JP2017087180A - Gas separation membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly practical gas separation membrane formed faultless and extremely thin on a porous support and excellent in a permeation constant for COand olefin.SOLUTION: A gas separation membrane for separating COand olefin comprises a porous support, and an oligosaccharide layer formed on the porous support. Said oligosaccharide is chemically modified by at least one of the functional groups composed of an amide group, an imide group, an imino group, a urea group, a carbonate group, an urethane group, a sulfonyl group and an ester group.SELECTED DRAWING: Figure 1

Description

The present invention relates to a gas separation membrane that exhibits excellent separation performance for CO ₂ , olefins and the like.

  Gas separation / concentration by a gas separation membrane is an energy-efficient, energy-saving and highly safe method as compared with a distillation method, a high-pressure adsorption method, or the like. Examples of pioneering practical examples include gas separation and concentration using a gas separation membrane, and hydrogen separation in an ammonia production process. Recently, a method for removing and recovering carbon dioxide, which is a greenhouse gas, from synthesis gas, natural gas, and the like by using a gas separation membrane has been actively studied (see Patent Documents 1, 2, and 3). ).

A general form of the gas separation membrane is one in which a separation layer is formed on the surface of a porous support. This form is effective for giving a large amount of gas permeation while giving the film some strength. The separation layer in this case refers to a layer composed only of a gas separating polymer.
In general, the performance of a gas separation membrane is expressed using a permeation rate and a separation coefficient as indices. The transmission speed is expressed by the following formula:
(Permeability coefficient of gas separating polymer) / (Thickness of separation layer)
Represented by As is clear from the above formula, in order to obtain a membrane having a high permeation rate, it is necessary to make the thickness of the separation layer as thin as possible. The separation factor is expressed as a ratio of the permeation speeds of the two gases to be separated, and is a value depending on the material of the gas separating polymer.

  From the above, in order to obtain practical performance as a gas separation membrane, it is necessary to make the thickness of the separation layer as thin as possible without any defects, and studies are actively conducted (Patent Documents 4 and 5, etc.). reference). As is clear from the above equation, the higher the gas permeability coefficient, the greater the permeation speed. That is, it is important to reduce the film thickness to the limit with a material having a large transmission coefficient and separation coefficient. This is because the gas separation membrane is ideally superior as the permeation rate / separation factor increases and becomes an efficient membrane process. The separation factor is represented by the ratio of the permeation speeds of the two gases to be separated, and is a value depending on the material of the gas separating polymer.

International Publication No. 2014/157069 JP 2011-161387 A Japanese Patent Laid-Open No. 9-898 Japanese Patent No. 5,507,079 Japanese Patent No. 5019502

  However, in the prior art, it has been difficult to form an extremely thin separation layer on the surface of the porous support without defects. The reason for this is that the formation of a uniform thin film on the surface of the porous support is hindered by the gas separating polymer entering the support. As a result, the gas separation performance is lowered (reduction in separation coefficient and reduction in permeation rate). Further, even if a separation layer having an extremely thin film thickness can be formed, a satisfactory transmission rate cannot be obtained if the gas separation polymer has a low permeability coefficient.

  From such a background, the present invention is intended to provide a gas separation membrane having high practicality by forming a separation layer having an extremely thin film thickness without any defects on a porous support and increasing the permeability coefficient. It was set as a problem to be solved by the invention. That is, if this problem can be achieved, it is possible to obtain a high transmission speed without defects. In order to solve this problem, intensive studies were conducted.

  In order to solve the above-mentioned problems, the present inventors have intensively studied. As a result, it has been found that a gas separation membrane having a structure formed from an oligosaccharide having a cross-linked structure on a porous support solves the above-mentioned problems, and the present invention has been made based on this finding. is there.

