Carbon dioxide absorbent composition

Abstract

The present invention provides a carbon dioxide absorbent composition containing a basic inorganic compound, a carbon dioxide capturing polymer, and a dispersion medium.

Description

Carbon dioxide absorbent composition

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

[0002] In recent years, there has been increasing discussion about global climate change, and as greenhouse gases such as carbon dioxide are thought to be one of the causes of climate change, measures to combat greenhouse gases such as carbon dioxide are being considered.

[0003] For example, Patent Document 1 discloses CO ２ gaseous CO ２ 1. A method for isolating a CO ２ The aqueous ammonia capture liquid is then reacted with gaseous CO to produce sequestered carbonate and aqueous ammonium salts. ２ and (b) combining the aqueous ammonium salt with geomass to produce a regenerated aqueous ammonia capture liquid.

[0004] However, in the technology of Patent Document 1, ammonia is used to produce carbon dioxide (CO ２ ) and uses gaseous ammonia, which requires four steps, including an absorption step and a regeneration step, resulting in poor efficiency.

[0005] JP 2023-78242 A

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a carbon dioxide absorbent composition capable of efficiently absorbing carbon dioxide.

[0007] The present inventors have conducted studies to achieve the above object and have found that a carbon dioxide absorbent composition containing a basic inorganic compound, a carbon dioxide-trapping polymer, and a dispersion medium can efficiently absorb carbon dioxide, thereby completing the present invention.

[0008] That is, the present invention provides the following carbon dioxide absorbent compositions. [1] A carbon dioxide absorbent composition containing a basic inorganic compound, a carbon dioxide-trapping polymer, and a dispersion medium. [2] The carbon dioxide absorbent composition according to [1], wherein the basic inorganic compound is a chloride, hydroxide, or oxide. [3] The carbon dioxide absorbent composition according to [1] or [2], wherein the basic inorganic compound contains an alkaline earth metal. [4] The carbon dioxide absorbent composition according to any of [1] to [3], wherein the carbon dioxide-trapping polymer is a polymer having a solubility of 1 g or more in 100 g of water at a temperature of 25°C. [5] The carbon dioxide absorbent composition according to any of [1] to [4], wherein the carbon dioxide-trapping polymer is a polymer having a degree of polymerization in the range of 10 to 20,000. [6] The carbon dioxide absorbent composition according to any of [1] to [5], wherein the content ratio of the basic inorganic compound to the carbon dioxide-trapping polymer is in the range of 50:1 to 1:50 by weight ratio of basic inorganic compound:carbon dioxide-trapping polymer. [7] The carbon dioxide absorbent composition according to any one of [1] to [6], wherein the content of the carbon dioxide trapping polymer is 1 to 100 parts by weight relative to 100 parts by weight of the dispersion medium. [8] The carbon dioxide absorbent composition according to any one of [1] to [7], wherein the content of the carbon dioxide trapping polymer is 2 to 60 parts by weight relative to 100 parts by weight of the dispersion medium. [9] The carbon dioxide absorbent composition according to any one of [1] to [8], wherein the carbon dioxide trapping polymer is at least one selected from polyethylene glycol, polyvinylpyrrolidone, and a cationic group-containing polymer having a cationic group in the polymer chain.

[0009] According to the present invention, it is possible to provide a carbon dioxide absorbent composition capable of efficiently absorbing carbon dioxide.

[0010] The carbon dioxide absorbent composition of the present invention is a composition containing a basic inorganic compound, a carbon dioxide-trapping polymer, and a dispersion medium.

[0011] The basic inorganic compound is a compound that, when dispersed or dissolved in water to form a dispersion or solution, exhibits basicity, and acts as a carbon dioxide absorbent. Examples of the basic inorganic compound include, but are not limited to, chlorides, hydroxides, and oxides, and more specifically, metal chlorides, metal hydroxides, and metal oxides. Examples of the basic inorganic compound include those containing alkali metals such as lithium, sodium, and potassium, and alkaline earth metals such as magnesium, calcium, and strontium as metals. Among these, from the viewpoint of carbon dioxide absorption, basic inorganic compounds containing alkaline earth metals are preferred, and those containing magnesium and calcium are more preferred.

[0012] Specific examples of basic inorganic compounds include magnesium compounds such as magnesium chloride, magnesium hydroxide, and magnesium oxide; calcium compounds such as calcium chloride, calcium hydroxide, and calcium oxide; sodium compounds such as sodium hydroxide; potassium compounds such as potassium hydroxide; etc. Among these, magnesium hydroxide, calcium hydroxide, sodium hydroxide, and potassium hydroxide are preferred, and magnesium hydroxide and calcium hydroxide are more preferred.

[0013] For example, when magnesium hydroxide or calcium hydroxide is used as the basic inorganic compound, it reacts with carbon dioxide according to the following formula to form magnesium carbonate or calcium carbonate, thereby absorbing carbon dioxide: Mg(OH) ２ +CO ２ → MgCO ３ +H ２ O Ca(OH) ２ +CO ２ → CaCO ３ +H ２ O

[0014] When sodium hydroxide or potassium hydroxide is used as the basic inorganic compound, it reacts with carbon dioxide to form sodium carbonate or potassium carbonate according to the following formula, thereby absorbing carbon dioxide: 2NaOH + CO ２ → Na ２ CO ３ +H ２ O 2KOH + CO ２ → K ２ CO ３ +H ２ O

[0015] In particular, carbonates such as magnesium carbonate and calcium carbonate that are produced after absorbing carbon dioxide are high-value-added materials that can be used for various applications, including cementing agents, and therefore, compounds in the form of carbonates after absorbing carbon dioxide can be effectively utilized by separating them from the carbon dioxide absorbent composition.

[0016] As the basic inorganic compound, a compound that is insoluble in the dispersion medium may be used, or a compound that is soluble in the dispersion medium may be used. When a compound that is insoluble in the dispersion medium is used as the basic inorganic compound, the carbon dioxide absorbent composition can be in the form of a dispersion liquid. When a compound that is soluble in the dispersion medium is used, the carbon dioxide absorbent composition can be in the form of a solution. For example, when a dispersion medium containing water is used and magnesium hydroxide or calcium hydroxide is used as the basic inorganic compound, these are water-insoluble or poorly water-soluble compounds, so the carbon dioxide absorbent composition can be in the form of a dispersion liquid. When a dispersion medium containing water is used and sodium hydroxide or potassium hydroxide is used as the basic inorganic compound, these are water-soluble compounds, so the carbon dioxide absorbent composition can be in the form of a solution.

[0017] The form of the basic inorganic compound is not particularly limited and may be any of particulate, plate-like, fibrous, etc., but is preferably particulate from the viewpoint of being able to further enhance the carbon dioxide absorption. The average particle size of the basic inorganic compound is not particularly limited, but is preferably 0.1 to 1000 μm, more preferably 1 to 100 μm.

[0018] The content of the basic inorganic compound in the carbon dioxide absorbent composition of the present invention is not particularly limited, but is preferably 1 to 200 parts by weight, more preferably 5 to 65 parts by weight, even more preferably 10 to 60 parts by weight, and still more preferably 40 to 55 parts by weight, relative to 100 parts by weight of the dispersion medium. By setting the content of the basic inorganic compound within the above range, the carbon dioxide absorbent composition can be made easy to handle and its carbon dioxide absorbency can be further improved.

[0019] The dispersion medium is not particularly limited and may be selected depending on the type of basic inorganic compound and the type of carbon dioxide trapping polymer. Examples of the dispersion medium include water and organic solvents such as alcohols such as ethanol, methanol, propanol, and butanol; ketones such as acetone, methyl ethyl ketone, 2-butanone, and acetophenone; nitriles such as acetonitrile; and amines such as dimethylamine, diethylamine, trimethylamine, triethylamine, and pyridine. From the standpoint of ease of handling, it is preferable to use a dispersion medium containing water. A mixture of water and an organic solvent such as an alcohol, ketone, nitrile, or amine may also be used, with a mixture of water and an alcohol being preferred. The water content in the dispersion medium is preferably 50 to 100% by weight.

[0020] The carbon dioxide trapping polymer may be any polymer that can draw carbon dioxide into the dispersion medium due to the affinity between carbon dioxide and the carbon dioxide trapping polymer. The carbon dioxide trapping polymer is not particularly limited, but is preferably a polymer containing a polar heteroatom other than carbon or hydrogen atoms, and more preferably a polymer containing a nitrogen or oxygen atom. In the present invention, the carbon dioxide absorbent composition contains a carbon dioxide trapping polymer in addition to a basic inorganic compound and a dispersion medium, thereby efficiently drawing carbon dioxide into the dispersion medium due to the affinity of the carbon dioxide trapping polymer, thereby further enhancing the carbon dioxide absorption by the basic inorganic compound. This allows the carbon dioxide absorbent composition of the present invention to efficiently absorb carbon dioxide.

[0021] Furthermore, since the carbon dioxide absorbent composition of the present invention is usually in the form of a dispersion or solution, it can be contained in a reaction vessel or the like in the form of a dispersion or solution and installed on a distribution path for a gas containing carbon dioxide to be treated to form a carbon dioxide absorption module. Since the carbon dioxide absorbent composition of the present invention can efficiently absorb carbon dioxide, the reaction vessel containing the carbon dioxide absorbent composition can be made relatively small. Furthermore, since a basic inorganic compound is used, there are fewer reaction steps and no gas is passed through. Furthermore, since carbon dioxide can be absorbed in a solid state, a compression operation can also be eliminated. Therefore, the carbon dioxide absorbent composition of the present invention enables the miniaturization and efficiency improvement of devices such as carbon dioxide absorption modules.

[0022] Incidentally, by including a carbon dioxide-trapping polymer, when the carbon dioxide absorbent composition is in the state of a dispersion, in addition to the effect of being able to efficiently absorb carbon dioxide, the following effect can also be achieved. That is, when the carbon dioxide absorbent composition is in the state of a dispersion, the action of the carbon dioxide-trapping polymer can make the dispersion stability of the dispersion excellent. In particular, when a basic inorganic compound becomes a compound in the form of a carbonate by absorbing carbon dioxide, its dispersibility in a dispersion medium such as water tends to decrease. However, the action of the carbon dioxide-trapping polymer can make the dispersion stability of the dispersion excellent even when it contains such a compound in the form of a carbonate.

[0023] The carbon dioxide-trapping polymer is preferably one that can exist in the carbon dioxide absorbent composition in a dissolved or swollen state in the dispersion medium. For example, when a dispersion medium containing water is used, the carbon dioxide-trapping polymer is preferably a polymer having a solubility of 1 g or more in 100 g of water at a temperature of 25°C, and more preferably a polymer having a solubility of 4 to 50 g. Note that, in the present invention, depending on the molecular weight, etc., of the carbon dioxide-trapping polymer, the polymer may swell in water. Therefore, in the present invention, the solubility in water is determined to be dissolved not only when the polymer is dissolved in water but also when the polymer swells in water, and the solubility is measured including the amount of swelling. Whether the polymer is dissolved or swollen in water can be determined, for example, by measuring absorbance or the like to determine whether light scattering, etc., derived from the carbon dioxide-trapping polymer that is not dissolved or swollen can be substantially observed. When the carbon dioxide-trapping polymer is present in the carbon dioxide absorbent composition in a state of being dissolved at a high concentration in the dispersion medium, the carbon dioxide trapping ability of the carbon dioxide absorbent composition is enhanced. By setting the solubility of the carbon dioxide trapping polymer in water within the above range, precipitation of the carbon dioxide trapping polymer can be suppressed, and the polymer can be made excellent in long-term stability.

[0024] The molecular weight and degree of polymerization of the carbon dioxide-trapping polymer may be arbitrary, but it is preferable that they are capable of being present in the carbon dioxide absorbent composition in a state of being dissolved at a high concentration in the dispersion medium. The carbon dioxide-trapping polymer is preferably a polymer having a degree of polymerization in the range of 10 to 20,000, more preferably 10 to 2,000. By setting the degree of polymerization to be equal to or less than the upper limit of the above range, carbon dioxide diffusion is improved and the carbon dioxide trapping ability can be further enhanced. On the other hand, by setting the degree of polymerization to be equal to or more than the lower limit of the above range, the carbon dioxide trapping ability of the carbon dioxide-trapping polymer itself can be further enhanced.

[0025] Specific examples of carbon dioxide trapping polymers include, but are not limited to, polyalkylene oxides such as polyethylene glycol, poly(ethylene glycol-co-propylene glycol), polyethylene oxide, and poly(ethylene oxide-co-propylene oxide); 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 sodium salts thereof; and cellulose derivatives and salts thereof such as hydroxyethyl cellulose, hydroxypropyl cellulose, and carboxymethyl cellulose. Among these, from the viewpoint of carbon dioxide absorption, polyalkylene oxides, polyvinylamides, polycarboxylic acids, and cationic group-containing polymers having cationic groups in the polymer chain are preferred, polyalkylene oxides, polyvinylamides, and cationic group-containing polymers having cationic groups in the polymer chain are more preferred, polyethylene glycol, polyvinylpyrrolidone, and cationic group-containing polymers having cationic groups in the polymer chain are particularly preferred, and cationic group-containing polymers having cationic groups in the polymer chain are more preferred. If the carbon dioxide trapping polymer is neutral or basic, it is less likely to interact with basic inorganic compounds or undergo acid-base reactions, and long-term storage stability can be further improved.

[0026] The cationic group-containing polymer having a cationic group in the polymer chain (hereinafter referred to as "cationic group-containing polymer" as appropriate) is not particularly limited as long as it is a polymer having a cationic group in the polymer chain, and may be a polymer having a cationic group in the main chain of the polymer, or a polymer having a cationic group in the side chain of the polymer, or further may be a polymer having a cationic group in the main chain and the side chain of the polymer.

[0027] Examples of cationic group-containing polymers include addition polymers of vinyl compounds, polyethers, polyethyleneimines, and polyoxazolines, as cationic group-containing polymers having cationic groups in their side chains. Examples of cationic group-containing polymers having cationic groups in their main chains include ionenes, epichlorohydrin-amine condensates, and polyamidepolyamine epichlorohydrin. These may have any other substituents, or may have some hydrogen atoms substituted with halogen atoms such as fluorine. Furthermore, the cationic group-containing polymer may be a polymer in which, in addition to a structural unit having a cationic group, a structural unit derived from a monomer not having a cationic group is copolymerized, and the pH may be adjusted by introducing a structural unit derived from an acidic monomer or a structural unit derived from a basic monomer.

[0028] The cationic group-containing polymer has a cationic group in the polymer chain. The counter anion for such a cationic group is not particularly limited, and examples thereof include imides such as fluorosulfonylimide, bistrifluoromethylsulfonylimide, and bispentafluoroethylsulfonylimide; halogens such as chlorides and bromides; tetrafluoroboric acid, hexafluorophosphate, dicyanoamide, tetracyanoborate, carbonate, alkylcarbonate, triflate, perchloric acid, nitric acid, sulfuric acid, alkylsulfuric acid, sulfonic acid, phosphoric acid, and alkylphosphate; and the like, but are not particularly limited thereto.

[0029] The cationic group-containing polymer is not particularly limited, but examples of polymers having cationic groups on the side chains of the polymer include cationic group-containing polyethers containing a repeating unit represented by the following general formula (1):

[0030] (In the above general formula (1), A ＋ represents a nitrogen-containing cationic group. － represents an anion.)

[0031] A ＋ Examples of the nitrogen-containing cationic group represented by the formula (I) include an amino group, a nitrogen-containing cationic aromatic group, and a nitrogen-containing cationic aliphatic group.

[0032] A ＋ As the nitrogen-containing cationic aromatic group as the 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 containing a cationic nitrogen-containing aromatic heterocycle may have a nitrogen atom in the ring and have aromaticity, and may have heteroatoms other than nitrogen atoms such as oxygen atoms and sulfur atoms, and some of the atoms constituting the heterocycle may be substituted with substituents. In addition, it may have a polycyclic structure in which two or more rings are condensed. Examples of such nitrogen-containing aromatic heterocyclic structures include five-membered heterocyclic rings such as an imidazole ring, a pyrrole ring, a thiazole ring, an oxazole ring, a pyrazole ring, and an isoxazole ring; six-membered heterocyclic rings such as a pyridine ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, and a triazine ring; and fused heterocyclic rings such as a quinoline ring, an isoquinoline ring, a quinoxaline ring, a quinazoline ring, a cinnoline ring, a purine ring, an indole ring, an isoindole ring, a benzimidazole ring, a benzoxazole ring, and a benzisoxazole ring. Among these, five-membered and six-membered heterocyclic rings are preferred, and an imidazole ring is more preferred.

[0033] The substituent of the nitrogen-containing aromatic heterocycle is not particularly limited, and examples thereof 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, etc. 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.

[0034] A ＋ The nitrogen-containing cationic aliphatic group as may be linear or branched, and may have a non-aromatic ring structure.

[0035] A ＋Specific examples of the nitrogen-containing cationic group represented by the formula (I) include an ammonium group; mono-substituted ammonium groups containing a cationic nitrogen atom, such as a methylammonium group, a butylammonium group, a cyclohexylammonium group, an anilinium group, a benzylammonium group, or an ethanolammonium group; di-substituted ammonium groups containing a cationic nitrogen atom, such as a dimethylammonium group, a diethylammonium group, a dibutylammonium group, or a nonylphenylammonium group; trimethylammonium group, triethylammonium group, n-butyldimethylammonium group, stearyldimethylammonium group, tributylammonium group, trivinylammonium group, triethanolammonium group, N,N-dimethylethanolammonium group, tri(2-ethoxyethyl)ammonium group, and heterocyclic groups containing a cationic nitrogen atom, such as a piperidinium group, a 1-methylpyrrolidinium group, a 1-butylpyrrolidinium group, an imidazolium group, a 1-methylimidazolium group, a 1-ethylimidazolium group, a 1-butyl-imidazolium group, a benzimidazolium group, a pyrrolium group, a 1-methylpyrrolium group, an oxazolium group, a benzoxazolium group, a pyrazolium group, an isoxazolium group, a pyridinium group, a 2,6-dimethylpyridinium group, a pyrazinium group, a pyrimidinium group, a pyridazinium group, a triazinium group, an N,N-dimethylanilinium group, a quinolinium group, an isoquinolinium group, an indolinium group, a quinoxalium group, and an isoquinoxalium group. Among these, a trisubstituted ammonium group containing a cationic nitrogen atom and a heterocyclic group containing a cationic nitrogen atom are preferred.

[0036] In the above general formula (1), X － The anion represented by A ＋ X is a counter anion of a nitrogen-containing cationic group represented by the formula: － For example, the monovalent anion is F － , Cl － ,Br － , I － Halide ions such as (FSO ２ ) ２ N－ , (CF ３ SO ２ ) ２ N － , (CF ３ CF ２ SO ２ ) ２ N － sulfonylimide ions such as CH ３ COO － , C3H7COO － , C.F. ３ COO － , PhCOO － (Ph represents a phenyl group), and other carboxylate ions; CH ３ SO ３ － , C.F. ３ SO ３ － sulfonate ions such as OH － , B.F. ４ － , P.F. ６ － , ClO ４ － , B(CN) ４ － , SCN － , (NC) ２ N － X － The anion may be a polyvalent anion or a polyanion having two or more monovalent anionic groups in the molecule. For example, the polyvalent anion may be a sulfate ion (SO ４ ２－ ) and carbonate ions (CO ３ ２－ For example, examples of polyanions having two or more monovalent anionic groups in the molecule include: － O ３ SCF2CF2CF2SO ３ － , － O ３ SCF2CF2SO ３ － , C.F. ３ SO ２ N － SO ２ CF2CF2OCF2CF2OCF2CF2SO２ N － SO ２ CF ３ Among them, from the viewpoint of carbon dioxide absorption, halide ions, BF ４ － is preferred, and Cl － , B.F. ４ － is more preferred.

[0037] In the cationic group-containing polyether, the units represented by the general formula (1) are each independent, and two or more types of units represented by the general formula (1) may be present in the cationic group-containing polyether. For example, in all of the repeating units represented by the general formula (1) in the cationic group-containing polyether, A ＋ All of the nitrogen-containing cationic groups represented by the general formula (1) may be the same kind of nitrogen-containing cationic group, or different kinds of nitrogen-containing cationic groups may be mixed. － All of the anions represented by the formula (I) may be the same kind of anion, or different kinds of anions may be mixed.

[0038] Examples of the repeating unit represented by the above general formula (1) include a 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. (In the above general formula (2), R １ ~R ４ each independently represents a hydrogen atom or a substituent, R ２ and R ３ may be bonded to each other. － represents an anion.)

[0039] In the above general formula (2), R １ ~R ４ R each independently represents a hydrogen atom or a substituent. Examples of the substituent include the same as those described above as the substituent of the nitrogen-containing aromatic heterocycle. １ ~R ４The substituent as R may be linear or branched, and may have a ring structure. １ ~R ４ The substituent as is preferably linear.

[0040] In the above general formula (2), R １ is not particularly limited as long as it is a hydrogen atom or a substituent, 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 in the alkyl group is preferably 0 to 12, more preferably 0 to 8, even more preferably 1 to 6, still more preferably 1 to 4, particularly preferably 1 to 3, and most preferably 1 or 2.

[0041] In the above general formula (2), R ２ ~R ４ are each independently a hydrogen atom or a substituent and are not particularly limited, but are each independently preferably a hydrogen atom or a hydrocarbon group, more preferably a hydrogen atom, an alkyl group or a vinyl group, further preferably a hydrogen atom or an alkyl group, and particularly preferably a hydrogen atom. ２ ~R ４ The number of carbon atoms in each of the groups is preferably 0 to 8, more preferably 0 to 6, even more preferably 0 to 4, still more preferably 0 to 3, particularly preferably 0 to 2, and most preferably 0 to 1.

[0042] In the above general formula (2), R ２ ~R ４ Among R, it is preferable that 1 to 3 represent a hydrogen atom, and more preferable that 2 to 3 represent a hydrogen atom. ２ ~R ４ Preferably, 0 to 2 of these represent a substituent such as a hydrocarbon group, and more preferably, 0 to 1 of these represent a substituent such as a hydrocarbon group.

[0043] X in the above general formula (2) － The anion represented by the formula (1) is X －The preferred embodiments are also the same as those of the anion represented by the formula:

[0044] The repeating unit represented by the general formula (2) above preferably contains an imidazolium group, a 1-methylimidazolium group, a 1-butylimidazolium group, a 1-hexylimidazolium group, or a 1-vinylimidazolium group, and more preferably contains a 1-methylimidazolium group.

[0045] The cationic group-containing polyether may contain a repeating unit other than the repeating unit represented by the general formula (1). The repeating unit other than the repeating unit represented by the general formula (1) is not particularly limited as long as it is derived from a monomer copolymerizable with the monomer that gives the repeating unit represented by the general formula (1), and examples thereof 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 type of repeating unit other than the repeating unit represented by the general formula (1) alone, or may contain two or more types.

[0046] The cationic group-containing polyether may contain two or more types of repeating units. In this case, the distribution pattern of the multiple repeating units is not particularly limited, but it is preferable that the repeating units have a random distribution.

[0047] The chain structure of the cationic group-containing polyether is not particularly limited, and may be a straight chain or a chain structure having branches such as grafts or radial branches.

[0048] The terminal group of the cationic group-containing polyether is not particularly limited and may be any monovalent group. Specific examples of the terminal group include a hydrogen atom, a halogen group, an alkyl group, a haloalkyl group, a hydroxyl group, and an azide group. The terminal group may be a nitrogen-containing cationic group (A ＋ ) and anion (X － ) may be a group consisting of

[0049] The content of the repeating units represented by the general formula (1) in the cationic group-containing polyether is not particularly limited, but the average number per molecule is preferably 1 to 100,000, more preferably 3 to 50,000, even more preferably 10 to 30,000, and particularly preferably 30 to 10,000.

[0050] The proportion of the repeating units represented by the general formula (1) in the cationic group-containing polyether is not particularly limited, but is preferably 5 to 100 mol %, more preferably 50 to 100 mol %, and even more preferably 80 to 100 mol %, based on the total repeating units of the cationic group-containing polyether.

[0051] The method for synthesizing the cationic group-containing polyether is not particularly limited, and any synthesis method can be adopted as long as it can produce the target polyether compound. As an example of the synthesis method, first, a base polymer (a polyether having no cationic group) is obtained by the following method (α) or (β).

[0052] (α) 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 epichlorohydrin, epibromohydrin, or epiiodohydrin, in the presence of a catalyst disclosed in JP 2010-53217 A, which catalyst comprises an onium salt of a compound containing an atom of Group 15 or 16 of the periodic table and a trialkylaluminum in which all of the alkyl groups contained are linear alkyl groups.

[0053] (β) A method of obtaining a base polymer by ring-opening polymerization of a monomer containing an oxirane monomer, which includes at least an epihalohydrin such as epichlorohydrin, epibromohydrin, or epiiodohydrin, in the presence of a catalyst prepared by reacting triisobutylaluminum with phosphoric acid and triethylamine, as disclosed in JP-B-46-27534.

[0054] 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 onium-converting agent containing a nitrogen-containing cationic group (onium-converting reaction), at least a part of the halogen groups constituting the epihalohydrin monomer units of the base polymer is converted into onium halide groups containing a nitrogen-containing cationic group, thereby forming an anion (X － ) is a halide ion. If necessary, the obtained polyether compound containing onium halide structural units can be mixed with an anion (X ) other than a halide ion. － ) with a salt of a metal cation to carry out an anion exchange reaction, thereby converting the halide ion constituting the onium halide group containing the nitrogen-containing cationic group into an anion other than the halide ion (X － ) can be converted to

[0055] The onium-containing agent containing a nitrogen-containing cationic group used in the reaction of the base polymer with the onium-containing agent containing a nitrogen-containing cationic group is a compound represented by the general formula (1)＋ For example, by using an imidazole compound corresponding to the imidazolium structure in general formula (2) as the onium forming agent, it is possible to form the repeating unit represented by general formula (2).

[0056] The method for reacting the base polymer with the onium-forming agent is not particularly limited, but a method of mixing the base polymer with the onium-forming agent is preferred. The method for mixing the base polymer with the onium-forming agent is also not particularly limited, but examples include a method of adding the onium-forming agent to a solution containing the base polymer and mixing them, a method of adding the base polymer to a solution containing the onium-forming agent and mixing them, and a method of preparing the onium-forming agent and the base polymer as separate solutions and mixing the two solutions.

[0057] In the reaction between the base polymer and the onium-forming agent, an inert solvent is preferably used, and may be either 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. Mixtures of these solvents are also preferably used. The amount of solvent used is not particularly limited, but is preferably used so that the base polymer concentration is 1 to 50% by mass, and more preferably 3 to 40% by mass.

[0058] The amount of onium-forming agent used when reacting the base polymer with the onium-forming agent is not particularly limited and may be determined depending on the content of the repeating unit represented by general formula (1) in the target polyether compound, etc. Specifically, the amount of onium-forming agent used is usually in the range of 0.01 to 100 mol, preferably 0.02 to 50 mol, more preferably 0.03 to 10 mol, and even more preferably 0.05 to 2 mol, per mol of epichlorohydrin units in the base polymer used.

[0059] The pressure when reacting the base polymer with the onium-containing agent is not particularly limited, but is usually 1 to 500 atm, preferably 1 to 100 atm, and particularly preferably 1 to 50 atm. The temperature during the reaction 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.

[0060] A polyether compound containing an onium halide structural unit and an anion other than a halide ion (X － The method for carrying out the anion exchange reaction by reacting a salt of a metal cation with a polyether compound containing an onium halide structural unit and an anion other than a halide ion (X － ) and a salt of a metal cation are mixed and reacted.

[0061] The conditions for carrying out the anion exchange reaction are not particularly limited, and include the steps of: reacting a polyether compound containing an onium halide structural unit with an anion other than a halide ion (X － Alternatively, the reaction may be carried out in the presence of other compounds such as an organic solvent. The amount of the salt used is not particularly limited, but is usually 0.01 to 100 mol, preferably 0.02 to 50 mol, and more preferably 0.03 to 10 mol, per mol of onium halide structural units of the onium halide structural unit-containing polyether compound used.

[0062] An anion other than a halide ion (X － The salt of lithium fluoride (Li(FSO2)2N) with a metal cation is not particularly limited, and examples thereof 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) ２ N), lithium methylsulfonate (LiCH3SO3), lithium trifluoromethylsulfonate (LiCF3SO3), potassium hydroxide (KOH), lithium perchlorate (LiClO4), sodium tetrafluoroborate (NaBF ４ In the case of salts of polyvalent anions and metal cations, silver sulfate (Ag ２ SO ４ ２－ ), sodium carbonate (Na ２ CO ３ ２－ For example, examples of salts of polyanions having two or more monovalent anionic groups in the molecule and metal cations include LiO ３ SCF2CF2CF2SO ３ Li, LiO ３ SCF2CF2SO ３ Li, Li ２ (CF ３ SO ２ NSO ２ CF2CF2OCF2CF2OCF2CF2SO ２ NSO ２ CF ３ ) etc.

[0063] The pressure during the anion exchange reaction is usually 1 to 500 atm, preferably 1 to 100 atm, and particularly preferably 1 to 50 atm. The reaction temperature is usually −30 to 200° C., preferably −15 to 180° C., and more preferably 0 to 150° C. The reaction time is usually 1 minute to 1,000 hours, preferably 3 minutes to 100 hours, more preferably 5 minutes to 10 hours, and even more preferably 5 minutes to 3 hours.

[0064] After the anion exchange reaction is completed, metal cations, halide ions, and salts thereof can be removed by washing with water or membrane separation using a semipermeable membrane, and the mixture containing the cationic group-containing polyether can be recovered. Alternatively, the mixture containing the cationic group-containing polyether can be recovered by extracting the cationic group-containing polyether with a solvent such as methanol. Furthermore, the desired cationic group-containing polyether can be recovered by a conventional method, such as drying under reduced pressure.

[0065] The degree of polymerization of the carbon dioxide-trapping polymer is not particularly limited, but is preferably 10 to 20,000, more preferably 10 to 10,000, and even more preferably 10 to 2,000. Having a degree of polymerization within the above range allows the content of the carbon dioxide-trapping polymer in the carbon dioxide absorbent composition to be adjusted to a desired amount while maintaining an appropriate viscosity of the carbon dioxide absorbent composition, thereby further improving the carbon dioxide absorbency. In particular, maintaining an appropriate viscosity of the carbon dioxide absorbent composition allows for good handleability during transfer to a reaction vessel, etc. The degree of polymerization of the carbon dioxide-trapping polymer can be calculated by performing GPC measurement and dividing the number-average molecular weight calculated in terms of standard polyethylene glycol by the molecular weight of the repeating unit. Furthermore, when a cationic group-containing polyether is used as the carbon dioxide-trapping polymer, the number-average molecular weight can be determined by the method described in the Examples below. If the degree of polymerization is too high, the viscosity of the composition will increase too much, slowing the diffusion of carbon dioxide and reducing the carbon dioxide trapping ability of the composition. If the degree of polymerization is too low, the carbon dioxide trapping ability of the carbon dioxide-trapping polymer itself will be reduced.

[0066] The content of the carbon dioxide trapping polymer in the carbon dioxide absorbent composition of the present invention is not particularly limited, but is preferably 1 to 100 parts by weight, more preferably 1.5 to 60 parts by weight, even more preferably 2 to 60 parts by weight, even more preferably 2.0 to 40 parts by weight, and particularly preferably 2.5 to 20 parts by weight, relative to 100 parts by weight of the dispersion medium. Furthermore, the content of the carbon dioxide trapping polymer relative to 100% by weight of the entire carbon dioxide absorbent composition is preferably 0.7% by weight or more, more preferably 2% by weight or more, even more preferably 3% by weight or more, and is preferably 20% by weight or less, more preferably 15% by weight or less, and even more preferably 10% by weight or less. By setting the content of the carbon dioxide trapping polymer within the above range, the carbon dioxide absorbency of the carbon dioxide absorbent composition can be further enhanced while maintaining the viscosity of the carbon dioxide absorbent composition within an appropriate range.

[0067] Furthermore, in the carbon dioxide absorbent composition of the present invention, the content ratio of the basic inorganic compound to the carbon dioxide trapping polymer, in terms of the weight ratio of basic inorganic compound to carbon dioxide trapping polymer, is preferably in the range of 50:1 to 1:50, more preferably in the range of 40:1 to 1:40, even more preferably in the range of 30:1 to 1:30, and even more preferably in the range of 30:1 to 3: 1. By setting the content ratio of the basic inorganic compound to the carbon dioxide trapping polymer within the above range, it is possible to further enhance the carbon dioxide absorbency.

[0068] Furthermore, the carbon dioxide absorbent composition of the present invention may contain various compounding agents in addition to the basic inorganic compound, the carbon dioxide-trapping polymer, and the dispersion medium. Examples of the compounding agents include an antioxidant; an ultraviolet absorber; a light-resistant stabilizer; a surfactant; an antifoaming agent; an electrolyte substance; a colorant (dye or pigment); a flame retardant; and an antistatic agent.

[0069] The method for preparing the carbon dioxide absorbent composition of the present invention is not particularly limited, but examples thereof include a method in which a carbon dioxide trapping polymer is dissolved in a dispersion medium and a basic inorganic compound is added to the obtained solution.

[0070] The carbon dioxide absorbent composition of the present invention can efficiently absorb carbon dioxide and therefore can be suitably used in applications requiring a reduction in carbon dioxide concentration. For example, the carbon dioxide absorbent composition of the present invention can be suitably used to reduce the carbon dioxide concentration of gases having a carbon dioxide concentration of preferably 400 ppm to 50%, more preferably 450 ppm to 30%. In particular, the carbon dioxide absorbent composition of the present invention can be suitably used to reduce the carbon dioxide concentration of gases having a relatively high carbon dioxide concentration, such as exhaust gas.

[0071] Since the carbon dioxide absorbent composition of the present invention is usually in the form of a dispersion or solution, it can be placed in a reaction vessel or the like in the form of a dispersion or solution and installed on a flow path of a carbon dioxide-containing gas to be treated to form a carbon dioxide absorption module, and by bringing the carbon dioxide-containing gas into contact with the carbon dioxide absorbent composition of the present invention, the carbon dioxide concentration in the gas can be efficiently absorbed and the carbon dioxide concentration can be suitably reduced. Furthermore, according to the carbon dioxide absorbent composition of the present invention, after carbon dioxide is absorbed by the basic inorganic compound, the basic inorganic compound that has absorbed carbon dioxide is contained in the carbon dioxide absorbent composition of the present invention in the form of a solid carbonate, and can therefore be relatively easily separated and recovered by using centrifugation, filtration, or the like, and can thereby be used as a high-value-added material that can be used in a variety of applications, including cement agents, etc.

[0072] 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. The terms "parts" are based on mass unless otherwise specified. The test methods used in these examples and comparative examples are as follows.

[0073] <Number Average Molecular Weight (Mn) and Molecular Weight Distribution (Mw / Mn)> (1) Number Average Molecular Weight (Mn) and Molecular Weight Distribution (Mw / Mn) of 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 a solvent. The measuring instrument used was an HLC-8320 (manufactured by Tosoh Corporation), and three TSKgel-α-M (manufactured by Tosoh Corporation) columns connected in series, and the detector used was a differential refractometer RI-8320 (manufactured by Tosoh Corporation).

[0074] (2) Number-Average Molecular Weight (Mn) of Imidazolium Structure-Containing Polyether Compound The number-average molecular weight (Mn) of the imidazolium structure-containing polyether compound obtained in Production Examples 2 and 3 was determined as follows. That is, 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 weights of the various monomer units constituting the polyether compound, and the contents of the various monomer units determined by the following (3). 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 then used as the number-average molecular weight (Mn) of the polyether compound.

[0075] (3) Structures of the base polymer and the imidazolium structure-containing polyether compound, and the content of the 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 the monomer units in the base polymer and the imidazolium structure-containing polyether compound were measured using a nuclear magnetic resonance (NMR) spectrometer as follows. That is, 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 dissolve it uniformly. Then, the obtained solution was subjected to NMR measurement, １H-NMR spectra were obtained, and the structure of the sample was assigned according to standard methods. 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. First, the number of moles of all oxirane monomer units, B1, was calculated from the integral of the protons derived from the oxirane monomer units in the main chain. Next, the number of moles of the repeating unit represented by general formula (2), B2, was calculated from the integral of the protons derived from the imidazolium structure in the repeating unit represented by general formula (2). The ratio (percentage) of B2 to B1 was then calculated as the content of the repeating unit represented by general formula (2) in the imidazolium structure-containing polyether compound.

[0076] <Carbon dioxide absorption treatment test> 200 g of a dispersion or solution of the carbon dioxide absorbent composition in a glass beaker was placed inside a plastic bag containing 10 L of air (carbon dioxide concentration 460 ppm), and a diaphragm pump with a 3 mm diameter silicone rubber hose connected to the air supply port and a CO ２ A concentration meter was installed. Then, the tip of a silicone rubber hose connected to a diaphragm pump was inserted to the bottom of a beaker containing a dispersion or solution of the carbon dioxide absorbent composition, thereby configuring the air in the plastic bag to be introduced into the dispersion or solution of the carbon dioxide absorbent composition via the diaphragm pump and the silicone rubber hose, and then the plastic bag was sealed. Next, the diaphragm pump was operated to send the air inside the plastic bag to the bottom of the beaker containing the dispersion or solution of the carbon dioxide absorbent composition at an air volume of 2.5 L / min, and the air in the plastic bag was continuously sent to and continuously brought into contact with the dispersion or solution of the carbon dioxide absorbent composition, thereby performing a carbon dioxide absorption treatment. The carbon dioxide absorption treatment was performed under conditions of 10 minutes or 20 minutes, and after the treatment was performed for 10 minutes or 20 minutes, the air supply was stopped. At this time, the carbon dioxide concentration of the air in the plastic bag during the carbon dioxide absorption treatment was measured using the CO ２ Measured using a densitometer. ２The concentration meter used was a CO ２ Concentration meter "ZG106" or Vaisala CO ２ An "Indigo 80" concentration meter was used. In the carbon dioxide absorption treatment test, the carbon dioxide absorption property was evaluated by calculating the carbon dioxide reduction rate according to the following formula: Carbon dioxide reduction rate = (initial carbon dioxide concentration - carbon dioxide concentration after carbon dioxide absorption treatment) / initial carbon dioxide concentration. In Examples 61 to 72, the carbon dioxide absorption treatment was carried out using a high carbon dioxide concentration gas (a mixed gas of carbon dioxide and nitrogen) with a carbon dioxide concentration of 48,700 to 50,900 ppm, instead of air (carbon dioxide concentration 460 ppm).

[0077] <Dispersion Stability of Dispersion after Test> 100 mL of the dispersion (slurry) of the carbon dioxide absorbent composition after the carbon dioxide absorption treatment was transferred from the beaker to a 100 mL glass measuring cylinder and left to stand for 10 minutes. Thereafter, the measuring cylinder was turned upside down, and the dispersion of the carbon dioxide absorbent composition was transferred back to the original beaker. At this time, the state of the dispersion of the carbon dioxide absorbent composition was observed, and the dispersion stability of the dispersion of the carbon dioxide absorbent composition after the test was evaluated according to the following criteria. ∘: No inorganic solid layer remained on the bottom of the measuring cylinder. ×: An inorganic solid layer remained on the bottom of the measuring cylinder. Furthermore, when an inorganic solid layer remained, the amount of the remaining inorganic solid layer was measured in mL using the scale on the measuring cylinder.

[0078] <Long-term storage stability of dispersion> 100 mL of the prepared dispersion (slurry) of the carbon dioxide absorbent composition was transferred to a 100 mL glass bottle with a lid and allowed to stand for 7 days. Thereafter, the bottle was vigorously stirred for 1 minute to disperse the settled inorganic components. ◯: No inorganic solid layer remained on the bottom of the glass bottle. Δ: An inorganic solid layer remained on the bottom of the glass bottle and was not completely dispersed.

[0079] Production Example 1 (Living Anionic Polymerization of Epichlorohydrin) 0.322 g of tetra-n-butylammonium bromide and 50 ml of toluene were added to an argon-purged glass reactor equipped with a stirrer and cooled to 0°C. Next, 0.148 g of triethylaluminum (1.3 equivalents relative to tetra-n-butylammonium bromide) dissolved in 5 ml of toluene was added and allowed to react for 15 minutes to obtain a catalyst composition. 10.0 g of epichlorohydrin was added to the resulting catalyst composition, and polymerization 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 terminate the reaction. The resulting polymerization reaction solution was washed with a 0.1 N aqueous hydrochloric acid solution to deash the catalyst residue, and then further washed with ion-exchanged 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 (base polymer) was 9.9 g. The number average molecular weight (Mn) of the obtained substance measured by GPC was 10,700, the degree of polymerization was 116, and the molecular weight distribution (Mw / Mn) was 1.18.

[0080] <Production Example 2> (Quaternization of epichlorohydrin oligomer with 1-methylimidazole) 8.0 g of the epichlorohydrin oligomer obtained above, 22.0 g of 1-methylimidazole, and 16.0 g of N,N-dimethylformamide were added to a glass reactor equipped with a stirrer and 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, and 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, １H-NMR measurement and elemental analysis identified the product as polyether compound A (cationic group-containing polyether composed of repeating units represented by the following formula (3)) having 1-methylimidazolium halide groups, in which the chloro groups in all epichlorohydrin units in the epichlorohydrin oligomer had been substituted with 1-methylimidazolium chloride groups and the bromo groups in all bromomethyl groups at the polymerization initiation terminals had been substituted with 1-methylimidazolium bromide groups. The resulting imidazolium structure-containing polyether compound A having a halide ion as a counter anion 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 measured by GPC. Its solubility in 100 g of water at 25°C was found to be 30 g or more.

[0081] <Production Example 3> (Anion exchange of imidazolium structure-containing polyether compound A having halide ions as counter anions with sodium tetrafluoroborate) 5.0 g of imidazolium structure-containing polyether compound A having halide ions as counter anions obtained in Production Example 2, 3.2 g of sodium tetrafluoroborate, and 100 mL of ion-exchanged water were added to a glass reactor equipped 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 the product 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 a reddish-brown resinous substance. Regarding the obtained resinous substance, １H-NMR spectroscopy and elemental analysis identified the resulting compound as imidazolium structure-containing polyether compound B having tetrafluoroborate anions as counter anions (a cationic group-containing polyether composed of repeating units represented by formula (4) below), in which all of the chloride ions and bromide ions in the starting material, imidazolium structure-containing polyether compound A having halide ions as counter anions, had been exchanged with tetrafluoroborate anions. The resulting imidazolium structure-containing polyether compound B having tetrafluoroborate anions as counter anions had a number average molecular weight (Mn) of 22,600, a molecular weight distribution (Mw / Mn) of 1.18, and a degree of polymerization of 116, as determined by GPC. Its solubility in 100 g of water at 25°C was found to be 5 g or more.

[0082] Example 1 To a glass reaction vessel equipped with a stirrer, 133 parts of ion-exchanged water and 6.8 parts of polyethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., number average molecular weight (Mn) in terms of polystyrene by GPC: 20,000, degree of polymerization: 450-mer, solubility in 100 g of water at a temperature of 25°C: 10 g or more) were added, and the mixture was stirred at room temperature for 10 minutes in air to prepare a uniform aqueous solution. Next, magnesium hydroxide (Mg(OH) ２ To the mixture was added 68 parts of a carbon dioxide absorbent composition (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., average particle size: 0.6 μm), and the mixture was stirred at room temperature for 10 minutes in air, thereby obtaining a carbon dioxide absorbent composition in the form of a uniformly mixed dispersion.

[0083] Then, using the obtained dispersion of the carbon dioxide absorbent composition, a carbon dioxide absorption treatment test, evaluation of the dispersion stability after the test, and long-term storage stability of the dispersion were carried out according to the above-mentioned methods.

[0084] Specifically, in the carbon dioxide absorption treatment test, the air in the plastic bag was continuously fed into the dispersion liquid of the carbon dioxide absorbent composition, and the carbon dioxide concentration inside the plastic bag was 460 ppm initially before the air feeding, but gradually decreased. After the air feeding was performed for 10 minutes, the carbon dioxide concentration inside the plastic bag at the time of stopping was measured as CO ２ When measured with a concentration meter, the concentration was 335 ppm, and the carbon dioxide reduction rate (carbon dioxide reduction rate = [initial carbon dioxide concentration - carbon dioxide concentration at the time of stopping the air supply] / initial carbon dioxide concentration) was 0.271. Furthermore, in Example 1, the dispersion stability of the carbon dioxide absorbent composition after the carbon dioxide absorption treatment was evaluated after the dispersion test, and it turned out that no inorganic solid layer remained on the bottom of the measuring cylinder (evaluation: ◯). Furthermore, to evaluate the long-term storage stability of the dispersion, the dispersion of the carbon dioxide absorbent composition after preparation was transferred to a 100 mL glass bottle with a lid and left to stand for 7 days, and then vigorously stirred for 1 minute to disperse the settled inorganic components, and it turned out that no inorganic solid layer remained (evaluation: ◯). The results are shown in Table 1.

[0085] Example 2: Instead of magnesium hydroxide, calcium hydroxide (Ca(OH) ２ A dispersion of a carbon dioxide absorbent composition was obtained in the same manner as in Example 1, except that 68 parts of PEG-100 sintered carbon dioxide absorbent (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., average particle size: 4.0 μm) was used, and evaluation was performed in the same manner. The results are shown in Table 1.

[0086] Examples 3 to 6 Dispersions of carbon dioxide absorbent compositions were obtained and evaluated in the same manner as in Example 1 or Example 2, except that the amounts of polyethylene glycol used were changed to the amounts shown in Table 1. The results are shown in Table 1.

[0087] Examples 7 and 8 A dispersion of a carbon dioxide absorbent composition was obtained in the same manner as in Example 1 or Example 2, except that 1.7 parts of polyethylene oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., number average molecular weight (Mn) as converted into polystyrene by GPC: 500,000, degree of polymerization: 11,400, solubility in 100 g of water at a temperature of 25° C.: 1 g or more) was used instead of polyethylene glycol. The results are shown in Table 1.

[0088] Examples 9 and 10 In Examples 9 and 10, polyvinyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., degree of polymerization 1500 to 1800, degree of saponification 78-82%) used in place of polyethylene glycol has low solubility in water at a temperature of 25°C, so it was dissolved in water at 100°C and then cooled to a temperature of 25°C. The solubility in 100 g of water immediately after cooling was 7 g or more. In Examples 9 and 10, a dispersion of a carbon dioxide absorbent composition was obtained in the same manner as in Example 1 or Example 2, except that 6.8 parts of polyvinyl alcohol was used, and evaluation was similarly carried out. The results are shown in Table 1.

[0089] Examples 11 and 12 A dispersion of a carbon dioxide absorbent composition was obtained in the same manner as in Example 1 or Example 2, except that 6.8 parts of polyvinylpyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd., number average molecular weight (Mn) as converted into polystyrene by GPC: 10,000, degree of polymerization: 90, solubility in 100 g of water at a temperature of 25° C.: 5 g or more) was used instead of polyethylene glycol. The results are shown in Table 1.

[0090] Examples 13 and 14 A dispersion of a carbon dioxide absorbent composition was obtained in the same manner as in Example 1 or Example 2, except that 6.8 parts of polyacrylic acid (Fujifilm Wako Pure Chemical Industries, Ltd., number average molecular weight (Mn) in terms of polystyrene measured by GPC: 25,000, degree of polymerization: 350, solubility in 100 g of water at a temperature of 25° C.: 5 g or more) was used instead of polyethylene glycol. The results are shown in Table 1.

[0091] Examples 15 and 16 A dispersion of a carbon dioxide absorbent composition was obtained and evaluated in the same manner as in Example 1 or Example 2, except that 6.8 parts of the imidazolium structure-containing polyether compound A obtained in Production Example 2 was used instead of polyethylene glycol. The results are shown in Table 1.

[0092] Examples 17 and 18 A dispersion of a carbon dioxide absorbent composition was obtained and evaluated in the same manner as in Example 1 or Example 2, except that 9.6 parts of the imidazolium structure-containing polyether compound B obtained in Production Example 3 was used instead of polyethylene glycol. The results are shown in Table 1.

[0093] Comparative Examples 1 and 2 Except for not using polyethylene glycol, a dispersion of a carbon dioxide absorbent composition was obtained and evaluated in the same manner as in Example 1 or Example 2. The results are shown in Table 1.

[0094]

[0095] <Evaluation of Examples 1 to 18 and Comparative Examples 1 and 2> As shown in Table 1, when a carbon dioxide absorbent composition containing a basic inorganic compound, a carbon dioxide trapping polymer, and a dispersion medium was subjected to a carbon dioxide absorption treatment, the carbon dioxide reduction rate was high and carbon dioxide could be absorbed with high efficiency. Furthermore, the dispersion of the carbon dioxide absorbent composition was excellent in dispersion stability after testing, and the dispersions of Examples 1 to 8, 11, 12, and 15 to 18 were also excellent in long-term storage stability.

[0096] <Examples 19 to 36> For the dispersions of the carbon dioxide absorbent compositions prepared in Examples 1 to 18, a carbon dioxide absorption treatment test was conducted with the treatment time set to 20 minutes, and the dispersion stability of the dispersions after the 20-minute carbon dioxide absorption treatment test was evaluated. The results are shown in Table 2.

[0097] <Comparative Examples 3 and 4> The dispersions of the carbon dioxide absorbent compositions prepared in Comparative Examples 1 and 2 were subjected to a carbon dioxide absorption treatment test with a treatment time of 20 minutes, and the dispersion stability of the dispersions after the 20-minute carbon dioxide absorption treatment test was evaluated. The results are shown in Table 2.

[0098] Comparative Examples 5 to 8 A dispersion of a carbon dioxide absorbent composition was obtained in the same manner as in Example 1, Example 9, Example 15, or Example 17, except that magnesium hydroxide was not used. Then, a carbon dioxide absorption treatment test was carried out on the obtained dispersion of the carbon dioxide absorbent composition, with the treatment time set to 20 minutes, and the dispersion stability of the dispersion after the 20-minute carbon dioxide absorption treatment test was evaluated. The results are shown in Table 2.

[0099]

[0100] <Evaluation of Examples 19 to 36 and Comparative Examples 3 to 8> As shown in Table 2, according to the carbon dioxide absorbent composition containing a basic inorganic compound, a carbon dioxide trapping polymer, and a dispersion medium, even when the carbon dioxide absorption treatment was carried out for 20 minutes, the carbon dioxide reduction rate could be made high and carbon dioxide could be absorbed with high efficiency. Furthermore, the dispersion of the carbon dioxide absorbent composition was excellent in dispersion stability after testing, and further, Examples 19 to 26, 29, 30, and 33 to 36 also had excellent long-term storage stability of the dispersion.

[0101] Example 37 Except for using 68 parts of sodium hydroxide (NaOH, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) instead of magnesium hydroxide, a carbon dioxide absorbent composition was obtained in the form of an aqueous solution in the same manner as in Example 1, and a carbon dioxide absorption treatment test was carried out in accordance with the method described above. The results are shown in Table 3.

[0102] Example 38 Except for using 68 parts of potassium hydroxide (KOH, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) instead of magnesium hydroxide, a carbon dioxide absorbent composition was obtained in the form of an aqueous solution in the same manner as in Example 1, and a carbon dioxide absorption treatment test was carried out in accordance with the method described above. The results are shown in Table 3.

[0103] <Examples 39 to 42> Solutions of carbon dioxide absorbent compositions were obtained and evaluated in the same manner as in Example 37 or Example 38, except that the amounts of polyethylene glycol used were changed to the amounts shown in Table 3. The results are shown in Table 3.

[0104] Examples 43 and 44 A solution of a carbon dioxide absorbent composition was obtained in the same manner as in Example 37 or Example 38, except that 1.7 parts of polyethylene oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., number average molecular weight (Mn): 500,000, degree of polymerization 11,400, solubility in 100 g of water at a temperature of 1 g or more at 25° C.) was used instead of polyethylene glycol, and evaluation was performed in the same manner. The results are shown in Table 3.

[0105] Examples 45 and 46 A dispersion of a carbon dioxide absorbent composition was obtained in the same manner as in Example 37 or Example 38, except that 6.8 parts of polyvinylpyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd., number average molecular weight (Mn) as converted into polystyrene by GPC: 10,000, degree of polymerization: 90, solubility in 100 g of water at a temperature of 25° C.: 5 g or more) was used instead of polyethylene glycol. The results are shown in Table 3.

[0106] Examples 47 and 48 A solution of a carbon dioxide absorbent composition was obtained and evaluated in the same manner as in Example 37 or Example 38, except that 9.6 parts of the imidazolium structure-containing polyether compound B obtained in Production Example 3 was used instead of polyethylene glycol. The results are shown in Table 3.

[0107] Comparative Examples 9 and 10 Except for not using polyethylene glycol, a solution of a carbon dioxide absorbent composition was obtained in the same manner as in Example 37 or Example 38, and evaluation was carried out in the same manner. The results are shown in Table 3.

[0108]

[0109] <Evaluation of Examples 37 to 48 and Comparative Examples 9 and 10> As shown in Table 3, according to the carbon dioxide absorbent composition containing a basic inorganic compound, a carbon dioxide trapping polymer, and a dispersion medium, even when sodium hydroxide or potassium hydroxide was used as the basic inorganic compound, it was possible to absorb carbon dioxide with high efficiency and the composition had excellent carbon dioxide absorbency.

[0110] Examples 49 to 60 The solutions of the carbon dioxide absorbent compositions prepared in Examples 37 to 48 were subjected to a carbon dioxide absorption treatment test with a treatment time of 20 minutes. The results are shown in Table 4.

[0111] <Comparative Examples 11 and 12> The solutions of the carbon dioxide absorbent compositions prepared in Comparative Examples 9 and 10 were subjected to a carbon dioxide absorption treatment test with a treatment time of 20 minutes. The results are shown in Table 4.

[0112]

[0113] <Evaluation of Examples 49 to 60 and Comparative Examples 11 and 12> As shown in Table 4, according to the carbon dioxide absorbent composition containing a basic inorganic compound, a carbon dioxide trapping polymer, and a dispersion medium, even when sodium hydroxide or potassium hydroxide was used as the basic inorganic compound and the carbon dioxide absorption treatment was carried out for 20 minutes, a high carbon dioxide reduction rate could be achieved and carbon dioxide could be absorbed with high efficiency.

[0114] Examples 61 to 76 Dispersions of carbon dioxide absorbent compositions were obtained in the same manner as in Examples 1 to 6 and 9 to 18, respectively, except that 100 parts of water and 33 parts of methanol were used as the dispersion medium instead of 133 parts of water. Then, using the obtained dispersions of carbon dioxide absorbent compositions, a carbon dioxide absorption treatment test was conducted with the treatment time set to 20 minutes, and the dispersion stability of the dispersions after the 20-minute carbon dioxide absorption treatment test was evaluated. The results are shown in Table 5.

[0115] <Comparative Examples 13 and 14> A dispersion of a carbon dioxide absorbent composition was obtained in the same manner as in Comparative Example 1 or Comparative Example 2, except that 100 parts of water and 33 parts of methanol were used as the dispersion medium instead of 133 parts of water. Then, using the obtained dispersion of the carbon dioxide absorbent composition, a carbon dioxide absorption treatment test was carried out with the treatment time set to 20 minutes, and the dispersion stability of the dispersion after the 20-minute carbon dioxide absorption treatment test was evaluated. The results are shown in Table 5.

[0116]

[0117] <Evaluation of Examples 61 to 76 and Comparative Examples 13 and 14> As shown in Table 5, according to the carbon dioxide absorbent composition containing a basic inorganic compound, a carbon dioxide trapping polymer, and a dispersion medium, even when methanol was used in addition to water as the dispersion medium and the carbon dioxide absorption treatment was carried out for 20 minutes, the carbon dioxide reduction rate could be made high, carbon dioxide could be absorbed with high efficiency, and further the dispersion stability of the dispersion was excellent.

[0118] <Examples 77 to 92> For the dispersions of the carbon dioxide absorbent compositions prepared in Examples 1 to 6 and 9 to 18, a carbon dioxide absorption treatment test was performed using a high carbon dioxide concentration gas (a mixed gas of carbon dioxide and nitrogen) having the carbon dioxide concentration shown in Table 6, and the treatment time was set to 20 minutes.The dispersion stability of the dispersions after the 20-minute carbon dioxide absorption treatment test was evaluated. The results are shown in Table 6.

[0119] <Comparative Examples 15 and 16> For the dispersions of the carbon dioxide absorbent compositions prepared in Comparative Examples 1 and 2, a carbon dioxide absorption treatment test was performed using a high carbon dioxide concentration gas (a mixed gas of carbon dioxide and nitrogen) having the carbon dioxide concentrations shown in Table 6, and the treatment time was set to 20 minutes. The dispersions after the 20-minute carbon dioxide absorption treatment test were evaluated for dispersion stability. The results are shown in Table 6.

[0120]

[0121] <Evaluation of Examples 77 to 92 and Comparative Examples 15 and 16> As shown in Table 6, the carbon dioxide absorbent composition containing a basic inorganic compound, a carbon dioxide trapping polymer, and a dispersion medium was able to achieve a high carbon dioxide reduction rate and absorb carbon dioxide with high efficiency even when a gas with a high carbon dioxide concentration was used, and furthermore, the dispersion stability of the dispersion was excellent.

Claims

1. A carbon dioxide absorbent composition containing a basic inorganic compound, a carbon dioxide trapping polymer, and a dispersion medium.

2. The carbon dioxide absorbent composition according to claim 1, wherein the basic inorganic compound is a chloride, hydroxide, or oxide.

3. The carbon dioxide absorbent composition according to claim 1 or 2, wherein the basic inorganic compound contains an alkaline earth metal.

4. The carbon dioxide absorbent composition according to any one of claims 1 to 3, wherein the carbon dioxide trapping polymer is a polymer having a solubility of 1 g or more in 100 g of water at 25°C.

5. The carbon dioxide absorbent composition according to any one of claims 1 to 4, wherein the carbon dioxide trapping polymer is a polymer having a degree of polymerization in the range of 10 to 20,000.

6. The carbon dioxide absorbent composition according to any one of claims 1 to 5, wherein the content ratio of the basic inorganic compound to the carbon dioxide trapping polymer is in the range of 50:1 to 1:50 in terms of the weight ratio of basic inorganic compound:carbon dioxide trapping polymer.

7. The carbon dioxide absorbent composition according to any one of claims 1 to 6, wherein the content of the carbon dioxide trapping polymer is 1 to 100 parts by weight per 100 parts by weight of the dispersion medium.

8. The carbon dioxide absorbent composition according to any one of claims 1 to 7, wherein the content of the carbon dioxide trapping polymer is 2 to 60 parts by weight per 100 parts by weight of the dispersion medium.

9. The carbon dioxide absorbent composition according to any one of claims 1 to 8, wherein the carbon dioxide trapping polymer is at least one selected from polyethylene glycol, polyvinylpyrrolidone, and a cationic group-containing polymer having a cationic group in the polymer chain.

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