Carbon dioxide absorbing composition

Abstract

To provide a carbon dioxide absorbing composition that can efficiently absorb carbon dioxide. [Solution] A carbon dioxide absorbing composition is provided, which contains a polymer having a number average molecular weight of 3,000 to 50,000 and an oxygen-containing organic solvent, is liquid at 25°C, and has a weight ratio of polymer to oxygen-containing organic solvent of 2:98 to 40:60.

Description

Technical Field

[0001] The present invention relates to a carbon dioxide absorbing composition capable of efficiently absorbing carbon dioxide. Background Art

[0002] In recent years, discussions on climate change at the global scale have intensified, and since greenhouse gases such as carbon dioxide are considered to be a factor contributing to climate change, measures to address greenhouse gases including carbon dioxide are under investigation.

[0003] For example, Patent Document 1 discloses a carbon dioxide absorbent containing a polyether compound having a nitrogen-containing cationic group.

[0004] In the technique of Patent Document 1, a polyether compound having a nitrogen-containing cationic group is supported on a porous membrane or the like to function as a carbon dioxide absorbent. Therefore, the technique of Patent Document 1 is applicable only to specific applications such as porous membranes, and its scope of application is limited. Furthermore, the carbon dioxide absorption efficiency is not necessarily sufficient. Prior Art Documents Patent Documents

[0005] Patent Document 1 International Publication No. 2023 / 042748 Summary of the Invention Problem to be Solved by the Invention

[0006] An object of the present invention is to provide a carbon dioxide absorbing composition capable of efficiently absorbing carbon dioxide. Means for Solving the Problem

[0007] The present inventors conducted studies to achieve the above objective and discovered that a carbon dioxide absorbing composition containing a polymer with a number average molecular weight of 3,000 to 50,000 and an oxygen-containing organic solvent in a predetermined ratio can efficiently absorb carbon dioxide, thus completing the present invention.

[0008] In other words, the present invention provides the following carbon dioxide absorbing composition. [1] A polymer having a number-average molecular weight of 3,000 to 50,000 and an oxygen-containing organic solvent, A carbon dioxide absorbing composition wherein the content ratio of the polymer to the oxygen-containing organic solvent is 2:98 to 40:60 in terms of the weight ratio of polymer to oxygen-containing organic solvent. [2] The carbon dioxide absorbing composition according to [1], wherein the oxygen-containing organic solvent is at least one selected from polyethylene glycol dimethyl ether, methanol, ethanol, N-methylpyrrolidone, and propylene carbonate. [3] The carbon dioxide absorbing composition according to [1] or [2], wherein the polymer contains at least one selected from alkylene oxide monomer units, hydroxyl group-containing monomer units and amide structure-containing monomer units as monomer units. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a carbon dioxide absorbing composition that can efficiently absorb carbon dioxide. [Modes for carrying out the invention]

[0010] The carbon dioxide absorption composition of the present invention contains a polymer having a number average molecular weight of 3,000 to 50,000 and an oxygen-containing organic solvent. The composition is one in which the content ratio of the polymer to the oxygen-containing organic solvent is 2:98 to 40:60 in terms of the weight ratio of polymer to oxygen-containing organic solvent.

[0011] Through diligent research, the inventors discovered that by combining a polymer with a number-average molecular weight of 3,000 to 50,000 with an oxygen-containing organic solvent in a predetermined ratio, the carbon dioxide absorption performance can be effectively enhanced by the action of the polymer with a number-average molecular weight of 3,000 to 50,000. Based on this finding, the present invention was completed. In particular, according to the present invention, when applied to a mixed gas containing carbon dioxide, the carbon dioxide contained in the mixed gas can be efficiently absorbed, thereby reducing the concentration of carbon dioxide in the mixed gas to a low level. Therefore, carbon dioxide contained in mixed gases containing carbon dioxide, such as exhaust gases from power plants, steel and cement industries, and natural gas, can be effectively removed.

[0012] The polymer used in this invention may be any polymer with a number average molecular weight (Mn) in the range of 3,000 to 50,000, but one with a number average molecular weight in the range of 3,250 to 47,500 is preferred, one with a number average molecular weight in the range of 3,500 to 45,000 is more preferred, and one with a number average molecular weight in the range of 3,750 to 42,500 is even more preferred. If the number average molecular weight is too small, the carbon dioxide absorption effect due to the addition of the polymer will be insufficient, on the other hand, if the number average molecular weight is too large, the viscosity of the carbon dioxide absorption composition will increase, and the carbon dioxide absorption performance will decrease.

[0013] Furthermore, the molecular weight distribution (Mw / Mn) of the polymer used in the present invention is not particularly limited, but is preferably 1.0 to 5.0, more preferably 1.0 to 4.0, and even more preferably 1.0 to 3.0. The number average molecular weight (Mn) and molecular weight distribution (Mw / Mn) can be calculated by gel permeation chromatography (GPC) measurement on a standard polystyrene basis or a standard polyethylene glycol basis. When a cation group-containing polyether described later is used as the polymer, the number average molecular weight (Mn) and molecular weight distribution (Mw / Mn) can be determined by the method described in the examples described later.

[0014] The polymer used in the present invention is not particularly limited, but from the viewpoint of being able to further enhance carbon dioxide absorption performance, it is preferable to have a monomer unit that contains at least one selected from alkylene oxide monomer units, hydroxyl group-containing monomer units, and amide structure-containing monomer units, and it is more preferable to have a monomer unit that contains at least one selected from alkylene oxide monomer units and hydroxyl group-containing monomer units.

[0015] Specific examples of polymers used in the present invention are not particularly limited, but include: polyethylene glycol, poly(ethylene glycol-CO-propylene glycol), polyethylene oxide, poly(ethylene oxide-CO-propylene oxide), poly(ethylene oxide-CO-epichlorohydrin), polyepichlorohydrin and other polyalkylene oxides; polyvinyl alcohol; cationic group-containing polymers having cationic groups in the polymer chain; polyvinylimidazole; polyacrylamides such as polyacrylamide, poly-N,N-dimethylacrylamide, and poly-N,N-diisopropylacrylamide; polyvinylamides such as polyvinylpyrrolidone; polycarboxylic acids such as polyacrylic acid and polymethacrylic acid and their sodium salts; cellulose derivatives such as hydroxyethylcellulose, hydroxypropylcellulose, and carboxymethylcellulose and their salts. Among these, polyalkylene oxides, polyvinylamides, and cation group-containing polymers having cation groups in the polymer chain are preferred from the viewpoint of carbon dioxide absorption performance, polyalkylene oxides, polyvinylamides, and cation group-containing polymers having cation groups in the polymer chain are more preferred, polyethylene glycol, polyepichlorohydrin, poly(ethylene oxide-CO-epichlorohydrin), polyvinylpyrrolidone, and cation group-containing polymers having cation groups in the polymer chain are particularly preferred, and polyepichlorohydrin and cation group-containing polymers having cation groups in the polymer chain are more preferred.

