KR102164259B1 - Copolymer, a process for producing the same, a gas separation membrane comprising the copolymer, and a composite membrane comprising the gas separation membrane - Google Patents

Abstract

The present invention relates to a copolymer, a method for producing the same, a gas separation membrane including the copolymer, and a composite membrane including the gas separation membrane. The copolymer of the present invention allows the produced gas separation membrane to maintain a stable structure through improved mechanical strength, prevents aggregation between monomers by introducing additives that selectively interact with functional groups in a copolymer chain, and can greatly improve gas selectivity by blocking the free volume. The copolymer is simply synthesized by free radical polymerization, and a synthesized solution can be used for coating a porous support without a separate precipitation or purification process, thereby enabling economical production of the gas separation membrane.

Description

Copolymer, a process for producing the same, a gas separation membrane comprising the copolymer, and a composite membrane comprising the gas separation membrane}

The present invention relates to a copolymer, a method for preparing the same, a gas separation membrane including the copolymer, and a composite membrane including the gas separation membrane.

As global warming accelerates, the capture of carbon dioxide gas, which accounts for the largest portion of greenhouse gases, has emerged as an important problem. There are two main methods of carbon dioxide capture, one before combustion and one after combustion. Capture before combustion is a process of increasing the purity of natural gas, and is a process of separating methane and carbon dioxide, and capture after combustion is a process of separating nitrogen and carbon dioxide. This gas separation has been studied continuously for decades.

Among these studies, polymer membranes showed high applicability as materials based on carbon, an abundant element. Among them, various studies have been conducted on polymer membranes having high carbon dioxide solubility through chemical interaction with carbon dioxide, but most of the polymers with high carbon dioxide affinity cannot maintain their shape and are stable. There is a problem that the structure cannot be maintained and the film is defective. Therefore, there is a need to develop a polymer gas separation membrane capable of maintaining a stable structure for a long time by securing mechanical strength.

Korean Patent Registration No. 10-1576052

Accordingly, the technical problem to be solved by the present invention is to provide a copolymer and a method for producing a gas separation membrane capable of maintaining a stable structure and improved gas selectivity.

In addition, it is to provide a gas separation membrane and a composite membrane comprising the copolymer.

One aspect of the present invention provides a copolymer of a carbon dioxide affinity monomer and a zwitter ion monomer.

Another aspect of the present invention provides a gas separation membrane comprising the copolymer.

Another aspect of the present invention provides a composite membrane in which the gas separation membrane is formed on a porous support.

Another aspect of the present invention is a step of polymerizing a carbon dioxide affinity monomer and a zwitterionic monomer in the presence of an initiator; And it provides a method for producing a copolymer comprising; and adding an additive containing Fe ³⁺ ions.

The copolymer of the present invention allows the gas separation membrane produced through improved mechanical strength to maintain a stable structure, prevents aggregation between monomers by introducing additives that selectively interact with functional groups in the copolymer chain, and blocks free volume Selectivity can be greatly improved. The copolymer is simply synthesized by free radical polymerization, and the synthesized solution can be used for coating a porous support without a separate precipitation or purification process, thereby enabling economical gas separation membrane production.

1 is a conceptual diagram of a composite film according to an embodiment of the present invention.
2A is a schematic diagram of a method for manufacturing a copolymer according to an embodiment of the present invention, and FIG. 2B is a schematic diagram showing a method for manufacturing a composite film according to an embodiment of the present invention.
3A is a ¹ H-NMR analysis result of a copolymer PS31 prepared according to an embodiment of the present invention, and FIG. 3B is a ¹ H-NMR analysis result of a copolymer PS41 prepared according to an embodiment of the present invention.
4 is an FT-IR spectrum of a copolymer prepared according to an embodiment of the present invention.
5 is an FT-IR spectrum of a copolymer including an additive according to an embodiment of the present invention.
FIG. 6A is a DSC analysis result of a composite film prepared by varying the ratio of monomers according to an embodiment of the present invention, and FIG. 6B is a DSC analysis result of a composite film prepared by varying the ratio of additives according to an embodiment of the present invention. to be.
7A is a TGA analysis result of a composite membrane prepared by varying the ratio of monomers according to an embodiment of the present invention, FIG. 7B means the amount of change in FIG. 7A, and FIG. 7C is an additive according to an embodiment of the present invention. It is the result of TGA analysis of the composite film prepared by varying the amount of, and FIG. 7D refers to the amount of change in FIG. 7C.
FIG. 8A is a TEM analysis result of PS31_0.0 manufactured according to an embodiment of the present invention, FIG. 8B is PS31_2.5, FIG. 8C is PS31_5.0, and FIG. 8D is PS31_10.
9A is a SAXS analysis result of a composite membrane prepared by varying the ratio of monomers according to an embodiment of the present invention, and FIG. 9B is a SAXS analysis result of a composite membrane prepared by varying the amount of additives according to an embodiment of the present invention. to be.
FIG. 10A shows an interface surface of a PS31_5.0 film manufactured according to an embodiment of the present invention contracted by liquid nitrogen, and FIG. 10B is a PS31_0.0 manufactured according to an embodiment of the present invention, and FIG. 10C is a PS31_2.5. , FIG. 10D is a result of SEM analysis of a cross section of PS31_5.0, FIG. 10E is PS31_7.5, and FIG. 10F is PS31_10.
11A is a result of a carbon dioxide adsorption curve over time of a composite membrane manufactured according to an embodiment of the present invention, and FIG. 11B is a result of measuring carbon dioxide permeability over time of a composite membrane manufactured according to an embodiment of the present invention. to be.
12A is a result of measuring a single gas permeability of a composite membrane prepared by varying the ratio of monomers according to an embodiment of the present invention, and FIG. 12B is a composite prepared by varying the ratio of monomers according to an embodiment of the present invention. This is the result of measuring the ideal selectivity of the membrane.
13A is a result of measuring a single gas permeability of a composite membrane manufactured by varying the amount of additives according to an embodiment of the present invention, and FIG. 13B is a composite manufactured by varying the amount of additives according to an embodiment of the present invention. This is the result of measuring the ideal selectivity of the membrane.
14 is a result of measuring the mixed gas separation performance of the composite membrane prepared according to an embodiment of the present invention.
15A is a CO ₂ /N ₂ Robeson Upper bound graph of the composite membrane manufactured according to an embodiment of the present invention, and FIG. 15B is a CO ₂ /CH ₄ Robeson Upper bound graph of the composite membrane manufactured according to an embodiment of the present invention. to be.

