JPH0582252B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a gas separation membrane and a method for manufacturing the same. More specifically, the present invention has a large permeability coefficient and a large separation coefficient, and a combustion equipment,
The present invention relates to a gas separation membrane that is suitably used in fields that require gas separation, such as the food industry, medical equipment, and waste treatment equipment, and a method for efficiently manufacturing the membrane. [Prior Art] Conventionally, various gas separation methods have been known, such as cooling condensation distillation, adsorption separation, and solvent extraction separation, but these methods require a large amount of energy and complexity. There were disadvantages such as the need for specialized equipment. Therefore, in recent years, many attempts have been made to reduce energy consumption by separating this gas using a membrane made of a porous material.
A method for separating gases using a membrane made of such a porous material is, for example, to improve the membrane strength of polyorganosiloxane, which has excellent selective permeability for gases, especially for oxygen molecules. For the purpose of
-64199 Publication, 58-163403 Publication, 58-
14928, etc.), those made from porous polymeric substances, and those using a composite membrane with a thin film on the surface of a porous support (Japanese Patent Publication No. 59-3201, etc.) are known. ing. However, the above-mentioned and the above-mentioned have the drawbacks that the gas permeation performance is not sufficient, and on the other hand, the selectivity is not sufficient. In addition, attempts have been made to impregnate the pores of porous polymeric materials with polyorganosiloxane, but this alone has the problem of low gas permeation performance and insufficient performance for practical use. Ta. On the other hand, a composite membrane for gas separation has been proposed in which a thin layer of metal such as silver is formed on the surface or inside of a polymer membrane (Japanese Unexamined Patent Publication No. 8510/1983). However, in this composite membrane, when air is allowed to permeate, the O ₂ /N ₂ separation coefficient is 1.0 when no thin metal layer is formed, whereas it increases to 3.0. The transmission coefficient is 1.1×10 ^-7 when no thin metal layer is formed, but it is considerably reduced to 7.0×10 ^-9 , and it cannot be said that the transmission coefficient is fully satisfactory. Furthermore, Nafion-Ag, which has silver attached via the sulfone group on the Nafion membrane that has a sulfone group,
Separation of oxygen and nitrogen using a composite membrane has been reported [J. Membrane Sci., Vol. 31, p. 227 (1987)]. However, in this Nafion-Ag composite membrane, the O ₂ /N ₂ separation coefficient is 2.0 when no silver is attached, but although it is significantly increased to 11.0, the permeability coefficient is 11.0 when no silver is attached. 1.0× while the case is 1.5×10 ^-9
It decreased slightly to 10 ^-9 , and the value of the transmission coefficient is not necessarily satisfactory. [Problems to be Solved by the Invention] The present invention overcomes the drawbacks of conventional gas separation membranes, and provides a gas separation membrane that has both a large separation coefficient and a large permeability coefficient, and has excellent selectivity and permeability. The purpose of this invention was to provide a method for efficiently manufacturing this product. [Means for Solving the Problem] As a result of extensive research to achieve the above object, the present inventors provided a thin layer of silver on the surface of a porous base material, and then impregnated this with a siloxane-based polymer. A gas separation membrane with a large separation coefficient and permeability coefficient can be obtained by drying the membrane after drying, or impregnating it with a crosslinkable siloxane polymer and then subjecting it to partial crosslinking. It has been discovered that a gas separation membrane with a further increased permeability coefficient can be obtained by solvent extraction to remove uncrosslinked siloxane-based polymers, and based on this knowledge, the present invention has been completed. That is, the present invention provides a gas separation membrane characterized in that a thin layer of silver is provided on the surface of a porous substrate, and a thin layer of an organosiloxane polymer is formed on the thin layer and on the inner walls of the pores. It provides: According to the invention, this gas separation membrane is produced by providing a thin layer of silver on the surface of a porous substrate, which is then impregnated with a siloxane polymer, and then dried or coated with a crosslinkable siloxane polymer. It can be