That is, the present invention is as follows.
[1] A gas separation membrane having at least a porous support and an oligosaccharide layer formed on the porous support, the oligosaccharide being an amide group, an imide group, an imino group, a urea group, a carbonate group The following specific wave number regions that are chemically modified with at least one functional group selected from the group consisting of a urethane group, a sulfonyl group, and an ester group, and the functional group has infrared absorption: an amide group, an imide group, or Imino group (1,700 cm ^{−1 to} 1,500 cm ⁻¹ ); urea group, carbonate group or urethane group (1,850 cm ^{−1 to} 1,650 cm ⁻¹ ); sulfonyl group (1,350 cm ^{−1 to} 1,300 cm) ^-1); ester group ^{(1,300cm -1 ~1,000cm} -1); and the peak absorbance a of the functional groups in, 1000 cm ^-1 ~ And a peak absorbance B oxygen bond, - carbon having an absorption at a wavenumber region of 100 cm ^-1
(Absorbance A) / (Absorbance B) = 0.05 or more and 5 or less, It is the said gas separation membrane characterized by the above-mentioned.
[2] The gas separation membrane according to [1], wherein the oligosaccharide layer includes at least a group selected from the group consisting of an amino group, an aldehyde group, a hydroxyl group, and a carboxyl group.
[3] The gas separation membrane according to [1] or [2], wherein the oligosaccharide is oligoglucosamine.
[4] The supply gas flow rate is 190 cc / min, the permeation gas flow rate is 50 cc / min, and the permeation rate of CO ₂ gas measured at 30 ° C. by an isobaric method in a humidified atmosphere is in the range of 1 GPU to 1000 GPU, In addition, the gas separation membrane according to any one of [1] to [3], wherein a CO ₂ / N ₂ separation coefficient α is in a range of 20 or more and 100 or less.
[5] The gas separation according to any one of [1] to [4], wherein the oligosaccharide layer contains a metal salt containing one or more metal atoms selected from the group consisting of Ag and Cu. It is a membrane.
[6] Using a mixed gas composed of 40% by mass of propane and 60% by mass of propylene, the supply-side gas flow rate was 190 cc / min, the permeate-side gas flow rate was 50 cc / min, and the measurement was performed at 30 ° C. in a humidified atmosphere by an isobaric method. The gas separation membrane according to [5], wherein a propylene gas permeation rate is 15 GPU to 1,500 GPU and a propylene / propane separation coefficient α is in a range of 50 to 1000.
[7] The method for producing a gas separation membrane according to any one of [1] to [6], wherein the following steps:
A step of producing a coating solution by mixing an aqueous solution in which an oligosaccharide is dissolved and an aqueous solution in which a crosslinking agent is dissolved at a temperature equal to or higher than room temperature;
Applying the obtained coating solution to the surface of the porous support;
The method is characterized by comprising:
[8] The method according to [7], wherein the surface of the porous support has pores having a pore diameter of 10 nm to 100 nm.

According to the present invention, it is possible to provide a gas separation membrane that exhibits a high permeation rate and a high separation performance with respect to CO ₂ , olefin, and the like.

It is a scanning electron microscope (SEM) image image | photographed about the gas separation membrane obtained in the example 2 of an analysis. It is a scanning electron microscope (SEM) image image | photographed about the gas separation membrane obtained in the analysis example 3. FIG. It is a reflection type infrared spectroscopy (IR-ATR) chart of the gas separation membrane obtained by analysis examples 4-6. 8 is a reflection infrared spectroscopy (IR-ATR) chart of a gas separation membrane obtained in Analysis Example 7.

Hereinafter, the present invention will be described in detail focusing on preferred forms thereof.
The gas separation membrane in the present embodiment includes a porous support and an oligosaccharide layer disposed on the porous support, and the oligosaccharide layer has a cross-linked structure.

[Porous support]
The porous support in the gas separation membrane of the present embodiment is a support made of a membrane having many fine holes penetrating the front and back of the membrane. This porous support has substantially no gas separation performance, but can give mechanical strength to the gas separation membrane of this embodiment. The shape may be, for example, a hollow fiber shape or a flat membrane shape.
The material of the porous support is not limited. From the viewpoint of chemical resistance and solvent resistance, polysulfone, polyether sulfone, PVDF, PTFE and the like are preferable; from the viewpoint of heat resistance, homopolymers or copolymers such as polyimide, polybenzoxazole and polybenzimidazole are preferable. One of these alone or a mixture thereof is preferred.
The average pore diameter of the porous support is preferably 1 nm or more and 1,000 nm or less, preferably 1 nm or more and 100 nm or less from the viewpoint of sufficiently ensuring both permeability and mechanical strength and adjusting the separation factor to an appropriate range. Is more preferable.
The film thickness of the porous support is preferably 5 μm or more and 200 μm or less from the viewpoint of achieving a good balance between mechanical strength and permeability.

When the porous support has a hollow fiber shape, the outer diameter is preferably 0.3 mm or more and 3 mm or less, and more preferably 0.5 mm or more and 1.5 mm or less. This is because if the outer diameter of the hollow fiber membrane is too small, problems such as difficulty in handling the hollow fiber occur when producing the hollow fiber membrane module; conversely, if the outer diameter of the hollow fiber membrane is too large. This is because the number of hollow fiber membranes that can be inserted into a cylindrical container of the same size is reduced, causing problems such as a reduction in filtration area.
The inner diameter of the hollow fiber-like porous support is preferably 0.05 mm or more and 1 mm or less, and more preferably 0.1 mm or more and 0.5 mm or less. This causes problems such as pressure loss and increased raw material costs if the hollow fiber inner diameter is too small; conversely, if the hollow fiber membrane inner diameter is too large, the membrane may break due to operating pressure. This is because.

These average pore diameter, film thickness, and outer shape and inner diameter of the hollow fiber can be adjusted to a desired range by controlling the production conditions of the porous support.
Only one hollow fiber-like porous support may be used, or a plurality of hollow supports may be used together. In the case of using a plurality of hollow fiber-like porous supports together, the number used is preferably 10 or more and 100,000 or less, more preferably 10,000 or more and 50,000 or less. preferable.