Hereinafter, various aspects and various embodiments of the present invention will be described in more detail.

One aspect of the present invention provides a copolymer of a carbon dioxide affinity monomer and a zwitter ion monomer. A polymer composed of only a carbon dioxide affinity monomer has an advantage of excellent carbon dioxide separation performance, but there is a problem in that the gas separation performance cannot be maintained for a long time due to the property of a fluid that cannot maintain its shape. Therefore, the copolymer of the present invention secured mechanical strength through ionic bonding by copolymerizing a zwitterionic monomer having both anions and cations with a carbon dioxide affinity monomer.

The carbon dioxide affinity monomer refers to a compound that is polymerized and chemically interacts with carbon dioxide. The carbon dioxide affinity monomer is poly (ethylene glycol) methyl ether methacrylate (poly (ethylene glycol) methyl ether methacrylate), 4-vinylpyridine (4-vinylpyridine), ethylene oxide (ethylene oxide), propylene oxide (propylene oxide) , Vinyl alcohol (vinyl alcohol), vinyl imidazole (vinyl imidazole), vinyl pyrrolidone (vinyl pyrrolidone) and may be any one selected from acrylonitrile (acrylonitrile). The poly(ethylene glycol) methyl ether methacrylate is preferable in that it has the best interaction with carbon dioxide among the carbon dioxide affinity monomers described above.

The carbon dioxide affinity monomer may be represented by the following formula (2).

[Formula 2]

In Formula 2, R ₁ and R ₂ are the same as or different from each other, and each independently hydrogen or an alkyl group having 1 to 6 carbon atoms, and n is an integer of 1 to 20.

More preferably, the carbon dioxide affinity monomer may be poly(ethylene glycol) methyl ether methacrylate having a number average molecular weight (M _n ) of 300 to 700 g mol ^-1 . If the number average molecular weight is less than 300 g mol ^-1, it is not preferable because the ratio of the ether functional group of the monomer is low, and if the number average molecular weight is more than 700 g mol ^-1, the repeating unit of the monomer is lengthened to form a structure, In addition to decreasing the solubility of carbon dioxide, there may be a problem in that unwanted gas also passes through the space between the structures formed with the ether functional groups.

The zwitterionic monomer may be represented by the following formula (3).

[Formula 3]

In Formula 3, R ₁ is Is hydrogen or alkyl group having 1 to 6 carbon atoms, R ₂ and R ₃ is the same as or different from each other and the alkyl group having 1 to 6 carbon atoms, each independently, wherein X is SO ₃ ^-, COO ^- is selected from, n is 0 to 4; And m is an integer of 0 to 4.

The zwitterionic monomer is any one selected from sulfobetaine methacrylate, carboxynetaine methacrylate, and 2-methacryloyloxyethyl phosphorylcholine. Can be The zwitterionic monomer refers to a monomer having an anion and a cation at the same time, and the mechanical strength of the separator may be secured by having an anion and a cation at the same time. Since the sulfobetaine methacrylate contains both anions and cations and is hydrophilic, an inorganic additive can be added because it has excellent miscibility and interaction with inorganic substances. It is preferable because the process is inexpensive.

The copolymer may be represented by the following formula (1).

[Formula 1]

In Formula 1, x and y are each independently an integer of 1 to 500, and n is an integer of 5 to 15.

Formula 1 corresponds to a copolymer of poly(ethylene glycol) methyl ether methacrylate and sulfobetaine methacrylate as a random copolymer.