produced by impregnating it and then subjecting it to a partial crosslinking treatment, or by providing a thin layer of silver on the surface of a porous substrate and then impregnating it with a crosslinkable siloxane polymer. By performing partial crosslinking treatment and further extracting and removing uncrosslinked siloxane polymer using a solvent, the gas separation membrane with a further increased permeability coefficient can be produced. The present invention will be explained in detail below. As the porous base material in the present invention, any material can be selected from conventionally used inorganic and organic materials as long as it has relatively large pores with an average pore diameter of about 0.1 to 10 μm. Can be used. Specific examples of this porous base material include:
Examples include nitrocellulose, cellulose acetate, acrylic polymers, fluororesins, polyolefins, polysulfones, polyethersulfones, vinyl chloride polymers, porous silica, and porous alumina. The average pore diameter of these porous substrates is
If it is less than 0.1 μm, gas permeation performance may be insufficient, and if it exceeds 10 μm, permeation selectivity tends to decrease, which is not preferable. There are no particular restrictions on the form of this porous base material; for example, any form such as a flat membrane, hollow fiber, or tube may be used;
Further, if desired, it may be supported by a porous ceramic support, a porous organic polymer support, a porous metal support, or the like. In the present invention, a thin layer of silver is first provided on the surface of the porous base material, and methods for providing this thin layer of silver include known methods such as vacuum evaporation, ion plating, and sputtering. The law can be used. When forming a thin layer of silver by a vacuum evaporation method, for example, a porous substrate and metallic silver are set in a Perugia type evaporation apparatus, and then the metallic silver is deposited under a sufficient vacuum of about 10 ^-6 torr. The tungsten boat containing the tungsten boat is heated to bring the silver vapor into contact with the surface of the porous substrate, causing silver to precipitate. The thickness of the thin silver layer thus formed can be adjusted as desired by changing the heating temperature and deposition time. The thickness of the thin layer is usually 50 to 5000 Å, preferably 100 to 1000 Å.
Selected within the range of Å. Regarding this thickness, it is important that the thin layer of silver does not block the micropores of the porous substrate. Therefore, when the pore diameter becomes large, the thickness should also be increased in accordance with the pore diameter of the micropores of the porous substrate used. In addition to the above method, a method may also be used in which a thin layer of silver is formed on the substrate by applying silver nitrate and then removing the silver nitrate. Alternatively, a method of applying or impregnating a paste in which fine silver particles are dispersed may be adopted. In these cases, the produced thin layer of silver tends to be thick, so it is preferable to apply the method to a porous substrate with a relatively large pore diameter. In the present invention, after a thin layer of silver is formed on the surface of a porous substrate in this manner, a treatment with a siloxane polymer is performed to further impart separability. Treatment methods using this siloxane-based polymer include (1) a method of impregnating with a siloxane-based polymer and then drying, (2) a method of impregnating with a cross-linkable siloxane-based polymer and then performing a partial cross-linking treatment, and (3) a method of partially cross-linking after impregnating with a cross-linkable siloxane-based polymer. Three methods are used: after impregnating the polymer, a partial crosslinking treatment is performed, and further, an uncrosslinked siloxane polymer is extracted and removed using a solvent. In the method (1) above, siloxane polymers that can exhibit sufficient effects by themselves, such as those with the general formula

[Formula R ¹ and R ² are hydrogen atoms, respectively]
silicone rubber represented by the following (alkyl group having 1 to 4 carbon atoms, phenyl group, vinyl group, etc., where n is a number indicating the degree of polymerization), and the general formula

[C] (R ¹ and R ² in the formula have the same meanings as above,
A is a segment of bisphenol A-type polycarbonate, aliphatic ether, polystyrene, etc.) using an appropriate solvent such as chloroform or n-
After dissolving it in hexane or the like and impregnating the porous material with a thin layer of silver on its surface, a drying process is performed. The impregnation treatment can be performed by commonly used methods such as dipping, spraying, and various coating methods.