[Oligosaccharide layer]
The oligosaccharide layer imparts practical gas separation performance to the gas separation membrane of this embodiment. This oligosaccharide layer has a crosslinked structure.
Examples of such oligosaccharides include oligoglucose, oligomannose, oligogalactose, oligoglucosamine, oligogalactosamine and the like.
The oligosaccharide here refers to those having 100 or less repeating units.
In the case where the oligosaccharide layer is formed from oligoglucosamine or oligogalactosamine, it is particularly preferable in that it has many amino groups capable of coordinating with a metal salt optionally added in a subsequent step.
The cross-linked structure in the oligosaccharide layer is a group consisting of a structure having an amide group, a structure having an imide group, a structure having an imino group, a structure having a urea group, a pyridinium group, a structure having a sulfone group, and a structure having an ester group. It is preferable from the point of easiness in manufacture to include one or more types of structures selected from:
The thickness of the oligosaccharide layer is preferably 0.01 μm or more and 5 μm or less, more preferably 0.01 μm or more and 3 μm or less, from the viewpoint of achieving a good balance between gas separation performance and permeability. More preferably, the thickness is 0.01 μm to 1 μm. This is because if the oligosaccharide layer is too thick, high permeability that is important in terms of practicality cannot be obtained.

Presence of a crosslinked structure in the oligosaccharide layer includes, for example, infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), solid nuclear magnetic resonance analysis (solid NMR), time-of-flight secondary ion mass spectrometry (TOF-SIMS), etc. Can be confirmed.
For example, in the case of infrared spectroscopy, an amide group, an imide group or an imino group has a wave number of 1,700 cm ^{−1 to} 1,500 cm ⁻¹ , and a urea group, carbonate group or urethane group has a wave number of 1,850 cm ^{−. In} the region of ^{1 to} 1,650 cm ⁻¹ , in the case of pyridinium group, in the region of wave number 1,700 cm ^{−1 to} 1,500 cm ⁻¹ , in the case of sulfone group, the wave number of 1,350 cm ^{−1 to} 1,300 cm ⁻¹ . In the case of an ester group, the region has absorption in the region of 1,300 cm ^{−1 to} 1,000 cm ⁻¹ .

Therefore, the existence and type of the crosslinked structure can be known from these peaks.
When an oligosaccharide having an amino group is used, it is preferable that the oligosaccharide layer has a cross-linking structure as described above and a part of the amino group derived from the oligosaccharide as a raw material remains. By having an amino group in the oligosaccharide layer, coordination with a metal salt that is optionally added in a later step is facilitated, and the resulting gas separation membrane is preferably applied to, for example, separation of olefin and paraffin. Will be able to.

The presence of the amino group in the oligosaccharide layer can be confirmed by, for example, infrared spectroscopy. Since the amino group has infrared absorption in a region having a wave number of 3,500 cm ^{−1 to} 3,000 cm ⁻¹ , the presence or absence of the amino group can be confirmed by examining the peak in this region.

  The abundance ratio between the oligosaccharide and the crosslinking agent in the oligosaccharide of the gas separation membrane of the present embodiment is evaluated by a functional group ratio defined as a ratio of the absorbance derived from the crosslinked structure in the infrared spectroscopic analysis to the absorbance derived from the oligosaccharide. be able to. The oligosaccharide layer in the gas separation membrane of this embodiment preferably has a functional group ratio of 0.05 or more and 2 or less, and more preferably 0.1 or more and 1 or less. If the functional group ratio is too low, crosslinking does not occur sufficiently, and there is a problem that practical gas separation performance cannot be obtained. Moreover, even if the functional group ratio is too high, there arises a problem that practical gas separation performance cannot be obtained.

Oligosaccharides having the infrared spectroscopic analysis, the wave number region of 1,100cm ^-1 ~1,000cm ^-1, the absorption attributable to C-O bonds. In the case of an amide group, an imide group or an imino group, the cross-linked structure has a wave number of 1,700 cm ^{−1 to} 1,500 cm ⁻¹ , and a urea group, carbonate group or urethane group has a wave number of 1,850 cm ⁻¹ to 1. , 650 cm ⁻¹ , in the case of pyridinium group, in the region of wave number 1,700 cm ^{−1 to} 1,500 cm ⁻¹ , in the case of sulfone group, in the region of wave number 1,350 cm ^{−1 to} 1,300 cm ⁻¹ , In the case of an ester group, it has absorption in the region of 1300 cm ^{−1 to} 1,000 cm ⁻¹ .

The oligosaccharide layer in the present embodiment may contain a metal salt. As a metal salt,
A metal ion selected from the group consisting of monovalent silver and monovalent copper, or a complex ion thereof;
An anion selected from the group consisting of F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , CN ⁻ , NO ₃ ⁻ , SCN ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , BF ₄ ⁻ , and PF ₆ ^−. The metal salt is preferably constituted.

  The concentration of the metal salt in the oligosaccharide layer is preferably 10% by mass to 70% by mass, more preferably 30% by mass to 70% by mass, and still more preferably 50% by mass to 70% by mass. This is because if the metal salt concentration is too low, highly practical gas separation performance cannot be obtained.

[Performance of gas separation membrane]
The gas separation membrane in this embodiment can be suitably used for separating CO ₂ from a CO ₂ / N ₂ mixed gas, for example. Specifically, the permeation rate Q of CO ₂ gas measured at 30 ° C. by a constant pressure type in a humidified atmosphere is 1 GPU to 100 GPU, with a supply side gas flow rate of 190 cc / min and a permeation side gas flow rate of 50 cc / min. , CO ₂ / N ₂ separation factor α is 20 or more and 100 or less. The permeation rate Q of the CO ₂ gas is preferably 5 GPU to 100 GPU, more preferably 10 GPU to 100 GPU. The separation factor α of CO ₂ / N ₂ is preferably 30 or more and 100 or less, and more preferably 40 or more and 100 or less.

  Furthermore, the gas separation membrane of the embodiment containing a metal salt in the oligosaccharide layer can be suitably used for separation of olefin and alkane. Specifically, for example, a mixed gas composed of 40% by mass of propane and 60% by mass of propylene is used, the supply side gas flow rate is 190 cc / min, the permeation side gas flow rate is 50 cc / min, and is 30 ° C. by an isobaric method in a humidified atmosphere. The propylene gas permeation rate Q measured in (1) is 15 GPU or more and 1,500 GPU or less, and the propylene / propane separation factor α is 50 or more and 1,000 or less. The permeation rate Q of propylene gas is preferably 50 GPU or more and 1,500 GPU or less, and more preferably 100 GPU or more and 1,500 GPU or less. The separation factor α of propylene / propane is preferably 100 or more and 1,000 or less, and more preferably 150 or more and 1,000 or less. These values should be measured under conditions of a propylene partial pressure of 1 atm or less, specifically 0.6 atm.

[Method for producing gas separation membrane]
Next, the manufacturing method of the gas separation membrane of this embodiment is demonstrated.
The gas separation membrane of the present embodiment was obtained by a step of producing a porous support, a step of reacting an oligosaccharide with a crosslinking agent to produce an aqueous solution containing a crosslinked oligosaccharide (crosslinked oligosaccharide aqueous solution), and The method includes a step of applying a crosslinked oligosaccharide aqueous solution to the surface of a porous support, and a step of allowing the porous support after the contact to stand and drying the coating solution.

(Method for producing porous support)
First, the manufacturing method of the porous support body preferably used for this embodiment is described.
The porous support can be obtained by a non-solvent induced phase separation method or a thermally induced phase separation method.
Below, the case where the hollow fiber membrane of a polyether sulfone is manufactured by the non-solvent induced phase separation method is demonstrated.
First, polyethersulfone (PES) is dissolved in a solvent to prepare a PES solution. The molecular weight of PES used in the present embodiment is preferably 2,000 or more and 100,000 or less, more preferably 10,000 or more and 50,000, as the number average molecular weight in terms of polystyrene measured by size exclusion chromatography. It is as follows. If the molecular weight is too low, it may cause problems such as not showing high practical durability; conversely, if the molecular weight is too large, the production of the porous support becomes difficult. This is because it may cause
In the present embodiment, the concentration of PES in the PES solution is preferably 15% by mass or more and 50% by mass or less, and more preferably 25% by mass or more and 40% by mass or less. If the concentration of PES is too low, it may cause problems such as not exhibiting high practical durability; conversely, if the concentration of PES is too high, the production of the porous support becomes difficult. This is because problems such as

  As the solvent of the PES solution, for example, a good solvent such as N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, dimethylsulfoxide; a poor solvent such as glycerin, ethylene glycol, triethylene glycol, polyethylene glycol, or the like is used. The mass ratio of good solvent / poor solvent in the PES solution is from 97/3 to 40 / in consideration of improving stability when the PES solution is used as a spinning dope, making it easy to obtain a homogeneous membrane structure, and the like. 60 is preferable.

  Next, spinning is performed using the PES solution obtained above as a spinning dope. The PES solution is discharged from the outer slit of the double tubular nozzle, and the core liquid is discharged from the center hole. The core liquid uses a fluid that is inert with respect to the PES solution that is the spinning dope. The inert fluid is a fluid that does not coagulate the spinning stock solution and is immiscible with the spinning stock solution, and may be either liquid or gas.

  Examples of the inert liquid include nonane, decane, undecane, dodecane, liquid paraffin, and isopropyl myristate. Examples of the inert gas include nitrogen and argon. When a fluid inert to the spinning dope is used as the core liquid, the hollow fiber membrane structure is easy to take a uniform structure, and the membrane structure easily changes due to the influence of surface tension during drying. be able to. The discharge amount of the core liquid is preferably 0.1 times or more and 10 times or less, more preferably 0.2 times or more and 8 times or less with respect to the discharge amount of the PES solution that is the spinning dope. By appropriately controlling the discharge amount of the core liquid and the discharge amount of the PES solution that is the spinning raw solution within the above range, a porous support having a preferable shape can be produced.

The spinning dope discharged from the nozzle is passed through the aerial traveling section, and then immersed in a coagulation tub to cause coagulation and phase separation to form a hollow fiber membrane. As the coagulation liquid in the coagulation layer, for example, water can be used.
The wet hollow fiber membrane pulled up from the coagulation tub is washed with a washing tub in order to remove the solvent and the like, and then dried through a dryer.
As described above, a hollow fiber-shaped porous support can be obtained.
Only one hollow fiber-like porous support may be used for the next step, or a plurality of hollow supports may be used for the next step.

  The porous support thus obtained is then reacted with an aqueous solution containing a crosslinked oligosaccharide (crosslinked oligosaccharide aqueous solution) by reacting the oligosaccharide with a crosslinking agent. The contact operation may be repeated a plurality of times. A drying step (solvent removal step) may optionally be provided after the contact operation.

Hereinafter, the production process of the coating liquid containing the crosslinked oligosaccharide, the contact with the crosslinked oligosaccharide aqueous solution, the drying process optionally performed thereafter, and the standing process will be described sequentially.
(Process for producing a crosslinked oligosaccharide aqueous solution)
The cross-linked oligosaccharide can be obtained by reacting the cross-linking agent with the oligosaccharide.
The modifying agent is at least one selected from the group consisting of an acid halogen group, a carboxylic anhydride group, an aldehyde group, a ketone group, and an isocyanate group as a reactive group capable of reacting with an amino group or a hydroxyl group in an oligosaccharide. It is a compound which has these groups. The cross-linking agent is preferably an aliphatic or aromatic compound having two or more groups selected from these groups in one molecule. Two or more reactive groups present in one molecule may be the same as or different from each other.

  Examples of the crosslinking agent in the present embodiment include, for example, aromatic acid halides such as trimesic acid halide, isophthalic acid halide, terephthalic acid halide, and trimethic acid halide; 1,2,3,4-butanetetracarboxylic dianhydride Aliphatic carboxylic anhydrides such as products; aromatic isocyanates such as toluene diisocyanate; aromatic aldehydes such as terephthalaldehyde and isophthalaldehyde; aliphatic aldehydes such as glutaraldehyde and malondialdehyde; aliphatic ketones such as 2,5-hexadione And vinyl sulfones such as VS-B and VS-C (manufactured by Fuji Film Fine Chemical); These crosslinking agents may be used alone or in combination of two or more.

Examples of the oligosaccharide include oligoglucose, oligomannose, oligogalactose, oligoglucosamine, oligogalactosamine and the like.
When the oligosaccharide is oligoglucosamine or oligogalactosamine, it is particularly preferable in that it has many amino groups capable of reacting with the modifying agent.

  The reaction may contain an organic solvent in a range of 80% by mass or less based on the total amount of the solvent. Examples of the organic solvent used here include alcohols such as methanol, ethanol, and propanol; polar solvents such as acetonitolyl, acetone, dioxane, and tetrahydrofuran; These organic solvents may be used alone or in combination of two or more.

  In the reaction, the concentration of the modifier and the oligosaccharide is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 5% by mass or less. When the concentration of the modifier and the oligosaccharide is 0.1% by mass or more, the reaction proceeds sufficiently.

A surfactant may be added to the reaction solution. The surfactant should be a nonionic surfactant from the viewpoint of not electrostatically repelling with the crosslinking agent and the oligosaccharide, and being uniformly dissolved in any of acidic, neutral, and basic aqueous solutions. Is preferred. Examples of the nonionic surfactant include a long-chain fatty acid ester of polyoxyethylene, a fluorine surfactant having a perfluoro group, and the like. Specific examples thereof include polyoxyethylene long-chain fatty acid esters such as Tween 20 (polyoxyethylene sorbitan monolaurate), Tween 40 (polyoxyethylene sorbitan monopalmitate), Tween 60 (polyoxyethylene sorbitan monostearate). , Tween 80 (polyoxyethylene sorbitan monooleate) (manufactured by Tokyo Chemical Industry Co., Ltd.), Triton-X100, Pluronic-F68, Pluronic-F127, etc .; Examples of fluorine surfactants having a perfluoro group include fluorine-based compounds And surfactants FC-4430, FC-4432 (manufactured by 3M Company), S-241, S-242, S-243 (above AGC Seimi Chemical) and the like.
The concentration of the surfactant in the reaction solution is preferably 0.001% by mass to 1% by mass and more preferably 0.01% by mass to 0.5% by mass with respect to the total amount. This is because if the concentration of the surfactant is too high, problems such as difficulty in dissolving the surfactant in the reaction solution may occur.

The reaction temperature is preferably 0 ° C. or higher and 100 ° C. or lower, and more preferably 20 ° C. or higher and 80 ° C. or lower. If the temperature is too low, there will be a problem that the reaction will not proceed sufficiently. Conversely, if the temperature is too high, the solvent will volatilize.
The reaction time is preferably 6 hours or longer and 36 hours or shorter, and more preferably 12 hours or longer and 24 hours or shorter. If the reaction time is too short, there is a problem that the reaction does not proceed sufficiently. Conversely, if the reaction time is too long, there is a problem that the production efficiency deteriorates.
The solution after the reaction is used as it is in the step of coating on the surface of the porous support as it is.

(Step of applying aqueous solution of crosslinked oligosaccharide to the surface of the porous support)
As a method for bringing the porous support into contact with the crosslinked oligosaccharide aqueous solution, for example, coating by a dip coating method (dipping method), a gravure coating method, a die coating method, a spray coating method or the like is preferable.
The temperature of the aqueous solution of the crosslinked oligosaccharide when contacting with the porous support is preferably 0 ° C. or higher and 100 ° C. or lower, and more preferably 20 ° C. or higher and 80 ° C. or lower. If the contact temperature is too low, there may be a problem that the aqueous solution of crosslinked oligosaccharide is not uniformly coated on the porous support; conversely, if the contact temperature is too high, the solvent of the aqueous solution of crosslinked oligosaccharide during contact This is because (water) may cause problems such as excessive volatilization. The contact time (immersion time) in the case of contact by the immersion method is preferably 15 minutes or more and 5 hours or less, and more preferably 30 minutes or more and 3 hours or less. If the contact time is too short, it may cause problems such as insufficient coating on the porous support; conversely, if the contact time is too long, the production efficiency of the gas separation membrane will decrease. May occur.

  After contacting the porous support with the crosslinked oligosaccharide aqueous solution, a drying step (solvent removal step) can be provided at a temperature below the melting point of the porous support. In this drying step, the porous support after contact is preferably in an environment of 80 ° C. or higher and 160 ° C. or lower, more preferably 120 ° C. or higher and 160 ° C. or lower, preferably 5 minutes or longer and 5 hours or shorter, more preferably 10 ° C. It can be carried out by allowing to stand for not less than 3 minutes and not more than 3 hours. This may cause problems such as inability to dry the solvent sufficiently if the drying temperature is too low or if the drying time is too short or both; This is because when the temperature is excessively high, the drying time is excessively long, or both of them, problems such as an increase in manufacturing cost and a decrease in manufacturing efficiency may occur.

(Method for producing a gas separation membrane having an oligosaccharide layer containing a metal salt)
The gas separation membrane in which the oligosaccharide layer contains a metal salt is produced by subjecting the gas separation membrane obtained as described above to further contact with a metal salt aqueous solution containing the desired metal salt. be able to.
The concentration of the metal salt in the metal salt aqueous solution is preferably 0.1 mol / L (M) or more and 50 M or less. When the concentration of the metal salt in the metal salt aqueous solution is 0.1 M or less, a highly practical separation performance is not exhibited in the separation of olefin and alkane. When this concentration exceeds 50M, inconveniences such as an increase in raw material cost occur.
The treatment of the gas separation membrane with the aqueous metal salt solution is preferably by immersion. The aqueous solution temperature during immersion is preferably 10 ° C. or higher and 90 ° C. or lower, and more preferably 20 ° C. or higher and 80 ° C. or lower. If the soaking temperature is too low, problems such as insufficient impregnation of the metal salt in the oligosaccharide layer may occur; conversely, if the soaking temperature is too high, the solvent of the metal salt aqueous solution ( Water) may volatilize excessively.
The gas separation membrane of this embodiment can be manufactured by the above manufacturing conditions.

Hereinafter, the present invention will be described more specifically with reference to examples and the like. However, the present invention is not limited to these examples.
[Example 1]
In this example, a hollow fiber made of polyether sulfone having an outer diameter of 500 μm, an inner diameter of 300 μm, a surface pore diameter of 50 nm, and a length of 20 cm was used as the porous support. Two hundred of these hollow fibers were bundled and stored in a cylindrical container, and the packaged one was used as the porous support in this example.
After stirring an aqueous solution containing 0.5% by mass of oligoglucosamine, 1% by mass of glutaraldehyde, and 0.5% by mass of acetic acid as other components at 25 ° C. for 24 hours, Tween 20 (trade name, manufactured by Tokyo Chemical Industry Co., Ltd.) Polyoxyethylene sorbitan monolaurate) was added at 0.2% by mass to prepare an oligosaccharide aqueous solution.
The porous support was immersed in the oligosaccharide aqueous solution at a speed of 1 cm / sec. After the entire support was immersed in the aqueous solution, the porous support was allowed to stand for 5 seconds. Thereafter, the hollow fiber gas separation membrane was manufactured by pulling up at a rate of 1 cm / sec and heating at 140 ° C. for 10 minutes.
Using the gas separation membrane obtained above, the permeation rate of CO ₂ and N ₂ was measured.
Measurement is performed by using a pure gas (CO ₂ and N ₂ on the supply side, helium on the permeation side), a supply side gas flow rate of 190 cc / min, a permeation side gas flow rate of 50 cc / min, and an isobaric system in a humidified atmosphere. Performed at a temperature of 30 ° C. The results are shown in Table 1.