The carbon dioxide affinity monomer is polyethylene glycol methyl ether methacrylate, the zwitterionic monomer is sulfobetaine methacrylate, the carbon dioxide affinity monomer and both The sex ionic monomer may be polymerized in a weight ratio of 2 to 5: 1. The carbon dioxide affinity monomer and the zwitterionic monomer may be polymerized in a weight ratio of 2 to 5: 1, more preferably 2.5 to 3.5: 1. When the zwitterionic monomer is polymerized less than the weight ratio of 2 to 5: 1, it may be difficult to secure mechanical strength when using the copolymer in a gas separation membrane, and when a large amount of zwitterionic monomer is polymerized, both Aggregation between sex ionic monomers occurs to increase the free volume, and it is not preferable because it can have a fragile property, which is an inherent property of zwitterionic monomers.

The carbon dioxide affinity monomer is any one or a mixture of two or more selected from poly(ethylene glycol) methyl ether methacrylate, ethylene oxide, and propylene oxide, and the copolymer may additionally include Fe ³⁺ ions. A free volume exists in the copolymer, which increases the permeability of the inert gas and consequently decreases the carbon dioxide selectivity. Since the Fe ³⁺ ion selectively interacts with the ether functional group present in the carbon dioxide affinity monomer, the free volume can be effectively blocked. As the Fe ³⁺ ions are added, the permeability of the inert gas decreases rapidly, and the solubility and selectivity of carbon dioxide increase.

The Fe ³⁺ ion may be included in an amount of 0.5 to 4% by weight based on the total weight of the copolymer. In the case of less than 0.5% by weight, it is difficult to expect the effect of improving the carbon dioxide solubility and selectivity by blocking the free volume, and in the case of more than 4% by weight, aggregation between the Fe ³⁺ ions occurs to reduce the carbon dioxide permeability and the mechanical properties of the membrane. Worsens. The Fe ³⁺ ions may more preferably be included in 1.5 to 3% by weight, and as can be seen in the examples to be described later, carbon dioxide selectivity rapidly in the range containing 1.5 to 3% by weight of Fe ³⁺ ions. It is more preferable in that it increases and has an effect of further improving the mechanical strength.

The copolymer does not have a peak at 1089 to 1109 cm ^-1 on the FT-IR spectrum, and may have a peak at 1066 to 1086 cm ^-1 . That is, when Fe ³⁺ ions are additionally included in the copolymer, the peak existing at 1089 to 1109 cm ^-1 moves to a range of 1066 to 1086 cm ^-1 . The peak present in the range of 1089 to 1109 cm ^-1 in the FT-IR spectrum corresponds to the peak of the ether bond of the carbon dioxide affinity monomer. As described above, since the Fe ³⁺ ion to weaken the binding energy of an ether bond as the ether bond and selectively interacting, and not having a peak at 1089 to 1109 cm ^-1, peaks 1066 to 1086 cm ^- Move to range ¹ .

Another aspect of the present invention provides a gas separation membrane comprising the copolymer.

According to one embodiment, the copolymer is represented by the following formula (1), additionally contains Fe ³⁺ ions, and the ideal carbon dioxide selectivity (CO) obtained by dividing the carbon dioxide single gas permeability value of the gas separation membrane by the methane single gas permeability value (CO ₂ /CH ₄ ) may be smaller than the mixed gas carbon dioxide selectivity (CO ₂ /CH ₄ ) measured using a mixed gas obtained by mixing carbon dioxide and methane in a volume ratio of 1: 1.

[Formula 1]

In Formula 1, x and y are each independently an integer of 1 to 500, and n is an integer of 5 to 15.

Gas selectivity is one of the important indicators for evaluating the performance of a gas separation membrane that separates carbon dioxide. The gas selectivity is divided into'ideal carbon dioxide selectivity', which is a value obtained by dividing the carbon dioxide single gas permeability value by the inert gas single gas permeability value, and the'mixed gas carbon dioxide selectivity' measured in the mixed gas. In general, the'mixed gas carbon dioxide selectivity' compared to the'ideal carbon dioxide selectivity' is known to reflect the performance exhibited in the actual gas separation process of a gas separation membrane. 'Ideal carbon dioxide selectivity' has a larger value than'mixed gas carbon dioxide selectivity'.

On the other hand, the gas separation membrane represented by Chemical Formula 1 according to the embodiment of the present invention and including the copolymer additionally containing Fe ³⁺ ions is a carbon dioxide single gas permeability value according to a general measurement method in the gas separation membrane field. The value divided by the methane single gas permeability value is defined as'ideal carbon dioxide selectivity', and the selectivity measured using a mixed gas in which carbon dioxide and methane are mixed in a volume ratio of 1: 1 is called'mixed gas carbon dioxide selectivity'. When defined, the mixed gas carbon dioxide selectivity has a larger value than the ideal carbon dioxide selectivity.

That is, in a general gas separation membrane, the'ideal carbon dioxide selectivity' has a property opposite to that of having a larger value than the'mixed gas carbon dioxide selectivity'. This case has not been reported so far, and this means that the gas separation membrane according to the embodiment of the present invention can exhibit more excellent performance in the actual carbon dioxide separation process.