[0016] The chain structure of the polymer used in the present invention is not particularly limited and may be linear, or it may be a branched chain structure such as a graft or radial structure.

[0017] A cation group-containing polymer having a cationic group in its polymer chain (hereinafter referred to as "cation group-containing polymer" as appropriate) can be any polymer having a cationic group in its polymer chain, and is not particularly limited. It may be a polymer having a cationic group in its main chain, or a polymer having a cationic group in its side chain, or even a polymer having cationic groups in both its main chain and side chain.

[0018] Examples of cationic group-containing polymers include addition polymers of vinyl compounds, polyethers, polyethyleneimines, and polyoxazolines, which have cationic groups in their side chains, and ionenes, epichlorohydrin-amine condensates, and polyamide polyamine epichlorohydrins, which have cationic groups in their main chains. These may have any other substituents, or some hydrogen atoms may be substituted with halogen atoms such as fluorine. Furthermore, cationic group-containing polymers may be copolymerized with structural units derived from monomers that do not have cationic groups, in addition to structural units that have cationic groups, and the pH may be adjusted by introducing structural units derived from acidic monomers or structural units derived from basic monomers.

[0019] A cation group-containing polymer has a cation group in its polymer chain. The counter anions for such cation groups are not particularly limited, but include, for example, imides such as fluorosulfonylimide, bistrifluoromethylsulfonylimide, and bispentafluoroethylsulfonylimide; halogens such as chlorides and bromides; and, but are not particularly limited, tetrafluoroboric acid, hexafluorophosphate, dicyanoamide, tetracyanoborate, carbonic acid, alkyl carbonate, triflate, perchloric acid, nitric acid, sulfuric acid, alkyl sulfuric acid, sulfonic acid, phosphoric acid, and alkyl phosphoric acid.

[0020] While there are no particular limitations on the cationic group-containing polymer, examples of polymers having cationic groups in their side chains include cationic group-containing polyethers containing repeating units represented by the following general formula (1).

[0021] [ka] (In the above general formula (1), A + represents a nitrogen-containing cation group. Also, in the above general formula (1), X - (This represents an anion.)

[0022] A + Examples of nitrogen-containing cationic groups represented by this formula include amino groups, nitrogen-containing cationic aromatic groups, and nitrogen-containing cationic aliphatic groups.

[0023] A +As a nitrogen-containing cationic aromatic group, a group containing a cationic nitrogen-containing aromatic heterocycle is preferred. The nitrogen-containing aromatic heterocycle in the cationic nitrogen-containing aromatic heterocycle in the group only needs to have a nitrogen atom in the ring and be aromatic, and may also have heteroatoms other than nitrogen, such as oxygen atoms and sulfur atoms, and some of the atoms constituting the heterocycle may be substituted by substituents. It may also take the form of a polycyclic structure in which two or more rings are fused. Examples of nitrogen-containing aromatic heterocycle structures include five-membered heterocycles such as imidazole rings, pyrrole rings, thiazole rings, oxazole rings, pyrazole rings, and isoxazole rings; six-membered heterocycles such as pyridine rings, pyrazine rings, pyrimidine rings, pyridazine rings, and triazine rings; and condensed heterocycles such as quinoline rings, isoquinoline rings, quinoxaline rings, quinazoline rings, sinnoline rings, purine rings, indole rings, isoindole rings, benzimidazole rings, benzoxazole rings, and benzoisoxazole rings. Among these, five-membered and six-membered heterocycles are preferred, and imidazole rings are more preferred.

[0024] The substituents on the nitrogen-containing aromatic heterocycle are not particularly limited, but examples include alkyl groups; cycloalkyl groups; alkenyl groups such as vinyl groups; aryl groups such as phenyl groups; arylalkyl groups; alkylaryl groups; alkoxyl groups; alkoxyalkyl groups; aryloxy groups; alkanol groups; hydroxyl groups; carbonyl groups; alkoxycarbonyl groups; amino groups; imino groups; nitrile groups; alkylsilyl groups; halogen atoms; and the like. The number of carbon atoms in these substituents is preferably 1 to 12, more preferably 1 to 8, and even more preferably 1 to 6.

[0025] A + The nitrogen-containing cationic aliphatic group may be linear or branched, and may also have a non-aromatic ring structure.

[0026] A +Specific examples of the nitrogen-containing cationic group represented by include ammonium groups; monosubstituted ammonium groups containing a cationic nitrogen atom such as methylammonium group, butylammonium group, cyclohexylammonium group, anilinium group, benzylammonium group, ethanolammonium group, etc.; disubstituted ammonium groups containing a cationic nitrogen atom such as dimethylammonium group, diethylammonium group, dibutylammonium group, nonylphenylammonium group, etc.; trisubstituted ammonium groups containing a cationic nitrogen atom such as trimethylammonium group, triethylammonium group, n-butyldimethylammonium group, stearyldimethylammonium group, tributylammonium group, trivinylammonium group, triethanolammonium group, N,N-dimethylethanolammonium group, tri(2-ethoxyethyl)ammonium group, etc.; heterocyclic groups containing a cationic nitrogen atom such as piperidinium group, 1-methylpyrrolidinium group, 1-butylpyrrolidinium group, imidazolium group, 1-methylimidazolium group, 1-ethylimidazolium group, 1-butyl-imidazolium group, benzimidazolium group, pyrrolium group, 1-methylpyrrolium group, oxazolium group, benzoxazolium group, pyrazolium group, isoxazolium group, pyridinium group, 2,6-dimethylpyridinium group, pyrazinium group, pyrimidinium group, pyridazinium group, triazinium group, N,N-dimethylanilinium group, quinolinium group, isoquinolinium group, indolinium group, quinoxalinium group, isoquinoxalinium group, etc. Among these, trisubstituted ammonium groups containing a cationic nitrogen atom and heterocyclic groups containing a cationic nitrogen atom are preferable.