In addition, the impregnation may be applied to the entire porous material or only to a desired part, and the impregnation operation may be performed on one side of the porous material (if the porous material is in the form of hollow fibers, , its inner or outer side)
It may be applied from the beginning, or it may be applied from both sides by immersing the entire porous material. The amount of this siloxane-based polymer to be used varies depending on the pore volume of the porous material used and the desired film thickness of the siloxane-based polymer to be formed, and cannot be determined unconditionally, but at least The amount is sufficient to impregnate the inside of the pores over the entire cross section, and is usually selected in the range of 10 to 500 parts by weight, preferably 20 to 250 parts by weight, per 100 parts by weight of the porous material. After impregnating with the siloxane polymer in this way, heat treatment is performed by normal means to evaporate the solvent, and the thin layer of silver provided on the surface of the porous material and the pores are heated. A thin layer of the organosiloxane polymer of desired thickness is formed on the inner wall. On the other hand, in methods (2) and (3) above, a crosslinkable siloxane polymer is used. As this crosslinkable siloxane polymer,
It is possible to use materials that are conventionally used as materials for separation membranes for gases such as oxygen. Such crosslinkable siloxane polymers include, for example, the general formula

[Chemical formula] (Y and Z in the formula are respectively -CH=CH ₂ ,
−NH ₂ , −OH, epoxy group, etc., and R ¹ , R ²
and n have the same meanings as above) Siloxane-based polymers and prepolymers having a functional group represented by the following can be mentioned. This crosslinkable siloxane-based polymer may optionally contain a crosslinking agent such as a bifunctional organic silane compound such as dimethyldichlorosilane or a trifunctional organic silane compound such as methyltrichlorosilane.
Additives such as polymerization accelerators, molecular weight regulators, anti-aging agents, and other polymers may be added. The type and proportion of the functional groups of the crosslinkable siloxane polymer and the type and amount of the crosslinking agent used if necessary can be appropriately selected depending on the desired properties of the gas separation membrane. If the crosslinkable siloxane polymer is in a liquid state, there is no need to use a solvent and it may be impregnated into the porous material as it is, but if it is a highly viscous liquid or solid, it may be diluted with an appropriate solvent. It is desirable to impregnate with The impregnation method and amount of impregnation are the same as in the case of (1) above. The crosslinkable siloxane polymer impregnated in this way may be crosslinked as is if no solvent is used, but if a solvent is used, the solvent is removed by evaporation etc. and then crosslinked. Alternatively, the solvent may be removed after the crosslinking treatment is performed without removing the solvent. As the crosslinking treatment, conventionally used methods such as a heat treatment method and an ultraviolet irradiation method can be used. The conditions for heat treatment depend on the type of crosslinkable siloxane polymer used, the type and amount of crosslinking agent, etc., and cannot be determined unconditionally, but are usually 10 to 150°C, preferably 50 to 100°C.