[Examples 2 to 10]
In Example 1 above, the surface pore size of the porous support as a raw material, the composition of the aqueous solution of the crosslinking agent and the aqueous oligosaccharide solution, the immersion order, and the heating temperature after immersion were as shown in Table 1, respectively. Produced a hollow fiber gas separation membrane by the same method as in Example 1, and measured the permeation rates of CO ₂ and N ₂ . The results are shown in Table 1.
Abbreviations in the surfactant type column in Table 1 have the following meanings.
(Surfactant type)
Tween 20: trade name, manufactured by Tokyo Chemical Industry Co., Ltd., polyoxyethylene sorbitan monolaurate FC-4430: Novec FC-4430, trade name, manufactured by 3M, fluorinated surfactant having a perfluoroalkyl group

[Example 11]
A hollow fiber gas separation membrane produced by the same method as in Example 1 was immersed in a 0.8 M sodium hydroxide solution (solvent = ethanol: water = (volume ratio 80:20)) for 3 days, and then distilled water 5 Washed twice. Then, the hollow fiber-like gas separation membrane containing a silver salt was obtained by immersing in 7M silver nitrate aqueous solution for 24 hours. About the oligosaccharide layers before and after containing this silver salt, the mass before and after immersion in the aqueous silver nitrate solution was measured and compared, and the concentration of the silver salt (silver nitrate) contained in the polyoligosaccharide layer was 67% by mass. It turns out that.
Using the hollow fiber gas separation membrane containing this silver salt, the permeation rate of propane and propylene was measured.
The measurement uses a mixed gas composed of propane and propylene on the permeate side (propane: propylene = 40: 60 (mass ratio)), helium on the supply side, supply gas flow rate of 50 cc / min, and permeate gas flow rate. Was 50 cc / min, and was performed at a measurement temperature of 30 ° C. by an isobaric method in a humidified atmosphere. The results are shown in Table 2.

[Example 12]
Oligoglucosamine 5 wt%, glutaraldehyde 2.5 wt%, reaction time 12 hours, surfactant Novec FC-4430 (trade name, manufactured by 3M, fluorinated surfactant having a perfluoroalkyl group) A hollow fiber-like gas separation membrane produced by the same method as in Example 1 except that the amount was changed to 0.05 wt% was treated with sodium hydroxide and silver nitrate by the same method as in Example 11 to contain a silver salt. A hollow fiber gas separation membrane was obtained. The concentration of silver salt (silver nitrate) contained in the polyoligosaccharide layer of the obtained gas separation membrane was measured by the same method as in Example 11. As a result, it was 65% by mass.
Using the hollow fiber gas separation membrane containing this silver salt, the permeation rate of propane and propylene was measured in the same manner as in Example 11. The results are shown in Table 2.

[Analysis Example 1]
With respect to the hollow fiber gas separation membrane produced by the same method as in Example 1, the relative element concentration on the outer surface was examined using an X-ray photoelectron spectrometer (XPS). The results are shown in Table 3.
As shown in Table 3, N derived from chitosan was detected on the surface of the gas separation membrane, and S serving as an index of polyethersulfone as a support was below the detection limit. From these results, it was shown that an oligosaccharide layer containing chitosan was present on the outer surface of the hollow fiber gas separation membrane.

[Analysis Examples 2-3]
For the hollow fiber gas separation membrane (Analysis Example 2) produced by the same method as in Example 1, and for the hollow fiber gas separation membrane (Analysis Example 3) produced by the method of Comparative Example 1, respectively, a scanning electron microscope (SEM) was used. ) To observe the cross section. The results are shown in FIG. 1 (Analysis Example 2) and FIG. 2 (Analysis Example 3), respectively.

  As shown in these figures, the thickness of the oligosaccharide layer was about 2 μm for the hollow fiber gas separation membrane (Analysis Example 2) and about 19 μm for the hollow fiber gas separation membrane (Analysis Example 3). Analysis Example 2 was able to suppress the penetration into the porous support by crosslinking the oligosaccharide. As a result, the film thickness could be reduced. On the other hand, in Analysis Example 3, encroachment into the porous support was caused, and the film thickness was increased. This is because the portion that has entered also becomes the film thickness of the gas separating polymer.

[Analysis Examples 4 to 7]
A hollow fiber gas separation membrane (Analysis Example 4) produced by the same method as in Example 1 except that VS-C was 0.5% by mass as a crosslinking agent, and VS-C was 0.4% by mass as a crosslinking agent. A hollow fiber gas separation membrane (Analytical Example 5) produced by the same method as in Example 1 except that VS-C was made 0.25% by mass as a crosslinking agent, and produced by the same method as in Example 1. Hollow fiber-like gas separation membrane (Analysis Example 6), glutaraldehyde 0.5% by weight, and Novec FC-4430 (trade name, manufactured by 3M, fluorine-based surfactant having a perfluoroalkyl group) as a surfactant Except for 0.01% by weight, the outer surface of the hollow fiber gas separation membrane (Analysis Example 7) produced by the same method as in Example 1 was used for reflection infrared spectroscopy (IR-ATR). Perform infrared absorption spectroscopy It was. The results are shown in FIG. 3 (Analysis Examples 4 to 6) and FIG. 4 (Analysis Example 7).

Referring to FIG. 3, peaks in the vicinity of 1300 cm ⁻¹ attributed to the sulfone group, which is a crosslinked structure, are observed from the surfaces of the hollow fiber-like gas separation membranes of Analysis Examples 4 to 6. From this, it was confirmed that the oligosaccharide layer in these gas separation membranes has a cross-linked structure having a sulfone group generated by the reaction of an amino group derived from chitosan and a vinyl sulfone group derived from VS-C. . Further, from the surface of the hollow fiber-like gas separation membrane of Analysis Example 7 shown in FIG. 4, a peak near a wave number of 1650 cm ⁻¹ attributed to the imino group that is a crosslinked structure is seen. From this, it was confirmed that the oligosaccharide layer in these gas separation membranes has a cross-linked structure having an imino group formed by the reaction of an amino group derived from chitosan and an aldehyde group derived from glutaraldehyde.
Table 4 shows the functional group ratio calculated as the ratio of the peak near 1060 cm ⁻¹ derived from the oligosaccharide to the sulfone group or imino group peak derived from the crosslinked structure.

  As shown in Table 4, the gas separation membrane excellent in gas component performance was shown to have a high functional group ratio and thus a high degree of crosslinking.

From the above examples, it has been verified that a gas separation membrane exhibiting highly practical separation performance can be produced according to the method for producing a gas separation membrane using a coating liquid containing a crosslinked oligosaccharide obtained by crosslinking an oligosaccharide with a crosslinking agent. It was done. The reason for this is that according to the production method of the present invention, the oligosaccharide is crosslinked, so that the gas separation layer can be prevented from entering deeply into the porous support, and the crosslinked oligosaccharide has a high permeability coefficient. It is guessed that.
On the other hand, as shown in Comparative Examples, gas separation membranes manufactured without reacting oligosaccharides with a crosslinking agent and gas separation membranes manufactured using polysaccharides instead of oligosaccharides show practical separation performance. There wasn't.

In the embodiment of the present invention, it is possible to provide a method for separating CO ₂ , olefin gas, and the like with energy saving and high safety.

1 SEM image of gas separation membrane of Example 1 obtained in Analysis Example 2 2 SEM image of gas separation membrane of Comparative Example 1 obtained in Analysis Example 3 3 Analysis Example 4
4 Analysis Example 5
5 Analysis Example 6
6 Analysis Example 7

Claims (8)

A gas separation membrane having at least an oligosaccharide layer formed on a porous support and the porous support, the oligosaccharide being an amide group, an imide group, an imino group, a urea group, a carbonate group, or a urethane group The following specific wave number region that is chemically modified with at least one functional group selected from the group consisting of sulfonyl group and ester group, and the functional group has infrared absorption: amide group, imide group or imino group ( 1,700 cm ^{−1 to} 1,500 cm ⁻¹ ); urea group, carbonate group or urethane group (1,850 cm ^{−1 to} 1,650 cm ⁻¹ ); sulfonyl group (1,350 cm ^{−1 to} 1,300 cm ⁻¹ ) ; ester group ^{(1,300cm -1 ~1,000cm} -1); and the peak absorbance a of the functional groups in, ^{1000 cm} -1 to 11 Carbon having an absorption at a wavenumber region of 0 cm ^-1 - and the peak absorbance B oxygen bond,
(Absorbance A) / (absorbance B) = 0.05 or more and 5 or less,
The gas separation membrane.   The gas separation membrane according to claim 1, wherein the oligosaccharide layer includes at least a group selected from the group consisting of an amino group, an aldehyde group, a hydroxyl group, and a carboxyl group.   The gas separation membrane according to claim 1 or 2, wherein the oligosaccharide is oligoglucosamine. The supply gas flow rate is 190 cc / min, the permeate gas flow rate is 50 cc / min, the permeation rate of CO ₂ gas measured at 30 ° C. by a constant pressure system in a humidified atmosphere is in the range of 1 GPU to 1000 GPU, and CO _2. The gas separation membrane according to any one of claims 1 to 3, wherein the separation coefficient α of / N ₂ is in the range of 20 or more and 100 or less.   The gas separation membrane according to any one of claims 1 to 4, wherein the oligosaccharide layer contains a metal salt containing one or more metal atoms selected from the group consisting of Ag and Cu.   Using a mixed gas composed of 40% by mass of propane and 60% by mass of propylene, the supply-side gas flow rate was 190 cc / min, the permeate-side gas flow rate was 50 cc / min, and the propylene gas measured at 30 ° C. in a humidified atmosphere at 30 ° C. The gas separation membrane according to claim 5, wherein the permeation rate is 15 GPU or more and 1,500 GPU or less, and the propylene / propane separation coefficient α is in the range of 50 or more and 1000 or less. It is a manufacturing method of the gas separation membrane as described in any one of Claims 1-6, Comprising: The following processes:
A step of producing a coating solution by mixing an aqueous solution in which an oligosaccharide is dissolved and an aqueous solution in which a crosslinking agent is dissolved at a temperature equal to or higher than room temperature;
Applying the obtained coating solution to the surface of the porous support;
The method comprising the steps of:   The method according to claim 7, wherein the surface of the porous support has pores having a pore diameter of 10 nm to 100 nm.