[0027] In the above general formula (1), X - The anion represented by is a counter anion for the nitrogen-containing cationic group represented by A + It is a counter anion for the nitrogen-containing cationic group represented by . As X - , for example, as monovalent anions, F - , Cl - , Br - , I - halide ions such as; (FSO2)2N -, (CF3SO2)2N - , (CF3CF2SO2)2N - Sulfonylimidide ions such as CH3COO - C3H7COO - CF3COO - PhCOO - (Ph indicates the phenyl group.) Carboxylate ions such as CH3SO3 - CF3SO3 - Sulfonoxide ions such as OH - BF4 - PF6 - ClO4 - , B(CN)4 - SCN - , (NC)2N - These are some examples. - The anion may be a polyvalent anion, or it may be a polyanion having two or more monovalent anionic groups in the molecule. For example, a polyvalent anion is the sulfate ion (SO4 2- ) and carbonate ions (CO3 2- Examples include: - O3SCF2CF2CF2SO3 - , - O3SCF2CF2SO3 - CF3SO2N - SO2CF2CF2OCF2CF2OCF2CF2SO2N - Examples include SO2CF3. In particular, from the perspective of carbon dioxide absorption, halide ions and BF4 - Preferably, Cl - BF4 - This is preferable.

[0028] In a cation group-containing polyether, the units represented by the general formula (1) are independent of each other, and two or more units represented by the general formula (1) may exist in the cation group-containing polyether. For example, in the entire repeating unit represented by the general formula (1) in the cation group-containing polyether, A +All of the nitrogen-containing cationic groups represented by may be of the same type, or they may be a mixture of different types of nitrogen-containing cationic groups. Furthermore, in the entire repeating unit represented by general formula (1) in the cationic group-containing polyether, X - All of the anions represented may be of the same type, or they may be a mixture of different types of anions.

[0029] Examples of repeating units represented by the above general formula (1) include the repeating unit represented by the following general formula (2). The repeating unit represented by the following general formula (2) is an oxirane unit containing an imidazolium structure. [ka] (In the above general formula (2), R 1 ~R 4 Each of these independently represents a hydrogen atom or a substituent, R 2 and R 3 They may be joined to each other. Also, in general formula (2), X - (This represents an anion.)

[0030] In the above general formula (2), R 1 ~R 4 Each of these independently represents a hydrogen atom or a substituent. Examples of substituents include those similar to those described above for nitrogen-containing aromatic heterocycles. 1 ~R 4 The substituents may be linear or branched, and may also have a ring structure. 1 ~R 4 The substituent is preferably linear in shape.

[0031] In the above general formula (2), R 1 R may be a hydrogen atom or a substituent, and is not particularly limited, but is preferably a hydrogen atom or a hydrocarbon group, more preferably a hydrocarbon group, even more preferably an alkyl group or an alkenyl group, particularly preferably an alkyl group or a vinyl group, and most preferably an alkyl group.1 The number of carbon atoms is preferably 0 to 12, more preferably 0 to 8, even more preferably 1 to 6, even more preferably 1 to 4, particularly preferably 1 to 3, and most preferably 1 to 2.

[0032] In the above general formula (2), R 2 ~R 4 Each of these may independently be a hydrogen atom or a substituent, and is not particularly limited, but each may independently be a hydrogen atom or a hydrocarbon group, more preferably a hydrogen atom, an alkyl group or a vinyl group, even more preferably a hydrogen atom or an alkyl group, and particularly preferably a hydrogen atom. 2 ~R 4 The number of carbon atoms is preferably 0 to 8, more preferably 0 to 6, even more preferably 0 to 4, even more preferably 0 to 3, particularly preferably 0 to 2, and most preferably 0 to 1.

[0033] In the above general formula (2), R 2 ~R 4 It is preferable that 1 to 3 of them represent hydrogen atoms, and more preferably that 2 to 3 of them represent hydrogen atoms. Also, R 2 ~R 4 It is preferable that 0 to 2 of these represent substituents such as hydrocarbon groups, and it is more preferable that 0 to 1 of them represent substituents such as hydrocarbon groups.

[0034] X in the general formula (2) above - The anion represented by is X in general formula (1). - Examples of anions similar to those represented by can be cited, and preferred embodiments are also similar.

[0035] The repeating unit represented by the above general formula (2) preferably contains an imidazolium group, a 1-methylimidasolium group, a 1-butylimidasolium group, a 1-hexylimidasolium group, or a 1-vinylimidasolium group, and more preferably contains a 1-methylimidasolium group.

[0036] The cationic group-containing polyether may contain repeating units other than the repeating unit represented by the general formula (1) above. The repeating units other than the repeating unit represented by the general formula (1) above may be any units derived from monomers copolymerizable with the monomer that gives the repeating unit represented by the general formula (1) above, and are not particularly limited, but examples include alkylene oxide monomer units such as ethylene oxide units, propylene oxide units, 1,2-butylene oxide units, and 1,2-octylene oxide units; aromatic oxirane monomer units such as styrene oxide units, epihalohydrin monomer units such as epichlorohydrin units, epibromohydrin units, and epiiodohydrin units; alkenyl group-containing oxirane monomer units such as allyl glycidyl ether units; aromatic ether group-containing oxirane monomer units such as phenyl glycidyl ether units; and (meth)acryloyl group-containing oxirane monomer units such as glycidyl acrylate units and glycidyl methacrylate units. Among these, alkylene oxide monomer units, epihalohydrin monomer units, and (meth)acryloyl group-containing oxirane monomer units are preferred, and ethylene oxide units, propylene oxide units, epichlorohydrin units, and glycidyl methacrylate units are more preferred. The cationic group-containing polyether may contain one repeating unit other than the repeating unit represented by the general formula (1) above, or it may contain two or more repeating units.

[0037] The cation group-containing polyether may contain two or more repeating units, in which case the distribution pattern of these multiple repeating units is not particularly limited, but it is preferable that it has a random distribution.

[0038] The chain structure of the cation group-containing polyether is not particularly limited and may be linear, or it may have a branched chain structure such as grafted or radial.