Usually 1 minute to 2 hours at a temperature in the range of
Preferably by heating for about 10 to 30 minutes,
Crosslinking takes place. In method (2), since extraction treatment with a solvent is not performed after the crosslinking treatment, it is important to impregnate the polymer to an extent that does not block the pores and then perform the crosslinking treatment. In method (3), after the crosslinking treatment, an extraction treatment with a solvent is performed to extract and remove the uncrosslinked siloxane polymer. This extraction treatment further increases the permeability coefficient of the resulting gas separation membrane. In order to perform extraction treatment using such a solvent, the degree of crosslinking in the crosslinking treatment is determined according to JIS K-
20-150 in penetration by 2220, preferably 50-80
It is desirable to adjust it so that it falls within the range of . If the degree of crosslinking is less than 20 in terms of penetration, the uncrosslinked siloxane polymer in the crosslinked product will not be effectively extracted and removed during extraction with a solvent, and an increase in the permeability coefficient cannot be expected. When it exceeds 150, most of the crosslinked product is extracted in the extraction process, and as a result, the selectivity of the gas molecule membrane may decrease. Examples of solvents used in this extraction process include aliphatic hydrocarbons such as hexane, heptane, and octane, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, benzene, toluene,
Aromatic hydrocarbons such as xylene, carbon tetrachloride, halogenated hydrocarbons such as dichloromethane, trichloroethane, tetrachloroethane, trichloroethylene, chlorobenzene, tetrahydrofuran,
Examples include cyclic ethers such as dioxane, but among these, aromatic hydrocarbons are preferred, and benzene, toluene, and xylene are particularly preferred. The conditions for the solvent extraction treatment vary depending on the type of crosslinked siloxane polymer and solvent used, and cannot be unconditionally determined, but usually 20
~150℃, preferably 50~100℃, usually 1 minute to 1 hour, preferably 10~100℃
The process will take about 30 minutes. After the solvent extraction process is performed in this manner, a washing process may be further performed using the above-mentioned solvent or the like, if desired. The remaining solvent can be dried by a conventional drying method, such as a heating drying method, a hot air drying method, a reduced pressure drying method, etc., to obtain a desired gas separation membrane. The gas separation membrane produced in this way is
As shown in the enlarged cross-sectional view of the surface of the figure, a thin silver layer 2 is formed on the surface of a porous substrate 1, and a thin layer of organosiloxane polymer is formed on the thin layer 2 and on the inner walls of the pores 3. It has a structure in which a layer 4 is provided, has large permeability coefficients and separation coefficients, is excellent in gas permeation performance and permeation selectivity, and has high membrane strength. This gas separation membrane may be used as it is without using a support, or may be supported on a support as described above, or may be supported on the support during the manufacturing process. can. Also,
The gas separation membrane may be used alone as it is, or two or more types may be stacked to form a multilayer structure as desired. [Examples] Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way. (Example 1) Silver was deposited by vacuum evaporation on the surface of a nitrocellulose porous membrane with a pore size of 0.3 μm, and the thickness was
A thin layer of silver of 250 Å was formed. Next, this was impregnated with a silicone rubber/chloroform solution and then dried to produce a gas separation membrane. Using the obtained gas separation membrane, the pressure was 1 Kg/cm ² ,
Air permeation tests were conducted at a temperature of 20°C. As a result, the permeability coefficient P=2.1×10 ^-8 cc・cm/cm ²・sec・cm
Hg, separation coefficient (O ₂ /N ₂ ) α = 3.3. In addition, as silicone rubber,

A compound having the structure [chemical formula] and a molecular weight of 30,000 was used. (Comparative Example 1) Comparative Example 1 was carried out in the same manner as in Example 1 except that the silicone rubber layer was not formed. As a result, P=6.0×10 ^-3 cc·cm/cm ² ·sec·cmHg, α=1.0. (Comparative Example 2) Comparative Example 2 was carried out in exactly the same manner as in Example 1, except that the thin layer of silver was not formed. As a result, P=2.2×10 ^-8 cc·cm/cm ² ·sec·cmHg, α=2.0. (Example 2) After vacuum-depositing silver on a nitrocellulose porous membrane with a pore size of 1.0 μm to form a thin layer of silver with a thickness of 300 Å, a liquid organosiloxane compound A was deposited.
(contains -SiH bond in molecule) and liquid organosiloxane compound B (contains -CH=CH ₂ bond in molecule)
A gas separation membrane was prepared by impregnating the membrane with a liquid composition in which the functional group molar ratio was 1:1, and heating the mixture at 70° C. for 2 hours to perform a crosslinking treatment. A permeation test similar to that in Example 1 was conducted using this membrane, and the results were as follows: P=2.2×10 ⁻⁸ cc·cm/cm ² ·sec·cmHg, α=4.0. (Comparative Example 3) The same procedure as in Example 2 was carried out except that the thin layer of silver was not formed in Example 2. As a result, P=2.6×10 ^-8 cc·cm/cm ² ·sec·cmHg, α=1.9. (Example 3) After vacuum-depositing silver on a polyethersulfone porous membrane with a pore size of 0.8 μm to provide a thin layer of silver with a thickness of 200 Å, a liquid organosiloxane compound C was applied.