Another aspect of the present invention provides a composite membrane in which the gas separation membrane is formed on a porous support. The porous support may be polysulfone having a porous structure, polyaniline, polyvinylidene fluoride, or the like.

Another aspect of the present invention is a step of polymerizing a carbon dioxide affinity monomer and a zwitterionic monomer in the presence of an initiator; And it provides a method for producing a copolymer comprising; and adding an additive containing Fe ³⁺ ions. The manufacturing method of the copolymer can solve the problem of insufficient mechanical strength that occurs when only the carbon dioxide affinity monomer is polymerized by preparing a copolymer with a zwitterionic monomer. Since it proceeds through free radical polymerization in the presence of an initiator, the manufacturing process is very simple and has the advantage that scale-up is possible.

In the copolymer containing the zwitterionic monomer, aggregation between zwitterions may occur. When aggregation occurs, there is a problem that it may be difficult to expect an effect of improving mechanical strength by the zwitterionic monomer. The additive containing Fe ³⁺ ions may be added to the copolymer to prevent aggregation of the zwitterionic monomer and effectively block the free volume through interaction with the ether functional group of the carbon dioxide affinity monomer.

In addition, the method for preparing the copolymer of the present invention has the advantage that an economical gas separation membrane can be manufactured by directly coating the prepared solution on the surface of the porous support without a separate precipitation or purification process.

The carbon dioxide affinity monomer is poly (ethylene glycol) methyl ether methacrylate (poly (ethylene glycol) methyl ether methacrylate), 4-vinylpyridine (4-vinylpyridine), ethylene oxide (ethylene oxide), propylene oxide (propylene oxide) , Vinyl alcohol (vinyl alcohol), vinyl imidazole (vinyl imidazole), vinyl pyrrolidone (vinyl pyrrolidone) and any one selected from acrylonitrile (acrylonitrile) Or it may be a mixture of two or more.

The carbon dioxide affinity monomer may be represented by the following formula (2).

[Formula 2]

In Formula 2, R ₁ and R ₂ are the same as or different from each other, and each independently hydrogen or an alkyl group having 1 to 6 carbon atoms, and n is an integer of 1 to 20.

The zwitterionic monomer may be represented by the following formula (3).

[Formula 3]

In Formula 3, R ₁ is Is hydrogen or alkyl group having 1 to 6 carbon atoms, R ₂ and R ₃ is the same as or different from each other and the alkyl group having 1 to 6 carbon atoms, each independently, wherein X is SO ₃ ^-, COO ^- is selected from, n is 0 to 4; And m is an integer of 0 to 4.

The zwitterionic monomer is any one selected from sulfobetaine methacrylate, carboxynetaine methacrylate, and 2-methacryloyloxyethyl phosphorylcholine. Or it may be a mixture of two or more.

The carbon dioxide affinity monomer and the zwitterionic monomer may be included in a weight ratio of 2 to 5: 1.

The copolymer may be represented by the following formula (1).

[Formula 1]

In Formula 1, in Formula 1, x and y are each independently an integer of 1 to 500, and n is an integer of 5 to 15.

The initiator may be any one or a mixture of two or more selected from dicumyl peroxide, azobisisobutyronitrile, and benzoyl peroxide.

The additive containing Fe ³⁺ ions may be any one or a mixture of two or more selected from FeCl ₃ and FeF ₃ . Additives, including the Fe ³⁺ ions Fe ³⁺ is a compound containing ions is applied, without limitation, anti-aggregation of the zwitterion monomer, but may serve to increase the selectivity of carbon dioxide prevents the free volume, the size of the anion When is too large, it is possible to reduce the gas selectivity in the copolymer chain, and thus, it is preferable that the anion is selected from FeCl ₃ and FeF ₃ having a small size or a mixture of two or more.

In the step of adding the additive containing Fe ³⁺ ions, the Fe ³⁺ ions may be added so that 0.5 to 4% by weight of the total weight of the copolymer is included. In a copolymer prepared so that the Fe ³⁺ ions are added to contain less than 0.5% by weight of the total weight of the copolymer, it cannot sufficiently play a role of increasing carbon dioxide selectivity by preventing aggregation of zwitterionic monomers and blocking free volume. In addition, if it is added in an amount exceeding 4% by weight, aggregation between additives containing Fe ³⁺ ions may occur, which may weaken the mechanical strength of the membrane, which is not preferable.

More preferably, the step of put the additive containing the Fe ³⁺ ions may be added so that the Fe ³⁺ ions contained 1.5 to 3% by weight total, based on the weight of the copolymer. As described above, the additive containing Fe ³⁺ ions may have a great influence on gas permeability and selectivity. When the Fe ³⁺ ions are included in the range of 1.5 to 3% by weight of the total weight of the copolymer, carbon dioxide It may be more preferable in that the selectivity rises rapidly. In addition, as can be seen in the examples to be described later, the gas separation membrane manufactured using the copolymer prepared in the above concentration range can be expected to have an effect of further improving mechanical strength.

In the step of polymerizing the carbon dioxide affinity monomer and the zwitterionic monomer in the presence of an initiator, the solvent may be any one or a mixture of two or more selected from water and dimethyl sulfoxide.

Hereinafter, a preferred embodiment is presented to aid the understanding of the present invention. However, these examples are for describing the present invention in more detail, and the scope of the present invention is not limited thereto, and various changes and modifications are possible within the scope and spirit of the present invention. It will be self-evident to those who have knowledge.

Example. Preparation of gas separation membrane

Materials used

Poly(oxyethylene methacrylate), POEM, poly(ethylene glycol) ether methacrylate, Mn = 500 g mol ^-1 ) Monomer and sulfobetaine methacrylate (sulfobetaine methacrylate, SBMA, [2-(Methacryloyloxy ) Monomer of ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, 95%), iron chloride (Iron(III) Chloride, FeCl ₃ , reagent grade 97%), dicumyl peroxide (DCP, 98%) polymer The synthesis initiator was purchased from Sigma-Aldrich. The porous polysulfone support was purchased from LG Chem.

Preparation of POEM-co-SBMA copolymer

Polymer copolymers were prepared using free radical polymerization. 2A is a schematic diagram of a method for preparing a copolymer according to an embodiment of the present invention. First, SBMA was dissolved in 100 mL of water, and then mixed with liquid POEM. Into the DCP 0.02 g, and purged with nitrogen for 30 minutes. Thereafter, polymerization was performed at 70° C. for 24 hours to complete a POEM-co-SBMA polymer solution.

POEM-co-SBMA/FeCl ₃ /Polysulfone composite membrane manufacturing

FeCl ₃ aqueous solution was added as an additive to the POEM-co-SBMA polymer solution, and the mixture was uniformly mixed. The FeCl ₃ contains 2.5 wt%, 5.0 wt%, 7.5 wt%, 10 wt%, and 12.5 wt%, respectively, based on the total weight of the synthesized copolymer (Fe ³⁺ ions included in the total weight of the synthesized copolymer are 0.86 wt. %, 1.72 wt%, 2.58 wt%, 3.44 wt%, 4.30 wt% included). The mixed solution was coated twice on a porous polysulfone support, and the coating was coated so that the thickness of the solution was 24 μm. 2B is a schematic diagram showing a method of manufacturing a composite membrane according to an embodiment of the present invention. The coated polysulfone support was dried at room temperature for 24 hours. 1 is a conceptual diagram of a composite film according to an embodiment of the present invention.

Naming of copolymer and composite membrane

The prepared copolymer was named according to the amount of POEM monomer and SBMA monomer used, and when 4 g of POEM monomer and 4 g of SBMA monomer (weight ratio 1: 1) were used, PS11, POEM monomer 6 g, SBMA monomer 2 g (weight ratio 3: 1) PS31, POEM monomer 4.8 g, SBMA monomer 3.2 g (weight ratio 3: 2) PS32, POEM monomer 6.4 g, SBMA monomer 1.6 g (weight ratio 4) : 1) When used, it was named PS41.

The composite membrane prepared using the PS31 copolymer was classified according to the wt% of FeCl ₃ included as an additive in the copolymer, and when 2.5 wt% FeCl ₃ was included, PS31_2.5 and 5.0 wt% FeCl ₃ were included. It was named PS31_5.0 when it was used, PS31_7.5 when 7.5 wt% FeCl ₃ was included, PS31_10 when 10 wt% FeCl ₃ was included, and PS31_12.5 when 12.5 wt% FeCl ₃ was included. In addition, when FeCl ₃ was not included, it was named PS31_0.0.

Comparative Example 1. P (POEM)

Poly(oxyethylene methacrylate) (POEM) having a number average molecular weight (M _n ) of 500 g mol ^-1 was used.

Experimental Example 1. Proton nuclear magnetic resonance (Proton nuclear magnetic resonance, ^One H-NMR) analysis

The synthesized copolymers PS31 and PS41 copolymer were analyzed through ¹ H-NMR spectroscopy. 3A is a ¹ H-NMR analysis result of a copolymer PS31 prepared according to an embodiment of the present invention, and FIG. 3B is a ¹ H-NMR analysis result of a copolymer PS41 prepared according to an embodiment of the present invention. The analysis was performed through ethylene oxide functional groups in the case of the POEM chain and tertiary amine and sulfone functional groups in the case of SBMA. As can be seen in FIGS. 3A and 3B, it was confirmed that SBMA of 25.2% for PS31 and 18.9% for PS41 was contained in the copolymer. Through the above results, it was confirmed that most of the monomers were well synthesized as a copolymer.

Experimental Example 2. Fourier-transform infrared spectroscopy (FT-IR) analysis

Further analysis of the copolymer synthesis was performed using the FT-IR spectrum. 4 is an FT-IR spectrum of a copolymer prepared according to an embodiment of the present invention. As can be seen in FIG. 4, a carbon double bond band (1620 cm ^-1 ) was not observed, and at the same time, an ethylene oxide functional group (1035 cm ^-1 ) contained in POEM and a sulfone contained in SBMA (523 , 601 cm ^-1 ) and CN binding (1035 cm ^-1 ) were observed simultaneously. In addition, as the C=O double bond energy in the ester functional group appeared more strongly after synthesis, it was possible to confirm the structural interference effect through the synthesis of the copolymer. When synthesizing the above results, it was confirmed that the synthesis of the POEM-co-SBMA copolymer was successfully performed.

In addition, FT-IR analysis of the copolymer containing the FeCl ₃ additive was performed. 5 is an FT-IR spectrum of a copolymer including an additive according to an embodiment of the present invention. When the FeCl ₃ additive was included, there was no change in other bands, but it was confirmed that the ether bond in the ethylene oxide functional group moved from 1099 to 1076 cm ^-1 , and the binding energy was weakened. Through this, it was confirmed that the Fe ³⁺ ion weakened the binding energy through the selective interaction with the oxygen of the ether bond.

Experimental Example 3. Differential Scanning Calorimetry (DSC) analysis

DSC analysis of the composite membrane prepared according to the SBMA synthesis ratio and the amount of additives was performed. FIG. 6A is a DSC analysis result of a composite film prepared by varying the ratio of monomers according to an embodiment of the present invention, and FIG. 6B is a DSC analysis result of a composite film prepared by varying the ratio of additives according to an embodiment of the present invention. to be.

As can be seen in FIG. 6A, in the case of P (POEM) synthesized with only POEM monomers, the structure of the POEM can be confirmed, and it can be seen that the structure gradually weakens as the use ratio of SBMA increases.

In addition, as can be seen in Fig. 6b, it was confirmed that the POEM structure disappeared so as not to be observed in the DSC curve as the amount of the FeCl ₃ additive increased. This means that the ether functional groups capable of interacting with carbon dioxide further increased, and the solubility of carbon dioxide could be predicted to increase.

Experimental Example 4. Thermogravimetric Analysis (TGA)

TGA analysis was performed according to the SBMA synthesis ratio and the amount of additives, and the results are shown in FIG. 7. 7A is a TGA analysis result of a composite film prepared by varying the ratio of monomers according to an embodiment of the present invention, and FIG. 7B indicates the amount of change in FIG. 7A. In addition, FIG. 7C is a TGA analysis result of a composite film prepared by varying the amount of additives according to an embodiment of the present invention, and FIG. 7D indicates the amount of change in FIG. 7C.

As can be seen in FIG. 7, in the case of P(POEM), one characteristic inflection point was observed, and in the case of P(SBMA), two characteristic inflection points were observed excluding moisture contained in the polymer. In the case of PS31 in which these two monomers were polymerized together, the inflection points shown in P(POEM) and P(SBMA) were combined to show a remodeling, which confirmed that the copolymer showed the properties of a random copolymer. In addition, when the additive was added, one distinct inflection point stood out, and through this, it was confirmed that one phase exhibited by the selective interaction of POEM and FeCl ₃ was expressed as the inflection point.

Experimental Example 5. Transmission Electron Microscopy (TEM) Analysis

The TEM analysis of the composite film prepared according to the above example was performed, and the results are shown in FIG. 8. FIG. 8A is a TEM analysis result of PS31_0.0 manufactured according to an embodiment of the present invention, FIG. 8B is PS31_2.5, FIG. 8C is PS31_5.0, and FIG. 8D is PS31_10.

As can be seen in FIG. 8, a black nano area (agglomerated SBMA area) could be observed. In the case of the pure polymer of FIG. 8A, the aggregated SBMA region was observed the largest. However, it was confirmed through the results of FIGS. 8b and 8c that as the addition amount of FeCl ₃ increased, the aggregated SBMA region gradually decreased as the additive selectively interacted with the POEM chain. Through the above results, it was confirmed that the POEM structure collapsed and the region capable of interacting with carbon dioxide increased. However, as can be seen through FIG. 8D, when FeCl ₃ was contained in an amount of 10 wt% or more, it was confirmed that aggregation of FeCl ₃ occurred and the aggregation phenomenon occurred in dark black.

Experimental Example 6. Small Angle X-ray Spectroscopy (SAXS)

Small-angle X-ray diffraction curve analysis confirmed the distance between polymer chains. This interval is called d-spacing and can be calculated by dividing 2π by the peak of q. 9A is a SAXS analysis result of a composite membrane prepared by varying the ratio of monomers according to an embodiment of the present invention, and FIG. 9B is a SAXS analysis result of a composite membrane prepared by varying the amount of additives according to an embodiment of the present invention. to be.

As can be seen in FIG. 9A, when SBMA was used as a monomer, d-spacing values of 5.5-5.7 nm were obtained. This refers to the chain spacing caused by SBMA ionic bonding.

In addition, as can be seen in FIG. 9B, when 2.5 wt% of an additive was added, structural collapse occurred due to selective interaction with POEM, and a temporarily increased d-spacing value of 6.2 nm was observed, and as the amount of addition increased ( 5.0, 7.5 wt%) decreased to 5.7 and 5.5 nm, which means that the space caused by structural collapse is filled with additives.

Experimental Example 7. Cross-sectional Scanning Electron Microscopy (SEM) Analysis of Composite Membrane

The cross section of the composite membrane was observed through SEM analysis. FIG. 10A shows an interface surface of a PS31_5.0 film manufactured according to an embodiment of the present invention contracted by liquid nitrogen, and FIG. 10B is a PS31_0.0 manufactured according to an embodiment of the present invention, and FIG. 10C is a PS31_2.5. , FIG. 10D is a result of SEM analysis of a cross section of PS31_5.0, FIG. 10E is PS31_7.5, and FIG. 10F is PS31_10.

When observing the cross section of the composite film, liquid nitrogen was used, and the interface of the composite film was contracted by the liquid nitrogen used at this time, and the result is shown in FIG. 10A. 10B to 10F show cross-sections of the prepared composite film, and it was confirmed that the prepared film had a thickness of 0.7-1 µm.

Experimental Example 8. Measurement of carbon dioxide solubility and permeability over time

Carbon dioxide solubility and transmittance of the composite membrane prepared according to the above example were measured. 11A is a result of a carbon dioxide adsorption curve over time of a composite membrane manufactured according to an embodiment of the present invention, and FIG. 11B is a result of measuring carbon dioxide permeability over time of a composite membrane manufactured according to an embodiment of the present invention. to be.

When SBMA monomer is used, it replaces the POEM chain with carbon dioxide affinity, and SBMA forms ionic bonds. The ionic bonding eventually reduces the site where carbon dioxide interacts, and exhibits a lower solubility than P (POEM). On the other hand, when additives are used, the effect of destroying the crystal phase of P (POEM) than the portion replaced by the ionic bonds and securing a site for advantageous interaction with carbon dioxide is much greater, so that it shows the highest solubility. It could be confirmed from 11a.

In addition, as can be seen in FIG. 11B, the carbon dioxide permeability over time shows a time trend similar to that of the carbon dioxide solubility curve over time, because after adsorption, carbon dioxide in an overdissolved state undergoes a process of desorption.

Experimental Example 9. Measurement of gas separation performance of composite membrane

The gas separation performance of the composite membrane prepared according to the above example was measured. 12A is a result of measuring a single gas permeability of a composite membrane prepared by varying the ratio of monomers according to an embodiment of the present invention, and FIG. 12B is a composite prepared by varying the ratio of monomers according to an embodiment of the present invention. This is the result of measuring the ideal selectivity of the membrane. The ideal selectivity is the permeability of a single gas divided by each other.

As can be seen in FIGS. 12A and 12B, as the SBMA ratio increases, the free volume increases, so that the permeability of the inert gas increases, and the solubility of carbon dioxide decreases, so that the permeability of carbon dioxide decreases. When SBMA was contained in an amount of 50 wt% or more, the coated thin film was easily broken due to the inherent properties of the polymer, and thus Knudsen diffusion tended to occur.

13A is a result of measuring a single gas permeability of a composite membrane manufactured by varying the amount of additives according to an embodiment of the present invention, and FIG. 13B is a result of measuring the single gas permeability of the composite membrane manufactured by varying the amount of additives according to an embodiment of the present invention. This is the result of measuring the ideal selectivity of the composite membrane.

As can be seen from FIGS. 13A and 13B, when the additive is added, the structure of the POEM is collapsed, and the permeability of the inert gas is rapidly reduced. However, in the case of carbon dioxide, the solubility increased because the interaction site increased due to the increase of the ether functional group. Through this, it was confirmed that it has very high selectivity values of carbon dioxide and nitrogen, carbon dioxide and methane.

In addition, the mixed gas separation performance of the composite membrane prepared according to the above example was measured. To measure the mixed gas separation performance, a gas mixed with carbon dioxide and methane at the same ratio was used. 14 is a result of measuring the mixed gas separation performance of the composite membrane prepared according to an embodiment of the present invention.

As can be seen in FIG. 14, the mixed gas permeability falls to less than half compared to the ideal gas permeability, but the selectivity rapidly increases. This is because the passage through which methane can diffuse during the permeation of the mixed gas is blocked through the selective interaction of carbon dioxide gas, and a higher selectivity can be obtained than the ideal gas separation performance.

15A is a CO ₂ /N ₂ Robeson Upper bound graph of the composite membrane manufactured according to an embodiment of the present invention, and FIG. 15B is a CO ₂ /CH ₄ Robeson Upper bound graph of the composite membrane manufactured according to an embodiment of the present invention. to be. As can be seen in FIG. 15, both the CO ₂ /N ₂ and CO ₂ /CH ₄ selectivity exceeded the Robeson upper bound line, which is one of the criteria for evaluating excellent gas separation membrane performance, through which the separation membrane of the above example It was confirmed that it has excellent gas separation performance.

On the other hand, as can be seen in FIG. 15, it was confirmed that the separator of the Example had a remarkably excellent performance compared to Pebax 1657, which is known as one of the polymer materials exhibiting excellent performance in separating carbon dioxide.

Experimental Example 10. Measurement of stability and mechanical strength of the separator

The separation membrane prepared according to the above example and the P (POEM) separation membrane of Comparative Example 1 were used to measure carbon dioxide single gas gas permeation performance over time. Through this, it could be confirmed whether the mechanical strength of the separator could be maintained for a long time. 16 is a result of measuring carbon dioxide permeability of a separator manufactured according to an embodiment of the present invention.

As can be seen in FIG. 16, when comparing the initial performance and the final performance, the PS31_0.0 membrane of Example maintained 79.8% carbon dioxide permeability from the initial performance 31.4 to the final performance 25.1, whereas the membrane of Comparative Example 1 The carbon dioxide permeation performance of 74.7% was maintained from the initial performance of 33.6 to the final performance of 25.1. Through this, it was confirmed that the separation membrane of the example has excellent stability and mechanical strength of the membrane.

Meanwhile, in the case of the PS31_7.5 membrane, as can be seen in FIG. 11B, it was confirmed that the stability and mechanical strength of the membrane can be maximized by the addition of additives, showing 88.4% of performance maintenance from the initial performance 16.8 to the final performance 14.9. .

Therefore, the copolymer of the present invention enables the gas separation membrane to maintain a stable structure through improved mechanical strength, prevents aggregation between monomers by introducing an additive that selectively interacts with functional groups in the copolymer chain, and increases free volume. By blocking, gas selectivity can be greatly improved. The copolymer is simply synthesized by free radical polymerization, and the synthesized solution can be used for coating a porous support without a separate precipitation or purification process, thereby enabling economical gas separation membrane production.

The above-described Examples and Comparative Examples are examples for explaining the present invention, and the present invention is not limited thereto. Since those of ordinary skill in the art to which the present invention pertains will be able to implement the present invention by various modifications therefrom, the technical protection scope of the present invention should be determined by the appended claims.

Claims (25)

As a copolymer of carbon dioxide affinity monomer and zwitterionic polymer,
The copolymer is represented by the following formula (1),
The copolymer additionally contains Fe ³⁺ ions,
The copolymer does not have a peak at 1089 to 1109 cm ^-1 on the FT-IR spectrum, and has a peak at 1066 to 1086 cm ^-1 :
[Formula 1]

In Formula 1, x and y are each independently an integer of 1 to 500, and n is an integer of 5 to 15. delete delete delete delete delete The method of claim 1,
The carbon dioxide affinity monomer is poly(ethylene glycol) methyl ether methacrylate,
The zwitterionic monomer is sulfobetaine methacrylate,
The carbon dioxide affinity monomer and the zwitterionic monomer is a copolymer that is polymerized in a weight ratio of 2 to 5: 1.
delete The method of claim 1,
The Fe ³⁺ ion is a copolymer containing 0.5 to 4% by weight based on the total weight of the copolymer. delete A gas separation membrane comprising the copolymer of claim 1. The method of claim 11,
The copolymer is represented by the following formula (1), and additionally contains Fe ³⁺ ions,
The ideal carbon dioxide selectivity (CO ₂ /CH ₄ ) obtained by dividing the carbon dioxide single gas permeability value of the gas separation membrane by the methane single gas permeability value is measured using a mixed gas obtained by mixing carbon dioxide and methane at a volume ratio of 1: 1. Small gas separation membrane compared to carbon dioxide selectivity (CO ₂ /CH ₄ ):
[Formula 1]

In Formula 1, x and y are each independently an integer of 1 to 500, and n is an integer of 5 to 15. A composite membrane in which the gas separation membrane of claim 11 is formed on a porous support.
Polymerizing the carbon dioxide affinity monomer and the zwitterionic monomer in the presence of an initiator; And
As a method for preparing a copolymer comprising; adding an additive containing Fe ³⁺ ions,
The copolymer is represented by the following formula (1),
The additive containing Fe ³⁺ ions is any one or a mixture of two or more selected from FeCl ₃ and FeF ₃ ,
In the step of the additives, including the Fe ³⁺ ion is method of producing a copolymer to input such that the Fe ³⁺ ions contained 1.5 to 3% by weight, based on the weight of the entire copolymer:
[Formula 1]

In Formula 1, x and y are each independently an integer of 1 to 500, and n is an integer of 5 to 15. delete delete delete delete The method of claim 14,
The carbon dioxide affinity monomer and the zwitterionic monomer is a method of producing a copolymer comprising a weight ratio of 2 to 5: 1.
delete The method of claim 14,
The initiator is dicumyl peroxide (Dicumyl peroxide), azobisisobutyronitrile (Azobisisobutyronitrile) and benzoyl peroxide (Benzoyl peroxide) any one or a mixture of two or more selected from the method of producing a copolymer.
delete delete delete The method of claim 14,
In the step of polymerizing the carbon dioxide affinity monomer and the zwitterionic monomer in the presence of an initiator, the solvent is any one or a mixture of two or more selected from water and dimethyl sulfoxide.

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