[0039] The terminal groups of a cationic polyether are not particularly limited and can be any monovalent group. Specific examples of terminal groups include hydrogen atoms, halogen groups, alkyl groups, haloalkyl groups, hydroxyl groups, azide groups, etc. Furthermore, the terminal group may be a nitrogen-containing cationic group (A) of the repeating unit represented by general formula (1). + ) and anion (X - ) may be a base consisting of the same thing.

[0040] The content of the repeating units represented by the above general formula (1) in the cation group-containing polyether is not particularly limited, but is preferably 1 to 10,000 on average per molecule, more preferably 3 to 1,000, even more preferably 10 to 500, and particularly preferably 30 to 300.

[0041] The proportion of the repeating units represented by the above general formula (1) in the cation group-containing polyether is not particularly limited, but is preferably 5 to 100 mol%, more preferably 10 to 100 mol%, and even more preferably 15 to 100 mol% of the total repeating units of the cation group-containing polyether.

[0042] The method for synthesizing cationic polyethers is not particularly limited, and any synthesis method can be used as long as it yields the desired polyether compound. As an example of a synthesis method, first, a base polymer (polyether without cationic groups) is obtained by the following method (α) or (β).

[0043] A method for obtaining a base polymer by ring-opening polymerization of a monomer containing an oxirane monomer, which contains at least an epihalohydrin such as (α)epichlorohydrin, epibromohydrin, or epiiodohydrin, in the presence of a catalyst disclosed in Japanese Patent Application Publication No. 2010-53217, which comprises an onium salt of a compound containing an atom of Group 15 or Group 16 of the periodic table and a trialkylaluminum in which all contained alkyl groups are linear alkyl groups.

[0044] A method for obtaining a base polymer by ring-opening polymerization of a monomer containing an oxirane monomer, which includes at least an epihalohydrin such as (β)epichlorohydrin, epibromohydrin, or epiiodohydrin, in the presence of a catalyst obtained by reacting triisobutylaluminum with phosphoric acid and triethylamine, as disclosed in Japanese Patent Publication No. 46-27534.

[0045] Then, by reacting the halogen groups constituting the epihalohydrin monomer units of the base polymer obtained by the above method (α) or (β) with an oniumizing agent containing a nitrogen-containing cationic group (oniumization reaction), at least a portion of the halogen groups constituting the epihalohydrin monomer units of the base polymer are converted into onium halide groups containing a nitrogen-containing cationic group, thereby forming an anion (X) in general formula (1). - A polyether compound containing onium halide structural units, which includes repeating units in which the ) is a halide ion, can be obtained. Furthermore, if necessary, the obtained onium halide structural unit-containing polyether compound can be combined with an anion other than a halide ion (X - By reacting a salt of (X) with a metal cation to carry out an anion exchange reaction, the halide ions constituting the onium halide group containing nitrogen-containing cationic groups are exchanged for an anion other than the halide ions (X). - It can be converted to ).

[0046] The oniuming agent containing nitrogen-containing cationic groups used when reacting a base polymer with an oniuming agent containing nitrogen-containing cationic groups is the nitrogen-containing cationic group (A) in general formula (1). + This is an oniating agent corresponding to the imidazolium structure in general formula (2). For example, by using an imidazole compound corresponding to the imidazolium structure in general formula (2) as the oniating agent, the repeating unit represented by general formula (2) can be formed.

[0047] The method for reacting the base polymer with the oniumizing agent is not particularly limited, but a method of mixing the base polymer and the oniumizing agent is preferred. The method of mixing the base polymer and the oniumizing agent is not particularly limited, but examples include adding the oniumizing agent to a solution containing the base polymer and mixing, adding the base polymer to a solution containing the oniumizing agent and mixing, or preparing the oniumizing agent and the base polymer as separate solutions and then mixing the two solutions.

[0048] When reacting the base polymer with the oniuming agent, an inert solvent is preferably used, and it may be nonpolar or polar. Examples of nonpolar solvents include aromatic hydrocarbons such as benzene and toluene; linear saturated hydrocarbons such as n-pentane and n-hexane; and alicyclic saturated hydrocarbons such as cyclopentane and cyclohexane. Examples of polar solvents include ethers such as tetrahydrofuran, anisole, and diethyl ether; esters such as ethyl acetate and ethyl benzoate; ketones such as acetone, 2-butanone, and acetophenone; aprotic polar solvents such as acetonitrile, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide; and protic polar solvents such as ethanol, methanol, and water. Mixed solvents of these are also preferably used. The amount of solvent used is not particularly limited, but it is preferably used so that the concentration of the base polymer is 1 to 50% by mass, and more preferably 3 to 40% by mass.

[0049] The amount of oniuming agent used when reacting the base polymer with the oniuming agent is not particularly limited and can be determined according to the content ratio of the repeating units represented by general formula (1) of the target polyether compound. Specifically, the amount of oniuming agent used is usually in the range of 0.01 to 100 moles, preferably 0.02 to 50 moles, more preferably 0.03 to 10 moles, and even more preferably 0.05 to 2 moles per mole of epichlorohydrin units of the base polymer used.

[0050] The pressure used when reacting the base polymer with the oniuming agent is not particularly limited, but is usually 1 to 500 atm, preferably 1 to 100 atm, and especially preferably 1 to 50 atm. The reaction temperature is also not particularly limited, but is usually 0 to 200°C, preferably 20 to 170°C, and more preferably 40 to 150°C. The reaction time is usually 1 minute to 1,000 hours, preferably 3 minutes to 800 hours, more preferably 5 minutes to 500 hours, and even more preferably 30 minutes to 200 hours.

[0051] Polyether compounds containing onium halide structural units and anions other than halide ions (X - The method for carrying out an anion exchange reaction by reacting a salt of (X) with a metal cation is not particularly limited, but involves a polyether compound containing an onium halide structural unit and an anion other than a halide ion (X) - A preferred method involves mixing a salt of ) and a metal cation and reacting them.

[0052] The conditions for carrying out the anion exchange reaction are not particularly limited, and involve an onium halide structural unit-containing polyether compound and an anion other than a halide ion (X - The mixture may consist only of a salt of the onium halide structure unit and a metal cation, or it may be carried out under conditions where other compounds such as organic solvents are present. The amount of salt used is not particularly limited, but is usually in the range of 0.01 to 100 moles, preferably 0.02 to 50 moles, and more preferably 0.03 to 10 moles, per mole of onium halide structure units in the onium halide structure unit-containing polyether compound used.

[0053] Anions other than halide ions (X) used in anion exchange reactions -The salts of lithium and metal cations are not particularly limited, but examples include lithium (bisfluorosulfonyl)imide (Li(FSO2)2N), lithium bis(trifluoromethylsulfonyl)imide (Li(CF3SO2)2N), lithium (bispentafluoroethylsulfonyl)imide (Li(CF3CF2SO2)2N), sodium acetate (CH3COONa), silver acetate (CH3COOAg), lithium butyrate (C3H7COOLi), lithium trifluoroacetate (CF3COOLi), lithium benzoate (PhCOOLi), potassium tetracyanoborate (KB(CN)4), lithium thiocyanate (LiSCN), lithium (biscyano)imide (Li(NC)2N), lithium methylsulfonate (LiCH3SO3), lithium trifluoromethylsulfonate (LiCF3SO3), potassium hydroxide (KOH), lithium perchlorate (LiClO4), and sodium tetrafluoroborate (NaBF4). Furthermore, in the case of a salt between a polyvalent anion and a metal cation, silver sulfate (Ag2SO4) 2- ), sodium carbonate (Na2CO3 2- Examples include the following. For instance, examples of salts of a polyanion having two or more monovalent anionic groups in its molecule and a metal cation include LiO3SCF2CF2CF2SO3Li, LiO3SCF2CF2SO3Li, and Li2(CF3SO2NSO2CF2CF2OCF2CF2OCF2CF2SO2NSO2CF3).

[0054] The pressure during the anion exchange reaction is typically 1 to 500 atm, preferably 1 to 100 atm, and particularly preferably 1 to 50 atm. The reaction temperature is typically -30 to 200°C, preferably -15 to 180°C, and more preferably 0 to 150°C. The reaction time is typically 1 minute to 1000 hours, preferably 3 minutes to 100 hours, more preferably 5 minutes to 10 hours, and even more preferably 5 minutes to 3 hours.

[0055] After the anion exchange reaction is complete, the mixture containing the cation-containing polyether can be recovered by removing metal cations, halide ions, and their salts through washing with water or other solvents and membrane separation using a semipermeable membrane or similar membrane. Alternatively, the mixture containing the cation-containing polyether can be recovered by extracting it using a solvent such as methanol. Furthermore, the desired cation-containing polyether can be recovered by conventional methods, such as vacuum drying.

[0056] The oxygen-containing organic solvent used in the present invention is not particularly limited, as long as it is an organic solvent having at least one oxygen atom, but examples include: dialkyl ethers of polyethylene glycol such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, pentaethylene glycol dimethyl ether, pentaethylene glycol diethyl ether, hexaethylene glycol dimethyl ether, and hexaethylene glycol diethyl ether; alcohols such as methanol, ethanol, propanol, and butanol; amide compounds such as N,N-dimethylformamide and N-methylpyrrolidone; carnates such as dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, propylene carbonate, and butylene carbonate; and among these, from the viewpoint of carbon dioxide absorption performance, dimethyl ether of polyethylene glycol, methanol, ethanol, N-methylpyrrolidone, and propylene carbonate are preferred, and tetraethylene glycol dimethyl ether, methanol, N-methylpyrrolidone, and propylene carbonate are more preferred.

[0057] In the carbon dioxide absorbing composition of the present invention, the content ratio of the polymer to the oxygen-containing organic solvent is 2:98 to 40:60 by weight ratio of polymer to oxygen-containing organic solvent, preferably 2:98 to 35:65, and more preferably 3:97 to 30:70. If the polymer content is too low, the carbon dioxide absorption effect due to the addition of the polymer will be insufficient, while if the polymer content is too high, the viscosity of the carbon dioxide absorbing composition will increase, reducing the carbon dioxide absorption performance.

[0058] Furthermore, the carbon dioxide absorbing composition of the present invention may contain various additives in addition to polymers and oxygen-containing organic solvents. Examples of additives include basic inorganic compounds, antioxidants, ultraviolet absorbers, light stabilizers, surfactants, defoamers, electrolytes, colorants (dyes and pigments), flame retardants, and antistatic agents.

[0059] The method for preparing the carbon dioxide absorption composition of the present invention is not particularly limited, but one method is to dissolve or disperse the polymer by adding and mixing it in an oxygen-containing organic solvent.

[0060] From the viewpoint of suitably absorbing carbon dioxide, the carbon dioxide absorbing composition of the present invention is preferably liquid at its operating temperature, and typically, it is preferably liquid at 25°C.

[0061] In particular, the carbon dioxide absorption composition of the present invention can be used in a liquid state, and by housing it in a reaction vessel or the like and placing it in the flow path of the gas containing carbon dioxide to be treated, it can be made into a carbon dioxide absorption module. With such a carbon dioxide absorption module, since the carbon dioxide absorption composition of the present invention can efficiently absorb carbon dioxide, the reaction vessel housing the carbon dioxide absorption composition can be made relatively small. Therefore, the carbon dioxide absorption composition of the present invention makes it possible to miniaturize and improve the efficiency of devices such as carbon dioxide absorption modules. [Examples]

[0062] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" refers to mass. The test methods used in this embodiment and comparative example are as follows:

[0063] <Number-average molecular weight (Mn) and molecular weight distribution (Mw / Mn)> (1) Number-average molecular weight (Mn) and molecular weight distribution (Mw / Mn) of the base polymer The number-average molecular weight (Mn), weight-average molecular weight (Mw), and molecular weight distribution (Mw / Mn) of the base polymer obtained in Production Example 1 were measured as polyethylene glycol equivalent values ​​by gel permeation chromatography (GPC) using dimethylformamide as the solvent. An HLC-8320 (Tosoh Corporation) was used as the measuring instrument, with three TSKgel-α-M (Tosoh Corporation) columns connected in series, and a differential refractometer RI-8320 (Tosoh Corporation) was used as the detector.

[0064] (2) Number average molecular weight (Mn) of polyether compounds containing imidazolium structure The number-average molecular weight (Mn) of the imidazolium structure-containing polyether compounds obtained in Production Examples 2-5 was determined as follows: First, the average molecular weight of all repeating units constituting the imidazolium structure-containing polyether compound was determined from the average molecular weight of the repeating units of the base polymer, the average molecular weight of the various monomer units constituting the polyether compound, and the content of the various monomer units determined by (3) below. Then, the value obtained by multiplying the number of repeating units of the base polymer by the average molecular weight of all repeating units constituting the imidazolium structure-containing polyether compound was taken as the number-average molecular weight (Mn) of the polyether compound.

[0065] (3) Structures of the base polymer and the imidazolium structure-containing polyether compound, and the content of monomer units in the base polymer and the imidazolium structure-containing polyether compound The structures of the base polymer and the imidazolium structure-containing polyether compound, and the content of monomer units in the base polymer and the imidazolium structure-containing polyether compound were measured as follows using a nuclear magnetic resonance apparatus (NMR). Specifically, first, 30 mg of a sample of the base polymer or the imidazolium structure-containing polyether compound was added to 1.0 mL of deuterated chloroform or deuterated dimethyl sulfoxide, and the mixture was shaken for 1 hour to uniformly dissolve the sample. Then, NMR measurement was performed on the obtained solution to 1 obtain a 1H-NMR spectrum, and the structure of the sample was assigned according to a conventional method. In addition, the content of the repeating unit represented by general formula (2) in the imidazolium structure-containing polyether compound containing the repeating unit represented by general formula (2) was calculated by the following method. Specifically, first, the number of moles B1 of all oxirane monomer units was calculated from the integrated value of protons derived from the oxirane monomer units in the main chain. Next, the number of moles B2 of the repeating unit represented by general formula (2) was calculated from the integrated value of protons derived from the imidazolium structure in the repeating unit represented by general formula (2). Then, the percentage of B2 relative to B1 was obtained as the content of the repeating unit represented by general formula (2) in the imidazolium structure-containing polyether compound.

[0066] <Determination of CO₂ concentration in gas phase by GC measurement> A TCD detector was mounted as a detector on GC7890 manufactured by Agilent Technologies, and HP PLOTQ + CP-Molsieve 5A was mounted as a column, and the CO₂ concentration in the gas phase was measured.

[0067] <CO₂ pressure at gas-liquid equilibrium> A PVT cell manufactured by Top Industrie was used to measure the gas-liquid equilibrium pressure at a predetermined solution amount and a predetermined CO₂ amount.

[0068] <Index of increase in CO2 solubility at equilibrium due to polymers> A predetermined amount of carbon dioxide absorption composition was introduced into a PVT cell manufactured by Top Industrie, and then a predetermined amount of CO2 was repeatedly introduced. The CO2 pressure at gas-liquid equilibrium was measured for each predetermined amount of CO2 introduced. Based on the measurement data, the amount of CO2 dissolved in the carbon dioxide absorption composition under 5 atmospheres of CO2 was calculated in weight percent. This was defined as the CO2 weight percent (I) of the carbon dioxide absorption composition at gas-liquid equilibrium. The carbon dioxide absorption composition was stirred at room temperature under vacuum for 5 minutes to confirm that all dissolved gases had evaporated before the above measurements were performed. Next, an oxygen-containing organic solvent constituting the carbon dioxide absorption composition was prepared. A predetermined amount of the oxygen-containing organic solvent was introduced into a PVT cell manufactured by Top Industrie, and then a predetermined amount of CO2 was repeatedly introduced. The CO2 pressure at vapor-liquid equilibrium was measured for each predetermined amount of CO2 introduced. Based on the measurement data, the amount of CO2 dissolved in the oxygen-containing organic solvent under 5 atmospheres of CO2 was calculated in weight percent. This was defined as the CO2 weight percent (II) at vapor-liquid equilibrium of the oxygen-containing organic solvent. The oxygen-containing organic solvent was stirred at room temperature under vacuum for 5 minutes to confirm that all dissolved gases had evaporated before the above measurements were performed. Then, the index of the increase in CO2 dissolution at equilibrium due to the polymer was determined according to the following formula. <Index of increase in CO2 solubility at equilibrium due to polymer> = <CO2 wt% (I) at gas-liquid equilibrium of carbon dioxide absorbing composition> / <CO2 wt% (II) at gas-liquid equilibrium of oxygen-containing organic solvent>

[0069] <Reduction rate of CO2 in the gas phase after 15 minutes> 100 g of carbon dioxide absorption composition was introduced into a 500 mL sealed glass container equipped with a magnetic stirrer. A mixed gas of CO2 and nitrogen (CO2:N2=23:77 (moles:moles)) was circulated through the glass container at 1 atmosphere, and stirring of the carbon dioxide absorption composition was started using the magnetic stirrer. After 1 minute, the flow of the mixed gas was stopped, and stirring was continued. After 15 minutes, the gas in the glass container was sampled and measured by GC to determine the CO2 concentration in the gas phase. This was defined as the CO2 concentration in the gas phase (i) [unit: %]. The carbon dioxide absorption composition was stirred at room temperature under vacuum for 5 minutes to confirm that all dissolved gases had evaporated before the above measurement was performed. Then, using the CO2 concentration of 23% in the mixed gas of CO2 and nitrogen (CO2:N2=23:77 (moles:moles)), the reduction rate of CO2 in the gas phase after 15 minutes was calculated according to the following formula. <Reduction rate of CO2 in the gas phase after 15 minutes> = ((23 - CO2 concentration after 15 minutes (i)) / 23) × 100

[0070] <Lower limit partial pressure (bar) of CO2 removal at equilibrium after 30 minutes> 100 g of carbon dioxide absorption composition was introduced into a 500 mL sealed glass container equipped with a magnetic stirrer. A mixed gas of CO2 and nitrogen (CO2:N2 = 23:77 (moles:moles)) was circulated through the glass container at 1 atmosphere, and stirring of the carbon dioxide absorption composition was started using the magnetic stirrer. After 1 minute, the flow of the mixed gas was stopped, and stirring was continued. After 30 minutes, the gas in the glass container was sampled and measured by GC, and the CO2 concentration in the gas phase was measured as a mole fraction. This was defined as the CO2 concentration in the gas phase (ii). The carbon dioxide absorption composition was stirred at room temperature under vacuum for 5 minutes to confirm that all dissolved gases had evaporated before the above measurement was performed. The lower limit partial pressure for CO2 removal at equilibrium after 30 minutes was calculated according to the following formula. <Lower limit partial pressure (bar) for CO2 removal at equilibrium after 30 minutes> = (CO2 concentration in the gas phase after 30 minutes (ii)) × 1.0 (bar)

[0071] <Manufacturing Example 1> (Living anionic polymerization of epichlorohydrin) 0.322 g of tetran-butylammonium bromide and 50 ml of toluene were added to a glass reactor with a stirrer, which had been purged with argon, and the mixture was cooled to 0°C. Next, 0.148 g of triethylaluminum (1.3 equivalents relative to tetran-butylammonium bromide) dissolved in 5 ml of toluene was added and the mixture was reacted for 15 minutes to obtain a catalyst composition. 10.0 g of epichlorohydrin was added to the obtained catalyst composition, and a polymerization reaction was carried out at 0°C. After the start of the polymerization reaction, the viscosity of the solution gradually increased. After 12 hours of reaction, a small amount of water was added to the polymerization reaction solution to stop the reaction. The obtained polymerization reaction solution was deashed of the catalyst residue by washing with a 0.1 N aqueous hydrochloric acid solution, and then washed with deionized water. The organic phase was then dried under reduced pressure at 50°C for 12 hours. The yield of the resulting colorless, transparent oily substance was 9.9 g. Furthermore, the obtained substance had a number-average molecular weight (Mn) of 10,700, a degree of polymerization of 116, and a molecular weight distribution (Mw / Mn) of 1.18, as determined by GPC. This compound was used as the base polymer (polyepichlorohydrin A).

[0072] <Manufacturing Example 2> (Quaternary merization of polyepichlorohydrin A by 1-methylimidazole) 8.0 g of polyepichlorohydrin A obtained in Production Example 1, 22.0 g of 1-methylimidazole, and 16.0 g of N,N-dimethylacetamide were added to a glass reactor with a stirrer purged with argon and heated to 80°C. After reacting at 80°C for 144 hours, the reaction was stopped by cooling to room temperature. A portion of the resulting reaction solution was withdrawn and dried under reduced pressure at 50°C for 120 hours, yielding 14.9 g of a reddish-brown resinous substance. Regarding this resinous substance, 1¹H-NMR measurements and elemental analysis revealed that polyether compound B (a cation-containing polyether consisting of repeating units represented by formula (3) below) has 1-methylimidazolium halide groups, in which all chloro groups in polyepichlorohydrin A are substituted with 1-methylimidazolium chloride groups, and all bromo groups of the polymerization initiation end bromomethyl groups are substituted with 1-methylimidazolium bromide groups. The obtained imidazolium structure-containing polyether compound B, which has a halide ion as a counteranion, had a number-average molecular weight (Mn) of 20,200, a molecular weight distribution (Mw / Mn) of 1.18, and a degree of polymerization of 116, as determined by GPC. [ka]

[0073] <Manufacturing Example 3> (Anion exchange of imidazolium structure-containing polyether compound B, which has a halide ion as a counter anion, by sodium tetrafluoroborate) 5.0 g of polyether compound B containing an imidazolium structure with a halide ion as a counteranion, obtained in Production Example 2, 1.6 g of sodium tetrafluoroborate, and 100 mL of deionized water were added to a glass reactor with a stirrer. After reacting at room temperature for 30 minutes, the mixture was dried under reduced pressure at 50°C for 12 hours to obtain a reddish-brown resinous substance. After dissolving and dispersing in acetonitrile, the acetonitrile solution was filtered through a 0.45 micrometer filter to remove inorganic salts. The acetonitrile was dried under reduced pressure at 50°C for 12 hours to obtain 6.4 g of the reddish-brown resinous substance. 1¹H-NMR spectroscopy and elemental analysis revealed that compound C, an imidazolium structure-containing polyether compound (consisting of repeating units represented by formula (4) below), was formed by replacing 50% of the chloride and bromide ions of imidazolium structure-containing polyether compound B, which had a halide ion as a counter anion, with tetrafluoroborate anions, chloride ions, and bromide ions as counter anions. The obtained imidazolium structure-containing polyether compound C, with a tetrafluoroborate anion as a counter anion, had a number-average molecular weight (Mn) of 20,100, a molecular weight distribution (Mw / Mn) of 1.18, and a degree of polymerization of 116, as determined by GPC. [ka]

[0074] <Manufacturing Example 4> (Quaternary merization of polyepichlorohydrin A by 1-methylimidazole) 35.0 g of polyepichlorohydrin A obtained in Production Example 1, 4.7 g of 1-methylimidazole, and 105.0 g of N,N-dimethylacetamide were added to a glass reactor with a stirrer purged with argon and heated to 120°C. After reacting at 120°C for 48 hours, the reaction was stopped by cooling to room temperature, and the resulting reaction solution was dried under reduced pressure at 50°C for 120 hours to obtain 31.2 g of a reddish-brown resinous substance. Regarding this resinous substance, 1¹H-NMR measurements and elemental analysis revealed that polyether compound D, containing 1-methylimidazolium halide groups, was a cation-containing polyether consisting of repeating units represented by formula (5) below. This was determined by substituting 13% of the chloromethyl groups of the epichlorohydrin units in polyepichlorohydrin A and the bromomethyl groups of the polymerization initiation end with 1-methylimidazolium halide groups. The obtained imidazolium structure-containing polyether compound D, having a halide ion as a counteranion, had a number-average molecular weight (Mn) of 11,700, a molecular weight distribution (Mw / Mn) of 1.18, and a degree of polymerization of 116, as determined by GPC. [ka]

[0075] <Manufacturing Example 5> (Anion exchange of imidazolium structure-containing polyether compound D having a halide ion as a counteranion with lithium trifluoromethanesulfonimide) 24.3 g of the imidazolium structure-containing polyether compound D, which has a halide ion as a counteranion, obtained in Production Example 4, 14.1 g of lithium trifluoromethanesulfonimide, and 300 mL of methanol were added to a glass reactor with a stirrer. After reacting at room temperature for 30 minutes, the mixture was dried under reduced pressure at 50°C for 12 hours to obtain a reddish-brown syrup-like substance. The reddish-brown syrup-like substance was dissolved in 100 mL of acetone, reprecipitated in 800 mL of water, and the supernatant was removed. This operation was repeated twice, and the settled reddish-brown syrup-like substance was dried under reduced pressure at 50°C for 12 hours to obtain 20.8 g of a reddish-brown oily substance. 1¹H-NMR spectroscopy and elemental analysis revealed that compound E, an imidazolium structure-containing polyether compound (a cation group-containing polyether consisting of repeating units represented by formula (6) below), was formed by replacing all chloride and bromide ions of the starting material, imidazolium structure-containing polyether compound D, which has a halide ion as a counter anion, with trifluoromethanesulfonimide anions. The obtained imidazolium structure-containing polyether compound E, having trifluoromethanesulfonimide anions as counter anions, had a number-average molecular weight (Mn) of 15,300, a molecular weight distribution (Mw / Mn) of 1.18, and a degree of polymerization of 116, as determined by GPC. [ka]

[0076] <Example 1> Ten parts of polyvinylpyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd., number-average molecular weight (Mn): 10,000, degree of polymerization 90) and ninety parts of N-methylpyrrolidone were added to a glass container equipped with a stirrer. The mixture was stirred under air at room temperature (25°C) for 30 minutes, and a homogeneous solution was confirmed to be obtained, thereby obtaining the carbon dioxide absorption composition of Example 1. The index of CO2 dissolution increase at equilibrium due to the polymer, the reduction rate of CO2 in the gas phase after 15 minutes, and the lower limit partial pressure of CO2 removal at equilibrium after 30 minutes were measured according to the above method. The results are shown in Table 1.

[0077] <Example 2> In a glass container equipped with a stirrer, 10 parts of polyether compound C and 90 parts of methanol were added and stirred under air at room temperature (25°C) for 30 minutes. After confirming that a homogeneous solution had been obtained, the carbon dioxide absorption composition of Example 2 was obtained, and measurements were performed in the same manner as in Example 1 according to the method described above. The results are shown in Table 1.

[0078] <Example 3> In a glass container equipped with a stirrer, 10 parts of polyepichlorohydrin A and 90 parts of tetraethylene glycol dimethyl ether were added and stirred under air at room temperature (25°C) for 30 minutes. After confirming that a homogeneous solution had been obtained, the carbon dioxide absorption composition of Example 3 was obtained, and measurements were performed in the same manner as in Example 1 according to the method described above. The results are shown in Table 1.

[0079] <Example 4> Ten parts of polyepichlorohydrin A and ninety parts of propylene carbonate were added to a glass container equipped with a stirrer, and the mixture was stirred under air at room temperature (25°C) for 30 minutes. After confirming that a homogeneous solution had been obtained, the carbon dioxide absorption composition of Example 4 was obtained, and measurements were performed in the same manner as in Example 1 according to the method described above. The results are shown in Table 1.

[0080] <Example 5> In a glass container equipped with a stirrer, 10 parts of polyethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., number-average molecular weight (Mn): 20,000 in standard polystyrene equivalents according to GPC, degree of polymerization: 450-mer) and 90 parts of methanol were added. The mixture was stirred under air at room temperature (25°C) for 30 minutes, and a homogeneous solution was confirmed to be obtained, thereby obtaining the carbon dioxide absorption composition of Example 5. Measurements were then performed in the same manner as in Example 1, according to the method described above. The results are shown in Table 1.

[0081] <Example 6> In a glass container equipped with a stirrer, 5 parts of polyepichlorohydrin A and 95 parts of tetraethylene glycol dimethyl ether were added and stirred under air at room temperature (25°C) for 30 minutes. After confirming that a homogeneous solution had been obtained, the carbon dioxide absorption composition of Example 6 was obtained, and measurements were performed in the same manner as in Example 1 according to the method described above. The results are shown in Table 1.

[0082] <Example 7> In a glass container equipped with a stirrer, 20 parts of polyepichlorohydrin A and 80 parts of tetraethylene glycol dimethyl ether were added and stirred under air at room temperature (25°C) for 30 minutes. After confirming that a homogeneous solution had been obtained, the carbon dioxide absorption composition of Example 7 was obtained, and measurements were performed in the same manner as in Example 1 according to the method described above. The results are shown in Table 1.

[0083] <Example 8> Three parts of polyepichlorohydrin A and ninety-seven parts of tetraethylene glycol dimethyl ether were added to a glass container equipped with a stirrer. The mixture was stirred under air at room temperature (25°C) for 30 minutes, and a homogeneous solution was confirmed to be obtained, thereby obtaining the carbon dioxide absorption composition of Example 8. Measurements were then performed in the same manner as in Example 1, according to the method described above. The results are shown in Table 1.

[0084] <Example 9> In a glass container equipped with a stirrer, 25 parts of polyether compound E and 75 parts of tetraethylene glycol dimethyl ether were added and stirred under air at room temperature (25°C) for 30 minutes. After confirming that a homogeneous solution had been obtained, the carbon dioxide absorption composition of Example 8 was obtained, and measurements were performed in the same manner as in Example 1 according to the method described above. The results are shown in Table 1.

[0085] <Comparative Examples 1-4> Using N-methylpyrrolidone, methanol, tetraethylene glycol dimethyl ether, and propylene carbonate as oxygen-containing organic solvents, the reduction rate of CO2 in the gas phase after 15 minutes and the lower limit partial pressure of CO2 removal at equilibrium after 30 minutes were measured according to the method described above. The results are shown in Table 1.

[0086] [Table 1]

[0087] As shown in Table 1, a carbon dioxide absorption composition containing a polymer with a number-average molecular weight of 3,000 to 50,000 and an oxygen-containing organic solvent in a predetermined ratio can increase the amount of CO2 dissolved at equilibrium compared to using only the oxygen-containing organic solvent, resulting in a higher reduction rate of CO2 in the gas phase after 15 minutes, a lower limit partial pressure for CO2 removal at equilibrium after 30 minutes, and excellent CO2 absorption efficiency (Examples 1-9).

Claims

1. It contains a polymer with a number-average molecular weight of 3,000 to 50,000 and an oxygen-containing organic solvent. A carbon dioxide absorbing composition wherein the content ratio of the polymer to the oxygen-containing organic solvent is 2:98 to 40:60 in terms of the weight ratio of polymer to oxygen-containing organic solvent.

2. The carbon dioxide absorbing composition according to claim 1, wherein the oxygen-containing organic solvent is at least one selected from polyethylene glycol dimethyl ether, methanol, ethanol, N-methylpyrrolidone, and propylene carbonate.

3. The carbon dioxide absorbing composition according to claim 1 or 2, wherein the polymer contains at least one selected from alkylene oxide monomer units, hydroxyl group-containing monomer units, and amide structure-containing monomer units as monomer units.

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