(Contains an epoxy group at the end) and liquid organosiloxane compound D (Contains an amino group at the end) in a liquid composition in which the molar ratio of the functional groups is 1:1. A gas separation membrane was produced by performing crosslinking treatment by heating for a period of time. A permeation test similar to that in Example 1 was conducted using this membrane, and the results were as follows: P=1.8×10 ⁻⁸ cc·cm/cm ² ·sec·cmHg, α=3.7. (Comparative Example 4) The same procedure as in Example 3 was carried out except that the thin layer of the organosiloxane polymer was not formed in Example 3. As a result, P=1.9×10 ^-2 cc·cm/cm ² ·sec·cmHg, α=1.0. (Example 4) After vacuum-depositing silver on a polysulfone porous membrane with a pore size of 0.8 μm to form a thin layer of silver with a thickness of 350 Å, a chloroform solution of an organosiloxane-based polymer-bisphenol A type polycarbonate block copolymer was applied. A gas separation membrane was prepared by impregnating and drying the membrane. A permeation test similar to that in Example 1 was conducted using this membrane, and the results were as follows: P=2.3×10 ⁻⁸ cc·cm/cm ² ·sec·cmHg, α=3.0. (Comparative Example 5) The same procedure as in Example 4 was carried out except that the thin layer of the organosiloxane polymer was not formed in Example 4. As a result, P=2.2×10 ⁻² cc·cm/cm ² ·sec·cmHg, α=1.0. (Example 5) Silver was vacuum-deposited on a glass fiber filter with a pore size of 0.65 μm to form a thin layer of silver with a thickness of 350 Å, and then liquid organosiloxane compound A and liquid organosiloxane compound B were added to this layer with functional group moles. The ratio is 1:
impregnated with a liquid composition mixed so as to be 1,
A gas separation membrane was produced by heating at 70°C for 2 hours to perform crosslinking treatment. A permeation test similar to that in Example 1 was conducted using this membrane, and the results were as follows: P=1.8×10 ⁻⁸ cc·cm/cm ² ·sec·cmHg, α=3.1. (Comparative Example 6) The same procedure as in Example 5 was carried out except that the thin layer of silver was not formed. As a result, P=2.2×10 ^-8 cc·cm/cm ² ·sec·cmHg, α=2.0. (Example 6) A membrane obtained in the same manner as in Example 2 was immersed in toluene, heated at 90°C for 30 minutes to extract uncrosslinked substances, and then dried to produce a gas separation membrane. did. A permeation test similar to that in Example 1 was conducted using this membrane, and the results were as follows: P=1.3×10 ^-6 cc·cm/cm ² ·sec·cmHg, α=2.9. (Example 7) An acrylic porous membrane with a pore size of 0.8 μm,
After vacuum-depositing silver to form a thin silver film with a thickness of 250 Å, liquid organosiloxane compound A and liquid organosiloxane compound B were mixed in a molar ratio of functional groups of 1:
impregnated with a liquid composition mixed so as to be 1,
A gas separation membrane was produced by heating at 70°C for 2 hours to perform crosslinking treatment. A permeation test similar to that in Example 1 was conducted using this membrane, and the results were as follows: P=2.4×10 ⁻⁸ cc·cm/cm ² ·sec·cmHg, α=4.1. (Example 8) A membrane obtained in the same manner as in Example 7 was immersed in toluene and heated at 90°C for 30 minutes to extract the uncrosslinked organosiloxane polymer, thereby producing a gas separation membrane. . A permeation test similar to that in Example 1 was carried out using this membrane, and the results were as follows: P=2.3×10 ^-6 cc·cm/cm ² ·sec·cmHg, α=2.8. (Comparative Example 6) The same procedure as in Example 8 was carried out except that the thin silver layer was not formed in Example 8.
