JP2813629B2 - Facilitated transport membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a facilitated transport membrane.

[0002]

2. Description of the Related Art As a prior art of a separation membrane, a facilitated transport membrane which holds an affinity substance (carrier) having an interaction with a specific substance on the membrane and selectively transports the substance is known. Facilitated transport membranes have excellent performance of selectively permeating the target substance, but generally have a liquid membrane shape, so it is difficult to maintain stable performance over a long period of time due to solution leakage, drying, etc. there were. Therefore, attempts have been made to gel the facilitated transport membrane and use it for separation. Examples of such a facilitated transport film include, for example, a gel film in which gelatin is coated on the surface of a polymer film, and a plasma polymerized layer of hydroxyethyl methacrylate laminated on the surface of the polymer film, and the polymer layer is allowed to pass through. A membrane swelled with a gaseous carrier aqueous solution (Japanese Patent Publication No. 3-63413) is known. In such a separation membrane having a structure in which a gel layer is laminated on the surface of a polymer film, the gel layer is easily separated from the polymer film of the base film due to swelling and shrinkage of the gel layer. Further, there is a problem that a pinhole is easily generated in the gel layer.
In order to obtain a gel layer without pinholes, it is necessary to increase the thickness of the gel layer, but in this case, there is a problem that the permeability of the substance to be separated is reduced.

[0003]

DISCLOSURE OF THE INVENTION The present invention relates to a facilitated transport film having a gel layer, in which the separation of the hydrogel layer is prevented and the thinned gel layer does not produce pinholes. It is an object to provide a transport membrane.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, the polymer containing an acrylic polymer as a main component is formed in the form of a film or a nonwoven fabric, and the surface is gelled by a hydrolysis reaction. A facilitated transport membrane is provided.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In a facilitated transport membrane (separation membrane) of the present invention, a gel layer having a separation function is composed of a polymer mainly composed of a water-soluble acrylic polymer having a mechanical strength (hereinafter, referred to as a “polymer”). (Also simply referred to as a polymer) or a nonwoven fabric fiber. In this case, the "surface portion of the polymer film or the polymer nonwoven fiber" does not mean a surface portion such as a polymer film or a polymer nonwoven fiber surface coated with another polymer and laminated. Literally means the surface portion of one polymer membrane or polymer non-woven fabric fiber. That is, the gel layer and the support layer are formed of the same polymer chain. Therefore, the polymer in the gel layer forming the surface portion and the polymer constituting the film or the nonwoven fabric fiber other than the surface portion are integrally bonded. For this reason, the gel layer is difficult to peel off. In addition, since the gel layer is formed by denaturing the supporting film, the thickness of the gel layer is small, and a pinhole-less film is easily obtained as compared with the case where the gel is coated. Further, since the gel layer can be easily made thin by controlling the denaturation reaction, a film having high permeability can be obtained.

[0006] The facilitated transport membrane of the present invention can be composed of a polymer membrane whose surface is formed on a gel layer. The polymer gel of the present invention is a polymer gel in which a three-dimensional crosslinked polymer swells in a liquid, and is not limited to only a hydrogel impregnated with water or an aqueous solution. Therefore, a separation membrane having a structure in which an organogel is formed on the surface of a polymer membrane that is insoluble in a certain organic solvent is also included.

In the polymer film used in the present invention, the thickness of the gel layer is not particularly limited.
It is good to be 00 μm, preferably 1 to 100 μm.

The polymer used in the present invention is formed into a film. This membrane is a flat membrane, spiral membrane, tubular membrane,
It can take various known forms such as a hollow fiber membrane. In addition, it can be a polymer film formed by a thermoforming property such as an extrusion molding method, a casting film and a solution-spun film cast in a liquid state on a plate, or a nonwoven fabric formed by heating a roll or a hot press. Can be a polymer film formed by melting the whole by heat and forming an integral film.

The polymer formed in a film form hydrolyzes a nitrile group bonded thereto into a carboxyl group, and absorbs a solution (water, aqueous solution, organic solvent solution). As a result, a polymer film having a gelled surface can be obtained.

[0010] A polymer membrane having a surface portion formed into a hydrogel can be used as a separation membrane for selectively permeating a water-soluble substance. In this case, examples of the water-soluble substance include various substances such as hydrophilic gas, metal ions, various salts, and physiologically active substances. Examples of the hydrophilic gas include water vapor,
CO ₂ , SO ₂ , NO ₂ , NO, CO, H ₂ S, NH ₃
Etc. are included. A polymer membrane having a surface formed of an organogel can be used as a separation membrane that selectively allows an oily substance to permeate. In this case, examples of the oily substance include various substances such as aliphatic hydrocarbons, aromatic hydrocarbons, higher alcohols, silicone oils, animal and vegetable oils, and various polymers.

The facilitated transport membrane of the present invention contains a carrier suitable for the object to be separated in the gel, thereby promoting the permeation of the substance to be separated and improving the separation efficiency. To obtain a gel layer containing a carrier, a method of using a solution containing a carrier as a solution for forming the gel layer, a method of contacting the gel layer with a solution containing the carrier, drying the gel layer, and then drying the carrier For example, a method of absorbing a solution containing the same can be adopted. The amount of the carrier contained in the gel layer is not particularly limited, but is usually 0.01 to 10 mol / kg, preferably 1 to 5 mol / kg in the solution contained in the gel.

As the carrier, for example, a carbon dioxide carrier can be shown. As the carbon dioxide carrier, potassium carbonate, sodium carbonate, cesium carbonate,
Alkali metal carbonates such as rubidium carbonate, alkali metal bicarbonates such as sodium hydrogen carbonate and potassium hydrogen carbonate,
Conventionally known compounds such as sulfites such as potassium sulfite and sodium sulfite, and amines such as ethanolamine, diethanolamine, triethanolamine, propanolamine, dipropanolamine, tripropanolamine, ethylenediamine and ethylenediamine monohydrochloride can be mentioned. In the case of the alkali metal salt described above,
As an auxiliary component, a polydentate ligand which forms a complex with an alkali metal, sodium arsenite, carbonic anhydrase, boric acid and the like can be used in combination. In addition, as a gas carrier, a sulfite such as potassium sulfite or sodium sulfite as an SO ₂ carrier, hemoglobin, CO (II) -Schiff salt as an oxygen carrier, Cu (NH ₄ ) ²⁺ as a carbon monoxide carrier, Cu _(Cl ^{2) 2-}
Water-soluble copper compound to produce a copper complex ions etc., as a carrier of H 2 _S, carbonate salts, and bicarbonate salts. Further, as an example of a metal ion carrier, Co
(II), Cu (II), Ni (II), Zn (II)
, A chelate extraction reagent such as hydroxy oxime and β-diketone, and Cd (II) and Pb (II) as carriers such as di (2-ethylhexyl) phosphate;
Organic phosphorus compounds such as acidic monophosphonic acid monoesters,
Carboxylic acids such as caproic acid and lauric acid, Cr (II)
Examples of the carrier include amines such as Primene JMT and tridodecylamine. In addition, it is possible to use Ag ⁺ as a carrier for ethylene, propylene, benzene, styrene and polyunsaturated fatty acids, organic phosphorus compounds such as trioctylphosphine oxide as an acid carrier, and various conventionally known carriers such as amines. it can. The carriers can also be used as a mixture.

When carbon dioxide is to be separated, the carrier is not limited to those described above, and various compounds having an affinity for carbon dioxide can be used. In particular, alkali metal carbonates and alkali metal bicarbonates are It is suitable because long-term durability of the separation membrane can be expected because of low thermal stability and low vapor pressure. When a carbonate and / or a bicarbonate is used, water is used as a solvent because the solubility of carbon dioxide is high and a high carrier concentration can be obtained. Generally, when the concentration of the carrier in the solution is high, the separation performance and the durability (water retention) tend to be improved.

As the material of the polymer membrane necessary for obtaining the facilitated transport membrane of the present invention, its availability, mechanical strength, ease of forming a gel layer, and the functional group of the gel are carboxyl groups. For this reason, an acrylonitrile polymer is used. Acrylonitrile polymer is a general term for polymers containing acrylonitrile as a polymerization component,
In addition to acrylonitrile homopolymer, copolymers of acrylonitrile and other monomers, graft copolymers of acrylonitrile and other polymers, and mixed polymers containing acrylonitrile-based polymers can be mentioned. The content of acrylonitrile contained in the acrylonitrile-based polymer is at least 5% by weight, preferably at least 30% by weight.
In the present specification, "the polymer is mainly an acrylonitrile-based polymer" means that the polymer is composed of an acrylonitrile-based polymer or the acrylonitrile-based polymer is the first component, that is, the function expression (gelation and mechanical Strength)
Means as the most useful component.

In order to transform the surface portion of such a polymer made of an acrylonitrile-based polymer into a carboxyl group-containing surface and form a gel layer, it is useful to use a method in which this polymer is subjected to alkaline hydrolysis. In this case, the alkali hydrolysis converts the alkali metal hydroxide to 6.5 to 8.5 mol /.
High-concentration alkaline aqueous solution containing 1 l, or 1 mol
0.5 to 5 mol in the coexistence of an electrolyte salt having a concentration of at least
/ L of an alkali metal hydroxide aqueous solution and the polymer. Sodium hydroxide is usually used as the alkali metal hydroxide, and various water-soluble metal salts such as sodium chloride and sodium nitrate are used as the electrolyte metal salt. By such an alkaline hydrolysis treatment, the nitrile group on the surface of the polymer is modified into a carboxyl group, and a gel layer is formed on the surface. The method for forming such a gel layer is described in, for example, Japanese Patent Publication No. 58-10508.

The structure of the polymer film formed in a film shape used in the present invention is not particularly limited, but an asymmetric structure is preferred.
A membrane having an asymmetric structure has advantages such as easy formation of a thin gel layer, high membrane strength, and excellent permeability of a separation target. An asymmetric membrane can be obtained by a phase separation method or the like. The film structure and manufacturing method are described in detail in "Basic of Synthetic Film" (Takeshi Matsuura, Kitami Shobo, 1981). The polymer membrane can take any form such as a flat membrane and a hollow fiber membrane.

The separation membrane of the present invention can be composed of a nonwoven fabric containing acrylonitrile-based polymer fibers whose surface is formed on a gel layer. Such a nonwoven fabric can be a wet nonwoven fabric (synthetic paper) or a dry nonwoven fabric.
In order to manufacture a wet nonwoven fabric, a short polymer fiber having an acrylonitrile polymer as a main component is used as a raw material, which is dispersed in water according to a conventionally known method, formed into a sheet, dried, and bonded. Solidifies into a nonwoven fabric. The nonwoven fabric in this case is a paper having fine through-holes, and is a so-called synthetic fiber. Examples of other fibers contained in the nonwoven fabric include polyolefin-based, polyester-based, polyamide-based, polyvinyl chloride-based, and polystyrene-based polymer fibers. In order to manufacture a dry nonwoven fabric, acrylonitrile-based polymer fibers are used as at least a part of the fiber web as a raw material thereof, and the fiber web is formed into a sheet according to a conventionally known method, and the whole is solidified by adhesion. Into a nonwoven fabric.

Next, the nonwoven fabric is subjected to a treatment for converting a nitrile group contained in the fiber into a carboxyl group, and the solution is absorbed to form a gel layer on the fiber surface. In this case, the nonwoven fabric including the gel layer on the surface thereof has fine pores closed by the gel layer, and is formed as a whole non-permeable. At this time, the air permeability is usually measured by an air permeation flow rate, and is set to 0.1 at a pressure difference of 0.1 kg / cm ² .
It is 1 liter / min · cm ² or less.

In the above-mentioned nonwoven fabric containing a gel layer,
The gel layer can include a carrier.

The nonwoven fabric for obtaining the facilitated transport membrane of the present invention is a nonwoven fabric containing a polymer fiber made of an acrylonitrile polymer. As the acrylonitrile-based polymer fiber, other than a fiber made of a homopolymer of acrylonitrile, a fiber made of an acrylonitrile-based copolymer containing acrylonitrile as a copolymer component, an acrylonitrile homopolymer or an acrylonitrile copolymer and another polymer And the like. The content of acrylonitrile contained in the nonwoven fabric containing the acrylonitrile-based polymer fiber is at least 30% by weight, preferably at least 50% by weight.

In order to transform the surface of the acrylonitrile-based polymer fiber contained in the nonwoven fabric into a gel, the nonwoven fabric fiber is alkali-hydrolyzed. The treatment can be carried out in the same manner as in the treatment of the polymer film. The non-woven fabric containing acrylonitrile-based polymer fibers whose surface has been denatured into a gel is described in detail in Japanese Patent Publication No. 2-2983.

In the separation membrane of the present invention, the gel layer comprises
If necessary, the polymer chains in the gel can be cross-linked to improve the film strength and the durability thereof. As a crosslinking method in this case, a method of adding a crosslinking agent to a solution used for forming a gel layer, an ultraviolet ray, γ
And a method of irradiating an electron beam or an electron beam. As the cross-linking agent, a compound having at least two functional groups reactive with active hydrogen such as ethylene glycol diglycidyl ether can be used.

In practice, the separation membrane needs to be finished in the form of a module. As the module, a hollow fiber module having the highest filling degree of the membrane area is generally used. The present invention is an effective technique in module creation. When preparing a hollow fiber module of the facilitated transport membrane, it is desirable to provide a separation function layer inside the hollow fiber from the viewpoint of protection of the separation function layer and uniformity of gas flow in the module. However, since the inner diameter of the hollow fiber used for separation is generally as small as 1 mm or less, it is difficult to coat the inside of the hollow fiber with a separation functional layer (gel) without a pinhole. ADVANTAGE OF THE INVENTION According to this invention, the hollow fiber module of the facilitated transport membrane which has a gel layer in an inner surface can be obtained easily. To this end, first, a skin layer is provided on the inner surface of the asymmetric hollow fiber membrane, and a leak test is performed on the surface of the hollow fiber to confirm that the polymer membrane has no pinhole. Next, a pinhole-less gel layer can be easily provided by knitting the inner surface of the hollow fiber membrane.

[0024]

Next, the present invention will be described in more detail with reference to examples.

Example 1 An acrylonitrile polymer containing 90 wt% acrylonitrile and 10 wt% methyl acrylate was dissolved in dimethylformamide (DMF) to obtain a polymer solution having a concentration of 20 wt%. Using water as the core liquid and the spinning bath, an asymmetric membrane having a dense layer on the inner surface of the hollow fiber membrane was obtained (ID =
0.4 mm, OD = 0.6 mm). This hollow fiber membrane was processed into a pencil module having an effective length of 10 cm. Next, the inside of the hollow fiber of the module was boiled with 30 wt% KOH for 10 minutes to modify the surface of the acrylonitrile-based polymer membrane by alkali hydrolysis, and then KOH was removed by washing with water and dried. The film obtained as described above was impregnated with a 2 mol / kg aqueous potassium carbonate solution and swelled to obtain a hydrogel film. No gel peeling was observed in the swollen state. As a test gas, a mixed gas of CO ₂ / N ₂ = 10/90 (volume ratio) was used at 25 ° C. under saturated steam at a flow rate of 100.
The solution was supplied to the membrane at a total pressure of 1 atm / ml / min. The pressure on the permeate side of the membrane was reduced, and the permeated gas was analyzed by gas chromatography to calculate the separation coefficient. As a result, the separation factor α
Was 100, and carbon dioxide could be effectively concentrated.

Comparative Example 1 A 5 wt% aqueous solution of a vinyl alcohol acrylic acid copolymer was treated with a polytetrafluoroethylene porous membrane hollow fiber (ID).
= Φ1 mm, OD = φ2 mm) The outer surface was dip-coated, air-dried overnight, and then heat-crosslinked at 120 ° C. for 1 hour. This film was impregnated with a 2 mol / kg aqueous potassium carbonate solution and swelled to obtain a hydrogel film. With swelling, the gel was partially exfoliated, and pinholes were generated. For this reason, test gas was supplied, but carbon dioxide could not be separated.

Example 2 An acrylonitrile-based polymer containing 90 wt% acrylonitrile and 10 wt% methyl acrylate was dissolved in dimethylformamide (DMF) to obtain a polymer solution having a concentration of 20 wt%. Using water as the core liquid and the spinning bath, an asymmetric membrane having a dense layer on the outer surface of the hollow fiber membrane was obtained (ID =
0.4 mm, OD = 0.6 mm). This hollow fiber membrane was processed into a pencil module having an effective length of 10 cm. Next, the outside of the hollow fiber of the module is boiled with 30% KOH for 10 minutes,
After the surface of the acrylonitrile-based polymer film was denatured by alkali hydrolysis, KOH was removed by washing with water and dried. Dodecyl acrylate was immobilized on the OH group by graft polymerization. This polymer layer was impregnated with a 2-bromodecane solution (1.2 mol / l) using n-dodecane as a solvent and gelled. An aqueous sulfuric acid solution containing 260 PPM of Ga is supplied to the supply side, and 2 mol of back-extracted liquid is supplied to the recovery side.
A 1 / l aqueous sulfuric acid solution was supplied. After operating for 2 hours, 80% or more of Ga could be recovered.

Example 3 Nonwoven fabric of acrylonitrile-based polymer gel fiber manufactured by Toyobo (nonwoven fabric in which a nitrile group is converted into a carboxyl group)
(Lanseal A) was impregnated with a 2 mol / kg aqueous solution of calcium carbonate, and then laminated on a polytetrafluoroethylene porous film (FP010, manufactured by Sumitomo Electric Industries, Ltd.) having a pore size of 0.1 μm to form a composite film. The effective membrane area is 9.62 cm ² . Example 1
As a result of evaluating the separation performance in the same manner as described above, the separation coefficient α = 2
30, CO ₂ permeation rate Q = 2 × 10 ⁻⁶ (cm ³ · cm
^-2 sec- ¹ cmHg- ¹ ).

[0029]

The facilitated transport membrane of the present invention is a membrane in which the surface of the polymer membrane or the polymer fiber constituting the membrane is denatured into a gel layer. This gel layer does not peel off due to swelling and shrinkage of the gel, and even if it is a thin layer, pinholes hardly occur. By using the facilitated transport membrane of the present invention, a target substance can be selectively recovered from a mixed gas or a mixed aqueous solution. In particular, by using the facilitated transport membrane of the present invention for recovering carbon dioxide contained in flue gas, the emission of carbon dioxide, which is a global warming gas, into the atmosphere can be suppressed. Therefore, it can be an effective means of global warming countermeasure technology.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makoto Nakabayashi 8th floor of 7th Oriental Maritime Building 2-8-11 Nishi-Shimbashi, Minato-ku, Tokyo Project for fixing CO2 etc. 72) Inventor Kazuhiro Okabe 2-8-11 Nishi-Shimbashi, Minato-ku, Tokyo 8th floor of the 7th Oriental Maritime Building The Institute for Global Environmental Technology, Project Room for CO2 fixation etc. (72) Inventor Kibumi Matsumiya Port of Tokyo 2-8-11 Nishi-Shimbashi-ku, Tokyo The 7th Oriental Maritime Building 8th Floor CO2 fixation project room (72) Inventor Hiroshi Mano 2-8-11 Nishi-Shimbashi, Minato-ku, Tokyo 7th Oriental Maritime Building 8th Floor Research Institute of Innovative Technology for the Earth, CO2 Fixation Project Room (72) Inventor Noriharu Niwa East 2-8-11 Nishi-Shimbashi, Minato-ku, Kyoto 7th Oriental Maritime Building 8th Floor Project Room for CO2 Fixation, etc. (72) Inventor Kenji Haraya 1-1-1 Higashi, Tsukuba-shi, Ibaraki Industrial Technology Examiner Wataru Sugie, National Institute of Materials Science and Technology (56) References JP-A-62-61619 (JP, A) JP-A-57-136903 (JP, A) JP-A-61-82806 (JP, A) JP-A-62-114604 (JP, A) JP-A-6-210145 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B01D 69/00 B01D 53/22 B01D 71/42

Claims (2)

(57) [Claims] 1. A polymer containing an acrylonitrile-based polymer as a main component is formed into a film or a nonwoven fabric, and the surface is modified into a carboxyl group by a hydrolysis reaction.
A facilitated transport membrane characterized by being gelled. 2. The facilitated transport membrane according to claim 1, wherein the gel contains a carrier.