00 W, preferably about 20 W, the polymerizable gas undergoes plasma polymerization (1) and is deposited as a thin film on the silicon compound layered on the surface of the dense layer of the polyetherimide asymmetric pore membrane. . The thickness of this thin film depends on the length of the glow discharge time or the flow rate f of the polymerizable gas.
Since the thickness increases approximately in proportion to il, the thickness can be adjusted to any desired thickness, for example, 1μ or 0.3μ.

The deposition thickness also increases or decreases depending on the increase or decrease in the output during glow discharge, but these film forming conditions are within a range that can be easily optimized by those familiar with the technology in this field.

In any case, in the present invention, it is necessary to deposit a defect-free uniform polymer film with the above-mentioned thickness.

One criterion for selecting the polymerizable gas is that the plasma-polymerized thin film is an extremely thin layer with a thickness of 1 μm or 0.3 μm or less, so that one component of the gas mixture to be separated is as impermeable as possible. In order to meet this criterion, general plasma-polymerizable monomers such as ethylene and styrene may be used, but a preferred group is the above-mentioned organosilane compounds, especially those containing double or triple bonds. Those having a saturated functional group are more preferred.

The present invention will be further explained below by way of examples.

Example T-1 Polyetherimide Ultem (ULTEM i GE)
A dope solution was prepared by dissolving 20% by weight of N-methyl 2-pyrrolidone in 80% by weight of N-methyl 2-pyrrolidone. This dope solution was cast onto a smooth glass plate with a doctor knife to a thickness of 300 μm, and the glass plate was immersed in distilled water. After the film solidified and peeled off, it was washed with water for 2 hours, and then heated at 4.5°C for 2 hours. After drying through ventilation, a sheet with an asymmetric pore diameter of approximately 170 μm in thickness was obtained.

The polyetherimide asymmetric pore membrane thus obtained was coated with polydimethylsiloxane-bisphenol A carbonate block copolymer (ps).

A solution prepared by dissolving 20% by weight of 99 (manufactured by Chisso Corporation) in 80% by weight of benzene was applied to a thickness of about 100 μm, and the solvent was evaporated and dried at room temperature.

When the gas permeation characteristics of the obtained composite membrane were evaluated, the oxygen permeation rate QO2 = 4. l'x 10-6cm87cm
”,”5ec-z Hg oxygen/nitrogen selective perms α02/
N2=5.1.

Example 2 A composite membrane obtained in exactly the same manner as in Example 1 was subjected to glow discharge in a reaction vessel for 30 minutes at LOW power after trimethylvinylsilane was introduced into the system at a flow rate of 2.0 cm3/min. A plasma polymerized film was deposited on the outermost surface of the composite film. When the gas permeation properties of the three-layer composite membrane obtained in this way were evaluated, Q02=7.0X10-
7cIna/z2・S6(-ffi)(gα02/Ng
=7.9.

Example 3 A solution prepared by dissolving polydimethylsiloxane-bisphenol A carbonate block copolymer (wt%) in 99% carbon tetrachloride was coated on a polyetherimide asymmetric pore membrane by a dipping method, and heated at 120°C/4.0°C. Vulcanized with hot air. When the gas permeation characteristics of the obtained composite membrane were evaluated, QO2=:4. ．． 2X 10-6cm1l
/cml Se(-Cm)(gαOR/N2'=6.5
Met.

Example-4 A composite membrane obtained in exactly the same manner as in Example-3 was subjected to glow discharge in a reaction vessel for 30 minutes at an output of 20 W while trimethylvinylsilane was introduced into the system at a flow rate of 0.7 c7n8/min. , a plasma polymerized film was deposited on the outermost surface of the composite film.

When the gas permeation characteristics of the 8-layer composite membrane obtained in this way were evaluated, it was found that QO2 = 8.7 x 10-7 mj / cmi sec
-CmHgα02/N2 = 7.8.

(Effects of the invention) Polyetherimide, which has excellent mechanical properties, cost, and heat resistance, is used as the material for the support, and a silicon compound that has excellent mechanical properties, film formability, and heat resistance, and does not require a vulcanization process, is used as the material for the support. By using a composite material, it has become possible to stably and uniformly manufacture a film with excellent mechanical properties and heat resistance, and it has also become possible to simplify the manufacturing process and reduce costs.

Furthermore, by using the plasma polymerization method under glow discharge, it has become possible to process ultrathin membranes of 1 μm or less to maintain high permeability and at the same time expand the range of selection of materials that provide high selectivity.

Agent Patent Attorney Tetsu Tsukasa::11. ;j=”
Procedural amendment May 9, 1982 Kazuo Wakasugi, Commissioner of the Japan Patent Office, 1, Indication of the case, Patent Application No. 59572, 1988, 2 Name of the invention: Gas selectively permeable composite membrane and its manufacturing method 3, Amendment. Relationship with the case of the person who filed the patent application Address of the patent applicant 5-15 Kitahama, Higashi-ku, Osaka Name (21
3) President of Sumitomo Electric, Ki Kogyo Co., Ltd. Tetsubu Yojo 4 Agent address: Within Sumitomo Electric Industries Co., Ltd., 1-1-3 Shimaya, Konohana-ku, Osaka (telephone: Osaka 4.6l-1031) Name (7881) Patent attorney Tetsushi Kamidai 6. Contents of the amendment in Detailed Description of the Invention Column 7 in the specification (1) Corrected “chituri” in line 14 of section 20 of the specification to “1 chitsuso” (2) Page 21 of the specification "Weight%" at the beginning of line 12 was corrected to "1% by weight." (3) Specification, page 21, line 14, "120°C/4.0 minutes hot air vulcanization" was changed to "40°C/1
5 minutes warm air drying” and correction procedure amendment date January 7, 1980 Kazuo Wakasugi, Official of the Japan Patent Office 1. Indication of the case 1982 Patent Application No. 59572 2 Title of the invention Gas selectively permeable composite membrane and its Manufacturing method 3, relationship with the case of the person making the amendment Patent applicant address 5-15 Kitahama, Higashi-ku, Osaka Name (21
3) President of Sumitomo Electric Industries, Ltd. Tetsubu 4/Agent Address: Within Sumitomo Electric Industries, Ltd., 1-1-3 Shimaya, Konohana-ku, Osaka (telephone: 461-1031 Osaka) 6 Inventions in the Subject Specification of Kashimasa Detailed explanation column 78 Contents of amendment (1) Insertion of ", plasma resistance" after "...heat resistance" in the 11th line of the 8th volume of the Kansai Specifications (2)
) Insert the following sentence between lines 5 and 6 of page 11 of the specification: ``Also, by having plasma resistance, plasma polymerized thin films can be deposited more stably and with high selectivity. It is also said that it has become possible to obtain a film of (3) Insert the following sentence between lines 7 and 8 on page 15 of the specification: ``However, the solvent or a-mixture solvent must not significantly reduce the strength of the genpoki. must be one of the criteria for selection.'' (4) After the last line F of page 16 of the specification cylinder, ``... will cause φ to occur.'' [Also, mastication,
Although two-component silicone rubber, which is often used as a product that does not require the addition of a vulcanizing agent, has been significantly improved compared to the general silicone rubber mentioned above, processes such as mixing and vulcanization are still required. However, compared to the silicon compound used in the present invention, it is disadvantageous in terms of uniformity of performance, reproducibility, and energy cost. ” (5) Page 22, line 11 of the specification

Claims (8)

[Claims] (1) Gas selective permeability characterized in that the composite membrane consisting of at least two layers has a structure in which the asymmetric pore size membrane shown in (4) below is laminated with the polymer thin film shown in (B) below. Composite membrane. (A) An asymmetric pore membrane comprising a polyetherimide having a dense layer having an average pore diameter of 0.5 μm or less, an average thickness of the dense layer of 10 μm or less, and mainly having repeating units represented by the structural formula: (B) A polymer thin film made of a silicon compound represented by the structural formula; R': an organic group RyR'; a monovalent functional group ffl + n i natural numbers; (2) At least one
2. The gas selectively permeable composite membrane according to claim 1, wherein an organosilane compound containing type 2 or type 3 packing is deposited by plasma polymerization by glow discharge. (3) The organosilane compound has the following structural formula: Rn5iX4-nn, 1-4 R; CH2=CH-, cH=c-. The gas selectively permeable composite membrane according to claim 2, which is a compound represented by CH2=CH-CH2-'XiHrC1*CHBrCH3CH2-. (4) Structural formula; RXi Main chain or side chain has few R, R', monovalent functional group m/n; silicon compound represented by a natural number is converted into polydimethylsiloxane-bisphenol, carbonate 1-floc copolymer, polydimethyl The gas selectively permeable composite membrane according to claim 1, characterized in that it is selected from among siloxane-α-methylstyrene block copolymers. (5) Structural formula: A polyetherimide consisting of a repeating unit represented by;
Prepare a solution containing a solvent and, if necessary, a swelling agent.
i%, contacted with a coagulant, removed the solvent, and dried to obtain an asymmetric pore membrane, in which the ridged layer of the asymmetric pore membrane had a structural formula; Organic groups R, R' having two aromatic rings; -monovalent functional groups m, n'; A solution containing a silicon compound represented by a natural number and a solvent is applied and dried. Claim 1
A method for producing a gas selectively permeable composite membrane as described in . (6) Organosilane compound containing at least one double bond or triple bond as monomer vapor at 5 torr
6. The method for producing a gas selectively permeable composite membrane according to claim 5, wherein the plasma polymerization source tta is deposited on the composite membrane consisting of at least two layers by causing glow discharge while supplying the following atmosphere. (7) Structural formula; Rn-5i -X4-1n; 1 to 1
- R; CHg=CH-, CH3C-. CH2=CH-CH2-. X;, H+ C1r CJ? 8 +CH3-cHz l
Claim 6, characterized in that the organosilane compound represented by
A method for producing a gas selectively permeable composite membrane as described in . (8) applying a solution comprising a polydimethylsiloxane-bisphenol A carbonate block copolymer or a polydimethylsiloxane-α-methylstyrene block copolymer and a solvent to the asymmetric pore membrane dense layer;
6. The method for producing a gas selectively permeable composite membrane according to claim 5, which comprises drying the membrane.