As a result, P=4.3×10 ⁻⁶ cc·cm/cm ² ·sec·cmHg, α=1.9. (Example 9) A paste in which fine silver particles were dispersed in toluene was applied to a nitrocellulose porous membrane with a pore size of 3.0 μm to a thickness of 0.1 μm, and dried.
Next, this is converted into liquid organosiloxane compound A.
and liquid organosiloxane compound B in a functional group molar ratio of 1:1, and then heated to 70° C. for 2 hours for crosslinking treatment to produce a gas separation membrane. A permeation test similar to that in Example 1 was conducted using this membrane, and the results were as follows: P=1.0×10 ⁻⁸ cc·cm/cm ² ·sec·cmHg, α=4.0. (Example 10) A paste in which fine silver particles were dispersed in toluene was applied to a nitrocellulose porous membrane with a pore size of 5.0 μm to a thickness of 0.3 μm, and dried.
Next, this is converted into liquid organosiloxane compound A.
and liquid organosiloxane compound B in a functional group molar ratio of 1:1, and then heated to 70° C. for 2 hours for crosslinking treatment to produce a gas separation membrane. A permeation test similar to that in Example 1 was conducted using this membrane, and the results were as follows: P=1.2×10 ⁻⁸ cc·cm/cm ² ·sec·cmHg, α=4.1. (Example 11) A membrane obtained in the same manner as in Example 9 was immersed in toluene, heated at 90°C for 30 minutes to extract uncrosslinked substances, and then dried to form a gas separation membrane. was created. Example 1 using this membrane
As a result of conducting a transmission test similar to the above, P=1.0×10 ^-6 cc·cm/cm ² ·sec·cmHg, α=2.5. (Example 12) A membrane obtained in the same manner as in Example 10 was immersed in toluene, heated at 90°C for 30 minutes to extract uncrosslinked substances, and then dried to form a gas separation membrane. was created. A permeation test similar to that in Example 1 was carried out using this membrane, and the results were as follows: P=3.4×10 ^-6 cc·cm/cm ² ·sec·cmHg, α=2.7. [Effects of the Invention] The gas separation membrane of the present invention has a thin layer of silver on the surface of a porous substrate, and furthermore, a thin layer of organosiloxane polymer is formed on the inner wall of the pores, thereby increasing the permeability coefficient. It maintains the current highest level (silicone-based material) and has a significantly improved separation coefficient of 3.0 to 4.5, and has excellent gas permeability and selection performance, and is suitable for use in combustion equipment, for example.
Suitable for use in fields that require gas separation, such as the food industry, medical equipment, and waste treatment equipment.

[Brief explanation of the drawing]

FIG. 1 is an enlarged surface view of one example of the gas separation membrane of the present invention, in which reference numeral 1 is a porous base material, 2 is a thin layer of silver, 3 is a pore, and 4 is an organosiloxane polymer. It is a thin layer.

Claims (1)

[Scope of Claims] 1. A gas characterized in that a thin layer of silver is provided on the surface of a porous substrate, and a thin layer of an organosiloxane polymer is formed on the thin layer and on the inner walls of the pores. Separation membrane. 2. Providing a thin layer of silver on the surface of a porous substrate, then impregnating it with a siloxane-based polymer and drying it, or impregnating it with a cross-linkable siloxane-based polymer and then performing a partial cross-linking process. A method for producing a gas separation membrane according to claim 1, characterized in that: 3 A thin layer of silver is provided on the surface of the porous substrate, and then a crosslinkable siloxane polymer is impregnated into the thin layer, followed by partial crosslinking treatment, and the uncrosslinked siloxane polymer is extracted and removed using a solvent. The method for producing a gas separation membrane according to claim 1, characterized in that: